OS08.6.A Novel role of ARF4-mediated retrograde trafficking as a driver of chemoresistance in GBM

Background

Glioblastoma (GBM) is the most common type of adult malignant brain tumor, with a median survival of only 21 months. This is partly due to the high rate of resistance to conventional therapy, including temozolomide (TMZ), leading to recurrence rates close to 100%. To identify the unknown genes driving the development of this resistance, we performed a genome-wide CRISPR knockout screen comparing a DMSO-treated population with a TMZ-treated population over 14 days. Results showed substantial enrichment of ~200 novel genes, including a previously unstudied gene ARF4—involved in retrograde trafficking to the nucleus. Here, we set out to characterize the mechanism by which ARF4 may be acting to promote chemoresistance.

Material and Methods

A whole-genome CRISPR-Cas9 sensitivity screen as well as a variety of in vitro and in vivo experiments, such as live-cell imaging, cell viability assays, and western blotting were conducted.

Results

Initial investigation into ARF4 showed significant elevations in expression at RNA and protein levels (p<0.05) in recurrent patient tumors, as well as a significant survival benefit in patient datasets when downregulated (p<0.05). Knocking out ARF4 resulted in significantly heightened sensitivity to TMZ in multiple GBM patient-derived xenograft lines and extended survival compared to the controls (p<0.01) in vivo. Further investigation via live-cell imaging of transferrin receptors, a retrograde transport marker, revealed that ARF4-knockdowns significantly inhibited retrograde trafficking, while ARF4-overexpressions resulted in an untenable increase in retrograde trafficking in vitro. This effect was also seen in TMZ-treated cells, which displayed enhanced trafficking dynamics, suggesting that ARF4-mediated retrograde trafficking is elevated during therapy to drive nuclear localization of key chemoresistance-promoting factors. We then performed an unbiased proteomics screen to identify which genes were being uniquely transported to the nucleus as a product of ARF4-mediated retrograde trafficking, which revealed enrichment of the EGFR signaling pathway in particular. Validation experiments confirmed a decrease in EGFR trafficking and nuclear EGFR expression in ARF4-knockdowns and an increase in EGFR trafficking and nuclear EGFR expression in ARF4-overexpression and TMZ-treated GBM cells. Furthermore, nuclear DNA-PK, a DNA repair protein known to be transcriptionally activated by EGFR, was similarly found to be downregulated in ARF4-knockdown conditions and elevated in ARF4-overexpression and TMZ-treated conditions.

Conclusion: Here, we show that ARF4 may be responsible for promoting chemoresistance through altered retrograde trafficking of EGFR specifically. Thus, our study has yielded a promising and novel therapeutic target for GBM, a disease desperately in need of new therapeutic strategies.

P02.01.B The telomere maintenance mechanism spectrum and its dynamics in gliomas

The activation of the telomere maintenance mechanism (TMM) is one of the critical drivers of cancer cell immortality. In gliomas, TERT expression and TERT promoter mutation are considered to reliably indicate telomerase activation, while ATRX mutation indicates alternative lengthening of telomeres (ALT). However, these relationships have not been extensively validated in tumor tissues. Here, we show through the direct measurement of telomerase activity and ALT in a large set of glioma samples that the TMM in glioma cannot be defined in the dichotomy of telomerase activity and ALT, regardless of TERT expression, TERT promoter mutation and ATRX mutation. Moreover, we observed that a considerable proportion of gliomas lack both telomerase activity and ALT (Neither group). And this Neither group exhibited evidence of slow growth potential. From a set of longitudinal samples from a separate cohort of glioma patients, we discovered that the TMM is not fixed but changes with glioma progression. Collectively, these results suggest that the TMM is a dynamic entity and that reflects the plasticity of the oncogenic biological status of tumor cells and that the TMM should be defined by the direct measurement of telomerase enzyme activity and evidence of ALT.

Priority Areas for Child Diaper Access: Low-Income Neighborhoods with Limited Retail Access to the Basic Need of Diapers

Introduction:

Although a requirement for the health and hygiene of young children, millions of US families with low-incomes have unmet needs for diapers. The present study explored retail options in Durham County, NC for purchasing diapers in low-income neighborhoods in effort to increase our understanding of the overall context of diaper need.

Methods:

During June 2018, we visited 63 retailers selling 2460 child diaper products in 29 census tracts with a median household income ≤200% of the federal poverty guideline. Corner stores were the only retailers to sell products without original packaging, including one corner store selling loose diapers for $1.49 each. Next, we calculated bus routes to determine accessibility of the retailer with the lowest prices and greatest selection. One-way bus travel from all other census tracts to a big-box store required taking two buses combined with an average of 11 min walking for an average travel time of 43 min. We deemed census tracts as “priority areas for diaper access” when they were characterized as: (1) low income and (2) low access with no retailer selling all of the 10 most common child diaper sizes.

Results:

Nearly half (n=13) of the census tracts in our sample met our criteria for priority areas. We compared neighborhood characteristics of priority areas with all other county census tracts. Families living in priority areas were statistically significantly more likely to: identify as Black or African American, face challenges affording housing costs, have homes or automobiles in need of repair, experience neighborhood violence, and have less educational attainment.

Social risk factors predicting outcomes of cervical myelopathy surgery

OBJECTIVE

Combinations of certain social risk factors of race, sex, education, socioeconomic status (SES), insurance, education, employment, and one's housing situation have been associated with poorer pain and disability outcomes after lumbar spine surgery. To date, an exploration of such factors in patients with cervical spine surgery has not been conducted. The objective of the current work was to 1) define the social risk phenotypes of individuals who have undergone cervical spine surgery for myelopathy and 2) analyze their predictive capacity toward disability, pain, quality of life, and patient satisfaction-based outcomes.

METHODS

The Cervical Myelopathy Quality Outcomes Database was queried for the period from January 2016 to December 2018. Race/ethnicity, educational attainment, SES, insurance payer, and employment status were modeled into unique social phenotypes using latent class analyses. Proportions of social groups were analyzed for demonstrating a minimal clinically important difference (MCID) of 30% from baseline for disability, neck and arm pain, quality of life, and patient satisfaction at the 3-month and 1-year follow-ups.

RESULTS

A total of 730 individuals who had undergone cervical myelopathy surgery were included in the final cohort. Latent class analysis identified 2 subgroups: 1) high risk (non-White race and ethnicity, lower educational attainment, not working, poor insurance, and predominantly lower SES), n = 268, 36.7% (class 1); and 2) low risk (White, employed with good insurance, and higher education and SES), n = 462, 63.3% (class 2). For both 3-month and 1-year outcomes, the high-risk group (class 1) had decreased odds (all p < 0.05) of attaining an MCID score in disability, neck/arm pain, and health-related quality of life. Being in the low-risk group (class 2) resulted in an increased odds of attaining an MCID score in disability, neck/arm pain, and health-related quality of life. Neither group had increased or decreased odds of being satisfied with surgery.

CONCLUSIONS

Although 2 groups underwent similar surgical approaches, the social phenotype involving non-White race/ethnicity, poor insurance, lower SES, and poor employment did not meet MCIDs for a variety of outcome measures. This finding should prompt surgeons to proactively incorporate socially conscience care pathways within healthcare systems, as well as to optimize community-based resources to improve outcomes and personalize care for populations at social risk.

Vitronectin-Derived Peptide Promotes Reparative Dentin Formation

Exposed dental pulp can maintain its vitality through a pulp-capping procedure with biocompatible materials, followed by reparative dentin formation. Our previous study demonstrated that a vitronectin-derived peptide (VnP-16) promotes osteoblast differentiation and concomitantly restrains osteoclast differentiation and resorptive function. In this study, we aimed to demonstrate that VnP-16 promotes odontoblast differentiation, mineralization, and reparative dentin formation in a pulp exposure model using a rat tooth. VnP-16 showed no cytotoxicity and promoted cellular behavior in human dental pulp cells, enhancing their differentiation into odontoblast-like cells and mineralization, effects that are comparable to those obtained with vitronectin. In a rat pulp exposure model, VnP-16 showed mild inflammatory responses at 2 and 4 wk or none. Mineral trioxide aggregate (MTA) demonstrated a tendency of early formation of reparative dentin at 2 wk when compared with recombinant human bone morphogenetic protein 2 (rhBMP-2) and VnP-16. However, VnP-16 induced reparative dentin formation similar to MTA and rhBMP-2 without inflammation at 4 wk. In addition, VnP-16 showed a thicker and homogeneous reparative dentin formation versus MTA and rhBMP-2. Collectively, these results suggest that VnP-16 can be a useful, direct pulp-capping agent for highly qualified reparative dentin formation by promoting cell behavior and odontoblastic differentiation of human dental pulp cells.

Laser ablative treatment of musicogenic epilepsy arising from dominant mesial temporal lobe: illustrative case

BACKGROUND

Musicogenic epilepsy (ME) is a rare reflex epilepsy in which seizures are triggered by musical stimuli. Prior descriptions of ME have suggested localization to the nondominant temporal lobe, primarily in neocortex. Although resection has been described as a treatment for ME, other surgical modalities, such as laser ablation, may effectively disrupt seizure networks in ME while incurring comparatively lower risks of morbidity. The authors described the use of laser ablation to treat ME arising from the dominant mesial temporal structures.

OBSERVATIONS

A 37-year-old woman with a 15-year history of drug-resistant ME was referred for surgical evaluation. Her seizures were triggered by specific musical content and involved behavioral arrest, repetitive swallowing motions, and word incomprehension. Diagnostic studies, including magnetic resonance imaging, single-photon emission computed tomography, magnetoencephalography, Wada testing, and stereoelectroencephalography, indicated seizure onset in the left (dominant) mesial temporal lobe. Laser interstitial thermal therapy was used to ablate the left mesial seizure onset zone. The patient was discharged on postoperative day two. At 18-month follow-up, she was seizure-free with no posttreatment neurological deficits.

LESSONS

Laser ablation can be an effective treatment option for well-localized forms of ME, particularly when seizures originate from the dominant mesial temporal lobe.

Systemic Therapy Type and Timing Effects on Radiation Necrosis Risk in HER2+ Breast Cancer Brain Metastases Patients Treated With Stereotactic Radiosurgery

Background

There is a concern that HER2-directed systemic therapies, when administered concurrently with stereotactic radiosurgery (SRS), may increase the risk of radiation necrosis (RN). This study explores the impact of timing and type of systemic therapies on the development of RN in patients treated with SRS for HER2+ breast cancer brain metastasis (BCBrM).

Methods

This was a single-institution, retrospective study including patients >18 years of age with HER2+ BCBrM who received SRS between 2013 and 2018 and with at least 12-month post-SRS follow-up. Presence of RN was determined via imaging at one-year post-SRS, with confirmation by biopsy in some patients. Demographics, radiotherapy parameters, and timing (“during” defined as four weeks pre- to four weeks post-SRS) and type of systemic therapy (e.g., chemotherapy, HER2-directed) were evaluated.

Results

Among 46 patients with HER2+ BCBrM who received SRS, 28 (60.9%) developed RN and 18 (39.1%) did not based on imaging criteria. Of the 11 patients who underwent biopsy, 10/10 (100%) who were diagnosed with RN on imaging were confirmed to be RN positive on biopsy and 1/1 (100%) who was not diagnosed with RN was confirmed to be RN negative on biopsy. Age (mean 53.3 vs 50.4 years, respectively), radiotherapy parameters (including total dose, fractionation, CTV and size target volume, all p>0.05), and receipt of any type of systemic therapy during SRS (60.7% vs 55.6%, p=0.97) did not differ between patients who did or did not develop RN. However, there was a trend for patients who developed RN to have received more than one agent of HER2-directed therapy independent of SRS timing compared to those who did not develop RN (75.0% vs 44.4%, p=0.08). Moreover, a significantly higher proportion of those who developed RN received more than one agent of HER2-directed therapy during SRS treatment compared to those who did not develop RN (35.7% vs 5.6%, p=0.047).

Conclusions

Patients with HER2 BCBrM who receive multiple HER2-directed therapies during SRS for BCBrM may be at higher risk of RN. Collectively, these data suggest that, in the eight-week window around SRS administration, if HER2-directed therapy is medically necessary, it is preferable that patients receive a single agent.

Impact of ascending aortic prosthetic grafts on early postoperative descending aortic biomechanics on cardiac magnetic resonance imaging

OBJECTIVES

Among patients with ascending thoracic aortic aneurysms, prosthetic graft replacement yields major benefits but risk for recurrent aortic events persists for which mechanism is poorly understood. This pilot study employed cardiac magnetic resonance to test the impact of proximal prosthetic grafts on downstream aortic flow and vascular biomechanics.

METHODS

Cardiac magnetic resonance imaging was prospectively performed in patients with thoracic aortic aneurysms undergoing surgical (Dacron) prosthetic graft implantation. Imaging included time resolved (4-dimensional) phase velocity encoded cardiac magnetic resonance for flow quantification and cine-cardiac magnetic resonance for aortic wall distensibility/strain.

RESULTS

Twenty-nine patients with thoracic aortic aneurysms undergoing proximal aortic graft replacement were studied; cardiac magnetic resonance was performed pre- [12 (4, 21) days] and postoperatively [6.4 (6.2, 7.2) months]. Postoperatively, flow velocity and wall shear stress increased in the arch and descending aorta (P < 0.05); increases were greatest in hereditary aneurysm patients. Global circumferential strain correlated with wall shear stress (r = 0.60-0.72, P < 0.001); strain increased postoperatively in the native descending and thoraco-abdominal aorta (P < 0.001). Graft-induced changes in biomechanical properties of the distal native ascending aorta were associated with post-surgical changes in descending aortic wall shear stress, as evidenced by correlations (r = -0.39-0.52; P ≤ 0.05) between graft-induced reduction of ascending aortic distensibility and increased distal native aortic wall shear stress following grafting.

CONCLUSIONS

Prosthetic graft replacement of the ascending aorta increases downstream aortic wall shear stress and strain. Postoperative increments in descending aortic wall shear stress correlate with reduced ascending aortic distensibility, suggesting that grafts provide a nidus for high energy flow and adverse distal aortic remodelling.

Management of Acute Traumatic Spinal Cord Injury: A Review of the Literature

Traumatic spinal cord injury (TSCI) is a debilitating disease that poses significant functional and economic burden on both the individual and societal levels. Prognosis is dependent on the extent of the spinal injury and the severity of neurological dysfunction. If not treated rapidly, patients with TSCI can suffer further secondary damage and experience escalating disability and complications. It is important to quickly assess the patient to identify the location and severity of injury to make a decision to pursue a surgical and/or conservative management. However, there are many conditions that factor into the management of TSCI patients, ranging from the initial presentation of the patient to long-term care for optimal recovery. Here, we provide a comprehensive review of the etiologies of spinal cord injury and the complications that may arise, and present an algorithm to aid in the management of TSCI.

Development of a high-resolution typing method for SLA-3, swine MHC class I antigen 3

We developed a high-resolution and comprehensive typing method for swine leukocyte antigen 3 (SLA-3), an MHC class I gene, employing locus-specific genomic PCR followed by subsequent direct sequencing. A total of 292 individuals from nine pure, one cross-breed and six cell lines were successfully typed. A total of 21 SLA-3 alleles were identified, of which four were found to be novel alleles. However, the allelic diversity of SLA-3 was lower than that of previously reported class I genes, SLA-1 and -2. More SLA-3 alleles were observed in the Landrace and Yorkshire breeds than the other breeds. SLA-3*04:01 was identified in seven out of nine breeds and was the most widely distributed allele across all breeds. Therefore, the typing method reported in this study completes our efforts to develop high-resolution typing methods for major SLA molecules, facilitating the combined analysis of major SLA genes from field samples, which is important to understand the relationship between the adaptive immune responses against pathogens and the immunogenetic makeup of an individual.

Robotic navigation in spine surgery: Where are we now and where are we going?

Robotic navigation is a new and rapidly emerging niche within minimally invasive spine surgery. The robotic arms-race began in 2004 and has resulted in no less than four major robotic surgical adjuncts. Current Food and Drug Administration (FDA)-approved applications of robotic navigation are limited to pedicle screw instrumentation, but new indications and experimental applications are rapidly emerging. As with any new technology, robotic navigation must be vetted for clinical efficacy, efficiency, safety, and cost-effectiveness. Given the rapid advancements made on a yearly basis, it is important to make frequent and objective assessments of the available technology. Thus, the authors seek to provide the most up-to-date review of the history, currently available technology, learning curve, novel applications, and cost effectiveness of today's available robotic systems as it relates to spine surgery.

Ventriculomegaly and postoperative lateral/third ventricular blood as predictors of cerebrospinal fluid diversion following posterior fossa tumor resection

OBJECTIVE

Postoperative hydrocephalus occurs in one-third of children after posterior fossa tumor resection. Although models to predict the need for CSF diversion after resection exist for preoperative variables, it is unknown which postoperative variables predict the need for CSF diversion. In this study, the authors sought to determine the clinical and radiographic predictors for CSF diversion in children following posterior fossa tumor resection.

METHODS

This was a retrospective cohort study involving patients ≤ 18 years of age who underwent resection of a primary posterior fossa tumor between 2000 and 2018. The primary outcome was the need for CSF diversion 6 months after surgery. Candidate predictors for CSF diversion including age, race, sex, frontal occipital horn ratio (FOHR), tumor type, tumor volume and location, transependymal edema, papilledema, presence of postoperative intraventricular blood, and residual tumor were evaluated using a best subset selection method with logistic regression.

RESULTS

Of the 63 included patients, 26 (41.3%) had CSF diversion at 6 months. Patients who required CSF diversion had a higher median FOHR (0.5 vs 0.4) and a higher percentage of postoperative intraventricular blood (30.8% vs 2.7%) compared with those who did not. A 0.1-unit increase in FOHR or intraventricular blood was associated with increased odds of CSF diversion (OR 2.9 [95% CI 1.3-7.8], p = 0.02 and OR 20.2 [95% CI 2.9-423.1], p = 0.01, respectively) with an overfitting-corrected concordance index of 0.68 (95% CI 0.56-0.80).

CONCLUSIONS

The preoperative FOHR and postoperative intraventricular blood were significant predictors of the need for permanent CSF diversion within 6 months after posterior fossa tumor resection in children.

Myocardial strain by 3D-speckle tracking echocardiography predicts long-term risk of cardiovascular morbidity and mortality in the general population: the Southall And Brent Revisited (SABRE) study

Background

Both left ventricular (LV) ejection fraction (EF) and Global Longitudinal Strain (GLS) by 2D-echocardiography predict mortality and cardiac events, and GLS may be superior to EF. 3D-speckle tracking echocardiography (3D-STE), a recently validated method, allows simultaneous assessment of EF, GLS and principal tangential strain (PTS), but its prognostic utility in the general population is unknown.

Purpose

We hypothesized that 3D-STE derived LV myocardial strains predict a composite of cardiac endpoints, and that GLS would be a better prognostic marker than EF. We also investigated the utility of PTS compared with GLS and EF.

Methods

A total of 529 individuals (69±6y; 76.6% male) from SABRE study, a UK-based tri-ethnic community cohort, underwent health examinations. The association between 3D-STE EF or multidirectional myocardial strains and a composite cardiac endpoints comprising coronary heart disease (fatal/non-fatal), heart failure hospitalization, new-onset arrhythmia was determined using Cox proportional hazards models with and without adjustment for potential confounders and Harrell's C statistics were calculated. Associations with cardiovascular (CV) mortality was examined as a secondary objective. The incremental value of 3D-STE EF, GLS and PTS in improving CV risk stratification by the established Framingham risk score (FRS) was investigated using a likelihood ratio test on a series of nested Cox proportional hazards models.

Results

During follow-up (median, 8y), there were 56 composite cardiac endpoints and 24 CV deaths. EF and radial strain were negatively associated, while GLS, global circumferential strain and PTS were positively associated with the composite cardiac endpoints in unadjusted models (Table 1). Associations were only marginally affected by adjustment for potential confounders although confidence intervals of the estimate increased slightly (Table 1). There was little difference in the C-statistics for EF, GLS or PTS for the composite cardiac endpoints (Table 1). Associations with CV mortality were generally weaker and only GLS showed some evidence of a positive association with CV mortality in unadjusted and adjusted models (Table 1). Compared to EF and GLS, PTS most improved the predictive value (model fit) of FRS for composite cardiac endpoints (Table 2). None of the measures convincingly improved calibration for CV mortality.

Conclusions

3D-STE-derived LV myocardial strains predicted adverse cardiac events and CV mortality in a multi-ethnic sample of the UK general population. PTS/3D-strain was an independent predictor of cardiac events with some evidence of it being a slightly better predictor than conventional indices of LV function (GLS and EF). Future prospective studies are needed to confirm and extend these findings.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The main SABRE study is supported by the Wellcome Trust and BHF.

55 Are Virtual Journal Clubs A Viable Alternative in The Covid-19 Era?

Introduction

During the COVID-19 pandemic, face to face journal clubs have been curtailed due to Governmental guidance for social distancing. We present an example of a virtual journal club set up for Orthopaedic senior house officers (SHOs) & trainees in the North West Thames (NWT) Deanery from April to August 2020.

Method

Our aims were to establish a regular online journal club for orthopaedic trainees in NWT that successfully met the objectives of the more established face to face meetings. Assessment of each session was evaluated using a post attendance survey created using an established online generator.

Results

64.4% (16/25 participants) had not attended a virtual journal club before, with 100% (33/33) reporting that they would attend another virtual journal club. 39.4% (13/33) of attendees agreed or strongly agreed that they could participate in sessions over more conventional meetings. 24.2% (8/33) of participants reported experiencing technical issues during the sessions. 90.9% (30/33) of respondents reporting the virtual model to be more convenient than standard journal clubs.

Conclusions

The potential benefits of significantly increased accessibility increased visiting expert contribution whilst still adhering to government guidelines; weighed against marginally less effective teaching nonetheless results in an overall benefit.

Inpatient mortality and healthcare resource utilization of nontraumatic intracerebral hemorrhage complications in the US

OBJECTIVE

Nontraumatic, primary intracerebral hemorrhage (ICH) accounts for 2 million strokes worldwide annually and has a 1-year survival rate of 50%. Recent studies examining functional outcomes from ICH evacuation have been performed, but limited work has been done quantifying the incidence of subsequent complications and their healthcare economic impact. The purpose of this study was to quantify the incidence and healthcare resource utilization (HCRU) for major complications that can arise from ICH.

METHODS

The IBM MarketScan Research databases were used to retrospectively identify patients with ICH from 2010 to 2015. Complications examined included cerebral edema, hydrocephalus, venous thromboembolic events (VTEs), pneumonia, urinary tract infections (UTIs), and seizures. For each complication, inpatient mortality and HCRU were assessed.

RESULTS

Of 25,322 adult patients included, 10,619 (42%) developed complications during the initial admission of ICH: 22% had cerebral edema, 11% hydrocephalus, 10% pneumonia, 6% UTIs, 5% seizures, and 5% VTEs. The inpatient mortality rates at 7 and 30 days for each complication of ICH ranked from highest to lowest were hydrocephalus (24% and 32%), cerebral edema (15% and 20%), pneumonia (8% and 18%), seizure (7% and 13%), VTE (4% and 11%), and UTI (4% and 8%). Hydrocephalus had the highest total cost (median $92,776, IQR $39,308-$180,716) at 7 days post-ICH diagnosis and the highest cumulative total cost (median $170,839, IQR $91,462-$330,673) at 1 year post-ICH diagnosis.

CONCLUSIONS

This study characterizes one of the largest cohorts of patients with nontraumatic ICH in the US. More than 42% of the patients with ICH developed complications during initial admission, which resulted in high inpatient mortality and considerable HCRU.