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Updated: Jan 21, 2026
Quantification of Circular RNAs Using Digital Droplet PCR
Published on: September 16, 2022
Circular RNAs are differentially expressed in prostate cancer and are potentially associated with resistance to
John Greene1,2, Anne-Marie Baird3,4,5,6, Orla Casey3
1Department of Histopathology and Morbid Anatomy, School of Medicine, Trinity College Dublin, Dublin 8, Ireland. greenejo@tcd.ie.
Abstract:
Most forms of castration-resistant prostate cancer (CRPC) are dependent on the androgen receptor (AR) for survival. While, enzalutamide provides a substantial survival benefit, it is not curative and many patients develop resistance to therapy. Although not yet fully understood, resistance can develop through a number of mechanisms, such as AR copy number gain, the generation of splice variants such as AR-V7 and mutations within the ligand binding domain (LBD) of the AR. circular RNAs (circRNAs) are a novel type of non-coding RNA, which can regulate the function of miRNA, and may play a key role in the development of drug resistance. circRNAs are highly resistant to degradation, are detectable in plasma and, therefore may serve a role as clinical biomarkers. In this study, AR-V7 expression was assessed in an isogenic model of enzalutamide resistance. The model consisted of age matched control cells and two sub-line clones displaying varied resistance to enzalutamide. circRNA profiling was performed on the panel using a high throughout microarray assay. Bioinformatic analysis identified a number of differentially expressed circRNAs and predicted five miRNA binding sites for each circRNA. miRNAs were stratified based on known associations with prostate cancer, and targets were validated using qPCR. Overall, circRNAs were more often down regulated in resistant cell lines compared with control (588 vs. 278). Of particular interest was hsa_circ_0004870, which was down-regulated in enzalutamide resistant cells (p ≤ 0.05, vs. sensitive cells), decreased in cells that highly express AR (p ≤ 0.01, vs. AR negative), and decreased in malignant cells (p ≤ 0.01, vs. benign). The associated parental gene was identified as RBM39, a member of the U2AF65 family of proteins. Both genes were down-regulated in resistant cells (p < 0.05, vs. sensitive cells). This is one of the first studies to profile and demonstrate discrete circRNA expression patterns in an enzalutamide resistant cell line model of prostate cancer. Our data suggests that hsa_circ_0004870, through RBM39, may play a critical role in the development of enzalutamide resistance in CRPC.
Insights
Circular RNAs (circRNAs) may drive enzalutamide resistance in castration-resistant prostate cancer (CRPC). This study found hsa_circ_0004870 down-regulation in resistant cells, suggesting a role in CRPC progression.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Castration-resistant prostate cancer (CRPC) often relies on the androgen receptor (AR) pathway.
- Enzalutamide is a key therapy, but resistance develops through mechanisms like AR variants (e.g., AR-V7).
- Circular RNAs (circRNAs) are emerging as regulators of gene expression and potential biomarkers.
Purpose of the Study:
- To investigate circRNA expression patterns in enzalutamide-resistant CRPC.
- To identify specific circRNAs involved in resistance mechanisms.
- To explore the potential of circRNAs as biomarkers for enzalutamide resistance.
Main Methods:
- Utilized an isogenic model of enzalutamide-resistant CRPC cells.
- Performed circRNA profiling using microarray assays.
- Conducted bioinformatic analysis to identify differentially expressed circRNAs and predict miRNA binding sites.
- Validated target gene and miRNA expression using qPCR.
Main Results:
- Identified distinct circRNA expression profiles in enzalutamide-resistant CRPC cells.
- Observed a general down-regulation of circRNAs in resistant cell lines compared to sensitive controls.
- Highlighted hsa_circ_0004870 as significantly down-regulated in resistant cells, correlating with AR expression and malignancy.
- Found the parental gene RBM39 also down-regulated in resistant cells.
Conclusions:
- circRNAs exhibit differential expression in enzalutamide-resistant CRPC.
- hsa_circ_0004870, potentially via its parental gene RBM39, may play a critical role in the development of enzalutamide resistance.
- circRNAs represent a promising area for further research into CRPC drug resistance and biomarker development.
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