CTLA4 and neoplasm: When tumors had reached an average volume of 40 mm3 (4×107 number of cells), mice were treated with carrier fluid treatment (mock; control) or injected with 2×106 viruses (OV) in the tumor, or injected with viral particles together with anti-CTLA-4 (OV-aCTLA-4) for 5 consecutive days [5].