ZEB1 expression is regulated by HIF-1α, and promotes epithelial-mesenchymal transition. (A) Reverse transcription-quantitative polymerase chain reaction was used to determine the level of ZEB1 mRNA expression in T24-P/T24-L/T24-NC/T24-L/siHIF-1α. ZEB1 was significantly elevated in T24-L, and transfection with siHIF-1α downregulated ZEB1 expression in T24-L cells, compared with the control. (B) Western blot analysis indicated that the protein level of HIF-1α, ZEB1, vimentin and N-cadherin was higher in T24-L cells than T24-P cells, whereas CK-18 expression was lower in T24-L cells. siHIF-1α transfection in T24-L led to the downregulation of ZEB1, Vimentin and N-Cadherin, but the upregulation of CK-18. ***P<0.001. ZEB1, zinc-finger E-box-binding homeobox 1; HIF-1α, hypoxia inducible factor-1α; T24-L, T24 lung metastasis cells; siHIF-1α, small interfering RNA against HIF-1α; T24-P, T24 parental cells; CK-18, cytokeratin-18; NC, negative control.