Diffuse intrinsic pontine gliomas (DIPG) are the most aggressive brain tumors in children with 5-year survival rates of only 2%. About 85% of all DIPG are characterized by a lysine-to-methionine substitution in histone 3, which leads to global H3K27 hypomethylation accompanied by H3K27 hyperacetylation. Hyperacetylation in DIPG favors the action of the Bromodomain and Extra-Terminal (BET) protein BRD4, and leads to the reprogramming of the enhancer landscape contributing to the activation of DIPG super enhancer-driven oncogenes. The activity of the acetyltransferase CREBbinding protein (CBP) is enhanced by BRD4 and associated with acetylation of nucleosomes at super enhancers (SE). In addition, CBP contributes to transcriptional activation through its function as a scaffold and protein bridge. Monotherapy with either a CBP (ICG-001) or BET inhibitor (JQ1) led to the reduction of tumor-related characteristics. Interestingly, combined treatment induced strong cytotoxic effects in H3.3K27M-mutated DIPG cell lines. RNA sequencing and chromatin immunoprecipitation revealed that these effects were caused by the inactivation of DIPG SE-controlled tumor-related genes. However, single treatment with ICG-001 or JQ1, respectively, led to activation of a subgroup of detrimental super enhancers. Combinatorial treatment reversed the inadvertent activation of these super enhancers and rescued the effect of ICG-001 and JQ1 single treatment on enhancer-driven oncogenes in H3K27Mmutated DIPG, but not in H3 wild-type pedHGG cells. In conclusion, combinatorial treatment with CBP and BET inhibitors is highly efficient in H3K27M-mutant DIPG due to reversal of inadvertent activation of detrimental SE programs in comparison with monotherapy.
Background The WHO Classification of Tumors of the Central Nervous System has undergone major restructuring. Molecularly defined diagnostic criteria were introduced in 2016 (revised 4th edition) and expanded in 2021 (5th edition) to incorporate further essential diagnostic molecular parameters. We investigated potential differences between specialists in perception of these molecularly defined subtypes for pediatric high-grade gliomas (pedHGG). Methods We designed a 22-question survey studying the impact of the revised 4th edition of the WHO classification on pedHGG. Data were collected and statistically analyzed to examine the spectrum of viewpoints and possible differences between neuro-oncologists and neuropathologists. Results 465 participants from 53 countries were included; 187 pediatric neuro-oncologists (40%), 160 neuropathologists (34%), and 118 additional experts (26%). Neuro-oncologists reported issues with the introduction of molecularly defined tumor types, as well as the abolishment or renaming of established tumor entities, while neuropathologists did not to the same extent. Both groups indicated less relevant or insufficient diagnostic definitions were available in 2016. Reported issues were classified and assessed in the 2021 WHO classification and a substantial improvement was perceived. However, issues of high clinical relevance remain to be addressed, including the definition of clinical phenotypes for diffuse intrinsic pontine glioma and gliomatosis cerebri. Conclusions Within the WHO classification of pediatric brain tumors, such as pedHGG, rapid changes in molecular characterization have been introduced. This study highlights the ongoing need for cross talk between pathologist and oncologist to advance the classification of pedHGG subtypes and ensure biological relevance and clinical impact.
Beckwith-Wiedemann spectrum, Simpson-Golabi-Behmel syndrome, familial adenomatous polyposis and trisomy 18 are the most common congenital conditions associated with an increased incidence of hepatoblastoma (HB). In patients with these genetic disorders, screening protocols for HB are proposed that include periodic abdominal ultrasound and measurement of alpha-fetoprotein levels. Surveillance in these children may contribute to the early detection of HB and possibly improve their chances of overall survival. Therefore, physicians must be aware of the high HB incidence in children with certain predisposing genetic diseases.
Purpose As there is no standard of care treatment for recurrent/progressing pediatric high-grade gliomas (pHGG), we aimed to gain an overview of different treatment strategies. Methods In a web-based questionnaire, members of the SIOPE-BTG and the GPOH were surveyed on therapeutic options in four case scenarios (children/adolescents with recurrent/progressing HGG). Results 139 clinicians with experience in pediatric neuro-oncology from 22 European countries participated in the survey. Most respondents preferred further oncological treatment in three out of four cases and chose palliative care in one case with marked symptoms. Depending on the case, 8–92% would initiate a re-resection (preferably hemispheric pHGG), combined with molecular diagnostics. Throughout all case scenarios, 55–77% recommended (re-)irradiation, preferably local radiotherapy > 20 Gy. Most respondents would participate in clinical trials and use targeted therapy (79–99%), depending on molecular genetic findings (BRAF alterations: BRAF/MEK inhibitor, 64–88%; EGFR overexpression: anti-EGFR treatment, 46%; CDKN2A deletion: CDK inhibitor, 18%; SMARCB1 deletion: EZH2 inhibitor, 12%). 31–72% would administer chemotherapy (CCNU, 17%; PCV, 8%; temozolomide, 19%; oral etoposide/trofosfamide, 8%), and 20–69% proposed immunotherapy (checkpoint inhibitors, 30%; tumor vaccines, 16%). Depending on the individual case, respondents would also include bevacizumab (6–18%), HDAC inhibitors (4–15%), tumor-treating fields (1–26%), and intraventricular chemotherapy (4–24%). Conclusion In each case, experts would combine conventional multimodal treatment concepts, including re-irradiation, with targeted therapy based on molecular genetic findings. International cooperative trials combining a (chemo-)therapy backbone with targeted therapy approaches for defined subgroups may help to gain valid clinical data and improve treatment in pediatric patients with recurrent/progressing HGG.
The aim of the HIT-HGG-2007 trial (ISRCTN19852453) was to demonstrate therapeutic non-inferiority of temozolomide radiochemotherapy for pediatric patients (3-18 years) with high-grade gliomas (pedHGG) in comparison to the cisplatinum-based radiochemotherapy of the two previous clinical trials HIT-GBM-C/-D. Between 06/2009 and 12/2016, 456 patients were enrolled at 79 centers in Germany, Austria, and Switzerland (n=18 dropouts, remaining patients for confirmatory analysis: n=438). 438 patients from HIT-GBM-C/-D served as historical control. All pedHGG diagnoses had been confirmed by central neuroradiological and neuropathological review. Primary objective was achieved since non-inferiority of HIT-HGG-2007 in comparison to HIT-GBM-C/-D as indicated by 6 months event-free survival (EFS) was statistically confirmed (p=0.0125). Statistical survival analyses even revealed a better overall survival (OS) and EFS for HIT-HGG-2007 patients in comparison to their HIT-GBM-C/-D counterparts (EFS: p<0.0001; OS: p=0.0328). While EFS subgroup analyses for pontine and non-pontine pedHGG also showed a better survival of HIT-HGG-2007 patients (median EFS pontine pedHGG: 8.2 (n=152; confidence interval (CI): 7.6-9.4) versus 6.2 (n=170; CI: 5.5-6.9) months, p=0.0079; median EFS non-pontine pedHGG: 10.7 (n=276; CI: 9.6-12.4) versus 7.4 (n=267; CI: 6.4-9.2) months, p<0.0001), OS was only improved in HIT-HGG-2007 patients with non-pontine pedHGG (median OS non-pontine pedHGG: 19.3 (CI: 16.8-23.3) versus 16.2 (CI: 14.2-19.1) months; p=0.0181) but not with pontine pedHGG (median OS pontine pedHGG: 11.4 months versus 11.3 months, p=0.4021) Toxicity profile of HIT-HGG-2007 seemed very favorable with most CTCAE (common toxicity criteria adverse event) ≥ grade 3 as hematological toxicity, hepatotoxicity, and neurotoxicity. Less toxicity was observed during concomitant radiochemotherapy in comparison to HIT-GBM-C/-D. Further subgroup survival analyses as well as the assessment of the impact of MGMT promoter methylation are ongoing. In conclusion, our data show non-inferiority of the HIT-HGG-2007 trial with increased survival and less toxicity when compared with previous trials HIT-GBM-C/-D.
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