THOR is a targetable epigenetic biomarker with clinical implications in breast cancer

BACKGROUND

Breast cancer (BC) is the most frequently diagnosed cancer and a leading cause of death among women worldwide. Early BC is potentially curable, but the mortality rates still observed among BC patients demonstrate the urgent need of novel and more effective diagnostic and therapeutic options. Limitless self-renewal is a hallmark of cancer, governed by telomere maintenance. In around 95% of BC cases, this process is achieved by telomerase reactivation through upregulation of the human telomerase reverse transcriptase (hTERT). The hypermethylation of a specific region within the hTERT promoter, termed TERT hypermethylated oncological region (THOR) has been associated with increased hTERT expression in cancer. However, its biological role and clinical potential in BC have never been studied to the best of our knowledge. Therefore, we aimed to investigate the role of THOR as a biomarker and explore the functional impact of THOR methylation status in hTERT upregulation in BC.

RESULTS

THOR methylation status in BC was assessed by pyrosequencing on discovery and validation cohorts. We found that THOR is significantly hypermethylated in malignant breast tissue when compared to benign tissue (40.23% vs. 12.81%, P < 0.0001), differentiating malignant tumor from normal tissue from the earliest stage of disease. Using a reporter assay, the addition of unmethylated THOR significantly reduced luciferase activity by an average 1.8-fold when compared to the hTERT core promoter alone (P < 0.01). To further investigate its biological impact on hTERT transcription, targeted THOR demethylation was performed using novel technology based on CRISPR-dCas9 system and significant THOR demethylation was achieved. Cells previously demethylated on THOR region did not develop a histologic cancer phenotype in in vivo assays. Additional studies are required to validate these observations and to unravel the causality between THOR hypermethylation and hTERT upregulation in BC.

CONCLUSIONS

THOR hypermethylation is an important epigenetic mark in breast tumorigenesis, representing a promising biomarker and therapeutic target in BC. We revealed that THOR acts as a repressive regulatory element of hTERT and that its hypermethylation is a relevant mechanism for hTERT upregulation in BC.

IMMU-18. FAVORABLE OUTCOME IN REPLICATION REPAIR DEFICIENT HYPERMUTANT BRAIN TUMORS TO IMMUNE CHECKPOINT INHIBITION: AN INTERNATIONAL RRD CONSORTIUM REGISTRY STUDY

Pediatric brain tumors with replication repair deficiency (RRD) are hypermutant and may respond to immune checkpoint inhibition (ICI). We performed a consortium registry study of ICI in recurrent RRD cancers. Clinical and companion biomarkers were collected longitudinally on all patients. Biomarkers included tumor mutational burden (TMB), neoantigens and genetic signatures obtained from whole genome and exome sequencing. Immune inference was obtained by RNAseq and T cell rearrangement was collected in the tumor and in blood throughout treatment. Of the 46 tumors on the study, 32 were brain tumors with glioblastoma in 96%. Rapid, objective responses (>50%) were observed in 50% of glioblastomas. Three year overall survival for the whole cohort was 48+/-8% which compares favorably with historical controls. Brain tumors fared worse with OS of 39+/-10% and late recurrences observed even after 2 years of therapy (p=0.02). Tumor size and acute “flare” constitute poor outcome throughout all cancers. While all tumors are hypermutant, TMB and predicted neoantigens correlated with response to ICI (p=0.02). Specific signatures extracted from SNVs and total mutations predicted response to ICI and favorable outcome (p=0.005). RNA inference and TCR reveal that the FLARE phenotype is mostly acute nonspecific immune response and not true progression. Finally, glioblastomas (n=8) which failed single agent ICI had favorable responses to combinational immunotherapies with prolonged survival of 65%+/-8% at one year after failure vs 0 for other patients (p=0.01). RRD glioblastomas exhibit favorable outcome and responses to ICI. Combinational therapies based on tumor and immune signatures of these cancers are necessary.

MODL-25. REPLICATION REPAIR DEFICIENT MOUSE MODELS PROVIDE INSIGHT ON HYPERMUTANT BRAIN TUMOURS, MECHANISMS OF IMMUNE EVASION, AND COMBINATORIAL IMMUNOTHERAPY

Replication repair deficiency (RRD) is the leading cause of hypermutant brain tumours in children. RRD is caused by defects in one of four mismatch repair (MMR) genes and mutations in POLE or POLD1. Such tumours are resistant to common therapeutic agents and animal models are needed to study RRD in vivo and test novel therapies like immune checkpoint inhibitors (ICIs). To model RRD brain tumours specifically, we engineered a Pole mutant mouse model harbouring the S459F mutation (Pole^S459F). We combined Pole^S459F mice with conditional Msh2 knockout (Msh2^LoxP) and Nestin-cre mice. All Nestin-cre⁺Msh2^LoxP/LoxPPole^S459F/+ mice rapidly succumbed to posterior fossa brain tumours between 8.6 and 12.4 weeks. Importantly, tumours exhibited hallmark “ultrahypermutation” (~350 mutations/Mb) and the corresponding signatures characteristic of human combined MMR and POLE-proofreading glioblastoma. Interestingly, Nestin-cre⁺Msh2^LoxP/LoxPPole^S459F/S459F mice failed to establish normal cerebella, suggesting such mutational loads may not support normal brain development. Furthermore, OLIG2-cre⁺Msh2^LoxP/LoxPPole^S459F/+ mice failed to develop tumors. Tumors transplanted into syngeneic vs immunocompromised animals egrafted well orthotopically in the mouse hindbrain but significantly less efficiently when engrafted subcutaneously. Furthermore, immunocompromised and subcutaneous tumors revealed striking differences in mutational burden and clonal architecture, suggestive of nonautonomous immunoediting. Finally, anti-PD1 was sufficient to treat subcutaneously engrafted tumors in immunocompetent animals. This first mouse model of immunocompetent, hypermutant brain tumors can be used to uncover unique characteristics of RRD tumour evolution and allow for immune based therapeutic preclinical testing. Experiments to assess combinational ICIs and other therapeutic interventions in orthotopically transplanted tumors will also be presented.

Combined genetic and epigenetic alterations of the TERT promoter affect clinical and biological behavior of bladder cancer

In urothelial bladder cancer (UBC), risk stratification remains an important unmet need. Limitless self‐renewal, governed by TERT expression and telomerase activation, is crucial for cancer progression. Thus, telomerase activation through the interplay of mutations (TERTp^Mut) and epigenetic alterations in the TERT promoter may provide further insight into UBC behavior. Here, we investigated the combined effect of TERTp^Mut and the TERT Hypermethylated Oncological Region (THOR) status on telomerase activation and patient outcome in a UBC international cohort (n = 237). We verified that TERTp^Mut were frequent (76.8%) and present in all stages and grades of UBC. Hypermethylation of THOR was associated with higher TERT expression and higher‐risk disease in nonmuscle invasive bladder cancers (NMIBC). TERTp^Mut alone predicted disease recurrence (HR: 3.18, 95%CI 1.84 to 5.51, p < 0.0001) but not progression in NMIBC. Combined THOR^high/TERTp^Mut increased the risk of disease recurrence (HR 5.12, p < 0.0001) and progression (HR 3.92, p = 0.025). Increased THOR hypermethylation doubled the risk of stage progression of both TERTp^wt and TERTp^Mut NMIBC. These results highlight that both mechanisms are common and coexist in bladder cancer and while TERTp^Mut is an early event in bladder carcinogenesis THOR hypermethylation is a dynamic process that contributes to disease progression. While the absence of alterations comprises an extremely indolent phenotype, the combined genetic and epigenetic alterations of TERT bring additional prognostic value in NMIBC and provide a novel insight into telomere biology in cancer.

What's new?

Telomerase reverse transcriptase (TERT) activation is central to cancer cell immortalization. It acts, however, through relatively unknown mechanisms. In urothelial bladder cancer (UBC) in particular, TERT activation can occur in the presence or absence of mutation, raising questions about alternative activation mechanisms. Our study shows that hypermethylation of the TERT promoter (THOR) plays a key part in UBC, being a dynamic and progressive process, with hypermethylation levels increasing with bladder cancer severity. Moreover, both hypermethylation and TERT promoter mutation contributed to increased telomerase expression. The findings provide insight into telomere biology in UBC and may be applicable to other tumors.

DNA hypermethylation within TERT promoter upregulates TERT expression in cancer

Replicative immortality is a hallmark of cancer cells governed by telomere maintenance. Approximately 90% of human cancers maintain their telomeres by activating telomerase, driven by the transcriptional upregulation of telomerase reverse transcriptase (TERT). Although TERT promoter mutations (TPMs) are a major cancer-associated genetic mechanism of TERT upregulation, many cancers exhibit TERT upregulation without TPMs. In this study, we describe the TERT hypermethylated oncological region (THOR), a 433-bp genomic region encompassing 52 CpG sites located immediately upstream of the TERT core promoter, as a cancer-associated epigenetic mechanism of TERT upregulation. Unmethylated THOR repressed TERT promoter activity regardless of TPM status, and hypermethylation of THOR counteracted this repressive function. THOR methylation analysis in 1,352 human tumors revealed frequent (>45%) cancer-associated DNA hypermethylation in 9 of 11 (82%) tumor types screened. Additionally, THOR hypermethylation, either independently or along with TPMs, accounted for how approximately 90% of human cancers can aberrantly activate telomerase. Thus, we propose that THOR hypermethylation is a prevalent telomerase-activating mechanism in cancer that can act independently of or in conjunction with TPMs, further supporting the utility of THOR hypermethylation as a prognostic biomarker.

Comprehensive Analysis of Hypermutation in Human Cancer

We present an extensive assessment of mutation burden through sequencing analysis of >81,000 tumors from pediatric and adult patients, including tumors with hypermutation caused by chemotherapy, carcinogens, or germline alterations. Hypermutation was detected in tumor types not previously associated with high mutation burden. Replication repair deficiency was a major contributing factor. We uncovered new driver mutations in the replication-repair-associated DNA polymerases and a distinct impact of microsatellite instability and replication repair deficiency on the scale of mutation load. Unbiased clustering, based on mutational context, revealed clinically relevant subgroups regardless of the tumors' tissue of origin, highlighting similarities in evolutionary dynamics leading to hypermutation. Mutagens, such as UV light, were implicated in unexpected cancers, including sarcomas and lung tumors. The order of mutational signatures identified previous treatment and germline replication repair deficiency, which improved management of patients and families. These data will inform tumor classification, genetic testing, and clinical trial design.

Abstract B09: DNA polymerase mutations trigger rapid onset of ultra-hypermutant malignant brain tumors in children with biallelic mismatch repair deficiency

Background: Biallelic Mismatch Repair Deficiency (bMMRD) is a childhood cancer predisposition syndrome caused by germline mutations in MSH2, MSH6, MLH1, and PMS2. The leading cause of death is malignant brain tumors. The genomic landscape and secondary somatic mutations of bMMRD brain tumors are unknown.

Methods: We analyzed 27 cancers and corresponding normal tissues from bMMRD patients using genome, exome sequencing and SNP-arrays. Additionally, we performed sequential sequencing from five primary and recurrent tumor pairs.

Results: BMMRD malignant brain tumors harbored massive numbers of substitution mutations (&gt;250/Mb), greater than all childhood and most adult cancers (&gt;7,000 analyzed). These cancers lacked copy number alterations (p&lt;0.01) and microsatellite instability as seen in sporadic glioblastoma and adult deficient MMR cancers respectively. All ultra-hypermutated bMMRD brain cancers acquired early and conserved somatic mutations in DNA polymerases ε or δ. We examined a panel of eight genes involved in brain tumor pathogenesis (TP53, EGFR,NF1, RB1, ATRX, PDGFRA, BRAF, ACVR1) and found that 80% of ultra-hypermutant tumors carried a mutation in five or more of these genes, with 70% of the mutations fitting the bMMRD/POL signature. Sequential tumor analysis revealed that brain tumors acquired over 20,000 mutations in less than 6 months during malignant transformation. However, recurrent glioblastomas did not display a higher mutation load than ultra-hypermutant primary tumors with a polymerase mutation.

Conclusions/Significance: Early-onset brain tumors from bMMRD patients have a unique mechanism of malignant progression through secondary mutations in DNA polymerases. During transformation, brain tumors quickly reach a threshold of mutations developed in a rapid burst once a mutation in a DNA polymerase is acquired. The high mutation load and threshold of bMMRD cancers may be its Achilles' heel, exploitable for diagnosis and therapeutic intervention.

Note: This abstract was not presented at the conference.

Citation Format: Adam Shlien, Brittany B. Campbell, Richard de Borja, Ludmil B. Alexandrov, Daniele Merico, David Wedge, Peter Van Loo, Patrick S. Tarpey, Paul Coupland, Aaron Pollett, Tatiana Lipman, Abolfazl Heidari, Shriya Deshmukh, Moritz Gerstung, Diana Merino, Manasa Ramakrishna, Marc Remke, Roland Arnold, Gagan B. Panigrahi, Samina Afzal, Valerie Larouche, Harriet Druker, Jordan Lerner-Ellis, Matthew Mistry, Rina Dvir, Ronald Grant, Ronit Elhasid, Roula Farah, Glenn P. Taylor, Paul C. Nathan, Sarah Alexander, Shay Ben-Shachar, Nada Jabado, Steven Gallinger, Shlohmi Constantini, Peter Dirks, Annie Huang, Steven W. Scherer, Richard G. Grundy, Carol Durno, Melyssa Aronson, M Stephen Meyn, Michael D. Taylor, Zachary F. Pursell, Christopher E. Pearson, David Malkin, P Andrew Futreal, Cynthia Hawkins, Eric Bouffet, Michael D. Taylor, Peter J. Campbell, Uri Tabori. DNA polymerase mutations trigger rapid onset of ultra-hypermutant malignant brain tumors in children with biallelic mismatch repair deficiency. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B09.

Combined hereditary and somatic mutations of replication error repair genes result in rapid onset of ultra-hypermutated cancers

DNA replication-associated mutations are repaired by two components: polymerase proofreading and mismatch repair. The mutation consequences of disruption to both repair components in humans are not well studied. We sequenced cancer genomes from children with inherited biallelic mismatch repair deficiency (bMMRD). High-grade bMMRD brain tumors exhibited massive numbers of substitution mutations (>250/Mb), which was greater than all childhood and most cancers (>7,000 analyzed). All ultra-hypermutated bMMRD cancers acquired early somatic driver mutations in DNA polymerase ɛ or δ. The ensuing mutation signatures and numbers are unique and diagnostic of childhood germ-line bMMRD (P < 10(-13)). Sequential tumor biopsy analysis revealed that bMMRD/polymerase-mutant cancers rapidly amass an excess of simultaneous mutations (∼600 mutations/cell division), reaching but not exceeding ∼20,000 exonic mutations in <6 months. This implies a threshold compatible with cancer-cell survival. We suggest a new mechanism of cancer progression in which mutations develop in a rapid burst after ablation of replication repair.

Abstract A20: hTERT promoter hypermethylation is a cancer signature which predicts survival and response to targeted therapy in pediatric nervous system tumors

Purpose: Defining grade of malignancy and disease progression is a major goal in pediatric neurooncology. Since telomerase is a hallmark of cancer, we examined whether promoter methylation of hTERT, the catalytic subunit of telomerase, can be a biomarker for malignancy, response to therapy and patient outcome.

Patients and methods: Whole genome methylation arrays (discovery cohort n=280), Sequenom and pyrosequencing of hTERT promoter (validation cohort, n=219) were performed on patient samples and normal tissues. Correlation between hTERT promoter methylation, telomere maintenance and patient outcome was performed.

Results: Using the discovery cohort, we uncovered a specific region upstream-of-the transcription-start-site (UTSS) of hTERT that is hypermethylated in 100% of malignant neoplasms that express hTERT and unmethylated in normal tissues and in low grade tumors lacking hTERT expression. In the validation cohort, this biomarker had positive and negative predictive values of 1.0 and 0.93, respectively. UTSS methylation increased in tumors as they evolved from low to high grade and from primary to metastatic. Furthermore, UTSS methylation was able to identify which low grade neoplasms would progress to malignant cancers. Ependymomas with and without UTSS methylation had 5-year overall survival of 51+/-10% and 95+/-5% respectively (p=0.0008). Finally, UTSS methylation could predict which tumors would respond to targeted therapy with telomerase inhibitor.

Conclusion: Hypermethylation of a specific region in the hTERT promoter is a cancer signature. It positively correlates with higher hTERT expression, tumor progression and poor prognosis. hTERT UTSS methylation may also represent a diagnostic tool and a therapeutic target for pediatric nervous system tumors.

Citation Format: Pedro castelo-branco, Sanaa Choufani, Stephen Mack, Denis Gallagher, Cindy Zhang, Tatiana Lipman, Nataliya Zhukova, Erin J. Walker, Diana Merino, Jonathan D. Jonathan, Cynthia Elizabeth, Noa Alon, Libo Zhang, Volker Hovestadt, Marcel Kool, David TW Jones, Sidney Croul, Cynthia Hawkins, Johann Hitzler, Jean C.Y. Wang, David Malkin, Sylvain Baruchel, Peter B. Dirks, Stefan Pfister, Michael Taylor, Rosanna Weksberg, Uri Tabori. hTERT promoter hypermethylation is a cancer signature which predicts survival and response to targeted therapy in pediatric nervous system tumors. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A20.

Methylation of the TERT promoter and risk stratification of childhood brain tumours: an integrative genomic and molecular study

BACKGROUND

Identification of robust biomarkers of malignancy and methods to establish disease progression is a major goal in paediatric neuro-oncology. We investigated whether methylation of the TERT promoter can be a biomarker for malignancy and patient outcome in paediatric brain tumours.

METHODS

For the discovery cohort, we used samples obtained from patients with paediatric brain tumours and individuals with normal brain tissues stored at the German Cancer Research Center (Heidelberg, Germany). We used methylation arrays for genome-wide assessment of DNA. For the validation cohort, we used samples obtained from several tissues for which full clinical and follow-up data were available from two hospitals in Toronto (ON, Canada). We did methylation analysis using quantitative Sequenom and pyrosequencing of an identified region of the TERT promoter. We assessed TERT expression by real-time PCR. To establish whether the biomarker could be used to assess and predict progression, we analysed methylation in paired samples of tumours that transformed from low to high grade and from localised to metastatic, and in choroid plexus tumours of different grades. Finally, we investigated overall survival in patients with posterior fossa ependymomas in which the identified region was hypermethylated or not. All individuals responsible for assays were masked to the outcome of the patients.

FINDINGS

Analysis of 280 samples in the discovery cohort identified one CpG site (cg11625005) in which 78 (99%) of 79 samples from normal brain tissues and low-grade tumours were not hypermethylated, but 145 (72%) of 201 samples from malignant tumours were hypermethylated (>15% methylated; p<0.0001). Analysis of 68 samples in the validation cohort identified a subset of five CpG sites (henceforth, upstream of the transcription start site [UTSS]) that was hypermethylated in all malignant paediatric brain tumours that expressed TERT but not in normal tissues that did not express TERT (p<0.0001). UTSS had a positive predictive value of 1.00 (95% CI 0.95-1.00) and a negative predictive value of 0.95 (0.87-0.99). In two paired samples of paediatric gliomas, UTSS methylation increased during transformation from low to high grade; it also increased in two paired samples that progressed from localised to metastatic disease. Two of eight atypical papillomas that had high UTSS methylation progressed to carcinomas, while the other six assessed did not progress or require additional treatment. 5-year overall survival was 51% (95% CI 31-71) for 25 patients with hypermethylated UTSS posterior fossa ependymomas and 95% (86-100) for 20 with non-hypermethylated tumours (p=0.0008). 5-year progression-free survival was 86% (68-100) for the 25 patients with non-hypermethylated UTSS tumours and 30% (10-50) for those with hypermethylated tumours (p=0.0008).

INTERPRETATION

Hypermethylation of the UTSS region in the TERT promoter is associated with TERT expression in cancers. In paediatric brain tumours, UTSS hypermethylation is associated with tumour progression and poor prognosis. This region is easy to amplify, and the assay to establish hypermethylation can be done on most tissues in most clinical laboratories. Therefore the UTSS region is a potentially accessible biomarker for various cancers.

FUNDING

The Canadian Institute of Health Research and the Terry Fox Foundation.

Neural tumor-initiating cells have distinct telomere maintenance and can be safely targeted for telomerase inhibition

PURPOSE

Cancer recurrence is one of the major setbacks in oncology. Maintaining telomeres is essential for sustaining the limitless replicative potential of such cancers. Because telomerase is thought to be active in all tumor cells and normal stem cells, telomerase inhibition may be nonspecific and have detrimental effects on tissue maintenance and development by affecting normal stem cell self-renewal.

METHODS

We examined telomerase activity, telomere maintenance, and stem cell maturation in tumor subpopulations from freshly resected gliomas, long-term, primary, neural tumor-initiating cells (TIC) and corresponding normal stem cell lines. We then tested the efficacy of the telomerase inhibitor Imetelstat on propagation and self-renewal capacity of TIC and normal stem cells in vitro and in vivo.

RESULTS

Telomerase was undetectable in the majority of tumor cells and specific to the TIC subpopulation that possessed critically short telomeres. In contrast, normal tissue stem cells had longer telomeres and undetectable telomerase activity and were insensitive to telomerase inhibition, which results in proliferation arrest, cell maturation, and DNA damage in neural TIC. Significant survival benefit and late tumor growth arrest of neuroblastoma TIC were observed in a xenograft model (P = 0.02). Furthermore, neural TIC exhibited irreversible loss of self-renewal and stem cell capabilities even after cessation of treatment in vitro and in vivo.

CONCLUSIONS

TIC exhaustion with telomerase inhibition and lack of telomerase dependency in normal stem cells add new dimensions to the telomere hypothesis and suggest that targeting TIC with telomerase inhibitors may represent a specific and safe therapeutic approach for tumors of neural origin.

Abstract 12: Metastatic neuroblastoma cancer stem cells display a mixed phenotype of tumor and niche origin required for survival

Neuroblastoma (NB) is a pediatric tumor of neural crest origin, and is the most common cancer of infancy. 50% of patients have metastases at diagnosis, of which 85% will die after multiple relapses from metastatic disease. We identified tumor-initiating cells (TICs) from bone marrow (BM) metastases of high-risk patients that are propagated as spheres and that have many properties of cancer stem cells, and form NB in mice with as few as 1 cell. To understand patient relapse and disease progression, we compared NB-TICs from BM with those from tumor and brain metastases and SKPs, a normal pediatric stem cell counterpart, by cDNA microarray, flow cytometry, and whole genome shotgun sequencing transcriptome analysis. BM-derived NB-TICs expressed primitive neural crest and neuronal markers as well as hematopoietic markers from primitive, myeloid, and B-cell lineages and contained VDJ gene rearrangements, which are normally associated with B-cell leukemias. Hematopoietic genes were not expressed or expressed at very low levels in tumor-derived sphere lines and a line from an NB brain metastasis, however brain metastasis-derived TICs expressed CD133, while BM-derived NB-TICs did not. Furthermore, we found that shRNA to CD74, which is upregulated in B-cell lymphoma and multiple myeloma and is a therapeutic target for those cancers, induced the rapid death of NB-TICs but not normal SKPs. Interestingly cells co-staining for the hematopoietic markers CD45 or CD74 and the neural neural progenitor marker nestin were found in BM smears of patients with relapsed NB in the bone marrow.

We suggest that metastatic TICs from some tumors adopt resident niche-specific gene expression signatures, which may aid diagnosis and the development of novel treatments. We hypothesize that drugs used for leukemia may be efficacious therapeutics for metastatic NB, and are currently testing this hypothesis in mouse models.

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 12.

Neuroprotective effects of the stable nitroxide compound Tempol on 1-methyl-4-phenylpyridinium ion-induced neurotoxicity in the Nerve Growth Factor-differentiated model of pheochromocytoma PC12 cells

Nerve growth factor (NGF) differentiated pheochromocytoma PC12 cells exposed to 1-methyl-4-phenylpyridinium (MPP+) toxin were used as an in vitro pharmacological model of Parkinson's disease to examine the neuroprotective effects of 4-hydroxy-2,2,6,6-tetramethyl piperidine-n-oxyl (Tempol), a free radical scavenger and a superoxide dismutase-mimetic compound. MPP+-induced PC12 cell death was measured 72 h after exposure to 1.5 mM MPP+ by the release of lactate dehydrogenease, caspase-3 activation and stimulation of survival and stress mitogen-activated protein kinases. Exposure of PC12 cells to MPP+ activated ERK1 and ERK2 (forty-fold over control after 72 h), JNK1 and JNK2 (fourfold after 48 h) and p-38alpha (tenfold after 24 h). Pretreatment of PC12 cells with 500 microM Tempol, 1 h before induction of the MPP+ insult, reduced by 70% the release of LDH into the medium, inhibited caspase-3 activity by 30% and improved by 33% mitochondrial function, effects correlated with a 70% reduction in ERK1 and ERK2 phosphorylation activity. These findings support the neuroprotective effect of Tempol in the MPP+-induced PC12 cell death model and its use as a potential drug for treatment of Parkinson's disease.

Describing the value of specialized distance education in pediatric oncology nursing

Working as specialists in a changing environment, advanced practice nurses in pediatric oncology (APN-POs) benefit from specific pediatric oncology education. The graduates of a pediatric nurse practitioner program in pediatric oncology completed a survey about their educational experience and its impact on their current practice. This practitioner program included a subspecialty education in pediatric oncology and an early form of distance learning. The respondents' answers parallel a number of emerging themes in APN-PO practice and education. Employing distance learning methods in providing subspecialty education holds important implications for future APN-PO education and practice and for the health care of communities throughout the country.

Power and influence in clinical effectiveness and evidence-based medicine

BACKGROUND

The need to base clinical interventions on valid findings of research has been a dominant theme in clinical practice during the last quarter of a century. However, there is much evidence showing that research evidence reaches everyday practice slowly. Solutions to this problem include evidence-based practice and implementation by guidelines and audit. Studies of these methods have included surveys of clinicians' views, implementation projects and evaluations of educational interventions, but they have not examined their implications for the power structure of clinical organizations. This is surprising, given the emphasis placed on medical power in sociological studies of health care.

METHODS

A framework derived from management theory defines and summarizes theories of power and influence under the headings: sources of power, overt methods of influence, unseen or covert methods of influence and individual response to influence. This framework is then used to analyse the power and influence possessed and exerted by general practitioners (GPs) and hospital consultants and how these are affected by evidence-based practice and guidelines and audit programmes.

OUTCOMES

GPs are seen as having less expert power than consultants and to be more compliant with externally managed guidelines and audit programmes. It is pointed out that compliance with guidelines and audit programmes helps GPs to meet their contractual requirement to be involved in clinical audit activities. Evidence-based practice, which directly challenges the authority of expert opinion is seen as a threat to the power of consultants, but a potential opportunity for GPs and other clinicians whose status is traditionally lower.

The future general practitioner: out of date and running out of time

In the late 1960s a Royal College of General Practitioners' working party produced a job description for the 'Future General Practitioner', together with an educational programme for vocational training. Despite the perceived success of vocational training, general practice remains academically disadvantaged compared with hospital medicine. Most general practitioners (GPs) have no contact with research or academic general practice, few achieve higher degrees compared with hospital consultants, and there are few academic posts in general practice. Junior doctors perceive general practice as offering less intrinsic job satisfaction than hospital medicine and recruitment is falling. Registrars who have completed vocational training are reluctant to commit themselves to general practice and often drift away from it. Schemes with an academic content, designed to retain doctors in general practice, have been well received but there are few career posts in academic general practice. Primary care groups and clinical governance will radically change the nature of general practice. GPs will no longer be at the centre of the primary health care team. Primary care trusts, serving populations of 100,000 or more at multiple sites, will still employ doctors but much of the traditional GP workload will be undertaken by nurses. Present day vocational training produces GPs without the skills that future 'community generalists' will need. Their training will be longer and their careers more structured than at present. They will use evidence-based practice routinely and be experts in information management, interpreting and managing complex diagnostic and therapeutic problems in the context of rapidly changing health technology.

Decision making, evidence, audit, and education: case study of antibiotic prescribing in general practice

OBJECTIVES

To describe a group general practice's implementation of a decision to prescribe 3 day courses of 200 mg trimethoprim twice daily for urinary tract infections in women and to compare 3 day courses with 5 and 7 day courses.

DESIGN

Record review, audit of trimethoprim prescribing for urinary tract infections, and critical appraisal of evidence originally presented in support of 3 day course.

SETTING

Group general practice in Newcastle upon Tyne.

DATA SOURCES

The records of all female patients aged 12 years and older who were prescribed trimethoprim for uncomplicated urinary tract infections during a 12 month period were reviewed. 271 valid records were identified.

DATA EXTRACTION

Prescribing rates for different courses of trimethoprim, rates of patients returning for second consultations, rates of urine cultures, results of cultures, results of critical appraisal of evidence.

RESULTS

114 of 271 (42%) prescriptions written at the first visit were for 3 day courses. 16 of 114 (14%) patients who had had a 3 day course of treatment returned for a second consultation compared with 6/83 (7.2%) of those who had had a 5 day course and 8/74 (11%) who had had a 7 day course. The difference between 3 day and 5 day courses in rates of returning for second consultations was 6.8% (95% CI -1.7% to 12.6%) and between 3 day and 7 day courses was 3.2% (-3.6% to 10.0%). Appraisal of the original evidence on which the practice based its recommendations showed that it was flawed. Additional evidence was found in the Cochrane Library.

CONCLUSIONS

Our original decision, made by consensus at a meeting of the practice's partners, had not led to a consistent change in practice. We did not find a significant increase in treatment failures among patients treated with the 3 day regimen.

Aggressive multimodality therapy for stage III esophageal cancer: a phase I/II study

BACKGROUND

Stage III advanced locoregional esophageal carcinoma is frequently unresectable and inconsistently represented in therapeutic trials of esophageal cancer.

METHODS

From 1992 to 1998, 34 of 131 total esophageal cancer patients were designated stage III (16 T3N1, 9 T4N0, 9 T4N1) and medically fit to enter a combined modality protocol with continuous infusion 5-fluorouracil (CIS-FU, 300 to 600 mg/m2/day), high-dose external beam irradiation (60 Gy), and interval esophagectomy. Staging before and after induction therapy included computed tomography; endoscopy, and endoscopic ultrasound.

RESULTS

Significant toxicity from induction therapy included death (5/34; 14.7%), pneumonitis (5/34; 14.7%), mucositis (13/34; 38%), and hand-foot syndrome (3/34; 8.8%). In addition to the five deaths, 11 patients did not proceed to operation because of development of esophagorespiratory fistula in 3, distant disease in 2, persistence of T4 stage in 2, progression of comorbidities in 2, and patient refusal in 2. There was a discrepancy between clinical complete response (cCR) at restaging 56% (19/34) and pathologic CR (pCR) noted at the time of operation (8/34; 23.5%). Complete resections were possible in 16 of 18 patients explored. Complications in 4 patients included: death (1), airway injury (1), chylothorax requiring reoperation (1), anastomotic leak (1), recurrent nerve injury with vocal cord paresis (2), and ascaris infection (1). Actuarial survival analysis using the Kaplan-Meier method and log-rank testing showed a 36-month survival of 20% for the group as a whole and 27% for patients restaged cCR (cCR vs PR, p = 0.0046). Treatment failure is predominantly distant, with good local control in resected patients. N0 node status was strongly associated with survival (N0 vs N1 p = 0.0024). There is a trend towards improved survival in the resected group (resected 22% vs nonresected 10% at 3 years, p = 0.17).

CONCLUSIONS

Response rates and survival are commensurate with multiple completed phase II and III trials. These are attained at a higher treatment-related mortality. T4 patients can be successfully resected in selected patients. Even in advanced disease, nodal status is a significant predictor of survival.

Coping behaviors at diagnosis and in adjustment one year later in children with diabetes

The aim of this investigation was to determine the contributions of coping behaviors used at diagnosis to medical (metabolic control) and psychosocial adjustment (self-perceived competence; adjustment) 1 year later. A total of 89 children (8 to 14 years of age; 48% male; 59% White) received follow-up quarterly from diabetes diagnosis to 1 year later. Findings indicated that, in general, although metabolic control worsened over the first year, psychosocial status and coping behaviors were stable. Boys had worse metabolic control than girls. Multiple regression analysis indicated that self-worth at 1 year postdiagnosis was associated with less use of spirituality (beta = -.44), more use of humor (beta = .28), and more positive self-care (beta = .28); and self-care was less likely to be positive in older children (r = .32). These variables accounted for 47% of the variance (39% adjusted) in general self-worth when entry self-worth was controlled. Poorer overall adjustment at 1 year postdiagnosis was associated with more use of avoidance behaviors (beta = -.47) and poorer self-care (beta = -.71); and more use of avoidance was associated with older age. These variables accounted for 62% of the variance (58% adjusted) in adjustment when adjustment at diagnosis was controlled. Poorer metabolic control was associated with more use of avoidance (beta = .30) and female gender (beta = .39), and avoidance behaviors were more common in older children (beta = .12). This model predicted 33% of the variance (25% adjusted) in metabolic control 1 year after diagnosis.