Prostate cancer is the predominant cause of cancer in men, but there is still a lack of biomarkers and treatments for metastatic spread. The initial promise of microRNAs to provide avenues to solve these problems has been dampened by the realisation that microRNAs co-exist in multiple functionally distinct isoforms, for example due to A-to-I editing. We recently found that A-to-I-editing of microRNA-379 (miR-379) was associated with prostate cancer, and that only the unedited isoform was negatively correlated with aggressive disease. Here, we set out to decipher the biological effects of unedited and edited miR-379 in prostate cancer cells. After transfection of four different prostate cancer cell lines with isoform-specific miR-379 mimics, we performed assays for cell growth, colony formation, migration, cell-cell adhesion, and analysed epithelial-mesenchymal transition (EMT) and stemness markers. We found that unedited miR-379 affected cell growth, with a promoting function in androgen receptor (AR)-negative cells and an inhibiting effect in AR-positive cells. This is supported by our in silico analysis that found unedited miR-379 targets are predicted to be predominantly involved in cellular proliferation whereas the targets of edited miR-379 are not. We further found that both miR-379 isoforms could promote colony formation, migration, and cell-cell adhesion. Overall, our data suggests that editing of miR-379 attenuates the growth-suppressive function of unedited miR-379 in androgen-sensitive prostate cancer cells, thereby promoting tumor growth.
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