Lung carcinoid cell lines have Bombesin‐like peptides and EGF receptors

The biochemical properties of lung cancer cell lines were investigated. Bombesin‐like peptides were present in three small cell lung cancer (SCLC) cell lines examined and three of four lung carcinoids but not in five non‐small cell lung cancer (NSCLC) cell lines. Therefore SCLC and some lung carcinoids, but not NSCLC, are enriched in neuroendocrine properties. In contrast, ¹²⁵I‐EGF bound with high affinity to all five NSCLC cell lines and three of four lung carcinoids but not to the three SCLC cell lines examined. For lung carcinoid cell line NCI‐H727, ¹²⁵I‐EGF bound with high affinity (Kd = 6 nM) to a single class of sites (Bmax = 110,000/cell). The ¹²⁵I‐EGF bound was rapidly internalized at 37°C but not 4°C. Using Western blot techniques and antiphosphotyrosine antibodies, EGF induced phosphorylation of a major 170 Kd protein. Using immunoprecipitation techniques and anti‐EGF recep‐tor antibodies a major 170 Kd protein was labeled. These data indicate that biologically active EGF receptors are present on NSCLC and lung carcinoid cell lines.