Our approach consists of expressing Fms-like tyrosine kinase 3 ligand (Flt3L) which induces dendritic cell (DC) infiltration into the brain parenchyma [28] in combination with the conditional cytotoxic gene Thymidine Kinase (TK) [27], [29], which in the presence of GCV induces tumor cell death. Here, FLT3LG is linked to neoplasm.