TGF beta regulates NK1R-Tr to affect the proliferation and apoptosis of breast cancer cells

Objectives: TGF beta promotes cancer aggressiveness in advanced stages. NK1R-Tr expression in advanced breast cancer has a pro-carcinogenic effect. In this study, we aimed to investigate the effect of the association of TGF beta with NK1R-Tr expression on the proliferation and apoptosis of breast cancer cells. Methods: Immunohistochemical staining and Western blot analysis were used to detect TGF beta and NK1R-Tr in breast cancer and paracancerous tissue samples. MDA-MB-231 and BT549 cells were stimulated with TGF beta after NK1R knockdown or treated with the NK1R antagonist aprepitant, and the effects of TGF beta and NK1R-Tr on proliferation and apoptosis were detected by CCK-8, colony formation and flow cytometry assays. In vivo xenograft models were used to further verify the effects of NK1R-Tr and TGF beta. The regulatory effects of Smad4 on NK1R promoter activity were confirmed by ChIP and dual-luciferase reporter assays. Results: The expression levels of TGF beta and NK1R-Tr were higher in breast cancer tissues than in adjacent tissues and were positively correlated in human breast cancer tissues. NK1R knockdown or aprepitant treatment in MDA-MB-231 and BT549 cells attenuated the effects of TGF beta on cell proliferation. The proportion of cells in G2/M phase significantly increased, the expression of cyclin B1 decreased, and the expression of P21 increased; these effects were weakened by TGF beta treatment. Apoptosis in breast cancer cells was significantly increased. In vivo xenograft models were used to further verify that NK1R-Tr and TGF beta promoted tumour growth. After TGF beta treatment, the binding capacity of Smad4 to the NK1R promoter, as well as luciferase activity, was enhanced. Conclusions: The expression levels of TGF beta and NK1R-Tr were higher in breast cancer tissues than in normal tissues, and both were correlated with a poor patient prognosis. TGF beta and NK1R-Tr promoted cell proliferation and inhibited apoptosis, and TGF beta regulated the expression of NK1R-Tr via Smad4.