Multiple signaling pathways mediate interleukin-4-induced 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase type 1 gene expression in human breast cancer cells.
The 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase (3beta-HSD) isoenzymes catalyze an essential step in the formation of all classes of active steroid hormones. We have recently shown that 3beta-HSD type 1 gene expression is specifically induced by interleukin (IL)-4 and IL-13 in breast human cancer cell lines and in normal human mammary epithelial cells in primary culture. There is evidence that IL-4 stimulates bifurcating signaling pathways in which the signal transducer and activator of transcription-6 (Stat6)-signal pathway is involved in differentiation and gene regulation, whereas insulin receptor substrate (IRS) proteins mediate the mitogenic action of IL-4. In fact, we have shown that Stat6 was activated by IL-4 in all cell lines studied where IL-4 induced 3beta-HSD expression, but not in those that failed to respond to IL-4. The present study was designed to investigate the potential contribution of IRS proteins and their downstream targets to IL-4-induced 3beta-HSD type 1 gene expression. IL-4 rapidly induced IRS-1 and IRS-2 phosphorylation in ZR-75-1 human breast cancer cell lines. Moreover, insulin-like growth factor (IGF)-I and insulin, which are well known to cause IRS-1 and IRS-2 phosphorylation, increased the stimulatory effect of IL-4 on 3beta-HSD activity. IRS-1 and IRS-2 are adapter molecules that provide docking sites for different SH2-domain-containing proteins such as the phosphatidylinositol (PI) 3-kinase. In this light, the inhibition of IL-4-induced 3beta-HSD expression by wortmannin and LY294002, two potent PI 3-kinase inhibitors, indicates the probable involvement of the PI 3-kinase signaling molecules in this response to IL-4. Furthermore, it has been suggested that the IRS proteins are part of the signaling complexes that lead to activation of the mitogen-activated protein (MAP) kinase by insulin; thus we investigated the potential role of the MAP kinase (MAPK) cascade in the IL-4 action. In ZR-75-1 cells, both the activation of MAPK by IL-4 and the IL-4-induced 3beta-HSD activity were completely blocked by PD98059, an inhibitor of MAPK activation. Wortmannin also blocked MAPK activation by IL-4, IGF-I, and insulin, suggesting that the MAPK cascade acts as a downstream effector of PI 3-kinases. To further understand the cross-talk between signaling pathways involved in IL-4 action, we investigated the possible involvement of protein kinase C (PKC). The potential role of PKC was suggested by the observation that the well known PKC activator phorbol-12-myristate-13-acetate (PMA) potentiated the IL-4-induced 3beta-HSD activity. Taken together, these findings suggest the existence of a novel mechanism of gene regulation by IL-4. This mechanism would involved the phosphorylation of IRS-1 and IRS-2, which transduce the IL-4 signal through a PI 3-kinase- and MAPK-dependent signaling pathway. The inability of IGF-I, insulin, and PMA to stimulate 3beta-HSD expression by themselves in the absence of IL-4 makes obvious the absolute requirement of an IL-4-specific signaling molecule. Our findings thus suggest that the multiple pathways downstream of IRS-1 and IRS-2 must act in cooperation with the IL-4-specific transcription factor Stat6 to mediate the induction of 31beta-HSD type 1 gene expression in ZR-75-1 human breast cancer cells.
Gingras
S
S
Medical Research Council Group in Molecular Endocrinology CHUL Research Center and Laval University, Quebec City, Canada.
Côté
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S
Simard
J
J
D000730:Androstadienes / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D015847:Interleukin-4 / Q000378:metabolism* / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011375:Progesterone Reductase / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D050800:STAT6 Transcription Factor; D015398:Signal Transduction; D013251:Steroid Isomerases / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I; D015847:Interleukin-4; D047908:Intracellular Signaling Peptides and Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D009025:Morpholines; D009097:Multienzyme Complexes; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D011375:Progesterone Reductase; D050800:STAT6 Transcription Factor; D013251:Steroid Isomerases; D013755:Tetradecanoylphorbol Acetate; D015534:Trans-Activators; D000077191:Wortmannin; C021425:3 beta-hydroxysteroid oxidoreductase-delta(5) 3-ketosteroid isomerase; C526292:IRS1 protein, human; C526297:IRS2 protein, human; C494101:STAT6 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one