http://informahealthcare.com/drt ISSN: 1061-186X (print), 1029-2330 (electronic)

J Drug Target, Early Online: 1–9 ! 2014 Informa UK Ltd. DOI: 10.3109/1061186X.2014.983522

REVIEW ARTICLE in liver and pancreas: the potential drug target for tumor therapy

Delin Kong*, Yicheng Zhao*, Tong Men, and Chun-Bo Teng

College of life science, Northeast Forestry University, Harbin, China

Abstract Keywords Cell behaviors, including proliferation, differentiation and apoptosis, are intricately controlled Cancer therapy, hepatic targeting, during organ development and tissue regeneration. In the past 9 years, the Hippo signaling in vitro model, tumor targeting pathway has been delineated to play critical roles in organ size control, tissue regeneration and tumorigenesis through regulating cell behaviors. In mammals, the core modules of the Hippo History signaling pathway include the MST1/2-LATS1/2 kinase cascade and the transcriptional co-activators YAP/TAZ. The activity of YAP/TAZ is suppressed by cytoplasmic retention due Received 5 September 2014 to phosphorylation in the canonical MST1/2-LATS1/2 kinase cascade-dependent manner or the Revised 21 October 2014 non-canonical MST1/2- and/or LATS1/2-independent manner. Hippo signaling pathway, which Accepted 29 October 2014 can be activated or inactivated by cell polarity, contact inhibition, mechanical stretch and Published online 3 December 2014 extracellular factors, has been demonstrated to be involved in development and tumorigenesis of liver and pancreas. In addition, we have summarized several small molecules currently available that can target Hippo-YAP pathway for potential treatment of hepatic and pancreatic cancers, providing clues for other YAP initiated cancers therapy as well.

Introduction buds, the progenitor cells give rise, through a stepwise

For personal use only. process, to endocrine, acinar and duct cells. Both liver and pancreas are important internal glands in The processes of hepatic and pancreatic regeneration in mammals, and each plays an obligatory role in orchestrating adult are well known and acknowledged [3]. In response to the balance between lipid and glucose metabolism [1]. The drug treatment or mechanical injury, mature hepatic and liver is responsible for storage of glycogen, production of bile pancreatic cells can rescue the damage via self-proliferation. In for lipid emulsification and secretion of a variety of serum the extensive necrosis, progenitors in organs will be induced to for homeostasis maintenance, whereas the pancreas proliferate and differentiate to achieve tissue regeneration. is a mixed gland with both exocrine and endocrine functions: However, regulatory disorders in the processes will lead to acinar is able to secrete enzymes including protease and abnormal phenotypes including cancers. lipase to digest food, while islet is able to secrete hormones The Hippo signaling pathway was first defined by genetic including glucagon and insulin to control glucose levels. mosaic screens in Drosophila, the core components of which

Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 Liver and pancreas are both derived from the endoderm. included two kinases, the Ste-like kinase HIPPO and the NDR During gastrulation, the endoderm germ layer is established family kinase Warts (WTS), and a Yorkie and forms a primitive gut tube that is subdivided into foregut, (Yki). In the year of 2005, Huang et al. [4] revealed the midgut and hindgut regions [2]. Fate mapping studies indicate signaling cascade: Hippo phosphorylates and activates WTS, that the embryonic liver originates from the ventral foregut and then p-WTS phosphorylates but inhibits Yki via blocking endoderm. The anterior portion of the hepatic diverticulum its translocation into nucleus, which leads to sequestration of gives rise to the liver and intrahepatic biliary tree, while the its target including CycE and Diap1. Two years later, posterior portion forms the gall bladder and extrahepatic bile Dong et al. [5] found that Hippo pathway was highly ducts. Like the liver, the pancreas develops as outgrowths of conserved from invertebrate to vertebrate and identified the the endoderm from the foregut–midgut junction at both dorsal core mammalian counterparts: MST1/2, LATS1/2 and YAP. and ventral directions. Finally, the ventral and dorsal pancre- Inactivation of the Hippo pathway induces YAP-mediated atic buds are fused to a whole pancreas. Within the pancreatic activation of various target genes that functionally result in cellular proliferation and outgrowth of organ size. Moreover, YAP has been implicated as an oncogene in solid tumors, * These authors contributed equally to this work. but its exact molecular mechanism in carcinogenesis still Address for correspondence: Chun-Bo Teng, E-mail: chunboteng@ remains unclear. It has been reported that several signaling nefu.edu.cn components of the Hippo pathway are implicated as tumor 2 D. Kong et al. J Drug Target, Early Online: 1–9

suppressors, while the downstream effector YAP, which is Regulation of the Hippo pathway negatively regulated by this signaling cascade, is proved to Activated by cell polarities functionally work as an oncogene in hepatic and pancreatic cancers. Ten years of researches demonstrate that the Hippo Both the liver and pancreas originate from the endodermal signaling is an intriguing pathway involved in organ size epithelia, in which cell proliferation, differentiation and control, tissue regeneration and tumorigenesis through apoptosis are closely related to the apical–basal polarity and modulating cell proliferation, differentiation and apoptosis. contact inhibition [16]. During embryogenesis, epithelial In this review, we will discuss the latest important findings on cells also exhibit planar cell polarity. The specialized the Hippo signaling pathway as well as possible means by structures are orientated within the plane of the epithelial which it can be targeted in the hepatic and pancreatic sheets [17]. In establishing planar cell polarity, the ligand development and tumorigenesis. and , DS and FAT [18], but not the subsequent pathway of Hippo signaling [8,19], are involved. Probably, the DS-FAT downstream complex formed by FRMD6, NF2 The Hippo signaling pathway components and KIBRA is relevant to the apical polarity, given that it is Nowadays, two kinds of Hippo signaling, canonical and non- located on the inner side of the apical cytoplasmic membrane. canonical, have been acknowledged. The canonical Hippo It is noteworthy that the apical–basal polarity is mainly signaling pathway consists of three parts: the upstream co-regulated by the apical polarity complexes PAR3/PAR6/ signaling components (ligands, receptors and cytoplasmic aPKC (PAR) and Crumbs/PALS1/PATJ (CRB), together with regulatory factors), the core kinases and their adaptors, and the basolateral polarity complex Scribble/DLG/LGL (SCRIB) the downstream transcriptional activators. Although the non- [20–22], all of which can activate Hippo signaling to regulate canonical Hippo signaling has not been fully elucidated yet, it cell proliferation (Figure 2). is clear that the two ways are distinct in the manner of YAP CRB controls the apical polarity of the epithelium regulation: in the canonical pathway, YAP phosphorylation is and couples Hippo signaling to sense cell density. When dependent on the MST1/2-LATS1/2 kinase cascade, whereas the breast epithelium-derived cell line Eh4 is cultured at in the non-canonical one, YAP inactivation does not require a high density, CRB can interact with the angiostatin MST1/2 and/or LATS1/2 [6]. binding Agiomotin (AMOT) in the presence of In Drosophila, surface ligand Dachsous (transmembrane PATJ. AMOT has been proved to bind to not only YAP/ cadherin, DS) and its receptor FAT have been identified as a TAZ on cytomembrane [9], but also to MST2 and LATS2 in common trigger of the Hippo signaling. DS1/2 and FAT4 are cytoplasm to activate the latter, thereby promoting phosphor- the homologous mammalian proteins; however, whether they ylation of YAP [23]. Further, p-YAP/TAZ can retain SMADs can be employed by the Hippo pathway still remains unclear in cytoplasm so as to block the TGF-b signaling and repress [7,8]. In mammals, plasma membrane linked protein FRMD6 the epithelial-mesenchymal transition (EMT) [24]. Another Drosophila Drosophila For personal use only. (Expanded in ), NF2 ( in ) apical complex PAR can be recruited by CRB from cytoplasm and KIBRA form a complex to activate MST1/2 (Mammalian to the apical membrane. It is also found to be localized at tight sterile 20-like kinase 1/2, HIPPO in Drosophila). With the junctions (TJ). KIBRA, one of the Hippo regulator compo- help of adaptor proteins SAV1 (Salvador 1, SAV in nents, is able to bind to PAR and TJ [25]. Otherwise, the Drosophila), MOBKL1A and MOBKL1B (Mps One Binder atypical aPKC in the PAR complex can kinase activator-like 1, MATS in Drosophila), MST1/2 can phosphorylate MST1/2, thereby regulating the activity of phosphorylate and activate LATS1/2 (Large tumor suppressor YAP indirectly [26]. 1/2, WTS in Drosophila) [9]. The requirement for MST1/2 to The basolateral complex SCRIB, composed of Scribble activate LATS1/2 might be cell type dependent. For instance, (SCRIB), Lethal giant larvae (LGL) and Discs large (DLG), MST1/2 knockout in mouse livers does not significantly has antagonistic effect against the PAR complex, resulting in affect LATS1/2 phosphorylation [10]. The transcription a suitable membrane proportion between apical and baso- Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 cofactors YAP/TAZ (Yes-associated protein/, Yki lateral sides. In human breast cells, SCRIB serves as an in Drosophila) are the main downstream targets of LATS1/2. adaptor to assemble a protein complex with MST, LATS and When phosphorylated by LATS1/2, p-YAP/TAZ will be TAZ, which are required for MST-dependent activation of bound by 14-3-3 protein and thus retained in cytoplasm [11]. LATS and ultimate TAZ phosphorylation [27,28]. In In humans, the serine 127 (serine 112 in mouse) of YAP and Drosophila, loss of functional LGL in the SCRIB complex the serine 89 (serine 87 in Mouse) of TAZ are required for alters the localization of HIPPO [29] and leads to an over- interaction with 14-3-3 protein. Some other serine residues growth phenotype. It is likely that the LGL-HIPPO regulation have also been shown to affect localization and function of is aPKC-dependent, as knockdown of aPKC in Hippo-mutant YAP/TAZ [12]. In case of the inactivation of the MST1/2- suppressed cell proliferation [30]. LATS1/2 kinase cascade, dephosphorylation of YAP/TAZ leads to its translocalization in nucleus, interaction with TEAD and MASK [13,14] and activation of target genes, Activated by cell junctions such as Cyclin E, AXL (AXL receptor tyrosine kinase), CTGF It is clear that the Hippo pathway plays an important role in (connective tissue growth factor) and Cyr61 (Cysteine- contact inhibition of epithelial cells, which is a well- rich angiogenic inducer 61), thereby regulation of cell known phenomenon in cell proliferation regulation. When proliferation, differentiation and apoptosis, as shown in cells are in contact, they usually adhere to one another Figure 1 [11,15]. through cell–cell junctions including adherent junctions (AJ) DOI: 10.3109/1061186X.2014.983522 Hippo signaling pathway in liver and pancreas 3

DROSOPHILA MAMMALS 1/2 S 1/2 D DS FAT4 FAT4

FRMD6 MERLIN/NF2 Expanded MERLIN KIBRA KIBRA P P MST1/2 HIPPO hSAV1 Ajuba SAV P P P P MOB1 MATS LATS1/2 WARTS P P 14-3-3 djubdj b P 14-3-3 YAP/TAZ P Yorkie YAP/TAZ YAP/TAZ P YYkiorkie Yorkie P

Yorkie YAP/TAZ CTGF,Gli2, Sd,Hth/Tsh,Mad,X Diap1,CyclinE TEADs,SMAD1/2/3,X Birc5,AREG

Inhibing apoptosis and promong proliferaon

Figure 1. Core kinases cascade of Hippo signaling pathway in drosophila and mammals. The core components of Hippo pathway are shown in yellow, while other components are shown in orange. The factors that promote the activity of YAP (Yes-associated protein) and TAZ (transcriptional co-activator with PDZ-binding motif) are shown in green, whereas those that inhibit YAP and TAZ activity are shown in red. Pointed arrowheads indicate activating interactions and blunt lines indicate inhibition. For personal use only. and TJ. Both junctions are able to activate the Hippo pathway, which was then translocated into nucleus to regulate since some junction components have been identified as apoptosis [36]. upstream regulators of the Hippo pathway. In mammals, cell adhesion mediated by homophilic Activated by mechanical forces binding of E-cadherin leads to YAP inactivation through binding to MERLIN and KIBRA [31]. Besides, the homo- Experimental data have established that cell behaviors are philic binding of E-cadherin is capable of recruiting a-catenin affected by mechanical force stimuli spreading through and b-catenin. Schlegelmilch and colleagues showed that extracellular matrix, cell junctions and ion channels. YAP is p-YAP, a-catenin and 14-3-3 can form a complex in the involved in the response of cells to stresses through activation cytoplasm. The a-catenin–14-3-3–p-YAP complex blocks of RhoA and alteration of the filamentous actin (F-actin)

Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 YAP from the protein phosphatase PP2A, which will depho- cytoskeleton [6,37]. However, whether the influence of the sphorylate and activate YAP [32,33]. mechanical strain on YAP is dependent on the canonical TJs are mainly located at the top of the basolateral sides of Hippo signaling still remains unclear. the adjacent epithelial cells. zonula occludens-1 (ZO-1), one F-actin plays an important role in cell behaviors including of the TJ proteins, can be combined with YAP/TAZ at their adhesion, migration and proliferation [38]. Interestingly, its WW domains with the help of the adaptor protein AMOT [34]. level is in positive correlation with YAP activity. In the As described above, AMOT can interact with MST and F-actin-enriched monolayer cells, a high abundance of LATS to facilitate YAP phosphorylation [23]. Interestingly, it nucleus-localized YAP was observed, while cells with has been recently shown that in cytoplasm the destructived F-actin displayed more cytoplasm-localized p130 splicing isoform of AMOT (AMOTp130) prevents the YAP [37,39,40]. Such association is mediated by the phosphorylation of YAP by blocking its WW domain access- AMOT family proteins, such as AMOTp130, in a LATS- ible to the kinase LATS1, whereas within nucleus, dependent manner. F-actin can compete with YAP for the AMOTp130 is associated with the transcriptional complex interaction with AMOTp130 thus inhibits AMOTp130- containing YAP and TEAD, and contributes to the regulation mediated cytoplasmic retention of YAP, whereas LATS, in of a subset of YAP target genes, many of which are relevant to synergy with F-actin perturbations, can phosphorylate free tumorigenesis [35]. Moreover, zonula occludens-2 (ZO-2) AMOTp130 to keep it from binding to F-actin thereby can be combined with YAP2 via the PDZ-binding motif, retaining more YAP in the cytoplasm [41]. 4 D. Kong et al. J Drug Target, Early Online: 1–9

FRMD6 MST1/2 PALS AMOT CRB KIBRA MERLIN LATS YAP PATJ MST1/2 ZO-1 p AMOT TJs LATS ZO-2 SAV MST1/2 TJs YAP p

PAR3 MOB1a/1b LATS1/2 PP2A PAR6 aPKC AJs β-catenin YAP p 14-3-3 α-catenin p MST1/2 LGL YAP LATS SCRIB YAP TAZ DLG p

YAP YAP YAP

TEAD MASK SMAD

CyclinE,CTGF,AXL,cyr61

Figure 2. Cell polarity and cell connection activate the Hippo pathway. The apical-basal polarity is mainly co-regulated by apical polarity-complex Par3/Par6/aPKC (PAR complexes), Crumbs/PALS1/PATJ (CRB complexes) and basolateral polarity complexes Scribble/DLG/LGL (SCRIB complexes). Cell–cell junctions including adherens junctions (AJ) and tight junctions (TJ) both formations are able to activate the Hippo signal.

In vitro, the kinase activity of LATS on YAP is shown to nucleus-localization shuttle of YAP according to the change

For personal use only. be modulated by small chemical molecules that interfere with of the matrix stiffness was LATS independent. Activation of microtubule (MT) assembly, indicating that MTs can regulate YAP/TAZ is regulated not only by the abundance of F-actin the Hippo pathway as well. In mammalian cells, the stability but also by the tensile force produced by cytoskeleton and of MTs is dependent on the control of TAO-1 by PAR-1 and tonofibrils, as it is sensitive to the inhibitors of ROCK, TAU, whereas TAO-1 is discovered to have physical MLCK and Myosin [47]. Despite unclear activation circuits interaction with the actin-regulators TESK1 and SPRED1 of YAP/TAZ in response to the matrix stiffness, with its [42], suggesting that TAO-1 acts at the interface of F-actin importance in the organ development and cell behaviors, and MTs [43]. Studies have shown that TAO-1 can serve as a future researches should focus more on the exploration of the partner of the Hippo pathway in phosphorylating HIPPO roles of YAP/TAZ playing in this process (Figure 3). directly [44]. This discovery provides an evidence for intricate links among MTs, F-actin and Hippo signaling [44,45].

Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 Regulation by extracellular factors A recent study in Drosophila displayed that increasing or decreasing the physical tension of the cytoskeleton affected Extracellular signaling molecules play important roles in cell cell proliferation by alteration of Yki activity, which was normal physiology and pathogenesis. At present, a variety of modulated by the F-actin-binding myosin. A high concentra- extracellular factors have been identified to regulate cell tion of myosin is usually observed at AJ, where it can bind to behaviors by activating YAP/TAZ directly or cross-talking a-catenin with high affinity under the assistance of Ajuba with the Hippo pathway indirectly. As reported in Drosophila, LIM (JUB), a tension sensor. When cells are confronted with epidermal growth factor receptor (EGFR) is able to facilitate tension force, the binding of myosin to a-catenin, triggered by cell proliferation in an Yki-dependent way. EGFR phosphor- JUB, will recruit WTS to regulate YAP, thereby controlling ylates the JUB protein via the RAS-RAF-MAPK kinase cell proliferation [46]. A similar mechanism might act in cascade, and then p-JUB binds to the kinase WTS and its mammalian cells given the conserved sensing apparatus and adaptor SAV to block WTS from phosphorylating Yki, pathway molecules. thereby releasing Yki into nucleus [48]. In mammals, there It should be noted that the response of cells to the exists a similar EGFR-Hippo pathway, in which activation of extracellular matrix hardness is distinct from that to the EGFR or RAS promotes phosphorylation of the JUB family mechanical forces. In cells cultured on hard matrix, YAP is protein WTIP and enhances the binding of WTIP to MST and located in nucleus at a high abundance, while cultured on soft LATS to inhibit YAP phosphorylation [48]. Recently, another matrix, the YAP nucleus-localization disappears. Such EGFR downstream pathway that is essential in cell growth, DOI: 10.3109/1061186X.2014.983522 Hippo signaling pathway in liver and pancreas 5 Figure 3. Mechanical stretch activates the Stress Tension Hippo pathway. The extracellular physical PCR

tension can influence the F-actin, which can G Ajuba α-catenin eventually alter YAP activity. GPCR,G Myosin protein-coupled receptor. β-catenin AJs MT TAO-1 MST1/2

AMOT RhoA LATS1/2 YAP P F-acn

YAP AMOT YAP F-acn

YAP TEAD Transcripon

Glucagon LPA,SIP EGFR wnt the PI3K pathway, has been demonstrated to communicate epinephrine Frizzled with the Hippo pathway. When activated by EGF, PI3K phosphorylates its downstream kinase PDK1, and then p- PBK SOS Gα 12/13 GS

PDK1 interacts with the adaptor protein SAV to restrain PDKI RB2 G LATS from phosphorylating YAP, leading to nuclear accu- RAS GSK3 β RAF Axin β-catenin mulation of YAP and cell proliferation [49]. P In addition to growth factors, several serum factors can SAV MEK APC also regulate cell proliferation via controlling YAP activity. MST1/2 MAPK Ajuba Lysophosphatidic acid (LPA) and sphingosine 1-phospho- P a LATS1/2 phate (S1P), residing in serum, act through G 12/13-coupled β-catenin MOBS

For personal use only. receptors to inhibit the Hippo kinases LATS1/2 and then promote the nucleus localization of YAP/TAZ [50,51].

Moreover, the PI3K-PDK1 pathway mediates the inhibitory YAP YAP P β-catenin effect of LPA on the Hippo pathway as well [49]. Another serum component thrombin binds to its Ga12/13-coupled YAP YAP receptor PAR1 to activate RhoA and F-actin polymeration or TEAD β-catenin tensile fiber formation, and then elevate YAP/TAZ activity [52]. Conversely, glucagon or epinephrine acts through their Transcrip on Gs-coupled receptors to activate LATS1/2 kinase activity and then inhibit YAP nuclear accumulation [50]. Figure 4. Extracellular factors activate or inhibit Hippo signaling Extracellular matrix, including fibronectin, laminin and pathway. A variety of extracellular factors have been identified activating

Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 collagen, binds to the cell surface integrin receptors to YAP/TAZ directly or cross talking with Hippo pathway indirectly. The MAPK signal is shown in grey. activate integrin-linked kinase (ILK) and exerts a great effect on cell survival, proliferation and migration. Recently, ILK is found to be able to suppress the Hippo pathway via presence of Wnt, YAP/TAZ are unloaded from the destruction inactivation of the myosin phosphatase MYPT1-PP1, which complex, allowing their nuclear accumulation and activation can dephosphorylate and activate Merlin. Inhibition of ILK in of both Wnt and YAP/TAZ dependent biological effects breast, prostate and colon tumor cells results in activation of (Figure 4) [55]. MST1 and LATS1 with concomitant inactivation of YAP/ Hippo pathway in liver and pancreas TAZ and TEAD-mediated transcription [53]. Wnt family proteins, a group of well-known secreted Recently, many researchers have revealed the function of glycoproteins, bind to a Frizzled family receptor to facilitate an Hippo pathway as a key regulator of organ growth, providing accumulation of b-catenin in cytoplasm and prevent its novel insight into the mechanisms that control organ size. translocation into nucleus to act as a transcriptional co- Although much progress has been made in understanding the activator of the TCF/LEF family [54]. There exists an extensive molecular mechanisms of among the crosstalk between Wnt and Hippo pathways. In the absence of cascade, other aspects such as functions in hepatic and Wnt, YAP/TAZ is essential for recruiting b-TrCP to the pancreatic developments have not been well explored and destruction complex of b-catenin and its inactivation. In the remain to be studied. In addition, it is considerable to 6 D. Kong et al. J Drug Target, Early Online: 1–9

recognize the Hippo signaling as a tumor suppressor pathway, Notch signaling pathway is an important co-effector in while the YAP/TAZ-TEAD transcription factor complex YAP-induced cell proliferation (Yimlamai et al., 2014). In represents a common target of oncogenic transformation HCC, YAP upregulates Jagged1 to trigger the Notch pathway [56]. Overactivation of the downstream effectors YAP and co- and then promotes the HES1-induced survival and migration, activator TAZ results in the development of cancers, which committing high-death rate in HCC patients [75]. YAP is indicates that YAP or TAZ may be an effective anticancer also found to have cross potentiation with b-catenin in target in tumor therapy [15,57]. Interestingly, in human hepatoblastoma. Immunohistochemical data displayed about cancers including medulloblastomas and esophagus tumor, 70% co-localization of YAP and b-catenin in the nuclei of none of them have been attributed to mutations or loss of the hepatoblastoma, but not hepatocellular carcinoma and core components of the Hippo pathway [58,59]. Given that intrahepatic bile duct cancer. Additionally, acute postnatal these cases have been well-summarized recently, we will overexpression of YAP1 and b-catenin in murine liver leads to discuss only hepatic and pancreatic development/cancer- rapid turmorigenesis, and mortality is as high as 100% within related reports in the following subsections. 11 weeks [76].

Regulation of liver development and tumorigenesis Regulation of pancreas development and by the Hippo pathway tumorigenesis by the Hippo pathway Liver development is intricately regulated by multiple signals, Pancreas consists of two types of glandular tissue: exocrine in which Hippo pathway plays a key role in liver size acini and endocrine islets, they are responsible for producing determination [60]. Conditional overexpression of YAP in enzymes to digest foods and hormones to sustain proper blood transgenic mouse led to a significant augment of liver via sugar levels, respectively [77]. During pancreas development, increasing cell number. Conversely, this phenotype was all exocrine and endocrine cells are derived from a same reverted back to the original level when overexpression was population of multipotent progenitors [78,79]. Recent reports stopped [59,61]. Similarly, loss of the Hippo signaling indicate that the Hippo pathway is involved in this process. upstream components including MST1/2, SAV or MERLIN YAP1 is highly expressed in mouse pancreatic multipotent in hepatocytes results in enlarged liver due to excessive cells at E12.5 [80], then its expression disappears in endocrine proliferation [62]. These data demonstrate that the Hippo progenitors and is limited in the exocrine progenitors at signaling regulates liver growth and size in vivo in a MST- E16.5, which are able to form ducts and acini. During the dependent manner. Interestingly, one report showed that second transition in pancreas development, overexpression of MST1/2 inactivation in the liver resulted in deregulation of YAP1 will repress both endocrine and exocrine differenti- MOB1 and YAP1 but not LATS1/2, indicating that MST1/2 ations. Unlike in liver, loss of MST1/2 or YAP does not affect inactivates YAP1 in liver through an intermediary kinase the pancreas size, whereas doxycycline-inducible overexpres- sion of YAP in mouse significantly decreases acinar cells,

For personal use only. distinct from LATS1/2 [10]. It has been found that liver cancer frequently harbors an increases ductal cells and causes late pancreatitis-like pheno- amplification of the Yap gene [64]. The constitutive expres- type [80,81]. At present, it is considered that YAP promotes sion of YAP-Ser127A or liver-specific knockout of Sav1 or pancreatic progenitor cell proliferation, but inhibits their Mst1/2 for a long-term cause overproliferation and anti- differentiation. Our study has indicated that knock-down apoptotic features of the hepatic cells resembling those in of YAP in pancreatic progenitors leads to proliferation liver cancer [65]. Furthermore, liver-specific knockout of the arrest [82]. upstream regulator NF2 (MERLIN) can also lead to carcino- Pancreatic ductal adenocarcinoma (PDAC) is one of the genesis [66,67], which has been already demonstrated to cancers with high mobility, as reported with a less than 5% result from increased YAP in nucleus [10]. Dramatically, the survival rate in 5 years post morbidity. Using the PDAC out-growth of liver oval progenitors was observed in Sav1, samples, YAP1 is detected by immunostaining to be abundant Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 Nf2 and Mst1/2 mutant mice [67–69]. In early views, hepatic in both nucleus and cytoplasm. YAP RNAi in BxPC-3 and tumorigenesis depends on a lack of differentiation of oval PAN-1 cell lines significantly suppresses cell proliferation progenitors [70]. However, recent reports did show that and anchorage-independent growth in soft agar, suggesting activation of YAP and disorder of the Hippo pathway was the positive regulation of YAP1 in PDAC formation [83]. capable of promoting mature hepatic cells dedifferentiation Genetic detection indicates that more than 90% of PDAC into oval cells, providing an assumption that the mature liver patients display mutations in proto-oncogene KRAS, which cells might be the origin of ductal carcinoma or other mixed constitutively activates RAF-MEK-ERK signal, resulting in abnormal cell proliferation [84,85]. In Trp53R172H mouse types of cancer [71]. +/+ In human hepatoma cell (HCC) samples, YAP is closely (KrasG12D ), pancreas-specific knockout of YAP pre- related to c-Myc, and its transcription can be promoted by vented PDAC effectively, showing that YAP is an important YAP acting on c-Abl. In turn, c-Myc is also capable of downstream effectors of KRAS in PDAC [86]. enhancing the expression of YAP [72]. In addition, YAP, activated via the non-canonical Hippo pathway, interacts with Application of small molecules targeting the the cyclic adenosine monophosphate response element-bind- Hippo pathway in potential therapy of liver ing protein (CREB) [73] to elevate the expression of the long and pancreas cancers non-coding RNA Malat1 (metastasis-associated lung adeno- Lack of effective drugs leads to the high recurrence of carcinoma transcript 1) to facilitate liver cancer [74]. the liver and pancreas cancers. Nowadays, doxorubicin is DOI: 10.3109/1061186X.2014.983522 Hippo signaling pathway in liver and pancreas 7

In addition, the chemical compound dobutamine has been MST1/2 Epinephrine shown to pharmacologically export YAP from nucleus by Dobutamine cAMP C19 activating heterotrimeric G protein [63]. C19, a newly Inhibitors of forskolin or phosphodiesterase LATS1/2 discovered small molecule inhibitor, is able to inhibit EMT and cell proliferation, so as to suppress tumorigenesis and miR-375 metastasis [91]. C19 can simultaneously inhibit Hippo, Wnt YAP and TGF-b pathways: it induces GSK3b-mediated TAZ P degradation, through activation of the Hippo kinases MST/ YAP P 14-3-3 LATS and the tumor suppressor kinase AMPK, which is an YAP upstream regulator of the degradation complex of YAP [92]. SRSF1 Besides, several other small molecules have been reported to VGLL4 PPIX Dobutamine be viable in targeting the upstream components of the Hippo tenin YAP YAP VP YAP HP pathway in preliminary experiments, including adrenoceptor β-ca TEAD inhibitors (dobutamine and epinephrine), forskolin and

Malat1 Transcripon phosphodiesterase (PDE) inhibitors, cAMP activators, LATS1/2 activators, YAP/TAZ phosphatase and inhibitors [19–21]. These molecules could be further tested as thera- Figure 5. Some small molecules have potential application in therapy of peutic candidates for liver, pancreas and other tissue cancers liver and pancreas cancer. Small molecules act on Hippo pathway through inhibiting its upstream kinase or downstream effectors. SRF1, (Figure 5). serine/arginine-rich splicing factor 1; VGLL4, vestigial-like protein 4; PPIX, protoporphyrinIX; VP, verteporfin; HP, hematoporphyrin. Conclusion The Hippo signaling pathway plays a significant role in the commonly used in the treatment of liver cancer. However, the physiology and pathology of liver and pancreas. Under normal overexpression of YAP leads to more resistant HCCs against physiological conditions, the Hippo pathway is controlled the doxorubicin-induced apoptosis [87]. For PDAC, there are precisely to guarantee cell response to the changes of polarity, no effective therapeutic drugs reported for KRAS so far. Since density, mechanical forces and extracellular signals. Under YAP is a key oncogene for liver cancer and an important co- pathological conditions, disorders of the Hippo pathway can factor for KRAS-carcinogenic PDAC, the Hippo signaling lead to tumorigenesis of liver and pancreas. Small molecules components are considered as therapeutic targets in liver and targeting the Hippo signaling components are viable to pancreas cancer. effectively inhibit experimental tumorigenesis of liver and The C-terminal PDZ-binding domain of YAP is highly pancreas. Exploration of the crosstalk between Hippo signaling conserved, which is responsible for multi-regulatory effects of and other pathways in liver and pancreas will gain further For personal use only. YAP. Loss of the PDZ-domain inhibits nucleus localization of insights into new strategies for modulating cell behaviors in YAP and the expression of CTGF significantly, as such the tissue growth, organ regeneration or cancer treatment. YAP-induced carcinogenesis [88]. In Drosophila, scalloped (TEAD homologue) is required in Acknowledgements excessive cell proliferation mediated by Yki but not in normal tissue growth, which implies that suppressing the scalloped We apologize for those primary works that are not cited in homologues may be able to selectively inhibit the YAP- this review for space constraints. We are thankful to Dr. M.H mediated tumor growth in mammals. It has been confirmed in and L.Y for their editing work on our manuscript and figures. mouse that dominant deactivation of TEAD in normal liver does not alter cell proliferation, but suppresses tumorigenesis Declaration of interest induced by YAP overexpression or NF2/MERLIN inactiva- The authors report no declarations of interest. D.K, Y.Z and Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 tion [89]. Administration of verteporfin, an inhibitor of the T.M wrote the main manuscript, C.B.T. supervised the project YAP-TEAD interaction, to the YAP-overexpressed mice can and gave final approval. Research in the laboratory of C.B.T. weaken tumorigenesis [89] and does not significantly influ- is supported by grants from the National Natural Science ence the liver development and homeostasis [66]. In a drug Foundation of China (No. 31272520 and J1210053). screen assay containing more than 3300 small molecules, besides verteporfin, more YAP-TEAD inhibitors such as References porphyrin, hematoporphyrin (HP) and protoporphyrin IX 1. Li MD, Li CM, Wang Z. The role of circadian clocks in metabolic (PPIX) were identified, and all of them are able to inhibit the disease. Yale J Biol Med 2012;85:387–401. disorders caused by the inactivation of the Hippo upstream 2. Zaret KS, Grompe M. Generation and regeneration of cells of the signals [90]. In a recent report, VGLL4 and YAP were liver and pancreas. Science 2008;322:1490–4. found to compete for the direct binding to TEAD. The binding 3. Dor Y, Stanger BZ. Regeneration in liver and pancreas: time to cut the umbilical cord? Sci STKE 2007;2007:pe66. domain of VGLL4 is essential for its regulatory effect, 4. Huang JB, Wu S, Barrera J, et al. The Hippo signaling pathway and several polypeptide analogs of VGLL4 are able to coordinately regulates cell proliferation and apoptosis by inactivat- repress tumors both in vivo and in vitro [91]. Above all, ing Yorkie, the Drosophila homolog of YAP. Cell 2005;122: disrupting the YAP–TEAD interaction by small molecules or 421–34. 5. Dong J, Feldmann G, Huang J, et al. Elucidation of a universal size- polypeptide analogs is feasible in curing the YAP-mediated control mechanism in Drosophila and mammals. Cell 2007a;130: carcinogenesis. 1120–33. 8 D. Kong et al. J Drug Target, Early Online: 1–9

6. Low BC, Pan CQ, Shivashankar GV, et al. YAP/TAZ as 32. Silvis MR, Kreger BT, Lien WH, et al. Alpha-catenin is a tumor mechanosensors and mechanotransducers in regulating organ size suppressor that controls cell accumulation by regulating the and tumor growth. FEBS Lett 2014;588:2663–70. localization and activity of the transcriptional coactivator Yap1. 7. Cappello S, Gray MJ, Badouel C, et al. Mutations in genes Sci Signal 2011;4:ra33. encoding the cadherin receptor-ligand pair DCHS1 and FAT4 33. Schlegelmilch K, Mohseni M, Kirak O, et al. Yap1 acts downstream disrupt cerebral cortical development. Nat Genet 2013;45:1300–8. of alpha-catenin to control epidermal proliferation. Cell 2011;144: 8. Bossuyt W, Chen CL, Chen Q, et al. An evolutionary shift in the 782–95. regulation of the Hippo pathway between mice and flies. Oncogene 34. Yi C, Troutman S, Fera D, et al. A tight junction-associated Merlin- 2014;33:1218–28. angiomotin complex mediates Merlin’s regulation of mitogenic 9. Zhao B, Li L, Lu Q, et al. Angiomotin is a novel Hippo pathway signaling and tumor suppressive functions. Cancer Cell 2011;19: component that inhibits YAP oncoprotein. Genes Dev 2011;25: 527–40. 51–63. 35. Yi C, Shen Z, Stemmer-Rachamimov A, et al. The p130 isoform of 10. Zhou D, Conrad C, Xia F, et al. Mst1 and Mst2 maintain hepatocyte angiomotin is required for Yap-mediated hepatic epithelial cell quiescence and suppress hepatocellular carcinoma development proliferation and tumorigenesis. Sci Signal 2013;6:ra77. through inactivation of the Yap1 oncogene. Cancer Cell 2009;16: 36. Oka T, Remue E, Meerschaert K, et al. Functional complexes 425–38. between YAP2 and ZO-2 are PDZ domain-dependent, and regulate 11. Zhao B, Li L, Lei Q, Guan KL. The Hippo-YAP pathway in organ YAP2 nuclear localization and signalling. Biochem J 2010;432: size control and tumorigenesis: an updated version. Genes Dev 461–72. 2010;24:862–74. 37. Zhao B, Li L, Wang L, et al. Cell detachment activates the Hippo 12. Kanai F, Marignani PA, Sarbassova D, et al. TAZ: a novel pathway via cytoskeleton reorganization to induce anoikis. Genes transcriptional co-activator regulated by interactions with 14-3-3 Dev 2012;26:54–68. and PDZ domain proteins. EMBO J 2000;19:6778–91. 38. Mammoto A, Ingber DE. Cytoskeletal control of growth and cell 13. Sansores-Garcia L, Atkins M, Moya IM, et al. Mask is required for fate switching. Curr Opin Cell Biol 2009;21:864–70. the activity of the Hippo pathway effector Yki/YAP. Curr Biol 39. Wada K, Itoga K, Okano T, et al. Hippo pathway regulation by cell 2013;23:229–35. morphology and stress fibers. Development 2011;138:3907–14. 14. Sidor CM, Brain R, Thompson BJ. Mask proteins are cofactors of 40. Aragona M, Panciera T, Manfrin A, et al. A mechanical checkpoint Yorkie/YAP in the Hippo pathway. Curr Biol 2013;23:223–8. controls multicellular growth through YAP/TAZ regulation by 15. Zhao B, Lei QY, Guan KL. The Hippo-YAP pathway: new actin-processing factors. Cell 2013;154:1047–59. connections between regulation of organ size and cancer. Curr Opin 41. Mana-capelli S, Paramasivam M, Dutta S, Mccollum D. Cell Biol 2008;20:638–46. Angiomotins link F-actin architecture to Hippo pathway signaling. 16. Ijichi H. Development of basic research of pancreatic cancer: from Mol Biol Cell 2014;25:1676–85. genetically-engineered mouse models to bedside. Nihon 42. King I, Heberlein U. Tao kinases as coordinators of actin and Shokakibyo Gakkai Zasshi 2014;111:1561–9. microtubule dynamics in developing neurons. Commun Integr Biol 17. St Johnston D, Ahringer J. Cell polarity in eggs and epithelia: 2011;4:554–6. parallels and diversity. Cell 2010;141:757–74. 43. Xiao ZG, Liu H, Fu JP, et al. Cloning of common carp SOCS-3 18. Thomas C, Strutt D. The roles of the cadherins fat and dachsous in gene and its expression during embryogenesis, GH-transgene and planar polarity specification in drosophila. Dev Dyn 2012;241: viral infection. Fish Shellfish Immunol 2010;28:362–71. 27–39. 44. Poon CL, Lin JI, Zhang X, Harvey KF. The sterile 20-like kinase 19. Irvine KD. Integration of intercellular signaling through the Hippo Tao-1 controls tissue growth by regulating the Salvador-Warts- pathway. Semin Cell Dev Biol 2012;23:812–17. Hippo pathway. Dev Cell 2011;21:896–906. 20. Tanentzapf G, Tepass U. Interactions between the crumbs, lethal 45. Boggiano JC, Vanderzalm PJ, Fehon RG. Tao-1 phosphorylates For personal use only. giant larvae and bazooka pathways in epithelial polarization. Nat Hippo/MST kinases to regulate the Hippo-Salvador-Warts tumor Cell Biol 2013;5:46–52. suppressor pathway. Dev Cell 2011;21:888–95. 21. Johnson K, Wodarz A. A genetic hierarchy controlling cell polarity. 46. Rauskolb C, Sun S, Sun G, et al. Cytoskeletal tension inhibits Nat Cell Biol 2003;5:12–14. Hippo signaling through an Ajuba-Warts complex. Cell 2014;158: 22. Bilder D, Schober M, Perrimon N. Integrated activity of PDZ 143–56. protein complexes regulates epithelial polarity. Nat Cell Biol 2013; 47. Dupont S, Morsut L, Aragona M, et al. Role of YAP/TAZ in 5:53–8. mechanotransduction. Nature 2011;474:179–83. 23. Paramasivam M, Sarkeshik A, Yates III JR, et al. Angiomotin 48. Reddy BV, Irvine KD. Regulation of Hippo signaling by EGFR- family proteins are novel activators of the LATS2 kinase tumor MAPK signaling through Ajuba family proteins. Dev Cell 2013;24: suppressor. Mol Biol Cell 2011;22:3725–33. 459–71. 24. Varelas X, Samavarchi-Tehrani P, Narimatsu M, et al. The crumbs 49. Fan R, Kim NG, Gumbiner BM. Regulation of Hippo pathway by complex couples cell density sensing to Hippo-dependent control of mitogenic growth factors via phosphoinositide 3-kinase and the TGF-beta-SMAD pathway. Dev Cell 2010;19:831–44. phosphoinositide-dependent kinase-1. Proc Natl Acad Sci USA Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 25. Yoshihama Y, Sasaki K, Horikoshi Y, et al. KIBRA suppresses 2013;110:2569–74. apical exocytosis through inhibition of aPKC kinase activity in 50. Yu FX, Zhao B, Panupinthu N, et al. Regulation of the Hippo-YAP epithelial cells. Curr Biol 2011;21:705–11. pathway by G-protein-coupled receptor signaling. Cell 2012;150: 26. Buther K, Plaas C, Barnekow A, Kremerskothen, J. KIBRA is a 780–91. novel substrate for protein kinase Czeta. Biochem Biophys Res 51. Miller E, Yang J, Deran M, et al. Identification of serum-derived Commun 2004;317:703–7. sphingosine-1-phosphate as a small molecule regulator of YAP. 27. Cordenonsi M, Zanconato F, Azzolin L, et al. The Hippo transducer Chem Biol 2012;19:955–62. TAZ confers cancer stem cell-related traits on breast cancer cells. 52. Regue L, Mou F, Avruch J. G protein-coupled receptors engage the Cell 2011;147:759–72. mammalian Hippo pathway through F-actin: F-Actin, assembled in 28. Chen D, Sun Y, Wei Y, et al. LIFR is a breast cancer metastasis response to Galpha12/13 induced RhoA-GTP, promotes depho- suppressor upstream of the Hippo-YAP pathway and a prognostic sphorylation and activation of the YAP oncogene. Bioessays 2013; marker. Nat Med 2012;18:1511–17. 35:430–5. 29. Grzeschik NA, Parsons LM, Allott ML, et al. Lgl, aPKC, and 53. Serrano I, Mcdonald PC, Lock F, et al. Inactivation of the Hippo Crumbs regulate the Salvador/Warts/Hippo pathway through two tumour suppressor pathway by integrin-linked kinase. Nat Commun distinct mechanisms. Curr Biol 2010;20:573–81. 2013;4:2976–88. 30. Klezovitch O, Fernandez TE, Tapscott SJ, Vasioukhin V. Loss of 54. Macdonald BT, Tamai K, He X. Wnt/beta-catenin signal- cell polarity causes severe brain dysplasia in Lgl1 knockout mice. ing: components, mechanisms, and diseases. Dev Cell 2009;17: Genes Dev 2004;18:559–71. 9–26. 31. Moleirinho S, Chang N, Sims AH, et al. KIBRA exhibits MST- 55. Azzolin L, Panciera T, Soligo S, et al. YAP/TAZ incorporation in independent functional regulation of the Hippo signaling pathway the beta-catenin destruction complex orchestrates the Wnt response. in mammals. Oncogene 2013;32:1821–30. Cell 2014;158:157–70. DOI: 10.3109/1061186X.2014.983522 Hippo signaling pathway in liver and pancreas 9

56. Johnson R, Halder G. The two faces of Hippo: targeting the Hippo human hepatocellular carcinoma. Gastroenterology 2013;144: pathway for regenerative medicine and cancer treatment. Nat Rev 1530–42.e12. Drug Discov 2014;13:63–79. 76. Tao J, Calvisi DF, Ranganathan S, et al. Activation of beta-catenin 57. Zhao Y, Khanal P, Savage P, et al. YAP-induced resistance of and Yap1 in human hepatoblastoma and induction of hepatocarci- cancer cells to antitubulin drugs is modulated by a Hippo- nogenesis in mice. Gastroenterology 2014;147:690–701. independent pathway. Cancer Res 2014;74:4493–503. 77. Gittes GK. Developmental biology of the pancreas: a comprehen- 58. Harvey KF, Zhang X, Thomas DM. The Hippo pathway and human sive review. Dev Biol 2009;326:4–35. cancer. Nat Rev Cancer 2013;13:246–57. 78. Gu G, Dubauskaite J, Melton DA. Direct evidence for the 59. Gomez M, Gomez V, Hergovich A. The Hippo pathway in disease pancreatic lineage: NGN3+ cells are islet progenitors and are and therapy: cancer and beyond. Clin Transl Med 2014;3:22–4. distinct from duct progenitors. Development 2002;129:2447–57. 60. Dong J, Feldmann G, Huang J, et al. Elucidation of a universal size- 79. Kawaguchi Y, Cooper B, Gannon M, et al. The role of the control mechanism in Drosophila and mammals. Cell 2007b;130: transcriptional regulator Ptf1a in converting intestinal to pancreatic 1120–33. progenitors. Nat Genet 2002;32:128–34. 61. Camargo FD, Gokhale S, Johnnidis J.B, et al. YAP1 increases organ 80. George NM, Day, CE, Boerner BP, et al. Hippo signaling regulates size and expands undifferentiated progenitor cells. Curr Biol 2007; pancreas development through inactivation of Yap. Mol Cell Biol 17:2054–60. 2012;32:5116–28. 62. Avruch J, Zhou D, Fitamant J, Bardeesy N. Mst1/2 signalling to 81. Gao T, Zhou D, Yang C, et al. Hippo signaling regulates Yap: gatekeeper for liver size and tumour development. Br J Cancer differentiation and maintenance in the exocrine pancreas. 2011;104:24–32. Gastroenterology 2013;144:1543–53, 1553 e1. 63. Bao Y, Nakagawa K, Yang Z, et al. A cell-based assay to screen 82. Zhang ZW, Men T, Feng RC, et al. miR-375 inhibits proliferation of stimulators of the Hippo pathway reveals the inhibitory effect of mouse pancreatic progenitor cells by targeting YAP1. Cell Physiol dobutamine on the YAP-dependent gene transcription. J Biochem Biochem 2013;32:1808–17. 2011;150:199–208. 83. Diep CH, Zucker KM, Hostetter G, et al. Down-regulation of Yes 64. Zender L, Spector MS, Xue W, et al. Identification and validation Associated Protein 1 expression reduces cell proliferation and of oncogenes in liver cancer using an integrative oncogenomic clonogenicity of pancreatic cancer cells. PLoS One 2012;7:e32783. approach. Cell 2006;125:1253–67. 84. Almoguera C, Shibata D, Forrester K, et al. Most human 65. Jie L, Fan W, Weiqi D, et al. The hippo-yes association protein carcinomas of the exocrine pancreas contain mutant c-K-ras pathway in liver cancer. Gastroenterol Res Pract 2013;2013: genes. Cell 1988;53:549–54. 187070. 85. Kong B, Qia C, Erkan M, et al. Overview on how oncogenic Kras 66. Zhang N, Bai H, David KK, et al. The Merlin/NF2 tumor promotes pancreatic carcinogenesis by inducing low intracellular suppressor functions through the YAP oncoprotein to regulate ROS levels. Front Physiol 2013;4:246–55. tissue homeostasis in mammals. Dev Cell 2010;19:27–38. 86. Zhang W, Nandakumar N, Shi Y, et al. Downstream of mutant 67. Benhamouche S, Curto M, Saotome I, et al. Nf2/Merlin controls progenitor homeostasis and tumorigenesis in the liver. Genes Dev KRAS, the transcription regulator YAP is essential for neoplastic 2010;24:1718–30. progression to pancreatic ductal adenocarcinoma. Sci Signal 2014; 68. Lee KP, Lee JH, Kim TS, et al. The Hippo-Salvador pathway 7:ra42. restrains hepatic oval cell proliferation, liver size, and liver 87. Huo X, Zhang Q, Liu AM, et al. Overexpression of Yes-associated tumorigenesis. Proc Natl Acad Sci USA 2010;107:8248–53. protein confers doxorubicin resistance in hepatocellullar carcinoma. 69. Lu L, Li, Y, Kim SM, et al. Hippo signaling is a potent in vivo Oncol Rep 2013;29:840–6. growth and tumor suppressor pathway in the mammalian liver. Proc 88. Shimomura T, Miyamura N, Hata S, et al. The PDZ-binding motif Natl Acad Sci USA 2010;107:1437–42. of Yes-associated protein is required for its co-activation of TEAD-

For personal use only. 70. Alison MR. Liver stem cells: implications for hepatocarcinogen- mediated CTGF transcription and oncogenic cell transforming esis. Stem Cell Rev 2005;1:253–60. activity. Biochem Biophys Res Commun 2014;443:917–23. 71. Yimlamai D, Christodoulou C, Galli GG, et al. Hippo pathway 89. Liu-Chittenden Y, Huang B, Shim JS, et al. Genetic and pharma- activity influences liver cell fate. Cell 2014;157:1324–38. cological disruption of the TEAD-YAP complex suppresses the 72. Xiao W, Wang J, Ou C, et al. Mutual interaction between YAP and oncogenic activity of YAP. Genes Dev 2012;26:1300–5. c-Myc is critical for carcinogenesis in liver cancer. Biochem 90. Li XJ, Leem SH, Park MH, Kim SM. Regulation of YAP through Biophys Res Commun 2013;439:167–72. an Akt-dependent process by 3,30-diindolylmethane in human colon 73. Wang J, Ma L, Weng W, et al. Mutual interaction between YAP and cancer cells. Int J Oncol 2013;43:1992–8. CREB promotes tumorigenesis in liver cancer. Hepatology 2013; 91. Jiao S, Wang H, Shi Z, et al. A peptide mimicking VGLL4 58:1011–20. function acts as a YAP antagonist therapy against gastric cancer. 74. Wang J, Wang H, Zhang Y, et al. Mutual inhibition between YAP Cancer Cell 2014;25:166–80. and SRSF1 maintains long non-coding RNA, Malat1-induced 92. Basu D, Lettan R, Damodaran K, et al. Identification, mechanism tumourigenesis in liver cancer. Cell Signal 2014;26:1048–59. of action, and antitumor activity of a small molecule inhibitor of

Journal of Drug Targeting Downloaded from informahealthcare.com by 61.180.240.144 on 12/03/14 75. Tschaharganeh DF, Chen X, Latzko P, et al. Yes-associated hippo, TGF-beta, and Wnt signaling pathways. Mol Cancer Ther protein up-regulates Jagged-1 and activates the Notch pathway in 2014;13:1457–67.