13. Cell membrane protein MS57A and MS57B are novel markers on gastric cancer cell lines and potential therapeutic targets of gastric cancer: Expressed on the gastric cancer cell surface defined by MS57-2.1 mAb

Summary: Our aim is to generate functional monoclonal antibodies (mAbs) against novel antigenic markers on the gastric cancer cell surface through an innovated high throughput screening (HTS) strategy. Mixed live cells from four gastric cancer cell lines (MKN45, SGC7901, BGC823 and MKN28) are used as the immunogen for A/J mice; A/J mouse spleen cells were then fused with mouse SP2/0 myeloma cells to generate monoclonal antibody hybridoma. Sixteen highly positive hybridoma colonies were selected from over 20,000 colonies in sixty-seven 96-well plates through screening using live cells (mixed four gastric cancer cells versus normal PBMC) staining and FACS-HTS strategy. Protein-A affinity purified mAbs were used to define the antigens, which were then confirmed as novel biomarkers on the gastric cancer cell surface through a combination of immunoprecipitation, mass spectrometry and other proteomic analysis.
Through the above-mentioned methods we have identified the target antigen of MS57-2.1 mAb: MS57A and MS57B. Both MS57A and MS57B are membrane bound glycosylated enzyme and belong to alkaline phosphatases family. RT-qPCR and Western Blot have proved that MS57A and MS57B are expressed in certain gastric cancer cell lines, which have not been reported before, and the in vitro experiments have proved that the utilization of MS57-2.1 mAb has a significant effect on gastric cancer cell migration and invasion. In vivo experiments are to be carried out to verify the function of MS57-2.1 mAbs on inhibiting gastric cancer cell migration and invasion.