Background: DCA increases pyruvate dehydrogenase activity via inhibition of pyruvate dehydrogenase kinase, which shunts pyruvate away from lactate production into the mitochondrial respiration, resulting in enhanced mitochondrial activity. As2O3 is approved for treatment of relapsed/refractory acute promyelocytic leukemia (APL). As2O3 as a single agent or in combination with cytarabine is ineffective for treatment of non-APL acute myeloid leukemia (AML) by most studies. As2O3 affects several different molecular targets and cellular functions such as decreasing mitochondrial membrane potential by opening permeability transition pore complex in membranes, reactive oxygen species production, and caspase pathways activation. We hypothesized that combination of DCA, as a mitochondrial respiration enhancer, and As2O3, which impairs mitochondrial activity, would have anti-leukemic synergistic effects and potentially overcome drug resistance particularly in relapsed/refractory AML.

Methods: IC50s for As2O3 and DCA were generated for two AML cell lines, MOLM-14 and MV4-11, the latter carries FLT3-ITD mutation. Cells were treated with DCA at IC30 and As2O3 either concurrently for 72 h or sequentially with 48 h exposure to DCA followed by the addition of As2O3 (100 nM - 5μM) for 48 h. Each experiment was terminated with WST-1 (Roche). Viability of cells was assessed by trypan blue exclusion. Experiments were performed in triplicate.

Results: IC50s for As2O3 and DCA were 0.88 ± 0.02 μM and 15.87 ± 1.22 mM for MOLM-14, 0.54 ± 0.03 μM and 19.08 ± 2.25 mM for MV4-11, respectively. When treated concurrently, the potentiation factors were 1.8 and 1.3 for MOLM-14 and MV4-11, respectively. When the cells were pretreated or "primed" with DCA for 48 h and then exposed to As2O3 for 48 h, the potentiation factors were 2 and 1.8 for MOLM-14 and MV4-11, respectively. Viability tests showed a 33-50% increase in cell kill when DCA and As2O3 were used in combination compared to As2O3 or DCA alone. The number of viable cells remaining after combination treatment was significantly lower than the number of viable cells after either treatment alone when treated sequentially or concurrently (p<0.05). Further mechanistic studies and preclinical models are ongoing to best predict the future clinical dose and schedule.

Conclusion: Combination of DCA (IC30, 11 mM) and As2O3 whether used sequentially or concurrently in AML cells caused significantly more cellular damage as compared to either drug alone. To the best of our knowledge, this is the first report of the combination of DCA+As2O3 against AML cells. These data suggest that targeting cellular metabolism in leukemia may provide a therapeutic option for AML patients with unfavorable risk, such as relapsed/refractory, FLT3-ITD or who are not candidates for cytotoxic agents and warrant further clinical investigation.

Citation Format: Ashkan Emadi, Mariola Sadowska, Brandon A. Carter-Cooper, Rena G. Lapidus, Edward A. Sausville. Targeting leukemia metabolism: augmentation of anti-leukemic activity of arsenic trioxide (As2O3) against non-APL AML cell lines in presence of dichloroacetate (DCA). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3268. doi:10.1158/1538-7445.AM2013-3268