Ionizing radiation is frequently used to treat solid tumors,as it causes DNA damage and kill cancer cells.However,damaged DNA is repaired involving poly-(ADP-ribose)polymerase-1(PARP-1)causing resistance to radiation ...Ionizing radiation is frequently used to treat solid tumors,as it causes DNA damage and kill cancer cells.However,damaged DNA is repaired involving poly-(ADP-ribose)polymerase-1(PARP-1)causing resistance to radiation therapy.Thus,PARP-1 represents an important target in multiple cancer types,including prostate cancer.PARP is a nuclear enzyme essential for single-strand DNA breaks repair.Inhibiting PARP-1 is lethal in a wide range of cancer cells that lack the homologous recombination repair(HR)pathway.This article provides a concise and simplified overview of the development of PARP inhibitors in the laboratory and their clinical applications.We focused on the use of PARP inhibitors in various cancers,including prostate cancer.We also discussed some of the underlying principles and challenges that may affect the clinical efficacy of PARP inhibitors.展开更多
Viewing cancer as a large,evolving population of heterogeneous cells is a common perspective.Because genomic instability is one of the fundamental features of cancer,this intrinsic tendency of genomic variation leads ...Viewing cancer as a large,evolving population of heterogeneous cells is a common perspective.Because genomic instability is one of the fundamental features of cancer,this intrinsic tendency of genomic variation leads to striking intratumor heterogeneity and functions during the process of cancer formation,development,metastasis,and relapse.With the increased mutation rate and abundant diversity of the gene pool,this heterogeneity leads to cancer evolution,which is the major obstacle in the clinical treatment of cancer.Cells rely on the integrity of DNA repair machineries to maintain genomic stability,but these machineries often do not function properly in cancer cells.The deficiency of DNA repair could contribute to the generation of cancer genomic instability,and ultimately promote cancer evolution.With the rapid advance of new technologies,such as single-cell sequencing in recent years,we have the opportunity to better understand the specific processes and mechanisms of cancer evolution,and让s relationship with DNA repair.Here,we review recent findings on how DNA repair affects cancer evolution,and discuss how these mechanisms provide the basis for critical clinical challenges and therapeutic applications.展开更多
OBJECTIVE To investigate the role of e IF3a in the regulation of DNA repair pathways in cancer chemotherapeutic response.METHODS Immunohistochemistry was used to determine the expression of e IF3a in lung and breast c...OBJECTIVE To investigate the role of e IF3a in the regulation of DNA repair pathways in cancer chemotherapeutic response.METHODS Immunohistochemistry was used to determine the expression of e IF3a in lung and breast cancer tissues followed by association analysis of e IF3a expression with patient′s response to chemotherapy.Ectopic overexpression and RNA interference knockdown of e IF3a were carried out in NIH3T3and H1299 cell lines,respectively,to determine the effect of altered e IF3a expression on cellular response to chemotherapeutic drugs by using MTT assay.The DNA repair capacity of these cells was evaluated by using host-cell reactivation,NHEJ and HR assay.Real-time reverse transcriptase PCR and Western Blot analyses were carried out to determine the effect of e IF3a on the DNA repair genes by using cells with altered e IF3a expression.RESULTS e IF3a expression associates with response of lung and breast cancer patients to platinum and anthracycline.e IF3a knockdown or overexpression,respectively,increased and decreased the cellular resistance to cisplatin and anthracycline anticancer drugs,DNA repair activity,and expression of NER and NHEJ DNA repair proteins.CONCLUSION e IF3a plays an important role in regulating the expression of NER and NHEJ DNA repair proteins which,in turn,contributes to cellular response to DNA-damaging anticancer drugs and patients′response to platinum and anthracycline chemotherapy.展开更多
Introduction: DNA repair enzymes continuously monitor DNA to correct damaged nucleotide residues generated by exposure to environmental mutagenic and cytotoxic compounds or carcinogens. Our objective was to investigat...Introduction: DNA repair enzymes continuously monitor DNA to correct damaged nucleotide residues generated by exposure to environmental mutagenic and cytotoxic compounds or carcinogens. Our objective was to investigate the association among XRCC1 (Arg399Gln and Arg194Trp), XRCC3 (Thr241Met), XPD-ERCC2 (Lys751Gln), APE1 (Asp241Glu), PARP-ADPRT (Val762Ala) DNA repair gene polymorphisms and lung cancer in Turkish population. Materials and Methods: Our patient group consists of 90 patients with lung cancer and the control group had 100 healthy individuals all of those smoking. DNA was extracted using the whole blood samples. PCR- RFLP technique was used to investigate the polymorphisms on target genes. Results: There was no significant difference in the genotype distributions of XPD Lys751Gln, XRCC1 Arg194Trp, XRCC3 Thr241Met, APE1 Asp241Glu between lung cancer patients and controls for each polymorphism (p > 0.05). However, there was a significant difference between the genotype distributions of XRCC1 Arg399Gln, and PARP Val762Ala in patients and the control group (p > 0.05). Discussion: Only the polymorphisms of XRCC1 codon 399 and PARP Val762Ala alleles are associated with the risk of lung cancer. Other genotypes were not related to lung cancer.展开更多
Although thousands of DNA damaging events occur in each cell every day,efficient DNA repair pathways have evolved to counteract them. The DNA repair machinery plays a key role in maintaining genomic stability by avoid...Although thousands of DNA damaging events occur in each cell every day,efficient DNA repair pathways have evolved to counteract them. The DNA repair machinery plays a key role in maintaining genomic stability by avoiding the maintenance of mutations. The DNA repair enzymes continuously monitor the chromosomes to correct any damage that is caused by exogenous and endogenous mutagens. If DNA damage in proliferating cells is not repaired because of an inadequate expression of DNA repair genes,it might increase the risk of cancer. In addition to mutations,which can be either inherited or somatically acquired,epigenetic silencing of DNA repair genes has been associated with carcinogenesis. Gastric cancer represents the second highest cause of cancer mortality worldwide. The disease develops from the accumulation of several genetic and epigenetic changes during the lifetime. Among the risk factors,Helicobacter pylori(H. pylori) infection is considered the main driving factor to gastric cancer development. Thus,in this review,we summarize the current knowledge of the role of H. pylori infection on the epigenetic regulation of DNA repair machinery in gastric carcinogenesis.展开更多
Pancreatic cancer is highly lethal. Current research that combines radiation with targeted therapy may dramatically improve prognosis. Cancerous cells are characterized by unstable genomes and activation of DNA repair...Pancreatic cancer is highly lethal. Current research that combines radiation with targeted therapy may dramatically improve prognosis. Cancerous cells are characterized by unstable genomes and activation of DNA repair pathways, which are indicated by increased phosphorylation of numerous factors, including H2 AX, ATM, ATR, Chk1, Chk2, DNA-PKcs, Rad51, and Ku70/Ku80 heterodimers. Radiotherapy causes DNA damage. Cancer cells can be made more sensitive to the effects of radiation(radiosensitization) through inhibition of DNA repair pathways. The synergistic effects, of two or more combined non-lethal treatments, led to coadministration of chemotherapy and radiosensitization in BRCA-defective cells and patients, with promising results. ATM/Chk2 and ATR/Chk1 pathways are principal regulators of cell cycle arrest, following DNA doublestrand or single-strand breaks. DNA double-stranded breaks activate DNA-dependent protein kinase, catalytic subunit(DNA-PKcs). It forms a holoenzyme with Ku70/Ku80 heterodimers, called DNA-PK, which catalyzes the joining of nonhomologous ends. This is the primary repair pathway utilized in human cells after exposure to ionizing radiation. Radiosensitization, induced by inhibitors of ATM, ATR, Chk1, Chk2, Wee1, PP2 A, or DNA-PK, has been demonstrated in preclinical pancreatic cancer studies. Clinical trials are underway. Development of agents that inhibit DNA repair pathways to be clinically used in combination with radiotherapy is warranted for the treatment of pancreatic cancer.展开更多
Objective Alkaline comet assay was used to evaluate DNA repair (nucleotide excision repair, NER) capacity of human fresh lymphocytes from 12 young healthy non-smokers (6 males and 6 females). Methods Lymphocytes were ...Objective Alkaline comet assay was used to evaluate DNA repair (nucleotide excision repair, NER) capacity of human fresh lymphocytes from 12 young healthy non-smokers (6 males and 6 females). Methods Lymphocytes were exposed to UV-C (254 nm) at the dose rate of 1.5 J/m2/sec. Novobiocin (NOV) and aphidicolin (APC), DNA repair inhibitors, were utilized to imitate the deficiency of DNA repair capacity at the incision and ligation steps of NER. Lymphocytes from each donor were divided into three grougs: UVC group, UVC plus NOV group, and UVC plus APC group. DNA single strand breaks were detected in UVC irradiated cells incubated for 0, 30, 60, 90, 120, 180, and 240 min after UVC irradiation. DNA repair rate (DRR) served as an indicator of DNA repair capacity. Results The results indicated that the maximum DNA damage (i.e. maximum tail length) in the UVC group mainly appeared at 90 min. The ranges of DRRs in the UVC group were 62.84%-98.71%. Average DRR value was 81.84%. The DRR difference between males and females was not significant (P<0.05). However, the average DRR value in the UVC plus NOV group and the UVC plus APC group was 52.98% and 39.57% respectively, which were significantly lower than that in the UVC group (P<0.01). Conclusion The comet assay is a rapid, simple and sensitive screening test to assess individual DNA repair (NER) capacity. It is suggested that the time to detect DNA single strand breaks in comet assay should include 0 (before UV irradiation), 90 and 240 min after exposure to 1.5 J·m-2 UVC at least. The DRR, as an indicator, can represent the individual DNA repair capacity in comet assay.展开更多
Tumors often have DNA repair defects, suggesting additional inhibition of other DNA repair pathways in tumors may lead to synthetic lethality. Accumulating data demonstrate that DNA repair-defective tumors, in particu...Tumors often have DNA repair defects, suggesting additional inhibition of other DNA repair pathways in tumors may lead to synthetic lethality. Accumulating data demonstrate that DNA repair-defective tumors, in particular homologous recombination (HR), are highly sensitive to DNA-damaging agents. Thus, HR-defective tumors exhibit potential vulnerability to the synthetic lethality approach, which may lead to new therapeutic strategies. It is well known that poly (adenosine diphosphate (ADP)-ribose) polymerase (PARP) inhibitors show the synthetically lethal effect in tumors defective in BRCA1 or BRCA2 genes encoded proteins that are required for efficient HR. In this review, we summarize the strategies of targeting DNA repair pathways and other DNA metabolic functions to cause synthetic lethality in HR-defective tumor cells.展开更多
Deficiencies in DNA repair due to inherited germ-line mutations in DNA repair genes cause increased risk of gastrointestinal(GI) cancer. In sporadic GI cancers, mutations in DNA repair genes are relatively rare. Howev...Deficiencies in DNA repair due to inherited germ-line mutations in DNA repair genes cause increased risk of gastrointestinal(GI) cancer. In sporadic GI cancers, mutations in DNA repair genes are relatively rare. However, epigenetic alterations that reduce expression of DNA repair genes are frequent in sporadic GI cancers. These epigenetic reductions are also found in field defects that give rise to cancers. Reduced DNA repair likely allows excessive DNA damages to accumulate in somatic cells. Then either inaccurate translesion synthesis past the un-repaired DNA damages or error-prone DNA repair can cause mutations. Erroneous DNA repair can also cause epigenetic alterations(i.e., epimutations, transmitted through multiple replication cycles). Some of these mutations and epimutations may cause progression to cancer. Thus, deficient or absent DNA repair is likely an important underlying cause of cancer. Whole genome sequencing of GI cancers show that between thousands to hundreds of thousands of mutations occur in these cancers. Epimutations that reduce DNA repair gene expression and occur early in progression to GI cancers are a likely source of this high genomic instability. Cancer cells deficient in DNA repair are more vulnerable than normal cells to inactivation by DNA damaging agents. Thus, some of the most clinically effective chemotherapeutic agents in cancer treatment are DNA damaging agents, and their effectiveness often depends on deficient DNA repair in cancer cells. Recently, at least 18 DNA repair proteins, each active in one of six DNA repair pathways, were found to be subject to epigenetic reduction of expression in GI cancers. Different DNA repair pathways repair different types of DNA damage. Evaluation of which DNA repair pathway(s) are deficient in particular types of GI cancer and/or particular patients may prove useful in guiding choice of therapeutic agents in cancer therapy.展开更多
Ovarian cancer(OC)is the sixth most common cancer and the seventh cause of death from cancer in women.The etiology and the ovarian carcinogenesis still need clarification although ovulation may be determinant due to i...Ovarian cancer(OC)is the sixth most common cancer and the seventh cause of death from cancer in women.The etiology and the ovarian carcinogenesis still need clarification although ovulation may be determinant due to its carcinogenic role in ovarian surface epithelium.The link between ovarian carcinogenesis and DNA repair is well established and it became clear that alterations in DNA damage response may affect the risk to develop OC.Polymorphisms are variations in the DNA sequence that exist in normal individuals of a population and are capable to change,among other mechanisms,the balance between DNA damage and cellular response.Consequently,genetic variability of the host has a great role in the development,progression and consequent prognosis of the oncologic patient as well as in treatment response.Standard treatment for OC patients is based on cytoreductive surgery,followed by chemotherapy with a platinum agent and a taxane.Although 80%of the patients respond to the first-line therapy,the development of resistance is common although the mechanisms underlying therapy failure remain mostly unknown.Because of their role in oncology,enzymes involved in the DNA repair pathways,like DNA Ligase IV(LIG4),became attractive study targets.It has been reported that variations in LIG4 activity can lead to a hyper-sensitivity to DNA damage,deregulation of repair and apoptosis mechanisms,affecting the susceptibility to cancer development and therapy response.To overcome resistance mechanisms,several investigations have been made and the strategy to target crucial molecular pathways,such as DNA repair,became one of the important areas in clinical oncology.This review aims to elucidate the link between DNA repair and OC,namely which concerns the role of LIG4 enzyme,and how genetic polymorphisms in LIG4 gene can modulate the activity of the enzyme and affect the ovarian carcinogenesis and treatment response.Moreover,we try to understand how LIG4 inhibition can be a potential contributor for the development of new cancer treatment strategies.展开更多
Over the past few decades, major strides have advanced the techniques for early detection and treatment of cancer. However, metastatic tumor growth still accounts for the majority of cancer-related deaths worldwide. I...Over the past few decades, major strides have advanced the techniques for early detection and treatment of cancer. However, metastatic tumor growth still accounts for the majority of cancer-related deaths worldwide. In fact, breast cancers are notorious for relapsing years or decades after the initial clinical treatment, and this relapse can vary according to the type of breast cancer. In estrogen receptor-positive breast cancers, late tumor relapses frequently occur whereas relapses in estrogen receptor-negative cancers or triple negative tumors arise early resulting in a higher mortality risk. One of the main causes of metastasis is tumor dormancy in which cancer cells remain concealed, asymptomatic, and untraceable over a prolonged period of time. Under certain conditions, dormant cells can re-enter into the cell cycle and resume proliferation leading to recurrence. However, the molecular and cellular regulators underlying this transition remain poorly understood. To date, three mechanisms have been identified to trigger tumor dormancy including cellular, angiogenic, and immunologic dormancies. In addition, recent studies have suggested that DNA repair mechanisms may contribute to the survival of dormant cancer cells. In this article, we summarize the recent experimental and clinical evidence governing cancer dormancy. In addition, we will discuss the role of DNA repair mechanisms in promoting the survival of dormant cells. This information provides mechanistic insight to explain why recurrence occurs, and strategies that may enhance therapeutic approaches to prevent disease recurrence.展开更多
Objective To compare the asbestos-induced DNA damage and repair capacities of DNA damage between 104 asbestos- exposed workers and 101 control workers in Qingdao City of China and to investigate the possible associati...Objective To compare the asbestos-induced DNA damage and repair capacities of DNA damage between 104 asbestos- exposed workers and 101 control workers in Qingdao City of China and to investigate the possible association between polymorphisms in codon 399 of XRCC1 and susceptibility to asbestosis. Methods DNA damage levels in peripheral blood lymphocytes were determined by comet assay, and XRCC1 genetic polymorphisms of DNA samples from 51 asbestosis cases and 53 non-asbestosis workers with a similar asbestos exposure history were analyzed by PCR/RFLP. Results The basal comet scores (3.95±2.95) were significantly higher in asbestos-exposed workers than in control workers (0.10±0.28). After 1 h H2O2 stimulation, DNA damage of lymphocytes exhibited different increases. After a 4 h repair period, the comet scores were 50.98±19.53 in asbestos-exposed workers and 18.32±12.04 in controls. The residual DNA damage (RD) was significantly greater (P<0.01) in asbestos-exposed workers (35.62%) than in controls (27.75%). XRCC1 genetic polymorphism in 104 asbestos-exposed workers was not associated with increased risk of asbestosis. But compared with polymorphisms in the DNA repair gene XRCC1 (polymorphisms in codon 399) and the DNA damage induced by asbestos, the comet scores in asbestosis cases with Gln/Gln, Gln/Arg, and Arg/Arg were 40.26±18.94, 38.03±28.22, and 32.01±11.65, respectively, which were higher than those in non-asbestosis workers with the same genotypes (25.58±11.08, 37.08±14.74, and 29.38±10.15). There were significant differences in the comet scores between asbestosis cases and non-asbestosis workers with Gln/Gln by Student’s t-test (P<0.05 or 0.01). The comet scores were higher in asbestosis workers with Gln/Gln than in those with Arg/Arg and in non-asbestosis workers exposed to asbestos, but without statistically significant difference. Conclusions Exposure to asbestos may be related to DNA damage or the capacity of cells to repair H2O2-induced DNA damage. DNA repair gene XRCC1 codon 399 may be responsible for the inter-individual susceptibility in DNA damage and repair capacities.展开更多
BACKGROUND: Recent studies have shown that the selective inhibitor of c-Jun N-terminal kinases(JNKs) signaling pathway, SP600125, exhibits neuronal protective effects in a rat model of brainischemia/reperfusion.OBJECT...BACKGROUND: Recent studies have shown that the selective inhibitor of c-Jun N-terminal kinases(JNKs) signaling pathway, SP600125, exhibits neuronal protective effects in a rat model of brainischemia/reperfusion.OBJECTIVE: To determine the mechanisms of neuroprotective effects of SP600125 in a rat modelof brain ischemia/reperfusion, and determine the role of the JNK signaling pathway inSP600125-induced effects.DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at theAnimal Experiment Center, Medical School of Xi'an Jiaotong University from June 2007 toSeptember 2008.MATERIALS: SP600125 was provided by Biosource, USA; rabbit anti-phospho-JNK(Thr183/Tyr185) polyclonal antibody from Cell Signaling Technology, USA; rabbit anti-X-ray repaircross-complementing protein 1 (XRCC1) and anti-Ku70 polyclonal antibodies from Santa CruzBiotechnology, USA; and TUNEL kit from Beijing Huamei Biology, China.METHODS: A total of 108 male, 4-month-old, Sprague Dawley rats were randomly assigned to threegroups, with 36 rats per group. The sham operation group and ischemia/reperfusion group (I/Rgroup) were intracerebroventricularly injected with 10 μL 1% DMSO. The SP600125-treated group(pre-SP group) was given 10 μL SP600125 (3 μg/μL). Thirty minutes later, brain ischemia wasinduced in the I/R and pre-SP groups using the four-vessel occlusion method. Specifically, wholebrain ischemia was induced for 6 minutes, and the clips were released to restore carotid artery bloodflow. Rats from each group were observed at 2, 6, 12, 24, 48, and 72 hours, with 6 rats for each timepoint. The sham operation group was treated with the same surgical exposure procedures, withexception of occlusion of the carotid artery.MAIN OUTCOME MEASURES: Hematoxylin-eosin staining was used to observe neuronal survivalin the hippocampal CA1 region, TUNEL was used to detect apoptosis in the hippocampal CA1region, and immunohistochemistry was used to detect expression of phospho-JNK, XRCC1, andKu70.RESULTS: Following brain ischemia/reperfusion, neuronal survival significantly decreased, and thenumber of apoptotic cells significantly increased (P < 0.01). Compared with the I/R group, neuronalsurvival significantly increased in the pre-SP group, and the number of apoptotic cells significantlydecreased (P < 0.01). Expression of phospho-JNK increased, and XRCC1 and Ku70 significantlydecreased (P < 0.05) following ischemia/reperfusion. Compared with the I/R group, expression ofphospho-JNK decreased, and XRCC1 and Ku70 significantly increased in the pre-SP group (P <0.05). Correlation analysis revealed an inverse correlation between phospho-JNK gray value andXRCC1 and Ku70 gray values in the hippocampal CA1 region (r = -0.983, -0.953, P < 0.01).CONCLUSION: SP600125 treatment decreased apoptosis induced by global brainischemia/reperfusion in the rat hippocampal CA1 region. Results suggested that the neuroprotectiveeffects were due to inhibited phosphorylation of JNK and reduced down-regulation of XRCC1 andKu70.展开更多
Although tobacco and alcohol consumption are two common risk factors of head and neck cancer (HNC), other specific etiologic causes, such as viral infection and genetic susceptibility factors, remain to be understood....Although tobacco and alcohol consumption are two common risk factors of head and neck cancer (HNC), other specific etiologic causes, such as viral infection and genetic susceptibility factors, remain to be understood. Human DNA is often damaged by numerous endogenous and exogenous mutagens or carcinogens, and genetic variants in interaction with environmental exposure to these agents may explain interindividual differences in HNC risk. Single nucleotide polymorphisms (SNPs) in genes involved in the DNA damage-repair response are reported to be risk factors for various cancer types, including HNC. Here, we reviewed epidemiological studies that have assessed the associations between HNC risk and SNPs in DNA repair genes involved in base-excision repair, nucleotide-excision repair, mismatch repair, double-strand break repair and direct reversion repair pathways. We found, however, that only a few SNPs in DNA repair genes were found to be associated with significantly increased or decreased risk of HNC, and, in most cases, the effects were moderate, depending upon locus-locus interactions among the risk SNPs in the pathways. We believe that, in the presence of exposure, additional pathway-based analyses of DNA repair genes derived from genome-wide association studies (GWASs) in HNC are needed.展开更多
A conventionally synthesized thio- and cyano-modified single-stranded poly(dNTP) sequences of different molecular sizes (20n - 200n) and the same lengths routine poly(dNTP) and poly(NTP) species were obtained through ...A conventionally synthesized thio- and cyano-modified single-stranded poly(dNTP) sequences of different molecular sizes (20n - 200n) and the same lengths routine poly(dNTP) and poly(NTP) species were obtained through the good services provided by the Russian Federal Bioorganic Products Group and by the ThermoFischer, Inc., and then tested for their impact on catalytic activities of β-like DNA polymerases from chromatin of HL-60, WERI-1A and Y-79 cells as well as for the affinity patterns in DNApolβ-poly(dNTP)/ (NTP) pairs, respectively. An essential link between the lengths of ultrashort (50n - 100n) single-stranded poly(dNTP) sequences of different structures and their inhibitory effects towards the cancer-specific DNA polymerases β has been found. A possible significance of this phenomenon for both DNA repair suppression in tumors and a consequent anti-cancer activity of the DNA repair related short poly(dNTP) fragments has been for the first time emphasized with a respect to their pharmacophore revealing potential. Thus, this work presents an experimental attempt to upgrade a contemporary attitude towards the DNA derived products applied for anti-cancer agenda, particularly, for acute myeloid leukemia and retinoblastoma cell DNA repair machinery breakdown. In this study, tumor specific DNA polymerases β were found of being the targets for attack promoted with the primer-like single-stranded DNA fragments followed by consequent cytostatic phenomena. A novel concept of the DNA related anti-cancer medicines is under discussion.展开更多
Acute myeloid leukemia (AML) is a clonal heterogeneous disease of the myeloid white blood cells. It is characterised by an accumulation of immature blast cells and a number of chromosomal and genetic mutations have be...Acute myeloid leukemia (AML) is a clonal heterogeneous disease of the myeloid white blood cells. It is characterised by an accumulation of immature blast cells and a number of chromosomal and genetic mutations have been identified. In both de novo and therapy-related AML, defective DNA repair mechanisms are responsible for some of these genetic abnormalities. Targeting the DNA repair mechanism has been shown to be successful against certain forms of solid tumors and may represent a novel therapeutic approach for AML.展开更多
We previously reported that many ingenol compounds derived from Euphoria kansui exhibit topoisomerase inhibitory activity. 20-O-ingenolEZ in these compounds exerted inhibitory effects on both topoisomerase II (topo II...We previously reported that many ingenol compounds derived from Euphoria kansui exhibit topoisomerase inhibitory activity. 20-O-ingenolEZ in these compounds exerted inhibitory effects on both topoisomerase II (topo II) activity and cell proliferative activity. Topoisomerase II inhibitors can be divided into the poison and catalytic inhibitor types and 20-O-ingenolEZ is a catalytic inhibitor and inhibits topo IIα through inhibition of ATPase activity, but induces topo II-mediated DNA damage and apoptosis in BLM-/- DT40 cells through the induction of the DNA damage checkpoint, similar to the poison type inhibitor adriamycin. The ATPase inhibitor of topo II ICRF-193 also showed poison-like characteristics in the same cell line. However, the inhibitory effects of ICRF-193 on the proliferation of BLM-/- DT40 cells differed from those of 20-O-ingenolEZ, as did the specificity of its inhibition of the proliferation of other cell lines. 20-O-ingenolEZ showed hypersensitive inhibition of the proliferation of MCF-7 cells and BLM-/- DT40 cells with mutated DNA repair-related genes.展开更多
文摘Ionizing radiation is frequently used to treat solid tumors,as it causes DNA damage and kill cancer cells.However,damaged DNA is repaired involving poly-(ADP-ribose)polymerase-1(PARP-1)causing resistance to radiation therapy.Thus,PARP-1 represents an important target in multiple cancer types,including prostate cancer.PARP is a nuclear enzyme essential for single-strand DNA breaks repair.Inhibiting PARP-1 is lethal in a wide range of cancer cells that lack the homologous recombination repair(HR)pathway.This article provides a concise and simplified overview of the development of PARP inhibitors in the laboratory and their clinical applications.We focused on the use of PARP inhibitors in various cancers,including prostate cancer.We also discussed some of the underlying principles and challenges that may affect the clinical efficacy of PARP inhibitors.
基金supported by the National Natural Science Foundation of China(Grant Nos.81672981 and 81972240).
文摘Viewing cancer as a large,evolving population of heterogeneous cells is a common perspective.Because genomic instability is one of the fundamental features of cancer,this intrinsic tendency of genomic variation leads to striking intratumor heterogeneity and functions during the process of cancer formation,development,metastasis,and relapse.With the increased mutation rate and abundant diversity of the gene pool,this heterogeneity leads to cancer evolution,which is the major obstacle in the clinical treatment of cancer.Cells rely on the integrity of DNA repair machineries to maintain genomic stability,but these machineries often do not function properly in cancer cells.The deficiency of DNA repair could contribute to the generation of cancer genomic instability,and ultimately promote cancer evolution.With the rapid advance of new technologies,such as single-cell sequencing in recent years,we have the opportunity to better understand the specific processes and mechanisms of cancer evolution,and让s relationship with DNA repair.Here,we review recent findings on how DNA repair affects cancer evolution,and discuss how these mechanisms provide the basis for critical clinical challenges and therapeutic applications.
基金The project supported by National High-tech R&D Program of China 863 Program Grant(2009AA022704)National Natural Science Foundation of China(81573463,81173129,81202595 and NIH Grant CA 94961)
文摘OBJECTIVE To investigate the role of e IF3a in the regulation of DNA repair pathways in cancer chemotherapeutic response.METHODS Immunohistochemistry was used to determine the expression of e IF3a in lung and breast cancer tissues followed by association analysis of e IF3a expression with patient′s response to chemotherapy.Ectopic overexpression and RNA interference knockdown of e IF3a were carried out in NIH3T3and H1299 cell lines,respectively,to determine the effect of altered e IF3a expression on cellular response to chemotherapeutic drugs by using MTT assay.The DNA repair capacity of these cells was evaluated by using host-cell reactivation,NHEJ and HR assay.Real-time reverse transcriptase PCR and Western Blot analyses were carried out to determine the effect of e IF3a on the DNA repair genes by using cells with altered e IF3a expression.RESULTS e IF3a expression associates with response of lung and breast cancer patients to platinum and anthracycline.e IF3a knockdown or overexpression,respectively,increased and decreased the cellular resistance to cisplatin and anthracycline anticancer drugs,DNA repair activity,and expression of NER and NHEJ DNA repair proteins.CONCLUSION e IF3a plays an important role in regulating the expression of NER and NHEJ DNA repair proteins which,in turn,contributes to cellular response to DNA-damaging anticancer drugs and patients′response to platinum and anthracycline chemotherapy.
文摘Introduction: DNA repair enzymes continuously monitor DNA to correct damaged nucleotide residues generated by exposure to environmental mutagenic and cytotoxic compounds or carcinogens. Our objective was to investigate the association among XRCC1 (Arg399Gln and Arg194Trp), XRCC3 (Thr241Met), XPD-ERCC2 (Lys751Gln), APE1 (Asp241Glu), PARP-ADPRT (Val762Ala) DNA repair gene polymorphisms and lung cancer in Turkish population. Materials and Methods: Our patient group consists of 90 patients with lung cancer and the control group had 100 healthy individuals all of those smoking. DNA was extracted using the whole blood samples. PCR- RFLP technique was used to investigate the polymorphisms on target genes. Results: There was no significant difference in the genotype distributions of XPD Lys751Gln, XRCC1 Arg194Trp, XRCC3 Thr241Met, APE1 Asp241Glu between lung cancer patients and controls for each polymorphism (p > 0.05). However, there was a significant difference between the genotype distributions of XRCC1 Arg399Gln, and PARP Val762Ala in patients and the control group (p > 0.05). Discussion: Only the polymorphisms of XRCC1 codon 399 and PARP Val762Ala alleles are associated with the risk of lung cancer. Other genotypes were not related to lung cancer.
文摘Although thousands of DNA damaging events occur in each cell every day,efficient DNA repair pathways have evolved to counteract them. The DNA repair machinery plays a key role in maintaining genomic stability by avoiding the maintenance of mutations. The DNA repair enzymes continuously monitor the chromosomes to correct any damage that is caused by exogenous and endogenous mutagens. If DNA damage in proliferating cells is not repaired because of an inadequate expression of DNA repair genes,it might increase the risk of cancer. In addition to mutations,which can be either inherited or somatically acquired,epigenetic silencing of DNA repair genes has been associated with carcinogenesis. Gastric cancer represents the second highest cause of cancer mortality worldwide. The disease develops from the accumulation of several genetic and epigenetic changes during the lifetime. Among the risk factors,Helicobacter pylori(H. pylori) infection is considered the main driving factor to gastric cancer development. Thus,in this review,we summarize the current knowledge of the role of H. pylori infection on the epigenetic regulation of DNA repair machinery in gastric carcinogenesis.
文摘Pancreatic cancer is highly lethal. Current research that combines radiation with targeted therapy may dramatically improve prognosis. Cancerous cells are characterized by unstable genomes and activation of DNA repair pathways, which are indicated by increased phosphorylation of numerous factors, including H2 AX, ATM, ATR, Chk1, Chk2, DNA-PKcs, Rad51, and Ku70/Ku80 heterodimers. Radiotherapy causes DNA damage. Cancer cells can be made more sensitive to the effects of radiation(radiosensitization) through inhibition of DNA repair pathways. The synergistic effects, of two or more combined non-lethal treatments, led to coadministration of chemotherapy and radiosensitization in BRCA-defective cells and patients, with promising results. ATM/Chk2 and ATR/Chk1 pathways are principal regulators of cell cycle arrest, following DNA doublestrand or single-strand breaks. DNA double-stranded breaks activate DNA-dependent protein kinase, catalytic subunit(DNA-PKcs). It forms a holoenzyme with Ku70/Ku80 heterodimers, called DNA-PK, which catalyzes the joining of nonhomologous ends. This is the primary repair pathway utilized in human cells after exposure to ionizing radiation. Radiosensitization, induced by inhibitors of ATM, ATR, Chk1, Chk2, Wee1, PP2 A, or DNA-PK, has been demonstrated in preclinical pancreatic cancer studies. Clinical trials are underway. Development of agents that inhibit DNA repair pathways to be clinically used in combination with radiotherapy is warranted for the treatment of pancreatic cancer.
文摘Objective Alkaline comet assay was used to evaluate DNA repair (nucleotide excision repair, NER) capacity of human fresh lymphocytes from 12 young healthy non-smokers (6 males and 6 females). Methods Lymphocytes were exposed to UV-C (254 nm) at the dose rate of 1.5 J/m2/sec. Novobiocin (NOV) and aphidicolin (APC), DNA repair inhibitors, were utilized to imitate the deficiency of DNA repair capacity at the incision and ligation steps of NER. Lymphocytes from each donor were divided into three grougs: UVC group, UVC plus NOV group, and UVC plus APC group. DNA single strand breaks were detected in UVC irradiated cells incubated for 0, 30, 60, 90, 120, 180, and 240 min after UVC irradiation. DNA repair rate (DRR) served as an indicator of DNA repair capacity. Results The results indicated that the maximum DNA damage (i.e. maximum tail length) in the UVC group mainly appeared at 90 min. The ranges of DRRs in the UVC group were 62.84%-98.71%. Average DRR value was 81.84%. The DRR difference between males and females was not significant (P<0.05). However, the average DRR value in the UVC plus NOV group and the UVC plus APC group was 52.98% and 39.57% respectively, which were significantly lower than that in the UVC group (P<0.01). Conclusion The comet assay is a rapid, simple and sensitive screening test to assess individual DNA repair (NER) capacity. It is suggested that the time to detect DNA single strand breaks in comet assay should include 0 (before UV irradiation), 90 and 240 min after exposure to 1.5 J·m-2 UVC at least. The DRR, as an indicator, can represent the individual DNA repair capacity in comet assay.
基金US Public Health Service Grants (Grant No. CA107640, to SNP)"Independent Innovation Foundation of Shandong University IIFSDU" (Grant No. 2010 TB017, to ZF)the National Natural Science Foundation of China (Grant No.81172527, to ZF and SNP) for financial support
文摘Tumors often have DNA repair defects, suggesting additional inhibition of other DNA repair pathways in tumors may lead to synthetic lethality. Accumulating data demonstrate that DNA repair-defective tumors, in particular homologous recombination (HR), are highly sensitive to DNA-damaging agents. Thus, HR-defective tumors exhibit potential vulnerability to the synthetic lethality approach, which may lead to new therapeutic strategies. It is well known that poly (adenosine diphosphate (ADP)-ribose) polymerase (PARP) inhibitors show the synthetically lethal effect in tumors defective in BRCA1 or BRCA2 genes encoded proteins that are required for efficient HR. In this review, we summarize the strategies of targeting DNA repair pathways and other DNA metabolic functions to cause synthetic lethality in HR-defective tumor cells.
文摘Deficiencies in DNA repair due to inherited germ-line mutations in DNA repair genes cause increased risk of gastrointestinal(GI) cancer. In sporadic GI cancers, mutations in DNA repair genes are relatively rare. However, epigenetic alterations that reduce expression of DNA repair genes are frequent in sporadic GI cancers. These epigenetic reductions are also found in field defects that give rise to cancers. Reduced DNA repair likely allows excessive DNA damages to accumulate in somatic cells. Then either inaccurate translesion synthesis past the un-repaired DNA damages or error-prone DNA repair can cause mutations. Erroneous DNA repair can also cause epigenetic alterations(i.e., epimutations, transmitted through multiple replication cycles). Some of these mutations and epimutations may cause progression to cancer. Thus, deficient or absent DNA repair is likely an important underlying cause of cancer. Whole genome sequencing of GI cancers show that between thousands to hundreds of thousands of mutations occur in these cancers. Epimutations that reduce DNA repair gene expression and occur early in progression to GI cancers are a likely source of this high genomic instability. Cancer cells deficient in DNA repair are more vulnerable than normal cells to inactivation by DNA damaging agents. Thus, some of the most clinically effective chemotherapeutic agents in cancer treatment are DNA damaging agents, and their effectiveness often depends on deficient DNA repair in cancer cells. Recently, at least 18 DNA repair proteins, each active in one of six DNA repair pathways, were found to be subject to epigenetic reduction of expression in GI cancers. Different DNA repair pathways repair different types of DNA damage. Evaluation of which DNA repair pathway(s) are deficient in particular types of GI cancer and/or particular patients may prove useful in guiding choice of therapeutic agents in cancer therapy.
基金Supported by Research Department of Portuguese League against Cancer(NRNorte)and Minister of Health of Portugal(CFICS-45/2007)
文摘Ovarian cancer(OC)is the sixth most common cancer and the seventh cause of death from cancer in women.The etiology and the ovarian carcinogenesis still need clarification although ovulation may be determinant due to its carcinogenic role in ovarian surface epithelium.The link between ovarian carcinogenesis and DNA repair is well established and it became clear that alterations in DNA damage response may affect the risk to develop OC.Polymorphisms are variations in the DNA sequence that exist in normal individuals of a population and are capable to change,among other mechanisms,the balance between DNA damage and cellular response.Consequently,genetic variability of the host has a great role in the development,progression and consequent prognosis of the oncologic patient as well as in treatment response.Standard treatment for OC patients is based on cytoreductive surgery,followed by chemotherapy with a platinum agent and a taxane.Although 80%of the patients respond to the first-line therapy,the development of resistance is common although the mechanisms underlying therapy failure remain mostly unknown.Because of their role in oncology,enzymes involved in the DNA repair pathways,like DNA Ligase IV(LIG4),became attractive study targets.It has been reported that variations in LIG4 activity can lead to a hyper-sensitivity to DNA damage,deregulation of repair and apoptosis mechanisms,affecting the susceptibility to cancer development and therapy response.To overcome resistance mechanisms,several investigations have been made and the strategy to target crucial molecular pathways,such as DNA repair,became one of the important areas in clinical oncology.This review aims to elucidate the link between DNA repair and OC,namely which concerns the role of LIG4 enzyme,and how genetic polymorphisms in LIG4 gene can modulate the activity of the enzyme and affect the ovarian carcinogenesis and treatment response.Moreover,we try to understand how LIG4 inhibition can be a potential contributor for the development of new cancer treatment strategies.
基金Supported by The DOD Innovator and Scholar Concept Award,No.W81XWH-12-1-0372
文摘Over the past few decades, major strides have advanced the techniques for early detection and treatment of cancer. However, metastatic tumor growth still accounts for the majority of cancer-related deaths worldwide. In fact, breast cancers are notorious for relapsing years or decades after the initial clinical treatment, and this relapse can vary according to the type of breast cancer. In estrogen receptor-positive breast cancers, late tumor relapses frequently occur whereas relapses in estrogen receptor-negative cancers or triple negative tumors arise early resulting in a higher mortality risk. One of the main causes of metastasis is tumor dormancy in which cancer cells remain concealed, asymptomatic, and untraceable over a prolonged period of time. Under certain conditions, dormant cells can re-enter into the cell cycle and resume proliferation leading to recurrence. However, the molecular and cellular regulators underlying this transition remain poorly understood. To date, three mechanisms have been identified to trigger tumor dormancy including cellular, angiogenic, and immunologic dormancies. In addition, recent studies have suggested that DNA repair mechanisms may contribute to the survival of dormant cancer cells. In this article, we summarize the recent experimental and clinical evidence governing cancer dormancy. In addition, we will discuss the role of DNA repair mechanisms in promoting the survival of dormant cells. This information provides mechanistic insight to explain why recurrence occurs, and strategies that may enhance therapeutic approaches to prevent disease recurrence.
基金This study was supported by a grant from National Natural Science Foundation of China (No. 30100147).
文摘Objective To compare the asbestos-induced DNA damage and repair capacities of DNA damage between 104 asbestos- exposed workers and 101 control workers in Qingdao City of China and to investigate the possible association between polymorphisms in codon 399 of XRCC1 and susceptibility to asbestosis. Methods DNA damage levels in peripheral blood lymphocytes were determined by comet assay, and XRCC1 genetic polymorphisms of DNA samples from 51 asbestosis cases and 53 non-asbestosis workers with a similar asbestos exposure history were analyzed by PCR/RFLP. Results The basal comet scores (3.95±2.95) were significantly higher in asbestos-exposed workers than in control workers (0.10±0.28). After 1 h H2O2 stimulation, DNA damage of lymphocytes exhibited different increases. After a 4 h repair period, the comet scores were 50.98±19.53 in asbestos-exposed workers and 18.32±12.04 in controls. The residual DNA damage (RD) was significantly greater (P<0.01) in asbestos-exposed workers (35.62%) than in controls (27.75%). XRCC1 genetic polymorphism in 104 asbestos-exposed workers was not associated with increased risk of asbestosis. But compared with polymorphisms in the DNA repair gene XRCC1 (polymorphisms in codon 399) and the DNA damage induced by asbestos, the comet scores in asbestosis cases with Gln/Gln, Gln/Arg, and Arg/Arg were 40.26±18.94, 38.03±28.22, and 32.01±11.65, respectively, which were higher than those in non-asbestosis workers with the same genotypes (25.58±11.08, 37.08±14.74, and 29.38±10.15). There were significant differences in the comet scores between asbestosis cases and non-asbestosis workers with Gln/Gln by Student’s t-test (P<0.05 or 0.01). The comet scores were higher in asbestosis workers with Gln/Gln than in those with Arg/Arg and in non-asbestosis workers exposed to asbestos, but without statistically significant difference. Conclusions Exposure to asbestos may be related to DNA damage or the capacity of cells to repair H2O2-induced DNA damage. DNA repair gene XRCC1 codon 399 may be responsible for the inter-individual susceptibility in DNA damage and repair capacities.
基金Supported by: the National Natural Science Foundation of China, No. 30571790
文摘BACKGROUND: Recent studies have shown that the selective inhibitor of c-Jun N-terminal kinases(JNKs) signaling pathway, SP600125, exhibits neuronal protective effects in a rat model of brainischemia/reperfusion.OBJECTIVE: To determine the mechanisms of neuroprotective effects of SP600125 in a rat modelof brain ischemia/reperfusion, and determine the role of the JNK signaling pathway inSP600125-induced effects.DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at theAnimal Experiment Center, Medical School of Xi'an Jiaotong University from June 2007 toSeptember 2008.MATERIALS: SP600125 was provided by Biosource, USA; rabbit anti-phospho-JNK(Thr183/Tyr185) polyclonal antibody from Cell Signaling Technology, USA; rabbit anti-X-ray repaircross-complementing protein 1 (XRCC1) and anti-Ku70 polyclonal antibodies from Santa CruzBiotechnology, USA; and TUNEL kit from Beijing Huamei Biology, China.METHODS: A total of 108 male, 4-month-old, Sprague Dawley rats were randomly assigned to threegroups, with 36 rats per group. The sham operation group and ischemia/reperfusion group (I/Rgroup) were intracerebroventricularly injected with 10 μL 1% DMSO. The SP600125-treated group(pre-SP group) was given 10 μL SP600125 (3 μg/μL). Thirty minutes later, brain ischemia wasinduced in the I/R and pre-SP groups using the four-vessel occlusion method. Specifically, wholebrain ischemia was induced for 6 minutes, and the clips were released to restore carotid artery bloodflow. Rats from each group were observed at 2, 6, 12, 24, 48, and 72 hours, with 6 rats for each timepoint. The sham operation group was treated with the same surgical exposure procedures, withexception of occlusion of the carotid artery.MAIN OUTCOME MEASURES: Hematoxylin-eosin staining was used to observe neuronal survivalin the hippocampal CA1 region, TUNEL was used to detect apoptosis in the hippocampal CA1region, and immunohistochemistry was used to detect expression of phospho-JNK, XRCC1, andKu70.RESULTS: Following brain ischemia/reperfusion, neuronal survival significantly decreased, and thenumber of apoptotic cells significantly increased (P < 0.01). Compared with the I/R group, neuronalsurvival significantly increased in the pre-SP group, and the number of apoptotic cells significantlydecreased (P < 0.01). Expression of phospho-JNK increased, and XRCC1 and Ku70 significantlydecreased (P < 0.05) following ischemia/reperfusion. Compared with the I/R group, expression ofphospho-JNK decreased, and XRCC1 and Ku70 significantly increased in the pre-SP group (P <0.05). Correlation analysis revealed an inverse correlation between phospho-JNK gray value andXRCC1 and Ku70 gray values in the hippocampal CA1 region (r = -0.983, -0.953, P < 0.01).CONCLUSION: SP600125 treatment decreased apoptosis induced by global brainischemia/reperfusion in the rat hippocampal CA1 region. Results suggested that the neuroprotectiveeffects were due to inhibited phosphorylation of JNK and reduced down-regulation of XRCC1 andKu70.
文摘Although tobacco and alcohol consumption are two common risk factors of head and neck cancer (HNC), other specific etiologic causes, such as viral infection and genetic susceptibility factors, remain to be understood. Human DNA is often damaged by numerous endogenous and exogenous mutagens or carcinogens, and genetic variants in interaction with environmental exposure to these agents may explain interindividual differences in HNC risk. Single nucleotide polymorphisms (SNPs) in genes involved in the DNA damage-repair response are reported to be risk factors for various cancer types, including HNC. Here, we reviewed epidemiological studies that have assessed the associations between HNC risk and SNPs in DNA repair genes involved in base-excision repair, nucleotide-excision repair, mismatch repair, double-strand break repair and direct reversion repair pathways. We found, however, that only a few SNPs in DNA repair genes were found to be associated with significantly increased or decreased risk of HNC, and, in most cases, the effects were moderate, depending upon locus-locus interactions among the risk SNPs in the pathways. We believe that, in the presence of exposure, additional pathway-based analyses of DNA repair genes derived from genome-wide association studies (GWASs) in HNC are needed.
文摘A conventionally synthesized thio- and cyano-modified single-stranded poly(dNTP) sequences of different molecular sizes (20n - 200n) and the same lengths routine poly(dNTP) and poly(NTP) species were obtained through the good services provided by the Russian Federal Bioorganic Products Group and by the ThermoFischer, Inc., and then tested for their impact on catalytic activities of β-like DNA polymerases from chromatin of HL-60, WERI-1A and Y-79 cells as well as for the affinity patterns in DNApolβ-poly(dNTP)/ (NTP) pairs, respectively. An essential link between the lengths of ultrashort (50n - 100n) single-stranded poly(dNTP) sequences of different structures and their inhibitory effects towards the cancer-specific DNA polymerases β has been found. A possible significance of this phenomenon for both DNA repair suppression in tumors and a consequent anti-cancer activity of the DNA repair related short poly(dNTP) fragments has been for the first time emphasized with a respect to their pharmacophore revealing potential. Thus, this work presents an experimental attempt to upgrade a contemporary attitude towards the DNA derived products applied for anti-cancer agenda, particularly, for acute myeloid leukemia and retinoblastoma cell DNA repair machinery breakdown. In this study, tumor specific DNA polymerases β were found of being the targets for attack promoted with the primer-like single-stranded DNA fragments followed by consequent cytostatic phenomena. A novel concept of the DNA related anti-cancer medicines is under discussion.
文摘Acute myeloid leukemia (AML) is a clonal heterogeneous disease of the myeloid white blood cells. It is characterised by an accumulation of immature blast cells and a number of chromosomal and genetic mutations have been identified. In both de novo and therapy-related AML, defective DNA repair mechanisms are responsible for some of these genetic abnormalities. Targeting the DNA repair mechanism has been shown to be successful against certain forms of solid tumors and may represent a novel therapeutic approach for AML.
文摘We previously reported that many ingenol compounds derived from Euphoria kansui exhibit topoisomerase inhibitory activity. 20-O-ingenolEZ in these compounds exerted inhibitory effects on both topoisomerase II (topo II) activity and cell proliferative activity. Topoisomerase II inhibitors can be divided into the poison and catalytic inhibitor types and 20-O-ingenolEZ is a catalytic inhibitor and inhibits topo IIα through inhibition of ATPase activity, but induces topo II-mediated DNA damage and apoptosis in BLM-/- DT40 cells through the induction of the DNA damage checkpoint, similar to the poison type inhibitor adriamycin. The ATPase inhibitor of topo II ICRF-193 also showed poison-like characteristics in the same cell line. However, the inhibitory effects of ICRF-193 on the proliferation of BLM-/- DT40 cells differed from those of 20-O-ingenolEZ, as did the specificity of its inhibition of the proliferation of other cell lines. 20-O-ingenolEZ showed hypersensitive inhibition of the proliferation of MCF-7 cells and BLM-/- DT40 cells with mutated DNA repair-related genes.
