FLT3-ITD regulation of the endoplasmic reticulum functions in acute myeloid leukemia.

The FLT3-ITD mutation represents the most frequent genetic alteration in newly diagnosed acute myeloid leukemia (AML) patient and is associated with poor prognosis. Mutation result in the retention of a constitutively active form of this receptor in the endoplasmic reticulum (ER) and the subsequent modification of its downstream effectors. Here, we assessed the impact of such retention on ER homeostasis and found that mutant cells present lower levels of ER stress due to the overexpression of ERO1α, one of the main proteins of the protein folding machinery at the ER. Overexpression of ERO1α resulted essential for ITD mutant cells survival and chemoresistance and also played a crucial role in shaping the type of glucose metabolism in AML cells, being the mitochondrial pathway the predominant one in those with a higher ER stress (non-mutated cells) and the glycolytic pathway the predominant one in those with lower ER stress (mutated cells). Our data indicate that FLT3 mutational status dictates the route for glucose metabolism in an ERO1α depending on manner and this provides a survival advantage to tumors carrying these ITD mutations.

Sweet syndrome induced by FLT3 inhibitors: case report and literature review.

BACKGROUND: Acute febrile neutrophilic dermatosis, also commonly referred to as Sweet syndrome, is often associated with tumors, infections, immune disorders and medications. FLT3 inhibitor-induced Sweet syndrome is a rare complication. METHODS AND RESULTS: We report a patient with relapsed and refractory acute monocytic leukemia harboring high-frequency FLT3-ITD and DNMT3a mutations. The FLT3 inhibitor gilteritinib was administered for reinduction therapy after failure of chemotherapy with a combination of venetoclax, decitabine, aclarubicin, cytarabine and granulocyte colony-stimulating factor. The leukemia patient achieved remission after 1 month of treatment. However, Sweet syndrome induced by gilteritinib, which was confirmed by skin biopsy, developed during induction therapy. Similar cases of Sweet syndrome following FLT3 inhibitor therapy for acute myeloid leukemia were reviewed. CONCLUSION: Attention should be given to this rare complication when FLT3 inhibitors are used for acute myeloid leukemia therapy, and appropriate treatments need to be administered in a timely manner.

[Fulminant Clostridioides difficile infection during treatment with FLT3 inhibitor for acute myeloid leukemia].

An 80-year-old man with FLT3-TKD mutation-positive acute myeloid leukemia (AML) relapsed during consolidation therapy with venetoclax/azacitidine and was started on gilteritinib as salvage therapy. On the day after treatment initiation, febrile neutropenia was observed, but the fever resolved promptly after initiation of antimicrobial therapy. On the fifth day after completion of antimicrobial therapy, the patient experienced fever and watery diarrhea over 10 times a day, and a diagnosis of Clostridioides difficile infection (CDI) was made based on stool examination. The patient was treated with intravenous metronidazole, but renal dysfunction, hypotension, and hypoxemia developed, and a CT scan showed pleural and intraperitoneal effusion, significant intestinal wall thickening, and intestinal dilatation. Fidaxomicin was started under general monitoring in the intensive care unit and response was achieved. The patient was discharged from the intensive care unit on the 18th day after the onset of CDI. We report this case not only due to the rarity of fulminant CDI during AML treatment, but also because it is a valuable example of effective treatment of fulminant CDI with fidaxomicin.

Unveiling the signaling network of FLT3-ITD AML improves drug sensitivity prediction.

Currently, the identification of patient-specific therapies in cancer is mainly informed by personalized genomic analysis. In the setting of acute myeloid leukemia (AML), patient-drug treatment matching fails in a subset of patients harboring atypical internal tandem duplications (ITDs) in the tyrosine kinase domain of the FLT3 gene. To address this unmet medical need, here we develop a systems-based strategy that integrates multiparametric analysis of crucial signaling pathways, and patient-specific genomic and transcriptomic data with a prior knowledge signaling network using a Boolean-based formalism. By this approach, we derive personalized predictive models describing the signaling landscape of AML FLT3-ITD positive cell lines and patients. These models enable us to derive mechanistic insight into drug resistance mechanisms and suggest novel opportunities for combinatorial treatments. Interestingly, our analysis reveals that the JNK kinase pathway plays a crucial role in the tyrosine kinase inhibitor response of FLT3-ITD cells through cell cycle regulation. Finally, our work shows that patient-specific logic models have the potential to inform precision medicine approaches.

Current knowledge about FLT3 gene mutations, exploring the isoforms, and protein importance in AML.

Acute myeloid leukaemia (AML) is a complex haematological malignancy characterised by diverse genetic alterations leading to abnormal proliferation of myeloid precursor cells. One of the most significant genetic alterations in AML involves mutations in the FLT3 gene, which plays a critical role in haematopoiesis and haematopoietic homeostasis. This review explores the current understanding of FLT3 gene mutations and isoforms and the importance of the FLT3 protein in AML. FLT3 mutations, including internal tandem duplications (FLT3-ITD) and point mutations in the tyrosine kinase domain (FLT3-TKD), occur in 25-30% in AML and are associated with poor prognosis. FLT3-ITD mutations lead to constitutive activation of the FLT3 signalling pathway, promoting cell survival and proliferation. FLT3-TKD mutations affect the tyrosine kinase domain and affect AML prognosis in various ways. Furthermore, FLT3 isoforms, including shorter variants, contribute to the complexity of FLT3 biology. Additionally, nonpathological polymorphisms in FLT3 are being explored for their potential impact on AML prognosis and treatment response. This review also discusses the development of molecular treatments targeting FLT3, including first-generation and next-generation tyrosine kinase inhibitors, highlighting the challenges of resistance that often arise during therapy. The final chapter describes FLT3 protein domain rearrangements and their relevance to AML pathogenesis.

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.

[Correlation of miR-155 Expression with Drug Sensitivity of FLT3-ITD+ Acute Myeloid Leukemia Cell Line and Its Mechanism].

OBJECTIVE: To investigate the correlation of miR-155 expression with drug sensitivity of FLT3-ITD+ acute myeloid leukemia (AML) cell line and its potential regulatory mechanism. METHODS: By knocking out miR-155 gene in FLT3-ITD+ AML cell line MV411 through CRISPR/Cas9 gene-editing technology, monoclonal cells were screened. The genotype of these monoclonal cells was validated by PCR and Sanger sequencing. The expression of mature miRNA was measured by RT-qPCR. The treatment response of doxorubicin, quizartinib and midostaurin were measured by MTT assay and IC50 of these drugs were calculated to identify the sensitivity. Transcriptome sequencing was used to analyze change of mRNA level in MV411 cells after miR-155 knockout, gene set enrichment analysis to analyze change of signaling pathway, and Western blot to verify expressions of key molecules in signaling pathway. RESULTS: Four heterozygotes with gene knockout and one heterozygote with gene insertion were obtained through PCR screening and Sanger sequencing. RT-qPCR results showed that the expression of mature miR-155 in the monoclonal cells was significantly lower than wild-type clones. MTT results showed that the sensitivity of MV411 cells to various anti FLT3-ITD+ AML drugs increased significantly after miR-155 knockout compared with wild-type clones. RNA sequencing showed that the mTOR signaling pathway and Wnt signaling pathway were inhibited after miR-155 knockout. Western blot showed that the expressions of key molecules p-mTOR, Wnt5α and ß-catenin in signaling pathway were down-regulated. CONCLUSION: Drug sensitivity of MV411 cells to doxorubicin, quizartinib and midostaurin can be enhanced significantly after miR-155 knockout, which is related to the inhibition of multiple signaling pathways including mTOR and Wnt signaling pathways.

Day-21 bone marrow findings incorrectly designate residual leukaemia in FLT3-mutated acute myeloid leukaemia treated with intensive induction plus midostaurin: a morphology-focused study.

Early induction response assessment with day-21 bone marrow (D21-BM) is commonly performed in patients with FLT3-mutated acute myeloid leukaemia (AML), where detection of residual leukaemia (RL; blasts ≥5%) typically results in the administration of a second induction course. However, whether D21-BM results predict for RL at the end of first induction has not been systematically assessed. This study evaluates the predictive role of D21-BM morphology in detecting RL following first induction. Between August 2018 and March 2022, all patients with FLT3-AML receiving 7+3 plus midostaurin, with D21-BM performed, were identified. Correlation between D21-BM morphology vs D21-BM ancillary flow/molecular results, as well as vs D28-BM end of first induction response, were retrospectively reviewed. Subsequently, D21-BMs were subjected to anonymised morphological re-assessments by independent haematopathologists (total in triplicate per patient). Of nine patients included in this study, three (33%) were designated to have RL at D21-BM, all of whom entered complete remission at D28-BM. Furthermore, only low-level measurable residual disease was detected in all three cases by flow or molecular methods at D21-BM, hence none proceeded to a second induction. Independent re-evaluations of these cases failed to correctly reassign D21-BM responses, yielding a final false positive rate of 33%. In summary, based on morphology alone, D21-BM assessment following 7+3 intensive induction plus midostaurin for FLT3-AML incorrectly designates RL in some patients; thus correlating with associated flow and molecular results is essential before concluding RL following first induction. Where remission status is unclear, repeat D28-BMs should be performed.

Discovery of a Novel Orally Bioavailable FLT3-PROTAC Degrader for Efficient Treatment of Acute Myeloid Leukemia and Overcoming Resistance of FLT3 Inhibitors.

Fms-like tyrosine receptor kinase 3 (FLT3) proteolysis-targeting chimeras (PROTACs) represent a promising approach to eliminate the resistance of FLT3 inhibitors. However, due to the poor druggability of PROTACs, the development of orally bioavailable FLT3-PROTACs faces great challenges. Herein, a novel orally bioavailable FLT3-ITD degrader A20 with excellent pharmacokinetic properties was discovered through reasonable design. A20 selectively inhibited the proliferation of FLT3-ITD mutant acute myeloid leukemia (AML) cells and potently induced FLT3-ITD degradation through the ubiquitin-proteasome system. Notably, oral administration of A20 resulted in complete tumor regression on subcutaneous AML xenograft models. Furthermore, on systemic AML xenograft models, A20 could completely eliminate the CD45+CD33+ human leukemic cells in murine and significantly prolonged the survival time of mice. Most importantly, A20 exerted significantly improved antiproliferative activity against drug-resistant AML cells compared to existing FLT3 inhibitors. These findings suggested that A20 could serve as a promising drug candidate for relapsed or refractory AML.

Narazaciclib, a novel multi-kinase inhibitor with potent activity against CSF1R, FLT3 and CDK6, shows strong anti-AML activity in defined preclinical models.

CSF1R is a receptor tyrosine kinase responsible for the growth/survival/polarization of macrophages and overexpressed in some AML patients. We hypothesized that a novel multi-kinase inhibitor (TKi), narazaciclib (HX301/ON123300), with high potency against CSF1R (IC50 ~ 0.285 nM), would have anti-AML effects. We tested this by confirming HX301's high potency against CSF1R (IC50 ~ 0.285 nM), as well as other kinases, e.g. FLT3 (IC50 of ~ 19.77 nM) and CDK6 (0.53 nM). An in vitro proliferation assay showed that narazaciclib has a high growth inhibitory effect in cell cultures where CSF1R or mutant FLT3-ITD variants that may be proliferation drivers, including primary macrophages (IC50 of 72.5 nM) and a subset of AML lines (IC50 < 1.5 µM). In vivo pharmacology modeling of narazaciclib using five AML xenografts resulted in: inhibition of MV4-11 (FLT3-ITD) subcutaneous tumor growth and complete suppression of AM7577-PDX (FLT3-ITD/CSF1Rmed) systemic growth, likely due to the suppression of FLT3-ITD activity; complete suppression of AM8096-PDX (CSF1Rhi/wild-type FLT3) growth, likely due to the inhibition of CSF1R ("a putative driver"); and nonresponse of both AM5512-PDX and AM7407-PDX (wild-type FLT3/CSF1Rlo). Significant leukemia load reductions in bone marrow, where disease originated, were also achieved in both responders (AM7577/AM8096), implicating that HX301 might be a potentially more effective therapy than those only affecting peripheral leukemic cells. Altogether, narazaciclib can potentially be a candidate treatment for a subset of AML with CSF1Rhi and/or mutant FLT3-ITD variants, particularly second generation FLT3 inhibitor resistant variants.

[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.

Landscape of FLT3 Variations Associated with Structural and Functional Impact on Acute Myeloid Leukemia: A Computational Study.

Acute myeloid leukemia (AML) is hallmarked by the clonal proliferation of myeloid blasts. Mutations that result in the constitutive activation of the fms-like tyrosine kinase 3 (FLT3) gene, coding for a class III receptor tyrosine kinase, are significantly associated with this heterogeneous hematologic malignancy. The fms-related tyrosine kinase 3 ligand binds to the extracellular domain of the FLT3 receptor, inducing homodimer formation in the plasma membrane, leading to autophosphorylation and activation of apoptosis, proliferation, and differentiation of hematopoietic cells in bone marrow. In the present study, we evaluated the association of FLT3 as a significant biomarker for AML and tried to comprehend the effects of specific variations on the FLT3 protein's structure and function. We also examined the effects of I836 variants on binding affinity to sorafenib using molecular docking. We integrated multiple bioinformatics tools, databases, and resources such as OncoDB, UniProt, COSMIC, UALCAN, PyMOL, ProSA, Missense3D, InterProScan, SIFT, PolyPhen, and PredictSNP to annotate the structural, functional, and phenotypic impact of the known variations associated with FLT3. Twenty-nine FLT3 variants were analyzed using in silico approaches such as DynaMut, CUPSAT, AutoDock, and Discovery Studio for their impact on protein stability, flexibility, function, and binding affinity. The OncoDB and UALCAN portals confirmed the association of FLT3 gene expression and its mutational status with AML. A computational structural analysis of the deleterious variants of FLT3 revealed I863F mutants as destabilizers of the protein structure, possibly leading to functional changes. Many single-nucleotide variations in FLT3 have an impact on its structure and function. Thus, the annotation of FLT3 SNVs and the prediction of their deleterious pathogenic impact will facilitate an insight into the tumorigenesis process and guide experimental studies and clinical implications.

Gilteritinib as Post-Transplant Maintenance for AML With Internal Tandem Duplication Mutation of FLT3.

PURPOSE: Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with AML harboring an internal tandem duplication mutation of FLT3 (FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit. METHODS: Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS. RESULTS: Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575). CONCLUSION: Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.

A phase 1 study of the irreversible FLT3 inhibitor FF-10101 in relapsed or refractory acute myeloid leukemia.

ABSTRACT: FLT3 tyrosine kinase inhibitors (TKIs) have clinical efficacy for patients with FLT3-mutated AML (acute myeloid leukemia), but their impact is limited by resistance in the setting of monotherapy and by tolerability problems when used in combination therapies. FF-10101 is a novel compound that covalently binds to a cysteine residue near the active site of FLT3, irreversibly inhibiting receptor signaling. It is effective against most FLT3 activating mutations, and, unlike other inhibitors, is minimally vulnerable to resistance induced by FLT3 ligand. We conducted a phase 1 dose escalation study of oral FF-10101 in patients with relapsed and/or refractory AML, the majority of whom harbored FLT3-activating mutations and/or had prior exposure to FLT3 inhibitors. Fifty-four participants enrolled in cohorts receiving doses ranging from 10 to 225 mg per day and 50 to 100 mg twice daily (BID). The dose limiting toxicities were diarrhea and QT prolongation. Among 40 response-evaluable participants, the composite complete response rate was 10%, and the overall response rate (including partial responses) was 12.5%, including patients who had progressed on gilteritinib. Overall, 56% of participants had prior exposure to FLT3 inhibitors. The recommended phase 2 dose was 75 mg BID. FF-10101 potentially represents a next-generation advance in the management of FLT3-mutated AML. This trial was registered at www.ClinicalTrials.gov as #NCT03194685.

Synthesis, kinase inhibition and anti-leukemic activities of diversely substituted indolopyrazolocarbazoles.

Pyrazole analogues of the staurosporine aglycone K252c, in which the lactam ring was replaced by a pyrazole moiety, were synthesized. In this series, one or the other nitrogen atoms of the indolocarbazole scaffold was substituted by aminoalkyl chains, aiming at improving protein kinase inhibition as well as cellular potency toward acute myeloid leukemia (AML) cell lines. Compound 19a, substituted at the N12-position by a 3-(methylamino)propyl group, showed high cellular activity in the low micromolar range toward three AML cell lines (MOLM-13, OCI-AML3 and MV4-11) with selectivity over non-cancerous cells (NRK, H9c2). 19a is also a highly potent inhibitor of the three Pim kinase isoforms, Pim-3 being the most inhibited with an IC50 value in the nanomolar range. A selectivity screening toward a panel of 50 protein kinases showed that 19a also potently inhibited PRK2 and to a lower extent AMPK, MARK3, GSK3ß and JAK3. Our results enhance the understanding of the structural characteristics of indolopyrazolocarbazoles essential for potent protein kinase inhibition with therapeutic potential against AML.

[FLT3-ITD mutation-positive acute myeloid leukemia undergoing clonal transition with PTPN11 mutation at relapse].

A 28-year-old man was diagnosed with acute myelomonocytic leukemia. He achieved complete remission (CR) after two cycles of induction therapy. However, after consolidation therapy, bone marrow aspiration performed to prepare for allogeneic hematopoietic stem cell transplantation revealed disease relapse. Companion diagnostics confirmed the presence of the FLT3-ITD mutation. The patient received gilteritinib monotherapy and achieved CR. Subsequently, he underwent unrelated allogeneic bone marrow transplantation. One year after transplantation, the patient relapsed, and gilteritinib was resumed. However, the leukemia progressed, and panel sequencing using a next-generation sequencer showed that the FLT3-ITD mutation disappeared. A mutation in PTPN11, which regulates the RAS/MAPK signaling pathway, was also detected. Gilteritinib was discontinued, and the patient achieved CR with salvage chemotherapy. He underwent related haploidentical peripheral blood stem cell transplantation but died of relapse. This was a case in which genetic analysis revealed clonal transition and acquisition of resistance to treatment.

Leukemic mutation FLT3-ITD is retained in dendritic cells and disrupts their homeostasis leading to expanded Th17 frequency.

Dendritic cells (DC) are mediators between innate and adaptive immune responses to pathogens and tumors. DC development is determined by signaling through the receptor tyrosine kinase Fms-like tyrosine kinase 3 (FLT3) in bone marrow myeloid progenitors. Recently the naming conventions for DC phenotypes have been updated to distinguish between "Conventional" DCs (cDCs) and plasmacytoid DCs (pDCs). Activating mutations of FLT3, including Internal Tandem Duplication (FLT3-ITD), are associated with poor prognosis for acute myeloid leukemia (AML) patients. Having a shared myeloid lineage it can be difficult to distinguish bone fide DCs from AML tumor cells. To date, there is little information on the effects of FLT3-ITD in DC biology. To further elucidate this relationship we utilized CITE-seq technology in combination with flow cytometry and multiplex immunoassays to measure changes to DCs in human and mouse tissues. We examined the cDC phenotype and frequency in bone marrow aspirates from patients with AML to understand the changes to cDCs associated with FLT3-ITD. When compared to healthy donor (HD) we found that a subset of FLT3-ITD+ AML patient samples have overrepresented populations of cDCs and disrupted phenotypes. Using a mouse model of FLT3-ITD+ AML, we found that cDCs were increased in percentage and number compared to control wild-type (WT) mice. Single cell RNA-seq identified FLT3-ITD+ cDCs as skewed towards a cDC2 T-bet- phenotype, previously shown to promote Th17 T cells. We assessed the phenotypes of CD4+ T cells in the AML mice and found significant enrichment of both Treg and Th17 CD4+ T cells in the bone marrow and spleen compartments. Ex vivo stimulation of CD4+ T cells also showed increased Th17 phenotype in AML mice. Moreover, co-culture of AML mouse-derived DCs and naïve OT-II cells preferentially skewed T cells into a Th17 phenotype. Together, our data suggests that FLT3-ITD+ leukemia-associated cDCs polarize CD4+ T cells into Th17 subsets, a population that has been shown to be negatively associated with survival in solid tumor contexts. This illustrates the complex tumor microenvironment of AML and highlights the need for further investigation into the effects of FLT3-ITD mutations on DC phenotypes and their downstream effects on Th polarization.

High FLT3 expression increases immune-cell infiltration in the tumor microenvironment and correlates with prolonged disease-free survival in patients with non-small cell lung cancer.

Most of the currently used cancer immunotherapies inhibit the programmed cell death protein 1 (PD1)-programmed cell death 1 ligand 1 (PDL1) axis of T-cells. However, dendritic cells (DCs) controlled by natural killer (NK) cells via the FMS-related tyrosine kinase 3 (FLT3) axis are necessary for activation of T-cells. The aim of the study was to evaluate FLT3 as a prognostic factor and determine its role in immune infiltration (with emphasis on NK cells and DCs). Using The Cancer Genome Atlas (TCGA) database, we performed bioinformatic analysis of the gene expression datasets of 501 lung squamous cell carcinoma (LUSC) and 515 lung adenocarcinoma (LUAD) patient who had corresponding clinical data [analysis was performed in R (version 4.2.0)]. Disease-free survival (DFS) differed between the FLT3-low and FLT3-high expression groups, respectively, in LUSC (61.0 vs 71.3 months P = 0.075) and LUAD (32.7 vs 47.5 months P = 0.045). A tumor microenvironment (TME) with high immune infiltration and rich in T-cell exhaustion markers was observed in the FLT3-high group. We showed overexpression of NK cell and DC gene signatures in the FLT3-high expression group as well as overexpression of key effector genes of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes protein (STING) pathway, which is crucial in response to radiotherapy. High expression of FLT3 in the TME was associated with immune cell infiltration (especially of NK cells and DCs), increased expression of T-cell exhaustion markers and expression of effector genes of the cGAS-STING pathway, which may consequently increase susceptibility to immunotherapy and radiotherapy. High FLT3 expression correlated with prolonged DFS in the LUSC and LUAD cohorts.

Postinduction molecular MRD identifies patients with NPM1 AML who benefit from allogeneic transplant in first remission.

ABSTRACT: Selection of patients with NPM1-mutated acute myeloid leukemia (AML) for allogeneic transplant in first complete remission (CR1-allo) remains controversial because of a lack of robust data. Consequently, some centers consider baseline FLT3-internal tandem duplication (ITD) an indication for transplant, and others rely on measurable residual disease (MRD) status. Using prospective data from the United Kingdom National Cancer Research Institute AML17 and AML19 studies, we examined the impact of CR1-allo according to peripheral blood NPM1 MRD status measured by quantitative reverse transcription polymerase chain reaction after 2 courses of induction chemotherapy. Of 737 patients achieving remission, MRD was positive in 19%. CR1-allo was performed in 46% of MRD+ and 17% of MRD- patients. We observed significant heterogeneity of overall survival (OS) benefit from CR1-allo according to MRD status, with substantial OS advantage for MRD+ patients (3-year OS with CR1-allo vs without: 61% vs 24%; hazard ratio [HR], 0.39; 95% confidence interval [CI], 0.24-0.64; P < .001) but no benefit for MRD- patients (3-year OS with CR1-allo vs without: 79% vs 82%; HR, 0.82; 95% CI, 0.50-1.33; P = .4). Restricting analysis to patients with coexisting FLT3-ITD, again CR1-allo only improved OS for MRD+ patients (3-year OS, 45% vs 18%; compared with 83% vs 76% if MRD-); no interaction with FLT3 allelic ratio was observed. Postinduction molecular MRD reliably identifies those patients who benefit from allogeneic transplant in first remission. The AML17 and AML19 trials were registered at www.isrctn.com as #ISRCTN55675535 and #ISRCTN78449203, respectively.