Detection of mutant cancer-derived circRNAs in extracellular vesicles by rolling circle amplification.

Circular RNAs (circRNAs) form during splicing as a closed ring and are more resistant to degradation than linear RNAs. Cells release circRNAs within membrane-bound extracellular vesicles (EVs), which transport DNA, RNA, and proteins. Whether circRNAs in EVs can be used as biomarkers remains uncertain. We aimed to identify mutant circRNAs in EVs to develop a new biomarker approach. We demonstrated that ovarian cancer cells release and enrich circRNAs in EVs. We detected mutant circular transcripts from TP53, KRAS, and PIK3CA genes in EVs from cancer cells. We noticed that circRNAs in EVs undergo intense rolling circle amplification (RCA), producing multiple copies of the mutant sequence. We revealed that increased reverse transcription time and extended PCR elongation time intensified RCA. Using our RCA protocol, we detected mutant circRNAs derived from the TP53 gene in EVs from the plasma of ovarian cancer-bearing animals. In this study, we present a new model of mutant circRNA amplification from EVs, which may provide a basis for a diagnostic test for ovarian cancer patients.