MiR-101 downregulation is involved in cyclooxygenase-2 overexpression in human colon cancer cells

Overexpressed cyclooxygenase-2 (COX-2) strongly contributes to the growth and invasiveness of tumoral cells in patients affected by colorectal cancer (CRC). It has been demonstrated that COX-2 overexpression depends on different cellular pathways involving both transcriptional and post-transcriptional regulations. We assumed that COX-2 expression could be regulated also by microRNAs (miRNAs) since these short RNA molecules participate to the fine regulation of several genes implicated in cell growth and differentiation. In this paper, we report the inverse correlation between COX-2 and miR-101 expression in colon cancer cell lines and we demonstrated in vitro the direct inhibition of COX-2 mRNA translation mediated by miR-101. Moreover, this correlation was supported by data collected ex vivo, in which colon cancer tissues and liver metastases derived from CRC patients were analyzed. These findings provide a novel molecular insight in the modulation of COX-2 at post-transcriptional level by miR-101 and strengthen the observation that miRNAs are highly implicated in the control of gene expression. An impairment of miR-101 levels could represent one of the leading causes of COX-2 overexpression in colon cancer cells.