Alterations of the p53 gene in Epstein-Barr virus-associated immunodeficiency-related lymphomas

Worldwide Prevalence of Epstein-Barr Virus in Patients with Burkitt Lymphoma: A Systematic Review and Meta-Analysis

Burkitt lymphoma (BL) is a form of B-cell malignancy that progresses aggressively and is most often seen in children. While Epstein-Barr virus (EBV) is a double-stranded DNA virus that has been linked to a variety of cancers, it can transform B lymphocytes into immortalized cells, as shown in BL. Therefore, the estimated prevalence of EBV in a population may assist in the prediction of whether this population has a high risk of increased BL cases. This systematic review and meta-analysis aimed to estimate the prevalence of Epstein-Barr virus in patients with Burkitt lymphoma. Using the appropriate keywords, four electronic databases were searched. The quality of the included studies was assessed using the Joanna Briggs Institute's critical appraisal tool. The results were reported as percentages with a 95% confidence interval using a random-effects model (CI). PROSPERO was used to register the protocol (CRD42022372293), and 135 studies were included. The prevalence of Epstein-Barr virus in patients with Burkitt lymphoma was 57.5% (95% CI: 51.5 to 63.4, n = 4837). The sensitivity analyses demonstrated consistent results, and 65.2% of studies were of high quality. Egger's test revealed that there was a significant publication bias. EBV was found in a significantly high proportion of BL patients (more than 50% of BL patients). This study recommends EBV testing as an alternative for predictions and the assessment of the clinical disease status of BL.

Helicobacter pylori and Epstein-Barr Virus Co-Infection in Gastric Disease: What Is the Correlation with p53 Mutation, Genes Methylation and Microsatellite Instability in a Cohort of Sicilian Population?

Genetic predisposition, environmental factors, and infectious agents interact in the development of gastric diseases. Helicobacter pylori (Hp) and Epstein-Barr virus (EBV) infection has recently been shown to be correlated with these diseases. A cross-sectional study was performed on 100 hospitalized Italian patients with and without gastric diseases. The patients were stratified into four groups. Significant methylation status differences among CDH1, DAPK, COX2, hMLH1 and CDKN2A were observed for coinfected (Hp-EBV group) patients; particularly, a significant presence of COX2 (p = 0.0179) was observed. For microsatellite instability, minor stability was described in the Hp-HBV group (69.23%, p = 0.0456). Finally, for p53 mutation in the EBV group, exon 6 was, significantly, most frequent in comparison to others (p = 0.0124), and in the Hp-EBV group exon 8 was, significantly, most frequent in comparison to others (p < 0.0001). A significant positive relationship was found between patients with infection (Hp, EBV or both) and p53 mutation (rho = 0.383, p = 0.0001), methylation status (rho = 0.432, p < 0.0001) and microsatellite instability (rho = 0.285, p = 0.004). Finally, we observed among infection and methylation status, microsatellite instability, and p53 mutation a significant positive relationship only between infection and methylation status (OR = 3.78, p = 0.0075) and infection and p53 mutation (OR = 6.21, p = 0.0082). According to our analysis, gastric disease in the Sicilian population has different pathways depending on the presence of various factors, including infectious agents such as Hp and EBV and genetic factors of the subject.

IGFBP7-AS1 is a p53-responsive long noncoding RNA downregulated by Epstein-Barr virus that contributes to viral tumorigenesis

Epstein-Barr virus (EBV) is closely related to the development of several malignancies, such as B-cell lymphoma (B-CL), by the mechanism through which these malignancies develop remains largely unknown. We previously observed downregulation of the long noncoding RNA (lncRNA) IGFBP7-AS1 in response to EBV infection. However, the role of IGFBP7-AS1 in EBV-associated cancers has not been clarified. Here, we found that expression of IGFBP7-AS1, as well as its sense gene IGFBP7, is decreased in EBV-positive B-CL cells and clinical tissues. IGFBP7-AS1 stabilizes IGFBP7 mRNA by forming a duplex based on their overlapping regions. The tumour suppressor p53 transcriptionally activates IGFBP7-AS1 expression by binding to the promoter region of the lncRNA gene. The IGFBP7-AS1 expression is able to be rescued in EBV-positive cells in wild-type (wt) p53-dependent manner. IGFBP7-AS1 inhibits the proliferation and promotes the apoptosis of B-CL cells. Moreover, tumorigenic properties due to the depletion of IGFBP7-AS1 were restored by exogenous expression of IGFBP7 or wt-p53. Furthermore, the functional p53/IGFBP7-AS1/IGFBP7 axis facilitates apoptosis by suppressing the production and secretion of the NPPB signal peptide and further regulating the cGMP-PKG signalling pathway. This study demonstrates that EBV promotes tumorigenesis, particularly in B-CL progression, by downregulating the novel p53-responsive lncRNA IGFBP7-AS1.

Attenuating the p53 Pathway in Human Cancers: Many Means to the Same End

The p53 pathway is perturbed in the majority of human cancers. Although this most frequently occurs through the direct mutation or deletion of p53 itself, there are a number of other alterations that can attenuate the pathway and contribute to tumorigenesis. For example, amplification of important negative regulators, MDM2 and MDM4, occurs in a number of cancers. In this work, we will review both the normal regulation of the p53 pathway and the different mechanisms of pathway inhibition in cancer, discuss these alterations in the context of the global genomic analyses that have been conducted across tumor types, and highlight the translational implications for cancer diagnosis and treatment.

The Epstein-Barr Virus BART microRNAs target the pro-apoptotic protein Bim

In Epstein-Barr Virus infected epithelial cancers, the alternatively spliced BamHI A rightward transcripts (BARTs) are abundantly expressed and are the template for two large clusters of miRNAs. This study indicates that both of these clusters independently can inhibit apoptosis in response to etoposide in an epithelial cell line. The Bcl-2 interacting mediator of cell death (Bim) was identified using gene expression microarrays and bioinformatic analysis indicated multiple potential binding sites for several BART miRNAs in the Bim 3'UTR. Bim protein was reduced by Cluster I and the individual expression of several miRNAs, while mRNA levels were unaffected. In reporter assays, the Bim 3' untranslated region (UTR) was inhibited by both clusters but not by any individual miRNAs. These results are consistent with the BART miRNAs downregulating Bim post-transcriptionally in part through the 3'UTR and suggest that there are miRNA recognition sites within other areas of the Bim mRNA.

Epstein-Barr virus in Burkitt's lymphoma: a role for latent membrane protein 2A

Burkitt's lymphoma (BL) is characterized by translocation of the MYC gene to an immunoglobulin locus. Transgenic mouse models have been used to study the molecular changes that are necessary to bypass tumor suppression in the presence of translocated MYC. Inactivation of the p53 pathway is a major step to tumor formation in mouse models that is also seen in human disease. Human BL is often highly associated with Epstein-Barr virus (EBV). The EBV latency protein latent membrane protein 2A (LMP2A) is known to promote B cell survival by affecting levels of pro-survival factors. Using LMP2A transgenic mouse models, we have identified a novel mechanism that permits lymphomagenesis in the presence of an intact p53 pathway. This work uncovers a contribution of EBV to molecular events that have documented importance in BL pathogenesis, and may underlie the poorly understood link between EBV and BL.

Transcriptional downregulation of p27KIP1 through regulation of E2F function during LMP1-mediated transformation

LMP1 induces the phenotypic transformation of fibroblasts and affects regulators of the cell cycle during this process. LMP1 decreases expression of the cyclin-dependent kinase inhibitor p27 and increases the levels and phosphorylation of cyclin-dependent kinase 2 and the retinoblastoma protein. In the present study, the effects of LMP1 on cell cycle progression and the mechanism of p27 downregulation by LMP1 were determined. Although p27 is frequently regulated at the posttranscriptional level during cell cycle progression and in cancer, LMP1 did not decrease ectopically expressed p27. However, LMP1 did decrease p27 RNA levels and inhibited the activity of p27 promoter reporters. The LMP1-regulated promoter element was mapped to a region containing two E2F sites. Electrophoretic mobility shift assays determined that the regulated cis element bound an inhibitory E2F complex containing E2F4 and p130. These findings indicate that LMP1 decreases p27 transcription through effects on E2F family transcription factors. This property likely contributes to the ability of LMP1 to stimulate cell cycle progression.

Presence of simian virus 40 in diffuse large B-cell lymphomas in Tunisia correlates with germinal center B-cell immunophenotype, t(14;18) translocation, and P53 accumulation

Previously we have reported the presence of simian virus 40 DNA in 56% of diffuse large B-cell lymphomas in Tunisia. Here, we investigated the relationship between the status of simian virus 40 and t(14;18) translocation, germinal center status, and P53 and BCL2 expression to assess the clinical and biological relevance of simian virus 40 presence in diffuse large B-cell lymphomas. Therefore, we evaluated by immunohistochemistry the expression patterns of CD10, BCL6, MUM1, BCL2, and P53 in 86 diffuse large B-cell lymphomas (48 simian virus 40-positive and 38 simian virus 40-negative cases). The t(14;18) translocation was investigated by polymerase chain reaction. Immunostaining patterns for CD10, BCL6, and MUM1 were used to subclassify diffuse large B-cell lymphoma cases as germinal center or non-germinal center phenotypes. Germinal center phenotype, t(14;18), P53, and BCL2 expression were found in 71, 30, 55, and 65% of cases, respectively. Interestingly, germinal center phenotype, t(14;18), and P53 accumulation were found to be more frequent in simian virus 40-positive cases than in simian virus 40-negative ones (81, 44, 69 vs 58, 13, 37%; P=0.018, 0.002, and 0.003, respectively). However, there were no correlations between the presence of simian virus 40 and the expression of CD10, BCL6, MUM1 and BCL2, patient's age and gender, clinical stage, or the International Prognosis Index. Multivariate logistic regression analyses revealed that the germinal center phenotype, P53 accumulation, and t(14;18) were independent factors for simian virus 40 association (P=0.029, 0.006, and 0.014, respectively). There were no significant differences in overall survival regarding P53, BCL2, or t(14;18) status. However, patients with germinal center phenotype or low International Prognosis Index scores displayed a significantly better survival than those with non-germinal center phenotype or high International Prognosis Index scores (P=0.003 and 0.0001, respectively). These two prognosis factors remain independent in multivariate analyses (P=0.001 and <0.0001, respectively). Interestingly, among patients with germinal center phenotype, simian virus 40-positive subgroup displayed a significantly shorter survival than simian virus 40-negative subgroup (P=0.034). In summary, these findings support a role of simian virus 40 in the pathogenesis of diffuse large B-cell lymphomas. On other hand, they suggest that a significant proportion of diffuse large B-cell lymphoma cases with germinal center phenotype may result from early transformation by simian virus 40, mainly those harboring the t(14;18). Modern Pathology (2008) 21, 282-296; doi:10.1038/modpathol.3800993; published online 28 December 2007.

Analysis of p53 and Bak gene mutations in lymphoproliferative disorders developing in rheumatoid arthritis

PURPOSE

Individuals affected by rheumatoid arthritis (RA) occasionally develop lymphoproliferative disorders (RA-LPD). To study the molecular changes underscoring the RA-LPD, mutations of p53 and Bak gene were analyzed in RA-LPD with (MTX-LPD) or without methotrexate treatment for RA (non-MTX-LPD).

METHODS

Histology and immunophenotype were immunohistochemically examined in 32 cases of MTX-LPD and 21 of non-MTX-LPD. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) followed by direct sequencing was employed to detect the mutations of p53 and Bak gene.

RESULTS

Frequency of p53 mutations in non-MTX-LPD (47.6%) was significantly higher than that in MTX-LPD (15.6%) (P < 0.05). Among the cases with non-Hodgkin's lymphoma (NHL), the largest category of RA-LPD, the frequency of p53 mutations in the non-MTX-NHL (47.6%) was significantly higher than that in the MTX-NHL (14.8%) (P < 0.05). Interval between the onset of RA and LPD development was significantly longer in LPD with p53 gene mutations (median 228 months) than that without mutations (133 months). LPD with p53 gene mutations had more advanced diseases and an unfavorable prognosis than those without mutations.

CONCLUSIONS

MTX-LPD and non-MTX-LPD show similar findings in clinical characteristics, histology, EBV positive rate, and frequency of Bak gene mutations. Whereas the non-MTX-LPD is distinct from the MTX-LPD in its significantly higher p53 mutation frequency.

Genetic, epigenetic, and clinicopathologic features of gastric carcinomas with the CpG island methylator phenotype and an association with Epstein-Barr virus

BACKGROUND

The CpG island methylator phenotype (CIMP), which is characterized by simultaneous methylation of the CpG islands of multiple genes, has been recognized as one of the important mechanisms in gastrointestinal carcinogenesis.

METHODS

Methylation of the 5 methylated-in-tumors (MINT) loci and 12 tumor-related genes in 78 primary gastric carcinomas was examined using combined bisulfite-restriction analysis. Epstein-Barr virus (EBV)-associated gastric tumors were detected using real-time polymerase chain reaction analysis followed by an evaluation of the correlations between CIMP status, EBV-association, and genetic alteration of p53 and K-ras. The authors compared the clinicopathologic features of gastric carcinomas that had high CIMP methylation (CIMP-H) with tumors that had low CIMP methylation (CIMP-L) or negative CIMP methylation (CIMP-N).

RESULTS

The methylation profiles of 12 genes showed nonrandom methylation, supporting the presence of CIMP in gastric carcinoma. No p53 mutations were detected among CIMP-H tumors, and no EBV association was detected in tumors that showed mutation of p53 and K-ras. In a multiple logistic regression model with CIMP-H as the dependent variable, proximal location (P = .011), diffuse type (P = .019), and less advanced pathologic TNM status (P = .043) contributed significantly to CIMP-H. Patients who had CIMP-N gastric tumors had a significantly worse survival than patients who had CIMP-H tumors (P = .004) or CIMP-L tumors (P = .012). EBV-associated tumors were associated strongly with CIMP-H, hypermethylation of tumor-related genes, and no p53 or K-ras mutation.

CONCLUSIONS

CIMP status appeared to be associated with distinct genetic, epigenetic, and clinicopathologic features in gastric carcinomas. The finding that gastric carcinomas arose through different molecular pathways may affect not only tumor characteristics but also patient prognosis.

LMP1 signaling and activation of NF-kappaB in LMP1 transgenic mice

Transgenic mice expressing Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) under the control of an immunoglobulin heavy-chain promoter and enhancer develop lymphoma at a threefold higher incidence than LMP1-negative mice. In vitro, LMP1 activates numerous signaling pathways including p38, c-Jun N terminal kinase (JNK), phosphatidylinositol 3 kinase (PI3K)/Akt, and NF-kappaB through interactions with tumor necrosis receptor-associated factors (TRAFs). These pathways are frequently activated in EBV-associated malignancies, although their activation cannot be definitively linked to LMP1 expression in vivo. In this study, interactions between LMP1 and TRAFs and the activation of PI3K/Akt, JNK, p38, and NF-kappaB were examined in LMP1 transgenic mice. LMP1 co-immunoprecipitated with TRAFs 1, 2, and 3. Akt, JNK, and p38 were activated in LMP1-positive and -negative splenocytes as well as LMP1-positive and -negative lymphomas. Multiple forms of NF-kappaB were activated in healthy splenocytes from LMP1 transgenic mice, in contrast to healthy splenocytes from LMP1-negative mice. However, in both LMP1-positive and -negative lymphomas, only the oncogenic NF-kappaB c-Rel, was specifically activated. Similarly to EBV-associated malignancies, p53 protein was detected at high levels in the transgenic lymphomas, although mutations were not detected in the p53 gene. These data indicate that NF-kappaB is activated in LMP1-positive healthy splenocytes; however, NF-kappaB c-Rel is specifically activated in both the transgenic lymphomas and in the rare lymphomas that develop in negative mice. The LMP1-mediated activation of NF-kappaB may contribute to the specific activation of c-Rel and lead to the increased development of lymphoma in the LMP1 transgenic mice.

TP53 gene mutation, an unfavorable prognostic factor for malignant lymphomas in autoimmune diseases

OBJECTIVES

To investigate whether mutations of the TP53 tumor suppressor gene are associated with a poor prognosis in lymphoproliferative disorders (LPD) developing in patients with a history of autoimmune disease (AID).

METHODS

Fifty patients, 15 males and 35 females ranging in age from 23 to 83 (median, 61) years, were examined. Rheumatoid arthritis (21 cases) is the commonest type of AID followed by systemic lupus erythematosus (10), dermatomyositis (9), progressive systemic sclerosis (4), and autoimmune hemolytic anemia (6). The interval between the diagnosis of AID and LPD ranged from 1 to 660 months (mean 42 months). Histological, immunohistological, and in situ hybridization studies revealed that 37 tumors were B cell lymphomas and 13 were T cell lymphomas with the Epstein-Barr virus genome present in the tumor cells in 24% of cases. Stage of disease was I in 15 cases, II in 5, III in 9, and IV in 21.

RESULTS

Polymerase chain reaction-single strand conformation polymorphism followed by direct sequencing revealed TP53 mutations in 45.9% of B cell and 53.8% of T cell lymphomas. The follow-up study revealed an unfavorable prognosis in cases with mutations compared with those without: the 1-year survival rate was 43.5 and 73.0% in B cell and 16.7 and 50% in T cell lymphoma, respectively.

CONCLUSIONS

The occurrence of a TP53 mutation is an unfavorable prognostic factor not only in B cell but also in T cell LPD in AID.

p53 alterations in sequential biopsies of Asian follicular lymphoma: a study of immunohistochemical staining pattern and gene mutations by PCR-SSCP in paraffin-embedded tissues

AIM

Tumour suppressor gene p53 is a common target in carcinogenesis, reported to be altered and functionally inactive in 70% of human cancers. Although p53 mutations are less commonly present in haematological malignancies when compared with other solid tumours, they have been reported in histological transformation of follicular lymphoma. We aimed to investigate the frequency of p53 gene alterations in paraffin-embedded tissue using commercially available PCR-SSCP, and to correlate the results with P53 protein expression by immunohistochemistry.

METHODS

Surgical samples from seven patients with a total of 17 sequential biopsies were retrieved for the study of p53 gene expression using immunohistochemical stain, and gene status by PCR-SSCP for exons 5-8. The tumours were graded according to the WHO classification criteria. P53 was distinctly over-expressed in five transformed higher grade biopsies, and all except one showed electrophoretic mobility shift in PCR-SSCP analysis. Sequencing analysis revealed single nucleotide substitutions in three of four of these high-grade transformed cases with band shift (75%), whereas some other studies reported a lower frequency of 25-30%, and mobility shift result was found to correlate with P53 expression. Lower grade tumours without P53 over-expression did not demonstrate band shift, and sequencing analysis did not reveal mutations.

CONCLUSIONS

We demonstrated the feasibility of adopting PCR-SSCP for screening of p53 mutations in archival tissue samples in this study, and there is a strong correlation of p53 gene over-expression and mutation events in high-grade transformed tumours.

Higher frequency of p53 gene mutations in diffuse large B-cell lymphoma with MALT component

p53 gene mutation is not a frequent event in the tumorigenesis of lymphomas and the expression of p53 protein is independent of p53 gene mutations. The present study aimed to investigate mutations in the p53 gene in a series of extranodal B-cell lymphomas, and its association with p53 protein expression. A total of 52 cases were graded histologically into Grade 1, Grade 2 and Grade 3 tumors and p53 protein expression was detected using immunohistochemistry. Mutations in the p53 gene were analyzed using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and mobility shifts were confirmed by direct sequencing. The tumors comprised 26 (50%) Grade 1, 9 (17%) Grade 2 and 15 (29%) Grade 3. A high proportion of Grade 2 (25%) tumors expressed p53 protein (P = 0.051) and carried p53 gene mutation (33%) (P = 0.218). However, p53 protein expression was not associated with p53 gene mutations (P = 0.057). Transversion mutations (88%) were more frequently detected than transition mutations (12%). The present study revealed that p53 gene mutations and p53 protein expression occurred in higher frequencies in Grade 2 tumors, which may be of pathogenetic importance. The high frequency of transversion mutations may reflect the influence of an etiological agent in the tumorigenesis of mucosa-associated lymphoid tissue (MALT lymphoma).

Malignancies in organ transplant recipients

The development of cancer in organ transplant recipients is well known; depressed immunosurveillance induced by the use of immunosuppressive agents for prevention of rejection is a causative factor. The types of malignancies in renal transplant patients vary geographically and are influenced by the type of immunosuppressant used. In the present study in Japan, malignancies had developed in 2.6% of renal transplant recipients; the observed number/expected number ratio was 2.78. For the primary sites, the relative risk in Japan was quite different from that in Western countries, with a lower frequency of skin cancer, an absence of Kaposi's sarcoma and higher frequencies of renal and thyroid cancer in Japan. Epstein-Barr virus is an oncogenic virus causing lymphoproliferative disorders in immunocompromised hosts. In renal transplant recipients, who usually receive hemodialysis before transplantation, human T lymphotrophic virus (HTLV)-1 is also oncogenic and causes adult T-cell leukemia/lymphoma. The HTLV-1 in donor blood might be transmitted to transplant recipients via transfusion during hemodialysis. The epidemiology and characteristics of representative malignancies in transplant recipients are described, with a review of pertinent literature.

Epstein-Barr virus-associated composite lymphoma composed of peripheral T-cell lymphoma and an anaplastic variant of a diffuse large B-cell type of non-Hodgkin's lymphoma and strongly expressing p53 protein

We report a case of composite lymphoma consisting of peripheral T-cell lymphoma and an anaplastic variant of diffuse large B-cell lymphoma (DLBCL) and associated with Epstein-Barr virus (EBV) infection and strong p53 expression. A 65-year-old Japanese woman developed fever and generalized lymphadenopathy. A biopsy of the cervical node revealed the morphology of malignant lymphoma with 2 kinds of lymphoma coexisting in 1 lymph node. One lymphoma type consisted of immunoblastic large cells with the T-cell marker phenotype CD3+, CD45RO/UCHL-1+, CD20/L26-, CD79-, CD10-, CD30-, and CD15-; the other type consisted of large cells with abundant cytoplasm and pleomorphic nuclei with the marker phenotype CD79+, CD20/L26+, CD45RO/UCHL-1-, CD3-, CD10-, CD30+, NPM/ALK-, and CD15-. Therefore, the diagnosis was composite lymphoma of peripheral T-cell lymphoma and an anaplastic variant of DLBCL, stage IVB, because the patient had bone marrow involvement with peripheral T-cell lymphoma. The biopsy led to findings of latent type II EBV-associated lymphoma in both the peripheral T-cell lymphoma and the anaplastic variant of DLBCL as the result of positive signals for EBV small RNAs by in situ hybridization, positive immunostaining results for EBV latent membrane protein 1 antibody, and negative immunostaining results for EBV nuclear antigen 2. Immunostaining of the mass with p53 antibody also yielded positive results for both types of lymphoma cells. This case suggests that the immunocompromised state of this patient with EBV-related peripheral T-cell lymphoma allowed the emergence of an EBV-related anaplastic variant of DLBCL and suggests a close relationship between p53 expression and latent EBV infection.

A case of Epstein-Barr Virus (EBV)-associated thymic carcinoid and investigation of existence of EBV-infected cells in thymus and thymic tumors

We describe the first case of Epstein-Barr virus (EBV)-associated thymic carcinoid tumor found by in situ hybridization (ISH) on paraffin-embedded sections. ISH revealed that both tumor cells and infiltrated lymphocytes were EBV positive, while a few EBV-infected lymphocytes were detected in 2 of 11 thymuses and 1 of 11 thymomas.

Improvement in the detection rate of t(14;18) translocation on paraffin-embedded tissue: a combination approach using PCR and FISH

AIMS

PCR has been the primary method used for the detection of t(14;18) translocation in formalin-fixed, paraffin-embedded tissues. This technique mainly targets the well-characterised breakpoint regions in chromosomes 14 and 18. FISH is now applicable on paraffin tissue sections and has been suggested to be capable of detecting essentially 100% of t(14;18) translocated cases. In this study, we described the application of both PCR and FISH for the detection of t(14;18) translocation.

METHODS

Fifty follicular lymphoma cases were retrieved from the files of the Department of Pathology, University of Malaya Medical Centre (UMMC). Nested PCR amplification of MBR/JH and mcr/JH was performed in these cases, and those cases that did not demonstrate the translocation were subjected to FISH analysis.

RESULTS

Thirty cases (60%) had t(14;18) translocation detected by PCR, 25 (50%) had breakpoint with MBR and five (10%) involved mcr. Twenty cases without detectable t(14;18) translocation by PCR were analysed by FISH. Eleven cases were successfully probed, and four of them showed positive translocation signal.

CONCLUSIONS

The combination of PCR and FISH analysis on paraffin tissue sections for the detection of t(14;18) translocation increases the sensitivity of detection from 60 to 68%. Problems encountered in our FISH analysis on tissue sections impose certain limitations in using this technique for retrospective screening of large number of samples. Therefore, we suggested the application of PCR as the first screening tool on retrospective archival materials, followed by FISH on those PCR-negative cases.

Does the correlation between EBNA-1 and p63 expression in breast carcinomas provide a clue to tumorigenesis in Epstein-Barr virus-related breast malignancies?

Several investigators have identified Epstein-Barr virus (EBV) particles in breast carcinomas, a fact that supports a role for EBV in mammary tumorigenesis. The possible mechanism involved in this process is not clear. The present study was carried out in an attempt to determine whether there is a relationship between latent infection with EBV and p53 and p63 expression in breast carcinomas. Immunohistochemistry developed with 3.3-diaminobenzidine tetrahydrochloride was performed in 85 formalin-fixed paraffin-embedded breast carcinomas using anti-EBV EBNA-1, anti-p63, anti-p53, anti-estrogen receptor (ER) and anti-progesterone receptor (PR) antibodies. The cases were selected to represent each of the various histologic types: intraductal carcinoma (N=12), grade I invasive ductal carcinoma (N=15), grade II invasive ductal carcinoma (N=15), grade III invasive ductal carcinoma (N=15), tubular carcinoma (N=8), lobular carcinoma (N=10), and medullary carcinoma (N=10). The ductal breast carcinomas were graded I, II and III based on the Scarff-Bloom and Richardson grading system modified by Elston and Ellis. One slide containing at least 1000 neoplastic cells was examined in each case. ER, PR, p63, p53 and EBNA-1 were positive in 60, 40, 11.8, 21.2 and 37.6% of carcinomas, respectively. There was a correlation between EBNA-1 and p63 expression (P<0.001), but not between EBNA-1 and p53 (P=0.10). These data suggest a possible role for p63 in the mammary tumorigenesis associated with Epstein-Barr virus infection.

Epstein-Barr virus-associated anaplastic large cell variant of diffuse large B-cell-type non-Hodgkin's lymphoma with concurrent p53 protein expression

In the new World Health Organization (WHO) classification of malignant lymphoma, anaplastic large cell lymphoma of B-cell phenotype is classified either as the anaplastic large cell variant of diffuse large B-cell lymphoma or as Hodgkin's lymphoma. A 71-year-old Japanese man developed fever and generalized lymphadenopathy. Biopsy of the right axillary node revealed morphology of malignant lymphoma in which large cells with abundant cytoplasm and pleomorphic nuclei were scattered among small lymphocytes. Immunostaining with various monoclonal antibodies revealed the large cells to be CD79+, CD20/L26+, CD45RO/UCHL-(1-), CD3-, CD10-, CD30+, NPM/ALK-, EMA-, CD15-, and bcl-(2-). Amplification of the J region of the immunoglobulin heavy chain by polymerase chain reaction revealed a single rearranged band. Therefore the diagnosis of anaplastic large cell variant of diffuse large B-cell lymphoma, stage IIIB, was made from the standpoint of the new WHO classification of malignant lymphoma. Biopsy led to findings of Epstein-Barr virus (EBV)-associated lymphoma with positive in situ hybridization results for EBV small RNAs, positive results of immunostaining with EBV latent membrane 1 antibody, and negative results of immunostaining with Epstein-Barr nuclear antigen 2. Results of immunostaining of the mass with p53 antibody also were positive for lymphoma cells. The findings in this case may suggest a close relationship between p53 expression and latent EBV infection.

Gene mutations in lymphoproliferative disorders of T and NK/T cell phenotypes developing in renal transplant patients

Post-transplantation lymphoproliferative disorder (PT-LPD) is characterized by lymphoid proliferation after organ or bone marrow transplantation. In Western countries, most cases of PT-LPD are B-cell-derived and Epstein-Barr virus-associated, in which alterations of c-myc, p53, and N-ras genes might play a role in disease progression. In Japan, PT-LPD of T- and NK/T-cell types are not uncommon in renal transplant patients. Mutations of p53 (exons 4 through 8), K-ras (exons 1 and 2), c-kit (exons 11 and 17), and beta-catenin genes (exon 3) in 12 cases of these diseases were analyzed by PCR single strand conformation polymorphism and then by direct sequencing. p53 gene mutations were detected in 5 of 5 cases of peripheral T-cell lymphoma, 3 (60%) of 5 cases of adult T-cell leukemia/lymphoma, and 1 of 2 cases of NK/T cell lymphoma. Twenty-five percent of T and NK/T cell lymphomas showed K-ras mutations. Mutations of c-kit and beta-catenin genes were found in 33% of cases. Among a total of 42 substitution mutations, 40 were transitions with involvement of CpG sites in 20 to 30% of cases. Most cases had at least one mutation that changed an amino acid, which might have provided the selection pressure for expansion. These findings suggested that p53 gene mutations might play a central role in development of peripheral T-cell lymphoma including adult T-cell leukemia/lymphoma in renal transplant patients.

Antiviral approaches for cancers related to Epstein-Barr virus and human papillomavirus

Epstein-Barr virus and human papillomaviruses (HPV) are DNA viruses underlying the carcinogenesis of 15-20% of human cancers worldwide. Viral oncoproteins are involved in malignant transformation and maintenance of the malignant phenotype, mainly through interaction between oncoproteins and products of tumour-suppressor genes. The use of vaccines to prevent the occurrence of HPV-related cancers is being investigated. Several approaches have been used to inhibit expression of viral oncoproteins. The first strategy uses antisense oligodeoxynucleotides against viral oncoproteins; downregulation of the oncoproteins can influence tumour cell growth and restore sensitivity to cytotoxic agents. Another approach uses antiviral drugs such as acyclic nucleoside phosphonates; inhibition of virus replication can lead to downregulation of viral oncoproteinsand ultimately reactivate tumour-suppressor-gene pathways. In addition, the combination of acyclic nucleoside phosphonates with conventional cytotoxic agents is more effective than either agent alone. These data provide the basis for a novel anticancer strategy to improve the therapeutic ratio in virus-related cancers, which needs to be further investigated for clinical applications.

Pooled analysis of p53 mutations in hematological malignancies

A computerized database is described that contains information about 507 mutations in the p53 gene of hematologic tumors and corresponding cell lines. Analysis of these mutations indicated the following findings: First, mutational spectrum analysis in these tumors was found to be similar to the pattern found for other solid tumors. However, when the patterns of base substitutions were examined separately according to the types of hematologic malignancies, followed by subgroup analysis, notable differences (in some cases of statistical significance) emerged. Second, mutational pattern analysis indicates that about 48% of base substitutions in hematologic tumors are suspected to be associated with carcinogen exposure. Third, deletions and insertions are localized mainly to exons 5-8 and repeated DNA sequences. However, the unusual profile of variations in frequency within each type of tumor suggests that, in addition to endogenous damage to template DNA, there is the factor of exposure to environmental physical and chemical carcinogens/mutagens. Fourth, p53 protein alterations analysis indicate that most of the changes in the amino acids are "semiconservative," presumably in order to avoid disrupting the structure of the p53 monomer. Consistent with this notion, structural mutations are more conservative than the binding mutations. Finally, molecular mechanisms that lead to p53 mutations, etiological factors that play a role in their formation, and the pathophysiological significance of consequent p53 protein alterations are discussed.

Lymphomas in patients with connective tissue disease. Comparison of p53 protein expression and latent EBV infection in patients immunosuppressed and not immunosuppressed with methotrexate

Cell cycle dysregulation as measured by p53 protein expression and latent Epstein-Barr (EBV) infection are important in the pathogenesis of lymphoma, particularly in immunosuppressed patients. Although latent EBV commonly is detected in lymphomas arising in patients with connective tissue disease who are immunosuppressed with methotrexate, p53 protein expression has not been reported. We compared the immunohistologic expression of p53 protein and the incidence of latent EBV infection in lymphomas arising in patients with connective tissue disease treated and not treated with methotrexate. Increased p53 staining was detected in 10 of 11 lymphomas arising in patients after methotrexate therapy vs 5 of 11 in patients not treated with methotrexate. Latent EBV was detected in 7 of 13 lymphomas arising in patients after methotrexate therapy vs 2 of 11 in patients not treated with methotrexate. Concordant p53 expression and latent EBV were detected in 5 of 7 lymphomas arising after treatment with methotrexate, including 1 that regressed after methotrexate therapy was withdrawn. These findings suggest that cell cycle dysregulation and EBV-related transformation are important in the pathogenesis of lymphomas arising in patients with connective tissue disease who are immunosuppressed with methotrexate.

Epstein Barr virus-associated lymphoproliferative-disorders primarily involving the skin

In cases of solid organ or bone marrow transplantation, up to 2 to 10% of patients may develop lymphoproliferative disorders (LPD), often induced by Epstein-Barr virus (EBV). Despite a morphology mimicking malignant lymphoma, in some cases the lesions will disappear completely after the degree of immunosuppression is lowered. Lately, similar processes have been described in non-transplant, immunosuppressed patients. A SNOMED search was performed on the database of three hospitals between 1990 and 1997, to identify patients with immunosuppression-related lymphoproliferative disorders (IR-LPD) involving primarily the skin. Two patients were identified. One was 2 years after kidney transplantation, and the other was being treated with methotrexate for dermatomyositis. In both biopsies, there was a diffuse perivascular proliferation of large lymphocytes with ample cytoplasm and pleomorphic nuclei, associated with extensive dermal and subcutaneous necrosis. Immunohistochemical studies revealed expression of CD20, CD45RO, CD43, CD30, EBV-LMP1, and EBV-NA2 by the atypical lymphocytes in both cases and, in one case, of the EBV-transcriptional replication activation protein. In both cases the lesions completely disappeared and have not recurred. Primary involvement of the skin by IR-LPD is very rare. Based on our results, it is possible that some of these cases in the skin contain EBV and co-express CD30 and T- and B-cell markers. The diagnosis of IR-LPD should be considered in cutaneous lymphoid proliferations in immunosuppressed patients. Before rendering an unequivocal diagnosis of malignant lymphoma, reduction of immunosuppression and follow-up of 4-8 weeks should be considered.

Functional analysis of the p53 protein in AIDS-related non-Hodgkin's lymphomas and polymorphic lymphoproliferations

Alteration of the tumour suppressor gene p53 is frequent in AIDS-related non-Hodgkin's lymphomas (AIDS-NHL), particularly in Burkitt's or Burkitt's-like lymphomas (BL/BLL). Since mechanisms of inactivation other than mutations have been advanced, the transcriptional activity of the p53 protein was studied in a functional assay in yeast in a series of AIDS-NHL lesions and compared with their morphology, immunohistochemistry (IHC) and single-strand conformation polymorphism (SSCP) analysis detection of other p53 abnormalities, Epstein-Barr virus (EBV) status, MDM-2 oncoprotein expression and c-MYC rearrangement. Polymorphic lymphoproliferations (PL), identified as precursors of NHL in HIV-patients, were also analysed in attempt to detect p53 modifications related to clonal progression. The functional assay detected p53 mutants in 40% (12/ 30) of the tumours: 50% (6/12) of BL/BLL, 40% (4/10) of diffuse large cell lymphomas (DLCL) and 25% (2/8) of PL. An oligoclonal or monoclonal population was identified in the two PL cases with mutant p53. An accumulation of the p53 protein was detected by IHC in 26% (8/30) of the tumours (five BL/BLL and three DLCL) and was associated with positive functional assay. In the 20 lesions tested by both of the screening methods for mutations, a p53 mutant pattern was detected in 55% of cases (11/20) and in 25% of cases (5/ 20) respectively with the functional assay and SSCP analysis of exons 5-8. There was no inverse correlation between the detection of EBV genome and the presence of p53 mutations and no overexpression of MDM-2 protein for the whole series. In conclusion, the functional assay was more sensitive than IHC and SSCP for the detection of p53 mutations in tumour samples. The mutations identified in AIDS-NHL lesions inactivate the p53 protein and in PL they could represent a selection of an aggressive clone.

A noncanonical poly(A) signal, UAUAAA, and flanking elements in Epstein-Barr virus DNA polymerase mRNA function in cleavage and polyadenylation assays

Two forms of the Epstein-Barr virus DNA polymerase (pol) mRNA (3.7 and 5.1 kb) have been detected, neither of which contains a canonical poly(A) signal. The 5.1-kb pol mRNA, which contains a rare poly(A) signal, UAUAAA, studied only in transcripts of Hepadnaviridae and a plant pararetrovirus, was analyzed in cleavage and polyadenylation assays. Incubation of the pol transcript in cell extracts produced relatively low efficiency of cleavage (12 to 14%), which was improved by conversion of the poly(A) signal to AAUAAA. Deletion of the UAUAAA signal abolished cleavage and polyadenylation. An auxiliary element, UUUGUA, 3-8 nt upstream of the poly(A) signal and two downstream core elements, a GU-rich sequence 36-46 nt, and an AUUUGUGU sequence 47-53 nt downstream of the signal (8-19 nt and 20-28 nt downstream of cleavage site) facilitated processing of pol mRNA. Replacement of sequences near the cleavage/poly(A) site affected cleavage accuracy. Binding of the 64-kDa cleavage stimulatory factor to the U-rich as well as the GU-rich elements correlated with cleavage efficiency. Thus the UAUAAA hexanucleotide plus the other cis-acting elements are clearly functional in the native pol mRNA, but are relatively inefficient. Implications of the use of an anomalous poly(A) signal and its elements are discussed.

Epstein-Barr virus latent membrane protein 1 blocks p53-mediated apoptosis through the induction of the A20 gene

Two Epstein-Barr virus (EBV)-associated malignancies, nasopharyngeal carcinoma and posttransplant lymphoma, rarely have mutations in the p53 tumor suppressor gene, suggesting that a viral protein interferes with p53 function. The EBV oncogene, LMP1, induces expression of the cellular antiapoptotic genes bcl-2 and A20 and could in this way interfere with p53-mediated apoptosis. Two derivatives of the p53-null epithelial cell line H1299 were prepared, one of which (H1299-p53) stably expressed a temperature-sensitive (ts) p53 protein, and another (H1299-p53+LMP1) which stably expressed both ts-p53 and latent membrane protein 1 (LMP1). At the permissive temperature, the p53 protein in the H1299-p53 cell line transcriptionally activated two of its target genes, the cyclin-dependent kinase inhibitor p21 and the mdm2 gene product, in an LMP1-independent manner. Upon serum withdrawal at the permissive temperature, p53-mediated apoptosis was induced in 50 to 60% of the cells. In the H1299-p53 cell line which stably expressed LMP1, however, only 20 to 25% of the cells underwent apoptosis. While stable expression of LMP1 did not affect levels of bcl-2 family members in these cells, it did induce expression of A20. Stable expression of A20 in the H1299-p53 cell line inhibited p53-mediated apoptosis equivalent to inhibition by LMP1. The induction of A20 may underlie the ability of LMP1 to protect EBV-infected epithelial cells from p53-mediated apoptosis.

Epstein-Barr virus (EBV)-associated smooth-muscle tumor arising in a post-transplant patient treated successfully for two PT-EBV-associated large-cell lymphomas. Case report

The association of Epstein-Barr virus (EBV) with smooth-muscle tumors was recently reported in the setting of acquired immunodeficiency syndrome (AIDS) and post-transplantation. We report a case of an EBV-associated smooth-muscle tumor arising in a post-transplant (PT) patient who previously was treated successfully for two EBV-associated PT large-cell lymphomas. A 4-year-old girl required cardiac transplantation for dilated cardiomyopathy when she was aged 23 months. Her PT regimen included cyclosporine, azothiaprine, and diltiazem. At 16 months PT, she presented with anemia, guaiac-positive stools, and an abdominal mass diagnosed as diffuse large-cell lymphoma of B-cell phenotype. Immunosuppressive therapy was reduced, and interferon and i.v. immunoglobulin were initiated. She rapidly developed signs of rejection, and a cardiac biopsy was performed, revealing grade IIIB rejection. Subsequently, immunosuppressive therapy increased. At 23 months PT, a biopsy was done of a large pelvic mass that was diagnosed as immunoblastic large-cell lymphoma. After treatment with chemotherapy and retinoic acid, the size of the mass markedly decreased. Follow-up computed tomography scan revealed multiple liver nodules. A needle biopsy of the liver showed a smooth-muscle tumor of indeterminate grade. Both the lymphomas and the smooth-muscle tumor contained EBV within > 95% of tumor cells by Epstein-Barr (EBER1) in situ hybridization, were of strain type A by Epstein-Barr nuclear antigen-2 (EBNA-2) polymerase chain reaction (PCR) and contained an identical 30 base-pair deletion (amino acids 346-355) of the latent membrane protein (LMP)-1 oncogene by PCR analysis. Notably, the initial large-cell lymphoma and the subsequent immunoblastic lymphoma each contained a unique p53 mutation, suggesting that they were distinct. These data suggest that the same virus contributed to the pathogenesis of both the malignant lymphomas and the smooth-muscle tumor.

Epstein-Barr virus nuclear antigen 2 and latent membrane protein independently transactivate p53 through induction of NF-kappaB activity

B-cell immortalization by Epstein-Barr virus (EBV) is dependent on permanent control of the cellular processes which normally regulate cell division and apoptosis, functions possessed by p53 in a number of normal cell types. In studies initiated to evaluate relationships between EBV latent genes and p53, p53 levels were found to increase approximately 10-fold 4 to 5 days after EBV infection of purified resting human B cells; the induced p53 was transcriptionally active. Latent membrane protein 1 and, to a lesser extent, EBV nuclear antigen 2 mediated the increase in p53 levels via activation of the NF-kappaB transcription factor.

DNA damage in human B cells can induce apoptosis, proceeding from G1/S when p53 is transactivation competent and G2/M when it is transactivation defective

Cisplatin treatment of Epstein-Barr virus-immortalized human B lymphoblastoid cell lines (LCLs) results in p53-mediated apoptosis which occurs largely in a population of cells at the G1/S boundary of the cell cycle. Cell cycle progression appears to be required for this apoptosis because arresting cells earlier in G1 inhibited apoptosis despite the accumulation of p53. Overexpression of wild-type p53 also induces apoptosis in an LCL. Therefore six mutant genes derived from Burkitt's lymphoma (BL) cells were assayed for their ability to induce apoptosis when similarly overexpressed. The same genes were analysed in transient transfection assays for their ability to transactivate appropriate reporter plasmids. A correlation between the ability of p53 to transactivate and induce apoptosis was revealed. The only mutant capable of transactivation also induced apoptosis. Further analysis of the BL lines in which p53 had been characterized showed that whereas some lines were essentially resistant to cisplatin, three were rapidly induced to undergo apoptosis. All three have a single p53 allele encoding a mutant which is incapable of transactivation or (for two tested) mediating apoptosis when expressed in an LCL. Cell cycle analysis revealed that this apparently p53-independent apoptosis did not follow G1 arrest but in fact occurred largely in cells distributed in the G2/M phase of the cell cycle. These data suggest the existence of a second checkpoint in the G2 or M phase which, in the absence of a functional p53, is the primary point of entry into the apoptosis programme following DNA damage.

Posttranscriptional stabilization underlies p53-independent induction of p21WAF1/CIP1/SDI1 in differentiating human leukemic cells

p21WAF/CIP1/SDI1 is a recently identified gene expressed in cells harboring wild-type but not mutant p53 gene. It encodes a nuclear protein of 21 kD which inhibits cyclin-dependent kinase activity. Constitutive p21WAF1/CIP1/SDI1 mRNA expression was detected in neoplastic cells from patients with various hematological malignancies as well as in normal bone marrow mononuclear cells and in myeloid and lymphoid cell lines independent of their p53 status. Induced differentiation of the p53-deficient promyelocytic HL-60 cells along the monocytic lineage by phorbol ester or 1a,25 dihydroxyvitamin D3 resulted in a marked increase of both p21WAF1/CIP1/SDI1 mRNA and protein expression due to enhanced mRNA stability. Differentiation towards the granulocytic lineage by all-trans retinoic acid or dimethylsulfoxide failed to produce this effect. p21WAF1/CIP1/SDI1 is an immediate early gene since its upregulation occurred independently of de novo protein synthesis. The induction of p21WAF1/CIP1/SDI1 expression and its regulation in p53-deficient differentiating leukemic cells support the idea of an additional, p53-independent role of p21WAF1/CIP1/SDI1 in human hematopoiesis.

The p53 and mdm-2 genes in human testicular germ-cell tumors

Mutations in the p53 gene are common in many cancers. They have been documented to occur in about 55% of all cancers of 51 different cell and tissue types. These mutations are accompanied by overexpression of the p53 protein in the nucleus of the cell, and this protein has lost its tumor suppressor function. In this study, 25 testicular germ-cell (TGC) tumors were tested for p53 mutations and the level of p53 protein expression. While 67% of the tumors overproduced the p53 protein in the nucleus of 10-60% of their cells, in all cases the DNA sequence of exons 4-9 of the p53 gene was wild type. In this tumor type, there was apparently no selection pressure for p53 mutations. The mdm-2 gene residues on chromosome 12 (12q13-q14), a chromosome often altered in TGC tumors. mdm-2 gene amplification (2.5- to 10-fold) was detected in three (12%) of these TGC tumors. These three tumors, and eight additional TGC tumors, overexpressed mdm-2 mRNA. There was a good correlation between overexpression of p53 protein and overexpression of mdm-2 mRNA (P = 0.01). This may well result from the fact that the level of mdm-2 mRNA is regulated by the p53 level. These studies demonstrate that TGC tumors fail to be selected for p53 mutations but nonetheless frequently expressed high levels of wild-type p53 protein in the cell nucleus. Perhaps this produces the excellent response to radiation and chemotherapy of these tumors, which generally have a good prognosis. Wild-type p53 may mediate apoptosis in these cells in response to the DNA damage.