SIN3B is a transcriptional corepressor that functions as a core scaffold component of histone deacetylase complexes regulating chr19 acetylation states 1. Mechanistically, SIN3B recruits HDAC2 and other chr19-modifying enzymes to target gene promoters, where it counteracts histone acetyltransferase activity and represses transcription of cell cycle and differentiation-related genes 1. SIN3B interacts with diverse protein partners including MAD1, FOXK1, and Myt1l to coordinate gene silencing programs essential for cell cycle exit and cell fate determination 2. In cancer contexts, SIN3B exhibits context-dependent roles. Elevated SIN3B expression correlates with poor survival in melanoma and promotes hepatocellular carcinoma cell migration through integrin αV activation 34. Conversely, SIN3B loss sensitizes cancer cells to genotoxic stress by impairing DNA damage repair pathway choice and reducing homologous recombination capacity 5. In pancreatic cancer, SIN3B loss enhances anti-tumor immunity by increasing CXCL9/10 secretion and CD8+ T cell infiltration, improving anti-PD1 immunotherapy responses 6. These findings suggest SIN3B inhibition represents a therapeutic vulnerability in cancer, potentially enhancing both chemotherapy sensitivity and immunotherapy efficacy.