Abstract:

Objective To investigate the expression of glioma stem cell（GSC） marker CD133，the tumor- associated macrophage （TAM） marker CD68 and the negative co- stimulatory molecule PD-L1 in different pathological grades of glioma tissue and their possible correlation. Methods Double immunofluorescence staining was used to detect co- expression of CD68 and PD-L1 protein in glioma tissues of different pathological grades. The expression of CD133，CD68 and PD-L1 genes in 30 cases of low- grade glioma tissue （grade Ⅰ and Ⅱ） and 30 cases of high- grade glioma tissue （grade Ⅲ and Ⅳ） were detected by quantitative real- time fluorescent PCR （qRT-PCR），and correlation with clinical pathological grade was analyzed. Results The majority of PD-L1-positive cells were TAMs，and as the pathological grade of gliomas increased，the co-expression of CD68 and PD-L1 increased. In glioma tissues，pathological grade positively correlated with levels of CD133 （r=0.647，P<0.001），CD68 （r=0.499，P<0.001），and PD-L1（r=0.445，P=0.001）. The expression levels of CD133，CD68 and PD-L1 were significantly higher in high-grade glioma tissue than in low-grade gliomas （P<0.05）. Expression of the CD133 gene positively correlated with that of the CD68 gene across all samples （r=0.525，P<0.001），in low-grade samples （r=0.518，P=0.005），and in high-grade samples（r=0.500，P=0.007）. Expression of the CD133 gene also positively correlated with that of the PD-L1 gene across all samples （r=0.431，P<0.001），in low- grade samples （r=0.398，P=0.036），and in high-grade samples （r=0.417，P=0.027）. Conclusion PD-L1 in glioma tissue is expressed mainly by TAMs in the tumor microenvironment. Expression of CD133，CD68 and PD-L1 relates closely to the tumor degree of malignancy.

Key words:  Brain neoplasms, Glioma stem cells, Tumor-associated macrophages, PD-L1, Double immunofluorescence staining, Quantitative real-time fluorescent PCR