CXCR4 and lung cancer: However, so far, it has been found that SDF-1 has two receptors: CXCR4 and CXCR7; Hence, to clarify whether SDF-1 binding to CXCR4 induced lung cancer EMT, RNA interference experiments were carried out to knock down CXCR4 expression in A549 and SPCA-1 cells.