The Biomarkers Core will serve as a collection and distribution point for blood and tissue samples related to Projects I, II, III, and IV as well as Core D. It will provide a resource and service for carrying out the laboratory analyses proposed in this application in support of the basic science and clinical trials. The Core will develop and be responsible for the appropriate sample collection, logging, tracking, storage, sample preparation procedures, sample processing, and distribution for all animal and human samples collected during the course of this proposal. It also will be responsible for the training of personnel involved in the collection and processing of study samples. In addition, the Core will be responsible for developing immunohistochemical and analytical methods for the measurement of targets from Projects I, II, III, and IV. The Biomarkers Core will perform assays and will work closely with the Biometry Core to provide data for reporting and interpretation. Quality assurance and quality control procedures will continue to be developed by the Biomarkers Core for sample acquisition, processing, and analysis procedures included in the proposal. The Biomarkers Core will develop and optimize methods for measuring the secondary laboratory-directed research endpoints proposed in each project. Endpoints to be analyzed by the Biomarkers Core include blood and skin levels of chemoprevention agents and micronutrients, histopathology and karyometric measurements on skin biopsies as well as immunohistochemical assays for cell proliferation, apoptosis, p53 protein expression, retinoid receptors, and other targets identified within the proposal.