Medulloblastoma (MB) is the most common lethal malignant pediatric brain tumor. Adjuvant immunotherapy for medulloblastoma has been proposed in both pre-clinical and clinical practice. To provide a precision strategy of designing immunotherapy for MB, the present study performed a descriptive analysis of immune microenvironment in a cohort and compared the differences between four subgroups of MB. Subtypes (WNT, SHH Group 3 and Group 4) of medulloblastoma were identified using K-means clustering according to the expression of signature genes. Tumor infiltrating immune cell population was assessed by both bio-informative algorithm based on gene expression and immunohistochemistry staining. Cytokines in tumor microenvironment were detected using Luminex. Gene Set Enrichment Analysis demonstrated a raised immune response in the SHH subgroup. Lymphocyte infiltration was low in all four subgroups, while more CD4+ T cells were observed in the Group 4 subtype. Programmed cell death protein 1 (PD1)/ ligand 1 (PD-L1) expression was absent in the cohort. The SHH subtype recruited more activated tumor associated macrophage/microglia compared with the other subgroups. Cytokines within the MB microenvironment were low compared with the glioblastoma samples. In contrast to glioblastoma, the immune microenvironment of pediatric MB is non-inflammatory and does not recruit many immune cells. These observations provide important considerations for the design of immunotherapeutic approaches for MB, such as inducing more lymphocytes into the tumor microenvironment.
Keywords:cytokine; immune microenvironment; medulloblastoma; tumor-associated macrophage; tumor-infiltrating lymphocyte.