The most well-studied and extensively used suicide gene/prodrug systems against glioblastoma are the herpes simplex virus (HSV) type 1 thymidine kinase (TK)/ganciclovir (GCV) and yeast cytosine deaminase/5-fluorocytosine (CD/5-FC) systems [8,9,14,15,16]. Here, TKT is linked to glioblastoma.