While there have been a number of successes in using mouse models to develop anticancer therapies, (e.g., aspirin, NSAIDS) [31] many cancer drugs shown to be efficacious in mouse models have failed human clinical trials, e.g., endostatin [33], hedgehog inhibitors, MMP inhibitors, anti-CD28 Mabs (TGN1412), and cancer vaccines, or these drugs were found to be safe in mice but toxic in humans. Here, CD28 is linked to cancer.