The rationale for this strategy was that PA-STK cells, injected in the vicinity of the patient’s tumor bulk, could make contact with, and seed themselves onto, the patient’s tumor cells in vivo and, after treatment with ganciclovir, could commit suicide and kill the patient’s tumor cells by a “direct” bystander mechanism (e.g. gap junction mediated transfer of the phosphorylated ganciclovir from the HSV-TK positive cells to the TK negative cells. This evidence concerns the gene TKT and neoplasm.