title: Autocrine GM-CSF transcription in the leukemic progenitor cell line KG1a is mediated by the transcription factor ETS1 and is negatively regulated through SECTM1 mediated ligation of CD7.
abstract: BACKGROUND
  CD7 expression is found on ~30% of acute myeloblastic leukemias (AML). The leukemic progenitor cell line KG1a (CD7+) constitutively expresses GM-CSF while the parental KG1 (CD7-) cell line does not. This study focuses on the molecular basis of CD7 mediated GM-CSF regulation.
  
  
  METHODS
  KG1a cells were treated with recombinant SECTM1-Fc protein, the PI3K kinase inhibitors wortmannin, LY292004, or PI4K activator spermine. Stable KG1-CD7+, KG1a-shCD7, KG1a-shETS1 as well as KG1a-GFP, KG1a-PKCβII-GFP cell lines were generated and the levels of CD7, GM-CSF and ETS-1 mRNA and protein were compared by real-time-PCR, western blotting, flow cytometry and ELISA.
  
  
  RESULTS
  SECTM1 is expressed in Human Bone Marrow Endothelial Cells (HBMEC) and its expression can be upregulated by both IFN-γ. KG1a cells demonstrated high expression levels of CD7 and ETS-1 allowing a constitutative signaling through the PI3K/Atk pathway to promote GM-CSF expression, while KG1 cells with low expression of CD7 and ETS-1 showed low GM-CSF expression. On KG1a cells GM-CSF expression could be negatively regulated by PI3K inhibitors or by recombinant SECTM1-Fc. Overexpression of CD7 in KG1 cells was insufficient to promote GM-CSF expression, while silencing of CD7 or ETS-1 resulted in reduced GM-CSF expression levels. Differentiation capable KG1a cells overexpressing PKCβII illustrated complete loss of CD7, but maintained normal levels of both ETS-1 and GM-CSF expression.
  
  
  CONCLUSIONS
  These findings add an additional layer to the previously described autocrine/paracrine signaling between leukemic progenitor cells and the bone marrow microenvironment and highlight a role for SECTM1 in both normal and malignant hematopoiesis.
  
  
  CONCLUSIONS
  This work shows that SECTM1 secreted from bone marrow stromal cells may interact with CD7 to influence GM-CSF expression in leukemic cells.
authors.affiliation: Institute for Transfusion Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Bade-Döding
authors.affiliation: Institute for Transfusion Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Göttmann
authors.affiliation: Institute for Transfusion Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Baigger
authors.affiliation: Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY 14226, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Farren
authors.affiliation: Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY 14226, USA.
authors.forename: Kelvin P
authors.initials: KP
authors.lastname: Lee
authors.affiliation: Institute for Transfusion Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Blasczyk
authors.affiliation: Institute for Transfusion Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany. Electronic address: huyton.trevor@mh-hannover.de.
authors.forename: Trevor
authors.initials: T
authors.lastname: Huyton
mesh_terms: D019011:Antigens, CD7 / Q000502:physiology*; D045744:Cell Line, Tumor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology*; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D050784:Proto-Oncogene Protein c-ets-1 / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D019011:Antigens, CD7; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D050784:Proto-Oncogene Protein c-ets-1; C494041:ETS1 protein, human; C111200:SECTM1 protein, human
keywords: Acute myeloid leukemia; CD7; ETS1; GM-CSF; Hematopoietic progenitors; SECTM1; secreted and transmembrane protein 1