SELPLG and breast cancer: Combinatorial targeting has recently been applied by Segaliny and colleagues, who produced MSCs that express P-selectin glycoprotein ligand-1 (PSGL-1)/Sialyl-Lewis X (SLEX) together with modified versions of CD and osteoprotegerin (OPG) to treat bone metastases of breast cancer (Segaliny et al., 2019).