Factors produced by macrophages and tumor cells: influence on the granulocytic precursor cells (CFU-C) in normal and tumor-bearing mice.

Some tumors are known to produce colony-stimulating factors (CSF). In mice bearing s.c. Ehrlich tumor (ET) we observed that tumor growth is responsible for hemopoietic perturbations in which the increase of granulocytic-macrophagic precursors (CFU-C) in bone marrow and in the spleen represents a remarkable aspect. CFU-C in bone marrow from ET-bearing mice are more sensitive than CFU-C from normal mice to CSF from L-cells (LC-CM), mouse embryo fibroblasts (MEF-CM) and from the same tumor (ET-CM). Macrophages from normal and from ET-bearing mice exert the same effect on the proliferation of normal bone marrow CFU-C. Bone marrow CFU-C from ET-bearing mice show an increased sensitivity to the inhibitory factors produced by macrophages from ET-bearing mice.