CXCR4 and cancer: SDF-1 is significantly upregulated in stromal fibroblasts of human skin SCCs relative to normal skin [32], and CXCR4 is upregulated in metastatic SCCs in comparison to normal skin and non-metastatic skin carcinomas [33], whereas CXCR7 expression is induced in 70% of patient skin SCC samples and is associated with cancer cell survival [34].