Infant Acute Myeloid Leukemia Research Articles

Fetal MLL-ENL Initiation Induces Developmental Stage-Specific Programs That Restrict Transformation and Depend on MLL3

Infant leukemias present as either acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML) and are commonly driven by KMT2A/ MLL rearrangements (MLLr). MLLr account for ~70% of infant ALL and ~50% of infant AML. Most of the MLLr that drive infant leukemias occur before birth and require very few cooperating mutations. These observations suggest that MLLr transform fetal/neonatal progenitors with great efficiency. However, this model introduces important paradoxes. First, the incidence of MLLr infant leukemia is ~20-fold lower than the incidence of adult MLLr leukemias. Second, fetal leukemias are exceedingly rare despite the fact that MLLr can arise before birth and require a low secondary mutation threshold for transformation. Third, even in mouse models that demonstrate efficient leukemogenesis, the fraction of MLLr progenitors that actually give rise to AML is quite small. Fourth, in our prior studies, we developed a doxycycline (DOX) inducible MLL-ENL mouse model (Tet-ME) to activate MLL-ENL and found that transformation efficiency is higher when MLL-ENL is induced shortly after birth rather than before birth (PMID: 31405949). These observations raise the question of whether fetal/neonatal progenitors carry intrinsic protection against transformation. To test whether fetal identity conveys protection against MLLr leukemia initiation, we activated MLL-ENL at embryonic day 10.5 (E10.5) or postnatal day 14 (P14), by removing DOX. We then assessed the leukemogenic potential of postnatal progenitors in transplantation assays. Strikingly, progenitors that expressed MLL-ENL from E10.5 onward could engraft efficiently but did not give rise to AML in recipient mice. In contrast, progenitors that expressed MLL-ENL induced from P14 onward gave rise to rapid, fully penetrant AML in recipient mice (Figure 1A). Our data show that MLL-ENL induces heritable epigenetic changes in fetal progenitors, that limit transformation potential after transplantation. To assess the unique response of fetal progenitors to MLL-ENL activation, we used our Tet-ME model and induced MLL-ENL before or after birth. We isolated P28 progenitors, repeated transplantation/survival assays and performed Cellular Indexing of Transcriptomes and Epitopes (CITE-seq), in parallel, to test whether MLL-ENL differentially reprograms pre- and post-natal progenitors (i.e., do P28 progenitors have distinct expression programs depending on when MLL-ENL is induced?). Hematopoietic progenitors had similar differentiation trajectories by pseudotime analysis, but distinct gene expression profiles after fetal and postnatal MLL-ENL induction. Some known MLL-ENL targets, including Hoxa9 and Pim1, were maintained at similar levels following fetal and postnatal induction. Other targets, including Meis1, Pbx1 and Sox4, were only expressed in the HSC/MPP cluster following postnatal induction. Metabolic and differentiation states also differed. As in the initial survival assays, MLL-ENL expressing progenitors only gave rise to AML following postnatal induction. We next sought to identify epigenetic regulators that enforce non-malignant cell fates following fetal MLL-ENL induction. We focused our screen on epigenetic factors with known tumor suppressor roles and identified the SET methyltransferase MLL3 as a candidate effector of fetal protection. Specifically, heterozygous Kmt2c deletions greatly accelerated AML initiation after fetal MLL-ENL induction, but not postnatal induction (Figure 1B). Notably, the MLL3/4 COMPASS-like complex was recently shown to antagonize the KMT2A-MENIN interaction and promote differentiation in AML cells. Our data reinforce the notion that there are ontological windows that permit or repress leukemic transformation. Quite surprisingly, fetal progenitors appear to be more resistant to transformation than neonatal progenitors, potentially accounting for the paucity of fetal MLLr leukemias. Infant leukemias that do occur must bypass heritable protective mechanisms, either via mutations or epigenetic reprogramming.

First mouse model of infant acute myeloid leukemia with t(7;12)(q36;p17).

Not available.

Hematopoietic Stem Cell (HSC)-Independent Progenitors Are Susceptible to Mll-Af9-Induced Leukemic Transformation.

Infant acute myeloid leukemia (AML) is a heterogeneous disease, genetically distinct from its adult counterpart. Chromosomal translocations involving the KMT2A gene (MLL) are especially common in affected infants of less than 1 year of age, and are associated with a dismal prognosis. While these rearrangements are likely to arise in utero, the cell of origin has not been conclusively identified. This knowledge could lead to a better understanding of the biology of the disease and support the identification of new therapeutic vulnerabilities. Over the last few years, important progress in understanding the dynamics of fetal hematopoiesis has been made. Several reports have highlighted how hematopoietic stem cells (HSC) provide little contribution to fetal hematopoiesis, which is instead largely sustained by HSC-independent progenitors. Here, we used conditional Cre-Lox transgenic mouse models to engineer the Mll-Af9 translocation in defined subsets of embryonic hematopoietic progenitors. We show that embryonic hematopoiesis is generally permissive for Mll-Af9-induced leukemic transformation. Surprisingly, the selective introduction of Mll-Af9 in HSC-independent progenitors generated a transplantable myeloid leukemia, whereas it did not when introduced in embryonic HSC-derived cells. Ex vivo engineering of the Mll-Af9 rearrangement in HSC-independent progenitors using a CRISPR/Cas9-based approach resulted in the activation of an aberrant myeloid-biased self-renewal program. Overall, our results demonstrate that HSC-independent hematopoietic progenitors represent a permissive environment for Mll-Af9-induced leukemic transformation, and can likely act as cells of origin of infant AML.

A pro B cell population forms the apex of the leukemic hierarchy in Hoxa9/Meis1-dependent AML

Relapse is a major challenge to therapeutic success in acute myeloid leukemia (AML) and can be partly associated with heterogeneous leukemic stem cell (LSC) properties. In the murine Hoxa9/Meis1-dependent (H9M) AML model, LSC potential lies in three defined immunophenotypes, including Lin−cKit+ progenitor cells (Lin−), Gr1+CD11b+cKit+ myeloid cells, and lymphoid cells (Lym+). Previous reports demonstrated their interconversion and distinct drug sensitivities. In contrast, we here show that H9M AML is hierarchically organized. We, therefore, tracked the developmental potential of LSC phenotypes. This unexpectedly revealed a substantial fraction of Lin− LSCs that failed to regenerate Lym+ LSCs, and that harbored reduced leukemogenic potential. However, Lin− LSCs capable of producing Lym+ LSCs as well as Lym+ LSCs triggered rapid disease development suggestive of their high relapse-driving potential. Transcriptional analyses revealed that B lymphoid master regulators, including Sox4 and Bach2, correlated with Lym+ LSC development and presumably aggressive disease. Lentiviral overexpression of Sox4 and Bach2 induced dedifferentiation of H9M cells towards a lineage-negative state in vitro as the first step of lineage conversion. This work suggests that the potency to initiate a partial B lymphoid primed transcriptional program as present in infant AML correlates with aggressive disease and governs the H9M LSC hierarchy.

3093 – SUBTYPE-SPECIFIC INDUCTION OF MITOCHONDRIAL APOPTOSIS AS A NOVEL THERAPEUTIC OPTION IN HIGH-FATALITY PEDIATRIC LEUKEMIA

A rare subtype of acute myeloid leukemia (AML) is acute megakaryoblastic leukemia (AMKL). Recurrent and mutually exclusive oncogenic fusions are detected in AMKL and are considered the transforming event in this disease. AMKL usually affects children below 3 years of age and is associated with less than 40% cure rates. In addition, the development of genotype tailored therapies is urgently needed in AMKL but greatly limited by the paucity of primary sample material. Our research group has established synthetic human models of high-fatality pediatric AMKL, driven by distinct oncogenic fusions, which phenocopy the disease in a patho-physiological context in mice. Inducers of mitochondria-mediated apoptosis, so called BH3 mimetics, recently entered the therapeutic arena in pediatric leukemia with promising results. Therefore, we set out to investigate the potential of Venetoclax (inhibitor of BCL-2) and Navitoclax (inhibitor of BCL-2, BCL-XL and BCL-W) as novel therapeutic options as a bridge to curative bone marrow transplantation in this high-fatality infant leukemia. Our research demonstrates that genetic and pharmacological inhibition of the pro-survival BCL-2 family member BCL-XL results in significant induction of apoptosis in our models of AMKL. In contrast, inhibition of BCL-2 does not induce apoptosis in our models, which is currently the most investigated BCL-family member in the clinic for other subtypes of AML (Venetoclax). In addition, Navitoclax showed promising in vivo activity with a significant decrease in infiltrating leukemic cells in bone-marrow and spleen after drug treatment in comparison to vehicle-only controls. In summary, this project will bring mechanistic insight into the role of apoptotic pathways in AMKL and greatly accelerate the identification of novel therapeutic options in high-fatality infant AML. A rare subtype of acute myeloid leukemia (AML) is acute megakaryoblastic leukemia (AMKL). Recurrent and mutually exclusive oncogenic fusions are detected in AMKL and are considered the transforming event in this disease. AMKL usually affects children below 3 years of age and is associated with less than 40% cure rates. In addition, the development of genotype tailored therapies is urgently needed in AMKL but greatly limited by the paucity of primary sample material. Our research group has established synthetic human models of high-fatality pediatric AMKL, driven by distinct oncogenic fusions, which phenocopy the disease in a patho-physiological context in mice. Inducers of mitochondria-mediated apoptosis, so called BH3 mimetics, recently entered the therapeutic arena in pediatric leukemia with promising results. Therefore, we set out to investigate the potential of Venetoclax (inhibitor of BCL-2) and Navitoclax (inhibitor of BCL-2, BCL-XL and BCL-W) as novel therapeutic options as a bridge to curative bone marrow transplantation in this high-fatality infant leukemia. Our research demonstrates that genetic and pharmacological inhibition of the pro-survival BCL-2 family member BCL-XL results in significant induction of apoptosis in our models of AMKL. In contrast, inhibition of BCL-2 does not induce apoptosis in our models, which is currently the most investigated BCL-family member in the clinic for other subtypes of AML (Venetoclax). In addition, Navitoclax showed promising in vivo activity with a significant decrease in infiltrating leukemic cells in bone-marrow and spleen after drug treatment in comparison to vehicle-only controls. In summary, this project will bring mechanistic insight into the role of apoptotic pathways in AMKL and greatly accelerate the identification of novel therapeutic options in high-fatality infant AML.

A B-cell developmental gene regulatory network is activated in infant AML.

Infant Acute Myeloid Leukemia (AML) is a poorly-addressed, heterogeneous malignancy distinguished by surprisingly few mutations per patient but accompanied by myriad age-specific translocations. These characteristics make treatment of infant AML challenging. While infant AML is a relatively rare disease, it has enormous impact on families, and in terms of life-years-lost and life limiting morbidities. To better understand the mechanisms that drive infant AML, we performed integrative analyses of genome-wide mRNA, miRNA, and DNA-methylation data in diagnosis-stage patient samples. Here, we report the activation of an onco-fetal B-cell developmental gene regulatory network in infant AML. AML in infants is genomically distinct from AML in older children/adults in that it has more structural genomic aberrations and fewer mutations. Differential expression analysis of ~1500 pediatric AML samples revealed a large number of infant-specific genes, many of which are associated with B cell development and function. 18 of these genes form a well-studied B-cell gene regulatory network that includes the epigenetic regulators BRD4 and POU2AF1, and their onco-fetal targets LIN28B and IGF2BP3. All four genes are hypo-methylated in infant AML. Moreover, micro-RNA Let7a-2 is expressed in a mutually exclusive manner with its target and regulator LIN28B. These findings suggest infant AML may respond to bromodomain inhibitors and immune therapies targeting CD19, CD20, CD22, and CD79A.

Early Hematopoietic Stem Cell Transplantation in the Treatment of High-Risk Infant Leukemia

INTRODUCTIONAcute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) are rare diseases in children less than one and two years old respectively. Infant ALL and AML demonstrates unique biological characteristics associated with aggressive clinical features, i.e. high frequency of KMT2A gene rearrangements, poor response to standard chemotherapy, and thus worse prognosis compared to older children. These patients (pts) are at high risk (HR). Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for HR infant leukemia especially in 1 st CR, but proportion of these patients unable to undergo allo-HSCT due to early events, mainly relapse or treatment-related toxicity during initial therapy. We investigated the role of early allo-HSCT from different types of donors. The primary end points were overall survival (OS), transplant-relate mortality (TRM), graft-versus-host disease (GVHD) free, relapse-free survival (GRFS). Secondary end points included neutrophil engraftment and acute and chronic GVHD. MethodsWe included 50 infants with HR ALL (n=10, of with MLLr+ n=6) and AML (n=40, of with MLLr+ n=14) in CR 1. Median age at allo-HSCT 12,5 months old (range from 4 m.o. till 35 m.o.). Median time from diagnosis to allo-HSCT was 9 months (range from 3 till 21). Donor of SCT was: MSD-10% (n=5), MUD-46% (n=23), Haplo-44% (n=22). Majority of patients, 86% received MAC based on busulfan 12-16mg/kg (n=43, including IV busulfan-20pts), 14% (n=7) received RIC based on melphalan 140 mg/m 2. GVHD prophylaxis consisted of PTCy±CNI and m-TOR inhibitor in 62% (n=31), seroprophylaxis±CNI in 38% (n=19). Median follow-up was 64,3 months (range 1-220). Patient data were censored at the time of death or last follow-up. Probabilities of OS and GRFS were estimated using Kaplan-Meier curves. TRM was defined as any death that occurred in the absence of disease relapse; relapse was a competing risk for this event. ResultsEngraftment rate was 82%. Cumulative incidences by day 100 of TRM in Haplo were 2% vs 4% in MSD+MUD (р=0,9). Ten-year rates OS in Haplo and MSD+MUD were 77,3% (±4,7%) vs 78,6% (±9%) respectively (p=0,73). Ten-year GRFS did not differ between two study cohorts being 50% vs 57% for Haplo and MSD+MUD (p=0,76). Clinically significant aGVHD (grades 2-4) after allo-HSCT was observed in 27% (n=6) Haplo and 32% (n=9) MSD+MUD (p=0,77). A total of 12% (n = 6) patients developed severe cGVHD. ConclusionsEarly allogeneic HSCT in 1 st CR from different types of donors, including haploidentical is associated with favorable outcomes in infant acute leukemias. This approach should be evaluated in further controlled clinical studies. DisclosuresKulagin: X4 Pharmaceuticals, Alexion, Apellis, Biocad: Research Funding; Novartis, Generium, Sanofi, Roche, Johnson & Johnson, Pfizer: Speakers Bureau.

SKIDA1 Sustains MLL-ENL-Expressing Hematopoietic Stem and Progenitor Cells

Chromosomal translocations involving the MLL1 gene often drive infant acute myeloid leukemia (AML). MLL fusion proteins (e.g., MLL-ENL, MLL-AF9, MLL-AF10) activate self-renewal programs in hematopoietic stem and progenitor cells, ultimately leading to transformation. The high frequency of MLL1 rearrangements in infant leukemias suggests that neonatal progenitors are uniquely poised to transform in response to these mutations. Indeed, we have recently shown that MLL-ENL initiates AML more efficiently in neonatal progenitors than in adult progenitors (Okeyo-Owuor et. al. Blood Advances, 2019). This raises the question of whether MLL-ENL induces key effectors of transformation more efficiently in neonatal progenitors than in adult progenitors. We identified Ski/Dach Domain Containing 1 (Skida1) as a gene that is highly induced by MLL-ENL in neonatal, but not adult hematopoietic progenitors. SKIDA1 is also highly expressed in human pediatric AML, and this expression is largely restricted to leukemias with MLL1 rearrangements. These observations suggest that Skida1 may be a critical, neonate-specific effector of MLL-ENL driven leukemogenesis.To test whether SKIDA1 plays a role in hematopoiesis and leukemogenesis, we generated a germline loss-of-function mouse allele. First, we tested whether loss of SKIDA1 perturbed hematopoiesis by flow cytometry. SKIDA1 deletion caused modest expansion of hematopoietic stem cells (HSCs) in neonates at post-natal day 0 (P0) and a modest decrease of hematopoietic committed progenitor cells (HPCs) at P14, but no changes in fetal or adult HSC/HPC numbers were observed. We then assessed HSC function by transplanting HSCs into lethally irradiated mice to assess their multi-lineage repopulating potential. Loss of SKIDA1 did not perturb HSC function at any stage of development, indicating a minor role in normal hematopoiesis. Next, we tested whether SKIDA1 modulates HSC or HPC numbers in the context of MLL-ENL expression. We crossed Skida1-/- mice to mice with a tetracycline inducible MLL-ENL transgene. The resulting mice (TetO-MLL-ENL; Vav1-Cre) express MLL-ENL specifically in hematopoietic cells beginning at embryonic day 10.5 (E10.5) in the absence of doxycycline, concordant with the onset of Vav1-Cre expression. When we induced MLL-ENL expression in Skida1 -/- mice, we observed near complete loss of HSCs and a severe reduction of HPCs. The reduction in HSC and HPC numbers in TetO-MLL-ENL; Vav1-Cre; Skida1 -/- neonates was far more severe than we observed in TetO-MLL-ENL; Vav1-Cre mice alone. Furthermore, this phenotype emerged between P0 and P14, indicating that it requires a neonatal context to manifest. This coincides with the developmental stage at which MLL-ENL most efficiently induces AML (Okeyo-Owuor et. al. Blood Advances, 2019). This data suggest that SKIDA1 helps sustain pre-leukemic MLL-ENL-expressing HSCs and HPCs shortly after birth. Ongoing studies will address the mechanism by which SKIDA1 regulates AML.Our current work raises two important points. First, SKIDA1 appears to have a far more important role in sustaining MLL-ENL-expressing progenitors than normal progenitors, raising the prospect for an excellent therapeutic window. Secondly, our findings show that age-specific MLL-ENL targets can shape pre-leukemic hematopoiesis and potentially AML initiation. This may help explain why MLL1 rearrangements account for a higher percentage of infant and childhood leukemias than adult leukemias. DisclosuresNo relevant conflicts of interest to declare.

Biology and Prognostic Markers in Young Children with Acute Myeloid Leukemia -the Jccg Study, JPLSG AML-05-

[Introduction] Acute myeloid leukemia (AML) in children aged < 12 months of age was conventionally defined as infant AML. On cytogenetic and molecular analysis, 11q23/ KMT2A rearrangement (KMT2A -R) was found to be the most frequent (approximately 50%) cause of infant AML. On prognostic analysis, infant AML was reported to have favorable outcome compared with AML in older children, and only KMT2A -R and RBM15-MKL1 were known to be intermediate-risk prognostic factors in infants. Although infants have been treated in the same regimens as older children, in some clinical trials, drug dosage for infants has been reduced to avoid severe toxicities. However, new findings in young children with AML have been recently accumulated. A recent report by an international expert panel of pediatric AML has proposed AML in children aged < 24 months of age as a distinct age-subgroup because their morphologic and cytogenetic/molecular characteristics were considered to be similar to those of infants (Creutzig et al, 2012). Moreover, recent studies have identified novel inv(16)(p13.3q24.3)/ CBFA2T3-GLIS2 and t(11;12)(p15;p13)/ NUP98-KDM5A fusion genes in AMKL. In this study, we investigated biology and prognosis of children aged < 5 years, to identify unique characteristics of young children with AML and propose a novel risk-stratification for them.[Patients and Methods] A total of 369 children with AML were enrolled in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 trial. In this study, we analyzed 133 children aged < 5 years (36%). We screened fusion genes of CBFA2T3-GLIS2, NUP98-KDM5A, RBM15-MKL1, KMT2A -Rs, NUP98-NSD1, FUS-ERG, DEK-NUP214, RUNX1-RUNX1T1, and CBFB-MYH11, and gene mutations of KIT, NRAS, KRAS, WT1, NPM1, KMT2A -PTD, FLT3 -ITD, CEBPA, ASXL1, ASXL2, and CSF3R .[Results] In clinical characteristics, no change was observed in the sex ratio with age. The WBC count at diagnosis was the highest in children aged 2 years (24-35months), and a trend of lower WBC in children aged > 2 years (> 35 months). On FAB classification, the proportion of M5 and M7 was observed to be decline with age. Among fusion genes, KMT2A -R was the most frequently identified fusion gene (23%), followed by RUNX1-RUNX1T1, CBFB-MYH11, and CBFA2T3-GLIS2 (13.5%, 9.8%, and 8.3%, respectively). Conversely, neither NUP98-NSD1 nor DEK-NUP214 was found. Although the frequencies of KMT2A -R and CBFA2T3-GLIS2 tended to decrease with age, the frequency of RUNX1-RUNX1T1 significantly increased with age. Among gene mutations, KIT and NRAS were the most frequent, and gene mutations other than ASXL1 and KMT2A -PTD were recurrently identified. When correlation of fusion genes with gene mutation was analyzed, 21 (68%) of 31 children with CBF-AML had gene mutations, whereas only 8 (16%) of 51 children with non-CBF-AML had gene mutations (p < 0.001). For fusion genes, 28 (90%) of 31 KMT2A -R-positive children were aged < 3 years (< 36 months) (90%), and 17 (94%) of 18 RUNX1-RUNX1T1 -positive children were aged > 2 years. Thus, according to these molecular characteristics of young children with AML, we defined children aged < 3 years as the youngest subgroup with distinct biology (n = 99). We further performed prognostic analyses of the youngest subgroup. According to recent previous studies that reported poor prognosis of CBFA2T3-GLIS2 and NUP98-KDM5A in AMKL, these fusions were combined to the same group. The Kaplan-Meier analyses revealed that CBFA2T3-GLIS2 / NUP98-KDM5A -positive children had the poorest outcome in OS, EFS, and CIR (38%, 13%, and 88%, respectively). Surprisingly, children with CBF-AML had the second poorest outcome in EFS and CIR (45% and 55%, respectively), although this subgroup had an excellent OS (100%), indicating that children with CBF-AML in the youngest subgroup have a high-risk of relapse and might need more intensified therapy as an initial treatment.[Conclusions] The youngest subgroup of pediatric AML had a unique biology. Children with CBFA2T3-GLIS2 and NUP98-KDM5A had the poorest outcome, and children with CBF-AML also had a high relapse rate. Because this subgroup is known to have a high incidence of severe side effects and late effects, a novel risk-stratified therapy restricted to young children is required. DisclosuresNo relevant conflicts of interest to declare.

CLEC12A and CD33 coexpression as a preferential target for pediatric AML combinatorial immunotherapy

AbstractEmerging immunotherapies such as chimeric antigen receptor T cells have advanced the treatment of acute lymphoblastic leukemia. In contrast, long-term control of acute myeloid leukemia (AML) cannot be achieved by single lineage-specific targeting while sparing benign hematopoiesis. In addition, heterogeneity of AML warrants combinatorial targeting, and several suitable immunotargets (HAVCR2/CD33 and HAVCR2/CLEC12A) have been identified in adult AML. However, clinical and biologic characteristics of AML differ between children and the elderly. Here, we analyzed 36 bone marrow (BM) samples of pediatric AML patients and 13 age-matched healthy donors using whole RNA sequencing of sorted CD45dim and CD34+CD38−CD45dim BM populations and flow cytometry for surface expression of putative target antigens. Pediatric AML clusters apart from healthy myeloid BM precursors in principal-component analysis. Known immunotargets of adult AML, such as IL3RA, were not overexpressed in pediatric AML compared with healthy precursors by RNA sequencing. CD33 and CLEC12A were the most upregulated immunotargets on the RNA level and showed the highest surface expression on AML detected by flow cytometry. KMT2A-mutated infant AML clusters separately by RNA sequencing and overexpresses FLT3, and hence, CD33/FLT3 cotargeting is an additional specific option for this subgroup. CLEC12A and CD33/CLEC12Adouble-positive expression was absent in CD34+CD38−CD45RA−CD90+ hematopoietic stem cells (HSCs) and nonhematopoietic tissue, while CD33 and FLT3 are expressed on HSCs. In summary, we show that expression of immunotargets in pediatric AML differs from known expression profiles in adult AML. We identify CLEC12A and CD33 as preferential generic combinatorial immunotargets in pediatric AML and CD33 and FLT3 as immunotargets specific for KMT2A-mutated infant AML.

Infant Acute Myeloid Leukemia: A Unique Clinical and Biological Entity.

Infant acute myeloid leukemia (AML) is a rare subgroup of AML of children <2 years of age. It is as frequent as infant acute lymphoblastic leukemia (ALL) but not clearly distinguished by study groups. However, infant AML demonstrates peculiar clinical and biological characteristics, and its prognosis differs from AML in older children. Acute megakaryoblastic leukemia (AMKL) is very frequent in this age group and has raised growing interest. Thus, AMKL is a dominant topic in this review. Recent genomic sequencing has contributed to our understanding of infant AML. These data demonstrated striking features of infant AML: fusion genes are able to induce AML transformation without additional cooperation, and unlike AML in older age groups there is a paucity of associated mutations. Mice modeling of these fusions showed the essential role of ontogeny in the infant leukemia phenotype compared to older children and adults. Understanding leukemogenesis may help in developing new targeted treatments to improve outcomes that are often very poor in this age group. A specific diagnostic and therapeutic approach for this age group should be investigated.

Infant Acute Myeloid Leukemia with t(X;6)(p11;q23)/MYB-GATA1- a First Female Case in the Entity

Introduction T(X;6)(p11;q23) is a rear but recurrent chromosomal translocation in infant acute myeloid leukemia (AML). It leads to the formation ofMYB-GATA1fusion gene that interferes with granulocyte lineage commitment thus causing AML preliminary with basophilic phenotype. Only males were seen previously in this entity [Dastugue et al. 1997, Belloni et al. 2011, Quelen et al. 2011]. Here we report extensive molecular characterization of 2 infant AML cases with t(X;6)(p11;q23)/MYB-GATA1enrolled in the Russian AML registration study with one of them being a girl. Case reports A boy aged 5,5 mo. with WBC 27,7*109/L and 45% blasts in bone marrow was diagnosed AML, M5a by morphological, cytochemical and immunological observations. He was treated according to AML-BFM-2004 protocol and received allogenic HSCT from matched unrelated donor in the first remission. Patient stays in complete remission for 4 years now. A girl aged 8 mo. was headed to a hospital with febrile fever and petechiae. She had initial WBC 33,8*109/L and 35% bone marrow blasts of basophilic phenotype. Spinal tap confirmed CNS involvement (cytosis 2,6/mm3, 3% blasts). Patient received induction therapy (cytarabine, etoposide, daunorubicin) and achieved a complete remission. However, she developed severe myelodepression and died of infection 3 mo. after the diagnosis. Results MYB-GATA1.GTG-banded karyotyping showed a rearrangement between chromosomes 6 and X as a sole abnormality in both patients - insertion of chromosome 6 material into Xp11 band in a boy and reciprocal translocation t(X;6)(p11;q23) in a girl. FISH for relevant age-specific translocations, includingKMT2Arearrangements and t(7;12)(q36;p12)/ETV6-HLXB, was negative. RNA-seq (TruSeqRNA, Illumina, San-Diego, CA, USA) revealedMYB-GATA1fusion expression with exon 8 - exon 5 junction identical in both patients which was validated by RT-PCR and Sanger sequencing. Direct genomic PCR confirmed breakpoints withinMYBintron 8 andGATA1intron 4 and uncovered patient-specific junctions (see Figure). Reciprocal fusions.The formation of reciprocal fusions was also shown in two studied patients. A boy demonstratedGATA1-TUBE(6q21) intron 4 - intron 7 junction. It is non-functional due to tail-to-tail transcriptional orientation. Such structures are likely to form sinceMYBandGATA1are located in an opposite genomic orientation, so our finding goes in line with previous unsuccessful attempts to look for reciprocalGATA1fusion transcripts expression [Quelen et al. 2011]. However, a girl patient had reciprocalGATA1-CD164fusion (exon 4 - exon 6) actively transcribed together with third fusionMYB-CD164. On the one hand, this confirms that additional event such as inversion of either chromosomal fragment is required for t(X;6)(p11;q23) to manifest. On the other hand, this is, to our knowledge, the first demonstration of reciprocalGATA1fusion transcript expression inMYB-GATA1-associated AML. Wild-type MYB and GATA1 expression.AlongsideMYB-GATA1expression both patients demonstrated the overexpression of wild-typeMYBby qPCR. This is in agreement with MYB overexpression being a feature of undifferentiated cells and diminishing during differentiation [Bartunek et al. 2003]. Wild-typeGATA1expression (its lossper se) is of key importance inMYB-GATA1-associated AL. It was previously proposed that the loss of wild-typeGATA1is essential for leukemogenesis in male patients as the only copy of this gene is disturbed by chromosomal translocation [Quelen et al. 2011]. We observed no wild-typeGATA1expression in our male patient. However, in the female patient wild-type GATA1 expression was present. Additional events.The samples were also screened for additional genetic events associated with myeloid neoplasia by targeted DNA NGS (QIAact Myeloid DNA UMI Panel, Qiagen, Hilden, Germany), fragment analysis (NPM1,FLT3-ITD) and Sanger sequencing (cKIT,FLT3-TKD). NoFLT3,NPM1and cKIT pathogenic variants were found. NoGATA1truncating mutations were found. Deleterious variants were found inNRASgene (p.G12C in a boy, p.G13D in a girl). Female patient also demonstrated pathogenic variants inKRAS(p.A59E) andJAK2(p.N683G). Conclusions Thus, here we report a first case of female patient with t(X;6)(p11;q23)/MYB-GATA1. This raises a question whetherGATA1insufficiency is the primary mechanisms of leukemogenesis in this genetic subgroup. Figure Disclosures No relevant conflicts of interest to declare.

Adoptively Transferred Donor-Derived Cytokine Induced Memory-like NK Cells Persist and Induce Remission in Pediatric Patient with Relapsed Acute Myeloid Leukemia after Hematopoietic Cell Transplantation

Acute myeloid leukemia (AML) accounts for 18% of pediatric leukemias. For high-risk AML, standard treatment includes multi-agent chemotherapy followed allogeneic hematopoietic cell transplantation (HCT). Despite a high remission rate, 50% of patients relapse and have a poor prognosis with &lt; 20% of patients surviving more than 3 years. Salvage chemotherapy alone or combined with donor lymphocyte infusions (DLI) have little curative potential, and new treatment strategies are needed for relapsed-refractory AML. Previous studies have shown that natural killer (NK) cells can be stimulated ex vivo with IL-12/15/18 to generate a memory-like phenotype with enhanced anti-leukemia effect. In adults with relapsed-refractory AML, adoptive transfer of MHC-haploidentical cytokine-induced memory-like (CIML or ML) NK cells induced remission in 54% of patients (PMID27655849). The infused donor ML NK cells expand in vivo but are rapidly eliminated following recovery of recipient T cells, providing a window of therapeutic activity of 2-3 weeks. We sought to test the safety and efficacy of ML NK cells for treatment of pediatric/young adult patients with post-HCT relapsed AML. We hypothesized that ML NK cells derived from the HCT donor would be well-tolerated, exhibit anti-leukemia activity, and expand with prolonged persistence following transfer into pediatric AML patients. Here, we report the results of the first pediatric patient treated on a phase I clinical trial using ML NK cell therapy for relapsed AML after allogeneic HCT (NCT03068819). Briefly, patients are treated with FLAG (fludarabine, cytarabine and granulocyte colony stimulating factor) salvage chemotherapy to reduce the bulk of AML and provide lymphodepletion for ML NK cell expansion. Two weeks after chemotherapy, a non-mobilized leukapheresis product is collected from the original HCT donor and processed into a T cell-based DLI and ML NK cells. The T cell DLI (1 x 106 T cells/kg) is immediately infused, and the ML NK cells are generated by stimulation with IL-12/15/18 ex vivo for 12-16 hours and then infused (10x106/kg). An 18-month-old male with infant AML had relapse of his leukemia 3 months after MHC-haploidentical HCT. Treatment with chemotherapy, including mitoxantrone and daunorubicin-cytarabine liposome, failed to induce remission. At the time of enrollment on the phase I trial, he had AML blasts in his bone marrow (Table 1). He was treated with FLAG chemotherapy followed by infusion of DLI and ML NK cells from the original haploidentical HCT donor. Assessment at 30 days, 3 months and 6 months post NK cell infusion showed complete remission with no evidence of leukemia and full donor engraftment. Remarkably, donor-derived ML NK cells expanded to 77% of donor lymphocytes on day 28 and still comprised 24% percent of lymphocytes at 6 months post infusion (Figure 1A-C). The expanded donor NK cell phenotype was consistent with ML NK cells (e.g., NKG2A+KIR+) utilizing CyTOF multidimensional analysis previously confirmed to identify ML NK cells (Figure 1D). The ML NK cells were functional as demonstrated by leukemia-triggered IFN-γ production immediately ex vivo from day 7-28 samples (Figure 1E-F). The patient's clinical course was complicated by mild gastrointestinal graft-versus-host disease that resolved with low-dose steroids and tociluzimab. These early results demonstrate proof-of-principle that adoptive transfer of donor-derived ML NK cells in combination with DLI is feasible and offers a novel immunotherapy option for patients with relapsed AML after HCT. Moreover, in this T and NK cell compatible immune environment post-HCT, donor ML NK cells expand and persist robustly in vivo for &gt; 6 months without exogenous cytokine support and have potent anti-leukemic activity. Thus, ML NK cells are a cellular therapy platform to treat AML that has relapsed after allogeneic HCT. Disclosures Cashen: Celgene: Other: Speaker's Bureau; Seattle Genetics: Other: Speaker's Bureau; Novartis: Other: Speaker's Bureau. Fehniger:Horizon Pharma PLC: Other: Consultancy (Spouse); Cyto-Sen Therapeutics: Consultancy.

A Distinct Oncofetal B-Cell Transcriptional Program Is Activated in Infant Acute Myeloid Leukemia and Reveals Novel Therapeutic Strategies

Infants with acute leukemia present special challenges, due in part to the unusual features of their disease. A clonal oncofusion protein is detectable in the vast majority of infants presenting with acute leukemia, whether myeloid (AML), lymphoblastic (ALL), or mixed-phenotype (MPAL). Many recurrent oncofusion proteins seen in this age group involve the KMT2A (formerly MLL, Mixed Lineage Leukemia) gene, located on chromosomal band 11q23, which is notorious for both lineage switching and poor clinical prognosis. Other fusions involve components of the nuclear pore complex (NUP98), chromatin modifiers (KAT6A), or lineage-associated pioneer factors (such as MYB and GLIS2). This diversity of oncofusion proteins has hampered efforts to develop targeted agents, and over half of infant cases eventually succumb to their disease. Previous work showed that infant ALL is distinct from childhood or adult ALL. Here we show that infant AML is similarly distinct from AML in other age groups, and this difference yields transformative opportunities to repurpose existing targeted and immune therapies. mRNA sequencing (RNAseq) analysis of over 1500 participants in Children's Oncology Group clinical trials revealed hundreds of infant-AML-specific transcripts, many associated with early B cell development. 18 of the affected genes form a canonical B-cell regulatory circuit, including the epigenetic regulators BRD4 and POU2AF1, and their onco-fetal targets LIN28B and IGF2BP3. These four genes also host hypo-methylated super-enhancers in most infant AML cases, but in few older patients. The MYC proto-oncogene is directly implicated in a regulatory loop involving microRNA let7a-2, which is expressed in a mutually exclusive manner with its target and regulator LIN28B (Fig 1A). By contrast, the WT1 gene, abundantly expressed in over 90% of AML cases from other age groups, is transcribed at low levels in most infant AML cases. Single-sample gene set enrichment analysis revealed that most cases of infant AML bear more similarity to infant B-cell ALL or MPAL than to AML in older children, adolescents, and adults (Fig 1B). Higher-order chromatin conformation further emphasizes these differences. The MYC proto-oncogene, a critical node in the gene regulatory network (Fig. 1A) observed across infant acute leukemia cases, is routinely amplified via trisomy 8 in this age group (and in fact all childhood leukemia). The IGF2BP3 gene, another critical node (Fig. 1A), is rarely deleted in infants (deletions of 7q tend to spare 7p15, and complex karyotype cases often retain two or more copies on derivative chromosomes). The immature humoral and adaptive immune system in infants complicates treatment in this age group, but also yields metabolic vulnerabilities which can be exploited to break the nearly ubiquitous positive feedback loop described herein. These age-specific differences suggest that alternative therapeutic targets and modalities are warranted not only in infant AML, but across infant acute leukemia more generally. The relatively small numbers of infant acute leukemia cases by lineage, along with common mechanisms that appear to sustain most cases of infant acute leukemia, and frequent clinical reports of lineage switching in infants regardless of morphology at presentation, all support this contention. Our results indicate that combination therapies coupling experimental ages (such as DFMO, which targets metabolic regulation of MYC, LIN28B, and let-7a via ornithine decarboxylase, and has shown substantial efficacy in MYCN-amplified neuroblastoma) with already approved agents such as BET inhibitors (which target BRD4) and blinatumomab (targeting CD19 as a canonical B-cell antigen) may be warranted. These immune-targeting combinations represent promising and potentially lineage-agnostic approach to improving outcomes for infants with acute leukemia, a group of patients for whom novel therapeutic strategies are desperately needed, and for whom less toxic, more effective, targeted combination therapies may spare a lifetime of late effects. Disclosures Pardo: Hematologics, Inc: Employment. Kaeding:Celgene: Employment. Loken:Hematologics, Inc: Employment, Equity Ownership. Farrar:Novartis: Research Funding.

Parental age and the risk of childhood acute myeloid leukemia: results from the Childhood Leukemia International Consortium

BackgroundParental age has been associated with several childhood cancers, albeit the evidence is still inconsistent. AimTo examine the associations of parental age at birth with acute myeloid leukemia (AML) among children aged 0–14 years using individual-level data from the Childhood Leukemia International Consortium (CLIC) and non-CLIC studies. Material/methodsWe analyzed data of 3182 incident AML cases and 8377 controls from 17 studies [seven registry-based case-control (RCC) studies and ten questionnaire-based case-control (QCC) studies]. AML risk in association with parental age was calculated using multiple logistic regression, meta-analyses, and pooled-effect estimates. Models were stratified by age at diagnosis (infants <1 year-old vs. children 1–14 years-old) and by study design, using five-year parental age increments and controlling for sex, ethnicity, birthweight, prematurity, multiple gestation, birth order, maternal smoking and education, age at diagnosis (cases aged 1–14 years), and recruitment time period. ResultsAdjusted odds ratios (ORs) and 95% confidence intervals (CIs) derived from RCC, but not from the QCC, studies showed a higher AML risk for infants of mothers ≥40-year-old (OR = 6.87; 95% CI: 2.12–22.25). There were no associations observed between any other maternal or paternal age group and AML risk for children older than one year. ConclusionsAn increased risk of infant AML with advanced maternal age was found using data from RCC, but not from QCC studies; no parental age-AML associations were observed for older children.

In Vitro Activity and Target Modulation of PV-10 Against Relapsed and Refractory Pediatric Leukemia

Introduction: Leukemias are the most common childhood cancers, accounting for 30% of all pediatric cancer diagnoses. Although the survival rate for pediatric leukemia has greatly improved, relapse is a major cause of treatment failure. Approximately 15-20% of pediatric acute lymphoblastic leukemia (ALL) patients and 30-40% of acute myeloid leukemia (AML) patients relapse, with relapsed ALL identified as the fourth most common malignancy in children. Treatment of relapsed pediatric leukemia includes intensification of chemotherapeutic regimens and use of bone marrow transplantation (BMT). However, increasing the intensity of combination chemotherapies and introduction of second-line drugs is often accompanied by cumulative toxicity with marginal incremental benefits. Therefore, research to identify and develop novel tolerable and effective agents is urgently needed. PV-10 (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is a novel therapeutic that induces direct cytotoxicity in adult and pediatric solid tumors and stimulates tumor specific immune activation through immunogenic cell death. Our studies aim to identify the potential of PV-10 in future clinical trials for relapsed and refractory pediatric leukemias.Methods: A panel of eleven cell lines derived from patients with either primary or relapsed pediatric leukemia (CEM-C1, CCRF-SB, Kasumi-1, KOPN8, Molm-13, Molt-3, Molt-4, MV4-11, SEM, SUP-B15 and TIB-202) and cells from three primary leukemia patient specimens (T-ALL, AML, Infant AML) were treated with increasing concentrations of PV-10 and cell viability was measured by alamar blue assay, 96 h post-treatment. Target modulation and induction of cell death pathways were investigated by western blot, phase-contrast microscopy and time-lapse video microscopy. Analysis of cell cycle alterations and induction of apoptosis were measured by flow cytometry. Combination studies will be performed to identify anti-cancer agents that are synergistic with PV-10 and animal models of pediatric leukemia used to identify the activity of PV-10 against pediatric leukemia in vivo.Results: PV-10 decreased cell viability in a concentration and time dependent manner in the eleven pediatric leukemia cell lines (mean IC50 93 µM), and three primary leukemia samples (mean IC50 122 µM) tested. Observation of four different leukemia cell lines (Molm-13, MV4-11, SEM, TIB-202) by phase-contrast and time-lapse video microscopy indicated that PV-10 was cytotoxic and not cytostatic to cells. Quantification of dead cells from time-lapse video microscopy experiments showed that PV-10 was cytotoxic in a cell line and concentration dependent manner. At 24 h post-treatment with 100 µM PV-10, 88% of MV4-11 cells, 69% of Molm-13 cells, 27% of TIB-202 cells and 25% of SEM cells had undergone cell death. When the concentration of PV-10 was increased to 200 µM, 100% of MV4-11 and Molm13 cells, 94% of SEM cells and 60% of TIB-202 cells had undergone cell death, 24 h after treatment. Additionally, observation by time-lapse video microscopy suggested that cells were dying by apoptosis, as treatment with PV-10 led to cell shrinkage. Induction of apoptosis by PV-10 was confirmed by dose and time dependent PARP cleavage, detected by western blot.Conclusions: Our studies provide first proof-of-concept pre-clinical data for the activity and mechanisms of action of PV-10 in pediatric leukemia. These data provide the rationale for additional studies and the formulation of an early-phase clinical trial for patients with relapsed and refractory pediatric leukemia. DisclosuresNo relevant conflicts of interest to declare.

Highlights of This Issue

Decades of investment into genomic science has led to a revolution in our understanding of the architecture of the human genome, genomic variation, and the biological consequences of the genome on human health and disease. Thanks to the technical and methodological advancements that enabled genome-wide association studies (GWAS), our understanding of the underlying genetics of most common diseases and traits has been fundamentally changed. Despite the many successes of GWAS, there remain unfulfilled promises. In this special CEBP Focus issue, some of the leading figures in GWAS research in the past decades summarize what we have learned from this line of research and where the field can contribute biological and clinical insights into cancer.Alcohol has been classified as a carcinogen since 1988 and is thought to account for 3% to 5% of cancer cases. Nevertheless, Scheideler and Klein found in a review of 32 studies that awareness of alcohol as a cancer risk factor is low. Awareness appears to be highest in the United Kingdom and Australia, but low in the United States. People are more likely to endorse alcohol as a risk factor when viewing it on a list of risk factors than when asked to identify risk factors in an open-ended format. Given the prevalence and burden of cancer, this insufficient awareness highlights the importance of developing informational and other campaigns.Marine ω-3 polyunsaturated fatty acids (PUFAs) may prevent colorectal cancer progression, but data in humans are limited. Van Blarigan and colleagues examined postdiagnostic marine ω-3 PUFAs and fish intake and survival among 1,011 colon cancer patients. Patients in the highest versus lowest quartile of marine ω-3 PUFAs had a 28% lower risk of cancer recurrence and death. Patients who consumed dark meat fish ≥1/week versus never had a 35% lower risk of cancer recurrence and death. These data suggest marine ω-3 PUFAs and dark fish may improve colon cancer survival. Clinical trials examining marine ω-3 PUFAs and colon cancer outcomes are needed.Previous studies have reported increased risks of pediatric acute lymphoblastic leukemia (ALL) among children born by cesarean delivery (CD). Utilizing both interview and medical record data from a case–control study of infant leukemia, Marcotte and colleagues comprehensively evaluated the association between CD and both infant ALL and infant acute myeloid leukemia. The analyses indicated an increased risk estimate for the association between CD and infant ALL. This study provides the first in-depth examination of CD and infant leukemia. The findings suggest that altered microbiota colonization may be involved in development of infant leukemia.

Septin 6 regulates engraftment and lymphoid differentiation potential of murine long-term hematopoietic stem cells

Septins are a family of filament-forming GTP-binding proteins that serve as scaffolds and diffusion barriers in various cellular processes. Septin 6 is known as a fusion partner of mixed-lineage leukemia in infant acute myeloid leukemia. The occurrence of the fusion gene is associated with a reduced expression of septin 6 itself. The role of septin 6 in hematopoiesis and whether it is involved in scaffolds within hematopoietic cells is not known. Septin 6-deficient hematopoietic stem cells (HSCs) present with an increased engraftment potential but altered lymphoid differentiation with a reduced contribution to the T-cell compartment and an increased B-cell contribution. Although multipotent progenitor cells showed a very distinct septin 6 filament organization and intracellular distribution, their function was not impaired by septin 6 deficiency. Our data therefore suggest a regulatory role for septin 6 in long-term HSC function and lymphoid lineage differentiation.

TET2 in Normal and Malignant Hematopoiesis.

The ten-eleven translocation (TET) family of enzymes were originally cloned from the translocation breakpoint of t(10;11) in infant acute myeloid leukemia (AML) with subsequent genomic analyses revealing somatic mutations and suppressed expression of TET family members across a range of malignancies, particularly enriched in hematological neoplasms. The TET family of enzymes is responsible for the hydroxylation of 5-methylcytosines (5-mC) to 5-hydroxymethylcytosine (5-hmC), followed by active and passive mechanisms leading to DNA demethylation. Given the complexity and importance of DNA methylation events in cellular proliferation and differentiation, it comes as no surprise that the TET family of enzymes is intricately regulated by both small molecules and regulatory cooperating proteins. Here, we review the structure and function of TET2, its interactions with cooperating mutations and small molecules, and its role in aberrant hematopoiesis.

Suggestion of MUC16 (c.39169C>T) Mutation As a Potential Candidate for Predisposition to Myeloid Malignancy Associated with Trisomy 21

While the majority of leukemia cases occur in the absence of any known predisposing factor, there are germline mutations that significantly increase the risk of developing hematopoietic malignancies in childhood. Germline testing for the predisposition to myeloid malignancies is becoming more common with the recognition of multiple familial syndromes. In USA, Clinical Laboratory Improvement Amendments (CLIA) approved testing exists for mutations in RUNX1, GATA2, CEBPA and the other genes of inherited bone marrow failure syndromes. Meanwhile, GATA1 mutation is almost associated with Down syndrome and in acute myeloid leukemia (AML) with acquired trisomy 21. We experienced a case of infant AML with trisomy 21 and coexisting mutation of MUC16.We experienced infant leukemia (FAB classification, AML M7, Acute megakaryoblasticleukemia) with trisomy 21 and coexisting MUC16, SCRIB, and CEBPA mutation in a 7-month-old boy. Peripheral blood (PB) was taken from the boy every day during hospitalization. Bone marrow (BM) examination was performed at initial diagnosis and after remission. All of PB and BM samples were collected with informed consent, and the study was reviewed and approved by the Institutional Review Board of Seoul National University College of Medicine. The selected five PB samples are demonstrated on Fig. 1. G-banding revealed trisomy 21 and fluorescent in situ hybridization (FISH) for chromosome enumeration 21 revealed 71% with trisomy 21 cells in his diagnosis. At first, we suspected transient abnormal myeloproliferative disease associated with mosaic Down syndrome and serially monitored the proportion of cells with trisomy 21 by FISH and the percentage of blast during hospitalization. Cells with trisomy 21 decreased as blast disappeared in PB during chemotherapy, suggesting trisomy 21 is acquired abnormality in leukemic cells.We performed target gene sequencing of 359 genes related to the hematologic neoplasm, bone marrow failure syndrome, and cancer susceptibility to selected five PB. In addition, to search for the inherited predisposition gene to AML, we also performed whole genome sequencing (WGS) with BM specimen at initial diagnosis and after achieving remission. These next generation sequencing (NGS) with the Illumina HiSeq2500 platform revealed MUC16 (c.39169C>T) is the only significant mutation that persisted throughout from initial diagnosis to post-remission status. Mutations which were seen at initial diagnosis but disappeared after achieving remission were SCRIB (c.2197G>A, p.Arg733Trp) and CEBPA (c.371G>A, p.Ala124Val).To investigate whether MUC16 (c.39169C>T) mutation is rare variant which can be detected in normal person, we screened MUC16 mutation in healthy control (n=365) and in patients with other hematologic diseases (adult myelodysplastic syndrome, n=155; adult aplastic anemia, n=57; adult myeloproliferative neoplasm, n=44; childhood myeloid neoplasm, n=26; inherited bone marrow failure syndrome, n=21; idiopathic eosinophilia, n=4; familiar hemophagocytic lymophohistiocytosis, n=10; congenital neutropenia, n=1) using allele-specific PCR. MUC16 (c.39169C>T) was found in none of them. Discovered site of MUC16 (c.39169C>T) was not reported in solid tumor as well, though the other sites of MUC16 were frequently reported. It is generally known that AML with trisomy 21 accompanies GATA1 mutation, but the infant AML in this study did not accompany GATA1 mutation, but rather, MUC16 mutation.In this patient, GATA1 mutation was not found throughout hospital course. Instead, here we suggest that the constitutional MUC16 (c.39169C>T) mutation coexerts with acquired trisomy 21 in the development of infant AML and that MUC16 (c.39169C>T) mutation is a potential candidate gene for predisposition to AML. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.