The Role Of CD226 In Colorectal Cancer

Background: The incidence rate of colorectal cancer ranks the third in the Western countries,and the incidence rate is gradually increasing with age.According to the 2015 cancer statistics in China,the incidence rate and mortality rate of colorectal cancer ranks the fifth among all malignant tumors.Additionally,approximate 20% of patients have occurred distant metastatisis,the liver is most common metastatic organ.At present,surgery could be the only cure for local colorectal cancer,although radiotherapy and chemotherapy are also important approaches for colorectal cancer treatment.For patients with advanced colorectal cancer,chemotherapy is the main choice.However,many newly onset patients with colorectal cancer were found to be middle and late stages,lost the surgery operation opportunity and lacked the effective treatments.The lack of understanding of the pathogenesis of colorectal cancer has limited the treatment options.In order to be able to predict and diagnose tumors in the early stage,people gradually realize the important role of abnormal changes of oncogene and tumor suppressor gene in the occurrence and development of malignant tumors,especially the loss of tumor suppressor gene function has been paid more and more attention.Tumor suppressor genes are kinds of negative regulatory genes that suppress the tumor occurance and development.In recent years,great progresseshave been achievedin the cloning and identification of these genes.Since 1986,retinoblastoma(Rb)has been firstly isolated,many human tumor suppressor genes have been cloned and identified so far.The mutation of tumor suppressor genes will greatly increase the individual's tumor susceptibility.Tumor suppressor genesare also observed to have somatic mutation in many sporadic diseases,becoming an inactive form.Considering that they are inactivated in the process of tumorigenesis or development,tumor suppressor genes are considered to be negative regulators of proliferation,or otherwise inhibit the normal function of tumorigenesis.With the development of molecular biology,more and more tumor suppressor genes have been found.In recent years,some scholars have found that the functional mutation of CD226 can increase the susceptibility of lung cancer in non-smoker.Another study indicates that CD226 is inactivated in a variety of tumors,and the survival rate and survival time of patients with high expression of CD226 are higher.Based on the above results,we speculated that CD226 might be a new tumor suppressor.CD226 is a member of immunoglobulin superfamily and belongs to type I transmembrane glycoprotein.Previous studies have shown that CD226 plays different biological functions in a variety of diseases.For example,CD226,as an adhesion molecule,can promote the migration of CTL cells to the inflamed area.As a costimulatory molecule,CD226,CD96 and TIGIT work together to regulate the function of NK cells and maintain the function of NK cells in many autoimmune diseases.In recent years,it has been found that CD226 is related to the occurrence and development of many kinds of tumors.However,the mechanism of CD226 in the carcinogenesis and development of cancer is still unclear.The expression of CD226 in colorectal cancer cells and its relationship with clinicopathological parameters are still unknown.In view of this,we found that CD226 expression was missing in a variety of malignant tumors by querying the database,and the patients with high expression of CD226 have higher postoperative survival rate and longer survival time.After that,IHC was used to detect the expression of CD226 in clinical tissue samples of colorectal cancer patients.It was found that the tumor with high expression of CD226 was smaller and less prone to lymph node metastasis.Thus,we preliminarily judged that CD226 is associated with the proliferation and migration of colorectal.Therefore,the purpose of this study is to investigate the role and mechanism of CD226 in the development of colorectal by observing the effect of CD226 on the proliferation,invasion and migration of colorectal.Objective: To explore the role and mechanisms of CD226 in colorectal cancer cells and provide new insight and targets into tumor treatment.Methods: Total 93 colorectal cancer patients with paraffin sections were collected from 924 th Hospital of the joint service support force of the People's Liberation Army(formerly 181 Hospital of the People's Liberation Army)during January 2017 to December 2018.20 freshly prepared samples from colorectal cancer patients were selected from the Third Affiliated Hospital of Sun Yat sen University from February 2019 to February 2020.After obtaining the informed consent of the patients,the clinical tissue samples of the patients were collected,and the expression of CD226 in the tumor tissue was observed by q PCR.The expression of CD226 in various tumor tissues was examined by querying TCGA database,and the expression of CD226 and survival rate and survival time of patientswas statistically analyzed.The relationship between CD226 and clinicopathological factors was explored by immunohistochemistry.Then cell experiments were carried out to further observe the role of CD226 in colorectal cancer cell lines.The expression of CD226 in five colorectal cancer cell lines was observed by q PCR and Western blot.CD226 overexpression / knockdown stable cell line was constructed by lentivirus vector,and the effect of CD226 on proliferation,invasion and metastasis of colorectal cancer cell lines was studied by CCK8,cell scratch and Transwell experiments.The effect of CD226 on the proliferation of tumor cells was verified by subcutaneous tumorigenesis in vivo.Finally,Western blot was used to explore the mechanisms of CD226 inhibiting the proliferation and metastasis of colorectal cancer cells.Results: 1.In order to explore the expression of CD226 in various tumor tissues and normal tissues and to determine whether CD226 is related to the survival time of patients,we queried the TCGA database,and the results showed that the expression of CD226 in various malignant tumor tissues was lower than that in normal tissues,and the expression of CD226 was related to the survival time and survival rate of patients.Clinical samples with high expression of CD226 had longer survival time and higher survival rate;clinical samples with low expression of CD226 had shorter survival time and lower survival rate.2.To further clarify the expression of CD226 in human intestinal cancer tissues.The q PCR results of 20 clinical samples showed that the expression of CD226 in intestinal cancer tissues was lower than that in distant cancer tissues.3.To explore the correlation between CD226 and clinicopathological factors,the expression of CD226 in clinicopathological sections of 93 patients with intestinal cancer was observed by immunohistochemistry.The staining results combined with clinical data showed that patients with high expression of CD226 had smaller tumor volume and were less prone to lymph node metastasis.4.Cell experiments verified that the proliferation ability and invasion and metastasis ability of CD226 high expression intestinal cancer cell lines were weakened,while the proliferation ability and invasion and metastasis ability of CD226 low expression intestinal cancer cell lines were enhanced.5.The results of subcutaneous tumorigenesis experiment in nude mice showed that compared with tumors formed by cells with low expression of CD226,tumors formed by cells with high expression of CD226 had smaller volume and weight,which verified the anti-tumor effect of CD226 in vivo.6.Western blot experiments showed that CD226 may exert its anti-cancer effect by inhibiting the phosphorylation of AKT.Conclusion: 1.CD226 is highly expressed in normal intestinal epithelial tissues and low expressed in intestinal cancer tissues,and its expression is closely related to tumor size and lymph node metastasis.2.CD226 may play an anticancer role by inhibiting the phosphorylation of AKT.