TRANSCRIPTIONAL REGULATION OF THE HUMAN LEUKEMIA INHIBITORY FACTOR GENE - MODULATION BY GLUCOCORTICOIDS AND ESTRADIOL

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine implicated in various pathological conditions, such as rheumatoid arthritis and o steoporosis. Despite its possible importance as a therapeutic target, very little is known about the regulation of human LIF. In particular, its regulation at the promoter level has not been studied so far, and was, therefore, the focus of the present work. After showing that Jur kat T lymphoma cells can be induced to express endogenous LIF mRNA, we used this cell line as a model to study the regulation of the human L IF promoter in transient transfection assays. For this purpose, a 666 bp fragment of the human LIF 5'-flanking region, amplified from genomi c DNA by nested polymerase chain reaction (PCR), was used for the cons truction of a luciferase reporter plasmid (hLIF666-Luc). In unstimulat ed Jurkat cells, the human LIF promoter showed low constitutive activi ty. The promoter was induced upon stimulation with phorbol ester (TPA) . Combined stimulation with TPA and the calcium ionophore ionomycin re sulted in strong synergistic induction of luciferase activity from the LIF promoter. Transfection experiments with deletion constructs (hLIF 274-Luc and hLIF82-Luc) located the region required for this induction to a 192 bp portion of the promoter, which carries two putative c-ets binding sites. We then investigated the effect of glucocorticoids and estradiol by cotransfecting the respective receptors. Both hormones s trongly inhibited the stimulation of the LIF promoter by TPA and ionom ycin. Since LIF is implicated in the pathogenesis of inflammatory and degenerative conditions, such as rheumatoid arthritis and osteoporosis , the finding that therapeutic agents employed in the treatment of suc h conditions, i.e. glucocorticoids and estrogens, can modulate the ind uction of LIF at the transcriptional level, is of particular interest. (C) 1997 Elsevier Science Ireland Ltd.