Endocrine-Related Cancer (2008) 15 721–743 REVIEW Pituitary tumor-transforming gene in endocrine and other neoplasms: a review and update

Fateme Salehi1, Kalman Kovacs1, Bernd W Scheithauer 3, Ricardo V Lloyd 3 and Michael Cusimano2

Departments of 1Laboratory Medicine and 2Neurosurgery, St Michael’s Hospital, 30 Bond Street, Toronto, Ontario, Canada M5B 1W8 3Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First Street, SW, Rochester, Minnesota 55905, USA (Correspondence should be addressed to F Salehi; Email: [email protected])

Abstract Pituitary tumor-transforming gene (PTTG) was only recently discovered. Its overexpression occurs in a wide variety of endocrine and non-endocrine tumors, including ones of pituitary, thyroid, ovary, breast, prostate, lung, esophagus, colon, and the central nervous system. It affects tumor invasiveness and recurrence in several systems, functions as a securin during cell cycle progression, and inhibits premature sister chromatid separation. PTTG is involved in multiple cellular pathways, including proliferation, DNA repair, transformation, angiogenesis induction, invasion, and the induction of genetic instability. In thyroid carcinomas, PTTG expression is a marker of invasiveness. PTTG is overexpressed in most pituitary adenomas, where it appears to correlate with recurrence and angiogenesis. Increasing evidence also points to the role of PTTG in endocrine organ development. For example, PTTG knockout mice show defective pancreatic b-cell proliferation. Herein, we review the current knowledge regarding PTTG-mediated pathways based on evidence from in vivo and in vitro studies as well as knockout mice models. We also summarize the issue of PTTG expression and its correlation with clinicopathologic parameters in patients with neoplasms, particularly of endocrine organs. In addition, we discuss in vitro and in vivo therapeutic models targeting PTTG overexpression. Endocrine-Related Cancer (2008) 15 721–743

Introduction aggressive behavior (Heaney et al. 2000, Boelaert et al. a The pituitary tumor-transforming gene (PTTG) was 2003 ). PTTG is implicated in several normal cellular first isolated from GH4 rat pituitary tumor cells (Pei & processes, including DNA damage repair, apoptosis, Melmed 1997). Subsequent studies demonstrated its and angiogenesis. It also interacts with a number of function as a securin, mediating sister chromatid factors both in vivo and in vitro. These include p53. separation during mitosis (Zou et al. 1999). The PTTG also possesses transactivating activity and PTTG family includes PTTG1, PTTG2, and PTTG3. induces upregulation of several other genes, specifi- In this review, we focus specifically on PTTG1, the cally basic fibroblast growth factor (bFGF) and c-myc most abundant and widely studied form of the (Zhang et al.1999b, Pei 2001, Hamid & Kakar 2004, substance, and will refer to PTTG1 as PTTG. Kim et al. 2006a, Tfelt-Hansen et al. 2006). In Subcutaneous injection of PTTG-transfected cells neoplasms, PTTG is thought to induce aneuploidy into nude mice has been shown to induce tumors and genetic instability. Recent evidence suggests that formation. Overexpression of PTTG reportedly occurs PTTG is implicated in stem cell proliferation as well as in several neoplasms, including pituitary tumors, as in cardiac hypertrophy, thus expanding the broad well as carcinomas of lung, breast, esophagus, colon, spectrum of processes which it regulates. PTTG rectum, and ovary. In colon and thyroid cancers, its knockout mouse models have been developed to expression is associated with tumor invasiveness and investigate the role of PTTG in tumor initiation and

Endocrine-Related Cancer (2008) 15 721–743 Downloaded from Bioscientifica.comDOI: 10.1677/ERC-08-0012 at 09/30/2021 01:03:52PM 1351–0088/08/015–721 q 2008 Society for Endocrinology Printed in Great Britain Online version via http://www.endocrinology-journals.orgvia free access F Salehi et al.: PTTG review progression particularly in the pituitary and thyroid Subcellular localization gland. Recently, Vlotides et al. (2007) reviewed PTTG Subcellular PTTG localization, particularly the signifi- action within the context of endocrine cell function. In cance of cytoplasmic versus nuclear expression, this review, we provide an update of the current remains controversial. Nuclear PTTG is thought to knowledge regarding the role of PTTG in physiologic function as a securin, inhibitor of premature sister and pathologic processes as well as its significance as a chromatid separation as well as a potential transcrip- prognostic indicator in human neoplasia. In vivo tional activator, whereas the role of cytoplasmic PTTG models of PTTG-targeted therapies are also discussed. remains unclear (Zhang et al. 1999b, Zhou et al. 2005, Kim et al. 2006a, Tfelt-Hansen et al. 2006). While differential PTTG localization may be due to the PTTG: structure and function variations in cell lines and tumor types examined, cell PTTG1, PTTG2, and PTTG3 cycle-dependent expression of PTTG may also account for the reported differences (Fujimoto et al. 1999, Zou In humans, PTTG1 exhibits 91 and 89% amino acid et al. 1999, Hunter et al. 2003, Akino et al. 2005). sequence homology with PTTG2 and PTTG3 respect- A summary of reported PTTG expression patterns is et al ively (Prezant . 1999). By RT-PCR, low levels of found in Tables 1 and 2. Translocation of PTTG from PTTG2 have been detected in normal pituitary, brain, cytoplasm to nucleus may be mediated by PTTG- placenta, small intestine, colon, liver, spleen, thymus, binding factor (PBF), which contains a nuclear prostate, testis and ovary, as well as pituitary localization signal (Chien & Pei 2000). Another adenomas, the primary fibroblast cell line LL-24, and mechanism proposed to be involved in PTTG transloca- et al et al in five cancer cell lines (Prezant . 1999, Chen . tion involves the mitogen-activated protein kinase 2000). By contrast, PTTG3 mRNA is extremely low or (MAPK) pathway. The expression of a constitutively et al absent in these tissues (Chen . 2000). A variant active form of MAPKK (MEK1) facilitated PTTG form of PTTG with no transactivating function or translocation to the nucleus in Cos-7 cells (Pei 2000). NIH3T3 cell-transforming ability has also been One recent study demonstrated that pituitary PTTG is a b detected (Wang & Melmed 2000 ); C-terminus secretory protein in pituitary tumor cells (Minematsu deletion reinstates both functions, suggesting that et al. 2007). Recently, Wierinckx et al. (2007) found variant PTTG forms may compete with other forms only nuclear PTTG expression to be predictive of and that their balance may determine function (Wang aggressive pituitary tumor behavior. Thus, PTTG b & Melmed 2000 ). The physiologic role and the subcellular localization appears to be a significant significance of PTTG2 and PTTG3 remain unclear. factor in determination of its tumorigenic role.

PTTG tissue expression Src homology (SH-3)-binding domain (SH-3BD) Early studies established that in normal tissue, PTTG The human PTTG C-terminus contains two proline- levels are seen in testis predominantly, with lower or rich motifs that form an SH-3BD, and enables PTTG to absent expression levels in other tissues (Pei & Melmed interact with SH-3-containing proteins (Dominguez 1997, Pei 1998). PTTG mRNA is expressed at high levels et al. 1998, Boelaert et al. 2004). Several studies have in all three major testicular cell lines (Leydig, Sertoli, and demonstrated the significance of SH-3BD in PTTG germ cells of GC2 type; Pei 1998). In the study of human functions, including its transforming ability, prolifera- tissues, strong PTTG mRNA expression has been found tive effects, transactivation activity, induced sodium in fetal liver and adult testis and thymus, expression being iodide symporter (NIS) expression, and as an inducer weak in colon, small intestine, brain, placenta, and of hormone secretion in pituitary cells (Pei 1998, 2000, pancreas (Pei & Melmed 1997, Pei 1998). The high level Heaney et al. 2001, Wang et al. 2001, Saez et al. 2002, of PTTG mRNA expression is seen in a variety of Boelaert et al. 2007). The SH-3BD of PTTG may also malignant tumor cell lines, including promyelocytic be of importance for its angiogenic effects (Zhang et al. leukemia HL-60, HeLa cell S3, chronic myelogenous 1999b, Ishikawa et al. 2001, McCabe et al. 2002, Saez leukemia K-562, lymphoblastic leukemia MOLT-4, et al. 2002, Boelaert et al. 2004, Kim et al. 2006a,b,c), Burkitt’s lymphoma Raji, colorectal adenocarcinoma thus providing a potential target in the treatment of SW480, lung carcinoma A549, and melanoma G361 tumors overexpressing PTTG. The isolation of SH-3- (Zhang et al.1999b). PTTG tissue-specific distribution, containing proteins that interact with PTTG would particularly its expression in testes, warrants further illuminate on the mechanisms of PTTG SH-3BD investigation to reveal PTTG tissue-specific functions. function.

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Table 1 Pituitary tumor-transforming gene (PTTG) nuclear and cytoplasmic localization in cell lines

Study Cell line Cytoplasmic Nuclear

A. Predominantly cytoplasmic PTTG localization Kim et al. (2007c) HCT166 CCC C Akino et al. (2005) Hepatocytes CCC K Mu et al. (2003) HeLa CCC C Cos-7 CCC C DU145 CCC C Yu et al. (2000b) JEG-3 CCC CC 3T3 CCC CC GH3 CCC CC AtT20 CCC CC SKOV3 CCC CC MCF-7 CCC CC COS-7 CCC CC B. Predominantly nuclear PTTG localization Dominguez et al. (1998) Jukrat cells CCCC C. Variable nuclear and cytoplasmic PTTG localization Chamaon et al. (2005) U87MG Variable* Variable* U138MG Variable* Variable* LN405 Variable* Variable* Mu et al. (2003) A459 Diffuse Diffuse DLD-1 Diffuse Diffuse NIH3T3 Diffuse Diffuse

CCC, predominant expression; CC, considerable expression; C, little expression; K, no expression; * variable, variable nuclear and cytoplasmic patterns.

Phosphorylation of PTTG interact with PTTG, thus suggesting that PTTG The phosphorylation of PTTG may facilitate its phosphorylation occurs via these two cascades (Wang translocation to the nucleus (Pei 2000) and has been & Melmed 2000a, Chamaon et al. 2005). PTTG observed in a cell cycle-dependent manner (Ramos- phosphorylation by DNA-dependent protein kinase Morales et al. 2000, Romero et al. 2001). Phosphoi- (DNA-PK) subunit (Ku70) has been demonstrated, but nositol-3-kinase (PI3K) and MAPK both physically its significance is unclear (Romero et al. 2001).

Table 2 Pituitary tumor-transforming gene (PTTG) localization in normal or neoplastic tissue

Study Tissue Cytoplasmic Nuclear

A. Predominantly cytoplasmic PTTG localization Minematsu et al. (2006) Pituitary adenomas CCC C Boelaert et al. (2003a,b) Fetal brain CK Adult brain CCC K Boelaert et al. (2003b) Pituitary adenomas CCC K Saez et al. (1999) Pituitary adenomas CCC C B. Predominantly nuclear PTTG localization Filippella et al. (2006) Pituitary adenomas KCCC Genkai et al. (2006) Gliomas KCCC Uccella et al. (2005) Pituitary adenomas CCCC Saez et al. (1999) Breast adenocarcinomas CC CCC Lung adenocarcinomas CC CCC Saez et al. (2002) Hodgkin’s lymphoma** KCC C. Variable PTTG localization Wierinckx et al. (2007) PRL pituitary tumors*** Variable*** Variable*** Winnepenninckx et al. (2006) Melanomas Variable* Variable*

CCC, predominant expression; CC, considerable expression; C, little expression; K, no expression; variable*, variable nuclear and cytoplasmic patterns; **, Reed–Sternberg cells; variable***, only cytoplasmic in non-invasive and invasive tumors, but both cytoplasmic and nuclear in aggressive–invasive ones.

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One study has shown that the expression of constitu- association and dissociation of PTTG by directly tively phosphorylated PTTG results in increased interacting with its C-terminus (Pei 1999). Interaction colony-forming ability and cell proliferation (Boelaert of PTTG with Ku70 has been demonstrated in vitro and et al. 2004). It will be important to distinguish between in vivo, PTTG forming a complex with Ku70 in intact the phosphorylated and non-phosphorylated PTTG HL-60 cells without affecting Ku70–Ku80 heterodimer expressions in future studies, to shed light on the role formation (Romero et al. 2001). Interestingly, DNA of phosphorylation in modulating PTTG function. double-stranded (dsDNA) breaks inhibited PTTG/ Ku70 interaction, thus suggesting that increased PTTG interacting factors DNA damage frees sequestered Ku70, which can then enhance DNA association with DNA-PK (Romero Sp1 et al. 2001). The proposed hypothesis is that PTTG Interaction of PTTG with Sp1, an important transcrip- functions as a regulator of DNA-PK. Finally, the c-myc tion factor involved in the regulation of several genes oncogene directly interacts with PTTG and is associated with cellular growth and differentiation upregulated by it (Pei 2001, Hamid & Kakar 2004). (Clem et al. 2003) is well documented (Pei 1998, Thus, PTTG, via interaction with a plethora of factors, Kakar 1999, Wang & Melmed 2000a, Clem et al. is implicated in a host of cellular and neoplastic 2003). It was recently proposed that the PTTG Sp1- functions including oncogenesis and DNA damage binding region may play a role in the development of repair. Further examination of the nature of such cardiac hypertrophy in transforming growth factor-b- interactions would aid our understanding of the precise inducible early gene knockout male mice (Rajamannan role of PTTG in cellular physiologic as well as et al. 2007). The Sp1-binding site has been shown to be neoplastic processes. important in the regulation of PTTG transcriptional activity (Pei 1998, Kakar 1999, Wang & Melmed 2000a, Clem et al. 2003). Additionally, PTTG and Sp1 PTTG regulatory factors were found to cooperatively mediate G1/S-phase transition (Tong et al. 2007). Recently, Chesnokova Estrogen et al. (2007) showed that PTTG binds to the p21 Estrogen regulation of PTTG expression has been promoter region via Sp1, thereby suppressing p21 shown to occur (Heaney et al. 1999, 2002, Yin et al. activity. Given the important function of transcription 2001). In a study by Yin et al. (2001) in two out of the factors in neoplastic mechanism, including apoptosis, four rat strains examined, estrogen increased pituitary angiogenesis, and metastasis (Xie et al. 2006), PTTG mRNA levels in parallel with estrogen induced characterization of their interaction with PTTG pituitary tumor development. In a dose- and time- requires further investigation. Recent studies of Sp1 dependent manner, lactotrope tumors induced by inhibition have shown promising anti-angiogenic and estrogen in Fischer rats, showed PTTG expression anti-fibrotic effects in prostate cancer as well as in within 24 h after estrogen treatment, reaching maximal kidney and lung fibrosis respectively (Chae et al. 2006, levels after 48 h (Heaney et al. 1999). In mice, estrogen Yuan et al. 2008). Thus, the effects of Sp1 inhibition in induced PTTG transcription in growth hormone neoplasms overexpressing PTTG should be investi- (GH)/prolactin (PRL)-secreting GH3 cells and pitu- gated and may provide a potential therapeutic target in itary PTTG mRNA levels both increased concomi- these neoplasms. tantly with the proestrus serum estradiol surge (Heaney et al. 2002). Estrogen regulation of PTTG expression Other interacting factors may actually be cell specific. For example, in U87 Physical interaction and binding of PTTG with several glioma cells, 17b-estradiol (E2) does not affect PTTG factors have been demonstrated. These include: S10, a mRNA levels (Tfelt-Hansen et al. 2004). Furthermore, ribosomal protein; HSJ2 (heat shock protein J2), a PTTG is induced in oophorectomized rats treated with human homolog of DnaJ; Ku70, the regulatory subunit estrogen in a strain-dependent manner similar to the of DNA-PK; and c-myc, an important mediator of cell ability of estradiol to induce pituitary tumors in these proliferation (Pei 1999, 2001, Romero et al. 2001, rats, thus suggesting that PTTG expression may Hamid & Kakar 2004). S10 is constitutively expressed mediate E2-induced pituitary tumorigenesis (Pei and associates with ribosomes, whereas HSJ2 is a 1998). Since most pituitary tumors express high levels novel homolog of human DnaJ, which mediates of estrogen receptors as well as PTTG, anti-estrogen dissociation of several protein complexes (Pei 1999). management of pituitary tumors may prove useful It is possible that S10 and DnaJ regulate ribosomal in suppressing PTTG expression and subsequently

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 724 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 suppress aggressive tumor behavior (Heaney et al. been shown to mediate G1- to S-phase transition as 2002, Wierinckx et al. 2007). well. The latter involves interaction with Sp1 (Tong et al. 2007). Whether the reported inconsistencies in Insulin the expression of PTTG in pituitary adenomas are due An effect of insulin and insulin-like growth factor to its cell cycle-dependent regulation should be taken (IGF-I) on PTTG expression has been demonstrated in into consideration in future studies. several cell lines (Chamaon et al.2005, Thompson & Kakar 2005). For example, two insulin-responsive sequences have been found in the PTTG promoter P53-dependent and P53-independent apoptosis region, thus implicating insulin and IGF-I regulation in PTTG overexpression induced p53 upregulation and PTTG expression (Kakar 1999). Treatment of human translocation to the nucleus, as well as apoptosis in glioma cell lines (LN405 and U87MG) with IGF-I or MCF-7 breast cancer cells that express wild-type p53 insulin resulted in PTTG protein expression via PI3K (Yu et al. 2000a). PTTG also induced P53-independent and MAPK (Chamaon et al. 2005). In addition, in apoptosis in MG-63 osteosarcoma cells deficient in MCF-7 breast cancer cells, insulin and IGF-I treatment p53, wherein p53 expression did not affect PTTG- each stimulated PTTG mRNA and/or protein synthesis induced apoptosis rate (Yu et al. 2000a). In insulin- in a dose- and time-dependent way, peak PTTG mRNA secreting insulinoma MIN6 cells, PTTG transfection levels being seen 48 h after insulin administration induced apoptosis, which increased overtime (Yu et al. (Thompson & Kakar 2005). 2006). Similarly, PTTG transfection of HEK293, a human embryonic kidney cell line expressing wild- Other regulatory factors type p53, induced elevated p53 protein expression and Several other factors are implicated in the regulation of C apoptosis, whereas transfection of PC-3 cells expres- PTTG expression. These include: Ca2 , hepatocyte sing a mutant p53 form did not (Hamid & Kakar 2004). growth factor, cyclosporine A, and hydrocortisone The analysis of p53 promoter showed increased (Stoika & Melmed 2002, Tfelt-Hansen et al. 2003, activity in MCF-7, PC-3, and HEK293 cells, implicat- 2004, Akino et al. 2005). ing transcriptional activation of p53 by PTTG (Hamid &Kakar2004). Additionally, PTTG transfection Cell cycle regulation and PTTG induced enhanced transcription and expression of By acting as a securin protein and inhibiting premature the Bax gene, a pro-apoptotic factor, in a dose- sister chromatid separation, PTTG plays an important dependent manner in MCF-7 and HEK293 cells. By role in mitosis. Cohesin binds sister chromatids during contrast, there was no change in Bax expression in metaphase and is degraded by separin to allow sister PC-3 cells that lacked a functional p53, suggesting that chromatid separation at anaphase. It has been shown PTTG modulation of the pro-apoptotic factor occurs that PTTG blocks sister chromatid separation during through p53. metaphase by binding to separin and preventing By contrast, inhibition of apoptosis by PTTG has cohesin degradation (Zou et al. 1999). The fact that also been shown. PTTG knockdown using short PTTGK/K mice are viable indicates that PTTG is not interfering RNA (siRNA) enhanced apoptosis in UV- required for sister chromatid separation, thus irradiated HeLa cells, whereas PTTG overexpression suggesting that there are other redundant mechanisms suppressed UV-induced apoptosis in these cells (Lai involved in this process (Yin et al. 2001). Nonetheless, et al. 2007). Similarly, transfection of SH-J1 hepatoma the PTTGK/K mouse embryo fibroblasts showed cells with siRNA against PTTG activated p53 and aneuploidy and aberrant chromosome morphology, induced apoptosis (Cho-Rok et al. 2006). In HCT116 including many binucleate and multinucleate cells colorectal cancer cells, PTTG depletion resulted in (Wang et al. 2001). The cells also demonstrated p53-dependent cytotoxicity (Cho-Rok et al. 2006). slower growth rate, shortened G1 and prolonged Bernal et al.(2002)similarly found that PTTG G2/M-phases, as well as premature centromere transfection of H1299 cells inhibited p53-dependent division (Mei et al. 2001, Wang et al. 2001). Although apoptosis in a dose-dependent way. P53 apoptotic PTTG expression appears to be cell cycle dependent effects were further enhanced in PTTGK/K cells and has been shown to be abrogated immediately after (Bernal et al. 2002). These results suggest that PTTG mitosis (Zou et al. 1999, Yu et al. 2000b), being may exert its oncogenic effects at least in part by degraded by an anaphase promoting complex that affecting p53-dependent pathways (Bernal et al. 2002) targets PTTG (Zou et al. 1999), PTTG has recently (Table 3).

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Table 3 Pituitary tumor-transforming gene (PTTG) and P53 interaction

Study Cell line System PTTG P53 Apoptosis

A. Studies showing PTTG has no effect on p53 Mu et al. (2003) A5491 PTTG OX [ NC – Mu et al. (2003) HeLa2 PTTG OX [ NC – B. Studies PTTG upregulates p53 Yu et al. (2006) MIN65 PTTG OX [ – [ Hamid & Kakar (2004) HEK293 (p53C/C)6 PTTG OX [[[ Hamid & Kakar (2004) MCF-7 (p53C/C)4 PTTG OX [[[ Hamid & Kakar (2004) PC-3 (p53K/K)7 PTTG OX [ NC NC Yu et al. (2000a) MG-63 (p53K/K)3 PTTG OX [ P53K/K NC Yu et al. (2000a) MCF-7 (p53C/C)4 PTTG OX [[[ C. Studies showing PTTG inhibits p53 or apoptosis Bernal & Hernandez (2007) HCT166 (PTTGK/K)9 PTTGK/K Y[– Bernal & Hernandez (2007) HeLa2 UV-induced apoptosisCsiRNA Y – [ PTTG Bernal & Hernandez (2007) HeLa2 UV-induced apoptosisCPTTG OX [ – Y Cho-Rok et al. (2006) SH-J110 PTTG siRNA Y[[ Kho et al. (2004) HCT1669 PTTG siRNA Y – [ Bernal et al. (2002) H12998 PTTG OX [YY Bernal et al. (2002) HCT166 (PTTGK/K)9 [p53-dependent apoptosis** Y[[ D. Studies showing PTTG suppression by p53 Chiu et al. (2006) RKO (p53C/C)9 Oxaliplatin* Y[– Chiu et al. (2006) SW480 (p53K/K)9 Oxaliplatin* NC – – Kho et al. (2004) HCT1669 Microarray analysis after [p53** Y by p53 [ – Zhou et al. (2003) U2OS (p53C/C)3 Doxorubicin and bleomycin*** Y[– Zhou et al. (2003) HCT116 (p53C/C)9 Doxorubicin and bleomycin*** Y[– Zhou et al. (2003) Saos2 (p53K/K)3 Doxorubicin and bleomycin*** NC p53K/K – Zhou et al. (2003) DLD-1 (p53K/K)9 Doxorubicin and bleomycin*** NC p53K/K –

1, lung cancer; 2, cervical cancer; 3, osteosarcoma; 4, breast cancer; 5, insulinoma; 6, embryonic kidney; 7, prostate cancer; 8, non- small cell lung carcinoma; 9, colorectal cancer; 10, hepatoma; [, overexpression; Y, depletion/decrease; NC, no change; –, not reported; OX, overexpression; *clinical anti-cancer drug, **genotoxic stress due to 5-flurouracil, ***DNA damaging drugs that induce strand breaks and activate, p53.

PTTG and cell proliferation et al. 2006) and in leiomyomas (Tsai et al. 2005). Further support for the pro-proliferative role of PTTG The effect of PTTG on cell proliferation is unclear, as was seen in PTTGK/K mice, which exhibited a studies have reported contradictory findings. Whereas, reduction in b-cell islet mass and a decrease in cell in its functional capacity as a securin, PTTG over- proliferation (Wang et al. 2003). Similarly, in mouse expression is expected to reduce cell proliferation by models of pituitary tumorigenesis (Chesnokova et al. arrest of mitosis and inhibition of sister chromatid 2005) and follicular thyroid cancer (Kim et al. 2007a), separation, as a cell-transforming oncogene one would PTTG ablation lead to decreased pituitary and thyroid expect a pro-proliferative action. Several PTTG cell proliferation respectively. PTTG expression was transfection/deletion as well as correlation studies associated with proliferation of pituitary cells, hepato- support the latter notion (Heaney et al. 2002, Wang cytes, the U87 glioma cell line, and cultured et al. 2003, Yao et al. 2003, Akino et al. 2005, leiomyoma cells (Heaney et al. 2002, Yao et al. Chesnokova et al. 2005, Tsai et al. 2005, Cho-Rok 2003, Akino et al. 2005, Tsai et al. 2005, Vlotides et al. et al. 2006, Filippella et al. 2006, Genkai et al. 2006, 2006). Several PTTG deletion studies using knockout Vlotides et al. 2006, Kim et al. 2007a, Rubinek et al. or siRNA techniques have also confirmed the 2007). stimulatory role of PTTG in proliferation of bone In clinical studies, a correlation has been demon- marrow stem cells, as well as of glioma, sarcoma, strated between PTTG expression and cell proliferation hepatoma, and corticotrope cells (Chesnokova et al. (Tsai et al. 2005, Filippella et al. 2006). For example, 2005, Cho-Rok et al. 2006, Genkai et al.2006, its expression correlated with proliferation marker Rubinek et al. 2007). immunopositivity, proliferating cell nuclear antigen By contrast, the anti-proliferative function of PTTG (PCNA) or Ki-67, in pituitary adenomas (Filippella has also been demonstrated in animal as well as in cell

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 726 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 transfection studies (Pei & Melmed 1997, Mu et al. Minematsu et al. 2006). Also, VEGF and PTTG 2003, Yu et al. 2006). In contrast to one report of showed co-localization (Minematsu et al. 2006). PTTG PTTG-induced cell proliferation in FTC133 follicular upregulation of inhibitor of DNA-binding-3 (ID3), an carcinoma cells (Kim et al. 2006b), other studies important mediator of VEGF induced angiogenesis and showed no correlation between PTTG expression and downregulation of thrombospondin-1 (TSP-1), an thyroid cancer cell proliferation (Saez et al. 2002, angiogenic inhibitor, has been demonstrated in Boelaert et al. 2003a). Although PTTG expression was FTC133 human follicular cancer cells (Kim et al. correlated with cell proliferation in the normal 2006b). Thus, PTTG appears to play an essential role in pituitary, no correlation was found in a series of 101 tumor angiogenesis and may provide a therapeutic pituitary adenomas (Minematsu et al. 2006). PTTG target in neoplasms with high vascular density. suppression of cell proliferation may occur through induction of apoptosis and delay of mitosis (Akino DNA repair and damage et al. 2005). PTTG binds to Ku70, the regulatory subunit of DNA- Hence, it is currently unclear whether PTTG PK, which is involved in repair of double-stranded promotes or suppresses cellular proliferation. Dose DNA breaks. The PTTG binding of Ku70 is inhibited dependency and/or phosphorylation status of by dsDNA breaks, with resultant freeing and activation PTTG may be additional factors affecting the of Ku70 and DNA repair mechanisms (Romero et al. stimulatory/inhibitory role of PTTG upon cell prolifer- 2001). Etoposide-induced dsDNA damage was elev- ation (Boelaert et al. 2003b, 2004). As neoplasia is ated in PTTG-transfected HCT116 cells and human intimately associated with cell proliferation, further fibroblasts and associated with lower Ku70 function, studies to illuminate on the role of PTTG in thus suggesting that PTTG suppresses Ku70 activity proliferation will be important. (Kim et al. 2007a). Similarly, PTTG-deficient bone marrow stem cells (Rubinek et al. 2007), as well as PTTG, FGF, and vascular endothelial growth pituitary gland cells (Chesnokova et al. 2007) showed factor (VEGF) upregulation of genes involved in DNA damage and repair pathways, supporting a role for PTTG in At least in part by induction of bFGF and VEGF suppression of these pathways. PTTG inhibition and/ angiogenic factors PTTG is involved in angiogenesis or proteosomal degradation as a result of DNA damage (McCabe et al. 2002, Kim et al. 2006a,b,c, 2007a, has also been demonstrated (Romero et al. 2001, Zhou Minematsu et al. 2006). Transactivation of FGF-2 by et al. 2003, Kim et al. 2007a). Additionally, a recent PTTG has been well documented (Zhang et al. 1999b, study by Bernal et al. (2008), demonstrated that loss of Kim et al. 2006a, Tfelt-Hansen et al. 2006). In a mouse PTTG in cell culture lead to hindered cell proliferation model of follicular thyroid cancer, PTTG deficiency after genotoxic stress (Bernal et al. 2008), providing a resulted in reduced FGF-2, FGF receptor (FGF-R1), potential rationale for PTTG overexpression in many and VEGF levels (Kim et al.2007a). Thus, an malignancies. These findings support a pivotal role for autocrine mechanism involving PTTG and bFGF may PTTG inhibition of DNA damage repair pathways exist (Heaney et al. 1999, Tsai et al. 2005). Both PTTG necessitating more research on this aspect of PTTG andbFGFexpressionswereincreasedinacute action in malignancies. leukemia, a positive correlation being noted between their expression levels (Cong et al. 2005). Concordant PTTG and FGF-2 expression patterns were detected in Genetic instability developing fetal brain cortex (Zou et al. 1999). PTTG- The association between PTTG overexpression and dependent bFGF and/or VEGF expression was increased aneuploidy as well as genetic instability in observed in several cell lines (Ishikawa et al. 2001, tumors and cell lines is well established (Mu et al. McCabe et al. 2002, Hunter et al. 2003, Tfelt-Hansen 2003, Yu et al. 2003, Kim et al. 2005, 2007a). In et al. 2003, Chen et al. 2004b). It was found that PTTG colorectal cancers patients, such instability correlates promoted human umbilical vein endothelial cell with higher tumor grade, indicating that PTTG and proliferation and tube formation, as well as in vitro genetic instability may be linked in these tumors (Kim vessel growth (Ishikawa et al. 2001). In pituitary et al. 2007a). PTTG expression also correlates with adenomas, a significant positive correlation was found aneuploidy in melanomas (Winnepenninckx et al. between VEGF and PTTG mRNA expressions, as well 2006) and in follicular as well as papillary thyroid as between PTTG and KDR (kinase insert domain carcinomas (Kim et al. 2005). In vitro transfection of receptor; VEGF receptor) mRNA (McCabe et al. 2002, colorectal (Kim et al. 2007a) and follicular thyroid

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 727 F Salehi et al.: PTTG review carcinoma cells (Kim et al. 2005) as well as of HeLa knockout and transgenic mouse models has confirmed and A549 cells (Mu et al. 2003) has been shown to the tumor-inducing capacity of PTTG in the pituitary. induce both genetic instability and aneuploidy. Indeed, Interestingly, PTTG deficiency in RbC/K mice cell transfection with a non-degradable PTTG mutant susceptible to pituitary tumor formation protects was shown to result in incomplete cytokinesis and lack against pituitary tumorigenesis (Chesnokova et al. of chromosomal segregation in 51 out of 55 cultured 2005), reducing tumor formation at 17 months from cells (Yu et al. 2003). Interestingly, aneuploidy was 86% in RbC/KPTTGC/C mice to 30% in RbC/K also evident in the pituitary gland cells of PTTG- PTTGK/K mice (Chesnokova et al. 2005). By deficient mice (Chesnokova et al.2007). Thus, contrast, pituitary-specific PTTG overexpression in aberrant PTTG expression is associated with aneu- RbC/K mice is associated with pituitary hyperplasia ploidy, which may significantly contribute to its and an increased incidence of adenoma development tumorigenic potential (Yu et al. 2003). (Donangelo et al. 2006). Similarly, pituitary-specific PTTGoverexpressioninawild-type background Invasion caused plurihormonal hyperplasia and induced micro- adenoma formation (Abbud et al. 2005). The TRbPV/PV Several studies have shown a correlation between mouse model of follicular thyroid carcinoma-produ- tumor PTTG expression and invasiveness. This is true cing distant metastasis has also been crossbred with of endocrinologically functioning pituitary adenomas PTTGK/K mice to create TRbPV/PV PTTGK/K as well as colorectal and breast carcinomas (Zhang mice. TRbPV/PV expresses a dominant negative et al. 1999a, Heaney et al. 2000, Solbach et al. 2004). mutation in the TRb, which results in thyroid hormone In the TRbPV/PV (thyroid receptor beta) model of resistance (Kim et al. 2007a,b). TRbPV/PV PTTGK/K follicular thyroid carcinoma, PTTG deficiency attenu- mice had smaller thyroid glands compared with the ates tumor vascular invasion and the occurrence of PTTGC/C mice and exhibited decreased thyrocyte lung metastasis (Kim et al. 2007a). Recently, PTTG proliferation as well as FTC aggressiveness reflected in regulation of matrix metalloproteinase 2 (MMP-2) has slower tumor progression and increased survival (Kim been shown, which may account for decreased tumor et al. 2007a). In PTTGK/K male mice, PTTG invasiveness in the PTTG-deficient TRbPV/PV mice deficiency affects pancreatic b-cell proliferation and (Malik & Kakar 2006). In vivo, PTTG overexpressing induces diabetes (Wang et al. 2003, Fraenkel et al. HEK293 cells injected into nude mice were seen to 2006), often associated with weight loss, increased induce increased MMP-2 expression and tumor food uptake, and polyuria as well as decreased islet formation. PTTG also facilitated endothelial tubule mass and b-cell proliferation (Wang et al. 2003). formation and growth in 3D Matrigel matrix, effects Thus, animal models have provided solid evidence of mediated through MMP-2 expression (Malik & Kakar tumor-inducing capacity of PTTG, particularly in 2006). Finally, PTTG depletion by siRNA reduces endocrine organs. tumor invasiveness in several glioma cell lines (Genkai et al. 2006). Thus, PTTG may stimulate mediators of tumor invasiveness, contributing to enhanced invasive PTTG in stem cells potential of tumors. Accordingly, PTTG targeting to That PTTGK/K mice develop organ-specific hypo- reduce or abrogate tumor invasiveness warrants further plasia suggests a role for PTTG in progenitor cell investigation. function (Wang et al. 2001). Indeed, the PTTG is transcribed in the one-cell stage of mouse development Transgenic models (Yao et al. 2003), the transcript showing a 39% Several models of PTTG deficiency have been increase in the zygote as compared with the oocyte. developed to study the role of PTTG in tumorigenesis Furthermore, gene profiling of immature and mature and in other pathophysiologic processes, including oocytes showed differential expression of PTTG3 diabetes (Wang et al. 2001, 2003, Abbud et al. 2005, during oocyte meiosis (Yao et al. 2003). Thus, PTTG Chesnokova et al. 2005, Donangelo et al. 2006, may play a role in zygote-stage gene activation (Yao Fraenkel et al. 2006, Kim et al. 2007a). Although et al. 2003). In a recent study, PTTG was shown to be PTTG knockout (PTTGK/K) mice initially appeared essential for maintenance and proliferation of bone viable and fertile (Wang et al. 2001), female sub- marrow stem cells (Rubinek et al.2007). Gene fertility, testicular and splenic hypoplasia, thymic profiling of proliferating and differentiated neural hyperplasia, and thrombocytopenia have been noted stem cells has shown PTTG to be one of the genes in these mice (Wang et al. 2001). The use of PTTG upregulated in proliferating neural progenitor cultures

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 728 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 as compared with differentiated neural cells (Karsten immunopositivity and tumor size or radiologic grade, et al. 2003). Similarly, PTTG is seen to be upregulated patient age, and gender or treatment (Filippella et al. following treatment of human mesenchymal stem cells 2006). In 27 of the 45 patients for which 1-year follow- with bone morphogenic protein, the upregulation being up was available, a cut-off of 2.9% for both PTTG associated with stem cell proliferation (Akino et al. and Ki-67 positivity predicted recurrence versus 2003). These findings cumulatively suggest that PTTG non-recurrence, Ki-67 being the superior predictor expression in stem and progenitor cells is associated (Filippella et al. 2006). These findings indicate the need with proliferative potential. for thorough investigation of the predictive value of PTTG as a marker of aggressive pituitary tumor behavior. PTTG in tumors Other studies have investigated a potential corre- lation between PTTG expression and pituitary tumor Endocrine tumors subtype. PTTG mRNA levels in 40 pituitary tumors Pituitary (12 GH, 5 PRL, 5 ACTH, and 18 non-functioning) PTTG expression in pituitary tumors has been showed elevated expression in GH-secreting adenomas demonstrated in several studies. In a study of 12 (2.7-fold) compared with non-functioning adenomas pituitary adenomas (six non-functioning, four GH, one (Hunter et al. 2003), suggesting cell type-dependent PRL, and one adrenocorticotropin hormone (ACTH)), expression of PTTG. In another study, although it was northern blot analysis showed elevated expression of higher in GH adenomas as compared with PRL and PTTG mRNA as compared with its low or undetectable ACTH adenomas, this difference was not statistically expression in non-tumoral pituitary (Saez et al. 1999). significant (Wang et al. 2003). Additionally, Zhang In addition, immunostaining of 36 pituitary adenomas et al. (1999a) found a significant difference in PTTG showed cytoplasmic PTTG immunoreactivity in all but association with tumor stage between non-functioning four pituitary adenomas (one PRL, one ACTH, and two and hormone-secreting pituitary neoplasms. This non-functioning); nuclear staining was observed in distinction suggests differences in the molecular only a few cells (Saez et al. 1999). mechanisms underlying PTTG-mediated tumor Several studies have investigated the potential initiation and/or progression (Zhang et al. 1999a). It predictive value of PTTG. A recent study of 25 PRL- is of note however, that Minematsu et al. (2006), secreting pituitary tumors showed that although PTTG examining 101 pituitary adenomas (29 GH, 12 PRL, expression did not per se predict aggressive behavior, 6 ACTH, 1 FSH, 3 thyroid-stimulating hormone nuclear PTTG staining was one of the histological (TSH), and 50 non-functioning) revealed elevated features (numerous mitoses, high Ki-67 index, and PTTG mRNA levels in most pituitary adenoma nuclear labeling of PTTG and P53) distinguishing subtypes; differences between them were not statisti- aggressive–invasive PRL tumors from those behaving cally significant. One study investigated anterior less aggressively (Wierinckx et al. 2007). Interestingly, pituitary hormone levels in relation to PTTG levels a comparative RT-PCR study of 54 pituitary adenomas in primary tumor cultures in vitro (Hunter et al. 2003). (13 GH, 10 PRL, 1 ACTH, and 30 non-functioning) The results showed that only GH levels were showed no correlation between tumor stage and PTTG significantly correlated with PTTG expression (Hunter mRNA levels in non-functioning adenomas, whereas in et al.2003). Presently, PTTG association with pituitary hormone-secreting tumors significantly higher PTTG tumor subtype remains unclear. expression was seen in invasive tumors (Zhang et al. As animal and in vitro studies have shown 1999a). With respect to tumor recurrence, examination correlations between expression and function of of 45 pituitary tumors (14 PRL, 8 GH, 6 ACTH, 11 PTTG and that of other factors including bFGF and luteinizing hormone (LH)/follicle-stimulating hormone VEGF, several studies have investigated such potential (FSH), and 6 non-functioning) demonstrated nuclear correlations in pituitary tumors. Using semi-quantita- PTTG immunoreactivity (using a monoclonal anti- tive RT-PCR analysis, PTTG and bFGF expressions body) in 89% of the tumors (Filippella et al.2006); its were examined in 41 human pituitary adenomas (8 GH, expression showed a strong correlation with Ki-67 7 PRL, 1 ACTH, 1 TSH, 15 non-functioning, and 8 immunopositivity, and was higher in recurrent tumors. plurihormonal); significant correlation was found The cut-off value separating recurring and non- between PTTG and bFGF expressions (RZ0.84; recurring tumors was 3.3% for PTTG immuno- Heaney et al. 1999). By contrast, although elevated positivity (60% sensitivity and 76% specificity). PTTG, FGF, and FGF-R1 levels were elevated in a There was no significant correlation between PTTG cohort of 111 pituitary adenomas, no correlation was

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 729 F Salehi et al.: PTTG review reported between PTTG and FGF or FGF-R1 secretion. Interestingly, they found VEGF secretion expression (McCabe et al. 2003). Nonetheless, FGF-R1 to be correlated with secretion of S100 protein, a expression was significantly higher in invasive adeno- marker of folliculostellate cells, suggesting that these mas (McCabe et al. 2003). In addition, PBF mRNA cells are the source of VEGF (Hunter et al.2003). That was elevated in all pituitary tumor subtypes. these results are inconsistent with the findings of other A significant correlation was observed between PBF studies showing a correlation between PTTG, VEGF, and PTTG expressions, but no significant correlation and KDR expressions may be due to the in vitro setting. was seen between PBF or PTTG mRNA expression The relationship between PTTG and VEGF and patient age, sex and estrogen status, and recurrence expressions in pituitary adenomas should be addressed or invasion (McCabe et al. 2003). Examination of 103 in future investigations. (out of 111) pituitary adenomas with suitable RNA (15 Mouse models of pituitary tumors have contributed GH, 4 PRL, 4 ACTH, 3 TSH, and 85 non-functioning) to our understanding of PTTG action (Fig. 1; Heaney showed a significant positive correlation between et al. 1999, Abbud et al. 2005, Chesnokova et al. 2005, PTTG and VEGF mRNA levels, as well as PTTG Donangelo et al. 2006). In the RbC/K mouse model, and KDR expression levels (McCabe et al. 2002). PTTG deficiency was protective for pituitary tumor Similarly, in another study, many tumor cells demon- development, delaying and reducing their incidence, strated PTTG co-localization with VEGF (Minematsu through inhibition of cellular proliferation (Chesno- et al. 2006). The analysis of CD34 immunopositivity kova et al. 2005). In a recent study, Chesnokova et al. and blood vessel distribution in tumors showed a high (2007) demonstrated that PTTG deficiency in mice is correlation between PTTG expression and microvas- associated with pituitary cell senescence, thereby cular density in GH-secreting pituitary adenomas restraining development of pituitary tumors. In (Minematsu et al. 2006). The authors suggested that keeping with the pro-tumorigenic role of PTTG in PTTG may be involved in angiogenic activity in the pituitary, pretumorous pituitary of RbC/K adenomas, and in cell proliferation in the normal PTTGC/C mice had elevated PTTG levels when pituitary (Minematsu et al. 2006). Although these compared with 2- to 4-month-old wild-type (WT) mice findings support the hypothesis that PTTG promotes (Chesnokova et al. 2005). angiogenesis through VEGF, Hunter et al. (2003) did PTTG-targeted overexpression in gonadotropes and not find any correlation between PTTG levels in thyrotropes, using the a-GSU (glycoprotein subunit) primary tumor cell cultures and in vitro VEGF promoter, was associated with focal hyperplasia and

Figure 1 Pituitary PTTG1 content correlates with gland plasticity and tumor formation potential. On the left side of the inverted triangle are listed mouse models with descending pituitary PTTG1 content, with or without the combination with tumorigenic RbC/K.Horizontal bars represent observed effects of the different genotypes on pituitary trophic status, which correlates with pituitary tumorigenic potential (arrow) (Reproduced with permission from Donangelo & Melmed 2005. Copyright 2007, The Endocrine Society).

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 730 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 increased neoplasia (Abbud et al. 2005). The hyper- cases of Hashimoto’s disease), the highest expression plastic and neoplastic LH and TSH cells overexpressed being seen in a subset of follicular adenomas, follicular PTTG. Surprisingly, using double immunostaining, carcinomas, and thyroid hyperplasias (Heaney et al. GH cells also expressed PTTG (Abbud et al. 2005). 2001). RT-PCR analysis of 66 lesions (25 multinodular Similarly, pituitary-targeted PTTG overexpression in goiter, 14 Graves’ disease, 8 follicular, and 19 the RbC/K also using the a-GSU promoter, resulted papillary cancers) showed that PTTG mRNA was in focal pituitary hyperplasia. The incidence of anterior 9.5-fold elevated in all 27 thyroid cancers as compared pituitary tumor development was increased in with normal thyroid tissue; no significant differences a-GSU.PTTGxRbC/– mice when compared with were noted between the two subtypes (Boelaert et al. RbC/K animals, there being no changes in the 2003a). The expression of PTTG protein paralleled the cumulative incidence of pituitary tumors when mRNA findings as evidenced by western blot analysis. intermediate lobe tumors were also considered Intriguingly, PCNA expression was not significantly (Donangelo et al. 2006). These findings clearly support elevated in thyroid neoplasms, suggesting that PTTG the role of PTTG in pituitary tumorigenesis (Fig. 1). expression and proliferation are likely unrelated in Recent characterization of PTTG-deficient mice thyroid cancer (Boelaert et al. 2003a). Although there showed that PTTGK/K mice pituitary glands exhib- was no significant association between PTTG mRNA ited senescence, associated with elevated p53, p21, and expression and the occurrence of metastasis, PTTG Bcl-2 expressions as well as slow cell cycle progression expression was significantly elevated in recurrent (Chesnokova et al. 2007). However, this senescence carcinomas. An independent association between was not associated with telomere shortening, a feature PTTG mRNA and early tumor recurrence was of premature aging (Chesnokova et al. 2007). confirmed by multiple regression analysis, suggesting The expression of PTTG in Fischer 344 rat pituitaries that PTTG may be used as a prognostic marker in et al a and human pituitary adenomas in vivo was shown to be differentiated thyroid cancers (Boelaert . 2003 ). Furthermore, PBF and PTTG expressions correlated estrogen dependent (Heaney et al. 1999). The levels of significantly in a cohort of 24 thyroid carcinomas (17 PTTG protein were suppressed by an average of 64% papillary and 7 follicular; Stratford et al. 2005). The following anti-estrogen treatment of primary pituitary expression of PBF was 3.3-fold increased over that of tumor cell cultures from four out of the eight invasive normal thyroid tissue. No evidence of mutations or pituitary macroadenomas (Heaney et al. 2002). In three sequence alterations was found in the coding region of of the four tumors, reduced PTTG levels were PBF in the 24 thyroid carcinomas studied (Stratford associated with decreased PCNA expression (47%); et al. 2005). PBF immunohistochemical expression reduced bFGF and Bcl-2 expressions were seen in two was evident both within nuclei and cytoplasm of of the four tumors (Heaney et al. 2002). normal thyroid glands and in thyroid carcinomas, great One study showed low hPTTG2 expression in variability being seen between different samples normal pituitary but moderately elevated levels in (Stratford et al. 2005). The causal relationship between some adenomas, suggesting that, in addition to PTTG1, PBF and PTTG expressions was confirmed by the PTTG2 plays a role in pituitary tumor development and transfection of primary follicular thyroid cancer progression (Prezant et al. 1999). PCR analysis of cultures with wild-type and SH-3 mutant PTTG, the DNA from 25 pituitary tumors (2 GH, 5 PRL, 2 ACTH, former resulting in significant PBF induction. By 2 TSH, and 14 non-functioning) failed to show any contrast, SH-3 mutant PTTG transfectants did not insertions/deletions or specific mutations. Thus, aber- induce significant PBF expression (Stratford et al. rant PTTG overexpression in pituitary adenomas may 2005). Stable PBF transfection of NIH3T3 cells have other causes, including epigenetic factors such as resulted in colony formation (Stratford et al. 2005). hypomethylation (Kanakis et al. 2003). In vivo, PBF overexpression stimulated tumor for- mation in nude mice (Stratford et al. 2005). Thyroid PTTG is associated with angiogenic pathways in Elevated PTTG levels in differentiated thyroid carci- thyroid carcinomas. A microarray study identified ID3 nomas have been documented by many studies and TSP-1, a pro- and anti-angiogenic genes respect- (Heaney et al. 2001, Boelaert et al. 2003a,b, Kim ively, as two genes differentially regulated following et al. 2005, 2006b, Stratford et al. 2005). Its mRNA PTTG transfection of primary thyroid cells (Kim et al. expression has been found to be increased in thyroid 2006b). Subsequent characterization of 34 thyroid lesions (9 follicular adenomas, 2 follicular carcinomas, carcinomas (8 follicular and 26 papillary) showed that 8 papillary carcinomas, 15 thyroid hyperplasias, and 3 similar to in vitro microarray results, PTTG and ID3

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 731 F Salehi et al.: PTTG review mRNA levels were significantly correlated in thyroid PTTG-deficient, TRbPV/PV mice developed smaller carcinomas; follicular thyroid cancers showed signifi- thyroids compared with the PTTGC/C mice, the basis cantly higher ID3 mRNA levels being higher in being inhibited thyroid cell proliferation (Kim et al. follicular than papillary carcinomas (Kim et al. 2007a). These same mice had longer survival times, 2006b). Although TSP-1 levels in normal and thyroid and the follicular thyroid carcinomas they developed carcinoma tissues were not significantly different, the were significantly less aggressive, having lower rates results being highly variable, there was a significant of vascular invasion and of lung metastasis; none- inverse correlation between PTTG and TSP-1 mRNA theless, no difference in the overall incidence of levels. Correlation of clinicopathologic parameters and follicular thyroid carcinoma development was noted gene expression showed ID3 expression to be (Kim et al. 2007a). These results indicate a role for significantly higher in patients over 45 years of age; PTTG in thyroid carcinoma progression rather than an independent association between ID3 and both initiation (Kim et al. 2007a). patient age and tumor type was also demonstrated Cell transfection studies have also examined the role (Kim et al. 2006b). TSP-1 expression was indepen- of PTTG in thyroid carcinomas (Kim et al. 2006b, dently associated with early tumor recurrence, TSP-1 Boelaert et al.2007). Transient PBF and PTTG expression in recurrences being lower than normal transfection of primary human thyroid cells resulted thyroids (Kim et al. 2006b). Taken together, these in NIS mRNA inhibition by 95 and 86% respectively results suggest that PTTG mediates angiogenesis by (Boelaert et al. 2007). SH-3 mutant PTTG also regulating angiogenic promoters and inhibitors (Kim suppressed NIS mRNA by 81%, somewhat less than et al. 2006b). The same group also found a significant intact PTTG. Iodide uptake was also reduced (59% WT correlation between VEGF and ID3 expression in 38 PTTG, 34% SH-3 mutant PTTG, and 68% PBF). thyroid carcinomas (9 follicular and 29 papillary; Kim PTTG or PBF and reporter construct co-transfection in et al b In vitro . 2006 ). treatment of FTC133 cells with rat thyroid FRTL-5 and human thyroid cells showed VEGF elevated ID3 mRNA and protein expressions repression of NIS promoter activity via the human (Kim et al. 2006b). Elevated expression of KDR upstream enhancer element. Mutations in various mRNA in these thyroid tumors was highly correlated promoter regions demonstrated specifically that a with increased PTTG mRNA expression. KDR mRNA complex paired box gene 8 (PAX8) upstream- expression was also associated with early recurrence as stimulating factor (USF1)-response element was well as lymph node metastasis (Kim et al. 2006b). The essential for NIS suppression by PTTG and PBF. findings of these studies suggest that PTTG may play a Further analysis showed that the USF1-response major role in angiogenesis through its involvement in element was particularly important for PTTG inhi- both pro- and anti-angiogenic pathways. bition of NIS, whereas PAX8, which was required for Another tumorigenic mechanism associated with elevated PTTG levels in thyroid neoplasms is DNA PBF action, was not essential for this effect (Boelaert ploidy status. A correlation between PTTG expression et al. 2007). Thus, PTTG appears to reduce thyroid and DNA ploidy status has been demonstrated in carcinoma sensitivity to radioiodine treatment by differentiated thyroid carcinomas (Kim et al. 2005). downregulating NIS, affecting the prognosis Fluorescent inter-simple sequence repeat PCR analysis of patients with differentiated thyroid carcinomas of 19 thyroid carcinomas (10 follicular and 9 papillary) (Boelaert et al. 2007). showed 6.7–72.7% increased genomic instability as Studies of the role of PTTG in thyroid carcinomas compared with normal thyroid samples, a result have proven promising by suggesting PTTG as a significantly correlated with PTTG mRNA expression. potential marker of aggressive tumor behavior. PTTG Instability was greater in follicular than in papillary functional studies in thyroid have shown its involve- thyroid carcinomas (Kim et al.2005). In vitro ment in both promotion and inhibition of angiogenic transfection of FTC133 thyroid follicular cells with pathways, as well as induction of genetic instability. PTTG resulted in a dose-dependent increase in genetic Extensive studies to further characterize the role of instability (Kim et al. 2005). Thus, PTTG over- PTTG in thyroid tumorigenesis are warranted. expression in thyroid carcinomas may promote tumor development by inducing genetic instability. Testis/ovary Recently developed mouse models have been used Using RT-PCR, high PTTG expression was demon- to investigate the role of PTTG in thyroid tumorigen- strated in ovarian tumors, including germ cell tumors, esis. The TRbPV/PV mouse develops metastasizing seminomatous and non-seminomatous germ cell follicular thyroid carcinoma (Kim et al. 2007a,b,c). tumors of the testis, including gonadal epithelial, sex

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 732 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 cord, and stromal tumors (Puri et al. 2001). High hyperglycemia in PTTGK/K mice (Wang et al. levels of PTTG mRNA are present in all three major 2003). In addition to pancreatic b-cell expansion testicular cell types (Leydig, Sertoli, and germ (GC2) being hindered as the mice aged, insulin secretion cells; Pei 1998). PTTG knockout mice have lower was significantly lower in PTTGK/K males compared testicular weights by 45–55%, hypoplasia being with male controls (13 vs 53 pg per islet per h; Wang more pronounced in sexually mature mice (Wang et al. 2003). Further evidence for the development of et al.2001). This suggests that PTTG may be sex hormone-dependent diabetes emerged from the implicated in G1- and S-phases regulation during study of gonadectomized PTTGK/K male mice spermatogenesis (Wang et al. 2001). The expression treated with estrogen (Wang et al. 2003). Interestingly, of PTTG was stage specific in spermatocytes and manipulation of sex steroid presence affected diabetes spermatids (Pei 1999). Although northern blot analysis development in PTTGK/K male mice. Gonadectomy of developing rat testis detected low PTTG levels by of PTTGK/K males and their subsequent treatment day 14, PTTG mRNA levels increased significantly, with estradiol prevented hyperglycemia (Fraenkel et al. reaching adult levels by day 28. Additionally, two 2006). The onset of diabetes was delayed due to K K PTTG interacting proteins, the ribosomal subunit gonadectomy in PTTG / male mice, and was protein S10 protein and a HSJ2, novel human further prevented when gonadectomy was combined homolog of DnaJ, a bacterial heat shock protein, with estradiol treatment. These findings indicate that the were identified in testicular cells. It was proposed that development of diabetes in PTTG-deficient mice is PTTG interaction with S10 mediates its ribosomal sexually dimorphic and can be reversed by sex steroid targeting and that HSJ2 may facilitate PTTG treatment. Reversal is thought to take place subsequent dissociation from ribosomes. The significance of to changes in peripheral insulin sensitivity as shown by such interaction, however, remains unclear (Pei 1999). insulin tolerance testing (Fraenkel et al. 2006). The 2C mechanisms underlying sexually dimorphic diabetes In rat H500 Leydig tumor cells, high Ca rapidly development in PTTG-deficient mice are not under- induced PTTG expression in a dose-dependent manner stood. In one cell culture study, the measurement of via transcriptional regulation and de novo PTTG C intracellular insulin in enhanced green fluorescent mRNA synthesis (Tfelt-Hansen et al. 2003). Ca2 - protein-coupled PTTG (PTTG-EGFP)-expressing induced PTTG stimulation was shown to be regulated MIN6 insulinoma cells showed similar levels to non- by the calcium-sensing receptor (CaR), a G-protein- transfected cells, indicating that PTTG does not coupled receptor (Tfelt-Hansen et al. 2003). CaR is influence insulin production or secretion (Yu et al. found to be expressed in many cancer cells (Li et al. 2006). PTTG function as a securin was confirmed in 2005), but PTTG upregulation is specific to H500 these cells; thus, defective insulin secretion was Leydig tumor cells. Thus, whether PTTG as a potential attributed to defective b-cell proliferation rather than marker in testicular cancers merits more studies. to a defect in cell differentiation or insulin production/ secretion (Yu et al. 2006). Pancreatic islets Evidence of the importance of PTTG in pancreatic b-cell proliferation emerged from PTTGK/K animals Non-endocrine tumors that presented with sexually dimorphic diabetes (Wang Brain tumors et al. 2003, Fraenkel et al. 2006, Yu et al. 2006). The expression of PTTG has been demonstrated in Examination of PTTGK/K pancreatic b-cell neogen- fetal as well as in adult brain (Boelaert et al.2003b, esis showed defective b-cell proliferation in associ- Pemberton et al. 2007). In the ventricular zone of the ation with normal differentiation of pancreatic ducts developing ferret cortex, PTTG was expressed during (Yu et al. 2006). PTTGK/K male mice reportedly E11.5–E13.5, peaked in its expression at E15.5, and develop diabetes, weight loss, increased food uptake, was mainly found in mitotically active compared with polyuria, and hyperglycemia (Wang et al.2003). differentiated tissue (Tarabykin et al. 2000). The levels Glucose tolerance tests elicited no response in of PTTG began to decrease at E18.5 and were PTTGK/K males, confirming glucose metabolism detectable in P2, but were no longer expressed in defects (Wang et al. 2003). Although insulin sensitivity adult brains (Tarabykin et al. 2000). In human fetal was not altered, reduced b-cell mass, decreased b-cell brain, PTTG mRNA and protein expressions were proliferation, and low insulin content were noted detectable from 7 weeks of gestation, significantly (Wang et al. 2003). The protective effect of estrogen lower PTTG expression being seen in the first and was evidenced by oophorectomy-induced fasting second trimesters as compared with the adult cerebral

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 733 F Salehi et al.: PTTG review cortex (adult, NZ12; fetal, NZ61; Boelaert et al. compared with a vector-transfected control), higher 2003b). Cell proliferation, determined by PCNA levels doses inhibit cell proliferation (86% compared with detected by western blots, was significantly higher in control; Boelaert et al. 2003b). An SH-3BD mutant fetal cortex as compared with adult cortex, indicating form abrogated the proliferative effect of low-dose that tissue PTTG levels may simply be a reflection of PTTG transfection (Boelaert et al. 2003b). The greater number of proliferating cells (Boelaert et al. intimate role of PTTG in brain cell proliferation was 2003b). PBF mRNA expression varies throughout fetal further supported in a study of murine PTTGK/K development, and is lower in the early second trimester model, where overexpression of separase and Rad21, in adult cortex (Boelaert et al. 2003b). By contrast, involved in sister chromatid separation and cohesion FGF-2 expression patterns parallel to those of PTTG. respectively, was seen (Pemberton et al.2007). In vitro, PTTG expression upregulates FGF-2 in fetal Microarray analysis of the brain in these mice showed neuronal NT-2 cells. It is of note that on SH-3BD upregulation of several mitosis-associated proteins, mutant form of PTTG is unable to induce elevations in including cyclin C and sestrin 2 (Pemberton et al. FGF-2 (Boelaert et al. 2003b). The functional 2007). These results suggest that coordinated significance of these variations in PTTG expression expression of PTTG and other mediators of mitosis, in fetal and adult brains is unclear and calls for future including separase and Rad21n, is required for studies. the normal development of murine brain (Pemberton PTTG expression is higher in neoplastic than in et al. 2007). normal astrocytes, whereas no differences in PBF PTTG is tenfold downregulated in Wallerian expression are noted (Tfelt-Hansen et al.2004). degeneration slow (Wld(S)) mutant mice, which Immunohistochemical staining of 44 glioma specimens feature blocked Wallerian degeneration of injured (9 astrocytomas, 9 anaplastic astrocytomas, and 26 axons and synapses, by the expression of a chimeric glioblastomas) showed nuclear PTTG expression, to be gene (Nmnat-1/truncated-Ube4b; Gillingwater et al. significantly higher in glioblastomas than in the lower 2006). In vitro transfection of HEK293 and neuronal grade astrocytomas (Genkai et al. 2006). In that PTTG NSC34 cells with Wld(S)-EGFP construct also immunoexpression showed a significant correlation stimulates PTTG1 expression, suggesting that PTTG with patient survival (Genkai et al. 2006), it was reduction plays a role in the neuroprotective effects of proposed to be a prognostic marker in such patients Wld(S) gene expression (Gillingwater et al. 2006). (Genkai et al. 2006). In yet another study, astrocytomas were found to show strong PTTG immunoreactivity, Breast whereas normal brain tissue was immunonegative (Chamaon et al.2005). Not surprisingly, PTTG PTTG expression in breast cancers has been docu- mRNA expression was also strong in malignant mented (Saez et al. 1999, Solbach et al. 2004, astrocytic tumors (glioblastoma multiforme IV and Ogbagabriel et al. 2005). High PTTG expression as anaplastic astrocytoma; Chamaon et al. 2005). Various determined by RT-PCR was demonstrated in both nuclear and cytoplasmic PTTG localization patterns in situ and infiltrating ductal carcinoma (Puri et al. were noted in astrocytoma cell lines U87MG, 2001). Lo et al. (2007) hypothesizing that genes U138MG, and LN405 as well as in rat embryonic associated with mitotic checkpoint may be a linked to astrocytes (Chamaon et al. 2005). The tumorigenic breast cancer, investigated single nucleotide poly- mechanisms associated with PTTG overexpression in morphisms (SNPs) in these genes including PTTG. brain neoplasms remain unclear. Their results indicated that PTTG SNPs were associ- Employing the siRNA technique, PTTG depletion in ated with increased risk of breast cancer development T98G, ON12, and U251 glioma cell lines resulted in a in women, suggesting that the loss of chromosomal decrease in cell proliferation and invasion as assessed integrity and aneuploidy may underlie breast tumor- by cell counts and Matrigel invasion assay (Genkai igenesis. However, the precise mechanism by which et al. 2006). By contrast, in fetal neuronal NT-2 cells, PTTG SNPs contribute to elevated incidence of breast PTTG repression by means of siRNA method resulted cancer is unclear and requires further research. in increased Rad21 and separase levels as well as PTTG was shown to be one of the four marker genes stimulation of cell proliferation (Pemberton et al. detected in circulating tumor cells in the blood of 2007). These contradictory results can be explained by Taiwanese women with breast cancer (nZ92). Detec- the dose-dependent association of PTTG levels and tion of these genes, including PTTG, correlated with cell proliferation. Whereas transfection with lower tumor size, histologic grade, the presence of lymph PTTG doses stimulates NT-2 cell proliferation (150% node metastasis, and tumor node metastasis (TNM)

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 734 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 stage (Chen et al. 2006). In one cohort of 90 breast downregulated following genotoxic stress (irradiation) tumors, cytoplasmic and nuclear PTTG expressions in C4-2 prostate carcinoma cells (Crosby et al. 2007). were seen as compared with low cytoplasmic In addition, the transcription factor E2F4 co-immuno- expression in normal breast tissue. PTTG expression precipitated with PTTG promoter regions, indicating was maximal in invasive ductal carcinoma, metastatic that following irradiation and DNA damage, E2F4 breast carcinoma, and breast carcinoma cell cultures. downregulates PTTG expression in order to minimize PTTG mRNA also correlated with invasion in breast the proliferation of DNA-damaged cells (Crosby et al. tumors (Ogbagabriel et al. 2005). The analysis of 2007). These studies implicate PTTG in proliferation PTTG mRNA in 72 breast carcinoma samples of prostate carcinoma cells. demonstrated a correlation between its expression and lymph node involvement as well as recurrence Uterus over a 5-year period of follow-up (Solbach et al. 2004). The analysis of 23 leiomyomas and paired normal Evidently, PTTG overexpression in breast cancers myometrial tissue samples demonstrated that PTTG is associated with tumor invasion and metastasis mRNA and protein expressions were significantly (Solbach et al. 2004, Ogbagabriel et al. 2005, Chen higher in leiomyomas the results being independent et al. 2006), but the contribution of PTTG to these of the menstrual cycles (Tsai et al. 2005). Immuno- aspects of neoplasia remains unclear. histochemical staining and western blotting showed In breast cancer MCF-7 cells, insulin and IGF-I higher PCNA expression in leiomyomas and a stimulate PTTG mRNA and protein expressions in a significant correlation between it and PTTG time- and dose-dependent manner (Thompson & Kakar expression. In addition, bFGF induced elevated 2005). The PI3K pathway was implicated in PTTG PTTG expression in a dose-dependent way within induction by insulin and IGF-I in these cells, since 48 h after initial treatment in cultured leiomyoma cells PI3K inhibitors completely abrogated PTTG induction. (Tsai et al. 2005). PTTG expression was associated It appears that MAPK was partially involved, as with increased cell proliferation, as evidenced by MAPK inhibitors partly reduced PTTG expression. increased expression of cell cycle regulators, cyclins A Thus, the PI3K cascade seems to be the dominant and B1, as well as by increased 3H-thymidine pathway by which insulin and IGF-I exert their PTTG- incorporation. PTTG transfection of leiomyoma cells inducing effect in breast carcinoma cells (Thompson & in culture resulted in increased bFGF and VEGF Kakar 2005). mRNA expressions. In turn, bFGF induced significant Although PTTG upregulation has been demonstrated PTTG expression, thus indicating the existence of a in breast carcinoma, PTTG was one of the genes positive feedback loop between bFGF and PTTG in downregulated after knockout of BRCA, a gene leiomyoma cells. The failure of estrogen and implicated in increased breast cancer risk (Bae et al. progesterone treatments of cultured leiomyoma to 2005). Microarray analysis showed downregulation of affect PTTG expression may partly explain the lack PTTG following BRCA siRNA knockout in prostate of efficacy of anti-estrogen and anti-progesterone DU-145 and MCF-7 breast carcinoma cell lines (Bae treatments in eradication of tumor (Tsai et al. 2005). et al.2005). These findings echo the role of BRCA in regulation of several mitotic spindle checkpoint proteins. Other cancers It appears that BRCA positively regulates PTTG levels, PTTG expression has been demonstrated in a variety of but the precise mechanisms of interaction between tumors and cancer cell lines (Dominguez et al. 1998, BRCA and PTTG remain unknown (Bae et al.2005). McCabe & Gittoes 1999, Heaney et al. 2000, Saez et al. 2002, Shibata et al. 2002, Honda et al. 2003, Ai Prostate et al. 2004, Grutzmann et al. 2004, Wen et al.2004, In a study of 41 prostate carcinoma specimens, 34 Zhou et al. 2005, Fujii et al. 2006, Kakar & Malik (83%) were found to express PTTG, a relatively high 2006, Rehfeld et al. 2006, Sato et al. 2006, Su et al. figure when compared with 36% of non-tumorous 2006, Wang et al. 2006, Winnepenninckx et al. 2006, prostate (Zhu et al. 2006). Transfection of PTTG into Kim et al. 2007a,b,c). Microarray analysis of 14 LNCaP prostate cancer cell line induced both cellular pancreatic ductal carcinomas and pancreatic carcinoma proliferation in vitro and tumor formation in nude mice cell lines identified PTTG1 as one of the differentially (Zhu et al. 2006). PTTG knockout using antisense expressed genes (Grutzmann et al. 2004). Similarly, PTTG leads to suppressed cell proliferation (Zhu et al. hybridization array identified PTTG as one of the 2006). Interestingly, PTTG was among the genes upregulated genes in human renal cell carcinoma (Ai

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 735 F Salehi et al.: PTTG review et al. 2004). High level of PTTG mRNA expression has expressed higher PTTG mRNA levels (Zhou et al. also been documented in leukemia, lung carcinoma, 2005). Several human cancer cell lines such as human lymphoma, and melanoma (McCabe & Gittoes 1999). ESCC cell lines KYSE180, KYSE410, KYSE510, and High levels of PTTG mRNA and protein were also other cancer cell lines showed strong PTTG mRNA demonstrated by northern blot and immunohistochem- expression. PTTG promoter activity was assessed by a istry in 78 non-small cell lung carcinomas (NSCLC) reporter construct and was found to be higher in these including large cell undifferentiated carcinoma as well cell lines, confirming high transcriptional activity of as moderately differentiated squamous cell carcinoma, the PTTG (Zhou et al. 2005). T cell factor (TCF)-4- levels being very low or undetectable in normal lung binding element was found to play an essential role in tissue (Honda et al. 2003). PTTG immunohistochemi- transcriptional regulation of PTTG by the b-catenin/ cal staining of 136 primary small cell lung carcinomas TCF pathway (Zhou et al. 2005). In 37 of the 48 (SCLC) and 91 primary NSCLC samples showed that ESCCs, PTTG mRNA was found to be highly 98% of NSCLC tumors and 64% of SCLC tumors overexpressed when compared with paired normal exhibited PTTG expression. SCLC patients in whom samples. Examination of clinicopathologic parameters the tumors had no or low-level PTTG immunopositi- showed PTTG mRNA expression to be significantly vity had a shorter survival time (265 vs 379 days) higher in tumors of high pathological stage IV disease, compared with those with higher PTTG levels (Rehfeld as compared with ones of stages 0–III (Shibata et al. et al. 2006). By contrast, in NSCLC patients, a reverse 2002). PTTG expression also correlated with lower correlation was observed; strong PTTG expression was survival times, as illustrated by Kaplan–Mier curves associated with a shorter survival time (306 vs (8.5 vs 14 months), but it was not an independent 463 days; Rehfeld et al. 2006). PTTG expression also prognostic indicator on multivariate analysis (Shibata correlated with more aggressive NSCLC tumors, et al. 2002). Nonetheless, univariate analysis showed lymph node, and distant metastases being more PTTG expression to be a prognostic indicator of frequent (Rehfeld et al.2006). The lung tumor cell survival (Shibata et al. 2002). lines A549 (lung carcinoma) and H1299 (NSCLC) also In a series of 68 colorectal carcinomas, PTTG showed high levels of PTTG (Solbach et al. 2005, expression was elevated in 71% (Heaney et al.2000). It Kakar & Malik 2006). was also increased in 85% of 20 colonic polyps (Heaney In a cohort of 89 patients with squamous cell et al.2000). High microvascular density and lymph node carcinomas of the head and neck (HNSCC), PTTG involvement significantly correlated with higher PTTG mRNA was significantly elevated when compared with expression (Heaney et al.2000). Examination of 22 very low or undetectable levels in normal adult mucosa colorectal carcinoma specimens showed PTTG mRNA of the upper respiratory and digestive tract (Solbach and protein expressions to be higher than in matched et al. 2005). Furthermore, the levels correlated with normal tissues (Kim et al.2007c). PTTG expression also tumor stage. In addition, both lymph node stages, the correlated with tumor stage. In vitro examination of most significant prognostic indicator in HNSCC, as PTTG overexpression in the HCT166 colorectal cell line well as tumor recurrence correlated significantly with found that PTTG induced genetic instability in a dose- PTTG levels. Thus, PTTG may serve as a prognostic dependent manner. In the 22 resected colorectal cancer marker in HNSCC (Solbach et al. 2005). specimens, such instability also correlated with higher Microarray analysis of esophageal carcinomas tumor grade, suggesting that PTTG expression and identified PTTG1 as one of the four potential tumor genetic instability are linked in the pathogenesis of markers, 2.4-fold higher expression levels being found colorectal cancer (Kim et al.2007c). In a series of 75 in a series of 20 primary esophageal carcinomas as primary gastric adenocarcinomas, PTTG immunohisto- compared with non-tumorous tissue (Sato et al. 2006). chemical expression was observed in 65% of cases, a As demonstrated by immunohistochemical staining of significant increase being seen in metastatic lymph node 69 primary esophageal squamous cell carcinoma deposits as compared with primary tumors; the obser- (ESCC) samples, in ESCC, PTTG co-localized with vation implicates PTTG in the development of lymph b-catenin (Zhou et al. 2005). The latter accumulated node metastasis (Wen et al.2004). within the cytoplasm (as opposed to its usual location A study of 62 hepatocellular carcinomas showed at the cell membrane) in most cases, 70% of which also increased PTTG expression compared with non- showed PTTG overexpression. Thus, there was a tumorous liver, there being a significant correlation significant correlation between PTTG and b-catenin between PTTG expression, a-fetoprotein increase and expressions (Zhou et al. 2005). When compared with microvascular density (Fujii et al. 2006). PTTG paired normal samples, 67% of the 27 ESCCs expression was also an independent prognostic marker

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 736 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743 of disease-free survival (Fujii et al. 2006). In yet another 2003). In addition, s.c. injection of GH3 cells series of 147 hepatocellular carcinomas, PTTG transfected with truncated PTTG demonstrated the expression was found in 61% but showed no correlation formation of smaller pituitary tumors in rats (Horwitz with survival (Su et al. 2006). PTTG expression was, et al. 2003). These results suggest PTTG may be a however, correlated with increased a-fetoprotein levels therapeutic target in the treatment of PRL-secreting and higher tumor stage (Su et al. 2006). pituitary adenomas and control of their hypersecretion In a series of 29 nodular and 29 superficial (Horwitz et al. 2003). Yet another study showed PTTG spreading melanomas, PTTG correlated with aneu- depletion by siRNA in U87 glioma cells, resulting in ploidy as well as the nodular type (Winnepenninckx inhibition of cell proliferation associated with reduced et al. 2006). The expression of PTTG mRNA in BrdU incorporation (Tfelt-Hansen et al.2004). multiple myeloma (NZ33) has been shown to be Related studies showed similar results. For example: significantly higher than in normal controls (Wang a) siRNA knockdown of PTTG in FTC133 follicular et al. 2006). Assessment of 28 patients with leukemia, thyroid carcinomas cells suppressed ID3 levels and lymphoma, or myelodysplastic disease showed that increased TSP-1 levels, a result in keeping with PTTG 70% of patients overexpressed PTTG compared with stimulation of angiogenic factors (Kim et al. 2006c), normal control samples, thus implicating the role of b) PTTG antisense transfection of the SK-OV-3 PTTG in hematopoietic disease (Dominguez et al. ovarian carcinoma cell line both reduced bFGF 1998). Immunohistochemical analysis of 72 B cell expression by 53% and suppressed colony formation and 37 T cell lymphomas, as well as 41 Hodgkin’s (Chen et al. 2004a), c) PTTG knockout using siRNA in lymphomas showed that 70% of B- and T-cell the lung cancer cell line H1299 resulted in reduced lymphomas and 73% of Hodgkin’s lymphomas show colony formation as assayed by the soft agar colony elevated PTTG expression. Among B-cell tumors, formation assay (Kakar & Malik 2006), d) nude mice plasma cell tumors, follicular lymphomas, and diffuse injected with PTTG siRNA-transfected H1299 cells large cell lymphomas showed the highest expression inhibited tumor development and growth without levels, but T cell lymphomas generally did show adverse effects (Kakar & Malik 2006), and e) the intense immunoreactivity. Northern blot analysis of expressions of Ki-67, bFGF, and CD34 were signifi- 35 of these lymphomas confirmed the immunohisto- cantly reduced in PTTG siRNA-transfected tumors chemical findings and demonstrated alteration of (Kakar & Malik 2006). PTTG at transcriptional levels. These results suggest Transfection of HeLa-S3 human cervical cancer that PTTG is involved in lymphoma initiation and/or cells with antisense PTTG mRNA decreased cell progression (Saez et al. 2002). viability and reduced the mitotic index. Alterations in In summary, PTTG is promising as a prognostic cell phenotype included aberrations in sister chromatid marker in a variety of neoplasm examined. In lung and separation, DNA bridges, and apoptosis (Solbach et al. hepatocellular carcinomas as well as in ESCC, PTTG 2005). Owing to its anti-tumor effects, PTTG antisense expression levels are predictive of survival time. has been proposed as a potential therapeutic target Additionally, PTTG levels are directly correlated (Solbach et al. 2005). Similarly, simply depleting with tumor stage in HNSCC, ESCC, and colorectal PTTG in T98G, ON12, and U251 glioma cell lines carcinomas. Higher PTTG levels in colorectal carci- using the siRNA technique resulted in decreased cell nomas are also associated with metastasis. Further proliferation and reduced invasion as studied by cell studies are needed to better characterize and standar- counts and the Matrigel invasion assay (Genkai et al. dize the predictive role of PTTG as a marker of 2006). Antisense injection of mice was unassociated aggressive tumor behavior. with side effects (Genkai et al. 2006). Adenoviral vector encoding siRNA to silence the PTTG resulted in PTTG depletion and in the SH-J1 hepatoma cell lines, PTTG and treatment induced apoptosis. In HCT116 colorectal cancer cells, Several in vitro and in vivo models have demonstrated PTTG silencing also showed dose-dependent cytotoxi- the therapeutic potential of PTTG (Horwitz et al. 2003, city. In vivo, growth inhibition of Huh-7 hepatoma cell Chen et al. 2004a, Tfelt-Hansen et al. 2004, Solbach lines and SH-J1 tumor xenografts in nude mice was et al. 2005, Cho-Rok et al. 2006, Genkai et al. 2006, achieved by PTTG silencing via siRNA. The results Kakar & Malik 2006). Disruption of PTTG pathways suggest the therapeutic potential of PTTG silencing in in PRL- and GH-secreting pituitary GH3 cells using a the treatment of hepatic tumors as well as other C-terminus truncated form of PTTG suppressed PRL neoplasms expressing high levels of PTTG (Cho-Rok promoter activity as well as secretion (Horwitz et al. et al. 2006).

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Conclusion Bae I, Rih JK, Kim HJ, Kang HJ, Haddad B, Kirilyuk A, Fan S, Avantaggiati ML & Rosen EM 2005 BRCA1 regulates PTTG is involved in a wide array of physiologic and gene expression for orderly mitotic progression. Cell oncogenic functions. Molecular and clinical studies Cycle 4 1641–1666. implicate PTTG in cell cycle regulation, DNA repair, Bernal JA & Hernandez A 2007 p53 stabilization can be genetic instability, transactivating function, angiogen- uncoupled from its role in transcriptional activation by loss esis, and tumor invasion. PTTG-deficient mouse of PTTG1/securin. JournalofBiochemistry141 737–745. models have contributed to our understanding of Bernal JA, Luna R, Espina A, Lazaro I, Ramos-Morales F, PTTG function as an oncogene. In many neoplasms, Romero F, Arias C, Silva A, Tortolero M & Pintor-Toro PTTG expression correlates with invasiveness and JA 2002 Human securin interacts with p53 and modulates tumor stage, thus suggesting that PTTG may be a p53-mediated transcriptional activity and apoptosis. prognostic biomarker. Indeed, PTTG downregulation Nature Genetics 32 306–311. in vitro and in vivo shows promise as a therapeutic tool. Bernal JA, Roche M, Mendez-Vidal C, Espina A, Tortolero Further investigations of the PTTG pathway and its M & Pintor-Toro JA 2008 Proliferative potential after role as a biomarker and therapeutic target are DNA damage and non-homologous end joining are warranted. affected by loss of securin. Cell Death and Differentiation 15 202–212. Boelaert K, McCabe CJ, Tannahill LA, Gittoes NJ, Holder Declaration of interest RL, Watkinson JC, Bradwell AR, Sheppard MC & Franklyn JA 2003a Pituitary tumor transforming gene and There is no conflict of interest that could be perceived as fibroblast growth factor-2 expression: potential prognostic prejudicing the impartiality of the research reported. indicators in differentiated thyroid cancer. Journal of Clinical Endocrinology and Metabolism 88 2341–2347. Boelaert K, Tannahill LA, Bulmer JN, Kachilele S, Chan SY, Funding Kim D, Gittoes NJ, Franklyn JA, Kilby MD & McCabe CJ This research did not receive any specific grant from any 2003b A potential role for PTTG/securin in the developing funding agency in the public, commercial or not-for-profit human fetal brain. FASEB Journal 17 1631–1639. sector. Boelaert K, Yu R, Tannahill LA, Stratford AL, Khanim FL, Eggo MC, Moore JS, Young LS, Gittoes NJ, Franklyn JA et al. 2004 PTTG’s C-terminal PXXP motifs modulate Acknowledgements critical cellular processes in vitro. Journal of Molecular Authors are indebted to the Jarislowsky Foundation and the Endocrinology 33 663–677. Lloyd Carr–Harris Foundation for their generous support. Boelaert K, Smith VE, Stratford AL, Kogai T, Tannahill LA, Watkinson JC, Eggo MC, Franklyn JA & McCabe CJ 2007 PTTG and PBF repress the human sodium iodide References symporter. Oncogene 26 4344–4356. Chae YM, Park KK, Lee IK, Kim JK, Kim CH & Chang YC Abbud RA, Takumi I, Barker EM, Ren SG, Chen DY, 2006 Ring-Sp1 decoy oligonucleotide effectively sup- Wawrowsky K & Melmed S 2005 Early multipotential presses extracellular matrix gene expression and fibrosis pituitary focal hyperplasia in the alpha-subunit of of rat kidney induced by unilateral ureteral obstruction. glycoprotein hormone-driven pituitary tumor-transform- Gene Therapy 13 430–439. ing gene transgenic mice. Molecular Endocrinology 19 Chamaon K, Kirches E, Kanakis D, Braeuninger S, 1383–1391. Dietzmann K & Mawrin C 2005 Regulation of the Ai J, Zhang Z, Xin D, Zhu H, Yan Q, Xin Z, Na Y & Guo Y pituitary tumor transforming gene by insulin-like-growth 2004 Identification of over-expressed genes in human factor-I and insulin differs between malignant and non- renal cell carcinoma by combining suppression subtrac- tive hybridization and cDNA library array. Science in neoplastic astrocytes. Biochemical and Biophysical China. Series C, Life Sciences 47 148–157. Research Communications 331 86–92. Akino K, Mineta T, Fukui M, Fujii T & Akita S 2003 Bone Chen L, Puri R, Lefkowitz EJ & Kakar SS 2000 Identification morphogenetic protein-2 regulates proliferation of human of the human pituitary tumor transforming gene (hPTTG) mesenchymal stem cells. Wound Repair and Regener- family: molecular structure, expression, and chromo- ation 11 354–360. somal localization. Gene 248 41–50. Akino K, Akita S, Mizuguchi T, Takumi I, Yu R, Wang XY, Chen G, Li J, Li F, Li X, Zhou J, Lu Y & Ma D 2004a Rozga J, Demetriou AA, Melmed S, Ohtsuru A et al. 2005 Inhibitory effects of anti-sense PTTG on malignant A novel molecular marker of pituitary tumor transforming phenotype of human ovarian carcinoma cell line gene involves in a rat liver regeneration. Journal of SK-OV-3. Journal of Huazhong University of Science and Surgical Research 129 142–146. Technology. Medical Sciences 24 369–372.

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Chen L, Liu YS, Wang LS, Yin HG, Hou QT, Liu ZX, Chen correlates with the proliferative activity and recurrence LH & Ling F 2004b Expression of pituitary tumor status of pituitary adenomas: a clinical and immunohis- transforming gene, endostatin, and basic fibroblast growth tochemical study. Clinical Endocrinology 65 536–543. factor mRNAs in invasive pituitary adenomas. Zhong Nan Fraenkel M, Caloyeras J, Ren SG & Melmed S 2006 Sex- Da Xue Xue Bao. Yi Xue Ban 29 651–653. steroid milieu determines diabetes rescue in pttg-null Chen CC, Chang TW, Chen FM, Hou MF, Hung SY, Chong mice. Journal of Endocrinology 189 519–528. IW, Lee SC, Zhou TH & Lin SR 2006 Combination of Fujii T, Nomoto S, Koshikawa K, Yatabe Y, Teshigawara O, multiple mRNA markers (PTTG1, Survivin, UbcH10 and Mori T, Inoue S, Takeda S & Nakao A 2006 Over- TK1) in the diagnosis of Taiwanese patients with breast expression of pituitary tumor transforming gene 1 in HCC cancer by membrane array. Oncology 70 438–446. is associated with angiogenesis and poor prognosis. Chesnokova V, Kovacs K, Castro AV, Zonis S & Melmed S Hepatology 43 1267–1275. 2005 Pituitary hypoplasia in PttgK/K mice is protective Fujimoto N, Maruyama S & Ito A 1999 Establishment of an for RbC/K pituitary tumorigenesis. Molecular Endo- estrogen responsive rat pituitary cell sub-line MtT/E-2. crinology 19 2371–2379. Endocrine Journal 46 389–396. Chesnokova V, Zonis S, Rubinek T, Yu R, Ben-Shlomo A, Genkai N, Homma J, Sano M, Tanaka R & Yamanaka R 2006 Kovacs K, Wawrowsky K & Melmed S 2007 Senescence Increased expression of pituitary tumor-transforming mediates pituitary hypoplasia and restrains pituitary gene (PTTG)-1 is correlated with poor prognosis in tumor growth. Cancer Research 67 10564–10572. glioma patients. Oncology Reports 15 1569–1574. Chien W & Pei L 2000 A novel binding factor facilitates Gillingwater TH, Wishart TM, Chen PE, Haley JE, nuclear translocation and transcriptional activation Robertson K, MacDonald SH, Middleton S, Wawrowski function of the pituitary tumor-transforming gene K, Shipston MJ, Melmed S et al. 2006 The neuroprotec- product. Journal of Biological Chemistry 275 tive WldS gene regulates expression of PTTG1 and 19422–19427. erythroid differentiation regulator 1-like gene in mice and Human Molecular Genetics 15 Chiu SJ, Hsu TS & Chao JI 2006 Opposing securin and p53 human cells. 625–635. Grutzmann R, Pilarsky C, Ammerpohl O, Luttges J, Bohme protein expression in the oxaliplatin-induced cytotoxicity A, Sipos B, Foerder M, Alldinger I, Jahnke B, Schackert of human colorectal cancer cells. Toxicology Letters 167 HK et al. 2004 Gene expression profiling of micro- 122–130. dissected pancreatic ductal carcinomas using high-density Cho-Rok J, Yoo J, Jang YJ, Kim S, Chu IS, Yeom YI, Choi DNA microarrays. Neoplasia 6 611–622. JY & Im DS 2006 Adenovirus-mediated transfer of Hamid T & Kakar SS 2004 PTTG/securin activates siRNA against PTTG1 inhibits liver cancer cell growth expression of p53 and modulates its function. Molecular in vitro and in vivo. Hepatology 43 1042–1052. Cancer 3 18. Clem AL, Hamid T & Kakar SS 2003 Characterization of the Heaney AP, Horwitz GA, Wang Z, Singson R & Melmed S role of Sp1 and NF-Y in differential regulation of PTTG/ 1999 Early involvement of estrogen-induced pituitary securin expression in tumor cells. Gene 322 113–121. tumor transforming gene and fibroblast growth Cong J, Wang HY & Zhang CL 2005 Expression and clinical factor expression in prolactinoma pathogenesis. Nature significance of PTTG and b-FGF in acute leukemia. Medicine 5 1317–1321. Zhongguo Shi Yan Xue Ye Xue Za Zhi 13 951–953. Heaney AP, Singson R, McCabe CJ, Nelson V, Nakashima M Crosby ME, Jacobberger J, Gupta D, Macklis RM & & Melmed S 2000 Expression of pituitary-tumour Almasan A 2007 E2F4 regulates a stable G2 arrest transforming gene in colorectal tumours. Lancet 355 response to genotoxic stress in prostate carcinoma. 716–719. Oncogene 26 1897–1909. Heaney AP, Nelson V, Fernando M & Horwitz G 2001 Dominguez A, Ramos-Morales F, Romero F, Rios RM, Transforming events in thyroid tumorigenesis and their Dreyfus F, Tortolero M & Pintor-Toro JA 1998 hpttg, a association with follicular lesions. Journal of Clinical human homologue of rat pttg, is overexpressed in Endocrinology and Metabolism 86 5025–5032. hematopoietic neoplasms. Evidence for a transcriptional Heaney AP, Fernando M & Melmed S 2002 Functional role activation function of hPTTG. Oncogene 17 2187–2193. of estrogen in pituitary tumor pathogenesis. Journal of Donangelo I & Melmed S 2005 Pathophysiology of pituitary Clinical Investigation 109 277–283. adenomas. Journal of Endocrinological Investigation 28 Honda S, Hayashi M, Kobayashi Y, Ishikawa Y, Nakagawa 100–105. K & Tsuchiya E 2003 A role for the pituitary tumor- Donangelo I, Gutman S, Horvath E, Kovacs K, Wawrowsky transforming gene in the genesis and progression of non- K, Mount M & Melmed S 2006 Pituitary tumor small cell lung carcinomas. Anticancer Research 23 transforming gene overexpression facilitates pituitary 3775–3782. tumor development. Endocrinology 147 4781–4791. Horwitz GA, Miklovsky I, Heaney AP, Ren SG & Melmed S Filippella M, Galland F, Kujas M, Young J, Faggiano A, 2003 Human pituitary tumor-transforming gene (PTTG1) Lombardi G, Colao A, Meduri G & Chanson P 2006 motif suppresses prolactin expression. Molecular Endo- Pituitary tumour transforming gene (PTTG) expression crinology 17 600–609.

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 739 F Salehi et al.: PTTG review

Hunter JA, Skelly RH, Aylwin SJ, Geddes JF, Evanson J, Kim DS, Franklyn JA, Smith VE, Stratford AL, Pemberton Besser GM, Monson JP & Burrin JM 2003 The HN, Warfield A, Watkinson JC, Ishmail T, Wakelam relationship between pituitary tumour transforming gene MJ & McCabe CJ 2007c Securin induces genetic (PTTG) expression and in vitro hormone and vascular instability in colorectal cancer by inhibiting double- endothelial growth factor (VEGF) secretion from human stranded DNA repair activity. Carcinogenesis 28 pituitary adenomas. European Journal of Endocrinology 749–759. 148 203–211. Lai Y, Xin D, Bai J, Mao Z & Na Y 2007 The important anti- Ishikawa H, Heaney AP, Yu R, Horwitz GA & Melmed S apoptotic role and its regulation mechanism of PTTG1 in 2001 Human pituitary tumor-transforming gene induces UV-induced apoptosis. Journal of Biochemistry and angiogenesis. Journal of Clinical Endocrinology and Molecular Biology 40 966–972. Metabolism 86 867–874. Li S, Huang S & Peng SB 2005 Overexpression of G protein- Kakar SS 1999 Molecular cloning, genomic organization, coupled receptors in cancer cells: involvement in tumor and identification of the promoter for the human pituitary progression. International Journal of Oncology 27 tumor transforming gene (PTTG). Gene 240 317–324. 1329–1339. Kakar SS & Malik MT 2006 Suppression of lung cancer Lo YL, Yu JC, Chen ST, Hsu GC, Mau YC, Yang SL, Wu PE with siRNA targeting PTTG. International Journal of & Shen CY 2007 Breast cancer risk associated with Oncology 29 387–395. genotypic polymorphism of the mitotic checkpoint genes: Kanakis D, Kirches E, Mawrin C & Dietzmann K 2003 a multigenic study on cancer susceptibility. Carcinogen- Promoter mutations are no major cause of PTTG esis 28 1079–1086. overexpression in pituitary adenomas. Clinical Endo- Malik MT & Kakar SS 2006 Regulation of angiogenesis and crinology 58 151–155. invasion by human Pituitary tumor transforming gene Karsten SL, Kudo LC, Jackson R, Sabatti C, Kornblum HI & (PTTG) through increased expression and secretion of Geschwind DH 2003 Global analysis of gene expression matrix metalloproteinase-2 (MMP-2). Molecular Cancer in neural progenitors reveals specific cell-cycle, signaling, 5 61. and metabolic networks. Developmental Biology 261 McCabe CJ & Gittoes NJ 1999 PTTG – a new pituitary 165–182. tumour transforming gene. Journal of Endocrinology 162 Kho PS, Wang Z, Zhuang L, Li Y, Chew JL, Ng HH, Liu ET 163–166. & Yu Q 2004 P53-regulated transcriptional program McCabe CJ, Boelaert K, Tannahill LA, Heaney AP, Stratford associated with genotoxic stress-induced apoptosis. AL, Khaira JS, Hussain S, Sheppard MC, Franklyn JA & Journal of Biological Chemistry 279 21183–21192. Gittoes NJ 2002 Vascular endothelial growth factor, its Kim D, Pemberton H, Stratford AL, Buelaert K, Watkinson receptor KDR/Flk-1, and pituitary tumor transforming JC, Lopes V, Franklyn JA & McCabe CJ 2005 Pituitary gene in pituitary tumors. Journal of Clinical Endocrino- tumour transforming gene (PTTG) induces genetic logy and Metabolism 87 4238–4244. instability in thyroid cells. Oncogene 24 4861–4866. McCabe CJ, Khaira JS, Boelaert K, Heaney AP, Tannahill Kim DS, Buchanan MA, Stratford AL, Watkinson JC, Eggo LA, Hussain S, Mitchell R, Olliff J, Sheppard MC, MC, Franklyn JA & McCabe CJ 2006a PTTG promotes a et al. novel VEGF-KDR-ID3 autocrine mitogenic pathway in Franklyn JA 2003 Expression of pituitary tumour thyroid cancer. Clinical Otolaryngology 31 246. transforming gene (PTTG) and fibroblast growth factor-2 Kim DS, Franklyn JA, Boelaert K, Eggo MC, Watkinson JC (FGF-2) in human pituitary adenomas: relationships to & McCabe CJ 2006b Pituitary tumor transforming gene clinical tumour behaviour. Clinical Endocrinology 58 (PTTG) stimulates thyroid cell proliferation via a vascular 141–150. endothelial growth factor/kinase insert domain receptor/ Mei J, Huang X & Zhang P 2001 Securin is not required inhibitor of DNA binding-3 autocrine pathway. Journal of for cellular viability, but is required for normal growth Clinical Endocrinology and Metabolism 91 4603–4611. of mouse embryonic fibroblasts. Current Biology 11 Kim DS, Franklyn JA, Stratford AL, Boelaert K, Watkinson 1197–1201. JC, Eggo MC & McCabe CJ 2006c Pituitary tumor- Minematsu T, Suzuki M, Sanno N, Takekoshi S, Teramoto A transforming gene regulates multiple downstream angio- & Osamura RY 2006 PTTG overexpression is correlated genic genes in thyroid cancer. Journal of Clinical with angiogenesis in human pituitary adenomas. Endo- Endocrinology and Metabolism 91 1119–1128. crine Pathology 17 143–153. Kim CS, Ying H, Willingham MC & Cheng SY 2007a The Minematsu T, Egashira N, Kajiya H, Takei M, Takekoshi S, pituitary tumor-transforming gene promotes angiogenesis Itoh Y, Tsukamoto H, Itoh J, Sanno N, Teramoto A et al. in a mouse model of follicular thyroid cancer. Carcino- 2007 PTTG is a secretory protein in human pituitary genesis 28 932–939. adenomas and in mouse pituitary tumor cell lines. Kim DS, Fong J, Read ML & McCabe CJ 2007b The Endocrine Pathology 18 8–15. emerging role of pituitary tumour transforming gene Mu YM, Oba K, Yanase T, Ito T, Ashida K, Goto K, (PTTG) in endocrine tumourigenesis. Molecular and Morinaga H, Ikuyama S, Takayanagi R & Nawata H 2003 Cellular Endocrinology 278 1–6. Human pituitary tumor transforming gene (hPTTG)

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 740 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743

inhibits human lung cancer A549 cell growth through heterodimer, the regulatory subunit of the DNA-depen- activation of p21(WAF1/CIP1). Endocrine Journal 50 dent protein kinase. Nucleic Acids Research 29 771–781. 1300–1307. Ogbagabriel S, Fernando M, Waldman FM, Bose S & Rubinek T, Chesnokova V, Wolf I, Wawrowsky K, Vlotides Heaney AP 2005 Securin is overexpressed in breast G & Melmed S 2007 Discordant proliferation and cancer. Modern Pathology 18 985–990. differentiation in pituitary tumor-transforming gene-null Pei L 1998 Genomic organization and identification of an bone marrow stem cells. American Journal of Physiology. enhancer element containing binding sites for multiple Cell Physiology 293 C1082–C1092. proteins in rat pituitary tumor-transforming gene. Saez C, Japon MA, Ramos-Morales F, Romero F, Segura DI, Journal of Biological Chemistry 273 5219–5225. Tortolero M & Pintor-Toro JA 1999 Hpttg is over- Pei L 1999 Pituitary tumor-transforming gene protein expressed in pituitary adenomas and other primary associates with ribosomal protein S10 and a novel human epithelial neoplasias. Oncogene 18 5473–5476. homologue of DnaJ in testicular cells. Journal of Saez C, Pereda T, Borrero JJ, Espina A, Romero F, Tortolero Biological Chemistry 274 3151–3158. M, Pintor-Toro JA, Segura DI & Japon MA 2002 Pei L 2000 Activation of mitogen-activated protein kinase Expression of hpttg proto-oncogene in lymphoid neopla- cascade regulates pituitary tumor-transforming gene sias. Oncogene 21 8173–8177. transactivation function. Journal of Biological Chemistry Sato F, Abraham JM, Yin J, Kan T, Ito T, Mori Y, Hamilton 275 31191–31198. JP, Jin Z, Cheng Y, Paun B et al. 2006 Polo-like kinase Pei L 2001 Identification of c-myc as a down-stream target and survivin are esophageal tumor-specific promoters. for pituitary tumor-transforming gene. Journal of Bio- Biochemical and Biophysical Research Communications logical Chemistry 276 8484–8491. 342 465–471. Pei L & Melmed S 1997 Isolation and characterization of a Shibata Y, Haruki N, Kuwabara Y, Nishiwaki T, Kato J, pituitary tumor-transforming gene (PTTG). Molecular Shinoda N, Sato A, Kimura M, Koyama H, Toyama T Endocrinology 11 433–441. et al. 2002 Expression of PTTG (pituitary tumor Pemberton HN, Franklyn JA, Boelaert K, Chan SY, Kim DS, transforming gene) in esophageal cancer. Kim C, Cheng SY, Kilby MD & McCabe CJ 2007 Japanese Journal of Clinical Oncology 32 233–237. Separase, securin and Rad21 in neural cell growth. Solbach C, Roller M, Fellbaum C, Nicoletti M & Kaufmann M Journal of Cellular Physiology 213 45–53. 2004 PTTG mRNA expression in primary breast cancer: a Prezant TR, Kadioglu P & Melmed S 1999 An intronless prognostic marker for lymph node invasion and tumor homolog of human proto-oncogene hPTTG is expressed recurrence. Breast 13 80–81. in pituitary tumors: evidence for hPTTG family. Solbach C, Roller M, Peters S, Nicoletti M, Kaufmann M & Journal of Clinical Endocrinology and Metabolism 84 Knecht R 2005 Pituitary tumor-transforming gene 1149–1152. (PTTG): a novel target for anti-tumor therapy. Anticancer Puri R, Tousson A, Chen L & Kakar SS 2001 Molecular Research 25 121–125. cloning of pituitary tumor transforming gene 1 from Stoika R & Melmed S 2002 Expression and function of ovarian tumors and its expression in tumors. Cancer pituitary tumour transforming gene for T-lymphocyte Letters 163 131–139. activation. British Journal of Haematology 119 Rajamannan NM, Subramaniam M, Abraham TP, Vasile VC, 1070–1074. Ackerman MJ, Monroe DG, Chew TL & Spelsberg TC Stratford AL, Boelaert K, Tannahill LA, Kim DS, Warfield A, 2007 TGFb inducible early gene-1 (TIEG1) and cardiac Eggo MC, Gittoes NJ, Young LS, Franklyn JA & McCabe hypertrophy: discovery and characterization of a novel CJ 2005 Pituitary tumor transforming gene binding factor: a signaling pathway. Journal of Cellular Biochemistry 100 novel transforming gene in thyroid tumorigenesis. 315–325. Journal of Clinical Endocrinology and Metabolism 90 Ramos-Morales F, Dominguez A, Romero F, Luna R, Multon 4341–4349. MC, Pintor-Toro JA & Tortolero M 2000 Cell cycle Su MC, Hsu HC, Liu YJ & Jeng YM 2006 Overexpression regulated expression and phosphorylation of hpttg proto- of pituitary tumor-transforming gene-1 in hepatocellular oncogene product. Oncogene 19 403–409. carcinoma. Hepatogastroenterology 53 262–265. Rehfeld N, Geddert H, Atamna A, Rohrbeck A, Garcia G, Tarabykin V, Britanova O, Fradkov A, Voss A, Katz LS, Kliszewski S, Neukirchen J, Bruns I, Steidl U, Fenk R Lukyanov S & Gruss P 2000 Expression of PTTG and et al. 2006 The influence of the pituitary tumor prc1 genes during telencephalic neurogenesis. Mechan- transforming gene-1 (PTTG-1) on survival of patients isms of Development 92 301–304. with small cell lung cancer and non-small cell lung Tfelt-Hansen J, Schwarz P, Terwilliger EF, Brown EM & cancer. Journal of Carcinogenesis 5 4. Chattopadhyay N 2003 Calcium-sensing receptor induces Romero F, Multon MC, Ramos-Morales F, Dominguez A, messenger ribonucleic acid of human securin, pituitary Bernal JA, Pintor-Toro JA & Tortolero M 2001 tumor transforming gene, in rat testicular cancer. Human securin, hPTTG, is associated with Ku Endocrinology 144 5188–5193.

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 741 F Salehi et al.: PTTG review

Tfelt-Hansen J, Yano S, Bandyopadhyay S, Carroll R, Brown Wen CY, Nakayama T, Wang AP, Nakashima M, Ding YT, EM & Chattopadhyay N 2004 Expression of pituitary Ito M, Ishibashi H, Matsuu M, Shichijo K & Sekine I 2004 tumor transforming gene (PTTG) and its binding Expression of pituitary tumor transforming gene in human protein in human astrocytes and astrocytoma cells: gastric carcinoma. World Journal of Gastroenterology 10 function and regulation of PTTG in U87 astrocytoma 481–483. cells. Endocrinology 145 4222–4231. Wierinckx A, Auger C, Devauchelle P, Reynaud A, Tfelt-Hansen J, Kanuparthi D & Chattopadhyay N 2006 Chevallier P, Jan M, Perrin G, Fevre-Montange M, Rey C, The emerging role of pituitary tumor transforming gene Figarella-Branger D et al. 2007 A diagnostic marker in tumorigenesis. Clinical Medicine & Research 4 set for invasion, proliferation, and aggressiveness of 130–137. prolactin pituitary tumors. Endocrine-Related Cancer 14 Thompson AD III & Kakar SS 2005 Insulin and IGF-1 887–900. regulate the expression of the pituitary tumor transform- Winnepenninckx V, Debiec-Rychter M, Belien JA, Fiten P, ing gene (PTTG) in breast tumor cells. FEBS Letters 579 Michiels S, Lazar V, Opdenakker G, Meijer GA, Spatz A 3195–3200. & van den Oord JJ 2006 Expression and possible role of Tong Y, Tan Y, Zhou C & Melmed S 2007 Pituitary tumor hPTTG1/securin in cutaneous malignant melanoma. transforming gene interacts with Sp1 to modulate G1/S Modern Pathology 19 1170–1180. cell phase transition. Oncogene 26 5596–5605. Xie K, Wei D & Huang S 2006 Transcriptional anti- Tsai SJ, Lin SJ, Cheng YM, Chen HM & Wing LY 2005 angiogenesis therapy of human pancreatic cancer. Expression and functional analysis of pituitary tumor Cytokine and Growth Factor Reviews 17 147–156. transforming gene-1 [corrected] in uterine leiomyomas. Yao YQ, Xu JS, Lee WM, Yeung WS & Lee KF 2003 Journal of Clinical Endocrinology and Metabolism 90 Identification of mRNAs that are up-regulated after 3715–3723. fertilization in the murine zygote by suppression Uccella S, Tibiletti MG, Bernasconi B, Finzi G, Oldrini R subtractive hybridization. Biochemical and Biophysical & Capella C 2005 Aneuploidy, centrosome Research Communications 304 60–66. alteration and securin overexpression as features of Yin H, Fujimoto N, Maruyama S & Asano K 2001 Strain pituitary somatotroph and lactotroph adenomas. difference in regulation of pituitary tumor transforming Analytical and Quantitative Cytology and Histology 27 gene (PTTG) in estrogen-induced pituitary tumorigenesis 241–252. in rats. Japanese Journal of Cancer Research 92 Vlotides G, Cruz-Soto M, Rubinek T, Eigler T, Auernhammer 1034–1040. CJ & Melmed S 2006 Mechanisms for growth factor- Yu R, Heaney AP, Lu W, Chen J & Melmed S 2000a induced pituitary tumor transforming gene-1 expression Pituitary tumor transforming gene causes aneuploidy and in pituitary folliculostellate TtT/GF cells. Molecular p53-dependent and p53-independent apoptosis. Journal of Endocrinology 20 3321–3335. Biological Chemistry 275 36502–36505. Vlotides G, Eigler T & Melmed S 2007 Pituitary tumor- Yu R, Ren SG, Horwitz GA, Wang Z & Melmed S transforming gene: physiology and implications for 2000b Pituitary tumor transforming gene (PTTG) tumorigenesis. Endocrine Reviews 28 165–186. Wang Z & Melmed S 2000a Characterization of the murine regulates placental JEG-3 cell division and survival: pituitary tumor transforming gene (PTTG) and its evidence from live cell imaging. Molecular Endo- promoter. Endocrinology 141 763–771. crinology 14 1137–1146. Wang Z & Melmed S 2000b Pituitary tumor Yu R, Lu W, Chen J, McCabe CJ & Melmed S 2003 transforming gene (PTTG) transforming and transactiva- Overexpressed pituitary tumor-transforming gene tion activity. Journal of Biological Chemistry 275 causes aneuploidy in live human cells. Endocrinology 144 7459–7461. 4991–4998. Wang Z, Yu R & Melmed S 2001 Mice lacking pituitary Yu R, Cruz-Soto M, Li Calzi S, Hui H & Melmed S 2006 tumor transforming gene show testicular and Murine pituitary tumor-transforming gene functions as a splenic hypoplasia, thymic hyperplasia, thrombocytope- securin protein in insulin-secreting cells. Journal of nia, aberrant cell cycle progression, and premature Endocrinology 191 45–53. centromere division. Molecular Endocrinology 15 Yuan HQ, Kong F, Wang XL, Young CY, Hu XY & Lou HX 1870–1879. 2008 Inhibitory effect of acetyl-11-keto-beta-boswellic Wang Z, Moro E, Kovacs K, Yu R & Melmed S 2003 acid on androgen receptor by interference of Sp1 binding Pituitary tumor transforming gene-null male mice exhibit activity in prostate cancer cells. Biochemical Pharma- impaired pancreatic beta cell proliferation and diabetes. cology 75 2112–2121. PNAS 100 3428–3432. Zhang X, Horwitz GA, Heaney AP, Nakashima M, Prezant Wang Z, Lu QY, Chen P, Zhang P & Cong YQ 2006 TR, Bronstein MD & Melmed S 1999a Pituitary tumor Expression of pituitary tumor-transforming gene in transforming gene (PTTG) expression in pituitary patients with multiple myeloma. Zhongguo Shi Yan Xue adenomas. Journal of Clinical Endocrinology and Ye Xue Za Zhi 14 1143–1145. Metabolism 84 761–767.

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access 742 www.endocrinology-journals.org Endocrine-Related Cancer (2008) 15 721–743

Zhang X, Horwitz GA, Prezant TR, Valentini A, Nakashima M, by beta-catenin/TCF pathway in human esophageal Bronstein MD & Melmed S 1999b Structure, expression, squamous cell carcinoma. International Journal of and function of human pituitary tumor-transforming gene Cancer 113 891–898. (PTTG). Molecular Endocrinology 13 156–166. Zhu X, Mao Z, Na Y, Guo Y, Wang X & Xin D 2006 Zhou Y, Mehta KR, Choi AP, Scolavino S & Zhang X 2003 Significance of pituitary tumor transforming gene 1 DNA damage-induced inhibition of securin expression is (PTTG1) in prostate cancer. Anticancer Research 26 mediated by p53. Journal of Biological Chemistry 278 1253–1259. 462–470. Zou H, McGarry TJ, Bernal T & Kirschner MW 1999 Zhou C, Liu S, Zhou X, Xue L, Quan L, Lu N, Zhang G, Bai J, Identification of a vertebrate sister-chromatid separation Wang Y, Liu Z et al. 2005 Overexpression of human inhibitor involved in transformation and tumorigenesis. pituitary tumor transforming gene (hPTTG), is regulated Science 285 418–422.

Downloaded from Bioscientifica.com at 09/30/2021 01:03:52PM via free access www.endocrinology-journals.org 743