Purpose: Pediatric recurrent medulloblastoma and atypical teratoid/rhabdoid tumor (ATRT) are largely incurable and warrant novel therapies. PNOC005 is a phase I clinical trial investigating the safety and tolerability of intratumoral or intrathecal administration of oncolytic measles virus (MV-NIS) in children and young adults with recurrent medulloblastoma or ATRT. Patients and Methods: We investigated (i) the safety of a measles virus variant, MV-NIS, in a pediatric phase I study and (ii) the mechanisms of MV-NIS and the potential benefit of combination with immune checkpoint inhibition (ICI). Pediatric patients with recurrent medulloblastoma or ATRT were treated with intratumoral injections for local recurrence or via lumbar puncture for disseminated recurrence. We evaluated local immune responses to MV-NIS with and without ICI via single-cell and bulk RNA sequencing in an intracranial, immunocompetent, syngeneic murine model. Results: MV-NIS given intratumorally or via repeat intrathecal dosing was safe. MV-NIS prolonged survival in murine models but did not demonstrate an additive benefit with ICI. No changes in tumor-infiltrating immune cell composition or activation were observed in response to MV-NIS treatment; however, MV-NIS induced local expression of neutralizing antibodies, complement cascade, and phagocytosis-related genes. Conclusions: This is the first trial investigating intratumoral as well as repeated intrathecal delivery of MV-NIS in children with medulloblastoma and ATRT. We show that the therapy is safe and well tolerated, with minimal adverse effects. Immune markers and biological correlates preliminarily indicate antiviral effects in tumors.

Diffuse midline glioma (DMG) is the most lethal of all childhood cancers. DMGs are driven by histone-tail-mutation-mediated epigenetic dysregulation and partner mutations in genes controlling proliferation and migration. One result of this epigenetic and genetic landscape is the overexpression of LIN28B RNA binding protein. In other systems, LIN28B has been shown to prevent let-7 microRNA biogenesis; however, let-7, when available, faithfully suppresses tumorigenic pathways and induces cellular maturation by preventing the translation of numerous oncogenes. Here, we review the current literature on LIN28A/B and the let-7 family and describe their role in gliomagenesis. Future research is then recommended, with a focus on the mechanisms of LIN28B overexpression and localization in DMG.

High-grade glial tumors represent the most morbid form of brain cancer

Purpose:Pediatric recurrent medulloblastoma and atypical teratoid/rhabdoid tumor (ATRT) are largely incurable and warrant novel therapies. PNOC005 is a phase I clinical trial investigating the safety and tolerability of intratumoral or intrathecal administration of oncolytic measles virus (MV-NIS) in children and young adults with recurrent medulloblastoma or ATRT.Patients and Methods:We investigated (i) the safety of a measles virus variant, MV-NIS, in a pediatric phase I study and (ii) the mechanisms of MV-NIS and the potential benefit of combination with immune checkpoint inhibition (ICI). Pediatric patients with recurrent medulloblastoma or ATRT were treated with intratumoral injections for local recurrence or via lumbar puncture for disseminated recurrence. We evaluated local immune responses to MV-NIS with and without ICI via single-cell and bulk RNA sequencing in an intracranial, immunocompetent, syngeneic murine model.Results:MV-NIS given intratumorally or via repeat intrathecal dosing was safe. MV-NIS prolonged survival in murine models but did not demonstrate an additive benefit with ICI. No changes in tumor-infiltrating immune cell composition or activation were observed in response to MV-NIS treatment; however, MV-NIS induced local expression of neutralizing antibodies, complement cascade, and phagocytosis-related genes.Conclusions:This is the first trial investigating intratumoral as well as repeated intrathecal delivery of MV-NIS in children with medulloblastoma and ATRT. We show that the therapy is safe and well tolerated, with minimal adverse effects. Immune markers and biological correlates preliminarily indicate antiviral effects in tumors.

Antiseizure medications, such as levetiracetam, are commonly used in glioma patients. Retrospective analyses evaluating effects of antiseizure medications on glioma patient survival have yielded inconsistent results, probably due to confounding factors of glioma subtype and drug class. Here we present retrospective real-world clinical data that demonstrate longer overall survival for children with diffuse midline glioma (DMG) who were taking levetiracetam, which was not evident in pediatric patients with hemispheric high-grade glioma. In preclinical models, levetiracetam reduces glioma proliferation and tumor burden, extending survival of mice bearing DMG orthotopic xenografts. These beneficial effects were not found in hemispheric high-grade glioma patient-derived orthotopic xenograft models. The subtype-specificity of this antiproliferative effect of levetiracetam is congruent with recent findings that GABAergic neuron-to-glioma synapses promote glioma growth in DMG but not hemispheric high-grade glioma. We demonstrate here that levetiracetam attenuates low-frequency GABAergic synaptic transmission in a glioma-specific manner, reducing GABAergic synaptic currents in DMG but not in healthy neurons. This effect is independent of action on SV2A, the chief mechanism by which levetiracetam functions to prevent and treat seizures. Taken together, these findings indicate a promising approach to target GABAergic synapses in DMG and suggest that use of levetiracetam in DMG should be further studied in future prospective clinical studies.

Diffuse midline glioma (DMG) is the most lethal of all childhood cancers. LIN28B is an RNA binding protein expressed in a variety of cancers, which suppresses the let-7 family of microRNAs, which in turn suppresses a plethora of oncogenes. However, the role of LIN28B in DMG has not yet been explored. Therefore, we sought to determine the pattern of expression and potential function of LIN28B in DMG using rare DMG cell lines. All studies were performed on DMG cell lines (n=6) and controls (normal human astrocytes n=1, human neural stem cells n=1). RNA-Seq was performed using single-read sequencing at 50bp on the Illumina NextSeq 500 Sequencing System. Cells were then treated with DMSO or the LIN28B inhibitor, LI71, and submitted to functional in vitro studies, as well as RNA-Seq and Western Blot analysis. Functional pathways analysis was subsequently performed on resulting gene expression values with Ingenuity Pathways Analysis (Qiagen). Differential LIN28B expression was demonstrated across cell lines, with DMG cells expressing greater LIN28B gene and protein levels compared to controls. LIN28B inhibition with small molecule inhibitor LI71 resulted in decreased cell proliferation and migration, in vitro. A total of 946 differentially expressed genes were identified between treatment groups (FC>2 or <-2, p<0.05). Functional pathways analysis of differentially expressed genes implicated Cancer and Neurological Disease as the top disease processes, with Cellular Movement as the top molecular process in cell lines expressing LIN28B. Further, inactivation of Myc signaling was implicated in cells treated with LI71. Our data demonstrates increased LIN28B expression in DMG cell lines compared with controls, with oncogenic effects on cell proliferation and migration. Further investigation of the LIN28B-let7 signaling axis is warranted in order to further explore LIN28B as a novel therapeutic target in DMG.