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:Transcriptional profiling of murine bone marrow c-kit+, Sca-1+ lineage neative (KSL) cells from p21CDKN1a-/- and p21+/+ overexpressing Flt3/ITD. The goal was to determine the effect on global gene expression by loss of p21 in Flt3/ITD transformed KSL cells Internal tandem duplication (ITD) mutations in the Flt3 gene (Flt3-ITD) are associated with poor prognosis in patients with acute myeloid leukemia (AML). Few inhibitors of Flt3-ITD are effective against Flt3-ITD+ AML due to the development of drug-resistance. In this study, we demonstrate that Flt3-ITD activates a novel pathway involving p21Cdkn1a (p21) and pre-B cell leukemia transcription factor 1 (Pbx1) that attenuates Flt3-ITD cell proliferation and is involved in the development drug resistance. Flt3-ITD up-regulated p21 expression in mouse bone marrow c-kit+-Sca-1+-Lin- (KSL) cells and in Ba/F3 cells. Loss of p21 expression enhanced growth factor-independent proliferation and sensitivity to cytarabine as a consequence of enriching the S+G2/M phase population concomitant with a significant increase in the expression of Pbx1, but not Evi-1, in Flt3-ITD+ cells. This enhancement of cell proliferation by loss of p21 was partially abrogated when Pbx1 expression was silenced in Flt3-ITD+ primary bone marrow colony-forming cells (CFCs) and Ba/F3 cells. Antagonizing Flt3-ITD using AC220, a selective inhibitor of Flt3-ITD, decreased the expression of p21, coincident with the up-regulation of Pbx1 mRNA and a rapid decline in the number of viable Flt3-ITD+ Ba/F3 cells, however the cells eventually became refractory to AC220. Overexpressing p21 in Flt3-ITD+ Ba/F3 cells delayed the emergence of cells refractory to AC220, whereas silencing p21 accelerated their development. These data demonstrate that Flt3-ITD is capable of inhibiting the proliferation of Flt3-ITD+ cells through the p21/Pbx1 axis and that antagonizing Flt3-ITD contributes to the subsequent development of cells refractory to Flt3-ITD inhibitor by disrupting p21 expression. biological replicates: 3 KSL cell replicates overexpressing ITD-Flt3 from p21+/+ and p21-/- cells, 1 KSL cell replicate from p21+/+ and p21-/- cells
Project description:Transcriptional profiling of murine bone marrow c-kit+, Sca-1+ lineage neative (KSL) cells from p21CDKN1a-/- and p21+/+ overexpressing Flt3/ITD. The goal was to determine the effect on global gene expression by loss of p21 in Flt3/ITD transformed KSL cells Internal tandem duplication (ITD) mutations in the Flt3 gene (Flt3-ITD) are associated with poor prognosis in patients with acute myeloid leukemia (AML). Few inhibitors of Flt3-ITD are effective against Flt3-ITD+ AML due to the development of drug-resistance. In this study, we demonstrate that Flt3-ITD activates a novel pathway involving p21Cdkn1a (p21) and pre-B cell leukemia transcription factor 1 (Pbx1) that attenuates Flt3-ITD cell proliferation and is involved in the development drug resistance. Flt3-ITD up-regulated p21 expression in mouse bone marrow c-kit+-Sca-1+-Lin- (KSL) cells and in Ba/F3 cells. Loss of p21 expression enhanced growth factor-independent proliferation and sensitivity to cytarabine as a consequence of enriching the S+G2/M phase population concomitant with a significant increase in the expression of Pbx1, but not Evi-1, in Flt3-ITD+ cells. This enhancement of cell proliferation by loss of p21 was partially abrogated when Pbx1 expression was silenced in Flt3-ITD+ primary bone marrow colony-forming cells (CFCs) and Ba/F3 cells. Antagonizing Flt3-ITD using AC220, a selective inhibitor of Flt3-ITD, decreased the expression of p21, coincident with the up-regulation of Pbx1 mRNA and a rapid decline in the number of viable Flt3-ITD+ Ba/F3 cells, however the cells eventually became refractory to AC220. Overexpressing p21 in Flt3-ITD+ Ba/F3 cells delayed the emergence of cells refractory to AC220, whereas silencing p21 accelerated their development. These data demonstrate that Flt3-ITD is capable of inhibiting the proliferation of Flt3-ITD+ cells through the p21/Pbx1 axis and that antagonizing Flt3-ITD contributes to the subsequent development of cells refractory to Flt3-ITD inhibitor by disrupting p21 expression.
Project description:The study was a comparison of gene expression using RNA-seq. We analyzed the stem and progenitor cells from WT and Vav-cre+ Tet2fl/fl Flt3-ITD (T2F3) mice. We isolated stem cells LSK (lin- sca+ kit+) and granulocyte-macrophage progenitors GMP (lin- sca- kit+ fcgr+ cd34+) cells from bone marrow. Comparisons were made across genotypes WT vs. T2F3 and cell types LSK vs. GMP. Comparison of WT and Tet2-/-Flt3ITD bone marrow stem and progenitor cells.
Project description:The study was a comparison of gene expression using RNA-seq. We analyzed the stem and progenitor cells from WT and Vav-cre+ Tet2fl/fl Flt3-ITD (T2F3) mice. We isolated stem cells LSK (lin- sca+ kit+) and granulocyte-macrophage progenitors GMP (lin- sca- kit+ fcgr+ cd34+) cells from bone marrow. Comparisons were made across genotypes WT vs. T2F3 and cell types LSK vs. GMP.
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 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: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.