Reptin depletion leads to reduced hTERT mRNA expression and telomerase activity in gastric and cervical cancer cells. C, P and R: Control, Pontin and Reptin siRNA, respectively. Bars: Standard deviations. The results were obtained from three to four independent experiments. (A) Reptin protein expression in gastric and cervical cancer cells and efficiency of Reptin knocking down by siRNA. Cells were treated with control, Reptin or Pontin siRNA for 72 hours and then analyzed for Reptin expression by immunoblotting assay. (B) Reduced hTERT mRNA expression in Reptin or Pontin siRNA-treated cells. The same sets of cells from as above were used to determine hTERT mRNA using rqPCR. Relative levels of hTERT mRNA are shown. (C) Reduced telomerase activity in Reptin or Pontin siRNA-treated cells. Cellular proteins were extracted from the cells above and telomerase activity was assessed using a Telomerase ELISA kit. The enzymatic activity was expressed as absorbance [optimal density (OD) in arbitrary units]. (D) Additive inhibitory effect on hTERT mRNA expression in cells treated with combination of Reptin and Pontin siRNAs. HGC-27 and HeLa cells were treated with Reptin or Pontin siRNA alone or both of them at the half concentration used in (B) and hTERT mRNA abundance was analyzed with rqPCR. Relative levels of hTERT mRNA are shown.