Over-expression of Chemokine Receptor CXCR4 Enhances Tumorigenesis of Basal Cell Carcinoma Beside the well-known role to regulate leukocyte trafficking, chemokines and their receptors also play important roles in the regulation of mitosis, apoptosis, survival and angiogenesis, which may enhance tumor growth or metastasis. Herein we investigated the possible involvements of chemokines and chemokine receptors in the pathogenesis of basal cell carcinoma (BCC), the most common human cancer with unique clinical behaviors featuring local invasion and extremely rare metastasis. Real-time quantitative RT-PCR (qPCR) was used to measure the expression levels of chemokine receptors in various human skin cancer cell lines including BCC, squamous cell carcinoma and melanomas. The expression level of CXCR4 in BCC cell line was ~64-fold more than in other cancer cell lines and normal controls (cultured human keratinocytes and fibroblasts). The expression of CXCR4 in BCC cell line was further confirmed using conventional RT-PCR and western blotting. Immunohistochemistry and in situ hybridization studies using tissue samples from BCC lesions showed clear CXCR4 staining as well. To determine whether CXCR4 alone may play an important role in BCC tumorigenesis, retroviral transduction was employed to transfer CXCR4 cDNA into BCC cell line. Magnetic beads selection using anti-CXCR4 mAb was then used to isolate CXCR4-expressing cells. CXCR4 expression by BCC was significantly enhanced. By qPCR, CXCR4-transduced BCC cells (CXCR4-BCC) expressed ~37- and ~14-fold more CXCR4 than wild-type BCC and vector-transduced BCC (pLNCX2-BCC) respectively. Magnetic beads selection further increased transduction efficiency. By flow cytometry, ~91% CXCR4-BCC showed clear staining with anti-CXCR4 mAb. CXCR4-BCC responded to CXCL12 (ligand for CXCR4, also known as SDF-1), shown by calcium flux functional assays. We next addressed whether over-expression of CXCR4 may alter BCC tumor progression in vitro
