Expression of superoxide dismutase 2 in gastric cancer and downregulation of its expression on biological characteristics

Abstract

Objective To examine the superoxide dismutase 2 (SOD2) expression in gastric cancer (GC) and the effect of downregulated SOD2 expression on proliferation and reactive oxygen species (ROS) level of GC cells. Methods The SOD2 expression of GC patient tissue and paired adjacent tissue was detected by immunohistochemical staining; The SOD2 expression of normal gastric epithelial cell GES1 and GC cells MKN1, MKN45, NUGC3, NUGC4, AGS, N87 was analyzed by Western blotting; SOD2 siRNA (siSOD2) was transfected into MKN1 and NUGC4 cells to downregulate SOD2 expression and set non-target control siRNA (siNTC) as the negative control; Cell proliferation and cellular ROS were determined using counting kit-8 (CCK-8) assay and cellular ROS detection assay kit. Results The positive percentage of SOD2 expression was 72.7% (48/66) in GC patient tissue and was 40.9% (27/66)in paired adjacent tissue. The difference was statistically significant (χ2=13.617, P=0.000). The SOD2 expression of GC cells was higher than that in gastric epithelial cell GES1 (tMKN1=23.062, PMKN1=0.002; tMKN45=5.648, PMKN45=0.030; tNUGC3=26.613, PNUGC3=0.001; tNUGC4=17.103, PNUGC4=0.003; tAGS=39.475, PAGS=0.001; tN87=37.677, PN87=0.001). The proliferation in GC cells MKN1 and NUGC4 with siSOD2 transfection was lower than that in control groups in 72 h, 96 h (MKN1, t72 h=6.329, P72 h=0.001; t96 h=10.487, P96 h=0.000), (NUGC4, t72 h=5.551, P72 h=0.003; t96 h=6.304, P96 h=0.001). The ROS level of siSOD2 and siNTC groups in MKN1 was 195.341±10.71, 99.439±9.311; the ROS level of siSOD2 and siNTC groups in NUGC4 was 181.561±14.502, 97.876±12.867. The ROS level of GC cells with siSOD2 transfection was significantly higher than the control group (MKN1, t=11.295, P=0.001), (NUGC4, t=23.476, P=0.000). Conclusion SOD2 expression is highly upregulated in GC patients and GC cells. Downregulation of SOD2 expression can decrease GC cell proliferation and increase cellular ROS. Key words: Gastric cancer; Superoxide dismutase 2; Reactive oxygen species; Proliferation