The Hallmarks of Precancer

Research on precancers, as defined as at-risk tissues and early lesions, is of high significance given the effectiveness of early intervention. We discuss the need for risk stratification to prevent overtreatment, an emphasis on the role of genetic and epigenetic aging when considering risk, and the importance of integrating macroenvironmental risk factors with molecules and cells in lesions and at-risk normal tissues for developing effective intervention and health policy strategies.

Molecular cartography uncovers evolutionary and microenvironmental dynamics in sporadic colorectal tumors

Colorectal cancer exhibits dynamic cellular and genetic heterogeneity during progression from precursor lesions toward malignancy. Analysis of spatial multi-omic data from 31 human colorectal specimens enabled phylogeographic mapping of tumor evolution that revealed individualized progression trajectories and accompanying microenvironmental and clonal alterations. Phylogeographic mapping ordered genetic events, classified tumors by their evolutionary dynamics, and placed clonal regions along global pseudotemporal progression trajectories encompassing the chromosomal instability (CIN+) and hypermutated (HM) pathways. Integrated single-cell and spatial transcriptomic data revealed recurring epithelial programs and infiltrating immune states along progression pseudotime. We discovered an immune exclusion signature (IEX), consisting of extracellular matrix regulators DDR1, TGFBI, PAK4, and DPEP1, that charts with CIN+ tumor progression, is associated with reduced cytotoxic cell infiltration, and shows prognostic value in independent cohorts. This spatial multi-omic atlas provides insights into colorectal tumor-microenvironment co-evolution, serving as a resource for stratification and targeted treatments.

Characterizing molecular subtypes of high-risk non-muscle-invasive bladder cancer in African American patients

BACKGROUND

We sought to determine whether differences in subtype distribution and differentially expressed genes exist between African Americans (AAs) and European Americans (EAs) in patients with high-risk nonmuscle-invasive bladder cancer (NMIBC).

METHODS

We performed a retrospective cohort study including 26 patients (14 AAs and 12 EAs) from the University of Texas Medical Branch and the Durham Veterans Affair Health Care System from 2010 to 2020 among treatment naïve, high-risk NMIBC. Profiled gene expressions were performed using the UROMOL classification system.

RESULTS

UROMOL racial subtype distributions were similar with class 2a being most common with 10 genes commonly upregulated in AAs compared to EAs including EFEMP1, S100A16, and MCL1 which are associated with progression to muscle-invasive bladder cancer, mitomycin C resistance, and bacillus Calmette-Guérin durability, respectively. We used single nuclei analysis to map the malignant cell heterogeneity in urothelial cancer which 5 distinct malignant epithelial subtypes whose presence has been associated with different therapeutic response prediction abilities. We mapped the expression of the 10 genes commonly upregulated by race as a function of the 5 malignant subtypes. This showed borderline (P = 0.056) difference among the subtypes suggesting AAs and EAs may be expected to have different therapeutic responses to treatments for bladder cancer. AAs were enriched with immune-related, inflammatory, and cellular regulation pathways compared to EAs, yet appeared to have reduced levels of the aggressive C3/CDH12 bladder tumor cell population.

CONCLUSIONS

While premature, gene expression differed between AAs and EAs, supporting potential race-based etiologies for muscle-invasion, response to treatments, and transcriptome pathway regulations.

Cabozantinib plus Nivolumab Phase I Expansion Study in Patients with Metastatic Urothelial Carcinoma Refractory to Immune Checkpoint Inhibitor Therapy

PURPOSE

This study investigated the efficacy and tolerability of cabozantinib plus nivolumab (CaboNivo) in patients with metastatic urothelial carcinoma (mUC) that progressed on checkpoint inhibition (CPI).

PATIENTS AND METHODS

A phase I expansion cohort of patients with mUC who received prior CPI was treated with cabozantinib 40 mg/day and nivolumab 3 mg/kg every 2 weeks until disease progression/unacceptable toxicity. The primary goal was objective response rate (ORR) per RECIST v.1.1. Secondary objectives included progression-free survival (PFS), duration of response (DoR), overall survival (OS), safety, and tolerability.

RESULTS

Twenty-nine out of 30 patients enrolled were evaluable for efficacy. Median follow-up was 22.2 months. Most patients (86.7%) received prior chemotherapy and all patients received prior CPI (median seven cycles). ORR was 16.0%, with one complete response and three partial responses (PR). Among 4 responders, 2 were primary refractory, 1 had a PR, and 1 had stable disease on prior CPI. Median DoR was 33.5 months [95% confidence interval (CI), 3.7-33.5], median PFS was 3.6 months (95% CI, 2.1-5.5), and median OS was 10.4 months (95% CI, 5.8-19.5). CaboNivo decreased immunosuppressive subsets such as regulatory T cells (Tregs) and increased potential antitumor immune subsets such as nonclassical monocytes and effector T cells. A lower percentage of monocytic myeloid-derived suppressor cells (M-MDSC) and polymorphonuclear MDSCs, lower CTLA-4 and TIM-3 expression on Tregs, and higher effector CD4+ T cells at baseline were associated with better PFS and/or OS.

CONCLUSIONS

CaboNivo was clinically active, well tolerated, and favorably modulated peripheral blood immune subsets in patients with mUC refractory to CPI.

Characterizing molecular subtypes of high-risk nonmuscle-invasive bladder cancer in African American patients

527

Background: Patients with high-risk non-muscle-invasive bladder cancer (NMIBC) have heterogeneous outcomes with African Americans (AAs) having worse survival than European Americans (EAs). It is unknown whether race-based biological differences contribute to this disparity. Methods: We performed a retrospective cohort study including patients from the University of Texas Medical Branch (UTMB) and the Durham VA Health Care System (DVAHCS) from 2010-2020 among treatment naïve, high-risk NMIBC. Profiled gene expressions of high-risk NMIBC by race were performed using the UROMOL classification system. Results: A total of 26 patients (14 AAs and 12 EAs) matched on age and sex were included with no significant difference in clinical stage group (CIS +/- T1 or TaHG vs. TaHG or T1, no CIS), smoking status, or progression. We found a similar racial UROMOL subtype distribution with class 2a being most common. A total of 10 genes were discovered to be commonly upregulated differentially expressed genes (up-DEGs) in AAs vs EAs. EFEMP1, which has been associated with progression to muscle-invasive bladder cancer (MIBC) in vitro, and S100A16 gene expression, which has been implicated with mitomycin C resistance in bladder cancer in vitro, was significantly more common among AAs. We used single nuclei analysis to map the malignant cell heterogeneity in urothelial cancer which five distinct malignant epithelial subtypes whose presence has been associated with different therapeutic response prediction ability. We mapped the expression of the 10 genes commonly up-DEGs by race as a function of the five malignant subtypes. This showed borderline (p = 0.056) differences among the subtypes suggesting AA and EA patients may be expected to have different therapeutic responses to treatments for BC. AAs were enriched with immune-related, inflammatory, and cellular regulation pathways compared to EAs, yet appeared to have reduced levels of the aggressive C3 bladder tumor cell population. Conclusions: In this small sample, we found similar subtype distribution among high-risk NMIBC patients according to race. However, gene expression differs by race, supporting potential novel race-based etiologies for differences in muscle-invasion, response to treatments, and transcriptome pathway regulations. Further biological studies in NMIBC molecular sub-stratification, associated treatment(s), and prognoses in a larger cohort are needed to support these hypotheses.

Drone versus ambulance for blood products transportation: an economic evaluation study

BACKGROUND

Medical transportation is an essential step in health care services, and includes ground, air and water transportation. Among the important uses of medical transportation is the delivery of blood products in the event of a clinical emergency. Drone technology is the latest technological advancement that may revolutionize medical transportation globally. Nonetheless, its economic evaluation is scant and insufficient, whilst its cost-effectiveness remains controversial. The aim of this study was to compare the cost-effectiveness of drone transportation versus the ambulance.

METHODS

The setting of the study was within a developing nation. An economic evaluation study of drone versus ambulance for emergency blood products transportation between the Sabah Women and Children Hospital (SWACH) and the Queen Elizabeth II Hospital (QEH2) on Borneo Island was conducted using the Cost-Effectiveness Analysis (CEA) technique. The total cost of each mode of transportation was calculated using the Activity Based Costing (ABC) method. Travel time was used as a denominator to estimate the Incremental Cost Effectiveness Ratio (ICER).

RESULTS

For one clinical emergency in SWACH, a round trip of blood products transportation from SWACH to QEH2 costs RM1,266.02 (USD307.09) when using the ambulance, while the drone costs RM1,313.28 (USD319.36). The travel time for the drone was much shorter (18 min) compared to the ambulance (34 min). The Cost-Effectiveness Ratio (CER) of ambulance transportation was RM37.23 (USD9.05) per minute whilst the CER of drone transportation was RM72.96 (USD17.74) per minute. The ICER of drone versus ambulance was - 2.95, implying an increase of RM2.95 in cost for every minute saved using a drone instead of an ambulance.

CONCLUSION

Although drone transportation of blood products costs more per minute compared to the ambulance, the significantly shorter transport time of the drone offset its cost. Thus, we believe there is good economic potential for drone usage for blood products transportation in developing nations particularly if the drone price decreases and its operational lifespan increases. Our limitation of a non-clinical denominator used in this study leads to the recommendation for use of clinical outcomes in future studies.

184 Effects of The Coronavirus Pandemic on Medical and Surgical Education: Results of An International Survey by The International Association of Student Surgical Societies (IASSS)

Aim

Coronavirus disease 2019 (COVID-19) presents a variety of unforeseen challenges to medical students and surgical trainees. Adaptations to the content and delivery of medical education are inevitable as institutions respond to the virus. Departments face significant restructuring, with important implications for training. Our aim was to assess the global impact of the first wave of COVID-19 on medical and surgical education.

Method

Between 12 May and 26 May 2020, an online survey was conducted and circulated to contacts of the International Association of Student Surgical Societies, including medical students and healthcare practitioners. All data were anonymous; no personal identifiable information was collected. Consent was implied by participation in the survey, which was on a voluntary basis.

Results

We collated 527 responses from 111 institutions across 26 countries. Globally, 93.5% of medical student placements were affected by the first wave of COVID-19, with examination restructuring and alternative teaching methods employed by 87.8% of medical schools. Trainee redeployment was common in both surgical (61.5%) and non-surgical (77.1%) disciplines. Surgical services were significantly affected, with reduced elective procedures in 93% of institutions. On an individual level, COVID-19 resulted in prolonged absence from clinical duties and mental health concerns at all levels of training.

Conclusions

Our data highlight drastic changes in medical and surgical education and practice as a result of the first wave of COVID-19. These changes are significant at all levels of training, both institutionally and individually. The pandemic is likely to have persistent consequences for future trainees in terms of education and career progression.

Inhibitory DAMPs in immunogenic cell death and its clinical implications

Dying (or dead) cells are increasingly recognized to impose significant biological influence within their tissues of residence—exerting paracrine effects through proteins and metabolites that are expressed or secreted during cellular demise. For example, certain molecules function as potent mitogens, promoting the repopulation of neighboring epithelial cells. And other myriad of factors—classified as damage-associated molecular patterns (DAMPs)—function as “find me” (attractant), “eat me” (engulfment), or “danger” (activation) signals for recruiting and activating effector immune cells (e.g., dendritic cells) to initiate inflammation. Since the discovery of immunogenic cell death (ICD), the current dogma posits DAMPs as immunological adjuvants for innate immune cell mobilization and activation, which ultimately leads to the antitumoral cross-priming of CD8⁺ T cells. However, what is currently unknown is how these immunostimulatory DAMPs are counteracted to avoid immune-overactivation. Our recent work builds on these fundamentals and introduces prostaglandin E₂ (PGE₂) as an ‘inhibitory' DAMP—a new variable to the ICD equation. Prostaglandin E₂ functions as an immunosuppressive counterpoise of adjuvant DAMPs; and thus, mechanistically precludes ICD. Furthermore, the long-debated immunogenicity of gemcitabine chemotherapy was revealed to be contingent on inhibitory DAMP blockade and not due to its inability to promote DAMP expression (i.e., calreticulin) as previously reported. These findings were intriguing. First, despite the presence of gemcitabine-induced hallmark DAMPs, the inhibitory DAMP (i.e., PGE₂) was sufficient to hinder the ICD-induced antitumoral immune response (Fig. 1a). And second, rather than pharmacologically substantiating immunostimulatory DAMPs as conventionally approached, the mitigation of the inhibitory DAMP—tipping the immunostimulatory and inhibitory DAMP balance in favor of immunostimulatory DAMPs—was sufficient to render the cell death immunogenic and converted gemcitabine into an ICD-inducing therapy (Fig. 1b). In this microreview, we extrapolate our findings and implicate the value of inhibitory DAMP(s) in drug discovery, its use for clinical prognosis, and as target(s) for therapeutic intervention.

Tipping the immunostimulatory and inhibitory DAMP balance to harness immunogenic cell death

Induction of tumor cell death is the therapeutic goal for most anticancer drugs. Yet, a mode of drug-induced cell death, known as immunogenic cell death (ICD), can propagate antitumoral immunity to augment therapeutic efficacy. Currently, the molecular hallmark of ICD features the release of damage-associated molecular patterns (DAMPs) by dying cancer cells. Here, we show that gemcitabine, a standard chemotherapy for various solid tumors, triggers hallmark immunostimualtory DAMP release (e.g., calreticulin, HSP70, and HMGB1); however, is unable to induce ICD. Mechanistic studies reveal gemcitabine concurrently triggers prostaglandin E2 release as an inhibitory DAMP to counterpoise the adjuvanticity of immunostimulatory DAMPs. Pharmacological blockade of prostaglandin E2 biosythesis favors CD103+ dendritic cell activation that primes a Tc1-polarized CD8+ T cell response to bolster tumor rejection. Herein, we postulate that an intricate balance between immunostimulatory and inhibitory DAMPs could determine the outcome of drug-induced ICD and pose COX-2/prostaglandin E2 blockade as a strategy to harness ICD.

Plasminogen activator inhibitor-2 (PAI-2) overexpression supports bladder cancer development in PAI-1 knockout mice in N-butyl-N- (4-hydroxybutyl)-nitrosamine- induced bladder cancer mouse model

BACKGROUND

Accumulating evidence suggests that plasminogen activator inhibitor-1 (PAI-1) plays an important role in bladder tumorigenesis by regulating cell cycle. However, it remains unclear whether and how inhibition of PAI-1 suppresses bladder tumorigenesis.

METHODS

To elucidate the therapeutic effect of PAI-1 inhibition, we tested its tumorigenicity in PAI-1 knockout (KO) mice exposed to a known bladder carcinogen.

RESULTS

PAI-1 deficiency did not inhibit carcinogen-induced bladder cancer in mice although carcinogen-exposed wild type mice significantly increased PAI-1 levels in bladder tissue, plasma and urine. We found that PAI-1 KO mice exposed to carcinogen tended to upregulate protein C inhibitor (PAI-3), urokinase-type plasminogen activator (uPA) and tissue-type PA (tPA), and significantly increased PAI-2, suggesting a potential compensatory function of these molecules when PAI-1 is abrogated. Subsequent studies employing gene expression microarray using mouse bladder tissues followed by post hoc bioinformatics analysis and validation experiments by qPCR and IHC demonstrated that SERPING1 is further downregulated in PAI-1 KO mice exposed to BBN, suggesting that SERPING1 as a potential missing factor that regulate PAI-2 overexpression (compensation pathway).

CONCLUSIONS

These results indicate that serpin compensation pathway, specifically PAI-2 overexpression in this model, supports bladder cancer development when oncoprotein PAI-1 is deleted. Further investigations into PAI-1 are necessary in order to identify true potential targets for bladder cancer therapy.

Prognostic Significance of Lymphocyte Infiltration and a Stromal Immunostaining of a Bladder Cancer Associated Diagnostic Panel in Urothelial Carcinoma

We set out to expand on our previous work in which we reported the epithelial expression pattern of a urine-based bladder cancer-associated diagnostic panel (A1AT, ANG, APOE, CA9, IL8, MMP9, MMP10, PAI1, SDC1, and VEGFA). Since many of the analytes in the bladder cancer-associated diagnostic signature were chemokines, cytokines, or secreted proteins, we set out to report the stromal staining pattern of the diagnostic signature as well as CD3⁺ (T-cell) cell and CD68⁺ (macrophage) cell staining in human bladder tumors as a snapshot of the tumor immune landscape. Immunohistochemical staining was performed on 213 tumor specimens and 74 benign controls. Images were digitally captured and quantitated using Aperio (Vista, CA). The expression patterns were correlated with tumor grade, tumor stage, and outcome measures. We noted a positive correlation of seven of the 10 proteins (excluding A1AT and IL8 which had a negative association and VEGFA had no association) in bladder cancer. The overexpression of MMP10 was associated with higher grade disease, while overexpression of MMP10, PAI1, SDC1 and ANG were associated with high stage bladder cancer and CA9 was associated with low stage bladder cancer. Increased tumor infiltration of CD68⁺ cells were associated with higher stage disease. Overall survival was significantly reduced in bladder cancer patients' whose tumors expressed eight or more of the 10 proteins that comprise the bladder cancer diagnostic panel. These findings confirm that the chemokines, cytokines, and secreted proteins in a urine-based diagnostic panel are atypically expressed, not only in the epithelial component of bladder tumors, but also in the stromal component of bladder tumors and portends a worse overall survival. Thus, when assessing immunohistochemical staining, it is important to report staining patterns within the stroma as well as the entire stroma itself.

A Consensus Molecular Classification of Muscle-invasive Bladder Cancer

Background:

Muscle-invasive bladder cancer (MIBC) is a molecularly diverse disease with heterogeneous clinical outcomes. Several molecular classifications have been proposed, but the diversity of their subtype sets impedes their clinical application.

Objective:

To achieve an international consensus on MIBC molecular subtypes that reconciles the published classification schemes.

Design, setting, and participants:

We used 1750 MIBC transcriptomic profiles from 16 published datasets and two additional cohorts.

Outcome measurements and statistical analysis:

We performed a network-based analysis of six independent MIBC classification systems to identify a consensus set of molecular classes. Association with survival was assessed using multivariable Cox models.

Results and limitations:

We report the results of an international effort to reach a consensus on MIBC molecular subtypes. We identified a consensus set of six molecular classes: luminal papillary (24%), luminal nonspecified (8%), luminal unstable (15%), stroma-rich (15%), basal/squamous (35%), and neuroendocrine-like (3%). These consensus classes differ regarding underlying oncogenic mechanisms, infiltration by immune and stromal cells, and histological and clinical characteristics, including outcomes. We provide a single-sample classifier that assigns a consensus class label to a tumor sample’s transcriptome. Limitations of the work are retrospective clinical data collection and a lack of complete information regarding patient treatment.

Conclusions:

This consensus system offers a robust framework that will enable testing and validation of predictive biomarkers in future prospective clinical trials.

Patient summary:

Bladder cancers are heterogeneous at the molecular level, and scientists have proposed several classifications into sets of molecular classes. While these classifications may be useful to stratify patients for prognosis or response to treatment, a consensus classification would facilitate the clinical use of molecular classes. Conducted by multidisciplinary expert teams in the field, this study proposes such a consensus and provides a tool for applying the consensus classification in the clinical setting.

Delayed diagnosis of tuberculosis: risk factors and effect on mortality among older adults in Hong Kong

OBJECTIVE

To assess the risk factors and effects of delayed diagnosis on tuberculosis (TB) mortality in Hong Kong.

METHODS

All consecutive patients with TB notified in 2010 were tracked through their clinical records for treatment outcome until 2012. All TB cases notified or confirmed after death were identified for a mortality survey on the timing and causes of death.

RESULTS

Of 5092 TB cases notified, 1061 (20.9%) died within 2 years of notification; 211 (4.1%) patients died before notification, 683 (13.4%) died within the first year, and 167 (3.3%) died within the second year after notification. Among the 211 cases with TB notified after death, only 30 were certified to have died from TB. However, 52 (24.6%) died from unspecified pneumonia/sepsis possibly related to pulmonary TB. If these cases are counted, the total TB-related deaths increases from 191 to 243. In 82 (33.7%) of these, TB was notified after death. Over 60% of cases in which TB diagnosed after death involved patients aged ≥80 years and a similar proportion had an advance care directive against resuscitation or investigation. Independent factors for TB notified after death included female sex, living in an old age home, drug abuse, malignancy other than lung cancer, sputum TB smear negative, sputum TB culture positive, and chest X-ray not done.

CONCLUSIONS

High mortality was observed among patients with TB aged ≥80 years. Increased vigilance is warranted to avoid delayed diagnosis and reduce the transmission risk, especially among elderly patients with co-morbidities living in old age homes.

Palliative care: the need of the modern era

There is a great need for palliative care in the modern era of medicine. Despite medical advances, patients with life-limiting illnesses still suffer significantly. Palliative care emerged a half century ago as an ethos based on compassion and care for patients and their families to relieve their suffering. It entails a paradigm shift from the biomedical model to the biopsychospiritual model. Palliative care is recognised by the World Health Organization as an essential part of the continuum of universal health coverage. In 2014, the World Health Assembly approved a resolution on "Strengthening of palliative care as a component of comprehensive care throughout the life course". Despite Hong Kong's relatively good local palliative care service coverage for patients who died of cancer and end-stage renal failure, service gaps for palliative care do exist among our ageing population with non-malignant life-limiting illnesses. We strongly urge the Hong Kong Government to develop our local palliative care policy in response to the World Health Assembly's resolution. Growing international and local evidence demonstrates the impacts of palliative care on patient outcomes, caregivers, and health care. Such outcomes can be service-based, disease-based, or symptom/suffering-based. The goal of palliative care is to relieve health-related suffering. Evidence-based management of pain, breathlessness, and psychospiritual suffering are discussed. Care in the end-of-life phase should be an integral part of palliative care, promoting patient choice, advance care planning, and good death.

Spin-transfer torque generated in graphene based topological insulator heterostructures

We studied the spin-transfer torque (STT) in graphene based normal-metal/topological-insulator/ferromagnet heterostructures (N/TI/F), which is induced by the helical spin-polarized current in the quantum spin Hall insulator. We found that the STT is comparable in magnitude to the STT in ferromagnetic-normal- ferromagnetic graphene junction, while not requiring additional ferromagnetic layer with fixed magnetization, which makes it advantageous for the manipulation of magnetic devices in spintronics. More interestingly, the STT is very robust in our proposed nanostructure, as it is immune to changes in the geometry due to an asymmetrically notch or the presence of random nanopores in the quantum spin Hall insulator. Our theoretical prediction suggests that graphene based quantum spin Hall insulator could be used for very efficient magnetization manipulation for magnetic materials.

A fully Bayesian latent variable model for integrative clustering analysis of multi-type omics data

Identification of clinically relevant tumor subtypes and omics signatures is an important task in cancer translational research for precision medicine. Large-scale genomic profiling studies such as The Cancer Genome Atlas (TCGA) Research Network have generated vast amounts of genomic, transcriptomic, epigenomic, and proteomic data. While these studies have provided great resources for researchers to discover clinically relevant tumor subtypes and driver molecular alterations, there are few computationally efficient methods and tools for integrative clustering analysis of these multi-type omics data. Therefore, the aim of this article is to develop a fully Bayesian latent variable method (called iClusterBayes) that can jointly model omics data of continuous and discrete data types for identification of tumor subtypes and relevant omics features. Specifically, the proposed method uses a few latent variables to capture the inherent structure of multiple omics data sets to achieve joint dimension reduction. As a result, the tumor samples can be clustered in the latent variable space and relevant omics features that drive the sample clustering are identified through Bayesian variable selection. This method significantly improve on the existing integrative clustering method iClusterPlus in terms of statistical inference and computational speed. By analyzing TCGA and simulated data sets, we demonstrate the excellent performance of the proposed method in revealing clinically meaningful tumor subtypes and driver omics features.

Creation of quasi-Dirac points in the Floquet band structure of bilayer graphene

We study the Floquet quasi-energy band structure of bilayer graphene when it is illuminated by two laser lights with frequencies [Formula: see text] and [Formula: see text] using Floquet theory. We focus on the dynamical gap formed by the conduction band with Floquet index  =  -1 and the valence band with Floquet index  =  +1 to understand how Dirac points can be formed. It is found that the dynamical gap does not have rotation symmetry in the momentum space, and quasi-Dirac points, where the conduction and valence bands almost touch, can be created when the dynamical gap closes along some directions with suitably chosen radiation parameters. We derive analytical expressions for the direction dependence of the dynamical gaps using Lowdin perturbation theory to gain a better understanding of the formation of quasi-Dirac points. When both radiations are circularly polarized, the gap can be exactly zero along some directions, when only the first and second order perturbations are considered. Higher order perturbations can open a very small gap in this case. When both radiations are linearly polarized, the gap can be exactly zero up to the fourth order perturbation and more than one quasi-Dirac point is formed. We also study the electron velocity around a dynamical gap and show that the magnitude of the velocity drops to values close to zero when the k vector is near to the gap minimum. The direction of the velocity also changes around the gap minimum, and when the gap is larger in value the change in the velocity direction is more gradual. The warping effect does not affect the formation of a Dirac point along the k _x axis, while it prevents its formation when there is phase shift between the two radiations.

Spin-polarized transport in graphene nanoribbons with Rashba spin-orbit interaction: the effects of spatial symmetry

We study the spin-dependent transport properties of graphene nanoribbons with Rashba spin-orbit interaction (SOI). It is found that highly spin polarized electrical currents can be produced in asymmetrically-notched graphene nanoribbons, and the polarization components are found to be along the x, y and z directions. The spin polarization is largely enhanced by breaking the spatial symmetries of ideal graphene nanoribbons with Rashba SOI, and the spin polarized electrical currents with higher flexibility in the orientation of the polarization can be generated. This offers new possibilities for the generation of high spin polarization in graphene nanoribbons without external magnetic fields.

The pattern of cervical smear abnormalities in marginalised women in Hong Kong

INTRODUCTION

"Ripple Action" and "WE Stand" are projects co-organised by the Hong Kong Women Doctors Association. The two projects organise free cervical screening for low-income women, new immigrants from Mainland China, and ethnic minority women. The objective of this study was to analyse the pattern of cervical smear abnormalities in these marginalised women.

METHODS

The study group consisted of 1189 marginalised women who participated in a free cervical screening campaign, including 324 low-income local Chinese, 540 new immigrants from Mainland China, and 325 ethnic minority women. The comparison group consisted of 1141 local Chinese who attended a well women clinic. The prevalence of cervical smear abnormalities was compared using Chi squared test.

RESULTS

In the study group, 42.6% of women had never had a cervical smear. Compared with the comparison group, they had a significantly higher prevalence of cervical smear abnormalities (13.7% vs 1.4%; P<0.001), including atypical smear (10.8% vs 0.5%; P<0.001), low-grade lesion (1.8% vs 0.8%; P=0.036), and high-grade lesion (1.1% vs 0.1%; P=0.002). Logistic regression analysis showed that the strongest predictors for abnormal cervical smear were being South Asian (odds ratio=11.859; 95% confidence interval, 4.635-30.341), South-East Asian (6.484; 3.192-13.171), or new immigrant from Mainland China (6.253; 2.463-15.877).

CONCLUSIONS

Marginalised women had a significantly higher prevalence of cervical smear abnormality than the general population and almost half had never had a cervical smear before. Outreach strategies are needed to enrol this population into screening programmes.

A valley and spin filter based on gapped graphene

We study highly valley- and spin-polarized current in single-layer gapped graphene without spin-orbit coupling. The structure considered is a three-barrier structure with one spin-splitting barrier and two electrical potential barriers with vector potentials. The electrons in the two valleys transmit differently because of the valley-dependent reflection between two adjacent barriers, while the spin-up and spin-down electrons transmit differently because of the spin splitting. The structure is different from other structures in which spin-orbit coupling plays an important role in the observation of valley- and spin-polarized current. We can control the spin and valley polarization by changing the width of the barrier or the strength of the spin splitting. The structure proposed in this paper can be used to make valley and spin devices.

Has Choosing Wisely® affected rates of dual-energy X-ray absorptiometry use?

Reducing overuse of tests such as dual-energy X-ray absorptiometry (DXA) scans in younger women is an important quality issue. We evaluated trends in DXA ordering before and after Choosing Wisely recommendations were released. We found no significant difference in ordering trends suggesting that other initiatives are needed to change behavior.

INTRODUCTION

Reducing overuse of tests such as dual-energy X-ray absorptiometry (DXA) scans in younger women is an important quality issue, but trends in care are difficult to change. We evaluated (1) trends in DXA ordering before and after the Choosing Wisely recommendation release and (2) patterns of key characteristics that indicate a potentially appropriate DXA scan order.

METHODS

We performed a retrospective longitudinal analysis of electronic health record data at a multi-specialty, ambulatory care network of 34 practices across Maryland and Washington, DC. Since the Choosing Wisely DXA recommendation was released April 2012, the study periods were April-December 2011 (pre-initiative) and April-December 2012 (post-initiative). Women between 50 and 64 years with primary care encounters, and primary care providers who saw ten or more women in the study population in both pre and post periods were included.

RESULTS

For 42,320 eligible patients, the mean provider ordering rate was 2.6 % pre-initiative and 2.0 % post-initiative; there was no significant difference in trend over time. Over 70 % of the population had no characteristics associated with potentially appropriate DXA ordering. Low body mass index, current smoker status, and osteopenia were the most common characteristics indicating potentially appropriate DXA orders. Patients with any of these three characteristics had DXA ordering rates between 3-20 %.

CONCLUSIONS

The trend in provider ordering rates of DXA scans did not decrease after the release of the DXA Choosing Wisely recommendation. Targeted initiatives addressing providers with high ordering rates will be needed to change behavior.

Nearly perfect valley filter in silicene

We demonstrate theoretically how a perfect valley filter can be obtained in silicene under the effects of a ferromagnetic stripe and an electric field perpendicular to silicene. A ferromagnetic stripe or an electric field alone can not generate any valley polarization in silicene, but a combination of them can make a perfect valley filter. Two configurations, one with magnetization of the ferromagnetic stripe being perpendicular to the silicene plane and one being parallel to the current direction, are considered. Our proposed device is useful for the realization of a valley beam filter in the development of valleytronic devices.

Bladder Cancer Molecular Taxonomy: Summary from a Consensus Meeting

The advent of Omics technologies has been key to the molecular subclassification of urothelial bladder cancer. Several groups have used different strategies to this aim, with partially overlapping findings. The meeting at the Spanish National Cancer Research Center-CNIO was held to discuss such classifications and reach consensus where appropriate. After updated presentations on the work performed by the teams attending the meeting, a consensus was reached regarding the existence of a group of Basal-Squamous-like tumors – designated BASQ – charaterized the high expression of KRT5/6 and KRT14 and low/undetectable expression of FOXA1 and GATA3. An additional tumor subgroup with urothelial differentiation features was recognized whose optimal molecular definition is required. For other subtypes described, more work is needed to determine how robust they are and how to best define them at the molecular level.

Abstract 5470: Blocking wound-induced tumor repopulation between chemotherapy cycles as a novel approach to abrogate chemoresistance

Acquired chemoresistance remains a major clinical issue in the management of advanced solid cancers. Initial response to cytotoxic chemotherapy is common, but certain patients progressively become unresponsive after multiple chemotherapy cycles. While causes of drug resistance are multiple and complex, here we approach this problem from a new angle: we studied whether repopulation of residual surviving cancer cells between chemotherapy cycles contributes to progressive chemoresistance. Currently the identity of repopulating cancer cells following chemotherapy is unknown, and the underlying molecular mechanisms that initiate tumor repopulation remain poorly understood. In the present study we use bladder cancer as a model and report that quiescent cancer stem cells (CSCs) are unexpectedly recruited to proliferate and repopulate residual tumors in response to chemotherapy-induced damage. This phenomenon is similar to how normal resident tissue stem cells mobilize to wound sites for tissue repair. We further investigate whether blockade of this wound-induced CSC repopulation can provide an innovative approach to abrogate chemoresistance.

Previously we showed that cytokeratin 14 (CK14) marks the most primitive bladder cancer cells and abundance of CK14+ cancer cells in patients correlates with poor survival. Here, we followed the standard clinical chemotherapy regimen with gap periods to allow recovery of normal tissues between treatment cycles. While one cycle of gemcitabine and cisplatin effectively reduced tumor growth in vivo, a generalized expansion of CK14+ CSCs occurred in residual tumors during these gap periods between cycles. Further analysis revealed the induction of a “wound-response” gene signature in residual tumors and active recruitment of quiescent CSCs into proliferation in response to chemotherapy-induced damage. We demonstrated that prostaglandin E2 (PGE2) released by neighboring dying cancer cells could induce CSC expansion in a paracrine manner. This undesirable CSC expansion could be abrogated by a PGE2 neutralizing antibody and Celecoxib, an FDA approved COX2 inhibitor that blocks PGE2 signaling. In vivo administration of Celecoxib blocked the induction of “wound-response” gene signature and significantly attenuated progressive development of chemoresistance in xenograft tumors, including primary xenografts derived from a patient who failed chemotherapy.These results revealed a new mechanism by which CSCs contribute to therapeutic resistance via repopulating residual tumors between chemotherapy cycles. Repopulation was initiated by dying cells that induced wound response and recruitment of CSCs to repair chemotherapy-induced damages. Therapeutic intervention with Celecoxib effectively blocked this process and improved chemotherapeutic response in bladder tumors, supporting further validation in other solid cancers.

Citation Format: Antonina V. Kurtova, Jing Xiao, Qianxing Mo, Senthil Pazhanisamy, Ross Krasnow, Seth P. Lerner, Fengju Chen, Terrence Roh, Erica Lay, Philip L. Ho, Keith S. Chan. Blocking wound-induced tumor repopulation between chemotherapy cycles as a novel approach to abrogate chemoresistance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5470. doi:10.1158/1538-7445.AM2015-5470

Sinogram Affirmed Iterative Reconstruction (SAFIRE) versus weighted filtered back projection (WFBP) effects on quantitative measure in the COPDGene 2 test object

PURPOSE

Assessing pulmonary emphysema using Quantitative CT of the lung depends on accurate measures of CT density. Sinogram-Affirmed-Iterative-Reconstruction (SAFIRE) is a new approach for reconstructing CT data acquired at significantly lower doses. However, quantitative effects of this method remain unexplored. The authors investigated the effects on the median values of materials in the COPDGene2 test-object as a function of the reconstruction method [weighted filtered back projection (WFBP) versus SAFIRE], test-object size, dose, and material composition using a Siemens SOMATOM Definition FLASH CT scanner.

METHODS

The COPDGene2 test-object contains eight materials; acrylic, water, four foams (20 lb, 12 lb, lung-equivalent, and 4 lb emphysema-equivalent), internal and external-air. The test-object was scanned with three different outer ring sizes, simulating three different body habitus. There is an average size (36 cm) Ring A, large size (40 cm) Ring B, and small size Ring C (30 cm). The CT protocol used 120 kVp, 0.5 s rotation, 1.0 pitch, and a 0.6 slice collimation with progressively decreasing x-ray exposure values, 11.94-0.74 mGy. With a thorax length of 30 cm, the corresponding effective doses would be 5.01-0.31 mSv. The effects of using SAFIRE versus WFBP were assessed using a two tailed t-test for each ring size, material, and dose. Multivariable linear regression was used to evaluate the relative effects of ring size, material composition, dose, and reconstruction method on the measured median value in HU.

RESULTS

SAFIRE versus WFBP, at the largest ring size and two lowest doses there was a significant difference in median values of 4 lb-foam, p<0.01. Using the smallest ring size at the lowest dose level there was a significant difference in the median value of 4 lb-foam, but the effect size was small, 1 HU. There is a significant difference in median values of both internal and external air using both the small and medium size rings at the three lowest dose levels, p<0.05. There are significant differences noted at both high and low dose levels when using the large ring size in the median values of internal and external air when, p<0.05. These effects on 4 lb-foam, inside and outside air are shown to be in part due to truncation effects on the median value since the lowest HU value in the CT scale used is -1024 HU. Multivariable linear regression results demonstrated significant effects on the measured material median value and standard deviation due to ring size, material composition, dose level, and reconstruction method, p<0.05.

CONCLUSIONS

The authors have shown that there is no significant effect on the median values obtained when using WFBP versus SAFIRE in materials with CT density between 120 and -856 HU using three different test-object sizes and CT doses that vary from 11.94 to 0.74 mGy. The authors have demonstrated there are significant effects on median values obtained when using WFBP versus SAFIRE in materials with CT density values between -937 and -1000 HU depending on the ring size and dose used. As expected, there is considerable reduction in image noise (lower standard deviation) using SAFIRE versus WFBP with all ring sizes, doses, and materials in the COPDGene2 test-object.

Effects of van der Waals interaction and electric field on the electronic structure of bilayer MoS2

The modification of the electronic structure of bilayer MoS2 by an external electric field can have potential applications in optoelectronics and valleytronics. Nevertheless, the underlying physical mechanism is not clearly understood, especially the effects of the van der Waals interaction. In this study, the spin orbit-coupled electronic structure of bilayer MoS2 has been investigated using the first-principle density functional theory. We find that the van der Waals interaction as well as the interlayer distance has significant effects on the band structure. When the interlayer distance of bilayer MoS2 increases from 0.614 nm to 0.71 nm, the indirect gap between the Γ and Λ points increases from 1.25 eV to 1.70 eV. Meanwhile, the energy gap of bilayer MoS2 transforms from an indirect one to a direct one. An external electric field can shift down (up) the energy bands of the bottom (top) MoS2 layer and also breaks the inversion symmetry of bilayer MoS2. As a result, the electric field can affect the band gaps, the spin-orbit interaction and splits the valance bands into two groups. The present study can help us understand more about the electronic structures of MoS2 materials for potential applications in electronics and optoelectronics.

Abstract 1928: Reporter construct for functional and real-time evaluation of cytokeratin 14+ bladder cancer stem cells

Bladder cancer is the fifth most common malignancy in the US. We recently reported that bladder cancer stem cells isolated by cell surface markers (i.e. CD44/CD90/CD49f) express a higher level of the intermediate filament cytokeratin 14 (CK14). Importantly, patients with a higher fraction of CK14+ cancer cells correlated with worse survival outcomes. Therefore, this CK14+ cancer cell subpopulation warrants further functional evaluation and characterization.

In the current study, we report the generation and characterization of a lentiviral reporter construct that carries the gene promoter region of human KRT14 gene upstream to a red fluorescent protein (tdTomato; Tm). With this reporter stably integrated into the genome of bladder cancer cells, the viable CK14+ cancer cell subpopulation could be isolated by FACS and visualized by fluorescent microscopy. We first validated the reporter by demonstrating that Tm+ cancer cells indeed express a higher level of KRT14 mRNA and relatively lower levels of differentiated cell markers (i.e. KRT18 and UPK1B) by qPCR. Next, we verified both in vitro and in vivo that CK14+/Tm+ cancer cells have functional properties of cancer stem cells by demonstrating their enriched sphere-forming ability and proficient engraftment as xenograft tumors in immunocompromised mice. Since neoadjuvant chemotherapy is a well-established treatment approach in patients with high-risk bladder cancer, we investigated CK14+ and CK14- cancer cells' response to the cytotoxic chemotherapy, gemcitabine/cisplatin (GC). FACS-purified CK14+/Tm+ cancer cells were more resistant to GC chemotherapy in vitro than CK14-/Tm- cancer cells. These findings were confirmed with in vivo studies using both patient-derived xenografts and immortalized bladder cancer xenografts. GC treated xenografts demonstrated a greater expansion of CK14+ cancer cells than vehicle treated controls. Additionally, we obtained a panel of human bladder cancer specimens from patients before and after neoadjuvant GC chemotherapy (n=15) and evaluated the CK14 status. An expansion or persistence of an infiltrating pattern of CK14 in post-neoadjuvant GC chemotherapy tumor specimens was associated with worse overall survival.

Collectively, these findings verified the unique intrinsic biological properties of CK14+/Tm+ bladder cancer cells and their response to GC chemotherapy. Ongoing experiments using fluorescence live imaging will evaluate Tm+/- bladder cancer cells' response to chemotherapy. The capacity to observe this CK14+/Tm+ subpopulation and their trace response to cytotoxic chemotherapy in these studies will open up new avenues to study the mechanisms of chemoresistance.

Citation Format: Philip L. Ho, Antonina Kurtova, Jing Xiao, Ross Krasnow, Erica Lay, Senthil Pazhanisamy, Seth P. Lerner, Keith S. Chan. Reporter construct for functional and real-time evaluation of cytokeratin 14+ bladder cancer stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1928. doi:10.1158/1538-7445.AM2014-1928

Abstract 4801: Stromal-mediated collagen I signal in promoting bladder cancer progression

Bladder cancer is the fifth most common malignancy, which is mostly incurable as invasive disease. It is clinically important to study the mechanisms underlying bladder cancer progression. While the tumor microenvironment is widely established to play an active role in epithelial cancers, its contribution to bladder cancer remains unexplored. The presence of cancer-associated fibroblasts (CAFs), characterized by the co-expression of vimentin, alpha-smooth muscle actin, and tenascin C, has been associated with invasive bladder cancer. Nevertheless, functional contributions of CAFs to bladder cancer progression have not been studied.

Here,we report the successful isolation and molecular characterization of bladder CAFs. We further investigate their functional roles on bladder cancer progression, with an emphasis on stromal secreted collagen I in the paracrine activation of discoidin domain receptor (DDR1) signaling in neighboring bladder cancer cells.

Using bioinformatics analysis we found that invasive bladder cancer patients with elevated expression of CAF genes have a poorer survival than those with lower CAF gene expression. Subsequently, we isolated and characterized CAFs from patient-derived tissues. Co-transplantation of CAFs and bladder cancer cells as xenograft tumors revealed high collagen I (COL1) deposition in these tumors formed, while molecular analyses uncovered CAFs as the primary source of COL1. Further experiments verified that COL1 as a single extracellular matrix component could phenocopy the tumor phenotype resembling those co-transplanted with CAFs and cancer cells. Further, pre-stimulation with COL1 could also enhance metastatic colonization of bladder cancer cells to lung. Molecular analysis of these COL1 stimulated cancer cells revealed up-regulation of the collagen receptor DDR1, but not integrins. Immunohistochemical analysis confirmed the presence of DDR1+ cancer cells adjacent to CAFs in the primary tumor site, with enhanced and exclusive expression of DDR1 in paired lung metastasis. Oncomine analysis showed that invasive bladder cancer expressed higher mRNA levels of COL1 and DDRs than non-invasive cancer, indicating that collagen I-DDR1 interaction may be a generalized phenomenon during invasive bladder cancer progression. To delineate the molecular mechanism downstream to collagen I-DDR1 we studied the interaction of DDR1 and STAT3, a factor we previously reported to drive invasive bladder cancer progression. Stimulation of bladder cancer cells with COL1 revealed a time kinetic increase in total and activated DDR1 protein associated with STAT3 phosphorylation. Further analysis of lung metastasis confirmed the co-localization of DDR1 and nuclear active STAT3. Collectively, these findings uncovered a role of CAFs in bladder cancer progression via stromal mediated collagen I signaling and warrant further analysis of therapeutic options to target signaling components downstream to collagen I.

Citation Format: Antonina V. Kurtova, Jing Xiao, Erica J. Lay, Qianxing Mo, Seth P. Lerner, David R. Rowley, Keith S. Chan. Stromal-mediated collagen I signal in promoting bladder cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4801. doi:10.1158/1538-7445.AM2014-4801

Anomalous quantized conductance in a half-metal/topological superconductor/half-metal junction

The composite topological superconductor (TS), which is made of one-dimensional spin-orbit coupled nanowire with proximity-induced superconductivity from an s-wave superconductor, is not a pure p-wave superconductor, but has a suppressed s-wave pairing. We calculate the conductance spectrum of a half-metal/TS/half-metal junction in order to probe the pairing states and the spin texture of the p-wave pairing. It is found that, besides the regular quantized conductance peak contributed by Majorana fermions (MFs) when the half-metal magnetization is parallel to the MF spin, an anomalous quantized conductance peak exists when they are almost antiparallel. The physical origin is the MF-assisted local Andreev reflection to condense s-wave pairings. The anomalous quantized conductance is also confirmed by the Kitaev's p-wave model with a nonzero s-wave pairing. The findings might provide a new way to find the MF.

The effect of interlayer coupling on electron transport in graphene nanoribbons: a potential method for nanoposition sensing

We report a study on the effect of electron transport in a monolayer armchair graphene nanoribbon due to coupling to another monolayer armchair graphene ribbon, which is put on top of the first one. The conductance of the bottom ribbon oscillates when the top ribbon moves, and the oscillation can be used to determine stepwise position changes of the top ribbon for step sizes as small as 3.68 Å. The conductance oscillation arises from the rapid electron probability oscillations in the lowest three subbands of an armchair graphene ribbon. The phenomenon has potential applications in nanoposition sensing.

Adsorbate electric fields on a cryogenic atom chip

We investigate the behavior of electric fields originating from adsorbates deposited on a cryogenic atom chip as it is cooled from room temperature to cryogenic temperature. Using Rydberg electromagnetically induced transparency, we measure the field strength versus distance from a 1 mm square of yttrium barium copper oxide (YBCO) patterned onto a yttria stabilized zirconia chip substrate. We find a localized and stable dipole field at room temperature and attribute it to a saturated layer of chemically adsorbed rubidium atoms on the YBCO. As the chip is cooled towards 83 K we observe a change in sign of the electric field as well as a transition from a localized to a delocalized dipole density. We relate these changes to the onset of physisorption on the chip surface when the van der Waals attraction overcomes the thermal desorption mechanisms. Our findings suggest that through careful selection of substrate materials, it may be possible to reduce the electric fields caused by atomic adsorption on chips, opening up experiments to controlled Rydberg-surface coupling schemes.

Disorder effect on the integer quantum Hall effect in trilayer graphene

We numerically investigate the disorder effect on the integer quantum Hall effect in a trilayer graphene (TLG) system by use of the Kubo formula. For a clean sample, both Bernal (ABA) and rhombohedral (ABC) stacked TLGs display the same quantum rule with abnormal quantized Hall plateaus σxy = νe(2)/h (ν =± 6, ± 10, ± 14,…) in the band center and normal quantized Hall plateaus at the band edges. In the presence of disorder, the Hall plateaus become obscure and the higher plateaus disappear first with the increase of the disorder; however, the Hall plateaus of the ABA-stacked TLG are destroyed more readily in comparison with the ABC-stacked one. The longitudinal conductance minimums of the system corresponding to the Hall plateaus become narrower and thinner with disorder, and those of the ABC-stacked TLG are comparatively more stable than those of the ABA structure. The findings indicate that the l = 3 chiral quasiparticles with cubic energy dispersion in ABC-stacked TLG have comparatively stronger immunity to the disorder than the l = 1 and 2 chiral quasiparticles in the ABA counterpart.

Surface roughness induced electron mobility degradation in InAs nanowires

In this work, we present a study of the surface roughness dependent electron mobility in InAs nanowires grown by the nickel-catalyzed chemical vapor deposition method. These nanowires have good crystallinity, well-controlled surface morphology without any surface coating or tapering and an excellent peak field-effect mobility up to 15,000 cm(2) V(-1) s(-1) when configured into back-gated field-effect nanowire transistors. Detailed electrical characterizations reveal that the electron mobility degrades monotonically with increasing surface roughness and diameter scaling, while low-temperature measurements further decouple the effects of surface/interface traps and phonon scattering, highlighting the dominant impact of surface roughness scattering on the electron mobility for miniaturized and surface disordered nanowires. All these factors suggest that careful consideration of nanowire geometries and surface condition is required for designing devices with optimal performance.

The preclinical anti-angiogenic and pro-apoptotic activity of lenalidomide in urothelial carcinoma (UC)

294

Background: Lenalidomide (Len) is an immunomodulatory drug (IMiD) approved for hematologic conditions and demonstrates immune modulation, anti-angiogenic activity and direct anti-tumor cytotoxicity. A rationale can be made to evaluate the preclinical activity of Len in UC. Methods: The in vitro anti-tumor activity of Len was evaluated in 4 human (5637, TCC-SUP, RT4, RT112) and 1 murine (MB49) cell line. Anti-proliferative activity activity (MTT assay), apoptosis (Annexin-FITC immunohistochemistry [IHC], flow cytometry) and cell viability by colony forming assay were measured. In vivo activity of daily oral Len 10 mg/kg or placebo orally for 5 days a week for up to 4 weeks was examined in syngeneic immunocompetent C57BL/6 mice bearing subcutaneous (SC) MB49-Luc25 tumors and RT4 subcutaneous xenografts. Tumors underwent immunohistochemistry (IHC) for microvessel density (CD31), apoptosis (cleaved caspase [cc]-3) and CD3+/CD20+ lymphocyte infiltration. Cereblon, a molecular target of Len was analyzed by IHC. Results: In vitro cultures for 3 days with daily repletion of Len showed significant pro-apoptotic activity (flow cytometry) at low micromolar concentrations attainable in human subjects (2.2 µM) against RT4 cells, a superficially invasive human UC cell line. Long-term cultures of RT4 cells for 2 weeks with daily repletion of Len significantly reduced cell viability and colony forming ability. Cereblon expression was numerically lower in sensitive RT4 cells compared to resistant 5637 cells (p=NS). In the immunocompetent model in vivo, Len did not decrease tumor size, or increase cc-3 and CD3+/CD20+ lymphocytes, but post-Len tumors exhibited decreased CD31 (p<0.05). In RT4 xenografts, Len significantly decreased the size of tumors and CD31, and increased cc-3 (all p<0.05). Cereblon expression increased in Len treated RT4 xenografts (p=0.024). Conclusions: Lenalidomide demonstrated selective preclinical activity against superficially invasive low grade human UC cells attributable to direct tumor cell apoptosis and anti-angiogenic activity. Clinical evaluation in patients with low grade or non-invasive UC and further study of cereblon as a predictive biomarker may be warranted.

Reference standard and statistical model for intersite and temporal comparisons of CT attenuation in a multicenter quantitative lung study

PURPOSE

The purpose of this study was to detect and analyze anomalies between a large number of computed tomography (CT) scanners, tracked over time, utilized to collect human pulmonary CT data for a national multicenter study: chronic obstructive pulmonary disease genetic epidemiology study (COPDGene).

METHODS

A custom designed CT reference standard "Test Object" has been developed to evaluate the relevant differences in CT attenuation between CT scanners in COPDGene. The materials used in the Test Object to assess CT scanner accuracy and precision included lung equivalent foam (-856 HU), internal air (-1000 HU), water (0 HU), and acrylic (120 HU). Nineteen examples of the Test Object were manufactured. Initially, all Test Objects were scanned on the same CT scanner before the Test Objects were sent to the 20 specific sites and 42 individual CT scanners that were used in the study. The Test Objects were scanned over 17 months while the COPDGene study continued to recruit subjects. A mixed linear effect statistical analysis of the CT scans on the 19 Test Objects was performed. The statistical model reflected influence of reconstruction kernels, tube current, individual Test Objects, CT scanner models, and temporal consistency on CT attenuation.

RESULTS

Depending on the Test Object material, there were significant differences between reconstruction kernels, tube current, individual Test Objects, CT scanner models, and temporal consistency. The two Test Object materials of most interest were lung equivalent foam and internal air. With lung equivalent foam, there were significant (p < 0.05) differences between the Siemens B31 (-856.6, ±0.82; mean ± SE) and the GE Standard (-856.6 ± 0.83) reconstruction kernel relative to the Siemens B35 reference standard (-852.5 ± 1.4). Comparing lung equivalent foam attenuation there were also significant differences between CT scanner models (p < 0.01), tube current (p < 0.005), and in temporal consistency (p < 0.005) at individual sites. However, there were no significant effects measurable using different examples of the Test Objects at the various sites compared to the reference scans of the 19 Test Objects. For internal air, significant (p < 0.005) differences were found between all reconstruction kernels (Siemens B31, GE Standard, and Phillips B) compared to the reference standard. There were significant differences between CT models (p < 0.005), and tube current (p < 0.005). There were no significant effects measurable using different examples of the Test Objects at the various sites compared to the reference scans of the 19 Test Objects. Differences, across scanners, between external air and internal air measures in this simple (relative to the in vivo lung) test object varied by as much as 15 HU.

CONCLUSIONS

The authors conclude that the Test Object designed for this study was able to detect significant effects regarding individual CT scanners that altered the CT attenuation measurements relevant to the study that are used to determine lung density. Through an understanding of individual scanners, the Test Object analysis can be used to detect anomalies in an individual CT scanner and to statistically model out scanner differences and individual scanner changes over time in a large multicenter trial.

The preclinical activity of lenalidomide in urothelial carcinoma (UC)

e15002

Background: Lenalidomide is approved for multiple myeloma and deletion 5q myelodysplastic syndromes (MDS) and demonstrates immune modulation, anti-angiogenic activity and direct anti-tumor cytotoxicity. A rationale can be made to evaluate the preclinical activity of lenalidomide in urothelial carcinoma (UC) based on the importance of these pathways. Methods: The in vitro anti-tumor activity of lenalidomide was evaluated in 4 human (5637, TCC-SUP, RT4, RT112) and 1 murine (MB49) cell line. Anti-proliferative activity activity (MTT assay), apoptosis (Annexin-FITC immunohistochemistry [IHC], flow cytometry) and cell viability by colony forming assay were measured. In vivo examination of activity of daily oral lenalidomide 10 mg/kg orally once daily or placebo for 4 weeks is examined in a syngeneic immunocompetent mouse model employing MB49-Luc25 cells injected subcutaneously in C57BL/6 mice. Murine tumors will be studied for anti-tumor activity. Results: In vitro activity of lenalidomide was detected at low ~1 µM concentrations (attainable in human subjects) against a non-invasive human UC cell line (RT4). Long-term cultures of RT4 cells for 10 days with daily repletion of lenalidomide reduced cell viability and colony forming ability to 75.6% of controls. Induction of apoptosis in RT4 was demonstrated by Annexin-FITC IHC and flow cytometry compared to control (30.11 vs. 14.74%). Invasive human UC cells and murine MB49 cells did not demonstrate apoptosis with lenalidomide exposure in vitro. Futher, lenalidomide did not inhibit overall tumor growth in the syngeneic immunocompetent murine model; immune activity and stem cell directed activity will be presented. Conclusions: Lenalidomide demonstrated preclinical anti-tumor activity against non-invasive human UC cells. Given its favorable toxicity profile compared to cytotoxic chemotherapy, clinical evaluation in patients with non-muscle-invasive bladder cancer and recurrence after BCG therapy may be warranted.

A bipolar spin-filtering effect in graphene zigzag nanoribbons with spin-orbit coupling

We predict a large spin-filtering effect in graphene zigzag nanoribbons in the presence of Rashba spin-orbit coupling. The spin polarization of the transmitted current reaches a maximum when the incoming electrons occupy only one subband and the outgoing electrons occupy two subbands (spin is not taken into account). This situation can be reached by applying a potential barrier or a width constriction to the incoming lead of the ribbon. A simple physical picture is provided to explain the spin-filtering effect. Because of the electron-hole symmetry and the time-reversal symmetry, the spin-filtering is antisymmetric for the hole when compared with that for the electron. So the bipolar spin-polarized current can be generated by tuning the Fermi energy across the Dirac point. Besides, the wedge-shaped constriction can modify the conductance spin polarization.

Pure spin current generation in monolayer graphene by quantum pumping

We study a method to generate pure spin current in monolayer graphene over a wide range of Fermi energy by adiabatic quantum pumping. The device consists of three gate electrodes and two ferromagnetic strips, which induce a spin-splitting in the graphene through the proximity effect. A pure spin current is generated by applying two periodic oscillating gate voltages. We find that the pumped pure spin current is a sensitive oscillatory function of the Fermi energy. Large spin currents can be found at Fermi energies where there are Fabry-Perot resonances in the barriers. Furthermore, we analyze the effects of the parameters of the system on the pumped currents. Our predicted pumped spin current can be of the order of 100 nA which is measurable using the current technology. The proposed method is useful in the realization of graphene spintronic devices.

The dynamical conductance of graphene tunnelling structures

The dynamical conductances of graphene tunnelling structures were numerically calculated using the scattering matrix method with the interaction effect included in a phenomenological approach. The overall single-barrier dynamical conductance is capacitative. Transmission resonances in the single-barrier structure lead to dips in the capacitative imaginary part of the response. This is different from the ac responses of typical semiconductor nanostructures, where transmission resonances usually lead to inductive peaks. The features of the dips depend on the Fermi energy. When the Fermi energy is below half of the barrier height, the dips are sharper. When the Fermi energy is higher than half of the barrier height, the dips are broader. Inductive behaviours can be observed in a double-barrier structure due to the resonances formed by reflection between the two barriers.

Transverse spin current in the s-wave/p-wave Josephson junction

We report a theoretical study on spin transport in the hybrid Josephson junction composed of singlet s-wave and triplet p-wave superconductor. The node of the triplet pair potential is considered perpendicular to the interface of the junction. Based on a symmetry analysis, we predict that there is no net spin density at the interface of the junction but instead a transverse mode-resolved spin density can exist and a nonzero spin current can flow transversely along the interface of the junction. The predictions are numerically demonstrated by means of the lattice Matsubara Green's function method. It is also shown that, when a normal metal is sandwiched in between two superconductors, both spin current and transverse mode-resolved spin density are only residing at two interfaces due to the smearing effect of the multimode transport. Our findings are useful for identifying the pairing symmetry of the p-wave superconductor and generating spin current.

Spin-polarized quantum pumping in bilayer graphene

We study adiabatic quantum pumping in bilayer graphene where two-barrier potentials are weakly modulated as pumping parameters. Comparing the results with those for a normal quantum pump of non-chiral quasiparticles, we find that the chirality of quasiparticles in bilayer graphene heavily affects the pumped current through chiral tunnelling. When an exchange splitting induced by the proximity of a ferromagnetic insulator is introduced, the pumped current becomes spin-polarized. It is interesting that an almost 100% polarized charge current and a pure spin current with vanishing charge current can all be achieved under suitable conditions. The experimental feasibility and the interlayer asymmetric effect in bilayer graphene caused by the gate and the ferromagnet structures are also discussed. The results are useful for spintronics applications based on graphene.

Spin accumulation in triplet Josephson junction

We employ a Hamiltonian method to study the equal-spin pairing triplet Josephson junction with different orbital symmetries of pair potentials. Both the spin/charge supercurrent and possible spin accumulation at the interface of the junction are analyzed by means of the Keldysh Green's function. It is found that a spontaneous angle-resolved spin accumulation can form at the junction's interface when the orbital symmetries of Cooper pairs in two triplet superconductors are different, the physical origin is the combined effect of the different orbital symmetries and different spin states of Cooper pairs due to the misalignment of two d vectors in triplet leads. An abrupt current reversal effect induced by misalignment of d vectors is observed and can survive in a strong interface barrier scattering because the zero-energy state appears at the interface of the junction. These properties of the p-wave Josephson junction may be helpful for identifying the order parameter symmetry.

Spin current pumped by a rotating magnetic field in zigzag graphene nanoribbons

We study electron spin resonance in zigzag graphene nanoribbons by applying a rotating magnetic field on the system without any bias. By using the nonequilibrium Green's function technique, the spin-resolved pumped current is explicitly derived in a rotating reference frame. The pumped spin current density increases with the system size and the intensity of the transverse rotating magnetic field. For graphene nanoribbons with an even number of zigzag chains, there is a nonzero pumped charge current in addition to the pumped spin current owing to the broken spatial inversion symmetry of the system, but its magnitude is much smaller than the spin current. The short-ranged static disorder from either impurities or defects in the ribbon can depress the spin current greatly due to the localization effect, whereas the long-ranged disorder from charge impurities can avoid inter-valley scattering so that the spin current can survive in the strong disorder for the single-energy mode.

Spin reversal effect in hybrid s(±)-wave/p-wave Josephson junction

We report a theoretical study on a hybrid Josephson junction consisting of a proposed s( ± )-wave ferropnictide superconductor and a p-wave superconductor. It is found that the relative π phase shift intrinsic to the s( ± )-wave pairing can lead to an accumulated spin reversal effect at the junction interface and that the critical current has a vanishing point with the variation of the ratio of the interface resistances for each band. The spin reversal effect also appears with an increase of temperature and meanwhile the critical current exhibits a reentrant behavior. These findings can not appear for a usual s-wave state, so that they can be used to discriminate the s( ± )-wave pairing in superconducting ferropnictides from the conventional s-wave symmetry.

Triplet Josephson current modulated by Rashba spin-orbit coupling

We study the Rashba spin-orbit coupling (RSOC) effect on the supercurrent in a clean triplet superconductor/two-dimensional electron gas/triplet superconductor (TS/2DEG/TS) junction, where RSOC is considered in the 2DEG region. Based on the Bogoliubov-de Gennes equation and quantum scattering method, we show that RSOC can lead to a 0-π oscillation of supercurrent and the abrupt current reversal effect. The current direction can be reversed by a tiny modulation of RSOC, and this is attributed to the equal spin pairing of the TS order parameter and the spin precession phase of the quasiparticle traveling in the RSOC region. The RSOC strength can be controlled by an electric field in experiments, thus our findings provide a purely electric means to modulate the supercurrent in TS Josephson junctions.

Spin-polarized transport induced by spin-pumping in a Rashba ring

The Keldysh Green's function method is employed to study spin-dependent electron transport through a Rashba ring with a quantum dot (QD) embedded in one of its arms. Zero charge bias is applied on the system while a rotating magnetic field is considered in the QD to pump pure spin current. The Rashba spin-orbital coupling (RSOC) can cause a spin precession phase of the electron passing through the ring, so that the quantum interference in the ring can lead to a spin-polarized charge current flowing in the leads and the arm without a QD, whereas only pure spin current is flowing in the other arm with a QD. It is shown that for low frequency ω of the rotating magnetic field, the pumped charge current is proportional to ω unlike the charge current produced by mono-parametric quantum charge pumping, which is usually proportional to ω(2). Moreover, the magnitude, the direction, as well as the spin-polarization of the charge current can be controlled by tuning the device parameters such as the QD energy level, the RSOC strength, and the strength of the electron tunneling between the leads and the QD. Hence the studied device may serve as a generating source for tunable spin-polarized current in the spintronics field.