CRE B5 Promotes The Formation Of Immunosuppressive Microenvironment In Colorectal Cancer By Regulating TGFB2

Background:Colorectal cancer(CRC)is one of the most common cancers in the world,with the third highest incidence and mortality.Metastasis is the main cause of death in colorectal cancer patients,and the prognoses of colorectal cancer with metastases are poor with a 5-year survival rate of 12-14%.Therefore,it is crucial to understand the potential mechanism of colorectal cancer metastasis.Tumor Microenvironment(TME)is the environment of tumor growth,and immune response is one of its biological characteristics.In the process of development of tumor,the immune response is constantly regulated and gradually forms immunosuppressive microenvironment,mediating the immune escape of tumor,which leads to tumor metastasis.Therefore,we aimed to investigate the formation mechanism of immunosuppressive microenvironment in colorectal cancer.cAMP Responsive Element Binding Protein 5(CREB5)is a transcriptional activator with high affinity for CRE,which involved in invasion and metastasis of colorectal cancer.Studies have shown that CREB5 was involved in inflammatory response and played a role in opioid-induced immunosuppression.In addition,the ATF/CREB family of CREB5 plays an important role in the immune response,inhibiting tissue damage and autoimmune response.This may be pathogenic in the context of tumor immunosurveillance.However,the role and mechanism of creb5 in colorectal cancer immune microenvironment have not been elucidated.To sum up,we proposed that CREB5 may regulate tumor immunity to mediate the formation of immunosuppressive microenvironment in colorectal cancer.Methods:1.CREB5 stable overexpression cell line was established in mouse colorectal cancer cells MC38,and CREB5 stable interference cell line was established in MC38K.The effect of CREB5 on the growth and invasion of colorectal cancer in vivo was detected by subcutaneous tumor-forming assay in mice.2.Flow cytometry analysis and immunohistofluorescence were used to detect the effect of CREB5 on immune cell infiltration in colorectal cancer.3.TCGA database was used to analyze the signal pathways related to the high expression of CREB5 in colorectal cancer by GSEA gene enrichment method,and potential target genes were analyzed.4.The effect of CREB5 on TGFB2 expression was detected by q-PCR assay.5.The effect of CREB5 on the polarization of RAW264.7 through TGFB2 was detected by flow cytometry analysis and RT-PCR using the method of co-culture of CREB5 stabilized bead and RAW264.7 cells.Result:1.The growth rate of MC38 cells in C57BL/6J mice was significantly increased after overexpression of CREB5,while the growth rate of MC38K cells in C57BL/6J mice was significantly inhibited after interference with CREB5.2.Overexpression of CREB5 enhanced the invasion of MC38 cells.3.After the overexpression of CREB5,the infiltration of MDSCs and M2 macrophages in colorectal cancer increased,while the infiltration of CD8+T cells decreased.After interference with CREB5,the infiltration of MDSCs and M2 macrophages in colorectal cancer was decreased,while the infiltration of CD8+T cells was increased.4.GSEA gene enrichment analysis showed that TGFβ signaling pathway was significantly enriched in the group with high CREB5 expression.5.CREB5 promotes TGFB2 transcription level expression in colorectal cancer cells.6.CREB5 promotes the polarization of M2-type macrophages in colorectal cancer through TGFB2.