Exosome-Mediated Transfer of circ_0000338 Enhances 5-Fluorouracil Resistance in Colorectal Cancer through Regulating MicroRNA 217 (miR-217) and miR-485-3p

Abstract

Background: Exosomes are microvesicles secreted by body cells for intercellular communication. Circular RNA circ_0000338 was found to present in extracellular vesicles and improve the chemo-resistance of colorectal cancer (CRC) cells. However, the role of exosomal circ_0000338 in 5-Fluorouracil (5-FU)-resistance in CRC is largely unknown. Methods: The levels of circ_0000338, microRNA (miR)-217 and miR-485-3p were detected using the qRT-PCR. The IC50 values of cells to 5-FU, cell proliferation and apoptosis were evaluated using CCK-8, colony formation, flow cytometry and western blot assays. The interaction between miR-217 or miR-485-3p and circ_0000338 was confirmed by RIP, dual-luciferase reporter and pull-down assays. Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy (TEM), nanosight tracking analysis (NTA) and western blot. Xenograft models were performed to analyze whether circ_0000338 loaded exosomes could re-resist CRC cells to 5-FU in vivo. Results: Circ_0000338 was elevated in 5-FU-resistant CRC tissues and cells, and circ_0000338 knockdown sensitized 5-FU-resistant CRC cells to 5-FU through enhancing apoptosis and decreasing proliferation in vitro. Mechanistically, circ_0000338 directly bound to miR-217 and miR-485-3p, and the inhibition of miR-217 or miR-485-3p reversed the effects of circ_0000338 knockdown on cell 5-FU resistance in CRC. Additionally, extracellular circ_0000338 could be incorporated into secreted exosomes and transmitted to 5-FU-sensitive cells. Treatment-sensitive cells with exosomes containing circ_0000338 reduced 5-FU response in CRC both in vitro and in vivo. Besides that, exosomal circ_0000338 was higher in patients exhibiting resistance to 5-FU, and showed well diagnostic efficiency in 5-FU resistant CRC. Conclusion: The delivery of circ_0000338 via exosomes enhanced 5-FU resistance in CRC through negative regulation of miR-217 and miR-485-3p, indicating a promising diagnostic and therapeutic marker for 5-FU-based chemotherapy in CRC patients.

Cellular irinotecan resistance in colorectal cancer and overcoming irinotecan refractoriness through various combination trials including DNA methyltransferase inhibitors: a review

“…Human CRC HT-29 cells were cultured in patient-derived decellularized Another example of the tumor microenvironment association with drug resistance is extracellular vehicles (EVs), which mediate intercellular communication between cancer cells. EVs can contain small molecules such as therapeutic drugs, mRNAs, miRNAs, or even proteins, such as drug efflux transporters [49,50] . Exosome-mediated transfer of circular RNA (circ_0000338) enhanced 5-FU resistance in circular RNAtransmitted human CRC cell lines, which was achieved through its direct binding with miR-217 and miR-485-3p.…”

“…Xavier et al [50] Exosome-mediated circular RNA transfer Circ_000038 was transferred to recipient cells in an exosomemediated fashion…”

Circular RNA CircPVT1 Inhibits 5-Fluorouracil Chemosensitivity by Regulating Ferroptosis Through MiR-30a-5p/FZD3 Axis in Esophageal Cancer Cells

“…Previous reports have validated that the chemoresistance rate of ESCC to 5‐FU is nearly 85% ( 20 , 21 ). Various studies indicated that circRNAs played a crucial role in modulating the chemosensitivity of cancer cells to 5‐FU treatment ( 22 , 23 ). Gao et al.…”

The Dual Role of Circular RNAs as miRNA Sponges in Breast Cancer and Colon Cancer

“…Radiation therapy in colon cells induces significant upregulation in the expression of circ_0001313, as well as the downregulation of miR-338-3p, thus increasing CRC tumor radioresistance and suggesting a positive correlation between CRC radioresistance and circ_0001313 [ 103 ]. Other circRNAs, such as circ_0020095 [ 104 ], circ_0005963 [ 101 ], and circ_0000338 [ 105 ], have similar functions as oncogenics involved in CRC tumors.…”