In the last decades, inhibition of histone deacetylases (HDAC) and mammalian target of rapamycin (mTOR) enzymes has emerged as a potential strategy (Yao et al., 2021) to reverse abnormal epigenetic changes associated with cancer, and several classes of HDAC and mTOR inhibitors have been found to have potent and specific anticancer activities in preclinical studies (Kawai et al., 2003; Fasolo and Sessa, 2012; Min et al., 2012; Tang et al., 2017; Bian et al., 2018; Guo et al., 2020; Yao et al., 2021). This evidence concerns the gene HDAC9 and cancer.