PDGFB and central nervous system cancer: This frequency was compared, with the Log-rank test, to the tumor occurrence observed when wild type PDGF-B-induced glioma cells were injected in wild type recipients (9 mice out of 12; p > 0.05), revealing that NG2-KO glioma cells are able to give rise to secondary tumors with high frequency, indistinguishably from wild type tumors.