MicroRNA-324 in Human Cancer: miR-324-5p and miR-324-3p Have Distinct Biological Functions in Human Cancer.

MicroRNAs (miRNAs) are small non-coding RNAs that have crucial regulatory functions in carcinogenesis. miR-324-5p and miR-324-3p are generated from the same hairpin RNA structure, however, both are diverse in their direct target genes and expression levels. We report that expression of miR-324-5p and -3p was frequently observed to be either up-regulated or down-regulated, and the selection preference of miR-324 for 5p and 3p arms significantly varied in various types or human cancer. Overexpression of miR-324-5p or -3p suppressed growth and invasion of breast cancer cells. Overexpression of miR-324-5p reduced the growth and invasive abilities of colorectal cancer cells, whereas miR-324-3p suppressed colorectal cancer cell invasion but did not influence cell growth. We conclude that miR-324-5p and miR-324-3p might have distinct biological functions, further complicating the regulatory network in human cancer. Therefore, the arm selection preference of miR-324 may be a method for modulating its function.