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Biochemical and Physical Characterizations of Tumor-associated Fetal Antigens¹

Department of Microbiology and Immunology, The Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27103

Tumor-associated fetal antigens (TAFA) were extracted from methylcholanthrene-induced fibrosarcomas and Moloney sarcoma virus (Soehner-Dmochowski strain) osteosarcomas. Tumors from New Zealand black rats were treated with hypertonic KCI and high-intensity sonication, and TAFA were solubilized from these lesions. Preparative affinity chromatography and isoelectric focusing techniques resolved TAFA into six different glycoproteins. TAFA with isoelectric points of pH 8.0 and 5.5 were found in each tumor and were subsequently characterized. Polyacrylamide gel electrophoresis and immunoelectrophoresis of TAFA I (pl 8.0) and TAFA II (pl 5.5) revealed, by chemical and serological techniques, their respective purity. Molecular weight determinations using sodium dodecyl sulfatepolyacrylamide gel electrophoresis were conducted; the molecular weight of TAFA I is approximately 10,000, and that of TAFA II is 3,500 to 4,000. Monospecific antiserum raised against each TAFA were prepared, and the expression of these antigens on embryonic and transformed syngeneic cells was determined by antibody-complement-dependent cytotoxicity assays. TAFA I and TAFA II are expressed on the membranes of rat embryo fibroblasts, and on fibrosarcoma and osteosarcoma cells. Quantitative absorptions of the monospecific antisera with purified TAFA I or TAFA II produced absorption curves which were utilized to establish an in vitro assay for TAFA. The presence of TAFA I and TAFA II on cell membranes was also evaluated using membrane immunofluorescence. Each antigen produced membrane capping in the presence of the homologous antiserum.

¹ This work was supported by National Cancer Institute Grant CA 19358 (NIH).

² To whom requests for reprints should be addressed.

Received 10/ 6/78. Accepted 2/15/79.