Investigation of circular RNA transcriptome in obesity-related endometrial cancer

The present study has investigated the circular RNA (circRNA) transcriptome of twenty obese and postmenopausal women, recruited in Australia, with endometrial cancer (EC). This paper expands on previous findings which evaluated the circRNA transcriptome of a similar cohort of six women recruited in the United States of America. EC is the most common gynaecological malignancy and the fifth most common cancer in women worldwide with obesity as one of its major risk factors. CircRNAs, a class of non-coding RNAs, are involved in many human diseases including cancer. As such the objective of this study was to investigate the circRNA transcriptome of these twenty women and identify circRNAs of interest. We obtained paired samples (EC and adjacent normal tissue) from the cohort of twenty women. Samples were subjected to ribosomal RNA depletion and sequencing performed using Illumina sequencing technology. CircRNAs were identified through CIRI2 and CIRCexplorer2 and common circRNAs extracted for differential expression with edgeR which met the criteria of counts per million > 0.1 and expressed in ≥ 10. We found that the overall abundance of circRNAs was lower in EC compared to adjacent non-cancerous endometrial tissue. We also identified hotspot genes, genes expressing over 10 distinct circRNA isoforms. There were 82 hotspot genes in normal tissue and 23 hotspot genes in EC. There were 174 significantly differentially expressed circRNAs, of which 172 were down-regulated and 2 were up-regulated in EC. The circRNAs identified from this study may act as diagnostic or prognostic biomarkers for EC in obese women. While the circRNA transcriptome of obesity-related EC has been investigated further work is required to determine their functional significance.