CHEK2 mutations in primary glioblastomas

Prevalence of pathogenic germline variants in adult-type diffuse glioma

Background

No consensus germline testing guidelines currently exist for glioma patients, so the prevalence of germline pathogenic variants remains unknown. This study aims to determine the prevalence and type of pathogenic germline variants in adult glioma.

Methods

A retrospective review at a single institution with paired tumor/normal sequencing from August 2018-April 2022 was performed and corresponding clinical data were collected.

Results

We identified 152 glioma patients of which 15 (9.8%) had pathogenic germline variants. Pathogenic germline variants were seen in 11/84 (13.1%) of Glioblastoma, IDH wild type; 3/42 (7.1%) of Astrocytoma, IDH mutant; and 1/26 (3.8%) of Oligodendroglioma, IDH mutant, and 1p/19q co-deleted patients. Pathogenic variants in BRCA2, MUTYH, and CHEK2 were most common (3/15, 20% each). BRCA1 variants occurred in 2/15 (13%) patients, with variants in NF1, ATM, MSH2, and MSH3 occurring in one patient (7%) each. Prior cancer diagnosis was found in 5/15 patients (33%). Second-hit somatic variants were seen in 3/15 patients (20%) in NF1, MUTYH, and MSH2. Referral to genetics was performed in 6/15 (40%) patients with pathogenic germline variants. 14/15 (93%) of patients discovered their pathogenic variant as a result of their paired glioma sequencing.

Conclusions

These findings suggest a possible overlooked opportunity for determination of hereditary cancer syndromes with impact on surveillance as well as potential broader treatment options. Further studies that can determine the role of variants in gliomagenesis and confirm the occurrence and types of pathogenic germline variants in patients with IDH wild type compared to IDH mutant tumors are necessary.

CHEK2 Alterations in Pediatric Malignancy: A Single-Institution Experience

Background: Approximately 10% of pediatric malignancies are secondary to germline alterations in cancer-predisposing genes. Checkpoint kinase 2 (CHEK2) germline loss-of-function variants have been reported in pediatric cancer patients, but clinical phenotypes and outcomes are poorly described. We present our single-institution experience of pediatric oncology patients with CHEK2 germline alterations, including clinical presentations and outcomes. Methods: Pediatric oncology patients with CHEK2 germline alterations were identified among those assessed by clinical or translational research at the Institute for Genomic Medicine at Nationwide Children’s Hospital. A chart review of disease course was conducted on identified patients. Results: We identified 6 patients with germline CHEK2 variants from a cohort of 300 individuals, including 1 patient with concurrent presentation of Burkitt lymphoma and neuroblastoma, 3 patients with brain tumors, 1 patient with Ewing sarcoma, and 1 patient with myelodysplastic syndrome. Three patients had a family history of malignancies. Four patients were in remission; one was undergoing treatment; one patient had developed treatment-related meningiomas. We review prior data regarding CHEK2 variants in this population, challenges associated with variant interpretation, and genetic counseling for individuals with CHEK2 variants. Conclusions: CHEK2 germline loss-of-function alterations occur in patients with a variety of pediatric tumors. Larger multicenter studies will improve our understanding of the incidence, phenotype, and molecular biology of CHEK2 germline variants in pediatric cancers.

The First Case Report of a Patient With Oligodendroglioma Harboring CHEK2 Germline Mutation

Introduction:CHEK2 (Checkpoint kinase 2) germline mutations were associated with an elevated risk of breast cancer, colorectal cancer, and other familiar cancers. Loss-of-function variants in CHEK2 are known to be pathogenic. Germline CHEK2 mutations have also been observed in medulloblastoma and primary glioblastomas. Currently, there is no direct evidence supporting the relationship of CHEK2 with central nervous system tumors.

Case presentation: A case of an oligodendroglioma patient harboring the germline CHEK2 p.R137* mutation was reported. CHEK2 p.R137* mutation occurred in the forkhead-associated domain. Given the absence of other known genetic predisposing risk factors, we considered that oligodendroglioma might be associated with the CHEK2 mutation. The patient in our case might have a high risk of breast cancer and other multiple primary tumors. Her siblings and offspring would have a 50% chance of having the same variant.

Conclusion: We reported a case of an oligodendroglioma patient with a family history of gastrointestinal tumors harboring the germline CHEK2 pathogenic variation. This is the first report of the association between the CHEK2 pathogenic variation and brain tumors that warrants further validation in larger cohorts.

Is CHEK2 a moderate-risk breast cancer gene or the younger sister of Li-Fraumeni?

The CHEK2 gene is mostly considered as a moderate breast cancer gene with the result that many clinicians have a narrow focus. We present the 10-year journey of a man who had five different cancers and had iterative genetic testing including for Li-Fraumeni syndrome, eventually to discover a pathogenic variant in the CHEK2 gene, possibly explaining his numerous cancers. This diagnosis offered him closure which he had desperately sought for well over a decade. A pathogenic variant in the CHEK2 gene can potentially explain these cancers because of its function as a tumour suppressor gene. Consideration is warranted of what this means for individuals with CHEK2 variants who may develop multiple cancers, their prognosis and whether different treatment modalities such as chemotherapy, radiotherapy or target agents would need modification. We encourage more research into the many faces of the CHEK2 gene and the potential for predisposition to multiple cancers.

Targeted Sequencing of Malignant Supratentorial Pediatric Brain Tumors Demonstrates a High Frequency of Clinically Relevant Mutations

Pediatric brain tumors cause more deaths than any other childhood malignancy, and the identification of potentially actionable genomic alterations in this rare heterogeneous group of tumors may improve treatment and outcome. The genetic landscape of common posterior fossa tumors has been described in the past several years, yet the classification of malignant pediatric supratentorial tumors remains controversial. Next-generation sequencing (NGS) is a promising tool to evaluate multiple genes concurrently. The clinical utility of NGS has not been proven in pediatric brain tumors. We identified patients diagnosed with high-grade supratentorial pediatric brain tumors resected between 2008 and 2012 at our institution. DNA from 12 formalin-fixed paraffin-embedded tumor samples from 9 patients was analyzed, including 3 paired samples from diagnosis and relapse. A panel of 194 cancer-related genes was sequenced using targeted next-generation deep sequencing. Genetic findings were correlated with histology, immunohistochemistry, treatment, and survival. We found one or more pathologic genetic change (mutation, amplification, or deletion) in 8 of 9 (89%) of patients studied. Epidermal Growth Factor Receptor ( EGFR) mutations were found in 3 patients, 2 of which had an exon 20 insertion not previously described in pediatric malignancy. Additional genetic changes were found in EGFR and Platelet-Derived Growth Factor Receptor Alpha ( PDGFRA) at relapse not present in the initial samples. Familial cancer predisposition syndromes were suggested by mutations found in 3 genes in 4 patients, including TP53, MSH2, and CHEK2. Seven of 9 patients in this study died of their disease. In summary, targeted deep sequencing may be used in rare pediatric brain tumors to identify driver mutations for targeted therapy, suggest constitutional and familial testing for cancer predisposition syndromes, and select molecular targets worthy of further study.

FGFR1 tyrosine kinase domain duplication in pilocytic astrocytoma with anaplasia

We report the case of a 27-yr-old male with visual field loss who had a 4.9-cm complex cystic mass in the right occipital lobe. Histologic examination showed pilocytic astrocytoma (PA) with anaplasia, and molecular characterization revealed FGFR1 duplication with additional variants of unknown significance in several genes (ARID1A, ARID1B, CHEK2, EPHA5, and MLL2). This is one of only a very few reported cases of anaplastic PA with characterization of molecular alterations.

Exploration of Involved Key Genes and Signaling Diversity in Brain Tumors

Brain tumors are becoming a major cause of death. The classification of brain tumors has gone through restructuring with regard to some criteria such as the presence or absence of a specific genetic alteration in the 2016 central nervous system World Health Organization update. Two categories of genes with a leading role in tumorigenesis and cancer induction include tumor suppressor genes and oncogenes; tumor suppressor genes are inactivated through a variety of mechanisms that result in their loss of function. As for the oncogenes, overexpression and amplification are the most common mechanisms of alteration. Important cell cycle genes such as p53, ATM, cyclin D2, and Rb have shown altered expression patterns in different brain tumors such as meningioma and astrocytoma. Some genes in signaling pathways have a role in brain tumorigenesis. These pathways include hedgehog, EGFR, Notch, hippo, MAPK, PI3K/Akt, and WNT signaling. It has been shown that telomere length in some brain tumor samples is shortened compared to that in normal cells. As the shortening of telomere length triggers chromosome instability early in brain tumors, it could lead to initiation of cancer. On the other hand, telomerase activity was positive in some brain tumors. It is suggestive that telomere length and telomerase activity are important diagnostic markers in brain tumors. This review focuses on brain tumors with regard to the status of oncogenes, tumor suppressors, cell cycle genes, and genes in signaling pathways as well as the role of telomere length and telomerase in brain tumors.

Discovering key regulatory mechanisms from single-factor and multi-factor regulations in glioblastoma utilizing multi-dimensional data

Glioblastoma (GBM) is the most common malignant brain cancer in adults. Investigating the regulatory mechanisms underlying GBM is effective for the in-depth study of GBM. The Cancer Genome Atlas (TCGA) project is producing large-scale data and makes the comprehensive study of the diverse regulatory mechanisms underlying GBM possible. Although there have been research studies on GBM with large-scale data, distinguishing different regulatory mechanisms and identifying the key regulation types remain challenging. In this study, we integrated multi-dimensional data of differentially expressed genes in GBM: copy number variation (CNV), gene expression, miRNA expression and methylation, by performing partial correlation analysis with the Lasso technique. Our results showed that there were single-factor and multi-factor regulatory mechanisms in GBM. In further analysis of the regulation subtypes, we discovered that single-factor and multi-factor regulations are potentially distinct in functionality. Moreover, multi-factor regulations especially the key regulation subtypes may be more relevant to GBM and affect many GBM-related genes such as ERBB2 and MAPK1. This study not only verifies the utility of multi-dimensional data integration into GBM research but also distinguishes the key multi-factor regulatory subtypes that may drive pathogenesis of GBM from various regulatory mechanisms.

CHEK2 (∗) 1100delC Mutation and Risk of Prostate Cancer

Although the causes of prostate cancer are largely unknown, previous studies support the role of genetic factors in the development of prostate cancer. CHEK2 plays a critical role in DNA replication by responding to double-stranded breaks. In this review, we provide an overview of the current knowledge of the role of a genetic variant, 1100delC, of CHEK2 on prostate cancer risk and discuss the implication for potential translation of this knowledge into clinical practice. Currently, twelve articles that discussed CHEK2 (∗)1100delC and its association with prostate cancer were identified. Of the twelve prostate cancer studies, five studies had independent data to draw conclusive evidence from. The pooled results of OR and 95% CI were 1.98 (1.23-3.18) for unselected cases and 3.39 (1.78-6.47) for familial cases, indicating that CHEK2 (∗)1100delC mutation is associated with increased risk of prostate cancer. Screening for CHEK2(∗)1100delC should be considered in men with a familial history of prostate cancer.

DNA damage response and anti-apoptotic proteins predict radiosensitization efficacy of HDAC inhibitors SAHA and LBH589 in patient-derived glioblastoma cells

HDAC inhibitors have radiosensitizing effects in established cancer cell lines. This study was conducted to compare the efficacy of SAHA, LBH589, Valproic Acid (VPA), MS275 and Scriptaid in the patient-derived glioblastoma model. In more detail, SAHA and LBH589 were evaluated to determine predictors of response. Acetylated-histone-H3, γH2AX/53BP1, (p)Chek2/ATM, Bcl-2/Bcl-XL, p21(CIP1/WAF1) and caspase-3/7 were studied in relation to response. SAHA sensitized 50% of cultures, LBH589 45%, VPA and Scriptaid 40% and MS275 60%. Differences after treatment with SAHA/RTx or LBH589/RTx in a sensitive and resistant culture were increased acetylated-H3, caspase-3/7 and prolonged DNA damage repair γH2AX/53BP1 foci. pChek2 was found to be associated with both SAHA/RTx and LBH589/RTx response with a positive predictive value (PPV) of 90%. Bcl-XL had a PPV of 100% for LBH589/RTx response. Incubation with HDACi 24 and 48 hours pre-RTx resulted in the best efficacy of combination treatment. In conclusion a subset of patient-derived glioblastoma cultures were sensitive to HDACi/RTx. For SAHA and LBH589 responses were strongly associated with pChek2 and Bcl-XL, which warrant further clinical exploration. Additional information on responsiveness was obtained by DNA damage response markers and apoptosis related proteins.

Germline rearrangements in families with strong family history of glioma and malignant melanoma, colon, and breast cancer

BACKGROUND

Although familial susceptibility to glioma is known, the genetic basis for this susceptibility remains unidentified in the majority of glioma-specific families. An alternative approach to identifying such genes is to examine cancer pedigrees, which include glioma as one of several cancer phenotypes, to determine whether common chromosomal modifications might account for the familial aggregation of glioma and other cancers.

METHODS

Germline rearrangements in 146 glioma families (from the Gliogene Consortium; http://www.gliogene.org/) were examined using multiplex ligation-dependent probe amplification. These families all had at least 2 verified glioma cases and a third reported or verified glioma case in the same family or 2 glioma cases in the family with at least one family member affected with melanoma, colon, or breast cancer.The genomic areas covering TP53, CDKN2A, MLH1, and MSH2 were selected because these genes have been previously reported to be associated with cancer pedigrees known to include glioma.

RESULTS

We detected a single structural rearrangement, a deletion of exons 1-6 in MSH2, in the proband of one family with 3 cases with glioma and one relative with colon cancer.

CONCLUSIONS

Large deletions and duplications are rare events in familial glioma cases, even in families with a strong family history of cancers that may be involved in known cancer syndromes.

Contribution of ATM and ATR to the resistance of glioblastoma and malignant melanoma cells to the methylating anticancer drug temozolomide

The major cytotoxic DNA adduct induced by temozolomide and other methylating agents used in malignant glioma and metastasized melanoma therapy is O(6)-methylguanine (O(6)-MeG). This primary DNA damage is converted by mismatch repair into secondary lesions, which block replication and in turn induce DNA double-strand breaks that trigger the DNA damage response (DDR). Key upstream players in the DDR are the phosphoinositide 3-kinases ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3 related (ATR). Here, we addressed the question of the importance of ATM and ATR in the cell death response following temozolomide. We show that (i) ATM- and ATR-mutated cells are hypersensitive to temozolomide, (ii) O(6)-MeG triggers ATM and ATR activation, (iii) knockdown of ATM and ATR enhances cell kill in gliobalstoma and malignant melanoma cells with a stronger and significant effect in ATR knockdown cells, (iv) ATR, but not ATM, knockdown abolished phosphorylation of H2AX, CHK1, and CHK2 in glioma cells, and (v) temozolomide-induced cell death was more prominently enhanced by pharmacologic inhibition of CHK1 compared with CHK2. The data suggest that ATM and, even better, ATR inhibition is a useful strategy in sensitizing cancer cells to temozolomide and presumably also other anticancer drugs.

Aberrant signaling pathways in glioma

Glioblastoma multiforme (GBM), a WHO grade IV malignant glioma, is the most common and lethal primary brain tumor in adults; few treatments are available. Median survival rates range from 12–15 months. The biological characteristics of this tumor are exemplified by prominent proliferation, active invasiveness, and rich angiogenesis. This is mainly due to highly deregulated signaling pathways in the tumor. Studies of these signaling pathways have greatly increased our understanding of the biology and clinical behavior of GBM. An integrated view of signal transduction will provide a more useful approach in designing novel therapies for this devastating disease. In this review, we summarize the current understanding of GBM signaling pathways with a focus on potential molecular targets for anti-signaling molecular therapies.

Loss of ATM/Chk2/p53 pathway components accelerates tumor development and contributes to radiation resistance in gliomas

Maintenance of genomic integrity is essential for adult tissue homeostasis and defects in the DNA-damage response (DDR) machinery are linked to numerous pathologies including cancer. Here, we present evidence that the DDR exerts tumor suppressor activity in gliomas. We show that genes encoding components of the DDR pathway are frequently altered in human gliomas and that loss of elements of the ATM/Chk2/p53 cascade accelerates tumor formation in a glioma mouse model. We demonstrate that Chk2 is required for glioma response to ionizing radiation in vivo and is necessary for DNA-damage checkpoints in the neuronal stem cell compartment. Finally, we observed that the DDR is constitutively activated in a subset of human GBMs, and such activation correlates with regions of hypoxia.

Characterization of rainbow trout CHK2 and its potential as a genotoxicity biomarker

Checkpoint kinase 2 (CHK2) plays a central and conserved role in the eukaryotic DNA damage response. Few cell cycle checkpoint proteins have been examined in aquatic organisms, and this study is the first to characterize CHK2 expression in a fish species. CHK2 was cloned from Oncorhynchus mykiss, the rainbow trout. The coding region extends over 5741 nucleotides in the genome, including 13 introns, and specifies a predicted 533 amino acid protein. Southern blot analysis revealed that CHK2 exists as a single copy in the rainbow trout genome. Recombinant protein representing the FHA domain was used to generate polyclonal anti-CHK2 antibodies. While CHK2 transcript levels were relatively low in gill and high in brain, the opposite was true for protein levels. Both gill and brain cell cultures were treated with bleomycin, which induces double-strand DNA breaks. There was no effect on levels of CHK2 in gill cells, suggesting that the protein is constitutively active in this tissue. In contrast, brain cells upregulated CHK2 in a dose-dependent manner. The tissue specific expression of CHK2 and its ability to respond to bleomycin treatment suggests that some checkpoint proteins may serve as suitable biomarkers for DNA damage in rainbow trout and other fish species.

Role of CHK2 in cancer development

DNA repair pathways enable tumour cells to survive DNA damage induced by external agents such as therapeutic treatments. Signalling cascades involved in these pathways comprise the DNA-dependent protein kinase (DNA-PK), Ataxia-telangiectasia mutated (ATM), ATM and Rad3 related (ATR) and checkpoint kinases I and 2 (Chk1/Chk2), among others. ATM and ATR phosphorylate, respectively, Chk2 and Chk1, leading to activation of checkpoints. Chk2 acts as a signal distributor, dispersing checkpoint signal to downstream targets such as p53, Cdc25A, Cdc25C, BRCA1 and E2F1. A role of Chk2 as a candidate tumour suppressor has been suggested based on both mouse genetics and somatic tumour studies. We will discuss here the possible role of this kinase in human carcinogenesis and the possibility to use it as a target to increment DNA damage in cancer cells in response to DNA-damaging therapies.

CHK2 kinase: cancer susceptibility and cancer therapy - two sides of the same coin?

In the past decade, CHK2 has emerged as an important multifunctional player in the DNA-damage response signalling pathway. Parallel studies of the human CHEK2 gene have also highlighted its role as a candidate multiorgan tumour susceptibility gene rather than a highly penetrant predisposition gene for Li-Fraumeni syndrome. As discussed here, our current understanding of CHK2 function in tumour cells, in both a biological and genetic context, suggests that targeted modulation of the active kinase or exploitation of its loss in tumours could prove to be effective anti-cancer strategies.

Variant of the CHEK2 gene as a prognostic marker in glioblastoma multiforme

OBJECTIVE

Germline mutations of the CHEK2 tumor suppressor gene have been found in families with the Li-Fraumeni syndrome (LFS). Patients with LFS experience a variety of cancers, including malignant astrocytomas. We investigated a potential role for a CHEK2 gene polymorphism in glioblastomas.

METHODS

A genetic polymorphism of the CHEK2 gene (CHEK2 SNP rs2017309 A/T) was genotyped in a series of glioblastoma patients (n = 213) and population controls (n = 192). Subsets of tumors were analyzed for loss of heterozygosity 22q(n = 66), loss of heterozygosity CHEK2 (n = 53), CHEK2 expression (n = 21), and CHEK2 coding sequence alterations (n = 18). CHEK2 SNP rs2017309 genotyping findings and traditional clinicopathological parameters were correlated with the patients' prognoses.

RESULTS

No association between the CHEK2 SNP and glioblastoma formation was observed. No CHEK2 coding sequence aberrations or tumors completely lacking CHEK2 protein were identified. However, the presence of the CHEK2 rs2017309 A allele was significantly associated with an adverse prognosis (P = 0.034), particularly among patients undergoing postoperative chemotherapy and radiotherapy (n = 28, median survival 10.5 versus 15.5 mo, P = 0.008). We could confirm the patients' age, Karnofsky Performance Scale score, and postoperative radiotherapy and chemotherapy (all P < 0.0001, log-rank test) as decisive prognostic factors.

CONCLUSION

Our data suggest that a CHEK2 gene polymorphism might correlate with the prognosis of glioblastoma patients. These findings may point to an as yet unrecognized role for the CHEK2 gene in glioblastomas.