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.