title: Cytoglobin, the newest member of the globin family, functions as a tumor suppressor gene.
abstract: Cytoglobin (CYGB) is a recently discovered vertebrate globin distantly related to myoglobin with unknown function. CYGB is assigned to chromosomal region 17q25, which is frequently lost in multiple malignancies. Previous studies failed to detect evidence for mutations in the CYGB gene. Recent studies provided preliminary evidence for increased methylation of the gene in lung cancer. Our study was aimed at investigating the role of CYGB as a tumor suppressor gene. By nested methylation-specific DNA sequencing analysis of lung and breast cancer cell lines and bronchial and mammary epithelial cell lines, we identified that methylation of a 110-bp CpG-rich segment of the CYGB promoter was correlated with gene silencing. We specifically targeted this sequence and developed a quantitative methylation-specific PCR assay, suitable for high-throughput analysis. We showed that the tumor specificity of CYGB methylation in discriminating patients with and without lung cancer, using biopsies and sputum samples. We further showed the tumor specificity of this assay with multiple other epithelial and hematologic malignancies. To show tumor suppressor activity of CYGB, we performed the following: (a) RNA interference-mediated knockdown of CYGB gene on colony formation in a CYGB expression-positive lung cancer cell line, resulting in increased colony formation; (b) enforced gene expression in CYGB expression-negative lung and breast cancer cell lines, reducing colony formation; and (c) identification of potential proximate targets down-stream of the CYGB genes. Our data constitute the first direct functional evidence for CYGB, the newest member of the globin family, as a tumor suppressor gene.
authors.affiliation: Hamon Center for Therapeutic Oncology Research, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA. Narayan.Shivapurkar@UTSouthwestern.edu
authors.forename: Narayan
authors.initials: N
authors.lastname: Shivapurkar
authors.forename: Victor
authors.initials: V
authors.lastname: Stastny
authors.forename: Naoki
authors.initials: N
authors.lastname: Okumura
authors.forename: Luc
authors.initials: L
authors.lastname: Girard
authors.forename: Yang
authors.initials: Y
authors.lastname: Xie
authors.forename: Clemens
authors.initials: C
authors.lastname: Prinsen
authors.forename: Frederik B
authors.initials: FB
authors.lastname: Thunnissen
authors.forename: Ignacio I
authors.initials: II
authors.lastname: Wistuba
authors.forename: Bogdan
authors.initials: B
authors.lastname: Czerniak
authors.forename: Eugene
authors.initials: E
authors.lastname: Frenkel
authors.forename: Jack A
authors.initials: JA
authors.lastname: Roth
authors.forename: Triantafillos
authors.initials: T
authors.lastname: Liloglou
authors.forename: George
authors.initials: G
authors.lastname: Xinarianos
authors.forename: John K
authors.initials: JK
authors.lastname: Field
authors.forename: John D
authors.initials: JD
authors.lastname: Minna
authors.forename: Adi F
authors.initials: AF
authors.lastname: Gazdar
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics; D000078842:Cytoglobin; D019175:DNA Methylation; D020869:Gene Expression Profiling; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D005914:Globins / Q000235:genetics*; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics; D009369:Neoplasms / Q000235:genetics*; D016133:Polymerase Chain Reaction; D014162:Transfection
chemical_list: C000627265:CYGB protein, human; D000078842:Cytoglobin; D005914:Globins
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