Clinical significance of the expression of inducible nitric oxide synthase in non-small cell lung cancer

Objective： To study the expressive characteristics of iNOS to the prognosis NSCLC patients. Methods： The expression in non-small cell lung carcinoma （NSCLC） and it＇s affection of iNOS was detected in 50 NSCLC tissues by Immunohistochemistry technology. Results： There was positive expression in NSCLC （positive rate 38.00%）. The expression of iNOS had a correlation with lymph node metastasis （P〈0.05）. There was no significant difference between positive expression of iNOS and lung cancer histological types, TNM stages, T stages （P〉0.05）. But the data suggested that there was a direct correlation between expression of iNOS and clinical prognosis （P〈0.05）. Conclusion： Positive expression of iNOS was observed in NSCLC, which correlated with postoperative survival time and lymph node metastasis. Although iNOS level had no significant relation with T stage, we find the positive rate in T2 stage was much higher than that in TI stage. The result suggested that positive expression of iNOS was related to bad clinical prognosis because of promoting tumor growth and metastasis.     

iNOS/COX-2与恶性肿瘤

诱导型一氧化氮合酶(iNOS)和环氧合酶2(COX-2)均与肿瘤发生、生长、转移及预后有关.在许多恶性肿瘤组织中,两者的表达一致上调,呈正相关,二者的联合表达与肿瘤的生物学行为密切相关.本文综述了iNOS/COX-2与恶性肿瘤的关系,并提出以iNOS/COX-2 为靶点的恶性肿瘤治疗和研究的思路.     

iNOS/COX-2与恶性肿瘤

诱导型一氧化氮合酶（iNOS）和环氧合酶2（COX-2）均与肿瘤发生、生长、转移及预后有关。在许多恶性肿瘤组织中,两者的表达一致上调,呈正相关,二者的联合表达与肿瘤的生物学行为密切相关。本文综述了iNOS/COX-2与恶性肿瘤的关系,并提出以iNOS/COX-2为靶点的恶性肿瘤治疗和研究的思路。     

Apoptosis of bladder transitional cell carcinoma T24 cells induced by adenovirus-mediated inducible nitric oxide synthase gene transfection

Objectives：To investigate the effects of adenovirus-mediated inducible nitric oxide synthase gene transfection on bladder transitional cell carcinoma T24 cells,and to provide novel insights and approaches to clinical therapies against bladder transitional cell carcinoma.Methods：Firstly,construct recombinant adenovirus vector pAd-iNOS of iNOS,followed by transfection of pAd-iNOS into HECK293 packaging cells.Thirdly,harvest recombinant adenovirus rAd-iNOS after amplification and purification procedures.Finally,transfect the recombinant adenovirus rAd-iNOS into human bladder carcinoma T24 cells and examine the effect of rAd-iNOS transfection on apoptosis of T24 and possible mechanism.Results：As shown by this study,the recombinant adenovirus rAd-iNOS was constructed successfully.The virus titer was 5.8×108 PFU/mL and recombinant was verified by PCR analysis.Transfection of adenovirus rAd-iNOS into T24 cells could induce secretion of high NO concentration,P53 protein expression upregulation,as well as promotion ofT24 cell apoptosis.Conclusions：The transfection of human bladder carcinoma T24 cells from recombinant adenovirus rAdiNOS was confirmed to induce intracellular iNOS over-expression,high production of NO,up-regulation of intracellular P53 expression and promotion of cell apoptosis.     

Mammary tumor latency is increased in mice lacking the inducible nitric oxide synthase

Nitric oxide (NO) and its metabolites are implicated in carcinogenesis and metastasis. Both stimulatory and inhibitory effects of NO have been reported in relation to breast cancer and its role in the development of malignancies and metastasis remains uncertain. We have used the polyomavirus middle T antigen (PyV-mT) targeted to the mouse mammary gland and bred into an inducible NO synthase (iNOS)-deficient C57Bl/6 strain to examine a role for nitric oxide in modulating tumors that develop in the complex environment of the whole animal. The development of hyperplasias was delayed to the extent that the earliest palpable tumors arose 2-4 weeks later in PyV-mT/iNOS(-/-) mice compared with PyV-mT/iNOS(+/+) mice, identifying a role for iNOS in early events in mammary tumor formation. Tumors that did develop in PyV-mT/iNOS(-/-) mice were characteristically well differentiated and had a cribriform pattern. Other tumors were myoepithelial adenocarcinomas with uniform nuclear size. In contrast, mice capable of iNOS activity typically developed solid nodular adenocarcinomas with a high mitotic index and pleomorphic nuclei. No significant effect of iNOS deficiency was found on vascular density in hyperplasias or tumors by examining CD31-positive vessels. The infiltration of lesions by macrophages, cells capable of significant NO production, remained unchanged in PyV-mT/iNOS(-/-) mice. Metastatic potential was retained by PyV-mT-transformed epithelium in the absence of iNOS, indicating that NO production by iNOS is not essential for this process. These results indicate a role for iNOS in tumorigenesis, particularly in the regulation of early events.     

Expression of inducible nitric oxide synthase in healthy pleura and in malignant mesothelioma

In this study we investigated the immunohistochemical expression of inducible nitric oxide synthase (iNOS) in a set of normal pleural mesothelial tissues, malignant mesotheliomas, mesothelioma cell lines and metastatic pleural adenocarcinomas. Furthermore, the expression of mRNA was assessed in four malignant mesothelioma cell lines in culture. Apoptosis and vascular density in malignant mesotheliomas was assessed by the TUNEL method and by immunohistochemistry with an antibody against FVIII-related antigen. Immunohistochemically mesothelial cells in non-neoplastic healthy pleural tissues were mostly negative for iNOS. Positivity for iNOS was observed in 28/38 (74%) and 24/25 (96%) of malignant mesotheliomas and metastatic pleural adenocarcinomas, respectively. Epithelial and mixed mesotheliomas expressed more often strong iNOS immunoreactivity compared to the sarcomatoid subtype (P = 0.023). Moreover, metastatic adenocarcinomas expressed more often iNOS positivity than mesotheliomas (P = 0.021). Experiments with the cell lines confirmed that malignant mesothelioma cells are capable of synthesizing iNOS. No significant association was found between iNOS expression and apoptosis or vascular density in malignant mesotheliomas. The higher expression of iNOS in the epithelial subtype of mesothelioma and pleural metastatic adenocarcinoma might be due to an increased sensitivity of these cell types to cytokine-mediated iNOS upregulation. The strong expression of iNOS suggests a putative role for NO in the growth and progression of these tumours.     

诱导型一氧化氮合酶在指导晚期鼻咽癌治疗方案选择中的价值

背景与目的:同期放化疗被认为是目前治疗晚期鼻咽癌(nasopharyngeal carcinoma,NPC)的最佳方案,但对于同期放化疗对哪一类患者最有效,哪种化疗药物与放疗联合疗效最佳等问题尚没有一致的结论。有学者推荐将顺铂(cisplatin,DDP)同期放化疗方案作为治疗晚期NPC的标准方案。由于顺铂能增加诱导型一氧化氮合成酶(inducible nitric oxide synthase,iNOS)的表达,使杀肿瘤的一氧化氮(NO)合成增加而抗瘤,因此我们考虑是否可以通过检测治疗前NPC组织中的iNOS的表达来对这种同期放化疗的疗效进行预测,并根据预测结果选择相应的治疗方案。本研究旨在探讨NPC肿瘤组织中诱导型iNOS的表达与DDP同期放化疗后鼻咽局部肿瘤全消与残留的关系,以便选择最合适的治疗方案,最大限度地提高鼻咽局部肿块全消率。方法:应用免疫组化法检测DDP同期放化疗后30例鼻咽局部肿块全消和30例鼻咽局部肿块残留的鼻咽部低分化鳞状细胞癌患者在接受治疗前的肿瘤组织中iNOS的蛋白表达情况。结果:iNOS阳性表达定位于NPC细胞的胞质和胞核内,且胞核染色比胞质更强。iNOS在NPC中总的阳性表达率为71.67%(43/60)。在30例肿块全消和30例肿块残留的NPC组织中,iNOS阳性表达率为分别为86.67%、53.33%,差异具有显著性(χ2=6.748,P=0.034)。两组间iNOS弱阳性及中等阳性表达差异无显著性,而强阳性表达全消组低于残留组,差异有显著性(χ2=4.246,P=0.039)。结论:治疗前检测iNOS在NPC组织中的表达,对预测DDP同期放化疗疗效有一定的价值,可根据其表达情况,选择相对合理的同期放化疗方案。     

诱导型一氧化氮合酶与乳腺癌临床病理的关系及意义

目的 :研究诱导型一氧化氮合酶(induciblenitricoxidesynthase ,iNOS )在乳腺癌中的表达及与乳腺癌临床病理因素的关系及意义。方法 :应用免疫组化的方法 ,研究 69例石蜡包埋的乳腺癌原发灶标本 ,切片后行iNOS染色。结果 :iN OS显色位于胞质。乳癌细胞内iNOS的表达与患者年龄、月经状况、组织学分级、脉管侵袭、ER、PR无关。肿瘤大小 <5cmiNOS阳性率 5 8 7% ( 2 7/4 6) ,≥ 5cmiN OS阳性率 69 6% ( 16/2 3 ) ,但两者无统计学意义。乳癌细胞内iNOS的表达与c erbB 2蛋白、TNM分期相关 ,且与乳腺癌远处转移、淋巴结转移有关。iNOS阳性患者 5年内生存率 ( 5 1 2 2 % )较阴性者( 65 3 8% )低。结论 :iNOS与某些临床病理指标有关。并在乳腺癌转移和预后中起重要作用     

Cytochrome-c mediated a bystander response dependent on inducible nitric oxide synthase in irradiated hepatoma cells

Background:

Radiation-induced bystander effect (RIBE) has important implication in tumour radiotherapy, but the bystander signals are still not well known.

Methods:

The role of cytochrome-c (cyt-c) and free radicals in RIBE on human hepatoma cells HepG2 was investigated by detecting the formation of bystander micronuclei (MN) and the generation of endogenous cyt-c, inducible nitric oxide (NO) synthase (iNOS), NO, and reactive oxygen species (ROS) molecules.

Results:

When HepG2 cells were cocultured with an equal number of irradiated HepG2 cells, the yield of MN in the nonirradiated bystander cells was increased in a manner depended on radiation dose and cell coculture time, but it was diminished when the cells were treated with cyclosporin A (CsA), an inhibitor of cyt-c release. Meanwhile the CsA treatment inhibited radiation-induced NO but not ROS. Both of the depressed bystander effect and NO generation in the CsA-treated cells were reversed when 5 μ cyt-c was added in the cell coculture medium. But these exogenous cyt-c-mediated overproductions of NO and bystander MN were abolished when the cells were pretreated with s-methylisothiourea sulphate, an iNOS inhibitor.

Conclusion:

Radiation-induced cyt-c has a profound role in regulating bystander response through an iNOS-triggered NO signal but not ROS in HepG2 cells.     

诱导型一氧化氮合酶与Bcl-2在鼻咽癌中的表达及意义

目的 探讨鼻咽癌组织中诱导型一氧化氮合酶（iNOS）与滤泡型B细胞淋巴瘤／白血病-2（Bcl-2）的表达情况及其意义。方法 采用免疫组织化学法检测50例鼻咽癌石蜡标本和15例慢性炎症的鼻咽黏膜标本中iNOS和Bcl-2蛋白表达情况。结果 慢性炎症的鼻咽黏膜中iNOS无表达,Bcl-2有表达,但局限于上皮的基底细胞层。在鼻咽癌组织中,iNOS阳性表达者细胞浆和胞核内出现棕黄色细颗粒,且胞核染色比胞浆更强;Bcl-2阳性表达者细胞浆或核膜上出现棕黄色细颗粒。鼻咽癌组织iNOS的阳性表达率为74.0％（37／50）,Bcl-2为82.0％（41／50）,与慢性炎症的鼻咽黏膜比较,差异均有统计学意义（P＜0.05）。在鼻咽癌组织中,iNOS与Bcl-2蛋白表达强度呈正相关（r=0.945,P＜0.05）;iNOS的表达与T分期及有无淋巴结转移有关,与年龄和性别无关;Bcl 2的表达与临床病理特征无关。结论 iNOS与Bcl 2的表达与鼻咽癌的发生、发展相关,进一步研究两者的关系对探索鼻咽癌新的治疗手段有重要意义。     

Involvement of nitric oxide on the pathogenesis of irinotecan-induced intestinal mucositis: role of cytokines on inducible nitric oxide synthase activation

Purpose

Intestinal mucositis and the closely associated diarrhea are common costly side effects of irinotecan. Cytokine modulators, such as thalidomide and pentoxifylline, are found capable of attenuating intestinal mucositis progression. Nitric oxide (NO) seems to be a key mediator of the antineoplastic drug toxicity. The aim of this study was to investigate the role of NO on the pathogenesis of intestinal mucositis, as well as the participation of cytokines upon inducible nitric oxide synthase (iNOS) expression in irinotecan-induced intestinal mucositis.

Methods

iNOS-knockout (iNOS^?/?) and C57BL/6 (WT, wild type) animals (n?=?5–6) were given either saline or irinotecan (60?mg/kg?i.p for 4?days), with or without pretreatment with aminoguanidine (50?mg/kg?s.c.), thalidomide (60?mg/kg?s.c), infliximab (5?mg/kg?i.v.), or pentoxifylline (1.7?mg/kg?s.c). On day 5, diarrhea was assessed, and following euthanasia, proximal intestinal samples were obtained for myeloperoxidase (MPO) and iNOS activity, morphometric analysis, western blot and immunohistochemistry to iNOS, cytokine dosage, and for in vitro evaluation of gut contractility.

Results

Irinotecan induced severe diarrhea and intestinal smooth muscle over-contractility, accompanied with histopathological changes. Additionally, increased MPO and iNOS activity and iNOS immunoexpression were found in WT animals treated with irinotecan. The rise in MPO, smooth muscle over-contractility, and diarrhea were abrogated in aminoguanidine-treated and iNOS^?/? mice. Moreover, through western blot, we verified that infliximab and pentoxifylline significantly inhibited irinotecan-induced iNOS expression. In addition, cytokine concentration was found only partially decreased in irinotecan-treated iNOS^?/? mice when compared with wild-type animals that were given irinotecan.

Conclusions

This study suggests a role of nitric oxide in the pathogenesis of irinotecan-induced intestinal mucositis and also provides evidence for the participation of cytokines on iNOS induction.     

Suppression of thymic lymphomas and increased nonthymic lymphomagenesis in Trp53-deficient mice lacking inducible nitric oxide synthase gene

Trp53-deficient mice spontaneously develop lymphomas, mainly of thymic origin, although the molecular mechanism remains largely unknown. As several interaction effects between p53 and iNOS have been reported, we hypothesized that iNOS activity in the thymus is causally linked to lymphomagenesis in Trp53-deficient mice. We therefore created mouse strains with different combinations of the Trp53 and iNOS genes. Western blot and histologic analyses showed that the iNOS protein was constitutively expressed in the thymus independently of Trp53 status and its expression was enhanced in Trp53+/- and Trp53-/- mice compared to Trp53+/+ mice. Homozygous disruption of iNOS decreased the incidence of thymic lymphomas by almost 40% (p=0.087) and 90% (p<0.05) in Trp53-/- and Trp53+/- mice, respectively, compared to the respective iNOS wild-type mice but significantly (p<0.05) increased the development of nonthymic lymphomas in Trp53-/- and Trp53+/- mice. Although iNOS gene disruption did not affect the phenotype of thymic lymphomas, absence of the iNOS gene shifted the spectrum of nonthymic lymphoma from the B-cell to the T-cell lineage. RT-PCR analysis revealed enhanced expression of IL-10, which could have a promoting effect on lymphomagenesis, even without any stimulation, in the spleen of aging mice with the gene combinations Trp53-/-iNOS-/- and Trp53+/-iNOS-/- but not Trp53-/-iNOS+/+ or Trp53+/-iNOS+/+. These results suggest that iNOS could increase the development of thymic lymphomas in Trp53-deficient mice. While iNOS may have protective effects against nonthymic lymphomagenesis, the regulation of cytokine production by iNOS may be involved in the underlying mechanism of antilymphomagenesis effects in the peripheral lymphoid organ.     

NF-kappaB inhibition impairs the radioresponse of hypoxic EMT-6 tumour cells through downregulation of inducible nitric oxide synthase

Hypoxic EMT-6 tumour cells displayed a high level of inducible nitric oxide synthase (iNOS) and an increased radiosensitivity after a 16 h exposure to lipopolysaccharide, a known activator of nuclear factor-kappaB (NF-kappaB). Both iNOS activation and radioresponse were impaired by the NF-kappaB inhibitors phenylarsine oxide and lactacystin. Contrasting to other studies, our data show that inhibition of NF-kappaB may impair the radioresponse of tumour cells through downregulation of iNOS.     

Use of retroviral vectors encoding murine inducible nitric oxide synthase gene to suppress tumorigenicity and cancer metastasis of murine melanoma

The purpose of this study was to determine whether retrovirus-mediated transfer of murine macrophage inducible nitric oxide synthase (iNOS) can produce inhibition of tumorigenicity and metastasis. Retroviral vectors encoding macrophage iNOS constructed in pLXSN, a retroviral vector with the iNOS gene under the control of a long terminal repeat promoter, were stably transfected into PA317 cells. Medium harvested from confluent monolayers of the virus-producing cell lines was used for infection of the murine K-1735 melanoma cells. Expression of iNOS was confirmed by northern and Western blot analyses. Functional iNOS protein expression was confirmed by bioassay of nitrite accumulation in the culture supernatant. Cells infected by a control iNOS-negative retrovirus produced fast-growing subcutaneous tumors and many lung metastases in nude mice, whereas iNOS-transduced cells produced slow-growing tumors and few lung metastases, showing that the infection of murine tumor cells by retroviruses harboring the iNOS gene can suppress tumorigenicity and metastasis.     

Immunostimulatory effects of low-dose cyclophosphamide are controlled by inducible nitric oxide synthase

Cyclophosphamide is a widely used chemotherapeutic drug that was recently applied as either an antiangiogenic/antivasculogenic or an immunostimulatory agent in combination with cancer immunotherapies. It has been previously shown that cyclophosphamide augments the efficacy of antitumor immune responses by depleting CD4+ CD25+ T regulatory cells and increasing both T-lymphocyte proliferation and T memory cells. Furthermore, cyclophosphamide was shown to mediate killing of circulating endothelial progenitors. However, the molecular basis for these observations has not yet been elucidated. We show here that the cyclophosphamide-mediated inhibition of inducible nitric oxide synthase is directly linked to its immunostimulatory but not to its antivasculogenic effects. Moreover, combined application of cyclophosphamide with a novel, oral DNA vaccine targeting platelet-derived growth factor B (PDGF-B), overexpressed by proliferating endothelial cells in the tumor vasculature, not only completely inhibited the growth of different tumor types but also led to tumor rejections in mice. These findings provide a new rationale at the molecular level for the combination of chemotherapy and immunotherapy in cancer treatment.     

The role of early expression of inducible nitric oxide synthase in human breast cancer

Nitric oxide synthases are expressed in breast cancer. To elucidate the clinical role of the inducible NOS (i-NOS) in human breast cancer, 161 primary breast cancer tissues were stained immunohistochemically. Staining patterns for i-NOS were correlated with classical prognostic factors such as lymph node status, age, hormonal receptor status, tumour size and tumour differentiation. With classical prognostic factors such as lymph node status, age, hormonal receptor status, tumour size and tumour differentiation. Patients survival was also analysed. Sixty-one percent of the tumours stained positively for i-NOS. Detection of i-NOS was positively correlated with increasing tumour size and decreasing tumour differentiation (P=0.018 and P=0.039, respectively). However, in the 50 year age group, i-NOS staining also correlated with lymph node status. Patients with i-NOS-positive breast carcinomas had a significantly worse overall survival rate versus those with negative stains (5-year survival rate 84.8% versus 67.1%; P=0.049; log-rank test). To date, this is the largest analysis of i-NOS expression in breast cancer patients and the only study to assess survival.     

Expression of inducible nitric oxide synthase in human breast cancer depends on tumor grade

Expression of inducible nitric oxide synthase (iNOS) by tumor cells has been suggested to abrogate metastasis in several tumor models, whereas constitutive NOS expression correlated positively with tumor grade in human breast carcinoma. Whether or not expression of one of the various NOS isoforms could predict the prognosis of breast cancer, however, has not been established. In the present report we investigated the cellular distribution of NOS isoforms in a series of benign and malignant breast tumors and in normal breast tissue. Immunohistochemistry revealed that in samples of benign disease the number of iNOS+epithelial cells or total epithelial cells was 69±16% (n=50). In samples of grade II invasive ductal breast carcinomas the number of iNOS+ tumor cells or total tumor cells was 62±20 (n=40), compared to 12±9 (n=40) in samples of grade III carcinomas (P<0.0001). iNOS protein was also identifiable in most of the epithelial cells of normal breast tissue (n=4). In contrast, eNOS protein was restricted to vascular endothelial cells in all of the specimens studied. Since the presence of tumor cell iNOS protein is inversely related to the tumors metastatic potential, we conclude that endogenous tumor cell mediated iNOS expression might have an inhibitory effect on the metastatic process in breast cancer.     

Increased inducible nitric oxide synthase in lung carcinoma of smokers

BACKGROUND: Cigarette smoking is well known to play an important role in the development of lung cancer. Inducible nitric oxide synthase (iNOS) can either promote or inhibit cell proliferation and growth, which makes its role in the development of malignant tumors controversial. The relation between cigarette smoking and iNOS in human lung cancer is unknown. METHODS: The study examined the levels of iNOS/NO in nonsmall-cell lung cancer (NSCLC) tissues of smokers and nonsmokers and in NSCLC cells (NCI-H23) treated by 4-(N-Methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a potent tobacco-specific carcinogen. RESULTS: The level of iNOS/NO was significantly higher in lung cancer tissues of smokers than that of nonsmokers. Unlike iNOS/NO, the activity of caspase-3 was reduced in the former compared with the latter. The expression of the cleaved caspase-3 was deceased in NCI-H23 cells treated with S-Nitroso-N-acetylpenicillamine (SNAP), an NO donor, whereas treatment with NG-methyl-L-arginine (NMA), an NO inhibitor, caused an increase in cleaved caspase-3. Consistent with the change in caspase-3, SNAP treatment inhibited cell death induced by UCN01, a potent cell death-inducer. NMA treatment greatly enhanced the sensitivity of the cells to UCN01. Further, the cells treated by NNK showed an increase in iNOS protein, accompanied by an elevation of cell proliferation. CONCLUSIONS: The study demonstrates that cigarette smoking promotes the level of iNOS/NO but suppresses the activity of caspase-3, which may lead to the proliferation and growth of lung cancer cells.     

Increased level of exhaled nitric oxide and up-regulation of inducible nitric oxide synthase in patients with primary lung cancer.

Monocyte-macrophage series have an important role in host surveillance against cancer. The cytotoxic/cytostatic activity of macrophages is, to a great extent, attributed to the up-regulation of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO). Here, in 28 patients with primary lung cancer and 20 control subjects, we measured the concentration of exhaled NO and nitrite in epithelial lining fluid (ELF) using a chemiluminescence NO analyser, and studied NOS expression in alveolar macrophages (AM) and lung tissues by flow cytometry; immunohistochemical analysis was also undertaken. The mean fluorescence intensity (FI) of iNOS expression in AM was significantly increased in patients with lung cancer (tumour side 263.5 +/- 15.2 FI, normal side 232.4 +/- 18.6 FI; n = 28) compared with that in control subjects (27.3 +/- 3.2 FI; n = 20, P< 0.001). The level of exhaled NO from cancer patients (16.9 +/- 0.9 p.p.b.; n = 28) was significantly higher than that in the control group (6.0 +/- 0.5 p.p.b.; n = 20, P < 0.001). The level of nitrite was also significantly higher in ELF from cancer patients (tumour side 271.1 +/- 28.9 nM and normal side 257.4 +/- 19.6 nM vs control subjects 32.9 +/- 4.1 nM; P< 0.001). The intensity of iNOS expression in AM was correlated with the level of exhaled NO (rs = 0.73, n = 76, P< 0.001) and the nitrite released in ELF (rs = 0.56, n = 76, P< 0.001). The nitrite generation of cultured AM from patients with lung cancer was significantly enhanced compared with that of control subjects after culture for 24 h (tumour side 5.75 +/- 0.69 and normal side 5.68 +/- 0.58 microM per 106 cells vs control group 38.3 +/- 3.6 nM per 106 cells; P< 0.001). The distribution of iNOS was identified in AM, tumour-associated macrophages, endothelium, chondrocytes, airway epithelium of both lungs and malignant cells (adenocarcinoma and alveolar cell carcinoma) of cancer patients. cNOS was labelled in alveolar macrophages, endothelial cells and nerve elements from lung tissue. Our results indicate that, in patients with primary lung cancer, the production of NO from alveolar macrophages was increased as a result of the up-regulation of iNOS activity. The increased NO production was not specific to the tumour side and might be attributed to the tumour-associated non-specific immunological and inflammatory processes of the host.