PTEN and central nervous system cancer: However, the CIS genes did not include a number of well-established glioma genes such as Egfr, Pdgfr, and Tp53, and there were only single insertions found in other important tumour-specific genes including Pten and Akt. This may be explained by certain insertion site preference biases of SB or that SB-induced gliomas represent only a subset of gliomas that is not driven by the major cancer drivers in most human gliomas.