title: A Rb1 promoter variant with reduced activity contributes to osteosarcoma susceptibility in irradiated mice.
abstract: BACKGROUND
  Syndromic forms of osteosarcoma (OS) account for less than 10% of all recorded cases of this malignancy. An individual OS predisposition is also possible by the inheritance of low penetrance alleles of tumor susceptibility genes, usually without evidence of a syndromic condition. Genetic variants involved in such a non-syndromic form of tumor predisposition are difficult to identify, given the low incidence of osteosarcoma cases and the genetic heterogeneity of patients. We recently mapped a major OS susceptibility QTL to mouse chromosome 14 by comparing alpha-radiation induced osteosarcoma in mouse strains which differ in their tumor susceptibility.
  
  
  METHODS
  Tumor-specific allelic losses in murine osteosacoma were mapped along chromosome 14 using microsatellite markers and SNP allelotyping. Candidate gene search in the mapped interval was refined using PosMed data mining and mRNA expression analysis in normal osteoblasts. A strain-specific promoter variant in Rb1 was tested for its influence on mRNA expression using reporter assay.
  
  
  RESULTS
  A common Rb1 allele derived from the BALB/cHeNhg strain was identified as the major determinant of radiation-induced OS risk at this locus. Increased OS-risk is linked with a hexanucleotide deletion in the promoter region which is predicted to change WT1 and SP1 transcription factor-binding sites. Both in-vitro reporter and in-vivo expression assays confirmed an approx. 1.5 fold reduced gene expression by this promoter variant. Concordantly, the 50% reduction in Rb1 expression in mice bearing a conditional hemizygous Rb1 deletion causes a significant rise of OS incidence following alpha-irradiation.
  
  
  CONCLUSIONS
  This is the first experimental demonstration of a functional and genetic link between reduced Rb1 expression from a common promoter variant and increased tumor risk after radiation exposure. We propose that a reduced Rb1 expression by common variants in regulatory regions can modify the risk for a malignant transformation of bone cells after radiation exposure.
authors.affiliation: Institute of Radiation Biology, Helmholtz-Center Munich, National Research Centre for Health and Environment, Ingolstadter Landstrasse 1, D-85764 Neuherberg, Germany. Rosemann@helmholtz-muenchen.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Rosemann
authors.forename: Iria
authors.initials: I
authors.lastname: Gonzalez-Vasconcellos
authors.forename: Tanja
authors.initials: T
authors.lastname: Domke
authors.forename: Virginija
authors.initials: V
authors.lastname: Kuosaite
authors.forename: Ralf
authors.initials: R
authors.lastname: Schneider
authors.forename: Markus
authors.initials: M
authors.lastname: Kremer
authors.forename: Jack
authors.initials: J
authors.lastname: Favor
authors.forename: Michaela
authors.initials: M
authors.lastname: Nathrath
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Atkinson
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D022981:Allelic Imbalance; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D063646:Carcinogenesis / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D033481:Chromosomes, Mammalian / Q000235:genetics; D003433:Crosses, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D056726:Genetic Association Studies; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D006801:Humans; D006824:Hybridization, Genetic; D054643:INDEL Mutation / Q000235:genetics; D008297:Male; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012516:Osteosarcoma / Q000235:genetics* / Q000473:pathology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011827:Radiation; D016160:Retinoblastoma Protein / Q000235:genetics*; D012307:Risk Factors
chemical_list: D020413:3' Untranslated Regions; D012333:RNA, Messenger; D016160:Retinoblastoma Protein
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