Chemo-resistance is considered a major obstacle in the clinical treatment of non-small-cell lung cancer (NSCLC). Circular RNA (circRNA) circ-RNF121 (hsa_circ_0023404) has been identified to be related to the cisplatin (DDP) resistance. However, the role and mechanism of circ-RNF121 in the DDP resistance in NSCLC are still unknown. Real-time quantitative PCR (RT-qPCR) was applied to detect the levels of circ-RNF121, microRNA-646 (miR-646) and SRY-related HMG box transcription factor 4 (SOX4). Cell viability, proliferation, apoptosis, migration, invasion and cell cycle progression were assessed by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), colony formation, flow cytometry, wound-healing, transwell and flow cytometry assays, severally. The binding relationship between miR-646 and circ-RNF121 or SOX4 was predicted by the circular RNA interactome or Target Scan Human7.2 and then verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. SOX4 protein level was measured by western blot assay. The biological role of circ-RNF121 on NSCLC tumor growth and drug resistance was examined by the xenograft tumor model in vivo. Circ-RNF121 and SOX4 were increased, and miR-646 was declined in DDP-resistant NSCLC tissues and cells. Furthermore, the circ-RNF121 deficiency could enhance DDP sensitivity by inhibiting cell proliferation, migration, invasion, cell cycle progression and promoting apoptosis in DDP-resistant NSCLC cells in vitro. Mechanically, circ-RNF121 served as a sponge of miR-646 to increase SOX4 expression. Circ-RNF121 knockdown improved the drug sensitivity of NSCLC in vivo. Circ-RNF121 silencing could reduce the DDP resistance of NSCLC cells by regulating SOX4 expression via miR-646. These findings hinted at a promising therapeutic target for NSCLC treatment.

中文翻译：

---

环状RNA circ-RNF121通过调节miR-646/SOX4轴促进非小细胞肺癌细胞的顺铂（DDP）耐药。

化疗耐药被认为是非小细胞肺癌（NSCLC）临床治疗的主要障碍。环状 RNA (circRNA) circ-RNF121 (hsa_circ_0023404) 已被确定与顺铂 (DDP) 耐药性相关。然而，circ-RNF121在NSCLC DDP耐药中的作用和机制仍不清楚。采用实时定量PCR（RT-qPCR）检测circ-RNF121、microRNA-646（miR-646）和SRY相关HMG box转录因子4（SOX4）的水平。通过 3-(4, 5-二甲基-2-噻唑基)-2, 5-二苯基-2-H-四唑溴化物 (MTT)、集落形成、分别进行流式细胞术、伤口愈合、Transwell 和流式细胞术测定。通过环状 RNA 相互作用组或 Target Scan Human7.2 预测 miR-646 与 circ-RNF121 或 SOX4 之间的结合关系，然后通过双荧光素酶报告基因和 RNA 免疫沉淀 (RIP) 测定进行验证。SOX4蛋白水平通过蛋白质印迹测定来测量。通过体内异种移植肿瘤模型检查了 circ-RNF121 对 NSCLC 肿瘤生长和耐药性的生物学作用。在 DDP 耐药的 NSCLC 组织和细胞中，Circ-RNF121 和 SOX4 增加，miR-646 减少。此外，circ-RNF121缺陷可以通过抑制细胞增殖、迁移、侵袭、细胞周期进程和促进体外DDP耐药NSCLC细胞凋亡来增强DDP敏感性。从机械角度来看，circ-RNF121 作为 miR-646 的海绵来增加 SOX4 的表达。Circ-RNF121敲低提高了NSCLC体内药物敏感性。Circ-RNF121沉默可以通过miR-646调节SOX4表达来降低NSCLC细胞的DDP耐药性。这些发现暗示了非小细胞肺癌治疗的一个有希望的治疗靶点。