Is the development of adenoma and carcinoma in proximal colon related to apolipoprotein E phenotype?

BACKGROUND & AIMS: Alterations in plasma lipoprotein levels and bile acid metabolism observed in patients with colorectal adenoma and carcinoma may reflect a genetic background predisposing to altered lipid metabolism and tumors. This study was designed to determine whether the polymorphism of apolipoprotein E, one of the key regulatory proteins in cholesterol metabolism, is associated with proximal or distal colonic neoplasia. METHODS: Apolipoprotein E phenotype was determined in 135 patients with colorectal adenoma, 122 patients with colorectal carcinoma, and 199 randomly selected control subjects. RESULTS: The frequency of the epsilon 4 allele of apolipoprotein E was low (0.075 and 0.073) in patients with proximal adenoma and those with carcinoma, respectively, compared with the control subjects (0.181) (P < 0.05). In patients with distal tumors, there was no alteration in epsilon 4 frequency. In all subjects with the epsilon 4 allele compared with subjects without epsilon 4, the odds ratio for proximal adenoma was 0.36 (95% confidence interval, 0.14-0.89), and the odds ratio for proximal carcinoma was 0.35 (95% confidence interval, 0.14-0.86). CONCLUSIONS: The data suggest that the epsilon 4 allele of apolipoprotein E provides protection from the development of adenoma and carcinoma of the proximal colon. These results support the theory that there are common susceptibility genes modulating the susceptibility to external carcinogenic factors.