Overexpression of the met/HGF receptor in renal cell carcinomas

The c-met oncogene encodes the receptor for hepatocyte growth factor/scatter factor (HGF/SF), a multifunctional cytokine able to mediate morphogenesis as well as mitogenesis, motogenesis and invasiveness of epithelial cells. HGF/SF has been implicated in branching tubulogenesis of the developing kidney and in regeneration after renal injury and nephrectomy. We have examined the expression of the met/HGF receptor in normal human kidney and tissues of the genito-urinary tract, and in 50 kidney neoplasms of different histotypes, using monoclonal antibodies (MAbs) against the met/HGF receptor and immunohistochemistry. In normal kidneys, weak staining restricted to the distal tubules was observed. Transitional cell carcinomas were consistently negative, whereas increased expression at various levels was found in 87% of renal cell carcinomas with different cytological features and histological patterns. Western blot analysis of samples showed that the met/HGF receptor found in the malignant cells exhibits features of the normal receptor. The met/HGF receptor is also overexpressed in a renal cell carcinoma cell line, whose motility is triggered by HGF/SF. Our data suggest that expression of the met/HGF receptor may be involved in the onset and progression of renal cell carcinomas. © 1996 Wiley-Liss, Inc.     

Overexpression of the c-MET/HGF receptor gene in human thyroid carcinomas.

The receptor for Hepatocyte Growth Factor is a transmembrane tyrosine kinase encoded by the c-MET oncogene. We have previously shown that the Met protein is expressed in several human epithelial tissues. The receptor is barely detectable, however, in normal thyroids and in specimens from patients affected by non-neoplastic thyroid diseases. Now we report that the expression of the Met/HGF receptor is increased a hundred fold in 22 out of 41 human carcinomas derived from the thyroid follicular epithelium. A comprehensive analysis of 15 cases showed that the overexpressing carcinomas belong to histotype variants correlated with negative prognosis and in all but one case there were evidences of locally advanced disease and/or distant metastases. The 11 benign adenomas and the 5 medullary carcinomas tested were negative. Western blot analysis with monoclonal antibodies directed against either the intracellular or the extracellular receptor domains failed to reveal major structural alterations. Southern blot analysis also demonstrated that the c-MET gene was not amplified nor rearranged. These data suggest a role for the overexpression of c-MET oncogene in the pathogenesis and progression of thyroid tumors derived from the follicular epithelium.     

The emerging role of MET/HGF inhibitors in oncology

The N-methyl-N′-nitroso-guanidine human osteosarcoma transforming gene (MET) receptor tyrosine kinase and its ligand hepatocyte growth factor (HGF) control cellular signaling cascades that direct cell growth, proliferation, survival, and motility. Aberrant MET/HGF activation has been observed in many tumor types, can occur by multiple mechanisms, and promotes cellular proliferation and metastasis via growth factor receptors and other oncogenic receptor pathways. Thus, MET/HGF inhibition has emerged as targeted anticancer therapies. Preclinically, neoplastic and metastatic phenotypes of several tumor cells, including non-small cell lung cancer, hepatocellular carcinoma, and gastric cancer, were abrogated by MET inhibition. Ongoing clinical development with tivantinib, cabozantinib, onartuzumab, crizotinib, rilotumumab, and ficlatuzumab has shown encouraging results. These trials have established a key role for MET in a variety of tumor types. Evidence is emerging for identification of aberrant MET activity biomarkers and selection of patient subpopulations that may benefit from targeted MET and HGF inhibitor treatment.     

HGF/c-Met axis drives cancer aggressiveness in the neo-adjuvant setting of ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy. Recently, NACT (Neo Adjuvant Chemotherapy) has been tested as alternative approach for the management of ovarian cancer patients. A biological predictor helpful in selecting patients for NACT would be desirable. This study was aimed at identifying actionable mechanisms of resistance to NACT.Expression of a panel of microRNAs was screened in a discovery set of 85 patients. Analysis of the potential targets was conducted in the same RNAs by calculating significant correlations between microRNAs and genes. Quantitative fluorescent immunohistochemistry was employed in a validation set of 109 patients.MiR-193a-5p was significantly overexpressed in the NACT setting. Analysis of its potential targets demonstrated that this microRNA is also significantly correlated with HGF and MET genes. Analysis of protein expression in samples taken before and after NACT demonstrated that both HGF and c-Met are increased after NACT. Patients who relapse shortly after NACT exhibited the highest relative basal expression of both HGF and c-Met, while the opposite phenomenon was observed in the best responders.Mir-193a-5p, HGF and c-Met expression may help select eligible patients for this modality of treatment. Moreover, inhibitors of this pathway may improve the efficacy of NACT.     

Overexpression of follicle-stimulating hormone receptor facilitates the development of ovarian epithelial cancer

We previously showed that the expressing level of FSH receptor (FSHR) increased from ovarian epithelial inclusions (OEIs) to benign ovarian epithelial tumors (OETs) and to borderline OETs, whereas FSHR levels decreased with an increase in carcinoma grade. The aim of this study was to investigate the role of FSHR in OET development. MCV152 cells with FSHR overexpression showed an increased cellular proliferation and invasive capacity, which was associated with reduced levels of prohibitin and RII-β expression and increased levels of HER-2/neu, c-Myc, and EGFR expression. Overexpression of FSHR may be associated with an elevated level of OET cell proliferation via an enhanced activity of potential oncogenic pathways. Therefore, the findings in this study suggest that overexpression of FSHR may play a role in OET development.     

Overexpression of leptin receptor predicts an unfavorable outcome in Middle Eastern ovarian cancer

Background  

Recent epidemiological studies have suggested that obesity is associated with ovarian cancer. Obesity hormone leptin and its receptor (Ob-R) contribute to tumor development by enhancing cell growth and survival. This study was design to investigate the prevalence of leptin and Ob-R in Middle Eastern epithelial ovarian cancer (EOC) and to analyze the role of leptin and the mechanisms under its action in EOC tissue sample and cell lines.     

NDRG2调控HGF/c-MET通路抑制结肠癌细胞的增殖

目的:探讨抑癌基因NDRG2通过调节HGF/c-MET信号通路,抑制结肠癌HT29细胞增殖的机制。方法:建立NDRG2过表达细胞株HT29-NDRG2及对照组HT29-Cherry,并于第1、2、3、4、5天以MTT法检测细胞增殖;以不同浓度的HGF（0ng/ml、1ng/ml、2ng/ml、4ng/ml、8ng/ml、10ng/ml）刺激HT29亲本细胞,并于第1、2、3天以MTT法检测HT29细胞的增殖;采用qPCR法检测NDRG2过表达细胞株HT29-NDRG2与对照组HT29-Cherry两组细胞中HGF的表达水平;Western blot检测HT29-Cherry和HT29-NDRG2两组细胞以及添加HGF（10ng/ml）刺激HT29亲本细胞后各组细胞中HGF/c-MET通路中关键分子的表达。结果:过表达NDRG2以及HGF刺激均可以显著抑制HT29细胞的增殖能力;NDRG2的高表达可以上调HGF的转录水平;HGF可以刺激c-MET和p-ERK1/2,并上调p 21和p 27,抑制HT29细胞的增殖;过表达NDRG2明显上调c-MET、p-ERK1/2,并诱导p 21和p 27的高表达,从而抑制HT29细胞的增殖。结论:NDRG2可以通过调节HGF/c-MET信号通路从而抑制结肠癌细胞HT29细胞的增殖能力。     

Overexpression of H-Ryk in epithelial ovarian cancer: prognostic significance of receptor expression.

H-Ryk is an atypical receptor tyrosine kinase that is expressed in a differentiation-specific manner in epithelial tissues. We have previously shown by in situ hybridization and immunohistochemistry that H-Ryk is overexpressed in malignant ovarian tumors. In addition, we have demonstrated that overexpression of H-Ryk is transforming in vitro and in vivo. To evaluate whether expression of H-Ryk is a prognostic factor in epithelial ovarian cancer, we carried out a retrospective study of 88 primary malignant ovarian tumors (28 serous tumors, 11 mucinous tumors, 29 endometrioid tumors, 13 clear cell tumors, 3 malignant mixed Mullerian tumors, 1 mixed epithelial tumor, 1 primary peritoneal tumor, 1 undifferentiated tumor, and 1 transitional carcinoma) diagnosed between 1990 and 1993 using immunohistochemistry. On univariate analysis, overall survival decreased significantly with age (P = 0.01); in patients with International Federation of Gynecology and Obstetrics (FIGO) stage II (P = 0.008), FIGO stage III (P < 0.001), and FIGO stage IV (P < 0.001) disease; and in patients with residual disease (residual disease < or = 2 cm, P = 0.007; residual disease > 2 cm, P < 0.001) after surgery. In addition, overexpression of the H-Ryk receptor in malignant epithelium (P = 0.04) and blood vessel (P = 0.01) was associated with a significantly decreased overall survival. H-Ryk blood vessel overexpression (P = 0.03), residual disease > 2 cm (P = 0.006), and residual disease < or = 2 cm (P = 0.01) conferred a significantly shorter progression-free survival. No correlation was found between H-Ryk overexpression and age, histological subtype, degree of differentiation, FIGO stage, or residual disease. Overall, after adjustment for all of the prognostic factors by multivariate analysis (Cox proportional hazards model), residual disease was the most powerful prognostic indicator for overall survival (P < 0.001) and progression-free survival (P = 0.01) in this patient subset. This implies that H-Ryk acts cooperatively with other biological factors in the pathogenesis of ovarian cancer.     

miR-130a-3p通过HGF/MET信号通路抑制乳腺癌细胞MCF-7 侵袭

目的：探究miR-130a-3p 通过HGF/MET信号通路调控上皮间质转化（epithelial-mesenchymal transition,EMT）影响乳腺癌细胞侵袭转移的分子机制。方法：收集承德医学院附属医院2018 年1 月至10 月收治的22 例乳腺癌患者癌组织和配对癌旁组织标本,乳腺癌细胞系（MCF-7、MDA-MB-231 和MDA-MB-453）和正常乳腺上皮细胞MCF10A来自承德医学院基础研究所,然后采用qPCR检测组织和细胞系中miR-130a-3p 的表达情况;将实验分为对照组、miR-130a-3p mimics 组、miR-130a-3p inhibitor组、PHA665752（MET小分子抑制剂）转染组及共转PHA665752+miR-130a-3p inhibitor 组,然后采用CCK-8 法和Transwell 实验分别检测MCF-7 细胞增殖活力、侵袭和迁移能力;WB实验检测MCF-7 细胞EMT和HGF/MET信号通路相关蛋白的表达情况;此外,采用双荧光素酶报告基因检测miR-130a-3p 与MET之间的靶向关系。结果：miR-130a-3p 在乳腺癌组织和细胞系中呈低表达;过表达miR-130a-3p 可抑制MCF-7 细胞增殖、侵袭、迁移和EMT;而抑制miR-130a-3p 出现相反的结果。双荧光素酶报告基因结果证实miR-130a-3p 靶向下调MET的表达水平,且miR-130a-3p 负调控HGF/MET信号通路的表达;进一步实验证明,miR-130a-3p 通过阻断HGF/MET信号通路抑制MCF-7 细胞增殖、侵袭、迁移和EMT。结论：miR-130a-3p 通过阻断HGF/MET信号通路抑制MCF-7 细胞EMT过程,进而抑制MCF-7 细胞侵袭转移。     

Targeting the HGF/Met signalling pathway in cancer

Under normal conditions, hepatocyte growth factor (HGF)-induced Met tyrosine kinase (TK) activation is tightly regulated by paracrine ligand delivery, ligand activation at the target cell surface, and ligand activated receptor internalisation and degradation. Despite these controls, HGF/Met signalling contributes to oncogenesis and tumour progression in several cancers and promotes aggressive cellular invasiveness that is strongly linked to tumour metastasis. The prevalence of HGF/Met pathway activation in human malignancies has driven rapid growth in cancer drug development programmes. Pathway inhibitors can be divided broadly into biologicals and low molecular weight synthetic TK inhibitors; of these, the latter now outnumber all other inhibitor types. We review here the basic properties of HGF/Met pathway antagonists now in preclinical and clinical development as well as the latest clinical trial results. The main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment include optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of optimal therapy combinations. The wealth of basic information, analytical reagents and model systems available concerning HGF/Met oncogenic signalling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective disease control.     

Overexpression and mutation of p53 in epithelial ovarian cancer

We examined p53 expression in 107 epithelial ovarian cancers with immunohistochemical techniques using monoclonal antibody PAb1801. High level expression of nuclear p53 protein was detected in the malignant epithelium in 54 (50%) of these cancers. Expression of p53 protein was undetectable in 13 benign gynecological tissues. p53 mRNA from three cancers that overexpressed the protein were sequenced and point mutations which altered the coding sequence of the highly conserved region of the gene were found in each case. Three cancers with undetectable protein levels also were sequenced and were found to be wild-type through the same region of the gene. As in other cancers, overexpression of the p53 protein in ovarian cancer appears to correlate closely with the presence of mutation in the p53 gene. p53 overexpression did not correlate with stage, histological grade, or the ability to perform optimal cytoreductive surgery. A significant correlation (P = 0.04) was observed between p53 overexpression and aneuploidy in advanced stage (III/IV) disease. There was no significant relationship between overall survival and p53 expression. Since mutation and overexpression of p53 are common in epithelial ovarian cancers, further studies are warranted to clarify the role of p53 in ovarian tumorigenesis.     

Prognostic relevance of longitudinal HGF levels in serum of patients with ovarian cancer

The pleiotropic protein hepatocyte growth factor (HGF) is the only known ligand of the tyrosine kinase mesenchymal–epithelial transition (cMET) receptor. The HGF/cMET pathway mediates invasion and migration of ovarian cancer cells, and upregulation of HGF/cMET pathway components has been associated with poor prognosis. This study investigated the clinical relevance of circulating HGF in serum of patients with ovarian cancer. Serum HGF (sHGF) was determined by enzyme‐linked immunosorbent assay in a total of 471 serum samples from 82 healthy controls and 113 patients with ovarian cancer (88.5% with ≥ FIGO III). Patient samples were collected at primary diagnosis and at four follow‐up time points throughout treatment and at disease recurrence. Patients with ovarian cancer showed elevated median sHGF levels at primary diagnosis, and sHGF levels transiently increased after surgery and normalized in the course of chemotherapy, even dropping below initial baseline. Higher levels of sHGF were an independent predictor for shorter overall survival (OS) (a) at primary diagnosis (HR = 0.41, 95% CI: 0.22–0.78, P = 0.006), (b) at longitudinal follow‐up time points (after surgery and before/during/after chemotherapy), (c) along the patients’ individual dynamics (HR = 0.21, 95% CI: 0.07–0.63, P = 0.005), and (d) among a subgroup analysis of patients with BRCA1/2 wild‐type ovarian cancer. This is the first study proposing sHGF as an independent prognostic biomarker for ovarian cancer at primary diagnosis and in the course of platinum‐based chemotherapy, irrespective of the postoperative residual disease after surgical debulking. sHGF could be implemented into clinical diagnostics as a CA125 auxiliary tumor marker for individualized prognosis stratification and sHGF‐guided therapy monitoring.     

Overexpression of HER-2/neu is associated with poor survival in advanced epithelial ovarian cancer

Previous studies have suggested that overexpression of HER-2/neu oncogene occurs in 15-40% of breast cancers and that overexpression is associated with poor prognosis. In the present report, we have used an immunohistochemical technique involving a monoclonal antibody specifically reactive with the external domain of HER-2/neu to study expression of HER-2/neu in frozen sections of normal ovary and advanced epithelial ovarian cancer. The intensity of staining for HER-2neu was always moderate or less (0-2+) in normal ovarian epithelium. Among 73 ovarian cancers, 50 (68%) had staining similar to that for normal ovarian epithelium (0-2+) while 23 (32%) stained heavily (3+). Survival of the 23 patients with high HER-2/neu expression (median, 15.7 months) was significantly worse (P = 0.001) than that of the 50 patients (median, 32.8 months) with normal HER-2/neu expression. In addition, patients whose tumors had high HER-2/neu expression were significantly less likely to have a complete response to primary therapy (P less than 0.05) or have a negative second-look laparotomy when serum CA 125 levels were normal preoperatively (P less than 0.05). These findings suggest that HER-2/neu deserves further evaluation as a prognostic marker in epithelial ovarian cancer.     

Transactivation of epidermal growth factor receptor through platelet-activating factor/receptor in ovarian cancer cells

Background

We previously identified platelet-activating factor receptor (PAFR) as being overexpressed in ovarian cancer and found that its ligand PAF evoked EGFR phosphorylation using the phospho-antibody microarray. Epidermal growth factor receptor (EGFR) are also overexpressed in ovarian cancer and contribute to the growth of ovarian cancer cells. Here, we investigated the mechanisms of crosstalk between PAFR and EGFR signaling in ovarian cancer cells to further determine whether the interaction between PAFR and EGFR synergistic contribute to the progression of ovarian cancer.

Methods

Expression and localization of PAFR in several ovarian cancer cell lines were assessed by Western blot, realtime-PCR and immunofluorescence. The ovarian cancer cells were stimulated with PAF or PAF and in some experiments also pharmacological inhibitors. Phosphorylation of proteins in signaling pathways were measured by Western blot. HB-EGF concentrations of the supernatant from stimulated ovarian cancer cells were measured by enzyme-linked immunosorbent assay.

Results

Our data show that PAF increases EGFR phosphorylation through PAFR in a time- and dose- dependent manner in SKOV-3 ovarian cancer cells. This transactivation is dependent on phospholipase C-β and intracellular calcium signaling. This pathway is also Src tyrosine kinase- and metalloproteinase- dependent. PAF triggers EGFR activation through the increased heparin-binding EGF-like growth factor (HB-EGF) release in metalloprotease-dependent manner. Several studies involving EGFR transactivation through G-protein coupled receptor (GPCR) have demonstrated EGFR-dependent increase in ERK1/2 phosphorylation. Yet in SKOV-3 cells, PAF treatment also increases ERK1/2 phosphorylation in a EGFR-independent manner.

Conclusions

The results suggest that in SKOV-3 ovarian cancer cells, PAF transactivates EGFR and downstream ERK pathways, thus diversifying the GPCR-mediated signal. The crosstalk between PAFR and EGFR suggests a potentially important signaling linkage between inflammatory and growth factor signaling in ovarian cancer cells.     

Overexpression of androgen receptor enhances the binding of the receptor to the chromatin in prostate cancer

Androgen receptor (AR) is overexpressed in the majority of castration-resistant prostate cancers (CRPCs). Our goal was to study the effect of AR overexpression on the chromatin binding of the receptor and to identify AR target genes that may be important in the emergence of CRPC. We have established two sublines of LNCaP prostate cancer (PC) cell line, one overexpressing AR 2-3-fold and the other 4-5-fold compared with the control cells. We used chromatin immunoprecipitation (ChIP) and deep-sequencing (seq) to identify AR-binding sites (ARBSs). We found that the number of ARBSs and the AR-binding strength were positively associated with the level of AR when cells were stimulated with low concentrations of androgens. In cells overexpressing AR, the chromatin binding of the receptor took place in 100-fold lower concentration of the ligand than in control cells. We confirmed the association of AR level and chromatin binding in two PC xenografts, one containing AR gene amplification with high AR expression, and the other with low expression. By combining the ChIP-seq and expression profiling, we identified AR target genes that are upregulated in PC. Of them, the expression of ZWINT, SKP2 (S-phase kinase-associated protein 2 (p45)) and FEN1 (flap structure-specific endonuclease 1) was demonstrated to be increased in CRPC, while the expression of SNAI2 was decreased in both PC and CRPC. FEN1 protein expression was also associated with poor prognosis in prostatectomy-treated patients. Finally, the knock-down of FEN1 with small interfering RNA inhibited the growth of LNCaP cells. Our data demonstrate that the overexpression of AR sensitizes the receptor binding to chromatin, thus, explaining how AR signaling pathway is reactivated in CRPC cells.     

MET receptor is a potential therapeutic target in high grade cervical cancer

Cervical cancer is one of the leading causes of death among women suffering from tumors. Current treatment options are insufficient. Here, we investigated the MET receptor as a potential molecular target in advanced cervical cancer. Downregulation of MET receptor expression via RNA interference in different cervical carcinoma cell lines dramatically decreased tumor growth and forced tumor differentiation in vivo. MET receptor silencing also led to a dramatic decrease in cell size and a decrease in proliferation rate under normal and stress conditions. MET receptor downregulation also resulted in decreased cyclin D1 and c-myc levels but did not increase apoptosis. Subsequent experiments showed that downregulation of the MET receptor decreased the expression of a key regulator of the epithelial-to-mesenchymal transition, SLUG. and increased the expression of E-cadherin, a hallmark of the epithelial phenotype. Moreover, MET downregulation impairs expression and signaling of CXCR4 receptor, responsible for invasive phenotype.Taken together, our results strongly suggest that the MET receptor influences the oncogenic properties of cervical carcinoma cells in vitro and in vivo. These findings highlight a unique role of the MET receptor in cervical carcinoma cells and indicate the MET receptor as a potential therapeutic target for advanced cervical carcinoma.     

Role of the IL-33/ST2 receptor axis in ovarian cancer progression

Ovarian cancer remains a significant health problem for women in the world due to its diagnosis at advanced stages of disease and the high mortality rate of patients. To date, ovarian cancer is frequently treated with tumor reduction surgery followed by platinum/paclitaxel-based chemotherapy; however, most patients eventually develop relapsed disease. The mRNA expression levels of interleukin-33 (IL-33) and the suppressor of tumorigenicity 2 (ST2) receptor are significantly upregulated in ovarian cancer tissues and metastatic tumor lesions. In addition, IL-33 and ST2 expression has been associated with a poor overall survival in patients with epithelial ovarian cancer. The IL-33 receptor ST2 is expressed as both a membrane-anchored receptor (ST2L) activated by IL-33, and as a soluble variant that exhibits anti-inflammatory properties. In the present review, the functions of the IL-33/ST2L axis in cells and their aberrant expression levels in ovarian cancer were discussed. In addition, targeting their expression as a novel strategy for the control of ovarian cancer progression was emphasized.     

Increased MET and HGF gene copy numbers are associated with trastuzumab failure in HER2-positive metastatic breast cancer

Background:To investigate whether copy number gain of MET or hepatocyte growth factor (HGF) affect trastuzumab sensitivity in HER2-positive metastatic breast cancer (MBC).Methods:We analysed 130 HER2-positive MBC treated with trastuzumab-based therapy. MET and HGF gene copy numbers (GCN) were assessed by fluorescence in situ hybridisation (FISH) in primary breast cancer samples. Receiver operating characteristic analysis was applied to find the best cutoff point for both MET and HGF GCN.Results:MET FISH-positive cases (N=36, mean 3.72) had a significantly higher trastuzumab failure rate (44.4% vs 16.0%; P=0.001) and a significantly shorter time to progression (5.7 vs 9.9 months; HR 1.74; P=0.006) than MET FISH-negative cases (N=94, mean <3.72). Hepatocyte growth factor GCN was evaluated in 84 cases (64.6%). Receiver operating characteristic analysis identified 33 HGF FISH-positive patients (mean HGF GCN 3.01). HGF FISH-positive status was significantly associated with higher risk of failure (30.3% vs 7.8%; P=0.007) as compared with HGF FISH-negative cases (N=51, mean <3.01). MET and HGF FISH-positive status was highly correlated (P<0.001) and combination of both biomarkers did not increase predictive value of either considered separately.Conclusion:High GCNs of MET and HGF associate with an increased risk of trastuzumab-based therapy failure in HER2-positive MBC.     

Radiation stimulates HGF receptor/c-Met expression that leads to amplifying cellular response to HGF stimulation via upregulated receptor tyrosine phosphorylation and MAP kinase activity in pancreatic cancer cells

Hepatocyte growth factor (HGF) is a stromal-derived cytokine that plays a crucial role in invasion and metastasis of tumor cells through the interaction with HGF receptor, c-Met, which is frequently overexpressed in pancreatic cancer. The present study was designed to investigate the change in HGF receptor and HGF-mediated signaling after irradiation in pancreatic cancer cells. Six cell lines from human pancreatic cancer were included in the study. Gamma-radiation was used for irradiation treatment. The changes in expression levels of c-Met were evaluated by immunoblot and confirmed morphologically by indirect immunofluorescence staining. Whether the resultant alteration in c-Met would cascade as biologically usable signals upon HGF ligation was traced by receptor tyrosine phosphorylation analysis and mitogen activated protein kinase (MAP kinase or MAPK) activity assay. The various biological responses to HGF (including cell proliferation, cell scattering, migration and invasion) were evaluated as well. We also used a 4-kringle antagonist of HGF, NK4, to block the HGF/c-Met signaling pathway. Both immunoblot and immunofluorescent analysis showed moderate increased expression of c-Met in 3 of 6 pancreatic cancer cell lines after irradiation. The actions seemed to be dose-responsible, which began at 3 hr and reached its peak value at 24 hr following irradiation. The radiation-increased expression of c-Met could transform into magnifying receptor tyrosine phosphorylation reaction and MAP kinase activity once the ligand was added, fairly corresponding with alteration in the receptor. Sequentially, the cellular responses to HGF, including scattering and invasion but not proliferation, were enhanced. Also, in the presence of HGF, the elevated receptor could help to recover the radiation-compromised cell migration. A recombinant HGF antagonist, NK4 could effectively block these aberrant effects activated by irradiation both in molecular and cellular levels, thus suggesting the deep involvement of the c-Met/HGF pathway in the enhanced malignant potential after irradiation. These results suggest that radiation may promote HGF-induced malignant biological behaviors of certain pancreatic cancer cells through the up-regulated HGF/c-Met signal pathway. Selectively targeted blockade of the HGF/c-Met pathway could help to abolish the enforced malignant behavior of tumor cells by irradiation and therefore may improve the efficacy of radiotherapy for pancreatic cancer.