Bone resorption in osteogenic sarcoma. I. Release of calcium by tumor cells, normal fibroblasts, and macrophages.

The bone calcium resorption activities of three different types of cells that are present either within or in the vicinity of an osteogenic sarcoma tumor mass were examined: osteogenic sarcoma cells, normal fibroblasts, and macrophages. Release of calcium was measured in bone organ cultures in live and killed 45Ca-labeled fetal or newborn mouse long bones. The bone explants, tibiae and humeri, were co-cultured with various numbers of effector cells in microwell plates. Cultured osteogenic sarcoma cells resorb calcium from both live and heat-devitalized bones in a cell-number-dependent manner. A reduced effect of the tumor cells on killed bone suggests that the release of calcium from living bone by tumor cells is mediated partially through stimulation of the endogenous bone-resorbing systems. Fibroblasts also resorb calcium both from live and killed bones but at a lower rate than osteogenic sarcoma cells. Peptone-elicited peritoneal macrophages are capable of sustaining calcium resorption from live bones as well as from bones devitalized by a mild nondenaturating method. Macrophages, however, failed to resorb calcium from heat-killed bones. The release of osseous calcium and bone damage associated with osteogenic sarcoma are manifestations of the resorbing properties and interactions among the tumor, bone, and host tumor infiltrating cells.