ABSTRACT
The t(8;21)(q22;q22) occurs frequently in acute myelogenous leukaemia and gives rise to the transcription factor fusion protein, RUNX1-RUNX1T1 (also known as AML1-ETO). To identify the genes dysregulated by the aberrant transcriptional activity of RUNX1-RUNX1T1, we used microarrays to determine the effect of this mutation on gene expression in human progenitor cells and during subsequent development. Gene signatures of these developmental subsets were very dissimilar indicating that effects of RUNX1-RUNX1T1 are highly context dependent. We focused on gene changes associated with the granulocytic lineage and identified a clinically relevant subset of these by comparison with 235 leukaemia patient transcriptional signatures. We confirmed the overexpression of a number of significant genes (Sox4, IL-17BR, CD200 and gamma-catenin). Further, we show that overexpression of CD200 and gamma-catenin is also associated with the inv(16) abnormality which like RUNX1-RUNX1T1 disrupts core binding factor activity. We investigated the functional significance of CD200 and gamma-catenin overexpression in normal human progenitor cells. The effect of IL17 on growth was also assessed. Individually, none of these changes were sufficient to recapitulate the effects of RUNX1-RUNX1T1 on normal development. These data provide the most comprehensive and pertinent assessment of the effect of RUNX1-RUNX1T1 on gene expression and demonstrate the highly context-dependent effects of this fusion gene.
Subject(s)
Core Binding Factor Alpha 2 Subunit/physiology , Gene Expression Regulation, Leukemic/genetics , Hematopoietic Stem Cells/metabolism , Leukemia, Myeloid, Acute/genetics , Neoplasm Proteins/genetics , Oncogene Proteins, Fusion/physiology , Transcription, Genetic/genetics , Antigens, CD/biosynthesis , Antigens, CD/genetics , Cell Line, Tumor/metabolism , Cell Lineage , Cells, Cultured/metabolism , Chromosomes, Human, Pair 21/genetics , Chromosomes, Human, Pair 21/ultrastructure , Chromosomes, Human, Pair 8/genetics , Chromosomes, Human, Pair 8/ultrastructure , Desmoplakins/genetics , Desmoplakins/physiology , Gene Expression Profiling , Hematopoietic Stem Cells/pathology , High Mobility Group Proteins/biosynthesis , High Mobility Group Proteins/genetics , Humans , Leukemia, Myeloid, Acute/pathology , Neoplasm Proteins/biosynthesis , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , RNA, Neoplasm/biosynthesis , RNA, Neoplasm/genetics , RUNX1 Translocation Partner 1 Protein , Receptors, Interleukin-17/biosynthesis , Receptors, Interleukin-17/genetics , Recombinant Fusion Proteins/physiology , SOXC Transcription Factors , Trans-Activators/biosynthesis , Trans-Activators/genetics , Translocation, Genetic , gamma Catenin/genetics , gamma Catenin/physiologyABSTRACT
CD38 expression is an important prognostic marker in chronic lymphocytic leukemia (CLL) with high levels of CD38 associated with shorter overall survival. In this study, we used gene expression profiling and protein analysis of highly purified cell-sorted CD38(+) and CD38(-) chronic lymphocytic leukemia cells to elucidate a molecular basis for the association between CD38 expression and inferior clinical outcome. Paired CD38(+) and CD38(-) CLL cells derived from the same patient were shown to be monoclonal by V(H) gene sequencing but despite this, CD38(+) CLL cells possessed a distinct gene expression profile when compared with their CD38(-) sub-clones. Importantly, CD38(+) CLL cells relatively over expressed vascular endothelial growth factor (VEGF) and appeared to preferentially utilize an internal autocrine VEGF survival loop. Elevated VEGF expression was associated with increased expression of the anti-apoptotic protein Mcl-1. Inhibition of VEGF receptor signaling also resulted in a reduction in cell viability. In contrast, exogenous VEGF caused a significant increase in CD38(-) CLL cell viability and a marked induction of Mcl-1; both effects were less obvious in CD38(+) CLL cells. Taken together, our data provide a biological rationale for the poor prognosis of CD38(+) CLL and indicate that both VEGF and Mcl-1 may prove to be useful therapeutic targets.