Histone deacetylase inhibitor pracinostat suppresses colorectal cancer by inducing CDK5-Drp1 signaling-mediated peripheral mitofission

Divisions at the periphery and midzone of mitochondria are two fission signatures that determine the fate of mitochondria and cells. Pharmacological induction of excessively asymmetric mitofission-associated cell death (MFAD) by switching the scission position from the mitochondrial midzone to the periphery represents a promising strategy for anticancer therapy. By screening a series of pan-inhibitors, we identified pracinostat, a pan-histone deacetylase (HDAC) inhibitor, as a novel MFAD inducer, that exhibited a significant anticancer effect on colorectal cancer (CRC) in vivo and in vitro. Pracinostat increased the expression of cyclin-dependent kinase 5 (CDK5) and induced its acetylation at residue lysine 33, accelerating the formation of complex CDK5/CDK5 regulatory subunit 1 and dynamin-related protein 1 (Drp1)-mediated mitochondrial peripheral fission. CRC cells with high level of CDK5 (CDK5-high) displayed midzone mitochondrial division that was associated with oncogenic phenotype, but treatment with pracinostat led to a lethal increase in the already-elevated level of CDK5 in the CRC cells. Mechanistically, pracinostat switched the scission position from the mitochondrial midzone to the periphery by improving the binding of Drp1 from mitochondrial fission factor (MFF) to mitochondrial fission 1 protein (FIS1). Thus, our results revealed the anticancer mechanism of HDACi pracinostat in CRC via activating CDK5-Drp1 signaling to cause selective MFAD of those CDK5-high tumor cells, which implicates a new paradigm to develop potential therapeutic strategies for CRC treatment.