Cadmium exposure and risk of pancreatic cancer: a meta-analysis of prospective cohort studies and case-control studies among individuals without occupational exposure history

Cadmium in biological samples and site-specific cancer risk and mortality: A systematic review of original articles and meta-analyses

BACKGROUND

Cadmium (Cd) is classified as a class 1 carcinogen by the IARC, yet uncertainty persists regarding the total burden of cancer (incidence and mortality) caused by exposure to it, due to the still limited evidence with regard to its aetiological role in cancer at several body sites.

OBJECTIVES AND METHODS

We searched PubMed and EMBASE for meta-analyses and original articles published by February 1st, 2024, that focused on the link between cadmium measured in biological samples (blood, urine, finger-/toe-nails, and hair) and site-specific cancer risk and mortality.

RESULTS

We included 9 meta-analyses and 57 original articles (of these, the design was retrospective in 38 and prospective in 19, and Cd levels were quantified in blood, n=33, urine, n=19, both blood and urine, n=2, or finger-/toenail, n=3). Current data consistently suggest a causal role of exposure to cadmium in pancreas, lung, and bladder carcinogenesis. Total cancer risk and mortality are also positively correlated with Cd levels in biological samples. The evidence is weak or inconclusive for the remaining cancer sites (including breast and prostate), mostly due to the limited number of studies available to date and/or methodological limitations.

DISCUSSION

Exposure to cadmium poses a risk for increased cancer incidence and mortality. Cadmium-related cancer burden might indeed be currently underestimated, as the amount of available evidence for most cancer sites and types is currently limited, and more research in the field is warranted. Continuing efforts to contain Cd pollution and mitigate associated health risk are also needed.

Matching traditional Chinese medicine and western medicine-based research: Advanced nutraceutical development for proactive gastric cancer prevention

Gastric cancer (GC), the third leading cause of cancer-related death globally, is complex and heterogeneous. This review explores multidisciplinary investigations of traditional Chinese medicine (TCM) combined with Western medical practices, emphasizing the development of nutraceuticals for cancer prevention. Using advanced analytical chemistry and food chemistry techniques, this study investigated how TCM components may be optimized for nutraceutical development. Focusing on molecular interactions with GC pathways, particularly the NF-κB, PI3K/Akt, and Wnt/β-catenin pathways, we examined the effects of TCM polyherbal formulas, extracts, and isolated compounds. These agents modulate apoptosis and cellular proliferation, underscoring their potential in preventive strategies. The convergence of nutraceutical and medicine food homology studies highlights a significant shift towards integrating TCM-derived compounds in a preventive health framework. This approach aims not only to enhance efficacy and reduce side effects but also to champion a preventive paradigm using personalized medicine to advance proactive health maintenance and disease prevention. The combination of TCM and western medical practices offers promising avenues for future research and practical applications in GC prevention.

Urine cadmium and urolithiasis: A systematic review and meta-analysis

Exposure to cadmium may increase risk of urolithiasis, but the results remain inconclusive. This systematic review and meta-analysis aimed to access the association between cadmium exposure and urolithiasis. We searched Medline/PubMed, Embase, Web of Science Core Collection, and Cochrane Central for studies. The primary outcome was the incidence of urolithiasis compared to reference groups. We used relative risk as the summary effect measure. This meta-analysis included eight observational studies and divided into 39 study populations. Among 63,051 subjects, 5018 (7.96%) individuals had urolithiasis. The results indicated that people with an increment of 0.1 μg/g creatinine in urinary cadmium had a 2% increased risk of urolithiasis (pooled relative risk [RR], 1.02; 95% confidence interval [CI], 1.01-1.03) and there is no difference in the risk of urolithiasis in high and low cadmium exposure levels. Meanwhile, people with an increment of 0.1 μg/L in urinary cadmium had a 4% increased risk of urolithiasis (pooled RR, 1.04; 95% CI, 1.02-1.07). Our findings also showed similar associations in both sex, different region (Sweden, China, and Thailand), general and occupational population. The results indicate that cadmium exposure was significantly associated with an elevated risk of urolithiasis. Therefore, it is imperative to take steps to minimize cadmium exposure.

The dynamic face of cadmium-induced Carcinogenesis: Mechanisms, emerging trends, and future directions

Cadmium (Cd) is a malleable element with odorless, tasteless characteristics that occurs naturally in the earth's crust, underground water, and soil. The most common reasons for the anthropological release of Cd to the environment include industrial metal mining, smelting, battery manufacturing, fertilizer production, and cigarette smoking. Cadmium-containing products may enter the environment as soluble salts, vapor, or particle forms that accumulate in food, soil, water, and air. Several epidemiological studies have highlighted the association between Cd exposure and adverse health outcomes, especially renal toxicity, and the impact of Cd exposure on the development and progression of carcinogenesis. Also highlighted is the evidence for early-life and even maternal exposure to Cd leading to devastating health outcomes, especially the risk of cancer development in adulthood. Several mechanisms have been proposed to explain how Cd mediates carcinogenic transformation, including epigenetic alteration, DNA methylation, histone posttranslational modification, dysregulated non-coding RNA, DNA damage in the form of DNA mutation, strand breaks, and chromosomal abnormalities with double-strand break representing the most common DNA form of damage. Cd induces an indirect genotoxic effect by reducing p53's DNA binding activity, eventually impairing DNA repair, inducing downregulation in the expression of DNA repair genes, which might result in carcinogenic transformation, enhancing lipid peroxidation or evasion of antioxidant interference such as catalase, superoxide dismutase, and glutathione. Moreover, Cd mediates apoptosis evasion, autophagy activation, and survival mechanisms. In this review, we decipher the role of Cd mediating carcinogenic transformation in different models and highlight the interaction between various mechanisms. We also discuss diagnostic markers, therapeutic interventions, and future perspectives.

An umbrella review of the evidence associating occupational carcinogens and cancer risk at 19 anatomical sites

Occupational exposure to carcinogens of increasing cancer risk have been extensively suggested. A robust assessment of these evidence is needed to guide public policy and health care. We aimed to classify the strength of evidence for associations of 13 occupational carcinogens (OCs) and risk of cancers. We searched PubMed and Web of Science up to November 2022 to identify potentially relevant studies. We graded the evidence into convincing, highly suggestive, suggestive, weak, or not significant according to a standardized classification based on: random-effects p value, number of cancer cases, 95% confidence interval of largest study, heterogeneity between studies, 95% prediction interval, small study effect, excess significance bias and sensitivity analyses with credibility ceilings. The quality of meta-analysis was evaluated by AMSTAR 2. Forty-eight articles yielded 79 meta-analyses were included in current umbrella review. Evidence of associations were convincing (class I) or highly suggeastive (class II) for asbestos exposure and increasing risk of lung cancer among smokers (RR = 8.79, 95%CI: 5.81-13.25 for cohort studies and OR = 8.68, 95%CI: 5.68-13.24 for case-control studies), asbestos exposure and increasing risk of mesothelioma (RR = 4.61, 95%CI: 2.57-8.26), and formaldehyde exposure and increasing risk of sinonasal cancer (RR = 1.68, 95%CI: 1.38-2.05). Fifteen associations were supported by suggestive evidence (class III). In summary, the current umbrella review found strong associations between: asbestos exposure and increasing risk of lung cancer among smokers; asbestos exposure and increasing risk of mesothelioma; and formaldehyde exposure and higher risk of sinonasal cancer. Other associations might be genuine, but substantial uncertainty remains.

Toxicity Tolerance in the Carcinogenesis of Environmental Cadmium

Cadmium (Cd) is an environmental toxicant of worldwide public health significance. Diet is the main non-workplace Cd exposure source other than passive and active smoking. The intestinal absorption of Cd involves transporters for essential metals, notably iron and zinc. These transporters determine the Cd body burden because only a minuscule amount of Cd can be excreted each day. The International Agency for Research on Cancer listed Cd as a human lung carcinogen, but the current evidence suggests that the effects of Cd on cancer risk extend beyond the lung. A two-year bioassay demonstrated that Cd caused neoplasms in multiple tissues of mice. Also, several non-tumorigenic human cells transformed to malignant cells when they were exposed to a sublethal dose of Cd for a prolonged time. Cd does not directly damage DNA, but it influences gene expression through interactions with essential metals and various proteins. The present review highlights the epidemiological studies that connect an enhanced risk of various neoplastic diseases to chronic exposure to environmental Cd. Special emphasis is given to the impact of body iron stores on the absorption of Cd, and its implications for breast cancer prevention in highly susceptible groups of women. Resistance to cell death and other cancer phenotypes acquired during Cd-induced cancer cell transformation, under in vitro conditions, are briefly discussed. The potential role for the ZnT1 efflux transporter in the cellular acquisition of tolerance to Cd cytotoxicity is highlighted.

Cadmium Toxicity and Health Effects-A Brief Summary

Cadmium (Cd) is a ductile metal in the form of a blueish or silvery-white powder. It is naturally found in soil (about 0.2 mg/kg), minerals, and water. Cd belongs to the group of toxic, carcinogenic, and stimulating elements. Its biological half-life in the human body ranges from 16 to even 30 years on average. Some lung diseases (such as emphysema, asthma, and bronchitis) and high blood pressure are thought to be related to slow poisoning. The symptoms of cadmium poisoning may vary depending on the time of exposure, the type of diet, and the age and health status of the exposed people. For non-smokers and non-occupational exposures, the only source of exposure is diet. The FAO/WHO recommends that the tolerable cadmium intake for an adult is approximately 0.4-0.5 mg/week (60-70 µg per day). Cadmium is primarily absorbed through the respiratory system (about 13-19% of Cd from the air), but it can also enter through the digestive system (about 10-44%), when dust is mixed and swallowed with saliva. The amount of accumulated Cd ranges from 0.14 to 3.2 ppm in muscles, 1.8 ppm in bones, and 0.0052 ppm in the blood. People who are most frequently exposed to heavy metals should be continuously monitored in order to maintain a healthy lifestyle, as well as to implement effective preventive measures and improve public health.

Estimation of health risks associated with dietary cadmium exposure

In much of the world, currently employed upper limits of tolerable intake and acceptable excretion of cadmium (Cd) (ECd/Ecr) are 0.83 µg/kg body weight/day and 5.24 µg/g creatinine, respectively. These figures were derived from a risk assessment model that interpreted β2-microglobulin (β2MG) excretion > 300 μg/g creatinine as a "critical" endpoint. However, current evidence suggests that Cd accumulation reduces glomerular filtration rate at values of ECd/Ecr much lower than 5.24 µg/g creatinine. Low ECd/Ecr has also been associated with increased risks of kidney disease, type 2 diabetes, osteoporosis, cancer, and other disorders. These associations have cast considerable doubt on conventional guidelines. The goals of this paper are to evaluate whether these guidelines are low enough to minimize associated health risks reliably, and indeed whether permissible intake of a cumulative toxin like Cd is a valid concept. We highlight sources and levels of Cd in the human diet and review absorption, distribution, kidney accumulation, and excretion of the metal. We present evidence for the following propositions: excreted Cd emanates from injured tubular epithelial cells of the kidney; Cd excretion is a manifestation of current tissue injury; reduction of present and future exposure to environmental Cd cannot mitigate injury in progress; and Cd excretion is optimally expressed as a function of creatinine clearance rather than creatinine excretion. We comprehensively review the adverse health effects of Cd and urine and blood Cd levels at which adverse effects have been observed. The cumulative nature of Cd toxicity and the susceptibility of multiple organs to toxicity at low body burdens raise serious doubt that guidelines concerning permissible intake of Cd can be meaningful.

The function of omega-3 polyunsaturated fatty acids in response to cadmium exposure

Throughout history, pollution has become a part of our daily life with the improvement of life quality and the advancement of industry and heavy industry. In recent years, the adverse effects of heavy metals, such as cadmium (Cd), on human health have been widely discussed, particularly on the immune system. Here, this review summarizes the available evidence on how Cd exposure may affect health. By analyzing the general manifestations of inflammation caused by Cd exposure, we find that the role of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) in vivo can counteract Cd-induced harm. Additionally, we elucidate the effects of n-3 PUFAs on the immune system, and analyze their prophylactic and therapeutic effects on Cd exposure. Overall, this review highlights the role of n-3 PUFAs in the pathological changes induced by Cd exposure. Although n-3 PUFAs remain to be verified whether they can be used as therapeutic agents, as rehabilitation therapy, supplementation with n-3 PUFAs is reliable and effective.

Unboxing the molecular modalities of mutagens in cancer

The etiology of the majority of human cancers is associated with a myriad of environmental causes, including physical, chemical, and biological factors. DNA damage induced by such mutagens is the initial step in the process of carcinogenesis resulting in the accumulation of mutations. Mutational events are considered the major triggers for introducing genetic and epigenetic insults such as DNA crosslinks, single- and double-strand DNA breaks, formation of DNA adducts, mismatched bases, modification in histones, DNA methylation, and microRNA alterations. However, DNA repair mechanisms are devoted to protect the DNA to ensure genetic stability, any aberrations in these calibrated mechanisms provoke cancer occurrence. Comprehensive knowledge of the type of mutagens and carcinogens and the influence of these agents in DNA damage and cancer induction is crucial to develop rational anticancer strategies. This review delineated the molecular mechanism of DNA damage and the repair pathways to provide a deep understanding of the molecular basis of mutagenicity and carcinogenicity. A relationship between DNA adduct formation and cancer incidence has also been summarized. The mechanistic basis of inflammatory response and oxidative damage triggered by mutagens in tumorigenesis has also been highlighted. We elucidated the interesting interplay between DNA damage response and immune system mechanisms. We addressed the current understanding of DNA repair targeted therapies and DNA damaging chemotherapeutic agents for cancer treatment and discussed how antiviral agents, anti-inflammatory drugs, and immunotherapeutic agents combined with traditional approaches lay the foundations for future cancer therapies.

Health significant alarms of toxic carcinogenic risk consumption of blood meal metals contamination in poultry at a gold mining neighborhood, northern Thailand

The proposes of this study were to compare THg (total mercury), Pb(Lead), Cd(Cadmium), and Mn (Manganese) contamination in poultry blood between polluted areas (≤ 25 km) and unpolluted areas (> 25 km) adjacent to the largest gold mining in northern Thailand. The THg level in the free-grazing duck in polluted areas was significantly higher than unpolluted area. Both THg and Pb levels in free-grazing duck were also highest in polluted areas. In contrast, the level of (Mn) in chicken blood was the highest in polluted areas. Cadmium in farmed duck from polluted areas was significantly higher than unpolluted areas. The target hazard quotient (THQ) and hazard index (HI) of Hg, Pb, Cd, and Mn in all age groups in both areas did not exceed 1, meaning there is no possibility of the non-carcinogenic toxicity. Whereas, the incremental lifetime cancer risk (ILCR) of both Pb and Cd exceeded 1 × 10^-4 in all age groups and these were particularly higher in the polluted area and considered to yield significant health effects of increasing the cancer risk. The ILCR in descending order for Pb and Cd was 13-18 years old = 18-35 years old > 6-13 years old = 35-65 years old > 3-6 years old > 65 up years old, respectively. The results revealed that the human cancer risk related to consuming poultry blood contaminated with both Pb and Cd in all age groups must be of concern, especially 13-18 and 18-35 years, it must be recommended to avoid raising animals in contaminated areas, especially free-grazing duck.

Exposure to cadmium and head and neck cancers: a meta-analysis of observational studies

Cadmium (Cd) is a widespread environmental pollutant. A number of observational studies have reported that Cd might be a cause of nasopharyngeal (NPC), pharyngeal (PC), or laryngeal cancers (LC). In this study evidence about the relation of Cd and NPC, PC, and LC has been summarized. A literature review was conducted until 20 June 2020 in PubMed, Ovid, Scopus, Web of Science and Google scholar databases to investigate the epidemiologic evidence for the relation between cadmium exposure and cancers of the nasopharynx, pharynx, and larynx. Ten articles were selected after careful screening of retrieved studies. All of these studies obtained a Newcastle-Ottawa Scale (NOS) quality score from 6 to 8. Due to high heterogeneity, in all analyses, random effect was used. The pooled results showed that cadmium levels in NPC (standard mean difference (SMD=0.55; 95% CI=0.20, 0.89; p=0.002) and PC (SMD=9.79; 95% CI=0.62, 18.96; p=0.036) patients/tissues were significantly higher than their controls. But cadmium levels were not significantly different between LC cases/tissues and their controls. (SMD=-0.05; 95% CI=-0.99, 0.89; p=0.921). Exposure to cadmium is likely to cause nasopharyngeal and pharyngeal cancer.

Timing of Toenail Collection and Concentrations of Metals in Pancreatic Cancer. Evidence Against Disease Progression Bias

Trace elements such as cadmium, arsenic, zinc or selenium increase or decrease risk of a wide range of human diseases. Their levels in toenails may provide a measure of mid-term intake of trace elements for studies in humans. However, in biologically and clinically aggressive diseases as pancreatic cancer, the progression of the disease could modify such concentrations and produce reverse causation bias. The aim was to analyze the influence of specific time intervals between several clinical events and the collection of toenails upon concentrations of trace elements in patients with pancreatic cancer. Subjects were 118 incident cases of pancreatic adenocarcinoma prospectively recruited in eastern Spain. Toenails were collected at cancer diagnosis, and soon thereafter interviews were conducted. Information on cancer signs and symptoms was obtained from medical records and patient interviews. Levels of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. General linear models adjusting for potential confounders were applied to analyze relations between log concentrations of trace elements and the time intervals, including the interval from first symptom of cancer to toenail collection (iST). Toenail concentrations of the 12 trace elements were weakly or not influenced by the progression of the disease or the diagnostic procedures. Concentrations of aluminum were slightly higher in subjects with a longer iST (age, sex and stage adjusted geometric means: 11.44 vs. 7.75 µg/g for iST > 120 days vs. ≤ 40 days). There was a weak inverse relation of iST with concentrations of zinc and selenium (maximum differences of about 20 and 0.08 µg/g, respectively). Conclusions: concentrations of the trace elements were weakly or not influenced by the development of the disease before toenail collection. Only concentrations of aluminum increased slightly with increasing iST, whereas levels of zinc and selenium decreased weakly. Even in an aggressive disease as pancreatic cancer, toenail concentrations of trace elements may provide a valid measure of mid-term intake of trace elements, unaffected by clinical events and disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-021-00436-2.

Cadmium tissue level in women diagnosed with breast cancer - A case control study

Breast cancer is at the forefront of female malignancy and the leading cause of cancer death among women. Gender, age, hormone therapy, smoking, exposure to endocrine disruptors and family history are significant breast cancer risk factors according to epidemiological data. Considering metalloestrogenic Cd property and a plethora of research work on hormone involvement in breast cancer the study aimed to determine Cd concentration in three compartments of breast cancer patients in relation to their blood hormone status. Further, as oxidative stress is a critical mechanism of Cd toxicity, the objective of this study was to determine potential changes in oxidative status homeostasis. The study enrolled 55 patients with breast cancer diagnosis and 41 healthy women with benign breast changes. Concentration of Cd was determined using graphite furnace atomic absorption spectrometry. Cadmium concentration in tumor tissue was significantly higher than control and almost four times higher than Cd concentration in the healthy surrounding tissue. Strong positive correlation was observed between Cd concentrations in changed breast tissue and FSH and LH levels, while the correlation was negative with estradiol level. Cancer patients had significantly increased blood total antioxidative status while total oxidative status did not significantly differ between study groups. The study revealed Cd implication in breast cancer onset following a significant odd ratio for Cd levels in changed tissue samples. Moreover, presented data confirmed sex hormone and oxidative status imbalance caused by Cd presence, closely related to cancer development.

Mercury in Pancreatic Cells of People with and without Pancreatic Cancer

Toxic metals have been implicated in the pathogenesis of pancreatic cancer. Human exposure to mercury is widespread, but it is not known how often mercury is present in the human pancreas and which cells might contain mercury. We therefore aimed to determine, in people with and without pancreatic cancer, the distribution and prevalence of mercury in pancreatic cells. Paraffin-embedded sections of normal pancreatic tissue were obtained from pancreatectomy samples of 45 people who had pancreatic adenocarcinoma, and from autopsy samples of 38 people without pancreatic cancer. Mercury was identified using two methods of elemental bio-imaging: (1) With autometallography, inorganic mercury was seen in islet cells in 14 of 30 males (47%) with pancreatic cancer compared to two of 17 males (12%) without pancreatic cancer (p = 0.024), and in 10 of 15 females (67%) with pancreatic cancer compared to four of 21 females (19%) without pancreatic cancer (p = 0.006). Autometallographic mercury was present in acinar cells in 24% and in periductal cells in 11% of people with pancreatic cancer, but not in those without pancreatic cancer. (2) Laser ablation-inductively coupled plasma-mass spectrometry confirmed the presence of mercury in islets that stained with autometallography and detected cadmium, lead, chromium, iron, nickel and aluminium in some samples. In conclusion, the genotoxic metal mercury is found in normal pancreatic cells in more people with, than without, pancreatic cancer. These findings support the hypothesis that toxic metals such as mercury contribute to the pathogenesis of pancreatic cancer.

Effects of lead and cadmium on the immune system and cancer progression

In our daily life, we are surrounded by harmful pollutants, including heavy metals that are not visible in the macroscopic view easily. Heavy metals can disrupt different aspects of human health, such as the immune system which has gained a lot of attention in recent decades. This had led to its rapid progression and new insights into its alterations in different diseases especially cancer. Heavy metals are non-biodegradable materials that exist in different parts of the food cycle, such as fruits and vegetables as commonly consumed foods and also unexpected sources such as street dust, that exists in the streets that we pass every day, soil, air, and water. These heavy metals can enter the human body through respiratory, cutaneous, and gastrointestinal pathways and then accumulate in different organs, leading to their encountering with various parts of the body. These sources and natural characteristics of heavy metals facilitate their interaction with the immune system. In this review, we investigated the effect of lead and cadmium, as pollutants that exist in many different parts of the human environment, on the immune system which is known to have a key role in the pathophysiology of cancer.

Comparison and Risk Assessment for Trace Heavy Metals in Raw Pu-erh Tea with Different Storage Years

This research conducted an exploration of the content of microelements (As, Cr, Cd, Pb, Cu, Zn, Mn, and Hg) in raw Pu-erh tea with different storage years. The contents of As, Cr, Cd, Pb, Cu, Zn, Mn, and Hg were 0.14, 0.82, 0.02, 0.52, 14.59, 33.51, 564.02, and 0.01 μg/g, respectively, and were all less than the national standard limit values in China. The target hazard quotients (THQs) of each heavy metal were all lower than 1, and the value of combined risk hazard index (HI) of all to adults was 0.221, which presents no health risk when consumed properly by adults of the raw Pu-erh tea infusions. Interestingly, there was no significant correlation between the heavy metal element (As, Cr, Cd, Pb, Cu, Zn, Mn, and Hg) contents and the THQ values of raw Pu-erh tea samples and storage years; the correlation coefficients (R²) range from 0.01 to 0.33 and from 0.01 to 0.57, respectively. The result showed that the storage years showed no effect on the exposure risk of heavy metals; the heavy metal elements in tea samples come from the atmosphere and soil.

The Effects of Cadmium Toxicity

Cadmium (Cd) is a toxic non-essential transition metal that poses a health risk for both humans and animals. It is naturally occurring in the environment as a pollutant that is derived from agricultural and industrial sources. Exposure to cadmium primarily occurs through the ingestion of contaminated food and water and, to a significant extent, through inhalation and cigarette smoking. Cadmium accumulates in plants and animals with a long half-life of about 25-30 years. Epidemiological data suggest that occupational and environmental cadmium exposure may be related to various types of cancer, including breast, lung, prostate, nasopharynx, pancreas, and kidney cancers. It has been also demonstrated that environmental cadmium may be a risk factor for osteoporosis. The liver and kidneys are extremely sensitive to cadmium's toxic effects. This may be due to the ability of these tissues to synthesize metallothioneins (MT), which are Cd-inducible proteins that protect the cell by tightly binding the toxic cadmium ions. The oxidative stress induced by this xenobiotic may be one of the mechanisms responsible for several liver and kidney diseases. Mitochondria damage is highly plausible given that these organelles play a crucial role in the formation of ROS (reactive oxygen species) and are known to be among the key intracellular targets for cadmium. When mitochondria become dysfunctional after exposure to Cd, they produce less energy (ATP) and more ROS. Recent studies show that cadmium induces various epigenetic changes in mammalian cells, both in vivo and in vitro, causing pathogenic risks and the development of various types of cancers. The epigenetics present themselves as chemical modifications of DNA and histones that alter the chromatin without changing the sequence of the DNA nucleotide. DNA methyltransferase, histone acetyltransferase, histone deacetylase and histone methyltransferase, and micro RNA are involved in the epigenetic changes. Recently, investigations of the capability of sunflower (Helianthus annuus L.), Indian mustard (Brassica juncea), and river red gum (Eucalyptus camaldulensis) to remove cadmium from polluted soil and water have been carried out. Moreover, nanoparticles of TiO2 and Al2O3 have been used to efficiently remove cadmium from wastewater and soil. Finally, microbial fermentation has been studied as a promising method for removing cadmium from food. This review provides an update on the effects of Cd exposure on human health, focusing on the cellular and molecular alterations involved.

Concentrations of trace elements and KRAS mutations in pancreatic ductal adenocarcinoma

Trace elements are a possible risk factor for pancreatic ductal adenocarcinoma (PDAC). However, their role in the occurrence and persistence of KRAS mutations remains unstudied. There appear to be no studies analyzing biomarkers of trace elements and KRAS mutations in any human cancer. We aimed to determine whether patients with KRAS mutated and nonmutated tumors exhibit differences in concentrations of trace elements. Incident cases of PDAC were prospectively identified in five hospitals in Spain. KRAS mutational status was determined through polymerase chain reaction from tumor tissue. Concentrations of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. Concentrations of trace elements were compared in 78 PDAC cases and 416 hospital-based controls (case-control analyses), and between 17 KRAS wild-type tumors and 61 KRAS mutated tumors (case-case analyses). Higher levels of iron, arsenic, and vanadium were associated with a statistically nonsignificant increased risk of a KRAS wild-type PDAC (OR for higher tertile of arsenic = 3.37, 95% CI 0.98-11.57). Lower levels of nickel and manganese were associated with a statistically significant higher risk of a KRAS mutated PDAC (OR for manganese = 0.34, 95% CI 0.14-0.80). Higher levels of selenium appeared protective for both mutated and KRAS wild-type PDAC. Higher levels of cadmium and lead were clear risk factors for both KRAS mutated and wild-type cases. This is the first study analyzing biomarkers of trace elements and KRAS mutations in any human cancer. Concentrations of trace elements differed markedly between PDAC cases with and without mutations in codon 12 of the KRAS oncogene, thus suggesting a role for trace elements in pancreatic and perhaps other cancers with such mutations. Environ. Mol. Mutagen., 60:693-703, 2019. © 2019 Wiley Periodicals, Inc.

Tobacco carcinogens and the methionine metabolism in human bladder cancer

Cigarette smoking is a strong risk factor for bladder cancer. It has been shown that the duration of smoking is associated with a poor prognosis and a higher risk of recurrence. This is due to tobacco carcinogens forming adducts with DNA and proteins that participate in the DNA repair mechanisms. Additionally, polymorphisms of genes responsible for methyl group transfer in the methionine cycle and dosages of vitamins (from diet and supplements) can cause an increased risk of bladder cancer. Upregulated DNA methyltransferase 1 expression and activity results in a high level of methylated products of metabolism, as well as hypermethylation of tumor suppressor genes. The development of a market that provides new inhibitors of DNA methyltransferase or alternatives for current smokers is essential not only for patients but also for people who are under the danger of secondhand smoking and can experience its long-term exposure consequences.

Environmental cadmium exposure and pancreatic cancer: Evidence from case control, animal and in vitro studies

Although profoundly studied, etiology of pancreatic cancer (PC) is still rather scarce. Some of established risk factors of PC are connected to an increased cadmium (Cd) body burden. Hence, the aim of this study was to investigate the role of this environmental pollutant in PC development by conducting human observational, experimental and in vitro studies. The case-control study included 31 patients with a histologically based diagnosis of exocrine PC subjected to radical surgical intervention as cases and 29 accidental fatalities or subjects who died of a nonmalignant illness as controls. Animal study included two treated groups of Wistar rats (15 and 30 mg Cd/kg b.w) and untreated control group, sacrificed 24 h after single oral exposure. In in vitro study pancreas hTERT-HPNE and AsPC-1 cells were exposed to different Cd concentrations corresponding to levels measured in human cancerous pancreatic tissue. Cd content in cancer tissue significantly differed from the content in healthy controls. Odds ratio levels for PC development were 2.79 (95% CI 0.91-8.50) and 3.44 (95% CI 1.19-9.95) in the third and fourth quartiles of Cd distribution, respectively. Animal study confirmed Cd deposition in pancreatic tissue. In vitro studies revealed that Cd produces disturbances in intrinsic pathway of apoptotic activity and the elevation in oxidative stress in pancreatic cells. This study presents three different lines of evidence pointing towards Cd as an agent responsible for the development of PC.

Potential interaction of cadmium chloride with pancreatic mitochondria: Implications for pancreatic cancer

Pancreatic cancer (PC) is insidious with a high mortality rate due to the lack of symptomology prior to diagnosis. Mitochondrial involvement in PC development is becoming accepted, and exposure to cadmium (Cd) is suspected of being a risk factor for the development of PC; however, the mechanisms involved remain unclear. In this study, we examined the role of Cd as a mitochondrial toxicant and whether alterations in mitochondrial function may be an underlying cause for the development of PC. In this study, cadmium chloride (CdCl2)‑mediated toxicity in hTERT‑HPNE and AsPC‑1 pancreatic cell lines was determined by MTT assay. We also investigated the release of LDH and the generation of free radicals. Mitochondrial toxicity assays were performed in media containing glucose (25 mM) or galactose (10 mM) and following exposure to CdCl2 (0‑100 µM) followed by MTT assay. For the confirmation of mitochondrial toxicity, we measured the release of ATP following exposure to CdCl2. Initial experiments confirmed that exposure to CdCl2 did not reduce the viability of either cell line until a concentration of >10 µM was used. Non‑linear analysis of the response curves revealed lethal concentration 50% (LC50) values for CdCl2 in the HPNE cells of 77 µM compared to 42 µM in the AsPC‑1 cells (P<0.01). The CdCl2‑mediated mitochondrial toxic effects were greater in the HPNE cells, suggesting a heightened sensitivity to the effects of CdCl2, not due to elevated oxidative stress. Increased mitochondrial toxic sensitivity was indicated by a 73.4% reduction in IC50 values in the HPNE cells cultured in galactose compared to culture in glucose media, whereas the AsPC‑1 cells exhibited a 58.8% reduction in IC50 values. In addition, the higher concentration of CdCl2 elicited a significant cell‑dependent effect on ATP release in both cell lines, suggestive of CdCl2 being a mitochondrial toxicant. Cell survival was unaffected following exposure to low concentrations of CdCl2; however, exposure did alter mitochondrial function (control cells > tumor cells). Therefore, the findings of this study indicate that the mitochondria may be a site of action for cadmium in promoting tumor development.

Toenail concentrations of trace elements and occupational history in pancreatic cancer

BACKGROUND

Some occupations potentially entailing exposure to cadmium, arsenic, lead, selenium, nickel, and chromium have been associated with an increased risk of exocrine pancreatic cancer (EPC), but no studies have assessed whether body concentrations of such compounds differed among subjects occupationally exposed and unexposed. No studies which found that exposure to such metals increased the risk of EPC assessed whether past occupations were the source of exposure.

OBJECTIVE

The aim was to analyse the relationship between toenail concentrations of trace elements and occupational history in EPC patients.

METHODS

The study included 114 EPC cases personally interviewed on occupational history and lifestyle factors. Occupations were coded according to the International Standard Classification of Occupations 1988. Selected occupational exposures were assessed by two industrial hygienists and with the Finnish job-exposure matrix (Finjem). Concentrations of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. Adjusted geometric means (aGMs) and 95% confidence intervals (95% CI) were calculated.

RESULTS

Patients occupationally exposed to aromatic hydrocarbon solvents (AHs) had higher concentrations of cadmium, manganese, lead, iron and vanadium. The aGM of cadmium concentrations for cases exposed to any pesticide was 0.056 μg/g [95% CI: 0.029-0.108], and, for unexposed cases, 0.023 μg/g [0.017-0.031]. Patients occupationally exposed to pesticides had higher concentrations of cadmium and manganese. Higher concentrations of vanadium, lead and arsenic were related to exposure to formaldehyde. Vanadium and lead were also associated with exposure to chlorinated hydrocarbon solvents, and arsenic was related to exposure to polycyclic aromatic hydrocarbons (PAHs).

CONCLUSIONS

Patients occupationally exposed to AHs, pesticides, chlorinated hydrocarbon solvents, formaldehyde, volatile sulphur compounds and PAHs had higher concentrations of several metals. These elements may account for some of the occupational risks previously reported for pancreatic cancer.

Cadmium-induced hepatocellular injury: Modulatory effects of γ-glutamyl cysteine on the biomarkers of inflammation, DNA damage, and apoptotic cell death

Cadmium is an extremely toxic pollutant that reaches human body through intake of the industrially polluted food and water as well as through cigarette smoking and exposure to polluted air. Cadmium accumulates in different body organs especially the liver. It induces tissue injury largely through inflammation and oxidative stress-based mechanisms. The aim of the current study was to investigate the ability of γ glutamyl cysteine (γGC) to protect against cadmium-induced hepatocellular injury employing Wistar rats as a mammalian model. The results of the current work indicated that γGC upregulated the level of the anti-inflammatory cytokine IL-10 and downregulated the levels of the pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in the cadmium-exposed rats. In addition, γGC reduced the liver tissues cadmium content in the cadmium-treated rats, suppressed the cadmium-induced hepatocellular apoptosis and oxidative modifications of cellular DNA, lipids, and proteins. Additionally, γGC enhanced the antioxidant potential of the liver tissues in the cadmium-treated rats as evidenced by a remarkable increase in the activity of the antioxidant enzymes superoxide dismutase and glutathione peroxidase and significant increase in the levels of the total antioxidant capacity and reduced glutathione as well as a significant reduction in oxidized to reduced glutathione (GSSG/GSH) ratio. Moreover, it effectively improved liver cell integrity in the cadmium-treated rats as demonstrated by a significant reduction in the serum activity of the liver enzymes (ALT and AST) and amelioration of the cadmium-evoked histopathological alterations. Together, these findings underscore, for the first time, the alleviating effects of γGC against cadmium-induced hepatocellular injury that is potentially mediated through reduction of liver tissue cadmium content along with modulation of both hepatocellular redox status and inflammatory cytokines.

Extract from Aronia melanocarpa L. Berries Prevents Cadmium-Induced Oxidative Stress in the Liver: A Study in A Rat Model of Low-Level and Moderate Lifetime Human Exposure to this Toxic Metal

The study investigated, in a rat model of low-level and moderate environmental exposure to cadmium (Cd; 1 or 5 mg Cd/kg diet, respectively, for 3 to 24 months), whether the co-administration of 0.1% extract from Aronia melanocarpa L. berries (AE) may protect against oxidative stress in the liver and in this way mediate this organ status. The intoxication with Cd, dose- and duration-dependently, weakened the enzymatic antioxidative barrier, decreased the concentrations of reduced glutathione and total thiol groups, and increased the concentrations of oxidized glutathione, hydrogen peroxide, xanthine oxidase, and myeloperoxidase in this organ. These resulted in a decrease in the total antioxidative status, increase in the total oxidative status and development of oxidative stress (increased oxidative stress index and malondialdehyde concentration) and histopathological changes in the liver. The administration of AE at both levels of Cd treatment significantly improved the enzymatic and nonenzymatic antioxidative barrier, decreased pro-oxidant concentration, and protected from the development of oxidative stress in the liver and changes in its morphology, as well as normalized the serum activities of liver enzymes markers. In conclusion, consumption of aronia products may prevent Cd-induced destroying the oxidative/antioxidative balance and development of oxidative stress in the liver protecting against this organ damage.

Roles of ROS, Nrf2, and autophagy in cadmium-carcinogenesis and its prevention by sulforaphane

Environmental and occupational exposures to cadmium increase the risk of various cancers, including lung cancer. The carcinogenic mechanism of cadmium, including its prevention remains to be investigated. Using fluorescence and electron spin resonance spin trapping, the present study shows that in immortalized lung cells (BEAS-2BR cells), exposure cadmium generated reactive oxygen species (ROS). Through ROS generation, cadmium increased the protein level of TNF-α, which activated NF-κB and its target protein COX-2, creating an inflammatory microenvironment. As measured by anchorage-independent colony formation assay, cadmium induced malignant cell transformation. Inhibition of ROS by antioxidants inhibited transformation, showing that ROS were important in the mechanism of this process. The inflammatory microenvironment created by cadmium may also contribute to the mechanism of the transformation. Using tandem fluorescence protein mCherry-GFP-LC3 construct, the present study shows that cadmium-transformed cells had a property of autophagy deficiency, resulting in accumulation of autophagosomes and increased p62. This protein upregulated Nrf2, which also upregulated p62 through positive feed-back mechanism. Constitutive Nrf2 activation increased its downstream anti-apoptotic proteins, Bcl-2 and Bcl-xl, resulting in apoptosis resistance. In untransformed BEAS-2BR cells, sulforaphane, a natural compound, increased autophagy, activated Nrf2, and decreased ROS. In cadmium-transformed BEAS-2BR cells, sulforaphane restored autophagy, decreased Nrf2, and decreased apoptosis resistance. In untransformed cells, this sulforaphane induced inducible Nrf2 to decrease ROS and possibly malignant cell transformation. In cadmium-transformed cells, it decreased constitutive Nrf2 and reduced apoptosis resistance. The dual roles of sulforaphane make this natural compound a valuable agent for prevention against cadmium-induced carcinogenesis.

Environmental exposure to cadmium-a risk for health of the general population in industrialized countries and preventive strategies

Cadmium (Cd) is a heavy metal belonging to the group of the main chemical pollutants of the natural and occupational environment in economically developed countries. The forecasts indicate that contamination of the environment with this toxic metal, and thus the exposure of the general population, will increase. Food (particularly plant products) is the main source of the general population exposure to this element. Moreover, an important, and often the main, source of intoxication with Cd is habitual tobacco smoking. Recent epidemiological studies have provided numerous evidence that even low-level environmental exposure to this toxic metal, nowadays occurring in numerous economically developed countries, creates a risk for health of the general population. The low-level lifetime exposure to this metal may lead to the damage to the kidneys, liver, skeletal system, and cardiovascular system, as well as to the deterioration of the sight and hearing. Moreover, it has been suggested that environmental exposure to this xenobiotic may contribute to the development of cancer of the lung, breast, prostate, pancreas, urinary bladder, and nasopharynx. Taking the above into account, the aim of this review article is to draw more attention to Cd as an environmental risk factor for the health of the general population and the need to undertake preventive actions allowing to reduce the risk of health damage due to a lifetime exposure to this toxic metal.

Pancreatic cancer: Current status and Challenges

PURPOSE OF THE REVIEW

The 5-year survival rate of patients with pancreatic cancer (PanCA) has remained stagnant. Unfortunately, the incidence is almost equal to mortality rates. These facts underscore the importance of concerted efforts to understand the pathology of this disease. Deregulation of multiple signaling pathways involved in a wide variety of cellular processes including proliferation, apoptosis, invasion, and metastasis contribute not only to cancer development but also to therapeutic resistance. The purpose of this review is to summarize current understanding of etiological factors including emerging evidence on the role of infectious agents, factors associated with therapeutic resistance and therapeutic options.

RECENT FINDINGS

The unique aspect of PanCA is "desmoplasia", a process that involves proliferation of stromal fibroblasts and collagen deposition in and around the filtrating cancer. Recent studies have identified pancreatic stellate cells (PSCs) as a potential source of such desmoplasia. Biphasic interactions between PSCs and cancer cells, endothelial cells, and/or myeloid derived suppressor cells in the tumor microenvironment contribute to pancreatic carcinogenesis.

SUMMARY

We summarize limitations of current therapeutic approaches and potential strategies to overcome these limitations using natural products including botanicals as adjuvant/neo-adjuvant for effective management of PanCA.

Cadmium Exposure as a Putative Risk Factor for the Development of Pancreatic Cancer: Three Different Lines of Evidence

Although profoundly studied, etiology of pancreatic cancer (PC) is still rather scant. Exposure to cadmium (Cd), a ubiquitous metal associated with well-established toxic and carcinogenic properties, has been hypothesized to one putative cause of PC. Hence, we analyzed recently published observational studies, meta-analyses, and experimental animal and in vitro studies with the aim of summarizing the evidence of Cd involvement in PC development and describing the possible mechanisms. Consolidation of epidemiological data on PC and exposure to Cd indicated a significant association with an elevated risk of PC among general population exposed to Cd. Cadmium exposure of laboratory animals was showed to cause PC supporting the findings suggested by human studies. The concordance with human and animal studies is buttressed by in vitro studies, although in vitro data interpretation is problematic. In most instances, only significant effects are reported, and the concentrations of Cd are excessive, which would skew interpretation. Previous reports suggest that oxidative stress, apoptotic changes, and DNA cross-linking and hypermethylation are involved in Cd-mediated carcinogenesis. Undoubtedly, a significant amount of work is still needed to achieve a better understanding of the Cd involvement in pancreatic cancer which could facilitate prevention, diagnosis, and therapy of this fatal disease.

Environmental risk factors for pancreatic cancer: an update

Pancreatic cancer (PC) is one of the most aggressive diseases. Only 10 % of all PC cases are thought to be due to genetic factors. Here, we analyzed the most recently published case-control association studies, meta-analyses, and cohort studies with the aim to summarize the main environmental factors that could have a role in PC. Among the most dangerous agents involved in the initiation phase, there are the inhalation of cigarette smoke, and the exposure to mutagenic nitrosamines, organ-chlorinated compounds, heavy metals, and ionizing radiations. Moreover, pancreatitis, high doses of alcohol drinking, the body microbial infections, obesity, diabetes, gallstones and/or cholecystectomy, and the accumulation of asbestos fibers seem to play a crucial role in the progression of the disease. However, some of these agents act both as initiators and promoters in pancreatic acinar cells. Protective agents include dietary flavonoids, marine omega-3, vitamin D, fruit, vegetables, and the habit of regular physical activity. The identification of the factors involved in PC initiation and progression could be of help in establishing novel therapeutic approaches by targeting the molecular signaling pathways responsive to these stimuli. Moreover, the identification of these factors could facilitate the development of strategies for an early diagnosis or measures of risk reduction for high-risk people.

Heavy Metal Accumulation is Associated with Molecular and Pathological Perturbations in Liver of Variola louti from the Jeddah Coast of Red Sea

Large amounts of waste water are discharged daily from the Jeddah Metropolitan Area into the Red Sea. Sewage draining into the Red Sea causes widespread chemical pollution that is toxic to aquatic ecosystems. The objective of this study was to investigate the extent of pollution and assess the presence of heavy metals in fish tissue and study their association with biological and biochemical alterations. The average concentrations of heavy metals found in hepatic tissues of Variola louti fish from the polluted area, namely Cd, Cr, Cu, Fe and Zn, were 1.74, 9.69, 47.48, 4020.01 and 229.47 µg/g liver, respectively, that were significantly higher than that of samples taken from reference area (0.24, 1.98, 20.12, 721.93, 129.21 µg/g liver, respectively). The fold change of heavy metals in fish from the polluted area with respect of that of the reference area followed the order Cd > Fe > Cr > Cu > Zn. Analysis of nuclear DNA revealed that hepatic tissues of fish samples from the polluted area showed a significant increase in apoptotic cells as detected by flow cytometry and formation DNA-ladder. In addition, hepatic sections from polluted area fishes showed more fibrotic changes and collagen deposition by hematoxylin-eosin staining and Masson's trichrome staining, respectively, compared to samples taken from the reference area. Moreover, the electrophoretic patterns of proteins of liver of fishes caught at the polluted area showed different patterns of proteins from that of the reference with bands at 42, 130 and 140 kDa, which is in a good agreement with the molecular weight of collagen type III. In conclusion, there were significant changes in the tissues of fishes in the polluted area at the cellular and the molecular levels that may be associated with an accumulation of heavy metals. Assessment of fishes as a sensitive biomonitor for the pollution of surface waters that may affect general health of human and wild life is conceivable.