In tumor models where CTLA-4 blockade demonstrated modest antitumor effects, such as in the SA1N fibrosarcoma, EMT-6 mammary carcinoma, and CT-26 colon carcinoma models, synergy was observed in combination with chemotherapy, independent of the intrinsic potency of the chemotherapeutic agent, which suggests that the chemotherapeutic agents tested in this study may potentiate the effect of anti-mCTLA-4 mAb in settings where CTLA-4 blockade may be efficacious. This evidence concerns the gene CTLA4 and colon carcinoma.