PPIA and plasma cell myeloma: In an interesting study, using multiple myeloma (MM) as a model of a B-cell malignancy that frequently colonizes the BM, it was shown that bone marrow endothelial cells (BMECs) secrete cyclophilin A (eCyPA), which promotes the migration, proliferation, and colonization of leukemic cells through binding to its receptor, CD147, on MM cells’ surface.