Figure 6. QKI inactivates oral CSCs via repression of SOX2. (A) Reduced QKI enhances the mRNA stability of SOX2. LV-miQKI cells and control Tca8113 cells were treated with Actinomycin D at time 0, and RNA was extracted at indicated time to examine the RNA stability. Increased SOX2 mRNA stability was detected in LV-miQKI cells. Data presented here are representative of 3 independent experiments. (B) Scheme of constructs used for dual luciferase assays. The position of the putative QRE sequence in the SOX2 3′UTR is depicted as a gray vertical bar. Sequence of the truncation is given below. (C) QKI regulates SOX2 expression by direct binding to the QRE located in SOX2 3′UTR. pGL3-SOX2 3′UTR WT or pGL3-SOX2 3′UTR TRUNCATION reporter and internal control vector pBind were cotransfected with the indicated plasmids for 24 h before luciferase activity examination. Fold induction was calculated and expressed as means ± SD (n = 3). **P < 0.01. (D) Knockdown efficiency of the 2 different small interfering RNAs targeting SOX2 mRNA levels of SOX2 were quantified by qPCR (left panel) and protein levels of SOX2 were detected by western blot (right panel) at 48 h post-transfection. (E) Representative images of spheres from Tca8113 LV-miQKI cells transfected with control siRNA or siRNA targeting SOX2 (left panel). Experiments were performed in triplicate, and data are shown as mean ± SD *P < 0.05 (right panel).