NES and central nervous system cancer: Another type of GEMM for BRAFV600E-mutated gliomas is the replication-competent avian sarcoma-leukosis retrovirus and the corresponding avian leukosis virus A (RCAS-TVA) system, which allows for somatic gene delivery to cells that are engineered to express cell surface receptor TVA using a cell type-specific promoter such as Nestin, which is a common marker for neural stem cells (112, 113).