等位基因特异PCR检测N-乙酰化转移酶遗传多态性研究

目的与方法：改良一种适用于流行病学研究的N－乙酰化转移酶（NAT2）基因型的等位基因特异PCR（AS－PCR）检测方法,分析了3个NAT2基因突变点：481T,590A,857A,并用此法对76例南京地区健康人群的NAT2基因型多态性进行了研究。从而也检验了该方法。结果：该人群中各基因频率,Wt(野生型）为0．5723：481T为0395,590A为0．2368,857A为1513。与白种人比较差异有显著性,而与文献报道的亚州人群频率分布物 基因一致,结论：南京地区健康人群中与快反应相关的NAT2基因型占多数（82．9％）,本文改良的AS－PCR检测方法验证为NAT2基因多态性研究的有效实验手段。     

Differences in N-acetylation genotypes between Caucasians and Black South Africans: implications for cancer prevention

Polymorphic N-acetyltransferase genes (NAT1 and NAT2) determine rapid or slow acetylation phenotypes, which are believed to affect cancer risk related to environmental exposure. Black South Africans have a unique incidence pattern of environment-related cancers, but genetic characteristics of this population are mostly unknown. In this study, we compared NAT1 and NAT2 allele distributions in 101 Black South Africans and 112 UK Caucasians. Frequencies of the rapid alleles were significantly higher in Black South Africans for both NAT1 and NA72. Putative rapid NAT1 genotypes due to the presence of either NAT1*10 or NAT1*11 were found in 74.3% of Black South Africans (only NAT1*10) and 42.0% of UK Caucasians (P < 0.0001). Similarly, NAT2 analysis showed that the presence of NA12*4, NAT2*12A, NAT2*12B, NA72*12C, and NAT2*13 alleles provided significantly higher (P = 0.0001) frequency of rapid acetylation genotypes among Black South Africans (60.4%) than in the Caucasian group (33.9%). The rapid acetylation genotype in Caucasians usually depended on the NAT2*4 allele presence. The significant differences in N-acetylation genotypes can be among the factors determining a distinctive cancer morbidity and mortality pattern observed in Black South Africans. Both further genetic characterization of different populations and development of preventive strategies adopted for ethnicities with different genetic backgrounds are needed to deal adequately with the emerging health care problems in developing multiethnic societies.     

Evaluation of Genetic Polymorphisms of N-acetyltransferase 2 and Relation with Chronic Myeloid Leukemia

Objectives: The N-Acetyltransferase 2 (NAT2) gene encodes a key enzyme involved in xenobiotic metabolism, which contributes to the detoxification of numerous cancer therapy-induced products. However, the NAT2 genotype/phenotype is not fully understood and few studies have reported its relationship with CML. The aim of this study was to determine whether its polymorphisms (C481T, G590A, 803A>G and 857G>A) have a role in chronic myeloid leukemia susceptibility (CML) in Sudanese population. Methods: We performed a case- control study. DNA from 200 CML patients and 100 controls was analyzed for the NAT2 polymorphisms using PCR-RFLP assay. Results: The study showed NAT2 polymorphisms 803AG are associated with CML protection by a factor of 2.3, (OR = 0.044, 95% CI: 0.020-0.095, p = 0. 000). The study indicated that the heterozygous (GA) and mutant (AA) variants of the G857A genotype also offer protection, (OR = 0.002, 95% CI: 0.002-0.019, p = 0. 000) and (OR = 0.018, 95% CI: 0.002-0.133, p = 0. 000), respectively. Conclusion: There was no significant difference in CML diagnosis among Sudanese cases with the 481C→T and 590G→A polymorphisms. But patients with the compound NAT2 genotypes 481CT/803 AG, 590AG/ 803AG, 590AG/ 803GG, 590AA/ 803AG and 590GG/ 803AG were found to have a reduced risk. The current study demonstrates that polymorphisms of NAT2 A803G and G857A might also act as protective factors against developing the disease.     

Functional characterization of single-nucleotide polymorphisms and haplotypes of human N-acetyltransferase 2

Human N-acetyltransferase 2 (NAT2) is polymorphic in humans and may associate with cancer risk by modifying individual susceptibility to cancers from carcinogen exposure. Since molecular epidemiological studies investigating these associations usually include determining NAT2 single-nucleotide polymorphisms (SNPs), haplotypes or genotypes, their conclusions can be compromised by the uncertainty of genotype-phenotype relationships. We characterized NAT2 SNPs and haplotypes by cloning and expressing recombinant NAT2 allozymes in mammalian cells. The reference and variant recombinant NAT2 allozymes were characterized for arylamine N-acetylation and O-acetylation of N-hydroxy-arylamines. SNPs and haplotypes that conferred reduced enzymatic activity did so by reducing NAT2 protein without changing NAT2 mRNA levels. Among SNPs that reduced catalytic activity, G191A (R64Q), G590A (R197Q) and G857A (G286E) reduced protein half-life but T341C (I114T), G499A (E167K) and A411T (L137F) did not. G857A (G286E) and the major haplotype possessing this SNP (NAT2 7B) altered the affinity to both substrate and cofactor acetyl coenzyme A, resulting in reduced catalytic activity toward some substrates but not others. Our results suggest that coding region SNPs confer slow acetylator phenotype by multiple mechanisms that also may vary with arylamine exposures.     

Effects of single nucleotide polymorphisms in human N-acetyltransferase 2 on metabolic activation (O-acetylation) of heterocyclic amine carcinogens

N-Acetyltransferase 2 (NAT2) catalyzes the O-acetylation of N-hydroxy heterocyclic amines such as N-hydroxy-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (N--OH--MeIQx) and N-hydroxy-2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (N--OH --PhIP) to DNA binding metabolites that initiate mutagenesis and carcinogenesis. NAT2 acetylator phenotype is associated with increased cancer risk. Single nucleotide polymorphisms (SNPs) have been identified in the NAT2 coding region. Although the effects of these SNPs on N-acetyltransferase activity have been reported, very little is known regarding their effects on O-acetylation activity. To investigate the functional consequences of SNPs in the NAT2 coding region on the O-acetylation of N-hydroxy heterocyclic amines, reference NAT2*4 and NAT2 variant alleles possessing one were cloned and expressed in yeast (Schizosaccaromyces pombe). T111C, C282T, C481T, C759T, and A803G (K268R) SNPs did not significantly (p > 0.05) modify O-acetylation catalysis with N--OH--PhIP or N--OH--MeIQx. C190T (R64W), G191A (R64Q), T341C (I114T), A434C (E145P), G590A (R197Q) and A845C (K282T) significantly (p < 0.01) reduced the O-acetylation of both N--OH--PhIP and N--OH--MeIQx, whereas G857A (G286E) significantly (p < 0.05) decreased catalytic activity towards the O-acetylation of N--OH--MeIQx but not N--OH--PhIP. These results have important implications towards the interpretation of molecular epidemiological studies of NAT2 genotype and cancer risk.     

N-acetyltransferase-2 gene polymorphisms and prostate cancer susceptibility in Latin American patients

We investigated the role of N-acetyltransferases (NAT) in prostate cancer (PCa) susceptibility. NAT are polymorphic in the population and metabolize important carcinogenic products directly involved in the tumor initiation process. This prospective case-control study utilized the polymerase chain reaction-based restriction fragment length polymorphism method and comprised a cohort of consecutive 478 individuals: 126 men with prostate cancer; 101 men with benign prostatic hyperplasia (BPH); and a control health population of 177 female and 74 male blood donors from the same region. NAT2 slow or fast acetylators genotypes were determined by the combination of four variant alleles. Lifetime occupational history, dietary patterns, cigarette smoking and other anamnestic data were obtained by interviews. We were not able to find any correlation among smoking, dietary patterns, parameters of tumor aggressiveness or patient outcome and any NAT2 genotypes or phenotypes considered in separate or in different combinations. However, there was an association between NAT2T481C (OR?=?0.47; 95% CI?=?0.26-0.84; P?=?0.01) and NAT2A803G (OR?=?0.57; 95% CI?=?0.33-0.97; P?=?0.04) polymorphisms and PCa protection. Conversely, the presence of NAT2G857A genotype increased the risk of PCa more than 3 times (OR?=?3.57; 95% CI?=?1.39-9.15; P?=?0.005). Slow acetylator NAT2*7A and NAT2*6B genotypes occurred in 10.31% of PCa but in none of BPH patients (P?=?0.0007). The control health population confirmed the results and allowed the exclusion of possible biases caused by gender influence on genotype inheritance and by the inclusion of not diagnosed prostate diseases patients among the control individuals. We suggest that the investigation of germline polymorphisms of NAT2 gene may be useful in the assessment of Latin American patients at risk of BPH and PCa.     

NAT2*7 allele is a potential risk factor for adult brain tumors in Taiwanese population.

Arylamine N-acetyltransferase-2 (NAT2) displays extensive genetic polymorphisms that affect the rates of acetylation of drugs and toxic compounds such as amine carcinogens. The association of NAT2 polymorphisms with adult brain tumors has been unclear. To investigate whether the NAT2 genotype is a risk factor of brain tumors, we determined the frequencies of three common polymorphisms in the NAT2 gene, NAT2*5 (T341C), NAT2*6 (G590A), and NAT2*7(G857A), in brain tumor patients and in age- and gender-matched control subjects (n = 27 in each group). Genotyping was carried out using PCR-RFLP and subjects were phenotyped as a fast or slow acetylator based on the genotypes. The odds ratio of NAT2*7 allele frequency was significantly higher in patients with brain tumor than in controls (odds ratio, 6.786; 95% confidence interval, 2.06-22.37; P = 0.003); in the mean time, NAT2*4/*7 genotype was significantly more common in the patient group than in controls (odds ratio, 6.19; 95% confidence interval, 1.68-22.79; P = 0.0039). The tumors in the patients with NAT2*7 allele tended to be high-grade astrocytoma or glioblastoma multiforme (P = 0.016). In conclusion, these data suggest that the presence of NAT2*7 allele might be a potential risk factor for the development of brain tumors in Taiwan.     

N-acetyltransferase 2 genetic variants confer the susceptibility to head and neck carcinoma: evidence from 23 case–control studies

Previous evidence indicated that N-acetyltransferase 2 (NAT2) polymorphisms might be a risk factor for several cancers. A number of studies have been conducted on the association between NAT2 polymorphisms and head and neck cancer (HNC) risk. Nevertheless, the results were conflicting. Published meta-analysis on this issue has generated inconclusive results. Thus, we aimed to derive a more precise estimation of the relationship by conducting an updated meta-analysis. Published data prior to August 2013 have been searched and screened. Subgroup analysis on ethnicity, source of controls, sample size, and genotyping method were also performed. As a result, a total of 23 case–control studies including 4,028 cases and 4,872 controls were selected for analysis. Interestingly, the results showed that NAT2 polymorphisms might increase HNC risk for the overall data (OR 1.23, 95 % CI 1.01–1.49). Moreover, in subgroup analyses according to ethnicity, data showed that slow acetylators might increase HNC susceptibility among Asians (OR 1.78, 95 % CI 1.27–2.49), but not among Caucasians or mixed ethnicities. In conclusion, NAT2 polymorphism might be a low-penetrant risk factor for HNC among Asians.     

Mutation analysis of the RECQL4 gene in sporadic osteosarcomas

Osteosarcoma (OS) is the most prevalent malignant tumor among cases of Rothmund-Thomson syndrome (RTS) with germline mutations of the RECQL4 gene, a member of the RecQ helicase family. We investigated the involvement of the RECQL4 gene in the development of OS unrelated to RTS. RECQL4 mRNA was detected in 9 of 9 OS cell lines by Northern blotting and 26 of 26 OS tumors by RT-PCR. Direct sequencing of the entire coding region along with flanking splice junctions and 13 small (< 100 bp) introns in 71 OS tumors revealed 2 sites with a single-base change causing an amino acid change (G1814A for R355Q and C2474T for P441S) and one site with a 6 bp inframe deletion (4837-42delTGCACC for CT857-8del). Identical genotypes were found in corresponding normal tissues in all cases, and the frequency of each allele was not significantly different between OS and control populations. Our data indicate that the RECQL4 gene is not a frequent target for somatic mutations in sporadic OS unrelated to RTS.     

The Nudix Hydrolase 15 (NUDT15) Gene Variants among Jordanian Arab Population

Background: Nudix Hydrolase 15 gene (NUDT15) encodes nucleotide triphosphate diphosphatase which metabolizesthe purine analog drugs, such as anticancer thiopurine and anti-gout allopurinol. Genetic variants on Nudix Hydrolase15 gene (NUDT15) gene effects the drug’s hydrolyses and hence increases the susceptibility to drug-induced toxicity.The NUDT15 gene has been genotyped in various ethnic groups, however, it has not been genotyped among theMiddle Eastern Arab Jordanian population. Aim: The current study aimed to identify NUDT15 genetic variants amongJordanian Arab population. Method: The DNA samples were isolated from leukocytes of 85 unrelated JordanianArab volunteers. The coding regions of NUDT15 gene; Exon 1,2 and 3, in addition to some regions of intron 1,2 and3’UTR, were amplified using polymerase chain reaction (PCR). the PCR products were then subjected to purificationand sequenced using Applied Biosystems Model (ABI3730x1). Results: Six NUDT15 genetic variants were foundamong the volunteers.The results were as followed: A novel synonymous variant 36A>G on exon 1 (6%, 95%CI=3- 9%), the intronic IVS1 +116C>T variant on intron 1 (0.6%, 95%CI= 0-2%), the non-synonymous variant on exon3; 415C>T (0.6%, 95%CI= 0-2%), A novel non-synonymous variant on exon 3; 404C>A (0.6%, 95%CI= 0-2%) , andtwo novel variants on 3’UTR ;502G>A (2%, 95%CI= 0.5-4%) and 588T>C (0.6%, 95%CI= 0-2%). NUDT15 36A>Gwasfound to be the most common allele among Jordanians was. In silico softwares predicted that the novel NUDT15404C>A was harmful and affected NUDT15 enzyme’sstability and function. Furthermore, the frequency of NUDT15IVS1 +116C>T , among Jordanians, showed to be significantly lower from what was reported in other ethnicities withap value > 0.05 on the other hand, the frequency of 415C>T variant showed to be similar to Europeans in contrast toAsians and Indians that showed to be significantly lower (p value > 0.05). Conclusions: The frequency of NUDT15genetic variants is low among the Jordanian volunteers and significantly lower than other ethnic groups. The findings ofthis study may increase our understanding of the inter-individual variation in the response to purine analog drugs. Furtherclinical studies are needed to investigate the influence of novel NUDT15 404C>A on drug metabolism and response.     

Tumour-necrosis factor-A polymorphisms and gastric cancer risk: a meta-analysis

Inflammation is one of the early phases in the development of gastric cancer. Therefore, several studies have examined the association of polymorphisms in tumour-necrosis factor-A gene (TNF-A) with gastric cancer risk. This meta-analysis reviews and summarises published evidence for these associations. Searching several databases yielded 24 independent studies that reported on the associations between TNF-A polymorphisms and gastric cancer risk. We analysed available data for the most commonly investigated polymorphisms: TNF-A -308G>A (23 studies), TNF-A -238G>A (9 studies), and TNF-A -857C>T (5 studies). Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated in the random-effects model using the DerSimonian-Laird method. Q-statistic and I(2)-statistic were calculated to examine heterogeneity, and funnel plots were plotted to examine small study effects. The overall ORs (95% CIs) for AG and AA genotypes vs GG genotype for TNF-A -308 were 1.09 (0.94-1.27) and 1.49 (1.11-1.99), respectively. For TNF-A -238, the corresponding ORs (95% CIs) were 1.05 (0.84-1.33) and 1.25 (0.30-5.26), respectively. The overall ORs (95% CIs) for CT and TT genotypes (vs CC) for TNF-A -857 were 1.06 (0.89-1.27) and 1.57 (0.91-2.70), respectively. The statistically significant association between TNF-A -308GG and gastric cancer was limited to western populations. This association showed little heterogeneity (I(2)=0) and remained consistently strong when analyses were limited to anatomic and histologic subtypes of gastric cancer, or limited to studies in which genotype frequencies were in Hardy-Weinberg equilibrium, or limited to larger studies. These same subgroup analyses did not change results associated with other polymorphisms. In conclusion, TNF-A -308AA genotype was associated with a statistically significant increased risk of gastric cancer, whereas other studied polymorphisms were not. The association between TNF-A -857TT genotype and gastric cancer was near significant, and may become significant if more studies are published.     

Candidate genetic modifiers of individual susceptibility to renal cell carcinoma: a study of polymorphic human xenobiotic-metabolizing enzymes.

The steady increase in sporadic renal cell carcinoma (RCC) observed in industrialized countries supports the notion that certain carcinogens present in the environment (tobacco smoke, drugs, pollutants, and dietary constituents) may affect the occurrence of RCC. Many of the enzymes dealing with such environmental factors are polymorphic and may, therefore, confer variable susceptibility to RCC. This case-control study was designed to test for an association between genetic polymorphism of enzymes involved in xenobiotic metabolism and the risk of sporadic RCC. Genomic DNA was obtained from 173 patients with RCC and 211 controls of Caucasian origin. We used PCR-RFLP to investigate polymorphism for the most common alleles at two cytochrome-P450 mono-oxygenases (CYP1A1 and CYP2D6), one NAD[P]H:quinone oxidoreductase (NQO1), three glutathione S-transferases (GSTM1, GSTT1, and GSTP1), and one N-acetyltransferase (NAT2) loci. The CYP1A1 (m) "variant" genotype, which contains at least one copy of the CYP1A1 variant alleles, was found to be associated with a 2.1-fold [95% confidence interval (CI), 1.1-3.9] increase in the risk of RCC. There was also a higher risk of RCC for subjects with the CYP1A1 (m) variant genotype combined with any of the following genotypes: GSTT1 (+) "active" [odds ratio (OR), 2.3; 95% CI, 1.2-4.5], GSTP1 (m) variant (OR, 2.4; 95% CI, 1.0-5.4), or NAT2 (-) "slow acetylator" (OR, 2.5; 95% CI, 1.1-5.5). A significant association was also found for the GSTM1 (-) "null" and GSTP1 (m) genotypes combined with either NAT2 (-) (OR, 2.6; 95% CI, 1.2-5.8) or CYP1A1 (m) (OR, 3.5; 95% CI, 1.1-11.2). The CYP2D6 (-) "poor metabolizer " and the NQO1 (-) "defective" genotypes were not clearly associated with a higher risk of RCC. Our data demonstrate for the first time a significant association between a group of pharmacogenetic polymorphisms and RCC risk. These positive findings suggest that interindividual variation in the metabolic pathways involved in the functionalization and detoxification of specific xenobiotics is an important susceptibility factor for RCC in Caucasians.     

Association of DNA repair gene XRCC1 polymorphisms with head and neck cancer in Korean population

Squamous cell carcinoma of the head and neck (SCCHN), which is relatively prevalent in Korea, is believed to be induced by environmental carcinogens and host genetic factors. Accumulating evidence has shown that genetic differences in DNA repair capacity resulting from genetic polymorphism influence the risk of environmental carcinogenesis. We therefore examined the associations of genetic polymorphisms in the DNA repair genes XRCC1 with the risk of SCCHN in a Korean population (hospital-based, case-control study; 147 cases and 168 controls). Three known polymorphisms in the XRCC1 gene were genotyped: R194W(C>T) in exon 6, R280H(G>A) in exon 9 and R399G(G>A) in exon 10. Although no significant associations were apparent with R280H(G>A) and R399G(G>A), a highly significant association (p = 0.0005) of R194W(C>T) with the increased risk (OR = 2.61; 95% CI 1.53-4.46) of SCCHN was detected among patients and normal controls under dominant model. The frequency of minor allele-containing genotypes (TT and CT) was much higher in SCCHN patients (51.8%) compared to that in normal controls (30.3%) (p = 0. 0005). When considering a relatively small number of cases (n = 147) and controls (n = 168) in our study, larger studies are needed to validate the genetic effects of XRCC1 polymorphisms in Asian populations. In conclusion, the result from our study provides additional evidence of an association of the XRCC1 polymorphism (Arg194Trp) with SCCHN as markers of genetic susceptibility in the Korean population.     

Promoter polymorphisms of tumor necrosis factor-alpha are associated with risk of gastric mucosa-associated lymphoid tissue lymphoma

Genes involved in regulating antimicrobial immunity and inflammation may modulate the risk of Helicobacter pylori-associated diseases. IL-1 and TNF-alpha are major cytokines detected in H. pylori-infected tissues. We aimed to determine the role of gene polymorphisms for these cytokines and their receptors in 2 distinct H. pylori-related gastric malignancies, adenocarcinoma (GAC) and maltoma. Genotyping for IL-1beta (-31 C/T, -511 C/T), TNF-alpha (-238 G/A, -308 G/A, -857 C/T, -863 C/A, -1031 T/C), TNFR1 (-383 A/C) and TNFR2 (196 G/T) was undertaken for 70 patients with maltoma and 204 patients with noncardia GAC and compared to 210 unrelated healthy controls. Genotype frequencies showed no differences among patients with GAC or maltoma and controls for IL-1beta, TNFR1 or TNFR2. The TNF-alpha -857 T variant was significantly underrepresented in maltoma compared to controls (6.4% vs. 14.3%, p = 0.018), conferring a 3-fold decrease in risk (OR = 0.33, 95% CI 0.15-0.75). Comparison of allele frequencies between GAC and controls failed to show any statistical significance for TNF-alpha polymorphisms. We concluded that TNF-alpha -857 T itself or a neighboring gene may modify the risk of maltoma. The differences in genetic background as well as divergent clinicopathologic features between GAC and maltoma support the notion that fundamental mechanistic differences exist in these 2 well-defined H. pylori-related malignancies.     

CDKN2A and CDK4 mutation analysis in Italian melanoma-prone families: functional characterization of a novel CDKN2A germ line mutation

Physical interaction between CDKN2A/p16 and CDK4 proteins regulates the cell cycle progression through the G1 phase and dysfunction of these proteins by gene mutation is implicated in genetic predisposition to melanoma. We analysed 15 Italian melanoma families for germ line mutations in the coding region of the CDKN2A gene and exon 2 of the CDK4 gene. One novel disease-associated mutation (P48T), 3 known pathological mutations (R24P, G101W and N71S) and 2 common polymorphisms (A148T and Nt500 G>C) were identified in the CDKN2A gene. In a family harbouring the R24P mutation, an intronic variant (IVS1, +37 G>C) of uncertain significance was detected in a non-carrier melanoma case. The overall incidence of CDKN2A mutations was 33.3%, but this percentage was higher in families with 3 or more melanoma cases (50%) than in those with only 2 affected relatives (25%). Noteworthy, functional analysis established that the novel mutated protein, while being impaired in cell growth and inhibition assays, retains some in vitro binding to CDK4/6. No variant in the p16-binding region of CDK4 was identified in our families. Our results, obtained in a heterogeneous group of families, support the view that inactivating mutations of CDKN2A contribute to melanoma susceptibility more than activating mutations of CDK4 and that other genetic factors must be responsible for melanoma clustering in a high proportion of families. In addition, they indicate the need for a combination of functional assays to determine the pathogenetic nature of new CDKN2A mutations.     

DNMT3B -149 C>T and -579 G>T Polymorphisms and Risk of Gastric and Colorectal Cancer: a Meta-analysis

Background: Numerous studies have investigated associations of DNA methyltransferase (DNMT) -149 C>T and -579 G>T polymorphisms with gastric cancer (GC) and colorectal cancer (CRC) susceptibility; however, the findings are inconsistent prompting the present meta-analysis. Materials and Methods: Related studies were identified from PubMed, Google scholar, and SID until 10 October 2015. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the associations. Results: Eleven studies were included based on the search criteria for CRC and GC related to the DNMT3B 149 C>T (3,353 cases and 4,936 controls) and DNMT3B 579 G>T (1,387 cases and 2,064 controls) polymorphisms. There was no significant association overall between DNMT3B -149 and 579 polymorphisms and the risk of cancer. In the stratified analysis by cancer type, DNMT3B 579G>T polymorphism was associated with the risk of CRC and GC. While the DNMT3B -149C/T polymorphism was related with a significantly increased risk of CRC in two tested models, dominant (GG+GT vs. TT: OR 0.51, 95 % CI 0.38-0.69; P = 0.00, Pheterogeneity=0.69, I2= 0 %) and heterozygote (GT vs. TT: OR 0.50, 95 % CI 0.37-0.69; P=0.00, Pheterogeneity=0.41, I2= 0 %), no evidence of any association with GC risk was observed as in the pooled analyses. Conclusions: More studies are needed to assess associations of DNMT3B -149C/T and DNMT3B 579G>T polymorphisms with cancer in different ethnicities with large population sizes to generate comprehensive conclusions     

Association of NAD(P)H: quinone oxidoreductase 1 (NQO1) C609T polymorphism with esophageal squamous cell carcinoma in a German Caucasian and a northern Chinese population

NAD(P)H: quinone oxidoreductase 1 (NQO1) is an antioxidant enzyme, important in the detoxification of environmental carcinogens. A single base substitution (C --> T) polymorphism at nucleotide 609 (null-allele) of NQO1 gene impairs stability and function of the NQO1 protein. To investigate the association of this NQO1 polymorphism with susceptibility to esophageal squamous cell carcinoma (ESCC), the NQO1 C609T genotypes were determined by PCR-RFLP analysis in 450 patients with ESCC (257 German Caucasians and 193 northern Chinese) and 393 unrelated healthy controls (252 German Caucasians and 141 northern Chinese). Additionally, NQO1 protein expression was determined by immunohistochemistry in a subset of 74 ESCC (50 German, 24 Chinese). A significant difference in NQO1 C609T genotype distribution was observed between Caucasian healthy controls (C/C, 73.4%; C/T, 25.0%; T/T, 1.6%) and Chinese healthy controls (C/C, 34.0%; C/T, 49.7%; T/T, 16.3%) (chi(2) = 68.40, P < 0.001). The NQO1 T/T genotype significantly increased the risk for developing ESCC in both Caucasian subjects (OR = 4.62, 95% CI = 1.54-13.86) and Chinese subjects (OR = 1.81, 95% CI = 1.04-3.15), compared with the combined C/C and C/T genotypes. In Chinese subjects, this increased susceptibility was pronounced in patients with family history of upper gastrointestinal cancers (OR = 2.18, 95% CI = 1.14-4.17). Immunohistochemical analysis showed NQO1 protein expression in 53 carcinomas, whereas 21 carcinomas were negative. Negativity for NQO1 expression correlated strongly with the NQO1 genotype, being present in 8.6% of cases with C/C, 22.2% of cases with C/T and 100% of cases with T/T genotype (chi(2) = 16.60, P < 0.001). In summary, the association of the NQO1 C609T polymorphism with ESCC in genetically distinct populations makes a strong argument for its importance in carcinogenesis of ESCC in the German Caucasian and the northern Chinese population.     

Association of NAT1 and NAT2 polymorphisms to urinary bladder cancer: significantly reduced risk in subjects with NAT1*10.

The role of hereditary polymorphisms of the arylamine N-acetyltransferase 1 (NAT1) gene in the etiology of urinary bladder cancer is controversial. NAT1 is expressed in the urothelium and may O-acetylate hydroxyl amines, particularly in subjects with low NAT2 activity. Thus, NAT1 polymorphisms may affect the individual bladder cancer risk by interacting with environmental factors (smoking and occupational risks) and by interacting with the NAT2 gene. We studied the frequencies of the NAT1 haplotypes *3, *4, *10, *11, *14, *15, *17, and *22 in 425 German bladder cancer patients and 343 controls by PCR-RFLP. NAT1*10 allelic frequency was lower in bladder cancer patients (15.1%) compared with controls (20.4%; P = 0.012). Genotypes that included NAT1*10 were significantly less frequent among the cases (odds ratio adjusted for age, gender, and smoking, 0.65; 95% confidence interval, 0.46-0.91; P = 0.013). Two subtypes of NAT1*11 were detected: *11A (-344T, -40T, 445A, 459A, 640G, and 1095A) and *11C (-344T, -40T, 459A, 640G, and 1095A). The allele frequency of NAT1*11 was 4.3% in the cases versus 3.9% in the controls. The rare low-active NAT1*14A was overrepresented in the cases (P = 0.026). With regard to the NAT2 genotype, our data showed: (a) a partial linkage of NAT1*10 to NAT2*4; (b) a clear underrepresentation of NAT1*10 genotypes among rapid NAT2 genotypes in the cases studied (odds ratio, 0.39; 95% confidence interval, 0.22-0.68; P = 0.001), and (c) a gene-gene-environment interaction. NAT2*slow/NAT1*4 genotype combinations with a history of occupational exposure were 5.96 (2.96-12.0) times more frequent in cancer cases than in controls without risk occupation (P < 0.0001). Hence, our data suggest that individuals provided with NAT2*4 and NAT1*10 are at a significantly lower risk for bladder cancer, particularly when exposed to environmental risk factors.     

Analysis of the DPYD gene implicated in 5-fluorouracil catabolism in a cohort of Caucasian individuals.

PURPOSE: Complete or partial loss of dihydropyrimidine dehydrogenase (DPD) function has been described in cancer patients with intolerance to fluoropyrimidine drugs like 5-fluorouracil (5-FU) or Xeloda. The intention of this population study is to assess and to evaluate gene variations in the entire coding region of the dihydropyrimidine dehydrogenase gene (DPYD), which could be implicated in DPD malfunction. EXPERIMENTAL DESIGN: A cohort of 157 individuals was genotyped by denaturing high-performance liquid chromatography; 100 of these genotypes were compared with functional studies on DPD activity and mRNA expression. RESULTS: Twenty-three variants in coding and noncoding regions of the DPYD gene were detected, giving rise to 15 common haplotypes with a frequency of >1%. Rare sequence alterations included a frameshift mutation (295-298delTCAT) and three novel point mutations, 1218G>A (Met406Ile), 1236G>A (Glu412Glu), and 3067C>T (Pro1023Ser). DPD enzyme activity showed high variation in the analyzed population and correlated with DPD mRNA expression. In particular, the novel variants were not accompanied with decreased enzyme activity. However, a statistically significant deviation from the median DPD activity of the population was associated with the mutations 1601G>A (Ser534Asn) and 2846A>T (Asp949Val). CONCLUSION: This work presents an analysis of DPYD gene variations in a large cohort of Caucasians. The results reflect the genetic and enzymatic variability of DPD in the population and may contribute to further insight into the pharmacogenetic disorder of DPD deficiency.     

Barriers to repeat mammography: cultural perspectives of African-American, Asian, and Hispanic women

Women of minority races and ethnicities have lower mammography return rates compared to Caucasians. To better understand barriers to mammography, we conducted six focus groups with 49 women of minority races and ethnicities (19 Asian, 16 African-American, and 14 Hispanic) recruited from outpatient medical clinics in Boston. Eligible women had at least one prior mammogram and no personal history of cancer. Discussions were recorded and transcribed, and thematic content analyses were performed. African-Americans and Hispanics felt that lack of insurance was not a barrier to mammography as they were aware of free programs. Some African-Americans avoided mammograms because they were fatalistic and believed that a breast cancer diagnosis would inevitably lead to death. African-Americans agreed that social issues, such as drug and domestic abuse, made obtaining preventive health care less important. Asian participants agreed that mammogram return rates were poor because appointments took time away from work. Asian and Hispanic women identified discourteous behavior by hospital staff as a barrier. Cultural barriers to repeat mammography appear to vary among different racial groups. Interventions to improve screening among minority populations may be more successful if they address group-specific concerns.