Ndrg2 Facilitates Colorectal Cancer Differentiation Through The Regulation Of P21 And P27

Colon cancer is one of the most common fatal malignancies in the world.The morbidity and mortality rates of colon cancer in both men and women were ranked in the top three.Differentiation shortage is one of the major features of cancer progression.Low differentiation of tumor cells showed higher proliferation and metastasis,lower survival rate and poor prognosis.However,the mechanism of colorectal cancer differentiation is not very clear.The molecular mechanism of colon cancer cell differentiation provided new therapeutic target and important clinical significance.Mitigating cell cycle progression is one of the important characteristics of cell differentiation.The transformation of G1 phase to S phase is mainly driven by cyclin-dependent kinase 2(CDK2).Cell cycle protein dependent kinase inhibitor(CDK inhibitor)mainly includes p21/Cip1 and p27/Kip1,which inhibited the activity of CDK.The specific regulatory mechanism of the process need further clarified.Ndrg2 is a member of Ndrg gene family.Our group used PCR reduce hybridization for the first foundation.Ndrg2 as a tumor suppressor was down-regulation in many tumors,sunch as breast cancer,hepatic carcinoma,colon cancer,which is positive correlated with p21 and p27.In our recent study,Ndrg2 inhibits the proliferation of colon cancer cells and participates in the metabolic recombination of colon cancer.Ndrg2 can inhibit TGF-β mediate EMT function and invasion and migration of colon cancer cells.In order to certify the relationship between Ndrg2 and tumor differentiation,we built Ndrg2 specific knockout mice Ndrg2-/-and combined with in vitro cytological analysis explore the role of Ndrg2 in the differentiation of colon cancer cells and its potential molecular mechanism.[objective] 1.To confirmed the Ndrg2 expression in colon cancer and influence in survival prognosis 2.To explored the correlation of Ndrg2 with the differentiation of colon epithelial cells in mice 3.To observed the way Ndrg2 promote stability of p21 and p27.[Method and Result] 1.Ndrg2 is related with the severity of colon cancer and survival prognosis of patients.In 112 colon cancer patients’ tissue chips,we detected the expression levels of Ndrg2 in colon cancer tissues and their corresponding cancers by immunohistochemical technique.From the statistical analysis we found that,Ndrg2 is positively correlated with colon cancer differentiation,and improved the prognosis of patients.2.Ndrg2 promote differentiation of intestinal epithelial cells in mice.To isolate the colon tissue of different months of wild type mice,we found that the expression level of Ndrg2,p21 and p27 increased gradually with the increase of the differentiation degree in colonic epithelial cells by western blot and immunofluorescent staining.After built genetically deficient mice Ndrg2-/-,the expression of Ndrg2、p21 and p27 significant reduction.The above results show that,Ndrg2 promoted the differentiation of intestinal epithelium by controlling p21 and p27.In order to demonstrate Ndrg2 promote colon cancer cell differentiation,we built the long-term or short-term induction of HCT-116 and HT-29 cell differentiation models.The expression of Ndrg2 as the degree of differentiation increases by western blot and RT-PCR.3.Ndrg2 inhibited p21 and p27 ubiquitination by the reduction of skp2The previous experimental results suggested that p21 and p27 may have been involved in the regulation of Colon cancer cell differentiation with Ndrg2.Firstly,from Actinomycin experiment we can see Ndrg2 overexpression inhibited Skp2 expression and improved the expression of p21 and p27.Secondly,the in vivo ubiquitination experiment shew that,the over expression of Ndrg2 lead to the depression of Skp2,which decreased p21 and p27 ubiquitination level and increased p21 and p27 stability.[Conclusion]Ndrg2 blocks p21 and p27 ubiquitination level,which in turn stabilizes p21 and p27 expression via Skp2 suppression.The Ndrg2 low/Skp2 high signature is correlated with poor patient outcome and could be considered as a diagnostic marker of CRCs.