Potassium channel-driven bioelectric signalling regulates metastasis in triple-negative breast cancer

BACKGROUND

There is a critical need to better understand the mechanisms that drive local cell invasion and metastasis to develop new therapeutics targeting metastatic disease. Bioelectricity is an important mediator of cellular processes and changes in the resting membrane potential (RMP) are associated with increased cancer cell invasion. However, whether the RMP can be used to target invading cancer cells is unknown.

METHODS

We employed both genetic and pharmacological manipulation of potassium channel activity and characterized the effects on breast cancer cell migration and invasion in vitro, and metastasis in an animal model of breast cancer.

FINDINGS

Our data demonstrate that altering the RMP of triple-negative breast cancer (TNBC) cells by manipulating potassium channel expression increases in vitro invasion, in vivo tumour growth and metastasis, and is accompanied by changes in gene expression associated with cell adhesion.

INTERPRETATION

We describe a novel mechanism for RMP-mediated cell migration involving cadherin-11 and the MAPK pathway. Importantly, we identify a new strategy to target metastatic TNBC in vivo by repurposing an FDA-approved potassium channel blocker. Our results demonstrate that bioelectricity regulates cancer cell invasion and metastasis which could lead to a new class of therapeutics for patients with metastatic disease.

FUNDING

This work was supported by the National Institutes of Health (R00-CA207866 to M.J.O.), Tufts University (Start-up funds from the School of Engineering to M.J.O., Tufts Collaborates Award to M.J.O. and M.L.), Allen Discovery centre program (Paul G. Allen Frontiers Group (12,171) to M.L.), and Breast Cancer Alliance Young Investigator Grant to M.J.O, Laidlaw Scholar funding to D.S. M.L. also gratefully acknowledges support of the Barton Family Foundation.

Abstract 2865: Repurposing potassium channel blockers to target metastasis in triple negative breast cancer

Despite the identification of pro-metastatic markers and signaling pathways that drive the invasion of triple negative breast cancer (TNBC), there are currently no treatments that directly target invading cells. Recent evidence suggests that the bioelectric state of cancer cells can drive cell proliferation and invasion, creating an opportunity to investigate new therapies that target the bioelectric state of a cell. Our previous data suggests that of the most abundant ions present in the body, potassium (K+) is most important for controlling the bioelectric state of TNBC cells, and that K+ flux affects the invasive properties of TNBC cells. Therefore, we hypothesized that blocking K+ channels would disrupt the bioelectric state and reduce 2D migration and 3D invasion. Four FDA-approved K+ channel blockers (amiodarone, carvedilol, imipramine, and thioridazine) were selected from the Repurposing Drugs in Oncology database based on inhibition target channels and mechanisms of action. Cell viability in human TNBC MDA-MB-231 and MDA-MB-468 cells was investigated and IC50 dose response curves were generated to determine that 5 µM and 10µM were the optimal doses to study further. Interestingly, while we determined that all four drugs reduced cell viability, amiodarone and carvedilol significantly changed the bioelectric state and reduced proliferation of TNBC cells compared to negative controls. Experiments are ongoing to evaluate the effects of these inhibitors on 2D migration, 3D invasion, and in an in vivo mouse xenograft study. Understanding the mechanism behind K+ channel inhibition in TNBC could give rise to new pharmacologic targets. In addition, supplementing existing metastatic TNBC regimens with a repurposed K+ channel blocker could potentially reduce development costs, decrease time to market, and provide a new treatment option to patients.

Citation Format: Priyanka Ram, Samantha L. Payne, Madeleine J. Oudin. Repurposing potassium channel blockers to target metastasis in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2865.

A class of costimulatory CD28-bispecific antibodies that enhance the antitumor activity of CD3-bispecific antibodies

T cell activation is initiated upon binding of the T cell receptor (TCR)/CD3 complex to peptide-major histocompatibility complexes ("signal 1"); activation is enhanced by engagement of a second "costimulatory" receptor, such as the CD28 receptor on T cells binding to its cognate ligand(s) on the target cell ("signal 2"). CD3-based bispecific antibodies act by replacing conventional signal 1, linking T cells to tumor cells by binding a tumor-specific antigen (TSA) with one arm of the bispecific and bridging to TCR/CD3 with the other. Although some of these so-called TSAxCD3 bispecifics have demonstrated promising antitumor efficacy in patients with cancer, their activity remains to be optimized. Here, we introduce a class of bispecific antibodies that mimic signal 2 by bridging TSA to the costimulatory CD28 receptor on T cells. We term these TSAxCD28 bispecifics and describe two such bispecific antibodies: one specific for ovarian and the other for prostate cancer antigens. Unlike CD28 superagonists, which broadly activate T cells and resulted in profound toxicity in early clinical trials, these TSAxCD28 bispecifics show limited activity and no toxicity when used alone in genetically humanized immunocompetent mouse models or in primates. However, when combined with TSAxCD3 bispecifics, they enhance the artificial synapse between a T cell and its target cell, potentiate T cell activation, and markedly improve antitumor activity of CD3 bispecifics in a variety of xenogeneic and syngeneic tumor models. Combining this class of CD28-costimulatory bispecific antibodies with the emerging class of TSAxCD3 bispecifics may provide well-tolerated, off-the-shelf antibody therapies with robust antitumor efficacy.

Abstract 4555: Selection of CD3 affinity allows generation of T-cell redirecting bispecific antibodies with unique pharmacokinetic and biodistribution properties

T-cell redirecting bispecific antibodies are an emerging class of therapeutic agents designed to simultaneously bind to T cells (via CD3) and tumor cell specific antigens (TSA), with the goal of inducing T cell-mediated killing of tumor cells. Despite promising pre-clinical and clinical efficacy from TSAxCD3 antibodies, these agents have associated toxicities that remain challenging. Here we present findings from a series of bispecific antibodies that were engineered to have a range of CD3 affinities, but which retained the same binding affinity to the selected tumor antigen. These agents were tested for killing of tumor cells in vitro, and for biodistribution, serum half-life, and anti-tumor activity in vivo. By altering the binding strength for CD3, bispecifics were generated that maintained potent killing of TSA+ cells but displayed differential profiles of cytokine release, pharmacokinetics, and biodistribution. Our results suggest that tuning CD3 affinity is a promising method to improve the therapeutic window of T cell-engaging bispecific antibodies.

Citation Format: Lauric Haber, Kara Olson, Robert Babb, Marcus Kelly, Alison Crawford, Marc Retter, David DiLillo, Erica Ullman, Jennifer Finney, Lauren Canova, Arpita Pawashe, Danica Chiu, Kristin Vazzana, Priyanka Ram, Katja Mohrs, Amanda Dorvilliers, Jenny Xiao, Sosina Makonnen, Carlos Hickey, Cody Arnold, Jason Giurleo, Supriya Patel, Richard Tavare, Ya Ping Chen, Gang Chen, William Olson, Gavin Thurston, John Chia-Yang Lin, Aynur Hermann, Jessica Kirshner, Eric J. Smith. Selection of CD3 affinity allows generation of T-cell redirecting bispecific antibodies with unique pharmacokinetic and biodistribution properties [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4555.

A PSMA-Targeting CD3 Bispecific Antibody Induces Antitumor Responses that Are Enhanced by 4-1BB Costimulation

Patients with hematologic cancers have improved outcomes after treatment with bispecific antibodies that bind to CD3 on T cells and that redirect T cells toward cancer cells. However, clinical benefit against solid tumors remains to be shown. We made a bispecific antibody that targets both the common prostate tumor-specific antigen PSMA and CD3 (PMSAxCD3) and provide evidence for tumor inhibition in several preclinical solid tumor models. Mice expressing the human extracellular regions of CD3 and PSMA were generated to examine antitumor efficacy in the presence of an intact immune system and PSMA expression in normal tissues. PSMAxCD3 accumulated in PSMA-expressing tissues and tumors as detected by immuno-PET imaging. Although PSMAxCD3 induced T-cell activation and showed antitumor efficacy in mice with low tumor burden, PSMAxCD3 lost efficacy against larger solid tumors, mirroring the difficulty of treating solid tumors in the clinic. Costimulatory receptors can enhance T-cell responses. We show here that costimulation can enhance the antitumor efficacy of PSMAxCD3. In particular, 4-1BB stimulation in combination with PSMAxCD3 enhanced T-cell activation and proliferation, boosted efficacy against larger tumors, and induced T-cell memory, leading to durable antitumor responses. The combination of CD3 bispecific antibodies and anti-4-1BB costimulation represents a therapeutic approach for the treatment of solid tumors.

Sensitive Detection of Minimal Residual Disease in Patients Treated for Early-Stage Breast Cancer

PURPOSE

Existing cell-free DNA (cfDNA) methods lack the sensitivity needed for detecting minimal residual disease (MRD) following therapy. We developed a test for tracking hundreds of patient-specific mutations to detect MRD with a 1,000-fold lower error rate than conventional sequencing.

EXPERIMENTAL DESIGN

We compared the sensitivity of our approach to digital droplet PCR (ddPCR) in a dilution series, then retrospectively identified two cohorts of patients who had undergone prospective plasma sampling and clinical data collection: 16 patients with ER+/HER2- metastatic breast cancer (MBC) sampled within 6 months following metastatic diagnosis and 142 patients with stage 0 to III breast cancer who received curative-intent treatment with most sampled at surgery and 1 year postoperative. We performed whole-exome sequencing of tumors and designed individualized MRD tests, which we applied to serial cfDNA samples.

RESULTS

Our approach was 100-fold more sensitive than ddPCR when tracking 488 mutations, but most patients had fewer identifiable tumor mutations to track in cfDNA (median = 57; range = 2-346). Clinical sensitivity was 81% (n = 13/16) in newly diagnosed MBC, 23% (n = 7/30) at postoperative and 19% (n = 6/32) at 1 year in early-stage disease, and highest in patients with the most tumor mutations available to track. MRD detection at 1 year was strongly associated with distant recurrence [HR = 20.8; 95% confidence interval, 7.3-58.9]. Median lead time from first positive sample to recurrence was 18.9 months (range = 3.4-39.2 months).

CONCLUSIONS

Tracking large numbers of individualized tumor mutations in cfDNA can improve MRD detection, but its sensitivity is driven by the number of tumor mutations available to track.

A Mucin 16 bispecific T cell–engaging antibody for the treatment of ovarian cancer

Advanced ovarian cancer is frequently treated with combination chemotherapy, but high recurrence rates show the need for therapies that can produce durable responses and extend overall survival. Bispecific antibodies that interact with tumor antigens on cancer cells and activating receptors on immune cells offer an innovative immunotherapy approach. Here, we describe a human bispecific antibody (REGN4018) that binds both Mucin 16 (MUC16), a glycoprotein that is highly expressed on ovarian cancer cells, and CD3, thus bridging MUC16-expressing cells with CD3+ T cells. REGN4018 induced T cell activation and killing of MUC16-expressing tumor cells in vitro. Binding and cytotoxicity of REGN4018 in vitro were minimally affected by high concentrations of CA-125, the shed form of MUC16, which is present in patients. In preclinical studies with human ovarian cancer cells and human T cells in immunodeficient mice, REGN4018 potently inhibited growth of intraperitoneal ovarian tumors. Moreover, in a genetically engineered immunocompetent mouse expressing human CD3 and human MUC16 [humanized target (HuT) mice], REGN4018 inhibited growth of murine tumors expressing human MUC16, and combination with an anti–PD-1 antibody enhanced this efficacy. Immuno-PET imaging demonstrated localization of REGN4018 in MUC16-expressing tumors and in T cell–rich organs such as the spleen and lymph nodes. Toxicology studies in cynomolgus monkeys showed minimal and transient increases in serum cytokines and C-reactive protein after REGN4018 administration, with no overt toxicity. Collectively, these data demonstrate potent antitumor activity and good tolerability of REGN4018, supporting clinical evaluation of REGN4018 in patients with MUC16-expressing advanced ovarian cancer.

Abstract 1777: REGN4018, a novel MUC16xCD3 bispecific T-cell engager for the treatment of ovarian cancer

Advanced ovarian cancer has a high rate of recurrence, thus there is a need for therapies that can produce durable responses and extend overall survival. Infiltrating CD3+ T cells are reported to correlate with improved clinical outcome in stage III/IV ovarian cancer. Bispecific antibodies that engage T cells via CD3 and a tumor antigen on ovarian tumor cells may be able to exploit these tumor-infiltrating T cells and have drawn interest as a novel strategy of antitumor immunotherapy.

Mucin16 (MUC16) is a well described antigen highly expressed in ovarian cancer and several other tumors. We generated a human bispecific antibody (REGN4018) that binds MUC16 on tumor cells and CD3, bridging MUC16-expressing cells with CD3+ T cells. REGN4018 demonstrates MUC16-directed T cell activation and polyclonal T cell killing of MUC16-expressing tumor cells in vitro and in vivo. Binding and cytotoxicity are minimally affected by high concentrations of CA-125, the shed form of MUC16 that is used as a biomarker for ovarian cancer.

Several murine tumor models were developed to determine the in vivo anti-tumor effects of REGN4018. As a xenogenic tumor model, human OVCAR-3 cells were grown as ascites in immunodeficient mice [NOD-SCID-IL2Rgamma deficient (NSG)] pre-implanted with human PBMC. Significant tumor inhibition by REGN4018 was observed at doses of ≥ 0.1 mg/kg. To enable investigation of clinical bispecific antibodies in tumor-bearing immune competent mice, mice were genetically engineered to humanize both CD3 and a part of MUC16 covering the antibody binding region. ImmunoPET imaging demonstrated localization of REGN4018 in both T cell-rich organs such as the spleen and lymph nodes as well as in MUC16-expressing tumors. REGN4018 inhibited growth of murine tumors transfected with human MUC16 in syngeneic tumor models at doses ≥ 0.05 mg/kg.

The safety and tolerability of REGN4018 were evaluated in cynomolgous monkey studies. REGN4018 administration resulted in a minimal and transient increase in serum cytokines and C-reactive protein with no overt toxicity. Collectively, these data show the potent anti-tumor activity and tolerability of REGN4018 and provide strong support for the clinical testing of REGN4018 in patients with MUC16-expressing ovarian cancers.

Citation Format: Alison Crawford, Lauric Haber, Kristin Vazzana, Lauren Canova, Priyanka Ram, Jennifer Principio, Arpita Pawashe, Curtis Colleton, Marcus Kelly, Sosina Makkonen, Carlos Hickey, Paurene Duramad, Stephen Godin, John Lin, Eric Smith, Gavin Thurston, Jessica R. Kirshner. REGN4018, a novel MUC16xCD3 bispecific T-cell engager for the treatment of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1777.

Efficacy of topical sucralfate vERSUs silver sulfadiazine in the management of burns: A 1-year randomized controlled trial

BACKGROUND

Several medications and topical agents have been used for burn injuries. Among them, 1% silver sulfadiazine is the most commonly used topical agent for partial thickness burns. Recent studies have reported that the healing of burns is delayed by silver sulfadiazine. Search for the ideal topical agent for burn injuries is an ongoing research. The current study is undertaken with sucralfate as topical agent for dressing of burn injuries.

AIM

To compare the efficacy of topical sucralfate with silver sulfadiazine in the healing of second degree superficial burns.

STUDY DESIGN

A one-year randomized controlled trial.

SETTING

Department of General Surgery, JN Medical College and KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi, India.

METHODOLOGY

A total of 60 patients with < 50% second degree superficial burns were enrolled for the study. Patients were equally divided into two groups. Patients in group A were treated with topical sucralfate dressing and those in group B were treated with dressing. Demographics, history, physical, and systemic examinations of the patients were recorded. Routine blood investigations and culture and sensitivity were also performed. SPSS 20.0 was used for the analysis.

RESULTS

In group A, the granulation appeared in less than 7 days in 15 (50%) patients, where as in group B, granulation appeared between 15 and 20 days in 17 (56.67%) patients (p = 0.149). The mean day of granulation was 8.11±3.92 days in group A compared to 8.93±3.29 days in group B (p = 0.396). The wound culture on day 1, 7 and 14 (p>0.050) did not differ significantly in both the groups.

CONCLUSION

Overall, topical sucralfate dressing is efficacious in terms of development of early granulation in the healing of second-degree superficial burns compared to silver sulfadiazine dressing while antimicrobial effect is comparable to that of silver sulfadiazine dressing. It hastened burn wound healing process in second-degree superficial burns and should be used as an alternative agent or in combination with other topical agents. However, multicentric trials with bigger sample size are needed to strengthen the concept.

Assessment of general practitioners by video observation of communicative and medical performance in daily practice: issues of validity, reliability and feasibility

OBJECTIVES

To develop a video assessment method for General Practitioners (GPs) by analysing issues of validity, reliability and feasibility of observation of videotaped regular consultations.

DESIGN

In a cross-sectional study consultations of 93 GPs were video recorded in the practice during 1 week. The GPs registered consultation and patient data in a logbook; 16 consultations per GP were selected using preset criteria. The quality of communicative and medical performance of these consultations was assessed by GP observers with a validated instrument. The validity of the procedure was evaluated by checking the content of each GP's sample using specific sample criteria. Selection bias was estimated by multiple regression analysis, with sample characteristics as independent variables and scores on communication and medical performance as dependent variables. The influence of observation on GPs and patients was assessed by a questionnaire. Generalizability theory was used to estimate reliability. Feasibility was assessed by conducting a questionnaire, by keeping accounts, and by checking the technical quality of the videotaped consultations.

SETTING

Universities of Nijmegen and Maastricht, The Netherlands.

SUBJECTS

General Practitioners (GPs).

RESULTS

The domain of general practice was well covered in the samples; content validity was satisfactory. With regard to the sample characteristics, only the total duration of consultations appeared to correlate significantly with both the score on communication and the score on medical performance. A majority (71%) of GPs reported not being influenced by the observation, except in the first cases, and recognizing their usual daily performance in the videotaped consultations. An acceptable level of reliability was reached after 2.5 hours of observation, i.e. 12 cases by a single observer. The method was well accepted by both GPs and patients. The costs were pound250 per GP.

CONCLUSIONS

Video assessment of GPs in daily practice according to the procedures described is a valid and reliable method, one which is useful for education and quality improvement. There is a trade-off between feasibility on one hand and validity, reliability and credibility on the other hand. Compared to investments in observation methods in standardized settings, the costs of video observation of GPs' actual performance are acceptable.

Assessment in general practice: the predictive value of written-knowledge tests and a multiple-station examination for actual medical performance in daily practice

This study compares the predictive values of written-knowledge tests and a standardized multiple-station examination for the actual medical performance of general practitioners (GPs) in order to select effective assessment methods to be used in quality-improvement activities. A comprehensive assessment was performed in four phases. First, 100 GPs from the southern part of the Netherlands were assessed by a general medical knowledge test and by a knowledge test on technical skills. Second, in order to check for time-order effects, participants were randomly divided into two groups of 50 each, comparable on scores of both knowledge tests and on professional characteristics. Finally, both groups went through a multiple station examination using standardized patients and a practice video assessment of real surgery, but in opposite orders. Consultations were videotaped and assessed by well-trained peer observers. The drop-out rate was 10%. In both groups the predictive value of medical knowledge tests, ranging from 0.43 to 0.56 (Pearson correlation disattenuated), proved to be comparable with the predictive value of the multiple-station examination for actual performance (0.33-0.59). The overall explained variance of scores of the practice video assessment, measured by multiple regression analysis with performance scores as dependent variables and scores on the knowledge tests and the multiple-station examination as independent variables was moderate (19%). A time-order effect showed in only one direction: from practice video assessment to the multiple-station examination. The GP's professional characteristics did not contribute to the explanation of variation in performance. Medical knowledge tests can predict actual clinical performance to the same extent as a multiple-station examination. Compared with a station examination, a knowledge test may be a good alternative method for assessment the procedures of a large number of practising GPs.

Assessment of practicing family physicians: comparison of observation in a multiple-station examination using standardized patients with observation of consultations in daily practice

PURPOSE

Looking for a valid, reliable, and feasible method to collect data on the performances of practicing family physicians, the authors compare the measurement characteristics of a multiple-station examination (MSE) using standardized patients with those of a video assessment of regular consultations in daily practice (practice video assessment, PVA).

METHOD

In a cross-sectional study, consultations of 90 family physicians were videotaped both in an MSE and in their daily practices. Peer-observers used a validated instrument (MAAS-Global) to assess the physicians' communication with patients and their medical performances. The physicians were randomly divided into two groups, comparable for demographic characteristics, and half underwent the assessments in reverse order to test for time-order effects. Content validity, criterion validity, reliability, and feasibility of the two methods were compared.

RESULTS

Content validity of the PVA was superior to that of the MSE, since the domain of general family practice care was better covered. Observed participants judged the videotaped practice consultations to be "natural," whereas hardly any family physician, after reviewing the videotaped consultations of the MSE, recognized his or her usual working style. Specific criteria made it possible to standardize real practice. Concerning criterion validity, only the medical-performance components of the two methods correlated. No correlation was found for the communication components. Real-practice performance proved to be less influenced by observation than was performance during the MSE. The reliabilities of the two methods, expected to be better in the controlled MSE, were comparable. The administration of the PVA was more flexible, less costly, and better accepted by the family physicians than was that of the MSE.

CONCLUSION

Assessment for quality improvement of family physicians' practices by video observation in daily practice is superior to video assessment in a simulated setting using standardized patients.

Assessment of practicing family physicians: comparison of observation in a multiple-station examination using standardized patients with observation of consultations in daily practice

PURPOSE

Looking for a valid, reliable, and feasible method to collect data on the performances of practicing family physicians, the authors compare the measurement characteristics of a multiple-station examination (MSE) using standardized patients with those of a video assessment of regular consultations in daily practice (practice video assessment, PVA).

METHOD

In a cross-sectional study, consultations of 90 family physicians were videotaped both in an MSE and in their daily practices. Peer-observers used a validated instrument (MAAS-Global) to assess the physicians' communication with patients and their medical performances. The physicians were randomly divided into two groups, comparable for demographic characteristics, and half underwent the assessments in reverse order to test for time-order effects. Content validity, criterion validity, reliability, and feasibility of the two methods were compared.

RESULTS

Content validity of the PVA was superior to that of the MSE, since the domain of general family practice care was better covered. Observed participants judged the videotaped practice consultations to be "natural," whereas hardly any family physician, after reviewing the videotaped consultations of the MSE, recognized his or her usual working style. Specific criteria made it possible to standardize real practice. Concerning criterion validity, only the medical-performance components of the two methods correlated. No correlation was found for the communication components. Real-practice performance proved to be less influenced by observation than was performance during the MSE. The reliabilities of the two methods, expected to be better in the controlled MSE, were comparable. The administration of the PVA was more flexible, less costly, and better accepted by the family physicians than was that of the MSE.

CONCLUSION

Assessment for quality improvement of family physicians' practices by video observation in daily practice is superior to video assessment in a simulated setting using standardized patients.

Structure and process: the relationship between practice management and actual clinical performance in general practice

OBJECTIVES

The precise relationship between practice management (structure) and the doctor's actual performance (process) in general practice is tenuous. Analysis of their mutual relationship may yield insight into the way they contribute to outcome and into corresponding assessment procedures.

METHOD

In a cross-sectional study, consultations of 93 GPs were videotaped in their own practice and assessed by peer-observers on medical performance and on communication with patients, followed by a practice visit by a non-physician observer using a validated Visitation Instrument to assess Practice management and organization (VIP). Pearson correlations (observed and disattenuated for unreliability of the instruments) between scores on 22 practice management dimensions and scores of 16 selected cases on medical performance and communication were calculated. The predictive value of specific practice management aspects for actual performance was determined by multiple regression analysis, with performance scores as dependent variables and scores on the 22 management dimensions and GPs' professional characteristics as independent variables.

RESULTS

Nine practice management dimensions correlated significantly with medical performance and so did five dimensions with actual communication. Overall, most associations were weak. Combined with demographic variables (age for medical performance and working single-handedly for communication), 26% of variance in medical performance scores could be explained by only three practice management dimensions. One practice dimension (delegation of medical tasks to the practice assistant) explained 11% of variance in communication with patients. Organization of quality assessment activities explained most of the variation in medical performance.

CONCLUSIONS

Practice management (structure) and actual performance (process) seem to be largely autonomous constructs. Quality improvement and assessment activities should emphasize that practice management is different from actual performance. Structure and process may contribute to patient outcome independently of each other.

Pelvic inflammatory disease isolates of Neisseria gonorrhoeae are distinguished by C1q-dependent virulence for newborn rats and by the sac-4 region

The virulence mechanism of Neisseria gonorrhoeae in pelvic inflammatory disease (PID) is not well understood, and an objective diagnostic method to identify patients with PID is lacking. We investigated the hypothesis that development of PID was associated with a C1q-dependent virulence property of gonococcal strains. Recent development of a C1q-dependent experimental model of gonococcal infection (S. Nowicki, M. Martens, and B. Nowicki, Infect. Immun. 63:4790-4794, 1995) created an opportunity to evaluate this hypothesis in vivo. Therefore, the virulence of 32 clinical isolates (18 PID isolates and 14 local infection [LI] isolates) was evaluated in experimental rat pups. A serum bactericidal assay was used to characterize a gonococcal serum-resistant (ser(r)) phenotype. PCR primers designed to amplify a suitable-size gonococcal sac-4 DNA fragment (unique for serum-resistant donor JC1) were used to evaluate the association of serum-resistant genotype sac-4 with two phenotypes: C1q-dependent virulence expressed in vivo and resistance to bactericidal activity of human serum expressed in vitro. Strains were also characterized by auxotyping and serotyping. Of 32 gonococcal strains, 15 (46.7%) caused C1q-dependent bacteremia in rat pups and were sac-4 positive and ser(r). However, of the 15 isolates, 13 (87%) represented strains associated with human PID and 2 (13%) were associated with LI. None of the strains that were completely serum-sensitive (ser(s)) and sac-4 negative produced C1q-dependent bacteremia in rat pups, suggesting that both ser(r) and sac-4 were required for infection. The serum-resistant recombinant recipient of sac-4 produced C1q-dependent bacteremia in the rat model similarly to the serum-resistant donor of sac-4; the serum-sensitive parent strain did not produce bacteremia. These data suggest that sac-4-mediated serum resistance conferred C1q-dependent virulence and is a unique characteristic associated with PID. These newly identified features may contribute to the understanding of the pathogenic mechanism of PID-associated strains and open perspectives for establishing novel diagnostic methods.

High mortality from cardiovascular disease and analysis of risk factors in Indian and Melanesian Fijians

BACKGROUND

In recent years, developing populations such as the Pacific island nation of Fiji, have seen decreases in infectious diseases and increasing frequency of cardiovascular diseases (CVD), diabetes and cancer. However, cohort studies of mortality in these populations are scarce. Here we report 11-year all-cause and cause-specific mortality rates and risk factors for total, CVD and coronary heart disease (CHD) for indigenous Melanesian and Asian Indian people of Fiji.

METHODS

Following a baseline risk factor survey in 1980, mortality surveillance continue until 1991 in a representative cohort of 1325 Melanesians and 1221 Indians from urban and rural areas of Fiji. Date and cause of death were recorded and total, CVD and CHD mortality rates calculated. Baseline predictors of mortality were assessed using Cox regression.

RESULTS

Total mortality rates in Melanesians were 15.9 and 9.2/1000 person-years, and in Indians were 13.5 and 6.8/1000 person-years, in men and women respectively. Death due to CHD was more common in men than women, and in Indian than Melanesian men, although total CVD deaths were more common in Melanesian men. Deaths due to CHD were more common in the urban than the rural area. After adjusting for other risk factors Indian ethnicity was associated with a significantly reduced risk of total and CVD mortality in men, and total mortality in women. Age and systolic blood pressure were consistently and independently associated with mortality from all causes, as well as CVD and CHD (except in Indian women). In men associations were also identified for total cholesterol with CVD and CHD mortality in Melanesians, and 2-hour plasma glucose with total and CVD mortality in Indians. In women, 2-hour glucose was important for total, CVD and CHD mortality in both ethnic groups as was smoking in Indians. Obesity had inconsistent associations with mortality.

CONCLUSION

Cardiovascular disease is now responsible for a large proportion of total mortality in both Indian and Melanesian Fijians. The major risk factors identified in Fijians are similar to those observed in developed populations.

Non-insulin-dependent diabetes and 11-year mortality in Asian Indian and Melanesian Fijians

This study reports 11-year all-cause and cause-specific mortality rates according to baseline glucose tolerance for a population-based sample of adult Melanesian and Indian Fijians (n = 2638), first surveyed in 1980. Risk factors for all-cause and cardiovascular disease (CVD) mortality in subjects with non-insulin-dependent diabetes (NIDDM) are also described. The baseline survey included 75 g oral glucose tolerance tests, measurements of blood pressure, body mass index, and triceps skinfold, assays of plasma cholesterol and triglycerides, electrocardiograms, and details of smoking habits and physical activity. Mortality status was ascertained for 2546 subjects through surveillance of death certificates, medical records and interview of subjects (or relatives). Mortality rates were increased in diabetic men and women of both ethnic groups: relative risks compared to subjects without diabetes at baseline were 1.7 (CI:0.9-3.1) and 2.0 (1.1-3.7) in Melanesian and 4.2 (2.7-6.5), 3.2 (1.9-5.7) in Indian men and women, respectively. A large proportion of mortality among diabetic subjects was attributed to CVD (62%, 66% in Melanesian and 54%, 58% in Indian men and women, respectively). Mortality rates tended to be higher in Melanesians than Indians, except for diabetic men where Indians had higher total and cardiovascular disease rates. In contrast to non-diabetic Fijians, diabetic women of both ethnic groups lost their relative protection from coronary heart disease (CHD). Cox regressions for diabetic subjects showed age and fasting plasma glucose to be independent predictors of all-cause mortality in men, and age, body mass index (inversely) and systolic blood pressure in women, but lipid concentrations, and cigarette smoking were not related. After accounting for conventional CVD risk factors, diabetes conferred significantly increased risk of total, CVD, and CHD mortality. The mortality experience of Melanesian and Indian Fijians with NIDDM is similar to that documented in developed populations, with excess mortality due to cardiovascular causes.

Isolation and identification of a protoheme IX derivative released during autolytic cleavage of human myeloperoxidase

Myeloperoxidase (MPO) is a functionally important component of the normal human neutrophil host defense system. This enzyme possesses a dimeric structure composed of two heavy-subunit/light-subunit protomers, with a heme-like prosthetic group covalently linked to each heavy subunit. Although MPO exhibits unusual spectral and enzymatic properties, the nature of the prosthetic group and its mode of linkage with the apoenzyme have not been determined. In an earlier report (K.L. Taylor, J. Pohl, and J.M. Kinkade, Jr. (1992) J. Biol. Chem. 267, 25282-25288), characterization of the autolytic cleavage of MPO led to the proposal that the prosthetic group was covalently linked to the apoenzyme via a methionyl sulfonium bond with Met409. In the present study, we have demonstrated that autolytic cleavage of MPO, followed by protease digestion under nonreducing conditions, effects the release of a macrocycle with visible and Raman spectral properties consistent with that of a protoheme IX derivative. Mass spectrometric analysis, in conjunction with metabolic labeling studies and recent X-ray crystallographic data, have led to the structural assignment of this macrocycle as 1,5-dihydroxymethyl-3,8-dimethyl-4-vinyl-2-(2'-methylthio) ethenylporphine-6,7-dipropionic acid-iron complex. Based on the mechanism of methionyl sulfonium bond cleavage, this structure is consistent with our earlier proposal that the MPO prosthetic group is covalently linked to the enzyme via a methionyl sulfonium bond and suggests that this linkage occurs through a peripheral vinyl substituent.

Computer modelling of glycolipids at membrane surfaces

Interactions of membrane anchored molecules such as glycolipids with a membrane surface are important in determining headgroup conformation. It is therefore essential to represent these membrane surface interactions in molecular modeling studies of glycolipids and other membrane bound molecules. We introduce here an energy term that represents the interaction of molecules with a membrane bilayer. This membrane interaction energy term has been added to the potential energy function of a molecular dynamics and mechanics program and has been parameterized using partition coefficients between an aqueous solution and a vesicular membrane for two model glycolipids.

Blood pressure changes with age in two ethnic groups in Fiji

Blood pressure was studied in urban and rural samples of the Melanesian and Indian populations of Fiji during a National Cardiovascular Disease and Diabetes Survey in 1980. Mean blood pressures rose with age and tended to be higher in urban than in rural populations, particularly in the middle age range. There was no clear or significant difference between the ethnic groups. When the prevalence of hypertension was studied (using WHO criteria) similar age, geographic and ethnic differences were found. Comparisons with data from 1960 revealed no significant change in mean blood pressures during the 20-year interval. Rural populations were leaner and appeared to consume less salt than did urban groups. There were positive and significant correlations between blood pressure and triceps skinfold thickness in most subgroups.

Prevalence of ischaemic ECG abnormalities according to the diabetes status in the population of Fiji and their associations with other risk factors

The prevalence of ECG abnormalities indicating the presence of coronary heart disease was examined in the Melanesian (444 men and 457 women) and Asian Indian (408 men and 435 women) population living in Fiji. The aim of the present analysis was to determine the levels of coronary risk factors in people with diabetes, impaired glucose tolerance (IGT) or normal glucose tolerance. The prevalence of ECG abnormalities suggesting coronary heart disease (Q-waves, ST-depression or T-wave changes) was higher among women than men and among Asian Indians than Melanesians. The prevalence of ECG abnormalities was highest in diabetic subjects, intermediate in people with IGT and lowest in people who had normal glucose tolerance. People with IGT were more likely than others to have high risk factor levels. In people with IGT the increased levels of other coronary risk factors might explain a great deal of the increased prevalence of the ECG abnormalities as compared with the prevalence in those with normal glucose tolerance. Also in diabetic subjects, the levels of other coronary risk factors were increased in those who had ECG abnormalities, but not more than was the case with IGT, so that diabetes itself seemed to remain as the major identified risk factor for ECG abnormalities. The prevalence of diabetes in our study populations, especially in Asian Indians, was very high. This suggests that diabetes is the major risk factor for coronary heart disease in such populations.

Magnetic field induced ordering of bile salt/phospholipid micelles: new media for NMR structural investigations

Micelles formed from sodium glycocholate and dimyristoylphosphatidylcholine are demonstrated to form a magnetic field orientable liquid crystal within narrow ranges of composition and temperature. The utility of this medium in structural investigations of biological membrane components using deuterium NMR is discussed.

Electrocardiographic abnormalities amongst Melanesian and Indian men of Fiji: prevalence and associated factors

Electrocardiograms were performed on 427 Melanesian and 391 Indian males aged 30-69 years surveyed in 1980. The age-adjusted prevalence of abnormalities in Minnesota coding suggesting coronary arterial disease was: Indians - 17.1%, Melanesians - 9.1%. This difference was significant at P less than 0.001. For the Melanesians body mass index, plasma uric acid, cholesterol and triglyceride and systolic blood pressure showed significant positive associations with electrocardiographic abnormalities in a univariate analysis, but only the plasma uric acid level was independently associated with such abnormalities following adjustment for these other factors in a multivariate analysis (P less than 0.001). For the Indians body mass index, systolic blood pressure, the presence of diabetes, urban residence and physical inactivity were positively associated with electrocardiographic abnormalities in the univariate analysis, but only body mass index (P less than 0.01), systolic blood pressure (P less than 0.01), and the 2-hour glucose level (P less than 0.01) were independently associated with such abnormalities when adjustment was made for the levels of the other factors.

Plasma uric acid level and its association with diabetes mellitus and some biologic parameters in a biracial population of Fiji

Plasma uric acid was investigated in a population survey on diabetes and cardiovascular risk factors among Melanesians and Asian Indians in Fiji in 1980. Plasma uric acid levels were elevated in men and women with impaired glucose tolerance in both ethnic groups. The lowest plasma uric acid levels were found in diabetic patients, especially in diabetic men. Even though obesity was positively associated with plasma uric acid, it did not explain the high plasma uric acid level in persons with impaired glucose tolerance. Body mass index had a significant and independent impact on plasma uric acid levels both in nondiabetic and diabetic men and women. The strongest predictor of plasma uric acid in the multiple regression analysis in our study populations was plasma creatinine: it alone explained 9% of the variation in men and 2% in women; and 24% in Melanesians and 5% in Asian Indians. Our findings suggest a strong renal involvement in the balance of plasma uric acid and may also reflect certain dietary patterns, such as a high intake of protein, fats, and certain local vegetables. Although the prevalence of hyperuricemia was high, 27% in both Melanesian men and women, 22% in Asian Indian men, and 11% in Asian Indian women, clinical gout was uncommon. Many predictor variables and their interactions were analyzed along with the reasons for the high plasma uric acid levels in persons with impaired glucose tolerance and for the low plasma uric acid levels in diabetic patients.

Sequels to screening for hypertension and diabetes mellitus in Fiji

We evaluated the outcome of a case-finding programme resulting from an epidemiological survey on diabetes and cardiovascular risk factors by re-interviewing 318 persons who had been found to have hypertension and/or diabetes mellitus in a population survey carried out in Fiji 1.5 years earlier in 1980. At re-examination, 34% of the hypertensive patients and 43% of the diabetic patients were not aware of their diagnosis. However, the proportion of treated hypertensive people was tripled and that of diabetic patients doubled. It was not possible to identify the characteristics of the persons who were missed in the follow-up. Many persons who were unaware of their condition regularly used, however, the existing health services available. On the other hand, several initially treated cases had no proper follow-up. More careful planning and development of comprehensive community-based programmes for hypertension and diabetes are needed in Fiji. Simple population screening for hypertension and diabetes may result in an extra work load and limit the available health care resources so that the overall outcome is not satisfactory.

Mortality and health service utilization amongst Melanesian and Indian diabetics in Fiji

A population-based survey of the biracial population of Fiji conducted in 1980 showed non-insulin dependent diabetes (NIDDM) prevalence to be high amongst urban Melanesians and Asian Indians. Follow-up of the cohort of urban residents has been conducted at the major sites of health service delivery in Suva, and surveillance now encompasses 4 years of such attendances. Age-adjusted mortality rates for diabetic subjects were increased compared with normal subjects (relative risks for 4 year mortality being 4.6 for Indians, P less than 0.01, and 1.5 for Melanesians, P greater than 0.1). Inpatient admission rates were also increased amongst diabetic subjects, but only significantly for the females. The relative risk of admission was 3.1 for Melanesian and 2.6 for Indian females (both significant at P less than 0.05). These results suggest that NIDDM in these populations is associated with several adverse health outcomes, and confirms for developing country populations the association of NIDDM with excess mortality noted amongst developed country populations.

Unusual electrocardiographic abnormality in leptospirosis: case reports

Unusual ECG changes of marked ST segment elevation in leads V1 to V3 are reported in four cases of severe icteric leptospirosis for the first time. These changes normalized rapidly with initiation of therapy and recovery in three patients. One patient died within hours of admission. The causes for the changes are not clear.

Physical activity and prevalence of diabetes in Melanesian and Indian men in Fiji

In Fiji Melanesian and Indian men, prevalence of diabetes is more than twice as high in those graded as sedentary or undertaking light activity as in those classed as performing moderate or heavy exercise. This difference was present in both ethnic groups, and maintained when age, obesity, and urban/rural- status were taken into account. It is concluded that, in the population under study, there is epidemiological evidence for the role of physical inactivity as an independent risk factor for Type 2 (non-insulin-dependent) diabetes.

Cardiovascular diseases and diabetes mellitus in Fiji: analysis of mortality, morbidity and risk factors

Mortality and hospital admissions due to cardiovascular diseases and diabetes mellitus have been increasing in Fiji steadily over the past 20 years. These diseases were present more frequently in the Indian than the Melanesian population of Fiji, but recently the steepest rise in prevalence rates occurred among the Melanesian population. The underlying conditions that contributed most to increasing mortality and morbidity were hypertension and diabetes mellitus. In 1978, the proportional mortality from diabetes mellitus was 6.0% (9.0% in persons aged >/= 40 years), and that from cardiovascular diseases was 30.3% (39% in those aged >/= 40 years). Ischaemic heart disease was the main cause of mortality and morbidity among the Indian population. This analysis of mortality and morbidity data is supported by the findings of a population survey, which showed that the prevalence rates of diabetes and hypertension in 1980 among urban Melanesians were similar to those among Indians. Urbanization and a modern life-style seem to play an important role in determining the disease pattern in Fiji, which is following the patterns in many industrial countries.

Prevalence of diabetes and impaired glucose tolerance in the biracial (Melanesian and Indian) population of Fiji: a rural-urban comparison

Rural-urban and ethnic comparisons of impaired glucose tolerance and diabetes mellitus were made in the biracial population of Fiji in 1980. No statistically significant differences existed in age-standardized impaired glucose tolerance prevalence between rural and urban groups or between Melanesians and Indians. The age-standardized prevalence of diabetes in the rural Melanesian male population was one-third that of the urban male population (1.1 vs. 3.5%). In females, there was a sixfold rural-urban difference (1.2 vs. 7.1%). By contrast, rural and urban Indians had similar rates (12.1 vs. 12.9% for males; 11.3 vs. 11.0% for females). Standardization of two-hour plasma glucose for age and obesity did not eliminate the rural-urban difference in plasma glucose concentration for Melanesian males and females. The results in Melanesians confirm previously reported rural-urban diabetes prevalence differences, and suggest that factors other than obesity, such as differences in physical activity, diet, stress, or other, as yet undetermined, factors contribute to this difference. The absence of a rural-urban difference in diabetes prevalence in Indians may suggest that genetic factors are more important for producing diabetes in this ethnic group, or that causative environmental factors such as diet operate similarly upon both the rural and the urban populations.

Seroepidemiology of infection with hepatitis B virus in Fiji

A batch of 984 sera obtained from a stratified sample of Melanesians and Indians living in rural and urban areas of Fiji in 1981 were for hepatitis B surface antigen (HBsAg) and antibody to hepatitis B core antigen (anti-HBc) by solid phase radioimmunoassay. The prevalence of hepatitis B infection (as measured by the sum of HBsAg and anti-HBc frequencies of HBsAg negative sera in the two groups) was 81.5% and 17.9%, respectively. No major differences were detected between urban and rural populations. While hepatitis B virus is endemic in Melanesians and Indians, the epidemiology of the infection shows certain differences. Among Melanesians, infection appears to be acquired early in life and peak prevalence of serologic markers of infection occurs during the second decade. Among the Indian population, the prevalence of markers increases steadily with age, presumably as a result of continuous exposure and infection throughout life. the high prevalence of infection and carriers among Melanesians is consistent with previous observations among Pacific populations. The lower prevalence of infection among Indians is remarkable, since they constitute almost half of the total population and live under similar conditions. Since the two populations remain largely separate in terms of housing and schooling, and intermarriage is uncommon, it is no possible to determine whether these differences merely represent different degrees of exposure to the virus or are the reflection of differences in susceptibility or response to infection.

Comparison of plain radiography, conventional tomography, and computed tomography in detecting intrathoracic lymph node metastases from lung carcinoma

Forty-two patients with T2 bronchogenic carcinoma were evaluated with plain radiography, conventional 55 degrees oblique hilar and anteroposterior mediastinal tomography, and computed tomography (CT) to compare their accuracy in assessing mediastinal and hilar nodal metastases. Definitive staging was achieved by thoracotomy and histopathological evaluation of resected specimens. All modalities demonstrated about the same accuracy; however, in the 25 patients with hilar and/or mediastinal lymphadenopathy, CT of the mediastinum was more sensitive but not more specific than the other two and conventional tomography was no more accurate than CT for hilar evaluation. Overall, no technique was accurate enough for routine staging; their value may lie in directing biopsy or in treatment planning in patients with inoperable disease.

HLA and non-insulin dependent diabetes in Fiji indians

HLA frequency distributions in Fiji Indians with non-insulin dependent diabetes were compared with those in control subjects with confirmed two-hour plasma glucose levels less than 7.8 mmol/L. Antigen frequencies at HLA-A and HLA-DR loci were similar in patients and controls. At HLA-B, there was a significant increase in Bw61 (Bw40.2) in diabetics, with a relative risk for this antigen of 4.8. Since a similar finding has been reported previously in South African Indians with Insulin-dependent diabetes, it is possible that wer have defined yet another genetically-distinct form of diabetes, especially prevalent in Indians. Alternatively, definition of new HLA alleles such as Bw61, a new subdivision of an established antigen, may reveal HLA associations with non-insulin dependent diabetes in European Caucasians also.

The relationship of computed tomography, gray-scale ultrasonography and radionuclide imaging in the evaluation of hepatic masses

Hepatic scintigraphy, gray-scale ultrasonography, and computed tomography have proven to be useful in the initial detection and evaluation of hepatic masses. These studies appear to be complimentary since each provides information not available from the others. Hepatic scintigraphy is currently the method of choice for the initial evaluation of the liver for mass lesions as it is easily performed, relatively inexpensive, and affords detectability of intrahepatic mass lesions at least as great as that of ultrasonography or computed tomography. When a definite or suspected abnormality is seen by hepatic scintigraphy, computed tomography or ultrasonography may be helpful in providing better anatomic definition or clarification of the nature of the abnormality. The choice between these latter two modalities depends on the type of scanning equipment available and the observer's experience with each method.