Multiple connections link FAK to cell motility and invasion

Endotoxin-induced vascular endothelial cell migration is dependent on TLR4/NF-κB pathway, NAD(P)H oxidase activation, and transient receptor potential melastatin 7 calcium channel activity

Endothelial dysfunction is decisive and leads to the development of several inflammatory diseases. Endotoxemia-derived sepsis syndrome exhibits a broad inflammation-induced endothelial dysfunction. We reported previously that the endotoxin, lipopolysaccharide (LPS), induces the conversion of endothelial cells (ECs) into activated fibroblasts, showing a myofibroblast-like protein expression profile. Enhanced migration is a hallmark of myofibroblast function. However, the mechanism involved in LPS-induced EC migration is no totally understood. Some studies have shown that the transient receptor potential melastatin 7 (TRPM7) ion channel is involved in fibroblast and tumor cell migration through the regulation of calcium influx. Furthermore, LPS modulates TRPM7 expression. However, whether TRPM7 is involved in LPS-induced EC migration remains unknown. Here, we study the participation of LPS as an inducer of EC migration and study the mechanism underlying evaluating the participation of the TRPM7 ion channel. Our results demonstrate that LPS induced EC migration in a dose-dependent manner. Furthermore, this migratory process was mediated by the TLR-4/NF-κB pathway and the generation of ROS through the PKC-activated NAD(P)H oxidase. In addition, LPS increased the intracellular calcium level and the number of focal adhesion kinase (FAK)-positive focal adhesions in EC. Finally, we demonstrate that using TRPM7 blockers or suppressing TRPM7 expression through siRNA successfully inhibits the calcium influx and the LPS-induced EC migration. These results point out TRPM7 as a new target in the drug design for several inflammatory diseases that impair vascular endothelium function.

FAK and paxillin dynamics at focal adhesions in the protrusions of migrating cells

Cell migration requires the fine spatiotemporal integration of many proteins that regulate the fundamental processes that drive cell movement. Focal adhesion (FA) dynamics is a continuous process involving coordination between FA and actin cytoskeleton, which is essential for cell migration. We studied the spatiotemporal relationship between the dynamics of focal adhesion kinase (FAK) and paxillin at FAs in the protrusion of living endothelial cells. Concurrent dual-color imaging showed that FAK was assembled at FA first, which was followed by paxillin recruitment to the FA. By tracking and quantifying FAK and paxillin in migrating cells, the normalized FAK/Paxillin fluorescence intensity (FI) ratio is > 1 (≈ 4 fold) at cell front, ≈ 1 at cell center, and < 1 at cell rear. The significantly higher FAK FI than paxillin FI at cell front indicates that the assembly of FAK-FAs occurs ahead of paxillin at cell front. To determine the time difference between the assemblies of FAK and paxillin at nascent FAs, FAs containing both FAK and paxillin were quantified by image analysis and time correlation. The results show that FAK assembles at the nascent FAs earlier than paxillin in the protrusions at cell front.

LOXL2 status correlates with tumor stage and regulates integrin levels to promote tumor progression in ccRCC

Clear cell renal cell carcinoma (ccRCC) is the most common histologically defined subtype of renal cell carcinoma (RCC). To define the molecular mechanism in the progression of ccRCC, we focused on LOX-like protein 2 (LOXL2), which is critical for the first step in collagen and elastin cross-linking. Using exon array analysis and quantitative validation, LOXL2 was shown to be significantly upregulated in clinical specimens of human ccRCC tumor tissues, compared with adjacent noncancerous renal tissues, and this elevated expression correlated with the pathologic stages of ccRCC. RNAi-mediated knockdown of LOXL2 resulted in marked suppression of stress-fiber and focal adhesion formation in ccRCC cells. Moreover, LOXL2 siRNA knockdown significantly inhibited cell growth, migration, and invasion. Mechanistically, LOXL2 regulated the degradation of both integrins α5 (ITGAV5) and β1 (ITGB1) via protease- and proteasome-dependent systems. In clinical ccRCC specimens, the expression levels of LOXL2 and integrin α5 correlated with the pathologic tumor grades. In conclusion, LOXL2 is a potent regulator of integrin α5 and integrin β1 protein levels and functions in a tumor-promoting capacity in ccRCC.

IMPLICATIONS

This is the first report demonstrating that LOXL2 is highly expressed and involved in ccRCC progression by regulating the levels of integrins α5 and β1.

Using real-time impedance-based assays to monitor the effects of fibroblast-derived media on the adhesion, proliferation, migration and invasion of colon cancer cells

Increasing our knowledge of the mechanisms regulating cell proliferation, migration and invasion are central to understanding tumour progression and metastasis. The local tumour microenvironment contributes to the transformed phenotype in cancer by providing specific environmental cues that alter the cells behaviour and promotes metastasis. Fibroblasts have a strong association with cancer and in recent times there has been some emphasis in designing novel therapeutic strategies that alter fibroblast behaviour in the tumour microenvironment. Fibroblasts produce growth factors, chemokines and many of the proteins laid down in the ECM (extracellular matrix) that promote angiogenesis, inflammation and tumour progression. In this study, we use a label-free RTCA (real-time cell analysis) platform (xCELLigence) to investigate how media derived from human fibroblasts alters cancer cell behaviour. We used a series of complimentary and novel experimental approaches to show HCT116 cells adhere, proliferate and migrate significantly faster in the presence of media from human fibroblasts. As well as this, we used the xCELLigence CIM-plates system to show that HCT116 cells invade matrigel layers aggressively when migrating towards media derived from human fibroblasts. These data strongly suggest that fibroblasts have the ability to increase the migratory and invasive properties of HCT116 cells. This is the first study that provides real-time data on fibroblast-mediated migration and invasion kinetics of colon cancer cells.

Carnosic acid inhibits the epithelial-mesenchymal transition in B16F10 melanoma cells: a possible mechanism for the inhibition of cell migration

Carnosic acid is a natural benzenediol abietane diterpene found in rosemary and exhibits anti-inflammatory, antioxidant, and anti-carcinogenic activities. In this study, we evaluated the effects of carnosic acid on the metastatic characteristics of B16F10 melanoma cells. When B16F10 cells were cultured in an in vitro Transwell system, carnosic acid inhibited cell migration in a dose-dependent manner. Carnosic acid suppressed the adhesion of B16F10 cells, as well as the secretion of matrix metalloproteinase (MMP)-9, tissue inhibitor of metalloproteinase (TIMP)-1, urokinase plasminogen activator (uPA), and vascular cell adhesion molecule (VCAM)-1. Interestingly, secretion of TIMP-2 increased significantly in B16F10 cells treated with 10 μmol/L carnosic acid. Additionally, carnosic acid suppressed the mesenchymal markers snail, slug, vimentin, and N-cadherin and induced epithelial marker E-cadherin. Furthermore, carnosic acid suppressed phosphorylation of Src, FAK, and AKT. These results indicate that inhibition of the epithelial-mesenchymal transition may be important for the carnosic acid-induced inhibition of B16F10 cell migration.

Movers and shakers: cell cytoskeleton in cancer metastasis

Metastasis is responsible for the greatest number of cancer deaths. Metastatic disease, or the movement of cancer cells from one site to another, is a complex process requiring dramatic remodelling of the cell cytoskeleton. The various components of the cytoskeleton, actin (microfilaments), microtubules (MTs) and intermediate filaments, are highly integrated and their functions are well orchestrated in normal cells. In contrast, mutations and abnormal expression of cytoskeletal and cytoskeletal-associated proteins play an important role in the ability of cancer cells to resist chemotherapy and metastasize. Studies on the role of actin and its interacting partners have highlighted key signalling pathways, such as the Rho GTPases, and downstream effector proteins that, through the cytoskeleton, mediate tumour cell migration, invasion and metastasis. An emerging role for MTs in tumour cell metastasis is being unravelled and there is increasing interest in the crosstalk between key MT interacting proteins and the actin cytoskeleton, which may provide novel treatment avenues for metastatic disease. Improved understanding of how the cytoskeleton and its interacting partners influence tumour cell migration and metastasis has led to the development of novel therapeutics against aggressive and metastatic disease.

LINKED ARTICLES

This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.

SOX2 enhances the migration and invasion of ovarian cancer cells via Src kinase

Ovarian cancer is the leading cause of death among gynecologic cancers and is the fifth leading cause of all cancer-related deaths among women. The development of novel molecular targets is therefore important to many patients. Recently, the SRY-related transcription factor SOX2 has been widely reported to be involved in multiple pathophysiological diseases, including maintenance of stem cell characteristics and carcinogenesis. Up to now, SOX2 has been mainly shown to promote the development of cancer, although its inhibitory roles in cancer have also been reported. However, the role of SOX2 in ovarian cancer is largely unknown. In the present study, we detected the expression of SOX2 in 64 human serous ovarian carcinoma (SOC) tissues and paired corresponding metastatic specimens using immunohistochemistry. The results showed that the expression of SOX2 in primary tumors is much lower than that in the corresponding metastatic lesions. We further found that SOX2 overexpression promotes proliferation, migration and invasion, while inhibiting adhesion abilities of SOC cells. Finally, we found that SOX2 targets Src kinase, a non-receptor tyrosine kinase that regulates cell migration, invasion and adhesion in SOC cells. Together, these results suggested that Src kinase is a key molecule in SOX2-mediated migration and invasion of SOC cells.

Bacterial proteins and peptides in cancer therapy: today and tomorrow

Cancer is one of the most deadly diseases worldwide. In the last three decades many efforts have been made focused on understanding how cancer grows and responds to drugs. The dominant drug-development paradigm has been the "one drug, one target." Based on that, the two main targeted therapies developed to combat cancer include the use of tyrosine kinase inhibitors and monoclonal antibodies. Development of drug resistance and side effects represent the major limiting factors for their use in cancer treatment. Nowadays, a new paradigm for cancer drug discovery is emerging wherein multi-targeted approaches gain ground in cancer therapy. Therefore, to overcome resistance to therapy, it is clear that a new generation of drugs is urgently needed. Here, regarding the concept of multi-targeted therapy, we discuss the challenges of using bacterial proteins and peptides as a new generation of effective anti-cancer drugs.

FAP-α (Fibroblast activation protein-α) is involved in the control of human breast cancer cell line growth and motility via the FAK pathway

BACKGROUND

Fibroblast Activation Protein alpha (FAP-α) or seprase is an integral membrane serine peptidase. Previous work has not satisfactorily explained both the suppression and promotion effects that have been observed in cancer. The purpose of this work was to investigate the role of FAP-α in human breast cancer. Expression of FAP-α was characterized in primary tumour samples and in cell lines, along with the effects of FAP-α expression on in vitro growth, invasion, attachment and migration. Furthermore the potential interaction of FAP-α with other signalling pathways was investigated.

RESULTS

FAP-α was significantly increased in patients with poor outcome and survival. In vitro results showed that breast cancer cells over expressing FAP-α had increased growth ability and impaired migratory ability. The growth of MDA-MB-231 cells and the adhesion and invasion ability of both MCF-7 cells and MDA-MB-231 cells were not dramatically influenced by FAP-α expression. Over-expression of FAP-α resulted in a reduction of phosphorylated focal adhesion kinase (FAK) level in both cells cultured in normal media and serum-free media. An inhibitor to FAK restored the reduced motility ability of both MCF-7exp cells and MDA-MB-231exp cells and prevented the change in phosphorylated FAK levels. However, inhibitors to PI3K, ERK, PLCΥ, NWASP, ARP2/3, and ROCK had no influence this.

CONCLUSIONS

FAP-α in significantly associated with poor outcome in patients with breast cancer. In vitro, FAP-α promotes proliferation and inhibits migration of breast cancer cells, potentially by regulating the FAK pathway. These results suggest FAP-α could be a target for future therapies.

Wild-type and mutant p53 differentially regulate NADPH oxidase 4 in TGF-β-mediated migration of human lung and breast epithelial cells

BACKGROUND

Transforming growth factor-beta (TGF-β) induces the epithelial-to-mesenchymal transition (EMT) leading to increased cell plasticity at the onset of cancer cell invasion and metastasis. Mechanisms involved in TGF-β-mediated EMT and cell motility are unclear. Recent studies showed that p53 affects TGF-β/SMAD3-mediated signalling, cell migration, and tumorigenesis. We previously demonstrated that Nox4, a Nox family NADPH oxidase, is a TGF-β/SMAD3-inducible source of reactive oxygen species (ROS) affecting cell migration and fibronectin expression, an EMT marker, in normal and metastatic breast epithelial cells. Our present study investigates the involvement of p53 in TGF-β-regulated Nox4 expression and cell migration.

METHODS

We investigated the effect of wild-type p53 (WT-p53) and mutant p53 proteins on TGF-β-regulated Nox4 expression and cell migration. Nox4 mRNA and protein, ROS production, cell migration, and focal adhesion kinase (FAK) activation were examined in three different cell models based on their p53 mutational status. H1299, a p53-null lung epithelial cell line, was used for heterologous expression of WT-p53 or mutant p53. In contrast, functional studies using siRNA-mediated knockdown of endogenous p53 were conducted in MDA-MB-231 metastatic breast epithelial cells that express p53-R280K and MCF-10A normal breast cells that have WT-p53.

RESULTS

We found that WT-p53 is a potent suppressor of TGF-β-induced Nox4, ROS production, and cell migration in p53-null lung epithelial (H1299) cells. In contrast, tumour-associated mutant p53 proteins (R175H or R280K) caused enhanced Nox4 expression and cell migration in both TGF-β-dependent and TGF-β-independent pathways. Moreover, knockdown of endogenous mutant p53 (R280K) in TGF-β-treated MDA-MB-231 metastatic breast epithelial cells resulted in decreased Nox4 protein and reduced phosphorylation of FAK, a key regulator of cell motility. Expression of WT-p53 or dominant-negative Nox4 decreased TGF-β-mediated FAK phosphorylation, whereas mutant p53 (R280K) increased phospho-FAK. Furthermore, knockdown of WT-p53 in MCF-10A normal breast epithelial cells increased basal Nox4 expression, whereas p53-R280K could override endogenous WT-p53 repression of Nox4. Remarkably, immunofluorescence analysis revealed MCF-10A cells expressing p53-R280K mutant showed an upregulation of Nox4 in both confluent and migrating cells.

CONCLUSIONS

Collectively, our findings define novel opposing functions for WT-p53 and mutant p53 proteins in regulating Nox4-dependent signalling in TGF-β-mediated cell motility.

Synthesis, biological evaluation, and molecular docking studies of novel 2-styryl-5-nitroimidazole derivatives containing 1,4-benzodioxan moiety as FAK inhibitors with anticancer activity

A series of 2-styryl-5-nitroimidazole derivatives containing 1,4-benzodioxan moiety (3a-3r) has been designed, synthesized and their biological activities were also evaluated as potential antiproliferation and focal adhesion kinase (FAK) inhibitors. Among all the compounds, 3p showed the most potent activity in vitro which inhibited the growth of A549 with IC50 value of 3.11 μM and Hela with IC50 value of 2.54 μM respectively. Compound 3p also exhibited significant FAK inhibitory activity (IC50=0.45 μM). Docking simulation was performed for compound 3p into the FAK structure active site to determine the probable binding model.

Retinoic acid reduces migration of human breast cancer cells: role of retinoic acid receptor beta

Breast cancer is the most common malignancy in women and the appearance of distant metastases produces the death in 98% of cases. The retinoic acid receptor β (RARβ) is not expressed in 50% of invasive breast carcinoma compared with normal tissue and it has been associated with lymph node metastasis. Our hypothesis is that RARβ protein participates in the metastatic process. T47D and MCF7 breast cancer cell lines were used to perform viability assay, immunobloting, migration assays, RNA interference and immunofluorescence. Administration of retinoic acid (RA) in breast cancer cells induced RARβ gene expression that was greatest after 72 hrs with a concentration 1 μM. High concentrations of RA increased the expression of RARβ causing an inhibition of the 60% in cell migration and significantly decreased the expression of migration-related proteins [moesin, c-Src and focal adhesion kinase (FAK)]. The treatment with RARα and RARγ agonists did not affect the cell migration. On the contrary, the addition of the selective retinoid RARβ-agonist (BMS453) significantly reduced cell migration comparable to RA inhibition. When RARβ gene silencing was performed, the RA failed to significantly inhibit migration and resulted ineffective to reduce moesin, c-Src and FAK expressions. RARβ is necessary to inhibit migration induced by RA in breast cancer cells modulating the expression of proteins involved in cell migration.

Novel roles of focal adhesion kinase in cytoplasmic entry and replication of influenza A viruses

Viruses modulate cellular signaling pathways at almost every step of the infection cycle. Cellular signaling pathways activated at later times of influenza infection have previously been investigated; however, early influenza virus-host cell interactions remain understudied. Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that regulates phosphatidylinositol 3-kinase (PI3K) activation and actin reorganization, two critical processes during influenza A virus (IAV) infection in most cell types. Using 6 influenza A virus strains (A/Puerto Rico/8/1934, A/Aichi/2/1968 × A/Puerto Rico/8/1934 reassortant [X-31], A/California/04/2009, mouse-adapted A/California/04/2009, A/WSN/1933, and A/New Caledonia/20/1999), we examined the role of FAK during IAV entry. We found that influenza virus attachment induced PI3K-dependent FAK-Y397 phosphorylation. Pharmacological FAK inhibition or expression of a kinase-dead mutant of FAK led to disruption of the actin meshwork that resulted in sequestration of IAV at the cell periphery and reduced virion localization to early endosomes. Additionally, FAK inhibition impeded viral RNA replication at later times of infection and ultimately resulted in significantly reduced viral titers in both A549 and differentiated normal human bronchial epithelial (NHBE) cells. Although not all tested strains activated FAK, all of them exhibited a reduction in viral replication in response to inhibition of FAK signaling. These findings highlight novel biphasic roles of FAK activation during IAV infection and indicate that FAK serves as a central link between receptor-mediated PI3K activation and actin reorganization during IAV infection.

IMPORTANCE

We found that FAK links early activation of PI3K and actin reorganization, thereby regulating influenza virus entry. Surprisingly, we also found that FAK can regulate viral RNA replication independently of its role in entry. Our study addresses a knowledge gap in the understanding of signaling events triggered by influenza virus that mediate its internalization and initiation of the infection cycle. Understanding of these fundamental molecular events will be necessary to identify novel host targets, such as FAK, and development of future anti-influenza virus therapeutics.

Heparin-binding EGF-like growth factor (HB-EGF) promotes cell migration and adhesion via focal adhesion kinase

BACKGROUND

Cell migration and adhesion are essential in intestinal epithelial wound healing and recovery from injury. Focal adhesion kinase (FAK) plays an important role in cell-extracellular matrix signal transduction. We have previously shown that heparin-binding EGF-like growth factor (HB-EGF) promotes intestinal epithelial cell (IEC) migration and adhesion in vitro. The present study was designed to determine whether FAK is involved in HB-EGF-induced IEC migration and adhesion.

MATERIALS AND METHODS

A scrape wound healing model of rat IECs was used to examine the effect of HB-EGF on FAK-dependent cell migration in vitro. Immunofluorescence and Western blot analyses were performed to evaluate the effect of HB-EGF on the expression of phosphorylated FAK (p-FAK). Cell adhesion assays were performed to determine the role of FAK in HB-EGF-induced cell adhesion on fibronectin (FN).

RESULTS

HB-EGF significantly increased healing after scrape wounding, an effect that was reversed in the presence of an FAK inhibitor 14 (both with P < 0.05). HB-EGF increased p-FAK expression and induced p-FAK redistribution and actin reorganization in migrating rat IECs. Cell adhesion and spreading on FN were significantly increased by HB-EGF (P < 0.05). FAK inhibitor 14 significantly inhibited both intrinsic and HB-EGF-induced cell adhesion and spreading on FN (both with P < 0.05).

CONCLUSIONS

FAK phosphorylation and FAK-mediated signal transduction play essential roles in HB-EGF-mediated IEC migration and adhesion.

Pelargonidin attenuates PDGF-BB-induced aortic smooth muscle cell proliferation and migration by direct inhibition of focal adhesion kinase

Pelargonidin is a natural red pigment found in fruits and vegetables, and has been reported to exhibit various effects potentially beneficial for human health. However, the possible preventive effects of pelargonidin toward atherosclerosis and mechanisms involved have not been investigated to date. Here, we compared the effects of pelargonidin and its glucoside-conjugated form, pelargonidin-3-glucoside (P3G), on proliferation and migration induced by platelet-derived growth factor (PDGF)-BB in human aortic smooth muscle cells (HASMCs). Pelargonidin, but not P3G, exhibited strong inhibitory effects against PDGF-BB-induced HASMC proliferation and migration, while suppressing PDGF-BB-induced ex vivo rat aortic ring sprouting. Immunoblot analysis revealed that pelargonidin inhibited PDGF-BB-induced phosphorylation of focal adhesion kinase (FAK) as well as F-actin reduction, whereas Src, mitogen-activated protein kinases (MAPKs) and Akt phosphorylation status were not altered. We also observed that the anti-proliferative and migratory effects of both pelargonidin and P3G corresponded with the extent of FAK inhibition. Both in vitro and ex vivo pull-down assays revealed that pelargonidin binds directly with FAK in an adenosine triphosphate-competitive manner, suggesting that FAK could be a molecular target of pelargonidin. Interestingly, pelargonidin did not exhibit inhibitory effects on the proliferation, migration or FAK phosphorylation of human umbilical vein endothelial cells (HUVECs). Taken together, our results suggest that pelargonidin exhibits potential preventive effects toward atherosclerosis through the attenuation of HASMC proliferation and migration, as well as aortic sprouting via the direct inhibition of FAK activity.

Role of Ras, ERK, and Akt in glucocorticoid-induced differentiation of embryonic rat somatotropes in vitro

This study investigated the roles of Ras, ERK, and Akt in the glucocorticoid-induced differentiation of growth hormone-producing pituitary cells in vitro. Pituicytes isolated from day-18 rat embryos were cultured with 50 mM dexamethasone in addition to specific inhibitors of Ras (manumycin; 0.5, 5, 50 nM), ERK (U0126, 10 μM), or Akt (LY294002, 25 μM). Differentiation was assessed using immunofluorescent staining of intracellular growth hormone. Radioimmunoassay and Western blot analyses were used to determine levels of secreted and intracellular growth hormone, respectively. Manumycin reduced the fraction of growth hormone-positive cells and dexamethasone-induced growth hormone secretion in a dose-dependent manner (both P < 0.001). In the absence of dexamethasone, LY294002 and U0126 did not alter the fraction of growth hormone-positive cells or intracellular growth hormone protein expression or secretion. Both LY294002 and U0126 alone significantly attenuated the fraction of dexamethasone-treated GH-positive cells and the secretion of GH compared to those of cells treated only with dexamethasone (50 nM for 44 h or 48 h) (all P < 0.05). Dexamethasone treatment alone did not change GH protein levels. Treatment of cells with a combination of LY294402 and U0126 significantly attenuated the fraction of dexamethasone-treated GH-positive cells, GH protein levels, and GH secretion compared to cells treated with dexamethasone alone (all P < 0.05). Moreover, dexamethasone-induced phosphorylation of GTP-Ras, ERK, and Akt was significantly attenuated by exposure to the respective inhibitors (P < 0.05). Taken together, our results indicate that Ras, ERK, and Akt are key effectors in the glucocorticoid-induced differentiation of growth hormone-secreting cells.

MDA-9/syntenin is a key regulator of glioma pathogenesis

BACKGROUND

The extraordinary invasiveness of human glioblastoma multiforme (GBM) contributes to treatment failure and the grim prognosis of patients diagnosed with this tumor. Consequently, it is imperative to define further the cellular mechanisms that control GBM invasion and identify promising novel therapeutic targets. Melanoma differentiation associated gene-9 (MDA-9/syntenin) is a highly conserved PDZ domain-containing scaffolding protein that promotes invasion and metastasis in vitro and in vivo in human melanoma models. To determine whether MDA-9/syntenin is a relevant target in GBM, we investigated its expression in tumor samples and involvement in GBM invasion and angiogenesis.

MATERIALS

We assessed MDA-9/syntenin levels in available databases, patient tumor samples, and human-derived cell lines. Through gain-of-function and loss-of-function studies, we analyzed changes in invasion, angiogenesis, and signaling in vitro. We used orthotopic xenografts with GBM6 cells to demonstrate the role of MDA-9/syntenin in GBM pathogenesis in vivo.

RESULTS

MDA-9/syntenin expression in high-grade astrocytomas is significantly higher than normal tissue counterparts. Forced overexpression of MDA-9/syntenin enhanced Matrigel invasion, while knockdown inhibited invasion, migration, and anchorage-independent growth in soft agar. Moreover, overexpression of MDA-9/syntenin increased activation of c-Src, p38 mitogen-activated protein kinase, and nuclear factor kappa-B, leading to elevated expression of matrix metalloproteinase 2 and secretion of interleukin-8 with corresponding changes observed upon knockdown. GBM6 cells that stably express small hairpin RNA for MDA-9/syntenin formed smaller tumors and had a less invasive phenotype in vivo.

CONCLUSIONS

Our findings indicate that MDA-9/syntenin is a novel and important mediator of invasion in GBM and a key regulator of pathogenesis, and we identify it as a potential target for anti-invasive treatment in human astrocytoma.

Cytoskeletal dynamics and lung fluid balance

This article examines the role of the endothelial cytoskeleton in the lung's ability to restrict fluid and protein to vascular space at normal vascular pressures and thereby to protect lung alveoli from lethal flooding. The barrier properties of microvascular endothelium are dependent on endothelial cell contact with other vessel-wall lining cells and with the underlying extracellular matrix (ECM). Focal adhesion complexes are essential for attachment of endothelium to ECM. In quiescent endothelial cells, the thick cortical actin rim helps determine cell shape and stabilize endothelial adherens junctions and focal adhesions through protein bridges to actin cytoskeleton. Permeability-increasing agonists signal activation of "small GTPases" of the Rho family to reorganize the actin cytoskeleton, leading to endothelial cell shape change, disassembly of cortical actin rim, and redistribution of actin into cytoplasmic stress fibers. In association with calcium- and Src-regulated myosin light chain kinase (MLCK), stress fibers become actinomyosin-mediated contractile units. Permeability-increasing agonists stimulate calcium entry and induce tyrosine phosphorylation of VE-cadherin (vascular endothelial cadherin) and β-catenins to weaken or pull apart endothelial adherens junctions. Some permeability agonists cause latent activation of the small GTPases, Cdc42 and Rac1, which facilitate endothelial barrier recovery and eliminate interendothelial gaps. Under the influence of Cdc42 and Rac1, filopodia and lamellipodia are generated by rearrangements of actin cytoskeleton. These motile evaginations extend endothelial cell borders across interendothelial gaps, and may initiate reannealing of endothelial junctions. Endogenous barrier protective substances, such as sphingosine-1-phosphate, play an important role in maintaining a restrictive endothelial barrier and counteracting the effects of permeability-increasing agonists.

A non-canonical role for Rgnef in promoting integrin-stimulated focal adhesion kinase activation

Rgnef (also known as p190RhoGEF or ARHGEF28) is a Rho guanine-nucleotide-exchange factor (GEF) that binds focal adhesion kinase (FAK). FAK is recruited to adhesions and activated by integrin receptors binding to matrix proteins, such as fibronectin (FN). Canonical models place Rgnef downstream of integrin-FAK signaling in regulating Rho GTPase activity and cell movement. Herein, we establish a new, upstream role for Rgnef in enhancing FAK localization to early peripheral adhesions and promoting FAK activation upon FN binding. Rgnef-null mouse embryo fibroblasts (MEFs) exhibit defects in adhesion formation, levels of FAK phosphotyrosine (pY)-397 and FAK localization to peripheral adhesions upon re-plating on FN. Rgnef re-expression rescues these defects, but requires Rgnef-FAK binding. A mutation in the Rgnef pleckstrin homology (PH) domain inhibits adhesion formation, FAK localization, and FAK-Y397 and paxillin-Y118 phosphorylation without disrupting the Rgnef-FAK interaction. A GEF-inactive Rgnef mutant rescues FAK-Y397 phosphorylation and early adhesion localization, but not paxillin-Y118 phosphorylation. This suggests that, downstream of FN binding, paxillin-pY118 requires Rgnef GEF activity through a mechanism distinct from adhesion formation and FAK activation. These results support a scaffolding role for Rgnef in FAK localization and activation at early adhesions in a PH-domain-dependent but GEF-activity-independent manner.

Loss of P53 facilitates invasion and metastasis of prostate cancer cells

Prostate cancer is a lethal cancer for the invasion and metastasis in its earlier period. P53 is a tumor suppressor gene which plays a critical role on safeguarding the integrity of genome. However, loss of P53 facilitates or inhibits the invasion and metastasis of tumor is still suspended. In this study, we are going to explain whether loss of P53 affect the invasion and metastasis of prostate cancer cells. To explore whether loss of P53 influences the invasion and metastasis ability of prostate cancer cells, we first compared the invasion ability of si-P53 treated cells and control cells by wound healing, transwell assay, and adhesion assay. We next tested the activity of MMP-2, MMP-9, and MMP-14 by western blot and gelatin zymography. Moreover, we employed WB and IF to identify the EMT containing E-cad, N-cad, vimentin, etc. We also examined the expression of cortactin, cytoskeleton, and paxillin by immunofluorescence, and tested the expression of ERK and JNK by WB. Finally, we applied WB to detect the expression of FAK, Src, and the phosphorylation of them to elucidate the mechanism of si-P53 influencing invasion and metastasis. According to the inhibition rate of si-P53, we choose the optimized volume of si-P53. With the volume, we compare the invasion and metastasis ability of Du145 and si-P53 treated cells. We find si-P53 promotes the invasion and metastasis in prostate cancer cells, increases the expression and activity of MMP-2/9 and MMP-14. Also, si-P53 promotes EMT and cytoskeleton rearrangement. Further analyses explain that this effect is associated with FAK-Src signaling pathway. Loss of P53 promotes the invasion and metastasis ability of prostate cancer cells and the mechanism is correlated with FAK-Src signaling pathway. P53 is involved in the context of invasion and metastasis.

Distinct FAK activities determine progenitor and mammary stem cell characteristics

Mammary stem cells (MaSC) and progenitor cells are important for mammary gland development and maintenance and may give rise to mammary cancer stem cells (MaCSC). Yet, there remains limited understanding of how these cells contribute to tumorigenesis. Here, we show that conditional deletion of focal adhesion kinase (FAK) in embryonic mammary epithelial cells (MaEC) decreases luminal progenitors and basal MaSCs, reducing their colony-forming and regenerative potentials in a cell-autonomous manner. Loss of FAK kinase activity in MaECs specifically impaired luminal progenitor proliferation and alveologenesis, whereas a kinase-independent activity of FAK supported ductal invasion and basal MaSC activity. Deficiency in luminal progenitors suppressed tumorigenesis and MaCSC formation in a mouse model of breast cancer. In contrast with the general inhibitory effect of FAK attenuation, inhibitors of FAK kinase preferentially inhibited proliferation and tumorsphere formation of luminal progenitor-like, but not MaSC-like, human breast cancer cells. Our findings establish distinct kinase-dependent and -independent activities of FAK that differentially regulate luminal progenitors and basal MaSCs. We suggest that targeting these distinct functions may tailor therapeutic strategies to address breast cancer heterogeneity more effectively.

Mammalian adenylyl cyclase-associated protein 1 (CAP1) regulates cofilin function, the actin cytoskeleton, and cell adhesion

CAP (adenylyl cyclase-associated protein) was first identified in yeast as a protein that regulates both the actin cytoskeleton and the Ras/cAMP pathway. Although the role in Ras signaling does not extend beyond yeast, evidence supports that CAP regulates the actin cytoskeleton in all eukaryotes including mammals. In vitro actin polymerization assays show that both mammalian and yeast CAP homologues facilitate cofilin-driven actin filament turnover. We generated HeLa cells with stable CAP1 knockdown using RNA interference. Depletion of CAP1 led to larger cell size and remarkably developed lamellipodia as well as accumulation of filamentous actin (F-actin). Moreover, we found that CAP1 depletion also led to changes in cofilin phosphorylation and localization as well as activation of focal adhesion kinase (FAK) and enhanced cell spreading. CAP1 forms complexes with the adhesion molecules FAK and Talin, which likely underlie the cell adhesion phenotypes through inside-out activation of integrin signaling. CAP1-depleted HeLa cells also had substantially elevated cell motility as well as invasion through Matrigel. In summary, in addition to generating in vitro and in vivo evidence further establishing the role of mammalian CAP1 in actin dynamics, we identified a novel cellular function for CAP1 in regulating cell adhesion.

Korean mistletoe lectin promotes proliferation and invasion of trophoblast cells through regulation of Akt signaling

Recently, Viscum album var. coloratum agglutinin (VCA) was shown to have various effects on cancer cells. However, most researchers are focused on high concentrations (1-1000 ng/ml) of VCA and its anti-cancer effects. Therefore, we wanted to know whether low concentrations of VCA have an effect on proliferation and invasion of human trophoblast cells (HTR-8/SVneo cell line). Cell proliferations at low concentration of VCA (1-10 pg/ml) were increased over 2-fold relative to the control. Also, gelatinolytic activities of matrix metalloproteinase-2 were increased after VCA treatment, while TIMP-1 expression was reduced. Furthermore, the expression of integrin subunits α5 and β1 were increased 1.5-fold when cells were treated with low dose of VCA (10 pg/ml). Lastly, VCA was able to promote trophoblast invasion through activation of the Akt signaling pathway. In conclusion, low concentrations of VCA can stimulate the ability of trophoblast cells to invade through the extracellular matrix in vitro.

Context-specific protein tyrosine kinase 6 (PTK6) signalling in prostate cancer

BACKGROUND

Protein tyrosine kinase 6 (PTK6) is an intracellular tyrosine kinase that is distantly related to SRC family kinases. PTK6 is nuclear in normal prostate epithelia, but nuclear localization is lost in prostate tumours. Increased expression of PTK6 is detected in human prostate cancer, especially at metastatic stages, and in other types of cancers, including breast, colon, head and neck cancers, and serous carcinoma of the ovary.

MATERIALS AND METHODS

Potential novel substrates of PTK6 identified by mass spectrometry were validated in vitro. The significance of PTK6-induced phosphorylation of these substrates was addressed using human prostate cell lines by knockdown of endogenous PTK6 or overexpression of targeted PTK6 to different intracellular compartments.

RESULTS

We identified AKT, p130CAS and focal adhesion kinase (FAK) as novel PTK6 substrates and demonstrated their roles in promoting cell proliferation, migration and resistance to anoikis. In prostate cancer cells, active PTK6 is primarily associated with membrane compartments, although the majority of total PTK6 is localized within the cytoplasm. Ectopic expression of membrane-targeted PTK6 transforms immortalized fibroblasts. Knockdown of endogenous cytoplasmic PTK6 in PC3 prostate cancer cells impairs proliferation, migration and anoikis resistance. However, re-introduction of PTK6 into the nucleus significantly decreases cell proliferation, suggesting context-specific functions for nuclear PTK6.

CONCLUSIONS

In human prostate cancer, elevated PTK6 expression, translocation of PTK6 from the nucleus to the cytoplasm and its activation at the plasma membrane contribute to increased phosphorylation and activation of its substrates such as AKT, p130CAS and FAK, thereby promoting prostate cancer progression.

Effects of progesterone and medroxyprogesterone on actin remodeling and neuronal spine formation

Sex steroids are important regulators of neuronal cell morphology, and this is critical for gender differences in brain function and dysfunction. Neuronal morphology is controlled by multiprotein complexes including moesin (a member of the ezrin/radixin/moesin family), focal adhesion kinase (FAK), or the Wiskott-Aldrich syndrome protein-family verprolin homologous (WAVE1) protein, controlling dynamic remodeling of the cytoskeleton and cell membrane. We investigated the actions of natural progesterone (P) and of the synthetic progestin medroxyprogesterone acetate (MPA) on actin remodeling, focal adhesion complex formation, and actin branching in rat cortical neurons. Treatment with P and, to a lesser extent, MPA, increases the number and density of dendritic spines. P increases the phosphorylation of moesin, FAK, and WAVE1, and their redistribution toward cell membrane sites where spines are formed. Signaling to moesin is achieved by PR via a Gα/Gβ-dependent signaling to the small GTPase Ras homolog gene family, member A and its related kinase, Rho-associated kinase-2. In parallel, WAVE1 recruitment is triggered by a Gαi/Gβ-dependent signaling of PR to c-Src, FAK, and Rac1 GTPase. Rac1 recruits cyclin-dependent kinase-5, which phosphorylates WAVE1. Silencing of moesin, FAK, or WAVE1 abrogates the increase in dendritic spines induced by progesterone. In all applications, MPA is found to act similar to P, albeit with a lower efficacy. In conclusion, our findings indicate that the control of actin polymerization and branching and focal adhesion complex formation via moesin, FAK, and WAVE1 is a key function of progesterone receptor in neurons, which may be relevant for the regulation of dendritic spine turnover and neuronal plasticity.

Integrin bi-directional signaling across the plasma membrane

Integrins are heterodimeric cell adhesion molecules that are important in many biological functions, such as cell migration, proliferation, differentiation, and survival. They can transmit bi-directional signals across the plasma membrane. Inside-out activating signal from some cell surface receptors bound with soluble agonists triggers integrins conformational change leading to high affinity for extracellular ligands. Then binding of ligands to integrins results in outside-in signaling, leading to formation of focal adhesion complex at the integrin cytoplasmic tail and activation of downstream signal pathways. This bi-directional signaling is essential for rapid response of cell to surrounding environmental changes. During this process, the conformational change of integrin extracellular and transmembrane/cytoplasmic domains is particularly important. In this review, we will summarize recent progress in both inside-out and outside-in signaling with specific focus on the mechanism how integrins transmit bi-directional signals through transmembrane/cytoplasmic domains.

Fragment-based discovery of new highly substituted 1H-pyrrolo[2,3-b]- and 3H-imidazolo[4,5-b]-pyridines as focal adhesion kinase inhibitors

Focal adhesion kinase (FAK) is considered as an attractive target for oncology, and small-molecule inhibitors are reported to be in clinical testing. In a surface plasmon resonance (SPR)-mediated fragment screening campaign, we discovered bicyclic scaffolds like 1H-pyrazolo[3,4-d]pyrimidines binding to the hinge region of FAK. By an accelerated knowledge-based fragment growing approach, essential pharmacophores were added. The establishment of highly substituted unprecedented 1H-pyrrolo[2,3-b]pyridine derivatizations provided compounds with submicromolar cellular FAK inhibition potential. The combination of substituents on the bicyclic templates and the nature of the core structure itself have a significant impact on the compounds FAK selectivity. Structural analysis revealed that the appropriately substituted pyrrolo[2,3-b]pyridine induced a rare helical DFG-loop conformation. The discovered synthetic route to introduce three different substituents independently paves the way for versatile applications of the 7-azaindole core.

ErbB/integrin signaling interactions in regulation of myocardial cell-cell and cell-matrix interactions

Neuregulin (Nrg)/ErbB and integrin signaling pathways are critical for the normal function of the embryonic and adult heart. Both systems activate several downstream signaling pathways, with different physiological outputs: cell survival, fibrosis, excitation-contraction coupling, myofilament structure, cell-cell and cell-matrix interaction. Activation of ErbB2 by Nrg1β in cardiomycytes or its overexpression in cancer cells induces phosphorylation of FAK (Focal Adhesion Kinase) at specific sites with modulation of survival, invasion and cell-cell contacts. FAK is also a critical mediator of integrin receptors, converting extracellular matrix alterations into intracellular signaling. Systemic FAK deletion is lethal and is associated with left ventricular non-compaction whereas cardiac restriction in adult hearts is well tolerated. Nevertheless, these hearts are more susceptible to stress conditions like trans-aortic constriction, hypertrophy, and ischemic injury. As FAK is both downstream and specifically activated by integrins and Nrg-1β, here we will explore the role of FAK in the heart as a protective factor and as possible mediator of the crosstalk between the ErbB and Integrin receptors. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.

Function of focal adhesion kinase scaffolding to mediate endophilin A2 phosphorylation promotes epithelial-mesenchymal transition and mammary cancer stem cell activities in vivo

Tyrosine kinases have been shown to play critical roles in cancer development and progression, and their inhibitors hold the potential as effective targeted therapies for breast and other cancers. However, some of these kinases like focal adhesion kinase (FAK) also possess scaffolding functions in intracellular signaling, but such kinase-independent functions of FAK or other kinases have not been examined in cancer directly in vivo. Here, we report that disruption of the function of FAK scaffolding through its Pro-878/881 motif suppressed mammary tumor growth and metastasis in a well characterized murine model of human breast cancer. P878A/P881A mutation in the endogenous FAK gene decreased the expression of markers for epithelial-mesenchymal transition (EMT) and mammary cancer stem cell (MaCSC) activities in tumors derived from mutant mice. This mutation disrupted the function of FAK scaffolding to mediate endophilin A2 phosphorylation at Tyr-315 by Src, leading to the decreased surface expression of MT1-MMP, as observed previously in transformed fibroblasts in vitro. Inhibition of the downstream components of this FAK scaffolding function by Y315F endophilin A2 mutant or MT1-MMP knockdown reduced markers for EMT and MaCSC activities. Conversely, bypass of the scaffolding function using the phosphorylation mimic mutant Y315E endophilin A2 or endophilin A2 knockdown rescued the decreased markers for EMT and MaCSCs as well as surface expression of MT1-MMP in tumor cells harboring the P878A/P881A mutation. Together, these results identify a novel role of FAK scaffolding function in breast cancer, which could serve as a new target in combination with kinase inhibition for more effective treatment strategies.

Antimigratory Effects of the Methanol Extract from Momordica charantia on Human Lung Adenocarcinoma CL1 Cells

Momordica charantia has been found to exhibit anticancer activity, in addition to its well-known therapeutic functions. We have demonstrated that the leaf extract of Momordica charantia (MCME) induces apoptosis in several human cancer cells through caspase- and mitochondria-dependent pathways. In this study, a different susceptibility to MCME was found in human lung adenocarcinoma CL1 cells with different metastatic ability, leading to the significant difference of cell viability and invasiveness between MCME-treated CL1-0 and CL1-5 cells. MCME was found to upregulate the expression of Wnt-2 and affect the migratory and invasive ability of CL1 cells through suppressed MMP-2 and MMP-9 enzymatic activities. We proposed that MCME mediates inhibition against migration of CL1 cells by reducing the expression and activation of Src and FAK to decrease the expression of downstream Akt, β-catenin, and MMPs.

Low-Rac1 activity downregulates MC3T3-E1 osteoblastic cell motility on a nanoscale topography prepared on polystyrene substrates in vitro

Surface roughness affects various cell activities, including osteoblast motility, which may have an effect on bone regeneration. Defective cell signaling, which is associated with the slow motility of osteoblasts on a substrate with rough topology at nanometer dimensions (Ra = 123.8 ± 29.1 nm), was studied. Osteoblasts grown on the rough surface at nanometer dimensions showed the high activities of small GTPase RhoA and Rho-associated kinase (ROCK) on the rough surface at nanometer dimensions and downregulated Rac1 activity compared to the smooth surface. The inhibition of ROCK in the cells with Y-27632, a specific ROCK inhibitor, reversed the low-cell motility. In addition, the transfection of constitutively active Rac1 reversed the low-cell motility. However, Rac1 inhibition abolished the reversal of low-cell motility induced by ROCK inhibition. These results indicate that upregulated RhoA/ROCK activity suppresses Rac1 activity to decrease the motility of osteoblasts on a rough surface at nanometer dimensions, and the low motility of osteoblasts on a rough surface at nanometer dimensions can be reversed by ROCK inhibition.

Ror2-Src signaling in metastasis of mouse melanoma cells is inhibited by NRAGE

The receptor tyrosine kinase (RTK) Ror2 plays important roles in developmental morphogenesis and mediates the filopodia formation in Wnt5a-induced cell migration. However, the function of Ror2 in noncanonical Wnt signaling resulting in cancer metastasis is largely unknown. Here, we show that Ror2 expression is higher in the highly metastatic murine B16-BL6 melanoma cells than in the low metastatic variant B16 cells. Overexpression of Ror2 increases the metastasis ability of B16 cells, and knockdown of Ror2 reduces the migration ability of B16-BL6 cells. Furthermore, the inhibition of Src kinase activity is critical for the Ror2-mediated cell migration upon Wnt5a treatment. The C-terminus of Ror2, which is deleted in brachydactyly type B (BDB), is essential for the mutual interaction with the SH1 domain of Src. Intriguingly, the Neurotrophin receptor-interacting MAGE homologue (NRAGE), which, as we previously reported, can remodel the cellular skeleton and inhibit cell-cell adhesion and metastasis of melanoma and pancreatic cancer, sharply blocks the interaction between Src and Ror2 and inhibits Ror2-mediated B16 cell migration by decreasing the activity of Src and focal adhesion kinase (FAK). Our data show that Ror2 is a potential factor in the tumorigenesis and metastasis in a Src-dependent manner that is negatively regulated by NRAGE.

Tetraspan TM4SF5-dependent direct activation of FAK and metastatic potential of hepatocarcinoma cells

Transmembrane 4 L six family member 5 (TM4SF5) plays an important role in cell migration, and focal adhesion kinase (FAK) activity is essential for homeostatic and pathological migration of adherent cells. However, it is unclear how TM4SF5 signaling mediates the activation of cellular migration machinery, and how FAK is activated during cell adhesion. Here, we showed that direct and adhesion-dependent binding of TM4SF5 to FAK causes a structural alteration that may release the inhibitory intramolecular interaction in FAK. In turn, this may activate FAK at the cell's leading edge, to promote migration/invasion and in vivo metastasis. TM4SF5-mediated FAK activation occurred during integrin-mediated cell adhesion. TM4SF5 was localized at the leading edge of the cells, together with FAK and actin-organizing molecules, indicating a signaling link between TM4SF5/FAK and actin reorganization machinery. Impaired interactions between TM4SF5 and FAK resulted in an attenuated FAK phosphorylation (the signaling link to actin organization machinery) and the metastatic potential. Our findings demonstrate that TM4SF5 directly binds to and activates FAK in an adhesion-dependent manner, to regulate cell migration and invasion, suggesting that TM4SF5 is a promising target in the treatment of metastatic cancer.

Soft tissue mechanotransduction in wound healing and fibrosis

Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration.

Protein tyrosine kinase 6 protects cells from anoikis by directly phosphorylating focal adhesion kinase and activating AKT

Protein tyrosine kinase 6 (PTK6) is a non-receptor tyrosine kinase expressed in epithelial cancers. Disruption of Ptk6 decreases AOM-induced colon tumorigenesis in mice by preventing STAT3 activation. Relocalization of PTK6 in prostate cancers contributes to increased growth. Although not expressed in normal breast or ovary, PTK6 promotes anchorage-independent survival of breast and ovarian tumor cells. We identified several potential PTK6 substrates in the human SW620 colon cancer cell line using mass spectrometry, including FAK (focal adhesion kinase). We show that FAK is a direct substrate of PTK6 in vitro and in vivo. Expression of membrane targeted active PTK6 (Palm-PTK6-YF) induces constitutive activation of FAK and cell morphology changes, which are independent of SRC family kinases in Src−/−, Yes−/−, Fyn−/− (SYF) mouse embryonic fibroblasts (MEFs). Palm-PTK6-YF expressing SYF cells are transformed and overcome contact inhibition, form colonies in transformation assays, proliferate in suspension, and form tumors in a xenograft model. Expression of FAK and Palm-PTK6-YF in Fak−/− MEFs synergistically activates AKT and protects cells against anoikis. However, expression of Palm-PTK6-YF in Akt1/2−/− MEFs fails to protect cells from anoikis, indicating AKT is critical in PTK6 and FAK mediated survival signaling. In a conditional Pten knockout murine prostate cancer model, we identify prostate epithelial cells with enhanced activation of endogenous PTK6 and FAK at the plasma membrane. Knockdown of PTK6 in the PC3 human prostate cancer cell line disrupts FAK and AKT activation and promotes anoikis, which can be rescued by exogenous expression of FAK. Our data reveal important roles for a PTK6-FAK-AKT signaling axis in promoting anchorage-independent cell survival.

Gleditsioside B, a triterpene saponin isolated from the anomalous fruits of Gleditsia sinensis Lam., abrogates bFGF-induced endothelial cell migration through preventing the activation of MMP-2 and FAK via inhibiting ERK and PI3K/AKT signaling pathways

Angiogenesis has become an attractive target for the treatment of certain diseases such as cancer and rheumatoid arthritis. Our previous studies demonstrated that the saponin fraction from Gleditsia sinensis fruits had anti-angiogenic potential, and Gleditsiosides B (GB) was probably the main active constituent. In the present study, we assessed the effect of GB on endothelial cell migration, a crucial event in angiogenesis, and explored the underlying mechanisms. The migration of endothelial cells was assessed by transwell. The expressions of MMP-2/-9 and TIMP-1/-2 were analyzed by Western blotting, and the activities of MMP-2/-9 were detected by gelatin zymography assay. Moreover, migration-related proteins and signaling pathways, including FAK, MAPKs and PI3K/AKT, were analyzed by Western blotting. It was shown that GB, at a concentration of 10 μM without significant cytotoxicity, could effectively abrogate the migration of human umbilical vein endothelial cells (HUVECs) induced by bFGF. GB also inhibited the expression and activity of MMP-2, elevated the expression of TIMP-1, and restrained the phosphorylations of FAK, ERK, PI3K and AKT in a concentration-dependent manner. The findings suggest that GB was able to abrogate the migration of endothelial cells through down-regulating the activation of MMP-2 and FAK via preventing ERK and PI3K/AKT signaling pathways.

Differential DNA copy number aberrations in the progression of cervical lesions to invasive cervical carcinoma

Host genomic alterations in addition to human papillomavirus (HPV) are needed for cervical precursor lesions to progress to invasive cancer because only a small percentage of women infected by the virus develop disease. However, the genomic alterations during the progression of cervical lesions have not been systematically examined. The aim of this study was to identify differential genomic alterations among cervical intraepithelial neoplasia CIN1, CIN2, CIN3 and cervical squamous cell carcinoma (SCC). Genomic alterations were examined for 15 cases each of CIN1, CIN2, CIN3 and SCC by array-based comparative genomic hybridization (array CGH). The chromosomal regions showing significant differential in DNA copy number aberrations (DCNAs) among CIN1, CIN2, CIN3 and SCC were successfully identified by resampling-based t-test. The chromosomal regions of 5q35.3 and 2q14.3 showed significant DCNAs between CIN1 and CIN2, and between CIN2 and CIN3, respectively, while a significant difference in DCNAs between CIN3 and SCC was observed at 1q24.3, 3p14.1, 3p14.2, 5q13.2, 7p15.3, 7q22.1 and 13q32.3. In addition, the status of DCNAs in 1q43, 2p11.2, 6p11.2, 7p21.1, 7p14.3, 10q24.1, 13q22.3, 13q34 and 16p13.3 was conserved throughout the progression of CIN to SCC. The presence of differential and common DCNAs among CIN1, CIN2, CIN3 and SCC supports that the CIN progression may include continual clonal selection and evolution. This approach also identified 34 probe sets consistently overexpressed when amplified, suggesting an unbiased identification of candidate genes in SCC during cervical cancer progression.

CLCA2, a target of the p53 family, negatively regulates cancer cell migration and invasion

The tumor suppressor p53 transcriptionally regulates a number of genes that are involved in cell-cycle inhibition, apoptosis and the maintenance of genetic stability. Recent studies suggest that p53 also contributes to the regulation of cell migration and invasion. Here, we show that human chloride channel accessory-2 (CLCA2) is a target gene of the p53 family (p53, p73 and p63). CLCA2 is induced by DNA damage in a p53-dependent manner. The p53 family proteins activate the CLCA2 promoter by binding directly to the conserved consensus p53-binding site present in the CLCA2 promoter. In terms of function, ectopic expression of CLCA2 inhibited cancer cell migration. In contrast, silencing CLCA2 with siRNA stimulated cancer cell migration and invasion. We also found that inactivation of CLCA2 enhanced the expression of focal adhesion kinase (FAK), as well as its promoter activation. A small-molecule FAK inhibitor reduced the effect of CLCA2 siRNA on cell migration and invasion, suggesting that CLCA2 inhibits cancer cell migration and invasion through suppression of the FAK signaling pathway. Furthermore, there was an inverse correlation between CLCA2 and FAK expression in 251 human breast cancer tissues. These results strongly suggest that CLCA2 is involved in the p53 tumor suppressor network and has a significant effect on cell migration and invasion.

Impaired c-src activation and motility defects in PEA3-null fibroblasts

Null mutations in the pea3 allele compromise the capacity of mammary tumors to metastasize in MMTV-Neu/ErbB2/HER2 transgenic mice, indicating a motility defect in PEA3-null cells. Cellular and biochemical analyses of established PEA3-null fibroblasts show impaired motility and aberrant localization of adhesion proteins in spreading cells. Our results show that PEA3-/- cells express normal levels of key adhesion components, but that spreading PEA3-null cells fail to activate c-src and to downregulate phospho-FAK(Y397), suggesting that focal adhesion signaling is impaired. Supporting this, biochemical analysis revealed that adhesion complex-associated proteins such as p130Cas failed to undergo tyrosine phosphorylation and dissociated from the adhesion complex with delayed kinetics. Overall our data show that the motility defects observed in PEA3-null cells are due to altered adhesion signaling.

Nuclear-localized focal adhesion kinase regulates inflammatory VCAM-1 expression

Kinase-inhibited FAK limits VCAM-1 production via nuclear localization and promotion of GATA4 turnover.

Vascular cell adhesion molecule–1 (VCAM-1) plays important roles in development and inflammation. Tumor necrosis factor–α (TNF-α) and focal adhesion kinase (FAK) are key regulators of inflammatory and integrin–matrix signaling, respectively. Integrin costimulatory signals modulate inflammatory gene expression, but the important control points between these pathways remain unresolved. We report that pharmacological FAK inhibition prevented TNF-α–induced VCAM-1 expression within heart vessel–associated endothelial cells in vivo, and genetic or pharmacological FAK inhibition blocked VCAM-1 expression during development. FAK signaling facilitated TNF-α–induced, mitogen-activated protein kinase activation, and, surprisingly, FAK inhibition resulted in the loss of the GATA4 transcription factor required for TNF-α–induced VCAM-1 production. FAK inhibition also triggered FAK nuclear localization. In the nucleus, the FAK-FERM (band 4.1, ezrin, radixin, moesin homology) domain bound directly to GATA4 and enhanced its CHIP (C terminus of Hsp70-interacting protein) E3 ligase–dependent polyubiquitination and degradation. These studies reveal new developmental and anti-inflammatory roles for kinase-inhibited FAK in limiting VCAM-1 production via nuclear localization and promotion of GATA4 turnover.

Disruption of the protein interaction between FAK and IGF-1R inhibits melanoma tumor growth

FAK (focal adhesion kinase) and IGF-1R (insulin-like growth factor receptor-1) directly interact with each other and thereby activate crucial signaling pathways that benefit cancer cells. Inhibition of FAK and IGF-1R function has been shown to significantly decrease cancer cell proliferation and increase sensitivity to chemotherapy and radiation treatment. As a novel approach in human melanoma, we evaluated the effect of a small-molecule compound that disrupts the protein interaction of FAK and IGF-1R. Previously, using virtual screening and functional testing, we identified a lead compound (INT2-31) that targets the known FAK-IGF-1R protein interaction site. We studied the ability of this compound to disrupt FAK-IGF-1R protein interactions, inhibit downstream signaling, decrease human melanoma cell proliferation, alter cell cycle progression, induce apoptosis and decrease tumor growth in vivo. INT2-31 blocked the interaction of FAK and IGF-1R in vitro and in vivo in melanoma cells and tumor xenografts through precluding the activation of IRS-1, leading to reduced phosphorylation of AKT upon IGF-1 stimulation. As a result, INT2-31 significantly inhibited cell proliferation and viability (range 0.05-10 μM). More importantly, 15 mg/kg of INT2-31 given for 21 d via intraperitoneal injection disrupted the interaction of FAK and IGF-1R and effectively decreased phosphorylation of tumor AKT, resulting in significant melanoma tumor regression in vivo. Our data suggest that the FAK-IGF-1R protein interaction is an important target, and disruption of this interaction with a novel small molecule (INT2-31) has potential anti-neoplastic therapeutic effects in human melanoma.

Knockdown of glucose-regulated protein 78 decreases the invasion, metalloproteinase expression and ECM degradation in hepatocellular carcinoma cells

Background

We have reported previously that overexpression of glucose-regulated protein 78 (GRP78) promotes the invasion of hepatocellular carcinoma. However, whether GRP78 knockdown affects the extracellular matrix degradation has not been elucidated. Here we are going to determine whether GRP78 knockdown affect the ECM degradation and the role of MMP-2 and MMP-9 in these process in hepatocellular carcinoma cells.

Methods

Human hepatocellular carcinoma cell line SMMC7721 and HepG2 were cultured in DMEM supplemented with 10% FBS, RT-PCR and western blot were used to detect the endogenous expression of GRP78, MMP-2, MMP-9 and TIMP-2 in SMMC7721 and HepG2. GRP78 shRNAs were transfected using lipofection2000. Transwell assay and wound healing assay were used to analyze the invasion of each transfectant. Gelatin zymography and FITC-gelatin degradation assay were employed to investigate the capabilities of ECM degradation of each transfectant. MTT assay was used to determine the proliferation status. Western blot was employed to detect the expression of matrix metalloproteinase 2(MMP-2), MMP-9, MMP-14, and tissue inhibitor of metalloproteinases 2(TIMP-2), focal adhesion kinase (FAK), ERK1/2, JNK and Src.

Results

According to the expression levels of GRP78, MMP-2, MMP-9, MMP-14 and TIMP-1 in hepatocellular carcinoma cell lines SMMC7721 and hepG2, we used SMMC7721 as the in vitro invasion model for further functional analysis. Using this model, we found that GRP78 knockdown decreased the invasion of tumor cells, and this inhibitory effect was independent of cell proliferation. In hepatocellular carcinoma cells, Grp78 knockdown inhibited ECM degradation and the decreased activity and expression of MMP-2, but not MMP-9 contributed largely to this impact. Further analysis revealed that the decreased activity and expression of MMP-2 is mediated by JNK.

Conclusion

Knockdown of GRP78 decreases ECM degradation, and downregulates the expression and activity of MMP-2 and TIMP-2. These results further demonstrate that GRP78 is a potential target for inhibiting the invasion of hepatocellular carcinoma cells.

Spermine, a molecular switch regulating EGFR, integrin β3, Src, and FAK scaffolding

Intracellular polyamine levels are highly regulated by the activity of ornithine decarboxylase (ODC), which catalyzes the first rate-limiting reaction in polyamine biosynthesis, producing putrescine, which is subsequently converted to spermidine and spermine. We have shown that polyamines regulate proliferation, migration, and apoptosis in intestinal epithelial cells. Polyamines regulate key signaling events at the level of the EGFR and Src. However, the precise mechanism of action of polyamines is unknown. In the present study, we demonstrate that ODC localizes in lamellipodia and in adhesion plaques during cell spreading. Spermine regulates EGF-induced migration by modulating the interaction of the EGFR with Src. The EGFR interacted with integrin β3, Src, and focal adhesion kinase (FAK). Active Src (pY418-Src) localized with FAK during spreading and migration. Spermine prevented EGF-induced binding of the EGFR with integrin β3, Src, and FAK. Activation of Src and FAK was necessary for EGF-induced migration in HEK293 cells. EGFR-mediated Src activation in live HEK293 cells using a FRET based Src reporter showed that polyamine depletion significantly increased Src kinase activity. In vitro binding studies showed that spermine directly binds Src, and preferentially interacts with the SH2 domain of Src. The physical interaction between Src and the EGFR was severely attenuated by spermine. Therefore, spermine acts as a molecular switch in regulating EGFR-Src coupling both physically and functionally. Upon activation of the EGFR, integrin β3, FAK and Src are recruited to EGFR leading to the trans-activation of both the EGFR and Src and to the Src-mediated phosphorylation of FAK. The activation of FAK induced Rho-GTPases and subsequently migration. This is the first study to define mechanistically how polyamines modulate Src function at the molecular level.

In vitro phosphorylation of the focal adhesion targeting domain of focal adhesion kinase by Src kinase

Focal adhesion kinase (FAK), a key regulator of cell adhesion and migration, is overexpressed in many types of cancer. The C-terminal focal adhesion targeting (FAT) domain of FAK is necessary for proper localization of FAK to focal adhesions and subsequent activation. Phosphorylation of Y926 in the FAT domain by the tyrosine kinase Src has been shown to promote metastasis and invasion in vivo by linking the FAT domain to the MAPK pathway via its interaction with growth factor receptor-bound protein 2. Several groups have reported that inherent conformational dynamics in the FAT domain likely regulate phosphorylation of Y926; however, what regulates these dynamics is unknown. In this paper, we demonstrate that there are two sites of in vitro Src-mediated phosphorylation in the FAT domain: Y926, which has been shown to affect FAK function in vivo, and Y1008, which has no known biological role. The phosphorylation of these two tyrosine residues is pH-dependent, but this does not reflect the pH dependence of Src kinase activity. Circular dichroism and nuclear magnetic resonance data indicate that the stability and conformational dynamics of the FAT domain are sensitive to changes in pH over a physiological pH range. In particular, regions of the FAT domain previously shown to regulate phosphorylation of Y926 as well as regions near Y1008 show pH-dependent dynamics on the microsecond to millisecond time scale.