HDAC9 and neoplasm: Preclinical studies have shown that inhibitors targeting DNA methyltransferases (DNMT), histone deacetylases (HDAC), enhancer of zeste homolog 2 (EZH2), bromodomain and extra-terminal domain (BET) proteins, and lysine-specific demethylase 1 (LSD-1), can improve anti-tumor efficacy of ICB.