製備GRP78之單株抗體與探討GRP78在腫瘤生成中之功能

Abstract

Drug resistance in cancer poses a profound challenge for the effective treatment of cancer, especially for advanced and metastatic cancers. Therefore, the discovery of a predictive factor for chemoresistance is critical for both screening and improving adjuvant therapies for cancer patients. The glucose-regulated protein GRP78, a major endoplasmic reticulum (ER) chaperone, is inducible under stress conditions that often characterize tumor microenvironments, may protect cancer cells and confer resistance to a variety of chemotherapeutic drugs. Notably, GRP78 can only be found on the cell surface of cancer cells but not normal cells opens up an exciting opportunity of targeting cell surface GRP78 function as well as using it as a cancer-targeted marker. In this study, we have generated twenty monoclonal antibodies (mAbs) specifically against GRP78. Among these mAbs, four mAbs, GRP78-Ab 17-1, GRP78-Ab 18-1, GRP78-Ab 19-5, and GRP78-Ab 20-7 exhibited higher specificity against surface GRP78 of a nasopharyngeal carcinoma (NPC) cell line, NPC-TW04 cells. Using these anti-GRP78 mAbs, we found that GRP78 is also overexpressed in other cancer cell lines, including CL1-5, MDA-MB 231 and HCT116. Interestingly, a small fraction of GRP78 was detected on several cancer cells surface, which includes NPC-TW04, A549, HepG2, H1299 and PAN-1. In addition, results from immunohistochemical staining of human surgical specimens reveled that GRP78 is up-regulated in both liver and oral cancers. To investigate the potential functions of GRP78, lentiviral vector expressing short hairpin RNA (shRNA) was used to suppress GRP78 expression in NPC-TW04. We found that knockdown of GRP78 significantly reduced cell growth, migration, and inhibited xenograft tumor growth. Taken together, our data suggest that GRP78 may serve as a new molecular target of cancer therapy, and the anti-GRP78 mAbs are useful for detection the surface GRP78 of cancer cells and development of ligand-targeted therapeutics for cancer.