Cao et al. showed that fibroblast growth factor 4 (FGF4), produced by B-cell lymphoma cells, activates fibroblast growth factor receptor 1 (FGFR1) in neighboring endothelial cells resulting in the upregulation of the Notch ligand Jagged1. This evidence concerns the gene FGF4 and B-cell non-Hodgkin lymphoma.