CXCR4 and skin basal cell carcinoma: Early comparative studies of the differential expression of chemokine receptors among pre-cancerous lesions, SCC, and BCC found the downregulation of CCR6 and the upregulation of CCR7 and CXCR4 in invasive SCC, but not in BCC and actinic keratosis, consistently with the metastatic capacity of this type of NMSC [47].