Inhibition of granulocyte colony-stimulating factor-mediated myeloid maturation by low level expression of the differentiation-defective class IV granulocyte colony-stimulating factor receptor isoform

Blood. 2000 Jun 1;95(11):3335-40.


In acute myeloid leukemia (AML), granulocyte colony-stimulating factor receptor (G-CSFR) proliferative and maturational signaling pathways are uncoupled. Seven human G-CSFR mRNA isoforms exist, named class I through class VII. The 183-amino acid cytosolic domain of the class I isoform provides all signaling activities. The class IV isoform is "differentiation defective" because the carboxy-terminal 87 amino acids are replaced with 34 amino acids of novel sequence. In more than 50% of AML samples, the class IV/class I G-CSFR mRNA ratio is aberrantly elevated compared to normal CD34(+) bone marrow cells. We hypothesized that the increased relative expression of class IV G-CSFR in AML uncouples proliferative and maturational G-CSFR signaling pathways. To test this, we transfected the G-CSF-responsive murine cell line 32Dcl3 with class IV G-CSFR cDNA. After 10 days of G-CSF stimulation, clones expressing class IV G-CSFR had greater percentages of myeloblasts and promyelocytes than controls (53% +/- 13% versus 3% +/- 2%). Differential counts over time demonstrated delayed G-CSF-driven maturation in 5 class IV-expressing clones, with 2 clones demonstrating a subpopulation that completely failed to differentiate. Heterologous class IV expression did not affect G-CSF-dependent proliferation. Class IV/murine G-CSFR mRNA ratios after 24 hours of G-CSF stimulation for 3 of the 5 clones (range, 0. 090 to 0.245; mean, 0.152 +/- 0.055) are within the range of class IV/class I mRNA ratios seen in patients with AML. This indicates that aberrantly increased relative class IV G-CSFR expression seen in AML can uncouple G-CSFR proliferative and maturational signaling pathways.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Differentiation / drug effects
  • Cell Line
  • Granulocyte Colony-Stimulating Factor / pharmacology*
  • Hematopoietic Stem Cells / cytology
  • Hematopoietic Stem Cells / drug effects
  • Hematopoietic Stem Cells / physiology*
  • Humans
  • Mitosis / drug effects
  • Neutrophils / cytology*
  • Neutrophils / drug effects
  • Neutrophils / physiology
  • Protein Isoforms / genetics
  • Protein Isoforms / physiology
  • RNA, Messenger / genetics
  • Receptors, Granulocyte Colony-Stimulating Factor / genetics
  • Receptors, Granulocyte Colony-Stimulating Factor / physiology*
  • Recombinant Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription, Genetic
  • Transfection


  • Protein Isoforms
  • RNA, Messenger
  • Receptors, Granulocyte Colony-Stimulating Factor
  • Recombinant Proteins
  • Granulocyte Colony-Stimulating Factor