Impaired DNA Repair Research Articles

The association between inefficient repair of oxidative DNA lesions and common polymorphisms of the key base excision repair genes as well as their expression levels in patients with Rheumatoid Arthritis

IntroductionRA is a common autoimmune heterogeneous joint disease of still unknown etiology. One of the characteristic features of RA is oxidative stress, most probably induced and stimulated by inappropriate B and T-cell activity. We have hypothesized, that oxidative stress together with impaired DNA damage response to oxidative DNA lesions could be responsible for increased incidence in RA patients of some diseases with genetic instability background such as lymphoma.Material and methodsWe determined the level of oxidative DNA lesions and the kinetics of removal of DNA damage induced by TBH in PBMCs of 30 RA patients and 30 healthy individuals. The metrics from DNA repair study were correlated with genotypes of common polymorphisms of key BER genes as well as their expression levels. DNA repair were evaluated by comet assay, the genotypes of the polymorphism were determined by Taqman Assay and PrimeTime qPCR Assay was used to analyze the expression profile of genes related to BER.ResultsWe observed an association between RA occurrences and impaired DNA repair in PBMCs. After dividing the subjects by controls’ quartiles of DNA repair efficiency, we found an association between an increased risk of RA and inefficient DNA Repair. We also identified interaction between inefficient DNA Repair and polymorphism of the UNG gene (rs246079), and lower expression of key BER genes – MUTH, NEIL3 and UNG.ConclusionsOur result suggest that the genetic variations within BER genes as well as epigenetic factors may be linked with RA by the modulation of the cellular response to oxidative stress.

MND1 and PSMC3IP control PARP inhibitor sensitivity in mitotic cells

The PSMC3IP-MND1 heterodimer promotes meiotic D loop formation before DNA strand exchange. In genome-scale CRISPR-Cas9 mutagenesis and interference screens in mitotic cells, depletion of PSMC3IP or MND1 causes sensitivity to poly (ADP-Ribose) polymerase inhibitors (PARPi) used in cancer treatment. PSMC3IP or MND1 depletion also causes ionizing radiation sensitivity. These effects are independent of PSMC3IP/MND1's role in mitotic alternative lengthening of telomeres. PSMC3IP- or MND1-depleted cells accumulate toxic RAD51 foci in response to DNA damage, show impaired homology-directed DNA repair, and become PARPi sensitive, even in cells lacking both BRCA1 and TP53BP1. Epistasis between PSMC3IP-MND1 and BRCA1/BRCA2 defects suggest that abrogated D loop formation is the cause of PARPi sensitivity. Wild-type PSMC3IP reverses PARPi sensitivity, whereas a PSMC3IP p.Glu201del mutant associated with D loop defects and ovarian dysgenesis does not. These observations suggest that meiotic proteins such as MND1 and PSMC3IP have a greater role in mitotic DNA repair.

Chronic endometritis and endometrial microsatellite instability: is there a connection?

Introduction One of the criteria of impaired DNA repair is microsatellite instability (MSI) resulting from functional insufficiency of the mismatched nucleotide repair (MMR) system, a complex of proteins (MLH-1, PMS- 2, MSH-2, MSH-6). No data on the study of MSI in chronic endometritis (CE) were found in the available literature.The aim of the study was to determine the structural features of microsatellite instability in the endometrium in female patients with chronic inflammation of the uterine mucosa.Materials and methods Group I consisted of 30 women with morphologically confirmed high-grade CE; Group II consisted of 30 patients with low-grade CE; Group III consisted of 30 women who sought pregnancy planning and had histologically unchanged endometrium. The degree of CE in patients in groups I and II was variable. We analyzed the expression levels of MLH-1-, MSH- 2-, MSH-6-, and PMS-2-proteins in the endometrium by estimating the staining area of nuclei and cytoplasm of the affected cells over the entire slice area. Nonparametric statistical methods with Mann-Whitney test were used. The value of probability of error was set at 0.05.Results There was a statistically significant decrease in the level of MMR protein expression in the endometrial samples from the Group I patients compared to the same indices in the Group II and III women. No statistically significant results were found when analyzing the level of MMR protein expression depending on the severity degree of CE.Discussion There was a statistically significant decrease in the expression level of the markers studied (MLH-1, PMS-2, MSH-2, MSH-6) in endometrial specimens from patients with low-activity CE compared to uterine mucosa biopsy specimens from highly active CE and mid-stage endometrial secretion phase specimens. The described morphological features of the uterine mucosa in patients with low-activity CE are consistent with the findings of other authors. The literature provides indications of structural features of MSI in pre-tumor and tumor processes in the uterine mucosa.Conclusion Endometrial samples with low activity and various degrees of CE show statistically significantly lower expression levels of MLH-1, PMS-2, MSH-2, MSH-6 when compared to biopsy specimens from highly active CE and normal endometrial samples, which may indicate pathogenetic heterogeneity in the development of inflammation in the endometrium.

KDM4C silencing inhibits cell migration and enhances radiosensitivity by inducing CXCL2 transcription in hepatocellular carcinoma

KDM4C, which is a histone lysine demethylase, has been proposed to participate in the malignant transformation and progression of several types of cancer. However, its roles in hepatocellular carcinoma (HCC) remain poorly understood. Here, we find that KDM4C protein expression is increased in HCC and promotes HCC cell growth, proliferation and migration. Furthermore, we provide evidence that depletion of KDM4C leads to a defective G2/M checkpoint, increases radiation-induced DNA damage, impairs DNA repair and enhances radiosensitivity in HCC cells. Using RNA sequencing, we identify that the chemokine CXCL2 is a downstream effector of KDM4C. KDM4C knockdown increases the binding of H3K36me3 to the promoter of CXCL2, thus upregulating CXCL2 expression and promoting CXCL2 secretion in HCC cells. Importantly, the observed effects of KDM4C depletion in HCC cells can be partially rescued by CXCL2 silencing. Thus, our findings reveal that KDM4C is involved in cell migration and radiosensitivity by modulating CXCL2 transcription, indicating that KDM4C may be a potential therapeutic target in HCC.

The RUNX Family of Proteins, DNA Repair, and Cancer.

The RUNX family of transcription factors, including RUNX1, RUNX2, and RUNX3, are key regulators of development and can function as either tumor suppressors or oncogenes in cancer. Emerging evidence suggests that the dysregulation of RUNX genes can promote genomic instability in both leukemia and solid cancers by impairing DNA repair mechanisms. RUNX proteins control the cellular response to DNA damage by regulating the p53, Fanconi anemia, and oxidative stress repair pathways through transcriptional or non-transcriptional mechanisms. This review highlights the importance of RUNX-dependent DNA repair regulation in human cancers.

Abstract 3856: Evaluation of replication protein A inhibitor, NERx329 in combination with EGFR mutant targeted therapy

Abstract Lung cancer is the leading cause of cancer related deaths worldwide with the majority (~80%) of patients diagnosed with non-small lung cancer (NSCLC). Targeted therapies directed against tumor initiating growth factor receptors are effective treatment options for driver mutation positive NSCLC. Osimertinib is a third-generation EGFR-Tyrosine Kinase inhibitor (TKI) that has activity against EGFR exon 19, exon 21, and T790M mutations. Unfortunately, Osimertinib treated patients acquire resistance and median progression free survival is 18 months. Moreover, Osimertinib does not cure stage IV EGFR mutant NSCLC. The acquisition of secondary mutations leading to activation of bypass pathways, MET amplification, EMT, compensatory pathway activation and histological transformation to small cell phenotype are major causes of acquiring resistance to EGFR TKIs. Proliferating cancer cells regularly experience a low level of replication stress. Additionally, receptor tyrosine kinases such as EGFR are known to interact with DNA repair proteins and impact DNA damage repair following chemotherapy, radiation therapy, and EGFR TKI treatment. However, the role of DNA repair pathways in EGFR-TKI resistance is unknown and the interaction between EGFR pathway, DNA damage, and repair pathways has not been fully elucidated. At low-level replicative stress promotes genomic instability but at a high level through mitotic catastrophe it causes cell death. Replication protein A is a critical sensor of the DNA damage response detecting replication stress. The small molecule inhibitor of RPA, NERx 329, sequesters active RPA and induces replication catastrophe and cell death. Here we demonstrate that NERx329 in combination with Osimertinib enhanced Osimertinib mediated cell death. CCk-8 assays performed after 48h of NERx329 and Osimertinib combination treatment result in a robust decrease in IC50 compared to single agent therapy. Dissection of signaling pathways leading to this death-promoting effect of NERx329 showed a combination of bypass pathway marker (AXL) and compensatory pathway marker (STAT) inhibition in AXL-high expressing EGFR mutant lung cancer cells. Whereas inhibition of STAT pathway was responsible for the death-promoting effect of NERx329 in AXL-low expressing EGFR mutant lung cancer cells. AXL and STAT inhibition are associated with induced DNA damage and impaired DNA repair. From these data, we infer that DNA damage repair pathways could be involved in TKI resistance and NERx329 could be a promising drug candidate for combination targeted therapy. Citation Format: Reshma Bhowmick, John J. Turchi, Shadia I. Jalal. Evaluation of replication protein A inhibitor, NERx329 in combination with EGFR mutant targeted therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3856.

Abstract 5956: Tumor-infiltrating neutrophil progenitors impair homologous DNA repair and promote sensitivity to PARP-inhibition

Abstract Tumor evolution is one of the major mechanisms responsible for acquiring therapy-resistant and more aggressive cancer clones. Whether the tumor microenvironment through immune-mediated mechanisms might promote the development of more aggressive cancer types is crucial for the identification of additional therapeutical opportunities. Here, we identified a novel subset of tumor-infiltrating neutrophils, defined as tumor-associated neutrophil progenitors (NePs). These NePs are enriched in highly proliferative hormone-dependent breast cancers and impair DNA repair capacity. Mechanistically, succinate secreted by tumor-associated NePs inhibits homologous recombination, promoting error-prone DNA repair through non-homologous end-joining regulated by PARP-1. Consequently, breast cancer cells acquire genomic instability, resulting in tumor progression and resistance to endocrine therapies. Selective inhibition of these pathways induces increased tumor cell kill in vitro and in vivo. Intra-tumor NePs score correlates with copy number alterations in highly proliferative hormone-dependent tumors from breast cancer patients. Treatment with PARP-1 inhibitors counteract the pro-tumorigenic effect of these neutrophils and reverses endocrine resistance. Citation Format: Arianna Calcinotto. Tumor-infiltrating neutrophil progenitors impair homologous DNA repair and promote sensitivity to PARP-inhibition. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5956.

421 A Phase 1 and Randomized Phase 2 Clinical Trial of Selinexor and Temozolomide in Recurrent Glioblastoma Among Adults: The Product of a Successful Team Science Approach

OBJECTIVES/GOALS: Selinexor is a novel XPO1 inhibitor that blocks nuclear export, thus impairing DNA repair and causing apoptosis. Our goal was to conduct preclinical and clinical studies to test our hypothesis that selinexor’s efficacy is boosted by priming with temozolomide and is associated with a tissue biomarker. METHODS/STUDY POPULATION: We leveraged a team science approach through the NCI Cancer Therapy Evaluation Program (CTEP) to design preclinical experiments, develop a novel RNAseq analysis pipeline, and use pre-existing clinical experience to open an early phase clinical trial for recurrent glioblastoma. Team members included a CTEP medical officer, cancer biologist, pharmacist, industry scientist, translational scientist, and early career clinician scientist mentored by an expert clinician scientist. Based on preclinical results, participants in the clinical trial experimental arm will receive sequential temozolomide 150mg/m2 on days 1-5 and a starting dose of selinexor 60mg on days 8 and 15 of a 28-day cycle. Participants in the control arm will receive monotherapy temozolomide. RESULTS/ANTICIPATED RESULTS: Sequential treatment of U87 cells and intracranial xenografts had superior DNA damage (É£H2A.X, cleaved PARP) and overall survival compared to combination or single-agent (HR 0.25 [95% CI, 0.07-0.84]; p=0.01, log-rank). We used the top-scoring gene pair method to identify an RNAseq signature associated with response to selinexor. We then designed a trial for first recurrent MGMT methylated glioblastoma. Primary objectives are safety and preliminary efficacy. Secondary objectives are overall response rate, efficacy, and validation of a molecular signature. Phase 1 dose finding (n=12) will be followed by a randomized phase 2 (n=72); using proportional hazards regression, RHR 0.5 with p DISCUSSION/SIGNIFICANCE: The NCI CTEP Project Team employs team science as a framework to successfully develop multidisciplinary collaborations, build investigator trial experience, and lead the way to future research opportunities. Our trial addresses a significant unmet need to offer novel therapies and molecular biomarkers in glioblastoma.

Antimutagenic 1,4-Dihydropyridine AV-153 Normalizes Expression of GLUT1, GLUT4, INOS, PARP1, and Gamma H2AX Histone in Myocardium of Rats with Streptozotocin Model of Diabetes Mellitus

Abstract Diabetic cardiomyopathy increases the risk of heart failure and worsens prognosis for diabetes mellitus (DM) patients. Its development depends on many factors, including modification of nitric oxide production and impaired DNA repair. The goal of the present work was to study in vivo effects of a 1,4-dihydropyridine AV-153, known as antimutagen and DNA-binder, on DNA integrity, and on the expression of several proteins involved in glucose transport, nitric oxide metabolism, and DNA repair in myocardium in diabetic rats. DM was induced in rats by streptozotocin (STZ) injection. Expression of proteins was studied by means of immunohistochemistry. Development of the STZ-induced DM significantly induced PARP1 and gamma H2AX histone, markers of DNA breakage, protein expression in heart tissue, while AV-153 administration decreased PARP1 and H2AX protein expression. In this model of diabetes, myocardial expression of iNOS was also significantly increased, but administration of AV-153 reduced it to normal levels. AV-153 also upregulated the expression of insulin-dependent GLUT4 and insulin-independent GLUT1 glucose transporters up to normal level in diabetic rats. Thus, AV-153 appears to be prospective for creation of a remedy for prevention of diabetic cardiomyopathy.

Differential expression of DNA repair genes and treatment outcome of chemoradiotherapy (CRT) in cervical cancer

Cervical cancer (CaCx) is the malignancy of uterine cervix which induce by human papillomavirus (HPV) infections. HPV infection starts with the induction of double-stranded breaks by increasing oxidative stress and modulation of DNA repair pathways. Deficiency in DNA repair pathways and accumulation of DNA damage increases mutation rates resulting in genomic instability and cancer development. Patients with HPV-associated CaCx display increased sensitivity to cisplatin-based chemoradiotherapy (CRT) and improved survival rates. However, the cellular mechanisms responsible for this characteristic difference are unclear. Here, we have evaluated expression of DNA repair genes in peripheral blood cells and correlated them with treatment outcomes. A total of 211 study subjects includes in the study comprised 103 CaCx patients and 108 healthy controls. All the study subjects were analyzed for the expression profile of DNA repair genes by using real-time PCR (RT-PCR). The differentially expressed DNA repair gene was correlated with the treatment outcome of CRT. OGG1, XRCC2, XRCC3, XRCC4 and XRCC6 genes were found to be significant (P = 0.001) down-regulated as compared to controls. While XRCC5 and RAD51 showed significant up-regulated (P = 0.024 and 0.041) in CaCx patients. XRCC6 was associated (P = 0.033) with poor vital while up-regulated RAD51 showed slight association (P = 0.075) with better vital with an increased 2.96- and 2.33-fold risk in the study population. In the case of overall survival, down-regulated XRCC4 was associated (P = 0.042) with poor survival (27 months) with the least hazard ratio (0.56 HR). Down-regulated OGG1 involved BER, XRCC2 and XRCC3 in homologous recombination and XRCC4, XRCC5 and XRCC6 in Non-homologous end-joining repair, which showed a deficiency of DNA repair capacity resulting caused of an accumulation of DNA damage and genome instability. Impaired DNA repair gene expression is responsible for poor prognosis and survival in CaCx. Therefore, these gene expressions can be considered a potential prognostic, diagnostic and therapeutic biomarker for CaCx.

Demographic, clinical, immunological, and molecular features of iranian national cohort of patients with defect in DCLRE1C gene

BackgroundDCLRE1C gene mutation leads to Artemis deficiency, a severe form of combined immunodeficiency (SCID). Impaired DNA repair and block in early adaptive immunity maturation results in T-B-NK+ immunodeficiency associated with radiosensitivity. Recurrent infections early in life are the main characteristic of Artemis patients.MethodAmong 5373 registered patients, 9 Iranian patients (33.3% female) with confirmed DCLRE1C mutation were identified since 1999–2022. The demographic, clinical, immunological and genetic features were collected through retrospective investigation of medical records and using next generation sequencing.ResultsSeven patients were born in a consanguineous family (77.8%). The median age of onset was 6.0 (5.0–17.0) months. Severe combined immunodeficiency (SCID) was clinically detected at a median (IQR) age of 7.0 (6.0–20.5) months, following a median diagnostic delay of 2.0 (1.0–3.5) months The most typical first presentation was pneumonia (44.4%) and otitis media (3.33%), followed by BCG lymphadenitis (22.2%) and gastroenteritis (11.1%). The most prevalent manifestations were respiratory tract infections (including otitis media) (66.6%) and chronic diarrhea (66.6%). In addition, juvenile idiopathic arthritis (P5) and celiac disease and idiopathic thrombocytopenic purpura (P9) as autoimmune disorders were reported in 2 patients. All patients had reduced B CD19+ and CD4+ cell counts. IgA deficiency occurred in 77.8% of individuals.ConclusionRecurrent infections particulary respiratory tract infection and chronic diarrhea during the first months of life in patients born to consanguineous parents should raise the suspicion for inborn errors of immunity, even in the presence of normal growth and development.

Alliance A031902 (CASPAR): A randomized phase (ph) 3 trial of enzalutamide with rucaparib/placebo in first-line metastatic castration-resistant prostate cancer (mCRPC).

TPS277 Background: Despite a growing number of treatment options for first-line mCRPC, approximately 40% of patients (pts) have radiographic progression within the first year. Co-inhibition of androgen receptor (AR) and PARP is a promising therapeutic strategy that leverages synthetic lethality induced by impaired double-strand DNA repair. Two phase III studies have shown improvement in radiographic progression-free survival (rPFS) in HRR-mutant pts with abiraterone + PARPi combinations vs abiraterone alone. However, the results in HRR-wild type pts are conflicting, with only one of the studies demonstrating a benefit with the abiraterone + PARPi combination. ENZ + RUCA has shown an acceptable safety profile & no significant drug-drug interactions (S-DDI) in a phase 1b trial. This allows its evaluation in mCRPC. Methods: CASPAR (A031902) is a phase 3 study in which 984 pts will be randomized on a 1:1 basis to ENZ plus RUCA/PBO. HRR gene aberration is not required for enrollment. All pts will undergo next-generation targeted exome sequencing from archival tumor tissue (new biopsy only required if no archival tissue is available). Treatment will be continued until disease progression and crossover is not allowed. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-2, biopsy-proven prostate adenocarcinoma, progressive (PSA or radiographic) disease per Prostate Cancer Working Group 3 guidelines, measurable or non-measurable disease per RECIST 1.1, no prior treatment for mCRPC (prior docetaxel, abiraterone, darolutamide, or apalutamide in non-mCRPC setting is allowed), no significant uncontrolled comorbidity, and no medications with S-DDI with ENZ/RUCA. Hierarchical co-primary endpoints are overall survival (OS) and rPFS. The OS analysis will be undertaken as a primary endpoint if the rPFS endpoint is met. For a one-sided logrank test with a type 1 error rate equal to 0.025, the study has 90% power to detect a hazard ratio (HR) of 0.71 in rPFS (median rPFS of 15 and 21 months in control and combination arms, respectively), and 80% power to detect an HR of 0.80 in OS (median OS of 32 and 40 months, respectively). Key secondary endpoints are rPFS and OS in pts with vs without pathogenic BRCA1, BRCA2, or PALB2 alterations; and differences in adverse events and quality of life (QOL) outcomes between the treatment arms. QOL assessments include Functional Assessment of Cancer Therapy–Prostate (FACT-P), Brief Pain Inventory Short Form (BPI-SF), and EQ-5D-5L. A key correlative endpoint is the sensitivity of ctDNA testing for HRR gene alterations. Enrollment began in July 2021 & the study is available for participation to all US-NCTN sites. Clinical trial information: NCT04455750 .

Polymorphisms in DNA Repair Genes and Association with Rheumatoid Arthritis in a Pilot Study on a Central European Population.

Rheumatoid arthritis (RA) is a chronic, multifactorial autoimmune disease characterized by chronic arthritis, a tendency to develop joint deformities, and involvement of extra-articular tissues. The risk of malignant neoplasms among patients with RA is the subject of ongoing research due to the autoimmune pathogenesis that underlies RA, the common etiology of rheumatic disease and malignancies, and the use of immunomodulatory therapy, which can alter immune system function and thus increase the risk of malignant neoplasms. This risk can also be increased by impaired DNA repair efficiency in individuals with RA, as reported in our recent study. Impaired DNA repair may reflect the variability in the genes that encode DNA repair proteins. The aim of our study was to evaluate the genetic variation in RA within the genes of the DNA damage repair system through base excision repair (BER), nucleotide excision repair (NER), and the double strand break repair system by homologous recombination (HR) and non-homologous end joining (NHEJ). We genotyped a total of 28 polymorphisms in 19 genes encoding DNA repair-related proteins in 100 age- and sex-matched RA patients and healthy subjects from Central Europe (Poland). Polymorphism genotypes were determined using the Taq-man SNP Genotyping Assay. We found an association between the RA occurrence and rs25487/XRCC1, rs7180135/RAD51, rs1801321/RAD51, rs963917/RAD51B, rs963918/RAD51B, rs2735383/NBS1, rs132774/XRCC6, rs207906/XRCC5, and rs861539/XRCC3 polymorphisms. Our results suggest that polymorphisms of DNA damage repair genes may play a role in RA pathogenesis and may be considered as potential markers of RA.

DNA repair in cardiomyocytes is critical for maintaining cardiac function in mice.

Heart failure has reached epidemic proportions in a progressively ageing population. The molecular mechanisms underlying heart failure remain elusive, but evidence indicates that DNA damage is enhanced in failing hearts. Here, we tested the hypothesis that endogenous DNA repair in cardiomyocytes is critical for maintaining normal cardiac function, so that perturbed repair of spontaneous DNA damage drives early onset of heart failure. To increase the burden of spontaneous DNA damage, we knocked out the DNA repair endonucleases xeroderma pigmentosum complementation group G (XPG) and excision repair cross-complementation group 1 (ERCC1), either systemically or cardiomyocyte-restricted, and studied the effects on cardiac function and structure. Loss of DNA repair permitted normal heart development but subsequently caused progressive deterioration of cardiac function, resulting in overt congestive heart failure and premature death within 6months. Cardiac biopsies revealed increased oxidative stress associated with increased fibrosis and apoptosis. Moreover, gene set enrichment analysis showed enrichment of pathways associated with impaired DNA repair and apoptosis, and identified TP53 as one of the top active upstream transcription regulators. In support of the observed cardiac phenotype in mutant mice, several genetic variants in the ERCC1 and XPG gene in human GWAS data were found to be associated with cardiac remodelling and dysfunction. In conclusion, unrepaired spontaneous DNA damage in differentiated cardiomyocytes drives early onset of cardiac failure. These observations implicate DNA damage as a potential novel therapeutic target and highlight systemic and cardiomyocyte-restricted DNA repair-deficient mouse mutants as bona fide models of heart failure.

The impact of oxidative stress-induced mitochondrial dysfunction on diabetic microvascular complications.

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycaemia, with absolute insulin deficiency or insulin resistance as the main cause, and causes damage to various target organs including the heart, kidney and neurovascular. In terms of the pathological and physiological mechanisms of DM, oxidative stress is one of the main mechanisms leading to DM and is an important link between DM and its complications. Oxidative stress is a pathological phenomenon resulting from an imbalance between the production of free radicals and the scavenging of antioxidant systems. The main site of reactive oxygen species (ROS) production is the mitochondria, which are also the main organelles damaged. In a chronic high glucose environment, impaired electron transport chain within the mitochondria leads to the production of ROS, prompts increased proton leakage and altered mitochondrial membrane potential (MMP), which in turn releases cytochrome c (cyt-c), leading to apoptosis. This subsequently leads to a vicious cycle of impaired clearance by the body's antioxidant system, impaired transcription and protein synthesis of mitochondrial DNA (mtDNA), which is responsible for encoding mitochondrial proteins, and impaired DNA repair systems, contributing to mitochondrial dysfunction. This paper reviews the dysfunction of mitochondria in the environment of high glucose induced oxidative stress in the DM model, and looks forward to providing a new treatment plan for oxidative stress based on mitochondrial dysfunction.

Disintegration of the NuRD Complex in Primary Human Muscle Stem Cells in Critical Illness Myopathy.

Critical illness myopathy (CIM) is an acquired, devastating, multifactorial muscle-wasting disease with incomplete recovery. The impact on hospital costs and permanent loss of quality of life is enormous. Incomplete recovery might imply that the function of muscle stem cells (MuSC) is impaired. We tested whether epigenetic alterations could be in part responsible. We characterized human muscle stem cells (MuSC) isolated from early CIM and analyzed epigenetic alterations (CIM n = 15, controls n = 21) by RNA-Seq, immunofluorescence, analysis of DNA repair, and ATAC-Seq. CIM-MuSC were transplanted into immunodeficient NOG mice to assess their regenerative potential. CIM-MuSC exhibited significant growth deficits, reduced ability to differentiate into myotubes, and impaired DNA repair. The chromatin structure was damaged, as characterized by alterations in mRNA of histone 1, depletion or dislocation of core proteins of nucleosome remodeling and deacetylase complex, and loosening of multiple nucleosome-spanning sites. Functionally, CIM-MuSC had a defect in building new muscle fibers. Further, MuSC obtained from the electrically stimulated muscle of CIM patients was very similar to control MuSC, indicating the impact of muscle contraction in the onset of CIM. CIM not only affects working skeletal muscle but has a lasting and severe epigenetic impact on MuSC.

IL-15 Prevents the Development of T-ALL from Aberrant Thymocytes with Impaired DNA Repair Functions and Increased NOTCH1 Activation.

We previously reported that NOD.Scid mice lacking interleukin-15 (IL-15), or IL-15 receptor alpha-chain, develop T-acute lymphoblastic leukemia (T-ALL). To understand the mechanisms by which IL-15 signaling controls T-ALL development, we studied the thymocyte developmental events in IL-15-deficient Scid mice from NOD and C57BL/6 genetic backgrounds. Both kinds of mice develop T-ALL characterized by circulating TCR-negative cells expressing CD4, CD8 or both. Analyses of thymocytes in NOD.Scid.Il15-/- mice prior to T-ALL development revealed discernible changes within the CD4-CD8- double-negative (DN) thymocyte developmental stages and increased frequencies of CD4+CD8+ double-positive cells with a high proportion of TCR-negative CD4+ and CD8+ cells. The DN cells also showed elevated expressions of CXCR4 and CD117, molecules implicated in the expansion of DN thymocytes. T-ALL cell lines and primary leukemic cells from IL-15-deficient NOD.Scid and C57BL/6.Scid mice displayed increased NOTCH1 activation that was inhibited by NOTCH1 inhibitors and blockers of the PI3K/AKT pathway. Primary leukemic cells from NOD.Scid.Il15-/- mice survived and expanded when cultured with MS5 thymic stromal cells expressing Delta-like ligand 4 and supplemented with IL-7 and FLT3 ligand. These findings suggest that IL-15 signaling in the thymus controls T-ALL development from aberrant thymocytes with an impaired DNA repair capacity and increased NOTCH1 activation.

Bulky Adducts in Clustered DNA Lesions: Causes of Resistance to the NER System.

The nucleotide excision repair (NER) system removes a wide range of bulky DNA lesions that cause significant distortions of the regular double helix structure. These lesions, mainly bulky covalent DNA adducts, are induced by ultraviolet and ionizing radiation or the interaction between exogenous/endogenous chemically active substances and nitrogenous DNA bases. As the number of DNA lesions increases, e.g., due to intensive chemotherapy and combination therapy of various diseases or DNA repair impairment, clustered lesions containing bulky adducts may occur. Clustered lesions are two or more lesions located within one or two turns of the DNA helix. Despite the fact that repair of single DNA lesions by the NER system in eukaryotic cells has been studied quite thoroughly, the repair mechanism of these lesions in clusters remains obscure. Identification of the structural features of the DNA regions containing irreparable clustered lesions is of considerable interest, in particular due to a relationship between the efficiency of some antitumor drugs and the activity of cellular repair systems. In this review, we analyzed data on the induction of clustered lesions containing bulky adducts, the potential biological significance of these lesions, and methods for quantification of DNA lesions and considered the causes for the inhibition of NER-catalyzed excision of clustered bulky lesions.

The Association of DNA Ligase 1 Rs20579 Polymorphism With Lung Cancer Risk Among Taiwanese.

Impaired DNA repair capacity may play a critical role in genome instability and carcinogenesis. However, the impact of DNA ligase 1 (Lig1) genotypes on tumorigenesis remains unclear. This study aimed to investigate the contribution of Lig1 rs20579 genotypes to the risk of developing lung cancer, and review the related literature. Polymerase chain reaction-restriction fragment length polymorphism analysis was used to determine the genotypes of Lig1 rs20579 and evaluate their association with lung cancer risk among 358 lung cancer cases and 716 age- and sex-matched cancer-free control subjects. The distribution of GG, AG, and AA genotypes for Lig1 rs20579 was 77.1%, 20.8%, and 2.1% among the controls, and 76.0%, 21.5%, and 2.5% among the lung cancer cases (p for trend=0.8686). There was no significant difference in the distribution of AG and AA genotypes between the two groups (p=0.8257 and 0.8098, respectively). Allelic frequency analysis indicated that individuals carrying the variant A allele for Lig1 rs20579 had a non-significant 1.07-fold higher risk of developing lung cancer than those carrying the wild-type G allele [95% confidence interval (CI)=0.82-1.40, p=0.6639]. Furthermore, no differential distribution of the Lig1 rs20579 genotype was found among non-smokers (p=0.9910) or smokers (p=0.9001). In contrast to Americans, Lig1 rs20579 genotypes do not appear to play a critical role in determining susceptibility to lung cancer among Taiwanese individuals.

Pigmented xeroderma: literature review and clinical case

Xeroderma pigmentosum (XP) is heterogeneous group of diseases associated with defects in DNA repair, inherited in an autosomal recessive manner. Exposure of DNA to UV radiation produces photoproducts based on multiple nucleic acids, which serve as a substrate for DNA excision repair (NER). Mutations in the NER pathway genes result in impaired DNA repair and it associated with variety of clinical syndromes, which include xeroderma pigmentosa, Cockaynes syndrome, and trichothiodystrophy. Some forms of the disease are accompanied by damage to the central nervous system. In recent years, precise molecular anomalies responsible for complementation patterns have been identified. All the patients with this disease have photosensitivity, an increased risk of skin cancer and melanoma, but there are number of differences between them. Considering the rare frequency of occurring this disease throughout the world, this article presents our own clinical observation of an 8-year-old patient with xeroderma pigmentosa. The first change on the girls skin appeared at the age of 2 months after insolation, in the form of hyperemia of the skin and blisters, later on multiple pigmented rashes of varying intensity appeared. Upon admission to the clinic, the girl had small dark brown spots and depigmented scars on her face and open areas of the body. Sequencing revealed the NGS variant in the hemizygous state in the XPA gene. Early diagnosis and preventive measures can dramatically improve and prolong the lives of patients. Considering the genetic heterogeneity, molecular diagnosis is an important step in the diagnosis and prognosis of the disease.