Establishment and characterization of two epithelial tumor cell lines (hne‐1 and hone‐1) latently infected with epstein‐barr virus and derived from nasopharyngeal carcinomas

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Abstract
Two epithelial tumor cell lines were established from biopsy specimens of 2 nasopharyngeal carcinomas (NPC) and designated HNE‐1 and HONE‐1. Uncloned HNE‐1 cells were found to be Epstein‐Barr virus (EBV) DNA‐positive when examined by Southern blot analysis up to passage 35, after which the EBV genome could no longer be detected. A similar loss of EBV DNA took place in uncloned HONE‐1 cells. However, HONE‐1 clone 40 cells are still EBV DNA‐positive up to passage 42 thus far and cell cultures contain 85–90% EBV nuclear antigen (EBNA)‐positive cells. The HNE‐1 cell line has been passaged more than 100 times and the uncloned HONE‐1 cells more than 90 times. The tumorigenicity of the HNE‐1 and HONE‐1 cells was demonstrated by tumor induction in nude mice. Karyotypic analysis of the HNE‐1 cells demonstrated an aneuploidy with a modal chromosomal number of 74 at passages 5 and 101 at passage 20; 18 marker chromosomes were identified. We have continued to map the EBV genome latently associated with the HNE‐1 and HONE‐1 cells using the Bam HI, EcoRI or Hind III restriction enzymes. Using EcoRI fragments A‐K as probes, we found that HNE‐1 EBV DNA is different from B95‐8 and HR‐1 EBV DNA in the EcoRI‐C region. The Bam HI map for HONE‐1 EBV DNA is very similar to the B95‐8 map; it contains the Bam HI‐Y fragment but without Bam HI B' and WI'. Differences were observed between HONE‐1 EBV DNA and B95‐8 DNA using the Hind III restriction enzyme. There was no evidence of spontaneous expression of the latent EBV genome in HNE‐1 cells, and attempts to induce replication of the latent EBV genome and rescue infectious virus have failed, suggesting a tightly restricted virus genome.