Dynamic junction remodeling and transient vascular disruption during cancer cell extravasation across the blood-brain barrier.

Brain metastasis is the major cause of cancer-related mortality and remains a critical challenge in clinical oncology. Extravasation of circulating cancer cells across blood-brain barrier (BBB) is the first crucial and rate-limiting step for brain metastasis growth. However, the dynamic changes of brain endothelial cell junction and vascular integrity during cancer cell extravasation across BBB remains unclear. Here, we established a knockin zebrafish line, Ki(cdh5-eGFP), in which EGFP is fused to the C-terminal of endogenous VE-cadherin, enabling in vivo real-time imaging of brain endothelial junction dynamics. Then, we established a brain metastasis model in Ki(cdh5-eGFP) zebrafish, and tracked the multistep cascade of cancer cell extravasation across BBB. We demonstrated that cancer cells cross brain vascular endothelial cells, accompanied by dynamic remodeling of VE-cadherin and transient disruption of vascular integrity. Our model transforms the BBB into a dynamically observable interface, enabling real-time visualization of junction remodeling during cancer cell extravasation, which will not only facilitate further mechanistic study, but also provide a valuable platform for preclinical drug screening.