A Murine Monoclonal Antibody that Recognizes an Extracellular Domain of the Human c‐erbB‐2 Protooncogene Product

A murine IgM monoclonal antibody, designated SV2-61, was generated against human c-erbB-2 gene-transfected NIH-3T3 (SV11) cells. SV2-61 defined a 185-kDa molecule present on the surface of SV11 cells, another line of c-erbB-2 gene-transfected NIH-3T3 (A4-15) cells, and MKN-7 human gastric cancer cell line carrying an amplified human c-erbB-2 gene. The SV2-61-defined antigen was found to show protein kinase activity in vitro. The SV2-61 was reactive with human c-erbB-2 gene-transfected NIH-3T3 cell lines but not with transfectants carrying c-erbB-2 gene mutants which lack a coding region for the extracellular domain. It was reactive with a portion of human epithelial cell lines but not with native NIH-3T3, TGF-alpha-coding gene-, activated c-raf gene- or Ha-ras gene-transfected NIH-3T3 cells, or non-epithelial human cells. These results indicate that the SV2-61 is an antibody which recognizes an extracellular domain of the c-erbB-2 gene product, 185-kDa protein.