Project description:Constitutive activation of FLT3 by ITD mutations is one of the most common genetic aberrations in AML, present in ~1/3 of cases. Patients harboring FLT3-ITD display worse clinical outcomes. The integration and advancement of FLT3 TKI in AML treatment provided significant therapeutic improvement. However, due to the emergence of resistance mechanisms, FLT3-ITD+ AML remains a clinical challenge. We performed an unbiased drug screen to identify 18 compounds as particularly efficacious against FLT3-ITD+ AML. Among these, we characterized two investigational compounds, WS6 and ispinesib, and two approved drugs, ponatinib and cabozantinib, in depth. We found that WS6, although not yet investigated in oncology, shows a similar mechanism and potency as ponatinib and cabozantinib. Interestingly, ispinesib and cabozantinib prevent activation of AXL, a key driver and mechanism of drug resistance in FLT3-ITD+ AML patients. We further investigated synergies between the selected compounds and found that combination treatment with ispinesib and cabozantinib or ponatinib shows high synergy in FLT3-ITD+ AML cell lines and patient samples. Together, we suggest WS6, ispinesib, ponatinib and cabozantinib as novel options for targeting FLT3-ITD+ AML. Whether combinatorial tyrosine kinase and kinesin spindle blockade is effective in eradicating neoplastic (stem) cells in FLT3-ITD+ AML remains to be determined in clinical trials.
Project description:BackgroundActivating mutations in the Fms-like tyrosine kinase 3 (FLT3) are among the most prevalent oncogenic mutations in acute myeloid leukaemia. Inhibitors selectively targeting FLT3 kinase have shown promising clinical activity; their success in the clinic, however, has been limited due to the emergence of acquired resistance.MethodsCCT245718 was identified and characterised as a dual Aurora A/FLT3 inhibitor through cell-based and biochemical assays. The ability of CCT245718 to overcome TKD-mediated resistance was evaluated in a cell line-based model of drug resistance to FLT3 inhibitors.ResultsCCT245718 exhibits potent antiproliferative activity towards FLT3-ITD + AML cell lines and strongly binds to FLT3-ITD and TKD (D835Y) mutants in vitro. Activities of both FLT3-ITD and Aurora A are also inhibited in cells. Inhibition of FLT3 results in reduced phosphorylation of STAT5, downregulation of survivin and induction of apoptotic cell death. Moreover, CCT245718 overcomes TKD-mediated resistance in a MOLM-13-derived cell line containing FLT3 with both ITD and D835Y mutations. It also inhibits FLT3 signalling in both parental and resistant cell lines compared to FLT3-specific inhibitor MLN518, which is only active in the parental cell line.ConclusionsOur results demonstrate that CCT245718 is a potent dual FLT3/Aurora A inhibitor that can overcome TKD-mediated acquired resistance.
Project description:The outcomes of FLT3-ITD acute myeloid leukaemia (AML) have been improved since the approval of FLT3 inhibitors (FLT3i). However, approximately 30-50% of patients exhibit primary resistance (PR) to FLT3i with poorly defined mechanisms, posing a pressing clinical unmet need. Here, we identify C/EBPα activation as a top PR feature by analyzing data from primary AML patient samples in Vizome. C/EBPα activation limit FLT3i efficacy, while its inactivation synergistically enhances FLT3i action in cellular and female animal models. We then perform an in silico screen and identify that guanfacine, an antihypertensive medication, mimics C/EBPα inactivation. Furthermore, guanfacine exerts a synergistic effect with FLT3i in vitro and in vivo. Finally, we ascertain the role of C/EBPα activation in PR in an independent cohort of FLT3-ITD patients. These findings highlight C/EBPα activation as a targetable PR mechanism and support clinical studies aimed at testing the combination of guanfacine with FLT3i in overcoming PR and enhancing the efficacy of FLT3i therapy.
Project description:One-third of newly diagnosed adult acute myeloid leukaemia (AML) carry FLT3 mutations, which frequently occur together with nucleophosmin (NPM1) mutations and are associated with worse prognosis. FLT3 inhibitors are widely used in clinics with limitations due to drug resistance. AML cells carrying FLT3 mutations in both mouse models and patients present low expression of GATA1, a gene involved in haematopoietic changes preceding AML. Here, we show that FLT3 inhibition induces cellular responses and restores the GATA1 pathway and functions in NPM1/FLT3-ITD mutated AML, thus providing a new mechanism of action for this drug.
Project description:FLT3-ITD mutations are prevalent mutations in acute myeloid leukaemia (AML). PRL-3, a metastasis-associated phosphatase, is a downstream target of FLT3-ITD. This study investigates the regulation and function of PRL-3 in leukaemia cell lines and AML patients associated with FLT3-ITD mutations. PRL-3 expression is upregulated by the FLT3-STAT5 signalling pathway in leukaemia cells, leading an activation of AP-1 transcription factors via ERK and JNK pathways. PRL-3-depleted AML cells showed a significant decrease in cell growth. Clinically, high PRL-3 mRNA expression was associated with FLT3-ITD mutations in four independent AML datasets with 1158 patients. Multivariable Cox-regression analysis on our Cohort 1 with 221 patients identified PRL-3 as a novel prognostic marker independent of other clinical parameters. Kaplan-Meier analysis showed high PRL-3 mRNA expression was significantly associated with poorer survival among 491 patients with normal karyotype. Targeting PRL-3 reversed the oncogenic effects in FLT3-ITD AML models in vitro and in vivo. Herein, we suggest that PRL-3 could serve as a prognostic marker to predict poorer survival and as a promising novel therapeutic target for AML patients.
Project description:Acute myeloid leukemia (AML) is an aggressive hematopoietic malignancy that is cured in as few as 15%-40% of cases. Tremendous improvements in AML prognostication arose from a comprehensive analysis of leukemia cell genomes. Among normal karyotype AML cases, mutations in the FLT3 gene are the ones most commonly detected as having a deleterious prognostic impact. FLT3 is a transmembrane tyrosine kinase receptor, and alterations of the FLT3 gene such as internal tandem duplications (FLT3-ITD) deregulate FLT3 downstream signaling pathways in favor of increased cell proliferation and survival. FLT3 tyrosine kinase inhibitors (TKI) emerged as a new therapeutic option in FLT3-ITD AML, and clinical trials are ongoing with a variety of TKI either alone, combined with chemotherapy, or even as maintenance after allogenic stem cell transplantation. However, a wide range of molecular resistance mechanisms are activated upon TKI therapy, thus limiting their clinical impact. Massive research efforts are now ongoing to develop more efficient FLT3 TKI and/or new therapies targeting these resistance mechanisms to improve the prognosis of FLT3-ITD AML patients in the future.
Project description:BackgroundMutations in the FMS-like tyrosine kinase 3 (FLT3) are associated with uncontrolled cellular functions that contribute to the development of acute myeloid leukaemia (AML). We performed computer simulations of the FLT3-dependent signalling network in order to study the pathways that are involved in AML development and resistance to targeted therapies.ResultsAnalysis of the simulations revealed the presence of alternative pathways through phosphoinositide 3 kinase (PI3K) and SH2-containing sequence proteins (SHC), that could overcome inhibition of FLT3. Inhibition of cyclin dependent kinase 6 (CDK6), a related molecular target, was also tested in the simulation but was not found to yield sufficient benefits alone.ConclusionsThe PI3K pathway provided a basis for resistance to treatments. Alternative signalling pathways could not, however, restore cancer growth signals (proliferation and loss of apoptosis) to the same levels as prior to treatment, which may explain why FLT3 resistance mutations are the most common resistance mechanism. Finally, sensitivity analysis suggested the existence of optimal doses of FLT3 and CDK6 inhibitors in terms of efficacy and toxicity.
Project description:Internal tandem duplication (-ITD) mutations of Fms-like tyrosine kinase 3 (FLT3) provide growth and pro-survival signals in the context of established driver mutations in FLT3 mutant acute myeloid leukemia (AML). Maternal embryonic leucine zipper kinase (MELK) is an aberrantly expressed gene identified as a target in AML. The MELK inhibitor OTS167 induces cell death in AML including cells with FLT3 mutations, yet the role of MELK and mechanisms of OTS167 function are not understood. OTS167 alone or in combination with tyrosine kinase inhibitors (TKIs) were used to investigate the effect of OTS167 on FLT3 signaling and expression in human FLT3 mutant AML cell lines and primary cells. We describe a mechanism whereby OTS167 blocks FLT3 expression by blocking FLT3 translation and inhibiting phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and eukaryotic translation initiation factor 4B (eIF4B). OTS167 in combination with TKIs results in synergistic induction of FLT3 mutant cell death in FLT3 mutant cell lines and prolonged survival in a FLT3 mutant AML xenograft mouse model. Our findings suggest signaling through MELK is necessary for the translation and expression of FLT3-ITD, and blocking MELK with OTS167 represents a viable therapeutic strategy for patients with FLT3 mutant AML.
Project description:Recurrent somatic internal tandem duplications (ITD) in the FMS-like tyrosine kinase 3 (FLT3) gene characterise approximately one third of patients with acute myeloid leukaemia (AML), and FLT3-ITD mutation status guides risk-adapted treatment strategies. The aim of this work was to characterise FLT3-ITD variant distribution in relation to molecular and clinical features, and overall survival in adult AML patients. We performed two parallel retrospective cohort studies investigating FLT3-ITD length and expression by cDNA fragment analysis, followed by Sanger sequencing in a subset of samples. In the two cohorts, a total of 139 and 172 mutant alleles were identified in 111 and 123 patients, respectively, with 22% and 28% of patients presenting with more than one mutated allele. Further, 15% and 32% of samples had a FLT3-ITD total variant allele frequency (VAF) < 0.3, while 24% and 16% had a total VAF ≥ 0.7. Most of the assessed clinical features did not significantly correlate to FLT3-ITD numerical variation nor VAF. Low VAF was, however, associated with lower white blood cell count, while increasing VAF correlated with inferior overall survival in one of the cohorts. In the other cohort, ITD length above 50 bp was identified to correlate with inferior overall survival. Our report corroborates the poor prognostic association with high FLT3-ITD disease burden, as well as extensive inter- and intrapatient heterogeneity in the molecular features of FLT3-ITD. We suggest that future use of FLT3-targeted therapy could be accompanied with thorough molecular diagnostics and follow-up to better predict optimal therapy responders.
Project description:Acute myeloid leukemia (AML) is a highly heterogeneous disease. Mutation with internal tandem duplication of fms-like tyrosine kinase-3 (FLT3-ITD) is one of the two most common driver mutations and the presence of FLT3-ITD delivers poor prognosis. A number of ongoing clinical efforts are focused on FLT3 inhibitor use to improve the outcomes of this otherwise difficult leukemia. Midostaurin has been shown to improve outcomes in FLT3-mutated AML in the frontline setting. Several FLT3 inhibitors, especially second-generation agents, have shown clinically meaningful activity in relapsed or refractory AML and in patients not amenable to intensive therapy. In this article, we briefly review the biology of FLT3 in the physiological state and its role in leukemogenesis. We present a detailed review of current clinical evidence of FLT3 inhibitors and their use in the induction, treatment of relapsed or refractory disease, and maintenance setting.