Blood selenium and glutathione peroxidase status in patients with colorectal cancer

Post-diagnosis dietary factors, supplement use and colorectal cancer prognosis: A Global Cancer Update Programme (CUP Global) systematic literature review and meta-analysis

The role of diet in colorectal cancer prognosis is not well understood and specific lifestyle recommendations are lacking. We searched for randomised controlled trials (RCTs) and longitudinal observational studies on post-diagnosis dietary factors, supplement use and colorectal cancer survival outcomes in PubMed and Embase from inception until 28th February 2022. Random-effects dose-response meta-analyses were conducted when at least three studies had sufficient information. The evidence was interpreted and graded by the CUP Global independent Expert Committee on Cancer Survivorship and Expert Panel. Five RCTs and 35 observational studies were included (30,242 cases, over 8700 all-cause and 2100 colorectal cancer deaths, 3700 progression, recurrence, or disease-free events). Meta-analyses, including 3-10 observational studies each, were conducted for: whole grains, nuts/peanuts, red and processed meat, dairy products, sugary drinks, artificially sweetened beverages, coffee, alcohol, dietary glycaemic load/index, insulin load/index, marine omega-3 polyunsaturated fatty acids, supplemental calcium, circulating 25-hydroxyvitamin D (25[OH]D) and all-cause mortality; for alcohol, supplemental calcium, circulating 25(OH)D and colorectal cancer-specific mortality; and for circulating 25(OH)D and recurrence/disease-free survival. The overall evidence was graded as 'limited'. The inverse associations between healthy dietary and/or lifestyle patterns (including diets that comprised plant-based foods), whole grains, total, caffeinated, or decaffeinated coffee and all-cause mortality and the positive associations between unhealthy dietary patterns, sugary drinks and all-cause mortality provided 'limited-suggestive' evidence. All other exposure-outcome associations provided 'limited-no conclusion' evidence. Additional, well-conducted cohort studies and carefully designed RCTs are needed to develop specific lifestyle recommendations for colorectal cancer survivors.

Selenium levels in colorectal cancer: A systematic review and meta-analysis of serum, plasma, and colorectal specimens

BACKGROUND

Colorectal cancer (CRC) is a growing public health problem. Several clinical studies have shown a potentially protective effect of selenium (Se), but the reports are inconsistent. The objective of the study was to examine the evidence for relation between serum/tissue Se status and CRC.

METHOD AND MATERIALS

In this Systematic Review and Meta-Analysis, we searched Cochrane Library, EBSCOhost, EMBASE, ProQuest, PubMed/MEDLINE, Scopus, and Web of Science for studies reporting serum/plasma/whole blood/tissue Se concentrations in CRC patients and controls for articles published till August 2023. Meta-analysis was performed, and study quality, heterogeneity, and small study effects were assessed. Based on a random effects model, summary mean differences in serum levels of Se between CRC patients and healthy controls, and Se levels between malignant and matched non-malignant tissue specimens were assessed.

RESULTS

After initial screening, a total of 24 studies (18 serum and 6 tissue studies) with a pooled total of 2640 participants were included in the meta-analysis. CRC patients had significantly lower serum Se levels than healthy controls, being the difference between the two equal to 3.73 µg/dl (95% CI: 6.85-0.61). However, the heterogeneity was very high, I2= 99% (p < 0.01). Our meta-analysis showed higher Se levels in CRC cancerous specimens than in matched healthy colon tissue: the increase was equal to 0.07 µg/g wet tissue weight (95% CI: 0.06-0.09; p= 0.02).

CONCLUSIONS

CRC patients have lower serum and higher colon cancerous tissue Se levels. Some factors, such as Se levels in different tumor grades of CRC need to be further considered for a more conclusive association between Se levels and risk of CRC.

Selenium May Be Involved in Esophageal Squamous Cancer Prevention by Affecting GPx3 and FABP1 Expression: A Case-Control Study Based on Bioinformatic Analysis

The role of selenium in the developmental process of esophageal cancer (EC) requires further investigation. To explore the relationship between selenium-related factors and EC through bioinformatic analysis, a case-control study was conducted to verify the results. Utilizing the GEPIA and TCGA databases, we delineated the differential expression of glutathione peroxidase 3 (GPx3) in EC and normal tissues, identified differentially expressed genes (DEGs), and a performed visualization analysis. Additionally, 100 pairs of dietary and plasma samples from esophageal precancerous lesions (EPLs) of esophageal squamous cancer (ESCC) cases and healthy controls from Huai'an district, Jiangsu, were screened. The levels of dietary selenium, plasma selenium, and related enzymes were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) or ELISA kits. The results showed lower GPx3 expression in tumor tissues compared to normal tissues. Further analysis revealed that DEGs were mainly involved in the fat digestion and absorption pathway, and the core protein fatty acid binding protein 1 (FABP1) was significantly upregulated and negatively correlated with GPx3 expression. Our case-control study found that selenium itself was not associated with EPLs risk. However, both the decreased concentration of GPx3 and the increase in FABP1 were positively correlated with the EPLs risk (p for trend = 0.035 and 0.046, respectively). The different expressions of GPx3 and FABP1 reflect the potential of selenium for preventing ESCC at the EPLs stage. GPx3 may affect myocardial infarction through FABP1, which remains to be further studied.

The Potential of Integrative Cancer Treatment Using Melatonin and the Challenge of Heterogeneity in Population-Based Studies: A Case Report of Colon Cancer and a Literature Review

Melatonin is a multifunctional hormone regulator that maintains homeostasis through circadian rhythms, and desynchronization of these rhythms can lead to gastrointestinal disorders and increase the risk of cancer. Preliminary clinical studies have shown that exogenous melatonin alleviates the harmful effects of anticancer therapy and improves quality of life, but the results are still inconclusive due to the heterogeneity of the studies. A personalized approach to testing clinical parameters and response to integrative treatment with nontoxic and bioavailable melatonin in patient-centered N-of-1 studies deserves greater attention. This clinical case of colon cancer analyzes and discusses the tumor pathology, the adverse effects of chemotherapy, and the dynamics of markers of inflammation (NLR, LMR, and PLR ratios), tumors (CEA, CA 19-9, and PSA), and hemostasis (D-dimer and activated partial thromboplastin time). The patient took melatonin during and after chemotherapy, nutrients (zinc, selenium, vitamin D, green tea, and taxifolin), and aspirin after chemotherapy. The patient's PSA levels decreased during CT combined with melatonin (19 mg/day), and melatonin normalized inflammatory markers and alleviated symptoms of polyneuropathy but did not help with thrombocytopenia. The results are analyzed and discussed in the context of the literature on oncostatic and systemic effects, alleviating therapy-mediated adverse effects, association with survival, and N-of-1 studies.

Correlation between Selenium and Zinc Levels and Survival among Prostate Cancer Patients

The most prevalent type of cancer among males is prostate cancer. Survival is considered quite good, but it can be further improved when risk factors are optimized. One of these factors is micronutrients, including Se and Zn. To our knowledge, the interaction between Se and Zn and prostate cancer remains undescribed. This study aimed to investigate the optimal levels of selenium (Se) and zinc (Zn) and their impact on the survival of individuals diagnosed with prostate cancer. A total of 338 prostate cancer patients were enrolled in this study, which was conducted in Poland between 2009 and 2015. Mass spectrometry, which uses inductively coupled plasma mass, was used to assess serum element levels before treatment. The study participants were categorized into quartiles (QI-QIV) based on the distributions of Se and Zn levels observed among surviving participants. Cox regression was used to assess the association between serum Se and Zn levels and the survival of prostate cancer patients. Our results reveal the effect of combined Se and Zn levels on survival in prostate cancer patients (SeQI-ZnQI vs. SeQIV-ZnQIV; HR = 20.9). These results need further research to establish Se/Zn norms for different populations.

Selenium dietary intake and survival among CRC patients

Background: Despite advances in prevention and treatment, colorectal cancer remains the second most common cause of cancer death. To date, little is known about the role of prediagnostic selenium intake in colorectal cancer survival. Objective: The purpose of the study was to verify whether selenium intake in habitual diet before diagnosis is associated with survival in colorectal cancer patients. Study design: This was a prospective observation of patients primarily recruited for a case-control study between 2000 and 2012 in Cracow, Poland. A group of 671 incident cases of colorectal cancer was included. Habitual diet was assessed using a validated 148-item food questionnaire. 338 deaths were identified throughout 2017 by the Polish National Vital Registry. To evaluate the impact of dietary selenium on survival, the multivariable Cox regression model was used. Results: After standardization for several potential confounders (including key determinants, such as radical surgery, chemotherapy, tumor stage, and dietary factors), a decrease in the risk of death from colorectal cancer was observed in the group with higher dietary selenium intake (≥48.8 μg/day, group mean: 63.9 μg/day) compared to the group with lower dietary selenium intake (<48.8 μg/day, mean: 38.5 μg/day) (HR=0.73; 95% CI: 0.54-0.98) (the median was used for categorization). Conclusion: Our study suggests selenium as an additional dietary factor which may be associated with survival among colorectal cancer patients referred to surgery. Due to the observational nature of the study, the results should be taken with caution. These preliminary findings, however, provide the basis for well-structured clinical trials.

Selenium in Cancer Rehabilitation-A Retrospective Study from a Specialized Clinic

BACKGROUND

Micronutrient deficiencies are common at the time of cancer diagnosis and are associated with worse prognosis. Little is known about them in cancer rehabilitation.

METHODS

Data from routine health-related quality of life (HRQOL) were analyzed at an inpatient cancer rehabilitation center. Rehabilitation patients completed the EORTC QLQ-C30 questionnaire before and after multidisciplinary rehabilitation treatment and three months after discharge. Selenium and zinc status were measured in whole blood at these three time points. In case of selenium deficiency, up to 600 µg selenium per day as sodium selenite was supplemented for three weeks during and for three months after rehabilitation.

RESULTS

A total of 271 patients (breast, colon, and pancreatic cancer) were included in the analysis. There was clinically meaningful improvement in many domains of the EORTC QLQ-C30 during rehabilitation. However, the effect often waned in the three months after. Prevalence for selenium deficiency varied between 34 to 90% depending on cancer type (breast < colon < pancreas). In contrast, zinc deficiency was rare. Daily selenium supplementation of 600 µg was more efficient to correct selenium deficiency compared to 300 µg selenium per day. Rehabilitation and increasing selenium status after rehabilitation were associated with improved global quality of life, physical and emotional functioning, and fatigue. In cancer patients with decreasing selenium status, values of global quality of life, physical and emotional functioning, and fatigue were back to the values at the beginning of rehabilitation.

CONCLUSIONS

Selenium deficiency is common in cancer patients admitted to a cancer rehabilitation clinic. Selenium supplementation during rehabilitation effectively corrected selenium deficiency in most cases. The positive effects of rehabilitation persisted longer when selenium status did not decrease after rehabilitation.

Serum Essential Elements and Survival after Cancer Diagnosis

In a prospective study, we measured the associations between three serum elements (Se, Zn and Cu) and the prognosis of 1475 patients with four different types of cancer (breast, prostate, lung and larynx) from University Hospitals in Szczecin, Poland. The elements were measured in serum taken after diagnosis and prior to treatment. Patients were followed from the date of diagnosis until death from any cause or until the last follow-up date (mean years of follow-up: 6.0-9.8 years, according to site). Kaplan-Meier curves were constructed for all cancers combined and for each cancer separately. Age-adjusted hazard ratios (HRs) were estimated using Cox regression. The outcome was all-cause mortality. A Se level in the highest quartile was also associated with a reduced mortality (HR = 0.66; 95%CI 0.49-0.88; p = 0.005) in all-cause mortality for all cancers combined. Zn level in the highest quartile was also associated with reduced mortality (HR = 0.55; 95%CI 0.41-0.75; p = 0.0001). In contrast, a Cu level in the highest quartile was associated with an increase in mortality (HR = 1.91; 95%CI 1.56-2.08; p = 0.0001). Three serum elements-selenium, zinc and copper-are associated with the prognosis of different types of cancer.

Selenium and cancer or adenoma related to the large bowel

The protective effect of selenium against colorectal cancer or adenoma is still a controversial issue. Although there are well-described (pato)physiological protective mechanisms of selenium against colorectal cancer, the results of the studies from 1998-2018 are inconclusive and need to be considered in the future. Neither observational nor experimental studies present consistent results. Although the Cochrane review showed that well-designed randomized clinical trials (RCTs) presented no beneficial effect of selenium supplementation on cancer incidence, well-designed RCTs confirming the protective effect of selenium supplementation against colorectal adenoma or colorectal polyp recurrence have been found in subject-related literature. In the reviewed studies, selenium concentration was measured in the blood serum/toenail or in diet. It is of great importance to highlight that blood selenium concentration depends on the concentration of this micronutrient in food, which in turn depends on selenium content in soil, bioavailability of selenium, which is different in various geographical regions, and forms of selenium. Selenium circulating in blood as a component of selenoproteins participates in oxidoreduction, thus reducing the risk of developing colorectal cancer. Despite this well-known protective mechanism against colorectal cancer occurrence, half of the reviewed studies did not confirm the protective properties of selenium. To sum up, the current state of knowledge on the association between selenium and colorectal cancer or adenoma has revealed not only inconclusive results of the studies, but has also shown that there is a need to conduct more prospective studies focused on selenium supplementation and colorectal cancer as this research is limited.

Extracellular Glutathione Peroxidase GPx3 and Its Role in Cancer

Mammalian cells possess a multifaceted antioxidant enzyme system, which includes superoxide dismutases, catalase, the peroxiredoxin/thioredoxin and the glutathione peroxidase systems. The dichotomous role of reactive oxygen species and antioxidant enzymes in tumorigenesis and cancer progression complicates the use of small molecule antioxidants, pro-oxidants, and targeting of antioxidant enzymes as therapeutic approaches for cancer treatment. It also highlights the need for additional studies to investigate the role and regulation of these antioxidant enzymes in cancer. The focus of this review is on glutathione peroxidase 3 (GPx3), a selenoprotein, and the only extracellular GPx of a family of oxidoreductases that catalyze the detoxification of hydro- and soluble lipid hydroperoxides by reduced glutathione. In addition to summarizing the biochemical function, regulation, and disease associations of GPx3, we specifically discuss the role and regulation of systemic and tumor cell expressed GPx3 in cancer. From this it is evident that GPx3 has a dichotomous role in different tumor types, acting as both a tumor suppressor and pro-survival protein. Further studies are needed to examine how loss or gain of GPx3 specifically affects oxidant scavenging and redox signaling in the extracellular tumor microenvironment, and how GPx3 might be targeted for therapeutic intervention.

Influence of the selenium level on overall survival in lung cancer

BACKGROUND

Although the results of studies in populations with low selenium status indicate an inverse correlation between body selenium levels and the risk of the lung cancer, the effect of this microelement on survival has not been studied.

MATERIALS AND METHODS

We performed a prospective study of 302 patients diagnosed with lung cancer in Szczecin, Poland. Selenium concentration in serum was measured at the time of diagnosis and before treatment. All patients were followed for a maximum of 80 months or until death. Vital status was obtained from the Polish National Death Registry.

RESULTS

Using Cox proportional hazard analysis, performed for all individuals with lung cancer, the hazard ratio (HR) for death from all causes was 1.25 (95% CI: 0.86-1.83, P = 0.99) for patients in the lowest tertile compared to those in the highest tertile of serum selenium levels. Among the patients with stage I disease this relationship was significant (HR-2.73; P = 0.01) for selenium level in tertile 1 (<57 μg/L) compared to tertile 3 (>69 μg/L, reference). The 80 months crude survival after diagnosis was 79.5% (95% CI: 68.5-92.4%) for individuals in the highest tertile and 58.1% (95% CI: 45.1-74.9%) for individuals in the lowest tertile with stage I lung cancer.

CONCLUSION

These results suggest that in patients undergoing treatment for stage I lung cancer, serum selenium levels at the time of diagnosis (>69 μg/L) may be associated with improved overall survival.

Roles for selenium and selenoprotein P in the development, progression, and prevention of intestinal disease

Selenium (Se) is a micronutrient essential to human health, the function of which is mediated in part by incorporation into a class of proteins known as selenoproteins (SePs). As many SePs serve antioxidant functions, Se has long been postulated to protect against inflammation and cancer development in the gut by attenuating oxidative stress. Indeed, numerous studies over the years have correlated Se levels with incidence and severity of intestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer (CRC). Similar results have been obtained with the Se transport protein, selenoprotein P (SELENOP), which is decreased in the plasma of both IBD and CRC patients. While animal models further suggest that decreases in Se or SELENOP augment colitis and intestinal tumorigenesis, large-scale clinical trials have yet to show a protective effect in patient populations. In this review, we discuss the function of Se and SELENOP in intestinal diseases and how research into these mechanisms may impact patient treatment.

Serum Se, Ni, and As are associated with HPV infection and CIN2+ among Uyghur women in rural China

Background

Cervical cancer incidence and mortality is high in Uyghur ethnics. Their life style and dietary habit were different from other ethnics living together. Study on the role of trace elements in HPV infection and cervical lesion of Uyghur minority is needed for future intervention and prevention work.

Methods

In total, 833 Uyghur women were randomly selected from the screening site and hospital. The concentrations of the trace elements As, Fe, Cd, Ni, Cu, Zn, Mn, and Se were determined by atomic absorption spectrophotometry and inductively coupled plasma atomic emission spectroscopy. Univariate analysis was performed with chi-squared test between the HPV-positive and HPV-negative groups and between the case group and the control group. Multivariate analysis was performed with logistic regression.

Results

An As concentration ≥ 0.02 mg/kg was a risk factor for HPV infection (OR > 1, P < 0.05), and Ni concentration ≥ 0.1232 mg/kg and Se concentration ≥ 0.02 mg/kg were protective factors (OR < 1, P < 0.05). Concentrations of Fe ≥ 6.9153 mmol/L and As ≥0.02 mg/kg were risk factors for CIN2+ (OR > 1, P < 0.05), and concentrations of Ni ≥0.0965 mg/kg and Se ≥0.02 mg/kg were protective factors (OR < 1, P < 0.05).

Conclusions

Low serum concentrations of Se and Ni and a high serum concentration of As might be related to HPV infection and CIN2+ in Uyghur women in rural China.

Effect of selenium supplementation on lipid profile in hemodialysis patients

Introduction: One of the major causes of mortality in chronic kidney disease (CKD) patients on hemodialysis is premature atherosclerosis. Selenium, a trace element involved in important enzymatic activities inside the body, has protective effects against lipid oxidation and inhibits cholesterol accumulation in blood vessels.

Objectives: To determine the effect of selenium supplementation on lipid profile in hemodialysis patients.

Patients and Methods: In this double-blinded randomized clinical trial which lasted for 3 months, 84 hemodialysis patients with selenium deficiency were divided into experimental group (received selenium supplementation) or control group (received placebo). Total cholesterol, low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), blood urea nitrogen (BUN), creatinine, and selenium level were measured before and after the study.

Results: Mean (±SD) serum LDL-C level significantly increased in experimental group from 85.66 (±31.12) to 109.12 (±32.29) mg/dl (P<0.001). Likewise, in control group serum LDL-C significantly increased from 80.55 (±21.13) to 97.05 (±28.07) mg/dl (P<0.001). However, with control of LDL-C effect before and after the study, it was revealed that LDL-C change was not statistically significant (P=0.21). Similarly, total cholesterol and triglyceride levels did not show significant changes before and after the study in any group.

Conclusion: Selenium supplementation had no beneficial effect on lipid profile in hemodialysis patients.

Selenium bioaccessibility in stomach, small intestine and colon: Comparison between pure Se compounds, Se-enriched food crops and food supplements

Selenium (Se) is an essential nutrient for humans as it plays an important role in glutathione peroxidase (GPx) activity. Moreover, it may reduce cancer risks. The objective of this work was to examine in vitro the bioaccessibility of Se in three different Se-enriched food supplements and two different Se-enriched food crops, with reference to two pure Se standards, and changes in its speciation during intestinal digestion. Selenate was found to be stable throughout the entire digestion, whereas incubation of selenomethionine resulted in the chemical and microbial production of minor metabolites. The bioaccessibility of Se in Se-enriched food supplements and food crops was found to be highest in the small intestine. Compared to SelenoPrecise and Se-ACE tablets, a yoghurt-based supplement exhibited a much lower Se bioaccessibility, possibly due to the presence of nano- or microparticles of elemental Se. Colon microbiota were found to primarily affect Se bioaccessibility in the colon environment, with the presence of inactivated microbiota resulting in a higher bioaccessibility. A higher potential of Se to reach the colon and become accessible in this phase may result in beneficial effects on the colon health.

The effect of selenium supplementation on acute phase reactants and thyroid function tests in hemodialysis patients

BACKGROUND

Selenium deficiency is a common problem in patients with chronic kidney disease (CKD). This micronutrient has anti-inflammatory and anti-oxidant effects. Selenium is also found in high concentrations in the thyroid gland.

OBJECTIVES

To determine the effect of selenium supplementation on thyroid function tests and acute phase reactants in hemodialysis patients.

PATIENTS AND METHODS

In this double-blinded randomized clinical in 3 months, 64 hemodialysis patients with selenium deficiency were divided into experimental (received selenium supplementation; 32 cases) or control group (received placebo; 32 cases). Erythrocyte sedimentation rate (ESR), ferritin, quantitative C-reactive protein (CRP) and thyroid function tests (TFTs) including thyroid stimulating hormone (TSH), T3 resin uptake (T3RU), and free T4 were measured before and after the intervention and compared between experimental and control groups.

RESULTS

At baseline, no significant difference was found between experimental and control groups regarding CRP, ESR and ferritin serum levels. Likewise, after intervention, no significant difference was found between experimental and control groups for CRP (14.77 ± 17.93 vs. 18.29 ± 21.56 mg/L), ESR (32.90 ± 32.62 vs. 33.91 ± 31.15 mm/h) and ferritin (528.6 ± 423.07 vs. 519.52 ± 345.59 ng/mL). At baseline, no significant difference was found between experimental and control groups regarding TFTs. Likewise, after intervention, no significant difference was found between experimental and control groups for TSH (3.7 ± 2.22 vs. 2.84 ± 1.88 µU/mL), free T4 (7.19 ± 1.98 vs. 7.02 ± 1.87 µg/dL) and T3RU (30.04 ± 2.28% vs. 29.2 ± 1.98%).

CONCLUSIONS

Oral selenium supplementation for three months did not have any significant effect on thyroid function tests or acute phase reactants.

Can selenium levels act as a marker of colorectal cancer risk?

Background

Selenium has attracted attention because of its antioxidant properties. Antioxidants protects cells from damage. Certain breakdown products of selenium are believed to prevent tumor growth by enhancing the immune cell activity and suppressing the development of tumor blood vessels. In this observational study, selenium level was measured in a series of patients from Poland and Estonia to determine a correlation between levels of this microelement and colorectal cancer risk.

Methods

A total of 169 colorectal cancer patients and 169 healthy controls were enrolled in the study after obtaining their informed consent. Selenium level in the blood serum was measured using Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The statistical analysis was performed by Fisher’s exact test.

Results

The threshold point of selenium level was 55 μg/l and 65 μg/l for Poland and Estonia respectively, for an increase in cancer risk. The lower levels of selenium were associated with greater risk of colorectal cancer.

Conclusions

The result reveals a significant strong association between low selenium level and the colorectal cancer risk in both Estonian and Polish populations.

Diet, gender, and colorectal neoplasia

The association between diet and colorectal cancer has been studied in depth for many decades, with equivocal results. It has been hypothesized that cancers arising in the distal and proximal colon have different pathologies, and therefore different risk factors. As such, it is possible that diet-related factors might influence colorectal neoplasia differently depending on the subsite. Recent evidence indicates that women may be more likely to develop proximal cancers than men. Additionally, the link between certain dietary factors and colorectal neoplasia in women seems to vary by menopausal status. Given these observations, women may be affected differently than men by diet-related factors. The objective of this article was therefore to review the data for diet and colorectal adenomas and cancer, and then attempt to address the potential differences in the association of diet-related factors and colorectal neoplasia in men and women. For total energy intake, selenium, and fiber, it seems that there may be slightly stronger effects in men as compared with women, whereas calcium and folate seem to affect both sexes similarly. With regard to vitamin D and colorectal cancer, women may exhibit stronger associations than men. Perhaps the most evidence for a sex-specific effect is observed for obesity, where more substantial direct relationships between body size and colorectal neoplasia have been reported for men than for women. However, this observation may be influenced by the differential effects in women by menopausal status. Further research on sex-specific dietary effects is warranted.

Trace element concentration distributions in breast, lung and colon tissues

The concentrations of Fe, Cu, Zn and Se in cancerous and benign tissues of breast, lung and intestine (colon) have been determined. In the cases when the element concentration has not been determined in all samples the Kaplan-Meier method has been used for the reconstruction of the original concentration distributions and estimation of the true mean concentrations and medians. Finally, the log-rank test has been applied to compare the elemental concentration distributions between cancerous and benign tissues of the same organ, between cancerous tissues and between benign tissues taken from different organs. Comparing benign and malignant neoplastic tissues, statistically significant differences have been found between Fe and Se concentration distributions of breast as well as for Cu and Zn in the case of lung tissues and in the case of colon tissues for Zn. The concentrations of all elements have been found to be statistically different in cancer tissues as well as in benign ones when comparing the different organs, i.e. groups 'breast-colon' and 'breast-lung'. Concentrations of Fe and Cu have been found to be statistically different in lung and colon cancerous tissues. For benign tissues of lung and colon a statistically significant difference has been found only for Zn.

Evaluation of colon cancer elements contents in serum using statistical methods

Classification of normal and different cancer groups (TNM classification) with univariate and multivariate statistical methods according to the contents of Cu, Fe, Mn, Se, and Zn in blood serum is discussed. All serum samples were digested by acid mixture in a microwave mineralization unit prior to the analysis by atomic absorption spectrometry. Results show that univariate methods can distinguish normal and cancer groups. Level of selenium evaluated as arithmetic mean with its standard deviation in colorectal cancer patients was (42.61 ± 23.76) µg L−1. Retransformed mean was used to evaluate levels of managanese (11.99 ± 1.71) µg L−1, copper (1.05 ± 0.06) mg L−1, zinc (2.14 ± 0.21) mg L−1, and iron (1.82 ± 0.22) mg L−1. Conclusions of multivariate statistical procedures (principal component analysis, hierarchical, and k-means clustering) do not correlate very well with the division of serum samples according to the TNM classification.

Studies into the Anticancer Effects of Selenomethionine against Human Colon Cancer

Colorectal cancer is the third most frequent fatal malignant neoplasm in the United States and is expected to cause significant morbidity and mortality. The recent recall of cyclooxygenase-2 inhibitors from clinical trials highlights the need to develop other agents for cancer chemoprevention trials. Intervention strategies with selenium compounds represent a viable option to reduce colon cancer. Here we discuss epidemiologic studies and ongoing clinical trials with selenium. In addition, we discuss preclinical mechanistic studies that provide insights into the biochemical and molecular bases for the anticancer effects of selenomethionine.

Selenium and colorectal adenoma: results of a pooled analysis

BACKGROUND

Secondary analyses of data from a large randomized clinical trial have suggested that intake of the trace element selenium reduces risk of colorectal neoplasia, but epidemiologic studies have not shown a consistent protective association.

METHODS

We conducted a combined analysis of data from three randomized trials--the Wheat Bran Fiber Trial, the Polyp Prevention Trial, and the Polyp Prevention Study--which tested the effects of various nutritional interventions for colorectal adenoma prevention among participants who recently had an adenoma removed during colonoscopy. Selenium concentrations were measured from blood specimens from a total of 1763 trial participants, and quartiles of baseline selenium were established from the pooled data. To estimate the association between baseline selenium and colorectal adenoma risk, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression modeling. All statistical tests were two-sided.

RESULTS

Individual study results among participants whose blood selenium concentrations were in the highest versus the lowest quartile varied in magnitude (Polyp Prevention Trial: OR = 0.67, 95% CI = 0.43 to 1.05; P(trend) = .21; Wheat Bran Fiber Trial: OR = 0.66, 95% CI = 0.40 to 1.10; P(trend) = .13, and Polyp Prevention Study: OR = 0.57, 95% CI = 0.34 to 0.95, P(trend) = .04). Analyses of the pooled data showed that individuals whose blood selenium values were in the highest quartile (median = 150 ng/mL) had statistically significantly lower odds of developing a new adenoma compared with those in the lowest quartile (OR = 0.66, 95% CI = 0.50 to 0.87; P(trend) = .006).

CONCLUSIONS

The inverse association between higher blood selenium concentration and adenoma risk supports previous findings indicating that higher selenium status may be related to decreased risk of colorectal cancer.

Review article: chemoprevention of colorectal cancer

Colorectal cancer is a disease with a high mortality at present, due to the late stage at which many cases present. Attention is therefore focusing on preventative strategies for colorectal cancer given that polyps appear to be identifiable and treatable precursor lesions of this disease. Endoscopic polypectomy has been shown to reduce the incidence of colorectal cancer and there is a good case for endoscopic screening of the general population. However, this will require a large amount of manpower and resources and its success will also depend on the overall compliance of the population. Epidemiological studies have shown that individuals reporting a regular intake of aspirin and other non-steroidal anti-inflammatory drugs have a reduced risk of developing colorectal polyps and cancer. Similarly, a number of natural substances, such as calcium and folate, when supplemented regularly in the diet, have also been linked to a possible decreased incidence of colorectal cancer. This has led to the concept of using such agents to reduce the number of cases of colorectal cancer. In this article, we review the current evidence for the use of these and other agents for the chemoprevention of colorectal cancer, together with theories as to their possible mechanisms of action.

Comparison of the serum selenium content of healthy adults living in the Antwerp region (Belgium) with recent literature data

Graphite furnace atomic absorption spectrometry, after improved matrix modification and using Zeeman background correction, was used to measure the serum selenium content of healthy adults living in the Antwerp region (Belgium). The mean serum concentration of 13 men and 13 women, sampled once a month during 1 year, was 84.3 +/- 9.4ng/ml with a broad range of 51.4-121.7 ng/ml. The intra-individual variation was remarkably high. Recent literature on selenium concentrations is reviewed and values are tabulated, with limitation to healthy adults and European countries. The mean serum selenium concentration measured corresponded well to older literature data for Belgium. The obtained values were found to be in the medium range compared with the literature data for other European countries.

Serum selenium and risk of large size colorectal adenomas in a geographical area with a low selenium status

OBJECTIVE

Selenium is a fundamental nutrient to human health that might have anticarcinogenic effects. Previous studies have assessed the possible relationship of selenium status to colorectal adenomas with controversial results. We primarily aimed to assess the relationship of serum selenium status with the presence of large size colorectal adenomas in subjects living in a poor selenium region. The serum selenium status in colorectal cancer was also evaluated.

METHODS

Serum selenium levels were measured in 28 patients with large size sporadic adenomatous polyps, 24 patients with colorectal adenocarcinomas, and 35 age-matched healthy individuals. A logistic regression analysis was performed to assess the relationship of serum selenium to colorectal adenomatous polyps after adjusting for confounding variables (age, sex, smoking habit, and alcohol drinking).

RESULTS

Among subjects aged < or = 60 yr, mean serum selenium levels were significantly lower in both patient groups (adenoma, 57.9 +/- 4.3 microg/L; cancer, 43.7 +/- 6.6 microg/L) than in healthy controls (88.9 +/- 8 microg/L) (p = 0.0001). There were no difference among subjects > 60 yr old. A significant inverse association between selenium status and the diagnosis of large size adenomatous polyps after adjusting for confounding variables was found (adjusted p = 0.029). Subjects with higher selenium status (> or = 75th percentile value of 82.11 microg/L) had a lower probability (OR = 0.17, 95% CI = 0.03-0.84) to be in the adenoma group than subjects with lower selenium status (< 82.11 microg/L). This association was more marked in subjects aged < or = 60 yr (adjusted p value = 0.04, OR = 0.08, 95% CI = 0.007-0.91), and was not significant in older subjects.

CONCLUSIONS

Results suggest that high selenium status may decrease the risk of large size adenomas in a low selenium region, and that this preventive effect seems to be exclusive to subjects < or = 60 yr. These results will need to be confirmed in additional epidemiological studies before recommending selenium supplementation in patients with colon adenomas.

Micronutrient status and glutathione peroxidase in bedridden patients on tube feeding

Deficiency of micronutrients, especially selenium, is common in critically ill patients. We investigated the micronutrient status (selenium, zinc, copper and manganese) and glutathione peroxidase (GSH-Px) activity in 30 tube-fed patients and 21 hospitalized non-tube-fed control patients. Serum levels of selenium, copper and manganese in tube-fed patients were significantly lower than in control patients (selenium: 4.85+/-1.38 microg/dl versus 8.67+/-1.45 pg/dl; copper: 44.7+/-36.9 microg/dl versus 92.1+/-21.2 microg/dl; manganese 0.59+/-0.41 microg/dl versus 1.52+/-0.59 microg/dl). However, zinc and log GSH-Px in the serum were similar in the two groups. Serum selenium concentration correlated with the daily intake of selenium in tube-fed patients, but zinc, copper and manganese concentrations did not correlate with the daily intake of the respective trace elements in tube-fed patients. Blood GSH-Px activity correlated positively with serum selenium concentrations in the control patients, but not in tube-fed patients. These results demonstrate that selenium content of enteral feed appears to be insufficient to maintain normal serum levels in elderly bedridden patients. Our findings emphasize the importance of monitoring micronutrient status in patients on enteral feeding to avoid trace element deficiencies.

Antioxidant nutrients: current dietary recommendations and research update

OBJECTIVE

To review the importance of antioxidant nutrients in the maintenance of health and the prevention and treatment of disease, with a focus on data pertaining to vitamin C, vitamin E, selenium, and carotenoids. A secondary objective was to discuss the new Dietary Reference Intakes released by the Institute of Medicine (IOM) for these nutrients.

DATA SOURCES

IOM reports on the use of antioxidant vitamins were reviewed for nutrient recommendations. In addition, a MEDLINE search was performed to identify recent research and review articles on the topic, which were analyzed to identify key research findings in the area.

DATA SYNTHESIS

The review discusses the biologic processes of oxidation reactions and antioxidants in biologic systems, provides an overview of information on selected antioxidant nutrients, and explores their role in the prevention and treatment of cancer, cardiovascular disease, ocular disorders, and respiratory disorders.

CONCLUSION

There appear to be significant health benefits from dietary antioxidants, as can be found in fruits and vegetables. Some prospective assessment of the effect of supplemental antioxidants also suggests benefit, especially for vitamin E; however, there are conflicting results in this area. Overall, it appears that antioxidant nutrients, especially those from food sources, have important roles in preventing pathogenic processes related to cancer, cardiovascular disease, macular degeneration, cataracts, and asthma, and may enhance immune function.

Essentiality of selenium in the human body: relationship with different diseases

In the present review different aspects related to the essential element selenium in the human organism are considered. A large number of human studies have been performed in order to improve knowledge on the influence of this element in the origin and development of several degenerative diseases. Selenium deficiencies among human beings as well as animals are being recognized worldwide to be related to a number of pathologies. This element has also the special characteristic that the range between its essential and toxic character is very close, and consequently daily dietary intake should be appropriately monitored in individuals. Nevertheless, nowadays there is still a lot of controversy about the optimum dietary level of this element in order to cure or to prevent the appearance of diseases such as cirrhosis, cancer, diabetes, or cardiovascular pathologies. Results obtained in several animal and epidemiological studies have indicated that Se could constitute a dietary factor with protective action against several degenerative diseases.

Effect of selenium supplementation on the activities of glutathione metabolizing enzymes in human hepatoma Hep G2 cell line

Cell culture is an important tool for studying injury to cells exposed to oxidative stress. The human hepatoblastoma derived Hep G2 cells retain their morphology and most of their function in culture and are therefore widely used as an in vitro model of human hepatocytes. Conventional cell culture media are deficient in selenium, which is essential for activation of glutathione peroxidase (GPx), a key enzyme in the defense against oxidative stress. Supplementation of the culture media with 1 microM sodium selenite increased the activities of total GPx by threefold and the selenium-dependent GPx by fourfold as compared to cells cultured in control media. The non-selenium-dependent GPx activity was unchanged. The activities of the other glutathione (GSH)-related enzymes were practically unchanged despite a tendency toward elevation. The activities of oxidized glutathione (GSSG) reductase and catalase increased by 22.4 and 27.4%, respectively. These relatively small increases did not carry statistical significance. Supplementation of tissue culture media with selenium may prove important, particularly for cell protection against oxidative stress.

Role of reactive oxygen species in apoptosis: implications for cancer therapy

Reactive oxygen species are widely generated in biological systems. Consequently humans have evolved antioxidant defence systems that limit their production. Intracellular production of active oxygen species such as *OH, O2- and H2O2 is associated with the arrest of cell proliferation. Similarly, generation of oxidative stress in response to various external stimuli has been implicated in the activation of transcription factors and to the triggering of apoptosis. Here we review how free radicals induce DNA sequence changes in the form of mutations. deletions, gene amplification and rearrangements. These alterations may result in the initiation of apoptosis signalling leading to cell death, or to the activation of several proto-oncogenes and or the inactivation of some tumour suppressor genes. The regulation of gene expression by means of oxidants, antioxidants and the redox state remains as a promising therapeutic approach. Several anticarcinogenic agents have been shown to inhibit reactive oxygen species production and oxidative DNA damage, inhibiting tumour promotion. In addition, recombinant vectors expressing radical-scavenging enzymes reduce apoptosis. In conclusion, oxidative stress has been implicated in both apoptosis and the pathogenesis of cancer providing contrived support for two notions: free radical reactions may be increased in malignant cells and oxidant scavenging systems may be useful in cancer therapy.