S4, a Selective Androgen Receptor Modulator, Suppresses Breast Cancer Progression via Cell Cycle Arrest, Apoptosis, and Metabolic Alterations

Breast cancer (BC) remains a leading cause of cancer-related mortality worldwide, highlighting the need for novel therapeutic strategies. Androgen receptor (AR) signaling has been implicated in BC progression, making it a potential target for treatment. Selective androgen receptor modulators (SARMs) have gained attention as alternatives to traditional hormone therapies. However, the effects of S4, a SARM, on BC have not been explored. This study investigates the impact of S4 on BC cell viability, proliferation, clonogenicity, migration, apoptosis, and cell cycle progression in MCF-7 and MDA-MB-231 cells. The results demonstrate that S4 significantly reduces BC cell viability in a dose-dependent manner, with IC50 values of 0.094 mM (MCF-7) and 0.067 mM (MDA-MB-231) after 24 hours. S4 suppresses clonogenicity and migration while promoting apoptosis and cell cycle arrest, with MCF-7 cells exhibiting S-phase arrest and MDA-MB-231 cells G0/G1-S arrest. Gene expression analysis reveals upregulation of tumor suppressor genes (CDKN1B and PUMA in MCF-7 cells, TP53, CDKN1A, and BAX in MDA-MB-231 cells, and GADD45A in both cells) and downregulation of oncogenes (ANKRD1, EDN1, CCND1 in MCF-7 cells, CXCL2 in MDA-MB-231 cells, CDK-6 and ATM in both cells), supporting the anti-carcinogenic effects of S4. Metabolomics profiling highlights significant alterations in phosphatidylcholine biosynthesis, catecholamine biosynthesis, and nucleotide metabolism, indicating a metabolic shift upon S4 treatment. These findings provide the first evidence of S4s potential as an anti-cancer agent in BC, suggesting that it exerts its effects by modulating gene expression and cellular metabolism. Further in-vivo studies are warranted to validate its therapeutic potential.