Mutant Diffuse Midline Glioma Research Articles

RARE-37. TREATMENT OF H3K27M MUTANT GLIOMAS WITH PANOBINOSTAT

Abstract Panobinostat (PBST) is a histone deacetylase inhibitor with biologic rationale in the treatment of gliomas harboring H3 K27M mutation. METHODS We performed a retrospective medical record review of adult patients with H3 K27M mutant diffuse midline glioma treated with PBST at Mayo Clinic (Rochester, MN). RESULTS Four patients were identified with a mean age 40 years (range 22–62 years). Tumor location was: spinal cord (thoracic n=1, cervical n=1), brainstem (n=1), and thalamus (n=1).Two patients underwent biopsy alone while two underwent a partial resection. Three patients were treated with radiation (36–54 Gy) immediately prior to PBST monotherapy, and one patient was treated with PBST monotherapy without preceding radiation. All patients were otherwise chemotherapy naïve and did not receive any concurrent chemotherapy with PBST. PBST was dosed at either 10 mg (n=1) or 20mg (n=3) administered on days 1, 3, 5, 8, 10 and 12 of 21 day cycles. The mean duration of PBST therapy was 5 months (range 2–11 months). PBST was well tolerated overall. One patient experienced an objective response per RANO criteria. Two patients continue on therapy (5 cycles, 12 cycles) with stable disease. One patient rapidly progressed after 2 cycles of PBST therapy. In contrast with the patients who derived benefit from PBST, this patient was younger (22) and had multifocal disease with leptomeningeal involvement at treatment onset. The average progression free survival post PBST initiation was 8 months. CONCLUSION This single institution case series shows promise that PBST may have therapeutic benefit in adult patients with H3 K27M mutant diffuse midline glioma.

Abstract 958: Anti-GD2 chimeric antigen receptor T cells as a potent immunotherapy regimen in xenograft models of histone 3 K27M mutant diffuse midline glioma

Abstract Histone 3 K27M mutated diffuse midline glioma (H3K27M DMG) is a universally fatal pediatric brain tumor. Despite improved understanding of the molecular origins of this disease, translations to improvement in clinical outcomes have yet to materialize. To date, there has been little target exploration for immunotherapy applications in H3K27M DMG. Here we report substantial preclinical efficacy of chimeric antigen receptor (CAR)-bearing T cells targeting the disialoganglioside GD2 in patient-derived orthotopic xenograft models of H3K27M DMG. GD2 is highly and uniformly expressed in patient-derived H3K27M DMG cultures, and in vitro assays demonstrate substantial target-dependent cytokine generation and target cell killing. Two H3 WT pediatric high-grade gliomas (HGG) cultures do not express significant levels of GD2, and the H3K27M mutation is associated with increased synthesis of ganglioside pathway synthesis enzymes, suggesting expression of the GD2 antigen is driven by H3K27M-induced transcriptional dysregulation. Single-dose systemic administration of GD2-4-1BBz-CAR T cells in multiple orthotopic xenograft models of H3K27M DMG achieves potent and lasting antitumor efficacy within a 4-week period of administration compared to a CD19-4-1BBz-CAR T cell control cohort. In brainstem xenografts, GD2-CAR T cell therapy cleared established tumor as measured by in vivo bioluminescence imaging and follow-up histology, and significantly prolonged survival. Using a fluorescently-labeled GD2-CAR, we demonstrate tumoricidal GD2-CAR T cells infiltrating the brain parenchyma and sparing of local neurons during tumor clearing. Treatment-associated neuroinflammation in brainstem xenografts is accompanied by transient ventriculomegaly due to swelling of the targeted tumors, which is accompanied by transient weight loss followed by full recovery. Similar swelling in thalamic xenograft models is lethal in a significant fraction of animals, presumably due to uncal herniation. These results demonstrate potent antitumor effects of GD2-directed CAR T cells in H3K27M DMG, and suggest an important role for neuroanatomic site in neurotoxicity associated with CAR T cell therapy. If these results are predictive of human response, GD2-directed CAR T cell therapy in the setting of careful clinical management could have a transformative impact upon H3K27M DMG outcomes. Citation Format: Christopher W. Mount, Robbie Majzner, Shree Sundaresh, Evan P. Arnold, Meena Kadapakkam, Samuel Haile, Louai Labanieh, Pamelyn Woo, Skyler P. Rietberg, Hannes Vogel, Michelle Monje, Crystal L. Mackall. Anti-GD2 chimeric antigen receptor T cells as a potent immunotherapy regimen in xenograft models of histone 3 K27M mutant diffuse midline glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 958.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

H3 K27M–mutant diffuse midline gliomas in different anatomical locations

The histone H3 K27M mutation has been frequently reported in most diffuse midline gliomas. However, the relationship between the H3 K27M mutation and clinical outcomes of gliomas from different anatomical locations is still not fully understood. A total of 120 patients with diffuse midline gliomas were selected for this retrospective observational study. The status of H3 K27M, ATRX, TP53, and IDH was evaluated using immunohistochemistry and Sanger sequencing. Of the 120 patients aged from 4 to 76 years (median, 27 years), 61 (50.8%) were harboring the H3 K27M mutation. Tumors were mainly located in the brainstem, ATRX thalamus, and spinal cord, but also in the cerebellum, corpus callosum, and the lateral ventricle. Patients with H3 K27M-mutant diffuse midline gliomas had a significantly shorter overall survival than H3 wild-type counterparts (P = .001). However, the H3 K27M mutation was mainly associated with a poorer prognosis in infratentorial gliomas compared with the corresponding H3 wild-type gliomas (P < .0001), but not in supratentorial gliomas (P = .603). Moreover, patients with H3 K27M-mutant gliomas in unusual anatomical locations had a better prognosis than did those with corresponding tumors in the brainstem. This study may provide guidance for better treatment stratification decisions for diffuse gliomas bearing the H3 K27M mutation, which arise in different locations of the brainstem, thalamus, spinal cord, or other sites.

Abstract PL05-03: Histone-3K27M mutant diffuse midline gliomas of childhood: Epigenetic pathogenesis and therapeutic opportunities

Abstract High-grade gliomas of childhood occur in a striking spatiotemporal pattern, with tumors of the midline occurring chiefly in the first decade of life and tumors of the cerebral lobes occurring later in adolescence and young adulthood. This pattern of gliomagenesis bespeaks dysregulation of a developmental process, and maps well onto discrete waves of developmental myelination of the nervous system, a process that spans over 3 decades in humans. Increasing data from our group and from others implicate myelin-forming precursor cells as putative cells of origin for the most common and best-studied diffuse midline glioma, diffuse intrinsic pontine glioma (DIPG). DIPG is a fatal pediatric cancer peaking in incidence at age 6-7 years with a median survival of only 9 months and 5-year survival of less than 1%. DIPG affects 300-400 children each year in the US and represents the leading cause of brain tumor-related death in children. Therapeutic options are limited, and effective treatment is direly needed. During the early part of this decade, next-generation sequencing technologies enabled a comprehensive view of the DIPG genome. DIPG and other diffuse gliomas of the midline structures of the central nervous system, in particular the thalamus and spinal cord, exhibit a specific and highly recurrent mutation in histone-3 (H3K27M). The H3K27M mutation, occurring in genes encoding histone H3.3 and H3.1, affect ~80% of DIPG cases and the majority of thalamic and spinal cord gliomas as well. The H3K27M mutation causes perturbation of Polycomb repressive complex 2 (PRC2) function, resulting in global hypomethylation of K27 in all H3 variants. The broad epigenetic dysregulation and characteristic gene expression changes that ensue are believed to be central to DIPG oncogenesis. We have generated a panel of patient-derived DIPG cultures and correlate orthotopic xenograft models and have used these new resources for drug screening efforts. DIPG cells are vulnerable to HDAC inhibition, which we found restores H3 trimethyl mark and normalizes gene expression, an unexpected finding that may be explained by actetyl groups on nearby residues sterically interfering with the interaction between PRC2 and the aberrant methionine. We have also found that DIPG is vulnerable to transcriptional disruption using bromodomain inhibition or CDK7 blockade. Targeting oncogenic transcription through either of these methods synergizes with HDAC inhibition, and DIPG cells resistant to HDAC inhibitor therapy retain sensitivity to CDK7 blockade. A clinical trial of panobinostat for DIPG is ongoing, and follow-on trials of combination therapy hold promise. Other forms of diffuse midline gliomas, including H3K27M-mutant gliomas of the spinal cord and thalamus, may respond similarly to therapeutic strategies targeting the regulation of gene expression. Identification of super-enhancers in DIPG highlights oligodendroglial lineage genes, supporting the hypothesis that precursor cells in the oligodendroglial lineage are the cell of origin, and reveals unexpected mechanisms mediating tumor viability and invasion, including potassium channel function and EPH receptor signaling. Also highlighted by super-enhancer analysis are genes traditionally involved in neuronal communication. Normal oligodendroglial lineage precursor cell function is critically regulated by interactions with active neurons during development and as part of ongoing neural plasticity. We have recently shown that neuronal activity robustly promotes the proliferation of both normal and neoplastic glial cells. A key mechanism mediating neuronal influences on glioma growth is the activity-regulated secretion of the synaptic protein neuroligin-3 into the glioma microenvironment. Blocking neuroligin-3 secretion by inhibiting the enzyme responsible for its cleavage and release from normal synapses has proven robustly effective in slowing the growth of DIPG and other gliomas in preclinical models. Targeting neuron-glioma interactions represents a promising and largely unexplored avenue for glioma therapy. A therapeutic strategy is thus emerging that involves a multipronged approach, targeting the cell-intrinsic vulnerabilities of histone-3 mutant gliomas together with key microenvironmental targets central to glioma growth and progression. Increasingly effective therapy for these deadly brain cancers of childhood will be enabled by answers to outstanding basic questions, such as why H3K27M-mutant gliomas occur only in midline structures, how the tumors hijack mechanisms of normal neural development and plasticity, and what mechanisms the tumor utilizes to evolve resistance to therapy. Citation Format: Michelle Monje. Histone-3K27M mutant diffuse midline gliomas of childhood: Epigenetic pathogenesis and therapeutic opportunities [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr PL05-03.