TLR4 and melanoma: Mouse models of breast and lung cancer revealed that endothelial cells can induce the expression of the axon-guidance gene Slit2 via TLR3, which facilitates the migration of cancer cells towards endothelial cells and intravasation.404 Moreover, studies in melanoma have reported that the activation of TLR4 in endothelial cells within the lungs can drive metastasis by releasing G-CSF and CXCL5, thereby recruiting PMN-MDSCs to lung tissue and creating a pro-metastatic niche.348