Abstract 2282: Decitabine response in FLT3-negative AML is associated with mitochondrial priming

To date, acute myeloid leukemia (AML) remains a poor-prognosis disease with only approximately 25% of patients surviving five years after being diagnosed (SEER – 2005-2011). There are a wide variety of treatment options ranging from intense chemotherapy to targeted therapies. Beyond tolerability, identifying the ideal treatment strategy for each patient remains a difficult task. Mitochondrial profiling of AML patient samples using Bcl-2 homology domain (BH3) mimetics has proven to accurately identify patients that respond to several therapies in AML. In this method, cancer cells are exposed to BH3 mimetics designed to test for susceptibility to induction of apoptosis. The readout, called “BH3-Priming” indicates anti-apoptotic protein dependencies in cancer cells. In this study, samples from AML patients that were treated with at least one cycle of the hypomethylating agent, decitabine, at The Ohio State University were collected and BH3 profiled (n = 64). The patients were assessed for a complete response to the drug and were characterized by several molecular biomarkers including FLT3 mutational status. We found that the FLT3 mutation negative patients (n = 32) who responded to decitabine had significantly higher mitochondrial responses to the BIM and HRK mimetics (p = 0.04) compared with non-responders. We also found that FLT3 mutant patients (n = 12) had significantly (p = 0.02) higher priming than those patients lacking those lesions. Surprisingly, despite being apparently more predisposed towards apoptosis, these patients are less likely to respond to decitabine (42% versus 20%) in vivo than those without these mutations. This could indicate that additional non-mitochondrial inhibitory mechanisms are present in those FLT3 mutant leukemias that prevent response to decitabine. To further examine the interaction between FLT3 and mitochondrial priming, we profiled engineered cell lines with and without FLT3 mutations. We found that mitochondrial priming was significantly lower (p = 0.03) in BAF3 cells with unmutated FLT3 compared with five BAF3 cell lines containing FLT3 mutations (ITD and TKD mutations). Further, we examined the Broad Institute9s Cancer Therapeutics Response database (CTRP v 2.0) for cancer cell line response to decitabine and found that wild type FLT3 cell lines that responded to decitabine had significantly higher mitochondrial priming than those that did not respond to the drug (p = 0.04), consistent with the patient data. Taken together, we have discovered that response to decitabine in AML cell lines and AML patient samples depends on mitochondrial dependencies and FLT3 mutational status. Genetic lesions in FLT3; however, may be able to over-ride mitochondrial responsiveness to pro-apoptotic factors, illustrating the probable need to measure multiple attribute types including genetics and ex vivo functional testing to accurately determine the likelihood of response to AML therapies. Citation Format: Elisha Dettman, Camille Doykan, Jo Ishizawa, Weiguo Zhang, Alison Walker, William Blum, Rebecca Klisovic, Michael Cardone, Michael Andreeff, Amy Johnson. Decitabine response in FLT3-negative AML is associated with mitochondrial priming. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2282.