Production of granulocyte-stimulating and bone cell-modulating activities from a neutrophilia hypercalcemia-inducing murine mammary cancer cell line.

We have previously shown that a transplantable murine tumor (CE mammary carcinoma) causes marked neutrophilia and excessive bone resorption in vivo. In order to understand the humoral mechanism of these tumor-induced phenomena, we successfully established a cell line (CE 816) and subsequently cloned CE mammary carcinoma cells in serum-free culture conditions. Cultured CE tumor cells continued to induce neutrophilia and hypercalcemia when they were transplanted back into mice. Conditioned medium (CM) prepared from the CE 816 cell line and control non-neutrophilia-inducing tumor cells were evaluated for stimulation of neutrophilic colony formation, embryonic bone cell proliferation, and bone resorption in vitro assays. Both the CE 816 and control tumor CM demonstrated colony-stimulating activity, but the CE 816 CM stimulated more neutrophilic colonies than the control tumor at all experimental conditions examined. The CE 816 CM demonstrated bone-resorbing activity but not control tumor CM. Both types of CM stimulated proliferation of embryonic bone cells. Production of colony-stimulating and bone-mitogenic activities was directly related to the tumor cell growth in vitro. CM prepared from four clones of CE tumor cells demonstrated both colony-stimulating and bone cell-mitogenic activities. These studies provided evidence that CE mammary carcinoma cells produce factors affecting granulopoiesis and bone cells in vitro, and these activities are clonal in origin.