茶对二甲基苯并蒽诱发金黄色地鼠口腔癌预防作用的研究

选用二甲基苯并蒽（ Ｄ Ｍ Ｂ Ａ）诱发的金黄色地鼠口腔癌模型，研究绿茶、茶色素和混合茶对口腔癌的预防作用，并探讨其防癌机制。试验设阳性对照组（局部涂０５％ Ｄ Ｍ Ｂ Ａ，每周３次，共１５周）、３个饮茶试验组（在涂 Ｄ Ｍ Ｂ Ａ２周前开始分别饮１５％ 绿茶、０１％ 茶色素和０５％ 混合茶至１５周实验结束）和阴性对照组（仅涂丙酮）。结果表明，与阳性对照组相比，绿茶、茶色素和混合茶组对平均瘤数目的抑制率分别为４２６％ 、５０８％ 和６７２％ ，平均瘤负荷抑制率分别为７９４％ 、８８５％ 和９５５％ ；在３组中以混合茶对口腔癌的抑制效果最强。在涂 Ｄ Ｍ Ｂ Ａ 后的第６、１０和１５周，３个茶试验组中均见到口腔上皮细胞微核形成，每核银染核仁组织区（ Ａｇ Ｎ Ｏ Ｒ）颗粒数目和表皮生长因子受体（ Ｅ Ｇ Ｆ Ｒ）的表达低于阳性对照组。表明饮茶对 Ｄ Ｍ Ｂ Ａ 诱发的动物口腔癌有明显的预防作用，而茶预防 Ｄ Ｍ Ｂ Ａ 引起的粘膜细胞 Ｄ Ｎ Ａ 损伤和抑制粘膜细胞增殖可能是其预防口腔癌的重要作用机制。

Effects of tea on DMBA-induced oral carcinogenesis in hamsters]

The preventive effects of green tea, tea pigments and mixed tea (a composite of whole water extract from green tea, tea polyphenols, and tea pigments) on 7, 12-dimethylbenz(a) anthracene(DMBA)-induced oral carcinogenesis in golden Syrian hamsters were studied. The hamsters were divided into five groups. i.e. the positive control group(the right buccal pouches of animal was topically treated with 0.5% DMBA in acetone three times per week for 15 weeks), three tea treated groups(1.5% green tea, 0.1% tea pigments and 0.5% mixed tea as the sole source of drinking water from two weeks before starting the DMBA treatment to the end of the experiment) and the negative control group(acetone applied topically). The results showed that in the 1.5% green tea, 0.1% tea pigments and 0.5% mixed tea groups, the inhibitory rates of the average number of tumor per hamster were 42.6%, 50.8% and 67.2% respectively, and the mean tumor burdens were 79% 89% and 95% respectively, compared with the positive control group. In the three tea groups, the frequency of micronucleated cells, the number of silver-stained nucleolar organizer regions (AgNOR), labeling index of proliferating cell nuclear antigen(PCNA) and the level of epidermal growth factor receptor(EGFR) expression in the oral mucosa cells were also less than those in the positive control group. These results clearly indicated that the mixed tea could effectively inhibit DMBA-induced oral carcinogenesis in hamsters. The mixed tea was more effective than green tea or tea pigments in this animal model. Protection of DNA from damage by carcinogen and suppression of cell proliferation was considered as important mechanisms of the anticarcinogenic effects of the mixed tea preparations.