Consistent Sequence Variation of Epstein-Barr Virus Nuclear Antigen 1 in Primary Tumor and Peripheral Blood Cells of Patients with Nasopharyngeal Carcinoma

• Published in: Clinical cancer research 2002-08, Vol.8 (8), p.2586-2590
• Main Authors: WANG, Wen-Yi, CHIEN, Yi-Chih, JAN, Jian-Sheng, CHUEH, Chun-Mei, LIN, Jin-Ching
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Carcinoma - mortality; Carcinoma - virology; DNA, Viral; Epstein-Barr Virus Nuclear Antigens - genetics; Humans; Lymphocytes - virology; Medical sciences; Models, Genetic; Nasopharyngeal Neoplasms - mortality; Nasopharyngeal Neoplasms - virology; Otorhinolaryngology (head neck, general aspects and miscellaneous); Otorhinolaryngology. Stomatology; Point Mutation; Polymerase Chain Reaction; Sequence Analysis, DNA; Species Specificity; Treatment Outcome; Tumors
• ISSN: 1078-0432; 1557-3265

Purpose: Nasopharyngeal carcinoma (NPC) has been provenas 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. Experimental Design: 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.