title: Over-representation of PPARgamma sequence variants in sporadic cases of glioblastoma multiforme: preliminary evidence for common low penetrance modifiers for brain tumour risk in the general population.
abstract: PPARgamma, the gamma isoform of a family of peroxisome proliferator activated receptors, plays a key role in adipocyte differentiation. Recently, its broad expression in multiple tissues and several epithelial cancers has been shown. Further, somatic loss of function mutations in PPARgamma have been found in primary colorectal carcinomas. We sought to determine if somatic high penetrance mutations in this gene might also play a role in glioblastoma multiforme (GBM). We also examined this gene to determine if common low penetrance polymorphic alleles might lend low level susceptibility to GBM in the general population. No somatic high penetrance mutations were detected in 96 sporadic GBMs. However, polymorphic alleles at codons 12 and 449 were significantly over-represented among the 27 unrelated American patients with sporadic GBM compared to 80 race matched controls. While nine (33%) were heterozygous for the P12A variant, c.34C/G (cytosine to guanine change at nucleotide 34), 12 (15%) controls were heterozygous for P12A (p<0.05). Similarly, 13 of 26 (50%) glioblastoma patients compared to 10 of 80 (12%) normal controls were found to have the heterozygous H449H polymorphism (p<0.001). The over-representation of H449H in glioblastoma patients was confirmed with a second validation set of American patients. When both American series were combined, polymorphic H449H was over-represented among cases versus controls (p<0.001) and there was a similar trend (p=0.07) for P12A. The precise mechanism for this association is unknown but these PPARgamma polymorphisms may be acting in a low penetrance predisposing manner. However, these associations were not found in a German population, possibly arguing that if these variants are in linkage disequilibrium with a third locus, then this effect is relatively new, after the settlement of the American colonies.
authors.affiliation: Clinical Cancer Genetics Program, Ohio State University, 420 W 12th Avenue, Room 690C MRF, Columbus, OH 43210, USA.
authors.forename: X P
authors.initials: XP
authors.lastname: Zhou
authors.forename: W M
authors.initials: WM
authors.lastname: Smith
authors.forename: O
authors.initials: O
authors.lastname: Gimm
authors.forename: E
authors.initials: E
authors.lastname: Mueller
authors.forename: X
authors.initials: X
authors.lastname: Gao
authors.forename: P
authors.initials: P
authors.lastname: Sarraf
authors.forename: T W
authors.initials: TW
authors.lastname: Prior
authors.forename: C
authors.initials: C
authors.lastname: Plass
authors.forename: A
authors.initials: A
authors.lastname: von Deimling
authors.forename: P M
authors.initials: PM
authors.lastname: Black
authors.forename: A J
authors.initials: AJ
authors.lastname: Yates
authors.forename: C
authors.initials: C
authors.lastname: Eng
mesh_terms: D000483:Alleles; D001932:Brain Neoplasms / Q000235:genetics*; D016009:Chi-Square Distribution; D003062:Codon / Q000235:genetics; D004252:DNA Mutational Analysis; D005787:Gene Frequency / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics*; D018095:Germ-Line Mutation / Q000235:genetics; D005858:Germany; D005909:Glioblastoma / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D015810:Linkage Disequilibrium / Q000235:genetics; D016555:Matched-Pair Analysis; D016017:Odds Ratio; D019683:Penetrance; D011110:Polymorphism, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014481:United States
chemical_list: D003062:Codon; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors