Peroxisome proliferator-activated receptors in tumorigenesis: Targets of tumour promotion and treatment

The peroxisome proliferator-activated receptors (PPAR) are ligand-activated transcription factors. There are three genes that code for the PPAR isoforms: PPAR alpha, PPAR beta and PPAR gamma. In the present review, studies characterizing the various PPAR isoforms are discussed. Peroxisome proliferator-activated receptor alpha has been implicated in the lipid-lowering effects of the fibrate drugs. Peroxisome proliferator-activated receptor gamma has a clear role in adipocyte differentiation and is therapeutically targeted by the thiazolidinedione drugs for the treatment of type II diabetes. The physiological role of PPAR beta is less well understood but, as described in the present review, recent studies have implicated it with a role in colon cancer. In the present review, particular attention is focused on the role of PPAR in the regulation of expression of proteins associated with cell cycle control and tumorigenesis.