HDAC9 and cervical carcinoma: Our previous work has also revealed that the combination of valproic acid (VPA), a clinically available HDAC inhibitor, and all-trans retinoic acid (ATRA) promotes synergistic effects in reactivating dormant RARβ2 and strongly inhibiting cervical cancer cell growth in vitro and in vivo by promoting differentiation via the PI3K/Akt pathway [19].