title: CXCL12/SDF-1 over-expression in human insulinomas and its biological relevance.
abstract: This study was performed on the basis of previously obtained investigative gene array data concerning the over-expression of CXCL12/SDF-1 in human insulinomas versus human pancreatic islet preparations. The presence of CXCL12/SDF-1 was studied by RT-qPCR in human insulinomas (n=8) versus pancreatic islets (n=3), and was found to be significantly up-regulated in the former (p<0.012). The mRNA data were confirmed by immunostaining and confocal microscopy of human normal pancreatic islets, which showed the absence of CXCL12 protein and high expression in insulinoma tissue. Individual human insulinoma cells at cytospins stained positive for CXCL12 in the paranuclear region. These morphological data were extended by consecutive immunoblotting for cell-compartment-specific marker proteins of fractions obtained by sucrose gradient fractionation using Rin-5F insulinoma cells. CXCL12-containing fractions were positive for the membrane marker NSF but negative for SNAP-25 and appeared at a lighter density in the gradient than heavy insulin granules, suggesting packaging in specific granules different from insulin. In order to determine the biological relevance of the protein in insulinomas, we investigated the colony-forming potential of human CXCL12 stable-transfected rat Rin-5F insulinoma cells. These clones secreted human CXCL12 and contained 50-1000-fold higher copy numbers compared to its endogenous rat homologue. In colony-forming assays, these transfectant clones developed greater colony numbers, which were larger than wild-type and sham transfectants. To elucidate the mechanism of action, we identified a CXCL12 transfectant-specific increase in the pro-survival factor Mn-SOD, which is considered important for the inactivation of reactive oxygen species, thereby prolonging cell survival. These data demonstrate the importance of CXCL12 in the tumor biology of insulinoma.
authors.affiliation: Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria.
authors.forename: Aysegul
authors.initials: A
authors.lastname: Ilhan
authors.forename: Anastasiya
authors.initials: A
authors.lastname: Nabokikh
authors.forename: Magdalena
authors.initials: M
authors.lastname: Maj
authors.forename: Melita
authors.initials: M
authors.lastname: Vidakovic
authors.forename: Jens H
authors.initials: JH
authors.lastname: Nielsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Prikoszovich
authors.forename: Bruno
authors.initials: B
authors.lastname: Niederle
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Base
authors.forename: Anton
authors.initials: A
authors.lastname: Luger
authors.forename: Ludwig
authors.initials: L
authors.lastname: Wagner
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000235:genetics*; D003001:Cloning, Molecular; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D007340:Insulinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010084:Oxidation-Reduction; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation / Q000502:physiology
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase