Pyk2 and FAK differentially regulate progression of the cell cycle

Squishy matters - Corneal mechanobiology in health and disease

The cornea, as a dynamic and responsive tissue, constantly interacts with mechanical forces in order to maintain its structural integrity, barrier function, transparency and refractive power. Cells within the cornea sense and respond to various mechanical forces that fundamentally regulate their morphology and fate in development, homeostasis and pathophysiology. Corneal cells also dynamically regulate their extracellular matrix (ECM) with ensuing cell-ECM crosstalk as the matrix serves as a dynamic signaling reservoir providing biophysical and biochemical cues to corneal cells. Here we provide an overview of mechanotransduction signaling pathways then delve into the recent advances in corneal mechanobiology, focusing on the interplay between mechanical forces and responses of the corneal epithelial, stromal, and endothelial cells. We also identify species-specific differences in corneal biomechanics and mechanotransduction to facilitate identification of optimal animal models to study corneal wound healing, disease, and novel therapeutic interventions. Finally, we identify key knowledge gaps and therapeutic opportunities in corneal mechanobiology that are pressing for the research community to address especially pertinent within the domains of limbal stem cell deficiency, keratoconus and Fuchs' endothelial corneal dystrophy. By furthering our understanding corneal mechanobiology, we can contextualize discoveries regarding corneal diseases as well as innovative treatments for them.

FAK inhibitor PF-562271 inhibits the migration and proliferation of high-grade serous ovarian cancer cells through FAK and FAK mediated cell cycle arrest

Focal adhesion kinase (FAK) is a promising therapeutic target for various cancers and its inhibitor development is in full swing. PF-562271 is a classic FAK inhibitor that has shown promising preclinical data and has been found to exhibit an anti-migration effect on some cancer cells. However, its anticancer effect on high-grade serous ovarian cancer (HGSOC) has not been reported. In this study, we evaluated the anti-migration and anti-proliferation effects of PF-562271 against HGSOC SKOV3 and A2780 cells, as well as the underlying mechanism. The results demonstrated that FAK was overexpressed in clinical HGSOC tissues and was positively correlated with the pathological progression of HGSOC. Moreover, HGSOC patients with high FAK expression levels exhibited low survival rates. PF-562271 treatment significantly inhibited the cell adhesion and migration of SKOV3 and A2780 cells by inhibiting p-FAK expression and decreasing the FA surface area. Additionally, PF-562271 treatment inhibited colony formation and induced cell senescence through G1 phase cell cycle arrest mediated DNA replication inhibition. Taken together, the findings demonstrated that FAK inhibitor PF-562271 significantly inhibits HGSOC cell adhesion, migration, and proliferation process through FAK and/or FAK mediated cell cycle arrest, and suggested that PF-562271 could serve as a potential oncotherapeutic agent for HGSOC targeting treatment.

The macrophage infectivity potentiator of Trypanosoma cruzi induces innate IFN-γ and TNF-α production by human neonatal and adult blood cells through TLR2/1 and TLR4

We previously identified the recombinant (r) macrophage (M) infectivity (I) potentiator (P) of the protozoan parasite Trypanosoma cruzi (Tc) (rTcMIP) as an immuno-stimulatory protein that induces the release of IFN-γ, CCL2 and CCL3 by human cord blood cells. These cytokines and chemokines are important to direct a type 1 adaptive immune response. rTcMIP also increased the Ab response and favored the production of the Th1-related isotype IgG2a in mouse models of neonatal vaccination, indicating that rTcMIP could be used as a vaccine adjuvant to enhance T and B cell responses. In the present study, we used cord and adult blood cells, and isolated NK cells and human monocytes to investigate the pathways and to decipher the mechanism of action of the recombinant rTcMIP. We found that rTcMIP engaged TLR1/2 and TLR4 independently of CD14 and activated the MyD88, but not the TRIF, pathway to induce IFN-γ production by IL-15-primed NK cells, and TNF-α secretion by monocytes and myeloid dendritic cells. Our results also indicated that TNF-α boosted IFN-γ expression. Though cord blood cells displayed lower responses than adult cells, our results allow to consider rTcMIP as a potential pro-type 1 adjuvant that might be associated to vaccines administered in early life or later.

Microglial Cytokines Induce Invasiveness and Proliferation of Human Glioblastoma through Pyk2 and FAK Activation

Simple Summary

Microglia infiltrate most gliomas and have been demonstrated to promote tumor growth, invasion, and treatment resistance. To develop improved treatment methods, that take into consideration the supporting role of microglia in tumor progression, the functional and mechanistic pathways of glioma–microglia interactions need to be identified and experimentally dissected. Our recent studies and literature reports revealed the overexpression of Pyk2 and FAK in glioblastomas. Pyk2 and FAK signaling pathways have been shown to regulate migration and proliferation in glioma cells, including microglia-promoted glioma cell migration. However, the specific factors released by microglia that modulate Pyk2 and FAK to promote glioma invasiveness and proliferation are poorly understood. The aim of this study was to identify key microglia-derived signaling molecules that induce the activation of Pyk2- and FAK-dependent glioma cell proliferation and invasiveness.

Abstract

Glioblastoma is the most aggressive brain tumor in adults. Multiple lines of evidence suggest that microglia create a microenvironment favoring glioma invasion and proliferation. Our previous studies and literature reports indicated the involvement of focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) in glioma cell proliferation and invasion, stimulated by tumor-infiltrating microglia. However, the specific microglia-released factors that modulate Pyk2 and FAK signaling in glioma cells are unknown. In this study, 20 human glioblastoma specimens were evaluated with the use of RT-PCR and western blotting. A Pierson correlation test demonstrated a correlation (0.6–1.0) between the gene expression levels for platelet-derived growth factor β(PDGFβ), stromal-derived factor 1α (SDF-1α), IL-6, IL-8, and epidermal growth factor (EGF) in tumor-purified microglia and levels of p-Pyk2 (Y579/Y580) and p-FAK(Y925) in glioma cells. siRNA knockdown against Pyk2 or FAK in three primary glioblastoma cell lines, developed from the investigated specimens, in combination with the cytokine receptor inhibitors gefitinib (1 μM), DMPQ (200 nM), and burixafor (1 μM) identified EGF, PDGFβ, and SDF-1α as key extracellular factors in the Pyk2- and FAK-dependent activation of invadopodia formation and the migration of glioma cells. EGF and IL-6 were identified as regulators of the Pyk2- and FAK-dependent activation of cell viability and mitosis.

Targeting FAK in anticancer combination therapies

Focal adhesion kinase (FAK) is both a non-receptor tyrosine kinase and an adaptor protein that primarily regulates adhesion signalling and cell migration, but FAK can also promote cell survival in response to stress. FAK is commonly overexpressed in cancer and is considered a high-value druggable target, with multiple FAK inhibitors currently in development. Evidence suggests that in the clinical setting, FAK targeting will be most effective in combination with other agents so as to reverse failure of chemotherapies or targeted therapies and enhance efficacy of immune-based treatments of solid tumours. Here, we discuss the recent preclinical evidence that implicates FAK in anticancer therapeutic resistance, leading to the view that FAK inhibitors will have their greatest utility as combination therapies in selected patient populations.

Biallelic mutations in LAMA5 disrupts a skeletal noncanonical focal adhesion pathway and produces a distinct bent bone dysplasia

Background

Beyond its structural role in the skeleton, the extracellular matrix (ECM), particularly basement membrane proteins, facilitates communication with intracellular signaling pathways and cell to cell interactions to control differentiation, proliferation, migration and survival. Alterations in extracellular proteins cause a number of skeletal disorders, yet the consequences of an abnormal ECM on cellular communication remains less well understood

Methods

Clinical and radiographic examinations defined the phenotype in this unappreciated bent bone skeletal disorder. Exome analysis identified the genetic alteration, confirmed by Sanger sequencing. Quantitative PCR, western blot analyses, immunohistochemistry, luciferase assay for WNT signaling were employed to determine RNA, proteins levels and localization, and dissect out the underlying cell signaling abnormalities.  Migration and wound healing assays examined cell migration properties.

Findings

This bent bone dysplasia resulted from biallelic mutations in LAMA5, the gene encoding the alpha-5 laminin basement membrane protein. This finding uncovered a mechanism of disease driven by ECM-cell interactions between alpha-5-containing laminins, and integrin-mediated focal adhesion signaling, particularly in cartilage. Loss of LAMA5 altered β1 integrin signaling through the non-canonical kinase PYK2 and the skeletal enriched SRC kinase, FYN. Loss of LAMA5 negatively impacted the actin cytoskeleton, vinculin localization, and WNT signaling.

Interpretation

This newly described mechanism revealed a LAMA5-β1 Integrin-PYK2-FYN focal adhesion complex that regulates skeletogenesis, impacted WNT signaling and, when dysregulated, produced a distinct skeletal disorder.

Funding

Supported by NIH awards R01 AR066124, R01 DE019567, R01 HD070394, and U54HG006493, and Czech Republic grants INTER-ACTION LTAUSA19030, V18-08-00567 and GA19-20123S.

Atypical Endocannabinoid Signaling Initiates a New Form of Memory-Related Plasticity at a Cortical Input to Hippocampus

Endocannabinoids (ECBs) depress transmitter release at sites throughout the brain. Here, we describe another form of ECB signaling that triggers a novel form of long-term potentiation (LTP) localized to the lateral perforant path (LPP) which conveys semantic information from cortex to hippocampus. Two cannabinoid CB1 receptor (CB1R) signaling cascades were identified in hippocampus. The first is pregnenolone sensitive, targets vesicular protein Munc18-1 and depresses transmitter release; this cascade is engaged by CB1Rs in Schaffer-Commissural afferents to CA1 but not in the LPP, and it does not contribute to LTP. The second cascade is pregnenolone insensitive and LPP specific; it entails co-operative CB1R/β1-integrin signaling to effect synaptic potentiation via stable enhancement of transmitter release. The latter cascade is engaged during LPP-dependent learning. These results link atypical ECB signaling to the encoding of a fundamental component of episodic memory and suggest a novel route whereby endogenous and exogenous cannabinoids affect cognition.

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.

Krüppel-like factor 8 activates the transcription of C-X-C cytokine receptor type 4 to promote breast cancer cell invasion, transendothelial migration and metastasis

Krüppel-like factor 8 (KLF8) has been strongly implicated in breast cancer metastasis. However, the underlying mechanisms remain largely unknown. Here we report a novel signaling from KLF8 to C-X-C cytokine receptor type 4 (CXCR4) in breast cancer. Overexpression of KLF8 in MCF-10A cells induced CXCR4 expression at both mRNA and protein levels, as determined by quantitative real-time PCR and immunoblotting. This induction was well correlated with increased Boyden chamber migration, matrigel invasion and transendothelial migration (TEM) of the cells towards the ligand CXCL12. On the other hand, knockdown of KLF8 in MDA-MB-231 cells reduced CXCR4 expression associated with decreased cell migration, invasion and TEM towards CXCL12. Histological and database mining analyses of independent cohorts of patient tissue microarrays revealed a correlation of aberrant co-elevation of KLF8 and CXCR4 with metastatic potential. Promoter analysis indicated that KLF8 directly binds and activates the human CXCR4 gene promoter. Interestingly, a CXCR4-dependent activation of focal adhesion kinase (FAK), a known upregulator of KLF8, was highly induced by CXCL12 treatment in KLF8-overexpressing, but not KLF8 deficient cells. This activation of FAK in turn induced a further increase in KLF8 expression. Xenograft studies showed that overexpression of CXCR4, but not a dominant-negative mutant of it, in the MDA-MB-231 cells prevented the invasive growth of primary tumor and lung metastasis from inhibition by knockdown of KLF8. These results collectively suggest a critical role for a previously unidentified feed-forward signaling wheel made of KLF8, CXCR4 and FAK in promoting breast cancer metastasis and shed new light on potentially more effective anti-cancer strategies.

Subcellular domain-dependent molecular hierarchy of SFK and FAK in mechanotransduction and cytokine signaling

Focal adhesion kinase (FAK) and Src family kinases (SFK) are known to play critical roles in mechanotransduction and other crucial cell functions. Recent reports indicate that they reside in different microdomains of the plasma membrane. However, little is known about their subcellular domain-dependent roles and responses to extracellular stimuli. Here, we employed fluorescence resonance energy transfer (FRET)-based biosensors in conjunction with collagen-coupled agarose gels to detect subcellular activities of SFK and FAK in three-dimensional (3D) settings. We observed that SFK and FAK in the lipid rafts and nonrafts are differently regulated by fluid flow and pro-inflammatory cytokines. Inhibition of FAK in the lipid rafts blocked SFK response to fluid flow, while inhibition of SFK in the non-rafts blocked FAK activation by the cytokines. Ex-vivo FRET imaging of mouse cartilage explants showed that intermediate level of interstitial fluid flow selectively decreased cytokine-induced SFK/FAK activation. These findings suggest that SFK and FAK exert distinctive molecular hierarchy depending on their subcellular location and extracellular stimuli.

The Horizon of Materiobiology: A Perspective on Material-Guided Cell Behaviors and Tissue Engineering

Although the biological functions of cell and tissue can be regulated by biochemical factors (e.g., growth factors, hormones), the biophysical effects of materials on the regulation of biological activity are receiving more attention. In this Review, we systematically summarize the recent progress on how biomaterials with controllable properties (e.g., compositional/degradable dynamics, mechanical properties, 2D topography, and 3D geometry) can regulate cell behaviors (e.g., cell adhesion, spreading, proliferation, cell alignment, and the differentiation or self-maintenance of stem cells) and tissue/organ functions. How the biophysical features of materials influence tissue/organ regeneration have been elucidated. Current challenges and a perspective on the development of novel materials that can modulate specific biological functions are discussed. The interdependent relationship between biomaterials and biology leads us to propose the concept of "materiobiology", which is a scientific discipline that studies the biological effects of the properties of biomaterials on biological functions at cell, tissue, organ, and the whole organism levels. This Review highlights that it is more important to develop ECM-mimicking biomaterials having a self-regenerative capacity to stimulate tissue regeneration, instead of attempting to recreate the complexity of living tissues or tissue constructs ex vivo. The principles of materiobiology may benefit the development of novel biomaterials providing combinative bioactive cues to activate the migration of stem cells from endogenous reservoirs (i.e., cell niches), stimulate robust and scalable self-healing mechanisms, and unlock the body's innate powers of regeneration.

Identification of epidermal growth factor receptor and its inhibitory microRNA141 as novel targets of Krüppel-like factor 8 in breast cancer

Krüppel-like factor 8 (KLF8) is a dual transcriptional factor critical for breast cancer progression. Epidermal growth factor receptor (EGFR) is frequently overexpressed in aggressive such as triple-negative breast cancer and associated with poor clinical outcomes. Here we report a novel KLF8-EGFR signaling axis in breast cancer. We identified a highly correlated co-overexpression between KLF8 and EGFR in invasive breast cancer cells and patient tumor samples. Overexpression of KLF8 in the non-tumorigenic MCF-10A cells induced the expression of EGFR, whereas knockdown of KLF8 from the MDA-MB-231 cells decreased it. Promoter activation and binding assays indicated that KLF8 promotes the EGFR expression by directly binding its gene promoter. We also revealed that KLF8 directly represses the promoter of miR141 and miR141 targets the 3′-untranslational region of EGFR transcript to inhibit EGFR translation. Treatment with the EGFR inhibitor AG1478 or overexpression of miR141 blocked the activity of ERK downstream of EGFR and inhibited KLF8-depndent cell invasiveness, proliferation and viability in cell culture and invasive growth and lung metastasis in nude mice. Conversely, overexpression of an inhibitory sponge of miR141 led to the opposite phenotypes. Taken together, these findings demonstrate a novel KLF8 to miR141/EGFR signaling pathway potentially crucial for breast cancer malignancy.

Structural Basis for the Interaction between Pyk2-FAT Domain and Leupaxin LD Repeats

Proline-rich tyrosine kinase 2 (Pyk2) is a nonreceptor tyrosine kinase and belongs to the focal adhesion kinase (FAK) family. Like FAK, the C-terminal focal adhesion-targeting (FAT) domain of Pyk2 binds to paxillin, a scaffold protein in focal adhesions; however, the interaction between the FAT domain of Pyk2 and paxillin is dynamic and unstable. Leupaxin is another member in the paxillin family and was suggested to be the native binding partner of Pyk2; Pyk2 gene expression is strongly correlated with that of leupaxin in many tissues including primary breast cancer. Here, we report that leupaxin interacts with Pyk2-FAT. Leupaxin has four leucine–aspartate (LD) motifs. The first and third LD motifs of leupaxin preferably target the two LD-binding sites on the Pyk2-FAT domain, respectively. Moreover, the full-length leupaxin binds to Pyk2-FAT as a stable one-to-one complex. Together, we propose that there is an underlying selectivity between leupaxin and paxillin for Pyk2, which may influence the differing behavior of the two proteins at focal adhesion sites.

Oxethazaine inhibits hepatitis B virus capsid assembly by blocking the cytosolic calcium-signalling pathway

Chronic hepatitis B virus (HBV) infection is a serious public health problem and may progress to liver fibrosis, cirrhosis and hepatocellular carcinoma. It is currently treated with PEGylated IFN-α2a and nucleoside/nucleotide analogues (NAs). However, PEGylated IFN treatment has problems of high cost, low efficiency and side effects. Long-term administration of NAs is necessary to avoid virus relapse, which can cause drug resistance and side effects. New efforts are now being directed to develop novel anti-HBV drugs targeting either additional viral targets other than viral DNA polymerase or host targets to improve the treatment of chronic hepatitis B. In this study, we discovered that oxethazaine, approved for clinic use in a few countries such as Japan, India, South Africa and Brazil, can dose-dependently reduce the levels of HBV envelope antigen, extracellular HBV DNA in supernatants and intracellular HBV total DNA. However, the levels of HBV cccDNA and HBV RNAs were not affected by oxethazaine treatment. Further study confirmed that oxethazaine acts on the virus assembly stage of the HBV life cycle. A study of the mechanisms of oxethazaine suggested that this drug inhibits HBV replication and capsid assembly by blocking the cytosolic calcium-signalling pathway. Moreover, oxethazaine could inhibit the replication of lamivudine/entecavir-dual-resistant and adefovir-resistant HBV mutants. In conclusion, our study suggests that oxethazaine may serve as a promising drug, or could be used as a starting point for anti-HBV drug discovery.

A Dual Role for the Nonreceptor Tyrosine Kinase Pyk2 during the Intracellular Trafficking of Human Papillomavirus 16

The infectious process of human papillomaviruses (HPVs) has been studied considerably, and many cellular components required for viral entry and trafficking continue to be revealed. In this study, we investigated the role of the nonreceptor tyrosine kinase Pyk2 during HPV16 pseudovirion infection of human keratinocytes. We found that Pyk2 is necessary for infection and appears to be involved in the intracellular trafficking of the virus. Small interfering RNA-mediated reduction of Pyk2 resulted in a significant decrease in infection but did not prevent viral entry at the plasma membrane. Pyk2 depletion resulted in altered endolysosomal trafficking of HPV16 and accelerated unfolding of the viral capsid. Furthermore, we observed retention of the HPV16 pseudogenome in the trans-Golgi network (TGN) in Pyk2-depleted cells, suggesting that the kinase could be required for the viral DNA to exit the TGN. While Pyk2 has previously been shown to function during the entry of enveloped viruses at the plasma membrane, the kinase has not yet been implicated in the intracellular trafficking of a nonenveloped virus such as HPV. Additionally, these data enrich the current literature on Pyk2's function in human keratinocytes.

IMPORTANCE

In this study, we investigated the role of the nonreceptor tyrosine kinase Pyk2 during human papillomavirus (HPV) infection of human skin cells. Infections with high-risk types of HPV such as HPV16 are the leading cause of cervical cancer and a major cause of genital and oropharyngeal cancer. As a nonenveloped virus, HPV enters cells by interacting with cellular receptors and established cellular trafficking routes to ensure that the viral DNA reaches the nucleus for productive infection. This study identified Pyk2 as a cellular component required for the intracellular trafficking of HPV16 during infection. Understanding the infectious pathways of HPVs is critical for developing additional preventive therapies. Furthermore, this study advances our knowledge of intracellular trafficking processes in keratinocytes.

Pyk2 promotes tumor progression in multiple myeloma

Proline-rich tyrosine kinase 2 (Pyk2) is a member of the focal adhesion kinase family that has been recently linked to tumor development. However, its role in modulating multiple myeloma (MM) biology and disease progression remains unexplored. We first demonstrated that patients with MM present with higher expression of Pyk2 compared with healthy individuals. By using loss-of-function approaches, we found that Pyk2 inhibition led to reduction of MM tumor growth in vivo as well as decreased cell proliferation, cell-cycle progression, and adhesion ability in vitro. In turn, overexpression of Pyk2 promoted the malignant phenotype, substantiated by enhanced tumor growth and reduced survival. Mechanistically, inhibition of Pyk2 reduced activation of Wnt/β-catenin signaling by destabilizing β-catenin, leading to downregulation of c-Myc and Cyclin D1. Furthermore, treatment of MM cells with the FAK/Pyk2 inhibitor VS-4718 effectively inhibited MM cell growth both in vitro and in vivo. Collectively, our findings describe the tumor-promoting role of Pyk2 in MM, thus providing molecular evidence for a novel tyrosine kinase inhibitor as a new therapeutic option in MM.

Quantitative phosphoproteomics reveals the protein tyrosine kinase Pyk2 as a central effector of olfactory receptor signaling in prostate cancer cells

The prostate-specific G-protein-coupled receptor 1 (PSGR1) is an olfactory receptor specifically expressed in the prostate gland. PSGR1 expression is elevated both in benign prostatic hyperplasia tissue and in prostate cancer. Stimulation of PSGR1 by the odorant β-ionone leads to an increase in the intracellular Ca(2+) concentration, activation of mitogen-activated protein (MAP) kinases and a decrease in prostate cancer cell proliferation. To further extend our knowledge about PSGR1 signaling in prostate cancer cells, we performed a quantitative phosphoproteomics study using stable isotope labeling by amino acids in cell culture and mass spectrometry. We report 51 differentially regulated phosphorylation sites in 24 proteins with functions in cytoskeletal remodeling, signaling and ion transport. Activation of PSGR1 evoked an increase in intracellular pH mediated by the sodium/hydrogen exchanger NHE1. Furthermore, we report the protein tyrosine kinase Pyk2 as a central effector of PSGR1 signaling cascades in LNCaP cells. Our data show that phosphorylation of p38 MAP kinase is triggered by Pyk2. In addition, we confirmed dephosphorylation of the tumor suppressor protein N-myc downstream regulated gene 1 (NDRG1) at Ser330 downstream of Pyk2. Since NDRG1 impacts oncogenic signaling pathways interfering with tumor progression, we suggest that the Pyk2-NDRG1 axis is possibly involved in conveying the anti-proliferative effect of β-ionone in prostate cancer cells. This article is part of a Special Issue entitled: Medical Proteomics.

Identification of epithelial stromal interaction 1 as a novel effector downstream of Krüppel-like factor 8 in breast cancer invasion and metastasis

Krüppel-like factor 8 (KLF8) is a transcriptional factor critical for metastatic progression of breast cancer. Epithelial stromal interaction 1 (EPSTI1), a recently identified stromal fibroblast-induced gene in non-invasive breast cancer cells is highly overexpressed in invasive breast carcinomas. The function and regulation of EPSTI1, however, remain largely unknown. In this paper, we report a novel KLF8 to EPSTI1 signaling pathway in breast cancer. Using various expression analyses, we revealed a high co-overexpression of KLF8 and EPSTI1 in invasive human breast cancer cells and patient tumors. Ectopic overexpression of KLF8 in the non-invasive, MCF-10A cells induced the EPSTI1 expression, whereas KLF8 knockdown from the invasive, MDA-MB-231 cells decreased the EPSTI1 expression. Promoter activation and binding analyses indicated that KLF8 promoted the EPSTI1 expression by directly acting on the EPSTI1 gene promoter. EPSTI1 knockdown dramatically reduced the KLF8-promoted MCF-10A cell invasion and ectopic expression of EPSTI1 in the non-invasive, MCF-7 cells is sufficient to induce the cell invasion. Experiments using nude mice demonstrated that the ectopic EPSTI1 granted the MCF-7 cells capability of both invasive growth in the breasts and metastasis to the lungs. Using co-immunoprecipitation coupled with mass spectrometry, we discovered that EPSTI1 interacts with the valosin containing protein (VCP), resulting in the degradation of IκBα and subsequent activation of NF-κB in the nucleus. These findings suggest a novel KLF8 to EPSTI1 to VCP to NF-κB signaling mechanism potentially critical for breast cancer invasion and metastasis.

Early responses of vascular endothelial cells to topographic cues

Vascular endothelial cells in vivo are exposed to multiple biophysical cues provided by the basement membrane, a specialized extracellular matrix through which vascular endothelial cells are attached to the underlying stroma. The importance of biophysical cues has been widely reported, but the signaling pathways that mediate cellular recognition and response to these cues remain poorly understood. Anisotropic topographically patterned substrates with nano- through microscale feature dimensions were fabricated to investigate cellular responses to topographic cues. The present study focuses on early events following exposure of human umbilical vein endothelial cells (HUVECs) to these patterned substrates. In serum-free medium and on substrates without protein coating, HUVECs oriented parallel to the long axis of underlying ridges in as little as 30 min. Immunocytochemistry showed clear differences in the localization of the focal adhesion proteins Src, p130Cas, and focal adhesion kinase (FAK) in HUVECs cultured on topographically patterned surfaces and on planar surfaces, suggesting involvement of these proteins in mediating the response to topographic features. Knockdown experiments demonstrated that FAK was not necessary for HUVEC alignment in response to topographic cues, although FAK knockdown did modulate HUVEC migration. These data identify key events early in the cellular response to biophysical stimuli.

Focal adhesion kinase knockdown modulates the response of human corneal epithelial cells to topographic cues

A rapidly expanding literature broadly documents the impact of biophysical cues on cellular behaviors. In spite of increasing research efforts in this field, the underlying signaling processes are poorly understood. One of the candidate molecules for being involved in mechanotransduction is focal adhesion kinase (FAK). To examine the role of FAK in the response of immortalized human corneal epithelial (hTCEpi) cells to topographic cues, FAK was depleted by siRNA transfection. Contrary to expectations, FAK knockdown resulted in an enhanced response with a greater number of hTCEpi cells aligned to the long axis of anisotropically ordered surface ridges and grooves. Both underlying topographic features and FAK depletion modulated the migration of corneal epithelial cells. The impact of FAK knockdown on both migration and alignment varied depending on the topographic cues to which the cells were exposed, with the most significant change observed on the biologically relevant size scale (400nm). Additionally, a change in expression of genes encoding perinuclear Nesprins 1 and 2 (SYNE1, 2) was observed in response to topographic cues. SYNE1/2 expression was also altered by FAK depletion, suggesting that these proteins might represent a link between cytosolic and nuclear signaling processes. The data presented here have relevance to our understanding of the fundamental processes involved in corneal cell behavior to topographic cues. These results highlight the importance of incorporating biophysical cues in the conduction of in vitro studies and into the design and fabrication of implantable prosthetics.

Effect of small interfering RNA transfection on FAK and DLC1 mRNA expression in OVCAR-3

RNA interference is an evolutionarily conserved cellular defense mechanism that protects cells from hostile genes and regulates the function of normal genes during growth and development. In this study, we established GFP-siFAK-DLC1 vector and transfect the vector into OVCAR-3 cells. RT-PCR and western blot analyses were performed for FAK, DLC1 mRNA, and protein expression in OVCAR-3 cells. ELISA method was used for caspase-3 and caspase-9 activities. These studies demonstrate that both recombinant pGFP-siFAK-DLC1 vector and pGFP-siCon-DLC1 vector may effectively promote DLC1 mRNA transcription and didn't affect siRNA effect. Recombinant vector (pGFP-siFAK-DLC1) may promote DLC1 gene expression, and effectively silence FAK gene expression. Silencing FAK mRNA expression and DLC1 mRNA expression may markedly enhance caspase-3 and caspase-9 activities in OVCAR-3 cells. These results showed that in ovarian cancer OVCAR-3 cell silencing FAK gene expression or / and increasing DLC-1 gene expression, could improve Caspase-3 and Caspase-9 protease activities. In the expression of DLC-1 and silence FAK expression group (double action group) effect was more significant as compared with the silence FAK gene group or expression of DLC-1 gene alone, difference was significant (p < 0.05).

Downregulation of FIP200 induces apoptosis of glioblastoma cells and microvascular endothelial cells by enhancing Pyk2 activity

The expression of focal adhesion kinase family interacting protein of 200-kDa (FIP200) in normal brain is limited to some neurons and glial cells. On immunohistochemical analysis of biopsies of glioblastoma tumors, we detected FIP200 in the tumor cells, tumor-associated endothelial cells, and occasional glial cells. Human glioblastoma tumor cell lines and immortalized human astrocytes cultured in complete media also expressed FIP200 as did primary human brain microvessel endothelial cells (MvEC), which proliferate in culture and resemble reactive endothelial cells. Downregulation of endogenous expression of FIP200 using small interfering RNA resulted in induction of apoptosis in the human glioblastoma tumor cells, immortalized human astrocytes, and primary human brain MvEC. It has been shown by other investigators using cells from other tissues that FIP200 can interact directly with, and inhibit, proline-rich tyrosine kinase 2 (Pyk2) and focal adhesion kinase (FAK). In the human glioblastoma tumor cells, immortalized human astrocytes, and primary human brain MvEC, we found that downregulation of FIP200 increased the activity of Pyk2 without increasing its expression, but did not affect the activity or expression of FAK. Coimmunoprecipitation and colocalization studies indicated that the endogenous FIP200 was largely associated with Pyk2, rather than FAK, in the glioblastoma tumor cells and brain MvEC. Moreover, the pro-apoptotic effect of FIP200 downregulation was inhibited significantly by a TAT-Pyk2-fusion protein containing the Pyk2 autophosphorylation site in these cells. In summary, downregulation of endogenous FIP200 protein in glioblastoma tumor cells, astrocytes, and brain MvECs promotes apoptosis, most likely due to the removal of a direct interaction of FIP200 with Pyk2 that inhibits Pyk2 activation, suggesting that FIP200 expression may be required for the survival of all three cell types found in glioblastoma tumors.

Compensatory function of Pyk2 protein in the promotion of focal adhesion kinase (FAK)-null mammary cancer stem cell tumorigenicity and metastatic activity

Mammary cancer stem cells (MaCSCs) have been identified as a rare population of cells capable of self-renewal to drive mammary tumorigenesis and metastasis. Nevertheless, relatively little is known about the intracellular signaling pathways regulating self-renewal and metastatic activities of MaCSCs in vivo. Using a recently developed breast cancer mouse model with focal adhesion kinase (FAK) deletion in mammary tumor cells (MFCKO-MT mice), here we present evidence suggesting a compensatory function of Pyk2, a FAK-related kinase, in the regulation of MaCSCs and metastasis in these mice. Increased expression of Pyk2 was found selectively in pulmonary metastatic nodules of MFCKO-MT mice, and its inhibition significantly reduced mammary tumor development and metastasis in these mice. Consistent with the idea of metastasis driven by MaCSCs, we detected selective up-regulation of Pyk2 in MaCSCs, but not bulk mammary tumor cells, of primary tumors developed in MFCKO-MT mice. We further showed that inhibition of Pyk2 in FAK-null MaCSCs significantly decreased their tumorsphere formation and migration in vitro as well as self-renewal, tumorigenicity, and metastatic activity in vivo. Last, we identified PI3K/Akt signaling as a major mediator of FAK regulation of MaCSCs as well as a target for the compensatory function of Pyk2 in FAK-null MaCSCs. Together, these results further advance our understanding of FAK and its related tyrosine kinase Pyk2 in regulation of MaCSCs in breast cancer and suggest that pharmaceutically targeting these kinases may hold promise as a novel treatment for the disease by targeting and eradicating MaCSCs.

The pathobiology of glioma tumors

The ongoing characterization of the genetic and epigenetic alterations in the gliomas has already improved the classification of these heterogeneous tumors and enabled the development of rodent models for analysis of the molecular pathways underlying their proliferative and invasive behavior. Effective application of the targeted therapies that are now in development will depend on pathologists' ability to provide accurate information regarding the genetic alterations and the expression of key receptors and ligands in the tumors. Here we review the mechanisms that have been implicated in the pathogenesis of the gliomas and provide examples of the cooperative nature of the pathways involved, which may influence the initial therapeutic response and the potential for development of resistance.

Fibronectin fragments mediate matrix metalloproteinase upregulation and cartilage damage through proline rich tyrosine kinase 2, c-src, NF-kappaB and protein kinase Cdelta

OBJECTIVE

Since fibronectin fragments (Fn-fs) enhance cartilage damage through integrins, the objective was to investigate the role of integrin linked kinases, focal adhesion kinase (FAK) and a soluble form of FAK, proline rich tyrosine kinase 2 (Pyk2) and cellular src kinase (c-src) and the transcription factor, nuclear factor kappaB (NF-kappaB) in cartilage damage.

METHODS

Bovine chondrocytes were cultured with various concentrations of three different Fn-fs, an amino-terminal 29 kDa, a gelatin binding 50 kDa and a central 140-kDa Fn-fs, each with progressively weaker cartilage damaging activity, or with native fibronectin (Fn), and lysates probed for activation of the selected kinases. Confocal microscopy was used to visualize intracellular location of activated kinases and NF-kappaB. Various kinase inhibitors were tested for their effects on Fn-f mediated upregulation of matrix metalloproteinase (MMP)-3 and -13 and cartilage proteoglycan (PG) depletion.

RESULTS

The Fn-fs kinetically enhanced phosphorylation of FAK but did not show a clear dose-response effect. The 29-kDa and 50-kDa Fn-fs enhanced phosphorylation of Pyk2, c-src and NF-kappaB to a much greater extent than the 140-kDa Fn-f and native Fn and did so as a function of dose. The 29-kDa Fn-f enhanced the phosphorylation of nuclear Pyk2 as compared with no treatment or native Fn. Inhibitors of Pyk2, c-src, NF-kappaB and protein kinase Cdelta (PKCdelta) decreased MMP upregulation and decreased Fn-f mediated damage to cartilage.

CONCLUSIONS

These studies enhance our knowledge of crucial factors in Fn-f mediated signaling in MMP upregulation and cartilage damage and because of the potential physiologic relevance of Fn-fs, provide a better knowledge of cartilage degeneration in general.

Differential effects of Pyk2 and FAK on the hypertrophic response of cardiac myocytes

The related cytoplasmic non-receptor tyrosine kinases Pyk2 (proline-rich tyrosine kinase 2) and FAK (focal adhesion kinase) have been implicated in phenylephrine-induced G-protein-coupled receptor-mediated signaling mechanisms leading to cardiomyocyte hypertrophy. We report that, in phenylephrine-stimulated neonatal rat ventricular myocytes (NRVM), Pyk2 augments expression of the hypertrophic marker atrial natriuretic factor (ANF) but reduces cytoskeletal organization and cell spreading. In contrast, FAK attenuates ANF production but does not alter cytoskeletal organization and cell spreading. Pyk2 and FAK exhibit differential localization in both unstimulated and phenylephrine-stimulated myocytes. Pyk2 catalytic activity is required for Pyk2 to augment ANF secretion but is not necessary to reduce cell spreading. Pyk2 autophosphorylation is required but not sufficient for Pyk2 to augment ANF secretion. Expression of the Pyk2 FERM domain as an autonomous fragment inhibits phenylephrine-mediated ANF secretion and reduces cell spreading. In addition, expression of the Pyk2 FERM domain inhibits the ability of Pyk2 to augment ANF secretion; this is correlated with reduced Pyk2 autophosphorylation. These data indicate that Pyk2 and FAK have different roles and occupy different positions in signaling pathways leading to the development of cardiomyocyte hypertrophy.

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

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

Focal adhesion kinase-related proline-rich tyrosine kinase 2 and focal adhesion kinase are co-overexpressed in early-stage and invasive ErbB-2-positive breast cancer and cooperate for breast cancer cell tumorigenesis and invasiveness

Early cancer cell migration and invasion of neighboring tissues are mediated by multiple events, including activation of focal adhesion signaling. Key regulators include the focal adhesion kinase (FAK) and FAK-related proline-rich tyrosine kinase 2 (Pyk2), whose distinct functions in cancer progression remain unclear. Here, we compared Pyk2 and FAK expression in breast cancer and their effects on ErbB-2-induced tumorigenesis and the potential therapeutic utility of targeting Pyk2 compared with FAK in preclinical models of breast cancer. Pyk2 is overexpressed in tissues from early and advanced breast cancers and overexpressed with both FAK and epidermal growth factor receptor-2 (ErbB-2) in a subset of breast cancer cases. Down-regulation of Pyk2 in ErbB-2-positive, FAK-proficient, and FAK-deficient cells reduced cell proliferation, which correlated with reduced mitogen-activated protein kinase (MAPK) activity. In contrast, Pyk2 silencing had little impact on cell migration and invasion. In vivo, Pyk2 down-regulation reduced primary tumor growth induced by a metastatic variant of ErbB-2-positive MDA 231 breast cancer cells but had little effect on lung metastases in contrast to FAK down-regulation. Dual reduction of Pyk2 and FAK expression resulted in strong inhibition of both primary tumor growth and lung metastases. Together, these data support the cooperative function of Pyk2 and FAK in breast cancer progression and suggest that dual inhibition of FAK and Pyk2 is an efficient therapeutic approach for targeting invasive breast cancer.

New molecular targets in angiogenic vessels of glioblastoma tumours

Antiangiogenesis approaches have the potential to be particularly effective in the treatment of glioblastoma tumours. These tumours exhibit extremely high levels of neovascularisation, which may contribute to their extremely aggressive behaviour, not only by providing oxygenation and nutrition, but also by establishing a leaky vasculature that lacks a blood-brain barrier. This leaky vasculature enables migration of tumour cells, as well as the build up of fluid, which exacerbates tissue damage due to increased intracranial pressure. Here, we discuss the considerable progress that has been made in the identification of the pro- and antiangiogenic factors produced by glioblastoma tumours and the effects of these molecules in animal models of the disease. The safety and efficacy of some of these approaches have now been demonstrated in clinical trials. However, the ability of tumours to overcome these therapies and to re-establish angiogenesis requires further clinical research regarding potential multimodality therapies, as well as basic research into the regulation of angiogenesis by as yet unidentified factors. Optimisation of noninvasive procedures for monitoring of angiogenesis would greatly facilitate such research.

Extended survival of Pyk2 or FAK deficient orthotopic glioma xenografts

Disease progression of glioblastoma involves a complex interplay between tumor cells and the peri-tumor microenvironment. The propensity of malignant glioma cells to disperse throughout the brain typifies the disease and portends a poor response to surgical resection, radiotherapy, and current chemotherapeutics. The focal adhesion kinases FAK and Pyk2 function as important signaling effectors in glioma through stimulation of pro-migratory and proliferative signaling pathways. In the current study, we examined the importance of Pyk2 and FAK in the pathobiology of malignant glioma in an intracranial xenograft model. We show that mice with xenografts established with glioma cells with specific knockdown of Pyk2 or FAK expression by RNA interference had significantly increased survival compared to control mice. Furthermore, the effect of inhibition of Pyk2 activity in xenografts was compared to the effect of knockdown of Pyk2 expression. Inhibition of Pyk2 activity by stable expression an autonomous FERM domain in glioma cells slowed disease progression in the intracranial xenograft model. In contrast, expression of a variant FERM domain that does not inhibit Pyk2 activity did not alter survival. These results substantiate the disease relevance of both Pyk2 and FAK in glioma and suggest a novel approach to target Pyk2 for therapeutic benefit.

Activation of KLF8 transcription by focal adhesion kinase in human ovarian epithelial and cancer cells

KLF8 (Krüppel-like factor 8) is a transcription factor downstream of focal adhesion kinase (FAK) important in the regulation of the cell cycle and also plays a critical role in oncogenic transformation and epithelial to mesenchymal transition. Here we report the mechanisms by which FAK regulates KLF8 expression in human ovarian epithelial and cancer cells. We show that the overexpression of both KLF8 and FAK in the human ovarian cancer cells as compared with the normal human ovarian surface epithelial cells is critical for cell growth. Using promoter luciferase reporter assays, we demonstrate that exogenous FAK strongly promotes the activity of the KLF8 promoter, and knockdown of FAK inhibits it. KLF8 promoter activity and mRNA levels are induced by expression of constitutively active (CA) phosphatidylinositol 3-kinase (PI3K) or CA-Akt but are repressed by dominant negative Akt or the PI3K inhibitor LY294002. Disruption of an Sp1 binding site in the KLF8 promoter abolishes the FAK- or Sp1-mediated promoter activation. Sp1 knockdown prevents the KLF8 promoter from being activated by Sp1 or CA-Akt, and expression of CA-Akt enhances Sp1 expression in SKOV3ip1 cells. Chromatin immunoprecipitation and oligonucleotide precipitation results show that Sp1 binds to the KLF8 promoter. Taken together, our data suggest that FAK induces KLF8 expression in human ovarian cancer cells by activating the PI3K-Akt signaling pathway, leading to the activation of KLF8 promoter by Sp1.

Cytobiological consequences of calcium-signaling alterations induced by human viral proteins

Since calcium-signaling regulates specific and fundamental cellular processes, it represents the ideal target of viral proteins, in order for the virus to control cellular functions and favour its persistence, multiplication and spread. A detailed analysis of reports focused on the impact of viral proteins on calcium-signaling has shown that virus-related elevations of cytosolic calcium levels allow increased viral protein expression (HIV-1, HSV-1/2), viral replication (HBx, enterovirus 2B, HTLV-1 p12(I), HHV-8, EBV), viral maturation (rotavirus), viral release (enterovirus 2B) and cell immortalization (EBV). Interestingly, virus-induced decreased cytosolic calcium levels have been found to be associated with inhibition of immune cells functions (HIV-1 Tat, HHV-8 K15, EBV LMP2A). Finally, several viral proteins are able to modulate intracellular calcium-signaling to control cell viability (HIV-1 Tat, HTLV-1 p13(II), HCV core, HBx, enterovirus 2B, HHV-8 K7). These data point out calcium-signaling as a key cellular target for viral infection and should stimulate further studies exploring new calcium-related therapeutic strategies.

Critical role of the FERM domain in Pyk2 stimulated glioma cell migration

The strong tendency of malignant glioma cells to invade locally into surrounding normal brain precludes effective surgical resection, reduces the efficacy of radiotherapy, and is associated with increased resistance to chemotherapy regimens. We report that the N-terminal FERM domain of Pyk2 regulates its promigratory function. A 3-dimensional model of the Pyk2 FERM domain was generated and mutagenesis studies identified residues essential for Pyk2 promigratory function. Model-based targeted mutations within the FERM domain decreased Pyk2 phosphorylation and reduced the capacity of Pyk2 to stimulate glioma cell migration but did not significantly alter the intracellular distribution of Pyk2. Expression of autonomous Pyk2 FERM domain fragments containing analogous mutations exhibited reduced capacity to inhibit glioma cell migration and Pyk2 phosphorylation relative to expression of an autonomous wild type FERM domain fragment. These results indicate that the FERM domain plays an important role in regulating the functional competency of Pyk2 as a promigratory factor in glioma.

KLF8 transcription factor participates in oncogenic transformation

Kruppel-like factor 8 (KLF8) is a member of the family of KLF transcription factors. Several KLF members have been shown to play a role in oncogenesis. We have previously demonstrated that KLF8 mediates cell cycle progression downstream of focal adhesion kinase (FAK) by upregulating cyclin D1. FAK plays a critical role in transformation and tumorigenesis and is aberrantly upregulated in many types of human cancer. Little is known about the function of KLF8 in these regards. Here we provide evidence suggesting a novel role of KLF8 in oncogenic transformation. We show that KLF8 expression is elevated in several types of human cancer cells and primary tumor tissues. Induced expression of ectopic KLF8 causes serum-independent growth and morphological transformation in NIH3T3 cells and enhances anchorage-independent growth of v-Src-transformed cells. In contrast, expression of a dominant-negative mutant of KLF8 dramatically suppresses the transformed phenotypes induced by v-Src. In addition, the KLF8-enhanced transformation in the v-Src cells was prevented by ablating cyclin D1 expression. Overall, these results indicate that KLF8 is required for v-Src-induced transformation and may play a role in tumor progression of human cancer.

Divergent regulation of Pyk2/CAKbeta phosphorylation by Ca2+ and cAMP in the hippocampus

Proline-rich tyrosine kinase 2 (Pyk2) is activated in neurones following NMDA receptor stimulation via PKC. Pyk2 is involved in hippocampal LTP and acts to potentiate NMDA receptor function. Elevations of intracellular Ca2+ and cAMP levels are key NMDA receptor-dependent triggering events leading to induction of hippocampal LTP. In this study, we compared the ability of A23187 (Ca2+ ionophore) or forskolin (adenylate cyclase activator) to modulate the phosphorylation of Pyk2 in rat hippocampal slices. Using an immunoprecipitation assay, phosphorylated Pyk2 levels were increased following treatment with A23187, levels peaking at around 10 min. Staurosporine, at concentrations inhibiting conventional and novel isoforms of PKC, and chelerythrine, at concentrations inhibiting the atypical PKC isoform PKMxi, were compared for their ability to attenuate the effect of A23187. Exposure of acute hippocampal slices to either chelerythrine or staurosporine completely blocked enhanced phosphorylation of Pyk2 by A23187, suggesting a possible involvement of PKMxi and typical PKCs in Pyk2 activation by Ca2+. In contrast, application of forskolin reduced phosphorylated Pyk2 below basal levels, suggesting that cAMP inhibits Pyk2. These results implicate Ca2+ and multiple forms of PKC in the activation of Pyk2 downstream of NMDA receptors and suggest that cAMP-dependent processes exert a suppressive action on Pyk2.

Adhesion and proliferation of fibroblasts on RF plasma-deposited nanostructured fluorocarbon coatings: Evidence of FAK activation

We used combined plasma-deposition process to deposit smooth and nanostructured fluorocarbon coatings on polyethylenethereftalate (PET) substrates, to obtain surfaces with identical chemical composition and different roughness, and investigate the effect of surface nanostructures on adhesion and proliferation of 3T3 Swiss Albino Mouse fibroblasts. Untreated PET and polystyrene (PS) were used as controls for cell culture. We have found that the statistically significant increase of cell proliferation rate and FAK (a nonreceptor tyrosine kinase) activation detected on ROUGH fluorocarbon surfaces is due to the presence of nanostructures. Changes in cytoskeletal organization and phospho FAK (tyr 397) localization were evident after 60 min on cells adhering to ROUGH surfaces. This change was characterized by the formation of actin stress fibers along lamellar membrane protrusion instead of usual focal contacts. Also the morphology of the adhering fibroblasts (60 min) adhering on ROUGH surfaces was found quite different compared to cells adhering on smooth ones.

High resolution genomic analysis of sporadic breast cancer using array-based comparative genomic hybridization

Introduction

Genomic aberrations in the form of subchromosomal DNA copy number changes are a hallmark of epithelial cancers, including breast cancer. The goal of the present study was to analyze such aberrations in breast cancer at high resolution.

Methods

We employed high-resolution array comparative genomic hybridization with 4,134 bacterial artificial chromosomes that cover the genome at 0.9 megabase resolution to analyze 47 primary breast tumors and 18 breast cancer cell lines.

Results

Common amplicons included 8q24.3 (amplified in 79% of tumors, with 5/47 exhibiting high level amplification), 1q32.1 and 16p13.3 (amplified in 66% and 57% of tumors, respectively). Moreover, we found several positive correlations between specific amplicons from different chromosomes, suggesting the existence of cooperating genetic loci. Queried by gene, the most frequently amplified kinase was PTK2 (79% of tumors), whereas the most frequently lost kinase was PTK2B (hemizygous loss in 34% of tumors). Amplification of ERBB2 as measured by comparative genomic hybridization (CGH) correlated closely with ERBB2 DNA and RNA levels measured by quantitative PCR as well as with ERBB2 protein levels. The overall frequency of recurrent losses was lower, with no region lost in more than 50% of tumors; the most frequently lost tumor suppressor gene was RB1 (hemizygous loss in 26% of tumors). Finally, we find that specific copy number changes in cell lines closely mimicked those in primary tumors, with an overall Pearson correlation coefficient of 0.843 for gains and 0.734 for losses.

Conclusion

High resolution CGH analysis of breast cancer reveals several regions where DNA copy number is commonly gained or lost, that non-random correlations between specific amplicons exist, and that specific genetic alterations are maintained in breast cancer cell lines despite repeat passage in tissue culture. These observations suggest that genes within these regions are critical to the malignant phenotype and may thus serve as future therapeutic targets.

Two N-myristoyltransferase isozymes play unique roles in protein myristoylation, proliferation, and apoptosis

N-myristoyltransferases (NMT) add myristate to the NH(2) termini of certain proteins, thereby regulating their localization and/or biological function. Using RNA interference, this study functionally characterizes the two NMT isozymes in human cells. Unique small interfering RNAs (siRNA) for each isozyme were designed and shown to decrease NMT1 or NMT2 protein levels by at least 90%. Ablation of NMT1 inhibited cell replication associated with a loss of activation of c-Src and its target FAK as well as reduction of signaling through the c-Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase pathway. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assays showed that depletion of either NMT isozyme induced apoptosis, with NMT2 having a 2.5-fold greater effect than NMT1. Western blot analyses revealed that loss of NMT2 shifted the expression of the BCL family of proteins toward apoptosis. Finally, intratumoral injection of siRNA for NMT1 or for both NMT1 and NMT2 inhibited tumor growth in vivo, whereas the same treatment with siRNA for NMT2 or negative control siRNA did not. Overall, the data indicate that NMT1 and NMT2 have only partially overlapping functions and that NMT1 is critical for tumor cell proliferation.

The tyrosine kinase pyk2 promotes migration and invasion of glioma cells

Glioblastoma multiforme is extraordinarily aggressive due to the propensity of cells to migrate away from the tumor core into the surrounding normal brain. In this report, we investigated the role of proline-rich tyrosine kinase 2 (Pyk2) and FAK with regard to influencing glioma cell phenotypes. Expression of Pyk2 stimulated glioma cell migration, whereas expression of FAK inhibited glioma cell migration and stimulated cell cycle progression. Pyk2 autophosphorylation was necessary, but not sufficient, to stimulate cellular migration. The N-terminal domain of Pyk2 is required for stimulation of migration as an N-terminally deleted variant of Pyk2 failed to stimulate migration, whereas expression of an autonomous Pyk2 N-terminal domain inhibited cell migration. Substitution of the C-terminal domain of Pyk2 with the corresponding domain of FAK stimulated cell migration as effectively as wild-type Pyk2; however, substitution of the N-terminal domain of Pyk2 with that of FAK inhibited cell migration, substantiating that the N-terminal domain of Pyk2 was required to stimulate migration. Silencing of Pyk2 expression by RNA interference significantly inhibited glioma migration. Cell migration was restored on re-expression of Pyk2, but expression of FAK in Pyk2 knockdown cells failed to restore migration. We conclude that Pyk2 plays a central role in the migratory behavior of glioblastomas.

Rapid tyrosine phosphorylation of focal adhesion kinase, paxillin, and p130Cas by gastrin in human colon cancer cells

Although the expression of CCK(2) receptors is widely reported in human colorectal cancers, little is known on its role in mediating the proliferative effects of mature amidated gastrin (G17 amide) on colorectal cancers. The purpose of the present study was to determine the effects of G17 amide on tyrosine phosphorylation of focal adhesion kinase (FAK), paxillin, and p130 Crk-associated substrate (p130(Cas)) in Colo 320 cells, a human colorectal cancer cell line which expresses CCK(2) receptors. By immunoprecipitation and immunoblotting, an increase in tyrosine phosphorylation of FAK (tyrosine-397), paxillin (tyrosine-31), and p130(Cas) was detected in a time- and dose-dependent manner. Overexpression of CCK(2) receptors in Colo 320 cells (Colo 320 WT) by stable transfection with the human CCK(2) receptor cDNA resulted in an increased tyrosine phosphorylation of FAK, paxillin, and p130(Cas). After incubation with 1 microM L-365,260, a specific CCK(2) receptor antagonist, this increase was completely inhibited. Our results demonstrate that in human colon cancer cells, gastrin caused a rapid tyrosine phosphorylation of FAK, paxillin, and p130(Cas) by activation of CCK(2) receptor. The phosphorylation of these proteins might be important in mediating gastrin effects on proliferation, apoptosis, and metastasis.

Focal adhesion kinase is required for endothelin-induced cell cycle progression of cultured astrocytes

When the brain is damaged, astrocytes often cause hyperplasia resulting in glial scar formation at the injured sites. Endothelins (ETs) have been shown to be involved in the pathophysiologic responses of astrocytes, including proliferation. In this study, we examined the mechanisms underlying the ET-induced astrocytic G1/S-phase cell cycle transition by focusing on focal adhesion kinase (FAK). A transient transfection with wild-type FAK was followed by an increase in bromodeoxyuridine (BrdU) incorporation into cultured rat astrocytes. The increases in BrdU incorporation induced by 100 nM ET-1 were not found in astrocytes transfected with dominant-negative FAK mutants (FRNK and dC14-FAK). The increases in BrdU incorporation induced by 10 nM phorbol 12-myristate 13-acetate (PMA) were not affected by the FAK mutants. Wild-type FAK did not induce stress fiber formation in cultured astrocytes. The dominant negative FAK mutant dC14-FAK did not prevent ET-induced astrocytic stress fiber formation. These results suggest that FAK mediated the astrocytic G1/S cell cycle transition induced by ET-1 downstream of the cytoskeletal actin reorganization.

Focal adhesion kinase is activated and mediates the early hypertrophic response to stretch in cardiac myocytes

Previously we reported that the rapid activation of the Fak/Src multicomponent signaling complex mediates load-induced activation of growth and survival signaling pathways in adult rat heart. In this study, we report that 5% to 20% (10-minute) cyclic stretch (1 Hz) of neonatal rat ventricular myocytes (NRVMs) was paralleled by increases of Fak phosphorylation at Tyr-397 (from 1.5- to 2.8-fold), as detected by anti-Fak-pY397 phosphospecific antibody. Moreover, 15% cyclic stretch lasting from 10 to 120 minutes increased Fak phosphorylation at Tyr-397 by 2.5- to 3.5-fold. This activation was accompanied by a dramatic change in Fak localization in NRVMs from densely concentrated in the perinuclear regions in nonstretched cells to aggregates regularly distributed along the myofilaments in stretched cells. Furthermore, a 4-hour cyclic stretch enhanced the activity of an atrial natriuretic factor (ANF) promoter-luciferase reporter gene by 2.7-fold. Disrupting endogenous Fak/Src signaling either by expression of a dominant-negative Fak mutant with phenylalanine substituted for Tyr-397 or by treatment with a c-Src pharmacological inhibitor (PP-2) markedly attenuated stretch-induced Fak activation and clustering at myofilaments and inhibited stretch-induced ANF gene activation. On the other hand, overexpression of wild-type Fak potentiated the stretch-induced Fak phosphorylation but did not enhance either baseline or stretch-induced ANF promoter-luciferase reporter gene activity compared with the responses of nontransfected NRVMs. These findings identify Fak as an important element in the early responses induced by stretch in cardiac myocytes, indicating that it may coordinate the cellular signaling machinery that controls gene expression program associated with load-induced cardiac myocyte hypertrophy.

Rigidity of collagen fibrils controls collagen gel-induced down-regulation of focal adhesion complex proteins mediated by alpha2beta1 integrin

Previous studies have shown that collagen gel overlay induced selective proteolysis of focal adhesion complex proteins in Madin-Darby canine kidney (MDCK) cells. In this study, we examined whether morphological and biochemical changes were present in cells cultured on collagen gel. We found that focal adhesion complex proteins, including focal adhesion kinase (FAK), talin, paxillin, and p130cas, but not vinculin, were decreased within 1 h when MDCK cells were cultured on collagen gel. Collagen gel-induced selective decrease of focal adhesion proteins was observed in all lines of cells examined, including epithelial, fibroblastic, and cancer cells. Matrigel also induced selective down-regulation of focal adhesion proteins. However, cells cultured on collagen gel- or matrigel-coated dishes did not show any changes of focal adhesion proteins. These data suggest that the physical nature of the gel, i.e. the rigidity, is involved in the expression of focal adhesion proteins. The collagen gel-induced down-regulation of focal adhesion complex proteins was caused by reduction of protein synthesis and activation of proteases such as calpain. Overexpression of a dominant negative mutant of discoidin domain receptor 1 (DDR1) or FAK-related non-kinase (FRNK) did not prevent collagen gel-induced down-regulation of the focal adhesion complex protein, whereas an anti-alpha2beta1 integrin-neutralizing antibody completely blocked it. Taken together, our results indicate that the rigidity of collagen gel controls the expression of focal adhesion complex proteins, which is mediated by alpha2beta1 integrin but not DDR1.

[Focal adhesion kinase (FAK), a multifunctional protein]

Focal adhesion kinase (FAK) is a cytoplasmic protein tyrosine kinase localized to regions called focal adhesions. Many stimuli can induce tyrosine phosphorylation and activation of FAK, including integrins and growth factors. The major site of autophosphorylation, tyrosine 397, is a docking site for the SH2 domains of Src family proteins. The other sites of phosphorylation are phosphorylated by Src kinases. Phosphorylated FAK binds proteins of focal adhesion and can activate them directly or indirectly by phosphorylation. These activated proteins forming the FAK complex facilitate the generation of downstream signals necessary to regulate cell functions, like motility, survival and proliferation. Dysregulation of FAK could participate in the development of cancer. This review will focus upon the mechanisms by which FAK transmits biochemical signals and elicits biological effects.

Identification of transcription factor KLF8 as a downstream target of focal adhesion kinase in its regulation of cyclin D1 and cell cycle progression

Focal adhesion kinase (FAK) is an important mediator of integrin signaling in the regulation of cell adhesion, migration, survival, and proliferation. Here we report the identification of the transcription factor KLF8 as a target of FAK in cell cycle regulation. KLF8 is induced by FAK and decreased by FAK dominant-negative mutant DeltaC14. Overexpression of KLF8 increases cell cycle progression, whereas inhibition of endogenous KLF8 by siRNA reduces it. Cyclin D1 promoter is identified as a target of KLF8, which is activated both directly by KLF8 binding to the GT box A and by an indirect mechanism through its repression of a potential inhibitory regulator of cyclin D1. Transcription activation of cyclin D1 by FAK requires both Ets family and KLF8 factors in a temporally differential manner. Together, our data provide further insights into molecular mechanism for FAK to regulate cell cycle progression.

Phosphospecific site tyrosine phosphorylation of p125FAK and proline-rich kinase 2 is differentially regulated by cholecystokinin receptor type A activation in pancreatic acini

The focal adhesion kinases, p125FAK and proline-rich kinase 2 (PYK2), are involved in numerous processes as adhesion, cytoskeletal changes, and growth. These kinases have 45% homology and share three tyrosine phosphorylation (TyrP) sites. Little information exists on the ability of stimulants to cause TyrP of each kinase site and the cellular mechanism involved. We explored the ability of the neurotransmitter/hormone, CCK, to stimulate TyrP at each site. In rat pancreatic acini, CCK stimulated TyrP at each site in both kinases. TyrP was rapid except for pY397FAK. The magnitude of TyrP differed with the different FAK and PYK2 sites. The CCK dose-response curve for TyrP for sites in each kinase was similar. CCK-JMV, an agonist of the high affinity receptor state and antagonist of the low affinity receptor state, was less efficacious than CCK at each FAK/PYK2 site and inhibited CCK maximal stimulation. Thapsigargin decreased CCK-stimulated TyrP of pY402PYK2 and pY925FAK but not the other sites. GF109203X reduced TyrP of only the PYK2 sites, pY402 and pY580. GF109203X with thapsigargin decreased TyrP of pY402PYK2 and the three FAK sites more than either inhibitor alone. Basal TyrP of pY397FAK was greater than other sites. These results demonstrate that CCK stimulates tyrosine phosphorylation of each of the three homologous phosphorylation sites in FAK and PYK2. However, CCK-stimulated TyrP at these sites differs in kinetics, magnitude, and participation of the high/low affinity receptor states and by protein kinase C and [Ca2+]i. These results show that phosphorylation of these different sites is differentially regulated and involves different intracellular mechanisms in the same cell.

FAK signaling in anaplastic astrocytoma and glioblastoma tumors

Focal adhesion kinase (FAK) is a non-receptor cytoplasmic-tyrosine kinase that is activated by several different cell surface receptors shown to be upregulated on glioblastoma cells (integrins alpha(v)beta3 and alpha(v)beta5, and the epidermal growth factor receptor). Activated FAK can signal through several different signaling pathways, which are reviewed here. Published data are summarized that have demonstrated 1) elevated FAK expression in anaplastic astrocytoma and glioblastoma tumor biopsy samples, 2) a role for FAK in the promotion of glioblastoma cell proliferation, survival and migration in vitro, and 3) a role for FAK in the promotion of glioblastoma cell proliferation in vivo in an animal model. The available data suggests that increased levels of FAK protein and activity may contribute to an increased ERK activity and cell proliferation in vivo in these tumors.

The N termini of focal adhesion kinase family members regulate substrate phosphorylation, localization, and cell morphology

The focal adhesion kinase (FAK) and cell adhesion kinase beta (CAKbeta, PYK2, CADTK, RAFTK) are highly homologous FAK family members, yet clearly have unique roles in the cell. Comparative analyses of FAK and CAKbeta have revealed intriguing differences in their activities. These differences were investigated further through the characterization of a set of FAK/CAKbeta chimeric kinases. CAKbeta exhibited greater catalytic activity than FAK in vitro, providing a molecular basis for differential substrate phosphorylation by FAK and CAKbeta in vivo. Furthermore, the N terminus may regulate catalytic activity since chimeras containing the FAK N terminus and CAKbeta catalytic domain exhibited a striking high level of catalytic activity and substrate phosphorylation. Unexpectedly, a modulatory role for the N termini in subcellular localization was also revealed. Chimeras containing the FAK N terminus and CAKbeta C terminus localized to focal adhesions, whereas chimeras containing the N and C termini of CAKbeta did not. Finally, prominent changes in cell morphology were induced upon expression of chimeras containing the CAKbeta N terminus, which were not associated with apoptotic cell death, cell cycle progression delay, or changes in Rho activity. These results demonstrate novel regulatory roles for the N terminus of FAK family kinases.