Intratumoral Heterogeneity of MAGED4 Expression in Oral Squamous Cell Carcinoma: Epigenetic Mechanisms and Therapeutic Implications.

Intratumoral heterogeneity poses significant challenges to the efficacy of cancer immunotherapy. Melanoma-associated antigen D4 (MAGED4) has been proposed as a potential immunotherapeutic target in oral squamous cell carcinoma (OSCC). This study aims to investigate the expression of MAGED4, focusing on its intratumoral expression heterogeneity and the underlying epigenetic regulation mechanism. Utilizing public online databases, immunohistochemical analyses of clinical specimens, and single-cell RNA sequencing data, we found that MAGED4 was overexpressed with significant intratumoral heterogeneity in OSCC tissues. Methylation-promoter luciferase reporter assays revealed that MAGED4 transcription was suppressed by DNA methylation at its promoter region. Additionally, co-expression analysis implicated a potential role for histone acetylation in regulating MAGED4. To functionally validate these findings, we treated OSCC cells with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (DAC) and histone deacetylase inhibitors trichostatin A (TSA) and valproic acid (VPA). The triple-drug combination treatment resulted in the most robust reactivation of MAGED4 expression, correlating with promoter DNA demethylation and enhanced acetylation of H3K9 and H3K27 at the MAGED4 promoter. Our findings elucidate critical epigenetic mechanisms contributing to MAGED4 heterogeneity in OSCC and highlight the potential of combination epigenetic therapies to reverse this heterogeneity, thereby providing a foundation for exploring such approaches to improve immunotherapeutic outcomes.