HDAC9 and ovarian cancer: In comparison, it took 3 months to develop resistance to the tyrokinase inhibitor STI571 by chronic myelogenous leukemia cell lines [58], 6 months to develop resistance to taxol in the human ovarian cancer cell line A2780 [59], and 12 weeks to develop resistance to the HDAC inhibitor valproic acid by renal cell carcinoma Caki-1 cells [60].