CCR4 and breast cancer: CD194 or C-C Chemokine receptor type 4 (CCR4) promotes breast cancer lung metastasis by downregulation of T regulatory cells [21,22], CD116 or Granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR) has also been shown to promote bone metastasis [23], and α-smooth muscle actin (α-SMA) is required for metastatic potential of human lung adenocarcinoma [24].