Investigation of HER2 overexpression in non-small cell lung cancer.

Lung cancer is the leading cause of mortality worldwide. The median survival of advanced disease is in the range of 8 to 10 months. Intrinsic or acquired drug resistance pose major challenges to the success of chemotherapy. The HER2 gene, also known as c-erbB-2 or neu, is a proto-oncogene that encodes a membrane-bound receptor tyrosine kinase of the epithelial growth factor receptor (EGFR) family. It has a possible role in tumor cell proliferation, tumor invasion, tumor metastasis and drug resistance. We retrospectively investigated 88 samples of non-small cell lung cancer (NSCLC) and assessed the correlation between HER2 expression and tumor histology. The expression of HER2 protein was analyzed by immunohistochemical staining (IHC) and HER2 DNA amplification was detected by using fluorescence in situ hybridization (FISH). HER2 overexpression (2+, 3+) was detected in 5 (5.7%) out of 88 specimens. All of the HER2-overexpressing tumors histologically proved to be squamous cell carcinoma (SCC). Cases with 2+ HER2 immunoreactivity showed either no amplification (3.875 and 2.525), or borderline amplification (4.75). Cases with 3+ HER2 immunoreactivity showed moderate amplification (7.35) and strong amplification (15-20 - cluster), respectively. The HER2 expression in NSCLC was relatively low in the selected Hungarian population; consequently, there is no indication for introduction of trastuzumab for the treatment of lung cancer.