Multiple myeloma (MM) is a hematologic malignancy that results from uncontrolled plasma cell proliferation. Circular RNAs are versatile regulators that influence cancer aggression. The pathogenic mechanism of circXPO1 in MM is still unknown. In this study, the expression of circXPO1, miR-495-3p, and DNA damage-induced transcription 4 (DDIT4) was detected. Knockdown and overexpression assays were used to evaluate the effect of circXPO1 on MM. Specifically, 5-ethynyl-2′-deoxyuridine and cell counting kit-8 assay were used to investigate cell proliferation. Meanwhile, flow cytometry was adopted to detect cell apoptosis and cell cycle. Apoptosis-associated and cell cycle-related proteins were detected by Western blot. Mechanistically, biotin RNA pull-down assay and dual-luciferase assay were implemented to verify the combination among miR495-3p and circXPO1 or DDIT4. The function of circXPO1 in vivo was explored in xenograft experiments. The results showed that circXPO1 was up-regulated in both MM samples and MM cell lines and miR-495-3p was down-regulated in MM patients. Silencing circXPO1 inhibited cell proliferation, increased apoptosis rates, and caused the G1 phase arrest. Overexpression of circXPO1 yielded opposite results. In addition, RNA pull-down experiment demonstrated the interaction between circXPO1 and miR-495-3p. Silencing miR-495-3p rescued the inhibitory function caused by the knockdown of circXPO1. DDIT4 was the target of miR-495-3p. Finally, silencing circXPO1 inhibited the growth of subcutaneous tumors in vivo. In conclusion, our findings showed that circXPO1 could promote MM progression via the miR-495-3p/DDIT4 axis.
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机译：多发性骨髓瘤 （MM） 是一种血液系统恶性肿瘤，由不受控制的浆细胞增殖引起。环状 RNA 是影响癌症侵袭性的多功能调节因子。circXPO1 在 MM 中的致病机制尚不清楚。本研究检测 circXPO1 、 miR-495-3p 和 DNA 损伤诱导转录 4 （DDIT4） 的表达。敲低和过表达测定用于评估 circXPO1 对 MM 的影响。具体来说，使用 5-乙炔基-2′-脱氧尿嘧啶和细胞计数试剂盒-8 测定来研究细胞增殖。同时，采用流式细胞术检测细胞凋亡和细胞周期。Western blot 检测细胞凋亡相关和细胞周期相关蛋白。从机制上讲，实施了生物素 RNA 下拉测定和双荧光素酶测定以验证 miR495-3p 与 circXPO1 或 DDIT4 的组合。在异种移植实验中探索了 circXPO1 在体内的功能。结果显示，circXPO1 在 MM 样本和 MM 细胞系中均上调，而 miR-495-3p 在 MM 患者中下调。沉默 circXPO1 抑制细胞增殖，增加细胞凋亡率，并导致 G1 期停滞。circXPO1 的过表达产生相反的结果。此外，RNA pull-down 实验证明了 circXPO1 与 miR-495-3p 之间的相互作用。沉默 miR-495-3p 挽救了敲低 circXPO1 引起的抑制功能。DDIT4 是 miR-495-3p 的靶点。最后，沉默 circXPO1 抑制了体内皮下肿瘤的生长。总之，我们的研究结果表明，circXPO1 可以通过 miR-495-3p/DDIT4 轴促进 MM 进展。
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