Ectopic and eutopic secretion of chorionic gonadotropin and its sub-nits in vitro: comparison of clonal strains from carcinomas of lung and placenta

Abstract

We compared rates of secretion in vitro of human chorionic gonadotropin (HCG) and its subunits alpha and beta by established clonal cell lines of a bronchogenic carcinoma (ChaGo) and a choriocarcinoma (JEG). Clones showing the highest secretion rates of either HCG or its subunits were studied: ChaGo-K1, a new clonal strain, and ChaGo-C5 and JEG-3, two previously reported clonal lines. Cells were grown under identical conditions in the same laboratory. Hormone and subunit concentrations were measured by radioimmunoassays. ChaGo-K1 and ChaGo-C5 secreted only alpha-subunit whereas JEG-3 secreted only HCG. Average peak secretion rates in picomoles/day/mg protein were: for ChaGo-K1, HCG less than 0.3, alpha=290, and beta less than 0.5; for ChaGo-C5, HCG less than 0.3, alpha=21, and beta less than 0.5; and for JEG-3, HCG=18, alpha less than 0.7, and beta less than 0.5. The ChaGo-K1 secretion rate of alpha was greater than that of any of out previously reported ChaGo clones. Significant quantities of estradiol and progesterone accumulated in the media of all three cell lines; however, only JEG-3 secreted detectable quantities of placental lactogen. Thus under identical culture conditions, a bronchogenic carcinoma clonal line secreted only alpha-subunit, whereas a choriocarcinoma line secreted only HCG; these findings implied major differences in cellular control mechanisms. Moreover, the ectopic secretions of alpha exceeded the eutopic trophoblastic secretion of HCG, which suggested that in certain cases ectopic protein production may be even more efficient than nonectopic production.