Paroxetine repurposing enhances antitumor immunity via SPOP-mediated PD-L1 ubiquitination and proteasomal degradation

作者：Mengting Xu, Saisai Tian, Hanchi Xu, Xinying Xue, Qing Zhang, Hongmei Hu, Gaosong Wu, Xiangxin Geng, Dianping Yu, Hanchen Xu, Mei Xie, Linyang Li, Xinru Li, Simeng Li, Shize Xie, Xuwen Lin, Shuzhen Lyu, Yutong Xie, Biao Zhang, Haiyang Zhou, Qun Wang, Weidong Zhang, Sanhong LIU · 发表于：Journal of Experimental & Clinical Cancer Research · 年份：2026 · DOI：10.1186/s13046-026-03648-z · 被引用次数：1 · 研究领域：Cancer, Stress, Anesthesia, and Immune Response、Tryptophan and brain disorders、Cancer Immunotherapy and Biomarkers

BACKGROUND: Immunotherapy targeting the PD-1/PD-L1 axis shows promise in colon and lung cancer treatment but faces challenges like high costs, low response rates, and drug resistance. Developing new small molecule inhibitors is complex. Repurposing existing drugs offers advantages, and paroxetine (PAR), an FDA approved antidepressant, has shown potential antitumor effects, yet its role as an immune checkpoint inhibitor is unclear. METHODS: In this study, we investigated PAR as an immune checkpoint inhibitor. We used various cell lines, including colon and lung cancer cells, and in vivo mouse models. Techniques such as Western blotting, flow cytometry, immunofluorescence, and immunohistochemistry were employed to analyze protein expression, cell surface marker levels, and immune cell populations. We also conducted gene knockdown and overexpression experiments, as well as molecular docking and binding assays. RESULTS: PAR downregulates PD-L1 protein levels in a concentration and time dependent manner in multiple cancer cell lines. In vivo, it inhibits tumor growth in colon and lung cancer mouse models by activating T cell immunity. Mechanistically, PAR binds to the Asp130 site of speckle-type POZ protein (SPOP), stabilizing this E3 ubiquitin ligase to promote PD-L1 ubiquitination and proteasomal degradation. Moreover, PAR combines with an anti-CTLA4 antibody enhances cancer cell inhibition, and it also suppresses AOM/DSS induced colon cancer. CONCLUSIONS: Our findings demonstra...