FERM control of FAK function: implications for cancer therapy

Low concentrations of saracatinib promote definitive endoderm differentiation through inhibition of FAK-YAP signaling axis

Optimizing the efficiency of definitive endoderm (DE) differentiation is necessary for the generation of diverse organ-like structures. In this study, we used the small molecule inhibitor saracatinib (SAR) to enhance DE differentiation of human embryonic stem cells and induced pluripotent stem cells. SAR significantly improved DE differentiation efficiency at low concentrations. The interaction between SAR and Focal Adhesion Kinase (FAK) was explored through RNA-seq and molecular docking simulations, which further supported the inhibition of DE differentiation by p-FAK overexpression in SAR-treated cells. In addition, we found that SAR inhibited the nuclear translocation of Yes-associated protein (YAP), a downstream effector of FAK, which promoted DE differentiation. Moreover, the addition of SAR enabled a significant reduction in activin A (AA) from 50 to 10 ng/mL without compromising DE differentiation efficiency. For induction of the pancreatic lineage, 10 ng/ml AA combined with SAR at the DE differentiation stage yielded a comparative number of PDX1+/NKX6.1+ pancreatic progenitor cells to those obtained by 50 ng/ml AA treatment. Our study highlights SAR as a potential modulator that facilitates the cost-effective generation of DE cells and provides insight into the orchestration of cell fate determination.

Acinar to β-like cell conversion through inhibition of focal adhesion kinase

Insufficient functional β-cell mass causes diabetes; however, an effective cell replacement therapy for curing diabetes is currently not available. Reprogramming of acinar cells toward functional insulin-producing cells would offer an abundant and autologous source of insulin-producing cells. Our lineage tracing studies along with transcriptomic characterization demonstrate that treatment of adult mice with a small molecule that specifically inhibits kinase activity of focal adhesion kinase results in trans-differentiation of a subset of peri-islet acinar cells into insulin producing β-like cells. The acinar-derived insulin-producing cells infiltrate the pre-existing endocrine islets, partially restore β-cell mass, and significantly improve glucose homeostasis in diabetic mice. These findings provide evidence that inhibition of the kinase activity of focal adhesion kinase can convert acinar cells into insulin-producing cells and could offer a promising strategy for treating diabetes.

Blood-testis barrier: a review on regulators in maintaining cell junction integrity between Sertoli cells

The blood-testis barrier (BTB) is formed adjacent to the seminiferous basement membrane. It is a distinct ultrastructure, partitioning testicular seminiferous epithelium into apical (adluminal) and basal compartments. It plays a vital role in developing and maturing spermatocytes into spermatozoa via reorganizing its structure. This enables the transportation of preleptotene spermatocytes across the BTB, from basal to adluminal compartments in the seminiferous tubules. Several bioactive peptides and biomolecules secreted by testicular cells regulate the BTB function and support spermatogenesis. These peptides activate various downstream signaling proteins and can also be the target themself, which could improve the diffusion of drugs across the BTB. The gap junction (GJ) and its coexisting junctions at the BTB maintain the immunological barrier integrity and can be the "gateway" during spermatocyte transition. These junctions are the possible route for toxicant entry, causing male reproductive dysfunction. Herein, we summarize the detailed mechanism of all the regulators playing an essential role in the maintenance of the BTB, which will help researchers to understand and find targets for drug delivery inside the testis.

Vinorelbine Improves the Efficacy of Sorafenib against Hepatocellular Carcinoma: A Promising Therapeutic Approach

Hepatocellular carcinoma (HCC) is a leading global cause of cancer-related mortality. Despite the widespread adoption of sorafenib as the standard HCC treatment, its efficacy is constrained, frequently encountering resistance. To augment the effectiveness of sorafenib, this study investigated the synergy of sorafenib and vinorelbine using 22 HCC patient-derived xenograft (PDX) models. In this study, mice bearing HCC tumors were treated with the vehicle, sorafenib (15 mg/kg), vinorelbine (3 mg/kg), and sorafenib-vinorelbine combination (Sora/Vino). Rigorous monitoring of the tumor growth and side effects coupled with comprehensive histological and molecular analyses was conducted. The overall survival (OS) of mice bearing HCC orthotopic tumors was also assessed. Our data showed a notable 86.4% response rate to Sora/Vino, surpassing rates of 31.8% for sorafenib and 9.1% for vinorelbine monotherapies. Sora/Vino significantly inhibited tumor growth, prolonged OS of mice bearing HCC orthotopic tumors (p < 0.01), attenuated tumor cell proliferation and angiogenesis, and enhanced necrosis and apoptosis. The combination therapy effectively suppressed the focal adhesion kinase (FAK) pathway, which is a pivotal player in cell proliferation, tumor angiogenesis, survival, and metastasis. The noteworthy antitumor activity in 22 HCC PDX models positions Sora/Vino as a promising candidate for early-phase clinical trials, leveraging the established use of sorafenib and vinorelbine in HCC and other cancers.

GMI, a Ganoderma microsporum protein, abolishes focal adhesion network to reduce cell migration and metastasis of lung cancer

BACKGROUND

Cancer metastasis is a major cause of cancer-related deaths, emphasizing the urgent need for effective therapies. Although it has been shown that GMI, a fungal protein from Ganoderma microsporum, could suppress primary tumor growth in a wide spectrum of cancer types, it is still unclear whether GMI exhibits anti-metastasis properties, particularly in lung cancers. Further investigation is needed.

AIMS AND OBJECTIVES

The objective of this study is to investigate the potential inhibitory effects of GMI on lung cancer metastasis in vivo. Utilizing systematic and comprehensive approaches, our research aims to elucidate the underlying molecular mechanisms responsible for the anti-metastatic effects.

MATERIALS AND METHODS

In vitro migration and cell adhesion assays addressed the epithelial-to-mesenchymal transition (EMT)-related phenotype. Proteomic and bioinformatic analyses identified the GMI-regulated proteins and cellular responses. GMI-treated LLC1-bearing mice were analyzed using IVIS Spectrum to assess the anti-metastatic effect.

KEY FINDINGS

GMI inhibits EMT as well as cell migration. GMI disrupts cell adhesion and downregulates integrin, resulting in inhibition of phosphorylated FAK. GMI induces macropinocytosis and lysosome-mediated degradation of integrin αv, α5, α6 and β1. GMI downregulates Slug via inhibition of FAK activity, which in turn enhances expressions of epithelial-related markers and decreases cell mobility. Mechanistically, GMI-induced FAK inhibition engenders MDM2 expression and enhances MDM2/p21/Slug complex formation, leading to Slug degradation. GMI treatment reduces the metastatic pulmonary lesion and prolongs the survival of LLC1-bearing mice.

SIGNIFICANCE

Our findings highlight GMI as a promising therapeutic candidate for metastatic lung cancers, offering potential avenues for further research and drug development.

Identification of defactinib derivatives targeting focal adhesion kinase using ensemble docking, molecular dynamics simulations and binding free energy calculations

Focal adhesion kinase (FAK) belongs to the nonreceptor tyrosine kinases, which selectively phosphorylate tyrosine residues on substrate proteins. FAK is associated with bladder, esophageal, gastric, neck, breast, ovarian and lung cancers. Thus, FAK has been considered as a potential target for tumor treatment. Currently, there are six adenosine triphosphate (ATP)-competitive FAK inhibitors tested in clinical trials but no approved inhibitors targeting FAK. Defactinib (VS-6063) is a second-generation FAK inhibitor with an IC50 of 0.6 nM. The binding model of VS-6063 with FAK may provide a reference model for developing new antitumor FAK-targeting drugs. In this study, the VS-6063/FAK binding model was constructed using ensemble docking and molecular dynamics simulations. Furthermore, the molecular mechanics/generalized Born (GB) surface area (MM/GBSA) method was employed to estimate the binding free energy between VS-6063 and FAK. The key residues involved in VS-6063/FAK binding were also determined using per-residue energy decomposition analysis. Based on the binding model, VS-6063 could be separated into seven regions to enhance its binding affinity with FAK. Meanwhile, 60 novel defactinib-based compounds were designed and verified using ensemble docking. Overall, the present study improves our understanding of the binding mechanism of human FAK with VS-6063 and provides new insights into future drug designs targeting FAK.Communicated by Ramaswamy H. Sarma.

Focal adhesion kinase-mediated signaling controls the onset of pancreatic cell differentiation

Signals from the endothelium play a pivotal role in pancreatic lineage commitment. As such, the fate of the epithelial cells relies heavily on the spatiotemporal recruitment of the endothelial cells to the embryonic pancreas. Although it is known that VEGFA secreted by the epithelium recruits the endothelial cells to the specific domains within the developing pancreas, the mechanism that controls the timing of such recruitment is poorly understood. Here, we have assessed the role of focal adhesion kinase (FAK) in mouse pancreatic development based on our observation that the presence of the enzymatically active form of FAK (pFAK) in the epithelial cells is inversely correlated with vessel recruitment. To study the role of FAK in the pancreas, we conditionally deleted the gene encoding focal adhesion kinase in the developing mouse pancreas. We found that homozygous deletion of Fak (Ptk2) during embryogenesis resulted in ectopic epithelial expression of VEGFA, abnormal endothelial recruitment and a delay in endocrine and acinar cell differentiation. The heterozygous mutants were born with no pancreatic phenotype but displayed gradual acinar atrophy due to cell polarity defects in exocrine cells. Together, our findings imply a role for FAK in controlling the timing of pancreatic lineage commitment and/or differentiation in the embryonic pancreas by preventing endothelial recruitment to the embryonic pancreatic epithelium.

Aggregation-Induced Emission (AIE) and Magnetic Resonance Imaging Characteristics for Targeted and Image-Guided siRNA Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer and remains a global health challenge. Small interfering RNA (siRNA) is a promising therapeutic modality that blocks multiple disease-causing genes without impairing cell structures. However, siRNA therapeutics still have off-target proportion and lack effective quantitative analysis method in vivo. Thus, a novel theragnostic nanoparticle with dual-mode imaging is synthesized for targeted and image-guided siRNA therapy of HCC. Survivin siRNA is carried by Poly-ethylenimine (PEI) and interacted with T7-AIE/Gd NPs, which are self-assembled of DSPE-PEG-DTPA(Gd), DSPE-PEG-Mal, DSPE-PEG-PEI, and TPE. The resulting theragnostic nanoparticles exhibit lower toxicity and high therapeutic effect, and excellent T1-weighted magnetic resonance imaging (MRI) and aggregation-induced emission (AIE) imaging performance. Moreover, in vivo MRI and AIE imaging indicate that this kind of theragnostic nanoparticles rapidly accumulates in the tumor due to active targeting and enhanced permeability and retention (EPR) effects. Sur@T7-AIE-Gd suppresses HCC tumor growth by inducing autophagy and destabilizes DNA integrity in tumor cells. The results suggest that T7-AIE-Gd nanoparticles carrying Survivin siRNA with dual-mode imaging characteristics are promising for targeted and image-guided siRNA therapy of hepatocellular carcinoma.

Phosphorylation of Focal Adhesion Kinase at Y925: Role in Glia-Dependent and Independent Migration through Regulating Cofilin and N-Cadherin

The adult neocortex is a six-layered structure, consisting of nearly continuous layers of neurons that are generated in a temporally strictly coordinated order. During development, cortical neurons originating from the ventricular zone migrate toward the Reelin-containing marginal zone in an inside-out arrangement. Focal adhesion kinase (FAK), one tyrosine kinase localizing to focal adhesions, has been shown to be phosphorylated at tyrosine 925 (Y925) by Src, an important downstream molecule of Reelin signaling. Up to date, the precise molecular mechanisms of FAK and its phosphorylation at Y925 during neuronal migration are still unclear. Combining in utero electroporation with immunohistochemistry and live imaging, we examined the function of FAK in regulating neuronal migration. We show that phosphorylated FAK is colocalized with Reelin positive Cajal-Retzius cells in the developing neocortex and hippocampus. Phosphorylation of FAK at Y925 is significantly reduced in reeler mice. Overexpression and dephosphorylation of FAK impair locomotion and translocation, resulting in migration inhibition and dislocation of both late-born and early-born neurons. These migration defects are highly correlated to the function of FAK in regulating cofilin phosphorylation and N-Cadherin expression, both are involved in Reelin signaling pathway. Thus, fine-tuned phosphorylation of focal adhesion kinase at Y925 is crucial for both glia-dependent and independent neuronal migration.

1,3,4-Oxadiazole Containing Compounds As Therapeutic Targets For Cancer Therapy

BACKGROUND

Cancer is the first or second leading cause of premature death in 134 of 183 countries in the world. 1,3,4-Oxadiazoles are five memebered heterocyclic rings containing two nitrogen (two atoms) and oxygen (one atom). They show better thermal stability, metabolic stability, aqueous solubility and lower lipophilicity than the other isomeric oxadiazoles. They are important class of heterocycles present in many drug structures like Raltegravir, Furamizole Tidazosin, Nesapidil, Setileuton (MK-0633) and Zibotentan. Presence of this nucleus in the therapeutics has made them an indispensable anchor for drug design and development. Several 1,3,4-oxadiazoles are prepared and reported as anticancer agents by numerous scientists worldwide.

OBJECTIVES

The present review discusses the anticancer potentials together with the molecular targets of 1,3,4-oxadiazoles reported since 2010. The structure activity relationship (SAR) and molecular docking simulation on different targets have also been discussed herein. Some of the important cancer targets have also been explored.

METHODS

The most potent 1,3,4-oxadiazoles reported in literature was highlighted in the manuscript. The anticancer activity was reported in terms of growth percent (GP), percent growth inhibition (%GI), GI50, IC50, and LC50 and TGI.

RESULTS

1,3,4-Oxadiazoles are an important heterocyclic scaffolds with broad spectrum biological activities. They may be either mono substituted or disubstituted and act as an indispensable anchor for drug design and discovery due to their thermal stability together with low lipophilicity. They exhibited anticancer potentials and showed the inhibitions of various cancer targets.

CONCLUSION

The discussion outlined herein will proved to be a helpful and vital tool for medicinal chemists investigating and working with 1,3,4-oxadiazoles and anticancer research programs.

Manipulation of Focal Adhesion Signaling by Pathogenic Microbes

Focal adhesions (FAs) serve as dynamic signaling hubs within the cell. They connect intracellular actin to the extracellular matrix (ECM) and respond to environmental cues. In doing so, these structures facilitate important processes such as cell-ECM adhesion and migration. Pathogenic microbes often modify the host cell actin cytoskeleton in their pursuit of an ideal replicative niche or during invasion to facilitate uptake. As actin-interfacing structures, FA dynamics are also intimately tied to actin cytoskeletal organization. Indeed, exploitation of FAs is another avenue by which pathogenic microbes ensure their uptake, survival and dissemination. This is often achieved through the secretion of effector proteins which target specific protein components within the FA. Molecular mimicry of the leucine-aspartic acid (LD) motif or vinculin-binding domains (VBDs) commonly found within FA proteins is a common microbial strategy. Other effectors may induce post-translational modifications to FA proteins through the regulation of phosphorylation sites or proteolytic cleavage. In this review, we present an overview of the regulatory mechanisms governing host cell FAs, and provide examples of how pathogenic microbes have evolved to co-opt them to their own advantage. Recent technological advances pose exciting opportunities for delving deeper into the mechanistic details by which pathogenic microbes modify FAs.

Involvement of the FAK Network in Pathologies Related to Altered Mechanotransduction

Mechanotransduction is a physiological process in which external mechanical stimulations are perceived, interpreted, and translated by cells into biochemical signals. Mechanical stimulations exerted by extracellular matrix stiffness and cell–cell contacts are continuously applied to living cells, thus representing a key pivotal trigger for cell homeostasis, survival, and function, as well as an essential factor for proper organ development and metabolism. Indeed, a deregulation of the mechanotransduction process consequent to gene mutations or altered functions of proteins involved in perceiving cellular and extracellular mechanics can lead to a broad range of diseases, from muscular dystrophies and cardiomyopathies to cancer development and metastatization. Here, we recapitulate the involvement of focal adhesion kinase (FAK) in the cellular conditions deriving from altered mechanotransduction processes.

Focal adhesion kinase: Insight into its roles and therapeutic potential in oesophageal cancer

Oesophageal cancer is associated with high morbidity and mortality rates because it is highly invasive and prone to recurrence and metastasis, with a five-year survival rate of <20%. Therefore, there is an urgent need for new methods aimed at improving therapeutic intervention. Several studies have shown that targeted therapy may be effective for the treatment of oesophageal cancer. Focal adhesion kinase (FAK), a non-receptor tyrosine kinase with kinase activity and scaffolding function, could be overexpressed in a variety of solid tumours, including oesophageal cancer. FAK participates in survival, proliferation, progression, adhesion, invasion, migration, epithelial-to-mesenchymal transition, angiogenesis, DNA damage repair, and other biological processes through multiple signalling pathways in cancer cells. It plays an important role in the occurrence and development of tumours and has been linked to the prognosis of oesophageal cancer. FAK has been suggested as a potential therapeutic target in oesophageal cancer; thus, the combination of FAK inhibitors with chemotherapy, radiotherapy, and immunotherapy is expected to prolong the survival of patients. This paper presents a brief overview of the structure of FAK and its potential role in oesophageal cancer, providing a rationale for the future application of FAK inhibitors in the treatment of the disease.

Antiatherogenic Effect of Resveratrol Attributed to Decreased Expression of ICAM-1 (Intercellular Adhesion Molecule-1)

Objective- Increasing evidence shows that resveratrol has antiatherogenic effects, but its underlying mechanisms are unknown. Thus, we evaluated the molecular mechanisms underlying the antiatherogenic effect of resveratrol. Approach and Results- Using the previously established mouse atherosclerosis model of partial ligation of the left carotid artery, we evaluated the role of resveratrol in antiatherosclerosis. We attempted to determine the mechanisms associated with focal adhesions using vascular endothelial cells. The results showed that resveratrol stimulated focal adhesion kinase cleavage via resveratrol-increased expression of lactoferrin in endothelial cells. Furthermore, we found that an N-terminal focal adhesion kinase fragment cleaved by resveratrol contained the FERM (band 4.1, ezrin, radixin, and moesin)-kinase domain. Furthermore, resveratrol inhibited lipopolysaccharide-stimulated adhesion of THP-1 human monocytes by decreased expression of ICAM-1 (intercellular adhesion molecule-1). A decreased ICAM-1 level was also observed in the left carotid artery of mice treated with resveratrol. To understand the relationship between resveratrol-induced antiinflammation and focal adhesion disruption, endothelial cells were transfected with FERM-kinase. Ectopically expressed FERM-kinase, the resveratrol-cleaved focal adhesion kinase fragment, was found in the nuclear fraction and inhibited the transcription level of icam-1 via the Nrf2 (nuclear factor erythroid 2-related factor 2)-antioxidant response element complex. Finally, ectopically expressed FERM-kinase blocked tumor necrosis factor-α- or IL- (interleukin) stimulated monocytic binding to endothelial cells. Conclusions- Our results show that resveratrol inhibits the expression of ICAM-1 via transcriptional regulation of the FERM-kinase and Nrf2 interaction, thereby blocking monocyte adhesion. These suppressive effects on the inflammatory mechanism suggest that resveratrol delayed the onset of atherosclerosis.

Randomized, Open-Label, Crossover Studies Evaluating the Effect of Food and Liquid Formulation on the Pharmacokinetics of the Novel Focal Adhesion Kinase (FAK) Inhibitor BI 853520

Background

BI 853520 is a potent inhibitor of focal adhesion kinase and is currently under clinical development for the treatment of non-hematological malignancies.

Objective

The objective of this study was to evaluate the effect of food and liquid dispersion on the pharmacokinetics of BI 853520 in two open-label, crossover substudies.

Patients and Methods

Sixteen patients with advanced solid tumors were enrolled in each substudy. The order of administration was randomized, and pharmacokinetic samples were collected for 48 h after administration of a 200 mg dose of BI 853520. Lack of effect would be demonstrated if the 90% confidence interval (CI) of the ratio of the adjusted geometric mean (GMR) of the area under the plasma curve (area under the plasma concentration–time curve from time zero to the last quantifiable concentration at t_z [\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{AUC}}_{{0{-}t_{\text{z}} }}$$\end{document}AUC0-tz] and observed area under the plasma concentration–time curve extrapolated from time zero to infinity [AUC_0–∞,obs]) and maximum plasma concentration (C_max) did not cross the 80–125% (bioequivalence) boundaries.

Results

Adjusted GMRs (90% CIs) for the fed versus fasted state were 92.46% (74.24–115.16), 98.17% (78.53–122.74), and 87.34% (71.04–107.38) for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{AUC}}_{{0{-}t_{\text{z}} }}$$\end{document}AUC0-tz, AUC_0–∞,obs, and C_max, respectively. Although the 90% CIs were not within bioequivalence limits for the food-effect study, the limited reductions in these pharmacokinetic parameters after administration with a high-fat meal are unlikely to be clinically relevant. Compared with a tablet, administration of BI 853520 as a liquid dispersion did not strongly affect \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{AUC}}_{{0{-}t_{\text{z}} }}$$\end{document}AUC0-tz, AUC_0–∞,obs, or C_max, resulting in adjusted GMRs (90% CIs) of 1.00 (0.92–1.09), 0.98 (0.90–1.07), and 0.93 (0.86–1.01), respectively.

Conclusions

These studies demonstrate that BI 853520 can be given with no food restrictions, and as a liquid dispersion, without strongly impacting pharmacokinetics. These pharmacokinetic properties may help make BI 853520 dosing more convenient and flexible, improving treatment compliance.

Clinical trials registration

ClinicalTrials.gov identifier: NCT01335269.

Electronic supplementary material

The online version of this article (10.1007/s11523-018-00618-0) contains supplementary material, which is available to authorized users.

Phase I Study of the Focal Adhesion Kinase Inhibitor BI 853520 in Japanese and Taiwanese Patients with Advanced or Metastatic Solid Tumors

BACKGROUND

Focal adhesion kinase (FAK) inhibitors have demonstrated anti-tumor activity preclinically and are currently being evaluated in humans. A first-in-human study evaluating the novel FAK inhibitor BI 853520 in a predominantly Caucasian population with advanced or metastatic non-hematologic malignancies demonstrated acceptable tolerability and favorable pharmacokinetics.

OBJECTIVE

This study was undertaken to investigate the safety, tolerability, and maximum tolerated dose (MTD) of BI 853520 in Japanese and Taiwanese patients with advanced solid tumors.

PATIENTS AND METHODS

In this open-label, phase I, dose-finding study, BI 853520 was administered once daily (QD) in a continuous daily dosing regimen with 28-day cycles and escalating doses to sequential cohorts of patients. Twenty-one patients (62% male; median age 65 years) were treated at two sites in Japan and Taiwan.

RESULTS

The median duration of treatment was 1.2 months (range 0.2-7.7). As no dose-limiting toxicities were observed during cycle 1 in the 50, 100, or 200 mg cohorts, the MTD of BI 853520 was determined to be 200 mg QD. Drug-related adverse events were reported in 19 patients (90%), and all except one were of grade 1 or 2. Pharmacokinetic parameters were supportive of a once-daily dosing schedule. A confirmed objective response rate of 5% and disease control rate of 29% were achieved; median duration of disease control was 3.7 months.

CONCLUSIONS

This trial demonstrated a manageable and acceptable safety profile, favorable pharmacokinetics, and potential anti-tumor activity of BI 853520 in pretreated Japanese and Taiwanese patients with advanced or metastatic solid tumors.

CLINICAL TRIALS REGISTRATION

NCT01905111.

Identification of new binding proteins of focal adhesion kinase using immunoprecipitation and mass spectrometry

Focal adhesion kinase (FAK) is a 125 kDa protein recruited as a participant in focal adhesion dynamics and serves as a signaling scaffold for the assembly and subsequent maturation of focal contact. Identification of new FAK binding proteins could reveal potential signaling targets and contribute to further development of therapeutic drugs in the treatment of colon cancer. Here, we applied a functional proteomic strategy to identify proteins that interact with FAK in human colon cancer cell line HCT-116. Proteins were targeted by coimmunoprecipitation with an anti-FAK antibody and resolved on 1D-SDS-PAGE. The gel was excised, reduced, alkylated, and trypsin digested. Tryptic peptides were separated by nano-LC-MS/MS by an LTQ-Orbitrap-Velos spectrometer. We identified 101 proteins in the immunocomplex under epithelial growth factor (EGF) stimulation. Three proteins, zyxin, nesprin-1, and desmoplakin, were discovered and validated using reciprocal immunoprecipitation and Western blot analysis. Then, we sought to study the biological relevance of these proteins by siRNA transfection of HCT-116 cells. According to the results, zyxin might play a central role as an upstream regulator to mediate critical cancer-related signaling pathways. Zyxin and nesprin-1 depletion significantly impaired cell migration and invasion capabilities. Additionally, we performed ELISA assays on serum samples from patients with colon cancer instead of cell models to quantify the protein levels of zyxin and nesprin-1. Our results suggested that zyxin and nesprin-1 are not only promising therapeutic targets but also potential diagnostic biomarkers for colon cancer.

The roles of nuclear focal adhesion kinase (FAK) on Cancer: a focused review

FAK is a tyrosine kinase overexpressed in cancer cells and plays an important role in the progression of tumors to a malignant phenotype. Except for its typical role as a cytoplasmic kinase downstream of integrin and growth factor receptor signaling, related studies have shown new aspects of the roles of FAK in the nucleus. FAK can promote p53 degradation through ubiquitination, leading to cancer cell growth and proliferation. FAK can also regulate GATA4 and IL-33 expression, resulting in reduced inflammatory responses and immune escape. These findings establish a new model of FAK from the cytoplasm to the nucleus. Activated FAK binds to transcription factors and regulates gene expression. Inactive FAK synergizes with different E3 ligases to promote the turnover of transcription factors by enhancing ubiquitination. In the tumor microenvironment, nuclear FAK can regulate the formation of new blood vessels, affecting the tumor blood supply. This article reviews the roles of nuclear FAK in regulating gene expression. In addition, the use of FAK inhibitors to target nuclear FAK functions will also be emphasized.

Evaluation of AAV-mediated delivery of shRNA to target basal-like breast cancer genetic vulnerabilities

Adeno-associated viral vectors (AAV) for gene therapy applications are gaining momentum, with more therapies moving into later stages of clinical development and towards market approval, namely for cancer therapy. The development of cytotoxic vectors is often hampered by side effects arising when non-target cells are infected, and their production can be hindered by toxic effects of the transgene on the producing cell lines. In this study, we evaluated the potential of rAAV-mediated delivery of short hairpin RNAs (shRNA) to target basal-like breast cancer genetic vulnerabilities. Our results show that by optimizing the stoichiometry of the plasmids upon transfection and time of harvest, it is possible to increase the viral titers and quality. All rAAV-shRNA vectors obtained efficiently transduced the BLBC cell lines MDA-MB-468 and HCC1954. In MDA-MB-468, transduction with rAAV-shRNA vector targeting PSMA2 was associated with significant decrease in cell viability and apoptosis induction. Importantly, rAAV2-PSMA2 also slowed tumor growth in a BLBC mouse xenograft model, thus potentially representing a therapeutic strategy against this type of cancer.

Inhibiting focal adhesion kinase: A potential target for enhancing therapeutic efficacy in colorectal cancer therapy

Focal adhesion kinase (FAK) is a major integrin-dependent tyrosine phosphorylated protein, recently, FAK association with colorectal cancer (CRC) has gained attention. The various cancer-promoting mechanisms that associated with FAK can be implicated in the progression of CRC. The interactions between structural features of FAK and various kinases could be closely related to growth, survival, and metastasis in CRC cells. These interactions include human epithelial growth factor receptor, c-Met, platelet-derived growth factor receptor, vascular endothelial growth factor receptor, and Src. Such interactions can trigger the survival signaling of CRC cells and are also involved signaling downstream of phosphatidylinositol 3-kinase, AKT, and the extracellular regulated kinase. Based on this scientific background, many pharmaceutical companies are taking efforts to develop FAK inhibitors to treat solid cancer including CRC. Although the anti-cancer efficacies have been noted in many studies, the commercial drugs have not been developed yet. Therefore, the FAK research on CRC is expected to gain momentum and be highly appreciated as a potential field for developing the new drugs. Therefore, the studies on FAK that effect on the progression of human CRC s would be possible to suggest various approaches to CRC treatment, and FAK could be a potential target as an anticancer candidate for CRC therapies.

Inhibiting focal adhesion kinase: A potential target for enhancing therapeutic efficacy in colorectal cancer therapy

Focal adhesion kinase (FAK) is a major integrin-dependent tyrosine phosphorylated protein, recently, FAK association with colorectal cancer (CRC) has gained attention. The various cancer-promoting mechanisms that associated with FAK can be implicated in the progression of CRC. The interactions between structural features of FAK and various kinases could be closely related to growth, survival, and metastasis in CRC cells. These interactions include human epithelial growth factor receptor, c-Met, platelet-derived growth factor receptor, vascular endothelial growth factor receptor, and Src. Such interactions can trigger the survival signaling of CRC cells and are also involved signaling downstream of phosphatidylinositol 3-kinase, AKT, and the extracellular regulated kinase. Based on this scientific background, many pharmaceutical companies are taking efforts to develop FAK inhibitors to treat solid cancer including CRC. Although the anti-cancer efficacies have been noted in many studies, the commercial drugs have not been developed yet. Therefore, the FAK research on CRC is expected to gain momentum and be highly appreciated as a potential field for developing the new drugs. Therefore, the studies on FAK that effect on the progression of human CRC s would be possible to suggest various approaches to CRC treatment, and FAK could be a potential target as an anticancer candidate for CRC therapies.

FAK auto-phosphorylation site tyrosine 397 is required for development but dispensable for normal skin homeostasis

Focal adhesion kinase (FAK) is an intensely studied non-receptor tyrosine kinase with roles in cancer and other common human diseases. Despite the large interest in FAK, the in vivo contribution of FAK auto-phosphorylation site tyrosine (Y) 397 to FAK function is incompletely understood. To study FAK Y397 in vivo we analyzed mice with 'non-phosphorylatable' Y-to-phenylalanine (F) and 'phospho-mimicking' Y-to-glutamate (E) mutations in the germline. We found that FAK Y397F mice die early during embryogenesis with abnormal angiogenesis like FAK kinase-dead mice. When Y397 is mutated to a glutamate mice survive beyond mid-gestation like mice where Y397 is lost by deletion of FAK exon 15. In culture, defects in proliferation, invasion and gene expression were more severe with the FAK Y397F than with the FAK Y397E mutation despite the inability of FAK Y397E to bind SRC. Conditional expression of FAK Y397F or Y397E in unchallenged avascular epidermis, however, resulted in no appreciable phenotype. We conclude that FAK Y397 is required for the highly dynamic tissue remodeling during development but dispensable for normal homeostasis of avascular epidermis. In contrast to the Y397F mutation, FAK Y397E retains sufficient biological activity to allow for development beyond mid-gestation.

Differences in cancer gene copy number alterations between Epstein-Barr virus-positive and Epstein-Barr virus-negative nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) treatment is mainly based on clinical staging. We hypothesize that better understanding of the molecular heterogeneity of NPC can aid in better treatment decisions. Therefore, the purpose of this study was to present our exploration of cancer gene copy-number alterations (CNAs) of Epstein-Barr virus (EBV)-positive and EBV-negative NPC.

METHODS

Multiplex ligation-dependent probe amplification was applied to detect CNAs of 36 cancer genes (n = 103). Correlation between CNAs, clinicopathological features, and survival were examined.

RESULTS

The CNAs occurred significantly more in EBV-negative NPC, with PIK3CA and MCCC1 (P < .001) gain/amplification occurring more frequently. Gain/amplification of cyclin-L1 (CCNL1) and PTK2 (P < .001) predict worse disease-free survival (DFS) in EBV-positive NPC.

CONCLUSION

The EBV-positive and EBV-negative NPC show some similarities in cancer gene CNAs suggesting a common pathogenic route but also important differences possibly indicating divergence in oncogenesis. Copy number gain/amplification of CCNL1 and PTK2 are possibly good predictors of survival in EBV-positive NPC.

Endogenous Control Mechanisms of FAK and PYK2 and Their Relevance to Cancer Development

Focal adhesion kinase (FAK) and its close paralogue, proline-rich tyrosine kinase 2 (PYK2), are key regulators of aggressive spreading and metastasis of cancer cells. While targeted small-molecule inhibitors of FAK and PYK2 have been found to have promising antitumor activity, their clinical long-term efficacy may be undermined by the strong capacity of cancer cells to evade anti-kinase drugs. In healthy cells, the expression and/or function of FAK and PYK2 is tightly controlled via modulation of gene expression, competing alternatively spliced forms, non-coding RNAs, and proteins that directly or indirectly affect kinase activation or protein stability. The molecular factors involved in this control are frequently deregulated in cancer cells. Here, we review the endogenous mechanisms controlling FAK and PYK2, and with particular focus on how these mechanisms could inspire or improve anticancer therapies.

Inhibition of cell migration by focal adhesion kinase: Time-dependent difference in integrin-induced signaling between endothelial and hepatoblastoma cells

Angiogenesis plays an important role in the development and progression of tumors, and it involves a series of signaling pathways contributing to the migration of endothelial cells for vascularization and to the invasion of cancer cells for secondary tumor formation. Among these pathways, the focal adhesion kinase (FAK) signaling cascade has been implicated in a variety of human cancers in connection with cell adhesion and migration events leading to tumor angiogenesis, metastasis and invasion. Therefore, the inhibition of FAK in endothelial and/or cancer cells is a potential target for anti-angiogenic therapy. In the present study, a small-molecule FAK inhibitor, 1,2,4,5-benzenetetramine tetrahydrochloride (Y15), was used to study the effects of FAK inhibition on the adhesion and migration behaviors of vascular endothelial cells (VECs) and human hepatoblastoma cells. Furthermore, the time-dependent differences in proteins associated with the integrin-mediated FAK/Rho GTPases signaling pathway within 2 h were examined. The results indicated that the inhibition of FAK significantly decreased the migration ability of VECs and human hepatoblastoma cells in a dose-dependent manner. Inhibition of FAK promoted cell detachment by decreasing the expression of focal adhesion components, and blocked cell motility by reducing the level of Rho GTPases. However, the expression of crucial proteins involved in integrin-induced signaling in two cell lines exhibited a time-dependent difference with increased duration of FAK inhibitor treatment, suggesting different mechanisms of FAK-mediated cell migration behavior. These results suggest that the mechanism underlying FAK-mediated adhesion and migration behavior differs among various cells, which is expected to provide evidence for future FAK therapy targeted against tumor angiogenesis.

The cancer cell adhesion resistome: mechanisms, targeting and translational approaches

Cell adhesion-mediated resistance limits the success of cancer therapies and is a great obstacle to overcome in the clinic. Since the 1990s, where it became clear that adhesion of tumor cells to the extracellular matrix is an important mediator of therapy resistance, a lot of work has been conducted to understand the fundamental underlying mechanisms and two paradigms were deduced: cell adhesion-mediated radioresistance (CAM-RR) and cell adhesion-mediated drug resistance (CAM-DR). Preclinical work has evidently demonstrated that targeting of integrins, adapter proteins and associated kinases comprising the cell adhesion resistome is a promising strategy to sensitize cancer cells to both radiotherapy and chemotherapy. Moreover, the cell adhesion resistome fundamentally contributes to adaptation mechanisms induced by radiochemotherapy as well as molecular drugs to secure a balanced homeostasis of cancer cells for survival and growth. Intriguingly, this phenomenon provides a basis for synthetic lethal targeted therapies simultaneously administered to standard radiochemotherapy. In this review, we summarize current knowledge about the cell adhesion resistome and highlight targeting strategies to override CAM-RR and CAM-DR.

Focal Adhesion Kinase (FAK) tyrosine 397E mutation restores the vascular leakage defect in endothelium-specific FAK-kinase dead mice

Focal adhesion kinase (FAK) inhibitors have been developed as potential anticancer agents and are undergoing clinical trials. In vitro activation of the FAK kinase domain triggers autophosphorylation of Y397, Src activation, and subsequent phosphorylation of other FAK tyrosine residues. However, how FAK Y397 mutations affect FAK kinase-dead (KD) phenotypes in tumour angiogenesis in vivo is unknown. We developed three Pdgfb-iCreert -driven endothelial cell (EC)-specific, tamoxifen-inducible homozygous mutant mouse lines: FAK wild-type (WT), FAK KD, and FAK double mutant (DM), i.e. KD with a putatively phosphomimetic Y397E mutation. These ECCre+;FAKWT/WT , ECCre+;FAKKD/KD and ECCre+;FAKDM/DM mice were injected subcutaneously with syngeneic B16F0 melanoma cells. Tumour growth and tumour blood vessel functions were unchanged between ECCre+;FAKWT/WT and ECCre-;FAKWT/WT control mice. In contrast, tumour growth and vessel density were decreased in ECCre+;FAKKD/KD and ECCre+;FAKDM/DM mice, as compared with Cre - littermates. Despite no change in the percentage of perfused vessels or pericyte coverage in either genotype, tumour hypoxia was elevated in ECCre+;FAKKD/KD and ECCre+;FAKDM/DM mice. Furthermore, although ECCre+;FAKKD/KD mice showed reduced blood vessel leakage, ECCre+;FAKDM/DM and ECCre-;FAKDM/DM mice showed no difference in leakage. Mechanistically, fibronectin-stimulated Y397 autophosphorylation was reduced in Cre+;FAKKD/KD ECs as compared with Cre+;FAKWT/WT cells, with no change in phosphorylation of the known Src targets FAK-Y577, FAK-Y861, FAK-Y925, paxillin-Y118, p130Cas-Y410. Cre+;FAKDM/DM ECs showed decreased Src target phosphorylation levels, suggesting that the Y397E substitution actually disrupted Src activation. Reduced VE-cadherin-pY658 levels in Cre+;FAKKD/KD ECs were rescued in Cre+FAKDM/DM ECs, corresponding with the rescue in vessel leakage in the ECCre+;FAKDM/DM mice. We show that EC-specific FAK kinase activity is required for tumour growth, angiogenesis, and vascular permeability. The ECCre+;FAKDM/DM mice restored the KD-dependent tumour vascular leakage observed in ECCre+;FAKKD/KD mice in vivo. This study opens new fields in in vivo FAK signalling. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Focal Adhesion Kinase Expression in Ameloblastoma: A Preliminary Observational Study

INTRODUCTION

Focal Adhesion Kinase (FAK) is a membrane-associated molecule, which plays a major role in tumourigenesis by promoting cell survival, proliferation, migration, and invasion. Hence, FAK is a well known molecule that has been targeted therapeutically for the treatment of various malignancies. Ameloblastoma (AB) is a locally invasive, destructive and recurrent benign odontogenic lesion. Based on these properties, we have hypothesized that odontogenic epithelium of AB could show increased expression of FAK.

AIM

To study the expression of FAK in odontogenic epithelium of AB using immunohistochemistry.

MATERIALS AND METHODS

Thirty four paraffin embedded AB and 17 Dental Follicle (DF) tissues were retrieved from archives. Immunohistochemical staining was performed using FAK antibody on 5 μm thick formalin fixed paraffin embedded sections. The expression of FAK was studied in ameloblast like cells and stellate reticulum-like cells and was graded as negative, weak and strong. The data was analysed using chi-square test and Fisher's-exact test.

RESULTS

In AB, both ameloblast like and stellate reticulum like cells showed positive expression of FAK in the cytoplasm in all the cases (34). The epithelial islands from all the DFs (17) were negative for FAK expression. The difference in the expression of FAK in ameloblast like and stellate reticulum like cells was statistically significant (p<0.0001). Statistically significant difference was observed in the expression of FAK in stellate reticulum like cells of AB and odontogenic epithelial islands of DF (p = 0.0017). All the AB cases showed strong expression of FAK in ameloblast like cells and negative expression was seen in all the cases of DF.

CONCLUSION

FAK was strongly expressed in AB as compared to epithelial islands of DF. FAK could be responsible for the neoplastic nature of AB and possibly play a role in tumour invasiveness.

Investigations of FAK inhibitors: a combination of 3D-QSAR, docking, and molecular dynamics simulations studies

Focal adhesion kinase (FAK) is one kind of tyrosine kinases that modulates integrin and growth factor signaling pathways, which is a promising therapeutic target because of involving in cancer cell migration, proliferation, and survival. To investigate the mechanism between FAK and triazinic inhibitors and design high activity inhibitors, a molecular modeling integrated with 3D-QSAR, molecular docking, molecular dynamics simulations, and binding free energy calculations was performed. The optimum CoMFA and CoMSIA models showed good reliability and satisfactory predictability (with Q² = 0.663, R² = 0.987, [Formula: see text] = 0.921 and Q² = 0.670, R² = 0.981, [Formula: see text] = 0.953). Its contour maps could provide structural features to improve inhibitory activity. Furthermore, a good consistency between contour maps, docking, and molecular dynamics simulations strongly demonstrates that the molecular modeling is reliable. Based on it, we designed several new compounds and their inhibitory activities were validated by the molecular models. We expect our studies could bring new ideas to promote the development of novel inhibitors with higher inhibitory activity for FAK.

The metabolic waste ammonium regulates mTORC2 and mTORC1 signaling

Two structurally and functionally distinct mammalian TOR complexes control cell growth and metabolism in physiological and pathological contexts including cancer. Upregulated glutaminolysis is part of the metabolic reprogramming occurring in cancer, providing fuels for growth but also liberating ammonium, a potent neurotoxic waste product. Here, we identify ammonium as a novel dose-dependent signal mediating rapid mTORC2 activation and further regulating mTORC1. We show that ammonium induces rapid RICTOR-dependent phosphorylation of AKT-S473, a process requiring the PI3K pathway and further involving the Src-family kinase YES1, the FAK kinase and the ITGβ1 integrin. Release of calcium from the endoplasmic reticulum store triggers rapid mTORC2 activation, similar to ammonium-induced activation, the latter being conversely prevented by calcium chelation.Moreover, in analogy to growth factors, ammonium triggers the AKT-dependent phosphoinhibition of the TSC complex and of PRAS40, two negative regulators of mTORC1. Consistent with mTORC1 stimulation, ammonium induces the inhibitory phosphorylation of 4EBP1, a negative regulator of protein biogenesis. Ammonium however dually impacts on the phosphorylation of p70S6K1 triggering a transient AKT-independent decrease in the phosphorylation of this second mTORC1 readout. Finally, we reveal ammonium as a dose-dependent stimulator of proliferation. This study underscores an mTORC2 and mTORC1 response to the so-called ammonium waste.

Activated tumor cell integrin αvβ3 cooperates with platelets to promote extravasation and metastasis from the blood stream

Metastasis is the main cause of death in cancer patients, and understanding mechanisms that control tumor cell dissemination may lead to improved therapy. Tumor cell adhesion receptors contribute to cancer spreading. We noted earlier that tumor cells can expressing the adhesion receptor integrin αvβ3 in distinct states of activation, and found that cells which metastasize from the blood stream express it in a constitutively high affinity form. Here, we analyzed steps of the metastatic cascade in vivo and asked, when and how the affinity state of integrin αvβ3 confers a critical advantage to cancer spreading. Following tumor cells by real time PCR, non-invasive bioluminescence imaging, intravital microscopy and histology allowed us to identify tumor cell extravasation from the blood stream as a rate-limiting step supported by high affinity αvβ3. Successful transendothelial migration depended on cooperation between tumor cells and platelets involving the high affinity tumor cell integrin and release of platelet granules. Thus, this study identifies the high affinity conformer of integrin αvβ3 and its interaction with platelets as critical for early steps during hematogenous metastasis and target for prevention of metastatic disease.

Focal Adhesion Kinase: Insight into Molecular Roles and Functions in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Due to the high incidence of post-operative recurrence after current treatments, the identification of new and more effective drugs is required. In previous years, new targetable genes/pathways involved in HCC pathogenesis have been discovered through the help of high-throughput sequencing technologies. Mutations in TP53 and β-catenin genes are the most frequent aberrations in HCC. However, approaches able to reverse the effect of these mutations might be unpredictable. In fact, if the reactivation of proteins, such as p53 in tumours, holds great promise as anticancer therapy, there are studies arguing that chronic activation of these types of molecules may be deleterious. Thus, recently the efforts on potential targets have focused on actionable mutations, such as those occurring in the gene encoding for focal adhesion kinase (FAK). This tyrosine kinase, localized to cellular focal contacts, is over-expressed in a variety of human tumours, including HCC. Moreover, several lines of evidence demonstrated that FAK depletion or inhibition impair in vitro and in vivo HCC growth and metastasis. Here, we provide an overview of FAK expression and activity in the context of tumour biology, discussing the current evidence of its connection with HCC development and progression.

The 2016 John J. Abel Award Lecture: Targeting the Mechanical Microenvironment in Cancer

Past decades of cancer research have mainly focused on the role of various extracellular and intracellular biochemical signals on cancer progression and metastasis. Recent studies suggest an important role of mechanical forces in regulating cellular behaviors. This review first provides an overview of the mechanobiology research field. Then we specially focus on mechanotransduction pathways in cancer progression and describe in detail the key signaling components of such mechanotransduction pathways and extracellular matrix components that are altered in cancer. Although our understanding of mechanoregulation in cancer is still in its infancy, some agents against key mechanoregulators have been developed and will be discussed to explore the potential of pharmacologically targeting mechanotransduction in cancer.

Twist promotes reprogramming of glucose metabolism in breast cancer cells through PI3K/AKT and p53 signaling pathways

Twist, a key regulator of epithelial-mesenchymal transition (EMT), plays an important role in the development of a tumorigenic phenotype. Energy metabolism reprogramming (EMR), a newly discovered hallmark of cancer cells, potentiates cancer cell proliferation, survival, and invasion. Currently little is known about the effects of Twist on tumor EMR. In this study, we found that glucose consumption and lactate production were increased and mitochondrial mass was decreased in Twist-overexpressing MCF10A mammary epithelial cells compared with vector-expressing MCF10A cells. Moreover, these Twist-induced phenotypic changes were augmented by hypoxia. The expression of some glucose metabolism-related genes such as PKM2, LDHA, and G6PD was also found to be upregulated. Mechanistically, activated β1-integrin/FAK/PI3K/AKT/mTOR and suppressed P53 signaling were responsible for the observed EMR. Knockdown of Twist reversed the effects of Twist on EMR in Twist-overexpressing MCF10A cells and Twist-positive breast cancer cells. Furthermore, blockage of the β1-integrin/FAK/PI3K/AKT/mTOR pathway by siRNA or specific chemical inhibitors, or rescue of p53 activation can partially reverse the switch of glucose metabolism and inhibit the migration of Twist-overexpressing MCF10A cells and Twist-positive breast cancer cells. Thus, our data suggest that Twist promotes reprogramming of glucose metabolism in MCF10A-Twist cells and Twist-positive breast cancer cells via activation of the β1-integrin/FAK/PI3K/AKT/mTOR pathway and inhibition of the p53 pathway. Our study provides new insight into EMR.

PIAS1-FAK Interaction Promotes the Survival and Progression of Non-Small Cell Lung Cancer

The sequence of genomic alterations acquired by cancer cells during tumor progression and metastasis is poorly understood. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that integrates cytoskeleton remodeling, mitogenic signaling and cell survival. FAK has previously been reported to undergo nuclear localization during cell migration, cell differentiation and apoptosis. However, the mechanism behind FAK nuclear accumulation and its contribution to tumor progression has remained elusive. We report that amplification of FAK and the SUMO E3 ligase PIAS1 gene loci frequently co-occur in non-small cell lung cancer (NSCLC) cells, and that both gene products are enriched in a subset of primary NSCLCs. We demonstrate that endogenous FAK and PIAS1 proteins interact in the cytoplasm and the cell nucleus of NSCLC cells. Ectopic expression of PIAS1 promotes proteolytic cleavage of the FAK C-terminus, focal adhesion maturation and FAK nuclear localization. Silencing of PIAS1 deregulates focal adhesion turnover, increases susceptibility to apoptosis in vitro and impairs tumor xenograft formation in vivo. Nuclear FAK in turn stimulates gene transcription favoring DNA repair, cell metabolism and cytoskeleton regulation. Consistently, ablation of FAK by CRISPR/Cas9 editing, results in basal DNA damage, susceptibility to ionizing radiation and impaired oxidative phosphorylation. Our findings provide insight into a mechanism regulating FAK cytoplasm-nuclear distribution and demonstrate that FAK activity in the nucleus promotes NSCLC survival and progression by increasing cell-ECM interaction and DNA repair regulation.

Anti-metastatic action of FAK inhibitor OXA-11 in combination with VEGFR-2 signaling blockade in pancreatic neuroendocrine tumors

The present study sought to determine the anti-tumor effects of OXA-11, a potent, novel small-molecule amino pyrimidine inhibitor (1.2 pM biochemical IC(50)) of focal adhesion kinase (FAK). In studies of cancer cell lines, OXA-11 inhibited FAK phosphorylation at phospho-tyrosine 397 with a mechanistic IC(50) of 1 nM in TOV21G tumor cells, which translated into functional suppression of proliferation in 3-dimensional culture with an EC(50) of 9 nM. Studies of OXA-11 activity in TOV21G tumor-cell xenografts in mice revealed a pharmacodynamic EC(50) of 1.8 nM, indicative of mechanistic inhibition of pFAK [Y397] in these tumors. OXA-11 inhibited TOV21G tumor growth in a dose-dependent manner and also potentiated effects of cisplatin on tumor cell proliferation and apoptosis in vitro and on tumor growth in mice. Studies of pancreatic neuroendocrine tumors in RIP-Tag2 transgenic mice revealed OXA-11 suppression of pFAK [Y397] and pFAK [Y861] in tumors and liver. OXA-11 given daily from age 14 to 17 weeks reduced tumor vascularity, invasion, and when given together with the anti-VEGFR-2 antibody DC101 reduced the incidence, abundance, and size of liver metastases. Liver micrometastases were found in 100 % of mice treated with vehicle, 84 % of mice treated with OXA-11, and 79 % of mice treated with DC101 (19-24 mice per group). In contrast, liver micrometastases were found in only 52 % of 21 mice treated with OXA-11 plus DC101, and those present were significantly smaller and less numerous. Together, these findings indicate that OXA-11 is a potent and selective inhibitor of FAK phosphorylation in vitro and in vivo. OXA-11 slows tumor growth, potentiates the anti-tumor actions of cisplatin and--when combined with VEGFR-2 blockade--reduces metastasis of pancreatic neuroendocrine tumors in RIP-Tag2 mice.

Role of focal adhesion kinase in oocyte-follicle communication

Germ cells require communication with associated somatic cells for normal gametogenesis, as exemplified by an oocyte that interacts with granulosa cells via paracrine factors as well as gap junctions located at sites of contact between these two cell types. The objective of the present study was to define the mechanisms by which cell-cell contact with the oocyte is controlled and to determine the extent that the oocyte actively participates in this association. Proline-rich tyrosine kinase 2 (PTK2), a focal adhesion kinase, was found to be activated at sites of contact between the oocyte and trans-zonal cell processes from the surrounding granulosa cells. In order to determine the functional significance of oocyte-derived PTK2 signaling in oocyte-follicle communication, an oocyte-specific Ptk2 knockout was produced through a breeding strategy pairing a floxed Ptk2-CAT-eGFP mouse with the Zp3-Cre line. Since Ptk2-null mice never develop to birth, this represents the first opportunity to define the role of PTK2 in oocyte-follicle communication. Ablation of Ptk2 within the developing oocyte resulted in lower fertility with reduced numbers of pups, lower rates of blastocyst formation, and reduced cell numbers per blastocyst. Follicles containing Ptk2-null oocytes exhibited reduced oocyte diameter, reduced numbers of connexin 37 and 43 foci at the oocyte surface, and impaired dye coupling between oocyte and granulosa cells. These findings are consistent with a model in which PTK2 plays a critical role in establishing or maintaining oocyte-granulosa cell contacts that are essential for gap junction-mediated communication between granulosa cells and the oocyte.

Focal adhesion kinase regulates the phosphorylation protein tyrosine phosphatase-α at Tyr789 in breast cancer cells

Protein tyrosine phosphatase (PTP)‑α regulates the phosphorylation of focal adhesion kinase (FAK), which is important in cellular signal transduction and integration of proteins. It has been demonstrated that a FAK‑Del33 mutation (deletion of exon 33; KF437463) in breast cancer tissues regulates cell migration through FAK/Src signaling activation. However, the detailed pathway for Src activation with FAK‑Del33 remains to be elucidated. The present study used a retroviral expression system to examine changes in PTPα phosphorylation affected by the FAK‑Del33 protein in breast cancer cells. Small interfering (si)RNA targeting PTPα interfered with the phosphorylation of Src. Wound‑healing and migration assays were performed to identify cell morphology and quantitative analysis was performed by examining band color depth in western blot analysis. Significant differences were observed in the phosphorylation level of PTPα at Tyr789 between the FAK‑Del33 and the wild‑type breast cancer cells, suggesting that FAK regulated the phosphorylation level of PTPα at Tyr789 in breast cancer mutant FAK‑Del33 cells. The gene expression profile with FAK siRNA did not alter the levels of phosphorylation in other mutants, including autophosphorylation disability (Y397F), ATP kinase dominant negative (K454R) and protein 4.1, ezrin, radixin, moesin domain attenuate (Δ375). FAK RNAi inhibited the activity of the FAK‑Del33 at the Src site and rescued the elevated cell migration and invasion. The present study demonstrated for the first time, to the best of our knowledge, an increase in the phosphorylation level of PTPα‑Tyr789 by its upstream activator, FAK‑Del33, leading to Src activation in certain breast cancer cells, which has significant implications for metastatic potential.

Cyclic mechanical stretching promotes migration but inhibits invasion of rat bone marrow stromal cells

Bone marrow stromal cells (BMSCs, also broadly known as bone marrow-derived mesenchymal stem cells) are multipotent stem cells that have a self-renewal capacity and multilineage differentiation potential. Mechanical stretching plays a vital role in regulating the proliferation and differentiation of BMSCs. However, little is known about the effects of cyclic stretching on BMSC migration and invasion. In this study, using a custom-made cell-stretching device, we studied the effects of cyclic mechanical stretching on rat BMSC migration and invasion using a Transwell Boyden Chamber. The protein secretion of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) was detected by gelatin zymography, and the activation of focal adhesion kinase (FAK) and extracellular signal regulated kinase1/2 (ERK1/2) was measured by western blot. We found that cyclic mechanical stretching with 10% amplitude at 1Hz frequency for 8h promotes BMSC migration, but reduces BMSC invasion. FAK and ERK1/2 signals were activated in BMSCs after exposure to cyclic stretching. In the presence of the FAK phosphorylation blocker PF573228 or the ERK1/2 phosphorylation blocker PD98059, the cyclic-stretch-promoted migration of BMSCs was completely suppressed. On the other hand, cyclic mechanical stretching reduced the secretion of MMP-2 and MMP-9 in BMSCs, and PF573228 suppressed the cyclic-stretch-reduced secretion of MMP-2 and MMP-9. The decrease of BMSC invasion induced by mechanical stretching is partially restored by PF573228 but remained unaffected by PD98059. Taken together, these data show that cyclic mechanical stretching promotes BMSC migration via the FAK-ERK1/2 signalling pathway, but reduces BMSC invasion by decreasing secretion of MMP-2 and MMP-9 via FAK, independent of the ERK1/2 signal.

Understanding the roles of FAK in cancer: inhibitors, genetic models, and new insights

Focal adhesion kinase (FAK) is a protein tyrosine kinase that regulates cellular adhesion, motility, proliferation and survival in various types of cells. Interestingly, FAK is activated and/or overexpressed in advanced cancers, and promotes cancer progression and metastasis. For this reason, FAK became a potential therapeutic target in cancer, and small molecule FAK inhibitors have been developed and are being tested in clinical phase trials. These inhibitors have demonstrated to be effective by inducing tumor cell apoptosis in addition to reducing metastasis and angiogenesis. Furthermore, several genetic FAK mouse models have made advancements in understanding the specific role of FAK both in tumors and in the tumor environment. In this review, we discuss FAK inhibitors as well as genetic mouse models to provide mechanistic insights into FAK signaling and its potential in cancer therapy.

FAK signaling in human cancer as a target for therapeutics

Focal adhesion kinase (FAK) is a key regulator of growth factor receptor- and integrin-mediated signals, governing fundamental processes in normal and cancer cells through its kinase activity and scaffolding function. Increased FAK expression and activity occurs in primary and metastatic cancers of many tissue origins, and is often associated with poor clinical outcome, highlighting FAK as a potential determinant of tumor development and metastasis. Indeed, data from cell culture and animal models of cancer provide strong lines of evidence that FAK promotes malignancy by regulating tumorigenic and metastatic potential through highly-coordinated signaling networks that orchestrate a diverse range of cellular processes, such as cell survival, proliferation, migration, invasion, epithelial-mesenchymal transition, angiogenesis and regulation of cancer stem cell activities. Such an integral role in governing malignant characteristics indicates that FAK represents a potential target for cancer therapeutics. While pharmacologic targeting of FAK scaffold function is still at an early stage of development, a number of small molecule-based FAK tyrosine kinase inhibitors are currently undergoing pre-clinical and clinical testing. In particular, PF-00562271, VS-4718 and VS-6063 show promising clinical activities in patients with selected solid cancers. Clinical testing of rationally designed FAK-targeting agents with implementation of predictive response biomarkers, such as merlin deficiency for VS-4718 in mesothelioma, may help improve clinical outcome for cancer patients. In this article, we have reviewed the current knowledge regarding FAK signaling in human cancer, and recent developments in the generation and clinical application of FAK-targeting pharmacologic agents.

New insights into FAK phosphorylation based on a FAT domain-defective mutation

Mounting evidence suggests that the FAK N-terminal (FERM) domain controls FAK phosphorylation and function; however, little is known regarding the role of the C terminal (FAT) domain in FAK regulation. We identified a patient-derived FAK mutant, in which a 27-amino acid segment was deleted from the C-terminal FAT domain (named FAK-Del33). When FAK-Del33 was overexpressed in specific tumor cell lines, Y397 phosphorylation increased compared with that observed in cells expressing FAK-WT. Here, we attempt to unveil the mechanism of this increased phosphorylation. Using cell biology experiments, we show that FAK-Del33 is incapable of co-localizing with paxillin, and has constitutively high Y397 phosphorylation. With a kinase-dead mutation, it showed phosphorylation of FAK-Del33 has enhanced through auto-phosphorylation. It was also demonstrated that phosphorylation of FAK-Del33 is not Src dependent or enhanced intermolecular interactions, and that the hyperphosphorylation can be lowered using increasing amounts of transfected FERM domain. This result suggests that Del33 mutation disrupting of FAT's structural integrity and paxillin binding capacity leads to incapable of targeting Focal adhesions, but has gained the capacity for auto-phosphorylation in cis.

Potential effect of matrix stiffness on the enrichment of tumor initiating cells under three-dimensional culture conditions

Cancer stem cell (CSC) or tumor initiating cell (TIC) plays an important role in tumor progression and metastasis. Biophysical forces in tumor microenvironment have an important effect on tumor formation and development. In this study, the potential effect of matrix stiffness on the biological characteristics of human head and neck squamous cell carcinoma (HNSCC) TICs, especially the enrichment of HNSCC TICs, was investigated under three-dimensional (3D) culture conditions by means of alginate gel (ALG) beads with different matrix stiffnesses. ALG beads with soft (21 kPa), moderate (70 kPa) and hard (105 kPa) stiffness were generated by changing alginate concentration. It was found that significant HNSCC TIC enrichment was achieved in the ALG beads with moderate matrix stiffness (70 kPa). The gene expression of stemness markers Oct3/4 and Nanog, TIC markers CD44 and ABCG2 was enhanced in cells under this moderate (70 kPa) stiffness. HNSCC TIC proportion was also highly enriched under moderate matrix stiffness, accompanying with higher tumorigenicity, metastatic ability and drug resistance. And it was also found that the possible molecular mechanism underlying the regulated TIC properties by matrix stiffness under 3D culture conditions was significantly different from 2D culture condition. Therefore, the results achieved in this study indicated that 3D biophysical microenvironment had an important effect on TIC characteristics and alginate-based biomimetic scaffolds could be utilized as a proper platform to investigate the interaction between tumor cells and 3D microenvironment.