A rat mammary carcinoma in vivo and in vitro: establishment of clonal lines of the tumor.

Clonal cell lines from a pituitary hormone-dependent rat mammary carcinoma were established. The growth of these cell lines in vitro is markedly stimulated in the presence of prolactin. The cells grow well in a medium supplemented with fetal-calf serum (generation time: 9-10 hr), but do not grow with calf serum. Fetal-calf serum supports little growth when the serum is subjected to anti-prolactin-affinity chromatography. Gel filtration of fetal-calf serum indicates that the growth stimulatory activity is in a large molecular weight material (close to 100,000), suggesting that prolactin is associated with another serum component. A variant of the original tumor, which does not require hormone for growth, was obtained, and clonal cell lines of this tumor were also established. These cells, in contrast to the hormone-dependent ones, grow well with either fetal-calf serum (with or without anti-prolactin treatment) or calf serum.