Our previous studies have demonstrated that Aquaporin 1 (AQP1) is overexpressed in breast cancer. However, the mechanism remains elusive. MicroRNA 320 (miR-320) downregulation has been reported in various types of cancers, and it may regulate AQP1 expression. In this study, miR-320 and AQP1 expressions were investigated by quantitative reverse transcription-PCR, in situ hybridization, and immunohistochemistry. The clinicopathological implications of these molecules were also analyzed. We found that miR-320 expression is downregulated in both plasma and tumor tissue in human breast cancer patients. Survival analysis showed that reduced expression of miR-320 and overexpression of AQP1 are associated with worse prognosis. Luciferase assays showed that miR-320 negatively regulates AQP1 expression. In addition, cell proliferation, migration, and invasion assays were performed to investigate the effects of miR-320 on breast cancer cells. Our results showed that miR-320 overexpression inhibits cell proliferation, migration, and invasion in breast cancer cells by downregulating AQP1. These observations suggested that miR-320 downregulation may enhance AQP1 expression in breast cancer, favoring tumor progression. Our findings indicated that miR-320 and AQP1 may serve as prognostic biomarkers and therapeutic targets in the treatment of breast cancer.
