| Looking for a new gastric cancer associated antigen and investigating its distribution in body fluid and tissue of tumor patients,is very important for study of oncogenesis and prevention of malignancy. Recently, some gastrointestinal cancer associated antigens, such as CEA, AFP, CA19-9, CA50, TAG72, POA, Dupan-2 etc, have been found and utilized for therapy monitoring, early detection of recurrent disease after surgery, and for the pre-operative determination of prognosis. But, they are not specific for diagnosis of gastric cancer.Recenty, several monoclonal antibodies against gastric cancer of the MG series ( MG5, MG9, MGd1,MGb1, MGe1 and MGc1 ) , were prepared in our laboratory and found to be useful in immunohistological and immunocytological diagnosis. In order to identify a new gastric cancer associated antigen as a useful tumor marker for study and diagnosis of gastrointestinal cancer, this study was taken to purify ,characterize and detect the corresponding antigens of MG monoclonal antibodies.purification and characterization of the corresponding antigens of MG series monoclonal antibodiesFresh gastric cancer tissues or gastric cancer cells from patients with metastized ascitic fluid, proved to be reactive with MG series monoclonal antibodies by ABC method, were respectively collected ,homogenized and extracted by nonidet P40 or chloroform and methanol reagents. The supernatant of the tumor extracts were collected and incubated with Concanavalin A-Sepharose 4B to isolate the carbohydrate compenents of tumor tissue. By means of monoclonal antibody affinity chromatography, the corresponding antigens defined by MG5,MG9,MGd1,MGc1,MGb1 and MGe1 were further purified from this carbohydrate components respectively.Characterization of purified antigen were performed on SDS-PAGE and immunoblotting according to the procedure of Towbin's system. Stained with coomassie blue, schiff's and...
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