Recently, we tested whether the combination of CD/5-fluorocytosine (5-FC) gene therapy, with the capability to kill tumor cells by converting 5-FC into 5-fluorouracil (5-FU) in the tumor tissue, along with an immunostimulatory GM-CSF gene, would further increase therapeutic efficacy and augment the magnitude of the antitumor immune response induced by the adjuvant effect of dying tumor cells (Figure). This evidence concerns the gene CSF2 and neoplasm.