Integrin α6-containing extracellular vesicles promote lymphatic remodelling for pre-metastatic niche formation in lymph nodes via interplay with CD151

Heterogeneous extracellular vesicles (EVs) from various types of tumours are acknowledged for inducing the formation of pre-metastatic “niches” in draining lymph nodes (LNs) to promote lymphatic metastasis. In order to identify the specific subpopulations of EVs involved, we performed high-resolution proteomic analysis combined with nanoflow cytometry of bladder cancer (BCa) tissue-derived EVs to identify a novel subset of tumour-derived EVs that contain integrin α6 (ITGA6⁺EVs) and revealed the positive correlation of ITGA6⁺EVs with the formation of pre-metastatic niche in draining LNs and lymphatic metastasis in multicentre clinical analysis of 820-case BCa patients. BCa-derived ITGA6⁺EVs induced E-selectin (SELE)-marked lymphatic remodelling pre-metastatic niche and promoted metastasis in draining LNs through delivering cargo circRNA-LIPAR to lymphatic endothelial cells in vivo and in vitro. Mechanistically, LIPAR linked ITGA6 to the switch II domain of RAB5A and sustained RAB5A GTP-bound activated state, thus maintaining the production of ITGA6⁺EVs loaded with LIPAR through endosomal trafficking. ITGA6⁺EVs targeted lymphatic vessels through ITGA6-CD151 interplay and released LIPAR to induce SELE overexpression-marked lymphatic remodelling pre-metastatic niche. Importantly, we constructed engineered-ITGA6 EVs to inhibit lymphatic pre-metastatic niche, which suppressed lymphatic metastasis and prolonged survival in preclinical models. Collectively, our study uncovers the mechanism of BCa-derived ITGA6⁺EVs mediating pre-metastatic niche and provides an engineered-EV-based strategy against BCa lymphatic metastasis.