JS-K, a GST-activated nitric oxide generator, induces DNA double-strand breaks, activates DNA damage response pathways, and induces apoptosis in vitro and in vivo in human multiple myeloma cells

Targeted therapy for non-small-cell lung cancer: New insights into regulated cell death combined with immunotherapy

Non-small-cell lung cancer (NSCLC), which has a high rate of metastatic spread and drug resistance, is the most common subtype of lung cancer. Therefore, NSCLC patients have a very poor prognosis and a very low chance of survival. Human cancers are closely linked to regulated cell death (RCD), such as apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. Currently, small-molecule compounds targeting various types of RCD have shown potential as anticancer treatments. Moreover, RCD appears to be a specific part of the antitumor immune response; hence, the combination of RCD and immunotherapy might increase the inhibitory effect of therapy on tumor growth. In this review, we summarize small-molecule compounds used for the treatment of NSCLC by focusing on RCD and pharmacological systems. In addition, we describe the current research status of an immunotherapy combined with an RCD-based regimen for NSCLC, providing new ideas for targeting RCD pathways in combination with immunotherapy for patients with NSCLC in the future.

The Triple Crown: NO, CO, and H2S in cancer cell biology

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are three endogenously produced gases with important functions in the vasculature, immune defense, and inflammation. It is increasingly apparent that, far from working in isolation, these three exert many effects by modulating each other's activity. Each gas is produced by three enzymes, which have some tissue specificities and can also be non-enzymatically produced by redox reactions of various substrates. Both NO and CO share similar properties, such as activating soluble guanylate cyclase (sGC) to increase cyclic guanosine monophosphate (cGMP) levels. At the same time, H2S both inhibits phosphodiesterase 5A (PDE5A), an enzyme that metabolizes sGC and exerts redox regulation on sGC. The role of NO, CO, and H2S in the setting of cancer has been quite perplexing, as there is evidence for both tumor-promoting and pro-inflammatory effects and anti-tumor and anti-inflammatory activities. Each gasotransmitter has been found to have dual effects on different aspects of cancer biology, including cancer cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and immunomodulation. These seemingly contradictory actions may relate to each gas having a dual effect dependent on its local flux. In this review, we discuss the major roles of NO, CO, and H2S in the context of cancer, with an effort to highlight the dual nature of each gas in different events occurring during cancer progression.

Nitric Oxide Prevents Glioblastoma Stem Cells' Expansion and Induces Temozolomide Sensitization

Glioblastoma multiforme (GBM) has high mortality and recurrence rates. Malignancy resilience is ascribed to Glioblastoma Stem Cells (GSCs), which are resistant to Temozolomide (TMZ), the gold standard for GBM post-surgical treatment. However, Nitric Oxide (NO) has demonstrated anti-cancer efficacy in GBM cells, but its potential impact on GSCs remains unexplored. Accordingly, we investigated the effects of NO, both alone and in combination with TMZ, on patient-derived GSCs. Experimentally selected concentrations of diethylenetriamine/NO adduct and TMZ were used through a time course up to 21 days of treatment, to evaluate GSC proliferation and death, functional recovery, and apoptosis. Immunofluorescence and Western blot analyses revealed treatment-induced effects in cell cycle and DNA damage occurrence and repair. Our results showed that NO impairs self-renewal, disrupts cell-cycle progression, and expands the quiescent cells' population. Consistently, NO triggered a significant but tolerated level of DNA damage, but not apoptosis. Interestingly, NO/TMZ cotreatment further inhibited cell cycle progression, augmented G0 cells, induced cell death, but also enhanced DNA damage repair activity. These findings suggest that, although NO administration does not eliminate GSCs, it stunts their proliferation, and makes cells susceptible to TMZ. The resulting cytostatic effect may potentially allow long-term control over the GSCs' subpopulation.

Fifty Years of Diazeniumdiolate Research: A Tribute to Dr. Larry K. Keefer

The pioneering studies of Dr. Larry Keefer and colleagues with diazeniumdiolates or NONOates as a platform have unraveled the chemical biology of many nitric oxides and have led to the design of a variety of promising therapeutic agents in oncology, gastroenterology, antimicrobials, wound healing, and the like. This dedication to Dr. Larry Keefer briefly highlights some of his studies using the diazeniumdiolate platform in the cancer arena.

Historical Perspectives of the Role of NO/NO Donors in Anti-Tumor Activities: Acknowledging Dr. Keefer's Pioneering Research

The role of nitric oxide (NO) in cancer has been a continuous challenge and particularly the contradictory findings in the literature reporting NO with either anti-cancer properties or pro-cancer properties. This dilemma was largely resolved by the level of NO/inducible nitric oxide synthase in the tumor environment as well as other cancer-associated gene activations in different cancers. The initial findings on the role of NO as an anti-cancer agent was initiated in the late 1990's in Dr. Larry Keefer's laboratory, who had been studying and synthesizing many compounds with releasing NO under different conditions. Using an experimental model with selected NO compounds they demonstrated for the first time that NO can inhibit tumor cell proliferation and sensitizes drug-resistant cancer cells to chemotherapy-induced cytotoxicity. This initial finding was the backbone and the foundation of subsequent reports by the Keefer's laboratory and followed by many others to date on NO-mediated anti-cancer activities and the clinical translation of NO donors in cancer therapy. Our laboratory initiated studies on NO-mediated anti-cancer therapy and chemo-immuno-sensitization following Keefer's findings and used one of his synthesized NO donors, namely, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETANONOate), throughout most of our studies. Many of Keefer's collaborators and other investigators have reported on the selected compound, O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl] diazen-1-ium-1,2-diolate (JS-K), and its therapeutic role in many tumor model systems. Several lines of evidence that investigated the treatment with NO donors in various cancer models revealed that a large number of gene products are modulated by NO, thus emphasizing the pleiotropic effects of NO on cancers and the identification of many targets of therapeutic significance. The present review reports historically of several examples reported in the literature that emanated on NO-mediated anti-cancer activities by the Keefer's laboratory and his collaborators and other investigators including my laboratory at the University of California at Los Angeles.

Effects of combination docetaxel with NO treatment to enhance the anti-nasopharyngeal carcinoma efficiency in vitro and in vivo

Nasopharyngeal carcinoma (NPC) is one of the major causes of death in Southern China. Due to the insidious location of NPC, the therapeutic effect of locoregionally advanced NPC is still unsatisfactory. In this work, to improve the treatment efficiency, combining DOC and JS-K to inhibit NPC cells (HNE-1) in vitro was investigated, as well as its possible mechanisms. Moreover, the in vivo effects of DOC and JS-K combination treatment were also evaluated in a xenograft model with HNE-1 cells. In vitro experiments including cell proliferation, migration ability, apoptosis, and expression levels of apoptosis-associated proteins revealed that the combination of DOC and JS-K was able to enhance antitumor effects. In vivo results further confirmed a significant treatment effect without obvious toxicity on mice. The present work provides a promising idea for the treatment of locally advanced NPC.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

Molecular Mechanisms of Cytotoxicty of NCX4040, the Non-Steroidal Anti-Inflammatory NO-Donor, in Human Ovarian Cancer Cells

NCX4040, the non-steroidal anti-inflammatory-NO donor, is cytotoxic to several human tumors, including ovarian tumor cells. We have found that NCX4040 is also cytotoxic against both OVCAR-8 and its adriamycin resistant (NCI/ADR-RES) tumor cell lines. Here, we have examined mechanism(s) for the cytotoxicity of NCX4040 in OVCAR-8 and NCI/ADR-RES cell lines. We found that NCX4040 induced significant apoptosis in both cell lines. Furthermore, NCX4040 treatment caused significant depletion of cellular glutathione, causing oxidative stress due to the formation of reactive oxygen/nitrogen species (ROS/RNS). Significantly more ROS/RNS were detected in OVCAR-8 cells than in NCI/ADR-RES cells which may have resulted from increased activities of SOD, glutathione peroxidase and transferases expressed in NCI/ADR-RES cells. NCX4040 treatment resulted in the formation of double-strand DNA breaks in both cells; however, more of these DNA breaks were detected in OVCAR-8 cells. RT-PCR studies indicated that NCX4040-induced DNA damage was not repaired as efficiently in NCI/ADR-RES cells as in OVCAR-8 cells which may lead to a differential cell death. Pretreatment of OVCAR-8 cells with N-acetylcysteine (NAC) significantly decreased cytotoxicity of NCX4040 in OVCAR-8 cells; however, NAC had no effects on NCX4040 cytotoxicity in NCI/ADR-RES cells. In contrast, FeTPPS, a peroxynitrite scavenger, completely blocked NCX4040-induced cell death in both cells, suggesting that NCX4040-induced cell death could be mediated by peroxynitrite formed from NCX4040 following cellular metabolism.

IFN-γ activates the tumor cell-intrinsic STING pathway through the induction of DNA damage and cytosolic dsDNA formation

Stimulator of interferon genes (STING) pathway activation predicts the effectiveness of targeting the PD-1/PD-L1 axis in lung cancer. Active IFN-γ signaling is a common feature in tumors that respond to PD-1/PD-L1 blockade. The connection between IFN-γ and STING signaling in cancer cells has not been documented. We showed that IFN-γ caused DNA damage and the accumulation of cytosolic dsDNA, leading to the activation of the cGAS- and IFI16-dependent STING pathway in lung adenocarcinoma cells. IFN-γ-induced iNOS expression and nitric oxide production were responsible for DNA damage and STING activation. Additional etoposide treatment enhanced IFN-γ-induced IFN-β and CCL5 expression. Tumor-infiltrating T cells stimulated with a combination of anti-CD3 and anti-PD-1 antibodies caused STING activation and increased IFN-β and CCL5 expression in lung adenocarcinoma. These effects were abrogated by the addition of an IFN-γ neutralizing antibody. Our results suggest that the activation of tumor-infiltrating T cells could alter the tumor microenvironment via the IFN-γ-mediated activation of STING signaling in cancer cells.

Pillars and Gaps of S-Nitrosylation-Dependent Epigenetic Regulation in Physiology and Cancer

Nitric oxide (NO) is a diffusible signaling molecule produced by three isoforms of nitric oxide synthase, which release NO during the metabolism of the amino acid arginine. NO participates in pathophysiological responses of many different tissues, inducing concentration-dependent effect. Indeed, while low NO levels generally have protective effects, higher NO concentrations induce cytotoxic/cytostatic actions. In recent years, evidences have been accumulated unveiling S-nitrosylation as a major NO-dependent post-translational mechanism ruling gene expression. S-nitrosylation is a reversible, highly regulated phenomenon in which NO reacts with one or few specific cysteine residues of target proteins generating S-nitrosothiols. By inducing this chemical modification, NO might exert epigenetic regulation through direct effects on both DNA and histones as well as through indirect actions affecting the functions of transcription factors and transcriptional co-regulators. In this light, S-nitrosylation may also impact on cancer cell gene expression programs. Indeed, it affects different cell pathways and functions ranging from the impairment of DNA damage repair to the modulation of the activity of signal transduction molecules, oncogenes, tumor suppressors, and chromatin remodelers. Nitrosylation is therefore a versatile tool by which NO might control gene expression programs in health and disease.

Recent Advances in Hydrogen Peroxide Responsive Organoborons for Biological and Biomedical Applications

Hydrogen peroxide is the most stable reactive oxygen species generated endogenously, participating in numerous physiological processes and abnormal pathological conditions. Mounting evidence suggests that a higher level of H₂ O₂ exists in various disease conditions. Thus, H₂ O₂ functions as an ideal target for site-specific bioimaging and therapeutic targeting. The unique reactivity of organoborons with H₂ O₂ provides a method for developing chemoselective molecules for biological and biomedical applications. This review highlights the design and application of boron-derived molecules for H₂ O₂ detection, and the utility of boron moieties toward masking reactive compounds leading to the development of metal prochelators and prodrugs for selectively delivering an active species at the target sites with elevated H₂ O₂ levels. Additionally, the emergence of H₂ O₂ -responsive theranostic agents consisting of both therapeutic and diagnostic moieties in one integrated system are discussed. The purpose of this review is to provide a better understanding of the role of boron-derived molecules toward biological and pharmacological applications.

O2-(2,4-dinitrophenyl) diazeniumdiolate derivative induces G2/M arrest via PTEN-mediated inhibition of PI3K/Akt pathway in hepatocellular carcinoma cells

OBJECTIVES

The study aimed to investigate whether G2/M arrest caused by O2-(2,4-dinitrophenyl) diazeniumdiolate derivative (JS-K) was related to PTEN-mediated inhibition of PI3K/Akt pathway in hepatocellular carcinoma cells.

METHODS

The cell apoptosis was detected by DAPI staining and Annexin V-FITC/PI dual staining. The cell cycle was analysed by PI staining. The expressions of cell cycle-related proteins, PTEN and PI3K/AKT pathway were measured by Western blot. The rat model of primary hepatic carcinoma was established with diethylnitrosamine to verify the antitumour effects of JS-K.

KEY FINDINGS

The morphological features of apoptosis were obviously reversed when the cells were pre-treated with bpv(pic), followed by treatment with JS-K. JS-K mediated G2/M arrest and down-regulated expressions of cyclin B1. Meanwhile, it up-regulated the expression of p-Cdk1, p-Chk2 and p-CDC25C while down-regulated that of Cdk1 and CDC25C. Furthermore, JS-K also enhanced the expressions of p21 and p27, PTEN and p53 while decreased the expressions of p-PTEN, PI3K and p-AKT. However, bpv(pic) and Carboxy-PTIO could reverse JS-K-induced G2/M cell arrest and PTEN-mediated inhibition of the PI3K/AKT pathway. The same results were also testified in the rat model of primary hepatic carcinoma.

CONCLUSIONS

JS-K caused G2/M arrest through PTEN-mediated inhibition of the PI3K/AKT pathway involving Chk2/CDC25C/Cdk1 checkpoint.

A nitric oxide-releasing prodrug promotes apoptosis in human renal carcinoma cells: Involvement of reactive oxygen species

Background

JS-K is a nitric oxide (NO)-releasing prodrug of the O2-arylated diazeniumdiolate group that shows pronounced cytotoxicity and antitumor properties in numerous cancer models, including in vitro as well as in vivo. Reactive oxygen species (ROS) induce carcinogenesis by altering the redox status, causing increment in vulnerability to oxidative stress.

Material and methods

To determine the effect of JS-K, a glutathione S-transferase (GST)-activated NO-donor prodrug, on the induction of ROS accumulation, proliferation, and apoptosis in human renal carcinoma cells, we measured the changes of cell proliferation, apoptosis, ROS growth, and initiation of the mitochondrial signaling pathway before and after JS-K treatment.

Results

In vitro, dose- and time-dependent development of renal carcinoma cells were controlled for JS-K, and JS-K also triggered ROS aggregation and cell apoptosis. Treatment with JS-K induces the levels of pro-apoptotic proteins (Bak and Bax) and decrease the number of anti-apoptotic protein (Bcl-2). In fact, JS-K-induced apoptosis was reversed by the antioxidant N-acetylcysteine, and oxidized glutathione, a pro-oxidant, improved JS-K-induced apoptosis. Finally, we demonstrated that in renal carcinoma cells, JS-K improved the chemosensitivity of doxorubicin.

Conclusion

Our data indicate that JS-K-released NO induce apoptosis of renal carcinoma cells by increasing ROS levels.

Identification of targets of JS-K against HBV-positive human hepatocellular carcinoma HepG2.2.15 cells with iTRAQ proteomics

JS-K, a nitric oxide-releasing diazeniumdiolates, is effective against various tumors. We have discovered that JS-K was effective against Hepatitis B virus (HBV)-positive HepG2.2.15 cells. This study used iTRAQ to identify differentially expressed proteins following JS-K treatment of HepG2.2.15 cells. Silenced Transgelin (shTAGLN-2.15) cells were constructed, and the cell viability was analyzed by the CCK8 assay after treatment with JS-K. There were 182 differentially expressed proteins in JS-K treated-HepG2.2.15 cells; 73 proteins were up-regulated and 109 proteins were down-regulated. These proteins were categorized according to GO classification. KEGG enrichment analysis showed that Endocytosis, Phagosome and Proteoglycans were the most significant pathways. RT-PCR confirmed that the expression levels of TAGLN, IGFBP1, SMTN, SERPINE1, ANXA3, TMSB10, LGALS1 and KRT19 were significantly up-regulated, and the expression levels of C5, RBP4, CHKA, SIRT5 and TRIM14 were significantly down-regulated in JS-K treated-HepG2.2.15 cells. Western blotting confirmed the increased levels of USP13 and TAGLN proteins in JS-K treated-HepG2.2.15 cells. Molecular docking revealed the binding of JS-K to TAGLN and shTAGLN-2.15 cells were resistant to JS-K cytotoxicity, suggesting that TAGLN could be an important target in JS-K anti-HBV-positive liver cancer cells. These proteomic findings could shed new insights into mechanisms underlying the effect of JS-K against HBV-related HCC.

The Role of Nitric Oxide in Cancer: Master Regulator or NOt?

Nitric oxide (NO) is a key player in both the development and suppression of tumourigenesis depending on the source and concentration of NO. In this review, we discuss the mechanisms by which NO induces DNA damage, influences the DNA damage repair response, and subsequently modulates cell cycle arrest. In some circumstances, NO induces cell cycle arrest and apoptosis protecting against tumourigenesis. NO in other scenarios can cause a delay in cell cycle progression, allowing for aberrant DNA repair that promotes the accumulation of mutations and tumour heterogeneity. Within the tumour microenvironment, low to moderate levels of NO derived from tumour and endothelial cells can activate angiogenesis and epithelial-to-mesenchymal transition, promoting an aggressive phenotype. In contrast, high levels of NO derived from inducible nitric oxide synthase (iNOS) expressing M1 and Th1 polarised macrophages and lymphocytes may exert an anti-tumour effect protecting against cancer. It is important to note that the existing evidence on immunomodulation is mainly based on murine iNOS studies which produce higher fluxes of NO than human iNOS. Finally, we discuss different strategies to target NO related pathways therapeutically. Collectively, we present a picture of NO as a master regulator of cancer development and progression.

E1 Enzymes as Therapeutic Targets in Cancer

Post-translational modifications of cellular substrates with ubiquitin and ubiquitin-like proteins (UBLs), including ubiquitin, SUMOs, and neural precursor cell-expressed developmentally downregulated protein 8, play a central role in regulating many aspects of cell biology. The UBL conjugation cascade is initiated by a family of ATP-dependent enzymes termed E1 activating enzymes and executed by the downstream E2-conjugating enzymes and E3 ligases. Despite their druggability and their key position at the apex of the cascade, pharmacologic modulation of E1s with potent and selective drugs has remained elusive until 2009. Among the eight E1 enzymes identified so far, those initiating ubiquitylation (UBA1), SUMOylation (SAE), and neddylation (NAE) are the most characterized and are implicated in various aspects of cancer biology. To date, over 40 inhibitors have been reported to target UBA1, SAE, and NAE, including the NAE inhibitor pevonedistat, evaluated in more than 30 clinical trials. In this Review, we discuss E1 enzymes, the rationale for their therapeutic targeting in cancer, and their different inhibitors, with emphasis on the pharmacologic properties of adenosine sulfamates and their unique mechanism of action, termed substrate-assisted inhibition. Moreover, we highlight other less-characterized E1s-UBA6, UBA7, UBA4, UBA5, and autophagy-related protein 7-and the opportunities for targeting these enzymes in cancer. SIGNIFICANCE STATEMENT: The clinical successes of proteasome inhibitors in cancer therapy and the emerging resistance to these agents have prompted the exploration of other signaling nodes in the ubiquitin-proteasome system including E1 enzymes. Therefore, it is crucial to understand the biology of different E1 enzymes, their roles in cancer, and how to translate this knowledge into novel therapeutic strategies with potential implications in cancer treatment.

CircRNA inhibits DNA damage repair by interacting with host gene

Background

Deregulated circular RNAs (circRNAs) are associated with the development of cancer and therapy resistance. However, functional research of circRNAs mostly focus on potential miRNA or protein binding and more potential regulation of circRNA on host gene DNA in cancers are yet to be inspected.

Method

We performed total RNA sequencing on clinical breast cancer samples and identified the expression patterns of circRNAs and corresponding host genes in patient blood, tumor and adjacent normal tissues. qPCR, northern blot and in situ hybridization were used to validate the dysregulation of circRNA circSMARCA5. A series of procedures including R-loop dot-blotting, DNA-RNA immunoprecipitation and mass spectrum, etc. were conducted to explore the regulation of circSMARCA5 on the transcription of exon 15 of SMARCA5. Moreover, immunofluorescence and in vivo experiments were executed to investigate the overexpression of circSMARCA5 with drug sensitivities.

Results

We found that circRNAs has average higher expression over its host linear genes in peripheral blood. Compared to adjacent normal tissues, circSMARCA5 is decreased in breast cancer tissues, contrary to host gene SMARCA5. The enforced expression of circSMARCA5 induced drug sensitivity of breast cancer cell lines in vitro and in vivo. Furthermore, we demonstrated that circSMARCA5 can bind to its parent gene locus, forming an R-loop, which results in transcriptional pausing at exon 15 of SMARCA5. CircSMARCA5 expression resulted in the downregulation of SMARCA5 and the production of a truncated nonfunctional protein, and the overexpression of circSMARCA5 was sufficient to improve sensitivity to cytotoxic drugs.

Conclusion

Our results revealed a new regulatory mechanism for circRNA on its host gene and provided evidence that circSMARCA5 may serve as a therapeutic target for drug-resistant breast cancer patients.

Differential nitric oxide induced by Mycobacterium bovis and BCG leading to dendritic cells apoptosis in a caspase dependent manner

Dendritic cells (DCs) are critical for both innate and adaptive immunity. Meanwhile, nitric oxide (NO) is a member of reactive nitrogen species (RNS) generally considered to play a key role in the bactericidal process in innate immunity against Mycobacterium tuberculosis complex infection. The present study therefore investigated the mechanism of NO production in murine DCs induced by Mycobacterium bovis (M.bovis) and its attenuated strain Bacillus Calmette-Guérin (BCG) infection. The expression of genes Slc7A1, Slc7A2, iNOS, and ArgI essential to NO synthesis was up-regulated in M.bovis/BCG infected DCs. IFN-γ addition further increased, while the iNOS inhibitor L-NMMA significantly inhibited their expression. Accordingly, the end products of arginine metabolism, NO and urea, were found to be significantly increased. In addition, BCG induced significantly higher levels of apoptosis in DCs compared to M.bovis shown by higher levels of DNA fragmentation using flow cytometry and release of mitochondrial Cytochrome C, and up-regulation of the genes caspase-3, caspase-8, caspase-9 and dffa critical to apoptosis by qRT-PCR detection and western blot analysis. Furthermore, IFN-γ increased, but L-NMMA decreased apoptosis of M.bovis/BCG infected DCs. In addition, mycobacterial intracellular survival was significantly reduced by IFN-γ treatment in BCG infected DCs, while slightly increased by L-NMMA treatment. Taken altogether, our data show that NO synthesis was differentially increased and associated with apoptosis in M.bovis/BCG infected DCs. These findings may significantly contribute to elucidate the pathogenesis of M.bovis.

Double-component diazeniumdiolate derivatives as anti-cancer agents

In this study, we synthesized a series of double-component O²-aryl diazeniumdiolate (DDNO) derivatives, of which each molecule can release up to four nitric oxide molecules. These compounds showed cytotoxic activities to cancer cells, such as human leukemia, breast cancer and lung cancer. Among them, compound 1 (DDNO-1) showed the highest specific activity to human leukemia cells. It induced cell apopotosis and arrest cell cycle of G₂/M phase. The JNK and p38 protein kinases were activated by compound 1 to induce cancer cell apoptosis. Compound 1 also increased pro-apoptotic Bax level, which is a same function compared to a reported NO donor, JS-K. More interestingly, it decreased the level of an anti-apoptotic member Bcl-2, which is an opposite effect compared to JS-K. Compound 1 could be developed as a new anti-cancer agent since it increases the Bax/Bcl-2 ratio to overcome the drug resistance.

Improvement of conventional anti-cancer drugs as new tools against multidrug resistant tumors

Multidrug resistance (MDR) is the dominant cause of the failure of cancer chemotherapy. The design of antitumor drugs that are able to evade MDR is rapidly evolving, showing that this area of biomedical research attracts great interest in the scientific community. The current review explores promising recent approaches that have been developed with the aim of circumventing or overcoming MDR. Encouraging results have been obtained in the investigation of the MDR-modulating properties of various classes of natural compounds and their analogues. Inhibition of P-gp or downregulation of its expression have proven to be the main mechanisms by which MDR can be surmounted. The use of hybrid molecules that are able to simultaneously interact with two or more cancer cell targets is currently being explored as a means to circumvent drug resistance. This strategy is based on the design of hybrid compounds that are obtained either by merging the structural features of separate drugs, or by conjugating two drugs or pharmacophores via cleavable/non-cleavable linkers. The approach is highly promising due to the pharmacokinetic and pharmacodynamic advantages that can be achieved over the independent administration of the two individual components. However, it should be stressed that the task of obtaining successful multivalent drugs is a very challenging one. The conjugation of anticancer agents with nitric oxide (NO) donors has recently been developed, creating a particular class of hybrid that can combat tumor drug resistance. Appropriate NO donors have been shown to reverse drug resistance via nitration of ABC transporters and by interfering with a number of metabolic enzymes and signaling pathways. In fact, hybrid compounds that are produced by covalently attaching NO-donors and antitumor drugs have been shown to elicit a synergistic cytotoxic effect in a variety of drug resistant cancer cell lines. Another strategy to circumvent MDR is based on nanocarrier-mediated transport and the controlled release of chemotherapeutic drugs and P-gp inhibitors. Their pharmacokinetics are governed by the nanoparticle or polymer carrier and make use of the enhanced permeation and retention (EPR) effect, which can increase selective delivery to cancer cells. These systems are usually internalized by cancer cells via endocytosis and accumulate in endosomes and lysosomes, thus preventing rapid efflux. Other modalities to combat MDR are described in this review, including the pharmaco-modulation of acridine, which is a well-known scaffold in the development of bioactive compounds, the use of natural compounds as means to reverse MDR, and the conjugation of anticancer drugs with carriers that target specific tumor-cell components. Finally, the outstanding potential of in silico structure-based methods as a means to evaluate the ability of antitumor drugs to interact with drug transporters is also highlighted in this review. Structure-based design methods, which utilize 3D structural data of proteins and their complexes with ligands, are the most effective of the in silico methods available, as they provide a prediction regarding the interaction between transport proteins and their substrates and inhibitors. The recently resolved X-ray structure of human P-gp can help predict the interaction sites of designed compounds, providing insight into their binding mode and directing possible rational modifications to prevent them from becoming P-gp drug substrates. In summary, although major efforts were invested in the search for new tools to combat drug resistant tumors, they all require further implementation and methodological development. Further investigation and progress in the abovementioned strategies will provide significant advances in the rational combat against cancer MDR.

Role of Oxygen and Nitrogen Radicals in the Mechanism of Anticancer Drug Cytotoxicity

Because of the emergence of drug-resistant tumor cells, successful treatments of human malignancies have been difficult to achieve in the clinic. In spite of various approaches to overcome multi drug resistance, it has remained challenging and elusive. It is, therefore, necessary to define and understand the mechanisms of drug-induced tumor cell killing for the future development of anticancer agents and for rationally designed combination chemotherapies. The clinically active antitumor drugs, topotecan, doxorubicin, etoposide, and procarbazine are currently used for the treatment of human tumors. Therefore, a great deal research has been carried to understand mechanisms of actions of these agents both in the laboratory and in the clinic. These drugs are also extensively metabolized in tumor cells to various reactive species and generate oxygen free radical species (ROS) that initiate lipid peroxidation and induce DNA damage. However, the roles of ROS in the mechanism of cytotoxicity remain unappreciated in the clinic. In addition to ROS, various reactive nitrogen species (RNS) are also formed in tumor cells and in vivo. However, the importance of RNS in cancer treatment is not clear and has remained poorly defined. This review discusses the current understanding of the formation and the significance of ROS and RNS in the mechanisms of various clinically active anticancer drugs.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Nitric oxide regulates the expression of heme carrier protein-1 via hypoxia inducible factor-1α stabilization

Photodynamic therapy (PDT) is a cancer therapy that capitalizes on cancer-specific porphyrin accumulation. We have investigated this phenomenon to propose the following three conclusions: 1) the mechanism underlying this phenomenon is closely related to both nitric oxide (NO) and heme carrier protein-1 (HCP-1), 2) NO inactivates ferrochelatase, and thus, the intracellular porphyrin levels in the cells are increased by the administration of an NO donor after 5-aminolevulinic acid treatment, 3) HCP-1 transports not only heme but also other porphyrins. Since NO stabilizes hypoxia-inducible factor (HIF)-1α, resulting in the upregulation of heme biosynthesis, HCP-1 expression can be increased by HIF-1α stabilization. In this study, we determined whether NO regulates HCP-1 expression by stabilizing HIF-1α expression. For this purpose, rat gastric cancer cell line RGK36 was treated with L-arginine or N6-(1-iminoethyl)-L-lysine (L-NIL). L-arginine treatment increased the intracellular NO concentration, and both HCP-1 and HIF-1α expression, while L-NIL treatment decreased them. Cytotoxicity of PDT was enhanced by L-arginine, following intracellular hemato-porphyrin dihydrochloride (HpD) accumulation. Both Cytotoxicity of PDT and HpD accumulation were decreased by L-NIL. The HCP-1 and HIF-1α expression, intracellular HpD accumulation and PDT cytotoxicity were decreased by 2-methoxyestradiol, which is a HIF-1α inhibitor. Moreover, these phenomena were not increased by a combination of both L-arginine and 2-Me. Thus, HCP-1 can be a downstream target of HIF-1α. These effects were also induced in the human gastric cancer cell line MKN45. Taken together, we conclude that HCP-1 expression is regulated by NO via HIF-1α stabilization.

Nitric Oxide Antagonism to Anti-Glioblastoma Photodynamic Therapy: Mitigation by Inhibitors of Nitric Oxide Generation

Many studies have shown that low flux nitric oxide (NO) produced by inducible NO synthase (iNOS/NOS2) in various tumors, including glioblastomas, can promote angiogenesis, cell proliferation, and migration/invasion. Minimally invasive, site-specific photodynamic therapy (PDT) is a highly promising anti-glioblastoma modality. Recent research in the authors' laboratory has revealed that iNOS-derived NO in glioblastoma cells elicits resistance to 5-aminolevulinic acid (ALA)-based PDT, and moreover endows PDT-surviving cells with greater proliferation and migration/invasion aggressiveness. In this contribution, we discuss iNOS/NO antagonism to glioblastoma PDT and how this can be overcome by judicious use of pharmacologic inhibitors of iNOS activity or transcription.

Gaseous signaling molecules and their application in resistant cancer treatment: from invisible to visible

Multidrug resistance (MDR) in cancer remains a critical obstacle for efficient chemotherapy. Many MDR reversal agents have been discovered but failed in clinical trials due to severe toxic effects. Gaseous signaling molecules (GSMs), such as oxygen, nitric oxide, hydrogen sulfide and carbon monoxide, play key roles in regulating cell biological function and MDR. Compared with other toxic chemosensitizing agents, GSMs are endogenous and biocompatible molecules with little side effects. Research show that GSM modulators, including pharmaceutical formulations of GSMs (combined with conventional chemotherapeutic drugs) and GSM-donors (small molecules with GSMs releasing property), can overcome or reverse MDR. This review discusses the roles of these four GSMs in modulating MDR, and summarizes GSMs modulators in treating cancers with drug resistance.

JS-K induces reactive oxygen species-dependent anti-cancer effects by targeting mitochondria respiratory chain complexes in gastric cancer

As a nitric oxide (NO) donor prodrug, JS‐K inhibits cancer cell proliferation, induces the differentiation of human leukaemia cells, and triggers apoptotic cell death in various cancer models. However, the anti‐cancer effect of JS‐K in gastric cancer has not been reported. In this study, we found that JS‐K inhibited the proliferation of gastric cancer cells in vitro and in vivo and triggered mitochondrial apoptosis. Moreover, JS‐K induced a significant accumulation of reactive oxygen species (ROS), and the clearance of ROS by antioxidant reagents reversed JS‐K‐induced toxicity in gastric cancer cells and subcutaneous xenografts. Although JS‐K triggered significant NO release, NO scavenging had no effect on JS‐K‐induced toxicity in vivo and in vitro. Therefore, ROS, but not NO, mediated the anti‐cancer effects of JS‐K in gastric cancer. We also explored the potential mechanism of JS‐K‐induced ROS accumulation and found that JS‐K significantly down‐regulated the core proteins of mitochondria respiratory chain (MRC) complex I and IV, resulting in the reduction of MRC complex I and IV activity and the subsequent ROS production. Moreover, JS‐K inhibited the expression of antioxidant enzymes, including copper‐zinc‐containing superoxide dismutase (SOD1) and catalase, which contributed to the decrease of antioxidant enzymes activity and the subsequent inhibition of ROS clearance. Therefore, JS‐K may target MRC complex I and IV and antioxidant enzymes to exert ROS‐dependent anti‐cancer function, leading to the potential usage of JS‐K in the prevention and treatment of gastric cancer.

Glutathione S-transferase π: a potential role in antitumor therapy

Glutathione S-transferase π (GSTπ) is a Phase II metabolic enzyme that is an important facilitator of cellular detoxification. Traditional dogma asserts that GSTπ functions to catalyze glutathione (GSH)-substrate conjunction to preserve the macromolecule upon exposure to oxidative stress, thus defending cells against various toxic compounds. Over the past 20 years, abnormal GSTπ expression has been linked to the occurrence of tumor resistance to chemotherapy drugs, demonstrating that this enzyme possesses functions beyond metabolism. This revelation reveals exciting possibilities in the realm of drug discovery, as GSTπ inhibitors and its prodrugs offer a feasible strategy in designing anticancer drugs with the primary purpose of reversing tumor resistance. In connection with the authors' current research, we provide a review on the biological function of GSTπ and current developments in GSTπ-targeting drugs, as well as the prospects of future strategies.

FAK alleviates radiation-induced rectal injury by decreasing apoptosis

Radiation-induced rectal injury is closely related with radiotherapy efficiency. Here, we investigated the effect of focal adhesion kinase (FAK) in radiation-induced rectal injury. Peripheral blood samples of patients with rectal cancer were collected prior to radiotherapy. Differentially expressed genes and copy number variations (CNVs) were analyzed by microarray analysis. The CTCAE v3.0 toxicity grades were used to assess acute rectal injury. The radiosensitivity of human intestinal epithelial crypt (HIEC) cells were assayed by colony formation, mitochondrial membrane potential, flow cytometry and western blotting. The rectums of C57BL/6 mice were X-irradiated locally with a single dose of 15 Gy. The effect of FAK on radiation-induced injury was investigated by hematoxylin-eosin (H&E) staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), immunohistochemistry (IHC) and quantitative real-time PCR (qRT-PCR). FAK mRNA level was inversely correlated with rectal injury severity in patient samples. A CNV amplification located on chromosome 8 was closely related with FAK. Further functional assays revealed increased levels of γH2AX expression and apoptosis-related proteins in FAK-silenced HIEC cells. The ratio of TUNEL, cl-caspase-3, cyto-c and bax/bcl-2 expression in the rectum mucosa treated with a FAK inhibitor increased significantly. These results demonstrated that FAK reduced radiation-induced rectal injury by decreasing apoptosis.

JS-K as a nitric oxide donor induces apoptosis via the ROS/Ca2+/caspase-mediated mitochondrial pathway in HepG2 cells

JS-K, (O²-(2, 4-dinitrophenyl) 1-[(4-ethoxycarbonyl) piperazin-1-yl] diazen 1-ium-1, 2-diolate), is a novel diazeniumdiolate-based nitric oxide donor prodrug. The present study investigated the relationship between reactive oxygen species (ROS) elevation, Ca²⁺ overload and mitochondrial disruption in JS-K-induced apoptosis. JS-K could significantly inhibit cell growth and induce apoptosis in a dose-dependent manner. Meanwhile, JS-K caused the accumulation of ROS, overload of Ca²⁺, decrease of mitochondrial membrane potential, release of cytochrome c (Cyt c) from mitochondria to the cytoplasm, increase of Bax-to-Bcl-2 ratio and activation of caspase- 9/3. NAC (an antioxidant) or BAPTA (an intracellular Ca²⁺ chelator) could partially reverse the above events, while BAPTA had little effect on the levels of ROS. Furthermore, pre-treatment with Carboxy-PTIO (a NO scavenger) significantly blocked the increasing of ROS, cytosolic Ca²⁺ and reversed the loss of mitochondrial membrane potential in JS-K-induced apoptosis. Taken together, the results suggested that NO released from JS-K could significantly induce HepG2 cell apoptosis through a ROS/Ca²⁺/caspase-mediated mitochondrial pathway.

Intracellular NO-Releasing Hyaluronic Acid-Based Nanocarriers: A Potential Chemosensitizing Agent for Cancer Chemotherapy

In this work, we investigate whether S-nitrosoglutathione (GSNO)-conjugated hyaluronic acid-based self-assembled nanoparticles (GSNO-HANPs) can be useful as a chemosensitizing agent to improve the anticancer activity of doxorubicin (DOX). The GSNO-HANPs were prepared by aqueous assembly of GSNO-conjugated HA with grafted poly(lactide- co-glycolide). Aqueous GSNO stability shielded within the assembled environments of the GSNO-HANPs was greatly enhanced, compared to that of free GSNO. The NO release from the GSNO-HANPs was facilitated in the presence of hyaluronidase-1 (Hyal-1) and ascorbic acid at intracellular concentrations. Microscopic analysis showed GSNO-HANPs effectively generated NO within the cells. We observed that NO made the human MCF-7 breast cancer cells vulnerable to DOX. This chemosensitizing activity was supported by the observation of an increased level of ONOO^- (peroxynitrite), a highly reactive oxygen species, upon co-treatment with the GSNO-HANPs and DOX. Apoptosis assays showed that GSNO-HANP alone exhibited negligible cytotoxic effects and reinforced apoptotic activity of DOX. Animal experiments demonstrated the effective accumulation of GSNO-HANPs in solid MCF-7 tumors and effectively suppressed tumor growth in combination with DOX. This hyaluronic acid-based intracellularly NO-releasing nanoparticles may serve as a significant chemosensitizing agent in treatments of various cancers.

Toxicity mechanism-based prodrugs: glutathione-dependent bioactivation as a strategy for anticancer prodrug design

INTRODUCTION

6-Mercaptopurine (6-MP) and 6-thioguanine (6-TG), two anticancer drugs, have high systemic toxicity due to a lack of target specificity. Therefore, increasing target selectivity should improve drug safety. Areas covered: The authors examined the hypothesis that new prodrug designs based upon mechanisms of kidney-selective toxicity of trichloroethylene would reduce systemic toxicity and improve selectivity to kidney and tumor cells. Two approaches specifically were investigated. The first approach was based upon bioactivation of trichloroethylene-cysteine S-conjugate by renal cysteine S-conjugate β-lyases. The prodrugs obtained were kidney-selective but exhibited low turnover rates. The second approach was based on the toxic mechanism of trichloroethylene-cysteine S-conjugate sulfoxide, a Michael acceptor that undergoes rapid addition-elimination reactions with biological thiols. Expert opinion: Glutathione-dependent Michael addition-elimination reactions appear to be an excellent strategy to design highly efficient anticancer drugs. Targeting glutathione could be a promising approach for the development of anticancer prodrugs because cancer cells usually upregulate glutathione biosynthesis and/or glutathione S-transferases expression.

Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma

Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.

Nitric oxide reduces oxidative stress in cancer cells by forming dinitrosyliron complexes

The chelatable iron pool (CIP) is a small but chemically significant fraction of total cellular iron. While this dynamic population of iron is limited, it is redox active and capable of generating reactive oxygen species (ROS) that can lead to oxidative stress which is associated with various pathologies. Nitric oxide (•NO), is a free radical signalling molecule that regulates numerous physiological and pathological conditions. We have previously shown that macrophages exposed to endogenously generated or exogenously administered nitric oxide (•NO) results in its interaction with CIP to form dinitrosyliron complexes with thiol containing ligands (DNICs). In this study we assessed the consequences of DNIC formation in cancer cells as •NO is known to be associated with numerous malignancies. Incubation of cancer cells with •NO led to a time and dose dependent increase in formation of DNICs. The formation of DNICs results in the sequestration of the CIP which is a major source of iron for redox reactions and reactive oxygen species (ROS) generation. Therefore, we set out to test the antioxidant effect of •NO by measuring the ability of DNICs to protect cells against oxidative stress. We observed that cancer cells treated with •NO were partially protected against H₂O₂ mediated cytotoxicity. This correlated to a concomitant decrease in the formation of oxidants when •NO was present during H₂O₂ treatment. Similar protective effects were achieved by treating cells with iron chelators in the presence of H₂O₂. Interestingly, •NO decreased the rate of cellular metabolism of H₂O₂ suggesting that a proportion of H₂O₂ is consumed via reactions with cellular iron. When the CIP was artificially increased by supplementation of cells with iron, a significant decrease in the cytoprotective effect of •NO was observed. Notably, •NO concentrations, at which cytoprotective and antioxidant effects were observed, correlated with concentration-dependent increases in DNIC formation. Collectively, these results demonstrate that •NO has antioxidant properties by its ability to sequester cellular iron. This could play a significant role in variety of diseases involving ROS mediated toxicity like cancer and neurodegenerative disorders where •NO has been shown to be an important etiologic factor.

The dichotomous role of H2S in cancer cell biology? Déjà vu all over again

Nitric oxide (NO) a gaseous free radical is one of the ten smallest molecules found in nature, while hydrogen sulfide (H2S) is a gas that bears the pungent smell of rotten eggs. Both are toxic yet they are gasotransmitters of physiological relevance. There appears to be an uncanny resemblance between the general actions of these two gasotransmitters in health and disease. The role of NO and H2S in cancer has been quite perplexing, as both tumor promotion and inflammatory activities as well as anti-tumor and antiinflammatory properties have been described. These paradoxes have been explained for both gasotransmitters in terms of each having a dual or biphasic effect that is dependent on the local flux of each gas. In this review/commentary, I have discussed the major roles of NO and H2S in carcinogenesis, evaluating their dual nature, focusing on the enzymes that contribute to this paradox and evaluate the pros and cons of inhibiting or inducing each of these enzymes.

Restoration of the prolyl-hydroxylase domain protein-3 oxygen-sensing mechanism is responsible for regulation of HIF2α expression and induction of sensitivity of myeloma cells to hypoxia-mediated apoptosis

Multiple myeloma (MM) is an incurable disease of malignant plasma B-cells that infiltrate the bone marrow (BM), resulting in bone destruction, anemia, renal impairment and infections. Physiologically, the BM microenvironment is hypoxic and this promotes MM progression and contributes to resistance to chemotherapy. Since aberrant hypoxic responses may result in the selection of more aggressive tumor phenotypes, we hypothesized that targeting the hypoxia-inducible factor (HIF) pathways will be an effective anti-MM therapeutic strategy. We demonstrated that MM cells are resistant to hypoxia-mediated apoptosis in vivo and in vitro, and that constitutive expression of HIF2α contributed to this resistance. Since epigenetic silencing of the prolyl-hydroxylase-domain-3 (PHD3) enzyme responsible for the O2-dependent regulation of HIF2α is frequently observed in MM tumors, we asked if PHD3 plays a role in regulating sensitivity to hypoxia. We found that restoring PHD3 expression using a lentivirus vector or overcoming PHD3 epigenetic silencing using a demethyltransferase inhibitor, 5-Aza-2'-deoxycytidine (5-Aza-dC), rescued O2-dependent regulation of HIF2α and restored sensitivity of MM cells to hypoxia-mediated apoptosis. This provides a rationale for targeting the PHD3-mediated regulation of the adaptive cellular hypoxic response in MM and suggests that targeting the O2-sensing pathway, alone or in combination with other anti-myeloma chemotherapeutics, may have clinical efficacy.

DEMETER plant DNA demethylase induces antiviral response by interferon signalling in animal cells

DNA methylation is a prominent epigenetic modification in plants and animals regulated by similar mechanisms but the process of DNA demethylation is profoundly different. Unlike vertebrates that require a series of enzymatic conversions of 5-methylcytosine (5mC) into other bases for DNA demethylation, plants utilize the DEMETER (DME) family of 5mC DNA glycosylases to catalyze a direct removal of 5mC from DNA. Here we introduced Arabidopsis DME into human HEK-293T cells to allow direct 5mC excision, and observed that direct DNA demethylation activity was successfully implemented by DME expression. In addition, DME induced diverse cellular responses such as cell proliferation inhibition, cell cycle dysregulation and S phase arrest. Microarray and methylome analyses revealed that DME upregulated a number of genes including cell cycle components, heat shock proteins, and notably, various interferon-stimulated genes. Moreover, DME-mediated DNA demethylation activated endogenous repeat elements, which are likely to form dsRNAs as viral mimics and eventually trigger interferon cascades to establish the antiviral state. This work demonstrates that plant DNA demethylase catalyzes DNA demethylation with a bypass of initial base conversion steps, and the interferon signaling plays a pivotal role to alleviate genotoxic stresses associated with DME-induced DNA demethylation in mammalian cells.

The nitric oxide donor JS-K sensitizes U87 glioma cells to repetitive irradiation

As a potent radiosensitizer nitric oxide (NO) may be a putative adjuvant in the treatment of malignant gliomas which are known for their radio- and chemoresistance. The NO donor prodrug JS-K (O2-(2.4-dinitrophenyl) 1-[(4-ethoxycarbonyl) piperazin-1-yl] diazen-1-ium-1,2-diolate) allows cell-type specific intracellular NO release via enzymatic activation by glutathione-S-transferases overexpressed in glioblastoma multiforme. The cytotoxic and radiosensitizing efficacy of JS-K was assessed in U87 glioma cells in vitro focusing on cell proliferation, induction of DNA damage, and cell death. In vivo efficacy of JS-K and repetitive irradiation were investigated in an orthotopic U87 xenograft model in mice. For the first time, we could show that JS-K acts as a potent cytotoxic and radiosensitizing agent in U87 cells in vitro. This dose- and time-dependent effect is due to an enhanced induction of DNA double-strand breaks leading to mitotic catastrophe as the dominant form of cell death. However, this potent cytotoxic and radiosensitizing effect could not be confirmed in an intracranial U87 xenograft model, possibly due to insufficient delivery into the brain. Although NO donor treatment was well tolerated, neither a retardation of tumor growth nor an extended survival could be observed after JS-K and/or radiotherapy.

JS-K, a nitric oxide prodrug, induces DNA damage and apoptosis in HBV-positive hepatocellular carcinoma HepG2.2.15 cell

Hepatocellular carcinoma (HCC) is the most important cause of cancer-related death, and 85% of HCC is caused by chronic HBV infection, the prognosis of patients and the reduction of HBV DNA levels remain unsatisfactory. JS-K, a nitric oxide-releasing diazeniumdiolates, is effective against various tumors, but little is known on its effects on HBV positive HCC. We found that JS-K reduced the expression of HBsAg and HBeAg in HBV-positive HepG2.2.15 cells. This study aimed to further examine anti-tumor effects of JS-K on HepG2.2.15 cells. The MTT assay and colony forming assay were used to study the cell growth inhibition of JS-K; scratch assay and transwell assay were performed to detect cell migration. The cell cycle was detected by flow cytometry. The immunofluorescence, flow cytometry analysis, and western blot were used to study DNA damage and cell apoptosis. JS-K inhibited HepG2.2.15 cell growth in a dose-dependent manner, suppressed cell colony formation and migration, arrested cells gather in the G2 phase. JS-K (1-20μM) increased the expression of DNA damage-associated protein phosphorylation H₂AX (γH₂AX), phosphorylation of checkpoint kinase 1 (p-Chk1), phosphorylation of checkpoint kinase 2 (p-Chk2), ataxia-telangiectasia mutated (ATM), phosphorylation of ataxia-telangiectasia mutated rad3-related (p-ATR) and apoptotic-associated proteins cleaved caspase-3, cleaved caspase-7, cleaved poly ADP-ribose polymerase (cleaved PARP). The study demonstrated JS-K is effective against HBV-positive HepG2.2.15 cells, the mechanisms are not only related to inhibition of HBsAg and HBeAg secretion, but also related with induction of DNA damage and apoptosis. JS-K is a promising anti-cancer candidate against HBV-positive HCC.

JS-K, a nitric oxide pro-drug, regulates growth and apoptosis through the ubiquitin-proteasome pathway in prostate cancer cells

Background

In view of the fact that JS-K might regulate ubiquitin E3 ligase and that ubiquitin E3 ligase plays an important role in the mechanism of CRPC formation, the goal was to investigate the probable mechanism by which JS-K regulates prostate cancer cells.

Methods

Proliferation inhibition by JS-K on prostate cancer cells was examined usingCCK-8 assays. Caspase 3/7 activity assays and flow cytometry were performed to examine whether JS-K induced apoptosis in prostate cancer cells. Western blotting and co-immunoprecipitation analyses investigated JS-K’s effects on the associated apoptosis mechanism. Real time-PCR and Western blotting were performed to assess JS-K’s effect on transcription of specific AR target genes. Western blotting was also performed to detect Siah2 and AR protein concentrations and co-immunoprecipitation to detect interactions of Siah2 and AR, NCoR1 and AR, and p300 and AR.

Results

JS-K inhibited proliferation and induced apoptosis in prostate cancer cells. JS-K increased p53 and Mdm2 concentrations and regulated the caspase cascade reaction-associated protein concentrations. JS-K inhibited transcription of AR target genes and down-regulated PSA protein concentrations. JS-K inhibited Siah2 interactions and also inhibited the ubiquitination of AR. With further investigation, JS-K was found to stabilize AR and NCoR1 interactions and diminish AR and p300 interactions.

Conclusions

The present results suggested that JS-K might have been able to inhibit proliferation and induce apoptosis via regulation of the ubiquitin-proteasome degradation pathway, which represented a promising platform for the development of new compounds for PCa treatments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3351-0) contains supplementary material, which is available to authorized users.

ATF3 reduces migration capacity by regulation of matrix metalloproteinases via NFκB and STAT3 inhibition in glioblastoma

Glioblastoma is associated with poor survival and a high recurrence rate in patients due to inevitable uncontrolled infiltrative tumor growth. The elucidation of the molecular mechanisms may offer opportunities to prevent relapses. In this study we investigated the role of the activating transcription factor 3 (ATF3) in migration of GBM cells in vitro. RNA microarray revealed that gene expression of ATF3 is induced by a variety of chemotherapeutics and experimental agents such as the nitric oxide donor JS-K (O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate). We found NFκB and STAT3 to be downstream targets inhibited by overexpression of ATF3. We demonstrate that ATF3 is directly involved in the regulation of matrix metalloproteinase expression and activation. Overexpression of ATF3 therefore leads to a significantly reduced migration capacity and induction of tissue inhibitors of matrix metalloproteinases. Our study for the first time identifies ATF3 as a potential novel therapeutic target in glioblastoma.

Discovery of phosphorodiamidate mustard-based O2-phosphorylated diazeniumdiolates with potent anticancer activity

Diazeniumdiolates are an important class of NO donors. Herein, we describe the design, synthesis and biological evaluation of a group of phosphorodiamidate mustard-based O²-phosphorylated diazeniumdiolates.

JS-K promotes apoptosis by inducing ROS production in human prostate cancer cells

Reactive oxygen species (ROS) are chemical species that alter redox status, and are responsible for inducing carcinogenesis. The purpose of the present study was to assess the effects of the glutathione S transferase-activated nitric oxide donor prodrug, JS-K, on ROS accumulation and on proliferation and apoptosis in human prostate cancer cells. Cell proliferation and apoptosis, ROS accumulation and the activation of the mitochondrial signaling pathway were measured. The results demonstrated that JS-K may inhibit prostate cancer cell growth in a dose- and time-dependent manner, and induce ROS accumulation and apoptosis in a dose-dependent manner. With increasing concentrations of JS-K, expression of pro-apoptotic proteins increased, but Bcl-2 expression decreased. Additionally, the antioxidant N-acetylcysteine reversed JS-K-induced cell apoptosis; conversely, the pro-oxidant glutathione disulfide exacerbated JS-K-induced apoptosis. In conclusion, the data suggest that JS-K induces prostate cancer cell apoptosis by increasing ROS levels.

Antagonistic Effects of Endogenous Nitric Oxide in a Glioblastoma Photodynamic Therapy Model

Gliomas are aggressive brain tumors that are resistant to conventional chemotherapy and radiotherapy. Much of this resistance is attributed to endogenous nitric oxide (NO). Recent studies revealed that 5-aminolevulinic acid (ALA)-based photodynamic therapy (PDT) has advantages over conventional treatments for glioblastoma. In this study, we used an in vitro model to assess whether NO from glioblastoma cells can interfere with ALA-PDT. Human U87 and U251 cells expressed significant basal levels of neuronal NO synthase (nNOS) and its inducible counterpart (iNOS). After an ALA/light challenge, iNOS level increased three- to fourfold over 24 h, whereas nNOS remained unchanged. Elevated iNOS resulted in a large increase in intracellular NO. Extent of ALA/light-induced apoptosis increased substantially when an iNOS inhibitor or NO scavenger was present, implying that iNOS/NO was acting cytoprotectively. Moreover, cells surviving a photochallenge exhibited a striking increase in proliferation, migration and invasion rates, iNOS/NO again playing a dominant role. Also observed was a large iNOS/NO-dependent increase in matrix metalloproteinase-9 activity, decrease in tissue inhibitor of metalloproteinase-1 expression and increase in survivin and S100A4 expression, each effect being consistent with accelerated migration/invasion as a prelude to metastasis. Our findings suggest introduction of iNOS inhibitors as pharmacologic adjuvants for glioblastoma PDT.

Nitric oxide: Friend or Foe in Cancer Chemotherapy and Drug Resistance: A Perspective

A successful treatment of cancers in the clinic has been difficult to achieve because of the emergence of drug resistant tumor cells. While various approaches have been tried to overcome multi-drug resistance, it has remained a major road block in achieving complete success in the clinic. Extensive research has identified various mechanisms, including overexpression of P-glycoprotein 170, modifications in activating or detoxification enzymes (phase I and II enzymes), and mutation and/or decreases in target enzymes in cancer cells. However, nitric oxide and/or nitric oxide-related species have not been considered an important player in cancer treatment and or drug resistance. Here, we examine the significance of nitric oxide in the treatment and resistance mechanisms of various anticancer drugs. Furthermore, we describe the significance of recently reported effects of nitric oxide on topoisomerases and the development of resistance to topoisomerase-poisons in tumor cells.

Nitric oxide released from JS-K induces cell death by mitotic catastrophe as part of necrosis in glioblastoma multiforme

The nitric oxide (NO) donor JS-K is specifically activated by glutathione S-transferases (GSTs) in GST-overexpressing cells. We have shown the induction of cell death in glioblastoma multiforme (GBM) cells at high JS-K doses but the mechanism remains unclear. The aim of this study was to determine whether NO-induced cell death is triggered by induction of apoptotic or necrotic pathways. For the first time, we demonstrate that NO induces cell death via mitotic catastrophe (MC) with non-apoptotic mechanisms in GBM cells. Moreover, the level of morphological changes indicating MC correlates with increased necrosis. Therefore, we conclude that MC is the main mechanism by which GBM cells undergo cell death after treatment with JS-K associated with necrosis rather than apoptosis. In addition, we show that PARP1 is not an exclusive marker for late apoptosis but is also involved in MC. Activating an alternative way of cell death can be useful for the multimodal cancer therapy of GBM known for its strong anti-apoptotic mechanisms and drug resistance.