Expression And Clinical Significance Of EGLN1 And PDK4 In Colorectal Cancer

Background and ObjectiveHypoxia and abnormal energy metabolism are the basic characteristics of solid tumor.Adaptation of of hypoxia provides survival and growth advantage for tumor cells.Upregulated in hypoxia melieu,hypoxia inducible factor(HIF)can regulate the metabolism and transformation of tumor,which plays an important role in the process of development and progression of cancer.More and more studies have shown that decreased HIF protein expression maybe the target of tumor therapy.It has been confirmed that Egl-9 Family Hypoxia Inducible Factor 1(EGLN1)is an important regulator of HIF,which is closely related with tumor cell proliferation,invasion and metastasis,but it is still unknown that what effect it has made on the metabolic reprogramming of tumor.We have found that the expression of EGLN1 is closely correlated with the expression of PDK4,there was no report about it.Warburg pointed out that the majority of tumor cells still choose to use glycolysis as the main energy supply way under aerobic conditions.The activity of Pyruvate Dehydrogenase Complex(PDC)is an important molecular event to start Warburg in tumor cells.Pyruvate Dehydrogenase kinase(PDK)inactivates PDC through phosphorylation,some suggested that the abnormal expression of PDK protein in some tumor tissues,which has much to do with the prognosis and the chemotherapy sensitivity of the patients.There are four isoforms of PDK: PDK1,PDK2,PDK3 and PDK4 in mammals,of which PDK4 has been shown to be an important substance in the regulation of PDC metabolism.But the expression of PDK4 in colorectal cancer and its relationship with the prognosis of colorectal cancer is not clear yet.Therefore,this study was designed to further confirm the effect of EGLN1 on invasion and metastasis of colorectal cancer,and discuss its possible molecular mechanism based on the previous work.Methods1.Immunohistochemical staining was applied for the detection of EGLN1 expression of colorectal cancer and its adjacent mucosa tissues.The results and the related clinical data were used to make a statistical analysis.2.To confirm the effect on colorectal cancer when knocking down EGLN1 in colorectal cancer cells,methods such as Western blot,cloning formation test,Transwell,CCK-8 proliferation test and scratch test et al were used in colorectal cancer cell line.3.The results of metabolic chip,IHC and the data from GEO database were combined to analyze the correlation between PDK4 and EGLN1.4.Immunohistochemical staining was employed for the measure of PDK4 expression of colorectal cancer and adjacent mucosa tissues.Then explore its clinical significance.Result1.Expression of EGLN1 protein was downregulated in colorectal c ancer tissues than in the adjacent mucosa(61.3% vs 38.9%,P<0.01).And it was closely correlated with differentiation degree,clinical stage and lymph metastasis of colorectal cancer(P<0.01).2.SW620 EGLN1 KD and LS174 T EGLN1KD cell lines were successfully established,the ability of cell proliferation,invasion and migration of EGLN1 protein was lower than that of the control,and it also promoted EMT.3.Expression of EGLN1 protein was negatively correlated with the expression of PDK4 protein via the analysis of the metabolic chip and the related data from IHC and GEO database.4.The high expression rate of PDK4 protein was significantly upregulated in the colorectal cancer tissues than in the adjacent mucosa tissues(57% vs 26.7%,P<0.01),which was significantly correlated with the differentiation degree,clinical stage and lymph node metastasis of chon cancer(P<0.05).The patients with higher expression level of PDK4 had poorer prognosis(P<0.01).Conclusion1.Expression of EGLN1 in colorectal cancer was deletion,which was significantly correlated with the clinical stage,differentiation degree and metastasis of colorectal cancer.These results suggest that the deletion of EGLN1 protein plays an important role on the occurrence and development of colorectal cancer2.Down regulation of EGLN1 expression promotes invasion and metastasis of colorectal cancer cells.3.Expression of EGLN1 protein was negatively correlated with the expression of PDK4 protein.4.The expression of PDK4 in colorectal carcinoma was higher than that in the adjacent mucosa,and it was correlated with the expression of the protein,which may be involved in the invasion and metastasis of colorectal cancer.