CLONING, EXPRESSION, AND CHARACTERIZATION OF A CDNA-ENCODING A NOVEL HUMAN GROWTH-FACTOR FOR PRIMITIVE HEMATOPOIETIC PROGENITOR CELLS

Multiple growth factors synergistically stimulate proliferation of pri mitive hematopoietic progenitor cells. A human myeloid cell line, KPB- M15, constitutively produces a novel hematopoietic cytokine, termed st em cell growth factor (SCGF), possessing species-specific proliferativ e activities. Here we report the molecular cloning, expression, and ch aracterization of a cDNA encoding human SCGF using a newly developed l ambda SHDM vector that is more efficient for differential and expressi on cloning. cDNA for SCGF encodes a 29-kDa polypeptide without N-linke d glycosylation. SCGF transiently produced by COS-1 cells supports gro wth of hematopoietic progenitor cells through a short-term liquid cult ure of bone marrow cells and exhibits promoting activities on erythroi d and granulocyte/macrophage progenitor cells in primary semisolid cul ture with erythropoietin and granulocyte/macrophage colony-stimulating factor, respectively. Expression of SCGF mRNA is restricted to myeloi d cells and fibroblasts, suggesting that SCGF is a growth factor funct ioning within the hematopoietic microenvironment. SCGF could disclose some human-specific mechanisms as yet unidentified from studies on the murine hematopoietic system.