CXCL12 and glioblastoma: NK cells genetically engineered with a chimeric antigen receptor (CAR) to over-express CXCR4 along with the target antigen receptor demonstrated enhanced mobilization towards CXCL12 (stromal cell-derived factor 1, SDF-1), the exclusive cognate ligand for CXCR4, and increased infiltration in a mouse model of glioblastoma [58].