Publications by authors named "Susan M Armstrong"

13 Publications

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Pathology Resident Evaluation During the Pandemic: Testing and Implementation of a Comprehensive Online Pathology Exam.

Acad Pathol 2021 Jan-Dec;8:23742895211013533. Epub 2021 May 11.

Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.

Despite global digitization, evaluating pathology trainees by paper exams remains the norm. As new social distancing practices require new ways of administering exams, we assessed the viability of an online format for in-house exams from the resident and examiner perspectives. First, pathology residents participated in a practice exam, while staff who were experienced in creating exams were given an online exam-creation demonstration. Subsequently, residents completed a formal 3-hour online exam comprised of multiple-choice, matching, short answer, and whole slide images in place of the paper exam regularly used to evaluate trainees. The experience of the participants was evaluated by surveys. Eighteen residents completed the practice exam; 67% were receptive to the new format and 94% were in favor of moving to digital exams. Seven staff evaluated the digital format and 6 were in favor of it. For the formal online in-house exam, 20 residents participated and 14 completed the survey. Feedback was generally positive with the most common issue being slow-loading digital slides. Exam scores stratified by postgraduate training years in a statistically significant manner, showing positive correlation with resident training level. The online exam format was preferred over paper exams by trainees, with support from both staff and trainees for a permanent transition. Online exams have clear advantages, but technical issues should be addressed before widespread implementation. Our study demonstrates that online exams are a feasible alternative for trainee assessment, especially in socially distanced environments.
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http://dx.doi.org/10.1177/23742895211013533DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120522PMC
May 2021

Biologic subtypes of melanoma predict survival benefit of combination anti-PD1+anti-CTLA4 immune checkpoint inhibitors versus anti-PD1 monotherapy.

J Immunother Cancer 2021 Jan;9(1)

Department of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada

Purpose: Anti-programmed cell death protein 1 (PD1)±anti-cytotoxic T-lymphocyte associated protein 4 (CTLA4) immune checkpoint inhibitors (ICIs) are standard therapeutic options for metastatic melanoma. We assessed whether biologic subtype according to primary tumor type or genomic subtype can function as predictive biomarkers for anti-PD1±anti-CTLA4 ICI in patients with advanced melanoma.

Methods: We performed a single-center retrospective cohort analysis of patients who received anti-PD1±anti-CTLA4 ICI for advanced melanoma between 2012 and 2019. Primary tumor type, and mutation status, and other covariates were abstracted from chart review. Log-rank tests and multivariable Cox regression models were used to assess differences in clinical progression-free (cPFS) and overall survival (OS).

Results: We identified 230 patients who received 249 lines of anti-PD1±anti-CTLA4 ICI for unresectable or metastatic disease. Of these patients, 74% were cutaneous, 11% mucosal, 8% unknown primary and 7% acral. and mutations were identified in 35% and 28% of patients, respectively. In multivariable analyses of the entire cohort, acral or mucosal primary tumor type, >3 metastatic sites, elevated LDH were predictive of shorter cPFS and OS. Combination ICI therapy was associated with longer cPFS (HR 0.57, 95% CI 0.38 to 0.86, p=0.007) and OS (HR 0.42, 95% CI 0.28 to 0.65, p<0.001). Combination ICI was significantly associated with longer OS in unknown primary and mucosal melanoma. There was a non-significant trend toward longer OS with anti-PD1+anti-CTLA4 in cutaneous melanoma, but not in acral melanoma. In multivariable analyses, combination ICI was associated with longer OS in (HR 0.24, 95% CI 0.10 to 0.62, p=0.003, n=69) and V600E/K (HR 0.47, 95% CI 0.24 to 0.90, p=0.024, n=86) mutant melanoma but not wild-type (n=94) melanoma.

Conclusions: In our cohort, primary melanoma tumor type and genomic subtype were independent predictive markers of cPFS and OS for patients with metastatic melanoma receiving anti-PD1 ICI. Primary tumor type and genomic subtype-including NRAS-should be further evaluated in prospective clinical trials to determine their value as predictive markers. Biologic subtypes may facilitate clinical decision-making when recommending combination ICI treatment (anti-PD1±anti-CTLA4) versus anti-PD1 alone for patients with metastatic melanoma.
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http://dx.doi.org/10.1136/jitc-2020-001642DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7831745PMC
January 2021

Do These Genes Make My Heart Look Fat? Why Molecular Changes Matter in Congenital Heart Disease.

Can J Cardiol 2020 07 17;36(7):997-999. Epub 2020 May 17.

Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Laboratory Medicine Program, University Health Network, Toronto, Ontario, Canada. Electronic address:

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http://dx.doi.org/10.1016/j.cjca.2020.05.020DOI Listing
July 2020

What's new in fibroblastic tumors?

Virchows Arch 2020 Jan 11;476(1):41-55. Epub 2019 Dec 11.

Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.

Over the last 10 years, a number of advances have been made in our understanding of fibroblastic and myofibroblastic tumors. The rapidly evolving field of molecular diagnostics has resulted in the recognition of new entities and better understanding of tumor pathogenesis, while careful clinicopathologic correlative analyses have led to improvements in modeling tumor behavior. This review will discuss new and emerging entities in fibroblastic neoplasia and provide updates on the pathogenesis, diagnosis, and prognostication of these diverse and challenging tumors.
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http://dx.doi.org/10.1007/s00428-019-02682-xDOI Listing
January 2020

Development, Sensibility, and Validity of a Systemic Autoimmune Rheumatic Disease Case Ascertainment Tool.

J Rheumatol 2017 01 1;44(1):18-23. Epub 2016 Nov 1.

From the Toronto Scleroderma Program, Division of Rheumatology, Department of Medicine, Toronto Western and Mount Sinai Hospitals; Division of Genetics and Development, and Health Care and Outcomes Research, Toronto Western Research Institute, University Health Network; Arthritis Centre of Excellence, Division of Rheumatology, Departments of Medicine and Immunology, University Health Network; Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada.

Objective: Case ascertainment through self-report is a convenient but often inaccurate method to collect information. The purposes of this study were to develop, assess the sensibility, and validate a tool to identify cases of systemic autoimmune rheumatic diseases (SARD) in the outpatient setting.

Methods: The SARD tool was administered to subjects sampled from specialty clinics. Determinants of sensibility - comprehensibility, feasibility, validity, and acceptability - were evaluated using a numeric rating scale from 1-7. Comprehensibility was evaluated using the Flesch Reading Ease and the Flesch-Kincaid Grade Level. Self-reported diagnoses were validated against medical records using Cohen's κ statistic.

Results: There were 141 participants [systemic lupus erythematosus (SLE), systemic sclerosis (SSc), rheumatoid arthritis, Sjögren syndrome (SS), inflammatory myositis (polymyositis/dermatomyositis; PM/DM), and controls] who completed the questionnaire. The Flesch Reading Ease score was 77.1 and the Flesch-Kincaid Grade Level was 4.4. Respondents endorsed (mean ± SD) comprehensibility (6.12 ± 0.92), feasibility (5.94 ± 0.81), validity (5.35 ± 1.10), and acceptability (3.10 ± 2.03). The SARD tool had a sensitivity of 0.91 (95% CI 0.88-0.94) and a specificity of 0.99 (95% CI 0.96-1.00). The agreement between the SARD tool and medical record was κ = 0.82 (95% CI 0.77-0.88). Subgroup analysis by SARD found κ coefficients for SLE to be κ = 0.88 (95% CI 0.79-0.97), SSc κ = 1.0 (95% CI 1.0-1.0), PM/DM κ = 0.72 (95% CI 0.49-0.95), and SS κ = 0.85 (95% CI 0.71-0.99). The screening questions had sensitivity ranging from 0.96 to 1.0 and specificity ranging from 0.88 to 1.0.

Conclusion: This SARD case ascertainment tool has demonstrable sensibility and validity. The use of both screening and confirmatory questions confers added accuracy.
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http://dx.doi.org/10.3899/jrheum.160327DOI Listing
January 2017

Influenza Virus Infection Induces Platelet-Endothelial Adhesion Which Contributes to Lung Injury.

J Virol 2016 02 4;90(4):1812-23. Epub 2015 Dec 4.

Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Canada Institute of Medical Science, University of Toronto, Toronto, Canada Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada Division of Respirology and Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada

Lung injury after influenza infection is characterized by increased permeability of the lung microvasculature, culminating in acute respiratory failure. Platelets interact with activated endothelial cells and have been implicated in the pathogenesis of some forms of acute lung injury. Autopsy studies have revealed pulmonary microthrombi after influenza infection, and epidemiological studies suggest that influenza vaccination is protective against pulmonary thromboembolism; however, the effect of influenza infection on platelet-endothelial interactions is unclear. We demonstrate that endothelial infection with both laboratory and clinical strains of influenza virus increased the adhesion of human platelets to primary human lung microvascular endothelial cells. Platelets adhered to infected cells as well as to neighboring cells, suggesting a paracrine effect. Influenza infection caused the upregulation of von Willebrand factor and ICAM-1, but blocking these receptors did not prevent platelet-endothelial adhesion. Instead, platelet adhesion was inhibited by both RGDS peptide and a blocking antibody to platelet integrin α5β1, implicating endothelial fibronectin. Concordantly, lung histology from infected mice revealed viral dose-dependent colocalization of viral nucleoprotein and the endothelial marker PECAM-1, while platelet adhesion and fibronectin deposition also were observed in the lungs of influenza-infected mice. Inhibition of platelets using acetylsalicylic acid significantly improved survival, a finding confirmed using a second antiplatelet agent. Thus, influenza infection induces platelet-lung endothelial adhesion via fibronectin, contributing to mortality from acute lung injury. The inhibition of platelets may constitute a practical adjunctive strategy to the treatment of severe infections with influenza.IMPORTANCE There is growing appreciation of the involvement of the lung endothelium in the pathogenesis of severe infections with influenza virus. We have recently shown that the virus can infect human lung endothelial cells, but the functional consequences of this infection are unknown (S. M. Armstrong, C. Wang, J. Tigdi, X. Si, C. Dumpit, S. Charles, A. Gamage, T. J. Moraes, and W. L. Lee, PLoS One 7:e47323, 2012, http://dx.doi.org/10.1371/journal.pone.0047323). Here, we show that this infection causes platelets to adhere to the lung endothelium. Importantly, blocking platelets using two distinct antiplatelet drugs improved survival in a mouse model of severe influenza infection. Thus, platelet inhibition may constitute a novel therapeutic strategy to improve the host response to severe infections with influenza.
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http://dx.doi.org/10.1128/JVI.02599-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4733979PMC
February 2016

A novel assay uncovers an unexpected role for SR-BI in LDL transcytosis.

Cardiovasc Res 2015 Nov 2;108(2):268-77. Epub 2015 Sep 2.

Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8 Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Interdepartmental Division of Critical Care Medicine and the Department of Medicine, University of Toronto, Toronto, ON, Canada

Aims: Retention of low-density lipoprotein (LDL) cholesterol beneath the arterial endothelium initiates an inflammatory response culminating in atherosclerosis. Since the overlying endothelium is healthy and intact early on, it is likely that LDL passes through endothelial cells by transcytosis. However, technical challenges have made confirming this notion and elucidating the mechanisms of transcytosis difficult. We developed a novel assay for measuring LDL transcytosis in real time across coronary endothelial cell monolayers; we used this approach to identify the receptor involved.

Methods And Results: Murine aortas were perfused ex vivo with LDL and dextran of a smaller molecular radius. LDL (but not dextran) accumulated under the endothelium, indicating that LDL transcytosis occurs in intact vessels. We then confirmed that LDL transcytosis occurs in vitro using human coronary artery endothelial cells. An assay was developed to quantify transcytosis of DiI-LDL in real time using total internal reflection fluorescence microscopy. DiI-LDL transcytosis was inhibited by excess unlabelled LDL, while degradation of the LDL receptor by PCSK9 had no effect. Instead, LDL colocalized partially with the scavenger receptor SR-BI and overexpression of SR-BI increased LDL transcytosis; knockdown by siRNA significantly reduced it. Excess HDL, the canonical SR-BI ligand, significantly decreased LDL transcytosis. Aortas from SR-BI-deficient mice were perfused ex vivo with LDL and accumulated significantly less sub-endothelial LDL compared with wild-type littermates.

Conclusion: We developed an assay to quantify LDL transcytosis across endothelial cells and discovered an unexpected role for SR-BI. Elucidating the mechanisms of LDL transcytosis may identify novel targets for the prevention or therapy of atherosclerosis.
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http://dx.doi.org/10.1093/cvr/cvv218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614686PMC
November 2015

The Tie2-agonist Vasculotide rescues mice from influenza virus infection.

Sci Rep 2015 Jun 5;5:11030. Epub 2015 Jun 5.

1] Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON [2] Department of Laboratory Medicine and Pathobiology, University of Toronto [3] Interdepartmental Division of Critical Care and Department of Medicine, University of Toronto.

Seasonal influenza virus infections cause hundreds of thousands of deaths annually while viral mutation raises the threat of a novel pandemic strain. Antiviral drugs exhibit limited efficacy unless administered early and may induce viral resistance. Thus, targeting the host response directly has been proposed as a novel therapeutic strategy with the added potential benefit of not eliciting viral resistance. Severe influenza virus infections are complicated by respiratory failure due to the development of lung microvascular leak and acute lung injury. We hypothesized that enhancing lung endothelial barrier integrity could improve the outcome. Here we demonstrate that the Tie2-agonist tetrameric peptide Vasculotide improves survival in murine models of severe influenza, even if administered as late as 72 hours after infection; the benefit was observed using three strains of the virus and two strains of mice. The effect required Tie2, was independent of viral replication and did not impair lung neutrophil recruitment. Administration of the drug decreased lung edema, arterial hypoxemia and lung endothelial apoptosis; importantly, Vasculotide is inexpensive to produce, is chemically stable and is unrelated to any Tie2 ligands. Thus, Vasculotide may represent a novel and practical therapy for severe infections with influenza.
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http://dx.doi.org/10.1038/srep11030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4457136PMC
June 2015

Influenza-Induced Priming and Leak of Human Lung Microvascular Endothelium upon Exposure to Staphylococcus aureus.

Am J Respir Cell Mol Biol 2015 Oct;53(4):459-70

1 Keenan Research Centre for Biomedical Science at St. Michael's Hospital, Toronto, Ontario, Canada.

A major cause of death after influenza virus infection is lung injury due to a bacterial superinfection, yet the mechanism is unknown. Death has been attributed to virus-induced immunosuppression and bacterial overgrowth, but this hypothesis is based on data from the preantibiotic era and animal models that omit antimicrobial therapy. Because of diagnostic uncertainty, most patients with influenza receive antibiotics, making bacterial overgrowth unlikely. Respiratory failure after superinfection presents as acute respiratory distress syndrome, a disorder characterized by lung microvascular leak and edema. The objective of this study was to determine whether the influenza virus sensitizes the lung endothelium to leak upon exposure to circulating bacterial-derived molecular patterns from Staphylococcus aureus. In vitro as well as in vivo models of influenza followed by S. aureus superinfection were used. Molecular mechanisms were explored using molecular biology, knockout mice, and human autopsy specimens. Influenza virus infection sensitized human lung endothelium to leak when challenged with S. aureus, even at low doses of influenza and even when the pathogens were given days apart. Influenza virus increased endothelial expression of TNFR1 both in vitro and in intact lungs, a finding corroborated by human autopsy specimens of patients with influenza. Leak was recapitulated with protein A, a TNFR1 ligand, and sequential infection caused protein A-dependent loss of IκB, cleavage of caspases 8 and 3, and lung endothelial apoptosis. Mice infected sequentially with influenza virus and S. aureus developed significantly increased lung edema that was protein A and TNFR1 dependent. Influenza virus primes the lung endothelium to leak, predisposing patients to acute respiratory distress syndrome upon exposure to S. aureus.
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http://dx.doi.org/10.1165/rcmb.2014-0373OCDOI Listing
October 2015

Endothelial activation and dysfunction in the pathogenesis of influenza A virus infection.

Virulence 2013 Aug 17;4(6):537-42. Epub 2013 Jul 17.

Faculty of Medicine, University of Toronto, Toronto, ON, Canada.

The development of severe influenza has been attributed, in part, to a heightened innate immune response. Recent evidence suggests that endothelial activation, loss of barrier function, and consequent microvascular leak may also serve important mechanistic roles in the pathogenesis of severe influenza. The aim of this review is to summarize the current evidence in support of endothelial activation and dysfunction as a central feature preceding the development of severe influenza. We also discuss the effect of influenza on platelet-endothelial interactions.
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http://dx.doi.org/10.4161/viru.25779DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5359731PMC
August 2013

The lung microvascular endothelium as a therapeutic target in severe influenza.

Antiviral Res 2013 Aug 16;99(2):113-8. Epub 2013 May 16.

Institute of Medical Science, University of Toronto, Canada.

Severe infections with influenza virus are characterized by acute respiratory distress syndrome (ARDS), a life-threatening disorder in which the alveolocapillary membrane in the lung becomes leaky. This leads to alveolar flooding, hypoxemia and respiratory failure. Recent data suggest that influenza virus can exert both direct and indirect effects on the lung endothelium, activating it and inducing microvascular leak. These findings raise the possibility that enhancing lung endothelial barrier integrity or modulating lung endothelial activation may prove therapeutically useful for severe influenza. In this paper, we review evidence that lung endothelial activation and vascular leak are a "final common pathway" in severe influenza, as has been reported in bacterial sepsis, and that enhancing endothelial barrier function may improve the outcome of illness. We describe a number of experimental therapies that have shown promise in preventing or reversing increased vascular leak in animal models of sepsis or influenza.
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http://dx.doi.org/10.1016/j.antiviral.2013.05.003DOI Listing
August 2013

Influenza infects lung microvascular endothelium leading to microvascular leak: role of apoptosis and claudin-5.

PLoS One 2012 24;7(10):e47323. Epub 2012 Oct 24.

Institute of Medical Science, University of Toronto, Toronto, Canada.

Severe influenza infections are complicated by acute lung injury, a syndrome of pulmonary microvascular leak. The pathogenesis of this complication is unclear. We hypothesized that human influenza could directly infect the lung microvascular endothelium, leading to loss of endothelial barrier function. We infected human lung microvascular endothelium with both clinical and laboratory strains of human influenza. Permeability of endothelial monolayers was assessed by spectrofluorimetry and by measurement of the transendothelial electrical resistance. We determined the molecular mechanisms of flu-induced endothelial permeability and developed a mouse model of severe influenza. We found that both clinical and laboratory strains of human influenza can infect and replicate in human pulmonary microvascular endothelium, leading to a marked increase in permeability. This was caused by apoptosis of the lung endothelium, since inhibition of caspases greatly attenuated influenza-induced endothelial leak. Remarkably, replication-deficient virus also caused a significant degree of endothelial permeability, despite displaying no cytotoxic effects to the endothelium. Instead, replication-deficient virus induced degradation of the tight junction protein claudin-5; the adherens junction protein VE-cadherin and the actin cytoskeleton were unaffected. Over-expression of claudin-5 was sufficient to prevent replication-deficient virus-induced permeability. The barrier-protective agent formoterol was able to markedly attenuate flu-induced leak in association with dose-dependent induction of claudin-5. Finally, mice infected with human influenza developed pulmonary edema that was abrogated by parenteral treatment with formoterol. Thus, we describe two distinct mechanisms by which human influenza can induce pulmonary microvascular leak. Our findings have implications for the pathogenesis and treatment of acute lung injury from severe influenza.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0047323PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3480371PMC
April 2013

Co-regulation of transcellular and paracellular leak across microvascular endothelium by dynamin and Rac.

Am J Pathol 2012 Mar 25;180(3):1308-1323. Epub 2011 Dec 25.

Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Division of Respirology and Interdepartmental Division of Critical Care Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada. Electronic address:

Increased permeability of the microvascular endothelium to fluids and proteins is the hallmark of inflammatory conditions such as sepsis. Leakage can occur between (paracellular) or through (transcytosis) endothelial cells, yet little is known about whether these pathways are linked. Understanding the regulation of microvascular permeability is essential for the identification of novel therapies to combat inflammation. We investigated whether transcytosis and paracellular leakage are co-regulated. Using molecular and pharmacologic approaches, we inhibited transcytosis of albumin in primary human microvascular endothelium and measured paracellular permeability. Blockade of transcytosis induced a rapid increase in paracellular leakage that was not explained by decreases in caveolin-1 or increases in activity of nitric oxide synthase. The effect required caveolin-1 but was observed in cells depleted of clathrin, indicating that it was not due to the general inhibition of endocytosis. Inhibiting transcytosis by dynamin blockade increased paracellular leakage concomitantly with the loss of cortical actin from the plasma membrane and the displacement of active Rac from the plasmalemma. Importantly, inhibition of paracellular leakage by sphingosine-1-phosphate, which activates Rac and induces cortical actin, caused a significant increase in transcytosis of albumin in vitro and in an ex vivo whole-lung model. In addition, dominant-negative Rac significantly diminished albumin uptake by endothelia. Our findings indicate that transcytosis and paracellular permeability are co-regulated through a signaling pathway linking dynamin, Rac, and actin.
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http://dx.doi.org/10.1016/j.ajpath.2011.12.002DOI Listing
March 2012
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