HDAC inhibitors regulate claudin-1 expression in colon cancer cells through modulation of mRNA stability.

Expression and cellular distribution of claudin-1, a tight junction protein, is dysregulated in colon cancer and its overexpression in colon cancer cells induced dedifferentiation and increased invasion. However, the molecular mechanism(s) underlying dysregulated claudin-1 expression in colon cancer remains poorly understood. Histone deacetylase (HDAC)-dependent histone acetylation is an important mechanism of the regulation of cancer-related genes and inhibition of HDACs induces epithelial differentiation and decreased invasion. Therefore, in this study, we examined the role of HDAC-dependent epigenetic regulation of claudin-1 in colon cancer. In this study, we show that sodium butyrate and Trichostatin A (TSA), two structurally different and widely used HDAC inhibitors, inhibited claudin-1 expression in multiple colon cancer cell lines. Further studies revealed modulation of claudin-1 mRNA stability by its 3'-UTR as the major mechanism underlying HDAC-dependent claudin-1 expression. In addition, overexpression of claudin-1 abrogated the TSA-induced inhibition of invasion in colon cancer cells suggesting functional crosstalk. Analysis of mRNA expression in colon cancer patients, showed a similar pattern of increase in claudin-1 and HDAC-2 mRNA expression throughout all stages of colon cancer. Inhibition of claudin-1 expression by HDAC-2-specific small interfering RNA further supported the role of HDAC-2 in this regulation. Taken together, we report a novel post-transcriptional regulation of claudin-1 expression in colon cancer cells and further show a functional correlation between claudin-1 expression and TSA-mediated regulation of invasion. As HDAC inhibitors are considered to be promising anticancer drugs, these new findings will have implications in both laboratory and clinical settings.