Cancer may affect hemopoiesis by altering the proliferative status of hemopoietic progenitor cells. In Lewis lung carcinoma (LLC), the proliferative rate of the granulocyte-macrophage colony-forming unit (culture) (GM-CFUc) was studied using in vivo hydroxyurea techniques. The disposal of mature elements to the periphery was also monitored during tumor growth. Neutrophilia, anemia, and splenic hypertrophy developed during the course of the disease. By Day 6 post-tumor implant, myeloid hyperplasia of the marrow was evident, but the content of GM-CFUc in LLC mice was smilar to that of control. However, by Day 11, the marrow of LLC mice displayed an increased concentration of GM-CFUc, which tripled by Day 19. There was an increased percentage of proliferating GM-CFUc in LLC mice by Day 6 which was highest by Day 11 and thereafter declined. The level of colony-stimulating activity was higher in the serum of tumor bearers than in that of controls. The early increase in proliferative rate of these early hemopoietic precursors can account for the later accumulation of GM-CFUc and myeloid elements in the marrow. Increased cycling of hemopoietic stem cells raises questions concerning the potential for early exhaustion of hemopoietic progenitor cells in these animals.
This work was supported in part by Veterans Administration Funds and by funds from the Ladies Auxiliary of the Veterans of Foreign Wars.