miR494 is an independent prognostic factor and promotes cell migration and invasion in colorectal cancer by directly targeting PTEN

Accumulating evidence has shown that micro­RNAs (miRNAs) are involved in multiple processes in cancer development and progression. Upregulation of miRNA494 (miR494) has been identified as an oncogenic miRNA and is associated with poor prognosis in several types of human cancer. However, the specific function of miR494 in colorectal cancer remains unclear. In this study we found that the expression of miR494 in colorectal cancer tissues and cell lines was much higher than in normal control tissues and cells, respectively. In addition, upregulation of miR494 more frequently occurred in tissue specimens with adverse clinical stage and the presence of distant metastasis. Moreover, multivariate survival analyses demonstrated that overexpression of miR494 is an independent prognostic factor for both progressionfree and overall survival. In addition miR494 promoted invasion and migration in colorectal cancer cells, and miR494 directly inhibited the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression by targeting its 3'untranslated region (3'UTR). Moreover, PTEN is down regulated and inversely correlated with miR494 expression in tissues. Thus, for the first time, we provided convincing evidence that upregulation of miR494 was associated with tumor aggressiveness and tumor metastasis and promoted cell migration and invasion by targeting PTEN gene in colorectal cancer, and miR494 is an independent prognostic marker for colorectal cancer patients.