EPZ-015666

Protein arginine methylation is an epigenetic modification involved in transcription, splicing and signal transduction and is mediated by protein arginine methyltransferases (PRMTs). PRMTs regulate various tumor angiogenesis pathways, including vascular endothelial growth factor receptor-2 (VEGFR-2) signaling. PRMT1, PRMT4, and PRMT5 activate distinct stages of angiogenesis. For example, inhibiting PRMT5 suppresses VEGF-induced vessel sprouting in experimental models while impairing hypoxia-inducible factor 1-alpha (HIF-1α) stability and VEGFR-2 phosphorylation. PRMT1 and PRMT4 similarly influence VEGF isoform expression, leading to increased angiogenesis. Targeting PRMTs in experimental models results in suppressed angiogenesis and reduced cancer progression. Several small-molecule PRMT inhibitors, including GSK3326595 and EPZ015666, have entered early-phase clinical trials for solid tumors. These agents show promise in inhibiting tumor angiogenesis, although there are toxicity concerns. This review examines the mechanistic basis and therapeutic rationale for targeting PRMTs in breast cancer and discusses combination approaches to overcome resistance. We integrate preclinical and emerging clinical data to highlight the potential antiangiogenic and tumor-suppressive effects of PRMT inhibitors, providing insights for future therapeutic strategies for breast cancer.