A dietary enzyme: alpha-methylacyl-CoA racemase/P504S is overexpressed in colon carcinoma.

Epidemiological studies have shown that consumption of red meat increases the risk of developing colon cancer. An enzyme, alpha-methylacyl CoA racemase (AMACR), also known as P504S, plays an important role in peroxisomal beta-oxidation of branched-chain fatty acids from red meat and dairy products. High expression of AMACR was recently found in prostate cancer. In this study, we investigated expression of AMACR in 242 cases of colonic tumors including 176 colorectal carcinomas, 38 colon adenomas and 28 hyperplastic (non-neoplastic) polyps by immunohistochemical analysis. The mRNA levels of AMACR expression in normal and colon cancer tissues were assessed by real-time PCR. Significant up-regulation of AMACR mRNA was found in colon carcinomas compared to normal tissue. There was very low or no expression of AMACR protein in normal colon, but AMACR was highly expressed in 76 and 75% of well and moderately differentiated colon carcinomas, respectively, and in 79% of adenomas. In contrast, only 4% of hyperplastic polyps expressed AMACR. Since this enzyme is involved in the metabolism of branched-chain fatty acids from beef, milk and dairy products, our results provide important molecular information regarding a possible link between diet and development of colon cancer. AMACR may also serve as a molecular marker for colon cancers and its precursor lesions.