Evaluation of DNA damage in oral precancerous and squamous cell carcinoma patients by single cell gel electrophoresis.

Context: Single cell gel electrophoresis (SCGE) or "comet assay" is a rapid and very sensitive fluorescent microscopic method for detecting various forms of DNA damage at individual cell level. Aims: The aim of the present study was to detect the extent of DNA damage in oral cancer, oral submucous fibrosis (OSMF) and leukoplakia in comparison to normal individual. Settings and Design: A total of 44 consecutive patients with oral cancer (n=26), leukoplakia (n=12) and OSMF (n=6) and 10 healthy normal volunteers with normal oral epithelia (controls) were recruited from Dr. R. Ahmed Dental College and Hospital and were assessed for the extent of DNA damage using SCGE following clinical diagnosis. Materials and Methods: Peripheral blood was collected by venepuncture and comet assay was performed using SCGE. Mean tail length was compared between diagnostic groups and between different oral habit groups using t-tests and analysis of variance (ANOVA). Pearson's product moment correlation was used to examine the linear association between the extent of DNA damage and oral habit pack-years. Scheffe's pair-wise test was employed to adjust for multiple comparisons. Results: None of the controls were associated with any oral habits. Mean (±SD) tail lengths (in mm) for cancer (24.95 ± 5.09) and leukoplakia (12.96 ± 2.68) were significantly greater than in controls (8.54 ± 2.55, P<0.05). After adjustment, well-, moderately, and poorly differentiated carcinomas had significantly greater tail length than controls. Whereas the extent of DNA damage in cancer cases was significantly greater in leukoplakia than in compared to OSMF (11.03 ± 5.92), the DNA damage in latter was not different from controls. DNA damage for people with any oral habit (19.78 ± 7.77) was significantly greater than those with no habits (8.54 ± 2.55; P<0.0001). Conclusions: DNA damage measured by SCGE is greater in leukoplakia and squamous cell carcinoma, but not in OSMF. Deleterious oral habits are also associated with greater DNA damage.