SAP30 (Sin3A-associated protein 30) is a core component of the histone deacetylase (HDAC) complex that mediates transcriptional repression through chr4 remodeling 1. SAP30 associates with Sin3A and HDAC1/2 to form a functional deacetylase complex capable of deacetylating core histone octamers 1. Beyond its classical role as a transcriptional corepressor, SAP30 possesses DNA-binding capabilities mediated by zinc-dependent modules and is regulated by phosphatidylinositol binding, enabling direct recruitment of deacetylating enzymes to nucleosomes 2. In cancer biology, SAP30 functions as a nonmutational oncoprotein upregulated in multiple malignancies. In breast cancer, SAP30 acts paradoxically as a coactivator by bridging SIN3 complex and MLL1 through homodimerization, enhancing chr4 accessibility and promoting genes involved in metastasis 3. In colorectal cancer, the METTL14-YTHDF1-SAP30 axis promotes glycolysis and oxaliplatin resistance 4, while in renal cell carcinoma, SAP30 suppresses MT1G expression to inhibit p53 activity and promote proliferation 5. In acute myeloid leukemia, UHRF1-SAP30 interaction represses MXD4, maintaining leukemia-initiating cell self-renewal 6. SAP30 upregulation correlates with poor prognosis across these cancer types, identifying it as a promising therapeutic target.