Comparison of the Carcinogenic Potential of Smokeless Tobacco and Smoked Tobacco by Quantifying the Excretion of Nicotine Metabolite NNAL in Patients with Oral Leukoplakia

From cultivation to cancer: formation of N-nitrosamines and other carcinogens in smokeless tobacco and their mutagenic implications

Tobacco use is a major cause of preventable morbidity and mortality globally. Tobacco products, including smokeless tobacco (ST), generally contain tobacco-specific N-nitrosamines (TSNAs), such as N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-butanone (NNK), which are potent carcinogens that cause mutations in critical genes in human DNA. This review covers the series of biochemical and chemical transformations, related to TSNAs, leading from tobacco cultivation to cancer initiation. A key aim of this review is to provide a greater understanding of TSNAs: their precursors, the microbial and chemical mechanisms that contribute to their formation in ST, their mutagenicity leading to cancer due to ST use, and potential means of lowering TSNA levels in tobacco products. TSNAs are not present in harvested tobacco but can form due to nitrosating agents reacting with tobacco alkaloids present in tobacco during certain types of curing. TSNAs can also form during or following ST production when certain microorganisms perform nitrate metabolism, with dissimilatory nitrate reductases converting nitrate to nitrite that is then released into tobacco and reacts chemically with tobacco alkaloids. When ST usage occurs, TSNAs are absorbed and metabolized to reactive compounds that form DNA adducts leading to mutations in critical target genes, including the RAS oncogenes and the p53 tumor suppressor gene. DNA repair mechanisms remove most adducts induced by carcinogens, thus preventing many but not all mutations. Lastly, because TSNAs and other agents cause cancer, previously documented strategies for lowering their levels in ST products are discussed, including using tobacco with lower nornicotine levels, pasteurization and other means of eliminating microorganisms, omitting fermentation and fire-curing, refrigerating ST products, and including nitrite scavenging chemicals as ST ingredients.

Plasma metabolite profiling and chemometric analyses of tobacco snuff dippers and patients with oral cancer: Relationship between metabolic signatures

BACKGROUND

Cancer of oral cavity is a seriously growing problem in many parts of the world. In Indian subcontinent, most of these cases have been attributed to the use of tobacco-related products. This study is focused on the identification of distinguishing metabolites of oral cancer in comparison with tobacco snuff dippers and healthy controls.

METHODS

A total of 234 plasma samples including 62 healthy controls, 81 tobacco snuff dippers, and 91 oral cancer samples were analyzed using mass spectrometry.

RESULTS

Twenty-nine of 3326 metabolites were found to distinguish among oral cancer, tobacco snuff dippers, and healthy controls using P-value ≤.001 and fold change ≥3. Prediction model was generated with an overall accuracy of 89.3%. Two metabolites, that is, stearyl alcohol and sucrose, can be used as predictive biomarkers showing progression of tobacco snuff dippers toward oral cancer.

CONCLUSION

The unique metabolite profile gives evidence of a strong correlation between tobacco snuff dipping and oral cancer.

Oral leukoplakia - is biopsy at the initial appointment a must?

BACKGROUND

Oral leukoplakia is a potentially malignant disorder of the oral cavity. Leukoplakias with chances of undergoing malignant transformation owing to the presence of dysplastic changes may not be clinically distinguishable from leukoplakias without dysplasia. The study was carried out to evaluate the usefulness of biopsy in assessing the clinico-pathologic correlations of oral leukoplakia at the patient's initial visit.

MATERIALS AND METHODS

Hospital records with clinical diagnosis of oral leukoplakia were retrospectively analysed. All these patients had undergone biopsy in their initial visit. Histopathological slides were reviewed and reported by a single pathologist. Diagnosis agreement was considered to be present if the clinical diagnosis matched the histopathological diagnosis. Misdiagnosis was considered if the clinical diagnosis did not match the histopathological diagnosis and underdiagnosis when malignancy was detected on histopathological examination.

RESULTS

A total of 115 patients were clinically diagnosed with oral leukoplakia. According to clinical appearance of the leukoplakia patch was categorized in to three types viz homogeneous leukoplakia (n= 24 i.e. 20.87%), speckled leukoplakia (n=76 i.e. 66.08%) and verrucous leukoplakia (n=15 i.e. 13.04%). Histopathological examination confirmed clinical diagnosis in 88 cases (a diagnosis agreement of 76.52%). Histopathological examination of 19 cases revealed a different diagnosis, thus categorized as misdiagnosis (16.52%) and 8 cases had unexpected malignancy which accounted for underdiagnosis in 6.96% cases. There was dysplasia in 45 (51.13%) of the histopathologically confirmed cases of leukoplakia.

CONCLUSION

The clinical appearance of suspicious white lesions does not provide a true nature of its disease status and malignant changes may be missed.