LncRNA DLEU2 contributes to Taxol resistance of gastric cancer cells through regulating the miR-30c-5p-LDHA axis

Gastric cancer (GC) is a human malignancy which is associated with high mortality rate and poor prognosis. In addition to surgery, chemo- and radio-therapies are effective strategies against GC at advanced or metastatic stage. Taxol is a traditionally anti-cancer drug which is applied to various types of cancer. However, development of drug resistance limited the anti-cancer effects of Taxol. Currently, the biological roles and mechanisms of non-coding RNA DLEU2 in Taxol resistant GC remain unclear. This study reported that DLEU2 was significantly upregulated and miR-30c-5p was remarkedly downregulated in gastric tumours and cell lines. Silencing DLEU2 or overexpression of miR-30c-5p effectively increased the Taxol sensitivity of GC cells. Through bioinformatics analysis, RNA pull-down and luciferase assay, we demonstrated that DLEU2 sponged miR-30c-5p to block its expression in GC cells. Moreover, from the established Taxol resistant GC cell line, we detected remarkedly upregulated DLEU2 and downregulated miR-30c-5p expressions and significantly elevated glucose metabolism. Under low glucose condition, Taxol resistant cells were more susceptible to Taxol. In addition, we showed overexpression of miR-30c-5p blocked glucose metabolism through inhibiting the LDHA, a glucose metabolism key enzyme by direct targeting the 3′UTR of LDHA. Finally, rescue experiments validated that restoration of miR-30c-5p in DLEU2-overexpressing Taxol resistant GC cells effectively overcame the DLEU2-promoted Taxol resistance. In summary, this study uncovered new roles and molecular mechanisms of the lncRNA DLEU2-promoted Taxol resistance of gastric cancer cells, presenting the DLEU2-miR-30c-5p-LDHA-glucose metabolism axis a potentially therapeutic target for treatment of Taxol resistant GC.

胃癌（GC）是一类高致死率、预后不良的人类恶性肿瘤。除手术治疗外，化疗与放疗是晚期或转移性胃癌的有效治疗策略。紫杉醇（Taxol）是一款广泛应用于多种癌症的传统抗癌药物，但其抗癌效果因耐药性的产生而受到限制。目前，非编码RNA DLEU2在紫杉醇耐药胃癌中的生物学功能及作用机制仍不明确。本研究发现，在胃癌组织及细胞系中，DLEU2的表达显著上调，而miR-30c-5p的表达则显著下调。沉默DLEU2或过表达miR-30c-5p均可有效提升胃癌细胞对紫杉醇的敏感性。通过生物信息学分析、RNA下拉实验及荧光素酶报告基因实验，本研究证实DLEU2可通过海绵吸附miR-30c-5p，抑制其在胃癌细胞中的表达。此外，在本研究构建的紫杉醇耐药胃癌细胞系中，我们检测到DLEU2表达显著上调、miR-30c-5p表达显著下调，且糖代谢水平显著升高。在低糖培养条件下，紫杉醇耐药细胞对紫杉醇的敏感性显著提升。进一步研究显示，过表达miR-30c-5p可通过直接靶向乳酸脱氢酶A（LDHA）的3'非翻译区（3′UTR），抑制该糖代谢关键酶的表达，从而阻断糖代谢进程。最终，拯救实验证实，在过表达DLEU2的紫杉醇耐药胃癌细胞中恢复miR-30c-5p的表达，可有效逆转DLEU2介导的紫杉醇耐药。综上，本研究揭示了长链非编码RNA（long non-coding RNA, lncRNA）DLEU2促进胃癌细胞紫杉醇耐药的全新功能与分子机制，提出DLEU2-miR-30c-5p-LDHA-糖代谢轴可作为治疗紫杉醇耐药胃癌的潜在治疗靶点。