A Novel Glial Growth Inhibitory Factor, Gliostatin, Derived from Neurofibroma

Neurofibroma tissue was investigated for the presence of glial growth modulators that would suppress the proliferation of glial cells. A novel endogenous polypeptide inhibitor of proliferation and DNA synthesis in glial cells, gliostatin, was purified from the extracts of neurofibroma by a procedure comprising dye and anion‐exchange column chromatography, and HPLC. A monoclonal antibody raised against partially purified gliostatin showed no cross‐reactivity with known cytokines, but adsorbed the growth inhibitory activity of gliostatin and immunochemi‐cally visualized the putative gliostatin bands on western blot analyses. Although the product showed an apparent M_r of 100,000 accompanied by an inhibitory activity on gel filtration column chromatography, it migrated at a lower apparent M_r of 50,000 under the reducing conditions on western blotting, indicating that a homodimeric structure of native gliostatin consisted of 50‐kDa subcomponents. Gliostatin was a potent growth inhibitor acting at nanomolar concentrations against all glial tumor cells and glia maturation factor‐stimulated astroblasts, but not neuronal cells.