Effective treatment of advanced solid tumors by the combination of arsenic trioxide and L-buthionine-sulfoximine

Buthionine sulfoximine and chemoresistance in cancer treatments: a systematic review with meta-analysis of preclinical studies

Buthionine sulfoximine (BSO) is a synthetic amino acid that blocks the biosynthesis of reduced glutathione (GSH), an endogenous antioxidant cellular component present in tumor cells. GSH levels have been associated with tumor cell resistance to chemotherapeutic drugs and platinum compounds. Consequently, by depleting GSH, BSO enhances the cytotoxicity of chemotherapeutic agents in drug-resistant tumors. Therefore, the aim of this study was to conduct a systematic review with meta-analysis of preclinical studies utilizing BSO in cancer treatments. The systematic search was carried out using the following databases: PubMed, Web of Science, Scopus, and EMBASE up until March 20, 2023, in order to collect preclinical studies that evaluated BSO, alone or in association, as a strategy for antineoplastic therapy. One hundred nine investigations were found to assess the cytotoxic potential of BSO alone or in combination with other compounds. Twenty-one of these met the criteria for performing the meta-analysis. The evidence gathered indicated that BSO alone exhibits cytotoxic activity. However, this compound is generally used in combination with other antineoplastic strategies, mainly chemotherapy ones, to improve cytotoxicity to carcinogenic cells and treatment efficacy. Finally, this review provides important considerations regarding BSO use in cancer treatment conditions, which might optimize future studies as a potential adjuvant antineoplastic therapeutic tool.

Construction of multifunctional mesoporous silicon nano-drug delivery system and study of dual sensitization of chemo-photodynamic therapy in vitro and in vivo

This study was conducted to construct a multifunctional nanodrug delivery system (NDDS) to deplete glutathione (GSH) in tumor cells and amplify oxidative stress, enhancing the synergistic effect of chemotherapy and photodynamic therapy (PDT). l-Buthionine-sulfoximine (BSO) and chlorin e6 (Ce6) were loaded into mesoporous silicon nanoparticles (MSN), and then MSN were modified with oxidized hyaluronic acid (OHA) as a pore-blocking agent. Cisplatin (Pt(II)) was further loaded by a coordination reaction with carboxyl groups in OHA to yield a multifunctional NDDS (denoted as MSN@OHA-Ce6/BSO/Pt). The physicochemical properties and antitumor activity of the prepared nanoparticles were characterized in detail. In vitro and in vivo experiments demonstrated that OHA was shed from MSN@OHA-Ce6/BSO/Pt under acidic conditions in tumors, resulting in the release of free BSO, Ce6, and Pt(II). The released BSO could reduce intracellular GSH expression by 48.8 %, effectively enhancing the PDT effect of Ce6 and the chemotherapy effect of Pt(II). Finally, the tumor inhibitory rate (vs saline) reached 73.8 % ± 2.5 % for MSN@OHA-Ce6/BSO/Pt in A549/DDP tumor-bearing nude mice. Therefore, the multifunctional NDDS significantly enhanced the synergistic effect of PDT and chemotherapy.

Self-activated arsenic manganite nanohybrids for visible and synergistic thermo/immuno-arsenotherapy

Arsenotherapy has been clinically exploited to treat a few types of solid tumors despite of acute promyelocytic leukemia using arsenic trioxide (ATO), however, its efficacy is hampered by inadequate delivery of ATO into solid tumors owing to the absence of efficient and biodegradable vehicles. Precise spatiotemporal control of subcellular ATO delivery for potent arsenotherapy thus remains challengeable. Herein, we report the self-activated arsenic manganite nanohybrids for high-contrast magnetic resonance imaging (MRI) and arsenotherapeutic synergy on triple-negative breast cancer (TNBC). The nanohybrids, composed of arsenic‑manganese-co-biomineralized nanoparticles inside albumin nanocages (As/Mn-NHs), switch signal-silent background to high proton relaxivity, and simultaneously afford remarkable subcellular ATO level in acidic and glutathione environments, together with reduced ATO resistance against tumor cells. Then, the nanohybrids enable in vivo high-contrast T₁-weighted MRI signals in various tumor models for delineating tumor boundary, and simultaneously yield efficient arsenotherapeutic efficacy through multiple apoptotic pathways for potently suppressing subcutaneous and orthotopic breast models. As/Mn-NHs exhibited the maximum tumor-to-normal tissue (T/N) contrast ratio of 205% and tumor growth inhibition rate of 88% at subcutaneous 4T1 tumors. These nanohybrids further yield preferable synergistic antitumor efficacy against both primary and metastatic breast tumors upon combination with concurrent thermotherapy. More importantly, As/Mn-NHs considerably induce immunogenic cell death (ICD) effect to activate the immunogenically "cold" tumor microenvironment into "hot" one, thus synergizing with immune checkpoint blockade to yield the strongest tumor inhibition and negligible metastatic foci in the lung. Our study offers the insight into clinically potential arsenotherapeutic nanomedicine for potent therapy against solid tumors.

Human prostate cancer cell epithelial-to-mesenchymal transition as a novel target of arsenic trioxide and curcumin therapeutic approach

BACKGROUND

Arsenic trioxide (As₂O₃) as an inorganic compound is used to treat various cancers and other diseases. It has been reported that arsenic trioxide induced cellular apoptosis in certain kinds of cancers, including prostate cancers. The present study aimed to elucidate the crucial cooperative role of arsenic trioxide and Curcumin and their ability to protect against prostate cancers by targeting the epithelial-to-mesenchymal transition and expression of apoptosis-related genes.

MATERIAL AND METHODS

The human prostate cell lines (LNCaP and PC3) were treated with different concentrations of Curcumin and As₂O₃ alone and combined to find effective doses and IC50 values. Percentages of apoptotic cells were evaluated by Annexin/P.I. staining, the proliferative inhibitory effect was assessed by Micro Culture Tetrazolium Test (MTT), and mRNA levels of KLK2, E-cadherin, SNAIL, angiogenesis genes (VEGFA and VEGFC), and apoptosis genes (BAX, Bcl₂, and P53) expression were investigated by the real-time PCR method. ANOVA and t-test were used to appraise the results.

RESULTS

For the first time, we presented that the combination therapy of Curcumin and As₂O₃ increases prostate cancer cell apoptosis and inhibits proliferation; Our data displayed that Curcumin (15 μM and 10 μM in PC3 and LNCap), As₂O₃ (8 μM and 5 μM in PC3 and LNCap), and also their combination (15 μM Curcumin and 8 μM As₂O₃ in PC3, 10 μM Curcumin and 5 μM As₂O₃ in LNCap cell lines) significantly increased the percentage of apoptotic cells and inhibited cell growth (P < 0.05) compared with each drug alone. Generally, both cell lines treated with the combination of Curcumin and As₂O₃ displayed decreased angiogenesis genes (VEGFA and VEGFC), apoptosis genes (BAX and Bcl2), and prostate cancer marker (KLK2), the zinc-finger protein (SNAIL); and an increase in expression (P < 0.05) of cell-cell adhesion molecule (E-cadherin) and tumor suppressor gene (P53) genes.

CONCLUSIONS

The antitumor effects of combination therapy with As₂O₃ and Curcumin have been displayed on prostate cancer cell lines (LNCaP and PC3), which probably originates from their potential to induce apoptosis and inhibit the growth of prostate cancer cells simultaneously.

A platinum(IV) prodrug strategy to overcome glutathione-based oxaliplatin resistance

Clinical efficacy of oxaliplatin is frequently limited by severe adverse effects and therapy resistance. Acquired insensitivity to oxaliplatin is, at least in part, associated with elevated levels of glutathione (GSH). In this study we report on an oxaliplatin-based platinum(IV) prodrug, which releases L-buthionine-S,R-sulfoximine (BSO), an inhibitor of glutamate-cysteine ligase, the rate-limiting enzyme in GSH biosynthesis. Two complexes bearing either acetate (BSO-OxOAc) or an albumin-binding maleimide (BSO-OxMal) as second axial ligand were synthesized and characterized. The in vitro anticancer activity of BSO-OxOAc was massively reduced in comparison to oxaliplatin, proving its prodrug nature. Nevertheless, the markedly lower intracellular oxaliplatin uptake in resistant HCT116/OxR cells was widely overcome by BSO-OxOAc resulting in distinctly reduced resistance levels. Platinum accumulation in organs of a colorectal cancer mouse model revealed higher tumor selectivity of BSO-OxMal as compared to oxaliplatin. This corresponded with increased antitumor activity, resulting in significantly enhanced overall survival. BSO-OxMal-treated tumors exhibited reduced GSH levels, proliferative activity and enhanced DNA damage (pH2AX) compared to oxaliplatin. Conversely, pH2AX staining especially in kidney cells was distinctly increased by oxaliplatin but not by BSO-OxMal. Taken together, our data provide compelling evidence for enhanced tumor specificity of the oxaliplatin(IV)/BSO prodrug.

Crosstalk Between ROS and Autophagy in Tumorigenesis: Understanding the Multifaceted Paradox

Cancer formation is a highly regulated and complex process, largely dependent on its microenvironment. This complexity highlights the need for developing novel target-based therapies depending on cancer phenotype and genotype. Autophagy, a catabolic process, removes damaged and defective cellular materials through lysosomes. It is activated in response to stress conditions such as nutrient deprivation, hypoxia, and oxidative stress. Oxidative stress is induced by excess reactive oxygen species (ROS) that are multifaceted molecules that drive several pathophysiological conditions, including cancer. Moreover, autophagy also plays a dual role, initially inhibiting tumor formation but promoting tumor progression during advanced stages. Mounting evidence has suggested an intricate crosstalk between autophagy and ROS where they can either suppress cancer formation or promote disease etiology. This review highlights the regulatory roles of autophagy and ROS from tumor induction to metastasis. We also discuss the therapeutic strategies that have been devised so far to combat cancer. Based on the review, we finally present some gap areas that could be targeted and may provide a basis for cancer suppression.

F-box protein FBXO41 plays vital role in arsenic trioxide-mediated autophagic death of cancer cells

Arsenic trioxide (ATO), a potent anti-neoplastic drug, is known to prevent cancer cell growth through induction of autophagic cell death. However, importance of cellular factors in ATO-mediated autophagic cell death is poorly understood. In this study, using biochemical and immunofluorescence techniques, we show that F-box protein FBXO41 plays a critical role in anti-proliferative activity of ATO. Our study reveals the importance of FBXO41 in induction of autophagic death of cancer cells by ATO. Further, we show that the autophagic cell death induced by FBXO41 is distinct and independent of apoptosis and necrosis, showing that FBXO41 may play vital role in inducing autophagic death of apoptosis resistant cancer cells. Overall, our study elucidates the importance of FBXO41 in ATO induced autophagic cell death to prevent cancer progression, which could be explored to develop promising cancer therapeutic strategy.

Enhanced antitumor effect of L-buthionine sulfoximine or ionizing radiation by copper complexes with 2,2´-biquinoline and sulfonamides on A549 2D and 3D lung cancer cell models

Two ternary copper(II) complexes with 2,2'-biquinoline (BQ) and with sulfonamides: sulfamethazine (SMT) or sulfaquinoxaline (SDQ) whose formulae are Cu(SMT)(BQ)Cl and Cu(SDQ)(BQ)Cl·CH₃OH, in what follows SMTCu and SDQCu, respectively, induced oxidative stress by increasing ROS level from 1.0 μM and the reduction potential of the couple GSSG/GSH². The co-treatment with L-buthionine sulfoximine (BSO), which inhibits the production of GSH, enhanced the effect of copper complexes on tumor cell viability and on oxidative damage. Both complexes generated DNA strand breaks given by-at least partially-the oxidation of pyrimidine bases, which caused the arrest of the cell cycle in the G2/M phase. These phenomena triggered processes of apoptosis proven by activation of caspase 3 and externalization of phosphatidylserine and loss of cell integrity from 1.0 μM. The combination with BSO induced a marked increase in the apoptotic population. On the other hand, an improved cell proliferation effect was observed when combining SDQCu with a radiation dose of 2 Gy from 1.0 μM or with 6 Gy from 1.5 μM. Finally, studies in multicellular spheroids demonstrated that even though copper(II) complexes did not inhibit cell invasion in collagen gels up to 48 h of treatment at the higher concentrations, multicellular resistance outperformed several drugs currently used in cancer treatment. Overall, our results reveal an antitumor effect of both complexes in monolayer and multicellular spheroids and an improvement with the addition of BSO. However, only SDQCu was the best adjuvant of ionizing radiation treatment.

Anticancer Therapeutic Effects of Cerium Oxide Nanoparticles: Known and Unknown Molecular Mechanisms

Cerium-based nanoparticles (CeNPs), particularly cerium oxide (CeO2), have been studied extensively for their antioxidant and prooxidant properties. However, their complete redox and enzyme-mimetic mechanisms of therapeutic action at the molecular...

Arsenic Trioxide-loaded nanoparticles Enhance the Chemosensitivity of Gemcitabine in Pancreatic Cancer via Reversal of Pancreatic Stellate Cells Desmoplasia through Targeting AP4/Galectin-1 Pathway

Pancreatic stellate cell (PSCs) constitutes the fibrotic tumor microenvironment composed of the stroma matrix, which blocks the penetration of Gemcitabine (GEM) in pancreatic adenocarcinoma (PDAC) and results in chemoresistance. We...

Copper arsenite-complexed Fenton-like nanoparticles as oxidative stress-amplifying anticancer agents

We report copper(II) arsenite (CuAS)-integrated polymer micelles (CuAS-PMs) as a new class of Fenton-like catalytic nanosystem that can display reactive oxygen species (ROS)-manipulating anticancer therapeutic activity. CuAS-PMs were fabricated through metal-catechol chelation-based formation of the CuAS complex on the core domain of poly (ethylene glycol)-b-poly(3,4-dihydroxy-L-phenylalanine) (PEG-PDOPA) copolymer micelles. CuAS-PMs maintained structural robustness under serum conditions. The insoluble state of the CuAS complex was effectively retained at physiological pH, whereas, at endosomal pH, the CuAS complex was ionized to release arsenite and cuprous Fenton catalysts (Cu⁺ ions). Upon endocytosis, CuAS-PMs simultaneously released hydrogen peroxide (H₂O₂)-generating arsenite and Fenton-like reaction-catalyzing Cu⁺ ions in cancer cells, which synergistically elevated the level of highly cytotoxic hydroxyl radicals (•OH), thereby preferentially killing cancer cells. Animal experiments demonstrated that CuAS-PMs could effectively suppress the growth of solid tumors without systemic in vivo toxicity. The design rationale of CuAS-PMs may provide a promising strategy to develop diverse oxidative stress-amplifying agents with great potential in cancer-specific therapy.

Targeting multidrug resistance-associated protein 1 (MRP1)-expressing cancers: Beyond pharmacological inhibition

Resistance to chemotherapy remains one of the most significant obstacles to successful cancer treatment. While inhibiting drug efflux mediated by ATP-binding cassette (ABC) transporters is a seemingly attractive and logical approach to combat multidrug resistance (MDR), small molecule inhibition of ABC transporters has so far failed to confer clinical benefit, despite considerable efforts by medicinal chemists, biologists, and clinicians. The long-sought treatment to eradicate cancers displaying ABC transporter overexpression may therefore lie within alternative targeting strategies. When aberrantly expressed, the ABC transporter multidrug resistance-associated protein 1 (MRP1, ABCC1) confers MDR, but can also shift cellular redox balance, leaving the cell vulnerable to select agents. Here, we explore the physiological roles of MRP1, the rational for targeting this transporter in cancer, the development of small molecule MRP1 inhibitors, and the most recent developments in alternative therapeutic approaches for targeting cancers with MRP1 overexpression. We discuss approaches that extend beyond simple MRP1 inhibition by exploiting the collateral sensitivity to glutathione depletion and ferroptosis, the rationale for targeting the shared transcriptional regulators of both MRP1 and glutathione biosynthesis, advances in gene silencing, and new molecules that modulate transporter activity to the detriment of the cancer cell. These strategies illustrate promising new approaches to address multidrug resistant disease that extend beyond the simple reversal of MDR and offer exciting routes for further research.

Engineering nanomedicine for glutathione depletion-augmented cancer therapy

Glutathione (GSH), the main redox buffer, has long been recognized as a pivotal modulator of tumor initiation, progression and metastasis. It is also implicated in the resistance of platinum-based chemotherapy and radiation therapy. Therefore, depleting intracellular GSH was considered a potent solution to combating cancer. However, reducing GSH within cancer cells alone always failed to yield desirable therapeutic effects. In this regard, the convergence of GSH-scavenging agents with therapeutic drugs has thus been pursued in clinical practice. Unfortunately, the therapeutic outcomes are still unsatisfactory due to untargeted drug delivery. Advanced nanomedicine of synergistic GSH depletion and cancer treatment has attracted tremendous interest because they promise to deliver superior therapeutic benefits while alleviating life-threatening side effects. In the past five years, the authors and others have demonstrated that numerous nanomedicines, by simultaneously delivering GSH-depleting agents and therapeutic components, boost not only traditional chemotherapy and radiotherapy but also multifarious emerging treatment modalities, including photodynamic therapy, sonodynamic therapy, chemodynamic therapy, ferroptosis, and immunotherapy, to name a few, and achieved decent treatment outcomes in a large number of rodent tumor models. In this review, we summarize the most recent progress in engineering nanomedicine for GSH depletion-enhanced cancer therapies. Biosynthesis of GSH and various types of GSH-consuming strategies will be briefly introduced. The challenges and perspectives of leveraging nanomedicine for GSH consumption-augmented cancer therapies will be discussed at the end.

Thioredoxin 1 is required for stress granule assembly upon arsenite-induced oxidative stress

Arsenic is a major water pollutant and health hazard, leading to acute intoxication and, upon chronic exposure, several diseases including cancer development. Arsenic exerts its pronounced cellular toxicity through its trivalent oxide arsenite (ASN), which directly inhibits numerous proteins including Thioredoxin 1 (Trx1), and causes severe oxidative stress. Cells respond to arsenic by inhibition of protein synthesis and subsequent assembly of stress granules (SGs), cytoplasmic condensates of stalled mRNAs, translation factors and RNA-binding proteins. The biological role of SGs is diverse and not completely understood; they are important for regulation of cell signaling and survival under stress conditions, and for adapting de novo protein synthesis to the protein folding capacity during the recovery from stress. In this study, we identified Trx1 as a novel component of SGs. Trx1 is required for the assembly of ASN-induced SGs, but not for SGs induced by energy deprivation or heat shock. Importantly, our results show that Trx1 is essential for cell survival upon acute exposure to ASN, through a mechanism that is independent of translation inhibition.

Role of Reductive versus Oxidative Stress in Tumor Progression and Anticancer Drug Resistance

Redox homeostasis is not only essential for the maintenance of normal physiological functions, but also plays an important role in the growth, survival, and therapy resistance of cancer cells. Altered redox balance and consequent disruption of redox signaling are implicated in the proliferation and progression of cancer cells and their resistance to chemo- and radiotherapy. The nuclear factor erythroid 2 p45-related factor (Nrf2) is the principal stress-responsive transcription factor that plays a pivotal role in maintaining cellular redox homeostasis. Aberrant Nrf2 overactivation has been observed in many cancerous and transformed cells. Uncontrolled amplification of Nrf2-mediated antioxidant signaling results in reductive stress. Some metabolic pathways altered due to reductive stress have been identified as major contributors to tumorigenesis. This review highlights the multifaceted role of reductive stress in cancer development and progression.

Free Radicals as a Double-Edged Sword: The Cancer Preventive and Therapeutic Roles of Curcumin

Free radicals, generally composed of reactive oxygen species (ROS) and reactive nitrogen species (RNS), are generated in the body by various endogenous and exogenous systems. The overproduction of free radicals is known to cause several chronic diseases including cancer. However, increased production of free radicals by chemotherapeutic drugs is also associated with apoptosis in cancer cells, indicating the dual nature of free radicals. Among various natural compounds, curcumin manifests as an antioxidant in normal cells that helps in the prevention of carcinogenesis. It also acts as a prooxidant in cancer cells and is associated with inducing apoptosis. Curcumin quenches free radicals, induces antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), and upregulates antioxidative protein markers-Nrf2 and HO-1 that lead to the suppression of cellular oxidative stress. In cancer cells, curcumin aggressively increases ROS that results in DNA damage and subsequently cancer cell death. It also sensitizes drug-resistant cancer cells and increases the anticancer effects of chemotherapeutic drugs. Thus, curcumin shows beneficial effects in prevention, treatment and chemosensitization of cancer cells. In this review, we will discuss the dual role of free radicals as well as the chemopreventive and chemotherapeutic effects of curcumin and its analogues against cancer.

Tumor targeted self-synergistic nanoplatforms for arsenic-sensitized photodynamic therapy

Development of antitumor agents with high efficiency and low toxicity is one of the most important goals for biomedical research. However, most traditional therapeutic strategies were limited due to their non-specificity and abnormal tumor microenvironments, causing a poor therapeutic efficiency and severe side effects. In this paper, a tumor targeted self-synergistic nanoplatform (designated as PAO@PCN@HA) was developed for chemotherapy sensitized photodynamic therapy (PDT) against hypoxic tumors. The efficient drug loading of phenylarsine oxide (PAO) in porphyrinic metal organic framework of PCN-224 as well as the surface modification of hyaluronic acid (HA) improved the targeted drug delivery and reduced the side effects of PAO at the therapeutic dose. Particularly, PAO as an arsenical-based chemotherapeutic agent could not only induce cell apoptosis by generating reactive oxygen species (ROS), but also regulate tumor microenvironments to improve the PDT effect of PCN-224 by mitigating hypoxia and consuming cellular GSH. Both in vitro and in vivo investigations confirmed an effective self-synergy of PAO@PCN@HA in hypoxic tumor therapy with a low systemic toxicity. This integration of microenvironment adjustment with tumor targeted self-synergistic mechanism might provide a new insight for the development of arsenic-based antitumor strategy for clinical applications.

Small molecules regulating reactive oxygen species homeostasis for cancer therapy

Elevated intracellular reactive oxygen species (ROS) and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. Compared with normal cells, cancer cells exhibit increased ROS to maintain their malignant phenotypes and are more dependent on the "redox adaptation" mechanism. Thus, there are two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to prevent or treat cancer. The first strategy, that is, chemoprevention, is to prevent or reduce intracellular ROS either by suppressing ROS production pathways or by employing antioxidants to enhance ROS clearance, which protects normal cells from malignant transformation and inhibits the early stage of tumorigenesis. The second strategy is the ROS-mediated anticancer therapy, which stimulates intracellular ROS to a toxicity threshold to activate ROS-induced cell death pathways. Therefore, targeting the regulation of intracellular ROS-related pathways by small-molecule candidates is considered to be a promising treatment for tumors. We herein first briefly introduce the source and regulation of ROS, and then focus on small molecules that regulate ROS-related pathways and show efficacy in cancer therapy from the perspective of pharmacophores. Finally, we discuss several challenges in developing cancer therapeutic agents based on ROS regulation and propose the direction of future development.

Highly stable and biocompatible hyaluronic acid-rehabilitated nanoscale MOF-Fe2+ induced ferroptosis in breast cancer cells

Intracellular amplification of oxidative stress has been proved to be an effective strategy to induce cancer cell death and the Fenton reaction was regarded as a robust way to generate ROS which are the main cause of amplified oxidative stress. However, current Fenton reaction-inducing agents lacked stability in the bio-environment and failed to exert their ideal catalytic performance. We, hereby, designed an Fe2+-based metal-organic framework (MOF) to deliver Fe2+ to cancer cells to trigger the Fenton reaction and produce excessive ROS. The obtained nano-scale MOF that was constructed by ferrous acetate and organic ligands (BDC-NH2) endowed itself with excellent stability in bio-media and pH responsively degraded itself to release Fe2+ in the acid tumor microenvironment. Such a characteristic demonstrated robust capacity to catalyze the Fenton reaction and produce considerable ROS and thus induced distinct Fe2+-mediated cell ferroptosis. Meanwhile, directly exploiting an Fe2+-based MOF to inhibit and kill cancer cells circumvented the potential adverse effects of loading drugs (like the cardiotoxicity of doxorubicin, and the nephrotoxicity and ototoxicity of cisplatin) and proved to be biocompatible in in vivo experiments. More importantly, observations of the in vivo antitumor experiment attested its impressive inhibition on cancer cells and amelioration on the physical health of treated mice. Our study thus presented a novel and biocompatible ferroptosis strategy to be applied in effective clinical cancer therapy.

Two-way magnetic resonance tuning and enhanced subtraction imaging for non-invasive and quantitative biological imaging

Distance-dependent magnetic resonance tuning (MRET) technology enables the sensing and quantitative imaging of biological targets in vivo, with the advantage of deep tissue penetration and fewer interactions with the surroundings as compared with those of fluorescence-based Förster resonance energy transfer. However, applications of MRET technology in vivo are currently limited by the moderate contrast enhancement and stability of T₁-based MRET probes. Here we report a new two-way magnetic resonance tuning (TMRET) nanoprobe with dually activatable T₁ and T₂ magnetic resonance signals that is coupled with dual-contrast enhanced subtraction imaging. This integrated platform achieves a substantially improved contrast enhancement with minimal background signal and can be used to quantitatively image molecular targets in tumours and to sensitively detect very small intracranial brain tumours in patient-derived xenograft models. The high tumour-to-normal tissue ratio offered by TMRET in combination with dual-contrast enhanced subtraction imaging provides new opportunities for molecular diagnostics and image-guided biomedical applications.

Specific "Unlocking" of a Nanozyme-Based Butterfly Effect To Break the Evolutionary Fitness of Chaotic Tumors

Chaos and the natural evolution of tumor systems can lead to the failure of tumor therapies. Herein, we demonstrate that iridium oxide nanoparticles (IrO_x ) possess acid-activated oxidase and peroxidase-like functions and wide pH-dependent catalase-like properties. The integration of glucose oxidase (GOD) unlocked the oxidase and peroxidase activities of IrO_x by the production of gluconic acid from glucose by GOD catalysis in cancer cells, and the produced H₂ O₂ was converted into O₂ to compensate its consumption in GOD catalysis owing to the catalase-like function of the nanozyme, thus resulting in the continual consumption of glucose and the self-supply of substrates to generate superoxide anion and hydroxyl radical. Moreover, IrO_x can constantly consume glutathione (GSH) by self-cyclic valence alternation of Ir^IV and Ir^III . These cascade reactions lead to a "butterfly effect" of initial starvation therapy and the subsequent pressure of multiple reactive oxygen species (ROS) to completely break the self-adaption of cancer cells.

Ultra-small Bi2S3 nanodot-doped reversible Fe(ii/iii)-based hollow mesoporous Prussian blue nanocubes for amplified tumor oxidative stress-augmented photo-/radiotherapy

Oxidative stress imbalance could be induced by the reversible redox property of Fe(ii/iii), thereby causing DNA damage and increasing the cell membrane permeability to realize enhanced photo-/radiotherapy.

Potential cytotoxic and anti-metastatic effects of berberine on gynaecological cancers with drug-associated resistance

Gynaecological disorders, such as cervical, ovarian, and endometrial cancers are the second most prevalent cancer types in women worldwide. Therapeutic approaches for gynaecological cancers involve chemotherapy, radiation, and surgery. However, lifespan is not improved, and novel medications are required. Among various phytochemicals, berberine, a well-known natural product, has been shown to be a promising cancer chemopreventive agent. Pharmacokinetics, safety, and efficacy of berberine have been investigated in the several experiments against numerous diseases. Here, we aimed to provide a literature review from available published investigations showing the anticancer effects of berberine and its various synthetic analogues against gynaecological disorders, including cervical, ovarian, and endometrial cancers. In conclusion, berberine has been found to efficiently inhibit viability, proliferation, and migration of cancer cells, mainly, via induction of apoptosis by both mitochondrial dependent and -independent pathways. Additionally, structural modification of berberine showed that berberine analogues can improve its antitumor effects against gynaecological cancers.

Fabrication of H2O2-driven nanoreactors for innovative cancer treatments

The increased production of hydrogen peroxide (H₂O₂) is a typical feature of cancerous cells. This feature is closely associated with elevated oxidative stress inside solid tumour microenvironments, which thus impairs either the growth of cancer cells or their sensitivity to many cancer therapeutics. To date, numerous innovative strategies that target tumour H₂O₂ have been designed for effective cancer treatment. More recently, with the rapid advancement of nanomedicine, several nanoreactors, which are highly efficient in converting endogenous H₂O₂ to more toxic reactive oxygen species, promoting in situ H₂O₂, or decomposing endogenous H₂O₂ to molecular oxygen for tumour hypoxia attenuation, have been designed and attempted for effective cancer treatment. This review focuses on the latest progress of such innovative H₂O₂-driven nanoreactor-mediated cancer treatments. Afterwards, future perspectives on the development of tumour H₂O₂-driven nanoreactor-mediated cancer treatments and their potential clinical translations will be discussed.

Cu/Zn-superoxide dismutase and wild-type like fALS SOD1 mutants produce cytotoxic quantities of H2O2 via cysteine-dependent redox short-circuit

The Cu/Zn−superoxide dismutase (SOD1) is a ubiquitous enzyme that catalyzes the dismutation of superoxide radicals to oxygen and hydrogen peroxide. In addition to this principal reaction, the enzyme is known to catalyze, with various efficiencies, several redox side-reactions using alternative substrates, including biological thiols, all involving the catalytic copper in the enzyme’s active-site, which is relatively surface exposed. The accessibility and reactivity of the catalytic copper is known to increase upon SOD1 misfolding, structural alterations caused by a mutation or environmental stresses. These competing side-reactions can lead to the formation of particularly toxic ROS, which have been proposed to contribute to oxidative damage in amyotrophic lateral sclerosis (ALS), a neurodegenerative disease that affects motor neurons. Here, we demonstrated that metal-saturated SOD1^WT (holo-SOD1^WT) and a familial ALS (fALS) catalytically active SOD1 mutant, SOD1^G93A, are capable, under defined metabolic circumstances, to generate cytotoxic quantities of H₂O₂ through cysteine (CSH)/glutathione (GSH) redox short-circuit. Such activity may drain GSH stores, therefore discharging cellular antioxidant potential. By analyzing the distribution of thiol compounds throughout the CNS, the location of potential hot-spots of ROS production can be deduced. These hot-spots may constitute the origin of oxidative damage to neurons in ALS.

Regulating intracellular ROS signal by a dual pH/reducing-responsive nanogels system promotes tumor cell apoptosis

Purpose: The levels of reactive oxygen species (ROS) in tumor cells are much higher than that in normal cells, and rise rapidly under the influence of exogenous or endogenous inducing factors, eventually leading to the apoptosis of tumor cells. Therefore, this study prepared a dual pH/reducing-responsive poly (N-isopropylacrylamide-co-Cinnamaldehyde-co-D-α-tocopheryl polyethylene glycol 1000 succinate, PssNCT) nanogels, which employed two exogenous ROS inducers, cinnamaldehyde (CA) and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), to selectively induce apoptosis by regulating ROS levels in tumor cells. Methods: The PssNCT nanogels were prepared by the free radical precipitation polymerization under the crosslink between pH-sensitive hydrazone and reducing-sensitive disulfide bonds, followed by the physicochemical and morphological characteristics investigations. Plasma stability, dual pH/reducing responsive degradation and in vitro release were also assessed. In cell experiments, cytotoxicity in different cells were first detected. The intracellular ROS levels and mitochondrial functions of tumor cells were then evaluated. Moreover, the apoptosis and western-blot assays were employed to verify the association between ROS levels elevation and apoptosis in tumor cells. Results: The nanogels exhibited a round-like hollow structure with the diameter smaller than 200nm. The nanogels were stable in plasma, while showed rapid degradation in acidic and reducing environments, thus achieving significant release of CA and TPGS in these media. Furthermore, the sufficient amplification of ROS signals was induced by the synergistically function of CA and TPGS on mitochondria, which resulted in the opening of the mitochondrial apoptotic pathway and enhanced cytotoxicity on MCF-7 cells. However, nanogels barely affected L929 cells owing to their lower intracellular ROS basal levels. Conclusion: The specific ROS regulation method achieved by these nanogels could be explored to selectively kill tumor cells according to the difference of ROS signals in different kinds of cells.

Arsenic Disulfide Combined with L-Buthionine-(S, R)-Sulfoximine Induces Synergistic Antitumor Effects in Two-Dimensional and Three-Dimensional Models of MCF-7 Breast Carcinoma Cells

Three-dimensionally (3D) cultured tumor cells (spheroids) exhibit more resistance to therapeutic agents than the cells cultured in traditional two-dimensional (2D) system (monolayers). We previously demonstrated that arsenic disulfide (As₂S2) exerted significant anticancer efficacies in both 2D- and 3D-cultured MCF-7 cells, whereas 3D spheroids were shown to be resistant to the As₂S₂ treatment. L-buthionine-(S, R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, has been regarded to be a potent candidate for combinatorial treatment due to its GSH modulation function. In the present study, we introduced BSO in combination with As₂S₂ at a low concentration to investigate the possible enhancing anticancer efficacy by the combinatorial treatment on 2D- and 3D-cultured MCF-7 cells. Our results presented for the first time that the combination of As₂S₂ and BSO exerted potent anticancer synergism in both MCF-7 monolayers and spheroids. The IC50 values of As₂S₂ in combinatorial treatment were significantly lower than those in treatment of As₂S₂ alone in both 2D- and 3D-cultured MCF-7 cells (P<0.01, respectively). In addition, augmented induction of apoptosis and enhanced cell cycle arrest along with the regulation of apoptosis- and cell cycle-related proteins, as well as synergistic inhibitions of PI3K/Akt signals, were also observed following co-treatment of As₂S₂ and BSO. Notably, the combinatorial treatment significantly decreased the cellular GSH levels in both 2D- and 3D-cultured MCF-7 cells in comparison with each agent alone (P<0.05 in each). Our results suggest that the combinatorial treatment with As₂S₂ and BSO could be a promising novel strategy to reverse arsenic resistance in human breast cancer.

Glutathione-Depleting Pro-Oxidant as a Selective Anticancer Therapeutic Agent

A main challenge in the development of anticancer drugs that eradicate cancer cells specifically with minimal toxicity to normal cells is to identify the cancer-specific properties. Cancer cells sustain a higher level of reactive oxygen species, owing to metabolic and signaling aberrations and unrestrained growth. Cancer cells are also furnished with a powerful reducing environment, owing to the overproduction of antioxidants such as glutathione (GSH). Therefore, the altered redox balance is probably the most prevailing property of cancer cells distinct from normal cells, which could serve as a plausible therapeutic target. In this work, we developed a GSH-depleting pro-oxidant, benzoyloxy dibenzyl carbonate, termed B2C, which is capable of rapidly declining GSH and elevating oxidative stress to a threshold level above which cancer cells cannot survive. B2C was designed to release quinone methide (QM) that rapidly depletes GSH through esterase-mediated hydrolysis. B2C was able to rapidly deplete GSH and induce an overwhelming level of oxidative stress in cancer cells, leading to mitochondrial disruption, activation of procaspase-3 and PARP-1, and cleavage of Bcl-2. In the study of tumor xenograft models, intravenously injected B2C caused apoptotic cell death in tumors and significantly suppressed tumor growth. These findings provide a new insight into the design of more effective anticancer drugs, which exploit altered redox balance in cancer cells.

Targeting mitochondria in cancer therapy could provide a basis for the selective anti-cancer activity

To determine the target of the recently identified lead compound NSC130362 that is responsible for its selective anti-cancer efficacy and safety in normal cells, structure-activity relationship (SAR) studies were conducted. First, NSC13062 was validated as a starting compound for the described SAR studies in a variety of cell-based viability assays. Then, a small library of 1,4-naphthoquinines (1,4-NQs) and quinoline-5,8-diones was tested in cell viability assays using pancreatic cancer MIA PaCa-2 cells and normal human hepatocytes. The obtained data allowed us to select a set of both non-toxic compounds that preferentially induced apoptosis in cancer cells and toxic compounds that induced apoptosis in both cancer and normal cells. Anti-cancer activity of the selected non-toxic compounds was confirmed in viability assays using breast cancer HCC1187 cells. Consequently, the two sets of compounds were tested in multiple cell-based and in vitro activity assays to identify key factors responsible for the observed activity. Inhibition of the mitochondrial electron transfer chain (ETC) is a key distinguishing activity between the non-toxic and toxic compounds. Finally, we developed a mathematical model that was able to distinguish these two sets of compounds. The development of this model supports our conclusion that appropriate quantitative SAR (QSAR) models have the potential to be employed to develop anti-cancer compounds with improved potency while maintaining non-toxicity to normal cells.

Arsenic trioxide encapsulated liposomes prepared via copper acetate gradient loading method and its antitumor efficiency

In this study, arsenic trioxide (ATO) was encapsulated in liposomes via copper acetate (Cu(OAc)₂) gradients and high entrapment efficiency of over 80% was obtained. The average particle size and the zeta-potential of the liposomes were detected to be 115.1 ± 29.1 nm and −21.97 ± 0.6 mV, respectively. The TEM images showed rod-like precipitates in the inner aqueous phase, which was supposed be due to the formation of insoluble ATO—Cu complex. The in vitro drug release of ATO—Cu liposomes exhibited a sustained release over 72 h, and the release rates decreased with the increase of the pH of release media. Pharmacokinetic and tissue distribution studies of ATO liposomes showed significantly reduced plasma clearance rate, increased AUC_0–12h and T_1/2, and improved tumor distribution of As compared to iv administration of ATO solution. The anti-tumor effect of ATO loaded liposomes to S180 tumor-bearing mice was significantly improved with a tumor inhibition rate of 61.2%, meanwhile the toxicity of encapsulated ATO was greatly decreased. In conclusion, ATO can be effectively encapsulated into liposomes by remote loading method via Cu(OAc)₂ gradients; the co-administration of ATO and Cu(II) via liposomal formulation may find wide applications in the treatment of various tumors.

Novel Combination of Arsenic Trioxide (As2O3) Plus Resveratrol in Inducing Programmed Cell Death of Human Neuroblastoma SK-N-SH Cells

AIM

Arsenic trioxide (As₂O₃), known as pi-shuang and the most toxic compound in traditional Chinese medicine, has been used as an antitumor agent for thousands of years. Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural phenol that has significant anti-bacterial, anti-fungaI and antiaging activities. Our study aimed to examine the combined anticancer effects of As₂O₃ and resveratrol against human neuroblastoma SK-N-SH cells, and elucidate the underlying intracellular signaling.

MATERIALS AND METHODS

SK-N-SH cells were treated with an extremely low-dose (2-4 μM) of As₂O₃ alone or combined with 75 μg/ml resveratrol for further comparisons. Cell viability, apoptotic signaling as well as synergistic cytotoxic effects were estimated using the MTT assay, microscopy observation, flow cytometric analysis for loss of mitochondrial membrane potential (MMP) and reactive oxygen species (ROS), and typical quantitative western blotting analysis. Student's t-test, and one- and two-way analysis of variance (ANOVA) were used for examination of significant differences.

RESULTS

The combined treatment was more effective than single treatment of As₂O₃ or resveratrol alone in suppressing cell viability, which correlated with the elevation of ROS levels. The intracellular mechanisms of cytotoxicity of As₂O₃ plus resveratrol were revealed as ROS accumulation and relative decrease of MMP, leading to activation of caspase-3 and -9, but not of caspase-1, -7 and-8. Combination treatment reduced the expression of B-cell lymphoma 2 (BCL2), BH3 interacting domain death agonist (BID), and BCL-x/L.

CONCLUSION

Combined treatment at extremely low concentration of two agents from natural products, As₂O₃ and resveratrol, has high potential as a cocktail of anticancer drugs for neuroblastoma.

Redox- and pH-Responsive Nanoparticles Release Piperlongumine in a Stimuli-Sensitive Manner to Inhibit Pulmonary Metastasis of Colorectal Carcinoma Cells

Redox-responsive nanoparticles having a diselenide linkage were synthesized to target pulmonary metastasis of cancer cells. Methoxy poly(ethylene glycol)-grafted chitosan (ChitoPEG) was crosslinked using selenocystine-acetyl histidine (Ac-histidine) conjugates (ChitoPEGse) for stimuli-responsive delivery of piperlongumine (PL). ChitoPEGse nanoparticles swelled in an acidic environment and became partially disintegrated in the presence of H2O2, resulting in an increase of particle size and in a size distribution having multimodal pattern. PL release increased under acidic conditions and in the presence of H2O2. Uptake of ChitoPEGse nanoparticles by CT26 cells significantly increased in acidic and redox state. PL-incorporated ChitoPEGse nanoparticles (PL NPs) showed similar anticancer activity in vitro against A549 and CT26 cells compared to PL itself. PL NP showed superior anticancer and antimetastatic activity in an in vivo CT26 cell pulmonary metastasis mouse model. Furthermore, an immunofluorescence imaging study demonstrated that PL NP conjugates were specifically delivered to the tumor mass in the lung. Conclusively, ChitoPEGse nanoparticles were able to be delivered to cancer cells with an acidic- or redox state-sensitive manner and then efficiently targeted pulmonary metastasis of cancer cells since ChitoPEGse nanoparticles have dual pH- and redox-responsiveness.

Extractive recovery and valorisation of arsenic from contaminated soil through phytoremediation using Pteris cretica

Contamination of ground water and soil by arsenic poses serious environmental challenges globally. A possible solution to this problem is through phytoremediation using hyper-accumulating plants. This study investigates phytoremediation of soil containing 200 ± 3 mg kg^-1 of arsenic using Pteris cretica ferns, and the strategies for arsenic extraction from the ferns biomass and subsequent conversions to valuable arsenic products. The Pteris cretica ferns achieved maximum arsenic accumulations of 4427 ± 79 to 4875 ± 96 mg of arsenic per kg dry biomass after 30 days. Extraction efficiencies of arsenic in the ferns fronds were 94.3 ± 2.1% for ethanol-water (1:1 v/v), 81.5 ± 3.2% for 1:1 (v/v) methanol-water, and 70.8 ± 2.9% for water alone. Molybdic acid process was used to recover 90.8 ± 5.3% of the arsenic, and 95.1 ± 4.6% of the phosphorus in the biomass extract. Quantitative precipitation of Mg₃(AsO₄)₂ and Mg₃(PO₄)₂ occurred on treatment of the aqueous solutions of arsenic and phosphorus after stripping at pH of 8-10. The efficiencies of Mg₃(AsO₄)₂ and Mg₃(PO₄)₂ precipitation were 96 ± 7.2% and 94 ± 3.4%, respectively. Arsenic nanoparticles produced from the recovered Mg₃(AsO₄)₂, using two-stage reduction process, had average particle diameters of 45.5 ± 11.3 nm. These nanoparticles are potentially valuable for medical applications, while the Mg₃(AsO₄)₂ could be converted to more valuable forms of arsenic or used as a pesticide, and the Mg₃(PO₄)₂ in fertiliser. Recovery of these valuable products from phytoremediation biomass would incentivise and drive commercial industries' participation in remediation of contaminated lands.

Nicotinamide Nucleotide Transhydrogenase as a Novel Treatment Target in Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is an aggressive malignancy with poor response to chemotherapy. In this study, we evaluated a potential new treatment target for ACC, focusing on the mitochondrial reduced form of NAD phosphate (NADPH) generator nicotinamide nucleotide transhydrogenase (NNT). NNT has a central role within mitochondrial antioxidant pathways, protecting cells from oxidative stress. Inactivating human NNT mutations result in congenital adrenal insufficiency. We hypothesized that NNT silencing in ACC cells will induce toxic levels of oxidative stress. To explore this, we transiently knocked down NNT in NCI-H295R ACC cells. As predicted, this manipulation increased intracellular levels of oxidative stress; this resulted in a pronounced suppression of cell proliferation and higher apoptotic rates, as well as sensitization of cells to chemically induced oxidative stress. Steroidogenesis was paradoxically stimulated by NNT loss, as demonstrated by mass spectrometry-based steroid profiling. Next, we generated a stable NNT knockdown model in the same cell line to investigate the longer lasting effects of NNT silencing. After long-term culture, cells adapted metabolically to chronic NNT knockdown, restoring their redox balance and resilience to oxidative stress, although their proliferation remained suppressed. This was associated with higher rates of oxygen consumption. The molecular pathways underpinning these responses were explored in detail by RNA sequencing and nontargeted metabolome analysis, revealing major alterations in nucleotide synthesis, protein folding, and polyamine metabolism. This study provides preclinical evidence of the therapeutic merit of antioxidant targeting in ACC as well as illuminating the long-term adaptive response of cells to oxidative stress.

Reactive oxygen species in haematopoiesis: leukaemic cells take a walk on the wild side

Oxidative stress is related to ageing and degenerative diseases, including cancer. However, a moderate amount of reactive oxygen species (ROS) is required for the regulation of cellular signalling and gene expression. A low level of ROS is important for maintaining quiescence and the differentiation potential of haematopoietic stem cells (HSCs), whereas the level of ROS increases during haematopoietic differentiation; thus, suggesting the importance of redox signalling in haematopoiesis. Here, we will analyse the importance of ROS for haematopoiesis and include evidence showing that cells from leukaemia patients live under oxidative stress. The potential sources of ROS will be described. Finally, the level of oxidative stress in leukaemic cells can also be harnessed for therapeutic purposes. In this regard, the reliance of front-line anti-leukaemia chemotherapeutics on increased levels of ROS for their mechanism of action, as well as the active search for novel compounds that modulate the redox state of leukaemic cells, will be analysed.

Modulation of reactive oxygen species via ERK and STAT3 dependent signalling are involved in the response of mesothelioma cells to exemestane

Pleural mesothelioma is a deadly form of cancer. The prognosis is extremely poor due to the limited treatment modalities. Uptake of asbestos fibres, the leading cause of mesothelioma, lead to the accumulation of reactive-oxygen-species (ROS). Interestingly, increasing ROS production by using ROS-generating drugs may offer a strategy to selectively trigger cell death. Exemestane, an aromatase inhibitor, has previously shown anti-tumor properties in mesothelioma preclinical models suggesting a role of G protein-coupled receptor 30 (GPR30) in the drug response. As exemestane, in addition to blocking estrogen biosynthesis, generates ROS that are able to arrest the growth of breast cancer, we explored the role of ROS, antioxidant defense system, and ROS-induced signalling pathways in mesothelioma cells during exemestane response. Here we report that exemestane treatment reduced cell proliferation with an increase in ROS production and reduction of cyclic adenosine monophosphate (cAMP) levels in MSTO-H211, Ist-Mes1, Ist-Mes2 and MPP89 exemestane-sensitive mesothelioma cell lines, but not in NCI-H2452 exemestane-insensitive mesothelioma cells. Exemestane induced a significant antioxidant response in NCI-H2452 cells, as highlighted by an increase in γ-glutamylcysteine levels, catalase (Cat), superoxide-dismutase and (SOD) and glutathione-peroxidase (GSH-Px) activity and nuclear factor E2-related factor 2 (Nrf2) activation, responsible for drug insensitivity. Conversely, exemestane elevated ROS levels along with increased ERK phosphorylation and a reduction of p-STA3 in exemestane-sensitive mesothelioma cells. ROS generation was the crucial event of exemestane action because ROS inhibitor N-acetyl-L-cysteine (NAC) abrogated p-ERK and p-STAT3 modulation and cellular death. Exemestane also modulates ERK and STAT3 signalling via GPR30. Results indicate an essential role of ROS in the antiproliferative action of exemestane in mesothelioma cells. It is likely that the additional oxidative insults induced by exemestane results in the lethal effects of mesothelioma cells by increasing ROS production. As such, manipulating ROS levels with exemestane seems to be a feasible strategy to selectively kill mesothelioma cells with less toxicity to normal cells by regulating ERK and STAT3 activity.

Copper as a target for prostate cancer therapeutics: copper-ionophore pharmacology and altering systemic copper distribution

Copper-ionophores that elevate intracellular bioavailable copper display significant therapeutic utility against prostate cancer cells in vitro and in TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice. However, the pharmacological basis for their anticancer activity remains unclear, despite impending clinical trails. Herein we show that intracellular copper levels in prostate cancer, evaluated in vitro and across disease progression in TRAMP mice, were not correlative with copper-ionophore activity and mirrored the normal levels observed in patient prostatectomy tissues (Gleason Score 7 & 9). TRAMP adenocarcinoma cells harbored markedly elevated oxidative stress and diminished glutathione (GSH)-mediated antioxidant capacity, which together conferred selective sensitivity to prooxidant ionophoric copper. Copper-ionophore treatments [CuII(gtsm), disulfiram & clioquinol] generated toxic levels of reactive oxygen species (ROS) in TRAMP adenocarcinoma cells, but not in normal mouse prostate epithelial cells (PrECs). Our results provide a basis for the pharmacological activity of copper-ionophores and suggest they are amendable for treatment of patients with prostate cancer. Additionally, recent in vitro and mouse xenograft studies have suggested an increased copper requirement by prostate cancer cells. We demonstrated that prostate adenocarcinoma development in TRAMP mice requires a functional supply of copper and is significantly impeded by altered systemic copper distribution. The presence of a mutant copper-transporting Atp7b protein (tx mutation: A4066G/Met1356Val) in TRAMP mice changed copper-integration into serum and caused a remarkable reduction in prostate cancer burden (64% reduction) and disease severity (grade), abrogating adenocarcinoma development. Implications for current clinical trials are discussed.

Investigation of the intracellular oxidative stress amplification, safety and anti-tumor effect of a kind of novel redox-responsive micelle

Redox-responsive FSST micelles with good biocompatibility can increase ROS levels in tumor cells and amplify oxidative stress, ultimately inducing apoptosis.

Multifaceted Roles of Glutathione and Glutathione-Based Systems in Carcinogenesis and Anticancer Drug Resistance

SIGNIFICANCE

Glutathione is the most abundant antioxidant molecule in living organisms and has multiple functions. Intracellular glutathione homeostasis, through its synthesis, consumption, and degradation, is an intricately balanced process. Glutathione levels are often high in tumor cells before treatment, and there is a strong correlation between elevated levels of intracellular glutathione/sustained glutathione-mediated redox activity and resistance to pro-oxidant anticancer therapy. Recent Advances: Ample evidence demonstrates that glutathione and glutathione-based systems are particularly relevant in cancer initiation, progression, and the development of anticancer drug resistance.

CRITICAL ISSUES

This review highlights the multifaceted roles of glutathione and glutathione-based systems in carcinogenesis, anticancer drug resistance, and clinical applications.

FUTURE DIRECTIONS

The evidence summarized here underscores the important role played by glutathione and the glutathione-based systems in carcinogenesis and anticancer drug resistance. Future studies should address mechanistic questions regarding the distinct roles of glutathione in different stages of cancer development and cancer cell death. It will be important to study how metabolic alterations in cancer cells can influence glutathione homeostasis. Sensitive approaches to monitor glutathione dynamics in subcellular compartments will be an indispensible step. Therapeutic perspectives should focus on mechanism-based rational drug combinations that are directed against multiple redox targets using effective, specific, and clinically safe inhibitors. This new strategy is expected to produce a synergistic effect, prevent drug resistance, and diminish doses of single drugs. Antioxid. Redox Signal. 27, 1217-1234.

Inhibition of E2F1 activity and cell cycle progression by arsenic via retinoblastoma protein

The regulation of cell cycle progression by steroid hormones and growth factors is important for maintaining normal cellular processes including development and cell proliferation. Deregulated progression through the G1/S and G2/M cell cycle transitions can lead to uncontrolled cell proliferation and cancer. The transcription factor E2F1, a key cell cycle regulator, targets genes encoding proteins that regulate cell cycle progression through the G1/S transition as well as proteins important in DNA repair and apoptosis. E2F1 expression and activity is inhibited by inorganic arsenic (iAs) that has a dual role as a cancer therapeutic and as a toxin that leads to diseases including cancer. An understanding of what underlies this dichotomy will contribute to understanding how to use iAs as a more effective therapeutic and also how to treat cancers that iAs promotes. Here, we show that quiescent breast adenocarcinoma MCF-7 cells treated with 17-β estradiol (E2) progress through the cell cycle, but few cells treated with E2 + iAs progress from G1 into S-phase due to a block in cell cycle progression. Our data support a model in which iAs inhibits the dissociation of E2F1 from the tumor suppressor, retinoblastoma protein (pRB) due to changes in pRB phosphorylation which leads to decreased E2F1 transcriptional activity. These findings present an explanation for how iAs can disrupt cell cycle progression through E2F1-pRB and has implications for how iAs acts as a cancer therapeutic as well as how it may promote tumorigenesis through decreased DNA repair.

ROS-modulated therapeutic approaches in cancer treatment

PURPOSE

Reactive oxygen species (ROS) are produced in cancer cells as a result of increased metabolic rate, dysfunction of mitochondria, elevated cell signaling, expression of oncogenes and increased peroxisome activities. Certain level of ROS is required by cancer cells, above or below which lead to cytotoxicity in cancer cells. This biochemical aspect can be exploited to develop novel therapeutic agents to preferentially and selectively target cancer cells.

METHODS

We searched various electronic databases including PubMed, Web of Science, and Google Scholar for peer-reviewed english-language articles. Selected articles ranging from research papers, clinical studies, and review articles on the ROS production in living systems, its role in cancer development and cancer treatment, and the role of microbiota in ROS-dependent cancer therapy were analyzed.

RESULTS

This review highlights oxidative stress in tumors, underlying mechanisms of different relationships of ROS and cancer cells, different ROS-mediated therapeutic strategies and the emerging role of microbiota in cancer therapy.

CONCLUSION

Cancer cells exhibit increased ROS stress and disturbed redox homeostasis which lead to ROS adaptations. ROS-dependent anticancer therapies including ROS scavenging anticancer therapy and ROS boosting anticancer therapy have shown promising results in vitro as well as in vivo. In addition, response to cancer therapy is modulated by the human microbiota which plays a critical role in systemic body functions.

Reactive Oxygen Species Synergize To Potently and Selectively Induce Cancer Cell Death

A distinctive feature of cancer cells is their elevated levels of reactive oxygen species (ROS), a trait that can cause cancer cells to be more sensitive to ROS-inducing agents than normal cells. ROS take several forms, each with different reactivity and downstream consequence. Here we show that simultaneous generation of superoxide and hydrogen peroxide within cancer cells results in significant synergy, potently and selectively causing cancer cell death. In these experiments superoxide is generated using the NAD(P)H quinone oxidoreductase 1 (NQO1) substrate deoxynyboquinone (DNQ), and hydrogen peroxide is generated using the lactate dehydrogenase A (LDH-A) inhibitor NHI-Glc-2. This combination reduces tumor burden and prolongs survival in a mouse model of lung cancer. These data suggest that simultaneous induction of superoxide and hydrogen peroxide can be a powerful and selective anticancer strategy.

Chrysin and silibinin sensitize human glioblastoma cells for arsenic trioxide

Arsenic trioxide (ATO) is highly efficient in treating acute promyelocytic leukemia. Other malignancies, however, are often less sensitive. Searching for compounds sensitizing arsenic resistant tumours for ATO the plant polyphenols, chrysin and silibinin, and the ATP binding cassette (ABC) transporter inhibitor MK-571, respectively, were investigated in human glioblastoma A-172 cells. The sensitivity of A-172 cells to ATO was characterized by a median cytotoxic concentration of 6 μM ATO. Subcytotoxic concentrations of chrysin, silibinin and MK-571, respectively, remarkably increased the sensitivity of the cells to ATO by factors of 4-6. Isobolographic analysis revealed synergistic interaction of the polyphenols and MK-571, respectively, with ATO. Sensitization by chrysin was associated with depletion of cellular glutathione and increased accumulation of arsenic. In contrast, silibinin and also MK-571 increased the accumulation of arsenic more strongly but without affecting the glutathione level. The increase of arsenic accumulation could be attributed to a decreased rate of arsenic export and, additionally, in the case of silibinin and MK-571, to an increasing amount of irreversibly accumulated arsenic. Direct interaction with ABC transporters stimulating export of glutathione and inhibiting export of arsenic, respectively, are discussed as likely mechanisms of the sensitizing activity of chrysin and silibinin.