Characterization of intron-1 haplotypes of the G protein beta 4 subunit gene--association with survival and progression in patients with urothelial bladder carcinoma.
OBJECTIVE
Polymorphisms in genes encoding subunits of heterotrimeric G proteins have been repeatedly associated with various cancers. As G beta gamma signaling is presumed to be involved in proliferation and invasion processes, we analyzed genetic variations in regulatory regions of GNB4, which encodes the G beta 4 subunit, for their potential influence on cancer progression.


METHODS
We characterized the promoter of GNB4 and screened the promoter as well as exon 1 and intron 1 for single nucleotide polymorphisms by sequencing 100 healthy controls. Following a haplotype analysis, we determined the functional impact upon gene expression of the defined haplotypes by reporter assays, electrophoretic mobility shift assay and western blot. In addition, these haplotypes were tested for their relation to the disease course of urothelial bladder cancer.


RESULTS
Whereas the promoter of GNB4 revealed no polymorphisms, 33 single nucleotide polymorphisms located in exon 1 and intron 1 were identified and together with a common exon-4 polymorphism implemented in haplotype analysis, which resulted in the determination of distinct haplotype blocks. Reporter activity was haplotype-dependently different (P=0.001). 1*1/1*1 showed increased G beta 4 protein (P=0.003), and bladder cancer patients carrying this diplotype displayed more progressive disease (P=0.046) and a significantly increased mortality (P=0.046). In multivariate analysis,the diplotypes were independent prognostic factors for survival and progression.


CONCLUSIONS
Intron-1 haplotypes of GNB4 may, thus, serve as predictive markers for progression and survival of patients suffering from bladder cancer.
Riemann
Kathrin
K
Institute of Pharmacogenetics, University Hospital, University of Duisburg-Essen, Essen, Germany. kathrin.riemann@uk-essen.de
Struwe
Henrike
H
Eisenhardt
Andreas
A
Obermaier
Brigitte
B
Schmid
Kurt W
KW
Siffert
Winfried
W
D020121:5' Untranslated Regions / Q000235:genetics; D000368:Aged; D002460:Cell Line; D003710:Demography; D018450:Disease Progression; D005260:Female; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D006801:Humans; D007438:Introns / Q000235:genetics*; D053208:Kaplan-Meier Estimate; D015810:Linkage Disequilibrium / Q000235:genetics; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D016016:Proportional Hazards Models; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology*; D019459:Urothelium / Q000473:pathology*
D020121:5' Untranslated Regions; C534984:GNB4 protein, human; D044387:GTP-Binding Protein beta Subunits