A Mass-Spectrometry-Based Approach to Distinguish Annular and Specific Lipid Binding to Membrane Proteins

Membrane proteins engage in a variety of contacts with their surrounding lipids, but distinguishing between specifically bound lipids, and non‐specific, annular interactions is a challenging problem. Applying native mass spectrometry to three membrane protein complexes with different lipid‐binding properties, we explore the ability of detergents to compete with lipids bound in different environments. We show that lipids in annular positions on the presenilin homologue protease are subject to constant exchange with detergent. By contrast, detergent‐resistant lipids bound at the dimer interface in the leucine transporter show decreased k_off rates in molecular dynamics simulations. Turning to the lipid flippase MurJ, we find that addition of the natural substrate lipid‐II results in the formation of a 1:1 protein–lipid complex, where the lipid cannot be displaced by detergent from the highly protected active site. In summary, we distinguish annular from non‐annular lipids based on their exchange rates in solution.

Abstract 2311: Analysis of glypican 3-targeted chimeric antigen receptor T cells in hepatocellular carcinoma cell and mouse models

Background: Glypican-3 (GPC3) is a cell surface protein that is highly expressed in hepatocellular carcinoma (HCC).

Methods and Results: In this report, we analyzed two chimeric antigen receptors (CARs) targeting GPC3, CAR (HN3) recognizes the N-lobe of GPC3 while CAR (hYP7) targets the C-lobe that is close to the cell surface. In a real-time cell cytolytic assay, we found that CAR (hYP7) T cells showed higher cytolytic activity than CAR(HN3) T cells at an E:T ratio of 2:1 when co-cultured with HepG2 cells for up to 140 hours. The Luminex analysis showed that CAR (hYP7) T cells produced significantly more Th1/Th2 cytokines and chemokines than CAR (HN3) T cells following exposure to Hep3B and HepG2 cells. In the Hep3B peritoneal dissemination xenograft mouse model, a single intraperitoneal infusion of CAR (hYP7) cells exhibited sustainable antitumor efficacy, and all of the mice survived without recurrence 10 weeks post treatment. Strikingly, we demonstrated that single injection of CAR (hYP7) T cells derived from either healthy donor or HCC patient significantly regressed tumor growth in the orthotopic HCC mouse model. Using a highly sensitive droplet digital PCR (ddPCR), we detected high frequencies of CAR T cells in the spleen and tumor microenvironment of mice in the CAR (hYP7) group. By contrast, CD19 CAR T cells showed no sign of gene integration in either tissue. More importantly, we found that CD8+ CAR (hYP7) T cells recovered from mouse spleens exhibited much higher lytic activity against HCC cells than CD4+ CAR (hYP7) T cells. Finally, we found that the GPC3-targeted CAR T cells downregulated the Wnt signaling in HCC cells.

Conclusion: The hYP7 antibody-derived GPC3-specific CAR is a promising therapeutic that could be tested for the treatment of advanced stage liver cancer.

Citation Format: Dan Li, Nan Li, Yifan Zhang, Haiying Fu, Zhijian Duan, Alissa Hummer, Hongjia Yang, Madeline B. Torres, Xiaoling Luo, Ling Su, Hu Zhu, Josh Kramer, Jinqiu Chen, Xiaolin Wu, Matthew Hall, Qun Wang, Stephen Hewitt, Tim Greten, Mitchell Ho. Analysis of glypican 3-targeted chimeric antigen receptor T cells in hepatocellular carcinoma cell and mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2311.

Artificial scotoma estimation based on population receptive field mapping

Population receptive field (pRF) mapping based on functional magnetic resonance imaging (fMRI) is an ideal method for obtaining detailed retinotopic information. One particularly promising application of pRF mapping is the estimation and quantification of visual field effects, for example scotomata in patients suffering from macular dysfunction or degeneration (MD) or hemianopic defects in patients with intracranial dysfunction. However, pRF mapping performance is influenced by a number of factors including spatial and temporal resolution, distribution of dural venous sinuses and patient performance. This study addresses the ability of current pRF methodology to assess the size of simulated scotomata in healthy individuals. The data demonstrate that central scotomata down to a radius of 2.35° (4.7° diameter) visual angle can be reliably estimated in single subjects using high spatial resolution protocols and multi-channel receive array coils.

Increased neural responses to empathy for pain might explain how acute stress increases prosociality

Recent behavioral investigations suggest that acute stress can increase prosocial behavior. Here, we investigated whether increased empathy represents a potential mechanism for this finding. Using functional magnetic resonance imaging, we assessed the effects of acute stress on neural responses related to automatic and regulatory components of empathy for pain as well as subsequent prosocial behavior. Stress increased activation in brain areas associated with the automatic sharing of others' pain, such as the anterior insula, the anterior midcingulate cortex, and the primary somatosensory cortex. In addition, we found increased prosocial behavior under stress. Furthermore, activation in the anterior midcingulate cortex mediated the effects of stress on prosocial behavior. However, stressed participants also displayed stronger and inappropriate other-related responses in situations which required them to take the perspective of another person, and to regulate their automatic affective responses. Thus, while acute stress may increase prosocial behavior by intensifying the sharing of others' emotions, this comes at the cost of reduced cognitive appraisal abilities. Depending on the contextual constraints, stress may therefore affect empathy in ways that are either beneficial or detrimental.

Eyetracker-based gaze correction for robust mapping of population receptive fields

Functional MRI enables the acquisition of a retinotopic map that relates regions of the visual field to neural populations in the visual cortex. During such a "population receptive field" (PRF) experiment, stable gaze fixation is of utmost importance in order to correctly link the presented stimulus patterns to stimulated retinal regions and the resulting Blood Oxygen Level Dependent (BOLD) response of the appropriate region within the visual cortex. A method is described that compensates for unstable gaze fixation by recording gaze position via an eyetracker and subsequently modifies the input stimulus underlying the PRF analysis according to the eyetracking measures. Here we show that PRF maps greatly improve when the method is applied to data acquired with either saccadic or smooth eye movements. We conclude that the technique presented herein is useful for studies involving subjects with unstable gaze fixation, particularly elderly patient populations.

Reduced connectivity in the uncinate fiber tract between the frontal cortex and limbic subcortical areas in social phobia

Introduction

Several fMRI and resting-state connectivity studies have demonstrated alterations in the limbic system and frontal areas in social anxiety disorder (SAD).

Aims

Here we used high-resolution whole-brain diffusion tensor imaging (DTI) to examine differences in anatomical connectivity between patients and controls in the white matter.

Methods

We examined 14 SAD patients (age 26.3 ± 9.0y) and 15 healthy controls (age 25.6 ± 3.3y) using DTI on a 3T Trio MRI scanner (Siemens, Germany). DTI acquisition with 1.6 mm isotropic resolution was performed in 30 directions and a maximum b-value of 800. Fractional anisotropy (FA) maps were obtained using FSL. Group analysis was performed in SPM8 (two sample t-test).

Results

The figure shows a coronal slice through the uncinate fasciculus. Arrows point to areas where SAD patients show decreased FA-values compared to controls (p < 0.05). Note that these areas are limited to the uncinate fasciculus and are found bilaterally.

Conclusion

Reduced FA-values indicate a reduction in anatomical connectivity strength. Our study thus clearly shows reduced connectivity strength in the uncinate fasciculus connecting frontal regions with limbic areas as the amygdalae and hippocampus. This reduced structural connectivity supports functional data demonstrating alterations of brain activation in the amygdala and prefrontal regions in social phobia.

Combined modality chemoradiation in elderly oesophageal cancer patients

We present a single institution experience with 5-FU, mitomycin-C based chemoradiation for the primary treatment of elderly patients with oesophageal cancer. Twenty-five patients with a median age of 77 years (range 66-88) with a diagnosis of stage II-III squamous cell or adenocarcinoma of the oesophagus were treated at Memorial Sloan Kettering from 1996 to 2001 with two cycles of concurrent 5-FU, mitomycin-C and 50.4 Gy. Owing to age and comorbidity, these patients were not considered surgical candidates. The Charlson comorbidity score was used to evaluate patient comorbidity. Nine patients (36%) experienced grade 3-4 haematologic toxicity. Of the 23 patients evaluable for response, 17 patients (68%) had a negative post-treatment endoscopy and CT scan without evidence of progressive disease. Eleven patients (44%) are alive and 10 (40%) remain without evidence of recurrent or progressive oesophageal cancer at a median follow-up of 35 months. The median overall survival was 35 months and 2-year survival 64%. There was no significant difference in overall survival between Charlson score /=2 (P=0.10). Similar survival was observed for patients with adenocarcinoma or squamous carcinoma. Primary chemoradiation with two cycles of 5-FU, mitomycin-C, and 50.4 Gy in elderly patients is an active regimen with moderate toxicity, despite the advanced age and heavy comorbidity burden of this cohort. Patients with local/regional oesophageal cancer with adequate functional status should not be excluded from potentially curative treatment based on age alone.

Phase I/II study of hepatic arterial therapy with floxuridine and dexamethasone in combination with intravenous irinotecan as adjuvant treatment after resection of hepatic metastases from colorectal cancer

PURPOSE

Patients who undergo resection of liver metastases from colorectal cancer have an average 2-year survival of 65%. With hepatic arterial infusion (HAI) plus systemic fluorouracil and leucovorin, 2-year survival increased to 86%. For further improvement in both local and systemic control, combinations of new systemic drugs with HAI are being explored. The purpose of this study was to determine the maximum-tolerated dose (MTD) of systemic irinotecan (CPT-11) and HAI floxuridine (FUDR) plus dexamethasone (DEX) as combination adjuvant therapy after liver resection.

PATIENTS AND METHODS

Ninety-six patients who underwent complete resection of liver metastases from colorectal cancer were treated with six monthly cycles of HAI FUDR plus DEX for 14 days of each 4-week cycle plus escalating doses of systemic CPT-11. The primary end points of the phase I/II study were the MTD and efficacy of this regimen.

RESULTS

The MTD for combined systemic CPT-11 and HAI FUDR was CPT-11 at 200 mg/m2 every other week and FUDR at 0.12 mg/kg x pump volume / pump flow rate. The dose-limiting toxicities were diarrhea and neutropenia. With a median follow-up time of 26 months, the 2-year survival rate is 89%. All of the 27 patients who were treated at the MTD are alive.

CONCLUSION

In patients who undergo resection of liver metastases from colorectal cancer, adding systemic CPT-11 to HAI therapy in an adjuvant regimen is feasible. This regimen seems to have comparable activity to fluorouracil and leucovorin, but further studies are needed to assess whether it improves local control or decreases extrahepatic recurrences.