Biological and computer-aided evaluation of 3-methoxy-13α-estrone-16α-diphenylphosphine oxide as a new antiestrogenic agent

Breast cancer, a leading cause of cancer-related mortality, often depends on estrogen receptor alpha (ERα) signaling for progression. This study evaluates [(3-methoxy-17-oxo-13α-estra-1,3,5(10)-trien-16α-yl)methyl]diphenylphosphine oxide (EDPO), a recently published organophosphorus 13α-estrone derivative, as a potential antiestrogenic agent. In our previous study, EDPO showed substantial antiproliferative effect against T47D breast cancer cells and UPCI-SCC-131 oropharyngeal squamous cell carcinoma cells, with IC₅₀ values of 7.2 µM and 5.3 µM, respectively. Using in silico, in vitro, and in vivo methods, EDPO demonstrated robust antiestrogenic activity comparable to that of fulvestrant. Molecular docking confirmed EDPO's effective binding to the ERα ligand-binding domain, disrupting estrogen signaling. In vitro, EDPO inhibited estrogen-mediated transcriptional activity, induced G1-phase cell cycle arrest, and significantly reduced the invasive capacity of breast cancer cells, as well as the extent of cell migration both in breast and oropharyngeal carcinoma cells. In vivo uterotrophic assay on immature rats revealed EDPO's ability to mitigate estrogen-induced uterine growth, validating its antiestrogenic effects. Moreover, in a murine triple-negative breast cancer (TNBC) model, EDPO significantly inhibited tumor growth, likely through immunomodulatory mechanisms that altered the tumor microenvironment. These findings highlight EDPO's multifaceted actions, combining antiestrogenic, antiproliferative, and antimetastatic effects. This study positions EDPO as a promising hit molecule for both ERα+ breast cancer and TNBC, addressing key challenges in current endocrine therapies and offering new avenues for breast cancer treatment.