Project description:We examined if the minimal residual disease (MRD) and the Allelic Ratio (AR) of FLT3 internal tandem duplication (ITD) mutated patients may be prognostic factors. We correlated these parameters both with event free survival (EFS), with incidence of relapse and with gene expression profile (GEP). GEP showed that patients with high-ITD-AR or persistent MRD had different expression profiles. Results indicated that the ITD-AR levels and the MRD after I induction course are associated with transcriptional oncogenic profiles, which highlight differences in epigenetic control that may explain the variability in outcome among FLT3-ITD patients
Project description:FLT3 activating mutations cause myeloproliferative neoplasms by deregulating hematopoietic progenitor cell growth, and acute myeloid leukemia is on the rise. Investigational drugs targeting mutant FLT3, including Quizartinib and Crenolanib, develop inherent and acquired resistance to FLT3 targeted therapy. FLT3 inhibitor resistance in AML is dependent on co-occurring mutations, parallel survival pathways, and/or subsequent FLT3-ITD mutations. Despite the high prevalence of FLT3 mutations and their clinical significance in AML, there are few targeted therapeutic options. We identified two novel naphthyridine-based FLT3 inhibitors (HSN608 and HSN748) that specifically target FLT3-ITD at sub-nanomolar concentrations and are effective against drug-resistant secondary mutations. In the current study, we evaluated these compounds antileukemic activity against FLT3-ITD and gatekeeper mutations in drug-resistant AML, relapsed/refractory AMLs with FLT3 mutations, and in vivo mouse models with combinations of epigenetic mutations TET2 with FLT3-ITD, and AML patients PDX. In these model systems, we demonstrate that HSN748 outperforms the FDA-approved FLT3 inhibitor Gilteritinib in terms of inhibitory activity against FLT3-ITD.
Project description:We performed genome-wide DNaseI hypersensitive site in FLT3-ITD and WT patient samples. We report corresponding gene expression, promoter methylation patterns of differential DHSs as well as differentially occupied TF binding motifs using surrounding DNAseI cut profiles. We examined association patterns of FLT3 ITD and WT AMLs and found that FLT3-ITD signaling is associated with common gene expression and chromatin signature. Examination of Runx1 binding sites in FLT3 ITD AML.
Project description:We performed genome-wide DNaseI hypersensitive site in FLT3-ITD and WT patient samples. We report corresponding gene expression, promoter methylation patterns of differential DHSs as well as differentially occupied TF binding motifs using surrounding DNAseI cut profiles. We examined association patterns of FLT3 ITD and WT AMLs and found that FLT3-ITD signaling is associated with common gene expression and chromatin signature. Examination of genome-wide DNaseI hypersensitivite sites in FLT3 ITD and WT AML.
Project description:Internal tandem duplications in the tyrosine kinase receptor FLT3 (FLT3-ITD) are among the most common lesions in acute myeloid leukemia (AML) and there exists a need for new forms of treatment. Using ex vivo drug sensitivity screening, we found that FLT3-ITD+ patient cells are particularly sensitive to HSP90 inhibitors. While it is well known that HSP90 is important for FLT3-ITD stability, we found that HSP90 family members play a much more complex role in FLT3-ITD signaling than previously appreciated. First, we found that FLT3-ITD activates the unfolded protein response (UPR), leading to increased expression of GRP94/HSP90B1. GRP94 rewires FLT3-ITD signaling by binding and retaining FLT3-ITD in the ER, where it aberrantly activates downstream signaling pathways. Second, HSP90 family proteins protect FLT3-ITD+ AML cells against apoptosis by alleviating proteotoxic stress, and treatment with HSP90 inhibitors results in proteotoxic overload that triggers UPR-induced apoptosis. Importantly, leukemic stem cells are strongly dependent upon HSP90 for their survival, and the HSP90 inhibitor ganetespib causes leukemic stem cell exhaustion in mouse PDX models. Taken together, our study reveals a molecular basis for HSP90 addiction of FLT3-ITD+ AML cells and provides a rationale for including HSP90 inhibitors in the treatment regime for FLT3-ITD+ AML.
Project description:Constitutively activating internal tandem duplication (ITD) alterations of the receptor tyrosine kinase FLT3 (Fms-like tyrosine kinase 3) are common in acute myeloid leukemia (AML) and classifies FLT3 as an attractive therapeutic target. So far, application of FLT3 small molecule inhibitors such as Sorafenib has resulted only in partial and transient clinical responses in FLT3-ITD+ patients. Only recently, a prolonged event-free survival has been observed in AML patients who were treated with Sorafenib in addition to standard therapy. Here, we studied the Sorafenib effect on proliferation in a panel of 13 FLT3-ITD- and FLT3-ITD+ AML cell lines. Sorafenib IC50 values ranged from 0.001 to 5.6 µM, whereas FLT3-ITD+ cells (MOLM-13, MV4;11) were found more sensitive to Sorafenib than FLT3-ITD- cells. However, we identified two FLT3-ITD- cell lines (MONO-MAC-1 and OCI-AML-2) which were also Sorafenib sensitive. Phosphoproteome analyses revealed that the affected pathways differed in Sorafenib sensitive FLT3-ITD- and FLT3-ITD+ cells. In MV4;11 cells Sorafenib suppressed mTOR signalling by inhibiting direct inhibition of FLT3. In MONO-MAC-1 cells Sorafenib inhibited the MEK/ERK pathway by inhibition of the RET tyrosine kinase. These data suggest that the FLT3 status in AML patients might not be the only predictive factor for a response to Sorafenib.
Project description:The presence of FLT3-ITD mutations in patients with acute myeloid leukemia (AML) is associated with poor clinical outcome. FLT3 tyrosine kinase inhibitors (TKIs), although effective in kinase ablation, do not eliminate FLT3-ITD+ leukemia stem cells (LSCs) which are potential sources of disease relapse, prompting us to ask whether FLT3-ITD protein regulates the AML LSCs survival through a kinase-independent mechanism. Here, we show that expression of PRMT1, the primary type I arginine methyltransferase, significantly increases in LSC-enriched CD34+CD38- populations relative to normal counterparts. Genetic PRMT1 depletion blocked AML CD34+ cell survival, and had more potent effects in AML cells from patients harboring FLT3-ITD. Our genome wide analysis of gene expression and PRMT1 conditional KO mouse study confirmed that PRMT1 preferentially cooperates with FLT3-ITD contributing to AML cell maintenance. Mechanistically, PRMT1 catalyzed FLT3-ITD protein methylation at arginines 972/973, and PRMT1 promoted leukemia cell growth in a FLT3 methylation-dependent manner. Moreover, effects of FLT3-ITD methylation in AML cells were in part due to crosstalk with FLT3-ITD phosphorylation at tyrosine 969 (Y969). Importantly, FLT3 methylation persisted in FLT3-ITD+ AML cells following TKI (AC220) treatment, indicating that methylation occurs independently of kinase activity. Finally, in both patient-derived xenograft (PDX) and murine AML models, combined administration of AC220 with a type I PRMT inhibitor (MS023) enhanced elimination of FLT3-ITD+ AML relative to AC220 treatment alone. Our study demonstrates that PRMT1-mediated FLT3 methylation promotes LSC activity and suggests that combining PRMT1 inhibition with FLT3 TKI treatment could be a promising approach to selectively target FLT3-ITD+ LSCs.
Project description:FLT3 is the most frequently mutated gene in AML â up to 40% of AML harbor an activating mutation within FLT3 gene. Though AML is a relatively rare disease, such a high mutability rate, as observed with FLT3 gene, is striking. To elucidate the molecular background of this phenomenon, we have established nine unique FLT3/ITD - carrying 32D cell lines and a set of controls, and subjected them to whole genome expression analysis and 2DE LC/MS proteomics. Data obtained on this so far largest set of ITD mutants indicates that in comparison to the wild type FLT3 expressing 32D cells and transduction controls, FLT3/ITD positive cells exhibit less mature expression profiles resembling ST-HSC and MkEP/CMP/LMPP progenitors. We hypothesize that FLT3/ITD might contribute not only to the proliferative advantage of FLT3/ITD positive cells, but also to their reprogramming towards less differentiated stages, thus strengthening their malignant properties. This finding might explain the pronounced mutation rate of the aberrantly expressed FLT3 gene in AML, and, also, the inferior prognosis of FLT3/ITD positive AML patients. Moreover, the microarray data has revealed biological differences among individual ITD variants â a finding supporting the recent clinical data on the prognostic impact of the size of individual ITDs. Keywords: genetic modification Nine stable 32D cell lines harboring unique human FLT3/ITD mutants, two parental 32 cell lines, two 32D stable cell lines harboring cloning vector only, and two 32D cell lines stably expressing human wild type FLT3 were subjected to the microarray analysis.