CXC motif chemokine receptor 4, the receptor for chemokine CXCL12/SDF-1 and a member of the G protein-coupled receptor superfamily, is overexpressed in various types of solid cancers, including non-small-cell lung cancer (NSCLC), breast cancer, colorectal cancer, and GC. This evidence concerns the gene CXCL12 and breast carcinoma.