SOX9 regulated proliferation and apoptosis of human lung carcinoma cells by the Wnt/β-catenin signaling pathway.

OBJECTIVE: Sex-determining region Y-box 9 (SOX9) is a transcription factor linked to stem cell maintenance and commonly over-expressed in solid cancers. In the present study, the effects of SOX9 on proliferation and apoptosis of human lung carcinoma cells and its mechanisms were investigated. MATERIALS AND METHODS: Following over-expression or knock-down of SOX9 in human lung carcinoma cell line A549, cell viability was evaluated using XTT method, and cell apoptosis was measured by Flow cytometry. Caspase-3, Caspase-8, Caspase-9 and SOX9 expression was measured by RT-PCR, and Wnt, phosphorylated Wnt (p-Wnt) and β-catenin expression was detected by Western Blot. RESULTS: Results showed that SOX9 expression was elevated in human lung carcinoma cells. Knocking down cellular SOX9 by short hairpin RNA (shRNA) decreased cell proliferation while promoted apoptosis of A549 cells. Furthermore, down-regulation of p-Wnt and β-catenin expression levels was detected in A549 cells lack of SOX9. However, over-expression of SOX9 played the opposite roles in proliferation and apoptosis of human lung carcinoma cells. To further demonstrate the functions of the Wnt/β-catenin signaling pathway in SOX9 regulated-cell functions, the inhibitor IWP-2 was used to block the activation of Wnt/β-catenin signal. No significant differences between IWP-2-treated cells and SOX9 plus IWP-2-treated cells suggested the existence of a regulatory role for SOX9 through targeting the Wnt/β-catenin pathway. CONCLUSIONS: These findings establish the significance of SOX9 in lung cancer pathobiology and heterogeneity, with implications for targeting the Wnt/β-catenin-SOX9 signaling pathway as a rational therapeutic strategy.