Global plant trait relationships extend to the climatic extremes of the tundra biome

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world.

Traditional plant functional groups explain variation in economic but not size-related traits across the tundra biome

AIM

Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups represent variation in six ecologically important plant traits.

LOCATION

Tundra biome.

TIME PERIOD

Data collected between 1964 and 2016.

MAJOR TAXA STUDIED

295 tundra vascular plant species.

METHODS

We compiled a database of six plant traits (plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, seed mass) for tundra species. We examined the variation in species-level trait expression explained by four traditional functional groups (evergreen shrubs, deciduous shrubs, graminoids, forbs), and whether variation explained was dependent upon the traits included in analysis. We further compared the explanatory power and species composition of functional groups to alternative classifications generated using post hoc clustering of species-level traits.

RESULTS

Traditional functional groups explained significant differences in trait expression, particularly amongst traits associated with resource economics, which were consistent across sites and at the biome scale. However, functional groups explained 19% of overall trait variation and poorly represented differences in traits associated with plant size. Post hoc classification of species did not correspond well with traditional functional groups, and explained twice as much variation in species-level trait expression.

MAIN CONCLUSIONS

Traditional functional groups only coarsely represent variation in well-measured traits within tundra plant communities, and better explain resource economic traits than size-related traits. We recommend caution when using functional group approaches to predict tundra vegetation change, or ecosystem functions relating to plant size, such as albedo or carbon storage. We argue that alternative classifications or direct use of specific plant traits could provide new insights for ecological prediction and modelling.

Use of targeted therapy in patients with metastatic renal cell carcinoma: clinical and economic impact in a Canadian real-life setting

Introduction

Outside of randomized controlled clinical trials, the understanding of the effectiveness and costs associated with targeted therapies for metastatic renal cell carcinoma (mrcc) is limited in Canada. The purpose of the present study was to use real-world prospective data to assess the effectiveness and cost of targeted therapies for patients with mrcc.

Methods

The Canadian Kidney Cancer Information System, a pan-Canadian database, was used to identify prospectively collected data relating to patients with mrcc. First- and subsequent-line time to treatment termination (ttt) was determined from therapy initiation time (sunitinib or pazopanib) to discontinuation of therapy. Kaplan-Meier survival curves were used to estimate the unadjusted and adjusted overall survival (os) by treatment. Unit treatment cost was used to estimate the cost by line of treatment and the total cost of therapy for the management of patients with mrcc.

Results

The study included 475 patients receiving sunitinib or pazopanib in the first-line setting. Patients were treated mostly with sunitinib (81%); 19% of patients were treated with pazopanib. The median ttt in the first line was 7.7 months for patients receiving sunitinib and 4.6 months for those receiving pazopanib (p < 0.001). The adjusted os was 32 months with sunitinib and 21 months with pazopanib (hazard ratio: 1.61; p < 0.01). The total median cost of first- and second-line treatments was $56,476 (interquartile range: $23,738-$130,447) for patients in the sunitinib group and $46,251 (interquartile range: $28,167-$91,394) for those in the pazopanib group.

Conclusions

For the two therapies, os differed significantly, with a higher median os being observed in the sunitinib group. The cost of treatment was higher in the sunitinib group, which is to be expected with longer survival.

Effects of alloantibodies to human leukocyte antigen on endothelial expression and serum levels of thrombomodulin

Essentials The effect of alloantibodies on the endothelial expression of thrombomodulin is unknown. Thrombomodulin was quantified in stimulated endothelial cells and measured in serum samples. Anti-human leukocyte antigen (HLA) I vs. II antibodies have different effects on thrombomodulin. Anti-HLA II antibodies may promote a prothrombotic state and contribute to microangiopathy.

SUMMARY

Rationale Thrombomodulin (TBM) is an anticoagulant and anti-inflammatory transmembrane protein expressed on endothelial cells. Donor-specific alloantibodies, particularly those against human leukocyte antigen (HLA) class II, are associated with microvascular endothelial damage in solid allografts. Objective Our aim was to characterize the effects of anti-HLA antibodies on endothelial expression of TBM, and in particular, the differential effects of anti-HLA class I compared with those of anti-HLA class II. Methods We used human glomerular microvascular endothelial cells to examine TBM expression on anti-HLA-treated cells, and we tested sera from transplant recipients for soluble TBM. Results We found that whereas membrane TBM expression increased in a dose-dependent manner in the presence of anti-HLA class I antibodies, treatment with anti-HLA class II led to minimal TBM expression on the endothelial surface but to a cytosolic accumulation. Platelet adhesion studies confirmed the functional impact of anti-HLA class II. Quantitative densitometry of the membrane lysates further suggested that anti-HLA class II impairs TBM glycosylation. Furthermore, we found a significant association between the presence of circulating anti-HLA class II antibodies in transplant recipients and low serum levels of TBM. Conclusion These results indicate that ligation of anti-HLA class I and II antibodies produces different effects on the endothelial expression of TBM and on serum levels of TBM in transplant recipients. Anti-HLA class II antibodies may be associated with a prothrombotic state, which could explain the higher occurrence of microangiopathic lesions in the allograft and the poor outcomes observed in patients with these alloantibodies.

Recommendations on breast cancer screening and prevention in the context of implementing risk stratification: impending changes to current policies

In recent years, risk stratification has sparked interest as an innovative approach to disease screening and prevention. The approach effectively personalizes individual risk, opening the way to screening and prevention interventions that are adapted to subpopulations. The international perspective project, which is developing risk stratification for breast cancer, aims to support the integration of its screening approach into clinical practice through comprehensive tool-building. Policies and guidelines for risk stratification-unlike those for population screening programs, which are currently well regulated-are still under development. Indeed, the development of guidelines for risk stratification reflects the translational aspects of perspective. Here, we describe the risk stratification process that was devised in the context of perspective, and we then explain the consensus-based method used to develop recommendations for breast cancer screening and prevention in a risk-stratification approach. Lastly, we discuss how the recommendations might affect current screening policies.

Unravelling the transcriptomic landscape of the major phase II UDP-glucuronosyltransferase drug metabolizing pathway using targeted RNA sequencing

A comprehensive view of the human UDP-glucuronosyltransferase (UGT) transcriptome is a prerequisite to the establishment of an individual's UGT metabolic glucuronidation signature. Here, we uncover the transcriptome landscape of the 10 human UGT gene loci in normal and tumoral metabolic tissues by targeted RNA next-generation sequencing. Alignment on the human hg19 reference genome identifies 234 novel exon-exon junctions. We recover all previously known UGT1 and UGT2 enzyme-coding transcripts and identify over 130 structurally and functionally diverse novel UGT variants. We further expose a revised genomic structure of UGT loci and provide a comprehensive repertoire of transcripts for each UGT gene. Data also uncover a remodelling of the UGT transcriptome occurring in a tissue- and tumor-specific manner. The complex alternative splicing program regulating UGT expression and protein functions is likely critical in determining detoxification capacity of an organ and stress-related responses, with significant impact on drug responses and diseases.

A novel UGT1 marker associated with better tolerance against irinotecan-induced severe neutropenia in metastatic colorectal cancer patients

The risk of severe irinotecan-induced neutropenia has been shown to be related to the UGT1 variant UGT1A1*28, which increases exposure to the potent metabolite SN-38. Our goal was to identify a novel UGT1 marker(s) using 28 haplotype-tagged single nucleotide polymorphisms genotyped by mass spectrometry. By characterizing the UGT1 sequence from a cohort of 167 Canadian metastatic colorectal cancer (mCRC) patients and a validation cohort of 250 Italian mCRC patients, we found rs11563250G, located in the intergenic region downstream of UGT1, to be significantly associated with reduced risk of severe neutropenia (odds ratio (OR)=0.21; P=0.043 and OR=0.27; P=0.036, respectively, and OR=0.31 when combined; P=0.001), which remained significant upon correction for multiple testing in the combined cohort (P=0.041). For the two-marker haplotype rs11563250G and UGT1A1*1 (rs8175347 TA6), the OR was of 0.17 (P=0.0004). Genetic testing of this marker may identify patients who might benefit from increased irinotecan dosing.

The impact of UGT1A8, UGT1A9, and UGT2B7 genetic polymorphisms on the pharmacokinetic profile of mycophenolic acid after a single oral dose in healthy volunteers

We studied whether polymorphisms in the UGT1A8, UGT1A9, and UGT2B7 genes, the enzymes producing the phenolic (MPAG) and acyl (AcMPAG) glucuronides of mycophenolic acid (MPA), could contribute to the interindividual variation observed in mycophenolate mofetil (MMF) pharmacokinetics (PKs). This study enrolled 17 healthy volunteers with no polymorphisms (controls) and 17 carriers of UGT1A9 -275/-2152 selected among 305 individuals genetically screened for UDP-glucuronosyltransferase (UGT) polymorphisms. Additional investigative groups included carriers of UGT1A8*2 (A173G) (n=9), UGT1A8*3 (C277Y) (n=4), and UGT1A9*3 (M33T) (n=5). Genetic analysis also included UGT2B7 to detect UGT2B7*2 (His268Tyr) and the promoter haplotype -1248A>G, -1241T>C, -1054T>C, -842G>A, -268A>G, -102T>C. Kinetics were measured in plasma and urine after a single 1.5 g oral dose of MMF, by high-performance liquid chromatography coupled with tandem mass spectrometry, over 12 h after drug intake. Compared to controls, MPA exposure was significantly lower for UGT1A9 -275/-2152 carriers, with no significant changes in MPAG. The estimates of enterohepatic (re)cycling (area under the concentration-time curve (AUC6-12 h/AUC0-12 h)) were significantly lower for MPA, MPAG, and AcMPAG in UGT1A9 -275/-2152 subjects. Compared with controls, UGT1A9*3 carriers had higher MPA and AcMPAG exposure, whereas homozygosity for the UGT1A8*2 allele and heterozygosity for UGT1A8*3 allele had no impact on MPA PKs. Compared with UGT2B7*1/*1 individuals (n=10), UGT2B7*2/*2 subjects (n=17) presented significantly higher free MPA C(max) values and elevated free and total MPA. Results indicate that after a single oral dose of MMF in healthy volunteers, specific UGT genotypes significantly alter MPA PKs and this clearly warrants additional studies with complete and detailed genetic profiling of UGT1A8, UGT1A9, and UGT2B7 genes.

Home range and movements of a wood turtle (Clemmys insculpta) population at the northern limit of its range

We studied the home ranges and seasonal movements of 20 wood turtles (Clemmys insculpta) living near the northern limit of their distribution in the Mauricie region, Quebec, Canada. We found average home-range areas of 28.3 ha. Wood turtles showed site fidelity; there was an average overlap of 60.7% in their home ranges, and 88.8% of the home-range centroids were not significantly different for the 2 years of the study. The home ranges were larger than those reported from studies in more southerly locations, leading us to hypothesize larger home-range territories with increasing latitude. Our analyses indicate that turtle movements could be grouped into four distinct activity periods during the active season: the prenesting, nesting, postnesting, and prehibernation periods. We found that wood turtles were closely associated with streams. Based on the importance of this habitat for the species, we suggest the establishment of protected buffer strips along streams used by wood turtles.

Relative enzymatic activity, protein stability, and tissue distribution of human steroid-metabolizing UGT2B subfamily members

Androgens and estrogens play major roles in cell differentiation, cell growth, and peptide secretion in steroid target tissues. In addition to the binding of these hormones to their receptors, formation and metabolism are important in the action of steroids. Metabolism of the potent steroid hormones includes glucuronidation, a major pathway of steroid elimination in liver and several steroid target tissues. Glucuronidation is catalyzed by UDP-glucuronosyltransferases (UGTs), which transfer the polar moiety from UDP-glucuronic acid to a wide variety of endogenous compounds, including steroid hormones. The UGT superfamily of enzymes is subdivided into two families, UGT1 and UGT2, on the basis of sequence homology. To date, six UGT2B proteins have been isolated, namely UGT2B4, UGT2B7, UGT2B10, UGT2B11, UGT2B15, and UGT2B17, all of which have been demonstrated to be active on steroid molecules, except for UGT2B10 and UGT2B11, for which no substrate was found. The relative activity of these enzymes on steroidal compounds remains unknown due to variable levels of UGT2B expression in different in vitro cell line models and various conditions of the enzymatic assays. Comparison of the glucuronidation rates of these enzymes requires a unique system for UGT2B protein expression, protein normalization, and enzymatic assays. In this study we have stably expressed UGT2B4, UGT2B7, UGT2B15, and UGT2B17 in the HK293 cell line, which is devoid of steroid UGT activity; characterized their kinetic properties relative to UGT protein expression; determined their transcript and protein stabilities; and established extensively their tissular distributions. UGT2B7 was demonstrated to glucuronidate estrogens, catechol estrogens, and androstane-3alpha,17beta-diol more efficiently than any other human UGTB isoform. UGT2B15 and UGT2B17 showed similar glucuronidation activity for androstane-3alpha,17beta-diol (30% lower than that of UGT2B7), whereas UGT2B17 demonstrated the highest activity for androsterone, testosterone, and dihydrotestosterone. UGT2B4 demonstrates reactivity toward 5alpha-reduced androgens and catechol estrogens, but at a significantly lower level than UGT2B7, 2B15, and 2B17. Cycloheximide treatment of stably transfected HK293 cells demonstrated that the UGT2B17 protein is more labile than the other enzymes; the protein levels decrease after 1 h of treatment, whereas other UGT2B proteins were stable for at least 12 h. Treatment of stable cells with actinomycin D reveals that UGT2B transcripts are stable for 12 h, except for the UGT2B4 transcript, which was decreased by 50% after the 12-h incubation period. Tissue distribution of the UGT2B enzymes demonstrated that UGT2B isoforms are expressed in the liver as well as in several extrahepatic steroid target tissues, namely, kidney, breast, lung, and prostate. This study clearly demonstrates the relative activities and the major substrates of human steroid-metabolizing UGT2B enzymes, which are expressed in a wide variety of steroid target tissues.

Isolation and characterization of the human UGT2B15 gene, localized within a cluster of UGT2B genes and pseudogenes on chromosome 4

Glucuronidation is a major pathway of androgen metabolism and is catalyzed by UDP-glucuronosyltransferase (UGT) enzymes. UGT2B15 and UGT2B17 are 95% identical in primary structure, and are expressed in steroid target tissues where they conjugate C19 steroids. Despite the similarities, their regulation of expression are different; however, the promoter region and genomic structure of only the UGT2B17 gene have been characterizedX to date. To isolate the UGT2B15 gene and other novel steroid-conjugating UGT2B genes, eight P-1-derived artificial chromosomes (PAC) clones varying in length from 30 kb to 165 kb were isolated. The entire UGT2B15 gene was isolated and characterized from the PAC clone 21598 of 165 kb. The UGT2B15 and UGT2B17 genes are highly conserved, are both composed of six exons spanning approximately 25 kb, have identical exon sizes and have identical exon-intron boundaries. The homology between the two genes extend into the 5'-flanking region, and contain several conserved putative cis-acting elements including Pbx-1, C/EBP, AP-1, Oct-1 and NF/kappaB. However, transfection studies revealed differences in basal promoter activity between the two genes, which correspond to regions containing non-conserved potential elements. The high degree of homology in the 5'-flanking region between the two genes is lost upstream of -1662 in UGT2B15, and suggests a site of genetic recombination involved in duplication of UGT2B genes. Fluorescence in situ hybridization mapped the UGT2B15 gene to chromosome 4q13.3-21.1. The other PAC clones isolated contain exons from the UGT2B4, UGT2B11 and UGT2B17 genes. Five novel exons, which are highly homologous to the exon 1 of known UGT2B genes, were also identified; however, these exons contain premature stop codons and represent the first recognized pseudogenes of the UGT2B family. The localization of highly homologous UGT2B genes and pseudogenes as a cluster on chromosome 4q13 reveals the complex nature of this gene locus, and other novel homologous UGT2B genes encoding steroid conjugating enzymes are likely to be found in this region of the genome.

UGT2B23, a novel uridine diphosphate-glucuronosyltransferase enzyme expressed in steroid target tissues that conjugates androgen and estrogen metabolites

Glucuronidation is widely accepted as a mechanism involved in the catabolism and elimination of steroid hormones from the body. However, relatively little is known about the enzymes involved, their specificity for the different steroids, and their site of expression and action. To characterize the pathway of steroid glucuronidation, a novel uridine diphosphate glucuronosyltransferase (UGT) enzyme was cloned and characterized. A 1768-bp complementary DNA, encoding UGT2B23 was isolated from a monkey liver library. Stable expression of UGT2B23 in human HK293 cells and Western blot analysis demonstrated the presence of a 51-kDa protein. The UGT2B23 transferase activity was tested with 62 potential endogenous substrates and was demonstrated to be active on 6 steroids and the bile acid, hyodeoxycholic acid. Kinetic analysis yielded apparent Michaelis constant (Km) values of 0.9, 13.5, 1.6, and 5.7 microM for the conjugation of androsterone (ADT), 3alpha-Diol, estriol, and 4-hydroxyestrone, respectively. RT-PCR analysis revealed that UGT2B23 transcript is expressed in several tissues, including the prostate, mammary gland, epididymis, testis, and ovary. Primary structure analysis shows that UGT2B23 is in the same family of enzymes as the previously characterized monkey isoforms UGT2B9 and UGT2B18, which are active on hydroxyandrogens. The characterization of UGT2B23 as a functional enzyme active on 3alpha-hydroxysteroids, and its expression in extrahepatic tissues, indicate that it may potentially play an important role in estrogen and androgen catabolism in peripheral steroid target tissues.

Alteration of human UDP-glucuronosyltransferase UGT2B17 regio-specificity by a single amino acid substitution

The glucuronidation of steroid hormones is catalyzed by a family of UDP-glucuronosyltransferase (UGT) enzymes. Previously, two cDNA clones, UGT2B15 and UGT2B17, which encode UGT enzymes capable of glucuronidating C19steroids, were isolated and characterized. These proteins are 95% identical in primary structure; however, UGT2B17 is capable of conjugating C19steroid molecules at both the 3alpha and 17beta-OH positions, whereas UGT2B15 is only active at the 17beta-OH position. To identify the amino acid residue(s) which may account for this difference in substrate specificity, a comprehensive study on the role of 15 residues which differ between UGT2B15 and UGT2B17 was performed by site-directed mutagenesis. The stable expression of UGT2B17 mutant proteins into HK293 cells demonstrated that the mutation of isoleucine 125, valine 181 and valine 455 to the residues found in UGT2B15 did not alter enzyme activity nor substrate specificity. Furthermore, mutation of the variant residues in UGT2B15 (serine 124, asparagine 125, phenylalanine 165) to the amino acid residues found in UGT2B17 did not alter enzyme activity nor substrate specificity. However, mutation of the serine residue at position 121 of UGT2B17 to a tyrosine, as found in UGT2B15, abolished the ability of UGT2B17 to conjugate androsterone at the 3alpha position, but still retained activity for dihydrotestosterone and 5alpha-androstane-3alpha, 17beta-diol, which have an OH-group at the 17beta position. Interestingly, mutation of tyrosine 121 in UGT2B15 to a serine abolished activity for C19steroids. It is suggested that the serine residue at position 121 in UGT2B17 is required for activity towards the 3alpha and not for the 17beta position of C19steroids, whereas the tyrosine 121 in UGT2B15 is necessary for UGT activity. Despite the high homology between UGT2B15 and UGT2B17, it is apparent that different amino acid residues in the two proteins are required to confer conjugation of C19steroid molecules.

Expression of the androgen metabolizing enzyme UGT2B15 in adipose tissue and relative expression measurement using a competitive RT-PCR method

OBJECTIVES

We have demonstrated previously that obesity in men was significantly associated with low plasma testosterone levels and higher concentrations of the androgen metabolite androstane-3 alpha, 17 beta-diol glucuronide, suggesting that androgen metabolism and elimination is increased in this condition. The objective of the present study was to investigate whether adipose tissue was a site of expression of the androgen metabolizing enzymes UDP-glucuronosyltransferases (UGT) 2B15 and 2B17.

DESIGN AND PATIENTS

Subcutaneous and visceral adipose tissue was obtained from male patients subjected to various abdominal surgeries.

MEASUREMENTS AND RESULTS

By performing reverse transcriptase-PCR (RT-PCR) amplification of mRNA extracted from adipose tissue samples, UGT2B15 transcript was detected in both subcutaneous and omental adipose tissue while UGT2B17 transcript expression was very low, or undetectable. A quantitative, competitive RT-PCR method was established and used to quantify UGT2B15 messenger RNA. The level of UGT2B15 expression was also measured in other human tissues. Although the major sites of expression were the liver and the lung, expression in adipose tissue was similar to levels found in the prostate, testis and mammary gland.

CONCLUSIONS

These results demonstrate for the first time that both subcutaneous and visceral adipose tissue express androgen metabolizing enzyme UGT2B15 mRNA and further support the role of adipose tissue as a site of steroid metabolism.

Characterization of UDP-glucuronosyltransferases active on steroid hormones

In recent years, the enzymes which are involved in the formation of DHT in steroid target tissues have been well investigated, however, enzymes responsible for the catabolism and elimination of steroids in these tissues, in particular the uridine diphospho-glucuronosyltransferase (UGT) family of enzymes, have received much less attention. We have recently demonstrated that human and monkey are unique in having high plasma levels of C19 steroid glucuronides. These circulating conjugates have been proposed to reflect the peripheral conversion of adrenal and gonadal C19 steroids to potent androgens, especially DHT. In humans, the presence of steroid UGT activities is found in the liver and several extrahepatic tissues including the prostate, mammary gland and ovary. In addition, UGT activities were observed in breast and prostate tumor cell lines such as MCF-7 and LNCaP, respectively. In agreement with the presence of steroid conjugating enzymes in extrahepatic tissues, UGT cDNA clones, which encode steroid conjugating proteins, have been isolated from libraries constructed from human and monkey prostate mRNA. The presence of UGT transcripts and proteins in extrahepatic tissues in both species, as determined by Northern blot, ribonuclease protection, specific RT-PCR, in situ hybridization, Western blot and immunocytochemistry analysis, indicate the relevance of steroid glucuronidation in tissues other than the liver. Knowing that both the human prostate and the human prostate cancer LNCaP cell line express steroid metabolizing proteins, including UGT enzymes, regulation of UGT mRNA and protein levels, as well as promoter activity was studied in these cells. The results demonstrate a differential regulation between the two highly related isoforms UGT2B15 and UGT2B17, where only the expression of UGT2B17 was affected following treatments of LNCaP cells with androgens, growth factors or cytokines. Steroid conjugation by UGT enzymes is potentially involved in hormone inactivation in steroid target tissues, thus modifications in UGT expression levels may influence hormonal responses.

Characterization and substrate specificity of UGT2B4 (E458): a UDP-glucuronosyltransferase encoded by a polymorphic gene

Variations in glucuronidation activities among different individuals have been reported; however, genetic polymorphisms in the genes encoding phase II drug metabolizing UDP-glucuronosyltransferases have not been studied extensively. A novel UGT2B cDNA clone UGT2B4(E458) was isolated from human prostate and LNCaP cell cDNA libraries. The cDNA encoding UGT2B4(E458) is 2097 bp in length and has an open reading frame of 1584 nucleotides encoding a protein of 528 amino acids. Characterization of the UGT2B4(E458) cDNA revealed nucleotide differences with the previously published UGT2B4 and UGT2B11 cDNAs. These variations in the UGT2B4 sequence lead to an amino acid change from aspartic acid to glutamic acid at position 458. In the previous UGT2B11 cDNA (which has subsequently been renamed UGT2B4 (L109,396, D458)), leucine residues are found at positions 109 and 396, whereas phenylalanines are present at these positions in the UGT2B4(D458) and UGT2B4(E458) enzymes. Analysing the genomic DNA of 26 unrelated Caucasian individuals demonstrated the presence of variant alleles encoding UGT2B4(D458) and UGT2B4(E458). Stable expression of UGT2B4(E458) cDNA in HK293 cells demonstrates the presence of a 52 kDa protein, which is in agreement with other characterized (UGT2B proteins. UGT2B4(E458) conjugates hyodeoxycholic acid (HDCA) as well as 4-hydroxyestrone (4-OH-E1), androstane-3alpha,17beta-diol (3alpha-diol) and androsterone (ADT). Specific reverse transcriptase-polymerase chain reaction analysis revealed expression of UGT2B4(D458) and UGT2B4(E458) transcripts in a wide range of extrahepatic tissues, including the liver, kidney, testis, mammary gland, prostate, placenta, adipose, adrenal, skin and lung. Our results suggest that UGT2B4(E458) and UGT2B(E458) are two widely expressed isoenzymes, and that polymorphism in the UGT2B4 gene might be responsible for differences in UGT2B4 enzymatic properties.

Isolation and characterization of a human orphan UDP-glucuronosyltransferase, UGT2B11

Glucuronidation is an important metabolic pathway for both endogenous and exogenous compounds. To isolate novel UGT2B cDNA clones, human prostate and LNCaP cell cDNA libraries were screened using a pool of steroid-specific UGT2B cDNA as probes. We have isolated a novel human cDNA of 1.7 kb in length containing an open reading frame of 1587 pb which encodes a deduced protein of 529 residues named UGT2B11. UGT2B11 share 91% identity in amino acids with UGT2B10, a UDP-glucuronosyltransferase (UGT) protein with unknown function. In agreement with other characterized UGT2B proteins, a Western blot analysis showed high levels of a 52-kDa protein present in a microsome preparation from HK293 cells stably transfected with the UGT2B11 cDNA. Despite the screening of 100 potential substrates, glucuronidation activity was not detected for the stably expressed UGT2B11 protein. However, UGT2B11 specific RT-PCR analysis revealed expression of the transcripts in a wide range of human tissues including the liver, kidney, mammary gland, prostate, skin, adipose, adrenal, and lung. The biological function of the UGT2B11 protein is unknown but its wide expression in human tissues raises the possibility that UGT2B11 may constitute an orphan UGT enzyme whose substrates specificity remain to be identified.

Effect of interleukins on UGT2B15 and UGT2B17 steroid uridine diphosphate-glucuronosyltransferase expression and activity in the LNCaP cell line

Cytokines are known to modulate the level of both phase 1 and phase 2 drug-metabolizing enzymes in hepatocytes. Although the effects of cytokines on cytochrome P450 (CYP450) enzymes are well understood, there is limited knowledge on how cytokines may affect steroid UDP-glucuronosyltransferase (UGT) phase 2 enzyme activity and expression in different cell types, including hepatocytes and steroid target cells. LNCaP cells, which is a human prostate cancer cell line, is a good model to study the effect of cytokines in steroid target cells because it is known to express steroidogenic enzymes, including UGT2B15 and UGT2B17, which are widely expressed steroid UGT enzymes known to conjugate androgens. In this study, we examined the possible interaction among interleukin-1alpha (IL-1alpha), IL-4, IL-6, and steroid UGT enzymes (UGT2B15 and UGT2B17). Treatment of LNCaP cells with IL-1alpha led to a dose-dependent inhibition of dihydrotestosterone (DHT) glucuronidation. IL-1alpha decreased both UGT activity and LNCaP cell proliferation in the absence and presence of DHT (0.5 nM); a maximal inhibition of 70% was observed. IL-6 inhibited LNCaP cell proliferation as well as the DHT-induced proliferation of these cells. However, neither IL-4 nor IL-6 significantly affected the formation of DHT glucuronide. Ribonuclease protection and Western blot analyses demonstrated a specific reduction of UGT2B17 transcript and protein levels in IL-1alpha-treated LNCaP cells. The level of UGT2B15 was not affected by cytokine treatments, indicating a differential regulation between these two UGT enzymes. Transfection experiments performed with the UGT2B17 gene promoter region indicates that the regulation occurs at the transcription level via putative cis-acting elements. This study indicates that cell proliferation and UGT expression in steroid-responsive cancer cells are differentially regulated depending on the cytokines present in the cell microenvironment.

Characterization and regulation of UDP-glucuronosyltransferases in steroid target tissues

Conjugation of compounds by glucuronidation is a pathway found in all vertebrates studied to date. Although, it is widely recognized that the liver is a major site of glucuronidation, it is now clear that extrahepatic tissues are also involved in the conjugation of compounds to which these tissues are exposed. High levels of androsterone glucuronide and androstane-3alpha,17beta-diol glucuronide found in the human prostate, breast cyst fluid and ovary follicular fluid suggest that glucuronidation of 5alpha-reduced C19 steroids occurs in these tissues. Recently, we have reported the tissue distribution of UGT2B15, which can conjugate steroids in several human extrahepatic steroid target tissues including the skin, breast and prostate. We have also isolated a new UGT2B cDNA encoding UGT2B17, that conjugates ADT which is the major 5alpha-reduced C19 steroid glucuronide in the circulation of humans. UGT2B17 is also widely distributed in several human steroid target tissues. This gene was mapped to human chromosome 4q13 and has an exon/intron structure similar to that of rat UGT2B1 and UGT2B2. Both UGT2B15 and UGT2B17, which are able to catalyze the glucuronidation of DHT, are expressed in LNCaP cells. Interestingly, glucuronidation of steroids is markedly regulated by several factors including androgens and growth factors. Treatment of LNCaP cells with dihydrotestosterone (DHT) and epidermal growth factor (EGF) caused a decrease of DHT glucuronidation and UGT2B mRNA levels. RNase protection assays showed a specific decrease of UGT2B17 transcript in LNCaP cells treated with DHT and EGF however, the level of UGT2B15 mRNA was not affected. As well, Western blot analysis demonstrated a diminution of UGT2B17 protein level in response to DHT and EGF. These results demonstrate a differential regulation of different isoforms of steroid conjugating UGTs present in human prostate LNCaP cells. In addition, UGT2B17 was shown to be more labile than UGT2B15 indicating that regulation of UGT2B17 expression would lead to a more rapid change in the level of glucuronidated steroids. Expression of exogenous UGT2B17 in LNCaP cells by gene transfer led to a significant decrease in the androgen response. This result indicates the ability of UGT enzymes to regulate the androgen response by conjugating androgens which abolishes their interaction with their receptor and facilitates their clearance from the cell. The glucuronidation of steroids by UGT enzymes is an important mechanism by which the levels of steroids is regulated in steroid target tissues.

Isolation and characterization of a simian UDP-glucuronosyltransferase UGT2B18 active on 3-hydroxyandrogens

A monkey cDNA, UGT2B18, encoding a UDP-glucuronosyltransferase (UGT) active on 3-hydroxyandrogens, has been isolated and characterized. Previous results suggested that the monkey represents the most appropriate animal model for studying the physiologic relevance of steroid UGTs. UGT2B18 was isolated from a cynomolgus monkey prostate cDNA library using human UGT2B7, UGT2B10 and UGT2B15 cDNA as probes. The cDNA is 1748 bp in length and contains an open reading frame of 1587 bp encoding a protein of 529 residues. The UGT2B18 cDNA clone was transfected into HK293 cells and a stable cell line expressing UGT2B18 protein was established. Western blot analysis of the UGT2B18-HK293 cell line using a human UGT2B17 polyclonal antibody (EL-93) revealed high expression of a 53 kDa UGT2B protein. The transferase activity of UGT2B18 was tested with over 60 compounds and was demonstrated to be principally active on C19 steroids having an hydroxyl group at position 3alpha of the steroid molecule. UGT2B18 was also active on planar phenols and bile acids. Kinetic analysis revealed that UGT2B18 glucuronidates 3-hydroxyandrogens with high velocity and affinity. Using cell homogenates, Km values of 5.1, 7.8 and 23 microM for androsterone (ADT), etiocholanolone and androstane-3alpha, 17beta diol (3alpha-diol) were obtained, respectively. Specific RT-PCR analysis demonstrated the expression of UGT2B18 transcripts in several tissues including liver, prostate, kidney, testis, adrenal, bile duct, bladder, colon, small intestine, cerebellum and pancreas suggesting a contribution of this isoenzyme to the high plasma levels of glucuronidated ADT and 3alpha-diol found in the cynomolgus monkey.

Effect of fibroblastic growth factors (FGF) on steroid UDP-glucuronosyltransferase expression and activity in the LNCaP cell line

It is now widely accepted that factors other than androgens are crucial in the normal and abnormal growth of the prostate. In addition to hormones, many polypeptide growth factors, including the fibroblast growth factor family (FGF), can act as potent mitogens on cell proliferation. The FGF family of growth factors are essential factors for both normal and abnormal proliferation of prostate cells. To study the effect of FGFs on steroid glucuronidation, we used the human prostate cancer LNCaP cell line which is known to be stimulated by FGF resulting in increased cell proliferation. LNCaP cells express steroid metabolizing enzymes including uridine diphosphoglucuronosyltransferases (UGTs). In addition, LNCaP cells treated with dihydrotestosterone (DHT) and epidermal growth factor (EGF) express differential levels of the human UGT2B15 and UGT2B17 transcripts. In the present study, we examined the possible interaction between FGF and steroid UGT enzymes. Results show a dose dependent inhibition of DHT glucuronide (DHT-G) formation following treatment (6 days) with acidic FGF (aFGF) and basic FGF (bFGF). When cells were treated with 10 ng/ ml of FGFs, we observed 33 and 51% inhibition of glucuronidation activity using aFGF and bFGF respectively. Ribonuclease protection analyses revealed a 2 and 3 fold increase of UGT2B15 mRNA expression following treatment with aFGF (50 ng/ml) and bFGF (10 ng/ml) respectively. However, a slight decrease in UGT2B17 transcripts was observed, demonstrating a differential regulation. Since a reduction in the glucuronidation of DHT or its 5alpha-reduced metabolites may contribute to an increase in intraprostatic androgen levels, down-regulation of UGTs by growth factors such as FGFs may increase the proliferation of androgen-dependent tumors.

Chromosomal localization, structure, and regulation of the UGT2B17 gene, encoding a C19 steroid metabolizing enzyme

UGT2B17 is a UDP-glucuronosyltransferase enzyme expressed in several extrahepatic steroid target tissues, including the human prostate, where it glucuronidates C19 steroids such as dihydrotestosterone (DHT), androsterone (ADT), and androstane-3alpha, 17beta-diol (3alpha-diol). To determine if UGT2B17 is regulated by physiological effectors of the human prostate, DHT and epidermal growth factor (EGF) were demonstrated to specifically down-regulate the steady-state levels of UGT2B17 transcript and protein in LNCaP cells (Guillemette et al., 1997). These results implicate regulation of UGT2B17 at the level of gene transcription, therefore, a P-1-derived artificial chromosome (PAC) clone of 120 kb containing the entire UGT2B17 gene was isolated. The gene is comprised of six exons spanning approximately 30 kb, and fluorescence in situ hybridization of the UGT2B17 PAC clone to normal human lymphocyte chromosomes, mapped the gene to chromosome 4q13. To determine if the 5'-flanking DNA of the UGT2B17 gene is sufficient to confer gene expression, a 2,942-bp fragment was subcloned into a luciferase reporter plasmid and yielded an activity of 25-fold over background when transfected in LNCaP cells. However, transfection of the construct into HK-293, MCF-7, JEG-3, and HepG2 cells yielded only a moderate activity of two- to five-fold over background. Treatment of transfected LNCaP cells with 10 nM R1881, a nonmetabolizable analog of DHT, and 10 ng/ml EGF decreased the luciferase activity by 60%. This suggests that at least part, if not all, of the inhibitory effect of EGF and DHT on UGT2B17 is at the level of transcription. Progressive 5' deletions of the UGT2B17 5'-flanking region in the luciferase constructs alleviated the inhibition by R1881 and EGF, and revealed several potential responsive elements that may confer the observed regulation of the UGT2B17 gene. This study demonstrates regulation of the UGT2B17 gene by physiological effectors of the human prostate and supports the hypothesis that UGT enzymes are involved in steroid metabolism in extrahepatic tissues.

Expression and characterization of a novel UDP-glucuronosyltransferase, UGT2B9, from cynomolgus monkey

Uridine diphosphate glucuronosyltransferases (UGTs) are important phase II detoxification enzymes. Despite the expression of UGT proteins in many species, previous results have suggested that simians represent the most appropriate animal model to study the glucuronidation of steroids in extrahepatic steroid target tissues. Northern blot analysis using a pool of human UGT2B cDNA probes demonstrated the expression of homologous UGT2B transcripts in several tissues including the liver, kidney, adrenal, breast, testis, and prostate of the cynomolgus monkey (Macacafascicularis). Western blot analyses using a polyclonal antibody raised against human UGT2B17 protein also demonstrated expression of homologous UGT2B proteins in monkey tissues. cDNA libraries were constructed from monkey liver and prostate mRNA and a novel UGT2B cDNA, UGT2B9, was isolated from both libraries. The UGT2B cDNA from the prostate library is 2,648 bp in length and contains an open reading frame of 1,587 bp encoding a protein of 529 residues. In vitro transcription/translation of the cDNA clone produced a protein of 52 kD. The UGT2B9 cDNA clone was transfected into HK293 cells and a stable cell line expressing UGT2B9 protein was established. The activity of UGT2B9 was tested with over 60 compounds and was demonstrated to be active on C18, C19, and C21 steroids, bile acids, and several xenobiotics including eugenol, 1-naphthol, and p-nitrophenol. Kinetic analysis revealed that UGT2B9 glucuronidates steroids with high affinity and efficiency with Km values of 0.2, 3.2, 0.2, and 1.8 microM for dihydrotestosterone, testosterone, androsterone, and 1,3,5,10-estratrien-3,4-diol-17-one, respectively. It is apparent that this simian UGT2B enzyme is specific for more different classes of steroids than any other UGT enzyme characterized to date, and may be related to the high plasma levels of glucuronidated C19 steroids found in the cynomolgus monkey.

Isolation and characterization of UGT2B15(Y85): a UDP-glucuronosyltransferase encoded by a polymorphic gene

Genetic polymorphisms occur in many of the drug metabolizing enzymes. However, the effect of polymorphisms in the genes encoding phase II drug metabolizing UDP-glucuronosyltransferases is still undescribed, despite the many reported cases of variations in glucuronidation activities. Characterization of the UGT2B15(Y85) cDNA, which was isolated from human prostate and LNCaP cell cDNA libraries, revealed 20 nucleotide differences between UGT2B15(Y85) and the previously characterized UGT2B15 protein UGT2B15(D85). However, only one of the two variations in the coding region leads to an amino acid change from aspartic acid to a tyrosine residue at position 85. The genomic DNA of 27 subjects were analysed by direct sequencing of polymerase chain reaction (PCR) products and demonstrated that UGT2B15(D85) and UGT2B15(Y85) are encoded by variant alleles prevalent in the Caucasian population. Expression of UGT2B15(D85) and UGT2B15(Y85) in HK293 cells demonstrated similar substrate specificities. Of the 65 potential substrates tested for activity, the proteins were active on phenolic compounds, coumarins, flavonoids, drugs and steroid hormones. Both proteins displayed similar Km values of 2.2 and 2.4 microM for androstane-3alpha,17beta-diol and dihydrotestosterone, respectively. However, results suggest that UGT2B15(Y85) has a higher Vmax than UGT2B15(D85). Specific reverse transcriptase (RT)-PCR analysis revealed expression of the UGT2B15 gene in a wide range of extrahepatic tissues including the human liver, kidney, testis, mammary gland, placenta, adipose, skin, uterus, prostate and lung. The wide expression of UGT2B15 in many tissues indicates that it is a major glucuronidation enzyme in humans.

Differential regulation of two uridine diphospho-glucuronosyltransferases, UGT2B15 and UGT2B17, in human prostate LNCaP cells

Although androgens are important regulators in the prostate, other effectors such as growth factors may also act to maintain normal function of the gland. Human prostate and human prostate cancer LNCaP cells express steroid conjugating uridine diphospho-glucuronosyltransferase (UGT) enzymes, and it was shown that the level of UGT activities and transcripts is down-regulated by androgens, especially dihydrotestosterone (DHT). In the present study, we examined the interaction between androgen, epidermal growth factor (EGF), and steroid UGT enzymes. The formation of DHT glucuronide (DHT-G) was inhibited by 47% when LNCaP cells were treated for 6 days with 10 ng/ml of EGF. Northern blot analysis also demonstrated a decrease in the steady-state level of UGT2B transcripts. Treatment with both DHT (0.5 nM) and EGF (10 ng/ml) caused a greater decrease of DHT glucuronidation and UGT2B messenger RNA levels than when the cells were treated with either compound alone. RNase protection assays showed that treatment with DHT and EGF caused a specific decrease of UGT2B17 transcript in LNCaP cells treated; however, the level of UGT2B15 messenger RNA was not affected. As well, Western blot analysis demonstrated a diminution of UGT2B17 protein level in response to DHT and EGF. These results demonstrate a differential regulation of different isoforms of steroid conjugating UGTs present in human prostate LNCaP cells. UGT2B17 was shown to be more labile than UGT2B15, indicating that regulation of UGT2B17 expression would lead to a more rapid change in the level of glucuronidated steroids.

Isolation and characterization of a novel cDNA encoding a human UDP-glucuronosyltransferase active on C19 steroids

To isolate cDNA clones encoding novel UGT2B enzymes, human prostate and LNCaP cell cDNA libraries were screened using a pool of steroid-specific UGT2B cDNA probes. In approximately 10(6) recombinants, we isolated 3 cDNA clones of 2.1 kilobases that encode a novel UGT2B enzyme. UGT2B17 is 95% identical with UGT2B15 and 91% identical with UGT2B8. Primary structure analysis of UGT2B17 based on the nucleotide sequence revealed a putative amino-terminal membrane insertion signal peptide, a carboxyl-terminal membrane-spanning region, and three potential asparagine-linked glycosylation sites. UGT2B17 cloned in the pBK-CMV expression vector was transfected into HK293 cells to obtain a stable clonal cell line expressing a high level of the active 53-kDa UGT2B17 enzyme. Of the over 60 endogenous and exogenous substances tested, 25 compounds revealed reactivity. The major substrates are eugenol > 4-methylumbelliferone > dihydrotestosterone > androstane-3alpha, 17beta-diol (3alpha-diol) > testosterone > androsterone (ADT). The apparent Km values obtained with tritiated steroids in intact cells were 0.4 microM for ADT, 0.7 microM for dihydrotestosterone, 1.0 microM for 3alpha-diol, and 3.4 microM for testosterone. Southern blot analysis of reverse transcription-polymerase chain reaction products revealed expression of UGT2B17 mRNA in various tissues including the liver, kidney, testis, uterus, placenta, mammary gland, adrenal gland, skin, and prostate. UGT2B17 is the first human uridine diphosphoglucuronosyltransferase enzyme expressed in extrahepatic tissues to have a specificity for ADT as well as testosterone, dihydrotestosterone, and 3alpha-diol.

Expression of transcripts encoding steroid UDP-glucuronosyltransferases in human prostate hyperplastic tissue and the LNCaP cell line

The UDP-glucuronosyltransferase (EC 2.4.1.17) enzymes transform many lipophilic compounds to more water-soluble products via conjugation with glucuronic acid. This conversion is responsible for enhancing the excretion of endogenous aglycones such as steroids. To date, several distinct isoforms of steroid UDP-glucuronosyltransferases (UGTs) have been isolated in the human liver. Among these UGTs, UGT2B7 is specific for estriol and 3,4-catechol estrogens, UGT2B15 glucuronidates 17beta-hydroxy-C19 steroids while UGT2B10 has as yet an undescribed activity. To further demonstrate the presence of UGTs in peripheral tissues we studied the expression of these enzymes in human prostate hyperplastic tissue and the LNCaP cell line. Metabolism studies using intact LNCaP cells in culture indicate the presence of UGT activities involved in the glucuronidation of 3alpha-hydroxysteroids (androsterone) and 17beta-hydroxysteroids (testosterone and dihydrotestosterone). Northern blot analysis of poly(A+) RNA from LNCaP cells and prostate using a UGT2B15 cDNA probe revealed two bands of 2.0 and 2.3 kb. In order to identify more specifically the mRNAs detected in Northern blot analysis we used RNase protection and RT-PCR, although, these approaches did not allow detection of UGT2B7 transcripts. Our studies demonstrate the presence of two UGT activities and at least two types of UGT transcripts in both the human prostate and the LNCaP.