Etiology Of Several Cancers Research Articles

Insight into mithramycin disruption of ETS transcription leads to improved understanding of more selective analogs

Fusion products with the ETS family of transcription factors play critical roles in the etiology of several cancers. In this issue of Structure, Hou etal. (2020) provide insight into allosteric mechanisms by which mithramycin and its analogs perturb protein-DNA interactions in higher-order complexes at a DNA enhancer site.

Abstract A20: Dietary ingestion of aristolochic acid: Mechanisms of exposure

Abstract Aristolochic acids (AA) are human carcinogens and nephrotoxins found in Aristolochia plants, including herbs used in traditional medicines throughout the world. Aristolochic acids can also be ingested as an environmental contaminant in food, which forms the basis of Balkan endemic nephropathy and associated upper tract urothelial cancer. Aristolactam DNA-adducts, formed after metabolism of AA, are promutagenic and are resistant to repair and readily detected in human tissue sample DNA decades after exposure. Thus, AL-DNA adducts are excellent biomarkers of exposure to this carcinogen. The mutational signature of AA is distinct for an environmental carcinogen and is recognized as Signature 22 in the COSMIC mutational signature database. Molecular epidemiology using the presence of adducts and/or the presence of Signature 22 has implicated AA in the etiology of several cancers, including upper-tract urothelial cancer, bladder cancer, renal cell clear cell carcinoma, hepatocellular carcinoma, and cholangiocarcinomas. In regions of the world reliant on traditional medicines, including much of Asia, the AA contribution to incidence of these cancers is significant. In the Balkan countries of Europe, the route of exposure is thought to occur via contamination of wheat harvests with Aristolochia plant material from weed growth. In endemic villages farming families traditionally have ingested primarily wheat flour milled from their own harvests. An alternative hypothesis is that decaying Aristolochia plants release the chemically stable aristolochic acids into the soil, and these are then taken up and concentrated by food plants. To distinguish between these hypotheses, we have obtained 25 flour samples from individual farms along the Croatia/Bosnia and Herzegovina border. To identify AA-contaminated flour, aristolochic acids were extracted from aliquots of the flour, reduced to aristolactams, and quantitated with an LC-ESI-MS/MS method. Several flour samples were indeed contaminated with AA in the range of 10–100 parts per billion. Secondly, we also extracted DNA from each flour sample. The direct contamination hypothesis predicts the presence of Aristolochia DNA in contaminated flour samples; the indirect contamination via decay hypothesis does not. Using widely accepted plant “barcode” PCR protocols, we amplified a portion of the rbcLa gene with generic primers that amplify the gene from all species. Within this PCR amplicon each plant species has a constellation of specific base-pairs. Thus, the contribution of all plant species to the flour sample can be determined by highly parallel sequencing of the amplicon. We will present the results of this next-gen sequencing to determine the contribution of Aristolochia to Balkan flour samples and correlation with aristolochic acid content. Citation Format: Viktoriya Sidorenko, Robert Rieger, Bojan Jelakovic, Thomas Rosenquist. Dietary ingestion of aristolochic acid: Mechanisms of exposure [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A20.

Dimerization of α-Conotoxins as a Strategy to Enhance the Inhibition of the Human α7 and α9α10 Nicotinic Acetylcholine Receptors.

The affinity of α-conotoxins, a class of nicotinic acetylcholine receptor (nAChR) peptide inhibitors, can be enhanced by dendrimerization. It has been hypothesized that this improvement arose from simultaneous binding of the α-conotoxins to several spatially adjacent sites. We here engineered several α-conotoxin dimers using a linker length compatible between neighboring binding sites on the same receptor. Remarkably, the dimer of α-conotoxin PeIA compared to the monomer displayed an increase in potency by 11-fold (IC50 = 1.9 nM) for the human α9α10 nAChR. The dimerization of α-conotoxin RgIA# resulted in a dual inhibitor that targets both α9α10 and α7 nAChR subtypes with an IC50 = ∼50 nM. The RgIA# dimer is therapeutically interesting because it is the first dual inhibitor that potently and selectively inhibits these two nAChR subtypes, which are both involved in the etiology of several cancers. We propose that the dimerization of α-conotoxins is a simpler and efficient alternative strategy to dendrimers for enhancing the activity of α-conotoxins.

Using bioinformatic tools to examine similarities between human PDL-1 protein and common tobacco (Nicotiana tabacum).

70 Background: Human CD274 receptor, known as programmed cell death 1 ligand 1 (RefSeq NP_054862.1), is an inhibitory ligand for Programmed cell death protein 1 (PD1). We aimed in this bioinformatic experiment to identify a homologous PDL-1 protein in plants. Methods: We chose to use tBLASTn because it compares a protein query sequence against a nucleotide sequence database dynamically translated in all six reading frames (both strands). We chose the EST database and restricted our search to plants (Viridiplantae). Results: Using the FASTA sequence of PDL-1 protein, the tBLASTn of the CD274 protein produced a single hit to Nicotiana tabacum (Common tobacco) cDNA, accession number FG181602.1 with E value of 2e-13 and score of 75.9. We translated the FASTA FG181602.1 through ExPASy and after inspecting the results of the 6 open reading frames (ORFs) in comparison with the matching homologous plant protein obtained through tBLASTn above, we found this “novel” protein which we named "PDL1LI". It has the following amino acid sequence: MHAVRRHRGEMHKVALLHNSFLIISILGSYADDFRVMVPTRRLTAARGHSVVLGCEFSPHFGPNPDLSSLVLTWQRQEDSRVVHSFYYERDQLAKQSSAYRNRTALFVTELSKGNASVRIENVGVTDAGRYLCTVSTNQGTNKAELQLDYGAFYTEPRLTINVNSSDVLLQYETEGFPAPVVIWKGEDGENLTDRMKTSVQSNEEMGLYYIKSSYTAPNTPLSLTFTLENHLLHQYLQRPVSYTGGQNSCFYQFIAPVVVS Gor4 shows that our novel PDL1LI protein is 181 amino acids long with 36% alpha helix, 18% extended strand and 46% random coil sequence. According to BLASTp, this protein contains an immunoglobulin domain found in the Ig superfamily in the first half of the protein, and specific domain hits to the Ig_HHLA2, V-set, and IGv domains, with e-values of 1.37e-28, 2.23e-08, and 1.73e-06. Conclusions: Of all the plants, we found a single homology for our original protein PDL1 only in Nicotiana tabacum. We named this novel protein PDL1LI. Tobacco has been implicated in the etiology of several cancers including lung cancer, bladder cancer, head and neck cancers, etc. A wet lab experiment is underway to isolate our novel protein PDL1LI and to study its properties including any possible inhibitory actions on T cells. If confirmed, then we would have elucidated a new carcinogenic mechanism of tobacco.

Birthweight, childhood overweight, height and growth and adult cancer risks: a review of studies using the Copenhagen School Health Records Register.

Most identified risk factors for cancer primarily occur in adulthood. As cancers generally have long latency periods, it is possible that risk factors acting earlier in life and accumulation of risks across the life course are important. Thus, focusing only on adult overweight as a modifiable risk factor may overlook childhood as an important aetiologic time window when body size is relevant for future cancer risks. The objective of this study was to review the evidence for associations between birthweight, body mass index (BMI), height and growth from 7-13 years and adult cancer risks based on studies using the Copenhagen School Health Records Register. The register contains measured anthropometric information on 372,636 children born in 1930-1989. All studies examining associations between early life body size and risks of adult cancer (until 85 years, diagnosed in 1968-2015) were included, comprising 31 studies on 16 different cancer sites. Cancer diagnoses were retrieved via individual-level linkages to the Danish Cancer Registry. Birthweight was differentially associated with bladder, breast, colon, glioma, Hodgkin's disease, liver, kidney (renal cell), melanoma, ovarian, rectal, testicular and thyroid cancer. BMI in childhood was positively associated with risks of bladder (only late childhood), colon, endometrial, kidney, liver, oesophageal (only late childhood), ovarian, pancreatic (<70 years), prostate (only before childhood height adjustment) and thyroid cancer, whereas it was inversely associated with breast cancer. Child height was positively associated with breast, colon, endometrial, glioma, Hodgkin's disease, kidney, melanoma, oesophageal (only women), ovarian, prostate, testicular and thyroid cancer and inversely associated with bladder cancer. Greater than average increases in childhood BMI or linear growth at ages 7-13 increased risks of several cancers. Early life body size and growth are associated with many, but not all adult cancers, suggesting that the aetiology of several cancers may lie earlier in life than previously thought.

The associations of anthropometric, behavioural and sociodemographic factors with circulating concentrations of IGF-I, IGF-II, IGFBP-1, IGFBP-2 and IGFBP-3 in a pooled analysis of 16,024 men from 22 studies.

Insulin‐like growth factors (IGFs) and insulin‐like growth factor binding proteins (IGFBPs) have been implicated in the aetiology of several cancers. To better understand whether anthropometric, behavioural and sociodemographic factors may play a role in cancer risk via IGF signalling, we examined the cross‐sectional associations of these exposures with circulating concentrations of IGFs (IGF‐I and IGF‐II) and IGFBPs (IGFBP‐1, IGFBP‐2 and IGFBP‐3). The Endogenous Hormones, Nutritional Biomarkers and Prostate Cancer Collaborative Group dataset includes individual participant data from 16,024 male controls (i.e. without prostate cancer) aged 22–89 years from 22 prospective studies. Geometric means of protein concentrations were estimated using analysis of variance, adjusted for relevant covariates. Older age was associated with higher concentrations of IGFBP‐1 and IGFBP‐2 and lower concentrations of IGF‐I, IGF‐II and IGFBP‐3. Higher body mass index was associated with lower concentrations of IGFBP‐1 and IGFBP‐2. Taller height was associated with higher concentrations of IGF‐I and IGFBP‐3 and lower concentrations of IGFBP‐1. Smokers had higher concentrations of IGFBP‐1 and IGFBP‐2 and lower concentrations of IGFBP‐3 than nonsmokers. Higher alcohol consumption was associated with higher concentrations of IGF‐II and lower concentrations of IGF‐I and IGFBP‐2. African Americans had lower concentrations of IGF‐II, IGFBP‐1, IGFBP‐2 and IGFBP‐3 and Hispanics had lower IGF‐I, IGF‐II and IGFBP‐3 than non‐Hispanic whites. These findings indicate that a range of anthropometric, behavioural and sociodemographic factors are associated with circulating concentrations of IGFs and IGFBPs in men, which will lead to a greater understanding of the mechanisms through which these factors influence cancer risk.

Association Between Nasopharyngeal Carcinoma and Cytomegalovirus in Sudan

Background: Oncogenic viruses has a great impact in the etiology of several human cancers. Human cytomegalovirus is found throughout all geographic locations and socioeconomic groups, and infects between 60% and 70% of adults in industrialized countries and almost 100% in emerging countries. The role of human cytomegalovirus in the etiology of several cancers was well established, but there is little data regarding its association with nasopharyngeal carcinoma, particularly in Sudan. Aim: Therefore, the aim of this study was to screen for the detection of human cytomegalovirus in tissue blocks obtained from Sudanese patients with nasopharyngeal carcinoma. Methods: Formalin fixed paraffin wax processed nasopharyngeal carcinoma tissue were obtained from 150 tissue blocks and retrospectively investigated for the presence of human cytomegalovirus using polymerase chain reaction. Results: Of the 150 nasopharyngeal carcinoma tissue specimens, human cytomegalovirus was identified in 53/150 (35.3%) of the samples. Out of the 53 samples infected with human cytomegalovirus, 33/97 (34%) were among males and 20/53 (37.7%) were among females. Of the 53 positive samples, 36/53 (68%) were found to harbor Epstein-Barr virus. Conclusion: The current study has shown a relatively considerable association between human cytomegalovirus and nasopharyngeal carcinoma. The great majority of samples sheltering human cytomegalovirus were also found to hide Epstein-Barr virus, which proposes the potentiality of Epstein-Barr virus over human cytomegalovirus.

Genetic variants in the inflammation pathway as predictors of recurrence and progression in non-muscle invasive bladder cancer treated with Bacillus Calmette-Guérin.

Inflammation plays a critical role in the etiology of several cancers and may affect their clinical outcome. Our objective was to assess the association of genetic variants within the inflammation pathway with recurrence and progression among non-muscle invasive bladder cancer (NMIBC) patients with or without Bacillus Calmette–Guérin (BCG) treatment. We genotyped 372 single nucleotide polymorphisms (SNPs) in 27 selected genes within the inflammation pathway in 349 patients diagnosed with NMIBC, followed by internal validation in 322 additional patients. We used Cox proportional hazards regression analyses to identify SNPs as predictors for recurrence and progression. In the discovery phase, we identified 20 variants that were significantly associated with recurrence outcomes and 15 SNPs significantly associated with progression in patients treated with BCG but not in the transurethral resection (TUR)-only group. In BCG treated patients, rs7089861 was the only SNP significantly associated with risk of progression in both the discovery phase (Hazard Ratio [HR]=3.15, 95% Confidence Interval [CI]: 1.38-7.22, P<0.01) and validation phase (HR=3.84, 95% CI: 1.64-9.0, P=0.002; meta-analysis HR=3.47, 95% CI: 1.92-6.28, P<0.001). Two variants, rs1800686 and rs2071081, had probable association with HRs of the same trend in the discovery and validation groups (meta-analysis P=0.002). These findings supported the notion that genetic variation of inflammation pathway may impact clinical outcome of NMIBC patients treated with BCG immunotherapy. Further validation of these results in order to improve risk stratification to identify patients most likely to benefit from BCG treatment versus upfront radical cystectomy and future development of potential targeted therapies are warranted.Significance StatementIn a two-stage study, we identified several genetic variants in the inflammation pathway associated with recurrence and progression in early-stage bladder cancer. In particular, variant rs7089861 was validated for progression among patients who underwent BCG immunotherapy. Several other variants showed marginal association with recurrence or progression. These findings suggest that inflammatory pathway genetic variants may influence clinical outcome of bladder cancer patients and help to select patients most appropriate for BCG treatment.

Dietary glycemic index, glycemic load, and cancer risk: results from the EPIC-Italy study

Factors linked to glucose metabolism are involved in the etiology of several cancers. High glycemic index (GI) or high glycemic load (GL) diets, which chronically raise postprandial blood glucose, may increase cancer risk by affecting insulin-like growth factor. We prospectively investigated cancer risk and dietary GI/GL in the EPIC-Italy cohort. After a median 14.9 years, 5112 incident cancers and 2460 deaths were identified among 45,148 recruited adults. High GI was associated with increased risk of colon and bladder cancer. High GL was associated with: increased risk of colon cancer; increased risk of diabetes-related cancers; and decreased risk of rectal cancer. High intake of carbohydrate from high GI foods was significantly associated with increased risk of colon and diabetes-related cancers, but decreased risk of stomach cancer; whereas high intake of carbohydrates from low GI foods was associated with reduced colon cancer risk. In a Mediterranean population with high and varied carbohydrate intake, carbohydrates that strongly raise postprandial blood glucose may increase colon and bladder cancer risk, while the quantity of carbohydrate consumed may be involved in diabetes-related cancers. Further studies are needed to confirm the opposing effects of high dietary GL on risks of colon and rectal cancers.

Consumption of fish and meats and risk of hepatocellular carcinoma: the European Prospective Investigation into Cancer and Nutrition (EPIC)

BackgroundWhile higher intake of fish and lower consumption of red/processed meats have been suggested to play a protective role in the etiology of several cancers, prospective evidence for hepatocellular carcinoma (HCC) is limited, particularly in Western European populations. MethodsThe associations of fish and meats with HCC risk were analyzed in the EPIC cohort. Between 1992 and 2010, 191 incident HCC were identified among 477 206 participants. Baseline diet was assessed using validated dietary questionnaires. A single 24-h diet recall from a cohort subsample was used for calibration. Multivariable proportional hazard regression was utilized to estimate hazard ratios (HR) and 95% confidence intervals (CI). In a nested case–control subset (HCC = 122), HBV/HCV status and liver function biomarkers were measured. ResultsHCC risk was inversely associated with intake of total fish (per 20 g/day increase, HR = 0.83, 95% CI 0.74–0.95 and HR = 0.80, 95% CI 0.69–0.97 before and after calibration, respectively). This inverse association was also suggested after adjusting for HBV/HCV status and liver function score (per 20-g/day increase, RR = 0.86, 95% CI 0.66–1.11 and RR = 0.74, 95% CI 0.50–1.09, respectively) in a nested case–control subset. Intakes of total meats or subgroups of red/processed meats, and poultry were not associated with HCC risk. ConclusionsIn this large European cohort, total fish intake is associated with lower HCC risk.

Processed meat consumption and risk of cancer: a multisite case-control study in Uruguay.

Background:The role of processed meat in the aetiology of several cancers was explored in detail.Methods:In the time period 1996–2004, a multisite case–control study was conducted in Montevideo, Uruguay. The study included 6 060 participants (3 528 cases and 2 532 controls) corresponding to cancers of the oral cavity, pharynx, oesophagus, stomach, colon, rectum, larynx, lung, female breast, prostate, urinary bladder, and kidney (renal cell carcinoma only).Results:The highest odds ratios (ORs) were positively associated with cancers of the colon, rectum, stomach, oesophagus, and lung. With the exception of renal cell carcinoma, the remaining cancer sites were significantly associated with elevated risks for processed meat consumption. Furthermore, mortadella, salami, hot dog, ham, and salted meat were strongly associated with risk of several cancer sites.Conclusion:It could be concluded that processed meat intake could be a powerful multiorgan carcinogen.

The association between inflammation‐related genes and serum androgen levels in men: The prostate, lung, colorectal, and ovarian study

Androgens and inflammation have been implicated in the etiology of several cancers, including prostate cancer. Serum androgens have been shown to correlate with markers of inflammation and expression of inflammation-related genes. In this report, we evaluated associations between 9,932 single nucleotide polymorphisms (SNPs) marking common genetic variants in 774 inflammation-related genes and four serum androgen levels (total testosterone [T], bioavailable T [BioT]; 5α-androstane-3α, 17β-diol glucuronide [3αdiol G], and 4-androstene-3,17-dione [androstenedione]), in 560 healthy men (median age 64 years) drawn from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Baseline serum androgens were measured by radioimmunoassay. Genotypes were determined as part of the Cancer Genetic Markers of Susceptibility Study genome-wide scan. SNP-hormone associations were evaluated using linear regression of hormones adjusted for age. Gene-based P values were generated using an adaptive rank truncated product (ARTP) method. Suggestive associations were observed for two inflammation-related genes and circulating androgen levels (false discovery rate [FDR] q-value <0.1) in both SNP and gene-based tests. Specifically, T was associated with common variants in MMP2 and CD14, with the most significant SNPs being rs893226G > T in MMP2 and rs3822356T > C in CD14 (FDR q-value = 0.09 for both SNPs). Other genes implicated in either SNP or gene-based tests were IK with T and BioT, PRG2 with T, and TNFSF9 with androstenedione. These results suggest possible cross-talk between androgen levels and inflammation pathways, but larger studies are needed to confirm these findings and to further clarify the interrelationship between inflammation and androgens and their effects on cancer risk.

Salt, processed meat and the risk of cancer

This study assesses the association between salt added at the table, processed meat and the risk of various cancers. Mailed questionnaires were completed by 19 732 patients with histologically confirmed incident cancer of the stomach, colon, rectum, pancreas, lung, breast, ovary, prostate, testis, kidney, bladder, brain, non-Hodgkin's lymphoma or leukaemia, and 5039 population controls,between 1994 and 1997. Measurement included information on socioeconomic status, lifestyle habits and diet. A 69-item food frequency questionnaire provided data on eating habits 2 years before the study. Odds ratios and 95% confidence intervals were derived through unconditional logistic regression. Compared with never adding salt at the table, always or often adding salt at the table was associated with an increased risk of stomach, lung, testicular and bladder cancer. Processed meat was significantly related to the risk of the stomach, colon, rectum, pancreas, lung, prostate, testis, kidney and bladder cancer and leukaemia; the odds ratios for the highest quartile ranged from 1.3 to 1.7. The findings add to the evidence that high consumption of salt and processed meat may play a role in the aetiology of several cancers.

A Population-Based Study of IGF Axis Polymorphisms and the Esophageal Inflammation, Metaplasia, Adenocarcinoma Sequence

Insulin-like growth factor (IGF) axis plays a key role in cell development, proliferation, and survival and is implicated in the etiology of several cancers. Few studies have examined the relationship between genetic variation of this axis and esophageal adenocarcinoma (EAC) or its precursors. In a population-based case-control study, we investigated the association of common polymorphisms of IGF-1, IGF-2, IGF-1 receptor, IGF binding protein-3, growth hormones (GH) 1 and GH2, and GH receptor with reflux esophagitis (RE), Barrett esophagus (BE), and EAC. Two hundred and thirty RE, 224 BE, 227 EAC cases, and 260 controls were studied. Gene polymorphisms were identified using publicly available online resources; 102 IGF axis tag and putatively functional single-nucleotide polymorphisms (SNPs) were analyzed using MassARRAY iPLEX and Taqman assays. Results were analyzed using Haploview. Three polymorphisms were disease-associated. IGF1 SNP rs6214 was associated with BE (adjusted P = .039). Using GG genotype as reference, odds ratio for BE in AA (wild-type) was 0.43 (95% confidence interval [CI], 0.24-0.75). GH receptor SNP rs6898743 was associated with EAC (adjusted P = .0112). With GG as reference, odds ratio for EAC in CC (wild-type) genotype was 0.42 (95% CI, 0.23-0.76). IGF1 (CA)(17) 185-bp allele was associated with RE (adjusted P = .0116). Using IGF1(non17) as reference, odds ratio for RE in IGF1(17) carriers was 7.29 (95% CI, 1.57-46.7). In this study, 3 polymorphisms of IGF genes were associated with EAC or its precursors. These polymorphisms may be markers of disease risk; independent validation of our findings is required. These results suggest the IGF pathway is involved in EAC development.

Intervention studies in exercise and cancer prevention.

The aim of this article is to examine the role of exercise randomized clinical trials and other intervention studies in defining the associations between physical activity and cancer prevention. To accomplish this, data from published randomized clinical trials and other intervention studies were reviewed and summarized. There are few intervention studies that specifically assess the effect of exercise on biomarkers for cancer. Some early work looking at exercise effect on endogenous sex hormones in premenopausal women is relevant to the etiology of several cancers including breast and endometrium, as risk of these cancers is increased in women with high levels of circulating estrogens. Several randomized clinical trials have assessed the effect of exercise on insulin, a potential cancer growth promoter. A smaller number of studies have assessed the impact of exercise interventions on insulin-like growth factor and insulin-like growth factor binding protein. Several small intervention trials have studied the effect of exercise on immune function. Two current randomized clinical trials focused on exercise effects on cancer biomarkers are outlined. Randomized clinical trials provide important information about the effect of exercise interventions on cancer biomarkers and other outcomes relevant to cancer.

Folate and breast cancer: the role of polymorphisms in methylenetetrahydrofolate reductase (MTHFR)

Evidence is growing that low folate status may be a factor in the aetiology of several cancers, including breast cancer. The methylenetetrahydrofolate reductase gene ( MTHFR), which has a key role in folate metabolism, is polymorphic. We report a case-control study of two functional polymorphisms in MTHFR, dietary folate intake and breast cancer. Sixty-two cases with invasive breast cancer and sixty-six general practice controls participated. Women reporting the highest dietary folate intake had non-significantly reduced breast cancer risk (odds ratio (OR)=0.49, 95% confidence interval (CI) 0.20–1.20). Risk was significantly lower for the 1298CC genotype compared to AA (OR=0.24, 95% CI 0.06–0.97). Relative to compound wild-type subjects, compound heterozygotes had moderately reduced risk (OR=0.47, 95% CI 0.11–1.92) and homozygote variants (677TT and/or 1298CC) greater reduced risk (OR=0.26, 95% CI 0.07–0.96); the trend was statistically significant. Patterns in risk with regard to genotype and folate combinations are broadly similar those reported for colorectal neoplasia. The roles of MTHFR and folate in breast cancer aetiology are likely to be complex.

Functional characterization of the human CYP1A1 negative regulatory element: modulation of Ah receptor mediated transcriptional activity.

The mechanisms that underly the regulation of human CYP1A1 have merited considerable attention because of their association both with toxic outcomes and the etiology of several cancers. Previous work conducted in this laboratory has identified a negative regulatory element (NRE) in the 5' region of this gene that appeared to modulate CYP1A1 transcriptional activity. This NRE is present in two functional copies, a high affinity 21-bp palindrome centered at position -784, and an additional element found within a GC-rich region between position -728 and -558. In this report, the regulatory function of the NREs in the context of the CYP1A1 promoter was evaluated. This was accomplished by substituting mutated elements for the corresponding wild-type element in a vector that contained human CYP1A1 sequences positions -1140 to +59 directing the transcription of the chloramphenicol acetyltransferase reporter gene. Expression vectors containing specific mutations in each or both NREs were characterized. We show that eliminating the binding of the CYP1A1 repressor protein to one or both repressor motifs results in a significant 2- to 3-fold increase in the inducibility of CYP1A1 promoter activity. Although mutation of both sites appeared to result in an increase in inducibility over that observed with only one site mutated, the effect was not additive. Such aberrant transcriptional activity correlates with the highly inducible aryl hydrocarbon hydroxylase phenotype that is a reported marker for individuals predisposed to lung cancer. Mutation of the NRE, or more likely, the cognate repressor protein(s), may provide a genetic basis for this phenotype.

Epstein-Barr virus latent infection in vivo.

Epstein-Barr virus (EBV) is an exclusively human herpes virus which is recognised as the causative agent of infectious mononucleosis and which is implicated in the aetiology of several cancers. However, it is particularly remarkable that this virus is harboured without causing symptoms for the lifetime of most immunocompetent adults. Virus and host have co-evolved over millions of years, achieving a balance between viral persistence and immune control. It is this dynamic equilibrium which is the focus of this review. The main site of viral persistence is within latently infected lymphocytes, although infectious virus is also released into saliva from productively infected cells in the oropharynx. In vitro, EBV efficiently transforms resting B cells to activated, perpetually dividing lymphoblasts. These express a repertoire of eight viral antigens, several of which have been found to be targets for cytotoxic T cell (CTL) responses in healthy carriers. Transformed lymphoblasts are susceptible to immune control in vivo, and are abundant only during primary infection or in individuals with impaired cell mediated immunity. Other types of viral latent infection have been identified in malignant cell lines, in which EBV expresses a more restricted range of antigens. These also may have their in vivo equivalents during natural infection in healthy carriers. It is likely that the virus evades elimination by the immune system by establishing infection in non-activated, relatively non immunogenic B cells, in which the main CTL target antigens are not expressed. Copyright 1997 John Wiley & Sons, Ltd.