Platelet-derived growth factor beta is a potent inflammatory driver in paediatric high-grade glioma

Abstract

Paediatric high-grade gliomas (HGGs) account for the most brain tumour-related deaths in children and have a median survival of 12–15 months. One promising avenue of research is the development of novel therapies targeting the properties of non-neoplastic cell-types within the tumour such as tumour associated macrophages (TAMs). TAMs are immunosuppressive and promote tumour malignancy in adult HGG; however, in paediatric medulloblastoma, TAMs exhibit anti-tumour properties. Much is known about TAMs in adult HGG, yet little is known about them in the paediatric setting. This raises the question of whether paediatric HGGs possess a distinct constituency of TAMs because of their unique genetic landscapes. Using human paediatric HGG tissue samples and murine models of paediatric HGG, we demonstrate diffuse midline gliomas possess a greater inflammatory gene expression profile compared to hemispheric paediatric HGGs. We also show despite possessing sparse T-cell infiltration, human paediatric HGGs possess high infiltration of IBA1+ TAMs. CD31, PDGFRβ, and PDGFB all strongly correlate with IBA1+ TAM infiltration. To investigate the TAM population, we used the RCAS/tv-a system to recapitulate paediatric HGG in newborn immunocompetent mice. Tumours are induced in Nestin-positive brain cells by PDGFA or PDGFB overexpression with Cdkn2a or Tp53 co-mutations. Tumours driven by PDGFB have a significantly lower median survival compared to PDGFA-driven tumours and have increased TAM infiltration. NanoString and quantitative PCR analysis indicates PDGFB-driven tumours have a highly inflammatory microenvironment characterized by high chemokine expression. In vitro bone marrow-derived monocyte and microglial cultures demonstrate bone marrow-derived monocytes are most responsible for the production of inflammatory signals in the tumour microenvironment in response to PDGFB stimulation. Lastly, using knockout mice deficient for individual chemokines, we demonstrate the feasibility of reducing TAM infiltration and prolonging survival in both PDGFA and PDGFB-driven tumours. We identify CCL3 as a potential key chemokine in these processes in both humans and mice. Together, these studies provide evidence for the potent inflammatory effects PDGFB has in paediatric HGGs.

A New Mouse Model of Diffuse Midline Glioma to Test Targeted Immunotherapies

“…Both de novo and orthotopically generated tumors have a heterogeneous expression of IL13Rα2, consistent with that found in pediatric diffuse midline gliomas and GBM. Consistent with T-cell infiltration described in pediatric gliomas 31,32,25 , IHC analysis of tumor microenvironment showed limited and scattered CD3 positive cells and a moderate presence of CD11b+ cells in both de novo and orthotopic diffuse midline tumors. Further analysis of the tumor microenvironment will be pursued to understand these findings better and to assess changes taking place upon the introduction of immunotherapy.…”

“…The cDNA encoding T2A-IL13Ra2 was synthesized by GenScript, subcloned into the RCAS-PDGFB-HA vector 25 following the PDGFB cDNA using CloneEZ method, and verified by Sanger sequencing (GenScript, Piscataway, NJ). The plasmid was amplified in DH5a cells (NewEngland Biolabs, Ipswich, MA; Cat #C2987H), and purified using plasmid purification midi-kit (Qiagen, Hilden, Germany; Cat # 12145).…”

Single-cell RNA Sequencing Reveals Immunosuppressive Myeloid Cell Diversity and Restricted Cytotoxic Effector Cell Trafficking and Activation During Malignant Progression in Glioma

“…In order to validate these results, we performed flow cytometry on dissociated brain tumor tissues of LGG and HGG. We quantified the percentages of CD45 high and CD11b+ cells, conventionally identified as bone marrow-derived myeloid cells (BMDM) [38, 39]. Using flow cytometry, we detected a 4-fold in vivo increase in the percentage of BMDM in HGG (11.5 ± 4.5%) compared to LGG (2.7 ± 1.5%) ( Figure 2C and 2D) .…”

The Promoting Effect of Traumatic Brain Injury on the Incidence and Progression of Glioma: A Review of Clinical and Experimental Research

“…Inflammation at the site of traumatic brain injury and glioma has been well documented in the literature. 63 , 64 Besides, ROS, the major contributor of oxidative stress, are metabolic byproducts originating from different sources in hypoxic 65 conditions and exhibit condition-dependent functions. 66 , 67 The activation of inflammation and oxidative stress are reported in both traumatic brain injury and glioma, and both conditions appear to share a common network of signaling for downstream functions ( Figure 2 ).…”