A novel monoclonal antibody to human stem cell factor and its effect on ex vivo stem cell expansion

Abstract

Hematopoietic stem cell (HSC) transplantation can be used to treat blood and immune system disorders. Stem cell factor (SCF) activates HSC self‐renewal and is being used to stimulate the ex vivo expansion of HSCs for the treatment of various hematologic diseases. The mechanism by which SCF stimulates and supports expansion of HSCs remains poorly understood. Our aim was to obtain novel monoclonal antibodies (mAb) for structural and functional characterization of SCF, and for optimization of ex vivo expansion of HSCs. Recombinant human SCF was used for production of mAb. A high‐titer mAb cell line (23C8) was found to be specific for SCF. In ex vivo cord blood expansion assays, the ability of SCF to stimulate the expansion of CD34+ cells was significantly inhibited by 23C8. Thus, it appears that the anti‐SCF mAb binds directly to a part of SCF that is critical for biological activity. Through peptide mapping and amino acid sequence analysis, we further identified the binding site of 23C8 on soluble SCF to the first 104 amino acids from the amino terminus. The novel anti‐SCF mAb will be valuable for further dissection of the functional domains of SCF and optimization of ex vivo expansion of HSCs. [Supported by State Scientific Key Projects for New Drug Research and Development (2011ZX09102–010‐04 and 2011ZX09401–027)]