GATA2 Regulates Constitutive PD-L1 and PD-L2 Expression in Brain Tumors

Abstract

Encouraging clinical results using immune checkpoint therapies to target the PD-1 axis in a variety of cancer types have paved the way for new immune therapy trials in brain tumor patients. However, the molecular mechanisms that regulate expression of the PD-1 pathway ligands, PD-L1 and PD-L2, remain poorly understood. To address this, we explored the cell-intrinsic mechanisms of constitutive PD-L1 and PD-L2 expression in brain tumors. PD-L1 and PD-L2 expression was assessed by flow cytometry and qRT-PCR in brain tumor cell lines and patient tumor-derived brain tumor-initiating cells (BTICs). Immunologic effects of PD-L2 overexpression were evaluated by IFN-γ ELISPOT. CD274 and PDCD1LG2 cis-regulatory regions were cloned from genomic DNA and assessed in full or by mutating and/or deleting regulatory elements by luciferase assays. Correlations between clinical responses and PD-L1 and PD-L2 expression status were evaluated in TCGA datasets in LGG and GBM patients. We found that a subset of brain tumor cell lines and BTICs expressed high constitutive levels of PD-L1 and PD-L2 and that PD-L2 overexpression inhibited neoantigen specific T cell IFN-γ production. Characterization of novel cis-regulatory regions in CD274 and PDCD1LG2 lead us to identify that GATA2 is sufficient to drive PD-L1 and PD-L2 expression and is necessary for PD-L2 expression. Importantly, in TCGA datasets, PD-L2 correlated with worse clinical outcomes in glioma patients.. By perturbing GATA2 biology, targeted therapies may be useful to decrease inhibitory effects of PD-L2 in the microenvironment. Glioblastoma (GBM) remains a challenging malignancy to treat. Poor clinical outcomes likely reflect aggressive GBM biology 1 , and growing evidence suggests that there is also signficant immunosuppression in GBM. Several immune resistance mechanisms have been described in GBM patients: increased regulatory T cells, indoleamine 2,3 dioxygenase activation, dysregulated antigen presentation, and STAT3-driven myeloid cell suppression, among others 1-3. Overexpression of inhibitory PD-L1 is another mechanism by which GBM cells may attenuate T cells 4,5 , which is important because PD-1/PD-L1 blocakde is FDA-approved for the treatment of many cancers. In GBM, PD-L1 expression is variable and occurs often without significant infiltrating lymphocytes, suggesting that it may be influenced by tumor intrinsic induction 6 rather than extrinsic stimulation. Several mechanisms can drive cell-intrinsic PD-L1 induction including PTEN loss 7 , aberrant signaling 8 , genomic amplification 9 , and post-translational modifications 10. However, it is unclear which of these mechanisms is most germane to brain tumors.

CRISPR activation screening identifies VGLL3 and GATA2 as transcriptional regulators of PD-L1

“…S1C). Overall, our results demonstrate that GATA2 and VGLL3 promote transcription of PD-L1 and PD-L2, a finding which for GATA2 was recently shown by others in glioblastoma cells as well (27).…”

“…While cytokine-induced PD-L1 expression and tumor cell expression of PD-L1 are studied in detail, it is unknown which factors drive constitutive expression in different immune cell subsets and other cell types such as endothelial cells and keratinocytes. Our data in combination with a study by Fu Y et al (27) show that GATA2 facilitates PD-L1 expression. GATA2 is predominantly expressed in various immune cell types, as well as endothelial cells, which both have significant PD-L1 expression.…”

Prognostic Gene Expression Signature in Patients With Distinct Glioma Grades

“…Besides, TLE3 upregulation may also induce cell cycle arrest and tumor growth suppression via inhibition of MAPK and AKT pathways (58,59). On the other hand, GATA2 upregulation induces cell surface PDL-1 and PDL-2 expression in brain tumors, and its inhibition has been reported to stimulate chemotherapy-mediated apoptosis in human AML cells overexpressing GATA2 (60,61). Further, BCL6 overexpression has pro-survival and proliferative activities of glioma cells; its expression in monocytes/macrophage lineage reduces the antitumor immune response and increases the immunosuppressive microenvironment.…”

Perspectives on immune checkpoint ligands: expression, regulation, and clinical implications

“…For example, a considerable proportion of peritoneal B1 B cells constitutively express PD-L2, which positivity enriches Phosphatidylcholine-specific B1 cells, as is crucial for innate defense against invading pathogens (46). Like PD-L1, PD-L2 is upregulated by IFN-γ treatment in tumor cells (11,19,47,48). In line with how IFN-γ orchestrates PD-L2 upregulation in tumor cells, IFN-β has a similar effect via promoting STAT3 interaction with PD-L2 promoter (11).…”