The reduction of plasma IGF-1 and the reduced mitogenic actions of IGF-1 may be related to the delayed occurrence of fatal neoplastic disease observed in both AL Ames dwarf and CR wild-type mice due to the substantial evidence suggesting that GH and IGF-1 levels play important roles in tumor development through their potent mitogenic and anti-apoptotic effects (9). This evidence concerns the gene GH1 and neoplasm.