The reason for the contrasting efficacy of Ad.IL-7/B7.1 between the two models, i.e., no efficacy against non-transplanted tumors (generated by intramuscular or subcutaneous 3MC injection) versus 87.5% efficacy against transplanted tumors (derived from 3MC-treated MC51-9 fibrosarcoma cells), remains unclear. This evidence concerns the gene IL7 and fibrosarcoma.