iNOS as a therapeutic target for treatment of human tumors

doi:10.1016/j.niox.2008.05.001

Nitric Oxide

Volume 19, Issue 2, September 2008, Pages 217-224

https://doi.org/10.1016/j.niox.2008.05.001 Get rights and content

Abstract

Nitric oxide synthase (NOS) has been shown to be overexpressed in a number of human tumors compared to normal tissues and therefore potentially represents an exploitable target in future anticancer therapies. To achieve this, there will be a need to profile tumors to identify those expressing high levels of NOS; alternatively, endogenous (low) levels of NOS could be modulated by induction or through gene therapy approaches. NOS consists of a reductase domain which shares a high degree of sequence homology with P450 reductase and this domain supplies reducing equivalents to a haem containing oxygenase domain that is responsible for the production of nitric oxide. Thus, there are a number of routes of exploitation. Firstly, to take advantage of the reductase domain to activate bioreductive drugs as has been exemplified with tirapazamine and now extended to AQ4N (1,4-bis{2-(dimethylamino-N-oxide)ethylamino}5,8-dihydroxy-anthracene-9,10-dione). Secondly, to take advantage of nitric oxide production for its ability to increase the sensitivity of resistant hypoxic cells to radiation. Lastly, to utilize inhibition of HIF-1 to amplify NO based therapies. In this review we provide examples/evidence of how these objectives can be achieved.

Section snippets

Nitric oxide synthase: Structure and isoforms

Nitric oxide synthase (NOS) is a dimeric enzyme that consists of two identical monomers; each monomer can be divided into two distinct catalytic domains: an NH₂-terminal oxygenase domain and a P450-like, haem containing COOH-terminal reductase domain (NOSR) [1]. The latter shares a high degree of sequence homology to NADPH: Cytochrome P450 reductase (P450R) [2]. The oxygenase domain is responsible for the production of NO by a two-step oxidation of l-arginine to l-citrulline in the presence of

Pathways of iNOS induction in human cells

Maximal induction of the iNOS gene necessitates two signals: IFNγ and one other stimulus such as an endotoxin, TNFα or IL1β. Stimuli such as TNFα or IL1β stimulate iNOS transcription by activation of the transcription factor NF-kB which binds to a kB element in the NOS promoter [13]. IFNγ activates the transcription factor IRF-1 (interferon regulatory factor-1), which also binds to elements in the NOS promoter [14], [15]. Synergism between NF-kB and IRF-1 is believed to be achieved partly

NOS expression in human tumors

The high incidence of tumor nitric oxide synthase expression reported in several studies strongly suggest that the enzyme is widely expressed and often up-regulated in multiple tumor tissues. Malignant neoplasms of the central nervous system express high levels of NOS predominantly in tumor and endothelial cells and the increased expression correlates with vascularization and higher tumor grade [20], [21]. The enzyme was primarily localized to the inflammatory cells within carcinomas of the

Hypoxia in tumors

Tumor hypoxia can cause resistance to chemotherapy, because as oxygen levels decrease in proportion to distance from the vasculature, the rate of cell proliferation also decreases [27] thus reducing the effectiveness of most anti-cancer drugs that target rapidly dividing cells [28]. Hypoxic cells most distant from blood vessels may also be exposed to lower concentrations of drug than cells in close proximity to blood vessels due to a greater diffusion distance and metabolism of the drug [29].

Bioreductive drugs

Lin et al. first suggested that a lower redox potential for tumor tissues relative to normal tissue could increase reductive activation of quinone based drugs in tumors [41]. This mechanism was not correct but the underlying rational led to the concept of using bioreductive drugs for selectively targeting hypoxic cells in tumors [42]. Many bioreductive prodrugs that act as hypoxia-selective cytotoxins have now been developed (Reviewed by Mckeown et al. [43]). The non-toxic prodrug must be a

NOS-mediated activation of bioreductive drugs

Tirapazamine (TPZ, 3-amino-1,2,4-benzotriazine-1,4-dioxide, SR 4233) was one of the first compounds to show specific hypoxic cytotoxicity [45] and demonstrate anti-tumor activity in clinical trials [46]. It was a significant improvement on previous quinone-containing, bioreductive alkylating agents [47], [48] because its differential toxicity towards hypoxic cells was much larger [45]. TPZ is activated in hypoxia to form the toxic moiety by one-electron reductases that add an electron to the

Tumor radiosensitizing effects of NO

Although, the role of NO as a radiosensitizer was first reported in hypoxic bacteria and human cells 50 years ago [66], [67], [68], it was not until recently that its potential radiosensitizing effects have been rediscovered in several studies showing that NO was almost as efficient as oxygen in increasing the radiosensitivity of cells [69], [70], [71], [72]. An elegant recent study conducted by Wardman et al. [73] showed that nitric oxide at 40 ppm caused significant radiosensitization of

Impact of NO on HIF-1α expression

Several studies reported the accumulation of HIF-1α and increased HIF-1 activity under the influence of nitric oxide in normoxia (21% oxygen) [82], [83], [84]. The inhibition of prolyl hydroxylase (PHD) activity by NO [85] and the activation of the PI3K/Akt pathway were reported to be involved in the regulation of HIF-1α stabilization by NO under these conditions [83]. However, there seems to be controversial reports on the effects of NO on HIF-1α stabilization under hypoxic conditions.

NO, HIF-1 and radiosensitivity

Radiation was also reported to cause an upregulation in HIF-1 expression levels in tumors, starting as early as 24 h with maximal expression levels reached 48 h post-radiation [95]. Several pathways have been suggested to be involved in HIF-1-mediated radiosensitization of tumors [96]. Firstly, HIF-1 enhances p53-phosphorylation in irradiated cells leading to apoptosis. HIF-1 also increases the glycolytic rate and maintains the mitotic drive, hence radiosensitizing tumors by maintaining the

NOS-based gene therapy

Although iNOS has been reported to be expressed in a number of tumors as described earlier, these endogenous levels can be very variable and may lead to low levels of NO production that can have pro-tumor effects. It is therefore an advantage to deliver high levels of exogenous iNOS to tumors to generate high concentrations of NO and activate bioreductive drugs.

The potential for iNOS in a suicide gene therapy approach was first demonstrated by Soler et al. [107], who showed a strong anti-tumor

Conclusion

The enzyme nitric oxide synthase with its two oxygenase domains and its reductase domains that are homologous to P450 reductase, has the potential to be exploited for cancer therapeutics.

A three pronged tumor attack of iNOS is summarized in Fig. 4. It can be used in combination with bioreductive drugs such as TPZ and AQ4N to target radio- and chemo-resistant hypoxic tumor cells. NOS also has the ability to produce high concentrations of NO which is a potent radiosensitizer as well as being

Acknowledgments

We thank Dr. Adrian Harris for supplying the breast tumor and normal tissue biopsies and Dr. Edwin Chinje for conducting NOS activity assays. This work has been funded by the Medical Research Council (Program G0500366) and the EU (Framework VI, Euroxy program). PhD studentships from the Ministry of Higher Education & Scientific Research of Algeria (M.M.) and the Medical Research Council (B.F.) are gratefully acknowledged.

References (112)

C. Nathan et al.
Regulation of biosynthesis of nitric oxide
J. Biol. Chem.
(1994)
S. Iida et al.
Identification of inducible calmodulin-dependent nitric oxide synthase in the liver of rats
J. Biol. Chem.
(1992)
R.M. Palmer et al.
Glucocorticoids do not affect the induction of a novel calcium-dependent nitric oxide synthase in rabbit chondrocytes
Biochem. Biophys. Res. Commun.
(1992)
M. Saura et al.
Interaction of interferon regulatory factor-1 and nuclear factor kappaB during activation of inducible nitric oxide synthase transcription
J. Mol. Biol.
(1999)
S. Rockwell et al.
Hypoxic fractions of human tumors xenografted into mice: a review
Int. J. Radiat. Oncol. Biol. Phys.
(1990)
J.D. Chapman
Measurement of tumor hypoxia by invasive and non-invasive procedures: a review of recent clinical studies
Radiother. Oncol.
(1991)
H.S. Swana et al.
Inducible nitric oxide synthase with transitional cell carcinoma of the bladder
J. Urol.
(1999)
D.M. Brizel et al.
Tumor hypoxia adversely affects the prognosis of carcinoma of the head and neck
Int. J. Radiat. Oncol. Biol. Phys.
(1997)
A.W. Fyles et al.
Oxygenation predicts radiation response and survival in patients with cervix cancer
Radiother. Oncol.
(1998)
T.H. Knocke et al.
Intratumoral pO2-measurements as predictive assay in the treatment of carcinoma of the uterine cervix
Radiother. Oncol.
(1999)

D.M. Brizel et al.

Oxygenation of head and neck cancer: changes during radiotherapy and impact on treatment outcome

Radiother. Oncol.

(1999)

K.A. Kennedy et al.

The hypoxic tumor cell: a target for selective cancer chemotherapy

Biochem. Pharmacol.

(1980)

S.R. McKeown et al.

Bioreductive drugs: from concept to clinic

Clin. Oncol. (R. Coll. Radiol)

(2007)

M. Jaffar et al.

Bioreductive and gene therapy approaches to hypoxic diseases

Adv. Drug Deliv. Rev.

(2001)

E.M. Zeman et al.

SR-4233: a new bioreductive agent with high selective toxicity for hypoxic mammalian cells

Int. J. Radiat. Oncol. Biol. Phys.

(1986)

S. Rockwell et al.

Mitomycin-C as a prototype bioreductive alkylating agent: in vitro studies of metabolism and cytotoxicity

Int. J. Radiat. Oncol. Biol. Phys.

(1982)

D.W. Siemann et al.

Potentiation of cisplatin activity by the bioreductive agent tirapazamine

Radiother. Oncol.

(1998)

J.B. Mitchell et al.

Redox generation of nitric oxide to radiosensitize hypoxic cells

Int. J. Radiat. Oncol. Biol. Phys.

(1998)

R.J. Griffin et al.

Radiosensitization of hypoxic tumor cells in vitro by nitric oxide

Int. J. Radiat. Oncol. Biol. Phys.

(1996)

B.F. Jordan et al.

Changes in tumor oxygenation/perfusion induced by the no donor, isosorbide dinitrate, in comparison with carbogen: monitoring by EPR and MRI

Int. J. Radiat. Oncol. Biol. Phys.

(2000)

K.B. Sandau et al.

Induction of hypoxia-inducible-factor 1 by nitric oxide is mediated via the PI 3K pathway

Biochem. Biophys. Res. Commun.

(2000)

K.B. Sandau et al.

Accumulation of HIF-1alpha under the influence of nitric oxide

Blood

(2001)

L.E. Huang et al.

Inhibition of hypoxia-inducible factor 1 activation by carbon monoxide and nitric oxide. Implications for oxygen sensing and signaling

J. Biol. Chem.

(1999)

J.H. Yin et al.

iNOS expression inhibits hypoxia-inducible factor-1 activity

Biochem. Biophys. Res. Commun.

(2000)

H. Kimura et al.

Effects of nitric oxide donors on vascular endothelial growth factor gene induction

Biochem. Biophys. Res. Commun.

(2002)

F. Li et al.

Regulation of HIF-1alpha stability through S-nitrosylation

Mol. Cell

(2007)

B.J. Moeller et al.

Radiation activates HIF-1 to regulate vascular radiosensitivity in tumors: role of reoxygenation, free radicals, and stress granules

Cancer Cell

(2004)

B.J. Moeller et al.

Pleiotropic effects of HIF-1 blockade on tumor radiosensitivity

Cancer Cell

(2005)

K.J. Williams et al.

Enhanced response to radiotherapy in tumours deficient in the function of hypoxia-inducible factor-1

Radiother. Oncol.

(2005)

B. Hemmens et al.

Enzymology of nitric oxide synthases

Methods Mol. Biol.

(1998)

D.S. Bredt et al.

Cloned and expressed nitric oxide synthase structurally resembles cytochrome P-450 reductase

Nature

(1991)

O.W. Griffith et al.

Nitric oxide synthases: properties and catalytic mechanism

Annu. Rev. Physiol.

(1995)

D.J. Stuehr

Structure-function aspects in the nitric oxide synthases

Annu. Rev. Pharmacol. Toxicol.

(1997)

W.K. Alderton et al.

Nitric oxide synthases: structure, function and inhibition

Biochem. J.

(2001)

Q.W. Xie et al.

Cloning and characterization of inducible nitric oxide synthase from mouse macrophages

Science

(1992)

J.A. Crowell et al.

Is inducible nitric oxide synthase a target for chemoprevention?

Mol. Cancer Ther.

(2003)

P.J. Andrew et al.

Enzymatic function of nitric oxide synthases

Cardiovasc. Res.

(1999)

M.W. Radomski et al.

Human colorectal adenocarcinoma cells: differential nitric oxide synthesis determines their ability to aggregate platelets

Cancer Res.

(1991)

E. Martin et al.

Role of interferon regulatory factor 1 in induction of nitric oxide synthase

J. Exp. Med.

(1994)

R. Kamijo et al.

Requirement for transcription factor IRF-1 in NO synthase induction in macrophages

Science

(1994)

D.S. Tendler et al.

Intersection of interferon and hypoxia signal transduction pathways in nitric oxide-induced tumor apoptosis

Cancer Res.

(2001)

G. Melillo et al.

A hypoxia-responsive element mediates a novel pathway of activation of the inducible nitric oxide synthase promoter

J. Exp. Med.

(1995)

C.S. Cobbs et al.

Expression of nitric oxide synthase in human central nervous system tumors

Cancer Res.

(1995)

O. Gallo et al.

Role of nitric oxide in angiogenesis and tumor progression in head and neck cancer

J. Natl. Cancer Inst.

(1998)

Z.J. Song et al.

Relationship between the expression of iNOS,VEGF,tumor angiogenesis and gastric cancer

World J. Gastroenterol.

(2002)

J.A. Lagares-Garcia et al.

Nitric oxide synthase as a marker in colorectal carcinoma

Am. Surg.

(2001)

L.L. Thomsen et al.

Nitric oxide synthase activity in human breast cancer

Br. J. Cancer

(1995)

E.C. Chinje et al.

17beta-Oestradiol treatment modulates nitric oxide synthase activity in MDA231 tumour with implications on growth and radiation response

Br. J. Cancer

(2002)

O. Amellem et al.

Cell inactivation and cell cycle inhibition as induced by extreme hypoxia: the possible role of cell cycle arrest as a protection against hypoxia-induced lethal damage

Cell Prolif.

(1991)

R.E. Durand

The influence of microenvironmental factors during cancer therapy

In Vivo

(1994)

Cited by (73)

Myoglobin mutant with enhanced nitrite reductase activity regulates intracellular oxidative stress in human breast cancer cells
2022, Archives of Biochemistry and Biophysics
Citation Excerpt :
Triple-negative breast cancer (TNBC) is one subtype of breast cancer characterized by the high risk of early recurrence and metastasis [2], a low survival rate, and poor prognosis [3,4]. Metastatic breast cancer cells are more sensitive to nitric oxide (NO) concentration, and gene therapy targeting NO has shown excellent therapeutic potential for metastatic breast cancers [5–7]. Therefore, the discovery of new therapeutic targets is of great significance.
Heme proteins play vital roles in regulating the reactive oxygen/nitrogen species (ROS/RNS) levels in cells. In this study, we overexpressed human wild-type (WT) myoglobin (Mb) and its double mutant, F43H/H64A Mb with enhanced nitrite reductase (NIR) activity, in the typical representative triple-negative breast cancer cell, MDA-MB-231 cells. The results showed that the overexpression of F43H/H64A Mb increased the level of nitric oxide (NO) and the degree of oxidative stress, and then activated Akt/MAPK mediated apoptotic cascade, whereas WT Mb showed the opposite effect. This study indicates that Mb plays an important role in maintaining the balance of the cellular redox system and could thus be a valuable target for cancer therapy.
Chemical similarities and differences among inhibitors of nitric oxide synthase, arginase and dimethylarginine dimethylaminohydrolase-1: Implications for the design of novel enzyme inhibitors modulating the nitric oxide pathway
2022, Bioorganic and Medicinal Chemistry
Citation Excerpt :
Nitric oxide (NO) is a cellular signalling molecule involved in numerous physiological processes including the maintenance of vascular tone and homeostasis,1 immune response,2 angiogenesis,3 and neurotransmission,4–5 Physiological NO concentrations are maintained within a tight range and, not surprisingly, alterations of NO synthesis are associated with pathological conditions including sepsis,6,inflammation,7 atherosclerosis,8–9 cancer,10–12 and pulmonary fibrosis.13–14
Nitric oxide (NO) is a signalling molecule that controls a multitude of regulatory functions including neurotransmission, vascular tone, immune response, and angiogenesis. Regulating NO concentrations in cells using small molecules is an active area of research in the treatment of several pathologies such as cardiovascular disease, cancer, and inflammatory conditions. Small molecule-inhibition of critical NO regulatory enzymes, NO synthase (NOS), arginase, and dimethylarginine dimethyaminohydrolase-1 (DDAH1), has shown therapeutic benefits as well as limitations and is a focus of current research. In recent years, DDAH1 has been explored as a potential target to indirectly regulate NO in diseases characterized by excessive NO production. This review discusses the biological and pathophysiological role of the NO pathway, the existing inhibitors of NOS, arginase and DDAH1, and the conventional and structure-guided structure–activity relationship studies involved in their discovery. The key structural elements of amino acid-derived inhibitors responsible for selective inhibition of each enzyme, and the chemical features responsible for dual enzyme inhibition are also discussed. Finally, a synthetic scheme for developing both selective and dual inhibitors using common starting materials is provided, offering unique insights in the quest for the rational design of novel NO pathway inhibitors.
Stress hormone-mediated acceleration of breast cancer metastasis is halted by inhibition of nitric oxide synthase
2019, Cancer Letters
Stress hormones have been shown to be important mediators in driving malignant growth and reducing treatment efficacy in breast cancer. Glucocorticoids can induce DNA damage through an inducible nitric oxide synthase (iNOS) mediated pathway to increase levels of nitric oxide (NO). Using an immune competent mouse breast cancer model and 66CL4 breast cancer cells we identified a novel role of NOS inhibition to reduce stress-induced breast cancer metastasis. On a mechanistic level we show that the glucocorticoid cortisol induces expression of keys genes associated with angiogenesis, as well as pro-tumourigenic immunomodulation. Transcriptomics analysis confirmed that in the lungs of tumour-bearing mice, stress significantly enriched pathways associated with tumourigenesis, some of which could be regulated with NOS inhibition. These results demonstrate the detrimental involvement of NOS in stress hormone signalling, and the potential future benefits of NOS inhibition in highly stressed patients.
The effect of nitric oxide on mitochondrial respiration
2019, Nitric Oxide - Biology and Chemistry
This article reviews the interactions between nitric oxide (NO) and mitochondrial respiration. Mitochondrial ATP synthesis is responsible for virtually all energy production in mammals, and every other process in living organisms ultimately depends on that energy production. Furthermore, both necrosis and apoptosis, that summarize the main forms of cell death, are intimately linked to mitochondrial integrity.
Endogenous and exogenous •NO inhibits mitochondrial respiration by different well-studied mechanisms and several nitrogen derivatives. Instantaneously, low concentrations of •NO, specifically and reversibly inhibit cytochrome c oxidase in competition with oxygen, in several tissues and cells in culture. Higher concentrations of •NO and its derivatives (peroxynitrite, nitrogen dioxide or nitrosothiols) can cause irreversible inhibition of the respiratory chain, uncoupling, permeability transition, and/or cell death. Peroxynitrite can cause opening of the permeability transition pore and opening of this pore causes loss of cytochrome c, which in turn might contribute to peroxynitrite-induced inhibition of respiration. Therefore, the inhibition of cytochrome c oxidase by •NO may be involved in the physiological and/or pathological regulation of respiration rate, and its affinity for oxygen, which depend on reactive nitrogen species formation, pH, proton motriz force and oxygen supply to tissues.
Nonenzymatic Posttranslational Protein Modifications: Mechanism and Associated Disease Pathologies
2019, Protein Modificomics: From Modifications to Clinical Perspectives
Posttranslational modifications (PTMs) of peptides and proteins are common strategies adopted in eukaryotic cells to help to regulate protein function, turn over, or structural allostery. These types of modifications have attracted attention in recent years, since there exists enough data and reports implicating them in pathogenesis and progression of various diseases. PTMs could be enzymatic or nonenzymatic. The nonenzymatic processes involve the spontaneous covalent modification of particular kind of amino acid present in the protein leading functional and structural alteration. Such modifications may include carbamylation, carbonylation, homocysteinylation, nitrosylation, and glycation, etc. The majority of such nonenzymatic protein modifications are confined to various stressful and disease patho-physiologies and, therefore, have broad clinical relevance. In this chapter we give precise descriptions of the mechanisms of the processes, and the related disease complications associated with the modification have also been described in detail. Future research perspectives have also been included.
Nonenzymatic posttranslational protein modifications: Mechanism and associated disease pathologies
2019, Molecular Nutrition: Vitamins
Posttranslational modifications (PTMs) of peptides and proteins are common strategies adopted in eukaryotic cells to help to regulate protein function, turn over, or structural allostery. These types of modifications have attracted attention in recent years, since there exists enough data and reports implicating them in pathogenesis and progression of various diseases. PTMs could be enzymatic or nonenzymatic. The nonenzymatic processes involve the spontaneous covalent modification of particular kind of amino acid present in the protein leading functional and structural alteration. Such modifications may include carbamylation, carbonylation, homocysteinylation, nitrosylation, and glycation, etc. The majority of such nonenzymatic protein modifications are confined to various stressful and disease patho-physiologies and, therefore, have broad clinical relevance. In this chapter we give precise descriptions of the mechanisms of the processes, and the related disease complications associated with the modification have also been described in detail. Future research perspectives have also been included.

View all citing articles on Scopus

¹: These authors contributed equally to the work.

View full text

ReviewiNOS as a therapeutic target for treatment of human tumors

Abstract

Section snippets

Nitric oxide synthase: Structure and isoforms

Pathways of iNOS induction in human cells

NOS expression in human tumors

Hypoxia in tumors

Bioreductive drugs

NOS-mediated activation of bioreductive drugs

Tumor radiosensitizing effects of NO

Impact of NO on HIF-1α expression

NO, HIF-1 and radiosensitivity

NOS-based gene therapy

Conclusion

Acknowledgments

J. Biol. Chem.

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

J. Mol. Biol.

Int. J. Radiat. Oncol. Biol. Phys.

Radiother. Oncol.

J. Urol.

Int. J. Radiat. Oncol. Biol. Phys.

Radiother. Oncol.

Radiother. Oncol.

Radiother. Oncol.

Biochem. Pharmacol.

Clin. Oncol. (R. Coll. Radiol)

Adv. Drug Deliv. Rev.

Int. J. Radiat. Oncol. Biol. Phys.

Int. J. Radiat. Oncol. Biol. Phys.

Radiother. Oncol.

Int. J. Radiat. Oncol. Biol. Phys.

Int. J. Radiat. Oncol. Biol. Phys.

Int. J. Radiat. Oncol. Biol. Phys.

Biochem. Biophys. Res. Commun.

Blood

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

Mol. Cell

Cancer Cell

Cancer Cell

Radiother. Oncol.

Enzymology of nitric oxide synthases

Methods Mol. Biol.

Cloned and expressed nitric oxide synthase structurally resembles cytochrome P-450 reductase

Nature

Nitric oxide synthases: properties and catalytic mechanism

Annu. Rev. Physiol.

Structure-function aspects in the nitric oxide synthases

Annu. Rev. Pharmacol. Toxicol.

Nitric oxide synthases: structure, function and inhibition

Biochem. J.

Cloning and characterization of inducible nitric oxide synthase from mouse macrophages

Science

Is inducible nitric oxide synthase a target for chemoprevention?

Mol. Cancer Ther.

Enzymatic function of nitric oxide synthases

Cardiovasc. Res.

Human colorectal adenocarcinoma cells: differential nitric oxide synthesis determines their ability to aggregate platelets

Cancer Res.

Role of interferon regulatory factor 1 in induction of nitric oxide synthase

J. Exp. Med.

Requirement for transcription factor IRF-1 in NO synthase induction in macrophages

Science

Intersection of interferon and hypoxia signal transduction pathways in nitric oxide-induced tumor apoptosis

Cancer Res.

A hypoxia-responsive element mediates a novel pathway of activation of the inducible nitric oxide synthase promoter

J. Exp. Med.

Expression of nitric oxide synthase in human central nervous system tumors

Cancer Res.

Role of nitric oxide in angiogenesis and tumor progression in head and neck cancer

J. Natl. Cancer Inst.

Relationship between the expression of iNOS,VEGF,tumor angiogenesis and gastric cancer

World J. Gastroenterol.

Nitric oxide synthase as a marker in colorectal carcinoma

Am. Surg.

Nitric oxide synthase activity in human breast cancer

Br. J. Cancer

Review
iNOS as a therapeutic target for treatment of human tumors