cIMPACT‐NOW (the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy) was established to provide a forum to evaluate and recommend proposed changes to future CNS tumor ...classifications. From 2016 to 2019 (Round 1), cIMPACT published four updates. Update 1 clarified the use of the term NOS (Not Otherwise Specified) and proposed use of the additional term NEC (Not Elsewhere Classified). Update 2 issued clarifications regarding two diagnoses: Diffuse Midline Glioma, H3 K27M‐mutant and Diffuse Astrocytoma/Anaplastic Astrocytoma, IDH‐mutant. Update 3 proposed molecular criteria that could be used in the setting of an IDH‐wildtype diffuse or anaplastic astrocytic glioma without histological features of glioblastoma to infer that the tumor would behave similarly to a grade IV glioblastoma. Update 4 suggested that, in children and young adults, subtypes of IDH‐wildtype/H3‐wildtype diffuse gliomas may have distinct clinical features in the setting of a BRAFV600E mutation, FGFR1 alteration, other MAPK pathway alteration, or a MYB or MYBL1 rearrangement. The practical diagnostic relevance of these cIMPACT proposals is highlighted in this summary.
The recent publication of the 2016 World Health Organization Classification of Tumors of the Central Nervous System (2016 CNS WHO) represents a significant advance in the classification of human ...brain tumors 1. For the first time, a CNS WHO classification defines diagnostic entities by combining molecular and histological information. In doing so, the classification facilitates more precise diagnosis of well-understood entities and clearer designation of less-understood entities, which will in turn allow further study and likely future advances in their classifications.
Epigenetic silencing of the O6‐methylguanine‐DNA methyltransferase (MGMT) gene promoter is associated with prolonged survival in glioblastoma patients treated with temozolomide (TMZ). We investigated ...whether glioblastoma recurrence is associated with changes in the promoter methylation status and the expression of MGMT and the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2 in pairs of primary and recurrent glioblastomas of 80 patients, including 64 patients treated with radiotherapy and TMZ after the first operation. Among the primary tumors, the MGMT promoter was methylated in 31 patients and unmethylated in 49 patients. In 71 patients (89%), the MGMT promoter methylation status of the primary tumor was retained at recurrence. MGMT promoter methylation, but not MGMT protein expression, was associated with longer progression‐free survival, overall survival and postrecurrence survival (PRS). Moreover, PRS was increased under salvage chemotherapy. Investigation of primary and recurrent glioblastomas of 43 patients did not identify promoter methylation in any of the four MMR genes. However, recurrent glioblastomas demonstrated significantly lower MSH2, MSH6 and PMS2 protein expression as detected by immunohistochemistry. In conclusion, reduced expression of MMR proteins, but not changes in MGMT promoter methylation, is characteristic of glioblastomas recurring after the current standards of care.
Mutations in the IDH1 and IDH2 genes encoding isocitrate dehydrogenases are frequently found in human glioblastomas and cytogenetically normal acute myeloid leukaemias (AML). These alterations are ...gain-of-function mutations in that they drive the synthesis of the ‘oncometabolite’ R-2-hydroxyglutarate (2HG). It remains unclear how IDH1 and IDH2 mutations modify myeloid cell development and promote leukaemogenesis. Here we report the characterization of conditional knock-in (KI) mice in which the most common IDH1 mutation, IDH1(R132H), is inserted into the endogenous murine Idh1 locus and is expressed in all haematopoietic cells (Vav-KI mice) or specifically in cells of the myeloid lineage (LysM-KI mice). These mutants show increased numbers of early haematopoietic progenitors and develop splenomegaly and anaemia with extramedullary haematopoiesis, suggesting a dysfunctional bone marrow niche. Furthermore, LysM-KI cells have hypermethylated histones and changes to DNA methylation similar to those observed in human IDH1- or IDH2-mutant AML. To our knowledge, our study is the first to describe the generation and characterization of conditional IDH1(R132H)-KI mice, and also the first report to demonstrate the induction of a leukaemic DNA methylation signature in a mouse model. Our report thus sheds light on the mechanistic links between IDH1 mutation and human AML.
Gliomas are the most common primary brain tumors in children and adults. We recently identified frequent alterations in chromatin remodelling pathways including recurrent mutations in
H3F3A
and ...mutations in
ATRX
(α-thalassemia/mental-retardation-syndrome-X-linked) in pediatric and young adult glioblastoma (GBM, WHO grade IV astrocytoma).
H3F3A
mutations were specific to pediatric high-grade gliomas and identified in only 3.4 % of adult GBM. Using sequencing and/or immunohistochemical analyses, we investigated ATRX alterations (mutation/loss of expression) and their association with
TP53
and
IDH1
or
IDH2
mutations in 140 adult WHO grade II, III and IV gliomas, 17 pediatric WHO grade II and III astrocytomas and 34 pilocytic astrocytomas. In adults, ATRX aberrations were detected in 33 % of grade II and 46 % of grade III gliomas, as well as in 80 % of secondary and 7 % of primary GBMs. They were absent in the 17 grade II and III astrocytomas in children, and the 34 pilocytic astrocytomas. ATRX alterations closely overlapped with mutations in
IDH1
/
2
(
p
< 0.0001) and
TP53
(
p
< 0.0001) in samples across all WHO grades. They were prevalent in astrocytomas and oligoastrocytomas, but were absent in oligodendrogliomas (
p
< 0.0001). No significant association of ATRX mutation/loss of expression and alternative lengthening of telomeres was identified in our cohort. In summary, our data show that ATRX alterations are frequent in adult diffuse gliomas and are specific to astrocytic tumors carrying
IDH1
/
2
and
TP53
mutations. Combined alteration of these genes may contribute to drive the neoplastic growth in a major subset of diffuse astrocytomas in adults.
To investigate whether TP53 mutation, 1p/19q codeletions, O(6)-methylguanylmethyltransferase (MGMT) promoter methylation, and isocitrate dehydrogenase 1 (IDH1) mutation predict natural course of ...disease or response to radiotherapy or chemotherapy or both in low-grade glioma patients.
Cohort A consisted of 89 patients with diffuse astrocytoma World Health Organization (WHO) grade II (n = 40), oligoastrocytoma (n = 23), or oligodendroglioma (n = 26) who did not receive radiotherapy or chemotherapy after first operation and were monitored until progression progressive disease (PD); n = 59 and beyond or until the end of follow-up (n = 30). Cohort B consisted of 50 patients with WHO grade II gliomas who received radiotherapy or chemotherapy at diagnosis. Tumors were analyzed for TP53 mutations, 1p/19q codeletions, MGMT promoter methylation, and IDH1 mutations.
Median progression-free survival (PFS) in cohort A was 4.1 years (95% CI: 3.1-5.1). No molecular marker was prognostic for PFS after surgery alone, using multivariate adjustment for histology, age, and extent of resection. IDH1 mutations were associated with prolonged survival from the diagnosis of PD in oligoastrocytomas (OA II)/oligodendrogliomas (O II) and with overall survival (OS) in all tumors. 1p/19q codeletion and IDH1 mutation were prognostic for PFS and OS in cohort B.
None of the parameters are sensitive prognostic biomarkers in WHO grade II glioma patients who do not receive radiotherapy or chemotherapy after surgery. Limitations of this study include the selection of patients with favorable outcome, the nonrandomized allocation of treatment, and the insufficient sample size to distinguish between effects of radiotherapy versus chemotherapy. Regardless of histology, IDH1 mutation status is the strongest prognostic marker for OS.
The outcome of patients with anaplastic gliomas varies considerably. Whether a molecular classification of anaplastic gliomas based on large-scale genomic or epigenomic analyses is superior to ...histopathology for reflecting distinct biological groups, predicting outcomes and guiding therapy decisions has yet to be determined. Epigenome-wide DNA methylation analysis, using a platform which also allows the detection of copy-number aberrations, was performed in a cohort of 228 patients with anaplastic gliomas (astrocytomas, oligoastrocytomas, and oligodendrogliomas), including 115 patients of the NOA-04 trial. We further compared these tumors with a group of 55 glioblastomas. Unsupervised clustering of DNA methylation patterns revealed two main groups correlated with
IDH
status: CpG island methylator phenotype (CIMP) positive (77.5 %) or negative (22.5 %). CIMP
pos
(
IDH
mutant) tumors showed a further separation based on copy-number status of chromosome arms 1p and 19q. CIMP
neg
(
IDH
wild type) tumors showed hallmark copy-number alterations of glioblastomas, and clustered together with CIMP
neg
glioblastomas without forming separate groups based on WHO grade. Notably, there was no molecular evidence for a distinct biological entity representing anaplastic oligoastrocytoma. Tumor classification based on CIMP and 1p/19q status was significantly associated with survival, allowing a better prediction of outcome than the current histopathological classification: patients with CIMP
pos
tumors with 1p/19q codeletion (CIMP-codel) had the best prognosis, followed by patients with CIMP
pos
tumors but intact 1p/19q status (CIMP-non-codel). Patients with CIMP
neg
anaplastic gliomas (GBM-like) had the worst prognosis. Collectively, our data suggest that anaplastic gliomas can be grouped by
IDH
and 1p/19q status into three molecular groups that show clear links to underlying biology and a significant association with clinical outcome in a prospective trial cohort.
Molecular genetic aberrations in the phosphoinositide 3‐kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway are common in human cancers including glioblastoma, yet, ...novel therapeutic approaches targeting this pathway in glioblastoma have not been successful. We hypothesized that molecular profiling in combination with in vitro drug sensitivity testing allows to identify signatures associated with sensitivity or resistance to PI3K/mTOR pathway inhibition. We analyzed the molecular mechanisms determining sensitivity to PI3K/mTOR inhibition using gene silencing or pharmacological target inhibition and proliferation, clonogenicity, or spherogenicity as readouts, in human long‐term glioma cell (LTC) lines and glioma‐initiating cells (GIC). Cultured glioma cells were universally sensitive to growth inhibition induced by PQR309, a novel, dual pan‐PI3K/mTOR antagonist. Cells exhibited profound growth arrest, but little apoptotic or necrotic cell death as confirmed by electron microscopy; yet, there was evidence of senescence. Cell lines with high basal levels of phosphorylated (active) AKT, low levels of phosphorylated (inactive) protein translation repressor eukaryotic initiation factor (eIF) 4E‐binding protein 1 (p4E‐BP1), and high levels of Ser9‐phosphorylated (inactive) glycogen synthase kinase 3 beta (pGSK3β) were more sensitive to PQR309. Accordingly, the activity of PQR309 was synergistically enhanced by AKT gene silencing or direct pharmacological AKT inhibition. In vivo studies confirmed the anti‐glioma activity of PQR309 alone or in combination with AKT inhibition in the orthotopic LN‐229 glioma xenograft model in nude mice. These data justify to explore combined targeted therapy approaches in glioblastoma that aim at down‐regulating AKT function to enhance the therapeutic potential of dual PI3K/mTOR inhibitors.
Molecular genetic aberrations in the PI3K/AKT/mTOR pathway are common in glioblastoma. We hypothesized that molecular profiling in combination with in vitro drug sensitivity testing may allow to identify signatures associated with sensitivity or resistance to PI3K/mTOR pathway inhibition. Cell lines with high basal levels of phosphorylated (active) AKT, low levels of phosphorylated (inactive) protein translation repressor 4E‐BP1, and high levels of Ser9‐phosphorylated (inactive) GSK3β were more sensitive to PQR309, a dual pan‐PI3K/mTOR antagonist in vitro.
PDF
