Karlan, B. | bioRxiv Science

bioRxiv2018

Integrated Molecular Profiling Studies to Characterize the Cellular Origins of High-Grade Serous Ovarian Cancer

Historically, high-grade serous ovarian cancers (HGSOCs) were thought to arise from ovarian surface epithelial cells (OSECs) but recent data implicate fallopian tube secretory epithelial cells (FTSECs) as the major precursor. We performed transcriptomic and epigenomic profiling to characterize molecular similarities between OSECs, FTSECs and HGSOCs. Transcriptomic signatures of FTSECs were preserved in most HGSOCs reinforcing FTSECs as the predominant cell-of-origin; though an OSEC-like signature was associated with increased chemosensitivity (Padj = 0.03) and was enriched in proliferative-type tumors, suggesting a dualistic model for HGSOC origins. More super-enhancers (SEs) were shared between FTSECs and HGSOCs than between OSECS and HGSOCs (P < 2.2 x 10-16). SOX18, ELF3 and EHF transcription factors (TFs) coincided with HGSOC SEs and represent putative novel drivers of tumor development. Our integrative analyses support a predominantly fallopian origin for HGSOCs and indicate tumorigenesis may be driven by different TFs according to cell-of-origin.

cancer biology↗

bioRxiv2018

Multi-Tissue Transcriptome-Wide Association Studies Identify 21 Novel Candidate Susceptibility Genes for High Grade Serous Epithelial Ovarian Cancer

Genome-wide association studies (GWASs) have identified about 30 different susceptibility loci associated with high grade serous ovarian cancer (HGSOC) risk. We sought to identify potential susceptibility genes by integrating the risk variants at these regions with genetic variants impacting gene expression and splicing of nearby genes. We compiled gene expression and genotyping data from 2,169 samples for 6 different HGSOC-relevant tissue types. We integrated these data with GWAS data from 13,037 HGSOC cases and 40,941 controls, and performed a transcriptome-wide association study (TWAS) across >70,000 significantly heritable gene/exon features. We identified 24 transcriptome-wide significant associations for 14 unique genes, plus 90 significant exon-level associations in 20 unique genes. We implicated multiple novel genes at risk loci, e.g. LRRC46 at 19q21.32 (TWAS P=1x10-9) and a PRC1 splicing event (TWAS P=9x10-8) which was splice-variant specific and exhibited no eQTL signal. Functional analyses in HGSOC cell lines found evidence of essentiality for GOSR2, INTS1, KANSL1 and PRC1; with the latter gene showing levels of essentiality comparable to that of MYC. Overall, gene expression and splicing events explained 41% of SNP-heritability for HGSOC (s.e. 11%, P=2.5x10-4), implicated at least one target gene for 6/13 distinct genome-wide significant regions and revealed 2 known and 26 novel candidate susceptibility genes for HGSOC.\n\nSTATEMENT OF SIGNIFICANCEFor many ovarian cancer risk regions, the target genes regulated by germline genetic variants are unknown. Using expression data from >2,100 individuals, this study identified novel associations of genes and splicing variants with ovarian cancer risk; with transcriptional variation now explaining over one-third of the SNP-heritability for this disease.

genomics↗