New possibilities for cancer therapy with advances in cancer immunology.

There has been progress over the last decade in addressing three questions: Are there cancer-associated antigens that could be targets for immunotherapy? Can the human immune system recognize cancer-associated antigens? Can an anti-cancer immune response affect cancer cells and lead to increased survival? Results from animal model studies have been interpreted by optimists as encouraging, and by pessimists as being irrelevant to human cancer. Earlier studies on "cancer vaccines" utilized heterogeneous cell extracts of cell components. Monoclonal antibodies have enabled identification of relevant cancer-associated antigens or epitopes, such as the ganglioside GM2, the carbohydrates TF and STn, and the peptide sequences of MUC-1. In parallel with research on immune adjuvants and measures designed to inhibit suppressor activity, these epitopes are being tested for their potential in the immunotherapy of solid tumors. It is clear that some of these cancer-associated epitopes are immunogenic in humans. Mixed responses may relate to cancer heterogeneity and may indicate the importance of multi-epitopic vaccines. Responses are encouraging, but are they relevant? Prolonged disease stability challenges us to re-think the goals of cancer therapy. Recent advances in the knowledge of the effect of cytokines on tumor antigen expression and the regulation of the immune response, coupled with advances in active specific immunotherapy, provide hope that biomodulation may become an important part of the therapy of solid tumors in the next century.