title: Increased SPHK2 Transcription of Human Colon Cancer Cells in Serum-Depleted Culture: The Involvement of CREB Transcription Factor.
abstract: Sphingosine kinases (SPHK) are important to determine cells' fate by producing sphingosine 1-phosphate. Reportedly, exogenous SPHK2 overexpression induces cell cycle arrest or cell death. However, the regulatory mechanism of SPHK2 expression has not been fully elucidated. Here, we analyzed this issue using human colon cancer cell lines under various stress conditions. Serum depletion (FCS(-)) but not hypoxia and glucose depletion increased mRNA, protein and enzyme activity of SPHK2 but not SPHK1. In HCT116 cells mostly used, SPHK2 activity was predominant over SPHK1, and serum depletion increased both nuclear and cytoplasmic SPHK2 activity. Based on previous reports analyzing cellular response after serum depletion, the temporal changes of intracellular signaling molecules and candidate transcription factors for SPHK2 were examined using serum-depleted HCT116 cells, and performed transfection experiments with siRNA or cDNA of candidate transcription factors. Results showed that the rapid and transient JNK activation followed by CREB activation was the major regulator of increased SPHK2 transcription in FCS(-) culture. EMSA and ChIP assay confirmed the direct binding of activated CREB to the CREB binding site of 5' SPHK2 promoter region. Colon cancer cells examined continued to grow in FCS(-) culture, although mildly, while hypoxia and glucose depletion suppressed cell proliferation or induced cell death, suggesting the different role of SPHK2 in different stress conditions. Because of the unique relationship observed after serum depletion, we examined effects of siRNA for SPHK2, and found the role of SPHK2 as a growth or survival factor but not a cell proliferation inhibitor in FCS(-) culture.
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Naoki
authors: N
authors: Mizutani
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Yukari
authors: Y
authors: Omori
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Koji
authors: K
authors: Tanaka
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Hiromi
authors: H
authors: Ito
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Akira
authors: A
authors: Takagi
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Tetsuhito
authors: T
authors: Kojima
authors: Bioinformatics Section, Center for Advanced Medicine and Clinical Research, Nagoya University Hospital, Nagoya, Japan.
authors: Masahiro
authors: M
authors: Nakatochi
authors: Department of Hematology, Kanazawa Medical University, Kanazawa, Japan.
authors: Hideo
authors: H
authors: Ogiso
authors: College of Life and Health Sciences, Chubu University, Kasugai, Japan.
authors: Yoshiyuki
authors: Y
authors: Kawamoto
authors: Department of Drug Information, Gifu Pharmaceutical University, Gifu, Japan.
authors: Mitsuhiro
authors: M
authors: Nakamura
authors: Division of Molecular Carcinogenesis, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Motoshi
authors: M
authors: Suzuki
authors: Department of Microbiology and Molecular Biology, Nihon Pharmaceutical University, Saitama, Japan.
authors: Mamoru
authors: M
authors: Kyogashima
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Keiko
authors: K
authors: Tamiya-Koizumi
authors: Tokai Gakuin University, Kakamigahara, Japan.
authors: Yoshinori
authors: Y
authors: Nozawa
authors: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors: Takashi
authors: T
authors: Murate
mesh_terms: D002454:Cell Differentiation; D049109:Cell Proliferation / Q000235:genetics*; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D016895:Culture Media, Serum-Free; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D006801:Humans; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D000099157:Sphingosine Kinase
chemical_list: D016895:Culture Media, Serum-Free; D017362:Cyclic AMP Response Element-Binding Protein; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D000099157:Sphingosine Kinase; C115163:CREB1 protein, human; C000594250:sphingosine kinase 2, human
keywords: CREB TRANSCRIPTION FACTOR; HUMAN COLON CANCER CELL LINES; JNK ACTIVATION; SERUM DEPRIVATION; SPHK2; TRANSCRIPTIONAL REGULATION