Coreceptor delivery of paracrine APRIL to Golgic BCMA lowers immunogenicity of B-cell lymphoma

APRIL is involved in the development of B-cell lymphomas. However, in tumors the source of APRIL is paracrine while one signaling receptor, BCMA, is intracellular, raising the question on how APRIL may signal. In fact, tumor cells internalized APRIL via their surface HSPG. Then, APRIL trafficked into endosomes to finally interact with Golgic BCMA, whose sequence harbors strong identities with sorting nexins. Intracellular APRIL/BCMA interactions activated the canonical NF-kB pathway, and mediated from tumor cells an immunosuppressive response including IL-10 upregulation. Absence of APRIL/BCMA interactions impaired tumor growth in mice, and APRIL internalization by tumor cells correlated with a reduced survival for patients. Taken together, the present study elucidates a fully intracellular signaling pathway, key to B-cell lymphoma development. Gene epression profiling of HBL-1 and BJAB cell lines treated by APRIL or EDA