PECAM1 and B-cell chronic lymphocytic leukemia: TAMs attract chronic lymphocytic leukemia (CLL) cells by secreting CXCL12 and CXCL13 and protect CLL cells from spontaneous or drug-induced apoptosis via CXCL12, BAFF, APRIL, CD31, and Plexin-B1 and activating the BCR signaling cascade [84].