GSTM1 copy number and promoter haplotype as predictors for risk of recurrence and/or second primary tumor in patients with head and neck cancer.

The objective of this study was to determine copy number variant (CNV) and promoter genetic variants in glutathione S-transferase Mu class 1 (GSTM1) and the risk of recurrence (REC)/second primary tumor (SPT) in patients with previously diagnosed early stage head and neck cancer. Among 441 subjects, 133 experienced REC and/or an SPT, while 308 had single primary disease. TaqMan real-time polymerase chain reaction was used to measure the exact copy number of GSTM1 and direct sequencing was used to determine genetic variants in the GSTM1 promoter region. Multivariate Cox regression analysis was performed to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) associated with copy number and genetic variants. REC/SPT-free survival times were compared by constructing Kaplan-Meier curves and differences between curves were tested by logrank test. Results showed a significantly decreased REC/SPT (HR = 0.57; 95% CI = 0.35-0.95) and longer REC/SPT-free survival in subjects with at least two copies of GSTM1 compared with the GSTM1 homozygous deletion, but not in those with one copy of GSTM1. The -498G, -426G, and -339T alleles were significantly associated with REC/SPT, with HRs of 0.11 (0.02-0.85), 0.28 (0.11-0.74) and 2.02 (1.07-3.82), respectively. Kaplan-Meier survival analysis showed that the -498G, -426G, and -339C alleles were also significantly associated with increased REC/SPT-free survival. Further haplotype analysis showed the haplotype P(-498G--426G--339C) carriers had decreased REC/SPT with a HR of 0.09 (95% CI 0.01-0.71) and increased REC/SPT-free survival compared with those with haplotype P(-498C--426A--339T). The P(-498C--426A--339T)-containing reporter construct had significantly increased luciferase expression. These results suggest that the GSTM1 CNV and promoter haplotype are better predictors of REC/SPTs of head and neck cancer than just measuring the presence/absence of GSTM1.

Association between GSTM1 copy number, promoter variants and susceptibility to urinary bladder cancer.

This study sought to determine the role of copy number variants (CNV) combined with other genetic variants in the Glutathione S-transferases Mu class1 (GSTM1) promoter in the development of urinary bladder cancer. TaqMan real-time PCR and direct sequencing were used to determine genetic variants. Haploblocks and haplotype were constructed and estimated by Haploview and Phase, respectively. Logistic regression revealed a significantly decreased bladder cancer risk in subjects with at least 2 copies of GSTM1 (OR=0.56; 95%CI=0.39-0.81) but not in those with 1 copy of the gene. GSTM1 promoter screening revealed an insertion variant (-1543TTCT) and 14 single nucleotide polymorphisms (SNPs) (-1529C>G, -1490A>G, -1143A>G, -888A>T, -498G>C, -486C>G, -471C>T, -426G>A, -344C>T, -343A>T, -341C>T, -339C>T, -304G>A, and -164C>T). Four haploblocks were evident by Haploview. There was no significant association between any single SNP/haplotype and bladder cancer risk. However, when stratified by copy number, the two copy carriers with the -1543 insertion had decreased bladder cancer risk (OR, 0.58; 95%CI, 0.32-0.10) and similar results were found in two copy carriers with -888 A, -486G, - 344 C, -343 A, -341 C allele and haplotype INS(-1543)-C(-1529)-A(-1429) in LD block 1, A(-1143)-A(-888) in LD block 2, C(-498)-G(-486)-T(-471) in LD block 3, C(-344)-A(-343)-C(-341)-C(-339) and C(-344)-A(-343)-C(-341)-T(-339) in LD block 4. These results suggest that GSTM1 CNV is a better predictor of bladder cancer susceptibility than measuring presence/absence of GSTM1 and other genetic variants also can modify bladder cancer risk.

Sequence variants in antioxidant defense and DNA repair genes, dietary antioxidants, and pancreatic cancer risk.

To investigate whether polymorphisms in genes related to oxidative stress act alone or in combination with antioxidants to modulate pancreatic cancer risk. Cases (n=189), ages ≥ 20 years, were ascertained in 1994-1998 from all hospitals in the Twin Cities and the Mayo Clinic. Controls (n=486) were randomly selected from the general population and frequency matched to cases by age and sex. After adjustment for confounders, individuals who were homozygous or heterozygous for the variant allele of SOD2 polymorphism (Ala16Val, rs4880) experienced a 43% lower risk than those who were homozygous for the wild-type allele [OR (95% CI): 0.57 (0.37, 0.89)]. Conversely, an increased risk was observed for the variant allele of hOGG1 polymorphism (Ser326Cys, rs1052133) compared with the wild-type allele [OR (95% CI) for Ser/Cys or Cys/Cys vs. Ser/Ser: 1.57 (1.04, 2.39)]. The protective effect of the variant allele of SOD2 was more pronounced among subjects with a low dietary intake (

Ultraperformance liquid chromatography-tandem mass spectrometry method for biomonitoring cooked meat carcinogens and their metabolites in human urine.

The cooked meat carcinogens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and their principal metabolites produced by cytochrome P450 and/or uridine diphosphate glucuronosyl transferases were simultaneously measured at the parts per trillion level in urine of omnivores, by ultraperformance liquid chromatography (UPLC) with a Michrom Advance CaptiveSpray source and a triple stage quadrupole mass spectrometer. Quantitation was performed in the selected reaction monitoring mode. The UPLC method is much more rapid and sensitive than our earlier capillary HPLC method: the duty cycle of the UPLC method is 19 min compared to 57 min for capillary HPLC. The performance of the UPLC assay was evaluated with urine samples from three subjects over 4 different days. The intraday and interday precisions of the estimates of PhIP, MeIQx, and their metabolites, reported as the coefficients of variation, were ≤10%. The limit of quantification (LOQ) values for PhIP and MeIQx were about 5 pg/mL, whereas the LOQ values of their metabolites ranged from 10 to 40 pg/mL. Furthermore, the identities of the analytes were corroborated by acquisition of full scan product ion spectra, employing between 0.5 and 5 pg of analyte for assay.

Functional genetic variants in the 3'-untranslated region of sulfotransferase isoform 1A1 (SULT1A1) and their effect on enzymatic activity.

Sulfotransferase isoform 1A1 (SULT1A1) is the most highly expressed hepatic sulfotransferase and is involved in the biotransformation of a wide variety of endo- and xenobiotics. A common single nucleotide polymorphism (SNP) in the coding region of SULT1A1, several proximal promoter SNPs, and copy number variation (CNV) are associated with altered enzymatic activity, but these variants do not fully account for the observed variation of SULT1A1 activity in human populations. In order to identify additional SNPs modulating SULT1A1 activity, we examined the 3'-untranslated region (UTR) of SULT1A1 in 97 liver samples. Direct sequencing revealed that two SNPs in the 3'-UTR (902A > G [rs6839] and 973C > T [rs1042157]) and one SNP in the 3'-flanking region (1307G > A [rs4788068]) were common. These SNPs are in absolute linkage disequilibrium with each other and in tight linkage with SULT1A1 1/2 (linkage coefficient D' 0.83) and are significantly associated with SULT1A1 messenger RNA (p = 0.001, 0.029, 0.021) and enzymatic activity (p = 0.022, 0.012, 0.027). We then examined the collective effects of 3'-UTR SNPs, SULT1A1 1/2, and CNV on SULT1A1 activity in 498 Caucasian and 127 African-American subjects by haplotype analysis. This analysis revealed that SULT1A1 1/2 does not contribute to the variation in SULT1A1 enzymatic activity when the 3'-UTR SNPs are included in the statistical model. Two major haplotypes (ACG and GTA) were significantly correlated with SULT1A1 activity, and when stratified by copy number, the SULT1A1 3'-UTR SNPs remain significantly associated with SULT1A1 enzymatic activity in Caucasians, but not in African-Americans. Subsequent functional characterization revealed that a microRNA, miR-631, regulates SULT1A1 expression in a genotype-specific manner.

Identification of carcinogen DNA adducts in human saliva by linear quadrupole ion trap/multistage tandem mass spectrometry.

DNA adducts of carcinogens derived from tobacco smoke and cooked meat were identified by liquid chromatography-electrospray ionization/multistage tandem mass spectrometry (LC-ESI/MS/MS(n)) in saliva samples from 37 human volunteers on unrestricted diets. The N-(deoxyguanosin-8-yl) (dG-C8) adducts of the heterocyclic aromatic amines 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-9H-pyrido[2,3-b]indole (AalphaC), 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), and the aromatic amine, 4-aminobiphenyl (4-ABP), were characterized and quantified by LC-ESI/MS/MS(n), employing consecutive reaction monitoring at the MS(3) scan stage mode with a linear quadrupole ion trap (LIT) mass spectrometer (MS). DNA adducts of PhIP were found most frequently: dG-C8-PhIP was detected in saliva samples from 13 of 29 ever-smokers and in saliva samples from 2 of 8 never-smokers. dG-C8-AalphaC and dG-C8-MeIQx were identified solely in saliva samples of three current smokers, and dG-C8-4-ABP was detected in saliva from two current smokers. The levels of these different adducts ranged from 1 to 9 adducts per 10(8) DNA bases. These findings demonstrate that PhIP is a significant DNA-damaging agent in humans. Saliva appears to be a promising biological fluid in which to assay DNA adducts of tobacco and dietary carcinogens by selective LIT MS techniques.

Polymorphisms in inflammatory genes, plasma antioxidants, and prostate cancer risk.

BACKGROUND: Presence of xenotropic murine leukemia virus-related virus and chronic inflammation in prostate tumor suggests that inflammation plays a role in prostate cancer etiology. This study investigated whether variants in inflammatory genes act alone or interact with plasma antioxidants to influence prostate cancer risk in a population-based case-control study in Central Arkansas. METHODS: Cases (n = 193) were men, aged 40-80, diagnosed with prostate cancer in three major hospitals in 1998-2003, and controls (n = 197) were matched to cases by age, race, and county of residence. RESULTS: After adjustment for confounders, polymorphisms in COX-2 (rs689466) and IL-8 (rs4073) were not significantly associated with prostate cancer risk. However, apparent interactions were observed between these genetic variants and plasma antioxidants on the risk of this malignancy. The protective effect of the mutant allele of the COX-2 polymorphism was more pronounced among subjects with high plasma levels of beta-cryptoxanthin, lycopene, beta-carotene, or selenium (>or=median) [e.g., OR (95% CI): 0.37 (0.15, 0.86) (AG/GG vs. AA) for beta-cryptoxanthin]. Conversely, the promoting effect of the variant allele of the IL-8 polymorphism was more remarkable in subjects with low plasma levels of Lutein/zeaxanthin, beta-cryptoxanthin, and beta-carotene (

A comprehensive approach to the profiling of the cooked meat carcinogens 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, and their metabolites in human urine.

A targeted liquid chromatography/tandem mass spectrometry-based metabolomics type approach, employing a triple stage quadrupole mass spectrometer in the product ion scan and selected reaction monitoring modes, was established to profile 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and their principal metabolites in the urine of omnivores. A mixed-mode reverse phase cation exchange resin enrichment procedure was employed to isolate MeIQx and its oxidized metabolites, 2-amino-8-(hydroxymethyl)-3-methylimidazo[4,5-f]quinoxaline (8-CH(2)OH-IQx) and 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH), which are produced by cytochrome P450 1A2 (P450 1A2). The phase II conjugates N(2)-(beta-1-glucosiduronyl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and N(2)-(3,8-dimethylimidazo[4,5-f]quinoxalin-2-yl)-sulfamic acid were measured indirectly, following acid hydrolysis to form MeIQx. The enrichment procedure permitted the simultaneous analysis of PhIP, N(2)-(beta-1-glucosidurony1)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, N3-(beta-1-glucosidurony1)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-1-methyl-6-(4'-hydroxy)-phenylimidazo[4,5-b]pyridine (4'-HO-PhIP), and the isomeric N(2)- and N3-glucuronide conjugates of the carcinogenic metabolite, 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP), which is formed by P450 1A2. The limit of quantification (LOQ) for MeIQx, PhIP, and 4'-HO-PhIP was approximately 5 pg/mL; the LOQ values for 8-CH(2)OH-IQx and IQx-8-COOH were, respectively, <15 and <25 pg/mL, and the LOQ values for the glucuronide conjugates of PhIP and HONH-PhIP were 50 pg/mL. The metabolism was extensive; less than 9% of the dose was eliminated in urine as unaltered MeIQx, and <1% was eliminated as unaltered PhIP. Phase II conjugates of the parent amines accounted for up to 12% of the dose of MeIQx and up to 2% of the dose of PhIP. 8-CH(2)OH-IQx and IQx-8-COOH accounted for up to 76% of the dose of MeIQx, and the isomeric glucuronide conjugates of HONH-PhIP accounted for up to 33% of the dose of PhIP that were eliminated in urine within 10 h of meat consumption. P450 1A2 significantly contributes to the metabolism of both HAAs but with marked differences in substrate specificity. P450 1A2 primarily catalyzes the detoxification of MeIQx by oxidation of the 8-methyl group, whereas it catalyzes the bioactivation of PhIP by oxidation of the exocyclic amine group.

Polymorphisms in hOGG1 and XRCC1 and risk of prostate cancer: effects modified by plasma antioxidants.

OBJECTIVES: To investigate whether polymorphisms in genes involved in the repair of oxidative DNA damage, modulate, and/or interact with antioxidants to influence prostate cancer risk in a population-based case-control study in Central Arkansas. Accumulating evidence indicates that oxidative stress plays a role in prostate carcinogenesis. METHODS: Cases (n = 193) included men aged 40-80 years, diagnosed with prostate cancer in 3 major hospitals in 1998-2003, and controls (n = 197) were matched to cases by age, race, and county of residence. RESULTS: After adjustment for confounders, subjects who were heterozygous or homozygous for the variant allele of the hOGG1 Ser326Cys polymorphism appeared to experience a lower risk of prostate cancer than those who were homozygous for the wild-type allele (odds ratio [OR] (95% confidence interval [CI]): 0.72 (0.46-1.10)]. Conversely, a significant increased risk was observed for individuals who carried 1 or 2 copies of the variant allele of the XRCC1 Arg399Gln polymorphism, compared with those who only harbored the wild-type allele (OR [95% CI]: 1.56 [1.01-2.45]). The above-mentioned associations were generally more pronounced among subjects with low plasma carotenoids or alpha-tocopherol (

Expression of sulfotransferase isoform 1A1 (SULT1A1) in breast cancer cells significantly increases 4-hydroxytamoxifen-induced apoptosis.

Previously, we reported a strong association of the high activity SULT1A1*1 allele and overall survival of patients receiving tamoxifen therapy, indicating that sulfation of 4-hydroxytamoxifen (4-OHT) via SULT1A1 may contribute to the therapeutic efficacy of tamoxifen treatment. In most, but not all cases, sulfation is considered to be an elimination pathway; therefore we sought to define the biological mechanism by which increased sulfation of tamoxifen could provide a therapeutic benefit. We compared the antiproliferative and apoptotic responses between MCF7-SULT1A1 expressing cells and control MCF7 pcDNA3 cells when treated with 4-OHT. We observed a greater than 30% decrease in cell proliferation in MCF7-SULT1A1 expressing cells at physiological concentrations of 4-OHT, and significant cell death in SULT1A1-expressing cells treated with 2µM 4-OHT for 48 hours compared to control cells (p<0.05). Within 24 hours of drug treatment, an 80% increase in apoptosis in SULT1A1-expressing cells was apparent when compared to similarly treated cells that did not express SULT1A1. We also observed an increase in endonuclease G, the primary endonuclease expressed in ER-dependent breast cancer cells, which participates in caspaseindependent apoptosis. These data confirm that SULT1A1-mediated biotransformation of 4-OHT is important in the efficacy of 4-OHT cytotoxicity in breast tumors, and reveals a potential role for sulfated metabolites in the efficacy of tamoxifen therapy.

Physical activity, diet, and pancreatic cancer: a population-based, case-control study in Minnesota.

Although mounting evidence suggests that insulin resistance is involved in pancreatic carcinogenesis, few epidemiologic studies have comprehensively investigated the role of lifestyle factors influencing this metabolic disorder in the etiology of pancreatic cancer. We sought to examine this problem in a case-control study conducted in 1994-1998 in Minnesota. Cases (n = 186), aged 20 yr or older, were ascertained from all hospitals in the metropolitan area of the Twin Cities and the Mayo Clinic; from the latter, only cases residing in the Upper Midwest of the United States were recruited. Controls (n = 554) were randomly selected from the general population and frequency matched to cases by age (within 5 yr) and sex. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using unconditional logistic regression. After adjustment for confounders, physical activity was associated with a reduced risk, but this protective effect was confined to light activity and moderate activity only (OR = 0.55, 95% CI = 0.30-0.97, P(trend) = 0.038 and OR = 0.51, 95% CI = 0.28-0.93, P(trend) = 0.07, for highest vs. lowest quartile, respectively). An increased risk was found for dietary intakes of energy and fat but was statistically significant for saturated and polyunsaturated fat only. Of note, no appreciable difference in the magnitude of the associations existed between saturated, monounsaturated, and polyunsaturated fat. Compared with individuals in the lowest quartile of fiber intake, the risk was approximately halved for those in the third (OR = 0.49, 95% CI = 0.26-0.94) and the highest quartile (OR = 0.52, 95% CI = 0.21-1.30). Our study lends support to the hypothesis that dietary and other lifestyle factors influencing insulin resistance modulate pancreatic cancer risk.

Phenotypic CYP2A6 variation and the risk of pancreatic cancer.

OBJECTIVE: Cytochrome P450 2A6 (CYP2A6) is an important metabolic enzyme capable of activating several procarcinogens, including dietary and tobacco-specific nitrosamines, which have been linked to pancreatic cancer. Positive associations between high CYP2A6 activity and lung and colorectal cancers have been reported. This is the first investigation of CYP2A6 activity and pancreatic cancer. DESIGN: In this case-control study of cancer of the exocrine pancreas, phenotypic CYP2A6 activity was measured using a ratio of urinary caffeine metabolites. Demographic, smoking, dietary and medical information were obtained by questionnaire. CYP2A6 phenotype, which is not influenced by smoking status, was measured for 90 cases and 470 controls. RESULTS: When modeled as a continuous variable, and adjusted for age, sex, race, education, current smoking status and chronic pancreatitis, the odds ratio (OR) per one unit of the natural log of the CYP2A6 ratio was 1.52 (95% confidence interval, CI: 1.09-2.12). In an adjusted categorical analysis, subjects in the uppermost quartile (based on controls) of CYP2A6 activity, when compared to the lower three quartiles, carried an 80% greater risk of pancreatic cancer (OR=1.80; 95% CI: 1.07-3.02). CONCLUSIONS: High levels of CYP2A6 activity, as measured by a caffeine phenotyping assay, were positively associated with pancreatic cancer in this casecontrol study among a Midwestern U.S. population.

Sulfotransferase 4A1.

In this review, we highlight the physical and enzymatic properties of the novel human sulfotransferase, SULT4A1. The gene is most highly expressed in selective regions of the brain, although work to date has failed to identify any specific endogenous substrate for the enzyme. SULT4A1 shares low homology with other human sulfotransferases. Nevertheless, it is highly conserved between species. Despite the low homology, it is structurally very similar to other cytosolic sulfotransferases with a conserved substrate binding domain, dimerization site and partial cofactor binding sites. However, the catalytic cavity is much smaller, and it has been suggested that the cofactor may not be accommodated within it. A recent link between variability in the 5'UTR of the SULT4A1 gene and schizophrenia has heightened interest in the endogenous function of the enzyme and its possible role in human disease.

Increased distributional variance of mitochondrial DNA content associated with prostate cancer cells as compared with normal prostate cells.

BACKGROUND: Mitochondria are key organelles for apoptosis, and mitochondrial DNA (mtDNA) content can regulate cancer progression. Increases in mtDNA mutations and deletions have been reported in cancer; however, a detailed investigation of mtDNA content in cancer cells has not yet been conducted. METHODS: Quantitative real-time PCR and improved extraction method were established to investigate the mtDNA content in a single prostate cell. RESULTS: The heterogeneity of mtDNA content was demonstrated between the clones of prostate cancer cell line LNCaP and individual cells in each clone. To investigate whether large distributional variance of mtDNA content is associated with cancer initiation and/or progression, we first compared PZ-HPV-7, an HPV-transformed normal prostate epithelial cell line, with CA-HPV-10, transformed from prostate cancer cells derived from the same donor. We found an enhanced distributional variance of mtDNA content in CA-HPV-10. Then, we investigated mtDNA content in individual cells in laser microdisssected cancer and adjacent normal cells from prostate cancer tissue specimens using quantitative real-time PCR method. Results showed that the mtDNA content per cell follows a higher skewed distribution in cancer cells as compared in normal cells. We also observed that mtDNA content was increased in seven of nine (78%) of prostate cancers compared to normal prostate tissue. CONCLUSIONS: These results indicate that prostate carcinogenesis may involve dysregulation of mtDNA content.

A variant of the Cockayne syndrome B gene ERCC6 confers risk of lung cancer.

Cockayne syndrome B protein (ERCC6) plays an essential role in DNA repair. However, the Cockayne syndrome caused by the ERCC6 defect has not been linked to cancer predisposition; likely due to the fact that cells with severe disruption of the ERCC6 function are sensitive to lesion-induced apoptosis, thus reducing the chance of tumorigenesis. The biological function and cancer susceptibility of a common variant rs3793784:C>G (c.-6530C>G) in the ERCC6 was examined. We show that the c.-6530C allele has lower binding affinity of Sp1 by EMSA and displays a lower transcriptional activity in vitro and in vivo. We then examined the contribution of this polymorphism to the risk of lung cancer in a case-control study with 1,000 cases and 1,000 controls. The case-control analysis revealed a 1.76-fold (P= x 10(-9)) excess risk of developing lung cancer for the c.-6530CC carriers compared with noncarriers. The c.-6530CC interacts with smoking to intensify lung cancer risk, with the odds ratio (OR)=9 for developing lung cancer among heavy smokers. Our data constituted strong evidence that ERCC6 rs3793784:C>G alters its transcriptional activity and may confer personalized susceptibility to lung cancer.

The UGT2B17 gene deletion polymorphism and risk of prostate cancer. A case-control study in Caucasians.

BACKGROUND: UDP-glucuronosyltransferase (UGT) 2B17 is a phase II metabolizing enzyme that mediates the glucuronidation of C(19) steroids. A deletion polymorphism in the UGT2B17 gene is associated with a substantial reduction in glucuronidation activity in vitro. METHODS: We examined the association between the UGT2B17 deletion polymorphism and the risk of incident prostate cancer in a population-based study from central Arkansas that included 411 Caucasian cases and 397 Caucasian controls. We developed a novel high-throughput procedure that uses real-time PCR and allelic discrimination for genotyping analysis. RESULTS: The prevalence of the UGT2B17 deletion [(0/0)] was 12% in the controls, which was consistent with previous population estimates and with Hardy Weinberg equilibrium. There was no association between the UGT2B17 deletion polymorphism and prostate cancer risk in unconditional logistic regression analysis. Compared to the wild-type group (+/+), the adjusted odds ratio (OR) was 0.89 (95% CI=0.55-1.45) for the homozygous deletion (0/0), and the OR was 0.99 (95% CI=0.73-1.35) for the heterozygote group (+/0). CONCLUSION: These findings show that the UGT2B17 deletion polymorphism is not associated with prostate cancer risk in Caucasians.

Plasma carotenoids and prostate cancer: a population-based case-control study in Arkansas.

Carotenoids possess antioxidant properties and thus may protect against prostate cancer. Epidemiological studies of dietary carotenoids and this malignancy were inconsistent, partially due to dietary assessment error. In this study, we aimed to investigate the relation between plasma concentrations of carotenoids and the risk of prostate cancer in a population-based case-control study in Arkansas. Cases (n = 193) were men with prostate cancer diagnosed in 3 major hospitals, and controls (n = 197) were matched to cases by age, race, and county of residence. After adjustment for confounders, plasma levels of lycopene, lutein/zeaxanthin, and beta-cryptoxanthin were inversely associated with prostate cancer risk. Subjects in the highest quartile of plasma lycopene (513.7 microg/l) had a 55% lower risk of prostate cancer than those in the lowest quartile (140.5 microg/l; P trend = 0.042). No apparent association was observed for plasma alpha-carotene and beta-carotene. Further adjustment for the other 4 carotenoids did not materially alter the risk estimates for plasma lycopene, lutein/zeaxanthin, and beta-cryptoxanthin but appeared to result in an elevated risk with high levels of plasma alpha-carotene and beta-carotene. The results of all analyses did not vary substantially by age, race, and smoking status. This study added to the emerging evidence that high circulating levels of lycopene, lutein/zeaxanthin, and beta-cryptoxanthin are associated with a low risk of prostate cancer.

Cystine-glutamate transporter SLC7A11 mediates resistance to geldanamycin but not to 17-(allylamino)-17-demethoxygeldanamycin.

The cystine-glutamate transporter SLC7A11 has been implicated in chemoresistance, by supplying cystine to the cell for glutathione maintenance. In the NCI-60 cell panel, SLC7A11 expression shows negative correlation with growth inhibitory potency of geldanamycin but not with its analog 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), which differs in the C-17 substituent in that the the methoxy moiety of geldanamycin is replaced by an amino group. Structure and potency analysis classified 18 geldanamycin analogs into two subgroups, "17-O/H" (C-17 methoxy or unsubstituted) and "17-N" (C-17 amino), showing distinct SLC7A11 correlation. We used three 17-O/H analogs and four 17-N analogs to test the role of the 17-substituents in susceptibility to SLC7A11-mediated resistance. In A549 cells, which are resistant to geldanamycin and strongly express SLC7A11, inhibition of SLC7A11 by (S)-4-carboxyphenylglycine or small interfering RNA increased sensitivity to 17-O/H, but had no effect on 17-N analogs. Ectopic expression of SLC7A11 in HepG2 cells, which are sensitive to geldanamycin and express low SLC7A11, confers resistance to geldanamycin, but not to 17-AAG. Antioxidant N-acetylcysteine, a precursor for glutathione synthesis, completely suppressed cytotoxic effects of 17-O/H but had no effect on 17-N analogs, whereas the prooxidant ascorbic acid had the opposite effect. Compared with 17-AAG, geldanamycin led to significantly more intracellular reactive oxygen species (ROS) production, which was quenched by addition of N-acetylcysteine. We conclude that SLC7A11 confers resistance selectively to 17-O/H (e.g., geldanamycin) but not to 17-N (e.g., 17-AAG) analogs partly as a result of differential dependence on ROS for cytotoxicity. Distinct mechanisms could significantly affect antitumor response and organ toxicity of these compounds in vivo.

Hair dye use, meat intake, and tobacco exposure and presence of carcinogen-DNA adducts in exfoliated breast ductal epithelial cells.

Diet and environmental exposures to aromatic and heterocyclic amines, and polycyclic aromatic hydrocarbons, are thought to be etiologic factors for breast cancer risk. In this study, we chose to quantify the major DNA adduct derived from one member of each of these classes of carcinogens in epithelial cell DNA isolated from human breast milk. Appreciable adducts were detected for each class, namely 2-amino-6-phenylimidazo[4,5-b]pyridine (PhIP), 4-aminobiphenyl (ABP) and benzo[a]pyrene. The effect of several metabolic genotypes on adduct levels were also investigated and higher PhIP and ABP adducts were associated with the rapid NAT2 and/or rapid NAT1 genotypes. The presence of ABP adducts was also significantly associated with the use of hair coloring products (OR=11.2, 95% CI=1.1-109.2) but not tobacco usage. These data indicate that women are exposed to several classes of dietary and environmental carcinogens and that metabolic genotype can be a susceptibility factor.