Serum selenium level and other risk factors for breast cancer among patients in a Malaysian hospital

Effect of Copper and Selenium Supplementation on the Level of Elements in Rats' Femurs under Neoplastic Conditions

A study was conducted to determine the effect of long-term supplementation with selenium and copper, administered at twice the level used in the standard diet of rats, on the content of selected elements in the femoral bones of healthy rats and rats with implanted LNCaP cancer cells. After an adaptation period, the animals were randomly divided into two experimental groups. The rats in the experimental group were implanted with prostate cancer cells. The rats in the control group were kept in the same conditions as those in the experimental group and fed the same diet, but without implanted cancer cells. The cancer cells (LNCaP) were intraperitoneally implanted in the amount of 1 × 106 (in PBS 0.4 mL) at the age of 90 days. The content of elements in the samples was determined by a quadrupole mass spectrometer with inductively coupled plasma ionization (ICP-MS). In the femoral bones of rats with implanted LNCaP cells, in the case of the standard diet and the copper-enriched diet, there was a marked decreasing trend in the content of the analysed elements relative to the control rats. This may indicate slow osteolysis taking place in the bone tissue. Contrasting results were obtained for the diet enriched with selenium; there was no significant reduction in the level of these elements, and there was even an increase in the concentrations of Fe and K in the bones of rats with implanted LNCaP cells. Particularly, numerous changes in the mineral composition of the bones were generated by enriching the diet with copper. The elements that most often underwent changes (losses) in the bones were cobalt, iron, manganese and molybdenum. The changes observed, most likely induced by the implantation of LNCaP cells, may indicate a disturbance of mineral homeostasis.

Genetic Variation Interacts with Selenium Exposure Regarding Breast Cancer Risk: Assessing Dietary Intake, Serum Levels and Genetically Elevated Selenium Levels

Selenium has been suggested to be protective regarding breast cancer risk but no overall effect has been established. Genetics may modify the effect. This study compares the effect of selenium exposure on breast cancer risk between women with different alleles in single-nucleotide polymorphisms (SNPs). The Malmö Cancer and Diet Study, a cohort including 17,035 women and >25 years of follow-up on breast cancer diagnosis, was used. Five promising SNPs regarding interaction with selenium exposure were selected from the literature: rs1050450, rs4880, rs3877899, rs7579, and rs71304. Selenium exposure was assessed in three ways: genetically elevated (n = 16,429), dietary intake (n = 15,891) and serum levels (n = 2037) at baseline. Cox regression and logistic regression analyses evaluated breast cancer risk from selenium exposure, stratified for the SNPs and adjusted for risk factors. A total of 1946 women were diagnosed with breast cancer. Women with T/T alleles in rs1050450 had lower breast cancer risk compared with C/C, HR 0.81 (0.68–0.96). Interaction by rs1050450 limited a protective effect of higher selenium intake to T/T carriers, HR 0.68 (0.43–1.08) for intermediate intake and HR 0.63 (0.40–1.00) for high intake. No interactions or risk differences were seen for other SNPs or for serum selenium or genetically elevated selenium. The results indicate that genetic variation in rs1050450 might affect breast cancer risk and that selenium exposure could be a possible modifiable risk factor for breast cancer among women with that variation.

Relationship Between Selenium in Human Tissues and Breast Cancer: a Meta-analysis Based on Case-Control Studies

Breast cancer is a common malignant tumor in women, and the anti-cancer effect of selenium (Se) is recognized. This meta-analysis was designed to determine the relationship between selenium levels in human tissue and breast cancer risk. Literatures published before August 2020 were systematically screened through PubMed, Web of Science, Scopus, and Elsevier. The related publication quality was evaluated by the Newcastle-Ottawa scale. We used random effect models for calculation and conducted sensitivity analysis and evaluation of publication bias. We identified 18 case-control studies, including 3374 women diagnosed with breast cancer and 3582 healthy controls. The results showed that the difference between the case group and the control group was - 0.53 μg/l [95%CI - 0.72 to - 0.34] (P < 0.001). Subgroup analysis showed a serum difference of - 1.14 μg/l [95%CI - 1.70 to - 0.58] (P < 0.001). The value of plasma was - 0.21 μg/l [95% CI - 0.37 to - 0.04] (P = 0.014). The value of toenail was - 0.21 μg/l [95% CI - 0.38 to - 0.03] (P = 0.021). In contrast, selenium levels in hair were not significantly associated with breast cancer risk. In the case-control studies, it was observed that selenium level in human tissues was negatively correlated with the risk of breast cancer, which may improve the understanding of the effects of selenium on human health.

Chemopreventive and Anticancer Property of Selenoproteins in Obese Breast Cancer

Obesity is a significant risk factor for various cancers including breast cancer resulting in an increased risk of recurrence as well as morbidity and mortality. Extensive studies on various pathways have been successful in establishing a biological relationship between obesity and breast cancer. The molecular classification of breast cancer includes five groups each having different responses to treatment. Increased levels of inflammatory cytokines seen in obese conditions drive the pro-proliferative pathways, such as the influx of macrophages, angiogenesis, and antiapoptotic pathways. Increased peripheral aromatization of androgens by aromatase increases the circulating estrogen levels which are also responsible for the association of obesity with breast cancer. Also, increased oxidative stress due to chronic low-grade inflammation in obese women plays an important role in carcinogenesis. Despite the availability of safe and effective treatment options for breast cancer, obese women are at increased risk of adverse outcomes including treatment-related toxicities. In the recent decade, selenium compounds have gained substantial interest as chemopreventive and anticancer agents. The chemical derivatives of selenium include inorganic and organic compounds that exhibit pro-oxidant properties and alter cellular redox homeostasis. They target more than one metabolic pathway by thiol modifications, induction of reactive oxygen species, and chromatin modifications to exert their chemopreventive and anticancer activities. The primary functional effectors of selenium that play a significant role in human homeostasis are selenoproteins like glutathione peroxidase, thioredoxin reductase, iodothyronine deiodinases, and selenoprotein P. Selenoproteins play a significant role in adipose tissue physiology by modulating preadipocyte proliferation and adipogenic differentiation. They correlate negatively with body mass index resulting in increased oxidative stress that may lead to carcinogenesis in obese individuals. Methylseleninic acid effectively suppresses aromatase activation thus reducing the estrogen levels and acting as a breast cancer chemopreventive agent. Adipose-derived inflammatory mediators influence the selenium metabolites and affect the proliferation and metastatic properties of cancer cells. Recently selenium nanoparticles have shown potent anticancer activity which may lead to a major breakthrough in the management of cancers caused due to multiple pathways. In this review, we discuss the possible role of selenoproteins as chemopreventive and an anticancer agent in obese breast cancer.

Association between selenium intake and breast cancer risk: results from the Women's Health Initiative

PURPOSE

It has been hypothesized that selenium (Se) can prevent cancer, and that Se deficiency may be associated with an increased risk of breast cancer. However, findings from epidemiological studies have been inconsistent. The objective of this study was to assess the association between Se intake and risk of breast cancer in the Women's Health Initiative (WHI).

METHODS

This study included 145,033 postmenopausal women 50-79 years who completed baseline questionnaires between October 1993 and December 1998, which addressed dietary and supplemental Se intake and breast cancer risk factors. The association between baseline Se intake and incident breast cancer was examined in Cox proportional hazards analysis.

RESULTS

During a mean follow-up of 15.5 years, 9487 cases of invasive breast cancer were identified. Total Se (highest versus lowest quartile: HR 1.00, 95% CI 0.92-1.09, P_trend = 0.66), dietary Se (highest versus lowest quartile: HR 0.99, 95% CI 0.89-1.08, P_trend = 0.61), and supplemental Se (yes versus no: HR 0.99, 95% CI 0.95-1.03) were not associated with breast cancer incidence.

CONCLUSIONS

This study indicates that Se intake is not associated with incident breast cancer among postmenopausal women in the United States. Further studies are needed to confirm our findings by using biomarkers such as toenail Se to reduce the potential for misclassification of Se status.

Simultaneous analysis of 25 trace elements in micro volume of human serum by inductively coupled plasma mass spectrometry (ICP-MS)

INTRODUCTION

In recent years, trace elements have gained importance as biomarkers in many chronic diseases. Unfortunately, the requirement for sample volume increases with the extent of investigation either for diagnosis or elucidating the mechanism of the disease. Here, we describe the method development and validation for simultaneous determination of 25 trace elements (lithium [Li], beryllium [Be], magnesium [Mg], aluminium [Al], vanadium [V], chromium [Cr], manganese [Mn], iron [Fe], cobalt [Co], nickel [Ni], copper [Cu], zinc [Zn], gallium [Ga], arsenic [As], selenium [Se], rubidium [Rb], strontium [Sr], silver [Ag], cadmium [Cd], caesium [Cs], barium [Ba], mercury [Hg], thallium [Tl], lead [Pb], uranium [U]) using only 20 μL of human serum.

METHODS

Serum samples were digested with nitric acid and hydrochloric acid (ratio 1:1, v/v) and analysed by inductively coupled plasma-mass spectrometry (ICP-MS). Seronorm®, a human-derived serum control material was used as quality control samples.

RESULTS

The coefficient of variations for both intra- and inter-day precisions were consistently <15% for all elements. The validated method was later tested on 30 human serum samples to evaluate its applicability.

CONCLUSION

We have successfully developed and validated a precise and accurate analytical method for determining 25 trace elements requiring very low volume of human serum.

A case-control study of breast cancer risk factors in 7,663 women in Malaysia

BACKGROUND

Breast cancer risk factors have been examined extensively in Western setting and more developed Asian cities/countries. However, there are limited data on developing Asian countries. The purpose of this study was to examine breast cancer risk factors and the change of selected risk factors across birth cohorts in Malaysian women.

METHODS

An unmatched hospital based case-control study was conducted from October 2002 to December 2016 in Selangor, Malaysia. A total of 3,683 cases and 3,980 controls were included in this study. Unconditional logistic regressions, adjusted for potential confounding factors, were conducted. The breast cancer risk factors were compared across four birth cohorts by ethnicity.

RESULTS

Ever breastfed, longer breastfeeding duration, a higher soymilk and soy product intake, and a higher level of physical activity were associated with lower risk of breast cancer. Chinese had the lowest breastfeeding rate, shortest breastfeeding duration, lowest parity and highest age of first full term pregnancy.

CONCLUSIONS

Our study shows that breastfeeding, soy intake and physical activity are modifiable risk factors for breast cancer. With the increasing incidence of breast cancer there is an urgent need to educate the women about lifestyle intervention they can take to reduce their breast cancer risk.

Selenium and breast cancer risk: A prospective nested case-control study on serum selenium levels, smoking habits and overweight

Previous research has not been conclusive regarding the association between selenium (Se) and breast cancer. This study was conducted to clarify if there is an association between prediagnostic serum Se levels and breast cancer risk. A population based cohort, the Malmö Diet and Cancer Study, was used and linked with the Swedish cancer registry up to 31 December 2013. Our study included 1,186 women with breast cancer and an equal number of controls. Selenium levels were analysed from stored serum samples. The included individuals were divided into quartiles based on Se value and we compared breast cancer cases with controls using logistic regression yielding odds ratios (OR) with 95% confidence intervals. Serum Se was also analysed as a continuous variable regarding breast cancer risk. The analyses were adjusted for established risk factors and stratified on smoking status and body mass index (BMI). When comparing the highest Se quartile with the lowest, the adjusted OR for breast cancer was 0.98 (0.75-1.26). With selenium as a continuous variable the adjusted OR was 1.00 (1.00-1.01) per 10 ng/ml. When comparing the highest with the lowest Se quartile in women with BMI > 25 kg/m² the adjusted OR was 0.77 (0.53-1.14). We conclude that it is unlikely that prediagnostic serum selenium is overall associated with breast cancer risk and no modifying effect from BMI or smoking was seen.

Serum selenium levels and prostate cancer risk: A MOOSE-compliant meta-analysis

Some observational studies have shown that elevated serum selenium levels are associated with reduced prostate cancer risk; however, not all published studies support these results. A literature search of PubMed, Embase, Medline, and the Cochrane Library up until September 2016 identified 17 studies suitable for further investigation. A meta-analysis was conducted on these studies to investigate the association between serum selenium levels and subsequent prostate cancer risk. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the overall OR of prostate cancer for the highest versus the lowest levels of serum selenium. We found a pooled OR (95% CI) of 0.76 (0.64, 0.91; P < 0.05). In subgroup analysis, an inverse association between serum selenium levels and prostate cancer risk was found in each of case-control studies, current and former smokers, high-grade cancer cases, advanced cancer cases, and different populations. Such correlations were not found for subgroups containing each of cohort studies, nonsmokers, low-grade cancer cases, and early stage cancer cases. In conclusion, our study suggests an inverse relationship between serum selenium levels and prostate cancer risk. However, further cohort studies and randomized control trials based on non-Western populations are required.

Selenium Exposure and Cancer Risk: an Updated Meta-analysis and Meta-regression

The objective of this study was to investigate the associations between selenium exposure and cancer risk. We identified 69 studies and applied meta-analysis, meta-regression and dose-response analysis to obtain available evidence. The results indicated that high selenium exposure had a protective effect on cancer risk (pooled OR = 0.78; 95%CI: 0.73-0.83). The results of linear and nonlinear dose-response analysis indicated that high serum/plasma selenium and toenail selenium had the efficacy on cancer prevention. However, we did not find a protective efficacy of selenium supplement. High selenium exposure may have different effects on specific types of cancer. It decreased the risk of breast cancer, lung cancer, esophageal cancer, gastric cancer, and prostate cancer, but it was not associated with colorectal cancer, bladder cancer, and skin cancer.

The Association Between Serum Levels of Selenium, Copper, and Magnesium with Thyroid Cancer: a Meta-analysis

There are conflicting reports on the correlation between serum levels of selenium (Se), copper (Cu), and magnesium (Mg) with thyroid cancer. The purpose of the present study is to clarify the association between Se, Cu, and Mg levels with thyroid cancer using a meta-analysis approach. We searched articles indexed in PubMed published as of January 2015 that met our predefined criteria. Eight eligible articles involving 1291 subjects were identified. Overall, pooled analysis indicated that subjects with thyroid cancer had lower serum levels of Se and Mg, but higher levels of Cu than the healthy controls [Se: standardized mean difference (SMD) = -0.485, 95% confidence interval (95%CI) = (-0.878, -0.092), p = 0.016; Cu: SMD = 2.372, 95%CI = (0.945, 3.799), p = 0.001; Mg: SMD = -0.795, 95%CI = (-1.092, -0.498), p < 0.001]. Further subgroup analysis found lower serum levels of Se in thyroid cancer in Norway [SMD = -0.410, 95%CI = (-0.758, -0.062), p = 0.021] and Austria [SMD = -0.549, 95%CI = (-0.743, -0.355), p < 0.001], but not in Poland (SMD = -0.417, 95%CI = (-1.724, 0.891), p = 0.532]. Further subgroup analysis also found that patients with thyroid cancer had higher serum levels of Cu in China [SMD = 1.571, 95%CI = (1.121, 2.020), p < 0.001] and Turkey [SMD = 0.977, 95%CI = (0.521, 1.432), p < 0.001], but not in Poland [SMD = 3.471, 95%CI = (-0.056, 6.997], p = 0.054]. In conclusion, this meta-analysis supports a significant association between serum levels of Se, Cu, and Mg with thyroid cancer. However, the subgroup analysis found that there was significant effect modification of Se, Cu levels by ethnic, like China and Poland. Thus, this finding needs further confirmation by a trans-regional multicenter study to obtain better understanding of causal relationship between Se, Cu, and Mg with thyroid cancer of different human races or regions.

The relationship between selenium levels and breast cancer: a systematic review and meta-analysis

Breast cancer is the most common cancer type. In several studies, hints have been provided that there is a correlation between selenium deficiency and the incidence of breast cancer. Findings of these published reports are, however, inconsistent. This study serves as a pioneering study aiming at combining the results of studies using a meta-analytic method. A total of 16 articles published between 1980 and 2012 worldwide were selected through searching PubMed, Scopus, and Google scholar databases, and the information were analyzed using a meta-analytic method [random effects model]. I (2) statistics were used to examine heterogeneity. The information was then analyzed by STATA version 12. In this study, due to the non-uniform methods used to measure selenium concentrations, selenium levels were measured in the various subgroups in both case and control groups. There were significant correlations between selenium concentration and breast cancer [P<0.05]. Hence, the mean risk differentiating criteria were estimated to be 0.63 [95% confidence interval [95% CI] 0.93 to 0.32] in serum and toenails. Subgroup analysis showed that the value in toenails was -0.07 [95% CI -0.16 to 0.03] and in serum -1.04 [95% CI 1.71 to -0.38]. In studies in which selenium concentrations were measured in serum, a significant correlation was observed between selenium concentration and breast cancer. In contrast, in studies in which selenium concentration was measured in toenails, the correlation was not significant. Therefore, the selenium concentration can be used as one predictor for breast cancer.