We generated murine high-grade gliomas with a genetic deletion of ephrinB2 by immortalizing and transforming astrocytes, isolated from the cerebral hemisphere of mice homozygous for a floxed ephrinB2 allele23, with the SV40 large T antigen and the V12-H-ras oncogene24, 25, 26. This evidence concerns the gene HRAS and central nervous system cancer.