Function And Mechanism Of ITGB4 Regulated By KLF4 In Gliomagenesis

Background: Glioma is the most common primary malignant brain tumor in the central nervous system.Despite great advancement in therapeutic techniques,such as surgery,radiotherapy and chemotherapy,the average survival time of patients with glioblastoma(GBM)is still only 12-15 months.There are now strong evidences that most of the malignant cells in GBM are produced by a rare self-renewing,multifunctional cancer cell,called cancer stem cells(CSCs).Gliomas are composed of a cell layer whose subsets can maintain and proliferate tumors because of their self-renewal ability and resistance to chemotherapy and radiotherapy.In recent years,many studies have shown that Glioma stem cells(GSCs)can well adapt to various key conditions,such as nutritional restrictions,hypoxia or exposure to chemotherapeutic drugs,and actively interact with microenvironmental factors to evade anti-tumor immune responses,promoting tumor angiogenesis and invasion.Because of these characteristics,GSCs are considered to be the cause of recurrence and poor prognosis in glioma patients.Therefore,it is of great significance to study the key regulatory factors that maintain these GSC characteristics for understanding the progress of glioma and studying new treatment methods.Integrin beta 4(ITGB4),also known as CD104,is a laminin-5 receptor expressed mainly in squamous epithelial cells,endothelial cells,immature thymocytes,Schwann cells(also known as Schwann cells)and fibroblasts of the peripheral nervous system.In tumors,ITGB4 was first identified as a tumor-specific antigen.Subsequent studies have shown that increased expression of ITGB4 is associated with malignant progression and adverse survival rates of skin,lung,head and neck and cervical squamous cell carcinoma(SCCs).Further studies have reported that ITGB4 is highly expressed in several cancers including breast cancer,bladder cancer,colon cancer,ovarian cancer,pancreatic cancer,prostate cancer and thyroid cancer,and is associated with poor prognosis.In cancer tissues,phosphorylation of ITGB4 cytoplasmic tail leads to its release from semidesmosomes and interaction with growth factor receptors,which promots the invasion and metastasis of cancer cells.Although ITGB4 has been reported to promote tumorigenesis in many cancers,its role in glioma remains unclear.Our study found for the first time that the expression of ITGB4 increased in GSC and glioblastoma tissues,and the elevated level of ITGB4 maintained the stem cell characteristics of GSC,promoted glioma cell migration and tumorigenesis,and was related to glioma grade.The data show that ITGB4 can promote the proliferation and migration of glioma.ITGB4 has the function of oncogene in glioma.Further studies have shown that KLF4,an important transcription factor,regulates the expression of ITGB4,enhances the stemness of glioma stem cells,and promotes the self-renewal of glioma stem cells and glioma tumourigenesis.This suggests that ITGB4 may be an effective and potential therapeutic target for glioma.Objective: To study the role of ITGB4 in gliomas and to demonstrate that ITGB4 promotes cell proliferation and migration by promoting the self-renewal ability of glioma stem cells.To explore the molecular mechanism of ITGB4 increase in glioma cell lines,it is proved that the transcription factor KLF4 up-regulates the expression of ITGB4,enhances the stemness of glioma stem cells,promotes the self-renewal of glioma stem cells and glioma tumourigenesis.Methods and Results: In this study,RNA sequencing was used to identify genes that may be involved in glioma regulation.We found increased expression of ITGB4 in glioma cells.The expression of ITGB4 in human glioma tissue was detected by immunohistochemistry,and the up-regulation was related to the grade of glioma.The expression of integrin beta 4(ITGB4)was confirmed by real-time quantitative polymerase chain reaction(qRT-PCR).The role of ITGB4 in glioma was studied by flow cytometry,transwell,colony formation and in vivo tumorigenicity test.Inhibition of ITGB4 in glioma cells decreased the self-renewal abilities of GSCs and suppressed the malignant and proliferation behaviours of glioma cells in vitro and in vivo.Further mechanism studies indicate that KLF4 up-regulates the expression of ITGB4,enhances the stemness of glioma stem cells,and promotes the self-renewal of glioma stem cells and glioma tumourigenesis.Conclusions: In summary,we found that ITGB4 has the function of oncogene in glioma.ITGB4 can promote the proliferation and migration of glioma.KLF4 regulates the expression of ITGB4 to enhance the stemness of glioma stem cells,thereby promoting the self-renewal of glioma stem cells and glioma tumourigenesis.These results provide a new scientific basis for further understanding the function of ITGB4 and the correlation between ITGB4 and tumors.