Advances in Mechanism of Action and Efficacy of CBP/p300 Inhibitors in Different Subtypes of Breast Cancer

Breast cancer is a highly heterogeneous malignancy with multiple molecular subtypes and variable treatment responses. Despite advances in endocrine therapy, HER2-targeted therapy, chemotherapy, and immunotherapy, treatment resistance and disease recurrence remain major clinical challenges. There is growing evidence that transcriptional plasticity and enhancer relinking contribute to tumor progression and treatment adaptation, highlighting the powerful role of epigenetic regulators. CREB-binding protein (CBP) and E1A-associated protein p300 (EP300) are transcriptional coactivators that regulate breast cancer enhancer activity and lineage-specific gene expression. Emerging research suggests that CBP/p300 is more of a context-dependent vulnerability point than a universal carcinogenic driver. ER-positive tumors exhibit a strong dependence on CBP/p300-mediated transcriptional programs, while the triple-negative breast cancer subgroup, including androgen receptor-positive and immunosuppressive tumors, may rely on CBP/p300-dependent signaling to maintain survival and treatment resistance. This is in contrast to their role in HER2-positive breast cancer. This review summarizes the biological functions of CBP/p300 in breast cancer and discusses subtype-specific vulnerability, biomarker-directed patient stratification, drug resistance mechanisms, rational combination strategies, and current translational challenges, emphasizing the need for precise treatment of breast cancer.