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Abstract Background The CBR3 V244M single nucleotide polymorphism has been linked to the risk of anthracycline-related cardiomyopathy in survivors of childhood cancer. There have been limited prospective studies examining the impact of CBR3 V244M on the risk for anthracycline-related cardiotoxicity in adult cohorts. Objectives This study evaluated the presence of associations between CBR3 V244M genotype status and changes in echocardiographic parameters in breast cancer patients undergoing doxorubicin treatment. Methods We recruited 155 patients with breast cancer receiving treatment with doxorubicin (DOX) at Roswell Park Comprehensive Care Center (Buffalo, NY) to a prospective single arm observational pharmacogenetic study. Patients were genotyped for the CBR3 V244M variant. 92 patients received an echocardiogram at baseline (t0 month) and at 6 months (t6 months) of follow up after DOX treatment. Apical two-chamber and four-chamber echocardiographic images were used to calculate volumes and left ventricular ejection fraction (LVEF) using Simpson’s biplane rule by investigators blinded to all patient data. Volumetric indices were evaluated by normalizing the cardiac volumes to the body surface area (BSA). Results Breast cancer patients with CBR3 GG and AG genotypes both experienced a statistically significant reduction in LVEF at 6 months following initiation of DOX treatment for breast cancer compared with their pre-DOX baseline study. Patients homozygous for the CBR3 V244M G allele (CBR3 V244) exhibited a further statistically significant decrease in LVEF at 6 months following DOX therapy in comparison with patients with heterozygous AG genotype. We found no differences in age, pre-existing cardiac diseases associated with myocardial injury, cumulative DOX dose, or concurrent use of cardioprotective medication between CBR3 genotype groups. Conclusions CBR3 V244M genotype status is associated with changes in echocardiographic parameters suggestive of early anthracycline-related cardiomyopathy in subjects undergoing chemotherapy for breast cancer.

Abstract: Until today, the physiologic role of human carbonyl reductase 3 (CBR3; SDR21C2), a member of the short-chain dehydrogenase/reductase superfamily remains obscure. Since the transcriptional regulation is closely related to the function of a protein, elucidation of the regulation of CBR3 should help to understand its physiologic role. We recently identified CBR3 as a novel target gene of Nrf2, a cellular sensor of oxidative stress. In this study, we provide for the first time evidence that pro-inflammatory stimuli induce the expression of the CBR3 gene. Treatment of human cancer cells HT-29 (colon) and HepG2 (liver) with TNF-α, IL-1β, and LPS induced CBR3 expression differentially. While TNF-α (50ng/ml) or IL-1β (1 and 10ng/ml), induced CBR3 mRNA expression in HT-29 cells (up to 10-fold) and HepG2 cells (up to 20-fold), LPS activated the CBR3 gene only in HepG2 cells. Furthermore, overexpression of the NFκB subunits p65 and p50 alone or in combination elevated CBR3 mRNA levels (3.9-fold) in HT-29 cells. According to our results, CBR3 is a novel target gene of inflammatory stimuli, and elucidation of its detailed role in inflammation deserves further investigation. [Copyright &y& Elsevier]

Abstract: Carbonyl reductase activity catalyzes the two electron reduction of several endogenous and exogenous carbonyl substrates. Recent data indicate that the expression of human carbonyl reductase 3 (CBR3) is regulated by the master redox switch Nrf2. Nrf2 binds to conserved antioxidant response elements (AREs) in the promoters of target genes. The presence of functional AREs in the CBR3 promoter has not yet been reported. In this study, experiments with reporter constructs showed that the prototypical Nrf2 activator tert-butyl hydroquinone (t-BHQ) induces CBR3 promoter activity in cultures of HepG2 (2.7-fold; p <0.05) and MCF-7 cells (22-fold; p <0.01). Computational searches identified a conserved ARE in the distal CBR3 promoter region (−2698 ARE). Deletion of this ARE from a 4212-bp CBR3 promoter construct impacted basal promoter activity and induction of promoter activity in response to treatment with t-BHQ. Deletion of −2698 ARE also impacted the induction of CBR3 promoter activity in cells overexpressing Nrf2. Electrophoretic mobility shift assays (EMSA) demonstrated increased binding of specific protein complexes to −2698 ARE in nuclear extracts from t-BHQ treated cells. The presence of Nrf2 in the specific nuclear protein–−2698 ARE complexes was evidenced in EMSA experiments with anti-Nrf2 antibodies. These data suggest that the distal −2698 ARE mediates the induction of human CBR3 in response to prototypical activators of Nrf2. [Copyright &y& Elsevier]

Mammalian selenoproteins have diverse functions, cellular locations, and evolutionary histories, but all use the amino acid selenocysteine (Sec), often present in the enzyme’s active site. Only about half of mammalian selenoproteins have been functionally characterized, with most being oxidoreductases. The cellular role of selenoprotein T (SelT), manifesting a CxxU motif in a thioredoxin-like fold and localized to Golgi and the endoplasmic reticulum, is not known. To examine its biological function, we knocked down SelT expression in mouse fibroblast cells and found that SelT deficiency alters cell adhesion and enhances the expression of several oxidoreductase genes, while decreasing the expression of genes involved in cell structure organization, suggesting the involvement of SelT in redox regulation and cell anchorage. Furthermore, we found that the loss of SelT elevates expression of another selenoprotein, selenoprotein W (SepW1). SelT and SepW1 belong to the same protein family, suggesting that SepW1 may functionally compensate for SelT. [ABSTRACT FROM AUTHOR]

The selenoenzyme glutathione peroxidase 4 (Gpx4) is an essential mammalian glutathione peroxidase, which protects cells against detrimental lipid peroxidation and governs a novel form of regulated necrotic cell death, called ferroptosis. To study the relevance of Gpx4 and of another vitally important selenoprotein, cytosolic thioredoxin reductase (Txnrd1), for liver function, mice with conditional deletion of Gpx4 in hepatocytes were studied, along with those lacking Txnrd1 and selenocysteine (Sec) tRNA (Trsp) in hepatocytes. Unlike Txnrd1- and Trsp-deficient mice, Gpx4−/− mice died shortly after birth and presented extensive hepatocyte degeneration. Similar to Txnrd1-deficient livers, Gpx4−/− livers manifested upregulation of nuclear factor (erythroid-derived)-like 2 (Nrf2) response genes. Remarkably, Gpx4−/− pups born from mothers fed a vitamin E-enriched diet survived, yet this protection was reversible as subsequent vitamin E deprivation caused death of Gpx4-deficient mice ~4 weeks thereafter. Abrogation of selenoprotein expression in Gpx4−/− mice did not result in viable mice, indicating that the combined deficiency aggravated the loss of Gpx4 in liver. By contrast, combined Trsp/Txnrd1-deficient mice were born, but had significantly shorter lifespans than either single knockout, suggesting that Txnrd1 plays an important role in supporting liver function of mice lacking Trsp. In sum our study demonstrates that the ferroptosis regulator Gpx4 is critical for hepatocyte survival and proper liver function, and that vitamin E can compensate for its loss by protecting cells against deleterious lipid peroxidation.