Role of nitric oxide in cancer biology

Integrative Bioinformatics Analysis of iNOS/NOS2 in gastric and colorectal cancer

Objective The aim of the present work was to investigate the expression of nitric oxide synthase 2 (iNOS/ NOS2) in colorectal and gastric cancers and evaluate its association with patient’s prognosis by integrated bioinformatics analysis.

Methods The data for present study was obtained from the TCGA, GTEx, and STRING database. iNOS/NOS2 mRNA expression in normal tissue and colorectal, and gastric cancer tissuea were investigated through the GTEx and TCGA database. iNOS/NOS2 gene mutations and frequency were analyzed in the TCGA database using the cBioPortal online data analysis tool. The protein-protein interaction (PPI) network of iNOS/NOS2 was constructed by STRING database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway of iNOS/NOS2 and relevant proteins involved in the PPI network were enriched and demonstrated by the bubble plot. Comparison of the overall survival(OS) and disease free survival(DFS) between samples expressing high and low levels of iNOS/NOS2 was analysis based on the TCGA databases through the GEPIA online data analysis tool.

Results For colon adenocarcinoma (COAD) and rectal adenocarcinoma(READ) iNOS/NOS2 mRNA expression levels in tumor tissue were significant higher than those of corresponding normal colorectal tissue (p<0.05). iNOS/NOS2 mutations were identified in both colorectal cancer and gastric cancer. Missense substitutions and synonymous substitution were the top two mutation types for colorectal and gastric cancer. The top positive and negative co-expressed genes correlated with iNOS/ NOS2 were TRIM40 (rpearson=0.56, p<0.05) and GDPD5 (rpearson=-0.41, p<0.05) in colorectal cancer respectively andCASP5 (rpearson=0.63,p<0.05) and PIAS3 (rpearson=-0.43,p<0.05) in gastric cancer. Twenty one proteins were included in the PPI network with 51 nodes and 345 edges which indicated the PPI enrichment wassignificant (p=1.0e-16). The KEGG of the included genes were mainly enriched in metabolic pathway and Jak-STAT signaling pathway. There was a significant difference indisease free survival (DFS) between samples expressing high and low iNOS/NOS2 (HR=0.37, p=0.044) in rectal cancer. The difference was not statistical between iNOS/NOS2 high and low expressing groups for overall survival(OS) or DFS in the colon cancer or gastric cancer(p>0.05).

Conclusions iNOS/NOS2 mRNA isup-regulated in tumor tissue compared to corresponding normal tissue in colorectal and gastric cancer which implement it in the development of colorectal and gastric cancers.

Gaseous nitrogen oxide promotes human lung cancer cell line A549 migration, invasion, and metastasis via iNOS-mediated MMP-2 production

Gaseous nitrogen oxide (gNO) is an important indoor and outdoor air pollutant. Many studies have indicated gNO causes lung tissue damage by its oxidation properties and free radicals. However, there are considerably few data on the association between lung cancer and gNO exposure. The purpose of this study was to examine whether gNO could contribute to the process of malignant progression of lung cancer. The results of wound-healing assay and in vitro transwell assay revealed that gNO-induced dose and time dependently the migration and invasion of A549 cells, a human lung cancer cell line, under noncytotoxic concentrations. gNO was able to induce release of NO from A549 cells, an effect that was mediated via the activation of inducible nitric oxide synthases (iNOS), but not constitutive isoforms, during the same treatment period. An increased expression of matrix metalloproteinase (MMP) and a coincided reduction in repress tissue inhibitors of metalloprotease-2 were observed upon the treatment of gNO. The gNO-mediated MMP-2 induction appeared to be a consequence of nuclear factor kappa B and activation protein-1 activation, because that their DNA binding activity was enhanced by gNO. All these influences of gNO were efficiently repressed by the pretreatment of a NOS inhibitor (N(G)-nitro-L-arginine methyl ester). Using a mouse model, we showed that gNO promoted A549 metastasis to the lung through a mechanism involving the iNOS-dependent MMP-2 activity. Our data imply that gNO exposure, which in turn led to iNOS activation and the enhancement of MMP-mediated cellular events, was related to lung cancer development.

A dose response study of inhaled nitric oxide in hypoxic respiratory failure in preterm infants

BACKGROUND

Inhaled nitric oxide (iNO) is used widely in newborn infants with hypoxic respiratory failure, despite the known and theoretical toxicity of iNO, and a relative lack of information about appropriate doses.

AIM

To determine whether a dose-response relationship existed for iNO in preterm infants.

DESIGN

A four-period, four-dose, cross-over design was used with iNO given for 15 min in a randomised sequence in concentrations of 5, 10, 20 and 40 parts per million (ppm), with a minimum 5 min wash-out period. Data on ventilatory, blood gas and other physiological measurements were recorded before and at the end of each period. The relationship of clinical response with iNO dose and period was analysed using multivariate regression.

SUBJECTS

Infants with gestational age < 34 weeks and < 28 days postnatal age with hypoxic respiratory failure were recruited.

OUTCOME MEASURE

A clinically significant dose-response was defined as a rise in the post-ductal arterial oxygen tension (PaO(2)) of at least 3 kPa.

RESULTS

Thirteen infants were recruited. At trial entry, ten were < 3 days of age; 11 were being treated with high frequency oscillatory ventilation; median (inter-quartile range) gestational age 27 (25-29) weeks; birthweight 983 (765-1120) g; oxygenation index 27.1 (21.8-28.8). Six infants (46%) showed a clinically significant response. After adjusting for period and patient effect, no evidence for an overall dose effect was identified (likelihood ratio test, p=0.34).

CONCLUSION

No evidence of a dose-response relationship with iNO was found in this study of very preterm infants with respiratory failure.

Inducible nitric oxide synthase (iNOS) in tumor biology: the two sides of the same coin

Inducible nitric oxide synthase (iNOS) is one of three key enzymes generating nitric oxide (NO) from the amino acid l-arginine. iNOS-derived NO plays an important role in numerous physiological (e.g. blood pressure regulation, wound repair and host defence mechanisms) and pathophysiological (inflammation, infection, neoplastic diseases, liver cirrhosis, diabetes) conditions. iNOS is the synthase isoform most commonly associated with malignant disease. Nevertheless, the role of iNOS during tumor development is highly complex, and incompletely understood. Both promoting and deterring actions have been described, presumably depending upon the local concentration of iNOS within the tumor microenvironment. In particular, pivotal effects such as malingnant transformation, angiogenesis, and metastasis are modulated by iNOS. On the other hand, NO derived from macrophages has a potentially cytotoxic/cytostatic effect upon tumor cells. Hence, therapeutical interference with iNOS activity is of considerable interest, especially in tumors where metastatic activity, host defence mechanisms and the level of differentiation seem to be correlated to iNOS expression. This review will aim to summarize the dual actions of iNOS as simultaneous tumor promoter and suppressor.

Diabetes and chronic nitrate therapy as co-determinants of somatic DNA damage in patients with coronary artery disease

Somatic DNA damage has been linked to coronary artery disease (CAD). However, whether genetic instability is linked to CAD per se or to concomitant potentially genotoxic metabolic and pharmacological factors remains still unclear. The aim of this study was to evaluate the determinants of somatic DNA damage in a large population of patients undergoing coronary angiography. A total of 278 in-hospital patients (215 men, age 61.8+/-0.7 years) were studied by using micronucleus assay (MN) in human lymphocytes, which is one of the most commonly used biomarker for somatic DNA damage. Significant CAD (>50% diameter stenosis) was present in 210 patients (179 men, age 62.3+/-0.7 years). Normal coronary arteries were observed in 68 patients (35 men, age 60.2+/-1.7 years). There were no significant differences between patients with and without CAD, but patients with multivessel disease had the highest MN levels (P=0.01). MN frequency was also found significantly higher in presence of type 2 diabetes (P<0.0001), dyslipidemia (P=0.048) and nitrate therapy (P=0.0002). A significant additive effect was also observed between diabetes and nitrate therapy (P=0.02). On multivariate logistic regression analysis, diabetes [odds ratio=6.8 (95% confidence interval, 3.2-14.5), P<0.0001] and nitrate therapy [odds ratio=2.4 (95% confidence interval, 1.3-4.7), P=0.01] remained the only significant determinants for the 50th percentile of MN (>12 per thousand). These results indicated that diabetes and, to a lesser extent, chronic nitrate therapy are major determinants of somatic DNA instability in patients with CAD. DNA damage might represent an additional pathogenetic dimension and a possible therapeutic target in the still challenging management of coronary artery disease concerning diabetics.

Colorectal cancer vaccines: principles, results, and perspectives

In the search for novel therapeutic approaches to treat patients with colorectal carcinoma, anticancer vaccination holds promise. A large body of preclinical and clinical evidence has demonstrated that the immune system can be polarized against malignant cells by means of several active specific immunotherapy strategies. Although no vaccination regimen can be currently recommended outside clinical trials, tumor response and immunologic findings observed in animal models and humans prompt researchers to explore further the antitumor potential of such biotherapy in an effort to reproduce in a larger set of patients the cascade of molecular events that characterizes the successful tumor immune rejection currently observed in a minority of vaccinated subjects. In this work, we summarize the principles and the main results of cancer vaccine strategies so far implemented for the treatment of patients with colorectal carcinoma. We also discuss the most recent preclinical tumor immunology insights that might change the way to design the next generation of cancer vaccines, hopefully improving the effectiveness of such a biotherapeutic approach.

Induction of endothelial nitric oxide synthase expression by melanoma sensitizes endothelial cells to tumor necrosis factor-driven cytotoxicity

PURPOSE

The cascade of molecular events leading to tumor necrosis factor (TNF)-mediated tumor regression is still incompletely elucidated. We investigated the role of endothelial nitric oxide synthase in determining the tumor-selective activity of TNF.

EXPERIMENTAL DESIGN

Using quantitative real-time PCR, endothelial nitric oxide synthase gene levels were measured in melanoma metastases of the skin and normal skin biopsies obtained from 12 patients before undergoing TNF-based therapy. In vitro, the ability of melanoma cells supernatant to affect endothelial nitric oxide synthase transcription by endothelial cells and the influence of nitric oxide synthase inhibition on TNF cytotoxicity toward endothelial cells was evaluated.

RESULTS

Endothelial nitric oxide synthase transcript abundance resulted significantly greater in tumor samples rather than in normal skin samples and in patients showing complete response to TNF-based treatment rather than in those showing partial/minimal response. In vitro, melanoma cells' supernatant induced endothelial nitric oxide synthase gene expression by endothelial cells. Nitric oxide synthase inhibition slowed endothelial cells proliferation and, if induced before TNF administration, decreased the cytokine-mediated cytotoxicity on endothelial cells.

CONCLUSIONS

Taken together, these findings support the hypothesis that high expression of endothelial nitric oxide synthase in the tumor microenvironment might increase or be a marker for endothelial cells sensitivity to TNF. These observations may have important prognostic and/or therapeutic implications in the clinical setting.

Cancer vaccine development: on the way to break immune tolerance to malignant cells

Exploiting a naturally occurring defense system, the immunotherapeutic approach embodies an ideal nontoxic treatment for cancer. Despite the evidence that immune effectors can play a significant role in controlling tumor growth either in natural conditions or in response to therapeutic manipulation, the cascade of molecular events leading to tumor rejection by the immune system remains to be fully elucidated. Nevertheless, some recent tumor immunology advancements might drastically change the way to design the next generation of cancer vaccines, hopefully improving the effectiveness of this therapeutic approach. In the present work, we will focus on three main areas of particular interest for the development of novel vaccination strategies: (a) cellular or molecular mechanisms of immune tolerance to malignant cells; (b) synergism between innate and adaptive immune response; (c) tumor-immune system interactions within the tumor microenvironment.

Chemopreventive effects of a selective nitric oxide synthase inhibitor on carcinogen-induced rat esophageal tumorigenesis

The inducible nitric oxide synthase (iNOS) generates a high concentration of nitric oxide (NO) in tissues. Increased NO production is associated with many disorders including esophageal cancer. Previous studies in our laboratory demonstrated an association between increased iNOS expression and the development of N-nitrosomethylbenzylamine (NMBA)-induced tumors in the rat esophagus. On the basis of these observations, we initiated a bioassay to evaluate the ability of S,S'-1,4-phenylene-bis(1,2-ethanediyl)bis-isothiourea (PBIT), a selective iNOS inhibitor, to prevent the progression of esophageal tumors in rats preinitiated with NMBA. Rats were given s.c. injections of NMBA (0.25 mg/kg body weight) three times per week for 5 weeks. One week later, they were fed a synthetic diet containing either 50 or 100 ppm PBIT until the end of the bioassay (25 weeks). PBIT reduced the incidence of esophageal cancer from 96% in NMBA-treated rats to 83% and 77% (P < 0.05) in rats treated with 50 and 100 ppm PBIT, respectively. Tumor multiplicity was reduced from 3.64 +/- 0.42 tumors per esophagus in NMBA-treated rats to 1.79 +/- 0.25 (P < 0.001) and 1.50 +/- 0.24 (P < 0.0001) in rats treated with 50 and 100 ppm PBIT, respectively. PBIT reduced the production of NO in NMBA-induced preneoplastic and papillomatous esophageal lesions when compared with comparable lesions in rats treated with NMBA only. iNOS mRNA expression was not modulated by PBIT. These observations suggest that iNOS plays a role in tumor development and that its selective inhibitor, PBIT, significantly inhibits esophageal tumor progression presumably through reducing the production of NO.

Up-regulation of inducible nitric oxide synthase in Helicobacter pylori-associated gastritis may represent an increased risk factor to develop gastric carcinoma of the intestinal type

The enzyme inducible nitric oxide synthase (iNOS) is part of the host innate defense system against bacterial infection. During chronic inflammation, like that seen with a Helicobacter pylori infection, constant nitric oxide production may lead to tissue and DNA damage, thus increasing the patient's risk for developing cancer. Several investigations on iNOS expression in H. pylori-associated gastritis have resulted in conflicting data. Therefore, we investigated the association between chronic H. pylori infection and iNOS expression in samples from stomach carcinoma patients as well as in antral biopsies from patients with H. pylori-associated gastritis. iNOS expression was analyzed by means of reverse transcriptase (RT)-PCR and quantified by competitive RT-PCR. To study in situ localization of iNOS in biopsy samples, immunohistochemistry was performed. iNOS enzyme activity was quantified using an arginine/citrulline assay. A significant increase in iNOS mRNA signal was only present in one-third of the analyzed patient biopsies with H. pylori-associated gastritis. These biopsies showed a 90% association with intestinal metaplasia and a 100% association with CagA-positive H. pylori. Intestinal metaplasia is discussed to be one step in the carcinogenesis of stomach cancer. Quantitation of iNOS transcripts and iNOS enzyme activity in non-cancerous mucosa of gastric cancer patients revealed a significant increase in iNOS transcripts and iNOS activity only in the mucosa of patients with stomach cancer of the intestinal type but not in the diffuse type. Our results support the hypothesis that CagA-positive H. pylori strains are associated with the expression and activity of iNOS, and therefore might contribute to the development of intestinal metaplasia leading to gastric cancer of the intestinal type.

Inhibition of the development of hepatocellular carcinomas by phenyl N-tert-butyl nitrone in rats fed with a choline-deficient, l-amino acid-defined diet

Effects of phenyl N-tert-butyl nitrone (PBN), a spin-trapping agent, on the development of frank cancers were examined in male Wistar rats fed with a choline-deficient, l-amino acid-defined (CDAA) diet for 70 weeks. PBN (0.065% in the drinking water) reduced incidences, multiplicities and possibly sizes of both hepatocellular adenomas and carcinomas when administered for all 70 weeks or only for the first 26 weeks, and those of carcinomas but not adenomas, when administered only for the last 44 weeks. These results indicate that PBN can prevent the development of frank HCCs in the CDAA diet model. The anti-carcinogenic effect of PBN may be ascribed to the prevention of both the development of HCAs and their malignant conversion to HCCs. If such findings can be generalized, PBN may be able to serve as a good tool to investigate molecular mechanisms underlying carcinogenic processes.

Depletion of deoxyribonucleoside triphosphate pools in tumor cells by nitric oxide

Nitric oxide displays pro- and anti-tumor activities, prompting further studies to better understand its precise role. Nitric oxide inhibits ribonucleotide reductase (RnR), the limiting enzyme for de novo dNTP synthesis. We report here the first detailed analysis of dNTP variations induced in tumor cells by NO. NO prodrugs induced a depletion in dNTP pools and an activation of the pyrimidine salvage pathway, as did hydroxyurea, the prototypic RnR inhibitor. In the presence of dipyridamole, which blocked salvaged dNTP synthesis, depletion of dNTP pools was also observed in tumor cells cocultured with macrophages expressing the high-output iNOS activity. This effect was rapid, reversible, blocked by NO scavengers, and cGMP independent. It was quantitatively correlated to iNOS activity. In the absence of dipyridamole, NO still induced a decrease in dATP concentration in tumor cells cocultured with macrophages, whereas surprisingly, concentrations of dCTP and dTTP expanded considerably, resulting in a strong imbalance in dNTP pools. NO prodrugs did not cause such an increase in pyrimidine dNTP, suggesting that pyrimidine nucleosides were released by NO-injured macrophages. Altered dNTP levels have been reported to promote mutagenesis and apoptosis. It is suggested that abnormal changes in dNTP pools in tumors might contribute to NO-dependent toxicity.

NO-NSAIDs and cancer: promising novel agents

Three potential applications of NO-donating NSAIDs in human cancer include their use: as chemopreventive agents; against already developed cancers (chemotherapy); and for the control of cancer symptoms, notably cancer pain. The evidence to date of greater safety and enhanced efficacy of NO-donating NSAIDs underscores their potential to prevent colon cancer and overcome the limitations of traditional NSAIDs. NO-donating NSAIDs affect several pathways critical to colon carcinogenesis and this may explain in part their greater efficacy in colon cancer prevention as assessed in preclinical models.

Effects of phenyl N-tert-butyl nitrone and its derivatives on the early phase of hepatocarcinogenesis in rats fed a choline-deficient, L-amino acid-defined diet

The present study examined the effects of various derivatives of a radical trapping agent, phenyl N-tert-butyl nitrone, on the early phase of hepatocarcinogenesis in male Wistar rats fed a choline-deficient, L-amino acid-defined diet for 16 weeks. The derivatives used were 4-hydroxyphenyl (a physiologically major metabolite), 3-hydroxyphenyl, 2-hydroxyphenyl and 2-sulfoxyphenyl N-tert-butyl nitrone, and their effects were studied in a comparison with those of the parent compound, phenyl N-tert-butyl nitrone. The sizes of putatively preneoplastic, glutathione S-transferase placental form-positive lesions and the levels of extra-nuclear oxidative injury of hepatocytes, using the formation of 2-thiobarbituric acid-reacting substances as a parameter, were decreased by all doses (0.009%, 0.045% and 0.090% in diet) of 4-hydroxyphenyl N-tert-butyl nitrone and only by the highest dose of 3-hydroxyphenyl N-tert-butyl nitrone and phenyl N-tert-butyl nitrone. While 4-hydroxyphenyl N-tert-butyl nitrone, 3-hydroxyphenyl N-tert-butyl nitrone and phenyl N-tert-butyl nitrone all enhanced and inhibited hepatocellular apoptosis in preneoplastic lesions and their surrounding tissue, respectively, only 4-hydroxyphenyl N-tert-butyl nitrone additionally inhibited hepatocyte proliferation both in preneoplastic lesions and their surrounding tissue. 2-Hydroxyphenyl or 2-sulfoxyphenyl N-tert-butyl nitrone did not exert any of the above effects. These results suggest that the selective induction of apoptosis in preneoplastic hepatocyte populations plays a crucial role in the inhibition of hepatocarcinogenesis derived by phenyl N-tert-butyl nitrone and its effective derivatives. Further, the metabolic conversion to 4-hydroxyphenyl N-tert-butyl nitrone may also be important for the inhibitory effects of phenyl N-tert-butyl nitrone on hepatocarcinogenesis.

Sp1 and krüppel-like factor family of transcription factors in cell growth regulation and cancer

The Sp/KLF family contains at least twenty identified members which include Sp1-4 and numerous krüppel-like factors. Members of the family bind with varying affinities to sequences designated as 'Sp1 sites' (e.g., GC-boxes, CACCC-boxes, and basic transcription elements). Family members have different transcriptional properties and can modulate each other's activity by a variety of mechanisms. Since cells can express multiple family members, Sp/KLF factors are likely to make up a transcriptional network through which gene expression can be fine-tuned. 'Sp1 site'-dependent transcription can be growth-regulated, and the activity, expression, and/or post-translational modification of multiple family members is altered with cell growth. Furthermore, Sp/KLF factors are involved in many growth-related signal transduction pathways and their overexpression can have positive or negative effects on proliferation. In addition to growth control, Sp/KLF factors have been implicated in apoptosis and angiogenesis; thus, the family is involved in several aspects of tumorigenesis. Consistent with a role in cancer, Sp/KLF factors interact with oncogenes and tumor suppressors, they can be oncogenic themselves, and altered expression of family members has been detected in tumors. Effects of changes in Sp/KLF factors are context-dependent and can appear contradictory. Since these factors act within a network, this diversity of effects may arise from differences in the expression profile of family members in various cells. Thus, it is likely that the properties of the overall network of Sp/KLF factors play a determining role in regulation of cell growth and tumor progression.

A symbiotic concept of autoimmunity and tumour immunity: lessons from vitiligo

Vitiligo is a skin disease in which melanocytes (MCs) are eradicated from lesional epidermis, resulting in disfiguring loss of pigment. MCs are destroyed by MC-reactive T cells, as well as other non-immune and immune components. Similarities exist between the autoimmunity observed in vitiligo and the tumour immunity observed in melanoma immuno-surveillance. An analysis of these mechanisms might lead to the development of new therapies for both vitiligo and melanoma.