Abstract PR15: MYC distal enhancers underlie ovarian cancer susceptibility in the 8q24.21 locus.
Authors: Gjyshi Anxhela , Mendoza-Fandino Gustavo , Woods Nicholas , Tyrer Jonathan , Lawrenson Kate , Buckley Melissa , Shen Howard , Carvalho Renato , Seo Ji-Heui , Phelan Catherine , Freedman Matthew , Goode Ellen , Sellers Thomas , Gayther Simon , Pharoah Paul , Monteiro Alvaro 
Published: May 2016

Background: In a Genome Wide Association Study (GWAS) on epithelial ovarian cancer (EOC), we identified single nucleotide polymorphism (SNP) associations (p&lt;10-8) in the 8q24.21 region. This region is characterized as a gene desert, which notably is also associated with other cancer types including prostate, colorectal, breast and urinary bladder cancer. We hypothesized that SNPs in this region function within enhancer elements that modify transcriptional regulation of a distant gene involved in ovarian cancer pathogenesis.

Methods: Guided by fine mapping analysis of the locus, we employed various methods to select functional SNPs with allele-specific effects in ovarian surface epithelial (OSE) and fallopian tube epithelial (FTE) cells, based on the hypothesis that both cell types may represent the cell of origin for high-grade serous ovarian cancer. Luciferase assays tested the ability of enhancer elements to activate transcription. Chromosome conformation capture (3C) assays quantified the physical interactions between putative enhancer elements and candidate target genes. Electrophoretic mobility shift assays (EMSA) and proteomics analysis were utilized to confirm transcription factor binding.

Results: We identified eight putative causal SNPs, which are in high Linkage Disequilibrium (LD) with the most significant SNP, rs1400482 (OR = 1.18, 95% CI 1.13 1.23; p = 2.5x10-13), residing within two distinct enhancer elements that display allele-specific activity in ovarian cells. Long-range physical interactions with the promoter region of the MYC oncogene, and to a lesser extent, the non-coding RNA, PVT1, establish these two genes as the targets of the enhancer elements containing the putative causal SNPs. We report evidence that the ATF1 transcription factor binds exclusively to the minor allele of variant rs2165806. Additionally, we report a comparative analysis testing the cell-type specific activity of different enhancer regions in breast, prostate, colorectal and ovarian cell lines.

Conclusion: In summary, this work highlights the regulatory landscape of the 8q24.21 locus and provides a mechanistic basis to understand susceptibility to ovarian cancer in this region.

Citation Format: Anxhela Gjyshi, Gustavo Mendoza-Fandino, Nicholas Woods, Jonathan Tyrer, Kate Lawrenson, Melissa Buckley, Howard Shen, Renato Carvalho, Ji-Heui Seo, Catherine Phelan, Matthew Freedman, Ellen Goode, Thomas Sellers, Simon Gayther, Paul Pharoah, Alvaro Monteiro. MYC distal enhancers underlie ovarian cancer susceptibility in the 8q24.21 locus. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr PR15.