CXCR4 and breast cancer: Liang et al. constructed an amiRNA by inserting a double-stranded miRNA gene against a C-X-C motif chemokine receptor 4 (CXCR4) into a miR-155-based RNAi expression vector, which exhibited a reduced expression level of CXCR4 and a suppressed migration and invasion in breast cancer cells [137].