Chromosome damaging effects of pan masala

Management of early oral cavity squamous cancers

Early oral cavity cancers comprise a favorable entity, amenable to clinical staging and single modality treatment. Surgery typically forms the mainstay of treatment and should ideally address both the primary and the neck in all cases. Careful attention must be paid to reconstruction and rehabilitation of such patients. Radical radiotherapy mainly in the form of brachytherapy can achieve excellent disease related and functional outcomes in a carefully chosen subset of patients. Increasingly, a subset of patients is being recognized, who harbor single or multiple adverse features on histopathology and may therefore benefit from escalation of adjuvant therapy. This review discusses the management of early oral cavity squamous carcinomas (Early OSCCs) in detail and highlights the dilemmas and controversies faced in the management of the same.

Smokeless tobacco (paan and gutkha) consumption, prevalence, and contribution to oral cancer

Smokeless tobacco consumption, which is widespread throughout the world, leads to oral submucous fibrosis (OSMF), which is a long-lasting and devastating condition of the oral cavity with the potential for malignancy. In this review, we mainly focus on the consumption of smokeless tobacco, such as paan and gutkha, and the role of these substances in the induction of OSMF and ultimately oral cancer. The list of articles to be examined was established using citation discovery tools provided by PubMed, Scopus, and Google Scholar. The continuous chewing of paan and swallowing of gutkha trigger progressive fibrosis in submucosal tissue. Generally, OSMF occurs due to multiple risk factors, especially smokeless tobacco and its components, such as betel quid, areca nuts, and slaked lime, which are used in paan and gutkha. The incidence of oral cancer is higher in women than in men in South Asian countries. Human oral epithelium cells experience carcinogenic and genotoxic effects from the slaked lime present in the betel quid, with or without areca nut. Products such as 3-(methylnitrosamino)-proprionitrile, nitrosamines, and nicotine initiate the production of reactive oxygen species in smokeless tobacco, eventually leading to fibroblast, DNA, and RNA damage with carcinogenic effects in the mouth of tobacco consumers. The metabolic activation of nitrosamine in tobacco by cytochrome P450 enzymes may lead to the formation of N-nitrosonornicotine, a major carcinogen, and micronuclei, which are an indicator of genotoxicity. These effects lead to further DNA damage and, eventually, oral cancer.

Panmasala chewing induces deterioration in oral health and its implications in carcinogenesis

ABSTRACT Panmasala containing tobacco was introduced in the Indian market during the 1970s. Panmasala consists of areca nut (betel nut), catechu, lime, cardamom, spices, and unspecified flavoring agents, etc., with tobacco locally known as gutkha or without tobacco (Plain or sada), and consumed abundantly in India and also other parts of the world, predominantly in South East Asian countries. Available studies demonstrate that the habits of chewing panmasala gutkha or plain by students and adolesescents are on the increase, which may lead to deterioration of oral health and other organ systems. Based on the experimental as well as clinical studies available on panmasala as well as on different components of panmasala, this review suggests that it has the potential in causation of various oral diseases such as Oral Sub Mucosis Fibrosis (OSMF) and leucoplakia which may lead to oral cancer. Studies reviewed on these chewing mixtures also reveal that it is likely to be carcinogenic, as tobacco and areca nut have carcinogenic potential and both have encompassing addictive potential leading to dependence on chewing mixture containing areca nut and tobacco. These mixtures might not only lead to cancer but may also affect other organs of the body, including oral hard tissues in the form of dental attrition and sensitivity. There is a need to consider the potential health hazards associated with the habits of these products, especially oral cancer. More research is needed to find out early changes which could be reversible and also intervention measures through education to desist people in indulging in such habits.

Association of betel nut with carcinogenesis: revisit with a clinical perspective

Betel nut (BN), betel quid (BQ) and products derived from them are widely used as a socially endorsed masticatory product. The addictive nature of BN/BQ has resulted in its widespread usage making it the fourth most abused substance by humans. Progressively, several additives, including chewing tobacco, got added to simple BN preparations. This addictive practice has been shown to have strong etiological correlation with human susceptibility to cancer, particularly oral and oropharyngeal cancers.

The PUBMED database was searched to retrieve all relevant published studies in English on BN and BQ, and its association with oral and oropharyngeal cancers. Only complete studies directly dealing with BN/BQ induced carcinogenesis using statistically valid and acceptable sample size were analyzed. Additional relevant information available from other sources was also considered.

This systematic review attempts to put in perspective the consequences of this widespread habit of BN/BQ mastication, practiced by approximately 10% of the world population, on oral cancer with a clinical perspective. BN/BQ mastication seems to be significantly associated with susceptibility to oral and oropharyngeal cancers. Addition of tobacco to BN has been found to only marginally increase the cancer risk. Despite the widespread usage of BN/BQ and its strong association with human susceptibility to cancer, no serious strategy seems to exist to control this habit. The review, therefore, also looks at various preventive efforts being made by governments and highlights the multifaceted intervention strategies required to mitigate and/or control the habit of BN/BQ mastication.

Evaluation of in vitro assays for assessing the toxicity of cigarette smoke and smokeless tobacco

BACKGROUND

In vitro toxicology studies of tobacco and tobacco smoke have been used to understand why tobacco use causes cancer and to assess the toxicologic impact of tobacco product design changes. The need for toxicology studies has been heightened given the Food and Drug Administration's newly granted authority over tobacco products for mandating tobacco product performance standards and evaluate manufacturers' health claims about modified tobacco products. The goal of this review is to critically evaluate in vitro toxicology methods related to cancer for assessing tobacco products and to identify related research gaps.

METHODS

PubMed database searches were used to identify tobacco-related in vitro toxicology studies published since 1980. Articles published before 1980 with high relevance also were identified. The data were compiled to examine (a) the goals of the study, (b) the methods for collecting test substances, (c) experimental designs, (d) toxicologic end points, and (e) relevance to cancer risk.

RESULTS

A variety of in vitro assays are available to assess tobacco smoke that address different modes of action, mostly using non-human cell models. However, smokeless tobacco products perform poorly in these assays. Although reliable as a screening tool for qualitative assessments, the available in vitro assays have been poorly validated for quantitative comparisons of different tobacco products. Assay batteries have not been developed, although they exist for nontobacco assessments. Extrapolating data from in vitro studies to human risks remains hypothetical.

CONCLUSIONS

In vitro toxicology methods are useful for screening toxicity, but better methods are needed for today's context of regulation and evaluation of health claims.

Evaluation of genotoxicity of pan masala employing chromosomal aberration and micronucleus assay in bone marrow cells of the mice

Pan masala is commonly consumed in south-east Asian and other oriental countries as an alternate of tobacco chewing and smoking. Genotoxic potential of pan masala (pan masala plain and pan masala with tobacco known as gutkha) was evaluated employing chromosome aberration (CA) and micronucleus (MN) assay in vivo. Animals were exposed to three different doses (0.5%, 1.5% and 3%) of pan masala plain (PMP) and gutkha (PMT) through feed for a period of 6 months and micronucleus and chromosomal aberrations were studied in the bone marrow cells. Induction of mean micronuclei in polychromatic erythrocytes (MNPCE) and normochromatic erythrocyte (MNNCE) was higher in both types of pan masala treated groups with respect to control group. Both pan masala plain and gutkha treatment significantly induced the frequency of MNPCE and MNNCE in the bone marrow cells, indicating the genotoxic potential. Furthermore, slight decline in the ratio of polychromatic erythrocytes to normochromatic erythrocytes was also noticed, suggesting the cytotoxic potential even though the ratio was statistically non significant. A dose-dependent, significant increase in chromosome aberration was observed in both types of pan masala treated mice with respect to control. However, no significant difference in micronucleus and chromosomal aberration induction was noticed between two types of pan masala exposed (PMP and PMT) groups. Results suggest that both types of pan masala, i.e. plain and gutkha, have genotoxic potential.

Expression of NF-kappaB parallels COX-2 expression in oral precancer and cancer: association with smokeless tobacco

Nuclear Factor-kappaB (NF-kappaB) activation and COX-2 overexpression have been reported in head and neck cancer, but the relationship between these proteins remains to be investigated. To determine the relationship between NF-kappaB and COX-2 in Smokeless Tobacco (ST) associated oral tumorigenesis, we performed immunohistochemistry in serial sections from 107 OSCCs, 78 oral precancerous lesions (OPLs) (58 hyperplasias, 20 dysplasias) and 15 histologically normal oral tissues and correlated with clinicopathological data. Significant increase in NF-kappaB and COX-2 immunopositivity was observed from normal oral mucosa to OPLs to OSCCs (p = 0.009 and p = 0.002 respectively). Upregulation of NF-kappaB and COX-2 was observed as early as in hyperplasia [p = 0.006; OR = 6.1 and p = 0.003; OR = 7.6, respectively]. Expression of both proteins was found to be significantly associated in OPLs (p = 0.000; OR = 12.6) and OSCCs (p = 0.001; OR = 4.0). Intriguingly, khaini consumption correlated with NF-kappaB immunopositivity in OPLs (p = 0.05, OR = 3.8) and OSCCs (p = 0.01, OR = 3.4) and with COX-2 expression in OPLs (p = 0.03; OR = 4.3). In vitro experimental system of ST associated oral carcinogenesis was used to demonstrate ST (khaini) and NNK mediated activation of NF-kappaB and COX-2, supporting the clinical data. In conclusion, this study demonstrates correlation between over expression of NF-kappaB and COX-2 in early precancerous stages of development of oral cancer and sustained elevation down the tumorigenic pathway, underscoring their potential as targets for early intervention. In vitro studies demonstrated that NNK may be one of the carcinogenic components of ST (khaini) inducing activation of NF-kappaB and COX-2 in oral precancer and cancer cells, suggesting plausible role in ST-induced oral carcinogenesis.

Clinical, pathological, cellular and molecular lesions caused by oral smokeless tobacco - a review

While carcinogenicity of smokeless tobacco (ST) to humans is well established the oral lesions that precede development of cancer are less well characterized. The clinical appearances of ST-associated lesions are variable. Epidemiological studies show a strong significant association of risk with chronic daily use but population differences are noted because of various commercial products in use. Morphological features observed are some what different to oral lesions caused by smoking and oral dysplasia in ST-associated lesions is less common. Effects of ST on oral keratinocytes observed in vitro include alterations in cell proliferation, apoptosis and activation of inflammatory markers. Genetic aberrations caused by ST include activation of ras, uncommon in smokers but mutational hot spots in p53 encountered are similar to those in smokers.

Curcumin down regulates smokeless tobacco-induced NF-κB activation and COX-2 expression in human oral premalignant and cancer cells

Smokeless tobacco (ST) consumption is a major cause of oral cancer in South East Asia including India. Recently, we showed that exposure to smokeless tobacco extract (STE) (khaini) results in increased expression and activation of nuclear factor-kappaB (NF-kappaB) and its downstream target cyclooxygenase-2 (COX-2) in human oral cell systems in vitro. The present study was designed to test the hypothesis that curcumin may inhibit the activation of NF-kappaB in ST exposed oral premalignant and cancer cells. Exposure of oral premalignant and cancer cells to curcumin resulted in significant decrease in cell viability and induced apoptosis. STE-induced nuclear translocation and DNA-binding activity of NF-kappaB were inhibited in curcumin pretreated oral premalignant and cancer cells in vitro. Curcumin treatment led to decreased expression of NF-kappaB and COX-2. The tobacco specific nitrosamine, 4-(methylnitrosamino-)-1-(3-pyridyl)-1-butanone (NNK), is one of the carcinogenic components of STE (khaini). We demonstrate that curcumin pretreatment abrogated NNK-induced activation of NF-kappaB and COX-2 expression, suggesting that NNK is one of the factors in STE (khaini) modulated by curcumin. In conclusion, our findings demonstrate for the first time that curcumin downregulates STE (khaini) or NNK-induced NF-kappaB and COX-2 in oral premalignant and cancer cells in vitro.

Novel molecular targets of smokeless tobacco (khaini) in cell culture from oral hyperplasia

Knowledge of molecular mechanism(s) implicated in smokeless tobacco (ST) associated oral carcinogenesis is meager. In an attempt to identify genes that are modulated by ST, we recently reported establishment of an oral epithelial cell culture, AMOL III from oral hyperplasia with hyperkeratosis of a khaini consumer. Herein we aimed to identify novel molecular targets of ST (khaini) in AMOL III cells using differential display. Fourteen novel differentially expressed genes (12 upregulated and 2 downregulated) were identified. These differentially expressed cDNAs were amplified, cloned, sequenced and confirmed by reverse northern blotting. Mainly these genes are components of transcriptional machinery, cell-cell adhesion, signaling, growth and transformation processes. The important novel molecular targets identified included activated leucocyte cell adhesion molecule (ALCAM), CDP-diacylglycerol-inositol 3-phosphatidyl transferase (phosphatidylinositol synthase), CDIPT, an important enzyme in phosphatidyl inositol biosynthesis, ribosomal protein (RPS23), KIAA0121 and growth and transformation factor, E2IG5. Semi-quantitative RT-PCR analysis of these five genes confirmed over-expression of these genes in oral pre-malignant lesions (OPLs) and oral squamous cell carcinomas (OSCCs) of ST consumers underscoring their biological relevance in ST-associated oral tumorigenesis. In depth studies are warranted to determine the functional significance of ALCAM and CDIPT in oral carcinogenesis.

Smokeless tobacco (khaini) extracts modulate gene expression in epithelial cell culture from an oral hyperplasia

Smokeless tobacco (ST) usage is a growing public health problem worldwide. Exposure to smokeless tobacco is carcinogenic to humans. The molecular mechanism(s) underlying ST associated oral carcinogenesis remain largely unknown. The major challenge is to identify the key factor(s) involved in malignant transformation of oral lesions. Knowledge of these factors will provide candidate diagnostic biomarkers and targets for early intervention. To identify the molecular targets in ST associated oral lesions, we established and purified cultures of epithelial cells (AMOL-III) from an oral leukoplakia with histological evidence of hyperplasia with hyperkeratosis from gingivo-buccal sulcus of a smokeless tobacco (khaini) consumer. Cell cultures were characterized and modulation of gene expression in response to smokeless tobacco extract (STE) was investigated using confocal microscopy and immunoblotting. AMOL-III cells showed altered expression of cell cycle regulators namely p53, p21waf1/cip1, hdm2, proliferation marker Ki67 and transcription factor Ets-1. These cells did not harbor HPV 16/18. No mutation was detected in H-Ras codon 12/13 or in p53 exons 5-9 in AMOL-III cells. STE treatment of these cells resulted in loss of pRb, RARbeta, p21 waf1/cip1 and O6-methyl guanine-DNA methyl transferase (MGMT) while the expression of cyclin D1 was increased. To our knowledge this is the first report to demonstrate that khaini modulates expression of multiple cellular targets including proteins involved in cell cycle regulation and DNA methylation, which may lead the oral epithelial cells down the carcinogenic pathway. This in vitro model system assumes importance in unraveling the cellular and molecular mechanisms implicated in smokeless tobacco associated early oral cancer progression.

Chemical composition and toxicity of Taiwanese betel quid extract

In this genotoxic study, the Ames Salmonella microsome test showed that an aqueous extract of betel quid did not induce mutagenicity in Salmonella typhimurium strains TA98 and TA100. Mammalian cell studies (Chinese hamster ovary K1 cell; CHO-K1 cell) revealed that only higher concentrations (100 and 1000 microg/ml) of aqueous extract weekly increased the frequencies of sister-chromatid exchange (SCE) in the absence of S9. Animal (male Sprague-Dawley rat) studies showed that low-dose feeding (0.53 g dry aqueous extract/kg diet) significantly increased the activities of glutathione (GSH) peroxidase and cytoplasmic glutathione S-transferase (cGST) of liver, high-dose feeding (26.5 g dry aqueous extract/kg diet) lowered the contents of GSH and total glutathione. The effect of an aqueous extract of betel quid on the oxidation of 2'-deoxyguanosine (2'-dG) to 8-hydroxy-2'-deoxyguanosine (8-OH-dG) evaluated that this aqueous extract may act as a pro-oxidant at lower dosage and may be dependent on the iron ions in the model system. However, the aqueous extract of betel quid showed antioxidant activity at higher doses by the ability of the scavenging effect of the hydroxyl radicals.

Observations on the effect of areca nut extracts on oral fibroblast proliferation

The effects of aqueous extracts of raw, baked and boiled areca nuts were tested on cultured human buccal mucosa fibroblasts. Cells were exposed to extract concentrations of 0, 50, 100, 150, 300 and 500 micrograms/ml. The arecoline and arecaidine content was determined in the extracts with HPLC and raw nut contained 5.5% m/m, baked nut 6.6% m/m and boiled nut 7.1% m/m. Extract concentrations of 50 to 150 micrograms/ml inhibited cell growth in a concentration-dependent manner but did not lead to total cell death during a 7 day period. However, total cell death did occur with concentrations of 300 and 500 micrograms/ml. It is concluded that areca nut extract is toxic to cultured fibroblasts and inhibits their proliferation in a concentration-dependent manner.

Pan masala--a genotoxic menace

Cytogenetic markers such as chromosome aberration (CA), sister-chromatid exchange (SCE) and micronucleated cells (MNC) were used to assess the genotoxic potential of dimethyl sulphoxide (DMSO) extract of pan masala with and without tobacco (PM-T and PM). Using in vitro short-term assays, the extracts were tested in the presence or absence of metabolic activation. In cultures without metabolic activation the extracts were found to increase the frequency of all the three parameters tested significantly, however those with activation elicited a weak response, implying that pan masalas contain solvent (DMSO)-soluble direct-acting mutagen.