Expression of miR-34 is lost in colon cancer which can be re-expressed by a novel agent CDF

BACKGROUND: Colorectal Cancer (CRC) is one of the leading causes of death worldwide. Numerous cellular events, including deregulated expression of microRNAs (miRNAs), specifically the family of miR-34 consisting of miR-34a, b and c, is known to regulate the processes of growth and metastasis. METHODS: We evaluated the expression of miR-34 in formalin-fixed paraffin-embedded (FFPE) human colon cancer tissue specimens compared to normal colonic mucosa. Moreover, we also assessed the expression of miR-34 in colon cancer cell lines treated with our newly developed synthetic analogue of curcumin referred as difluorinated curcumin (CDF) compared to well known inhibitor of methyl transferase. RESULTS: We found that the expression of miR-34a and miR-34c was down-regulated in colon cancer specimens compared to normal colonic mucosa and the loss of expression was also consistent with data from colon cancer cell lines. This down-regulation was attributed to promoter hypermethylation, because we found that the treatment of colon cancer cells with 5-aza-2´-deoxycytidine, a methyltransferase inhibitor, markedly induced the levels of miR-34a and miR-34c expression. Likewise, CDF was very effective in the re-expression of miR-34a and miR-34c, which was consistent with inhibition of cell growth of both chemo-sensitive and chemo-resistant colon cancer cells. The re-expression of miR-34 led to a marked reduction in the expression of its target gene, Notch-1. CONCLUSION: The loss of expression of miR-34 in colon cancer is in part due to promoter hypermethylation of miR-34, which can be re-expressed with our novel agent CDF, suggesting that CDF could be a novel demethylating agent for restoring the expression of miR-34 family, and thus CDF could become a newer therapeutic agent for the treatment of colon cancer.