To investigate the anticancer effects of the novel hydroxamic acid-derived histone deacetylase (HDAC) inhibitor MHY218, its efficacy was compared to that of suberoylanilide hydroxamic acid (SAHA) in human ovarian cancer cells. The anticancer effects of MHY218 on cell viability, cell cycle regulation and apoptosis were investigated. In addition, MHY218 or SAHA was administered for 28 days in a tumor carcinomatosis model with SKOV-3 cells. MHY218 significantly reduced the expression of HDAC4 and

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... DAC7 in SKOV-3 cells. Similarly, MHY218 also inhibited total HDAC, HDAC1, HDAC4 and HDAC7 enzyme activity in a concentration-dependent manner. The anticancer effect of MHY218 (IC 50 , 3.2 μM) was more potent than SAHA (IC 50 , 3.9 μM) in suppressing the SKOV-3 cell viability. Moreover, MHY218 markedly increased expression of p21 WAF1/CIP1 , which acts as a cell cycle inhibitor. Cell cycle analysis showed that the high dose (5 μM) of MHY218 significantly increased the proportion of cells in the G2/M phase. In particular, MHY218 and SAHA significantly increased the sub-G1 population and the number of TUNELpositive apoptotic cells compared with those in the untreated control. These results were confirmed by analysis of poly-ADP ribose polymerase (PARP), where MHY218 and SAHA increased the level of an 85-kDa fragment resulting from PARP cleavage as well as caspase-3 activity. Likewise, MHY218-induced apoptosis through caspase-3 activation was confirmed by the increase in the release of cytochrome c and Bax/Bcl-2 ratio. In an in vivo tumor carcinomatosis model, the growth of transplanted SKOV-3 cells was inhibited by 71% after treatment with MHY218 (10 mg/kg), whereas SAHA (25 mg/kg) suppressed growth by 48%. These results indicate that MHY218 is a potent HDAC inhibitor that targets regulating multiple aspects of cancer cell death and might have preclinical value in ovarian cancer chemotherapy, warranting further investigation.