Recent studies suggest a potential role of lipid lowering drugs, fibrates and statins, in anticancer treatment. One candidate for tumor chemoprevention is fenofibrate, which is a potent agonist of peroxisome proliferator activated receptor alpha (PPARalpha). Our results demonstrate elevated expression of PPARalpha in the nuclei of neoplatic cells in 12 out of 13 cases of medulloblastoma, and of PPARgamma in six out of 13 cases. Further analysis demonstrated that aggressive mouse medulloblastoma cells, BsB8, express PPARalpha in the absence PPARgamma, and human medulloblastoma cells, D384 and Daoy, express both PPARalpha and PPARgamma. Mouse and human cells responded to fenofibrate by a significant increase of PPAR-mediated transcriptional activity, and by a gradual accumulation of cells in G1 and G2/M phase of the cell cycle, leading to the inhibition of cell proliferation and elevated apoptosis. Preincubation of BsB8 cells with fenofibrate attenuated IGF-I-induced IRS-1, Akt, ERKs and GSK3beta phosphorylation, and inhibited clonogenic growth. In Daoy and D384 cells, fenofibrate also inhibited IGF-I-mediated growth responses, and simultaneous delivery of fenofibrate with low dose of the IGF-IR inhibitor, NVP-AEW541, completely abolished their clonogenic growth and survival. These results indicate a strong supportive role of fenofibrate in chemoprevention against IGF-I-induced growth responses in medulloblastoma.