title: Allele-specific regulation of FGFR2 expression is cell type-dependent and may increase breast cancer risk through a paracrine stimulus involving FGF10.
abstract: BACKGROUND
  SNPs rs2981582 and rs2981578, located in a linkage disequilibrium block (LD block) within intron 2 of the fibroblast growth factor receptor 2 gene (FGFR2), are associated with a mildly increased breast cancer risk. Allele-specific regulation of FGFR2 mRNA expression has been reported previously, but the molecular basis for the association of these variants with breast cancer has remained elusive to date.
  
  
  METHODS
  mRNA levels of FGFR2 and three fibroblast growth factor genes (FGFs) were measured in primary fibroblast and epithelial cell cultures from 98 breast cancer patients and correlated to their rs2981578 genotype. The phosphorylation levels of downstream FGFR2 targets, FGF receptor substrate 2α (FRS2α) and extracellular signal-regulated kinases 1 and 2 (ERK1/2), were quantified in skin fibroblasts exposed to FGF2. Immunohistochemical markers for angiogenesis and lymphocytic infiltrate were semiquantitatively assessed in 25 breast tumors.
  
  
  RESULTS
  The risk allele of rs2981578 was associated with increased FGFR2 mRNA levels in skin fibroblasts, but not in skin epithelial cell cultures. FGFR2 mRNA levels in skin fibroblasts and breast fibroblasts correlated strongly in the patients from whom both cultures were available. Tumor-derived fibroblasts expressed, on average, eight times more FGFR2 mRNA than the corresponding fibroblasts from normal breast tissue. Fibroblasts with higher FGFR2 mRNA expression showed more FRS2α and ERK1/2 phosphorylation after exposure to FGF2. In fibroblasts, higher FGFR2 expression correlated with higher FGF10 expression. In 25 breast tumors, no associations between breast tumor characteristics and fibroblast FGFR2 mRNA levels were found.
  
  
  CONCLUSIONS
  The influence of rs2981578 genotypes on FGFR2 mRNA expression levels is cell type-dependent. Expression differences correlated well with signaling levels of the FGFR2 pathway. Our results suggest that the increased breast cancer risk associated with SNP rs2981578 is due to increased FGFR2 signaling activity in stromal fibroblasts, possibly also involving paracrine FGF10 signaling.
authors.affiliation: Department of Clinical Genetics, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. p.e.a.huijts@lumc.nl
authors.forename: Petra E A
authors.initials: PE
authors.lastname: Huijts
authors.forename: Minka
authors.initials: M
authors.lastname: van Dongen
authors.forename: Moniek C M
authors.initials: MC
authors.lastname: de Goeij
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: van Moolenbroek
authors.forename: Freek
authors.initials: F
authors.lastname: Blanken
authors.forename: Maaike P G
authors.initials: MP
authors.lastname: Vreeswijk
authors.forename: Esther M
authors.initials: EM
authors.lastname: de Kruijf
authors.forename: Wilma E
authors.initials: WE
authors.lastname: Mesker
authors.forename: Erik W
authors.initials: EW
authors.lastname: van Zwet
authors.forename: Rob A E M
authors.initials: RA
authors.lastname: Tollenaar
authors.forename: Vincent T H B M
authors.initials: VT
authors.lastname: Smit
authors.forename: Christi J
authors.initials: CJ
authors.lastname: van Asperen
authors.forename: Peter
authors.initials: P
authors.lastname: Devilee
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000368:Aged; D000483:Alleles; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D051526:Fibroblast Growth Factor 10 / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics* / Q000378:metabolism; D012016:Reference Values; D015398:Signal Transduction; D012867:Skin / Q000166:cytology / Q000378:metabolism; D017154:Stromal Cells / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C496463:FGF10 protein, human; C106534:FRS2 protein, human; D051526:Fibroblast Growth Factor 10; D008565:Membrane Proteins; C496353:FGFR2 protein, human; D051497:Receptor, Fibroblast Growth Factor, Type 2; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3