Correlation between encoded protein overexpression and copy number of the HER2 gene with survival in non-small cell lung cancer

The HER2 oncogene, which encodes the tyrosine kinase receptor, is commonly overexpressed in several types of cancer. Treatment using a humanized monoclonal antibody bound to HER2 product is becoming standard therapy for advanced breast cancer. Overexpression occurs in approximately 30% of non-small cell lung cancers (NSCLCs) and has been associated with poor prognosis. However, the frequency of a genetic aberration in the HER2 gene in lung cancer and the association between gene amplification and prognosis are poorly defined. To clarify these relationships, we simultaneously analyzed protein overexpression by immunohistochemistry (IHC) and determined the gene copy number by FISH in 50 surgical specimens of NSCLC. A low-grade increase in the copy number (3 to 8 copies) of the HER2 gene was detected in 44% of tumors. Most represented polysomy of chromosome 17. Protein overexpression was observed in 26%. Overexpression was detected in adenocarcinoma more frequently than in squamous cell carcinoma. No significant correlation was observed between copy number increase and overexpression. Neither gene copy number increase nor overexpression correlated with survival. We conclude that the significance of HER2 status in NSCLC is different from that in breast cancer because high-grade amplification occurs rarely. (C) 2002 Wiley-Liss, Inc.