HDAC9 and neoplasm: To attenuate tumor drug resistance, researchers have undertaken numerous experiments and created a variety of related drugs that induce the polarization from M2-like to M1-like macrophages174, including but not limited to CSF-1R antagonists, PI3Kγ inhibitors, bromodomain-containing protein 4 (BRD4) inhibitors, Signal-regulatory protein alpha (SIRPα) inhibitors and histone deacetylase (HDAC) inhibitors.