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Oxaliplatin (OXA) resistance is the major obstacle to the anticancer effects of chemotherapy in colorectal cancer (CRC) patients. MicroRNAs (miRNAs) play an important role in the chemoresistance of various tumors. Our objective is to clarify the underlying mechanism of miRNAs in chemoresistance and provide a potential strategy to improve the response of CRC patients to chemotherapeutics. : MiRNA microarray and Real-time PCR were performed to compare changes in miRNA expression between oxaliplatin-resistant and the parental cells. CCK8, apoptosis assay, immunofluorescence and xenograft studies were used to elucidate the impact of miR-27b-3p on regulating chemoresistance. Luciferase reporter assay and western blot were carried to assess the regulatory role of miR-27b-3p in ATG10 expression. The effects of miR-27b-3p and ATG10 on autophagy were investigated by GFP-LC3 fluorescence microscopy, transmission electron microscopy, and western blot. ChIP assay and luciferase assay were performed to test the c-Myc's occupancy on the miR-27B promoter. : We observed that miR-27b-3p expression was significantly downregulated in oxaliplatin-resistant cell lines (SW480-OxR and HCT116-OxR) compared to the corresponding parental cell lines and that miR-27b-3p expression was positively correlated with disease-free survival (DFS) time in colorectal cancer patients. MiR-27b-3p could sensitize colorectal cancer cells to oxaliplatin in vitro and in vivo. Under oxaliplatin treatment, chemoresistant cells showed a higher autophagy level than parental cells. Moreover, we also identified that miR-27b-3p inhibited the expression of ATG10 at the posttranscriptional level, thus inhibiting autophagy. Further study demonstrated that c-Myc can inhibit the expression of miR-27b-3p via binding to the promoter region of miR-27B gene. : Our study identifies a novel c-Myc/miR-27b-3p/ATG10 signaling pathway that regulates colorectal cancer chemoresistance. These results suggest that miR-27b-3p is not only a potential indicator for evaluating efficiency of chemotherapy, but also a valuable therapeutic target for CRC, especially for patients with chemoresistance.

奥沙利铂（OXA）耐药性是结直肠癌（CRC）患者化疗抗癌效果的主要障碍。microRNAs（miRNAs）在各种肿瘤的化疗耐药性中发挥着重要作用。我们的目的是阐明 miRNAs 在化疗耐药性中的潜在机制，并提供一种潜在的策略来提高 CRC 患者对化疗的反应。

方法

采用 miRNA 微阵列和实时 PCR 比较奥沙利铂耐药细胞株与亲本细胞株之间 miRNA 表达的变化。CCK8、凋亡检测、免疫荧光和异种移植研究用于阐明 miR-27b-3p 调节化疗耐药性的作用。荧光素酶报告基因和 Western blot 用于评估 miR-27b-3p 对 ATG10 表达的调控作用。通过 GFP-LC3 荧光显微镜、透射电子显微镜和 Western blot 研究 miR-27b-3p 和 ATG10 对自噬的影响。ChIP assay 和 luciferase assay 用于检测 c-Myc 在 miR-27B 启动子上的占有率。

结果

我们观察到，与相应的亲本细胞系相比，奥沙利铂耐药细胞系（SW480-OxR 和 HCT116-OxR）中 miR-27b-3p 的表达明显下调，并且 miR-27b-3p 的表达与结直肠癌患者的无病生存（DFS）时间呈正相关。miR-27b-3p 可在体外和体内增强结直肠癌细胞对奥沙利铂的敏感性。在奥沙利铂处理下，耐药细胞比亲本细胞表现出更高的自噬水平。此外，我们还发现 miR-27b-3p 通过转录后水平抑制 ATG10 的表达，从而抑制自噬。进一步的研究表明，c-Myc 可以通过结合 miR-27B 基因的启动子区域抑制 miR-27b-3p 的表达。