Marlies Wagner

Dual targeting of glioblastoma with chimeric antigen receptor-engineered natural killer cells overcomes heterogeneity of target antigen expression and enhances antitumor activity and survival

ABSTRACT Epidermal growth factor receptor (EGFR) and its mutant form EGFRvIII are overexpressed in a large proportion of glioblastomas (GBM). Immunotherapy with an EGFRvIII-specific vaccine has shown efficacy against GBM in clinical studies. However, immune escape by antigen-loss variants and lack of control of EGFR wild-type positive clones limit the usefulness of this approach. Chimeric antigen receptor (CAR)-engineered natural killer (NK) cells may represent an alternative immunotherapeutic strategy. For targeting to GBM, we generated variants of the clinically applicable human NK cell line NK-92 that express CARs carrying a composite CD28-CD3ζ domain for signaling, and scFv antibody fragments for cell binding either recognizing EGFR, EGFRvIII, or an epitope common to both antigens. In vitro analysis revealed high and specific cytotoxicity of EGFR-targeted NK-92 against established and primary human GBM cells, which was dependent on EGFR expression and CAR signaling. EGFRvIII-targeted NK-92 only lysed EGFRvIII-positive GBM cells, while dual-specific NK cells expressing a cetuximab-based CAR were active against both types of tumor cells. In immunodeficient mice carrying intracranial GBM xenografts either expressing EGFR, EGFRvIII or both receptors, local treatment with dual-specific NK cells was superior to treatment with the corresponding monospecific CAR NK cells. This resulted in a marked extension of survival without inducing rapid immune escape as observed upon therapy with monospecific effectors. Our results demonstrate that dual targeting of CAR NK cells reduces the risk of immune escape and suggest that EGFR/EGFRvIII-targeted dual-specific CAR NK cells may have potential for adoptive immunotherapy of glioblastoma.

Quantitative T*2-mapping based on multi-slice multiple gradient echo flash imaging: retrospective correction for subject motion effects.

Numerous clinical and research applications for quantitative mapping of the effective transverse relaxation time T*2 have been described. Subject motion can severely deteriorate the quality and accuracy of results. A correction method for T*2 maps acquired with multi‐slice multiple gradient echo FLASH imaging is presented, based on acquisition repetition with reduced spatial resolution (and consequently reduced acquisition time) and weighted averaging of both data sets, choosing weighting factors individually for each k‐space line to reduce the influence of motion. In detail, the procedure is based on the fact that motion artifacts reduce the correlation between acquired and exponentially fitted data. A target data set is constructed in image space, choosing the data yielding best correlation from the two acquired data sets. The k‐space representation of the target is subsequently approximated as linear combination of original raw data, yielding the required weighting factors. As this method only requires a single acquisition repetition with reduced spatial resolution, it can be employed on any clinical system offering a suitable sequence with export of modulus and phase images. Experimental results show that the method works well for sparse motion, but fails for strong motion affecting the same k‐space lines in both acquisitions. Magn Reson Med, 2011.

Within-lesion differences in quantitative MRI parameters predict contrast enhancement in multiple sclerosis.

To investigate the relationship between quantitative magnetic resonance imaging (qMRI) and contrast enhancement in multiple sclerosis (MS) lesions. We compared maps of T1 relaxation time, proton density (PD), and magnetization transfer ratio (MTR) between lesions with and without contrast enhancement as quantified by the amount of T1 shortening postcontrast agent (CA).

Age-Related Changes of Cerebral Autoregulation: New Insights with Quantitative T2′-Mapping and Pulsed Arterial Spin-Labeling MR Imaging

BACKGROUND AND PURPOSE: Cerebral perfusion and O2 metabolism are affected by physiologic age-related changes. High-resolution motion-corrected quantitative T2′-imaging and PASL were used to evaluate differences in deoxygenated hemoglobin and CBF of the gray matter between young and elderly healthy subjects. Further combined T2′-imaging and PASL were investigated breathing room air and 100% O2 to evaluate age-related changes in cerebral autoregulation. MATERIALS AND METHODS: Twenty-two healthy volunteers 60–88 years of age were studied. Two scans of high-resolution motion-corrected T2′-imaging and PASL-MR imaging were obtained while subjects were either breathing room air or breathing 100% O2. Manual and automated regions of interest were placed in the cerebral GM to extract values from the corresponding maps. Results were compared with those of a group of young healthy subjects previously scanned with the identical protocol as that used in the present study. RESULTS: There was a significant decrease of cortical CBF (P < .001) and cortical T2′ values (P < .001) between young and elderly healthy subjects. In both groups, T2′ remained unchanged under hyperoxia compared with normoxia. Only in the younger but not in the elderly group could a significant (P = .02) hyperoxic-induced decrease of the CBF be shown. CONCLUSIONS: T2′-mapping and PASL in the cerebral cortex of healthy subjects revealed a significant decrease of deoxygenated hemoglobin and of CBF with age. The constant deoxyHb level breathing 100% O2 compared with normoxia in young and elderly GM suggests an age-appropriate cerebral autoregulation. At the younger age, hyperoxic-induced CBF decrease may protect the brain from hyperoxemia.

T2′ Imaging Within Perfusion-Restricted Tissue in High-Grade Occlusive Carotid Disease

Background and Purpose— Quantitative T2′ imaging presumably detects regional changes in the relation of oxygenated and deoxygenated hemoglobin. Regional differences in hemoglobin oxygenation might reflect areas with increased oxygen extraction for compensation of reduced perfusion pressure. We investigated quantitative T2′ imaging in patients with high-grade stenoses of brain-supplying arteries and hypothesized that T2′ values are lower in perfusion-restricted areas as compared with normally perfused tissue. Methods— Eighteen patients (15 men; mean age±SD, 54±12.8 years) with unilateral symptomatic or asymptomatic high-grade extracranial or intracranial internal carotid artery or proximal middle cerebral artery stenosis/occlusion were included. MR examination included perfusion-weighted imaging and quantitative, motion-corrected mapping of T2′ time. Time-to-peak and mean transit time maps were thresholded for different degrees of perfusion delays (eg, >0 seconds, ≥2 seconds) compared with the contralateral hemisphere. Mean T2′ values in areas of impaired perfusion were compared with T2′ values in corresponding contralateral or ipsilateral, normoperfused areas. Results— Mean size of perfusion-impaired areas in time-to-peak maps (time-to-peak delay >0 seconds) was 10.8 mL (±6.3) and 11.5 mL (±6.4) in mean transit time maps (mean transit time delay >0 seconds). T2′ values were significantly (P<0.01) lower in all perfusion-restricted compared with corresponding contralateral brain areas (ipsilateral versus contralateral). For time-to-peak delay >0 seconds, T2′ values were 115 ms (±9) versus 125 ms (±12). For mean transit time delay >0 seconds, T2′ values were 115 ms (±9) versus 128 ms (±10). Differences in T2′ values increased with the severity of the perfusion delay. Ipsilateral T2′ values outside the perfusion-disturbed areas did not differ from contralateral T2′ values. Conclusions— Motion-corrected T2′ imaging presumably detects areas with increased oxygen extraction within perfusion-restricted tissue in patients with high-grade occlusive vessel disease.

Quantitative T2′-Mapping in Acute Ischemic Stroke

Background and Purpose— Quantitative T2′-mapping detects regional changes in the relation of oxygenated and deoxygenated haemoglobine and might reflect areas with increased oxygen extraction. T2′-mapping in conjunction with an elaborate algorithm for motion correction was performed in patients with acute large-vessel stroke, and quantitative T2′-values were determined within the diffusion-weighted imaging lesion and perfusion-restricted tissue. Methods— Eleven patients (median age, 71 years) with acute middle cerebral or internal carotid artery occlusion underwent MRI before scheduled endovascular treatment. MR-examination included diffusion- and perfusion-weighted imaging and quantitative, motion-corrected mapping of T2′. Time-to-peak maps were thresholded for different degrees of perfusion delays (eg, ≥0 s, ≥ 2s) when compared with a reference time-to-peak value from healthy contralateral tissue. Mean T2′-values in areas with reduced apparent diffusion coefficient and in areas with impaired perfusion were compared with T2′-values in corresponding contralateral areas. Results— Median time between symptom onset and MRI was 238 minutes. T2′-values were significantly reduced within the apparent diffusion coefficient -lesion when compared with contralateral healthy tissue (83 ms [67, 97] versus 97 ms [91, 111]; P<0.003). In perfusion-restricted tissue, T2′-values were also significantly lower when compared with contralateral healthy tissue (ie, for time to peak, ≥0 s 93 ms [86, 102] versus 104 [90, 110]; P=0.008) but were significantly higher than within the apparent diffusion coefficient lesion. The severity of the perfusion impairment had no influence on median T2′-values. Conclusions— Motion-corrected T2′-mapping reveals significant and gradually declining values from healthy to perfusion-disturbed to apparent diffusion coefficient-restricted tissue. Current T2′-mapping can differentiate between the ischemic core and the perfusion-impaired areas but not on its own between penumbral and oligemic tissue.

The U Sign: Tenth Landmark to the Central Region on Brain Surface Reformatted MR Imaging

BACKGROUND AND PURPOSE: Identification of the central region is of special importance to avoid neurologic deficits in brain surgery. Brain surface reformatted images (Mercator view) map the frontoparietal brain surface in 1 view and provide a synopsis of the most important landmarks. In this view, the U-shaped subcentral gyrus appears as a distinctive anatomic structure enclosing the Sylvian end of the central sulcus. The purpose of this study was to add the subcentral gyrus as a new landmark to the central region (U sign) and to compare its frequency and applicability with common landmarks in healthy hemispheres. MATERIALS AND METHODS: Mercator views of 178 hemispheres in 100 patients were generated from 3D MR imaging datasets. The hemispheres were evaluated on Mercator views for the presence or absence of each of the 9 common landmarks and the new U sign identifying the central region. RESULTS: The new landmark U sign was most common (96.6%), followed by the thin postcentral gyrus sign (95.5%). The least common landmark was the Ω-shaped handknob (54.5%). None of the landmarks could be identified in all hemispheres. All landmarks could be identified bilaterally in only 1.3% of patients. CONCLUSIONS: On the Mercator view, the new U sign is an applicable and even the most frequent landmark to identify the central region. Considering the variability of the anatomic structures of the brain, including the motor hand area, the synopsis of all 10 landmarks on this surface-reformatting projection is a helpful adjunct to standard MR imaging projections to identify the central region.

Increased risk of delayed cerebral ischemia in subarachnoid hemorrhage patients with additional intracerebral hematoma.

OBJECTIVE Delayed cerebral ischemia (DCI) has a major impact on the outcome of patients suffering from aneurysmal subarachnoid hemorrhage (SAH). The aim of this study was to assess the influence of an additional intracerebral hematoma (ICH) on the occurrence of DCI. METHODS The authors conducted a single-center retrospective analysis of cases of SAH involving patients treated between 2006 and 2011. Patients who died or were transferred to another institution within 10 days after SAH without the occurrence of DCI were excluded from the analysis. RESULTS Additional ICH was present in 123 (24.4%) of 504 included patients (66.7% female). ICH was classified as frontal in 72 patients, temporal in 24, and perisylvian in 27. DCI occurred in 183 patients (36.3%). A total of 59 (32.2%) of these 183 patients presented with additional ICH, compared with 64 (19.9%) of the 321 without DCI (p = 0.002). In addition, DCI was detected significantly more frequently in patients with higher World Federation of Neurosurgical Societies (WFNS) grades. The authors compared the original and modified Fisher Scales with respect to the occurrence of DCI. The modified Fisher Scale (mFS) was superior to the original Fisher Scale (oFS) in predicting DCI. Furthermore, they suggest a new classification based on the mFS, which demonstrates the impact of additional ICH on the occurrence of DCI. After the different scales were corrected for age, sex, WFNS score, and aneurysm site, the oFS no longer was predictive for the occurrence of DCI, while the new scale demonstrated a superior capacity for prediction as compared with the mFS. CONCLUSIONS Additional ICH was associated with an increased risk of DCI in this study. Furthermore, adding the presence or absence of ICH to the mFS improved the identification of patients at the highest risk for the development of DCI. Thus, a simple adjustment of the mFS might help to identify patients at high risk for DCI.

Quantitative T2, T2*, and T2′ MR imaging in patients with ischemic leukoaraiosis might detect microstructural changes and cortical hypoxia

IntroductionQuantitative MRI with T2, T2*, and T2′ mapping has been shown to non-invasively depict microstructural changes (T2) and oxygenation status (T2* and T2′) that are invisible on conventional MRI. Therefore, we aimed to assess whether T2 and T2′ quantification detects cerebral (micro-)structural damage and chronic hypoxia in lesions and in normal appearing white matter (WM) and gray matter (GM) of patients with ischemic leukoaraiosis (IL). Measurements were complemented by the assessment of the cerebral blood flow (CBF) and the degree of GM and WM atrophy.MethodsEighteen patients with IL and 18 age-matched healthy controls were included. High-resolution, motion-corrected T2, T2*, and T2′ mapping, CBF mapping (pulsed arterial spin labeling, PASL), and segmentation of GM and WM were used to depict specific changes in both groups. All parameters were compared between patients and healthy controls, using t testing. Values of p < 0.05 were accepted as statistically significant.ResultsPatients showed significantly increased T2 in lesions (p < 0.01) and in unaffected WM (p = 0.045) as well as significantly increased T2* in lesions (p = 0.003). A significant decrease of T2′ was detected in patients in unaffected WM (p = 0.027), while no T2′ changes were observed in GM (p = 0.13). Both unaffected WM and GM were significantly decreased in volume in the patient-group (p < 0.01). No differences of PASL-based CBF could be shown.ConclusionNon-invasive quantitative MRI with T2, T2*, and T2′ mapping might be used to detect subtle structural and metabolic changes in IL. Assessing the grade of microstructural damage and hypoxia might be helpful to monitor disease progression and to perform risk assessment.

T2′- and PASL-based perfusion mapping at 3 Tesla: influence of oxygen-ventilation on cerebral autoregulation

To use T2′‐mapping together with Pulsed Arterial Spin Labeling (PASL) providing quantitative information of deoxygenation level and cerebral blood flow (CBF) in the cerebral gray matter to obtain simultaneous information about the cerebral oxygen metabolism and the resulting cerebral vasoreactivity under normoxic and hyperoxic conditions.