CYP1A1, cigarette smoking, and colon and rectal cancer

Dietary, addictive and habitual factors, and risk of colorectal cancer

BACKGROUND

In Pakistan, the incidence of colorectal cancer (CRC) has sharply increased in recent years. Although several studies have reported global risk factors for CRC, no study has been conducted in Khyber Pakhtunkhwa (KPK), Pakistan, to investigate the risk factors associated with the increased CRC burden in this population.

OBJECTIVES

Therefore, we conducted a clinical survey using a case-control study design to explore the risk factors associatd with CRC.

METHODS

In the present study, one control was enrolled for each case. Both cases and controls were asked to complete a questionnaire to gather data. We analyzed all data using SPSS.

RESULTS

Our study found that certain dietary factors, such as consuming fast food (OR: 3.0; P = 0.0001) and reusing ghee (OR: 2.45; P = 0.0001) and oil (OR: 4.30; P = 0.0001), increase the risk of CRC. Additionally, use of tobacco products like smoking cigarettes (OR: 1.91; P = 0.0001) and using snuff (OR: 3.72; P = 0.0001) significantly increases the risk of CRC. Certain habitual factors, including binge eating (OR: 2.42; P = 0.0001) and spending excessive time watching TV (OR: 1.98; P = 0.0001), also increase the odds of developing CRC. However, our study also identified some protective factors against CRC, such as consuming vegetables (OR: .41; P = 0.0001), developing healthy eating habits (OR: .61; P = 0.0001), and maintaining regular sleeping patterns (OR: .45; P = 0.0001).

CONCLUSION

Given these findings, targeted health education is necessary to prevent the increase in CRC in this area. We also recommend developing and enforcing appropriate control guidelines for cancer risk factors to curb the incidence of CRC.

Role of Cytochrome P450 3A4 in Cancer Drug Resistance: Challenges and Opportunities

One of the biggest obstacles to the treatment of diseases, particularly serious conditions like cancer, is therapeutic resistance. The process of drug resistance is influenced by a number of important variables, including MDR genes, drug efflux, low-quality medications, inadequate dosage, etc. Drug resistance must be addressed, and new combinations based on the pharmacokinetics/pharmacodynamics (PK-PD) characteristics of the partner pharmaceuticals must be developed in order to extend the half-lives of already available medications. The primary mechanism of drug elimination is hepatic biotransformation of medicines by cytochrome P450 (CYP) enzymes; of these CYPs, CYP3A4 makes up 30-40% of all known cytochromes that metabolize medications. Induction or inhibition of CYP3A4-mediated metabolism affects the pharmacokinetics of most anticancer drugs, but these details are not fully understood and highlighted because of the complexity of tumor microenvironments and various influencing patient related factors. The involvement of CYPs, particularly CYP3A4 and other drug-metabolizing enzymes, in cancer medication resistance will be covered in the current review.

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Anticancer, antiplatelet, gastroprotective and hepatoprotective effects of camel urine: A scoping review

Camel urine has traditionally been used to treat multiple human diseases and possesses the most beneficial effects amongst the urine of other animals. However, scientific review evaluating the anticancer, antiplatelet, gastroprotective and hepatoprotective effects of camel urine is still scarce. Thus, this scoping review aimed to provide scientific evidence on the therapeutic potentials of camel urine. Three databases were searched to identify relevant articles (Web of Science, PubMed and Scopus) up to September 2020. Original articles published in English that investigated the effects of camel urine in various diseases were included. The literature search identified six potential articles that met all the inclusion criteria. Three articles showed that camel urine possesses cytotoxic activities against different types of cancer cells. Two studies revealed camel urine's protective effects against liver toxicity and gastric ulcers, whilst another study showed the role of camel urine as an antiplatelet agent. All studies demonstrated significant positive effects with different effective dosages. Thus, camel urine shows promising therapeutic potential in treating human diseases, especially cancer. However, the standardised dosage and potential side effects should be determined before camel urine could be offered as an alternative treatment.

Risk of Colorectal Carcinoma May Predispose to the Genetic Variants of the GST, CYP450, and TP53 Genes Among Nonsmokers in the Saudi Community

PURPOSE

Colorectal carcinoma (CRC) represents a considerable public health burden in Saudi Arabia. Several candidate genes and genetic variants have been associated with morbidity and mortality among patients with CRC. We explored whether allelic variants of the GSTM1, GSTT1, CYP450 (rs4646903 and rs1048943), and TP53 (rs1042522) genes predisposed nonsmoking Saudi individuals to increased risk for CRC.

PATIENTS AND METHODS

DNA from buccal cells of 158 participants (80 with CRC and 78 healthy controls) were analyzed for five SNPs using conventional PCR and TaqMan genotyping assays. The SNPStats software was utilized to choose the best interactive inheritance mode for selected SNPs (https://www.snpstats.net).

RESULTS

The mean age of diagnosis was 62.4±13.5 years (range, 40-83 years), with those aged 71-80 years and those aged 40-50 years accounting for the most diagnoses (35.7% and 28.6% of diagnosis, respectively). The GSTM1 and TP53 rs1042522 SNPs were associated with CRC (OR= 3.7; P< 0.0001, and OR= 1.6; P= 0.033, respectively). A plausible contribution to CRC was observed for the GSTM1 and TP53 rs1042522 SNPs (x 2 Yates= 14.7; P= 0.00013, and x 2 Yates= 11.2; P= 0.0008, respectively), while the GSTT1 null variant did not affect risk. Heterozygosity in the CYP450 (rs4646903 and rs1048943 SNPs) was associated with a significant risk for CRC. The GSTM1/GSTT1 and CYP450 rs4646903/rs1048943 SNP pairs were in linkage disequilibrium, and the associations were statistically significant (P= 0.01 and P= 4.6x10‒7, respectively).

CONCLUSION

The GSTM1 and TP53 rs1042522 variants can increase the development of CRC in Saudi nonsmokers. Even the presence of one copy of a variant allele in the CYP1A1 gene can predispose CRC risk. Additional studies should also examine other SNP combinations with lifestyle factors that may help prevent, rather than facilitate, colorectal tumorigenesis.

Biological roles of cytochrome P450 1A1, 1A2, and 1B1 enzymes

Human cytochrome P450 enzymes (CYPs) play a critical role in various biological processes and human diseases. CYP1 family members, including CYP1A1, CYP1A2, and CYP1B1, are induced by aryl hydrocarbon receptors (AhRs). The binding of ligands such as polycyclic aromatic hydrocarbons activates the AhRs, which are involved in the metabolism (including oxidation) of various endogenous or exogenous substrates. The ligands that induce CYP1 expression are reported to be carcinogenic xenobiotics. Hence, CYP1 enzymes are correlated with the pathogenesis of cancers. Various endogenous substrates are involved in the metabolism of steroid hormones, eicosanoids, and other biological molecules that mediate the pathogenesis of several human diseases. Additionally, CYP1s metabolize and activate/inactivate therapeutic drugs, especially, anti-cancer agents. As the metabolism of drugs determines their therapeutic efficacy, CYP1s can determine the susceptibility of patients to some drugs. Thus, understanding the role of CYP1s in diseases and establishing novel and efficient therapeutic strategies based on CYP1s have piqued the interest of the scientific community.

Epigenetic Regulation of Differentially Expressed Drug-Metabolizing Enzymes in Cancer

Drug metabolism is a biotransformation process of drugs, catalyzed by drug-metabolizing enzymes (DMEs), including phase I DMEs and phase II DMEs. The aberrant expression of DMEs occurs in the different stages of cancer. It can contribute to the development of cancer and lead to individual variations in drug response by affecting the metabolic process of carcinogen and anticancer drugs. Apart from genetic polymorphisms, which we know the most about, current evidence indicates that epigenetic regulation is also central to the expression of DMEs. This review summarizes differentially expressed DMEs in cancer and related epigenetic changes, including DNA methylation, histone modification, and noncoding RNAs. Exploring the epigenetic regulation of differentially expressed DMEs can provide a basis for implementing individualized and rationalized medication. Meanwhile, it can promote the development of new biomarkers and targets for the diagnosis, treatment, and prognosis of cancer. SIGNIFICANCE STATEMENT: This review summarizes the aberrant expression of DMEs in cancer and the related epigenetic regulation of differentially expressed DMEs. Exploring the epigenetic regulatory mechanism of DMEs in cancer can help us to understand the role of DMEs in cancer progression and chemoresistance. Also, it provides a basis for developing new biomarkers and targets for the diagnosis, treatment, and prognosis of cancer.

p53 protein expression affected by TP53 polymorphism is associated with the biological behavior and prognosis of low rectal cancer

Low rectal cancer is a subtype of colorectal cancer at a special anatomic site with distinct biological behavior. TP53 is one of the most important cancer suppressor genes, and its structural variation and abnormal expression has been revealed to be associated with multiple cancer types. However, to the best of our knowledge, the association of p53 protein expression with its gene polymorphism, biological behavior and prognosis in low rectal cancer has not been clarified. Therefore, the current study aimed to explore these associations. In the present study, 347 patients with low rectal cancer and 353 controls were enrolled. Kompetitive Allele-Specific Polymerase Chain Reaction was used to detect five polymorphic sites of the TP53 gene (rs1042522, rs12947788, rs1625895, rs2909430 and rs12951053), while immunohistochemistry was used to detect the protein expression of TP53. The associations between p53 protein expression and TP53 polymorphism, biological behavior and prognosis in low rectal cancer were systematically analyzed. In low rectal cancer, p53 protein expression was markedly higher in TP53 rs1042522 mutant carriers compared with that in other genotypes where expression was higher in poorly differentiated, III-IV phase and T3-4 phase tumors, and in III-IV phase female patients. The survival time of patients with low p53 protein expression was evidently longer in females, non-smokers and patients >60 years old. In summary, p53 protein expression was identified to be affected by TP53 rs1042522 polymorphism, and was associated with the biological behavior and prognosis of low rectal cancer. TP53 rs1042522 and the associated protein expression could be used as indicators for biological behavior and prognosis in low rectal cancer.

Genetic variant in miR-21 binding sites is associated with colorectal cancer risk

Single nucleotide polymorphisms (SNPs) within binding sites of microRNAs (miRNAs) could modify cancer susceptibility by changing the binding affinity of miRNAs on their target mRNA 3'-untranslated regions (UTRs). MicroRNA-21 (miR-21) is involved in the development of colorectal cancer. However, the relationship between SNPs within the binding sites of miR-21 and colorectal cancer risk has not been widely investigated. A case-control study including 1147 patients and 1203 controls was performed to evaluate the association of SNPs in miR-21 binding sites and colorectal cancer risk. Dual-luciferase reporter assays and functional assays were performed to evaluate the effects of miR-21. The SNP rs6504593 C allele conferred an increased risk of colorectal cancer compared with the T allele in an additive model (odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.04-1.36, P = 0.011). Dual-luciferase reporter assays demonstrated that the rs6504593 T allele negatively post-transcriptionally regulated IGF2BP1 by altering the binding affinity of miR-21. Additionally, colorectal cancer cells transiently transfected with miR-21 mimics promoted cell proliferation and suppressed apoptosis, whereas inhibition of miR-21 decreased cell growth. These data suggest that the miR-21 binding site SNP rs6504593 in the IGF2BP1 3'-UTR may alter IGF2BP1 expression and contribute to colorectal cancer risk.

CYP2E1 and GSTM1 gene polymorphisms, environmental factors, and the susceptibility to lung cancer

OBJECTIVE

To investigate the relationships between the CYP2E1 RsaI polymorphism, GSTM1 polymorphism, and the susceptibility to lung cancer, along with the interactions between environmental factors and these genes.

METHODS

A case-control study was carried out to explore the independent effect of gene polymorphisms on risk of lung cancer, and the combined effects of gene loci. The stratification analysis of age, sex, smoking, and drinking combined with positive loci was also analyzed, and any interaction was identified.

RESULTS

The logistic regression analysis showed that there were statistical relationships between the CYP2E1 RsaI TT genotype and lung cancer, GSTM1 (-) and lung cancer. The combined effect's analysis of these 2 loci showed that, with an increase in the number of risk alleles, the risk of lung cancer also increased (supposing 0 risk allele as the reference group). Subjects carrying 3 risk alleles had the highest risk of developing lung cancer with an adjusted OR = 10.38 (95% CI 2.10-51.35). Stratified analysis showed that, in women, nonsmoking subjects, or nondrinking subjects, the combined effects could increase the risk of lung cancer; no heterogeneity was found between these layers except sex. The interaction analysis showed that, supposing the male, GSTM1 (+) genotype as the reference, the female, GSTM1 (-) genotype had a significantly increased risk of lung cancer (OR = 2.17 [1.01-4.70]); when the non-smoking, GSTM1 (+) genotype subjects was the reference group, smoking, GSTM1 (+) genotype subjects and smoking, GSTM1 (-) genotype subjects had significantly higher risk of lung cancer (OR = 2.00 [1.01-3.96], OR = 2.89 [1.28-6.54]).

CONCLUSION

CYP2E1 RsaI TT genotype was a protective factor against the development of lung cancer, while GSTM1 (-) genotype was a risk factor for lung cancer. Increases in the number of the risk alleles also increased lung cancer risk. GSTM1 (-) genotype, sex, and smoking status might interact in the incidence of lung cancer.

CYP1A1m1 and CYP2C9*2 and *3 polymorphism and risk to develop ARV-associated hepatotoxicity and its severity

Non-nucleoside reverse transcriptase inhibitors are metabolized in the liver by cytochrome P450 (CYP) isoenzymes. Variations in the genes encoding these enzymes may influence the activity of corresponding metabolizing enzymes. This study aimed at assessing association of CYP2C9*2 430C/T, CYP2C9*31075A/C, and CYP1A1m1 3801T/C polymorphism with risk to develop ARV Antiretroviral-associated hepatotoxicity and its severity. In this case-control study, genotyping of CYP2C9*2, CYP2C9*3, and CYP1A1m1 genes was done in 34 HIV-infected individuals with hepatotoxicity and 131 without hepatotoxicity, and 153 unrelated healthy individuals using PCR-RFLP. CYP1A1m13801CC genotype was likely to be associated with severe ARV-associated hepatotoxicity (OR = 1.78, p = 0.70). CYP1A1m13801CC genotype and combined genotype TC + CC were likely to be associated with development of ARV-associated hepatotoxicity (OR = 2.57, p = 0.08; OR = 1.42, p = 0.17). CYP1A1m1 3801CC genotype among advanced and intermediate HIV disease stage was likely to be associated with advancement of disease (OR = 2.56, p = 0.77; OR = 2.37, p = 0.45). CYP2C9*31075AC genotype among alcohol users was likely to be associated with development of ARV-associated hepatotoxicity (OR = 1.67, p = 0.38). CYP1A1m1 3801TC genotype and combined genotype TC + CC among nevirapine users were likely to be associated with severe ARV-associated hepatotoxicity (OR = 3.68, p = 0.27; OR = 4.91, p = 0.13). Among those who received nevirapine, presence of CYP1A1m1 3801TC genotype was likely to be associated with increased risk of development of ARV-associated hepatotoxicity (OR = 1.50, p = 0.78). CYP1A1m1 3801TC, 3801CC, and CYP2C9*3 1075AC genotypes among combined alcohol + nevirapine users increased the risk of development of ARV-associated hepatotoxicity (OR = 1.41, p = 0.53; OR = 1.49, p = 0.83; OR = 1.78, p = 0.35). In conclusion, individuals with CYP1A1m13801CC and 3801TC genotypes independently and in the presence of alcohol and nevirapine usage is likely to be associated with increased risk of development of ARV-associated hepatotoxicity, its severity, and advancement of disease. CYP2C9*31075AC genotype with combined alcohol and nevirapine usage indicated a risk for development of ARV-associated hepatotoxicity.

Dietary Flavonoids, CYP1A1 Genetic Variants, and the Risk of Colorectal Cancer in a Korean population

The role of dietary flavonoid intake in colorectal carcinogenesis might differ according to flavonoid subclasses and individual genetic variants related to carcinogen metabolism. Therefore, we examined whether greater dietary intake of flavonoid subclasses was associated with a lower risk of colorectal cancer and whether CYP1A1 genetic variants altered this association. A semi-quantitative food frequency questionnaire was used to assess the dietary intake of six flavonoid subclasses (flavonols, flavones, flavanones, flavan-3-ols, anthocyanidins, and isoflavones) in 923 patients with colorectal cancer and 1,846 controls; furthermore, CYP1A1 genetic variants (rs4646903 and rs1048943) were genotyped. Among the subclasses of flavonoids, higher intake of flavonols and flavan-3-ols showed a stronger association with a reduced risk of colorectal cancer after adjusting for potential confounding factors. Carriers of the CYP1A1 rs4646903 CC homozygous variant showed a reduced risk of rectal cancer compared with that in TT carriers. The inverse association between dietary flavonol intake and colorectal cancer risk was stronger among carriers of the CC homozygous variant than among T allele carriers (P for interaction = 0.02), particularly for rectal cancer (P for interaction = 0.005). In conclusion, the effect of dietary flavonoid intake on colorectal cancer risk differs according to flavonoid subclasses and CYP1A1 genetic variants.

Associations between CYP1A1 rs1048943 A > G and rs4646903 T > C genetic variations and colorectal cancer risk: Proof from 26 case-control studies

Cytochrome P450 1A1 (CYP1A1) enzyme is one of the most important metabolizing enzymes responsible for the metabolism of numerous xenobiotics. Numerous individual case-control studies have investigated the associations between the CYP1A1 rs1048943 A > G and rs4646903 T > C genetic variations and colorectal cancer (CRC) risk, but the conclusions were controversial. To obtain a scientific conclusion, we performed a meta-analysis based on a total of 26 publications, including 20 studies with 8665 cases and 9953 controls on rs1048943 A > G and 19 studies with 6416 cases and 7551 controls on rs4646903 T > C, respectively. The pooled analysis indicated that rs1048943 A > G was associated with an increased risk of CRC (G vs. A: OR = 1.28, 95% CI = 1.08-1.52; GG vs. AA: OR = 1.54, 95% CI = 1.25-1.91; GA vs. AA: OR = 1.26, 95% CI = 1.00-1.60; GG/GA vs. AA: OR = 1.31, 95% CI = 1.05-1.64; GG vs. GA/AA. OR = 1.56, 95% CI = 1.26-1.91). Stratification analysis showed the association between rs1048943 A > G and CRC risk was more obvious in studies with the population-based (PB) design or high quality score. The association between rs4646903 T > C and CRC risk did not reach statistical significance in the pooled analysis as well as stratification analysis. This meta-analysis demonstrated CYP1A1 rs1048943 A > G may increase the susceptibility to CRC instead of rs4646903 T > C. This conclusion suggested CYP1A1 may contribute to the pathogenesis of CRC.

Comparative Expression Analysis of Cytochrome P450 1A1, Cytochrome P450 1B1 and Nuclear Receptors in the Female Genital and Colorectal Tissues of Human and Pigtailed Macaque

This manuscript summarizes our recent progress in examine the CYP1A1 and CYP1B1 as well as a number of nuclear receptors in the female genital and colorectal tissues of human and pigtailed macaque. Understanding the nuclear receptor mediated regulation of CYP1A1 and 1B1 expression in these tissues is necessary for identifying cancer risk factors and developing CYP1A1/1B1-targeted anti-cancer therapeutics. However, there is a lack of systematic and comparative analysis of the expression profile of CYP1A1, 1B1 and NRs in the female genital and colorectal tissues of human and clinically relevant animal models. The current study aims to fill this gap. We found CYP1A1, CYP1B1 and a number of nuclear receptors were expressed in the female genital and colorectal tissues of human and macaque. However, the mRNA level and protein localization of these CYP enzymes and NRs depended on the type of tissue examined.

Cytochrome P450 (CYP) 1A1 and CYP1B1 activate hormonal and environmental procarcinogens, and are associated with carcinogenesis in female genital and colorectal tissues. Understanding the nuclear receptor (NR) mediated regulation of CYP expression in these tissues is necessary for identifying cancer risk factors and developing CYP1A1/1B1-targeted anti-cancer therapeutics. The study aims to analyze the expression profile of CYP1A1, 1B1 and NRs in the female genital and colorectal tissues of human and pigtailed macaques. We found that compared to the liver, human CYP1A1 mRNA level in the genital and colorectal tissues was significantly lower, while the CYP1B1 level was significantly higher. CYP1A1 protein was mainly localized in the plasma membrane of the uterine and endocervical epithelial cells. The CYP1B1 protein was concentrated in the nucleus of genital and colorectal tissues. Fourteen NRs in the genital tract and 12 NRs in colorectal tissue were expressed at levels similar to or higher than the liver. The expression and localization of CYP1A1, CYP1B1, and NRs in macaque tissues were usually comparable to those of human tissues. In addition, menopause did not significantly alter the ectocervical mRNA levels of CYP1A1, CYP1B1, or NRs.

Cytochrome P450 1A1 gene polymorphisms and digestive tract cancer susceptibility: a meta-analysis

Cytochrome P450 1A1 (CYP1A1) is a phase I enzyme that regulates the metabolism of environmental carcinogens and alter the susceptibility to various cancers. Many studies have investigated the association between the CYP1A1 MspI and Ile462Val polymorphisms and digestive tract cancer (DTC) risk in different groups of populations, but their results were inconsistent. The PubMed and Embase Database were searched for case–control studies published up to 30th September, 2015. Data were extracted and pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the relationship. Totally, 39 case–control studies (9094 cases and 12,487 controls) were included. The G allele in Ile/Val polymorphism was significantly associated with elevated DTC risk with per‐allele OR of 1.24 (95% CI = 1.09–1.41, P = 0.001). Similar results were also detected under the other genetic models. Evidence was only found to support an association between MspI polymorphism and DTC in the subgroups of caucasian and mixed individuals, but not in the whole population (the dominant model: OR = 1.19, 95% CI = 0.94–1.91, P = 0.146). In conclusion, our results suggest that the CYP1A1 polymorphisms are potential risk factors for DTC. And large sample size and well‐designed studies with detailed clinical information are needed to more precisely evaluate our founding.

SASH1, a new potential link between smoking and atherosclerosis

OBJECTIVE

We have previously reported that SASH1 expression is increased in circulating human monocytes from smokers and was positively correlated with the number of carotid atherosclerotic plaques. The aim of this study was to further validate the link between smoking, SASH1 and atherosclerosis within the vascular wall and to assess the impact of SASH1 expression on endothelial cell functions.

METHOD

Human carotids with atherosclerotic plaques were obtained from 58 patients (45 of them with known smoking status: smoker, non-smoker, ex-smokers), and were processed for gene expression analyses and immunostaining. To investigate its function, SASH1 was silenced in human aortic endothelial cells (HAECs) using two different siRNA and subcellular localization of SASH1 was determined by immunostaining and subcellular fractionation. Subsequently the transcriptomic analyses and functional experiments (wound healing, WST-1 proliferation or Matrigel assays) were performed to characterize SASH1 function.

RESULTS

SASH1 was expressed in human vascular cells (HAECs, smooth muscle cells) and in monocytes/macrophages. Its tissue expression was significantly higher in the atherosclerotic carotids of smokers compared to non-smokers (p < 0.01). In HAECs, SASH1 was expressed mostly in the cytoplasm and SASH1 knockdown resulted in an increased cell migration, proliferation and angiogenesis. Transcriptomic and pathway analyses showed that SASH1 silencing results in a decreased CYP1A1 expression possibly through the inhibition of TP53 activity.

CONCLUSION

We showed that SASH1 expression is increased in atherosclerotic carotids in smokers and its silencing affects endothelial angiogenic functions; therefore we provide a potential link between smoking and atherosclerosis through SASH1 expression.

Cytochrome P450 in Cancer Susceptibility and Treatment

Cytochrome 450 (CYP450) designates a group of enzymes abundant in smooth endoplasmic reticulum of hepatocytes and epithelial cells of small intestines. The main function of CYP450 is oxidative catalysis of various endogenous and exogenous substances. CYP450 are implicated in phase I metabolism of 80% of drugs currently in use, including anticancer drugs. They are also involved in synthesis of various hormones and influence hormone-related cancers. CYP450 genes are highly polymorphic and their variants play an important role in cancer risk and treatment. Association studies and meta-analyses have been performed to decipher the role of CYP450 polymorphisms in cancer susceptibility. Cancer treatment involves multimodal therapies and evaluation of CYP450 polymorphisms is necessary for pharmacogenetic assessment of anticancer therapy outcomes. In addition, CYP450 inhibitors are being evaluated for improved pharmacokinetics and oral formulation of several anticancer drugs.

Cytochrome P450 1A1, 2E1 and GSTM1 gene polymorphisms and susceptibility to colorectal cancer in the Saudi population

BACKGROUND

The Saudi population has experienced a sharp increase in colorectal and gastric cancer incidences within the last few years. The relationship between gene polymorphisms of xenobiotic metabolizing enzymes and colorectal cancer (CRC) incidence has not previously investigated among the Saudi population. The aim of the present study was to investigate contributions of CYP1A1, CYP2E1, and GSTM1 gene polymorphisms.

MATERIALS AND METHODS

Blood samples were collected from CRC patients and healthy controls and genotypes were determined by polymerase chain reaction restriction fragment length polymorphism and sequencing.

RESULTS AND CONCLUSIONS

CYP2E1*6 was not significantly associated with CRC development (odd ratio=1.29; confidence interval 0.68-2.45). A remarkable and statistically significant association was observed among patients with CYP1Awt/*2A (odd ratio=3.65; 95% confidence interval 1.39-9.57). The GSTM1*0/*0 genotype was found in 2% of CRC patients under investigation. The levels of CYP1A1, CYP2E1 and GSTM1 mRNA gene expression were found to be 4, 4.2 and 4.8 fold, respectively, by quantitative real time PCR. The results of the present case-control study show that the studied Saudi population resembles Caucasians with respect to the considered polymorphisms. Investigation of genetic risk factors and susceptibility gene polymorphisms in our Saudi population should be helpful for better understanding of CRC etiology.

Expression of selected cytochrome P450 isoforms and of cooperating enzymes in colorectal tissues in selected pathological conditions

The current interest in CYP expression in the colon results from its uniqueness as a target organ for cancer. To date, the CYP expression profiles in the colon have not yet been subject of comprehensive research. In this study, we investigated 40 patients with Crohn's disease, 40 with ulcerative colitis, and 40 healthy subjects as a control group. Colon tissues were fixed, dehydrated, cleared in xylene and embedded in paraffin. Sections were prepared from paraffin blocks for immunohistochemical staining with specific antibodies. We used antibodies to the human CYP1A1, CYP2B6, CYP2C9, CYP2E1 and CYP3A4 isoforms, as well as antibodies to the human glycoprotein P, glutathione-S transferase and antibody to the UDP-glucuronosyltransferase. The sections were stained immunohistochemically and examined using light microscopy. Cellular localization was determined, and computer image analysis was used. In all cases with Crohn's disease, the proteins studied showed at least a twofold expression. Ulcerative colitis showed a much weaker influence regarding the expression of the proteins studied but in case of CYP2C9 and UDP-glucuronosyltransferase, a decrease of expression was observed.

CYP1A1, GSTM1, GSTT1 and NQO1 polymorphisms and colorectal adenomas in Japanese men

AIM: To investigate the role of functional genetic polymorphisms of metabolic enzymes of tobacco carcinogens in the development of colorectal adenomas.

METHODS: The study subjects were 455 patients with colorectal adenomas and 1052 controls with no polyps who underwent total colonoscopy in a preretirement health examination at two Self Defense Forces hospitals. The genetic polymorphisms studied were CYP1A1*2A (rs 4646903), CYP1A1*2C (rs 1048943), GSTM1 (null or non-null genotype), GSTT1 (null or non-null genotype) and NQO1 C609T (rs 1800566). Genotypes were determined by the polymerase chain reaction (PCR)-restriction fragment length polymorphism or PCR method using genomic DNA extracted from the buffy coat. Cigarette smoking and other lifestyle factors were ascertained by a self-administered questionnaire. The associations of the polymorphisms with colorectal adenomas were examined by means of OR and 95%CI, which were derived from logistic regression analysis. Statistical adjustment was made for smoking, alcohol use, body mass index and other factors. The gene-gene interaction and effect modification of smoking were evaluated by the likelihood ratio test.

RESULTS: None of the five polymorphisms showed a significant association with colorectal adenomas, nor was the combination of GSTM1 and GSTT1. A borderline significant interaction was observed for the combination of CYP1A1*2C and NQO1 (P = 0.051). The OR associated with CYP1A1*2C was significantly lower than unity among individuals with the NQO1 609CC genotype. The adjusted OR for the combination of the CYP1A1*2C allele and NQO1 609CC genotype was 0.61 (95%CI: 0.42-0.91). Although the interaction was not statistically significant (P = 0.24), the OR for individuals carrying the CYP1A1*2C allele and GSTT1 null genotype decreased significantly compared with those who had neither CYP1A1*2C allele nor GSTT1 null genotype (adjusted OR: 0.69, 95%CI: 0.49-0.97). Smoking did not modify the associations of the individual polymorphisms with colorectal adenomas. There was no measurable effect modification of smoking even regarding the combination of the genetic polymorphisms of the phase I and phase II enzymes.

CONCLUSION: Combination of the CYP1A1*2C and NQO1 609CC genotypes was associated with a decreased risk of colorectal adenomas regardless of smoking status.

Meta-analyses of colorectal cancer risk factors

PURPOSE

Demographic, behavioral, and environmental factors have been associated with increased risk of colorectal cancer (CRC). We reviewed the published evidence and explored associations between risk factors and CRC incidence.

METHODS

We identified 12 established non-screening CRC risk factors and performed a comprehensive review and meta-analyses to quantify each factor's impact on CRC risk. We used random-effects models of the logarithms of risks across studies: inverse-variance weighted averages for dichotomous factors and generalized least squares for dose-response for multi-level factors.

RESULTS

Significant risk factors include inflammatory bowel disease (RR = 2.93, 95 % CI 1.79-4.81); CRC history in first-degree relative (RR = 1.80, 95 % CI 1.61-2.02); body mass index (BMI) to overall population (RR = 1.10 per 8 kg/m(2) increase, 95 % CI 1.08-1.12); physical activity (RR = 0.88, 95 % CI 0.86-0.91 for 2 standard deviations increased physical activity score); cigarette smoking (RR = 1.06, 95 % CI 1.03-1.08 for 5 pack-years); and consumption of red meat (RR = 1.13, 95 % CI 1.09-1.16 for 5 servings/week), fruit (RR = 0.85, 95 % CI 0.75-0.96 for 3 servings/day), and vegetables (RR = 0.86, 95 % CI 0.78-0.94 for 5 servings/day).

CONCLUSIONS

We developed a comprehensive risk modeling strategy that incorporates multiple effects to predict an individual's risk of developing CRC. Inflammatory bowel disease and history of CRC in first-degree relatives are associated with much higher risk of CRC. Increased BMI, red meat intake, cigarette smoking, low physical activity, low vegetable consumption, and low fruit consumption were associated with moderately increased risk of CRC.

Harmine and harmaline downregulate TCDD-induced Cyp1a1 in the livers and lungs of C57BL/6 mice

We previously demonstrated that Peganum harmala L. extract and its main active constituents, harmine and harmaline inhibit the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated induction of the carcinogen-activating enzyme, Cyp1a1, in vitro. However, the effect of both alkaloids on Cyp1a1 in vivo has not been investigated. Therefore, the aim of this study is to examine the effect of harmine and harmaline on TCDD-mediated induction of Cyp1a1 in mice livers and lungs. C57BL/6 male mice were distributed into four groups (n = 6). First group received vehicle, while the second group received TCDD (i.p.). The third and fourth groups received either harmine or harmaline (i.p.) × 3 times along with TCDD one time with the mid dose of harmine and harmaline. All mice were sacrificed after 14 h from TCDD injection, and livers and lungs were isolated. The effect of harmine and harmaline on TCDD-mediated induction of Cyp1a1 mRNA, protein, and activity levels was determined using real-time PCR, Western blot analysis, and 7-ethoxyresurofin as a substrate, respectively. Our results showed that harmine and harmaline significantly decreased the TCDD-mediated induction of Cyp1a1 in both the livers and lungs. We concluded that harmine and harmaline are promising candidate to inhibit TCDD-mediated induction of Cyp1a1 in mice hepatic and extrahepatic tissues.

Absence of association between N-acetyltransferase 2 acetylator status and colorectal cancer susceptibility: based on evidence from 40 studies

BACKGROUND AND OBJECTIVES

N-Acetyltransferase (NAT) 2 is an important enzyme involved in the metabolism of different xenobiotics, including potential carcinogens, whose phenotypes were reported to be related to individual susceptibility to colorectal cancer (CRC). However, the results remain conflicting. To assess the relationship between NAT2 phenotypes and CRC risk, we performed this meta-analysis.

METHODS

A comprehensive literature search was conducted to identify all case-control or cohort studies of NAT2 acetylator status on the susceptibility of CRC by searching of PubMed and EMBASE, up to May 20, 2011. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association.

RESULTS

A total of over 40,000 subjects from 40 published literatures were identified by searching the databases. No significantly elevated CRC risk in individuals with NAT2 slow acetylators compared with fast acetylators was found when all studies pooled (OR = 0.95, 95% CI: 0.87-1.04, I(2) = 52.6%). While three studies contributed to the source of heterogeneity were removed, there was still null result observed (OR = 0.96, 95% CI: 0.90-1.03, P = 0.17 for heterogeneity, I(2) = 17.8%). In addition, we failed to detect any associations in the stratified analyses by race, sex, source of controls, smoking status, genotyping methods or tumor localization. No publication bias was observed in this study.

CONCLUSIONS

This meta-analysis suggests that the NAT2 phenotypes may not be associated with colorectal cancer development.

Camel milk modulates the expression of aryl hydrocarbon receptor-regulated genes, Cyp1a1, Nqo1, and Gsta1, in murine hepatoma Hepa 1c1c7 cells

There is a traditional belief in the Middle East that camel milk may aid in prevention and treatment of numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of camel milk to modulate the expression of a well-known cancer-activating gene, Cytochrome P450 1a1 (Cyp1a1), and cancer-protective genes, NAD(P)H:quinone oxidoreductase 1 (Nqo1) and glutathione S-transferase a1 (Gsta1), in murine hepatoma Hepa 1c1c7 cell line. Our results showed that camel milk significantly inhibited the induction of Cyp1a1 gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent Cyp1a1 inducer and known carcinogenic chemical, at mRNA, protein, and activity levels in a concentration-dependent manner. In addition, camel milk significantly decreased the xenobiotic responsive element (XRE)-dependent luciferase activity, suggesting a transcriptional mechanism is involved. Furthermore, this inhibitory effect of camel milk was associated with a proportional increase in heme oxygenase 1. On the other hand, camel milk significantly induced Nqo1 and Gsta1 mRNA expression level in a concentration-dependent fashion. The RNA synthesis inhibitor, actinomycin D, completely blocked the induction of Nqo1 mRNA by camel milk suggesting the requirement of de novo RNA synthesis through a transcriptional mechanism. In conclusion, camel milk modulates the expression of Cyp1a1, Nqo1, and Gsta1 at the transcriptional and posttranscriptional levels.

The association of NAT1 polymorphisms and colorectal carcinoma risk: evidence from 20,000 subjects

Published data on the association between N-acetyltransferase 1 (NAT1) gene polymorphisms and colorectal carcinoma (CRC) susceptivity are inconclusive. To derive a more precise estimation of the association, we conducted this meta-analysis. Data were collected from electronic databases: PubMed, EMBASE, with the last report up to May 2010. The odds ratio (OR) and corresponding 95% confidence intervals (CIs) were used to assess the strength of the association. A total of 20 individual studies including 8,219 cases and 11,498 controls based on the search criteria were involved. Meta-analysis was performed for slow versus rapid acetylation genotypes of NAT1. We found no association between NAT1 polymorphisms and CRC in overall population (OR = 0.96, 95% CI = 0.88-1.05 P = 0.05 for heterogeneity) without significant publication bias present. In subgroup analyses, similar results were found in different ethnicities, source of controls, genotyping methods and adjustment. Current meta-analysis suggests that lack of association between the NAT1 polymorphisms and individual risk to CRC.

Harmaline and harmalol inhibit the carcinogen-activating enzyme CYP1A1 via transcriptional and posttranslational mechanisms

Dioxins are known to cause several human cancers through activation of the aryl hydrocarbon receptor (AhR). Harmaline and harmalol are dihydro-β-carboline compounds present in several medicinal plants such as Peganum harmala. We have previously demonstrated the ability of P. harmala extract to inhibit TCDD-mediated induction of Cyp1a1 in murine hepatoma Hepa 1c1c7 cells. Therefore, the aim of this study is to examine the effect of harmaline and its main metabolite, harmalol, on dioxin-mediated induction of CYP1A1 in human hepatoma HepG2 cells. Our results showed that harmaline and harmalol at concentrations of (0.5-12.5μM) significantly inhibited the dioxin-induced CYP1A1 at mRNA, protein and activity levels in a concentration-dependent manner. The role of AhR was determined by the inhibition of the TCDD-mediated induction of AhR-dependent luciferase activity and the AhR/ARNT/XRE formation by both harmaline and harmalol. In addition, harmaline significantly displaced [(3)H]TCDD in the competitive ligand binding assay. At posttranslational level, both harmaline and harmalol decreased the protein stability of CYP1A1, suggesting that posttranslational modifications are involved. Moreover, the posttranslational modifications of harmaline and harmalol involve ubiquitin-proteasomal pathway and direct inhibitory effects of both compounds on CYP1A1 enzyme. These data suggest that harmaline and harmalol are promising agents for preventing dioxin-mediated effects.

Transcriptional and posttranslational inhibition of dioxin-mediated induction of CYP1A1 by harmine and harmol

Dioxins are widespread environmental contaminants that induce the carcinogen-activating enzyme, cytochrome P450 1A1 (CYP1A1) through an aryl hydrocarbon receptor (AhR)-dependent mechanism. We previously demonstrated that harmine inhibits the dioxin-mediated induction of Cyp1a1 activity in murine hepatoma cells. Therefore, the aim of this study is to determine the effect of harmine and its main metabolite, harmol, on the dioxin-mediated induction of CYP1A1 in human HepG2 and murine Hepa 1c1c7 hepatoma cells. Our results showed that harmine and harmol significantly inhibited the dioxin-mediated induction of CYP1A1 at mRNA, protein, and activity levels in a concentration-dependent manner in human and murine hepatoma cells. Moreover, harmine and harmol inhibited the AhR-dependent luciferase activity and the activation and transformation of AhR using the electrophoretic mobility shift assay. In addition, harmine and harmol displaced [(3)H]TCDD in the competitive ligand binding assay. At posttranslational level, both harmine and harmol decreased the protein stability of CYP1A1, suggesting that posttranslational mechanism is involved. Furthermore, we demonstrated that the underlying mechanisms of the posttranslational modifications of both compounds involve ubiquitin-proteasomal pathway and direct inhibitory effects of CYP1A1 enzyme. We concluded that harmine and its metabolite, harmol, are new inhibitors of dioxin-mediated effects.

Polycyclic aromatic hydrocarbons and digestive tract cancers: a perspective

Cancers of the colon are most common in the Western world. In majority of these cases, there is no familial history and sporadic gene damage seems to play an important role in the development of tumors in the colon. Studies have shown that environmental factors, especially diet, play an important role in susceptibility to gastrointestinal (GI) tract cancers. Consequently, environmental chemicals that contaminate food or diet during preparation become important in the development of GI cancers. Polycyclic aromatic hydrocarbons (PAHs) are one such family of ubiquitous environmental toxicants. These pollutants enter the human body through consumption of contaminated food, drinking water, inhalation of cigarette smoke, automobile exhausts, and contaminated air from occupational settings. Among these pathways, dietary intake of PAHs constitutes a major source of exposure in humans. Although many reviews and books on PAHs and their ability to cause toxicity and breast or lung cancer have been published, aspects on contribution of diet, smoking and other factors toward development of digestive tract cancers, and strategies to assess risk from exposure to PAHs have received much less attention. This review, therefore, focuses on dietary intake of PAHs in humans, animal models, and cell cultures used for GI cancer studies along with epidemiological findings. Bioavailability and biotransformation processes, which influence the disposition of PAHs in body and the underlying causative mechanisms of GI cancers, are also discussed. The existing data gaps and scope for future studies is also emphasized. This information is expected to stimulate research on mechanisms of sporadic GI cancers caused by exposure to environmental carcinogens.

Glutathione S-transferase (GST) gene polymorphisms, cigarette smoking and colorectal cancer risk among Chinese in Singapore

Cigarette smoking is a risk factor for colorectal cancer. Putative colorectal procarcinogens in tobacco smoke include polycyclic aromatic hydrocarbons and heterocyclic aromatic amines that are known substrates of glutathione S-transferases (GSTs). This study examined the influence of functional GST gene polymorphisms on the smoking-colorectal cancer association in a population known to be minimally exposed to dietary sources of these procarcinogens. Incident cases of colorectal cancer (n = 480) and matched controls (n = 1167) were selected from the Singapore Chinese Health Study, a population-based prospective cohort of 63 257 men and women who have been followed since 1993. We determined the deletion polymorphisms of GSTM1 and GSTT1 and the functional polymorphism at codon 105 of GSTP1 for each subject. A three level composite GST index was used to examine if GST profile affected a smoker's risk of developing colorectal cancer. While there was no statistically significant association between cigarette smoking and colorectal cancer risk among subjects absent of any at-risk GST genotypes, smokers possessing two to three at-risk GST genotypes exhibited a statistically significant increased risk of colorectal cancer compared with non-smokers (P = 0.0002). In this latter stratum, heavy smokers exhibited a >5-fold increased risk relative to never-smokers (odds ratio, 5.43; 95% confidence interval, 2.22-13.23). Subjects with one at-risk GST genotype displayed a statistically significant but weaker association with smoking. These findings suggest that GST gene polymorphisms influence interindividual susceptibility to smoking-associated colorectal cancer. Our data indicate an important role for GST enzymes in the detoxification of colorectal carcinogens in tobacco smoke.

Polymorphisms of Metabolizing Enzymes and Susceptibility to Ethmoid Intestinal-type Adenocarcinoma in Professionally Exposed Patients

Intestinal-type adenocarcinoma (ITAC) of ethmoid is a rare tumor associated with occupational exposure to wood and leather dusts. Polymorphisms in xenobiotic metabolizing enzymes play an important role in gene-environment interactions and may contribute to a high degree of variance in individual susceptibility to cancer risk. The aim of this study was to investigate by polymerase chain reaction the role of polymorphisms at CYP1A1 and GSTM1 genes in 30 ethmoid ITAC patients and 79 healthy donors. The distribution of Thr/Asn genotype at CYP1A1 codon 461 was significantly overrepresented among the patients (23.3%; P = .0422), whereas the Ile/Val genotype at CYP1A1 codon 462 was not significantly different between cases and controls (P = .76). The GSTM1 null genotype was not significantly different between cases and control (P = 1), but we observed that the combined codon 461 Thr/Asn and GSTM1 null genotype was overrepresented in the patient group (P = .0019). The results reveal that patients with CYP1A1 codon 461 polymorphism may be at high genetic risk of ITAC and that the risk increases in the presence of combined polymorphism of CYP1A1 and GSTM1 null genotype. This strongly suggests that CYP1A1 codon 461 and GSTM1 null genotype may be useful in selecting exposed individuals at risk for ethmoid ITAC.

Association between CYP1A1 polymorphism and colorectal cancer risk: a meta-analysis

Colorectal cancer is one of the most common forms of cancer and is the third leading cause of cancer-related death worldwide. Published data on the association between CYP1A1 (MspI and Ile ( 462 ) Val) polymorphisms and colorectal cancer risk are inconclusive. To address these issues, we carried out a meta-analysis of available case-control study. Online electronic searches of PubMed were performed. We identified 17 studies (6,673 colorectal cancer patients and 8,102 control subjects) that examined the association between CYP1A1 (MspI and Ile ( 462 ) Val) polymorphisms and risk of colorectal cancer. For CYP1A1 MspI polymorphism, we performed a meta-analysis from 13 studies including 5,468 cases and 6,492 controls. Overall, there was no statistically significant association between CYP1A1 MspI polymorphism and colorectal cancer susceptibility. In the subgroup analyses based on ethnicities, no statistically significant associations were observed in all genetic models. With respect to CYP1A1 Ile ( 462 ) Val polymorphism, a total of 14 studies including 6,654 cases and 7,859 controls were involved in this meta-analysis. The CYP1A1 Ile ( 462 ) Val polymorphism was associated with risk of colorectal cancer. Ethnic subgroup analyses revealed that significant associations were found in Asians and Caucasians. In summary, this meta-analysis suggests that CYP1A1 Ile ( 462 ) Val polymorphism was a low-penetrance susceptibility gene in colorectal cancer development. On the contrary, CYP1A1 MspI polymorphism does not seem capable of modifying colorectal cancer risk.

CYP1A1, CYP2E1, and GSTM1 gene polymorphisms and susceptibility to colorectal and gastric cancer among Lebanese

Mutations in the genes encoding enzymes involved in the metabolism of chemical carcinogens can significantly affect the risk of cell transformation and cancer development. The resident Lebanese population has experienced a sharp increase in cancer incidence within the last few years. The relationship between gene polymorphisms of metabolic enzymes and gastrointestinal (GI) cancer incidence was not previously investigated. The aim of this study was to investigate the relationship between CYP1A1, CYP2E1, and GSTM1 gene polymorphisms and GI cancer incidence among Lebanese. Blood and/or paraffin-embedded biopsy samples were collected from patients and healthy controls. The genotypes were determined by polymerase chain reaction and polymerase chain reaction-restriction fragment length polymorphism. The results of the present case-control study show that the studied Lebanese population generally resembles Caucasian populations with respect to the considered polymorphisms. Further, the GSTM1*0/*0 genotype is a significant risk factor for gastric (odds ratio = 4.1; 95% confidence interval: 1.2-14.5) and colorectal cancers (odds ratio = 3.8; 95% confidence interval: 1.7-8.5); on the other hand, CYP1A1*2A and CYP2E1*6 alone are not significantly associated with GI cancer development, although CYP1A1*2A was more frequent among patients. A remarkable and statistically significant 36.5-fold increase in the risk of gastric cancer was observed among patients with CYP1A1*2A/*2A combined with GSTM1*0/*0. The investigation of genetic risk factors and susceptibility gene polymorphisms in Lebanese is helpful for better understanding of GI cancer etiology.

Association of CYP1A1 Gene Polymorphism with Ischemic Stroke in South Indian Population

Stroke is a major cause of morbidity and mortality worldwide. Genetic and environmental factors are involved in the pathogenesis of stroke. Hypertension, diabetes mellitus, and cigarette smoking are the major risk factors, and smoking doubles the risk of ischemic stroke. Smoking cessation decreased the risk for ischemic stroke. CYP1A1 is the phase I metabolizing enzyme which plays a key role in metabolic activation of polycyclic aromatic hydrocarbons which are present in cigarette smoke and considered carcinogenic. So far, the association of CYP1A1 gene polymorphism with stroke has not been investigated in Indian population. So, the study is taken up to evaluate the association of this polymorphism with ischemic stroke in a South Indian population. We genotyped 215 ischemic stroke patients and 162 age-matched controls using polymerase chain reaction-restriction fragment length polymorphism. Statistical analysis showed that CYP1A1 "CC" genotype is associated with five times increased risk of ischemic stroke (odds ratio (OR) = 5.14; 95% confidence interval (95% CI) = 1.14-23.14, p = 0.01), while "TT" (OR = 0.78, 95% CI = 0.51-1.19, p = 0.25) and "TC" (OR = 1.04, 95% CI = 0.67-1.60, p = 0.85) genotypes were nonsignificant with the increased risk of stroke. T and C allele frequencies in stroke were 76.5% and 23.5% as against 81.8% and 18.2% in control group, respectively, thus, suggesting no statistically significant differences in the T (OR = 0.72, 95% CI = 0.50-1.03, p = 0.07) and C (OR = 1.37, 95% CI = 0.96-1.97, p = 0.07) allele frequencies between the two groups. The distribution of CYP1A1 genotypes and allelic frequency within the stroke subtypes showed a significant association of CC genotype only in intracranial large artery atherosclerosis (OR = 5.21, 95% CI = 1.03-26.38, p = 0.02) while other subtypes did not show any association. Further analysis of CYP1A1 genotypes in patients and control subjects with smoking habit also showed a similar trend. Hence, we conclude that the CYP1A1 CC genotype is associated with the increased risk of ischemic stroke.

CYP1A1 Ile462Val polymorphism contributes to colorectal cancer risk: A meta-analysis

AIM: To study the relation between CYP1A1 Ile462Val polymorphism and colorectal cancer risk by meta-analysis.

METHODS: A meta-analysis was performed to investigate the relation between CYP1A1 Ile462Val polymorphism and colorectal cancer risk by reviewing the related studies until September 2010. Data were extracted and analyzed. Crude odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of relation between CYP1A1 Ile462Val polymorphism and colorectal cancer risk.

RESULTS: Thirteen published case-control studies including 5336 cases and 6226 controls were acquired. The pooled OR with 95% CI indicated that CYP1A1 Ile462Val polymorphism was significantly related with colorectal cancer risk (Val/Val vs Ile/Ile: OR = 1.47, 95% CI: 1.16-1.86, P = 0.002; dominant model: OR = 1.33, 95% CI: 1.01-1.75, P = 0.04; recessive model: OR = 1.49, 95% CI: 1.18-1.88, P = 0.0009). Subgroup ethnicity analysis showed that CYP1A1 Ile462Val polymorphism was also significantly related with colorectal cancer risk in Europeans (Ile/Val vs Ile/Ile: OR = 1.22, 95% CI: 1.05-1.42, P = 0.008; dominant model: OR = 1.24, 95% CI: 1.07-1.43, P = 0.004) and Asians (Val/Val vs Ile/Ile: OR = 1.40, 95% CI: 1.07-1.82, P = 0.01; recessive model: OR = 1.46, 95% CI: 1.12-1.89, P = 0.005).

CONCLUSION: CYP1A1 Ile462Val may be an increased risk factor for colorectal cancer.

Camel urine inhibits the cytochrome P450 1a1 gene expression through an AhR-dependent mechanism in Hepa 1c1c7 cell line

AIM OF THE STUDY

Drinking camel urine has been used traditionally to treat numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of three different camel urines (virgin, lactating, and pregnant source) to modulate a well-known cancer-activating enzyme, the cytochrome P450 1a1 (Cyp1a1) in murine hepatoma Hepa 1c1c7 cell line.

MATERIALS AND METHODS

The effect of different camel urines, compared to bovine urines, on Cyp1a1 mRNA was determined using real-time polymerase chain reaction. Cyp1a1 protein and catalytic activity levels were determined using Western blot analysis and 7-ethoxyresorufin as a substrate, respectively. The role of aryl hydrocarbon receptor (AhR)-dependent mechanism was determined using electrophoretic mobility shift assay (EMSA) and the AhR-dependent luciferase reporter gene.

RESULTS

All types of camel, but not bovine, urines differentially inhibited the induction of Cyp1a1 gene expression by TCDD, the most potent Cyp1a1 inducer and known carcinogenic chemical. Importantly, virgin camel urine showed the highest degree of inhibition at the activity level, followed by lactating and pregnant camel urines. Furthermore, we have shown that virgin camel urine significantly inhibited the TCDD-mediated induction of Cyp1a1 at the mRNA and protein expression levels. Mechanistically, the ability of virgin camel urine to inhibit Cyp1a1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and DNA binding as determined by EMSA, suggesting that AhR-dependent mechanism is involved.

CONCLUSIONS

The present work provides the first evidence that camel urine but not that of bovine inhibits the TCDD-mediated toxic effect by inhibiting the expression of Cyp1a1, at both transcriptional and post-transcriptional levels through an AhR-dependent mechanism.

Genetic variation in the bioactivation pathway for polycyclic hydrocarbons and heterocyclic amines in relation to risk of colorectal neoplasia

Animal work implicates chemical carcinogens, such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HAAs) as contributing to the development of colorectal cancer (CRC). The epidemiologic evidence, however, remains inconsistent possibly due to intra-individual variation in bioactivation of these compounds. We conducted a case-control study of colorectal adenoma (914 cases, 1185 controls) and CRC (496 cases, 607 controls) among Japanese Americans, European Americans and Native Hawaiians to investigate the association of genetic variation in the PAH and HAA bioactivation pathway (CYP1A1, CYP1A2, CYP1B1, AHR and ARNT) identified through sequencing with risk of colorectal neoplasia, as well as their interactions with smoking and intakes of red meat and HAAs. The A allele for ARNT rs12410394 was significantly inversely associated with CRC [odds ratios (ORs) and 95% confidence intervals (CIs) for GG, AG and AA genotypes: 1.00, 0.66 (0.48-0.89), 0.54 (0.37-0.78), P(trend) = 0.0008] after multiple comparison adjustment. CYP1A2 rs11072508 was marginally significantly associated with CRC, where each copy of the T allele was associated with reduced risk (OR: 0.72, 95% CI: 0.58-0.88, P(trend) = 0.0017). No heterogeneity of genetic effects across racial/ethnic groups was detected. In addition, no significant interaction was observed after adjusting for multiple testing between genetic variants and pack-years of smoking, intake of red meat or HAAs (PhIP, MeIQx, Di-MeIQx or total HAAs) or NAT2 genotype (Rapid versus Slow or Intermediate). This study suggests that the genomic region around ARNT rs12410394 may harbor variants associated with CRC.

Interactions between cigarette smoking and selected polymorphisms in xenobiotic metabolizing enzymes in risk for colorectal cancer: A case-only analysis

The metabolism of xenobiotics is complex and involves multiple steps and multiple enzymes. Genetic variation in the genes encoding these enzymes as well as the level of exposure to the substrates of these enzymes could alter metabolism and clearance of potential carcinogens and thus alter cancer susceptibility. This study examined interaction effect between smoking and two single nucleotide polymorphisms (SNPs)-CYP1A1 c.1384A>G (p.Ile462Val) and EPHX1 c.337T>C (p.Tyr113His)-in modulating colorectal cancer (CRC) risk. The SNPs were selected a priori based on functional significance. In a case-only analysis, unconditional logistic regression was used to examine the associations between smoking and each SNP and between the two SNPs in 786 patients with nonfamilial CRC. There was significant multiplicative interaction for CRC risk between smoking and EPHX1 c.337T>C (odds ratio [OR] = 1.37, 95% confidence interval [CI] = 1.03-1.81, P = 0.03), particularly among smokers with a history of greater than 20 pack-years of smoking (OR = 1.52, 95% CI = 1.07-2.16, P = 0.02). In addition, there was gene-gene interaction between EPHX1 c.337T>C and CYP1A1 c.1384A>G (OR = 1.61, 95% CI = 1.02-2.55, P = 0.04). Smokers with any variant allele of EPHX1 were at increased risk for CRC, as were individuals with any variant allele of CYP1A1 together with any variant allele of EPHX1. Thus, the study of gene-environment and gene-gene interactions may help to identify high-risk subgroups that can be targeted for intensive smoking cessation and CRC screening interventions.

Cigarette smoking, genetic variants in carcinogen-metabolizing enzymes, and colorectal cancer risk

The risk of colorectal cancer associated with smoking is unclear and may be influenced by genetic variation in enzymes that metabolize cigarette carcinogens. The authors examined the colorectal cancer risk associated with smoking and 26 variants in carcinogen metabolism genes in 1,174 colorectal cancer cases and 1,293 population-based controls recruited in Canada by the Ontario Familial Colorectal Cancer Registry from 1997 to 2001. Adjusted odds ratios were calculated by multivariable logistic regression. Smoking for >27 years was associated with a statistically significant increased colorectal cancer risk (adjusted odds ratio (AOR) = 1.25, 95% confidence interval (CI): 1.02, 1.53) in all subjects. Colorectal cancer risk associated with smoking was higher in males for smoking status, duration, and intensity. The CYP1A1-3801-CC (AOR = 0.47, 95% CI: 0.23, 0.94) and CYP2C9-430-CT (AOR = 0.82, 95% CI: 0.68, 0.99) genotypes were associated with decreased risk, and the GSTM1-K173N-CG (AOR = 1.99, 95% CI: 1.21, 3.25) genotype was associated with an increased risk of colorectal cancer. Statistical interactions between smoking and genetic variants were assessed by comparing logistic regression models with and without a multiplicative interaction term. Significant interactions were observed between smoking status and SULT1A1-638 (P = 0.02), NAT2-857 (P = 0.01), and CYP1B1-4390 (P = 0.04) variants and between smoking duration and NAT1-1088 (P = 0.02), SULT1A1-638 (P = 0.04), and NAT1-acetylator (P = 0.03) status. These findings support the hypothesis that prolonged cigarette smoking is associated with increased risk of colorectal cancer and that this risk may be modified by variation in carcinogen metabolism genes.

Cigarette smoking, genetic polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study

Background

It is uncertain whether smoking is related to colorectal cancer risk. Cytochrome P-450 CYP1A1, glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1) are important enzymes in the metabolism of tobacco carcinogens, and functional genetic polymorphisms are known for these enzymes. We investigated the relation of cigarette smoking and related genetic polymorphisms to colorectal cancer risk, with special reference to the interaction between smoking and genetic polymorphism.

Methods

We used data from the Fukuoka Colorectal Cancer Study, a population-based case-control study, including 685 cases and 778 controls who gave informed consent to genetic analysis. Interview was conducted to assess lifestyle factors, and DNA was extracted from buffy coat.

Results

In comparison with lifelong nonsmokers, the odds ratios (OR) of colorectal cancer for <400, 400-799 and ≥800 cigarette-years were 0.65 (95% confidence interval [CI], 0.45-0.89), 1.16 (0.83-1.62) and 1.14 (0.73-1.77), respectively. A decreased risk associated with light smoking was observed only for colon cancer, and rectal cancer showed an increased risk among those with ≥400 cigarette-years (OR 1.60, 95% CI 1.04-2.45). None of the polymorphisms under study was singly associated with colorectal cancer risk. Of the gene-gene interactions studied, the composite genotype of CYP1A1*2A or CYP1A1*2C and GSTT1 polymorphisms was associated with a decreased risk of colorectal cancer, showing a nearly statistically significant (P_interaction = 0.06) or significant interaction (P_interaction = 0.02). The composite genotypes of these two polymorphisms, however, showed no measurable interaction with cigarette smoking in relation to colorectal cancer risk.

Conclusions

Cigarette smoking may be associated with increased risk of rectal cancer, but not of colon cancer. The observed interactions between CYP1A1 and GSTT1 polymorphisms warrant further confirmation.

The effect of secondhand smoke exposure on the association between active cigarette smoking and colorectal cancer

BACKGROUND

Studies published prior to 1980 failed to find an association between smoking and colorectal cancer, while subsequent studies reported an association after accounting for a three to four decade initiation period. The aims of this study were to determine the effect of accounting for secondhand smoke (SHS) exposure on the association between smoking and colorectal cancer and to determine the association between SHS and colorectal cancer.

METHODS

Approximately 1,200 colorectal cancer cases treated at Roswell Park Cancer Institute between 1982 and 1998 were matched to 2,400 malignancy-free controls. The effect of accounting for SHS exposure was determined by comparing the odds ratios (OR) for each smoking variable in the overall sample and then for those who reported no current SHS exposure.

RESULTS

A small, significant increase in colorectal cancer odds was noted for heavy, long-term smoking males when not accounting for SHS exposure (>45 PY: OR = 1.34; 95% CI 1.04-1.72). OR increased when the analyses were restricted to individuals reporting no current SHS exposure (>45 PY: OR = 2.40; 95% CI 1.36-4.23).

CONCLUSIONS

Accounting for SHS exposure resulted in a substantial increase in the odds of colorectal cancer for all smoking variables in this study. Future studies should account for SHS exposure when examining the association between smoking and colorectal cancer.

Glucosinolates in Brassica vegetables: the influence of the food supply chain on intake, bioavailability and human health

Glucosinolates (GLSs) are found in Brassica vegetables. Examples of these sources include cabbage, Brussels sprouts, broccoli, cauliflower and various root vegetables (e.g. radish and turnip). A number of epidemiological studies have identified an inverse association between consumption of these vegetables and the risk of colon and rectal cancer. Animal studies have shown changes in enzyme activities and DNA damage resulting from consumption of Brassica vegetables or isothiocyanates, the breakdown products (BDP) of GLSs in the body. Mechanistic studies have begun to identify the ways in which the compounds may exert their protective action but the relevance of these studies to protective effects in the human alimentary tract is as yet unproven. In vitro studies with a number of specific isothiocyanates have suggested mechanisms that might be the basis of their chemoprotective effects. The concentration and composition of the GLSs in different plants, but also within a plant (e.g. in the seeds, roots or leaves), can vary greatly and also changes during plant development. Furthermore, the effects of various factors in the supply chain of Brassica vegetables including breeding, cultivation, storage and processing on intake and bioavailability of GLSs are extensively discussed in this paper.

Examining the association between cigarette smoking and colorectal cancer using historical case-control data

BACKGROUND

The majority of recent, well-designed studies have shown that long-term cigarette smoking increases colorectal cancer risk, but older studies with shorter durations of exposure often found no association. This study aimed to examine colorectal cancer risk by smoking exposure using data collected in the late-1950s and early-1960s.

METHODS

This case-control study examined colorectal cancer risk by lifetime smoking history. There were 1365 patients who visited Roswell Park Cancer Institute (RPCI) between 1957 and 1965 diagnosed with primary, incident colorectal cancers that were matched to 4096 malignancy-free controls on gender and age. Odds ratios were calculated using separate logistic regression models for each smoking exposure, while controlling for other tobacco use, county of residence, race, age, gender, and body mass index (BMI).

RESULTS

The adjusted OR for individuals who reported their greatest level of smoking to be more than 1 pack/day was 0.87 (95% CI=0.67-1.15). Among those who smoked 42 or more years, the adjusted OR was 0.89 (95% CI=0.68-1.15) compared to those who never smoked. For individuals who smoked more than 45 pack-years, the OR was 0.92 (95% CI=0.72-1.19). The results did not differ significantly by gender, although men had considerably greater exposure compared to women. Results also did not differ by colorectal sub-site.

CONCLUSION

No association was found between long-term cigarette smoking and colorectal cancer risk. These results are in accord with studies that followed cohorts throughout the 1950s and 1960s. Methodological limitations, such as missing data on covariates and the higher incidence of smoking-related illness in a hospital setting, may have contributed to the null results found in this study. Prolonged population exposure to cigarettes and perhaps a changing product may explain why more recent studies have reported a positive association between smoking and colorectal cancer.

Cigarette smoking and risk of colorectal cancer among Norwegian women

OBJECTIVE

The association between cigarette smoking and colorectal cancer (CRC) is still not established. In 2002, Norwegian women had the second highest incidence of CRC in the world. A large proportion of Norwegian women are ever smokers. We examined the association between cigarette smoking and CRC incidence among Norwegian women.

METHODS

We followed 68,160 women, aged 30-69 years, from the Norwegian Women and Cancer Study who completed a questionnaire in 1996 or 1998 by linkages to national registers through 31 December 2005. Rate ratios (RRs) and 95% confidence intervals (CIs) were estimated by fitting Cox proportional hazard models. Subsequently, we estimated the population attributable fraction.

RESULTS

Altogether, 425 incident cases of primary, invasive CRC were identified. Ever smokers had a 20% increased risk of CRC (RR = 1.2; 95% CI = 1.0-1.5), a 30% increased risk of colon (RR = 1.3; 95% CI = 1.0-1.7), and a 10% increased risk of rectal (RR = 1.1; 95% CI = 0.7-1.5) cancer compared to never smokers. The population attributable fraction was estimated to be 12% which indicated that approximately one in eight of the CRC cases could have been prevented at a population level.

CONCLUSION

Our results support the hypothesis that cigarette smoking is a preventable cause of CRC among women.

Lifestyle, genes, and cancer

It is estimated that almost 1.5 million people in the USA are diagnosed with cancer every year. However, due to the substantial effect of modifiable lifestyle factors on the most prevalent cancers, it has been estimated that 50% of cancer is preventable. Physical activity, weight loss, and a reduction in alcohol use can strongly be recommended for the reduction of breast cancer risk. Similarly, weight loss, physical activity, and cessation of tobacco use are important behavior changes to reduce colorectal cancer risk, along with the potential benefit for the reduction of red meat consumption and the increase in folic acid intake. Smoking cessation is still the most important prevention intervention for reducing lung cancer risk, but recent evidence indicates that increasing physical activity may also be an important prevention intervention for this disease. The potential benefit of lifestyle change to reduce prostate cancer risk is growing, with recent evidence indicating the importance of a diet rich in tomato-based foods and weight loss. Also, in the cancers for which there are established lifestyle risk factors, such as physical inactivity for breast cancer and obesity for colorectal cancer, there is emerging information on the role that genetics plays in interacting with these factors, as well as the interaction of combinations of lifestyle factors. Integration of genetic information into lifestyle factors can help to clarify the causal relationships between lifestyle and genetic factors and assist in better identifying cancer risk, ultimately leading to better-informed choices about effective methods to enhance health and prevent cancer.

Role of xenobiotic metabolic enzymes in cancer epidemiology

The cause of the majority of cancers is poorly understood albeit multifactorial. The ultimate consequence of etiological factors where defined is an alteration within the cellular genotype, which is manifested in the cells acquiring malignant phenotype. There are several environmental carcinogens that contribute to carcinogenesis. These carcinogens are metabolized by a large number of enzymes, including the cyto-chrome P 450 group, glutathione-S-transferase (GST), the uridine glucuronyl transferase (UGT) super-family, alcohol-metabolizing enzymes, sulphatases, etc. These enzymes can either inactivate carcinogens or in some cases generate reactive moieties that lead to carcinogenesis. This review summarises the available evidence regarding the role of xenobiotic metabolic enzymes and their role in cancer epidemiology. The available data and studies have identified correlates between expression of various metabolizing enzymes with risk of malignancies known to be induced by their substrates. The data may have relevance in one population but not for another for a specific malignancy and at times may be conflicting. We believe that with mature data in the future it may be possible to stratify patients by risk.

Genetic variation in genes for the xenobiotic-metabolizing enzymes CYP1A1, EPHX1, GSTM1, GSTT1, and GSTP1 and susceptibility to colorectal cancer in Lynch syndrome

Individuals with Lynch syndrome are predisposed to cancer due to an inherited DNA mismatch repair gene mutation. However, there is significant variability observed in disease expression likely due to the influence of other environmental, lifestyle, or genetic factors. Polymorphisms in genes encoding xenobiotic-metabolizing enzymes may modify cancer risk by influencing the metabolism and clearance of potential carcinogens from the body. In this retrospective analysis, we examined key candidate gene polymorphisms in CYP1A1, EPHX1, GSTT1, GSTM1, and GSTP1 as modifiers of age at onset of colorectal cancer among 257 individuals with Lynch syndrome. We found that subjects heterozygous for CYP1A1 I462V (c.1384A>G) developed colorectal cancer 4 years earlier than those with the homozygous wild-type genotype (median ages, 39 and 43 years, respectively; log-rank test P = 0.018). Furthermore, being heterozygous for the CYP1A1 polymorphisms, I462V and Msp1 (g.6235T>C), was associated with an increased risk for developing colorectal cancer [adjusted hazard ratio for AG relative to AA, 1.78; 95% confidence interval, 1.16-2.74; P = 0.008; hazard ratio for TC relative to TT, 1.53; 95% confidence interval, 1.06-2.22; P = 0.02]. Because homozygous variants for both CYP1A1 polymorphisms were rare, risk estimates were imprecise. None of the other gene polymorphisms examined were associated with an earlier onset age for colorectal cancer. Our results suggest that the I462V and Msp1 polymorphisms in CYP1A1 may be an additional susceptibility factor for disease expression in Lynch syndrome because they modify the age of colorectal cancer onset by up to 4 years.

CYP1A1 and GSTM1 genetic polymorphisms in lung cancer populations exposed to arsenic in drinking water

Region II of Chile is the most important copper mining area in the world and it shows the highest lung cancer mortality rate in the country (35/100,000). The population in Antofagasta, the main city of Region II, was exposed from 1958 to 1970 to 860 microg m(-3) arsenic (As) in drinking water and has currently been declining to 40 microg m(-3). Glutathione serves as a reducing agent and glutathione S-transferase (GST) may have an important role in As methylation capacity and body retention. In the current study, the null genotype of GSTM1 and the MspI polymorphism of CYP450 1A1 were investigated in lung cancer patients and in healthy volunteers of Region II. In males, the 2A genotype of MspI represented a highly significant estimated relative lung cancer risk (OR=2.60). Relative lung cancer risk for the combined 2A/null GSTM1 genotypes was 2.51, which increased with the smoking habit (OR=2.98). In Region II, the cancer mortality rate for As-associated cancers at least partly might be related to differences in As biotransformation. Genetic biomarkers such as 2A and GSTM1 polymorphisms in addition to DR70 as screening biomarkers might provide relevant information to identify individuals with a high risk for lung cancer as prevention and protection actions to protect public health.