Circular RNAs (circRNAs) have been documented to be aberrantly expressed in many types of malignancies and involved in cancer progression. However, their role in thyroid cancer (TC) remains largely unknown. Our study aimed to explore the role and mechanism of circUBAP2 in TC. The differentially expressed circRNAs in TC tissues were identified using GSE18105 from gene expression omnibus (GEO) database. CircUBAP2 and miR-370-3p expression was analyzed using qRT-PCR. The stability of circUBAP2 was confirmed by actinomycin D and RNase R. The subcellular localization of circUBAP2 was detected using cell fractionation assay. Cell proliferation, apoptosis, and invasion were evaluated using MTT, flow cytometry analysis, and Transwell invasion assay, respectively. The interaction between circUBAP2 and miR-370-3p was predicted using bioinformatics analysis and validated by luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation. CircUBAP2 was upregulated and miR-370-3p was downregulated in TC tissues and cells. CircUBAP2 was highly stable, resistant to RNase R digestion, and predominantly localized in the cytoplasm. CircUBAP2 knockdown inhibited cell proliferation and invasion and triggered apoptosis in TC cells. Bioinformatics analysis showed that circUBAP2 contained putative binding sites of miR-370-3p. CircUBAP2 acted as a sponge to inhibit miR-370-3p expression. Mechanistically, miR-370-3p inhibition abolished the effects of circUBAP2 on proliferation, apoptosis, and invasion in TC cells. Taken together, CircUBAP2 knockdown impeded the proliferation and invasion and induced apoptosis in TC cells via sponging miR-370-3p.

环状 RNA (circRNA) 已被证明在许多类型的恶性肿瘤中异常表达并参与癌症进展。然而，它们在甲状腺癌 (TC) 中的作用仍然很大程度上未知。我们的研究旨在探索circUBAP2在TC中的作用和机制。使用来自基因表达综合（GEO）数据库的 GSE18105 鉴定 TC 组织中差异表达的 circRNA。使用 qRT-PCR 分析 CircUBAP2 和 miR-370-3p 表达。circUBAP2 的稳定性通过放线菌素 D 和 RNase R 确认。使用细胞分级测定法检测 circUBAP2 的亚细胞定位。分别使用 MTT、流式细胞术分析和 Transwell 侵袭试验评估细胞增殖、凋亡和侵袭。circUBAP2 和 miR-370-3p 之间的相互作用通过生物信息学分析进行预测，并通过荧光素酶报告基因分析、RNA 下拉分析和 RNA 免疫沉淀进行验证。TC 组织和细胞中 CircUBAP2 上调，miR-370-3p 下调。CircUBAP2 高度稳定，对 RNase R 消化具有抗性，并且主要定位于细胞质中。CircUBAP2 敲低抑制细胞增殖和侵袭并引发 TC 细胞凋亡。生物信息学分析表明，circUBAP2 含有 miR-370-3p 的推定结合位点。CircUBAP2 充当海绵来抑制 miR-370-3p 的表达。从机制上讲，miR-370-3p 抑制消除了 circUBAP2 对 TC 细胞增殖、凋亡和侵袭的影响。综合起来，