Hamster 협낭점막 DMBA-유도 구강상피암의 二相발암과정(Two-Phase Carcinogenesis)에 관한 세포학적 연구

THE HISTOPATHOLOGICAL STUDY ON TWO-PHASE CARCINOGENESIS OF DMBA-INDUCED ORAL CARCINOMA IN HAMSTER BUCCAL POUCH

Studies related to two-phase mechanism of carcinogenesis have been rarely carried out on oral mucosa. The present study was undertaken to investigate the histopathological and ultrastructural changes during two-phase carcinogenesis of 9, 10-Dimethyl-1,2-Benzanthracene (DMBA)-induced oral carcinoma on the mucosa of hamster buccal pouch. The purposes of this study were to demonstrate two-phase mechanism of chemical carcinogenesis on oral mucosa, and to investigate histopathological changes on early potential changes of oral carcinoma. Golden Syrian Hamsters-6 week old-were used in this experimental study, and divided into control and four experimental groups, and experimental groups were painted with DMBA in heavy mineral oil on left buccal pouch three times weekly as follows: Experimental Group Ⅰ(32): Painting with 0.5 % DMBA for 16 weeks. Experimental Group Ⅱ(32): Painting with 0.1 % DMBA for 10 weeks, no-treatment for a following 6 week period. Experimental Group Ⅲ(20): Painting with 0.1 % DMBA for 10 weeks after prior treatment as Group Ⅱ. Experimental Group Ⅳ(20): Painting with 0.5 % DMBA for 10 weeks after prior treatment as Group Ⅱ. The animals were sacrificed every week serially, and chemical-treated buccal mucosae were excised and examined grossly, light-microscopically and electron-microscopically. The obtained results were as follows.: 1. In Group Ⅰ, hyperkeratosis, squamoid (differentiated) and basaloid (undifferentiated) epithelial hyperplasia, dysplasia, papillomatous growth, carcinoma in situ, and invasive carcinoma were all seen on light microscope. Early carcinoma was detected in the 8th. week experimental group initially. 2. In Group Ⅱ, hyperkeratosis, squamoid and basaloid epithelial hyperplasia were observed, but dysplasia or papillomatous growth etc. were not seen. 3. In Group Ⅱ, any specific changes were not observed on light-microscope after cessation of chemical treatment, but continuous changes of nuclear, intercellular space and basement membrane were seen on electron-microscope. 4. In Group Ⅲ, hyperkeratosis, squamoid and basaloid epithelial hyperplasia, dysplasia, and papillomatous growth were observed, and carcinoma in situ was also detected in the 9th. week. These changes were much significant than in Group Ⅱ, but far less than in Group Ⅳ. 5. In Group Ⅳ, dysplasia, carcinoma in situ and invasive carcinoma had been detected two weeks earlier, and basaloid epithelial hyperplasia were markedly presented than in Group Ⅰ. In this study, the author suggest that Initiation-Promotion Phases were presented on experimental carcinogenesis of buccal mucosa, initiation phase had definite cellular changes, and also these changes were irreversible and had cancer-potentiality.