Proteomic analysis of differentially expressed proteins in vitamin C-treated AGS cells

BACKGROUND: Vitamin C (ascorbic acid) is an essential nutrient of most living tissues that readily acts as a strong reducing agent, which is abundant in fruits and vegetables. Although, it inhibits cell growth in many human cancer cells in vitro, treatment in cancer is still controversial. Hence, the purpose of this study was to investigate the molecular mechanism of the inhibitory effect of vitamin C on AGS cell growth, and protein profiles in AGS cells after exposure to vitamin C treatment, by using proteomic tools. RESULTS: Vitamin C showed a cytotoxic effect on AGS cells (IC50 300 μg/mL) and, 20 differentially expressed proteins (spot intensities which show ≥2 fold change and statistically significant, p<0.05 between the control and vitamin-C treated group) were successfully identified by assisted laser desorption/ ionization-time of flight/mass spectrometry (MALDI-TOF/MS). Of the 20 proteins, six were up-regulated and fourteen were down-regulated. Specifically, 14-3-3σ, 14-3-3ϵ, 14-3-3δ, tropomyosin alpha-3 chain and tropomyosin alpha-4 chain were down-regulated and peroxiredoxin-4 and thioredoxin domain-containing proteins 5 were up-regulated. The identified proteins are mainly involved in cell mobility, antioxidant and detoxification, signal transduction and protein metabolism. Further, the expressions of 14-3-3 isoforms were verified with immuno-blotting analysis. CONCLUSIONS: Our proteome results suggest that the apoptosis related proteins were involved in promoting and regulating cell death of AGS cells, and might be helpful to understand the molecular mechanism of vitamin C on AGS cell growth inhibition.