RECOMBINANT HUMAN STEM-CELL FACTOR STIMULATES INCREASED NUMBERS OF PERIPHERAL-BLOOD AND MARROW CFU-GM, BFU-E, CFU-MIX, HPP-CFC AND CD34+ CELLS IN BABOONS

Recombinant human stem cell factor (SCF), the lignand for human c-kit, by itself stimulates little in vitro proliferation by marrow hematopoietic colony-forming cells (CFC) from baboons, but stimulates increases in the number and size of colonies formed in response to IL-3, G-CSF, GM-CSF, and erythropoietin alone or in combination. SCF given to baboons stimulates increases in peripheral blood cells of multiple myeloid and lymphoid lineages and increases marrow cellularity. The present studies demonstrate that SCF given to baboons also stimulates significant increases in CFU-GM, BFU-E, CFU-MIX, HPP-CFC, and detectable CD34+ cells in blood. These changes are dose dependent. SCF stimulated a doubling of marrow cellularity and modest increases in the frequency of CFC, consistent with an absolute increase in the total number of CFC in marrow. No adverse events were observed. The findings suggests a role for SCF (c-kit ligand) in stimulating expansion of hematopoietic CFC of multiple types in blood and marrow for potential therapeutic purposes.