Abstract 4666: Anti-leukemic activity of a novel histone deacetylase inhibitor, CG200745, via induction of mitochondrial dysfunction in acute myeloid leukemia

Abstract

Abstract Background: Acute myeloid leukemia (AML) can be cured by cytotoxic chemotherapy, but about half of patients with AML fail to obtain long-term survival, mostly due to chemotherapy-resistance. Novel therapeutic approaches are needed to overcome the resistance. Many studies have shown that histone deacetylase (HDAC) activity is elevated in human cancers and HDAC inhibitors (HDIs) induce expression of genes critical for tumor growth arrest and apoptosis. To date, the US FDA approves two HDIs, vorinostat (SAHA) and romidepsin (FK228), for treatment of cutaneous T-cell lymphoma. CG200745 {(E)-2-(Naphthalen-1-yloxymethyl)-oct-2-enedioic acid 1-[(3-dimethylamino-propyl)-amide] 8-hydroxyamide]} is a novel hydroxamate-based pan-HDI. We examined anti-leukemic activities of CG200745 in AML and we also compared the effects of CG200745 and SAHA in vitro and in vivo. Materials and methods: For cell proliferation assay, 7 human AML and other leukemia cell lines (HL60, K562, Molm13, MV4, NB4, U937, and KG-1) were cultured with HDIs (CG200745 and SAHA) and cell viability was determined by CCK-SK kit. Cell cycle analysis was performed using a flow cytometer. For western blotting of acetylation and apoptosis induction, antibodies to acetylated (on Lys 18) histone H3, histone H3, PARP, XIAP, caspases-3, –8, and –9, and actin were used. For measuring membrane potential of mitochondria, a flow cytometer was used after staining with TMRE. We established a murine leukemic model with infusing WEHI-3 leukemia cells in BALB/c mice, and tested anti-leukemic effects of HDIs in vivo. Lastly, we obtained leukemic cells from patients with AML and performed cell proliferation assay using CellTiter 96® Aqueous One Solution Reagent. Results: CG200745 and SAHA successfully inhibited HDAC activities in human leukemic cell lines. Both agents decreased cell viability in a dose-dependent manner and IC50 values were lower with CG200745 than with SAHA in all leukemic cell lines except one (KG-1). In U937 cell line, flow cytometry showed the accumulation of S population by both HDIs. Exposure of the cells to the HDIs resulted in activation of caspase-9 and –3, increase of PARP cleavage, and decrease of XIAP. Activation of caspase-8 was not noted. TMRE fluorescence levels decreased after treatment of HDIs in a dose-dependent manner and were correlated with decrease of XIAP and increase of apoptosis. Decrease of mitochondrial membrane potential was more prominent with CG200745 compared to SAHA. In both murine leukemic model using WEHI-3 leukemic cells and CellTiter assay using leukemic cells from AML patients, CG200745 showed more significant anti-leukemic activities than SAHA. Conclusion: CG200745 has significant anti-leukemic activities against AML cells and the effects appear to be mediated by activation of the intrinsic apoptotic pathway and induction of mitochondrial dysfunction. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4666. doi:1538-7445.AM2012-4666