[Show abstract][Hide abstract] ABSTRACT: Evidence suggests that global methylation levels in blood cell DNA may be a biomarker for cancer risk. To date, most studies have used genomic DNA isolated from blood or urine as a surrogate marker of global DNA methylation levels in bladder tumor tissue.
A subset of 50 bladder cancer cases was selected from the New England Bladder Cancer Case-Control Study. Genomic DNA was isolated from buffy coat, buccal cells, serum, and formalin-fixed, paraffin-embedded tissue for each participant. DNA methylation at four CpG sites within the long interspersed nucleotide element (LINE-1) repetitive element was quantified using pyrosequencing and expressed as a mean methylation level across sites.
Overall, the mean percent (%) LINE-1 5-methylcytosine (%5MeC) level was highest in serum (80.47% ± 1.44%) and lowest in bladder tumor DNA (61.36% ± 12.74%) and levels varied significantly across tissue types (P = 0.001). An inverse association between LINE-1 mean %5MeC and tumor stage (P = 0.001) and grade (P = 0.002) was observed. A moderate correlation between patient-matched serum and buffy coat DNA LINE-1 %5MeC levels was found (r = 0.32, P = 0.03) but levels were uncorrelated among other matched genomic DNA samples.
The mean promoter LINE-1 %5MeC measurements were correlated between buffy coat and serum DNA samples. No correlation was observed between genomic DNA sources and tumor tissues; however a significant inverse association between tumor percent LINE-1 methylation and tumor stage/grade was found.
LINE-1 methylation measured in case blood DNA did not reflect that observed in bladder tumor tissue but may represent other factors associated with carcinogenesis.
[Show abstract][Hide abstract] ABSTRACT: Leukocyte global DNA methylation levels are currently being considered as biomarkers of cancer susceptibility and have been associated with risk of several cancers. In this study, we aimed to examine the association between long interspersed nuclear elements (LINE-1) methylation levels, as a biomarker of global DNA methylation in blood cell DNA, and renal cell cancer risk.
LINE-1 methylation of bisulfite-converted genomic DNA isolated from leukocytes was quantified by pyrosequencing measured in triplicate, and averaged across 4 CpG sites. A total of 328 RCC cases and 654 controls frequency-matched(2∶1) on age(±5years), sex and study center, from a large case-control study conducted in Central and Eastern Europe were evaluated.
LINE-1 methylation levels were significantly higher in RCC cases with a median of 81.97% (interquartile range[IQR]: 80.84-83.47) compared to 81.67% (IQR: 80.35-83.03) among controls (p = 0.003, Wilcoxon). Compared to the lowest LINE-1 methylation quartile(Q1), the adjusted ORs for increasing methylation quartiles were as follows: OR(Q2) = 1.84(1.20-2.81), OR(Q3) = 1.72(1.11-2.65) and OR(Q4) = 2.06(1.34-3.17), with a p-trend = 0.004. The association was stronger among current smokers (p-trend<0.001) than former or never smokers (p-interaction = 0.03). To eliminate the possibility of selection bias among controls, the relationship between LINE-1 methylation and smoking was evaluated and confirmed in a case-only analysis, as well.
Higher levels of LINE-1 methylation appear to be positively associated with RCC risk, particularly among current smokers. Further investigations using both post- and pre-diagnostic genomic DNA is warranted to confirm findings and will be necessary to determine whether the observed differences occur prior to, or as a result of carcinogenesis.
[Show abstract][Hide abstract] ABSTRACT: To investigate the risk of renal cell carcinoma (RCC) in Central and Eastern Europe in relation to exposure to known and suspected carcinogenic metals.
During 1999-2003, the authors conducted a hospital-based study in Czech Republic, Poland, Romania and Russia, including 1097 cases of RCC and 1476 controls. Occupational exposure to arsenic, cadmium, chromium(III), chromium(VI), lead and nickel was assessed by teams of local industrial hygiene experts, based on detailed occupational questionnaires.
The ORs for RCC were 1.55 (95% CI 1.09 to 2.21) for exposure to lead and 1.40 (95% CI 0.69 to 2.85) for exposure to cadmium. No clear monotonic exposure-response relation was apparent for either duration of exposure or cumulative exposure to either metal, although the OR for the highest category of cumulative exposure to lead was 2.25 (95% CI 1.21 to 4.19). Exposure to other metals did not entail an increased risk of RCC.
For cadmium, the lack of statistical significance of most results, potential confounding and the absence of clear dose-response relations suggest that an association with RCC is unlikely to be causal. In the case of lead, however, the elevated risk in the category of highest cumulative exposure is noteworthy and justifies further investigation.
Full-text · Article · Sep 2011 · Occupational and environmental medicine
[Show abstract][Hide abstract] ABSTRACT: The Summer Curriculum in Cancer Prevention has been sponsored by the National Cancer Institute's Cancer Prevention Fellowship Program for over two decades. This curriculum includes a 4-week course entitled "Principles and Practice of Cancer Prevention and Control." The ultimate goal of this course is to present the most current cancer prevention research to a diverse workforce of researchers and practitioners eager to address the current challenges in this field. The course covers the current status of cancer prevention research and practice, ranging from epidemiology and clinical practice, and from basic to behavioral science research. It is comprised of lectures grouped into nine modules representing broad and specific topics relevant to cancer prevention. Course participants come from a broad cross-section of career stages, professions, and research interests, and are from across the USA and other countries. Over time and in response to feedback from participants, the course has developed to meet the needs and expectations of this diverse audience, and may serve as a model for those interested in cancer prevention education and training in other countries.
Preview · Article · Jul 2011 · Journal of Cancer Education
[Show abstract][Hide abstract] ABSTRACT: Epidemiologic studies are reporting associations between lead exposure and human cancers. A polymorphism in the 5-aminolevulinic acid dehydratase (ALAD) gene affects lead toxicokinetics and may modify the adverse effects of lead.
The objective of this study was to evaluate single-nucleotide polymorphisms (SNPs) tagging the ALAD region among renal cancer cases and controls to determine whether genetic variation alters the relationship between lead and renal cancer. Occupational exposure to lead and risk of cancer was examined in a case-control study of renal cell carcinoma (RCC). Comprehensive analysis of variation across the ALAD gene was assessed using a tagging SNP approach among 987 cases and 1298 controls. Occupational lead exposure was estimated using questionnaire-based exposure assessment and expert review. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression.
The adjusted risk associated with the ALAD variant rs8177796(CT/TT) was increased (OR = 1.35, 95%CI = 1.05-1.73, p-value = 0.02) when compared to the major allele, regardless of lead exposure. Joint effects of lead and ALAD rs2761016 suggest an increased RCC risk for the homozygous wild-type and heterozygous alleles ((GG)OR = 2.68, 95%CI = 1.17-6.12, p = 0.01; (GA)OR = 1.79, 95%CI = 1.06-3.04 with an interaction approaching significance (p(int) = 0.06). No significant modification in RCC risk was observed for the functional variant rs1800435(K68N). Haplotype analysis identified a region associated with risk supporting tagging SNP results.
A common genetic variation in ALAD may alter the risk of RCC overall, and among individuals occupationally exposed to lead. Further work in larger exposed populations is warranted to determine if ALAD modifies RCC risk associated with lead exposure.
[Show abstract][Hide abstract] ABSTRACT: Previous analyses from the National Health and Nutrition Examination Survey (NHANES III) have found that elevated blood lead levels may be associated with cardiovascular mortality, cancer mortality, and all-cause mortality. The 5-aminolevulinic acid dehydratase (ALAD) G177C genetic polymorphism (rs 1800435) affects lead toxicokinetics and may alter the adverse effects of lead exposure. We examined whether the ALAD G177C single nucleotide polymorphism (SNP) affects the relationship between lead and mortality.
We analyzed a subset of 3349 genotyped NHANES III participants at least 40 years of age. Using Cox proportional hazards regression, we estimated the relative risk of all-cause, cardiovascular disease, and cancer mortality by ALAD genotype, and by blood lead levels (<5 μg/dL vs. ≥5 μg/dL). We also tested whether the ALAD genotype modified the relationship between blood lead level and mortality.
The adjusted overall relative risk for participants with the variant ALAD genotype was decreased for all-cause mortality (hazards ratio = 0.68; [95% confidence interval = 0.50-0.93]) compared with persons having the common GG genotype. There was some suggestion that higher lead levels were associated with cancer mortality (1.48 [0.92-2.38]). We observed no convincing interaction effect between ALAD genotype and blood lead level on mortality risk.
The ALAD genotype may be associated with decreased mortality from all causes and from cancer. This association does not seem to be affected by lead exposure.
No preview · Article · Mar 2011 · Epidemiology (Cambridge, Mass.)
[Show abstract][Hide abstract] ABSTRACT: Aberrant cytosine methylation in promoter regions leads to gene silencing associated with cancer progression. A number of DNA methyltransferase inhibitors are known to reactivate silenced genes; including 5-azacytidine and 2-(1H)-pyrimidinone riboside (zebularine). Zebularine is a more stable, less cytotoxic inhibitor compared to 5-azacytidine. To determine the mechanistic basis for this difference, we carried out a detailed comparisons of the interaction between purified DNA methyltransferases and oligodeoxyribonucleotides (ODNs) containing either 5-azacytosine or 2-(1H)-pyrimidinone in place of the cytosine targeted for methylation. When incorporated into small ODNs, the rate of C5 DNA methyltransferase inhibition by both nucleosides is essentially identical. However, the stability and reversibility of the enzyme complex in the absence and presence of cofactor differs. 5-Azacytosine ODNs form complexes with C5 DNA methyltransferases that are irreversible when the 5-azacytosine ring is intact. ODNs containing 2-(1H)-pyrimidinone at the enzymatic target site are competitive inhibitors of both prokaryotic and mammalian DNA C5 methyltransferases. We determined that the ternary complexes between the enzymes, 2-(1H)-pyrimidinone inhibitor, and the cofactor S-adenosyl methionine are maintained through the formation of a reversible covalent interaction. The differing stability and reversibility of the covalent bonds may partially account for the observed differences in cytotoxicity between zebularine and 5-azacytidine inhibitors.
Full-text · Article · Jun 2009 · Biochemical pharmacology
[Show abstract][Hide abstract] ABSTRACT: The Agricultural Health Study (AHS) is a prospective cohort study of licensed pesticide applicators from Iowa and North Carolina enrolled between 1993 and 1997. EPTC (S-ethyl-N,N-dipropylthiocarbamate) is a thiocarbamate herbicide used in every region of the United States. The U.S. Environmental Protection Agency reports that EPTC is most likely not a human carcinogen; however, the previous epidemiologic data on EPTC exposure and cancer risk were limited.
The purpose of this study was to examine cancer incidence and EPTC use in 48,378 male pesticide applicators enrolled in the AHS.
We estimated the rate ratio (RR) and 95% confidence intervals (CIs) for all cancers and selected cancer sites using Poisson regression. We assessed EPTC exposure using two quantitative metrics: lifetime exposure days and intensity-weighted lifetime exposure days, a measure that accounts for application factors that modify personal exposure likelihood.
Among the 9,878 applicators exposed to EPTC, 470 incident cancer cases were diagnosed during the follow-up period ending December 2004 compared with the 1,824 cases among individuals reporting no use. Although EPTC was associated with colon cancer in the highest tertile of both lifetime exposure days and intensity-weighted lifetime days (RR = 2.09; 95% CI, 1.26-3.47 and RR = 2.05; 95% CI, 1.34-3.14, respectively) and the trend test was < 0.01 for both, the pattern of RR was not monotonic with increasing use. There was a suggestion of an association with leukemia. No other associations were observed.
In this analysis, EPTC use appeared to be associated with colon cancer and leukemia. However, given the relatively small number of cases in the highest exposure tertile, results should be interpreted with caution, and further investigations are needed.
Full-text · Article · Dec 2008 · Environmental Health Perspectives
[Show abstract][Hide abstract] ABSTRACT: Four presentations focused on the influence of dietary constituents on histone modification and their subsequent effects on gene expression and/or cellular phenotype. In the first presentation, sulforaphane, a cancer-protective compound found in cruciferous vegetables, was reported to inhibit histone deacetylase (HDAC) activity using both in vitro and in vivo models. Most interesting was the finding that in healthy human subjects, a single ingestion of 68 g (1 cup) of broccoli sprouts inhibited HDAC activity in circulating peripheral blood mononuclear cells 3–6 h after consumption, with concomitant induction of histone H3 and H4 acetylation. Because of these findings, participants discussed whether eating large amounts of broccoli early in life could result in deleterious rather than beneficial effects. Although sulforaphane has been shown to selectively induce apoptosis in cancer cells but not in normal cells, additional research is warranted to determine beneficial versus deleterious responses to BFCs during vulnerable periods. The next presentation concerned the effect of diallyl disulfide (DADS) from garlic on histone acetylation status in vitro, in human tumor colon cell lines, and in a non-tumorigenic animal model. In the in vivo model, histone H4 and H3 acetylation was increased in isolated colonocytes following administration of DADS. Discussion centered on the need to perform a dose-response experiment because only a very high dose of DADS was utilized in the work presented. Interestingly, data analyzed from cDNA expression arrays suggested that DADS could modulate the expression of genes encoding proteins involved in several cellular processes including cell cycle regulation, proliferation, metabolism, detoxication, signal transduction, and protein transport.
[Show abstract][Hide abstract] ABSTRACT: Members of Shc family conventionally serve as critical adaptors in tyrosine phosphorylation signal transduction pathways. p66(Shc) protein, a member of Shc family, is predominantly expressed in epithelial cells, whereas the regulation of its expression remains an enigma. We describe the effect of steroid hormones on the protein level of p66(Shc) and growth stimulation in hormone-sensitive human prostate, testicular and breast cancer cells. In DHT-treated androgen-sensitive prostate cancer LNCaP C-33 cells, the protein level of p66(Shc) was elevated by approximately 3-fold, correlating with increased cell growth. This DHT effect on p66(Shc) protein level and growth regulation was also observed in another androgen-sensitive prostate cancer cell line MDA PCa2b as well as 2 testicular cancer cell lines, Tera-1 and Tera-2 cells. Similarly, the female sex hormone estrogen had a stimulating effect on p66(Shc) protein level and proliferation in estrogen-sensitive MCF-7 breast cancer cells. The upregulation of p66(Shc) protein level by DHT was competitively abolished by Casodex, an androgen antagonist used to treat prostate cancer. Moreover, immunohistochemical analyses showed that the p66(Shc) protein level was significantly higher in primary prostate tumors than in adjacent non-cancerous cells (p < 0.05). The data collectively indicate that p66(Shc) protein levels correlate with steroid hormone-stimulated cell growth and prostate carcinogenesis.
Full-text · Article · Feb 2004 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: Enzymatic DNA methylation of carbon 5 of cytosines is an epigenetic modification that plays a role in regulating gene expression, differentiation, and tumorigenesis. DNA (cytosine-C5)-methyltransferase-1 is the enzyme responsible for maintaining established methylation patterns during replication in mammalian cells. It is composed of a large ( approximately 1100 amino acids (a.a.)) amino-terminal region containing many putative regulatory domains and a smaller ( approximately 500 a.a.) carboxy-terminal region containing conserved, catalytic domains. In this study, murine DNA (cytosine C5)-methyltransferase-1, fused to an amino-terminal hexahistidine tag, was expressed by infecting Spodoptera frugiperda cells for 46 h with a recombinant baculovirus carrying the DNA (cytosine-C5)-methyltransferase-1 cDNA. A total of 3 x 10(8) infected S. frugiperda cells yielded approximately 1 mg of full-length, hexahistidine-tagged DNA (cytosine-C5)-methyltransferase-1, which was purified approximately 450-fold from RNase-treated S. frugiperda cell extracts by nickel affinity chromatography. The characterization of hexahistidine-tagged DNA (cytosine-C5)-methyltransferase-1 through DNA methylation and inhibitor-binding assays indicated that the purified enzyme had at least a 30-fold higher catalytic efficiency with hemimethylated double-stranded oligodeoxyribonucleotide substrates than unmethylated substrates and was most active with small oligodeoxyribonucleotide substrates with a capacity for forming stem-loop structures. The expression and purification procedures reported here differ significantly from the original reports of baculovirus-mediated hexahistidine-tagged DNA (cytosine-C5)-methyltransferase-1 expression and purification by nickel affinity chromatography and provide a consistent yield of active enzyme.
No preview · Article · Jul 2002 · Protein Expression and Purification