title: Characterizing heterogeneity in leukemic cells using single-cell gene expression analysis.
abstract: BACKGROUND
  A fundamental challenge for cancer therapy is that each tumor contains a highly heterogeneous cell population whose structure and mechanistic underpinnings remain incompletely understood. Recent advances in single-cell gene expression profiling have created new possibilities to characterize this heterogeneity and to dissect the potential intra-cancer cellular hierarchy.
  
  
  RESULTS
  Here, we apply single-cell analysis to systematically characterize the heterogeneity within leukemic cells using the MLL-AF9 driven mouse model of acute myeloid leukemia. We start with fluorescence-activated cell sorting analysis with seven surface markers, and extend by using a multiplexing quantitative polymerase chain reaction approach to assay the transcriptional profile of a panel of 175 carefully selected genes in leukemic cells at the single-cell level. By employing a set of computational tools we find striking heterogeneity within leukemic cells. Mapping to the normal hematopoietic cellular hierarchy identifies two distinct subtypes of leukemic cells; one similar to granulocyte/monocyte progenitors and the other to macrophage and dendritic cells. Further functional experiments suggest that these subtypes differ in proliferation rates and clonal phenotypes. Finally, co-expression network analysis reveals similarities as well as organizational differences between leukemia and normal granulocyte/monocyte progenitor networks.
  
  
  CONCLUSIONS
  Overall, our single-cell analysis pinpoints previously uncharacterized heterogeneity within leukemic cells and provides new insights into the molecular signatures of acute myeloid leukemia.
authors.forename: Assieh
authors.initials: A
authors.lastname: Saadatpour
authors.forename: Guoji
authors.initials: G
authors.lastname: Guo
authors.forename: Stuart H
authors.initials: SH
authors.lastname: Orkin
authors.forename: Guo-Cheng
authors.initials: GC
authors.lastname: Yuan
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D019295:Computational Biology / Q000379:methods*; D020869:Gene Expression Profiling; D015973:Gene Expression Regulation, Leukemic; D053263:Gene Regulatory Networks; D018740:Genetic Heterogeneity; D042381:Granulocyte Precursor Cells / Q000378:metabolism; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D055017:Monocyte-Macrophage Precursor Cells / Q000378:metabolism; D009374:Neoplasms, Experimental; D059010:Single-Cell Analysis / Q000379:methods*