| Norrin is a secretory protein encoded by the Norrie disease pseudoglioma gene(NDP),the pathogenic gene of Norrie disease,and belongs to the TGF-? family.Currently,studies on Norrin focused on retina,and revealed that Norrin promotes retinalangiogenesis by activating Wnt/?-catenin pathway.Other reports demonstrated that Norrin and its downstream binding molecules,Frizzled-4 and Lrp5,hadan expression in colon cancer cell lines and tumor tissues and that Norrin might play a significant role in the progression of colon cancer,indicating that the function of Norrin was not confined to retina and it might have a role in cancer.Gastric cancer is a common type of cancer arising from the gastrointestinal tract greatly damaginghuman health.The oncogenesis and progression of gastric cancer are complicated processes with a number of molecules and signaling pathways involved.Although numerous reports have been released on various aspects of gastric cancer,much still remains unknown about it,especially with its poor outcome in advanced stage.As a result,a deeper understanding of the molecular mechanism of the oncogenesis and progression regarding gastric cancer has important implications for the treatment of gastric cancer.Methods and results1)Immunohistochemical staining and clinicopathologic data were analyzed and evaluated.Norrin was found to express higher in gastric cancer tissues compared with adjacent normal tissues.The expression level of Norrin was not correlated with gender,age,tumor location,tumor size and histological type(P>0.05).The expression level of Norrin was correlated with Lauren classification,differentiation,TNM stage and post-operation survival(P<0.05).Western blotting was conducted to analyze the expression of Norrin in three gastric cancer cell lines with different differential levels,SGC7901,AGS and BGC823 and our results demonstrated that Norrin highly expressed in the poorly differentiated BGC823 compared with a lower expression in better differentiated cell lines SGC7901 and AGS(P<0.01).2)Norrin was knocked down in BGC823 by lentiviral transfection and Lv-sh-Norrin group and Lv-sh-ctrl group were established.Flow cytometry was conducted to evaluate the apoptosis rate of Lv-sh-Norrin and Lv-sh-ctrl cells and our results showed that Lv-sh-Norrin group had a higher apoptotic rate than the Lv-sh-ctrl group(12.26±0.70% vs.7.58±0.68%,P<0.05).3)The expression of anti-apoptotic proteins Mcl-1 and Bcl-2 was downregulated while the pro-apoptotic proteins Bax and Cleaved Caspase-3 upregulated(P<0.05)in Lv-sh-Norrin group compared with the Lv-sh-ctrl group through Western blotting analysis.However,the expression of Frizzled-4 and Lrp5 did not show significant difference in the two groups(P>0.05).Conclusion1)Immunohistochemical analysis showed a different expression of Norrin in tumor tissues and adjacent normal tissues.Moreover,analysis of Norrin expression and the clinicopathologic data indicated that Norrin was correlated with Lauren classification,differentiation,TNM stage and post-operation survival.Moreover,the expression level of Norrin was different in gastric cancers with different differentiation levels.Our results demonstrated that Norrin might be a cancer promoting molecular playing a role in the progression of gastric cancer.2)Norrin was successfully knocked down in BGC823 and the Lv-sh-Norrin cells might be used in further study.The apoptosis rate of Lv-sh-Norrin cells increased with control cells,indicating that Norrin promoted the progression of gastric cancer through inhibiting the apoptosis of cancer cells.3)Knockdown of Norrin leads to the imbalance of apoptosis-related proteins through upregulatingthe expression of Bax and Cleaved Caspase-3 and downregulatingthe expression of Mcl-1 and Bcl-2,resulting in the promotion of apoptosis.Our results implies that Norrin promotes the oncogenesis and progression of gastric cancer though inhibiting the apoptosis of gastric cancer and promoting the viability of gastric cancer cells. |
PDF Full Text Request