M2型巨噬细胞来源的XBP1调控SREBP2对结直肠癌细胞奥沙利铂耐药性的影响OA

Objective To investigate the impact of X-box binding protein 1(XBP1)derived from M2-type macrophages on oxaliplatin(Ox)resistance in colorectal cancer(CRC)cells by modulating sterol regulatory element binding protein 2(SREBP2).Methods HCT116,SW480,and LoVo cells were cultured in Ox-containing medium for 48 h.The cell line that was most sensitive to Ox was selected,and the CRC-Ox resistant cell line was established by the method of gradually increasing drug concentration.Ox-sensitive parental cells(HCT116-S)and Ox-resistant cells(HCT116-R)were treated with M0-conditioned medium(M0-CM)and M2-CM,respectively,to observe the effects of M0-CM and M2-CM on the cells.According to the treatment conditions,the cells were divided into M0-CM+HCT116-S group,M2-CM+HCT116-S group,M0-CM+HCT116-R group,and M2-CM+HCT116-R group.To study the effect of XBP1 activation in M2-type macrophages on the growth and OX-resistance of HCT116 cells,HCT116-R cells were divided into overexpression negative control(oe-NC)M2-CM group(M2oe-NC-CM group),M2oe-NC-CM+Ox group,XBP1 overexpression M2-CM group(M2oe-XBP1-CM group),and M2oe-XBP1-CM+Ox group.To study the effect of SREBP2 knockdown on HCT116-R cells,HCT116-R cells were divided into normal control group,SREBP2 small interference RNA group(si-SREBP2 group),M2oe-XBP1-CM group,and si-SREBP2+M2oe-XBP1-CM group.CCK-8 assay was used to detect the viability of HCT116 cells in each group.The invasion capacity of CRC cells was detected by Transwell assay.Flow cytometry was used to detect the apoptosis rate.The mRNA level of SREBP2 was detected by qRT-PCR.The protein expression levels of XBP1 and SREBP2 were detected by Western blotting.M2-type macrophages and HCT116 cells transfected with empty vector or oe-XBP1 were subcutaneously inoculated into nude mice to construct a tumor-bearing nude mouse model.The tumor volume and weight were compared among groups,and the expression levels of XBP1 and SREBP2 in tumors were detected by immunohistochemical staining.Results The results of CCK-8 assay showed that,compared with SW480 and LoVo cell lines,Ox could significantly inhibit the viability of HCT116 cells(P<0.05).Compared with M0-CM+HCT116-S group,cell viability and invasion capacity in M2-type-CM+HCT116-S group were significantly increased,while the apoptosis rate was significantly decreased(P<0.05).Compared with M0-CM+HCT116-R group,cell viability and invasion capacity in M2-CM+HCT116-R group were significantly increased,while the apoptosis rate was significantly decreased(P<0.05).Compared with M0-CM+HCT116-R group,the XBP1 protein expression level in cells of M2-CM+HCT116-R group was notably increased(P<0.05).Compared with M2oe-NC-CM group,cell viability and invasion capacity in M2oe-XBP1-CM group were significantly increased,and the apoptosis rate was significantly decreased(P<0.05).Compared with M2oe-NC-CM+Ox group,overexpression of XBP1 significantly increased the expression levels of SREBP2 mRNA and protein(P<0.05).Compared with control group,cell viability and invasion capacity were decreased,while the apoptosis rate was significantly increased in si-SREBP2 group(P<0.05).Compared with M2oe-XBP1-CM group,the cell viability and invasion capacity in si-SREBP2+M2oe-XBP1-CM group were decreased,and cell apoptosis was increased(P<0.05).In vivo experimental results showed that overexpression of XBP1 reversed the inhibition of Ox on tumor growth and upregulated SREBP2 protein expression in nude mice(P<0.05).Conclusion XBP1 derived from M2-type macrophages significantly enhances Ox resistance in CRC cells by activating SREBP2.