HeLa cells secrete α subunit of glycoprotein tropic hormones

Abstract

THE HeLa line, derived from a carcinoma of the cervix, was the first continuous human tissue culture line to be established in vitro¹, and has been one of the primary sources for the study of human cell biology. Although such studies have documented the biosynthesis of certain intra-cellular and membrane proteins^2–4, there has been little specific characterisation of proteins secreted by these lines. The human glycoprotein tropic hormones, thyroid-stimulating hormone (HTSH), follicle-stimulating hormone (HFSH), luteinising hormone (HLH), and chorionic gonadotropin (HCG), are each composed of two subunits—an immunologically indistinguishable and probably common α subunit (‘α’) and distinct β subunits which confer biological specificity on the complete molecule^5–8. Complete hormones and free, isolated subunits are secreted by their normal cells of origin in pituitary or placenta under a variety of physiological and neoplastic circumstances^9–11. Furthermore, complete hormones and isolated subunits can even be secreted ectopically—that is, by tissue which does not in normal conditions produce these proteins. Since ectopic a secretion has been documented for a variety of neoplasms, both in vivo¹² and in vitro¹³, we examined the possibility that HeLa lines might also ectopically secrete the α subunit. We have found that three different HeLa strains secrete a substance immunologically indistinguishable from the α subunit, with secretion rates differing by as much as 50-fold.