Cost and response criteria are the new challenges

The immune system and cancer The immune system functions by recognizing signals (antigens) on the surface of invading organisms as “nonself” and mounting a response that ultimately leads to the death of these organisms. Because tumors are made up of our own cells they often don’t display these signals and are therefore more or less tolerated by the body. When tumors do display unusual proteins on their surface that could be recognized as nonself, they are able to actively subvert the subsequent immune response. Indeed, the property of immune evasion has now been added to the list of cancer hallmarks – the key features defined by Weinberg and Hanahan that allow a cell to become malignant. It has become clear that there are several ways in which tumors achieve a state of immune tolerance. Several of these mechanisms have been targeted for novel therapies and have resulted in the establishment of durable antitumor immune responses that are known as immunotherapies.