Unknown,Transcriptomics,Genomics,Proteomics

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Effect of genetic Zfx deletion on gene expression in Notch induced T-ALL

ABSTRACT: Acute myeloid leukemia (AML) and acute T-lymphoblastic leukemia (T-ALL) maintain the undifferentiated phenotype and proliferative capacity of their respective cells of origin, hematopoietic stem/progenitor cells and immature thymocytes. The mechanisms that maintain these progenitor-like characteristics are poorly understood. We report that the transcription factor Zfx is required for the development and propagation of experimental AML caused by MLL-AF9 fusion, and of T-ALL caused by Notch1 activation. In both leukemia types, Zfx activated progenitor-associated gene expression programs and prevented differentiation. Key Zfx target genes included mitochondrial enzymes Ptpmt1 and Idh2, whose overexpression partially rescued the propagation of Zfx-deficient AML. These studies identify a common mechanism that controls the cell-of-origin characteristics of acute leukemias derived from disparate lineages and transformation mechanisms. Independent primary Notch induced T-ALL cell lines were created by retroviral transduction of Notch-IC into hematopoietic progenitors carrying the tamoxifen inducible Cre-ER transgene and the Zfx conditional (Zfx fl/y) allele (lines 14843, 14844, 14846). T-ALL cells generated from each line were isolated from moribund mice and transplanted into sublethally irradiated secondary recipients. Ten days after transplant when T-ALL cells had appeared in the blood of the secondary recipients, they were treated by gavage with either Vehicle or Tamoxifen (5 mg /day for three days) to induce Zfx deletion in leukemia cells. 48 hours after the final Tamoxifen treatment, the mice were sacrificed and T-ALL cells were recovered by FACS for microarray studies.

ORGANISM(S): Mus musculus

SUBMITTER: Stuart Weisberg

PROVIDER: E-GEOD-43020 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Acute myeloid leukemia (AML) propagates as a cellular hierarchy which is maintained by a rare subpopulation of self-renewing leukemia-initiating cells (LICs). These LICs phenotypically resemble HSCs and early myeloid progenitors, and they are functionally defined by their ability to reconstitute AML in xenografted mice. Common transcriptional regulators are believed to drive self-renewal of LICs and normal stem cells. Examples include the histone methyltransferase, MLL and its main targets, the transcription factors HOXA9 and MEIS1; the polycomb group protein, BMI-1; and the Wnt/β-catenin signaling pathway4-9. In AML patients, LICs have been shown to share broad gene expression signatures with hematopoietic stem cells (HSCs) and, in some cases, with embryonic stem cells (ESCs). Moreover, increased expression of these stem cell signatures has been linked to tumor aggressiveness. Elucidating the molecular determinants of stem cell properties in LICs has the potential to improve AML therapy and clarify the relationship between cancer and stem cell biology in general. Here we show that the propagation of LICs in AML depends on Zfx, a transcription factor required for the self-renewal of ESCs and HSCs. Using mouse models, we found that Zfx is required for AML propagation and LIC maintenance. We defined a Zfx-driven gene expression program in murine LICs that correlates with existing stem cell-related gene expression signatures in AML patients. Using a novel, stroma-based RNAi screening strategy, we identified functionally important Zfx target genes. Two of these genes – FAM92A1 and DOCK7 - are required for human AML cell propagation; moreover, their expression levels strongly correlate with AML patient survival across the full spectrum of AML subtypes. Together, our results characterize a novel gene expression program that orchestrates critical stem cell properties of LICs, and drives aggressiveness of AML. Independent primary MLL-AF9 AML cell lines were created carrying the tamoxifen inducible Cre-ER transgene and either the Zfx wild-type (wt/y) (lines 10977, 10980) or the Zfx conditional (Zfx fl/y) allele (lines 10949, 10950, 10986). AML cells generated from each line were isolated from moribund mice and cultured with or without 4-hydroxytamoxifen for 72 hours to induce Cre. After Cre induction, c-Kit + cells were purified by FACS and processed for microarray studies.

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Effect of genetic Zfx deletion on gene expression in Notch induced T-ALL

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