Immunoelectron microscopic localization of gelatinase A in human gastrointestinal and skin carcinomas: difference between cancer cells and fibroblasts.

Previous reports revealed a discrepancy in gelatinase A localization in human cancers; i.e., protein localization in cancer cells and mRNA localization in stromal fibroblastic cells. To clarify this, we conducted immunoelectron microscopic study of gelatinase A in cancer and stromal cells in human gastrointestinal and skin carcinomas. Although both carcinoma cells and fibroblasts were positive for gelatinase A, the subcellular localizations were different. On immunoelectron microscopy, fibroblasts showed immunoreactivity in the lumen of the rough endoplasmic reticulum (rER) or in the cytosol on the surface of rER, demonstrating synthesis of the protein. Carcinoma cells showed diffuse deposition of gelatinase A in the cytosol, suggesting the accumulation of the antigen both in adenocarcinoma and squamous cell carcinoma. Immunoreactivity along the cell membrane was demonstrated in one case of skin carcinoma. Macrophages showed also diffuse deposition of gelatinase A in the cytosol. In conclusion, we found a qualitative difference of gelatinase A localization between carcinoma cells and fibroblasts, and concluded that carcinoma cells may not be important in the secretion of gelatinase A.