Nitric oxide improves cisplatin cytotoxicity in head and neck squamous cell carcinoma

Ru(II) based dual nitric oxide donors: electrochemical and photochemical reactivities and vasorelaxant effect with no cytotoxicity

The synthesized complexes, cis-[Ru(NO)(NO2)(phen)2](PF6)2 (NONO2P) and cis-[Ru(NO)(NO2)(bpy)2](PF6)2 (NONO2B), were characterized by using elemental analysis, voltammetry and electronic and vibrational spectroscopy. Under electrochemical and photochemical stimulation in an aqueous medium, there are indications of the formation of complexes, which suggests that the nitro and nitrosyl groups are converted into nitric oxide. Both compounds do not show cytotoxic activity against human umbilical vein endothelial cells (HUVECs). The cis-[Ru(NO)(NO2)(phen)2](PF6)2 complex presented vasorelaxation activity in superior mesenteric arteries from Wistar rats: the biphasic concentration-response curve indicates two sites of action. In the presence of NO scavengers, we observed an impaired relaxing effect induced by NONO2P, suggesting that the vasorelaxant effect is due to NO production from this compound.

Metal complexes for catalytic and photocatalytic reactions in living cells and organisms

The development of organometallic catalysis has greatly expanded the synthetic chemist toolbox compared to only exploiting "classical" organic chemistry. Although more widely used in organic solvents, metal-based catalysts have also emerged as efficient tools for developing organic transformations in water, thus paving the way for further development of bio-compatible reactions. However, performing metal-catalysed reactions within living cells or organisms induces additional constraints to the design of reactions and catalysts. In particular, metal complexes must exhibit good efficiency in complex aqueous media at low concentrations, good cell specificity, good cellular uptake and low toxicity. In this review, we focus on the presentation of discrete metal complexes that catalyse or photocatalyse reactions within living cells or living organisms. We describe the different reaction designs that have proved to be successful under these conditions, which involve very few metals (Ir, Pd, Ru, Pt, Cu, Au, and Fe) and range from in cellulo deprotection/decaging/activation of fluorophores, drugs, proteins and DNA to in cellulo synthesis of active molecules, and protein and organelle labelling. We also present developments in bio-compatible photo-activatable catalysts, which represent a very recent emerging area of research and some prospects in the field.

Nitrate increases cisplatin chemosensitivity of oral squamous cell carcinoma via REDD1/AKT signaling pathway

Although cisplatin is one of the chemotherapeutics most frequently used in oral squamous cell carcinoma (OSCC) treatment, it exerts multiple side effects and poor chemosensitivity. Nitrate reportedly demonstrates several beneficial biological functions, and synthesized nitrates enhance the therapeutic efficacy of chemotherapy. However, the role of inorganic nitrate in cisplatin chemotherapy remains unclear. We therefore investigated the effect of inorganic nitrate exerted on cisplatin sensitivity in OSCC. We found that nitrate did not affect OSCC cell growth and apoptosis in OSCC cells and OSCC xenograft tumor animal studies. Cisplatin induced REDD1 expression and AKT activation in OSCC. However, nitrate could increase cisplatin chemosensitivity, reduce its REDD1 expression, and attenuate AKT signaling activation in OSCC cells. Dysregulation of high levels of REDD1, which could enhance AKT activation, was positively associated with poor prognosis in OSCC patients. Thus, reduced REDD1 expression and retarded AKT activation induced by inorganic nitrate might be a new potential approach to the sensitization of oral cancer to cisplatin treatment in the future.

General Strategy for Integrated Bioorthogonal Prodrugs: Pt(II)-Triggered Depropargylation Enables Controllable Drug Activation In Vivo

Bioorthogonal decaging reactions for controllable drug activation within complex biological systems are highly desirable yet extremely challenging. Herein, we find a new class of Pt(II)-triggered bioorthogonal cleavage reactions in which Pt(II) but not Pt(IV) complexes effectively trigger the cleavage of O/N-propargyl in a variety of ranges of caged molecules under biocompatible conditions. Based on these findings, we propose a general strategy for integrated bioorthogonal prodrugs and accordingly design a prodrug 16, in which a Pt(IV) moiety is covalently connected with an O²-propargyl diazeniumdiolate moiety. It is found that 16 can be specifically reduced by cytoplasmic reductants in human ovarian cancer cells to liberate cisplatin, which subsequently stimulates the cleavage of O²-propargyl to release large amounts of NO in situ, thus generating synergistic and potent tumor suppression activity in vivo. Therefore, Pt(II)-triggered depropargylation and the integration concept might provide a general strategy for broad applicability of bioorthogonal cleavage chemistry in vivo.

Evaluation of a Synergistic Effect of L-Arginine on the Anticancer Activity of Doxorubicin by Using a Co-culture System

In the early stage of tumor development, tumor-associated macrophages (TAM) works to suppress tumor growth by secreting soluble factors including nitric oxide (NO). L-Arginine (Arg) is a substrate of nitric oxide synthase (NOS) expressed in TAM. Here we examined whether NO produced from Arg by macrophages works to enhance the effect of the anti-cancer drug, doxorubicin (Dox) by using a co-culture system of cancer cells with macrophages. By employing colorimetric analyses methods (Griess Reagent and Cell Counting kit-8), we found that NO produced from Arg by co-cultured macrophages could enhance the cytotoxic effect of Dox to cancer cells. Moreover, we found that augmentation is affected by the order of the addition of Arg and Dox. A prior addition of Arg to Dox and simultaneous addition showed the same enhancement effect, but a prior addition of Dox to Arg abolished the augmentation. This suggests that the co-administration of Arg with Dox would be an effective treatment to improve chemo-therapies.

Carry-On Nitric-Oxide Luggage for Enhanced Chemotherapeutic Efficacy

In this work, we proposed a carry-on nitric-oxide (NO) luggage strategy for enhanced chemotherapeutic efficacy. A stimuli-responsive NO-releasing polypeptide was prepared as the building block to assemble into a micelle as a chemodrug-carrier. The micelle was anchored with cRGD peptide with the aim of targeting to tumors' neoangiogenesis. In situ generation of NO at the tumor site can promote the neovascularization to recruit more chemotherapeutics. Besides, the introduced exogenous NO can directly induce apoptosis, synergistically with the chemotherapeutics. A specific near-infrared-region (NIR) NO-probe was also developed to be coloaded to the micelle to report the in situ NO-release. In vitro and in vivo experiments were performed to demonstrate the targeting capability, increased accumulation, real-time NO-release reporting phenomenon, improved antitumor efficacy, and favorable biosafety. Embedding NO into drug cargo as carry-on luggage for enhanced chemotherapeutic efficacy, hopefully, can cast new lights and build a basic principle in the future clinical translation of nanomedicines.

Intracellular NO-Generator Based on Enzyme Trigger for Localized Tumor-Cytoplasm Rapid Drug Release and Synergetic Cancer Therapy

Nitric oxide (NO) is an important biological messenger implicated in tumor therapy. However, current NO release systems suffer from some disadvantages, such as hydrolysis during blood circulation, poor specificity, and robust irradiation for stimuli. Accordingly, we constructed an intracellular enzyme-triggered NO-generator to achieve tumor cytoplasm-specific disruption and localized rapid drug release. Diethylamine NONOate (DEA/NO) was used as a NO donor and conjugated with hyaluronic acid (HA) to form self-assembly micelle (HA-DNB-DEA/NO), and encapsulate chemotherapeutic agent (doxorubicin (DOX)) into its hydrophobic core (DOX@HA-DNB-DEA/NO). After HA receptor mediated internalization into tumor cells, HA shell would undergo digestion into small conjugated pieces by hyaluronidase. Meanwhile, DOX@HA-DNB-DEA/NO also responded to the intratumoral overexpressed glutathion and glutathione S-transferase π, leading to the intracellular NO production and controlled DOX rapid release. In vitro and in vivo results proved the enzyme-dependent and enhanced targeting delivery profile, and demonstrated that NO and DOX could colocate in specific tumor site, which provided a precondition for exerting their synergistic efficacy. Moreover, expression of p53 protein was upregulated in tumor tissue after treatment, indicating that NO induced cell apoptosis mediated by tumor suppressor gene p53. Overall, this intelligent drug loaded NO-generator might perform as an enhancer to realize better clinical outcomes.

NO prodrug-conjugated, self-assembled, pH-responsive and galactose receptor targeted nanoparticles for co-delivery of nitric oxide and doxorubicin

Targeted delivery and controlled release of nitric oxide (NO) locoregionally are in high demand and challenging in cancer treatment. Herein, we report an example of galactose receptor targeted, pH-responsive and self-assembled nanoparticle-based delivery of the NO prodrug O²-(2,4-dinitrophenyl) 1-[4-(propargyloxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (alkynyl-JSK), which was chemically conjugated to an amphiphilic block copolymer through a click reaction for the first time. The assembled NO prodrug nanoparticles show high NO capacity (the content of the NO prodrug in the copolymer, ∼23.4% (w/w)), good stability and a sustained NO release pattern with unique glutathione/glutathione S-transferase (GSH/GST) activated NO-releasing kinetics. Such NO-loaded nanoparticles exhibit superior cytotoxicity to HepG2 cells. More importantly, in combination with doxorubicin (DOX) chemotherapy a significant synergistic therapeutic effect was achieved, due to its excellent galactose receptor-targeting capability, rapid acid-triggered DOX release and sustained NO release. Our findings indicate that these multifunctional nanoparticles can serve as an efficient NO and chemotherapeutic agent delivery platform, holding great promise in cancer combinatorial treatment.

Synthesis and biological evaluation of stilbene derivatives coupled to NO donors as potential antidiabetic agents

The work is focused on the design of drugs that prevent and treat diabetes and its complications. A novel class of stilbene derivatives were prepared by coupling NO donors of alkyl nitrate and were fully characterised by NMR and other techniques. These compounds were tested in vitro activity, including α-glucosidase inhibitory activity, aldose reductase (AR) inhibitory activity and advanced glycation end products (AGEs) formation inhibitory activity. A class of modified compounds could play a significant effect for treatment of diabetic complications. Target compounds 3e and 7c offered a potential drug design concept for the development of therapeutic or preventive agents for diabetes and its complications.

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 and reactive oxygen species: Clues to target oxidative damage repair defective breast cancers

The identification of various biomolecules in cancer progression and therapy has led to the exploration of the roles of two cardinal players, namely Nitric Oxide (NO) and Reactive Oxygen Species (ROS) in cancer. Both ROS and NO display bimodal fashions of functional activity in a concentration dependent manner, by inducing either pro- or anti- tumorigenic signals. Researchers have identified the potential capability of NO and ROS in therapies owing to their role in eliciting pro-apoptotic signals at higher concentrations and their ability to sensitize cancer cells to one another as well as to other therapeutics. We review the prospects of NO and ROS in cancer progression and therapy, and analyze the role of a combinatorial therapy wherein an NO donor (SNAP) is used to sensitize the oxidative damage repair defective, triple negative breast cancer cells (HCC 1937) to a potent ROS inducer. Preliminary findings support the potential to employ various combinatorial regimes for anti-cancer therapies with regard to exploiting the chemo-sensitization property of NO donors.

Nitric oxide-mediated sensitization of resistant tumor cells to apoptosis by chemo-immunotherapeutics

The generation of NO by the various NO synthases in normal and malignant tissues is manifested by various biological effects that are involved in the regulation of cell survival, differentiation and cell death. The role of NO in the cytotoxic immune response was first revealed by demonstrating the induction of iNOS in target cells by immune cytokines (e.g. IFN-γ, IL-1, TNF-α, etc.) and resulting in the sensitization of resistant tumor cells to death ligands-induced apoptosis. Endogenous/exogenous NO mediated its immune sensitizing effect by inhibiting NF-κΒ activity and downstream, inactivating the repressor transcription factor YY1, which inhibited both Fas and DR5 expressions. In addition, NO-mediated inhibition of NF-κΒ activity and inhibition downstream of its anti-apoptotic gene targets sensitized the tumor cells to apoptosis by chemotherapeutic drugs. We have identified in tumor cells a dysregulated pro-survival/anti-apoptotic loop consisting of NF-κB/Snail/YY1/RKIP/PTEN and its modification by NO was responsible, in large, for the reversal of chemo and immune resistance and sensitization to apoptotic mechanisms by cytotoxic agents. Moreover, tumor cells treated with exogenous NO donors resulted in the inhibition of NF-κΒ activity via S-nitrosylation of p50 and p65, inhibition of Snail (NF-κΒ target gene), inhibition of transcription repression by S-nitrosylation of YY1 and subsequent inhibition of epithelial-mesenchymal transition (EMT), induction of RKIP (inhibition of the transcription repressor Snail), and induction of PTEN (inhibition of the repressors Snail and YY1). Further, each gene product modified by NO in the loop was involved in chemo-immunosensitization. These above findings demonstrated that NO donors interference in the regulatory circuitry result in chemo-immunosensitization and inhibition of EMT. Overall, these observations suggest the potential anti-tumor therapeutic effect of NO donors in combination with subtoxic chemo-immuno drugs. This combination acts on multiple facets including reversal of chemo-immune resistance, and inhibition of both EMT and metastasis.

Nitric oxide releasing d-α-tocopheryl polyethylene glycol succinate for enhancing antitumor activity of doxorubicin

Nitric oxide (NO) has attracted much attention for its antitumor activity and synergistic effects when codelivered with anticancer agents. However, due to its chemical instability and short half-life, delivering gaseous NO directly to tumors is still challenging. Herein, we synthesized a NO releasing polymer, nitrate functionalized d-α-tocopheryl polyethylene glycol succinate (TNO3). TNO3 was able to self-assemble into stable micelles in physiological conditions, accumulate in tumors, and release ∼90% of NO content in cancer cells for 96 h. It further exhibited significant cancer cell cytotoxicity and apoptosis compared with nitroglycerine (GTN). Notably, TNO3 could also serve as an enhancer for the common chemotherapeutic drug doxorubicin (DOX). Codelivering TNO3 with DOX to hepatocarcinoma HepG2 cancer cells strengthened the cellular uptake of DOX and enabled the synergistic effect between NO and DOX to induce higher cytotoxicity (∼6.25-fold lower IC50). Moreover, for DOX-based chemotherapy in tumor-bearing mice, coadministration with TNO3 significantly extended the blood circulation time of DOX (14.7-fold t1/2, 6.5-fold mean residence time (MRT), and 13.7-fold area under curve (AUC)) and enhanced its tumor accumulation and penetration, thus resulting in better antitumor efficacy. In summary, this new NO donor, TNO3, may provide a simple but effective strategy to enhance the therapeutic efficacy of chemotherapeutic drugs.

Multi-arm polymeric nanocarrier as a nitric oxide delivery platform for chemotherapy of head and neck squamous cell carcinoma

Nitric oxide is a cell signaling molecule that can be a potent inducer of cell death in cancers at elevated concentrations. However, NO is also toxic to normal tissues and chronic exposure at low levels can induce tumor growth. We have designed a polymeric carrier system to deliver nitric oxide locoregionally to tumorigenic tissues at micromolar concentrations. A highly water solubility and biodegradable multi-arm polymer nanocarrier, sugar poly-(6-O-methacryloyl-d-galactose), was synthesized using MADIX/RAFT polymerization, and utilized to deliver high concentrations of nitric oxide to xenografts of human head and neck squamous cell carcinoma (HNSCC). The in vitro release of the newly synthesized nitric oxide donor, O(2)-(2,4-dinitrophenyl) 1-[4-(2-hydroxy)ethyl]-3-methylpiperazin-1-yl]diazen-1-ium-1,2-diolate and its corresponding multi-arm polymer-based nanoconjugate demonstrated a 1- and 2.3-fold increase in half-life, respectively, compared to the release half-life of the nitric oxide-donor prodrug JS-K. When administered to tumor-bearing nude mice, the subcutaneously injected multi-arm polymer nitric oxide nanoparticles resulted in 50% tumor inhibition and a 7-week extension of the average survival time, compared to intravenous JS-K therapy. In summary, we have developed an effective nitric oxide anti-cancer chemotherapy that could be administered regionally to provide the local disease control, improving prognosis for head and neck cancers.

Insight into the 6-thiopurine-mediated termination of the invasive motility of tumor cells derived from inflammatory breast cancer

Our study showed that a combination of 6-thiopurine (6-TP) drugs and a redox agent effectively inhibits the motility of SUM cells derived from human inflammatory breast cancer (IBC) cells and RhoC-overexpressed mammary epithelium cells. This 6-TP-mediated inhibition of cell motility occurs because the treated 6-TPs target and inactivate RhoC. A molecular mechanism for inactivation by the 6-TP-mediated RhoC is proposed by which treated TPs are converted in cells into 6-thioguanosine phosphate (6-TGNP). This 6-TGNP in turn reacts with the Cys(20) side chain of the redox-sensitive GXXXCGK(S/T)C motif of RhoC to produce a 6-TGNP-RhoC disulfide adduct. A redox agent synergistically enhances the formation process of this disulfide. The adduct that is formed impedes RhoC guanine nucleotide exchange, which populates an inactive RhoC. Our results suggest that 6-TGNP can also react with the redox-sensitive GXXXCGK(S/T)C and GXXXXGK(S/T)C motif of RhoA and Rac, respectively, to produce a 6-TGNP-RhoA and 6-TGNP-Rac disulfide adduct. However, given that RhoC has been shown to be overexpressed in ∼90% of IBC lesions, the populated RhoC but not other Rho proteins is likely to be a primary target for 6-TPs and a redox agent to terminate the metastasis of IBC.

Targeting nitric oxide for cancer therapy

A blueprint for the ideal anticancer molecule would include most of the properties of nitric oxide (NO•), but the ability to exploit these characteristics in a therapeutic setting requires a detailed understanding of the biology and biochemistry of the molecule. These properties include the ability of NO• to affect tumour angiogenesis, metastasis, blood flow and immuno surveillance. Furthermore NO• also has the potential to enhance both radio- and chemotherapy. However, all of these strategies are dependent on achieving appropriate levels of NO•, since endogenous levels of NO• appear to have a clear role in tumour progression. This review aims to summarize the role of NO• in cancer with particular emphasis on how the properties of NO• can be exploited for therapy.

Nitric oxide synthase gene therapy enhances the toxicity of cisplatin in cancer cells

BACKGROUND

Nitric oxide (NO.) derived from donor drugs has been shown to be an effective chemosensitizer in vitro. We investigated the combination of inducible nitric oxide synthase (iNOS) gene transfer, driven by a strong constitutive promoter (cytomegalovirus; CMV) with the DNA cross-linking agent cisplatin in mouse and human tumour cell lines.

METHODS

Proof of principal experiments were performed in the radiation-induced fibrosarcoma-1 (RIF-1) murine cell line. Cells were transfected with constitutively expressed CMV/iNOS plasmid DNA using a cationic lipid vector, before exposure to cisplatin. In vivo efficacy was determined in an intradermal RIF-1 tumour model, with intraperitoneal administration of cisplatin. Additionally, treatment potential was investigated in various human tumour cell lines including human prostate (DU145 and PC3) and human colon (HT29 and HCT116) cancer cell lines. Experimental endpoints were established using western blot, Greiss test, clonogenic assay and tumour growth delay.

RESULTS

Transfection of RIF-1 tumour cells in vitro with the CMV/iNOS significantly enhanced the cytotoxicity of cisplatin (0.2-1.0 microM). In vivo transfer of CMV/iNOS by direct injection into established RIF-1 tumours caused a significant (p = 0.0027) delay in tumour growth. CMV/iNOS gene transfer in vitro resulted in the strong expression of iNOS DNA in all cell lines, and significantly increased levels of NO. in all cell lines except HCT116.

CONCLUSIONS

Significant chemosensitization of cisplatin cytotoxicity was observed in the presence of NO. derived from the overexpression iNOS. We conclude that p53 status of the various cell lines was unlikely to be responsible for cisplatin-induced apoptosis.

Solid tumor physiology and hypoxia-induced chemo/radio-resistance: novel strategy for cancer therapy: nitric oxide donor as a therapeutic enhancer

Hypoxia exists in solid tumor tissues due to abnormal vasculature, vascular insufficiency, treatment or malignancy related anemia, and low intratumor blood flow. Hypoxic status in solid tumor promotes accumulation of hypoxia-inducible factor-1 alpha which is promptly degraded by proteasomal ubiquitination under normoxic conditions. However, under hypoxic conditions, the ubiquitination system for HIF-1 alpha is inhibited by inactivation of prolyl hydroxylase which is responsible for hydroxylation of proline in the oxygen-dependent degradation domain of HIF-1 alpha. HIF-1 alpha is an important transcriptional factor that codes for hundreds of genes involved in erythropoiesis, angiogenesis, induction of glycolytic enzymes in tumor tissues, modulation of cancer cell cycle, cancer proliferation, and cancer metastasis. Hypoxia and accumulation of HIF-1 alpha in solid tumor tissues have been reported to associate with resistance to chemotherapy, radiotherapy, and immunotherapy and poor prognosis. Production of vascular endothelial growth factor (VEGF) in cancer cells is regulated by the activated HIF-1 mediated system. An increase in VEGF levels subsequently induces HIF-1 alpha accumulation and promotes tumor metastasis by angiogenesis. Recently, angiogenesis targeting therapy using humanized VEGF antibody and VEGF receptor tyrosine kinase inhibitors have been used in solid cancer therapy. Nitric oxide (NO) is a unique chemical gaseous molecule that plays a role as a chemical messenger involved in vasodilator, neurotransmitter, and anti-platelet aggregation. In vivo, NO is produced and released from three different isoforms of NO synthase (NOS) and from exogenously administered NO donors. In cancer science, NO has been mainly discussed as an oncogenic molecule over the past decades. However, NO has recently been noted in cancer biology associated with cancer cell apoptosis, cancer cell cycle, cancer progression and metastasis, cancer angiogenesis, cancer chemoprevention, and modulator for chemo/radio/immuno-therapy. The presence and activities of all the three isoforms of NOS and were detected in cancer tissue components such as cancer cells, tumor-associated macrophages, and vascular endothelium. Overexpression of iNOS in cancer tissues has been reported to associate with poor prognosis in patients with cancers. On the other hand, NO donors such as nitroglycerin have been demonstrated to improve the effects of cancer therapy in solid cancers. Nitroglycerin has been used safely for a long time as a potent vasodilator for the treatment of ischemic heart diseases or heart failure. Therefore, we think highly of clinical use of nitroglycerin as a novel cancer therapy in combination with anticancer drugs for improvement of cancer therapeutic levels. In this review article, we demonstrate the unique physiological characteristics of malignant solid tumors, several factors in solid tumors resulting in resistance for cancer therapies, and the effects of NO from NOS or exogenous NO-donating drugs on malignant cells. Furthermore, we refer to promising therapeutic roles of NO and NO-donating drugs for novel treatments in solid tumors.

Nitric oxide-induced resistance or sensitization to death in tumor cells

This report summarizes the present state of our knowledge pertaining to the NO-induced resistance or sensitization of tumor cell death. The effects of NO and its synergy with members of the TNF family, with cytotoxic drugs, and with ionizing radiations have been investigated. The dual effect of NO-induced resistance or sensitization and the underlying molecular mechanisms are discussed.

Effect of artemisinins and other endoperoxides on nitric oxide-related signaling pathway in RAW 264.7 mouse macrophage cells

Artemisinin is the active principle of the Chinese herb Artemisia annua L. In addition to its anti-malarial activity, artemisinin and its derivatives have been shown to exert profound anti-cancer activity. The endoperoxide moiety in the chemical structure of artemisinin is thought to be responsible for the bioactivity. Here, we analyzed the cytotoxicity and the ability of artemisinin, five of its derivatives, and two other endoperoxides to inhibit generation of nitric oxide (NO). In the RAW 264.7 mouse macrophage cell line, the well-established model cell line to analyze NO generation, artesunate revealed the highest ability to inhibit NO production among all compounds tested. In cytotoxicity assays (XTT assay), the IC(50) value of RAW 264.7 cells for artesunate was determined to be 3.1+/-0.7 microM. In order to associate the cytotoxic effects with specific alteration in gene expression related to NO metabolism and signaling, whole genome mRNA microarray analyses were conducted. RAW 264.7 cells were treated with artesunate using DMSO as vehicle control followed by microarray analysis. A total of 36 genes related to NO metabolism and signaling were found to be differentially expressed upon exposure to artesunate. Apart from NO-related genes, the expression of genes associated with other functional groups was also analyzed. Out of 24 functional groups, differential expression was most prominent in genes involved in cell-to-cell signaling and interactions. Further refinement of this analysis showed that the pathways for cAMP-mediated signaling and Wnt/beta-catenin signaling were most closely related to changes in mRNA expression. In conclusion, NO generation and signaling play a role in exhibiting cytotoxic activity of artesunate. In addition, other signaling pathways also contribute to the inhibitory effect of artesunate towards RAW 264.7 cells pointing to a multi-factorial mode of action of artesunate.

Nitric oxide boosts chemoimmunotherapy via inhibition of acid sphingomyelinase in a mouse model of melanoma

Cisplatin is one of the most effective anticancer drugs, but its severe toxic effects, including depletion of immune-competent cells, limit its efficacy. We combined the systemic treatment with cisplatin with intratumor delivery of dendritic cells (DC) previously treated ex vivo with a pulse of nitric oxide (NO) released by the NO donors (z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]-diazen-1-ium-1,2-diolate or isosorbide dinitrate. We found that this chemoimmunotherapy, tested in the B16 mouse model of melanoma, was significantly more efficacious than cisplatin alone, leading to tumor regression and animal survival at low doses of cisplatin that alone had no effect. Tumor cure was not observed when combining cisplatin with DCs not exposed to NO donors, indicating the key role of the pretreatment with NO. We investigated the mechanisms responsible for the synergic effect of NO-treated DCs and cisplatin and found that NO-treated DCs were protected both in vitro and in vivo from cisplatin-induced cytotoxicity. Cisplatin triggered DC apoptosis through increased expression and activation of acid sphingomyelinase; pretreatment of DCs with NO donors prevented such activation and inhibited activation of the downstream proapoptotic events, including generation of ceramide, activation of caspases 3 and 9, and mitochondrial depolarization. The effects of NO were mediated through generation of its physiologic messenger, cyclic GMP. We conclude that NO and NO generating drugs represent promising tools to increase the efficacy of chemoimmunotherapies in vivo, promoting the survival and increasing the function of injected cells by targeting a key pathway in cisplatin-induced cytotoxicity.

Human osteocalcin: a strong promoter for nitric oxide synthase gene therapy, with specificity for hormone refractory prostate cancer

BACKGROUND

Gene therapy has been identified as a promising treatment strategy for hormone refractory prostate cancer (HRPC). We report, for the first time, the use of the human osteocalcin (hOC) promoter to control inducible nitric oxide synthase (iNOS) transgene expression in HRPC.

METHODS

Human prostate carcinoma cells (PC3, DU145, LNCaP), colon cancer cells (HT29) and human microvascular endothelial cells (HMEC-1) were transfected in vitro with constitutively driven CMV/iNOS or hOC/iNOS plasmid DNA by cationic lipid vector. End points of these experiments were Western blotting, NO(.) generation using the Greiss test to measure accumulated nitrite, and clonogenic assay.

RESULTS

Transfection of the hOC/iNOS plasmid increased iNOS protein and total nitrite levels in PC3 and DU145 cells, but not LNCaP or HT29. Transfection with CMV/iNOS or hOC/iNOS resulted in no additional cytotoxicity in androgen-dependent LNCaP cells or in the non-prostate cell lines. However, transfection with either construct resulted in a greatly reduced cell survival (to 10-20%) in the androgen-independent PC3 and DU145 cell lines.

CONCLUSIONS

Utilising the tumour-type specific properties of the hOC promoter in tandem with the iNOS gene, we have demonstrated target cell specificity, and transgene activation, in the androgen-independent prostate cancer cell lines (PC3 and DU145), an effect absent in normal and androgen-dependent cells. Furthermore, the levels of NO(.) generated are comparable with those seen generated with constitutively (CMV)-driven iNOS. The data obtained from this study provide a basis for future development of hOC/iNOS gene therapy.

Nitric oxide prodrugs and metallochemotherapeutics: JS-K and CB-3-100 enhance arsenic and cisplatin cytolethality by increasing cellular accumulation

Development of chemotherapeutic resistance is a major cause of pharmacologic failure in cancer treatment. One mechanism of resistance in tumor cells is the overexpression of glutathione S-transferases (GSTs) that serve two distinct roles in the development of drug resistance via the formation of glutathione conjugates with drugs for their cellular efflux, and the inhibition of the mitogen-activated protein kinase pathway. To target GST-based resistance to chemotherapeutics, a series of nitric oxide (NO)-releasing diazeniumdiolates was synthesized and shown to release NO on reaction with GST and/or glutathione. Two diazeniumdiolates, JS-K [O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate] and CB-3-100 [O2-(2,4-dinitrophenyl) 1-[4-(N,N-diethylcarboxamido)piperazin-1-yl]diazen-1-ium-1,2-diolate], were studied on their ability in reversing arsenic and cisplatin resistance in a rat liver cell line that is tumorigenic and shows acquired tolerance to arsenic and cisplatin, with overexpression of GSTs. The enhanced cytolethality produced by the NO donors was accompanied by increased accumulation of arsenic and platinum within cells and by enhanced activation of mitogen-activated protein kinase members c-jun-NH-kinase and extracellular signal-regulated kinase. Our data indicate that JS-K and CB-3-100 are promising lead compounds for the possible development of a novel class of adjuvant chemotherapeutic agents potentially capable of reversing arsenic and cisplatin resistance in certain tumor cells.

Endogenous production and exogenous exposure to nitric oxide augment doxorubicin cytotoxicity for breast cancer cells but not cardiac myoblasts

We studied the effect of nitric oxide (*NO) on the anticancer activity of doxorubicin. When MCF-7 human breast cancer cells were exposed to an aqueous solution of *NO delivered as a bolus 30 min prior to doxorubicin, the cytotoxic effect as measured in a clonogenic assay was increased (doxorubicin alone, 40% survival, doxorubicin plus *NO, 5% survival). The *NO donor diethylamine nitric oxide, but not inactivated donor, also yielded an increase in doxorubicin cytotoxicity. The sequence was important since the simultaneous application of *NO with doxorubicin yielded only a small augmentation of effect, and the exposure of the cells to doxorubicin prior to the *NO obliterated the augmentation. Prior depletion of glutathione by incubation of the cells for 24h with D,L-buthionine-S,R-sulfoximine (BSO) further increased the cytotoxicity so that BSO plus *NO plus doxorubicin killed all of the clones. MCF-7 cells transduced with inducible nitric oxide synthase gene (iNOS) through an adenoviral vector overexpressed iNOS and produced increased amounts of nitrite, an indicator of increased *NO production. These iNOS transduced cells were more susceptible to doxorubicin than vector control or wild-type cells. Cell cycle progression of iNOS transduced cells was not different from controls. Likewise, iNOS transduction resulted in no change in cellular glutathione levels. For comparison, we examined the effect of iNOS transduction on the sensitivity of MCF-7 to edelfosine, a membrane-localizing anticancer drug without direct DNA interaction. Insertion of the iNOS had no effect on killing of the MCF-7 cells by this ether lipid class drug. We also tested the effect of iNOS transduction on doxorubicin sensitivity of H9c2 rat heart-derived myoblasts. We found no augmentation of cytotoxicity by *NO, and this observation offers potential therapeutic tumor selectivity by using *NO with doxorubicin. Therefore, we conclude that *NO produced intracellularly by iNOS overexpression or delivered as a bolus sensitizes human breast cancer cells in culture to doxorubicin, but not to a cardiac cell line or to edelfosine. This augmentation is not due to a modulation of cell cycle distribution or measurable cellular glutathione resulting from the transduction.