Oct4 interacts with KPNA2 in vitro. A549 and SPC cells were treated with KPNA2-specific siRNA for 72 h. The nucleus and cytoplasm protein expression levels of Oct4 and KPNA2 were analyzed by western blotting (A). Expression of β-actin and lamin-B served as loading controls for the cytosolic and the nuclear fractions, respectively. Real-time PCR analyses of KPNA2 and Oct4 mRNA expression in cancer cells (B). Immunofluorescence staining showing the localization of Oct4 and KPNA2 in A549 and SPC cancer cell lines (C). Relative fluorescence levels of Oct4 were measured in cells after KPNA2 siRNA treatment. Relative fluorescence ratios of Oct4:DAPI are indicated as the mean ± SD for four fields for siNC and siKPNA2 (D). *P < 0.05. Co-immunoprecipitation of KPNA2 and Oct4 in A549 and SPC cells (E): whole cell lysates were immunoprecipitated with KPNA2 antibody and analyzed by western blotting with the anti-Oct4 antibody.