Exosomal circular RNA NT5E driven by heterogeneous nuclear ribonucleoprotein A1 induces temozolomide resistance by targeting microRNA-153 in glioma cells

Abstract

Abstract Objectives Exosomally transferred circular RNAs (circRNAs) are critical in cancer. However, the study of exosomal circRNAs in glioma resistance remains limited. Here, we further investigated the function and mechanism of exosomal circular RNA NT5E (circNT5E) in temozolomide-resistant glioma cells (TMZ-GCs). Methods Exosomes were isolated from TMZ-GCs and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting. CircNT5E, microRNA-153 (miR-153), and heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) levels were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in TMZ-sensitive and TMZ-resistant GCs and in treated TMZ-GCs. In addition, the colocalization of circNT5E and miR-153 was confirmed by fluorescence in situ hybridization (FISH) and dual-luciferase reporter assays. Internalization of exosomes was observed by immunofluorescence staining. TMZ resistance, proliferation, and pAKTser473 protein levels were evaluated by a Cell Counting Kit-8 (CCK-8) assay, an EdU incorporation assay, and Western blotting, respectively. In addition, tumor growth was examined using a xenograft tumor model in nude mice. Results We first proved that circNT5E was highly abundant in exosomes derived from TMZ-GCs. Then, we discovered that circNT5E could serve as a miR-153 sponge. Finally, knockdown of circNT5E reduced TMZ resistance and cell proliferation and downregulated AKTser473 phosphorylation by targeting miR-153 in TMZ-GCs. Moreover, our data revealed that exosomes derived from TMZ-GCs also had obvious effects on inducing the TMZ resistance and proliferation of GCs. Moreover, we revealed that the packaging of circNT5E into exosomes can be driven by hnRNP A1. Conclusions Collectively, our findings proved that exosomal circNT5E transferred in a manner mediated by hnRNPA1 could accelerate TMZ resistance by targeting miR-153 in GCs, indicating that exosomal circNT5E is a therapeutic target for TMZ-resistant glioma.