In gliomas where both alleles of Ink4a, Arf, Pten were deleted at tumor initiation, and in regions of gliomas dominated by progeny in tumors with initially heterozygous deletion of these tumor suppressors, both progeny cells and recruited cells expressed PDGFRα, with <5% tumors co-expressing EGFR (Figure 4e; Figure S6a–c; data not shown) [14]–[16], [33]. The gene discussed is CDKN2A; the disease is central nervous system cancer.