Kim Hogyoung, Elkins Emma, Islam Rahib, Cao Bo, Abbes Nour, Battles Kaela, Kim Sihyoung, Kim Sichan, Williams Christopher
College of Pharmacy, Xavier University of Louisiana, New Orleans, LA 70125, USA.
College of Arts and Sciences, Xavier University of Louisiana, New Orleans, LA 70125, USA.
Cancers (Basel). 2024 Jul 10;16(14):2501. doi: 10.3390/cancers16142501.
Aberrant estrogen receptor (ERα) signaling mediates detrimental effects of tamoxifen including drug resistance and endometrial hyperplasia. ERα36, an alternative isoform of ERα, contributes to these effects. We have demonstrated that CK2 modulates ERα expression and function in breast cancer (BCa). Here, we assess if CX-4945 (CX), a clinical stage CK2 inhibitor, can disrupt ERα66 and ERα36 signaling in BCa. Using live cell imaging, we assessed the antiproliferative effects of CX in tamoxifen-sensitive and tamoxifen-resistant BCa cells in monolayer and/or spheroid cultures. CX-induced alterations in ERα66 and ERα36 mRNA and protein expression were assessed by RT-PCR and immunoblot. Co-immunoprecipitation was performed to determine the differential interaction of ERα isoforms with HSP90 and CK2 upon CX exposure. CX caused concentration-dependent decreases in proliferation in tamoxifen-sensitive MCF-7 and tamoxifen-resistant MCF-7 Tam1 cells and significantly repressed spheroid growth in 3D models. Additionally, CX caused dramatic decreases in endogenous or exogenously expressed ERα66 and ERα36 protein. Silencing of CK2β, the regulatory subunit of CK2, resulted in destabilization and decreased proliferation, similar to CX. Co-immunoprecipitation demonstrated that ERα66/36 show CK2 dependance for interaction with molecular chaperone HSP90. Our findings show that CK2 functions regulate the protein stability of ERα66 and ERα36 through a mechanism that is dependent on CK2β subunit and HSP90 chaperone function. CX may be a component of a novel therapeutic strategy that targets both tamoxifen-sensitive and tamoxifen-resistant BCa, providing an additional tool to treat ERα-positive BCa.
异常的雌激素受体（ERα）信号传导介导了他莫昔芬的有害作用，包括耐药性和子宫内膜增生。ERα36是ERα的一种变体亚型，促成了这些作用。我们已经证明，酪蛋白激酶2（CK2）调节乳腺癌（BCa）中ERα的表达和功能。在此，我们评估临床阶段的CK2抑制剂CX-4945（CX）是否能破坏BCa中的ERα66和ERα36信号传导。利用活细胞成像技术，我们评估了CX在单层和/或球体培养的他莫昔芬敏感和他莫昔芬耐药BCa细胞中的抗增殖作用。通过逆转录聚合酶链反应（RT-PCR）和免疫印迹法评估CX诱导的ERα66和ERα36 mRNA及蛋白表达的变化。进行免疫共沉淀以确定CX暴露后ERα亚型与热休克蛋白90（HSP90）和CK2的差异相互作用。CX导致他莫昔芬敏感的MCF-7细胞和他莫昔芬耐药的MCF-7 Tam1细胞的增殖呈浓度依赖性下降，并在三维模型中显著抑制球体生长。此外，CX导致内源性或外源性表达的ERα66和ERα36蛋白显著减少。CK2的调节亚基CK2β沉默导致不稳定并降低增殖，类似于CX。免疫共沉淀表明，ERα66/36与分子伴侣HSP90的相互作用显示出对CK2的依赖性。我们的研究结果表明，CK2功能通过一种依赖于CK2β亚基和HSP90伴侣功能的机制调节ERα66和ERα36的蛋白质稳定性。CX可能是一种新型治疗策略的组成部分，该策略针对他莫昔芬敏感和他莫昔芬耐药的BCa，为治疗ERα阳性BCa提供了一种额外的工具。
