葡萄糖調節蛋白78（GRP78）：在靶向給藥治療胃癌的策略中所扮演之角色

Abstract

The survivals of gastric cancer (GC) patients are associated with early diagnosis and effective treatments. Therefore, it is urgent for the discovery of early GC biomarkers and tumor targeting therapeutics. The aims of this study was to uncover putative tissue biomarkers of GC using two-dimensional differential gel electrophoresis (2D-DIGE) and then apply one of these specific markers in GC treatment. We finally found three putative biomarkers of GC with significant differences in expression level compared to adjacent normal tissue, including glucose regulated protein 78 (GRP78) and glutathione s-transferase pi (GSTpi) with increased expression level, and alpha-1 antitrypsin (A1AT) with reduced expression level. The overexpressed GRP78 was used as a targeted protein for guiding the drugs to tumor cells, leading to more effective treatment for GC xenografts. Our results demonstrated that the designated GRP78 binding peptide (GRP78BP) based on the sequence, WIFPWIQL, was selectively prone to recognize and bind to GC MKN45 cells in vitro, and also improve the delivery efficiency of polymeric micelles-encapsulated drugs into tumor cells, displaying better therapeutic outcome in experimental animals. Furthermore, we designed and manufactured the GRP78BP-guided polymeric micelles for nuclear imaging detection of tumors. The thiolated GRP78BP was first labeled with Mal-PEG-PCL and then mixed with diethylenetriamine penta-acetate (DTPA) linked PEG-PCL to form the GRP78BP-micelles-DTPA. The coupling efficiency of micelles with radioactive isotope, indium (In)-111, was measured and analyzed using instant thin layer chromatography (ITLC). The coupling efficiencies of DTPA-micelles and GRP78BP-micelles-DTPA with In-111 were measured as 85% and 93%, respectively. For characterizing and tracing tumors, the radiated In-111-targeting tumors were detected and imaged in xenograft murine using a nanoSPECT/CT. The results revealed that the radioactive intensity measured in the animals administrated with GRP78BP-gauided micelles-In-111 was statistically higher than that in animals with administration of micelles-In-111, demonstrating that GRP78BP improved the tracing micelles accumulation to the tumor tissue by more than 2 fold (p<0.05) increase. This strategy of GRP78-mediated drug targeting system may bring chemotherapeutic drugs with more precise targeting to tumor cells, leading to increase therapeutic efficacy and to minimize side effects on patients. Our results indicated that the GC biomarker GRP78 is a probing target in the applications of tumor diagnosis and theapy. This novel GRP78BP-guided micelle agent may be applied into clinical practice for complementing the histological diagnosis and tumor chemotherapy