Abstract
Breast cancer is the leading cause of death and morbidity among women. A major challenge for clinical management of breast cancer is the dissemination of breast cancer cells from the primary tumor site via lymphatic drainage, resulting in metastatic tumor spread. Recent studies have found that high expression of the microRNA miR-146a-5p is associated with better survival outcomes for breast cancer patients. However, the mechanisms for this prognostic benefit are not fully elucidated, including whether or not miR-146a-5p plays a role in suppression of lymphatic dissemination. In this study, we investigated the role and uncovered functional mechanisms of miR-146a-5p in breast cancer. We found that high expression of miR-146a-5p is associated with better clinical outcomes, specifically in the patients with N0 breast cancer. In culture, miR-146a-5p overexpression in MCF-7 breast cancer cells suppressed cell migration and lymphangiogenesis in lymphatic endothelial cells. When implanted in the mammary fat pad of mice, we observed that miR-146a-5p overexpressing MCF-7 suppressed lymphatic dissemination but had no effect on tumor progression in the primary site. This suppression was associated with fewer disseminated cancer cells and reduced lymphangiogenesis in the draining and distal lymph nodes. In conclusion, these results suggest that miR-146a-5p can exhibit a protective role against breast cancer metastasis, and it can be a therapeutic target for breast cancer.