Since specific HDAC family members, such as HDAC6, are overexpressed in different tumor types (Chen et al., 2022; Kim et al., 2022; Liu et al., 2016; Menbari et al., 2020), the development of selective HDACi has corroborated the idea of a focused targeted therapy, rather than using pan-HDACi that may exert multiple effects. This evidence concerns the gene HDAC9 and neoplasm.