[A study on effect of mechanical irritation in development and progression of tongue cancer]

It is considered that the mechanical irritation acts as an inducer in the canceration process of tongue cancer. The purpose of this study was to clarify the effect of mechanical irritation on the development and progression of tongue cancer. Leukoplakia and cancer were produced on the hamster tongue by paratripsis and applying 1% DMBA acetone solution 3 times per week for 8 or 10 weeks, and there after only paratripsis was continued. The effect of mechanical irritation was examined histopathologically. The intensity of DNA damage caused by mechanical irritation was investigated by measuring the activity of Poly (ADP-ribose) polymerase (PADPRP), which is an enzyme associated with DNA damage. After carcinogenic treatment, canceration of leukoplakia and early carcinoma progressed into become advanced carcinoma histopathologically by mechanical irritation only. In the precancerous condition, active oxygen was found in part of the subepitherial inflammatory cell infiltration and in part of the cancer cells of carcinoma. The activity of PADPRP increased during the scratching period. These results suggest that the mechanical irritation acts accelatively in canceration and progression of tongue cancer and causes DNA damage.