In fact, studies have shown that some unique subpopulations of mesenchymal stem cells in multiple myeloma highly express the Toll-like receptor 4 (TLR4) gene, which in turn increases the expression of CD54 and interleukin-6 (IL-6), which is directly related to the crosstalk between MM MSCs and MM cells [16]. Here, TLR4 is linked to plasma cell myeloma.