Inhibition of glioma cell proliferation by neural stem cell factor

Neural stem cells (NSC) have unique differentiation-, proliferation-, and motility properties. To investigate whether they secrete factors that interfere with the proliferation of glioma cells, we grew glioma cells in conditioned medium (CM) obtained from cultures of neurospheres including neural stem / progenitor cells (NSPC) isolated from embryonic (E14)- or adult mouse brain or fetal human brain. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and BrdU-labeling assays showed that CM from NSPC (NSPC/CM) contained factor(s) that inhibited the proliferation of glioma cells by 28-87%. Filter-fractionation of NSPC/CM revealed that the 50,000-100,000 nominal molecular weight limit (NMWL) fraction contained the inhibitory activity. On the basis of these observations we transplanted 203G glioma cells and/or NSPC into the intrathecal space of the cisterna magna of mice to investigate whether NSPC interfere with the proliferation of glioma cells in vivo. Mice transplanted with both 203G and NSPC survived significantly longer than did mice transplanted only with 203G. We concluded that NSPC secrete factor(s) that may control glioma cell proliferation.