Genotoxic effects of tobacco use in residents of hilly areas and foot hills of Western Ghats, Southern India

Smoking and smokeless tobacco consumption is a significant risk factor that provokes genetic alterations. The present investigation was to evaluate the biomarkers of genotoxicity including micronucleus (MN), chromosome aberrations (CA) and DNA strand breaks among tobacco consumers and control individuals residing in hilly areas of Western Ghats, Tamilnadu, South India. This study included 268 tobacco consumers with equal number of controls. The tobacco consumers were divided into Group I (<10 years of tobacco consumption with an age range from 15 to 35 years) and group II (>10 years consumption above 35 years of age). Chromosome aberration (CA) and comet assay were performed using blood and micronucleus assay from exfoliated buccal epithelial cells obtained from tobacco consumers and controls. Elevated levels of CA were found in group II (Chromatid type: 2.39 ± 1.13 and chromosome type: 1.44 ± 1.24) exposed subjects, high micronucleus and DNA damage (TL:4.48 ± 1.24 and TM:3.40 ± 1.58) levels were significantly (p < 0.05) observed in both smoking and smokeless tobacco consumers when comparison with group I and controls. This study also observed a lack of awareness among the tobacco consumers about the harmful health effects of tobacco. Tobacco consumption contributes to the significant alteration in genetic materials. In addition, a high rate of spontaneous abortion was also seen in the studied population.

Assessment of genotoxic and molecular mechanisms of cancer risk in smoking and smokeless tobacco users

Inexpensive forms of tobacco are widely used in developing countries such as India. We have evaluated genotoxicity endpoints (chromosome aberrations, micronucleus frequency, comet assay) and polymorphisms of the XRCC1 and p53 genes among smokers and smokeless tobacco (SLT) users in rural Tamilnadu, South India. Cytogenetic, DNA damage and SNP analyses were performed on peripheral blood samples; micronucleus frequency was measured in peripheral blood and buccal mucosa exfoliated cells. Both categories of tobacco users had elevated levels of genotoxic damage. SNP analysis of tobacco users revealed that 17% carry the XRCC1 gln399gln genotype and 19% carry the p53 pro72pro genotype. Both genotypes are associated with increased risk of cancer.

Genotoxicity assessment in smokeless tobacco users: a case-control study

India has a long history of tobacco, which includes chewing tobacco and smoking tobacco in various forms. Initially, the smokeless tobacco chewing habit was seen among the majority of the farmers who cultivated tobacco; but in recent years, smokeless tobacco is available in many forms and is cheaper as well and hence it is widely being used among literate and illiterate people. The subjects of our study are living in hilly regions of Yerkaud in Salem district, South India. Most of the inhabitants of our study area are illiterate and more particularly they are unaware of the health effects due to tobacco use. Recent epidemiological reports have strongly indicated the association of cancer risk with usage of smokeless tobacco. The prime aim of our study is to evaluate the genotoxic effects of tobacco use by analysing the cytogenetic end points such as chromosome aberrations in peripheral blood and micronucleus in peripheral blood and buccal cells. About 85 smokeless tobacco users were enrolled for the study and same numbers of age- and sex-matched nontobacco users were also enrolled to serve as controls. The result of our study revealed that tobacco users displayed varied levels of elevated chromosomal damage and micronucleated cells than nontobacco users. The variation in the extent of genetic damage was dependent on the duration of the tobacco use. In conclusion, this study might be helpful in creating awareness on the hazards of the smokeless tobacco products among the global population as a whole for those who chose such products as a cheap alternative to tobacco smoke.

XRCC1 gene variants and possible links with chromosome aberrations and micronucleus in active and passive smokers

Tobacco addiction is a major risk for diseases such as cancers, heart attack, etc. Tobacco smoke constitutes environmental toxins that are the major preventable leading cause of death worldwide. We investigated the influence of tobacco smoke on cytogenetic parameters (chromosomal aberrations and micronuclei) and the influence of XRCC1 arg399gln polymorphism on the cytogenetic parameters of the exposed subjects. The cases for this study include active and passive smokers. They were divided into three groups in accordance with duration of exposure to tobacco smoke. We observed changes in the frequency of chromosomal aberrations and micronuclei among the exposed subjects and controls. Of the three groups of exposed subjects, group III of active smokers and group III of passive smokers showed higher number of chromosomal aberrations and micronuclei when compared to controls, group I and group II of active and passive smokers. The XRCC1 arg399gln polymorphic variant gln/gln, influenced the extent of genotoxic damage in chromosomes and frequency of in micronuclei the three variants (arg/arg, arg/gln and gln/gln), gln/gln harbored significantly (P<0.05) higher number of aberrations than the arg/arg and arg/gln. In this context, the results observed in our study indicated that the single nucleotide polymorphism on XRCC1codon 399 influenced the frequencies of chromosomal aberrations and micronuclei.

No association between the Trp53 codon 72 polymorphism and head and neck cancer: a case-control study in a South Indian population

Genetic polymorphisms are important for predispositions to several human cancers. In the tumour suppressor Trp53 gene, a codon 72 polymorphism is frequent in the form of a single nucleotide polymorphism that leads to substitution of an arginine for a proline. In the present study, we analysed the association of Trp53 codon 72 polymorphs with head and neck cancer through a case-control study approach with PCR-RFLP of DNA from blood of 47 clinically confirmed patients and 52 healthy controls. The Pro (Trp5372P) and Arg (Trp5372R) allele frequencies in the healthy controls were 0.44 and 0.56, and not significantly different from those in the cancer patients at 0.56 and 0.44. The genotype distribution in the controls was 32.7% Arg/Arg, 46.2% Arg/Pro and 21.2% Pro/Pro and in the cancer patients 17.0% Arg/Arg, 53.2% Arg/Pro and 29.8% Pro/Pro. No significant difference in the distribution of genotypes between head and neck cancer patients and healthy controls (P=0.18, χ2 test) was observed. We conclude no association of Trp53 codon 72 polymorphism was observed with head and neck cancer susceptibility.