Background The incidence of breast cancer ranks the first among female malignant tumors. Although the effect of breast cancer treatment strategies has been very ideal and the mortality rate of breast cancer has decreased, some patients are still not sensitive to these, which eventually leads to rapid recurrence, metastasis and poor prognosis. Ferroptosis is a kind of Regulated cell death, which induced by accumulation of lipid peroxidation products and Reactive Oxygen Species (ROS). It is quite different from apoptosis and autophagy in cell morphological characteristics and biochemical indicators. According to the latest studies, ferroptosis can reduce the activity of GPX4 (Gutathione Peroxidase 4) in cells and accumulate ROS and lipid Peroxidase products through iron metabolism, ROS metabolism, amino acid metabolism and lipid metabolism, etc., thus causing ferroptosis. Ferroptosis is a hotspot in the study of drug resistance and metastasis of breast cancer. Simvastatin is a kind of commonly used oral cholesterol-lowering drugs, belongs to the HMG CoA reductase inhibitors. Some clinical studies have shown that statins can reduce the risk of a variety of cancers, including breast cancer, and the risk of recurrence. Other basic experiment show lipophilic statins have anti-cancer effect. Simvastatin is the most lipophilic of all statins in use. Recent studies have found that simvastatin can be used in combination with docetaxel to enhance the effect of chemotherapy in prostate cancer, but has not been reported in breast cancer. In this study, we investigated whether simvastatin could induce ferroptosis in breast cancer by inhibiting GPX4 and play the role of chemotherapy sensitization in combination with docetaxel. Methods (1) CCK8 assay was used for cell proliferation in vitro by simvastatin and docetaxel in breast cancer cells MDA-MB-231 and MCF-7. (2) The anti-cancer effect of simvastatin in vivo was verified by xenograft experiments in nude mice. (3) GPX4 mRNA and protein levels were detected by qPCR and Western blot. (4) GPXs activity test, ROS level test and MDA level test were used for ferroptosis detection.(5) the expression of ferroptosis-related genes ACSL4, PTGS2 and NOX1 was detected by qPCR.(6) anti-tumor effect of simvastatin combined with docetaxel in breast cancer cells mda-mb-231 and McF-7 was detected in vitro by CCK8 method.(7) By MDA-MB-231 tumor xenograft models surveyed anti-tumor activity of simvastatin and docetaxel. Results CCK8 results showed that simvastatin significantly inhibited cell proliferation in breast cancer cells MDA-MB-231 and MCF-7 (P<0.001), with the IC50 values of MDA-MB-231 was 4.67um and MCF-7 was 81.53um,. In the xenograft experiments of nude mice, it was found that compared with the control group, the tumor volume of the simvastatin group was significantly reduced. In qPCR and Western blot, simvastatin was found to significantly inhibit GPX4 mRNA and protein expression. Compared with the control group, in breast cancer cells MDA-MB-231 and MCF-7, simvastatin can reduce the activity of GPXs and increase the level of ROS and MDA, thus causing ferroptosis in breast cancer cells. qPCR showed that ferroptosis -related gene ACSL4 and PTGS2, which are related to lipid metabolism, and ROS metabolism were significantly increased. In the xenograft experiments of nude mice, it was found that compared with the control group and the single drug group, the tumor volume of simvastatin combined with docetaxel group was significantly reduced. Conclusion Simvastatin can inhibit the proliferation of breast cancer cells both in vivo and in vitro, inhibit the expression of breast cancer cell MDA-MB-231 and MCF-7 GPX4, and induce ferroptosis. Besides, simvastatin sensitizes the effect of docetaxel.

Citation Format: Sihong Lu, Nan Shao, Jong Bi, Ying Lin. Simvastatin induces ferroptosis in breast cancer cells by inhibiting GPX4 and sensitizes chemotherapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-44.