Hybrid polar histone deacetylase inhibitor induces apoptosis and CD95/CD95ligand expression in human neuroblastoma

Inhibitors of histone deacetylase (HDAC) have been shown to have both apopt otic and differentiating effects on various tumor cells, M-carboxycinnamic acid bishydroxamide (CBHA) is a recently developed hybrid polar compound st ructurally related to hexamethylene bisacetamide. CBHA is a potent inhibito r of HDAC activity. CBHA induces cellular growth arrest and differentiation in model tumor systems, We undertook an investigation of the effects of CB HA on human neuroblastoma cell lines in vitro, When added to cultures of a panel of neuroblastoma cell lines, CBHA induced the accumulation of acetyla ted histones H3 and H4, consistent with the inhibition of HDAC, Concentrati ons of CBHA between 0.5 mu M and 4 mu M led to apoptosis in nine of nine ne uroblastoma cell lines, Apoptosis was assessed by DNA fragmentation analysi s and the appearance of a sub-G(1) (<2N ploidy) population by flow cytometr ic analysis. The addition of a caspase inhibitor (benzyloxyrarbonyl-Val-Ala -Asp-fluoromethyl ketone) completely abrogated CBHA-induced apoptosis in th ree of three cell lines. The addition of cycloheximide greatly reduced CBHA -induced apoptosis, suggesting that apoptotic induction was dependent on de novo protein synthesis. In addition, CBHA induced the expression of both C D95 (APO-1/Fas) and CD95 ligand within 12 h, The effect of CBHA on human ne uroblastoma cells suggests that this agent and structurally related synthet ic hybrid polar compounds have therapeutic potential for the treatment of t his malignancy.