cDCBLD2 mediates sorafenib resistance in hepatocellular carcinoma by sponging miR-345-5p binding to the TOP2A coding sequence

Sorafenib is a first-line chemotherapy drug for treating advanced hepatocellular carcinoma (HCC). However, its therapeutic effect has been seriously affected by the emergence of sorafenib resistance in HCC patients. The underlying mechanism of sorafenib resistance is unclear. Here, we report a circular RNA, cDCBLD2, which plays an important role in sorafenib resistance in HCC. We found that cDCBLD2 was upregulated in sorafenib-resistant (SR) HCC cells, and knocking down cDCBLD2 expression could significantly increase sorafenib-related cytotoxicity. Further evidence showed that cDCBLD2 can bind to microRNA (miR)-345-5p through a competing endogenous RNA mechanism, increase type IIA topoisomerase (TOP2A) mRNA stability through a miRNA sponge mechanism, and reduce the effects of sorafenib treatment on HCC by inhibiting apoptosis. Our findings also suggest that miR-345-5p can negatively regulate TOP2A levels by binding to the coding sequence region of its mRNA. Additionally, targeting cDCBLD2 by injecting a specific small interfering RNA (siRNA) could significantly overcome sorafenib resistance in a patient-derived xenograft (PDX) mouse model of HCC. Taken together, our study provides a proof-of-concept for a potential strategy to overcome sorafenib resistance in HCC patients by targeting cDCBLD2 or TOP2A. Comparative gene expression profiling analysis of RNA-seq data for HCCLM3-SR cells and its KD derivatives (si_cDCBLD2, si_CTRL).

索拉非尼（Sorafenib）是治疗晚期肝细胞癌（hepatocellular carcinoma, HCC）的一线化疗药物。然而，HCC患者体内出现索拉非尼耐药后，其治疗效果会受到严重制约，目前该耐药现象的潜在分子机制仍未明确。本研究报道了一种环状RNA（circular RNA）cDCBLD2，其在HCC索拉非尼耐药进程中发挥关键调控作用。研究发现，cDCBLD2在索拉非尼耐药（SR）HCC细胞中表达显著上调；敲低cDCBLD2的表达，可显著增强索拉非尼诱导的细胞毒性。进一步实验证据表明，cDCBLD2可通过竞争内源RNA（competing endogenous RNA）机制结合微小RNA（miR）-345-5p，并借助miRNA海绵效应提升IIA型拓扑异构酶（TOP2A）的mRNA稳定性，最终通过抑制细胞凋亡，削弱索拉非尼对HCC细胞的治疗效果。本研究同时证实，miR-345-5p可通过结合TOP2A mRNA的编码序列区，负向调控其蛋白表达水平。此外，在HCC患者来源异种移植（PDX）小鼠模型中，注射靶向cDCBLD2的特异性小干扰RNA（siRNA），可显著逆转索拉非尼耐药表型。综上，本研究为通过靶向cDCBLD2或TOP2A，攻克HCC患者的索拉非尼耐药问题提供了概念验证。本研究还对HCCLM3-SR细胞及其敲低对照组衍生物（si_cDCBLD2、si_CTRL）的RNA测序数据开展了比较基因表达谱分析。