The prevalence of low selenium levels in adult patients undergoing bone marrow transplantation: a brief communication

Therapeutic Benefits of Selenium in Hematological Malignancies

Supplementing chemotherapy and radiotherapy with selenium has been shown to have benefits against various cancers. This approach has also been shown to alleviate the side effects associated with standard cancer therapies and improve the quality of life in patients. In addition, selenium levels in patients have been correlated with various cancers and have served as a diagnostic marker to track the efficiency of treatments or to determine whether these selenium levels cause or are a result of the disease. This concise review presents a survey of the selenium-based literature, with a focus on hematological malignancies, to demonstrate the significant impact of selenium in different cancers. The anti-cancer mechanisms and signaling pathways regulated by selenium, which impart its efficacious properties, are discussed. An outlook into the relationship between selenium and cancer is highlighted to guide future cancer therapy development.

Selenium and selenoproteins in prostanoid metabolism and immunity

Selenium (Se) is an essential trace element that functions in the form of the 21st amino acid, selenocysteine (Sec) in a defined set of proteins. Se deficiency is associated with pathological conditions in humans and animals, where incorporation of Sec into selenoproteins is reduced along with their expression and catalytic activity. Supplementation of Se-deficient population with Se has shown health benefits suggesting the importance of Se in physiology. An interesting paradigm to explain, in part, the health benefits of Se stems from the observations that selenoprotein-dependent modulation of inflammation and efficient resolution of inflammation relies on mechanisms involving a group of bioactive lipid mediators, prostanoids, which orchestrate a concerted action toward maintenance and restoration of homeostatic immune responses. Such an effect involves the interaction of various immune cells with these lipid mediators where cellular redox gatekeeper functions of selenoproteins further aid in not only dampening inflammation, but also initiating an effective and active resolution process. Here we have summarized the current literature on the multifaceted roles of Se/selenoproteins in the regulation of these bioactive lipid mediators and their immunomodulatory effects.

Selenium suppresses leukemia through the action of endogenous eicosanoids

Eradicating cancer stem-like cells (CSC) may be essential to fully eradicate cancer. Metabolic changes in CSC could hold a key to their targeting. Here, we report that the dietary micronutrient selenium can trigger apoptosis of CSC derived from chronic or acute myelogenous leukemias when administered at supraphysiologic but nontoxic doses. In leukemia CSC, selenium treatment activated ATM-p53-dependent apoptosis accompanied by increased intracellular levels of reactive oxygen species. Importantly, the same treatment did not trigger apoptosis in hematopoietic stem cells. Serial transplantation studies with BCR-ABL-expressing CSC revealed that the selenium status in mice was a key determinant of CSC survival. Selenium action relied upon the endogenous production of the cyclooxygenase-derived prostaglandins Δ(12)-PGJ2 and 15d-PGJ2. Accordingly, nonsteroidal anti-inflammatory drugs and NADPH oxidase inhibitors abrogated the ability of selenium to trigger apoptosis in leukemia CSC. Our results reveal how selenium-dependent modulation of arachidonic acid metabolism can be directed to trigger apoptosis of primary human and murine CSC in leukemia.

The efficacy of selenium in prevention of oral mucositis in patients undergoing hematopoietic SCT: a randomized clinical trial

Oral mucositis (OM) is a complication of high-dose chemotherapy (HDC) followed by hematopoietic SCT (HSCT) with few effective treatments. Selenium has a cytoprotective role via the glutathione peroxidase (Glu.Px) enzyme and prevents chemotherapy-induced toxicities. We performed a double-blind, randomized, placebo-controlled study to evaluate the efficacy of selenium on the prevention of OM in 77 patients with leukemia, undergoing allogeneic HSCT. Thirty-seven patients received oral selenium tablets (200 mcg twice daily) from the starting day of HDC to 14 days after transplantation. OM was evaluated daily for 21 days after transplantation according to World Health Organization oral toxicity scale. The incidence of severe OM (grades 3-4) was significantly lower in the selenium group (10.8% vs 35.1%, P<0.05). We noted that the duration of objective OM (grades 2-4), excluding patient's self-declaration (grade 1), was significantly shorter in the selenium group (3.6±1.84 vs 5.3±2.2 days, P=0.014). Significant elevations in serum selenium level and plasma Glu.Px activity were observed 7 and 14 days after transplantation compared with baseline in the selenium group. We conclude that selenium can reduce the duration and severity of OM after HDC. Clinicaltrial.org ID: NCT01432873.

Dietary selenium for the mitigation of radiation injury: effects of selenium dose escalation and timing of supplementation

We recently reported that daily dietary supplementation with 100 µg selenium (a dose exceeding a rat's nutritional requirement by about 33-fold) initiated immediately after total-body irradiation (TBI) and maintained for 21 weeks mitigates radiation nephropathy in a rat model as indicated by blood urea nitrogen (BUN) levels and histopathological criteria (Radiat Res. 2009; 17:368-73). In this follow-up study, we explored the risks and benefits of delaying the onset of supplementation, shortening periods of supplementation, and escalating selenium supplementation beyond 100 µg/day. Supplementation with 200 µg selenium/day (as selenite or seleno-l-methionine) substantially improved the mitigation of radiation nephropathy by lowering BUN levels at 4 months after TBI from 115 to as low as 34 mg/dl and by proportionally lowering the incidence of histopathological abnormalities. Shortening the period of supplementation to 3 or 2 months did not compromise efficacy. Delaying the onset of supplementation for 1 week reduced but did not abrogate the mitigation of radiation nephropathy. Supplementation with 300 µg/day mitigated radiation nephropathy less effectively than 200 µg and was poorly tolerated. Rats that had been given 10 Gy of TBI were less tolerant of high-dose selenium than nonirradiated rats. This reduced tolerance of high-dose selenium would need to be taken into consideration when selenium is used for the mitigation of radiation injury in victims of nuclear accidents or acts of radiological terrorism. The high dose requirements, the pronounced threshold effect, and the superior performance of selenite suggest that the mitigation of radiation nephropathy involves mechanisms that go beyond the induction of selenoproteins.