FAK overexpression is correlated with tumour invasiveness and lymph node metastasis in oesophageal squamous cell carcinoma

Estrogen regulates endometrial cell cytoskeletal remodeling and motility via focal adhesion kinase

OBJECTIVE

To explore the effects of 17β-estradiol (E(2)) on cytoskeletal remodeling and motility of endometrial stromal cells (ESC) and Ishikawa cells and to characterize the role of focal adhesion kinase (FAK) in these processes.

DESIGN

In vitro study of cytoskeletal remodeling and cellular morphology and motility in ESC or Ishikawa cells.

SETTING

University research center.

PATIENT(S)

Endometrial samples obtained from women requiring endometrial biopsies.

INTERVENTION(S)

Treatments with E(2) and multiple inhibitors of signaling pathways.

MAIN OUTCOME MEASURE(S)

Activation of FAK, actin remodeling, membrane morphology, cell motility, and invasion.

RESULT(S)

Estrogen induces a rapid and concentration-related FAK phosphorylation in ESC and Ishikawa cells. In this time frame, FAK localizes to the plasma membrane at sites of focal adhesion complexes formation, as shown by immunofluorescence. Phosphorylation of FAK in the presence of estrogen depends on the recruitment of both estrogen receptor α and estrogen receptor β and of a rapid G protein-dependent signaling to c-Src and phosphatidylinositol 3-OH kinase. Activation of FAK in ESC and Ishikawa cells is required for estrogen-induced horizontal migration and invasion of three-dimensional matrices of endometrial cells.

CONCLUSION(S)

Estrogen enhances cytoskeletal and membrane remodeling in ESC and Ishikawa cells by controlling FAK, thus resulting in enhanced cell motility and invasion. These findings may have clinical relevance for the development of new therapeutic strategies for the prevention or control of endometrial diseases.

Focal adhesion kinase serves as a marker of cervical lymph node metastasis and is a potential therapeutic target in tongue cancer

PURPOSE

The aims of the present study were to examine whether focal adhesion kinase (FAK) expression is correlated with cervical lymph node metastasis of tongue cancer and to investigate the roles of FAK in the process of cancer cell migration, invasion and anoikis resistance using the human tongue cancer cell line, Tca8113.

METHODS

FAK expression was evaluated in 5 normal oral mucosa, 10 premalignant lesions, 80 primary tongue cancers and 41 lymph node metastases using anti-FAK immunohistochemistry. The migration, invasion and anoikis resistance of tongue cancer cells were evaluated using wound healing assays, invasion assays and anoikis induction. The effect of FAK inhibition was evaluated using RNA interference (RNAi).

RESULTS

In total, 55 of 80 primary tongue cancers (69%) showed high expression of FAK, and 25 of 80 tumors (31%) and all normal oral mucosa or premalignant lesions showed low expression of FAK. There was a significant correlation between FAK expression and the cervical lymph node metastasis of tongue cancer. Moreover, RNAi-mediated FAK reduction decreased tongue cancer cell migration, invasion and anoikis resistance.

CONCLUSIONS

These results suggest that FAK may serve as a marker of cervical lymph node metastasis of tongue cancer and that RNAi targeting FAK could serve as a potential therapeutic for the treatment of tongue cancer.

Decreased expression of focal adhesion kinase is associated with a poor prognosis in extrahepatic bile duct carcinoma

Extrahepatic bile duct (EBD) carcinoma is a relatively rare neoplasm worldwide, and its prognostic outcome remains unfavorable. Therefore, it is necessary to investigate molecular biologic features of EBD carcinomas. Focal adhesion kinase (FAK) plays a pivotal role in cell adhesion, survival, migration, and signal transduction, but FAK expression in EBD carcinomas has not been evaluated. We measured FAK expression in 76 EBD carcinomas using immunohistochemistry and evaluated its correlation with tumor progression, clinicopathologic factors, and patient outcome. FAK was expressed specifically in the cytoplasm of all normal biliary epithelia (100%). Most dysplastic epithelia also showed positive FAK expression except for 2 cases (92%), whereas EBD carcinomas showed positive FAK expression in 53 (77%) of 76 cases (P < .001, versus normal epithelia). FAK expression tended to be gradually reduced along as dysplasia progressed to carcinoma. Although FAK expression had no association with clinicopathologic factors, the positive FAK expression group showed significantly better survival than the negative FAK expression group (P < .05). However, FAK expression was not an independent prognostic factor by multivariate analysis. In conclusion, FAK expression was significantly lower in EBD carcinomas than in normal biliary epithelia and decreased expression of FAK seemed to be indicative of a poor prognosis, suggesting that FAK might play an inhibitory role for tumor progression in EBD carcinomas. It is important to notice the role of FAK in tumor progression when treatments targeting FAK are performed.

FAK is involved in invasion and metastasis of hepatocellular carcinoma

Studies have shown that focal adhesion kinase (FAK) is overexpressed in several human tumors and plays an important role in tumor progression. However, the role and underlying mechanisms of FAK in hepatocellular carcinoma (HCC) progression remains to be elucidated. In this study, we examined FAK and phosphorylated FAK Tyr397 expression in a large series of HCCs. We found that both FAK and phosphorylated FAK Tyr397 were overexpressed in HCC samples and HCC cell lines. Increased FAK and phosphorylated FAK Tyr397 expressions were correlated with tumor stage, vascular invasion and intrahepatic metastasis in HCC. Furthermore, HCC cell adhesion, migration and invasion were substantially impaired by siRNA-mediated knockdown of FAK expression, whereas cell growth, apoptosis and cell cycle distribution were not affected. In addition, depletion of FAK induced a significant reduction in expressions and activities of both MMP-2 and MMP-9. Taken together, FAK contributes to invasion and metastasis of HCC partly through regulating expressions and activations of both MMP-2 and MMP-9, suggesting FAK could be a promising therapeutic target for HCC.

Progress in researches about focal adhesion kinase in gastrointestinal tract

Focal adhesion kinase (FAK) is a 125-kDa non-receptor protein tyrosine. Growth factors or the clustering of integrins facilitate the rapid phosphorylation of FAK at Tyr-397 and this in turn recruits Src-family protein tyrosine kinases, resulting in the phosphorylation of Tyr-576 and Tyr-577 in the FAK activation loop and full catalytic FAK activation. FAK plays a critical role in the biological processes of normal and cancer cells including the gastrointestinal tract. FAK also plays an important role in the restitution, cell survival and apoptosis and carcinogenesis of the gastrointestinal tract. FAK is over-expressed in cancer cells and its over-expression and elevated activities are associated with motility and invasion of cancer cells. FAK has been proposed as a potential target in cancer therapy. Small molecule inhibitors effectively inhibit the kinase activity of FAK and show a potent inhibitory effect for the proliferation and migration of tumor cells, indicating a high potential for application in cancer therapy.

Receptor-interacting protein shuttles between cell death and survival signaling pathways

Cross-talk between apoptosis and survival signaling pathways is crucial for regulating tissue processes and mitigating disease. We report that anoikis-apoptosis triggered by loss of extracellular matrix contacts-activates a CD95/Fas-mediated signaling pathway regulated by receptor-interacting protein (RIP), a kinase that shuttles between CD95/Fas-mediated cell death and integrin/focal adhesion kinase (FAK)-mediated survival pathways. RIP's death domain was critical for RIP and Fas association to mediate anoikis. Fas or RIP attenuation reduced this association and suppressed anoikis, whereas their overexpression had the reverse effect. Overexpressing FAK restored RIP and FAK association and inhibited anoikis. Thus, RIP shuttles between CD95/Fas death and FAK survival signaling to mediate anoikis.

Role of p53/FAK association and p53Ser46 phosphorylation in staurosporine-mediated apoptosis: wild type versus mutant p53-R175H

A novel survival role of focal adhesion kinase (FAK) that involves its nuclear translocation and direct association with p53 has been demonstrated. Here we examined the relationship between the p53/FAK interaction and Ser46 phosphorylation of p53 (p-p53(Ser46)) in the apoptotic regulation of human esophageal squamous cell carcinoma (HOSCC) cell lines, expressing either wild type (wt) p53 or mutant (mt) p53-R175H. In contrast to the wt p53 cell lines, the mt p53-R175H cell line was resistant to staurosporine (STS)-mediated detachment and caspase-3 activation. Furthermore, despite the resistance of mt p53-R175H to Ser46 phosphorylation, both wt and mt HOSCC cells translocate FAK into the nucleus and maintain the p53/FAK interaction post STS treatment. These findings provide unique insight into how tumor cells harboring the R175H mutant may resist chemotherapeutic intervention.

Signal transduction by focal adhesion kinase in cancer

Cellular interactions with extracellular matrix play essential roles in tumor initiation, progression and metastasis. Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase identified as a key mediator of signaling by integrins, a major family of cell surface receptors for extracellular matrix, as well as other receptors in both normal and cancer cells. FAK is activated by integrins through disruption of an auto-inhibitory intra-molecular interaction between its kinase domain and the amino terminal FERM domain. The activated FAK forms a binary complex with Src family kinases which can phosphorylate other substrates and trigger multiple intracellular signaling pathways to regulate various cellular functions. Subcellular localization of FAK in focal adhesions is essential for FAK signaling, which is another distinguishing feature of the kinase. Integrin-FAK signaling has been shown to activate a number of signaling pathways through phosphorylation and protein-protein interactions to promote tumorigenesis. FAK also plays a prominent role in tumor progression and metastasis through its regulation of both cancer cells and their microenvironments including cancer cell migration, invasion, epithelial to mesenchymal transition, and angiogenesis. More recently, a role for FAK in tumor initiation and progression has been demonstrated directly using xenograft as well as conditional knockout mouse models. In agreement with these experimental data, overexpression and activation of FAK have been found in a variety of human cancers. A number of small molecule inhibitors for FAK have been developed and in various phases of testing for cancer treatments. Overall, the intensive research on FAK signaling in cancer have yielded a wealth of information on this pivotal kinase and these and future studies are leading to potentially novel therapies for cancer.

Molecular markers of micrometastasis in oral cavity carcinomas

Objective: To examine the expression of candidate markers for micrometastasis.

Study Design: Cross-sectional analysis of subjects with oral cavity carcinomas who underwent sentinel lymph node biopsy (SLNB) and subsequent immunohistochemical (IHC) analysis.

Subjects and Methods: Two groups were identified based on SLNB status: negative SLNB (19/30) and positive SLNB (11/30). Specimens underwent IHC using conjugated monoclonal antibodies for membrane type-1 matrix metalloproteinase (MT1-MMP), CD44, focal adhesion kinase-1, and E-cadherin. Staining results were evaluated to determine if a particular marker was associated with SLNB status or other histopathologic prognosticators.

Results: For MT1-MMP, 21 percent (3/14) of evaluable specimens stained positively in the SLNB(−) group and 67 percent (4/6) stained positively in the SLNB(+) group ( P = 0.12). No statistically significant association was seen between any marker's staining pattern and SLNB status alone. When MT1-MMP staining was evaluated in tumors with SLNB(+) or perineural invasion (PNI) present on histopathology, six of nine specimens (67%) stained positively for MT1-MMP, vs one of 11 (9%) in specimens lacking either negative prognosticator ( P = 0.016, RR = 7.33).

Conclusion: Preliminary results suggest that MT1-MMP positivity in primary tumor specimens may identify aggressive tumor types, evidenced by the presence of micrometastasis or PNI.

Expression of lysyl oxidase is correlated with lymph node metastasis and poor prognosis in esophageal squamous cell carcinoma

BACKGROUND

Lysyl oxidase (LOX), an extracellular matrix-remodeling enzyme, has been reported to regulate tumor metastasis. We investigated the clinical significance of LOX expression in esophageal squamous cell carcinoma (ESCC).

METHODS

We examined LOX expression in ESCC cell lines by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blotting. We also examined LOX expression by real-time RT-PCR in 39 surgically resected ESCC and by immunohistochemistry in 122 surgically resected ESCC.

RESULTS

LOX messenger RNA (mRNA) was expressed at a high level in TTn (originating from an ESCC metastatic lesion); at a moderate level in TE-2 and TE-15; and at a low level in TE-1, TE-8, and TE-13. In Western blotting, all cell lines expressed the catalytically inactive 50-kDa LOX at approximately the same levels, but catalytically active 32-kDa LOX was overexpressed only in TTn. LOX mRNA levels in ESCC tissues were significantly higher than those observed in normal esophageal tissues (P < 0.001) and had no significant correlation with tumor-node-metastasis (TNM) factors. High LOX protein expression had a significant correlation with presence of lymph node metastasis (P = 0.009) and number of lymph node metastases (P = 0.047). Overall and cancer-specific survival rates of patients with ESCC with high LOX expression were significantly lower than those of patients with ESCC with low LOX expression (P = 0.024 and P = 0.012). Univariate and multivariate analyses revealed that high LOX protein expression was an independent prognostic factor for ESCC.

CONCLUSIONS

Our findings suggest that LOX can serve as a predictive marker of lymph node metastasis and prognosis in ESCC.

Overexpressed focal adhesion kinase predicts a higher incidence of extrahepatic metastasis and worse survival in hepatocellular carcinoma

Focal adhesion kinase plays a critical role in cancer progression, invasion, and metastasis. Although focal adhesion kinase overexpression indicates poor prognoses for hepatocellular carcinoma, its role in hepatocellular carcinoma metastasis has not been well investigated. In this study, 55 hepatocellular carcinoma patients were enrolled, and their primary liver tumors as well as 18 matched metastases were subjected to semiquantitative immunohistochemistry analysis of focal adhesion kinase expression. Overexpression of focal adhesion kinase was observed in 34 (61.8%) of 55 primary tumors and significantly predicted subsequent extrahepatic metastases (P = .04). Metastatic tumors expressed higher focal adhesion kinase than their matched primaries (P = .010). Focal adhesion kinase overexpression indicated both worse overall 5-year survival rate (51.5% +/- 8.7% versus 90.2% +/- 6.6%; P = .004) and 5-year progression-free survival rate (51.5% +/- 8.7% versus 90.2% +/- 6.6%; P = .041). Taken together, we demonstrated here that focal adhesion kinase expression is significantly related to subsequent hepatocellular carcinoma metastasis. Focal adhesion kinase is thus considered as a reasonable target for novel therapies against hepatocellular carcinoma progression and metastasis.

Targeting focal adhesion kinase with dominant-negative FRNK or Hsp90 inhibitor 17-DMAG suppresses tumor growth and metastasis of SiHa cervical xenografts

Focal adhesion kinase (FAK), a nonreceptor protein tyrosine kinase and key modulator of integrin signaling, is widely expressed in different tissues and cell types. Recent evidence indicates a central function of FAK in neoplasia where the kinase contributes to cell proliferation, resistance to apoptosis and anoikis, invasiveness, and metastasis. FAK, like other signaling kinases, is dependent on the chaperone heat shock protein 90 (Hsp90) for its stability and proper function. Thus, inhibition of Hsp90 might be a way of disrupting FAK signaling and, consequently, tumor progression. FAK is expressed in high-grade squamous intraepithelial lesions and metastatic cervical carcinomas but not in nonneoplastic cervical mucosa. In SiHa, a cervical cancer cell line with characteristics of epithelial-to-mesenchymal transition, the stable expression of dominant-negative FAK-related nonkinase decreases anchorage independence and delays xenograft growth. FAK-related nonkinase as well as the Hsp90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin both negatively interfere with FAK signaling and focal adhesion turnover. Short-term 17-dimethylaminoethylamino-17-demethoxygeldanamycin treatment prolongs survival in a SiHa lung metastasis model and chronic administration suppresses tumor growth as well as metastatic spread in orthotopic xenografts. Taken together, our data suggest that FAK is of importance for tumor progression in cervical cancer and that disruption of FAK signaling by Hsp90 inhibition might be an avenue to restrain tumor growth as well as metastatic spread.

Paxillin-Y118 phosphorylation contributes to the control of Src-induced anchorage-independent growth by FAK and adhesion

Background

Focal adhesion kinase (FAK) and Src are protein tyrosine kinases that physically and functionally interact to facilitate cancer progression by regulating oncogenic processes such as cell motility, survival, proliferation, invasiveness, and angiogenesis.

Method

To understand how FAK affects oncogenesis through the phosphorylation of cellular substrates of Src, we analyzed the phosphorylation profile of a panel of Src substrates in parental and v-Src-expressing FAK+/+ and FAK-/- mouse embryo fibroblasts, under conditions of anchorage-dependent (adherent) and -independent (suspension) growth.

Results

Total Src-induced cellular tyrosine phosphorylation as well as the number of phosphotyrosyl substrates was higher in suspension versus adherent cultures. Although the total level of Src-induced cellular phosphorylation was similar in FAK+/+ and FAK-/- backgrounds, the phosphorylation of some substrates was influenced by FAK depending on adherence state. Specifically, in the absence of FAK, Src induced higher phosphorylation of p190RhoGAP, paxillin (poY118) and Crk irrespective of adhesion state, PKC-δ (poY311), connexin-43 (poY265) and Sam68 only under adherent conditions, and p56Dok-2 (poY351) and p120catenin (poY228) only under suspension conditions. In contrast, FAK enhanced the Src-induced phosphorylation of vinculin (poY100 and poY1065) and p130CAS (poY410) irrespective of adherence state, p56Dok-2 (poY351) and p120catenin (poY228) only under adherent conditions, and connexin-43 (poY265), cortactin (poY421) and paxillin (poY31) only under suspension conditions. The Src-induced phosphorylation of Eps8, PLC-γ1 and Shc (poY239/poY240) were not affected by either FAK or adherence status. The enhanced anchorage-independent growth of FAK-/-[v-Src] cells was selectively decreased by expression of paxillin^Y118F, but not by WT-paxillin, p120catenin^Y228F or Shc^Y239/240F, identifying for the first time a role for paxillin^poY118 in Src-induced anchorage-independent growth. Knockdown of FAK by siRNA in the human colon cancer lines HT-25 and RKO, resulted in increased paxillin^poY118 levels under suspension conditions as well as increased anchorage-independent growth, supporting the notion that FAK attenuates anchorage-independent growth by suppressing adhesion-dependent phosphorylation of paxillin^Y118.

Conclusion

These data suggest that phosphorylation of Src substrates is a dynamic process, influenced temporally and spatially by factors such as FAK and adhesion.

Overexpression and significance of focal adhesion kinase in hepatocellular carcinoma and its relationship with HBV infection

The prognosis of the hepatocellular carcinoma is influenced by its invasion and metastasis. Interacting with a number of oncogenes, HBV infection is a high risk factor for HCC. Overexpression of Focal adhesion kinase (FAK), a novel oncogene, has been suggested to play an important role in tumorigenesis and progression of many cancers, including HCC. However, the relationship between HBV infection and FAK for HCC prognosis is still unclear. A retrospective study of 89 archival specimens of subjects with histologically confirmed HCC was carried out. Immunohistochemistry was utilized to examine the expression of FAK. Then the FAK expression was analyzed with index of HCC, especially with HBsAg and HBV DNA. FAK overexpression was detected in 38/89 of the tumors. FAK overexpression in HCC significantly correlated with HBsAg (P = 0.033), HBV DNA level (P = 0.005), vascular invasion of HCC (P = 0.000*), and TNM stage (P = 0.003). FAK-positive patients exhibited a lower survival rate compared with those with negative FAK expression. Overexpression of FAK might have a correlation with HBV infection and contribute to HCC progression, raising the possibility of FAK overexpression as a potential marker for a poor prognosis in HCC.

Expression and clinical significance of focal adhesion kinase in the two distinct histological types, intestinal and diffuse, of human gastric adenocarcinoma

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase protein, acts as an early modulator of integrin signaling cascade, regulating basic cellular functions. In transformed cells, unopposed FAK signaling has been considered to promote tumor growth, progression and metastasis. The aim of this study was to assess the clinical significance of FAK expression in the two distinct histological types of human gastric neoplasia. FAK expression was assessed immunohistochemically in tumoral samples of 66 gastric adenocarcinoma cases, 30 intestinal and 36 diffuse type, and was statistically analyzed in relation to various clinicopathological characteristics, tumor proliferative capacity and patients' survival. In intestinal type carcinomas, enhanced FAK expression was significantly associated with increased tumor proliferative capacity (P = 0.012). In diffuse type carcinomas, FAK staining intensity was significantly correlated with tumor size (P = 0.026) and disease stage (P = 0.024), presenting also a borderline association with nodal status (P = 0.053). In diffuse type carcinomas, enhanced FAK expression was significantly associated with longer overall survival times (log-rank test, P = 0.014), being also identified as an independent prognostic factor in multivariate analysis (Cox regression, P = 0.016). In contrast, patients with intestinal type tumors and enhanced FAK expression were characterized by shorter overall survival times, without though reaching statistical significance (log-rank test, P = 0.092). The current data support evidence that FAK protein may be considered as a diagnostic and prognostic marker in gastric neoplasia. Further studies conducted on larger clinical samples and highlighting on the distinct impact of the two histological types are warranted to delineate the clinical significance of FAK protein in gastric neoplasia.

Focal adhesion kinase expression in human neuroblastoma: immunohistochemical and real-time PCR analyses

PURPOSE

The focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase important in signaling between cells and their extracellular matrix. Studies have shown that FAK expression is up-regulated in several human tumors and is related to tumor progression. We recently found an increase in p125(FAK) expression in human neuroblastoma cells lines and wished to determine its expression in human neuroblastoma specimens and evaluate for a possible correlation between p125(FAK) expression and known prognostic factors for neuroblastoma. We hypothesized that p125(FAK) expression would be up-regulated in advanced human neuroblastomas.

EXPERIMENTAL DESIGN

Using immunohistochemical techniques with monoclonal antibody 4.47 specific for p125(FAK) expression, we analyzed 70 formalin-fixed, paraffin-embedded human neuroblastoma specimens for p125(FAK) staining. In addition, real-time PCR was used to determine the abundance of FAK mRNA in 17 matched human neuroblastoma mRNA specimens.

RESULTS

FAK staining was present in 51 of the 70 tumor specimens (73%). Immunohistochemical staining of p125(FAK) in the ganglion-type tumor cells correlated with advanced International Neuroblastoma Staging System tumor stages and FAK mRNA abundance. In addition, p125(FAK) staining was significantly increased in stage IV tumors with amplification of the N-MYC oncogene.

CONCLUSIONS

These novel findings provide evidence that FAK is expressed by advanced-stage neuroblastoma and provide a rationale for targeting FAK in the treatment of this tumor.

Involvement of focal adhesion kinase in cellular invasion of head and neck squamous cell carcinomas via regulation of MMP-2 expression

Focal adhesion kinase (FAK) is considered intimately involved in cancer progression. Our previous research has demonstrated that overexpression of FAK is an early and frequent event in squamous cell carcinomas of the supraglottic larynx, and it is associated with the presence of metastases in cervical lymph nodes. The purpose of this study was to examine the functional role of FAK in the progression of head and neck squamous cell carcinomas (HNSCC). To this end, expression of FAK-related nonkinase (FRNK) or small interfering RNA (siRNA) against FAK was used to disrupt the FAK-induced signal transduction pathways in the HNSCC-derived SCC40 and SCC38 cell lines. Similar phenotypic effects were observed with the two methodological approaches in both cell lines. Decreased cell attachment, motility and invasion were induced by FRNK and FAK siRNA, whereas cell proliferation was not impaired. In addition, increased cell invasion was observed upon FAK overexpression in SCC cells. FRNK expression resulted in a downregulation of MMP-2 and MMP-9 expression. Interestingly, MMP-2 overexpression in FRNK-expressing cells rescued FRNK inhibition of cell invasion. This is the first demonstration of a direct rescue of impaired cell invasion by the re-expression of MMP-2 in a tumour cell type with decreased expression of functional FAK. Collectively, these data reported here support the conclusion that FAK enhances invasion of HNSCC by promoting both increased cell motility and MMP-2 production, thus providing new insights into possible therapeutic intervention strategies.

An altered fibronectin matrix induces anoikis of human squamous cell carcinoma cells by suppressing integrin alpha v levels and phosphorylation of FAK and ERK

Fibronectin regulates many cellular processes, including migration, proliferation, differentiation, and survival. Previously, we showed that squamous cell carcinoma (SCC) cell aggregates escape suspension-induced, p53-mediated anoikis by engaging in fibronectin-mediated survival signals through focal adhesion kinase (FAK). Here we report that an altered matrix, consisting of a mutated, nonfunctional high-affinity heparin-binding domain and the V region of fibronectin (V+H-), induced anoikis in human SCC cells; this response was blocked by inhibitors of caspase-8 and caspase-3. Anoikis was mediated by downregulation of integrin alpha v in a panel of SCC cells and was shown to be proteasome-dependent. Overexpression of integrin alpha v or FAK inhibited the increase in caspase-3 activation and apoptosis, whereas suppression of alpha v or FAK triggered a further significant increase in apoptosis, indicating that the apoptosis was mediated by suppression of integrin alpha v levels and dephosphorylation of FAK. Treatment with V+H- decreased the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, and direct activation of ERK by constitutively active MEK1, an ERK kinase, increased ERK1 and ERK2 phosphorylation and inhibited the increase in apoptosis induced by V+H-. ERK acted downstream from alpha v and FAK signals, since alpha v and FAK overexpression inhibited both the decrease in ERK phosphorylation and the increase in anoikis triggered by V+H-. These findings provide evidence that mutations in the high-affinity heparin-binding domain in association with the V region of fibronectin, or altered fibronectin matrices, induce anoikis in human SCC cells by modulating integrin alpha v-mediated phosphorylation of FAK and ERK.

Activation of FAK/PI3K/Rac1 signaling controls actin reorganization and inhibits cell motility in human cancer cells

We have recently identified a specific signaling pathway that regulates actin reorganization in malignant human breast and prostate epithelial cells associated with FAK, PI-3K and Rac1 activation. Here we report that this pathway operates in MCF7 cells upon activation of membrane androgen receptors (mAR). Stimulation of mAR by the non-permeable testosterone-BSA conjugate resulted in early actin reorganization documented by quantitative measurements of actin dynamics and morphological analysis of microfilament organization. This effect was regulated by early phosphorylation of FAK and subsequent PI-3K and Rac1 activation. The functional role of this pathway was further shown in A375 melanoma cells. Treatment with the opioid antagonist alpha(s1) casomorphin resulted in rapid and potent actin remodeling in A375 cells, regulated by rapid activation of the FAK/PI-3K/Rac1 signaling. Pretreatment of both cell lines with the specific PI-3K inhibitor wortmannin blocked actin reorganization. Interestingly, wound healing assays revealed that testosterone-BSA and alpha (s1) casomorphin significantly inhibited MCF7 and A375 cell motility respectively. These effects were abrogated through blockade of PI-3K signaling by wortmannin. The results presented here indicate that actin reorganization through FAK/PI3-K/Rac-1 activation operates in various human cancer cell systems supporting a functional role for FAK/PI-3K/Rac1/actin signaling in controlling cell motility.

Overexpression of focal adhesion kinase in head and neck squamous cell carcinoma is independent of fak gene copy number

The development of human malignancies can involve the aberrant regulation of intracellular signal transduction pathways that regulate cell-extracellular matrix interactions.

PURPOSE

In the current study, we aimed to evaluate focal adhesion kinase (FAK) at both genetic and protein expression levels in head and neck squamous cell carcinomas (HNSCC) and to explore the prognostic significance of FAK.

EXPERIMENTAL DESIGN

A total of 211 tissue specimens, including 147 primary tumors, 56 lymph node metastases, 3 benign hyperplasias, and 5 dysplasias, were analyzed using immunohistochemistry. The fak gene dosage was determined in 33 tumors. Correlations among DNA, protein, and clinicopathologic variables were analyzed.

RESULTS

FAK protein was overexpressed in HNSCCs compared with corresponding normal mucosa. High expression levels were found in 62% of the samples. Positive immunostaining was also detected in benign hyperplasias and preinvasive dysplastic lesions. All lymph node metastases examined showed FAK overexpression, with significant correlation with the expression in matched primary tumor. DNA copy number ratios for fak were higher in 39% of the tumors compared with normal mucosa. However, elevated FAK expression did not correlate with gains on DNA level, and not all cases with an amplification of the fak gene displayed protein overexpression. Similar data were obtained in five HNSCC-derived cell lines, in which FAK mRNA levels were precisely correlated with FAK protein levels. FAK protein overexpression in tumors correlated with nodal metastases.

CONCLUSIONS

These findings suggest an involvement of FAK in the onset and progression of HNSCC and provide an insight into a mechanism of FAK activation alternative to gene amplification.

Focal adhesion kinase and p53 signaling in cancer cells

The progression of human cancer is characterized by a process of tumor cell motility, invasion, and metastasis to distant sites, requiring the cancer cells to be able to survive the apoptotic pressures of anchorage-independent conditions. One of the critical tyrosine kinases linked to these processes of tumor invasion and survival is the focal adhesion kinase (FAK). FAK was first isolated from human tumors, and FAK mRNA was found to be upregulated in invasive and metastatic human breast and colon cancer samples. Recently, the FAK promoter was cloned, and it has been found to contain p53-binding sites. p53 inhibits FAK transcription, and recent data show direct binding of FAK and p53 proteins in vitro and in vivo. The structure of FAK and p53, proteins interacting with FAK, and the role of FAK in tumorigenesis and FAK-p53-related therapy are reviewed. This review focuses on FAK signal transduction pathways, particularly on FAK and p53 signaling, revealing a new paradigm in cell biology, linking signaling from the extracellular matrix to the nucleus.

Identification of potential biomarkers for measuring inhibition of Src kinase activity in colon cancer cells following treatment with dasatinib

Elevated levels of Src kinase expression have been found in a variety of human epithelial cancers. Most notably in colon cancer, elevated Src expression correlates with malignant potential and is also associated with metastatic disease. Dasatinib (BMS-354825) is a novel, orally active, multi-targeted kinase inhibitor that targets Src family kinases and is currently under clinical evaluation for the treatment of solid tumors. However, the effects of dasatinib on epithelial tumors are not fully understood. We show that concentrations of dasatinib that inhibit Src activity do not inhibit proliferation in 10 of 12 colon cancer cells lines. However, inhibition of integrin-dependent adhesion and migration by dasatinib correlated with inhibition of Src activity, suggesting that dasatinib may have anti-invasive or anti-metastatic activity and antiproliferative activity in epithelial tumors. Using phospho-specific antibodies, we show that inhibition of Src activity in colon cancer cell lines correlates with reduced phosphorylation of focal adhesion kinase and paxillin on specific Src-dependent phosphorylation sites. We have validated the use of phospho-specific antibodies against Src Tyr(419) and paxillin Tyr(118) as biomarkers of dasatinib activity in vivo. Colon carcinoma-bearing mice treated with dasatinib showed a decrease in both phospho-Src Tyr(419) and phospho-paxillin Tyr(118) in peripheral blood mononuclear cells, which correlated with inhibition of Src activity in the colon tumors. Thus, peripheral blood mononuclear cells may provide a useful surrogate tissue for biomarker studies with dasatinib using inhibition of Src Tyr(419) and paxillin Tyr(118) phosphorylation as read-outs of Src activity.

Increased expression of tissue transglutaminase in pancreatic ductal adenocarcinoma and its implications in drug resistance and metastasis

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive neoplastic diseases and is virtually incurable. The molecular mechanisms that contribute to the intrinsic resistance of PDAC to various anticancer therapies are not well understood. Recently, we have observed that several drug-resistant and metastatic tumors and tumor cell lines expressed elevated levels of tissue transglutaminase (TG2). Because PDAC exhibits inherent resistance to various drugs, we determined the constitutive expression of TG2 in 75 PDAC and 12 PDAC cell lines. Our results showed that 42 of 75 (56%) PDAC tumor samples expressed higher basal levels of TG2 compared with the normal pancreatic ducts [odds ratio (OR), 2.439; P = 0.012]. The increased expression of TG2 in PDAC was strongly associated with nodal metastasis (OR, 3.400; P = 0.017) and lymphovascular invasion (OR, 3.055; P = 0.045). Increased expression of TG2 was also evident in all 12 cell lines examined. The elevated expression of TG2 in PDAC cell lines was associated with gemcitabine resistance and increased invasive potential. Overexpression of catalytically active or inactive (C(277)S mutant) TG2 induced focal adhesion kinase (FAK) activation and augmented invasive functions in the BxPC-3 cell line. Conversely, down-regulation of TG2 by small interfering RNA attenuated FAK phosphorylation. Immunoprecipitation and confocal microscopy data revealed that TG2 was associated with FAK protein in PDAC cells. The activated FAK colocalized with TG2 at focal adhesion points. These results show for the first time that elevated expression of TG2 can induce constitutive activation of FAK and thus may contribute to the development of drug resistance and invasive phenotypes in PDAC.

Weak expression of focal adhesion kinase (pp125FAK) in patients with cervical cancer is associated with poor disease outcome

PURPOSE

The pp125 focal adhesion kinase (FAK) plays a pivotal role in tumor cell signaling. FAK expression has been linked to tumor cell invasion and metastasis, but data on cervical cancer are inconclusive. Our goal was to investigate FAK expression in cervical cancer and to assess whether its expression correlates with prognosis.

EXPERIMENTAL DESIGN

FAK expression was examined using immunohistochemistry with sections from 162 resected cervical cancer specimens. Kaplan-Meier survival curves were used to determine the significance of FAK expression in the prognosis of cervical cancer patients.

RESULTS

Specific FAK expression was found in the tumor cells, whereas normal cervical epithelium showed barely any FAK expression. Of 162 invasive cervical cancer specimens, 55 (34%) revealed weak expression of FAK, whereas moderate and strong expression was found in 63 (39%) and 44 (27%) tumors, respectively. Patients with tumors expressing weak amounts of FAK were characterized by a significantly poorer overall survival compared with those with moderate and high intratumoral FAK expression (P = 0.002). Weak expression of FAK correlated with pelvic lymph node metastasis (P = 0.026) and recurrent disease (P = 0.013). Multivariate Cox regression analysis revealed decreased FAK expression and pelvic lymph node metastasis to be significant independent factors predictive of poor disease outcome (hazard ratio, 0.36; P = 0.005; hazard ratio, 2.38; P = 0.018, respectively).

CONCLUSIONS

Weak expression of FAK in invasive cervical cancer is a strong independent predictor of poor patient outcome. Further studies are warranted to elucidate whether FAK expression analysis is a suitable tool identifying patients at high risk even at an early clinical stage.

Focal adhesion kinase: a potential target in cancer therapy

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that plays an important role in signal transduction pathways that are initiated at sites of integrin-mediated cell adhesions and by growth factor receptors. FAK is a key regulator of survival, proliferation, migration and invasion: processes that are all involved in the development and progression of cancer. FAK is also linked to oncogenes at both a biochemical and functional level. Moreover, overexpression and/or increased activity of FAK is common in a wide variety of human cancers, implicating a role for FAK in carcinogenesis. Given the important role of FAK in a large number of processes involved in tumorigenesis, metastasis and survival signalling FAK should be regarded as a potential target in the development of anti-cancer drugs. Therefore, selective inhibitors of FAK need to be developed. Combination of these selective FAK inhibitors with cytotoxic agents could be a very promising anti-cancer therapy.

Clinical significance of focal adhesion kinase in resectable pancreatic cancer

Focal adhesion kinase (FAK) is a non-receptor, cytoplasmic protein tyrosine kinase that is involved in the regulation of cellular signaling, migration, apoptosis, and cell cycle progression. Previous reports have shown that FAK is expressed in various kinds of cancer tissues and cancer cell lines; however, no information is available about human pancreatic carcinoma specimens. Tissue such specimens were obtained from 50 patients who underwent pancreatic resection for pancreatic invasive ductal carcinoma at our institute from 1996 to 2002. Immunohistochemical analysis of FAK was performed in the resected specimens. Focal adhesion kinase expression in seven human pancreatic cancer cell lines was analyzed by reverse transcription polymerase chain reaction (PCR) analysis and Western blot analysis. Focal adhesion kinase expression was detected in 24 of 50 cases (48%). There was a statistically significant correlation between FAK expression and tumor size (P=0.004), although FAK expression did not significantly correlate with other factors such as tumor histological grade, lymph node metastasis, distant metastasis, histological stage, and overall survival. Reverse transcription PCR analysis and Western blot analysis showed that FAK was expressed in all seven pancreatic cancer cell lines. Focal adhesion kinase expression was not directly related to clinicopathological factors except tumor size in pancreatic carcinoma. Focal adhesion kinase expression may not be a prognostic marker for pancreatic cancer patients.

RhoA and RhoC proteins promote both cell proliferation and cell invasion of human oesophageal squamous cell carcinoma cell lines in vitro and in vivo

There is growing evidence that Rho proteins are deregulated by overexpression in tumours; and according to some reports, this correlates with disease progression. Our previous clinical study had demonstrated a correlation between RhoA expression and tumour progression in oesophageal squamous cell carcinoma (ESCC). These findings prompted us to study, using nude mice, pathological roles of Rho proteins in human ESCC cells. Western blot analysis in ESCC cell lines, in addition to cell proliferation and in vitro migration assays, were performed to observe the malignant potential of RhoA and RhoC in untransfected and transfected cells. Constitutively active RhoA, RhoC and dominant negative RhoA (dnRhoA) proteins were transfected to ESCC (TE-1 and TE-2) cells. The stably transfected cells were injected into nude mice, and the growth and metastasis of these cells to the lungs were analysed. Tumour tissues were then examined using immunohistochemical methods for proteins Ki-67 (MIB-1), FAK, MMP-1, MMP-9 and TIMP-3. Protein levels of RhoA and RhoC in ESCC cell lines were visualised by Western blotting, and showed highest expression in TE-2 cells. Results from the migration assay illustrated that both RhoA and RhoC play a role in migration of ESCC cells. In TE-2 transfected cells, RhoC showed greater migration compared to RhoA. By using an experimental metastasis model in nude mice, RhoA was found to promote more tumour growth than RhoC, whereas RhoC induced lung metastasis in comparison to RhoA. Ki-67 labelling index was used to evaluate the proliferation potential of tumour tissue inoculated from nude mice. In TE-2 cells RhoA gave a proliferation capacity of 24.8+/-0.5, which was significantly higher than those of TE-2 RhoC 10+/-0.4 (P<0.01). Strong immunoreactivity for FAK, MMP-1 and MMP-9 proteins was present in all tumour cells. By contrast, loss of TIMP-3 expression was observed in all tumour cells. In conclusion, our results indicate that pro-oncogenic Rho proteins are involved in promoting tumour growth, cell migration and metastasis in human ESCC cells in nude mice. The results from this study suggest that active Rho proteins may induce a transforming effect that leads to a malignant phenotype.

Differences of onset age and survival rates in esophageal squamous cell carcinoma cases with and without family history of upper gastrointestinal cancer from a high-incidence area in North China

BACKGROUND

Gene expression analyses indicate that there are 152 genes of which the expression differs significantly in esophageal squamous cell carcinoma (ESCC) cases with positive as opposed to those with negative family history of upper gastrointestinal cancer (FHUGIC) in the high-incidence area for ESCC in northern China. However, the question as to whether there is any difference of onset age or survival rates in the familial and sporadic cases of ESCC in the area is unknown.

AIMS

To investigate the differences of onset age or survival rates in the familial and sporadic cases of ESCC for surgically treated ESCC patients from the high-incidence area.

METHODS

Retrospective analyses were performed on the clinicopathologic and survival data of ESCC cases (N = 1715) who had undergone surgery alone from 1985 to 1994 in Hebei Cancer Center, a provincial cancer center established primarily to treat esophageal cancer in the high-incidence area, to investigate the differences. All the patients had been native residents of the high-incidence area in northern China. Student's t-test was used to test the difference of onset ages, and Cox Proportional Hazard Model was used to examine the differences of survival rates in the familial and sporadic cases of ESCC.

RESULTS

Although the familial cases of ESCC had had a significantly earlier onset than the sporadic cases (P < 0.00), they experienced relatively lower survival rates than the sporadic cases after surgery. The differences of survival rates in the familial and sporadic cases were significant for patients above the age of 50 years (P(Wald) = 0.04) and for the T(is, 1)N(0)M(0) group (P(Wald) = 0.04), the differences were bigger for early-staged than for the later-stage groups, and the differences persisted when adjusted for or stratified by confounding factors such as sex, age (under versus above the age of 50 years), smoking, drinking, cancer segment location, surgery year (calendar year), stage (UICC 4th Ed, 1987), and Resection category. Overall, cases under the age of 50 years old showed a higher survival curve than cases above the age of 50 years old, and this was especially true for the familial case group where the difference was significant (P(Wald) = 0.03).

CONCLUSION

The findings suggest that the familial ESCC may develop earlier, and may have a poorer prognosis than the sporadic ESCC. Both earlier onset and poorer outcome may be important features for the familial as opposed to the sporadic cases of ESCC. The association between younger onset age and higher survival rates found for the familial cases may indicate some survival benefit for early discovery for people with positive FHUGIC in the high-incidence area.

Design and synthesis of 7H-pyrrolo[2,3-d]pyrimidines as focal adhesion kinase inhibitors. Part 2

A series of 2-amino-9-aryl-7H-pyrrolo[2,3-d]pyrimidines were designed and synthesized as focal adhesion kinase (FAK) inhibitors using molecular modeling in conjunction with a co-crystal structure. Chemistry was developed to introduce functionality onto the 9-aryl ring, which resulted in the identification of potent FAK inhibitors. In particular, compound 32 possessed single-digit nanomolar IC(50) and represents one of the most potent FAK inhibitors discovered to date.

Intrinsic focal adhesion kinase activity controls orthotopic breast carcinoma metastasis via the regulation of urokinase plasminogen activator expression in a syngeneic tumor model

Expression of focal adhesion kinase (FAK) is elevated in malignant breast cancer, yet the role of intrinsic FAK activity in promoting tumor progression remains undefined. Here, we have inhibited FAK activity or expression in murine 4T1 breast carcinoma cells via dominant-negative focal adhesion kinase-related non-kinase (FRNK) or anti-FAK short hairpin RNA (shRNA) expression, respectively. Neither FRNK nor FAK shRNA ( approximately 80% reduced FAK levels) affected 4T1 proliferation in culture, whereas reduced FAK activity or expression blocked 4T1 cell invasion through Matrigel and resulted in 2-3-fold lower urokinase plasminogen activator (uPA) expression. Control 4T1 cells implanted into mammary fat pads of BALB/c mice exhibited spontaneous metastasis to the lungs, to the peritoneal cavity, and resulted in 90% lethality within 21 days. Whereas FAK shRNA-expressing 4T1 cells formed tumors in mice with low levels of apoptosis, when mammary-injected, these cells did not exhibit lung metastasis after 21 days and caused only 40% lethality up to 60 days. Transient re-expression of wild-type but not kinase-dead FAK in 4T1 FAK shRNA cells promoted uPA production and mammary to lung metastasis within 7 days. In fact, stable human uPA overexpression in 4T1 FAK shRNA cells promoted Matrigel invasion and lung metastasis equal to 4T1 controls. Conversely, treatment with plasminogen activator inhibitor-1 or neutralizing antibody to uPA blocked Matrigel invasion of 4T1 control cells. These studies provide the first direct proof that FAK catalytic activity can facilitate metastatic breast cancer progression by regulating uPA expression.

Focal adhesion proteins as markers of malignant transformation and prognostic indicators in breast carcinoma

Focal adhesion kinase (FAK) is one of the central signaling molecules found at focal adhesion sites, which are specific areas on the cell membrane where cells attach to extracellular matrix proteins. Focal adhesion kinase interacts with multiple signaling and adaptor molecules and effects several signaling pathways. Overexpression of FAK and its substrate c-Src has been implicated in malignant transformation and acquisition of an invasive tumor phenotype of different tissues. Overexpression of the multidomain protein paxillin, which is also a FAK ligand and a c-Src substrate, has been associated with less malignant tumor behavior. The purpose of this study was to analyze the involvement of integrin signaling molecules FAK, c-Src, and paxillin in malignant transformation of the breast epithelium. Using phosphospecific antibodies FAK-pY(397) and Src-pY(416), we demonstrated that neither activation of FAK nor activation of c-Src correlates with development of invasive tumor properties. However, activation of both FAK and c-Src correlates with malignant transformation. We further demonstrated that overexpression of paxillin also correlates with malignant transformation and is a marker of a less invasive tumor phenotype. Using tissue microarray, we demonstrated that expression and activation of paxillin inversely correlated with lymph node metastases and lymphovascular invasion, respectively. No correlation between paxillin expression and activation and tumor grade, estrogen, progesterone, and Her2/Neu receptor expression was found. In summary, focal adhesion proteins FAK and c-Src can be used as markers of malignant transformation in epithelial cells but not invasive phenotype, whereas expression and activation of paxillin may represent a good prognosticator in breast carcinoma.

Focal adhesion kinase and Src phosphorylations in HGF-induced proliferation and invasion of human cholangiocarcinoma cell line, HuCCA-1

AIM

To study the role of focal adhesion kinase (FAK) and its association with Src in hepatocyte growth factor (HGF)-induced cell signaling in cholangiocarcinoma progression.

METHODS

Previously isolated HuCCA-1 cells were re-characterized by immunofluorescent staining and reverse transcriptase-polymerase chain reaction assay for the expression of cytokeratin 19, HGF and c-Met mRNA. Cultured HuCCA-1 cells were treated with HGF and determined for cell proliferation and invasion effects by MTT and invasion assays. Western blotting, immunoprecipitation, and co-immunoprecipitation were also performed to study the phosphorylation and interaction of FAK and Src. A novel Src inhibitor (AZM555130) was applied in cultures to investigate the effects on FAK phosphorylation inhibition and on cell proliferation and invasion.

RESULTS

HGF enhanced HuCCA-1 cell proliferation and invasion by mediating FAK and Src phosphorylations. FAK-Src interaction occurred in a time-dependent manner that Src was proved to be an upstream signaling molecule to FAK. The inhibitor to Src decreased FAK phosphorylation level in correlation with the reduction of cell proliferation and invasion.

CONCLUSION

FAK plays a significant role in signaling pathway of HGF-responsive cell line derived from cholangiocarcinoma. Autophosphorylated Src, induced by HGF, mediates Src kinase activation, which subsequently phosphorylates its substrate, FAK, and signals to cell proliferation and invasion.

High focal adhesion kinase expression in invasive breast carcinomas is associated with an aggressive phenotype

Focal adhesion kinase (FAK) is a protein tyrosine kinase expressed in invasive breast cancer that regulates antiapoptotic signaling. We have examined FAK expression by immunohistochemistry using anti-FAK 4.47 in breast tumor samples from a large population-based, case-control study of women participating in the University of North Carolina Breast Specialized Programs of Research Excellence (SPORE), Carolina Breast Cancer Study. In this population, 629 formalin-fixed, paraffin-embedded tissue sections were stained for FAK and scored as high (3+ or 4+ intensity and > or = 90% positive cells) or otherwise. High FAK expression was associated with poor prognostic indicators including high mitotic index (>10 mitoses per 10 consecutive high-power fields), nuclear grade 3, architectural grade 3, estrogen and progesterone receptor negative, and HER-2/neu overexpressed using CB11 antibody. The association of high FAK expression with HER-2/neu overexpression lends further support that HER-2/neu and FAK collaborate to promote tumorigenesis. The presence of strong FAK expression in many high grade, estrogen- and progesterone-negative breast carcinomas indicates that FAK may be an attractive target for therapeutic intervention.

Tumor cells caught in the act of invading: their strategy for enhanced cell motility

Invasion of neighboring extracellular matrix tissue, the lymphatic system and blood vessels is a key element of tumor cell metastasis in many epithelial tumors. Understanding the cell motility pathways that contribute to invasion can provide new approaches and targets for anticancer therapy. The recent convergence of technologies for expression profiling and intravital imaging has revealed the identities of some of the genes that contribute to motility and chemotaxis of cancer cells in tumors. In particular, the genes encoding a minimum motility machine are coordinately upregulated in tumor cells collected by an in vivo invasion assay. These results support a "tumor microenvironment invasion model" and provide new target opportunities for cancer therapy.

The role of focal-adhesion kinase in cancer - a new therapeutic opportunity

Focal-adhesion kinase (FAK) is an important mediator of growth-factor signalling, cell proliferation, cell survival and cell migration. Given that the development of malignancy is often associated with perturbations in these processes, it is not surprising that FAK activity is altered in cancer cells. Mouse models have shown that FAK is involved in tumour formation and progression, and other studies showing that FAK expression is increased in human tumours make FAK a potentially important new therapeutic target.

Integrin signaling in malignant melanoma

Cell adhesion and migration are essential for embryonic development, tissue regeneration, but also for tumor development. The physical link between the extracellular matrix (ECM) and the actin cytoskeleton is mainly mediated by receptors of the integrin family. Through signals transduced upon integrin ligation to ECM proteins, this family of proteins plays key roles in regulating tumor growth and metastasis as well as tumor angiogenesis. During melanoma development, changes in integrin expression, intracellular control of integrin functions and signals perceived from integrin ligand binding impact upon the ability of tumor cells to interact with their environment and enable melanoma cells to convert from a sessile, stationary to a migratory and invasive phenotype. Antagonists of several integrins are now under evaluation in clinical trials to determine their potential as therapeutics for malignant melanoma and other kinds of cancer.

Correlation between RhoA overexpression and tumour progression in esophageal squamous cell carcinoma

AIMS

The aim of this study was to clarify the clinico-pathologic outcome and prognostic significance of RhoA in esophageal squamous cell carcinoma (ESCC).

METHODS

Immunohistochemical staining for RhoA was performed on surgical specimens obtained from 122 patients with ESCC.

RESULTS

There were significant correlations among RhoA overexpression and TNM clinical classification (depth of invasion, P=0.028; presence of regional lymph node metastasis, P=0.009; presence of distant metastasis, P=0.003; staging P=0.006), lymphatic invasion (P=0.002), and blood-vessel invasion (P=0.004). The five-year survival rates for ESCC patients with RhoA overexpression were significantly lower than those in patients with RhoA under-expression (P=0.002).

CONCLUSIONS

Our results demonstrated immunohistochemically that the expression of RhoA protein appeared to be correlated with tumour progression of ESCC. Patients with RhoA overexpression tended to have poor prognosis compared with patients with RhoA under-expression.

Tyrosine kinase inhibitors in cancer therapy

Cancer is the second leading cause of death in the western world. Despite advances in diagnosis and treatment, overall survival of patients remains poor. Scientific advances in recent years have enhanced our understanding of the biology of cancer. Human protein tyrosine kinases (PTKs) play a central role in human carcinogenesis and have emerged as the promising new targets. Several approaches to inhibit tyrosine kinase have been developed. These agents have shown impressive anticancer effects in preclinical studies and are emerging as promising agents in the clinic. The remarkable success of BCR-ABL tyrosine kinase inhibitor imatinib (STI571) in the treatment of chronic myeloid leukaemia has particularly stimulated intense research in this field. At least 30 inhibitors are in various stages of clinical development in cancer, and about 120 clinical trials are ongoing worldwide. In this review, we focus on the role of tyrosine kinases in cancer and the development of specific small molecule inhibitors for therapy. We also provide a critical analysis of the current data on tyrosine kinase inhibitors and highlight areas for future research. Issues with regards to the design of clinical trials with such agents are also discussed. Innovative approaches are needed to fully evaluate the potential of these agents, and a concerted international effort will hopefully help to integrate these inhibitors in cancer therapy in the near future.

High expression of focal adhesion kinase (p125FAK) in node-negative breast cancer is related to overexpression of HER-2/neu and activated Akt kinase but does not predict outcome

INTRODUCTION

Focal adhesion kinase (FAK) regulates multiple cellular processes including growth, differentiation, adhesion, motility and apoptosis. In breast carcinoma, FAK overexpression has been linked to cancer progression but the prognostic relevance remains unknown. In particular, with regard to lymph node-negative breast cancer it is important to identify high-risk patients who would benefit from further adjuvant therapy.

METHODS

We analyzed 162 node-negative breast cancer cases to determine the prognostic relevance of FAK expression, and we investigated the relationship of FAK with major associated signaling pathways (HER2, Src, Akt and extracellular regulated kinases) by immunohistochemistry and western blot analysis.

RESULTS

Elevated FAK expression did not predict patient outcome, in contrast to tumor grading (P = 0.005), Akt activation (P = 0.0383) and estrogen receptor status (P = 0.0033). Significant positive correlations were observed between elevated FAK expression and HER2 overexpression (P = 0.001), as well as phospho-Src Tyr-215 (P = 0.021) and phospho-Akt (P < 0.001), but not with phospho-ERK1/2 (P = 0.108). Western blot analysis showed a significant correlation of FAK Tyr-861 activation and HER2 overexpression (P = 0.01).

CONCLUSIONS

Immunohistochemical detection of FAK expression is of no prognostic significance in node-negative breast cancer but provides evidence that HER2 is involved in tumor malignancy and metastatic ability of breast cancer through a novel signaling pathway participating FAK and Src.

Gene-expression profile changes correlated with tumor progression and lymph node metastasis in esophageal cancer

PURPOSE

The purpose of this research was to identify molecular clues to tumor progression and lymph node metastasis in esophageal cancer and to test their value as predictive markers.

EXPERIMENTAL DESIGN

We explored the gene expression profiles in cDNA array data of a 36-tissue training set of esophageal squamous cell carcinoma (ESCC) by using generalized linear model-based regression analysis and a feature subset selection algorithm. By applying the identified optimal feature sets (predictive gene sets), we trained and developed ensemble classifiers consisting of multiple probabilistic neural networks combined with AdaBoosting to predict tumor stages and lymph node metastasis. We validated the classifier abilities with 18 independent cases of ESCC.

RESULTS

We identified 71 genes of 1289 cancer-related genes of which the expression correlated with tumor stages. Of the 71 genes, 47 significantly differed between the Tumor-Node-Metastasis pT1/2 and pT3/4 stages. Cell cycle regulators and transcriptional factors possibly promoting the growth of tumor cells were highly expressed in the early stages of ESCC, whereas adhesion molecules and extracellular matrix-related molecules possibly promoting invasiveness increased in the later stages. For lymph node metastasis, we identified 44 genes with predictive values, which included cell adhesion molecules and cell membrane receptors showing higher expression in node-positive cases and cell cycle regulators and intracellular signaling molecules showing higher expression in node-negative cases. The ensemble classifiers trained with the selected features predicted tumor stage and lymph node metastasis in the 18 validation cases with respective accuracies of 94.4% and 88.9%. This demonstrated the reproducibility and predictive value of the identified features.

CONCLUSION

We suggest that these characteristic genes will provide useful information for understanding the malignant nature of ESCC as well as information useful for personalizing the treatments.

Squamous cell carcinoma cell aggregates escape suspension-induced, p53-mediated anoikis: fibronectin and integrin alphav mediate survival signals through focal adhesion kinase

Resistance to anoikis, or apoptosis triggered by detachment from the extracellular matrix (ECM), lengthens the survival of malignant cells, facilitating reattachment and colonization of secondary sites. To examine the molecular mechanisms underlying resistance to anoikis in human oral squamous cell carcinoma (SCC) cells, we cultured human squamous carcinoma (HSC-3) cells in suspension on plates coated with poly-2-hydroxyethyl methacrylate, which blocks access to the ECM. Cells in suspension that formed multicellular aggregates had significantly lower levels of apoptosis than single cells. Aggregates, but not single cells, had high levels of fibronectin. Preincubation with a cyclic arginine-glycine-aspartic acid peptide or fibronectin-blocking antibody significantly increased anoikis. Single cells had markedly lower expression of the integrin alpha(v) receptor than aggregates. Blocking alpha(v) function with a blocking antibody or by transfection with an antisense oligonucleotide increased apoptosis and inhibited aggregation. In single cells but not aggregates, phosphorylation of the integrin-associated focal adhesion kinase (FAK) at tyrosine 397 was reduced, and p53 levels were increased. Apoptosis was increased by blocking FAK with an antisense oligonucleotide and reduced by blocking p53. These findings show that SCC cells escape suspension-induced anoikis by forming multicellular aggregates that avail themselves of fibronectin survival signals mediated by integrin alpha(v). Single cells in suspension that do not form aggregates undergo anoikis because of decreased FAK phosphorylation and increased p53 levels. Thus, SCC cells appear to use neighboring cells and the ECM molecule FN to promote the metastatic phenotype.

Focal adhesion kinase is overexpressed in hepatocellular carcinoma and can be served as an independent prognostic factor

BACKGROUND/AIMS

The development of human malignancies can be attributed to aberrant regulation of intracellular signal transduction pathways. In the current study, we aimed to evaluate focal adhesion kinase (FAK), a non-receptor tyrosine kinase, expression in hepatocellular carcinoma (HCC), and to explore the prognostic significance of FAK.

METHODS

We investigated FAK mRNA expression in 60 HCC specimens using quantitative real-time reverse transcription polymerase chain reaction analysis, and the correlation between FAK expression and clinicopathologic parameters. FAK protein expression was examined using Western blot analysis and an immunohistochemical study.

RESULTS

We found that FAK mRNA was overexpressed in HCCs compared with the corresponding non-cancerous liver tissues (P=0.0008). The FAK overexpression correlated significantly with tumor size (P=0.034) and serum AFP level (P=0.030). Univariate and multivariate analyses revealed that FAK mRNA expression was an independent prognostic factor for disease-free (risk ratio 3.83; P=0.024) and overall (risk ratio 7.14; P=0.015) survival. Besides, we confirmed immunohistochemically that the FAK protein was detectable in cancer cells despite non-expression in corresponding non-cancerous tissues.

CONCLUSIONS

Our results suggest that FAK mRNA expression has prognostic significance for the survival of patients with HCC.