Topoisomerase IIβ immunoreactivity (IR) co-localizes with neuronal marker-IR but not glial fibrillary acidic protein-IR in GLI3-positive medulloblastomas: an immunohistochemical analysis of 124 medulloblastomas from the Japan Children's Cancer Group.

We previously reported observing GLI3 in medulloblastomas expressing neuronal markers (NM) and/or glial fibrillary acidic protein (GFAP). Furthermore, patients with medulloblastomas expressing NM or GFAP tended to show favorable or poor prognosis, respectively. In the present study, we focused on the role of topoisomerase IIβ (TOP2β) as a possible regulator for neuronal differentiation in medulloblastomas and examined the pathological roles of GLI3, NM, GFAP, and TOP2β expressions in a larger population. We divided 124 medulloblastomas into three groups (NM-/GFAP-, NM +/GFAP-, and GFAP +) based on their immunoreactivity (IR) against NM and GFAP. The relationship among GLI3, NM, GFAP, and TOP2β was evaluated using fluorescent immunostaining and a publicly available single-cell RNA sequencing dataset. In total, 87, 30, and 7 medulloblastomas were classified as NM-/GFAP-, NM + /GFAP-, and GFAP +, and showed intermediate, good, and poor prognoses, respectively. GLI3-IR was frequently observed in NM +/GFAP-  and GFAP + , and TOP2β-IR was frequently observed only in NM +/GFAP-  medulloblastomas. In fluorescent immunostaining, TOP2β-IR was mostly co-localized with NeuN-IR but not with GFAP-IR. In single-cell RNA sequencing, TOP2β expression was elevated in CMAS/DCX-positive, but not in GFAP-positive, cells. NM-IR and GFAP-IR are important for estimating the prognosis of patients with medulloblastoma; hence they should be assessed in clinical practice.