FBXW5 blunts RIGI/MDA5/IFN signaling to drive immune evasion and chemo-immune resistance in triple-negative breast cancer models
Xin Li, Tong Chen, Wenjing Zhao, Jiaxing Li, Yifan Shang, Bing Chen, Lijuan Wang, Ning Zhang, Xiaoli Kong, Yiran Liang, Yaming Li, Chen Li, Dianwen Han, Xi Chen, Shan Jiang, Chao Yang, Dan Luo, Tingting Ma, Qifeng Yang
Xin Li, Tong Chen, Wenjing Zhao, Jiaxing Li, Yifan Shang, Bing Chen, Lijuan Wang, Ning Zhang, Xiaoli Kong, Yiran Liang, Yaming Li, Chen Li, Dianwen Han, Xi Chen, Shan Jiang, Chao Yang, Dan Luo, Tingting Ma, Qifeng Yang
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Research Article Cell biology Immunology Oncology

FBXW5 blunts RIGI/MDA5/IFN signaling to drive immune evasion and chemo-immune resistance in triple-negative breast cancer models

Abstract

Triple-negative breast cancer (TNBC), characterized by aggressive behavior and poor prognosis, presents a formidable clinical challenge. Despite guideline endorsement of chemoimmunotherapy as a standard treatment in TNBC, durable responses remain rare, largely due to an immunologically “cold” tumor microenvironment (TME). Through integrated analysis, we identified the F-box protein FBXW5 as a tumor-intrinsic immunosuppressive regulator, whose expression is elevated in immunologically “cold” TNBC and correlates with dismal patient survival. Genetic knockdown of murine Fbxw5 suppressed tumor growth, reinvigorated CD8+ T cell–mediated antitumor immunity, and sensitized TNBC tumors to both single-agent and combined chemoimmunotherapy in preclinical models. Mechanistically, FBXW5 acts within the SKP1/CUL1/F-box protein E3 ligase complex to bind RIGI and MDA5, promoting their K27-linked polyubiquitination and subsequent SQSTM1-mediated autophagic degradation. This process blunts cytosolic RNA sensing and type I interferon signaling, thereby limiting CD8+ T cell infiltration and activation. Our findings establish FBXW5 as a master regulator of the “cold” TME, presenting a potential predictive biomarker and actionable therapeutic target for enhancing chemoimmunotherapy in TNBC.

Authors

Xin Li, Tong Chen, Wenjing Zhao, Jiaxing Li, Yifan Shang, Bing Chen, Lijuan Wang, Ning Zhang, Xiaoli Kong, Yiran Liang, Yaming Li, Chen Li, Dianwen Han, Xi Chen, Shan Jiang, Chao Yang, Dan Luo, Tingting Ma, Qifeng Yang

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Figure 3

FBXW5 modulates type I IFN signaling via physical interaction with RIGI and MDA5.

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FBXW5 modulates type I IFN signaling via physical interaction with RIGI ...
(A) ELISA of IFN-β and CXCL10 in supernatants from MDA-MB-468 cells treated with HMW poly(I:C) (3 μg/mL). (B) RT-qPCR of CXCL10 mRNA in MDA-MB-468 cells with HMW poly(I:C) treatment. si, siRNA. (C) Western blot analysis of indicated protein expression upon indicated treatment. TBK1, tank binding kinase 1. (D) Luciferase assays of IFNB1 promoter activity in HEK293T cells cotransfected with FBXW5 and the indicated signaling components. (E) PLAs visualizing the spatial proximity of FBXW5 with MDA5 or RIGI in the cytoplasm. The images are representative of 3 independent experiments (scale bars: 10 μm). (F) Silver staining and mass spectrometry of FBXW5-specific immunoprecipitates identifying RIGI/MDA5 as interacting partners. (G) Co-IP analysis of FBXW5/RIGI/MDA5 interaction in TNBC cells transfected with poly(I:C) HMW (3 μg/mL) or poly(I:C) LMW (10 μg/mL). (H) Schematic representation of truncated constructs of FBXW5. ΔC, ΔF, and ΔN refer to the C-terminal, F-box, and N-terminal deletion constructs of FBXW5, respectively. (I) Interaction of RIGI/MDA5 with FBXW5 truncations analyzed by co-IP. (J) Immunoblotting analysis of indicated protein levels in MDA-MB-468 cells expressing full-length FBXW5 or Δ133-466 mutant upon indicated treatment. (K and L) Schematic representation of truncated constructs of MDA5 and RIGI. (M) Interaction of FBXW5 with RIGI/MDA5 truncations analyzed by co-IP. (N) AlphaFold3 modeling of FBXW5/RIGI/MDA5 interactions. Red asterisks denote specific protein bands to distinguish them from nonspecific signals. Statistical significance was determined by unpaired 2-tailed Welch’s t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.