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 Institute's 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.

Sequential azacitidine plus lenalidomide in previously treated elderly patients with acute myeloid leukemia and higher risk myelodysplastic syndrome

The outcome of sequential azacitidine with lenalidomide has not been reported in previously treated patients with acute myeloid leukemia (AML) and higher risk myelodysplastic syndrome (MDS). This study describes a phase 2 study evaluating the safety and efficacy of this combination in elderly patients with AML and MDS with prior hypomethylating agent (HMA) and/or immunomodulatory agent exposure. Patients were treated on a 42-day cycle with azacitidine at 75 mg/m2 SQ/IV daily on days 1-7, followed by lenalidomide 50 mg orally daily on days 8-28. The median number of treatment cycles on study was two (range = 1-11). Of 32 evaluable patients, the overall response rate was 25%. Neutropenic fever was the most common serious adverse event, but overall the combination was well-tolerated. The median overall survival (OS) for responders vs non-responders was 9.8 vs 4.0 months, respectively (HR = 0.36, p = 0.016). In conclusion, this combination demonstrated modest clinical activity in this poor risk population.

Abstract 3400: Mitochondrial profiling in AML patients treated with an Alvocidib containing regimen reveals MCL1 dependency in responder bone marrow

Background.  Molecular profiles may provide insights into the likelihood of responding to traditional cytotoxic chemotherapy as well as important clues to the success of novel targeted agents.  The anti-apoptotic BCL-2 family proteins have previously been shown to facilitate pro-survival and resistance to chemotherapy in AML, multiple myeloma, as well as in other types of cancer. Measuring the function of these proteins using BH3 profiling has proven to provide useful information in predicting AML treatment response with traditional ara-c based treatment. Here, we sought to determine if such an approach might detect response with the addition of Alvocidib to ara-c-based chemotherapy. Mitochrondrial apoptosis signaling was assessed in AML patients treated with Alvocidib, ara-c and mitoxantrone (FLAM).  Methods.  Pretreatment peripheral blood mononuclear cell and bone marrow specimens from 63 patients treated with FLAM were measured for mitochondrial outer membrane permeabilization following incubation with BH3 peptides as a surrogate for BCL-2 protein family function. Results.  Analysis of the priming states (mitochondrial depolarization) in the patients who underwent complete remission (CR), compared with those who did not (NR), revealed that NOXA priming was significantly higher in CR bone marrow samples (median 44.5%) compared with NR samples (median 5.2%, p = 0.006). NOXA is known to interact most directly with MCL1, suggesting that these cancer cells may be MCL1 dependent. An additional multi-peptide algorithm using three BH3 members was also identified (involving BAD, PUMA, and BIM), which may also indirectly support MCL1 dependency. These BH3 priming profiles were both additive to known risk factors associated with clinical response to chemotherapy, including cytogenetic risk factors. Receiver operating characteristic (ROC) curve analysis of NOXA priming plus cytogenetics and MDS history indicated that these variables were highly predictive of response to FLAM (AUC-0.92, p = 0.0002). This correlation is distinct from our previous work which showed that the priming due to the BIM peptide predicts response to traditional ara-c based treatment. This work provides a basis for further studies into the MCL1 dependent action of Alvocidib, as well as a potential biomarker for identification of patients likely to respond to FLAM.

Citation Format: Elisha J. Dettman, Steven L. Warner, Camille Doykan, Melissa Arn, Noel Blake, David J. Bearss, Michael Cardone, Bruce D. Smith. Mitochondrial profiling in AML patients treated with an Alvocidib containing regimen reveals MCL1 dependency in responder bone marrow. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3400. doi:10.1158/1538-7445.AM2015-3400

Abstract 340: Mitochondrial priming of new targeted agents in acute myeloid leukemia

As numerous molecularly targeted agents are entering clinical trials, predictive testing is highly desirable. We investigated if response to certain agents correlates with the recently reported method of BH3 profiling (Chonghaile TN et al, Science, 2011), a functional assay developed by Letai's group that measures tumor cell mitochondrial priming by measuring mitochondrial outer membrane permeabilization (MOMP) following exposure to the peptide-mimicking BH3 domains of BH3-only proteins. Mitochondrial priming has been reported to be correlated with clinical responses to conventional chemotherapy in solid tumors and hematological malignancies (Vo TT et al, Cell, 2012, Pierceall W et al, Mol Cancer Ther, 2013).

Twenty-two AML lines were tested. Cells were permeabilized with digitonin and exposed to standardized doses of BH3 peptides (BIM, PUMA, NOXA, BAD, BMF, HRK, or PUMA2A). JC-1 was used for detection of MOMP and served as a measure of sensitivity to each peptide (reported as %[BH3 peptide]). Also, BCL-2, BCL-XL and MCL-1 expression levels were determined by Western blot. In addition to studies of untreated cells, treatment effects of different anti-leukemia drugs (AraC, Nutlin-3a, KPT-330 [Selinexor] and ABT-199) were determined over a wide dose range and denoted as ([specific apoptosis] = [(%Annexin V+ cells at each dose) - (%Annexin V+ cells at 0 μM)]/[100- (%Annexin V+ cells at 0 μM)]). Mixed linear models were used for analysis. As expected, ABT-199 sensitivity positively correlated with %[BAD]-%[HRK] (|β| = 3.22, p < 0.001), which is compatible with BCL-2 dependency of ABT-199 (while BAD is binding to BCL-2 and BCL-XL, HRK is binding to BCL-XL only and the difference is therefore BCL-2-specific). This was supported by the observed correlation between %[BAD]-%[HRK] and BCL-2 protein expression levels (r=0.619; p = 0.018). AraC sensitivity showed a similar correlation with %[BAD]-%[HRK] (|β| = 1.61, P < 0.05). KPT-330 sensitivity in p53 wild-type cell lines positively correlated with %[PUMA] (|β| = 0.92, P = 0.054), consistent with the notion that KPT-330 induces PUMA through p53 activation. Unexpectedly, Nutlin-3a activity did not correlate with any of the BH3 peptides. Results indicate that ABT-199, KPT-330 and Nutlin-3a show different modes of action in terms of BH3 peptide dependency, supporting potential combination effects of these agents. For ABT-199, increased MCL1 levels were associated with diminished cytotoxicity (r=0.532; p=0.05), as expected. For Ara-C, a similar correlation with MCL-1 was noted (r=0.505; p=0.06), but no correlations were observed for Nutlin-3a and KPT-330.

In conclusion, BH3 profiling is a promising tool to predict the BH3 peptide dependency of the BH3-mimetic ABT-199 and the XPO1-inhibitor KPT-330. Functional BH3-profiling appears to be superior to the static quantitation of Bcl-2 family protein levels in AML. Furthermore, mitochondrial priming may be useful for the rational design of new combination therapies.

Citation Format: Jo Ishizawa, Kensuke Kojima, Seshagiri R. Duvvuri, Teresa McQueen, Vivian R. Ruvolo, Graciela M. Nogueras-Gonzalez, Xuelin Huang, William Pierceall, Michael Cardone, Ryan Lena, Camille Doykan, Sharon Shacham, Michael Kauffman, Marina Konopleva, Michael Andreeff. Mitochondrial priming of new targeted agents in acute myeloid leukemia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 340. doi:10.1158/1538-7445.AM2014-340

Abstract 907: Bcl-xL dependence predicts response to alvocidib in chronic lymphocytic leukemia patients

Introduction. Chronic lymphocytic leukemia (CLL) patients may benefit from personalized strategies targeting specific therapies to individuals with favorable molecular profiles. Many therapeutics exhibit response in a subset of patients, and factors such as age or cytogenetics are insufficient to predict treatment success with high accuracy. We assessed mitochondrial functionality in apoptosis signaling for identification of CLL patients likely to exhibit clinical response to treatment with alvocidib. Effects of this agent have been shown to involve pathways of apoptosis, providing the rationale for our study. Patients and Methods. Relapsed/refractory patients comprising OSU0055 and Sanofi EFC6663 clinical trials were analyzed. Pretreatment peripheral blood mononuclear cell (PBMC) specimens were divided into training and validation sets for response-correlative assessment. Blinded to outcomes, we analyzed specimens by flow cytometry-based BH3 profiling, indirectly measuring induction of mitochondrial outer membrane permeabilization in response to treatment with BH3-only peptides (Bim, Noxa, Bad, Bmf, Hrk) as surrogates for Bcl-2 family functions. Findings were correlated with disease characteristics and treatment outcome in the proof-of-principal set and tested for confirmation in the validation set. Results. Response data were available for 62 patients; training and test sets comprised 30 and 32 patients, respectively. Regression analyses indicated a correlation between clinical response (ordered 3 categories; PD, SD, PR) and priming in training set with Bim(0.1) (p=.014) and Hrk (p=.0098), that later validated in the test set for both markers (p=.0051 and p=.015, respectively). In total (n=62), Bim regression displayed a p=.0027 and Hrk regression a p=.00046. When analyzed as PD/SD vs PR, the combined cohort yielded Bim p=.04, and Hrk p=.0039 by logistic regression. Using area under the receiver operating curve (AUC) to quantify the accuracy of outcome prediction, Bim AUC = 0.73 (CI[.60-.85]; p=.0004) and Hrk AUC = .73 (CI[.61-.86]; p=.0002). Hrk benefitted from adjustment for trisomy12 status (AUC=0.83; CI[.71-.95]; p<.0001). Analysis of BH3 profiling and tumor lysis syndrome (TLS) indicated correlation between TLS and Bad priming (p=.012 log regression; AUC=.75; CI[.60-.89]; p=.0007) that benefitted from inclusion of ECOG status and patient age (AUC=.85; CI[.73-.97]; p<.0001). Conclusion. Bim and Hrk are significantly associated with response and, thus, engaging Bcl-xL dependence may be a component of response to alvocidib in relapsed CLL patients. Interestingly, TLS is predicted by a distinct BH3 profiling peptide readout, Bad, consistent with alvocidib-associated TLS driven by Bcl-2-dependency. Taken together, these biomarkers may predict patient response to investigational CDK inhibitors in CLL and concurrently identify patients at risk for treatment-related toxicity.

Citation Format: William E. Pierceall, Steven L. Warner, Ryan J. Lena, Camille Doykan, Noel Blake, Michael Elashoff, Daniel D. Von Hoff, David J. Bearss, Michael H. Cardone, Michael Grever, Mark C. Lanasa, John C. Byrd, Amy J. Johnson. Bcl-xL dependence predicts response to alvocidib in chronic lymphocytic leukemia patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 907. doi:10.1158/1538-7445.AM2014-907

Mcl-1 dependence predicts response to vorinostat and gemtuzumab ozogamicin in acute myeloid leukemia

Older adults with acute myeloid leukemia (AML) are commonly considered for investigational therapies, which often only benefit subsets of patients. In this study, we assessed whether BH3 profiling of apoptotic functionality could predict outcomes following treatment with vorinostat (histone deacetylase inhibitor) and gemtuzumab ozogamicin (GO; CD33-targeted immunoconjugate). Flow cytometry of BH3 peptide priming with Noxa (anti-apoptotic protein Mcl-1 modulator) correlated with remission induction (p=.026; AUC=0.83 [CI: 0.65-1.00; p=.00042]: AUC=0.88 [CI:0.75-1.00] with age adjustment) and overall survival (p=.027 logistic regression; AUC=0.87 [0.64-1.00; p=.0017]). This Mcl-1-dependence suggests a pivotal role of Bcl-2 family protein-mediated apoptosis to vorinostat/GO in AML patients.