MLC1 and cancer: Herein, we showed that C-C motif chemokine ligand 2 (CCL2)- C-C motif chemokine receptor 4 (CCR4) signaling, but not the CCL2- C-C motif chemokine receptor 2 (CCR2) axis, induces the formation of the vav guanine nucleotide exchange factor 2 (Vav2)- Rac family small GTPase 1 (Rac1) complex to activate the phosphorylation of myosin light chain (MLC), which is involved in the regulation of cell motility and cancer metastasis.