Human leukocyte antigen-G overexpression predicts poor clinical outcomes in low-grade gliomas

•High HLA-G expression was found to serve as a potential biomarker for predicting aggressive tumor grades.•We found HLA-G expression could also serve as a potential predictor of the histological subtype in low-grade gliomas.•Elevated HLA-G expression was first indicated as an independent predictor of poor clinical outcomes in patients with low-grade gliomas.

Overexpression of human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex class-I molecule associated with immunosuppression, has been reported in various human malignancies. In the present study, we examined the role of HLA-G in gliomas. Clinical characteristics, mRNA expression microarrays and follow-up data pertaining to 293 patients with histologically confirmed gliomas were analyzed. The expression levels of HLA-G were compared between different grades of gliomas and correlated with progression-free survival (PFS) and overall survival (OS) to evaluate its prognostic value. We found that HLA-G was overexpressed in gliomas as compared to that in normal brain tissue samples (− 1.288 ± 0.265). The highest expression levels were in glioblastomas (GBMs), anaplastic gliomas (AGs) and low-grade gliomas (LGGs), in that order (0.328 ± 0.778, 0.176 ± 0.881, − 0.388 ± 0.686, respectively). Significant inter-group differences were observed between low-grade and high-grade glioma tissues (p < 0.001 and p < 0.001, t-test, AGs and GBMs, respectively). More astrocytoma patients exhibited increased HLA-G expression as compared to other LGG patients (p = 0.004, Chi-square test). Significant differences were observed with respect to PFS and OS (p = 0.009 and 0.032, log-rank test, for PFS and OS, respectively) between the high- and low-expression subgroups in patients with LGGs. On Cox regression analysis, overexpression of HLA-G appeared to be an independent predictor of clinical outcomes (p = 0.007 and 0.026, for PFS and OS, respectively). Our results suggest that HLA-G expression may serve as a potential biomarker for predicting aggressive tumor grades of gliomas and for histological subtype of LGGs. Elevated HLA-G expression could serve as an independent predictor of poor clinical outcomes in patients with low-grade gliomas.

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