John L. Marshall, MD

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Novel Vaccines for the Treatment of Gastrointestinal Cancers

November 1st 2005

Continuing advances in immunology and molecular biology duringthe past several decades have provided optimism that immunomodulatorystrategies may be clinically useful in patients with cancer.Key advances have included: (1) recognition of the critical role of theantigen-presenting cell and greatly improved understanding of antigenprocessing and presentation, including the molecular interactionsbetween HLA molecules and antigenic epitopes on the antigen-processingcell and the receptors on T cells, and (2) the roles ofcostimulatory molecules such as B7.1, ICAM-1, and LFA-3 in the inductionand maintenance of an immune response. In addition, newtechniques have allowed us to identify immunogenic antigenic determinants,alter their binding affinities, and evaluate the overall successof the intervention through both in vivo and in vitro assays.Carcinoembryonic antigen (CEA) is overexpressed in a large numberof gastrointestinal, lung, and breast cancers. Clinical trials have establishedtreatment protocols using viral vectors to immunize patients toCEA without producing deleterious autoimmune phenomena. By combiningvarious vectors to include MUC-1 and/or CEA plus costimulatorymolecules in a prime-and-boost regimen, we are beginning to see signsthat this intervention can not only produce changes in immune functionbut also potentially improve clinical outcomes. Phase III studies totest these hypotheses are under way.