Brain metastasis-associated fibroblasts secrete fucosylated PVR/CD155 that induces breast cancer invasion

Brain metastasis cancer-associated fibroblasts (bmCAFs) are emerging as crucial players in the develop-ment of breast cancer brain metastasis (BCBM), but our understanding of the underlying molecular mecha-nisms is limited. In this study, we aim to elucidate the pathological contributions of fucosylation (the post -translational modification of proteins by the dietary sugar L-fucose) to tumor-stromal interactions that drive the development of BCBM. Here, we report that patient-derived bmCAFs secrete high levels of polio virus receptor (PVR), which enhance the invasive capacity of BC cells. Mechanistically, we find that HIF1a transcriptionally upregulates fucosyltransferase 11, which fucosylates PVR, triggering its secretion from bmCAFs. Global phosphoproteomic analysis of BC cells followed by functional verification identifies cell -cell junction and actin cytoskeletal signaling as modulated by bmCAF-secreted,-fucosylated PVR. Our findings delineate a hypoxia-and fucosylation-regulated mechanism by which bmCAFs contribute to the invasiveness of BCBM in the brain.