Risk assessment of oral cancer in patients with pre-cancerous states of the oral cavity using micronucleus test and challenge assay.

Oral cancer is a common malignancy, ranking first among all cancers in Western and Asian countries. Use of tobacco is regarded as a major risk factor, along with age and gender. Oral cancer is preceded by some benign lesions or conditions, which are termed pre-cancerous. Only one-third of people at the pre-cancerous stage of disease succumb to cancer. No biomarker is available to identify people with pre-cancerous lesions or conditions at high risk of developing cancer. The focus of this study was to explore such biomarkers. The study included 129 untreated people with cancer, 138 untreated people at the pre-cancerous stage and 176 control participants. For statistical analysis of this data, analysis of variance and t-test were used. Three biomarkers (i.e. micronucleus test [MNT], comet assay and challenge comet assay were used. MNT and comet assay were carried out on buccal epithelial cells. In addition, challenge comet assay was carried out on peripheral blood leucocytes by using mutagen MNNG sensitivity of DNA after DNA repair. A significant stepwise increase in the DNA damage (basal/MNNG-treated/post-repair) was observed in buccal epithelial cells and peripheral blood leucocytes from control to pre-cancer patients and from pre-cancer to cancer patients. Micronucleus frequency also increased in the same way. Considerable inter-individual and inter-cellular variability in DNA damage was observed, which increased from control to pre-cancer patients and from pre-cancer to cancer patients. The outliers among patients with pre-cancerous states were identified on the basis of more than mean +2 SD limits for comet tail length, as well as mean percentage of micronuclei. Hence, those participants whose cells showed high basal DNA damage, extreme sensitivity to MNNG and reduced repair were identified as high-risk individuals.