Endothelin expression in human megakaryoblastic leukemia cell lines and normal platelet precursors

The aim of the present investigation was to determine whether endothelin (ET) could be expressed in and released from the human leukemia megakaryoblastic cell lines HEL, MEG-01, DAMI and the normal human platelet progenitors. Using the reverse transcriptase-polymerase chain reaction (RT-PCR) on total RNA isolated from the cells, we amplified a cDNA of the expected size (453 bp). Southern-blotting hybridization revealed that RT-PCR products from the cell lines were specific of ET-1 mRNA. Immunocytochemical analyses highlighted immunoreactive ET-1 in the cytoplasm of these cells which also released the mature peptide. ET-1 release from the three cell lines was increased by thrombin exposure. Although MEG-01 cells express ET receptors, ET-1, the selective ETB agonist sarafotoxin 6C and the non-selective ET-receptor antagonist PD 142893 showed no proliferative or antiproliferative action in basal or stimulating medium. This indicated a lack of autocrine ET-mediated effect on growth. These results demonstrate for the first time that human megakaryoblastic leukemia cell lines and normal bone marrow platelet precursors express ET-1 mRNA and release the mature peptide.