Antitumor initiating potential of rosmarinic acid in 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch carcinogenesis.

Oral cancer accounts for 40%-50% of all cancers in India. Tobacco and alcohol are the major etiological factors contributing to its pathogenesis. The aim of the present study was to explore the key mechanism behind the inhibitory effects of rosmarinic acid against 7,12-dimethylbenz(a)anthracene (DMBA)-induced oral carcinogenesis by evaluating the status of biochemical markers (lipid peroxidation, antioxidants, and detoxification enzymes) and immunoexpression patterns of p53 and bcl-2 proteins. Oral tumors were developed by painting the buccal pouches of golden Syrian hamsters with 0.5% DMBA in liquid paraffin 3 times a week for 14 weeks. We noticed 100% tumor formation in hamsters treated with DMBA alone, and the tumors were histopathologically confirmed as well-differentiated squamous cell carcinoma. Oral administration of rosmarinic acid (100 mg/kg body wt) to DMBA-treated hamsters completely prevented the tumor formation. In addition, rosmarinic acid significantly returned the status of biochemical and molecular markers to near normal range in DMBA-treated hamsters. The results of the present study suggest that rosmarinic acid suppresses oral carcinogenesis by stimulating the activities of detoxification enzymes, improves the status of lipid peroxidation and antioxidants, and downregulates the expression of p53 and bcl-2 during DMBA-induced oral carcinogenesis.