Urinary isothiocyanates; glutathione S-transferase M1, T1, and P1 polymorphisms; and risk of colorectal cancer: the Multiethnic Cohort Study

Characterization, biological activity, and anticancer effect of green-synthesized gold nanoparticles using Nasturtium officinale L

BACKGROUND

Nanostructured materials used have unique properties and many uses in nanotechnology. The most striking of these is using herbal compounds for the green synthesis of nanoparticles. Among the nanoparticle types used for green synthesis, gold nanoparticles (AuNPs) are used for cancer therapy due to their stable structure and non-cytotoxic. Lung cancer is the most common and most dangerous cancer worldwide in terms of survival and prognosis. In this study, Nasturtium officinale (L.) extract (NO), which contains biomolecules with antioxidant and anticancer effects, was used to biosynthesize AuNPs, and after their characterization, the effect of the green-synthesized AuNPs against lung cancer was evaluated in vitro.

METHODS

Ultraviolet‒visible (UV‒Vis) spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), multiple analysis platform (MAP), and Fourier transform infrared (FT-IR) spectroscopy analyses were performed to characterize the AuNPs prepared from the N. officinale plant extract. Moreover, the antioxidant activity, total phenolic and flavonoid contents and DNA interactions were examined. Additionally, A549 lung cancer cells were treated with 2-48 µg/mL Nasturtium officinale gold nanoparticles (NOAuNPs) for 24 and 48 h to determine the effects on cell viability. The toxicity of the synthesized NOAuNPs to lung cancer cells was determined by the 3-(4,5-dimethylthiazol-2-il)-2,5-diphenyltetrazolium bromide (MTT) assay, and the anticancer effect of the NOAuNPs was evaluated by apoptosis and cell cycle analyses using flow cytometry.

RESULTS

The average size of the NPs was 56.4 nm. The intensities of the Au peaks from EDS analysis indicated that the AuNPs were synthesized successfully. Moreover, the in vitro antioxidant activities of the NO and NOAuNPs were evaluated; these materials gave values of 31.78 ± 1.71% and 31.62 ± 0.46%, respectively, in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay at 200 g/mL and values of 25.89 ± 1.90% and 33.81 ± 0.62%, respectively, in the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. The NO and NOAuNPs gave values of 0.389 ± 0.027 and 0.308 ± 0.005, respectively, in the ferrous ion reducing antioxidant capacity (FRAP) assay and values of 0.078 ± 0.009 and 0.172 ± 0.027, respectively, in the copper ion reducing antioxidant capacity (CUPRAC) assay. When the DNA cleavage activities of NO and the NOAuNPs were evaluated via hydrolysis, both samples cleaved DNA starting at a concentration of 25 g/mL in the cell culture analysis, while the nanoformulation of the NO components gave greater therapeutic and anticancer effects. We determined that the Au nanoparticles were not toxic to A549 cells. Moreover, after treatment with the half-maximal inhibitory concentration (IC50), determined by the MTT assay with A549 cells, we found that at 24 and 48 h, while the necrosis rates were high in cells treated with NO, the rates of apoptosis were greater in cells treated with NOAuNPs. Notably, for anticancer treatment, activating apoptotic pathways that do not cause inflammation is preferred. We believe that these results will pave the way for the use of NOAuNPs in in vitro studies of other types of cancer.

CONCLUSION

In this study, AuNPs were successfully synthesized from N. officinale extract. The biosynthesized AuNPs exhibited toxicity to and apoptotic effects on A549 lung cancer cells. Based on these findings, we suggest that green-synthesized AuNPs are promising new therapeutic agents for lung cancer treatment. However, since this was an in vitro study, further research should be performed in in vivo lung cancer models to support our findings and to explain the mechanism of action at the molecular level.

Cruciferous Vegetables and Their Bioactive Metabolites: from Prevention to Novel Therapies of Colorectal Cancer

The Brassicaceae family, known as cruciferous vegetables, includes many economically important species, mainly edible oil plants, vegetable species, spice plants, and feed plants. Cruciferous vegetables are foods rich in nutritive composition and are also a good source of dietary fiber. Besides, cruciferous vegetables contain various bioactive chemicals known as glucosinolates and S-methyl cysteine sulfoxide, including sulphur-containing cancer-protective chemicals. Numerous studies have reported that daily intake of sulphurous vegetables helps prevent cancer formation and reduces cancer incidence, especially in colorectal cancer, through various mechanisms. The potential mechanisms of these compounds in preventing cancer in experimental studies are as follows: protecting cells against DNA damage, inactivating carcinogenic substances, showing antiviral and antibacterial effects, triggering apoptosis in cells with disrupted structure, inhibiting tumour cell migration causing metastasis and the development of tumour-feeding vessels (angiogenesis). These beneficial anticancer effects of cruciferous vegetables are generally associated with glucosinolates in their composition and some secondary metabolites, as well as other phenolic compounds, seed oils, and dietary fiber in the literature. This review aims to examine to the roles of cruciferous vegetables and their important bioactive metabolites in the prevention and treatment of colorectal cancer.

Validity of dietary isothiocyanate intake estimates from a food frequency questionnaire using 24 h urinary isothiocyanate excretion as an objective biomarker: the JPHC-NEXT protocol area

BACKGROUND/OBJECTIVES

Isothiocyanate (ITC) is formed via the hydrolysis of glucosinolates by myrosinase, found in cruciferous vegetables. Although myrosinase is inactivated by the cooking process, no studies have incorporated the effect of cooking into the estimation of dietary ITC intake or evaluated the validity. We evaluated the validity of dietary ITC intake estimated from a food frequency questionnaire (FFQ), and urinary ITC levels using 24 h urine samples or a WFR (weighed food record), and evaluated the reproducibility of dietary ITC in two FFQs administered at an interval of 1-year.

SUBJECTS/METHODS

The JPHC-NEXT Protocol Area included a total of 255 middle-aged participants across Japan. We calculated dietary ITC intake from WFR and two FFQs by assuming that cooked cruciferous vegetables contain zero ITC. Urinary ITC excretion was measured at two points during summer and winter. The validity and reproducibility of dietary ITC intake estimated by FFQ were assessed using Spearman's correlation coefficients.

RESULTS

Although we observed a moderate correlation between dietary ITC intake derived from a 12-day WFR and urinary ITC excretion, notwithstanding the cooking process, the correlation between dietary ITC intake estimated by FFQ and mean urinary ITC excretion was low. However, the correlation was improved when we compared urinary ITC excretion and a 3-day WFR or FFQ collected during winter. Our FFQ showed good reproducibility.

CONCLUSION

Although seasonality is a critical factor, dietary ITC intake estimated using an FFQ showed moderate validity and reproducibility and can be used in future epidemiological studies.

Metabolic Fate of Dietary Glucosinolates and Their Metabolites: A Role for the Microbiome

Robust evidence shows that phytochemicals from cruciferous vegetables, like broccoli, are associated with numerous health benefits. The anti-cancer properties of these foods are attributed to bioactive isothiocyanates (ITCs) and indoles, phytochemicals generated from biological precursor compounds called glucosinolates. ITCs, and particularly sulforaphane (SFN), are of intense interest as they block the initiation, and suppress the progression of cancer, through genetic and epigenetic mechanisms. The efficacy of these compounds is well-demonstrated in cell culture and animal models, however, high levels of inter-individual variation in absorption and excretion of ITCs is a significant barrier to the use of dietary glucosinolates to prevent and treat disease. The source of inter-individual ITC variation has yet to be fully elucidated and the gut microbiome may play a key role. This review highlights evidence that the gut microbiome influences the metabolic fate and activity of ITCs. Human feeding trials have shown inter-individual variations in gut microbiome composition coincides with variations in ITC absorption and excretion, and some bacteria produce ITCs from glucosinolates. Additionally, consumption of cruciferous vegetables can alter the composition of the gut microbiome and shift the physiochemical environment of the gut lumen, influencing the production of phytochemicals. Microbiome and diet induced changes to ITC metabolism may lead to the decrease of cancer fighting phytochemicals such as SFN and increase the production of biologically inert ones like SFN-nitrile. We conclude by offering perspective on the use of novel “omics” technologies to elucidate the interplay of the gut microbiome and ITC formation.

Composition of the Gut Microbiome Influences Production of Sulforaphane-Nitrile and Iberin-Nitrile from Glucosinolates in Broccoli Sprouts

Isothiocyanates, such as sulforaphane and iberin, derived from glucosinolates (GLS) in cruciferous vegetables, are known to prevent and suppress cancer development. GLS can also be converted by bacteria to biologically inert nitriles, such as sulforaphane-nitrile (SFN-NIT) and iberin-nitrile (IBN-NIT), but the role of the gut microbiome in this process is relatively undescribed and SFN-NIT excretion in humans is unknown. An ex vivo fecal incubation model with in vitro digested broccoli sprouts and 16S sequencing was utilized to explore the role of the gut microbiome in SFN- and IBN-NIT production. SFN-NIT excretion was measured among human subjects following broccoli sprout consumption. The fecal culture model showed high inter-individual variability in nitrile production and identified two sub-populations of microbial communities among the fecal cultures, which coincided with a differing abundance of nitriles. The Clostridiaceae family was associated with high levels, while individuals with a low abundance of nitriles were more enriched with taxa from the Enterobacteriaceae family. High levels of inter-individual variation in urine SFN-NIT levels were also observed, with peak excretion of SFN-NIT at 24 h post broccoli sprout consumption. These results suggest that nitrile production from broccoli, as opposed to isothiocyanates, could be influenced by gut microbiome composition, potentially lowering efficacy of cruciferous vegetable interventions.

Current Knowledge and Challenges on the Development of a Dietary Glucosinolate Database in the United States

Glucosinolates (GSLs) are a group of cancer chemopreventive sulfur-containing compounds found primarily in Brassica vegetables. The goals of this study were to summarize the current knowledge and discuss the challenges of developing a dietary GSL database for US foods. A systematic literature search was conducted for the period 1980-2020. Thirty articles were found to meet all inclusion and exclusion criteria; 27 GSLs were reported in 16 different vegetables. GSLs identified and quantified ranged from 3 for winter cress to 16 for cabbage. In general, the experimental designs of these 30 studies did not fully consider the factors related to the data quality. Enormous variations of GSLs are observed between different vegetables and in the same vegetables. In conclusion, the studies on GSLs in commonly consumed vegetables are still limited, and some data may be outdated. Currently available data are not sufficient to develop a valid GSL database in the United States.

Individual and combined effects of GSTM1 and GSTT1 polymorphisms on colorectal cancer risk: an updated meta-analysis

BACKGROUND

The presence or absence of glutathione S-transferase M1 gene (GSTM1) and glutathione S-transferase T1 gene (GSTT1) polymorphisms, and their combined effects have been suggested as a risk factor for colorectal cancer (CRC). However, the results are inconsistent.

OBJECTIVES

An updated meta-analysis was performed to solve the controversy.

METHODS

Meta-analyses of Observational Studies in Epidemiology (MOOSE) guidelines were used.

RESULTS

Overall, the GSTM1 null genotype was associated with an increased CRC risk in Caucasians (odds ratio (OR) = 1.14, 95% confidence interval (CI): 1.05-1.23), Asians (OR = 1.19, 95% CI: 1.08-1.32), high-quality studies (OR = 1.12, 95% CI: 1.06-1.18). Moreover, the GSTM1 null genotype was also associated with an increased colon cancer risk (OR = 1.32, 95% CI: 1.16-1.51). The GSTT1 null genotype was also associated with an increased CRC risk in Asians (OR = 1.08, 95% CI: 1.02-1.15) and Caucasians (OR = 1.24, 95% CI: 1.09-1.41). Moreover, The GSTT1 null genotype was associated with an increased rectal cancer risk (OR = 1.13, 95% CI: 1.01-1.27, I2 = 8.3%) in subgroup analysis by tumor location. Last, the GSTM1 null/GSTT1 null genotype was associated with an increased CRC risk in Asians.

CONCLUSION

This meta-analysis indicates that the GSTM1 and GSTT1 null genotypes are associated with increased CRC risk in Asians and Caucasians, and the GSTM1 null/GSTT1 null genotype was associated with increased CRC risk in Asians.

Cruciferous Vegetables and Risk of Cancers of the Gastrointestinal Tract

Cancers of the oropharyngeal tissues, oesophagus, stomach, and colorectum are amongst the most common causes of death from cancer throughout the world. Higher consumption of fruits and vegetables is thought to be protective, and cruciferous vegetables are of particular interest because of their unique role as a source of biologically active glucosinolate breakdown products. A literature review of primary studies and meta-analyses indicates that higher consumption of cruciferous vegetables probably reduces the risk of colorectal and gastric cancers by approximately 8% and 19%, respectively. Some studies support the hypothesis that the protective effect against colorectal cancer is modified by genetic polymorphisms of genes regulating the expression of enzymes of the glutathione S-transferase family, but due to contradictory findings the evidence is currently inconclusive. Despite these promising findings, future epidemiological research on the protective effects of cruciferous plants will depend critically upon accurate measurement of dietary exposure, both to the vegetables themselves, and to their active constituents. The development of sensitive chemical assays has facilitated the measurement of urinary excretion of isothiocyanate metabolites as an objective biomarker of intake, but sampling strategies need to be optimized in order to assess long-term exposures at the population level.

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast cancer.

A principal mechanism for the cancer chemopreventive activity of phenethyl isothiocyanate is modulation of carcinogen metabolism

Isothiocyanates are small molecules characterized by high chemical reactivity that allows them to interact readily with cellular constituents eliciting a plethora of biological activities. They are present exclusively in cruciferous vegetables, as glucosinolates, the intake of which has been associated with cancer chemoprevention. When the physical structure of these vegetables is disturbed, e.g. during mastication, the enzyme myrosinase is released and converts the glucosinolates to isothiocyanates (R-N=C=S), where R can be aliphatic or aromatic. Although sulforaphane, an aliphatic isothiocyanate, has received most attention worldwide, the most extensively studied aromatic isothiocyanate is phenethyl isothiocyanate (PEITC), and there are substantial differences in biological activity between the two sub-classes. In animal cancer models, PEITC effectively antagonized the carcinogenicity of chemicals, especially nitrosocompounds. A principal mechanism of their action is to protect the integrity of DNA by decreasing the levels of the genotoxic metabolites of chemical carcinogens. Extensive studies established that PEITC modulates the metabolism of the tobacco-specific carcinogenic nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by inhibiting its cytochrome P450-mediated bioactivation. Moreover, PEITC is a potent inducer of detoxification enzymes such as quinone reductase, glutathione S-transferase and glucuronosyl transferase. PEITC is rapidly absorbed and is characterized by a large bioavailability; Cmax concentrations achieved in plasma after dietary intake are sufficient to modulate carcinogen metabolism. PEITC is primarily metabolized by glutathione conjugation and is excreted in the urine and bile as the mercapturate. The ability of PEITC to perturb carcinogen metabolism through modulation of cytochrome P450 and phase II detoxification enzymes is comprehensively and critically reviewed.

Nutrients, foods, and colorectal cancer prevention

Diet has an important role in the development of colorectal cancer. In the past few decades, findings from extensive epidemiologic and experimental investigations have linked consumption of several foods and nutrients to the risk of colorectal neoplasia. Calcium, fiber, milk, and whole grains have been associated with a lower risk of colorectal cancer, and red meat and processed meat have been associated with an increased risk. There is substantial evidence for the potential chemopreventive effects of vitamin D, folate, fruits, and vegetables. Nutrients and foods also may interact, as a dietary pattern, to influence colorectal cancer risk. Diet likely influences colorectal carcinogenesis through several interacting mechanisms. These include the direct effects on immune responsiveness and inflammation, and the indirect effects of overnutrition and obesity-risk factors for colorectal cancer. Emerging evidence also implicates the gut microbiota as an important effector in the relationship between diet and cancer. Dietary modification therefore has the promise of reducing colorectal cancer incidence.

Gene-diet interactions and their impact on colorectal cancer risk

A number of studies have evaluated the role of gene-diet interaction in the etiology of colorectal cancer (CRC). Historically, these studies focused on established dietary risk factors and genes involved in their metabolism. However, results from these candidate gene studies were inconsistent, possibly due to multiple testing and publication bias. In recent years, genome-wide association studies have identified a number of CRC susceptibility loci, and subsequent meta-analyses have observed limited evidence that diet may modify the risk associated with these susceptibility loci. Statistical techniques have been recently developed to evaluate the presence of interaction across the entire genome; results from these genome-wide studies have demonstrated limited evidence of interaction and have failed to replicate results from candidate gene studies and those using established susceptibility loci. However, larger sample sizes are likely needed to elucidate modest or weak interaction in genome-wide studies of gene-diet interaction.

Phenethyl isothiocyanate: a comprehensive review of anti-cancer mechanisms

The epidemiological evidence suggests a strong inverse relationship between dietary intake of cruciferous vegetables and the incidence of cancer. Among other constituents of cruciferous vegetables, isothiocyanates (ITC) are the main bioactive chemicals present. Phenethyl isothiocyanate (PEITC) is present as gluconasturtiin in many cruciferous vegetables with remarkable anti-cancer effects. PEITC is known to not only prevent the initiation phase of carcinogenesis process but also to inhibit the progression of tumorigenesis. PEITC targets multiple proteins to suppress various cancer-promoting mechanisms such as cell proliferation, progression and metastasis. Pre-clinical evidence suggests that combination of PEITC with conventional anti-cancer agents is also highly effective in improving overall efficacy. Based on accumulating evidence, PEITC appears to be a promising agent for cancer therapy and is already under clinical trials for leukemia and lung cancer. This is the first review which provides a comprehensive analysis of known targets and mechanisms along with a critical evaluation of PEITC as a future anti-cancer agent.

Correlates of self-reported dietary cruciferous vegetable intake and urinary isothiocyanate from two cohorts in China

OBJECTIVE

To assess correlations between cruciferous vegetable intake and urinary isothiocyanate (ITC) level, in addition to glutathione S-transferase (GST) genotypes and other individual factors.

DESIGN

The study included cohort participants whose urinary ITC levels had been previously ascertained. Urinary ITC was assessed using HPLC. Usual dietary intake of cruciferous vegetables was assessed using a validated FFQ and total dietary ITC intake was calculated. Recent cruciferous vegetable intake was determined. GST genotypes were assessed using duplex real-time quantitative PCR assays. Spearman correlations were calculated between the covariates and urinary ITC levels and linear regression analyses were used to calculate the mean urinary ITC excretion according to GST genotype.

SETTING

Urban city in China.

SUBJECTS

The study included 3589 women and 1015 men from the Shanghai Women's and Men's Health Studies.

RESULTS

Median urinary ITC level was 1.61 nmol/mg creatinine. Self-reported usual cruciferous vegetable intake was weakly correlated with urinary ITC level (r s=0.1149; P<0.0001), while self-reported recent intake was more strongly correlated with urinary ITC (r s=0.2591; P<0.0001). Overall, the GST genotypes were not associated with urinary ITC level, but significant differences according to genotype were observed among current smokers and participants who provided an afternoon urine sample. Other factors, including previous gastrectomy or gastritis, were also related to urinary ITC level.

CONCLUSIONS

The study suggests that urinary secretion of ITC may provide additional information on cruciferous vegetable intake and that GST genotypes are related to urinary ITC level only in some subgroups.

Urinary isothiocyanates level and liver cancer risk: a nested case-control study in Shanghai, China

Experimental studies have provided evidence that isothiocyanates (ITCs) from cruciferous vegetables may modulate carcinogen metabolism and facilitate carcinogen detoxification and reduce cancer risk. However, no epidemiological studies on liver cancer were reported. This study investigates the association between urinary ITCs levels and liver cancer risk among men and women in Shanghai, China. A nested case-control study of 217 incident cases of liver cancer and 427 matched controls identified from the Shanghai Women's Health Study and Shanghai Men's Health Study was conducted. Conditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) summarizing the association between urinary ITCs levels and liver cancer risk. Compared to those with undetectable ITCs, nonsignificantly inverse association was observed among detectable (OR = 0.80; 95% CI = 0.51-1.26), below-median (OR = 0.76; 95% CI = 0.47-1.24), and above-median concentration (OR = 0.86; 95% CI = 0.52-1.41) with liver cancer risk. Similar patterns were observed when urinary ITCs levels were categorized into tertiles or quartiles. Although our study firstly focused on the association between urinary ITCs exposure and liver cancer risk, we did not find significant results. Future multicenter prospective, different population studies are warranted to validate our findings.

A systemic review of glutathione S-transferase P1 Ile105Val polymorphism and colorectal cancer risk

OBJECTIVES

To investigate the correlation between glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism and colorectal cancer (CRC) risk.

METHODS

Studies were identified to investigate the association between GSTP1 Ile105Val polymorphism and CRC risk. Systematic computerized searches of the PubMed, Chinese National Knowledge Infrastructure, WANFANG and SinoMed were performed. Summary odds ratios (OR) and 95% confidence intervals (95% CI) were used to measure GSTP1 Ile105Val polymorphisms and CRC risk.

RESULTS

A total of 23 retrospective studies were included in the meta-analysis. During all studies including 6,981 cases and 8,977 controls, sample sizes ranged from 146 to 2,144. Overall, the pooled results revealed that Ile105Val polymorphism was not associated with CRC risk and confused results were found in subgroup analyses. Further meta-analyses were conducted after excluding low-quality studies. GSTP1 Ile105Val is associated with increased risk of CRC limited in studies with matched control. There was no significant heterogeneity in all genetic comparisons, but heterogeneity existed in subgroup analyses of heterozygous and dominant comparisons. The meta-regression analyses indicated that matched controls were the significant factor influencing between-study heterogeneity in all possible influential factors including published year, ethnicity, source of control, sample size, Hardy-Weinberg equilibrium (HWE) in control and matched controls. Sensitivity analysis revealed the pooled ORs were not changed before and after removal of each single study in all genetic comparisons, indicating the robustness of the results.

CONCLUSIONS

GSTP1 Ile105Val might be associated with increased risk of CRC. However, more high-quality case-control studies should be performed to confirm the authenticity of our conclusion.

Induction of epoxide hydrolase, glucuronosyl transferase, and sulfotransferase by phenethyl isothiocyanate in male Wistar albino rats

Phenethyl isothiocyanate (PEITC) is an isothiocyanate found in watercress as the glucosinolate (gluconasturtiin). The isothiocyanate is converted from the glucosinolate by intestinal microflora or when contacted with myrosinase during the chopping and mastication of the vegetable. PEITC manifested protection against chemically-induced cancers in various tissues. A potential mechanism of chemoprevention is by modulating the metabolism of carcinogens so as to promote deactivation. The principal objective of this study was to investigate in rats the effect of PEITC on carcinogen-metabolising enzyme systems such as sulfotransferase (SULT), N-acetyltransferase (NAT), glucuronosyl transferase (UDP), and epoxide hydrolase (EH) following exposure to low doses that simulate human dietary intake. Rats were fed for 2 weeks diets supplemented with PEITC at 0.06 µmol/g (low dose, i.e., dietary intake), 0.6 µmol/g (medium dose), and 6.0 µmol/g (high dose), and the enzymes were monitored in rat liver. At the Low dose, no induction of the SULT, NAT, and EH was noted, whereas UDP level was elevated. At the Medium dose, only SULT level was increased, whereas at the High dose marked increase in EH level was observed. It is concluded that PEITC modulates carcinogen-metabolising enzyme systems at doses reflecting human intake thus elucidating the mechanism of its chemoprevention.

Cruciferous vegetables, glutathione S-transferase polymorphisms, and the risk of colorectal cancer among Chinese men

PURPOSE

To assess the associations between cruciferous vegetable (CV) intake, GST gene polymorphisms, and colorectal cancer (CRC) in a population of Chinese men.

METHODS

Using incidence density sampling, CRC cases (N = 340) diagnosed before December 31, 2010 within the Shanghai Men's Health Study were matched to noncases (N = 673). CV intake was assessed from a food frequency questionnaire and by isothiocyanate levels from spot urine samples. GSTM1 and GSTT1 were categorized as null (0 copies) versus non-null (1 or 2 copies). Conditional logistic regression was used to calculate odds ratios and 95% confidence intervals for the association between CV intake and GST gene variants with CRC, and statistical interactions were evaluated.

RESULTS

CRC risk was not associated with CV intake, whether measured by self-report or by urinary isothiocyanate nor with GST gene variants. No statistical interactions were detected between CV intake and GST gene variants on the odds of CRC. Stratifying by timing of urine sample collection and excluding CRC cases diagnosed in the first 2 years did not materially alter the results.

CONCLUSIONS

This study provides no evidence supporting the involvement of CV intake in the development of CRC in Chinese men.

Cruciferous vegetables and risk of colorectal neoplasms: a systematic review and meta-analysis

Evidence shows cruciferous vegetables exhibit chemoprotective properties, commonly attributed to their rich source of isothiocyanates. However, epidemiological data examining the association between cruciferous vegetable intake and colorectal neoplasms have been inconclusive. This meta-analysis examines the epidemiological evidence to characterize the association between cruciferous vegetable intake and risk of developing colorectal neoplasms. Thirty-three articles were included in the meta-analysis after a literature search of electronic databases. Subgroup analysis for individual cruciferae types (n = 8 studies) and GST polymorphism (n = 8 studies) were performed. Pooled adjusted odds ratios (ORs) comparing highest and lowest categories of dietary pattern scores were calculated. Results show a statistically significant inverse association between cruciferous vegetable intake and colon cancer [OR = 0.84; 95% confidence interval (CI): 0.72-0.98; P value heterogeneity < 0.001]. Broccoli in particular exhibited protective benefits against colorectal (CRC) neoplasms (OR = 0.80; 95% CI: 0.65-0.99; P value heterogeneity = 0.02). Stratification by GST genotype reveals that the GSTT1 null genotype confers a reduction in CRC risk (OR = 0.78; 95% CI: 0.64-0.95; P value heterogeneity = 0.32). This study provides support to the hypothesis that cruciferous vegetable intake protects against cancer of the colon. This study also demonstrates the significance of gene-diet interactions and the importance of assessing individual cruciferous vegetables.

Glutathione S-transferase T1 gene polymorphism and colorectal cancer risk: an updated analysis

BACKGROUND AND OBJECTIVE

The association between glutathione S-transferase T1 (GSTT1) gene polymorphisms and colorectal cancer (CRC) susceptibility is still controversial. In order to clarify the effect of GSTT1 genotype on the CRC risk, we carried out an updated meta-analysis of published case-control studies to provide more precise evidence.

METHODS

Two investigators independently searched the databases of Pubmed, EMBASE and China National Knowledge Infrastructure (CNKI) up to October 15, 2012. Crude odds ratios (OR) and 95% confidence intervals (CI) were calculated to investigate the strength of the association in a fixed- or random-effects model depending on statistical heterogeneity.

RESULTS

Forty-six case-control studies with 15,373 colorectal cancer cases and 21,238 controls were included. Overall, the pooled results indicated that GSTT1 null genotype was significantly associated with increased CRC risk (OR=1.21, 95% CI=1.10-1.33). When stratifying for ethnicity and control sources, we also observed positive association between GSTT1 null genotype and increased risk of CRC. When stratifying by the location, we found there was a statistically significant association in the rectal cancer (OR=1.28, 95% CI=1.01-1.64), but not in colon cancer (OR=1.27, 95% CI=0.94-1.73). Subgroup analyses for Dukes stage, histological differentiation of CRC and smoking habit did not reveal any significant differences in genotype distribution. In addition, we observed a strong correlation between increased CRC risk and the combined GSTM1 and GSTT1 null genotype.

CONCLUSIONS

This meta-analysis suggests that the GSTT1 null genotype may contribute to increased risk of colorectal cancer. More well-designed studies based on larger population are needed to confirm our results.

The protective effect of coffee consumption on cutaneous melanoma risk and the role of GSTM1 and GSTT1 polymorphisms

PURPOSES

The authors examined the association between coffee consumption and cutaneous melanoma and the implication of GSTM1 and GSTT1 polymorphisms.

METHODS

A hospital-based case-control study was conducted in the inpatient wards of IDI-San Carlo Rome, Italy, including 304 incident cases of cutaneous melanoma and 305 controls. Information on socio-demographic characteristics, medical history, smoking, sun exposure, pigmentary characteristics and diet was collected for all subjects. Within the study, individual patterns at two polymorphic genes (GSTM1 and GSTT1) belonging to glutathione S-transferases family were investigated in 188 cases of cutaneous melanoma and 152 controls. Logistic regression was the method used to estimate odds ratio and 95 % confidence intervals.

RESULTS

High frequency of coffee drinking (>once daily), compared with low-frequency consumption of coffee (≤7 times weekly) was associated with a protective effect for cutaneous melanoma (OR 0.46; 95 % CI 0.31-0.68) after adjusting for sex, age, education, hair colour, common nevi, skin phototype, and sunburn episodes in childhood. When stratified by GSTM1 and GSTT1 genotype, the protective effect of coffee was extremely high for subjects with both GSTM1 and GSTT1 null polymorphisms (OR 0.01; 95 % CI 0.0003-0.54).

CONCLUSIONS

Our results show a protective effect of coffee consumption for cutaneous melanoma, in particular for those with homozygous deletion for GSTM1 and GSTT1.

The GSTP1 Ile105Val polymorphism is not associated with susceptibility to colorectal cancer

The glutathione S transferase (GST) family is a major part of cellular defense mechanisms against endogenous and exogenous substances, many of which have carcinogenic potential. Alteration in the expression level or structure of the glutathione-S-transferase (GST) enzymes may lead to inadequate detoxification of potential carcinogens and consequently contribute to cancer development. A member of the glutathione-S-transferase (GST) family, GSTP1, is an attractive candidate for involvement in susceptibility to carcinogen-associated colorectal cancer. An A>G transition in exon 5 resulting in an Ile105Val amino acid substitution has been identified which alters catalytic efficiency. The present study investigated the possible impact of Ile105Val GSTP1 polymorphism on susceptibility to colorectal cancer. in Jordan We examined 90 tissue samples previously diagnosed with colorectal carcinoma, and 56 non-cancerous colon tissues. DNA was extracted from paraffin embedded tissues and the status of the GSTP1 polymorphism was determined using a polymerase chain reaction restriction fragment length polymorphism (RFLP) method. No statistically significant differences were found between colorectal cancer cases and controls for the GSTP1 Ile/Ile, Ile/Val and Val/Val genotypes. The glutathione S-transferase polymorphism was not associated with risk in colorectal cancer cases in Jordan stratified by age, sex, site, grade or tumor stage. In conclusion, the GSTP1 Ile105Val polymorphism is unlikely to affect the risk of colorectal cancer.

Interaction between GSTP1 Val allele and H. pylori infection, smoking and alcohol consumption and risk of gastric cancer among the Chinese population

Glutathione S-transferase P1 (GSTP1) is a critical enzyme in the phase II detoxification pathway. One of the common functional polymorphisms of GSTP1 is A→G at nucleotide 313, which results in an amino acid substitution (Ile105Val) at the substrate binding site and reduced catalytic activity. We evaluated the interaction between GSTP1 Val allele and Helicobacter pylori infection, smoking and alcohol consumption, increasing the risk of gastric cancer among the Chinese population. Information on potential gastric cancer risk factors and blood specimens were collected from 618 incident gastric cancer cases and 1,830 non-cancer controls between March 2002 and December 2011 in Liaoning Province, China. GSTP1 Ile105Val was genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and polymerase chain reaction-restriction fragment length polymorphism. Serum levels of anti-H. pylori IgG were measured by ELISA. Odds ratio (OR) and 95% confidence interval (CI) were calculated using multivariate logistic regression, adjusted by sex and age. The risk of gastric cancer was significantly elevated in patients with the GSTP1 Val/Val genotype (adjusted OR = 3.324; 95% CI = 1.790–6.172). An elevated risk of gastric cancer was observed in patients with H. pylori infection, smoking, or alcohol consumption, and together with the GSTP1 Ile/Val +Val/Val genotype (OR = 3.696; 95% CI = 2.475–5.521; OR = 1.638; 95% CI = 1.044–2.571; OR = 1.641; 95% CI = 0.983–2.739, respectively) (p<0.05). The GSTP1 Val allele shows an interaction with smoking, alcohol consumption, and especially H. pylori infection for increasing the risk of gastric cancer. These findings could demonstrate new pathophysiological pathways for the development of gastric cancer.

Characterization of the temporal induction of hepatic xenobiotic-metabolizing enzymes by glucosinolates and isothiocyanates: requirement for at least a 6 h exposure to elicit complete induction profile

A mechanism of action of chemopreventive glucosinolates/isothiocyanates, established largely in vitro, is to modulate carcinogen-metabolizing enzymes. Extrapolation in vivo involves relating in vitro concentrations to plasma/tissue concentrations attained in vivo, thus assuming that even transient exposure modulates enzyme activity. To test this hypothesis, precision-cut rat liver slices were incubated with glucosinolates for up to 24 h, and the O-dealkylation of methoxyresorufin and ethoxyresorufin was determined; increased activities were observed only at incubations of at least 6 h. To evaluate phase II enzymes, isothiocyanates, namely, sulforaphane, erucin, and phenethyl isothiocyanate, were similarly incubated; quinone reductase increased after incubation for 6 h or longer. When glutathione S-transferase was monitored, the phenethyl isothiocyanate-manifested rise necessitated at least a 6 h incubation, whereas in the case of sulforaphane and erucin, the activity was elevated after only 2 h. It is inferred that a rise in carcinogen-metabolizing enzymes by glucosinolates/isothiocyanates necessitates tissue exposure of at least 6 h.

Recent advances in understanding of interactions between genes and diet in the etiology of colorectal cancer

At an international level, colorectal cancer (CRC) is a major cause of morbidity and mortality. Diet plays a major etiologic role, and a range of putative dietary carcinogens have been identified. The probability with which these lead to mutations, and thereby cause cancer, is strongly impacted by variants in genes coding for xenobiotic metabolizing or DNA repair enzymes. Nutrient deficiencies also play a role, which will be exacerbated by variants in metabolic genes. However, many of the causal genes in sporadic CRC have hitherto proved elusive. The power of large international collaborations, coupled with genome-wide association studies, has implicated a major functional role of the tumour growth factor-β pathway in CRC susceptibility. Nutrient regulation of gene expression may be especially important here. Future large collaborative studies must consider gene-gene and gene-diet interactions, coupled with high throughput genomic technologies, in order to uncover the relative roles of genetic variants, mutagenic xenobiotics, nutrient imbalance and gene expression in the etiology of CRC.

GSTM1, GSTT1, GSTP1, GSTA1 and colorectal cancer risk: a comprehensive meta-analysis

Glutathione S-transferases (GSTs) catalyse reactions between glutathione and lipophilic compounds with electrophilic centres, leading to neutralisation of toxic compounds, xenobiotics and products of oxidative stress. Controversy exists about whether GST polymorphisms (GSTM1 null/present genotype, GSTT1 null/present genotype, GSTP1 Ile105Val and GSTA1 *A/*B) represent risk factors for colorectal cancer. This meta-analysis aims to examine the associations between the above-mentioned polymorphisms and colorectal cancer risk. Forty-four studies were eligible for GSTM1 (11,998 colorectal cancer cases, 17,552 controls), 34 studies for GSTT1 (8596 cases, 13,589 controls), 19 studies for GSTP1 (5421 cases, 7671 controls) and four studies for GSTA1 polymorphism (1648 cases, 2039 controls). Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. Separate analyses were conducted on Caucasian and Chinese populations. Where appropriate, sensitivity analysis concerning the deviation of genotype frequencies in controls from the Hardy-Weinberg equilibrium was performed. GSTM1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.150, 95% confidence interval (CI): 1.060-1.248, random effects); no significant association was detected for Chinese subjects (pooled OR=1.025, 95% CI: 0.903-1.163, fixed effects). Similarly, GSTT1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.312, 95% CI: 1.119-1.538, random effects); the association in Chinese subjects was not significant (pooled OR=1.068, 95% CI: 0.788-1.449, random effects). Concerning GSTP1 Ile105Val no significant associations were demonstrated in either race. GSTA1 *A/*B polymorphism was not associated with colorectal cancer risk. GSTM1 and GSTT1 null genotypes confer additional risk for colorectal cancer in Caucasian populations.

Isothiocyanate exposure, glutathione S-transferase polymorphisms, and colorectal cancer risk

BACKGROUND

Isothiocyanates, compounds found primarily in cruciferous vegetables, have been shown in laboratory studies to possess anticarcinogenic activity. Glutathione S-transferases (GSTs) are involved in the metabolism and elimination of isothiocyanates; thus, genetic variations in these enzymes may affect in vivo bioavailability and the activity of isothiocyanates.

OBJECTIVE

The objective was to prospectively evaluate the association between urinary isothiocyanate concentrations and colorectal cancer risk as well as the potential modifying effect of GST genotypes on the association.

DESIGN

A nested case-control study of 322 cases and 1251 controls identified from the Shanghai Women's Health Study was conducted.

RESULTS

Urinary isothiocyanate concentrations were inversely associated with colorectal cancer risk; the inverse association was statistically significant or nearly significant in the GSTM1-null (P for trend = 0.04) and the GSTT1-null (P for trend = 0.07) genotype groups. The strongest inverse association was found among individuals with both the GSTM1-null and the GSTT1-null genotypes, with an adjusted odds ratio of 0.51 (95% CI: 0.27, 0.95), in a comparison of the highest with the lowest tertile of urinary isothiocyanates. No apparent associations between isothiocyanate concentration and colorectal cancer risk were found among individuals who carried either the GSTM1 or GSTT1 gene (P for interaction < 0.05).

CONCLUSION

This study suggests that isothiocyanate exposure may reduce the risk of colorectal cancer, and this protective effect may be modified by the GSTM1 and GSTT1 genes.

An updating meta-analysis of the glutathione S-transferase T1 polymorphisms and colorectal cancer risk: a HuGE review

INTRODUCTION

GSTT1 status has been extensively studied as a colorectal cancer risk factor. However, the results are inconsistent. To examine this controversy, we performed a meta-analysis to evaluate the relationship between GSTT1 polymorphism and colorectal cancer.

MATERIALS AND METHODS

We performed a literature search using PUBMED, EMBASE, Cochrane Library, and HuGNet database to February 2009, with no restrictions. All articles were independent and contained the minimum information necessary to estimate the colorectal cancer risk associated with GSTT1 null. Summary odds ratio (ORs) and 95% confidence intervals (CIs) were calculated using random-effect or fixed-effect models based on the heterogeneity of included studies.

RESULTS

A total of 23 case-control studies, including a total of 11,057 subjects (5,058 cases and 5,999 controls), that related to GSTT1 polymorphism and risk of colorectal cancer were identified and included for analysis. The random-effect meta-analyses of all the 23 studies suggested that there was a small increased risk of colorectal cancer for individuals with GSTT1 null (OR was 1.23; 95% CI 1.02-1.49; I (2) = 76.9%, P for heterogeneity <0.001). The fixed-effect meta-analyses reached a similar results in Caucasians populations of ten studies (OR = 1.39; 95% CI 1.21-1.59; I (2) = 29.8%, P for heterogeneity = 0.171) and Asians populations of five studies (OR = 1.23; 95% CI 1.04-1.45; I (2) = 0.0%, P for heterogeneity = 0.428), with as inversely association in the other ethnic populations from four studies (OR = 0.69; 95% CI 0.54-0.877; I (2) = 0.0%, P for heterogeneity = 0.58).

CONCLUSION

There was a small increased risk of colorectal cancer for individuals with GSTT1 null, especially for Caucasians populations and Asian populations.

Glutathione-S-transferase (GSTM1, GSTT1) and the risk of gastrointestinal cancer in a Korean population

AIM: To evaluate the association of glutathione S-transferase mu (GSTM1) and glutathione S-transferase theta (GSTT1) null genotypes with the risk of gastric cancer (GC) and colorectal cancer (CRC) in a South Korean population.

METHODS: We conducted a population-based, large-scale case-control study including 2213 GCs, 1829 CRCs, and 1699 controls. Null and non-null genotypes of GSTM1 and GSTT1 were determined using real-time PCR.

RESULTS: The null genotypes of GSTM1 and GSTT1 were not significantly associated with elevated risk of gastric (OR = 1.070, 95% CI = 0.935-1.224; OR = 1.101, 95% CI = 0.963-1.259, respectively) or colorectal cancer (OR = 1.065, 95% CI = 0.923-1.228; OR = 1.041, 95% CI = 0.903-1.200, respectively). The frequency of the combined null GST genotype was not different between the two cancer groups and controls. Moreover, smoking, drinking, and age did not modify the association between these genotypes and the risk of gastric or colorectal cancer.

CONCLUSION: GSTM1 and GSTT1 null genotypes were not associated with increased risk of GC or CRC in Koreans.

Glutathione S-transferase P1 Ile105Val polymorphism and colorectal cancer risk: a meta-analysis and HuGE review

Colorectal cancer is the third most common form of cancer and the fourth most frequent cause of cancer deaths worldwide. Its development is influenced by both environmental and genetic factors. The glutathione S-transferase P1 gene (GSTP1) is a particularly attractive candidate for colorectal cancer susceptibility because it codes the enzyme involved in the metabolism of environmental carcinogens such as polycyclic aromatic hydrocarbons (PAHs). However, epidemiologic findings have been inconsistent. To investigate a putative association of GSTP1 Ile105Val polymorphism with the risk of colorectal cancer, we performed a meta-analysis and HuGE review of 16 published case-control studies (involving a total of 4386 colorectal cancer patients and 7127 controls). We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. Overall, the comparison of Val versus Ile allele showed no differential susceptibility to colorectal cancer (OR=0.98, 95% CI: 0.92-1.04). A protective effect was found in recessive, with an OR of 0.86 (95% CI: 0.76-0.98). Whereas no significant association was observed in either dominant or codominant model. In stratified subgroup analysis, no effect of Val allele was seen in subjects of Caucasian and Asian descent, and in healthy and hospital controls. In conclusion, the meta-analysis suggests that the GSTP1 Ile105Val polymorphism is unlikely to increase considerably the risk of sporadic colorectal cancer, and it should be confirmed in further studies.

Plasma carotenoids, retinol, and tocopherols and postmenopausal breast cancer risk in the Multiethnic Cohort Study: a nested case-control study

Introduction

Assessments by the handful of prospective studies of the association of serum antioxidants and breast cancer risk have yielded inconsistent results. This multiethnic nested case-control study sought to examine the association of plasma carotenoids, retinol, and tocopherols with postmenopausal breast cancer risk.

Methods

From the biospecimen subcohort of the Multiethnic Cohort Study, 286 incident postmenopausal breast cancer cases were matched to 535 controls on age, sex, ethnicity, study location (Hawaii or California), smoking status, date/time of collection and hours of fasting. We measured prediagnostic circulating levels of individual carotenoids, retinol, and tocopherols. Conditional logistic regression was used to compute odds ratios and 95% confidence intervals.

Results

Women with breast cancer tended to have lower levels of plasma carotenoids and tocopherols than matched controls, but the differences were not large or statistically significant and the trends were not monotonic. No association was seen with retinol. A sensitivity analysis excluding cases diagnosed within 1 year after blood draw did not alter the findings.

Conclusions

The lack of significant associations in this multiethnic population is consistent with previously observed results from less racially-diverse cohorts and serves as further evidence against a causal link between plasma micronutrient concentrations and postmenopausal breast cancer risk.