Inhibitory activity on murine granulocytic colony formation of bone marrow cell-conditioned medium obtained from colony-stimulating factor-producing tumor-bearing nude mice.

The effects of bone marrow-conditioned medium obtained from colony-stimulating factor-producing tumor-bearing nude mice (G-BM-CM) on mouse and human granulocyte-macrophage colony formation and mouse erythroid colony and burst formation were studied. Addition of G-BM-CM into the mouse granulocyte-macrophage colony-forming system containing colony-stimulating activity more strongly inhibited granulocyte colony formation than did mixed granulocyte-macrophage and macrophage colony formation, while it did not change the number of granulocyte colonies formed by human bone marrow cells stimulated by human granulocyte colony-stimulating activity. Addition of G-BM-CM slightly increased mouse erythroid colony and burst numbers when it was added into an erythroid colony-forming system stimulated by erythropoietin (1 unit/ml), and into the erythroid burst-forming system stimulated by erythropoietin (1 unit/ml) and 7% spleen cell-conditioned medium. These results might indicate that G-BM-CM mainly blocked commitment of mouse granulocyte-macrophage colony-forming cells to granulocytic progeny.