Immunohistochemical study of the expression of drug-resistant proteins in large cell neuroendocrine carcinoma of the lung.

Abstract

In 1999, the World Health Organization categorized pulmonary large cell neuroendocrine carcinoma as a variant of large cell carcinoma. However, an optimal treatment for large cell neuroendocrine carcinoma has not been established yet. Recently, multimodality therapy combining both surgery and adjuvant chemotherapy has been reported as a useful treatment for large cell neuroendocrine carcinoma, but the effect of chemotherapy on it has not yet been fully investigated. Thus, we evaluated immunohistochemical data of the expression of drug-resistant proteins in large cell neuroendocrine carcinoma. We identified 10 large cell neuroendocrine carcinomas (1.2%) out of 850 primary lung cancers that had been surgically resected. We examined the immunohistochemical staining of three drug-resistant proteins, namely, P-glycoprotein, metallothionein and glutathione S-transferase-pi to compare large cell neuroendocrine carcinoma with other histological types of lung cancer. The mean tumor cell positivity rates for P-glycoprotein, metallothionein and glutathione S-transferase-pi in large cell neuroendocrine carcinoma were 0%, 2.4 +/- 3.6% and 35.0 +/- 37.5%, respectively. The positivity rates for P-glycoprotein and glutathione S-transferase-pi were significantly lower than those in adenocarcinoma (P = 0.0003, P = 0.0009). The positivity rate for glutathione S-transferase-pi was also lower than that in squamous cell carcinoma (P = 0.0387). These drug-resistant proteins showed similar expression pattern in both large cell neuroendocrine carcinoma and small cell carcinoma except glutathione S-transferase-pi. Immunohistochemical expression of drug-resistant proteins in large cell neuroendocrine carcinoma was lower than that in adenocarcinoma and squamous cell carcinoma, and differences exist in drug-resistance between large cell neuroendocrine carcinoma and small cell carcinoma.