Cancer rejection by the immune system: forcing the check-points of tumor immune escape.

Although the immune system can recognize and kill malignant cells, tumor immune surveillance or immunotherapy are largely insufficient in controlling cancer. The mechanisms underlying tumor immune escape are still to be fully dissected. An important emerging concept is that tumor and tumor-infiltrating host cells can alter the metabolism of some amino acids with a profound impact on antitumor immunity. Such mechanisms constitute potential check-points for tumor-specific T-lymphocytes, which must be considered in the design of novel immunotherapeutic approaches.