Culture of human cervical cancer cells, SiHa, in the presence of fibronectin activates MMP-2

IRAK1 deficiency potentiates the efficacy of radiotherapy in repressing cervical cancer development

IRAK1 has been implicated in promoting development of various types of cancers and mediating radioresistance. However, its role in cervical cancer tumorigenesis and radioresistance, as well as the potential underlying mechanisms, remain poorly defined. In this study, we evaluated IRAK1 expression in radiotherapy-treated cervical cancer tissues and found that IRAK1 expression is negatively associated with the efficacy of radiotherapy. Consistently, ionizing radiation (IR)-treated HeLa and SiHa cervical cancer cells express a lower level of IRAK1 than control cells. Depletion of IRAK1 resulted in reduced activation of the NF-κB pathway, decreased cell viability, downregulated colony formation efficiency, cell cycle arrest, increased apoptosis, and impaired migration and invasion in IR-treated cervical cancer cells. Conversely, overexpressing IRAK1 mitigated the anti-cancer effects of IR in cervical cancer cells. Notably, treatment of IRAK1-overexpressing IR-treated HeLa and SiHa cells with the NF-κB pathway inhibitor pyrrolidine dithiocarbamate (PDTC) partially counteracted the effects of excessive IRAK1. Furthermore, our study demonstrated that IRAK1 deficiency enhanced the anti-proliferative role of IR treatment in a xenograft mouse model. These collective observations highlight IRAK1's role in mitigating the anti-cancer effects of radiotherapy, partly through the activation of the NF-κB pathway. SUMMARY: IRAK1 enhances cervical cancer resistance to radiotherapy, with IR treatment reducing IRAK1 expression and increasing cancer cell vulnerability and apoptosis.

Nanomedicine Strategies for Targeting Tumor Stroma

The tumor stroma, or the microenvironment surrounding solid tumors, can significantly impact the effectiveness of cancer therapies. The tumor microenvironment is characterized by high interstitial pressure, a consequence of leaky vasculature, and dense stroma created by excessive deposition of various macromolecules such as collagen, fibronectin, and hyaluronic acid (HA). In addition, non-cancerous cells such as cancer-associated fibroblasts (CAFs) and the extracellular matrix (ECM) itself can promote tumor growth. In recent years, there has been increased interest in combining standard cancer treatments with stromal-targeting strategies or stromal modulators to improve therapeutic outcomes. Furthermore, the use of nanomedicine, which can improve the delivery and retention of drugs in the tumor, has been proposed to target the stroma. This review focuses on how different stromal components contribute to tumor progression and impede chemotherapeutic delivery. Additionally, this review highlights recent advancements in nanomedicine-based stromal modulation and discusses potential future directions for developing more effective stroma-targeted cancer therapies.

The inhibition of HeLa cells proliferation through SPARCL1 mediated by SPP1

Secreted protein acidic and rich in cysteines-like 1 (SPARCL1) is implicated in tumor progression and considered as a tumor suppressor. Aim of the study is to investigate the role of SPARCL1 in the regulation of tumor biology. SPARCL1 expression in human cervical cells was determined through western blot and RT-PCR. The effects of SPARCL1 overexpression on cell proliferation, migration and invasion were evaluated through CCK8 assay, colony formation assay, Wound healing assay and Transwell assay, respectively. The gain function of Secreted phosphor protein 1 (SPP1) was also evaluated in these cell functions. We observed that SPARCL1 expression at protein levels and transcription levels was lower in HeLa cells than that in Ect1/E6E7 cells. When SPARCL1 was overexpressed in HeLa cells, cell proliferation, migration and invasion were greatly repressed. Additionally, SPARCL1 overexpression markedly downregulated SPP1 expression at transcription levels. Mechanistical study revealed that SPP1 overexpression could greatly counteract the effects of SPARCL1 overexpression on the aforementioned cell processes and inhibit the phosphorylation of focal adhesion kinase (FAK) and extracellular regulated protein kinases (ERK). Our findings indicated that HeLa cells overexpressing SPARCL1 showed weaker abilities of proliferation, migration and invasion, and its effects could be neutralized by SPP1 overexpression possibly via FAK/ERK pathway. The relationship of SPARCL1 and SPP1 could help us to further understand the pathogenesis of cervical cancer and SPARCL1/SPP1 could be beneficial therapeutic targets in cervical cancer.

Semen affects the biological behavior of HeLa cells by altering ERK signaling

INTRODUCTION

The aim of the study was to investigate the effects of human semen on the proliferation, survival, migration and invasion of HeLa cervical cancer cells by analyzing the extracellular regulated protein kinase (ERK) pathway.

MATERIAL AND METHODS

HeLa cells were stimulated with different concentrations of human semen. MTT assay was used to analyze the effects on cell proliferation. Apoptosis in the different experimental groups was quantified by Annexin V-FITC/PI staining. The effect of seminal plasma on in vitro invasiveness of cells was evaluated using transwell assay. Western blotting was used to evaluate ERK pathway activation.

RESULTS

Human semen promoted HeLa cell proliferation; ERK1/2 phosphorylation and c-myc expression also increased with increasing semen concentration. U0126 inhibited semen-induced ERK1/2 phosphorylation, c-myc upregulation and cell proliferation. Compared with the control group, semen did not significantly affect the apoptotic rate of HeLa cells (p > 0.05). The transwell assays showed that compared with the control group, the number of invading cells increased significantly with increasing semen concentration, and the difference was significant (p < 0.05) when 1 : 50 semen was added, suggesting that semen promotes the invasion of cervical cancer cells. Western blotting indicated that ERK1/2 phosphorylation began to increase when 1 : 100 semen was added; with increasing semen concentration, ERK1/2 phosphorylation was significantly up-regulated, and the expression of its downstream target gene, c-myc, was also up-regulated (p < 0.05).

CONCLUSIONS

Semen promoted the proliferation of HeLa cells by activating the ERK pathway and showed increased tumorigenic potential in vivo. Human seminal plasma might be a potential factor contributing to the development of cervical cancer.

ARHGAP1 overexpression inhibits proliferation, migration and invasion of C-33A and SiHa cell lines

ARHGAP1, also known as RhoGAP, RhoGAP1, CDC42GAP and p50rhoGAP, is officially named Ras homology (Rho) GTPase-activating protein 1, which is one of the key members of RhoGAPs. Growing evidences demonstrate that several RhoGAPs are suppressed or downregulated in cancers. Thus, the aim of this study was to explore the effects of ARHGAP1 on cervical carcinoma cells. The human cervical carcinoma cells C-33A and SiHa were transduced with lentivirus targeting ARHGAP1 (lenti-ARHGAP1). Cellular proliferation, migration and invasion assays, as well as quantitative real-time polymerase chain reaction and Western blot assays, were performed in the control, negative control (infected with lentivirus) and ARHGAP1+-infected groups. Results showed that overexpression of ARHGAP1 markedly inhibited the proliferation of both C-33A and SiHa cells at 24 h, 48 h and 72 h in a time-dependent manner (n=3, P<0.01). Migration and invasion of C-33A and SiHa cells were suppressed after the transduction with lenti-ARHGAP1 compared with the controls (n=3, P<0.01). In addition, several tumor cellular process-related proteins, such as matrix metallopeptidase 2, zinc finger E-box binding homeobox 1, Cyclin B1, twist family bHLH transcription factor 1 and proliferating cell nuclear antigen, were all downregulated in ARHGAP1-overexpressed C-33A and SiHa cells and proved to be targets of ARHGAP1. This study indicated that ARHGAP1 may have a positive function on antitumor activity in the treatment of cervical cancer.

Pedrosa F, Souza EM, Costa FF, Klassen G. Fibronectin affects transient MMP2 gene expression through DNA demethylation changes in non-invasive breast cancer cell lines

Metastasis accounts for more than 90% of cancer deaths. Cells from primary solid tumors may invade adjacent tissues and migrate to distant sites where they establish new colonies. The tumor microenvironment is now recognized as an important participant in the signaling that induces cancer cell migration. An essential process for metastasis is extracellular matrix (ECM) degradation by metalloproteases (MMPs), which allows tumor cells to invade local tissues and to reach blood vessels. The members of this protein family include gelatinase A, or MMP-2, which is responsible for the degradation of type IV collagen, the most abundant component of the basal membrane, that separates epithelial cells in the stroma. It is known that fibronectin is capable of promoting the expression of MMP-2 in MCF7 breast cancer cells in culture. In addition, it was already shown that the MMP2 gene expression is regulated by epigenetic mechanisms. In this work, we showed that fibronectin was able to induce MMP2 expression by 30% decrease in its promoter methylation. In addition, a histone marker for an open chromatin conformation was significantly increased. These results indicate a new role for fibronectin in the communication between cancer cells and the ECM, promoting epigenetic modifications.

Laminin induces matrix metalloproteinase-9 expression and activation in human cervical cancer cell line (SiHa)

PURPOSE

Interaction between cell surface integrin receptors and extracellular matrix (ECM) components plays an important role in cell survival, proliferation and migration including tumor development and invasion. Matrix metalloproteinases (MMP) are a family of metalloproteinases capable of digesting ECM and facilitate cell migration. Binding of ECM to integrins initiates signaling cascades modulating expression and activity of different MMPs. The present study investigates whether laminin-mediated signaling modulates matrix metalloproteinases (MMP) expression and activity in human cervical cancer cell (SiHa).

METHODS

Western blot, immunocytochemistry, ELISA, zymography, RT-PCR, EMSA and wound-healing assay were used.

RESULTS

Culture of SiHa cells on laminin (LN)-coated surface induces MMP-9 expression and activation. Wound-healing assay showed that SiHa cells migrate much faster on laminin-coated surface than that of control. LN-induced MMP-9 expression and activation was appreciably reduced with treatment of extracellular signal-regulated kinase (ERK) inhibitor, phosphatidylinositol-3-kinase (PI-3K) inhibitor and anti-α2 antibody. Phosphorylation of focal adhesion kinase (FAK), ERK, and PI-3K was increased upon LN stimulation. LN induces nuclear translocation of PI-3K and nuclear factor kappa B (NF-κB). LN increases DNA-binding activity of NF-κB and activator protein-1 (AP-1) to MMP-9 promoter.

CONCLUSIONS

Our findings indicate laminin-induced MMP-9 expression and activation possibly via α2β1 integrin-mediated signaling involving FAK, PI-3K, ERK followed by transcriptional upregulation of MMP-9.

Expression of integrins and Toll-like receptors in cervical cancer: effect of infectious agents

We hypothesized that development of cervical cancer is associated with alterations in the expression of innate immune receptors, i.e. integrins and TLRs, and that these alterations can be induced by infectious agents. We have studied the expression of these proteins in cervical biopsy tissues and cervical cancer-derived cell lines HeLa, CaSki, SiHa, C-33 A, and ME180. Immunohistochemistry analysis demonstrated an increase in integrin αv, β3, β4, and β6 expression in the epithelium during the development of cervical cancer. A clear trend towards higher expression of integrin β6 in cell lines harbouring human papillomavirus (HPV) genetic material, compared to HPV-negative C-33 A, was observed. To investigate whether bacterial infection can alter the expression of TLRs and integrins, we infected HeLa cells by two pathogens, Escherichia coli and Pseudomonas aeruginosa, using a common bacterium of the female genital tract, Lactobacillus reuteri, as a control. Infection with E. coli or P. aeruginosa, but not with L. reuteri, significantly altered the expression of TLR and integrins, particularly of TLR4 and integrin β6. Considering that both integrin β6 and TLR4 play important roles in tumorigenesis, our data suggest that bacterial infection may trigger cancer development in HPV-infected cervical epithelium.

Expression pattern of matrix metalloproteinases in human gynecological cancer cell lines

Background

Matrix metalloproteinases (MMPs) are involved in the degradation of protein components of the extracellular matrix and thus play an important role in tumor invasion and metastasis. Their expression is related to the progression of gynecological cancers (e.g. endometrial, cervical or ovarian carcinoma). In this study we investigated the expression pattern of the 23 MMPs, currently known in humans, in different gynecological cancer cell lines.

Methods

In total, cell lines from three endometrium carcinomas (Ishikawa, HEC-1-A, AN3 CA), three cervical carcinomas (HeLa, Caski, SiHa), three chorioncarcinomas (JEG, JAR, BeWo), two ovarian cancers (BG-1, OAW-42) and one teratocarcinoma (PA-1) were examined. The expression of MMPs was analyzed by RT-PCR, Western blot and gelatin zymography.

Results

We demonstrated that the cell lines examined can constitutively express a wide variety of MMPs on mRNA and protein level. While MMP-2, -11, -14 and -24 were widely expressed, no expression was seen for MMP-12, -16, -20, -25, -26, -27 in any of the cell lines. A broad range of 16 MMPs could be found in the PA1 cells and thus this cell line could be used as a positive control for general MMP experiments. While the three cervical cancer cell lines expressed 10-14 different MMPs, the median expression in endometrial and choriocarcinoma cells was 7 different enzymes. The two investigated ovarian cancer cell lines showed a distinctive difference in the number of expressed MMPs (2 vs. 10).

Conclusions

Ishikawa, Caski, OAW-42 and BeWo cell lines could be the best choice for all future experiments on MMP regulation and their role in endometrial, cervical, ovarian or choriocarcinoma development, whereas the teratocarcinoma cell line PA1 could be used as a positive control for general MMP experiments.

Benzyl isothiocyanate (BITC) inhibits migration and invasion of human gastric cancer AGS cells via suppressing ERK signal pathways

Metastasis suppressors and associated other regulators of cell motility play a critical initial role in tumor invasion and metastases. Benzyl isothiocyanate (BITC) is a hydrolysis compound of glucotropaeolin in dietary cruciferous vegetables. BITC has been found to exhibit prevention of cancers in laboratory animals and might also be chemoprotective in humans. Here, the purpose of this study was to investigate the effects of BITC on cell proliferation, migration, invasion and mitogen-activated protein kinase (MAPK) pathways of AGS human gastric cancer cells. Wound healing and Boyden chamber (migration and invasion) assays demonstrated that BITC exhibited an inhibitory effect on the abilities of migration and invasion in AGS cancer cells. BITC suppressed cell migration and invasion of AGS cells in a dose-dependent manner. Results from Western blotting indicated that BITC exerted an inhibitory effect on the ERK1/2, Ras, GRB2, Rho A, iNOS, COX-2 for causing the inhibitions of MMP-2, -7 and -9 then followed by the inhibitions of invasion and migration of AGS cells in vitro. BITC also promoted MKK7, MEKK3, c-jun, JNK1/2, VEGF, Sos1, phosphoinositide 3-kinase (PI3K), PKC, nuclear factor-kappaB (NF-κB) p65 in AGS cells. Results from real-time polymerized chain reaction (PCR) showed that BITC inhibited the gene expressions of MMP-2,-7 -9, FAK, ROCK1 and RhoA after BITC treatment for 24 and 48 hours in AGS cells. Taken together, the finding may provide new mechanisms and functions of BITC, which inhibit migration and invasion of human gastric cancer AGS cells.

Fibronectin-integrin mediated signaling in human cervical cancer cells (SiHa)

Interaction between cell surface integrin receptors and extracellular matrix (ECM) components plays an important role in cell survival, proliferation, and migration, including tumor development and invasion of tumor cells. Matrix metalloproteinases (MMPs) are a family of metalloproteinases capable of digesting ECM components and are important molecules for cell migration. Binding of ECM to integrins initiates cascades of cell signaling events modulating expression and activity of different MMPs. The aim of this study is to investigate fibronectin-integrin-mediated signaling and modulation of MMPs. Our findings indicated that culture of human cervical cancer cell (SiHa) on fibronectin-coated surface perhaps sends signals via fibronectin-integrin-mediated signaling pathways recruiting focal adhesion kinase (FAK) extracellular signal regulated kinase (ERK), phosphatidyl inositol 3 kinase (PI-3K), integrin-linked kinase (ILK), nuclear factor-kappa B (NF-kappaB), and modulates expression and activation of mainly pro-MMP-9, and moderately pro-MMP-2 in serum-free culture medium.

Multifunctional effect of epigallocatechin-3-gallate (EGCG) in downregulation of gelatinase-A (MMP-2) in human breast cancer cell line MCF-7

AIMS

The tumor inhibiting property of green tea polyphenol epigallocatechin-3-gallate (EGCG) is well documented. Studies reveal that matrix-metalloproteinases (MMPs) play pivotal roles in tumor invasion through degradation of basement membranes and extracellular matrix (ECM). We studied the effect of EGCG on matrixmetalloproteinases-2 (MMP-2), the factors involved in activation, secretion and signaling molecules that might be involved in the regulation of MMP-2 in human breast cancer cell line, MCF-7.

MAIN METHODS

MCF-7 was treated with EGCG (20 muM, 24 h), the effect of EGCG on MMP-2 expression, activity and its regulatory molecules were studied by gelatin zymography, Western blot, quantitative and semi-quantitative real time RT-PCR, immunoflourescence and cell adhesion assay.

KEY FINDINGS

EGCG treatment reduced the activity, protein expression and mRNA expression level of MMP-2. EGCG treatment reduced the expression of focal adhesion kinase (FAK), membrane type-1-matrix metalloproteinase (MT1-MMP), nuclear factor-kappa B (NF-kB), vascular endothelial growth factor (VEGF) and reduced the adhesion of MCF-7 cells to ECM, fibronectin and vitronectin. Real time RT-PCR revealed a reduced expression of integrin receptors alpha5, beta1, alphav and beta3 due to EGCG treatment.

SIGNIFICANCE

Down regulation of expression of MT1-MMP, NF-kB, VEGF and disruption of functional status of integrin receptors may indicate decreased MMP-2 activation; low levels of FAK expression might indicate disruption in FAK-induced MMP-2 secretion and decrease in activation of phosphatidyl-inositol-3-kinase (PI-3K), extracellular regulated kinase (ERK) indicates probable hindrance in MMP-2 regulation and induction. We propose EGCG as potential inhibitor of expression and activity of pro-MMP-2 by a process involving multiple regulatory molecules in MCF-7.

Epithelial-mesenchymal transition in cervical cancer: correlation with tumor progression, epidermal growth factor receptor overexpression, and snail up-regulation

PURPOSE

Acquisition of epithelial-mesenchymal transition (EMT) by primary carcinoma cells is associated with disrupted epithelial integrity, local invasion, and ultimately metastasis. Little is known about the existence and function of EMT in cervical cancer. This study aims to investigate the regulation of EMT in cervical squamous cell carcinoma.

EXPERIMENTAL DESIGN

We investigated the molecular events of EMT in surgical specimens, which present the progression of cervical carcinoma. Two cervical cancer cell lines and the primary culture of normal cervical epithelia were used to study the regulatory mechanisms of EMT.

RESULTS

The chronic epidermal growth factor (EGF) treatment induces the elongation of cell shape, increases cell scattering, and enhances cell invasion. EGF treatment down-regulates E-cadherin and up-regulates vimentin in cervical cancer cells. These characteristics are consistent with the morphologic changes, molecular events, and functional significance of EMT. EGF receptor (EGFR) signaling inactivates glycogen synthase kinase-3beta, which results in the nuclear accumulation of up-regulated Snail and then leads to EMT program. alpha(5)beta(1) integrin signaling and extracellular matrix fibronectin can modulate EGF-induced EMT. Importantly, the immunofluorescent stainings of surgical specimens indicate that cervical carcinoma progression is accompanied by EGFR overexpression, which is in parallel with decreased E-cadherin and increased vimentin. Up-regulation and nuclear accumulation of Snail correlate with EMT program in tumor tissues.

CONCLUSION

EGF cooperates with alpha(5)beta(1) integrin signaling to induce EMT in cervical cancer cells via up-regulated Snail. Blockade of EGFR activity or expression may provide a potential target for the treatment of cervical cancer progression.

Benzyl isothiocyanate inhibits metalloproteinase-2/-9 expression by suppressing the mitogen-activated protein kinase in SK-Hep1 human hepatoma cells

Benzyl isothiocyanate (BITC) is a hydrolysis compound of glucotropaeolin in cruciferous vegetables. Many studies have reported that BITC prevents cancers in laboratory animals and might also be chemoprotective in humans. The purpose of this study was to investigate the effects of BITC on cell proliferation, metastasis, and MAPK pathways of SK-Hep1 human hepatocellular carcinoma cells. BITC suppressed SK-Hep1 cell proliferation in a dose-dependent manner, and exposure to 1 and 5 microM BITC reduced cell proliferation by 25% and 30%, respectively. The expression of matrix metalloproteinase (MMP)-2, MMP-9, and membrane type-1/MMP (MT-1/MMP) is a known risk factor for metastatic disease. Gelatin zymography analysis revealed a significant downregulation of MMP-2/-9 protein expression in SK-Hep1 cells treated with 0.1-5 microM BITC. BITC treatment caused dose-dependent decreases in MMP-2/-9 and MT1-MMP mRNA levels as determined by RT-PCR. BITC also increased the mRNA levels of tissue inhibitors of matrix metalloproteinases-2 (TIMP-2) 1.3- and 1.5-fold after a 24 h exposure to 1 and 5 microM BITC, respectively. Increased TIMP-2 expression is mediated by the downregulation of MMP-2 and MT1-MMP. BITC inhibited the phosphorylation activities of all three major mitogen-activated protein kinases (MAPKs) in a dose-dependent manner. BITC at 5 microM reduced the ERK1/2 phosphorylation activity by 50% and p38 activity by 70%. BITC also reduced the p-JNK1/2 level by 30% and 70% at 1 and 5 microM treatments, respectively. These data may represent anti-metastatic activities of BITC through the suppression of MAPKs in SK-Hep1 cells.

Rapid expression and activation of MMP-2 and MMP-9 upon exposure of human breast cancer cells (MCF-7) to fibronectin in serum free medium

Interactions between tumour cells and the extracellular matrix (ECM) strongly influence tumour development, affecting cell survival, proliferation and migration. Many of these interactions are mediated through a family of cell surface receptors named integrins. Fibronectin and its integrin receptors play important roles in tumour development. The alpha5beta 1 integrin interacts with the central cell adhesive region of fibronectin and requires both the RGD and synergy sites for maximal binding. Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases. They are capable of digesting the different components of the ECM and basement membrane. The ECM gives structural support to cells and plays a central role in cell adhesion, differentiation, proliferation and migration. Binding of ECM to integrins modulates expression and activity of the different MMPs. Our experimental findings demonstrate that cultivation of human breast cancer cells, MCF-7, in serum free medium in the presence of fibronectin upregulates the activity of MMP-2 and MMP-9. Blocking of alpha5beta 1 integrin with anti-alpha5 monoclonal antibody inhibits the fibronectin-induced MMP activation response appreciably. This strongly indicates alpha5beta 1 mediated signalling events in activation of MMP-2 and MMP-9. Phosphorylation of FAK and PI-3 kinase and the nuclear translocation of ERK and NF-kappaB upon fibronectin binding demonstrate possible participation of the FAK/PI-3K/ERK signalling pathways in the regulation of MMP-2 activity.

Membrane-type 1 matrix metalloproteinase is regulated by sp1 through the differential activation of AKT, JNK, and ERK pathways in human prostate tumor cells

We and other investigators have previously shown that membrane-type 1 matrix metalloproteinase (MT1-MMP) is overexpressed in invasive prostate cancer cells. However, the mechanism for this expression is not known. Here, we show that MT1-MMP is minimally expressed in nonmalignant primary prostate cells, moderately expressed in DU-145 cells, and highly expressed in invasive PC-3 and PC-3N cells. Using human MT1-MMP promoter reporter plasmids and mobility shift assays, we show that Sp1 regulates MT1-MMP expression in DU-145, PC-3, and PC-3N cells and in PC3-N cells using chromatin immunoprecipitation analysis and silencing RNA. Investigation of signaling pathway showed that DU-145 cells express constitutively phosphorylated extracellular stress-regulated kinase (ERK), whereas PC-3 and PC-3N cells express constitutively phosphorylated AKT/PKB and c-Jun NH2 terminal kinase (JNK). We show that MT1-MMP and Sp1 levels are decreased in PC-3 and PC-3N cells when phosphatidylinositol-3 kinase and JNK are inhibited, and that MT1-MMP levels are decreased in DU-145 cells when MEK is inhibited. Transient transfection of PC-3 and PC-3N cells with a dominant-negative JNK or p85, and of DU-145 cells with a dominant negative ERK, reduces MT1-MMP promoter activity. These results indicate differential signaling control of Sp1-mediated transcriptional regulation of MT1-MMP in prostate cancer cell lines.

MMP-2 functions as a negative regulator of chondrogenic cell condensation via down-regulation of the FAK-integrin beta1 interaction

Matrix metalloprotease-2 (MMP-2) has the capacity to degrade cartilage extracellular matrix molecules, the turnover of which is an essential event in chondrogenesis. Here, we investigated the functional role of MMP-2 in chondrogenesis of leg bud mesenchymal cells. Small interference RNA (siRNA)-mediated knockdown of mmp-2 promoted precartilage condensation and chondrogenesis. Treatment with bafilomycin A1, an MMP-2 activator, or GM6001, an MMP inhibitor, at the pre-condensation stage resulted in the inhibition or promotion of chondrogenesis, respectively. By comparison, treatment at the post-condensation stage had little or no effect on chondrogenesis. These results indicate that MMP-2 is involved in the regulation of cell condensation. Inhibition of MMP-2 activity by mmp-2 specific siRNA increased the protein level of fibronectin, and integrins alpha5 and beta1. The interaction between focal adhesion kinase (FAK) and integrin beta1 leading to tyrosine phosphorylation of FAK was also enhanced. Moreover, inactivation of p38MAPK down-regulated the level of MMP-2 mRNA and activity, and increased mesenchymal cell condensation in parallel with enhanced phosphorylation of FAK. Taken together, our data indicate that MMP-2 mediates the inhibitory signals of p38MAPK during mesenchymal cell condensation by functioning as a negative regulator of focal adhesion activity regulated by FAK via interactions with fibronectin through integrin beta1.