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Alphones S, Chatterjee U, Singh A, Das A, Zameer L, Achari R, Bhattacharya A, Roy P. Immunohistochemical screening for mismatch repair protein deficiency in paediatric high-grade gliomas - institutional experience and review of literature. Childs Nerv Syst 2021; 37:2521-2530. [PMID: 34097097 DOI: 10.1007/s00381-021-05229-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 05/24/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE Immunohistochemical (IHC) testing for mismatch repair (MMR) deficiency (MMRD) is used as a screening tool to identify microsatellite instability in various cancers (especially colon). This not only identifies hereditary cancer syndromes like Lynch and constitutional mismatch repair deficiency (CMMRD) but also aids in prognostication and prediction of sensitivity to checkpoint inhibitor drugs. There are very few reported studies on MMRD status of pediatric high-grade gliomas (pHGG) and none from the Indian subcontinent. The aim of this study is to evaluate the frequency of MMRD in pHGG and to assess if there is a need for universal screening with immunohistochemistry. METHODS Paraffin blocks of consecutive cases of pHGG (< 18 years) were retrieved from 2 centres, and IHC with four MMR antibodies - MLH1, PMS2, MSH2 and MSH6 - was performed using tissue microarray-based technique. RESULTS Three out of nine cases (33%) studied showed loss of staining. One case had loss of MSH2 and MSH6 confirmed by gene sequencing. Eight of the cases were glioblastoma. One case of IDH1-mutated anaplastic astrocytoma showed loss of MLH1 and PMS2 staining. Isolated PMS2 loss was noted in 1 case, where the non-tumour cells also showed loss of staining, indicative CMMRD syndrome. This patient had prior colon cancer with isolated PMS2 loss and responded to check-point inhibitor therapy with nivolumab. CONCLUSION Our study shows that the frequency of MMRD to be about one-third of pHGG. Universal IHC screening for MMRD in all pHGGs may benefit early diagnosis and play a role in therapeutic decisions. A larger multi-institutional study will help better assess the prevalence and treatment implications in MMRD tumours.
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Affiliation(s)
- Sheena Alphones
- Department of Pathology, Tata Medical Center, Kolkata, India
| | | | - Angad Singh
- Department of Pathology, Tata Medical Center, Kolkata, India
| | - Anirban Das
- Department of Pediatric Oncology, Tata Medical Center, Kolkata, India
| | - Lateef Zameer
- Department of Pathology, Tata Medical Center, Kolkata, India
| | - Rimpa Achari
- Department of Radiation Oncology, Tata Medical Center, Kolkata, India
| | | | - Paromita Roy
- Department of Pathology, Tata Medical Center, Kolkata, India.
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Kafka A, Bačić M, Tomas D, Žarković K, Bukovac A, Njirić N, Mrak G, Krsnik Ž, Pećina‐Šlaus N. Different behaviour of DVL1, DVL2, DVL3 in astrocytoma malignancy grades and their association to TCF1 and LEF1 upregulation. J Cell Mol Med 2019; 23:641-655. [PMID: 30468298 PMCID: PMC6307814 DOI: 10.1111/jcmm.13969] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 09/04/2018] [Accepted: 09/27/2018] [Indexed: 01/21/2023] Open
Abstract
Key regulators of the Wnt signalling, DVL1, DVL2 and DVL3, in astrocytomas of different malignancy grades were investigated. Markers for DVL1, DVL2 and DVL3 were used to detect microsatellite instability (MSI) and gross deletions (LOH), while immunohistochemistry and immunoreactivity score were used to determine the signal strengths of the three DVL proteins and transcription factors of the pathway, TCF1 and LEF1. Our findings demonstrated that MSI at all three DVL loci was constantly found across tumour grades with the highest number in grade II (P = 0.008). Collectively, LOHs were more frequent in high-grade tumours than in low grade ones. LOHs of DVL3 gene were significantly associated with grade IV tumours (P = 0.007). The results on protein expressions indicated that high-grade tumours expressed less DVL1 protein as compared with low grade ones. A significant negative correlation was established between DVL1 expression and malignancy grades (P < 0.001). The expression of DVL2 protein was found similar across grades, while DVL3 expression significantly increased with malignancy grades (P < 0.001). The signal strengths of expressed DVL1 and DVL3 were negatively correlated (P = 0.002). However, TCF1 and LEF1 were both significantly upregulated and increasing with astrocytoma grades (P = 0.001). A positive correlation was established between DVL3 and both TCF1 (P = 0.020) and LEF1 (P = 0.006) suggesting their joint involvement in malignant progression. Our findings suggest that DVL1 and DVL2 may be involved during early stages of the disease, while DVL3 may have a role in later phases and together with TCF1 and LEF1 promotes the activation of Wnt signalling.
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Affiliation(s)
- Anja Kafka
- Laboratory of Neuro‐oncologyCroatian Institute for Brain ResearchSchool of MedicineUniversity of ZagrebZagrebCroatia
- Department of BiologySchool of MedicineUniversity of ZagrebZagrebCroatia
| | | | - Davor Tomas
- Department of PathologySchool of MedicineUniversity of ZagrebZagrebCroatia
- Department of PathologyUniversity Hospital Center “Sisters of Charity”ZagrebCroatia
| | - Kamelija Žarković
- Department of PathologySchool of MedicineUniversity of ZagrebZagrebCroatia
- Division of PathologyUniversity Hospital Center “Zagreb”ZagrebCroatia
| | - Anja Bukovac
- Laboratory of Neuro‐oncologyCroatian Institute for Brain ResearchSchool of MedicineUniversity of ZagrebZagrebCroatia
- Department of BiologySchool of MedicineUniversity of ZagrebZagrebCroatia
| | - Niko Njirić
- Laboratory of Neuro‐oncologyCroatian Institute for Brain ResearchSchool of MedicineUniversity of ZagrebZagrebCroatia
- Department of NeurosurgeryUniversity Hospital Center “Zagreb”School of MedicineUniversity of ZagrebZagrebCroatia
| | - Goran Mrak
- Department of NeurosurgeryUniversity Hospital Center “Zagreb”School of MedicineUniversity of ZagrebZagrebCroatia
| | - Željka Krsnik
- Department of NeuroscienceCroatian Institute for Brain ResearchSchool of MedicineUniversity of ZagrebZagrebCroatia
| | - Nives Pećina‐Šlaus
- Laboratory of Neuro‐oncologyCroatian Institute for Brain ResearchSchool of MedicineUniversity of ZagrebZagrebCroatia
- Department of BiologySchool of MedicineUniversity of ZagrebZagrebCroatia
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Abstract
: More than 1.6 million new cases of cancer will be diagnosed in the U.S. in 2016, resulting in more than 500,000 deaths. Although chemotherapy has been the mainstay of treatment in advanced cancers, immunotherapy development, particularly with PD-1 inhibitors, has changed the face of treatment for a number of tumor types. One example is the subset of tumors characterized by mismatch repair deficiency and microsatellite instability that are highly sensitive to PD-1 blockade. Hereditary forms of cancer have been noted for more than a century, but the molecular changes underlying mismatch repair-deficient tumors and subsequent microsatellite unstable tumors was not known until the early 1990s. In this review article, we discuss the history and pathophysiology of mismatch repair, the process of testing for mismatch repair deficiency and microsatellite instability, and the role of immunotherapy in this subset of cancers. IMPLICATIONS FOR PRACTICE Mismatch repair deficiency has contributed to our understanding of carcinogenesis for the past 2 decades and now identifies a subgroup of traditionally chemotherapy-insensitive solid tumors as sensitive to PD-1 blockade. This article seeks to educate oncologists regarding the nature of mismatch repair deficiency, its impact in multiple tumor types, and its implications for predicting the responsiveness of solid tumors to immune checkpoint blockade.
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Lee V, Murphy A, Le DT, Diaz LA. Mismatch Repair Deficiency and Response to Immune Checkpoint Blockade. Oncologist 2016; 21:1200-1211. [PMID: 27412392 DOI: 10.1634/theoncologist.2016-0046] [Citation(s) in RCA: 184] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Accepted: 05/04/2016] [Indexed: 02/06/2023] Open
Abstract
: More than 1.6 million new cases of cancer will be diagnosed in the U.S. in 2016, resulting in more than 500,000 deaths. Although chemotherapy has been the mainstay of treatment in advanced cancers, immunotherapy development, particularly with PD-1 inhibitors, has changed the face of treatment for a number of tumor types. One example is the subset of tumors characterized by mismatch repair deficiency and microsatellite instability that are highly sensitive to PD-1 blockade. Hereditary forms of cancer have been noted for more than a century, but the molecular changes underlying mismatch repair-deficient tumors and subsequent microsatellite unstable tumors was not known until the early 1990s. In this review article, we discuss the history and pathophysiology of mismatch repair, the process of testing for mismatch repair deficiency and microsatellite instability, and the role of immunotherapy in this subset of cancers. IMPLICATIONS FOR PRACTICE Mismatch repair deficiency has contributed to our understanding of carcinogenesis for the past 2 decades and now identifies a subgroup of traditionally chemotherapy-insensitive solid tumors as sensitive to PD-1 blockade. This article seeks to educate oncologists regarding the nature of mismatch repair deficiency, its impact in multiple tumor types, and its implications for predicting the responsiveness of solid tumors to immune checkpoint blockade.
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Affiliation(s)
- Valerie Lee
- Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland, USA
| | - Adrian Murphy
- Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland, USA
| | - Dung T Le
- Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland, USA
| | - Luis A Diaz
- The Swim Across America Laboratory, Baltimore, Maryland, USA the Ludwig Center for Cancer Genetics and Therapeutics, Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland, USA
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Zhao Y, Zheng ZC, Luo YH, Piao HZ, Zheng GL, Shi JY, Zhang T, Zhang JJ. Low-Frequency Microsatellite Instability in Genomic Di-Nucleotide Sequences Correlates with Lymphatic Invasion and Poor Prognosis in Gastric Cancer. Cell Biochem Biophys 2014; 71:235-41. [DOI: 10.1007/s12013-014-0189-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Mizoguchi M, Hata N, Suzuki SO, Fujioka Y, Murata H, Amano T, Nakamizo A, Yoshimoto K, Iwaki T, Sasaki T. Pediatric glioblastoma with oligodendroglioma component: aggressive clinical phenotype with distinct molecular characteristics. Neuropathology 2013; 33:652-7. [PMID: 23530875 DOI: 10.1111/neup.12029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Accepted: 01/30/2013] [Indexed: 12/28/2022]
Abstract
The 2007 World Health Organization classification defined a new variant of glioblastoma (GBM) containing oligodendroglioma foci as GBM with an oligodendroglioma component (GBMO), which shows a favorable clinical outcome compared with "classic" GBM. However, all of the reported cases of GBMO have been adult cases, with no previous reports of pediatric cases. In this report, we demonstrated molecular characteristics of a pediatric GBMO case, showing aggressive clinical behavior with 8-month overall survival. The case showed neither isocitrate dehydrogenase 1/2 genes (IDH1/2) mutation nor 1p/19q co-deletion, a hallmark of oligodendroglioal tumors. In addition, microsatellite instability, leading to the putative mechanism of temozolomide (TMZ) resistance, was frequently detected. Molecular genetic analysis may provide critical prognostic and therapeutic insights, especially for the pediatric glioma containing oligodendroglioma components.
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Gilheeney SW, Kieran MW. Differences in molecular genetics between pediatric and adult malignant astrocytomas: age matters. Future Oncol 2012; 8:549-58. [PMID: 22646770 DOI: 10.2217/fon.12.51] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The microscope - the classical tool for the investigation of cells and tissues - remains the basis for the classification of tumors throughout the body. Nowhere has this been more true than in the grading of astrocytomas. In spite of the fact that our parents warned us not to judge a book by its cover, we have continued to assume that adult and pediatric malignant gliomas that look the same, will have the same mutations, and thus respond to the same therapy. Rapid advances in molecular biology have permitted us the opportunity to go inside the cell and characterize the genetic events that underlie the true molecular heterogeneity of adult and pediatric brain tumors. In this paper, we will discuss some of the important clinical differences between pediatric and adult gliomas, with a focus on the molecular analysis of these different age groups.
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Affiliation(s)
- Stephen W Gilheeney
- Pediatric Neuro-Oncology, Dana-Farber Children's Hospital Cancer Center, Boston, MA, USA.
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Mismatch repair deficiency: a temozolomide resistance factor in medulloblastoma cell lines that is uncommon in primary medulloblastoma tumours. Br J Cancer 2012; 107:1399-408. [PMID: 22976800 PMCID: PMC3494444 DOI: 10.1038/bjc.2012.403] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Tumours are responsive to temozolomide (TMZ) if they are deficient in O(6)-methylguanine-DNA methyltransferase (MGMT), and mismatch repair (MMR) proficient. METHODS The effect of TMZ on medulloblastoma (MB) cell killing was analysed with clonogenic survival assays. Expression of DNA repair genes and enzymes was investigated using microarrays, western blot, and immunohistochemistry. DNA sequencing and promoter methylation analysis were employed to investigate the cause of loss of the expression of MMR gene MLH1. RESULTS Temozolomide exhibited potent cytotoxic activity in D425Med (MGMT deficient, MLH1 proficient; IC(50)=1.7 μM), moderate activity against D341Med (MGMT proficient, MLH1 deficient), and DAOY MB cells (MGMT proficient, MLH1 proficient). MGMT inhibitor O(6)-benzylguanine sensitised DAOY, but not D341Med cells to TMZ. Of 12 MB cell lines, D341Med, D283Med, and 1580WÜ cells exhibited MMR deficiency due to MLH1 promoter hypermethylation. DNA sequencing of these cells provided no evidence for somatic genetic alterations in MLH1. Expression analyses of MMR and MGMT in MB revealed that all patient specimens (n=74; expression array, n=61; immunostaining, n=13) are most likely MMR proficient, whereas some tumours had low MGMT expression levels (according to expression array) or were totally MGMT deficient (3 out of 13 according to immunohistochemistry). CONCLUSION A subset of MB may respond to TMZ as some patient specimens are MGMT deficient, and tumours appear to be MMR proficient.
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Viana-Pereira M, Lee A, Popov S, Bax DA, Al-Sarraj S, Bridges LR, Stávale JN, Hargrave D, Jones C, Reis RM. Microsatellite instability in pediatric high grade glioma is associated with genomic profile and differential target gene inactivation. PLoS One 2011; 6:e20588. [PMID: 21637783 PMCID: PMC3102740 DOI: 10.1371/journal.pone.0020588] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 05/06/2011] [Indexed: 12/14/2022] Open
Abstract
High grade gliomas (HGG) are one of the leading causes of cancer-related deaths in children, and there is increasing evidence that pediatric HGG may harbor distinct molecular characteristics compared to adult tumors. We have sought to clarify the role of microsatellite instability (MSI) in pediatric versus adult HGG. MSI status was determined in 144 patients (71 pediatric and 73 adults) using a well established panel of five quasimonomorphic mononucleotide repeat markers. Expression of MLH1, MSH2, MSH6 and PMS2 was determined by immunohistochemistry, MLH1 was assessed for mutations by direct sequencing and promoter methylation using MS-PCR. DNA copy number profiles were derived using array CGH, and mutations in eighteen MSI target genes studied by multiplex PCR and genotyping. MSI was found in 14/71 (19.7%) pediatric cases, significantly more than observed in adults (5/73, 6.8%; p = 0.02, Chi-square test). MLH1 expression was downregulated in 10/13 cases, however no mutations or promoter methylation were found. MSH6 was absent in one pediatric MSI-High tumor, consistent with an inherited mismatch repair deficiency associated with germline MSH6 mutation. MSI was classed as Type A, and associated with a remarkably stable genomic profile. Of the eighteen classic MSI target genes, we identified mutations only in MSH6 and DNAPKcs and described a polymorphism in MRE11 without apparent functional consequences in DNA double strand break detection and repair. This study thus provides evidence for a potential novel molecular pathway in a proportion of gliomas associated with the presence of MSI.
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Affiliation(s)
- Marta Viana-Pereira
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- Section of Paediatric Oncology, Institute of Cancer Research, Sutton, Surrey, United Kingdom
| | - Alicia Lee
- Section of Paediatric Oncology, Institute of Cancer Research, Sutton, Surrey, United Kingdom
| | - Sergey Popov
- Section of Paediatric Oncology, Institute of Cancer Research, Sutton, Surrey, United Kingdom
- Paediatric Oncology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom
| | - Dorine A. Bax
- Section of Paediatric Oncology, Institute of Cancer Research, Sutton, Surrey, United Kingdom
| | - Safa Al-Sarraj
- Department of Clinical Neuropathology, Kings College Hospital, London, United Kingdom
| | | | - João N. Stávale
- Department of Pathology, Federal University of São Paulo, São Paulo, Brazil
| | - Darren Hargrave
- Paediatric Oncology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom
| | - Chris Jones
- Section of Paediatric Oncology, Institute of Cancer Research, Sutton, Surrey, United Kingdom
- Paediatric Oncology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom
- * E-mail: (RMR); (CJ)
| | - Rui M. Reis
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- Molecular Oncology Research Center, Barretos Cancer Hospital, Barretos, Brazil
- * E-mail: (RMR); (CJ)
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Frosina G. DNA repair and resistance of gliomas to chemotherapy and radiotherapy. Mol Cancer Res 2009; 7:989-99. [PMID: 19609002 DOI: 10.1158/1541-7786.mcr-09-0030] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The importance of DNA repair as a resistance mechanism in gliomas, the most aggressive form of brain tumor, is a clinically relevant topic. Recent studies show that not all cells are equally malignant in gliomas. Certain subpopulations are particularly prone to drive tumor progression and resist chemo- and radiotherapy. Those cells have been variably named cancer stem cells or cancer-initiating cells or tumor-propagating cells, owing to their possible (but still uncertain) origin from normal stem cells. Although DNA repair reduces the efficacy of chemotherapeutics and ionizing radiation toward bulk gliomas, its contribution to resistance of the rare glioma stem cell subpopulations is less clear. Mechanisms other than DNA repair (in particular low proliferation and activation of the DNA damage checkpoint response) are likely main players of resistance in glioma stem cells and their targeting might yield significant therapeutic gains.
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Affiliation(s)
- Guido Frosina
- Molecular Mutagenesis & DNA Repair Unit, Istituto Nazionale Ricerca Cancro, Largo Rosanna Benzi n. 10, 16132 Genova, Italy.
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Viana-Pereira M, Almeida I, Sousa S, Mahler-Araújo B, Seruca R, Pimentel J, Reis RM. Analysis of microsatellite instability in medulloblastoma. Neuro Oncol 2009; 11:458-67. [PMID: 19179424 DOI: 10.1215/15228517-2008-115] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Medulloblastoma is the most common malignant brain tumor in children. The presence of microsatellite instability (MSI) in brain tumors, particularly medulloblastomas, has not been properly addressed. The aim of the present study was to evaluate the role of MSI in medulloblastoma carcinogenesis. MSI status was determined in 36 patients using a pentaplex PCR of quasimonomorphic markers (NR27, NR21, NR24, BAT25, and BAT26). Methylation status of mismatch repair (MMR) genes was achieved by methylation-specific multiplex ligation-dependent probe amplification (MLPA). In addition, MutS homolog 6 (MSH6) expression was determined by immunohistochemistry. Mutations of 10 MSI target genes (TCF4, XRCC2, MBD4, MRE11, ATR, MSH3, TGFBR2, RAD50, MSH6, and BAX) were studied by pentaplex PCR followed by analysis with GeneScan 3.7 software. Mutation analysis of hotspot regions of beta-catenin (CTNNB1) and BRAF (v-raf murine sarcoma viral oncogene homolog B1) oncogenes was performed by PCR single-strand conformation polymorphism analysis followed by direct sequencing. Among the 36 tumors, we found four (11%) cases with instability, one with high MSI and three with low MSI. Methylation analysis of MMR genes in cases presenting shifts on the MSI markers revealed mild hypermethylation of MSH6 in 75% of cases, yet MSH6 was expressed in all the tumors. The MSI target genes MBD4 (methyl-CpG binding domain protein 4) and MRE11 (meiotic recombination 11 homolog A) were mutated in two different tumors. No CTNNB1 or BRAF mutations were found. This study is the most comprehensive analysis of MSI in medulloblastomas to date. We observed the presence of MSI together with mutations of MSI target genes in a small fraction of cases, suggesting a new genetic pathway for a role in medulloblastoma development.
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Affiliation(s)
- Marta Viana-Pereira
- Life and Health Sciences Research Institute, School of Health Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
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Giunti L, Cetica V, Ricci U, Giglio S, Sardi I, Paglierani M, Andreucci E, Sanzo M, Forni M, Buccoliero AM, Genitori L, Genuardi M. Type A microsatellite instability in pediatric gliomas as an indicator of Turcot syndrome. Eur J Hum Genet 2009; 17:919-27. [PMID: 19156169 DOI: 10.1038/ejhg.2008.271] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Microsatellite instability (MSI) is present in hereditary conditions due to mismatch repair (MMR) gene mutations. Following MSI analysis, tumor samples are classified into MSS (stable), MSI-L (low instability), and MSI-H (high instability) based on the fraction of unstable loci. Another MSI-based classification takes into account the size difference between mutant alleles in tumor DNA compared to wild-type alleles; two types of MSI, A and B, are recognized using this approach, type A being characterized by smaller, more subtle allelic shifts compared to type B. Biallelic mutations of MMR genes are associated with pediatric cancers, including glial tumors, in Turcot syndrome type 1 (TS1). However, most TS1-associated gliomas so far analyzed did not display MSI. We investigated the frequency of MSI in a series of 34 pediatric gliomas of different grade using a panel of five mononucleotide quasimonomorphic markers. Subtle qualitative changes were observed for the majority of markers in two glioblastomas (5.9% of the total series and 33.3% of glioblastomas). In both cases, family histories were compatible with TS1, and mutations of the PMS2 and MLH1 genes were identified. In one family, the MSI patterns were compared between the glioblastoma and a colon cancer from an affected relative, showing a clear qualitative difference, with the former displaying type A and the latter type B instability, respectively. These results were confirmed using additional microsatellite markers, indicating that knowledge of the association between TS1-related glial tumors and subtle type A MSI is important for full ascertainment of TS1 patients and appropriate counselling.
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Affiliation(s)
- Laura Giunti
- Medical Genetics Unit, Meyer Children's University Hospital, Florence, Italy
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