Activated C-Abl Tyrosine Kinase in Malignant Solid Tumors

J Lin and R Arlinghaus

Department of Molecular Pathology, MD Anderson Cancer Center, University of Texas, Houston, TX, USA

Mutant forms of the c-ABL gene are well known to be lesser degree in acute lymphocytic B-cell leukemia. Over involved in hematopoietic malignancies such as chronic 95% of CML patients have an abnormal chromosome myeloid leukemia (CML). CML patients possess a fused 22 known as the Philadelphia chromosome (Ph). The Ph BCR-ABL gene that activates the Abl tyrosine kinase fuses 50 portions of BCR to the second exon of the domain within Bcr-Abl. In general fusion proteins that c-ABL gene. The first exon of c-ABL encodes sequences cause oligomerization of Abl lead to activation of its involved in the autoinhibition of the c-Abl tyrosine tyrosine kinase activity. In this review, we highlight recent kinase, so deletion of these sequences is thought to discoveries indicating that the activated c-Abl tyrosine contribute to the activated state of the Abl tyrosine kinase, not as a fusion protein, plays an important role in kinase domain. malignant solid tumors of lung and breast. Our recent findings demonstrate that activated c-Abl Oncogene (2008) 27, 4385–4391; doi:10.1038/onc.2008.86; tyrosine kinase may also play a role in non-small cell published online 7 April 2008 lung cancer (NSCLC) (Lin et al., 2005, 2007). Activation of c-Abl tyrosine kinase in some solid tumors is further Keywords: c-Abl; FUS1; NSCLC; lung cancer; supported by studies from Plattner and co-workers imatinib; breast cancer (Srinivasan and Plattner, 2006; Srinivasan et al., 2008), whose findings indicate active c-Abl tyrosine kinase plays a role in aggressive human breast cancer cell lines.

Introduction Activated c-Abl in non-small cell lung cancer The c-Abl protein is a tightly regulated nonreceptor tyrosine kinase that is involved in the regulation of cell Lung cancer, the leading cause of cancer-related proliferation, cell survival, cell adhesion, cell migration mortalities in the United States (US Cancer Statistics and apoptosis. The c-Abl protein is located both in the Working Group, 2004), is divided into two major nucleus and the cytoplasm. In the nucleus, c-Abl protein subgroups, small cell lung carcinomas (SCLC) and is known to be activated in response to DNA damage NSCLC. Depending on the type and stage of the and contributes to apoptosis (Wang, 2000). Cytoplasmic disease, treatment for lung cancer includes tumor c-Abl is associated with growth factor receptor signaling resection, chemotherapy and radiation therapy. that can affect cell mobility and cell adhesion (Taage- Recently, new approaches in the treatment of NSCLC pera et al., 1998). The oncogenic effects of Abl are have arisen from the discovery that the epithelial growth believed to reside in cytoplasmic forms of c-Abl. Several factor receptor (EGFR) is frequently overexpressed and studies have shown that c-Abl is downregulated in part activated in NSCLC (Bunn and Franklin, 2002; Dowell by intramolecular interactions that provide autoinhibi- and Minna, 2005). Importantly, loss of sequences within tory kinase effects (Pendergast, 2002; Pluk et al., 2002; chromosome 3p is frequently seen in both SCLC and Hantschel et al., 2003). Studies have also found that NSCLC, providing evidence of tumor suppressor genes c-Abl kinase activity is regulated by intermolecular (TSGs) in this chromosomal region (Girard et al., 2000; interactions with negative regulators, which include Zabarovsky et al., 2002). The FUS1 gene has been Bcr (Liu et al., 1996; Ling et al., 2003), PAG (Wen identified in the 3p21.3 critical chromosomal region and and Van Etten, 1997), F-actin (Woodring et al., 2003) is considered a novel TSG (Ji et al., 2002; Zabarovsky and phosphoinositides (Plattner and Pendergast, 2003). et al., 2002). The c-Abl protein is widely expressed in all tissues and Our studies showing that the c-Abl tyrosine kinase is until recently oncogenically activated forms of Abl were involved in NSCLC began during a screening of believed to be restricted to hematopoietic malignancies, synthetic peptides that had inhibitory activity towards principally chronic myeloid leukemia (CML) and to a the c-Abl tyrosine kinase in an assay involving the phosphorylation of a GST-Crk peptide. The c-Crk protein is a known target of the c-Abl kinase. Of Correspondence: Professor R Arlinghaus, Department of Molecular Pathology, The MD Anderson Cancer Center, University of Texas, interest, increased levels of c-Crk are associated with an 1515 Holcomb Boulevard, Houston, TX 77054, USA. aggressive phenotype in lung adenocarcinoma (Miller E-mail: [email protected] et al., 2003). This screening assay revealed that a small Activated c-Abl in lung and breast cancer cell lines J Lin and R Arlinghaus 4386 peptide derived from sequences deleted in a mutant 2008). The mechanism of Fus1 tumor suppressor FUS1, that lacks tumor suppressor activity, strongly activity is currently unknown. A deletion mutant of inhibited the recombinant 45 kDa Abl tyrosine kinase. FUS1 (FUS1 (1–80)) has been isolated and character- This Fus1 peptide was not functional unless a stearate ized from human NSCLC cell lines; it lacks the last 30 group was linked to the N terminus. (Lin et al., 2007). amino acids encoded by the FUS1 gene (Kondo et al., At the time Fus1 was not known to be involved with 2001; Ji et al., 2002). These deleted sequences encode the c-Abl, nor was it known that Fus1 may be an inhibitor Abl inhibitory peptide sequences described above. of the c-Abl tyrosine kinase. We verified Fus1’s ability Myristoylation of Fus1 at the N terminus is also to downregulate Abl kinase by showing that the above- required for the tumor suppressing function of FUS1. mentioned Fus1 peptide strongly inhibited a purified Myristoylation of Fus1 has been shown to increase the full-length human-activated c-Abl tyrosine kinase half-life of the Fus1 protein and appears to be involved (Lin et al., 2007). in the regulation of the subcellular localization of Fus1 It has been shown that normal lung tissue expresses to the cytoplasm (Uno et al., 2004) (Figure 1). The lack Fus1, whereas a majority of primary lung tumor of Fus1 myristoylation has been found in NSCLC samples do not express Fus1 (Uno et al., 2004). A new primary tumors (Uno et al., 2004). Of interest, the study has shown that 100% of human SCLC tissue myristic acid, which is bound to the N-terminal segment samples (22 samples) and 82% of human NSCLC tissue of c-Abl isoform 1b, is thought to be involved in samples (281) had a loss or reduction of Fus1, while in autoinhibition of c-Abl (Hantschel et al., 2003). contrast no normal or abnormal epithelial sites showed In our studies, two human NSCLC cell lines (A549 complete lack of Fus1 expression (Prudkin et al., 2008). and H1299) contained a tyrosine kinase active c-Abl In addition, for NSCLC they found that loss of Fus1 protein as determined by immune complex kinase expression is a significant independent adverse prog- assays. Importantly, both cell lines are defective for nostic factor for overall patient survival (Prudkin et al., the Fus1 protein expression (Kondo et al., 2001). In

Tumor Suppressor Function +

Fus1 sequence: 1 mgasgskarg lwpfasaagg ggseaagaeq 31 alvrprgrav ppfvftrrgs mfydedgdla 61 hefyeetivt kngqkraklr rvhknlipqg ivkldhprih 101 vdfpvilyev Figure 1 Structure–function relationships of the tumor suppressor gene FUS1. (a) Only myristoylated full-length wild-type Fus1 exhibits tumor suppressor activity. Myristoylation mutant and the C-terminal-truncated Fus1 proteins do not show tumor suppressor activity. Our ﬁndings show that only the myristoylated full-length Fus1 downregulates c-Abl tyrosine kinase (Lin et al., 2007). (b) The Fus1 peptide sequence. The underlined portion is the sequence of the full-length Fus1 peptide, which when co-valently linked to a stearate residue, has the ability to downregulate c-Abl kinase. Of note, amino acids 81–96, shown in the underlined portion, that are in the Fus1 peptide that inhibits c-Abl tyrosine kinase are part of the deleted sequences which are lacking in FUS1 (1–80) (Lin et al., 2007).

Oncogene Activated c-Abl in lung and breast cancer cell lines J Lin and R Arlinghaus 4387 contrast, normal lung fibroblast cell line CCD16, which surrounding the myristolation site of Fus1 for effective expresses Fus1 tumor suppressor protein, did not c-Abl kinase inhibition (Figure 2). express an activated c-Abl tyrosine kinase. Lysates of the NSCLC cell lines also contained a tyrosine- phosphorylated c-Abl protein, as shown by immune complex western blotting (Lin et al., 2007). The presence Activated c-Abl in human breast cancer of a steady-state tyrosine-phosphorylated c-Abl protein is indicative of an activated c-Abl protein. Recent findings by Plattner and co-workers (Srinivasan Imatinib mesylate (TN Gleevec, Novartis Pharma- and Plattner, 2006; Srinivasan et al., 2008) indicate that ceuticals, East Hanover, NJ, USA) is widely known for c-Abl may play an important role in breast cancer. its ability to inhibit the activated tyrosine kinase activity Plattner’s previous studies have shown that endogenous of c-Abl and Bcr-Abl (Buchdunger et al., 1996). A c-Abl is activated downstream of growth factors, such previous study has shown that imatinib (Gleevec) as EFGR and platelet-derived growth factor receptor inhibited the growth of NSCLC cell line A549 in vitro (Plattner et al., 1999). Human breast cancers have (Zhang et al., 2003). We therefore tested the effects of deregulated constitutively activated EGFR family imatinib on colony formation of H1299 cells in soft members, including EGFR1 and ErbB2 (Ross and agar. Imatinib treatment (concentrations 1–5 mM) Fletcher, 1998). Their initial study of active Abl kinases strongly inhibited the colony-forming ability of H1299 in breast cancer cell lines demonstrated that active Abl cells; both the number and size of colonies were kinases, both c-Abl and Arg, promote invasion of inhibited (Lin et al., 2007). We note that imatinib at aggressive human breast cancer cell lines (Srinivasan these low concentrations had little effect on the and Plattner, 2006). Their results show that c-Abl proliferation of the H1299 cells in cell culture. So the directly binds to EGFR after EGF stimulation and this primary inhibitory effects of imatinib were confined to leads to activation of Abl kinase and that treatment of the oncogenic behavior of H1299 cells, as measured by aggressive breast cancer cells with an EGFR inhibitor formation of growth of the cells in soft agar. leads to a decrease in active Abl kinase. They also show that activated Src kinase in aggressive breast cancer cell lines can activate c-Abl kinase. While it has been shown that Src kinase is activated downstream of Possible mechanism of the inhibition of c-Abl tyrosine EGFR (Osherov and Levitzki, 1994), Srinivasan and kinase by Fus1 Plattner (2006) show that activated Src kinase can activate c-Abl kinase in an EGFR-independent manner. Although identified as a TSG, the biochemical function They further show that inhibition of Abl kinases, either of Fus1 protein is unknown. Clues as to its possible by imatinib or siRNA, reduced the invasion of the activities can be gained from structure–function rela- aggressive breast cancer cells (Srinivasan and Plattner, tionships of wild type and mutant forms of the Fus1 2006). protein (Figure 1). A deletion mutant of FUS1 (FUS Abl as a downstream target of Src in breast cancer is 1–80) lacks its tumor suppressor function (Lin et al., supported by a recent study that shows that a decrease 2007). Thus, the C-terminal 30 amino acids within the of Src kinase by a known Src inhibitor leads to a Fus1 protein is important for its tumor suppressor decrease of Abl kinase human breast cancer cell lines function and for its ability to downregulate c-Abl. (Sirvent et al., 2007). Sirvent et al. (2007) further show Our co-expression studies indicate that Fus1 (1–80) that Abl is involved in a Src/Abl/Rac/JNK/STAT3 maintains its ability to associate with c-Abl (either signaling cascade that is important in cell transforma- directly or indirectly) despite it being defective in kinase tion. In addition, they also show that a Src/Abl/Rac/ inhibition (Lin et al., 2007). Therefore, Fus1 and c-Abl ERK5 survival pathway is activated in human breast associate through sequences within the first 80 amino cancer cell lines. acids of Fus1. In this regard, sequences surrounding the A subsequent study (Srinivasan et al., 2008) indicates myristoylation site near the N terminus of Fus1 might that Abl and Arg are required in breast cancer cell lines also play some role in c-Abl kinase binding and possibly for other oncogenic events and properties including: kinase inhibition (Figure 2). Detailed studies using phosphorylation of Stat3 (which activates pathways that X-ray crystallography indicate that the myristolation are needed for breast cancer development and progres- group at the N terminus of c-Abl 1b is one of the sion), anchorage-independent growth, inhibition of significant components of autoinhibition of c-Abl, as the apoptosis caused by nutrient deprivation and accelerating myristoyl group is associated with a hydrophobic cleft G1–S phase transition. In an experiment similar to ours, within the catalytic domain of c-Abl (Hantschel et al., Srinivasan et al. (2008) demonstrates that Abl kinase 2003). Since the Fus1 inhibitory peptide requires the contributes to aggressive breast cancer anchorage- N-terminal stearate acid moiety for inhibitory activity independent growth by inhibiting colony formation of (Lin et al., 2007) and since stearic acid and myristic acid breast cancer cells in soft agar through treatment with are similar in structure (C18 compared to C15 fatty imatinib. Their findings also identified the insulin-like acids, respectively), the Abl kinase inhibition by Fus1 growth factor 1 receptor (IGF-1R) as a novel activator may require binding of both C-terminal Fus1 sequences, of Abl kinases. Importantly, they show that G1–S the myristoyl group itself and N-terminal sequences transition by IGF-1R requires activation of Abl kinases

Oncogene Activated c-Abl in lung and breast cancer cell lines J Lin and R Arlinghaus 4388 N-Lobe Kinase

Fus 1 ATP C-terminus Binding Site

Fus 1

Activation Loop (Y412) N-terminal Cap ?? N-Lobe Kinase Myristoylation Binding Pocket C-Lobe Kinase Y245

Activation Loop (Y412)

Myristoylation Binding Pocket C-Lobe Kinase N-Lobe Kinase

GF F-actin ??

Actin Binding Domain Activation Loop (Y412) Fus 1 Fus 1 C-terminus

Myristoylation Binding C-Lobe Kinase Pocket Figure 2 Possible mechanisms of inhibition of the c-Abl tyrosine kinase by Fus1. The left diagram demonstrates c-Abl in an inactive form, inhibited by both intramolecular interactions (N-terminal cap fold over, myristoylation ‘lock’, SH2/kinase domain linker acting as an internal scaffold linking the SH3 domain and N-lobe of the kinase domain and SH2 domain interaction with the C-lobe of the kinase domain) and intermolecular interactions (F-actin binding to the F-actin-binding domain and SH2 domain). The two diagrams on the right represent two possible models of interaction of Fus1 with c-Abl that lead to inhibition of c-Abl kinase inhibition. The myristoylated Fus1 binds to the myristoylation binding pocket of c-Abl and the C terminus of Fus 1 (encased by a rectangle) may interact with either the N-lobe ATP-binding site or Fus1 may interact with the C-lobe activation loop leading to the downregulation of c-Abl tyrosine kinase. Note: Phosphorylation of Y245 and Y412 are events that lead to the activation of Abl kinase. When Abl kinase is inactive, Y245, located in the SH2/kinase domain linker, is sequestered between the SH3 domain and N-lobe of the kinase domain and Y412, located in the activation loop, is internalized in the C-lobe of the kinase domain.

(Srinivasan et al., 2008). Plattner and co-workers NSCLC. This is important since NSCLC accounts for conclude that ‘since activation of Abl kinases affects approximately 80% of all lung cancers. Currently, multiple steps of breast cancer development and NSCLC patients have few options for therapy. Pioneer- progression, Abl kinase inhibitors are likely to be ing findings by John Minna (University of Texas effective agents for treatment of breast cancers contain- Southwestern in Dallas) and Jack Roth (MD Anderson ing highly active Abl kinases’. Cancer Center, Houston, TX, USA) and their co- workers have shown that most NSCLC patients have a deficiency in FUS1 expression (Ji et al., 2002; Zabarovsky et al., 2002). Our studies indicate that one Implications of activated c-Abl tyrosine kinase in human of the key targets of FUS1 protein is the c-Abl tyrosine NSCLC and human breast cancer kinase. Experiments on two NSCLC cell lines (A549 and H1299) show that these cells contain an activated Abl Since c-Abl is activated in some human cell lines of tyrosine kinase (Lin et al., 2007). Importantly, both cell NSCLC that have reduced expression of the TSG FUS1 lines are defective for the Fus1 protein expression. (Lin et al., 2007), these findings raise the possibility that The H1299 cell line forms colonies in soft agar, c-Abl may be a useful new target in FUS1-deficient indicating their ability to proliferate without the need

Oncogene Cell membrane EGFR P P P P Y1173 P Src U C bl P U U U Cbl P Cbl

Abl Abl P P Phosphotyrosine

Ubiquitin Active Abl U ciae -b nln n ratcne ellines Arlinghaus cell R cancer and breast Lin and J lung in c-Abl Activated

P Cbl U Fus1 U

Cbl U

Figure 3 Model for c-Abl activation in non-small cell lung cancer and breast cancer. Overexpression of epithelial growth factor receptor (EGFR) is present in both non-small cell lung cancer (NSCLC) and breast cancer (Ross and Fletcher, 1998; Bunn and Franklin, 2002). Activation of EGFR leads to activation of c-Abl kinase (Srinivasan and Plattner, 2006). Activated Src kinase in breast cancer cell lines also activate c-Abl kinase. Of note, EGFR activation does activate Src kinase (Osherov and Levitzki, 1994; Plattner et al., 1999), but Src kinase can activate c-Abl in an EGFR-independent manner (Srinivasan and Plattner, 2006). Activated c-Abl kinase enhances EGFR deregulation by prevention of EGFR internalization by phosphorylating Tyr 1173 of EGFR and prevention of Cbl translocation to the cell membrane (Tanos and Pendergast, 2006). In NSCLC, and possibly breast cancer, lack of the Fus1 tumor suppressor protein would prevent downregulation of active c-Abl tyrosine kinase. Besides EGFR, the insulin-like growth factor 1 receptor (IGF-1R) has been shown to activate c- Abl in breast cancer (Srinivasan et al., 2008) and thus IGF-1R may also play an important role in the constitutive activation of the c-Abl kinase in NSCLC. Oncogene 4389 Activated c-Abl in lung and breast cancer cell lines J Lin and R Arlinghaus 4390 for a matrix, a property of many tumor-forming cells. to activated c-Abl and malignant properties of the Imatinib mesylate (Gleevec), the Abl kinase inhibitor effected lung cells. Also of interest, deletions in the that is highly successful in the treatment of CML, 3p21.3 region have also been found in breast tumors, strongly inhibited growth of H1299 cells in soft agar at raising the question of whether some forms of breast physiological doses of imatinib (Lin et al., 2007). cancer with elevated c-Abl may also be deficient in Similarly, treatment of invasive human breast cancer FUS1 (Ji et al., 2002). cell line, MDA-MB-435, expressing activated c-Abl with As pointed out by Srinivasan et al. (2008), there is imatinib in soft agar assays also lead to a decrease in size conflicting experimental evidence regarding the role of and number of colonies (Srinivasan et al., 2008). While Abl kinases in proliferation and survival. Activation of further studies, especially in animal models, are needed c-Abl promotes proliferation, cell cycle progression and/ to confirm these findings, nevertheless these findings or cell survival in some cell contexts and inhibits growth suggest that imatinib or other c-Abl kinase inhibitors and/or viability in others. Normal Abl in properly may have medical utility in the treatment of some forms regulated cells may play dual roles in promotion of cell of NSCLC and breast cancer. Additional support for proliferation or inhibition of cell cycle or even cell use of imatinib in treatment of NSCLC patients has apoptosis depending on the context. However, Abl been found in a recent mouse study and a patient study, activated by deregulated EGFR/IGF-1R, as in breast both of which suggest that an important therapeutic cancer cells (Srinivasan and Plattner, 2006; Srinivasan option for NSCLC patients would be a combination et al., 2008) or loss of Fus1, as in NSCLC cells of imatinib with chemotherapy for treatment of this (Lin et al., 2007), is more similar to the constitutively aggressive cancer (Vlahovic et al., 2006; Negri et al., activated Abl kinase found in mutant forms of Abl 2007). (v-Abl or Bcr-Abl), whose unregulated Abl kinase Adding to c-Abl’s possible oncogenic role in both promote cell proliferation, cell survival and oncogenic NSCLC and breast cancer, a recent study has demon- transformation. strated that activated Abl kinase has a novel role in the regulation of EGFR endocytosis (Figure 3). Active Abl kinase phosphorylates EGFR on Tyr1173 and blocks Cbl translocation to the cell membrane, Summary both events lead to the impairment of EGFR internalization (Tanos and Pendergast, 2006). This role of The results of two groups (Srinivasan and Plattner, 2006; active Abl kinase is of great significance, as over- Lin et al., 2007; Srinivasan et al., 2008) indicate that the expression of EGFR in both NSCLC and breast cancer Abl tyrosine kinase may play a crucial role in solid is known to contribute to these malignancies. Therefore, tumors malignancies involving NSCLC tumors and it may be that inhibition of Abl kinase may lead to a breast tumors, and that this important proto-oncogene decrease in cell surface EGFR in breast cancer and may have an oncogenic impact beyond that of hemato- NSCLC. poietic cell lineages. In the lung tumors, a known TSG In the NSCLC effects described by our group product, Fus1, interacts with c-Abl causing downregula- (Lin et al., 2007), it appears that the key event leading ting of the Abl tyrosine kinase. NSCLC is frequently to the activation of c-Abl kinase is either the functional associated with loss of FUS1 gene expression, which may or physical elimination of the Fus1 gene product. The lead to c-Abl tyrosine kinase activation (Lin et al., 2007). loss of FUS1 gene product appears to occur in most In the breast cancer system, activation of c-Abl tyrosine NSCLC patients (Kondo et al., 2001; Ji et al., 2002; kinase appears downstream of deregulated EGFR and/ Prudkin et al., 2008). In the case of breast cancer, or the IGF-1 receptor (Srinivasan and Plattner, 2006; activation of c-Abl appears to be a downstream effector Srinivasan et al., 2008). of EGFR/IGF-1 receptor activation (Srinivasan and It could be hypothesized from the results of these two Plattner, 2006; Srinivasan et al., 2008). This mechanism groups that Abl activation in NSCLC and breast cancer of Abl kinase activation may well contribute to may be a late occurring event that contributes to the activated c-Abl kinase in NSCLC as well, as EGFR is aggressive growth and metastasis of these solid tumors. known to be overexpressed in NSCLC (Bunn and As Srinivasan et al. (2008) point out, since Abl kinase is Franklin, 2002). IGF-1R overexpression has been found activated by EGFR, IGF-1R and Src, Abl is a point of in some lung cancers (LeRoith et al., 1995), and a recent convergence of three pathways and therefore is an ideal study has shown that inhibition of IGF-1R in human target versus trying to target three separate pathways. NSCLC cell line A549 results in cell cycle arrest, We hypothesize that imatinib or other c-Abl kinase enhances the apoptotic response and inhibits: cell inhibitors, or treatment involving FUS1 itself, in the proliferation, adhesion, invasion and migration case of NSCLC (Ito et al., 2004), when combined with (Ma et al., 2007). Therefore, it is possible that activation current therapies for NSCLC and breast cancer, would of cell surface receptors like EGFR might play a role in greatly increase the efficacy of current therapy, and as c-Abl activation in lung cancer, as well as breast cancers Srinivasan and Plattner (2006) state, ‘Abl kinase (Figure 3). However, when Fus1 is expressed, even inhibitors may be effective in overcoming EGFR drug though receptor may be required for c-Abl activation, it resistance’. Further investigation of c-Abl involvement may not be sufficient. We would propose the combina- in these two types of solid tumor malignancies is tion of receptor activation and Fus1 deficiency will lead warranted.

Oncogene Activated c-Abl in lung and breast cancer cell lines J Lin and R Arlinghaus 4391 References

Buchdunger E, Zimmerman J, Mett H, Meyer T, Muller M, Druker B Pendergast A. (2002). The Abl family kinases: mechanisms of et al. (1996). Inhibition of the Abl protein-tyrosine kinase in vitro regulation and signaling. Adv Cancer Res 85: 51–100. and in vivo by a 2-phenylaminopyrimidine derivative. Cancer Res 56: Plattner R, Kadlec L, DeMali K, Kazlauskas A, Pendergast A. (1999). 100–104. c-Abl is activated by growth factors and Src family kinases and has Bunn P, Franklin W. (2002). Epidermal growth factor receptor a role in the cellular response to PDGF. Genes Dev 13: 2400–2411. expression, signal pathway, and inhibitors in non-small cell lung Plattner R, Pendergast AM. (2003). Activation and signaling of the cancer. Semin Oncol 29(5 Suppl 14): 38–44. Abl tyrosine kinase: bidirectional link with phosphoinositide Dowell J, Minna J. (2005). Chasing mutations in the epidermal growth signaling. Cell Cycle 2: 273–274. factor in lung cancer. N Engl J Med 352: 830–832. Pluk H, Dorey K, Superti-Furga G. (2002). Autoinhibition of c-Abl. Girard L, Zochbauer-Muller S, Virmani A, Gazdar A, Minna J. Cell 108: 247–259. (2000). Genome-wide allelotyping of lung cancer identifies new Prudkin L, Behrens C, Liu D, Zhou X, Ozburn N, Bekele B et al. regions of allelic loss, differences between small cell lung cancer (2008). Loss and reduction of Fus1 protein expression is a frequent and non-small cell lung cancer, and loci clustering. Cancer Res 60: phenomenon in the pathogenesis of lung cancer. Hum Cancer Biol 4894–4906. 14: 41–47. Hantschel O, Nagar B, Guettler S, Kretzschmar J, Dorey K, Kuryian J Ross S, Fletcher A. (1998). The HER-2/neu oncogene in breast cancer: et al. (2003). A myristoyl/phosphotyrosine switch regulates c-Abl. prognostic factor, predictive factor, and target for therapy. Stem Cell 112: 845–857. Cells 16: 413–428. Ito I, Ji L, Tanaka F, Saito Y, Gopalan B, Branch C et al. (2004). Sirvent A, Boureux A, Simon V, Leroy C, Roche S. (2007). The Liposomal vector mediated delivery of the 3p FUS1 gene tyrosine kinase Abl is required for Src-transforming activity in demonstrates potent antitumor activity against human lung cancer mouse fibroblasts and human breast cancer cell lines. Oncogene 26: in vivo. Cancer Gene Ther 11: 1–7. 7313–7323. Ji L, Nishizaki M, Gao B, Burbee D, Kondo M, Kamibayashi C et al. Srinivasan D, Plattner R. (2006). Activation of Abl tyrosine kinases (2002). Expression of several genes in the human chromosome promotes invasion of aggressive breast cancer cells. Cancer Res 66: 3p21.3 homozygous deletion region by an adenovirus vector results 5648–5655. in tumor suppressor activities in vitro and in vivo. Cancer Res 62: Srinivasan D, Sims J, Plattner R. (2008). Aggressive breast cancer cells 2715–2720. are dependent on activated Abl kinases for proliferation, anchorage- Kondo M, Ji L, Kamibayashi C, Tomizawa Y, Randle D, Sekido Y independent growth and survival. Oncogene 27: 1095–1105. et al. (2001). Overexpression of candidate tumor suppressor gene Taagepera S, McDonald D, Loeb J, Whitaker L, McElroy A, Wang J FUS1 isolated from the 3p21.3 homozygous deletion region leads to et al. (1998). Nuclear-cytoplasmic shuttling of C-ABL tyrosine G1 arrest and growth inhibition of lung cancer cells. Oncogene 20: kinase. Proc Natl Acad Sci USA 95: 7457–7462. 6258–6262. Tanos B, Pendergast AM. (2006). Abl tyrosine kinase regulates LeRoith D, Werner H, Beitner-Johnson D, Roberts C. (1995). endocytosis of the epidermal growth factor receptor. J Biol Chem Molecular and cellular aspects of the insulin-like growth factor I 28: 32714–32723. receptor. Endocr Rev 16: 143–163. Uno F, Sasaki J, Nishizaki M, Carboni G, Xu K, Atkinson E et al. Lin J, Sun T, Ji L, Deng W, Roth J, Minna J et al. (2007). Oncogenic (2004). Myristoylation of the fus1 protein is required for tumor activation of c-Abl in non-small cell lung cancer cells lacking FUS1 suppression in human lung cancer cells. Cancer Res 64: 2969–2976. expression: inhibition of c-Abl by the tumor suppressor gene U.S. Cancer Statistics Working Group (2004). U.S. Cancer Statistics: product Fus1. Oncogene 26: 6989–6996. 2001 Incidence and Mortality. U.S. Department of Health and Lin J, Sun T, Lin J, Minna J, Roth J, Arlinghaus R. (2005). Activated Human Services, Centers for Disease Control and Prevention and c-Abl in FUS1 haploinsufficient non-small cell lung carcinoma. 96th National Cancer Institute: Atlanta. Annual American Association for Cancer Research (Abstract 2877). Vlahovic G, Rabbani Z, Herndon II J, Dewhirst M, Vujaskovic Z. Ling X, Ma G, Sun T, Liu J, Arlinghaus R. (2003). Bcr and Abl (2006). Treatment with imatinib in NSCLC is associated with interaction: oncogenic activation of c-Abl by sequestering Bcr. decrease if phosphorylated PDGFR-b and VEGF expression, Cancer Res 63: 298–303. decrease in interstitial fluid pressure and improvement of oxygena- Liu J, Wu Y, Arlinghaus R. (1996). Sequences within the first exon of tion. Br J Cancer 95: 1013–1019. BCR inhibit the activated tyrosine kinases of c-Abl and the Bcr-Abl Wang J. (2000). Regulation of cell death by the Abl tyrosine kinase. oncoprotein. Cancer Res 56: 5120–5124. Oncogene 19: 5643–5650. Ma Z, Dong A, Kong M, Qian J. (2007). Silencing of the type 1 Wen S, Van Etten R. (1997). The PAG gene product, a stress-induced insulin-like growth factor receptor increases the sensitivity to protein with antioxidant properties, is an Abl SH3-binding protein apotosis and inhibits invasion in human lung adenocarcinoma and a physiological inhibitor of c-Abl tyrosine kinase activity. Genes A549 cells. Cell Mol Biol Lett 12: 556–572. Dev 11: 2456–2467. Miller C, Chen G, Gharib T, Wang H, Thomas D, Misek D et al. Woodring P, Hunter T, Wang J. (2003). Regulation of F-actin- (2003). Increased C-CRK proto-oncogene expression is associated dependent processes by the Abl family of tyrosine kinases. J Cell with an aggressive phenotype in lung adenocarcinomas. Oncogene Science 116(Part 13): 2613–2626. 22: 7950–7957. Zabarovsky E, Lerman M, Minna J. (2002). Tumor suppressor genes Negri T, Casieri P, Miselli F, Orsenigo M, Piacenza C, Stacchiotti S on chromosome 3p involved in the pathogenesis of lung and other et al. (2007). Evidence for PDGFR-a, PDGFR-b and KIT cancers. Oncogene 21: 6915–6935. deregulation in an NSCLC patient. Br J Cancer 96: 180–181. Zhang P, Gao W, Turner S, Ducatman B. (2003). Gleevec (STI-571) Osherov N, Levitzki A. (1994). Epidermal-growth-factor-dependent inhibits lung cancer cell growth (A549) and potentiates the cisplatin activation of the Src-family kinases. Eur J Biochem 225: 1047–1053. effect in vitro. Mol Cancer 2:1.

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