Perspectives on the chemical etiology of breast cancer

Long-Term Exposure of Early-Transformed Human Mammary Cells to Low Doses of Benzo[a]pyrene and/or Bisphenol A Enhances Their Cancerous Phenotype via an AhR/GPR30 Interplay

It is of utmost importance to decipher the role of chronic exposure to low doses of environmental carcinogens on breast cancer progression. The early-transformed triple-negative human mammary MCF10AT1 cells were chronically (60 days) exposed to low doses (10⁻¹⁰ M) of Benzo[a]pyrene (B[a]P), a genotoxic agent, and/or Bisphenol A (BPA), an endocrine disruptor. Our study revealed that exposed MCF10AT1 cells developed, in a time-dependent manner, an acquired phenotype characterized by an increase in cancerous properties (anchorage independent growth and stem-like phenotype). Co-exposure of MCF10AT1 cells to B[a]P and BPA led to a significantly greater aggressive phenotype compared to B[a]P or BPA alone. This study provided new insights into the existence of a functional interplay between the aryl hydrocarbon receptor (AhR) and the G protein-coupled receptor 30 (GPR30) by which chronic and low-dose exposure of B[a]P and/or BPA fosters the progression of MCF10AT1 cells into a more aggressive substage. Experiments using AhR or GPR30 antagonists, siRNA strategies, and RNAseq analysis led us to propose a model in which AhR signaling plays a “driver role” in the AhR/GPR30 cross-talk in mediating long-term and low-dose exposure of B[a]P and/or BPA. Retrospective analysis of two independent breast cancer cohorts revealed that the AhR/GPR30 mRNA expression signature resulted in poor breast cancer prognosis, in particular in the ER-negative and the triple-negative subtypes. Finally, the study identified targeting AhR and/or GPR30 with specific antagonists as a strategy capable of inhibiting carcinogenesis associated with chronic exposure to low doses of B[a]P and BPA in MCF10AT1 cells. Altogether, our results indicate that the engagement of both AhR and GPR30 functions, in particular in an ER-negative/triple-negative context of breast cells, favors tumor progression and leads to poor prognosis.

DDT exposure during pregnancy and DNA methylation alterations in female offspring in the Child Health and Development Study

Studies measuring dichlorodiphenyltrichloroethane (DDT) exposure during key windows of susceptibility including the intrauterine period suggest that DDT exposure is associated with breast cancer risk. We hypothesized that prenatal DDT exposure is associated with DNA methylation. Using prospective data from 316 daughters in the Child Health and Development Study, we examined the association between prenatal exposure to DDTs and DNA methylation in blood collected in midlife (mean age: 49 years). To identify differentially methylated regions (DMRs) associated with markers of DDTs (p,p'-DDT and the primary metabolite of p,p'-DDT, p,p'-DDE, and o,p'-DDT, the primary constituents of technical DDT), we measured methylation in 30 genes important to breast cancer. We observed DDT DMRs in three genes, CCDC85A, CYP1A1 and ZFPM2, each of which has been previously implicated in pubertal development and breast cancer susceptibility. These findings suggest prenatal DDT exposure may have life-long consequence through alteration in genes relevant to breast cancer.

Mechanistic evidence that benzo[a]pyrene promotes an inflammatory microenvironment that drives the metastatic potential of human mammary cells

Benzo[a]pyrene (B(a)P) is a major cancer-causing contaminant present in food such as cooked meats and cereals, and is ubiquitous in the environment in smoke derived from the combustion of organic material. Exposure to B(a)P is epidemiologically linked with the incidence of breast cancer. Although B(a)P is recognized as a complete genotoxic carcinogen, thought to act primarily via CYP-mediated metabolic activation to DNA-damaging species, there is also evidence that B(a)P exposure elicits other biological responses that promote development of the cancer phenotype. Here in mechanistic studies using human mammary cells MCF-7 and MDA-MB-231, we have explored mechanisms whereby B(a)P (10^- 8 to 10^- 5M) promotes inflammation pathways via TNF-α and NFκB leading to IL-6 upregulation, microRNA (Let7a, miR21 and miR29b) dysregulation and activation of VEGF. The miRNA dysregulation is associated with altered expression of inflammation mediators and increased migration and invasive potential of human mammary cancer cells. Our data suggest that mammary cell exposure to B(a)P results in perturbation of inflammation mediators and dysregulation of tumorigenic miRNAs, leading to an inflammation microenvironment that facilitates migration and invasion of mammary epithelial cells. These properties of B(a)P, together with its well-established metabolic activation to DNA-damaging species, offer mechanistic insights into its carcinogenic mode of action.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

There is no relationship between SOD2 Val-16Ala polymorphism and breast cancer risk or survival

Breast cancer is the most common diagnosed cancer among females worldwide. Superoxide dismutase 2 (SOD2), an antioxidant enzyme, may break the balance between the oxidant and antioxidant system to induce various diseases. The present study aimed to clarify the association between the SOD2 Val-16Ala polymorphism and breast cancer risk or survival. Thus, a meta-analysis of the relevant articles retrieved from PubMed and EMBASE databases was conducted to illuminate the association with odd ratios (ORs) or hazards ratios (HRs). A total of 26 eligible publications (n=38,008) were available in risk analysis and eight publications (n=5,746) in survival analysis. The results demonstrated a marginal association between breast cancer risk and SOD2 polymorphism in Caucasian patients [TT vs. CT + CC: (OR, 0.94; 95% confidence interval (CI), 0.88-1.00)]. However, no other positive results were observed in risk and survival of breast cancer in the whole study [T vs. C: (OR, 0.99; 95% CI, 0.96-1.02); CT vs. CC: (OR, 1.00; 95% CI, 0.95-1.05); TT vs. CC: (OR, 0.98; 95% CI, 0.92-1.05); TT vs. CT + CC: (OR, 1.00; 95% CI, 0.95-1.05); CT + TT vs. CC: (OR, 0.99; 95% CI, 0.95-1.05)]. The present meta-analysis indicated that there was no significant relationship between SOD2 Val-16Ala polymorphism and breast cancer risk or survival, although in Caucasian patients, the SOD2 TT genotype may marginally decrease the risk of breast cancer in comparison to the CT + CC genotype.

Circulating levels of angiogenesis-related growth factors in breast cancer: A study to profile proteins responsible for tubule formation

The present study exploited a versatile in vitro endothelial cell/fibroblast co-culture cell system to investigate the association between angiogenesis and breast cancer by comparing the capacity of plasma from women with breast cancer and age-matched controls, to influence tubule formation and modulate angiogenesis in vitro, and to identify plasma circulating factors which might be responsible. Plasma from women with breast cancer (n=8) (added on day 7 after co-culture establishment) significantly increased tubule formation by 57% (P<0.01) when compared to cultures grown in culture medium lacking in vascular endothelial growth factor (VEGF) and fetal bovine serum (FBS), whereas plasma from controls (n=8) did not. Higher levels of VEGF, tumour necrosis factor-α (TNFα) and interleukin (IL)-6, but not leptin, were observed in plasma samples of the breast cancer group compared to the control group (n=20 in each group). In independent experiments, the effects of VEGF, TNFα, IL-6 and leptin were assessed and it was found that tubule formation was differentially affected whether these inflammatory cytokines or adipokines were added individually or in combination to the co-culture system. Using Proteome Profiler human angiogenesis array kits, 12 out of 55 angiogenesis-related proteins were differentially expressed in plasma from the breast cancer group compared to the control group. Pro-angiogenic proteins included: amphiregulin, artemin, coagulation factor III, fibroblast growth factor (FGF) acidic, GDNF, IL-8, macrophage inflammatory protein (MIP)-1α, platelet derived growth factor-AB/platelet derived growth factor-BB (PDGF-AB/PDGF-BB) and VEGF, whereas anti-angiogenic proteins were: angiopoietin-2, serpin F1 and serpin B5. In addition, FGF acidic was further identified as differentially expressed, with increased expression, when plasma samples from the normal and cancer groups, which induced an increase in tubule formation, were compared to one another. In conclusion, the present study identified angiogenesis-related proteins circulating in the serum of women with breast cancer that are likely to facilitate the growth and metastasis of breast cancer, in part through their influence on tubule formation, and, therefore, may be potential targets for new cancer therapies.

Assessment of Risk Factors of Obesity and Diet on Breast Cancer in Ankara, Turkey

OBJECTIVE

To determine the risk factors of obesity and diet on breast cancer in Ankara, Turkey.

METHODS

A case-controlled study was carried out on newly diagnosed 40 breast cancer patients [patient group (PC)] and 40 volunteer individuals [control group (CG)] with no diagnosis of cancer and history of cancer in the family with similar characteristics to the age and gender-matched patient group between March and July 2016. All the individuals were administered a questionnaire by face-to-face interview method.

RESULTS

The mean menarche age, age at first birth and menopause age were 13.0±1.17, 22.6±3.78 and 44.33±2.39 years in PG and 12.3±0.95, 21.6±2.99, 46.71±2.41 years in CG, respectively. The mean BMI values were determined as 28.1±6.75 kg/m² in PG and 30.1±6.18 kg/m² in CG (p>0.05). It was determined that intake of vitamin C and fiber decreases the risk of breast cancer. Also, eating quickly and smoking were risk factors for breast cancer (p<0.05).

CONCLUSION

This study indicated that there are relationships between menarche age, menopause age, and age at first birth, eating quickly, smoking and breast cancer. Conversely, there are significant negative relationships between dietary fiber, vitamin C intake and breast cancer. As a result, it can be said that there is a link between breast cancer and lifestyle factors and a reduction in the risk of developing breast cancer can be achieved through changes in diet, one of the lifestyle factors.

Diaminomesitylene

The title compound, C9H14N2(systematic name: 2,4,6-trimethylbenzene-1,3-diamine), is almost planar (r.m.s. deviation = 0.025 Å). In the crystal, molecules are linkedviaN—H...N hydrogen bonds, forming zigzag chains along theb-axis direction. Only one of the four N-bonded H atoms forms a hydrogen bond, perhaps due to steric crowding. The chains are linked by C—H...π interactions, forming sheets lying parallel to thebcplane

Breast cancer risk in relation to TP53 codon 72 and CDH1 gene polymorphisms in the Bangladeshi women

Pharmacogenomic studies play a significant role in understanding the risk of breast cancer where genetic abnormalities are implicated as the etiology of cancer. Various polymorphisms of tumor suppressor gene TP53 and E-cadherin (CDH1) have been found to be associated with increased breast cancer risk worldwide. This study aimed to analyze the contribution of TP53 and CDH1 gene anomalies in breast cancer risk in the Bangladeshi breast cancer patients. For risk determination, 310 patients with breast cancer and 250 controls from Bangladeshi women were recruited who are matched up with age and use of contraceptives with patients. Genetic polymorphisms were detected by using polymerase chain reaction restriction fragment length polymorphism. A significant association was found between TP53Arg72Pro (rs1042522) and CDH1 -160 C/A (rs16260) polymorphisms and breast cancer risk. In case of P53rs1042522 polymorphism, Arg/Pro (P = 0.0053, odds ratio (OR) = 1.69) and Pro/Pro (P = 0.018, OR = 1.83) genotypes were associated with increased risk of breast cancer in comparison to the Arg/Arg genotype. Arg/Pro + Pro/Pro genotype and Pro allele also increased the risk of breast cancer (P = 0.002, OR = 1.73; P = 0.004, OR = 1.43, respectively). In case of CDH1rs16260 polymorphism, C/A heterozygote and combined C/A + A/A genotypes were found to be strongly associated (P = 0.005, OR = 1.67; P = 0.0037, OR = 1.68) with increased risk of breast cancer. The variant A allele also increased the breast cancer risk (P = 0.0058, OR = 1.52). The present study demonstrates that P53Arg72Pro and CDH1rs16260 polymorphisms are associated with elevated breast cancer risk in the Bangladeshi population.

Association between XRCC3 Thr241Met Polymorphism and Risk of Breast Cancer: Meta-Analysis of 23 Case-Control Studies

Background

Studies have shown that gene and environmental factors, such as BRCA1/2 mutations, ionized radiation, and chemical carcinogens, are related with breast cancer. X-ray repair cross-complementing group 3 (XRCC3) is involved in homologous repair of double DNA breaks. It was reported that Thr241Met single-nucleotide polymorphism (SNP) in XRCC3 is associated with increased risk of breast cancer. However, the finding remains controversial. The current meta-analysis aims to determine whether XRCC3 Thr241Met polymorphism is associated with increased risk of breast cancer.

Material/Methods

We performed a meta-analysis of association between XRCC3 T241M polymorphism and the risk of breast cancer. Crude odds ratios (ORs) together with 95% confidence intervals (CIs) were used to assess the strength of association in dominant, recessive, and homozygote models.

Results

We included 23 studies consisting of 13513 cases and 14100 controls in our study. For meta-analysis on the entire database, association of the SNP and breast cancer risk was observed in recessive (OR=1.10, 95% CI: 1.03–1.18, p=0.005) and homozygote (OR=1.09, 95% CI: 1.01–1.18, p=0.023) models. For the analysis on the Asian population subgroup, association of the SNP and breast cancer risk was also observed in recessive (OR=1.615, 95% CI: 1.17–2.228, p=0.004) and homozygote (OR=1.609, 95% CI: 1.154-2.241, p=0.005) models. For the evaluation of the patients without family history of breast cancer, association of the SNP and breast cancer risk was observed in dominant (OR=1.364, 95% CI: 1.096–1.698, p=0.005), recessive (OR=1.336, 95% CI: 0.999–1.788, p=0.051) and homozygote (OR=1.492, 95% CI: 1.085–2.051, p=0.014) models.

Conclusions

We can conclude that XRCC3 Thr241Met polymorphism might be associated with breast cancer risk, especially in Asian populations and in patients without family history of breast cancer.

Chemical exposures in the workplace and breast cancer risk: A prospective cohort study

We investigated the relationship between workplace chemical exposures and breast cancer risk among women enrolled in the Sister Study, a prospective cohort study of US and Puerto Rican women. A total of 47,640 participants reported work outside of the home. Workplace exposure to eleven agents (acids, dyes or inks, gasoline or other petroleum products, glues or adhesives, lubricating oils, metals, paints, pesticides, soldering materials, solvents and stains or varnishes) was characterized based on self-reports of frequency and duration of use. Approximately 14% of the study population reported exposure to only one agent and 11% reported working with two or more of the 11 agents in their lifetime. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for each agent, adjusting for established breast cancer risk factors. During follow-up, 1,966 cases of breast cancer were reported. Although there were no significant associations between ever use of the eleven agents evaluated and breast cancer risk, women with cumulative exposure to gasoline or petroleum products at or above the highest quartile cutoff had an elevated risk of total (HR: 2.3, 95%CI: 1.1-4.9) and invasive (HR: 2.5, 95%CI: 1.1-5.9) breast cancer compared with women in the lowest quartile group (ptrend  = 0.03). Workplace exposure to soldering materials was associated with an increased risk of premenopausal breast cancer (HR = 1.8, 95% CI = 1.1-3.0). Findings support the need for further studies to elucidate the role of occupational chemicals in breast cancer etiology.

Bacterial degradation of monocyclic aromatic amines

Aromatic amines are an important group of industrial chemicals, which are widely used for manufacturing of dyes, pesticides, drugs, pigments, and other industrial products. These compounds have been considered highly toxic to human beings due to their carcinogenic nature. Three groups of aromatic amines have been recognized: monocyclic, polycyclic, and heterocyclic aromatic amines. Bacterial degradation of several monocyclic aromatic amines has been studied in a variety of bacteria, which utilizes monocyclic aromatic amines as their sole source of carbon and energy. Several degradation pathways have been proposed and the related enzymes and genes have also been characterized. Many reviews have been reviewed toxicity of monocyclic aromatic amines; however, there is lack of review on biodegradation of monocyclic aromatic amines. The aim of this review is to summarize bacterial degradation of monocyclic aromatic amines. This review will increase our current understanding of biochemical and molecular basis of bacterial degradation of monocyclic aromatic amines.

Reactive oxygen species-mediated breast cell carcinogenesis enhanced by multiple carcinogens and intervened by dietary ergosterol and mimosine

Most breast cancers occur sporadically due to long-term exposure to low-dose carcinogens in the diet and the environment. Specifically, smoke, polluted air, and high-temperature cooked meats comprise multiple carcinogens, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), benzo[α]pyrene (B[α]P), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). We sought to determine if these carcinogens act together to induce breast cell carcinogenesis, and if so, whether noncytotoxic dietary agents could intervene. We demonstrated that coexposure to physiologically achievable doses of NNK, B[α]P, and PhIP (NBP) holistically enhanced initiation and progression of breast cell carcinogenesis. Reactive oxygen species (ROS) and activation of the ERK pathway were transiently induced by NBP in each exposure, and cross talk between reinforced ROS elevation and ERK activation played an essential role in increased DNA oxidation and damage. After cumulative exposures to NBP, this cross talk contributed to enhanced initiation of cellular carcinogenesis and led to enhanced acquisition of cancer-associated properties. Using NBP-induced transient changes, such as ROS elevation and ERK pathway activation, and cancer-associated properties as targeted endpoints, we revealed, for the first time, that two less-studied dietary compounds, ergosterol and mimosine, at physiologically achievable noncytotoxic levels, were highly effective in intervention of NBP-induced cellular carcinogenesis. Combined ergosterol and mimosine were more effective than individual agents in blocking NBP-induced transient endpoints, including ROS-mediated DNA oxidation, which accounted for their preventive ability to suppress progression of NBP-induced cellular carcinogenesis. Thus, dietary components, such as mushrooms containing ergosterol and legumes containing mimosine, should be considered for affordable prevention of sporadic breast cancer associated with long-term exposure to environmental and dietary carcinogens.

Chronic exposure to combined carcinogens enhances breast cell carcinogenesis with mesenchymal and stem-like cell properties

Breast cancer is the most common type of cancer affecting women in North America and Europe. More than 85% of breast cancers are sporadic and attributable to long-term exposure to small quantities of multiple carcinogens. To understand how multiple carcinogens act together to induce cellular carcinogenesis, we studied the activity of environmental carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), and dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using our breast cell carcinogenesis model. Our study revealed, for the first time, that combined NNK and B[a]P enhanced breast cell carcinogenesis chronically induced by PhIP in both non-cancerous and cancerous breast cells. Co-exposure was more potent than sequential exposure to combined NNK and B[a]P followed by PhIP in inducing carcinogenesis. Initiation of carcinogenesis was measured by transient endpoints induced in a single exposure, while progression of carcinogenesis was measured by acquisition of constitutive endpoints in cumulative exposures. Transient endpoints included DNA damage, Ras-Erk-Nox pathway activation, reactive oxygen species elevation, and increased cellular proliferation. Constitutive endpoints included various cancer-associated properties and signaling modulators, as well as enrichment of cancer stem-like cell population and activation of the epithelial-to-mesenchymal transition program. Using transient and constitutive endpoints as targets, we detected that a combination of the green tea catechins ECG and EGCG, at non-cytotoxic levels, was more effective than individual agents in intervention of cellular carcinogenesis induced by combined NNK, B[a]P, and PhIP. Thus, use of combined ECG and EGCG should be seriously considered for early intervention of breast cell carcinogenesis associated with long-term exposure to environmental and dietary carcinogens.

Cancer-promoting and Inhibiting Effects of Dietary Compounds: Role of the Aryl Hydrocarbon Receptor (AhR)

Polyaromatic hydrocarbons, heterocyclic aromatic amines and dioxin-like compounds are environmental carcinogens shown to initiate cancer in a number of tissue types including prostate and breast. These environmental carcinogens elicit their effects through interacting with the aryl hydrocarbon receptor (AhR), a ligand activated transcription factor. Naturally occurring compounds found in fruits and vegetables shown to have anti-carcinogenic effects also interact with the AhR. This review explores dietary and environmental exposure to chemical carcinogens and beneficial natural compounds whose effects are elicited by the AhR.

Induction of human breast cell carcinogenesis by triclocarban and intervention by curcumin

More than 85% of breast cancers are sporadic and attributable to long-term exposure to environmental carcinogens and co-carcinogens. To identify co-carcinogens with abilities to induce cellular pre-malignancy, we studied the activity of triclocarban (TCC), an antimicrobial agent commonly used in household and personal care products. Here, we demonstrated, for the first time, that chronic exposure to TCC at physiologically-achievable nanomolar concentrations resulted in progressive carcinogenesis of human breast cells from non-cancerous to pre-malignant. Pre-malignant carcinogenesis was measured by increasingly-acquired cancer-associated properties of reduced dependence on growth factors, anchorage-independent growth and increased cell proliferation, without acquisition of cellular tumorigenicity. Long-term TCC exposure also induced constitutive activation of the Erk-Nox pathway and increases of reactive oxygen species (ROS) in cells. A single TCC exposure induced transient induction of the Erk-Nox pathway, ROS elevation, increased cell proliferation, and DNA damage in not only non-cancerous breast cells but also breast cancer cells. Using these constitutively- and transiently-induced changes as endpoints, we revealed that non-cytotoxic curcumin was effective in intervention of TCC-induced cellular pre-malignancy. Our results lead us to suggest that the co-carcinogenic potential of TCC should be seriously considered in epidemiological studies to reveal the significance of TCC in the development of sporadic breast cancer. Using TCC-induced transient and constitutive endpoints as targets will likely help identify non-cytotoxic preventive agents, such as curcumin, effective in suppressing TCC-induced cellular pre-malignancy.

Genetic polymorphisms of CYP2E1, GST, and NAT2 enzymes are not associated with risk of breast cancer in a sample of Lebanese women

Changes in the activity of drug metabolizing enzymes (DMEs) are potentially associated with cancer risk. This relationship is attributed to their involvement in the bioactivation of multiple procarcinogens or the metabolism of multiple substrates including an array of xenobiotics and environmental carcinogens. 326 Lebanese women of whom 99 were cancer free (controls) and 227 were diagnosed with breast cancer (cases) were included. Blood for DNA was collected and medical charts were reviewed. Three genotyping methods were employed including: (1) restriction fragment length polymorphism (RFLP) for CYP2E1*5B, CYP2E1*6, NAT2*5 and NAT2*6; (2) gel electrophoresis for GSTM1 and GSTT1; and (3) real-time PCR for GSTP1 Ile/Val polymorphism. We analyzed the relationship between genetic susceptibilities in selected xenobiotic metabolizing genes and breast cancer risk. Allele frequencies were fairly similar to previously reported values from neighboring populations with relevant migration routes. There were no statistically significant differences in the distribution of variant carcinogen metabolizing genes between cases and controls even after adjusting for age at diagnosis, menopausal status, smoking, and alcohol intake. Despite its limitations, this is the first study that assesses the role of genetic polymorphisms in DMEs with breast cancer in a sample of Lebanese women. Further studies are needed to determine the genetic predisposition and gene-environment interactions of breast cancer in this population.

Mesenchymal and stem-like cell properties targeted in suppression of chronically-induced breast cell carcinogenesis

Stem-like cells and the epithelial-to-mesenchymal transition (EMT) program are postulated to play important roles in various stages of cancer development, but their roles in breast cell carcinogenesis and intervention remain to be clarified. We investigated stem-like cell- and EMT-associated properties and markers in breast epithelial cells chronically exposed to low-dose 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and benzo[a]pyrene in the presence and absence of the preventive agents green tea catechins and grape seed extract. Our results indicate that stem-like cell- and EMT-associated properties and markers should be seriously considered as new cancer-associated indicators for detecting breast cell carcinogenesis and as endpoints for intervention of carcinogenesis.

Association between manganese superoxide dismutase gene polymorphism and breast cancer risk: a meta-analysis of 17,842 subjects

The aim of this meta-analysis was to explore the association between the manganese superoxide dismutase (MnSOD) gene polymorphism and breast cancer risk, and to investigate the interaction of this gene polymorphism with known risk factors for breast cancer. Crude odds ratios (ORs) with 95% confidence intervals (CIs) for breast cancer risk associated with co-dominant models [valine/alanine (Val/Ala) vs. Val/Val, Ala/Ala vs. Val/Val], a dominant model (Val/Ala + Ala/Ala vs. Val/Val) and a recessive model (Ala/Ala vs. Val/Ala + Val/Val) were statistically estimated. This meta‑analysis included 8,102 breast cancer cases and 9,740 controls from 14 published case-control studies. The data revealed no significant association between the MnSOD polymorphism and the risk of developing breast cancer. However, upon subgroup analyses, the risk was significantly increased in premenopausal women with the dominant model of the MnSOD gene polymorphism (OR, 1.15; 95% CI, 1.01-1.31). Statistically significant increased risks were also identified in women with the MnSOD genotypes containing the Ala allele who had a tobacco smoking history (OR, 1.17; 95% CI, 1.02-1.34), a higher body mass index (OR, 1.26; 95% CI, 1.02-1.56) or who used oral contraceptives (OR, 1.98; 95% CI, 1.34-2.93). By contrast, there was no significant association between breast cancer risk and alcohol consumption and ethnicity. This meta‑analysis demonstrated no statistically significant association between the MnSOD gene polymorphism and breast cancer susceptibility, except in premenopausal women with certain unhealthy lifestyle habbits.

Intervention of human breast cell carcinogenesis chronically induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

More than 85% of breast cancers are sporadic and attributable to long-term exposure to environmental carcinogens, such as those in the diet, through a multistep disease process progressing from non-cancerous to premalignant and malignant stages. The chemical carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the most abundant heterocyclic amines found in high-temperature cooked meats and is recognized as a mammary carcinogen. However, the PhIP's mechanism of action in breast cell carcinogenesis is not clear. Here, we demonstrated, for the first time, that cumulative exposures to PhIP at physiologically achievable, pico to nanomolar concentrations effectively induced progressive carcinogenesis of human breast epithelial MCF10A cells from a non-cancerous stage to premalignant and malignant stages in a dose- and exposure-dependent manner. Progressive carcinogenesis was measured by increasingly- acquired cancer-associated properties of reduced dependence on growth factors, anchorage-independent growth, acinar-conformational disruption, proliferation, migration, invasion, tumorigenicity with metastasis and increased stem-like cell populations. These biological changes were accompanied by biochemical and molecular changes, including upregulated H-Ras gene expression, extracellular signal-regulated kinase (ERK) pathway activation, Nox-1 expression, reactive oxygen species (ROS) elevation, increased HIF-1α, Sp1, tumor necrosis factor-α, matrix metalloproteinase (MMP)-2, MMP-9, aldehyde dehydrogenase activity and reduced E-cadherin. The Ras-ERK-Nox-ROS pathway played an important role in not only initiation but also maintenance of cellular carcinogenesis induced by PhIP. Using biological, biochemical and molecular changes as targeted endpoints, we identified that the green tea catechin components epicatechin-3-gallate and epigallocatechin-3-gallate, at non-cytotoxic doses, were capable of suppressing PhIP-induced cellular carcinogenesis and tumorigenicity.

Expression and mutational status of RON in neoplastic lesions of the breast: analysis of MSP/RON signaling in ductal carcinoma in situ and invasive ductal carcinoma

Recepteur d'origine nantais (RON) is a receptor tyrosine kinase closely related to MET and involved in tumorigenesis. We investigated the roles of aberrations in RON and its ligand, macrophage-stimulating protein (MSP), in invasive ductal carcinoma (IDC, n = 81), ductal carcinoma in situ (DCIS, n = 26), and in benign lesions (n = 20) of mammary gland. Expression of RON and MSP was evaluated by immunohistochemistry and the mutational status of a region containing the proteolytic cleavage site in exon 1 and each exon of the kinase domain (exon 14-20) of RON was screened by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis. The proportion of cases positive for RON expression was significantly different between malignant [86% (92/107)] and benign [40% (8/20)] lesions. RON expression was positive in both IDC and DCIS [90% (73/81) and 73% (19/26), respectively], whereas MSP expression was present in 54% (44/81) of IDC and absent in DCIS. RON expression correlated significantly with the histological grade of DCIS. No mutations were detected in the examined regions of RON in breast cancer samples as confirmed by PCR-SSCP. The findings suggest the involvement of RON expression in the development of breast cancer, and that an autocrine/paracrine loop of RON seems to affect tumor invasiveness.

Green tea catechin intervention of reactive oxygen species-mediated ERK pathway activation and chronically induced breast cell carcinogenesis

Long-term exposure to low doses of environmental carcinogens contributes to sporadic human breast cancers. Epidemiologic and experimental studies indicate that green tea catechins (GTCs) may intervene with breast cancer development. We have been developing a chronically induced breast cell carcinogenesis model wherein we repeatedly expose non-cancerous, human breast epithelial MCF10A cells to bioachievable picomolar concentrations of environmental carcinogens, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), to progressively induce cellular acquisition of cancer-associated properties, as measurable end points. The model is then used as a target to identify non-cytotoxic preventive agents effective in suppression of cellular carcinogenesis. Here, we demonstrate, for the first time, a two-step strategy that initially used end points that were transiently induced by short-term exposure to NNK and B[a]P as targets to detect GTCs capable of blocking the acquisition of cancer-associated properties and subsequently used end points constantly induced by long-term exposure to carcinogens as targets to verify GTCs capable of suppressing carcinogenesis. We detected that short-term exposure to NNK and B[a]P resulted in elevation of reactive oxygen species (ROS), leading to Raf-independent extracellular signal-regulated kinase (ERK) pathway activation and subsequent induction of cell proliferation and DNA damage. These GTCs, at non-cytotoxic levels, were able to suppress chronically induced cellular carcinogenesis by blocking carcinogen-induced ROS elevation, ERK activation, cell proliferation and DNA damage in each exposure cycle. Our model may help accelerate the identification of preventive agents to intervene in carcinogenesis induced by long-term exposure to environmental carcinogens, thereby safely and effectively reducing the health risk of sporadic breast cancer.

Green tea catechin extract in intervention of chronic breast cell carcinogenesis induced by environmental carcinogens

Sporadic breast cancers are mainly attributable to long-term exposure to environmental factors, via a multi-year, multi-step, and multi-path process of tumorigenesis involving cumulative genetic and epigenetic alterations in the chronic carcinogenesis of breast cells from a non-cancerous stage to precancerous and cancerous stages. Epidemiologic and experimental studies have suggested that green tea components may be used as preventive agents for breast cancer control. In our research, we have developed a cellular model that mimics breast cell carcinogenesis chronically induced by cumulative exposures to low doses of environmental carcinogens. In this study, we used our chronic carcinogenesis model as a target system to investigate the activity of green tea catechin extract (GTC) at non-cytotoxic levels in intervention of cellular carcinogenesis induced by cumulative exposures to pico-molar 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P). We identified that GTC, at a non-cytotoxic, physiologically achievable concentration of 2.5 µg/mL, was effective in suppressing NNK- and B[a]P-induced cellular carcinogenesis, as measured by reduction of the acquired cancer-associated properties of reduced dependence on growth factors, anchorage-independent growth, increased cell mobility, and acinar-conformational disruption. We also detected that intervention of carcinogen-induced elevation of reactive oxygen species (ROS), increase of cell proliferation, activation of the ERK pathway, DNA damage, and changes in gene expression may account for the mechanisms of GTC's preventive activity. Thus, GTC may be used in dietary and chemoprevention of breast cell carcinogenesis associated with long-term exposure to low doses of environmental carcinogens.

Grape seed proanthocyanidin suppression of breast cell carcinogenesis induced by chronic exposure to combined 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and benzo[a]pyrene

Breast cancer is the most common type of cancer among women in northern America and northern Europe; dietary prevention is a cost-efficient strategy to reduce the risk of this disease. To identify dietary components for the prevention of human breast cancer associated with long-term exposure to environmental carcinogens, we studied the activity of grape seed proanthocyanidin extract (GSPE) in suppression of cellular carcinogenesis induced by repeated exposures to low doses of environmental carcinogens. We used combined carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), at picomolar concentrations, to repeatedly treat noncancerous, human breast epithelial MCF10A cells to induce cellular acquisition of cancer-related properties of reduced dependence on growth factors, anchorage-independent growth, and acinar-conformational disruption. Using these properties as biological target endpoints, we verified the ability of GSPE to suppress combined NNK- and B[a]P-induced precancerous cellular carcinogenesis and identified the minimal, noncytotoxic concentration of GSPE required for suppressing precancerous cellular carcinogenesis. We also identified that hydroxysteroid-11-beta-dehydrogenase 2 (HSD11B2) may play a role in NNK- and B[a]P-induced precancerous cellular carcinogenesis, and its expression may act as a molecular target endpoint in GSPE's suppression of precancerous cellular carcinogenesis. And, the ability of GSPE to reduce gene expression of cytochrome-P450 enzymes CYP1A1 and CYP1B1, which can bioactivate NNK and B[a]P, possibly contributes to the preventive mechanism for GSPE in suppression of precancerous cellular carcinogenesis. Our model system with biological and molecular target endpoints verified the value of GSPE for the prevention of human breast cell carcinogenesis induced by repeated exposures to low doses of multiple environmental carcinogens.

Meta-analysis of two ERCC2 (XPD) polymorphisms, Asp312Asn and Lys751Gln, in breast cancer

The excision repair cross-complementing group 2 gene (ERCC2) plays a key role in DNA repair. Several polymorphisms in the ERCC2 gene have been described, including the commonly occurring Lys751Gln and Asp312Asn polymorphisms. Studies investigating the association of these polymorphisms with breast cancer risk produced controversial results. To evaluate these associations presented in diverse populations, we have conducted a meta-analysis based on 40 studies from 33 publications in PubMed which included analyses of Lys751Gln (14,545 cases, 15,352 controls) and Asp312Asn polymorphisms (16,254 cases, 14,006 controls). Overall findings of both polymorphisms have implicated null effects (OR = 1.01-1.03) when the analyses were limited to the statistically powerful (≥80%) studies. Although modestly increased statistically significant breast cancer risk was detected in the underpowered studies (≤80%), removal of outliers resulted in null associations. Ethnic stratification showed non-significant and relatively null associations for both polymorphisms with breast cancer risk for the overall Caucasians as well as North American and the European sub-populations. Although statistically increased and decreased risks were observed for the homogenous populations of African-Americans (Lys751Gln, OR 1.25, 95% CI 1.03-1.53, P = 0.03) and Asians (Asp312Asn, ORs: 0.53-0.55, P values: 0.02-0.03), respectively, this may be the result of small sample size. Analyses of the homogeneous adduct studies, with relatively large sample size, exhibited increased risk for Lys751Gln (OR 1.20, 95% CI (1.02-1.41), P = 0.03) and Asp312Asn (OR 1.17 95% CI 1.02-1.34, P = 0.03) under the dominant genetic model. In conclusion, our results suggest null associations of both polymorphisms in the overall and the Caucasian subgroups, although some effects can be suggested for relatively smaller minority studies. Increased risk effect was more visible when the adduct studies are considered, suggesting the role of these polymorphisms in the presence of exposure to DNA damaging agents.

A critical assessment of geographic clusters of breast and lung cancer incidences among residents living near the Tittabawassee and Saginaw Rivers, Michigan, USA

OBJECTIVES

To assess previously determined geographic clusters of breast and lung cancer incidences among residents living near the Tittabawassee and Saginaw Rivers, Michigan, using a new set of environmental factors.

MATERIALS AND METHODS

Breast and lung cancer data were acquired from the Michigan Department of Community Health, along with point source pollution data from the U.S. Environmental Protection Agency. The datasets were used to determine whether there is a spatial association between disease risk and environmental contamination. GIS and spatial techniques were combined with statistical analysis to investigate local risk of breast and lung cancer.

RESULTS AND CONCLUSION

The study suggests that neighborhoods in close proximity to the river were associated with a high risk of breast cancer, while increased risk of lung cancer was detected among neighborhoods in close proximity to point source pollution and major highways. Statistically significant (P Collapse

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MESH Headings

• Adolescent
• Adult
• Age Distribution
• Breast Neoplasms/chemically induced
• Breast Neoplasms/epidemiology
• Cluster Analysis
• Discriminant Analysis
• Environmental Exposure/adverse effects
• Environmental Pollution/adverse effects
• Female
• Geographic Information Systems
• Humans
• Incidence
• Industry
• Lung Neoplasms/chemically induced
• Lung Neoplasms/epidemiology
• Male
• Michigan/epidemiology
• Middle Aged
• Odds Ratio
• Residence Characteristics
• Retrospective Studies
• Risk Factors
• Rivers
• Soil Pollutants/poisoning
• Water Pollutants, Chemical/poisoning
• Young Adult

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Affiliation(s)

Olga A. Guajardo Advanced Geospatial Analysis Lab, Department of Geography and Environmental Resources, Southern Illinois University, 1000 Faner Drive, MC 4514, Carbondale, IL 62901-4514, USA
Tonny J. Oyana Advanced Geospatial Analysis Lab, Department of Geography and Environmental Resources, Southern Illinois University, 1000 Faner Drive, MC 4514, Carbondale, IL 62901-4514, USA

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MDR1 (C3435T) polymorphism: relation to the risk of breast cancer and therapeutic outcome

P-glycoprotein (PGP), the product of the MDR1 gene, is a transmembrane active efflux pump for a variety of carcinogens and cytostatics. It has been suggested that MDR1 polymorphisms contribute to the variability in cancer risk and therapeutic outcome. We examined the relevance of C3435T polymorphism in relation to breast cancer susceptibility, clinical and pathological characteristics of breast carcinoma, the therapeutic response and hematologic toxicities after anthracycline-based chemotherapy. A significant association between allele frequencies and histological type, stage and histological grade was observed (P=0.024, 0.014, 0.006, respectively, chi(2)-test or Fisher's exact test). We also found significantly higher (P=0.019, chi(2)-test) T allele frequency in breast cancer patients (n=221) than in controls (n=113). A significantly enhanced therapeutic outcome after neoadjuvant therapy (n=38; P=0.021, Fisher's exact test) and longer time to progression after anthracycline-based chemotherapy (n=102; P=0.049, log-rank test) were observed in CC homozygotes. However, no significant association between hematologic toxicities and C3435T polymorphism was detectable.

Responses of PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) in MCF-7 cells are culture condition dependent

To compare the effects of the food toxin 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and estradiol in hormone-responsive MCF-7 cells, the cells were exposed to different concentrations of either PhIP or estradiol. The effect of various culture conditions (e.g. phenol red, FBS, vehicle (DMSO/EtOH) and seeding density) on responses was studied. Cells were continuously grown with steroid-containing or -deprived medium, or switched from steroid-containing to -deprived medium for the experiments to minimize the effect of background estrogenicity. Effects of PhIP and estradiol on cell viability and proliferation were determined by ATP analysis and Ki-67 immunocytochemistry. Expression of estrogen receptor alpha, cell stress markers (p53 and ERK) and estrogen responsive proteins (c-myc and ERK) were immunoblotted. All concentrations of estradiol induced cell proliferation, viability and changes in protein expression, typical for estrogenic responses. PhIP, however, increased viability only at low concentrations and depending on culture conditions. No changes in protein expressions by PhIP were noted, not even when switching cells from steroid-containing to -deprived medium which down-regulated the expression of proteins at basal level. Vehicle affected significantly viability, especially after exposure to PhIP, but not protein expression while medium changes affected both. In conclusion, the effects of PhIP and estradiol in MCF-7 cells are dependent on culture conditions. The detected PhIP-induced changes are weaker compared to those induced by estradiol.

The FAS ligand promoter polymorphism, rs763110 (-844C>T), contributes to cancer susceptibility: evidence from 19 case-control studies

The potentially functional polymorphism, rs763110 (-844C>T), in the promoter region of the FAS ligand (FASL) gene, has been implicated in cancer risk, but individually published studies show inconclusive results. To derive a more precise estimation of the association between the FASL rs763110 and risk of cancer, we performed a meta-analysis of 19 published studies that included 11,105 cancer cases and 11,372 controls. We used odds ratios (ORs) and 95% confidence intervals (CIs) to assess the strength of the associations. Overall, the rs763110 CT and TT variant genotypes were associated with a significantly reduced cancer risk of all cancer types in different genetic models (homozygote comparison: OR=0.80, 95% CI: 0.68-0.95, P(heterogeneity)=0.001; heterozygote comparison: OR=0.82, 95% CI: 0.72-0.95, P(heterogeneity)<0.001; dominant model comparison: OR=0.82, 95% CI: 0.71-0.94, P(heterogeneity)<0.001; and recessive model comparison: OR=0.88, 95% CI: 0.81-0.96, P(heterogeneity)=0.074). In the stratified analyses, the risk remained for studies of the smoking-related cancers and Asian populations, or population-based studies in all the genetic models. Although some modest bias could not be eliminated, this meta-analysis suggests that the FASL rs763110 T allele has a possible protective effect on cancer risk.

DNA repair gene XPD polymorphisms and cancer risk: a meta-analysis based on 56 case-control studies

Genetic variations in the XPD gene may increase cancer susceptibility by affecting the capacity for DNA repair. Several studies have investigated this possibility; however, the conclusions remain controversial. Therefore, we did a systematic review and executed a meta-analysis to explore the association. From 56 studies, a total of 61 comparisons included 25,932 cases and 27,733 controls concerning the Lys 751Gln polymorphism; 35 comparisons included 16,781 cases and 18,879 controls in the case of Asp 312 Asn were reviewed. In this analysis, small associations of the XPD Lys 751 Gln polymorphism with cancer risk for esophageal cancer [for Lys/Gln versus Lys/Lys: odds ratio (OR), 1.34; 95% confidence interval (95% CI), 1.10-1.64; for Gln/Gln versus Lys/Lys: OR, 1.61; 95% CI, 1.16-2.25] and acute lymphoblastic leukemia (for Gln/Gln versus Lys/Lys: OR, 1.83; 95% CI, 1.21-2.75) are revealed. Overall, individuals with the Gln/Gln genotype have a small cancer risk compared with Lys/Lys genotype for the reviewed cancer in total (OR, 1.10; 95% CI, 1.03-1.16). Subtle but significant cancer risk was observed for the XPD Asp 312 Asn polymorphism in bladder cancer (for Asp/Asn versus Asp/Asp: OR, 1.24; 95% CI, 1.06-1.46). No significant associations were found for other cancers separately and all the reviewed cancer in total assessed for the Asp 312 Asn polymorphism. Our study suggests that XPD is a candidate gene for cancer susceptibility regardless of environmental factors.

Precancerous carcinogenesis of human breast epithelial cells by chronic exposure to benzo[a]pyrene

To understand carcinogenesis of human breast epithelial cells induced by chronic exposure to environmental pollutants, we studied biological and molecular changes in progression of cellular carcinogenesis induced by accumulated exposures to the potent environmental carcinogen benzo[a]pyrene (B[a]P). Increasing exposures of human breast epithelial MCF10A cells to B[a]P at picomolar concentrations resulted in cellular transformation from a noncancerous stage to precancerous substages, in which cells acquired the cancerous abilities of a reduced dependence on growth factors, anchorage-independent growth, and disruption in acini formation on reconstituted basement membranes. Using cDNA microarrays, we detected seven upregulated genes related to human cancers in B[a]P-transformed MCF10A cells. Using this model, we verified that green tea catechin significantly (P < 0.05) suppressed B[a]P-induced carcinogenesis. Our studies indicate that this cellular model may serve as a cost-efficient, in vitro system, mimicking the chronic carcinogenesis of breast cells that likely occurs in early stages of carcinogenesis in vivo, to identify agents that inhibit cellular carcinogenesis.

Importance of TP53 codon 72 and intron 3 duplication 16bp polymorphisms in prediction of susceptibility on breast cancer

Background

TP53 is one of major tumour suppressor genes being essential in preservation of genome integrity. Two very common polymorphisms have been demonstrated to contribute to cancer susceptibility and tumour behaviour. The purpose of this study was to evaluate the role of Arg72Pro and PIN3 Ins16bp polymorphisms in TP53 gene as genetic susceptibility and predictive markers to breast cancer.

Methods

We analysed DNA samples from 264 breast cancer patients and 440 controls, for TP53 Arg72Pro and PIN3 Ins16bp polymorphisms using PCR-RFLP.

Results

We observed that women with A2A2 genotype have increased risk for developing breast cancer, either in women with or without familial history (FH) of the disease (OR = 4.40, 95% CI 1.60–12.0; p = 0.004; OR = 3.88, 95% CI 1.18–12.8; p = 0.026, respectively). In haplotype analysis, statistically significant differences were found between TP53 Arg-A2 haplotype frequencies and familial breast cancer cases and the respective control group (OR = 2.10, 95% CI 1.08–4.06; p = 0.028). Furthermore, both TP53 polymorphisms are associated with higher incidence of lymph node metastases.

Conclusion

Our findings suggest TP53 PIN3 Ins16bp polymorphism as a real risk modifier in breast cancer disease, either in sporadic and familial breast cancer. Furthermore, both TP53 polymorphisms are associated with higher incidence of lymph node metastases.

Human breast biomonitoring and environmental chemicals: use of breast tissues and fluids in breast cancer etiologic research

Extensive research indicates that the etiology of breast cancer is complex and multifactorial and may include environmental risk factors. Breast cancer etiology and exposure to xenobiotic compounds, diet, electromagnetic fields, and lifestyle have been the subject of numerous scientific inquiries, but research has yielded inconsistent results. Biomonitoring has been used to explore associations between breast cancer and levels of environmental chemicals in the breast. Research using breast tissues and fluids to cast light on the etiology of breast cancer is, for the most part, predicated on the assumption that the tissue or fluid samples either contain measurable traces of the environmental agent(s) associated with the cancer or that they retain biological changes that are biomarkers of such exposure or precursors of carcinogenic effect. In this paper, we review breast cancer etiology research utilizing breast biomonitoring. We first provide a brief synopsis of the current state of understanding of associations between exposure to environmental chemicals and breast cancer etiology. We then describe the published breast cancer research on tissues and fluids, which have been used for biomonitoring, specifically human milk and its components, malignant and benign breast tissue, nipple aspirate fluid (NAF) and breast cyst fluid. We conclude with a discussion on recommendations for biomonitoring of breast tissues and fluids in future breast cancer etiology research. Both human milk and NAF fluids, and the cells contained therein, hold promise for future biomonitoring research into breast cancer etiology, but must be conducted with carefully delineated hypotheses and a scientifically supportable epidemiological approach.

Precancerous model of human breast epithelial cells induced by NNK for prevention

Epidemiological investigations have suggested that exposure to tobacco and environmental carcinogens increase the risk of developing human breast cancer. In light of the chronic exposure of human breast tissues to tobacco and environmental carcinogens, we have taken an approach of analyzing cellular changes of immortalized non-cancerous human breast epithelial MCF10A cells during the acquisition of cancerous properties induced by repeated exposure to the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) at a low concentration of 100 pM. We found that accumulated exposures of MCF10A cells to NNK result in progressive development of cellular carcinogenesis from a stage of immortalization to precancerous sub-stages of acquiring a reduced dependence on growth factors and acquiring anchorage-independent growth. Using Matrigel for MCF10A cells to form size-restricted acini, we detected that exposures to NNK resulted in altered acinar conformation. Analysis of gene expression profiles by cDNA microarrays revealed up- and down-regulated genes associated with NNK-induced carcinogenesis. Using this cellular carcinogenesis model as a target system to identify anticancer agents, we detected that grape seed proanthocyanadin extract significantly suppressed NNK-induced carcinogenesis of MCF10A cells. Our studies provide a carcinogenesis-cellular model mimicking the accumulative exposure to carcinogens in the progression of human breast epithelial cells to increasingly acquire cancerous properties, as likely occurs in the development of precancerous human breast cells. Our cellular model also serves as a cost-efficient, in vitro system to identify preventive agents that inhibit human breast cell carcinogenesis induced by chronic exposures to carcinogens.

Breast cancer screening for Korean women must consider traditional risks as well as two genetic risk factors: genetic polymorphisms and inheritable gene mutations

Asian women worldwide have increasing rates of breast cancer due to acculturation which may be altering, gene to gene and/or, genetic and environmental interactions at the cellular level. The purpose of this integrative review is to alert nurses and physicians to rising rates of breast cancer among Korean women and to a need for breast health screening programs in the United States that are more culturally responsive and attentive to the effects of acculturation and genetic risk factors. A comprehensive review of the English and Korean literature pertaining to rising incidence of breast cancer among Korean women in their homeland and in the United States is retraced since 1983. Korean women in Korea and in the United States face similar barriers to cancer screening services. Korean women need knowledge about the effect of acculturation on breast cancer risk and patterns of familial inheritance of breast cancer. Screening is especially important among younger women (younger than age 35), those with a strong family history, and women in community settings where acculturation has its greatest impact. Nurse clinicians and researchers who aim to improve breast cancer screening among minority women must pay closer attention to these risk factors and design culturally competent services and evaluation research. In the United States and Korea, Korean nurses are needed to specialize in breast cancer screening as well as cancer genetic risk assessment and genetic counseling.

DNA repair polymorphisms might contribute differentially on familial and sporadic breast cancer susceptibility: a study on a Portuguese population

The purpose of this study was to evaluate the role of polymorphisms in DNA repair genes as genetic indicators of susceptibility to familial and sporadic breast cancer. We analysed DNA samples from 285 breast cancer patients and 442 control subjects, for XRCC1 Arg399Gln, XPD Lys751Gln, RAD51 G135C and XRCC3 Thr241Met polymorphisms using PCR-RFLP. We observed that women carriers of XRCC1 399Gln genotypes and without family history of breast cancer have a protective effect concerning this disease (OR = 0.54 95% CI 0.35-0.84; p = 0.006). Furthermore, we found that carriers of XRCC3 241Met genotypes without FH have an increased susceptibility of breast cancer (OR = 2.21 95% CI 1.42-3.44; p < 0.001). Additionally, we verified an increased risk of breast cancer in women with FH and carrying RAD51 135C genotypes (OR = 2.17 95% CI 1.19-3.98; p = 0.012). Our results suggest XRCC1 Arg399Gln and XRCC3 Thr241Met DNA repair polymorphisms as important biomarkers to sporadic breast cancer susceptibility, as well as, RAD51 G135C polymorphism as a real risk modifier in familial breast cancer cases.

Occupation and Breast Cancer: A Canadian Case-Control Study

A local collaborative process was launched in Windsor, Ontario, Canada to explore the role of occupation as a risk factor for cancer. An initial hypothesis-generating study found an increased risk for breast cancer among women aged 55 years or younger who had ever worked in farming. On the basis of this result, a 2-year case-control study was undertaken to evaluate the lifetime occupational histories of women with breast cancer. The results indicate that women with breast cancer were nearly three times more likely to have worked in agriculture when compared to the controls (OR = 2.80 [95% CI, 1.6-4.8]). The risk for those who worked in agriculture and subsequently worked in automotive-related manufacturing was further elevated (OR = 4.0 [95% CI, 1.7-9.9]). The risk for those employed in agriculture and subsequently employed in health care was also elevated (OR = 2.3 [95% CI, 1.1-4.6]). Farming tended to be among the earlier jobs worked, often during adolescence. While this article has limitations including the small sample size and the lack of information regarding specific exposures, it does provide evidence of a possible association between farming and breast cancer. The findings indicate the need for further study to determine which aspects of farming may be of biological importance and to better understand the significance of timing of exposure in terms of cancer risk.

Angiotensin-converting enzyme gene insertion/deletion polymorphism and breast cancer risk

BACKGROUND

The renin-angiotensin system plays an important role in homeostasis and lately, its main effector, angiotensin II, has been attributed with angiogenic and growth factor actions in the breast tissue. Previous studies have shown that the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene accounts for the variability of ACE plasma concentrations. The use of ACE inhibitors and the ACE I/D polymorphism may be linked to breast cancer risk. In this study, we evaluate the relationship of the ACE I/D polymorphism with breast cancer risk in Caucasian postmenopausal women.

METHODS

The ACE I/D polymorphism was genotyped in 4,117 women participants in the Rotterdam Study. Baseline information was obtained through a questionnaire. We conducted a logistic regression and survival analysis to assess the risk of breast cancer by the ACE genotype.

RESULTS

The DD carriers showed a significantly increased risk of developing breast cancer when compared with the II carriers (odds ratio, 1.86; 95% confidence interval, 1.06-3.27; P = 0.03). This association remained after adjusting for other risk factors, including body mass index, age at menarche, age at menopause, hormone replacement therapy, and hypertension. Our survival analysis showed that the cancer-free survival was significantly reduced in DD compared with II carriers (hazard ratio, 1.80; 95% confidence interval, 1.07-3.01; P = 0.03).

CONCLUSIONS

Our results suggest that the ACE I/D polymorphism plays an important role in breast cancer risk and disease-free survival in Caucasian postmenopausal women.

Assessing spatio-temporal variability of risk surfaces using residential history data in a case control study of breast cancer

BACKGROUND: Most analyses of spatial clustering of disease have been based on either residence at the time of diagnosis or current residence. An underlying assumption in these analyses is that residence can be used as a proxy for environmental exposure. However, exposures earlier in life and not just those in the most recent period may be of significance. In breast cancer, there is accumulating evidence that early life exposures may contribute to risk. We explored spatio-temporal patterns of risk surfaces using data on lifetime residential history in a case control study of breast cancer, and identified elevated areas of risk and areas potentially having more exposure opportunities, defined as risk surfaces in this study. This approach may be more relevant in understanding the environmental etiology of breast cancer, since lifetime cumulative exposures or exposures at critical times may be more strongly associated with risk for breast cancer than exposures from the recent period. RESULTS: A GIS-based exploratory spatial analysis was applied, and spatio-temporal variability of those risk surfaces was evaluated using the standardized difference in density surfaces between cases and controls. The significance of the resulting risk surfaces was tested and reported as p-values. These surfaces were compared for premenopausal and postmenopausal women, and were obtained for each decade, from the 1940s to 1990s. We found strong evidence of clustering of lifetime residence for premenopausal women (for cases relative to controls), and a less strong suggestion of such clustering for postmenopausal women, and identified a substantial degree of temporal variability of the risk surfaces. CONCLUSION: We were able to pinpoint geographic areas with higher risk through exploratory spatial analyses, and to assess temporal variability of the risk surfaces, thus providing a working hypothesis on breast cancer and environmental exposures. Geographic areas with higher case densities need further epidemiologic investigation for potential relationships between lifetime environmental exposures and breast cancer risk. Examination of lifetime residential history provided additional information on geographic areas associated with higher risk; limiting exploration of chronic disease clustering to current residence may neglect important relationships between location and disease.

Genomic instability in histologically normal breast tissues: implications for carcinogenesis

Breast cancer is an important contributor to morbidity and mortality in society, but factors that affect the cause of the disease are poorly defined. Genomic instability drives tumorigenic processes in invasive carcinomas and premalignant breast lesions, and might promote the accumulation of genetic alterations in apparently normal tissues before histological abnormalities are detectable. Evidence suggests that genomic changes in breast parenchyma affect the behaviour of epithelial cells, and ultimately might affect tumour growth and progression. Inherent instability in genes that maintain genomic integrity, as well as exogenous chemicals and environmental pollutants, have been implicated in breast-cancer development. Although molecular mechanisms of tumorigenesis are unclear at present, carcinogenic agents could contribute to fields of genomic instability localised to specific areas of the breast. Understanding the functional importance of genomic instability in early carcinogenesis has important implications for improvement of diagnostic and treatment strategies.

The epidemiology of pesticide exposure and cancer: A review

Cancer is a multifactorial disease with contributions from genetic, environmental, and lifestyle factors. Pesticide exposure is recognized as an important environmental risk factor associated with cancer development. The epidemiology of pesticide exposure and cancer in humans has been studied globally in various settings. Insecticides, herbicides, and fungicides are associated with hemopoetic cancers, and cancers of the prostate, pancreas, liver, and other body systems. The involvement of pesticides in breast cancer has not yet been determined. In developing countries, sufficient epidemiologic research and evidence is lacking to link pesticide exposure with cancer development. Agricultural and industrial workers are high-risk groups for developing cancer following pesticide exposure. Children of farm workers can be exposed to pesticides through their parents. Maternal exposure to pesticides can pose a health risk to the fetus and the newborn. The organophosphates are most the commonly used compounds, but the organochlorines are still permitted for limited use in developing countries. Pesticide exposure, independently or in synergism with modifiable risk factors, is associated with several types of cancer.

Occupational exposures to extremely low frequency magnetic fields and postmenopausal breast cancer

BACKGROUND

The association between occupational exposure to extremely low frequency magnetic fields (ELF-MF) and risk of postmenopausal breast cancer was assessed in a case-control study.

METHODS

Breast cancer cases were compared to cancer controls. Interviewers elicited information on risk factors and on lifetime work history. Industrial hygienists assigned to each job average duration of exposure to ELF-MF at four levels of intensities ("none," <0.2 microT; "low," 0.2-<0.5microT; "medium," 0.5-<1microT; "high," > or =1-10microT). Unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

A total number of 608 cases and 667 controls participated. Adjusting for accepted breast cancer risk factors, we found an OR of 1.13 for lifetime occupational exposure to ELF-MF at medium or high intensities. Risks were larger for exposures before age 35 (OR = 1.40), and statistically significant for exposures before 35 among cases with progesterone receptor positive tumors (OR = 1.56, 95% CI=1.02-2.39).

CONCLUSIONS

There appears to be a small increased risk for breast cancer among postmenopausal women exposed occupationally to ELF-MF.

Primary prevention protects public health

It is widely accepted that epidemiological data provide the only reliable evidence of a carcinogenic effect in humans, but epidemiology is unable to provide early warning of a cancer risk. The experimental approach to carcinogenicity can ascertain and predict potential cancer risks to humans in time for primary prevention to be successful. Unfortunately, only in rare instances were experimental data considered sufficiently convincing per se to stimulate the adoption of preventive measures. The experimental testing of environmental agents is the second line of defense against potential human carcinogens. The first line is the testing of synthesized agents, be these pesticides, medical drugs, or industrial chemical/physical agents, at the time of their development. We do not know, however, how many substances have been prevented from entering the environment because most tests are carried out by commercial or private laboratories and results are rarely released. A better understanding of the mechanisms underlying the sequence of events of the carcinogenesis process will eventually lead to a more accurate characterization and quantification of risks. However, the ways that mechanistic data have been used lately for evaluating evidence of carcinogenicity have not necessarily meant that the evaluations were more closely oriented toward public health. A tendency has surfaced to dismiss the relevance of long-term carcinogenicity studies. In the absence of absolute certainty, rarely if ever reached in biology, it is essential to adopt an attitude of responsible caution, in line with the principles of primary prevention, the only one that may prevent unlimited experimentation on the entire human species.