PROGESTIN-DEPENDENT STIMULATION OF THE HUMAN LEUKEMIA INHIBITORY FACTOR PROMOTER IN SKUT-1B UTERINE-TUMOR CELLS

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine which is es sential for implantation in rodents and is expressed during the proges terone-dominated secretory phase of the menstrual cycle in the human e ndometrium. However, the effect of progestin on the transcriptional re gulation of the LIF promoter has not been studied so far. In the prese nt study, we used a luciferase reporter plasmid bearing 666 bp of the human LIF promoter (hLIF666-Luc) to investigate the effects of progest in on the transcriptional regulation of LIF in SKUT-1B uterine tumor c ells. Jurkat T-lymphoma cells were used for comparison. Since both cel l lines are devoid of functional progesterone receptors (PR), we co-tr ansfected the cells with hLIF666-Luc and an expression vector for the human PR form B (PR-B) or A (PR-A). Addition of the progesterone agoni st MPA (medroxy-progesterone acetate, 2.5 x 10(-7) M) resulted in indu ction of LIF transcription only in SKUT-1B cells, while it had no effe ct in Jurkat cells. Both PR forms were effective in inducing the LIF p romoter in SKUT-1B cells when activated by MPA. However, the induction through PR-A was inhibited more efficiently by the progestin antagoni st RU 486. We next investigated the stimulatory effect of MPA in SKUT- 1B cells on deletion constructs (h274LIF-Luc, h148LIF-Luc and h82LIF-L uc) and found that it is maintained on these fragments. Thus, 82 bp ar e sufficient to mediate this effect. Our results show that the human L IF promoter is active in uterine tumor cells, and that it is different ially regulated by progestin in cells of uterine and lymphoid origin. (C) 1997 Elsiever Science Ireland Ltd.