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

Stabilization of the nitric oxide (NO) prodrugs and anticancer leads, PABA/NO and Double JS-K, through incorporation into PEG-protected nanoparticles

We report the stabilization of the nitric oxide (NO) prodrugs and anticancer lead compounds, PABA/NO (O(2)-{2,4-dinitro-5-[4-(N-methylamino)benzoyloxy]phenyl} 1-(N,N-dimethylamino)diazen-1-ium-1,2-diolate) and "Double JS-K" 1,5-bis-{1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diol-2-ato}-2,4-dinitrobenzene, through their incorporation into polymer-protected nanoparticles. The prodrugs were formulated in block copolymer-stabilized nanoparticles with sizes from 220 to 450 nm by a novel rapid precipitation process. The block copolymers, with polyethylene glycol (PEG) soluble blocks, provide a steric barrier against NO prodrug activation by glutathione. Too rapid activation and NO release has been a major barrier to effective administration of this class of compounds. The nanoparticle stabilized PABA/NO are protected from attack by glutathione as evidenced by a significant increase in time taken for 50% decomposition from 15 min (unformulated) to 5 h (formulated); in the case of Double JS-K, the 50% decomposition time was extended from 4.5 min (unformulated) to 40 min (formulated). The more hydrophobic PABA/NO produced more stable nanoparticles and correspondingly more extended release times in comparison with Double JS-K. The hydrophobic blocks of the polymer were either polystyrene or polylactide. Both blocks produced nanoparticles of approximately the same size and release kinetics. This combination of PEG-protected nanoparticles with sizes appropriate for cancer targeting by enhanced permeation and retention (EPR) and delayed release of NO may afford enhanced therapeutic benefit.

JS-K, a nitric oxide prodrug, has enhanced cytotoxicity in colon cancer cells with knockdown of thioredoxin reductase 1

BACKGROUND

The selenoenzyme thioredoxin reductase 1 has a complex role relating to cell growth. It is induced as a component of the cellular response to potentially mutagenic oxidants, but also appears to provide growth advantages to transformed cells by inhibiting apoptosis. In addition, selenocysteine-deficient or alkylated forms of thioredoxin reductase 1 have also demonstrated oxidative, pro-apoptotic activity. Therefore, a greater understanding of the role of thioredoxin reductase in redox initiated apoptotic processes is warranted.

METHODOLOGY

The role of thioredoxin reductase 1 in RKO cells was evaluated by attenuating endogenous thioredoxin reductase 1 expression with siRNA and then either inducing a selenium-deficient thioredoxin reductase or treatment with distinct redox challenges including, hydrogen peroxide, an oxidized lipid, 4-hydroxy-2-nonenol, and a nitric oxide donating prodrug. Thioredoxin redox status, cellular viability, and effector caspase activity were measured.

CONCLUSIONS/SIGNIFICANCE

In cells with attenuated endogenous thioredoxin reductase 1, a stably integrated selenocysteine-deficient form of the enzyme was induced but did not alter either the thioredoxin redox status or the cellular growth kinetics. The oxidized lipid and the nitric oxide donor demonstrated enhanced cytotoxicity when thioredoxin reductase 1 was knocked-down; however, the effect was more pronounced with the nitric oxide prodrug. These results are consistent with the hypothesis that attenuation of the thioredoxin-system can promote apoptosis in a nitric oxide-dependent manner.

Nitric oxide induces early viral transcription coincident with increased DNA damage and mutation rates in human papillomavirus-infected cells

High-risk human papillomavirus (HPV) infections are necessary but insufficient causes of cervical cancers. Other risk factors for cervical cancer (e.g., pregnancy, smoking, infections causing inflammation) can lead to high and sustained nitric oxide (NO) concentrations in the cervix, and high NO levels are related to carcinogenesis through DNA damage and mutation. However, the effects of NO exposure in HPV-infected cells have not been investigated. In this study, we used the NO donor DETA-NO to model NO exposure to cervical epithelium. In cell culture media, 24-hour exposure to 0.25 to 0.5 mmol/L DETA-NO yielded a pathologically relevant NO concentration. Exposure of cells maintaining episomal high-risk HPV genomes to NO increased HPV early transcript levels 2- to 4-fold but did not increase viral DNA replication. Accompanying increased E6 and E7 mRNA levels were significant decreases in p53 and pRb protein levels, lower apoptotic indices, increased DNA double-strand breaks, and higher mutation frequencies when compared with HPV-negative cells. We propose that NO is a molecular cofactor with HPV infection in cervical carcinogenesis, and that modifying local NO cervical concentrations may constitute a strategy whereby HPV-related cancer can be reduced.

Synthesis and evaluation of piperazine and homopiperazine analogues of JS-K, an anti-cancer lead compound

Here we report a number of novel JS-K structural analogues with sub-micromolar anti-proliferative activities against human leukemia cell lines HL-60 and U937; JS-K is the anti-cancer lead compound O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate. The ability of these compounds to generate intracellular nitric oxide correlated well with their observed anti-proliferative effects: analogues that had potent inhibitory activity against leukemia cells formed elevated levels of intracellular nitric oxide.

Gene expression profiling for nitric oxide prodrug JS-K to kill HL-60 myeloid leukemia cells

The nitric oxide (NO) prodrug JS-K is shown to have anticancer activity. To profile the molecular events associated with the anticancer effects of JS-K, HL-60 leukemia cells were treated with JS-K and subjected to microarray and real-time RT-PCR analysis. JS-K induced concentration- and time-dependent gene expression changes in HL-60 cells corresponding to the cytolethality effects. The apoptotic genes (caspases, Bax, and TNF-alpha) were induced, and differentiation-related genes (CD14, ITGAM, and VIM) were increased. For acute phase protein genes, some were increased (TP53, JUN) while others were suppressed (c-myc, cyclin E). The expression of anti-angiogenesis genes THBS1 and CD36 and genes involved in tumor cell migration such as tissue inhibitors of metalloproteinases, were also increased by JS-K. Confocal analysis confirmed key gene changes at the protein levels. Thus, multiple molecular events are associated with JS-K effects in killing HL-60, which could be molecular targets for this novel anticancer NO prodrug.

JS-K, an arylating nitric oxide (NO) donor, has synergistic anti-leukemic activity with cytarabine (ARA-C)

We have designed prodrugs that release nitric oxide (NO) on metabolism by glutathione S-transferases (GST). This design exploits the upregulation of GST in acute myeloid leukemia (AML) cells. O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K, a member of this class) has potent anti-leukemic activity. HL-60 myeloid leukemia cells were used for in vitro studies of the combination of JS-K with daunorubicin (DAUNO), cytarabine (ARA-C) or etoposide (ETOP) using the median effect method to determine synergistic, antagonistic, or additive effects. Combinations of JS-K added simultaneously, 2h before or 2h after the other compounds were used. JS-K and DAUNO were antagonistic in all three drug sequences. JS-K and ETOP were also antagonistic but to a lesser degree. JS-K and ARA-C showed strong synergy. The combination index at the 50% fraction affected was 0.37+/-0.23, 0.24+/-0.27, and 0.15+/-0.11 for simultaneous, JS-K first and ARA-C first additions, respectively. JS-K by itself induced DNA strand breaks at relatively high concentrations. However, at submicromolar concentrations, it significantly augmented ARA-C-induced DNA strand breaks. NMR spectroscopy revealed no evidence of chemical interaction between JS-K and the other chemotherapeutic agents. We conclude that ARA-C and JS-K have synergistic anti-leukemic activity and warrant further exploration in combination.

Aryl bis(diazeniumdiolates): potent inducers of S-glutathionylation of cellular proteins and their in vitro antiproliferative activities

A number of bis(diazeniumdiolates) that we designed to release up to 4 mol of nitric oxide (NO) and that are structural analogues of the NO prodrug and anticancer lead compound O(2)-{2,4-dinitro-5-[4-(N-methylamino)benzoyloxy]phenyl} 1-(N,N-dimethylamino)diazen-1-ium-1,2- diolate (PABA/NO) were synthesized and studied. A majority of these compounds yielded higher levels of NO, were better inhibitors of proliferation of a number of cancer cell lines, and more rapidly induced substantially increased levels of S-glutathionylation of cellular proteins in comparison with PABA/NO. In most cases, the antiproliferative activity and extents of S-glutathionylation correlated well with levels of intracellular NO release. We report bis(diazeniumdiolates) to be a class of S-glutathionylating agents with potent antiproliferative and S-glutathionylating activity.

Synthesis, mechanistic studies, and anti-proliferative activity of glutathione/glutathione S-transferase-activated nitric oxide prodrugs

Nitric oxide (NO) prodrugs such as O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K) are a growing class of promising NO-based therapeutics. Nitric oxide release from the anti-cancer lead compound, JS-K, is proposed to occur through a nucleophilic aromatic substitution by glutathione (GSH) catalyzed by glutathione S-transferase (GST) to form a diazeniumdiolate anion that spontaneously releases NO. In this study, a number of structural analogues of JS-K were synthesized and their chemical and biological properties were compared with those of JS-K. The homopiperazine analogue of JS-K showed anti-cancer activity that is comparable with that of JS-K but with a diminished reactivity towards both GSH and GSH/GST; both the aforementioned compounds displayed no cytotoxic activity towards normal renal epithelial cell line at concentrations where they significantly diminished the proliferation of a panel of renal cancer cell lines. These properties may prove advantageous in the further development of this class of nitric oxide prodrugs as cancer therapeutic agents.

Nitric oxide prodrug JS-K inhibits ubiquitin E1 and kills tumor cells retaining wild-type p53

Nitric oxide (NO) is a major effector molecule in cancer prevention. A number of studies have shown that NO prodrug JS-K (O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate) induces apoptotic cell death in vitro and in vivo, indicating that it is a promising new therapeutic for cancer. However, the mechanism of its tumor-killing activity remains unclear. Ubiquitin plays an important role in the regulation of tumorigenesis and cell apoptosis. Our earlier report has shown that inactivation of the ubiquitin system through blocking E1 (ubiquitin-activating enzyme) activity preferentially induces apoptosis in p53-expressing transformed cells. As E1 has an active cysteine residue that could potentially interact with NO, we hypothesized that JS-K could inactivate E1 activity. E1 activity was evaluated by detecting ubiquitin-E1 conjugates through immunoblotting. JS-K strikingly inhibits the ubiquitin-E1 thioester formation in cells in a dose-dependent manner with an IC(50) of approximately 2 microM, whereas a JS-K analog that cannot release NO did not affect these levels in cells. Moreover, JS-K decreases total ubiquitylated proteins and increases p53 levels, which is mainly regulated by ubiquitin and proteasomal degradation. Furthermore, JS-K preferentially induces cell apoptosis in p53-expressing transformed cells. These findings indicate that JS-K inhibits E1 activity and kills transformed cells harboring wild-type p53.

New drugs in multiple myeloma

PURPOSE OF REVIEW

Advances in the understanding of multiple myeloma pathogenesis have led to the development of innovative targeted therapies and improved management of this aggressive hematological neoplasia. This review will focus on the clinical trials that have reinforced the use of these new agents. Also, we will briefly take a look at the newer drugs making their way out of the laboratory and into early phase studies.

RECENT FINDINGS

During the past decade new multiple myeloma therapies featuring bortezomib and lenalidomide have come to light, whereas known agents such as thalidomide and arsenic trioxide have been reintroduced as key factors in multiple myeloma management. These new agents and their combinations have shown increased response rates and have added more options for patients with multiple myeloma whose disease has become resistant to conventional therapy. With these drug therapies has come a more targeted approach to treatment enabling not only improved antimyeloma efficacy but also the use of decreased dosing enhancing the safety and tolerability of these regimens. Newer agents including the histone deacetylase, hsp90, mammalian target of rapamycin and Akt inhibitors are showing promise preclinically and are now being assessed in phase I/II trials.

SUMMARY

This new antimultiple myeloma arsenal has shown its worth in both the relapsed/refractory and frontline setting and provides valuable options for patients with this debilitating disease.

TIMP-2 mediates the anti-invasive effects of the nitric oxide-releasing prodrug JS-K in breast cancer cells

Introduction

Tumor invasion and metastasis remain a major cause of mortality in breast cancer patients. High concentrations of nitric oxide (NO) suppress tumor invasion and metastasis in vivo. NO prodrugs generate large amounts of NO upon metabolism by appropriate intracellular enzymes, and therefore could have potential in the prevention and therapy of metastatic breast cancer.

Methods

The present study was designed to determine the effects of the NO-releasing prodrug O²-(2,4-dinitrophenyl) 1- [(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K) on breast cancer invasion and the mechanisms involved. MDA-MB-231, MDA-MB-231/F10, and MCF-7/COX-2 were the three breast cancer cell lines tested. NO levels were determined spectrophotometrically using a NO assay kit. Invasion and the expression of matrix metalloproteinases (MMPs) and tissue inhibitor of MMPs were determined using Matrigel invasion assays, an MMP array kit and ELISAs. The activity and expression of extracellular signal-regulated kinase 1/2, p38, and c-Jun N-terminal kinase mitogen-activated protein kinases were determined using western blot analyses.

Results

Under conditions by which JS-K was not cytotoxic, JS-K significantly decreased (P < 0.05) the invasiveness of breast cancer cells across the Matrigel basement membrane, which was directly correlated with NO production. JS-43-126, a non-NO-releasing analog of JS-K, had no effect on NO levels or invasion. JS-K increased (P < 0.05) TIMP-2 production, and blocking TIMP-2 activity with a neutralizing antibody significantly increased (P < 0.05) the invasive activity of JS-K-treated cells across Matrigel. JS-K decreased p38 activity, whereas the activity and the expression of extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase were unaffected.

Conclusion

We report the novel findings that JS-K inhibits breast cancer invasion across the Matrigel basement membrane, and NO production is vital for this activity. Upregulation of TIMP-2 production is one mechanism by which JS-K mediates its anti-invasive effects. JS-K and other NO prodrugs may represent an innovative biological approach in the prevention and treatment of metastatic breast cancer.

NO-donating NSAIDs and cancer: an overview with a note on whether NO is required for their action

Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) consist of a conventional NSAID to which an NO-releasing moiety is attached covalently, often via a spacer molecule. NO-NSAIDs represent an emerging class of compounds with chemopreventive properties against a variety of cancers, demonstrated in preclinical models including cell culture systems and animal tumor models; their potential efficacy in humans has not been assessed. Their mechanism of action appears complex and involves the generation of reactive oxygen species, suppression of microsatellite instability in mismatch repair-deficient cells, and modulation of several signaling cascades that culminate in inhibited cell renewal and enhanced apoptosis. NO, long appreciated to be able to protect from and also promote cancer, is released form NO-NSAIDs and constitutes their defining property. Existing data are consistent with the notion that NO may mediate their anticancer effect. In addition there is evidence that long-term administration of NO-donating compounds is not associated with increased incidence of colon cancer. Whether NO release is required for the anticancer effect of NO-NSAIDs has being questioned by recent data indicating that, at least in the case of NO-aspirin, the NO-releasing moiety may serve as a leaving group while the spacer actually being the moiety responsible for its pharmacological action. Regardless of mechanistic issues, these compounds promise to contribute to the control of cancer.

Synthesis and in vitro anti-leukemic activity of structural analogues of JS-K, an anti-cancer lead compound

Structural analogues of JS-K, an anti-cancer lead compound, were prepared and their in vitro anti-leukemic activity was determined. The rate of nitric oxide release from the corresponding diazeniumdiolate anions did not appear to affect the anti-leukemic activity of the prodrug forms. Two compounds with potent inhibitory activity and a potentially favorable toxicological profile were identified.

From the bench to the bedside: emerging new treatments in multiple myeloma

Within the last decade, several novel classes of anti-myeloma therapeutics have become available. The clinical successes achieved by thalidomide, lenalidomide, and the proteasome inhibitor bortezomib, and in particular the ability of these agents to lead to major clinical responses in patients resistant to conventional or high-dose chemotherapy, have highlighted the importance of expanding further the spectrum of classes of agents utilized for the treatment of myeloma. Herein, we review the current status for the development of novel anti-myeloma agents, with emphasis on classes of therapeutics which have already translated into clinical trials or those in advanced stages of preclinical development. These include second-generation proteasome inhibitors (NPI-0052 and PR-171), heat shock protein 90 (hsp90) inhibitors, 2-methoxyestradiol, histone deacetylase (HDAC) inhibitors (e.g. SAHA and LBH589), fibroblast growth factor receptor 3 (FGF-R3) inhibitors, insulin-like growth factor 1 receptor (IGF-1R) inhibitors, mTOR inhibitors, monoclonal antibodies, and agents specifically targeting the tumor microenvironment, such as defibrotide.

MLN3897, a novel CCR1 inhibitor, impairs osteoclastogenesis and inhibits the interaction of multiple myeloma cells and osteoclasts

The interaction between osteoclasts (OCs) and multiple myeloma (MM) cells plays a key role in the pathogenesis of MM-related osteolytic bone disease (OBD). MM cells promote OC formation and, in turn, OCs enhance MM cell proliferation. Chemokines are mediators of MM effects on bone and vice versa; in particular, CCL3 enhances OC formation and promotes MM cell migration and survival. Here, we characterize the effects of MLN3897, a novel specific antagonist of the chemokine receptor CCR1, on both OC formation and OC-MM cell interactions. MLN3897 demonstrates significant impairment of OC formation (by 40%) and function (by 70%), associated with decreased precursor cell multinucleation and down-regulation of c-fos signaling. OCs secrete high levels of CCL3, which triggers MM cell migration; conversely, MLN3897 abrogates its effects by inhibiting Akt signaling. Moreover, MM cell-to-OC adhesion was abrogated by MLN3897, thereby inhibiting MM cell survival and proliferation. Our results therefore show novel biologic sequelae of CCL3 and its inhibition in both osteoclastogenesis and MM cell growth, providing the preclinical rationale for clinical trials of MLN3897 to treat OBD in MM.