Expression of glucose-regulated protein 78 (GRP78) and its regulator microrna-181 during the development and progression of ovarian cancer.
5579 Background: Ovarian cancer (OVCA) is a lethal malignancy of women with a distinct pattern of metastasis through peritoneal dissemination. Sustained exposure of the ovaries to oxidative stress due to inflammatory processes including ovulatory genotoxicity, makes the ovarian microenvironment conducive to malignant cell proliferation. GRP78 is a stress-inducible protein which resides in the endoplasmic reticulum of the cell. Thus GRP78 may be a marker of ovarian tumor associated stress and could represent a therapeutic target for OVCA. The goal of this study was to examine if GRP78 expression increases in association with OVCA development and determine the molecular mechanism of its increase in ovarian tumors. Methods: All tissues were collected from patients who underwent surgery and processed for immunohistochemistry (IHC), proteomic study (2D-WB) and miRNA expression. Expression of GRP78 was examined in paraffin sections of normal ovaries (n = 20), benign (serous cystadenoma, n = 15 and cystadenofibroma, n = 5) and ovaries with papillary serous carcinoma at early stage (n= 20 at stages I and II) and late stage (n = 20, stages III and IV) by IHC and confirmed by 2D-WB (representative samples). Changes in miRNA-181 (post-translation regulator of GRP78) expression were examined by qRT-PCR. Results: GRP78 expression by normal ovarian surface epithelium and epithelium of benign tumors was very weak. In contrast, the intensity of GRP78 expression was significantly (p<0.05) high in early stage OVCA and increased further in late stage OVCA. An immunoreactive band of 78kDa detected by 2D-WB confirmed IHC observations. In contrast, expression of miRNA-181 by malignant tumors significantly (p<0.05) decreased as the tumor progressed to late stages. Conclusions: The results of the present study suggest that GRP78 expression is associated with the development and progression of malignant ovarian tumors. Increase in GRP78 expression was associated with the down-regulation of miRNA-181. Expression of GRP78 by malignant ovarian epithelium represents a potential marker with usefulness for targeted drug delivery. Support: Elmer and Sylvia Sramek Foundation.