title: Epigenetic regulation of CXCR4 expression by the ocular microenvironment.
abstract: OBJECTIVE
  Expression of the chemokine receptor CXCR4 by tumors is associated with metastatic migration and invasion of tumor cells. The importance of CXCR4 expression by uveal melanomas in metastasis to the liver was recently demonstrated when injection of CXCR4-negative uveal melanoma cells into mice resulted in reduced liver metastasis compared with CXCR4-positive uveal melanoma cells. Factors in the eye can induce downregulation of genes by epigenetic mechanisms. This study examined whether epigenetic regulation by the ocular environment induced downregulation of CXCR4 expression.
  
  
  METHODS
  LS174T colon cancer cells were injected in the anterior chamber (AC), subcutaneously (SC), or in the spleen capsule to induce liver metastasis in immune-deficient mice. CXCR4 gene transcription was analyzed by RT-PCR, and protein expression was determined by flow cytometry. Methyltransferase and histone deacetylase activities were determined by ELISA. Treatment with either 5-Aza-2-deoxycytidine (5-Aza) or trichostatin A (TSA) was used to induce demethylation or inhibit histone deacetylases, respectively.
  
  
  RESULTS
  AC-derived LS174T cells showed lower CXCR4 gene expression compared with SC-, liver-derived, or wild-type tumor cells. AC-derived LS174T tumor cells expressed methyltransferase activity compared with SC-, liver-derived, and wild-type tumor cells. Deacetylase activity was elevated in AC-derived LS174T tumor cells compared with SC-derived, liver-derived, and wild-type tumor cells. Treatment of AC-derived LS174T tumor cells with 5-Aza upregulated CXCR4 expression. TSA treatment did not restore CXCR4 expression.
  
  
  CONCLUSIONS
  These studies demonstrate that ocular microenvironment factors induce methylation and downregulation of tumor CXCR4 expression.
authors.affiliation: Department of Ophthalmology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057, USA.
authors.forename: Haochuan
authors.initials: H
authors.lastname: Li
authors.forename: Jerry Y
authors.initials: JY
authors.lastname: Niederkorn
authors.forename: Leila
authors.initials: L
authors.lastname: Sadegh
authors.forename: Jessamee
authors.initials: J
authors.lastname: Mellon
authors.forename: Peter W
authors.initials: PW
authors.lastname: Chen
mesh_terms: D000818:Animals; D000867:Anterior Chamber / Q000378:metabolism* / Q000473:pathology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002432:Cecum / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D000077209:Decitabine; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D005434:Flow Cytometry; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D056572:Histone Deacetylase Inhibitors / Q000008:administration & dosage; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006877:Hydroxamic Acids / Q000008:administration & dosage; D007267:Injections; D007279:Injections, Subcutaneous; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D011401:Promoter Regions, Genetic; D019718:Receptors, CXCR4 / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation
chemical_list: D000964:Antimetabolites, Antineoplastic; C514936:CXCR4 protein, mouse; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D019718:Receptors, CXCR4; C012589:trichostatin A; D000077209:Decitabine; D006655:Histone Deacetylases; D008239:Lysine; D001374:Azacitidine