Receptor-Guided Targeted Protein Degradation Collapses Extracellular Vesicle-Driven Tumor-Stroma Crosstalk

Abstract Extracellular vesicles (EVs) are critical mediators of tumor-stromal communication within the tumor microenvironment (TME), where reciprocal signaling between cancer cells and cancer-associated fibroblasts (CAFs) fuels malignant progression and therapeutic resistance. Here, we report a degrader-antibody conjugate (DAC) platform, Ctx-ETAC, in which the clinically approved anti-EGFR antibody cetuximab (Ctx) delivers an engineered proteolysis-targeting chimera (PROTAC) payload, ETAC, selectively into EGFR-expressing tumor cells and activated CAFs via receptor-mediated endocytosis. ETAC integrates indomethacin as the COX-2 ligand, a VHL-recruiting peptide, and a cathepsin B (Cat-B)-cleavable azidoacetyl-RR linker; conjugation to Ctx was achieved by a two-step bioorthogonal strategy, yielding an average drug-to-antibody ratio of 4.21. The resulting Ctx-ETAC ensures biomarker-selective payload activation in both tumor cells and activated CAFs, markedly reducing EV secretion by 95.5% and thereby disrupting their crosstalk. This disruption of EV-mediated communication reprograms CAFs toward a quiescent phenotype and reshapes the non-small cell lung cancer microenvironment into an antitumor state. In a xenograft model, Ctx-ETAC achieves markedly superior tumor suppression compared with Ctx monotherapy, without systemic toxicity. These findings establish receptor-guided targeted protein degradation as a strategy to disrupt EV-driven tumor-stromal communication and provide a new framework for microenvironment-directed cancer therapy.