Replication of Mammary Tumor Virus in Tumor Cell Cultures: Dependence on Hormone-Induced Cellular Organization2

Abstract

Short-term cultures of mammary adenocarcinoma cells of BALB/cfC3H female mice were cultivated in medium supplemented with 7% fetal calf serum. They were virtually inactive in the de novo production of mammary tumor virus (MTV). Replication and release of MTV were induced in these cultures by addition of insulin and hydrocortisone to culture media. This induction was mediated by the development of 3-dimensional cellular units, “domes.” The effects of insulin and hydrocortisone on dome development and MTV induction were functionally separable. Hydrocortisone acted without mitogenic stimulation of epithelial cells, though pretreatment of cultures with insulin and mitogenic stimulation were required for the subsequent hydrocortisone effect. Hydrocortisone did not modify kinetics of MTV replication per infected epithelial cell. Prolactin did not measurably influence MTV production.