Context: In many cancers, specific subpopulations of cells appear to be uniquely capable of initiating and maintaining tumors. The strongest support for this cancer stem cell model comes from transplantation assays in immune-deficient mice indicating that human acute myeloid leukemia (AML) is organized as a cellular hierarchy driven by self-renewing leukemia stem cells (LSC). This model has significant implications for the development of novel therapies, but its clinical significance remains unclear.
Association of a leukemic stem cell gene expression signature with clinical outcomes in acute myeloid leukemia.
Disease, Disease stage, Subject
View SamplesAcute Myeloid Leukemia AML is a cancer in which the process of normal cell hematopoietic differentiation is disrupted. Evidence exists that AML comprises a hierarchy with leukemic stem cells giving rise to more differentiated, but immature and functionally incompetent populations. The similarity of these AML subpopulations to normal stages of hematopoietic differentiation has not been dissected comprehensively at the transcriptional level. Here we introduce Normal Memory Analysis (NorMA), a data analysis method that extracts from omic data the remnants of the healthy normal-like phenotype. Applying NorMA to gene expression data from AML uncovered a wealth of information in the normal-like component of data: the normal hematopoietic memory of AML tumor cells. We found significant variation within the patient population, and we found strong association of this normal hematopoietic memory with survival. We found that undifferentiated NorMA phenotype has significantly worse survival than differentiated NorMA phenotype, showing that the NorMA classification of tumors captures a biologically meaningful stratification of patients, with highly significant survival association. Patients with NorMA phenotype in the undifferentiated Hematopoietic Stem Cell HSC stage had the worst survival, with median survival time under 6 months. We further found significant survival differences between tumor groups with differentiated NorMA phenotype, depending on their hematopoietic path: AML patients with NorMA phenotype in megakaryocyte-erythroid progenitor MEP stage had significantly better survival than those with NorMA phenotype in granulocyte-macrophage progenitor GMP stage. Thus NorMA produced a stratification of AML cohorts by differentiation stage, with significant outcome differences. It also provided clean molecular signatures for these stages. NorMA can be used in many other contexts, to explore for example the tumor cell of origin, or disease predisposition.
An LSC epigenetic signature is largely mutation independent and implicates the HOXA cluster in AML pathogenesis.
Specimen part
View SamplesBCRABL1+ precursor B-cell acute lymphoblastic leukemia (BCR ABL1+ B-ALL) is an aggressive hematopoietic neoplasm characterized by a block in differentiation due in part to the somatic loss of transcription factors required for B-cell development. We hypothesized that overcoming this differentiation block by forcing cells to reprogram to the myeloid lineage would reduce the leukemogenicity of these cells. We found that primary human BCRABL1+ B-ALL cells could be induced to reprogram into macrophage-like cells by exposure to myeloid differentiation-promoting cytokines in vitro or by transient expression of the myeloid transcription factor C/EBP or PU.1. The resultant cells were clonally related to the primary leukemic blasts but resembled normal macrophages in appearance, immunophenotype, gene expression, and function. Most importantly, these macrophage-like cells were unable to establish disease in xenograft hosts, indicating that lineage reprogramming eliminates the leukemogenicity of BCRABL1+ B-ALL cells, and suggesting a previously unidentified therapeutic strategy for this disease. Finally, we determined that myeloid reprogramming may occur to some degree in human patients by identifying primary CD14+ monocytes/ macrophages in BCRABL1+ B-ALL patient samples that possess the BCRABL1+ translocation and clonally recombined VDJ regions.
Reprogramming of primary human Philadelphia chromosome-positive B cell acute lymphoblastic leukemia cells into nonleukemic macrophages.
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Robust enumeration of cell subsets from tissue expression profiles.
Specimen part, Disease, Disease stage
View SamplesWe introduce CIBERSORT, a method for characterizing cell composition of complex tissues from their gene expression profiles. When applied to enumeration of hematopoietic subsets in RNA mixtures from fresh, frozen, and fixed tissues, including solid tumors, CIBERSORT outperformed other methods with respect to noise, unknown mixture content, and closely related cell types. CIBERSORT should enable large-scale analysis of RNA specimens for cellular biomarkers and therapeutic targets (http://cibersort.stanford.edu).
Robust enumeration of cell subsets from tissue expression profiles.
Specimen part, Disease, Disease stage
View SamplesWe introduce CIBERSORT, a method for characterizing cell composition of complex tissues from their gene expression profiles. When applied to enumeration of hematopoietic subsets in RNA mixtures from fresh, frozen, and fixed tissues, including solid tumors, CIBERSORT outperformed other methods with respect to noise, unknown mixture content, and closely related cell types. CIBERSORT should enable large-scale analysis of RNA specimens for cellular biomarkers and therapeutic targets (http://cibersort.stanford.edu).
Robust enumeration of cell subsets from tissue expression profiles.
Specimen part, Disease
View SamplesPrimary effusion lymphoma is an aggressive B-cell lymphoma most commonly diagnosed in HIV-positive patients and universally associated with Kaposis sarcoma-associated herpesvirus (KSHV). Chemotherapy treatment of PEL yields only short-term remissions in the vast majority of patients yet efforts to develop superior therapeutic approaches have been impeded by lack of animal models that more accurately mimic human disease. To address this issue we developed a direct xenograft model, UM-PEL-1, by transferring freshly-isolated human PEL cells into the peritoneal cavities of NOD/SCID mice without in vitro cell growth. We utilized this model to show that bortezomib induces PEL remission and extends overall survival of mice bearing lymphomatous effusions. Transcriptome analysis by genomic arrays revealed that bortezomib downregulated cell cycle progression, DNA replication, and Myc-target genes.
Efficacy of bortezomib in a direct xenograft model of primary effusion lymphoma.
Cell line
View SamplesPlasmablastic lymphoma is a high grade B cell lymphoma with plasmablastic morphology and a terminally differentiated B cell immunophenotype, usually arising in the setting of immunodeficiency and often demonstrating Epstein Barr Virus positivity. The molecular and genetic mechanisms underlying the pathogenesis of PBL are largely unknown. To better understand its pathogenesis, herein we have analyzed global gene expression of PBL and compared that to gene expression profiles of diffuse large B cell lymphoma. While overlaps in transcriptomes between these malignancies were identified, we have shown that the gene expression profile of plasmablastic lymphoma is distinct, demonstrating striking downregulation of B cell receptor signaling genes, BCL6, BCL11A SPI-B, targets of NFKB1, and upregulation of mitochondrial genes, PRMT5, MYC and MYC targets and IL21, implicating these alterations in the pathogenesis of this lymphoma. In addition we show the usefulness of SWAP-70 immunohistochemistry in the differentiation of immunoblastic diffuse large B cell lymphoma and plasmablastic lymphoma. Our findings provide justification for considering plasmablastic lymphoma as a specific lymphoma entity and provide insight into the unique transcriptional aberrations occurring in this high-grade lymphoma.
Gene expression analysis of plasmablastic lymphoma identifies downregulation of B-cell receptor signaling and additional unique transcriptional programs.
Specimen part
View SamplesFollicular lymphoma (FL) shows heterogenous expression of the cell surface B-cell marker, CD20. In order to investigate whether this heterogeneity also marks underlying transcriptional heterogeneity, we sorted tumor B-cells from 8 FL specimens based upon their intermediate or high expression of CD20 and transcriptionally profiled them.
Hierarchy in somatic mutations arising during genomic evolution and progression of follicular lymphoma.
Sex, Age, Subject
View SamplesLMO2 regulates gene expression facilitating the formation of multipartite DNA-binding complexes. In B cells, LMO2 is specifically up-regulated in the Germinal Center (GC) reaction and is expressed in GC-derived non-Hodgkins lymphomas. LMO2 is one of the most powerful prognostic indicators in DLBCL patients. However, its function in GC B cells and DLBCL is currently unknown. In the present study we characterized the LMO2 transcriptome and interactome in DLBCL cells. LMO2 regulates genes implicated in kinetochore function, chromosome assembly and mitosis. Overexpression of LMO2 in DLBCL cell lines results in centrosome amplification. In DLBCL, the LMO2 complex contains some of the traditional partners such as LDB1, E2A, HEB, Lyl1, ETO2 and SP1, but not TAL1 or GATA proteins. Furthermore, we identified novel LMO2 interacting partners: ELK1, NFATc1 and LEF-1 proteins. Reporter assays revealed that LMO2 increases transcriptional activity of NFATc1 and decreases transcriptional activity of LEF-1 proteins. Overall, our studies identified a novel LMO2 transcriptome and interactome in DLBCL and provide a platform for future elucidation of LMO2 function in GC B-cells and DLBCL pathogenesis.
Identification of LMO2 transcriptome and interactome in diffuse large B-cell lymphoma.
Specimen part, Cell line
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