Outgrowth of grafts containing different ratios of hormone-dependent and independent mouse mammary tumor cells

The growth properties of grafts composed of different mixtures of hormone-dependent and independent GR mouse mammary tumor cells were investigated. Grafts containing only hormone-dependent mammary tumor cells yielded tumors in 4–6 weeks in estrone plus progesterone treated castrated mice, but not in castrated mice that were not treated with hormones. Grafts containing only autonomous mammary tumor cells yielded tumors in about 2 weeks in both hormone-treated and untreated castrated mice. Grafts containing mixtures of hormone-dependent and autonomous cells yielded tumors in 2 weeks both in hormone-treated and untreated castrates, even when the grafts contained predominantly hormone-dependent cells (up to 90%). These results indicate that the growth behavior of heterogeneous mammary tumor grafts that contain more than 10% autonomous cells, is essentially determined by these cells. Growth of the autonomous cells is not markedly affected by the presence of hormone-dependent cells in the grafts.