RESUMO
The fibroblast growth factor receptor 2 (FGFR2) locus is consistently the top hit in genome-wide association studies for oestrogen receptor-positive (ER(+)) breast cancer. Yet, its mode of action continues to be controversial. Here, we employ a systems biology approach to demonstrate that signalling via FGFR2 counteracts cell activation by oestrogen. In the presence of oestrogen, the oestrogen receptor (ESR1) regulon (set of ESR1 target genes) is in an active state. However, signalling by FGFR2 is able to reverse the activity of the ESR1 regulon. This effect is seen in multiple distinct FGFR2 signalling model systems, across multiple cells lines and is dependent on the presence of FGFR2. Increased oestrogen exposure has long been associated with an increased risk of breast cancer. We therefore hypothesized that risk variants should reduce FGFR2 expression and subsequent signalling. Indeed, transient transfection experiments assaying the three independent variants of the FGFR2 risk locus (rs2981578, rs35054928 and rs45631563) in their normal chromosomal context show that these single-nucleotide polymorphisms (SNPs) map to transcriptional silencer elements and that, compared with wild type, the risk alleles augment silencer activity. The presence of risk variants results in lower FGFR2 expression and increased oestrogen responsiveness. We thus propose a molecular mechanism by which FGFR2 can confer increased breast cancer risk that is consistent with oestrogen exposure as a major driver of breast cancer risk. Our findings may have implications for the clinical use of FGFR2 inhibitors.
Assuntos
Neoplasias da Mama/genética , Receptor alfa de Estrogênio/genética , Predisposição Genética para Doença , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/genética , Neoplasias da Mama/patologia , Receptor alfa de Estrogênio/metabolismo , Estrogênios/genética , Estrogênios/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica , Estudo de Associação Genômica Ampla , Genótipo , Haplótipos , Humanos , Células MCF-7 , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/biossíntese , Transdução de Sinais , Biologia de SistemasRESUMO
Genetic mapping studies have identified multiple cancer susceptibility regions at chromosome 8q24, upstream of the MYC oncogene. MYC has been widely presumed as the regulated target gene, but definitive evidence functionally linking these cancer regions with MYC has been difficult to obtain. Here we examined candidate functional variants of a haplotype block at 8q24 encompassing the two independent risk alleles for prostate and breast cancer, rs620861 and rs13281615. We used the mapping of DNase I hypersensitive sites as a tool to prioritise regions for further functional analysis. This approach identified rs378854, which is in complete linkage disequilibrium (LD) with rs620861, as a novel functional prostate cancer-specific genetic variant. We demonstrate that the risk allele (G) of rs378854 reduces binding of the transcription factor YY1 in vitro. This factor is known to repress global transcription in prostate cancer and is a candidate tumour suppressor. Additional experiments showed that the YY1 binding site is occupied in vivo in prostate cancer, but not breast cancer cells, consistent with the observed cancer-specific effects of this single nucleotide polymorphism (SNP). Using chromatin conformation capture (3C) experiments, we found that the region surrounding rs378854 interacts with the MYC and PVT1 promoters. Moreover, expression of the PVT1 oncogene in normal prostate tissue increased with the presence of the risk allele of rs378854, while expression of MYC was not affected. In conclusion, we identified a new functional prostate cancer risk variant at the 8q24 locus, rs378854 allele G, that reduces binding of the YY1 protein and is associated with increased expression of PVT1 located 0.5 Mb downstream.
Assuntos
Cromossomos Humanos Par 8/genética , Loci Gênicos/genética , Predisposição Genética para Doença/genética , Neoplasias da Próstata/genética , RNA não Traduzido/genética , Alelos , Sequência de Bases , Sítios de Ligação/genética , Neoplasias da Mama/genética , Linhagem Celular Tumoral , Neoplasias do Colo/genética , Sequência Consenso , Feminino , Regulação Neoplásica da Expressão Gênica , Genótipo , Células HCT116 , Humanos , Masculino , Modelos Biológicos , Polimorfismo de Nucleotídeo Único/genética , Neoplasias da Próstata/patologia , RNA não Traduzido/metabolismo , Ativação Transcricional/genética , Fator de Transcrição YY1/metabolismoRESUMO
Recent genome-wide association studies have identified a breast cancer susceptibility locus on 16q12 with an unknown biological basis. We used a set of single nucleotide polymorphism (SNP) markers to generate a fine-scale map and narrowed the region of association to a 133 kb DNA segment containing the largely uncharacterized hypothetical gene LOC643714, a short intergenic region and the 5' end of TOX3. Re-sequencing this segment in European subjects identified 293 common polymorphisms, including a set of 26 highly correlated candidate causal variants. By evaluation of these SNPs in five breast cancer case-control studies involving more than 23 000 subjects from populations of European and Southeast Asian ancestry, all but 14 variants could be excluded at odds of <1:100. Most of the remaining variants lie in the intergenic region, which exhibits evolutionary conservation and open chromatin conformation, consistent with a regulatory function. African-American case-control studies exhibit a different pattern of association suggestive of an additional causative variant.
