Effect of hormones on primary cell cultures from pregnancy-dependent mouse mammary tumors.

No hormone combination was successful in maintaining long term primary cultures of pregnancy-dependent mammary tumors. Insulin provided the most consistent dose dependent stimulatory effect on short term proliferation as measured by 3H-TdR incorporation into DNA. Insulin in combination with corticosterone and prolactin produced the greatest stimulatory effect in most tumors. Both insulin at 5 microgram/ml and insulin, prolactin and hydrocortisone induced a partially synchronous wave of DNA synthesis in restimulated cultures. The time course of the wave of DNA synthesis was different for different hormone treatments. Insulin as 5 microgram/ml caused an earlier wave of DNA synthesis than insulin, prolactin plus corticosterone.