The Proliferative and Antiapoptotic Actions of Growth Hormone and Insulin-Like Growth Factor-1 Are Mediated through Distinct Signaling Pathways in the Pro-B Ba/F3 Cell Line

• Published in: Endocrinology (Philadelphia) 2001-07, Vol.142 (7), p.2968-2977
• Main Authors: Baixeras, Elena, Jeay, Sébastien, Kelly, Paul A., Postel-Vinay, Marie-Catherine
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; AKT protein; Apoptosis; Beta cells; Cell culture; Cell cycle; Cell proliferation; Cell survival; Cyclin-dependent kinase inhibitor p21; Cyclins; Gene expression; Growth factors; Growth hormones; Insulin; Insulin-like growth factor I; Insulin-like growth factors; Interleukin 3; Kinases; mRNA; Stimulation; Survival; Transfection
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/endo.142.7.8242

Abstract Biological actions of GH can be direct or mediated through insulin-like growth factor I (IGF-I). In the interleukin-3 (IL-3)-dependent Ba/F3 cell line, IGF-I induces cell cycle entry and proliferation. Ba/F3 cells expressing the rat GH receptor (Ba/F3 GHR cells) have been shown to escape from apoptosis and to proliferate under GH stimulation. Using the Ba/F3 GHR cell model, we sought to dissect the signals elicited specifically by IGF-I or GH. In contrast to IGF-I or IL-3, GH is able to maintain cell cycle entry of Ba/F3 GHR cells cultured for 7 days in the absence of serum. The presence of IGF-I messenger RNA was not detected by RT-PCR, and by RIA, IGF-I was not found in culture medium of Ba/F3 GHR cells, unstimulated or stimulated by GH. Moreover, the addition of an anti-IGF-I antibody that blocks IGF-I effects suggests that the actions of GH are not mediated by IGF-I, but appear to be direct. GH or IGF-I stimulation increased expression of cyclins A and D1 with comparable kinetics, whereas expression of p21waf1/cip1 seemed delayed in IGF-I-stimulated cells compared with that in GH-stimulated cells. Contrary to GH or IL-3, IGF-I did not induce nuclear factor-κB DNA-binding activity in Ba/F3 cells. Inhibition of nuclear factor-κB through expression of the mutant IκBα (A32/36) abrogated the GH-mediated survival signal, but did not result in alterations of the cell cycle in Ba/F3 GHR cells treated with IGF-I. Phosphatidylinositol 3-kinase was required for both survival and proliferative responses to IGF-I. Transfection of a dominant negative form of AKT (AH-AKT) resulted in suppression of IGF-I-mediated cell survival, but not of the antiapoptotic effect of GH in Ba/F3 GHR cells. Thus, GH and IGF-I are able to promote cell survival and proliferation through independent and different pathways in Ba/F3 cells.