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Tumor treating fields increases membrane permeability in glioblastoma cells.

ABSTRACT: Glioblastoma is the most common yet most lethal of primary brain cancers with a one-year post-diagnosis survival rate of 65% and a five-year survival rate of barely 5%. Recently the U.S. Food and Drug Administration approved a novel fourth approach (in addition to surgery, radiation therapy, and chemotherapy) to treating glioblastoma; namely, tumor treating fields (TTFields). TTFields involves the delivery of alternating electric fields to the tumor but its mechanisms of action are not fully understood. Current theories involve TTFields disrupting mitosis due to interference with proper mitotic spindle assembly. We show that TTFields also alters cellular membrane structure thus rendering it more permeant to chemotherapeutics. Increased membrane permeability through the imposition of TTFields was shown by several approaches. For example, increased permeability was indicated through increased bioluminescence with TTFields exposure or with the increased binding and ingress of membrane-associating reagents such as Dextran-FITC or ethidium D or with the demonstration by scanning electron microscopy of augmented number and sizes of holes on the cellular membrane. Further investigations showed that increases in bioluminescence and membrane hole production with TTFields exposure disappeared by 24?h after cessation of alternating electric fields thus demonstrating that this phenomenom is reversible. Preliminary investigations showed that TTFields did not induce membrane holes in normal human fibroblasts thus suggesting that the phenomenom was specific to cancer cells. With TTFields, we present evidence showing augmented membrane accessibility by compounds such as 5-aminolevulinic acid, a reagent used intraoperatively to delineate tumor from normal tissue in glioblastoma patients. In addition, this mechanism helps to explain previous reports of additive and synergistic effects between TTFields and other chemotherapies. These findings have implications for the design of combination therapies in glioblastoma and other cancers and may significantly alter standard of care strategies for these diseases.

SUBMITTER: Chang E

PROVIDER: S-EPMC6281619 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Project description:Background and objective200 kHz tumor treating fields (TTFields) is clinically approved for newly-diagnosed glioblastoma (nGBM). Because its effects on conventional surveillance MRI brain scans are equivocal, we investigated its effects on perfusion MRI (pMRI) brain scans.MethodsEach patient underwent institutional standard pMRI: dynamic contrast-enhanced (DCE) and dynamic susceptibility contrast (DSC) pMRI at three time points: baseline, 2-, and 6-months on-adjuvant therapy. At each timepoint, the difference between T1 pre- versus post-contrast tumor volume (ΔT1) and these pMRI metrics were evaluated: normalized and standardized relative cerebral blood volume (nRCBV, sRCBV); fractional plasma volume (Vp), volume of extravascular extracellular space (EES) per volume of tissue (Ve), blood-brain barrier (BBB) permeability (Ktrans), and time constant for gadolinium reflux from EES back into the vascular system (Kep). Between-group comparisons were performed using rank-sum analysis, and bootstrapping evaluated likely reproducibility of the results.ResultsAmong 13 pMRI datasets (11 nGBM, 2 recurrent GBM), therapies included temozolomide-only (n = 9) and temozolomide + TTFields (n = 4). No significant differences were found in patient or tumor characteristics. Compared to temozolomide-only, temozolomide + TTFields did not significantly affect the percent-change in pMRI metrics from baseline to 2 months. But during the 2- to 6-month period, temozolomide + TTFields significantly increased the percent-change in nRCBV (+26.9% [interquartile range 55.1%] vs -39.1% [37.0%], p = 0.049), sRCBV (+9.5% [39.7%] vs -30.5% [39.4%], p = 0.049), Ktrans (+54.6% [1768.4%] vs -26.9% [61.2%], p = 0.024), Ve (+111.0% [518.1%] vs -13.0% [22.5%], p = 0.048), and Vp (+98.8% [2172.4%] vs -24.6% [53.3%], p = 0.024) compared to temozolomide-only.ConclusionUsing pMRI, we provide initial in-human validation of pre-clinical studies regarding the effects of TTFields on tumor blood volume and BBB permeability in GBM.

Project description:BackgroundTo date, there has been no large-scale, real-world study of the health-related quality of life outcomes for patients using tumor treating fields (TTFields) therapy for glioblastoma (GBM) treatment.MethodsA survey was mailed to 2,815 patients actively using TTFields for treatment of GBM in the USA (n = 2,182) and Europe (n = 633). The survey included patient-reported demographic and clinical information, as well as EuroQol's EQ-5D-5L and visual analogue scale (EQ-VAS) overall health score.ResultsA total of 1,106 applicable patients responded to the survey (USA = 782 and Europe = 324), with a mean age of 58.6 years (SD = 12.3). The average time since diagnosis and time using TTFields were 21.5 months (SD = 25.1) and 13.5 months (SD = 13.2), respectively. Over 61% of patients had been diagnosed at least 1 year prior and 28.4% at least 2 years prior; 45 patients (4.2%) had been diagnosed at least 5 years prior. Progressed disease was reported in 307 patients, while 690 reported non-progressed disease. Regression analyses showed that GBM disease progression and older age had predictable negative associations (p < 0.001) with most EQ-5D-5L dimensions and the EQ-VAS. However, longer time since diagnosis was associated with improved self-care (p < 0.05), usual activities (p < 0.01), and EQ-VAS (p < 0.05) overall and in patients with progressed disease (p < 0.01, p < 0.05, and p < 0.01, respectively). Additionally, longer time using TTFields was associated with improved mobility (p < 0.05), self-care (p < 0.001), usual activities (p < 0.01), and EQ-VAS (p < 0.01) overall; with improved EQ-VAS in progression-free patients (p < 0.05); and with improved mobility (p < 0.05), self-care (p < 0.01), usual activities (p < 0.05), and EQ-VAS (p < 0.05) in patients with progressed disease.ConclusionThis is the largest real-world study of patient-reported quality of life in GBM and TTFields treatment to date. It shows unsurprising negative associations between quality of life and disease progression and older age, as well as more novel, positive associations between quality of life and longer time since diagnosis and time using TTFields therapy.

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Tumor treating fields increases membrane permeability in glioblastoma cells.

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