title: Serum/glucocorticoid-regulated kinase 1 (SGK1) is a prominent target gene of the transcriptional response to cytokines in multiple myeloma and supports the growth of myeloma cells.
abstract: Multiple myeloma (MM) is a paradigm for a malignant disease that exploits external stimuli of the microenvironment for growth and survival. A thorough understanding of the complex interactions between malignant plasma cells and their surrounding requires a detailed analysis of the transcriptional response of myeloma cells to environmental signals. We determined the changes in gene expression induced by interleukin (IL)-6, tumor necrosis factor-α, IL-21 or co-culture with bone marrow stromal cells in myeloma cell lines. Among a limited set of genes that were consistently activated in response to growth factors, a prominent transcriptional target of cytokine-induced signaling in myeloma cells was the gene encoding the serine/threonine kinase serum/glucocorticoid-regulated kinase 1 (SGK1), which is a down-stream effector of PI3-kinase. We could demonstrate a rapid, strong and sustained induction of SGK1 in the cell lines INA-6, ANBL-6, IH-1, OH-2 and MM.1S as well as in primary myeloma cells. Pharmacologic inhibition of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway abolished STAT3 phosphorylation and SGK1 induction. In addition, small hairpin RNA (shRNA)-mediated knock-down of STAT3 reduced basal and induced SGK1 levels. Furthermore, downregulation of SGK1 by shRNAs resulted in decreased proliferation of myeloma cell lines and reduced cell numbers. On the molecular level, this was reflected by the induction of cell cycle inhibitory genes, for example, CDKNA1/p21, whereas positively acting factors such as CDK6 and RBL2/p130 were downregulated. Our results indicate that SGK1 is a highly cytokine-responsive gene in myeloma cells promoting their malignant growth.
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: U-M
authors.initials: UM
authors.lastname: Fagerli
authors.forename: K
authors.initials: K
authors.lastname: Ullrich
authors.forename: T
authors.initials: T
authors.lastname: Stühmer
authors.forename: T
authors.initials: T
authors.lastname: Holien
authors.forename: K
authors.initials: K
authors.lastname: Köchert
authors.forename: R U
authors.initials: RU
authors.lastname: Holt
authors.forename: O
authors.initials: O
authors.lastname: Bruland
authors.forename: M
authors.initials: M
authors.lastname: Chatterjee
authors.forename: H
authors.initials: H
authors.lastname: Nogai
authors.forename: G
authors.initials: G
authors.lastname: Lenz
authors.forename: J D
authors.initials: JD
authors.lastname: Shaughnessy
authors.forename: S
authors.initials: S
authors.lastname: Mathas
authors.forename: A
authors.initials: A
authors.lastname: Sundan
authors.forename: R C
authors.initials: RC
authors.lastname: Bargou
authors.forename: B
authors.initials: B
authors.lastname: Dörken
authors.forename: M
authors.initials: M
authors.lastname: Børset
authors.forename: M
authors.initials: M
authors.lastname: Janz
mesh_terms: D001854:Bone Marrow Cells / Q000187:drug effects / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology*; D015536:Down-Regulation / Q000235:genetics; D006801:Humans; D017874:Immediate-Early Proteins / Q000172:deficiency / Q000235:genetics*; D053612:Janus Kinases / Q000378:metabolism; D009101:Multiple Myeloma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics*; D034622:RNA Interference; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects* / Q000235:genetics*; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D016207:Cytokines; D017874:Immediate-Early Proteins; D053612:Janus Kinases; D017346:Protein Serine-Threonine Kinases; D050796:STAT3 Transcription Factor; D000099184:Serum-Glucocorticoid Regulated Kinases