Frequent overexpression of the c-kit protein in large cell neuroendocrine carcinoma of the lung.

Overexpression of receptor-type tyrosine kinases in various cancers is associated with an aggressive tumor phenotype and poor outcome, but their expression had never been evaluated in large cell neuroendocrine carcinoma (LCNEC) of the lung. In the present study, we investigated the expression of three receptor tyrosine kinases, epidermal growth factor receptor (EGFR), c-erbB-2, and c-kit protein, by comparing surgically resected 40 LCNECs with other neuroendocrine (NE) lung tumors: 9 typical carcinoids (TCs), 5 atypical carcinoids (ACs), and 13 small cell lung carcinomas (SCLCs). None of the NE lung tumors showed expression of EFGR or c-erbB-2, but c-kit was overexpressed in 55% of the LCNEC tumor cells and 46% of the SCLC tumor cells. None of the clinicopathologic factors in either the LCNEC or SCLC patients correlated with c-kit overexpression. The finding that c-kit expression in LCNEC is similar to its expression in SCLC suggests that inhibition of c-kit may be effective as a therapy targeting LCNEC as well as SCLC.