XPA Gene Research Articles

CRISPR-Cas9 Knockout Screens Identify DNA Damage Response Pathways and BTK as Essential for Cisplatin Response in Diffuse Large B-Cell Lymphoma.

The recurrence of diffuse large B-cell lymphoma (DLBCL) has been observed in 40% of cases. The standard of care for refractory/relapsed DLBCL (RR-DLBCL) is platinum-based treatment prior to autologous stem cell transplantation; however, the prognosis for RR-DLBCL patients remains poor. Thus, to identify genes affecting the cisplatin response in DLBCL, cisplatin-based whole-genome CRISPR-Cas9 knockout screens were performed in this study. We discovered DNA damage response (DDR) pathways as enriched among identified sensitizing CRISPR-mediated gene knockouts. In line, the knockout of the nucleotide excision repair genes XPA and ERCC6 sensitized DLBCL cells to platinum drugs irrespective of proliferation rate, thus documenting DDR as essential for cisplatin sensitivity in DLBCL. Functional analysis revealed that the loss of XPA and ERCC6 increased DNA damage levels and altered cell cycle distribution. Interestingly, we also identified BTK, which is involved in B-cell receptor signaling, to affect cisplatin response. The knockout of BTK increased cisplatin sensitivity in DLBCL cells, and combinatory drug screens revealed a synergistic effect of the BTK inhibitor, ibrutinib, with platinum drugs at low concentrations. Applying local and external DLBCL cohorts, we addressed the clinical relevance of the genes identified in the CRISPR screens. BTK was among the most frequently mutated genes with a frequency of 3-5%, and XPA and ERCC6 were also mutated, albeit at lower frequencies. Furthermore, 27-54% of diagnostic DLBCL samples had mutations in pathways that can sensitize cells to cisplatin. In conclusion, this study shows that XPA and ERCC6, in addition to BTK, are essential for the response to platinum-based drugs in DLBCL.

Efficient Induction of Apoptosis in Lung Cancer Cells Using Bismuth Sulfide Nanoparticles.

The use of nanomaterial-based radiosensitizers to improve the therapeutic ratio has gained attraction in radiotherapy. Increased radiotoxicity applied to the tumor region may result in adverse impact on the unexposed normal cells to the radiation, a phenomenon known as radiation-induced bystander effect (RIBE). This study aimed to investigate the effect of Bi2S3@BSA nanoparticles (NPs) as radiosensitizers on the enhancement of bystander response in non-irradiated cells. Lung carcinoma epithelial cells were exposed to 6 MV x-ray photons at different doses of 2 and 8 Gy, with and without Bi2S3@BSA NPs. The irradiated-cell's conditioned medium (ICCM) was collected and incubated with MCR-5 human fetal lung fibroblasts. This study showed that ICCM collected from 2-Gy-irradiated A549 cells in the presence of Bi2S3@BSA NPs reduced the cell viability of MCR-5 bystander cells more than ICCM collected from irradiated cells without NPs (P<0.05), whereas such a difference was not observed after 8-Gy radiation. The mRNA expression of the BAX and XPA genes, as well as the cell death rate in MCR-5 bystander cells, revealed that the Bi2S3@BSA NPs significantly improved bystander response at 2-Gy (P<0.05), but the efficacy was not statistically significant after 8-Gy Irradiation. The results indicated that the presence of NPs did not affect bystander response enhancement at higher concentrations. These findings highlighted the potential use of radiation-enhancing agents and their benefits in radiotherapy techniques with high doses per fraction.

Cross-species investigation into the requirement of XPA for nucleotide excision repair.

After reconstitution of nucleotide excision repair (excision repair) with XPA, RPA, XPC, TFIIH, XPF-ERCC1and XPG, it was concluded that these six factors are the minimal essential components of the excision repair machinery. All six factors are highly conserved across diverse organisms spanning yeast to humans, yet no identifiable homolog of the XPA gene exists in many eukaryotes including green plants. Nevertheless, excision repair is reported to be robust in the XPA-lacking organism, Arabidopsis thaliana, which raises a fundamental question of whether excision repair could occur without XPA in other organisms. Here, we performed a phylogenetic analysis of XPA across all species with annotated genomes and then quantitatively measured excision repair in the absence of XPA using the sensitive whole-genome qXR-Seq method in human cell lines and two model organisms, Caenorhabditis elegans and Drosophila melanogaster. We find that although the absence of XPA results in inefficient excision repair and UV-sensitivity in humans, flies, and worms, excision repair of UV-induced DNA damage is detectable over background. These studies have yielded a significant discovery regarding the evolution of XPA protein and its mechanistic role in nucleotide excision repair.

A Significant Increasing Risk Association between Cigarette Smoking and XPA and XPC Genes Polymorphisms.

Cigarette smoking (CS) is a major cause of various serious diseases due to tobacco chemicals. There is evidence suggesting that CS has been linked with the DNA damage repair system, as it can affect genomic stability, inducing genetic changes in the genes involved in the repair system, specifically the nucleotide excision repair (NER) pathway, affecting the function and/or regulation of these genes. Single nucleotide polymorphism (SNP), along with CS, can affect the work of the NER pathway and, therefore, could lead to different diseases. This study explored the association of four SNPs in both XPA and XPC genes with CS in the Saudi population. The Taq Man genotyping assay was used for 220 healthy non-smokers (control) and 201 healthy smokers to evaluate four SNPs in the XPA gene named rs10817938, rs1800975, rs3176751, and rs3176752 and four SNPs in the XPC gene called rs1870134, rs2228000, rs2228001, and rs2607775. In the XPA gene, SNP rs3176751 showed a high-risk association with CS-induced diseases with all clinical parameters, including CS duration, CS intensity, gender, and age of smokers. On the other hand, SNP rs1800975 showed a statistically significant low-risk association with all clinical parameters. In addition, rs10817938 showed a high-risk association only with long-term smokers and a low-risk association only with younger smokers. A low-risk association was found in SNP rs3176752 with older smokers. In the XPC gene, SNP rs2228001 showed a low-risk association only with female smokers. SNP rs2607775 revealed a statistically significant low-risk association with CS-induced diseases, concerning all parameters, except for male smokers. However, SNP rs2228000 and rs1870134 showed no association with CS. Overall, the study results demonstrated possible significant associations (effector/and protector) between CS and SNPs polymorphisms in DNA repair genes, such as XPA and XPC, except for rs2228000 and rs1870134 polymorphisms.

DNA Repair Pathway in Ovarian Cancer Patients Treated with HIPEC.

DNA repair pathways are essential for maintaining genome stability, and understanding the regulation of these mechanisms may help in the design of new strategies for treatments, the prevention of platinum-based chemoresistance, and the prolongation of overall patient survival not only with respect to ovarian cancer. The role of hyperthermic intraperitoneal chemotherapy (HIPEC) together with cytoreductive surgery (CRS) and adjuvant systemic chemotherapy is receiving more interest in ovarian cancer (OC) treatment because of the typical peritoneal spread of the disease. The aim of our study was to compare the expression level of 84 genes involved in the DNA repair pathway in tumors and the paired peritoneal metastasis tissue of patients treated with CRS/platinum-based HIPEC with respect to overall patient survival, presence of peritoneal carcinomatosis, treatment response, and alterations in the BRCA1 and BRCA2 genes. Tumors and metastatic tissue from 28 ovarian cancer patients collected during cytoreductive surgery before HIPEC with cisplatin were used for RNA isolation and subsequent cDNA synthesis. Quantitative real-time PCR followed. The most interesting findings of our study are undoubtedly the gene interactions among the genes CCNH, XPA, SLK, RAD51C, XPA, NEIL1, and ATR for primary tumor tissue and ATM, ATR, BRCA2, CDK7, MSH2, MUTYH, POLB, and XRCC4 for metastases. Another interesting finding is the correlation between gene expression and overall survival (OS), where a low expression correlates with a worse OS.

Impact of DNA repair polymorphisms on DNA instability biomarkers induced by lead (Pb) in workers exposed to the metal

Although the mechanisms of Pb-induced genotoxicity are well established, a wide individual's variation response is seen in biomarkers related to Pb toxicity, despite similar levels of metal exposure. This may be related to intrinsic variations, such as genetic polymorphisms; moreover, very little is known about the impact of genetic variations related to DNA repair system on DNA instability induced by Pb. In this context, the present study aimed to assess the impact of SNPs in enzymes related to DNA repair system on biomarkers related to acute toxicity and DNA damage induced by Pb exposure, in individuals occupationally exposed to the metal. A cross-sectional study was run with 154 adults (males, >18 years) from an automotive batteries' factory, in Brazil. Blood lead levels (BLL) were determined by ICP-MS; biomarkers related to acute toxicity and DNA instability were monitored by the buccal micronucleus cytome (BMNCyt) assay and genotyping of polymorphisms of MLH1 (rs1799977), OGG1 (rs1052133), PARP1 (rs1136410), XPA (rs1800975), XPC (rs2228000) and XRCC1 (rs25487) were performed by TaqMan assays. BLL ranged from 2.0 to 51 μg dL−1 (mean 20 ± 12 μg dL−1) and significant associations between BLL and BMNCyt biomarkers related to cellular proliferation and cytokinetic, cell death and DNA damage were observed. Furthermore, SNPs from the OGG1,XPA and XPC genes were able to modulate interactions in nuclear bud formation (NBUDs) and micronucleus (MNi) events. Taken together, our data provide further evidence that polymorphisms related to DNA repair pathways may modulate Pb-induced DNA damage; studies that investigate the association between injuries to genetic material and susceptibilities in the workplace can provide additional information on the etiology of diseases and the determination of environmentally responsive genes.

Pigmented xeroderma: literature review and clinical case

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

Cell migration is impaired in XPA-deficient cells.

Xeroderma pigmentosum (XP) is a hereditary disorder characterized by photosensitivity, predisposition to skin cancers, and neurological abnormalities including microcephaly and progressive neurodegeneration. A lack of nucleotide excision repair (NER) in patients with XP can cause hypersensitivity to the sun, leading to skin cancer, whereas the etiology of the neuronal symptoms of XP remains ambiguous. There are various neurological disorders that perturb neuronal migration, causing mislocalization and disorganization of the cortical lamination. Here, we investigated the role of the XP group-A (Xpa) gene in directed cell migration. First, we adopted an in utero electroporation method to transduce shRNA vectors into the murine embryonic cerebral cortex for the in vivo knockdown of Xpa. Xpa-knockdown neurons in the embryonic cerebral cortex showed abnormal cell migration, cell cycle exit, and differentiation. The genotype-phenotype relationship between the lack of XPA and cell migration abnormalities was confirmed using both a scratch assay and time-lapse microscopy in XP-A patient-derived fibroblasts. Unlike healthy cells, these cells showed impairment in overall mobility and the direction of motility. Therefore, abnormal cell migration may explain neural tissue abnormalities in patients with XP-A.

Clinical and molecular characterization of Xeroderma pigmentosum in Moroccan population: a case series of 40 patients

BackgroundXeroderma pigmentosum (XP) is a rare autosomal recessive skin disorder characterized by hyperpigmentation, premature skin aging, ocular and cutaneous photosensitivity with increased risk of skin tumors. XP is caused by mutations in DNA repair genes that protect cells from UV-induced DNA damage. The current study aims to investigate, on clinical and genetic basis, Moroccan XP patients. We explored by direct sequencing the involvement of the prevalent XPA and XPC genes mutations: nonsense mutation (c.682C>T, p.Arg228X) and a two-base-pair (2 bp) deletion (c.1643 1644delTG or p.Val548Ala fsX25), respectively, in 40 index cases from 37 unrelated families in Moroccan population.ResultsEarly skin and ocular manifestations were detected with high rate of malignancy. Cutaneous lesions progressed to malignant skin tumor in 70% of cases. Ocular tumors were also observed in 11 patients including BCC in eight cases, SCC in three cases and melanoma in four cases. Among the 40 patients, there were 20 homozygous cases for the 2 bp deletion in the XPC gene and 9 homozygous cases carrying the nonsense XPA mutation.ConclusionThese findings obtained in the present study revealed that the XPC gene mutation (c.1643 1644delTG, p.Val548AlafsX25) is the major cause of Xeroderma pigmentosum in our population. The c.682C>T (p.Arg228X) mutation is relatively associated with moderate phenotype in XP group A Moroccan families. This result will also contribute to improving the molecular diagnosis of XP disease and will have a significant impact on improving the care of Moroccan patients and their relatives.

ATM DNA METHYLATION ASSOCIATED WITH POOR PROGNOSIS AND LEUKEMIA TRANSFORMATION IN MYELODYSPLASTIC SYNDROME PATIENTS

Myelodysplastic syndrome (MDS) is a clonal disease of hematopoietic progenitors with a risk of progressing to acute myeloid leukemia. MDS etiology is mainly related to age, but one of the risk factors is exposure to pesticides that causes aberrant reprogramming of the genome by DNA methylation. The aim of this work was evaluating the methylation profile of genes acting in the single-strand DNA (ssDNA) repair (CSA, CSB, XPA, XPC and XPG) and double-strand DNA (dsDNA) repair (ATM, BRCA1, BRCA2, LIG4 and RAD51), and its relationship with gene expression. The analysis was performed using bone marrow samples from 56 MDS patients, 69 farmers exposed to pesticides and 10 controls without exposition or MDS. The methylation profile and gene expression were evaluated using pyro-sequencing technique and quantitative real-time PCR. Regarding ssDNA repair genes, in cases with MDS, patients under 60 years old showed a higher methylation for the XPA and CSB genes than patients over 60 years old (p = 0.008; p = 0.017). Furthermore, XPA showed increased methylation levels in initial forms of MDS (p = 0.019). The MDS group presented a higher percentage of XPA methylation than exposed farmers (p = 0.000) and the control group (p = 0.011). In the prognostic classification, lower risk presented higher methylation than high-risk (p = 0.027). Among the dsDNA repair genes methylation in MDS patients, only ATM gene showed significant results with increase of methylation levels in (1) males (p = 0.037); (2) patients aged up to 60 years (p = 0.002) and (3) those who progressed to AML (p = 0.016). Regarding the methylation between the groups of exposed farmers, MDS advanced forms and controls, we also detected significant differences with levels always increased in the control group: ATM (control group vs. farmers p = 0.000), BRCA1 exposed vs. control group, p = 0.001; MDS vs. control, p = 0.001;), BRCA2 (farmers vs. control, p = 0.027; MDS vs. control, p = 0.004), LIG4 (farmers vs. control, p = 0.001; MDS vs. control, p = 0.012) and RAD51 (farmers vs. controls, p = 0.047). The correlation analysis between methylation and expression showed a positive and strong correlation for LIG4 gene in the advanced forms MDS group (r = 0.798) and a positive and weak correlation for BRCA1 gene in the exposed farmers group (r = 0.340). Surprisingly, in the ssDNA repair genes, the expression and methylation of both farmers and MDS patients were not correlated, suggesting that the change in the expression of these genes is not motivated by the DNA methylation mechanism. Furthermore, the analysis of dsDNA repair genes in this study corroborates the phenomenon of relative hypermethylation in some DNA repair genes in MDS.

Insights Into Functional and Structural Impacts of nsSNPs in XPA-DNA Repairing Gene

Single nucleotide polymorphisms (SNPs) are the most common type of genetic variation in people. SNPs are valuable resource for exploring the genetic basis of disease. The XPA gene provides a way to produce a protein used to repair damaged DNA. This study used the computational methods to classify SNPs and estimate their probability of being neutral or deleterious. The purpose of this analysis is to predict the effect of nsSNPs on the structure and function of XPA proteins. Data was collected from the NCBI hosted dbSNP. The authors examined the pathogenic effect of 194 nsSNPs in the XPA gene with computational tools. Four nsSNPs (C126S, C126W, R158S, and R227Q) those potentially effect on structure and function of the XPA protein were identified with combination of SIFT, PolyPhen, Provean, PHD-SNP, I-Mutant, ConSurf server and Project HOPE. This is the first comprehensive analysis in which XPA gene variants studied using in silico methods and this research able to gain further insight into XPA protein variants and function.

PAICS is related to glioma grade and can promote glioma growth and migration.

Glioma is a common malignant tumour of the brain. In this study, we aimed to investigate diagnostic biomarkers and its role in glioma. Weighted gene co‐expression network analysis (WGCNA) and Cytoscape software were used to screen the marker genes in glioma. RT‐qPCR and Western blotting methods were performed to determine the expression of PAICS, ERCC1 and XPA genes in glioma tissues. Expression level of PAICS in different grades of glioma was examined by immunohistochemistry. CCK8 and Colony formation assays were used to detect cell proliferation. Cell adhesion assay was used to detect adhesion ability. Wound healing and transwell tests were used to detect cell migration ability. Flow cytometry was used to detect cell cycle and apoptosis. According to the predicted co‐expression network, we identified the hub gene PAICS. Furthermore, we observed that PAICS expression level was up‐regulated in glioma tissues compared with normal tissues, and the expression level was correlated with the grade of glioma. Moreover, we found PAICS can promote glioma cells proliferation and migration in vitro. Flow cytometry results showed that si‐PAICS cells were stalled at the G1 phase compared with the si‐NC cells and knocking down PAICS expression can increase apoptotic rate. PAICS can regulate the mRNA and protein levels of nucleotide excision repair pathway core genes ERCC1 and XPA. l‐aspartic acid can affect the expression of PAICS and then inhibit glioma cell proliferation. Our results indicated that PAICS can promote glioma proliferation and migration. PAICS may act as a potential diagnostic marker and a therapeutic target for glioma.

Time-Dependent Induction of the Nucleotide Excision Repair Gene XPA and RAD51 in Homologous Recombination in Human Lymphocytes Exposed to Low Doses of Ionizing Radiation

Introduction: The aim of the present study was to understand the effect of low-doses of ionizing radiation (LDIR) on repair genes expression in blood samples that were taken from healthy donors. The next purpose was to examine the time-effect on the modified gene expression caused by low-doses of ionizing radiation. Material and method: The RNA of peripheral blood lymphocytes (PBLs) taken from four healthy donors was isolated at different time points after exposure included 4, 24, 48, 72, and 168 hours and then cDNA was synthesized. Modification of XPA and RAD51 expression levels due to LDIR (2, 5, 10 cGy) were evaluated by relative quantitative reverse transcription-polymerase chain reaction.Results: Significant up-regulation of both repair genes was observed at the 4 and 168 h following to 10 cGy. Also, this dose could increase expression levels of RAD51 at 48 and 72 h after radiation. For lower doses at 5 cGy, only XPA levels were significantly up-regulated after 168 h. A significant regression was found between the XPA levels and the dose, at 168 h after irradiation to PBLs that can represent a new potential biomarker for biological dosimetry purposes.Conclusion: The results of this study could support the hypothetical role of the different DNA repair pathways in response to LDIR. This led us to propose a molecular biodosimetry method for ionizing radiation in the range of LDIR.

Clinical and Mutational Spectrum of Xeroderma Pigmentosum in Egypt: Identification of Six Novel Mutations and Implications for Ancestral Origins

Xeroderma pigmentosum is a rare autosomal recessive skin disorder characterized by freckle-like dry pigmented skin, photosensitivity, and photophobia. Skin and ocular symptoms are confined to sun exposed areas of the body. Patients have markedly increased risk for UV-induced skin, ocular, and oral cancers. Some patients develop neurodegenerative symptoms, including diminished tendon reflexes and microcephaly. In this study, we describe clinical and genetic findings of 36 XP patients from Egypt, a highly consanguineous population from North Africa. Thorough clinical evaluation followed by Sanger sequencing of XPA and XPC genes were done. Six novel and seven previously reported mutations were identified. Phenotype-genotype correlation was investigated. We report clinical and molecular findings consistent with previous reports of countries sharing common population structure, and geographical and historical backgrounds with implications on common ancestral origins and historical migration flows. Clinical and genetic profiling improves diagnosis, management, counselling, and implementation of future targeted therapies.

The Relationship of XPA and XPC Gene Polymorphisms with the Risk of Colorectal Cancer in Iran

Background: The objective of this study was to investigate the effect of several XPA and XPC polymorphisms on the risk of colorectal cancer (CRC) in northeastern Iran. Method: 180 CRC patients and 160 healthy subjects participated in this case-control study. We determined the genotypes by RFLP-PCR and PIRA-PCR, and analyzed the results using logistic regression and ᵡ2-test. Result: Our findings showed that only BMI could affect the risk of cancer among the studied demographic factors. Three of the four polymorphisms studied, namely XPA A23G, XPC rs2228000 C > T and XPC rs2228001 A > C, did not correlate with CRC (P-values > 0.05); however, the polymorphism of XPC poly AT (PAT) increased the risk of CRC (P= 0.024). The XPC rs2228000 C> T polymorphism increased the CRC risk only in patients aged 50 or more. The risk of CRC in heterozygote individuals (XPC PAT D/I) was higher than that of homozygous individuals (XPC PAT D/D); also, at least one PAT I variant allele increased the likelihood of CRC (for PAT D/I OR =2.168; 95% CI = 1.809-4.319: and for PAT D/I and PAT I/I OR = 1.810; 95% CI = 1.165-2.813). The XPC haplotypes were similar between the cases and controls, and P-values were >0.05. Conclusion: In the whole population, XPC PAT polymorphism, overweightness, and XPC rs2228000 C>T polymorphism in elderly people are related to CRC. Therefore, they can probably be considered as markers of CRC in Iran.

Regulation of ultraviolet radiation-induced cutaneous DNA damage by type I interferons

Abstract Type I interferons (IFNs) are cytokines, that are important regulators of immune responses and are downregulated in human cancers, including skin cancer. Solar ultraviolet (UV) radiation is a proven environmental carcinogen, and exposure to solar radiation contributes to the high prevalence of skin cancer. The carcinogenic effects of UV light can be attributed to the formation of cyclobutane pyrimidine dimers (CPD) and errors in repair and replication of DNA. It is believed that type I IFNs reduce cellular proliferation and allow DNA repair in various diseases. Interferon receptor 1 (IFNAR1) is critical for signaling of type I IFNs. We hypothesized that type I IFNs (IFNα/β) will repair UVB induced DNA damage in mice. To test our hypothesis, shaved mice lacking IFNAR1 and wild type mice on a C57BL/6 background were irradiated with single dose of UVB radiation (100 mJ/cm2). Skin samples were examined for CPD by immunofluorescence and ELISA. We found that mice lacking IFNAR1 had more CPD as evident by ELISA and histology. In order to determine the cell type, which produces type I IFNs in skin after UVB exposure, single cell suspensions were prepared from irradiated skin samples and stained for type I IFNs using flow cytometry. We found that type I IFNs were produced by inflammatory monocytes (CD45+CD11b+Ly6C+). We also found that DNA repair gene XPA was downregulated in the mice lacking IFNAR1. In conclusion, our studies show that mice lacking the IFNAR1 had decreased repair of UVB induced CPD in the skin. Our ongoing studies will elucidate whether type I IFNs regulate development of UVB induced skin tumors.

DNA repair gene polymorphism (XPA and XPG) and risk of urinary bladder cancer in North-Indian population

PurposeTo assess XPA A23G (rs1800975) and XPG Asp1104His (rs17655) polymorphism as risk factors for urinary bladder cancer in North-Indian population. MethodsThe prevalence of genetic polymorphisms of XPA and XPG was investigated in cases and age-gender matched healthy controls. XPA and XPG genes were genotyped using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. ResultsThe XPA GG and XPG CC genotypes were significantly associated with UBC risk (adjusted OR = 3.78, 95% CI = 1.40-10.18, p ≤ 0.05 and adjusted OR = 4.00, 95% CI = 1.19-13.43, p ≤ 0.05 respectively). After stratifying the genotypes by age, gender and smoking status, risk for carriers of XPA (AG + GG) genotype was significantly higher for males and smokers (adjusted OR = 2.55, 95% CI = 1.30–5.03, adjusted OR = 2.36, 95% CI = 1.14–4.85, p ≤0.05 respectively) while the risk for carriers of the XPG (GC + CC) genotype was significantly high for younger (median age ≤60) individuals and females (adjusted OR = 2.13, 95% CI = 1.05–4.35, adjusted OR = 18.12, 95% CI = 1.20–272.73, p ≤0.05 respectively). ConclusionXPA and XPG polymorphism might be significant risk factor in North-Indian population and acquisition of these genetic variations together with smoking might trigger urinary bladder cancer development. Further pathway based studies on larger population are warranted to confirm our conclusion. Clinical significanceThe XPA-A23G and XPG-Asp1104His genetic variations could be used as UBC susceptibility markers in North-Indian population. These SNPs could be useful biomarkers for UBC prognosis or diagnosis and thus could help in enhancing the survival rates of UBC patients and improving patient care. However, before making any further conclusion, we suggest these genetic variations should be further explored using a larger study sample for their role as potential clinical biomarkers or therapeutic targets. The role of other SNPs, gene-gene interactions and gene-environment interactions should also be taken into consideration while estimating the genetic risk of these SNPs on UBC development.

Evaluation of gene expression levels in the diagnosis of lung adenocarcinoma and malignant pleural mesothelioma.

This study aims to evaluate gene expression levels in the diagnosis of lung adenocarcinoma and malignant pleural mesothelioma both which have a distinct treatment and prognosis. Between January 2012 and January 2014, 12 newly diagnosed patients with a lung adenocarcinoma, 12 patients with malignant pleural mesothelioma, and eight healthy individuals as the control group were included. After treatment of the fresh samples of lung adenocarcinoma stored at -80°C for ribonucleic acid isolation, and paraffin-embedded tissues of patients with malignant pleural mesothelioma were deparaffinized, complementary deoxyribonucleic acid synthesis and expression of 84 genes associated with deoxyribonucleic acid repair were analyzed via real-time polymerase chain reaction assay. According to the expression of tumor cells, expression of each fold change was calculated. The BRCA1, BRCA2, CDK7, MLH3, MSH4, NEIL3, SMUG1, UNG, XRCC2, and XRCC4 genes showed more than five-fold higher expression in the patients with lung adenocarcinomas, compared to the control group. The patients with malignant pleural mesothelioma showed a five-fold higher expression in the APEX2, BRCA1, BRCA2, CDK7, MLH1, MLH3, MSH3, MSH4, NEIL3, PARP2, PARP3, PMS1, RAD50, RAD51, RAD51B, RAD51D, RAD52, RPA3, SMUG1, UNG, XPA, XRCC2, and XRCC4 genes, compared to the control group. Comparing malignant pleural mesothelioma with lung adenocarcinoma cases, we found that CDK7, MLH1, TREX1, PRKDC, XPA, PMS1, UNG, and RPA3 genes were overexpressed. Our study results showed differences between expression profiles of deoxyribonucleic acid repair genes in lung adenocarcinoma and malignant pleural mesothelioma cells. Based on our study results, we suggest that TREX1, PRKDC, and PMS1 genes may play a key role in the differential diagnosis of these two entities.

Role of H3K18ac-regulated nucleotide excision repair-related genes in arsenic-induced DNA damage and repair of HaCaT cells.

Arsenic is an environmental poison and is a grade I human carcinogen that can cause many types of damage to the body. The skin is one of the main target organs of arsenic damage, but the molecular mechanisms underlying arsenic poisoning are not clear. Arsenic is an epigenetic agent. Histone acetylation is one of the earliest covalent modifications to be discovered and is closely related to the occurrence and development of tumors. To investigate the role of acetylated histone H3K18 (H3K18 ac) in arsenic-induced DNA damage, HaCaT cells were exposed to sodium arsenite (NaAsO2) for 24 h. It was found that arsenic induced the downregulation of xeroderma pigmentosum A, D, and F (XPA, XPD, and XPF-nucleotide excision repair (NER)-related genes) expression, as well as histone H3K18 ac expression, and aggravated DNA damage. Chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR) analysis showed that H3K18 acetylation in the promoter regions of XPA, XPD, and XPF was downregulated. In addition, the use of the histone deacetylase inhibitor trichostatin A (TSA) partially inhibited arsenic-induced DNA damage, inhibited deacetylation of H3K18 ac in the promoter regions of XPA, XPD, and XPF genes, increased acetylation of H3K18, and promoted the transcriptional expression of NER-related genes. Our study revealed that NaAsO2 induces DNA damage and inhibits the expression of NER-related genes, while TSA increases the H3K18 ac enrichment level and promotes the transcriptional expression of NER, thereby inhibiting DNA damage. These findings provide new ideas for understanding the molecular mechanisms underlying arsenic-induced skin damage.

145P - Breast cancer in young women of Kazakh population depending on germline mutations: Results of next-generation sequencing

BackgroundBreast cancer (BC) represents the most common malignancy and has the highest mortality among women, both in the world and in Kazakhstan. Approximately 20-30% of cases of hereditary breast cancer are caused by presence of BRCA1 and BRCA2 genes defects. Also, there are additional genes which can increase the risk of BC and they are still under study.The aim of this study was to identify new, detectable and objective markers of key cancer genes by next-generation sequencing (NGS) in BC patients. MethodsThe study included 194 unrelated patients (the av/age 34.25 ± 4.56) with BC. Genomic DNA was obtained from peripheral blood,next-generation sequencing was performed using TruSightCancer Kit on the MiSeq platform,studio Variant was used to annotate genetic variants. ResultsIn total, 61 pathogenic variants (all in heterozygous state) were found in 56 (28.9%) patients,the vast majority of variants located in BRCA1 (n=19/56; 33.9%), 15 in BRCA2 (26.8%). The frequency of pathogenic variants in genes TP53 (8.9%), PALB2 (5.4%), MSH6 (5.4%), CHEK2 (3.6%), SDHB (3.6%), and WRN (3.6%) were higher than those genes APC, ATM, FANCA, FANCM, MSH2, NBN, NF1, PMS1, PMS2, and XPA which include only one deleterious variants. The analysis of mutation type has revealed 28 frameshift mutations, 15 stop-gain mutations, 8 missense mutations, 8 splice site variants, 1 start lost variant, and 1 synonymous variant. In total, 43 mutations were unique, 15 of them represented novel variants. Those new mutations have not been previously mentioned in the LOVD and ClinVar databases and have not been described in publications. Population frequency of all detected pathogenic mutations in 1000G, ESP6500 and ExAC databases were less than 1%. 73.8% of the mutations were available in the dbSNP database. The most common pathogenic variants were c.5329dupC and c.5341-2delA (c.5278-2delA) in BRCA1 gene, accounting for 10.7% (n=6/56) and 8.9% of patients (n=5/56), respectively. ConclusionsNGS showed frequent and novel germline mutations in BRCA1/2, CHEK2, TP53 and PALB2. After the final statistical data processing, diagnostic and prevention tools for key genes will be developed and included in the National guidelines for cancer diseases. Legal entity responsible for the studyKazakh Institute of Oncology and Radiology Institute of General Genetics and Cytology. FundingThe Ministry of Healthcare of the Republic of Kazakhstan. DisclosureAll authors have declared no conflicts of interest.