Chromosomal breaks at the origin of small tandem DNA duplications.

Small tandem DNA duplications in the range of 15 to 300 base-pairs play an important role in the aetiology of human disease and contribute to genome diversity. Here, we discuss different proposed mechanisms for their occurrence and argue that this type of structural variation mainly results from mutagenic repair of chromosomal breaks. This hypothesis is supported by both bioinformatical analysis of insertions occurring in the genome of different species and disease alleles, as well as by CRISPR/Cas9-based experimental data from different model systems. Recent work points to fill-in synthesis at double-stranded DNA breaks with complementary sequences, regulated by end-joining mechanisms, to account for small tandem duplications. We will review the prevalence of small tandem duplications in the population, and we will speculate on the potential sources of DNA damage that could give rise to this mutational signature. With the development of novel algorithms to analyse sequencing data, small tandem duplications are now more frequently detected in the human genome and identified as oncogenic gain-of-function mutations. Understanding their origin could lead to optimized treatment regimens to prevent therapy-induced activation of oncogenes and might expose novel vulnerabilities in cancer.

MicroRNA networks in FLT3-ITD acute myeloid leukemia.

MiR-126 and miR-155 are key microRNAs (miRNAs) that regulate, respectively, hematopoietic cell quiescence and proliferation. Herein we showed that in acute myeloid leukemia (AML), the biogenesis of these two miRNAs is interconnected through a network of regulatory loops driven by the FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD). In fact, FLT3-ITD induces the expression of miR-155 through a noncanonical mechanism of miRNA biogenesis that implicates cytoplasmic Drosha ribonuclease III (DROSHA). In turn, miR-155 down-regulates SH2-containing inositol phosphatase 1 (SHIP1), thereby increasing phosphor-protein kinase B (AKT) that in turn serine-phosphorylates, stabilizes, and activates Sprouty related EVH1 domain containing 1 (SPRED1). Activated SPRED1 inhibits the RAN/XPO5 complex and blocks the nucleus-to-cytoplasm transport of pre-miR-126, which cannot then complete the last steps of biogenesis. The net result is aberrantly low levels of mature miR-126 that allow quiescent leukemia blasts to be recruited into the cell cycle and proliferate. Thus, miR-126 down-regulation in proliferating AML blasts is downstream of FLT3-ITD­dependent miR-155 expression that initiates a complex circuit of concatenated regulatory feedback (i.e., miR-126/SPRED1, miR-155/human dead-box protein 3 [DDX3X]) and feed-forward (i.e., miR-155/SHIP1/AKT/miR-126) regulatory loops that eventually converge into an output signal for leukemic growth.

Sorafenib plus triplet therapy with venetoclax, azacitidine and homoharringtonine for refractory/relapsed acute myeloid leukemia with FLT3-ITD: A multicenter phase 2 study.

BACKGROUND: Patients with relapsed or refractory acute myeloid leukemia (R/R AML) and FLT3-internal tandem duplication (FLT3-ITD) respond infrequently to salvage chemotherapy. OBJECTIVE: To investigate the efficacy of sorafenib plus triplet therapy with venetoclax, azacitidine, and homoharringtonine (VAH) as a salvage therapy in this population. METHODS: This multicenter, single-arm, phase 2 study was conducted at 12 hospitals across China. Eligible patients had R/R AML with FLT3-ITD (aged 18-65 years) who were treated with VAH. The primary endpoint was composite complete remission (CRc) after two cycles. Secondary outcomes included the overall response rate (ORR), safety, and survival. RESULTS: Between July 9, 2020, and March 19, 2022, 58 patients were assessed for eligibility, 51 of whom were enrolled. The median patient age was 47 years (interquartile range [IQR] 31-57). CRc was 76.5% with ORR of 82.4%. At a median follow-up of 17.7 months (IQR, 8.7-24.7), the median duration of CRc was not reached (NR), overall survival was 18.1 months (95% confidence interval [CI], 11.8-NR) and event-free survival was 11.4 months (95% CI, 5.6-NR). Grade 3 or 4 adverse events occurring in ≥10% of patients included neutropenia in 47 (92.2%), thrombocytopenia in 41 (80.4%), anemia in 35 (68.6%), febrile neutropenia in 29 (56.9%), pneumonia in 13 (25.5%), and sepsis in 6 (11.8%) patients. Treatment-related death occurred in two (3.9%) patients. CONCLUSIONS: The sorafenib plus VAH regimen was well tolerated and highly active against R/R AML with FLT3-ITD. This regimen may be a suitable therapeutic option for this population, but larger population trials are needed to be explored. TRIAL REGISTRATION: Clinical Trials Registry: NCT04424147.

Inhibition of NRF2 signaling overcomes acquired resistance to arsenic trioxide in FLT3-mutated Acute Myeloid Leukemia.

De novo acute myeloid leukemia (AML) patients with FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD) have worse treatment outcomes. Arsenic trioxide (ATO) used in the treatment of acute promyelocytic leukemia (APL) has been reported to be effective in degrading the FLT3 protein in AML cell lines and sensitizing non-APL AML patient samples in-vitro. We have previously reported that primary cells from FLT3-ITD mutated AML patients were sensitive to ATO in-vitro compared to other non-M3 AML and molecular/pharmacological inhibition of NF-E2 related factor 2 (NRF2), a master regulator of antioxidant response improved the chemosensitivity to ATO and daunorubicin even in non FLT3-ITD mutated cell lines and primary samples. We examined the effects of molecular/pharmacological suppression of NRF2 on acquired ATO resistance in the FLT3-ITD mutant AML cell line (MV4-11-ATO-R). ATO-R cells showed increased NRF2 expression, nuclear localization, and upregulation of bonafide NRF2 targets. Molecular inhibition of NRF2 in this resistant cell line improved ATO sensitivity in vitro. Digoxin treatment lowered p-AKT expression, abrogating nuclear NRF2 localization and sensitizing cells to ATO. However, digoxin and ATO did not sensitize non-ITD AML cell line THP1 with high NRF2 expression. Digoxin decreased leukemic burden and prolonged survival in MV4-11 ATO-R xenograft mice. We establish that altering NRF2 expression may reverse acquired ATO resistance in FLT3-ITD AML.

Co-occurrence of Erdheim-Chester disease and clonally evolving acute myeloid leukemia with FLT3-ITD and PTPN11 mutations.

Erdheim-Chester disease (ECD) is a rare histiocytosis that tends to co-exist with other myeloid malignancies. Here, we use genetic and transcriptomic sequencing to delineate a case of co-occurring BRAFV600E-mutated ECD and acute myeloid leukemia (AML), followed by AML remission and relapse. The AML relapse involved the extinction of clones with KMT2A-AFDN and FLT3-ITD, and the predominance of PTPN11-mutated subclones with distinct transcriptomic features. This case report has highlighted the screening for other myeloid malignancies at the diagnosis of ECD and the clinical significance of PTPN11-mutated AML subclones that require meticulous monitoring.

Exploration of ETV6::ABL1-positive AML with concurrent NPM1 and FLT3-ITD mutations.

ETV6::ABL1 is a rare fusion gene that found in MPN, ALL, and AML. It has a complex and diverse formation mechanism due to the reciprocal orientations of the ETV6 and ABL1 genes relative to the centromeres. NPM1 is frequently mutated in adult AML, often accompanied by FLT3-ITD, which suggests molecular synergisms in AML pathogenesis. Previous reports on ETV6::ABL1 mostly focus on FLT3-ITD. In this study, we present a case of AML with ETV6::ABL1, along with NPM1 and FLT3-ITD. The patient showed a rapid increase in primitive cells at the initial stage, along with the presence of immature granulocytes and erythrocytes. Through cytogenetic analysis, fluorescence in situ hybridization (FISH), and RNA-seq, we elucidated the mechanism behind the formation of the ETV6::ABL1 fusion gene. Despite conventional chemotherapy failure and rapid tumor proliferation, we attempted to add FLT3 inhibitor sorafenib to the treatment, along with chemotherapy bridging to haploidentical transplantation. After haplo-HSCT, a combination of sorafenib and dasatinib was administered as maintenance therapy. The patient achieved complete remission (CR) and maintained it for 11 months. The intricate genetic landscape observed in this case presents diagnostic dilemmas and therapeutic challenges, emphasizing the importance of a comprehensive understanding of its implications for disease classification, risk stratification, and treatment selection.

Ningetinib, a novel FLT3 inhibitor, overcomes secondary drug resistance in acute myeloid leukemia.

BACKGROUND: FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) is a common mutation type in acute myeloid leukemia (AML) and is usually associated with poor patient prognosis. With advancements in molecular diagnostics and the development of tyrosine kinase inhibitors (TKI), the overall survival (OS) of AML patients with FLT3-ITD mutations has been prolonged to some extent, but relapse and drug resistance are still substantial challenges. Ningetinib is a novel TKI against various kinases in relation to tumour pathogenesis and is undergoing clinical trials of lung cancer. In this study, we explored the antitumor activity of ningetinib against AML with FLT3 mutations both in vivo and in vitro. METHODS: Cell proliferation assays were performed in AML cell lines and Ba/F3 cells expressing various FLT3 mutations to validate the antileukemic activity of ningetinib in vitro. Immunoblot assays were used to verify the effect of ningetinib on the FLT3 protein and downstream pathways. Molecular docking and CETSA were used to validate the interaction of ningetinib with target proteins. The survival benefit of ningetinib in vivo was assessed in Ba/F3-FLT3-ITD-, MOLM13, Ba/F3-FLT3-ITD-F691L-, MOLM13-FLT3-ITD-F691L-induced leukemia mouse models. We also used patient-derived primary cells to determine the efficacy of ningetinib. RESULTS: Ningetinib inhibited cell proliferation, blocked the cell cycle, induced apoptosis and bound FLT3 to inhibit its downstream signaling pathways, including the STAT5, AKT and ERK pathways, in FLT3-ITD AML cell lines. In the mouse models with FLT3-ITD and FLT3-ITD-F691L mutation, ningetinib showed superior anti-leukemia activity to existing clinical drugs gilteritinib and quizartinib, significantly prolongating the survival of mice. In addition, ningetinib exhibited activity against patient-derived primary cells harboring FLT3-ITD mutations. CONCLUSION: Overall, our study confirmed the therapeutic role of ningetinib in AML with FLT3-ITD mutations, providing a potential new option for clinically resistant patients.

High DOCK1 expression identifies a distinct prognostic subgroup of pediatric acute myeloid leukemia: Results of the Japanese Pediatric Leukemia/Lymphoma Study Group AML-05 trial.

BACKGROUND: The molecular pathogenesis of acute myeloid leukemia (AML) was dramatically clarified over the latest two decades. Several important molecular markers were discovered in patients with AML that have helped to improve the risk stratification. However, developing new treatment strategies for relapsed/refractory acute myeloid leukemia (AML) is crucial due to its poor prognosis. PROCEDURE: To overcome this difficulty, we performed an assay for transposase-accessible chromatin with sequencing (ATAC-seq) in 10 AML patients with various gene alterations. ATAC-seq is based on direct in vitro sequencing adaptor transposition into native chromatin, and is a rapid and sensitive method for integrative epigenomic analysis. ATAC-seq analysis revealed increased accessibility of the DOCK1 gene in patients with AML harboring poor prognostic factors. Following the ATAC-seq results, quantitative reverse transcription polymerase chain reaction was used to measure DOCK1 gene expression levels in 369 pediatric patients with de novo AML. RESULTS: High DOCK1 expression was detected in 132 (37%) patients. The overall survival (OS) and event-free survival (EFS) among patients with high DOCK1 expression were significantly worse than those patients with low DOCK1 expression (3-year EFS: 34% vs. 60%, p < .001 and 3-year OS: 60% vs. 80%, p < .001). To investigate the significance of high DOCK1 gene expression, we transduced DOCK1 into MOLM14 cells, and revealed that cytarabine in combination with DOCK1 inhibitor reduced the viability of these leukemic cells. CONCLUSIONS: Our results indicate that a DOCK1 inhibitor might reinforce the effects of cytarabine and other anti-cancer agents in patients with AML with high DOCK1 expression.

Design and synthesis 1H-Pyrrolo[2,3-b]pyridine derivatives as FLT3 inhibitors for the treatment of Acute myeloid Leukemia.

Acute myeloid leukemia (AML) is the most common type of blood cancer and has been strongly correlated with the overexpression of Fms-like tyrosine kinase 3 (FLT3), a member of the class III receptor tyrosine kinase family. With the emergence of FLT3 internal tandem duplication alteration (ITD) and tyrosine kinase domain (TKD) mutations, the development of FLT3 small molecule inhibitors has become an effective medicinal chemistry strategy for AML. Herein, we have designed and synthesized two series of 1H-pyrrolo[2,3-b]pyridine derivatives CM1-CM24, as FLT3 inhibitors based on F14, which we previously reported, that can target the hydrophobic FLT3 back pocket. Among these derivates, CM5 showed significant inhibition of FLT3 and FLT3-ITD, with inhibitory percentages of 57.72 % and 53.77 % respectively at the concentration of 1 µΜ. Furthermore, CM5 demonstrated potent inhibition against FLT3-dependent human AML cell lines MOLM-13 and MV4-11 (both harboring FLT3-ITD mutant), with IC50 values of 0.75 µM and 0.64 µM respectively. In our cellular mechanistic studies, CM5 also effectively induces apoptosis by arresting cell cycle progression in the G0/G1 phase. In addition, the amide and urea linker function were discussed in detail based on computational simulations studies. CM5 will serve as a novel lead compound for further structural modification and development of FLT3 inhibitors specifically targeting AML with FLT3-ITD mutations.

Identification of a novel mutation of the FLT3 gene located on the juxtamembrane domain from acute myeloid leukemia patients.

BACKGROUND: FLT3 gene mutations are genetic abnormality that caused leukemogenesis. Furthermore, presence of FLT3 mutations is associated with poor prognosis in AML. This study aimed to identify FLT3 gene mutations so that it can be used as a genetic reference for the AML patients in Indonesian population. METHODS: This cross-sectional study recruited 63 AML de novo patients between August 2021 and July 2023 at Cipto Mangukusumo General Hospital and Dharmais Cancer Hospital. We collected peripheral blood from the patients for DNA isolation. FLT3 gene mutation was detected using PCR method, then followed by the Sanger sequencing. Novel mutation in exon-14 continued to in silico study using SWISS MODEL server for modelling protein and PyMOL2 software for visualizing the protein model. RESULTS: Frequency FLT3-ITD mutation was 22% and 6 (10%) patients had a novel mutation on juxtamembrane domain. The number of FLT3-ITD insertions was 24 bp to 111 bp, with a median of 72 bp. Novel mutation indicated a change in the protein sequence at amino acid number 572 from Tyrosine to Valine and formed a stop codon (UGA) at amino acid position ins572G573. In-silico study from novel mutation showed the receptor FLT3 protein was a loss of most of the juxtamembrane domain and the entire kinase domain. CONCLUSION: A novel FLT3 gene mutation was found in this study in the juxtamembrane domain. Based on the sequencing analysis and in silico studies, this mutation is likely to affect the activity of the FLT3 receptor. Therefore, further studies on this novel mutation are needed.

Emerging DNA Methylome Targets in FLT3-ITD-Positive Acute Myeloid Leukemia: Combination Therapy with Clinically Approved FLT3 Inhibitors.

OPINION STATEMENT: The internal tandem duplication (ITD) mutation of the FMS-like receptor tyrosine kinase 3 (FLT3-ITD) is the most common mutation observed in approximately 30% of acute myeloid leukemia (AML) patients. It represents poor prognosis due to continuous activation of downstream growth-promoting signaling pathways such as STAT5 and PI3K/AKT. Hence, FLT3 is considered an attractive druggable target; selective small FLT3 inhibitors (FLT3Is), such as midostaurin and quizartinib, have been clinically approved. However, patients possess generally poor remission rates and acquired resistance when FLT3I used alone. Various factors in patients could cause these adverse effects including altered epigenetic regulation, causing mainly abnormal gene expression patterns. Epigenetic modifications are required for hematopoietic stem cell (HSC) self-renewal and differentiation; however, critical driver mutations have been identified in genes controlling DNA methylation (such as DNMT3A, TET2, IDH1/2). These regulators cause leukemia pathogenesis and affect disease diagnosis and prognosis when they co-occur with FLT3-ITD mutation. Therefore, understanding the role of different epigenetic alterations in FLT3-ITD AML pathogenesis and how they modulate FLT3I's activity is important to rationalize combinational treatment approaches including FLT3Is and modulators of methylation regulators or pathways. Data from ongoing pre-clinical and clinical studies will further precisely define the potential use of epigenetic therapy together with FLT3Is especially after characterized patients' mutational status in terms of FLT3 and DNA methlome regulators.

N-(3-Methoxyphenyl)-6-(7-(1-methyl-1H-pyrazol-4-yl)imidazo[1,2-a]pyridin-3-yl)pyridin-2-amine is an inhibitor of the FLT3-ITD and BCR-ABL pathways, and potently inhibits FLT3-ITD/D835Y and FLT3-ITD/F691L secondary mutants.

Activating mutations within FLT3 make up 30 % of all newly diagnosed acute myeloid leukemia (AML) cases, with the most common mutation being an internal tandem duplication (FLT3-ITD) in the juxtamembrane region (25 %). Currently, two generations of FLT3 kinase inhibitors have been developed, with three inhibitors clinically approved. However, treatment of FLT3-ITD mutated AML is limited due to the emergence of secondary clinical resistance, caused by multiple mechanism including on-target FLT3 secondary mutations - FLT3-ITD/D835Y and FLT3-ITD/F691L being the most common, as well as the off-target activation of alternative pathways including the BCR-ABL pathway. Through the screening of imidazo[1,2-a]pyridine derivatives, N-(3-methoxyphenyl)-6-(7-(1-methyl-1H-pyrazol-4-yl)imidazo[1,2-a]pyridin-3-yl)pyridin-2-amine (compound 1) was identified as an inhibitor of both the FLT3-ITD and BCR-ABL pathways. Compound 1 potently inhibits clinically related leukemia cell lines driven by FLT3-ITD, FLT3-ITD/D835Y, FLT3-ITD/F691L, or BCR-ABL. Studies indicate that it mediates proapoptotic effects on cells by inhibiting FLT3 and BCR-ABL pathways, and other possible targets. Compound 1 is more potent against FLT3-ITD than BCR-ABL, and it may have other possible targets; however, compound 1 is first step for further optimization for the development of a balanced FLT3-ITD/BCR-ABL dual inhibitor for the treatment of relapsed FLT3-ITD mutated AML with multiple secondary clinical resistant subtypes such as FLT3-ITD/D835Y, FLT3-ITD/F691L, and cells co-expressing FLT3-ITD and BCR-ABL.

Discovery of a potent Gilteritinib-based FLT3-PROTAC degrader for the treatment of Acute myeloid leukemia.

Fms-like tyrosine receptor kinase 3 (FLT3) proteolysis targeting chimeras (PROTACs) emerge as a promising approach to overcome the limitations of FLT3 inhibitors, while the development of orally bioavailable FLT3-PROTACs faces great challenges. Here, we report the rational design and evaluation of a series of Gilteritinib-based FLT3-PROTACs. Among them, B3-2 exhibited the strongest antiproliferative activity against FLT3-ITD mutant AML cells, and significantly induced FLT3-ITD protein degradation. Mechanistic investigations demonstrated that B3-2 induced FLT3-ITD degradation in a ubiquitin-proteasome-dependent manner. More importantly, B3-2 exhibited an oral bioavailability of 5.65%, and oral administration of B3-2 showed good antitumor activity in MV-4-11 xenograft models. Furthermore, B3-2 showed strong antiproliferative activity against FLT3 resistant mutations, highlighting its potential in overcoming drug resistance.

Treatment of three pediatric AML co-expressing NUP98-NSD1, FLT3-ITD, and WT1.

During the treatment of 89 pediatric patients with Acute Myeloid Leukemia (AML) at the Hematology Department of Kunming Medical University's Children's Hospital from 2020 to 2023, three patients were identified to co-express the NUP98-NSD1, FLT3-ITD, and WT1 gene mutations. The bone marrow of these three patients was screened for high-risk genetic mutations using NGS and qPCR at the time of diagnosis. The treatment was administered following the China Children's Leukemia Group (CCLG)-AML-2019 protocol. All three patients exhibited a fusion of the NUP98 exon 12 with the NSD1 exon 6 and co-expressed the FLT3-ITD and WT1 mutations; two of the patients displayed normal karyotypes, while one presented chromosomal abnormalities. During the induction phase of the CCLG-AML-2019 treatment protocol, the DAH (Daunorubicin, Cytarabine, and Homoharringtonine) and IAH (Idarubicin, Cytarabine, and Homoharringtonine) regimens, in conjunction with targeted drug therapy, did not achieve remission. Subsequently, the patients were shifted to the relapsed/refractory chemotherapy regimen C + HAG (Cladribine, Homoharringtonine, Cytarabine, and G-CSF) for two cycles, which also failed to induce remission. One patient underwent Haploidentical Hematopoietic Stem Cell Transplantation (Haplo-HSCT) and achieved complete molecular remission during a 12-month follow-up period. Regrettably, the other two patients, who did not receive transplantation, passed away. The therapeutic conclusion is that pediatric AML patients with the aforementioned co-expression do not respond to chemotherapy. Non-remission transplantation, supplemented with tailor-made pre- and post-transplant strategies, may enhance treatment outcomes.

CALCRL knockdown suppresses cancer stemness and chemoresistance in acute myeloid leukemia with FLT3-ITD and DNM3TA-R882 double mutations.

Acute myeloid leukemia (AML) patients with FLT3 internal tandem duplication (FLT3-ITD) and DNA methyltransferase 3A (DNMT3A) R882 double mutations had a worse prognosis compared with AML with FLT3-ITD or DNMT3A R882 single mutation. This study was designed to explore the specific role of Calcitonin Receptor Like (CALCRL) in AML with FLT3-ITD and DNMT3A R882 double mutations. MOLM13 cells were transduced with CRISPR knockout sgRNA constructs to establish the FTL3-ITD and DNMT3A-R882 double-mutated AML cell model. Quantitative real-time PCR and Western blot assay were carried out to examine corresponding gene and protein expression. Methylation of CALCRL promoter was measured by methylation-specific PCR (MSP). Cell viability, colony formation, flow cytometry, and sphere formation assays were conducted to determine cell proliferation, apoptosis, and stemness. MOLM13 cells were exposed to stepwise increasing concentrations of cytarabine (Ara-C) to generate MOLM13/Ara-C cells. An in vivo AML  animal model was established, and the tumor volume and weight were recorded. TUNEL assay was adopted to examine cell apoptosis in tumor tissues. DNMT3A-R882 mutation upregulated the expression of CALCRL while downregulated the DNA methylation level of CALCRL in MOLM13 cells. CALCRL knockdown greatly inhibited cell proliferation, promoted apoptosis and repressed cell stemness, accompanied with the downregulated Oct4, SOX2, and Nanog in DNMT3A-R882-mutated MOLM13 cells and MOLM13/Ara-C cells. Furthermore, CALCRL knockdown restricted tumor growth and the chemoresistance of AML in vivo, as well as inducing cell apoptosis in tumor tissues. Together, these data reveal that CALCRL is a vital regulator of leukemia cell survival and resistance to chemotherapy, suggesting CALCRL as a promising therapeutic target for the treatment of FTL3-ITD and DNMT3A-R882 double-mutated AML.

UBTF-internal tandem duplication as a novel poor prognostic factor in pediatric acute myeloid leukemia.

The prognosis of pediatric acute myeloid leukemia (AML) has improved via stratification therapy. However, relapse or death occurs in 30%-40% of cases. Novel genetic factors for pediatric AML need to be elucidated to improve prognosis. We detected recurrent internal tandem duplication in upstream binding transcription factor (UBTF-ITD) in 1.2% (6/503) of Japanese pediatric patients with de novo AML. No UBTF-ITD was detected in 175 adult patients with AML or in 65 cell lines that included 15 AML, 39 acute lymphoblastic leukemia, five chronic myeloid leukemia, and six neuroblastoma cell lines. All UBTF-ITDs were found in exon 13 and shared a duplicated region. UBTF-ITD was more frequently detected in patients with trisomy 8, FLT3-ITD, WT1 mutation, and/or high PRDM16 expression (trisomy 8, 3/6; FLT3-ITD, 5/6; WT1 mutation, 2/6; and high PRDM16 expression, 6/6). Gene expression patterns of patients with UBTF-ITD were similar to those of patients with NUP98::NSD1 or FUS::ERG. Survival analysis of the AML-05 cohort revealed that patients with UBTF-ITD had worse outcomes than those without UBTF-ITD (3-year event-free survival, 20% vs. 55%; 3-year overall survival, 40% vs. 74%). Moreover, among the 27 patients with trisomy 8, all three patients with UBTF -ITD had a poor prognosis resulting in early events (relapse or non-complete remission) within 1 year. Our findings suggest that UBTF-ITD may be a novel and significant prognostic factor for pediatric patients with AML.

[Acute myeloid leukemia with central nervous system involvement successfully treated with gilteritinib].

A 69-year-old woman was referred to our hospital due to hyperleukocytosis. We diagnosed acute myeloid leukemia and started induction therapy with the CAG regimen (aclarubicin, cytarabine and filgrastim). However, the patient was refractory to the initial treatment and developed quadriplegia, and a cerebrospinal fluid (CSF) test showed elevated blasts. We then performed intrathecal chemotherapy, and the number of blasts in CSF gradually decreased. But only two cycles of intrathecal therapy were possible due to severe methotrexate-induced mucositis. The leukemia cells had fms-like kinase 3-internal tandem duplication (FLT3-ITD), so we started treatment with oral gilteritinib. The patient then achieved hematological complete remission. Her paralysis was also resolving, and the CSF was clear of blasts for more than 6 months. Some reports show that gilteritinib may penetrate the CNS, and this case also supports the effectiveness of gilteritinib on CNS leukemia.

IGF2BP2 promotes lncRNA DANCR stability mediated glycolysis and affects the progression of FLT3-ITD + acute myeloid leukemia.

Internal tandem duplication (ITD) is the most common type of FLT3 mutation (FLT3-ITD), accounting for about 25% of AML patients. The expression of DANCR in FLT3-ITD AML had not been paid attention to, and whether its regulatory relationship with IGF2BP2 can affect the progression of FLT3-ITD AML was unclear. Our study sought to verify the biological role of IGF2BP2 as an m6A reading protein in FLT3-ITD AML. To further explore the role and mechanism of DANCR in AML, and provide a basis for the screening of biomarkers and the development of targeted drugs. The results show that IGF2BP2 was upregulated in FLT3-ITD+ AML patients and cells. Si-IGF2BP2 could inhibit the proliferation, glycolytic and promote the apoptosis in MV4-11 cells. IGF2BP2 could promote the DANCR RNA stability. This discovery will provide new horizons for early screening and targeted therapy of FLT3-ITD+ AML.

Prognostic impact of FLT3-ITD mutation on NPM1+ acute myeloid leukaemia patients and related molecular mechanisms.

The prognosis of acute myeloid leukaemia (AML) patients carrying NPM1 mutations is significantly worse when accompanied by FLT3-ITD mutations. However, accurate quantitative detection of FLT3-ITD mutations remains challenging. To identify a novel biomarker in NPM1+ FLT3-ITD+ AML patients for more accurate stratification, we analysed the differential gene expression between the NPM1+ FLT3-ITD+ and NPM1+ FLT3-ITD- groups in five public AML datasets and identified a biomarker by taking the intersection of differentially expressed genes. We validated this biomarker in bone marrow samples from NPM1+ AML patients at the Peking University Institute of Haematology and analysed its prognostic significance. BCAT1 expression was higher in the NPM1+ FLT3-ITD+ group than in the NPM1+ FLT3-ITD- group in all seven cohorts. BCAT1 was able to predict the prognosis of NPM1+ FLT3-ITD+ AML patients, and its predictive ability was superior to that of the FLT3-ITD allelic ratio (AR). FLT3-targeted inhibitor quizartinib reduced BCAT1 expression. BCAT1 knockdown using lentiviral vectors led to the downregulation of MYC expression. Thus, we identified BCAT1 as a novel biomarker for NPM1+ FLT3-ITD+ AML patients. The FLT3-ITD/BCAT1/MYC signalling pathway may play a biological role in promoting the occurrence and development of AML in FLT3-ITD+ cell lines.

Subclinical minute FLT3-ITD clone can be detected in clinically FLT3-ITD-negative acute myeloid leukaemia at diagnosis.

Recent advances in next-generation sequencing (NGS) have enabled the detection of subclinical minute FLT3-ITD. We selected 74 newly diagnosed, cytogenetically normal acute myeloid leukaemia (AML) samples in which FLT3-ITD was not detected by gel electrophoresis. We sequenced them using NGS and found minute FLT3-ITDs in 19 cases. We compared cases with clinically relevant FLT3-ITD (n = 37), cases with minute FLT3-ITD (n = 19) and cases without detectable FLT3-ITD (n = 55). Molecular characteristics (location and length) of minute FLT3-ITD were similar to those of clinically relevant FLT3-ITD. Survival of cases with minute FLT3-ITD was similar to that of cases without detectable FLT3-ITD, whereas the relapse rate within 1 year after onset was significantly higher in cases with minute FLT3-ITD. We followed 18 relapsed samples of cases with clinically FLT3-ITD-negative at diagnosis. Two of 3 cases with minute FLT3-ITD relapsed with progression to clinically relevant FLT3-ITD. Two of 15 cases in which FLT3-ITD was not detected by NGS relapsed with the emergence of minute FLT3-ITD, and one of them showed progression to clinically relevant FLT3-ITD at the second relapse. We revealed the clonal dynamics of subclinical minute FLT3-ITD in clinically FLT3-ITD-negative AML. Minute FLT3-ITD at the initial AML can expand to become a dominant clone at relapse.