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Garth Powis

Bio: Garth Powis is an academic researcher from Discovery Institute. The author has contributed to research in topics: Thioredoxin & Thioredoxin reductase. The author has an hindex of 57, co-authored 194 publications receiving 11475 citations. Previous affiliations of Garth Powis include University of Texas Health Science Center at Houston & Mayo Clinic.


Papers
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Journal ArticleDOI
TL;DR: Single-agent vemurafenib did not show meaningful clinical activity in patients with BRAF V600E mutant CRC, and combination strategies are now under development and may be informed by the presence of intratumor heterogeneity of KRAS and NRAS mutations.
Abstract: Purpose BRAF V600E mutation is seen in 5% to 8% of patients with metastatic colorectal cancer (CRC) and is associated with poor prognosis. Vemurafenib, an oral BRAF V600 inhibitor, has pronounced activity in patients with metastatic melanoma, but its activity in patients with BRAF V600E–positive metastatic CRC was unknown. Patients and Methods In this multi-institutional, open-label study, patients with metastatic CRC with BRAF V600 mutations were recruited to an expansion cohort at the previously determined maximum-tolerated dose of 960 mg orally twice a day. Results Twenty-one patients were enrolled, of whom 20 had received at least one prior metastatic chemotherapy regimen. Grade 3 toxicities included keratoacanthomas, rash, fatigue, and arthralgia. Of the 21 patients treated, one patient had a confirmed partial response (5%; 95% CI, 1% to 24%) and seven other patients had stable disease by RECIST criteria. Median progression-free survival was 2.1 months. Patterns of concurrent mutations, microsatellit...

551 citations

Journal ArticleDOI
TL;DR: The mammalian thioredoxins are a family of small redox proteins that undergo NADPH-dependent reduction by thiOREDoxin reductase and in turn reduce oxidized cysteine groups on proteins.
Abstract: The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin-1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.

534 citations

Journal ArticleDOI
Garth Powis1
TL;DR: The evidence for a relationship between radical formation and the biological activity of the antitumor quinones is evaluated and it is suggested that cardiotoxicity and skin toxicity may also be related to oxygen radical formation.

407 citations

Journal Article
TL;DR: The results suggest that Trx-1 increases HIF-1alpha protein levels in cancer cells and increases VEGF production and tumor angiogenesis.
Abstract: Hypoxia-inducible factor 1 (HIF-1), a heterodimer of HIF-1alpha and HIF-1beta subunits, is a transcriptional activator central to the cellular response to low oxygen that includes metabolic adaptation, angiogenesis, metastasis, and inhibited apoptosis. Thioredoxin-1 (Trx-1) is a small redox protein overexpressed in a number of human primary tumors. We have examined the effects of Trx-1 on HIF activity and the activation of downstream genes. Stable transfection of human breast carcinoma MCF-7 cells with human Trx-1 caused a significant increase in HIF-1alpha protein levels under both normoxic (20% oxygen) and hypoxic (1% oxygen) conditions. Trx-1 increased hypoxia-induced HIF-1 transactivation activity measured using a luciferase reporter under the control of the hypoxia response element. Changes in HIF-1alpha mRNA levels did not account for the changes observed at the protein level, and HIF-1beta protein levels did not change. Trx-1 transfection also caused a significant increase in the protein products of hypoxia-responsive genes, including vascular endothelial growth factor (VEGF) and nitric oxide synthase 2 in a number of different cell lines (MCF-7 human breast and HT29 human colon carcinomas and WEHI7.2 mouse lymphoma cells) under both normoxic and hypoxic conditions. The pattern of expression of the different isoforms of VEGF was not changed by Trx-1. Transfection of a redox-inactive Trx-1 (C32S/C35S) markedly decreased levels of HIF-1alpha protein, HIF-1 transactivating activity, and VEGF protein in MCF-7 cells compared with empty vector controls. In vivo studies using WEHI7.2 cells transfected with Trx-1 showed significantly increased tumor VEGF and angiogenesis. The results suggest that Trx-1 increases HIF-1alpha protein levels in cancer cells and increases VEGF production and tumor angiogenesis.

355 citations

Journal ArticleDOI
TL;DR: The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by Thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins as mentioned in this paper.
Abstract: The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin- 1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.

342 citations


Cited by
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Journal ArticleDOI
TL;DR: Attention is focussed on the ROS/RNS-linked pathogenesis of cancer, cardiovascular disease, atherosclerosis, hypertension, ischemia/reperfusion injury, diabetes mellitus, neurodegenerative diseases, rheumatoid arthritis, and ageing.

12,240 citations

Journal ArticleDOI
TL;DR: Hypoxia-inducible factor 1 (HIF-1) activates the transcription of genes that are involved in crucial aspects of cancer biology, including angiogenesis, cell survival, glucose metabolism and invasion.
Abstract: Hypoxia-inducible factor 1 (HIF-1) activates the transcription of genes that are involved in crucial aspects of cancer biology, including angiogenesis, cell survival, glucose metabolism and invasion. Intratumoral hypoxia and genetic alterations can lead to HIF-1alpha overexpression, which has been associated with increased patient mortality in several cancer types. In preclinical studies, inhibition of HIF-1 activity has marked effects on tumour growth. Efforts are underway to identify inhibitors of HIF-1 and to test their efficacy as anticancer therapeutics.

6,024 citations

Journal ArticleDOI
TL;DR: It is argued that modulating the unique redox regulatory mechanisms of cancer cells might be an effective strategy to eliminate these cells.
Abstract: Increased generation of reactive oxygen species (ROS) and an altered redox status have long been observed in cancer cells, and recent studies suggest that this biochemical property of cancer cells can be exploited for therapeutic benefits. Cancer cells in advanced stage tumours frequently exhibit multiple genetic alterations and high oxidative stress, suggesting that it might be possible to preferentially eliminate these cells by pharmacological ROS insults. However, the upregulation of antioxidant capacity in adaptation to intrinsic oxidative stress in cancer cells can confer drug resistance. Abrogation of such drug-resistant mechanisms by redox modulation could have significant therapeutic implications. We argue that modulating the unique redox regulatory mechanisms of cancer cells might be an effective strategy to eliminate these cells.

4,369 citations

Journal ArticleDOI
TL;DR: In this article, the authors propose that persistent metabolism of glucose to lactate even in aerobic conditions is an adaptation to intermittent hypoxia in pre-malignant lesions, which leads to microenvironmental acidosis requiring evolution to phenotypes resistant to acid-induced cell toxicity.
Abstract: If carcinogenesis occurs by somatic evolution, then common components of the cancer phenotype result from active selection and must, therefore, confer a significant growth advantage. A near-universal property of primary and metastatic cancers is upregulation of glycolysis, resulting in increased glucose consumption, which can be observed with clinical tumour imaging. We propose that persistent metabolism of glucose to lactate even in aerobic conditions is an adaptation to intermittent hypoxia in pre-malignant lesions. However, upregulation of glycolysis leads to microenvironmental acidosis requiring evolution to phenotypes resistant to acid-induced cell toxicity. Subsequent cell populations with upregulated glycolysis and acid resistance have a powerful growth advantage, which promotes unconstrained proliferation and invasion.

4,361 citations

Journal ArticleDOI
TL;DR: Estimates can be used to more fully understand the redox biochemistry that results from oxidative stress, which hopefully will provide a rationale and understanding of the cellular mechanisms associated with cell growth and development, signaling, and reductive or oxidative stress.

4,274 citations