Colony-forming ability of pluripotent hematopoietic stem cells in mice following tumor transplantation

The mechanism of tumor-induced hematological alterations at the level of pluripotent hematopoietic stem cells (CFU-S) was investigated in mice bearing transplantable ascites tumor, Sarcoma 180. Tumor growth for 10 days caused neutrophilic leukocytosis and decline in hemoglobin and RBC values in the peripheral blood, and significant reduction (p less than 0.05) in the concentration as well as absolute number of CFU-S in the femoral marrow but an increment in the spleen. Intraperitoneal administration of cell-free ascitic fluid caused similar alterations of CFU-S in normal mice, but heat-killed tumor cells failed to elicit such response. Tumor cell-conditioned medium when injected into normal mice caused CFU-S alterations in a pattern similar to that of tumor-bearing animals. It is concluded that alterations of CFU-S following tumor transplantation is attributable to tumor growth rather than the presence of dead or necrotic cells in the tumor inoculum. It is likely that tumor cells elaborate some factor(s) which mediate such changes.