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Vanoli A, Perfetti V, Furlan D, Neri G, Viglio A, Sessa F, Martino M, Di Sabatino A, Solcia E, La Rosa S. Long Survival and Prolonged Remission after Surgery and Chemotherapy in a Metastatic Mismatch Repair Deficient Pancreatic Neuroendocrine Carcinoma with MLH1/PMS2 Immunodeficiency and Minimal Microsatellite Shift. Endocr Pathol 2020; 31:411-417. [PMID: 32388775 DOI: 10.1007/s12022-020-09622-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pancreatic neuroendocrine carcinomas (NECs) are rare and very aggressive neoplasms with dismal prognosis, especially when metastatic or with negative prognostic factors, such as vascular invasion. To the best of our knowledge, no case of pancreatic NEC with mismatch repair deficiency has been reported to date. We describe a 62-year-old patient who underwent pancreaticoduodenectomy for a NEC located in the pancreatic head, with peripancreatic lymph node metastases. Tumor necrosis was prominent and the Ki67 proliferative index was 60%. One year after the diagnosis, the patient experienced recurrence with a left supraclavicular lymph node metastasis, which was surgically removed, followed by standard cisplatin-etoposide chemotherapy. Neoplastic cells showed combined loss of expression of MLH1 and PMS2 in both primary tumor and lymph node metastasis. Microsatellite instability (MSI) test using a mononucleotide repeats pentaplex PCR (BAT-25, BAT-26, NR-21, NR-22, and NR-24) revealed minimal mononucleotide shifts showing deletion of less than 3 bp at NR-21, BAT-26, NR-24, and NR-22 loci. MLH1 methylation analysis revealed absence of the gene promoter methylation. BRAF and KRAS mutations were not detected. In gut, NECs' mismatch repair deficiency phenotype has been reported in about 10% of cases, and it represents an independent factor of more favorable outcome. Likewise, our patient is currently alive with a follow-up of more than 12 years after pancreaticoduodenectomy, by itself an unexpected finding for such an aggressive neoplasm.
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Affiliation(s)
- Alessandro Vanoli
- Anatomic Pathology Unit, Department of Molecular Medicine, University of Pavia, and IRCCS San Matteo Hospital, Via Carlo Forlanini 16, 27100, Pavia, Italy.
| | | | - Daniela Furlan
- Anatomic Pathology Unit, Department of Medicine and Surgery, University of Insubria, Varese, Italy
| | - Giuseppe Neri
- Anatomic Pathology Unit, Department of Molecular Medicine, University of Pavia, and IRCCS San Matteo Hospital, Via Carlo Forlanini 16, 27100, Pavia, Italy
| | - Alessandra Viglio
- Anatomic Pathology Unit, Department of Molecular Medicine, University of Pavia, and IRCCS San Matteo Hospital, Via Carlo Forlanini 16, 27100, Pavia, Italy
| | - Fausto Sessa
- Anatomic Pathology Unit, Department of Medicine and Surgery, University of Insubria, Varese, Italy
| | - Michele Martino
- Department of Internal Medicine, IRCCS San Matteo Hospital and University of Pavia, Pavia, Italy
| | - Antonio Di Sabatino
- Department of Internal Medicine, IRCCS San Matteo Hospital and University of Pavia, Pavia, Italy
| | - Enrico Solcia
- Anatomic Pathology Unit, Department of Molecular Medicine, University of Pavia, and IRCCS San Matteo Hospital, Via Carlo Forlanini 16, 27100, Pavia, Italy
| | - Stefano La Rosa
- Institute of Pathology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
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Segura SE, Pedra Nobre S, Hussein YR, Abu-Rustum NR, Weigelt B, Soslow RA, DeLair DF. DNA Mismatch Repair-deficient Endometrial Carcinosarcomas Portend Distinct Clinical, Morphologic, and Molecular Features Compared With Traditional Carcinosarcomas. Am J Surg Pathol 2020; 44:1573-1579. [PMID: 32804882 PMCID: PMC8259346 DOI: 10.1097/pas.0000000000001561] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Uterine carcinosarcomas (UCSs) are aggressive neoplasms composed of high-grade malignant epithelial and mesenchymal elements with most (∼90%) showing TP53 abnormalities. A subset, however, shows mismatch repair deficiency (MMR-D). We sought to describe their clinical, morphologic, and molecular features. Clinicopathologic data of MMR-D UCSs were recorded including age, stage, follow-up, mismatch repair and p53 immunohistochemistry (IHC), MLH1 promoter methylation status, and germline alterations, TP53 mutation status, microsatellite instability and mutational burden by massively parallel sequencing. Seventeen (6.2%) MMR-D were identified among 276 UCSs. Of MMR-D UCSs, the median age was 60 years. mismatch repair IHC loss is as follows: MLH1/PMS2 65%, MSH2/MSH6 18%, MSH6 12%, and PMS2 6%. MLH1 promoter methylation and Lynch syndrome was identified in 47% and 12% of cases, respectively. Cases with p53 IHC showed the following patterns: wild-type 70%, aberrant 20%, and equivocal 10%. Of cases with sequencing, 88% were hypermutated and microsatellite instability high. High-grade endometrioid, undifferentiated, and clear cell carcinoma was present in 53%, 41%, and 6% of cases, respectively and 47% also showed a low-grade endometrioid component. Most patients presented at an early stage (67%) and upon follow-up, 18% died of disease, 65% showed no evidence of disease, while 18% are alive with disease. Patients with MMR-D UCS are younger than the reported median age (70 y) for traditional UCS and most do not show p53 abnormalities. Low-grade endometrioid and undifferentiated carcinoma were seen in approximately half of all cases. Although UCSs have a high tendency for early extrauterine spread, most patients in our cohort presented at an early stage and at follow-up were no evidence of disease. MMR-D UCSs display distinct clinical, morphologic, and molecular features compared with traditional UCSs.
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Affiliation(s)
| | | | | | - Nadeem R Abu-Rustum
- Gynecology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY
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Takahashi N, Rajapakse VN, Pongor L, Kumar S, Tlemsani C, Erwin-Cohen R, Young HA, Hewitt S, Wei JS, Khan J, Villarino AV, Trepel JB, Thomas A. Dynamics of genomic and immune responses during primary immunotherapy resistance in mismatch repair-deficient tumors. Cold Spring Harb Mol Case Stud 2020; 6:a005678. [PMID: 33028646 PMCID: PMC7552928 DOI: 10.1101/mcs.a005678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 08/10/2020] [Indexed: 12/22/2022] Open
Abstract
Mismatch repair-deficient (dMMR) cancers generate a substantial number of immunogenic neoantigens, rendering them sensitive to immunotherapy. Yet, there is considerable variability in responses, and roughly one-half of dMMR cancers are refractory to immunotherapy. Here we study a patient with dMMR lung cancer refractory to immunotherapy. The tumor exhibited typical dMMR molecular features, including exceptionally high frameshift insertions and deletions (indels). Despite the treatment inducing abundant intratumoral T-cell infiltrates, it failed to elicit tumor regression, pointing to the T cells lacking cytotoxic activity. A post-treatment tumor demonstrated compound heterozygous frameshift deletions located upstream of the kinase domain in the gene encoding JAK1 protein, down-regulation of JAK1 and mediators of its signal transduction, and total loss of JAK1 phosphorylation. Importantly, one of the JAK1 mutations, despite not being detected in the pretreatment tumor, was found at low variant allele frequency in the pretreatment circulating tumor DNA, suggesting clonal selection of the mutation. To our knowledge, this report provides the most detailed look yet at defective JAK1 signaling in the context of dMMR and immunotherapy resistance. Together with observations of JAK1 frameshift indels being enriched in dMMR compared with MMR-proficient tumors, our findings demonstrate the critical function of JAK1 in immunological surveillance of dMMR cancer.
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Affiliation(s)
- Nobuyuki Takahashi
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Vinodh N Rajapakse
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Lorinc Pongor
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Suresh Kumar
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Camille Tlemsani
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Rebecca Erwin-Cohen
- Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Howard A Young
- Laboratory of Cancer Immunometabolism, Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Stephen Hewitt
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Jun S Wei
- Genetics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Javed Khan
- Genetics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Alejandro V Villarino
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, Florida 33136, USA
| | - Jane B Trepel
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Anish Thomas
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
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Hodel KP, Sun MJS, Ungerleider N, Park VS, Williams LG, Bauer DL, Immethun VE, Wang J, Suo Z, Lu H, McLachlan JB, Pursell ZF. POLE Mutation Spectra Are Shaped by the Mutant Allele Identity, Its Abundance, and Mismatch Repair Status. Mol Cell 2020; 78:1166-1177.e6. [PMID: 32497495 PMCID: PMC8177757 DOI: 10.1016/j.molcel.2020.05.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 04/10/2020] [Accepted: 05/11/2020] [Indexed: 12/11/2022]
Abstract
Human tumors with exonuclease domain mutations in the gene encoding DNA polymerase ε (POLE) have incredibly high mutation burdens. These errors arise in four unique mutation signatures occurring in different relative amounts, the etiologies of which remain poorly understood. We used CRISPR-Cas9 to engineer human cell lines expressing POLE tumor variants, with and without mismatch repair (MMR). Whole-exome sequencing of these cells after defined numbers of population doublings permitted analysis of nascent mutation accumulation. Unlike an exonuclease active site mutant that we previously characterized, POLE cancer mutants readily drive signature mutagenesis in the presence of functional MMR. Comparison of cell line and human patient data suggests that the relative abundance of mutation signatures partitions POLE tumors into distinct subgroups dependent on the nature of the POLE allele, its expression level, and MMR status. These results suggest that different POLE mutants have previously unappreciated differences in replication fidelity and mutagenesis.
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Affiliation(s)
- Karl P Hodel
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Meijuan J S Sun
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Nathan Ungerleider
- Department of Pathology, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA
| | - Vivian S Park
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Leonard G Williams
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA; BioInnovation Program, Tulane University, New Orleans, LA 70112, USA
| | - David L Bauer
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Victoria E Immethun
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Jieqiong Wang
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA
| | - Zucai Suo
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
| | - Hua Lu
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA
| | - James B McLachlan
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Zachary F Pursell
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA.
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Abstract
Recent studies have suggested an increased risk of prostate cancer in men with Lynch syndrome driven by germline mutations in mismatch repair (MMR) genes. However, the incidence and clinical implication of MMR deficiency in sporadic prostate cancers remain poorly understood. We immunohistochemically stained for MLH1, MSH2, MSH6, and PMS2 in a set of tissue microarray consisting of 220 radical prostatectomy specimens and evaluated the relationship between loss of their expression and available clinicopathological features. MLH1, MSH2, MSH6, and PMS2 were lost in 2 (0.9%), 6 (2.7%), 37 (16.8%), and 27 (12.3%) prostate cancers, respectively. Loss of at least 1 MMR protein was identified in 50 (22.7%) cases. There were no statistically significant associations between MMR deficiency and patient age, family history of prostate cancer, Gleason score, or pT/pN stage. Nonetheless, the levels of preoperative prostate-specific antigen (PSA) were significantly (P = .015) higher in patients with MMR deficiency (mean ± SD: 9.12 ± 9.01 ng/mL) than in those without abnormal MMR (5.76 ± 3.17 ng/mL). There were 15 (6.8%) cases showing loss of at least 2 MMR proteins, which was not significantly associated with PSA level or tumor grade/stage. Additionally, 5 and 2 cases showed losses of at least 3 MMR proteins and all 4 proteins, respectively. Kaplan-Meier analysis revealed no significant associations between loss of MLH1 (P = .373), MSH2 (P = .348), MSH6 (P = .946), or PMS2 (P = .681), or at least 1 (P = .477), 2 (P = .486), or 3 (P = .352) MMR proteins and biochemical recurrence. Further analyses of the data on programmed death-ligand 1 (PD-L1) expression previously stained in the same set of tissue microarray demonstrated associations between loss of ≥2 MMR proteins and a higher rate of PD-L1 expression in cancer cells (17.2% vs 5.2%; P = .033) as well as between cases showing both loss of ≥1 MMR protein(s) and PD-L1 expression in tumor-infiltrating immune cells vs a higher risk of biochemical recurrence (P = .045). MMR protein loss was seen in a subset of prostate cancers. Interestingly, it was associated with significantly higher levels of PSA. Moreover, immunohistochemical detection of MMR proteins together with other proteins, such as PD-L1, might be helpful in predicting tumor recurrence following radical prostatectomy.
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Affiliation(s)
| | | | - Hiroshi Miyamoto
- Department of Pathology and Laboratory Medicine
- Department of Urology
- James P. Wilmot Cancer Institute, University of Rochester Medical Center, Rochester, NY
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Polychronidou G, Kotoula V, Manousou K, Kostopoulos I, Karayannopoulou G, Vrettou E, Bobos M, Raptou G, Efstratiou I, Dionysopoulos D, Chatzopoulos K, Lakis S, Chrisafi S, Tsolakidis D, Papanikolaou A, Dombros N, Fountzilas G. Mismatch repair deficiency and aberrations in the Notch and Hedgehog pathways are of prognostic value in patients with endometrial cancer. PLoS One 2018; 13:e0208221. [PMID: 30521558 PMCID: PMC6283658 DOI: 10.1371/journal.pone.0208221] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 11/14/2018] [Indexed: 12/13/2022] Open
Abstract
The aim of this study was to investigate the prognostic value of the Hedgehog (Gli, Patched-1, Shh, Smo) and Notch (Jag1, Notch2, Notch3) pathway members, in comparison to a panel of proteins (ER, PgR, HER2/neu, Ki67, p53, p16, PTEN and MMR) previously suggested to be involved in the pathogenesis of endometrial cancer, in association with clinical outcome and standard clinicopathological characteristics. A total of 204 patients with histological diagnosis of endometrial cancer treated from 2004 to 2013 were included. The evaluation of protein expression was assessed by immunohistochemistry. Univariate analysis showed that higher Ki67 labeling, expression of PTEN, p16, Notch2 and Notch3 proteins, as well as MMR proficiency were associated with increased relapse and mortality rate. Additionally, Patched-1 protein expression was associated with worse DFS, while p53 overexpression was associated with worse OS. In multivariate analyses, patients with MMR proficient tumors had more than double risk for death than patients with MMR deficient (MMRd) tumors (adjusted HR = 2.19, 95% CI 1.05–4.58, p = 0.036). Jag1 positivity conferred reduced mortality risk (HR = 0.48, 95% CI 0.23–0.97, p = 0.042). However, as shown by hierarchical clustering, patients fared better when their tumors expressed high Jag1 protein in the absence of Notch2 and Notch3, while they fared worse when all three proteins were highly expressed. Patched-1 positivity conferred higher risk for relapse (HR = 2.04, 95% CI 1.05–3.96, p = 0.036). Aberrant expression of key components of the Notch and Hedgehog signaling pathways, as well as MMRd may serve as independent prognostic factors for recurrence and survival in patients with endometrial cancer.
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Affiliation(s)
- Genovefa Polychronidou
- Department of Medical Oncology, Papageorgiou Hospital, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
- * E-mail: (GP); (VK)
| | - Vassiliki Kotoula
- Department of Pathology, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
- Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece
- * E-mail: (GP); (VK)
| | - Kyriaki Manousou
- Section of Biostatistics, Hellenic Cooperative Oncology Group, Data Office, Athens, Greece
| | - Ioannis Kostopoulos
- Department of Pathology, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
| | - Georgia Karayannopoulou
- Department of Pathology, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
| | - Eleni Vrettou
- Department of Pathology, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
| | - Mattheos Bobos
- Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Georgia Raptou
- Department of Pathology, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
| | | | - Dimitrios Dionysopoulos
- Department of Medical Oncology, Papageorgiou Hospital, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece
| | - Kyriakos Chatzopoulos
- Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Sotirios Lakis
- Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Sofia Chrisafi
- Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Dimitrios Tsolakidis
- First Department of Obstetrics and Gynaecology, Papageorgiou General Hospital, Aristotle University of Thessaloniki, Thessaloniki
| | - Alexios Papanikolaou
- First Department of Obstetrics and Gynaecology, Papageorgiou General Hospital, Aristotle University of Thessaloniki, Thessaloniki
| | | | - George Fountzilas
- Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece
- Aristotle University of Thessaloniki, Thessaloniki, Greece
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Gupta D, Lin B, Cowan A, Heinen CD. ATR-Chk1 activation mitigates replication stress caused by mismatch repair-dependent processing of DNA damage. Proc Natl Acad Sci U S A 2018; 115:1523-1528. [PMID: 29378956 PMCID: PMC5816205 DOI: 10.1073/pnas.1720355115] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The mismatch repair pathway (MMR) is essential for removing DNA polymerase errors, thereby maintaining genomic stability. Loss of MMR function increases mutation frequency and is associated with tumorigenesis. However, how MMR is executed at active DNA replication forks is unclear. This has important implications for understanding how MMR repairs O6-methylguanine/thymidine (MeG/T) mismatches created upon exposure to DNA alkylating agents. If MeG/T lesion recognition by MMR initiates mismatch excision, the reinsertion of a mismatched thymidine during resynthesis could initiate futile repair cycles. One consequence of futile repair cycles might be a disruption of overall DNA replication in the affected cell. Herein, we show that in MMR-proficient HeLa cancer cells, treatment with a DNA alkylating agent slows S phase progression, yet cells still progress into the next cell cycle. In the first S phase following treatment, they activate ataxia telangiectasia and Rad3-related (ATR)-Checkpoint Kinase 1 (Chk1) signaling, which limits DNA damage, while inhibition of ATR kinase activity accelerates DNA damage accumulation and sensitivity to the DNA alkylating agent. We also observed that exposure of human embryonic stem cells to alkylation damage severely compromised DNA replication in a MMR-dependent manner. These cells fail to activate the ATR-Chk1 signaling axis, which may limit their ability to handle replication stress. Accordingly, they accumulate double-strand breaks and undergo immediate apoptosis. Our findings implicate the MMR-directed response to alkylation damage as a replication stress inducer, suggesting that repeated MMR processing of mismatches may occur that can disrupt S phase progression.
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Affiliation(s)
- Dipika Gupta
- Neag Comprehensive Cancer Center, UConn Health, Farmington, CT 06030-3101
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101
| | - Bo Lin
- Neag Comprehensive Cancer Center, UConn Health, Farmington, CT 06030-3101
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101
| | - Ann Cowan
- R. D. Berlin Center for Cell Analysis and Modeling, UConn Health, Farmington, CT 06030
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030
| | - Christopher D Heinen
- Neag Comprehensive Cancer Center, UConn Health, Farmington, CT 06030-3101;
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101
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Cionca FL, Dobre M, Dobrea CM, Iosif CI, Comănescu MV, Ardeleanu CM. Mutational status of KRAS and MMR genes in a series of colorectal carcinoma cases. Rom J Morphol Embryol 2018; 59:121-129. [PMID: 29940619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
BACKGROUND The KRAS gene mutation is the most common somatic change in colorectal carcinoma (CRC) and is predictive of resistance to anti-epidermal growth factor receptor (EGFR) therapy in the metastatic forms. Microsatellite instability (MSI), a mismatch repair (MMR) system defect, accounts for 15-20% of all CRCs, more frequent in early stages. CRCs with MSI present better prognosis, a distinct histopathological aspect and a different response to chemotherapy. Patients with both KRAS wild type and MSI have a reduced risk of dissemination and recurrence. MATERIALS AND METHODS Our study included formalin-fixed paraffin-embedded tissue samples from 40 patients with metastatic CRCs, aged between 40 and 71 years old, gender (males/females) ratio 2.33:1. The MMR proteins were analyzed using an indirect bistadial immunohistochemical (IHC) technique with monoclonal antibodies. KRAS mutations were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. RESULTS Of the 40 tumors analyzed, 40% presented KRAS mutations located in codon 12 or codon 13. IHC expression of MMR proteins revealed a microsatellite stable status in 35 cases, including 15 cases with mutated KRAS. MSI status was identified in five cases (four with KRAS wild type). All MSI tumors had a poorer histological differentiation and four cases revealed a mucinous phenotype. Eighty percent of the patients with MSI status were older women. CONCLUSIONS Our study demonstrates a 20% frequency of mutated KRAS in MSI CRCs, the incidence of KRAS mutations being inversely correlated with MSI status in these tumors. MMR protein deficient CRCs tend to occur in older females, have a poorer differentiation and are frequently associated with KRAS wild type.
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Affiliation(s)
- Florina Lucia Cionca
- "Victor Babes" National Institute for Research and Development in Pathology and Biomedical Sciences, Bucharest, Romania;
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Abstract
DNA molecules are not completely stable, they are subject to chemical or photochemical damage and errors that occur during DNA replication resulting in mismatched base pairs. Through mechanistic studies Paul Modrich showed how replication errors are corrected by strand-directed mismatch repair in Escherichia coli and human cells.
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Affiliation(s)
- Paul Modrich
- Howard Hughes Medical Institute and Department of Biochemistry, Duke University, Medical Center, Durham, NC, 27710, USA.
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10
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Abstract
Highly conserved MutS homologs (MSH) and MutL homologs (MLH/PMS) are the fundamental components of mismatch repair (MMR). After decades of debate, it appears clear that the MSH proteins initiate MMR by recognizing a mismatch and forming multiple extremely stable ATP-bound sliding clamps that diffuse without hydrolysis along the adjacent DNA. The function(s) of MLH/PMS proteins is less clear, although they too bind ATP and are targeted to MMR by MSH sliding clamps. Structural analysis combined with recent real-time single molecule and cellular imaging technologies are providing new and detailed insight into the thermal-driven motions that animate the complete MMR mechanism.
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Affiliation(s)
- Richard Fishel
- From the Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210 and the Department of Physics and the Biophysics Program, The Ohio State University, Columbus, Ohio 43210
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11
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Fukui K. [Regulatory mechanism for DNA mismatch repair endonuclease]. Seikagaku 2015; 87:212-217. [PMID: 26571579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
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12
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Abstract
Homologous recombination (HR) and mismatch repair (MMR) are inextricably linked. HR pairs homologous chromosomes before meiosis I and is ultimately responsible for generating genetic diversity during sexual reproduction. HR is initiated in meiosis by numerous programmed DNA double-strand breaks (DSBs; several hundred in mammals). A characteristic feature of HR is the exchange of DNA strands, which results in the formation of heteroduplex DNA. Mismatched nucleotides arise in heteroduplex DNA because the participating parental chromosomes contain nonidentical sequences. These mismatched nucleotides may be processed by MMR, resulting in nonreciprocal exchange of genetic information (gene conversion). MMR and HR also play prominent roles in mitotic cells during genome duplication; MMR rectifies polymerase misincorporation errors, whereas HR contributes to replication fork maintenance, as well as the repair of spontaneous DSBs and genotoxic lesions that affect both DNA strands. MMR suppresses HR when the heteroduplex DNA contains excessive mismatched nucleotides, termed homeologous recombination. The regulation of homeologous recombination by MMR ensures the accuracy of DSB repair and significantly contributes to species barriers during sexual reproduction. This review discusses the history, genetics, biochemistry, biophysics, and the current state of studies on the role of MMR in homologous and homeologous recombination from bacteria to humans.
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Affiliation(s)
- Maria Spies
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
| | - Richard Fishel
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University Medical Center and Comprehensive Cancer Center, Columbus, Ohio 43210 Human Genetics Institute, The Ohio State University Medical Center, Columbus, Ohio 43210 Physics Department, The Ohio State University, Columbus, Ohio 43210
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Abstract
Three processes act in series to accurately replicate the eukaryotic nuclear genome. The major replicative DNA polymerases strongly prevent mismatch formation, occasional mismatches that do form are proofread during replication, and rare mismatches that escape proofreading are corrected by mismatch repair (MMR). This review focuses on MMR in light of increasing knowledge about nuclear DNA replication enzymology and the rate and specificity with which mismatches are generated during leading- and lagging-strand replication. We consider differences in MMR efficiency in relation to mismatch recognition, signaling to direct MMR to the nascent strand, mismatch removal, and the timing of MMR. These studies are refining our understanding of relationships between generating and repairing replication errors to achieve accurate replication of both DNA strands of the nuclear genome.
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Affiliation(s)
- Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, North Carolina 27709;
| | - Dorothy A Erie
- Department of Chemistry and Curriculum in Applied Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina 27599-3290;
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14
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Ahmad M, Tuteja R. Emerging importance of mismatch repair components including UvrD helicase and their cross-talk with the development of drug resistance in malaria parasite. Mutat Res 2014; 770:54-60. [PMID: 25771870 DOI: 10.1016/j.mrfmmm.2014.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 08/14/2014] [Accepted: 09/17/2014] [Indexed: 06/04/2023]
Abstract
Human malaria is an important parasitic infection responsible for a significant number of deaths worldwide, particularly in tropical and subtropical regions. The recent scenario has worsened mainly because of the emergence of drug-resistant malaria parasites having the potential to spread across the world. Drug-resistant parasites possess a defective mismatch repair (MMR); therefore, it is essential to explore its mechanism in detail to determine the underlying cause. Recently, artemisinin-resistant parasites have been reported to exhibit nonsynonymous single nucleotide polymorphisms in genes involved in MMR pathways such as MutL homolog (MLH) and UvrD. Plasmodium falciparum MLH is an endonuclease required to restore the defective MMR in drug-resistant W2 strain of P. falciparum. Although the role of helicases in eukaryotic MMR has been questioned, the identification and characterization of the UvrD helicase and their cross-talk with MLH in P. falciparum suggests the possible involvement of UvrD in MMR. A comparative genome-wide analysis revealed the presence of the UvrD helicase in Plasmodium species, while it is absent in human host. Therefore, PfUvrD may emerge as a suitable drug target to control malaria. This review study is focused on recent developments in MMR biochemistry, emerging importance of the UvrD helicase, possibility of its involvement in MMR and the emerging cross-talk between MMR components and drug resistance in malaria parasite.
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Affiliation(s)
- Moaz Ahmad
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Renu Tuteja
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110067, India.
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15
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Droeser RA, Hirt C, Viehl CT, Frey DM, Nebiker C, Huber X, Zlobec I, Eppenberger-Castori S, Tzankov A, Rosso R, Zuber M, Muraro MG, Amicarella F, Cremonesi E, Heberer M, Iezzi G, Lugli A, Terracciano L, Sconocchia G, Oertli D, Spagnoli GC, Tornillo L. Clinical impact of programmed cell death ligand 1 expression in colorectal cancer. Eur J Cancer 2013; 49:2233-42. [PMID: 23478000 DOI: 10.1016/j.ejca.2013.02.015] [Citation(s) in RCA: 344] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 01/29/2013] [Accepted: 02/10/2013] [Indexed: 12/22/2022]
Abstract
BACKGROUND Programmed cell death 1 (PD-1) receptor triggering by PD ligand 1 (PD-L1) inhibits T cell activation. PD-L1 expression was detected in different malignancies and associated with poor prognosis. Therapeutic antibodies inhibiting PD-1/PD-L1 interaction have been developed. MATERIALS AND METHODS A tissue microarray (n=1491) including healthy colon mucosa and clinically annotated colorectal cancer (CRC) specimens was stained with two PD-L1 specific antibody preparations. Surgically excised CRC specimens were enzymatically digested and analysed for cluster of differentiation 8 (CD8) and PD-1 expression. RESULTS Strong PD-L1 expression was observed in 37% of mismatch repair (MMR)-proficient and in 29% of MMR-deficient CRC. In MMR-proficient CRC strong PD-L1 expression correlated with infiltration by CD8(+) lymphocytes (P = 0.0001) which did not express PD-1. In univariate analysis, strong PD-L1 expression in MMR-proficient CRC was significantly associated with early T stage, absence of lymph node metastases, lower tumour grade, absence of vascular invasion and significantly improved survival in training (P = 0.0001) and validation (P = 0.03) sets. A similar trend (P = 0.052) was also detectable in multivariate analysis including age, sex, T stage, N stage, tumour grade, vascular invasion, invasive margin and MMR status. Interestingly, programmed death receptor ligand 1 (PDL-1) and interferon (IFN)-γ gene expression, as detected by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in fresh frozen CRC specimens (n = 42) were found to be significantly associated (r = 0.33, P = 0.03). CONCLUSION PD-L1 expression is paradoxically associated with improved survival in MMR-proficient CRC.
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Affiliation(s)
- Raoul A Droeser
- Department of Surgery, University Hospital of Basel, Switzerland; Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland.
| | - Christian Hirt
- Department of Surgery, University Hospital of Basel, Switzerland; Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Carsten T Viehl
- Department of Surgery, University Hospital of Basel, Switzerland
| | - Daniel M Frey
- Department of Surgery, University Hospital of Basel, Switzerland
| | - Christian Nebiker
- Department of Surgery, University Hospital of Basel, Switzerland; Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Xaver Huber
- Department of Surgery, University Hospital of Basel, Switzerland
| | - Inti Zlobec
- Institute of Pathology, University of Bern, Switzerland
| | | | | | - Raffaele Rosso
- Department of Surgery, Ospedale Regionale di Lugano, Switzerland
| | - Markus Zuber
- Department of Surgery, Kantonsspital Olten, Switzerland
| | - Manuele Giuseppe Muraro
- Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Francesca Amicarella
- Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Eleonora Cremonesi
- Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Michael Heberer
- Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Giandomenica Iezzi
- Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | | | | | - Giuseppe Sconocchia
- Institute of Translational Pharmacology, National Council Research, Rome, Italy
| | - Daniel Oertli
- Department of Surgery, University Hospital of Basel, Switzerland
| | - Giulio C Spagnoli
- Institute for Surgical Research and Hospital Management ICFS, Department of Biomedicine, University of Basel, Switzerland
| | - Luigi Tornillo
- Institute of Pathology, University of Basel, Switzerland
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16
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Williams SA, Wilson JB, Clark AP, Mitson-Salazar A, Tomashevski A, Ananth S, Glazer PM, Semmes OJ, Bale AE, Jones NJ, Kupfer GM. Functional and physical interaction between the mismatch repair and FA-BRCA pathways. Hum Mol Genet 2011; 20:4395-410. [PMID: 21865299 PMCID: PMC3196888 DOI: 10.1093/hmg/ddr366] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/14/2011] [Accepted: 08/15/2011] [Indexed: 12/27/2022] Open
Abstract
Fanconi anemia (FA) is a rare genetic disorder characterized by bone marrow failure and an increased risk for leukemia and cancer. Fifteen proteins thought to function in the repair of DNA interstrand crosslinks (ICLs) comprise what is known as the FA-BRCA pathway. Activation of this pathway leads to the monoubiquitylation and chromatin localization of FANCD2 and FANCI. It has previously been shown that FANCJ interacts with the mismatch repair (MMR) complex MutLα. Here we show that FANCD2 interacts with the MMR proteins MSH2 and MLH1. FANCD2 monoubiquitylation, foci formation and chromatin loading are greatly diminished in MSH2-deficient cells. Human or mouse cells lacking MSH2 or MLH1 display increased sensitivity and radial formation in response to treatment with DNA crosslinking agents. Studies in human cell lines and Drosophila mutants suggest an epistatic relationship between FANCD2, MSH2 and MLH1 with regard to ICL repair. Surprisingly, the interaction between MSH2 and MLH1 is compromised in multiple FA cell lines, and FA cell lines exhibit deficient MMR. These results suggest a significant role for MMR proteins in the activation of the FA pathway and repair of ICLs. In addition, we provide the first evidence for a defect in MMR in FA cell lines.
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Affiliation(s)
| | - James B. Wilson
- Department of Biochemistry and Cell Biology, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | | | | | - Andrei Tomashevski
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229, USA and
| | - Sahana Ananth
- Department of Biochemistry and Cell Biology, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Peter M. Glazer
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - O. John Semmes
- Department of Microbiology and Molecular Cell Biology, Center for Biomedical Proteomics, Eastern Virginia Medical School, Norfolk, VA 23507, USA
| | | | - Nigel J. Jones
- Department of Biochemistry and Cell Biology, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Gary M. Kupfer
- Division of Pediatric Hematology-Oncology, Department of Pediatrics
- Department of Pathology
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17
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Sugai T, Uesugi N, Habano W, Suzuki K. [Microsatellite instability]. Nihon Rinsho 2011; 69 Suppl 3:84-93. [PMID: 22213936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Affiliation(s)
- Tamotsu Sugai
- Division of Molecular Diagnostic Pathology, Department of Pathology, School of Medicine, Iwate Medical University
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18
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Zhao DB, Chandler I, Chen ZM, Pan HC, Popat S, Shao YF, Houlston RS. Mismatch repair, minichromosome maintenance complex component 2, cyclin A, and transforming growth factor β receptor type II as prognostic factors for colorectal cancer: results of a 10-year prospective study using tissue microarray analysis. Chin Med J (Engl) 2011; 124:483-490. [PMID: 21362268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023] Open
Abstract
BACKGROUND The expression of genes encoding a number of pathogenetic pathways involved in colorectal cancer could potentially act as prognostic markers. Large prospective studies are required to establish their relevance to disease prognosis. METHODS We investigated the relevance of 19 markers in 790 patients enrolled in a large randomised trial of 5-fluorouracil using immunohistochemistry and chromogenic in situ hybridisation. The relationship between overall 10-year survival and marker status was assessed. RESULTS Minichromosome maintenance complex component 2 (MCM2) and cyclin A were significantly associated with overall survival. Elevated MCM2 expression was associated with a better prognosis (HR = 0.63, 95%CI: 0.46 - 0.86). Cyclin A expression above the median predicted an improved patient prognosis (HR = 0.71, 95%CI: 0.53 - 0.95). For mismatch repair deficiency and transforming growth factor β receptor type II (TGFBRII) overexpression there was a borderline association with a poorer prognosis (HR = 0.69, 95%CI: 0.46 - 1.04 and HR = 2.11, 95%CI: 1.02 - 4.40, respectively). No apparent associations were found for other markers. CONCLUSION This study identified cell proliferation and cyclin A expression as prognostic indicators of patient outcome in colorectal cancer.
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Affiliation(s)
- Dong-bing Zhao
- Department of Abdominal Surgical Oncology, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
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19
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Li SY, Zhang XY, Zhang X, Lan Y, Hua ZC. A convenient fluorescent-labeled assay for in vitro measurement of DNA mismatch repair activity. Biomed Environ Sci 2010; 23:496-501. [PMID: 21315249 DOI: 10.1016/s0895-3988(11)60013-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 09/17/2010] [Indexed: 05/30/2023]
Abstract
OBJECTIVE The assay of DNA mismatch repair (MMR) activity can be used as a biomarker for environmental condition detection and human disease diagnosis. Radioactive ³²P-endlabeled DNA containing mismatch is extensively used as the substrate for MMR activity analyses. The aim of the present study is to develop a simple non-radioactive, but equally specific and sensitive method for the MMR activity assay. METHODS A fluorescent label was chosen to replace the radioactive isotope label. Sensitive evaluation of the fluorescent label was carried out for the first time, and then the fluorescent label was compared with the isotope label in the MMR activity and DNA binding assays. RESULT LOD (limit of detection) of the fluorescent label was about 0.1 fmol and the relative signal strength displayed a pretty good linear relationship. Moreover, the fluorescent label method has equivalent sensitivity and performance as compared with the classical radioactive method in experiments. CONCLUSION In light of the sensitivity, reproducibility, safety, rapidity and long lifespan of the fluorescent label, this improved method can be applied to evaluation of biologic and toxic effects of environmental pollutants on man and other forms of life.
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Affiliation(s)
- Shi-Ying Li
- The State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Center of Hepatobiliary Diseases, School of Stomatology and Affiliated Stomatological Hospital, Nanjing University, Nanjing 210093, Jiangsu, China
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20
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Jiang Z, Jin S, Yalowich JC, Brown KD, Rajasekaran B. The mismatch repair system modulates curcumin sensitivity through induction of DNA strand breaks and activation of G2-M checkpoint. Mol Cancer Ther 2010; 9:558-68. [PMID: 20145018 PMCID: PMC2837109 DOI: 10.1158/1535-7163.mct-09-0627] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The highly conserved mismatch (MMR) repair system corrects postreplicative errors and modulates cellular responses to genotoxic agents. Here, we show that the MMR system strongly influences cellular sensitivity to curcumin. Compared with MMR-proficient cells, isogenically matched MMR-deficient cells displayed enhanced sensitivity to curcumin. Similarly, cells suppressed for MLH1 or MSH2 expression by RNA interference displayed increased curcumin sensitivity. Curcumin treatment generated comparable levels of reactive oxygen species and the mutagenic adduct 8-oxo-guanine in MMR-proficient and MMR-deficient cells; however, accumulation of gammaH2AX foci, a marker for DNA double-strand breaks (DSB), occurred only in MMR-positive cells in response to curcumin treatment. Additionally, MMR-positive cells showed activation of Chk1 and induction of G(2)-M cell cycle checkpoint following curcumin treatment and inhibition of Chk1 by UCN-01 abrogated Chk1 activation and heightened apoptosis in MMR-proficient cells. These results indicate that curcumin triggers the accumulation of DNA DSB and induction of a checkpoint response through a MMR-dependent mechanism. Conversely, in MMR-compromised cells, curcumin-induced DSB is significantly blunted, and as a result, cells fail to undergo cell cycle arrest, enter mitosis, and die through mitotic catastrophe. The results have potential therapeutic value, especially in the treatment of tumors with compromised MMR function.
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Affiliation(s)
- Zhihua Jiang
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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21
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Abstract
The human genome encodes numerous enzymes capable of deaminating polynucleotides. While they are capable of exquisite specificity, occasionally they result in hypermutation where up to 90 per cent of cytidine or adenosine residues may be edited. As such, they constitute a formidable anti-viral barrier, for no virus can survive such a high mutation rate. As the APOBEC3 group of cytidine deaminases edit single-stranded viral DNA, the crucial question is can they hyperedit chromosomal DNA? Everything points to a positive answer. Nonetheless, hypermutants per se have not yet been described, probably being countered by highly efficient mismatch repair. For the APOBEC3 genes, not only is their physiological function unknown, but also their role in the induction of cancer remains to be determined. Yet given the pace of research, all this is certain to change in the next few years.
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Affiliation(s)
| | | | - Simon Wain-Hobson
- Molecular Retrovirology Unit, CNRS URA 3015, Institut Pasteur28 rue du Docteur Roux, 75724 Paris cedex 15, France
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22
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He Y, Zhuang ZX, He CH, Liu RQ. [DNA mismatch repair enzyme hMSH2 genetic polymorphism in southern Chinese Han population]. Zhonghua Yi Xue Yi Chuan Xue Za Zhi 2003; 20:256-8. [PMID: 12778459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
OBJECTIVE To study hMSH2 genetic polymorphism in southern Chinese Han population. METHODS The basic materials and blood samples from 163 southern Chinese were collected. The mutations of exon 6 and exon 7 of hMSH2 gene were investigated by PCR-SSCP, followed by DNA sequencing. RESULTS Fragments of 250 bp including exon 6 and fragments of 323 bp including exon 7 of hMSH2 gene were amplified by multiple PCR. The allele frequencies of C18, A82 and B39 type mutations were 0.0184, 0.0031, 0.0031, respectively. The gene frequencies and gene type frequencies of three polymorphism sites in normal population accorded with Hardy-Weinberg equilibrium (P>0.05). The heterozygosity of C18 type mutation (0.0361) was the highest. CONCLUSION There were three polymorphism sites in exon 7 of hMSH2 gene in southern Chinese Han population, among which the genotype frequency of C18 type was the highest, suggesting that C18 type mutation be a useful genetic mark.
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Affiliation(s)
- Yun He
- Faculty of Preventive Medicine, School of Public Health, Sun Yat-Sen University, Guangzhou, Guangdong, 510080 PR China.
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