Molecular origins of cancer: cancer immunology

Major conceptual and technical advances in immunology over the past 25 years have led to a new understanding of cellular and molecu-lar interplays between the immune system and a tumor. This review deals with important new concepts in antitumor immunity and their application to im-munotherapy. T umor A n tigens Identification The immune system can respond to cancer cells in two ways: by reacting against tumor-specific antigens (molecules that are unique to cancer cells) or against tu-mor-associated antigens (molecules that are expressed differently by cancer cells and normal cells).1 Immunity to carcinogen-induced tumors in mice is directed against the products of unique mutations of normal cellular genes. These mutant proteins are tumor-specific antigens.2 Tumors caused by viruses display viral anti-gens that serve as tumor antigens. Examples are the products of the E6 and E7 genes of the human papillomavirus, the causative agent of cervical carcinoma,3 and EBNA-1, the Epstein–Barr virus nuclear antigen expressed by Burkitt’s lym-phoma and nasopharyngeal-carcinoma cells.