Methylcholanthrene-induced murine fibrosarcoma cell line BMT-11 secretes granulocyte colony-stimulating factor

Murine fibrosarcoma cell line BMT-11 was induced with 3-methylcholanthrene and maintained in culture. Transplantation of BMT-11 into syngeneic C57BL/6 mice produced leukocytosis consisting of marked increments of neutrophils and monocytes associated with massive splenomegaly. In order to elucidate the mechanisms of this leukemoid reaction, we studied the changes occurring in hematopoietic progenitor cells in BMT-11-transplanted mice. The numbers of granulocyte-macrophage colony-forming units (CFU-GM), erythroid colony-forming units (CFU-E), erythroid burst-forming units (BFU-E), and mixed colony-forming units (CFU-Mix) in the spleen showed dramatic 216-fold, 18-fold, 64-fold, and 80-fold increases, respectively, relative to the value in the control mice 5 weeks after the BMT-11 implantation. In contrast, the levels of progenitor cells in the bone marrow remained within normal limits. The nature of the colony-stimulating factor (CSF) secreted from BMT-11 tumor cells was also studied. BMT-11-conditioned medium (BMT-11-CM), BMT-11 tumor extract, and sera from the mice bearing transplanted BMT-11 tumor contained CSF that stimulated mainly granulocyte and macrophage lineages. Furthermore, the expression of the granulocyte colony-stimulating factor (G-CSF) gene in BMT-11 cells were detected by Northern blot analysis.