CXCL12-CXCR4/CXCR7 axis contributes to cell motilities of oral squamous cell carcinoma

The chemokine CXCL12 and its receptors CXCR4 and CXCR7 might play important roles in the occurrence and development of oral squamous cell carcinoma (OSCC). While CXCR4 expression is associated to initiation and progression of OSCC, the role of CXCR7, the recently founded second CXCL12 receptor, has not yet been elucidated in OSCC. In this study, CXCR4 and CXCR7 expressions were evaluated using western blot and quantitative RT-PCR in OSCC cells. AMD3100 (CXCR4 antagonist) was used to inhibit the activation of CXCR4. In contrast to CXCR4, effective CXCR7 small interfering RNA (siRNA) segments were used to silence CXCR7 in OSCC cells. The biological effects of CXCL12-CXCR4/CXCR7 axis on OSCC cell lines were studied by CCK-8 and transwell assay. As determined by RT-PCR and Western blot, CXCR7 expression was significantly downregulated after siRNA transfection in OSCC cells, and thus significantly promoted OSCC cell migration and invasion in vitro. The relative roles of the two CXCL12 receptors were further assessed by CXCR7 knockdown or deactivate CXCR4 receptor alone, or in combination, in the OSCC cells. In vitro functional analyses indicated that, in response to their common ligand (CXCL12), both receptors induced inhibition of proliferation and migration in OSCC cells in a dose-dependent manner. Exogenous CXCL12 could promote cell migration and invasion. In conclusion, our results indicated that CXCL12 which combined its receptor CXCR4 and CXCR7 together could promote cell motilities of OSCC.