Influence of the selenium level on overall survival in lung cancer

Preoperative Serum Selenium Concentrations and Disease-Specific Survival in Patients With Oral Cancer: A Long-Term Follow-Up Study

BACKGROUND

Serum selenium (Se) concentration has been reported to be associated with the incidence of oral cancer. The association between serum Se and long-term survival in oral cancer patients is still unclear.

PURPOSE

The purpose of this study is to measure the association between serum Se and disease-specific survival (DSS).

STUDY DESIGN, SETTING, AND SAMPLE

This was a single-center, prospective cohort study conducted at the First Affiliated Hospital of Fujian Medical University (Fujian Province, China) from September 2011 to December 2018. The inclusion criteria were patients with newly diagnosed primary oral cancer confirmed by histology. The exclusion criteria were patients with recurrent oral cancer or metastatic cancer.

PREDICTOR VARIABLE

The predictor variable is the preoperative serum Se concentration measured using inductively coupled plasma-mass spectrometry.

MAIN OUTCOME VARIABLE(S)

The primary outcome variable is DSS calculated from the date of diagnosis to the date of death due to oral cancer or the end of follow-up, whichever occurred first.

COVARIATES

The covariates were age, sex, occupation, education level, body mass index, surgery therapy, adjuvant therapy, tumor node metastasis stage, and pathological grading.

ANALYSES

Kaplan-Meier survival analysis, Cox proportional hazards regression, and restricted cubic spline regression were utilized. P value < .05 was significant.

RESULTS

The sample was composed of 235 subjects with a median age of 59 years (ranged from 20 to 80 years) and 142 (60.43%) were male. The median follow-up was 54.90 months (interquartile range: 35.47). Se levels were associated with DSS (unadjusted hazard ratio [HR] = 0.70; 95% confidence interval [CI]: 0.54-0.91) suggesting that higher levels of Se are associated with longer or improved DSS. After adjustment of age, sex, occupation, education level, residence, tumor node metastasis stage, pathological grading, surgery therapy, radiotherapy, and chemotherapy, patients with higher serum Se had a better DSS (aHR = 0.67; 95% CI: 0.49-0.92). Of note, we found that the association between serum Se and DSS was observed only in patients with radiotherapy (aHR = 0.49; 95% CI: 0.33-0.73). And the protective effect of radiotherapy on survival was only observed in patients with higher Se concentrations (aHR = 0.36; 95% CI: 0.20-0.63). Additionally, there was a multiplicative interaction between Se and radiotherapy on the prognosis of oral cancer patients (Pinteraction<0.01).

CONCLUSION AND RELEVANCE

Our findings suggest that a high Se concentration might contribute to better DSS among oral cancer patients, and the effect may partly depend on radiotherapy treatment. Given these findings, additional research should focus on the role of Se in DSS among oral cancer patients and the interaction with radiotherapy.

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.

Association between blood heavy metals and lung cancer risk: A case-control study in China

BACKGROUND

Exposure to various metals has been reported to lead to lung cancer. However, few studies focused on the combined effects of metal mixture.

OBJECTIVE

To explore the relationship between metal mixture and lung cancer patients.

METHODS

Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the concentration of 8 heavy metals (V, Cr, Mn, Se, Mo, Cd, Ba and Pb) in serum samples of 86 cases and 105 controls in the Tianjin Lung Cancer Cohort. Logistic regression models were used to estimate the effect of each metal on the risk of lung cancer. The restricted cubic spline function was applied to describe the dose-response relationship between various metal concentrations and lung cancer risk. Bayesian Kernel Machine Regression (BKMR), Weighted Quantile Sum (WQS) and Quantile G-Computation (QGC) were employed to explore the effects of metal mixtures as a whole on lung cancer.

RESULTS

An increased risk of lung cancer was associated with higher blood Mo concentration (adjusted OR = 2.94, 95% CI = 1.03-8.74 for tertile 2 vs. tertile 1). Higher Se concentration in blood may have protective effects on the risk of lung cancer (adjusted OR = 0.18, 95% CI = 0.06-0.51 for tertile 3 vs. tertile 1, p-trend <0.001). In addition, Se and Cd may have an antagonism effect on the occurrence of lung cancer (RERI and 95% CI = -0.95 [-31.77, -0.07]; AP and 95% CI = -0.95 [-5.16 -0.74]). Although the metal mixture did not show a significant effect on lung cancer as a whole, this may be due to the offsetting effect between positive and negative effects.

CONCLUSIONS

Our research indicates that Se has a promising anti-cancer application, but it is necessary to prevent the role of Cd that antagonize Se in lung cancer.

Matched analysis of circulating selenium with the breast cancer selenotranscriptome: a multicentre prospective study

INTRODUCTION

Low serum selenium and altered tumour RNA expression of certain selenoproteins are associated with a poor breast cancer prognosis. Selenoprotein expression stringently depends on selenium availability, hence circulating selenium may interact with tumour selenoprotein expression. However, there is no matched analysis to date.

METHODS

This study included 1453 patients with newly diagnosed breast cancer from the multicentric prospective Sweden Cancerome Analysis Network - Breast study. Total serum selenium, selenoprotein P and glutathione peroxidase 3 were analysed at time of diagnosis. Bulk RNA-sequencing was conducted in matched tumour tissues. Fully adjusted Cox regression models with an interaction term were employed to detect dose-dependent interactions of circulating selenium with the associations of tumour selenoprotein mRNA expression and mortality.

RESULTS

237 deaths were recorded within ~ 9 years follow-up. All three serum selenium biomarkers correlated positively (p < 0.001). All selenoproteins except for GPX6 were expressed in tumour tissues. Single cell RNA-sequencing revealed a heterogeneous expression pattern in the tumour microenvironment. Circulating selenium correlated positively with tumour SELENOW and SELENON expression (p < 0.001). In fully adjusted models, the associations of DIO1, DIO3 and SELENOM with mortality were dose-dependently modified by serum selenium (p < 0.001, p = 0.020, p = 0.038, respectively). With increasing selenium, DIO1 and SELENOM associated with lower, whereas DIO3 expression associated with higher mortality. Association of DIO1 with lower mortality was only apparent in patients with high selenium [above median (70.36 µg/L)], and the HR (95%CI) for one-unit increase in log(FPKM + 1) was 0.70 (0.50-0.98).

CONCLUSIONS

This first unbiased analysis of serum selenium with the breast cancer selenotranscriptome identified an effect-modification of selenium on the associations of DIO1, SELENOM, and DIO3 with prognosis. Selenium substitution in patients with DIO1-expressing tumours merits consideration to improve survival.

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.

Review on the health-promoting effect of adequate selenium status

Selenium is an essential microelement involved in various biological processes. Selenium deficiency increases the risk of human immunodeficiency virus infection, cancer, cardiovascular disease, and inflammatory bowel disease. Selenium possesses anti-oxidant, anti-cancer, immunomodulatory, hypoglycemic, and intestinal microbiota-regulating properties. The non-linear dose-response relationship between selenium status and health effects is U-shaped; individuals with low baseline selenium levels may benefit from supplementation, whereas those with acceptable or high selenium levels may face possible health hazards. Selenium supplementation is beneficial in various populations and conditions; however, given its small safety window, the safety of selenium supplementation is still a subject of debate. This review summarizes the current understanding of the health-promoting effects of selenium on the human body, the dietary reference intake, and evidence of the association between selenium deficiency and disease.

Minerals and Cancer: Overview of the Possible Diagnostic Value

Simple Summary

Minerals are important but often overlooked compounds that are required for a variety of cellular biochemical processes and pathways that regulate cell proliferation. Their dietary imbalance, which is becoming more common in the diets of industrialized countries, is linked to an increased risk of cancer. The current review will present some of the most important minerals for human physiology and evaluate their potential application as cancer biomarkers.

Abstract

Cancer is the second leading cause of death worldwide and is expected to increase by one-third over the next two decades, in parallel with the growing proportion of the elderly population. Treatment and control of cancer incidence is a global issue. Since there is no clear way to prevent or cure this deadly malignancy, diagnostic, predictive, and prognostic markers for oncological diseases are of great therapeutic value. Minerals and trace elements are important micronutrients for normal physiological function of the body. They are abundant in natural food sources and are regularly included in dietary supplements whereas highly processed industrial food often contains reduced or altered amounts of them. In modern society, the daily intake, storage pools, and homeostasis of these micronutrients are dependent on certain dietary habits and can be thrown out of balance by malignancies. The current work summarizes the data on minerals and trace elements associated with abnormal accumulation or depletion states in tumor patients and discusses their value as potential tumor-associated biomarkers that could be introduced into cancer therapy.

Prediagnostic Blood Selenium Status and Mortality among Patients with Colorectal Cancer in Western European Populations

A higher selenium (Se) status has been shown to be associated with lower risk for colorectal cancer (CRC), but the importance of Se in survival after CRC diagnosis is not well studied. The associations of prediagnostic circulating Se status (as indicated by serum Se and selenoprotein P (SELENOP) measurements) with overall and CRC-specific mortality were estimated using multivariable Cox proportional hazards regression among 995 CRC cases (515 deaths, 396 from CRC) in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Se and SELENOP serum concentrations were measured on average 46 months before CRC diagnosis. Median follow-up time was 113 months. Participants with Se concentrations in the highest quintile (≥100 µg/L) had a multivariable-adjusted hazard ratio (HR) of 0.73 (95% CI: 0.52-1.02; Ptrend = 0.06) for CRC-specific mortality and 0.77 (95% CI: 0.57-1.03; Ptrend = 0.04) for overall mortality, compared with the lowest quintile (≤67.5 µg/L). Similarly, participants with SELENOP concentrations in the highest (≥5.07 mg/L) compared with the lowest quintile (≤3.53 mg/L) had HRs of 0.89 (95% CI: 0.64-1.24; Ptrend = 0.39) for CRC-specific mortality and 0.83 (95% CI: 0.62-1.11; Ptrend = 0.17) for overall mortality. Higher prediagnostic exposure to Se within an optimal concentration (100-150 µg/L) might be associated with improved survival among CRC patients, although our results were not statistically significant and additional studies are needed to confirm this potential association. Our findings may stimulate further research on selenium's role in survival among CRC patients especially among those residing in geographic regions with suboptimal Se availability.

Selenium stimulates the antitumour immunity: Insights to future research

Selenium is an essential trace element for regulating immune functions through redox-regulating activity of selenoproteins (e.g. glutathione peroxidase), protecting immune cells from oxidative stress. However, in cancer, selenium has biological bimodal action depending on the concentration. At nutritional low doses, selenium, depending on its form, may act as an antioxidant, protecting against oxidative stress, supporting cell survival and growth, thus, plays a chemo-preventive role; while, at supra-nutritional higher pharmacological doses, selenium acts as pro-oxidant inducing redox signalling and cell death. To date, many studies have been conducted on the benefits of selenium intake in reducing the risk of cancer incidence at the nutritional level, indicating that likely selenium functions as an immunostimulator, i.e. reversing the immunosuppression in tumour microenvironment towards antitumour immunity by activating immune cells (e.g. M₁ macrophages and CD8⁺ T-lymphocytes) and releasing pro-inflammatory cytokines such as interferon-gamma; whereas, fewer studies have explored the effects of supra-nutritional or pharmacological doses of selenium in cancer immunity. This review, thus, systematically analyses the current knowledge about how selenium stimulates the immune system against cancer and lay the groundwork for future research. Such knowledge can be promising to design combinatorial therapies with Selenium-based compounds and other modalities like immunotherapy to lower the adverse effects and increase the efficacy of treatments.

Serum Selenium Level and 10-Year Survival after Melanoma

Melanoma is one of the most aggressive human malignancies. The determination of prognostic biomarkers is important for the early detection of recurrence and for the enrollment of the patients into different treatment regimens. Herein, we report the 10-year survival of 375 melanoma patients depending on their serum selenium levels. The study group was followed up from the date of melanoma diagnosis until death or 2020. Patients were assigned to one of four categories, in accordance with the increasing selenium level (I-IV quartiles). The subgroup with low selenium levels had a significant lower survival rate in relation to patients with high selenium levels, HR = 8.42; p = 0.005 and HR = 5.83; p = 0.02, for uni- and multivariable models, respectively. In the univariable analysis, we also confirmed the association between Breslow thickness, Clark classification and age at melanoma prognosis. In conclusion, a low serum selenium level was associated with an increased mortality rate in the 10 years following melanoma diagnosis. Future studies in other geographic regions with low soil selenium levels should be conducted to confirm our findings.

Influence of the Levels of Arsenic, Cadmium, Mercury and Lead on Overall Survival in Lung Cancer

The effects of heavy metals on cancer risk have been widely studied in recent decades, but there is limited data on the effects of these elements on cancer survival. In this research, we examined whether blood concentrations of the heavy metals arsenic, cadmium, mercury and lead were associated with the overall survival of lung cancer patients. The study group consisted of 336 patients with lung cancer who were prospectively observed. Blood concentrations of heavy metals were measured to study the relationship between their levels and overall survival using Cox proportional hazards analysis. The hazard ratio of death from all causes was 0.99 (p = 0.94) for arsenic, 1.37 (p = 0.15) for cadmium, 1.55 (p = 0.04) for mercury, and 1.18 (p = 0.47) for lead in patients from the lowest concentration quartile, compared with those in the highest quartile. Among the patients with stage IA disease, this relationship was statistically significant (HR = 7.36; p < 0.01) for cadmium levels in the highest quartile (>1.97–7.77 µg/L) compared to quartile I (0.23–0.57 µg/L, reference). This study revealed that low blood cadmium levels <1.47 µg/L are probably associated with improved overall survival in treated patients with stage IA disease.

Translational Nanotherapeutics Reprograms Immune Microenvironment in Malignant Pleural Effusion of Lung Adenocarcinoma

Malignant pleural effusion (MPE) remains a treatment bottleneck in advanced lung cancer, due to its complicated microenvironments and "cold" immunity. Therefore, the search for therapeutic drugs to transform MPE to functionally "hot" one could advance the development of effective immunotherapeutic strategy. Herein, translational selenium nanoparticles coated with immune-modulating macromolecule lentinan (SeNPs@LNT) are designed to restore the dysfunctional immune cells in patient-derived MPE microenvironment. Internalization of the SeNPs@LNT can effectively reduce the immunosuppressive status by enhancing the proliferation of CD4⁺ T cells and natural killer cells, and remodeling the tumor associated macrophages into tumoricidal M1 phenotype in MPE derived from patients presenting low Se levels in blood and pleural effusion. Th1, cytotoxic T cell, γδ T, and B cell functions are upregulated, and Th2, Th17, and Treg cells activity is downregulated. Furthermore, SeNPs@LNT can be gradually metabolized into SeCys2 to promote the production of metabolites associated with tumor growth inhibition and immune response activation in MPE microenvironment. In contrast, lung cancer markers and vitamin B6 metabolism are decreased. The translational SeNP-based nanotherapeutic strategy restores functional "cold" MPE to "hot" MPE to activate the immune responses of various immune cells in MPE of lung cancer patients.

Serum Selenium Level Predicts 10-Year Survival after Breast Cancer

In a recent prospective study, we reported an association between a low serum selenium level and five-year survival among breast cancer patients. We now have updated the cohort to include 10-year survival rates. A blood sample was obtained from 538 women diagnosed with first primary invasive breast cancer between 2008 and 2015 in the region of Szczecin, Poland. Blood was collected before initiation of treatment. Serum selenium levels were quantified by mass spectroscopy. Each patient was assigned to one of four quartiles based on the distribution of serum selenium levels in the whole cohort. Patients were followed from diagnosis until death or last known alive (mean follow-up 7.9 years). The 10-year actuarial cumulative survival was 65.1% for women in the lowest quartile of serum selenium, compared to 86.7% for women in the highest quartile (p < 0.001 for difference). Further studies are needed to confirm the protective effect of selenium on breast cancer survival. If confirmed this may lead to an investigation of selenium supplementation on survival of breast cancer patients.

Serum and Whole Blood Cu and Zn Status in Predicting Mortality in Lung Cancer Patients

Alterations in circulating Cu and Zn are negative predictors of survival in neoplastic patients and are known during lung cancer. However, no data on predicting mortality of lung cancer patients based on the level of these elements in the blood have been presented to date. The aims of this prospective cohort study were as follows: (i) To evaluate the disturbances in serum and whole blood Cu and Zn, (ii) to assess the relationships between serum and whole blood Cu and Zn status and clinical, sociodemographic, and nutritional data, and (iii) to investigate the association of Cu and Zn status with all-cause mortality in lung cancer. Naïve-treatment lung cancer patients (n = 167) were characterized in terms of sociodemographic, clinical, and anthropometric data and dietary intake and compared with sex-matched control subjects (n = 48). Whole blood and serum Cu and Zn status was determined by atomic absorption spectrometry. Cox proportional hazards models adjusted for multiple confounders/mediators were used to estimate the association between all-cause death and Cu and Zn status. Sex, cardiovascular disease, chronic obstructive pulmonary disease, clinical stage, and hemoglobin, platelet, and glucose concentrations significantly differentiated Cu and Zn status. All-cause mortality in lung cancer patients was positively associated with serum Cu levels, Cu:Zn ratio, and whole blood Zn levels. However, an advanced clinical stage of disease was the strongest predictor of all-cause mortality. Circulatory status of Cu and Zn might be included in routine clinical characteristics of patients with lung cancer patients as additional prognostic variables, but only after further more detail studies.

Downregulation of histone-lysine N-methyltransferase EZH2 inhibits cell viability and enhances chemosensitivity in lung cancer cells

Histone-lysine N-methyltransferase EZH2 (EZH2) is the principle component of the polycomb repressive complex 2 (PRC2)/embryonic ectoderm development protein-EZH2 complex, which promotes tumorigenesis by repressing transcription of tumor suppressor genes. EZH2 is considered a key marker in several types of cancer, such as colorectal and prostate cancer. However, the molecular mechanisms and clinical value of EZH2 in lung cancer have not yet been fully investigated. The aim of the present study was to investigate the functions of EZH2 in lung cancer progression and to determine whether treatment with an EZH2 inhibitor enhanced the chemosensitivity of lung cancer cells to cisplatin (CDDP). At the logarithmic growth phase, A549 cells were treated with a small interfering (si)RNA-EZH2, and cell viability was detected using an MTT assay. The degree of apoptosis and cell cycle were detected using flow cytometry. Cell migration and invasion were detected via wound healing and Transwell Matrigel assays. According to information from the Gene Expression Omnibus database, the results of the present study demonstrated that EZH2 was upregulated in lung cancer. Furthermore, overexpression of EZH2 was associated with poor patient prognosis, while EZH2 knockdown inhibited cell viability and migration, and enhanced apoptosis and chemosensitivity in a lung cancer cell line. EZH2 knockdown and treatment of A549 cells using EZH2 inhibitor elevated the inhibitory effects of CDDP on cell viability and apoptosis. Western blot and reverse transcription-quantitative PCR analyses were performed to assess the expression levels of relative protein and mRNA, respectively, in A549 cells treated with siRNA-EZH2 or with CDDP. Overall, the results of the present study demonstrated that high EZH2 expression was associated with poor prognosis, accompanied with a potential impairment of migration and viability in lung cancer cells. These findings suggest that EZH2 may act as a candidate molecular target for gene therapy, and treatment with EZH2 inhibitor may be used to increase chemosensitivity to CDDP agents in lung cancer.

Selenium and Copper as Biomarkers for Pulmonary Arterial Hypertension in Systemic Sclerosis

Circulating selenoprotein P (SELENOP) constitutes an established biomarker of Se status. SELENOP concentrations are reduced in inflammation and severe disease. Recently, elevated SELENOP levels have been suggested as diagnostic marker and therapeutic target in pulmonary arterial hypertension (PAH). We decided to re-evaluate this hypothesis. A group of healthy controls (n = 30) was compared with patients suffering from systemic sclerosis (SSc, n = 66), one third with SSc-related PAH. Serum was analysed for trace elements and protein biomarkers, namely SELENOP, glutathione peroxidase 3 (GPx3) and ceruloplasmin (CP). Compared to controls, patients with SSc-related PAH displayed reduced serum Se (91 ± 2 vs. 68 ± 2 µg/L) and SELENOP concentrations (3.7 ± 0.8 vs. 2.7 ± 0.9 mg/L), along with lower GPx3 activity (278 ± 40 vs. 231 ± 54 U/L). All three biomarkers of Se status were particularly low in patients with skin involvement. Serum Cu was not different between the groups, but patients with SSc-related PAH showed elevated ratios of Cu/Se and CP/SELENOP as compared to controls. Our data indicate that patients with SSc-related PAH are characterized by reduced Se status in combination with elevated CP, in line with other inflammatory diseases. Further analyses are needed to verify the diagnostic value of these TE-related biomarkers in PAH.

Biochemical Markers of Saliva in Lung Cancer: Diagnostic and Prognostic Perspectives

The aim of the work is to study the metabolic characteristics of saliva in lung cancer for use in early diagnosis and determining the prognosis of the disease. The patient group included 425 lung cancer patients, 168 patients with non-cancerous lung diseases, and 550 healthy volunteers. Saliva samples were collected from all participants in the experiment before treatment and 34 biochemical saliva parameters were determined. Participants were monitored for six years to assess survival rates. The statistical analysis was performed by means of Statistica 10.0 (StatSoft) program and R package (version 3.2.3). To construct the classifier, the Random Forest method was used; the classification quality was assessed using the cross-validation method. Prognostic factors were analyzed by multivariate analysis using Cox's proportional hazard model in a backward step-wise fashion to adjust for potential confounding factors. A complex of metabolic changes occurring in saliva in lung cancer is described. Seven biochemical parameters were identified (catalase, triene conjugates, Schiff bases, pH, sialic acids, alkaline phosphatase, chlorides), which were used to construct the classifier. The sensitivity and specificity of the method were 69.5% and 87.5%, which is practically not inferior to the diagnostic characteristics of markers routinely used in the diagnosis of lung cancer. Significant independent factors in the poor prognosis of lung cancer are imidazole compounds (ICs) above 0.478 mmol/L and salivary lactate dehydrogenase activity below 545 U/L. Saliva has been shown to have great potential for the development of diagnostic and prognostic tests for lung cancer.

Insights into cancer and neurodegenerative diseases through selenoproteins and the connection with gut microbiota - current analytical methodologies

Introduction: Selenium plays many key roles in health especially in connection with cancer and neurodegenerative diseases. However, it needs to be appreciated that the essentiality/toxicity of selenium depends on both, a narrow range of concentration and the chemical specie involved. In this context, selenoproteins are essential biomolecules against these disorders, mainly due to its antioxidant action. To this end, analytical methodologies may allow identifying and quantifying individual selenospecies in human biofluids and tissues. Areas covered: This review focus on the role of selenoproteins in medicine, with special emphasis in cancer and neurodegenerative diseases, considering the possible link with gut microbiota. In particular, this article reviews the analytical techniques and procedures recently developed for the absolute quantification of selenoproteins and selenometabolites in human biofluids and tissues. Expert commentary: The beneficial role of selenium in human health has been extensively studied and reviewed. However, several challenges remain unsolved as discussed in this article: (i) speciation of selenium (especially selenoproteins) in cancer and neurodegenerative disease patients; (ii) supplementation of selenium in humans using functional foods and nutraceuticals; (iii) the link between selenium and selenoproteins expression and the gut microbiota and (iv) analytical methods and pitfalls for the absolute quantification of selenoproteins and selenometabolites.