title: Histone-acetylated control of fibroblast growth factor receptor 2 intron 2 polymorphisms and isoform splicing in breast cancer.
abstract: Recent genome-wide association studies have identified fibroblast growth factor receptor (FGFR)2 as one of a few candidate genes linked with breast cancer susceptibility. In particular, the disease-predisposing allele of FGFR2 is inherited as a 7.5-kb region within intron 2 that harbors eight single nucleotide polymorphisms. The relationship between these single nucleotide polymorphisms and FGFR2 gene expression remains unclear. Here we show the common occurrence of polymorphisms within the intron 2 region in a panel of 10 breast cancer cell lines. High FGFR2-expressing cell lines such as MCF-7 cells displayed polymorphic sequences with constitutive histone acetylation at multiple intron 2 sequences harboring putative transcription binding sites. Knockdown of Runx2 or CCAAT enhancer binding protein beta in these cells resulted in diminished endogenous FGFR2 gene expression. In contrast FGFR2-negative MDA-231 cells were wild type and showed evidence of histone 3/4 deacetylation at the rs2981578, rs10736303, and rs7895676 disease-associated alleles that harbor binding sites for Runx2, estrogen receptor, and CCAAT enhancer binding protein beta, respectively. Histone deacetylation inhibition with trichostatin A resulted in enhanced acetylation at these intron 2 sites, an effect associated with robust FGFR2 reexpression. Isoform analysis proved reexpression of the FGFR2-IIIc variant the splicing of which was positively influenced by trichostatin A-mediated recruitment of the Fas-activated serine/threonine phosphoprotein survival protein. Our findings highlight the potential role of histone acetylation in modulating access to selected polymorphic sites within intron 2 as well as downstream splicing sites in generating variable FGFR2 levels and isoforms in breast cancer.
authors.affiliation: Department of Medicine, and the Endocrine Oncology Site Group, Princess Margaret Hospital, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2M9.
authors.forename: Xuegong
authors.initials: X
authors.lastname: Zhu
authors.forename: Sylvia L
authors.initials: SL
authors.lastname: Asa
authors.forename: Shereen
authors.initials: S
authors.lastname: Ezzat
mesh_terms: D000107:Acetylation; D017398:Alternative Splicing; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D006657:Histones / Q000737:chemistry*; D006801:Humans; D007438:Introns; D015674:Mammary Neoplasms, Animal / Q000378:metabolism*; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D011110:Polymorphism, Genetic; D020033:Protein Isoforms; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics*
chemical_list: D006657:Histones; D020033:Protein Isoforms; D051497:Receptor, Fibroblast Growth Factor, Type 2