MiR‐34b/c‐5p and the neurokinin‐1 receptor regulate breast cancer cell proliferation and apoptosis

OBJECTIVES: MiR‐34 is a tumour suppressor in breast cancer. Neurokinin‐1 receptor (NK1R), which is the predicted target of the miR‐34 family, is overexpressed in many cancers. This study investigated the correlation and clinical significance of miR‐34 and NK1R in breast cancer. MATERIALS AND METHODS: Western blotting, quantitative reverse transcription‐PCR (qRT‐PCR) and luciferase assays were conducted to analyse the regulation of NK1R by miR‐34 in MDA‐MB‐231, MCF‐7, T47D, SK‐BR‐3 and HEK‐293 T cells. MiR‐34b/c‐5p, full‐length NK1R (NK1R‐FL) and truncated NK1R (NK1R‐Tr) expression in fifty patients were quantified by qRT‐PCR and correlated with their clinicopathological parameters. CCK‐8 assays, colony formation assays and flow cytometry were used to measure cell proliferation and apoptosis in MDA‐MB‐231 and MCF‐7 cells transfected with miR‐34b/c‐5p or NK1R‐siRNA and before treatment with or without Substance P (SP), an endogenous peptide agonists of NK1R. The effect of NK1R antagonist aprepitant was also investigated. In vivo xenograft models were used to further verify the regulation of NK1R by miR‐34b/c‐5p. RESULTS: Expression levels of miR‐34b/c‐5p and NK1R‐Tr, but not NK1R‐FL, were associated with enhanced malignant potential, such as tumour stage and Ki67 expression. The overexpression of miR‐34b/c‐5p or NK1R silencing potently suppressed cell proliferation and induced G2/M phase arrest and the apoptosis of MDA‐MB‐231 and MCF‐7 cells. The NK1R antagonist aprepitant had similar effects. In vivo studies confirmed that miR‐34b/c‐5p overexpression or NK1R silencing reduced the tumorigenicity of breast cancer. In addition, SP rescued the effects of miR‐34b/c‐5p overexpression or NK1R silencing on cell proliferation and apoptosis in vitro and in vivo assays. CONCLUSIONS: MiR‐34b/c‐5p and NK1R contribute to breast cancer cell proliferation and apoptosis and are potential targets for breast cancer therapeutics.