Metabolomic Profiling Reveals Key Metabolic Alterations in MCF7 Tamoxifen-Resistant Cells Following EPAS1 Inhibition

Tamoxifen (TAM) is a frontline therapy for luminal A breast cancer, yet acquired resistance poses a significant clinical challenge. This study investigates the molecular and metabolic basis of TAM resistance in MCF7/Tam1 cells, focusing on EPAS1 (HIF-2α)-driven hypoxia-induced metabolic reprogramming and the potential of the EPAS1 inhibitor PT2977 to restore TAM sensitivity. Comparative transcriptomic analysis revealed upregulation of EPAS1 along with enrichment of hypoxia-associated pathways, including JAK-STAT, TGF-beta, and lipid metabolism in resistant cells. Untargeted LC-MS/MS metabolomics identified 1,039 significantly altered metabolites, with notable dysregulation in glutamate and glutathione metabolism, the Warburg effect, and fatty acid oxidation. Mechanistically, EPAS1 promoted fatty acid uptake via CD36 and enhanced glutamine metabolism through SLC1A5, contributing to redox balance and cell survival under TAM stress. Treatment with PT2977 disrupted these metabolic pathways, as evidenced by PCA and Venn analyses, leading to a dose-dependent normalization of metabolite profiles and selective reduction in cell viability. These findings highlight EPAS1-mediated metabolic reprogramming as a key driver of TAM resistance and support EPAS1 inhibition by PT2977 as a promising therapeutic strategy to overcome resistance in luminal A breast cancer.