Project description:mRNA expression regulated by FLT3/ITD and Cxcl12 were compared in the Ba/F3 cells expressing wild type FLT3 or FLT3/ITD and incubated with or without Cxcl12.
Project description:Fms-like tyrosine kinase 3 (Flt3) tyrosine kinase inhibitors (Flt3-TKI) have improved outcomes for patients with Flt3-mutated acute myeloid leukemia (AML) but are limited by resistance and relapse, suggesting persistence of leukemia stem cells (LSC). Here we utilized a Flt3-internal tandem duplication (Flt3-ITD) and Tet2-deleted AML genetic mouse model to characterize Flt3-ITD AML LSC and their resistance to Flt3-TKI. We show that LSC were enriched within the primitive ST-HSC population. CXCl12-expressing osteoprogenitors were increased in the Flt3-ITD AML marrow and FLT3-ITD LSC showed increased expression of the CXCL12 receptor CXCR4. CXCL12 deletion from the microenvironment enhanced AML targeting by combined Flt3-TKI and chemotherapy treatment with enhanced LSC targeting. We found that both treatment and CXCL12 deletion partially reduced p38 mitogen-activated protein kinase (p38) signaling with increased, but not complete, reduction seen with combined treatment and CXCL12 deletion. Our studies suggest that p38 contributes to CXCL12-mediated maintenance of AML LSC following Flt3-TKI and chemotherapy treatment, but that p38 inhibition enhances AML LSC response to treatment to a greater extent than CXCL12 deletion alone. This study supports a role for p38 signaling in CXCL12-mediated protection of AML LSC from treatment and provide a rationale for targeting p38 signaling to enhance Flt3-ITD AML targeting.
Project description:We used whole genome microarray expression profiling as a discovery platform to identify genes regulated by FLT3-ITD activity. Viral particles with pMY-puro, pMY-puro-FLT3-ITD-1 or pMY-puro-FLT3-ITD-2, were generated using PLAT-gp packaging cells and infected to K562 cells. The vector-transduced cells were selected with 2µg/ml puromycin treatment.
Project description:ITD mutations in the FLT3 gene occur in the 30% of acute myeloid leukemia patients. The integration of ITD in the tyrosine kinase domain (TKD-ITD) of the FLT3 receptor has been shown to confer resistance to standard chemotherapy treatment. We applied state-of-the-art, high-sensitive, mass spectrometry (MS)-based (phospho)proteomics to investigate the molecular mechanisms underlying the sensitivity to cytarabine therapy in FLT3-ITD cells.
Project description:The miR-155-dependent differences in gene expression in the HSPC compartment of FLT3-ITD mice is unknown. In this experiment, we performed RNA sequencing on FLT3-ITD and FLT3-ITD miR-155-/- mouse LKS cells.
Project description:CircMYBL2 is more highly expressed in AML patients with FLT3-ITD mutations than in those without the FLT3-ITD mutation. We found that circMYBL2 knockdown specifically inhibits proliferation and promotes the differentiation of FLT3-ITD AML cells in vitro and in vivo. We used the ribosome profiling and RNA-seq libraries sequenced with Illumina HiSeq 2500 to identify the mRNA that circMYBL2 targeted. Interestingly, we found that circMYBL2 significantly influences the protein level of mutant FLT3 kinase, which contributes to the activation of FLT3-ITD-dependent signaling pathways. Mechanistically, circMYBL2 enhanced the translational efficiency of FLT3 kinase by increasing the binding of PTBP1 to FLT3 mRNA. Moreover, circMYBL2 knockdown impaired the cytoactivity of inhibitor-resistant FLT3-ITD-positive cells, with a significant decrease in FLT3 kinase expression, followed by the inactivation of its downstream pathways. In summary, we are the first to reveal a circRNA that specifically influences FLT3-ITD AML and regulates FLT3 kinase levels through translational regulation, suggesting that circMYBL2 may be a potential therapeutic target for FLT3-ITD AML.
Project description:we observed synergistic cytotoxic effects, preferentially reducing cell proliferation and inducing apoptosis in FLT3/ITD+ AML cell lines and in primary AML cells. Furthermore, the combination of FLT3-TKI and GSI eradicated leukemic cells and prolonged survival in a FLT3/ITD+ patient derived xenograft (PDX) AML model. Mechanistically, decreased expression of CXCR3 that lead to down-regulated ERK signaling was partially responsible for the observed synergy. Our findings suggest that combined therapies of FLT3-TKIs with GSI may be exploited as a potential therapeutic strategy to treat FLT3/ITD+ AML.
Project description:We want to obtain FLT3-ITD gene signature. To do so, we transduced CB CD34+ cells with mock or FLT3-ITD vectors and performed RNA sequencing (RNA-Seq). Two Groups: Group1: CB CD34+ cells transduced with mock vector; Group2: CB CD34+ cells transduced with FLT3-ITD vector;
Project description:FLT3/ITD-SmoM2 mice developed rapidly fatal myeloid leukemia compared to FLT3/ITD only mice, suggesting that overactivation of the Hedgehog signaling pathway via SmoM2 can drive myeloid disease progression We used the Affymetrix Mouse 430_2.0 microarray to detail global gene expression responsible for disease progression in sorted bone marrow cells and found that the Hedgehog signaling pathway contributes to disease progression by enhancing FLT3 signaling
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.