NCL-CB11, a new monoclonal antibody recognizing the internal domain of the c-erbB-2 oncogene protein effective for use on formalin-fixed, paraffin-embedded tissue.

The c-erbB-2 proto-oncogene encodes a 190 k Mr protein representing a putative growth factor receptor with considerable homology to the EGF receptor. Gene amplification and overexpression of the oncogene protein have been demonstrated in a variety of tumours including breast cancer, where it is associated with a poor prognosis. In this study we have produced and characterized a mouse monoclonal antibody, designated NCL-CB11, to the c-erbB-2 protein. NCL-CB11 was generated to a synthetic peptide sequence corresponding to a site of predicted antigenicity near the C-terminus of the internal domain of the protein. NCL-CB11 produces intense membrane-associated immunohistochemical staining in a proportion of human cancer cells. The specificity of the antibody is supported by Western blotting and immunoprecipitation studies. Reactivity with an internal site of the protein is confirmed by the necessity of cell permeabilization for reactivity in fluorescence-activated cell sorter (FACS) analysis. A high degree of correlation between immunohistochemical staining using NCL-CB11, and c-erbB-2 gene amplification has been observed. NCL-CB11 should prove to be a valuable reagent for investigations into the pathological significance of c-erbB-2 protein expression.