Talking Trials: An arts-based exploration of attitudes to clinical trials amongst minority ethnic members of the South Riverside Community of Cardiff.

INTRODUCTION: Clinical trials must include diverse participants to ensure the wide applicability of results. However, people from ethnic minorities are included in clinical trials at rates lower than expected given their share of the population. Working with South Riverside Community Development Centre (SRCDC), Talking Trials used public engagement to foster discussions around the underrepresentation of those from minority ethnic communities in clinical trials and to identify and address concerns surrounding trial participation. METHODS: We conducted three workshops with 13 co-researchers from minority ethnic backgrounds. We explored perceptions and understanding of clinical trials alongside participatory art activities to help move away from verbocentric methods of communication. These artworks formed an exhibition that was presented to the community, prompting further discussions and engagement. FINDINGS: Co-production workshops were an effective tool to introduce the public to trial research. With little knowledge of clinical trials at the beginning of the process, our co-researchers formed a cohesive group, sharing initial fears and mistrust towards trials. As conversations progressed these attitudes clearly shifted. Artwork produced during the workshops was incorporated into an exhibition. Quotes and creative pieces from the group were included to reflect the themes identified. Presenting the exhibition at Riverside Festival enabled further engagement with a wider diverse community. The focus on co-production helped build a network of individuals new to research and keen to become involved further. CONCLUSION: Inclusive and democratic co-production, enriched by participatory art practices, provided a powerful means of enabling our group to create new insights and foster new relationships. Projects like Talking Trials can diversify the research process itself-for example, four co-researchers have commenced lay research partner roles on trial management groups and a lay advisory group is in development. PATIENT OR PUBLIC CONTRIBUTION: Three members of staff at SRCDC were on the project delivery group and involved in the initial project design, subsequently helping to connect us with members of the Riverside community to work as co-researchers. Two of the SRCDC staff are co-authors of this manuscript. The project had 13 public co-researchers guiding the direction of this research and creating the artwork displayed in the art exhibition.

Co-production of guidance and resources to implement principled participant information leaflets (PrinciPILs).

Background: The way information about potential benefits and harms of trial is presented within participant information leaflets (PILs) varies widely and may cause unnecessary 'nocebo' effects. The Medical Research Council (MRC) funded a project that developed seven principles to reduce this variation. However, guidance has not been produced to facilitate the implementation of the principles. Stakeholder involvement is recommended to optimise the way these principles are disseminated and explained. To co-produce recommendations for developing: (1) user-friendly guidance for users of the principles; and (2) resources that support the implementation of the principles. Methods: We held a co-production workshop with representation from the following professional groups: the Health Research Authority (HRA), research ethics committee members, and trial managers. Two rounds of discussions focused on generating recommendations for guidance and resources that support the implementation of the seven principles. Extensive low inference style ethnographic notes were taken, and the data were analysed thematically using deductive codes. The data was collected on October 14, 2022. Results: 25 participants attended a hybrid workshop. Participants recommended that both researchers designing PILs and research ethics committee members should use the principles, and that that they should be simple, mention both benefits and harms explicitly, include examples of visual representations, and provide the evidence base for the principles. Conclusions: We were able to co-produce recommendations for developing and implementing the seven principles within PILs. These recommendations can now be implemented to reduce unexplained variation in the way potential benefits and harms are shared within PILs.

Trial participants need to know about the potential benefits and harms of trial interventions to make an informed decision about whether to take part in a clinical trial. Yet the way they are told about these benefits and harms varies widely. We developed seven principles that can reduced this variability. We held a workshop with members of ethics committees and other stakeholders to develop the best way to implement the principles. 25 participants attended the workshop, and we were able to make useful recommendations that will improve the way trial participants are told about risks and benefits of trial treatments.

Patient reported outcomes and recruitment rates following the introduction of principled patient information leaflets (PrinciPILs): Protocol for a meta-analysis.

Background: The way potential benefits and harms of trial interventions are shared within patient information leaflets (PILs) varies widely and may cause unnecessary harms ("nocebo effects"). The aim of this meta-analysis will be to evaluate the influence on recruitment rates and early effects on patient reported adverse events of principled patient information leaflets (PrinciPILs) compared with standard PILs. Methods: Eligible studies will include those that report the effects on recruitment and patient reported adverse events of PrinciPILs compared to standard PILs. We will include in this meta-analysis all the standard PILs in studies within trials (SWATs) of PrinciPILs that were developed as part of the Medical Research Council (MRC) funded PrinciPIL project. By publishing this as a living meta-analysis, we will allow the meta-analysis to be updated with future SWATs of PrinciPILs. We will use the Cochrane Risk of Bias tool to evaluate the risk of bias for each outcome. We will report the total number of studies and participants analysed and the characteristics of included studies (including details of intervention, comparators, outcomes). For dichotomous data, we will calculate the risk difference and the risk ratio (RR) and 95% confidence intervals (CIs). For continuous outcomes we will use weighted mean differences with 95% CIs or standardized mean differences with 95% CIs. We will investigate heterogeneity by visually inspecting the forest plot and by considering the I 2 test result. We will assess the certainty warranted for each outcome using the Grading of Recommendations Assessment Development and Evaluation (GRADE). Ethics approval is not applicable since no original data will be collected. The results will be disseminated through peer-reviewed publication and conference presentations. Discussion: We will discuss the limitations of the meta-analysis including study risk of bias, inconsistency, heterogeneity, and imprecision. A general interpretation of the results and important implications will be provided.

People who take part in randomised trials need to understand the risks as well as the benefits of taking part. Most 'patient information leaflets' (PILs) that describe trial treatments include information about harms. Yet only some PILs contain information about potential benefits. This variation is confusing. Also, the over-emphasis on harms can cause "nocebo" effects, which are the harms caused by expecting something bad to happen. To solve these problems, we have developed seven principles that ensure that information about potential benefits and harms in PILs is balanced and consistent. We will now compare PILs that have been developed according to our principles (we call these 'PrinciPILs') with PILs that have not been developed with our principles. We will test whether PrinciPILs reduce nocebo effects and improve trial recruitment. Here we have described our plans to test the effect of PrinciPILs in a few trials.

Developing principles for sharing information about potential trial intervention benefits and harms with patients: report of a modified Delphi survey.

BACKGROUND: The way information about potential harms of trial intervention is shared within participant information leaflets (PILs) varies widely and can cause subjective 'nocebo' harms. This study aimed to develop principles to improve the composition of information about potential trial intervention benefits and harms within PILs so that variability and avoidable harms are reduced. METHODS: We conducted a two-round modified online Delphi survey, followed by a consensus meeting. For the first round of the survey, 27 statements were developed based on previous research and relevant guidance from the UK, the USA and the World Health Organization. Participants included members from each of the following stakeholder groups: patient and public representatives, research ethics committee members, industry representatives, medico-legal experts, psychologists and trial managers. Each participant was asked to rate their degree of agreement or disagreement with each statement on a 9-point Likert scale. In the second round, participants were invited to reappraise their ratings after reviewing the results of the first round. Finally, two members from each stakeholder group participated in a meeting to confirm those statements for which there was agreement. RESULTS: Two hundred and fifty participants completed round 1, and 201 participants completed round 2. In round 1, consensus was reached for 16 statements. In round 2, consensus was reached for an additional three statements. The consensus meeting confirmed the survey results and consolidated the statements. This process resulted in seven principles: (1) all potential harms of a given intervention should be listed, (2) all potential harms should be separated into serious and less serious, (3) it must be made explicit that not all potential harms are known, (4) all potential benefits should be listed, (5) all potential benefits and harms need to be compared with what would happen if the participant did not take part in the trial, (6) suitable visual representations should be added where appropriate and (7) information regarding potential benefits and harms should not be presented apart by one or more pages. CONCLUSIONS: Our modified Delphi process successfully generated seven principles that can and should be used to guide how information is conveyed to patients in information leaflets regarding potential trial benefits and harms.

Palliative radiotherapy combined with stent insertion to reduce recurrent dysphagia in oesophageal cancer patients: the ROCS RCT.

BACKGROUND: Most patients with oesophageal cancer present with incurable disease. For those with advanced disease, the mean survival is 3-5 months. Treatment emphasis is therefore on effective palliation, with the majority of patients requiring intervention for dysphagia. Insertion of a self-expanding metal stent provides rapid relief but dysphagia may recur within 3 months owing to tumour progression. Evidence reviews have called for trials of interventions combined with stenting to better maintain the ability to swallow. OBJECTIVES: The Radiotherapy after Oesophageal Cancer Stenting (ROCS) study examined the effectiveness of palliative radiotherapy, combined with insertion of a stent, in maintaining the ability to swallow. The trial also examined the impact that the ability to swallow had on quality of life, bleeding events, survival and cost-effectiveness. DESIGN: A pragmatic, multicentre, randomised controlled trial with follow-up every 4 weeks for 12 months. An embedded qualitative study examined trial experiences in a participant subgroup. SETTING: Participants were recruited in secondary care, with all planned follow-up at home. PARTICIPANTS: Patients who were referred for stent insertion as the primary management of dysphagia related to incurable oesophageal cancer. INTERVENTIONS: Following stent insertion, the external beam radiotherapy arm received palliative oesophageal radiotherapy at a dose of 20 Gy in five fractions or 30 Gy in 10 fractions. MAIN OUTCOME MEASURES: The primary outcome was the difference in the proportion of participants with recurrent dysphagia, or death, at 12 weeks. Recurrent dysphagia was defined as deterioration of ≥ 11 points on the dysphagia scale of the European Organisation of Research and Treatment of Cancer Quality of Life Questionnaire oesophago-gastric module questionnaire. Secondary outcomes included quality of life, bleeding risk and survival. RESULTS: The study recruited 220 patients: 112 were randomised to the usual-care arm and 108 were randomised to the external beam radiotherapy arm. There was no evidence that radiotherapy reduced recurrence of dysphagia at 12 weeks (48.6% in the usual-care arm compared with 45.3% in the external beam radiotherapy arm; adjusted odds ratio 0.82, 95% confidence interval 0.40 to 1.68; p = 0.587) and it was less cost-effective than stent insertion alone. There was no difference in median survival or key quality-of-life outcomes. There were fewer bleeding events in the external beam radiotherapy arm. Exploration of patient experience prompted changes to trial processes. Participants in both trial arms experienced difficulty in managing the physical and psychosocial aspects of eating restriction and uncertainties of living with advanced oesophageal cancer. LIMITATIONS: Change in timing of the primary outcome to 12 weeks may affect the ability to detect a true intervention effect. However, consistency of results across sensitivity analyses is robust, including secondary analysis of dysphagia deterioration-free survival. CONCLUSIONS: Widely accessible palliative external beam radiotherapy in combination with stent insertion does not reduce the risk of dysphagia recurrence at 12 weeks, does not have an impact on survival and is less cost-effective than inserting a stent alone. Reductions in bleeding events should be considered in the context of patient-described trade-offs of fatigue and burdens of attending hospital. Trial design elements including at-home data capture, regular multicentre nurse meetings and qualitative enquiry improved recruitment/data capture, and should be considered for future studies. FUTURE WORK: Further studies are required to identify interventions that improve stent efficacy and to address the multidimensional challenges of eating and nutrition in this patient population. TRIAL REGISTRATION: Current Controlled Trials ISRCTN12376468 and Clinicaltrials.gov NCT01915693. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 31. See the NIHR Journals Library website for further project information.

Most people are diagnosed with oesophageal (gullet) cancer when it is already at an advanced stage. Losing the ability to swallow food and even fluids is very common when patients are approaching the last months of life. Placing a flexible metal tube, or stent, in the gullet opens it up and improves the ability to swallow quickly. Unfortunately this can fail after around 3 months because the cancer grows and presses on the stent. We designed this trial to see if giving a small dose of radiotherapy alongside insertion of the stent would allow more people to remain swallowing well after 3 months. This could then improve their quality of life and reduce hospitalisation towards the end of life. It may also reduce bleeding from the gullet, as well as other symptoms. We recruited 220 people across the UK, randomly assigning them to have the stent as usual or the stent and a low dose of radiotherapy. We collected a lot of information from the participants at home on how the cancer, the stent and the radiotherapy affected their ability to swallow and their quality of life. Overall, the study showed that the radiotherapy did not improve the ability to swallow 3 months following stent insertion and was less cost-effective than stent insertion alone. It seemed to reduce the risk of bleeding from the tumour itself, but patients found that radiotherapy made them tired and attending extra hospital visits could be troublesome. We also learned that, even after a stent was inserted, patients still struggled with food and needed more support with managing daily life with the stent. The trial results are important. They show that, to answer questions such as these, studies should use different ways of assessing what works, particularly focusing on patients' and families' viewpoints. The results will guide doctors to not routinely give radiotherapy in this situation. The results also suggest that, after the insertion of a stent, patients need extra help in managing their diet, their worries about the stent and their worries about the future.

Palliative radiotherapy after oesophageal cancer stenting (ROCS): a multicentre, open-label, phase 3 randomised controlled trial.

BACKGROUND: Patients with advanced oesophageal cancer have a median survival of 3-6 months, and most require intervention for dysphagia. Self-expanding metal stent (SEMS) insertion is the most typical form of palliation in these patients, but dysphagia deterioration and re-intervention are common. This study examined the efficacy of adjuvant external beam radiotherapy (EBRT) compared with usual care alone in preventing dysphagia deterioration and reducing service use after SEMS insertion. METHODS: This was a multicentre, open-label, phase 3 randomised controlled trial based at cancer centres and acute care hospitals in England, Scotland, and Wales. Patients (aged ≥16 years) with incurable oesophageal carcinoma receiving stent insertion for primary management of dysphagia were randomly assigned (1:1) to receive usual care alone or EBRT (20 Gy in five fractions or 30 Gy in ten fractions) plus usual care after stent insertion. Usual care was implemented according to need as identified by the local multidisciplinary team (MDT). Randomisation was via the method of minimisation stratified by treating centre, stage at diagnosis (I-III vs IV), histology (squamous or non-squamous), and MDT intent to give chemotherapy (yes vs no). The primary outcome was difference in proportions of participants with dysphagia deterioration (>11 point decrease on patient-reported European Organisation for Research and Treatment of Cancer quality of life questionnaire-oesophagogastric module [QLQ-OG25], or a dysphagia-related event consistent with such a deterioration) or death by 12 weeks in a modified intention-to-treat (ITT) population, which excluded patients who did not have a stent inserted and those without a baseline QLQ-OG25 assessment. Secondary outcomes included survival, quality of life (QoL), morbidities (including time to first bleeding event or hospital admission for bleeding event and first dysphagia-related stent complications or re-intervention), and cost-effectiveness. Safety analysis was undertaken in the modified ITT population. The study is registered with the International Standard Randomised Controlled Trial registry, ISRCTN12376468, and ClinicalTrials.gov, NCT01915693, and is completed. FINDINGS: 220 patients were randomly assigned between Dec 16, 2013, and Aug 24, 2018, from 23 UK centres. The modified ITT population (n=199) comprised 102 patients in the usual care group and 97 patients in the EBRT group. Radiotherapy did not reduce dysphagia deterioration, which was reported in 36 (49%) of 74 patients receiving usual care versus 34 (45%) of 75 receiving EBRT (adjusted odds ratio 0·82 [95% CI 0·40-1·68], p=0·59) in those with complete data for the primary endpoint. No significant difference was observed in overall survival: median overall survival was 19·7 weeks (95% CI 14·4-27·7) with usual care and 18·9 weeks (14·7-25·6) with EBRT (adjusted hazard ratio 1·06 [95% CI 0·78-1·45], p=0·70; n=199). Median time to first bleeding event or hospital admission for a bleeding event was 49·0 weeks (95% CI 33·3-not reached) with usual care versus 65·9 weeks (52·7-not reached) with EBRT (adjusted subhazard ratio 0·52 [95% CI 0·28-0·97], p=0·038; n=199). No time versus treatment interaction was observed for prespecified QoL outcomes. We found no evidence of differences between trial group in time to first stent complication or re-intervention event. The most common (grade 3-4) adverse event was fatigue, reported in 19 (19%) of 102 patients receiving usual care alone and 22 (23%) of 97 receiving EBRT. On cost-utility analysis, EBRT was more expensive and less efficacious than usual care. INTERPRETATION: Patients with advanced oesophageal cancer having SEMS insertion for the primary management of their dysphagia did not gain additional benefit from concurrent palliative radiotherapy and it should not be routinely offered. For a minority of patients clinically considered to be at high risk of tumour bleeding, concurrent palliative radiotherapy might reduce bleeding risk and the need for associated interventions. FUNDING: National Institute for Health Research Health Technology Assessment Programme.

Injury resulting from targeted violence: An emergency department perspective.

BACKGROUND: Hate crimes - those perpetrated because of perceived difference, including disability, race, religion, sexual orientation or transgender status - have not been studied at the point of the victim's hospital emergency department (ED) use. AIM: To investigate the frequency, levels of physical harm and circumstances of targeted violence in those seeking treatment at EDs in three UK cities. METHOD: In a multimethods study, face-to-face semi-structured interviews were conducted with 124 adult ED attenders with violent injuries. Victim and perpetrator socio-demographics were recorded. Patient narratives about perceived motives and circumstances were transcribed, uploaded onto NVivo for thematic analysis. RESULTS: Nearly a fifth (23, 18.5%) of the injured patients considered themselves to have been attacked by others motivated by hostility or prejudice to their 'difference' (targeted violence). Thematic analyses suggested these prejudices were to appearance (7 cases), racial tension (5 cases), territorial association (3 cases) and race, religious or sexual orientation (8 cases). According to victims, alcohol intoxication was particularly relevant in targeted violence (estimated reported frequency 90% and 56% for targeted and non-targeted violence, respectively). CONCLUSIONS: Our findings support a broader concept of hate victimisation and suggest that emergency room violence surveys could act as a community tension sensor and early warning system in this regard. Tackling alcohol misuse seems as important in this as in other forms of violence perpetration. Copyright © 2017 John Wiley & Sons, Ltd.

Group psycho-education for bipolar disorder.

Psycho-education is an established intervention for various physical and mental health conditions. This article describes a psycho-education programme developed for people with bipolar disorder. The courses appear to have been beneficial to participants and appraisal of the intervention is ongoing. One area that needs further consideration is whether courses should be run by a person who has bipolar disorder; the advantages and disadvantages of this are discussed.

Mechanisms of the different DNA adduct forming potentials of the urban air pollutants 2-nitrobenzanthrone and carcinogenic 3-nitrobenzanthrone.

2-Nitrobenzanthrone (2-NBA) has recently been detected in ambient air particulate matter. Its isomer 3-nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen identified in diesel exhaust. We compared the efficiencies of human enzymatic systems [hepatic microsomes and cytosols, NAD(P)H:quinone oxidoreductase 1 (NQO1), xanthine oxidase, NADPH:cytochrome P450 reductase, N,O-acetyltransferases, and sulfotransferases] and human primary hepatocytes to activate 2-NBA and its isomer 3-NBA to species forming DNA adducts. In contrast to 3-NBA, 2-NBA was not metabolized at detectable levels by the tested human enzymatic systems and enzymes expressed in human hepatocytes, and no DNA adducts detectable by (32)P-postlabeling were generated by 2-NBA. Even NQO1, the most efficient human enzyme to bioactive 3-NBA, did not activate 2-NBA. Molecular docking of 2-NBA and 3-NBA to the active site of NQO1 showed similar binding affinities; however, the binding orientation of 2-NBA does not favor the reduction of the nitro group. This was in line with the inhibition of 3-NBA-DNA adduct formation by 2-NBA, indicating that 2-NBA can compete with 3-NBA for binding to NQO1, thereby decreasing the metabolic activation of 3-NBA. In addition, the predicted equilibrium conditions favor a 3 orders of magnitude higher dissociation of N-OH-3-ABA in comparison to N-OH-2-ABA. These findings explain the very different genotoxicity, mutagenicity, and DNA adduct forming potential of the two compounds. Collectively, our results suggest that 2-NBA possesses a relatively lower risk to humans than 3-NBA.

Rat cytochromes P450 oxidize 2-nitrophenol, a human metabolite of carcinogenic 2-nitroanisole.

OBJECTIVES: 2-Nitrophenol (2-NP) is the major detoxification metabolite of an important industrial pollutant and a potent carcinogen, 2-nitroanisole (2-NA). Characterization of the products of 2-NP metabolism by rat hepatic microsomes containing cytochromes P450 (CYPs) and identification of the major CYP enzymes participating in this process are aims of this study. METHODS: HPLC with UV detection was employed for the separation and characterization of 2-NP metabolites. Inducers and inhibitors of CYPs and rat recombinant CYPs were used to characterize the enzymes participating in 2-NP oxidation. RESULTS: Rat hepatic microsomes oxidize 2-NP to its hydroxylated metabolite, 2,5-dihydroxynitrobenzene (2,5-DNB). No nitroreductive metabolism leading to the formation of o-aminophenol was evident when using rat hepatic microsomes. Selective CYP inhibitors and hepatic microsomes of rats pre-treated with specific CYP inducers were used to characterize CYPs oxidizing 2-NP in rat livers. Based on these studies, we attribute most of 2-NP oxidation in rat liver to CYP2E1 and 3A, followed by CYP2D and 2C. Among recombinant rat CYP enzymes tested in this study, CYP2E1 and 2C11 were the most effective enzymes oxidizing 2-NP. Oxidation of 2-NP by rat CYP2E1 exhibits the Michaelis-Menten kinetics, having the Km value of 0.35 mM. CONCLUSION: The results found in this study, the first report on the metabolism of 2-NP by rat hepatic microsomes and rat CYP enzymes, demonstrate that CYP2E1 is the major enzyme oxidizing this compound in rat liver.

Genotoxic mechanisms for the carcinogenicity of the environmental pollutants and carcinogens o-anisidine and 2-nitroanisole follow from adducts generated by their metabolite N-(2-methoxyphenyl)-hydroxylamine with deoxyguanosine in DNA.

An aromatic amine, o-anisidine (2-methoxyaniline) and its oxidative counterpart, 2-nitroanisole (2-methoxynitrobenzene), are the industrial and environmental pollutants causing tumors of the urinary bladder in rats and mice. Both carcinogens are activated to the same proximate carcinogenic metabolite, N-(2-methoxyphenyl)hydroxylamine, which spontaneously decomposes to nitrenium and/or carbenium ions responsible for formation of deoxyguanosine adducts in DNA in vitro and in vivo. In other words, generation of N-(2-methoxyphenyl)hydroxylamine is responsible for the genotoxic mechanisms of the o-anisidine and 2-nitroanisole carcinogenicity. Analogous enzymes of human and rat livers are capable of activating these carcinogens. Namely, human and rat cytochorme P4502E1 is the major enzyme oxidizing o-anisidine to N-(2-methoxyphenyl)hydroxylamine, while xanthine oxidase of both species reduces 2-nitroanisole to this metabolite. Likewise, O-demethylation of 2-nitroanisole, which is the detoxication pathway of its metabolism, is also catalyzed by the same human and rat enzyme, cytochorme P450 2E1. The results demonstrate that the rat is a suitable animal model mimicking the fate of both carcinogens in humans and suggest that both compounds are potential carcinogens also for humans.

Oxidation of carcinogenic 2-nitroanisole by rat cytochromes P450 - similarity between human and rat enzymes.

2-Nitroanisole (2-NA) is an important industrial pollutant and a potent carcinogen for rodents. Understanding which cytochrome P450 (CYP) enzymes are involved in its metabolism are important to assess an individual's susceptibility to this environmental carcinogen. The aim of this study was to evaluate the efficiency of rat hepatic CYPs to oxidize 2-NA, to examine the metabolites formed during such an oxidation, and to compare such efficiencies of rat CYPs with those of human. 2-NA is oxidized by rat hepatic microsomes to 2-nitrophenol (2-NP) as the major metabolite, and to 2,6-dihydroxynitrobenzene (2,6-DNB) and 2,5-dihydroxynitrobenzene (2,5-DNB) as the minor products. All these metabolites are suggested as detoxication products. Using hepatic microsomes of rats pre-treated with specific CYP inducers and microsomes from Baculovirus transfected insect cells expressing recombinant rat and human CYP enzymes we found that rat recombinant CYP2E1, 2D2, 2B2, 2C6 and 1A1, as well as orthologous human CYP enzymes are the most efficient enzymes metabolizing 2-NA. However, human CYP1A1 oxidize 2-NA with a higher efficiency than the enzyme of rats. The results show the participation of orthologous CYPs in 2-NA oxidation by both species and underline the suitability of rat species as a model to evaluate human susceptibility to 2-NA.

Oxidative detoxication of carcinogenic 2-nitroanisole by human, rat and rabbit cytochrome P450.

OBJECTIVES: The detoxifying metabolism of a potent rodent carcinogen, 2-nitroanisole (2-NA) by human, rabbit and rat cytochromes P450 (P450) was investigated. Comparison between P450s of experimental animals and humans is essential for the extrapolation of animal carcinogenicity data to the human situation and to assess health risk. METHODS: HPLC with UV detection was employed for the separation and characterization of 2-NA metabolites formed by hepatic microsomes, human recombinant P450s and purified rat and rabbit P450s. RESULTS: An O-demethylated metabolite of 2-NA, 2-nitrophenol (2-NP), and two oxidation products of this metabolite [2,5-dihydroxynitrobenzene (2,5-DNB) and 2,6-dihydroxynitrobenzene (2,6-DNB)] were generated by microsomes and P450s from the species investigated, but at different levels. All the metabolites are detoxication products. 2-NP is the major metabolite generated by rabbit and rat microsomes, but 2,5-DNB is the predominant product in human microsomes. Using human recombinant P450s and purified rodent P450s, we found that human P450 2E1, 1A1 and 2B6 as well as orthologous animal P450s were the most efficient enzymes oxidizing 2-NA to 2-NP, while P450 2E1 and 1A1 were the most effective in the formation of 2,5-DNB and 2,6-DNB. In human hepatic microsomes, 2-NA was oxidized mainly by P4502E1. 2-NA and its reductive metabolite o-anisidine induced rat hepatic and renal P450 1A1/2 and NAD(P)H:quinone oxidoreductase (NQO1), thus modifying their own detoxication and/or activation pathways. CONCLUSIONS: The data demonstrated the participation of orthologous P450s in 2-NA oxidation by all species and indicated that the rat and rabbit might serve as suitable models to mimic 2-NA oxidation in man.