| Background:Gliomas are the most common tumors of the Central Nervous System (CNS),accounting for more than40%of all primary brain and CNS malignant tumors. Gliomasare glial malignancies, classified according to the2007World HealthOrganization(WHO) classification into astrocytomas, oligodendrogliomas or the mixedtumors oligoastrocytomas, based on histopathological features. Grade I and grade IIbelong to the low malignancy degree, while grade III and IV belong to high levelmalignant. The latest research shows that it is easy for the low-grade gliomas totransformated to high-grade gliomas. The poor prognosis of patients with malignantglioma calls for the development of novel therapeutic approaches to improve thesurvival of these patients.Immune suppression and immune escape prompt tumorigenesis, progress, invasionand remote metastasis. The PD-L1/PD-1pathway is a key regulator of the crucial balancebetween stimulatory and inhibitory signals needed for effective immune responses tomicrobes and for self-tolerance. Studies in the past demonstrate that the tumors escapefrom the host immune system by negative attenuation of tumor-specific T cell responsesvia PD-L1/PD-1interactions. So blockade of the B7-H1pathway could lead to a newstrategy for therapeutic purposes in the control of glioma.Objective：To validate the relationships between B7-H1and gliomas. For further validation, twoshort hairpin RNA(shRNA) targeting B7-H1was designed and constructed into lentivirus and was used to infect glioblastoma cell cell U87MG. The knockdown efficiency wasconfirmed by flow cytometry. Then we investigate the effect of B7-H1knockdown on cellproliferation and apoptosis in human glioma U87cell．Methods and Results：In human glioma specimens, we found that B7-H1was positively correlated withdegree of malignancy in gliomas in the protein level by immunohistochemistry stainingand Western Blot. Indirect immunofluorescence assay and Western Blot showed highexpression of B7-H1in glioma cell line U87and U251, moderate expression in A172andT98, and low expression in SHG44. Knockdown of B7-H1in the glioma U87cell line wasdone by lentivirus infection which express shRNA targeting B7-H1. The knockdownefficiency was confirmed by flow cytometry. Compared with control group，the surfaceexpression of B7-H1was downregulated from53.2%to26.7%and20.6%，respectively．qRT-PCR showed that the expression of B7-H1mRNA was1.36±0.28incontrol group, which decreased to0.67±0.16and0.52±0.15when B7-H1wasdownregulated. Western blot showed that the expression of B7-H1was inhibited and theinhibition rate was56.4%±1.7%and47.0%±1.5%when B7-H1was downregulated. Toexplore cytostatic effect of B7-H1knockdown on human glioma cells and suppresses thegrowth of the GBM cell line，cell viability was examined by the3-(4,5-dimethyl)-2,5diphenyl tetrazolium bromide (MTT) assay, result showed absorbance values ofknockdown groups (0.451±0.02and0.342±0.016) were lower than control group(0.58±0.02), indicated cell proliferation was significantly inhibited. Then we investigated theeffect of B7-H1knockdown on the apoptosis of glioma U87MG cells by combinedannexin V/PI dual staining assay, flow cytometry showed obvious apoptosis was inducedin B7-H1knockdown U87cells, the early apoptotic rate increased from0.1%to12.8%and13.2%．Conclusion：There is difference about B7-H1expression in human glioma specimens and gliomacell lines. The downregulation of B7-H1can efficiently inhibit cell proliferation andpromote apoptosis in U87cells, indicating that B7-H1might be a potential target for gene therapy of glioma. |
PDF Full Text Request