Tumor Necrosis Factor‐a Stimulates Colony Formation by a Megakaryoblastic Leukemia Cell Line, CMK

Abstract

The CMK cell line is an acute megakaryoblastic leukemia cell line established from a patient with Down's syndrome, and is known to possess characteristics of normal megakaryocytes. Several cytokines with the ability to stimulate megakaryopoiesis, such as interleukin‐3 (IL‐3), interleukin‐6 (IL‐6) and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), stimulated colony formation by CMK cells. The present study revealed that tumor necrosis factor‐α (TNF‐α) stimulated colony formation by CMK cells; the potency was almost equal to that of IL‐3, IL‐6 or GM‐CSF. Scatchard plot analysis revealed that CMK cells possess two types of specific binding sites for TNF‐α. The high‐affinity binding sites had an affinity constant of 0.18 nM, and numbered 5,000. The low‐affinity binding sites had an affinity constant of 1.8 nM/and numbered 19,000. These results raise the possibility that TNF‐α can act as a growth‐stimulating agent on megakaryocyte‐Iineage cell line.