Expression and localization of GRP75 in human epithelial tumors and normal tissues

Using differential display mRNA techniques, the authors found cDNA of the heat shock 70 protein known as GRP75 overexpressed in ovarian cancer cell lines. In the current study, the authors used immunohistochemistry to characterize the expression pattern of GRP75 in ovarian carcinomas and compared it with epithelial tumors originating from the female reproductive tract, epithelial neoplasms from non-gynecologic sites (colon, pancreas, breast, and lung), and various normal tissues. The authors also developed an antigen capture ELISA assay to determine if GRP75 can be detected in tumors, ascites, or sera of patients with advanced mullerian adenocarcinomas. All epithelial tumors from the ovary and the female reproductive tract were positive for GRP75 expression with moderate to strong staining intensity; stromal expression of GRP75 was generally weak or absent. Adenocarcinomas from the colon, lung, pancreas, and breast also stained strongly positive for GRP75. The epithelial cells of all normal tissues examined were positive for GRP75, and strong staining was also seen in the corpora lutea, hepatocytes, enteric neural plexus of the esophagus and colon, and placental cytotrophoblast and syncytiotrophoblast, and in subpopulations of pancreatic acinar cells. The ELISA assay detected GRP75 in tumor lysates and ascitic fluid, but not sera, of patients with mullerian adenocarcinomas. The authors conclude that GRP75 is highly expressed in both benign and malignant epithelium, as well as cells of specialized function from a variety of tissues.