Myeloma BMSCs can generate a microenvironment that supports myeloma stem cells through the CXCR4 signaling pathway, the result of which is that, when growing on myeloma BMSCs, the percentage of SP cells is higher than that of control BMSCs, and SP cells have stronger clone formation ability than control BMSCs [16,19]. Here, CXCR4 is linked to plasma cell myeloma.