AbstractIntroductionAcute Myeloid Leukemia Research Articles

Abstract B115: Racial and ethnic disparities in the incidence and mortality trends of acute myeloid leukemia in the United States

Abstract Introduction Acute myeloid leukemia (AML) is the most common type of leukemia among adults and carries a poor prognosis. This study aimed to assess the temporal trends of AML incidence and mortality for different racial and ethnic groups in the United States (US). Methods We obtained data on AML incidence and mortality (years 1999-2019) for all 50 states and the District of Columbia from the US Cancer Statistics database maintained by the Centers for Disease Control and Prevention. Using the JoinPoint regression program, we calculated the annual percent change (APC), average annual percent change (AAPC), and correspondent p values. A positive APC indicated an increasing trend, while a negative APC meant a decreasing trend. Results From 1999 to 2019, AML incidence trends varied among different racial and ethnic groups. Non-Hispanic White(NHW) and Hispanic populations showed no significant changes during the period. Whereas non-Hispanic Black (NHB) individuals had an AAPC of 0.8 (p=.03), mainly driven by increases in 2006-2012 (APC=3.7, p<.01). Among non-Hispanic Asians/Pacific Islanders (NHAPI) and non-Hispanic American Indians or Alaska Natives (NHAIAN), AML incidence increased steadily with APCs of 0.7 and 2.2, respectively (both ps<.01). Furthermore, when considering different age groups, there were variations in AML incidence by race and ethnicity. Among people aged <65 years, NHW, NHB, NHAPI and NHAIAN populations experienced a consistent increase in AML incidence with APCs of 0.5 (p<.01), 1.0 (p<.01), 0.9 (p<.01), and 1.8 (p=.04), respectively. However, among Hispanic individuals, AML incidence only showed an increasing trend during years 2008-2013 (APC=3.1, p=.02). For individuals aged ≥65 years, among NHW individuals, AML incidence increased in 2008-2012 by 6.2% per year (p<.01), then decreased by 0.9% per year in 2012-2019 (p=.04). In contrast, among NHB, Hispanic and NHAPI populations, AML incidence increased with APCs of 1.4 (p<.01), 0.7 (p=.03), and 0.8 (p=.02) in 1999-2019, respectively. There was no significant change in incidence among NHAIAN individuals in 1999-2019. Regarding mortality trends, variations were also observed among different racial and ethnic groups. NHW Americans first displayed an increasing trend with APCs of 4.6 in 1999-2001 (p=.03), and 0.6 in 2001-2009 (p=.03), but a decreasing trend in 2009-2019 (APC=-0.3, p=.05). No changes in mortality were observed among NHB Americans. Hispanic individuals exhibited a steadily increasing trend in mortality during 1999-2019 (APC=0.5, p=.02). NHAPI had an AAPC of 1.0 (p=.02), which was primarily attributable to increase in 1999-2010 (APC=2.5, p<.01). Mortality among NHAIAN individuals was steady in 1999-2019. Conclusion In the US, NHB individuals, NHAPI and NHAIAN experienced an increased incidence of AML during 1999-2019, while trends of increasing mortality were observed among Hispanic individuals and NHAPI over the same period. Further research is needed to identify factors associated with the heavier burden of disease in racial and ethnic minoritized populations. Citation Format: Lixin Kang, Xiaomei Ma, Nikolai A. Podoltsev, Jessica M. Stempel, Rong Wang. Racial and ethnic disparities in the incidence and mortality trends of acute myeloid leukemia in the United States [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B115.

Quantity and Functional Exhaustion of Mucosal-Associated Invariant T Cells in Acute Myeloid Leukemia: Friends or Foes?

Abstract Introduction Acute Myeloid Leukemia (AML) is a hematological malignancy affecting hematopoietic progenitor cell differentiation, proliferation, and cell cycle progression, possibly involving disturbances in host immune function. Comprehensive understanding of the immune system composition and function in AML patients is crucial for developing novel immunotherapeutic strategies. Mucosa-Associated Invariant T cells (MAITs), as a subset of unconventional T cells, bridge innate and adaptive immunity and have been predominantly studied in the context of mucosa-related cancers. However, their role in AML remains largely unexplored. Investigating the association between MAITs and AML is of significant importance for understanding the immune escape mechanisms in AML, developing novel immunotherapeutic approaches, and predicting patient prognosis. Methods This study aimed to delineate the longitudinal immune profile of MAITs during AML pathogenesis and treatment, which may contribute to understanding immunological changes of MAITs in AML and predicting patient prognosis. In this prospective study, we collected peripheral blood or bone marrow samples from 131 AML patients, including 99 newly diagnosed cases, 18 in remission, and 14 in relapse, as well as 69 healthy controls. We performed multi-parameter flow cytometry for phenotypic and functional analysis of MAITs and explored their relationship with disease features, progression, and prognosis. Results We initially demonstrated that MAITs reflected immunological defects in AML patients. MAITs showed signs of depletion in both frequency and absolute count at initial diagnosis (p<0.0001) (Fig. 1A), especially in the CD8 + MAITs subset. The frequency of MAITs reflected AML cell genetics, tumor burden, disease status, and treatment responsiveness (Fig. 1B). AML patients exhibited reduced frequency of effector memory MAITs (p<0.0001) and increased frequency of terminal differentiated MAITs (p<0.0001) in peripheral blood (Fig. 1C), indicating altered reactivity of MAIT cells to antigen stimulation. MAITs displayed a state of high activation and even exhaustion, as evidenced by upregulated PD-1 expression. Impaired secretion of Th1-type cytokines and increased secretion of Th17-type cytokines (Fig. 1D), granzyme B, and perforin were observed in MAITs, while MAITs also shifted towards secreting tumor-promoting cytokines such as IL-8. Lower frequency of MAITs was correlated with inferior Overall Survival (OS) and Progression-Free Survival (PFS) (Fig. 1E). Multivariate analysis identified MAITs frequency <2.12% as an independent prognostic factor affecting OS. Conclusion Our study highlights the role of MAITs in immunological defects in Acute Myeloid Leukemia and reveals their functional impairment and enhanced tumor-promoting effects. The frequency of MAITs in peripheral blood reflects the genetic features, tumor burden, disease status, and treatment responsiveness of AML patients. Lower frequency of MAITs is associated with inferior OS and PFS, serving as a prognostic indicator for AML.

Azacitidine and its role in the upfront treatment of acute myeloid leukemia

ABSTRACT Introduction Acute myeloid leukemia (AML) predominantly affects elderly population. This poses challenges in management, as patients are frequently not candidates for intensive therapy given comorbidities or frailty. Currently, azacitidine (AZA), either as monotherapy or in combination regimens, is the backbone treatment in this group of patients. Areas covered We review the mechanism of action, pharmacology, clinical efficacy, and safety of AZA. It reviews current combination therapies of AZA with other targeted therapies for the treatment of newly diagnosed AML. Expert opinion AZA is a cornerstone for the treatment of patients considered ineligible for intensive chemotherapy induction, but better results and therapies are required for these patients. AZA has shown synergistic properties when combined with other medications. Its safety profile and few drug interactions make it a suitable medication to use as backbone. Newer therapies are being combined with AZA, demonstrating safety and in cases, improved responses, and survival. AZA/venetoclax has emerged as the standard of care for patients who are ineligible for intensive chemotherapy. Doublet and triplet combinations are increasingly being studied. With the results observed in elderly patients, the intensive chemotherapy paradigm might be put to test in younger populations, with AZA combinations being at the forefront.

Pharmacoeconomic considerations for acute myeloid leukemia pharmacotherapy

Introduction Acute myeloid leukemia (AML) is a rare blood cancer with a poor prognosis. Recently, targeted drugs have improved survival both in the elderly and in fit patients. However, as monthly costs of targeted agents are high, regulatory bodies often impose restrictions on their use. Areas Covered The authors review the value-for-cost of targeted drugs such as gemtuzumab ozogamycin, CPX-351, midostaurin, gilteritinib, glasdegib, venetoclax, oral azacytidine and enasidenib used to treat adult AML. EMBASE and TRIP databases, together with authority web sites were searched for technology assessments. Add-on drugs, namely midostaurin and gemtuzumab ozogamycin, have been reported to have the best pharmacoeconomic profile for newly diagnosed fit patients with FLT3 mutation or favorable/intermediate cytogenetics, since allogeneic transplant rates were stable or reduced. Most of the other drugs, on the other hand, did not achieve highly favorable cost-for-benefit, due to a poor absolute survival gain and/or increased transplant rates. Expert opinion The cost of most targeted therapies for AML in unfit patients seems unfair in comparison to the absolute survival advantage provided in fit patients. Point of cure and transplant outcomes should be standardized to allow comparability among the models.

Study of Bone Marrow Lymphocyte Subset in Acute Myeloid Leukemia.

Introduction Acute myeloid leukemia (AML) is a heterogenous disorder consisting of clonal expansion of myeloblasts. Tumor immunity plays an important part in the pathobiology of AML. Understanding the components of tumor immunity is important for understanding tumor pathogenesis and the principles of immunotherapy. Methods We studied 41 patients with AML, for total lymphocyte, CD4 positive helper T cells, CD8 positive cytotoxic T cells, and CD16/56 positive natural killer (NK) cells proportion. Quantification was done on bone marrow aspirate sample by flowcytometry. Whenever available, post induction bone marrow was also analyzed for the lymphocyte subset. Results No significant difference was noted in the percentage of blasts among the three risk categories: favorable, intermediate, and adverse. However, there was significant difference in the total lymphocyte among the risk stratification groups, being highest in the favorable group and lowest in the adverse group. CD8 positive cytotoxic T cells were significantly less in Acute Promyelocytic Leukemia (APML) cases ( p = 0.001). Total lymphocytes were, however, more numerous in APML ( p = 0.005). NK cell proportion was not significantly different between APML and non-APML patients. On completion of induction chemotherapy, bone marrow samples for 12 patients could be processed for lymphocyte subset. On comparing the baseline against the post induction bone marrow, it was observed that there was significant increment in the proportion of CD4 positive T lymphocytes ( p = 0.046). Conclusion There is a difference in lymphocyte subset amongst patients with AML. Larger studies including functional aspects are needed to better define the role of lymphocytes in disease pathogenesis.

Genetic Modulators of Niclosamide Sensitivity and Resistance in Acute Myeloid Leukemia

Introduction Acute myeloid leukemia (AML) is a malignancy of myeloid progenitor cells that leads to the accumulation of immature blasts in the blood and bone marrow. While the 5-year relative survival rate has increased from 6.4% to 28.7% in the last 40 years, death rates have remained steady at 3-4%. Less toxic, more effective targeted treatments are needed to improve outcomes for patients with AML. Previous studies identified cAMP response element-binding protein (CREB) as a potential therapeutic target for AML therapy. CREB is overexpressed in AML and is associated with poor prognosis. We identified a small molecule, XX-650-23, that inhibits interaction between CREB and its co-activator, CREB Binding Protein. However, XX-650-23 does not have optimal physical chemical properties for clinical application in humans. Niclosamide, an FDA approved anthelmintic drug, shares structural similarity with XX-650-23, and suppresses the proliferation of AML cells in vitro and in vivo by inhibiting CREB-dependent signaling. The aim of this study is to define the molecular pathways that mediate the effects of niclosamide in AML cells. This will allow for more precise selection of patient populations for treatment, identify potential sources of niclosamide resistance and reveal combination therapies that make use of the distinct pathways targeted. Methods To identify genetic factors modulating cellular sensitivity to niclosamide treatment, we performed a CRISPR/Cas9 library screen in the presence or absence of niclosamide. HL60 cells expressing Cas9 were infected with a custom sgRNA lentivirus library of 220 genes from a previous genome-wide shRNA screen. After puromycin selection, HL60 cells expressing pooled sgRNAs were grown in either niclosamide or 0.1% DMSO for 20 days. Genomic DNA was extracted from control and niclosamide-treated cells. Frequency of sgRNA were measured by next generation sequencing and analyzed using the Cas9 high-throughput maximum likelihood estimator (casTLE) algorithm. Results Sixty-five gene hits were found to be significant (p≤0.05). Of the top 220 hits from the previous genome-wide shRNA screen, 26 were identified as positive hits (p ≤0.05) in the CRISPR/Cas9 knock out screen. The CRISPR screen identified genes enriched in a number of pathways including programmed cell death, nucleotide biosynthesis, mitochondrial processes and canonical glycolysis, as measured by gene ontology term analysis. Numerous gene deletions conferred resistance to niclosamide treatment. Genes DHODH (score= 123; effect= 2.9) and HSPA9 (score= 144; effect = 2.5), involved in nucleotide biosynthesis and mitochondrial processes, were significantly enriched in the surviving population. Perturbation of known metabolic pathways sensitized AML cells to niclosamide, including ATP synthase F1 subunit beta (ATP5B) (score= 316; effect= -5.1), hexokinase 2 (HK2) (score= 312; effect= -5.4), phosphofructokinase (PFKP) (score= 195; effect= -1.9) and mitochondrial phosphate carrier protein (SLC25A3) (score= 271; effect= -7.8). SLC25A3 and ATP5B play a role in oxidative phosphorylation and mitochondrial proton transmembrane transport, whereas HK2 and PFKP are key to glycolysis, suggesting that niclosamide's mechanism of action is dependent on energy metabolism. Furthermore, we found that disruption of Bcl-2 (BCL2) was sensitizing to niclosamide treatment (score= 129; effect= -4.7). To confirm the sensitizing effect of Bcl-2 inhibition on niclosamide treatment, HL60 cells were treated with niclosamide and Bc1-2 inhibitor venetoclax. Pretreatment of HL60 cells with niclosamide led to significantly decreased cell viability upon venetoclax treatment (p<0.0001). Simultaneous treatment of HL60 cells with niclosamide and venetoclax had a synergistic effect on cellular viability, with combination index values <1 at ED50 to ED90 (Chou-Talalay method). Overall, our study identified genes with strong signatures for cell death, nucleotide biosynthesis, mitochondrial function and metabolic processes. Compounds inhibiting genes identified in this screen could be combined with niclosamide for synergistic effect. Targets overrepresented in the surviving population represent sources of resistance to niclosamide therapy. This study provides insight into mechanisms of action and resistance in AML cells treated with niclosamide and novel targets for combination therapy. Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: Niclosamide is an anthelmintic, FDA approved to treat tapeworm infections.

Abstract 6118: A primary mouse model of AML as a new way to screen novel therapeutics and treatment combinations

Abstract Introduction Acute myeloid leukemia (AML) is a disease characterized by the proliferation of undifferentiated myeloid blasts, promoting bone marrow failure, infectious complications, and death. Progress in developing treatments for AML has been slow and clinical outcomes outside of bone marrow transplant are poor. A limitation to progress is the availability of reproducible murine models of AML. As such, there is a critical need to develop new models to quickly screen new therapeutics and treatment combinations. Here we have optimized the engraftment of a spontaneous Idh2R140Q/Flt3ITD murine AML (developed by Shih et al 2017) for rapid in vivo screening of compounds and combination strategies. Methods Spleen derived AML cells from a spontaneous Idh2R140Q/Flt3ITD murine AML were engrafted i.v. into NCG mice. Disease progression was monitored by flow cytometry and LC-MS/MS measurement of plasma D-2-hydroxyglutarate (D2HG), the product of mutant IDH2. At 1 week post-engraftment animals were enrolled onto treatment arms, which included enasidenib (IDH2), gilteritinib (Flt3), a dihydroorotate dehydrogenase (DHODH) inhibitor, and combination arms. In follow-up studies, non-tumor bearing C57Bl/6 mice were treated with various doses of treatment combinations and blood counts, serum liver chemistry, and weight loss were used to evaluate toxicity. Results The time from engraftment to terminal disease can be precisely adjusted to experimental needs, enabling an aggressive 21-day disease course for rapid screening or a more protracted 1.5 month course that limits the initial number of cells required and allows for the testing of slower-acting differentiating agents. We show that enasidenib, gilteritinib, and a DHODH inhibitor all slow disease progression and prolong survival, and that DHODH inhibition may have a greater effect on survival than IDH2 inhibition. We also show that DHODH inhibition lowers plasma D2HG. Importantly, we identify that combining DHODH and IDH2 inhibition is untenable and results in lethal GI toxicity. This was validated in non-tumor bearing mice, where even low doses of DHODH/IDH2 inhibitors in combination resulted in cytopenias and rapid weight loss. Discussion Developing combination treatment regimens is likely to be key to achieving long-term remission for many AML patients; however, efforts to develop these combinations are often stymied by in vitro results that fail to translate to the in vivo setting, particularly unexpected toxicities that are not recognized in vitro. We show that our AML engraftment model can be used to identify and develop pre-clinical compounds and allow us to quickly identify and abandon treatment combinations that are toxic in vivo. Our hope is that this work enables the rapid identification and development of the best novel therapeutics and treatment combinations, such that valuable time and resources can be utilized to their greatest translational effect. Citation Format: Mariah L. Johnson, Ola A. Elgamal, Bonnie Harrington, Allison Mustonen, Amy Lehman, Chad Bennett, Kyle R. Dzwigalski, Kasey L. Hill, Mitch A. Phelps, Jean Truxall, Thomas Goodwin, Alan H. Shih, Ross L. Levine, Erin Hertlein, John C. Byrd. A primary mouse model of AML as a new way to screen novel therapeutics and treatment combinations [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6118.

87 Epidemiology Study of Elderly Patients with Acute Myeloid Leukaemia at a Haematological Tertiary Referral Centre

Abstract Introduction Acute Myeloid Leukemia (AML) is a rare disease with a high incidence in the elderly. Our aim is to report the incidence of elderly patients with AML at a haematological tertiary referral centre. Method We have collected data from 2007 till 2017 from the main Malaysian haematological tertiary referral centre involving all the 1225 AML patients. Out of those, 182 elderly patients aged 65 and above with AML were examined. The patients had at least 2 years follow-up. Results The elderly represented 14.9% of the 1225 patients who presented with acute myeloid leukemia to the centre. There were 182 elderly patients with AML which were subdivided to the unspecified AML of 154 patients, 1 patient with M1, 4 patients with M2, 6 patients with M3, 5 patients with M4, 8 patients with M5, 2 patients with M6 and 2 patients with M7. There were 109 males and 73 females. The majority of the patients were Chinese (n=85) representing 46.7% of the patients, followed by the Malay (n=76), Indian (n=19) and lastly others (n=2). The average age at diagnosis was 71 years. There were 136 deaths and the mortality rate was 74.7%. The average age of the patients who had passed away (n=136) was 71.4 years. The average age of the patients who are still living (n=42) was 76.5 years. Conclusion The incidence of elderly AML is increasing. The younger patients with AML are known to have better survival rate in comparison to the elderly. More research is needed to explore the reasons for the higher mortality in the elderly and the ways to improve the outcome of this elderly population as our lifespan increases and Malaysia heads towards an ageing nation.

Significant Features of DNA Methylation at Bivalent Promotor and Repressed Polycomb Regions in Pediatric AML-the Jccg Study, JPLSG AML-05-

Introduction Acute myeloid leukemia (AML) is a clinically and biologically heterogeneous hematologic malignancy characterized by various genetic alterations. Currently, DNA methylation patterns were reported to be associated with molecular subtypes, chromosomal abnormalities, gene fusion, and prognosis in AML. Furthermore, previous study reported that aberrant cancer-associated DNA hypermethylation targets CpG islands characterized by bivalent chromatin in human embryonic stem cells (hESCs), and the bivalent chromatin signature in hESCs was a key determinant of the instructive program for aberrant DNA methylation. Thus, we analyzed genome-wide DNA methylation in 64 pediatric patients with AML to reveal its association with clinical features, genetic alterations, and prognostic impact. Methods Between 2006 and 2010, 443 pediatric patients with de novo AML (0-17 years) participated in the Japanese AML-05 trial conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group. Of these, 64 patients were enrolled in this study. The cytogenetic features of 64 patients were as follows: normal karyotype, 28; RUNX1-RUNX1T1, 8; KMT2A rearrangement, 15; complex karyotype, 6; and other cytogenetics, 7. This cohort included 15 patients with FLT3-internal tandem duplication (ITD), 8 with CEBPA biallelic mutations, 5 with high MECOM (EVI1) expression, and 17 with high PRDM16 (MEL1) expression. We performed genome-wide DNA methylation analysis using Infinium MethylationEPIC BeadChip (Illumina) in 64 pediatric patients. Results and Discussion 824,848 methylation sites per sample were analyzed in 64 pediatric patients with AML. To capture DNA methylation differences across samples, we selected 567 CpG sites which showed most variable methylation values between 64 individuals such as standard deviations across samples were more than 0.3. The unsupervised hierarchical clustering of DNA methylation data from 567 CpG sites generated 4 clusters (clusters 1-4) with distinct molecular and clinical characteristics. Cluster 1 or 2 was the lowest or highest methylation level, respectively. Clusters 3 and 4 showed intermediate methylation level. Cluster 1 was characterized by RUNX1-RUNX1T1 and KMT2A rearrangement with low MECOM expression, which are known as favorable prognostic factors. Clusters 2 and 4 were composed of patients with the molecular features showing adverse outcome such as FLT3-ITD, KMT2A-PTD and/or normal karyotype with high PRDM16 expression. Interestingly, KMT2A rearrangement with high MECOM expression, considered as the adverse prognostic factor, were included in clusters 2 or 4. As for KMT2A rearrangement, nine of 15 patients with KMT2A rearrangement harbored KMT2A-MLLT3. Of these, five of nine classified into the hypomethylation group, and all five patients had no event. On the other hand, remaining four patients with KMT2A-MLLT3 all relapsed. All patients with normal karyotype with CEBPA biallelic mutations considered as the favorable factor were found in cluster 3. When we focused on CpG sites with significant difference in their methylation values between patients with and without FLT3-ITD, 15 FLT3-ITD patients were divided into two clusters (clusters A and B) by the hierarchical clustering. Remarkably, 8 FLT3-ITD positive patients in cluster A showed significantly worse overall survival (OS) and event-free survival (EFS) when compared with those in cluster B (5-year OS, 13% vs. 100%, P = 0.002; 5-year EFS 0% vs. 86%, P < 0.001). Next, 244 CpG sites significantly associated with PRDM16 expression were extracted to investigate the relationship between PRDM16 expression and DNA methylation profiles. Interestingly, patients with high and low PRDM16 expression showed distinct methylation pattern, respectively. Furthermore, most of hypermethylated sites gene were PRDM16 gene body in patients with high PRDM16 expression and located at important regions which were the targets of repressed polycomb in reference cells. As for 567 CpG sites which were used for the unsupervised hierarchical clustering, 168 of 567 (30%) CpG sites colocalized at bivalent promoter regions in reference leukemic blast cells, and the hypermethylation of bivalent promoter regions tended to be related to worse outcome. These results indicate DNA methylation plays key role for leukemogenesis and is remarked as a novel biomarker to predict prognosis. Disclosures Ogawa: ChordiaTherapeutics, Inc.: Consultancy, Equity Ownership; RegCell Corporation: Equity Ownership; Kan Research Laboratory, Inc.: Consultancy; Asahi Genomics: Equity Ownership; Qiagen Corporation: Patents & Royalties; Dainippon-Sumitomo Pharmaceutical, Inc.: Research Funding.

Abstract 1340: High NK cell number predicts poor overall survival in de novo treatment naive acute myeloid leukemia

Abstract Introduction Acute myeloid leukemia (AML) is a deadly disease associated with high mortality and morbidity. Previous studies report defects in NK cell maturation and function in AML patients leading to innate immune evasion. Considering that the number of NK cells may be an important indicator of innate immune regulation of AML, our group sought to understand the prognostic significance of NK cell number in de novo AML patients. Methods Patient samples were obtained from the Oregon Health and Science University (OHSU) Pathology Department between September 2010 and March 2016. This cohort study includes 82 newly diagnosed adult AML patients who had a bone marrow biopsy that was subjected to flow cytometry and a targeted-NGS panel within 30 days prior to induction treatment. Patients were excluded if they had antecedent hematological diseases or therapy-related AML. Bone marrow immunophenotyping was performed using the Ion Torrent PGM platform. Absolute numbers of NK cells were estimated from flow cytometric analysis of the bone marrow samples whereby lymphocytes were identified based on CD45 staining and light side scatter and NK cells were defined as CD3-/CD56+. Results This retrospective cohort of 82 newly diagnosed AML patients were 53.7% male with a median age of 61 years (range 18 - 83). Using 2017 ELN risk stratification guidelines, 36.6% of patients were classified as favorable, 26.8% as intermediate, and 36.6% as adverse. Absolute NK cell numbers in the bone marrow ranged from 1 to 896 cells/μl with a median of 98. When stratifying NK cells by staining intensity to identify subpopulations, the number of CD56 bright NK cells ranged from 0 to 69 cells/μl (median 3) and the number of CD56 dim NK cells ranged from 1 to 585 cells/μl (median 77). Overall survival (OS) was measured from diagnosis to date of death or last contact and varied from 1 day to 5.7 years (median 20.5 months). There were 3 deaths in the first week after diagnosis. Separate Cox proportional hazards regression models were applied to each NK cell group in both the univariable and multivariable settings, with the latter models accounting for patient age and ELN risk. Higher absolute numbers of NK cells (CD3-/CD56+) were significantly correlated with worse OS in both model settings, with a multivariable p-value of 0.001. The number of bright NK cells was a significant predictor of OS in the univariable model but lost significance when controlling for other variables. However, similar to the number of all NK cells and contrary to previous reports, higher counts of dim NK cells were significantly associated with shorter survival times, with a multivariable p-value of 0.001. Conclusions In this study, we show that higher NK cell numbers at diagnosis are associated with worse OS and thus play an important role in prognostication for AML patients. This association with survival is most evident in patients at least 60 years old or those with intermediate or adverse ELN risk. Citation Format: Weiwei Wang, Guang Fan, Andy Kaempf, evan Lind, Tomi Mori, Byung Park, Jennifer Saultz. High NK cell number predicts poor overall survival in de novo treatment naive acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1340.

Decreased CD4+-Th/CD8+-Tc ratio in Bone marrow at diagnosis of acute myeloid leukemia Predicts Increased Risk of Graft-Versus-Host-Disease in Transplant Patients

Abstract Introduction Acute myeloid leukemia (AML) is an aggressive disease with high morbidity and mortality. Transplant is one of the most important treatments for AML. However, graft-versus-host-disease (GVHD) remains one of major problems in transplant patients. Since immune repertoire plays an important role in the GVHD occurrence, we investigate the relationship between lymphocyte subsets and the risk of GVHD. Methods 60 initial diagnostic flow data of AML transplant patients were reviewed (Oregon Health and Science University 2010 to 2016, 30 females and 30 males, with a median age of 51.417 years, range 13–72). 36 patients with GVHD including acute and chronic GVHD while 24 patients without GVHD. The lymphocyte subsets were analyzed including CD3+T-cells, CD3+CD4+Th, CD3+CD8+Tc, CD4/CD8 ratio, CD19+CD20+B, CD19+CD5+B1, CD3+CD56+NKT, CD3−CD56+NK, and three NK subsets (CD56brightNK, CD56normalNK, CD56dimNK). Results As to the overall survival (OS), there’s no statistic difference between age<60 years old or age ≥60 years. Compared with non-GVHD group, decreased percentage (%) of Th, increased % of Tc & low Th/Tc ratio were observed in GVHD group (P=0.0281, P=0.0394, P=0.0340 accordingly). Receiver operating characteristic (ROC) analysis indicates that low Th/Tc ratio predicts increased risk of GVHD (P=0.0231, AUC=0.663, 95% Confidence Interval is 0.530 to 0.780). There’re no statistic differences between GVHD and non-GVHD for all other lymphocyte subsets percentage (P>0.05). Conclusions AML patients with GVHD post transplant have a lower Th cell percentage and higher Tc cell percentage at diagnosis. This is to say, decreased Th/Tc ratio in BM of initial diagnosed AML patients may predict a high risk of GVHD post transplant.

DEFINING THE IMMUNE MICROENVIRONMENT IN PATIENTS WITH ACUTE MYELOID LEUKEMIA

Abstract Introduction Acute myeloid leukemia (AML) is the most common blood cancer in adults. Despite intensification of chemotherapeutic regimens, survival rates have plateaued. AML is therefore a candidate for novel immune therapeutics such as immune checkpoint inhibitors (ICIs). We aim to identify the relevant lymphoid and myeloid cell subsets present in the bone marrow of patients with AML, evaluating their differentiation and activation status. We are also performing functional assays to further define the status of T cells in the AML microenvironment. Methods Immunophenotyping was performed on mononuclear cells from fresh AML patient bone marrow using mass cytometry consisting of 5 panels of 35 antibodies each. Functional assays measured both the proliferative capacity and cytokine production profile of bone marrow T cells in the presence of various ICIs. Results Bone marrow samples from 17 patients with AML and 7 healthy donors have been collected and analyzed to date. Conclusion Our results show that the immune microenvironment is very heterogeneous between patients, with some differential responses to ICIs suggesting that certain subsets of AML may be potential candidates for immunotherapy.