Calbindin-D28k (CaBP-28k), a calcium binding protein, buffers intracellular Ca2+. CaBP-28k has anti-apoptotic properties in neuronal and osteoblastic cells. Endometrial cancer is the most common invasive gynecologic malignancy but CaBP-28k expression in the apoptotic signaling is poorly understood. In this study, we investigated whether CaBP-28k expression is regulated by hydrogen peroxide H2O2-induced cell death in human endometrial Ishikawa cells. Ishikawa cells were treated with H2O2 in a dose-dependent manner (0, 0.25, 0.5, 1.0, 1.5, 2 mM), and time-dependent manner (0, 15, 30, 60, 90, 120 min). Then the protein expressions of Bax, p53 and caspase 3 were determined by western blot analysis. Treatment with H2O2- induced an increase in Bax and p53 expressions at the translational level in 1 mM and 60 min. Interestingly, over-expression of CaBP-28k caused a decrease in Bax, p53 and caspase 3 on H2O2-induced apoptosis in the Ishikawa cells. These results suggest that expression of CaBP-28k blocked up-regulation of apoptosis-related genes. In addition, the knockdown of CaBP-28k using a small inhibitory RNA resulted in an elevation of H2O2-induced cell death, whereas cell survival was increased in CaBP-28k over-expressing cells, providing additional evidence that the induction of CaBP-28k expression may be associated with survival signaling in H2O2- mediated oxidative cell death.

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