CXCR4 and AL amyloidosis: As the murine prostate cancer cell line TRAMP-C1 suppresses the ability of RAW 264.7 cells to differentiate into osteoclasts [22], Exos are secreted from non-small-cell lung cancer cells, which can enhance osteoclast differentiation in RAW 264.7 cells through activating EGFR phosphorylation [23], Exos secreted from multiple myeloma cells can promote the surviving and migrating abilities of osteoclast precursors via elevating the expression of CXCR4 [24], and osteoclast precursors and osteoblasts are internalized by extracellular vesicles extracted from PC3 culture medium [25].