Effect of Salivary Epidermal Growth Factor on Hamster Oral Carcinogenesis

表皮生长因子（EGF）是一种多肽激素，由下颌下腺分泌，刺激许多组织中的细胞增殖。它已被证明，表皮生长因子可能会增加皮肤中的甲基胆蒽的致癌潜力，并刺激小鼠乳腺肿瘤的发生。然而，EGF在口腔癌发生中的作用还没有详细研究。本研究以6周龄雄性叙利亚仓鼠为实验动物，用0.5%二甲基-1，2-苯并蒽（DMBA）的矿物油溶液涂于两侧颊囊，每两周一次，共6周，观察涎腺切除对DMBA诱发的仓鼠颊囊肿瘤形成的影响。实验开始后第7周，第2 ~ 4组仓鼠接受涎腺切除术。此后，在第1组和第2组中，每周三次皮下注射0.9% NaCl溶液，持续8周。第3组和第4组分别以0.025mg/Kg和0.25mg/Kg的剂量皮下注射尿抑胃素/EGF，每周三次。16周后终止实验，各组动物体重、肝、肾重量无显著性差异。第1 ~ 4组平均每个颊囊肿瘤数分别为3.4、2.1、2.5个。分别为3.2。组2与组1、组4比较差异有显著性（P<0.05）。在单位颊囊肿瘤体积方面，第1组和第4组的数值高于第2组，但差异不显著。当计数胃肿瘤数量时，组1和组4的值显著高于组2。结果提示，DMBA诱发的仓鼠颌下腺分泌的EGF可能在其诱发的颊囊和胃肿瘤的形成中起重要作用。

Epidermal Growth Factor (EGF) is a polypeptide hormone that is secreted by submandibular gland and stimulates cellular proliferation in many tissues. It has been shown that EGF may enhance the carcinogenic potential of methylcholanthrene in the skin and stimulate mouse mammary tumorigenesis. However, the role of EGF in the oral carcinogeneisis has not been studied in detail. In the present study, the effect of sialoadenectomy on the 9, 10-Dimethy-1, 2Benzanthrwacene (DMBA) -induced tumor formation in hamster cheek pouch was investigated.Six-week-old male syrian hamsters were treated by painting both cheek pouches biweekly with a 0.5% solution of DMBA dissolved in mineral oil for 6 weeks. On the 7th week after the beginning of the experiment, hamsters in group 2 to 4 received sialoadenectomy. Thereafter, in group 1 and 2 the animals were given subcutaneous injections of 0.9% NaCl solution thrice weekly for 8 weeks. In group 3 and 4, urogastrone/EGF was injected subcutaneously thrice weekly at the doses of 0.025 mg/Kg and 0.25 mg/Kg, respectively. The experiment was terminated after 16 weeks.There was no significant difference in body weights and the weights of liver and kidney among the comparable groups of animals. The mean numbers of tumor per cheek pouch in group 1 to 4 were 3.4, 2.1, 2.5. and 3.2, respectively. The difference between group 2 and group 1 or group 4 was significat (P<0.05, Student's t test). In regard to tumor volume per cheek pouch, the values of group 1 and group 4 were higher than that in group 2, though the difference was not significant. When the number of stomach tumors was counted, the values of group 1 and group 4 were significantly higher than that in group 2. These findings indicate that EGF synthesized in hamster submandibular gland may play an important role in the formation of cheek pouch and stomach tumors induced by DMBA.