When average tumor volume reached about 400 mm3, the tumors were injected with either Ad-pless-TK, Ad-ERE73 (1 + 2)-ARF (−13)-TK, Ad-ERE73 (3 + 4)-ARF (−13)-TK (1 × 1010 PFU), or PBS (3 mice per group). Here, TKT is linked to neoplasm.