Effect of hormones and epidermal growth factor on the growth of the hormone-responsive 13762NF rat mammary tumor in collagen gel culture.

The hormone-responsive mammary tumor 13762NF of the F344 rat was cultured in a collagen gel matrix with the use of a serum-free medium supplemented with hormones and epidermal growth factor (EGF). Hydrocortisone (F) had the greatest effect on cell growth. EGF had no growth-promoting activity when used alone, but it had a significant effect when used with F. There was also a population of cells responsive to progesterone (P) and prolactin (PRL). P synergized with EGF as well as with PRL to promote growth. 17 beta-Estradiol alone or in combination with other hormones had no growth-promoting activity. Receptor levels in the tumor were high for glucocorticoids, intermediate for P and EGF, and low for estrogens. Metastasis in the lung and lymph node showed the same basic hormonal responses as the parent tumor. Cultured cells produced tumors with the same histopathology as the parent tumor when transplanted back into female rats; they had the same receptor levels and when placed back in culture showed a growth response to the same set of hormones. The tumor cells formed colonies that were spherical, which was different from the branching structures formed by normal mammary cells in collagen gel.