title: Autocrine stimulation by prolactin of hormone-responsive breast cancer growth in culture.
abstract: Evidence obtained in human breast cancer cell lines in culture suggests that estradiol stimulates the synthesis of secretory proteins which may, in turn, mediate its mitogenic effect. We questioned whether a similar mechanism could mediate the growth-promoting effect of PRL in the N-nitrosomethylurea-induced rat mammary tumor grown in soft agar, where PRL exerts a dose-dependent colony-stimulating effect. Conditioned medium obtained from PRL-treated tumors, but not from control tumors, was found to exert a significant dose-dependent colony-stimulating effect when added to N-nitrosomethylurea-induced mammary tumors plated in soft agar under serum-free medium conditions. The growth-promoting action of conditioned medium from PRL-treated tumors was abolished by pretreatment with heat, trypsin, and Concanavalin-A, suggesting the possible glycoprotein nature of the oPRL-induced growth factor(s). These results provide support for the novel hypothesis that estradiol and PRL may support the growth of hormone-responsive breast cancer through a similar mechanism.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003208:Concanavalin A / Q000502:physiology; D003470:Culture Media; D004967:Estrogens / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D014357:Trypsin
chemical_list: D003470:Culture Media; D004967:Estrogens; D003208:Concanavalin A; D011388:Prolactin; D014357:Trypsin