Despite being the leading cause of cancer-related childhood mortality, pediatric gliomas have been relatively understudied, and the repurposing of immunotherapies has not been successful. Whole-transcriptome sequencing, single-cell sequencing, and sequential multiplex immunofluorescence were used to identify an immunotherapeutic strategy that could be applied to multiple preclinical glioma models. MAPK-driven pediatric gliomas have a higher IFN signature relative to other molecular subgroups. Single-cell sequencing identified an activated and cytotoxic microglia (MG) population designated MG-Act in BRAF-fused, MAPK-activated pilocytic astrocytoma (PA), but not in high-grade gliomas or normal brain. T cell immunoglobulin and mucin domain 3 (TIM3) was expressed on MG-Act and on the myeloid cells lining the tumor vasculature but not normal brain vasculature. TIM3 expression became upregulated on immune cells in the PA microenvironment, and anti-TIM3 reprogrammed ex vivo immune cells from human PAs to a proinflammatory cytotoxic phenotype. In a genetically engineered murine model of MAPK-driven, low-grade gliomas, anti-TIM3 treatment increased median survival over IgG- and anti–PD-1–treated mice. Single-cell RNA-Seq data during the therapeutic window of anti-TIM3 revealed enrichment of the MG-Act population. The therapeutic activity of anti-TIM3 was abrogated in mice on the CX3CR1 MG–KO background. These data support the use of anti-TIM3 in clinical trials of pediatric low-grade, MAPK-driven gliomas.

A recently published JCI paper revealed that cancer-associated fibroblasts (CAFs) are present in glioblastoma and are defined by the presence of 9 transcriptional markers (1). CAFs can form a barrier around cancer cells that prevents their detection by T cells (2). The normal brain has low levels of collagen, but deposition increases in gliomas, especially around vessels. In addition to collagen facilitating tumor invasion and providing a niche for cancer stem cells, collagen has also been shown to trigger immune suppression through LAIR1-mediated T cell exhaustion and alternative activation of macrophages (3, 4). CAFs were identified from single cells isolated from 21 samples (high-grade gliomas [HGGs], 5; pilocytic astrocytomas [PAs], 13; and normal brains [NBs], 3) by examining differential expressed genes against known CAF markers and CAF subtype markers (Figure 1A). The percentage of CAFs was a function of glioma grade, with 1% CAFs present in NBs/low-grade gliomas and nearly 20% in HGGs with an enrichment of the immunomodulatory CAF subtype (Figure 1, B and C). Gene ontology analysis suggested CAF-mediated immune suppression and migration inhibition (Figure 1D). To ascertain the collagen types produced by CAFs, scRNA-Seq data from our pediatric glioma cohort complemented with public adult glioblastoma data sets (5) were analyzed and showed that CAFs expressed COL6A1/A2 > COL4A1, COL9A3, COL12A1 > COL1A (Figure 1E and Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/ JCI176613DS1). ELISA confirmed collagen production by human glioblastoma CAFs at 773 μg/mL. Within the public data set (5), the CAF populations are included in the pericyte compartment. Pericytes expressed the greatest diversity of collagen subtypes and were the main source of COL1A1/A2, COL3A1, COL4A1/A2, COL5A1/A2, COL6A1/A2/A3, and COL18A1; endothelial cells were also a source of COL4A1/A2 and COL18A1. Glioma cells expressed modest levels of COL6A1 and COL9A3 (Supplemental Figure 1A). Prognostic analysis of collagen subtypes from The Cancer Genome Atlas revealed that 6 types were negatively associated with outcome, including COL1A2 (high vs. low expression, 12.3 vs. 16.1 months; HR = 0.68; P = 0.03); COL6A1 (11.9 vs. 15.9 months; HR = 0.53; P = <0.01); COL8A2 (12.6 vs. 15 months; HR = 0.65; P = 0.02); COL22A1 (11.8 vs. 15.4 months; HR = 0.67; P = 0.03); COL24A1 (11.8 vs. 15 months; HR = 0.64; P = 0.01); and COL27A1 (11.8 vs. 15.8 months; HR = 0.63; P = 0.01) (Supplemental Figure 1B). Among the most frequently expressed and prognostic collagens, COL1A2, COL4A1, and COL6A1 were enriched near the hyperplastic vessels and microvascular proliferation, whereas COL1A2 and COL4A1 were enriched in the perinecrotic regions (Supplemental Figure 1C). To validate these findings, multiplex imaging demonstrated that CAFs were embedded in COL6A1/A2 within HGGs (Figure 1F and Supplemental Video 1). COL1A and COL4A were expressed in tumor glomeruloid struc

Utilizing a Scoping Review strategy in the domain of immune biology to identify immune therapeutic targets, knowledge gaps for implementing immune therapeutic strategies for pediatric brain tumors was assessed. The analysis demonstrated limited efforts to date to characterize and understand the immunological aspects of tumor biology with an over-reliance on observations from the adult glioma population. Foundational knowledge regarding the frequency and ubiquity of immune therapeutic targets is an area of unmet need along with the development of immune-competent pediatric tumor models to test therapeutics and especially combinatorial treatment. Opportunities arise in the evolution of pediatric tumor classification from histological to molecular with targeted immune therapeutics.

Little is known about the genomic alterations in chordoma, with the exception of loss of SMARCB1, a core member of the SWI/SNF complex, in poorly differentiated chordomas. A TBXT duplication and rs2305089 polymorphism, located at 6q27, are known genetic susceptibility loci. A comprehensive genomic analysis of the nuclear and mitochondrial genomes in pediatric chordoma has not yet been reported. In this study, we performed WES and mtDNA genome sequencing on 29 chordomas from 23 pediatric patients. Findings were compared with that from whole-genome sequencing datasets of 80 adult patients with skull base chordoma. In the pediatric chordoma cohort, 81% of the somatic mtDNA mutations were observed in NADH complex genes, which is significantly enriched compared with the rest of the mtDNA genes (P = 0.001). In adult chordomas, mtDNA mutations were also enriched in the NADH complex genes (P < 0.0001). Furthermore, a progressive increase in heteroplasmy of nonsynonymous mtDNA mutations was noted in patients with multiple tumors (P = 0.0007). In the nuclear genome, rare likely germline in-frame indels in ARID1B, a member of the SWI/SNF complex located at 6q25.3, were observed in five pediatric patients (22%) and four patients in the adult cohort (5%). The frequency of rare ARID1B indels in the pediatric cohort is significantly higher than that in the adult cohort (P = 0.0236, Fisher’s exact test), but they were both significantly higher than that in the ethnicity-matched populations (P < 5.9e−07 and P < 0.0001174, respectively). Implications: germline ARID1B indels and mtDNA aberrations seem important for chordoma genesis, especially in pediatric chordoma.

Somatic malignancies arising in mature teratomas are exceedingly rare entities and even more so are those arising in immature teratomas. Here, we present a unique case of a 13-year-old who initially underwent ovarian sparing cystectomy for a 7.7 cm left ovarian mass with a pre-operative diagnosis of mature cystic teratoma. Histologically, all 3 germ cell layers were present and immature neuroepithelial tubules were also identified. Subsequent sections revealed a nodular lesion composed of neuropil, neuroblasts with a spectrum of maturation, and Schwannian-type stroma. The neuroblasts were diffusely positive for PHOX2B. Neuroblastoma arising in an immature teratoma has only been described in the literature once previously in an adult patient.