Generation and characterization of new HER2 monoclonal antibodies

Antibodies are among the most commonly used research and diagnostic tools. Antibody type and clonality are important in any assay as they can influence epitope detection. HER2 oncoprotein is overexpressed or undergoes gene amplification in approximately 30% of invasive breast carcinomas and 20% of gastric adenocarcinomas. Overexpression of HER2 is primarily detected by immunohistochemistry (IHC) on neoplastic tissue sections. We produced five murine hybridoma clones secreting monoclonal antibodies (MAbs) against HER2 protein. For hybridoma production, spleen cells from BALB/c mice immunized with a recombinant fragment of the extracellular portion of HER2 (rHER2) were fused to SP2/O-Ag14 cells, selected in HAT medium and screened by indirect ELISA. MAbs secreted were characterized according to isotypes, functional affinity constants, reaction with the native protein in MCF-7 cells by indirect immunofluorescence and in tissue sections from HER2 positive breast cancer specimens by IHC. Two MAbs were IgG2b and three were IgG1, and their affinity constants ranged from 6 × 107 to 1 × 109 M−1. All MAbs reacted with the native protein and two stained strongly the membrane of neoplastic cells overexpressing HER2. These two MAbs could be useful in assaying HER2 overexpression in human tissues for research and possibly diagnostic purposes after a proper large-scale validation study.