Oncostatin M Induces Growth Arrest of Mammary Epithelium Via a CCAAT/Enhancer-Binding Protein ␦-Dependent Pathway1
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Vol. 1, 601–610, June 2002 Molecular Cancer Therapeutics 601 Oncostatin M Induces Growth Arrest of Mammary Epithelium via a CCAAT/enhancer-binding Protein ␦-dependent Pathway1 Julie A. Hutt and James W. DeWille2 These cytokines signal by binding to cell surface receptors, Department of Veterinary Biosciences [J. A. H., J. W. D.] and Division of which consist of cytokine-specific binding subunits and a Molecular Biology and Cancer Genetics, Ohio State Comprehensive common signaling subunit, glycoprotein 130 (2, 3). OSM is Cancer Center [J. W. D.], The Ohio State University, Columbus, Ohio 43210 produced by a variety of cell types, including neoplastic breast epithelial cells (4). Other IL-6-type cytokines are also produced by normal and neoplastic breast epithelium and Abstract breast adipose cells (4). Furthermore, the IL-6 expression Oncostatin M (OSM), an interleukin 6-type cytokine, level in some types of mammary carcinoma is inversely cor- induces sustained up-regulation of CCAAT/enhancer- related with the histological grade of malignancy (5, 6). binding protein (C/EBP) ␦ mRNA and protein in OSM stimulates proliferation of some cell types, such as nonneoplastic HC11 mouse mammary epithelial cells. myeloma cells and Kaposi’s sarcoma cells, and inhibits pro- This up-regulation is dependent on signaling by liferation of others, such as melanoma cells and normal and phospho-Stat3 (signal transducers and activators of neoplastic mammary epithelial cells (7–12). In normal and transcription). The same signaling pathway is activated neoplastic human mammary epithelial cells, OSM inhibits cell in two human breast cancer cell lines, a neoplastic cycle progression, with a reduction in the proportion of S- mouse mammary epithelial cell line and a second phase cells and an adoption of morphological phenotype nonneoplastic mouse mammary epithelial cell line. characteristic of differentiated breast epithelial cells (11–13). [3H]Thymidine incorporation and flow cytometry However, little is known about the signaling pathways in- demonstrate that OSM inhibits the growth of HC11 volved in determining whether OSM induces cell proliferation cells by reducing the number of S-phase cells. These or growth inhibition. To understand the biological role of phenotypic changes are accompanied by reduced OSM in the mammary gland and enhance the effectiveness expression of S-phase genes with a corresponding of OSM as a therapeutic agent, an understanding of the increased expression of G0 genes in HC11 cells. OSM-activated signaling pathways leading to growth arrest Reduction of C/EBP␦ protein in HC11 cells by of normal and neoplastic cells is of crucial importance. expression of a C/EBP␦ antisense construct inhibits Recent studies have demonstrated that OSM and IL-6 OSM-mediated growth arrest. These data demonstrate simultaneously induce growth inhibition and increased mi- that OSM induces up-regulation of C/EBP␦ via a Stat3- gration of T47D breast cancer cells via different, simulta- dependent pathway in mammary epithelial cells and neously activated signaling pathways (14). The growth inhi- that the growth inhibition induced by OSM depends on bition induced by both OSM and IL-6 depends on Stat3 the presence of C/EBP␦. activation, but no downstream mediators of growth arrest have been identified. The increased cell migration induced by Introduction IL-6 is independent of Stat3 and depends on activation of the OSM3 has recently been proposed for use as a potential MAPK/phosphatidylinositol 3Ј-kinase pathway. This sug- cancer therapeutic agent, due to its ability to induce growth gests that the ultimate cell fate depends on a balance be- arrest of normal and neoplastic human breast epithelial cells tween the different cytokine-activated signaling pathways. (1). OSM is a member of the IL-6 family of cytokines, which Stats are latent cytoplasmic transcription factors, which, also includes IL-6, IL-11, LIF, and ciliary neurotrophic factor. upon activation by tyrosine phosphorylation, form homo- or heterodimers, translocate to the nucleus, and bind consen- sus DNA sequences to activate transcription. Stat3 has pre- viously been shown to be involved in regulation of both Received 2/20/02; revised 4/22/02; accepted 4/29/02. proliferation and growth arrest, depending on the cell type 1 Supported in part by NIH Grant RR00136CA (to J. A. H.) and NIH Grants CA 57607 and P30CA16058 from the National Cancer Institute (to (15–19). Several human breast cancer cell lines exhibit dys- J. W. D.). regulation of Stat3 signaling characterized by constitutively 2 To whom requests for reprints should be addressed, at Department of activated Stat3 (20, 21). In contrast, Stat3 activation in the Veterinary Biosciences, The Ohio State University, 1900 Coffey Road, Columbus, OH 43210. Phone: (614) 292-4261; Fax: (614) 292-6473; E- involuting mouse mammary gland has been proposed as the mail: [email protected]. “driving force” for mammary epithelial apoptosis (22–24). 3 The abbreviations used are: OSM, oncostatin M; IL, interleukin; LIF, Conditional Stat3 knockout in the involuting mouse mam- leukemia inhibitory factor; C/EBP, CCAAT/enhancer-binding protein; JAK, Janus kinase; EGF, epidermal growth factor; TRPM2, testosterone re- mary gland confers delayed involution (25). Previous work pressed specific message 2; CP, cyclophilin; Stat, signal transducers and from our laboratory demonstrates that mammary gland in- activators of transcription; MAPK, mitogen-activated protein kinase; FBS, fetal bovine serum; ATCC, American Type Culture Collection; TK, thymi- volution in vivo and serum and growth factor withdrawal in dine kinase; ERK, extracellular signal-regulated kinase. vitro result in Stat3 activation, with subsequent Stat3 binding Downloaded from mct.aacrjournals.org on September 23, 2021. © 2002 American Association for Cancer Research. 602 OSM Induces Growth Arrest of Mammary Epithelium via C/EBP␦ to the acute phase response element of the C/EBP␦ pro- (Peprotech, Rocky Hill, NJ), and OSM (mouse and human; moter, increased Stat3-dependent C/EBP␦ transcription, R&D Systems, Minneapolis, MN). and, ultimately, growth arrest and apoptosis of mammary Transfections. To make the bulk-transfected C/EBP␦ an- epithelium (26–28). Thus, these contrasting roles for Stat3 in tisense cell lines, HC11 cells were transfected with the mammary epithelium demonstrate that there are other fac- pcDNA3-C/EBP␦ antisense plasmid or the empty pcDNA3 tors (presumably other signaling pathways) that interact with plasmid using Transfectam reagent (Promega, Madison, WI; the Stat3 pathway to influence the ultimate fate of the cell. Ref. 38). Selection was carried out in the presence of 700 C/EBP␦ is a member of the C/EBP family of leucine zipper g/ml Geneticin (Invitrogen Life Technologies, Inc.) for 2 DNA-binding proteins, which have been implicated in the weeks. Clonal cell lines were established from individual ␦ control of growth and differentiation in a variety of tissue and colonies, and Western blotting identified the 1 clone as cell types (29–34). The six C/EBP family members (␣, , ␦, ␥, having maximal inhibition of C/EBP␦ protein expression. ⑀, and C/EBP homologous protein-10) form homo- or het- Other colonies were pooled to establish bulk transfected cell ␦ erodimers with C/EBPs and other leucine zipper proteins and lines to dilute the influence of clonal variation. The 1 anti- bind to DNA to activate or repress transcription (35, 36). sense plasmid has been described previously (38). ␦ C/EBP has an important role in the induction of G0 growth Northern Blot Analysis. Total RNA was isolated from arrest and apoptosis in cultured mouse mammary epithelium cultured cells using RNazol B (Tel-Test, Friendswood, TX). in response to serum and growth factor withdrawal (37, 38). Northern blots were carried out using standard procedures To investigate the signaling pathways involved in the (40). Blots were probed with the following random primer- OSM-mediated growth arrest response of mammary epithe- labeled ([␣-32P]dCTP) cDNAs: C/EBP␦, C/EBP (a generous lial cells, nonneoplastic HC11 mouse mammary epithelial gift of Dr. Steven McKnight; University of Texas Southwest- cells were treated with OSM. The work described herein ern Medical Center), GAS1 (growth arrest-specific gene 1; a demonstrates that the OSM-induced growth arrest response generous gift of Dr. Claudio Schneider; Cosorzio Interuniver- in HC11 cells and other mouse mammary epithelial cells is sitario Biotecnologie), TRPM 2, TK, and histone 2B (Oncor, similar to what occurs in human mammary epithelium. OSM Gaithersburg, MD). Cyclophilin receptor protein partial cDNA treatment of HC11 cells decreases [3H]thymidine incorpora- was used as a constitutive probe. Fold induction was calcu- tion and reduces the number of S-phase cells, with corre- lated from densitometric measurements taken using an sponding increases in expression of G0 genes and decreases AlphaImager 2000 (Alpha Innotech, Staffordshire, United in expression of S-phase genes. In addition, in both mouse Kingdom). Figures depicting multiple mRNAs were either and human mammary epithelium, OSM induces sustained coprobed or stripped and sequentially reprobed. Results are Stat3 phosphorylation and phospho-Stat3-dependent representative of experiments performed two to four times. C/EBP␦ up-regulation. Furthermore, we show that the Western Blot Analysis. Whole cell protein lysates were growth arrest response induced by OSM is markedly dimin- prepared from tissue culture cells. Cells were