miR-139 targets CXCR4 and inhibits the proliferation and metastasis of laryngeal squamous carcinoma cells

Our previous studies have showed that chemokine receptor 4 (CXCR4) was over-expressed in laryngeal squamous cell carcinoma (LSCC). However, the mechanism underlying aberrant CXCR4 expression remains unclear. To investigate the roles played by miRNAs in CXCR4 overexpression in LSCC, putative miR-139 was predicted through computational algorithms, including TargetScan, PicTar and miRBase, and luciferase reporter assay was explored to confirm that whether CXCR4 was directly regulated by miR-139. Then, quantitative real-time PCR, immunohistochemistry and in situ hybridization methods were employed to detect the expression of miR-139 and CXCR4 in primary LSCC tissues, normal adjacent mucosal tissues and metastatic lesions derived from 40 LSCC patients in the Second Hospital, Xi'An JiaoTong University. Finally, gain-and loss-of-function assays were adopted to explore the effects of miR-139 and CXCR4 on proliferation, invasion and metastasis of the human LSCC cell line Hep-2 in vitro and in vivo. Our results showed that miR-139 dampened CXCR4 expression, and CXCR4 was directly targeted by miR-139. Additionally, the expression of miR-139 was reduced in alignment with the progression of primary to metastatic LSCC. Moreover, an inverse correlation was observed between miR-139 and CXCR4 protein levels in LSCC specimens. Functional analyses demonstrated that ectopic expression of miR-139 inhibited cell proliferation, migration and metastasis of Hep-2 cells in vitro and in vivo. Similar to the observations seen in restoring miR-139 expression, dampening of CXCR4 expression inhibited cell growth, migration and invasion, whereas miR-139 overexpression reversed the pro-metastatic effect of CXCR4. Taken together, we conclude that miR-139 targets CXCR4 and inhibits proliferation and metastasis of LSCC.