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Gene expression of viable human AML cells purified by FACS from bone marrows of three AML PDX treated by PBS(vehicle) or cytarabine

ABSTRACT: It has been hypothesized that chemotherapy resistant human acute myeloid leukemia (AML) cells are enriched in an immature phenotype, cellular quiescence and leukemic initiating cells (LICs). However, these hypotheses have never been validated completely in vivo. We have developed a physiologically relevant chemotherapeutic approach with cytosine arabinoside AraC using patient-derived xenograft (PDX) models. AraC-treated AML cells are not consistently enriched for either immature cells or quiescent cells. AraC treatment does not enrich for LICs as measured by limiting dilution in secondary transplantations. Rather chemotherapy resistant cells in vivo have high levels of reactive oxygen species (ROS) and a gene signature consistent with oxidative phosphorylation (OXPHOS). Treatment of human HIGH OXPHOS but not LOW OXPHOS AML cell lines showed chemotherapy resistance in vivo, showing that essential mitochondrial functions make significant contributions to AraC resistance in AML. Accordingly, targeting mitochondrial OXPHOS metabolism through the inhibition of mitochondrial protein synthesis, the electron transfer chain or fatty acid oxidation induced an energetic shift towards LOW OXPHOS and strongly enhanced anti-leukemic effects of AraC in AML cells. These results demonstrate that chemotherapy resistance in AML is not necessarily associated with stemness but is highly dependent on a distinct oxidative metabolism, and that the HIGH OXPHOS gene signature is a robust hallmark of the AraC response in PDX and a promising therapeutic avenue to treat AML residual disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE97631 | GEO | 2017/06/25

SECONDARY ACCESSION(S): PRJNA382494

REPOSITORIES: GEO

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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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Gene expression of viable human AML cells purified by FACS from bone marrows of three AML PDX treated by PBS(vehicle) or cytarabine

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