HDAC4 and breast cancer: Similar to HDAC4, HDAC5 also displays a regulatory effect on tumor resistance in breast cancer, which is related to its regulation of cell proliferation, cell differentiation and autophagy (Hsieh et al., 2015b; Li et al., 2016; Cao et al., 2017; Huang et al., 2017; Cao et al., 2018; Xue et al., 2019).