Diet-gene interactions in p53-deficient mice: Insulin-like growth factor-1 as a mechanistic target

Progress in cancer prevention research is being facilitated by the use of animal models displaying specific genetic susceptibilities for cancer, such as mice deficient in one (+/-) or both (-/-) alleles of the p53 tumor suppressor gene. Our lab, which focuses on nutrition (particularly energy balance/obesity) and molecular carcinogenesis, has shown in p53-/- mice that calorie restriction (CR) increases the latency of spontaneous tumor development (mostly lymphomas) similar to75%, decreases serum insulin-like growth factor (IGF)-1 and leptin levels, and induces apoptosis in immature (lymphoma-susceptible) thymocytes. In heterozygous p53-deficient (p53+/-) mice, CR and a one day/wk fast each significantly delay spontaneous tumor development (a mix of lymphomas, sarcomas, and epithelial tumors) and decreases serum IGF-1 and leptin levels, even when begun late in life. We are presently comparing and combining CR and exercise (treadmill and running wheel) to further elucidate the relationships between energy balance, p53, and tumorigenesis in these models. Furthermore, we have capitalized on the susceptibility of p53+/- mice to chronic, low-dose aromatic amine-induced bladder carcinogenesis to develop a model for evaluating bladder cancer prevention approaches. Using this model, we have established that IGF-1 mediates many of the anti-cancer effects of CR. We are currently conducting oligonucleotide microarray studies to further characterize diet-gene interactions underlying the anti-cancer effects of CR and to determine which of the CR-responsive genes are IGF-1 dependent.