Genetic susceptibility of nasopharyngeal carcinoma

Abstract

Nasopharyngeal carcinoma (NPC) is a rare tumor in most parts of the world but occurs at relatively high rates among Chinese (30-50 per 100,000 people/year). The disease also occurs at moderate frequencies (3-10 per 100,000 people/year) in several non-Chinese ethnic groups such as Malays, Thai and Vietnamese. Emigrant Chinese population in several countries continue to show a higher incidence of NPC than the respective indigenous populations. Numerous factors, such as environment and genetics, have been associated with the risk of developing NPC. The environmental factors include infection with the Epstein-Barr virus (EBV), as well as frequently consumption high level of nitrosamine from preserved food such as salted fish. In addition, host fac tors also play a major role for NPC development. Unique alleles of human leukocyte antigen (HLA) and cytochrome P4502E1 (CYP2E1) have been shown to be associated with high relative risk from several Asia ethnic groups and Chinese in Taiwan, respectively. This study evaluated whether EBV receptor (CR2), polymeric immunoglobulin receptor (pIgR), and CYP2E1 were NPC susceptibility genes. The first two genes may involve the mechanism of EBV infection into nasopharyngeal epithelium. The CYP2E1 is an enzyme involved in the metabolic activation of various procarcinogens especially nitrosamine. A case-control study was conducted on 255 cases diagnosed with NPC and 297 healthy controls including Thai, Chinese, and Thai-Chinese in Thailand to evaluate the correlation between the polymorphism of each gene and NPC. The similar role of CYP2E1 as in Taiwan was revealed in this study from people living in Thailand [RR = 2.10; 95%CI = 0.90-4.96], Whereas relative risk of CR2 in this study did not reveal statistical significance, the pIgR showed its potential to be a susceptibility gene of NPC patients from total sample group [RR = 1.38; 95%C I = 1.05-1.82], and who have Chinese ancestor [RR = 2.81; 95%CI = 1.52-5.34], This data may indicate how EBV enters nasopharyngeal epithelium and why the disease has high frequency in Chinese population.