| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Regular Articles |
From the Department of Pathology, City of Hope National Medical Center, Duarte, California
| Abstract |
|---|
|
|
|---|
| Introduction |
|---|
|
|
|---|
The importance of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in the development of hepatocellular carcinoma (HCC) has been well established by epidemiological and molecular studies.7,8 Epidemiological studies have also shown that EBV infection often overlaps with HBV and HCV infections where the incidence of HCC is high, such as in Africa, Japan, and Taiwan. Sugawara and colleagues9 recently demonstrated that EBV DNA could be detected in 37% of Japanese HCC patients by Southern blot hybridization. In a second study, EBV DNA was detected in 33% of cases of HCV-associated HCC in Japanese patients by polymerase chain reaction (PCR) assay.10 These results suggest that EBV may play a role in the carcinogenesis of HCC.
The incidence of EBV infection in American HCC patients has not been studied. We investigated EBV expression in 41 HCC patients from the Los Angeles area, studying EBV viral proteins (LMP-1, EBNA-1, ZEBRA) by immunohistochemistry, EBV viral RNA (EBER-1) by in situ hybridization, and the presence of EBV viral DNA (LMP-1 and EBNA-4) by PCR assay.
| Materials and Methods |
|---|
|
|
|---|
Cases of HCC (primary and metastatic) were found in the surgical
pathology file at the Department of Pathology at City of Hope National
Medical Center. Forty-one cases were selected from the years 1974 to
1999. The tissues had been routinely fixed in 10% neutral formalin and
embedded in paraffin. One paraffin tissue block with tumor was selected
from each case. The cases were also examined for unusual number of
lymphocytes (including plasmacytoid lymphocytes), which are defined as
clusters or sheets of small lymphoid cells accounting for
10% of
tumor volume, either within the tumor or at the infiltrating edges. The
clinical data and hepatitis serum testing results were abstracted from
the medical record. The serum HBV antigen test was performed in all 41
patients, whereas the serum HCV antibody test was performed in 29
patients after 1990.
EBER-1 in Situ Hybridization
The in situ hybridization study methods have been previously described.11 Briefly, we used a probe from a region of the EBV genome that is actively transcribed in latently infected cells, a 30-base oligonucleotide complementary to a portion (bp 69 to 98) of the EBER-1 gene. The sequence was 5'-AGA CAC CGT CCT CAC CAC CCG GGA CTT GTA-3' (Operon Technologies, San Pablo, CA). The probe was labeled with biotin at its 3' end. Paraffin sections were deparaffinized and digested with pronase (nuclease-free). Sections were incubated with prehybridization solution and then hybridized with sheared salmon sperm and yeast tRNA along with the appropriate amount of probe. The probe was used at a concentration of 0.25 ng/µl with overnight hybridization. Sections were then incubated in a solution of avidin-alkaline phosphatase conjugate, washed for 3 minutes, incubated in McGadeys substrate, briefly washed in distilled water, air-dried, and coverslipped. No counterstain was used. A poly d(T) was used as a control for total RNA preservation, and a known EBV-positive case of nasopharyngeal carcinoma was used as a positive control. A case was considered positive if the nucleus, or nucleus and cytoplasm, of a tumor cell stained dark blue or black.
EBNA-1, LMP-1, and ZEBRA Immunohistochemistry
Dr. Grasser (Abteilung Virologie, Institut fur Medizinische Mikrobiologie und Hygiene and Institut fur Pathologie, Universitaatakliniken des Saarlandes, Homburg, Germany) kindly provided the rat monoclonal antibody clone 2B4 to EBV EBNA-1.12 We also used two other antibodies, mouse monoclonal antibody clone CS1-4 to LMP-1 protein (DAKO, Carpinteria, CA) and clone BZ.1 to ZEBRA (BamHI Z fragment, Epstein-Barr-replication activator) protein (DAKO). EBNA-1, LMP-1, and ZEBRA immunohistochemistry were performed in all 41 cases of HCC. Paraffin sections were deparaffinized and rehydrated in a graded alcohol series. Two of the antibodies required heat-induced epitope retrieval using 100 mmol/L of ethylenediaminetetraacetic acid buffer (pH 8.0) or 10 mmol/L citrate buffer (pH 6.0), for EBNA-1 and ZEBRA, respectively, in a steamer (Black and Decker, Shelton, CT) at 100°C for 20 minutes. The sections were then incubated with 2B4 at 1:500 dilution at room temperature overnight, with CS1-4 at 1:320, or with BZ.1 at 1:20 dilution at room temperature for 40 minutes and washed three times (5 minutes each) with phosphate-buffered saline (PBS) buffer. The sections were then incubated with a biotinylated goat, anti-rat antibody (Vector Laboratories, Burlingame, CA) (for EBNA-1) at a dilution of 1:150, or biotinylated goat, anti-mouse/anti-rabbit antibody (Ventana Medical Systems, Tucson, AZ) (for LMP-1 and ZEBRA) at a dilution of 1:8, followed by application of two washes (5 minutes each) of PBS buffer, followed by avidin-biotin complex (Vector). The slides were counterstained with hematoxylin. Sections of known EBV-positive classical Hodgkins disease were used as positive controls for EBNA-1 and LMP-1, and tissue sections of infectious mononucleosis were used as a positive control for ZEBRA. Positive staining was interpreted as nuclear or granular nuclear (EBNA-1), membrane and cytoplasmic (LMP-1), or nuclear (ZEBRA) in the tumor cells.
PCR Studies for EBNA-4 and EBV-LMP-1
Viral genomic DNA was extracted from formalin-fixed, paraffin-embedded tumor tissues, using 0.2 mg/ml of proteinase K digestion buffer overnight, followed by denaturation by boiling. The PCR studies were performed with 2 µl of extracted DNA in a 30-µl mixture containing 50 mmol/L KCl, 10 mmol/L Tris buffer, pH 8.3, 50 µm of each deoxynucleotide triphosphate, 2.5 mmol/L MgCl2, 1 U of Taq polymerase (Perkin Elmer, Foster City, CA), and 20 pmol of each primer. We used primers for EBNA-4 that flank the DNA region coding for epitopes of 399 to 408 and 416 to 424 of the prototype B95.8 EBV virus, using the nucleotide positions 96541 to 96540 and nucleotide positions 96770 to 96751 (EBV GenBank Accession Number V01555), respectively: EBNA-4 + 5'-GAG GAG GAA GAC AAG AGT GG-3' and EBNA-45'-GAT TCA GGC GTG GCT CTT GG-3'. The expected EBNA-1 PCR product size was 230 bp. We also used primers for the EBV-LMP-1 gene that flank the site of the characteristic 30-bp deletion of LMP-1 gene, using the nucleotide positions 168350 to 168331 and nucleotide positions 168190 to 168209 (EBV GenBank Accession Number V01555), respectively: LMP-1 + 5'-CGG AAG AGG TTG AAA ACA AA-3' and LMP-25'-GTG GGG GTC GTC ATC ATC TC-3'. The expected LMP-1 gene product size was 161 bp. After initial denaturation for 5 minutes at 95°C, 45 amplification cycles were performed as follows: denaturing at 94°C for 30 seconds, annealing at 58°C for 30 seconds, and extension at 72°C for 40 seconds. A final extension at 72°C for 7 minutes completed the PCR amplification. The PCR setup and the work after PCR were performed in separate laboratories to minimize the possibility of contamination. Primers flanking ß-globin gene were used as a positive control for DNA preservation (expected PCR product size was 268 bp), whereas a known EBV-positive case of T/NK cell lymphoma was used as a positive control.
| Results |
|---|
|
|
|---|
The ages of the patients ranged from 16 to 89 years old with a mean age of 58 years and a median age of 62 years. Sixteen of 41 were Asians (39%) and 25 were Caucasians. One third were women (13 of 41) and two-thirds were men (28 of 41). Paraffin sections of all 41 cases contained invasive HCC; 11 were well differentiated, 21 were moderately differentiated, and 10 were poorly differentiated. Of the 41 cases, 22 were wedge resection or autopsy specimens, and 19 were liver biopsy specimens. For the wedge resection and autopsy specimens, the tumor size ranged from 1.5 cm to 24 cm with a mean size of 9.8 cm.
Incidence of HBV and HCV Infection
Sixteen of 41 cases were seropositive for HBV and 9 of 29 cases
(after 1990) were seropositive for HCV. In total, 22 of the 41 cases
were seropositive for HBV and/or HCV. Of 22 cases with evidence of HBV
and/or HCV infection, only 1 case showed evidence of EBNA-1 positivity
(case 3 in Table 1
) by
immunohistochemistry. Eleven of 22 patients were Asians and 11 were
Caucasians. The incidence of HBV and/or HCV infection was higher in
Asian-American HCCs (69%, 11 of 16) than in Caucasian-American HCCs
(44%, 11 of 25).
|
Forty-one cases of HCC were hybridized with poly d(T) and EBER-1.
All cases showed strong nuclear positivity for poly d(T) (control for
RNA preservation). Of the 41 cases, only 1 case showed nuclear
positivity for EBER-1 (Table 1
and Figure 1
). In this case, rare nuclei of the
infiltrating lymphocytes were positive, whereas the tumor cell nuclei
were negative. The EBER-1-positive cells constituted <0.1% of the
total cell population.
|
Two of the 41 cases of HCC were positive for EBNA-1, showing a
granular nuclear staining (Table 1
and Figure 2A
). Tumor cells, and not lymphocytes,
were positive for EBNA-1. The percentage of EBNA-1-positive tumor cells
was <0.1% of the total tumor cells in both positive cases. One of the
41 cases showed nuclear positivity for ZEBRA in rare lymphocytes
(<0.1%) (Figure 2B)
. None of the 42 cases was positive for LMP-1.
|
DNA from formalin-fixed and paraffin-embedded tissues of all 41 cases were purified and amplified with primers flanking EBV-LMP-1, EBNA-4, and ß-globulin (control for DNA preservation). Strong ß-globin amplified bands were identified from all 41 cases, indicating that the quality and quantity of the purified DNAs were good. None of the 41 cases showed amplified EBV-LMP-1 or EBNA-4 DNA bands.
Correlation of EBV Gene Expression with Lymphocytic Infiltration
Eleven of the 41 cases (27%) of HCC showed a prominent lymphoplasmacytic infiltrate. In these cases, the majority of the infiltrating lymphocytes were located between tumor nodules. Prominent lymphocytic infiltration was present in the EBER-positive case, the ZEBRA-positive case, and one of two EBNA-1-positive cases.
Co-Expression of EBV Genes in HCC
Of the four (4 of 41) EBV-positive cases, none co-expressed more
than one EBV viral gene (Table 1)
.
EBV Gene Expression in Different Ethnic Groups
The two EBNA-1-positive HCCs both occurred in Asian patients (2 of 16, 12.5%). The ZEBRA-positive HCC and the EBER-1-positive HCC occurred in Caucasians (1 of 25, 4% each).
| Discussion |
|---|
|
|
|---|
1 in
1000 to 1 in 10,000 lymphocytes are EBV-positive in EBV-seropositive
individuals.15
Only a small population of latently
infected B-lymphocytes enters the lytic cycle, marked by expression of
nuclear ZEBRA protein. Case 1 and case 2 (Table 1)EBNA-1 immunohistochemistry, using the 2B4 monoclonal antibody, gave granular nuclear staining in rare neoplastic cells in two cases of HCC. Neither of these two cases was positive for any other EBV gene products, nor did PCR studies reveal evidence of EBV genomes in the tissues. We cannot rule out the possibility that these signals are nonspecific and not actually reflective of the presence of EBV. The 2B4 monoclonal antibody has shown nonspecific staining in various EBV-negative tissue samples, including normal breast tissue, and in various other epithelia.16,17
In two separate studies, Sugawara and colleagues9,10 detected EBV DNA in 37% and 40% of HCCs in Japanese population by PCR (detecting EBV BamHI W sequences) and Southern blot hybridization, respectively. The majority of these Japanese HCCs had evidence of HBV and HCV infection. The incidence of EBV positivity in HCV-positive HCC was found be much higher than HBV-positive HCCs (by a 10:1 ratio). The authors concluded that the EBV-infected HCCs might use the BamHI Q promoter to transcribe the EBNA-1 gene, but not other EBNA, EBER, LMP, or ZEBRA genes. This novel restricted EBNA-1 latent gene expression in HCC tissues has not yet been reported in other EBV-infected cells or malignancies. Two human tumors that are associated with restricted EBNA-1 expression are Burkitts lymphoma18 and gastric carcinoma.19 However, EBERs are always expressed in these two malignancies. Whether the restricted EBNA-1 expression in HCC is a novel, previously unidentified latency pattern remains to be resolved.
There are several differences in experimental design between the current study and the study by Sugawara and colleagues, including the use of different PCR primers, a different patient population, and the HCV status in HCC.10 They amplified the BamHI W region of EBV DNA by PCR, whereas in current study, we amplified EBV-LMP-1 and EBNA-4 DNA. The BamHI W region is reiterated 7 to 12 times in the EBV genome, thus providing a good target for the detection of EBV in a sample in which a small viral copy number might be expected.20 Unlike the BamHI W region, there is only one copy of LMP-1 DNA and one copy of EBNA-4 DNA in EBV genome. However, after 45 cycles of PCR amplification, the differences between amplified BamHI W DNA and amplified LMP-1 and EBNA-4 DNAs may be minimal. We have not had difficulty identifying evidence of EBV infection in other EBV-associated neoplasms using an identical technique.4,21-23 Therefore, we do not think that the choice of PCR primers should significantly affect the overall results. Furthermore, EBV DNA was also detected by Southern blot hybridization in one Japanese study, indicating a relatively high level of EBV that should certainly have been detected by PCR if present.
Geographical variation in the frequency of EBV infection has been
observed in many EBV-associated neoplasms, including nasopharyngeal
carcinoma, Burkitt lymphoma, and Hodgkins disease. For example, the
incidence of EBV infection in African Burkitt lymphoma is much higher
than in many other parts of the world, and the incidence of
EBV-associated Hodgkins lymphoma is higher in Latin America than in
developed countries.22,24
There are few studies directly
comparing EBV-associated gastric carcinoma in Japanese
versus American patients, although EBV involvement has been
observed in
7% of gastric carcinoma in Japan,25
16%
in Los Angeles,21
and 10.2% in Japanese American man and
women in Hawaii.26
Therefore, the limited epidemiological
data on EBV infection in Japanese and American gastric carcinomas
cannot explain why the EBV infection rate is higher (30 to 40%) in
Japanese HCCs than in American HCCs. The highest recorded rate of HCC
in America occurs among ethnic Asians (American-Chinese or
American-Japanese) in Los Angeles.27
Yet, in the current
study, we did not observe an increased EBV infection rate in
Asian-American HCCs, nor did we observe difference in the EBV infection
rate between Asian-American HCCs and non-Asian-American HCCs from the
Los Angeles area. Thus it seems that ethnic background may not play a
significant role in the frequency of EBV infection in HCC.
In the study by Sugawara and colleagues,9
31 of 35 cases
(80%) of Japanese HCC had HCV and/or HBV infection. In the current
study, we observed
60% of American HCC patients had HBV and/or HCV
infection. In addition, the incidence of HBV and/or HCV antigenemia in
American patients with HCC is >90%.28
Thus the hepatitis
virus status should not have affected the final results of EBV
infection in American HCC patients. Pathological studies have shown
that >80% of patients with HCC have cirrhosis.29
HCC is
unusual in patients with primary chronic viral hepatitis but is common
when the cirrhosis is secondary to chronic viral
hepatitis.27
Epidemiological studies have suggested that
most cases of cirrhosis associated with HCC were caused by infection
with HBV and HCV. Therefore, chronic hepatitis-associated cirrhosis per
se seems to predispose to HCC,30
whereas the possibility
of direct carcinogenic effects of HBV and HCV are still under
study.31
EBV EBNA-1 has been proposed to play an indirect
role in the carcinogenesis of HCC by enhancing HCV
replication.32
Therefore, the co-infection EBV and HCV may
contribute to HCC in the Japanese population by inducing hepatic
cirrhosis.
| Footnotes |
|---|
Accepted for publication June 18, 2001.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
H-J Delecluse, R Feederle, B O'Sullivan, and P Taniere Epstein Barr virus-associated tumours: an update for the attention of the working pathologist J. Clin. Pathol., December 1, 2007; 60(12): 1358 - 1364. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. L. Glaser, J. L. Hsu, and M. L. Gulley Epstein-Barr Virus and Breast Cancer: State of the Evidence for Viral Carcinogenesis Cancer Epidemiol. Biomarkers Prev., May 1, 2004; 13(5): 688 - 697. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. zur Hausen, J. van Beek, E. Bloemena, F. J. ten Kate, C. J. L. M. Meijer, and A. J. C. van den Brule No role for Epstein-Barr virus in Dutch hepatocellular carcinoma: a study at the DNA, RNA and protein levels J. Gen. Virol., July 1, 2003; 84(7): 1863 - 1869. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |