Catechol Quinones of Estrogens in the Initiation of Breast, Prostate, and Other Human Cancers: Keynote Lecture

Functional variant rs10175368 which affects the expression of CYP1B1 plays a protective role against breast cancer in a Chinese Han population

OBJECTIVE

Cytochrome P450 1B1 ( CYP1B1 ) genetic variants are relevant in the pathogenesis of breast cancer. Exploring the relationships between CYP1B1 functional variants and breast cancer could improve our understanding of breast cancer molecular pathophysiology.

METHODS

This is a two-stage hospital-based case-control study of a Chinese Han population. Genotyping was performed to identify candidate gene variants. 3DSNP, ANNOVAR, and RegulomeDB were used to determine functional single nucleotide polymorphisms (SNPs). The relationship between candidate variants and breast cancer risk was evaluated through unconditional logistic regression analysis. The PancanQTL platform was used to perform cis and trans expression quantitative trait loci (eQTL) analysis of positive SNPs. The GSCA platform was then used to compare the gene expression levels of potential target genes between breast cancer tissue and normal tissue adjacent to the cancer.

RESULTS

rs10175368-T acted as a protective factor against breast cancer based on an additive model [odds ratio (OR) = 0.722, 95% confidence interval (CI) = 0.613-0.850; P < 0.001], and was identified as a protective factor in the postmenopausal population (OR = 0.601; 95% CI, 0.474-0.764; P < 0.001). eQTL analysis and analysis of differential expression in carcinoma and paracancerous tissues revealed that the expression level of CYP1B1 - AS1 was associated with rs10175368 and that CYP1B1-AS1 had significantly higher expression levels in breast cancer tissues than in paracancerous tissues.

CONCLUSION

We show, for the first time in a Chinese Han population, that the functional variant rs10175368 plays a protective role against breast cancer, especially in the postmenopausal population.

Mechanistic Effects of Estrogens on Breast Cancer

PURPOSE

Current concepts regarding estrogen and its mechanistic effects on breast cancer in women are evolving. This article reviews studies that address estrogen-mediated breast cancer development, the prevalence of occult tumors at autopsy, and the natural history of breast cancer as predicted by a newly developed tumor kinetic model.

METHODS

This article reviews previously published studies from the authors and articles pertinent to the data presented.

RESULTS

We discuss the concepts of adaptive hypersensitivity that develops in response to long-term deprivation of estrogen and results in both increased cell proliferation and apoptosis. The effects of menopausal hormonal therapy on breast cancer in postmenopausal women are interpreted based on the tumor kinetic model. Studies of the administration of a tissue selective estrogen complex in vitro, in vivo, and in patients are described. We review the various clinical studies of breast cancer prevention with selective estrogen receptor modulators and aromatase inhibitors. Finally, the effects of the underlying risk of breast cancer on the effects of menopausal hormone therapy are outlined.

DISCUSSION

The overall intent of this review is to present data supporting recent concepts, discuss pertinent literature, and critically examine areas of controversy.

Hexestrol Deteriorates Oocyte Quality via Perturbation of Mitochondrial Dynamics and Function

Hexestrol (HES) is a synthetic non-steroidal estrogen that was widely used illegally to boost the growth rate in livestock production and aquaculture. HES can also be transferred to humans from treated animals and the environment. HES has been shown to have an adverse effect on ovarian function and oogenesis, but the potential mechanism has not been clearly defined. To understand the potential mechanisms regarding how HES affect female ovarian function, we assessed oocyte quality by examining the critical events during oocyte maturation. We found that HES has an adverse effect on oocyte quality, indicated by the decreased capacity of oocyte maturation and early embryo development competency. Specifically, HES-exposed oocytes exhibited aberrant microtubule nucleation and spindle assembly, resulting in meiotic arrest. In addition, HES exposure disrupted mitochondrial distribution and the balance of mitochondrial fission and fusion, leading to aberrant mitochondrial membrane potential and accumulation of reactive oxygen species. Lastly, we found that HES exposure can increase cytosolic Ca²⁺ levels and induce DNA damage and early apoptosis. In summary, these results demonstrate that mitochondrial dysfunction and perturbation of normal mitochondrial fission and fusion dynamics could be major causes of reduced oocyte quality after HES exposure.

Urinary oestrogen steroidome as an indicator of the risk of localised prostate cancer progression

BACKGROUND

Prostate cancer (PCa) is the most common cancer in North American men. Beyond the established contribution of androgens to disease progression, growing evidence suggest that oestrogen-related pathways might also be of clinical importance. The aim of this study was to explore the association of urinary oestrogen levels with clinical outcomes.

METHODS

Urine samples from the prospective multi-institutional PROCURE cohort were collected before RP for discovery (n = 259) and validation (n = 253). Urinary total oestrogens (unconjugated + conjugated), including oestrone and oestradiol, their bioactive and inactive catechol and methyl derivatives (n = 15), were measured using mass spectrometry (MS).

RESULTS

The median follow-up time for the discovery and replication cohorts was 7.6 and 6.5 years, respectively. Highly significant correlations between urinary oestrogens were observed; however, correlations with circulating oestrogens were modest. Our findings indicate that higher levels of urinary oestriol and 16-ketoestradiol were associated with lower risk of BCR. In contrast, higher levels of 2-methoxyestrone were associated with an increased risk of development of metastasis/deaths.

CONCLUSIONS

Our data suggest that urinary levels of oestriol and 16-ketoestradiol metabolites are associated with a more favourable outcome, whereas those of 2-methoxyestrone are associated with an elevated risk of metastasis after RP. Further studies are required to better understand the impact of oestrogens on disease biology and as easily accessible urine-based risk-stratification markers.

Human Family 1-4 cytochrome P450 enzymes involved in the metabolic activation of xenobiotic and physiological chemicals: an update

This is an overview of the metabolic activation of drugs, natural products, physiological compounds, and general chemicals by the catalytic activity of cytochrome P450 enzymes belonging to Families 1-4. The data were collected from > 5152 references. The total number of data entries of reactions catalyzed by P450s Families 1-4 was 7696 of which 1121 (~ 15%) were defined as bioactivation reactions of different degrees. The data were divided into groups of General Chemicals, Drugs, Natural Products, and Physiological Compounds, presented in tabular form. The metabolism and bioactivation of selected examples of each group are discussed. In most of the cases, the metabolites are directly toxic chemicals reacting with cell macromolecules, but in some cases the metabolites formed are not direct toxicants but participate as substrates in succeeding metabolic reactions (e.g., conjugation reactions), the products of which are final toxicants. We identified a high level of activation for three groups of compounds (General Chemicals, Drugs, and Natural Products) yielding activated metabolites and the generally low participation of Physiological Compounds in bioactivation reactions. In the group of General Chemicals, P450 enzymes 1A1, 1A2, and 1B1 dominate in the formation of activated metabolites. Drugs are mostly activated by the enzyme P450 3A4, and Natural Products by P450s 1A2, 2E1, and 3A4. Physiological Compounds showed no clearly dominant enzyme, but the highest numbers of activations are attributed to P450 1A, 1B1, and 3A enzymes. The results thus show, perhaps not surprisingly, that Physiological Compounds are infrequent substrates in bioactivation reactions catalyzed by P450 enzyme Families 1-4, with the exception of estrogens and arachidonic acid. The results thus provide information on the enzymes that activate specific groups of chemicals to toxic metabolites.

Assessing anti-estrogenic effects of AHR ligands in primary human and rat endometrial epithelial cells

Unopposed estrogenic action in the uterus can lead to the development of endometrial cancer in both humans and rats. Aryl hydrocarbon receptor (AHR) activation gives rise to anti-estrogenic actions and may consequently reduce the development of endometrial cancer. In this study, the anti-estrogenic potential of the AHR ligands 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and DELAQ, a metabolite of the pharmaceutical laquinimod, was assessed in in primary human and rat endometrial epithelial cells (EECs) with and without co-exposure to endogenous hormones. In human EECs, estradiol and progesterone did not affect AHR gene expression, but in rat EECs, progesterone decreased Ahre xpression (1.4-fold). In accordance, AHR-mediated induction of Cyp1a1/1b1 expression by DELAQ and TCDD decreased in hormone-treated rat EECs. DELAQ was 22-fold more potent than TCDD in human EECs in inducing CYP1A1/1B1 gene expression, while DELAQ was approximately 16-33-fold less potent than TCDD in rat EECs. In human EECs, 10 nM DELAQ decreased estradiol-induced expression of growth-regulated estrogen receptor binding 1 (GREB1) by 1.8-fold. In rat EECs, both DELAQ and TCDD did not affect the expression of estradiol-induced genes. This study shows that AHR ligand DELAQ, but not TCDD, causes anti-estrogenic effects in primary human EECs. Furthermore, although AHR-mediated CYP1A1/1B1/Cyp1a1/1b1 induction by DELAQ and TCDD was stronger in rat EECs than human EECs, this did not result in apparent anti-estrogenic effects in the rat cells. This study shows that primary human and rat endometrial cells respond differently towards hormones and AHR ligands. This should be considered in human risk assessment based on rodent studies.

4-Hydroxyestrone, an Endogenous Estrogen Metabolite, Can Strongly Protect Neuronal Cells Against Oxidative Damage

Earlier studies showed that endogenous estrogens have neuroprotective effect against oxidative damage. The present study seeks to investigate the protective effect of various endogenous estrogen metabolites against oxidative neurotoxicity in vitro and in vivo. Using immortalized mouse hippocampal neuronal cells as an in vitro model, 4-hydroxyestrone, an estrone metabolite with little estrogenic activity, is found to have the strongest neuroprotective effect against oxidative neurotoxicity among 25 endogenous estrogen metabolites tested, and its protective effect is stronger than 17β-estradiol. Similarly, 4-Hydroxyestrone also exerts a stronger protective effect than 17β-estradiol against kanic acid-induced hippocampal oxidative damage in rats. Neuroprotection by 4-hydroxyestrone involves increased cytoplasmic translocation of p53 resulting from SIRT1-mediated deacetylation of p53. Analysis of brain microsomal enzymes shows that estrogen 4-hydroxylation is the main metabolic pathway in the central nervous system. Together, these results show that 4-hydroxyestrone is an endogenous neuroestrogen that can strongly protect against oxidative neuronal damage.

Qualitative and quantitative differences in estrogen biotransformation in human breast glandular and adipose tissues: implications for studies using mammary biospecimens

Because of its assumed role in breast cancer etiology, estrogen biotransformation (and interaction of compounds therewith) has been investigated in human biospecimens for decades. However, little attention has been paid to the well-known fact that large inter-individual variations exist in the proportion of breast glandular (GLT) and adipose (ADT) tissues and less to adequate tissue characterization. To assess the relevance of this, the present study compares estrogen biotransformation in GLT and ADT. GLT and ADT were isolated from 47 reduction mammoplasty specimens derived from women without breast cancer and were characterized histologically and by their percentages of oil. Levels of 12 unconjugated and five conjugated estrogens were analyzed by GC- and UHPLC-MS/MS, respectively, and levels of 27 transcripts encoding proteins involved in estrogen biotransformation by Taqman^® probe-based PCR. Unexpectedly, one-third of specimens provided neat GLT only after cryosection. Whereas 17β-estradiol, estrone, and estrone-3-sulfate were detected in both tissues, estrone-3-glucuronide and 2-methoxy-estrone were detected predominately in GLT and ADT, respectively. Estrogen levels as well as ratios 17β-estradiol/estrone and estrone-3-sulfate/estrone differed significantly between GLT and ADT, yet less than between individuals. Furthermore, estrogen levels in GLT and ADT correlated significantly with each other. In contrast, levels of most transcripts encoding enzymes involved in biotransformation differed more than between individuals and did not correlate between ADT and GLT. Thus, mixed breast tissues (and plasma) will not provide meaningful information on local estrogen biotransformation (and interaction of compounds therewith) whereas relative changes in 17β-estradiol levels may be investigated in the more abundant ADT.

A decision tree-based integrated testing strategy for tailor-made carcinogenicity evaluation of test substances using genotoxicity test results and chemical spaces

Genotoxicity evaluation has been widely used to estimate the carcinogenicity of test substances during safety evaluation. However, the latest strategies using genotoxicity tests give more weight to sensitivity; therefore, their accuracy has been very low. For precise carcinogenicity evaluation, we attempted to establish an integrated testing strategy for the tailor-made carcinogenicity evaluation of test materials, considering the relationships among genotoxicity test results (Ames, in vitro mammalian genotoxicity and in vivo micronucleus), carcinogenicity test results and chemical properties (molecular weight, logKow and 179 organic functional groups). By analyzing the toxicological information and chemical properties of 230 chemicals, including 184 carcinogens in the Carcinogenicity Genotoxicity eXperience database, a decision tree for carcinogenicity evaluation was optimised statistically. A decision forest model was generated using a machine-learning method-random forest-which comprises thousands of decision trees. As a result, balanced accuracies in cross-validation of the optimised decision tree and decision forest model, considering chemical space (71.5% and 75.5%, respectively), were higher than balanced accuracy of an example regulatory decision tree (54.1%). Moreover, the statistical optimisation of tree-based models revealed significant organic functional groups that would cause false prediction in standard genotoxicity tests and non-genotoxic carcinogenicity (e.g., organic amide and thioamide, saturated heterocyclic fragment and aryl halide). In vitro genotoxicity tests were the most important parameters in all models, even when in silico parameters were integrated. Although external validation is required, the findings of the integrated testing strategies established herein will contribute to precise carcinogenicity evaluation and to determine new mechanistic hypotheses of carcinogenicity.

Estrogenic Active Stilbene Derivatives as Anti-Cancer Agents: A DFT and QSAR Study

Exploring different quantum chemical quantities for lead compounds is an ongoing approach in identifying crucial structural activity related features that are contributing into their biological activities. Herein, activity-related quantum chemical calculations were performed for the selected estrogenic stilbene derivatives using density functional theory (DFT) with B3LYP functional and 6-311++G** basis set. In addition, specific activity-related geometry-independent drug-like properties are discussed for these derivatives. To obtain the mathematical model that correlates the chemical descriptors with their measured estrogenic activities, the quantitative structure activity relationship (QSAR) is established using multiple linear regression (MLR) and support vector regression (SVR) methods. Satisfactory fit with a reasonable regression correlation coefficient (${\rm{R}}^{2}= 0.78$R2=0.78) between predicted and experimental $pEC_{50}$pEC50 values is observed using MLR method. The present study identifies the essential physicochemical descriptors that effectively contribute in the estrogenic activity. The applied approach provides helpful insight into the designing novel estrogenic agents with improved anticancer activities.

A lateral flow immunochromatographic strip test for rapid detection of hexoestrol in fish samples

A lateral flow immunochromatographic strip test was developed for rapid and sensitive on-site detection of hexoestrol (HES) residues in fish samples with colloidal gold labelling of the anti-HES monoclonal antibody. The strip is composed of a sample pad, a conjugate reagent pad, an absorbent pad and a test membrane containing a control line and a test line. The sensitivity (half inhibitory concentration, IC50) of the strip in the detection of fish extract samples was confirmed to be 1.86 µg kg-1, and the limit of detection value was 0.62 µg kg-1. For intra-assay and inter-assay reproducibility, recoveries of HES-spiked samples ranged from 86.3% to 92.3% and 85.8% to 93.4%, coefficients of variation were 2.91-4.64% and 4.24-5.17%, respectively. High-performance liquid chromatography was employed to confirm the performance of the strip. The strip test takes less than 10 min, and thus provides a repaid method for on-site detection of HES residues.

Occupational exposure to benzene, toluene, xylene and styrene and risk of prostate cancer in a population-based study

OBJECTIVES

While several monocyclic aromatic hydrocarbons are classified as definite or possible carcinogens to humans, little data exist on their role in prostate cancer (PCa). We examined occupational exposure to benzene, toluene, xylene (BTX) and styrene and PCa risk in a population-based case-control study in Montreal, Canada.

METHODS

Cases aged ≤75 years diagnosed with PCa in 2005-2009 (n=1920) and population controls frequency-matched on age (n=1989) provided detailed work histories. Experts evaluated the certainty, frequency and concentration of exposure to monocyclic aromatic hydrocarbons in each job lasting ≥2 years. Logistic regression estimated OR and 95% CIs for PCa risk, adjusting for potential confounders.

RESULTS

Exposures to BTX were highly intercorrelated, except for durations of exposure at substantial levels. Ever exposure to any BTX was associated with overall PCa (OR 1.27, 95% CI 1.05 to 1.53), while the OR for styrene was 1.19. However, increases in risk were largely confined to low-grade tumours, with ORs of 1.33 (95%CI 1.08 to 1.64) and 1.41 (95% CI 0.85 to 2.31) for ever exposure to any BTX and styrene, respectively, and a duration response pattern for any BTX. Risks for low-grade tumours were elevated among men exposed ≥25 years at substantial levels of benzene (OR 2.32) and styrene (OR 2.44). Some cumulative exposure categories showed increased risks but without clear trends.

CONCLUSION

Exposure to any BTX was associated with higher risks of overall PCa. Prolonged exposures at the substantial level to benzene and styrene increased risks of low-grade tumours. These novel findings were independent from PCa screening.

GPER is involved in the regulation of the estrogen-metabolizing CYP1B1 enzyme in breast cancer

The cytochrome P450 1B1 (CYP1B1) is a heme-thiolate monooxygenase involved in both estrogen biosynthesis and metabolism. For instance, CYP1B1 catalyzes the hydroxylation of E2 leading to the production of 4-hydroxyestradiol that may act as a potent carcinogenic agent. In addition, CYP1B1 is overexpressed in different tumors including breast cancer. In this scenario, it is worth mentioning that CYP1B1 expression is triggered by estrogens through the estrogen receptor (ER)α in breast cancer cells. In the present study, we evaluated whether the G protein estrogen receptor namely GPER may provide an alternate route toward the expression and function of CYP1B1 in ER-negative breast cancer cells, in main players of the tumor microenvironment as cancer associated fibroblasts (CAFs) that were obtained from breast cancer patients, in CAFs derived from a cutaneous metastasis of an invasive mammary ductal carcinoma and in breast tumor xenografts. Our results show that GPER along with the EGFR/ERK/c-Fos transduction pathway can lead to CYP1B1 regulation through the involvement of a half-ERE sequence located within the CYP1B1 promoter region. As a biological counterpart, we found that both GPER and CYP1B1 mediate growth effects in vitro and in vivo. Altogether, our data suggest that estrogens in ER-negative cell contexts may engage the alternate GPER signaling toward CYP1B1 regulation. Estrogen-CYP1B1 landscape via GPER should be taken into account in setting novel pharmacological approaches targeting breast cancer development.

Antioxidant activities of novel resveratrol analogs in breast cancer

The objective of the present study was to characterize the role of novel resveratrol (Res) analogs: 4-(E)-{(4-hydroxyphenylimino)-methylbenzene, 1, 2-diol} (HPIMBD) and 4-(E)-{(p-tolylimino)-methylbenzene-1,2-diol} (TIMBD) as potent antioxidants against breast cancer. Non-neoplastic breast epithelial cell lines MCF-10A and MCF-10F were treated with 17β-estradiol (E2), Res, HPIMBD, and TIMBD for up to 72 h. mRNA and protein levels of antioxidant genes, superoxide dismutase 3 (SOD3) and N-quinoneoxidoreductase-1 (NQO1) and transcription factors, nuclear factor erythroid 2-related factor (Nrf) 1, 2 and 3 were quantified after the above treatments. Generation of reactive oxygen species (ROS) was measured by CM-H2-DCFDA and oxidative-DNA damage was determined by measuring 8-hydroxy-2-deoxyguanosine (8-OHdG). HPIMBD and TIMBD scavenged cellular ROS production, attenuated oxidative DNA damage, increased mRNA and protein expression levels of SOD3 and NQO1 and activated Nrf signaling pathway. Our studies demonstrate that HPIMBD and TIMBD have the potential as novel antioxidants to prevent development of breast cancer.

Estrogen Repression of MicroRNAs Is Associated with High Guanine Content in the Terminal Loop Sequences of Their Precursors

Widespread microRNA (miRNA) repression is a phenomenon observed in mammals after exposure to cigarette smoke and in many types of cancer. A comprehensive reduction in miRNA expression after treatment with the hormone estrogen has also previously been described. Here, we reveal a conserved association of miRNA downregulation after estrogen exposure in zebrafish, mouse, and human breast cancer cell line, with a high guanine content in the terminal loop sequences of their precursors, and offer a possible link between estrogen-related miRNA-adducts formation and carcinogenesis. We also show common gene expression patterns shared by breast cancer tumors and estrogen-treated zebrafish, suggesting that this organism can be used as a powerful model system for the study of human breast cancer.

STAR and AKR1B10 are down-regulated in high-grade endometrial cancer

Endometrial cancer is the most frequent gynecological malignancy in the developed world. The majority of cases are estrogen dependent, and are associated with diminished protective effects of progesterone. Endometrial cancer is also related to enhanced inflammation and decreased differentiation. In our previous studies, we examined the expression of genes involved in estrogen and progesterone actions in inflammation and tumor differentiation, in tissue samples from endometrial cancer and adjacent control endometrium. The aims of the current study were to examine correlations between gene expression and several demographic characteristics, and to evaluate changes in gene expression with regard to histopathological and clinical characteristics of 51 patients. We studied correlations and differences in expression of 38 genes involved in five pathophysiological processes: (i) estrogen-stimulated proliferation; (ii) estrogen-dependent carcinogenesis; (iii) diminished biosynthesis of progesterone: (iv) enhanced formation of progesterone metabolites; and (v) increased inflammation and decreased differentiation. Spearman correlation coefficient analysis shows that expression of PAQR7 correlates with age, expression of SRD5A1, AKR1B1 and AKR1B10 correlate with body mass, while expression of SRD5A1 and AKR1B10 correlate with body mass index. When patients with endometrial cancer were stratified based on menopausal status, histological grade, myometrial invasion, lymphovascular invasion, and FIGO stage, Mann-Whitney U tests revealed significantly decreased expression of STAR (4.4-fold; adjusted p=0.009) and AKR1B10 (9-fold; adjusted p=0.003) in high grade versus low grade tumors. Lower levels of STAR might lead to decreased de-novo steroid hormone synthesis and tumor differentiation, and lower levels of AKR1B10 to diminished elimination of toxic electrophilic carbonyl compounds in high-grade endometrial cancer. These data thus reveal the potential of STAR and AKR1B10 as prognostic biomarkers, which calls for further validation at the protein level.

Whole flaxseed diet alters estrogen metabolism to promote 2-methoxtestradiol-induced apoptosis in hen ovarian cancer

The study reported here demonstrates that a flaxseed-supplemented diet causes ovarian tumors in the laying hen to undergo apoptosis, resulting in a reduction of tumor burden, reducing the frequency and severity of ovarian cancer. We have previously shown in normal ovaries that flaxseed and its components down-regulate ERalpha and alter the expression of enzymes that metabolize estrogen. In this study, we analyzed the effects of the two main components of whole flaxseed, ligan and omega 3 fatty acids on estrogen metabolism and the estrogen receptor in ovarian tumors. ER alpha expression was up-regulated in the ovarian tumors and was not affected by diet. Liver CYP1A1 expression was significantly increased by the whole flaxseed diet with a corresponding increase in 2-methoxyestradiol plasma levels. We also observed increased p38 and ERK 1/2 MAPK activation in the ovary as well as an increase in apoptosis in the tumor epithelium. SMAD 7, a factor involved in the 2-methoxyestradiol-mediated apoptosis pathway was also up-regulated in tumors from the whole flaxseed diet group. 2-methoxyestradiol-induced antitumor effects were further validated by in human ovarian cancer cells. This study details the effect of flaxseed diet on estrogen metabolism and demonstrates the antiovarian cancer effects of 2-methoxyestradiol.

Interaction of bisphenol A 3,4-quinone metabolite with glutathione and ribonucleosides/deoxyribonucleosides in vitro

Bisphenol A is a monomer used in the manufacture of polycarbonate plastic products, epoxy resin-based food can liners and flame retardants. To determine the genotoxic potential of bisphenol A, the mechanism of the reactions between the reactive electophilic bisphenol A 3,4-quinone (BPAQ) with glutathione and ribonucleosides/deoxyribonucleosides were studied. The obtained results demonstrated that BPAQ reacted with 2'-deoxyguanosine (dG)/guanosine (G), 2'-deoxyadenosine (dA)/adenosine (A), but not with 2'-deoxycytidine (dC)/cytidine (C) and thymidine (T)/uridine (U) in aqueous acetic acid. The reactions were accompanied by loss of deoxyribose, and the rate of depurination by deoxyribonucleoside adducts were faster than that of ribonucleoside adducts. In mixtures of ribonucleosides and deoxyribonucleosides treated with BPAQ, reactions occurred more readily with dG/G than dA/A. The structures of the modified bases were confirmed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). We also found that BPAQ reacted readily with glutathione (GSH) in aqueous acetic acid, and characterized the BPAQ-GSH conjugate by ESI-MS/MS. The in vitro data of depurinating DNA/RNA adducts and BPAQ-GSH adducts may provide appropriate reference for the identification of BPAQ adducts in environmental and biological systems.

A Novel Sensitive Method to Measure Catechol-O-Methyltransferase Activity Unravels the Presence of This Activity in Extracellular Vesicles Released by Rat Hepatocytes

There is a clear need for drug treatments to be selected according to the characteristics of an individual patient, in order to improve efficacy and reduce the number and severity of adverse drug reactions. One of the main enzymes to take into account in pharmacogenomics is catechol O-methyltransferase (COMT), which catalyzes the transfer of a methyl group from S-adenosylmethionine to catechols and catecholamines, like the neurotransmitters dopamine, epinephrine, and norepinephrine. Although, most of this enzyme is associated to intracellular vesicles, recently it has also been detected in extracellular vesicles secreted by hepatocytes and in serum circulating vesicles. COMT has implications in many neurological and psychiatric disorders like Parkinson's disease, chronic fatigue, pain response, schizophrenia, and bipolar disorders. Remarkably, genetic variations of COMT affect its activity and are associated to various human disorders from psychiatric diseases to estrogen-induced cancers. Consequently, the establishment of new methods to evaluate COMT activity is an important aspect to investigate the biology of this drug-metabolizing enzyme. Herein, we have developed a sensitive and selective method to determine COMT activity. We first optimized the activity in rat liver incubated with two different substrates; norepinephrine and dopamine. The enzymatically formed products (normetanephrine and 3-methoxytyramine, respectively) were extracted by solid-phase extraction using weak cation exchange cartridges, chromatographically separated, and detected and quantified using a mass spectrometer. The range of quantitation for both products was from 0.005 to 25 μg/mL. This methodology offers acceptable recovery for both enzymatic products (≥75%) and good accuracy and precision (≤15%). The lower limit of quantifications were 0.01 and 0.005 μM for 3-methoxytyramine and normetanephrine, respectively. Importantly, this sensitive assay was able to detect the presence of COMT activity in extracellular vesicles secreted by hepatocytes supporting a potential role of these vesicles in catecholamines and catecholestrogens metabolisms. In addition, the presence of COMT activity in extracellular vesicles opens new possibilities to develop tools to evaluate personalized drug response in a low invasive manner.

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

This report provides a review of stem cells/progenitor cells and their responses to ionising radiation in relation to issues relevant to stochastic effects of radiation that form a major part of the International Commission on Radiological Protection's system of radiological protection. Current information on stem cell characteristics, maintenance and renewal, evolution with age, location in stem cell 'niches', and radiosensitivity to acute and protracted exposures is presented in a series of substantial reviews as annexes concerning haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. This foundation of knowledge of stem cells is used in the main text of the report to provide a biological insight into issues such as the linear-no-threshold (LNT) model, cancer risk among tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age. Knowledge of the biology and associated radiation biology of stem cells and progenitor cells is more developed in tissues that renew fairly rapidly, such as haematopoietic tissue, intestinal mucosa, and epidermis, although all the tissues considered here possess stem cell populations. Important features of stem cell maintenance, renewal, and response are the microenvironmental signals operating in the niche residence, for which a well-defined spatial location has been identified in some tissues. The identity of the target cell for carcinogenesis continues to point to the more primitive stem cell population that is mostly quiescent, and hence able to accumulate the protracted sequence of mutations necessary to result in malignancy. In addition, there is some potential for daughter progenitor cells to be target cells in particular cases, such as in haematopoietic tissue and in skin. Several biological processes could contribute to protecting stem cells from mutation accumulation: (a) accurate DNA repair; (b) rapidly induced death of injured stem cells; (c) retention of the DNA parental template strand during divisions in some tissue systems, so that mutations are passed to the daughter differentiating cells and not retained in the parental cell; and (d) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the niche. DNA repair mainly occurs within a few days of irradiation, while stem cell competition requires weeks or many months depending on the tissue type. The aforementioned processes may contribute to the differences in carcinogenic radiation risk values between tissues, and may help to explain why a rapidly replicating tissue such as small intestine is less prone to such risk. The processes also provide a mechanistic insight relevant to the LNT model, and the relative and absolute risk models. The radiobiological knowledge also provides a scientific insight into discussions of the dose and dose-rate effectiveness factor currently used in radiological protection guidelines. In addition, the biological information contributes potential reasons for the age-dependent sensitivity to radiation carcinogenesis, including the effects of in-utero exposure.

Selective electrochemical detection of hydroquinone and catechol at a one-step synthesised pine needle-like nano-CePO4 modified carbon paste electrode

A pine needle-like nano-CePO₄ modified carbon paste electrode was successfully constructed for simultaneous detection of hydroquinone and catechol sensitively and selectively.

Evidence of estrone-sulfate uptake modification in young and middle-aged rat prostate

High plasma exposure to estrogens is often associated with prostate cancer. Reducing this phenomenon may present therapeutic benefits. The involvement of estrone sulphate (E1S), the most abundant circulating estrogen in men, has been partially studied in this age-related pathology. To investigate the consequences of plasma E1S overload on blood and prostate sex steroid levels and inflammatory tissue responses, young and middle-aged male rats were treated with E1S with or without steroid sulfatase (STS) inhibitor STX64 for 21 consecutive days. A plasma and prostate tissue steroid profile was determined. STS activity, mRNA expression of E1S organic anion transporting polypeptides (slco1a2, slco2b1, slco4a1) and pro-inflammatory cytokines (Il1-beta, Il6, TNF-alpha) were evaluated in prostate tissue according to age and treatment group. A significant correlation between plasma and prostate steroid levels related to hormone treatment was observed in all rat age groups. However, while the E1S level in prostate tissue increased in middle-aged treated rats (p<0.0001), no significant variation was observed in young treated rats. The protective effect of STX64 during E1S infusion was observed by the maintenance of low free estrogen concentrations in both plasma and tissue. However, this protection was not associated with mRNA expression stability of pro-inflammatory cytokines in older rat prostate. These results suggest that E1S uptake in rat prostate cells increases during aging. Therefore, if a similar phenomenon existed in men, preventively reducing the STS activity could be of interest to limit uptake of estrogens in prostate when high E1S plasma level is assayed.

Dietary γ-Tocopherol-Rich Mixture Inhibits Estrogen-Induced Mammary Tumorigenesis by Modulating Estrogen Metabolism, Antioxidant Response, and PPARγ

This study evaluated the anticancer activity and mechanism of action of a γ-tocopherol-rich tocopherol mixture, γ-TmT, in two different animal models of estrogen-induced breast cancer. The chemopreventive effect of γ-TmT at early (6 weeks), intermediate (18 weeks), and late (31 weeks) stages of mammary tumorigenesis was determined using the August-Copenhagen Irish rat model. Female rats receiving 17β-estradiol (E2) implants were administered with different doses (0%, 0.05%, 0.1%, 0.3%, and 0.5%) of γ-TmT diet. Treatment with 0.3% and 0.5% γ-TmT decreased tumor volume and multiplicity. At 31 weeks, serum concentrations of E2 were significantly decreased by γ-TmT. γ-TmT preferentially induced expression of the E2-metabolizing enzyme CYP1A1, over CYP1B1 in the rat mammary tissues. Nrf2-dependent antioxidant response was stimulated by γ-TmT, as evident from enhanced expression of its downstream targets, NQO1, GCLM, and HMOX1. Serum concentrations of the oxidative stress marker, 8-isoprostane, were also decreased in the γ-TmT-treated groups. Treatment with γ-TmT increased expression of PPARγ and its downstream genes, PTEN and p27, whereas the cell proliferation marker, PCNA, was significantly reduced in γ-TmT-treated mammary tumors. In an orthotopic model in which human MCF-7 breast cancer cells were injected into the mammary fat pad of immunodeficient mice, γ-TmT inhibited E2-dependent tumor growth at all the doses tested. In conclusion, γ-TmT reduced mammary tumor development, in part through decreased E2 availability and reduced oxidative stress in mammary tissues; γ-TmT could thus be an effective agent for the prevention and treatment of E2-induced breast cancer.

NF-κB increased expression of 17β-hydroxysteroid dehydrogenase 4 promotes HepG2 proliferation via inactivating estradiol

Hepatocellular carcinoma (HCC) arises in a setting of chronic inflammation induced by inflammatory cytokines, such as nuclear factor-kappaB (NF-κB). HCC is a male-predominant cancer that can be attenuated by estradiol (E2) in vitro and in vivo. Although 17β-hydroxysteroid dehydrogenase 4 (HSD17B4) has been implicated as an estradiol-inactivating enzyme, and its promoter sequence contains two putative NF-κB elements: it is currently unknown whether HSD17B4 is the link between inflammation, estradiol and proliferation in hepatoma cells. In this study, HepG2 cells were used to investigate the role of HSD17B4 in the proliferation of liver cancer cells treated with the NF-κB activator, tumor necrosis factor-alpha (TNF-α), with the inhibitor of NF-κB activation, pyrrolidinedithiocarbamate (PDTC), or with a related specific siRNA. We demonstrated that the human HSD17B4 gene is a target for NF-κB activation in inflammation-stimulated HepG2 cells. HSD17B4 is up-regulated via the binding of activated NF-κB to the distal NF-κB-responsive element via TNF-α stimulation, which then promotes cell proliferation by decreasing the levels of E2 and enhancing the expression of interleukin 6 (IL-6), cyclin D1 and proliferating cell nuclear antigen (PCAN). These results from HepG2 cells are consistent with the observation that HSD17B4 is highly expressed and activated NF-κB is highly co-localized with the NF-κB-responsive element of HSD17B4 in liver tumor tissues from HCC patients. Our findings indicate for the first time that HSD17B4 plays an important role in aggravated HCC progression and provides a novel therapeutic target for HCC.

Association between CYP1B1 gene polymorphisms and risk factors and susceptibility to laryngeal cancer

Background

The aim of this study was to investigate the association between polymorphism of the cytochrome P450 1B1 (CYP1B1) gene, a metabolic enzyme gene, and the susceptibility to laryngeal cancer among the Chinese Han population.

Material/Methods

In a case-control study, we investigated polymorphisms in the CYP1B1 gene (rs10012, rs1056827, and rs1056836) with a real-time quantitative polymerase chain reaction (PCR) assay (TaqMan). The study was conducted with 300 Chinese Han patients with laryngeal cancer and 300 healthy Chinese Han subjects in a control group. We also studied the interactions between genetic polymorphism and risk factors such as smoking and alcohol consumption in the pathogenesis of laryngeal cancer.

Results

There were statistically significant differences in the distributions of the rs1056827 and rs1056836 genotypes between the 2 groups. Regarding rs1056827, carriers of the T allele had a significantly higher risk of laryngeal cancer than the G-allele carriers (OR=1.4339, 95% CI: 1.1268–1.8247; P=0.0034). The difference was still statistically significant after adjusting for factors such as age, sex, smoking, and drinking (adjusted OR=1.743, 95% CI: 1.124–3.743, P<0.001). However, regarding rs1056836, the G allele carriers had a significantly lower risk of laryngeal cancer than the C allele carriers (OR=0.5557, 95% CI: 0.3787–0.8154; P=0.0027). The difference was statistically significant even after adjusting for factors such as age, sex, smoking, and drinking (adjusted OR=0.5641, 95% CI: 0.3212–0.8121, P=0.001). Subjects who carry the C-T-C haplotype have a significantly increased incidence of laryngeal cancer. We also found that CYP1B1 rs1056827 polymorphism had synergistic effects with smoking or alcohol consumption regarding the risk of laryngeal cancer.

Conclusions

CYP1B1 gene polymorphism is closely related to the onset of laryngeal cancer. There is a mutually synergistic effect between smoking, alcohol consumption, and CYP1B1 gene polymorphisms regarding laryngeal cancer.

Quercetin-3-O-glucronide inhibits noradrenaline binding to α2-adrenergic receptor, thus suppressing DNA damage induced by treatment with 4-hydroxyestradiol and noradrenaline in MCF-10A cells

Risk factors for breast cancer include estrogens such as 17β-estradiol (E2) and high stress levels. 4-Hydroxyestradiol (4-OHE2), a metabolite of E2 formed preferentially by cytochrome P450 1B1, is oxidized to E2-3,4-quinone, which reacts with DNA to form depurinating adducts that exert genotoxicity and carcinogenicity. Endogenous catecholamines such as adrenaline (A) and noradrenaline (NA) are released from the adrenal gland and sympathetic nervous system during exposure to stress. Here, we found that treatment with 4-OHE2 (3 μM) and NA (3 nM) significantly induced the phosphorylation of histone H2AX (γ-H2AX), one of the earliest indicators of DNA damage, and apurinic (AP) sites via the α2-adrenergic receptor (α2-AR) in human mammary epithelial MCF-10A cells. As an inverse association between a higher intake of flavonoids and breast cancer risk has previously been suggested from epidemiological studies, we investigated the effects of quercetin-3-O-glucuronide (Q3G), a circulating metabolite of quercetin in the blood, on 4-OHE2- and NA-induced γ-H2AX and AP sites. Q3G (0.1 μM) suppressed their induction and inhibited the binding of [(3)H]-NA to α2-AR. These results suggest that Q3G acts as an α2-AR antagonist and that it could be used as a chemopreventive agent for stress-promoted breast cancer.

Natural antioxidants exhibit chemopreventive characteristics through the regulation of CNC b-Zip transcription factors in estrogen-induced breast carcinogenesis

The objective of the present study was to characterize the role of resveratrol (Res) and vitamin C (VC) in prevention of estrogen-induced breast cancer through regulation of cap "n"collar (CNC) b-zip transcription factors. Human breast epithelial cell line MCF-10A was treated with 17β-estradiol (E2) and VC or Res with or without E2. mRNA and protein expression levels of CNC b-zip transcription factors nuclear factor erythroid 2-related factor 1 (Nrf1), nuclear factor erythroid 2 related factor 2 (Nrf2), nuclear factor erythroid 2 related factor 3 (Nrf3), and Nrf2-regulated antioxidant enzymes superoxide dismutase 3 (SOD3) and

NAD(P)H

quinone oxidoreductase 1 (NQO1) were quantified. The treatment with E2 suppressed, whereas VC and Res prevented E2-mediated decrease in the expression levels of SOD3, NQO1, Nrf2 mRNA, and protein in MCF-10A cells. The treatment with E2, Res, or VC significantly increased mRNA and protein expression levels of Nrf1. 17β-Estradiol treatment significantly increased but VC or Res decreased Nrf3 mRNA and protein expression levels. Our studies demonstrate that estrogen-induced breast cancer might be prevented through upregulation of antioxidant enzymes via Nrf-dependent pathways.

Quercetin-3-O-glucuronide inhibits noradrenaline-promoted invasion of MDA-MB-231 human breast cancer cells by blocking β₂-adrenergic signaling

Endogenous catecholamines such as adrenaline (A) and noradrenaline (NA) are released from the adrenal gland and sympathetic nervous system during exposure to stress. The adrenergic system plays a central role in stress signaling, and excessive stress was found to be associated with increased production of reactive oxygen species (ROS). Overproduction of ROS induces oxidative damage in tissues and causes the development of diseases such as cancer. In this study, we investigated the effects of quercetin-3-O-glucuronide (Q3G), a circulating metabolite of quercetin, which is a type of natural flavonoid, on the catecholamine-induced β2-adrenergic receptor (β2-AR)-mediated response in MDA-MB-231 human breast cancer cells expressing β2-AR. Treatment with A or NA at concentrations above 1μM generated significant levels of ROS, and NA treatment induced the gene expression of heme oxygenase-1 (HMOX1), and matrix metalloproteinase-2 (MMP-2) and -9 (MMP9). Inhibitors of p38 MAP kinase (SB203580), cAMP-dependent protein kinase (PKA) (H-89), activator protein-1 (AP-1) transcription factor (SR11302), and NF-κB and AP-1 (Tanshinone IIA) decreased MMP2 and MMP9 gene expression. NA also enhanced cAMP induction, RAS activation and phosphorylation of ERK1/2. These results suggested that the cAMP-PKA, MAPK, and ROS-NF-κB pathways are involved in β2-AR signaling. Treatment with 0.1μM Q3G suppressed ROS generation, cAMP and RAS activation, phosphorylation of ERK1/2 and the expression of HMOX1, MMP2, and MMP9 genes. Furthermore, Q3G (0.1μM) suppressed invasion of MDA-MB-231 breast cancer cells and MMP-9 induction, and inhibited the binding of [(3)H]-NA to β2-AR. These results suggest that Q3G may function to suppress invasion of breast cancer cells by controlling β2-adrenergic signaling, and may be a dietary chemopreventive factor for stress-related breast cancer.

Urinary estrogen metabolites and self-reported infertility in women infected with Schistosoma haematobium

BACKGROUND

Schistosomiasis is a neglected tropical disease, endemic in 76 countries, that afflicts more than 240 million people. The impact of schistosomiasis on infertility may be underestimated according to recent literature. Extracts of Schistosoma haematobium include estrogen-like metabolites termed catechol-estrogens that down regulate estrogen receptors alpha and beta in estrogen responsive cells. In addition, schistosome derived catechol-estrogens induce genotoxicity that result in estrogen-DNA adducts. These catechol estrogens and the catechol-estrogen-DNA adducts can be isolated from sera of people infected with S. haematobium. The aim of this study was to study infertility in females infected with S. haematobium and its association with the presence of schistosome-derived catechol-estrogens.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional study was undertaken of female residents of a region in Bengo province, Angola, endemic for schistosomiasis haematobia. Ninety-three women and girls, aged from two (parents interviewed) to 94 years were interviewed on present and previous urinary, urogenital and gynecological symptoms and complaints. Urine was collected from the participants for egg-based parasitological assessment of schistosome infection, and for liquid chromatography diode array detection electron spray ionization mass spectrometry (LC/UV-DAD/ESI-MSn) to investigate estrogen metabolites in the urine. Novel estrogen-like metabolites, potentially of schistosome origin, were detected in the urine of participants who were positive for eggs of S. haematobium, but not detected in urines negative for S. haematobium eggs. The catechol-estrogens/ DNA adducts were significantly associated with schistosomiasis (OR 3.35; 95% CI 2.32-4.84; P≤0.001). In addition, presence of these metabolites was positively associated with infertility (OR 4.33; 95% CI 1.13-16.70; P≤0.05).

CONCLUSIONS/SIGNIFICANCE

Estrogen metabolites occur widely in diverse metabolic pathways. In view of the statistically significant association between catechol-estrogens/ DNA adducts and self-reported infertility, we propose that an estrogen-DNA adduct mediated pathway in S. haematobium-induced ovarian hormonal deregulation could be involved. In addition, the catechol-estrogens/ DNA adducts described here represent potential biomarkers for schistosomiasis haematobia.

BRCAness: a deeper insight into basal-like breast tumors

The molecular scenario of breast cancer has become more complex in the last few years. Distinguishing between BRCA-associated, sporadic, HER2-enriched and triple-negative tumors is not sufficient to allow effective clinical management. Basal-like breast cancer, a subtype of triple-negative breast cancer, differs from others grouped under this heading. Commonalities between BRCA-related tumors and basal-like breast cancers (BRCAness phenotype) are highly relevant to ongoing clinical trials, in particular those investigating targeted therapies (e.g. PARP inhibitors) in sporadic breast tumors. The 'gold standard' to identify basal-like phenotype is DNA microarray, but integrated results could provide a panel of biomarkers helpful in identifying 'BRCAness' tumors (e.g. copy number aberrations, abnormal protein localization and altered transcriptional levels) and other molecular targets, such as APE1,the inhibition of which is emerging as an attractive breast cancer treatment in certain therapeutic settings.

Gene expression profile and toxic effects in human bronchial epithelial cells exposed to zearalenone

Zearalenone (ZEA), a mycoestrogen produced by Fusarium fungal species, is mainly found in cereal crops such as maize, wheat and barley. Although ZEA has been reported to be present in air, little is known about the health risk or the molecular basis of action when lung cells are exposed to ZEA. As ZEA has a similar structure to estrogen, its potential risk as an endocrine disrupting chemical (EDC) has thus aroused both environmental and public health concerns. The purpose of this study is to identify the responses and underlying molecular changes that occur when human bronchial epithelial BEAS-2B cells are exposed to ZEA. Differential gene expression profiles were identified in cells that were treated with 40 µM ZEA for 6 h and 24 h by high-throughput microarray analysis using Affymetrix Human Gene 2.0 GeneChip. The array results showed that after ZEA treatment, 262 genes at 6 h and 1073 genes at 24 h were invovled in the differential regulation. Pathway analysis revealed that diverse cellular processes were affected when lung cells were exposed to ZEA resulting in impaired response to DNA damage, cell cycle arrest, down-regulation of inflammatory responses and alterations of epigenetic marks. Results of further experiments indicated that 40 µM ZEA decreased cell viability, induced apoptosis and promoted reactive oxygen species (ROS) generation in a time-dependent manner. Immuno-suppressive effects of ZEA were further revealed through the suppression of lipopolysaccharide (LPS)-induced expression of pro-inflammatory cytokines (IL-6, IL-8 and IL-1β). Interestingly, the level of global DNA methylation was markedly decreased after 24 h exposure to ZEA. Collectively, these observations suggested that a broad range of toxic effects are elicited by ZEA. Particularly, ROS may play a pivotal role in ZEA-induced cell death. These adverse effects observed in lung cells suggest that exposure to ZEA may increase susceptibility of lung cells to diseases and required further investigations.

COMT polymorphism influences decrease of ovarian follicles and emerges as a predictive factor for premature ovarian insufficiency

Background

Estrogens are important factors in the female reproductive functions and are processed by a number of enzymes along their metabolic pathway. The COMT gene constitutes a crucial element in estrogen metabolism and is assumed to be involved in the development of Premature Ovarian Insufficiency (POI). This study aimed to determine whether the presence of the COMT Val/Met polymorphism (rs4680) is associated to the risk of developing POI.

Findings

In this case–control study, we evaluated 96 infertile women with POI and 120 fertile women as controls, after obtaining a detailed history of the disease and follicle-stimulating hormone measurements, besides karyotype determination and fragile-X premutation syndrome investigation. COMT (Val/Met) genotypes were identified by real time PCR (genotyping TaqMan assay), and the results were statistically analyzed. A statistically significant difference was found in the distribution of COMT genotypes (p = 0.003) and alleles (p = 0.015) between the POI patients and the control group.

Conclusion

We were able to demonstrate a strong association between the COMT Val/Met polymorphism and the risk of premature ovarian insufficiency in the Brazilian women evaluated. However, further studies in larger populations are necessary to confirm these findings.

Tocopherols inhibit oxidative and nitrosative stress in estrogen-induced early mammary hyperplasia in ACI rats

Oxidative stress is known to play a key role in estrogen-induced breast cancer. This study assessed the chemopreventive activity of the naturally occurring γ-tocopherol-rich mixture of tocopherols (γ-TmT) in early stages of estrogen-induced mammary hyperplasia in ACI rats. ACI rats provide an established model of rodent mammary carcinogenesis due to their high sensitivity to estrogen. Female rats were implanted with 9 mg of 17β-estradiol (E2) in silastic tubings and fed with control or 0.3% γ-TmT diet for 1, 3, 7, and 14 d. γ-TmT increased the levels of tocopherols and their metabolites in the serum and mammary glands of the rats. Histological analysis revealed mammary hyperplasia in the E2 treated rats fed with control or γ-TmT diet. γ-TmT decreased the levels of E2-induced nitrosative and oxidative stress markers, nitrotyrosine, and 8-oxo-dG, respectively, in the hyperplastic mammary tissues. 8-Isoprostane, a marker of oxidative stress in the serum, was also reduced by γ-TmT. Noticeably, γ-TmT stimulated Nrf2-dependent antioxidant response in the mammary glands of E2 treated rats, evident from the induced mRNA levels of Nrf2 and its downstream antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase. Therefore, inhibition of nitrosative/oxidative stress through induction of antioxidant response is the primary effect of γ-TmT in early stages of E2-induced mammary hyperplasia. Due to its cytoprotective activity, γ-TmT could be a potential natural agent for the chemoprevention of estrogen-induced breast cancer.

Estrogen biosynthesis, phase I and phase II metabolism, and action in endometrial cancer

Endometrial cancer is the most common gynecological malignancy in the developed World. Based on their histopathology, clinical manifestation, and epidemiology, the majority of endometrial cancer cases can be divided into two groups: the more prevalent type 1 which is associated with unopposed estrogen exposure; and the less common type 2, which is usually not associated with hyper-estrogenic factors. This manuscript overviews the published data on the expression of genes encoding the estrogen biosynthetic enzymes, the phase I and phase II estrogen metabolic enzymes, and the estrogen receptors in endometrial cancer, at the mRNA, protein and enzyme activity levels. The potential role of altered expression of these enzymes and receptors in cancerous versus control endometrial tissue, and the implication of estrogens in tumor initiation and promotion, are discussed. Finally, based on the published data, a model of estrogen metabolism and actions is proposed for pre-cancerous and cancerous endometrial tissue, and the role of the estrogens in the progression of endometrial cancer from endometrial hyperplasia is suggested.

A review on the role of quinones in renal disorders

Quinones are electron and proton carriers that play a primary role in the aerobic metabolism of virtually every cell in nature. Most physiological quinones are benzoquinones. They undergo highly regulated redox reactions in the mitochondria, Golgi apparatus, plasma membrane and endoplasmic reticulum. Important consequences of these electron transfer reactions are the production of and protection against reactive oxygen species (ROS). Quinones have been extensively studied for both their cytotoxic as well as cellular protective properties and they have been particularly useful in rational drug design. The role of quinones in medicine is explored in this literature review with a particular focus on renal diseases. Due to their high basal metabolism and detoxification role, the kidneys are particularly sensitive to oxidative stress. Regardless of the underlying etiology, ROS plays an important role in both acute kidney injury (AKI) and chronic kidney diseases (CKD). Depending on the oxidative state of the kidney, quinones can be nephrotoxoic or nephro-protective. Many factors play a role in the interaction between quinones and the kidney and the consequences of this are just beginning to be explored.

Genotoxicity and inactivation of catechol metabolites of the mycotoxin zearalenone

Zearalenone (ZEN) is a highly estrogenic mycotoxin produced by Fusarium species. The adverse effects of ZEN and its reductive metabolite α-zearalenol (α-ZEL) are often compared to those of 17β-estradiol (E2) and estrone (E1). These endogenous steroidal estrogens are associated with an increased risk for cancer, which may be mediated by two mechanisms, i.e. (1) hormonal activity and (2) genotoxic effects after cytochrome P450-catalyzed metabolic activation to catechols. Like E1 and E2, ZEN and α-ZEL exhibit marked estrogenicity and also undergo aromatic hydroxylation to catechol metabolites. The subsequent methylation of catechols by catechol-O-methyltransferase (COMT) is generally considered as a detoxifying pathway. Imbalances between the activation and inactivation reactions can lead to the formation of reactive semiquinones and quinones, which can alkylate DNA or produce reactive oxygen species by redox cycling. In the present study, the genotoxicity of the catechol metabolites of ZEN, α-ZEL, E1 and E2 was determined in a cell-free system by measuring 8-oxo-2'-deoxyguanosine using a LC-DAD-MS(2) method. Each of the individual catechols of ZEN, α-ZEL, E1 and E2 induced oxidative DNA damage in calf thymus DNA. The ranking order of the DNA damaging activity was 15-hydroxy-ZEN/α-ZEL ≈ 2/4-hydroxy-E1/E2 > 13-hydroxy-ZEN/α-ZEL. When hepatic microsomes from different species were incubated with ZEN, the rat had the highest activity for catechol formation, followed by human, mouse, pig and steer. The amount of catechol metabolites correlated directly with the amount of oxidative damage in calf thymus DNA. The ranking order for the rate of methylation by human hepatic COMT was 2-hydroxy-E1/E2 >> 4-hydroxy-E1/E2 >> 13/15-hydroxy-ZEN/α-ZEL. Thus, the catechol metabolites of the mycoestrogen ZEN and its reductive metabolite α-ZEL exhibit a DNA-damaging potential comparable to that of the catechol metabolites of E1 and E2, but are much poorer substrates for inactivation by human COMT.

Lung cancer in never smokers

Lung cancer in never smokers (LCINS) is the seventh leading cause of death among solid tumors. The main risk factor for lung cancer is smoking; however, approximately 15% of lung cancer patients have never smoked. LCINS is more frequent in women, irrespective of geographical location, nevertheless, the highest incidence has been found in South-East Asia. The histological incidence of adenocarcinoma is higher in the group of never smokers than squamous cell carcinoma. There is a familial clustering of lung cancer that is more pronounced in never smokers, where the family history was associated with an increased risk. Genome-wide association studies identified certain chromosomal aberrations in LCINS. Furthermore, the oncogenic mutation pattern is distinct in nonsmoking patients: activating mutations of EGFR or anaplastic lymphoma kinase are more frequent. The etiology of LCINS includes several environmental factors as well, such as environmental tobacco smoke, viral and hormonal factors, a variety of pulmonary diseases and certain occupational exposures. It is now established that EGFR-tyrosine kinase inhibitor treatment (erlotinib and geftinib) in lung cancer is more effective in LCINS, owing to the higher incidence of EGFR mutation in nonsmokers. Despite the growing body of information on LCINS in recent years there is a need to further investigate the pathogenesis of this particular lung cancer. Future studies on LCINS should try to tackle the issues of prevention, early diagnosis and the exploration of novel therapeutic targets to combat lung cancer disease.

Catechol metabolites of zeranol and 17β-estradiol: a comparative in vitro study on the induction of oxidative DNA damage and methylation by catechol-O-methyltransferase

α-Zearalanol (α-ZAL, zeranol) is a highly estrogenic macrocyclic β-resorcylic acid lactone, which is used as a growth promotor for cattle in various countries. We have recently reported that α-ZAL and its major metabolite zearalanone (ZAN) are hydroxylated at the aromatic ring by microsomes from human liver in vitro, thereby forming two catechol metabolites each. Thus, the oxidative metabolism of α-ZAL and ZAN resembles that of the endogenous steroidal estrogens 17β-estradiol (E2) and estrone (E1), which also give rise to two catechols each. As these catechol metabolites are believed to mediate the carcinogenicity of E2 and E1 by causing oxidative DNA damage and DNA adducts, their methylation by catechol-O-methyltransferase (COMT) is an important inactivation pathway. Here we report that hepatic microsomes from five species generate catechol metabolites of α-ZAL and ZAN, the highest amounts being formed by human liver microsomes, followed by rat, mouse, steer and swine. The microsomal extracts and the individual catechols of α-ZAL, ZAN, E2 and E1 were found to induce oxidative DNA damage, as measured by the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine in a cell-free system. The ranking of pro-oxidant activity was 15-HO-ZAN>15-HO-α-ZAL≈4-HO-E2/E1≈2-HO-E2/E1>13-HO-ZAN>13-HO-α-ZAL. With respect to the rate of methylation by human hepatic COMT, the ranking was 2-HO-E2/E1>>4-HO-E2/E1>15-HO-α-ZAL/ZAN>>13-HO-α-ZAL/ZAN. Thus, some catechol metabolites of α-ZAL and ZAN are better pro-oxidants and poorer substrates of COMT than the catechols of E2 and E1. These findings warrant further investigations into the genotoxic potential of α-ZAL, which may constitute another biological activity in addition to its well-known estrogenicity.

Estrogen metabolism and risk of breast cancer in postmenopausal women

BACKGROUND

Estrogens are recognized causal factors in breast cancer. Interindividual variation in estrogen metabolism may also influence the risk of breast cancer and could provide clues to mechanisms of breast carcinogenesis. Long-standing hypotheses about how estrogen metabolism might influence breast cancer have not been adequately evaluated in epidemiological studies because of the lack of accurate, reproducible, and high-throughput assays for estrogen metabolites.

METHODS

We conducted a prospective case-control study nested within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). Participants included 277 women who developed invasive breast cancer (case subjects) and 423 matched control subjects; at PLCO baseline, all subjects were aged 55-74 years, postmenopausal and not using hormone therapy, and provided a blood sample. Liquid chromatography-tandem mass spectrometry was used to measure serum concentrations of 15 estrogens and estrogen metabolites, in unconjugated and conjugated forms, including the parent estrogens, estrone and estradiol, and estrogen metabolites in pathways defined by irreversible hydroxylation at the C-2, C-4, or C-16 positions of the steroid ring. We calculated hazard ratios (HRs) approximating risk in highest vs lowest deciles of individual estrogens and estrogen metabolites, estrogens and estrogen metabolites grouped by metabolic pathways, and metabolic pathway ratios using multivariable Cox proportional hazards models. All statistical tests were two-sided.

RESULTS

Nearly all estrogens, estrogen metabolites, and metabolic pathway groups were associated with an increased risk of breast cancer; the serum concentration of unconjugated estradiol was strongly associated with the risk of breast cancer (HR = 2.07, 95% confidence interval [CI] = 1.19 to 3.62). No estrogen, estrogen metabolite, or metabolic pathway group remained statistically significantly associated with the risk of breast cancer after adjusting for unconjugated estradiol. The ratio of the 2-hydroxylation pathway to parent estrogens (HR = 0.66, 95% CI = 0.51 to 0.87) and the ratio of 4-hydroxylation pathway catechols to 4-hydroxylation pathway methylated catechols (HR = 1.34, 95% CI = 1.04 to 1.72) were statistically significantly associated with the risk of breast cancer and remained so after adjustment for unconjugated estradiol.

CONCLUSIONS

More extensive 2-hydroxylation of parent estrogens is associated with lower risk, and less extensive methylation of potentially genotoxic 4-hydroxylation pathway catechols is associated with higher risk of postmenopausal breast cancer.

COMT polymorphism and the risk of endometriosis-related infertility

Estrogens are important factors in the development of endometriosis, and can induce cell proliferation and stimulate cell division. COMT constitutes a crucial element in estrogen metabolism and has been suggested to be involved in the development of endometriosis. This study had the objective of to determine whether the presence of COMT val/met polymorphism (rs4680) increases the risk to endometriosis in infertile patients. A case-control study that included 198 infertile women with endometriosis, 71 infertile women without endometriosis, and 168 fertile women as control group of the Faculdade de Medicina do ABC. COMT (val/met) genotypes were identified by real time PCR (genotyping TaqMan assay) and the results were analyzed statistically by χ² test. The data showed no statistical difference in the distribution of COMT genotypes neither between infertile patients with endometriosis and control group (p = 0.567), regardless disease degree, nor between infertile patients without endometriosis and control group (p = 0.460). In conclusion, the COMT val/met polymorphism is not associated to endometriosis-related infertility in the Brazilian population evaluated. However, more studies in larger populations are necessary to confirm these results.

How can grafted breast cancer models be optimized?

Breast cancer is the most frequent spontaneous malignancy diagnosed in women and is characterized by a broad histological diversity. Progression of the disease has a metastasizing trend and can be resistant to hormonal and chemotherapy. Animal models have provided some understanding of these features and have allowed new treatments to be proposed. However, these models need to be revised because they have some limitations in predicting the clinical efficacy of new therapies. In this review, we discuss the biological criteria to be taken into account for a realistic animal model of breast cancer graft (tumor implantation site, animal immune status, histological diversity, modern imaging). We emphasize the need for more stringent monitoring criteria, and suggest adopting the human RECIST (Response Evaluation Criteria in Solid Tumors) criteria to evaluate treatments in animal models.

Partial inhibition of estrogen-induced mammary carcinogenesis in rats by tamoxifen: balance between oxidant stress and estrogen responsiveness

Epidemiological and experimental evidences strongly support the role of estrogens in breast tumor development. Both estrogen receptor (ER)-dependent and ER-independent mechanisms are implicated in estrogen-induced breast carcinogenesis. Tamoxifen, a selective estrogen receptor modulator is widely used as chemoprotectant in human breast cancer. It binds to ERs and interferes with normal binding of estrogen to ERs. In the present study, we examined the effect of long-term tamoxifen treatment in the prevention of estrogen-induced breast cancer. Female ACI rats were treated with 17β-estradiol (E2), tamoxifen or with a combination of E2 and tamoxifen for eight months. Tissue levels of oxidative stress markers 8-iso-Prostane F_2α (8-isoPGF_2α), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase, and oxidative DNA damage marker 8-hydroxydeoxyguanosine (8-OHdG) were quantified in the mammary tissues of all the treatment groups and compared with age-matched controls. Levels of tamoxifen metabolizing enzymes cytochrome P450s as well as estrogen responsive genes were also quantified. At necropsy, breast tumors were detected in 44% of rats co-treated with tamoxifen+E2. No tumors were detected in the sham or tamoxifen only treatment groups whereas in the E2 only treatment group, the tumor incidence was 82%. Co-treatment with tamoxifen decreased GPx and catalase levels; did not completely inhibit E2-mediated oxidative DNA damage and estrogen-responsive genes monoamine oxygenase B1 (MaoB1) and cell death inducing DFF45 like effector C (Cidec) but differentially affected the levels of tamoxifen metabolizing enzymes. In summary, our studies suggest that although tamoxifen treatment inhibits estrogen-induced breast tumor development and increases the latency of tumor development, it does not completely abrogate breast tumor development in a rat model of estrogen-induced breast cancer. The inability of tamoxifen to completely inhibit E2-induced breast carcinogenesis may be because of increased estrogen-mediated oxidant burden.