Cases Of Acute Myelogenous Leukemia Research Articles

Transplant Eligible and Ineligible Elderly Patients with AML-A Genomic Approach and Next Generation Questions.

The management of elderly patients diagnosed with acute myelogenous leukemia (AML) is complicated by high relapse risk and comorbidities that often preclude access to allogeneic hematopoietic cellular transplantation (allo-HCT). In recent years, fast-paced FDA drug approval has reshaped the therapeutic landscape, with modest, albeit promising improvement in survival. Still, AML outcomes in elderly patients remain unacceptably unfavorable highlighting the need for better understanding of disease biology and tailored strategies. In this review, we discuss recent modifications suggested by European Leukemia Network 2022 (ELN-2022) risk stratification and review recent aging cell biology advances with the discussion of four AML cases. While an older age, >60 years, does not constitute an absolute contraindication for allo-HCT, the careful patient selection based on a detailed and multidisciplinary risk stratification cannot be overemphasized.

Mitotic recombinatory evolution in acute leukemia

A cohort of leukemia cases is presented with ancillary testing that includes microarray studies, karyotyping, FISH, and RNA sequencing to illustrate clonal evolution. Common evolution etiology with each case is apparent homologous mitotic recombination (HMR). The cohort includes: four cases of Pre B-cell acute lymphoblastic leukemia (B-ALL) with a single translocation derivative (19)t(1;19)(q23.3;p13.3), an acute myelogenous leukemia (AML) case with a paracentric inversion of 11q13.3q23 in both homologues confirmed as a rare KMT2A-MAML2 gene fusion, and a transplant patient in AML relapse with a t(6;11)(6q27;q23) and evolution to an additional derivative 6 chromosome. The PBX1-TCF3 fusion in the t(1;19) B-ALL subgroup has long been associated with clones that show either the balanced translocation (∼25%) or the unbalanced single derivative 19 (∼75%). Evidence from the CMAs and FISH is consistent with HMR initiating at either the PBX1 translocation breakpoint or at a more proximal long arm site that mediates the evolution to the unbalanced form. This is contrary to the previous assumptions of either nondisjunction duplication of the normal homologue with loss of the translocation derivative 1 or an original trisomy 1 that loses the translocation derivative 1. Relapse from an unrelated transplant donor created unique allele dosage ratios in the microarray of the AML patient with the t(6;11) KMT2A-AFDN fusion. An HMR-based evolution initiation site proximal to the 6q27 AFDN fusion gene is evident in the microarray of chromosome 6, the known oncogenic fusion derivative. The HMR selection driver in both AML cases is very likely associated with the DNA doubling of the oncogenic fusions in 6q and 11q, respectively. Since the oncogenic derivatives in the 1;19 cases are clearly the retained derivative 19, selection for the HMR clonal evolution in 1q is apparently based on the known proliferative advantage of extra copies of 1q in B-ALL and other malignancies. Although selection-based HMR can effectively initiate at any site proximal to a driver gene fusion, it appears that the translocation breaksite is common for many translocations. In addition, evidence from HMR evolution related distal 11q mutations, numerous unbalanced CCND1/IGH translocations, and the double MAML2/KMT2A presented in this study suggest that a recombinatorial "hot spot" exists near the CCND1 gene in many rearrangements or mutations within 11q.

Abstract IA020: Therapeutic targeting of MLL complexes in cancer

Abstract Inappropriate expression of genes such as the homeotic (HOX) genes is found in up to 40% of cases of Acute Myelogenous Leukemia (AML). Two well-defined genetic subsets, those with MLL-rearrangements and those with NPM1 mutations, are known to possess high-level expression of HOX and MEIS1 genes and have been shown to be dependent on continued expression of these genes. Recent studies have defined the chromatin-bound protein complexes that maintain this aberrant gene expression. Furthermore, multiple groups including ours have now developed small molecule inhibitors of chromatin-associated complexes. Some of these small molecules, including those targeting DOT1L, EZH2, and Bromodomains are at various stages of clinical development. Another approach to target chromatin associated complexes is via disruption of protein-protein interactions. One such protein-protein interaction that is being targeted is the interaction between the histone methyltransferase MLL1 and Menin, an approach that has also been shown to reverse leukemogenic HOX/MEIS1 gene expression. We have developed novel, potent and orally bioavailable MLL1-Menin inhibitors and have brought one of these small molecules to clinical assessment. Inhibition of the MLL1-Menin interaction in MLL-rearranged and NPM1 mutant AML cells leads to loss of Menin from chromatin, destabilization of the Menin protein and specific changes in chromatin state that include loss of the MLL1 complex at select loci. This results in selective reversal of leukemogenic gene expression, changes in occupancy of multiple other chromatin complexes, rapid cellular differentiation and cell death. Also, we have recently found this interaction to be critical in subtypes of Sarcoma opening up novel potential therapeutic opportunities. These molecules have remarkable preclinical activity in human disease models including patient derived xenograft (PDX) models, show minimal toxicity and are now in phase I/II clinical trials. Inhibition of protein-protein interactions represents a potentially effective approach to destabilize chromatin associated complexes for cancer therapy. Citation Format: Scott A. Armstrong. Therapeutic targeting of MLL complexes in cancer. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr IA020.

Expansion of a CD8+ Temra Population and Activating T-Cell Interactions Characterize the Graft Versus Leukemia Response in Relapsed AML

Graft-versus-leukemia (GvL) activity underlies the curative potential of allogeneic hematopoietic stem cell transplantation. Its effectiveness is well-exemplified by donor lymphocyte infusion (DLI), an established adoptive cellular therapy for treatment of relapsed disease. Whereas ~80% of chronic myelogenous leukemia (CML) patients achieve durable remissions to DLI, responses for acute myelogenous leukemia (AML) are only 15-20%. We hypothesized that systematic characterization of immune cell composition and cellular interactions within the marrow tumor microenvironment in relation to DLI would illuminate the molecular basis of the disease-specific susceptibility to GvL. Given the heterogeneous nature of AML, we suspected AML response to comprise more complex leukemic-immune cell interactions than in CML. To these ends, we generated 5’ single-cell RNA- and TCR-sequencing (scTCRseq) and cell surface marker profiling (scCITE-seq) on 24 bone marrow biopsy samples collected before and after DLI from 9 patients with relapsed AML (5 responders [R], 4 nonresponders [NR]). We merged this dataset with our previously reported CML dataset (14 patients, 8 R, 6 NR [PMID: 34758319]) and batch corrected these data with scVI to obtain a total of 414,000 high-quality single-cell transcriptomes for analysis. Evaluation of the immune cell subset proportions over time revealed 10 populations with distinct dynamics in AML responders to DLI but not CML, while 3 other populations showed similar dynamics across diseases. Both CML and AML DLI response were associated with pre-treatment enrichment of an NK cell population highly expressing XCL1, XCL2, CCL3, CCL4, CCL4L2, and CCL5, consistent with a tumor-infiltrating expression profile. Unique to CML (i.e. not observed in AML), in addition to post-DLI enrichment of the TPEX population previously identified, we found a γδ-like T cell population and a classical dendritic cell population exhibiting post-DLI enrichment associated with response to DLI. In AML, response to DLI was most consistently associated with expansion of a CD8+ T cell population (6.03% of total pre-DLI cells vs 18.31% post-DLI for R [p=0.016] compared to 8.68% pre-DLI vs 9.55% post-DLI for NR [p=0.454]) and a naïve B cell population (4.02% pre-DLI vs 11.68% post-DLI for R [p=0.002] compared to 5.42% pre-DLI vs 5.17% post-DLI for NR [p=0.471]). The CD8+ T cell population was characterized by high expression of cytotoxicity genes (e.g. GZMA, GZMB, GZMH, GZMM, PRF1, KLRG1, TOX, EOMES, TBX21) and was most consistent with a T effector memory re-expressing RA (TEMRA) profile, supported by high CD45RA expression by scCITE-seq. This population also highly expressed ZNF683, which encodes the transcription factor Hobit, known to regulate cytotoxicity in CD8+ T cells. Differential gene expression between AML R and NR TEMRA cells revealed enriched expression of ZNF683, GZMH, NKG7, CCL5, and CXCR4 in R and the exhaustion marker TIGIT and the senescence marker KLRG1 in NR. scTCR-seq of the TEMRA subset demonstrated clonal expansion and differentiation into a more proliferative expression profile post-DLI. Among AML cases, 2-20% of the post-DLI repertoire of responders originated from the DLI product while no TCR from the DLI product was detected in the single NR patient available for analysis. We applied predictive interaction modeling among all 50 cell type pairs using CellPhoneDB (PMID: 32103204), which utilizes a publicly available curated database of receptor-ligand interactions. Predicted interactions unique to R between CD8+ TEMRA and AML leukemia cells included CD226-PVR, CD6-ALCAM, and CD46-JAG1, which have been associated with T cell activation. Interactions unique to NR between CD8+ TEMRA and AML leukemia included the inhibitory interactions TIGIT-NECTIN and PTPRC-MRC1. These interactions were not observed in CML patients in either R or NR between CD8+ TEMRA and CML cells, suggesting disease-specific response and resistance mechanisms. Here we show that response to DLI in AML is associated with largely distinct expansion of immune cell populations compared to CML, including not only T cells but an orchestration of B, NK, and myeloid cell subsets. AML responders were uniquely characterized by expansion of a TEMRA subset marked by high expression of the pro-cytotoxic gene ZNF683. Further investigation is needed to evaluate the role of this population in mediating GvL response.

Diagnostic Imaging Radiation in Severe Sickle Cell Disease: Cancer Risk Implications

Introduction: Patients with sickle cell disease (SCD) are repeatedly exposed to diagnostic radiation. Radiographs, computed tomography (CT) and nuclear medicine scans are often ordered for suspected complications caused by sickle cell disease that exposes patients with SCD to ionizing or another form of radiation. A few studies of low-dose cumulative radiation exposure (in people without SCD) suggest that 30 to 100 mSv over 30 decades is associated with higher excess risk of leukemia. New epidemiologic data of low quality suggests that individuals with sickle cell disease (SCD) accumulate “driver mutations” for acute myelogenous leukemia (AML) about 20-30 years earlier than the general population, and have higher risk of AML. In a gene therapy protocol with a few dozen patients, 2 cases of AML have occurred in sickle cell disease and none in thalassemia. It has been reported that children with SCD are frequently exposed to ionizing radiation in the form of plain radiographs, fluoroscopy, computed tomography (CT) scans, bone scans, and other tests. Exposure to ionizing radiation during childhood carries a risk of developing cancer that is directly related to the total radiation dose.Epidemiological data has demonstrated an increase both in diagnostic radiation and in actual or predicted resultant cancer diagnosis. Children are particularly vulnerable to radiation-induced cancer because they are still actively growing and thus are at greater risk of acquiring an oncogenic mutation in an actively dividing cell.Hypothesis: Frequent diagnostic imaging for children and adults with SCD can have significant cumulative radiation exposure that could add excess risk of AML.Methods:The study design was a retrospective chart review. The sample was selected to be enriched for the most severely-affected children and adults in the Sickle Cell Center at UI Health, which provides medical care for over 700 patients with SCD. The subgroup on chronic erythrocytapheresis blood transfusionswere selected as a sample of severe of SCD who are more likely to be exposed to repeated diagnostic radiation. Many have had stroke, which often leads to repeated head CT and cerebral angiograms. Others had pulmonary embolism or acute chest syndrome, which can lead to chest CT angiograms. Other SCD complications with high risk of morbidity or morbidity lead to similar likelihood that patients on chronic exchange transfusion therapy would have histories of multiple imaging studies. Medical records were reviewed for the type and number of all radiographic tests, especially CT scans, during the 10-year period 2011-2020. A second observer confirmed a subset of charts. Standard references were used to estimate radiation exposure in mSv for each type of test. The sum of mSv for each individual was a rough estimate of cumulative radiation in 10 years. The IRB approved the protocol.Results:Chart review on 39 patients (ages 16 - 60y) identified 1,030 radiographic tests with a mean of 26.4 tests/patient. Seven patients had > 50 tests, and one patient had > 100 tests over a 10-year period. Thirty-three patients had at least one CT scan. Eighteen patients had at least 3 CT scans. Twenty patients had cumulative radiation exposure > 30 mSv over a 10-year period, 4 patients had > 100 mSv, and one patient had > 200 mSv. Plain radiographs comprised 71% (736) of the studies and relatively low dose radiation exposure.Discussion:This retrospective study estimated that diagnostic radiography exposed 20 of 39 patients with severe SCD to the range of 30 to 200 mSv over 10 years, mostly from numerous CT scans. This range of cumulative radiation exposure has mixed evidence about possible heightened risk of AML and other cancers. The study is limited by the small sample at a single institution and a heavy bias toward patients with stroke and chest complications, but this severely-affected subgroup comprises many of those eligible for transplant and gene therapy in SCD. Cumulative exposure to diagnostic radiation might be one mechanism for the unexplained patterns of AML in SCD after gene therapy that led to a pause in SCD gene therapy studies for a few months in 2021. Further studies are needed. DisclosuresHsu: Global Blood Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aruvant: Consultancy, Membership on an entity's Board of Directors or advisory committees; Hoffman LaRoche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forma Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cyclerion: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Imara: Research Funding; Eli Lilly: Research Funding; Baxalta / Shire / Takeda: Research Funding.

Phase 1/2, Open-Label, Dose Escalation, Dose Expansion Study of Menin Inhibitor DSP-5336 in Adult Patients (pts) with Acute Leukemia with and without Mixed-Lineage Leukemia (MLL)-Rearrangement or Nucleophosmin 1 (NPM1) Mutation

Relapsed or refractory acute leukemia (AL) in adults, including acute myelogenous leukemia (AML) and acute lymphocytic leukemia (ALL), still represents a significant unmet need. Once AML or ALL relapses after initial treatment, the prognosis is extremely limited, with median survival <6 mo for AML and <1 y for ALL. This is especially true of AML or ALL with MLL rearrangements (MLLr) or relapsed AML with NPM1 mutations. Translocations of the MLL gene, found in approximately 5% to 10% of adult patients with AL, result in an aggressive subtype of leukemia, with a median overall survival (OS) of approximately 9 months and a very high rate of relapse after standard induction therapy for AML or ALL. The NPM1 mutation (NPM1m) is seen in approximately 30-35% of adult AML cases, most commonly in de novo AML, and is associated with a more favorable prognosis in newly diagnosed AML. However, this favorable prognostic effect is lost in the presence of concomitant FLT3-internal tandem duplication (ITD) mutations, which are seen in 40% to 50% of AML with mutated NPM1.These genomic alterations have been the focus for the development of DSP-5336, a novel small-molecule oral therapy that prevents binding of the menin protein to MLL fusion proteins that drive leukemogenesis.In nonclinical studies, DSP-5336 showed selective cell growth inhibitory activity against humanAL cell lines with MLLr or NPM1m. In addition, evidence of antitumor activity and survival advantage was demonstrated in 3 AML xenograft models with MLLr and/or NPM1m. Treatment with DSP-5336 may result in the reduction of leukemic cells, offering therapeutic benefits that include achieving complete remission and prolonged survival in patients with relapsed or refractory AML with MLLr or NPM1m or pts with relapsed or refractory ALL with MLLr.An open-label, single-arm, phase 1/2 study (NCT04988555) of DSP-5336 is being started to evaluate the safety and efficacy of DSP-5336 and determine the recommended phase 2 dose (RP2D) in adults aged ≥18 y with relapsed/refractory AML or ALL after at least one line of standard therapy, including hematopoietic stem cell transplant. Key inclusion criteria are ECOG performance status 0-2 and adequate cardiac, renal, and hepatic function. Patients on the strong CYP3A4 inhibitors ketoconazole, itraconazole, or isavuconazole, are excluded unless they can be safely taken off these medications or switched to another antifungal medication at least 7 days prior to start of study treatment.Patients will be dosed twice daily for 28 days per cycle. The study design is depicted below in Figure 1. In phase 1, 21-30 pts will be enrolled into multiple ascending dose cohorts (1-6 pts per dose level), with dose escalation determined using a two-parameter Bayesian logistic regression model. Determination of the RP2D will be informed by the maximum biologic effect or maximum tolerated dose, whichever is lower. The phase 2 study will include arm A (relapsed or refractory AML with MLLr) and arm B (relapsed or refractory AML with NPM1m) (Figure 1). Patients will be treated at the RP2D to evaluate clinical activity and safety, which will be monitored using Bayesian posterior probability to optimize enrollment with Bayesian stopping rules. Bayesian monitoring of responses will be started after the first 10 enrolled patients are evaluable for efficacy. Study endpoints are summarized in Table 1. [Display omitted] DisclosuresDaver: Genentech: Consultancy, Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Sevier: Consultancy, Research Funding; Hanmi: Research Funding; Trillium: Consultancy, Research Funding; Trovagene: Consultancy, Research Funding; Novartis: Consultancy; ImmunoGen: Consultancy, Research Funding; FATE Therapeutics: Research Funding; Glycomimetics: Research Funding; Abbvie: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Novimmune: Research Funding; Jazz Pharmaceuticals: Consultancy, Other: Data Monitoring Committee member; Dava Oncology (Arog): Consultancy; Celgene: Consultancy; Syndax: Consultancy; Shattuck Labs: Consultancy; Agios: Consultancy; Kite Pharmaceuticals: Consultancy; SOBI: Consultancy; STAR Therapeutics: Consultancy; Karyopharm: Research Funding; Newave: Research Funding. Affinito: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Cai: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Dobrowolska: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Dow: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Eguchi: Sumitomo Dainippon Pharma: Current Employment. Song: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Stoudemire: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Watanbe: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Komarnitsky: Sumitomo Dainippon Pharma Oncology, Inc: Current Employment.

Tetraploidy in Acute Myeloid Leukemia Is Associated with Poor Outcomes Regardless of the Presence of Favorable Risk Features, and Requires an Allogeneic Stem Cell Transplant in First Remission

Introduction: While tetraploidy (92 chromosomes) and near-tetraploidy (>80 chromosomes) confer favorable prognosis in B-cell lineage pediatric acute lymphoblastic leukemia, their prognostic significance in acute myelogenous leukemia (AML) remains ill-defined. Moreover, the mechanisms underlying their pathobiology and impact on known prognostic factors in AML are unknown. Combining data collected at our institution along with a review of the literature, we provide the most complete analysis of tetraploidy and near-tetraploidy in AML including data on biology, treatment outcomes, impact on other prognostic markers, and survival to assist in clinical management.Patients and methods: A systematic literature search was performed and included studies published from June 1st, 1994 to June 1st, 2017 in PubMed, Embase, and Web of Science. We used the key words tetraploidy, near-tetraploidy, acute myeloid leukemia, acute myelogenous leukemia, and AML. Data was tabulated regarding the following seven variables: Fluorescence in situ hybridization (FISH) analysis, molecular analysis, karyotype, risk status, overall survival (OS), history of allogeneic stem cell transplantation, and chemotherapy. Data was reported as percent and total number of cases with available data of each variable.Results and discussion: We identified 104 AML cases with confirmed tetraploidy or near-tetraploidy (102 cases in 24 articles, and 2 cases from our institution). Incidence was nearly equal between tetraploidy (55/104) and near-tetraploidy (49/104). The median age at diagnosis was 54. A notable male predominance was observed with a male-to-female ratio of 2.2:1 (71 males and 33 females). While insufficient molecular data were available to include in risk stratification, cytogenetics including FISH and karyotype were available in all cases. We stratified our cases irrespective of tetraploidy or near-tetraploidy into favorable risk (defined by the presence of the following genetic alterations in core-binding factors: inv(16) or t(16;16) or t(8;21), or t(15;17)), unfavorable risk (defined by complex karyotype [≥3 clonal chromosomal abnormalities], monosomal karyotype, 5q-, 7q-, -5,-7, t(6;9), inv(3), t(3;3), 11q23 - non t(9;11), t(9;22)) and intermediate risk (the rest). Consistent with the literature, cases with other cytogenetic abnormalities in addition to those defined in the favorable-risk group, were included within the favorable-risk category (Byrd Blood 2002). Interestingly, t(8;21) was the only favorable risk feature represented, seen in 13 patients (12.5%), thus grouped under favorable-risk AML. 51 patients (49.0%) were grouped under unfavorable-risk AML and included 24 patients with complex karyotype, 9 patients with -7, 7 patients with 5q-, 4 patients with -5, 1 patient with 7q-, 1 patient with t(9;22), 3 patients with both -5 and -7, 1 patient with both 5q- and -7, and 1 patient with both -5 and 7q-. Intermediate risk was observed in 40 patients (38.5%) who were found to have normal or non-defined cytogenetics. We used the Kaplan-Meier method to stratify survival data, and the log-rank test to compare the survival between subgroups. The overall outcomes were poor, the median OS (mOS) of the whole cohort was 6 months (M) (Figure 1A). The prognosis was equally poor for both tetraploidy (mOS 6.2M) and near-tetraploidy (mOS 6M) (P=0.81; Figure 1B). Surprisingly, risk stratification showed no impact on overall survival (P=0.57; Figure 1C), which suggest that the unfavorable risk imposed by tetraploidy or near-tetraploidy may overcome favorable-risk features, such as t(8;21), challenging current data on AML risk stratification. Twenty-one patients (20.2%) had an allogeneic stem cell transplantation. Interestingly, we noticed a significant improvement in outcomes (mOS 17M) in patients who received an allogeneic stem cell transplantation compared to those who did not (mOS 4M) (P=0.0085; Figure 1D).Conclusion: Regardless of the risk status, the prognosis of tetraploid or near-tetraploid AML is dismal and should be incorporated within the unfavorable risk group. Prompt evaluation for allogeneic stem cell transplant should be initiated at diagnosis. Indeed, longer survival can be achieved with chemotherapy followed by allogeneic stem cell transplantation at first complete remission. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Variable Expression Levels of the Hematopoietic Stem Cell Surface Antigen ESAM Depict Heterogeneity and Fluctuations in Leukemic Stem Cells

Traditionally, hematopoietic stem cells (HSCs) have been regarded as a homogeneous cell population. However, many studies have shown that populations of HSCs are essentially heterogenous. Moreover, several recent studies have proposed that HSCs exhibit fluctuating biological characteristics. Although the physiological significance of this heterogeneity and fluctuation is unclear, we presume that these qualities enable HSCs to flexibly demonstrate their self-renewal or differentiation abilities dependent on physiological demands. It is, therefore, unsurprising that such heterogeneity and fluctuation is also seen in leukemic stem cells (LSCs), and that they are involved in the development of resistance to treatment.We have previously demonstrated that the endothelial-cell selective adhesion molecule (ESAM) is an important marker of HSCs in humans and mice (Blood 2009, Exp Hematol 2013), and that the expression level of this molecule indicates the activation status of HSCs (J Immunol 2012). Furthermore, we found that a subset of leukemic cells exhibit elevated levels of ESAM expression on their surfaces (Exp Hematol 2013). Approximately two-thirds of acute myelogenous leukemia cases in humans were found to be positive for ESAM expression. Since ESAM was found to be useful in monitoring the fluctuating status of HSCs after 5-FU treatment, we posited that the marker could be used to characterize LSCs.In this study, we used ESAM expression levels as an index to analyze the heterogeneity and fluctuation in LSC populations. Flow cytometric analysis of the human leukemia cell lines KG1a and CMK revealed wide-ranging heterogeneity in ESAM expression levels, with up to a 1000-fold difference in variation, even among individual cells derived from the same clone. When these cell populations were roughly fractionated into ESAM-high or ESAM-low expression groups, the ESAM-high expression group showed a higher proliferative capacity in culture. Interestingly, however, the expression levels of ESAM were not maintained indefinitely at the same level in these groups. In four weeks, both ESAM-high and ESAM-low cell fractions developed heterogeneous ESAM expression distributions similar to that in the parent cell lines. Furthermore, when single cells were sorted and cultured, each cell showed a self-renewal ability and the heterogenous nature of ESAM expression levels was reconstructed in each population derived from these single cells. These results suggest that populations of LSCs develop heterogeneity and have a fluctuating nature.When the transcriptomes of ESAM-low and ESAM-high KG1a cells were compared using RT-PCR, the expression of the transforming growth factor beta receptor type 2 (TGFBR2) gene was found to be higher in the ESAM-low cells. Reportedly, the transforming growth factor beta (TGFβ) signaling pathway is involved in various biological processes such as cell proliferation, differentiation, and migration. In tumor cells, this pathway is involved in reducing proliferation and accelerating invasion. Based on this information, it was considered likely that the TGFβ signaling pathway is involved in the heterogeneity of ESAM expression. When TGFβ1 (5 ng/ml) was added to a culture of KG1a cells (grown in RPMI 1640 medium with 10% fetal bovine serum (FBS)), the heterogeneity of ESAM expression in the population became more pronounced, mainly due to a decrease in ESAM expression in some cells.A transcriptomic analysis of cells exhibiting decreased ESAM expression after TGFβ1 stimulation showed that these cells had a higher expression of TGFBR2 than cells not exhibiting a decrease in ESAM expression. Since the presence of 10% FBS in the culture medium provides natural TGFβ1 at a concentration of ~1 ng/ml, we conducted culture experiments without FBS. When KG1a cells were cultured in serum-free medium, the ESAM-low fraction disappeared and the heterogeneity of ESAM expression could not be replicated. However, the heterogeneity of ESAM expression in KG1a cultures could be replicated in serum-free medium by the addition of 1 ng/ml TGFβ1. These results suggest that the TGFβ signaling pathway is involved in inducing heterogeneity in ESAM expression in cell populations. The fluctuation of ESAM expression levels could be caused by differences in TGF sensitivity, which in turn, may confer certain benefits to LSCs, such as drug resistance and promoting invasiveness. DisclosuresYokota:Celgene: Research Funding; MSD K.K.: Research Funding; CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Pfizer Inc.: Research Funding; Shionogi & Co., Ltd.: Research Funding. Ezoe:Taiho Pharmaceutical Co., LTD.: Research Funding. Shibayama:Novartis Pharma K.K.: Honoraria, Research Funding; Bristol-Meyer Squibb K.K.: Honoraria, Research Funding; Ono Pharmaceutical Co.,LTD.: Honoraria, Research Funding; Jansen Pharmaceutical K.K.: Honoraria; Fujimoto Pharmaceutical Co.: Honoraria, Research Funding; Takeda Pharmaceutical Co.,LTD.: Honoraria, Research Funding; Mundipharma K.K.: Honoraria, Research Funding; Celgene K.K.: Honoraria, Research Funding. Oritani:MOCHIDA PHARMACEUTICAL: Speakers Bureau; Celgene: Speakers Bureau; Bristol-Myers Squibb: Research Funding, Speakers Bureau; Novartis Pharma: Consultancy, Speakers Bureau. Kanakura:Kyowa Hakko Kirin: Research Funding; Chugai Pharmaceutical: Research Funding; Pfizer: Research Funding; Bristol Myers: Research Funding; Alexion Pharmaceuticals, Inc.: Honoraria, Research Funding; Fujimotoseiyaku: Research Funding; Eisai: Research Funding; Astellas: Research Funding; Nippon Shinyaku: Research Funding; Toyama Chemical: Research Funding; Shionogi: Research Funding.

Combined Blockage of E-Selectin and CXCR4 (GMI-1359) Enhances Anti-Leukemia Effect of FLT3 Inhibition (Sorafenib) and Protects Hematopoiesis in Pre-Clinical AML Models

Acute myelogenous leukemia (AML) is characterized by an accumulation of abnormal white blood cells. Internal tandem duplications in the fms-like tyrosine kinase 3 (FLT3-ITD) account for 30% of adult AML cases and confer poor prognosis (Nakao et al., Leukemia 1996). FLT3 inhibitors like sorafenib efficiently eliminate circulating leukemia blasts, but frequently not in the bone marrow (BM), which suggests a protective effect of the BM niche for leukemic stem cell survival (Zhang et al., JNCI 2008). The homing of AML cells in BM is mediated chiefly by the adhesion to E-selectin on endothelial cells (ECs) and by CXCR4-directed cellular migration to stromal CXCL12 (SDF1) sources (Chien et al., Blood 2013; Peled and Tavor, Theranostics 2013). In many respects, BM homing signals are shared between leukemia and hematopoietic stem cells (HSCs). Our previous study demonstrated that targeting E-selectin/CXCR4 with the dual E-selectin/CXCR4 antagonist GMI-1359 markedly reduced leukemia cell adhesion to ECs and mesenchymal stem cells, reduced the BM-mediated protection of leukemic cells during FLT3-targeted therapy in vitro, and effectively reduced leukemia cellularity in the BM in vivo (Zhang et al., Can Res suppl 2016). Further, GMI-1359 combined with cytarabine/daunorubicin provided a profound survival benefit in mice with FLT3-mutated leukemia (Zhang et al., Blood suppl 2015). In the present study, we sought to evaluate dual E-selectin/CXCR4 blockage in the context of FLT3 inhibition by sorafenib in vivo, and to better understand the underlying mechanism. We compared expression levels of E-selectin ligands and CXCR4 in FLT3 inhibitor-sensitive Ba/F3-FLT3-ITD cells and their inhibitor-resistant counterparts Ba/F3-FLT3-ITD+D835Y and Ba/F3-FLT3-ITD+F691L. Resistant cells expressed 1.7 to ~5.6-fold higher levels of total E-selectin ligand detected by a soluble E-selectin reagent, and 10-fold higher levels of CXCR4. In addition, BM-mimetic hypoxia culture profoundly upregulated the cell surface expression of E-selectin ligands and CXCR4 on leukemia cells. We evaluated anti-leukemia effects of co-targeting E-selectin/CXCR4 and FLT3 with GMI-1359 and sorafenib in a patient-derived AML xenograft (PDX) model harboring FLT3-ITD and WT1 mutations. We observed that addition of GMI-1359 to sorafenib greatly reduced leukemia cellularity compared to sorafenib alone, and as much as by 92%, 82%, 69% and 45% in, respectively, liver, lung, spleen and BM (Fig. 1) as compared with vehicle-treated mice (p &amp;lt; 0.05). As expected, the number of circulating leukemia cells transiently increased. The GMI-1359/sorafenib combination improved mouse survival (median survival 138.5 versus 109, 87 and 126 days for the GMI-1359/sorafenib versus vehicle, GMI-1359 and sorafenib, respectively, p &amp;lt; 0.001). Using intravital 2-photon microscopy, we observed AML cell behavior in calvarial BM and their response to acute GMI-1359 bolus infusion. Remarkably, AML cell mobility began to increase in the BM microenvironment as soon as 20 min after treatment (Fig. 2), followed by intravasation and cellular outflow through the BM capillary vasculature over the next 2-4 hours. Moreover, although BM homing signals are thought to be shared between leukemia and HSCs, the combination therapy improved hematopoiesis parameters compared to sorafenib alone. In particular, this important effect was associated with increased numbers of megakaryocytes (2.1-fold), myelocytes (2.1-fold), and erythrocytes (7.1-fold) in BM (p &amp;lt; 0.01). The underlying mechanism(s) of hematopoiesis protection by GMI-1359 are under investigation. Conclusion: Co-inhibition of E-selectin/CXCR4 enhances the anti-leukemia efficacy of FLT3 inhibition and preserves hematopoiesis in the BM in a PDX model of AML. Disclosures Fogler: GlycoMimetics: Current Employment, Current equity holder in publicly-traded company, Patents &amp; Royalties. Magnani:GlycoMimetics, Inc.: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees, Patents &amp; Royalties. Zal:Daiichi-Sankyo: Research Funding; Moleculin Biotech, Inc.: Research Funding. Andreeff:Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Centre for Drug Research &amp; Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy.

Analyzing How Elderly Acute Myeloid Leukemia Patients Are Treated, an Institutional Experience

Rationale: Treatment of acute myelogenous leukemia (AML) remains a challenge in elderly populations, those with comorbid conditions, and patients with poor performance status indices. The optimal choice for induction therapy as well as further agent selection is unclear, and current guidelines recommend enrollment in a controlled clinical trial. Methods: Institutional cases of AML via an electronic medical record query performed in November 2017 containing cases of AML in patients 65 years of age or greater from 01/01/2000 to 06/21/2017 were extracted. Instances of acute myelogenous leukemia were identified by ICD codes. Age, gender, induction therapy, cytogenetics, molecular analyses, and overall survival were collected. Results: A total of 61 cases of AML in patients aged 65 or greater were identified, with those having incomplete data being excluded from analysis. The mean age of included patients was 78.9 years of age, 35 were male and 26 were female. 60 confirmed deaths were recorded. 26 patients received conventional 7+3 (42.6%), 22 received a hypomethylating agent (HMA) (31.1%), 16 (26.2%) did not receive treatment. Conclusion: Our institutional data showed overall survival was significantly longer when treated with 7+3, 354 days (95% CI [93, 614]), vs. 61 days (95% CI [15, 107]). Similarly, OS was significantly longer when treated with HMA, 303 days (95% CI [23, 583]). Risk of death, accordingly, was as follows: 7+3 HR .347 (.179-.672), HMA HR .348 (.173-.703). Our institutional mortality data reasonably reflected SEER data analysis reported by Medeiros et al concerning untreated patients, but trended toward a greater OS for those treated with 7+3 or HMA. Registry data, as well as our institutional data, demonstrate a survival benefit to intensive chemotherapy and palliative chemotherapy, while controlled trials have not shown this benefit consistently in elderly populations. Practices regarding induction therapy vary greatly between institutions. Determination of which elderly patients to treat with intensive therapy remains difficult.

Leukemic transformation and second cancers in 3649 patients with high-risk essential thrombocythemia in the EXELS study

EXELS, a post-marketing observational study, is the largest prospective study of high-risk essential thrombocythemia (ET) patients, with an observation time of 5 years. EXELS found higher event rates of acute leukemia transformation in patients treated with hydroxycarbamide (HC). In the current analysis, we report age-adjusted rates of malignant transformation from 3460 EXELS patients exposed to HC, anagrelide (ANA), or both. At registration, 481 patients had ANA treatment without HC exposure, 2305 had HC without ANA exposure, and 674 had been exposed to both. Standard incidence ratios (SIRs) were calculated using data from the Cancer Incidence in Five Continents database to account for differences in age-, gender-, and country-specific background rates. SIRs for acute myelogenous leukemia (AML) were high in ET patients. SIRs for AML were high in HC-treated patients, but AML was rare in ANA-treated patients; no cases of AML were found in patients only treated with ANA. No statistically significant difference was seen between SIRs for ANA and HC treatment for AML or skin cancer. SIRs for other cancers were similar in the HC and ANA groups and close to 1, indicating little difference in risk. Although statistically inconclusive, this study strengthens concerns regarding possible leukemogenic risk with HC treatment. (NCT00202644)

Salvage extracorporeal membrane oxygenation in induction-associated acute respiratory distress syndrome in acute leukemia patients: A case series.

The prognosis of hematologic malignancies has improved over the past three decades. However, the prognosis in hematologic malignancies with severe acute respiratory distress syndrome has remained poor. Initial reports regarding the utility of extracorporeal membrane oxygenation in hematologic malignancies have been controversial, with limited evaluations of acute leukemia patients supported by extracorporeal membrane oxygenation. We conducted a retrospective review of patients with acute leukemia who developed acute respiratory distress syndrome requiring veno-venous extracorporeal membrane oxygenation support at our facility from July 2015 through August 2017. Four cases of acute myelogenous leukemia with respiratory failure and acute respiratory distress syndrome treated with veno-venous extracorporeal membrane oxygenation while undergoing induction chemotherapy were identified. All patients completed induction therapy with addition of extracorporeal membrane oxygenation support, with two patients dying secondary to their acute leukemia and the other two surviving to allogeneic hematopoietic stem cell transplant. Overall, 75% (three of four) survived to decannulation with a 1-year survival rate following extracorporeal membrane oxygenation of 50% (two of four). Currently, the use of extracorporeal membrane oxygenation in patients with hematologic malignancies who develop severe acute respiratory distress syndrome remains controversial. Although extracorporeal membrane oxygenation in post-allogeneic hematopoietic stem cell transplant is associated with poorer outcomes, our data suggest that salvage extracorporeal membrane oxygenation support is a viable option to manage moderate to severe acute respiratory distress syndrome while completing therapeutic chemotherapy and following in the peri-induction phase of acute leukemia.

20. Two cases of acute myelogenous leukemia with positive FLT3- internal tandem duplication (ITD): Follow up and enrolment in clinical trials

20. Two cases of acute myelogenous leukemia with positive FLT3- internal tandem duplication (ITD): Follow up and enrolment in clinical trials

Selective Inhibition of the Myeloid Src-Family Kinase Fgr Potently Suppresses AML Cell Growth in Vitro and in Vivo.

Acute myelogenous leukemia (AML) is the most common hematologic malignancy in adults and is often associated with constitutive tyrosine kinase signaling. These pathways involve the nonreceptor tyrosine kinases Fes, Syk, and the three Src-family kinases expressed in myeloid cells (Fgr, Hck, and Lyn). In this study, we report remarkable anti-AML efficacy of an N-phenylbenzamide kinase inhibitor, TL02-59. This compound potently suppressed the proliferation of bone marrow samples from 20 of 26 AML patients, with a striking correlation between inhibitor sensitivity and expression levels of the myeloid Src family kinases Fgr, Hck, and Lyn. No correlation was observed with Flt3 expression or mutational status, with the four most sensitive patient samples being wild-type for Flt3. Kinome-wide target specificity profiling coupled with in vitro kinase assays demonstrated a narrow overall target specificity profile for TL02-59, with picomolar potency against the myeloid Src-family member Fgr. In a mouse xenograft model of AML, oral administration of TL02-59 for 3 weeks at 10 mg/kg completely eliminated leukemic cells from the spleen and peripheral blood while significantly reducing bone marrow engraftment. These results identify Fgr as a previously unrecognized kinase inhibitor target in AML and TL02-59 as a possible lead compound for clinical development in AML cases that overexpress this kinase independent of Flt3 mutations.

Distinct Patterns of PD-L1 and PD-L2 Expression By Tumor and Non-Tumor Cells in Patients with MM, MDS and AML

Introduction:Programmed death-ligand 1 (PD-L1) contributes to tumor escape from immune surveillance by binding to programmed death-1 (PD-1), a negative regulator of T-cell responses. PD-L1 is expressed by both tumor cells and immune cells in the tumor microenvironment. In contrast, the role of PD-L2 in tumor immunity is unclear. To better understand the contribution of PD-L1/L2 to immune escape in marrow-based hematologic malignancies, we used multi-color flow cytometry and immunohistochemistry (IHC) to characterize cell-specific PD-L1/PD-L2 expression in patients with multiple myeloma (MM), myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML).Results:PD-L1 was detectable (> 2% positive cells) in 100% of patients, with distinct disease-specific patterns. PD-L1 was expressed most widely in MM, predominantly by malignant plasma cells (median, 95% of plasma cells; n = 5) and lymphocytes (median, 12% of marrow lymphocytes; n = 5). In contrast, in MDS and AML, PD-L1 was more commonly expressed by non-tumor hematopoietic cells: MDS median, 36% of CD34− myeloid precursors and 47% of lymphocytes (n = 13) vs 12% of CD34+ myeloid blasts; AML median, 19% of CD34− myeloid precursors and 26% of lymphocytes (n = 7) vs 16% of CD34+ myeloid blasts were PD-L1+. A higher proportion of CD8+ T cells expressed PD-L1 compared with CD4+ T cells in all 3 malignancies: the CD8:CD4 ratio for PD-L1+ T cells was 3.02 in MM (n = 11), 1.92 in MDS (n = 10), and 1.29 in AML (n = 7). PD-L2 expression was largely absent in AML and MDS (< 2% of CD34+ blasts or lymphocytes expressed PD-L2 (n = 13 MDS and n = 7 AML) but was expressed in a subset of patients with MM on plasma cells (median, 18%; n = 5) but not lymphocytes (< 2%). Across all indications on both tumor cells and lymphocytes, PD-L1 was expressed by a larger fraction of cells than PD-L2 (AML: CD34+ blasts, P < .01 and lymphocytes, P = .005 [n = 7]; MDS: CD34+ blasts, P < .01 and lymphocytes, P = .0001 [n = 13]; MM: plasma cells, P = .03 and lymphocytes, P = .04 [n = 5]). These results were confirmed in a distinct set of 16 cases of primary AML analyzed independently, with detectable PD-L1 expression on myeloid blasts in 14 of 16 cases (88%) without co-expression of PD-L2 (0 of 16 cases). Comparisons of flow cytometry and IHC revealed that some IHC methods may underestimate the prevalence of PD-L1/PD-L2 in marrow-based hematologic malignancies, and results comparing different methods for detecting PD-L1/PD-L2 in the bone marrow will be presented.Conclusions:PD-L1 is highly prevalent in MM, MDS and AML, with significant expression by non-tumor hematopoietic cells, particularly CD8+ T cells. PD-L2 expression was largely absent in myeloid diseases but detectable in MM. Interestingly, PD-L1 expression was most common on tumor cells in MM and on non-tumor hematopoietic cells in MDS, whereas expression on non-tumor and tumor cells in AML was comparable. These data support clinical development of anti-PD-L1/PD-1 therapies in MM, MDS and AML. Future analyses will determine whether different patterns of PD-L1 expression are associated with clinical efficacy.Authors M Dail, L Yang, S Rodig, and J Venstrom contributed equally to this work. DisclosuresDail:Genentech, Inc.: Employment. Green:Genentech, Inc.: Employment. Ma:Genentech, Inc.: Employment. Robert:Genentech, Inc.: Employment. Kadel:Genentech, Inc.: Employment. Koeppen:Roche: Employment, Equity Ownership. Adamkewicz:Genentech, Inc.: Employment. Byon:Genentech, Inc.: Employment. Woodard:Genentech, Inc.: Employment. Rodig:Bristol-Myers Squibb: Honoraria, Research Funding; Perkin Elmer: Membership on an entity's Board of Directors or advisory committees. Venstrom:Genentech: Employment.

CLINICAL MANIFESTATIONS OF SECONDARY APLASIA AFTER CHEMOTHERAPY

Objectives. Our aims were to highlight the clinical signs and symptoms of secondary bone marrow aplasia after intensive chemotherapy. Material and methods. We included in the study group 20 children with intensive cytostatic treatment aged between 9 months and 18 years, all the patients were hospitalized in the hemato-oncology department of the Pediatric Clinic Targu-Mures with the following diagnoses: acute lymphoblastic leukemia, Wilms tumor, acute myelogenous leukemia, Hodgkin lymphoma, non-Hodgkin lymphoma, neuroblastoma, and round small cell desmoplastic tumor. The inclusion criteria was the intensive chemotherapy, exclusion criteria was maintenance cytostatic treatment. It was made a dynamic clinical-biological observation protocol to note the clinical considerations of the aplastic periods after each cytostatic treatment. Bone marrow aplasia was certified by the neutropenia, anemia and thrombocytopenia. Results and discussions. The majority pathology in our study group was lymphoblastic acute leukemia (60%), followed by Wilms tumor, and one case of acute myelogenous leukemia, Hodgkin lymphoma, non-Hodgkin lymphoma, neuroblastoma, and round small cell desmoplastic tumor the distribution of age groups respecting literature data. All the patients were treated with international protocols, and after each cure followed the secondary bone marrow aplasia with the afferent pathologies: anemia, thrombocytopenia, mucositis, infections with different localizations, zona zoster reactivation. Conclusions. Secondary bone marrow aplasia duration and severity differ by cancer type. We observed the most severe clinical complications in the ALL and AML patients. Infectious complications have evolved with the individualized shades probably generated by immunological peculiarities.

Automatic recognition of acute myelogenous leukemia in blood microscopic images using K-means clustering and support vector machine

Acute myelogenous leukemia (AML) is a subtype of acute leukemia, which is characterized by the accumulation of myeloid blasts in the bone marrow. Careful microscopic examination of stained blood smear or bone marrow aspirate is still the most significant diagnostic methodology for initial AML screening and considered as the first step toward diagnosis. It is time-consuming and due to the elusive nature of the signs and symptoms of AML; wrong diagnosis may occur by pathologists. Therefore, the need for automation of leukemia detection has arisen. In this paper, an automatic technique for identification and detection of AML and its prevalent subtypes, i.e., M2-M5 is presented. At first, microscopic images are acquired from blood smears of patients with AML and normal cases. After applying image preprocessing, color segmentation strategy is applied for segmenting white blood cells from other blood components and then discriminative features, i.e., irregularity, nucleus-cytoplasm ratio, Hausdorff dimension, shape, color, and texture features are extracted from the entire nucleus in the whole images containing multiple nuclei. Images are classified to cancerous and noncancerous images by binary support vector machine (SVM) classifier with 10-fold cross validation technique. Classifier performance is evaluated by three parameters, i.e., sensitivity, specificity, and accuracy. Cancerous images are also classified into their prevalent subtypes by multi-SVM classifier. The results show that the proposed algorithm has achieved an acceptable performance for diagnosis of AML and its common subtypes. Therefore, it can be used as an assistant diagnostic tool for pathologists.

Optimizing Effects of mTOR Inhibition in Acute Myelogenous Leukemia

Introduction: Mammalian target of rapamycin (mTOR) signaling has previously been identified as a possible therapeutic target in acute myelogenous leukemia (AML), as the PI3K/AKT/mTOR pathway has been shown to be upregulated in blasts of up to 90% of AML cases through the constitutive loss of the tumor suppressor PTEN. The activation of this pathway is implicated in synthesis of prosurvival transcription and translational factors responsible for cellular resistance to apoptosis, resistance to chemotherapy, and enhanced survival in the marrow microenvironment. Unfortunately, exploitation of this pathway has been largely ineffective in clinical studies. A second mTOR complex (mTORC2) will reestablish the activation of the first when the first mTOR complex (mTORC1) is shut down under treatment with traditional rapalogs, such as rapamycin and everolimus. Additionally, the cellular process of autophagy has been postulated to be a protective mechanism for leukemic blasts during treatment with mTOR inhibitors, therefore decreasing their efficacy. For these reasons, this work explores means to optimize mTOR pathway inhibition by examining effects of dual mTORC inhibition (OSI027), dual PI3K/mTOR inhibition (BEZ235/Dactilosib), combination of mTOR inhibitors with a histone deacetylase inhibitor with ability to inhibit AKT (LBH589/Panobinostat), and the combination of mTOR inhibitors with hypomethylating agents able to overcome the hypermethylation of mTOR pathway components such as TSC1, TSC2 and PTEN (decitabine/5-azacytidine).Materials and Methods: Primary AML leukapheresis samples obtained with informed consent were cultured for 48 hours in the presence of OSI027, LBH589 (Novartis), BEZ235 (Novartis), decitabine, or OSI027 in combination with each of these individual inhibitors and compared with control culture conditions. Cells were stained with annexinV and DAPI as previously described, and the percent of living, pre-apoptotic, necrotic and dead cells were determined via flow cytometry. Synergy calculations were completed using Calcusyn™ software as described by Chao and Talalay (1977). Autophagic flux was determined in the OSI027 and LBH589 combination exposure via flow cytometry using anti-LC3. Lastly, protein expression under treatment with various combinations was determined via standard western blotting techniques.Results: The MV411 AML cell line was utilized to establish efficacy of combination exposures. These cells expressed phosphorylated (p)Akt (ser 473), p4EBP1, and pmTOR. OSI027 10µM, LBH589 1µM, and BEZ235 10nM were able to inhibit pmTOR, pAKT, and p4EBP1 expression as determined by western blotting. In the MV411 cell line, IC50s were determined, and combination indices were determined for OSI027+BEZ235, panobinostat+BEZ235, and panobinostat+OSI027; all of which demonstrated synergy. In primary AML samples, the combination of OSI027 10uM and LBH589 10nM significantly increased the percentage of dead cells in comparison to OSI027 treatment alone. Additionally in primary AML blasts, pmTOR and pAKT expression were decreased in the combination of OSI027 and LBH589 when compared to single agent treatment via western blot. The combination of OSI027 and LBH589 demonstrated a significant reduction in the autophagic flux in comparison to OSI027 treatment alone, suggesting an anti-autophagic effect, which correlates with the increased rates of cellular death in the combination. It was also found in AML cell lines that the combination of 10 µM azacytidine and 100 nM rapamycin resulted in synergistic suppression of U937, MV411, and KG1a survival as measured by MTT. No synergy was noted in the HL60 cell line. This combination effectively suppressed CFU-L in primary AML cases and suppressed p70S6K and p4EBP1 expression more than either agent alone by western blotting. The combination of decitabine 500nM with OSI027 10uM did not demonstrate an increase in apoptotic cells in primary blasts compared to OSI027 alone.Conclusions: Based on these findings, we conclude that mTOR inhibition in AML cell lines and primary samples can be enhanced through dual mTORC inhibition, PI3K modulation, and histone deacetylase inhibition. This may occur through suppression of activated pathway mediators or through suppression of autophagic flux. These results suggest that there is merit in exploring these combinations for therapeutic potential in AML. DisclosuresPortwood:ImmunoGen: Research Funding. Wang:ImmunoGen: Research Funding.

Loss-of-Function Mutations of MIR142 May Contribute to Leukemogenesis By Expanding the Pool of Myeloid-Biased HSCs

MicroRNA (miRNA) expression is sometimes dysregulated in acute myelogenous leukemia (AML), and this dysregulation has been suggested to play a role in leukemic transformation. However, somatic mutations in miRNAs are infrequent in AML. Through whole genome or exome sequencing of 200 cases of de novo AML, The Cancer Genome Atlas (NEJM 2013) identified recurring point mutations in MIR142. Heterozygous point mutations of MIR142 were identifiedin 3 cases, and bi-allelic mutations in 1 case (total incidence of 2%). All of these mutations localized to the "seed" sequence of miR-142-3p, which is critical for determining mRNA target specificity. Accordingly, we show that mutated miR-142 is unable to suppress several well-known targets of miR-142. Surprisingly, sequencing of small non-coding RNAs in AML cases carrying MIR142 mutations showed a selective loss of miR-142-5p expression. Indeed, we provide evidence that mutant miR-142-3p is selectively loaded into the RNA-induced silencing complex (RISC), resulting in degradation of miR-142-5p. Collectively, these data show that MIR142 mutations in AML likely disrupt both miRNA-142-5p and miRNA-142-3p function.To model the effect of the loss of miR-142 on hematopoiesis, we analyzed Mir142-/- mice. Prior studies in zebrafish showed that knockdown of miR-142-3p results in reduced hematopoietic stem cells (HSCs) and impaired myelopoiesis (Fan, Blood, 2014; Lu, Cell Research, 2013). Sun et al reported impaired T-cell responses in Mir142-/- mice (Sun, JCI 2015). Here, we show that loss of miR-142 is associated with a modest increase in bone marrow and splenic neutrophils. Erythroid precursors in the bone marrow are significantly reduced with a corresponding increase in the spleen. Consistent with these data, granulocyte-macrophage progenitors (GMPs) in the bone marrow are significantly increased, while megakaryocyte-erythroid progenitors (MEP) are significantly decreased. While the total number of phenotypic HSCs (CD150+ CD48- Kit+ Sca+ lineage- cells) in the bone marrow is similar to control mice, a marked increase in the percentage of CD229- myeloid-biased HSCs was observed in Mir142-/- mice (69.4% ± 3.4) versus control mice (29.2% ± 3.3; P <0.001). Consistent with these findings, competitive repopulation assays show that the long-term repopulating activity and self-renewal capacity of Mir142-/- HSCs is normal. However, lineage analysis of these mice revealed a strong myeloid bias. Together, these data suggest that miR-142 expression in HSCs normally inhibits commitment to the myeloid lineage.To assess the hematopoietic cell-intrinsic leukemogenic potential of the loss of miR-142, we transplanted Mir142-/- bone marrow into irradiated wild-type mice, and a tumor watch was established. No myeloproliferative disorder (MPD) was observed after one year of follow-up, suggesting that loss of Mir142 is not sufficient to induce AML in mice. All 4 human AML cases carrying MIR142 mutations also harbor mutations in IDH1/2. To assess the functional importance of this association, we transduced Mir142-/- hematopoietic stem and progenitor cells (HSPCs) with a lentivirus expressing a canonical IDH2 mutation, R172H. These cells were then transplanted into irradiated mice and a tumor watch was established. Consistent with a prior report, expression of mutant IDH2 alone induced a MPD characterized by increased myeloid cells, anemia, and splenomegaly (Sasaki, Nature 2012). Surprisingly, the concomitant loss of Mir142 did not affect the latency or penetrance of MPD; the only significant difference observed was a more severe anemia.Collectively, these data suggest that the loss-of-function mutations of MIR142 found in AML likely do not promote leukemogenesis by enhancing self-renewal capacity or inhibiting myeloid differentiation. Rather, our data suggest that these mutations promote leukemogenesis by expanding the pool of myeloid-biased HSCs, thereby increasing the likelihood of acquiring additional cooperating events, such as mutant IDH1/2. This model may explain the surprising lack of cooperativity between miR-142 loss and R172H IDH2, since these experimental mice were generated using a large number of transduced HSPCs. DisclosuresNo relevant conflicts of interest to declare.

Reduced Intensity Versus Myeloablative Conditioning for Allogeneic Stem Cell Transplantation in Acute Myeloid Leukemia

▪IntroductionReduced intensity conditioning (RIC) regimens for allogeneic hematopoietic stem cell transplantation (SCT) offer a potential treatment for otherwise incurable cases of acute myelogenous leukemia (AML) with less associated toxicity compared to myeloablative conditioning (MAC). Eradication of malignant cells after RIC depends largely on the graft-versus leukemia effect (GVL). These regimens are becoming increasingly popular, particularly in older patients or those with comorbidities. They may also be offered to otherwise healthy patients based on personal or physician preference, as there is growing evidence that overall survival may be equivalent for both treatments. We retrospectively reviewed the charts of Saskatoon Cancer Centre patients receiving either RIC or MAC to compare the incidence and grade of graft versus host disease (GVHD), progression free survival (PFS), and overall survival (OS).MethodsWe identified 74 patients who underwent HSCT for AML in complete remission (CR) between January 2000- December 2013. Of these patients, 55 received MAC and 19 received RIC.Median age at HSCT was 48 years (range 18-68). In the group receiving MAC, 36% of patients were >50 years, whereas 74% of patients receiving RIC were >50 yrs of age.ResultsPatients receiving RIC experienced greater incidence of chronic GVHD (63% vs 41%, p=.09) and relapse (54% vs 30%, p=.07). Incidence of acute GVHD was the same for either regimen (53%).Median overall survival was similar (39 vs 38 months), with lower early mortality in RIC later overtaking MAC at 27 months. Progression free survival demonstrated a non-statistically significant advantage for MAC (median 43 vs 49 months).ConclusionRIC has been associated with greater incidence of chronic GVHD and relapse, with no difference in overall survival. Patients receiving RIC are more likely to be >50 years of age, making comparisons challenging. The results of this review suggest that MAC is the preferred regimen for patients who can tolerate its toxic effects due to reduced incidence of chronic GVHD and relapse, however the similarity in overall survival makes the choice of either conditioning regimen reasonable. Future studies to identify the best conditioning regimen are warranted.Overall Survival [Display omitted] Progression Free Survival [Display omitted] DisclosuresNo relevant conflicts of interest to declare.