The Function And Regulation Mechanism Of OLR1 In The Invasion And Metastasis Of Pancreatic Cancer

BackgroundPancreatic cancer is a lethal tumor in the digestive tract.The overall five-year survival rate is less than 9%.The main reason is that most patients have atypical early symptoms and are prone to distant metastasis,which leads to local progress or distant metastasis when diagnosed.Therefore,studying the metastasis mechanism of pancreatic cancer is of great significance to find new therapeutic targets.Oxidized low-density lipoprotein receptor 1(OLR1)is a type Ⅱ membrane surface glycoprotein.Previous studies about OLR1 focused on the field of cardiovascular and cerebrovascular diseases such as atherosclerosis and diabetes.In recent years,more and more studies show that OLR1 may also participate in the occurrence and development of cancer,especially in the metastasis of tumor.Our previous study found that OLR1 may be involved in regulating the biological behavior of pancreatic cancer.However,the specific role and mechanism of OLR1 in pancreatic cancer are not clear.Therefore,we will further study the role and mechanism of OLR1 in pancreatic cancer.ObjectiveStudy the effect of OLR1 on the proliferation,invasion,migration and chemoresistance of pancreatic cancer cells;Explore the specific mechanism of OLR1 regulating the invasion and metastasis of pancreatic cancer;Detect the expression of OLR1 in pancreatic cancer tissues and evaluate its clinical significance.MethodsFirstly,the expression of OLR1 was up-regulated or down regulated in pancreatic cancer cell lines and CCK8 assay,Wound-healing assay and Transwell chamber were used to detect the effects of OLR1 on the biological behaviors of pancreatic cancer cells,such as proliferation,invasion,migration,wound healing and chemosensitivity.Secondly,RT-qPCR,Western Blot,transcriptome sequencing,bioinformatics analysis,chromatin immunocoprecipitation,immunofluorescence and double luciferase reporter gene experiments were used to explore the molecular mechanism of OLR1 regulating the invasion and metastasis of pancreatic cancer.The invasion and metastasis of pancreatic cancer effected by OLR1 was confirmed in vivo by constructing subcutaneous tumor,tail vein tumor,orthotopic tumor and spleen injection tumor models in nude mice.Finally,the expression levels of OLR1,c-myc and HMGA2 in pancreatic cancer tissues were detected by immunohistochemical staining,and the clinical value of OLR1,c-myc and HMGA2 as prognostic markers of pancreatic cancer patients was evaluated.ResultsExperiments in vitro showed that up-regulation of OLR1 expression level can promote the proliferation,invasion,migration and wound healing of pancreatic cancer cells and reduce the chemosensitivity of pancreatic cancer cells to gemcitabine;on the contrary,down-regulation of OLR1 expression level can inhibit the proliferation,invasion,migration and wound healing of pancreatic cancer cells and increase the chemosensitivity of pancreatic cancer cells to gemcitabineExperiments in vivo showed that up-regulation of OLR1 can promote the growth of subcutaneous transplanted pancreatic cancer,knockdown of OLR1 inhibited the growth of subcutaneous transplanted tumor of pancreatic cancer,as well as the distant metastasis of tail vein injection transplanted tumor,orthotopic transplanted tumor of pancreas and spleen injection transplanted tumor.In terms of mechanism,OLR1 can up-regulate the expression of c-myc and HMGA2,and promote the invasion and metastasis of pancreatic cancer by regulating them.C-myc can combine with HMGA2 promoter region to promote the transcription and expression of HMGA2,and promote the invasion and metastasis of pancreatic cancer by regulating HMGA2.HMGA2 can lead to the decrease of E-cadherin protein expression level,the increase of snail and β-catenin expression level in pancreatic cancer cells,which leads to epithelial to mesenchymal transition(EMT),which promotes the invasion and metastasis of pancreatic cancer cells.These results suggested that OLR1 can promote the transcription of HMGA2 through c-myc to mediate EMT of pancreatic cancer cells,and eventually lead to invasion and metastasis of pancreatic cancer cells.The results of immunohistochemical staining in clinical tissue samples showed that OLR1 is mainly distributed in the membrane and cytoplasm of pancreatic cancer cells and significantly over expressed in pancreatic cancer compared with paracancerous tissue.The expression level of OLR1 was correlated with the differentiation degree,N stage and TNM stage of the patients,and was an independent risk factor for poor prognosis of pancreatic cancer patients;OLR1 was positively correlated with the expression of c-myc and HMGA2 in pancreatic cancer tissue,and when the three were combined,the more kinds of proteins were over expressed,the worse the prognosis of patients was,so OLR1/c-Myc/HMGA2 could be used as combined prognostic markers for pancreatic cancer patients.ConclusionOLR1 can promote the transcription of HMGA2 by up regulating the expression level of c-myc,and make pancreatic cancer develop EMT,so as to promote the invasion and metastasis of pancreatic cancer cells.OLR1 is highly expressed in pancreatic cancer,and the OLR1/c-myc/HMGA2 pathway may be a combined prognostic marker and potential therapeutic target for pancreatic cancer patients.