title: Expression of stage-specific embryonic antigen-4 (SSEA-4) defines spontaneous loss of epithelial phenotype in human solid tumor cells.
abstract: Stage-specific embryonic antigen-4 (SSEA-4) is a glycosphingolipid, which is overexpressed in some cancers and has been linked to disease progression. However, little is known about the functions of SSEA-4 and the characteristics of SSEA-4 expressing tumor cells. Our studies identified SSEA-4 expression on a subpopulation of cells in many solid tumor cell lines but not in leukemic cell lines. Fluorescence-activated cell sorting-sorted SSEA-4(+) prostate cancer cells formed fibroblast-like colonies with limited cell-cell contacts, whereas SSEA-4(-) cells formed cobblestone-like epithelial colonies. Only colonies derived from SSEA-4(+) cells were enriched for pluripotent embryonic stem cell markers. Moreover, major epithelial cell-associated markers Claudin-7, E-cadherin, ESRP1 and GRHL2 were down-regulated in the SSEA-4(+) fraction of DU145 and HCT-116 cells. Similar to cell lines, SSEA-4(+) primary prostate tumor cells also showed down-regulation of epithelial cell-associated markers. In addition, they showed up-regulation of epithelial-to-mesenchymal transition as well as mesenchymal markers. Furthermore, SSEA-4(+) cells escape from adhesive colonies spontaneously and form invadopodia-like migratory structures, in which SSEA-4, cortactin as well as active pPI3K, pAkt and pSrc are enriched and colocalized. Finally, SSEA-4(+) cells displayed strong tumorigenic ability and stable knockdown of SSEA-4 synthesis resulted in decreased cellular adhesion to different extracellular matrices. In conclusion, we introduce SSEA-4 as a novel marker to identify heterogeneous, invasive subpopulations of tumor cells. Moreover, increased cell-surface SSEA-4 expression is associated with the loss of cell-cell interactions and the gain of a migratory phenotype, suggesting an important role of SSEA-4 in cancer invasion by influencing cellular adhesion to the extracellular matrix.
authors.affiliation: Department of Internal Medicine II, Division of Hematology, Immunology, Oncology, Rheumatology and Pulmonology, University Clinic of Tübingen, Tübingen, Germany.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Sivasubramaniyan
authors.affiliation: Department of Internal Medicine II, Division of Hematology, Immunology, Oncology, Rheumatology and Pulmonology, University Clinic of Tübingen, Tübingen, Germany Department of Urology, University Clinic of Tübingen, Tübingen, Germany.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Harichandan
authors.affiliation: Department of Pediatric Stem Cell Transplantation, University Children's Hospital, Tübingen 72076, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Schilbach
authors.affiliation: Institute of Clinical Anatomy and Cell Analysis, Eberhard Karls University of Tübingen, Tübingen, Germany.
authors.forename: Andreas F
authors.initials: AF
authors.lastname: Mack
authors.affiliation: Department of Urology, University Clinic of Tübingen, Tübingen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Bedke
authors.affiliation: Department of Urology, University Clinic of Tübingen, Tübingen, Germany.
authors.forename: Arnulf
authors.initials: A
authors.lastname: Stenzl
authors.affiliation: Department of Internal Medicine II, Division of Hematology, Immunology, Oncology, Rheumatology and Pulmonology, University Clinic of Tübingen, Tübingen, Germany.
authors.forename: Lothar
authors.initials: L
authors.lastname: Kanz
authors.affiliation: Discovery Oncology, Pharma Research and Early Development, Roche Diagnostics GmbH, Penzberg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Niederfellner
authors.affiliation: Department of Internal Medicine II, Division of Hematology, Immunology, Oncology, Rheumatology and Pulmonology, University Clinic of Tübingen, Tübingen, Germany hans-joerg.buehring@uni-tuebingen.de.
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Bühring
mesh_terms: D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D057167:Claudins / Q000235:genetics / Q000378:metabolism; D051356:Cortactin / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005109:Extracellular Matrix / Q000737:chemistry / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D011467:Prostate / Q000378:metabolism* / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D055746:Stage-Specific Embryonic Antigens / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C473255:CLDN7 protein, human; C495868:CTTN protein, human; D015820:Cadherins; D057167:Claudins; D051356:Cortactin; D004268:DNA-Binding Proteins; C539364:ESRP1 protein, human; C470830:GRHL2 protein, human; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D055746:Stage-Specific Embryonic Antigens; D014157:Transcription Factors; C066584:stage-specific embryonic antigen-4; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: SSEA-4; adhesion; epithelial-to-mesenchymal transition; invadopodia; invasion