RESUMO
BACKGROUND: Recently, much attention has been focused on the role of protease inhibitors such as acid stable trypsin inhibitor (ASTI) in the invasive growth of malignant tumors. However, there are no report on expression of ASTI from premalignant and/or malignant skin tumors. OBJECTIVES: In the present study the expression of ASTI was investigated in the different type of premalignant and/or, malignant skin tumors in attempt to clarify the relation between the expression of the ASTI and malignancy. METHODS: For the detection of ASTI in the tumor tissue, the immunoperoxidase techniques that used mouse antibody raised against highly purified ASTI. The degree of ASTI immunoreactivity was semiquantitatively assessed for staining intensity as the percentage of ASTI-positive cells. RESULTS: ASTI immunoreactivity was detected in most of the premalignant and malignant skin tissues. Especially, ASTI expression was present widespread in squamous cell carcinoma(SCC) with strong cytoplasmic membrane, where as in normal epidermis they were primarily present in the horny layer. The strong staining was the SCC, keratoacanthoma, Bowen's disease, actinic keratosis, basal cell epithelioma, Paget's disease in decreasing order. The significant difference in the staining intensity was observed between SCC and other groups. CONCLUSION: Results of immunohistochemical studies suggest that the tumor cells themselves could produce ASTI. Considering the suggestion that ASTI is a self protector, inhibitor to proteolytic protease as well as growth-stimulating factor. The present findings may indicate that ASTI expressed in malignant cells may play a role possibly closely associated with tumor development.