Original StudyNucleotide Excision Repair Capacity and XPC and XPD Gene Polymorphism Modulate Colorectal Cancer Risk
Introduction
The global statistic reports place colorectal cancer (CRC) within the 3 most common type of cancer, with 1.36 million incidences in 2012. Most cases occur in developed countries where it is associated with specific lifestyles for those regions.1 Regarding molecular features, CRC has been categorized into 3 phenotypes: microsatellite instability, CpG (5′—C—phosphate—G—3′) island methylator phenotype, and chromosomal instability (CIN). It is estimated that the CIN pathway appears in 70% to 85% of CRC.2 CIN-positive cells are characterized by an abnormal number of chromosomes, subchromosomal genomic amplifications, and loss of heterozygosity. Up to now, a number of studies have highlighted several mechanisms significant in the course of CIN, namely chromosome segregation defects, telomere dysfunction, or DNA damage response.3 Nonetheless, much uncertainty still exists about the origin and CIN development. In recent years, one of the most studied issues in this context of loss of genomic stability are widely defined DNA damage and pathways engaged in their repair. A lot of attention has been devoted to determine the role of oxidative DNA damage and mechanism responsible for its removing, base excision repair (BER) in pathogenesis of many human diseases. Among hundreds of publications on BER in cancer, the dominant are case-control studies that attempt to identify new molecular markers for cancer within BER gene polymorphisms. In reviewing the literature, one might notice that a few BER gene polymorphisms gained particular attention. Extensively exploration of 8-oxoguanine DNA glycosylase 1 (OGG1) Ser326Cys and several MUTYH gene single-nucleotide polymorphism (SNP) variants have brought many contradictory results, and meta-analyses summaries indicate a rather modest or lack of association with CRC.4, 5
In our previous work on CRC, we have investigated the gap-filling stage of BER to asses efficiency of this process and determine some SNPs that might modulate CRC risk. Our findings showed a higher CRC risk for certain variants of DNA ligase 3 (LIG3) and exonuclease 1 (EXO1) and also the effect of decreasing the cancer risk for the 242Arg/Arg of human DNA polymerase beta (POLB). Using an in vitro radiolabeling assay we observed a weaker ability for BER-dependent gap-filling of apurinic/apyrimidinic sites in lymphocytes and colon tissue taken from CRC patients compared with healthy control subjects.6
In fact, oxidative damage is only one of many types of DNA lesions. In this study we attempted to consider the implications of the nucleotide excision repair (NER) pathway engaged in repair in a wide range of different origin lesions. Typically, NER is listed as a biochemical tool to deal with UV-induced damage such as cyclobutane–pyrimidine dimers, 6–4 pyrimidine–pyrimidone photoproduct. Logically, location of colon tissues seems to have a poor relation with CRC development on the basis of UV-induced DNA damage. Other substrates for NER enzymes that can be distinguished are DNA adducts formed by natural mutagens (benzo[a]pyrene, various aromatic amines)7 as well as synthetic factors (chemotherapeutic agents: temozolomide, streptozotocin)8, 9 The most dangerous are interstrand crosslinks (ICLs) generated by bifunctional alkylating agents like cisplatin, nitrogen mustard, and diepoxybutane. By covalent binding of the two DNA strands, ICL completely blocks the ability to transcribe and replicate and thus disturbs genome integrity, which is a therapeutic activity against cancer. There are some reports to imply that 20 unrepaired crosslinks might be sufficient to kill mammalian cells.10
Nucleotide excision repair is a relatively well described mechanism that can be differentiated in 2 subpathways: operating on whole-genome global genome NER (ggNER), and active only within transcribing regions transcription-coupled NER (tcNER). Besides the various targets, both subpathways require a different set of proteins to recognize a lesion site and initiate repair. Details has been reviewed in many articles.11, 12, 13 Xeroderma pigmentosum (XP) disease which causes UV-sensitivity in patients, is an excellent example of genetic impairment that shows an inability to perform ggNER, had a great impact on the discovery and study of NER. What is essential in terms of cancer, bearers of XP mutations are 1000-fold more likely to have skin and eye cancer.14 In contrast, the other NER-deficient disorder, Cockayne syndrome (CS), which is characterized by postnatal failure of brain growth and many somatic and neurological symptoms, and also causes sun sensitivity in patients, yet no relation with cancer development has been observed. CS genetic hallmark that specifically entails tcNER failure, which suggests potentially less important role for this pathway in carcinogenesis.15 A much debated question is whether some genetic variants can modulate the way in which cells respond to environmental factors and act in favor or against mutagenic events. Although many studies investigating SNPs have been released, the results are still equivocal and inconclusive. The complex of XPC is the initial damage recognition factor in ggNER.16 XPC recognizes a wide variety of lesions that thermodynamically destabilize DNA duplexes, including UV-induced photoproducts (cyclopyrimidine dimers and 6–4 photoproducts), adducts formed by environmental mutagens such as benzo[a]pyrene or various aromatic amines, certain oxidative endogenous lesions such as cyclopurines, and adducts formed by cancer chemotherapeutic drugs such as cisplatin.17 The presence of XPC is required for assembly of the other core NER factors and progression through the NER pathway in vitro as well as in vivo. The XPD Excision repair cross-complementing rodent repair deficiency, complementation group 2 (ERCC2) is a protein of tcNER, which is a part of human transcriptional initiation factor Transcription factor II Human (TFIIH) and has adenosine triphosphate (ATP)-dependent helicase activity. The XPD gene encodes for a 2.3-kilobase mRNA containing 22 exons and 21 introns.18 The XPD protein is a 760-amino acid polypeptide with a size of 87 kDa. Defects in this gene can result in 3 different disorders: the cancer-prone syndrome xeroderma pigmentosum complementation group D.
This investigation was a classic case-control study enriched with analysis of NER efficiency in patients suffering from CRC. We selected 2 common polymorphisms on XPC (Lys939Gln) and XPD (Lys751Gln) genes to find out whether they have potential to alter risk of CRC development and/or progression. The main selection criteria for SNPs were the crucial role that particular gene plays in NER and availability of previous reports to suggest a polymorphism–cancer relationship in relation to other cancers. Many retrospective studies address subjects on the basis of far-reaching theoretical assumptions and loose connections to disease polymorphisms, whereas sometimes very little is known about the role of a particular mechanism in illness development. In designing our research we included an in vitro method to examine general NER efficiency in lymphocytes and tissue. Therefore in this report we intend not only to reveal a genotype–case relation but also provide the view on potency of NER in patients and healthy people. We believe the data gathered in this study shows that NER might play a certain role in the pathogenesis of CRC.
Section snippets
Samples
Genotype detection was performed on DNA isolated from peripheral blood lymphocytes. A random sample of 221 patients with CRC was recruited from Military Medical Academy University Teaching Hospital-Central Veterans’ Hospital in Lodz. Eligibility criteria required all of the individuals to have histopathologically diagnosed CRC and no family history within relatives of the first- and second-degree. The TNM cancer staging notation system has been applied to characterize patients, which is
Results
The distribution of genotypes and alleles corresponded to the predicted HW proportion (P < .05) in control as well as CRC groups, and both tested SNPs.
At the outset we compared the direct relation between particular variants’ exposure in cases and controls. None of differences in distribution of XPD (Lys751Gln) genotypes were statistically significant for CRC risk. Further statistical tests revealed increased risk of CRC for XPC Gln939Gln and Glu allele. Table 2 shows frequency and odds ratios
Discussion
DNA repair has an essential role in protecting the genome from damage by endogenous and environmental agents. Multiple genetic alterations contribute to CRC susceptibility. Further, increasing number of studies provided evidence that genetic modifications such as germline polymorphisms in DNA repair pathway genes can either change protein coding or alter the levels of transcription or translation, thereby reducing DNA repair capacity and inducing genetic instability or carcinogenesis.22 In the
Conclusion
Considering all of our observations we hypothesize that XPC gene alterations are more relevant for CRC development risk because XPC is the initial damage recognition factor in ggNER. That is why overall repair capacity of the cell is compromised making this cell more susceptible for cancer transformation. The XPD (ERCC2), however, is a protein of tcNER that is why its negative influence is more profound in intensively transcribing cells such as cancer cells. Our data also indicate clearly
Disclosure
The authors declare no conflict of interest.
Acknowledgments
This study was supported by the Polish Ministry of Science and Higher Education grant N N402 422138 and Medical University of Lodz research tasks no 502-03/5-108-05/502-54-155, 502-03/5-108-05/502-54-183 and NCN Grant no 2015/19/B/NZ5/01421.
References (33)
- et al.
The chromosomal instability pathway in colon cancer
Gastroenterology
(2010) - et al.
Distinct roles for the XPB/p52 and XPD/p44 subcomplexes of TFIIH in damaged DNA opening during nucleotide excision repair
Mol Cell
(2007) - et al.
Irreparable DNA cross-links and mammalian cell lethality with bifunctional alkylating agents
Chem Biol Interact
(1981) Nucleotide excision repair II: from yeast to mammals
Trends Genet
(1993)- et al.
Xeroderma pigmentosum, trichothiodystrophy and Cockayne syndrome: a complex genotype–phenotype relationship
Neuroscience
(2007) - et al.
Xeroderma pigmentosum group C protein complex is the initiator of global genome nucleotide excision repair
Mol Cell
(1998) - et al.
Polymorphisms of DNA repair genes XPD and XRCC1 and risk of cataract development
Exp Eye Res
(2007) - et al.
Detection and measurement of nucleotide excision repair synthesis by mammalian cell extracts in vitro
Methods
(1995) - et al.
Associations between XPC polymorphisms and risk of cancers: a meta-analysis
Eur J Cancer
(2008) XPD structure reveals its secrets
DNA Repair
(2008)
Impaired nucleotide excision repair pathway as a possible factor in pathogenesis of head and neck cancer
Mutat Res Mol Mech Mutagen
Colorectal cancer: molecular features and clinical opportunities
Clin Biochem Rev
Meta-analysis of mismatch repair polymorphisms within the Cogent Consortium for Colorectal Cancer Susceptibility
PLoS One
Meta-analysis of the association between hOGG1 Ser326Cys polymorphism and risk of colorectal cancer based on case–control studies
J Cancer Res Clin Oncol
Efficiency of base excision repair of oxidative DNA damage and its impact on the risk of colorectal cancer in the Polish population
Oxid Med Cell Longev
Molecular mechanisms of mammalian global genome nucleotide excision repair
Chem Rev
Cited by (8)
Canonical and uncanonical pathogenic germline variants in colorectal cancer patients by next-generation sequencing in a European referral center
2022, ESMO OpenCitation Excerpt :Noticeably, the carrier of PTCH1 PVs did not show the phenotypic hallmarks of the associated syndrome, nor did their relatives. Polymorphisms in genes like XPC have been associated with modest increases in CRC risk.29 However, the role of rare PVs in CRC, which is currently not part of their recognized clinical spectrum, remains to be defined.
DNA repair, NFKβ, and TP53 polymorphisms associated with potentially malignant disorders and oral squamous cell carcinoma in Argentine patients
2021, Oral Surgery, Oral Medicine, Oral Pathology and Oral RadiologyCitation Excerpt :However, no association was observed between the genotypes of the XPD Lys751 Gln and cases or controls. Studies of colorectal cancer showed no association between the 751 Gln variant and this cancer in Polish patients.25 However, studies conducted in digestive tract and lung cancers in Chinese populations showed an association between the Gln/Gln phenotype and cancer.26
Genetic status of patients with colorectal cancer
2021, Voprosy OnkologiiDNA damage response pathways in cancer predisposition and metastasis
2020, 'Essentials of Cancer Genomic, Computational Approaches and Precision MedicineNucleotide excision repair pathway gene polymorphisms are associated with risk and prognosis of colorectal cancer
2020, World Journal of GastroenterologyIdentification of novel pathogenic MSH2 mutation and new DNA repair genes variants: Investigation of a Tunisian Lynch syndrome family with discordant twins
2019, Journal of Translational Medicine
Bartosz Mucha and Dariusz Pytel equally contributed to this manuscript and share first co-authorship.