Inhibition of hepatocellular carcinoma invasion by suppression of claudin-10 in HLE cells.

Previously, we showed that down-regulation of claudin-10 (CLDN-10) in hepatocellular carcinoma is associated with prolonged disease-free survival after curative surgery. Claudins are important tight junction components. Increasing evidence shows that claudins are involved in cancer progression but each member of claudins is specifically expressed in a variety of malignancies. The biological role of CLDN-10 in hepatocellular carcinoma is unexplored. In the current study, we investigated the CLDN-10 function in two different hepatocellular carcinoma cell lines by in vitro assays with the CLDN-10 overexpression and small interfering RNA-mediated knockdown transfectants. We observed that overexpression of CLDN-10 conferred malignant phenotypes to hepatocellular carcinoma cells, Hep3B, which lack CLDN-10 expression, by promoting cancer cell survival, motility, and invasiveness. More importantly, matrix metalloproteinase 2 (MMP2) was up-regulated. Increase in mRNA transcription and protein expression of membrane type 1-MMP (MT1-MMP) was also observed in the CLDN-10 transfectants, where MT1-MMP was a protease shown to promote intrahepatic metastasis in hepatocellular carcinoma in our earlier study. In addition, CLDN-1, CLDN-2, and CLDN-4 was up-regulated in CLDN-10 overexpression transfectants, indicating that the expression of CLDN-10 in cancer cells might affect the expression levels of its family members. On the contrary, small interfering RNA-based knockdown of CLDN-10 in HLE, an invasive cell line with high level of CLDN-10 expression, abolished invasion and strongly decreased activation of MMPs and claudin members expression. These findings showed that CLDN-10 is functionally involved in hepatocellular carcinoma invasion and is a potential target for hepatocellular carcinoma therapy.