Characterization of a murine tumor of spontaneous origin with selective hepatic metastasis.

: The primary objective of this study was to establish the identity and characteristics of a murine uterine tumor of spontaneous origin in a C57Bl/6 Ros mouse that selectively metastasized to the liver. The primary tumor contained a minimum of two different cell types. One cell type was elongated and spindly and readily adhered to a plastic coated surface. From it, a permanent cell line, termed RCS-1 was established. The RCS-1 cell line was poorly tumorigenic in normal C57Bl/6 Ros mice. The other cell type, designated RCS-2, was more rounded in structure. It was maintained in vivo, enzymatically dissociated and used after short-term in vitro cell culture. The RCS-2 cells had phagocytic vacuoles, Fc, and C3 receptors. These cells phagocytosed antibody coated SRBCs and opsonized zymosan. Furthermore, these cells generated the superoxide anion. Thus, the RCS-2 cells are of macrophage origin. The spontaneous and experimental pattern of metastasis of the RCS-2 tumor cells was established. The RCS-2 tumor cells selectively metastasized to the liver by the hematogenous route. Metastatic RCS-2 tumor cells obtained from the liver (RCS-2M) retained their macrophage characteristics. These studies indicate that this murine uterine tumor of spontaneous origin consists of two cell types. One cell type is a reticulum cell sarcoma.