Can selenium be a modifier of cancer risk in CHEK2 mutation carriers?

Trace elements and the thyroid

Trace elements, such as iodine and selenium (Se), are vital to human health and play an essential role in metabolism. They are also important to thyroid metabolism and function, and correlate with thyroid autoimmunity and tumors. Other minerals such as iron (Ir), lithium (Li), copper (Co), zinc (Zn), manganese (Mn), magnesium (Mg), cadmium (Cd), and molybdenum (Mo), may related to thyroid function and disease. Normal thyroid function depends on a variety of trace elements for thyroid hormone synthesis and metabolism. These trace elements interact with each other and are in a dynamic balance. However, this balance may be disturbed by the excess or deficiency of one or more elements, leading to abnormal thyroid function and the promotion of autoimmune thyroid diseases and thyroid tumors.The relationship between trace elements and thyroid disorders is still unclear, and further research is needed to clarify this issue and improve our understanding of how trace elements mediate thyroid function and metabolism. This paper systematically reviewed recently published literature on the relationship between various trace elements and thyroid function to provide a preliminary theoretical basis for future research.

Selenium Deficiency—From Soil to Thyroid Cancer

Selenium (Se) is an essential micronutrient present in human diet, entering in the composition of selenoproteins as selenocysteine (Se-Cys) amino acid. At the thyroid level, these proteins play an important role as antioxidant and in hormone metabolism. Selenoproteins are essential for the balance of redox homeostasis and antioxidant defense of mammalian organisms, while the corresponding imbalance is now recognized as the cause of many diseases including cancer. The food chain is the main source of Se in human body. Dietary intake is strongly correlated with Se content in soil and varies according to several factors such as geology and atmospheric input. Both Se deficiency and toxicity have been associated with adverse health effects. This review synthesizes recent data on the transfer of Se from soil to humans, Se U-shaped deficiency and toxicity uptake effects and particularly the impact of Se deficiency on thyroid cancer.

Selenium Diminishes Docetaxel-Induced Cell Death, Oxidative Stress, and Inflammation in the Laryngotracheal Epithelium of the Mouse

Docetaxel (DOCX) kills tumor cells through the formation of microtubules, calcium ion influx, apoptosis, and inflammation. However, DOCX has adverse effect on normal tissues through the production of reactive oxygen species (ROS), despite the adverse effect was inhibited by antioxidants. We investigated the protective role of selenium against DOCX-induced apoptosis and mitochondrial oxidative injury in laryngotracheal epithelial (LARYN) cells of mice. Thirty-two mice were divided into four groups (n = 8). The first group was used as a control. The second and third groups were treated with sodium selenite (Na-Sel) and DOCX, respectively. The fourth group was the combined group of Na-Sel and DOCX. At the end of the experiment, LARYN mucosa and cells were obtained from the mice. In the LARYN cells, the cell viability level was low in DOCX group, although glutathione peroxidase activity and cell viability level were increased by the treatment of Na-Sel. Increased lipid peroxidation, intracellular ROS, mitochondrial membrane depolarization, cell death levels, TNF-α, IL-1β, IL-6, caspase -3, and -9 activities in the DOCX group of LARYN cells were diminished by the treatment of Na-Sel. In conclusion, DOCX increased mitochondrial ROS, cell death, and inflammation in the LARYN cells, although the increase was reduced in the cells by Na-Sel treatment. DOCX-induced adverse oxidant, inflammatory, and apoptotic effects in the tissue might be reduced by the Na-Sel treatment.

Selenium Overcomes Doxorubicin Resistance in Their Nano-platforms Against Breast and Colon Cancers

Colon cancer in men and breast cancer in women are regarded as major health burdens, accounting for majority of cancer diagnoses globally. Doxorubicin (DOX) resistance in breast and colon cancers represents the main reason of unsuccessful therapy. The rationale of this study is to explore whether selenium nanoparticles (nano-Se) can overcome this resistance obstacle of DOX nanoparticles (nano-DOX) in these cancerous cells. Nano-Se and nano-DOX were manufactured and characterized using electron microscopy and Malvern ZetaSizer, applied separately or in the form of combinatorial regimen against human breast cancer cells (MCF7 and MDA-MB-231) and human colorectal cancer cells (HCT 116 and Caco-2). Cytotoxicity, early/late apoptosis, necrosis, cellular zinc, glucose uptake, and redox status were assessed after applying different nano-treatments versus their free counterparts. Nano-DOX induces cytotoxicity in MCF7 and Caco-2 more than MDA-MB-231 and HCT 116 cancerous cells. In addition, nano-DOX plus nano-Se diminish MCF7 and Caco-2 chemoresistance higher than MDA-MB-231 and HCT 116 cancerous cells. Moreover, Se and DOX nano-platforms inhibit glucose uptake. Furthermore, nano-DOX increases nitric oxide (NO) and malondialdehyde (MDA) in cancer cells' media, while nano-DOX combination with nano-Se rebalances the redox status with zinc augmentation. We reported that Caco-2 cancer cells are more sensitive than HCT 116 cancer cells to nano-DOX and nano-Se. Nano-DOX plus nano-Se induces cytotoxicity-mediated late apoptosis in Caco-2 more than HCT 116 cell lines. This de novo strategy could have great power to overcome the problem of DOX resistance during colon cancer therapy.

Nutritional status and follicular-derived thyroid cancer: An update

The incidence of differentiated thyroid cancer has been increasing in the last decades all over the world. Such a steady growth cannot be entirely attributable to more intensive thyroid nodule screening and more sensitive diagnostic procedures. Several environmental factors have changed with sufficient rapidity in the same time frame and may represent credible candidates for this increase. They include modified iodine intake, lifestyle-associated risk factors, exposure to various toxic compounds, pollutants and xenobiotics, nutritional deficiencies, eating habits and comorbidities. Foremost, nutritional patterns have gained high interest as possible promoters and modifiable risk factors for thyroid cancer in recent years. The aim of this narrative review is to focus on the relationship between thyroid cancer and nutritional factors, dietary habits and obesity. Low iodine intake has been associated to increased risk of thyroid cancer, favoring the development of more aggressive histotypes. Moreover, correction of iodine deficiency can shift thyroid cancer subtypes toward less aggressive forms, without affecting the overall risk for cancer. Actually, evidence regarding the association between selenium and vitamin D deficiency and thyroid cancer is very limited, despite their well-known anti-cancer potentials, and the clinical usefulness of their supplementation is still uncertain in this setting. Albeit the relationship between single foods and thyroid cancer is difficult to examine, fish and iodine-rich foods, vegetables, and fruits might exert protective effects on thyroid cancer risk. Conversely, no clear association has been found for other foods to date. Lastly, a clear association between obesity and the risk of thyroid cancer, with more aggressive behavior, seems to emerge from most studies, likely involving variations in thyroid function and chronic inflammation mediated by cytokines, insulin, leptin and adiponectins. Although no definite association between dietary factors and thyroid cancer has been firmly established so far, some nutritional patterns, together with excessive weight, seem to play a relevant role in thyroid cancer carcinogenesis as well as in its severity and aggressiveness. These effects may play an additive role to the well-established one exerted by environmental carcinogens, such as pollutants and radiation exposure.

Selenium Nanoparticles Induce the Chemo-Sensitivity of Fluorouracil Nanoparticles in Breast and Colon Cancer Cells

Drug resistance is a major challenge of breast and colon cancer therapies leading to treatment failure. The main objective of the current study is to investigate whether selenium nanoparticles (nano-Se) can induce the chemo-sensitivity of 5-fluorouracil (FU)-encapsulated poly (D, L-lactide-co-glycolide) nanoparticles (nano-FU) in breast and colon cancer cell lines. Nano-Se and nano-FU were synthesized and characterized, then applied individually or in combination upon MCF7, MDA-MB-231, HCT 116, and Caco-2 cancerous cell lines. Cytotoxicity, cellular glucose uptake, and apoptosis, as well as malondialdehyde (MDA), nitric oxide (NO), and zinc (Zn) levels, were investigated upon the different treatments. We have resulted that nano-FU induced cell death in MCF7 and Caco-2 more effectively than MDA-MB-231 and HCT 116 cell lines. Moreover, nano-FU plus nano-Se potentiate MCF7 and Caco-2 chemo-sensitivity were higher than MDA-MB-231 and HCT 116 cancerous cell lines. It is relevant to note that Se and FU nano-formulations inhibited cancer cell bioenergetics via glucose uptake slight blockage. Furthermore, nano-FU increased the levels of NO and MDA in media over cancer cells, while their combinations with nano-Se rebalance the redox status with Zn increment. We noticed that MCF7 cell line is sensitive, while MDA-MB-231 cell line is resistant to Se and nano-Se. This novel approach could be of great potential to enhance the chemo-sensitivity in breast and colon cancer cells.

Renal cell carcinoma risk associated with lower intake of micronutrients

Kidney cancer incidence in African Americans (AA) is higher than among European Americans (EA); reasons for this disparity are not fully known. Dietary micronutrients may have a protective effect on renal cell carcinoma (RCC) development by inhibiting oxidative DNA damage and tumor growth. We evaluated whether any micronutrient associations differed by race in the US Kidney Cancer Study. 1142 EA and AA RCC cases and 1154 frequency‐matched controls were enrolled in a population‐based case‐control study between 2002 and 2007. Dietary micronutrient intake was derived from an interviewer‐administered diet history questionnaire. RCC risk associated with micronutrient intake was estimated using adjusted odds ratios from logistic regression comparing lower to highest quartiles of intake and sample weighting. Inverse associations with RCC risk were observed for α‐carotene, β‐carotene, lutein zeaxanthin, lycopene, vitamin A, folate, thiamin, vitamin C, α‐tocopherol, β‐tocopherol, γ‐tocopherol, and selenium. A trend for β‐cryptoxanthin was suggested among EA but not AA or the total sample (P‐interaction = .04). Otherwise, findings did not differ by race, gender, age, or smoking status. The increase in RCC risk associated with lower micronutrient intake is similar within AA and EA populations. A diet rich in sources of micronutrients found in fruits, vegetables, and nuts may help to reduce the overall risk of RCC.

Selenoproteins in human body: focus on thyroid pathophysiology

Selenium (Se) has a multilevel, complex and dynamic effect on the human body as a major component of selenocysteine, incorporated into selenoproteins, which include the selenocysteine-containing enzymes iodothyronine deiodinases. At the thyroid level, these proteins play an essential role in antioxidant protection and hormone metabolism. This is a narrative review based on PubMed/Medline database research regarding thyroid physiology and conditions with Se and Se-protein interferences. In humans, Se-dependent enzyme functions are best expressed through optimal Se intake, although there is gap in our knowledge concerning the precise mechanisms underlying the interrelation. There is a good level of evidence linking low serum Se to autoimmune thyroid diseases and, to a lesser extent, differentiated thyroid cancer. However, when it comes to routine supplementation, the results are heterogeneous, except in the case of mild Graves' orbitopathy. Autoimmune hypothyroidism is associated with a state of higher oxidative stress, but not all studies found an improvement of thyroid function after Se was introduced as antioxidant support. Meanwhile, no routine supplementation is recommended. Low Se intake is correlated with an increased risk of developing antithyroid antibodies, its supplementation decreasing their titres; there is also a potential reduction in levothyroxine replacement dose required for hypothyroidism and/or the possibility that it prevents progression of subclinical hypothyroidism, although not all studies agree. In thyroid-associated orbitopathy, euthyroidism is more rapidly achieved if the micronutrient is added to traditional drugs, while controls appear to benefit from the microelement only if they are deficient; thus, a basal assay of Se appears advisable to better select patients who need substitution. Clearly, further Se status biomarkers are required. Future introduction of individual supplementation algorithms based on baseline micronutrient levels, underlying or at-risk clinical conditions, and perhaps selenoprotein gene polymorphisms is envisaged.

Selenium, cadmium and diazinon insecticide in tissues of rats after peroral exposure

The concentrations of selenium (Se), cadmium (Cd) and diazinon (DZN) in selected tissues of rats after an oral administration in various combinations were analyzed. Male rats were orally dosed with diazinon (40 mg.L-1), diazinon (40 mg.L-1) +selenium (5 mg.L-1), diazinon (40 mg.L-1) +cadmium (30 mg.L-1), and diazinon (40 mg.L-1) +selenium (5 mg.L-1) +cadmium (30 mg.L-1) in drinking water. After 90 days of per oral administration of compounds, the samples of liver, kidney, muscle tissue (m. quadriceps femoris), and adipose tissue were collected. The content of DZN was analyzed using Gas Chromatography - Mass Spectrometry (GC-MS), Cd was analyzed using an Electrothermal Atomic Absorption Spectrometry (ETAAS) and Se using a Hydride Generation Atomic Absorption Spectrometry (HG-AAS) methods. Cadmium significantly increased in liver and kidney after DZN +Cd and DZN +Se +Cd administration. Se significantly increased in liver of DZN +Se, DZN +Se +Cd and DZN +Cd exposed rats, in kidney of DZN +Se and DZN +Se +Cd and DZN +Cd, and in muscle of DZN +Se +Cd group. Highest DZN content was found in the adipose tissue in DZN, DZN +Cd and DZN +Se +Cd but not in combined exposure with Se. Anyway, the differences between the control and experimental groups were not significant. The results indicate that cadmium and selenium accumulate mainly in liver, kidney and selenium also in muscle after p.o. administration but diazinon concentrations increases were not signifcant. The co-administration of diazinon, Se and Cd affects the content of these compounds in the organism and the accumulation rate depends on the combination of administered compounds. Diazinon and cadmium could contribute to the selenium redistribution in the organism after the peroral intake.

Essential Metals Zinc, Selenium, and Strontium Protect against Chromosome Damage Caused by Polycyclic Aromatic Hydrocarbons Exposure

Essential metals play important roles in maintaining cellular homeostasis, but the effects of their interaction with the environmental pollutants are still not very well-known in human subjects. The aim of this study was to evaluate the roles of essential metals and their interactions with polycyclic aromatic hydrocarbons (PAHs) on chromosome damage, an early carcinogenic event. A total of 1245 male workers were included in this study and the levels of 11 urinary essential metals, 12 urinary PAH metabolites, plasma concentrations of benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydotetrol-albumin (BPDE-Alb) adducts, and lymphocyte micronucleus (MN) frequencies were monitored. We found that zinc (Zn), selenium (Se), and strontium (Sr) have significant inverse dose-response relationships with MN frequencies (all P < 0.05). Furthermore, the protective roles of Zn, Se, and Sr were mainly shown among subjects with high levels of BPDE-Alb adducts. Significant effect modification of BPDE-Alb adducts on the associations of Zn, Se, and Sr with MN frequencies was observed (all Pinteraction < 0.05). Our study showed evidence that Zn, Se, and Sr play protective roles in reducing chromosome damage, and these effects can be modified by PAH exposure levels. These findings add potential evidence for the preventive effects of Zn, Se, and Sr against carcinogenesis in human subjects.

The favourable effects of long-term selenium supplementation on regression of cervical tissues and metabolic profiles of patients with cervical intraepithelial neoplasia: a randomised, double-blind, placebo-controlled trial

This study was conducted to assess the effects of long-term Se administration on the regression and metabolic status of patients with cervical intraepithelial neoplasia grade 1 (CIN1). This randomised, double-blind, placebo-controlled trial was carried out among fifty-eight women diagnosed with CIN1. To diagnose CIN1, we used specific diagnostic procedures of biopsy, pathological diagnosis and colposcopy. Patients were randomly assigned to two groups to receive 200 μg Se supplements as Se yeast (n 28) or placebo (n 28) daily for 6 months. After 6 months of taking Se supplements, a greater percentage of women in the Se group had regressed CIN1 (88·0 v. 56·0 %; P=0·01) compared with those in the placebo group. Long-term Se supplementation, compared with the placebo, resulted in significant decreases in fasting plasma glucose levels (-0·37 (sd 0·32) v. +0·07 (sd 0·63) mmol/l; P=0·002), serum insulin levels (-28·8 (sd 31·2) v. +13·2 (sd 40·2) pmol/l; P<0·001), homeostatic model assessment of insulin resistance values (-1·3 (se 1·3) v. +0·5 (se 1·4); P<0·001) and a significant elevation in quantitative insulin sensitivity check index (+0·03 (sd 0·03) v. -0·01 (sd 0·01); P<0·001). In addition, patients who received Se supplements had significantly decreased serum TAG (-0·14 (sd 0·55) v. +0·15 (sd 0·38) mmol/l; P=0·02) and increased HDL-cholesterol levels (+0·13 (sd 0·21) v. -0·01 (sd 0·15) mmol/l; P=0·003). In addition, compared with the placebo group, there were significant rises in plasma total antioxidant capacity (+186·1 (sd 274·6) v. +42·8 (sd 180·4) mmol/l; P=0·02) and GSH levels (+65·0 (sd 359·8) v. -294·2 (sd 581·8) μmol/l; P=0·007) and a significant decrease in malondialdehyde levels (-1·5 (sd 2·1) v. +0·1 (sd 1·4) μmol/l; P=0·001) among those who took Se supplements. Overall, taking Se supplements among patients with CIN1 led to its regression and had beneficial effects on their metabolic profiles.

Genetics of breast cancer: a topic in evolution

A hereditary predisposition to breast cancer significantly influences screening and follow-up recommendations for high-risk women. However, in patients with a suggestive personal and/or family history, a specific predisposing gene is identified in <30% of cases. Up to 25% of hereditary cases are due to a mutation in one of the few identified rare, but highly penetrant genes (BRCA1, BRCA2, PTEN, TP53, CDH1, and STK11), which confer up to an 80% lifetime risk of breast cancer. An additional 2%-3% of cases are due to a mutation in a rare, moderate-penetrance gene (e.g. CHEK2, BRIP1, ATM, and PALB2), each associated with a twofold increase in risk. Prediction models suggest that there are unlikely to be additional yet to be identified high-penetrance genes. Investigation of common, low-penetrance alleles contributing to risk in a polygenic fashion has yielded a small number of suggestive single-nucleotide polymorphisms (SNPs), but the contributive risk of an individual SNP is quite small. Mutation testing is currently recommended for individual genes in the appropriate clinical setting where there is a high index of suspicion for a specific mutated gene or syndrome. Next-generation sequencing offers a new venue for risk assessment. At the present time, there are clear clinical guidelines for individuals with a mutation in a high-penetrance gene. Otherwise, standard models are used to predict an individual's lifetime risk by clinical and family history rather than genomic information.

Thyroid function and serum copper, selenium, and zinc in general U.S. population

Association of the levels of serum selenium (Se), zinc (Zn), and copper (Cu) with thyroid function was assessed by analyzing data from National Health and Nutrition Examination Survey for the cycle 2011-2012. Thyroid function variables analyzed were as follows: thyroid-stimulating hormone (TSH), free and total triiodothyronine (FT3, TT3), free and total thyroxine (FT4, TT4), and thyroglobulin (TGN). Regression models with log-transformed values of thyroid hormones as independent variables and age, race/ethnicity, smoking and iodine sufficiency status, respondents' education, and levels of Se, Zn, and Cu as dependent variables were fitted. For males, levels of Zn were associated with decreased levels of FT4 and TT4, and levels of Cu were associated with increased levels of FT4 and TT4. For females, levels of Cu were associated with increased levels of TT3 and TT4. Smoking was found to be associated with lower levels of TSH and higher levels of TGN in males. Smoking was found to be associated with lower levels of TT4 in females. Males had about 5-10% higher levels of both Se and Zn, but as much as 20% lower levels of Cu than females. Smoking was associated with lower levels of Zn, but higher levels of Cu in males.