Our laboratory developed many genetically engineered mouse models of cancer, establishing the concept of tumor maintenance, enabling new cancer gene discovery and their functional validation, elucidating cancer gene functions particularly regulation of the immune system, and driving many drug development programs. We pioneered cross-species comparative oncogenomics to enable the efficient identification of new oncogenes for drug discovery and new biomarkers for clinical prognostication. We have disseminated our models and our knowledge to the community via the first transgenic facility, many national meetings and an NCI-sponsored training course.