EXPRESSION OF TRUNCATED PROOPIOMELANOCORTIN GENE TRANSCRIPT IN HUMAN LEUKEMIA-CELL LINES

Although previous studies have suggested that human peripheral blood m ononuclear cells (PBMCs) may express pro-opiomelanocortin (POMC) mRNA and synthesize its related peptides, the patho-physiological role of P OMC expressed in peripheral cells is not known. In this study, we inve stigated the POMC gene expression in various types of human leukemia c ell lines by Northern blot analysis and the reverse transcribed-polyme ase chain reaction (RT-PCR) method. The POMC mRNA was not detected by Northern blot analysis in all cell lines tested except the Jurkat cell line which is derived from T-lymphoblastic leukemia. The POMC mRNA ex pressed in the Jurkat cells was smaller than that in the human anterio r pituitary gland. The RT-PCR method revealed that a truncated-POMC tr anscript could be detected not only in lymphoblastic leukemia cells bu t also in erythroid and myeloid cells. Interestingly, two cell lines o f monocytic leukemia, J-111 and U937, did not express the truncated-PO MC mRNA. Treatment with concanavalin-A stimulated truncated POMC mRNA expression and ACTH-like immunoreactivity in lymphoblastic leukemia ce lls with T-(Jurkat) and B-(BALL-1) lymphocyte phenotypes. These result s confirm that human leukemia cells except for monocytic cells express a truncated-POMC mRNA as well as in the human normal PBMC.