Cucurbitacin B stimulates PD-1 immunotherapy response in malignant breast cancer by covalent targeting MTCH2

  • Phytomedicine. 2025 Jun 20:145:157017. doi: 10.1016/j.phymed.2025.157017.
Qianqian Xu  1 ,  Zeyu Jiang  1 ,  Yuqi Pan  1 ,  Sheng Li  1 ,  Zehong Cao  2 ,  Shengjie Hua  1 ,  Ruolan Yang  1 ,  Qinman He  2 ,  Hao Wu  2 ,  Hongmei Wen  2 ,  Bo Hang  3 ,  Hongli Yu  4 ,  Xinzhi Wang  5
Affiliations
  • 1. College of Pharmacy, Nanjing University of Chinese Medicine, Xianlin Avenue No. 138, Nanjing, Jiangsu, 210046, PR China; China Jiangsu Key Laboratory of Research and Development in Marine Bio-resource Pharmaceutics, Xianlin Avenue No. 138, Nanjing, Jiangsu, 210046, PR China.
  • 2. College of Pharmacy, Nanjing University of Chinese Medicine, Xianlin Avenue No. 138, Nanjing, Jiangsu, 210046, PR China.
  • 3. Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94710, USA. Electronic address: [email protected].
  • 4. College of Pharmacy, Nanjing University of Chinese Medicine, Xianlin Avenue No. 138, Nanjing, Jiangsu, 210046, PR China. Electronic address: [email protected].
  • 5. College of Pharmacy, Nanjing University of Chinese Medicine, Xianlin Avenue No. 138, Nanjing, Jiangsu, 210046, PR China; China Jiangsu Key Laboratory of Research and Development in Marine Bio-resource Pharmaceutics, Xianlin Avenue No. 138, Nanjing, Jiangsu, 210046, PR China. Electronic address: [email protected].
PMID: 40582210 DOI: 10.1016/j.phymed.2025.157017
Abstract

Background: Effective therapies for malignant breast Cancer are urgently needed, as resistance and immunosuppressive microenvironments limit PD-1 blockade efficacy. The natural product Cucurbitacin B (CuB) reportedly sensitizes breast Cancer to PD-1 immunotherapy, yet its molecular mechanism is undefined.

Purpose: Here, we sought to identify the direct molecular targets of CuB and elucidate the mechanisms responsible for its synergy with PD-1 blockade in breast Cancer.

Study design and methods: We used Quantitative Thiol Reactivity Profiling (QTRP) to identify CuB-binding proteins. Binding interactions were validated using microscale thermophoresis (MST), cellular thermal shift assay (CETSA), and activity-based protein profiling (ABPP). The functional outcomes of CuB-protein interactions were explored using in vitro, ex vivo, and in vivo models, including cell lines, tumor organoids, and animal models of invasive breast Cancer.

Results: We identified the mitochondrial outer membrane protein MTCH2, often overexpressed in aggressive breast Cancer, as a direct covalent target of CuB. CuB binding to MTCH2 disrupted mitochondrial integrity, causing mitochondrial DNA (mtDNA) release into the cytosol and subsequent activation of the cGAS-STING innate immune pathway. This culminated in type I interferon production, activation of tumor-associated neutrophils, and enhanced anti-tumor immunity. Co-administration of CuB and PD-1 blockade demonstrated significant synergistic efficacy in preclinical breast Cancer models.

Conclusions: This work elucidates a novel mechanism by which CuB enhances anti-tumor immunity: covalent targeting of MTCH2 triggers mitochondrial dysfunction and cGAS-STING pathway activation. Our findings establish MTCH2 as a key node linking mitochondrial function to tumor immunogenicity and provide a rationale for combining CuB, or potentially MTCH2 modulators, with PD-1 blockade for treating malignant breast Cancer.

Keywords
Aggressive breast cancer; Cucurbitacin B; MTCH2; Tumor-associated neutrophils; mtDNA-cGAS-STING; Ιmmunotherapy response.
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