Induction of chemokine receptor CXCR4 expression by transforming growth factor-ß1 in human basal cell carcinoma cells.

ABSTRACT

BACKGROUND: Higher CXCR4 expression enhances basal cell carcinoma (BCC) invasion and angiogenesis. The underlying mechanism of increased CXCR4 expression in invasive BCC is still not well understood. OBJECTIVE: To investigate the mechanisms involved in the regulation of CXCR4 expression in invasive BCC. METHODS: We used qRT-PCR, RT-PCR, Western blot, and flow cytometric analyses to examine different CXCR4 levels among the clinical samples, co-cultured BCC cells and BCC cells treated with recombinant transforming growth factor-ß1 (TGF-ß1) and connective tissue growth factor (CTGF). Immunohistochemical studies were used to demonstrate the correlation between TGF-ß1 and CXCR4 expressions. The signal transduction pathway and transcriptional regulation were confirmed by treatments with chemical inhibitors, neutralizing antibodies, or short interfering RNAs, as well as luciferase reporter activity. RESULTS: Invasive BCC has higher TGF-ß1 and CTGF levels compared to non-invasive BCC. Non-contact dermal fibroblasts co-culture with human BCC cells also increases the expression of CXCR4 in BCC cells. Treatment with recombinant human TGF-ß1, but not CTGF, enhanced the CXCR4 levels in time- and dose-dependent manners. The protein level and surface expression of CXCR4 in human BCC cells was increased by TGF-ß1 treatment. TGF-ß1 was intensely expressed in the surrounding fibroblasts of invasive BCC and was positively correlated with the CXCR4 expression of BCC cells. The transcriptional regulation of CXCR4 by TGF-ß1 is mediated by its binding to the TGF-ß receptor II and phosphorylation of the extracellular signal-related kinase 1/2 (ERK1/2)-ETS-1 pathway. CONCLUSION: TGF-ß1 induces upregulation of CXCR4 in human BCC cells by phosphorylation of ERK1/2-ETS-1 pathway.