RAC1 and lung carcinoma: The CXCR4/C-X-C motif chemokine ligand 12 (CXCL12) signaling axis regulates lung cancer cell migration through the activation of Ras-related C3 botulinum toxin substrate 1 (RAC1), MMPs and multiple signaling pathways, including extracellular regulated protein kinase (ERK) and NF-κB [43].