Circular RNAs (circRNAs) are the class of noncoding RNA associated with physiological and pathological conditions. The circRNAs have been upregulated in diverse types of cancer that are involved in tumorigenesis, proliferation, invasion and metastasis. This study aimed to compare the expression of circRNAs between normal colon epithelial cells (CCD841 CoN), primary colon cancer cells (SW480), and metastatic malignant cells (SW620), while also validating the expression of selected circRNAs across these colon cancer cell lines.

RNA sequencing was performed on normal colon epithelial cells (CCD841 CoN), and primary (SW480) and metastatic (SW620) colon cancer cell lines. Differential expression, gene ontology (GO) and KEGG pathway enrichment analysis were conducted on the RNA-seq data. Selected upregulated circRNAs were also validated by RT-qPCR.

Differentially expressed circRNA analysis identified 906 and 935 upregulated circRNAs in SW480 and SW620, respectively, compared to CCD 841 CoN. Additionally, 184 circRNAs were upregulated in SW620 compared to SW480 cells. KEGG pathway analysis of differentially expressed circRNA-associated genes between SW480, SW620, and CCD841 CoN highlighted pathways involved in cancer development and progression. The analysis revealed significant enrichment in pathways related to cellular processes, human diseases, and genetic information processing, with distinct alterations observed in the metastatic SW620 and primary SW480 cells compared to normal colon epithelial cells (CCD841CoN). The circRNAs derived from FIRRE and PROX1 genes showed high-ranking expression in both SW480 and SW620 cell lines. The candidate circFIRRE (hsa_circ_0001944) was dramatically increased by 2789.55 ± 551.44 and 7593.61 ± 818.72 folds in SW480 and SW620, respectively, compared to the normal colon epithelial cells. Additionally, circPROX1 (hsa_circ_0111952) was also highly upregulated by 1810.88 ± 477.11 and 2851.46 ± 498.75 folds in SW480 and SW620, respectively.

This study identifies some predominant levels of circRNAs in primary and metastatic colon cancer cells. The finding reveals high expression of circFIRRE and cirPROX1, with even greater levels in the metastatic cancer cell line. The overexpression characteristics of these circRNAs may serve as potential tumor biomarkers for diagnostic, prognostic, or therapeutic applications. However, additional studies are essential to enhance understanding of biological mechanisms and roles in colon cancer progression.