epz-6438 and Brain-Neoplasms

Topics: Adolescent; Animals; Antineoplastic Combined Chemotherapy Protocols; Benzamides; Biphenyl Compounds; Brain Neoplasms; Chemoradiotherapy; Child; Cisplatin; Combined Modality Therapy; Drug Evaluation, Preclinical; Enhancer of Zeste Homolog 2 Protein; Enzyme Inhibitors; Female; Gene Expression Profiling; Humans; Infant; Male; Mice, Inbred NOD; Mice, SCID; Morpholines; Pyridones; Radiotherapy Dosage; Xenograft Model Antitumor Assays

Medulloblastoma (MB) is the most common malignant brain tumor in children and among the subtypes, Group 3 MB has the worst outcome. Here, we perform an in vivo, patient-specific screen leading to the identification of Otx2 and c-MYC as strong Group 3 MB inducers. We validated our findings in human cerebellar organoids where Otx2/c-MYC give rise to MB-like organoids harboring a DNA methylation signature that clusters with human Group 3 tumors. Furthermore, we show that SMARCA4 is able to reduce Otx2/c-MYC tumorigenic activity in vivo and in human cerebellar organoids while SMARCA4 T910M, a mutant form found in human MB patients, inhibits the wild-type protein function. Finally, treatment with Tazemetostat, a EZH2-specific inhibitor, reduces Otx2/c-MYC tumorigenesis in ex vivo culture and human cerebellar organoids. In conclusion, human cerebellar organoids can be efficiently used to understand the role of genes found altered in cancer patients and represent a reliable tool for developing personalized therapies.

Topics: Benzamides; Biphenyl Compounds; Brain Neoplasms; Carcinogenesis; Cell Line, Tumor; Cerebellar Neoplasms; DNA Helicases; DNA Methylation; Enhancer of Zeste Homolog 2 Protein; Gene Expression Regulation, Neoplastic; Humans; Medulloblastoma; Morpholines; Nuclear Proteins; Organoids; Otx Transcription Factors; Proto-Oncogene Proteins c-myc; Pyridones; Stem Cells; Transcription Factors

Diffuse intrinsic pontine glioma (DIPG) is an aggressive brain tumor that is located in the pons and primarily affects children. Nearly 80% of DIPGs harbor mutations in histone H3 genes, wherein lysine 27 is substituted with methionine (H3K27M). H3K27M has been shown to inhibit polycomb repressive complex 2 (PRC2), a multiprotein complex responsible for the methylation of H3 at lysine 27 (H3K27me), by binding to its catalytic subunit EZH2. Although DIPGs with the H3K27M mutation show global loss of H3K27me3, several genes retain H3K27me3. Here we describe a mouse model of DIPG in which H3K27M potentiates tumorigenesis. Using this model and primary patient-derived DIPG cell lines, we show that H3K27M-expressing tumors require PRC2 for proliferation. Furthermore, we demonstrate that small-molecule EZH2 inhibitors abolish tumor cell growth through a mechanism that is dependent on the induction of the tumor-suppressor protein p16

Topics: Animals; Benzamides; Biphenyl Compounds; Brain Neoplasms; Brain Stem Neoplasms; Cell Line, Tumor; Cell Proliferation; Chromatin Immunoprecipitation; Chromatography, Liquid; CRISPR-Cas Systems; Cyclin-Dependent Kinase Inhibitor p16; Disease Models, Animal; Enhancer of Zeste Homolog 2 Protein; Gene Knockout Techniques; Glioblastoma; Glioma; Histones; Humans; Immunohistochemistry; In Situ Hybridization, Fluorescence; Indazoles; Mice; Mice, SCID; Molecular Targeted Therapy; Morpholines; Mutation; Neoplasm Transplantation; Neural Stem Cells; Polycomb Repressive Complex 2; Pyridones; Tandem Mass Spectrometry; Tumor Suppressor Protein p14ARF

Glioblastoma multiforme (GBM) and diffuse intrinsic pontine glioma (DIPG) belong to the most aggressive cancers in children with poor prognosis and limited therapeutic options. Therapeutic targeting of epigenetic proteins may offer new treatment options. Preclinical studies identified Enhancer of Zeste Homolog 2 (EZH2) within polycomb repressor complex 2 (PRC2) as a potential epigenetic anti-tumor target in adult GBM cells but similar inhibition studies in pediatric GBM/DIPG were still missing. Moreover, approximately 30% of pediatric high grade gliomas (pedHGG) including GBM and DIPG harbor a lysine 27 mutation (K27M) in histone 3.3 (H3.3) which is correlated with poor outcome and was shown to influence EZH2 function.. The present study investigated the correlation of expression of EZH2 and other PRC2 genes (EZH1, SUZ12, EED) with overall survival of pediatric GBM patients and the cytotoxic impact of EZH2 inhibition by the novel agent Tazemetostat in pediatric GBM/DIPG cells harboring either a H3.3 mutation or a H3 wildtype.. EZH2 gene expression does not correlate with survival of pedHGG patients, and EZH2 inhibition does not induce significant cytotoxicity in pedHGG cells independently of H3.3 mutations.. We suggest that EZH2 inhibition might not offer an effective single agent treatment option for paedHGG patients. However, the therapeutic efficacy in combination with cytotoxic and/or other epigenetically active agents still has to be elucidated.

Topics: Adolescent; Benzamides; Biphenyl Compounds; Brain Neoplasms; Cell Line, Tumor; Cell Survival; Child; Child, Preschool; DNA Mutational Analysis; Enhancer of Zeste Homolog 2 Protein; Epigenesis, Genetic; Female; Gene Expression Regulation; Glioblastoma; Glioma; Histones; Humans; Male; Morpholines; Pyridones; Statistics as Topic; Tumor Cells, Cultured; Young Adult