Abstract
Epigenetic regulation is a fundamental mechanism controlling gene expression and cellular function, primarily mediated through reversible modifications such as DNA methylation, histone acetylation, and chromatin remodeling. Dysregulation of critical epigenetic enzymes, including histone deacetylases (HDACs), DNA methyltransferases (DNMTs), and bromodomain and extraterminal domain (BET) proteins, has been closely associated with tumor initiation, progression, metastasis, immune evasion, and resistance to conventional therapies. Targeting these epigenetic regulators with small-molecule inhibitors or degraders has emerged as a promising therapeutic strategy, capable of reprogramming aberrant transcriptional networks and reshaping the tumor microenvironment. Beyond direct cytotoxic effects, epigenetic drugs have demonstrated the ability to enhance antitumor immunity by restoring antigen presentation, promoting immunogenic cell death, modulating cytokine profiles, and reversing local immune suppression. Recent preclinical and clinical studies have highlighted the potential of combining epigenetic therapies with immune checkpoint inhibitors to achieve synergistic antitumor responses and overcome resistance mechanisms. This review provides a comprehensive summary of the mechanisms of action, pharmacological characteristics, and clinical applications of epigenetic drugs, with a focus on innovative combination strategies and ongoing translational advancements. We also discuss future directions, emphasizing the need to improve drug specificity, minimize off-target effects, integrate personalized immunotherapeutic approaches, and identify predictive biomarkers to optimize patient selection and clinical outcomes. Overall, epigenetic therapy represents a versatile and evolving avenue for precision oncology with broad implications for tumor control and immunomodulation.