TKT and glioblastoma: Adipose tissue mesenchymal stem cells (Ad-MSCs) genetically engineered to express the herpes simplex virus thymidine kinase (TK) in combination with the administration of ganciclovir (GCV) prodrug are a potentially effective treatment in different types of human tumors, highlighting glioblastoma [6, 7] having been employed in I/II clinical trials on gastrointestinal tumors [8].