Association of Elevated Expression of the c‐erbB‐2 Protein with Spread of Breast Cancer

We analyzed amplification and expression of the c‐erbB‐2 gene in human breast cancers. Southern blot hybridization analysis demonstrated amplification of the c‐erbB‐2 gene in 10 out of 50 tumor DNAs examined. The degree of amplification was three‐ to twenty‐fold relative to normal placenta. The c‐erbB‐2 protein could be analyzed in 39 tumor tissues of the 50 samples by immune‐blotting, and elevated expression of the c‐erbB‐2 protein was found in 15 cases. On the other hand, expression of the c‐erbB‐2 products was not detected in normal breast tissues either by immuno‐blotting or by immuno‐histological analysis. These data indicate that transcriptional and/or translational activation of c‐erbB‐2 might occur in some breast cancers in addition to activation by gene amplification. The elevated expression of the C‐erbB‐2 protein was most strongly correlated with lymph‐node metastasis (P< 0.001), suggesting that c‐erbB‐2 expression is involved in promotion of the lymph‐node metastasis of human breast cancers. Therefore, immuno‐histological diagnosis with anti‐c‐erbB‐2 antibody might be useful as an indicator to predict lymph‐node involvement in breast cancer.