Multihormonal control of cell proliferation: opposite effects of two stimulators (17 beta-estradiol and L-triiodothyronine) and one inhibitor (dexamethasone) on F4Z2 pituitary tumor cells.
From the MtTF4 tumor of rat pituitary origin we established the F4Z2 cell line whose growth is stimulated by 17 beta-estradiol (E2). Taking E2 actions as references we investigated actions of other effectors on the proliferation, protein, and insulin growth factor-I (IGF-I) secretions of F4F2 cells. Dexamethasone (Dex) and L-T3 were chosen because they have also intracellular receptors and they act in pituitary cells. Cells were cultured in 96-well plates in RPMI 1640 medium supplemented either with charcoal-treated fetal calf serum (CT-FCS) or with BSA and transferrin. Hormones were added at the time of seeding and cells were counted 2-10 days later without renewing the culture medium. The accumulation of immunoreactive IGF-I in conditioned medium was used as an index of IGF-I secretion. For studies on protein secretion, cells were incubated for 24 h with [35S]methionine and labeled proteins were separated by polyacrylamide gel electrophoresis. We found that: 1) L-T3, like E2, stimulated in a dose-dependent and specific manner the proliferation of F4Z2 cells cultured in the presence of 5% CT-FCS; EC50 was: 1 X 10(-11) M and 0.2 X 10(-11) M for L-T3 and E2, respectively. In contrast, L-T3 but not E2 remained active in serum-free medium; 2) Dex was a strong inhibitor of cell proliferation in serum-free medium and in medium supplemented with 5% CT-FCS (EC50: 5 X 10(-9) M). The antiglucocorticoid RU 38 486 prevented this inhibitory effect; 3) when a stimulator (E2 or L-T3) was simultaneously incubated with the inhibitor (Dex) the number of cells depended on the ratio of hormone concentrations. When there was no large excess of one effector this number was intermediary between those counted in the presence of each hormone separately and L-T3 was more potent than E2 in preventing Dex inhibition; 4) Dex, E2, and L-T3 modified the electrophoretic patterns of secreted proteins but there was no evidence for a correlation between these modifications and the inhibition or the stimulation of cell proliferation, and 5) the accumulation of immunoreactive IGF-I was insensitive to E2, increased by L-T3, and markedly decreased by Dex. L-T3 but not E2 prevented the effect of Dex.(ABSTRACT TRUNCATED AT 400 WORDS)
Zhou-Li
F
F
INSERM-U 329, Hôpital Debrousse, Lyon, France.
Joly-Pharaboz
M O
MO
Bouillard
B
B
Albaladejo
V
V
Nicolas
B
B
Andre
J
J
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003470:Culture Media; D003907:Dexamethasone / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D006728:Hormones / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000378:metabolism / Q000473:pathology*; D014284:Triiodothyronine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D003470:Culture Media; D006728:Hormones; D009363:Neoplasm Proteins; D014284:Triiodothyronine; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone