Abstract P5-03-12: Selenocystine inhibits triple-negative breast cancer cell proliferation by inducing cell apoptosis and S-phase arrest

Abstract

Abstract Introduction: Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with limited effective treatment options. New therapeutic approaches are urgently needed to improve the prognosis of TNBC. Reactive oxygen species (ROS) are inherent byproducts of oxidative metabolism, and forced stimulation of glucose oxidation in cancer cells raises oxidative stress and sensitizes cells to different stresses. Therefore, targeting the antioxidant capacity of cancer cells has become a promising anticancer strategy. As a redox modulator, selenocystine (SeC) has received a great deal of attention and has been shown effective against human melanoma, hormone receptor-positive breast cancer, and cancers of liver, lung and cervical in vitro. However, whether SeC exerts an anticancer effect on TNBC cells has never been explored. Methods: The dose-response effects and time course of effects of SeC on three different TNBC cell lines, MDA-MB-231, MDA-MB-436 and MDA-MB-468, were investigated in this study. Cellular viability was determined by the CCK-8 assay and cell morphology were recorded under a light microscope. Cellular apoptosis was detected using Annexin V/PI staining assay and cell cycle distribution was analyzed by flow cytometry. Results: SeC induced cell growth inhibition in all three TNBC cell lines. For 24, 48 and 72 hours of SeC treatments, the IC50 values were 40.8, 12.8 and 9.2 μM for MDA-MB-231 cells; 14.6, 5.4 and 3.0 μM for MDA-MB-436 cells; and 69.6, 29.3 and 19.9 μM for MDA-MB-468 cells. The changes of cellular morphology of TNBC cells in response to SeC treatment were similar to those cells undergoing apoptotic pathway. This result was confirmed by Annexin V/PI staining assays (Table 1). Cell cycle analysis further revealed that SeC also induced S-phase arrest in a dose-dependent manner (Table 2). Conclusion: In summary, SeC inhibited TNBC cell viability in a dose- and time-dependent manner which was attributed to the induction of apoptosis and S-phase arrest. Our finding indicates that SeC is a potential therapeutic agent for TNBC. Table 1. Apoptotic rate of TNBC cells after SeC treatment.Conc.(μM)MDA-MB-231MDA-MB-436MDA-MB-46805.8 %18.1 %26.7 %1025.5 %45.8 %60.7 %2040.1 %67.1 %70.9 %4054.7 %70.7 %74.5 % Table 2. SeC induces S-phase arrest in TNBC cells in a dose-dependent manner. Conc.(μM)G0/G1 (%)S (%)G2/M (%)MDA-MB-231016.655.927.5 1050.139.310.6 2045.548.16.4 4041.753.05.3MDA-MB-436042.127.630.3 1036.335.028.7 2034.340.725.0 4032.445.422.2MDA-MB-468059.123.717.2 1054.929.315.8 2050.135.714.2 4043.843.113.1 Citation Format: Long M, Qiu W, Wu J, Liu R, Su H. Selenocystine inhibits triple-negative breast cancer cell proliferation by inducing cell apoptosis and S-phase arrest. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-03-12.