Potential role for peroxisome proliferator activated receptor (PPAR) in preventing colon cancer.
BACKGROUND
Peroxisome proliferator activated receptors (PPARs) are nuclear hormone receptors involved in genetic control of many cellular processes. PPAR and PPAR have been implicated in colonic malignancy. Here we provide three lines of evidence suggesting an inhibitory role for PPAR in colorectal cancer development.


METHODS
Levels of PPAR mRNA and protein in human colorectal cancers were compared with matched non-malignant mucosa using RNAse protection and western blotting. APC(Min)/+ mice were randomised to receive the PPAR activator methylclofenapate 25 mg/kg or vehicle for up to 16 weeks, and small and large intestinal polyps were quantified by image analysis. The effect of methylclofenapate on serum stimulated mitogenesis (thymidine incorporation), linear cell growth, and annexin V and propidium iodide staining were assessed in human colonic epithelial cells.


RESULTS
PPAR (mRNA and protein) expression levels were significantly depressed in colorectal cancer compared with matched non-malignant tissue. Methylclofenapate reduced polyp area in the small intestine from 18.7 mm(2) (median (interquartile range 11.1, 26.8)) to 9.90 (4.88, 13.21) mm(2) (p=0.003) and in the colon from 9.15 (6.31, 10.5) mm(2) to 3.71 (2.71, 5.99) mm(2) (p=0.009). Methylclofenapate significantly reduced thymidine incorporation and linear cell growth with no effect on annexin V or propidium iodide staining.


CONCLUSIONS
PPAR may inhibit colorectal tumour progression, possibly via inhibition of proliferation, and may be an important therapeutic target.
Jackson
L
L
Wolfon Digestive Diseases Centre, University of Nottingham, UK.
Wahli
W
W
Michalik
L
L
Watson
S A
SA
Morris
T
T
Anderton
K
K
Bell
D R
DR
Smith
J A
JA
Hawkey
C J
CJ
Bennett
A J
AJ
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology; D002992:Clofenapate / Q000494:pharmacology; D015179:Colorectal Neoplasms / Q000235:genetics / Q000517:prevention & control*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007417:Intestinal Polyps / Q000235:genetics / Q000517:prevention & control*; D008024:Ligands; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000235:genetics; D011897:Random Allocation; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured
D016588:Anticarcinogenic Agents; D008024:Ligands; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D002992:Clofenapate