Abstract：
Tamoxifen (TAM) is the primary drug for treating estrogen receptor alpha-positive (ER+) breast cancer (BC). However, resistance to TAM can develop in some patients, limiting its therapeutic efficacy. The ubiquitin-specific protease (USP) family has been associated with the development, progression, and drug resistance of various cancers. To explore the role of USPs in TAM resistance in BC, we used qRT-PCR to compare USP expression between TAM-sensitive (MCF-7 and T47D) and TAM-resistant cells (MCF-7R and T47DR). We then modulated USP46 expression and examined its impact on cell proliferation, drug resistance (via CCK-8 and EdU experiments), glycolysis levels (using a glycolysis detection assay), protein interactions (confirmed by co-IP), and protein changes (analyzed through Western blotting). Our findings revealed that USP46 was significantly overexpressed in TAM-resistant BC cells, leading to the inhibition of the ubiquitin degradation of polypyrimidine tract-binding protein 1 (PTBP1). Overexpression of PTBP1 increased the PKM2/PKM1 ratio, promoted glycolysis, and intensified TAM resistance in BC cells. Knockdown of USP46 induced downregulation of PTBP1 protein by promoting its K48-linked ubiquitination, resulting in a decreased PKM2/PKM1 ratio, reduced glycolysis, and heightened TAM sensitivity in BC cells. In conclusion, this study highlights the critical role of the USP46/PTBP1/PKM2 axis in TAM resistance in BC. Targeted therapy against USP46 may represent a promising strategy to improve the prognosis of TAM-resistant patients.
摘要：
他莫昔芬（TAM）是治疗雌激素受体α阳性（ER）乳腺癌（BC）的主要药物。然而,对TAM的耐药性会在一些患者中发展，限制其治疗功效。泛素特异性蛋白酶（USP）家族已经与发展有关，programming,和各种癌症的耐药性。探讨USPs在BC抗TAM中的作用，我们使用qRT-PCR比较了TAM敏感细胞（MCF-7和T47D）和TAM耐药细胞（MCF-7R和T47DR）之间的USP表达。然后我们调节USP46表达并检查其对细胞增殖的影响,耐药性（通过CCK-8和EdU实验），糖酵解水平（使用糖酵解检测测定法），蛋白质相互作用（通过co-IP确认），和蛋白质变化（通过蛋白质印迹分析）。我们的研究结果表明，USP46在TAM抗性BC细胞中显著过表达，导致抑制聚嘧啶束结合蛋白1（PTBP1）的泛素降解。PTBP1的过表达增加了PKM2/PKM1比值,促进糖酵解，并增强了BC细胞的TAM抗性。USP46的敲低通过促进其K48连接的泛素化诱导PTBP1蛋白的下调,导致PKM2/PKM1比率降低，糖酵解减少，并提高了BC细胞的TAM敏感性。总之,本研究强调了USP46/PTBP1/PKM2轴在BCTAM耐药中的关键作用.针对USP46的靶向治疗可能是改善TAM耐药患者预后的有希望的策略。
