Transformation-related antigens identified by monoclonal antibodies.

Abstract

Tumor-cell proteins that were antigenic in a syngeneic animal were identified by immunoprecipitation with monoclonal antibodies. Spleen cells of BALB/c [embryonic] mice immunized with plasma membranes of Kirsten RNA sarcoma virus-transformed BALB/3T3 [fibroblast] cells were fused with NS-1 [mouse] myeloma cells. Antibodies secreted into the culture fluid from these hybridomas were distinguished by their reactivity against proteins of different target cells. A total of 191 cultures were established; 143 produced antibodies that bound to BALB/3T3 cells transformed by the RNA sarcoma virus, of which antibodies from 82 bound to BALB/3T3 transformed with SV40 and antibodies from 56 bound to BALB/3T3 cells. Thus, > 50% of the cultures produced antibodies that possibly were specific to antigens of the transformed cell. Twenty different hybridomas were cloned and antibodies from 8 of these immunoprecipitated 5 proteins. A protein of .apprx. 32,000 daltons was precipitated from BALB/3T3 cells transformed by the RNA sarcoma virus, SV40, or methylcholanthrene, but not from untransformed BALB/3T3 cells. A protein of .apprx. 300,000 daltons was precipitated from all 4 cell lines; precipitation was enhanced in the viral transformed cells. Proteins of .apprx. 57,000, 54,000 and 8500 daltons were immunoprecipitated from all 4 cell lines.