Reciprocal activating crosstalk between c-Met and caveolin 1 promotes invasive phenotype in hepatocellular carcinoma.

c-Met, the receptor for Hepatocyte Growth Factor (HGF), overexpressed and deregulated in Hepatocellular Carcinoma (HCC). Caveolin 1 (CAV1), a plasma membrane protein that modulates signal transduction molecules, is also overexpressed in HCC. The aim of this study was to investigate biological and clinical significance of co-expression and activation of c-Met and CAV1 in HCC. We showed that c-Met and CAV1 were co-localized in HCC cells and HGF treatment increased this association. HGF-triggered c-Met activation caused a concurrent rise in both phosphorylation and expression of CAV1. Ectopic expression of CAV1 accelerated c-Met signaling, resulted in enhanced migration, invasion, and branching-morphogenesis. Silencing of CAV1 downregulated c-Met signaling, and decreased migratory/invasive capability of cells and attenuated branching morphogenesis. In addition, activation and co-localization of c-Met and CAV1 were elevated during hepatocarcinogenesis. In conclusion reciprocal activating crosstalk between c-Met and CAV1 promoted oncogenic signaling of c-Met contributed to the initiation and progression of HCC.

Associations of VEGF/VEGF-receptor and HGF/c-Met promoter polymorphisms with progression/regression of retinopathy of prematurity.

PURPOSE: To determine the effect(s) of vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR-2), hepatocyte growth factor (HGF), and HGF receptor (c-Met) polymorphisms on progression/regression of retinopathy of prematurity (ROP) in premature infants. MATERIALS AND METHODS: This study comprised both a prospective analysis and a clinically relevant laboratory investigation. Enrolled were 123 Turkish preterm infants--gestational age (GA), ≤34 weeks; birth weight (BW), ≤1500 g--from a single tertiary care center. Infants were grouped as those who had undergone laser therapy (Group 1, n = 42), those with spontaneously regressed ROP (Group 2, n = 50), and those with no ROP (controls) (Group 3, n = 31). VEGF (-634) C and VEGF (-460) C polymorphisms were analyzed using the PCR-restriction fragment length polymorphism (RFLP) (PCR-RFLP) technique. VEGFR-2, HGF, and c-Met gene promoter polymorphisms were determined by direct sequencing. RESULTS: Mean GAs and BWs of infants in Groups 1 and 2 were statistically significantly lower than those of Group 3 (p = 0.001). Frequencies of VEGF (-634) C and VEGF (-460) C polymorphisms were similar for all groups. We found a +32G→A single-nucleotide polymorphism (SNP) in the promoter region of the VEGFR-2 gene. HGF and c-Met gene promoter polymorphisms were not found in any group. CONCLUSIONS: Our results indicate that there is no association between the carrier states of gene promoter polymorphisms VEGF (-634) C, VEGF (-460) C, and VEGFR-2, and progression or spontaneous regression of ROP in preterm infants. The absence of HGF and c-Met polymorphisms in our study groups suggests that polymorphisms in the minimal promoters of these genes are not involved in the pathogenesis of ROP.

Cooperative interaction of MUC1 with the HGF/c-Met pathway during hepatocarcinogenesis.

BACKGROUND: Hepatocyte growth factor (HGF) induced c-Met activation is known as the main stimulus for hepatocyte proliferation and is essential for liver development and regeneration. Activation of HGF/c-Met signaling has been correlated with aggressive phenotype and poor prognosis in hepatocellular carcinoma (HCC). MUC1 is a transmembrane mucin, whose over-expression is reported in most cancers. Many of the oncogenic effects of MUC1 are believed to occur through the interaction of MUC1 with signaling molecules. To clarify the role of MUC1 in HGF/c-Met signaling, we determined whether MUC1 and c-Met interact cooperatively and what their role(s) is in hepatocarcinogenesis. RESULTS: MUC1 and c-Met over-expression levels were determined in highly motile and invasive, mesenchymal-like HCC cell lines, and in serial sections of cirrhotic and HCC tissues, and these levels were compared to those in normal liver tissues. Co-expression of both c-Met and MUC1 was found to be associated with the differentiation status of HCC. We further demonstrated an interaction between c-Met and MUC1 in HCC cells. HGF-induced c-Met phosphorylation decreased this interaction, and down-regulated MUC1 expression. Inhibition of c-Met activation restored HGF-mediated MUC1 down-regulation, and decreased the migratory and invasive abilities of HCC cells via inhibition of ß-catenin activation and c-Myc expression. In contrast, siRNA silencing of MUC1 increased HGF-induced c-Met activation and HGF-induced cell motility and invasion. CONCLUSIONS: These findings indicate that the crosstalk between MUC1 and c-Met in HCC could provide an advantage for invasion to HCC cells through the ß-catenin/c-Myc pathway. Thus, MUC1 and c-Met could serve as potential therapeutic targets in HCC.

Differential expression of Caveolin-1 in hepatocellular carcinoma: correlation with differentiation state, motility and invasion.

BACKGROUND: Caveolin-1 is the main component of caveolae membrane structures and has different roles during tumorigenesis in different cancer types with varying expression profiles, indicating that the role of caveolin-1 varies according to tumor type. In this study, we investigated the role and expression of caveolin-1 in hepatocellular carcinogenesis. METHODS: We analyzed the expression of Caveolin-1 in 96 hepatocellular carcinoma (HCC), 29 cirrhosis, 20 normal liver tissues and 9 HCC cell lines by immunostaining and western blotting, respectively. After caveolin-1 was stably transfected to HepG2 and Huh7 cells, the effects of Caveolin-1 on the cellular motility, matrix invasion and anchorage-independent growth were studied. Also, caveolae structure was disrupted in endogenously caveolin expressing cells, SNU 449 and SNU 475 by addition of methyl-beta-cyclodextrin and analyzed cellular motility and invasion. RESULTS: In HCC cell lines, Caveolin-1 expression is correlated to differentiation and basal motility status of these cells. The percentage of Caveolin-1 positivity was found extremely low in normal liver tissue (5%) while it was increased in cirrhosis (45%) and in HCC (66%) (p = 0.002 and p = 0.001 respectively). Cav-1 expression in poorly differentiated HCC samples has been found significantly higher than well differentiated ones (p = 0.001). The caveolin-1 expression was found significantly higher in tumor cells than its peritumoral cirrhotic tissues in HCC samples (p < 0.001). Additionally, the patients with positive staining for Caveolin-1 had significantly higher portal vein invasion than those with negative staining (p = 0.02). Caveolin-1 overexpression increased motility and invasion of HepG2 and Huh7 cells. And disruption of caveolae results in a dramatic decline in both motility and invasion abilities in SNU-449 and SNU-475 cells. Furthermore, caveolin-1 overexpression resulted in down-regulation of E-cadherin while up-regulation of Vimentin. Also, it increased secreted MMP-2 and expression levels of MMP-9 and MT1-MMP. There was no significant difference in colony formation in soft agar between stable clones and parental ones. CONCLUSION: In conclusion, stepwise increase in Cav-1 expression in neoplastic stage with respect to pre-neoplastic stage during hepatocellular carcinogenesis and its ability to stimulate HCC cell motility and invasiveness indicate that this protein plays a crucial role in tumor progression.