HDAC9 and cancer: This confirms the inhibition of the PI3K and HDAC activities by CUDC‐907 and is consistent with previous observations in other cancer cells.28 In addition, we also found that CUDC‐907 decreased ERK (Thr202/Tyr204), MEK1/2 (Ser271/221), and STAT3 (Tyr705) phosphorylation, suggesting a blockage of both the RAF/MEK/ERK and STAT3 signalling pathways.