In the present study, we cross-bred nestin/IGF-I Tg mice, in which transgene expression starts prenatally and is detectable in the cerebellar primordium as early as embryonic day 13 [15], with Ptc1+/- mice, a faithful model of medulloblastoma recapitulating the histopathology of the human tumor. This evidence concerns the gene IGF1 and neoplasm.