A fast and sensitive size-exclusion chromatography method for plasma extracellular vesicle proteomic analysis

Extracellular vesicles (EVs) carry diverse biomolecules derived from their parental cells, making their components excellent biomarker candidates. However, purifying EVs is a major hurdle in biomarker discovery since current methods require large amounts of samples, are time-consuming and typically have poor reproducibility. Here we describe a simple, fast, and sensitive EV fractionation method using size exclusion chromatography (SEC) on a fast protein liquid chromatography (FPLC) system. Our method uses a Superose 6 Increase 5/150, which has a bed volume of 2.9 mL. The FPLC system and small column size enable reproducible separation of only 50 µL of human plasma in 15 minutes. To demonstrate the utility of our method, we used longitudinal samples from a group of individuals that underwent intense exercise. A total of 838 proteins were identified, of which, 261 were previously characterized as EV proteins, including classical markers, such as cluster of differentiation (CD)9 and CD81. Quantitative analysis showed low technical variability with correlation coefficients greater than 0.9 between replicates. The analysis captured differences in relevant EV-proteins involved in response to physical activity. Our method enables fast and sensitive fractionation of plasma EVs with low variability, which will facilitate biomarker studies in large clinical cohorts.

A Phase 1b/2 Study of Atezolizumab with or Without Bacille Calmette-Guérin in Patients with High-risk Non-muscle-invasive Bladder Cancer

BACKGROUND

Bacille Calmette-Guérin (BCG) is the standard therapy after transurethral resection of bladder tumour for high-risk non-muscle-invasive bladder cancer (NMIBC). However, post-BCG recurrence/progression occurs frequently, and noncystectomy options are limited.

OBJECTIVE

To evaluate the safety and clinical activity of atezolizumab ± BCG in high-risk BCG-unresponsive NMIBC.

DESIGN, SETTING, AND PARTICIPANTS

This phase 1b/2 GU-123 study (NCT02792192) treated patients with BCG-unresponsive NMIBC who had carcinoma in situ with atezolizumab ± BCG.

INTERVENTION

Patients in cohorts 1A and 1B received atezolizumab 1200 mg IV q3w for ≤96 wk. Those in cohort 1B also received standard BCG induction (six weekly doses) and maintenance courses (three doses weekly starting at month 3) with optional maintenance at 6, 12, 18, 24, and 30 mo.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Coprimary endpoints were safety and 6-mo complete response (CR) rate. Secondary endpoints included 3-mo CR rate and duration of CR; 95% confidence intervals were calculated using the Clopper-Pearson method.

RESULTS AND LIMITATIONS

At data cut-off (September 29, 2020), 24 patients were enrolled (cohort 1A, n = 12; cohort 1B, n = 12), and the recommended BCG dose was 50 mg in cohort 1B. Four patients (33%) had adverse events (AEs) leading to BCG dose modification/interruption. Three patients (25%) in cohort 1A reported atezolizumab-related grade 3 AEs; cohort 1B had no atezolizumab- or BCG-related grade ≥3 AEs. No grade 4/5 AEs were reported. The 6-mo CR rate was 33% in cohort 1A (median duration of CR, 6.8 mo) and 42% in cohort 1B (median duration of CR, not reached [≥12 mo]). These results are limited by the small sample size of GU-123.

CONCLUSIONS

In this first report of the atezolizumab-BCG combination in NMIBC, atezolizumab ± BCG was well tolerated, with no new safety signals or treatment-related deaths. Preliminary results suggested clinically meaningful activity; the combination favoured a longer duration of response.

PATIENT SUMMARY

We studied atezolizumab with and without bacille Calmette-Guérin (BCG) to determine whether this combination was safe and had clinical activity in patients with high-risk noninvasive bladder cancer (high-grade bladder tumours that affect the outermost lining of the bladder wall) that has previously been treated with BCG and is still present or occurred again. Our results suggest that atezolizumab with or without BCG was generally safe and could be used to treat patients unresponsive to BCG.

Surgery in Early Metastatic Seminoma: A Phase II Trial of Retroperitoneal Lymph Node Dissection for Testicular Seminoma With Limited Retroperitoneal Lymphadenopathy

PURPOSE

The long-term toxicities of chemotherapy and radiotherapy can represent a significant burden to testicular cancer survivors. Retroperitoneal lymph node dissection (RPLND) is an established treatment for testicular germ cell tumors with minimal late morbidity although little data exist on its efficacy in early metastatic seminoma. Surgery in early metastatic seminoma is a prospective phase II single-arm, multi-institutional trial of RPLND as first-line treatment for testicular seminoma with clinically low-volume retroperitoneal lymphadenopathy.

PATIENTS AND METHODS

Twelve sites in the United States and Canada prospectively enrolled adult patients with testicular seminoma and isolated retroperitoneal lymphadenopathy (1-3 cm). Open RPLND was performed by certified surgeons with a primary end point of 2-year recurrence-free survival (RFS). Complication rates, pathologic up/downstaging, recurrence patterns, adjuvant therapies, and treatment-free survival were assessed.

RESULTS

A total of 55 patients were enrolled, with a median (IQR) largest clinical lymph node size of 1.6 cm (1.3-1.9). RPLND pathology demonstrated a median (IQR) largest lymph node size of 2.3 cm (0.9-3.5); nine patients (16%) were pN0, 12 (22%) pN1, 31 (56%) pN2, and 3 (5%) pN3. One patient received adjuvant chemotherapy. With a median (IQR) follow-up of 33 months (12.0-61.6), 12 patients experienced recurrence, with a 2-year RFS of 81% and a recurrence rate of 22%. Of the patients who experienced recurrence, 10 were treated with chemotherapy and two underwent additional surgery. At last follow-up, all patients who experienced a recurrence were disease-free and the 2-year overall survival was 100%. Four patients (7%) experienced short-term complications, and four patients experienced long-term complications including incisional hernia (1) and anejaculation (3).

CONCLUSION

RPLND is a treatment option for testicular seminoma with clinically low-volume retroperitoneal lymphadenopathy and is associated with low long-term morbidity.

Is a "Urology Intern Boot Camp" Needed?

INTRODUCTION

The preparation of medical students for internship during medical school is variable, which can negatively affect the performance and confidence of new urology residents year 1. The primary objective is to assess the need for a workshop/curriculum to prepare medical students transitioning to urology residency. Our secondary objective is to identify the appropriate workshop/curriculum design and to identify the needed topics.

METHODS

A survey was developed to evaluate the utility of a Urology Intern Boot Camp for incoming first year urology residents utilizing 2 existing intern boot camp models from other surgical disciplines. Urology Intern Boot Camp content and format and programmatic structure were also considered. The survey was sent to all first- and second-year urology residents and urology residency program directors and chairs.

RESULTS

A total of 730 surveys were sent, including 362 first- and second-year urology residents and 368 program directors/chairs. Responses were received from 63 residents and 80 program directors/chairs for an overall response rate of 20%. Only 9% of urology programs provide a Urology Intern Boot Camp. Interest in participating in Urology Intern Boot Camp was high with 92% of residents interested. Programmatic support for a Urology Intern Boot Camp was also high with 72% of program directors/chairs willing to allow time off and 51% willing to financially support intern participation.

CONCLUSIONS

There is significant interest from urology residents and program directors/chairs in providing incoming urology interns a boot camp. The format of the Urology Intern Boot Camp preferred was a combination of didactics and hands-on skills, and a hybrid delivery model of virtual and in-person carried out in multiple sites around the country.

Access to urologists for participation in research: An analysis of NCI's Community Oncology Research Program landscape survey

Purpose

Urological cancer clinical trials face accrual challenges, which may stem from structural barriers within cancer programs. We sought to describe the extent to which urology cancer care providers are available within community cancer research programs and explore the role of oncology practice group ownership in their access to urology practices to participate in research.

Materials and methods

We conducted secondary analysis of organizational survey data collected in 2017 among National Cancer Institute Community Oncology Research Program practice groups. We used logistic regression to assess the association of self-reported access to urologists to participate in research and oncology practice group ownership type: independent, payor-provider, health-system, or public ownership.

Results

Of the 209 community oncology practice groups in the analysis sample, 133 (63.6%) had access to urologists for research participation. Ownership was not statistically significantly associated with access to urology practices after controlling for other covariates (p = 0.4). Instead, having a hospital outpatient clinic (p = 0.008) and identifying as a safety-net hospital (p = 0.035) were both positively significantly associated with access to urologists to participate in research.

Conclusions

Two-thirds of community cancer research groups have access to urology. Oncology ownership status was not associated with access to urologists for research. Research groups may need support to increase their capacity to engage non-oncology cancer care providers in research.

Experiences of Mental Distress during COVID-19: Thematic Analysis of Discussion Forum Posts for Anxiety, Depression, and Obsessive-Compulsive Disorder

The psychological impact of the COVID-19 pandemic on coronavirus patients, health care workers, and the general population is clear. Relatively few studies have, however, considered the impact of the pandemic on those with pre-existing mental health conditions. Therefore, the present study investigates the personal experiences of those with anxiety, depression, and obsessive-compulsive disorder during COVID-19. We conducted a qualitative study utilising Reddit discussion forum posts. We conducted three separate thematic analyses from 130 posts in subreddit forums aimed for people identifying with anxiety, depression, and obsessive-compulsive disorder. We identified a number of similar discussion forum themes (e.g., COVID-19 intensifying symptoms and a lack of social support), as well as themes that were unique to each forum type (e.g., hyperawareness and positive experiences during the pandemic). Findings should guide future practice and the support provided to those living with mental distress.

Development, acceptability, appropriateness and appeal of a cancer clinical trials implementation intervention for rural- and minority-serving urology practices

Background

Few community urologists offer cancer patients the opportunity to participate in cancer clinical trials, despite national guidelines that recommend it, depriving an estimated 260,000 urological cancer patients of guideline-concordant care each year. Existing strategies to increase urologists’ offer of clinical trials are designed for resource-rich environments and are not feasible for many community urologists. We sought to design an implementation intervention for dissemination in under-resourced community urology practices and to compare its acceptability, appropriateness and adoption appeal among trial-naïve and trial-experienced urologists.

Methods

We used a design-for-dissemination approach, informed by the Theoretical Domains Framework and Behavior Change Wheel, to match determinants of the clinical trial offer to theoretically informed implementation strategies. We described the implementation intervention in evaluation workshops offered at urology professional society meetings. We surveyed participants to assess the implementation intervention’s acceptability and appropriateness using validated instruments. We also measured adoption appeal, intention to adopt and previous trial offer.

Results

Our design process resulted in a multi-modal implementation intervention, comprised of multiple implementation strategies designed to address six domains from the Theoretical Domains Framework. Evaluation workshops delivered at four meetings, convened five separate professional societies. Sixty-one percent of those offered an opportunity to participate in the implementation intervention indicated intention to adopt. Average implementation intervention acceptability and appropriateness ratings were 4.4 and 4.4 (out of 5), respectively. Acceptability scores were statistically significantly higher among those offering trials compared to those not (p = 0.03). Appropriateness scores did not differ between those offering trials and those not (p = 0.24). After urologists ranked their top three innovation attributes, 43% of urologists included practice reputation in their top three reasons for offering clinical trials; 30% listed practice differentiation among their top three reasons. No statistically significant differences were found between those who offered trials and those who did not among any of the innovation attributes.

Conclusions

LEARN|INFORM|RECRUIT is a promising implementation intervention to address low accrual to clinical trials, poised for implementation and effectiveness testing. The implementation intervention is appealing to its target audience and may have equal uptake among trial-naïve and trial-experienced practices.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3658-z) contains supplementary material, which is available to authorized users.

Improving the quality of operative reports for transurethral resection of bladder tumor surgery in resident education

INTRODUCTION

To assess the quality of resident dictations for transurethral resection of bladder tumor (TURBT). One indicator of surgical quality is the completeness of the operative report. Surprisingly, there is a paucity of standardized operative templates for TURBT and little formalized instruction for learners. The quality of TURBT dictations was assessed and areas of improvement were determined after implementation of a 10 item TURBT checklist.

MATERIALS AND METHODS

A retrospective review of the last 50 TURBT operative reports dictated by residents was performed. A 'TURBT checklist' was used assessing 10 key factors in documentation. A formal training session regarding TURBT dictations was given with TURBT checklists handed out to each trainee. Fifty TURBT dictations were subsequently analyzed.

RESULTS

TURBT dictations improved across the board following checklist implementation. Total number of checklist items dictated increased to 7.0 from 2.6 prior (p < 0.05). When stratified by resident experience, TURBT dictations improved across different resident years (p < 0.05). Junior resident dictations statistically improved in every checklist item (p < 0.05). Senior resident dictations improved in almost every category but only two reached statistical significance. A regression model demonstrated checklist implantation to be a significant predictor of improvement in mean number of checklist items dictated independent of PGY level.

CONCLUSIONS

Our study demonstrates that prior to implementation, TURBT operative dictations performed by residents lacked many of the critical components required for a quality TURBT. However, once properly instructed, a relatively simple 'checklist' can be easily implemented and serve as a teaching tool for residents in training to ensure critical procedural elements are documented.

The IASLC Mesothelioma Staging Project: Proposals for the M Descriptors and for Revision of the TNM Stage Groupings in the Forthcoming (Eighth) Edition of the TNM Classification for Mesothelioma

INTRODUCTION

The M component and TNM stage groupings for malignant pleural mesothelioma (MPM) have been empirical. The International Association for the Study of Lung Cancer developed a multinational database to propose evidence-based revisions for the eighth edition of the TNM classification of MPM.

METHODS

Data from 29 centers were submitted either electronically or by transfer of existing institutional databases. The M component as it currently stands was validated by confirming sufficient discrimination (by Kaplan-Meier analysis) with respect to overall survival (OS) between the clinical M0 (cM0) and cM1 categories. Candidate stage groups were developed by using a recursive partitioning and amalgamation algorithm applied to all cM0 cases.

RESULTS

Of 3519 submitted cases, 2414 were analyzable and 84 were cM1 cases. Median OS for cM1 cases was 9.7 months versus 13.4 months (p = 0.0013) for the locally advanced (T4 or N3) cM0 cases, supporting inclusion of only cM1 in the stage IV group. Exploratory analyses suggest a possible difference in OS for single- versus multiple-site cM1 cases. A recursive partitioning and amalgamation-generated survival tree on the OS outcomes restricted to cM0 cases with the newly proposed (eighth edition) T and N components indicates that optimal stage groupings for the eighth edition will be as follows: stage IA (T1N0), stage IB (T2-3N0), stage II (T1-2N1), stage IIIA (T3N1), stage IIIB (T1-3N2 or any T4), and stage IV (any M1).

CONCLUSIONS

This first evidence-based revision of the TNM classification for MPM leads to substantial changes in the T and N components and the stage groupings.

The IASLC Mesothelioma Staging Project: Proposals for Revisions of the T Descriptors in the Forthcoming Eighth Edition of the TNM Classification for Pleural Mesothelioma

INTRODUCTION

The current T component for malignant pleural mesothelioma (MPM) has been predominantly informed by surgical data sets and consensus. The International Association for the Study of Lung Cancer undertook revision of the seventh edition of the staging system for MPM with the goal of developing recommendations for the eighth edition.

METHODS

Data elements including detailed T descriptors were developed by consensus. Tumor thickness at three pleural levels was also recorded. An electronic data capture system was established to facilitate data submission.

RESULTS

A total of 3519 cases were submitted to the database. Of those eligible for T-component analysis, 509 cases had only clinical staging, 836 cases had only surgical staging, and 642 cases had both available. Survival was examined for T categories according to the current seventh edition staging system. There was clear separation between all clinically staged categories except T1a versus T1b (hazard ratio = 0.99, p = 0.95) and T3 versus T4 (hazard ratio = 1.22, p = 0.09), although the numbers of T4 cases were small. Pathological staging failed to demonstrate a survival difference between adjacent categories with the exception of T3 versus T4. Performance improved with collapse of T1a and T1b into a single T1 category; no current descriptors were shifted or eliminated. Tumor thickness and nodular or rindlike morphology were significantly associated with survival.

CONCLUSIONS

A recommendation to collapse both clinical and pathological T1a and T1b into a T1 classification will be made for the eighth edition staging system. Simple measurement of pleural thickness has prognostic significance and should be examined further with a view to incorporation into future staging.

Electrically and Hybrid-Induced Muscle Activations: Effects of Muscle Size and Fiber Type

The effect of three electrical stimulation (ES) frequencies (10, 35, and 50 Hz) on two muscle groups with different proportions of fast and slow twitch fibers (abductor pollicis brevis (APB) and vastus lateralis (VL)) was explored. We evaluated the acute muscles’ responses individually and during hybrid activations (ES superimposed by voluntary activations). Surface electromyography (sEMG) and force measurements were evaluated as outcomes. Ten healthy adults (mean age: 24.4 ± 2.5 years) participated after signing an informed consent form approved by the university Institutional Review Board. Protocols were developed to: 1) compare EMG activities during each frequency for each muscle when generating 25% Maximum Voluntary Contraction (MVC) force, and 2) compare EMG activities during each frequency when additional voluntary activation was superimposed over ES-induced 25% MVC to reach 50% and 75% MVC. Empirical mode decomposition (EMD) was utilized to separate ES artifacts from voluntary muscle activation. For both muscles, higher stimulation frequency (35 and 50Hz) induced higher electrical output detected at 25% of MVC, suggesting more recruitment with higher frequencies. Hybrid activation generated proportionally less electrical activity than ES alone. ES and voluntary activations appear to generate two different modes of muscle recruitment. ES may provoke muscle strength by activating more fatiguing fast acting fibers, but voluntary activation elicits more muscle coordination. Therefore, during the hybrid activation, less electrical activity may be detected due to recruitment of more fatigue-resistant deeper muscle fibers, not reachable by surface EMG.

Transurethral Photoacoustic Endoscopy for Prostate Cancer: A Simulation Study

The purpose of this study was to optimize the configuration of a photoacoustic endoscope (PAE) for prostate cancer detection and therapy monitoring. The placement of optical fiber bundles and ultrasound detectors was chosen to maximize the photoacoustic imaging penetration depth. We performed both theoretical calculations and simulations of this optimized PAE configuration on a prostate-sized phantom containing tumor and various photosensitizer concentrations. The optimized configuration of PAE with transurethral light delivery simultaneously increases the imaging penetration depth and improves image quality. Thermal safety, investigated via COMSOL Multiphysics, shows that there is only a 4 mK temperature rise in the urethra during photoacoustic imaging, which will cause no thermal damage. One application of this PAE has been demonstrated for quasi-quantifying photosensitizer concentrations during photodynamic therapy. The sensitivity of the photoacoustic detection for TOOKAD was 0.18 ng/mg at a 763 nm laser wavelength. Results of this study will greatly enhance the potential of prostate PAE for in vivo monitoring of drug delivery and guidance of the laser-induced therapy for future clinical use.

A Germline Variant on Chromosome 4q31.1 Associates with Susceptibility to Developing Colon Cancer Metastasis

We tested for germline variants showing association to colon cancer metastasis using a genome-wide association study that compared Ashkenazi Jewish individuals with stage IV metastatic colon cancers versus those with stage I or II non-metastatic colon cancers. In a two-stage study design, we demonstrated significant association to developing metastatic disease for rs60745952, that in Ashkenazi discovery and validation cohorts, respectively, showed an odds ratio (OR) = 2.3 (P = 2.73E-06) and OR = 1.89 (P = 8.05E-04) (exceeding validation threshold of 0.0044). Significant association to metastatic colon cancer was further confirmed by a meta-analysis of rs60745952 in these datasets plus an additional Ashkenazi validation cohort (OR = 1.92; 95% CI: 1.28–2.87), and by a permutation test that demonstrated a significantly longer haplotype surrounding rs60745952 in the stage IV samples. rs60745952, located in an intergenic region on chromosome 4q31.1, and not previously associated with cancer, is, thus, a germline genetic marker for susceptibility to developing colon cancer metastases among Ashkenazi Jews.

The International Association for the Study of Lung Cancer Lung Cancer Staging Project: Proposals for the Revision of the Clinical and Pathologic Staging of Small Cell Lung Cancer in the Forthcoming Eighth Edition of the TNM Classification for Lung Cancer

INTRODUCTION

Small cell lung cancer (SCLC) is commonly classified as either limited or extensive, but the Union for International Cancer Control TNM Classification of Malignant Tumours seventh edition (2009) recommended tumor, node, and metastasis (TNM) staging based on analysis of the International Association for the Study of Lung Cancer (IASLC) database.

METHODS

Survival analyses were performed for clinically and pathologically staged patients presenting with SCLC from 1999 through 2010. Prognosis was compared in relation to the TNM seventh edition staging to serve as validation and analyzed in relation to proposed changes to the T descriptors found in the eighth edition.

RESULTS

There were 5002 patients: 4848 patients with clinical and 582 with pathological stages. Among these, 428 had both. Survival differences were confirmed for T and N categories and maintained in relation to proposed revisions to T descriptors for seventh edition TNM categories and proposed changes in the eighth edition. There were also survival differences, notably at 12 months, in patients with brain-only single-site metastasis (SSM) compared to SSM at other sites, and SSM without a pleural effusion showed a better prognosis than other patients in the M1b category.

CONCLUSION

We confirm the prognostic value of clinical and pathological TNM staging in patients with SCLC, and recommend continued usage for SCLC in relation to proposed changes to T, N, and M descriptors for NSCLC in the eighth edition. However, for M descriptors, it remains uncertain whether survival differences in patients with SSM in the brain simply reflect better treatment options rather than better survival based on anatomic extent of disease.

An analysis of the association between prostate cancer risk loci, PSA levels, disease aggressiveness and disease-specific mortality

BACKGROUND

Genome-wide association studies have identified multiple single-nucleotide polymorphsims (SNPs) associated with prostate cancer (PCa). Although these SNPs have been clearly associated with disease risk, their relationship with clinical outcomes is less clear. Our aim was to assess the frequency of known PCa susceptibility alleles within a single institution ascertainment and to correlate risk alleles with disease-specific outcomes.

METHODS

We genotyped 1354 individuals treated for localised PCa between June 1988 and December 2007. Blood samples were prospectively collected and de-identified before being genotyped and matched to phenotypic data. We investigated associations between 61 SNPs and disease-specific end points using multivariable analysis and also determined if SNPs were associated with PSA at diagnosis.

RESULTS

Seven SNPs showed associations on multivariable analysis (P<0.05), rs13385191 with both biochemical recurrence (BR) and castrate metastasis (CM), rs339331 (BR), rs1894292, rs17178655 and rs11067228 (CM), and rs11902236 and rs4857841 PCa-specific mortality. After applying a Bonferroni correction for number of SNPs (P<0.0008), the only persistent significant association was between rs17632542 (KLK3) and PSA levels at diagnosis (P=1.4 × 10(-5)).

CONCLUSIONS

We confirmed that rs17632542 in KLK3 is associated with PSA at diagnosis. No significant association was seen between loci and disease-specific end points when accounting for multiple testing. This provides further evidence that known PCa risk SNPs do not predict likelihood of disease progression.

A recessive founder mutation in regulator of telomere elongation helicase 1, RTEL1, underlies severe immunodeficiency and features of Hoyeraal Hreidarsson syndrome

Dyskeratosis congenita (DC) is a heterogeneous inherited bone marrow failure and cancer predisposition syndrome in which germline mutations in telomere biology genes account for approximately one-half of known families. Hoyeraal Hreidarsson syndrome (HH) is a clinically severe variant of DC in which patients also have cerebellar hypoplasia and may present with severe immunodeficiency and enteropathy. We discovered a germline autosomal recessive mutation in RTEL1, a helicase with critical telomeric functions, in two unrelated families of Ashkenazi Jewish (AJ) ancestry. The affected individuals in these families are homozygous for the same mutation, R1264H, which affects three isoforms of RTEL1. Each parent was a heterozygous carrier of one mutant allele. Patient-derived cell lines revealed evidence of telomere dysfunction, including significantly decreased telomere length, telomere length heterogeneity, and the presence of extra-chromosomal circular telomeric DNA. In addition, RTEL1 mutant cells exhibited enhanced sensitivity to the interstrand cross-linking agent mitomycin C. The molecular data and the patterns of inheritance are consistent with a hypomorphic mutation in RTEL1 as the underlying basis of the clinical and cellular phenotypes. This study further implicates RTEL1 in the etiology of DC/HH and immunodeficiency, and identifies the first known homozygous autosomal recessive disease-associated mutation in RTEL1.

Molecular dynamics simulation study of the interaction of cationic biocides with lipid bilayers: aggregation effects and bilayer damage

A novel class of phenylene ethynylene polyelectrolyte oligomers (OPEs) has been found to be effective biocidal agents against a variety of pathogens. The mechanism of attack is not yet fully understood. Recent studies have shown that OPEs cause catastrophic damage to large unilamellar vesicles. This study uses classical molecular dynamics (MD) simulations to understand how OPEs interact with model lipid bilayers. All-atom molecular dynamics simulations show that aggregates of OPEs inserted into the membrane cause significant structural damage and create a channel, or pore, that allows significant leakage of water through the membrane on the 0.1 μs time scale.

Prevalence and predictors of posttraumatic stress disorder in adult survivors of childhood cancer: A report from the Childhood Cancer Survivor Study

CRA10002

Background: This study examined prevalence and demographic- and disease-related correlates of posttraumatic stress disorder (PTSD) among 6,542 adult childhood cancer survivors and 368 siblings from the Childhood Cancer Survivor Study. Methods: Subjects were dichotomized based on full PTSD criteria, using the Foa PTSD self-report measure to assess posttraumatic stress symptoms of intrusion of unwanted memories, avoidance of event reminders, and increased startle response, and the Brief Symptom Inventory-18 and the SF-36 subscale, role limitation due to emotional health, to evaluate clinical distress or impaired function. A self-report questionnaire provided demographic information and medical abstraction provided cancer reatment data. Multivariable generalized linear models were used to compare prevalence of PTSD among cancer survivors to siblings and to examine relationships between PTSD and demographic and disease-related factors. Relative risks (RR) were calculated based on a Poisson distribution with robust error variances. Results: Five hundred eighty-nine (9%) childhood cancer survivors and 8 (2%) siblings met criteria for a diagnosis of PTSD (RR = 3.83, 95% CI 1.96–7.48, p < 0.0001). Among cancer survivors, there was significantly more PTSD reported by women from minority backgrounds (p < 0.05). Other demographic factors associated with PTSD were having less than a college education (p < 0.05), being unmarried (p < 0.001), having an annual income less than $20,000 (p < 0.05) and being unemployed (p = 0.001). Risk of PTSD was significantly higher for survivors diagnosed at ages 15 to 20 years (p < 0.05). PTSD was more common among survivors treated with intensive chemotherapy (p < 0.05) or radiation therapy (p < 0.001) and who relapsed or developed a second malignant neoplasm (p < 0.001). Neuroblastoma and Wilms tumor survivors had a significantly lower risk of PTSD than did leukemia survivors (p < 0.05). Conclusions: While the majority of childhood cancer survivors did not demonstrate PTSD, a clinically significant number did meet diagnostic criteria. Prospective assessment of survivors with high risk demographic-, diagnosis-, and treatment-related characteristics should be considered as part of long-term health screening.

No significant financial relationships to disclose.

Prevalence and predictors of posttraumatic stress disorder in adult survivors of childhood cancer: A report from the Childhood Cancer Survivor Study

CRA10002

The full, final text of this abstract will be available in Part II of the 2009 ASCO Annual Meeting Proceedings, distributed onsite at the Meeting on May 30, 2009, and as a supplement to the June 20, 2009, issue of the Journal of Clinical Oncology.

No significant financial relationships to disclose.

pH-induced conformational changes of AcrA, the membrane fusion protein of Escherichia coli multidrug efflux system

The multidrug efflux system AcrA-AcrB-TolC of Escherichia coli expels a wide range of drugs directly into the external medium from the bacterial cell. The mechanism of the efflux process is not fully understood. Of an elongated shape, AcrA is thought to span the periplasmic space coordinating the concerted operation of the inner and outer membrane proteins AcrB and TolC. In this study, we used site-directed spin labeling (SDSL) EPR (electron paramagnetic resonance) spectroscopy to investigate the molecular conformations of AcrA in solution. Ten AcrA mutants, each with an alanine to cysteine substitution, were engineered, purified, and labeled with a nitroxide spin label. EPR analysis of spin-labeled AcrA variants indicates that the side chain mobilities are consistent with the predicted secondary structure of AcrA. We further demonstrated that acidic pH induces oligomerization and conformational change of AcrA, and that the structural changes are reversible. These results suggest that the mechanism of action of AcrA in drug efflux is similar to the viral membrane fusion proteins, and that AcrA actively mediates the efflux of substrates.