KLF8 promotes cancer stem cell-like phenotypes in osteosarcoma through miR-429-SOX2 signaling

Krüppel-like factor 8 (KLF8) regulates critical gene transcription associated with different types of cancer. A novel paradigm in tumor biology suggests that the initiation and progression of osteosarcoma (OS) are driven by osteosarcoma stem cell-like cells (OSCs), but the role and underlying mechanisms of KLF8 in OSCs are poorly elucidated. In this study, an obviously increased level of KLF8 is shown in 9 out of 10 primary OS tissues and is associated with the poor progression-free interval. Significantly, KLF8 expression in CD133+ OSCs is higher than that in CD133- counterparts. By knocking down KLF8 in CD133+ OSCs, we show that si-KLF8-OSCs can hardly form compact spheres. In the meantime, infection with si-KLF8 in CD133+ OSCs results in the downregulation of OCT4 and SOX2; increased adriamycin (ADM) sensitivity; and decreased tumorigenic potential in vivo. Mechanisms study demonstrates that KLF8 directly binds the miR-429 promoter region and regulates its expression transcriptionally. Furthermore, we indicate that miR-429 directly targets SOX2 to mediate cancer stem cell-like features in CD133+ OSCs. In the clinic, miR-429 levels are negatively associated with KLF8 levels in OS, suggesting that an elevated KLF8/miR-429 ratio may have clinical value as a predictive biomarker. In conclusion, targeting the KLF8-miR-429-SOX2 signaling pathway may provide an effective therapeutic approach to suppress the initiation and progression of OS.