KLF9 inhibits the proliferation, invasion, and migration of renal cell carcinoma through the SDF-1/CXCR4 axis

Altered Kruppel-like factor 9 (KLF9) expression can regulate the progression of several cancers, including renal cell carcinoma (RCC). This study was conducted to investigate the role of KLF9 in the proliferation, invasion, and migration of RCC cells via regulation of stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4). The expression patterns of KLF9, SDF-1, and CXCR4 in the experimental cell lines were determined by real-time quantitative polymerase chain reaction and Western blotting. After transfection of the KLF9 siRNA and KLF9 pcDNA, cell proliferation, invasion, and migration were evaluated by experiments including cell counting kit-8, colony formation, and Transwell assays. The binding of KLF9 to the SDF-1 promoter was analyzed by chromatin immunoprecipitation and dual-luciferase assay. The rescue experiment was performed using the recombinant SDF-1 protein and KLF9 pcDNA. KLF9 was downregulated in the RCC cells. KLF9 knockdown induced the proliferation, invasion, and migration of RCC cells, whereas KLF9 overexpression elicited the opposite roles. Mechanically, KLF9 bound to the SDF-1 promoter, repressed SDF-1 transcription, and reduced the SDF-1/CXCR4 expression levels. Activation of the SDF-1/CXCR4 axis attenuated the inhibitory role of KLF9 overexpression in RCC cell growth. Ordinarily, KLF9 suppressed the proliferation, invasion, and migration of RCC cells by repressing the SDF-1/CXCR4 signaling.