Production of Colony-stimulating Factor by Malignant Leukocytes

There is considerable evidence supporting a role for colony-stimulating factor (CSF) as a humoral regulator of leukopoiesis. Data on CSF levels in the serum and urine of patients with leukemia and on the in vitro responsiveness of leukemic cells to CSF have suggested a basis for considering leukemia as a primary disorder of leukopoietic regulation. We examined the question of leukemic cell production of CSF. Conditioned medium from cultured leukemic cells was tested for colony-stimulating activity against normal human bone marrow using a two-layer agar colony assay technique. The cells from patients with acute myelogenous leukemia and a patient with chronic myelogenous leukemia in blast crisis did not elaborate CSF nor did acute lymphocytic leukemia cells. CSF production was documented with cells obtained from patients with chronic myelogenous leukemia in the chronic phase and two patients with acute myelomonocytic leukemia. In acute leukemia the cellular production of CSF correlated closely with morphologic and functional maturation along the monocyte-macrophage line. Evidence was obtained that the adherent cells within the leukemic population were primarily responsible for CSF production. We interpret these data to indicate that neoplastic hematopoietic cells may produce CSF in relation to their capacity for mononuclear leukocyte differentiation.