Establishment and characterization of a new human megakaryoblastic cell line (SET-2) that spontaneously matures to megakaryocytes and produces platelet-like particles

A new factor-independent megakaryoblastic cell line, designated SET-2, was established from the peripheral blood of a patient with leukemic transforma tion of essential thrombocythemia (ET), SET-2 expressed CD 4, 7, 13, 33, 34 , 36, 38, 41, 61, 71, 117, 126, 130 and c-mpl, In addition, it spontaneousl y produced numerous platelet-like particles in liquid culture. These partic les were shown to be the same size as normal platelets, and to express CD 3 6, 38, 41, 61 and 71, Proliferation of SET-2 was not influenced by thrombop oietin (TPO) and other hemopoietic cytokines, SET-2 was found to express th e platelet-specific proteins such as platelet factor 4 and P-thromboglobuli n. The levels of expression were not altered by TPO, SET-2 also secreted in terleukin-6 into the supernatants, as well as normal megakaryocytes, These results suggest that SET-P spontaneously matures to megakaryocytes and prod uces platelet-like particles. These findings indicate that SET-2 may be use ful for investigating the proliferation and differentiation mechanisms of l eukemia cells and the role of c-mpl on megakaryoblasts, megakaryocytes, and platelets in ET.