Citations

Optoacoustic, or photoacoustic, imaging combines the penetration capabilities of ultrasound imaging with the contrast mechanism of optical absorption related to the photoacoustic effect. To enable modeling of photoacoustic measurements and imaging applications, the problem can be divided into modeling of the optical photon propagation and the resulting acoustic wave propagation. In highly scattering media such as soft tissues, Monte Carlo (MC) methods are used to evaluate photon propagation, absorption and the subsequent generation of a heat source that produces the photoacoustic effect. Acoustic wave equations are then used to model the propagation of the sound in the medium. However, if the appropriate physics could be modeled with a single tool, there would be advantages of consistency in spatial and temporal domains as well as easier integration of the optical and acoustic simulations. We propose using MC methods for optical photon propagation and for the acoustic wave propagation. The simulations are split into two stages for the optical photon propagation and the acoustic phonon propagation. We describe how the same MC framework is used to model photon propagation and acoustic phonon propagation. We will then demonstrate this new combined MC framework in models of photoacoustic problems in homogeneous and heterogeneous cases. These results will be compared with results from using k-Wave models for the acoustic wave propagation. The correspondence between k-Wave the acoustic MC model are shown to be in good agreement.

Abstract Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described epileptogenic tumor characterized by oligodendroglioma-like components, aberrant CD34 expression, and genetic MAPK pathway activation through alterations such as BRAF V600E mutation, and FGFR2-KIAA1598/CTNNA3 and FGFR3-TACC3 fusions. We report the molecular profiling of PLNTY in 9 patients, 7 female: 2 male, median age at diagnosis of 16 years (range, 5–34). All tumors were supratentorial with diagnostic morphological features of PLNTY including oligodendroglioma-like areas and strong diffuse CD34 immunostaining. Four (of 9; 44%) tumors were positive for BRAF V600E immunostain, indicating the presence of a BRAF V600E mutation. The 6 cases evaluated for IDH status were negative by IDH1-R132H immunostain (n=5; 3 BRAF V600E-negative and 2 BRAF V600E-positive) or by NGS (n=1; BRAF V600E-negative). Oncoscan chromosomal microarray performed in 5 BRAF V600E-negative tumors showed recurrent copy number changes including gain of whole chromosomes 5, 7, 8, 9, 12, 18, 19, 20, 21 and X, and loss of chromosomes 1, 2, 10q, 13, 22 and Xq. The 10q losses (n=2) were highly suggestive of an FGFR2-KIAA1598 and of a potentially novel FGFR2 underlying fusion event in one case each. Custom targeted neuro-oncology DNA and RNA NGS panel performed in 2 cases revealed a fusion similar to fusions previously reported in pilocytic astrocytoma: one with a KIAA1549-BRAF (exon 15-exon 9) fusion associated with a 7q34 ~785 kilobase deletion rather than the characteristic ~2 megabase duplication seen in pilocytic astrocytoma, and another with a QKI-NTRK2 (exon 6-exon 15) fusion associated with a 9q21 ~191 kilobase duplication disrupting NTRK2. The KIAA1549-BRAF fusion-positive case also had a TP53 mutation with loss of whole chromosome 17, suggesting TP53 complete inactivation. This study confirms that PLNTY is a low-grade neuroepithelial tumor with frequent MAPK pathway activation and expands the spectrum of MAPK activating alterations observed in PLNTY.

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor. Median survival is 15 months despite surgery, radiation, and chemotherapy. Immunotherapy is promising but GBM-mediated immunosuppression remains a barrier. Recently, extracellular vesicles (EVs) have been implicated in GBM-mediated immunosuppression through expression of the immune checkpoint molecule PD-L1. Data from our group has suggested this is predominantly through induction of immunosuppressive monocytes including myeloid-derived suppressor cells (MDSCs) and non-classical monocytes (NCMs). PD-L1 expression is increased in most nucleated cells following IFN-γ exposure. We, therefore, sought to determine if IFN-γ exposure would result in super-induction of immunosuppressive GBM EVs. EVs were harvested in vitro from matched differentiated and stem-like human GBM cell lines +/- IFN-γ. IFN-γ exposure did not alter EV production or expression of common EV markers but increased PD-L1 expression in EVs from differentiated but not stem-like GBM cells. In keeping with our earlier findings, no direct inhibition of T cell proliferation by stem-like or differentiated GBM EVs was observed regardless of IFN-γ exposure or PD-L1 expression. In contrast, differentiated but not stem-like GBM cell EVs induced MDSC and NCM differentiation from normal monocytes. This was increased following IFN-γ exposure and was dependent upon PD-L1 expression. Monocytes exposed to differentiated but not stem-like GBM cell EVs inhibited T cell proliferation in a similar manner (increased with IFN-γ exposure, decreased with PD-L1 knockdown). Thus, IFN-γ exposure results in super-induction of immunosuppressive EVs from differentiated but not stem-like GBM cells that increase MDSC and NCM differentiation in normal monocytes and increase their ability to inhibit T cell proliferation. These effects are dependent upon PD-L1 up-regulation induced by IFN-γ. This may be an important mechanism GBMs utilize to suppress anti-tumor T cell responses that are typically accompanied by increased IFN-γ expression.

Abstract Glioblastoma (GBM) is the most common and lethal primary brain tumor, and novel therapeutic strategies that make a substantial impact on outcomes are sorely needed. Immunotherapies have shown great promise in the treatment of a number of cancers in recent year, and a concerted effort is being made to apply these treatment paradigms to GBM. However, many GBM patients exhibit profound immunosuppression, likely limiting the efficacy of such approaches. The mechanisms of this immunosuppression are poorly understood, but tumor-derived extracellular vesicles (EVs), may play a role. We demonstrate that GBM-derived EVs induce the development of myeloid-derived suppressor cells (MDSCs) and non-classical monocytes (NCMs). We further demonstrate that these EV-induced monocytic cells are immunosuppressive, resulting in impaired T cell proliferation upon co-culture. We found that the immunosuppressive effects of tumor-derived EVs appear to be driven by the induction of these immunosuppressive monocytes, as EV treatment of T cells did not significantly impact T cell proliferation. Further, we sought to characterize the important of programmed death ligand 1 (PD-L1) in the induction of these immunosuppressive monocyte populations. We found PD-L1 to be expressed in the EVs from GBM cell lines, and that modulation in PD-L1 expression via either constitutive overexpression or shRNA-mediated knockdown resulted in concordant changes in expression in tumor-derived EVs. We demonstrate that PD-L1 is important for the induction of NCM but not for MDSCs. Taken together, these findings point to a significant role for tumor-derived EVs in the induction of immunosuppressive monocytes in GBM, and that these cells may be a driving force of systemic immunosuppression. PD-L1 is one factor expressed in EVs that has immunomodulatory properties, but additional EV cargo likely plays a major role in the induction of immunosuppressive cells.

Abstract Systemic immunosuppression following neurological insults including stroke, traumatic brain injury, and glioblastoma (GBM) causes mortality and leads to failure of immune-modulating therapies. Exact immunological nature and the underlying mechanisms of this immunosuppression are unknown. Our goal was to define effects of neurological insults given exclusively to the brain on the thymus. The thymus is the primary immune organ responsible for T-cell development and maintenance both in children and in adults. We evaluated the brain-thymus communication using the following neurological insults: physical injury, CNS viral infection, sterile injury, tumor implantation, and seizures. All insults resulted in significant thymic involution that was reversible upon clearance of the insult. Thymic involution did not occur following similar peripheral insults. We next demonstrated that the GL261 model of GBM recapitulates hallmark features of peripheral immunosuppression observed in GBM patients including low CD4 T-cell counts. Thus, we aimed to further study the immunosuppression affecting the thymus in this clinically relevant model. Principle component analysis following RNA-sequencing of thymi from naïve and glioma-bearing mice revealed unbiased separation of the groups suggesting that the thymus is directly affected by a brain tumor. To determine the extent to which thymic involution was caused by a soluble factor we employed parabiosis. We demonstrated that thymic involution was transferable from glioma-bearing to non-tumor-bearing parabionts. Similarly, serum taken from GL261 glioma-bearing mice potently inhibited proliferation of T-cells in vitro. Together our data demonstrate that CNS-specific insults, regardless of nature, cause immunosuppression by prompting thymic involution through circulating factors. This accounts at least partially for immune deficiencies observed following neurological injuries. Identification of this suppressive factor is crucial in designing future therapeutics for GBM patients, and patients with other acute and chronic neurological trauma.

Background: Temporary mechanical circulatory support (MCS) devices provide hemodynamic assistance for shock refractory to pharmacological treatment. Most registries have focused on single devices or specific etiologies of shock, limiting data regarding overall practice patterns with temporary MCS in cardiac intensive care units. Methods: The CCCTN (Critical Care Cardiology Trials Network) is a multicenter network of tertiary CICUs in North America. Between September 2017 and September 2018, each center (n=16) contributed a 2-month snapshot of consecutive medical CICU admissions. Results: Of the 270 admissions using temporary MCS, 33% had acute myocardial infarction-related cardiogenic shock (CS), 31% had CS not related to acute myocardial infarction, 11% had mixed shock, and 22% had an indication other than shock. Among all 585 admissions with CS or mixed shock, 34% used temporary MCS during the CICU stay with substantial variation between centers (range: 17%–50%). The most common temporary MCS devices were intraaortic balloon pumps (72%), Impella (17%), and veno-arterial extracorporeal membrane oxygenation (11%), although intraaortic balloon pump use also varied between centers (range: 40%–100%). Patients managed with intraaortic balloon pump versus other forms of MCS (advanced MCS) had lower Sequential Organ Failure Assessment scores and less severe metabolic derangements. Illness severity was similar at high- versus low-MCS utilizing centers and at centers with more advanced MCS use. Conclusions: There is wide variation in the use of temporary MCS among patients with shock in tertiary CICUs. While hospital-level variation in temporary MCS device selection is not explained by differences in illness severity, patient-level variation appears to be related, at least in part, to illness severity.

Abstract Purpose A case of vancomycin enzyme immunoassay (EIA) interference confirmed by high-performance liquid chromatography (HPLC) is described. Summary Therapeutic drug monitoring is standard of practice in vancomycin dosing and monitoring in order to maximize the pharmacodynamic effects and minimize toxicity. After a 52-year-old woman received 5 doses of vancomycin, serum concentrations continued to rise for several days in the absence of ongoing vancomycin administration. Despite persistently elevated vancomycin concentrations, the patient clinically deteriorated and required treatment with an alternative agent. Subsequently, serum concentrations were processed via HPLC and analyzed for percent protein binding. Confirmatory analysis revealed substantially lower concentrations by HPLC than were obtained by EIA and an abnormal elevation in protein binding. After discharge from the index admission, the patient returned 11 months later and had a dectectable vancomycin concentration by EIA prior to receipt of vancomycin. HPLC analysis confirmed the true concentration was undetectable. Though the exact interfering substance was not identified, the above discrepancy in concentrations between the two assay methods indicates the presence of assay interference, and adds to the available literature suggesting similar occurrences. This case is particularly troubling given that the level of interference was not such that it would lead a clinician to immediately suspect interference, and the patient experienced treatment failure. Conclusion Falsely elevated values for serum vancomycin concentration, measured by EIA, contributed to treatment failure in a patient. The substance presumably responsible for EIA interferences was not identified.

Abstract Background: In contrast to the rapid increase in thyroid cancer (TC) incidence, thyroid cancer mortality rates have remained low and stable over the last decades. In Ecuador, however, TC mortality has increased and to determine possible drivers, a retrospective analysis of all patients attending a thyroid cancer referral center in Ecuador was conducted. Methods: From June 2014 to December 2017, a cross-sectional study was conducted at the Hospital de Especialidades Eugenio Espejo (HEEE), a regional reference public hospital for endocrine neoplasia in adults in Quito, Ecuador. We identified the mechanism of detection, histopathology and treatment modalities from a patient interview and review of clinical records. Results: Among 452 patients, 74.8% were young adults and 94.2% (426) of patients were female. 13.7% had a family history of thyroid cancer, and median of tumor size was 2 cm. The incidental finding was 54.2% whereas 45.8% was non-incidental. Thyroid cancer histology reported that 93.3% had papillary thyroid cancer (PTC), 2.7% follicular, 1.5% Hurtle cells, 1.6% medullary, 0.7% poor differentiated, and 0.2% anaplastic carcinoma. The mean MACIS (metastasis, age, completeness, invasion, and size) score was 4.95 (CI 4.15-5.95) with 76.2% of the thyroid cancer patients having MACIS score equal or less than 6. The very low and low risk of recurrence was 18.1% (79) and 62% (271) respectively. An analysis of 319 patients with non-metastatic thyroid cancer showed that 10.7% (34) of patients had surgical complications. Moreover, around 62.5% (80 from 128 patients with thyroglobulin laboratory results) of TC patients had a stimulated-thyroglobulin (sTg) value equal or higher than 2 ng/ml. Overall, a poor surgical outcome was present in 35.1% (112) patients. Out of 436 patients with differentiated thyroid carcinoma (DTC), 86% (n=375) received radioactive iodine (RAI). Conclusion: Thyroid cancer histological characteristics and method of diagnosis are like the ones described in other reports without any evidence of the high frequency of aggressive thyroid cancer histology. However, we observed evidence of overtreatment and poor surgical outcomes that demand additional studies to understand their association with thyroid cancer mortality in Ecuador.

Abstract Background Quantitative nucleic acid amplification (QNAT) tests are cornerstone for the management of CMV disease after organ transplantation. We assessed the potential impact of viral load results obtained by two commercial WHO international standard-calibrated NAT in solid-organ (SOT) and hematopoietic stem cell transplant (HSCT) recipients. Methods Sixty-four patients (36 SOT and 28 HSCT) had plasma CMV viral load assessed using the COBAS AmpliPrep/COBAS TaqMan CMV Test (CAP/CTM; lower limit of quantification [LLoQ] at 137 IU/mL) and cobas 6800 System (cobas CMV; LLoQ at 35 IU/mL). Viral load values were correlated with clinical course and outcomes. Results Forty-three of 64 patients (67.2%) had CMV infection or disease (asymptomatic, 67.4%; gastrointestinal disease, 16.3%; pneumonitis 4.7%) at median of 4.4 months (IQR 1.4 to 7.7) from transplantation. At CMV infection diagnosis, viral load results (mean ± SD) were almost two-fold higher when measured by cobas CMV (19,456 ± 51,618 IU/mL) compared with CAP/CTM (10,504 ± 27,744 IU/mL; P = 0.04). Time to onset of CMV viremia was significantly shorter (11.5 days; P < 0.001) while viral clearance was significantly longer (12.75 days; P < 0.001) by cobas CMV when compared with CAP/CTM. Persistent viremia was observed with cobas CMV in 44% of patients at the time of first negative results by CAP/CTM. Patients with negative results by cobas CMV at the end of antiviral treatment had a significantly lower need for re-treatment (OR 0.26, 95% CI 0.04 to 0.99, P = 0.05). Conclusion Our study highlights significant differences between CMV QNAT assays despite calibration to the WHO-international standard. The significant differences in the degree (almost two-fold), time to onset (12 days difference) and clearance (13 days difference) of CMV viremia between two automated commercial QNAT assays have direct implications in the care of transplant recipients. Persistence of low-level viremia was observed in samples that reached negative threshold by CAP/CTM, when tested using the more sensitive cobas CMV. Clearance of CMV viremia, when assessed by the more sensitive cobas CMV, was significantly associated with a lower need for re-treatment. Disclosures All authors: No reported disclosures.