The Potential Mechanism Of Angiotensin ? Regulating Breast Cancer Progression

Objective:In this study,we tried to explore the biological impact and the underlying mechanism of angiotensin ? on the breast cancer,and then,the effect of angiotensin?on the number and the immunosuppressive function of the myeloid-derived suppressor cells?MDSCs?.Method:?1?Breast cancer tumor-bearing mice models were established by subcutaneous injection of 4T1 cells.Tumor-bearing mice were randomly divided into normal tumor-bearing mice group and losartan treatment group.To observe the growth of tumors,the volumes and weights were measured and calculated.After sacrificing the mice,angiotensin ? and TNF-?were determined by ELISA.In addition,the proportions of total MDSCs,G-MDSCs and M-MDSCs in spleens and tumors were also determined by flow cytometry?FCM?.?2?4T1 cells,pre-treated with or without losartan for 2h,were incubated with angiotensin?to detect the proliferation,migration and invasion.Proliferation was detected by CCK8 assay.Migration was detected by cell migration assay.Invasion was detected by cell invasion assay.The expression of AT₁R and p-STAT3 were detected by Western blot.In addition,using Stattic to inhibit the activation of STAT3,the proliferation,migration and invasion of 4T1 cells induced by angiotensin?were also observed.?3?G-MDSCs were isolated from spleens of tumor-bearing mice by immunomagnetic bead sorting?MACS?.Then,G-MDSCs were treated with angiotensin?to detect the immunosuppressive capacity of G-MDSCs.The inhibitory effect of G-MDSCs on the proliferation of CD8⁺T cells was detected by FCM.The expression of Arg-1 in sorted G-MDSCs was determined by Western blot.Result:?1?Compared with the normal tumor-bearing mice group,after losartan treatment,the volumes and weights of tumors were significantly reduced?P<0.05?.Meanwhile,the contents of angiotensin ? and TNF-? in the serum of tumor-bearing mice were also reduced.In addition,the results of FCM showed that,the ratios of G-MDSCs in tumors,G-MDSCs in spleens and total MDSCs in spleens were significantly reduced?P<0.05?,while the ratio of M-MDSCs was not significantly changed in tumors and spleens.?2?Ang ? promoted the proliferation,migration,and invasion of 4T1 cells?P<0.05?.After Ang ? treatment,the expression of AT₁R and the phosphorylation of STAT3 in the 4T1 cells were also upregulated.Pre-treatment of 4T1 cells with losartan could reverse the proliferation,migration and invasion of 4T1 cells induced by angiotensin ?,downregulating the expression of AT₁R and the phosphorylation of STAT3?P<0.05?.Stattic could partially attenuate the effects of angiotensin ? on the proliferation,migration and invasion of 4T1 cells?P<0.05?.?3?FCM results showed that angiotensin ? enhanced the immunosuppressive function of G-MDSCs.Western blot results showed that the expression of Arg-1 in G-MDSCs was significantly increased after stimulation with Ang?.Conclusion:?1?Ang ? can effectively activate the phosphorylation of STAT3 by acting on AT₁R and participate in the regulation of the biological behavior of breast cancer.?2?Ang ? promotes the immunosuppressive function of G-MDSCs.