Increased nitric oxide levels and iNOS over-expression in oral squamous cell carcinoma

Oxidative Stress in the Pathogenesis of Oral Cancer

Oxidative stress, arising from an imbalance between reactive oxygen species (ROS) and antioxidants, contributes significantly to oral cancer such as oral squamous cell carcinoma (OSCC) initiation, promotion, and progression. ROS, generated both internally and externally, induce cellular damage including DNA mutations and lipid peroxidation, fostering oncogene activation and carcinogenesis. The objective of this review was to cover and analyze the interplay between ROS and antioxidants, influencing the key processes such as cell proliferation, apoptosis, and angiogenesis, shaping the trajectory of OSCC development. Despite the promise of antioxidants to halt cancer progression and mitigate oxidative damage, their therapeutic efficacy remains debated. The conducted literature search highlighted potential biomarkers that indicate levels of oxidative stress, showing promise for the early detection and monitoring of OSCC. Furthermore, melatonin has emerged as a promising adjunct therapy for OSCC, exerting antioxidant and oncostatic effects by modulating tumor-associated neutrophils and inhibiting cancer cell survival and migration. In addition, this review aims to shed light on developing personalized therapeutic strategies for patients with OSCC such as melatonin therapy, which will be discussed. Research is needed to elucidate the underlying mechanisms and clinical implications of oxidative stress modulation in the context of oral cancer.

Enhancing immune regulation in vitro: the synergistic impact of 3'-sialyllactose and osteopontin in a nutrient blend following influenza virus infection

Natural components of breast milk, human milk oligosaccharides (HMOs) and osteopontin (OPN) have been shown to have a variety of functional activities and are widely used in infant formulas. However, the preventive and therapeutic effects of both on influenza viruses are not known. In this study, antiviral assays using a human laryngeal carcinoma cell line (HEP-2) showed that 3'-sialyllactose (3'-SL) and OPN had the best antiviral ability with IC50 values of 33.46 μM and 1.65 μM, respectively. 3'-SL (10 μM) and OPN (4 μM) were used in combination to achieve 75% inhibition. Further studies found that the combination of 200 μg/mL of 3'-SL with 500 μg/mL of OPN exerted the best antiviral ability. The reason for this was related to reduced levels of the cytokines TNF-α, IL-6, and iNOS in relation to mRNA expression. Plaque assay and TCID50 assay found the same results and verified synergistic effects. Our research indicates that a combination of 3'-SL and OPN can effectively reduce inflammatory storms and exhibit anti-influenza virus effects through synergistic action.

Targeting Nitric Oxide: Say NO to Metastasis

Utilizing targeted therapies capable of reducing cancer metastasis, targeting chemoresistant and self-renewing cancer stem cells, and augmenting the efficacy of systemic chemo/radiotherapies is vital to minimize cancer-associated mortality. Targeting nitric oxide synthase (NOS), a protein within the tumor microenvironment, has gained interest as a promising therapeutic strategy to reduce metastatic capacity and augment the efficacy of chemo/radiotherapies in various solid malignancies. Our review highlights the influence of nitric oxide (NO) in tumor progression and cancer metastasis, as well as promising preclinical studies that evaluated NOS inhibitors as anticancer therapies. Lastly, we highlight the prospects and outstanding challenges of using NOS inhibitors in the clinical setting.

The implications of nitric oxide metabolism in the treatment of glial tumors

Glial tumors are the most common intracranial malignancies. Unfortunately, despite such a high prevalence, patients' prognosis is usually poor. It is related to the high invasiveness, tendency to relapse and the resistance of tumors to traditional methods of treatment. An important link in the aspect of these issues may be nitric oxide (NO) metabolism. It is a very complex mechanism with multidirectional effects on the neoplastic process. Depending on the concentration axis, it can both exert pro-tumor action as well as contribute to the inhibition of tumorigenesis. The latest observations show that the control of its metabolism can be very helpful in the development of new methods of treating gliomas, as well as in increasing the effectiveness of the agents currently used. The influence of nitric oxide and nitric oxide synthase (NOS) activity on glioma stem cells seem to be of particular importance. The use of specific inhibitors may allow the reduction of tumor growth and its tendency to relapse. Another important feature of GSCs is their conditioning of glioma resistance to traditional forms of treatment. Recent studies have shown that modulation of NO metabolism can suppress this effect, preventing the induction of radio and chemoresistance. Moreover, nitric oxide is involved in the regulation of a number of immune mechanisms. Adequate modulation of its metabolism may contribute to the induction of an anti-tumor response in the patients' immune system.

Significance of Serum Nitric Oxide and Superoxide Dismutase in Oral Submucous Fibrosis and Squamous Cell Carcinoma: A Comparative Study

Introduction:

This study aimed at comparative analysis of serum nitric oxide (NO) and superoxide dismutase (SOD) levels as therapeutic and prognostic biomarkers in patients with oral submucous fibrosis (OSMF) and squamous cell carcinoma (SCC).

Materials and Methods:

Eighty-seven patients were grouped into Group I (n = 29, OSMF), Group II (n = 29, oral SCC), and Group III (n = 29, controls). Two ml of venous blood was collected from patients after overnight fast to avoid any dietary influence on the serum beta-carotene. Standard protocols were followed in transfer, storage, and processing of blood. Modified copper-cadmium reduction method for rapid assay to estimate the serum NO and Enzychrom™ SOD assay kit to determine SOD levels were used.

Results:

The mean level of NO level in Group I, Group II, and Group III was 42.49, 50.08, and 32.81, respectively, and mean level of SOD in Group I, Group II, and Group III were 207.65, 196.93, and 226.57, respectively. The P values were calculated and were statistically significant (<0.001).

Conclusion:

An increase in level of oxidant NO in OSMF followed by SCC and decrease in level of antioxidant SOD in OSMF followed by SCC were noted. These levels of NO and antioxidant SOD can be used as prognostic and therapeutic biomarkers.

Neuroendocrine Factors and Head and Neck Squamous Cell Carcinoma: An Affair to Remember

Head and neck squamous cell carcinoma (HNSCC) is one of the most aggressive malignancies. Therefore, the major goal of cancer treatment is inhibition of tumor cell growth and of metastasis development. In order to choose the best management option for HNSCC patients, we need to identify reliable prognostic factors and to develop new molecular techniques in order to obtain a better understanding of therapy resistance. By acting as neurohormones, neurotransmitters, or neuromodulators, the neuroendocrine factors are able to signal the maintenance of physiological homeostasis or progression to malignant disease. Certain neuropeptides possess strong antitumor properties acting as tumor suppressors and immunomodulators, providing additional benefits for future potential therapeutic strategies. In light of the current understanding, cancer starts as a localized disease that can be effectively treated if discovered on proper time. Unfortunately, more than often cancer cells migrate to the surrounding tissues generating distant metastases, thus making the prognosis and survival in this stage much worse. As cellular migration is mandatory for tumor invasion and metastasis development, searching for alternate controllers of these processes, such as the neuroendocrine factors, it is an active tremendous task.

Neuroendocrine factors: The missing link in non‑melanoma skin cancer (Review)

Non‑melanoma skin cancer (NMSC) is the most common form of cancer worldwide, comprising 95% of all cutaneous malignancies and approximately 40% of all cancers. In spite of intensive efforts aimed towards awareness campaigns and sun‑protective measures, epidemiological data indicate an increase in the incidence of NMSC. This category of skin cancers has many common environmental triggers. Arising primarily on sun‑exposed skin, it has been shown that ultraviolet radiation is, in the majority of cases, the main trigger involved in the pathogenesis of NMSC. Aside from the well‑known etiopathogenic factors, studies have indicated that several neuroactive factors are involved in the carcinogenesis of two of the most common types of NMSC, namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), with the exception of penile SCC, for which a paucity of specific data on their pathogenic role exists. The complex interaction between the peripheral nervous system and target cells in the skin appears to be mediated by locally released neuroendocrine factors, such as catecholamines, substance P, calcitonin gene‑related peptide and somatostatin, as well as neurohormones, such as proopiomelanocortin and its derived peptides, α‑melanocyte‑stimulating hormone and adrenocorticotropin. All these factors have been, at least at some point, a subject of debate regarding their precise role in the pathogenesis of NMSC. There is also a significant body of evidence indicating that psychological stress is a crucial impact factor influencing the course of skin cancers, including SCC and BCC. Numerous studies have suggested that neuroendocrine factor dysregulation, as observed in stress reactions, may be involved in tumorigenesis, accelerating the development and progression, and suppressing the regression of NMSC. Further studies are required in order to elucidate the exact mechanisms through which neuroactive molecules promote or inhibit cutaneous carcinogenesis, as this could lead to the development of more sophisticated and tailored treatment protocols, as well as open new perspectives in skin cancer research.

Interleukin-22 and Cyclosporine in Aggressive Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinomas (SCCs) account for up to 10,000 deaths annually in the United States. Most of the more than 700,000 SCCs diagnosed are cured by excision with clear margins; however, metastasis can occur despite seemingly adequate treatment in some cases. Immune-suppressed organ transplant recipients are 60 to 100 times more likely to develop SCC than immune-competent individuals. Transplant-associated SCCs occur more frequently and behave more aggressively, showing higher risk of recurrence and metastasis. This article identifies a potential role for interleukin-22 in driving SCC proliferation, particularly in solid organ transplant recipients taking cyclosporine.

The Expression and Correlation of iNOS and p53 in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is the most prevalent form of oral cancer. Inducible nitric oxide synthase (iNOS) and p53 are associated with a variety of human cancers, but their expression and interaction in OSCC have not been fully explored. In this study, we investigated the expression of iNOS and p53 in OSCC and their correlation with tumor development and prognosis. In addition, we explored the interaction of iNOS and p53 in OSCC. The expression of iNOS and p53 in OSCC was investigated using immunohistochemical method and their interaction was studied using RNAi technique. Our results showed that the expression of both iNOS and p53 was significantly correlated with tumor stages and pathological grade of OSCC (P < 0.05). In contrast, there was no correlation between iNOS and p53 expression and lymph node metastasis (P < 0.05). The OSCC survival rate was negatively associated with iNOS expression, but not with p53. A significant increase in the expression of the p53 was observed when iNOS expression was knocked down. The immunoexpression of iNOS is correlated with tumorigenesis and prognosis of OSCC and may serve as a prognostic marker.

Production and physiological role of NO in the oral cavity

Nitric oxide (NO) is a free radical which is produced from a wide variety of cells and tissues in the human body. NO is involved in the regulation of many physiological processes, such as vascular relaxation, neurotransmission, immune regulation, and cell death. NO is generated by nitric oxide synthase (NOS), which has three identified isoforms: neuronal type NOS (nNOS), endothelial type NOS (eNOS), and inducible type NOS (iNOS). Different isoforms are expressed depending on the organs, tissues, and cells, and investigation of the types and functions of enzymes expressed in various tissues is underway. The oral cavity is a space in which marked changes have been detected in NO levels, and each tissue is constantly influenced by NO. NO is a component of saliva and is produced by oral bacteria in the oral cavity and released by NOS expressed in oral mucosa. NOS isoforms expressed under normal conditions differ among the oral organs. In addition, the overexpression of NOS was involved in carcinogenesis and tumor growth progression. This review summarized the expression of NOS and functions of NO in oral cavity organs, and their roles in diseases and the influences of treatments.

Expression of cyclooxygenase-2, 12-lipoxygenase, and inducible nitric oxide synthase in head and neck squamous cell carcinoma

AIM

The objective of this study was to investigate whether cyclooxygenase-2 (COX-2), 12-lipoxygenase (12-LOX), and inducible nitric oxide synthase (iNOS) have a role in carcinogenesis of head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

Twenty-two patients with HNSCC were included in the study. Cancer tissues and adjacent normal mucosa were obtained from each patient. Real-time PCR was used to assess the expression of COX-2, 12-LOX, and iNOS.

RESULTS

COX-2 and 12-LOX mRNA expressions are significantly increased in HNSCC compared with adjacent normal mucosa. Expression of iNOS was not significantly elevated in overall head and neck cancer tissues compared with normal mucosa. However, iNOS expression was found to be significantly elevated in patients with laryngeal cancer.

CONCLUSION

These data suggest that COX-2 and 12-LOX may play a role in carcinogenesis of head and neck cancer. iNOS as well as COX-2 and 12-LOX may play a role in carcinogenesis of laryngeal cancer.

Expression of inducible nitric oxide synthase in carcinomas and sarcomas affecting the oral cavity

Context:

Inducible nitric oxide synthase (iNOS) is a cytoplasmic enzyme which plays a crucial role in the pathogenesis of oral carcinomas and sarcomas.

Aims:

The objective of this study was to analyze the immunohistochemical expression of iNOS in carcinomas and sarcomas affecting the oral cavity in order to understand the possible role of iNOS in their biologic behavior and to correlate iNOS expression with lymph node metastasis in carcinomas and sarcomas.

Settings and Design:

Patients, who attended the oral diagnosis department of Vinayaka Missions Sankarachariyar Dental College, were screened, for the purpose of the study. Besides these, paraffin-embedded tissue blocks were also retrieved from archives of the Oral and Maxillofacial Pathology Department. A total of 40 cases (20 carcinomas and 20 sarcomas) were selected for the study.

Subjects and Methods:

A total of 40 cases (20 carcinomas and 20 sarcomas) were selected for the study. Five apparently normal tissues were obtained from the tumor adjacent normal tissue to be used as a control. These were subjected to immunohistochemical staining using antibody to iNOS and evaluated.

Statistical Analysis Used:

The results were analyzed using the Chi-square test.

Results:

Among the 20 carcinomas 19 showed a positive immunoreactivity for iNOS and 1 case was negative. Among the 19 immunopositive iNOS cases of carcinomas, 15 cases showed positive lymph node metastasis. Among the sarcomas, positive immunoreactivity for iNOS was seen in 10 hard tissue sarcomas, while the remaining 10 soft tissue sarcomas were negative for iNOS expression. The results were analyzed using the Chi-square test.

Conclusions:

iNOS is a reliable marker for lymph node metastasis in carcinomas irrespective of the histologic grade. The high expression in carcinomas shows that the carcinomas elaborate more angiogenesis for growth compared with the sarcomas with the exception of hard tissue sarcomas.

Insights into the diverse effects of nitric oxide on tumor biology

Among its many roles in cellular biology, nitric oxide (·NO) has long been associated with cancers both as a protumorigenic and as an antitumorigenic agent. The dual nature of this signaling molecule in varied settings is attributable to its temporal and concentration-dependent effects that produce different phenotypes. The steady-state ·NO concentration within the cell is a balance between its rate of enzymatic synthesis from the three nitric oxide synthase (NOS) isoforms and consumption via numerous metabolic pathways and demonstrates strong dependence on the tissue oxygen concentration. NOS expression and ·NO production are often deregulated and associated with numerous types of cancers with dissimilar prognostic outcomes. ·NO influences several facets of tumor initiation and progression including DNA damage, chronic inflammation, angiogenesis, epithelial-mesenchymal transition, and metastasis, to name a few. The role of ·NO as an epigenetic modulator has also recently emerged and has potentially important mechanistic implications in regulating transcription of oncogenes and tumor-suppressor genes. ·NO-derived cellular adducts such as dinitrosyliron complexes and the formation of higher nitrogen oxides further alter its cellular behavior. Among anticancer strategies, the use of NOS as a prognostic biomarker and modulation of ·NO production for therapeutic benefit have gained importance over the past decade. Numerous ·NO-releasing drugs and NOS inhibitors have been evaluated in preclinical and clinical settings to arrest tumor growth. Taken together, ·NO affects various arms of cancer signaling networks. An overview of this complex interplay is provided in this chapter.

Nitric oxide synthase 2 (NOS2) expression in histologically normal margins of oral squamous cell carcinoma

The activity of Nitric Oxide Synthase 2 (NOS2) was found in oral squamous cell carcinomas (OSCC) but not in normal mucosa. Molecular changes associated to early carcinogenesis have been found in mucosa near carcinomas, which is considered a model to study field cancerization. The aim of the present study is to analyze NOS2 expression at the histologically normal margins of OSCC.

STUDY DESIGN

Eleven biopsy specimens of OSCC containing histologically normal margins (HNM) were analyzed. Ten biopsies of normal oral mucosa were used as controls. The activity of NOS2 was determined by immunohistochemistry. Salivary nitrate and nitrite as well as tobacco and alcohol consumption were also analyzed. The Chi-squared test was applied.

RESULTS

Six out of the eleven HNM from carcinoma samples showed positive NOS2 activity whereas all the control group samples yielded negative (p=0.005). No statistically significant association between enzyme expression and tobacco and/or alcohol consumption and salivary nitrate and nitrite was found.

CONCLUSION

NOS2 expression would be an additional evidence of alterations that may occur in a state of field cancerization before the appearance of potentially malignant morphological changes.

Levels of biological markers of nitric oxide in serum of patients with squamous cell carcinoma of the oral cavity

The aim of the study was a determination of the levels of nitric oxide (NO) and its biological markers such as malonyldialdehyde (MDA) and nitrotyrosine in the serum of patients with squamous cell carcinoma (SCC) of the oral cavity and identification of the relationships between NO and those markers. These studies were performed on patients with SCC of the oral cavity before and after treatment. Griess reaction was used for the estimation of the total concentration of NO in serum. The nitrotyrosine level in serum was assessed with an enzyme-linked immunosorbent assay (ELISA) kit, and MDA level using a spectrophotometric assay. Higher concentrations of NO in blood serum were determined in patients with stage IV of the disease before treatment in comparison to the control group and patients with stages II and III of the disease. Moreover, higher concentrations of MDA and nitrotyrosine were determined in the serum of patients in all stages of the disease in comparison to healthy people. After treatment, lower concentrations of NO in the serum of patients with stage IV of the disease were observed in comparison to the amounts obtained prior to treatment. In addition, lower levels of nitrotyrosine in the serum of patients with all stages of the disease were recorded, whereas higher concentrations of MDA were determined in these patients in comparison to results obtained before treatment. The compounds formed with the contribution of NO, such as MDA and nitrotyrosine, may lead to cancer progression in patients with SCC of the oral cavity, and contribute to formation of resistance to therapy in these patients as well. Moreover, the lack of a relationship between concentrations of NO and MDA, and between NO and nitrotyrosine in serum suggests that the process of lipid peroxidation and nitration in patients with SCC does not just depend on NO.

Nitric oxide synthase and breast cancer: role of TIMP-1 in NO-mediated Akt activation

Prediction of therapeutic response and cancer patient survival can be improved by the identification of molecular markers including tumor Akt status. A direct correlation between NOS2 expression and elevated Akt phosphorylation status has been observed in breast tumors. Tissue inhibitor matrix metalloproteinase-1 (TIMP-1) has been proposed to exert oncogenic properties through CD63 cell surface receptor pathway initiation of pro-survival PI3k/Akt signaling. We employed immunohistochemistry to examine the influence of TIMP-1 on the functional relationship between NOS2 and phosphorylated Akt in breast tumors and found that NOS2-associated Akt phosphorylation was significantly increased in tumors expressing high TIMP-1, indicating that TIMP-1 may further enhance NO-induced Akt pathway activation. Moreover, TIMP-1 silencing by antisense technology blocked NO-induced PI3k/Akt/BAD phosphorylation in cultured MDA-MB-231 human breast cancer cells. TIMP-1 protein nitration and TIMP-1/CD63 co-immunoprecipitation was observed at NO concentrations that induced PI3k/Akt/BAD pro-survival signaling. In the survival analysis, elevated tumor TIMP-1 predicted poor patient survival. This association appears to be mainly restricted to tumors with high NOS2 protein. In contrast, TIMP-1 did not predict poor survival in patient tumors with low NOS2 expression. In summary, our findings suggest that tumors with high TIMP-1 and NOS2 behave more aggressively by mechanisms that favor Akt pathway activation.

Nitric oxide and oral cancer: a review

Nitric oxide (NO), a short-lived, endogenously produced gas, plays key role in various physiological as well as pathological processes. NO-inducing cell signaling events within the cell producing it and the diffusibility of it in other cells have led to the discovery of various physiological functions of NO including vasodilation, respiration, cell migration, immune response and apoptosis. On the other hand, excessive and unregulated NO synthesis has been implicated in many pathophysiological conditions including cancer. Research on NO, during the past few years is one of the growing areas in cancer biology. The high incidence of oral cancer and precancer has been linked with habits of tobacco chewing and smoking and NO has been said as the "messenger of death" in tobacco related diseases. NO seems to play a part in various stages of carcinogenesis from initiation to progression. However, there is considerable controversy and confusion in understanding its role in cancer biology. It is said to have both, tumoricidal as well as tumor promoting effects and these depend on its timing, location and concentration. Further, NO has also been shown to have antitumor, chemopreventive and therapeutic abilities. Here is an overview in which efforts are made to understand the role of this molecule in oral carcinogenesis.

Enhanced nitrosative and oxidative stress with decreased total antioxidant capacity in patients with oral precancer and oral squamous cell carcinoma

OBJECTIVE

Interaction between reactive oxygen species (ROS) and reactive nitrogen species (RNS) is a crucial determinant in the etiology of oral squamous cell carcinoma (OSCC), and antioxidants protect against cellular and molecular damage caused by these. This study aims to evaluate ROS and RNS, together with the total antioxidant capacity (TAC), in serum and tissues of OSCC patients.

METHOD

Total nitric oxide (TNO), malondialdehyde (MDA), and TAC were evaluated using a UV visible spectrophotometer in the serum of 30 controls, 30 precancer and 30 OSCC patients and in tissues of 10 controls and 30 OSCC patients.

RESULTS

MDA and TNO were significantly elevated with concomitant depletion of TAC in serum and tissues of OSCC patients when compared to controls. A significant positive correlation (p = 0.01), at different levels between TNO and MDA in OSCC patients, was found, which increased with the grade of OSCC.

CONCLUSION

An increase in the levels of TNO, NO-mediated lipid peroxidation, resulting in an increase in MDA levels, the positive TNO-MDA correlation with a deranged antioxidant defense system as demonstrated by significantly low levels of TAC; when all these facts are taken together, we can conjecture that oxidative DNA damage, a vital phenomenon for carcinogenesis, occurs due to the interplay of ROS, RNS and TAC.

Association of clinicopathologic parameters with the expression of inducible nitric oxide synthase and vascular endothelial growth factor in mucoepidermoid carcinoma

BACKGROUND

The roles that inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF) play in tumorigenesis have been given special attention. In many tumors, their expression is upregulated. In addition, iNOS can stimulate the expression of VEGF. This study was carried out to investigate the expression of iNOS and VEGF as well as their relationship with angiogenesis and the clinicopathological characteristics of mucoepidermoid carcinoma (MEC).

METHOD

The expression of iNOS and VEGF was detected by Streptavidin-peroxidase immunohistochemistry, and microvessel density (MVD) was determined by anti-CD34 antibody staining in 70 MEC cases and 40 normal salivary gland tissues (NSG). Follow-up was performed on the 70 patients with MEC. Non-parametric tests were performed for the comparison of iNOS and VEGF expression.

RESULTS

The positive expression rates of iNOS and VEGF were successively enhanced in NSG, well-differentiated and poorly differentiated MEC (P < 0.05). MVD counts were positively correlated with the expression levels of iNOS and VEGF in MEC (P < 0.05). The expression of iNOS was positively correlated with the expression of VEGF (P < 0.05). iNOS and VEGF expression were significantly associated with tumor differentiation, size metastasis, and relapse (P < 0.05) but were not correlated lymph node metastasis and metastasis.

CONCLUSION

Inducible nitric oxide synthase can stimulate the expression of VEGF, and their expression status may help assess tumor malignancy and patient prognosis.

Expression of the membrane-cytoskeletal linker Ezrin in salivary gland adenoid cystic carcinoma

OBJECTIVE

The aim of this study was to investigate the relationship between membrane cytoskeleton linker protein Ezrin and CD44v6, iNOS, Ki-67, and clinicopathologic characteristics, and the prognostic significance of Ezrin expression in salivary gland adenoid cystic carcinoma (SACC).

STUDY DESIGN

Immunohistochemistry and reverse-transcription polymerase chain reaction were used to quantify the expression of Ezrin, CD44v6, inducible nitric oxide synthase (iNOS), and Ki-67 in 75 primary SACCs, 25 tumor-free salivary tissues, and 2 SACC cell lines (ACC-M and ACC-2). Survival analysis was performed to find the prognostic significance of Ezrin expression.

RESULTS

Expressions of Ezrin, CD44v6, iNOS, and Ki-67 in SACC tissues, especially with distant metastasis, were significantly higher than in tumor-free tissues. Ezrin mRNA and protein levels in ACC-M cells were significantly higher than in ACC-2 cells. Ezrin, CD44v6, iNOS, and Ki-67 expressions were significantly higher in solid pattern than in cribriform and tubular patterns. Ezrin and its partners, CD44v6, iNOS, and Ki-67, were significantly related to tumor size, clinical stage, perineural and vascular invasion, and recurrence. Furthermore, Ezrin had an independent prognostic effect on overall survival.

CONCLUSIONS

The increased expression of Ezrin and its partners, CD44v6, iNOS, and Ki-67, in SACC correlated with histologic patterns, may play a role in distant metastasis, and might indicate poor clinical outcome.

Red Mold Rice Mitigates Oral Carcinogenesis in 7,12-Dimethyl-1,2-Benz[a]anthracene-Induced Oral Carcinogenesis in Hamster

The prevalence of oral tumor has exponentially increased in recent years; however, the effective therapies or prevention strategies are not sufficient. Red mold rice is a traditional Chinese food, and several reports have demonstrated that red mold rice had an anti-tumor effect. However, the possible anti-tumor mechanisms of the red mold rice are unclear. In this study, we examined the anti-tumor effect of red mold rice on 7,12-dimethyl-1,2-benz[a]anthracene (DMBA)-induced oral tumor in hamster. The ethanol extract of red mold rice (RMRE) treatment significantly decreases the levels of DMBA-induced reactive oxygen species, nitro oxide and prostaglandin E₂ than those of the lovastatin-treated group (P < .001). Moreover, RMRE decreases the formation of oral tumor induced by DMBA. Monacolin K, monascin, ankaflavin or other red mold rice metabolites had been reported to decrease inflammation and oxidative stress and exerted anti-tumor effects. Therefore, we evaluated the anti-inflammation and anti-oxidative stress effects of monacolin K, monascin, ankaflavin and citrinin in lipopolysaccharide-treated RAW264.7 cells. We found that RMRE reduced the LPS-induced nitrite levels in RAW264.7 cells better than monacolin K, monascin, ankaflavin or citrinin (P < .05).

Effects of red mold dioscorea on oral carcinogenesis in DMBA-induced hamster animal model

Monascus-fermented products offer valuable therapeutic benefits and have been extensively used for centuries in East Asia. Dioscorea has been proved to have anti-cancer effect. The aim of this study is to investigate the anti-tumor ability of the ethanol extract of red mold dioscorea (RMDE) on 7,12-dimethyl-1,2-benz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. We induced oral squamous cell carcinoma (OSCC) in the buccal pouch of male Syrian golden hamsters by painting with 0.5% DMBA three times a week for 14 weeks. From 9 to 14 weeks, a dose of 50, 100, and 200 mg RMDE per kg body weight were painting with the hamsters for 6 weeks on days alternate to the DMBA application. The results demonstrated that RMDE decreased nitric oxide (NO), reactive oxygen species (ROS), and prostaglandin E(2) (PGE(2)) overexpression in hamster buccal pouches in the DMBA treatment group and increased p53, serum tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) to significantly stimulate caspase-8 and -3 activities, indicating that RMDE reduced oxidative damage causing by DMBA and induced apoptosis in oral cancer cells. Therefore, RMDE may have therapeutic potentials against OSCC.

Inflammatory infiltrate, microvessel density, vascular endothelial growth factor, nitric oxide synthase, and proliferative activity in soft tissues below intraorally welded titanium bars

BACKGROUND

The aim of the present study is a comparative evaluation of inflammatory infiltrate, microvessel density, vascular endothelial growth factor, nitric oxide synthase, and proliferative activity in soft tissues below intraorally welded titanium bars.

METHODS

Twenty-two patients participated in this study. All patients carried immediately loaded one-stage titanium implants splinted with intraorally welded titanium bars. Each patient underwent two gingival biopsies, a control biopsy harvested from an area of mucosa 5 mm away from the titanium bar and a test biopsy from the mucosa below the titanium bar, which were histologically and immunohistochemically processed.

RESULTS

No fractures or radiographically detectable alterations of the welded frameworks were present. In all the cases examined, the average of the modified plaque index was 1, no suppuration or bleeding on probing was present, and probing depth was < or =3 mm. However, the immunohistochemical analysis revealed some differences. The inflammatory infiltrate was mostly present in test sites and its extension was much larger than in control sites. Statistically significant differences were found in microvessel density and Ki-67 expression among control and test groups (P <0.0001). The high intensity of vascular endothelial growth factor, nitric oxide synthase 1, and nitric oxide synthase 3 expression were mainly detected in the test group, whereas the low intensities were mostly expressed in controls, with statistically significant differences (P <0.0001).

CONCLUSIONS

In the present study, the immunohistochemical analysis shows that the tissues below the titanium bars underwent a higher rate of inflammatory and reparative processes. However, further long-term studies, where clinical and immunohistochemical data are collected in parallel, should be conducted for a better understanding of the expression pattern of inflammation markers.

Protection of Monascus-fermented dioscorea against DMBA-induced oral injury in hamster by anti-inflammatory and antioxidative potentials

Monascus -fermented products offer valuable therapeutic benefits and have been extensively used in East Asia. This study investigated the prevention of oral tumor formation and antioxidative ability of the ethanol extracts from red mold dioscorea (RMDE) on 7,12-dimethyl-1,2-benz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. The HBP was painted with DMBA three times per week for 14 weeks, and animals were painted with celecoxib, RMDE (50, 100, and 200 mg/kg of bw), and ethanol extracts from dioscorea (200 mg/kg of bw) on days alternate to the DMBA application. The results demonstrated that RMDE attenuated tumor formation by elevating the antioxidase activity and suppressing the overproduction of reactive oxygen species, nitric oxide, prostaglandin E(2), and pro-inflammatory cytokines in the HBP caused by DMBA induction. These results indicated that RMDE exerted anti-inflammatory and antioxidative activity to prevent oral cancer. Therefore, the metabolite from Monascus fermentation may serve as a possible functional edible substance for the prevention of oral cancer.

Peripheral endothelin B receptor agonist-induced antinociception involves endogenous opioids in mice

Endothelin-1 (ET-1) produced by various cancers is known to be responsible for inducing pain. While ET-1 binding to ETAR on peripheral nerves clearly mediates nociception, effects from binding to ETBR are less clear. The present study assessed the effects of ETBR activation and the role of endogenous opioid analgesia in carcinoma pain using an orthotopic cancer pain mouse model. mRNA expression analysis showed that ET-1 was nearly doubled while ETBR was significantly down-regulated in a human oral SCC cell line compared to normal oral keratinocytes (NOK). Squamous cell carcinoma (SCC) cell culture treated with an ETBR agonist (10(-4)M, 10(-5)M, and 10(-6) M BQ-3020) significantly increased the production of beta-endorphin without any effects on leu-enkephalin or dynorphin. Cancer inoculated in the hind paw of athymic mice with SCC induced significant pain, as indicated by reduction of paw withdrawal thresholds in response to mechanical stimulation, compared to sham-injected and NOK-injected groups. Intratumor administration of 3mg/kg BQ-3020 attenuated cancer pain by approximately 50% up to 3h post-injection compared to PBS-vehicle and contralateral injection, while intratumor ETBR antagonist BQ-788 treatment (100 and 300microg/kg and 3mg/kg) had no effects. Local naloxone methiodide (500microg/kg) or selective mu-opioid receptor antagonist (CTOP, 500microg/kg) injection reversed ETBR agonist-induced antinociception in cancer animals. We propose that these results demonstrate that peripheral ETBR agonism attenuates carcinoma pain by modulating beta-endorphins released from the SCC to act on peripheral opioid receptors found in the cancer microenvironment.

Endothelin-A receptor antagonism attenuates carcinoma-induced pain through opioids in mice

We previously reported that endothelin A (ET-A) receptor antagonism attenuates carcinoma-induced pain in a cancer pain mouse model. In this study, we investigated the mechanism of ET-A receptor-mediated antinociception and evaluated the role of endogenous opioid analgesia. Squamous cell carcinoma (SCC) cell culture treated with the ET-A receptor antagonist (BQ-123) at 10(-6) M and 10(-5) M significantly increased production and secretion of beta-endorphin and leu-enkephalin, respectively. Behavioral studies were performed by inducing tumors in the hind paw of female nude mice with local injection of cells derived from a human oral SCC. Significant pain, as indicated by reduction in withdrawal thresholds in response to mechanical stimulation, began at 4 days after SCC inoculation and lasted to 18 days, the last day of measurement. Local administration of either naloxone methiodide (500 microg/kg), selective antagonists for mu-opioid receptor (CTOP, 500 microg/kg), or delta-opioid receptor (naltrindole, 11 mg/kg) but not kappa-opioid receptor (nor-BNI, 2.5 mg/kg) significantly reversed antinociception observed from ET-A receptor antagonism (BQ-123, 92 mg/kg) in cancer animals. These results demonstrate that antagonism of peripheral ET-A receptor attenuates carcinoma pain by modulating release of endogenous opioids to act on opioid receptors in the cancer microenvironment.

PERSPECTIVE

This article proposes a novel mechanism for ET-A receptor antagonist drugs in managing cancer-induced pain. An improved understanding of the role of innate opioid analgesia in ET-A receptor-mediated antinociception might provide novel alternatives to morphine therapy for the treatment of cancer pain.

Inhibition of VEGF expression in tongue squamous cancer cells via RNA interference silencing of iNOS gene

The purpose of this study was to investigate the regulatory role of the inducible nitric oxide synthase (iNOS) gene on vascular endothelial growth factor (VEGF) expression in oral squamous cancer cells. The RNA interference (RNAi) technique was used to silence iNOS gene expression by transfecting an expression vector containing short hairpin RNA (shRNA) for iNOS into Tca8113 tongue squamous cancer cells using cationic liposomes. Reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting were used to monitor iNOS and VEGF mRNA, as well as protein expression. iNOS mRNA expression was significantly downregulated 24 and 36 h after transfection, and iNOS protein expression was significantly downregulated at 36 and 48 h (P<0.05 versus control), showing that effective silencing was achieved. VEGF mRNA was significantly decreased 24 and 36 h post-transfection, and VEGF protein expression was significantly decreased at 36 and 48 h (P<0.05). RNAi can decrease iNOS gene expression and achieve a gene silencing effect. iNOS gene silencing reduces VEGF expression levels in Tca8113 cells. Thus, there is a relationship between iNOS and VEGF expression in tongue squamous cancer cells.

Oxidant-antioxidant status in blood and tumor tissue of oral squamous cell carcinoma patients

BACKGROUND AND OBJECTIVE

Increased oxidative and nitrosative stress associated with disturbances in antioxidant defense system have been implicated in the pathogenesis of several diseases, most notably oral cancer. The aim of this study was to evaluate the oxidant-antioxidant status in blood samples and tumor tissue in oral squamous cell carcinoma (OSCC) patients in comparison with the healthy controls.

METHODS

Blood and tumor tissue samples from the diseased individuals and the normal controls were analyzed for malondialdehyde (MDA) and nitric oxide (NO) as indicators of oxidative stress and nitrosative stress respectively; superoxide dismutase (SOD) and catalase enzymes as indicators of antioxidant defense by UV visible spectrophotometer.

RESULTS

Malondialdehyde and NO levels were significantly elevated in the blood and tissue samples of OSCC patients as compared with the healthy controls. The antioxidant enzymes SOD and catalase were significantly reduced in tissue samples of OSCC group than in the control group while in the erythrocytes, catalase levels were significantly reduced and the SOD levels were higher in OSCC group in comparison with the healthy controls.

INTERPRETATION AND CONCLUSION

Increased levels of MDA and NO indicate an increase in the oxidative stress in OSCC patients associated with a deficient antioxidant defense mechanism. This oxidant-antioxidant imbalance may be considered as one of the factors responsible for pathogenesis of cancer. Future studies regarding assessment of oxidant-antioxidant status in OSCC patients in view of selecting appropriate mode of therapy and the effectiveness of such therapy in limiting the tumor progression and recurrence is to be carried out.

Topical application of a bioadhesive black raspberry gel modulates gene expression and reduces cyclooxygenase 2 protein in human premalignant oral lesions

Reduced expression of proapoptotic and terminal differentiation genes in conjunction with increased levels of the proinflammatory and angiogenesis-inducing enzymes, cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS), correlate with malignant transformation of oral intraepithelial neoplasia (IEN). Accordingly, this study investigated the effects of a 10% (w/w) freeze-dried black raspberry gel on oral IEN histopathology, gene expression profiles, intraepithelial COX-2 and iNOS proteins, and microvascular densities. Our laboratories have shown that freeze-dried black raspberries possess antioxidant properties and also induce keratinocyte apoptosis and terminal differentiation. Oral IEN tissues were hemisected to provide samples for pretreatment diagnoses and establish baseline biochemical and molecular variables. Treatment of the remaining lesional tissue (0.5 g gel applied four times daily for 6 weeks) began 1 week after the initial biopsy. RNA was isolated from snap-frozen IEN lesions for microarray analyses, followed by quantitative reverse transcription-PCR validation. Additional epithelial gene-specific quantitative reverse transcription-PCR analyses facilitated the assessment of target tissue treatment effects. Surface epithelial COX-2 and iNOS protein levels and microvascular densities were determined by image analysis quantified immunohistochemistry. Topical berry gel application uniformly suppressed genes associated with RNA processing, growth factor recycling, and inhibition of apoptosis. Although the majority of participants showed posttreatment decreases in epithelial iNOS and COX-2 proteins, only COX-2 reductions were statistically significant. These data show that berry gel application modulated oral IEN gene expression profiles, ultimately reducing epithelial COX-2 protein. In a patient subset, berry gel application also reduced vascular densities in the superficial connective tissues and induced genes associated with keratinocyte terminal differentiation.

iNOS expression in oral and gastrointestinal tract mucosa

It is known that the overproduction of nitric oxide (NO) by nitric oxide synthase (NOS) occurs during the progression of various inflammatory diseases in intestinal tract. NOS inhibitors or inducible nitric oxide synthase (iNOS) gene expression inhibitors should be considered as potential anti-inflammatory agents, as NO synthesized by iNOS is related to various pathophysiological processes including inflammation. In order to understand the relationship between iNOS and pathological reactions such as the inflammatory process and malign transformation clearly, the existence and amount of constitutive expression should be determined. It is crucial to comprehend the harmful and protective amounts of iNOS expressions in order to clarify the relationship between iNOS and pathological processes. Evidently, only after this inspection is it possible to utilize iNOS as a marker and treatment instrument during the diagnosis and treatment of malign transformation and the inflammatory process.

Inducible nitric oxide synthase: correlation with extracapsular spread and enhancement of tumor cell invasion in head and neck squamous cell carcinoma

BACKGROUND

Extracapsular nodal spread is a major prognostic indicator in head and neck cancer. Nitric oxide (NO), primarily produced by the enzyme inducible NO synthase (iNOS), has a large number of actions in cancer biology, but no studies have investigated its possible role in extracapsular spread or tumor invasion.

METHODS

Immunochemistry was used to study iNOS expression in 48 patients with either extracapsular or encapsulated metastasis. In vitro invasion assays were performed using H357 (an oral squamous cell carcinoma cell line) using the iNOS inhibitor drug, 1400 W.

RESULTS

iNOS expression was significantly associated with extracapsular spread, with 22/27 cases showing positive iNOS expression compared with 8/21 cases in the encapsulated group (p = .01). Invasion of H357 cells was inhibited by 1400 W at concentrations of 100 microM and 1 mM (p = .002, p = .003).

CONCLUSION

iNOS protein seems to be associated with extracapsular spread and invasion in head and neck cancer. Further studies are required to understand this role more fully.

Survivin and inducible nitric oxide synthase production during 4NQO-induced rat tongue carcinogenesis: A possible relationship

This study was undertaken to investigate, by immunohistochemistry, the expression of survivin and inducible nitric oxide synthase during 4NQO-induced rat tongue carcinogenesis. Male Wistar rats were distributed into three groups of 10 animals each and treated with 50 ppm 4NQO solution through their drinking water for 4, 12, and 20 weeks. Ten animals were used as negative control. Although no histopathological abnormalities were induced in the epithelium after 4 weeks of carcinogen exposure, survivin and iNOS were expresssed (p<0.05) in some cells of the 'normal' oral epithelium. In pre-neoplastic lesions at 12 weeks following carcinogen exposure, the levels of survivin and iNOS were increased (p<0.05) when compared to negative control, being the strongest effect observed to iNOS. In well-differentiated squamous cell carcinoma induced after 20 weeks of treatment with 4NQO, survivin and iNOS were expressed in some tumor cells. Lack of immunoreactivity for both markers was observed in the negative control group. Taken together, our results support the belief that expression of survivin and iNOS are early events during malignant transformation and conversion of the oral mucosa.

Effect of peripheral endothelin-1 concentration on carcinoma-induced pain in mice

In this study, we investigated the role of the peripheral endothelin-1 (ET-1) concentration in a cancer pain model. To test the hypothesis that the concentration of ET-1 in the tumor microenvironment is important in determining the level of cancer pain we used two cancer pain mouse models that differed significantly in production of ET-1. The two mouse cancer models were produced by injection of cells derived from a human oral squamous cell carcinoma (SCC) and melanoma into the hind paw of female mice. Pain, as indicated by reduction in withdrawal thresholds in response to mechanical stimulation, was significantly greater in the SCC group than the melanoma group. The peripheral concentration of ET-1 within the cancer microenvironment was significantly greater in the SCC group. Intra-tumor expression of both ET-1 mRNA and ET-1 protein were significantly higher in the SCC model compared to the melanoma model. ET receptor antagonism was effective as an analgesic for cancer pain in the SCC model only. To address the potential confounding factor of tumor volume we evaluated the contribution of tumor volume to cancer pain in the two models. The mean volumes of the tumors in the melanoma group were significantly greater than the tumors in the SCC group. In both groups, the pain level correlated with tumor volume, but the correlation was stronger in the melanoma group. We conclude that ET-1 concentration is a determinant of the level of pain in a cancer pain mouse model and it is a more important factor than tumor volume in producing cancer pain. These results suggest that future treatment regimens for cancer pain directed at ET-1 receptor antagonism show promise and may be tumor type specific.

Enhanced lipid peroxidation and nitric oxide products with deranged antioxidant status in patients with head and neck squamous cell carcinoma

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) can function both as initiators and promoters in carcinogenesis. Antioxidants provide protection against cellular and molecular damage caused by ROS and RNS. We conducted a study to evaluate the levels of lipid peroxidation products, nitric oxide (NO) products and antioxidants in patients with head and neck squamous cell carcinoma (HNSCC). Fifty one HNSCC patients, 33 healthy tobacco smokers/chewers as tobacco user controls, and 37 non-smokers/chewers as normal controls were recruited for this study. Lipid peroxidation products, NO products and antioxidants were measured using spectrophotometric methods. Lipid peroxidation products, including lipid hydroperoxide (LHP) and malondialdehyde (MDA), nitric oxide (NO) products, including nitrite (NO(2)(-)), nitrate (NO(3)(-)), and total nitrite (TNO(2)(-)) were found to be significantly elevated with a concomitant depletion of antioxidants in HNSCC patients as compared to tobacco users and normal controls. These derangements were also evident albeit to a lesser degree in tobacco users as compared to normal controls. Results from this study demonstrate a potential involvement of both ROS and RNS in the pathogenesis of HNSCC and also illustrate the risk of ROS/RNS induced damage healthy tobacco users are exposed to, implicating their higher risk for upper aerodigestive tract cancer.

Peripheral endothelin A receptor antagonism attenuates carcinoma-induced pain

In this study we investigated the role of endothelin-1 (ET-1) and its peripheral receptor (ET-A) in carcinoma-induced pain in a mouse cancer pain model. Tumors were induced in the hind paw of female mice by local injection of cells derived from a human oral squamous cell carcinoma (SCC). Significant pain, as indicated by reduction in withdrawal thresholds in response to mechanical stimulation, began at four days after SCC inoculation and lasted to 28 days, the last day of measurement. Intra-tumor expression of both ET-1 mRNA and ET-1 protein were significantly upregulated compared to normal tissue, and local administration of the ET-A receptor selective antagonist, BQ-123 (100 microM) significantly elevated withdrawal thresholds, indicating the induction of an antinociceptive effect. These findings support the suggestion that ET-1 and ET-A receptors contribute to the severity of carcinoma-induced soft tissue cancer pain.

Elevated salivary endothelin levels in oral cancer patients--a pilot study

The analysis of saliva has been proposed as a potentially rapid, non-invasive method to monitor and diagnose patients with oral disease. In this study we measured salivary endothelin-1 (ET-1) levels in patients diagnosed with oral squamous cell carcinoma (SCC) prior to treatment. We demonstrate significantly elevated salivary ET-1 levels in the oral SCC group (4.37+/-1.35pg/ml), relative to the control group (1.16+/-0.29pg/ml). ET-1 and ET-1 mRNA were also measured in oral SCC tissue specimens and compared to normal oral epithelial controls. The concentration of ET-1 in the oral SCC specimens was 17.87+/-4.0pg/ml and in the normal epithelial controls the concentration of ET-1 was 5.43+/-2.5pg/ml. ET-1 mRNA was significantly overexpressed in 80% (8/10) of the oral SCC specimens. Our results demonstrate the potential utility of salivary analysis for ET-1 levels to monitor patients at risk for oral SCC.

Inflammatory infiltrate, microvessel density, nitric oxide synthase expression, vascular endothelial growth factor expression, and proliferative activity in peri-implant soft tissues around titanium and zirconium oxide healing caps

BACKGROUND

The aim of the present study in humans was to conduct a comparative immunohistochemical evaluation of vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) expression, inflammatory infiltrate, proliferative activity expression, and microvessel density (MVD) in peri-implant soft tissues of titanium and zirconium oxide healing caps.

METHODS

Five patients, three men and two women (aged 30 to 66 years; mean: 49 years), participated in this study. All patients received dental implants that were 3.8 mm in diameter and 11 mm in length. All implants were left to heal in a non-submerged (single-stage) mode. Healing caps (3.8 mm in diameter and 3.0 mm in height) were inserted in all implants. Half of the implants were supplied with standard, prefabricated caps of commercially pure titanium, whereas the other half were provided with test zirconium oxide caps. After a 6-month healing period, a gingival biopsy was performed with a circular scalpel (5.5 mm in diameter) around the healing caps of both groups, without unscrewing or removing the healing caps. The dimensions of the gingival biopsies were 1.7 mm (5.5-3.8 mm) in thickness and 3 mm in height.

RESULTS

Statistically significant differences were found in the microvessel density between titanium and zirconium oxide healing caps and group II (P < or = 0.0001). Statistically significant differences were likewise found in the low and high intensities of NOS1, NOS3, and VEGF (P < or = 0.0001). In conclusion, the high intensity of NOS1, NOS3, and VEGF were mostly expressed in the titanium group, whereas the low intensity of NOS1, NOS3, and VEGF were mostly expressed in the zirconium oxide group.

CONCLUSIONS

In our specimens, the inflammatory infiltrate was mostly present in the titanium specimens. Their extension was much larger than that of the zirconium oxide specimens. Higher values of MVD were observed in the titanium specimens (29.1 versus 15.8). In addition, a higher expression of VEGF intensity was observed in the peri-implant tissues of titanium healing caps, whereas predominantly lower expressions of VEGF intensity were noted around the zirconium oxide healing caps. The Ki-67 expression was higher in the titanium specimens. All these data revealed that the tissues around titanium healing caps underwent a higher rate of inflammation-associated processes, most probably correlated to the higher inflammation processes observed in these tissues. A higher intensity expression of NOS1 and NOS3 was recorded in the tissues around titanium, whereas, on the contrary, a lower intensity of expression was found in the tissues around zirconium oxide specimens. These latter data indicate that the higher expression of these two mediators could be correlated to the higher amount of bacteria present around the titanium samples.

Nitric oxide and metastatic cell behaviour

Nitric oxide (NO) is a pleiotropic signalling molecule that subserves a wide variety of basic cellular functions and also manifests itself pathophysiologically. As regards cancer and its progression, however, the reported role of NO appears surprisingly inconsistent. In this review, we focus on metastasis, the process of cancer cell spread and secondary tumour formation. In a 'reductionist' approach, we consider the metastatic cascade to be made up of a series of basic cellular behaviours (such as proliferation, apoptosis, adhesion, secretion migration, invasion and angiogenesis). We evaluate how NO controls such behaviours, in comparison with normal cells. The available information suggests strongly that NO signalling would be expected to regulate these behaviours both positively and negatively and this probably leads to the observed apparent variability in the NO status of cancer cells and tissues. Thus, the role of NO in cancer is more complex than previously thought. A number of suggestions are made, including consideration of novel mechanisms, such as ion channels, in order to achieve a more consistent and integrated understanding of NO signalling in cancer and to realise its clinical potential.

Inhibitory effect of inducible nitric oxide synthase inhibitors on DMBA-induced hamster buccal-pouch squamous-cell carcinogenesis

We investigated the effects of two NOS inhibitors (AG and l-NAME) on DMBA-induced hamster buccal-pouch carcinogenesis. Six hundred Syrian golden hamsters were split into two divisions (I and II); divisions split into three groups (experimental groups A and B, control group C); and each group into subgroups of 20 (A1-A6, B1-B6 and C1-C3). The pouches of animals in groups A1-A3 were painted first with AG of differing concentrations (10, 20, and 30 micromol/ml) and then 30 min later with DMBA (0.5%), thrice weekly for 9 weeks. Subgroups A4-A6 only received AG treatment. Groups B1 to B6 were similarly treated with l-NAME. Animals in division II were treated in the same manner for 13 weeks. Post-mortem analysis revealed that both inhibitors can suppress the development of epithelial dysplasias and squamous-cell carcinomas. An associated increase in the numbers of epithelial hyperplasias was paralleled by a decrease in iNOS protein expression. This animal model can be employed to evaluate the potential use of iNOS inhibitors as novel therapeutic tools for oral squamous-cell carcinogenesis.