miR-3188 Enhances Sensitivity of Breast Cancer Cells to Ionizing Radiation by Down-regulating Rictor.

BACKGROUND/AIM Rictor is an adaptor protein essential for mTORC2, which regulates cell growth and survival. The aim of this study was to identify microRNAs (miR) that down-regulate Rictor and investigate their function on breast cancer cell survival. MATERIALS AND METHODS Trypan blue assay, MTT assay, polymerase chain reaction analysis, luciferase reporter assay and western blot analysis were carried out in breast cancer cell lines HCC1954, MDA-MB-231, SK-BR-3, and BT474. RESULTS miR-3188 overexpression suppressed the expression of Rictor and inhibited cell viability in HCC1954 and MDA-MB-231, highly Rictor-expressing breast cancer cells. In addition, miR-3188 overexpression decreased the protein level of p-AKT at Ser473, a substrate of mTORC2. Moreover, miRNA-3188 overexpression sensitized breast cancer cells to ionizing radiation (IR) by down-regulating Rictor and p-AKT. CONCLUSION miR-3188 enhances IR sensitivity by affecting the mTORC2/AKT signalling pathway by altering the expression of Rictor, which could be a promising therapeutic strategy for the future treatment of breast cancer.