Phagocytosis and degradation of elastin by normal and tumor cells in culture.

Heteroploid, diploid, and primary kidney cells from several species have been examined in culture for their capacity to ingest and solubili ze elastin, an important component of con nective tissue. Established human heteroploid cell lines and viral-trans formed tumorigenic hamster cells actively phagocytized and degraded intracellular elastin. In contrast, established human diploid fibroblasts did not phagocytize elastin. Epithelial-like cellular elements of primary kidney cultures were less active phagocytically toward elastin than heteroploid cells and some what less active elastolytically. Fibroblast-like components of renal cultures, like human diploid fibroblasts, did not ingest fiber. Uptake of elastin fiber by heteroploid cells could be essen tially abolished by treatment with mild alkali, suggesting the removal of fiber-cell receptor substance. Fiber ingestion and degradation of Hep-2 cells, accompanied by an increased metabolic activity, were modified by tempera ture, inhibitors of RNA and protein synthesis, and serum content. These findings suggest that phagocytosis of elastin is an active energy-requiring, receptor-dependent process. Tumor and stromal cells in culture overlaid with elastin re semble to some degree host-tumor interface prior to invasion and destruction of blood vessel, tendon, and skin. These studies suggest that tumor and stromal cells provide models in which each cell type independently may be examined for its capacity to modify and catabolize fibrous components of connective tis sue. Such models permit the characterization of these destruc tive events at the extracellular, the cellular, and the subcellular level.