Fan et al. found that in patient specimens of untreated TNBC, cancer stem cells produced extracellular vesicles enriched for TSPAN8 (EVs-TSPAN8), which interacted with CD103 on T cells via a paracrine signaling mechanism – independent of canonical EV internalization – inducing activation of the LKB1-AMPK-FOXP3 axis. This resulted in enhanced Foxp3 expression, which further increased CD103 expression, resulting in a positive feedback loop that enhanced the formation of pro-tumor CD103+Foxp3+ Tregs. In mouse models of TNBC, neutralizing EVs-TSPAN8+ synergized with anti-PD-1, reducing tumor growth and increasing survival.

Contributed by Lauren Hitchings

ABSTRACT: Tumor cells evade anti-tumor immunity by reprogramming tumor microenvironment (TME). Using multiplexed single-cell proteomics to analyze 50 TME-associated proteins across treatment-naive triple-negative breast cancer (TNBC) specimens, we discovered that cancer stem cells (CSCs) drive differentiation and expansion of regulatory T cells (Tregs) via extracellular vesicle (EV)-mediated paracrine signaling. TSPAN8, an integral membrane protein on CSC-derived EVs, interacts with CD103 (integrin αEβ7) on T cells, triggering the formation of LKB1-STRAD-MO25 complex and sequential phosphorylation of LKB1 and AMPKα. This cascade enhances FOXP3 expression, which transactivates CD103, creating a positive feedback loop that drives clonal expansion of immunosuppressive CD103+FOXP3+ Tregs and their associated niche. This EV membrane topology-based mechanism operates independently of canonical EV cargo internalization. Neutralizing EVs-TSPAN8+ with a monoclonal antibody synergized with anti-PD-1 therapy in preclinical models, suggesting a potential approach targeting both CSCs and TME immunosuppression, particularly in TNBC subpopulation with high TSPAN8+ CSCs.

Author Info: (1) State Key Laboratory of Systems Medicine for Cancer, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China; Precision Research Cent er for Refractory Diseases, Shanghai Jiao Tong University Pioneer Research Institute for Molecular and Cell Therapies, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, State Key Laboratory of Innovative Immunotherapy, School of Pharmacy, Shanghai Jiao Tong University, Shanghai 20080, China; Breast and Thyroid Surgery Department, General Surgery Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China. (2) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. (3) Department of Breast, The International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, No. 910 Hengshan Road, Shanghai, China. (4) State Key Laboratory of Systems Medicine for Cancer, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China. (5) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. (6) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. (7) Department of Oncology, Suzhou Kowloon Hospital, Shanghai Jiao Tong University School of Medicine, Suzhou 21500, China. (8) State Key Laboratory of Systems Medicine for Cancer, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China. (9) State Key Laboratory of Systems Medicine for Cancer, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China. (10) State Key Laboratory of Systems Medicine for Cancer, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China. (11) Research Unit of Immune Regulation and Immune Diseases of Chinese Academy of Medical Sciences, Shanghai Jiao Tong University School of Medicine-Affiliated Renji Hospital, Shanghai 200127, China. (12) Cancer Center, Faculty of Health Science, University of Macau, Macau 999078, China. (13) State Key Laboratory of Genetic Engineering, School of Life Sciences and Human Phenome Institute, Shanghai Cancer Center, Fudan University, Shanghai 200032, China. (14) Shanghai Key Laboratory of Medical Epigenetics, State International Co-laboratory of Medical Epigenetics and Metabolism, Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China. (15) Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China. (16) Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China. (17) Department of Surgery, The Chinese University of Hong Kong Prince of Wales Hospital, Shatin 999077, Hong Kong SAR, China. (18) State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, CAS, Shanghai 200031, China. (19) Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University, Chongqing 400038, China. (20) Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China. (21) Shanghai Key Laboratory of Cancer Systems Regulation and Clinical Translation, Jiading District Central Hospital Affiliated Shanghai University of Medicine & Health Sciences, Shanghai 201800, China. (22) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. (23) Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, China. Electronic address: gem23@163.com. (24) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. Electronic address: drtaozhh@126.com. (25) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China. Electronic address: liuwenting1015@163.com. (26) Department of Medical Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China; State Key Laboratory of Systems Medicine for Cancer, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20080, China. Electronic address: whx365@126.com.