Biomedical Engineering Reference
In-Depth Information
10
Clinical Applications of Plasma Epstein-Barr Virus DNA
Analysis and Protocols for the Quantitative Analysis
of the Size of Circulating Epstein-Barr Virus DNA
K. C. Allen Chan and Y. M. Dennis Lo
Summary
Nasopharyngeal carcinoma (NPC) is one of the most common cancers in Southern
China. Epstein-Barr virus (EBV) infection is an important etiological factor of NPC. The
fact that EBV genome is present in almost all NPC tissues renders it an ideal tumor
marker for NPC. To date, quantitative analysis of plasma EBV DNA has been shown to
be clinically useful for the detection, monitoring, and prognostication of NPC. In addi-
tion, the molecular nature of circulating EBV DNA has recently been identified as that
of free DNA fragments; it is not contained inside intact virions. By quantitative size
analysis, it is further demonstrated that more than 80% of these DNA fragments are less
than 180 bp in size. In this chapter, the clinical applications of plasma EBV DNA analysis
and the protocols for the quantitative analysis of the size of circulating EBV DNA will be
discussed.
Key Words:
EBV DNA; NPC; plasma DNA; size analysis.
1. Introduction
Epstein-Barr virus (EBV) has been implicated in the pathogenesis of several
cancers including nasopharyngeal carcinoma (NPC) and some lymphomas
(
1
)
.
In Southern China, EBV genome could be demonstrated in almost all NPC
tumor tissues
(
2
,
3
)
. Although EBV infection is closely associated with NPC,
initially, the idea of using circulating EBV DNA for the detection of NPC
was not very popular among scientists because of the high prevalence of EBV
infection in Southeast Asia. More than 95% of adults living in this area have
been infected by EBV
(
4
)
and the virus would reside in some resting B-lympho-
cytes in a latent state
(
1
)
. Therefore, scientists believed that EBV DNA would
be detectable in a high proportion of healthy individuals. However, in 1998,
