What affects medical students’ applications to five-year FRCPC emergency medicine programs?

Purpose: To compare the impact of institutional and epidemiologic factors on differences in application trends of Canadian medical graduates (CMGs) from different medical schools to FRCPC emergency medicine (EM) residency programs. Methods: This was a retrospective cohort study. Data from 2013-2018 were obtained from the Canadian Resident Matching Service (CaRMS) database and standardized questionnaires sent to Canadian medical schools. Results: CaRMS data were available for all schools and survey data was available for 76% schools. Five schools yielded significantly higher rates of applications to FRCPC-EM programs (8.8-13.1%, p<0.05), and 5 schools had significantly lower rates compared to the national mean (2.9-5.1%, p<0.05). Increased exposure to EM (a core rotation and/or elective rotation in EM in the third year of medical school at home-school) yielded 28-55% higher application rates (p<0.001). The presence of an FRCPC-EM residency program at the applicant's home school, and a home school program with 5 or more CMG residency positions at a CMG’s increased the application rates by 39 and 17%, respectively (p<0.05). Conclusion: These data demonstrate a significant difference in application rates of CMGs graduating from Canadian medical schools and certain factors may affect application rates. This information could be used by medical schools to modify curricula, increase exposure to EM, and contribute towards addressing the forecasted national shortage of EM physicians.

Magnetic resonance imaging in the diagnosis of white matter signal abnormalities

Background White matter abnormalities (WMAs) pose a diagnostic challenge when trying to establish etiologic diagnoses. During childhood and adult years, genetic disorders, metabolic disorders and acquired conditions are included in differential diagnoses. To assist clinicians and radiologists, a structured algorithm using cranial magnetic resonance imaging (MRI) has been recommended to aid in establishing working diagnoses that facilitate appropriate biochemical and genetic investigations. This retrospective pilot study investigated the validity and diagnostic utility of this algorithm when applied to white matter signal abnormalities (WMSAs) reported on imaging studies of patients seen in our clinics. Methods The MRI algorithm was applied to 31 patients selected from patients attending the neurometabolic/neurogenetic/metabolic/neurology clinics at a tertiary care hospital. These patients varied in age from 5 months to 79 years old, and were reported to have WMSAs on cranial MRI scans. Twenty-one patients had confirmed WMA diagnoses and 10 patients had non-specific WMA diagnoses (etiology unknown). Two radiologists, blinded to confirmed diagnoses, used clinical abstracts and the WMSAs present on patient MRI scans to classify possible WMA diagnoses utilizing the algorithm. Results The MRI algorithm displayed a sensitivity of 100%, a specificity of 30.0% and a positive predicted value of 74.1%. Cohen's kappa statistic for inter-radiologist agreement was 0.733, suggesting "good" agreement between radiologists. Conclusions Although a high diagnostic utility was not observed, results suggest that this MRI algorithm has promise as a clinical tool for clinicians and radiologists. We discuss the benefits and limitations of this approach.

Abstract P2-02-10: Circulating cells from the tumor microenvironment as liquid biopsy biomarkers alongside circulating tumor cells in metastatic breast cancer

Background: Metastasis is a multistep process that involves the shedding of tumor cells in the peripheral circulation. These Circulating Tumor Cells (CTCs) have prognostic implications in patients with metastatic breast cancer (MBC). Cancer Associated Fibroblasts (CAFs) are a major component of the breast tumor microenvironment. The reciprocal signaling between tumor cells and its microenvironment promotes carcinogenesis, invasion, and metastasis. Studies in mouse models have shown that metastatic cells can bring their own stromal components from the primary site to the site of metastasis, and that these cotraveling stromal cells provide an early growth advantage to the accompanying metastatic cancer cells. CAFs have not been identified in the peripheral circulation. Using a microfilter capture technique, we discovered non-tumor, non-immune cells in the blood of metastatic patients and identified these cells as circulating CAFs (cCAFs). The purpose of this study is to demonstrate the presence of cCAFs as a biomarker of metastasis simultaneously with CTCs in patients with MBC.

Materials and Methods: We identified 20 patients with MBC (Metastatic/MET Group) and 10 patients with cured breast cancer (Ductal carcinoma in situ or Stage I post definitive treatment with &gt;5 years of disease free survival i.e. Localized/LOC Group). A total of 7.5 ml of peripheral blood was obtained from each patient. The enumeration of CTCs and cCAFs was carried out by the microfilter capture technique. Identification of these cells was done by a triple immunofluorescence staining for pan-CK (cytokeratin), FAP (Fibroblast Activated Protein) and CD45. cCAFs were identified as CK-, FAP+, CD45- cells and CTCs as CK+, CD45- cells. Identification and confirmation of cCAF was also carried out in parallel samples by a simultaneous FAP/α-Smooth Muscle Actin staining.

Results: cCAFs were detected in 17/20 (85%) MET patients but in only 2/10 (20%) LOC patients. CTCs were detected in 20/20 (100%) MET patients and in 8/10 (80%) LOC patients. The counts of CTCs and cCAFs in MET group ranged between 1-98 (median 13.5) and 0-117 (median 4), respectively. The counts of CTCs and cCAFs in the LOC group ranged between 1-14 (median 6) and 0-2 (median 0), respectively. For patients with exhibited cCAFs, 2/10 LOC and 5/17 MET patients had cCAFs counts of 2 or less. Although the sample size was small, patients exhibiting cCAFs (odds ratio=22.67, 95% CI: 3.14-163.63, p=0.002) were more likely to be in MET group than LOC group.

Conclusion: This is the first demonstration that CAFs, the predominant mesenchymal cell in the breast tumor microenvironment, are shed into the circulation and can be identified and enumerated as cCAFs in MBC patients along with CTCs. There was a clear difference in the numbers of CTCs and cCAFs levels between the MET and the LOC groups suggesting that CTCs and cCAFs are associated with advanced stage disease. While most patients, both in the LOC and MET group, exhibited CTCs, very few LOC patients exhibited cCAFs. We suggest that cCAFs could independently or along with CTCs serve as liquid biopsy biomarkers of metastasis. Validation of these findings in a larger cohort of patients will be presented during the meeting.

Citation Format: Parajuli R, Ao Z, Shah SH, Sengul TK, Lippman ME, Datar R, El-Ashry D. Circulating cells from the tumor microenvironment as liquid biopsy biomarkers alongside circulating tumor cells in metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-10.

Acute activation of eNOS by statins involves scavenger receptor-B1, G protein subunit Gi, phospholipase C and calcium influx

BACKGROUND AND PURPOSE

Statins (HMG CoA reductase inhibitors) have beneficial effects independent of reducing cholesterol synthesis and this includes their ability to acutely activate endothelial nitric oxide synthase (eNOS). The mechanism by which this occurs is largely unknown and thus we characterized the pathways by which statins activate NOS, including involvement of scavenger receptor-B1 (SR-B1), which is expressed in endothelial cells and maintains cholesterol concentrations.

EXPERIMENTAL APPROACH

Nitric oxide production was monitored in bovine aortic endothelial cells (BAECs) exposed to lovastatin (LOV) or pravastatin (PRA) for 10-20 min, alone or following pre-exposure to the end product of HMG-CoA reductase (mevalonate), G protein inhibitors (pertussis/cholera toxins), phospholipase C (PLC) inhibitor (U-73122), or intracellular and extracellular calcium chelators - BAPTA-AM and EGTA (respectively), or a function blocking antibody to SR-B1.

KEY RESULTS

Both statins increased NO production in a rapid, dose-dependent and HMG-CoA reductase-independent manner. Inhibiting Gi protein or PLC almost completely blocked statin-induced NO generation. Additionally, removing extracellular calcium inhibited statin-induced NO production. COS-7 cells co-transfected with eNOS and SR-B1 increased NO production when exposed to LOV or high-density lipoprotein (HDL), an agonist of SR-B1. These effects were not observed in COS-7 cells with eNOS alone or co-transfected with bradykinin receptor 2, indicating specificity for SR-B1. Further, pretreatment of BAEC with blocking antibody for SR-B1 blocked NO responses to statins and HDL.

CONCLUSIONS AND IMPLICATIONS

LOV and PRA acutely activate eNOS through pathways that include the cell surface receptor SR-B1, Gi protein, phosholipase C and entry of extracellular calcium into endothelial cells.

Effects of subtoxic concentrations of benzoyl peroxide on cell lipid metabolism

Benzoyl peroxide (BP), a tumor promoter, has been shown to cause free-radical-induced lipid peroxidation and membrane damage at toxic concentrations. However, its effects on lipid metabolism at concentrations that were not overtly toxic have not been investigated. The purpose of the current study was to examine the effects of BP and its final degradation product, benzoic acid (BA), on lipid metabolism. Two cell lines, hamster cheek pouch (HCP) and human monocytes (THP-1), were used to determine the effects of BP, BA, and BP combined with FeCl2 on cell lipid metabolism. Cells were exposed to BP and 14C acetate for 24 h, or cells with prelabeled lipids were harvested, and the lipids were extracted and separated with the use of thin-layer chromatography. Lipid metabolism of some neutral lipids such as triglycerides was altered for both cell types in response to BP. Also, cholesterol content was reduced in THP-1 cells and a phospholipid, phosphatidylethanolamine (PE), was reduced in HCP cells. The final degradation product of BP, BA, failed to elicit any response in lipid metabolism. Subtoxic concentrations of BP induced changes in neutral lipids such as triglycerides and cholesterol. The metabolism of major phospholipids except PE remained unchanged. The effects were related to BP and its degradation and varied with the cell type.

Cantilever-based optical deflection assay for discrimination of DNA single-nucleotide mismatches

Characterization of single-nucleotide polymorphisms is a major focus of current genomics research. We demonstrate the discrimination of DNA mismatches using an elegantly simple microcantilever-based optical deflection assay, without the need for external labeling. Gold-coated silicon AFM cantilevers were functionalized with thiolated 20- or 25-mer probe DNA oligonucleotides and exposed to target oligonucleotides of varying sequence in static and flow conditions. Hybridization of 10-mer complementary target oligonucleotides resulted in net positive deflection, while hybridization with targets containing one or two internal mismatches resulted in net negative deflection. Mismatched targets produced a stable and measurable signal when only a four-base pair stretch was complementary to the probe sequence. This technique is readily adaptable to a high-throughput array format and provides a distinct positive/negative signal for easy interpretation of oligonucleotide hybridization.

Origin of nanomechanical cantilever motion generated from biomolecular interactions

Generation of nanomechanical cantilever motion from biomolecular interactions can have wide applications, ranging from high-throughput biomolecular detection to bioactuation. Although it has been suggested that such motion is caused by changes in surface stress of a cantilever beam, the origin of the surface-stress change has so far not been elucidated. By using DNA hybridization experiments, we show that the origin of motion lies in the interplay between changes in configurational entropy and intermolecular energetics induced by specific biomolecular interactions. By controlling entropy change during DNA hybridization, the direction of cantilever motion can be manipulated. These thermodynamic principles were also used to explain the origin of motion generated from protein-ligand binding.

Dynamics of protein recovery from process filtration systems using microporous membrane filter cartridges

The purpose of this report is to address the concern for protein concentration recovery through membrane filter cartridges at the process scale. Filtration systems consisting of pre- and/or final membrane filter cartridges were evaluated for protein concentration recovery under typical manufacturing conditions of continuous flow and high throughput volumes. Results of the study conclusively demonstrate that consideration of the protein adsorptive properties and recovery performance of cartridge filters can provide efficient bio-burden and particulate control without compromising protein yields. Understanding the dynamics of protein recovery through various prefilter and final filter cartridges can play an important role in the proper selection of a filtration system to ensure optimal life and protein yield when filtering dilute protein solutions.