In various cancers, abnormal USP9X expression is involved in tumor genesis, progression, apoptosis, and metastasis. However, the relationship between USP9X abnormal expression and cisplatin resistance in nasopharyngeal carcinoma (NPC) cells remains unclear. Using qRT-PCR and western blot, we detected the expressions of USP9X and β-catenin in NPC cells. The effects of USP9X on cell cisplatin resistance, proliferation, apoptosis, and metastasis were examined by CCK-8 assay, flow cytometry, wound-healing assay, and Transwell chamber assay. Co-IP assay, qRT-PCR, and western blot were performed to explore the detailed molecular mechanism of USP9X-β-catenin and its effect on the protein levels of MDR1, MRP2, Bcl-2, Bax, MMP2, and MMP9. We found that USP9X and β-catenin expressions in cisplatin-resistance cell lines (HNE1/DDP) were much higher than cisplatin-sensitive cell lines (HNE1) at both mRNA and protein levels. Co-IP assay demonstrated that USP9X was immunoprecipitated with β-catenin in NPC cells. Knockdown of USP9X was able to partially reverse cisplatin-resistance, increased cisplatin-induced apoptosis, and decreased the capacities of proliferation, migration, and invasion. Overexpression of USP9X can increase cisplatin resistance in NPC cells. Moreover, knockdown of USP9X expression can significantly reduce the expressions of MDR1, MRP2, Bcl-2, MMP2, and MMP9, but significantly increased the expression of Bax. These findings indicate that USP9X high expression plays a significant part in cisplatin-resistance of NPC. This study elucidated the possible mechanism of cisplatin resistance in NPC cells and may have implications for the therapeutic reversal of cisplatin resistance.

中文翻译：

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敲除 USP9X 通过降低鼻咽癌细胞中 β-连环蛋白的表达来逆转顺铂耐药。

在各种癌症中，异常的 USP9X 表达与肿瘤发生、进展、细胞凋亡和转移有关。然而，USP9X 异常表达与鼻咽癌 (NPC) 细胞顺铂耐药之间的关系仍不清楚。使用 qRT-PCR 和蛋白质印迹，我们检测了 NPC 细胞中 USP9X 和 β-catenin 的表达。通过CCK-8测定、流式细胞术、伤口愈合测定和Transwell小室测定检查USP9X对细胞顺铂耐药、增殖、凋亡和转移的影响。进行 Co-IP 测定、qRT-PCR 和蛋白质印迹以探索 USP9X-β-连环蛋白的详细分子机制及其对 MDR1、MRP2、Bcl-2、Bax、MMP2 和 MMP9 蛋白水平的影响。我们发现顺铂耐药细胞系 (HNE1/DDP) 中 USP9X 和 β-catenin 的表达在 mRNA 和蛋白质水平上都远高于顺铂敏感细胞系 (HNE1)。Co-IP 测定表明 USP9X 与 NPC 细胞中的 β-连环蛋白免疫沉淀。敲低 USP9X 能够部分逆转顺铂耐药，增加顺铂诱导的细胞凋亡，并降低增殖、迁移和侵袭能力。USP9X 的过表达可增加 NPC 细胞的顺铂耐药性。此外，敲低 USP9X 表达可显着降低 MDR1、MRP2、Bcl-2、MMP2 和 MMP9 的表达，但显着增加 Bax 的表达。这些发现表明，USP9X 高表达在 NPC 的顺铂耐药中起重要作用。