ENDOTHELIN EXPRESSION IN HUMAN MEGAKARYOBLASTIC LEUKEMIA-CELL LINES AND NORMAL PLATELET PRECURSORS

The aim of the present investigation was to determine whether endothel in (ET) could be expressed in and released from the human leukemia meg akaryoblastic cell lines HEL, MEG-01, DAMI and the normal human platel et progenitors. Using the reverse transcriptase-polymerase chain react ion (RT-PCR) on total RNA isolated from the cells, we amplified a cDNA of the expected size (453 bp). Southern-blotting hybridization reveal ed that RT-PCR products from the cell lines were specific of ET-1 mRNA . Immunocytochemical analyses highlighted immunoreactive ET-1 in the c ytoplasm of these cells which also released the mature peptide. ET-1 r elease from the three cell lines was increased by thrombin exposure. A lthough MEG-01 cells express ET receptors, ET-1, the selective ETB ago nist sarafotoxin 6C and the non-selective ET-receptor antagonist PD 14 2893 showed no proliferative or antiproliferative action in basal or s timulating medium. This indicated a lack of autocrine ET-mediated effe ct on growth. These results demonstrate for the first time that human megakaryoblastic leukemia cell lines and normal bone narrow platelet p recursors express ET-1 mRNA and release the mature peptide. (C) 1997 E lsevier Science B.V.