A potent hydroxamic acid-based, small-molecule inhibitor A452 preferentially inhibits HDAC6 activity and induces cytotoxicity toward cancer cells irrespective of p53 status

HDAC6-selective inhibitors are novel epigenetic anticancer agents. However, their precise mechanisms of action are incompletely understood. We investigated the anticancer mechanisms of the novel potent and selective HDAC6 inhibitor A452 compared with current clinically tested HDAC6 inhibitor ACY-1215. We demonstrate that A452 effectively inhibits the cell growth and viability of various cancer cell types, irrespective of p53 status. A452-induced apoptosis as evidenced by activated caspase 3 and PARP, increased Bak and Bax and decreased Bcl-xL. Moreover, A452 shifted cells away from antiapoptotic (AKT and ERK) pathways and toward proapoptotic (p38) pathways. A452 triggered DNA damage via increased γH2AX and activation of the checkpoint kinase Chk2. A452 induced the suppression of cell migration and invasion. Interestingly, A452 upregulated the expression of PD-L1, which regulates the PD-1 inhibitory pathway in T cells. Overall, our results suggest that A452 is more effective as an anticancer agent than ACY-1215. Therefore, therapeutically targeting HDAC6 may represent a novel strategy for cancer treatment irrespective of the p53 mutation status.