miR-4732-5p promotes breast cancer progression by targeting TSPAN13.

MiR-4732-5p was previously found to be dysregulated in nipple discharge of breast cancer. However, the expression and function of miR-4732-5p in breast cancer remain largely unknown. Here, the expression of miR-4732-5p was detected using quantitative real-time PCR in breast cancer tissues and cell lines. Cell proliferation, apoptosis, migration and invasion assays were performed to examine the effects of miR-4732-5p in breast cancer. In addition, mRNA sequencing, bioinformatics analysis, Western blot and luciferase assays were performed to identify the target of miR-4732-5p. Overall, miR-4732-5p was significantly down-regulated in breast cancer tissues, especially in lymph node metastasis (LNM)-negative tissues, compared with adjacent normal tissues. However, it was more highly expressed in LNM-positive breast cancer tissues, compared with LNM-negative ones. Expression of miR-4732-5p was positively correlated with lymph node metastasis, larger tumour size, advanced clinical stage, high Ki-67 levels and poor prognosis. MiR-4732-5p promoted cell proliferation, migration and invasion in breast cancer. MiR-4732-5p directly targeted the 3'-UTR of tetraspanin 13 (TSPAN13) and suppressed TSPAN13 expression at the mRNA and protein levels. These results suggested that miR-4732-5p may serve as a tumour suppressor in the initiation of breast cancer, but as a tumour promoter in breast cancer progression by targeting TSPAN13.