title: Etiological factors of nasopharyngeal carcinoma.
abstract: Nasopharyngeal carcinoma (NPC) is a common disease among southern Chinese. The major etiological factors proposed for NPC pathogenesis include genetic susceptibility, environment factors and EBV infection. In the high risk population, genetic susceptibility to NPC has been mapped to the HLA loci and adjacent genes in MHC region on chromosome 6p21. Consumption of preserved food including salted fish has been implicated in its etiology in earlier studies. Its contribution to pathogenesis of NPC remains to be determined. A decreasing trend of NPC incidence was observed in Hong Kong, Taiwan and Singapore in recent years which may be accounted by a change of dietary habits. A comprehensive epidemiological study will help to elucidate the relative importance of various risk factors in the pathogenesis of NPC. Despite the close association of EBV infection with NPC, the etiological role of EBV in NPC pathogenesis remains enigmatic. EBV infection in primary nasopharyngeal epithelial cells is uncommon and difficult to achieve. EBV does not transform primary nasopharyngeal epithelial cells into proliferative clones, which contrasts greatly with the well-documented ability of EBV to transform and immortalize primary B cells. Genetic alterations identified in premalignant nasopharyngeal epithelium may play crucial roles to support stable EBV infection. Subsequently, latent and lytic EBV gene products may drive clonal expansion and transformation of premalignant nasopharyngeal epithelial cells into cancer cells. Stromal inflammation in nasopharyngeal mucosa is believed to play an important role in modulating the growth and possibly drive the malignant transformation of EBV-infected nasopharyngeal epithelial cells. Furthermore, there are increasing evidences supporting a role of EBV infection to evade host immune surveillance. EBV-infected cells may have selective growth advantages in vivo by acquiring a stress-resistance phenotype. Understanding the etiological factors and pathogenesis of NPC will contribute effectively to the prevention and treatment of this disease.
authors.affiliation: Department of Anatomy and Center for Cancer Research, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: gswtsao@hku.hk.
authors.forename: Sai Wah
authors.initials: SW
authors.lastname: Tsao
authors.affiliation: Department of Anatomy and Center for Cancer Research, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Yim Ling
authors.initials: YL
authors.lastname: Yip
authors.affiliation: Department of Anatomy and Center for Cancer Research, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Chi Man
authors.initials: CM
authors.lastname: Tsang
authors.affiliation: Department of Anatomy and Center for Cancer Research, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Pei Shin
authors.initials: PS
authors.lastname: Pang
authors.affiliation: Department of Anatomy and Center for Cancer Research, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Victoria Ming Yi
authors.initials: VM
authors.lastname: Lau
authors.affiliation: Department of Anatomy and Center for Cancer Research, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region.
authors.forename: Guitao
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Anatomical and Cellular Pathology and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: kwlo@cuhk.edu.hk.
authors.forename: Kwok Wai
authors.initials: KW
authors.lastname: Lo
mesh_terms: D002681:China / Q000453:epidemiology; D020031:Epstein-Barr Virus Infections / Q000150:complications; D020022:Genetic Predisposition to Disease; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D015995:Prevalence
keywords: EBV; Etiology; Immune evasion; Nasopharyngeal carcinoma; Stromal inflammation