Project description:We used CRISPR/Cas9 system to generate WT Control and RUNX1-KO MDS-L cells isolated as single clones from the parental MDS-L cell line. We have observed that RUNX1-KO MDS-L cells are resistant to Lenalidomide-induced cell death compared to WT Control MDS-L cells We have treated WT and RUNX1-KO MDS-L cells with 1µM Lenalidomide for 24h or 72h and performed expression analysis
Project description:While del(5q) MDS patients comprise a well-defined hematological subgroup, the molecular basis underlying its origin and the reason behind the relapse to lenalidomide remains unknown. Using scRNAseq on CD34+ progenitor cells from patients with del(5q) MDS we were able to identify cells harboring the deletion, enabling us to deeply characterize the transcriptional impact of this genetic insult on disease pathogenesis and treatment response. We found, across all patients, an enrichment of del(5q) cells in GMP and megakaryocyte-erythroid progenitors not described to date. Interestingly, both del(5q) and non-del(5q) cells presented similar transcriptional lesions when compared to progenitors from healthy individuals, indicating that all cells, and not only those harboring the deletion, are altered in these patients and may contribute to aberrant hematopoietic differentiation. However, GRN analysis revealed a group of regulons with aberrant activity in del(5q) cells that could be responsible for triggering altered hematopoiesis, pointing to a more prominent role of these cells in the phenotype of these patients. An analysis of del(5q) MDS patients achieving hematological response upon lenalidomide treatment showed that the drug reverted several transcriptional alterations in both del(5q) and non-del(5q) cells, but other lesions remained, which may be responsible for potential future relapses. Moreover, lack of hematological response was associated with the inability of lenalidomide to reverse transcriptional alterations. Collectively, this study provides a deep characterization of del(5q) and non-del(5q) cells at single-cell resolution, revealing previously unknown transcriptional alterations that could contribute to disease pathogenesis, or lack of responsiveness to lenalidomide.
Project description:Interstitial deletion of the long arm of chromosome 5 (del(5q)) is the commonest structural genomic variant in myelodysplastic syndromes (MDS). Lenalidomide (LEN) is the treatment of choice for patients with del(5q) MDS, but half of the responding patients become resistant within two years. TP53 mutations are detected in ~20% of patients who become resistant to LEN. Our data show that patients who become resistant to LEN harbor either TP53 or RUNX1 mutations or loss of RUNX1 expression. Here we show that LEN-induced degradation of IKZF1 permits a RUNX1/GATA2 complex to drive megakaryocytic differentiation and consequent del(5q) MDS progenitor cell death via CRBN-mediated CSNK1A1 degradation. Overexpression of GATA2 is able to restore LEN sensitivity in the context of RUNX1 or TP53 mutations by enhancing LEN-induced megakaryocytic differentiation. Screening for TP53 and RUNX1 mutations or downregulation should identify patients resistant to LEN, and strategies to activate GATA2 may resensitize del(5q) MDS cells to LEN
Project description:Interstitial deletion of a single copy of chromosome 5q is the most frequent cytogenetic alteration in Myelodysplastic Syndromes (MDS), which results in reduced dosage of numerous genes. Furthermore, the extent of the 5q deletion determines disease severity, suggesting cooperation between deleted genes in the proximal and distal regions of del(5q). Although the contribution of individual genes to the pathogenesis of del(5q) MDS has been investigated, less is known about the epistatic interactions and/or cooperation between neighboring deleted genes. Deletion of TRAF-interacting protein with forkhead-associated domain B (TIFAB) and miR-146a, two haploinsufficient genes in del(5q) MDS, has been previously reported to activate the Toll-like receptor (TLR) signaling cascade in hematopoietic stem/progenitor cells (HSPC) by increasing TRAF6 protein stability and mRNA translation, respectively. To investigate the epistasis of TIFAB and miR-146a, we generated a mouse model in which Tifab and miR-146a were simultaneously deleted (Tifab-/-;miR-146a-/-, dKO). Herein, we report that combined hematopoietic-specific deletion of Tifab and miR-146a results in more rapid and severe cytopenia, and progression to a fatal bone marrow (BM) failure-like disease as compared to Tifab- or miR-146adeficiency alone. HSPC from Tifab-/-, miR-146a-/-, and dKO mice exhibit enrichment of gene 69 regulatory networks associated with innate immune signaling. Moreover, a subset of the differentially expressed genes is controlled synergistically following deletion of Tifab and miR-146a. Notably, nearly half of these defined synergy response genes identified in the mouse models were aberrantly expressed in del(5q) MDS HSPC when TIFAB (5q31) and miR-146a (5q33.3) were both deleted. Thus, synergistic control of gene expression following deletion of epistatic haploinsufficient genes in del(5q) MDS may be an underlying mechanism of the diseased state.
Project description:Despite the high response rates of individuals with myelodysplastic syndrome (MDS) with deletion of chromosome 5q (del(5q)) to treatment with lenalidomide (LEN) and the recent identification of cereblon (CRBN) as the molecular target of LEN, the cellular mechanism by which LEN eliminates MDS clones remains elusive. Here we performed an RNA interference screen to delineate gene regulatory networks that mediate LEN responsiveness in an MDS cell line, MDSL. We identified GPR68, which encodes a G-protein-coupled receptor that has been implicated in calcium metabolism, as the top candidate gene for modulating sensitivity to LEN. LEN induced GPR68 expression via IKAROS family zinc finger 1 (IKZF1), resulting in increased cytosolic calcium levels and activation of a calcium-dependent calpain, CAPN1, which were requisite steps for induction of apoptosis in MDS cells and in acute myeloid leukemia (AML) cells. In contrast, deletion of GPR68 or inhibition of calcium and calpain activation suppressed LEN-induced cytotoxicity. Moreover, expression of calpastatin (CAST), an endogenous CAPN1 inhibitor that is encoded by a gene (CAST) deleted in del(5q) MDS, correlated with LEN responsiveness in patients with del(5q) MDS. Depletion of CAST restored responsiveness of LEN-resistant non-del(5q) MDS cells and AML cells, providing an explanation for the superior responses of patients with del(5q) MDS to LEN treatment. Our study describes a cellular mechanism by which LEN, acting through CRBN and IKZF1, has cytotoxic effects in MDS and AML that depend on a calcium- and calpain-dependent pathway.
Project description:TRAF-interacting protein with forkhead-associated domain B (TIFAB) is a haploinsufficient gene in del(5q) Myelodysplastic syndrome (MDS). Hematopoietic-specific deletion of Tifab results in progressive bone marrow (BM) and blood defects, including skewed hematopoietic stem/progenitor cells (HSPC) proportions, altered myeloid differentiation, and progressive cytopenia. A subset of mice transplanted with Tifab knockout (KO) hematopoietic cells develop a bone marrow failure (BMF)-like disease with neutrophil dysplasia and cytopenia. In competitive transplants, Tifab KO HSPC are out-competed by wild-type (WT) cells, suggesting a cell-intrinsic HSPC defect. Gene expression analysis of Tifab KO HSPC identified dysregulation of immune-related signatures, and hypersensitivity to Toll-like receptor 4 (TLR4) stimulation. TIFAB also forms a complex with TRAF6, a mediator of immune signaling, and reduces TRAF6 protein stability by a lysosome-dependent mechanism. In contrast, TIFAB loss increases TRAF6 protein and the dynamic range of TLR4 signaling in HSPC, contributing to ineffective hematopoiesis. Moreover, combined deletion of TIFAB and miR-146a, two genes associated with del(5q) MDS/AML, results in a cooperative increase in TRAF6 expression and hematopoietic dysfunction in vivo. Re-expression of TIFAB in human del(5q) leukemic cells results in attenuated TLR4 signaling and reduced cell viability. These findings underscore the importance of efficient regulation of innate immune/TRAF6 signaling within HSPC by TIFAB, and its cooperation with miR-146a as it relates to the pathogenesis of hematopoietic malignancies, such as del(5q) MDS/AML.
Project description:We explored the effects of dexamethasone and lenalidomide, individually and in combination, on the differentiation of primary human bone marrow progenitor cells in vitro. Both agents promote erythropoiesis, increasing the absolute number of erythroid cells produced from normal CD34+ cells and from CD34+ cells with the types of ribosome dysfunction found in DBA and del(5q) MDS. However, the drugs had distinct effects on the production of erythroid progenitor colonies; dexamethasone selectively increased the number burst-forming units-erythroid (BFU-E), while lenalidomide specifically increased colony-forming units-erythroid (CFU-E). Use of the drugs in combination demonstrates that their effects are not redundant.
Project description:TRAF-interacting protein with forkhead-associated domain B (TIFAB) is a haploinsufficient gene in del(5q) Myelodysplastic syndrome (MDS). Hematopoietic-specific deletion of Tifab results in progressive bone marrow (BM) and blood defects, including skewed hematopoietic stem/progenitor cells (HSPC) proportions, altered myeloid differentiation, and progressive cytopenia. A subset of mice transplanted with Tifab knockout (KO) hematopoietic cells develop a bone marrow failure (BMF)-like disease with neutrophil dysplasia and cytopenia. In competitive transplants, Tifab KO HSPC are out-competed by wild-type (WT) cells, suggesting a cell-intrinsic HSPC defect. Gene expression analysis of Tifab KO HSPC identified dysregulation of immune-related signatures, and hypersensitivity to Toll-like receptor 4 (TLR4) stimulation. TIFAB also forms a complex with TRAF6, a mediator of immune signaling, and reduces TRAF6 protein stability by a lysosome-dependent mechanism. In contrast, TIFAB loss increases TRAF6 protein and the dynamic range of TLR4 signaling in HSPC, contributing to ineffective hematopoiesis. Moreover, combined deletion of TIFAB and miR-146a, two genes associated with del(5q) MDS/AML, results in a cooperative increase in TRAF6 expression and hematopoietic dysfunction in vivo. Re-expression of TIFAB in human del(5q) leukemic cells results in attenuated TLR4 signaling and reduced cell viability. These findings underscore the importance of efficient regulation of innate immune/TRAF6 signaling within HSPC by TIFAB, and its cooperation with miR-146a as it relates to the pathogenesis of hematopoietic malignancies, such as del(5q) MDS/AML. We performed an expression analysis on sorted lineage-Sca1+cKit+ (LSK) isolated from bone marrow (BM) of 3 month old mice transplanted with Tifab+/+ (WT) or Tifab-/- (KO) BM cells (n = 3 mice/group). We selected this time point to capture the gene expression profile of Tifab-/- LSK after engraftment but prior to overt hematopoietic failure. Total RNA was extracted, purified, reverse transcribed, labeled, and hybridized onto the GeneChip MoGene 2.0 ST Array (Affymetrix). Comparison comprises mRNA expression profile of Tifab+/+ LSK vs. Tifab-/- LSK.
Project description:Interstitial deletion of the long arm of chromosome 5 (del(5q)) is the commonest structural genomic variant in myelodysplastic syndromes (MDS). Lenalidomide (LEN) is the treatment of choice for patients with del(5q) MDS, but half of the responding patients become resistant within two years. TP53 mutations are detected in ~20% of patients who become resistant to LEN. Our data show that patients who become resistant to LEN harbor either TP53 or RUNX1 mutations or loss of RUNX1 expression. Here we show that LEN-induced degradation of IKZF1 permits a RUNX1/GATA2 complex to drive megakaryocytic differentiation and consequent del(5q) MDS progenitor cell death via CRBN-mediated CSNK1A1 degradation. Overexpression of GATA2 is able to restore LEN sensitivity in the context of RUNX1 or TP53 mutations by enhancing LEN-induced megakaryocytic differentiation. Screening for TP53 and RUNX1 mutations or downregulation should identify patients resistant to LEN, and strategies to activate GATA2 may resensitize del(5q) MDS cells to LEN.
Project description:We explored the effects of dexamethasone and lenalidomide, individually and in combination, on the differentiation of primary human bone marrow progenitor cells in vitro. Both agents promote erythropoiesis, increasing the absolute number of erythroid cells produced from normal CD34+ cells and from CD34+ cells with the types of ribosome dysfunction found in DBA and del(5q) MDS. However, the drugs had distinct effects on the production of erythroid progenitor colonies; dexamethasone selectively increased the number burst-forming units-erythroid (BFU-E), while lenalidomide specifically increased colony-forming units-erythroid (CFU-E). Use of the drugs in combination demonstrates that their effects are not redundant. Human CD34+ cells were cultured for 48 hours in the erythroid differentiation media described above with the addition of 40 ng/mL of FMS-like tyrosine kinase 3 (flt-3; Miltenyi Biotech) and 15 ng/mL of Granulocyte colony-stimulating factor (G-CSF; Amgen). Cells were cultured in the presence of the drugs of interest for 24 hours. RNA was purified using Trizol (Invitrogen). RNA was amplified and labeled by in vitro transcription and hybridized to the Affymetrix HT Human Genome U133A Array. Three replicates per condition.