Abstract 1857: Intracellular protein GP128 is a novel tumor angiogenesis marker on gastric cancer cell lines and GI tissues: Ectopic expression on the cell surface defined by MS38-2.1 mAb

Abstract

Abstract Our aim is to generate monoclonal antibodies (mAbs) against novel markers on the cancer cell surface using an innovated high throughput screening (HTS) strategy. Mixed live cells from four gastric cancer cell lines (MKN45, SGC7901, BGC823 and MKN28) were used as the immunogen for A/J mice: spleen cells were then fused with mouse SP2/0 myeloma cells to generate monoclonal antibody hybridomas. The 16 highly positive hybridoma colonies were selected from 20,000 colonies in sixty-seven 96-well plates through screening using live cell (gastric cancer cells versus normal PBMC) staining and FACS-HTS technology. Protein-A affinity purified mAbs were used to define the antigens, which were confirmed as novel biomarkers on the cancer cell surface using microarray, mass and proteomic analyses. Protein microarray analysis with the MS38-2.1 mAb identified an intracellular protein GP128 (e.g., SPRR3) as the most likely a novel cancer biomarker. The immunohistochemical profiles of MS38-2.1 mAb in GI (gastric and colorectal) cancer tissues were found to be significantly higher (P<0.01) than those in normal GI tissues, and confirmed to be restricted to the small- and medium-sized blood vessels and the cancer cells. Human SPRR3 belongs to a family of small proline-rich repeat proteins that is normally expressed intracellularly. Our findings demonstrate that GP128, like SPRR3, could be ectopically expressed in the extracellular matrix in GI cancers. Conclusion: Our results demonstrate that the intracellular protein GP128 might play a role in gastrointestinal cancer development. This investigation also provides an example of identification of potential cancer biomarkers through a novel screening technique. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1857. doi:1538-7445.AM2012-1857