The use of genetically engineered mice has grown exponentially. Transgenic deficient mice are now widely used to study: the process of malignant transformation, tumor suppressor genes, chemoprevention, carcinogenesis and organ-specific cancers. In fact, the genetic manipulation of mice is used in virtually every field of biomedical investigation. It is arguably the most potent tool available to dissect gene function in physiology and pathophysiology. However, because of the prohibitive costs and the technical sophistication required to establish these procedures within individual laboratories, it is essential to support these technologies as a shared resource. This requires an efficient and cost-effective common facility that enables individual investigators to have both transgenic mice expressing genes of interest and mice carrying gene disruptions created for them. The techniques available from this Resource place these potent tools for analysis in the hands of all of our investigators. When used in combination with the other modern techniques supplied by the Center's Histology and Molecular Pathology facilities, it gives our investigators unlimited opportunities to examine pathogenetic processes from several perspectives simultaneously. Our current facility has an established track record of enabling the creation of both transgenic mice and knockout mouse strains for multiple Cancer Center laboratories. Without such a centralized resource, most laboratories would not be in a position to utilize these pow4erful models, severely limiting the research and granting opportunities for our biomedical and cancer research community, severely limiting the research and granting opportunities for our biomedical and cancer research community. The Transgenic Mouse Shared Resource of UCSD Cancer Center is widely respected in the community and regarded as an essential resource for modern cancer research. It substantially improves the quality, quantity and creativity of the research, while also enhancing cost-effectiveness and efficiency.