HDAC9 and breast cancer: Existing evidences indicate that HDAC inhibitors repress breast cancer cells proliferation,26,27 angiogenesis,28 and regulate anti-tumor immunity.29,30 Furthermore, several studies have demonstrated that HDAC regulates events implicated in breast cancer progression, including self-renewal and expansion of stem cells, invasion and metastasis.31 Numerous clinical trials are underway to evaluate the use of HDAC inhibitors against breast cancer.