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

Streptococcus anginosus: the potential role in the progression of gastric cancer

Gastric cancer (GC) is among the most common and aggressive malignancies worldwide, characterized by a poor prognosis. Research on its pathogenesis and progression continues to evolve. Streptococcus anginosus (S. anginosus, SA) is a Gram-positive coccus commonly found in the oral cavity and upper respiratory tract, serving as a commensal bacterium in the oral, gastrointestinal, and genitourinary tracts. It is frequently associated with abscess formation in various organs and tissues, as well as other purulent infections. In recent years, S. anginosus has gained increasing attention for its role in GC progression, potentially leading to chronic gastric inflammation and precancerous lesions, and ultimately promoting the development of GC. Emerging evidence indicates a strong association between S. anginosus and the malignant progression and unfavorable prognosis of GC. This review summarizes the role and underlying mechanisms of S. anginosus in GC and proposes that S. anginosus plays a pivotal role in its initiation and progression, underscoring its potential therapeutic significance.

Photobiomodulation Exerts Anti-Inflammatory and Antioxidant Effects Reducing the Development of Tumors Elicited by 4-NQO in the Mice Tongue

OBJECTIVE

Evaluate the influence of photobiomodulation in a model of oral carcinogenesis induced by 4-nitroquinoline-n-oxide (4-NQO).

SUBJECTIVE

Ninety-six Swiss mice received topical application of 1% 4-NQO on tongue dorsum, for 20 weeks. The tongue was subjected to photobiomodulation with red (71.4 J/cm2) and infrared laser (142.8 J/cm2) starting at week 0, 12, and 16. After 20 weeks, tongues were removed for the following analyzes: histological assessment, immunohistochemical reactions (cyclin D1/Ki-67/TGF-β1), quantification of MPO, n-AG, MDA, GSH, total proteins, TNF-α, IL-1β, and IL-6 levels.

RESULTS

4-NQO showed significant increase in the frequency of carcinoma (p < 0.001), and in the immunostaining for cyclin D1/Ki-67/TGF-β1 (p < 0.005), along with increased levels of TNF- α, IL-1β, IL-6, MPO, n-AG, MDA, and total proteins (p < 0.001), that were reduced by photobiomodulation with red and infrared lasers (p < 0.005).

CONCLUSION

Photobiomodulation reduces tumor development, accompanied by reduced inflammatory cells and content of cytokines and oxidative markers associated with carcinogenesis.

E-Cigarette effects on oral health: A molecular perspective

Electronic cigarettes (e-cigarettes) have emerged as a potential alternative to traditional smoking and may aid in tobacco harm reduction and smoking cessation. E-cigarette use has notably increased, especially among young non-tobacco users, raising concerns due to the unknown long-term health effects. The oral cavity is the first and one of the most crucial anatomical sites for the deposition of e-cigarette aerosols. E-cigarette aerosols contain nicotine, flavors, volatile organic compounds, heavy metals, carcinogens, and other hazardous substances. These aerosols impact the oral cavity, disrupting host-microbial interactions and triggering gingivitis and systemic diseases. Furthermore, oral inflammation and periodontitis can be caused by proinflammatory cytokines induced by e-cigarette aerosols. The toxic components of e-cigarette aerosols increase the cellular reactive oxygen species (ROS) levels, reduce antioxidant capacity, increase DNA damage, and disrupt repair processes, which may further contribute to harmful effects on oral epithelum, leading to inflammatory and pre-malignant oral epithelial lesions. In this review, we analyze the toxicological properties of compounds in e-cigarette aerosols, exploring their cytotoxic, genotoxic, and inflammatory effects on oral health and delving into the underlying molecular mechanisms. Further research is essential to understand the impact of e-cigarettes on oral health and make informed regulatory decisions based on reliable scientific evidence.

Energy Metabolic Profile in Oral Potentially Malignant Disorders and Oral Squamous Cell Carcinoma: A Preliminary Landscape of Warburg Effect in Oral Cancer

We hypothesized that cell energy metabolic profiles correlate with normal, dysplastic, and tumor cell/tissue statuses and may be indicators of aggressiveness in oral squamous cell carcinoma (OSCC) cells. The energy-related proteins that were differentially expressed in human OSCC fragments (n = 3) and their adjacent epithelial tissue (TAE) were verified using mass spectrometry (MS). Immunohistochemistry for 4-hydroxynonenal (4-HNE) was performed to evaluate the oxidative stress patterns in OSCC (n = 10), epithelial dysplasia (n = 9), and normal epithelial (n = 4) biopsies. The metabolic energy profile of OSCC aggressiveness was investigated in human OSCC cell lines with different levels of epithelial-mesenchymal transition proteins. The genes associated with the proteins found by MS in this study were analyzed using survival analysis (OS), whereas the genes associated with a poorer prognosis were analyzed using context-specific expression, Gene Ontology (GO) and Cancer Hallmarks for function enrichment analysis. The rationale for all experimental approach was to investigate whether the variation in energy metabolism profile accompanies the different phenotypes (from epithelial to mesenchymal) during the epithelial-mesenchymal transition. All OSCC fragments exhibited an increase in glycolysis-related proteins and a decrease in mitochondrial activity compared to the TAE region (p < 0.05), probably due to the downregulation of pyruvate dehydrogenase and antioxidant proteins. Additionally, the OSCC cell lines with a mesenchymal profile (SCC4, SCC9, and SCC25) had a lower mitochondrial mass and membrane potential and generated lower levels of reactive oxygen and nitrogen species than the TAE region. When we analyzed 4-HNE, the reactive species levels were increased in the epithelial regions of OSCC and potentially malignant lesions. A decrease in the levels of 4-HNE/reactive species was observed in the connective tissue underlying the dysplastic regions and the OSCC invasion zone. Based on this scenario, aggressive OSCC is associated with high glycolytic and oxidative metabolism and low mitochondrial and antioxidant activities, which vary according to the differentiation level of the tumor cells and the stage of carcinogenesis.

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.

Assessment of Antioxidant Enzyme Superoxide Dismutase (SOD) in Oral Cancer: Systematic Review and Meta-Analysis

Objective

The present article aims to comprehensively review the existing literature on superoxide dismutase (SOD) levels, an antioxidant enzyme, in oral cancer.

Method

An extensive literature search was conducted across various databases, including PubMed, Wiley Online Library, Science Direct, and Cross Reference, spanning 1998-2023. At the outset, 1,177 articles were initially identified, and 907 studies were excluded due to irrelevance or duplication of the research question. Subsequently, 270 articles underwent screening evaluation, resulting in the selection of 85 articles meeting the inclusion criteria. Following this, 68 articles underwent a full-text comprehensive assessment, and ultimately, 39 were chosen for data extraction. The risk of bias in the designated articles was assessed using the Newcastle-Ottawa Scale. Finally, 13 studies were meticulously selected, offering consistent data for the ensuing meta-analysis. Meta-analysis was executed using comprehensive meta-analysis (CMA) version 3 software (Bio Stat Inc., Englewood, NJ, USA). The meta-analysis findings revealed a statistically significant decrease in SOD levels in both erythrocyte samples (P < 0.001) and tissue samples (P < 0.05) among individuals with oral cancer (OSCC) compared to the normal control group. Conversely, the analysis of three studies on salivary samples demonstrated a significant increase (P < 0.05) in SOD levels in the oral cancer group compared to the healthy controls.

Conclusion

This systematic review underscores a statistically significant decline in SOD levels observed across diverse bio-samples in individuals with oral cancer, indicating an excess of oxidative stress (OS). Additional research is needed to delve into the relationship between SOD levels and clinic-pathological prognostic markers within the oral cancer cohort. Such investigations have the potential to significantly contribute to the development of prognostic tools grounded in OS, thereby guiding strategies for treatment planning.

New insights into redox-related risk factors and therapeutic targets in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common cancer in the oral cavity accounting for 90 % of oral cancer with a global incidence of 350.000 new cases per year. Curative resection along with adjuvant radiation therapy or a combination of radiotherapy with chemotherapy remain as gold standard in treating OSCC. Still, local recurrence, lymph nodal recurrence, and complications of radiation remain the main cause of tumor-related mortality. Reactive oxygen species are not only correlated to the etiology of OSCC due to oxidative DNA damage, lipid peroxidation or effecting signal transduction cascades that effect cell proliferation and tumorigenesis, but are also of great interest in the therapy of OSCC patients. As induced oxidative stress can be used therapeutically for the induction of tumor cell death, redox targets might be a therapeutic addition to the conventional treatment options. In this review, we discuss markers of impaired redox homeostasis as well as potential redox-related treatment targets in OSCC.

Oxidative Stress Enzyme as Markers in Oral Potentially Malignant Disorders and Oral Squamous Cell Carcinoma Patients

Oxidative stress is a recognized factor that poses a significant risk for the development of Oral Squamous Cell Carcinoma (OSCC) and Oral Submucous Fibrosis (OSMF), as it leads to the generation of Reactive Oxygen Species. In recent years, there has been significant research on the enzymes MDA (malondialdehyde) and SOD (superoxide dismutase), investigating their potential role in the development of OPMD and OSCC. These enzymes have emerged as promising biomarkers due to their ability to provide a less invasive, cost-effective, and objective diagnostic method. Furthermore, they can be used to monitor disease progression and assess the effectiveness of therapy. The aim of this study was to assess the levels of MDA and SOD in the serum of patients diagnosed with OSCC and OSMF. Study group comprised of 60 patients, out of which 20 cases of clinically diagnosed OSCC patients and 20 cases of OSMF and 20 cases pf control comprising of healthy patients were recruited. Estimation MDA and SOD was done by ELISA. The statistical analysis was done using SPSS analysis. When comparing the levels of MDA and SOD between the OSCC and OSMF groups and the control group, statistically significant findings indicated elevated levels of malondialdehyde and reduced levels of superoxide dismutase in both the OSCC and OSMF groups. In this study, the assessment of lipid peroxidation through MDA levels revealed elevated concentrations in both the OSCC and OSMF groups when compared to the control group. Specifically, the order of MDA levels was observed as OSCC > OSMF > Control. Conversely, antioxidant enzyme levels, such as SOD, exhibited decreased concentrations in the OSCC and OSMF groups compared to the control group, with the order of SOD levels being Control > OSMF > OSCC. Consequently, the findings suggest that MDA and SOD can be considered potential biomarkers for identifying and monitoring OSCC and OSMF diseases.

Antioxidant and Antiproliferative Activities of Several Garlic Forms

It is hypothesized that garlic, Allium sativum, might protect against oxidative stress that causes damage to cells and tissues leading to the development of various health conditions including cancer. However, it is not known whether garlic's potential anticancer benefits differ by form of garlic consumed. This study aimed to quantify and compare the in vitro antioxidant and antiproliferative activity of several garlic forms in water and alcohol extracts including fresh garlic, fresh garlic set aside, heated garlic, heated garlic set aside, garlic powder, black garlic, two commercially available garlic supplements. Antioxidant activity of different garlic forms were measured using three assays: DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay, superoxide assay, and hydroxyl assay. In vitro effects of garlic extracts were investigated against the most common lung cancer subtypes: H520, H1975, and A549 cell lines using the sulforhodamine B (SRB) assay. Among free radical scavenging assays, Garlicin®, a commercially available supplement, displayed high antioxidant activity in water and alcohol extracts (DPPH assay: 2.02 mg AAE (mg ascorbic acid equivalent)/g garlic and 3.53 mg AAE/g garlic, respectively; superoxide assay: 6.73 mg AAE/g garlic and 7.13 mg AAE/g garlic, respectively). In the hydroxyl assay, water extract of fresh garlic crushed and set aside for 10 min showed the highest antioxidant activity. Garlicin® alcohol extract and fresh garlic water extracts strongly inhibited the proliferation of H1975, A549 and H520 cells. Other forms of garlic including garlic powder and black garlic exhibited low antioxidant and antiproliferative activity. Our results demonstrate that the preparation and processing methods of garlic may lead to different antioxidant benefits.

Assessment of glutathione peroxidase enzyme response and total antioxidant status in oral cancer - Systematic review and meta-analysis

BACKGROUND

Oxidative stress induced by free radical accumulation contributes to many pathologies, including cancer. Antioxidant defense system fails to scavenge free radicals when it is excessively accumulated. Assessing individual antioxidant enzymes and total antioxidant capacity could direct the customized therapeutic strategies.

OBJECTIVE

Evaluation of total antioxidant status and enzyme glutathione peroxidase activity in the oral cancer group compared to the healthy control group.

METHOD

The literature search included databases PubMed, Science Direct, Wiley Online Library, Cochrane and Cross Reference between 1999 and 2021. The database search was completed in the month of August 2022. The extracted data were analyzed by Comprehensive Meta-Analysis (CMA) version 3 software (Biostat Inc. Englewood, NJ). Based on search strategies, 1435 articles have been retrieved from the database. In the segregated articles, 1365 were excluded due to duplicated articles, animal studies, low-quality studies, articles unrelated to the research question, and with unmatched objectives. Based on inclusion criteria, 70 articles were selected for full-text valuation. However, 33 articles were found highly suitable for inclusion and data extraction. Finally, 11 articles were selected for meta-analysis.

RESULTS

The meta-analysis of four included studies of tissue samples showed a significantly (p < .001) increased GPx activity in the oral cancer group, when compared to the control group, whereas three included studies of erythrocyte samples displayed a significantly (p < .001) decreased GPx activity in the oral cancer group than the control group with the pooled standardized mean difference value of -2.766 moles/min/g Hb at 95% CI (-3.297 to -2.234). The meta-analysis of the included studies depicted an insignificant (p = .947) reduction of salivary TAS levels in the oral cancer group when compared to the control group.

CONCLUSION

Our systematic review and meta-analysis depict antioxidant GPx enzyme activity in the regional tissue samples of the oral cancer group differs from other systemic biological fluid samples compared to the healthy control group.

Evaluating the protective role of Deglycyrrhizinated licorice root supplement on bleomycin induced pulmonary oxidative damage

The goal of this study was to investigate the protective effect of licorice supplements in a rat model of Bleomycin-induced lung oxidative damage over a duration of one month. The rats were randomly divided into six groups (n = 10 per group). Control group; Bleomycin group (B): rats were IP injected with bleomycin 5 mg/kg twice weekly. Licorice group (L): rats received orally 300 mg/kg licorice extract. Bleomycin and a low dose of Licorice group (BLLG): rats received orally 75 mg/kg licorice daily and injected as the B group. Bleomycin and a middle dose of Licorice group (BMLG): rats received orally 150 mg/kg licorice daily and injected as the Bleomycin group. Bleomycin and a high dose of Licorice group (BHLG): rats received orally 300 mg/kg licorice daily and injected as the Bleomycin group. Treatment with Bleomycin induced inflammation and oxidative damage to the lungs expressed in the disturbance of the measured parameters in the blood serum, the lung tissue, and the broncholavage fluid. In addition to the decreased expression of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and catalase (CAT) in the lung tissues. Bleomycin caused deformative changes in the histopathological and cellular examination of the lungs especially in the alveolar cells and the interstitial space. On the other hand, treated the bleomycin group with different doses of licorice supplement activates the antioxidant defense mechanism and attenuates the oxidative damage and damage induced to the lung. In conclusion, Deglycyrrhizinated licorice root supplement provided strong antioxidant and protective effects on Bleomycin-induced lung damage.

Early Posttransplant Mobilization of Monocytic Myeloid-derived Suppressor Cell Correlates With Increase in Soluble Immunosuppressive Factors and Predicts Cancer in Kidney Recipients

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) increase in patients with cancer and are associated with poor prognosis; however, their role in transplantation is not yet understood. Here we aimed to study the MDSC effects on the evolution of kidney transplant recipients (KTRs).

METHODS

A cohort of 229 KTRs was prospectively analyzed. Two myeloid cells subsets. CD11bCD33CD14CD15HLA-DR (monocytic MDSC [M-MDSC]) and CD11bCD33CD14CD15HLA-DR (monocytes), were defined by flow cytometry. The suppressive capacity of myeloid cells was tested in cocultures with autologous lymphocytes. Suppressive soluble factors, cytokines, anti-HLA antibodies, and total antioxidant capacity were quantified in plasma.

RESULTS

Pretransplant, M-MDSC, and monocytes were similar in KTRs and healthy volunteers. M-MDSCs increased immediately posttransplantation and suppressed CD4 and CD8 T cells proliferation. M-MDSCs remained high for 1 y posttransplantation. Higher M-MDSC counts at day 14 posttransplant were observed in patients who subsequently developed cancer, and KTRs with higher M-MDSC at day 14 had significantly lower malignancy-free survival. Day 14 M-MDSC >179.2 per microliter conferred 6.98 times (95% confidence interval, 1.28-37.69) more risk to develop cancer, independently from age, gender, and immunosuppression. Early posttransplant M-MDSCs were lower in patients with enhanced alloimmune response as represented by anti-HLA sensitization. M-MDSC counts correlated with higher circulatory suppressive factors arginase-1 and interleukin-10, and lower total antioxidant capacity.

CONCLUSIONS

Early posttransplant mobilization of M-MDSCs predicts cancer and adds risk as an independent factor. M-MDSC may favor an immunosuppressive environment that promotes tumoral development.

Arecoline N-oxide initiates oral carcinogenesis and arecoline N-oxide mercapturic acid attenuates the cancer risk

Arecoline N-oxide (ANO), an oxidative metabolite of the areca nut, is a predictable initiator in carcinogenesis. The mechanisms of arecoline metabolites in human cancer specimens is still limited. This present study aims to estimate the oral squamous cell carcinoma (OSCC) inductive activity between arecoline metabolites in human cancer specimens/OSCC cells. We have collected 22 pairs (tumor and non-tumor part) of patient's specimens and checked for clinical characteristics. The identification of arecoline and its metabolites levels by using LC-MS/MS. The NOD/SCID mice model was used to check the OSCC inductive activity. The tumor part of OSCC samples exhibited higher levels of arecoline and ANO. Besides, ANO treated mice accelerates the NOTCH1, IL-17a and IL-1β expressions compared to the control mice. ANO exhibited higher cytotoxicity, intracellular ROS levels and decline in antioxidant enzyme levels in OC-3 cells. The protein expression of NOTCH1 and proliferation marker levels are significantly lower in NOM treated cells. Overall, ANO induced initial stage carcinogenesis in the oral cavity via inflammation, ROS and depletion of antioxidant enzymes. Arecoline N-oxide mercapturic acid (NOM) attenuates the initiation of oral carcinogenesis.

NADPH oxidase 5α promotes the formation of CD271 tumor-initiating cells in oral cancer

Oral tongue squamous cell carcinoma (OTSCC) has a distinctive cell sub-population known as tumor-initiating cells (TICs). CD271 is a functional TIC receptor in head and neck cancers. The molecular mechanisms governing CD271 up-regulation remains unclear. Oxidative stress is a contributing factor in TIC development. Here, we explored the potential role of NADPH oxidase 5 (NOX5) and its regulatory mechanism on the development of CD271-expressing OTSCC. Our results showed that the splice variant NOX5α is the most prevalent form expressed in head and neck cancers. NOX5α enhanced OTSCC proliferation, migration, and invasion. Overexpression of NOX5α increased the size of OTSCC xenograft significantly in vivo. The tumor-promoting functions of NOX5α were mediated through the reactive oxygen species (ROS)-generating property. NOX5α activated ERK singling and increased CD271 expression at the transcription level. Also, NOX5α reduces the sensitivity of OTSCC to cisplatin and natural killer cells. The findings indicate that NOX5α plays an important part in the development of TIC in OTSCC.

Wine Consumption and Oral Cavity Cancer: Friend or Foe, Two Faces of Janus

The health benefits of moderate wine consumption have been extensively studied during the last few decades. Some studies have demonstrated protective associations between moderate drinking and several diseases including oral cavity cancer (OCC). However, due to the various adverse effects related to ethanol content, the recommendation of moderate wine consumption has been controversial. The polyphenolic components of wine contribute to its beneficial effects with different biological pathways, including antioxidant, lipid regulating and anti-inflammatory effects. On the other hand, in the oral cavity, ethanol is oxidized to form acetaldehyde, a metabolite with genotoxic properties. This review is a critical compilation of both the beneficial and the detrimental effects of wine consumption on OCC.

Oxidative stress, neutrophil elastase and IGFBP7 levels in patients with oropharyngeal cancer and chronic periodontitis

OBJECTIVE

The present study focused on investigating levels of oxidative stress, neutrophil elastase (NE), and insulin-like growth factor-binding protein 7 (IGFBP7) in oropharyngeal cancers (OC) with the presence and absence of periodontitis.

MATERIALS AND METHODS

A healthy non-periodontitis group (H-NP; n = 20), a systemically healthy chronic periodontitis group (H-P; n = 20), a non-periodontitis group with OC (OC-NP; n = 12), and a chronic periodontitis group with OC (OC-P; n = 16) formed the study groups. The levels of NE and IGFBP7 were measured in gingival crevicular fluid (GCF) and saliva. In addition, oxidative status was determined by evaluating total oxidant status (TOS), total antioxidant status (TAS), and OSI (TOS/TAS).

RESULTS

Gingival crevicular fluid NE was higher in all the groups compared with the H-NP group (p < .01). Salivary NE was higher in the OC-P and H-P groups compared with the H-NP and OC-NP groups (p < .05). Salivary IGFBP7 was significantly higher in the OC-NP and OC-P groups compared with the H-NP and H-P groups (p < .001). GCF TOS and OSI levels were significantly higher in all groups compared with the H-NP group (p < .05).

CONCLUSIONS

Gingival crevicular fluid NE levels were lower in healthy conditions compared with periodontal disease and OC. Salivary NE levels were higher in periodontal disease compared to states with no periodontal disease. Salivary IGFBP7 levels were higher in OC. Further analyses may help determine whether high salivary IGFBP7 levels distinguish OC from healthy conditions.

The risks of ubiquinone and β-carotene deficiency and metabolic disorders in patients with oral cancer

Background

Cancer development is mediated by oxidative stress and inflammation, which may correlate with metabolic disorders. The aim of this study was to evaluate antioxidant vitamins status and metabolic parameters in patients with oral cancer according to tumor-node-metastasis (TNM) stages.

Methods

A total of 194 patients with oral cancer were enrolled in this study. The patients were stratified for four groups according to cancer stages and that the statistics are comparisons across these groups. The levels of antioxidant vitamins (ubiquinone, β-carotene, vitamin A and E), metabolic parameters, oxidative stress, antioxidant enzymes activity, and inflammatory markers were measured.

Results

More than half of the subjects had high blood pressure, central obesity, hyperglycemia, and hyperlipidemia regardless of TNM stage. With regard to antioxidant vitamins status, 46 and 94% of patients had β-carotene and ubiquinone deficiency, respectively. Patients in T3 and T4 stages had significantly lower antioxidant enzyme (catalase, p = 0.03) activity and higher inflammatory markers levels (high sensitivity C-reactive protein and interleukin-6, p < 0.01) than patients in the other stages. In addition, the level of β-carotene was negatively associated with waist circumference, and ubiquinone was positively associated with the level of high-density lipoprotein cholesterol (p < 0.05). Higher β-carotene and ubiquinone levels were negatively associated with hypertriglyceridemia and the risk of metabolic syndrome (p < 0.05).

Conclusions

A high proportion of patients with oral cancer had ubiquinone or β-carotene deficiency and metabolic disorders. The level of ubiquinone or β-carotene was negatively associated with the risk of central obesity, hypertriglyceridemia, and metabolic syndrome. Since patients with oral cancer suffer from high oxidative stress and inflammation (particularly in the T3 and T4 stages), supplementation with antioxidant vitamins such as ubiquinone or β-carotene could be preferentially applied.

Tobacco and oral squamous cell carcinoma: A review of carcinogenic pathways

INTRODUCTION

Tobacco is one of the most important risk factors for premature death globally. More than 60 toxic chemicals in tobacco can invade the body’s various systems. Oral squamous cell carcinoma (OSCC) is a pathological type of oral cancer, accounting for over 90% of oral cancers. A vast quantity of scientific, clinical and epidemiological data shows that tobacco is associated with the development of oral squamous cell carcinoma, and its carcinogenic pathways may be complicated.

METHODS

We conducted a thorough electronic search by Cochrane, EMBASE and PubMed to identify relevant studies. Studies published up to the end of October 2018 were included. After assessing and selecting articles based on eligibility criteria, studies were classified and elaborated according to the pathogenesis.

RESULTS

Tobacco as an important risk factor can cause epigenetic alteration of oral epithelial cells, inhibit multiple systemic immune functions of the host, and its toxic metabolites can cause oxidative stress on tissues and induce OSCC. In addition, some specific viruses such as EBV and HPV are thought to play a role in the development of OSCC.

CONCLUSIONS

Oral cancer ranks eighth among the most common causes of cancer-related deaths worldwide, and tobacco is one the most important carcinogenic factors of OSCC. This review of the literature attempts to provide directions and ideas for future related research, and emphasizes the need for efforts to reduce tobacco consumption.

Controlled release of 18-β-glycyrrhetic acid by nanodelivery systems increases cytotoxicity on oral carcinoma cell line

The topical treatment for oral mucosal diseases is often based on products optimized for dermatologic applications; consequently, a lower therapeutic effect may be present. 18-β-glycyrrhetic acid (GA) is extracted from Glycirrhiza glabra. The first aim of this study was to test the cytotoxicity of GA on PE/CA-PJ15 cells. The second aim was to propose and test two different delivery systems, i.e. nanoparticles and fibers, to guarantee a controlled release of GA in vitro. We used chitosan and poly(lactic-co-glycolic) acid based nanoparticles and polylactic acid fibers. We tested both delivery systems in vitro on PE/CA-PJ15 cells and on normal human gingival fibroblasts (HGFs). The morphology of GA-loaded nanoparticles (GA-NPs) and fibers (GA-FBs) was investigated by electron microscopy and dynamic light scattering; GA release kinetics was studied spectrophotometrically. MTT test was used to assess GA cytotoxicity on both cancer and normal cells. Cells were exposed to different concentrations of GA (20-500 μmol l^-1) administered as free GA (GA-f), and to GA-NPs or GA-FBs. ROS production was evaluated using dichlorodihydrofluorescein as a fluorescent probe. Regarding the cytotoxic effect of GA on PE/CA-PJ15 cells, the lowest TC₅₀ value was 200 μmol l^-1 when GA was added as GA-NPs. No cytotoxic effects were observed when GA was administered to HGFs. N-acetyl Cysteine reduced mortality induced by GA-f in PE/CA-PJ15 cells. The specific effect of GA on PE/CA-PJ15 cells is mainly due to the different sensitivity of cancer cells to ROS over-production; GA-NPs and GA-FBs formulations increase, in vitro, this toxic effect on oral cancer cells.

Reactive oxygen species in cancer stem cells of head and neck squamous cancer

One of the greatest challenges in systemic treatment of head and neck squamous cell carcinoma (HNSCC) is a small tumor cell population, namely, cancer stem-like cells (CSC). CSC can regenerate and maintain a heterogenic tumor by their self-renewal capacity. Their potential ability to be more resistant to and survival after chemo- and radiation therapy was also identified. Further studies have shown that reactive oxygen species (ROS) contribute to this CSC-associated resistance. In this review, we focus on the current knowledge of HNSCC-CSC, with regard to ROS as a possible and novel therapeutic approach in targeting CSC.

Current relevance of hypoxia in head and neck cancer

Head and Neck cancer (HNC) is a complex mix of cancers and one of the more common cancers with a relatively poor prognosis. One of the factors that may assist us in predicting survival and allow us to adjust our treatment strategies is the presence of tumor hypoxia. In this overview we aim to evaluate the current evidence and potential clinical relevance of tumor hypoxia in head and neck cancer according to an extensive search of current literature.An abundance of evidence and often contradictory evidence is found in the literature. Even the contradictory evidence and comparisons are difficult to judge as criteria and methodologies differ greatly, furthermore few prospective observational studies exist for verification of the pre-clinical studies. Despite these discrepancies there is clear evidence of associations between prognosis and poor tumor oxygenation biomarkers such as HIF-1α, GLUT-1 and lactate, though these associations are not exclusive. The use of genetic markers is expanding and will probably lead to significantly more and complex evidence. The lack of oxygenation in head and neck tumors is of paramount importance for the prediction of treatment outcomes and prognosis. Despite the wide array of conflicting evidence, the drive towards non-invasive prediction of tumor hypoxia should continue.

Increased sensitivity of African American triple negative breast cancer cells to nitric oxide-induced mitochondria-mediated apoptosis

Background

Breast cancer is a complex heterogeneous disease where many distinct subtypes are found. Younger African American (AA) women often present themselves with aggressive form of breast cancer with unique biology which is very difficult to treat. Better understanding the biology of AA breast tumors could lead to development of effective treatment strategies. Our previous studies indicate that AA but not Caucasian (CA) triple negative (TN) breast cancer cells were sensitive to nitrosative stress-induced cell death. In this study, we elucidate possible mechanisms that contribute to nitric oxide (NO)-induced apoptosis in AA TN breast cancer cells.

Methods

Breast cancer cells were treated with various concentrations of long-acting NO donor, DETA-NONOate and cell viability was determined by trypan blue exclusion assay. Apoptosis was determined by TUNEL and caspase 3 activity as well as changes in mitochondrial membrane potential. Caspase 3 and Bax cleavage, levels of Cu/Zn superoxide dismutase (SOD) and Mn SOD was assessed by immunoblot analysis. Inhibition of Bax cleavage by Calpain inhibitor, and levels of reactive oxygen species (ROS) as well as SOD activity was measured in NO-induced apoptosis. In vitro and in vivo effect of NO treatment on mammary cancer stem cells (MCSCs) was assessed.

Results and discussion

NO induced mitocondria-mediated apoptosis in all AA but not in CA TN breast cancer cells. We found significant TUNEL-positive cells, cleavage of Bax and caspase-3 activation as well as depolarization mitochondrial membrane potential only in AA TN breast cancer cells exposed to NO. Inhibition of Bax cleavage and quenching of ROS partially inhibited NO-induced apoptosis in AA TN cells. Increase in ROS coincided with reduction in SOD activity in AA TN breast cancer cells. Furthermore, NO treatment of AA TN breast cancer cells dramatically reduced aldehyde dehydrogenase1 (ALDH1) expressing MCSCs and xenograft formation but not in breast cancer cells from CA origin.

Conclusions

Ethnic differences in breast tumors dictate a need for tailoring treatment options more suited to the unique biology of the disease.

Piperlongumine Suppresses Proliferation of Human Oral Squamous Cell Carcinoma through Cell Cycle Arrest, Apoptosis and Senescence

Oral squamous cell carcinoma (OSCC), an aggressive cancer originating in the oral cavity, is one of the leading causes of cancer deaths in males worldwide. This study investigated the antitumor activity and mechanisms of piperlongumine (PL), a natural compound isolated from Piper longum L., in human OSCC cells. The effects of PL on cell proliferation, the cell cycle, apoptosis, senescence and reactive oxygen species (ROS) levels in human OSCC cells were investigated. PL effectively inhibited cell growth, caused cell cycle arrest and induced apoptosis and senescence in OSCC cells. Moreover, PL-mediated anti-human OSCC behavior was inhibited by an ROS scavenger N-acetyl-l-cysteine (NAC) treatment, suggesting that regulation of ROS was involved in the mechanism of the anticancer activity of PL. These findings suggest that PL suppresses tumor growth by regulating the cell cycle and inducing apoptosis and senescence and is a potential chemotherapy agent for human OSCC cells.

Paraoxonase-2 (PON2) protects oral squamous cell cancer cells against irradiation-induced apoptosis

PURPOSE

Patients with oral squamous cell carcinomas (OSCC) often receive radiotherapy to preferentially induce apoptosis of cancer cells through generation of overwhelming DNA damage. This is amplified by generation of reactive oxygen species (ROS), thereby causing oxidative stress and cell death. However, tumors resist through different mechanisms, including upregulation of anti-apoptotic factors and enhanced ROS resistance. We recently reported that the antioxidative enzyme PON2 significantly enhances cellular stress resistance by attenuating mitochondrial ROS-mediated apoptosis. Further, PON2 is often upregulated in cancer. This prompted us to investigate its yet unknown role in the protection of OSCC against irradiation-induced cell death.

METHODS

PON2 expression was determined after 7 Gy singular irradiation in four OSCC cell lines (PCI-13, PCI-52, SCC-4, SCC-68) accompanied by the detection of caspase 3/7 activity. A direct role of PON2 was tested by siRNA-mediated knockdown. In vivo PON2 expression was tested in five patients with oral carcinoma and compared with healthy mucosa for the evaluation of clinical significance.

RESULTS

PON2 is variably expressed in OSCC in vitro and in vivo. Compared with the other cell lines, SCC-4 cells showed twofold more basal PON2 (p ≤ 0.05) and the lowest caspase 3/7 activity after singular irradiation (p ≤ 0.05). Contrarily, irradiation led to 1.2-fold induction of PON2 in PCI-13 with no effect on SCC-4 (≤0.05), suggesting that PON2 levels reflect the cells' irradiation sensitivity. In agreement, PON2 knockdown resulted in significant higher apoptosis rates (p ≤ 0.05).

CONCLUSION

Our findings give first evidence that upregulation of PON2 may protect OSCC against irradiation-induced apoptosis.

Enicostemma littorale prevents tumor formation in 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch carcinogenesis

Oral cancer is one of the most common malignancies worldwide, and India has recorded the highest annual incidence of oral cancer in comparison with other countries. Altered lipid peroxidation and antioxidant status along with defect in detoxification cascade have been implicated in the pathogenesis of several cancers including oral cancer. The aim of this study was to investigate the chemopreventive potential of ethanolic extract of Enicostemma littorale leaves (ElELet) in 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Oral tumor was developed in the buccal pouches of male golden Syrian hamsters by painting with 0.5% DMBA three times a week for 14 weeks. We observed 100% tumor formation with increase in tumor volume and tumor burden in the hamsters treated with DMBA alone. Imbalance in phase I (cytochrome P450 and cytochrome b5) and phase II (glutathione reductase, glutathione- S-transferase, glutathione, and Deoxythymidine-diaphorase (DT)-diaphorase) detoxification agents and lipid peroxidation by-products (thiobarbituric acid reactive substances) and antioxidant (superoxide dismutase, catalase, glutathione peroxidase, and vitamins E and C) status was noticed in hamsters treated with DMBA alone. Oral administration of ElELet at a dose of 250 mg/kg body weight to hamsters treated with DMBA significantly prevented both precancerous and cancerous lesions in the oral cavity. ElELet modulated the status of phase I and II detoxification agents and antioxidants in favor of the suppression of oral carcinogenesis. This study thus suggests that E. littorale might have inhibited the oral carcinogenesis in DMBA-treated hamsters through its antioxidant potential. The present findings are also substantiated by histological studies during DMBA-induced oral carcinogenesis.

Efficacy of quercetin against chemically induced murine oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common form of head and neck cancer, and oxidative damage is associated with the development of OSCCs. Antioxidants have therefore been proposed for use as chemoprotective agents against different types of cancer. In the present study, the effect of the antioxidant quercetin, administered at doses of 10 and 100 mg/kg/day, was investigated in an experimental murine model of 4-nitroquinoline 1-oxide (4-NQO)-induced carcinogenesis. The survival of the treated animals, the plasmatic levels of reduced glutathione and the type and severity of lesions (according the International Histological Classification of Tumors and Bryne's Multifactorial Grading System for the Invasive Tumor Front) were assessed. Additionally, the organization of the extracellular matrix was analyzed by carbohydrate and collagen histochemistry, and immunohistochemistry was used to assess the expression of the tumor markers proliferating cell nuclear antigen and mutated p53. The results indicate that, despite the promising effect of quercetin in other studies, this drug is ineffective as a chemoprotective agent against 4-NQO-induced OSCC in mice at the assayed doses.

Estimation of salivary nitric oxide in oral precancer patients

The role of nitric oxide (NO) in the initiation, promotion and progression of cancer has been the subject of speculation and conflicting reports in the literature. The high incidence of oral cancer and precancer has been linked to tobacco chewing and smoking habits; NO is considered an indicator of tobacco-related diseases. We compared salivary NO levels in oral precancer and normal patients. Unstimulated whole saliva was collected from 15 patients with oral precancer (group 1) and 15 healthy age and sex matched subjects (group 2). Salivary nitrite levels were estimated using a colorimetric method and a spectrophotometer. The salivary nitrite concentration of group 2 (median = 4.21 μg/ml) was significantly less than for group 1 (median = 12.91 μg/ml). We have added evidence concerning involvement of NO in the pathogenesis of oral cancer, but whether it is a potentially carcinogenic agent at the concentration at which it is present in oral precancer patients requires further evaluation.

Serum total antioxidant capacity in oral carcinoma patients

Context:

Oxidative stress is a major determinant in carcinogenesis and serum total antioxidant capacity (TAC) indirectly reflects the level of oxidative stress. Although oral cancer is the third most frequent cancer in Indian population, there are no standard noninvasive marker for early detection and monitoring therapeutic response in oral cancer patients.

Aims:

This study was carried out to investigate implications of serum TAC in oral cancer by evaluating pre- and post-operative levels in oral cancer patients.

Settings and Designs:

It was a prospective single blinded study.

Subjects and Methods:

Serum TAC was measured using ferric-reducing antioxidant power assay. Pre- and post-operative values were estimated and compared in 30 oral cancer patients who underwent surgery.

Statistical Analysis Used:

Paired t-test was used to compare pre- and post-operative values.

Results:

Compared to the normal value, both pre- and post-operative serum TAC were significantly low in oral cancer patients. However, there was no statistically significant difference between pre- and postoperative levels.

Conclusions:

In this study, low mean serum TAC was detected in oral cancer patients. However, its diagnostic and prognostic significance in oral cancer needs further investigation.

Oxidative stress in the oral cavity: sources and pathological outcomes

Oxidative stress (OS), an imbalance in the oxidant-antioxidant equilibrium, is thought to be involved in the development of many seemingly unrelated diseases. Oral cavity tissues are a unique environment constantly exposed to internal and external compounds and material hazards as almost no other part of the human body. Some of the compounds are capable of generating OS. Here, the main groups of endogenous as well as exogenous OS sources are presented, followed by their oxidative effect on the salivary contents and function. The oxidative mechanisms in oral cells and their pathologic influence are also discussed.

Long-term effects of varying consumption of ω3 fatty acids in ear, nose and throat cancer patients: assessment 1 year after radiotherapy

A prospective 1-year follow-up study in ear, nose, and throat (ENT) cancer patients was carried out one year after radiotherapy to assess the effect of varying consumption of ω3 fatty acid according to whether they consumed more or less than the 50th percentile of ω3 fatty acids. Clinical, analytical, inflammatory (CRP and IL-6), and oxidative variables (TAC, GPx, GST, and SOD) were evaluated. The study comprised 31 patients (87.1% men), with a mean age of 61.3 ± 9.1 years. Hematological variables showed significant differences in the patients with a lower consumption of ω3 fatty acids. A lower mortality and longer survival were found in the group with ω3 fatty acid consumption ≥50th percentile but the differences were not significant. No significant difference was reached in toxicity, inflammation, and oxidative stress markers. The group with ω3 fatty acid consumption <50th percentile significantly experienced more hematological and immune changes.

Oxidative stress and mitochondrial dysfunction across broad-ranging pathologies: toward mitochondria-targeted clinical strategies

Beyond the disorders recognized as mitochondrial diseases, abnormalities in function and/or ultrastructure of mitochondria have been reported in several unrelated pathologies. These encompass ageing, malformations, and a number of genetic or acquired diseases, as diabetes and cardiologic, haematologic, organ-specific (e.g., eye or liver), neurologic and psychiatric, autoimmune, and dermatologic disorders. The mechanistic grounds for mitochondrial dysfunction (MDF) along with the occurrence of oxidative stress (OS) have been investigated within the pathogenesis of individual disorders or in groups of interrelated disorders. We attempt to review broad-ranging pathologies that involve mitochondrial-specific deficiencies or rely on cytosol-derived prooxidant states or on autoimmune-induced mitochondrial damage. The established knowledge in these subjects warrants studies aimed at elucidating several open questions that are highlighted in the present review. The relevance of OS and MDF in different pathologies may establish the grounds for chemoprevention trials aimed at compensating OS/MDF by means of antioxidants and mitochondrial nutrients.

Correlation between superoxide dismutase 1 and 2 polymorphisms and susceptibility to oral squamous cell carcinoma

Oxidative stress is significant in numerous types of cancer. Tobacco smoke, an important risk factor for oral squamous cell carcinoma (OSCC), is able to generate reactive oxygen species (ROS) and cause oxidative DNA damage. Superoxide dismutase (SOD) is an endogenous antioxidant enzyme that is critical in limiting the oxidative burden effectively. The purpose of this study was to investigate the effects of the mitochondrial SOD2 and Cu/Zn enzyme SOD1 gene polymorphisms on the susceptibility to and clinicopathological characteristics of OSCC, as well as the synergistic effect between these gene polymorphisms and the well-known risk factor of tobacco consumption. Patients with clinically diagnosed OSCC (n=362) and healthy normal individuals (n=358) were investigated for four single nucleotide polymorphisms (SNPs; rs4880, rs5746136, rs1804450 and rs11556620) by polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing methods. Following adjustment for other confounders, no significant difference was observed in the rs5746136 SOD2 SNPs between the patients and controls. However, the incidence of the CT genotype of SOD2 SNP rs4880 was higher in the patients than in normal subjects in the additive model [CT vs. TT; P=0.045; adjusted odds ratio (AOR)=1.484; 95% confidence interval (CI), 1.009–2.182] and in the dominant model (CT/CC vs. TT; P=0.022; AOR=1.559; 95% CI, 1.067–2.278). For those who smoked, the incidence of the CT genotype of rs4880 increased markedly in the patients compared with the controls in the additive model (CT vs. TT; P=0.003; AOR=2.325; 95% CI, 1.330–4.064) and in the dominant model (CT/CC vs. TT; P=0.001; AOR=2.448; 95% CI, 1.417–4.230). For SOD1, polymorphisms at rs1804450 and rs11556620 were not present in any of the OSCC or control subjects. The results suggest that SOD2 rs4880 may be involved in the tumorigenesis of OSCC and may be useful as a genetic susceptibility marker for OSCC.

Oxidative and antioxidative mechanisms in oral cancer and precancer: a review

Development of cancer in humans is a multistep process. Complex series of cellular and molecular changes participating in cancer development are mediated by a diversity of endogenous and exogenous stimuli and important amongst this is generation of reactive oxygen species (ROS). Reactive radicals and non-radicals are collectively known as ROS. These can produce oxidative damage to the tissues and hence are known as oxidants in biological system. Many researchers have documented the role of ROS in both initiation and promotion of multistep carcinogenesis. To mitigate the harmful effects of free radicals, all aerobic cells are endowed with extensive antioxidant defence mechanisms. Lowered antioxidant capacity or the oxidant-antioxidant imbalance can lead to oxidative damage to cellular macromolecules leading to cancer. Oral cavity cancer is an important cancer globally and tobacco is the primary etiological factor in its development. Tobacco consumption exposes the oral epithelium to toxic oxygen and nitrogen free radicals that can affect host antioxidant defence mechanisms. Elevated levels of ROS and Reactive Nitrogen Species (RNS) and lowered antioxidants are found in oral precancer and cancer. Protection can be provided by various antioxidants against deleterious action of these free radicals. Treatment with antioxidants has the potential to prevent, inhibit and reverse the multiple steps involved in oral carcinogenesis. This review is an attempt to understand the interesting correlation between ROS and RNS mediated cell damage and enzymatic and non-enzymatic defence mechanisms involved in oral cancer development and its progression and the use of antioxidants in oral cancer prevention and treatment.

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.

Elevated snail expression mediates tumor progression in areca quid chewing-associated oral squamous cell carcinoma via reactive oxygen species

BACKGROUND

Snail is an important transcription factor implicated in several tumor progression and can be induced by reactive oxygen species (ROS). Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). Therefore, we hypothesize that the major areca nut alkaloid arecoline may induce Snail via ROS and involve in the pathogenesis of areca quid chewing-associated OSCC.

METHODOLOGY/PRINCIPAL FINDING

Thirty-six OSCC and ten normal oral epithelium specimens were examined by immunohistochemistry and analyzed by the clinico-pathological profiles. Cytotoxicity, 2', 7'-dichlorofluorescein diacetate assay, and western blot were used to investigate the effects of arecoline in human oral keratinocytes (HOKs) and oral epithelial cell line OECM-1 cells. In addition, antioxidants N-acetyl-L-cysteine (NAC), curcumin, and epigallocatechin-3 gallate (EGCG) were added to find the possible regulatory mechanisms. Initially, Snail expression was significantly higher in OSCC specimens (p<0.05). Elevated Snail expression was associated with lymph node metastasis (p = 0.031) and poor differentiation (p = 0.017). Arecoline enhanced the generation of intracellular ROS at the concentration higher than 40 µg/ml (p<0.05). Arecoline was also found to induced Snail expression in a dose- and time-dependent manner (p<0.05). Treatment with NAC, curcumin, and EGCG markedly inhibited arecoline induced Snail expression (p<0.05).

CONCLUSION/SIGNIFICANCE

Our results suggest that Snail overexpression in areca quid chewing-associated OSCC is associated with tumors differentiation and lymph node metastasis. Arecoline-upregulated Snail expression may be mediated by ROS generation. In addition, arecoline induced Snail expression was downregulated by NAC, curcumin, and EGCG.

Nitric oxide and cancer: a review

Nitric oxide (NO), is a ubiquitous, water soluble, free radical gas, which plays key role in various physiological as well as pathological processes. Over past decades, NO has emerged as a molecule of interest in carcinogenesis and tumor growth 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 which depend on its timing, location, and concentration. NO has been suggested to modulate different cancer-related events including angiogenesis, apoptosis, cell cycle, invasion, and metastasis. On the other hand, it is also emerging as a potential anti-oncogenic agent. Strategies for manipulating in vivo production and exogenous delivery of this molecule for therapeutic gain are being investigated. However, further validation and experimental/clinical trials are required for development of novel strategies based on NO for cancer treatment and prevention. This review discusses the range of actions of NO in cancer by performing an online MEDLINE search using relevant search terms and a review of the literature. Various mechanisms by which NO acts in different cancers such as breast, cervical, gastric,colorectal, and head and neck cancers are addressed. It also offers an insight into the dichotomous nature of NO and discusses its novel therapeutic applications for cancer prevention and treatment.

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.