Background: Epstein-Barr virus (EBV) has been proposed to be closely associated with nasopharyngeal carcinoma (NPC). To evaluate the actual relationship, EBV was analyzed in nine established NPC cell lines and in four original NPC biopsy specimens.
Experimental design: We used Southern blot analysis alone or after polymerase chain reaction to determine whether EBV was present in our NPC cell lines. We also used in situ nucleic acid hybridization and in situ polymerase chain reaction to identify EBV in 4 original biopsy specimens. For comparison, we investigated the cell lines for the presence of human papilloma virus type 16 (HPV-16) and human cytomegalovirus (HCMV).
Results: Southern blots alone for detection of 3 viruses in 9 cell lines were all negative. PCR plus Southern blotting revealed that 5 cell lines contained EBV in earlier passages, and all became negative in later passages. Some cell lines also contained HPV-16 and HCMV. At earlier passages, some cell lines contained EBV, HPV-16, and HCMV concurrently. Three out of four biopsy specimens contained EBV in certain tumor cells, lymphocytes, and glandular epithelia.
Conclusions: These findings indicate that EBV, HPV-16, and HCMV may be present in certain NPC cell lines and in only a small fraction of each positive cell line, and that a cell line may contain these three viruses concurrently. EBV is present not only in a fraction of tumor cells, but also in some lymphocytes and glandular epithelia in biopsy specimens. It is present as an episomal form but not as an integrated form in the infected cells, suggesting that the carcinogenesis of non-EBV containing NPC tumor cells is not related to EBV infection.