Premalignant Lesions as Targets for Cancer Vaccines

The job of the immune system is to respond to signals released by tissues that are being destroyed by foreign invaders, such as viruses and bacteria, and to destroy the invaders. These signals have been termed “danger” signals (1). Destruction of tissues by uncontrolled cell growth characteristic of cancer is expected to also generate danger signals, albeit possibly qualitatively different due to the absence of infectious agents. Evidence that the immune system not only detects the presence of cancer but also destroys it and remembers it through the recognition of tumor-specific antigens was provided in the late 1950's (2) and has been confirmed many times in increasingly more sophisticated animal models and in cancer patients. What has not been fully accepted, however, in part because supporting data are only now emerging, is that the immune system can recognize precursors of cancer...