title: Efficient immortalization of primary nasopharyngeal epithelial cells for EBV infection study.
abstract: Nasopharyngeal carcinoma (NPC) is common among southern Chinese including the ethnic Cantonese population living in Hong Kong. Epstein-Barr virus (EBV) infection is detected in all undifferentiated type of NPC in this endemic region. Establishment of stable and latent EBV infection in premalignant nasopharyngeal epithelial cells is an early event in NPC development and may contribute to its pathogenesis. Immortalized primary nasopharyngeal epithelial cells represent an important tool for investigation of EBV infection and its tumorigenic potential in this special type of epithelial cells. However, the limited availability and small sizes of nasopharyngeal biopsies have seriously restricted the establishment of primary nasopharyngeal epithelial cells for immortalization. A reliable and effective method to immortalize primary nasopharyngeal epithelial cells will provide unrestricted materials for EBV infection studies. An earlier study has reported that Bmi-1 expression could immortalize primary nasopharyngeal epithelial cells. However, its efficiency and actions in immortalization have not been fully characterized. Our studies showed that Bmi-1 expression alone has limited ability to immortalize primary nasopharyngeal epithelial cells and additional events are often required for its immortalization action. We have identified some of the key events associated with the immortalization of primary nasopharyngeal epithelial cells. Efficient immortalization of nasopharyngeal epithelial cells could be reproducibly and efficiently achieved by the combined actions of Bmi-1 expression, activation of telomerase and silencing of p16 gene. Activation of MAPK signaling and gene expression downstream of Bmi-1 were detected in the immortalized nasopharyngeal epithelial cells and may play a role in immortalization. Furthermore, these newly immortalized nasopharyngeal epithelial cells are susceptible to EBV infection and supported a type II latent EBV infection program characteristic of EBV-infected nasopharyngeal carcinoma. The establishment of an efficient method to immortalize primary nasopharyngeal epithelial cells will facilitate the investigation into the role of EBV infection in pathogenesis of nasopharyngeal carcinoma.
authors.affiliation: Cancer Biology Laboratory, Department of Anatomy, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Pokfulam, Hong Kong SAR, China.
authors.forename: Yim Ling
authors.initials: YL
authors.lastname: Yip
authors.forename: Pei Shin
authors.initials: PS
authors.lastname: Pang
authors.forename: Wen
authors.initials: W
authors.lastname: Deng
authors.forename: Chi Man
authors.initials: CM
authors.lastname: Tsang
authors.forename: Musheng
authors.initials: M
authors.lastname: Zeng
authors.forename: Pok Man
authors.initials: PM
authors.lastname: Hau
authors.forename: Cornelia
authors.initials: C
authors.lastname: Man
authors.forename: Yuesheng
authors.initials: Y
authors.lastname: Jin
authors.forename: Anthony Po Wing
authors.initials: AP
authors.lastname: Yuen
authors.forename: Sai Wah
authors.initials: SW
authors.lastname: Tsao
mesh_terms: D002277:Carcinoma; D002461:Cell Line, Transformed; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D020031:Epstein-Barr Virus Infections / Q000378:metabolism* / Q000473:pathology; D005260:Female; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System; D008297:Male; D009296:Nasal Cavity / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D009297:Nasal Mucosa / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000378:metabolism / Q000473:pathology / Q000821:virology; D010614:Pharynx / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D063150:Polycomb Repressive Complex 1 / Q000378:metabolism; D017735:Virus Latency
chemical_list: C069077:BMI1 protein, human; D063150:Polycomb Repressive Complex 1