Claudin-10 enhanced metastatic potential in hepatocellular carcinoma with MMP activation and modified expression profile of other claudin family members

Abstract

Background: Claudins, a group of integral membrane proteins, are important components of tight junctions. Increasing evidence shows that claudins are differentially regulated in a variety of malignancies and involved in cancer progression. Previously, we demonstrated that downregulation of CLDN-10 in hepatocellular carcinoma (HCC) is associated with prolonged disease-free survival after curative surgery. The biological function of CLDN-10 in carcinogenesis is lacking. The aim of the current study is to evaluate the biological function of CLDN-10 in HCC by functional assays. Material and Methods: CLDN-10 was overexpressed in Hep3B, an HCC cell line with low invasive ability and siRNA-mediated knockdown of CLDN- 10 was performed in a highly invasive HCC cell line, HLE. The effect on invasion, migration, proliferation and survival was then investigated by in vitro function assays. MMP levels were evaluated by gelatin zymography. Expressions of MT1-MMP and claudin family members were examined by semi-quantitative RT-PCR and Western blotting. Results: Functional studies demonstrated that increased expression of CLDN-10 enhanced the metastatic potential of HCC by promoting cancer cell survival, motility and invasiveness. More importantly, in the CLDN- 10 transfectants, there was increase in mRNA transcription and protein expression of MT1-MMP, a protease shown to promote intrahepatic metastasis in HCC in our earlier study. In addition, CLDN-1, -2 and -4 was up-regulated in CLDN-10 overexpression transfectants, indicating that the expression of claudin family members in cancer cells might affect each other. On the contrary, CLDN-10 siRNA strongly inhibited invasion, MMP2 and MT1-MMP expression. These findings highlighted that CLDN- 10 promotes metastatic potential in HCC by enhancing invasion through up-regulation of MT1-MMP and MMP2 expression. Conclusion: CLDN-10 is important for MMP activation, HCC invasion and migration. It also modifies the claudin family expression profile. These findings underline the contributions of CLDN-10 in HCC progression.