HDAC9 and neoplasm: HDAC inhibition can profoundly affect anti-tumor immune responses, including enhancing MHC class I antigen presentation,445 promoting M1-like polarization of TAMs,446,447 and depleting MDSCs.448 HDAC inhibition can maintain intra-tumoral macrophages with a pro-inflammatory tumoricidal phenotype and preserve their ability to conduct ADCC needed by ADCC-dependent therapeutic antibodies,449 which cannot be achieved by the depletion of TAMs (Fig. 4).