KLF3 expression is positively regulated by Sp1. A, The mRNA level of Sp1 was detected by real‐time PCR. Compared with the normal tissues, Sp1 was upregulated in lung cancer tissues, P < 0.001. B, Western blot analysis revealed that Sp1 was upregulated in lung cancer tissues. C, Immunohistochemical analysis indicated that the level of Sp1 was increased in lung cancer tissues compared to that in normal tissues (×400). D and E, The mRNA and protein levels of Sp1 were examined by real‐time PCR and Western blot. The results showed that Sp1 was overexpressed in lung cancer cell lines. ** indicates that P < 0.001 vs HBECs. F and G, Real‐time PCR results showed that KLF3 expression was downregulated after silencing the expression of Sp1 in A549 and 95D cells. Mean ± SD. **indicates that P < 0.01; # indicates that P < 0.001. H, Western blot analysis confirmed that knockdown the expression of Sp1 significantly reduced KLF3 expression