The Promising IgSF11 Immune Checkpoint Is Highly Expressed in Advanced Human Gliomas and Associates to Poor Prognosis

Abstract

Glioma is the most prevalent primary brain tumor. Immune checkpoint blockade has made a great stride in mending patient's clinical outcome for multiple types of cancers. However, PD-1, CTLA-4, or VEGF blockade exhibited only poor outcome in glioma patients. This study aimed to explore the expression and role of IgSF11, an emerging immune checkpoint and a ligand of VISTA, in human gliomas. IgSF11 mRNA expression was assessed in human glioma patients at different grades using 2 independent cohorts, a set of 52 Moroccan samples, including 20 glioma tissues, 22 PBMC samples taken before and 10 PBMC samples taken after surgery; and a series of 667 patients from TCGA. In parallel, immunohistochemistry was performed to evaluate IgSF11 protein staining. IgSF11 gene expression was significantly upregulated in high grade glioma tissues, compared to low grade. IgSF11 protein also showed a significant expression in low and high-grade gliomas. Interestingly, IgSF11 expression seemed to correlate positively with other critical immune checkpoints such as PD1, PDL-1, VISTA, and surprisingly negatively with CTLA-4. Although, T cell markers appeared higher in advanced gliomas, T cell-produced pro-inflammatory genes showed similar expression levels, highly likely because of the potent immunosuppressive microenvironment. Indeed, increased expression of IgSF11 in advanced human gliomas associated with a poor overall survival. Our data strongly suggest that IgSF11 is an immune checkpoint, which is upregulated in advanced human gliomas and contributes to the immunosuppressive state resulting in a poor clinical outcome in glioma patients. IgSF11 could be considered as a possible promising therapeutic target in advanced human gliomas.

Keywords: IgSF11; PDL-1; VISTA; glioblastoma; glioma; immune checkpoint.

Figure 1

IgSF11 gene expression is upregulated in high grade glioma tissues. IgSF11 expression was assessed using RT-PCR analysis. (A) Higher expression of IgSF11 gene in healthy donors, glioma tissues, and PBMC of the same patients before surgery (Pre-G-PBMC) compared to PBMC after surgery (Post-G PBMC). (B) Elevated expression of IgSF11 in advanced glioma grade (grade III-IV).

Figure 2

IgSF11 transcripts strongly expressed in high grade glioma in the TCGA cohort. RNAseq of glioma patients (n = 667) were evaluated using TCGA database. (A) IgSF11 gene showed strong expression levels in high grade gliomas. (B) Astrocytoma exhibited high expression levels of IgSF11 compared to Oligodendroglioma and Oligoastrocytoma. (C) Classical and Proneural glioma molecular subtypes showed high IgSF11 expression in comparison with mesenchymal and neural. (D) IgSF11 mRNA expression showed high expression levels compared with PDL-1.

Figure 3

IgSF11 protein was detected in human gliomas. IgSF11 protein was detected in human glioma tissues using immunohistochemistry assay. (A) Negative control staining in normal testis tissue with mouse IgG1 isotype control (magnification x20). (B) Positive staining of IgSF11 in normal testis (magnification x20). (C) Negative control staining of glioma cases with mouse IgG1 isotype control (magnification x 10). (D) Positive staining of IgSF11 in low grade glioma (Astrocytoma I) (magnification x10). (E) Positive staining of IgSF11 in high grade glioma (Glioblastoma) (magnification x10). (F) Positive staining of IgSF11 on endothelial cells (magnification x 20). (G) Positive staining of IgSF11 on tumor cells (magnification x 40). (H) Positive staining of IgSF11 on inflammatory cells (magnification x 20).

Figure 4

IgSF11 expression positively correlated with critical immune checkpoint regulators. (A) IgSF11 presented positive correlation with PDL-1. (B) IgSF11 positively correlated with PD-1. (C) IgSF11 positively correlated with VISTA. (D) IgSF11 negatively correlated with CTLA-4.

Figure 5

High expression of IgSF11 transcripts correlated to an immunosuppressive microenvironment of glioma patients. (A) CD4 and CD8 gene expression were elevated in high IgSF11 expression. (B) Anti-tumoral genes (IFNγ, Granzyme B, IL-2) exhibited no significant difference in high versus low IgSF11 expression profile. (C) TGFβ showed strong expression levels in glioma patients with high IgSF11 expression.

Figure 6

Elevated expression of IgSF11 in glioma patients associated to a poor overall survival. (A) IgSF11 upregulated in glioma patients with IDHwt compared with IDHmut status. (B) High IgSF11, PD-1 and VISTA expression levels associated to a poor overall survival. (C) Elevated expression of both IgSF11 and PD-1 in the same glioma patients correlated to a poorer overall survival.