Shang Yuanyuan, Wang Lingfei, Zhu Zhe, Gao Wei, Li Dan, Zhou Zhuqing, Chen Lin, Fu Chuan-Gang
Department of General Surgery and Colorectal Surgery, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China.
Department of Oncology, The 903rd Hospital of PLA, Hangzhou, China.
Front Oncol. 2021 Jan 11;10:582239. doi: 10.3389/fonc.2020.582239. eCollection 2020.
Resistance to radiotherapy is the main reason causing treatment failure in locally advanced rectal cancer. MicroRNAs (miRNAs) have been well demonstrated to regulate cancer development and progression. However, how miRNAs regulate radiotherapy resistance in colorectal cancer remains unknown. Herein, we established two human colorectal cancer cell lines resistant to radiotherapy, named HCT116-R and RKO-R, using the strategy of fractionated irradiation. The radioresistant phenotypical changes of the two cell lines were validated by cell viability assay, colony formation assay and apoptosis assay. The miRNA expression profilings of HCT116-R and RKO-R were determined using RNA-seq analyses, and further confirmed by quantitative real-time PCR. Multiple miRNAs, including miR-423-5p, miR-7-5p, miR-522-3p, miR-3184-3p, and miR-3529-3p, were identified with altered expression in both of the radiotherapy-resistant cells, compared to the parental cells. The downregulation of miR-423-5p was further validated in the rectal cancer tissues from radiotherapy-resistant patients. Silencing of miR-423-5p in parental HCT116 and RKO cells decreased the sensitivity to radiation treatment, and inhibited the radiation-induced apoptosis. In consistence, overexpression of miR-423-5p in HCT116-R and RKO-R cells partially rescued their sensitivity to radiotherapy, and promoted the radiation-induced apoptosis. Bcl-xL (Bcl-2-like protein 1) was predicted to be a potential target gene for miR-423-5p, and miR-423-5p/Bcl-xL axis could be a critical mediator of radiosensitivity in colorectal cancer cells. The current finding not only revealed a novel role of miR-423-5p in regulating the radiosensitivity in colorectal cancer, but also suggested miR-423-5p as a molecular candidate for combination therapy with radiation to treat colorectal cancer.
放疗抵抗是导致局部晚期直肠癌治疗失败的主要原因。微小RNA（miRNA）已被充分证明可调节癌症的发生和发展。然而，miRNA如何调节结直肠癌的放疗抵抗仍不清楚。在此，我们采用分次照射策略建立了两种耐放疗的人结直肠癌细胞系，命名为HCT116-R和RKO-R。通过细胞活力测定、集落形成测定和凋亡测定验证了这两种细胞系的放疗抵抗表型变化。使用RNA测序分析确定了HCT116-R和RKO-R的miRNA表达谱，并通过定量实时PCR进一步证实。与亲代细胞相比，在两种放疗抗性细胞中均鉴定出多个表达改变的miRNA，包括miR-423-5p、miR-7-5p、miR-522-3p、miR-3184-3p和miR-3529-3p。在放疗抗性患者的直肠癌组织中进一步验证了miR-423-5p的下调。在亲代HCT116和RKO细胞中沉默miR-423-5p会降低对放射治疗的敏感性，并抑制放射诱导的凋亡。一致地，在HCT116-R和RKO-R细胞中过表达miR-423-5p可部分恢复其对放疗的敏感性，并促进放射诱导的凋亡。Bcl-xL（Bcl-2样蛋白1）被预测为miR-423-5p的潜在靶基因，miR-423-5p/Bcl-xL轴可能是结直肠癌细胞放射敏感性的关键介质。目前的发现不仅揭示了miR-423-5p在调节结直肠癌放射敏感性中的新作用，还表明miR-423-5p作为与放疗联合治疗结直肠癌的分子候选物。
