Expression profiling and identification of potential molecular targets for therapy in pulmonary large-cell neuroendocrine carcinoma.

The prognosis for patients with large-cell neuroendocrine carcinoma (LCNEC) of the lung is extremely poor, and an optimal treatment has not yet been established. It has been recently reported that molecular-targeted therapies, such as tyrosine kinase inhibitors for epidermal growth factor receptor (EGFR), are effective in patients with lung carcinoma. In efforts to improve the prognosis of patients with LCNEC, we analyzed gene expression, gene mutations and immunohistochemical (IHC) expression of known molecular targets in LCNECs, and compared the expression to that of lung adenocarcinomas (ACs). Thirteen patients with primary LCNEC and 14 patients with AC were analyzed. We evaluated IHC expression for c-KIT, human epidermal growth factor receptor type 2 (HER2) and vascular endothelial growth factor (VEGF), gene mutations for EGFR, K-ras and c-kit, and gene expression using fluorescence in situ hybridization for EGFR. In cases with LCNEC, the IHC expression of c-KIT, HER2 and VEGF was 76.9, 30.8 and 100%, respectively. There was a significant difference in the IHC expression of c-KIT and HER2 between the LCNEC and AC cases. Two cases of LCNEC had overexpression of HER2, and the frequency of EGFR gene mutations was higher in the the AC group, with only a single EGFR mutation (exon 18) identified in the LCNEC group. Although LCNEC had a higher rate of expression of c-KIT by IHC, no c-kit gene mutations were found. These findings suggest a potential role for anti-VEGF-, anti-c-KIT- and possibly anti-HER2-targeted agents in the treatment of LCNEC.