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Leukoplakia is well known as a precancerous lesion of oral squamous cell carcinoma. Therefore, it is important to treat leukoplakia for preventing patients from oral cancer. In this study, we analyzed effects of green tea extract (GTE) on eight human oral cancer cell lines. Thereafter, we applied a GTE ointment for oral leukoplakia and investigated efficacy and histopathological changes.

IC50s of GTE and GTE ointment on eight cell lines ranged between 74.1 and 313 ug/ml and between 21.8 and 77.9 ug/ml, respectively. Thus, GTE ointment was more effective than GTE in vitro. From these results, we produced 10% GTE ointment and applied it to patients.

Ten consenting patients with oral leukoplakia after histopathologic examination of biopsy material (6 men and 4 women) between August 2005 and January 2006 were treated with 0.5 g of a 10% GTE ointment for at least 60 days by applying to the affected area three times a day. Each lesion was monitored macroscopically. The serum concentration of catechin was measured before, during, and after administration. In addition, biopsy was performed before and after administration, and immunohistochemical techniques (ki-67LI ) were used to ascertain changes in cellular proliferation and apoptosis. No clinical or laboratory adverse reactions were seen during or after administration. Macroscopic observations revealed leukoplakia disappeared, reduction or thinning of leukoplakia in four patients. The serum concentration of EGCg increased immediately after administration and remained high throughout the administration period. When leukoplakia disappeared histopathologically, the new oral tissue was histologically healthy, and even when leukoplakia did not disappear, favorable changesin ki-67LI occurred before and after administration. These findings suggest the effectiveness of local GTE administration in the treatment of oral leukoplakia.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA