Oxidative Stress In Tumor Cells Research Articles

NSAIDs-induced oxidative stress sensitizes tumor cells to T cell cytotoxicity through the TRAIL-DR5 axis

Abstract Adoptive T cell therapy (ACT) has shown promising therapeutic outcomes in patients with hematological malignancies. However, the success of ACT is limited to a small fraction of treated patients. Hence, developing new strategies to enhance the potency of ACT are urgently needed for better therapeutic outcomes. Our previous study demonstrated that inducing oxidative stress in tumor cells is critically involved in tumor rejection by ACT. In the current study, we report that indomethacin, a prototypical non-steroidal anti-inflammatory drug (NSAID), can intensify ROS in tumor cells and sensitize them to ACT. Mechanistically, our data indicate that indomethacin treatment leads to enhanced expression of death receptor 5 (DR5) in tumor cells, rendering them more susceptible to TNF-related apoptosis-inducing ligand (TRAIL)-induced cell death. We found that tumor-specific T cells upregulated TRAIL expression upon adoptive transfer. Using genetic-based approaches, we showed that DR5-deficient tumor cells were unresponsive to the beneficial effect of indomethacin, while overexpressing TRAIL in donor T cells led to further improvement in mouse survival. Collectively, our study demonstrates that the pro-oxidative feature of selected NSAIDs can be exploited to augment the efficacy of T cell therapy. Our findings provide a strong rationale for targeting tumor redox to achieve more effective tumor destruction through the combination of pro-oxidants and ACT.

Syntheses of metal oxide-gold nanocomposites for biological applications

A range of synthetic approaches for metal oxide-gold nanocomposites from conventional method such as chemical vapor deposition (CVD), pulse laser ablation to more simple and facile synthetic approaches using mild condition have been discussed. These nanocomposites have found diverse potential biological applications including cell imaging, photothermal therapy, chemotherapy, radiotherapy, determining oxidative stress in tumor cells, glucose oxidation, enzyme mimic activity, nitrogen fixation and diagnosis purpose such as detecting cancer biomarkers such as prostate protein antigen (PSA), alpha fetoprotein (AFP), melanoma adhesion molecule antigen (CD146), DNA sensing. The biosensing applications along with quantitative estimation of bioanalytes such as choline (CHO), NADH, epinephrine (EP), 17β-estradiol (E2), uric acid (UA), ascorbic acid (AA), glucose and dopamine, α-synuclein, amyloid beta (Aβ) peptide, glutathione (GSH), calcium dipicolinate have been explored with these nanocomposites as platforms. Abnormal levels of hydrazine (principal component of various pharmaceutical derivative), Cr(VI), tertracyclin (broad spectrum antibiotic), 6-mercaptopurine (anticancer drug), Bisphenol A (BPA), chlorpyrifos and carbamate pesticides have been estimated with these metal oxide-gold nanocomposites. Various detection strategies for quantitative analysis based on electrochemical, fluorometric and colorimetric methods have been briefly summarized.

One-Step Integration of Tumor Microenvironment-Responsive Calcium and Copper Peroxides Nanocomposite for Enhanced Chemodynamic/Ion-Interference Therapy.

Recently, various metal peroxide nanomaterials have drawn increasing attention as an efficient hydrogen peroxide (H2O2) self-supplying agent for enhanced tumor therapy. However, a single kind of metal peroxide is insufficient to achieve more effective antitumor performance. Here, a hyaluronic acid modified calcium and copper peroxides nanocomposite has been synthesized by a simple one-step strategy. After effective accumulation at the tumor site due to the enhanced permeability and retention (EPR) effect and specific recognition of hyaluronate acid with CD44 protein on the surface of tumor cells, plenty of Ca2+, Cu2+, and H2O2 can be simultaneously released in acid and hyaluronidase overexpressed tumor microenvironment (TME), generating abundant hydroxyl radical through enhanced Fenton-type reaction between Cu2+ and self-supplying H2O2 with the assistance of glutathione depletion. Overloaded Ca2+ can lead to mitochondria injury and thus enhance the oxidative stress in tumor cells. Moreover, an unbalanced calcium transport channel caused by oxidative stress can further promote tumor calcification and necrosis, which is generally defined as ion-interference therapy. As a result, the synergistic effect of Fenton-like reaction by Cu2+ and mitochondria dysfunction by Ca2+ in ROS generation is performed. Therefore, a TME-responsive calcium and copper peroxides nanocomposite based on one-step integration has been successfully established and exhibits a more satisfactory antitumor efficiency than any single kind of metal peroxide.

Multifunctional carbon monoxide nanogenerator as immunogenic cell death drugs with enhanced antitumor immunity and antimetastatic effect

The limited effect of immune checkpoint blockade (ICB) immunotherapy is subjected to the immuno-suppressive tumor microenvironment (TME). It is still a challenge to reverse the immune-suppressive state in clinical cancer therapy. Immunogenic cell death (ICD) is a way for inducing the therapeutical tumor immune system. In this work, carbon monoxide (CO) gas therapy is used to boost antitumor immunity for tumor control, metastasis and recurrence prevention. Briefly, CO2-g–C3N4–Au@ZIF-8@F127 (CCAZF) is proposed to integrate gas therapy and immunotherapy into a photocatalytic nanogenerator for overcoming the limitations of monotherapy. CCAZF exhibits a highly effective light-controllable release behavior of CO, which gradually aggravates the oxidative stress in tumor cells to induce ICD. With the induction of ICD, CO therapy enhances immune responses and enables efficient immune cells activated. When combined with ICB, CCAZF displays an enhanced immune effect, which mediates the regression of primary and distal tumors. This strategy of in-situ photocatalytic CO therapy furthest avoids the toxicity from CO leakage and provides a new method to design novel ICD inducers.

Arsenene Nanodots with Selective Killing Effects and their Low-Dose Combination with ß-Elemene for Cancer Therapy.

Arsenical drugs have achieved hallmark success in treating patients with acute promyelocytic leukemia, but expanding their clinical utility to solid tumors has proven difficult with the contradiction between the therapeutic efficacy and the systemic toxicity. Here, leveraging efforts from materials science, biocompatible PEGylated arsenene nanodots (AsNDs@PEG) with high monoelemental arsenic purity that can selectively and effectively treat solid tumors are synthesized. The intrinsic selective killing effect of AsNDs@PEG is closely related to high oxidative stress in tumor cells, which leads to an activated valence-change of arsenic (from less toxic As0 to severely toxic oxidation states), followed by decreased superoxide dismutase activity and massive reactive oxygen species (ROS) production. These effects occur selectively within cancer cells, causing mitochondrial damage, cell-cycle arrest, and DNA damage. Moreover, AsNDs@PEG when applied in a multi-drug combination strategy with β-elemene, a plant-derived anticancer drug, achieves synergistic antitumor outcomes, and its newly discovered on-demand photothermal properties facilitate the elimination of the tumors without recurrence, potentially further expanding its clinical utility. In line of the practicability for a large-scale fabrication and negligible systemic toxicity of AsNDs@PEG (even at high doses and with repetitive administration), a new-concept arsenical drug with high therapeutic efficacy for selective solid tumor therapy is provided.

SUCLA2-coupled regulation of GLS succinylation and activity counteracts oxidative stress in tumor cells

Glutaminase regulates glutaminolysis to promote cancer cell proliferation. However, the mechanism underlying glutaminase activity regulation is largely unknown. Here, we demonstrate that kidney-type glutaminase (GLS) is highly expressed in human pancreatic ductal adenocarcinoma (PDAC) specimens with correspondingly upregulated glutamine dependence for PDAC cell proliferation. Upon oxidative stress, the succinyl-coenzyme A (CoA) synthetase ADP-forming subunit β (SUCLA2) phosphorylated by p38 mitogen-activated protein kinase (MAPK) at S79 dissociates from GLS, resulting in enhanced GLS K311 succinylation, oligomerization, and activity. Activated GLS increases glutaminolysis and the production of nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione, thereby counteracting oxidative stress and promoting tumor cell survival and tumor growth in mice. In addition, the levels of SUCLA2 pS79 and GLS K311 succinylation, which were mutually correlated, were positively associated with advanced stages of PDAC and poor prognosis for patients. Our findings reveal critical regulation of GLS by SUCLA2-coupled GLS succinylation regulation and underscore the regulatory role of metabolites in glutaminolysis and PDAC development.

Bioresponsive prodrug nanogel-based polycondensate strategy deepens tumor penetration and potentiates oxidative stress

• A bioresponsive DPH prodrug nanogels were synthesized by conjugating purpurin 18 with 10-hydroxycamplothecin. • The high glutathione will be consumed, and ROS can be generated after laser irradiation. • Excess ROS damages the mitochondria, thus exhibit low Δψm, exerting long-term oxidative stress. • The DPH nanogel showed an enhanced chemo-photodynamic therapy with real-time MR/NIRF dual-modal imaging. Currently single photosensitizers or chemotherapeutics implemented in clinic present huge challenges in terms of non-selective toxicity, physiological instability and unfavorable therapeutic efficacy. Herein, we designed a versatile polycondensate-based strategy for the preparation of redox-responsive prodrug nanogels (NGs) for enhanced synergistic cancer therapy. Concretely, based on a reductive cross-linking of purpurin 18 (P18) and 10-hydroxycamplothecin (HCPT), a well-designed prodrug nanogel (denoted as DPH NGs) with suitable size (~67 nm) was fabricated, which exhibited high drug loading, controlled drug release and deepened tumor penetration. The high concentration of glutathione (GSH) in the tumor microenvironment (TME) is capable of being consumed by dense disulfide bonds in DPH NGs, promoting the generation of reactive oxygen species (ROS) after irradiation at 660 nm, thus reshape the TME to reinforce photodynamic therapy against malignancies. In addition, P18 can be served as a powerful NIR fluorescence (NIRF)/ magnetic resonance (MR) imaging ability. Pleasantly, DPH NGs showed amplified oxidative stress in tumor cells to achieve an enhanced chemo-photodynamic therapy with the real-time MR/NIRF dual-modal imaging. Our findings in this study may blow up a storm for devising a simple and versatile strategies for multi-drug delivery and combined cancer therapy.

Cancer-associated Cachexia, Reactive Oxygen Species and Nutrition Therapy

Cancer-related Cachexia (CAC) is a syndrome occurring in many cancer patients, with a detrimental effect on their survival. Recent reports have outlined that the syndrome may be partly explained by the deleterious and pro-inflammatory action of Reactive Oxygen Species (ROS). This review focuses on nutrients that theoretically could counteract the oxidative stress in tumor cells, fundamentally due to their antioxidant activity. The preclinical and clinical results obtained with the nutritional elements selenium, melatonin, taurine, carnosine, coenzyme Q10 (ubiquinone), and omega-3 polyunsaturated fatty acids (PUFA's) are discussed in the light of the pathophysiology of CAC. This should indicate that they are viable candidates for the treatment of CAC, with the ultimate goal to promote patient survival. Combination therapy with diet modification added to the novel pharmaceutical agent ghrelin, a hormone with anti-inflammatory properties, represents a promising concept.

Abstract 4095: Adding fuel to the fire: Augmenting the efficacy of adoptive T-cell therapy with pro-oxidants

Abstract Cancer cells face increased oxidative stress driven by oncogene activation, tumor suppressor gene mutation and increased metabolism. Even though cancer cells can resist this redox imbalance by activating various antioxidant defense mechanisms, they are more susceptible to further redox disruption by pro-oxidants. Our previous study indicated that adoptive T-cell therapy (ACT) leads to heightened oxidative stress in tumor cells reflected by depletion of cellular antioxidant glutathione (GSH), accumulation of reactive oxygen species (ROS), and presence of oxidative DNA damages. Based on this observation, we propose that intensifying oxidative stress in tumor with pro-oxidants can sensitize cancer cells to ACT and lead to improved therapeutic outcomes. In this study, we used clinically relevant ACT models to screen a panel of pro-oxidant agents for their ability to potentiate the antitumor effects of ACT. We identified several clinically applicable pro-oxidants, including some commonly used non-steroidal anti-inflammatory drugs (NSAIDs), that can benefit the infusion of tumor-specific CD4+ T cells or CD19-targeting CAR T cells. Our data provide a rationale for combining selected pro-oxidants with ACT to achieve synergistic antitumor effect. Citation Format: Nada Aboelella, Gang Zhou, Kateryna Fesenkova, Zhi-chun Ding. Adding fuel to the fire: Augmenting the efficacy of adoptive T-cell therapy with pro-oxidants [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 4095.

IL-8 protects prostate cancer cells from GSK-3β-induced oxidative stress by activating the mTOR signaling pathway.

Both oxidative stress and inflammation play important roles in prostate cancer cell apoptosis or proliferation; however, the mechanisms underlying these processes remain unclear. Thus, we selected interleukin-8 (IL-8) as the bridge between inflammation and cancer cell oxidative stress-induced death and aimed to confirm its connection with mTOR and Glycogen synthase kinase-3 beta (GSK-3β). We overexpressed GSK-3β and observed its effect on reactive oxygen species (ROS) and oxidative stress-induced cell death. IL-8 was then upregulated or downregulated to determine its impact on preventing cell damage due to GSK-3β-induced oxidative stress. In addition, we overexpressed or knocked down mTOR to confirm its role in this process. Real-time PCR, Western blotting, transcription, Cell Counting Kit 8 (CCK-8), and flow cytometry analyses were performed in addition to the use of other techniques. IL-8 promotes prostate cancer cell proliferation and decreases apoptosis, whereas GSK-3β activates the caspase-3 signaling pathway by increasing ROS and thereby induces oxidative stress-mediated cell death. In addition, mTOR can also decrease activation of the caspase-3 signaling pathway by inhibiting GSK-3 and thus decreasing ROS production. Moreover, the inhibitory effect of IL-8 on GSK-3β occurs through the regulation of mTOR. The results of this study highlight the importance of GSK-3β, which increases the production of ROS and thereby induces oxidative stress in tumor cells, whereas IL-8 and mTOR attenuate oxidative stress to protect prostate cancer cells through inhibition of GSK-3β.

Induction of Oxidative Stress in Tumor Cells: A New Strategy for Drug Therapy of Malignant Tumors

Abstract—Tumor cells have a higher basal ROS level than normal cells. This phenomenon may provide grounds for the development of novel antitumor drugs that are capable of selectively inducing oxidative stress in tumor cells. This approach can involve agents that induce ROS production and/or inhibit cellular enzymatic antioxidant systems. Thioredoxin reductase is a key enzyme in such systems. Overexpression of thioredoxin reductase has been shown in several types of tumors of hematopoietic, lymphoid, and other tissues. The results of studies of the antitumor activities of various synthetic and natural substances that are able to inhibit thioredoxin reductase are summarized. It is shown that thioredoxin reductase inhibition results in an increase in ROS level in tumor cells and oxidative damage of cells followed by apoptosis mainly via the mitochondrial pathway.

Protection of prostate cancer cells from GSK-3β-induced oxidative stress by Il-8 through activating the mTOR signaling pathway.

311 Background: Both oxidative stress and inflammation play important roles in prostate cancer cell apoptosis or proliferation. However, the mechanisms underlying these processes remain unclear. Thus, we chose IL-8 as the bridge between inflammation and cancer cell oxidative stress-induced death and confirmed its connection with mTOR and GSK-3beta. Methods: We overexpressed GSK-3beta and observed the effect of GSK-3beta on reactive oxygen species (ROS) and cell death induced by oxidative stress. Then, IL-8 was upregulated or downregulated to determine its impact on preventing cells from damage by GSK-3beta-induced oxidative stress. In addition, we confirmed the role of mTOR in this process through its overexpression or knockdown. Real-time PCR, Western blotting, transcription, Cell Counting Kit 8, flow cytometry and other techniques were used. Results: IL-8 promotes prostate cancer cell proliferation and decreases apoptosis, while GSK-3beta induces cell death by oxidative stress through the activation of the caspase-3 signaling pathway by increasing ROS. In addition, mTOR can also decrease the activation of the caspase-3 signaling pathway by inhibiting GSK--3beta and thus decreasing ROS production. Moreover, the inhibitory effect of IL-8 on GSK-3beta occurs through the regulation of mTOR. Conclusions: The results of this study highlight the importance of GSK-3beta, which increases the production of ROS and then induces oxidative stress in tumor cells, while IL-8 and mTOR attenuate the oxidative stress to protect prostate cancer cells through the inhibitor GSK-3beta.

Valproic acid inhibits the protective effects of stromal cells against chemotherapy in breast cancer: Insights from proteomics and systems biology.

Interaction between tumor and stromal cells is beginning to be decoded as a contributor to chemotherapy resistance. Here, we aim to take a system-level approach to explore a mechanism by which stromal cells induce chemoresistance in cancer cells and subsequently identify a drug that can inhibit such interaction. Using a proteomic dataset containing quantitative data on secretome of stromal cells, we performed multivariate analyses and found that bone-marrow mesenchymal stem cells (BM-MSCs) play the most protective role against chemotherapeutics. Pathway enrichment tests showed that secreted cytokines from BM-MSCs activated 4 signaling pathways including Janus kinase-signal transducer and activator of transcription, phosphatidylinositol 3-kinase-protein kinase B, and mitogen-activated protein kinase, transforming growth factor-β in cancer cells collectively leading to nuclear factorkappa-light-chain-enhancer of activated B cells (NF-kB) transcription factor activation. Basedon the data from integrated Library of Integrated Network-Based Cellular Signatures (iLINCs) program, we found that among different drugs, valproic acid (VA) affected the expression of 34 genes within the identified pathways that are activated by stromal cells. Our in vitro experiments confirmed that VA inhibits NF-kB activation in cancer cells. In addition, analyzing gene expression data in patients taking oral VA showed that this drug decreased expression of antioxidant enzymes culminating in increased oxidative stress in tumor cells. These results suggest that VA confines the protective role of stromal cells by inhibiting the adaptation mechanisms toward oxidative stress which is potentiated by stromal cells. Since VA is an already prescribed drug manifesting anticancer effects, this study provides a mechanistic insight for combination of VA with chemotherapy in the clinical setting.

Engineering Multifunctional RNAi Nanomedicine To Concurrently Target Cancer Hallmarks for Combinatorial Therapy

AbstractCancer hallmarks allow the complexity and heterogeneity of tumor biology to be better understood, leading to the discovery of various promising targets for cancer therapy. An amorphous iron oxide nanoparticle (NP)‐based RNAi strategy is developed to co‐target two cancer hallmarks. The NP technology can modulate the glycolysis pathway by silencing MCT4 to induce tumor cell acidosis, and concurrently exacerbate oxidative stress in tumor cells via the Fenton‐like reaction. This strategy has the following features for systemic siRNA delivery: 1) siRNA encapsulation within NPs for improving systemic stability; 2) effective endosomal escape through osmotic pressure and/or endosomal membrane oxidation; 3) small size for enhancing tumor tissue penetration; and 4) triple functions (RNAi, Fenton‐like reaction, and MRI) for combinatorial therapy and in vivo tracking.

Engineering Multifunctional RNAi Nanomedicine To Concurrently Target Cancer Hallmarks for Combinatorial Therapy.

Cancer hallmarks allow the complexity and heterogeneity of tumor biology to be better understood, leading to the discovery of various promising targets for cancer therapy. An amorphous iron oxide nanoparticle (NP)-based RNAi strategy is developed to co-target two cancer hallmarks. The NP technology can modulate the glycolysis pathway by silencing MCT4 to induce tumor cell acidosis, and concurrently exacerbate oxidative stress in tumor cells via the Fenton-like reaction. This strategy has the following features for systemic siRNA delivery: 1) siRNA encapsulation within NPs for improving systemic stability; 2) effective endosomal escape through osmotic pressure and/or endosomal membrane oxidation; 3) small size for enhancing tumor tissue penetration; and 4) triple functions (RNAi, Fenton-like reaction, and MRI) for combinatorial therapy and in vivo tracking.

Synergistic enhancement of topotecan-induced cell death by ascorbic acid in human breast MCF-7 tumor cells

Topotecan, a derivative of camptothecin, is an important anticancer drug for the treatment of various human cancers in the clinic. While the principal mechanism of tumor cell killing by topotecan is due to its interactions with topoisomerase I, other mechanisms, e.g., oxidative stress induced by reactive free radicals, have also been proposed. However, very little is known about how topotecan induces free radical-dependent oxidative stress in tumor cells. In this report we describe the formation of a topotecan radical, catalyzed by a peroxidase-hydrogen peroxide system. While this topotecan radical did not undergo oxidation-reduction with molecular O2, it rapidly reacted with reduced glutathione and cysteine, regenerating topotecan and forming the corresponding glutathiyl and cysteinyl radicals. Ascorbic acid, which produces hydrogen peroxide in tumor cells, significantly increased topotecan cytotoxicity in MCF-7 tumor cells. The presence of ascorbic acid also increased both topoisomerase I-dependent topotecan-induced DNA cleavage complex formation and topotecan-induced DNA double-strand breaks, suggesting that ascorbic acid participated in enhancing DNA damage induced by topotecan and that the enhanced DNA damage is responsible for the synergistic interactions of topotecan and ascorbic acid. Cell death by topotecan and the combination of topotecan and ascorbic acid was predominantly due to necrosis of MCF-7 breast tumor cells.

Rapid quantification of glutaminase 2 (GLS2)-related metabolites by HILIC-MS/MS

Glutamine, glutamate and glutathione are key modulators of excessive oxidative stress in tumor cells. In this study, we developed a rapid and accurate HILIC-MS/MS method to simultaneously determine concentrations of cellular glutamine, glutamate and glutathione. A bared silica HILIC column was employed to analyze these polar metabolites. The LC-MS parameters were optimized to achieve high sensitivity and selectivity. The analysis can be completed within 4 min under optimal conditions. The method was validated in terms of accuracy, precision, and linearity. Intra-day (n = 9) precision was within 2.68–6.24% among QCs. Inter-day precision (n = 3) was below 12.4%. The method accuracy was evaluated by the recovery test, and the accuracy for three analytes were between 91.6 and 110%. The developed method was applied to study antioxidant function of GLS2 in non-small cell lung cancer cells. Changes in concentrations of glutamine, glutamate and glutathione revealed that the overexpression of GLS2 could effectively decrease oxidative stress. In summary, this study developed a rapid HILIC-MS/MS method for quantification of GLS2-related metabolites that could facilitate elucidation of the role of GLS2 in tumor development.

Nucleophosmin Regulates Intracellular Oxidative Stress Homeostasis via Antioxidant PRDX6.

Reactive oxygen species (ROS) play both deleterious and beneficial roles in cancer cells. Nucleophosmin (NPM) is heavily implicated in cancers of diverse origins, being its gene over-expression in solid tumors or frequent mutations in hematological malignancies. However, the role and regulatory mechanism of NPM in oxidative stress are unclear. Here, we found that NPM regulated the expression of peroxiredoxin 6 (PRDX6), a member of thiol-specific antioxidant protein family, consequently affected the level and distribution of ROS. Our data indicated that NPM knockdown caused the increase of ROS and its relocation from cytoplasm to nucleoplasm. In contrast, overexpression or cytoplasmic localization of NPM upregulated PRDX6, and decreased ROS. In addition, NPM knockdown decreased peroxiredoxin family proteins, including PRDX1, PRDX4, and PRDX6. Co-immunoprecipitation further confirmed the interaction between PRDX6 and NPM. Moreover, NSC348884, an inhibitor specifically targeting NPM oligomerization, decreased PRDX6 and significantly upregulated ROS. These observations demonstrated that the expression and localization of NPM affected the homeostatic balance of oxidative stress in tumor cells via PRDX6 protein. The regulation axis of NPM/PRDX/ROS may provide a novel therapeutic target for cancer treatment. J. Cell. Biochem. 118: 4697-4707, 2017. © 2017 Wiley Periodicals, Inc.

Spatio-temporal changes in glutathione and thioredoxin redox couples during ionizing radiation-induced oxidative stress regulate tumor radio-resistance

Ionizing radiation (IR)-induced oxidative stress in tumor cells is effectively managed by constitutive and inducible antioxidant defense systems. This study was initiated to understand the relative contribution of different redox regulatory systems in determining the tumor radio-resistance. In this study, human T-cell lymphoma (Jurkat) cells were exposed to IR (4 Gy) and monitored for the spatio-temporal changes in cellular redox regulatory parameters. We monitored the changes in the levels of reactive oxygen species (ROS) (total, mitochondrial, primary, and secondary), thiols (total, surface, and intracellular), GSH/GSSG ratio, antioxidant enzyme activity viz. thioredoxin (Trx), Trx reductase (TrxR), glutathione peroxidase, and glutathione reductase with respect to time. We have also measured protein glutathionylation. We observed that tumor cells mount a biphasic response after IR exposure which can be divided into early (0–6 h) and late (16–48 h) responses in terms of changes in cellular redox parameters. During early response, constitutively active GSH and Trx systems respond to restore cellular redox balance to pre-exposure levels and help in activation of redox-sensitive transcription factor Nrf-2. During late response, increase in the levels of antioxidants GSH and Trx rescue cells against IR-mediated damage. We observed that disruption of either glutathione or thioredoxin metabolism led to partial impairment of ability of cells to survive against IR-induced damage. But simultaneous disruption of both the pathways significantly increased radio sensitivity of Jurkat cells. This highlighted the importance of these two antioxidant pathways in regulating redox homeostasis under conditions of IR-induced oxidative stress.

Anti-Myeloma Activity of a Novel Free Radical Inducer Rrx-001

Background and Rationale: Multiple Myeloma (MM) remains incurable despite the advent of novel drugs, highlighting the need for further identification of factors mediating disease progression and resistance. The bone marrow (BM) microenvironment confers growth, survival, and drug resistance in MM cells. Studies to date suggest an important role of BM hypoxia (low oxygenation) in MM cell survival, drug resistance, migration, and metastasis. Therapies targeting the MM cell in its BM milieu under hypoxic conditions may therefore achieve responses in patients resistant to various therapies. Recent studies led to the development of a novel aerospace-industry derived Phase 2 molecule RRx-001 with epigenetic and NO-donating properties. RRx-001 generates reactive oxygen and nitrogen species (RONS), which induces oxidative stress in tumor cells. Importantly, RRx-001 is also a potent vascular disrupting agent, which further provides rationale for utilizing RRx-001 as a therapeutic agent since tumor-associated angiogenesis is a characteristic of MM. A Phase I clinical trial has shown RRx-001 to have antitumor activity in heavily pretreated cancer patients and to be safe and well tolerated with no dose-limiting toxicities (Reid et al. J Clin Oncol 32:5s, 2014 suppl; abstr 2578). Here we examined the anti-MM activity of RRx-001 using in vitro and in vivo models of MM.Materials and methods: MM cell lines, patient MM cells, and peripheral blood mononuclear cells (PBMCs) from normal healthy donors were utilized to assess the anti-MM activity of RRx-001 alone or in combination with other agents. Drug sensitivity, cell viability, apoptosis, and migration assays were performed using WST, MTT, Annexin V staining, and transwell Inserts, respectively. Synergistic/additive anti-MM activity was assessed by isobologram analysisusing “CalcuSyn” software program. Signal transduction pathways were evaluated using immunoblotting. ROS release, nitric oxide generation, and mitochondrial membrane potential was measured as previously described (Chauhan et al., Blood, 2004, 104:2458). In vitro angiogenesis was assessed using matrigel capillary-like tube structure formation assays. DNMT1 activity was measured in protein lysates using EpiQuik DNMT1 assay kit. 5-methyl cytosine levels were analyzed in gDNA samples using methylflash methylated DNA quantification kit from Enzo life sciences; USA. For xenograft mouse model, CB-17 SCID-mice were subcutaneously inoculated with MM.1S cells as previously described (Chauhan et al., Blood, 2010, 115:834). Statistical significance of data was determined using a Student’st test. RRx-001 was obtained from RadioRx Inc., CA, USA; bortezomib, SAHA, and pomalidomide were purchased from Selleck chemicals, USA.Results: Treatment of MM cell lines (MM.1S, MM.1R, RPMI-8226, OPM2, H929, Dox-40 ARP-1, KMS-11, ANBL6.WT, ANBL6.BR, and LR5) and primary patient cells for 24h significantly decreased their viability (IC50 range 1.25nM to 2.5nM) (p < 0.001; n=3) without markedly affecting PBMCs from normal healthy donors, suggesting specific anti-MM activity and a favorable therapeutic index for RRx-001. Tumor cells from 3 of 5 patients were obtained from patients whose disease was progressing while on bortezomib, dexamethasone, and lenalidomide therapies. Moreover, RRx-001 inhibits proliferation of MM cells even in the presence of BM stromal cells. Mechanistic studies show that RRx-001-triggered apoptosis is associated with 1) induction of DNA damage response signaling via ATM/p53/gH2AX axis; 2) activation of caspases mediating both intrinsic and extrinsic apoptotic pathways; 3) increase in oxidative stress through release of ROS and generation of NO; and 4) decrease in DNA methyltransferase (DNMT1) enzymatic activity and global methylation levels. Furthermore, RRx-001 blocked migration of MM cells and angiogenesis. In vivo studies using subcutaneous human MM xenograft models show that RRx-001 is well tolerated and inhibits tumor growth. Finally, combining RRx-001 with bortezomib, SAHA, or pomalidomide induces synergistic anti-MM activity and overcomes drug resistance.Conclusion: Our preclinical studies showing efficacy of RRx-001 in MM disease models provide the framework for clinical trial of RRx-001, either alone or in combination, to improve outcome in relapsed and refractory MM patients. DisclosuresRichardson:Oncopeptides AB: Membership on an entity’s Board of Directors or advisory committees; Celgene: Membership on an entity’s Board of Directors or advisory committees; Millennium: Membership on an entity’s Board of Directors or advisory committees. Oronsky:RadioRx Inc, : Employment. Scicinski:RadioRx Inc,: Employment. Chauhan:Triphase Accelerator: Consultancy. Anderson:Celgene: Consultancy; Millenium: Consultancy; Onyx: Consultancy; Gilead: Consultancy; Sanofi Aventis: Consultancy; BMS: Consultancy; Oncopep/Acetylon: Equity Ownership.