title: Hypothesis: a novel route for immortalization of epithelial cells by Epstein-Barr virus.
abstract: Transfection of primate tissue explants with a specific sub-fragment (p31) of EBV DNA results in epithelial (but no other) cells proliferating indefinitely (becoming 'immortalized') without evidence of a 'growth crisis'. Molecular evidence supports integration of viral information into the host chromosome, and an early genotypic alteration involving specific amplification of a sub-component (IR1) of p31 DNA, followed by apparent loss of viral DNA from chromosomes, consistent with a 'hit and run' mechanism. However, analysis at the individual cell level during long-term culture, by FISH techniques, reveals chromosomal alterations, and viral sequences surviving within double minute (DM) bodies. Changing growth patterns occurring at different stages during propagation (>a year in culture) may be explained by sporadic reintegration of surviving viral DNA into the host chromosome. Notably, throughout culture, telomere lengths in chromosomal DNAs do not alter but rather retain the length observed in the primary cell populations. Introduction of a growth stimulating function of EBV, BARF1, into the immortalized, non-clonable epithelial cells under conditions which permit overexpression, allows clonal populations to be derived. Based on the data, mechanisms of immortalization, in the absence of a proven viral oncogene in p31 DNA, and possible genes involved, are considered.
authors.affiliation: Viral Oncology Unit, Department of Medicine, Imperial College of Science, Technology and Medicine, Norfolk Place, London W2 1PG, UK.
authors.forename: Yanning
authors.initials: Y
authors.lastname: Gao
authors.forename: Yong-Jie
authors.initials: YJ
authors.lastname: Lu
authors.forename: Shao-An
authors.initials: SA
authors.lastname: Xue
authors.forename: Honglin
authors.initials: H
authors.lastname: Chen
authors.forename: Nina
authors.initials: N
authors.lastname: Wedderburn
authors.forename: Beverly E
authors.initials: BE
authors.lastname: Griffin
mesh_terms: D000818:Animals; D002144:Callithrix; D002460:Cell Line; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D002875:Chromosomes / Q000648:ultrastructure; D002999:Clone Cells; D004279:DNA, Viral / Q000032:analysis; D004847:Epithelial Cells / Q000166:cytology / Q000648:ultrastructure / Q000821:virology*; D005784:Gene Amplification; D004854:Herpesvirus 4, Human / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008957:Models, Genetic; D016615:Telomere / Q000648:ultrastructure; D016662:Virus Integration
chemical_list: D004279:DNA, Viral