Abstract 5356: Inactivation of Foxo3a and increased expression of Id1 by the Epstein-Barr Virus-encoded LMP1 facilitates resistance to TGF-β-mediated growth inhibition in nasopharyngeal epithelial cells

The universal association of Nasopharyngeal carcinoma (NPC) with EBV underscores the importance of EBV infection to the development of this disease. The EBV-encoded Latent Membrane Protein-1 (LMP1) is believed to be a key factor in NPC development due to its ability to induce cellular transformation in various cell types. As a viral mimic of CD40, LMP1 functions as a constitutively active TNF receptor, altering multiple signal cascades and activating a plethora of downstream targets. LMP1 has been shown to inactivate the transcriptional activity of Foxo3a, a tumor suppressor that can inhibit the proliferation of tumor cells. LMP1 has also been found to increase expression of Id1, a transcriptional repressor that can inhibit the expression of differentiation-linked genes. Here, we report that inactivation of Foxo3a by LMP1 facilitates Id1 induction. Using a panel of LMP1 mutants, we identified the CTAR1 domain of LMP1 as being responsible for Foxo3a inactivation and Id1 upregulation.

Through the use of dominant negative proteins, shRNA silencing or selective pharmacological inhibitors, we demonstrate that Foxo3a inactivation by LMP1 is mediated through the LMP1 CTAR1 domain and requires activation of the Akt and Erk-MAPK signaling pathways. Whilst engagement of the Akt, Erk-MAPK and NIK-dependent noncanonical NF-κB pathways by LMP1 are involved in Id1 upregulation, we found that LMP1 CTAR2 domain-mediated IKKβ-dependent canonical NF-κB signaling negatively regulates Id1 expression, suggesting that CTAR2 may antagonize CTAR1-mediated regulation of Id1. LMP1 has been shown to inhibit TGFβ-mediated growth inhibition by disrupting various facets of TGFβ signaling. Here we show that stable “knock-down” of Id1 in LMP1 expressing NP69 cells after stable expression of Id1-specific shRNA, reduced the growth inhibitory effect of TGFβ. The interplay between LMP1, Foxo3a and Id1 is likely to contribute to the characteristic resistance of LMP1 to TGFβ-mediated signaling and cell growth arrest. The data presented in this study may offer a novel therapeutic approach for EBV associated epithelial cancers.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5356.

CD40 ligand induced cytotoxicity in carcinoma cells is enhanced by inhibition of metalloproteinase cleavage and delivery via a conditionally-replicating adenovirus

Background

CD40 and its ligand (CD40L) play a critical role in co-ordinating immune responses. CD40 is also expressed in lymphoid malignancies and a number of carcinomas. In carcinoma cells the physiological outcome of CD40 ligation depends on the level of receptor engagement with low levels promoting cell survival and high levels inducing cell death. The most profound induction of cell death in carcinoma cells is induced by membrane-bound rather than recombinant soluble CD40L, but like other TNF family ligands, it is cleaved from the membrane by matrix metalloproteinases.

Results

We have generated a replication-deficient adenovirus expressing a mutant CD40L that is resistant to metalloproteinase cleavage such that ligand expression is retained at the cell membrane. Here we show that the mutated, cleavage-resistant form of CD40L is a more potent inducer of apoptosis than wild-type ligand in CD40-positive carcinoma cell lines. Since transgene expression via replication-deficient adenovirus vectors in vivo is low, we have also engineered a conditionally replicating E1A-CR2 deleted adenovirus to express mutant CD40L, resulting in significant amplification of ligand expression and consequent enhancement of its therapeutic effect.

Conclusions

Combined with numerous studies demonstrating its immunotherapeutic potential, these data provide a strong rationale for the exploitation of the CD40-CD40L pathway for the treatment of solid tumours.

Is human papillomavirus viral load a clinically useful predictive marker? A longitudinal study

BACKGROUND

It has been suggested that in women who test positive for high-risk human papillomavirus (HPV) types, viral load can distinguish women who are at increased risk of cervical neoplasia from those who are not.

METHODS

Quantitative PCR (qPCR) was used to measure HPV copy number in serial samples taken from 60 and 58 young women previously found to have incident cervical HPV16 or HPV18 infections, respectively, using GP5+/GP6+ primers; women provided at least three samples for qPCR testing, at least one of which was positive.

RESULTS

A 10-fold increase in HPV16 or HPV18 copy number was associated with a modestly increased risk of acquiring a cytologic abnormality [HPV16: hazards ratio, 1.76 (95% confidence interval, 1.38-2.25); HPV18: hazards ratio, 1.59 (95% confidence interval, 1.25-2.03)]. However, in most women, copy number increased during follow-up, before decreasing again. In women with a HPV16 infection, the median copy number per 1,000 cells was 7.7 in their first qPCR HPV-positive sample, 1,237 in the sample yielding the maximum copy number, and 7.8 in their last qPCR HPV-positive sample; corresponding copy numbers for women with HPV18 infection were 2.3, 87, and 2.4. Maximum HPV16 and HPV18 copy number did not differ significantly between women who acquired an incident cervical cytologic abnormality and those who did not.

CONCLUSION

Whereas large relative increases in copy number are associated with an increased risk of abnormality, a single measurement of viral load made at an indeterminate point during the natural history of HPV infection does not reliably predict the risk of acquiring cervical neoplasia. Therefore, a single measure of HPV viral load cannot be considered a clinically useful biomarker.

Role of the Epstein-Barr virus-encoded latent membrane protein-1, LMP1, in the pathogenesis of nasopharyngeal carcinoma

Although frequently expressed in Epstein-Barr virus (EBV)-positive malignancies, the contribution of the oncogenic latent membrane protein-1 (LMP1) to the pathogenesis of nasopharyngeal carcinoma remains to be fully defined. As a key effector in EBV-driven B-cell transformation in vitro, LMP1 also displays oncogenic properties in rodent fibroblasts, and exhibits similar effects in epithelial cells. LMP1 functions as a viral mimic of the TNFR family member, CD40, engaging a plethora of signaling pathways including: NF-kappaB, JNK/p38 (SAPK), PI3-kinase and ERK-MPK. The constitutive activation of these pathways appears central in the ability of LMP1 to induce multiple morphological and phenotypic alterations. Here we review the effects of LMP1 on epithelial cell growth transformation, and its putative role in the pathogenesis of nasopharyngeal carcinoma, focusing on key areas of proliferation, survival, cell motility and invasion.

Epstein-Barr virus-encoded EBNA1 inhibits the canonical NF-kappaB pathway in carcinoma cells by inhibiting IKK phosphorylation

BACKGROUND

The Epstein-Barr virus (EBV)-encoded EBNA1 protein is expressed in all EBV-associated tumours, including undifferentiated nasopharyngeal carcinoma (NPC), where it is indispensable for viral replication, genome maintenance and viral gene expression. EBNA1's transcription factor-like functions also extend to influencing the expression of cellular genes involved in pathways commonly dysregulated during oncogenesis, including elevation of AP-1 activity in NPC cell lines resulting in enhancement of angiogenesis in vitro. In this study we sought to extend these observations by examining the role of EBNA1 upon another pathway commonly deregulated during carcinogenesis; namely NF-kappaB.

RESULTS

In this report we demonstrate that EBNA1 inhibits the canonical NF-kappaB pathway in carcinoma lines by inhibiting the phosphorylation of IKKalpha/beta. In agreement with this observation we find a reduction in the phosphorylation of IkappaBalpha and reduced phosphorylation and nuclear translocation of p65, resulting in a reduction in the amount of p65 in nuclear NF-kappaB complexes. Similar effects were also found in carcinoma lines infected with recombinant EBV and in the EBV-positive NPC-derived cell line C666-1. Inhibition of NF-kappaB was dependent upon regions of EBNA1 essential for gene transactivation whilst the interaction with the deubiquitinating enzyme, USP7, was entirely dispensable. Furthermore, in agreement with EBNA1 inhibiting p65 NF-kappaB we demonstrate that p65 was exclusively cytoplasmic in 11 out of 11 NPC tumours studied.

CONCLUSIONS

Inhibition of p65 NF-kappaB in murine and human epidermis results in tissue hyperplasia and the development of squamous cell carcinoma. In line with this, p65 knockout fibroblasts have a transformed phenotype. Inhibition of p65 NF-kappaB by EBNA1 may therefore contribute to the development of NPC by inducing tissue hyperplasia. Furthermore, inhibition of NF-kappaB is employed by viruses as an immune evasion strategy which is also closely linked to oncogenesis during persistent viral infection. Our findings therefore further implicate EBNA1 in playing an important role in the pathogenesis of NPC.

In-vitro studies with ceftazidime against aerobic gram-negative bacilli and Bacteroides fragilis group

The in-vitro susceptibility of recent clinical isolates of Gram-negative bacilli has been assessed for ceftazidime and compared to amikacin, gentamicin, carbenicillin, piperacillin, cefoperazone, moxalactam, ceftriaxone and ceftizoxime. Using the ICS-WHO agar dilution method, we found that ceftazidime was the most active beta-lactam agent tested against 147 isolates of Pseudomonas aeruginosa, with a mode MIC=2 mg/l and all but 2% of isolates inhibited at 32 mg/l. 100% of indole-positive and negative Proteus spp., 90% of Citrobacter spp., 100% of Acinetobacter spp. and 98% of Enterobacter spp. were inhibited. A total of 142 isolates from the latter 5 groups of organisms were tested. Cefoperazone and moxalactam were slightly more active by weight than ceftazidime versus Enterobacter spp., but against other Gram-negative bacilli ceftazidime was similar or more potent. Additionally, 72 clinical isolates of Bacteroides fragilis group were tested against ceftazidime, cefoperazone, ceftizoxime, ceftriaxone, and cefoxitin. Against these organisms cefoxitin and ceftizoxime were most active. Ceftazidime demonstrates potent in-vitro activity against Ps. aeruginosa and Enterobacteriaceae, but it is relatively less active against Bacteroides fragilis group than cefoxitin and ceftizoxime.

Cigarette smoking is an independent risk factor for cervical intraepithelial neoplasia in young women: a longitudinal study

Repeated measurements of smoking, cervical human papillomavirus (HPV) status and sexual behaviour were used to measure the risk of high-grade cervical intraepithelial neoplasia (CIN) in relation to changes in smoking and cervical HPV status, and to explore the impact of smoking on the acquisition and duration of incident cervical HPV infection. Included in this longitudinal analysis are 1485 women aged 15–19 years: 1075 were HPV-negative and cytologically normal at recruitment; 410 were HPV-positive, cytologically abnormal or both, at this time. Women re-attended every 6 months, when samples were taken for cytological and virological examination. Current smoking intensity was associated with an increased risk of high-grade CIN, after controlling for cervical HPV status (compared to non-smokers, hazards ratio (HR) for 10 or more cigarettes per day = 2.21, 95% confidence interval (CI) 1.19–4.12, p-trend = 0.008). In women who were HPV-negative and cytologically normal at recruitment, current smoking was not significantly associated with the risk of acquiring a cervical HPV infection, after controlling for life-time number of partners and age of oldest partner (HR = 1.13, 95% CI 0.90–1.41); nor did it prolong the length of time during which HPV could be detected (HR = 1.03, 95% CI 0.78–1.34). Current smoking intensity is an independent risk factor for high-grade CIN in young women, after controlling for cervical HPV infection.

Disruption of the E2 gene is a common and early event in the natural history of cervical human papillomavirus infection: a longitudinal cohort study

Integration of high-risk human papillomavirus (HPV) types into the host-cell genome disrupts the HPV regulatory E2 protein, resulting in a loss of negative feedback control of viral oncogene expression; this disruption has been considered a critical event in the pathogenesis of cervical neoplasia, and a potential biomarker of progressive disease. However, using serial samples taken from a cohort of young women who were recruited soon after they first had sexual intercourse, we show that disruption of the E2 gene is a common and early event in the natural history of incident cervical HPV infections. The E2 gene was significantly more likely to be disrupted in women who tested positive for HPV18 in their baseline sample than in those who tested positive for HPV16 [26% versus 58%; relative risk, 2.26; 95% confidence interval (CI), 1.38-3.71; chi(2), 9.23; 1 degree of freedom (df); P = 0.002]. Among women with an intact E2 gene in their baseline sample, the median time to first detection of E2 disruption was also shorter for those who tested positive for HPV18 than HPV16 (5.7 versus 10.9 months; hazards ratio, 1.93; 95% CI, 0.84-4.44; chi(2), 2.49; 1 df; P = 0.11). This tendency for HPV18 to integrate early, coupled with the substantial reduction in viral load in HPV18-positive samples in which E2 is disrupted, may explain why HPV18-associated disease is often reported to be characterized by minor cytologic changes, which underestimate the severity of the underlying histologic abnormality.

Novel non-steroidal p160 coactivator interactions in tamoxifen resistant breast cancer

Abstract #3038

While most breast cancer patients initially respond to endocrine therapy, 30-40% of cases relapse within 5 years of treatment. Translational studies from our group and others have provided substantial evidence of a significant role for p160 family of Steroid Receptor Co-activator (SRC) proteins in the development of resistance to endocrine therapy. In this study we have investigated novel non-steroidal SRC-1 interactions in endocrine resistant breast cancer.
 A mass-spectrometry-based screen was used to identify proteins which differentially interact with SRC-1 in endocrine resistant compared with endocrine sensitive breast cancer cells. The developmental protein, HOXC11, was confirmed as an SRC-1 interacting partner. HOXC11 was shown to be over-expressed in tamoxifen-resistant cells using immunocytochemistry and was observed to translocate to the nucleus and peri-nuclear region when cells were treated with tamoxifen. In a breast cancer TMA (n=560) HOXC11 was found to correlate with disease recurrence and metastasis (local and distant). Moreover, in addition to associating with SRC-1, HOXC11 was found to be a strong predictor of reduced disease-free survival on endocrine treatment (Hazard ratio: 5.79; p<0.0001).
 Bioinformatic analysis identified S100β as a target gene of the HOXC11 transcription factor. Interestingly, the s100 family of calcium binding proteins has been associated with poor outcome and reduced disease-free survival in melanoma. Reporter assays were used to confirm HOXC11 as a mediator of S100β transcription. Regulation of the target gene in the presence of tamoxifen was shown to be modified by activation of protein kinase A (PKA) which has previously been implicated in the enhancement of tamoxifenÂs agonist profile. Here we have defined HOXC11 as a non-steroidal interacting partner of SRC-1; furthermore, this interaction appears to be regulated by the activation of PKA. HOXC11 expression in our breast cancer patient cohort associated with poor survival and the development of metastatic disease. This study provides evidence of a novel mechanism at play in endocrine resistant breast cancer cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3038.

Coassociation of ERα and p160 proteins predicts resistance to endocrine treatment; SRC-1 is an independent predictor of breast cancer recurrence

Abstract #3032

The p160 coactivators AIB1 and SRC-1 are known to play a critical role in modulating transcription in breast cancer cells in conjunction with ligand-bound estrogen receptor. The interactions of the p160 proteins with this nuclear receptor are also important in the development of resistance to endocrine treatments. Using quantitative coassociation immunofluorescent microscopy, the colocalisation of the p160s and ERα was increased in the LY2 endocrine resistant cell line following treatment with the anti-estrogen tamoxifen in comparison to the endocrine sensitive MCF-7 cell line. In cell cultures derived from patient tumours at the time of primary surgery prior to treatment, there was an increase in association of the coactivators with ERα following treatment with estrogen but dissociation was evident in the presence of tamoxifen. Immunohistochemical staining of a tissue microarray, constructed from 560 breast cancer patients, revealed that SRC-1 was a strong predictor of reduced disease-free survival, both in patients receiving adjuvant tamoxifen treatment and untreated patients (p<0.0001 and p=0.0111 respectively). AIB1 was not a significant independent predictor of disease recurrence. SRC-1 was assigned a hazard ratio of 2.12 when survival analysis using a Cox proportional hazards model was applied. Quantitative coassociation analysis of the p160 coactivators with ERα in the patient TMA revealed significantly stronger colocalisation of SRC-1 and ERα in patients who are known to have relapsed than those patients who did not recur (p=0.00001). This data suggests SRC-1 is pivotal in tumour aggressiveness and is a powerful predictor of progression of disease in breast cancer patients.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3032.

Epstein-Barr virus-encoded EBNA1 modulates the AP-1 transcription factor pathway in nasopharyngeal carcinoma cells and enhances angiogenesis in vitro

The Epstein-Barr virus (EBV)-encoded EBNA1 protein is expressed in all virus-associated tumours, including nasopharyngeal carcinoma (NPC), where it plays an essential role in EBV genome maintenance, replication and transcription. Previous studies suggest that EBNA1 may have additional effects relevant to oncogenesis, including enhancement of cell survival, raising the possibility that EBNA1 may influence cellular gene expression. We have recently demonstrated by gene expression microarray profiling in an NPC cell model that EBNA1 influences the expression of a range of cellular genes, including those involved in transcription, translation and cell signalling. Here, we report for the first time that EBNA1 enhances activity of the AP-1 transcription factor in NPC cells and demonstrate that this is achieved by EBNA1 binding to the promoters of c-Jun and ATF2, enhancing their expression. In addition, we demonstrate elevated expression of the AP-1 targets interleukin 8, vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1alpha in response to EBNA1 expression, which enhances microtubule formation in an in vitro angiogenesis assay. Furthermore, we confirm elevation of VEGF and the phosphorylated isoforms of c-Jun and ATF2 in NPC biopsies. These findings implicate EBNA1 in the angiogenic process and suggest that this viral protein might directly contribute to the development and aggressively metastatic nature of NPC.

A phase II study of adoptive immunotherapy using dendritic cells pulsed with tumor lysate in patients with hepatocellular carcinoma

This is a phase II clinical trial investigating the safety and efficacy of intravenous vaccination with mature autologous dendritic cells (DCs) pulsed ex vivo with a liver tumor cell line lysate (HepG2) in patients with advanced hepatocellular carcinoma (HCC). HCC is an attractive target for immunotherapy as evidenced by an active recruitment of tumor-infiltrating lymphocytes that are capable of lysing autologous tumor cells in ex vivo studies. DCs are the most potent antigen-presenting cells, with the capacity to take up, process, and present tumor antigens to T cells and stimulate an immune response, thus providing a rational platform for vaccine development. Thirty-five patients with advanced HCC and not suitable for radical or loco-regional therapies received a maximum of six DC vaccinations each at 3-week intervals. In total, 134 DC infusions were administered with no significant toxicity and no evidence of autoimmunity. Twenty-five patients who received at least three vaccine infusions were assessed clinically for response. The radiologically determined disease control rate (combined partial response and stable disease >or=3 months) was 28%. In 17 patients the baseline serum alpha-fetoprotein (AFP) was >or= 1,000 ng/mL; in four of these patients, it fell to <30% of baseline following vaccination. In one patient there was a radiological partial response associated with a fall in AFP to <10% of baseline. Immune responses were assessed using an ELIspot assay of interferon-gamma (IFN-gamma) release. In several cases there was induction of T cell responses to the vaccine and/or AFP following vaccination.

CONCLUSION

Autologous DC vaccination in patients with HCC is safe and well tolerated with evidence of antitumor efficacy assessed radiologically and serologically, with generation of antigen-specific immune responses in some cases.

Epstein–Barr virus-encoded LMP1 induces a hyperproliferative and inflammatory gene expression programme in cultured keratinocytes

SCC12F cells are a line of keratinocytes that retain the capacity for terminal differentiation in vitro. We showed previously that the Epstein–Barr virus (EBV)-encoded oncogene latent membrane protein 1 (LMP1) altered SCC12F morphology in vitro, downregulated cell–cell-adhesion molecule expression and promoted cell motility. In organotypic raft culture, LMP1-expressing cells failed to stratify and formed poorly organized structures which displayed impaired terminal differentiation. To understand better the mechanism(s) by which LMP1 induces these effects, we generated SCC12F cells in which LMP1 expression is inducible. Following induction, these cells exhibited phenotypic changes similar to those observed previously and allowed us to investigate the effects of LMP1 expression on cellular pathways associated with growth, differentiation and morphology. Using microarrays and a number of confirmatory techniques, we identified sets of differentially expressed genes that are characteristically expressed in inflammatory and hyperproliferative epidermis, including chemokines, cytokines and their receptors, growth factors involved in promoting epithelial cell motility and proliferation and signalling molecules that regulate actin filament reorganization and cell movement. Among the genes whose expression was differentially induced significantly by LMP1, the induction of IL-1β and IL-1α was of particular interest, as many of the LMP1-regulated genes identified are established targets of these cytokines. Our findings suggest that alterations in the IL-1 signalling network may be responsible for many of the changes in host-cell gene expression induced in response to LMP1. Identification of these LMP1-regulated genes helps to define the mechanism(s) by which this oncoprotein influences cellular pathways that regulate terminal differentiation, cell motility and inflammation.

Expression of the Epstein-Barr virus-encoded Epstein-Barr virus nuclear antigen 1 in Hodgkin's lymphoma cells mediates Up-regulation of CCL20 and the migration of regulatory T cells

In approximately 50% of patients with Hodgkin's lymphoma (HL), the Epstein-Barr virus (EBV), an oncogenic herpesvirus, is present in tumor cells. After microarray profiling of both HL tumors and cell lines, we found that EBV infection increased the expression of the chemokine CCL20 in both primary Hodgkin and Reed-Sternberg cells and Hodgkin and Reed-Sternberg cell-derived cell lines. Additionally, this up-regulation could be mediated by the EBV nuclear antigen 1 protein. The higher levels of CCL20 in the supernatants of EBV-infected HL cell lines increased the migration of CD4(+) lymphocytes that expressed FOXP3, a marker of regulatory T cells (Tregs), which are specialized CD4(+) T cells that inhibit effector CD4(+) and CD8(+) T cells. In HL, an increased number of Tregs is associated with the loss of EBV-specific immunity. Our results identify a mechanism by which EBV can recruit Tregs to the microenvironment of HL by inducing the expression of CCL20 and, by doing so, prevent immune responses against the virus-infected tumor population. Further investigation of how EBV recruits and modifies Tregs will contribute not only to our understanding of the pathogenesis of virus-associated tumors but also to the development of therapeutic strategies designed to manipulate Treg activity.

DNA tumour viruses promote tumour cell invasion and metastasis by deregulating the normal processes of cell adhesion and motility

Approximately 15-20% of global cancer incidence is causally linked to viral infection, yet the low incidence of cancers in healthy infected individuals suggests that malignant conversion of virus-infected cells occurs after a long period as a result of additional genetic modifications. There are four families of viruses that are now documented to be involved in the development of human cancers which include members of the polyomavirus, hepadnavirus, papillomavirus and herpesvirus families. Although a number of these viruses are implicated in the aetiology of lymphomas or leukaemias, the vast majority are associated with malignancies of epithelial cells. In epithelial tissues, several classes of proteins are involved in maintaining tissue architecture, including those that promote cell-cell adhesion, and others, which mediate cell-matrix interactions. Proteins representative of all classes are frequently altered in malignant tumour cells that possess invasive and metastatic properties. Malignant tumour cells acquire mechanisms to degrade basement membranes and invade the underlying tissue. Many viruses encode proteins which engage signalling pathways that affect one or more of these mechanisms. It is believed that activation of these processes by chronic viral infection can, under certain circumstances, promote tumour cell invasion and metastasis. This review will take a brief look at the current knowledge of viral-induced alterations in cell motility and invasiveness in the context of tumour invasion and metastasis.

CD154 tone sets the signaling pathways and transcriptome generated in model CD40-pluricompetent L3055 Burkitt's lymphoma cells

Activated B cells reacting to small amounts of CD40L (CD154) maintain homeostasis by suppressing default apoptosis. Additional outcomes, particularly differentiation, demand higher CD40 occupancy. Here, focusing on survival, we compared changes in the transcriptome of pleiotropically competent, early passage L3055 Burkitt's lymphoma cells confronted with low (picomolar) and high (nanomolar) concentrations of CD154 to gain insight into how a single receptor sets these distinct phenotypes. Of 267 genes altering transcriptional activity in response to strong CD154 tone, only 25 changed coordinately on low receptor occupancy. Seven of the top nine common up-regulated genes were targets of NF-kappaB. Direct measurement and functional inhibition of the NF-kappaB pathway revealed it to be central to a CD40-dependent survival signature. Although the canonical NF-kappaB axis was engaged by both signaling strengths equally, robust alternative pathway activation was a feature selective to a strong CD40 signal. Discriminatory exploitation of the two separate arms of NF-kappaB activation may indicate a principle whereby a cell senses and reacts differentially to shifting ligand availability. Identifying components selectively coupling CD40 to each axis could indicate targets for disruption in B cell pathologies underpinned by ectopic and/or hyper-CD154 activity such as neoplasia and some autoimmunities.

Combining gene and immunotherapy for prostate cancer

The nitroreductase (NR)/CB1954 enzyme prodrug system has given promising results in pre-clinical studies and is currently being assessed in phase I and II clinical trials in prostate cancer. Enhanced cell killing by apparent immune-mediated mechanisms has been shown in pancreatic and colorectal cancer models, by co-expressing murine granulocyte macrophage colony-stimulating factor (GM-CSF) with NR in a single replication deficient adenoviral vector. This consists of the CMV immediate early promotor driving expression of NR, with an internal ribosome entry site (IRES) and the gene for murine GM-CSF (mGM-CSF). To examine if similar enhancement of tumour cell killing could be produced in prostate cancer, the TRAMP model was chosen. Results illustrate that the combination of suicide gene therapy using NR and CB1954, with cytokine stimulation with mGM-CSF gives an improved response compared with either modality alone. The mechanism of this improved response is however likely to be non-immune based as it lacks a memory effect.

Down-regulation of the TGF-beta target gene, PTPRK, by the Epstein-Barr virus encoded EBNA1 contributes to the growth and survival of Hodgkin lymphoma cells

The Epstein-Barr virus (EBV) contributes to the growth and survival of Hodgkin lymphoma (HL) cells. Here we report that down-regulation of the transforming growth factor-beta (TGF-beta) target gene, protein tyrosine phosphatase receptor kappa (PTPRK), followed EBV infection of HL cells and was also more frequently observed in the Hodgkin and Reed-Sternberg (HRS) cells of EBV-positive compared with EBV-negative primary HL. The viability and proliferation of EBV-positive HL cells was decreased by overexpression of PTPRK, but increased following the knockdown of PTPRK expression in EBV-negative HL cells, demonstrating that PTPRK is a functional tumor suppressor in HL. EBV suppressed the TGF-beta-mediated activation of PTPRK expression, suggesting disruption of TGF-beta signaling upstream of PTPRK. This was confirmed when we showed that the Epstein-Barr nuclear antigen-1 (EBNA1) decreased Smad2 protein levels and that this was responsible for PTPRK down-regulation. EBNA1 decreased the half-life of Smad2 but did not interact with Smad2. By down-regulating Smad2 protein expression, EBNA1 apparently disables TGF-beta signaling, which subsequently decreases transcription of the PTPRK tumor suppressor. We speculate that loss of the phosphatase function of PTPRK may activate as-yet-unidentified growth-promoting protein tyrosine kinases, which in turn contribute to the pathogenesis of EBV-positive HL.

Epstein-Barr virus-encoded EBNA1 regulates cellular gene transcription and modulates the STAT1 and TGFbeta signaling pathways

The Epstein-Barr virus (EBV)-encoded EBNA1 protein is expressed in all virus-associated tumors where it plays an essential role in the maintenance, replication and transcription of the EBV genome. Transcriptional profiling of EBNA1-expressing carcinoma cells demonstrated that EBNA1 also influences the expression of a range of cellular genes including those involved in translation, transcription and cell signaling. Of particular interest was the ability of EBNA1 to enhance expression of STAT1 and sensitize cells to interferon-induced STAT1 activation with resultant enhancement of major histocompatibility complex expression. A negative effect of EBNA1 on the expression of TGFbeta1-responsive betaig-h3 and PAI-1 genes was confirmed at the protein level in EBV-infected carcinoma cells. This effect resulted from the ability of EBNA1 to repress TGFbeta1-induced transcription via a reduction in the interaction of SMAD2 with SMAD4. More detailed analysis revealed that EBNA1 induces a lower steady-state level of SMAD2 protein as a consequence of increased protein turnover. These data show that EBNA1 can influence cellular gene transcription resulting in effects that may contribute to the development of EBV-associated tumors.

C4b binding protein binds to CD154 preventing CD40 mediated cholangiocyte apoptosis: a novel link between complement and epithelial cell survival

Activation of CD40 on hepatocytes and cholangiocytes is critical for amplifying Fas-mediated apoptosis in the human liver. C4b-Binding Protein (C4BP) has been reported to act as a potential surrogate ligand for CD40, suggesting that it could be involved in modulating liver epithelial cell survival. Using surface plasmon resonance (BiaCore) analysis supported by gel filtration we have shown that C4BP does not bind CD40, but it forms stable high molecular weight complexes with soluble CD40 ligand (sCD154). These C4BP/sCD154 complexes bound efficiently to immobilised CD40, but when applied to cholangiocytes they failed to induce apoptosis or proliferation or to activate NFkB, AP-1 or STAT 3, which are activated by sCD154 alone. Thus C4BP can modulate CD40/sCD154 interactions by presenting a high molecular weight multimeric sCD154/C4BP complex that suppresses critical intracellular signalling pathways, permitting cell survival without inducing proliferation. Immunohistochemistry demonstrated co-localisation and enhanced expression of C4BP and CD40 in human liver cancers. These findings suggest a novel pathway whereby components of the complement system and TNF ligands and receptors might be involved in modulating epithelial cell survival in chronic inflammation and malignant disease.

The natural history of cervical HPV infection: unresolved issues

The identification of high-risk human papillomavirus (HPV) types as a necessary cause of cervical cancer offers the prospect of effective primary prevention and the possibility of improving the efficiency of cervical screening programmes. However, for these opportunities to be realized, a more complete understanding of the natural history of HPV infection, and its relationship to the development of epithelial abnormalities of the cervix, is required. We discuss areas of uncertainty, and their possible effect on disease prevention strategies.