Consistent sequence variation of Epstein-Barr virus nuclear antigen 1 in primary tumor and peripheral blood cells of patients with nasopharyngeal carcinoma.
OBJECTIVE
Nasopharyngeal carcinoma (NPC) has been proven as a cancer associated with Epstein-Barr virus (EBV). This study was performed to examine sequence variations of the EBV nuclear antigen 1 gene (EBNA-1) in primary tumor and peripheral-blood cells of NPC patients from Taiwan.


METHODS
DNA extracted from freshly frozen tumor tissues and corresponding peripheral-blood cells of 13 previously untreated NPC patients were subjected to PCR and direct sequencing using EBNA-1-specific primers. We compared the sequence data and analyzed the clinical outcomes.


RESULTS
We obtained a 100% positive-detection rate of EBV DNA in the primary tumors of all patients irrespective of the degree of differentiation. The EBNA-1 gene of all tumor samples was the "V-val" strain, showing the same clustered point mutations. They included 21 nucleotide exchanges, leading to 14 amino-acid mutations and 6 silent exchanges, relative to B95-8 cell line. Two of 13 tumors exhibited an additional point mutation at codon 585. EBV DNA was also detected in peripheral-blood cells of 9 of 13 patients under our experimental conditions. Direct-sequencing data showed match alterations of EBNA-1 gene between the primary tumor and peripheral-blood cells. Tumor relapse was observed in four of nine patients with detectable EBNA-1 DNA in their peripheral-blood cells, whereas none of the four patients without detectable EBNA-1 DNA in their peripheral-blood cells developed tumor relapse.


CONCLUSIONS
Results of the current study represents the first demonstration of consistent sequence variation of EBNA-1 in primary tumors and peripheral-blood cells. Clinical observations support that the presence of EBV DNA in the peripheral-blood cells may arise from disseminated cancer cells, resulting in a higher relapse rate and poor prognosis.
Wang
Wen-Yi
WY
Department of Basic Medicine, Hung Kuang Institute of Technology, Taichung, Taiwan.
Chien
Yi-Chih
YC
Jan
Jian-Sheng
JS
Chueh
Chun-Mei
CM
Lin
Jin-Ching
JC
D002277:Carcinoma / Q000401:mortality / Q000821:virology*; D004279:DNA, Viral; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics*; D006801:Humans; D008214:Lymphocytes / Q000821:virology; D008957:Models, Genetic; D009303:Nasopharyngeal Neoplasms / Q000401:mortality / Q000821:virology*; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D016896:Treatment Outcome
D004279:DNA, Viral; D019309:Epstein-Barr Virus Nuclear Antigens; C417029:EBV-encoded nuclear antigen 1