Local concentration of folate binding protein GP38 in sections of human ovarian carcinoma by in vitro quantitative autoradiography(540 views) Li PY, Del Vecchio S, Fonti R, Carriero MV, Potena MI, Botti G, Miotti S, Lastoria S, Menard S, Colnaghi MI, Salvatore M
Affiliations: Medicina Nucleare, II Facoltá di Medicina, Via S. Pansini, 5, 80131 Naples, Italy
References: Not available.
Local concentration of folate binding protein GP38 in sections of human ovarian carcinoma by in vitro quantitative autoradiography
Folate binding protein (FBP) GP38 is a membrane-associated glycoprotein that mediates the intracellular transport of folates. The enhanced expression of FBP in ovarian carcinomas provided a rational basis for clinical studies with specific monoclonal antibodies and some newly synthesized antifolate drugs. Because the outcome of these clinical studies ultimately depends on the degree of FBP expression, we measured the local concentration of FBP using I-125-MOv18 monoclonal antibody and quantitative autoradiography. Methods: Tissue sections from 37 specimens of ovarian carcinoma and 13 nonmalignant ovaries were incubated with increasing concentrations of I-125-MOv18 with and without an excess of unlabeled antibody. Tissue-bound radioactivity was measured by quantitative autoradiography. Results: Folate binding protein was found to be overexpressed in 91% of nonmucinous ovarian carcinomas, with local concentrations ranging between 1.14 and 82.84 pmole/g, Adjacent tumor sections simultaneously studied with I-125-MOv18 and a I-125-labeled folio add derivative showed matching and superimposable regional distributions of bound radioactivity of the two radioligands, indicating that the antigen, specifically recognized by I-125-MOv18 in nonmucinous ovarian carcinomas, is capable of binding folates. Nonmalignant ovaries did not contain measurable amounts of antigen when assayed with (125)MOv18 but showed a limited and specific binding of the I-125-folic acid derivative to tissue sections, The autoradiographic findings were confirmed by testing sections from mixtures of antigen-positive and antigen-negative cells, by immunoperoxidase staining with MOv18 on tumor sections and by biochemical identification of FBP in membrane fractions from tissue samples. Conclusion: Folate binding protein is overexpressed up to 80-90-fold in nonmucinous ovarian carcinomas compared with nonmalignant ovaries. Quantitation of FBP may provide a useful tool in the design of clinical studies with specific monoclonal antibodies and certain antifolate drugs that enter the cell through FBP.
Local concentration of folate binding protein GP38 in sections of human ovarian carcinoma by in vitro quantitative autoradiography
No results.
Local concentration of folate binding protein GP38 in sections of human ovarian carcinoma by in vitro quantitative autoradiography