Lifelong football training influences miR-1303 serum expression and human breast cancer MCF-7 cells motility: a pilot study

Introduction: MicroRNAs (miRNAs) are key components in the interaction between lifestyle-related risk factors and cancer development. In particular, miR-1303 expression is deregulated in breast cancer tissues, with elevated levels associated with poor prognosis. We have previously shown that regular exercise reduces the expression of this miRNA in skeletal muscle. The present pilot study aimed to evaluate the impact of lifelong football training on circulating miR-1303 expression and miR-1303 modulation on proliferation, migration, and invasion pathways in human breast cancer MCF-7 cells. Methods: Blood samples were collected from 17 veteran football players (VPG) and 17 healthy, untrained males (CG) of matching age (74.4 ± 4.3 years). Serum levels of testosterone, estradiol, IGF-1, insulin (ELISA), and miR-1303 (RT-qPCR) were measured. MCF-7 cells were treated with serum collected from VPG, CG or transfected with 25 μM miR-1303 mimic or inhibitor or miRNA mimic negative control. Cell proliferation and invasion were assessed using Wound healing assays and Transwell assay, respectively. Western blotting and RTqPCR were performed to evaluate the expression of key migration and invasion markers. Results: We demonstrated, for the first time, that miR-1303 expression was lower in VPG serum than in CG and paralleled the lower expression previously found in skeletal muscle. Overexpression of miR-1303 increases the proliferation and motility of MCF-7 breast cancer cells and is correlated with increased expression of β-catenin, c-Myc, and MMP2 genes and decreased expression of p21 and p27 proteins, all key markers involved in migration and invasion pathways. These events were reversed by treatment with the miR-1303 inhibitor. Interestingly, treatment of MCF-7 cells with sera from VPG, with low level of c- miR-1303, parallels the effects mediated by miR-1303 inhibition. Discussion: Our findings suggest that lifelong football training may counteract MCF-7 cell proliferation and invasion activities and that miR-1303 is one of the factors mediating the effects of long-term football training on breast cancer cells.