Production of erythropoietin‐like activity by human renal and hepatic carcinomas in cell culture

Two types of human cancers, a renal cell carcinoma and a hepatocellular carcinoma, were investigated in vitro; both produced a marked erythrocytosis in each patient. These tumors, when transplanted into athymic nude mice, produced a remarkable erythrocytosis in the host mice. To analyze this phenomenon, the primary cultures from these xenotransplanted tumors were performed. To obtain pure tumor cell cultures, cells derived from host nude mice were eliminated by the treatment with the antiserum raised against nude mouse cells. Epithelial cells derived from each tumor attached and grew in the cultures. The conditioned media from both tumor cells revealed high erythropoietic stimulatory activities. We have characterized these erythropoietin‐like activities by size‐exclusion high‐performance liquid chromatography. Three peaks of erythropoietin‐like activities were noted after bovine serum albumin region. The molecular weights were estimated at about 55,000, 40,000, and 33,000, respectively. The results suggested that the human renal cell and hepatocellular carcinomas produced erythropoietin‐like activities in vitro in culture and that erythrocytosis found in patients with cancer and in nude mice transplanted with the tumors was attributable to production of the erythropoietin‐like activities by the tumor cells themselves.