Pathological expression of mitochondrial genome-derived circRNA SCAR/mc-COX2 and its ceRNA network in colorectal cancer: implications for clinical significance

Mitochondrial-encoded circular RNAs (mecciRNAs) are a newly discovered class of mitochondrial-encoded non-coding RNAs (mt-ncRNAs) that play important biological roles in the cell. This study aimed to examine the expression profile of SCAR/mc-COX2 (has_circ_0089762) in colorectal cancer (CRC) and its relationship with clinicopathological variables. Furthermore, to better understand SCAR/mc-COX2's functional role in CRC, we constructed a competing endogenous RNA (ceRNA) network. Quantitative real-time PCR (qRT-PCR) was employed to analyze the expression levels of SCAR/mc-COX2 in 40 pairs of CRC samples, consisting of 40 tumor samples and 40 adjacent non-tumoral samples from patients. The ceRNA regulatory network was constructed using online bioinformatics tools. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and Gene Ontology (GO) enrichment analysis were conducted using the Enrichr database. The results demonstrated a significant decrease in SCAR/mc-COX2 expression in tumor tissues compared to adjacent non-tumoral tissues (p-value<0.05). In another finding, a significant relationship was observed between pathological T staging and the expression status of SCAR/mc-COX2 (p-value=0.02). Additionally, the Receiver Operating Characteristic (ROC) curve analysis revealed that SCAR/mc-COX2 had an area under the curve (AUC) of 0.77, with 80% sensitivity and 75% specificity. Finally, a ceRNA regulatory network including SCAR/mc-COX2, 5 miRNA, and 9 mRNAs was found. These findings suggest that SCAR/mc-COX2 may act as a tumor suppressor in CRC, and its dysregulation could play a crucial role in the pathophysiology of this cancer. The significant association with pathological T staging and its robust diagnostic performance (AUC = 0.77, sensitivity = 80%, specificity = 75%) highlight its potential as a novel biomarker for CRC detection and prognosis. Further functional studies are required to elucidate its precise role in CRC tumorigenesis and clinical applicability.