Transcriptome and DNA methylation analyses highlight the role of menstrual cycle phase in tumorigenesis of endometriosis-related ovarian carcinoma histotypes [RNA-Seq]

Epithelial ovarian cancer, or ovarian carcinoma (OC), is a diverse disease. Two of the rarer subtypes, clear cell OC (CCOC) and endometrioid OC (ENOC), both arise from ovarian endometriotic cysts, particularly atypical endometriosis. CCOC and ENOC have similar mutation profiles and share a common cell of origin, but their cellular phenotypes and clinical outcomes are distinct; in particular, CCOC has poor clinical survival. The most well-known difference between the histotypes is the universal overexpression of HNF1B (Hepatocyte nuclear factor-1ß) in clear cell tumors and overexpression of ESR1 in ENOC. It is not well understood how these discrete histotypes arise from the same cell of origin. Via transcriptional (n=57) and DNA methylation analysis (N=127) of these rare tumors, we show that CCOC closely resembles secretory endometrium in transcriptional profile; whereas ENOC transcriptomes resemble proliferative endometrium. Overall design: 57 tumor samples from clear cell ovarian cancer (N=28) or endometrioid ovarian cancer (N=29) were profiled with RNAseq