CTLA4 and prostate cancer: Subsequent trials in solid tumor models have been tested; OX40 and anti-CTLA-4 in ovarian carcinoma (ID8), prostate cancer (TRAMP1), anti-CD137 and CTLA-4 blockade in MC38 colon cancer and GL261 glioblastoma, demonstrating synergy between CD137, PD-1, and CTLA-4[109–113].