Reduced poly(ADP-ribosyl)ation in lymphocytes of laryngeal cancer patients: results of a case-control study

PARP1 rs1136410 C/C genotype associated with an increased risk of esophageal cancer in smokers

DNA repair system plays a crucial role in maintaining genomic integrity and stability and in protecting against cancer. Poly(ADP-ribose) polymerase 1 (PARP1) functions as a key enzyme in the base excision repair (BER) pathway. Single nucleotide polymorphism (SNP) that could affect the function or expression of PARP1 gene might be associated with the risk of cancer. This study was designed to evaluate the association between PARP1 SNPs and the susceptibility to esophageal squamous cell carcinoma (ESCC) in a population from Cixian, a high incidence region from northern China. In 574 ESCC patients and 577 controls, PARP1 rs1136410 and rs8679 SNPs were genotyped by polymerase chain reaction ligase detection reaction (PCR-LDR) method. Upper gastrointestinal cancer (UGIC) family history enhanced the risk of ESCC (the sex-, age- and smoking status-adjusted OR 1.355, 95% CI 1.071-1.715). Overall, rs1136410 and rs8679 SNPs did not modify the risk of ESCC. When stratified by sex, age, smoking status and UGIC family history, the rs1136410 C/C genotype was associated with an increased risk of ESCC in smokers compared to T/T or T/C genotype (the sex-, age- and UGIC family history-adjusted OR 1.696, 95% CI 1.032-2.787). In Cixian high incidence region from northern China, smokers with rs1136410 C/C genotype might have higher susceptibility to ESCC than those with T/T or T/C genotype. These high-risk individuals receiving periodic upper gastrointestinal fiber tests might facilitate early detection and early treatment of ESCC.

Development of a Human Leukocyte Antigen Score to Predict Progression-Free Survival in Head and Neck Squamous Cell Carcinoma Patients

Background

In personalized medicine and treatment stratification of head and neck squamous cell carcinoma (HNSCC), the heterogeneous genetic background of patients is not considered. Human leukocyte antigen (HLA) alleles and HLA haplotypes (HLA traits) are linked to development of HNSCC and affect progression-free survival (PFS) of HNSCC patients but most head and neck oncologists are not familiar with HLA typing. Hence, we developed an HLA-score abstracting from complexity of HLA-typing results to facilitate potential use of HLA-associated hazard ratios (HR) for prognostic stratification.

Methods

The HR for PFS of 8 HLA traits shown to be independent predictors (Pi) of PFS in a test cohort (TC) of 90 HNSCC patients were used to build the HLA-score based on the natural logarithm (ln) of the Pi-associated HR. Crude ln-transformed HR of the eight Pi, alleles B*13 (2), B*35 (1), B*51 (2), DQB1*06 (1), homozygous Cw (1), homozygous DRB4 (2), and haplotypes A*01/B*08 (−6) and B*08/C*07 (4), were summed up to yield the individual patient’s HLA-score. Receiver operating characteristic (ROC) and Kaplan–Meier curves were used to proof the suitability of the HLA-score as prognostic marker for PFS. An independent validation cohort (iVC) of 32 patients treated in the larynx-organ preservation trial DeLOS-II was utilized for validation.

Results

The individual HLA-scores (range −2 to 6) in TC classified HNSCC patients regarding PFS. ROC analysis (area under the curve = 0.750, 95% CI 0.665–0.836; P = 0.0000034) demonstrated an optimum cutoff for the HLA-score at 0.5 (97.9% sensitivity, 34.7% specificity), and 70/90 patients in TC with HLA-score > 0 had significant reduced PFS (P = 0.001). Applying the same classifier (HLA-score > 0) confirmed these findings in the iVC revealing reduced PFS of 25/32 patients (P = 0.040).

Conclusion

HLA traits constitute critical Pi. Considering the HLA-score may potentially facilitate the use of genetic information from HLA typing for prognostic stratification, e.g., within clinical trials.

HLA traits linked to development of head and neck squamous cell carcinoma affect the progression-free survival of patients

BACKGROUND

Personalized medicine and treatment stratification of patients with head and neck squamous cell carcinoma (HNSCC) today mostly ignore genetic heterogeneity in HNSCC but especially the patient's genetic background. We hypothesized that particular human leukocyte antigen (HLA) class I (HLA-A, B, Cw) and II proteins (DR, DQ) confer susceptibility for and influence development of HNSCC and may be prognostic factors for progression-free survival (PFS).

METHODS

90 consecutive HNSCC patients of the prospective observational cohort study LIFE treated between 08/2010 and 05/2011 at the University Leipzig underwent low resolution typing of HLA-A, B, Cw, DR, and DQ. Antigen and haplotype frequencies were compared to those in German blood donors. Effects on PFS were analyzed using Kaplan-Meier curves and Cox models.

RESULTS

HNSCC patients had overall altered HLA-B frequencies (P<0.05); frequencies of B∗44 were lower, those of B∗13, B∗52, and B∗57 increased (P<0.05). Almost all other antigen frequencies showed no deviation. Homozygous HLA-Cw and DRB4 were frequent and associated with reduced PFS (P<0.05). Altered haplotype frequencies were common and particular haplotypes accompanied by differing PFS. B∗13/Cw∗06 carriers had poorest outcome (P=0.011). However, multivariate Cox proportional hazard models revealed 3 clinical covariates (localization oropharynx, loco-regional metastasis, and T4 category), HPV16-DNA positivity, and 10 HLA traits as independent predictors for PFS.

CONCLUSIONS

The relevance of the genetic background of HNSCC patients calls for future research to clarify the role of HLA traits in HNSCC and if PFS depends on HLA.

Trial watch - inhibiting PARP enzymes for anticancer therapy

Poly(ADP-ribose) polymerases (PARPs) are a members of family of enzymes that catalyze poly(ADP-ribosyl)ation (PARylation) and/or mono(ADP-ribosyl)ation (MARylation), two post-translational protein modifications involved in crucial cellular processes including (but not limited to) the DNA damage response (DDR). PARP1, the most abundant family member, is a nuclear protein that is activated upon sensing distinct types of DNA damage and contributes to their resolution by PARylating multiple DDR players. Recent evidence suggests that, along with DDR, activated PARP1 mediates a series of prosurvival and proapoptotic processes aimed at preserving genomic stability. Despite this potential oncosuppressive role, upregulation and/or overactivation of PARP1 or other PARP enzymes has been reported in a variety of human neoplasms. Over the last few decades, several pharmacologic inhibitors of PARP1 and PARP2 have been assessed in preclinical and clinical studies showing potent antineoplastic activity, particularly against homologous recombination (HR)-deficient ovarian and breast cancers. In this Trial Watch, we describe the impact of PARP enzymes and PARylation in cancer, discuss the mechanism of cancer cell killing by PARP1 inactivation, and summarize the results of recent clinical studies aimed at evaluating the safety and therapeutic profile of PARP inhibitors in cancer patients.

The C allele of a synonymous SNP (rs1805414, Ala284Ala) in PARP1 is a risk factor for susceptibility to breast cancer in Saudi patients

BACKGROUND

Genetic aberrations of DNA repair enzymes are known to be common events associated with different cancer entities. The aim of the present study was to analyze genetic associations of rs1805404 (Asp81Asp) and rs1805414 (Ala284Ala) in the PARP1 gene with the risk of breast cancer in Saudi Arabia.

MATERIALS AND METHODS

These two SNP's were analyzed in a primary study group of breast cancer patients and healthy control subjects. Genotypes were determined by TaqMan SNP testing and analyzed using Chi-square or t test and logistic regression analysis with SPSS16.0 software.

RESULTS AND CONCLUSIONS

Results showed that rs1805414 was associated with a significantly increased susceptibility to breast cancer, significant risk being observed for the TC, CC and TC+CC genotypes. In conclusion PARP1 rs1805414 SNP polymorphisms may be involved in the etiology of breast cancer in the Saudi population. In contrast, PARP1 rs1805404 did not show any significant association in overall in breast cancer samples when compared to healthy controls. Confirmation of our findings in larger populations of different ethnicities may provide evidence for a role of the PARP1 gene in breast carcinoma developnment.

Involvement of PARP-1 Val762Ala polymorphism in the onset of cervical cancer in caucasian women

BACKGROUND AND OBJECTIVE

Data on the Val762Ala (rs1136410) polymorphism in the poly(adenosine diphosphate [ADP]-ribose) polymerase 1 (PARP-1) gene as a risk factor for various types of cancers in different ethnicities are inconsistent. We studied this association in a Caucasian population.

METHODS

Using high-resolution melting curve analysis (HRM), we studied the distribution of the PARP-1 Val762Ala polymorphism in patients with cervical cancer (n = 446) and in controls (n = 491).

RESULTS

Logistic regression analysis adjusting for age, pregnancy, oral contraceptive use, tobacco smoking, and menopausal status demonstrated that the PARP-1 Val762Ala polymorphism was associated with an increased risk of cervical cancer. The adjusted odds ratio (OR) for patients with the Ala/Val genotype versus the Val/Val genotype was 1.381 (95 % CI = 1.025-1.859, p = 0.033), and the adjusted OR for the Ala/Ala or Ala/Val genotype versus the Val/Val genotype was 1.403 (95 % CI = 1.057-1.863, p = 0.019). The p value from the chi-square test of the trend observed for the PARP-1 Val762Ala polymorphism was statistically significant (p trend = 0.0123). Stratified analyses of the PARP-1 Val762Ala genotype distribution and cervical cancer risk showed that the age-adjusted OR of Ala/Ala or Ala/Val vs Val/Val for pregnancy was 1.388 (95 % CI = 1.027-1.877, p = 0.0328), 1.773 (95 % CI = 1.145-2.745, p = 0.0100) for contraceptive use, and 1.604 (95 % CI = 1.132-2.272, p = 0.0077) for postmenopausal women. The age-adjusted OR of Ala/Val vs Val/Val for contraceptive use was 1.769 (95 % CI = 1.114-2.809, p = 0.0154) and for postmenopausal women was 1.577 (95 % CI = 1.094-2.272, p = 0.0143).

CONCLUSION

Our studies suggest that the PARP-1 Val762Ala polymorphism may be a genetic risk factor for cervical cancer.

Association between PARP-1 V762A polymorphism and breast cancer susceptibility in Saudi population

Genetic aberrations of DNA repair enzymes are known to be common events and to be associated with different cancer entities. Aim of the following study was to analyze the genetic association of rs1136410 (Val762Ala) in PARP1 gene with the risk of breast cancer using genotypic assays and insilico structural predictions. Genotypic analysis of individual locus showed statistically significant association of Val762Ala with increased susceptibility to breast cancer. Protein structural analysis was performed with Val762Ala variant allele and compared with the predicted native protein structure. Protein prediction analysis showed that this nsSNP may cause changes in the protein structure and it is associated with the disease. In addition to the native and mutant 3D structures of PARP1 were also analyzed using solvent accessibility models for further protein stability confirmation. Taken together, this the first study that confirmed Val762Ala variant has functional effect and structural impact on the PARP1 and may play an important role in breast cancer progression in Saudi population.

The protein poly(ADP-ribosyl)ation system: its role in genome stability and lifespan determination

The processes that lead to violation of genome integrity are known to increase with age. This phenomenon is caused both by increased production of reactive oxygen species and a decline in the efficiency of antioxidant defense system as well as systems maintaining genome stability. Accumulation of different unrepairable genome damage with age may be the cause of many age-related diseases and the development of phenotypic and physiological signs of aging. It is also clear that there is a close connection between the mechanisms of the maintenance of genome stability, on one hand, and the processes of spontaneous tumor formation and lifespan, on the other. In this regard, the system of protein poly(ADP-ribosyl)ation activated in response to a variety of DNA damage seems to be of particular interest. Data accumulated to date suggest it to be a kind of focal point of cellular processes, guiding the path of cell survival or death depending on the degree of DNA damage. This review summarizes and analyzes data on the involvement of poly(ADP-ribosyl)ation in various mechanisms of DNA repair, its interaction with progeria proteins, and the possible role in the development of spontaneous tumors and lifespan determination. Special attention is given to the relationship between various polymorphisms of the human poly(ADP-ribose) polymerase-1 gene and longevity.

Association between PARP-1 V762A polymorphism and cancer susceptibility: a meta-analysis

Poly(ADP-ribose) polymerase-1 (PARP-1 catalyzes poly(ADP-ribosyl)ation to various proteins involved in many cellular processes, including DNA damage detection and repair and cell proliferation and death. PARP-1 has been implicated in human carcinogenesis, but the association between the most-studied PARP-1 V762A polymorphism (rs1136410) and risk of various cancers was reported with inconclusive results. The aim of this study was to assess the association between the PARP-1 V762A polymorphism and cancer risk. A meta-analysis of 21 studies with 12,027 cancer patients and 14,106 cancer-free controls was conducted to evaluate the strength of the association using odds ratio (OR) with 95% confidence interval (CI). Overall, no significant association was found between the PARP-1 V762A polymorphism and cancer risk. In the stratified analyses, however, it was found that the variant A allele of the PARP-1 V762A polymorphism was associated with an increased risk of cancer among Asian populations (VA + AA vs. VV: OR = 1.11, 95% CI: 1.01-1.23; P(heterogeneity) = 0.210), but a decreased risk of cancer (VA + AA vs. VV: OR = 0.89, 95% CI: 0.80-1.00; P(heterogeneity) = 0.004) among Caucasian populations, especially for glioma risk (OR = 0.79, 95% CI: 0.69-0.90; P(heterogeneity) = 0.800). This meta-analysis found evidence for an association of the PARP-1 V 762A polymorphism with increased risk of cancer among Asians, but decreased risk of cancer among Caucasians, particularly of glioma. Further well-designed studies with large sample sizes of different ethnic populations and different cancer types are warranted to confirm these findings.

Head and neck cancer: effective prevention in youth and predictive diagnostics for personalised treatment strategies according to biological differences

This article focuses on squamous cell carcinomas of the larynx, pharynx and oral cavity which count nearly 90% of the head and neck squamous cell carcinomas (HNSCC). Individual susceptibility depends on an individually given genetic background and/or acquired conditions or factors elevating the risk of HNSCC including smoking, alcohol abuse, and improper oral hygiene. A key issue in HNSCC pathogenesis is their development within large preneoplastic fields of mucosal epithelium made up of genetically altered cells that are clonally related to the carcinoma. Other individual differences in development of HNSCC comprise infection with pathogenic microbes and oncogenic human papillomavirus (HPV) subtypes like HPV 16 (a strong risk factor mainly for oropharyngeal cancer). Interestingly, the presence of HPV 16 also goes in line with better outcome after therapy. Vaccination against HPV infection in children plays an increasing role in prevention strategies and probably also reduces the oncogenic risk for HNSCC.

No associations of polymorphisms in ADPRT with hepatitis B virus clearance and hepatocellular carcinoma occurrence in a Korean population

AIM

  The human adenosine diphosphate ribosyl transferase (ADPRT) gene might significantly affect cancer by encoding poly(ADP-ribose) polymerase 1 enzyme (PARP-1) and promoting an important role in cellular responses to DNA damage, genomic stabilization and regulation of tumor suppressor genes. We explored whether polymorphisms of ADPRT affect clearance of hepatitis B virus (HBV) infection or risk of hepatocellular carcinoma (HCC) occurrence in a Korean HBV cohort.

METHODS

  Genotyping was performed in a total of 1066 subjects composed of 434 spontaneously recovered (SR) subjects as normal controls and 632 chronic carriers (CC) of HBV who were further classified into 325 patients with liver cirrhosis (LC)/chronic hepatitis (CH) and 307 patients with HCC.

RESULTS

  Logistic analyses of six common single nucleotide polymorphisms (SNP) and their haplotypes revealed that none of the polymorphisms were significantly associated with clearance of HBV infection and HCC occurrence, except for nominal evidence of association between haplotype 2 (ht2) with HBV clearance (P = 0.05). In the analysis of age of HCC occurrence which is an important factor in disease progression to HCC, results from Cox proportional hazards showed that none of the variants were significantly associated with onset age of HCC occurrence, although a nominal signal in ht4 (P = 0.03, but P(corr)  > 0.05) was initially detected.

CONCLUSION

  Although ADPRT is an important gene for cellular responses and tumor regulations, our study provides evidence that ADPRT variations do not affect HBV clearance and HCC occurrence.

Genetic variation in DNA repair pathway genes and melanoma risk

Reduced DNA repair capacity has been proposed as a predisposing factor for melanoma. We comprehensively evaluated 1463 genetic variants across 60 DNA repair-related pathway genes in relation to melanoma risk in a nested case-control study of 218 melanoma cases (20% on head and neck) and 218 matched controls within the Nurses' Health Study (NHS). We then genotyped the two variants with the smallest P value in two replication sets: 184 melanoma cases (28% on head and neck) and 184 matched controls in the Health Professionals Follow-Up Study (HPFS); and 183 melanoma cases (10% on head and neck) and 183 matched controls in the NHS. The SNP rs3219125 in the PARP1 gene was significantly associated with melanoma risk in the discovery set (odds ratio (OR) 3.14; 95% confidence interval (CI) 1.70-5.80) and in the HPFS replication set (OR, 1.92; 95% CI, 1.05-3.54) but not in the NHS replication set (OR, 1.07; 95% CI, 0.58-1.97). In the joint analysis, the OR was 1.89 (95% CI, 1.34-2.68) for this polymorphism, and this increased risk was more pronounced among patients with lesions in head/neck (OR, 3.19; 95% CI, 1.77-5.73 for head/neck, and OR, 1.54; 95% CI, 1.03-2.30 for other sites, P value for heterogeneity test=0.036). Our findings suggest the possible involvement of the PARP1 variant in melanoma development, especially for sites with high sun exposure. Further work on fine-mapping and on the functional characterization of this and linked SNPs in this region is required.

Genome Instability and Bleomycin Sensitivity Test

Procjena individualne osjetljivosti na mutagene često je dio istraživanja u epidemiološkim studijama koje prate pojavnost zloćudnih bolesti u populacijama. Posljedica djelovanja mutagena u genomu izloženih osoba jest nastanak osoba jest nastanak određene, manje ili veće, količine oštećenja, uvjetovane individualnim razlikama u osjetljivosti. Viša razina takve genomske nestabilnosti znači opasnost (rizik) od razvoja zloćudnih bolesti. Interindividualne razlike u odgovoru na mutagene obično se povezuju i s promijenjenom (većinom smanjenom) sposobnosti (kapacitetom) za popravak DNA. Citogenetičke studije su pokazale da je genom tumorskih stanica nestabilniji od normalnih, a time i skloniji akumuliranju oštećenja, bilo da je nestabilnost uzrokovana nasljeđem, izloženošću ili kombinacijom tih dvaju učinaka. U oboljelih ispitanika utvrđena je povećana učestalost kromatidnih i kromosomskih aberacija naspram normalne populacije te sklonost razvoju određenih vrsta neoplazija. U praćenju povezanosti promijenjenog odgovora i pojavnosti tumora služe nam različiti biomarkeri. Kao indirektni pokazatelji uspješnosti popravka DNA često se rabe testovi osjetljivosti na mutagene u kulturama limfocita periferne krvi. Jedan od takvih testova je i bleomicinski test. Radiomimetik i citostatik, a po strukturi glikopeptid, bleomicin se u stanici prevodi u aktivni oblik sposoban cijepati molekulu DNA što uzrokuje brojne jednolančane i dvolančane lomove. Kao jednostavna i jeftina metoda, zasniva se na utvrđivanju ukupnog broja jednolančanih lomova u kromosomima limfocita uzgajanih u staničnoj kulturi koji su u uvjetima in vitro tijekom kasne G2-faze staničnog ciklusa bili izloženi bleomicinu. Ovaj revijalni rad daje pregled utjecaja raznih faktora na rezultate samog testa i pokazuje njegovu široku primjenu u proučavanju genomske nestabilnosti koju najčešće uzrokuje kombinacija raznih faktora.

PARP-1 Val762Ala polymorphism is associated with reduced risk of non-Hodgkin lymphoma in Korean males

Background

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme that plays a role in DNA repair, differentiation, proliferation, and cell death. The polymorphisms of PARP-1 have been associated with the risk of various carcinomas, including breast, lung, and prostate. We investigated whether PARP-1 polymorphisms are associated with the risk of non-Hodgkin lymphoma (NHL).

Methods

Subjects from a Korean population consisting of 573 NHL patients and 721 controls were genotyped for 5 PARP-1 polymorphisms (Asp81Asp, Ala284Ala, Lys352Lys, IVS13+118A>G, and Val762Ala) using High Resolution Melting polymerase chain reaction (PCR) and an automatic sequencer.

Results

None of the 5 polymorphisms were associated with overall risk for NHL. However, the Val762Ala polymorphism was associated with reduced risk for NHL in males [odds ratio (OR), 0.62; 95% confidence interval (CI), 0.41-0.93 for CC genotype and OR, 0.84; 95% CI, 0.60-1.16 for TC genotype] with a trend toward a gene dose effect (p for trend, 0.02). The Asp81Asp (p for trend, 0.04) and Lys352Lys (p for trend, 0.03) polymorphisms revealed the same trend. In an association study of PARP-1 haplotypes, the haplotype-ACAAC was associated with decreased risk of NHL in males (OR, 0.75; 95% CI, 0.59-0.94).

Conclusion

The present data suggest that Val762Ala, Asp81Asp, and Lys352Lys polymorphisms and the haplotype-ACAAC in PARP-1 are associated with reduced risk of NHL in Korean males.

Changes in poly(ADP-ribose) level modulate the kinetics of DNA strand break rejoining

ADP-ribose polymers are rapidly synthesized in cell nuclei by the poly(ADP-ribose) polymerases PARP-1 and PARP-2 in response to DNA strand interruptions, using NAD(+) as precursor. The level of induced poly(ADP-ribose) formation is proportional to the level of DNA damage and can be decreased by NAD(+) or PARP deficiency, followed by poor DNA repair and genomic instability. Here we studied the correlation between poly(ADP-ribose) level and DNA strand break repair in lymphoblastoid Raji cells. Poly(ADP-ribose) synthesis was induced by 100 microM H(2)O(2) and intensified by the 1,4-dihydropyridine derivative AV-153. The level of poly(ADP-ribose) in individual cells was analyzed by quantitative in situ immunofluorescence and confirmed in whole-cell extracts by Western blotting, and DNA damage was assessed by alkaline comet assays. Cells showed a approximately 100-fold increase in poly(ADP-ribose) formation during the first 5 min of recovery from H(2)O(2) treatment, followed by a gradual decrease up to 15 min. This synthesis was completely inhibited by the PARP inhibitor NU1025 (100 microM) while the cells treated with AV-153, at non-genotoxic concentrations of 1 nM-10 microM, showed a concentration-dependent increase of poly(ADP-ribose) level up to 130% after the first minute of recovery. The transient increase in poly(ADP-ribose) level was strongly correlated with the speed and efficiency of DNA strand break rejoining (correlation coefficient r > or = 0.92, p<0.05). These results are consistent with the idea that poly(ADP-ribose) formation immediately after genome damage reflects rapid assembly and efficient functioning of repair machinery.

Analysis of genetic variants of the poly(ADP-ribose) polymerase-1 gene in breast cancer in French patients

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme that catalyzes the poly(ADP-ribosyl)ation of target proteins in response to DNA damage and has been proposed to play a role in DNA repair, recombination, transcription, cell death, cell proliferation, as well as in stabilization of the genome. We have recently shown that PARP-1 deficiency causes mammary tumorigenesis in mice. In the present study, we investigated whether genetic variants and single nucleotide polymorphisms (SNPs) of PARP-1 contribute to human breast cancer. To this end, we screened all PARP-1 exons, 7.1kb of intron-exon junction and 1.0-kb promoter sequences in 83 French patients with breast cancer and 100 controls by direct sequencing of genomic DNA. Twenty rare genetic variants of PARP-1, including c.1148C>A (Ser383Tyr), c.1354C>A (Arg452Arg), c.2819A>G (Lys940Arg) were detected in nine (10.8%) breast cancers of these patients. Among 31 polymorphic sites examined, five haplotype-tagging SNPs (htSNPs) of PARP-1 were identified. Interestingly, the genotype distribution of htSNP c.852T>C (Ala284Ala) was likely associated with loss of estrogen- and progesterone-receptor expression. The present study implies that genetic variants of PARP-1 may contribute to breast cancerogenesis and that PARP-1 htSNP c.852T>C (Ala284Ala) may influence hormonal therapy of breast cancer.

Identification of proteins within the nuclear factor-kappa B transcriptional complex including estrogen receptor-alpha

OBJECTIVE

The objective of the study was to determine whether cross-talk occurs between estrogen receptors (ERs) and nuclear factor-kappa-B (NF-kappaB), to assess the functional consequences of such an ER/NF-kappaB interaction, and to identify other unknown regulatory proteins that may participate in the NF-kappaB transcriptional complex.

STUDY DESIGN

Electromobility gel shifts, reporter gene assays, and mass spectrometry were used to identify proteins interacting with the NF-kappaB deoxyribonucleic acid (DNA) response element.

RESULTS

ER and the p65 subunit of NF-kappaB colocalized on DNA. This interaction was inhibitory for ER transcriptional activity. Sequencing of proteins bound to the NF-kappaB/DNA complex identified DNA-modifying enzymes, scaffolding proteins, chaperones, and elements of the nuclear matrix.

CONCLUSION

These studies have identified an inhibitory interaction between estrogen receptors and the p65 subunit of NF-kappaB with implications for estrogen action in pregnancy and cancer. New accessory proteins have also been identified that bind to protein complexes on the NF-kappaB DNA response element.

Genetic risk profiles for cancer susceptibility and therapy response

Cells in the body are permanently attacked by DNA-reactive species, both from intracellular and environmental sources. Inherited and acquired deficiencies in host defense mechanisms against DNA damage (metabolic and DNA repair enzymes) can modify cancer susceptibility as well as therapy response. Genetic profiles should help to identify high-risk individuals who subsequently can be enrolled in preventive measures or treated by tailored therapy regimens. Some of our attempts to define such risk profiles are presented. Cancer susceptibility: Single nucleotide polymorphisms (SNPs) in metabolic and repair genes were investigated in a hospital-based lung cancer case-control study. When evaluating the risk associated with different genotypes for N-acetyltransferases (Wikman et al. 2001) and glutathione-S-transferases (Risch et al. 2001), it is mandatory to distinguish between the three major histological subtypes of lung tumors. A promoter polymorphism of the myeloperoxidase gene MPO was shown to decrease lung cancer susceptibility mainly in small cell lung cancer (SCLC) (Dally et al. 2002). The CYP3A4*1B allele was also linked to an increased SCLC risk and in smoking women increased the risk of lung cancer eightfold (Dally et al. 2003b). Polymorphisms in DNA repair genes were shown to modulate lung cancer risk in smokers, and reduced DNA repair capacity elevated the disease risk (Rajaee-Behbahani et al. 2001). Investigations of several DNA repair gene variants revealed that lung cancer risk was only moderately affected by a single variant but was enhanced up to approximately threefold by specific risk allele combinations (Popanda et al. 2004). Therapy response: Inter-individual differences in therapy response are consistently observed with cancer chemotherapeutic agents. Initial results from ongoing studies showed that certain polymorphisms in drug transporter genes (ABCB1) differentially affect response outcome in histological subgroups of lung cancer. Stronger beneficial effects were seen in non-small cell lung cancer (NSCLC) patients following gemcitabine and in SCLC patients following etoposide-based treatment. Several DNA repair parameters (polymorphisms, RNA expression, and DNA repair capacity) were measured in vitro in lymphocytes of patients before radiotherapy and correlated with the occurrence of acute side effects (radio-hypersensitivity). Our initial analysis of several repair gene variants in breast cancer patients (n = 446) who received radiotherapy revealed no association of single polymorphisms and the development of side effects (moist desquamation of the irradiated normal skin). The risk for this side effect was, however, strongly reduced in normal weight women carrying a combination of XRCC1 399Gln and APE1 148Glu alleles, indicating that these variants afford some protection against radio-hypersensitivity (Chang-Claude et al. 2005). Based on these data we conclude that specific metabolic and DNA repair gene variants can affect cancer risk and therapy outcome. Predisposition to hereditary cancer syndromes is dominated by the strong effects of some high-penetrance tumor susceptibility genes, while predisposition to sporadic cancer is influenced by the combination of multiple low-penetrance genes, of which as a major challenge, many disease-relevant combinations remain to be identified. Before translating these findings into clinical use and application for public health measures, large population-based studies and validation of the results will be required.

PARP1 Val762Ala polymorphism reduces enzymatic activity

Poly(ADP-ribose) polymerase 1 (PARP1) modifies a variety of nuclear proteins by poly(ADP-ribosyl)ation, and plays diverse roles in molecular and cellular processes. A common PARP1 single nucleotide polymorphism (SNP) at codon 762, resulting in the substitution of alanine (Ala) for valine (Val) in the catalytic domain has been implicated in susceptibility to cancer. To characterize the functional effect of this polymorphism on PARP1, we performed in vitro enzymatic analysis on PARP1-Ala762 and PARP1-Val762. We found that PARP1-Ala762 displayed 57.2% of the activity of PARP1-Val762 for auto-poly(ADP-ribosyl)ation and 61.9% of the activity of PARP1-Val762 for trans-poly(ADP-ribosyl)ation of histone H1. The kinetic characterization revealed that the K(m) of PARP1-Ala762 was increased to a 1.2-fold of the K(m) of PARP1-Val762 for trans-poly(ADP-ribosyl)ation. Thus, the PARP1 Val762Ala polymorphism reduces the enzymatic activity of PARP1 by increasing K(m). This finding suggests that different levels of poly(ADP-ribosyl)ation by PARP1 might aid in understanding the cancer risk of carriers of the PARP1 Val762Ala polymorphism.

Poly(ADP-ribose) polymerase-1 plays a role in suppressing mammary tumourigenesis in mice

The DNA strand break-binding molecule, poly(ADP-ribose) polymerase-1 (PARP-1), plays a role in DNA repair, chromosomal stability, transcription and cell death. Accumulating evidence suggests that dysfunction of PARP-1 contributes to tumorigenesis. Here, we report that PARP-1 deficiency causes mammary carcinoma formation in female mice, and that the introduction of Trp53 mutations accelerates the onset and shortens the latency of mammary tumorigenesis. We show that PARP-1 deficiency results in chromosomal aneuploidy and centrosome amplification, which are substantiated by the inactivation of Trp53 in primary mammary epithelial (PME) cells. In addition, PARP-1 deficiency compromises p53 activation and impairs BRCA1 recruitment to the sites of DNA damage in PME cells. PARP-1 complementation partly rescues the defective DNA damage response mediated by p53 and BRCA1. The present study thus identifies a role of PARP-1 in suppressing mammary tumorigenesis in vivo and suggests that dysfunction of PARP-1 may be a risk factor for breast cancer in humans.

Perspectives on the molecular epidemiology of aerodigestive tract cancers

Improving laboratory techniques and the greater availability of genetic data have led to a flurry of publications from molecular epidemiologic studies on aerodigestive tract cancers. Inconsistent results have been observed in studies of sequence variants, due to limitations such as small sample size, possible detection of false positives, moderate prior probabilities that each SNP confers a substantial increase in cancer risk, and publication bias. Meta- and pooled-analyses were shown to be effective in elucidating modest increases in aerodigestive tract cancer risk attributable to sequence variants. Phenotypic assays developed to quantify an individual's DNA repair capacity have been applied to epidemiological studies on aerodigestive tract cancers. Epigenetic events have also been studied in tumor progression and as susceptibility factors for aerodigestive tract cancers, in smaller scale studies. It is imperative that limitations of previous studies are addressed for future research in the molecular epidemiology of aerodigestive tract cancers. Some recommendations for future research are to: (i) incorporate multiple markers of different types (ex. genotype and phenotype data), (ii) enhance statistical power by conducting studies with larger sample size, and developing consortia to coordinate research efforts, (iii) improve marker selection via a hybrid strategy of incorporating data on evolutionary biology and physico-chemical properties of amino acids, with haplotype/tag SNP data, (iv) employ novel statistical methods such as hierarchical modeling with Bayesian adjustments, false positive reporting probability and modeling of complex pathways. Consortia have been initiated for head and neck cancer (International Head and Neck Cancer Epidemiology Consortium (INHANCE)) and lung cancer (International Lung Cancer Consortium (ILCCO)) with the aim to share comparable data, to focus on rare subgroups such as nonsmokers and to coordinate laboratory analyses. Such collaborative efforts and integration across disciplines will be essential in contributing to the elucidation of genetic susceptibility to aerodigestive tract cancers.

Poly(ADP-ribose). The most elaborate metabolite of NAD+

One of the most drastic post-translational modification of proteins in eukaryotic cells is poly(ADP-ribosyl)ation, catalysed by a family enzymes termed poly(ADP-ribose) polymerases (PARPs). In the human genome, 18 different genes have been identified that all encode PARP family members. Poly(ADP-ribose) metabolism plays a role in a wide range of biological structures and processes, including DNA repair and maintenance of genomic stability, transcriptional regulation, centromere function and mitotic spindle formation, centrosomal function, structure and function of vault particles, telomere dynamics, trafficking of endosomal vesicles, apoptosis and necrosis. In this article, the most recent advances in this rapidly growing field are summarized.

Poly(ADP-ribose)polymerase activity is reduced in circulating mononuclear cells from type 2 diabetic patients

Poly(ADP-ribose)polymerase (PARP-1), a nuclear enzyme activated by DNA strand breaks, is involved in DNA repair, aging, inflammation, and neoplastic transformation. In diabetes, reactive oxygen and nitrogen species occurring in response to hyperglycemia cause DNA damages and PARP-1 activation. Because circulating mononuclear cells (MNCs) are involved in inflammation mechanisms, these cells were chosen as the experimental model to evaluate PARP-1 levels and activity in patients with type 2 diabetes. MNCs were isolated from 25 diabetic patients (18 M, 7 F, age, 63.5 +/- 10.2 years, disease duration 17.7 +/- 8.2 years) and 11 age and sex matched healthy controls. PARP-1 expression and activity were analyzed by semi-quantitative PCR, Western and activity blot, and immunofluorescence microscopy. PARP-1-mRNA expression was increased in MNCs from all diabetic patients versus controls (P < 0.01), whereas PARP-1 content and activity were significantly lower in diabetic patients (P < 0.0001). To verify whether low PARP-1 levels and activity were due to a proteolytic effect of caspase-3 like, the latter activation was measured by a fluorimetric assay. Caspase-3 activity in MNCs was significantly higher in diabetic patients versus control subjects (P < 0.0001). The different PARP-1 behavior in MNCs from patients with type 2 diabetes could therefore be responsible for the abnormal inflammation and infection responses in diabetes.

The ADPRT V762A genetic variant contributes to prostate cancer susceptibility and deficient enzyme function

The ADP-ribosyltransferase (ADPRT) gene encodes a zinc-finger DNA-binding protein, poly(ADP-ribose) polymerase-1 (PARP-1), that modifies various nuclear proteins by poly(ADP-ribosyl)ation and functions as a key enzyme in the base excision repair pathway. We have conducted two studies to test whether an amino acid substitution variant, ADPRT V762A (T2444C), is associated with prostate cancer (CaP) risk and decreased enzyme function. The first study used genomic DNA samples from an ongoing, clinic-based case-control study (488 cases and 524 controls) to show that a higher percentage of the CaP cases carried the ADPRT 762 AA genotype than controls (4% versus 2%). In Caucasians, the AA genotype was significantly associated with increased CaP risk [odds ratio (OR), 2.65; 95% confidence interval (CI), 1.08-6.49], and the VA genotype was associated with a slight but not significantly increased CaP risk (OR, 1.18; 95% CI, 0.85-1.64) using VV as the referent group after adjustment for age, benign prostatic hyperplasia, and family history. Furthermore, this association was stronger in younger (<65) men (OR, 4.77; 95% CI, 1.01-22.44) than older (> or =65) men (OR, 1.78; 95% CI, 0.55-5.82). The second study used freshly isolated peripheral lymphocytes from 354 cancer-free subjects to demonstrate that the ADPRT 762 A allele contributed to significantly lower adenosine diphosphate ribosyl transferase (ADPRT)/PARP-1 activities in response to H2O2 in a gene dosage-dependent manner (P < 0.0001, test for linear trend). The PARP-1 activities (mean +/- SD dpm/10(6) cells) were 18,554 +/- 9,070 (n=257), 14,847 +/- 7,082 (n=86), and 12,155 +/- 6,334 (n=11) for VV, VA, and AA genotypes, respectively. This study is the first to provide evidence that the ADPRT V762A-genetic variant contributes to CaP susceptibility and altered ADPRT/PARP-1 enzyme function in response to oxidative damage.

Poly(ADP-ribose) polymerase-1, a novel partner of progesterone receptors in endometrial cancer and its precursors

Endometrial carcinomas are the most common malignancy of the female genital tract. Although the downregulation of the progesterone receptor (PR) in the progression of endometrioid carcinomas (ECs) has been well documented, the mechanism of PR alteration in endometrioid carcinogenesis is poorly understood. Recently, biochemical studies have shown that the DNA strand break-sensing molecule poly(ADP-ribose) polymerase (PARP-1) was associated with the DNA binding domain of PR. In our present study, we show that in normal endometrial epithelium, the expression level of PARP-1 protein is high in the proliferative phase but markedly decreases during the secretory phase. Interestingly, PARP-1 expression gradually increases in nonatypical and atypical endometrial hyperplasia, reaching its highest level in grade I, and decreases significantly toward grade III ECs. Notably, PARP-1 and PR expressions, in each stage, are positively correlated (p < 0.0001), with the exception of nonendometrioid carcinomas. Thus, these data suggest that PARP-1 is substantially involved in the regulation of progesterone action in the development of ECs.

Induction of poly(ADP-ribosyl)ation and DNA damage in human peripheral lymphocytes after treatment with (-)-epigallocatechin-gallate

With regard to a future use of tea polyphenols in intervention trials with individuals at high cancer risk, the effects of the tea ingredient (-)-epigallocatechin gallate (EGCG) on poly(ADP-ribose) (PAR) levels and on DNA damage were investigated in human lymphocytes. A dose- and time-dependent elevation of both PAR formation as assessed by quantitative immunofluorescence analysis and DNA damage as assessed by the comet assay were observed after treatment with EGCG at 20, 40 and 80 microM for 10-240 min. Maximum levels of PAR formation and of DNA damage were observed after 10 min at all concentrations tested. Increased PAR levels were still detectable by 240 min in the 40 and 80 microM groups. At the lowest concentration, which is near the physiological peak values found after tea ingestion, PAR formation was not correlated with DNA damage. Here, EGCG led to pronounced PAR levels, whereas the comet assay was almost negative. In contrast, such marked differences in time course and extent of both genotoxicity and PAR formation following EGCG treatment were not detected after gamma-irradiation. Our results suggest that the known chemopreventive effects of EGCG, the main constituent of tea, may be partly attributed to an induction of PAR formation.