Liquid biopsy tracking during sequential chemo-radiotherapy identifies distinct prognostic phenotypes in nasopharyngeal carcinoma.

Liquid biopsies have the utility for detecting minimal residual disease in several cancer types. Here, we investigate if liquid biopsy tracking on-treatment informs on tumour phenotypes by longitudinally quantifying circulating Epstein-barr virus (EBV) DNA copy number in 673 nasopharyngeal carcinoma patients undergoing radical induction chemotherapy (IC) and chemo-radiotherapy (CRT). We observe significant inter-patient heterogeneity in viral copy number clearance that is classifiable into eight distinct patterns based on clearance kinetics and bounce occurrence, including a substantial proportion of complete responders (≈30%) to only one IC cycle. Using a supervised statistical clustering of disease relapse risks, we further bin these eight subgroups into four prognostic phenotypes (early responders, intermediate responders, late responders, and treatment resistant) that are correlated with efficacy of chemotherapy intensity. Taken together, we show that real-time monitoring of liquid biopsy response adds prognostic information, and has the potential utility for risk-adapted treatment de-intensification/intensification in nasopharyngeal carcinoma.

Proposed modifications and incorporation of plasma Epstein-Barr virus DNA improve the TNM staging system for Epstein-Barr virus-related nasopharyngeal carcinoma.

BACKGROUND: The prognosis of patients who have Epstein-Barr virus (EBV)-related nasopharyngeal carcinoma (NPC) in which the tumor tissues harbor EBV have a better prognosis than those without EBV-related NPC. Therefore, the eighth edition of the TNM staging system could be modified for EBV-related NPC by incorporating the measurement of plasma EBV DNA. METHODS: In total, 979 patients with NPC who received intensity-modulated radiotherapy (IMRT) were retrospectively reviewed. Recursive partitioning analysis was conducted based on tumor (T) classification, lymph node (N) classification, and EBV DNA measurement to derive objectively the proposed stage groupings. The validity of the proposed stage groupings was confirmed in a prospective cohort of 550 consecutive patients who also received with IMRT. RESULTS: The pretreatment plasma EBV DNA level was identified as a significant, negative prognostic factor for progression-free survival and overall survival in univariate analysis (all P < .001) and multivariate analysis (all P < .05). Recursive partitioning analysis of the primary cohort to incorporate EBV DNA generated the following proposed stage groupings: stage RI (T1N0), RIIA (T2-T3N0 or T1-T3N1, EBV DNA ≤2000 copies/mL), stage RIIB (T2-T3N0 or T1-T3N1, EBV DNA >2000 copies/mL; T1-T3N2, EBV DNA ≤2000 copies/mL), stage RIII (T1-T3N2, EBV DNA >2000 copies/mL; T4N0-N2), and stage RIVA (any T and N3). In the validation cohort, the 5-year progression-free survival rate was 100%, 87.9%, 76.7%, 68.7%, and 50.4% for proposed stage RI, RIIA, RIIB, RIII, and RIV NPC, respectively (P < .001). Compared with the eighth edition TNM stage groupings, the proposed stage groupings incorporating EBV DNA provided better hazard consistency, hazard discrimination, outcome prediction, and sample size balance. CONCLUSIONS: The proposed stage groupings have better prognostic performance than the eighth edition of the TNM staging system. EBV DNA titers should be included in the TNM staging system to assess patients who have EBV-related NPC.

Reactivation of Latent Epstein-Barr Virus: A Comparison after Exposure to Gamma, Proton, Carbon, and Iron Radiation.

Among the many stressors astronauts are exposed to during spaceflight, cosmic radiation may lead to various serious health effects. Specifically, space radiation may contribute to decreased immunity, which has been documented in astronauts during short- and long-duration missions, as evidenced by several changes in cellular immunity and plasma cytokine levels. Reactivation of latent herpes viruses, either directly from radiation of latently infected cells and/or from perturbation of the immune system, may result in disease in astronauts. Epstein‒Barr virus (EBV) is one of the eight human herpes viruses known to infect more than 90% of human adults and persists for the life of the host without normally causing adverse effects. Reactivation of several latent viruses in astronauts is well documented, although the mechanism of reactivation is not well understood. We studied the effect of four different types of radiation, (1) 137Cs gamma rays, (2) 150-MeV protons, (3) 600 MeV/n carbon ions, and (4) 600 MeV/n iron ions on the activation of lytic gene transcription and of reactivation of EBV in a latently infected cell line (Akata) at doses of 0.1, 0.5, 1.0, and 2.0 Gy. The data showed that for all doses used in this study, lytic gene transcription was induced and median viral loads were significantly higher for all types of radiation than in corresponding control samples, with the increases detected as early as four days post-exposure and generally tapering off at later time points. The viability and size of EBV-infected Akata cells were highly variable and exhibited approximately the same trend in time for all radiation types at 0.1, 0.5, 1.0, and 2.0 Gy. This work shows that reactivation of viruses can occur due to the effect of different types of radiation on latently infected cells in the absence of changes or cytokines produced in the immune system. In general, gamma rays are more effective than protons, carbon ions, and iron ions in inducing latent virus reactivation, though these high-energy particles did induce more sustained and later reactivation of EBV lytic gene transcription. These findings also challenge the common relative biological effectiveness concept that is often used in radiobiology for other end points.

The role of oxidative stress in EBV lytic reactivation, radioresistance and the potential preventive and therapeutic implications.

Epstein-Barr virus (EBV) is an important cancer causing virus. Cancer associated with EBV account for approximately 1.5% of all cancers, and represent 1.8% of all cancer deaths worldwide. EBV reactivation plays an important role in the development of EBV-related diseases and is closely related with patients' survival and clinical stages of EBV-related cancers. The therapy regarding to EBV-related cancers is very urgent, especially in endemic areas. Generating oxidative stress is a critical mechanism by which host cells defend against infection by virus. In addition, ROS-mediated oxidative stress plays a significant but paradoxical role acting as a "double-edged sword" to regulate cellular response to radiation, which is the main therapy strategy for EBV-related cancers, especially nasopharyngeal carcinoma. Therefore, in this review we primarily discuss the possible interplay among the oxidative stress, EBV lytic reactivation and radioresistance. Understanding the role of oxidative stress in EBV lytic reactivation and radioresistance will assist in the development of effective strategies for prevention and treatment of EBV-related cancers.

Integrative genomic and proteomic analyses identifies glycerol-3-phosphate acyltransferase as a target of low-dose ionizing radiation in EBV infected-B cells.

PURPOSE: We sought to gain a better understanding of the low-dose ionizing radiation (LDIR)-induced molecular changes in transformed pre-malignant cells in their microenvironment. MATERIALS AND METHODS: The cellular response to LDIR was compared and contrasted using immortalized human Epstein-Barr virus-infected B-cells (EBV-B) in mono-culture, co-culture with human bone marrow derived stromal cells (MSC), or under the LDIR-induced bystander effect. The resulting alterations in protein and gene expression (including microRNA, miRNA) were evaluated by isobaric tags for relative and absolute quantification (iTRAQ) proteomics assay, western blot, cDNA array and quantitative reverse transcription polymerase chain reaction (RT-PCR), respectively. RESULTS: The miRNAs let7a, miR-15b, miR-16, and miR-21, and a lipid metabolic miRNA hub miR-23b, were upregulated after LDIR exposure in the mono-cultured EBV-B cells, but were downregulated in EBV-B cells co-irradiated with MSC. A lipid biosynthesis enzyme glycerol-3-phosphate acyltransferase, the common target of these miRNA, was downregulated at the level of protein and mRNA expression in the LDIR-exposed, mono-cultured EBV-B cells and upregulated MSC co-cultured EBV-B cells. CONCLUSIONS: These results suggest a putative miRNA regulatory mechanism controlling the LDIR-induced stress response, and illustrate that LDIR exposure, and the cell's microenvironment, can affect specific gene expression, both directly and indirectly, resulting in altered protein expression.

Efficacy of the ND:YAG laser therapy on EBV and HSV1 contamination in periodontal pockets.

AIM: The aim of this retrospective multicenter study was to verify the efficacy of Nd:YAG laser in the treatment of periodontal pockets infected by Epstein-Barr Virus (EBV) and Herpes Simplex Virus 1 (HSV1). METHODS: Subgingival plaque samples of 291 Italian periodontal patients were analyzed by Real Time PCR to evaluate the frequency of both viruses before and after Nd:YAG laser-assisted periodontal treatment. RESULTS: Before treatment, EBV and HSV1 were observed in 29.9% and in 3.8% of periodontal patients respectively, while co-infection with both viruses was detected in 1.7% of cases. Periodontal Nd:YAG laser treatment ("Periodontal Biological Laser-Assisted Therapy", PERIOBLAST) produced statistical significant benefits, especially in EBV periodontal infection: 78.2% of EBV positive patients became EBV-negative following treatment. CONCLUSIONS: Results of this preliminary study highlight that EBV is found in periodontal pockets more frequently than HSV1, supporting the theory of the potential role of EBV in the onset and progression of periodontal disease. Moreover, our data showed that Nd:YAG laser-assisted periodontal treatment (Perioblast) is also effective in case of viral infection, validating evidences that it represents a successful alternative approach to traditional periodontal protocols.

Epstein-Barr virus glycoprotein gB and gHgL can mediate fusion and entry in trans, and heat can act as a partial surrogate for gHgL and trigger a conformational change in gB.

UNLABELLED: Epstein-Barr virus (EBV) fusion with an epithelial cell requires virus glycoproteins gHgL and gB and is triggered by an interaction between gHgL and integrin αvß5, αvß6, or αvß8. Fusion with a B cell requires gHgL, gp42, and gB and is triggered by an interaction between gp42 and human leukocyte antigen class II. We report here that, like alpha- and betaherpesviruses, EBV, a gammaherpesvirus, can mediate cell fusion if gB and gHgL are expressed in trans. Entry of a gH-null virus into an epithelial cell is possible if the epithelial cell expresses gHgL, and entry of the same virus, which phenotypically lacks gHgL and gp42, into a B cell expressing gHgL is possible in the presence of a soluble integrin. Heat is capable of inducing the fusion of cells expressing only gB, and the proteolytic digestion pattern of gB in virions changes in the same way following the exposure of virus to heat or to soluble integrins. It is suggested that the Gibbs free energy released as a result of the high-affinity interaction of gHgL with an integrin contributes to the activation energy required to cause the refolding of gB from a prefusion to a postfusion conformation. IMPORTANCE: The core fusion machinery of herpesviruses consists of glycoproteins gB and gHgL. We demonstrate that as in alpha- and betaherpesvirus, gB and gHgL of the gammaherpesvirus EBV can mediate fusion and entry when expressed in trans in opposing membranes, implicating interactions between the ectodomains of the proteins in the activation of fusion. We further show that heat and exposure to a soluble integrin, both of which activate fusion, result in the same changes in the proteolytic digestion pattern of gB, possibly representing the refolding of gB from its prefusion to its postfusion conformation.

Modeling the repair of DNA strand breaks caused by γ-radiation in a minichromosome.

The objective of the studies described here was the development of a mathematical model which would fit experimental data for the repair of single and double strand breaks induced in DNA in living cells by exposure to ionizing radiation, and which would allow to better understand the processes of DNA repair. DNA breaks are believed to play the major role in radiation-induced lethality and formation of chromosome deletions, and are therefore crucial to the response of cells to radiotherapy. In an initial model which we reported on the basis of data for the repair of Epstein-Barr minichromosomes in irradiated Raji cells, we assumed that DNA breaks are induced only at the moment of irradiation and are later removed by repair systems. This work gives a development of that mathematical model which fits the experimental results more precisely and suggests strongly that DNA breaks are generated not only by direct irradiation but also later, probably by systems engaged in repair of oxidative damage.

Epstein-Barr virus DNA load in nasopharyngeal brushings and whole blood in nasopharyngeal carcinoma patients before and after treatment.

PURPOSE: Nasopharyngeal carcinoma (NPC) is consistently associated with Epstein-Barr virus (EBV) and highly prevalent in Indonesia. EBV-DNA load can be used for early diagnosis and may have prognostic value. In this study, EBV-DNA load was evaluated in minimal invasive nasopharyngeal (NP) brushings and whole blood for initial diagnosis and therapy assessment against the standard-of-care diagnosis by biopsy with EBV-RISH and standard EBV-IgA serology. EXPERIMENTAL DESIGN: NP brushings and blood samples were collected from 289 consecutive ENT patients suspected of NPCs and 53 local healthy controls. EBV-DNA load was quantified by real-time PCR and serology by peptide-based EBV-IgA ELISA. Tissue biopsies were examined by routine histochemistry and by EBER RNA in situ hybridization. RESULTS: Repeated NP brushing was well tolerated by patients and revealed high viral load in the 228 NPC cases at diagnosis than 61 non-NPC cancer cases and healthy controls (P < 0.001). The diagnostic value of EBV-DNA load in blood and EBV-IgA serology was inferior to the NP brush results. The level of EBV-DNA load in brushes of patients with NPC was not related to T, N, or M stage, whereas elevated EBV-DNA load in blood correlated with N and M stage. EBV-DNA levels in brushings and whole blood showed a significant reduction at 2 months after treatment (P = 0.001 and P = 0.005, respectively), which was not reflected in EBV-IgA serology. CONCLUSIONS: NP brush sampling combined with EBV-DNA load analysis is a minimal invasive and well-tolerated diagnostic procedure, suited for initial diagnosis and follow-up monitoring of NPCs.

Nuclear factor-Y and Epstein Barr virus in nasopharyngeal cancer.

PURPOSE: The Epstein Barr virus (EBV) is intimately associated with nasopharyngeal cancer (NPC) in a latent state expressing a limited number of genes. The process of switching from latency to replication is not well understood, particularly in response to DNA stress; hence, the focus of this study is on an EBV-positive NPC model. EXPERIMENTAL DESIGN: C666-1 cells were exposed to radiation (2-15 Gy) or cisplatin (0.1-50 microg/mL) assayed subsequently for relative EBV copy number (BamHI) and lytic gene expression (BRLF1 and BZLF1) using quantitative real-time PCR. Chromatin immunoprecipitation was conducted to assess the interaction of the transcription factor nuclear factor-Y (NF-Y) with promoter sequences. RESULTS: Radiation-induced and cisplatin-induced BamHI expression, along with increased levels of BRLF1 and BZLF1 in a dose-dependent and time-dependent manner, associated with the immediate nuclear transactivation of the transcription factor NF-Y and its own increased transcription of NF-Y subunits 8 h posttreatment. In silico analysis revealed three putative NF-Y consensus-binding sequences in the promoter region of BRLF1, which all interacted with NF-Y in response to radiation and cisplatin, confirmed using chromatin immunoprecipitation. Introduction of dominant-negative NF-YA reduced BRLF1 expression after radiation and cisplatin by 2.8-fold; in turn, overexpression of NF-YA resulted in a 2-fold increase in both BRLF1 and BZLF1 expression. CONCLUSIONS: These results show that NF-Y is an important mediator of EBV stress response in switching from a latent to lytic state. This novel insight could provide a potential therapeutic strategy to enhance NPC response to radiation and cisplatin.

Quantitative plasma/serum EBV DNA load by LMP2A determination in an Italian cohort of NPC patients.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is frequently associated with Epstein-Barr virus (EBV), but little is known about the EBV DNA prevalence on peripheral blood in Western Countries, where the tumour is not endemic and its incidence is low. OBJECTIVES: To set up and evaluate an internally controlled qualitative polymerase chain reaction (PCR) followed by quantitative competitive PCR for the detection of EBV DNA in clinical specimens. To investigate whether EBV DNA load in peripheral blood was a consistent feature of Italian NPC patients. MATERIALS AND METHODS: A PCR assay based on latent membrane protein 2A (LMP2A) sequence amplification was chosen. Best assay conditions, sensitivity and reproducibility were determined. Sixty-four sera and 63 plasma from an Italian cohort of 39 NPC patients were analyzed. Samples from 5 patients followed up after radiotherapy were also assayed. Qualitative and quantitative beta-globin amplification was performed in parallel in order to provide an independent control for amplification competence of DNA and to investigate whether EBV DNA levels could be due to intracellular EBV viral genomes from cells lysed during plasma/serum collection. RESULTS: Twenty-five patients had undifferentiated carcinoma (UC) and 14 squamous cell carcinoma (SCC). EBV DNA has been quantified in 58 and 9% of the UC and SCC cases, respectively. No statistically significative differences were observed between the EBV DNA levels (469 vs 750 copies/ml, P=0.16) and prevalence (64 vs 57%, chi2(1)=0.22, P=0.64) in plasma and serum samples. Increased EBV viremia was found in patients with considerable extension of the primary tumour (172 vs 2250 copies/ml, low vs high tumour burden). Three UC subjects, which had detectable pre-treatment EBV DNA levels, became negative after radiotherapy. Clinical examination revealed that all had complete tumour regression. CONCLUSIONS: These PCR procedures allow an accurate and reproducible estimation of plasma/serum EBV DNA load in NPC patients living in non endemic areas, being strictly associated with UC WHO III and with tumour severity.

Suppression of EBV release from irradiated B lymphoblastoid cell-lines: superior activity of ganciclovir compared with acyclovir.

BACKGROUND: B lymphoblastoid cell-lines (BLCL), generated by exposure of PBMC to a laboratory strain of EBV, are commonly utilized in the preparation of T cells used for immunotherapy. Although most B cells are latently infected, BLCL contain a subset of cells that harbor infectious virus, which could be released into the infusion product during preparation. To reduce this known risk, laboratories have pretreated BLCL for > or = 14 days with 100 microM acyclovir (ACV), an inhibitor of viral DNA polymerase, prior to use. We tested the effectiveness of ACV in preventing the release of infectious virus from irradiated fresh and previously frozen BLCL, and compared its effects with those of ganciclovir (GCV). METHODS: BLCL were grown for 14 days in medium containing various doses of ACV or GCV, washed, irradiated, and tested for the presence of infectious virus in co-culture assays with cord blood mononuclear cells(CBMC) (21 CBMC to BLCL). B-cell transformation was assessed at 3-4 weeks of culture. RESULTS: Both fresh and previously frozen BLCL released infectious virus, which transformed nearly all (92%) of CBMC co-cultures (n = 52). Transformation was not prevented by treatment with 100 microM ACV (88%, n = 52). Increasing the ACV dose to 200 microM (or 50 microg/mL) still allowed transformation in 4/9 (44%) cultures, while this and higher doses severely reduced the proliferation rate of the BLCL during ACV exposure. Infectious virus release was detectable within 1 day of ACV removal and BLCL irradiation. In contrast, GCV was able to prevent infectious virus release in 12/12 co-cultures at a concentration (15 microM) that only modestly reduced BLCL growth. DISCUSSION: These results indicate that GCV is more effective at preventing release of infectious EBV from irradiated BLCL than ACV at concentrations that do not severely inhibit B-cell growth.

Experimental treatment of Epstein-Barr virus-associated primary central nervous system lymphoma.

Primary central nervous system lymphoma (PCNSL) that arises in immune-deficient patients is an aggressive B-cell neoplasm that is universally associated with the EBV. Patients with EBV(+) PCNSL face a particularly poor prognosis with median survival times of 2-12 months despite aggressive management with radiation therapy. We have developed a preclinical model of EBV(+) PCNSL to explore strategies that specifically target EBV-infected B lymphoblasts in vivo. Stereotactic implantation of EBV-transformed human lymphoblastoid B-cell lines into the caudate nucleus of the nude rat resulted in lethal CNS tumor burden manifested by the onset of focal neurological symptoms within 21 days. Histological evaluation at autopsy revealed a multifocal, perivascular human EBV(+) lymphoblastic B-cell infiltrate that displayed a latency type III EBV gene expression profile similar to PCNSL that develops in some immune-deficient patients. Radiation (1600 cGy) of lymphoblastoid B-cell lines resulted in up-regulation of the EBV thymidine kinase (EBV-TK) transcript and sensitization of these cells to drug-induced apoptosis using nucleoside analogs. Enhanced expression of EBV-TK mRNA in EBV(+) PCNSL tumors by radiation therapy occurred in a dose-dependent fashion. In vivo trials using the nude rat PCNSL model demonstrated significantly improved mean survival time (MST) with single fraction whole-brain radiotherapy (WBRT) and antiviral therapy consisting of zidovudine (AZT) and ganciclovir (GCV; MST 41.3 +/- 3.3 days; P = 0.05), compared with either antiviral therapy (MST 32.1 +/- 1.1 days) or WBRT alone (MST 22 +/- 0.8 days). We found constitutive and abundant EBV-TK mRNA expression in a stereotactic core biopsy specimen from a solid organ transplant patient with EBV(+) PCNSL. Withdrawal of immunosuppression did not result in disease regression. This patient achieved a complete response after therapy with high-dose AZT and GCV in the absence of WBRT, and remains in remission on oral maintenance AZT/GCV therapy 3 years after diagnosis. These results suggest that antiviral therapies can be effectively explored in vivo using a preclinical animal model of human EBV(+) PCNSL with subsequent translation to patients with EBV(+) PCNSL.

Flow cytometry analysis of gamma-radiation-induced Epstein-Barr virus reactivation in lymphocytes.

Epstein-Barr virus (EBV), a member of the gamma-herpesvirus family, is involved in the development of several diseases, and the infection is believed to persist for life in latent form. Ionizing radiation at clinically relevant doses may increase the amount of virus reactivation in B cells, and the combination of radiation with stress could amplify EBV reactivation. In vitro experiments were performed on several cell lines, including EBV-positive Burkitt lymphoma cells. The presence of the immediate-early protein ZEBRA, which is a hallmark of EBV reactivation, was evaluated using flow cytometry, which enabled us to measure the percentage of ZEBRA-positive cells. The process was studied previously in the EBV-positive Burkitt lymphoma cell line B95-8. Forty-eight hours after irradiation alone, 13.6 and 19.9% ZEBRA-positive cells were observed at 2 and 4 Gy, respectively, compared to the basal level of 1.85%. Thus irradiation induces EBV reactivation. The addition of a glucocorticoid (the final effector of the stress response) had no effect on EBV reactivation in our model. However, the combination of radiation and treatment with a glucocorticoid (dexamethasone) increased the expression of ZEBRA in B95-8 cells (15.8 and 28.75% of the cells was positive at 24 and 48 h after gamma irradiation, respectively). Thus the combination of gamma radiation and a glucocorticoid may play an important role in EBV reactivation.

[Induction of IgG and IgM production by Epstein-Barr virus protein].

AIM: To detect the production of IgG and IgM by cultured umbilical blood B cell stimulated by UV and heat-inactivated Epstein-Barr virus (EBV). METHODS: Mononuclear cells were isolated routinely from umbilical blood, then monocytes, NK cells and cytotoxic T cells were eliminated by L-leucine methy ester method; remained T cells were eliminated by AET-SRBC rosette method. The purified B cells were treated with UV or heat-inactivated EBV respectively and cultured in complete IMDM. The IgG and IgM in the supernatant were detected by ELISA. RESULTS: The IgG and IgM production(A value) in UV-inactivated EBV group increased from 18th day to 30 th day after stimulation compared with the baseline. The A value of all time points in heat-inactivated EBV group had no significant difference. CONCLUSION: UV-inactivated EBV may induce IgG and IgM production with a time-effect relationship, suggesting that EBV protein is a key component of stimulating Ig production. This result provide the basis for the further researching the effects of functional EBV protein on the production of natural autoantibodies (NAA).

Generation of EBV-specific CTLs suitable for adoptive immunotherapy of EBV-associated lymphoproliferative disease following allogeneic transplantation.

Lymphoproliferative disease induced by EBV (EBV-LPD) is a complication of allogeneic transplantation caused by T-cell immunodeficiency. EBV-LPD responds poorly to conventional treatment modalities. Recently, adoptive transfer of EBV-specific, HLA-class I-restricted CTL lines was shown to be effective both as prophylaxis and as treatment of EBV-LPD. The CTL lines are produced by in vitro selection of EBV-specific memory T cells contained in MNC of EBV-seropositive individuals by repeated stimulation with irradiated EBV-transformed cells. The non-EBV-reactive and potentially alloreactive cells remain unactivated. Twenty-one CTL lines were initiated. All were successfully generated and shown to be HLA-restricted and EBV-specific as well as CD8/CD4 and CD45RO positive T cells. The majority of the CTL lines were generated from BMT donors, but two CTL lines were obtained from solid organ transplant recipients receiving immunosuppression. Evidence of probable in vivo efficacy is presented. Development of efficient adoptive T-cell strategies for EBV-positive malignancies could serve as a model for treatment of other viral or malignant disorders.

Activation of lytic Epstein-Barr virus (EBV) infection by radiation and sodium butyrate in vitro and in vivo: a potential method for treating EBV-positive malignancies.

The consistent presence of the EBV genome in certain tumors offers the potential for novel EBV-directed therapies. Switching the latent form of EBV infection present in most EBV-positive tumor cells into the cytolytic form may be clinically useful because lytic EBV infection leads to host cell destruction, and very few normal cells contain the EBV genome. It would also be therapeutically advantageous to induce expression of EBV-encoded lytic proteins that convert the nucleoside analogues ganciclovir (GCV) and 3'-azido-3'deoxythymidine (AZT) into their active, cytotoxic forms. In this report, we have explored two different approaches for activating the lytic form of EBV infection in tumors. We show that gamma-irradiation at clinically relevant doses induces lytic EBV infection in lymphoblastoid cell lines in vitro as well as in EBV-positive B-cell tumors in SCID mice. In addition, sodium butyrate (given as a single i.p. dose) is effective for activating lytic viral infection in some EBV tumor types in SCID mice. We also examined whether low-dose gamma-irradiation treatment of EBV-positive lymphoblastoid cells in vitro promotes GCV or AZT susceptibility. The combination of radiation with either GCV or AZT induced significantly more cell killing in vitro than either radiation or prodrug treatment alone. Most importantly, we found that the combination of gamma-irradiation and GCV was much more effective in treating EBV-positive lymphoblastoid tumors in SCID mice than either agent alone. Thus, GCV or AZT treatment could potentially enhance the therapeutic efficacy of radiation therapy for EBV-positive lymphomas in patients.

Epstein-Barr virus DNA in serum/plasma as a tumor marker for nasopharyngeal cancer.

Nasopharyngeal cancer (NPC) constitutes a type of carcinoma encountered frequently in Southern China, among Eskimos of the Arctic region, and to a lesser extent in Southeast Asia. Because EBV DNA present in plasma or serum of NPC patients has proven to represent a promising noninvasive tumor marker, the present study was designed to determine the incidence of serum/plasma EBV DNA by nested PCR during various disease management stages. By this method, we could detect EBV DNA in plasma/serum of 98 of 167 NPC patients prior to treatment, compared with 10 of 77 samples derived from healthy blood donors serving as controls, with a similar prevalence observed in plasma versus serum. Investigation of 13 patients subjected to radiotherapy revealed plasma EBV DNA to persist in the plasma of one case, whereas among the remaining patients, it had vanished during the early phase of treatment. Finally, with 52 samples derived from 37 NPC patients during follow-up, we established 100% specificity and 0% false-positive rate for plasma DNA detection by nested PCR. Moreover, we subjected 24 known EBV DNA-positive serum samples to DNase digestion prior to DNA extraction and amplification to differentiate between free and encapsulated viral DNA, which demonstrated complete absence of the human beta-globin genomic DNA in contrast to EBV DNA detectable in 14 samples. In conclusion, applying this noninvasive method, serum/plasma EBV DNA constitutes a reliable tumor marker prior to, during, and after treatment of NPC.

Quantitative analysis of cell-free Epstein-Barr virus DNA in plasma of patients with nasopharyngeal carcinoma.

Using real-time quantitative PCR, cell-free EBV DNA was detectable in the plasma of 96% (55 of 57) of nasopharyngeal carcinoma (NPC) patients (median concentration, 21058 copies/ml) and 7% (3 of 43) of controls (median concentration, 0 copies/ml). Advanced-stage NPC patients had higher plasma EBV DNA levels than those with early-stage disease. At 1 month after completion of radiotherapy, plasma EBV DNA was undetectable in 7 of 15 subjects (47%) but remained high in the remaining 8 subjects (53%). Clinical examination revealed that all of the former seven subjects had complete tumor regression, whereas six of the eight latter subjects exhibited evidence of disease persistence or had developed distant metastases. These results suggest that quantitative analysis of plasma EBV DNA may be a useful clinical and research tool in the screening and monitoring of NPC patients.