Molecular characterization of the human excision repair gene ERCC-1: cDNA cloning and amino acid homology with the yeast DNA repair gene RAD10

When DNA-damage responses meet innate and adaptive immunity

When cells proliferate, stress on DNA replication or exposure to endogenous or external insults frequently results in DNA damage. DNA-Damage Response (DDR) networks are complex signaling pathways used by multicellular organisms to prevent DNA damage. Depending on the type of broken DNA, the various pathways, Base-Excision Repair (BER), Nucleotide Excision Repair (NER), Mismatch Repair (MMR), Homologous Recombination (HR), Non-Homologous End-Joining (NHEJ), Interstrand Crosslink (ICL) repair, and other direct repair pathways, can be activated separately or in combination to repair DNA damage. To preserve homeostasis, innate and adaptive immune responses are effective defenses against endogenous mutation or invasion by external pathogens. It is interesting to note that new research keeps showing how closely DDR components and the immune system are related. DDR and immunological response are linked by immune effectors such as the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway. These effectors act as sensors of DNA damage-caused immune response. Furthermore, DDR components themselves function in immune responses to trigger the generation of inflammatory cytokines in a cascade or even trigger programmed cell death. Defective DDR components are known to disrupt genomic stability and compromise immunological responses, aggravating immune imbalance and leading to serious diseases such as cancer and autoimmune disorders. This study examines the most recent developments in the interaction between DDR elements and immunological responses. The DDR network's immune modulators' dual roles may offer new perspectives on treating infectious disorders linked to DNA damage, including cancer, and on the development of target immunotherapy.

XPF interacts with TOP2B for R-loop processing and DNA looping on actively transcribed genes

Co-transcriptional RNA-DNA hybrids can not only cause DNA damage threatening genome integrity but also regulate gene activity in a mechanism that remains unclear. Here, we show that the nucleotide excision repair factor XPF interacts with the insulator binding protein CTCF and the cohesin subunits SMC1A and SMC3, leading to R-loop-dependent DNA looping upon transcription activation. To facilitate R-loop processing, XPF interacts and recruits with TOP2B on active gene promoters, leading to double-strand break accumulation and the activation of a DNA damage response. Abrogation of TOP2B leads to the diminished recruitment of XPF, CTCF, and the cohesin subunits to promoters of actively transcribed genes and R-loops and the concurrent impairment of CTCF-mediated DNA looping. Together, our findings disclose an essential role for XPF with TOP2B and the CTCF/cohesin complex in R-loop processing for transcription activation with important ramifications for DNA repair-deficient syndromes associated with transcription-associated DNA damage.

Tissue-infiltrating macrophages mediate an exosome-based metabolic reprogramming upon DNA damage

DNA damage and metabolic disorders are intimately linked with premature disease onset but the underlying mechanisms remain poorly understood. Here, we show that persistent DNA damage accumulation in tissue-infiltrating macrophages carrying an ERCC1-XPF DNA repair defect (Er1^F/−) triggers Golgi dispersal, dilation of endoplasmic reticulum, autophagy and exosome biogenesis leading to the secretion of extracellular vesicles (EVs) in vivo and ex vivo. Macrophage-derived EVs accumulate in Er1^F/− animal sera and are secreted in macrophage media after DNA damage. The Er1^F/− EV cargo is taken up by recipient cells leading to an increase in insulin-independent glucose transporter levels, enhanced cellular glucose uptake, higher cellular oxygen consumption rate and greater tolerance to glucose challenge in mice. We find that high glucose in EV-targeted cells triggers pro-inflammatory stimuli via mTOR activation. This, in turn, establishes chronic inflammation and tissue pathology in mice with important ramifications for DNA repair-deficient, progeroid syndromes and aging.

DNA damage is associated with metabolic disorders, but the mechanism in unclear. Here, the authors show that persistent DNA damage induced by lack of the endonuclease XPF-ERCC1 triggers extracellular vesicle biogenesis in tissue infiltrating macrophages, and that vesicle uptake stimulates glucose uptake in recipient cells, leading to increased inflammation.

Function and Interactions of ERCC1-XPF in DNA Damage Response

Numerous proteins are involved in the multiple pathways of the DNA damage response network and play a key role to protect the genome from the wide variety of damages that can occur to DNA. An example of this is the structure-specific endonuclease ERCC1-XPF. This heterodimeric complex is in particular involved in nucleotide excision repair (NER), but also in double strand break repair and interstrand cross-link repair pathways. Here we review the function of ERCC1-XPF in various DNA repair pathways and discuss human disorders associated with ERCC1-XPF deficiency. We also overview our molecular and structural understanding of XPF-ERCC1.

Effect of lanthanum chloride on tumor growth and apoptosis in human ovarian cancer cells and xenograft animal models

Ovarian cancer is the leading cause of mortality resulting from gynecologic cancer. A common anti-ovarian tumor drug is cisplatin; however, repeated use of cisplatin causes severe resistance and leads to poor long-term survival rate in ovarian cancer patients. Recently, it was reported that lanthanum chloride (LaCl₃) may inhibit tumor growth and induce apoptosis in certain cancer cells. In the present study, the effect of LaCl₃ on ovarian cancer was determined in vivo and in vitro. A cisplatin-sensitive human ovarian cancer cell line, COC1, was used in the current study. A xenograft animal model of ovarian cancer was established injecting COC1 or cisplatin-resistant COC1 cells (COC1/DDP) cells into mice. A TUNEL assay was used to determine the apoptosis of the COC1 or COC1/DDP cells and a immunohistochemical assay was conducted to measure the expression of B-cell lymphoma-2, Ki67, breast cancer 1 (BRCA)1, BRCA2 and excision repair cross-complementation group 1 in COC1 or COC1/DDP cells. It was observed that LaCl₃ promoted apoptosis in COC1 and COC1/DDP cells. In addition, LaCl₃ plus cisplatin led to further increase in the expression levels of tumor suppressor genes and decrease in the expression of oncogenes. Furthermore, application of LaCl₃ and cisplatin inhibited tumor growth in vivo in a xenograft animal model. These results indicated the synergistic role of LaCl₃ on cisplatin-induced inhibition of cancer cell proliferation and tumor growth, providing a potential and effective candidate for the treatment of ovarian tumors.

Genetic variants in the nucleotide excision repair pathway genes and gastric cancer susceptibility in a southern Chinese population

BACKGROUND

Potentially functional polymorphisms can modulate protein activities and host's DNA repair capacity, thereby influencing cancer susceptibility. The association of the polymorphisms in the nucleotide excision repair core pathway genes and gastric cancer susceptibility remains largely unknown.

METHODS

Here, we systematically analyzed the associations between nine polymorphisms in four key genes (XPA, ERCC1, ERCC2, and ERCC4) in the nucleotide excision repair pathway and gastric cancer risk in a Chinese population including 1142 patients and 1173 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the risk associations.

RESULTS

We observed that ERCC1 rs2298881 CA variant genotype was associated with an increased gastric cancer risk (CA vs. CC: adjusted OR [AOR]=1.33, 95% CI=1.09-1.62; dominant model: AOR=1.32, 95% CI=1.10-1.60). However, ERCC1 rs3212986 AA variant genotype was identified as a protective factor for gastric cancer (AA vs. CC: AOR=0.73, 95% CI=0.54-0.98; recessive model: AOR=0.72, 95% CI=0.54-0.96). Genotype-based mRNA expression analysis further indicated that the rs2298881 A allele was associated with decreased ERCC1 mRNA expression.

CONCLUSION

In all, these results indicated that the ERCC1 polymorphisms may affect the risk of gastric cancer in the Chinese Han population.

Different splicing isoforms of ERCC1 affect the expression of its overlapping genes CD3EAP and PPP1R13L, and indicate a potential application in non-small cell lung cancer treatment

Numerous genes are arranged in complex overlapping and interlaced patterns, and such arrangements potentially contribute to the regulation of gene expression. Previous studies have demonstrated that a region in chromosome 19q13.2-3 encompassing the overlapping genes excision repair cross-complementation group 1 (ERCC1), CD3e molecule associated protein (CD3EAP) and protein phosphatase 1 regulatory subunit 13 like (PPP1R13L) was found to be associated with the risk and prognosis of non-small cell lung cancer (NSCLC). The present study confirmed the hypothesis that there are co-expression patterns among these overlapping genes. The suggestive bioinformatic evidence of The Cancer Genome Atlas was verified by quantitative polymerase chain reaction (qPCR) analysis of NSCLC tissue samples. In addition, a cisplatin-induced DNA damage cell model was assessed by microarray analysis, qPCR and 3' rapid amplification of cDNA ends (3'RACE) to verify and quantify the expression levels of co-expressed alternative splicing isoforms in the NSCLC tissues, as well as in cancer A549 and normal 16HBE cells. The expression of CD3EAP exon 1 was demonstrated to be significantly associated with PPP1R13L exon 1, while CD3EAP exon 3 was significantly associated with ERCC1 exon 11 in normal and NSCLC tissues. It was observed that short transcripts of ERCC1, CD3EAP and PPP1R13L are co-expressed in A549 cells and full-length transcripts are co-expressed in 16HBE cells. Furthermore, a novel transcriptional regulation pattern was described based on the positional associations of overlapping genes. The region encompassing the overlapping genes ERCC1, CD3EAP and PPP1R13L may be involved in linking the upstream and downstream genes, while the different splicing isoforms of ERCC1 affect the expression of its overlapping genes, suggesting potential application in cisplatin resistance in NSCLC treatment.

ERCC1-XPF cooperates with CTCF and cohesin to facilitate the developmental silencing of imprinted genes

Inborn defects in DNA repair are associated with complex developmental disorders whose causal mechanisms are poorly understood. Using an in vivo biotinylation tagging approach in mice, we show that the nucleotide excision repair (NER) structure-specific endonuclease ERCC1-XPF complex interacts with the insulator binding protein CTCF, the cohesin subunits SMC1A and SMC3 and with MBD2; the factors co-localize with ATRX at the promoters and control regions (ICRs) of imprinted genes during postnatal hepatic development. Loss of Ercc1 or exposure to MMC triggers the localization of CTCF to heterochromatin, the dissociation of the CTCF-cohesin complex and ATRX from promoters and ICRs, altered histone marks and the aberrant developmental expression of imprinted genes without altering DNA methylation. We propose that ERCC1-XPF cooperates with CTCF and cohesin to facilitate the developmental silencing of imprinted genes and that persistent DNA damage triggers chromatin changes that affect gene expression programs associated with NER disorders.

Association between XRCC1 and ERCC1 single-nucleotide polymorphisms and the efficacy of concurrent radiochemotherapy in patients with esophageal squamous cell carcinoma

The aim of the present study was to investigate the association between single-nucleotide polymorphisms (SNPs) in X-ray repair cross-complementing 1–399 (XRCC1-399) or excision repair cross-complementation group 1–118 (ERCC1-118) and the short-term efficacy of radiochemotherapy, tumor metastasis and relapse, as well as the survival time in patients with esophageal squamous cell carcinoma (ESCC). TaqMan probe-based quantitative polymerase chain reaction (qPCR) was conducted to examine the levels of XRCC1-399 and ERCC1-118 SNPs in the peripheral blood of 50 patients with pathologically confirmed ESCC. In addition, the associations between different genotypes and short-term therapeutic efficacy [the complete remission (CR) rate], tumor metastasis and relapse, as well as the survival time following concurrent radiochemotherapy, were determined. A total of 50 ESCC patients who received concurrent radiochemotherapy were enrolled. It was found that the short-term therapeutic efficacy (CR rate) was higher in the group of patients carrying the homozygous mutation of XRCC1-399 (A/A genotype) than in the group of patients without the XRCC1-399 mutation (G/G genotype). In addition, the CR rate was significantly increased in patients carrying one or two ERCC1-118 C alleles (C/C or C/T genotype) compared with patients lacking the C allele (T/T genotype). The differences were statistically significant (A/A vs. G/G, P=0.014; TT vs. C/T+C/C, P=0.040). During the follow-up period, the group of patients carrying the homozygous mutation of XRCC1-399 (A/A genotype) exhibited a markedly reduced risk of metastasis and relapse compared with the group of patients carrying non-mutated XRCC1-399 (G/G genotype; P=0.031). By contrast, ERCC1-118 SNP was not associated with the risk of metastasis and recurrence (P>0.05). The combined results of univariate and multivariate Cox regression analysis showed that the SNP in ERCC1-118 was closely associated with survival time. The mean survival time was significantly prolonged in patients carrying 1 or 2 C alleles (C/C or C/T genotype) compared with patients lacking the C allele (T/T genotype) [T/T vs. C/C, HR=12.96, 95% confidence interval (CI)=3.08–54.61, P<0.001; TT vs. C/T+C/C, HR=11.71, 95% CI=3.06–44.83, P<0.001]. However, XRCC1-399SNP had no effect on survival time (P>0.05). XRCCl-399 SNP was associated with the short-term therapeutic efficacy (the CR rate) and tumor metastasis/relapse in ESCC patients who received the docetaxel plus cisplatin (TP) regimen-based concurrent radiochemotherapy. By contrast, ERCC1-118 SNP was significantly associated with the short-term therapeutic efficacy (the CR rate) and survival time in ESCC patients who received TP regimen-based concurrent radiochemotherapy.

The ERCC1 and ERCC4 (XPF) genes and gene products

The ERCC1 and ERCC4 genes encode the two subunits of the ERCC1-XPF nuclease. This enzyme plays an important role in repair of DNA damage and in maintaining genomic stability. ERCC1-XPF nuclease nicks DNA specifically at junctions between double-stranded and single-stranded DNA, when the single-strand is oriented 5' to 3' away from a junction. ERCC1-XPF is a core component of nucleotide excision repair and also plays a role in interstrand crosslink repair, some pathways of double-strand break repair by homologous recombination and end-joining, as a backup enzyme in base excision repair, and in telomere length regulation. In many of these activities, ERCC1-XPF complex cleaves the 3' tails of DNA intermediates in preparation for further processing. ERCC1-XPF interacts with other proteins including XPA, RPA, SLX4 and TRF2 to perform its functions. Disruption of these interactions or direct targeting of ERCC1-XPF to decrease its DNA repair function might be a useful strategy to increase the sensitivity of cancer cells to some DNA damaging agents. Complete deletion of either ERCC1 or ERCC4 is not compatible with viability in mice or humans. However, mutations in the ERCC1 or ERCC4 genes cause a remarkable array of rare inherited human disorders. These include specific forms of xeroderma pigmentosum, Cockayne syndrome, Fanconi anemia, XFE progeria and cerebro-oculo-facio-skeletal syndrome.

Association of ERCC1 polymorphisms (rs3212986 and rs11615) with the risk of head and neck carcinomas based on case-control studies

PURPOSE

Current data regarding association between ERCC1 polymorphisms and the risk of head and neck squamous cell carcinomas (HNSCC) have shown controversial results. The current study aims to achieve a more accurate estimation of the association between two well-characterized ERCC1 polymorphisms (rs3212986 and rs11615) and HNSCC risk by a meta-analysis of all eligible studies.

METHODS

The meta-analysis was performed by reviewing seven studies on the ERCC1 C8092A (rs3212986) polymorphism including 2055 cases and 2635 controls and four studies on the T19007C (rs11615) polymorphism including 910 cases and 1337 controls.

RESULTS

For ERCC1 rs3212986 polymorphism, no significant association with HNSCC was found in overall analysis, but subgroup analysis revealed that a significant association of the rs3212986 polymorphism was found among Asians (A vs. C: OR 0.83; 95% CI 0.70-0.99) but not Caucasians. For ERCC1 rs11615 polymorphism, a significant association with HNSCC (TC + CC vs. TT: OR 1.23; 95% CI 1.03-1.47) was found in overall analysis. Consistently, subgroup analysis revealed that significant associations of the rs3212986 polymorphism were found among Asians (C vs. T: OR 1.32; 95% CI 1.04-1.69) and in laryngeal carcinoma (CC vs. TC + TT: OR 1.32; 95% CI 1.02-1.72).

CONCLUSION

The findings of the meta-analysis indicated that a decreased risk for the ERCC1 rs3212986 polymorphism was found among Asians, and an increased risk for the ERCC1 rs11615 polymorphism was found in overall HNSCC, especially in Asian subgroup and laryngeal site, suggesting that ERCC1 rs3212986 polymorphism in Asians may act as a protective factor and rs11615 polymorphism may be a risk factor for HNSCC.

ERCC1 and BRCA1 mRNA expression predicts the clinical outcome of non-small cell lung cancer receiving platinum-based chemotherapy

Objective: We conducted a perspective study to investigate the association between mRNA expression quantities of ERCC1, BRCA1, RRM1 and RRM2 and response to chemotherapy and clinical outcome of advance Non-Small Cell Lung Cancer.(NSCLC).

Methods: Two hundred eight patients who were diagnosed as advanced stage NSCLC were included in our study. A fluorescence-based and real-time detection method was used to determine the relative cDNA quantification for ERCC1, BRCA1, RRM1 and RRM2, and β-actin was used as the reference gene.

Results: The median expression levels of ERCC1, BRCA1, RRM1 and RRM2 mRNA were 0.67±0.17, 0.095±0.012, 0.24±0.17 and 2.45±0.32, respectively. Our study found that the low ERCC1 (OR=1.82, 95% CI=1.01-3.20) and Low BRCA1 (OR=2.53, 95%CI=1.38-4.64) mRNA expression was more likely to response to chemotherapy when compared with high expression, respectively. Multivariate Cox regression analysis indicated that patients with low mRNA expression of ERCC1 and BRCA1 attained 0.43 (OR=0.43, 95%CI=0.27-0.89) and 0.37 (OR=0.37, 95%CI=0.22-0.66) fold risk of death from NSCLC. However, we found RMM1 and RRM2 mRNA expression could not influence the response to chemotherapy and clinical outcome of NSCLC.

Conclusion: ERCC1 and BRCA1 mRNA expression could be important predictive markers for individualized platinum-based chemotherapy for NSCLC patients.

Association of single nucleotide polymorphisms of ERCC1 and XPF with colorectal cancer risk and interaction with tobacco use

We investigated the association between polymorphisms in excision repair cross-complementation group 1 (ERCC1) (rs3212986, rs2298881 and rs11615) and xeroderma pigmentosum-complementation group F (XPF) (rs2276466 and rs6498486) and risk of colorectal cancer. A 1:1 matched case-control study was conducted. Conditional regression analysis indicated that individuals carrying the ERCC1 rs3212986 TT genotype and T allele had a marginally increased risk of colorectal cancer when compared with subjects with the GG genotype. Similarly, subjects carrying the rs11615 TT genotype and T allele had a marginally increased risk of colorectal cancer when compared with those with the CC genotype. Stratified analysis revealed that individuals with rs3212986 TT who were current or former smokers had a significantly increased risk of colorectal cancer, and a significant interaction was found between this SNP and cigarette smoking. In conclusion, our study suggests that rs3212986 and rs11615 polymorphisms are associated with risk of colorectal cancer in a Chinese population, particularly in smokers. This finding could be useful in revealing the genetic characteristics of colorectal cancer, and suggests more effective strategies for prevention and treatment.

Polymorphisms in the ERCC1 and XPF genes and risk of breast cancer in a Chinese population

Inherited functional single-nucleotide polymorphisms (SNPs) in DNA repair genes may influence the capability of DNA repair and contribute to the risk of breast cancer. We therefore performed a case-control study to investigate the association of three in excision repair cross-complimentary group 1 (ERCC1) and three in xeroderma pigmentosum complementation group F (XPF) with the risk of breast cancer. Genotyping of ERCC1 (rs2298881, rs3212986, and rs11615) and XPF (rs2276465, rs6498486, and rs2276466) was performed in a 384-well plate format on the MassARRAY(®) platform. Odds ratios and their corresponding 95% confidence intervals were used to assess the effect of each SNP on breast cancer risk. The ERCC1 rs11615 variant A/A genotype was associated with increased breast cancer risk in codominant, dominant, and recessive models, and XPF rs6498486 variant C/C genotype carriers have a significantly increased breast cancer risk in codominant, dominant, and recessive models. Individuals with both the ERCC1 rs11615 A allele and XPF rs6498486 C allele had a heavy increased risk of breast cancer compared to double wild-type homozygotes. The present study shows that the ERCC1 rs11615 and XPF rs6498486 polymorphisms are associated with breast cancer risk in a Chinese population. Further large-scale studies are required to elucidate whether these ERCC1 and XPF SNPs interact with environmental factors in the development of breast cancer.

Polymorphisms in ERCC1 and XPF genes and risk of gastric cancer in an eastern Chinese population

BACKGROUND

Inherited functional single nucleotide polymorphisms (SNPs) in DNA repair genes may alter DNA repair capacity and thus contribute to cancer risk.

METHODS

Three ERCC1 functional SNPs (rs2298881C>A, rs3212986C>A and rs11615G>A) and two XPF/ERCC4 functional SNPs (rs2276466C>G and rs6498486A>C) were genotyped for 1125 gastric adenocarcinoma cases and 1196 cancer-free controls by Taqman assays. Odds ratios (OR) and 95% confidence intervals (CI) were used to estimate risk associations, and false-positive report probabilities (FPRP) were calculated for assessing significant findings.

RESULTS

ERCC1 rs2298881C and rs11615A variant genotypes were associated with increased gastric cancer risk (adjusted OR=1.33, 95% CI=1.05-1.67 for rs2298881 AC/CC and adjusted OR=1.23, 95% CI=1.05-1.46 for rs11615 AG/AA, compared with their common genotype AA and GG, respectively). Patients with 2-3 ERCC1 risk genotypes had significant increased risk (adjusted OR=1.56, 95% CI=1.27-1.93), compared with those with 0-1 ERCC1 risk genotypes, and this risk was more significantly in subgroups of never drinkers, non-gastric cardia adenocarcinoma (NGCA) and clinical stage I+II. All these risks were not observed for XPF SNPs.

CONCLUSIONS

These findings suggest that functional ERCC1 SNPs may contribute to risk of gastric cancer. Larger and well-designed studies with different ethnic populations are needed to validate our findings.

Nucleotide excision repair and anti-cancer chemotherapy

DNA repair is an important effector of anti-cancer drug resistance. In recent years, it has become apparent that DNA repair is an extremely complex process. Processes within DNA repair that may contribute to one or more drug resistance phenotypes include; O-6-alkyltransferase activity, base excision repair, mismatch repair, nucleotide excision repair, and gene specific repair. Clearly, several of these processes may show increased activity within any single cell, or tumor, at any one time. This review attempts to touch briefly upon the question of the distinctions between each of these specific pathways; and then seeks to expand on nucleotide excision repair as a possible effector of cellular and clinical resistance to platinum-based anticancer therapy.

DNA repair endonuclease ERCC1-XPF as a novel therapeutic target to overcome chemoresistance in cancer therapy

The ERCC1–XPF complex is a structure-specific endonuclease essential for the repair of DNA damage by the nucleotide excision repair pathway. It is also involved in other key cellular processes, including DNA interstrand crosslink (ICL) repair and DNA double-strand break (DSB) repair. New evidence has recently emerged, increasing our understanding of its requirement in these additional roles. In this review, we focus on the protein–protein and protein–DNA interactions made by the ERCC1 and XPF proteins and discuss how these coordinate ERCC1–XPF in its various roles. In a number of different cancers, high expression of ERCC1 has been linked to a poor response to platinum-based chemotherapy. We discuss prospects for the development of DNA repair inhibitors that target the activity, stability or protein interactions of the ERCC1–XPF complex as a novel therapeutic strategy to overcome chemoresistance.

Deficient expression of DNA repair enzymes in early progression to sporadic colon cancer

Background

Cancers often arise within an area of cells (e.g. an epithelial patch) that is predisposed to the development of cancer, i.e. a "field of cancerization" or "field defect." Sporadic colon cancer is characterized by an elevated mutation rate and genomic instability. If a field defect were deficient in DNA repair, DNA damages would tend to escape repair and give rise to carcinogenic mutations.

Purpose

To determine whether reduced expression of DNA repair proteins Pms2, Ercc1 and Xpf (pairing partner of Ercc1) are early steps in progression to colon cancer.

Results

Tissue biopsies were taken during colonoscopies of 77 patients at 4 different risk levels for colon cancer, including 19 patients who had never had colonic neoplasia (who served as controls). In addition, 158 tissue samples were taken from tissues near or within colon cancers removed by resection and 16 tissue samples were taken near tubulovillous adenomas (TVAs) removed by resection. 568 triplicate tissue sections (a total of 1,704 tissue sections) from these tissue samples were evaluated by immunohistochemistry for 4 DNA repair proteins. Substantially reduced protein expression of Pms2, Ercc1 and Xpf occurred in field defects of up to 10 cm longitudinally distant from colon cancers or TVAs and within colon cancers. Expression of another DNA repair protein, Ku86, was infrequently reduced in these areas. When Pms2, Ercc1 or Xpf were reduced in protein expression, then either one or both of the other two proteins most often had reduced protein expression as well. The mean inner colon circumferences, from 32 resections, of the ascending, transverse and descending/sigmoid areas were measured as 6.6 cm, 5.8 cm and 6.3 cm, respectively. When combined with other measurements in the literature, this indicates the approximate mean number of colonic crypts in humans is 10 million.

Conclusions

The substantial deficiencies in protein expression of DNA repair proteins Pms2, Ercc1 and Xpf in about 1 million crypts near cancers and TVAs suggests that the tumors arose in field defects that were deficient in DNA repair and that deficiencies in Pms2, Ercc1 and Xpf are early steps, often occurring together, in progression to colon cancer.

Use of gene targeting to study recombination in mammalian cell DNA repair mutants

The study of gene function has been greatly facilitated by the development of strategies to modify genomic DNA. Gene targeting is one of the most successfully applied techniques used to examine the roles of specific genes in a wide variety of model systems from yeast to mammals. Our laboratory has pioneered the use of the Chinese hamster ovary (CHO) cell culture model system to study pathways of DNA repair and recombination at the hemizygous CHO APRT locus. By using a simple and effective gene targeting method, we have generated a number of DNA repair-deficient cell lines that have been used in targeted recombination experiments to investigate pathways of recombinational repair in somatic mammalian cells. These methods can be readily customized to generate a variety of cell lines deficient in specific genes of interest and can be applied to study the roles of other DNA repair proteins in pathways of mammalian recombinational repair.

Nucleotide excision repair gene ERCC1 polymorphisms contribute to cancer susceptibility: a meta-analysis

Individual studies of the associations between excision repair cross-complimentary group 1 (ERCC1) polymorphisms and cancer susceptibility have shown inconclusive results. To derive a more precise estimation of the relationship between three well-characterised polymorphisms on ERCC1 and the risk of cancer, we performed a meta-analysis based on 48 publications. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the associations. We found that ERCC1 17677A (rs3212961) variant genotypes were associated with significantly increased overall risk of cancer without substantial heterogeneity (AA versus CC, OR = 1.36, 95% CIs: 1.10-1.68; AC versus CC: OR = 1.11, 95% CIs: 0.99-1.26; dominant comparison: AA/AC versus CC: OR = 1.15, 95% CIs: 1.02-1.29; recessive comparison: AA versus AC/CC: OR = 1.25, 95% CIs: 1.05-1.49). The ERCC1 19007 C (rs11615) allele had null effects on overall risk of cancer; but in the stratified analyses, we observed an elevated association in Asian populations with homozygote variants and hospital-based controls. In addition, during further stratified analyses of cancer groups, homozygote variants were found that are associated with lung cancer and smoking-related cancers. Also, the observed ERCC1 19007 C heterozygote variant contributes to the development of skin cancer. However, the ERCC1 8092C > A (rs3212986) polymorphism did not appear to have an effect on cancer risk. Additionally, no evidence of publication bias was observed in these polymorphisms. Our meta-analysis supports the conclusion that the ERCC1 17677A > C and ERCC1 19007T > C polymorphisms, but not the ERCC1 8092C > A polymorphism, are low-penetrance risk factors for cancer development.

Genetic polymorphisms in XRCC1 associated with radiation therapy in prostate cancer

Radiation therapy is a potentially curative, important treatment option in localized prostate cancer. However, at 8 years after radiation therapy, even in the best risk subset of patients, approximately 10% of patients will experience clinical disease recurrence. The identification of molecular markers of treatment success or failure may allow for the development of strategies to further improve treatment outcomes. Herein, we investigated five molecular markers of DNA repair. 513 patients with castrate-resistant prostate cancer (CRPC), including 284 patients who received radiotherapy, 229 patients without radiotherapy and 152 healthy individuals were genotyped for five polymorphisms in DNA excision repair genes:ERCC1 N118N (500C>T), XPD K751Q (2282A>C), XRCC1 R194W (685C>T), XRCC1 R399Q (1301G>A) and PARP1 V762A(2446T>C). The distribution of genetic polymorphisms in the patients with CRPC and in healthy controls was compared,and the association between the polymorphisms and overall survival was investigated. The polymorphisms evaluated did not show differences between the patient group and the healthy controls, nor did they show a trend toward an association with survival. However, in the radiation treated subgroup, the median survival time was associated with the XRCC1 haplotype. The median survival time was 11.75 years for patients with the R399Q AA /R194W CC haplotype,12.17 years for patients with the R399Q AG/R194W CC haplotype, 6.665 years for patients with the R399Q AG/R194WCT haplotype, and 6.21 years for patients with the R399Q GG/R194W CT haplotype (p = 0.034). This association was not found when all patients were investigated. We conclude that the genetic polymorphisms in XRCC1 may affect the outcome in patients who received radiotherapy for localized prostate cancer.

Clinicopathologic significance of ERCC1, thymidylate synthase and glutathione S-transferase P1 expression for advanced gastric cancer patients receiving adjuvant 5-FU and cisplatin chemotherapy

The objective of this study was to determine whether the expressions of the excision cross-complementing (ERCC1), thymidylate synthase (TS) and glutathione S-transferase P1 (GSTP1) are predictive of clinical outcomes in advanced gastric cancer (AGC) patients receiving treatment with adjuvant 5-fluorouracil (5-FU) and cisplatin (FP) chemotherapy. One hundred forty nine patients were included in this study. ERCC1 and GSTP1 expression was correlated significantly with tumor size (p = 0.040, p = 0.018, respectively). Stage and positive lymph node ratio were associated independently with disease free survival (DFS) and overall survival (OS). Both ERCC1 and GSTP1 expression had a significant impact on OS (hazard ratio = 0.069, p = 0.021). TS expression was not related to DFS and OS.

[ERCC1 expression as a predictor of survival after operation in stage I non-small cell lung cancer patients]

BACKGROUND AND OBJECTIVE

Proteins of the nucleotide excision repair pathway can repair DNA damage. The excision repair cross-complementing (ERCC) gene family reduce damagement of DNA by nucleotide excision and repair. The aim of this study is to investigate the expressions of ERCC1 (members of DNA repair gene family) in patients with non-small cell lung cancer (NSCLC) as well as their clinical prognostic significance.

METHODS

Expression levels ofERCC1 were detected by IHC in 118 stage I NSCLC patients. Kaplan-Meier survival curve, and Cox multivariate regression analysis were used for statistical analysis.

RESULTS

The patients with high expression of ERCC1 had significantly longer survival time than those with low expression of ERCC1, and Cox multivariate regression analysis showed that expression of RRM1 was an independent prognostic factor for NSCLC patients.

CONCLUSION

NSCLC patients with high ERCC1 expression have a better survival when compared to patients with low ERCC1 expression. Therefore, an intact DNA repair mechanism may reduce the accumulation of genetic aberrations that are thought to contribute to a tumor malignant potential and therefore the risk of relapse after definitive treatment.

Stochastic and reversible assembly of a multiprotein DNA repair complex ensures accurate target site recognition and efficient repair

Computational modeling and quantitative analysis show that although accumulation of repair complexes can take hours, the individual components rapidly exchange between the nucleoplasm and DNA damage sites.

To understand how multiprotein complexes assemble and function on chromatin, we combined quantitative analysis of the mammalian nucleotide excision DNA repair (NER) machinery in living cells with computational modeling. We found that individual NER components exchange within tens of seconds between the bound state in repair complexes and the diffusive state in the nucleoplasm, whereas their net accumulation at repair sites evolves over several hours. Based on these in vivo data, we developed a predictive kinetic model for the assembly and function of repair complexes. DNA repair is orchestrated by the interplay of reversible protein-binding events and progressive enzymatic modifications of the chromatin substrate. We demonstrate that faithful recognition of DNA lesions is time consuming, whereas subsequently, repair complexes form rapidly through random and reversible assembly of NER proteins. Our kinetic analysis of the NER system reveals a fundamental conflict between specificity and efficiency of chromatin-associated protein machineries and shows how a trade off is negotiated through reversibility of protein binding.

Role of ERCC1 promoter hypermethylation in drug resistance to cisplatin in human gliomas

Overexpression of ERCC1 mRNA is associated with drug resistance to cisplatin in human gliomas, but the role of the ERCC1 promoter in drug resistance has not been demonstrated. We have used sodium bisulfite sequencing to compare ERCC1 promoter methylation patterns in cisplatin-sensitive and cisplatin-resistant glioma cells. The levels of ERCC1 DNA methylation, mRNA and protein in 32 human glioma samples were examined by methylation specific PCR, real-time RT-PCR and immunohistochemistry, respectively. Meanwhile, cisplatin sensitivities to these human glioma samples were tested by histoculture drug response assay. Hypermethylation was observed in the upstream 5Kb region of the ERCC1 promoter of cisplatin-sensitive glioma cell lines. ERCC1 DNA methylation levels were highly variable in 32 human glioma samples ranging from 0.1 to 0.87, which have shown significant difference between cisplatin-sensitive samples and cisplatin-resistant samples (p < 0.05). The relative expression levels of ERCC1 mRNA in 32 glioma samples were also variable from 0.01 to 5.71. No detectable or low expression of ERCC1 protein was shown in 7 glioma samples. ERCC1 promoter methylation was inversely correlated to mRNA expression (r = -0.903 p = 0.001) as well as protein expression (r = -0.884 p = 0.001). Moreover, ERCC1 mRNA expression was significantly associated with protein levels (r = 0.840 p = 0.001). In summary, the aberrant CpG island methylation in ERCC1 promoter region exists in human glioma cell lines as well as clinical glioma samples. ERCC1 DNA methylation could regulate the expression of downstream mRNA and protein, and was associated with cisplatin chemosensitivity.

Associations between polymorphisms in DNA repair genes and glioblastoma

A pooled analysis was conducted to examine the association between select variants in DNA repair genes and glioblastoma multiforme, the most common and deadliest form of adult brain tumors. Genetic data for approximately 1,000 glioblastoma multiforme cases and 2,000 controls were combined from four centers in the United States that have conducted case-control studies on adult glioblastoma multiforme, including the National Cancer Institute, the National Institute for Occupational Safety and Health, the University of Texas M. D. Anderson Cancer Center, and the University of California at San Francisco. Twelve DNA repair single-nucleotide polymorphisms were selected for investigation in the pilot collaborative project. The C allele of the PARP1 rs1136410 variant was associated with a 20% reduction in risk for glioblastoma multiforme (odds ratio(CT or CC), 0.80; 95% confidence interval, 0.67-0.95). A 44% increase in risk for glioblastoma multiforme was found for individuals homozygous for the G allele of the PRKDC rs7003908 variant (odds ratio(GG), 1.44; 95% confidence interval, 1.13-1.84); there was a statistically significant trend (P = 0.009) with increasing number of G alleles. A significant, protective effect was found when three single-nucleotide polymorphisms (ERCC2 rs13181, ERCC1 rs3212986, and GLTSCR1 rs1035938) located near each other on chromosome 19 were modeled as a haplotype. The most common haplotype (AGC) was associated with a 23% reduction in risk (P = 0.03) compared with all other haplotypes combined. Few studies have reported on the associations between variants in DNA repair genes and brain tumors, and few specifically have examined their impact on glioblastoma multiforme. Our results suggest that common variation in DNA repair genes may be associated with risk for glioblastoma multiforme.

Association of ERCC1 polymorphisms and susceptibility to nasopharyngeal carcinoma

The normal function of excision repair cross complementing group 1 (ERCC1) is essential for maintaining genomic integrity and preventing cellular neoplastic transformation, and multiple studies have reported an association between ERCC1 polymorphisms and increased risk of cancers. To test whether the genetic variants of ERCC1 gene modify the risk of nasopharyngeal carcinoma (NPC), we compared the 8092 C > A and 19007 C > T single nucleotide polymorphisms (SNPs) and the haplotypes of ERCC1 between 267 patients with NPC and 304 healthy controls. Linkage disequilibrium was observed between the two SNPs loci (D' = 0.861). Significant differences of allele frequencies were found for ERCC1 8092C > A between the cases and controls. Individuals with 8092 C allele showed 1.411-fold (OR = 1.411, 95% CI, 1.076-1.850, P = 0.014) increased risk of developing NPC, and the CC haplotype was associated with a significantly increased risk of NPC (OR = 1.712; 95% CI, 1.211-2.421; P = 0.013). No interactions were found between 8092C > A polymorphism and genders, smoking status and alcohol consumption. These results suggested that the polymorphism of ERCC1 8092 C > A might be a contributing factor in the development of NPC in Chinese population.

XPF/ERCC4 and ERCC1: their products and biological roles

ERCC4 is the gene mutated in XPF cells and also in rodent cells representing the mutant complementation groups ERCC4 and ERCC 11. The protein functions principally as a complex with ERCC1 in a diversity of biological pathways that include NER, ICL repair, telomere maintenance and immunoglobulin switching. Sorting out these roles is an exciting and challenging problem and many important questions remain to be answered. The ERCC1/ERCC4 complex is conserved across most species presenting an opportunity to examine some functions in model organisms where mutants can be more readily generated and phenotypes more quickly assessed.

Ethnic disparities in Americans of European descent versus Americans of African descent related to polymorphic ERCC1, ERCC2, XRCC1, and PARP1

Nucleotide excision repair (NER) and base excision repair (BER) pathways are DNA repair pathways that are important in carcinogenesis and in response to DNA-damaging chemotherapy. ERCC1 and ERCC2 are important molecular markers for NER; XRCC1 and PARP1 are important molecular markers for BER. Functional polymorphisms have been described that are associated with altered expression levels of these genes and with altered DNA repair capability. We assayed genomic DNA from 156 Americans of European descent and 164 Americans of African descent for the allelic frequencies of specific polymorphisms of ERCC1 N118N (500C>T), ERCC1 C8092A, ERCC2 K751Q (2282A>C), XRCC1 R399Q (1301G>A), XRCC1 R194W (685C>T), and PARP1 V762A (2446T>C). Differences were observed between Americans of European descent and Americans of African descent in the allelic frequencies of the ERCC1 N118N polymorphism (P < 0.000001). Differences were also observed between these two ethnic groups for ERCC2 K751Q (P = < 0.006675), XRCC1 R399Q (P < 0.000001), and PARP1 V762A (P = 0.000001). The ERCC1 N118N polymorphic variant that is seen most commonly in Americans of European descent is associated with a measurable reduction in NER function. ERCC1-mediated reduction in NER functionality affects the repair of cisplatin-DNA lesions.

Predictors of response and survival for neoadjuvant treated patients with esophageal adenocarcinoma

Mainly patients with advanced esophageal adenocarcinoma who respond to neoadjuvant chemotherapy show a significant survival benefit after resection. Therefore, prediction of response before treatment is desirable. The aim of this study was to assess genetic predictors of response and survival for patients with esophageal adenocarcinoma prior to neoadjuvant therapy. Thirty-two patients with advanced esophageal adenocarcinoma who underwent neoadjuvant therapy with resection of their tumor were analyzed for thymidylate synthase (TS), excision repair cross complementing (ERCC1) and Gluthatione S-transferase (GSTP-1) mRNA levels prior to the treatment. These results were analyzed in regards of response and survival. In total, 18 patients responded to this protocol. Seventeen of those did show a gene expression level at or below the respective median of at least one gene. This had a profound impact on survival, demonstrating an increase in survival for patients who have TS, ERCC1, or GSTP-1 mRNA level at or below the median. These results demonstrate a potential predictive value of a gene expression profile available prior to therapy. These data have to be confirmed by a larger prospective trial.

No association of ERCC1 C8092A and T19007C polymorphisms to cancer risk: a meta-analysis

ERCC1 (excision repair cross complementation group 1) is a subunit of the nucleotide excision repair complex, which can perform DNA strand incision correction of DNA damage. Association studies on the ERCC1 polymorphisms (C8092A and T19007C) in cancer had shown conflicting results. We performed a meta-analysis from all eligible case-control studies to assess the purported associations. Overall, the 19007C allele (3 853 patients and 4 349 controls) showed no significant effect on cancer risk compared to 19007T allele (P=0.39, odds ratio (OR)=0.95; 95% confidence interval (CI) 0.85-1.06, P(heterogeneity)=0.001) in all subjects. Meta-analysis under other genetic contrasts did not reveal any significant association of T19007C to cancer in all subjects, Caucasians and Asians. The 19007C allele (2 279 patients and 2 808 controls) showed no significant effect on lung cancer risk compared to 19007T allele (P=0.72, OR=0.94, 95% CI 0.69-1.29, P(heterogeneity)=0.0001) in all subjects. No significant effect of 8092A allele (3 865 patients and 3 750 controls) on cancer risk in all subjects (P=0.85, OR=1.01, 95% CI 0.94-1.08, P(heterogeneity)=0.92) and in Caucasians and Asians compare to 8092C. No evidences of association of C8092A (501 patients and 620 controls) to squamous cell carcinoma were found. The accumulated evidence indicated ERCC1 T19007C and C8092A might not be risk factors for cancer. Significant between-study heterogeneity existed in T19007C, which arose from a study showing significant protecting effect of 19007C allele compare to 19007T allele in smokers. More studies based on larger, stratified case-control population should be required to further evaluate the role of ERCC1 C8092A and T19007C polymorphisms in different cancer, especially in smokers.

Increased mRNA expression levels of ERCC1, OGG1 and RAI in colorectal adenomas and carcinomas

BACKGROUND

The majority of colorectal cancer (CRC) cases develop through the adenoma-carcinoma pathway. If an increase in DNA repair expression is detected in both early adenomas and carcinomas it may indicate that low repair capacity in the normal mucosa is a risk factor for adenoma formation.

METHODS

We have examined mRNA expression of two DNA repair genes, ERCC1 and OGG1 as well as the putative apoptosis controlling gene RAI, in normal tissues and lesions from 36 cases with adenomas (mild/moderat n = 21 and severe n = 15, dysplasia) and 9 with carcinomas.

RESULTS

Comparing expression levels of ERCC1, OGG1 and RAI between normal tissue and all lesions combined yielded higher expression levels in lesions, 3.3-fold higher (P = 0.005), 5.6-fold higher (P < 3.10-5) and 7.7-fold higher (P = 0.0005), respectively. The levels of ERCC1, OGG1 and RAI expressions when comparing lesions, did not differ between adenomas and CRC cases, P = 0.836, P = 0.341 and P = 0.909, respectively. When comparing expression levels in normal tissue, the levels for OGG1 and RAI from CRC cases were significantly lower compared to the cases with adenomas, P = 0.012 and P = 0.011, respectively.

CONCLUSION

Our results suggest that increased expression of defense genes is an early event in the progression of colorectal adenomas to carcinomas.

Regulation of DNA repair gene expression in human cancer cell lines

Although most advanced cancers are incurable, the majority of testicular germ cell tumors can be cured using cisplatin-based combination chemotherapy. The nucleotide excision repair (NER) pathway removes most DNA adducts produced by cisplatin, and the low levels of NER in testis tumor cells may explain why these cancers are curable. Three NER proteins: ERCC1, XPF, and XPA, are present at low levels in testis tumor cell lines, and addition of these proteins to protein extracts of testis tumor cells increases their in vitro DNA repair capacity to normal levels. The aim of this study was to identify the mechanism responsible for the low levels of these DNA repair proteins. The levels of the mRNA transcripts for ERCC1, XPF, and XPA were measured in a panel of 14 different human cancer cell lines, using real-time PCR. Three ERCC1 splice variants were identified and quantitated. Three alternative transcription start points (TSPs) were identified for ERCC1 but none were testis-specific. The significantly lower levels of ERCC1, XPF, and XPA protein in testis tumor cell lines cannot be explained solely by differences in transcriptional efficiency or mRNA stability. For ERCC1, post-transcriptional control by alternative splicing does not account for the testis-specific low levels of protein expression. Pulse-chase experiments showed that the half-life of ERCC1 protein in a testis tumor cell line was not significantly different to that in a prostate cancer cell line. Taken together, these results suggest that constitutive levels of these DNA repair proteins are controlled at the level of translation.

Identification of differentially expressed genes in cutaneous squamous cell carcinoma by microarray expression profiling

Background

Carcinogenesis is a multi-step process indicated by several genes up- or down-regulated during tumor progression. This study examined and identified differentially expressed genes in cutaneous squamous cell carcinoma (SCC).

Results

Three different biopsies of 5 immunosuppressed organ-transplanted recipients each normal skin (all were pooled), actinic keratosis (AK) (two were pooled), and invasive SCC and additionally 5 normal skin tissues from immunocompetent patients were analyzed. Thus, total RNA of 15 specimens were used for hybridization with Affymetrix HG-U133A microarray technology containing 22,283 genes. Data analyses were performed by prediction analysis of microarrays using nearest shrunken centroids with the threshold 3.5 and ANOVA analysis was independently performed in order to identify differentially expressed genes (p < 0.05). Verification of 13 up- or down-regulated genes was performed by quantitative real-time reverse transcription (RT)-PCR and genes were additionally confirmed by sequencing. Broad coherent patterns in normal skin vs. AK and SCC were observed for 118 genes.

Conclusion

The majority of identified differentially expressed genes in cutaneous SCC were previously not described.

Effects of polymorphisms in ERCC1, ASE-1 and RAI on the risk of colorectal carcinomas and adenomas: a case control study

BACKGROUND

The risk of sporadic colorectal cancer is mainly associated with lifestyle factors and may be modulated by several genetic factors of low penetrance. Genetic variants represented by single nucleotide polymorphisms in genes encoding key players in the adenoma carcinoma sequence may contribute to variation in susceptibility to colorectal cancer. In this study, we aimed to evaluate whether the recently identified haplotype encompassing genes of DNA repair and apoptosis, is associated with increased risk of colorectal adenomas and carcinomas.

METHODS

We used a case-control study design (156 carcinomas, 981 adenomas and 399 controls) to test the association between polymorphisms in the chromosomal region 19q13.2-3, encompassing the genes ERCC1, ASE-1 and RAI, and risk of colorectal adenomas and carcinomas in a Norwegian cohort. Odds ratio (OR) and 95% confidence interval (CI) were estimated by binary logistic regression model adjusting for age and gender.

RESULTS

The ASE-1 polymorphism was associated with an increased risk of adenomas, OR of 1.39 (95% CI 1.06-1.81), which upon stratification was apparent among women only, OR of 1.66 (95% CI 1.15-2.39). The RAI polymorphism showed a trend towards risk reduction for both adenomas (OR of 0.70, 95% CI 0.49-1.01) and carcinomas (OR of 0.49, 95% CI 0.21-1.13) among women, although not significant. Women who were homozygous carriers of the high risk haplotype had an increased risk of colorectal cancer, OR of 2.19 (95% CI 0.95-5.04) compared to all non-carriers although the estimate was not statistically significant.

CONCLUSION

We found no evidence that the studied polymorphisms were associated with risk of adenomas or colorectal cancer among men, but we found weak indications that the chromosomal region may influence risk of colorectal cancer and adenoma development in women.

MZF1 possesses a repressively regulatory function in ERCC1 expression

ERCC1 is a critical gene within the nucleotide excision repair pathway. Overexpression of ERCC1 through promoter-mediating transcriptional regulation is associated with repair of cisplatin-induced DNA damage and clinical resistance to platinum-chemotherapy. Several transcriptional repressors and activators within the 5'-flanking region of the ERCC1 gene may be involved in the up-regulation of this gene. Minimal sequence within the promoter region required for ERCC1 transcription was analyzed by CAT assay and demonstrated that the region of -220 to -110 is essential to constitutive expression of ERCC1 gene in ovarian cancer cell line A2780/CP70. A more forward upstream region seems to be responsible for cisplatin-induced expression. Study of the functional cis-element in this region by electrophoretic mobility shift assay indicates that a MZF1-like site as well as an AP1-like site responded in a time-dependent manner to cisplatin stimulation with altered binding activities. EMSA with MZF1 ZN1-4 consensus oligonucleotides suggests that the MZF1 N-terminal domain of zinc finger cluster may bind to the MZF1-like site of the ERCC1 promoter region. MZF1 mRNA in A2780/CP70 cells decreased upon cisplatin exposure as analyzed by quantitative PCR, suggesting that MZF1 may mediate cisplatin-invoked gene expression in these cells. Overexpression of MZF1 repressed the ERCC1 promoter activity as determined in co-transfection assay, suggesting that MZF1 might be a repressor of ERCC1 transcription upon cisplatin exposure. In summary, our studies revealed a core promoter region and adjacent drug-responsible region within the ERCC1 promoter. The drug-responsible region contains cis-elements of activator, AP1 and repressor, MZF1. In response to cisplatin treatment, decreased MZF1 and increased AP1 binding activities appear to be the leading mechanism of up-regulation of ERCC1 expression. Our findings imply potential therapeutic strategies to antagonize drug resistant mechanisms in treatment of human ovarian cancer.

Lack of association between DNA repair gene ERCC1 polymorphism and risk of lung cancer in a Chinese population

The ERCC1 (Excision Repair Cross Complementation Group 1) gene is involved in the nucleotide excision repair pathway. This study was designed to examine whether ERCC1 Asn118Asn (G19007A) polymorphism, which has been associated with risk of some cancers among Caucasians, may be associated with risk of lung cancer in a Chinese population. ERCC1 Asn118Asn (G19007A) genotypes were determined in DNA samples from 151 cases and 143 controls. The distribution of genotypes between cases and controls was not associated with an increased risk of lung cancer (AA versus GG: adjusted OR (odds ratio) = 1.41, 95% CI (confidence interval) = 0.76-2.59; AG versus GG: adjusted OR = 0.78, 95% CI = 0.47-1.29; and AA + AG versus GG: adjusted OR = 0.93, 95% CI = 0.73-1.19). The frequency A (0.20) of the A-allele was significantly lower among these Chinese controls than in the Caucasian control populations (A = 0.54-0.65) (All P < 0.001). No statistically significant effects of age, histological subtype or smoking were found. These findings suggest that ERCC1 Asn118Asn (G19007A) polymorphism may play a limited role for lung cancer in this Chinese population.

Repair of genome destabilizing lesions

Living organisms are constantly exposed to detrimental agents both from the environment (e.g. ionizing radiation, ultraviolet light, natural and synthetic chemicals) and from endogenous metabolic processes (e.g. oxidative and hydrolytic reactions), resulting in modifications of proteins, lipids and DNA. Proteins and lipids are degraded and resynthesized, but the DNA is replicated only during cell division, when DNA damage may result in mutation fixation. Thus the DNA damage generated has the potential to lead to carcinogenesis, cell death, or other genetic disorders in the absence of efficient error-free repair. Because modifications in DNA sequence or structure may be incompatible with its essential role in preservation and transmission of genetic information from generation to generation, exquisitely sensitive DNA repair pathways have evolved to maintain genomic stability and cell viability. This review focuses on the repair and processing of genome destabilizing lesions and helical distortions that differ significantly from the canonical B-form DNA in mammalian cells. In particular, we discuss the introduction and processing of site-specific lesions in mammalian cells with an emphasis on psoralen interstrand crosslinks.

Small interfering RNA-induced suppression of ERCC1 enhances sensitivity of human cancer cells to cisplatin

The level of excision repair cross-complementing 1 (ERCC1) gene expression, which is important in the repair of the cisplatin-DNA adducts, is reported to be related to the level of cisplatin resistance in tumor cells. Therefore, ERCC1 is an attractive target to confer increased cellular sensitivity to cisplatin-based chemotherapy. We designed, synthesized, and utilized small interfering RNAs (siRNAs) that were selective for ERCC1 and investigated their effectiveness in altering the repair capacity of the cells to cisplatin-DNA damage as well as the resistance of the cells to cisplatin. Twenty-four and 48h after transfecting ERCC1 siRNA1 and siRNA2 targeting the two different regions of the ERCC1 transcript, both the ERCC1 mRNA and protein expression were significantly inhibited, whereas the mock or control siRNA had no effect. The suppression of ERCC1 expression in the HeLa S3 cells led to a decrease in the repair activity of cisplatin-induced DNA damage along with a decrease in the cell viability against platinum-based drugs, such as cisplatin, carboplatin, and oxaliplatin. A similar increased sensitivity to cisplatin and decreased repair activity were also observed for siRNA-mediated ERCC1 silencing in the MCF-7 and HCT116 cells. This study is the first to demonstrate the feasibility of utilizing ERCC1 siRNAs to specifically reduce the ERCC1 expression level in human cancer cells and provides direct evidence for the potential use of ERCC1 siRNA as a chemotherapy-sensitizing agent.

ERCC1 Expression Is a Predictor of Survival in Resected Patients With Non-small Cell Lung Cancer

STUDY OBJECTIVES

Proteins of the nucleotide excision repair pathway repair DNA damage. The excision repair cross-complementing (ERCC) gene family reduces damage to DNA by nucleotide excision and repair. Impaired nuclear excision repair could lead to increased genomic instability that in turn could lead to a more malignant phenotypic behavior of tumors. We therefore evaluated the effect of intratumoral ERCC1 expression on survival in non-small cell lung cancer (NSCLC) patients who underwent surgical resection for cure.

DESIGN

Resected tumor and the corresponding normal lung specimens from 51 patients with NSCLC who underwent surgical resection were immediately frozen in liquid nitrogen. Total RNA was extracted, reverse transcribed, and amplified with intron-spanning primers. Quantitation for ERCC1 was done using the Taqman procedure, and gene expression was normalized using 18SrRNA expression as internal reference with ERCC1 levels expressed a unit-less ratio.

RESULTS

Tumoral ERCC1 expression ranged from 4.96 to 2,008, with a median value of 54.76. Using an ERCC1 value of 50 to dichotomize the cohort, there was a statistically significant difference in median survival for patients with ERCC1 expression > 50 (94.6 months) compared to < 50 (35.5 months) [p = 0.01]. Multivariate analysis revealed that high ERCC1 expression independently predicted for longer survival. There were no significant correlations between ERCC1 expression in tumor tissue and normal lung.

CONCLUSIONS

We conclude that resected NSCLC patients with high ERCC1 expression (> 50) have a better survival when compared to patients with low ERCC1 expression (< 50). We postulate that an intact DNA repair mechanism may reduce the accumulation of genetic aberrations that are thought to contribute to a tumors malignant potential and therefore the risk of relapse after definitive treatment. Future adjuvant and neoadjuvant chemotherapy trials in NSCLC could stratify patients according to their ERCC1 expression levels.

Tailored Chemotherapy for Colorectal Cancer: A New Approach to Therapy

The treatment of colorectal cancer has advanced over the past several years with the introduction of several active agents. Determining which patients to treat with chemotherapy and choosing optimal treatment would allow practioners to maximize the benefit of chemotherapy. Several prognostic and predictive markers have been identified and include oncogenes, tumor suppressor genes, genes involved in angiogenic and apoptotic pathways and cell proliferation, and those encoding targets of chemotherapy. Specifically, prognostic markers include deletion of 18q (DCC), p27 and microsatellite instability. Predictive markers are those that may determine efficacy of drugs used in colorectal cancer such as fluropyrimidines and oxaliplatin. Alterations in gene expression, protein expression and polymorphic variants in genes encoding thymidylate synthase, dihydropyrimidine dehydrogenase, and thymidine phosphorylase and excision repair cross-complementing genes (ERCC1) may be useful as markers for clinical drug response, survival and host toxicity. The integration of these prognostic and predictive markers would allow individualized treatment for patients, maximizing therapeutic effect and minimizing exposure to toxicity.

Physical and functional interaction between the XPF/ERCC1 endonuclease and hRad52

The XPF/ERCC1 heterodimer is a DNA structure-specific endonuclease that participates in nucleotide excision repair and homology-dependent recombination reactions, including DNA single strand annealing and gene targeting. Here we show that XPF/ERCC1 is stably associated with hRad52, a recombinational repair protein, in human cell-free extracts and that these factors interact directly via the N-terminal domain of hRad52 and the XPF protein. Complex formation between hRad52 and XPF/ERCC1 concomitantly stimulates the DNA structure-specific endonuclease activity of XPF/ERCC1 and attenuates the DNA strand annealing activity of hRad52. Our results reveal a novel role for hRad52 as a subunit of a DNA structure-specific endonuclease and are congruent with evidence implicating both hRad52 and XPF/ERCC1 in a number of homologous recombination reactions. We propose that the ternary complex of hRad52 and XPF/ERCC1 is the active species that processes recombination intermediates generated during the repair of DNA double strand breaks and in homology-dependent gene targeting events.