Selective arm-usage of pre-miR-1307 dysregulates angiogenesis and affects breast cancer aggressiveness

Background: Breast cancer is the leading cause of cancer-related mortality in women. Deregulation of miRNAs is frequently observed in breast cancer and affects tumor biology. A pre-miRNA, such as pre-miR-1307, gives rise to several mature miRNA molecules with distinct functions. However, the impact of global deregulation of pre-miR-1307 and its individual mature miRNAs in breast cancer has not been investigated in breast cancer, yet. Results: Here, we found significant upregulation of three mature miRNA species derived from pre-miR-1307 in human breast cancer tissue. Surprisingly, the overexpression of pre-miR-1307 in breast cancer cell lines resulted in reduced xenograft growth and impaired angiogenesis. Mechanistically, overexpression of miR-1307-5p altered the secretome of breast cancer cells and reduced endothelial cell sprouting. Consistently, expression of miR-1307-5p was inversely correlated with endothelial cell fractions in human breast tumors pointing at an anti-angiogenic role of miR-1307-5p. Importantly, the arm usage of miR-1307 and other miRNAs was highly correlated, which suggests an undefined common regulatory mechanism. Conclusions: In summary, miR-1307-5p reduces angiogenesis in breast cancer, thereby antagonizing the oncogenic effects of miR-1307-3p. Our results emphasize the importance of future research on the regulation of miRNA arm selection in cancer. The underlying mechanisms might inspire new therapeutic strategies aimed at shifting the balance towards tumor-suppressive miRNA species.