Grade II and III gliomas are generally slowly progressing brain cancers, many of which eventually transform into more aggressive tumors. Despite recent findings of frequent mutations in IDH1 and ...other genes, knowledge about their pathogenesis is still incomplete. Here, combining two large sets of high-throughput sequencing data, we delineate the entire picture of genetic alterations and affected pathways in these glioma types, with sensitive detection of driver genes. Grade II and III gliomas comprise three distinct subtypes characterized by discrete sets of mutations and distinct clinical behaviors. Mutations showed significant positive and negative correlations and a chronological hierarchy, as inferred from different allelic burdens among coexisting mutations, suggesting that there is functional interplay between the mutations that drive clonal selection. Extensive serial and multi-regional sampling analyses further supported this finding and also identified a high degree of temporal and spatial heterogeneity generated during tumor expansion and relapse, which is likely shaped by the complex but ordered processes of multiple clonal selection and evolutionary events.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, UILJ, UKNU, UL, UM, UPUK
Glioblastoma (GBM), the most common primary brain tumor, is the most aggressive human cancers, with a median survival rate of only 14.6 months. Temozolomide (TMZ) is the frontline chemotherapeutic ...drug in GBM. Drug resistance is the predominant obstacle in TMZ therapy. Drug resistance occurs via multiple pathways such as DNA mismatch repair and base excision repair systems, by which glioma cells acquire chemoresistance to some extent (5% and 95%, respectively). Histone3 Lysin27 residue-acetylation (H3K27ac) status regulates cis-regulatory elements, which increases the likelihood of gene transcription. Histone deacetylase (HDAC) complex deacetylate lysine residues on core histones, leading to a decrease in gene transcription. In cis-regulatory element regions, complexes with HDAC repress histones by H3K27ac deacetylation. The cis-regulating and three-dimensional transcriptional mechanism is called “super-enhancer”. RET finger protein (RFP) is a protein that is expressed in many kinds of cancer. RFP forms a protein complex with HDAC1. The disruption of the RFP–HDAC1 complex has resulted in increased drug sensitivity in other cancers. We conclude that the downregulation of RFP or the disruption of the RFP/HDAC1 complex leads to an increase in TMZ efficacy in glioblastoma by changing histone modifications which lead to changes in cell division, cell cycle and apoptosis.
Isocitrate dehydrogenase-mutant low-grade gliomas (IDHmut-LGG) grow slowly but frequently undergo malignant transformation, which eventually leads to premature death. Chemotherapy and radiotherapy ...treatments prolong survival, but can also induce genetic (or epigenetic) alterations involved in transformation. Here, we developed a mathematical model of tumor progression based on serial tumor volume data and treatment history of 276 IDHmut-LGGs classified by chromosome 1p/19q codeletion (IDH
/1p19q
and IDH
/1p19q
) and performed genome-wide mutational analyses, including targeted sequencing and longitudinal whole-exome sequencing data. These analyses showed that tumor mutational burden correlated positively with malignant transformation rate, and chemotherapy and radiotherapy significantly suppressed tumor growth but increased malignant transformation rate per cell by 1.8 to 2.8 times compared with before treatment. This model revealed that prompt adjuvant chemoradiotherapy prolonged malignant transformation-free survival in small IDHmut-LGGs (≤ 50 cm
). Furthermore, optimal treatment differed according to genetic alterations for large IDHmut-LGGs (> 50 cm
); adjuvant therapies delayed malignant transformation in IDH
/1p19q
but often accelerated it in IDH
/1p19q
. Notably, PI3K mutation was not associated with malignant transformation but increased net postoperative proliferation rate and decreased malignant transformation-free survival, prompting the need for adjuvant therapy in IDH
/1p19q
. Overall, this model uncovered therapeutic strategies that could prevent malignant transformation and, consequently, improve overall survival in patients with IDHmut-LGGs. SIGNIFICANCE: A mathematical model successfully estimates malignant transformation-free survival and reveals a link between genetic alterations and progression, identifying precision medicine approaches for optimal treatment of IDH-mutant low-grade gliomas.
Glioblastoma is one of the most malignant forms of cancer, for which no effective targeted therapy has been found. Although The Cancer Genome Atlas has provided a list of fusion genes in ...glioblastoma, their role in progression of glioblastoma remains largely unknown. To search for novel fusion genes, we obtained RNA‐seq data from TGS‐01 human glioma‐initiating cells, and identified a novel fusion gene (HMGA2‐EGFR), encoding a protein comprising the N‐terminal region of the high‐mobility group AT‐hook protein 2 (HMGA2) fused to the C‐terminal region of epidermal growth factor receptor (EGFR), which retained the transmembrane and kinase domains of the EGFR. This fusion gene product showed transforming potential and a high tumor‐forming capacity in cell culture and in vivo. Mechanistically, HMGA2‐EGFR constitutively induced a higher level of phosphorylated STAT5B than EGFRvIII, an in‐frame exon deletion product of the EGFR gene that is commonly found in primary glioblastoma. Forced expression of HMGA2‐EGFR enhanced orthotopic tumor formation of the U87MG human glioma cell line. Furthermore, the EGFR kinase inhibitor erlotinib blocked sphere formation of TGS‐01 cells in culture and inhibited tumor formation in vivo. These findings suggest that, in addition to gene amplification and in‐frame exon deletion, EGFR signaling can also be activated by gene fusion, suggesting a possible avenue for treatment of glioblastoma.
What's new?
Fusion genes are promising targets for the development of novel drug therapies against glioblastoma. Little is known, however, about their role in the disease. Here, a novel fusion gene, HMGA2‐EGFR, was identified from a human glioblastoma specimen containing glioma‐initiating cells (GICs). Forced expression of the HMGA2‐EGFR fusion protein induced transformation of NIH3T3 fibroblasts and, in glioblastoma cells, induced STAT5B phosphorylation, similar to the known EGFR mutant EGFRvIII. HMGA2‐EGFR overexpression also accelerated the growth of orthotopic U87MG tumors in mice, while the EGFR inhibitor erlotinib suppressed tumor formation by HMGA2‐EGFR‐expressing GICs and prolonged the survival of tumor‐bearing mice.
Comprising more than 80 % of malignant brain tumors, glioma has proven to be a daunting cause of mortality in a vast majority of the human population. Progressive and extensive research on malignant ...glioma has substantially enhanced our understanding of glioma cell biology and molecular pathology. Subtypes of glioma such as astrocytoma and oligodendroglioma are currently grouped together into one pathological class, where they show many differences in histology and molecular etiology. This indicates that it may be beneficial to consider a new and radical subclassification. Thus, we summarize recent developments in glioblastoma multiforme (GBM) subtypes, immunohistochemical analyses useful for diagnoses and the biological evaluation and therapeutic implications of gliomas in this review.
World Health Organization grade II and III gliomas most frequently occur in the central nervous system (CNS) in adults. Gliomas are not circumscribed; tumor edges are irregular and consist of tumor ...cells, normal brain tissue, and hyperplastic reactive glial cells. Therefore, the tumors are not fully resectable, resulting in recurrence, malignant progression, and eventual death. Approximately 69-80% of grade II and III gliomas harbor mutations in the isocitrate dehydrogenase 1 gene (IDH1), of which 83-90% are found to be the IDH1-R132H mutation. Detection of the IDH1-R132H mutation should help in the differential diagnosis of grade II and III gliomas from other types of CNS tumors and help determine the boundary between the tumor and normal brain tissue. In this study, we established a highly sensitive antibody-based device, referred to as the immuno-wall, to detect the IDH1-R132H mutation in gliomas. The immuno-wall causes an immunoreaction in microchannels fabricated using a photo-polymerizing polymer. This microdevice enables the analysis of the IDH1 status with a small sample within 15 min with substantially high sensitivity. Our results suggested that 10% content of the IDH1-R132H mutation in a sample of 0.33 μl volume, with 500 ng protein, or from 500 cells is theoretically sufficient for the analysis. The immuno-wall device will enable the rapid and highly sensitive detection of the IDH1-R132H mutation in routine clinical practice.
Abstract Glioblastoma (GBM), the most common primary brain tumor, is the most aggressive human cancers, with a median survival rate of only 14.6 months. Temozolomide (TMZ) is the frontline ...chemotherapeutic drug in GBM. Drug resistance is the predominant obstacle in TMZ therapy. Drug resistance occurs via multiple pathways such as DNA mismatch repair and base excision repair systems, by which glioma cells acquire chemoresistance to some extent (5% and 95%, respectively). Histone3 Lysin27 residue-acetylation (H3K27ac) status regulates cis-regulatory elements, which increases the likelihood of gene transcription. Histone deacetylase (HDAC) complex deacetylate lysine residues on core histones, leading to a decrease in gene transcription. In cis-regulatory element regions, complexes with HDAC repress histones by H3K27ac deacetylation. The cis-regulating and three-dimensional transcriptional mechanism is called "super-enhancer". RET finger protein (RFP) is a protein that is expressed in many kinds of cancer. RFP forms a protein complex with HDAC1. The disruption of the RFP-HDAC1 complex has resulted in increased drug sensitivity in other cancers. We conclude that the downregulation of RFP or the disruption of the RFP/HDAC1 complex leads to an increase in TMZ efficacy in glioblastoma by changing histone modifications which lead to changes in cell division, cell cycle and apoptosis.
Isocitrate dehydrogenase 1
(
IDH1
), which localizes to the cytosol and peroxisomes, catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG) and in parallel converts NADP
+
to ...NADPH.
IDH1
mutations are frequently detected in grades 2–4 gliomas and in acute myeloid leukemias (AML). Mutations of
IDH1
have been identified at codon 132, with arginine being replaced with histidine in most cases. Mutant
IDH1
gains novel enzyme activity converting α-KG to
d
-2-hydroxyglutarate (2-HG) which acts as a competitive inhibitor of α-KG. As a result, the activity of α-KG-dependent enzyme is reduced. Based on these findings, 2-HG has been proposed to be an oncometabolite. In this study, we established HEK293 and U87 cells that stably expressed
IDH1
-
WT
and
IDH1
-
R132H
and investigated the effect of glutaminase inhibition on cell proliferation with 6-diazo-5-oxo-
l
-norleucine (DON). We found that cell proliferation was suppressed in
IDH1
-
R132H
cells. The addition of α-KG restored cell proliferation. The metabolic features of 33 gliomas with wild type
IDH1
(
IDH1
-
WT
) and with
IDH1
-
R132H
mutation were examined by global metabolome analysis using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). We showed that the 2-HG levels were highly elevated in gliomas with
IDH1
-
R132H
mutation. Intriguingly, in gliomas with
IDH1
-
R132H
, glutamine and glutamate levels were significantly reduced which implies replenishment of α-KG by glutaminolysis. Based on these results, we concluded that glutaminolysis is activated in gliomas with
IDH1
-
R132H
mutation and that development of novel therapeutic approaches targeting activated glutaminolysis is warranted.
Glioblastoma (GBM), the most common primary brain tumor, is the most aggressive human cancers, with a median survival rate of only 14.6 months. Temozolomide (TMZ) is the frontline chemotherapeutic ...drug in GBM. Drug resistance is the predominant obstacle in TMZ therapy. Drug resistance occurs via multiple pathways such as DNA mismatch repair and base excision repair systems, by which glioma cells acquire chemoresistance to some extent (5% and 95%, respectively). Histone3 Lysin27 residue-acetylation (H3K27ac) status regulates cis-regulatory elements, which increases the likelihood of gene transcription. Histone deacetylase (HDAC) complex deacetylate lysine residues on core histones, leading to a decrease in gene transcription. In cis-regulatory element regions, complexes with HDAC repress histones by H3K27ac deacetylation. The cis-regulating and three-dimensional transcriptional mechanism is called “super-enhancer”. RET finger protein (RFP) is a protein that is expressed in many kinds of cancer. RFP forms a protein complex with HDAC1. The disruption of the RFP–HDAC1 complex has resulted in increased drug sensitivity in other cancers. We conclude that the downregulation of RFP or the disruption of the RFP/HDAC1 complex leads to an increase in TMZ efficacy in glioblastoma by changing histone modifications which lead to changes in cell division, cell cycle and apoptosis.
RET finger protein (RFP) forms a complex with histone deacetylase 1, resulting in aberrant deacetylation of H3K27ac and dysregulation of cis-regulatory elements. We evaluated the modulatory effects ...of RFP knockdown on cis-regulatory elements, gene expression, and chemosensitivity to temozolomide both in glioblastoma cells and in an intracranial glioblastoma model. The combination of RFP knockdown and temozolomide treatment markedly suppressed the glioblastoma cell growth due to oxidative stress and aberrant cell cycle and increased survival time in mice with glioblastoma. ChIP-seq and RNA-seq revealed that RFP knockdown increased or decreased activity of numerous cis-regulatory elements that lie adjacent to genes that control functions such as apoptosis, mitosis, DNA replication, and cell cycle: FOXO1, TBP2, and PARPBP. This study suggests that RFP contributes to chemoresistance via aberrant deacetylation of histone H3 at K27, whereas dysregulation of RFP-associated cis-regulatory elements in glioma and RFP knockdown combined with temozolomide is an effective treatment strategy for lethal glioma.
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•RET finger protein (RFP) binds to histone deacetylase 1 in glioblastoma cells•RFP regulates H3K27acetylation and cis-regulatory elements•Knockdown of RFP modulates elements of oxidative stress and base excision repair•Knockdown of RFP overcomes chemoresistance in glioblastoma in vitro and in vivo
Ranjit et al. demonstrate that the RET finger protein (RFP), which forms a complex with histone deacetylase 1 in glioma cells, also alters H3K27 acetylation patterns and cis-regulatory elements. Furthermore, RFP knockdown regulates the factors of oxidative stress and base excision repair, thereby enhancing temozolomide chemosensitivity in glioblastoma.
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