The Development of Model System for Maxillary Cancer

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Development of an animal model for maxillary cancer is the major object of this study, because there are no reliable systems to induce tumors selectively in the nasal and paranasal cavities. Two novel methods were conducted. First, 25mu1 of 0.5% 9,10-dimethy1-1,2-benzanthracene (DMBA) dissolved in dimethyl sulfoxide (DMSO) was injected into the left maxillary sinus of the hamsters once weekly for 10 weeks. Thereafter, hamsters were left untreated for 10 weeks. Carcinomas were induced in 83%(10/12) of the hamsters at the injected side of nasal and paranasal cavities. whereas tumors were not demonstrated in 12 hamsters treated with DMSO.Second, 2% DMBA was injected once into the left maxillary sinus in which oxycellulose had been inserted previously. Sixteen weeks after the DMBA administration, three hamsters showed prominent swelling in the left buccal area and the experiment was terminated. Maxillary tumors were demonstrated in 73%(8/11) of the hamsters and were found to be sarcoma his … More tologically. When we attempted to induce maxillary cancer with the use of published method, i.e., subcutaneous injection of diethylnitrosoures, tumors were induced, but carcinoma was not frequently demonstrated. These findings indicate that repeated injection of 0.5% DMBA into the maxillary sinus is a reliable method to induce squamous cell carcinoma in the nasal and paranasal cavities.The role of epidermal growth factor (EGF) in the oral carcinogenesis was investigated with the use of hamster cheek pouch model. The cheek pouches of the hamsters were painted with 0.5% DMBA twice weekly for 6 weeks. Thereafter, sialoadenectomy, removalf submandibular glands, or sham operation was performed in the hamsters. Subsequently, cheek pouches were treated with EGF(10mug/kg body weight) or vehicle thrice weekly for a further 6 weeks. At 14 weeks, the mean number of cheek pouch tumors in the EGF-treated hamsters was significantly higher than that in the vehicle-treated hamsters. Thus, EGF synthesized in the submandibular glands enhances the development of DMBA-induced cheek pouch tumors. However, EGF may not promote the malignant conversion of papilloma cells, because EGF did not increase the proportion of carcinomas in the tumors. Less