CXCR4 and breast cancer: To assess the downstream effects of CXCR4-CCR7 heterodimerization, both non-metastatic T47D and metastatic MDA-MB-231 breast cancer cell lines were co-transfected with the mixture of CXCR4-H and CCR7-M or with a control vector containing only DmrA domain, and were treated with the dimerizer drug ACH, or left untreated, followed by the addition of chemokine ligands.