Small cell carcinoma cell lines contain opioid peptides and receptors

Abstract

Two human small cell carcinoma cell lines were assayed for total opioid and beta‐endorphin‐like immunoreactivity. Small cell carcinoma cell line NCI‐H146 contained approximately 1.1 pmol/mg protein of total opioid immunoreactivity. This material was similar in size and immunoreactive determinants to C‐terminally modified beta‐endorphin. Small cell carcinoma cell line NCI‐H187 contained approximately 0.2 pmol/mg protein total opioid immunoreactivity, which was of low molecular weight. NCI‐H187 also contained approximately 1.2 pmol/mg protein of material similar in size and immunoreactive determinants to beta‐lipotropin. The two small cell carcinoma cell lines were also examined for opioid receptors with the use of [³H]‐etorphine as ligand. Both cell lines contained between 50 and 100 fmol/mg protein of specific, saturable, high‐affinity opioid receptor binding sites. Together, these findings suggest a possible autocrine role for opioids in small cell carcinoma of the lung.