Association between cadmium and breast cancer risk according to estrogen receptor and human epidermal growth factor receptor 2: epidemiological evidence

Non-occupational exposure to cadmium and breast cancer: A comprehensive and critical review

Breast cancer (BC) is a multifactorial disease with unresolved etiology. Environmental pollutants, primarily trace metals, play a pivotal role in the pathophysiological cascade of malignant tumors, including BC. In this up-to-date review, we comprehensively and critically examined the relationship between cadmium (Cd) and BC. For this purpose, peer-reviewed studies from relevant databases (PubMed, SCOPUS, and Cochrane Library) over the last 40 years were retrieved and analyzed. We found that in vitro and in vivo studies strongly support the view that Cd has harmful effects on breast health. According to the human studies, we found that Cd could be responsible for the development and progression of malignant breast tumors due to markedly higher levels in clinical matrices of cases (whole blood, urine, breast tissue, keratin materials) than in clinical matrices of controls. Cadmium does not appear to affect BC density. In contrast, Cd has been found to have a detrimental effect on sex hormones, disrupting the balance of estrogen and androgen. We found that studies looking at dietary Cd intake and BC risk generally (without measuring urine or blood Cd) do not support the association between dietary Cd intake and BC risk. In notable contrast, studies looking at dietary Cd intake and BC risk by measuring Cd in urine or blood generally support this association. The effect of airborne Cd on BC risk was weak, but in favor of specific histological forms, primarily ER-/PR- invasive tubular breast carcinomas. Regardless of the intake route of Cd into the body, it can be concluded that Cd has a harmful effect on breast health. However, well-designed longitudinal, mechanistic, meta-analytic, and other studies are urgently needed to confirm the exact role of environmental Cd in breast carcinogenesis.

Heavy-metal associated breast cancer and colorectal cancer hot spots and their demographic and socioeconomic characteristics

PURPOSE

Cancer registries offer an avenue to identify cancer clusters across large populations and efficiently examine potential environmental harms affecting cancer. The role of known metal carcinogens (i.e., cadmium, arsenic, nickel, chromium(VI)) in breast and colorectal carcinogenesis is largely unknown. Historically marginalized communities are disproportionately exposed to metals, which could explain cancer disparities. We examined area-based metal exposures and odds of residing in breast and colorectal cancer hotspots utilizing state tumor registry data and described the characteristics of those living in heavy metal-associated cancer hotspots.

METHODS

Breast and colorectal cancer hotspots were mapped across Kentucky, and area-based ambient metal exposure to cadmium, arsenic, nickel, and chromium(VI) were extracted from the 2014 National Air Toxics Assessment for Kentucky census tracts. Among colorectal cancer (n = 56,598) and female breast cancer (n = 77,637) diagnoses in Kentucky, we used logistic regression models to estimate Odds Ratios (ORs) and 95% Confidence Intervals to examine the association between ambient metal concentrations and odds of residing in cancer hotspots, independent of individual-level and neighborhood risk factors.

RESULTS

Higher ambient metal exposures were associated with higher odds of residing in breast and colorectal cancer hotspots. Populations in breast and colorectal cancer hotspots were disproportionately Black and had markers of lower socioeconomic status. Furthermore, adjusting for age, race, tobacco and neighborhood factors did not significantly change cancer hotspot ORs for ambient metal exposures analyzed.

CONCLUSION

Ambient metal exposures contribute to higher cancer rates in certain geographic areas that are largely composed of marginalized populations. Individual-level assessments of metal exposures and cancer disparities are needed.

Domestic dogs as environmental sentinel in comparative toxicologic pathology: Assessment of metals and rare earth elements concentrations in healthy and neoplastic mammary glands

Quantification of trace element concentrations in human and animal tissues has acquired great importance in the last few years, considering the pivotal role of these elements in several physiological and pathological processes. Variations in their concentrations appear to have a role in the development and advancement of diseases in both humans and animals, for example, cancer. The purpose of this study was to investigate the concentration of rare earth elements and metals in healthy and neoplastic Formalin-Fixed Paraffin-Embedded (FFPE) mammary gland tissue of dogs. All samples were processed to have a quantitative determination of inorganic elements including metals of known toxicological interest such as Pb, Cd, Tl, As, Hg, the trace elements Mn, Fe, Co, Cu, Zn, Se, and other elements including Cr, V, Mo, Ni, Sb, W, Sn. Moreover, rare earth elements (REEs) (Sc, Y, Lu, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) were also investigated. Cu and Mo concentrations in mammary cancerous tissue were greater than those in normal mammary glands (p < 0.05). In non-neoplastic tissue increased concentrations of Cd, Co, Ni, Tl, and V were also reported (p < 0.05). The mammary tissue of healthy individuals had greater concentrations of REEs than the neoplastic mammary glands (p < 0.05). The results of our study confirmed differences in mammary inorganic element concentrations between healthy and neoplastic groups, highlighting the potential relevance of these fluctuations in toxicologic pathology.

Application of human biomonitoring data to support policy development, raise awareness and environmental public health protection among countries within the HBM4EU project

Most countries have acknowledged the importance of assessing and quantifying their population's internal exposure from chemicals in air, water, soil, food and other consumer products due to the potential health and economic impact. Human biomonitoring (HBM) is a valuable tool which can be used to quantify such exposures and effects. Results from HBM studies can also contribute to improving public health by providing evidence of individuals' internal chemical exposure as well as data to understand the burden of disease and associated costs thereby stimulating the development and implementation of evidence-based policy. To have a holistic view on HBM data utilisation, a multi-case research approach was used to explore the use of HBM data to support national chemical regulations, protect public health and raise awareness among countries participating in the HBM4EU project. The Human Biomonitoring for Europe (HBM4EU) Initiative (https://www.hbm4eu.eu/) is a collaborative effort involving 30 countries, the European Environment Agency (EEA) and the European Commission (contracting authority) to harmonise procedures across Europe and advance research into the understanding of the health impacts of environmental chemical exposure. One of the aims of the project was to use HBM data to support evidence based chemical policy and make this information timely and directly available for policy makers and all partners. The main data source for this article was the narratives collected from 27 countries within the HBM4EU project. The countries (self-selection) were grouped into 3 categories in terms of HBM data usage either for public awareness, policy support or for the establishment HBM programme. Narratives were analysed/summarised using guidelines and templates that focused on ministries involved in or advocating for HBM; steps required to engage policy makers; barriers, drivers and opportunities in developing a HBM programme. The narratives reported the use of HBM data either for raising awareness or addressing environmental/public health issues and policy development. The ministries of Health and Environment were reported to be the most prominent entities advocating for HBM, the involvement of several authorities/institutions in the national hubs was also cited to create an avenue to interact, discuss and gain the attention of policy makers. Participating in European projects and the general population interest in HBM studies were seen as drivers and opportunities in developing HBM programmes. A key barrier that was cited by countries for establishing and sustaining national HBM programmes was funding which is mainly due to the high costs associated with the collection and chemical analysis of human samples. Although challenges and barriers still exist, most countries within Europe were already conversant with the benefits and opportunities of HBM. This article offers important insights into factors associated with the utilisation of HBM data for policy support and public awareness.

Urinary Concentrations of Endocrine-Disrupting Metals and Prevalent Breast Cancer in US Women

The toxic metals cadmium, lead, and mercury are endocrine-disrupting agents that could produce estrogenic effects involving breast carcinogenesis. In this study, we further explored the relationship between exposure to these metals and prevalent breast cancer among female participants, aged 20 years or older, in the 2007-2016 National Health and Nutrition Examination Survey (NHANES). Exposure was determined by measuring urinary concentrations of metals using inductively coupled plasma mass spectrometry. Urine creatinine-corrected concentrations of metals were calculated for each study participant. Multivariate logistic regression models were constructed to examine the association between urinary metals and prevalent breast cancer, adjusting for potential confounders. Of the 3352 study participants, 106 had been diagnosed with breast cancer (weighted prevalence, 3.13%). The results show that women with breast cancer had significantly higher urinary concentrations of lead and cadmium (both p < 0.0001) than those without breast cancer. After adjusting for all the covariates included in the study, however, only urinary lead was shown to be significantly associated with increased prevalence of breast cancer, with an odds ratio of 2.95 (95% CI: 1.13, 7.70) in the highest quartile of urinary lead concentrations (≥ 0.71 µg/g creatinine) as compared with the lowest quartile. No statistically significant associations were observed between urine cadmium or mercury levels and breast cancer. This study demonstrates a potential association between lead exposure and prevalent breast cancer among US women. Prospective and mechanistic studies are warranted to further investigate this interaction and explore the role of lead in breast carcinogenesis.

Receptor-Mediated Targeting in Breast Cancer through Solid Lipid Nanoparticles and Its Mechanism

Nanoparticles have gained prominence in many areas and domains worldwide, such as metallic NP, carbon dots, quantum dots, polymeric NP, nano-suspension, nanocrystals, solid lipid nanoparticles (SLN), etc. and have been applied in the field of medicine as nanomedicine with promising results. Rise in cancer mortality rate has been an issue for a long time with female breast cancer as one of the most detected cancers. No permanent treatment has been developed till date could combat breast cancer with minimum side effects that are not long-lasting as there is no proper technique through which the anticancer drugs can recognize benign or malignant or normal cells that causes systematic toxicity. Advancement in technology has led to the discovery of many biological pathways and mechanisms. Tumor cells or cancer cells overexpress some high-affinity receptors that can be targeted to deliver the anticancer drugs at specific site using these pathways and mechanisms. Solid lipid nanoparticles (SLN) are among some of the excellent drug delivery systems, especially stealth SLN (sSLN). SLN, when conjugated with a ligand (called as sSLN), has affinity and specificity towards a specific receptor, and can deliver the drug in breast cancer cells overexpressing the receptors. Using this technique, various investigations have reported better anti-breast cancer activity than simple SLN (non-conjugated to ligand or no receptor targeting). This review includes the investigations and data on receptor-mediated targeting in breast cancer from 2010 to 2021 by searching different databases. Overall, information on SLN in different cancers is reviewed. In vivo investigations, pharmacokinetics, biodistribution, and stability are discussed to describe the efficacy of sSLN. Investigations included in this review demonstrate that sSLN delivers the drug by overcoming the biological barriers and shows enhanced and better activity than non-conjugated SLN which also verifies that a lesser concentration of drug can show anti-breast cancer activity. The efficacy of medicines could be increased with lower cancer deaths through stealth-SLN. Due to the low cost of synthesis, biocompatibility and easy to formulate, more study is needed in vitro and in vivo so that this novel technique could be utilized in the treatment of human breast cancer.

Ambient air emissions of endocrine-disrupting metals and the incidence of hormone receptor- and HER2-dependent female breast cancer in USA

Limited evidence exists on the relationship between exposure to endocrine-disrupting metals in ambient air and hormone receptor- and HER2-dependent breast cancer. This study investigates the association between ambient air emissions of endocrine-disrupting metals and the incidence of female breast cancer of different receptor status. County-level data from the US national datasets were analyzed for the association between emissions of various metals including arsenic, cadmium, chromium VI, lead, and mercury, and the annual age-adjusted incidence of hormone receptor-dependent breast cancer for 1990-2016 and HER2-dependent breast cancer for 2010-2016 using adjusted linear regression models. Lead emissions showed the strongest association among the metals examined with the incidence of different receptor status breast cancers, including ER-positive, ER-negative, PR-negative, HER2-negative, and Triple-negative breast cancers, with the adjusted β ranging from 917.26 for ER-negative to 3182.37 for HER2-negative breast cancer. Arsenic and mercury showed significant associations with the incidence of ER-positive, ER-negative, PR-positive, and PR-negative breast cancers. However, cadmium emissions were only significantly associated with ER-negative breast cancer. Moreover, chromium was not associated with any subtypes of breast cancer. Among all of the metals, only lead and mercury emissions showed significant associations with HER2-negative and Triple-negative breast cancer incidence. The results from this study suggest that increased exposure to endocrine-disrupting metals, especially lead, in ambient air could be associated with an increased incidence of female breast cancers with various receptor status in the US. Prospective studies are warranted to further explore this relationship.

Exposure to airborne cadmium and breast cancer stage, grade and histology at diagnosis: findings from the E3N cohort study

Molecular studies suggest that cadmium due to its estrogenic properties, might play a role in breast cancer (BC) progression. However epidemiological evidence is limited. This study explored the association between long-term exposure to airborne cadmium and risk of BC by stage, grade of differentiation, and histological types at diagnosis. A nested case-control study of 4401 cases and 4401 matched controls was conducted within the French E3N cohort. A Geographic Information System (GIS)-based metric demonstrated to reliably characterize long-term environmental exposures was employed to evaluate airborne exposure to cadmium. Multivariable adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression models. There was no relationship between cadmium exposure and stage of BC. Also, no association between cadmium exposure and grade of differentiation of BC was observed. However, further analyses by histological type suggested a positive association between cadmium and risk of invasive tubular carcinoma (ITC) BC [OR_{Q5 vs Q1} = 3.4 (95% CI 1.1-10.7)]. The restricted cubic spline assessment suggested a dose-response relationship between cadmium and ITC BC subtype. Our results do not support the hypothesis that airborne cadmium exposure may play a role in advanced BC risk, but suggest that cadmium may be associated with an increased risk of ITC.

Metals and Breast Cancer Risk: A Prospective Study Using Toenail Biomarkers

The role of metals in breast cancer is of interest because of their carcinogenic and endocrine-disrupting capabilities. Evidence from epidemiologic studies remains elusive, and prior studies have not investigated metal mixtures. In a case cohort nested within the Sister Study (enrolled in 2003-2009; followed through September 2017), we measured concentrations of 15 metals in toenails collected at enrollment in a race/ethnicity-stratified sample of 1,495 cases and a subcohort of 1,605 women. We estimated hazard ratios and 95% confidence intervals for each metal using Cox regression and robust variance. We used quantile g-computation to estimate the joint association between multiple metals and breast cancer risk. The average duration of follow-up was 7.5 years. There was little evidence supporting an association between individual metals and breast cancer. An exception was molybdenum, which was associated with reduced incidence of overall breast cancer risk (third tertile vs. first tertile: hazard ratio = 0.82, 95% confidence interval: 0.67, 1.00). An inverse association for antimony was observed among non-Hispanic Black women. Predefined groups of metals (all metals, nonessential metals, essential metals, and metalloestrogens) were not strongly associated with breast cancer. This study offers little support for metals, individually or as mixtures, as risk factors for breast cancer. Mechanisms for inverse associations with some metals warrant further study.

Is Cadmium a Risk Factor for Breast Cancer - Results from a Nested Case-Control Study Using Data from the Malmö Diet and Cancer Study

BACKGROUND

Some studies have shown that cadmium (Cd) is associated with breast cancer risk. One hypothesis is that Cd has estrogen-like properties. This case-control study investigated the association between breast cancer risk and blood Cd (BCd) levels.

METHODS

All breast cancers in the Malmö Diet and Cancer cohort were identified through linkage to the Swedish Cancer Registry, baseline (1991-1996) through 2014. Two controls per case were selected from the same cohort. BCd was analyzed at baseline. Associations were analyzed using logistic regression.

RESULTS

Mean BCd was 0.51 μg/L among 1,274 cases and 0.46 among 2,572 controls. There was an overall increased risk of breast cancer [OR, 1.18; 95% confidence interval (CI), 1.05-1.36] per μg/L of BCd. An increased risk was, however, only found at high BCd [OR, 1.34 (95% CI, 1.05-1.73)] for BCd more than 1.20 μg/L. The group with the highest BCd was mainly smokers. A spline indicated that at BCd less than 1.0 μg/L, the OR was not increased. The association with BCd was stronger in current smokers and at body mass index (BMI) above 25, while no modification due to receptor status was found.

CONCLUSIONS

The results indicated increased risk of breast cancer only for high Cd exposure, which occurred mainly among smokers. This made it difficult to disentangle the effects of smoking and Cd, despite inclusion of smoking habits in the models.

IMPACT

This study provides support for reducing Cd exposure through smoking cessation and dietary choice. On the population level, preventive measures against Cd pollution are warranted.

Elemental bioimaging shows mercury and other toxic metals in normal breast tissue and in breast cancers

OBJECTIVE

Exposure to toxic metals such as mercury has been proposed to be a risk factor for the development of breast cancer since some metals can promote genetic mutations and epigenetic changes. We sought to find what toxic metals are present in normal breast tissue and in the tumours of women who had mastectomies for invasive ductal breast carcinoma.

MATERIALS AND METHODS

Formalin-fixed paraffin-embedded blocks from mastectomies for breast carcinoma were examined from 50 women aged 34-69 years. Paraffin blocks selected for elemental analysis were from breast tissue not involved by carcinoma and from the carcinoma itself. Seven micrometer-thick sections were stained with autometallography to demonstrate the presence of mercury, and subjected to laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to confirm the presence of mercury and to detect other toxic metals.

RESULTS

Autometallography-detected mercury was seen in intraductal secretions and some luminal epithelial cells of normal breast lobules in 26 (55%) of the 47 samples where lobules were present, and in 10 (23%) of carcinomas from the 44 samples where carcinoma was present. In eight samples ductal carcinoma in situ was present and one of these contained mercury. LA-ICP-MS confirmed the presence of mercury in samples that stained with autometallography, and detected lead, iron, nickel, aluminium, chromium and cadmium in some samples.

CONCLUSIONS

Mercury was present in normal breast lobules in more than half of mastectomy samples that contained an invasive carcinoma, and in a smaller proportion of carcinomas and ductal carcinomas in situ. Other toxic metals that may interact synergistically with mercury could be detected in some samples. These findings do not provide direct evidence that toxic metals such as mercury play a role in the pathogenesis of breast cancer, but suggest that future molecular biological investigations on the role of toxic metals in breast cancer are warranted.

Chronic long-term exposure to cadmium air pollution and breast cancer risk in the French E3N cohort

Cadmium, due to its estrogen-like activity, has been suspected to increase the risk of breast cancer; however, epidemiological studies have reported inconsistent findings. We conducted a case-control study (4,059 cases and 4,059 matched controls) nested within the E3N French cohort study to estimate the risk of breast cancer associated with long-term exposure to airborne cadmium pollution, and its effect according to molecular subtype of breast cancer (estrogen receptor negative/positive [ER-/ER+] and progesterone receptor negative/positive [PR-/PR+]). Atmospheric exposure to cadmium was assessed using a Geographic Information System-based metric, which included subject's residence-to-cadmium source distance, wind direction, exposure duration and stack height. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression. Overall, there was no significant association between cumulative dose of airborne cadmium exposure and the risk of overall, premenopausal and postmenopausal breast cancer. However, by ER and PR status, inverse associations were observed for ER- (ORQ5 vs. Q1  = 0.63; 95% CI: 0.41-0.95, ptrend  = 0.043) and for ER-/PR- breast tumors (ORQ4 vs. Q1  = 0.62; 95% CI: 0.40-0.95, ORQ5 vs. Q1  = 0.68; 95% CI: 0.42-1.07, ptrend  = 0.088). Our study provides no evidence of an association between exposure to cadmium and risk of breast cancer overall but suggests that cadmium might be related to a decreased risk of ER- and ER-/PR- breast tumors. These observations and other possible effects linked to hormone receptor status warrant further investigations.

Environmental exposures, stem cells, and cancer

An estimated 70-90% of all cancers are linked to exposure to environmental risk factors. In parallel, the number of stem cells in a tissue has been shown to be a strong predictor of risk of developing cancer in that tissue. Tumors themselves are characterized by an acquisition of "stem cell" characteristics, and a growing body of evidence points to tumors themselves being sustained and propagated by a stem cell-like population. Here, we review our understanding of the interplay between environmental exposures, stem cell biology, and cancer. We provide an overview of the role of stem cells in development, tissue homeostasis, and wound repair. We discuss the pathways and mechanisms governing stem cell plasticity and regulation of the stem cell state, and describe experimental methods for assessment of stem cells. We then review the current understanding of how environmental exposures impact stem cell function relevant to carcinogenesis and cancer prevention, with a focus on environmental and occupational exposures to chemical, physical, and biological hazards. We also highlight key areas for future research in this area, including defining whether the biological basis for cancer disparities is related to effects of complex exposure mixtures on stem cell biology.

Endocrine-disrupting metals in ambient air and female breast cancer incidence in US

Metals could act as endocrine disruptors that mimic the actions of hormones, such as estrogens, and contribute to the development and progression of breast cancer. In this study, we examined the association between ambient air emissions of several endocrine-disrupting metals and the incidence of female breast cancer in the United States by analyzing county-level data from national datasets. Linear regression analysis was conducted to evaluate the association in unadjusted and adjusted models. Of the metals analyzed, air emissions of arsenic, cadmium, lead, and mercury, but not chromium VI, were significantly associated with the incidence of all breast cancers, after adjusting for potential confounders. Emissions of arsenic, lead, and mercury were found to be significantly associated with the incidence of estrogen receptor (ER)-positive breast cancer. Among these metals, air emissions of lead showed the strongest association with breast cancer incidence with the β of 3756.66 (95% CI: 1660.29, 5853.03) for all breast cancers and 2433.85 (440.59, 4427.10) for ER-positive breast cancer. Our results demonstrate that exposure to endocrine-disrupting metals in ambient air may be associated with an increased incidence of breast cancer in the United States. Further studies are needed to explore these interactions and to elucidate mechanisms of action.

Toenail-Based Metal Concentrations and Young-Onset Breast Cancer

Several metals have carcinogenic properties, but their associations with breast cancer are not established. We studied cadmium, a metalloestrogen, and 9 other metals-arsenic, cobalt, chromium, copper, mercury, molybdenum, lead, tin, and vanadium--in relation to young-onset breast cancer (diagnosis age <50 years), which tends to be more aggressive than and have a different risk profile from later-onset disease. Recent metal exposure was measured by assessing element concentrations, via inductively coupled plasma mass spectrometry, in toenail clippings of 1,217 disease-discordant sister pairs in the US-based Sister (2003-2009) and Two Sister (2008-2010) studies. Conditional logistic regression was used to calculate odds ratios and 95% confidence intervals. After correcting for differential calendar time of sample collection, no statistically significant associations were observed between any metals and breast cancer. Vanadium had the largest odds ratio (for fourth vs. first quartile, odds ratio = 1.54, 95% confidence interval: 0.75, 3.16; P for trend = 0.21). The association between cadmium and young-onset breast cancer was near null, with no evidence of a dose-response relationship (for fourth vs. first quartile, odds ratio = 0.95, 95% confidence interval: 0.64, 1.43; P for trend = 0.64). Positive associations between urinary cadmium concentrations and breast cancer have been reported in case-control studies, but we observed no such association between young-onset breast cancer and toenail concentrations of any assessed metals.

Cadmium Exposure Inhibits Branching Morphogenesis and Causes Alterations Consistent With HIF-1α Inhibition in Human Primary Breast Organoids

Developmental cadmium exposure in vivo disrupts mammary gland differentiation, while exposure of breast cell lines to cadmium causes invasion consistent with the epithelial-mesenchymal transition (EMT). The effects of cadmium on normal human breast stem cells have not been measured. Here, we quantified the effects of cadmium exposure on reduction mammoplasty patient-derived breast stem cell proliferation and differentiation. Using the mammosphere assay and organoid formation in 3D hydrogels, we tested 2 physiologically relevant doses of cadmium, 0.25 and 2.5 µM, and tested for molecular alterations using RNA-seq. We functionally validated our RNA-seq findings with a hypoxia-inducible factor (HIF)-1α activity reporter line and pharmaceutical inhibition of HIF-1α in organoid formation assays. 2.5 µM cadmium reduced primary mammosphere formation and branching structure organoid formation rates by 33% and 87%, respectively. Despite no changes in mammosphere formation, 0.25 µM cadmium inhibited branching organoid formation in hydrogels by 73%. RNA-seq revealed cadmium downregulated genes associated with extracellular matrix formation and EMT, while upregulating genes associated with metal response including metallothioneins and zinc transporters. In the RNA-seq data, cadmium downregulated HIF-1α target genes including LOXL2, ZEB1, and VIM. Cadmium significantly inhibited HIF-1α activity in a luciferase assay, and the HIF-1α inhibitor acriflavine ablated mammosphere and organoid formation. These findings show that cadmium, at doses relevant to human exposure, inhibited human mammary stem cell proliferation and differentiation, potentially through disruption of HIF-1α activity.

Cadmium Exposure and Risk of Breast Cancer by Histological and Tumor Receptor Subtype in White Caucasian Women: A Hospital-Based Case-Control Study

As the majority of experimental studies suggest cadmium being metalloestrogen, we examined cadmium/breast cancer (BC) association by histological and tumor receptor subtype in 509 invasive BC patients and 1170 controls. Urinary cadmium was determined by atomic absorption spectrometry, and categorized using tertiles of its distribution in the controls: <0.18, 0.18–0.33, >0.33 kg × 10⁻⁹/kg × 10⁻³ creatinine. Relative to the lowest category of urinary cadmium adjusted odds ratio (OR) of ductal BC was 1.18 (95% confidence interval (CI): 0.89–1.58) in the intermediate and 1.53 (95% CI: 1.15–2.04) in the highest category. There was a significant association for hormone receptor-positive ductal BC: ORs per category increase were 1.34 (95% CI: 1.14–1.59) for estrogen receptor-positive (ER+), 1.33 (95% CI: 1.09–1.61) for progesterone receptor-positive (PR+) and 1.35 (95% CI: 1.11–1.65) for ER+/PR+ BC. We found a significant association between cadmium and human epidermal growth factor receptor 2-negative (HER2−) ductal BC. The strongest association with cadmium was for ER+/PR+/HER2− ductal BC. The associations between cadmium and lobular BC with hormone receptor-positive and HER2− were positive but insignificant. There was no evidence that the associations with cadmium differed for cancers with different tumor histology (p-heterogeneity > 0.05). This study provides evidence that urinary cadmium is associated with the risk of hormone receptor-positive and HER2− breast cancer independent of tumor histology.

Dietary cadmium and risk of breast cancer subtypes defined by hormone receptor status: A prospective cohort study

Diet is the primary source of cadmium-a proven Group 1 human carcinogen-for non-smokers. Observational studies investigating the effect of cadmium from food sources on breast cancer risk have produced inconsistent results. We examined the association between dietary cadmium and risk of breast cancer defined by estrogen receptor (ER), progesterone receptor (PR) and HER2 status, in 8924 women recruited to a prospective study between 1987 and 1992. Dietary cadmium intake was estimated using a semi-quantitative food frequency questionnaire at baseline. During a median of 22 years of follow-up, 451 incident cases of breast cancer were identified through the Varese Cancer Registry. Multivariable-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) for breast cancer and receptor-defined breast cancer subtypes were estimated for quintiles of dietary cadmium intake, adjusting for confounding factors. Mean dietary cadmium intake was 7.8 (standard deviation 1.4) μg/day. Women with highest quintile of cadmium intake had a greater risk of breast cancer (HR 1.54; 95% CI, 1.06-2.22; p trend = 0.028) than those with lowest quintile of intake. Women premenopausal at recruitment had HR = 1.73 (95% CI, 1.10-2.71, highest vs. lowest quintile); postmenopausal women had HR = 1.32 (95% CI, 1.05-1.66 for each standard deviation increase in cadmium). Cadmium-related risk of breast cancer did not vary with ER, PR or HER2 status (p-heterogeneity not significant). These findings support the hypothesis that dietary cadmium is a risk factor for breast cancer.

Toenail-Based Metal Concentrations and Young-Onset Breast Cancer

Several metals have carcinogenic properties, but their associations with breast cancer are not established. We studied cadmium, a metalloestrogen, and 9 other metals-arsenic, cobalt, chromium, copper, mercury, molybdenum, lead, tin, and vanadium--in relation to young-onset breast cancer (diagnosis age <50 years), which tends to be more aggressive than and have a different risk profile from later-onset disease. Recent metal exposure was measured by assessing element concentrations, via inductively coupled plasma mass spectrometry, in toenail clippings of 1,217 disease-discordant sister pairs in the US-based Sister (2003-2009) and Two Sister (2008-2010) studies. Conditional logistic regression was used to calculate odds ratios and 95% confidence intervals. After correcting for differential calendar time of sample collection, no statistically significant associations were observed between any metals and breast cancer. Vanadium had the largest odds ratio (for fourth vs. first quartile, odds ratio = 1.36, 95% confidence interval: 0.84, 2.21; P for trend = 0.17). Cadmium was associated with a small increase in risk, with no evidence of a dose-response relationship (for fourth vs. first quartile, odds ratio = 1.15, 95% confidence interval: 0.82, 1.60; P for trend = 0.67). Positive associations between urinary cadmium concentrations and breast cancer have been reported in case-control studies, but we observed no such association between young-onset breast cancer and toenail concentrations of any assessed metals.

Airborne metals and polycyclic aromatic hydrocarbons in relation to mammographic breast density

BACKGROUND

Breast density is strongly related to breast cancer. Identifying associations between environmental exposures and density may elucidate relationships with breast cancer. Metals and polycyclic aromatic hydrocarbons (PAHs) may influence breast density via oxidative stress or endocrine disruption.

METHODS

Study participants (n = 222,581) underwent a screening mammogram in 2011 at a radiology facility in the Breast Cancer Surveillance Consortium. Zip code residential levels of airborne PAHs and metals (arsenic, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium) were assessed using the 2011 EPA National Air Toxics Assessment. Breast density was measured using the Breast Imaging-Reporting and Data System (BI-RADS) lexicon. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI) for the individual air toxics and dense breasts (BI-RADS 3 or 4). Weighted quantile sum (WQS) regression was used to model the association between the air toxic mixture and density.

RESULTS

Higher residential levels of arsenic, cobalt, lead, manganese, nickel, or PAHs were individually associated with breast density. Comparing the highest to the lowest quartile, higher odds of having dense breasts were observed for cobalt (OR = 1.60, 95% CI 1.56-1.64) and lead (OR = 1.56, 95% CI 1.52-1.64). Associations were stronger for premenopausal women. The WQS index was associated with density overall (OR = 1.22, 95% CI 1.20-1.24); the most heavily weighted air toxics were lead and cobalt.

CONCLUSIONS

In this first study to evaluate the association between air toxics and breast density, women living in areas with higher concentrations of lead and cobalt were more likely to have dense breasts.

Metallic Air Pollutants and Breast Cancer Risk in a Nationwide Cohort Study

BACKGROUND

Toxic metals show evidence of carcinogenic and estrogenic properties. However, little is known about the relationship between airborne metals and breast cancer. We evaluated the risk of breast cancer in relation to exposure to toxic metallic substances in air, individually and combined, in a US-wide cohort.

METHODS

Sister Study participants (n = 50,884), breast cancer-free women who had a sister with breast cancer were recruited, from 2003 to 2009. The 2005 Environmental Protection Agency National Air Toxic Assessment's census-tract estimates of metal concentrations in air (antimony, arsenic, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium) were matched to participants' enrollment residence. We used Cox regression to estimate the association between quintiles of individual metals and breast cancer incidence and weighted quantile sum regression to model the association between the metal mixture and breast cancer.

RESULTS

A total of 2,587 breast cancer cases were diagnosed during follow-up (mean = 7.4 years). In individual chemical analyses comparing the highest to lowest quintiles, postmenopausal breast cancer risk was elevated for mercury (hazard ratio [HR] = 1.3, 95% confidence interval [CI], 1.1, 1.5), cadmium (HR = 1.1, 95% CI, 0.96, 1.3), and lead (HR = 1.1, 95% CI, 0.98, 1.3). The weighted quantile sum index was associated with postmenopausal breast cancer (odds ratio [OR] = 1.1, 95% CI, 1.0, 1.1). Consistent with the individual chemical analysis, the most highly weighted chemicals for predicting postmenopausal breast cancer risk were lead, cadmium, and mercury. Results were attenuated for overall breast cancer.

CONCLUSIONS

Higher levels of some airborne metals, specifically mercury, cadmium, and lead, were associated with a higher risk of postmenopausal breast cancer.

Chronic cadmium exposure aggravates malignant phenotypes of nasopharyngeal carcinoma by activating the Wnt/β-catenin signaling pathway via hypermethylation of the casein kinase 1α promoter

BACKGROUND

Our previous study has shown that cadmium (Cd) exposure is not only a risk factor for nasopharyngeal carcinoma (NPC), but also correlated with the clinical stage and lymph node metastasis. However, the underlying molecular events of Cd involved in NPC progression remain to be elucidated.

PURPOSE

The objective of this study was to decipher how Cd impacts the malignant phenotypes of NPC cells.

METHODS

NPC cell lines CNE-1 and CNE-2 were continuously exposed with 1 μM Cd chloride for 10 weeks, designating as chronic Cd treated NPC cells (CCT-NPC). MTT assay, colony formation assay and xenograft tumor growth were used to assess cell viability in vitro and in vivo. Transwell assays were performed to detect cell invasion and migration. The protein levels of E-cadherin, N-cadherin, Vimentin as well as β-catenin and casein kinase 1α(CK1α) were measured by Western blot. Immunofluorescence staining was used to observe the distribution of filament actin (F-actin), β-catenin and CK1α. The mRNA levels of downstream target genes of β-catenin were detected by RT-PCR. Wnt/β-catenin signaling activity was assessed by TOPFlash/FOPFlash dual luciferase report system. MS-PCR was used to detect the methylation status of CK1α. Finally, the activation of Wnt/β-catenin pathway and cell biological properties were examined following treatment of CCT-NPC cells with 5-aza-2-deoxy-cytidine(5-aza-CdR).

RESULTS

CCT-NPC cells showed an increase in cell proliferation, colony formation, invasion and migration compared to the parental cells. Cd also induced cytoskeleton reorganization and epithelial-to-mesenchymal transition. Upregulation and nuclear translocation of β-catenin and increased luciferase activity accompanied with transcription of downstream target genes were found in CCT-NPC cells. Treatment of CCT-CNE1 cells with 5-aza-CdR could reverse the hypermethylation of CK1α and attenuate the cell malignancy.

CONCLUSION

These results support a role for chronic Cd exposure as a driving force for the malignant progression of NPC via epigenetic activation of the Wnt/β-catenin pathway.

Blood levels of cadmium and lead in relation to breast cancer risk in three prospective cohorts

Cadmium and lead have been classified as carcinogens by the International Agency for Research on Cancer. However, their associations with breast cancer risk are unknown despite their persistence in the environment and ubiquitous human exposure. We examined associations of circulating levels of cadmium and lead with breast cancer risk in three case-control studies nested within the Cancer Prevention Study-II (CPS-II) LifeLink Cohort, European Prospective Investigation into Cancer and Nutrition - Italy (EPIC-Italy) and the Northern Sweden Health and Disease Study (NSHDS) cohorts. Metal levels were measured in stored erythrocytes from 1,435 cases and 1,433 controls using inductively coupled plasma-mass spectrometry. Summary relative risks (RR) and 95% confidence intervals (CI) were calculated using random-effects models with each study result weighted by the within- and between-study variances. I² values were calculated to estimate proportion of between study variation. Using common cut-points, cadmium levels were not associated with breast cancer risk in the CPS-II cohort (continuous RR = 1.01, 95% CI 0.76-1.34), but were inversely associated with risk in the EPIC- Italy (continuous RR = 0.80, 95% CI 0.61-1.03) and NSHDS cohorts (continuous RR = 0.73, 95% CI 0.54-0.97). The inverse association was also evident in the meta-analysis (continuous RR = 0.84, 95% CI 0.69-1.01) with low between-study heterogeneity. Large differences in lead level distributions precluded a meta-analysis of their association with breast cancer risk; no associations were found in the three studies. Adult cadmium and lead levels were not associated with higher risk of breast cancer in our large meta-analysis.

Blood cadmium levels associated with short distant metastasis-free survival time in invasive breast cancer

Distant metastasis is strongly associated with poor prognosis of breast cancer. Cadmium (Cd) exposure was previously found associated with breast cancer incidence. We explored the associations of blood cadmium levels (BCLs) and clinicopathologic characteristics with invasive breast cancer distant metastasis. Blood samples were collected and analyzed for BCLs by graphite-furnace atomic absorption spectrometry. Clinicopathologic characteristics, including basic clinical information and tumor characteristics, were obtained from medical records. Breast cancer distant metastasis-free survival (DMFS) time was calculated at follow-up. The associations of BCLs and clinicopathologic characteristics with DMFS time were examined by Kaplan-Meier method and Cox regression analysis, and associations between BCLs and tumor characteristics were also explored. Blood Cd level was positively associated with distant metastasis, clinical stage, BMI, and age. On univariate analysis, older age at diagnosis, family history of breast cancer, high N classification and clinical stage, positivity for human epidermal growth factor receptor 2, and high BCLs were associated with short DMFS time. On multivariate analysis model, older age at diagnosis, family history of breast cancer, high N classification, and BCLs were predictors for breast cancer distant metastasis. BCLs were a risk factor for short DMFS time of invasive breast cancer. BCLs and some clinicopathologic factors affect breast cancer distant metastasis, which needs further epidemiological and experimental studies to confirm.

Cadmium, arsenic, selenium and iron- Implications for tumor progression in breast cancer

The aim of this study was to determine Cd (cadmium) and As (arsenic) contents in human breast cancer tissues, investigate their interactions with Se (selenium) and Fe (iron), and assess their further implications for tumor progression. Metal contents were determined in 42 tissue sets (tumor and adjacent tissue) collected from 42 women diagnosed with primary breast cancer. Analytical methods included AAS and ICP-MS techniques. Significantly higher contents of Cd (p=0.0003), Se (p<0.0001) and Fe (p=0.0441) whereas significantly lower content of As (p<0.0001) were observed in tumors as compared to adjacent tissues. There was a significant positive correlation between Cd and As contents in tumor tissue. However, only Cd was significantly associated with histological type of tumor, its size, grading and progesterone receptor status. This study support the role of Cd in breast cancer risk and progression. The possible link between As exposure and breast cancer is still not clear.

Recombinant heat shock protein 27 (HSP27/HSPB1) protects against cadmium-induced oxidative stress and toxicity in human cervical cancer cells

Cadmium (Cd) is a carcinogen with several well-described toxicological effects in humans, but its molecular mechanisms are still not fully understood. Overexpression of heat shock protein 27 (HSP27/HSPB1)-a multifunctional protein chaperone-has been shown to protect cells from oxidative damage and apoptosis triggered by Cd exposure. The aims of this work were to investigate the potential use of extracellular recombinant HSP27 to prevent/counteract Cd-induced cellular toxicity and to evaluate if peroxynitrite was involved in the development of Cd-induced toxicity. Here, we report that the harmful effects of Cd correlated with changes in oxidative stress markers: upregulation of reactive oxygen species, reduction in nitric oxide (NO) bioavailability, increment in lipid peroxidation, peroxynitrite (PN), and protein nitration; intracellular HSP27 was reduced. Treatments with Cd (100 μM) for 24 h or with the peroxynitrite donor, SIN-1, decreased HSP27 levels (~50%), suggesting that PN formation is responsible for the reduction of HSP27. Pre-treatments of the cells either with Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) (a pharmacological inhibitor of NO synthase) or with recombinant HSP27 (rHSP27) attenuated the disruption of the cellular metabolism induced by Cd, increasing in a 55 and 52%, respectively, the cell viability measured by CCK-8. Cd induced necrotic cell death pathways, although apoptosis was also activated; pre-treatment with L-NAME or rHSP27 mitigated cell death. Our findings show for the first time a direct relationship between Cd-induced toxicity and PN production and a role for rHSP27 as a potential therapeutic agent that may counteract Cd toxicity.

Association between lifetime exposure to passive smoking and risk of breast cancer subtypes defined by hormone receptor status among non-smoking Caucasian women

Tobacco smoking is inconsistently associated with breast cancer. Although some studies suggest that breast cancer risk is related to passive smoking, little is known about the association with breast cancer by tumor hormone receptor status. We aimed to explore the association between lifetime passive smoking and risk of breast cancer subtypes defined by estrogen receptor and progesterone receptor status among non-smoking Caucasian women. A hospital-based case-control study was performed in 585 cases and 1170 controls aged 28-90 years. Information on lifetime passive smoking and other factors was collected via a self-administered questionnaire. Logistic regression was used for analyses restricted to the 449 cases and 930 controls who had never smoked actively. All statistical tests were two-sided. Adjusted odds ratio of breast cancer was 1.01 (95% confidence interval (CI): 0.72-1.41) in women who experienced exposure to passive smoking at work, 1.88 (95% CI: 1.38-2.55) in women who had exposure at home, and 2.80 (95% CI: 1.84-4.25) in women who were exposed at home and at work, all compared with never exposed regularly. Increased risk was associated with longer exposure: women exposed ≤ 20 years and > 20 years had 1.27 (95% CI: 0.97-1.66) and 2.64 (95% CI: 1.87-3.74) times higher risk of breast cancer compared with never exposed (Ptrend < 0.001). The association of passive smoking with hormone receptor-positive breast cancer did not differ from that with hormone receptor-negative breast cancer (Pheterogeneity > 0.05). There was evidence of interaction between passive smoking intensity and menopausal status in both overall group (P = 0.02) and hormone receptor-positive breast cancer group (P < 0.05). In Caucasian women, lifetime exposure to passive smoking is associated with the risk of breast cancer independent of tumor hormone receptor status with the strongest association in postmenopausal women.

Cadmium-induced immune abnormality is a key pathogenic event in human and rat models of preeclampsia

With increased industrial development, cadmium is an increasingly important environmental pollutant. Studies have identified various adverse effects of cadmium on human beings. However, the relationships between cadmium pollution and the pathogenesis of preeclampsia remain elusive. The objective of this study is to explore the effects of cadmium on immune system among preeclamptic patients and rats. The results showed that the cadmium levels in the peripheral blood of preeclamptic patients were significantly higher than those observed in normal pregnancy. Based on it, a novel rat model of preeclampsia was established by the intraperitoneal administration of cadmium chloride (CdCl2) (0.125 mg of Cd/kg body weight) on gestational days 9-14. Key features of preeclampsia, including hypertension, proteinuria, placental abnormalities and small foetal size, appeared in pregnant rats after the administration of low-dose of CdCl2. Cadmium increased immunoglobulin production, mainly angiotensin II type 1-receptor-agonistic autoantibodies (AT1-AA), by increasing the expression of activation-induced cytosine deaminase (AID) in B cells. AID is critical for the maturation of antibody and autoantibody responses. In addition, angiotensin II type 1-receptor-agonistic autoantibody, which emerged recently as a potential pathogenic contributor to PE, was responsible for the deposition of complement component 5 (C5) in kidneys of pregnant rats via angiotensin II type 1 receptor (AT1R) activation. C5a is a fragment of C5 that is released during C5 activation. Selectively interfering with C5a signalling by a complement C5a receptor-specific antagonist significantly attenuated hypertension and proteinuria in Cd-injected pregnant rats. Our results suggest that cadmium induces immune abnormalities that may be a key pathogenic contributor to preeclampsia and provide new insights into treatment strategies of preeclampsia.

Associations of urinary cadmium with circulating sex hormone levels in pre- and postmenopausal Japanese women

BACKGROUND

Exposure to cadmium has been suspected as a risk factor for breast cancer. The present study examined the associations between urinary cadmium levels and circulating sex hormone levels that are linked to breast cancer risk in healthy women.

METHODS

The study subjects were 396 premenopausal Japanese women who had regular menstrual cycles less than 40 days long and 207 postmenopausal Japanese women. Urinary cadmium was measured using spot urine samples. Plasma estradiol, testosterone, and dehydroepiandrosterone sulfate were measured. Additionally, the follicle-stimulating hormone, luteinizing hormone, and sex hormone-binding globulin were measured for premenopausal women.

RESULTS

In premenopausal women, the urinary cadmium level either expressed in μg per liter or per g of urine creatinine was significantly inversely associated with total and free testosterone levels after controlling for age, body mass index, smoking status, alcohol intake, and the phase of the menstrual cycle. Total and free testosterone levels were 14.6% and 15.0% lower, respectively, in women in the highest quartile of urinary cadmium per g creatinine in those in the lowest quartile. In postmenopausal women, the urinary cadmium in μg per liter as well as per g creatinine was significantly inversely associated with the estradiol level after controlling for covariates. The estradiol level was 25.8% lower in women in the highest tertile of urinary cadmium per g creatinine than in those in the lowest tertile.

CONCLUSIONS

The data suggest inverse associations between urinary cadmium and the plasma estradiol or testosterone level in Japanese women.

Systematic network assessment of the carcinogenic activities of cadmium

Cadmium has been defined as type I carcinogen for humans, but the underlying mechanisms of its carcinogenic activity and its influence on protein-protein interactions in cells are not fully elucidated. The aim of the current study was to evaluate, systematically, the carcinogenic activity of cadmium with systems biology approaches. From a literature search of 209 studies that performed with cellular models, 208 proteins influenced by cadmium exposure were identified. All of these were assessed by Western blotting and were recognized as key nodes in network analyses. The protein-protein functional interaction networks were constructed with NetBox software and visualized with Cytoscape software. These cadmium-rewired genes were used to construct a scale-free, highly connected biological protein interaction network with 850 nodes and 8770 edges. Of the network, nine key modules were identified and 60 key signaling pathways, including the estrogen, RAS, PI3K-Akt, NF-κB, HIF-1α, Jak-STAT, and TGF-β signaling pathways, were significantly enriched. With breast cancer, colorectal and prostate cancer cellular models, we validated the key node genes in the network that had been previously reported or inferred form the network by Western blotting methods, including STAT3, JNK, p38, SMAD2/3, P65, AKT1, and HIF-1α. These results suggested the established network was robust and provided a systematic view of the carcinogenic activities of cadmium in human.

Urinary Cadmium and Risk of Invasive Breast Cancer in the Women's Health Initiative

Cadmium is a widespread heavy metal pollutant that may act as an exogenous estrogenic hormone. Environmental cadmium exposure has been associated with risk of breast cancer in retrospective studies. We prospectively assessed the relationship between cadmium exposure, evaluated by creatinine-normalized urinary cadmium concentration, and invasive breast cancer among 12,701 postmenopausal women aged ≥50 years in a Women's Health Initiative study of bone mineral density. After a median of 13.2 years of follow-up (1993-2010), 508 cases of invasive breast cancer and 1,050 comparison women were identified for a case-cohort analysis. Multivariable Cox regression was used to calculate hazard ratios and 95% confidence intervals. Risk of breast cancer was not associated with urinary cadmium parameterized either in quartiles (comparing highest quartile with lowest, hazard ratio = 0.80, 95% confidence interval: 0.56, 1.14; P for trend = 0.20) or as a log-transformed continuous variable (per 2-fold higher urinary cadmium concentration, hazard ratio = 0.94, 95% confidence interval: 0.86, 1.03). We did not observe an association between urinary cadmium and breast cancer risk in any subgroup examined, including never smokers and women with body mass index (weight (kg)/height (m)(2)) less than 25. Results were consistent in both estrogen receptor-positive and estrogen receptor-negative tumors. Our results do not support the hypothesis that environmental cadmium exposure is associated with risk of postmenopausal breast cancer.

Association Between Cd Exposure and Risk of Prostate Cancer: A PRISMA-Compliant Systematic Review and Meta-Analysis

Several observational studies on the association between Cd exposure and risk of prostate cancer have yielded inconsistent results. To address this issue, we conducted a meta-analysis to evaluate the correlation between Cd exposure and risk of prostate cancer.Relevant studies in PubMed and Embase databases were retrieved until October 2015. We compared the highest and lowest meta-analyses to quantitatively evaluate the relationship between Cd exposure and risk of prostate cancer. Summary estimates were obtained using a random-effects model.In the general population, high Cd exposure was not associated with increased prostate cancer (OR 1.21; 95% CI 0.91-1.64), whereas the combined standardized mortality ratio of the association between Cd exposure and risk of prostate cancer was 1.66 (95% CI 1.10-2.50) in populations exposed to occupational Cd. In addition, high D-Cd intake (OR 1.07; 95% CI 0.96-1.20) and U-Cd concentration (OR 0.86; 95% CI 0.48-1.55) among the general population was not related to the increased risk of prostate cancer. In the dose analysis, the summary relative risk was 1.07 (95% CI 0.73-1.57) for each 0.5 μg/g creatinine increase in U-Cd and 1.02 (95% CI 0.99-1.06) for each 10 μg/day increase of dietary Cd intake. However, compared with nonoccupational exposure, high occupational Cd exposure may be associated with the increased risk of prostate cancer.This meta-analysis suggests high Cd exposure as a risk factor for prostate cancer in occupational rather than nonoccupational populations. However, these results should be carefully interpreted because of the significant heterogeneity among studies. Additional large-scale and high-quality prospective studies are needed to confirm the association between Cd exposure and risk of prostate cancer.

Association between cadmium exposure and renal cancer risk: a meta-analysis of observational studies

Cadmium (Cd) is a widespread environmental pollutant and has been a recognized carcinogen for several decades. Many observational studies reported Cd exposure might be one cause of renal cancer. However, these findings are inconsistent. We conducted a meta-analysis to evaluate the relationship between cadmium exposure and renal cancer risk. A comprehensive PubMed and Embase search was conducted to retrieve observational studies meeting our meta-analysis criteria. A combined odds ratio (OR) and corresponding 95% confidence interval (CI) were applied to assess the association between Cd exposure and renal cancer risk. The meta-analysis showed that a high Cd exposure significantly increased renal cancer 1.47 times (OR = 1.47; 95% CI = 1.27 to 1.71, for highest versus lowest category of cadmium categories). The significant association remained consistent when stratified by geographic region and gender, however mixed results were produced when stratified by sample size, study design, NOS score, adjustment for covariates, effects measure, and exposure type. Our results indicated that a high Cd exposure was associated with increased renal cancer risk and the association was higher for occupational exposure compared with non-occupational exposure. This meta-analysis suggests that a high Cd exposure may be a risk factor for renal cancer in occupational population.

Urinary cadmium concentration and risk of breast cancer: a systematic review and dose-response meta-analysis

Cadmium is a toxic and persistent heavy metal with estrogenic activities. We conducted a systematic review and meta-analysis of cohort, case-control, and cross-sectional studies of the association between urinary cadmium concentration, a biomarker of cadmium exposure, and breast cancer risk. Studies were identified by searching PubMed and Embase (to March 15, 2015) and by reviewing the reference lists of pertinent articles. Study-specific risk estimates were combined by using a random-effects model. We identified 2 cohort studies (with 67 breast cancer deaths) and 5 case-control studies and 1 cross-sectional study (with 1,416 cases and 5,083 controls) on urinary cadmium concentration in relation to breast cancer risk. The studies were published during the past 10 years (2006-2015). There was no consistent association between urinary cadmium and breast cancer mortality in the cohort studies. In case-control and cross-sectional studies, the pooled odds ratios were 2.24 (95% confidence interval: 1.50, 3.34; I(2) = 63.4%) for the highest versus lowest category of cadmium concentration and 1.66 (95% confidence interval: 1.23, 2.25) for each 0.5-µg/g creatinine increase of cadmium concentration. This meta-analysis suggests that a high cadmium exposure may be a risk factor for breast cancer, but large prospective studies are needed to confirm this finding.

Differential DNA methylation profile of key genes in malignant prostate epithelial cells transformed by inorganic arsenic or cadmium

Previous work shows altered methylation patterns in inorganic arsenic (iAs)- or cadmium (Cd)-transformed epithelial cells. Here, the methylation status near the transcriptional start site was assessed in the normal human prostate epithelial cell line (RWPE-1) that was malignantly transformed by 10μM Cd for 11weeks (CTPE) or 5μM iAs for 29weeks (CAsE-PE), at which time cells showed multiple markers of acquired cancer phenotype. Next generation sequencing of the transcriptome of CAsE-PE cells identified multiple dysregulated genes. Of the most highly dysregulated genes, five genes that can be relevant to the carcinogenic process (S100P, HYAL1, NTM, NES, ALDH1A1) were chosen for an in-depth analysis of the DNA methylation profile. DNA was isolated, bisulfite converted, and combined bisulfite restriction analysis was used to identify differentially methylated CpG sites, which was confirmed with bisulfite sequencing. Four of the five genes showed differential methylation in transformants relative to control cells that was inversely related to altered gene expression. Increased expression of HYAL1 (>25-fold) and S100P (>40-fold) in transformants was correlated with hypomethylation near the transcriptional start site. Decreased expression of NES (>15-fold) and NTM (>1000-fold) in transformants was correlated with hypermethylation near the transcriptional start site. ALDH1A1 expression was differentially expressed in transformed cells but was not differentially methylated relative to control. In conclusion, altered gene expression observed in Cd and iAs transformed cells may result from altered DNA methylation status.

Residential exposure to estrogen disrupting hazardous air pollutants and breast cancer risk: the California Teachers Study

BACKGROUND

Some studies show increased breast cancer risk from exposure to xenoestrogens, but few have explored exposures via ambient air, which could impact large populations.

OBJECTIVES

This study explored the association between breast cancer risk and residential exposures to ambient estrogen disruptors among participants in a large cohort study, the California Teachers Study.

METHODS

Participants consisted of 112,379 women free of breast cancer and living at a California address in 1995/1996. Eleven hazardous air pollutants from the US Environmental Protection Agency 2002 list were identified as estrogen disruptors based on published endocrine disrupting chemical lists and literature review. Census-tract estrogen disruptor air concentrations modeled by the US Environmental Protection Agency in 2002 were assigned to participants' baseline addresses. Cox proportional hazards models were used to estimate hazard ratios associated with exposure to each estrogen disruptor and a summary measure of nine estrogenic hazardous air pollutants among all participants and selected subgroups, adjusting for age, race/birthplace, socioeconomic status, and known breast cancer risk factors.

RESULTS

Five thousand three hundred sixty-one invasive breast cancer cases were identified between 1995 and 2010. No associations were found between residential exposure to ambient estrogen disruptors and overall breast cancer risk or hormone receptor-positive breast cancer risk, nor among targeted subgroups of participants (pre-/peri-menopausal women, post-menopausal women, never-smokers, non-movers, and never-smoking non-movers). However, elevated risks for hormone receptor-negative tumors were observed for higher exposure to cadmium compounds and possibly inorganic arsenic among never-smoking non-movers.

CONCLUSION

Long-term, low-dose exposure to ambient cadmium compounds or possibly inorganic arsenic may be a risk factor for breast cancer.

Associations between cadmium exposure and circulating levels of sex hormones in postmenopausal women

Recent epidemiological as well as in vivo and in vitro studies collectively suggest that the metalloestrogen cadmium (Cd) could be a potential risk factor for hormone-related cancers in particularly breast cancer. Assessment of the association between Cd exposure and levels of endogenous sex hormones is of pivotal importance, as increased levels of such have been associated with a higher risk of breast cancer in postmenopausal women. The present study investigated the perceived relationship (multivariable-adjusted linear regression analyses) between Cd exposure [blood Cd (B-Cd) and urinary Cd (U-Cd)], and serum levels of androstenedione, testosterone, estradiol, and sex-hormone binding globulin (SHBG), in 438 postmenopausal Swedish women without hormone replacement therapy (HRT). A significant positive association between B-Cd (median 3.4 nmol/L) and serum testosterone levels, as well as a significant inverse association between B-Cd and serum estradiol levels and with the estradiol/testosterone ratio were encountered. However, U-Cd (median 0.69 nmol/mmol creatinine) was inversely associated with serum estradiol levels only. Our data may suggest that Cd interferes with the levels of testosterone and estradiol in postmenopausal women, which might have implications for breast cancer risk.