Hormone requirements of the pregnancy-dependent mammary tumor of GR/A mice: an in vitro study.
The hormones required for cell replication and structural integrity of the inbred GR/A mouse strain-derived, pregnancy-dependent mammary tumor (PDT) were studied with the use of explant organ culture. Through 6 days of culture, a combination of insulin (I), progesterone (P), and prolactin was sufficient to maintain continued cell replication, tissue architecture, and cell integrity. In contrast, the GR/A pregnancy-independent mammary tumors (PIT) required only I to sustain cell replication. Syngeneic transplants of PDT explants after culture yielded predominantly ductal outgrowths with no PIT. These findings are consistent with data obtained in vivo and suggest that the extreme dependence of this tumor on the hormones of pregnancy is best accounted for by considering P to be the pivotal control hormone which, in turn, acts with constitutively present I and pregnancy-stimulated pituitary and placental prolactin activities to promote tumor growth.
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects; D005260:Female; D006728:Hormones / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D051379:Mice; D008815:Mice, Inbred Strains; D009924:Organ Culture Techniques; D010907:Pituitary Hormones / Q000494:pharmacology; D011247:Pregnancy; D011252:Pregnancy Complications, Neoplastic / Q000473:pathology*; D011374:Progesterone / Q000494:pharmacology; D011388:Prolactin / Q000494:pharmacology
D006728:Hormones; D007328:Insulin; D010907:Pituitary Hormones; D011374:Progesterone; D011388:Prolactin