The high CXCR4 expression in the TNBC primary xenograft tumors, but not in the cell culture, caused us to ask if the CXCR4 stromal-expressed ligand, CXCL12, was responsible for the MDMX-associated upregulation of CXCR4 in the tumor [4]. This evidence concerns the gene CXCR4 and neoplasm.