Assessment of preventive effect of melatonin on conversion of oral premalignant lesions to squamous cell carcinoma: An animal study on mice

There is a direct association between survival rate of patients with oral cancer and the stage of the disease at the time of diagnosis. Early preventive actions which stall the progression or reversethe malignant lesions are very important. Different studies have shown the preventive effect of melatonin on progression of skin cancers, fibrosarcoma, endometrial carcinoma and protective effect on hepatocarcinogenesis. The aim of this study was to assess the effect of melatonin in preventing the progression of oral premalignant lesions to malignant lesions and squamous cell carcinoma (SCC). In order to induction of premalignant lesions, all subjects were received 50 mg/ml water-soluble carcinogen 4-nitroquinoline-1-oxide for 14 weeks. Then subjects were divided into 3 groups each containing 8 mice.Group 1 received 2 mg/L, group 2 received 20 mg/L melatonin in drinking water, and group 3 received only water without melatonin as the control group. In week 22, all mice were euthanized; their tongues were totally removed and photographs were taken from all visible lesions. Samples were evaluated to determine dysplasia. Statistical analysis was performed with SPPS statistics version 15 using descriptive analysis (mean, standard deviation, mode, frequency). Kruskal-Wallis test was used to compare the mean differences between study groups, and if the difference was significant, chi-square test was performed. A p value of less than 0.05 was considered statistically significant. Our study findings showed that melatonin couldregress the progression of malignant lesions by reducing its size. Moreover it was found that melatonin is significantly more effective on reducing the size of lesions at lower doses (2 mg/L). Although the dysplastic grade and thenumber of lesions were decreased in melatonin recipient groups, but the difference was not statistically significant. The current study has shown that melatonin dose-dependently reduces the size and diameter of malignant lesions.