Melatonin down-regulates microRNA-10a and decreases invasion and migration of triple-negative breast cancer cells

Breast cancer metastasis is one of the main factors associated with high mortality rates among patients. MicroRNAs (miRNAs) play an important role in gene expression regulation, and are associated with the metastatic process in breast cancer. Melatonin, a hormone secreted mainly in the pineal gland, has several oncostatic effects. The aim of this study was to investigate the action of melatonin in the modulation of miRNA-10a-5p and its association with metastatic mechanisms. We have evaluated the effects of melatonin on cell viability in MDA-MB-468 cell line after 24 hours of treatment. MDA-MB-468 and MDA-MB-231 cells were either transfected with inhibitor of miR-10a, or received a scrambled miRNA sequence as a negative control, then these cells were treated with or without melatonin. Gene expression of miR-10a was verified by real-time PCR. Invasion and migration assay using matrigel inserts were performed. The protein expression was analyzed by western blotting to quantify the epithelial-mesenchymal transition (EMT) markers (E-cadherin, claudin 7, and vimentin) and proliferation marker (PIK3CA). Our results showed that melatonin (1 mM) significantly decreased cell viability, and also affected miR-10a expression, which suppressed cell invasion and migration. Melatonin reduced vimentin and claudin 7 protein expressions, and increased E-cadherin. In contrast, inhibition of miR-10a reduced vimentin and did not modulate claudin 7 and E-cadherin. In conclusion, we demonstrated the effectiveness of melatonin in decreasing miR-10a, affecting invasion and migration, and proteins involved with the EMT process, which supports its potential role in the regulation of metastasis.