Erythropoietin levels in the course of a patient with erythropoietin-producing renal cell carcinoma and transplantation of this tumor in nude mice.

Erythropoietin was measured by exhypoxic polycythemic mouse method in the course of a 64-yr-old male with renal cell carcinoma associated with erythrocytosis. Serum erythropoietin fluctuated with progression of the disease. Preoperative elevated erythropoietin (0.11 U/ml, p greater than 0.05) subsided after nephrectomy and again increased with developing lung metastasis (0.1 U/ml, p greater than 0.02). Erythropoietin was markedly increased in the tumorous extracts from primary renal cell carcinoma in the kidney (0.2 U/g, p greater than 0.01) and lung metastasis (0.8 U/g, p greater than 0.01). Renal cell carcinoma from the lung metastasis was transplanted into nude mice, resulting in erythrocytosis in some of these mic. In the erythrocytotic mice, erythropoietin was elevated to levels of 0.25--0.9 U/g (p greater than 0.01) in the tumorous extracts and increased (0.67 U/ml, p greater than 0.02) in the serum. These results indicate that this renal cell carcinoma is an erythropoietin-producing tumor, and this tumor has been successfully transplanted in nude mice for the first time.