Epitranscriptional regulation of TGF-β pseudoreceptor BAMBI by m6A/YTHDF2 drives extrinsic radioresistance
Liangliang Wang, … , Hua Laura Liang, Ralph Weichselbaum
Liangliang Wang, … , Hua Laura Liang, Ralph Weichselbaum
Published December 15, 2023
Citation Information: J Clin Invest. 2023;133(24):e172919. https://doi.org/10.1172/JCI172919.
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Research Article Immunology Oncology

Epitranscriptional regulation of TGF-β pseudoreceptor BAMBI by m6A/YTHDF2 drives extrinsic radioresistance

Abstract

Activation of TGF-β signaling serves as an extrinsic resistance mechanism that limits the potential for radiotherapy. Bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) antagonizes TGF-β signaling and is implicated in cancer progression. However, the molecular mechanisms of BAMBI regulation in immune cells and its impact on antitumor immunity after radiation have not been established. Here, we show that ionizing radiation (IR) specifically reduces BAMBI expression in immunosuppressive myeloid-derived suppressor cells (MDSCs) in both murine models and humans. Mechanistically, YTH N6-methyladenosine RNA-binding protein F2 (YTHDF2) directly binds and degrades Bambi transcripts in an N6-methyladenosine–dependent (m6A-dependent) manner, and this relies on NF-κB signaling. BAMBI suppresses the tumor-infiltrating capacity and suppression function of MDSCs via inhibiting TGF-β signaling. Adeno-associated viral delivery of Bambi (AAV-Bambi) to the tumor microenvironment boosts the antitumor effects of radiotherapy and radioimmunotherapy combinations. Intriguingly, combination of AAV-Bambi and IR not only improves local tumor control, but also suppresses distant metastasis, further supporting its clinical translation potential. Our findings uncover a surprising role of BAMBI in myeloid cells, unveiling a potential therapeutic strategy for overcoming extrinsic radioresistance.

Authors

Liangliang Wang, Wei Si, Xianbin Yu, Andras Piffko, Xiaoyang Dou, Xingchen Ding, Jason Bugno, Kaiting Yang, Chuangyu Wen, Linda Zhang, Dapeng Chen, Xiaona Huang, Jiaai Wang, Ainhoa Arina, Sean Pitroda, Steven J. Chmura, Chuan He, Hua Laura Liang, Ralph Weichselbaum

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Figure 3

BAMBI suppresses MDSC migration and suppressive function via inhibiting TGF-β signaling.

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BAMBI suppresses MDSC migration and suppressive function via inhibiting ...
(A) WT and Bambi-KD BM-MDSCs as indicated were used for Transwell assay. The attached cells on the Transwell membrane were visualized under a light microscope and quantified. n = 3 per group. (B) MC38 tumor–bearing Ccr2-KO mice (CD45.2) were adoptively transferred with 1 × 106 WT, Bambi-KD, and BAMBI-overexpressing (BAMBI-OE) BM-MDSCs (CD45.1) via i.v. injection. On the same day, mice were treated with tumor-local IR (20 Gy, 1 dose). Three days after IR, the number of tumor-infiltrating CD45.1+CD11b+Ly6Chi cells was determined by flow cytometry. n = 4 per group. (C) Heatmap showing qPCR analysis of relative mRNA expression of indicated genes in WT, Bambi-KD, and BAMBI-OE MDSCs. qPCR data were normalized to Gapdh. n = 3 per group. (D) Flow cytometry analysis of an in vitro proliferation assay showing the frequency of proliferating CD8+ T cells when cocultured with WT, Bambi-KD, and BAMBI-OE MDSCs. n = 5 per group. (E) Immunoblot analysis of signaling associated proteins and phosphorylated (p-) proteins as indicated in WT, Bambi-KD, and BAMBI-OE MDSCs treated with murine recombinant TGF-β. Blots were run in parallel, and left and right panels were run at different times. (F) WT, Bambi-KD, Tgfbr2-KO, and Bambi-KD/Tgfbr2-KO BM-MDSCs were used for adoptive transfer into MC38 tumor–bearing Ccr2-KO mice. On the same day, mice were treated by with tumor-local IR. Three days after IR, the number of tumor-infiltrating CCR2+CD11b+Ly6Chi cells was determined by flow. n = 4 per group. (G) Flow cytometry analysis of an in vitro proliferation assay showing the frequency of proliferating CD8+ T cells when cocultured with different BM-MDSCs as indicated. n = 4 per group. Data are represented as means ± SEM. One of 2 or 3 representative experiments is shown. Statistical analysis was performed using 2-sided, unpaired Student’s t test (A, F, and G) or 1-way ANOVA with Bonferroni’s multiple-comparison tests (B and D). *P < 0.05; **P < 0.01; ****P < 0.0001.