Gli1在鼻咽癌组织中的表达及临床意义

目的:探讨神经胶质瘤相关癌基因1(Gli1)在鼻咽癌组织中的表达及其临床意义.方法:免疫组化方法检测89例鼻咽癌组织及21例正常鼻咽组织中Gli1的表达情况,分析Gli1的表达与与鼻咽癌患者临床病理参数及预后之间的关系.结果:Gli1在鼻咽癌组织的表达水平显著高于正常鼻咽组织(P＜0.01),且Gli1的表达水平与鼻咽癌的T分期、淋巴结转移程度及临床分期显著相关(P＜0.05).此外,Gli1蛋白表达越高,患者的生存时间也明显缩短.结论:Gli1在鼻咽癌组织中呈过表达,可能在鼻咽癌的发生、发展中起重要作用,Gli1有可能成为鼻咽癌治疗的新靶点之一.     

Gli1在食管鳞状细胞癌中的表达及与预后的关系

目的:探讨Hh信号通路关键因子Gli1在食管鳞状细胞癌(ESCC)中的表达及临床意义,并分析其与预后的关系.方法:食管鳞状细胞癌组织及癌旁正常食管组织各88例,采用免疫组织化学法检测Gli1的表达,另用Western-blot方法检测其中30例ESCC的Gli1的表达,Pearson卡方检验分析Gli1表达与临床病理特征之间的关系.单因素Kaplan-Meier法分析Gli1表达与预后的关系.Cox比例风险回归评估Gli1表达与预后的关系.结果:食管鳞状细胞癌组织中Gli1的表达在蛋白水平明显高于食管正常鳞状上皮,Gli1在ESCC中免疫组化阳性表达率为71.59％ (63/88),Gli1在癌旁正常食管鳞状上皮中免疫组化阳性表达率为6.82％ (6/88),差异有统计学意义(P＜0.05).Western blot法证实Gli1蛋白在ESCC组织中表达上调,与癌旁正常食管组织中的表达比较,差异有统计学意义(P ＜0.001).Gli1高表达与肿瘤病理分期及淋巴结转移密切相关(P＜0.05).单因素分析Kaplan-Meier法提示Gli1阳性表达组与阴性表达组生存率之间的差别有统计学意义(Log-rank test,P=0.005).结论:食管鳞状细胞癌中Gli1的表达比较普遍,与ESCC的预后密切相关,可作为预测转移潜能和预后判断的有价值的指标.     

Gli1蛋白及E-cadherin蛋白在宫颈癌中的表达及临床意义

目的:探讨Gli1蛋白及E-cadherin蛋白在宫颈癌中的表达及临床意义.方法:应用免疫组化SP法检测50例宫颈癌组织、30例宫颈上皮内瘤变(CIN)组织、40例正常组织中Gli1蛋白及E-cadherin蛋白的表达.结果:Gli1蛋白在宫颈癌组织中明显高于正常宫颈组织(P＜0.05),E-cadherin蛋白在宫颈癌组织中明显低于正常宫颈组织(P＜0.05).结论:Gli1蛋白的高表达及E-cadherin蛋白的低表达与宫颈癌的病理分级、临床分期、淋巴转移等密切相关,且两者在宫颈癌的表达呈负相关.     

联合检测Shh Gli1 Snail及E-cadher in在胃癌中的表达及其意义

目的:探讨Shh、Gli1、Snail及E-cadherin在胃癌中的表达及意义.方法:采用免疫组化方法检测54例胃癌组织、癌旁组织及30例正常人胃黏膜组织中Shh、Gli1、Snail及E-cadherin的表达情况,并与临床病理资料做对照分析.结果:胃癌组织中Shh、Gli1、Snail及E-cadherin阳性表达率分别为68.52%、61.11%、77.78%、25.93%;癌旁组织27.78%、24.07%、40.74%、70.37%:正常胃粘膜组织36.67%、26.67%、30.00%、96.67%.四种蛋白在胃癌组织和癌旁组织中的表达差异均具有统计学意义(P＜0.05).Shh、Gli1及Snail在癌旁组织及正常胃黏膜组织中的表达差异均无统计学意义(P＜0.05),E-eadherin有统计学意义(P＜0.05);四种蛋白的表达均与胃癌的分化程度、淋巴结转移相关(P＜0.05),其中Shh、Gli1及Snail与胃癌浸润深度有关(P＜0.05),而E-cadherin 无关(P＞0.05);四种蛋白的表达与性别、年龄、位置及远处转移均无相关性(P＞0.05);Shh、Gli1和Snail三者之间在胃癌中的表达呈正相关(P＜0.05),而这三个蛋白表达与E-cadherin呈负相关(P＜0.05).结论:Hedgehog信号通路与上皮间质转换(epithelial-mesenchymal transition,EMT)分子在胃癌组织中皆异常表达,提示异常激活的Hedgehog信号通路可能引起EMT分子的异常表达.这在胃癌的发生发展中可能起到一定的作用.     

胃癌组织HIF-1α和iNOS表达及其意义

目的:探索缺氧诱导因子1α(HIF-1α)和诱导型一氧化氮合酶 (iNOS) 在胃癌组织中的表达水平及两者相关性.方法:采用免疫组化SP法检测85例胃癌组织和癌旁正常胃组织中的HIF-1α和iNOS的表达,并分析其相互关系.结果:HIF-1α和iNOS在胃癌组织中的表达水平(76.47%和71.76%)明显高于癌旁正常胃组织中(0)的表达水平(P＝0.000), HIF-1α和iNOS的表达与胃癌的临床TNM分期、浸润程度和淋巴结转移有关(P<0.05),与组织学类型无关(P>0.05), HIF-1α的表达与iNOS的表达呈正相关r=0.761, P<0.05. 结论: HIF-1α可能通过上调iNOS的蛋白表达促进肿瘤血管生成, HIF-1α与iNOS的高表达与胃癌的发生、浸润和转移密切相关.     

胃癌组织中Caveolin-1,Paxillin的表达及其临床生物学意义

目的:探讨Caveolin-1和Paxillin在正常胃黏膜,胃上皮内瘤变和胃腺癌组织中的表达及其与胃癌发生发展和浸润转移的关系.方法: 应用SP法检测20例正常胃黏膜、30例胃上皮内瘤变、58例胃腺癌组织中Caveolin-1和Paxillin的表达.结果: 正常胃黏膜、上皮内瘤变、胃腺癌组织中,Caveolin-1的阳性率呈递减趋势,组间差异有统计学意义(P<0.05),Caveolin-1 表达与分化程度、TNM分期、淋巴结转移有关(P<0.05);Paxillin阳性率在胃癌组织与其他两组的表达差异有统计学意义(P<0.05),Paxillin表达与年龄、分化程度、TNM分期、淋巴结转移、脉管转移有关(P<0.05).结论: caveolin-1和Paxillin表达降低或缺失在胃癌的浸润转移等恶性进展过程中起重要作用;Paxillin与胃癌的发生密切相关;胃癌中Caveolin-1蛋白和Paxillin蛋白表达呈正相关.     

Versican和TGF-β1在胃癌中的表达及临床意义

目的:研究胃癌组织中Versican和TGF-β1的表达及其与胃癌细胞增殖的关系。方法:用免疫组织化学方法检测80例胃癌组织和30例癌旁正常组织中Versican、TGF-β1和Ki-67的表达。结果:Versican在胃癌中的阳性率显著高于正常胃黏膜(P=0.001）。主要表达于胃癌间质纤维母细胞的胞浆，且与胃癌的分化程度、临床分期及淋巴结转移显著相关（P<0.05）；胃癌中TGF-β1的阳性率和Ki-67表达均显著高于正常胃黏膜（P<0.001），且均与浸润深度、临床分期和淋巴结转移相关（P<0.05）；在胃癌组织中Versican与TGF-β1的表达呈正相关（r=0.256，P=0.022）。结论:胃癌组织中Versican和TGF-β1的表达异常增高，二者均可促进胃癌细胞的生长，并且与胃癌的临床病理特征有关，为胃癌的治疗提供了潜在的靶点。     

GIi1和Foxm1在胃癌中的表达及其临床意义

  目的  探讨Ihedgehog信号通路分子Glil与转录因子Foxml在胃癌中的表达及其与临床病理特征的关系。  方法  收集临床胃癌病理标本70例及其相应癌旁正常组织30例, 采用免疫组化SP法检测G1i1与Foxml蛋白在胃癌及正常组织中的表达, 分析两者的相关性, RT-PCR检测两者mRNA在胃癌组织与正常组织的表达情况。  结果  Glil和Foxml在正常胃粘膜组织中低表达或者不表达, Glil和Foxml在胃癌中的表达明显高于正常组织, 差异具有统计学意义(P < 0.05)。Gllil在胃癌中的表达与组织分化程度、淋巴结转移相关(P < 0.05), 而Foxml在胃癌中的表达仅与淋巴结转移相关(P < 0.05), 两者的表达与患者的性别、年龄、肿瘤的大小、浸润程度无显著相关(P>0.05)。且Glil和FoXnll在胃癌组织中的表达呈正相关(r=0.897, P < 0.05)。  结论  Glil和FoXnll在胃癌中的高表达可能与胃癌的发生发展有关, 两者的正相关说明在胃癌的发生中两者有协同及相互调节的作用j两者联合检测可以成为胃癌检测、判断预后的指标, 对新药物的开发及对胃癌化疗有一定的指导作用。      

自噬因子Beclin 1和LC3表达与胃癌临床病理特征的相关性研究

目的 探讨自噬因子Beclin 1和LC3表达与胃癌临床病理特征的相关性.方法 采用免疫组织化学方法,检测胃癌组织中自噬因子Beclin 1和LC3的表达情况.结果 Beclin 1蛋白在胃癌组织中的表达率为42.5%(51/120),在癌旁组织其表达率为93.3%(112/120),两者比较有显著性差异(χ2=21.3,P<0.05);LC3蛋白在胃癌组织中的表达率为90.0%(108/120),明显高于癌旁组织的表达率(29.3%,34/120),两者有显著性差异(χ2=24.8,P<0.05).Beclin 1和LC3蛋白表达与胃癌肿瘤分化程度和淋巴结转移密切相关,P<0.05.结论 自噬因子Beclin1和LC3表达可能与胃癌的发生发展有关.     

胃癌缺氧诱导因子-1α与bcl-XL表达的关系

目的 研究缺氧诱导因子-1α(HIF-lα)与bcl-XL在胃癌中表达的相互关系,探讨它们在胃癌的发生、发展、浸润和转移中的作用.方法 应用免疫组织化学SP法检测54例胃癌中HIF-1α、bcl-XL的表达情况,采用SPSS12.0软件包进行统计分析,并应用该软件包对HIF-1α、bcl-XL在胃癌中的表达情况作相关分析.探讨HIF-lα、bcl-XL与胃癌临床病理因素的关系.结果 HIF-1α在胃癌中的表达率(74.07%)明显高于正常胃组织(0),两者比较差异有统计学意义(P＜0.01);HIF-1α的表达与胃癌TNM分期、肿瘤浸润深度和淋巴结转移显著相关(P＜0.05或P＜0.01).bcl-XL在胃癌和正常胃组织中阳性率分别为53.7%和33.3%(P＜0.05);bcl-XL阳性率与胃癌组织学分级、TNM分期、淋巴结转移显著相关(P＜0.05).胃癌组织中HIF-1α与bcl-XL的表达呈正相关(r=0.41,P＜0.05).结论 HIF-1α和bcl-XL在胃癌的发生、发展中起重要作用,联合检测可作为判断胃癌恶性程度和预后的指标.     

Polymorphisms in GSTM1, GSTT1 and CYP1A1 and risk of pancreatic adenocarcinoma

A prospective study of 149 unselected incident cases of pancreatic adenocarcinoma and 146 ethnically-matched controls found no associations between GSTM1 (adjusted odds ratio (AOR) 1.14), GSTT1 (AOR: 1.19) and CYP1A1 (AOR: 1.08) polymorphisms and pancreatic cancer susceptibility. Smoking and drinking status did not affect results. These polymorphisms do not appear to be important gene modifiers in pancreatic cancer.     

GSTM1, GSTT1 and GSTP1 polymorphisms and lung cancer risk

Previous studies have suggested that GST genotypes may play a role in determining susceptibility to lung cancer, though the data are often conflicting. In this study we investigated GSTM1, GSTT1 and GSTP1 status in relation to lung cancer risk in patients attending a Manchester bronchoscopy clinic. Cases were all patients (n=94) currently with, or with a history of, tumours of the lung, trachea or bronchus. The control group were all other patients (n=165) who were free of benign and malignant tumours both at the time of, or prior to, diagnosis. All patients were interviewed for information on lifestyle risk factors, and DNA extracted from bronchial lavage and blood samples was used for genotyping. GSTM1 null genotype was associated with decreased lung cancer risk (odds ratio (OR) 0.50, 95% confidence interval (CI) 0.29–0.87), particularly among men (OR 0.43, 95% CI 0.21–0.87) and those above the median age (OR 0.33, 95% CI 0.15–0.70). No difference in GSTT1 and GSTP1 genotype distribution was seen between cases and controls. The GSTM1 null genotype was associated with a decreased risk of squamous cell carcinoma: the OR, adjusted for age, sex and pack years was 0.32 (95% CI 0.12–0.82). As previous studies have reported that the GSTM1 null genotype is associated with an increased lung cancer risk, further work is required to determine whether the observed association is true, or whether it arises from bias or confounding factors.     

Polymorphisms in CYP1B1, GSTM1, GSTT1 and GSTP1, and susceptibility to breast cancer

Polymorphisms in the cytochrome P450 1B1 (CYP1B1) and glutathione S-transferase (GST) drug metabolic enzymes, which are responsible for metabolic activation/detoxification of estrogen and environmental carcinogens, were analyzed for their association with breast cancer risk in 541 cases and 635 controls from a North Carolina population. Each polymorphism, altering the catalytic function of their respective enzymes, was analyzed in Caucasian and African-American women. As reported in previous studies, individual polymorphisms did not significantly impact breast cancer risk in either Caucasian or African-American women. However, African-American women exhibited a trend towards a protective effect when they had at least one CYP1B1 119S allele (OR=0.53; 95% CI=0.20-1.40) and increased risk for those women harboring at least one CYP1B1 432V allele (OR=5.52; 95% CI=0.50-61.37). Stratified analyses demonstrated significant interactions in younger (age < or =60) Caucasian women with the CYP1B1 119SS genotype (OR=3.09; 95% CI=1.22-7.84) and younger African-American women with the GSTT1 null genotype (OR=4.07; 95% CI=1.12-14.80). A notable trend was also found in Caucasian women with a history of smoking and at least one valine allele at GSTP1 114 (OR=2.12; 95% CI=1.02-4.41). In Caucasian women, the combined GSTP1 105IV/VV and CYP1B1 119AA genotypes resulted in a near 2-fold increase in risk (OR=1.96; 95% CI=1.04-3.72) and the three way combination of GSTP1 105IV/VV, CYP1B1 119AS/SS and GSTT1 null genotypes resulted in an almost 4-fold increase in risk (OR=3.97; 95% CI=1.27-12.40). These results suggest the importance of estrogen/carcinogen metabolic enzymes in the etiology of breast cancer, especially in women before the age of 60, as well as preventative measures such as smoking cessation.     

CYP1B1 and hormone-induced cancer

Cancers in hormone-responsive tissues (e.g., breast, ovary, endometrium, prostate) occur at high incidence rates worldwide. However, their genetic basis remains poorly understood. Studies to date suggest that endogenous/exogenous oestrogen and environmental carcinogens may play a role in development and/or progression of hormone-induced cancers via oxidative oestrogen metabolism. Cytochrome P450 1B1 is a key enzyme in its oestrogen metabolism pathway, giving rise to hydroxylation and conjugation. Although CYP1B1 is expressed in many cancers, particularly high levels of expression are observed in oestrogen-mediated disease. CYP1B1 is more readily found in tumour tissue compared to normal. Given the role of CYP1B1 in pro-carcinogen and oestrogen metabolism, polymorphisms in CYP1B1 could result in modifications in its enzyme activity and subsequently lead to hormone-mediated carcinogenesis. CYP1B1 may also be involved in progression of the disease by altering the tissue response to hormones and clinical response to chemotherapy. The exact mechanism behind these events is complex and unclear. Only a few functional single nucleotide polymorphisms of CYP1B1 are known to result in amino acid substitutions and have been extensively investigated. Studies examining the contribution of different CYP1B1 alleles to hormone-mediated cancer risks are inconsistent. The main focus of this review is to appraise the available studies linking the pathogenesis of the hormone-induced cancers to various CYP1B1 polymorphisms. Additionally, we explore the role of a neuronal protein, γ-synuclein, in CYP1B1-mediated pathogenesis.     

Genetic polymorphisms of CYP1A1, GSTM1 and GSTT1 genes and lung cancer risk

Genetic polymorphisms of the genes encoding for the xenobiotic metabolizing enzymes result in individual variations in the efficiency of detoxification of environmental carcinogens, and have been extensively associated with variable risk for lung neoplasms in different ethnic and environmental backgrounds. In this study, using PCR-RFLP based assays, we investigated the distribution of genetic polymorphisms in CYP1A1, GSTM1 and GSTT1 genes in Greek lung cancer patients (N=122) and healthy controls (N=178). The frequency of CYP1A1 m1 homozygous genotype was 0.04 in patients and 0.02 in controls (detected in 4.10% of patients and in 1.69% of controls, respectively), that of GSTM1 null genotype was 0.52 in patients and 0.54 in controls, whereas those of GSTT1 null genotype was 0.17 and 0.11, in patients and controls, respectively. The GSTM1 null genotype was more frequent in adenocarcinoma, as well as in lung cancer patients with history of chronic obstructive pulmonary disease (COPD). The GSTT1 null genotype correlated with advanced age of the patients at the time of diagnosis. Three combinations of rare genotypes - in subjects carrying simultaneously deviations from the common genotype in more than one gene - were over-represented in lung cancer patients, compared to control population, and were furthermore significantly associated with history of heavy tobacco consumption in lung cancer patients. The results imply involvement of specific genotype combinations of CYP1A1, GSTM1 and GSTT1 alleles in the development of lung cancer in heavy smokers.     

Genetic polymorphisms of SULT1A1 and SULT1E1 and the risk and survival of breast cancer.

We examined whether common single nucleotide polymorphisms (SNP) in SULT1A1 (c.779G>A, *14A>G, and *85C>T) and SULT1E1 (IVS1-447C>A, IVS4-1653T>C, and *959G>A) genes influenced the risk and survival of breast cancer. Our study population consisted of 989 histologically confirmed sporadic breast cancer patients and 1,054 controls without history of cancer recruited from three teaching hospitals in Seoul. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated by logistic regression model. In the survival analysis for 529 breast cancer patients with completed treatments, the hazard ratios (HR) were calculated with Cox proportional hazard model. Women with the SULT1E1 *959 GA/AA genotype had a moderately decreased breast cancer risk compared with those with the GG genotypes (OR, 0.8; 95% CI, 0.70-1.00). When the haplotypes were considered, the homozygous *959 AA genotype together with the IVS4-1653 T>C base change (CTA-CCA haplotype) was associated with halved breast cancer risk (OR, 0.5; 95% CI, 0.24-0.88) compared with the wild type CTG-CTG haplotype. No other significant overall association was observed between the SULT1A1 and SULT1E1 SNPs nor haplotypes and breast cancer risk. When stratified by survival, patients with the SULT1E1 IVS4-1653 TC/CC genotypes showed a >3-fold risk of recurrence (HR, 3.2; 95% CI, 1.39-7.48) compared with those with the TT genotype. Moreover, when the haplotypes were considered, the SULT1E1 *959 G>A base change together with the IVS4-1653 T>C base change (CTG-CCA haplotype) was associated with a >4-fold risk of breast cancer (OR, 4.2; 95% CI, 1.15-15.15). These findings suggest that genetic polymorphisms of SULT1E1 are associated with increased risk and a disease free survival of breast cancer in Korean women.     

CYP1A1, GSTM1, and GSTP1 genetic polymorphisms and urinary 1-hydroxypyrene excretion in non-occupationally exposed individuals.

The CYP1A1 and glutathione S-transferase enzymes (e.g., GSTM1 and GSTP1) are involved in the activation and conjugation of polycyclic aromatic hydrocarbons (PAHs), respectively, and are controlled by genes that are polymorphic. The CYP1A1*2 allelic variant has been associated with elevated urinary 1-hydroxypyrene (1-OHP), a proposed marker for internal dose of activated PAHs, in coke-oven workers. We investigated whether this association could be observed at low exposure levels, such as those experienced by the general population. We conducted a cross-sectional study among 188 individuals (106 Japanese, 60 Caucasians, and 22 Hawaiians) who were selected as controls in a population-based case-control study and provided lifestyle information, a 12-h urine specimen, and a blood sample. 1-OHP was analyzed by high-performance liquid chromatography after enzymatic hydrolysis. Lymphocyte DNA was used for PCR-based genotyping. Smokers excreted twice as much 1-OHP (geometric mean, 0.51 nmol/12 h) as nonsmokers (geometric mean, 0.27 nmol/12 h; P = 0.006). Overall and among nonsmokers, 1-OHP urinary levels did not differ by CYP1A1, GSTM1, or GSTP1 genotypes. However, after adjusting for age, ethnicity, and number of cigarettes per day, smokers with at least one CYP1A1*2 variant allele excreted 2.0-fold more 1-OHP than smokers with the wild-type genotype (P = 0.02). Similar results were obtained for the CYP1A1*3 variant allele. The present data add to the growing evidence suggesting that individuals with the (linked) CYP1A1*2 or *3 variant alleles have a greater capacity to activate PAHs from tobacco smoke and occupational exposure and, as a result, are at greater risk for PAH-related cancers, especially certain respiratory cancers.     

CYP1A1, GSTM1, and GSTT1 polymorphisms and breast cancer risk in Brazilian women

The frequency of CYP1A1 (CYP1A1*2A), GSTM1, and GSTT1 polymorphisms, as well as the main risk factors associated with breast cancer were studied in Brazilian women, with malignant breast cancer (n=128), or age-matched controls (n=256). Only a family history of breast cancer presented a significant risk (OR=3.00, CI=1.27-7.06). Among non-whites, the CYP1A1*2A allele was underrepresented among patients. Statistical analysis indicated that this polymorphism may decrease the risk of breast cancer among these individuals, particularly after adjusting for the risk presented by selected risk factors (OR=0.30, 95% CI=0.12-0.76).     

Methoxyestrogens exert feedback inhibition on cytochrome P450 1A1 and 1B1

Cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1) catalyze the oxidative metabolism of 17 beta-estradiol (E2) to catechol estrogens (2-OHE2 and 4-OHE2) and estrogen quinones, which may lead to DNA damage. Catechol-O-methyltransferase catalyzes the methylation of catechol estrogens to methoxyestrogens (2-MeOE2, 2-OH-3-MeOE2, and 4-MeOE2), which simultaneously lowers the potential for DNA damage and increases the concentration of 2-MeOE2, an antiproliferative metabolite. In this study, we showed that CYP1A1 and CYP1B1 recognized as substrates both the parent hormone E2 and the methoxyestrogens. Using purified recombinant enzymes, we demonstrated that CYP1A1 and CYP1B1 O-demethylated the methoxyestrogens to catechol estrogens according to Michaelis-Menten kinetics. Both CYP1A1 and CYP1B1 demethylated 2-MeOE2 and 2-OH-3-MeOE2 to 2-OHE2, whereas CYP1B1 additionally demethylated 4-MeOE2 to 4-OHE2. Because the P450-mediated oxidation of E2 and the O-demethylation of methoxyestrogens both yielded identical catechol estrogens as products, we used deuterated E2 (E2-d4), unlabeled methoxyestrogens, and gas chromatography/mass spectrometry to examine both reactions simultaneously. Kinetic analysis revealed that methoxyestrogens acted as noncompetitive inhibitors of E2 oxidation with K(i) ranging from 27 to 153 micro M. For both enzymes, the order of inhibition by methoxyestrogens was 2-OH-3-MeOE2 > or = 2-MeOE2 > 4-MeOE2. Thus, methoxyestrogens exert feedback inhibition on CYP1A1- and CYP1B1-mediated oxidative estrogen metabolism, thereby reducing the potential for estrogen-induced DNA damage.     

Meta- and pooled analyses of GSTM1, GSTT1, GSTP1, and CYP1A1 genotypes and risk of head and neck cancer.

Sequence variation in the GSTM1, GSTT1, GSTP1, and CYP1A1 genes may potentially alter susceptibility to head and neck cancers, although evidence from previous studies has not been consistent. To explore these associations, we conducted a meta-analysis of 31 published case-control studies (4635 cases and 5770 controls) and a pooled analysis of original data from nine published and two unpublished case-control studies (2334 cases and 2766 controls). In the meta-analysis, the summary odds ratios (ORs) for head and neck cancer were 1.23 [95% confidence interval (95% CI), 1.06-1.42] for the GSTM1 null genotype, 1.17 (95% CI, 0.98-1.40) for the GSTT1 null genotype, 1.10 (95% CI, 0.92-1.31) for carrying the GSTP1 Val105 allele, and 1.35 (95% CI, 0.95-1.82) for carrying the CYP1A1 Val462 allele. The pooled analysis ORs were 1.32 (95% CI, 1.07-1.62) for the GSTM1 null genotype, 1.25 (95% CI, 1.00-1.57) for the GSTT1 null genotype, 1.15 (95% CI, 0.86-1.53) for carrying the GSTP1 Val105 allele, and 0.98 (95% CI, 0.75-1.29) for carrying the CYP1A1 Val462 allele. Increasing risk of head and neck cancer was observed with inheritance of increasing numbers of modest risk genotypes at the three GST loci (P for trend = 0.04), with the combination of carrying the GSTM1 null, GSTT1 null, and GSTP1 Val105 alleles conferring an OR of 2.06 (95% CI, 1.11-3.81). In conclusion, both the meta- and pooled analysis support modest associations of GSTM1 and GSTT1 genotypes with head and neck cancer risk, and our pooled analysis supports the notion of greater risk when genotypes at multiple GST loci are considered in a multigenic model.