Expression of endothelin receptor subtypes in bronchial tumors

The importance of endothelin-1 (ET-1) in cell growth, migration and stimulation of angiogenesis suggests that ET-1 may play a role in tumor progression. The expression of the ET-1 receptors ETA (ET(A)R) and ETB (ET(B)R) was analyzed by immunohistochemistry in fragments of human lung carcinomas. Samples were obtained from 11 patients with adenocarcinoma (ADK), 12 with squamous cell carcinoma (SCC) and 8 patients with small cell carcinoma (SCLC). Morphologically normal airway areas adjacent to the tumors served as controls. ADK and SCC samples had ET(A)R and ET(B)R levels similar to normal tissues; however, the ET(A)R/ET(B)R ratio was higher in ADK than in SCC. We also observed the presence of endothelin receptors in SCLC, although the ET(A)R levels and the ratio ET(A)R/ET(B)R were lower than in normal tissue and in other carcinomas. In conclusion, both ET(A)R and ET(B)R are present in lung carcinomas but at different levels, according to the histological type of tumor.