The expression of human placental-type glutathione S-transferase (GST-pi) was investigated in human cutaneous squamous cell carcinoma (SCC) and normal skin using Northern blot and immunohistochemical analysis. In Northern blot examination, the expression of GST-pi transcript was recognized in all instances, and SCC showed a significantly higher expression of GST-pi than normal skin. In immunohistochemical examination, GST-pi was stained well in the cytoplasm of all cells of the stratum granulosum, many cells of the stratum spinosum and a few cells of the stratum basale in normal skin. Some cells of the stratum spinosum and almost all cells of the stratum basale showed only a weakly positive or almost negative reaction for GST-pi. No nuclear staining of GST-pi was obvious in normal epidermal cells. In SCC, many cells showed strong positivity for GST-pi in the cytoplasm, and some were obviously accompanied by nuclear staining of GST-pi. These findings suggest that GST-pi exists mainly in many cells in the upper layers of the normal epidermis and that GST-pi is involved in the process of carcinogenesis.

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The expression of human placental type glutathione S-transferase (GST-pi) was investigated in human cutaneous carcinoma in situ, that is, actinic keratosis and Bowen's disease, and compared with that in normal skin, using Northern blot and immunohistochemical analysis. In Northern blot examination, the expression of GST-pi transcript was recognized in all instances. Carcinoma in situ showed significantly higher expressions of GST-pi than normal skin. In the immunohistochemical examination, nuclear staining of GST-pi was noticed in some dysplastic cells of carcinoma in situ, especially in Bowen's disease. In actinic keratosis, a framework appearance was noticed in the staining pattern at a lower magnification because the lower part of the cytoplasm of dysplastic cells lining the stratum basale was positive for GST-pi, and all cells of the stratum granulosum and more cells of the stratum spinosum showed stronger GST-pi positive reaction than normal skin. In Bowen's disease, GST-pi positive, dysplastic cells existed throughout the epidermis. Because GST-pi positive, dysplastic cells and GST-pi positive, normal looking squamous cells made the GST-pi positive cell nests throughout the epidermis, and GST-pi positive, dysplastic cells, and GST-pi negative, normal looking cells coexisted in the parabasal layer, they showed a sawtooth appearance in the staining pattern at a lower magnification. These findings suggest that GST-pi is involved in the process of carcinogenesis.

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