Antitumor efficacy of RGD modified viruses in the spleen-to-liver colorectal cancer model. Enhanced therapeutic effect of RGD modified replication competent adenoviruses in spleen-to-liver colorectal cancer model. To imitate clinical metastatic colorectal cancer, hepatic tumors were induced in mice by intrasplenic injection of HCT116 colorectal cancer cells. WT, WT-RGD, or WT-RGDK viruses at dose of 3 × 10e10 VP were injected via tail vein in two consecutive days (days 23 and 24). (A) Hepatic tumor growth was followed with MRI thereafter. Relative tumor volumes normalized to the day before virus treatment (day -1) tumor volumes are presented. Each data point represents mean of 2 to 11 measurements ± SEM. *, p < 0.05; **, p < 0.01. (B) The survival of animals was assessed. No statistically significant differences in the survival of animals between treatment groups were observed. (C) Virus replication in liver tumors was assessed three days after systemic administration. Mock animals received PBS only. Pfu/ml values obtained from TCID50 test were normalized for tumor volume. Each dot represents an individual liver tumor. All viruses replicated in the liver tumor tissue and no statistically significant differences were seen between virus treated groups.