结直肠癌(CRC)是消化道常见的恶性肿瘤，具有高发病率和死亡率。外泌体环状RNA(circRNA)已被证明与癌症的恶性进展有关，包括CRC。其中一种名为circ_0005100(命名为circ_FMN2)的circRNA已被证明能促进CRC细胞增殖和迁移。然而，外泌体中circ_FMN2是否参与了CRC进展仍不清楚。从CRC患者血清中分离出外泌体，并使用透射电镜进行鉴定。使用Western印迹法测试外泌体标志物、增殖相关标记物、转移相关标记物和musashi-1(MSI1)的蛋白水平。使用qPCR检测circ_FMN2、microRNA(miR)-338-3p和MSI1的表达水平。使用流式细胞术、克隆形成试验、MTT试验和Transwell试验测定细胞周期、凋亡、克隆形成能力、存活率、迁移和侵袭。进行双荧光素酶报告试验以评估miR-338-3p与circ_FMN2或MSI1之间的相互作用。使用BALB/c裸鼠进行动物实验。在CRC患者血清和CRC细胞中过表达circ_FMN2。过表达的外泌体circ_FMN2可促进CRC细胞增殖、转移并抑制凋亡。circ_FMN2作为miR-338-3p海绵。miR-338-3p的过表达逆转了circ_FMN2对CRC进展的促进作用。发现MSI1是miR-338-3p的靶点，其过表达撤销了miR-338-3p对CRC进展的抑制作用。此外，外泌体circ_FMN2的过表达还可以促进CRC肿瘤在体内生长。外泌体circ_FMN2通过miR-338-3p/MSI1轴加速了CRC的进展，揭示外泌体circ_FMN2可能是CRC治疗的一个靶点。©2023年。作者(们)独家授权给Springer Science+Business Media，LLC，Springer Nature的一部分。

Colorectal cancer (CRC) is a common malignancy of the gastrointestinal tract with high incidence and mortality. Exosomal circular RNA (circRNA) has been shown to be associated with the malignant progression of cancers, including CRC. Circ_0005100 (named as circ_FMN2) has been shown to promote CRC cell proliferation and migration. However, whether exosomal circ_FMN2 participated in CRC progression remains unclear.Exosomes were isolated from the serum of CRC patients and then identified using transmission electron microscope. Western blot assay was used to test the protein levels of exosome markers, proliferation-related marker, metastasis-related markers and musashi-1 (MSI1). The expression levels of circ_FMN2, microRNA (miR)-338-3p and MSI1 were detected by qPCR. Flow cytometry, colony formation assay, MTT assay, and transwell assay were employed to measure cell cycle, apoptosis, colony formation ability, viability, migration and invasion. Dual-luciferase reporter assay was performed to assess the interaction between miR-338-3p and circ_FMN2 or MSI1. BALB/c nude mice was used to conduct animal experiments.Circ_FMN2 was overexpressed in the exosomes of CRC patient's serums and CRC cells. Overexpressed exosomal circ_FMN2 could promote CRC cell proliferation, metastasis, and suppress apoptosis. Circ_FMN2 acted as miR-338-3p sponge. MiR-338-3p overexpression reversed the promotion effect of circ_FMN2 on CRC progression. MSI1 was found to be a target of miR-338-3p, and its overexpression revoked the inhibitory effect of miR-338-3p on CRC progression. Furthermore, exosomal circ_FMN2 overexpression also could facilitate CRC tumor growth in vivo.Exosomal circ_FMN2 accelerated CRC progression through miR-338-3p/MSI1 axis, revealing that exosomal circ_FMN2 might be a target for CRC treatment.© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.