title: SOX5 is involved in balanced MITF regulation in human melanoma cells.
abstract: BACKGROUND
  Melanoma is a cancer with rising incidence and new therapeutics are needed. For this, it is necessary to understand the molecular mechanisms of melanoma development and progression. Melanoma differs from other cancers by its ability to produce the pigment melanin via melanogenesis; this biosynthesis is essentially regulated by microphthalmia-associated transcription factor (MITF). MITF regulates various processes such as cell cycling and differentiation. MITF shows an ambivalent role, since high levels inhibit cell proliferation and low levels promote invasion. Hence, well-balanced MITF homeostasis is important for the progression and spread of melanoma. Therefore, it is difficult to use MITF itself for targeted therapy, but elucidating its complex regulation may lead to a promising melanoma-cell specific therapy.
  
  
  METHODS
  We systematically analyzed the regulation of MITF with a novel established transcription factor based gene regulatory network model. Starting from comparative transcriptomics analysis using data from cells originating from nine different tumors and a melanoma cell dataset, we predicted the transcriptional regulators of MITF employing ChIP binding information from a comprehensive set of databases. The most striking regulators were experimentally validated by functional assays and an MITF-promoter reporter assay. Finally, we analyzed the impact of the expression of the identified regulators on clinically relevant parameters of melanoma, i.e. the thickness of primary tumors and patient overall survival.
  
  
  RESULTS
  Our model predictions identified SOX10 and SOX5 as regulators of MITF. We experimentally confirmed the role of the already well-known regulator SOX10. Additionally, we found that SOX5 knockdown led to MITF up-regulation in melanoma cells, while double knockdown with SOX10 showed a rescue effect; both effects were validated by reporter assays. Regarding clinical samples, SOX5 expression was distinctively up-regulated in metastatic compared to primary melanoma. In contrast, survival analysis of melanoma patients with predominantly metastatic disease revealed that low SOX5 levels were associated with a poor prognosis.
  
  
  CONCLUSIONS
  MITF regulation by SOX5 has been shown only in murine cells, but not yet in human melanoma cells. SOX5 has a strong inhibitory effect on MITF expression and seems to have a decisive clinical impact on melanoma during tumor progression.
authors.affiliation: GMP & T Cell Therapy Unit, German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. Schacht@stud.uni-heidelberg.de.|Integrated Research and Treatment Center, Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, D-07747, Jena, Germany. Schacht@stud.uni-heidelberg.de.
authors.forename: Theresa
authors.initials: T
authors.lastname: Kordaß
authors.affiliation: GMP & T Cell Therapy Unit, German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. c.weber@dkfz.de.
authors.forename: Claudia E M
authors.initials: CE
authors.lastname: Weber
authors.affiliation: Integrated Research and Treatment Center, Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, D-07747, Jena, Germany. marcus.oswald@leibniz-hki.de.|Network Modeling, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute Jena, Beutenbergstrasse 11a, 07745, Jena, Germany. marcus.oswald@leibniz-hki.de.
authors.forename: Marcus
authors.initials: M
authors.lastname: Oswald
authors.affiliation: Integrated Research and Treatment Center, Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, D-07747, Jena, Germany. volker.ast@leibniz-hki.de.|Network Modeling, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute Jena, Beutenbergstrasse 11a, 07745, Jena, Germany. volker.ast@leibniz-hki.de.
authors.forename: Volker
authors.initials: V
authors.lastname: Ast
authors.affiliation: Skin Cancer Unit, German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. m.bernhardt@dkfz.de.|Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, Mannheim, Germany. m.bernhardt@dkfz.de.
authors.forename: Mathias
authors.initials: M
authors.lastname: Bernhardt
authors.affiliation: Skin Cancer Unit, German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. d.novak@dkfz.de.|Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, Mannheim, Germany. d.novak@dkfz.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Novak
authors.affiliation: Skin Cancer Unit, German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. j.utikal@dkfz.de.|Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, Mannheim, Germany. j.utikal@dkfz.de.
authors.forename: Jochen
authors.initials: J
authors.lastname: Utikal
authors.affiliation: GMP & T Cell Therapy Unit, German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. s.eichmueller@dkfz.de.
authors.forename: Stefan B
authors.initials: SB
authors.lastname: Eichmüller
authors.affiliation: Integrated Research and Treatment Center, Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, D-07747, Jena, Germany. rainer.koenig@uni-jena.de.|Network Modeling, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute Jena, Beutenbergstrasse 11a, 07745, Jena, Germany. rainer.koenig@uni-jena.de.|Theoretical Bioinformatics, German Cancer Research Center, INF 580, 69121, Heidelberg, Germany. rainer.koenig@uni-jena.de.
authors.forename: Rainer
authors.initials: R
authors.lastname: König
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D003198:Computer Simulation; D005453:Fluorescence; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000473:pathology*; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics* / Q000378:metabolism; D009361:Neoplasm Invasiveness; D010641:Phenotype; D011382:Programming, Linear; D034741:RNA, Small Interfering / Q000378:metabolism; D015203:Reproducibility of Results; D055755:SOXD Transcription Factors / Q000378:metabolism*; D055757:SOXE Transcription Factors / Q000378:metabolism; D016019:Survival Analysis; D014162:Transfection
chemical_list: D051739:Microphthalmia-Associated Transcription Factor; D034741:RNA, Small Interfering; C527923:SOX10 protein, human; C490301:SOX5 protein, human; D055755:SOXD Transcription Factors; D055757:SOXE Transcription Factors; D049452:Green Fluorescent Proteins