Our previous studies have shown that a combined conditional cytotoxic-immunotherapy approach using adenoviral vectors (Ad) that express the immunostimulatory cytokine human soluble fms-like tyrosine kinase 3 ligand (hsFlt3L, Ad-hsFlt3L), and the conditionally cytotoxic Herpes Simplex Type 1- thymide kinase (TK, Ad-TK) induces tumor regression, long-term survival, and immunological memory in rats and mice bearing large intracranial syngeneic glioblastomas or intracranial melanomas [7]–[10]. Here, TKT is linked to glioblastoma.