HDAC9 and cancer: In tumors, histone deacetylation promotes the development and metastasis of various cancers by silencing a large number of chromosomal regions containing tumor suppressor genes, whereas HDAC inhibitors can affect the expression of cancer-associated genes, which in turn exerts an inhibitory effect in a wide range of malignancies (Li and Seto, 2016; Hassell, 2019; Mekala et al., 2022).