Selective modulation of the therapeutic efficacy of anticancer drugs by selenium containing compounds against human tumor xenografts

The Role of Selenium in Pathologies: An Updated Review

Selenium is an essential microelement required for a number of biological functions. Selenium—and more specifically the amino acid selenocysteine—is present in at least 25 human selenoproteins involved in a wide variety of essential biological functions, ranging from the regulation of reactive oxygen species (ROS) concentration to the biosynthesis of hormones. These processes also play a central role in preventing and modulating the clinical outcome of several diseases, including cancer, diabetes, Alzheimer’s disease, mental disorders, cardiovascular disorders, fertility impairments, inflammation, and infections (including SARS-CoV-2). Over the past years, a number of studies focusing on the relationship between selenium and such pathologies have been reported. Generally, an adequate selenium nutritional state—and in some cases selenium supplementation—have been related to improved prognostic outcome and reduced risk of developing several diseases. On the other hand, supra-nutritional levels might have adverse effects. The results of recent studies focusing on these topics are summarized and discussed in this review, with particular emphasis on advances achieved in the last decade.

A stratified randomized double-blind phase II trial of celecoxib for treating patients with cervical intraepithelial neoplasia: The potential predictive value of VEGF serum levels: An NRG Oncology/Gynecologic Oncology Group study

PURPOSE

To examine the effect of celecoxib on cervical intraepithelial neoplasia 3 (CIN 3). This is a NRG Oncology/Gynecologic Oncology Group study with translational biomarkers.

PATIENTS AND METHODS

Patients with CIN 3 were randomized to celecoxib 400mg once daily (67 patients) or placebo (63 patients) for 14-18weeks. The primary outcome measure was histologic regression. A test of equal probabilities of success between two therapies was conducted, using Fisher's Exact Test at alpha=10% and 90% power when the treatment arm boosted the probability of success by 30%. Translational analysis included cervical tissue HPV genotyping, COX-2 expression in biopsies, and serum celecoxib and VEGF levels.

RESULTS

In primary analysis, histologic regression was not significantly higher in the celecoxib group (40%) than in the placebo group (34.1%). However, exploratory analyses suggest patients with high serum VEGF levels exhibited greater regression in the celecoxib arm (47.3%) than in the placebo arm (14.3%). Regression rates were similar by treatment group in patients with low VEGF. VEGF levels increased over time in the placebo group, but remained the same in the treatment group. COX-2 expression in cervical biopsies declined from pre-treatment to the end of treatment with celecoxib; it did not change with placebo.

CONCLUSIONS

Celecoxib at 400mg once daily for 14-18weeks did not significantly decrease the severity of CIN 3 compared with placebo except, possibly, in subjects with high baseline VEGF. Therefore, serum VEGF levels might identify patients who may benefit from celecoxib or other therapies, personalizing future chemoprevention trials for CIN 3.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Our systematic review has demonstrated that antioxidant supplements may increase mortality. We have now updated this review.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements for prevention of mortality in adults.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index Expanded, and Conference Proceedings Citation Index-Science to February 2011. We scanned bibliographies of relevant publications and asked pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Random-effects and fixed-effect model meta-analyses were conducted. Risk of bias was considered in order to minimise the risk of systematic errors. Trial sequential analyses were conducted to minimise the risk of random errors. Random-effects model meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Seventy-eight randomised trials with 296,707 participants were included. Fifty-six trials including 244,056 participants had low risk of bias. Twenty-six trials included 215,900 healthy participants. Fifty-two trials included 80,807 participants with various diseases in a stable phase. The mean age was 63 years (range 18 to 103 years). The mean proportion of women was 46%. Of the 78 trials, 46 used the parallel-group design, 30 the factorial design, and 2 the cross-over design. All antioxidants were administered orally, either alone or in combination with vitamins, minerals, or other interventions. The duration of supplementation varied from 28 days to 12 years (mean duration 3 years; median duration 2 years). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects model meta-analysis (21,484 dead/183,749 (11.7%) versus 11,479 dead/112,958 (10.2%); 78 trials, relative risk (RR) 1.02, 95% confidence interval (CI) 0.98 to 1.05) but significantly increased mortality in a fixed-effect model (RR 1.03, 95% CI 1.01 to 1.05). Heterogeneity was low with an I(2)- of 12%. In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. Meta-regression analysis did not find a significant difference in the estimated intervention effect in the primary prevention and the secondary prevention trials. In the 56 trials with a low risk of bias, the antioxidant supplements significantly increased mortality (18,833 dead/146,320 (12.9%) versus 10,320 dead/97,736 (10.6%); RR 1.04, 95% CI 1.01 to 1.07). This effect was confirmed by trial sequential analysis. Excluding factorial trials with potential confounding showed that 38 trials with low risk of bias demonstrated a significant increase in mortality (2822 dead/26,903 (10.5%) versus 2473 dead/26,052 (9.5%); RR 1.10, 95% CI 1.05 to 1.15). In trials with low risk of bias, beta-carotene (13,202 dead/96,003 (13.8%) versus 8556 dead/77,003 (11.1%); 26 trials, RR 1.05, 95% CI 1.01 to 1.09) and vitamin E (11,689 dead/97,523 (12.0%) versus 7561 dead/73,721 (10.3%); 46 trials, RR 1.03, 95% CI 1.00 to 1.05) significantly increased mortality, whereas vitamin A (3444 dead/24,596 (14.0%) versus 2249 dead/16,548 (13.6%); 12 trials, RR 1.07, 95% CI 0.97 to 1.18), vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07), and selenium (2670 dead/39,779 (6.7%) versus 1468 dead/22,961 (6.4%); 17 trials, RR 0.97, 95% CI 0.91 to 1.03) did not significantly affect mortality. In univariate meta-regression analysis, the dose of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002 to 1.001, P = 0.002).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.

Synthesis and evaluation of the anti-inflammatory properties of selenium-derivatives of celecoxib

Celecoxib is a selective cyclooxygenase (COX)-2 inhibitor used to treat inflammation, while selenium is known to down-regulate the transcription of COX-2 and other pro-inflammatory genes. To expand the anti-inflammatory property, wherein celecoxib could inhibit pro-inflammatory gene expression at extremely low doses, we incorporated selenium (Se) into two Se-derivatives of celecoxib, namely; selenocoxib-2 and selenocoxib-3. In vitro kinetic assays of the inhibition of purified human COX-2 activity by these compounds indicated that celecoxib and selenocoxib-3 had identical K(I) values of 2.3 and 2.4μM; while selenocoxib-2 had a lower K(I) of 0.72μM. Furthermore, selenocoxib-2 inhibited lipopolysaccharide-induced activation of NF-κB leading to the down-regulation of expression of COX-2, iNOS, and TNFα more effectively than selenocoxib-3 and celecoxib in RAW264.7 macrophages and murine bone marrow-derived macrophages. Studies with rat liver microsomes followed by UPLC-MS-MS analysis indicated the formation of selenenylsulfide conjugates of selenocoxib-2 with N-acetylcysteine. Selenocoxib-2 was found to release minor amounts of Se that was effectively inhibited by the CYP inhibitor, sulphaphenazole. While these studies suggest that selenocoxib-2, but not celecoxib and selenocoxib-3, targets upstream events in the NF-κB signaling axis, the ability to effectively suppress NF-κB activation independent of cellular selenoprotein synthesis opens possibilities for a new generation of COX-2 inhibitors with significant and broader anti-inflammatory potential.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Animal and physiological research as well as observational studies suggest that antioxidant supplements may improve survival.

OBJECTIVES

To assess the effect of antioxidant supplements on mortality in primary or secondary prevention randomised clinical trials.

SEARCH STRATEGY

We searched The Cochrane Library (Issue 3, 2005), MEDLINE (1966 to October 2005), EMBASE (1985 to October 2005), and the Science Citation Index Expanded (1945 to October 2005). We scanned bibliographies of relevant publications and wrote to pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention. Included participants were either healthy (primary prevention trials) or had any disease (secondary prevention trials).

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Trials with adequate randomisation, blinding, and follow-up were classified as having a low risk of bias. Random-effects and fixed-effect meta-analyses were performed. Random-effects meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Sixty-seven randomised trials with 232,550 participants were included. Forty-seven trials including 180,938 participants had low risk of bias. Twenty-one trials included 164,439 healthy participants. Forty-six trials included 68111 participants with various diseases (gastrointestinal, cardiovascular, neurological, ocular, dermatological, rheumatoid, renal, endocrinological, or unspecified). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects meta-analysis (relative risk [RR] 1.02, 95% confidence interval [CI] 0.99 to 1.06), but significantly increased mortality in a fixed-effect model (RR 1.04, 95% CI 1.02 to 1.06). In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. In the trials with a low risk of bias, the antioxidant supplements significantly increased mortality (RR 1.05, 95% CI 1.02 to 1.08). When the different antioxidants were assessed separately, analyses including trials with a low risk of bias and excluding selenium trials found significantly increased mortality by vitamin A (RR 1.16, 95% CI 1.10 to 1.24), beta-carotene (RR 1.07, 95% CI 1.02 to 1.11), and vitamin E (RR 1.04, 95% CI 1.01 to 1.07), but no significant detrimental effect of vitamin C (RR 1.06, 95% CI 0.94 to 1.20). Low-bias risk trials on selenium found no significant effect on mortality (RR 0.91, 95% CI 0.76 to 1.09).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Vitamin A, beta-carotene, and vitamin E may increase mortality. Future randomised trials could evaluate the potential effects of vitamin C and selenium for primary and secondary prevention. Such trials should be closely monitored for potential harmful effects. Antioxidant supplements need to be considered medicinal products and should undergo sufficient evaluation before marketing.

A randomized trial of a 6-week course of celecoxib on proteinuria in diabetic kidney disease

BACKGROUND

Preclinical data suggest that cyclooxygenase 2 inhibitors decrease proteinuria and preserve glomerular structure in animal models of diabetic nephropathy. The objective of this study is to compare the efficacy and safety of celecoxib with placebo for decreasing proteinuria in patients with diabetic nephropathy.

STUDY DESIGN

Placebo-controlled double-blinded crossover design.

SETTING & PARTICIPANTS

24 patients with type 1 or 2 diabetes mellitus, proteinuria with protein of 500 mg/d or greater, and serum creatinine level of 3.0 mg/dL or less.

INTERVENTION

Patients were randomly assigned to: (1) 6 weeks of celecoxib followed by a 3-week washout period, followed by 6 weeks of placebo followed by another 3-week washout; or (2) 6 weeks of placebo followed by a 3-week washout, followed by 6 weeks of celecoxib followed by another 3-week washout period. All patients were administered quinapril, 20 to 40 mg/d, or irbesartan, 150 to 300 mg/d. All patients were administered aspirin, 81 mg/d.

OUTCOMES & MEASUREMENTS

Proteinuria was assessed by means of protein-creatinine ratio. Data were analyzed using the mixed-effect statistical model.

RESULTS

There was no significant difference in urinary proteinuria after 6 weeks of treatment with placebo or celecoxib (proteinuria ratio, celecoxib versus placebo, 1.041; 95% confidence interval, 0.846 to 1.282). Celecoxib had no significant effect on potassium or estimated glomerular filtration rate. Frequencies of adverse events were similar between the placebo and celecoxib treatments.

LIMITATIONS

This pilot study was not designed to evaluate the safety or long-term clinical effects of celecoxib.

CONCLUSIONS

Celecoxib, 200 mg/d, for 6 weeks did not alter proteinuria. Few adverse events were noted in this high-risk population.

Celecoxib inhibits meningioma tumor growth in a mouse xenograft model

BACKGROUND

Treatments for recurrent meningiomas are limited. We previously demonstrated universal expression of COX-2 in meningiomas and dose-dependent growth inhibition in vitro with celecoxib, a COX-2 inhibitor. We therefore tested the effects of celecoxib on meningioma growth in a mouse xenograft model.

METHODS

Meningioma cell lines (IOMM-Lee, CH157-MN, WHO grade I primary cultured tumor) were transplanted into flanks of nude mice fed mouse chow with celecoxib at varying concentrations (0, 500, 1000, 1500 ppm) ad libitum. Tumors were measured biweekly and processed for MIB-1, Factor VIII, COX-2, and VEGF, and assayed with transferase-mediated dUTP-biotin nick-end labeling (TUNEL).

RESULTS

Celecoxib reduced growth of mean tumor volume by 66% (P < .05), 25% (P > .05), and 65% (P < .05) compared with untreated controls in IOMM-Lee, CH157-MN, and benign tumors, respectively. IOMM-Lee tumors removed from celecoxib treatment regained a growth rate similar to the control. Blood vessel density decreased and apoptotic cells increased in treated flank tumors. Diminished COX-2 expression and VEGF were observed in treated IOMM-Lee tumors. Mean plasma celecoxib levels were 845, 1540, and 2869 ng/mL, for low-, medium-, and high-dose celecoxib, respectively.

CONCLUSIONS

Celecoxib inhibits meningioma growth in vivo at plasma levels achievable in humans. Celecoxib-treated tumors were less vascular with increased apoptosis. IOMM-Lee tumors treated with celecoxib showed decreased COX-2 and VEGF expression. COX-2 inhibitors may have a role in the treatment of recurrent meningiomas.

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Ubiquitous expression of cyclooxygenase-2 in meningiomas and decrease in cell growth following in vitro treatment with the inhibitor celecoxib: potential therapeutic application

OBJECT

Meningiomas are the second most common symptomatic primary central nervous system tumor in adults. Findings of epidemiological studies link meningiomas with a history of head trauma, indicating a causal relationship between the inflammatory response and meningioma tumorigenesis. Cyclooxygenase-2 (COX-2), an inducible inflammatory enzyme, converts arachidonic acid to prostaglandins, which have angiogenic, cell-proliferative, and antiapoptotic effects. The authors investigated COX-2 expression in meningiomas and the effects of celecoxib, a COX-2 inhibitor, on meningioma cell growth in vitro.

METHODS

Four meningioma surgical specimens were immunohistochemically stained and graded (0 to 4) for COX-2. In addition, a Western blot analysis was performed to detect the presence of COX-2. Human meningioma cells grown in cell culture were treated with vehicle or celecoxib (0.25-1 mM). An immunohistochemical analysis of COX-2, a methylthiotetrazole cell proliferation assay, a TUNEL apoptosis assay, and a Western blot analysis for the proapoptotic protein BAX were performed in vitro. One hundred eleven (87%) of 128 benign meningiomas and six (86%) of seven atypical meningiomas displayed a high COX-2 immunoreactivity (Grade 4 staining). In the Western blot analysis all four surgical specimens (100%) stained positive for a 70-kD band consistent with COX-2. Celecoxib inhibited cell growth in a dose-dependent fashion and induced apoptosis by Day 2, with no change noted in the expression of the BAX protein.

CONCLUSIONS

The COX-2 enzyme is universally expressed in meningiomas. Celecoxib inhibits meningioma growth in vitro in a dose-dependent fashion, with evidence of apoptosis. Inhibitors of COX-2 may have a role in the treatment of recurrent meningiomas.

Probiotics used in human studies

GOAL

To investigate the literature from 1980 to 2004 for the types of studies and organisms used as probiotics in human studies and diseases.

METHODS

PubMed search for probiotic organisms used in studies from 1980 to August 2004. The data from those papers were evaluated for organisms used, dose, vehicle, frequency, and investigator's report of positive or negative results.

RESULTS

A total of 185 manuscripts were identified. Investigators reported results of both single and multiple organisms in the same manuscript. A single organism was used in 125 reports, and multiple organisms, ranging from 2 to 9, were used in 60 reports. Positive results were reported in 239 clinical situations and negative results reported in 49 in a total of 288 clinical conclusions drawn by the respective investigators. The studies are tabulated in this review.

CONCLUSION

There is a large literature available in credible journals that report benefit of probiotic administration using a wide range of doses, organisms, and clinical situations. Most of the studies are simple reports of a clinical situation and require additional evaluation.