[Study of sequence variations of Epstein-Barr virus LMP1 gene in nasopharyngeal carcinoma].
OBJECTIVE
To detect the sequence variations frequently found within the N- and C-terminal regions of Epstein-Barr virus (EBV) LMP1 gene in nasopharyngeal carcinoma (NPC) and to study the underlying mechanisms.


METHODS
Fresh tumor tissues were sampled from 63 patients with untreated NPC encountered in Affiliated Tumor Hospital of Sun Yat-sen University, Guangzhou. The N-terminal region of EBV LMP1 gene was amplified with nested polymerase chain reaction (PCR), followed by XhoI enzyme digestion. Nested PCR was also employed to detect the 30 base pairs deletion within the C-terminal region. Four-colored fluorescence terminator sequencing method was applied for bi-directional solid-phase sequencing of the 8 representative PCR products in 4 cases of NPC. The DNA sequence within the N- and C-terminal regions of LMP1 gene was then analyzed.


RESULTS
There were 4 patterns of sequence variations, namely, wt-XhoI/wt-LMP1 (4 cases, 6.3%), wt-XhoI and XhoI-loss/del-LMP1 (4 cases, 6.3%), wt-XhoI/del-LMP1 (5 cases, 7.9%) and XhoI-loss/del-LMP1 (50 cases, 79.5%), detected in the 63 studied cases. Sequence analysis showed that the EBV LMP1 gene had underwent non-synonymous and synonymous substitutions, as compared with the prototype of B95-8 cells. The ratio of non-synonymous to synonymous substitutions was 2.25.


CONCLUSIONS
XhoI-loss/del-LMP1 is the predominant sequence variation pattern of EBV LMP1 gene in NPC from Guangzhou. The XhoI-loss variation seems to develop on top of del-LMP1. When compared with the EBV LMP1 gene in peripheral blood B-lymphocytes of virus carriers and in preinvasive epithelial lesions (reported previously), it is likely that the sequence variation patterns of LMP1 gene may represent 4 different phases of intrahost evolution of EBV during nasopharyngeal carcinogenesis.
Department of Pathology, Affiliated Tumor Hospital of Sun Yat-sen University, Guangzhou 510060, China.
Su-xia
SX
Lin
Yong-sheng
YS
Zong
Min
M
Zhang
An-jia
AJ
Han
Bi-ling
BL
Zhong
Ying-jie
YJ
Liang
D000328:Adult; D000368:Aged; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D014644:Genetic Variation; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009303:Nasopharyngeal Neoplasms / Q000821:virology*; D017354:Point Mutation; D017422:Sequence Analysis, DNA; D014763:Viral Matrix Proteins / Q000235:genetics*
D004279:DNA, Viral; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D014763:Viral Matrix Proteins; C034510:CTCGAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific