Yu Shiyi, Si Yue, Xu Miao, Wang Ying, Liu Chengxu, Bi Caili, Sun Maoqiu, Sun Haibo
Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Key Laboratory of Experimental & Translational Non-Coding RNA Research, Yangzhou University, Yangzhou, Jiangsu, China.
Department of Thyroid and Breast Surgery, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu, China.
J Biol Chem. 2025 Jan;301(1):108070. doi: 10.1016/j.jbc.2024.108070. Epub 2024 Dec 10.
The combination of CDK4/6 inhibitors (CDK4/6i) and endocrine therapy is the first-line therapy for ER+/Her2-breast cancer; however, the development of drug resistance limited the efficacy of the agents. Although activation of the IFN signaling pathway has been identified as a critical driver of intrinsic and acquired CDK4/6i resistance, it remains unknown how the IFN signaling pathway was activated in resistant cells. Here, we report that NSRP1, a regulator of alternative mRNA splicing is downregulated in CDK4/6i resistant breast cancer cells and contributes to CDK4/6i resistance by mediating alternative splicing of NSD2 mRNA and activation of the IFN signaling pathway. Knockdown of NSRP1 reduces CDK4/6i (palbociclib) sensitivity of MCF7 cells while overexpression of NSRP1 sensitizes MCF7-PalR cells towards palbociclib treatment. Mechanistically, RNA sequencing suggests that NSRP1 knockdown strongly activates the IFN signaling pathway in MCF7 cells and elevates the expression of most of the "IFN-related palbociclib-resistance Signature" (IRPS) genes. NSRP1 also regulates numerous alternative splicing (AS) events in breast cancer cells, several of which are key regulators of the IFN signaling pathway. Among them, the inclusion of NSD2 exon 2 is elevated upon NSRP1 knockdown. Our data further show that the inclusion of NSD2 exon 2 is increased in breast cancer and associated with the poor prognosis of patients. In addition, including NSD2 exon 2 elevates NSD2 protein expression to activate the IFN signaling pathway. This study unveils the critical role of NSRP1 in regulating the IFN signaling pathway and the CDK4/6i resistance, which could be a promising biomarker for predicting therapy response.
细胞周期蛋白依赖性激酶4/6抑制剂（CDK4/6i）与内分泌治疗联合是雌激素受体阳性/人表皮生长因子受体2阴性（ER+/Her2-）乳腺癌的一线治疗方案；然而，耐药性的产生限制了这些药物的疗效。虽然干扰素（IFN）信号通路的激活已被确定为内在性和获得性CDK4/6i耐药的关键驱动因素，但IFN信号通路在耐药细胞中是如何被激活的仍不清楚。在此，我们报告称，NSRP1（一种可变mRNA剪接调节因子）在CDK4/6i耐药的乳腺癌细胞中表达下调，并通过介导NSD2 mRNA的可变剪接和激活IFN信号通路来促进CDK4/6i耐药。敲低NSRP1可降低MCF7细胞对CDK4/6i（哌柏西利）的敏感性，而NSRP1的过表达则使MCF7-PalR细胞对哌柏西利治疗敏感。从机制上讲，RNA测序表明，敲低NSRP1可强烈激活MCF7细胞中的IFN信号通路，并提高大多数“IFN相关哌柏西利耐药特征”（IRPS）基因的表达。NSRP1还调节乳腺癌细胞中的许多可变剪接（AS）事件，其中一些是IFN信号通路的关键调节因子。其中，NSRP1敲低后NSD2外显子2的包含率升高。我们的数据进一步表明，NSD2外显子2的包含率在乳腺癌中增加，并且与患者的不良预后相关。此外，包含NSD2外显子2可提高NSD2蛋白表达以激活IFN信号通路。本研究揭示了NSRP1在调节IFN信号通路和CDK4/6i耐药中的关键作用，这可能是预测治疗反应的一个有前景的生物标志物。
