The NPC risk associated with the CYP2E1 polymorphism was estimated for each study by odds ratios (OR) together with its 95 % confidence interval (CI), respectively.
The fact that Human nasopharynx expresses CYP2E1 suggests that CYP2E1 may play an important role in the course of NPC by indirect carcinogens nitrosamines.
Nitrosamine consumption and polymorphisms in CYP2E1, the product of which is involved in the activation of nitrosamines into reactive intermediates, have been shown to be associated with nasopharyngeal carcinoma (NPC) risk.
The higher RR found for the same genotype in distinct populations confirmed that CYP2E1 is one of several NPC susceptibility genes and that the RsaI minus variant is one mutation that affects phenotype.
Individuals homozygous for an allele of the CYP2E1 gene that is detected by Rsa I digestion (c2 allele) were found to have an increased risk of nasopharyngeal carcinoma (relative risk [RR] = 2.6; 95% confidence interval [CI] = 1.2-5.7); this effect was limited to nonsmokers (RR = 9.3; 95% CI = 2.7-32) and was not affected by alcohol consumption.
Similarly, subjects homozygous for the variant form of the CYP2E1 gene by RsaI digestion were at 7.7-fold excess risk of developing NPC (95% confidence interval = 0.87-68).