Proteomic study on sodium selenite-induced apoptosis of human cervical cancer HeLa cells

Sodium selenite can induce the apoptosis of cancer cells, however its mechanism has seldom been studied via proteomics. In this paper, human cervical cancer HeLa cells were investigated by MTT assay and morphological observation to get appropriate selenite concentrations for proteomic study. Results showed that selenite at concentrations larger than 10 μmol/L significantly inhibited the viability of HeLa cells. 40 μmol/L selenite was in the appropriate range for proteomic study. After 24 h treatment with 40 μmol/L selenite, total proteins were extracted from the cells and applied to two-dimensional gel electrophoresis (2DE). Those proteins with their expression levels altered at least 2-fold comparing to the control were picked up for protein identification via MALDI-TOF mass spectrometry and further confirmed by Western blot analysis. About 1000 spots were detected by the software in each 2DE gel, among which 13 differentially expressed proteins were identified by mass spectrometry and most of them are relevant to oxidative stress, such as peroxiredoxins, superoxide dismutase, quinolinate phosphoribosyl transferase, and D-dopachrome tautomerase. Meanwhile, reactive oxygen species (ROS) and mitochondrial membrane potential were also detected by flow cytometry and laser confocal scanning microscope. An increase in ROS generation and a decrease in mitochondrial membrane potential were detected in the selenite-treated cells compared with the control, which are consistent with the down-expression of antioxidative proteins in proteomics. Those results indicate that selenite induces the apoptosis of HeLa cells via ROS-mediated mitochondrial pathway. The present study also implies the potentiality of selenium in cervical cancer treatment.