Expression of focal adhesion kinase and phosphorylated focal adhesion kinase in squamous cell carcinoma of the larynx

Integrative Analysis Reveals STC2 as a Prognostic Biomarker of Laryngeal Squamous Cell Carcinoma

Stanniocalcin 2 (STC2) is involved in many tumour types, but it remains unclear what its biological function is in laryngeal squamous cell carcinoma (LSCC). Therefore, we investigated STC2's expression, potential function, and prognostic significance of in LSCC. The expression and prognosis of STC2 in LSCC were described using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. In the TCGA database, the relationship between STC2 and immune infiltration, expression of immune cell chemokine and receptor genes, immune cell molecular marker genes, and epithelial‒mesenchymal transition (EMT) marker genes were analysed. The biological processes involved in STC2 and its expression-related genes were analysed comprehensively using bioinformatics. The single-gene ceRNA network of STC2 was constructed in the TCGA database. Finally, LSCC patients' tumour tissue STC2 expression was verified. STC2 silencing with the RNAi technique was used for the determination of cellular functions in a laryngeal cancer cell line. STC2 expression was higher in most tumours, including LSCC, than in normal tissues and was associated with poor prognosis. The relative proportions of naïve B, plasma, follicular helper T, and macrophage M0 cells in LSCC and normal samples differed significantly. STC2 expression correlated significantly positively with that of TGFB1 (biomarker of Tregs) and significantly negatively with that of D79A and CD19 (biomarkers of B cells). Furthermore, STC2 affected chemokine and receptor gene expression in immune cells. STC2 expression correlated with EMT marker gene expression in LSCC. STC2 was enriched in the PI3K/AKT signalling pathway, extracellular matrix (ECM) organisation, ECM-receptor interaction, and other tumour-related signalling pathways. STC2 was highly expressed in our clinical samples. N-cadherin and vimentin expression were decreased in the TU686 cell line after successful silencing of STC2, indicating that high STC2 expression may prompt LSCC cells to adopt a mesenchymal cell phenotype. STC2 silencing substantially reduced proliferation and migration in the TU686 cell line. STC2 may be a promising predictive biomarker for tumours, providing new approaches for LSCC diagnosis and treatment monitoring.

Molecular and functional insight into focal adhesion kinases: Therapeutic implications for oral malignancies

Oral carcinoma is the sixth most common cancer globally, with one death occurring every hour. Focal adhesion kinase (FAK) is an intercellular protein tyrosine kinase, a key indicator of the development of oral cancer. FAK overexpression leads to the initiation and significant progression of metastasis in head and neck cancers, indicating its vital role in cancer progression and potential as a biomarker for early oral malignant transformation. The present review elaborates on FAK's function in oral malignancies since it could serve as a biomarker of the initial stages of oral malignant transformation and a possible predictive factor for risk assessment.

FAK/IL-8 axis promotes the proliferation and migration of gastric cancer cells

Gastric cancer (GC) is one of the most common malignancies in China and is associated with high mortality. The occurrence and development of gastric cancer are related to genetic and environmental factors. Focal adhesion kinase (FAK) is a cytoplasmic nonreceptor protein tyrosine kinase that is activated by the extracellular matrix and growth factors. FAK is highly expressed in cancer and promotes its development by regulating cancer cell proliferation, migration, and angiogenesis. The expression of IL-8 is increased in many types of malignant tumor cells and is linked to their proliferation, migration, invasion, angiogenesis, and EMT. In this study, we found FAK to be essential for the proliferation, migration, and peritoneal metastasis of gastric cancer cells. To examine the molecular regulatory mechanisms of FAK in the peritoneal dissemination of gastric cancer, we performed RNA-seq analysis of MKN-45-FAK-/- and MKN45 cells and demonstrated that IL-8 was downregulated in FAK-deficient cells. Conversely, we confirmed that IL-8 activates FAK activity. We established that IL-8 promotes the proliferation, colony formation, and migration of gastric cancer cells that are partially mediated by FAK. Thus, we propose that an IL-8-FAK-IL-8 positive feedback loop effects the proliferation and migration of gastric cancer cells.

G9a Promotes Invasion and Metastasis of Non-Small Cell Lung Cancer through Enhancing Focal Adhesion Kinase Activation via NF-κB Signaling Pathway

Potential roles of euchromatic histone methyltransferase 2 (EHMT2 or G9a) in invasion and metastasis are not well understood in non-small cell lung cancer (NSCLC). Here, we investigated the effect and underlying mechanisms of G9a and therapeutic implications of targeting G9a in the invasion and metastasis of NSCLC. Overexpression of G9a significantly enhanced in vitro proliferation and invasion, while knockdown of G9a drastically suppressed in vivo growth and metastasis of A549 and H1299 NSCLC cells. Knockdown or inhibition of G9a significantly decreased the expression of focal adhesion kinase (FAK) protein and activation of FAK pathway. In addition, defactinib, a potent FAK inhibitor, partially abolished the G9a-enhanced invasion in these NSCLC cells. Furthermore, targeting G9a was found to suppress NF-κB transcriptional activity in NSCLC cells through stabilizing NF-κB inhibitor alpha (IκBα), while an NF-κB inhibitor Parthenilide partially abolished the G9a-enhanced FAK activation, which suggests that G9a-enhanced invasion and activation of FAK is mediated by elevated NF-κB activity. Notably, a strong positive correlation between the IHC staining of G9a and phosphorylated FAK proteins was identified in H1299 xenografts and 159 cases of NSCLC tissues (R = 0.408). IMPLICATIONS: The findings of this study strongly demonstrate that G9a may promote invasion and metastasis of NSCLC cells by enhancing FAK signaling pathway via elevating NF-κB transcriptional activity, indicating potential significance and therapeutic implications of these pathways in the invasion and metastasis of NSCLCs that overexpress G9a protein.

Role of Focal Adhesion Kinase in Small-Cell Lung Cancer and Its Potential as a Therapeutic Target

Small-cell lung cancer (SCLC) represents 15% of all lung cancers and it is clinically the most aggressive type, being characterized by a tendency for early metastasis, with two-thirds of the patients diagnosed with an extensive stage (ES) disease and a five-year overall survival (OS) as low as 5%. There are still no effective targeted therapies in SCLC despite improved understanding of the molecular steps leading to SCLC development and progression these last years. After four decades, the only modest improvement in OS of patients suffering from ES-SCLC has recently been shown in a trial combining atezolizumab, an anti-PD-L1 immune checkpoint inhibitor, with carboplatin and etoposide, chemotherapy agents. This highlights the need to pursue research efforts in this field. Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that is overexpressed and activated in several cancers, including SCLC, and contributing to cancer progression and metastasis through its important role in cell proliferation, survival, adhesion, spreading, migration, and invasion. FAK also plays a role in tumor immune evasion, epithelial-mesenchymal transition, DNA damage repair, radioresistance, and regulation of cancer stem cells. FAK is of particular interest in SCLC, being known for its aggressiveness. The inhibition of FAK in SCLC cell lines demonstrated significative decrease in cell proliferation, invasion, and migration, and induced cell cycle arrest and apoptosis. In this review, we will focus on the role of FAK in cancer cells and their microenvironment, and its potential as a therapeutic target in SCLC.

Focal Adhesion Kinase (FAK) Overexpression and Phosphorylation in Oral Squamous Cell Carcinoma and their Clinicopathological Significance

Focal adhesion kinase (FAK) is involved in progression of various cancers, and FAK overexpression has been associated with cancer invasion and metastasis. However, the involvement of FAK expression in the clinicopathological malignancy of oral squamous cell carcinoma (OSCC) remains unknown. In addition, there is no consensus regarding the role of p16 expression in OSCC. In this study, the immunohistochemically measured expression of FAK, phosphorylated FAK (FAKpY397) and p16 expressions and their associations with clinicopathological features and 5-year survival rates were examined in surgical samples from 70 patients with primary OSCC. FAK and FAKpY397 were expressed at high levels in 42 cases (60.0%) and 34 cases (48.6%), respectively, and 9 cases (12.9%) were positive for p16. FAK expression was significantly correlated with local recurrence, subsequent metastasis, and the mode of invasion. FAKpY397 expression was significantly correlated with both N classification and the mode of invasion. p16 expression was significantly correlated with clinical stage only. Patients having high expression of FAK, FAKpY397, or both showed significantly worse prognosis, but p16 expression showed no significant relation to prognosis. The results suggested that overexpression and phosphorylation of FAK in OSCC may affect cancer progression, such as local invasion and lymph node metastasis, and thereby contribute to life prognosis.

Formin-like 3 regulates RhoC/FAK pathway and actin assembly to promote cell invasion in colorectal carcinoma

AIM

To clarify the underlying mechanism of formin-like 3 (FMNL3) in the promotion of colorectal carcinoma (CRC) cell invasion.

METHODS

The in vitro biological function analyses of FMNL3 were performed by gain- and loss-of function approaches. Changes in the F-actin cytoskeleton were detected by the technologies of phalloidin-TRITC labeling and confocal microscopy. The signaling pathway mediated by FMNL3 was explored by western blot, gelatin zymograph assay, co-immunoprecipitation (co-IP), immunofluorescence co-localization, and glutathione S-transferase (GST) pull-down assay.

RESULTS

The in vitro experimental results showed that FMNL3 significantly promoted the proliferation, invasion, and migration of CRC cells (P < 0.05 and P < 0.01). Moreover, FMNL3 regulated the remodeling of actin-based protrusions such as filopodia and lamellipodia in a RhoC-dependent manner. The western blot and gelatin zymograph assay results indicated that FMNL3 was involved in the RhoC/ focal adhesion kinase (FAK) pathway and acted as an effector of RhoC to activate the downstream signaling of p-FAK as well as p-MAPK and p-AKT. This resulted in the increased expression of matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9) and vascular endothelial growth factor (VEGF), and the subsequent promotion of CRC cell invasion. The results of TAE226, U0126 or Ly294002 treatment confirmed an essential role of FMNL3 in activation of the RhoC/FAK pathway and the subsequent promotion of CRC invasion. Co-IP, co-localization and GST pull-down assays showed the direct interaction of FMNL3 with RhoC in vivo and in vitro.

CONCLUSION

FMNL3 regulates the RhoC/FAK signaling pathway and RhoC-dependent remodeling of actin-based protrusions to promote CRC invasion.

Involvement of FAK-ERK2 signaling pathway in CKAP2-induced proliferation and motility in cervical carcinoma cell lines

Cervical carcinoma is the fourth most common cause of death in woman, caused by human papillomavirus (HPV) infections and arising from the cervix. Cytoskeleton-associated protein 2 (CKAP2), also known as tumor-associated microtubule-associated protein, has been linked to tumorigenic effects. In the present study, we screened CKAP2 as a new candidate gene which promotes development of cervical carcinoma, in two independent datasets (TCGA and GSE27678). Results showed that CKAP2 expression was significantly up-regulated in cervical cancerous tissues compared with normal counterparts. Gene set enrichment analysis (GSEA) showed that metastasis, cell cycle and FAK pathways were related with elevated CKAP2 expression. Knockdown of CKAP2 expression significantly inhibited cell proliferation, migration and invasion both in HeLa and C-33A cells. And depletion of CKAP2 down-regulated the expression of metastasis and cell cycle related proteins as well as the phosphorylation of ERK2 (p-ERK2), except E-cadherin. In vivo experiment revealed that knockdown of CKAP2 inhibited C-33A cells proliferation. However, FAK inhibitor PF-562271 and ERK2 inhibitor VX-11e treatment significantly inhibited CKAP2 overexpression-induced cell proliferation, migration and invasion in SiHa cells. In conclusion, our study suggests that CKAP2 acts as a functional oncogene in cervical carcinoma development and may exert its function by targeting FAK-ERK2 signaling pathway.

Focal adhesion kinase maintains, but not increases the adhesion of dental pulp cells

Focal adhesion kinase (FAK) functions as a key enzyme in the integrin-mediated adhesion-signalling pathway. Here, we aimed to investigate the effects of FAK on adhesion of human dental pulp (HDP) cells. We transfected lentiviral vectors to silence or overexpress FAK in HDP cells ex vivo. Early cell adhesion, cell survival and focal contacts (FCs)-related proteins (FAK and paxillin) were examined. By using immunofluorescence, the formation of FCs and cytoskeleton was detected, respectively. We found that both adhesion and survival of HDP cells were suppressed by FAK inhibition. However, FAK overexpression slightly inhibited cell adhesion and exhibited no change in cell survival compared with the control. A thick rim of cytoskeleton accumulated and smaller dot-shaped FCs appeared in FAK knockdown cells. Phosphorylation of paxillin (p-paxillin) was inhibited in FAK knockdown cells, verifying that the adhesion was inhibited. Less cytoskeleton and elongated FCs were observed in FAK-overexpressed cells. However, p-paxillin had no significant difference compared with the control. In conclusion, the data suggest that FAK maintains cell adhesion, survival and cytoskeleton formation, but excessive FAK has no positive effects on these aspects.

Focal adhesion kinase overexpression and its impact on human osteosarcoma

Focal adhesion kinase (FAK) has been implicated in tumorigenesis in various malignancies. We sought to examine the expression patterns of FAK and the activated form, phosphorylated FAK (pFAK), in human osteosarcoma and to investigate the correlation of FAK expression with clinicopathologic parameters and prognosis. In addition, the functional consequence of manipulating the FAK protein level was investigated in human osteosarcoma cell lines. Immunohistochemical staining was used to detect FAK and pFAK in pathologic archived materials from 113 patients with primary osteosarcoma. Kaplan-Meier survival and Cox regression analyses were performed to evaluate the prognoses. The role of FAK in the cytological behavior of MG63 and 143B human osteosarcoma cell lines was studied via FAK protein knock down with siRNA. Cell proliferation, migration, invasiveness and apoptosis were assessed using the CCK8, Transwell and Annexin V/PI staining methods. Both FAK and pFAK were overexpressed in osteosarcoma. There were significant differences in overall survival between the FAK-/pFAK- and FAK+/pFAK- groups (P = 0.016), the FAK+/pFAK- and FAK+/pFAK+ groups (P = 0.012) and the FAK-/pFAK- and FAK+/pFAK+ groups (P < 0.001). There were similar differences in metastasis-free survival between groups. The Cox proportional hazards analysis showed that the FAK expression profile was an independent indicator of both overall and metastasis-free survival. SiRNA-based knockdown of FAK not only dramatically reduced the migration and invasion of MG63 and 143B cells, but also had a distinct effect on osteosarcoma cell proliferation and apoptosis. These results collectively suggest that FAK overexpression and phosphorylation might predict more aggressive biologic behavior in osteosarcoma and may be an independent predictor of poor prognosis.

Expression of pY397 FAK promotes the development of non-small cell lung cancer

Focal adhesion kinase (FAK) expression has been identified as associated with cancer development and metastasis. Autophosphorylation of FAK at tyrosine (Y) 397 (pY397) performs a critical role in tumor cell signaling. However, few studies have evaluated the expression of pY397 FAK in non-small cell lung cancer (NSCLC). In the present study, pY397 FAK expression in NSCLC was investigated using immunohistochemistry. pY397 FAK staining scores were compared between various groups of specimens and the associations between clinical and pathological characteristics were investigated. A Kaplan-Meier survival curve was used to determine the association between pY397 FAK expression and the prognosis of NSCLC patients. The results of the present study revealed that pY397 FAK expression was localized to the cytoplasm of lung cells, and that pY397 FAK was overexpressed in NSCLC tissues, as well as associated metastatic tissues, when compared with the corresponding non-tumor tissues. However, no significant difference was identified between the pY397 FAK expression in primary lesions and lymph node metastases. Furthermore, pY397 FAK staining scores were not found to be associated with the tumor size, gender, degree of differentiation, histotypes, presence of lymph node metastases or survival rate of NSCLC patients. These results indicate that pY397 FAK is involved with the development of NSCLC, but is not a prognostic marker for the disease.

Combination of heat shock protein 90 and focal adhesion kinase inhibitors synergistically inhibits the growth of non-small cell lung cancer cells

Discovery of effective drug combinations is a promising strategy to improve patient survival. This study explores the impact of heat shock protein 90 (Hsp90) inhibition in combination with focal adhesion kinase (FAK) inhibitor on the growth of non-small cell lung cancer cells (NSCLC cells). Our data show that 17-N-Allylamino-17-demethoxygeldanamycin (17-AAG), a well-studied Hsp90 inhibitor, synergized with FAK inhibitor, PF-573228, on the growth inhibition of NSCLC cells. This combination effect was confirmed using additional chemically distinct Hsp90 inhibitor, STA-9090, which is currently undergoing phase 3 clinical evaluation. Co-treatment of NSCLC cells with Hsp90 and FAK inhibitors significantly enhanced the inhibition on long-term colony formation compared to that with single agent. Inhibition of FAK exacerbated the G₂ cell cycle arrest and annexin-V apoptotic staining induced by 17-AAG. Further mechanistic studies revealed that the combination of Hsp90 and FAK inhibitors reduced the activity of canonical proliferative and survival Akt-mTOR signaling, and increased pro-apoptotic caspase activation. Interestingly, FAK inhibition alone induced feedback activation of pro-survival Erk signaling, which was abrogated by co-treatment with Hsp90 inhibitors. Both Hsp90 and FAK inhibitors are undergoing clinical evaluation. Our studies suggest the tandem of Hsp90 and FAK inhibitors may provide an effective treatment option for NSCLC patients.

Biglycan enhances gastric cancer invasion by activating FAK signaling pathway

Biglycan (BGN) is an important member of small leucine-rich proteoglycans family, and has been implicated in oncogenesis and development of various human cancer types. Here we report that BGN promotes tumor invasion and metastasis of gastric cancer both in vitro and in vivo. BGN expression is significantly higher in gastric cancer tissues and associated with lymph node metastasis, depth of tumor invasion and TNM stage. BGN enhances gastric cancer cell wound healing, migration and invasion ability as well as the tube formation ability of endothelial cells in vitro. Animal experiments results in vivo are consistent with outcomes in vitro. BGN induces increased phosphorylation of FAK (Tyr576/577, Tyr925 and Tyr397) and Paxillin. These results indicate that BGN is upregulated, and plays an oncogenic role, in gastric cancer metastasis by activating the FAK signaling pathway.

Regulation of estrogen receptor α function in oral squamous cell carcinoma cells by FAK signaling

Estrogen receptor α (ERA) is a DNA-binding transcription factor that plays an important role in the regulation of cell growth. Previous studies indicated that the expression of ERα in cell lines and tumors derived from oral squamous cell carcinoma (OSCC). The aim of this study was to examine the activity and function of ERα in OSCC cells and the mechanism underlying ERα activation. Immunochemical analyses in benign (n=11) and malignant (n=21) lesions of the oral cavity showed that ERα immunoreactivity was observed in 43% (9/21) of malignant lesions, whereas none of benign lesions showed ERα immunoreactivity. The ERα expression was also found in three OSCC cell lines and its transcriptional activity was correlated with cell growth. Addition of estradiol stimulated cell growth, whereas treatment of tamoxifen or knockdown of ERα expression caused reduced cell growth. Interestingly, the expression and activity of focal adhesion kinase (FAK) were associated with the phosphorylation of ERα at serine 118 in OSCC cells. Elevated expression of FAK in the slow-growing SCC25 cells caused increases in ERα phosphorylation, transcriptional activity, and cell growth rate, whereas knockdown of FAK expression in the rapid-growing OECM-1 cells led to reduced ERα phosphorylation and activity and retarded cell growth. Inhibition of the activity of protein kinase B (AKT), but not ERK, abolished FAK-promoted ERα phosphorylation. These results suggest that OSCC cells expressed functional ERα, whose activity can be enhanced by FAK/AKT signaling, and this was critical for promoting cell growth. Thus, FAK and ERα can serve as the therapeutic targets for the treatment of OSCC.

Somatic copy number alterations by whole-exome sequencing implicates YWHAZ and PTK2 in castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) is the most aggressive form of prostate cancer (PCa) and remains a significant therapeutic challenge. The key to the development of novel therapeutic targets for CRPC is to decipher the molecular alterations underlying this lethal disease. The aim of our study was to identify therapeutic targets for CRPC by assessing somatic copy number alterations (SCNAs) by whole-exome sequencing on five CRPC/normal paired formalin-fixed paraffin-embedded (FFPE) samples, using the SOLiD4 next-generation sequencing (NGS) platform. Data were validated using fluorescence in situ hybridization (FISH) on a PCa progression cohort. PTK2 and YWHAZ amplification, mRNA and protein expression were determined in selected PCa cell lines. Effects of PTK2 inhibition using TAE226 inhibitor and YWHAZ knock-down on cell proliferation and migration were tested in PC3 cells in vitro. In a larger validation cohort, the amplification frequency of YWHAZ was 3% in localized PCa and 48% in CRPC, whereas PTK2 was amplified in 1% of localized PCa and 35% in CRPC. YWHAZ knock-down and PTK2 inhibition significantly affected cell proliferation and migration in the PC3 cells. Our findings suggest that inhibition of YWHAZ and PTK2 could delay the progression of the disease in CRPC patients harbouring amplification of the latter genes. Furthermore, our validated whole-exome sequencing data show that FFPE tissue could be a promising alternative for SCNA screening using next-generation sequencing technologies.

The role of FAK in tumor metabolism and therapy

Focal adhesion kinase (FAK) plays a vital role in tumor cell proliferation, survival and migration. Altered metabolic pathways fuel rapid tumor growth by accelerating glucose, lipid and glutamine processing. Besides the mitogenic effects of FAK, evidence is accumulating supporting the association between hyper-activated FAK and aberrant metabolism in tumorigenesis. FAK can promote glucose consumption, lipogenesis, and glutamine dependency to promote cancer cell proliferation, motility, and survival. Clinical studies demonstrate that FAK-related alterations of tumor metabolism are associated with increased risk of developing solid tumors. Since FAK contributes to the malignant phenotype, small molecule inhibition of FAK-stimulated bioenergetic and biosynthetic processes can provide a novel approach for therapeutic intervention in tumor growth and invasion.

Requirement of PEA3 for transcriptional activation of FAK gene in tumor metastasis

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase critically involved in cancer metastasis. We found an elevation of FAK expression in highly metastatic melanoma B16F10 cells compared with its less metastatic partner B16F1 cells. Down-regulation of the FAK expression by either small interfering RNA or dominant negative FAK (FAK Related Non-Kinase, FRNK) inhibited the B16F10 cell migration in vitro and invasiveness in vivo. The mechanism by which FAK activity is up-regulated in highly metastatic cells remains unclear. In this study, we reported for the first time that one of the Est family proteins, PEA3, is able to transactivate FAK expression through binding to the promoter region of FAK. We identified a PEA3-binding site between nucleotides -170 and +43 in the FAK promoter that was critical for the responsiveness to PEA3. A stronger affinity of PEA3 to this region contributed to the elevation of FAK expression in B16F10 cells. Both in vitro and in vivo knockdown of PEA3 gene successfully mimicked the cell migration and invasiveness as that induced by FAK down-regulation. The activation of the well-known upstream of PEA3, such as epidermal growth factor, JNK, and ERK can also induce FAK expression. Furthermore, in the metastatic human clinic tumor specimens from the patients with human primary oral squamous cell carcinoma, we observed a strong positive correlation among PEA3, FAK, and carcinoma metastasis. Taking together, we hypothesized that PEA3 might play an essential role in the activation of the FAK gene during tumor metastasis.

Krüppel‑like factor expression and correlation with FAK, MMP‑9 and E‑cadherin expression in hepatocellular carcinoma

Whether a focal adhesion kinase (FAK)‑Krüppel‑like factor 8 (KLF8)‑matrix metalloproteinase (MMP)‑9/E‑cadherin signaling axis exists in hepatocellular carcinoma (HCC) remains unknown. In the present study, KLF8 expression and its clinicopathological significance in HCC was investigated to determine the correlation between KLF8 and FAK, MMP‑9 and E‑cadherin expression. Tissues were obtained from 60 surgically resected HCC and normal tumor‑adjacent tissues. KLF8, FAK, MMP‑9 and E‑cadherin expression levels were examined by quantitative real‑time reverse transcription polymerase chain reaction (qRT‑PCR) and immunohistochemistry. In addition, KLF8, FAK, MMP‑9 and E‑cadherin protein expression levels were examined by western blot analysis in 5 portal vein cancer emboli and corresponding HCC tissues. The clinicopathological data of the HCC patients were retrospectively analyzed. KLF8 mRNA expression was found to be significantly upregulated in HCC tumor tissues compared with normal tumor‑adjacent tissues (P<0.05). KLF8 protein was highly expressed in portal vein cancer emboli. KLF8 expression level was significantly higher in tumors with advanced TNM stages and vascular invasion compared with that in tumors with early TNM stage and absence of vascular invasion (P<0.05). KLF8 protein and mRNA expression in HCC positively correlated with that of FAK (r=0.362, P<0.001; and r=0.377, P<0.01, respectively) and MMP‑9 (r=0.392, P<0.01; and r=0.336, P<0.01, respectively), but negatively correlated with E‑cadherin (r=‑0.364, P<0.01; and r=‑0.410, P<0.01, respectively). Results of the current study highlight a novel FAK‑KLF8‑MMP‑9/E‑cadherin signaling axis during HCC progression.

Focal adhesion kinase overexpression: correlation with lymph node metastasis and shorter survival in oral squamous cell carcinoma

BACKGROUND

Focal adhesion kinase (FAK) has been identified as a key mediator in tumor progression. The objective of this study was to determine the role of FAK as a predictor of neck node metastasis and poor prognosis in oral squamous cell carcinomas (OSCCs).

METHODS

FAK expression in normal oral mucosa and in 69 OSCCs was examined by immunohistochemistry, and the percentage of stained cells was recorded. The correlation of these findings with clinicopathologic variables and survival was studied.

RESULTS

FAK expression in OSCCs was heterogeneous: 33.3% of cases showed weak expression; 23.2%, moderate expression, and 33.3% cases showed high expression. FAK expression significantly correlated with tumor size (p = .010), neck node metastasis (p = .01), and local tumor recurrence (p = .01). FAK expression was an independent prognostic factor in the survival analysis (p = .017).

CONCLUSIONS

Increased expression of FAK may play a role in invasiveness and metastasis of OSCCs, which contribute to poor prognosis and low survival.

In oral squamous cell carcinoma, high FAK expression is correlated with low P53 expression

Focal adhesion kinase (FAK) and p53 have been associated with metastatic activity and a poor prognosis in oral squamous cell carcinoma (OSCC). Recently, a feedback mechanism in which FAK regulates p53 has been proposed. The present study aims to determine the role of p53 in FAK regulation in these tumors. FAK and p53 expression was examined by immunohistochemistry in normal oral mucosa and in 67 oral squamous cell carcinomas. p16(INK4a) was also studied in view of its association with human papillomavirus infection. The association between FAK and p53 was subsequently analyzed. FAK expression in OSCCs was heterogeneous: 22 (33 %) cases showed weak expression, 16 (24 %) showed moderate expression, and 22 (33 %) cases showed high expression. Regarding p53, 31 of 67 (46 %) available tumor specimens showed negative staining, and 36 of 67 (54 %) showed positive nuclear staining for p53. FAK expression was inversely correlated with p53 expression (Fisher's exact test, p = 0.005). There was no association between p16(INK4a) and p53 or FAK expression. In conclusion, our results support the hypothesis that FAK activity might be involved in the down-regulation of p53 expression in OSCC.

Thymoquinone reduces migration and invasion of human glioblastoma cells associated with FAK, MMP-2 and MMP-9 down-regulation

Glioblastoma represent the most frequent primary tumors of the central nervous system and remain among the most aggressive human cancers as available therapeutic approaches still fail to contain their invasiveness. Many studies have reported elevated expression of the Focal Adhesion Kinase (FAK) protein in glioblastoma, associated with an increase in the rates of both migration and invasion. This designates FAK as a promising target to limit invasiveness in glioblastoma. Thymoquinone (TQ), the main phytoactive compound of Nigella sativa has shown remarkable anti-neoplasic activities on a variety of cancer cells. Here, we studied the anti-invasive and anti-migratory effects of TQ on human glioblastoma cells. The results obtained indicated that TQ treatment reduced migration, adhesion and invasion of both U-87 and CCF-STTG1 cells. This was accompanied by a drastic down-regulation of FAK, associated with a reduction of ERK phosphorylation as well as MMP-2 and MMP-9 secretion. This study provides new data on FAK regulation by a natural product (TQ) which could be of a great value for the development of novel therapies in glioblastoma.

Endothelial FAK as a therapeutic target in disease

Focal adhesions (FA) are important mediators of endothelial cytoskeletal interactions with the extracellular matrix (ECM) via transmembrane receptors, integrins and integrin-associated intracellular proteins. This communication is essential for a variety of cell processes including EC barrier regulation and is mediated by the non-receptor protein tyrosine kinase, focal adhesion kinase (FAK). As FA mediate the basic response of EC to a variety of stimuli and FAK is essential to these responses, the idea of targeting EC FAK as a therapeutic strategy for an assortment of diseases is highly promising. In particular, inhibition of FAK could prove beneficial in a variety of cancers via effects on EC proliferation and angiogenesis, in acute lung injury (ALI) via the attenuation of lung vascular permeability, and in rheumatoid arthritis via reductions in synovial angiogenesis. In addition, there are potential therapeutic benefits of FAK inhibition in cardiovascular disease and diabetic nephropathy as well. Several drugs that target EC FAK are now in existence and include agents currently under investigation in preclinical models as well as drugs that are readily available such as the sphingolipid analog FTY720 and statins. As the role of EC FAK in the pathogenesis of a variety of diseases continues to be explored and new insights are revealed, drug targeting of FAK will continue to be an important area of investigation and may ultimately lead to highly novel and effective strategies to treat these diseases.

Effects of stable knockdown of Aurora kinase A on proliferation, migration, chromosomal instability, and expression of focal adhesion kinase and matrix metalloproteinase-2 in HEp-2 cells

Overexpression of Aurora kinase A (AURKA) is frequently observed in various cancers, including laryngeal squamous cell carcinoma (LSCC). We investigated the effects of knockdown of AURKA on laryngeal cancer HEp-2 cells both in vitro and in vivo. A plasmid containing short hairpin (sh)RNA against AURKA was constructed and transfected into HEp-2. Measurements included the CCK-8 assay for viability and proliferation, flow cytometry for apoptosis and effects on the mitotic checkpoint, a trans-well assay for migration, immunofluorescence for assessment of genomic instability, and western blotting for protein expression. AURKA knockdown inhibited proliferation, migration, and colony formation in vitro and tumorigenicity in vivo. The knockdown induced the accumulation of cells in G2-M phase and eventual apoptosis. Knockdown of AURKA caused delayed entry into mitosis after treatment with nocodazole, reduced chromosomal instability, and decreased expression of focal adhesion kinase (FAK), phosphorylated FAK, and matrix metalloproteinase-2 (MMP-2), key regulators in cell adhesion and invasion. Knockdown of AURKA inhibits the growth and invasiveness of this LSCC cell line both in vitro and in vivo. These effects may partially result from the reduced expression of FAK and MMP-2. Knockdown of AURKA expression may represent a promising therapeutic strategy for the treatment of LSCC.

Focal adhesion kinase as a cancer therapy target

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that resides at the sites of focal adhesions. The 125 kDa FAK protein is encoded by the FAK gene located on human chromosome 8q24. Structurally, FAK consists of an amino-terminal regulatory FERM domain, a central catalytic kinase domain, and a carboxy-terminal focal adhesion targeting domain. FAK has been shown to be an important mediator of cell adhesion, growth, proliferation, survival, angiogenesis and migration, all of which are often disrupted in cancer cells. Normal tissues have low expression of FAK, while primary and metastatic tumors significantly overexpress this protein. This review summarizes expression of FAK by immunohistochemical staining in different tumor types and presents several FAK inhibition therapy approaches.

Anoikis mediators in oral squamous cell carcinoma

Anoikis - apoptotic cell death triggered by loss of extracellular matrix (ECM) contacts - is dysregulated in many chronic debilitating and fatal diseases. Mechanisms rendering tumor cells resistant to anoikis, although not completely understood, possess significant therapeutic promise. In death receptor-mediated anoikis mechanisms, focal adhesion kinase (FAK) and receptor-interacting protein (RIP) dissociate, leading to association of RIP with Fas, formation of the death-inducing signaling complex (DISC), activation of caspase-3, and propagation of anoikis. In contrast, anoikis resistance is accomplished through constitutive activation of survival pathways that include integrin-dependent activation of FAK and extracellular-signal-regulated kinase (ERK). In addition, FAK and RIP association confers anoikis resistance by inhibiting the association of RIP with Fas and formation of the death signaling complex, which allows cells to escape anoikis. Up-regulation of CD44 also contributes to survival signals and promotes anoikis resistance. This review will focus on the roles of death receptors, prosurvival pathways, and the molecular players involved in anoikis escalation and resistance in oral squamous cell carcinoma.

The role of the focal adhesion protein PINCH1 for the radiosensitivity of adhesion and suspension cell cultures

Focal adhesion (FA) signaling mediated by adhesion to extracellular matrix and growth factor receptors contributes to the regulation of the cellular stress response to external stimuli. Critical to focal adhesion assembly and signaling is the adapter protein PINCH1. To evaluate whether the prosurvival function of PINCH1 in radiation cell survival depends on cell adhesion, we examined PINCH1^fl/fl and PINCH1^−/− mouse embryonic fibroblasts and human cancer cell lines. Here, we found that the enhanced cellular radiosensitivity mediated by PINCH1 depletion observed under adhesion conditions is conserved when cells are irradiated under suspension conditions. This unsuspected finding could not be explained by the observed modification of adhesion and growth factor associated signaling involving FAK, Paxillin, p130^CAS, Src, AKT, GSK3β and ERK1/2 under suspension and serum withdrawal relative to adhesion conditions with serum. Our data suggest that the adapter protein PINCH1 critically participates in the regulation of the cellular radiosensitivity of normal and malignant cells similarly under adhesion and suspension conditions.

Identification of tetranectin as a potential biomarker for metastatic oral cancer

Lymph node involvement is the most important predictor of survival rates in patients with oral squamous cell carcinoma (OSCC). A biomarker that can indicate lymph node metastasis would be valuable to classify patients with OSCC for optimal treatment. In this study, we have performed a serum proteomic analysis of OSCC using 2-D gel electrophoresis and liquid chromatography/tandem mass spectrometry. One of the down-regulated proteins in OSCC was identified as tetranectin, which is a protein encoded by the CLEC3B gene (C-type lectin domain family 3, member B). We further tested the protein level in serum and saliva from patients with lymph-node metastatic and primary OSCC. Tetranectin was found significantly under-expressed in both serum and saliva of metastatic OSCC compared to primary OSCC. Our results suggest that serum or saliva tetranectin may serve as a potential biomarker for metastatic OSCC. Other candidate serum biomarkers for OSCC included superoxide dismutase, ficolin 2, CD-5 antigen-like protein, RalA binding protein 1, plasma retinol-binding protein and transthyretin. Their clinical utility for OSCC detection remains to be further tested in cancer patients.

Expression of focal adhesion kinase and phosphorylated focal adhesion kinase in human gliomas is associated with unfavorable overall survival

Human glioma is a malignancy that has no effective systemic therapy. Focal adhesion kinase (FAK) is overexpressed in various invasive and metastatic tumor cells. To investigate its prognostic value in human gliomas, which currently is unknown, we examined the expression patterns of FAK and its activated form, phospho-FAK (FAK pY397), and analyzed the correlation between their expression and prognosis in patients with gliomas. Immunohistochemical staining was performed to detect FAK and phospho-FAK expression patterns in the biopsies from 96 patients with primary gliomas. Kaplan-Meier survival and Cox regression analyses were performed to evaluate the prognosis of patients. As a result, the immunohistochemical analysis revealed that FAK and phospho-FAK both were associated significantly with the Karnofsky performance scale (KPS) score and World Health Organization (WHO) grades of patients with gliomas. Especially, the positive expression rates of FAK and phospho-FAK were significantly higher in patients with a higher grade (P = 0.01 and 0.02, respectively) and a lower KPS score (P = 0.006 and 0.008, respectively). The patients with FAK positive expression correlated with a poor prognosis of human gliomas (P = 0.006) as well as phospho-FAK (P = 0.01). The survival rate of the patients with FAK+/phospho-FAK+ expression was the lowest (P < 0.05), and conjoined expressions of FAK/phospho-FAK were an independent prognostic indicator of human gliomas (P < 0.05). In conclusion, the results suggest that the elevated expression of FAK and phospho-FAK is an important feature of human glioma. A combined detection of FAK/phospho-FAK coexpression may benefit us in the prediction of the prognosis of human glioma.

The dual kinase complex FAK-Src as a promising therapeutic target in cancer

Focal adhesion kinase (FAK) and steroid receptor coactivator (Src) are intracellular (nonreceptor) tyrosine kinases that physically and functionally interact to promote a variety of cellular responses. Plenty of reports have already suggested an additional central role for this complex in cancer through its ability to promote proliferation and anoikis resistance in tumor cells. An important role for the FAK/Src complex in tumor angiogenesis has also been established. Furthermore, FAK and Src have been associated with solid tumor metastasis through their ability to promote the epithelial mesenchymal transition. In fact, a strong correlation between increased FAK/Src expression/phosphorylation and the invasive phenotype in human tumors has been found. Additionally, an association for FAK/Src with resistances to the current anticancer therapies has already been established. Currently, novel anticancer agents that target FAK or Src are under development in a broad variety of solid tumors. In this article we will review the normal cellular functions of the FAK/Src complex as an effector of integrin and/or tyrosine kinase receptor signaling. We will also collect data about their role in cancer and we will summarize the most recent data from the FAK and Src inhibitors under clinical and preclinical development. Furthermore, the association of both these proteins with chemotherapy and hormonal therapy resistances, as a rationale for new combined therapeutic approaches with these novel agents, to abrogate treatment associated resistances, will also be reviewed.

Inhibition of focal adhesion kinase suppresses the adverse phenotype of endocrine-resistant breast cancer cells and improves endocrine response in endocrine-sensitive cells

Acquired resistance to endocrine therapy in breast cancer is a major clinical problem. Previous reports have demonstrated that cell models of acquired endocrine resistance have altered cell-matrix adhesion and a highly migratory phenotype, features which may impact on tumour spread in vivo. Focal adhesion kinase (FAK) is an intracellular kinase that regulates signalling pathways central to cell adhesion, migration and survival and its expression is frequently deregulated in breast cancer. In this study, we have used the novel FAK inhibitor PF573228 to address the role of FAK in the development of endocrine resistance. Whilst total-FAK expression was similar between endocrine-sensitive and endocrine-resistant MCF7 cells, FAK phosphorylation status (Y397 or Y861) was altered in resistance. PF573228 promoted a dose-dependent inhibition of FAK phosphorylation at Y397 but did not affect other FAK activation sites (pY407, pY576 and pY861). Endocrine-resistant cells were more sensitive to these inhibitory effects versus MCF7 (mean IC(50) for FAK pY397 inhibition: 0.43 μM, 0.05 μM and 0.13 μM for MCF7, TamR and FasR cells, respectively). Inhibition of FAK pY397 was associated with a reduction in TamR and FasR adhesion to, and migration over, matrix components. PF573228 as a single agent (0-1 μM) did not affect the growth of MCF7 cells or their endocrine-resistant counterparts. However, treatment of endocrine-sensitive cells with PF573228 and tamoxifen combined resulted in greater suppression of proliferation versus single agent treatment. Together these data suggest the importance of FAK in the process of endocrine resistance, particularly in the development of an aggressive, migratory cell phenotype and demonstrate the potential to improve endocrine response through combination treatment.

Bortezomib suppresses focal adhesion kinase expression via interrupting nuclear factor-kappa B

AIMS

Bortezomib is a potent proteasome inhibitor currently used to treat various malignancies with promising results. To explore the role of bortezomib in reducing cancer cell migration and inducing apoptosis, we evaluated the effects of bortezomib on the expression of focal adhesion kinase (FAK).

MAIN METHODS

Various types of cancer cells including lung cancer A549, H1299; a breast cancer MCF7; a hepatocellular carcinoma Huh7, and a tongue squamous cell carcinoma SCC-25 were treated with different concentrations of bortezomib or MG-132 as indicated for 24h. Protein and mRNA levels were determined by Western blotting and real-time PCR. Apoptosis was analyzed by caspase 3 cleavage and activity. FAK promoter and NFkappaB binding activities were measured by luciferase-reporter method. NFkappaB subunit p65 binding capacity was determined by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis.

KEY FINDINGS

Both bortezomib and another proteasome inhibitor, MG-132, significantly reduced FAK expression, suppressed cancer cell migration and increased cell apoptosis. Results of real-time PCR and promoter activity assay revealed that bortezomib decreased FAK expression through transcriptional inactivation. Results of FAK promoter activity and ChIP assays in A549 and H1299 cells indicated that bortezomib suppressed FAK activity through a p53-independent pathway. Furthermore, reduction of NFkappaB binding capacity demonstrated by EMSA and ChIP assay suggested that NFkappaB plays an important role in bortezomib suppressing FAK expression.

SIGNIFICANCE

These results suggested that FAK is downregulated by bortezomib through a proteasome-dependent NFkappaB inhibitory mechanism. Thus, FAK could be a potential molecular target of bortezomib for therapeutic strategy.

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.

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.

FAK expression regulation and therapeutic potential

Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that localizes to cellular focal adhesions or cell contacts within the extracellular matrix. FAK is activated by a variety of cell surface receptors and transmits signals to a range of targets. FAK participates in growth factor receptor-mediated signaling pathways and plays essential roles in cell survival, proliferation, migration, and invasion. In the present chapter, the mechanisms of FAK activation, the modulation of FAK function by phosphorylation, and the mechanisms regulating FAK expression are reviewed. Overexpression of FAK is widely observed in numerous tumor types, and is used as a marker for invasion and metastasis. FAK could be therapeutically targeted at various levels, such as at the level of FAK gene transcription by regulating its transcription factor(s) with siRNA, at the FAK mRNA level with FAK siRNA, or at the protein level. At the protein level, FAK's localization to focal adhesions could be disrupted by expression of dominant-negative FAK-Related Non-Kinase or its focal adhesion targeting domain, and its kinase activity could be inhibited by FIP200, the FAK kinase domain-interacting protein and kinase-activity inhibitor. In recent years, small molecule inhibitors against FAK transcription and activation have been discovered, and these will provide additional approaches for potential tumor therapies.

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.

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.

OipA plays a role in Helicobacter pylori-induced focal adhesion kinase activation and cytoskeletal re-organization

The initial signalling events leading to Helicobacter pylori infection associated changes in motility, cytoskeletal reorganization and elongation of gastric epithelial cells remain poorly understood. Because focal adhesion kinase (FAK) is known to play important roles in regulating actin cytoskeletal organization and cell motility we examined the effect of H. pylori in gastric epithelial cells co-cultured with H. pylori or its isogenic cag pathogenicity island (PAI) or oipA mutants. H. pylori induced FAK phosphorylation at distinct tyrosine residues in a dose- and time-dependent manner. Autophosphorylation of FAK Y397 was followed by phosphorylation of Src Y418 and resulted in phosphorylation of the five remaining FAK tyrosine sites. Phosphorylated FAK and Src activated Erk and induced actin stress fibre formation. FAK knock-down by FAK-siRNA inhibited H. pylori-mediated Erk phosphorylation and abolished stress fibre formation. Infection with oipA mutants reduced phosphorylation of Y397, Y576, Y577, Y861 and Y925, inhibited stress fibre formation and altered cell morphology. cag PAI mutants reduced phosphorylation of only FAK Y407 and had less effect on stress fibre formation than oipA mutants. We propose that activation of FAK and Src are responsible for H. pylori-induced induction of signalling pathways resulting in the changes in cell phenotype important for pathogenesis.

Inhibition of cell motility by troglitazone in human ovarian carcinoma cell line

Background

Troglitazone (TGZ) is a potential anticancer agent. Little is known about the effect of this agent on cancer cell migration.

Methods

Human ovarian carcinoma cell line, ES-2 cells were treated with various concentrations of TGZ. Cell migration was evaluated by wound-healing and Boyden chamber transwell experiments. PPARγ expression was blocked by PPARγ small interfering RNA. The effects of TGZ on phosphorylation of FAK, PTEN, Akt were assessed by immunoblotting using phospho-specific antibodies. The cellular distribution of paxillin, vinculin, stress fiber and PTEN was assessed by immunocytochemistry.

Results

TGZ dose- and time-dependently impaired cell migration through a PPARγ independent manner. TGZ treatment impaired cell spreading, stress fiber formation, tyrosine phosphorylation of focal adhesion kinase (FAK), and focal adhesion assembly in cells grown on fibronectin substratum. TGZ also dose- and time-dependently suppressed FAK autophosphorylation and phosphorylation of the C-terminal of PTEN (a phosphatase). At concentration higher than 10 μM, TGZ caused accumulation of PTEN in plasma membrane, a sign of PTEN activation.

Conclusion

These results indicate that TGZ can suppress cultured ES-2 cells migration. Our data suggest that the anti-migration potential of TGZ involves in regulations of FAK and PTEN activity.

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.

Bortezomib inhibits cell-cell adhesion and cell migration and enhances epidermal growth factor receptor inhibitor-induced cell death in squamous cell cancer

The lack of cell-cell adhesion and increased migration are key characteristics of cancer cells. The loss of expression of cell adhesion components and overexpression of components critical for cell migration, such as focal adhesion kinase (FAK), correlate with poor prognosis. Because alteration of protein turnover affects the expression levels and, in turn, may influence protein function, we investigated the effects of the proteasome inhibitor bortezomib on cell adhesion and migration in oral squamous cell cancer cell lines SCC68 and SCC15. Following treatment with bortezomib, protein levels of adherens junction components such as E-cadherin were unchanged. The desmosomal linker protein desmoplakin level was increased, whereas the protein level of the desmosomal cadherin, desmoglein 2, was diminished. Reduced desmoglein 2 levels correlated with the diminished strength of mechanical cell-cell adhesion. The protein level of the epidermal growth factor receptor (EGFR) increased after proteasome inhibition and EGFR inhibition with the EGFR-specific tyrosine kinase inhibitor PKI166 was able to restore cell-cell adhesion. Furthermore, we found that the combination of PKI166 with bortezomib enhanced the rate of cell death. Although the FAK protein level was unchanged following bortezomib treatment, recruitment of FAK phosphorylated at tyrosine residue 397 to the periphery of the cell was induced. Migration was reduced following treatment with bortezomib, which could potentially be explained by a prominent but disorganized actin fiber network revealed through immunofluorescence. Collectively, our results suggest that proteasome inhibition using bortezomib affects cell adhesion and cell migration profoundly and provides a rationale for its clinical use in conjunction with an EGFR inhibitor.

PC cell-derived growth factor overexpression promotes proliferation and survival of laryngeal carcinoma

PC cell-derived growth factor is a novel growth factor for tumor formation and progression. No comprehensive literature concerning PC cell-derived growth factor expression status and its biological function in squamous cell carcinoma, especially in the larynx, is, however, available. The target of this study is to evaluate the clinical significance of PC cell-derived growth factor and the potential of small interfering RNA-induced genetic silencing of PC cell-derived growth factor as a supplementary therapeutic way for laryngeal squamous cell carcinoma. A total of 146 primary laryngeal cancer, 108 adult laryngeal papilloma and 41 laryngeal leukoplakia samples, as well as 10 normal larynx tissues were investigated. The PC cell-derived growth factor mRNA level was examined by real-time polymerase chain reaction and protein localization by immunohistochemistry. The biological function of PC cell-derived growth factor was assessed by transfection of small interfering RNA PC cell-derived growth factor construction. The PC cell-derived growth factor protein levels and mRNA levels of the laryngeal squamous cell carcinomas were significantly higher than those of normal laryngeal tissues (P<0.001). Simultaneously, the difference in the levels of mRNA and protein between those of laryngeal precancerous lesions (papilloma/leukoplakia) and those of normal tissues was significant (P<0.05, P<0.05), whereas those of laryngeal precancerous lesions (papilloma/leukoplakia) were significantly lower than those of laryngeal squamous cell carcinomas (P<0.05, P<0.05). Strong PC cell-derived growth factor expression was associated with lymph node metastases in laryngeal squamous cell carcinoma (P<0.05). Functional studies on Hep-2 cell lines demonstrated that the attenuation of PC cell-derived growth factor expression levels led to diminished cell proliferation rates (P<0.001), anchorage-independent growth in vitro (P<0.001), tumor forming in vivo (P<0.01) and resistance to apoptosis (P<0.001). PC cell-derived growth factor is a pivotal autocrine growth factor in the tumorigenesis of laryngeal squamous cell carcinoma. Our findings also indicate that PC cell-derived growth factor is a logical and potential target for early diagnosis, specific therapy and prognosis of laryngeal squamous cell carcinoma.

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.

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.

Integrin-mediated cell–matrix interactions for prosurvival and antiapoptotic signaling after genotoxic injury

Interactions of cells with their microenvironment modify the cellular sensitivity of normal and tumor cells for radiation- and drug-induced genotoxic injury. The preexistent or acquired cellular resistance against such agents aggravates anticancer therapies and, therefore, complicates the recovery of patients. Recently, integrin-mediated adhesion was shown to improve cell survival of both normal and cancer cells following DNA damage. Here, I will discuss the role of integrins and integrin-mediated signaling cascades in the survival or death response upon genotoxic stress. Detailed knowledge of the responsible molecular processes might provide implications for putative therapies targeting integrins or integrin-associated molecules to achieve an optimization of anticancer treatments.

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.

Molecular mediators of metastasis in head and neck squamous cell carcinoma

BACKGROUND

The presence of regional metastasis in patients with head and neck squamous cell carcinoma (HNSCC) is a common and adverse event associated with poor prognosis and high mortality. Although significant improvements in standard therapies have increased the efficacy of local tumor management, the high incidence of tumor recurrence has resulted in limited improvements in overall survival rates. Understanding the molecular mechanisms that mediate HNSCC invasion and metastasis may enable identification of novel therapeutic targets for the prevention and management of tumor dissemination.

METHODS

A literature review was performed.

RESULTS

Several biologic mediators and mechanisms that have been implicated in HNSCC metastasis, such as cell adhesion molecules, proteolytic enzymes, growth factor signaling, metastasis suppressor genes, and chemokine receptors were reviewed.

CONCLUSIONS

Prevention of HNSCC metastasis is an important clinical objective that requires an increased understanding of the molecular mechanisms of tumor invasion and dissemination.

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.