Evaluation of Prognostic Significance of AgNORs and PCNA during 9,10-dimethyl-1,2-benzantracene(DMBA)-induced Hamster Buccal Pouch Carcinogenesis

ABSTRACT

The purpose of this study is to evaluate the prognostic significance of argyrophilic nucleoalr organizer regions (AgNORs) and proliferating cell nuclear antigen (PCNA) by using DMBA hamster buccal pouch carcinogenesis which provides a good experimental model in reproducing steps from precancerous lesions to invasive squamous cell carcinomas. The buccal pouches of 50 Syrian hamsters were applied with 0.5% DMBA in mineral oil three times a week to reproduce various lesions from precancerous ones such as hyperkeratosis or epithelial dysplasia to invasive squamous cell carcinomas. Their sections were stained with H & E, and silver colloid, and processed immunohistochemically by being applied with monoclonal antibody to PCNA. The histopathologic examainations were done and the counts of AgNORs were evaluated. The PCNA labelling indices on each lesions were evaluated. The correlation between histopathological grades and counts of AgNORs or PCNA labelling indices were evaluated. The number of AgNORs was 2.22+/-0.22 in control group, 3.46+/-0.72 in carcinoma in situ (CIS), 3.78+/-0.63 in squamous cell carcinoma (SCC), respectively. AgNORs significantly increased in severe epithelial dysplasia, CIS, and SCC compared with normal tissue (P<0.05). The PCNA Labeling Index (LI) was 39.47+/-6.68% in control group, 79.61+/-4.14% in CIS, and 85.43+/-6.25% in SCC, respectively. PCNA LI also significantly increased in epithelial dysplasia, CIS, and SCC compared with normal tissue (P<0.05). The number of AgNORs, AgNOR area, and PCNA LI slightly increased in the advancing front than in the center of SCC, but, it was not statistically significant. It appeared that there were a good correlation between the number of AgNORs and PCNA LI (Pierson correlation coefficient 0.649, P<0.001). These results suggested that the number of AgNORs and the PCNA LI could be useful markers for evaluating the risk of malignant transformation and prognosis of SCC. It was thought that the clinical usefulness of these markers should be verified by using human tissue specimens.