A functional genetic polymorphism on human carbonyl reductase 1 (CBR1 V88I) impacts on catalytic activity and NADPH binding affinity

The Influence of CYP2B6, GSTP1, and SLCO1B1 Star Allele-Predicted Phenotypes and CBR1 Genetic Variants on Effectiveness Outcomes in Patients With Hepatocellular Carcinoma Receiving Doxorubicin via Transarterial Chemoembolization

We investigated the influence of CYP2B6, GSTP1, and SLCO1B1 star allele-predicted phenotypes and CBR1 variants on clinical outcomes in patients with HCC receiving DOX via TACE. A prospective cohort of patients with HCC underwent DOX therapy via TACE. Selected genes were genotyped in germline DNA samples from the final cohort (82 patients) via Axiom Precision Medicine Diversity (PMD) Research Array technology. The Kaplan-Meier (KM) method and Cox proportional hazards (CPH) model were employed to find independent clinical and genetic predictors of overall survival (OS) and progression-free survival (PFS) after TACE. Based on univariate and combined association analyses of genetic factors, the star alleles predicting the phenotypic status of three genes (CYP2B6, GSTP1, and SLCO1B1) did not significantly modify the response potential of DOX via TACE, as indicated by OS or PFS. Conversely, we found a novel association between two CBR1 polymorphisms (rs3787728 and rs1005695) and interindividual differences in OS and PFS. The presence of a heterozygous genotype (TC or CG at either locus, which were highly frequent in our cohort), probably with greater CBR metabolic activity, appeared to have an expressive influence by negatively modulating the consequences of DOX locoregional therapy on HCC by shortening the median OS (KM p = 0.02 and 0.04, respectively) and median PFS (KM p = 0.05 and 0.023, respectively) in comparison to those with other haplotypes. Exploratory PGx studies involving a wider HCC cohort and targeting more DOX-related genes are needed to replicate our findings. Trial Registration: NCT06313047 (Study Details | Pharmacogenetic of Doxorubicin in HCC. | clinicaltrials.gov).

SNP's use as a potential chemotoxicity stratification tool in breast cancer: from bench to clinic

Breast cancer (BC) remains one of the most prevalent malignancies affecting women worldwide, necessitating ongoing research to improve treatment outcomes and minimize adverse effects associated with chemotherapy. This article explores the role of genetic variations, particularly single nucleotide polymorphisms (SNPs), in influencing the efficacy and toxicity of chemotherapeutic agents used in BC treatment. It highlights the impact of polymorphisms in drug metabolism and transport genes, such as UDP-glucuronosyltransferase 1A1 (UGT1A1), carbonyl reductase 1 (CBR1), and ATP-binding cassette multidrug transporter (ABCB1) on the risk of adverse effects, including cardiotoxicity and hematological toxicities. By identifying specific SNPs associated with drug response and toxicity, this research underscores the potential for personalized medicine approaches to optimize treatment regimens, enhance therapeutic efficacy, and minimize side effects in BC patients. The findings advocate for the integration of genetic screening in clinical practice to improve patient outcomes and tailor chemotherapy based on individual genetic profiles.

Carbonyl reductase 1: a novel regulator of blood pressure in Down syndrome

Approximately one in every 800 children is born with the severe aneuploid condition of Down syndrome (DS), a trisomy of chromosome 21. Low blood pressure (hypotension) is a common condition associated with DS and can have a significant impact on exercise tolerance and quality of life. Little is known about the factors driving this hypotensive phenotype, therefore therapeutic interventions are limited. Carbonyl reductase 1 (CBR1) is an enzyme contributing to the metabolism of prostaglandins, glucocorticoids, reactive oxygen species and neurotransmitters, encoded by a gene (CBR1) positioned on chromosome 21 with the potential to affect blood pressure. Utilising telemetric blood pressure measurement of genetically modified mice, we tested the hypothesis that CBR1 influences blood pressure and that its overexpression contributes to hypotension in DS by evaluating possible contributing mechanisms in vitro. In a mouse model of DS (Ts65Dn), which exhibits hypotension, CBR1 activity was increased and pharmacological inhibition of CBR1 ed to increased blood pressure. Mice heterozygous null for Cbr1 had reduced CBR1 enzyme activity and elevated blood pressure. Further experiments indicate that the underlying mechanisms include alterations in both sympathetic tone and prostaglandin metabolism. We conclude that CBR1 activity contributes to blood pressure homeostasis and inhibition of CBR1 may present a novel therapeutic opportunity to correct symptomatic hypotension in DS.

The Link between Prostanoids and Cardiovascular Diseases

Cardiovascular diseases are the leading cause of global deaths, and many risk factors contribute to their pathogenesis. In this context, prostanoids, which derive from arachidonic acid, have attracted attention for their involvement in cardiovascular homeostasis and inflammatory processes. Prostanoids are the target of several drugs, but it has been shown that some of them increase the risk of thrombosis. Overall, many studies have shown that prostanoids are tightly associated with cardiovascular diseases and that several polymorphisms in genes involved in their synthesis and function increase the risk of developing these pathologies. In this review, we focus on molecular mechanisms linking prostanoids to cardiovascular diseases and we provide an overview of genetic polymorphisms that increase the risk for cardiovascular disease.

Loxoprofen enhances intestinal barrier function via generation of its active metabolite by carbonyl reductase 1 in differentiated Caco-2 cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used worldwide as antipyretic analgesics and agents for rheumatoid arthritis and osteoarthritis, but known to cause damage to the gastrointestinal mucosae as their serious adverse effects. Few studies showed the impairment of intestinal epithelial barrier function (EBF) by high concentrations (0.5-1 mM) of NSAIDs, but the underlying mechanism is not fully understood. This study is aimed at clarifying effects at a low concentration (50 μM) of three NSAIDs, loxoprofen (Lox), ibuprofen and indomethacin, on intestinal EBF using human intestinal epithelial-like Caco-2 cells. Among those NSAIDs, Lox increased the transepithelial electric resistance (TER) value, decreased the paracellular Lucifer yellow CH (LYCH) permeability, and upregulated claudin (CLDN)-1, -3 and -5, indicating that low doses of Lox enhanced EBF through increasing expression of CLDNs. Lox is known to be metabolized to a pharmacologically active metabolite, (2S,1'R,2'S)-loxoprofen alcohol (Lox-RS), by carbonyl reductase 1 (CBR1), which is highly expressed in human intestine. CBR1 was expressed in the Caco-2 cells, and the pretreatment with a CBR1 inhibitor suppressed both the Lox-evoked CLDN upregulation and EBF enhancement. In addition, the treatment of the cells with Lox-RS resulted in higher TER value and lower LYCH permeability than those with Lox. Thus, Lox-RS synthesized by CBR1 may greatly contribute to the improving efficacy of Lox on the barrier function. Since EBF is decreased in inflammatory bowel disease, we finally examined the effect of Lox on EBF using the Caco-2/THP-1 co-culture system, which is used as an in vitro inflammatory bowel disease model. Lox significantly recovered EBF which was impaired by inflammatory cytokines secreted from THP-1 macrophages. These in vitro observations suggest that Lox enhances intestinal EBF, for which the metabolism of Lox to Lox-RS by CBR1 has an important role.

Carbonyl reduction pathway in hepatic in vitro metabolism of anthracyclines: Impact of structure on biotransformation rate

Carbonyl reduction biotransformation pathway of anthracyclines (doxorubicin, daunorubicin) is a significant process, associated with drug metabolism and elimination. However, it also plays a pivotal role in anthracyclines-induced cardiotoxicity and cancer resistance. Herein, carbonyl reduction of eight anthracyclines, at in vivo relevant concentrations (20 μM), was studied in human liver cytosol, to describe the relationship between their structure and metabolism. Significant differences of intrinsic clearance between anthracyclines, ranging from 0,62-74,9 μL/min/mg were found and associated with data from in silico analyses, considering their binding in active sites of the main anthracyclines-reducing enzymes: carbonyl reductase 1 (CBR1) and aldo-keto reductase 1C3 (AKR1C3). Partial atomic charges of carbonyl oxygen atom were also determined and considered as a factor associated with reaction rate. Structural features, including presence or absence of side-chain hydroxy group, a configuration of sugar chain hydroxy group, and tetracyclic rings substitution, affecting anthracyclines susceptibility for carbonyl reduction were identified.

The enzymology of the human prostanoid pathway

Prostanoids are short-lived autocrine and paracrine signaling molecules involved in a wide range of biological functions. They have been shown to be intimately involved in many different disease states when their regulation becomes dysfunctional. In order to fully understand the progression of any disease state or the biological functions of the well state, a complete evaluation of the genomics, proteomics, and metabolomics of the system is necessary. This review is focused on the enzymology for the enzymes involved in the synthesis of the prostanoids (prostaglandins, prostacyclins and thromboxanes). In particular, the isolation and purification of the enzymes, their enzymatic parameters and catalytic mechanisms are presented.

Inhibitory effect of carbonyl reductase 1 against peritoneal progression of ovarian cancer: evaluation by ex vivo 3D-human peritoneal model

The current authors previously reported that a carbonyl reductase 1 (CR1) DNA-dendrimer complex could potentially be used in gene therapy for peritoneal metastasis of ovarian cancer. The aims of the current study were to observe the cellular dynamics of peritoneal metastasis of epithelial ovarian cancer cells and to ascertain changes in the dynamics of ovarian cancer cells as a result of transfection of CR1 DNA. (1) Artificial human peritoneal tissue (AHPT) was seeded with serous ovarian cancer cells, and the process leading to development of peritoneal carcinomatosis was observed over time. (2) Peritoneal carcinomatosis was produced in mice and compared to a model using AHPT to determine the appropriateness of AHPT. (3) CR1 DNA was transfected into cancer cells seeded on AHPT, and the dynamics of cancer cells were observed over time. (1) Cancer cells perforated the mesothelium, leaving normal mesothelium intact. However, the cells proliferated between the layers of the mesothelium, forming a mass. After 24 h, cancer cells had invaded the lymphatics, and after 48-72 h cancer cells had invaded deep into the mesothelium, where they formed a mass. (2) Invasion of the peritoneum by cancer cells in a murine model of peritoneal carcinomatosis resembled that in a model using AHPT, and results substantiated the reproducibility of peritoneal carcinomatosis in AHPT. (3) Proliferation of cells transfected with CR1 DNA was significantly inhibited on AHPT, and necrosis was evident. Nevertheless, cancer cell invasion deep into the mesothelium was not inhibited. Use of a new tool, AHPT, in an in vitro model of peritoneal metastasis revealed that CR1 DNA inhibited cancer cell proliferation. CR1 DNA does not play a role in inhibiting invasion of the mesothelium during peritoneal metastasis, but it does affect cancer cell proliferation. Results suggested that CR1 DNA inhibits cancer cell proliferation via necrosis.

Comparative Transcriptomics Reveal Key Sheep (Ovis aries) Hypothalamus LncRNAs that Affect Reproduction

The diverse functions of long noncoding RNAs (lncRNAs), which execute their functions mainly through modulating the activities of their target genes, have been have been widely studied for many years (including a number of studies involving lncRNAs in the ovary and uterus). Herein, for the first time, we detect lncRNAs in sheep hypothalami with FecB++ through RNA Sequencing (RNA-Seq) and identify a number of known and novel lncRNAs, with 622 and 809 found to be differentially expressed in polytocous sheep in the follicular phase (PF) vs. monotocous sheep in the follicular phase (MF) and polytocous sheep in the luteal phase (PL) vs. monotocous sheep in the luteal phase (ML), respectively. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed based on the predicted target genes. The most highly enriched GO terms (at the molecular function level) included carbonyl reductase (NADPH), 15-hydroxyprostaglandin dehydrogenase (NADP+), and prostaglandin-E2 9-reductase activity in PF vs. MF, and phosphatidylinositol-3,5-bisphosphate binding in PL vs. ML was associated with sheep fecundity. Interestingly, the phenomena of valine, leucine, and isoleucine degradation in PL vs. ML, and valine, leucine, and isoleucine biosynthesis in PF vs. MF, were present. In addition, the interactome of lncRNA and its targets showed that MSTRG.26777 and its cis-targets ENSOARG00000013744, ENSOARG00000013700, and ENSOARG00000013777, and MSTRG.105228 and its target WNT7A may participate in the sheep reproductive process at the hypothalamus level. Significantly, MSTRG.95128 and its cis-target Forkhead box L1 (FOXG1) were shown to be upregulated in PF vs. MF but downregulated in PL vs. ML. All of these results may be attributed to discoveries of new candidate genes and pathways related to sheep reproduction, and they may provide new views for understanding sheep reproduction without the effects of the FecB mutation.

Low carbonyl reductase 1 expression is associated with poor prognosis in patients with oral squamous cell carcinoma

Carbonyl reductase 1 (CBR1) is an enzyme that catalyzes the reduction of numerous compounds by using NADPH-dependent oxidoreductase activity. Decreased expression of CBR1 is associated with disease progression and an unfavorable outcome in several types of malignancies. The purpose of the current study was to determine whether CBR1 expression could be a useful prognostic factor in patients with oral squamous cell carcinoma (OSCC). Therefore, its mechanisms of action were investigated in order to understand how CBR1 affects cancer cell behavior in vitro. CBR1 expression was evaluated using immunohistochemistry and tissue samples obtained from 90 patients with OSCC. The associations between CBR1 expression, clinicopathological characteristics and patient survival were also analyzed. In addition, the role of CBR1 in cancer cell invasion and metastasis was examined, along with its underlying molecular mechanisms, via transfecting CBR1-siRNA into the HSC2 human OSCC cell line. Immunohistochemical analysis revealed that biopsy tissue samples of 71.1% of the patients with OSCC were positive for CBR1. In addition, CBR1 expression status was correlated with the N classification (P<0.0001), stage (P=0.0018) and outcome (P=0.0095). Furthermore, a statistical correlation was determined between the protein expression status and overall survival (P=0.0171). In vitro studies indicated that the suppression of CBR1 by CBR1-siRNA increased cancer cell proliferative, wound healing and migratory abilities. These findings suggest that low expression levels of CBR1 may affect cancer prognosis, and that CBR1 may have potential as a prognostic factor for patients with OSCC.

Decreased carbonyl reductase 1 expression promotes tumor growth via epithelial mesenchymal transition in uterine cervical squamous cell carcinomas

Purpose

Carbonyl reductase 1 (CBR1) is involved in cancer progression. Recently, the authors reported that the loss of CBR1 expression is associated with a poor prognosis in uterine cervical cancer. Here, we investigated whether the decreased CBR1 expression promotes cancer progression by inducing the epithelial mesenchymal transition (EMT).

Methods

Antisense constructs of CBR1 complementary DNA (antisense clones) and the empty vectors (control clones) were transfected into human uterine cervical squamous cell carcinoma cell lines (SKG II and SiHa) and the proliferation and EMT marker expression of these clones were analyzed in vitro. In an in vivo study, 10⁷ cells of the antisense and control clones were subcutaneously injected into nude mice and the tumorigenesis was observed for 8 weeks.

Results

With the decreased CBR1 expression, the proliferation of the antisense clones increased, accompanied by a decrease in epithelial markers (E-cadherin and cytokeratin) and an increase in mesenchymal markers (fibronectin, alpha-smooth muscle actin, and N-cadherin), which suggests EMT induction. In the in vivo study, the tumor volume in the antisense group was significantly larger than that in the control group.

Conclusion

Decreased CBR1 expression promotes tumor growth by inducing EMT in uterine cervical squamous cell carcinomas.

Transcriptional regulation of the canine carbonyl reductase 1 gene (cbr1) by the specificity protein 1 (Sp1)

The clinical use of anthracyclines to treat various canine cancers is limited by the development of cardiotoxicity. The intra-cardiac synthesis of anthracycline C-13 alcohol metabolites (e.g. daunorubicinol) contributes to the development of cardiotoxicity. Canine carbonyl reductase 1 (cbr1) catalyzes the reduction of daunorubicin into daunorubicinol. Recent mapping of the cbr1 locus by sequencing DNA samples from dogs from various breeds revealed a cluster of conserved motifs for the transcription factor Sp1 in the putative promoter region of cbr1. We hypothesized that the variable number of Sp1 motifs could impact the transcription of canine cbr1. In this study, we report the functional characterization of the canine cbr1 promoter. Experiments with reporter constructs and chromatin immunoprecipitation show that cbr1 transcription depends on the binding of Sp1 to the proximal promoter. Site-directed mutagenesis experiments suggest that the variable number of Sp1 motifs impacts the transcription of canine cbr1. Inhibition of Sp1-DNA binding decreased canine cbr1 mRNA levels by 54% in comparison to controls, and also decreased enzymatic carbonyl reductase activity for the substrates daunorubicin (16%) and menadione (23%). The transactivation of Sp1 increased the expression of cbr1 mRNA (67%), and increased carbonyl reductase activity for daunorubicin (35%) and menadione (27%). These data suggest that the variable number of Sp1 motifs in the canine cbr1 promoter may impact the pharmacodynamics of anthracyclines in canine cancer patients.

The use of matrix coating assisted by an electric field (MCAEF) to enhance mass spectrometric imaging of human prostate cancer biomarkers

In this work, we combined a newly developed matrix coating technique - matrix coating assisted by an electric field (MCAEF) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to enhance the imaging of peptides and proteins in tissue specimens of human prostate cancer. MCAEF increased the signal-to-noise ratios of the detected proteins by a factor of 2 to 5, and 232 signals were detected within the m/z 3500-37500 mass range on a time-of-flight mass spectrometer and with the sinapinic acid MALDI matrix. Among these species, three proteins (S100-A9, S100-A10, and S100-A12) were only observed in the cancerous cell region and 14 proteins, including a fragment of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 2, a fragment of cAMP-regulated phosphoprotein 19, 3 apolipoproteins (C-I, A-I, and A-II), 2 S100 proteins (A6 and A8), β-microseminoprotein, tumor protein D52, α-1-acid glycoprotein 1, heat shock protein β-1, prostate-specific antigen, and 2 unidentified large peptides at m/z 5002.2 and 6704.2, showed significantly differential distributions at the p < 0.05 (t-test) level between the cancerous and the noncancerous regions of the tissue. Among these 17 species, the distributions of apolipoprotein C-I, S100-A6, and S100-A8 were verified by immunohistological staining. In summary, this study resulted in the imaging of the largest group of proteins in prostate cancer tissues by MALDI-MS reported thus far, and is the first to show a correlation between S100 proteins and prostate cancer in a MS imaging study. The successful imaging of the three proteins only found in the cancerous tissues, as well as those showing differential expressions demonstrated the potential of MCAEF-MALDI/MS for the in situ detection of potential cancer biomarkers. Copyright © 2015 John Wiley & Sons, Ltd.

Inhibitory effect of carbonyl reductase 1 on ovarian cancer growth via tumor necrosis factor receptor signaling

We investigated the mechanisms of the inhibitory effect of carbonyl reductase 1 (CR1) on ovarian cancer growth mediated by the activation of the tumor necrotic factor receptor (TNFR) pathway. OVCAR-3 and TOV21G cells overexpressing CR1 were constructed by transfecting them with CR1 cDNA by lipofection. CR1-overexpressing and control OVCAR-3 and TOV21G cells were injected subcutaneously into nude mice and the tumor growth was compared between the two groups for 3-4 weeks. The expression of TNFR1 and TNFR2 in tumors was examined immunohistochemically at the end of the experiment. Expression levels of caspase-8 and -3 activated by TNFR1, c-Jun activated by TNFR2, and NF-κB activated by both TNFR1 and TNFR2 were determined using immunohistochemistry and western blot analysis. Tumor growth was significantly suppressed in mice injected with CR1-overexpressing cells. Tumor volume in the CR1 induction group decreased temporarily until 2 weeks. Tumor cell membranes in both CR1 induction and control groups were positive for TNFR1 expression; however, total protein levels did not differ between the two groups. TNFR-2 expression was comparatively weak in both groups. The expression of NF-κB and c-Jun was weaker in the CR1 induction group than in control. In contrast, caspase-8 and -3 expression was higher in the CR1 induction group. Furthermore, the number of apoptotic cells was significantly greater in tumors that appeared after injections of both types of CR1-overexpressing cells than in those of control cancer cells. These results suggest that CR1 induces apoptosis by activating the caspase pathway via binding to TNFR1.

Characterization of the Canine Anthracycline-Metabolizing Enzyme Carbonyl Reductase 1 (cbr1) and the Functional Isoform cbr1 V218

The anthracyclines doxorubicin and daunorubicin are used in the treatment of various human and canine cancers, but anthracycline-related cardiotoxicity limits their clinical utility. The formation of anthracycline C-13 alcohol metabolites (e.g., doxorubicinol and daunorubicinol) contributes to the development of anthracycline-related cardiotoxicity. The enzymes responsible for the synthesis of anthracycline C-13 alcohol metabolites in canines remain to be elucidated. We hypothesized that canine carbonyl reductase 1 (cbr1), the homolog of the prominent anthracycline reductase human CBR1, would have anthracycline reductase activity. Recombinant canine cbr1 (molecular weight: 32.8 kDa) was purified from Escherichia coli. The enzyme kinetics of "wild-type" canine cbr1 (cbr1 D218) and a variant isoform (cbr1 V218) were characterized with the substrates daunorubicin and menadione, as well as the flavonoid inhibitor rutin. Canine cbr1 catalyzes the reduction of daunorubicin to daunorubicinol, with cbr1 D218 and cbr1 V218 displaying different kinetic parameters (cbr1 D218 Km: 188 ± 144 μM versus cbr1 V218 Km: 527 ± 136 μM, P < 0.05, and cbr1 D218 Vmax: 6446 ± 3615 nmol/min per milligram versus cbr1 V218 Vmax: 15539 ± 2623 nmol/min per milligram, P < 0.01). Canine cbr1 also metabolized menadione (cbr1 D218 Km: 104 ± 50 μM, Vmax: 2034 ± 307 nmol/min per milligram). Rutin acted as a competitive inhibitor for the reduction of daunorubicin (cbr1 D218 Ki: 1.84 ± 1.02 μM, cbr1 V218 Ki: 1.38 ± 0.47 μM). These studies show that canine cbr1 metabolizes daunorubicin and provide the necessary foundation to characterize the role of cbr1 in the variable pharmacodynamics of anthracyclines in canine cancer patients.

Bioactivation of loxoprofen to a pharmacologically active metabolite and its disposition kinetics in human skin

Loxoprofen (LX) is a prodrug-type non-steroidal anti-inflammatory drug which is used not only as an oral drug but also as a transdermal formulation. As a pharmacologically active metabolite, the trans-alcohol form of LX (trans-OH form) is generated after oral administration to humans. The objectives of this study were to evaluate the generation of the trans-OH form in human in vitro skin and to identify the predominant enzyme for its generation. In the permeation and metabolism study using human in vitro skin, both the permeation of LX and the formation of the trans-OH form increased in a time- and dose-dependent manner after the application of LX gel to the skin. In addition, the characteristics of permeation and metabolism of both LX and the trans-OH form were examined by a mathematical pharmacokinetic model. The K_m value was calculated to be 10.3 mm in the human in vitro skin. The predominant enzyme which generates the trans-OH form in human whole skin was identified to be carbonyl reductase 1 (CBR1) by immunodepletion using the anti-human CBR1 antibody. The results of the enzyme kinetic study using the recombinant human CBR1 protein demonstrated that the K_m and V_max values were 7.30 mm and 402 nmol/min/mg protein, respectively. In addition, it was found that no unknown metabolites were generated in the human in vitro skin. This is the first report in which LX is bioactivated to the trans-OH form in human skin by CBR1. Copyright © 2015 John Wiley & Sons, Ltd.

Resveratrol reduces the hypoxia-induced resistance to doxorubicin in breast cancer cells

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is known to enhance the cytotoxicity of the anticancer drug doxorubicin. On the other hand, breast cancer MCF-7 cells acquire resistance to doxorubicin under hypoxic conditions. In this study, we investigated the effect of resveratrol on hypoxia-induced resistance to doxorubicin in MCF-7 cells. Resveratrol and its derivative 3,5-dihydroxy-4'-methoxy-trans-stilbene, but not 3,5-dimethoxy-4'-hydroxy-trans-stilbene, cancelled hypoxia-induced resistance to doxorubicin at a concentration of 10 μM. Carbonyl reductase 1 (CBR1) catalyzes the conversion of doxorubicin to its metabolite doxorubicinol, which is much less effective than doxorubicin. Hypoxia increased the expression of CBR1 at both mRNA and protein levels, and knockdown of CBR1 inhibited hypoxia-induced resistance to doxorubicin in MCF-7 cells. Knockdown of hypoxia-inducible factor (HIF)-1α repressed the hypoxia-induced expression of CBR1. Resveratrol repressed the expression of HIF-1α protein, but not HIF-1α mRNA, and decreased hypoxia-activated HIF-1 activity. Resveratrol repressed the hypoxia-induced expression of CBR1 at both mRNA and protein levels. Likewise, 3,5-dihydroxy-4'-methoxy-trans-stilbene decreased the hypoxia-induced expression of CBR1 protein, but not 3,5-dimethoxy-4'-hydroxy-trans-stilbene. Furthermore, resveratrol decreased the expression of HIF-1α protein even in the presence of the proteasome inhibitor MG132 in hypoxia. Theses results indicate that in MCF-7 cells, HIF-1α-increased CBR1 expression plays an important role in hypoxia-induced resistance to doxorubicin and that resveratrol and 3,5-dihydroxy-4'-methoxy-trans-stilbene decrease CBR1 expression by decreasing HIF-1α protein expression, perhaps through a proteasome-independent pathway, and consequently repress hypoxia-induced resistance to doxorubicin.

Induction of PGF2α synthesis by cortisol through GR dependent induction of CBR1 in human amnion fibroblasts

Abundant evidence indicates a pivotal role of prostaglandin F2α (PGF2α) in human parturition. Both the fetal and maternal sides of the fetal membranes synthesize PGF2α. In addition to the synthesis of PGF2α from PGH2 by PGF synthase (PGFS), PGF2α can also be converted from PGE2 by carbonyl reductase 1 (CBR1). Here, we showed that there was concurrent increased production of cortisol and PGF2α in association with the elevation of CBR1 in human amnion obtained at term with labor versus term without labor. In cultured primary human amnion fibroblasts, cortisol (0.01-1μM) increased PGF2α production in a concentration-dependent manner, in parallel with elevation of CBR1 levels. Either siRNA-mediated knockdown of glucocorticoid receptor (GR) expression or GR antagonist RU486 attenuated the induction of CBR1 by cortisol. Chromatin immunoprecipitation (ChIP) showed an increased enrichment of both GR and RNA polymerase II to CBR1 promoter. Knockdown of CBR1 expression with siRNA or inhibition of CBR1 activity with rutin decreased both basal and cortisol-stimulated PGF2α production in human amnion fibroblasts. In conclusion, CBR1 may play a critical role in PGF2α synthesis in human amnion fibroblasts, and cortisol promotes the conversion of PGE2 into PGF2α via GR-mediated induction of CBR1 in human amnion fibroblasts. This stimulatory effect of cortisol on CBR1 expression may partly explain the concurrent increases of cortisol and PGF2α in human amnion tissue with labor, and these findings may account for the increased production of PGF2α in the fetal membranes prior to the onset of labor.

Effects of Sublethal Exposure to a Glyphosate-Based Herbicide Formulation on Metabolic Activities of Different Xenobiotic-Metabolizing Enzymes in Rats

The activities of different xenobiotic-metabolizing enzymes in liver subcellular fractions from Wistar rats exposed to a glyphosate (GLP)-based herbicide (Roundup full II) were evaluated in this work. Exposure to the herbicide triggered protective mechanisms against oxidative stress (increased glutathione peroxidase activity and total glutathione levels). Liver microsomes from both male and female rats exposed to the herbicide had lower (45%-54%, P < 0.01) hepatic cytochrome P450 (CYP) levels compared to their respective control animals. In female rats, the hepatic 7-ethoxycoumarin O-deethylase (a general CYP-dependent enzyme activity) was 57% higher (P < 0.05) in herbicide-exposed compared to control animals. Conversely, this enzyme activity was 58% lower (P < 0.05) in male rats receiving the herbicide. Lower (P < 0.05) 7-ethoxyresorufin O-deethlyase (EROD, CYP1A1/2 dependent) and oleandomycin triacetate (TAO) N-demethylase (CYP3A dependent) enzyme activities were observed in liver microsomes from exposed male rats. Conversely, in females receiving the herbicide, EROD increased (123%-168%, P < 0.05), whereas TAO N-demethylase did not change. A higher (158%-179%, P < 0.01) benzyloxyresorufin O-debenzylase (a CYP2B-dependent enzyme activity) activity was only observed in herbicide-exposed female rats. In herbicide-exposed rats, the hepatic S-oxidation of methimazole (flavin monooxygenase dependent) was 49% to 62% lower (P < 0.001), whereas the carbonyl reduction of menadione (a cytosolic carbonyl reductase-dependent activity) was higher (P < 0.05). Exposure to the herbicide had no effects on enzymatic activities dependent on carboxylesterases, glutathione transferases, and uridinediphospho-glucuronosyltransferases. This research demonstrated certain biochemical modifications after exposure to a GLP-based herbicide. Such modifications may affect the metabolic fate of different endobiotic and xenobiotic substances. The pharmacotoxicological significance of these findings remains to be clarified.

Identification of carbonyl reductase 1 as a resveratrol-binding protein by affinity chromatography using 4'-amino-3,5-dihydroxy-trans-stilbene

The mechanisms by which resveratrol (3,4',5-trihydroxy-trans-stilbene) elicits diverse health benefits remain unclear because the intracellular target molecules of resveratrol are poorly defined. We screened resveratrol-binding proteins from lysates of MCF-7 breast cancer cells using resveratrol-affinity resin, which was constructed by immobilizing 4'-amino-3,5-dihydroxy-trans-stilbene on activated CH-Sepharose. On SDS-PAGE, two bands were detected as proteins that specifically bound to the resveratrol-affinity resin. One of these, a 30-kDa protein, was identified as human carbonyl reductase 1 (CBR1) by hybrid linear ion trap/time-of-flight mass spectrometry. Similarly, recombinant CBR1 bound to the resveratrol-affinity resin in the absence of resveratrol, but not in the presence of resveratrol. Among its activities, CBR1 catalyzes a NADPH-dependent reduction of the anticancer drug doxorubicin to the cardiotoxin doxorubicinol. The effects of doxorubicin on viability of MCF-7 cells were enhanced by resveratrol, 3,5-dihydroxy-4'-methoxy-trans-stilbene, 3,4'-dihydroxy-5-methoxy-trans-stilbene, and 4'-amino-3,5-dihydroxy-trans-stilbene at concentrations of 1 and 10 μM. Resveratrol and these derivatives inhibited CBR1 activities to a similar degree at concentrations of 100 and 200 μM. However, 3,5-dimethoxy-4'-hydroxy-trans-stilbene and m-hydroquinone had no influence on doxorubicin cytotoxicity or CBR1 activity. Resveratrol inhibited CBR1 activity through an apparent mix of competitive (Ki=55.8 μM) and noncompetitive (αKi=164 μM; α=2.98) inhibition kinetics. These results indicate that (i) resveratrol enhances the cytotoxic effects of doxorubicin on MCF-7 cells; (ii) the moiety that contains the 3,5-dihydroxyl groups of resveratrol, but not the m-hydroquinone structure alone, is required to bind CBR1; and (iii) resveratrol acts as a mixed-type inhibitor of CBR1 activity on doxorubicin.

Assessment of a putative proton relay in Arabidopsis cinnamyl alcohol dehydrogenase catalysis

Extended proton relay systems have been proposed for various alcohol dehydrogenases, including the Arabidopsis thaliana cinnamyl alcohol dehydrogenases (AtCADs). Following a previous structural biology investigation of AtCAD5, the potential roles of three amino acid residues in a putative proton relay system, namely Thr49, His52 and Asp57, in AtCAD5, were investigated herein. Using site-directed mutagenesis, kinetic and isothermal titration calorimetry (ITC) analyses, it was established that the Thr49 residue was essential for overall catalytic conversion, whereas His52 and Asp57 residues were not. Mutation of the Thr49 residue to Ala resulted in near abolition of catalysis, with thermodynamic data indicating a negative enthalpic change (ΔH), as well as a significant decrease in binding affinity with NADPH, in contrast to wild type AtCAD5. Mutation of His52 and Asp57 residues by Ala did not significantly change either catalytic efficiency or thermodynamic parameters. Therefore, only the Thr49 residue is demonstrably essential for catalytic function. ITC analyses also suggested that for AtCAD5 catalysis, NADPH was bound first followed by p-coumaryl aldehyde.

A pharmacology-based comparison of the activity of albendazole and flubendazole against Echinococcus granulosus metacestode in sheep

Cyst echinococcosis (CE) is a zoonotic disease caused by the larval stage of the Echinococcus granulosus helminth parasite. The work reported here aimed to compare the efficacy of albendazole (ABZ) and flubendazole (FLBZ) against CE in naturally infected sheep. Additionally, their comparative pharmacokinetic behaviour and the assessment of serum liver enzymes activities were studied. Twelve (12) naturally infected sheep were allocated to the following experimental groups: unmedicated control group, FLBZ-treated and ABZ-treated. Treatments were orally performed every 48 h, over 55 days at dose rate of 10 (FLBZ) and 8.5 (ABZ) mg/kg (equimolar dose rates). The efficacy of the drug treatments was based on protoscoleces' vitality/viability. The kinetic disposition assessment included the Initial and Final Kinetic Studies which implicated the collection of blood samples after both the first and the last drug administration. Blood samples were processed to measure drug concentrations by HPLC. The protoscoleces' vitality observed in the untreated control group (98%) was significantly reduced in the presence of both ABZ and FLBZ. 90% of mice inoculated with protoscoleces in the control group developed hydatid cysts in their peritoneal cavity (viability study). However, only 25% (FLBZ) and 33% (ABZ) of mice inoculated with protoscoleces recovered from treated sheep, developed hydatid cysts in their abdominal cavity. Reduced FLBZ (R-FLBZ) was the main metabolite recovered in the bloodstream after oral administration of FLBZ to sheep. Low plasma concentrations of FLBZ parent drug were measured up to 48 h post-administration. ABZ was not detected in plasma at any time post-treatment, being its metabolites ABZ sulphoxide (ABZSO) and ABZ sulphone (ABZSO₂) recovered in plasma. Hepatotoxicity due to the continued treatment with either ABZ or FLBZ was not observed. A 3-fold increase ethoxyresorufin O-deethylase activity, a cytochrome P450 1A (CYP1A)-dependent enzyme reaction, was observed in liver microsomes obtained from sheep receiving ABZ, compared to those of the unmedicated and FLBZ-treated animals. In conclusion, FLBZ is an available anthelmintic which may be developed into an effective and safe drug for the human CE treatment. Despite the low plasma concentrations measured by FLBZ/R-FLBZ, an important reduction in protoscoleces' vitality was observed in cysts located in sheep liver. Modern pharmaceutical technology may help to greatly improve FLBZ systemic exposure improving its efficacy against CE.

Impact of genetic polymorphisms on chemotherapy toxicity in childhood acute lymphoblastic leukemia

The efficacy of chemotherapy in pediatric acute lymphoblastic leukemia (ALL) patients has significantly increased in the last 20 years; as a result, the focus of research is slowly shifting from trying to increase survival rates to reduce chemotherapy-related toxicity. At the present time, the cornerstone of therapy for ALL is still formed by a reduced number of drugs with a highly toxic profile. In recent years, a number of genetic polymorphisms have been identified that can play a significant role in modifying the pharmacokinetics and pharmacodynamics of these drugs. The best example is that of the TPMT gene, whose genotyping is being incorporated to clinical practice in order to individualize doses of mercaptopurine. However, there are additional genes that are relevant for the metabolism, activity, and/or transport of other chemotherapy drugs that are widely use in ALL, such as methotrexate, cyclophosphamide, vincristine, L-asparaginase, etoposide, cytarabine, or cytotoxic antibiotics. These genes can also be affected by genetic alterations that could therefore have clinical consequences. In this review we will discuss recent data on this field, with special focus on those polymorphisms that could be used in clinical practice to tailor chemotherapy for ALL in order to reduce the occurrence of serious adverse effects.

Carbonyl reductase mRNA abundance and enzymatic activity as potential biomarkers of oxidative stress in marine fish

Carbonyl reductase (CBR) is an enzyme involved in protection from oxidative stress. In rainbow trout (Oncorhynchus mykiss), the hepatic mRNA abundance of the two isoforms (A and B) is increased after exposure to treated sewage effluents, as well as after exposure with β-naphthoflavone (β-NF) and the pro-oxidant paraquat. In this study, we show that the same chemicals similarly increase the single known hepatic CBR mRNA level and CBR catalytic activity in the coastal living eelpout (Zoarces viviparus). Hepatic CBR mRNA abundance and catalytic activity were also compared between eelpout collected at contaminated and reference sites on the Swedish west coast, but no differences were observed. In conclusion, CBR is a potential biomarker candidate for monitoring the exposure and effects of AhR agonists and/or pro-oxidants in the marine environment, but more research is needed to investigate temporal regulation as well as dose dependency for different chemicals. The mRNA and enzymatic assays presented in this study provide two additional tools for researchers interested in expanding their biomarker battery.

Carbonyl reduction of mequindox by chicken and porcine cytosol and cloned carbonyl reductase 1

Mequindox (MEQ) is a novel synthetic quinoxaline 1,4-dioxides derivative, which is widely used as a veterinary drug and animal feed additive. However, the metabolic mechanism of MEQ is rarely reported. The N-oxide reduction mechanism of MEQ was reported in our previous work. In this article, the toxicity and the reduction of the carbonyl of MEQ were studied. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium assays demonstrated that the carbonyl-reduced MEQ, 2-isoethanol MEQ was much less toxic than MEQ. High-performance liquid chromatography analysis showed that the cytosol extracts of chicken and pig livers were able to reduce MEQ to 2-isoethanol MEQ and the reaction was NADPH-dependent. Further study via enzyme-inhibitory experiment revealed that carbonyl reductase 1 (CBR1) participated in this metabolism. The enzyme activity analysis showed that both chicken CBR1 (cCBR1) and porcine CBR1 (pCBR1) were capable of catalyzing the carbonyl reduction of MEQ and its N-oxide reductive metabolite, 1-deoxymequindox. By comparison of the kinetic constants, we observed that the activity of cCBR1 was higher than pCBR1 to MEQ and the standard substrate of CBR1, menadione. On the other hand, both CBR1s exhibited higher activity to 1-deoxymequindox than MEQ. Mutation analysis suggested that the difference of amino acid at position 141/142 may be one possible reason that caused the activity difference between cCBR1 and pCBR1. Thus far, CBR1 was first reported to participate in the carbonyl reduction of MEQ. Our results will be helpful to recognize the metabolic pathways of quinoxaline drugs deeply and to provide a theoretical basis for controlling the negative effects of these drugs.

Carbonyl reduction of bupropion in human liver

Bupropion is metabolized extensively in humans by oxidative and reductive processes. CYP2B6 mediates oxidation of bupropion to hydroxybupropion, but the enzyme(s) catalyzing carbonyl reduction of bupropion to erythro- and threohydrobupropion in human liver is unknown. The objective of this study was to examine the enzyme kinetics of bupropion reduction in human liver. In human liver cytosol, the reduction of bupropion to erythro-and threohydrobupropion was NADPH dependent with Cl(int) values of 0.08 and 0.60 µL·min(-1)mg(-1) protein, respectively. Bupropion reduction in liver microsomes was also NADPH dependent with Cl(int) values of 10.4 and 280 µL·min(-1)mg(-1) protein, respectively. Formation of erythro-and threohydrobupropion in microsomes exceeded that in cytosol by 70 and 170 fold, respectively. Menadione, an inhibitor of cytosolic carbonyl reducing enzymes (e.g. CBRs), inhibited erythro-and threohydrobupropion formation in cytosol with IC(50) of 30 and 54 µM, respectively. In microsomes 18β-glycyrrhetinic acid, an inhibitor of microsomal carbonyl reductases (e.g. 11β-HSDs), inhibited their formation with IC(50) of 25 and 26 nM, respectively. Our findings, in agreement with recent human placental studies, show that carbonyl reducing enzymes in hepatic microsomes are significant players in bupropion reduction. Contrary to past studies, we found that threohydrobupropion (not hydroxybupropion) is the major microsomal generated hepatic metabolite of bupropion.

Anthracycline cardiotoxicity

INTRODUCTION

Anthracyclines are widely prescribed anticancer agents that cause a dose-related cardiotoxicity, often aggravated by nonanthracycline chemotherapeutics or new generation targeted drugs. Anthracycline cardiotoxicity may occur anytime in the life of cancer survivors. Understanding the molecular mechanisms and clinical correlates of cardiotoxicity is necessary to improve the therapeutic index of anthracyclines or to identify active, but less cardiotoxic analogs.

AREAS COVERED

The authors review the pharmacokinetic, pharmacodynamic and biochemical mechanisms of anthracycline cardiotoxicity and correlate them to clinical phenotypes of cardiac dysfunction. Attention is paid to bioactivation mechanisms that converted anthracyclines to reactive oxygen species (ROS) or long-lived secondary alcohol metabolites. Preclinical aspects and clinical implications of the "oxidative stress" or "secondary alcohol metabolite" hypotheses are discussed on the basis of literature that cuts across bench and evidence-based medicine. Interactions of anthracyclines with comorbidities or unfavorable lifestyle choices were identified as important cofactors of the lifetime risk of cardiotoxicity and as possible targets of preventative strategies.

EXPERT OPINION

Anthracycline cardiotoxicity is a multifactorial process that needs to be incorporated in a translational framework, where individual genetic background, comorbidities, lifestyles and other drugs play an equally important role. Fears for cardiotoxicity should not discourage from using anthracyclines in many oncologic settings. Cardioprotective strategies are available and should be used more pragmatically in routine clinical practice.

A rapid, reproducible, on-the-fly orthogonal array optimization method for targeted protein quantification by LC/MS and its application for accurate and sensitive quantification of carbonyl reductases in human liver

Liquid chromatography (LC)/mass spectrometry (MS) in selected-reactions-monitoring (SRM) mode provides a powerful tool for targeted protein quantification. However, efficient, high-throughput strategies for proper selection of signature peptides (SP) for protein quantification and accurate optimization of their SRM conditions remain elusive. Here we describe an on-the-fly, orthogonal array optimization (OAO) approach that enables rapid, comprehensive, and reproducible SRM optimization of a large number of candidate peptides in a single nanoflow-LC/MS run. With the optimized conditions, many peptide candidates can be evaluated in biological matrixes for selection of the final SP. The OAO strategy employs a systematic experimental design that strategically varies product ions, declustering energy, and collision energy in a cycle of 25 consecutive SRM trials, which accurately reveals the effects of these factors on the signal-to-noise ratio of a candidate peptide and optimizes each. As proof of concept, we developed a highly sensitive, accurate, and reproducible method for the quantification of carbonyl reductases CBR1 and CBR3 in human liver. Candidate peptides were identified by nano-LC/LTQ/Orbitrap, filtered using a stringent set of criteria, and subjected to OAO. After evaluating both sensitivity and stability of the candidates, two SP were selected for quantification of each protein. As a result of the accurate OAO of assay conditions, sensitivities of 80 and 110 amol were achieved for CBR1 and CBR3, respectively. The method was validated and used to quantify the CBRs in 33 human liver samples. The mean level of CBR1 was 93.4 +/- 49.7 (range: 26.2-241) ppm of total protein, and of CBR3 was 7.69 +/- 4.38 (range: 1.26-17.9) ppm. Key observations of this study: (i) evaluation of peptide stability in the target matrix is essential for final selection of the SP; (ii) utilization of two unique SP contributes to high reliability of target protein quantification; (iii) it is beneficial to construct calibration curves using standard proteins of verified concentrations to avoid severe biases that may result if synthesized peptides alone are used. Overall, the OAO method is versatile and adaptable to high-throughput quantification of validated biomarkers identified by proteomic discovery experiments.

Two nonsynonymous single nucleotide polymorphisms of human carbonyl reductase 1 demonstrate reduced in vitro metabolism of daunorubicin and doxorubicin

Carbonyl reductases (CBRs) are a group of metabolic enzymes belonging to the short-chain dehydrogenase family with NADPH-dependent oxidoreductase activity. These enzymes are known to metabolize the anthracyclines doxorubicin (DOX) and daunorubicin (DAUN). Both DOX and DAUN are highly effective in cancer therapy; however, there is considerable interpatient variability in adverse effects seen in patients undergoing treatment with these drugs. This may be attributed to altered metabolism associated with nonsynonymous single nucleotide polymorphisms (ns-SNPs) in the genes encoding for CBRs. In this study, we examine the effect of the V88I and P131S mutations in the human CBR1 gene on the metabolism of anthracyclines to their respective major metabolites, doxorubicinol and daunorubicinol. Kinetic studies using purified, histidine-tagged, recombinant enzymes in a high-performance liquid chromatography-fluorescence assay demonstrated that the V88I mutation leads to a significantly reduced maximal rate of activity (V(max)) (2090 +/- 112 and 257 +/- 11 nmol/min x mg of purified protein for DAUN and DOX, respectively) compared with that for the wild-type (3430 +/- 241 and 364 +/- 37 nmol/min x mg of purified protein for DAUN and DOX, respectively). In the case of the P131S mutation, a significant increase in substrate affinity (K(m)) was observed for DAUN only (89 +/- 13 microM) compared with that for the wild-type (51 +/- 13 microM). In the presence of either anthracycline, both variants exhibited a 20 to 40% decrease in catalytic efficiency (k(cat)/K(m)) compared with that for the wild-type enzyme. Therefore, the ns-SNPs generating both these mutations may alter bioavailability of these anthracyclines in cancer patients and should be examined in clinical studies as potential biomarkers for DAUN- and DOX-induced adverse effects.

Pharmacogenetics of human carbonyl reductase 1 (CBR1) in livers from black and white donors

Carbonyl reductase 1 (CBR1) reduces the anticancer drug doxorubicin into the cardiotoxic metabolite doxorubicinol. We documented the hepatic expression of CBR1 in samples from white and black donors. Concordance between ethnicity and geographical ancestry was examined with ancestry informative markers. Livers from blacks and whites showed similar CBR1 mRNA levels (CBR1 mRNA(blacks) = 4.8 +/- 4.3 relative -fold versus CBR1 mRNA(whites) = 3.6 +/- 3.6 relative -fold; p = 0.217). CBR1 protein levels did not differ between both groups (CBR1(blacks) = 8.0 +/- 3.4 nmol/g cytosolic protein versus CBR1(whites) = 9.0 +/- 4.6 nmol/g cytosolic protein; p = 0.347). The CBR1 3'-untranslated region polymorphism 1096G>A was detected in DNA samples from whites (p = 0.875; q = 0.125), and livers with homozygous G/G genotypes showed a trend toward higher CBR1 mRNA levels compared with samples with heterozygous G/A genotypes [CBR1 1096G>A((G/G)) = 4.1 +/- 4.1 relative -fold versus CBR1 1096G>A((G/A)) = 3.0 +/- 2.5 relative-fold; p = 0.266]. CBR1 1096G>A genotype status was associated with CBR1 protein levels (p = 0.030) and CBR activity expressed as the rate of synthesis of doxorubicinol (p = 0.028). Our findings warrant further studies to evaluate the impact of CBR1 1096G>A genotype status on the variable pharmacodynamics of anthracycline drugs.

A survey of the year 2007 literature on applications of isothermal titration calorimetry

Elucidation of the energetic principles of binding affinity and specificity is a central task in many branches of current sciences: biology, medicine, pharmacology, chemistry, material sciences, etc. In biomedical research, integral approaches combining structural information with in-solution biophysical data have proved to be a powerful way toward understanding the physical basis of vital cellular phenomena. Isothermal titration calorimetry (ITC) is a valuable experimental tool facilitating quantification of the thermodynamic parameters that characterize recognition processes involving biomacromolecules. The method provides access to all relevant thermodynamic information by performing a few experiments. In particular, ITC experiments allow to by-pass tedious and (rarely precise) procedures aimed at determining the changes in enthalpy and entropy upon binding by van't Hoff analysis. Notwithstanding limitations, ITC has now the reputation of being the "gold standard" and ITC data are widely used to validate theoretical predictions of thermodynamic parameters, as well as to benchmark the results of novel binding assays. In this paper, we discuss several publications from 2007 reporting ITC results. The focus is on applications in biologically oriented fields. We do not intend a comprehensive coverage of all newly accumulated information. Rather, we emphasize work which has captured our attention with originality and far-reaching analysis, or else has provided ideas for expanding the potential of the method.

Genotype of human carbonyl reductase CBR3 correlates with doxorubicin disposition and toxicity

OBJECTIVES

Doxorubicin is a cytotoxic drug with potential for severe myelosuppression that is highly variable and poorly predictable.

METHODS

We correlated CBR1 and CBR3 genotypes with the pharmacokinetics and pharmacodynamics of doxorubicin in 101 Southeast Asian breast cancer patients receiving first-line doxorubicin.

RESULTS

A common CBR3 11G>A variant was associated with lower doxorubicinol area under the concentration-time curve (AUC)/doxorubicin AUC metabolite ratio (P=0.009, GG vs. AA; trend test, P=0.004), lower CBR3 expression in breast tumor tissue (P=0.001, GG vs. AA), greater tumor reduction (P=0.015, GG vs. AA), and greater percentage reduction of leukocyte and platelet counts at nadir (trend test, P < or = 0.03). Chinese and Malays had higher frequency of the CBR3 11G>A variant than Indians (P < or = 0.002). Another variant CBR3 730G>A was associated with higher doxorubicinol AUC (P=0.009, GG vs. AA) and CBR3 expression in breast tumor tissue (P=0.001, GG vs AA).

CONCLUSION

Polymorphisms in CBR3 may explain interindividual and interethnic variability of doxorubicin pharmacokinetics and pharmacodynamics.

CBR1 and CBR3 pharmacogenetics and their influence on doxorubicin disposition in Asian breast cancer patients

The present study aimed to identify polymorphic genes encoding carbonyl reductases (CBR1, CBR3) and investigate their influence on doxorubicin disposition in Asian breast cancer patients (n = 62). Doxorubicin (60 mg/m(2)) was administered every 3 weeks for four to six cycles and the pharmacokinetic parameters were estimated using non-compartmental analysis (WinNonlin). The Mann-Whitney U-test was used to assess genotypic-phenotypic correlations. Five CBR1 (-48G>A, c.219G>C, c.627C>T, c.693G>A, +967G>A) and CBR3 (c.11G>A, c.255C>T, c.279C>T, c.606G>A, c.730G>A) polymorphisms were identified. The CBR1 D2 diplotypes were characterized by the presence of at least one variant allele at the c.627C>T and +967G>A loci. Patients in the CBR1 D1 diplotype group had significantly higher clearance (CL) normalized to body surface area (BSA) (CL/BSA[L/h/m(2)]: median 25.09; range 16.44-55.66) and significantly lower exposure levels; area under curve (AUC(0-infinity)/dose/BSA [h/m(5)]; median 15.08; range 6.18-38.03) of doxorubicin compared with patients belonging to the CBR1 D2 diplotype group (CL/BSA[L/h/m(2)]; median 20.88; range 8.68-31.79, P = 0.014; and AUC(0-infinity)/dose/BSA[h/m(5)]; median 21.35; range 9.82-67.17, P = 0.007 respectively). No significant influence of CBR3 polymorphisms on the pharmacokinetics of doxorubicin were observed in Asian cancer patients. The present exploratory study shows that CBR1 D2 diplotypes correlate with significantly higher exposure levels of doxorubicin, suggesting the possibility of lowered intracellular conversion to doxorubicinol in these patients. Further evaluation of carbonyl reductase polymorphisms in influencing the treatment efficacy of doxorubicin-based chemotherapy in Asian cancer patients are warranted.

Inhibition of polymorphic human carbonyl reductase 1 (CBR1) by the cardioprotectant flavonoid 7-monohydroxyethyl rutoside (monoHER)

PURPOSE

Carbonyl reductase 1 (CBR1) reduces the anticancer anthracyclines doxorubicin and daunorubicin into the cardiotoxic metabolites doxorubicinol and daunorubicinol. We evaluated whether the cardioprotectant monoHER inhibits the activity of polymorphic CBR1.

METHODS

We performed enzyme kinetic studies with monoHER, CBR1 (CBR1 V88 and CBR1 I88) and anthracycline substrates. We also characterized CBR1 inhibition by the related flavonoids triHER and quercetin.

RESULTS

MonoHER inhibited the activity of CBR1 V88 and CBR1 I88 in a concentration-dependent manner. The IC(50) values of monoHER were lower for CBR1 I88 compared to CBR1 V88 for the substrates daunorubicin and doxorubicin (daunorubicin, IC(50)-CBR1 I88 = 164 microM vs. IC(50)-CBR1 V88 = 219 microM; doxorubicin, IC(50)-CBR1 I88 = 37 microM vs. IC(50)-CBR1 V88 = 59 microM; p < 0.001). Similarly, the flavonoids triHER and quercetin exhibited lower IC(50) values for CBR1 I88 compared to CBR1 V88 (p < 0.001). MonoHER acted as a competitive CBR1 inhibitor when using daunorubicin as a substrate Ki = 45 +/- 18 microM. MonoHER acted as an uncompetitive CBR1 inhibitor for the small quinone substrate menadione Ki = 33 +/- 17 microM.

CONCLUSIONS

The cardioprotectant monoHER inhibits CBR1 activity. CBR1 V88I genotype status and the type of anthracycline substrate dictate the inhibition of CBR1 activity.

Influence of ABCB1 and ABCG2 polymorphisms on doxorubicin disposition in Asian breast cancer patients

The influence of three high frequency ABCB1 polymorphisms (c.1236C>T, c.2677G>A/T, and c.3435C>T) and the ABCG2 c.421C>A polymorphism on the disposition of doxorubicin in Asian breast cancer patients receiving adjuvant chemotherapy was investigated in the present study. The allelic frequency of the ABCB1 c.1236T, c.2677T, c.2677A, and c.3435T variants were 60%, 38%, 7%, and 22%, respectively, and the frequency of the ABCG2 c.421A allele was 23%. Pairwise analysis showed increased exposure levels to doxorubicin in patients harboring at least one ABCB1 c.1236T allele (P = 0.03). Patients homozygous for the CC-GG-CC genotype had significantly lower doxorubicin exposure levels compared to the patients who had CT-GT-CT (P = 0.02) and TT-TT-TT genotypes (P = 0.03). Significantly increased clearance of doxorubicin was also observed in patients harboring CC-GG-CC genotypes when compared to patients harboring the CT-GT-CT genotype (P = 0.01). Patients harboring the CC-GG-CC genotypes had significantly lower peak plasma concentrations of doxorubicinol compared to patients who had TT-TT-TT genotypes (P = 0.03). No significant influences on doxorubicin pharmacokinetic parameters were observed in relation to the ABCG2 c.421C>A polymorphism. In conclusion, the present exploratory study suggests that the three high frequency linked polymorphisms in the ABCB1 gene might be functionally important with regards to the altered pharmacokinetics of doxorubicin in Asian breast cancer patients, resulting in significantly increased exposure levels and reduced clearance.

Cardiotoxicity of antitumor drugs

Many antitumor drugs cause "on treatment" cardiotoxicity or introduce a measurable risk of delayed cardiovascular events. Doxorubicin and other anthracyclines cause congestive heart failure that develops in a dose-dependent manner and reflects the formation of toxic drug metabolites in the heart. Cardiovascular events may occur also with other chemotherapeutics, but the dose or metabolism dependence of such events are less obvious and predictable. Drugs targeted to tumor-specific receptors or metabolic routes were hoped to offer a therapeutic gain while also sparing the heart and other healthy tissues; nonetheless, many such drugs still cause moderate to severe cardiotoxicity. Targeted drugs may also engage a cardiotoxic synergism with "old-fashioned" chemotherapeutics, as shown by the higher than expected incidence of anthracycline-related congestive heart failure that occurred in patients treated with doxorubicin and the anti HER2 antibody Trastuzumab. Mechanism-based considerations and retrospective analyses of clinical trials now form the basis for a new classification of cardiotoxicity, type I for anthracyclines vs type II for Trastuzumab. Such a classification may serve a template to accommodate other paradigms of cardiotoxicity induced by new drugs and combination therapies. Of note, laboratory animal models did not always anticipate the mechanisms and/or metabolic determinants of cardiotoxicity induced by antitumor drugs or combination therapies. Toxicologists and regulatory agencies and clinicians should therefore join in collaborative efforts that improve the early identification of cardiotoxicity and minimize the risks of cardiac events in patients.