Besides studies of the PPARα knockout mice [106, 107], other approaches to determine the PPARα transcriptome includes overexpression studies in fibroblasts [16], exposure of hepatoma cell lines to synthetic PPARα agonist [108], and in vivo examinations of the alterations in the gene expression pattern of mouse and monkey liver [109, 110] and mouse intestine [111] in response to agonist treatment. This evidence concerns the gene PPARA and hepatocellular carcinoma.