Cao et al. showed that production of FGF4 by B-cell lymphoma and its interaction with FGFR1 receptor upregulates the Notch ligand Jagged 1 on neighboring ECs that reciprocally induces an autocrine loop of Notch2-Hey1 signaling in B cell lymphoma. The gene discussed is JAG1; the disease is B-cell non-Hodgkin lymphoma.