Sex steroid hormones in relation to Barrett's esophagus: an analysis of the FINBAR Study

Previously, we observed strong positive associations between circulating concentrations of free testosterone and free dihydrotestosterone (DHT) in relation to Barrett's esophagus in a US male military population. To replicate these findings, we conducted a second study of sex steroid hormones and Barrett's esophagus in the Factors Influencing the Barrett/Adenocarcinoma Relationship (FINBAR) Study based in Northern Ireland and Ireland. We used mass spectrometry to quantitate EDTA plasma concentrations of nine sex steroid hormones and ELISA to quantitate sex hormone-binding globulin in 177 male Barrett's esophagus cases and 185 male general population controls within the FINBAR Study. Free testosterone, free DHT, and free estradiol were estimated using standard formulas. Multivariable logistic regression estimated odds ratios (OR) and 95% confidence intervals (95%CI) of associations between exposures and Barrett's esophagus. While plasma hormone and sex hormone-binding globulin concentrations were not associated with all cases of Barrett's esophagus, we did observe positive associations with estrogens in younger men (e.g. estrone + estradiol OR_{continuous per ½IQR}  = 2.92, 95%CI:1.08, 7.89), and free androgens in men with higher waist-to-hip ratios (e.g. free testosterone OR_{continuous per ½IQR}  = 2.71, 95%CI:1.06, 6.92). Stratification by body mass index, antireflux medications, and geographic location did not materially affect the results. This study found evidence for associations between circulating sex steroid hormones and Barrett's esophagus in younger men and men with higher waist-to-hip ratios. Further studies are necessary to elucidate whether sex steroid hormones are consistently associated with esophageal adenocarcinogenesis.

Characterization of cAMP-phosphodiesterase activity in bovine seminal plasma

The second messenger cyclic adenosine monophosphate (cAMP) has a central role in sperm physiology. Extracellular cAMP can be sequentially degraded into 5'AMP and adenosine by ecto-phosphodiesterases (ecto-PDE) and ecto-nucleotidases, a phenomenon called extracellular cAMP-adenosine pathway. As cAMP-adenosine pathway is involved in sperm capacitation, we hypothesize that extracellular PDEs are functionally present in seminal plasma. Exclusively measuring cAMP-PDE activity, total activity in bovine seminal plasma was 10.1 ± 1.5 fmoles/min/μg. Using different family-specific PDE inhibitors, we showed that in seminal plasma, the major cAMP-PDE activity was papaverine sensitive (47.5%). These data support the presence of PDE10 in bovine seminal plasma and was further confirmed by western blot. In epididymal fluid, total cAMP-PDE activity was 48.2 ± 14.8 fmoles/min/μg and we showed that the major cAMP-PDE activity was 3-isobutyl-methylxanthine insensitive and thus ascribed to PDE8 family. PDE10A mRNAs were found in the testis, epididymis, and seminal vesicles. cAMP-PDE activity is present in bovine seminal plasma and epididymal fluid. The results suggest a role for ecto-PDEs present in those fluids in the signaling pathways involved in sperm functions.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for UGT1A1 and Atazanavir Prescribing

The antiretroviral protease inhibitor atazanavir inhibits hepatic uridine diphosphate glucuronosyltransferase (UGT) 1A1, thereby preventing the glucuronidation and elimination of bilirubin. Resultant indirect hyperbilirubinemia with jaundice can cause premature discontinuation of atazanavir. Risk for bilirubin-related discontinuation is highest among individuals who carry two UGT1A1 decreased function alleles (UGT1A1*28 or *37). We summarize published literature that supports this association and provide recommendations for atazanavir prescribing when UGT1A1 genotype is known (updates at www.pharmgkb.org).

Transcriptomic analysis of cyclic AMP response in bovine cumulus cells

Acquisition of oocyte developmental competence needs to be understood to improve clinical outcomes of assisted reproduction. The stimulation of cumulus cell concentration of cyclic adenosine 3'5'-monophosphate (cAMP) by pharmacological agents during in vitro maturation (IVM) participates in improvement of oocyte quality. However, precise coordination and downstream targets of cAMP signaling in cumulus cells are largely unknown. We have previously demonstrated better embryo development after cAMP stimulation for first 6 h during IVM. Using this model, we investigated cAMP signaling in cumulus cells through in vitro culture of cumulus-oocyte complexes (COCs) in the presence of cAMP raising agents: forskolin, IBMX, and dipyridamole (here called FID treatment). Transcriptomic analysis of cumulus cells indicated that FID-induced differentially expressed transcripts were implicated in cumulus expansion, steroidogenesis, cell metabolism, and oocyte competence. Functional genomic analysis revealed that protein kinase-A (PKA), extracellular signal regulated kinases (ERK1/2), and calcium (Ca(2+)) pathways as key regulators of FID signaling. Inhibition of PKA (H89) in FID-supplemented COCs or substitution of FID with calcium ionophore (A23187) demonstrated that FID activated primarily the PKA pathway which inhibited ERK1/2 phosphorylation and was upstream of calcium signaling. Furthermore, inhibition of ERK1/2 phosphorylation by FID supported a regulation by dual specific phosphatase (DUSP1) via PKA. Our findings imply that cAMP (FID) regulates cell metabolism, steroidogenesis, intracellular signaling and cumulus expansion through PKA which modulates these functions through optimization of ERK1/2 phosphorylation and coordination of calcium signaling. These findings have implications for development of new strategies for improving oocyte in vitro maturation leading to better developmental competence.

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.

Cyclic adenosine monophosphate (cAMP)-specific phosphodiesterase is functional in bovine mammary gland

Previous studies have shown that using nonspecific phosphodiesterase (PDE) inhibitors such as caffeine improved milk production, supporting the premise that modulation of intracellular concentration of cyclic nucleotides (cyclic AMP, cyclic guanosine 3'-5'-monophosphate) is involved. Intracellular cyclic nucleotides are degraded by the PDE enzyme family. The contribution of type IV PDE (PDE4) in the secretion of casein has been reported in rat mammary gland. The objective of this study was to demonstrate the functional presence of the PDE4 family in the bovine mammary gland. To understand the enzymatic expression pattern in the mammary gland, tissue samples were taken randomly from udders obtained from a local slaughterhouse. Reverse transcription PCR revealed that the PDE4D transcript was amplified, and the expected size fragment was obtained in a 1% agarose gel. Sequence analysis of the amplicon resulted in 99% homology to PDE4D. Moreover, Western blotting using a specific PDE4D antibody has confirmed that the protein of the isoenzyme PDE4D1 is present. A clear immunoreactive signal was also observed within the acini where epithelial cells are located. Assaying cyclic AMP PDE activity reported a total activity of 38.71 +/- 3.22 fmol/min per microg of total protein. Rolipram, a specific PDE4 inhibitor, showed a sensitive activity of 8.48 +/- 1.28 fmol/min per microg of total protein, indicating that PDE4 is responsible for one-fifth of the total enzymatic activity of PDE in the mammary gland. To further validate the presence of PDE4D in the bovine mammary epithelial cells, protein extracts from bovine mammary epithelial cells were separated on SDS-PAGE gels, and PDE4D protein was detected. The PDE assays reported a total activity of 30.16 +/- 4.82 fmol/min per microg of total protein. Rolipram showed a sensible activity of 11.91 +/- 5.93 fmol/min per microg of total protein. In conclusion, these results not only demonstrate the presence of PDE4D transcript and protein, but also show an active enzyme, suggesting a functional role of PDE4D in bovine mammary gland.

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.

Pharmacogenomics of human UDP-glucuronosyltransferase enzymes

UDP-glucuronosyltransferase (UGT) enzymes comprise a superfamily of key proteins that catalyze the glucuronidation reaction on a wide range of structurally diverse endogenous and exogenous chemicals. Glucuronidation is one of the major phase II drug-metabolizing reactions that contributes to drug biotransformation. This biochemical process is also involved in the protection against environmental toxicants, carcinogens, dietary toxins and participates in the homeostasis of numerous endogenous molecules, including bilirubin, steroid hormones and biliary acids. Over the years, significant progress was made in the field of glucuronidation, especially with regard to the identification of human UGTs, study of their tissue distribution and substrate specificities. More recently, the degree of allelic diversity has also been revealed for several human UGT genes. Some polymorphic UGTs have demonstrated a significant pharmacological impact in addition to being relevant to drug-induced adverse reactions and cancer susceptibility. This review focuses on human UGTs, the description of the nature of polymorphic variations and their functional impact. The pharmacogenomic implication of polymorphic UGTs is presented, more specifically the role of UGT polymorphisms in modifying cancer risk and their impact on individual risk to drug-induced toxicities.

Tobacco carcinogen-detoxifying enzyme UGT1A7 and its association with orolaryngeal cancer risk

BACKGROUND

UDP-glucuronosyltransferase 1A7 (UGT1A7) detoxifies several tobacco carcinogens. We determined whether UGT1A7 expression is observed in normal orolaryngeal tissue and whether UGT1A7 allelic variations are associated with the risk for orolaryngeal cancer.

METHODS

UGT1A7 expression in normal orolaryngeal tissue was determined by semiquantitative reverse transcription-polymerase chain reaction (PCR). Buccal cell DNA isolated from 194 case subjects with orolaryngeal cancer and from 388 control subjects who were matched by sex, age, and race was subjected to UGT1A7 genotyping with the use of combined PCR-restriction fragment length polymorphism and allelic discrimination analysis. All statistical tests were two-sided.

RESULTS

UGT1A7 messenger RNA was expressed at similar levels in the esophagus, tongue, tonsil, floor of the mouth, and larynx. Genotyping revealed the presence of three variant reduced-activity UGT1A7 alleles in both Caucasians and African-Americans. Individuals with any of the predicted low-activity UGT1A7 genotypes had an increased risk of orolaryngeal cancer (odds ratio [OR] = 3.7; 95% confidence interval [CI] = 1.7 to 8.7) relative to subjects with the wild-type genotype. Both Caucasians and African-Americans with the low-activity genotypes had statistically significantly increased orolaryngeal cancer risk compared with Caucasians and African-Americans with the wild-type genotype (OR = 2.8 [95% CI = 1.1 to 7.6] and OR = 6.2 [95% CI = 1.2 to 31], respectively). For subjects with the predicted low-activity genotypes, the risks of oral cavity cancer (OR = 4.2; 95% CI = 1.7 to 10) and laryngeal cancer (OR = 3.7; 95% CI = 0.99 to 14) were similar. There was no association between UGT1A7 genotype and orolaryngeal cancer risk in never smokers, whereas subjects with predicted low-activity UGT1A7 genotypes who were light smokers (OR = 3.7; 95% CI = 1.1 to 12) or heavy smokers (OR = 6.1; 95% CI = 1.5 to 25) had an increased risk.

CONCLUSIONS

The tissue expression of UGT1A7 is consistent with the possibility of a physiologic role in orolaryngeal cancer. Variations in the UGT1A7 gene that reduce UGT1A7 activity may affect the risk of smoking-related orolaryngeal cancer.

Association of genetic polymorphisms in UGT1A1 with breast cancer and plasma hormone levels

UDP-glucuronosyltransferases (UGTs) catalyze the detoxification and the elimination of a large number of endogenous and exogenous compounds in the liver and extrahepatic tissues. One of the UGT1A family members, UGT1A1, is involved in estradiol metabolism and, therefore, represents a candidate gene in breast carcinogenesis. A common insertion/deletion polymorphism in the TATA-box of the promoter region of UGT1A1 results in decreased initiation of transcription. In a previous study, we found a positive association between the UGT1A1 low-transcriptional alleles and premenopausal breast cancer risk in an African-American population. In the present study, we sought to determine whether the low-transcription UGT1A1 promoter allele, UGT1A1*28 [A(TA)(7)TAA], was associated with increased breast cancer risk among primarily Caucasian women in a nested case-control study within the Nurses' Health Study cohort. No significant association between the UGT1A1*28 [A(TA)(7)TAA] allele and breast cancer was observed. Compared with women homozygous for the UGT1A1*1 [A(TA)(6)TAA] allele, the relative risk was 0.80 (confidence interval, 0.49-1.29) for women homozygous for the UGT1A1*28 allele. The effect of the UGT1A1 genotype on plasma hormone levels in postmenopausal women not using hormone replacement was also evaluated, and overall, no significant differences in hormone levels by genotypes were observed. When restricted to women who had at least one UGT1A1*28 allele and a body mass index at blood draw of >27 kg/m(2), particularly in combination with the cytochrome p450c17alpha genotype, estrone and estradiol levels tended to vary by UGT1A1 genotypes. The results presented do not support a strong association between the UGT1A1 promoter polymorphism and the risk of breast cancer.

Structural heterogeneity at the UDP-glucuronosyltransferase 1 locus: functional consequences of three novel missense mutations in the human UGT1A7 gene

One of the most important mechanisms involved in host defense against xenobiotic chemicals and endogenous toxins is the glucuronidation catalysed by UDP-glucuronosyltransferase enzymes (UGT). The role of genetic factors in determining variable rates of glucuronidation is not well understood, but phenotypic evidence in support of such variation has been reported. In the present study, six single nucleotide polymorphisms were discovered in the first exon of the UGT1A7 gene, which codes for the putative substrate-binding domain, revealing a high structural heterogeneity at the UGT1 gene locus. The new UGT1A7 proteins differ in their primary structure at amino acid positions 129, 131 and 208, creating four distinct UGT1A7 allelic variants in the human population: UGT1A7*1 (N129 R131 W208), *2 (K129 K131 W208), *3 (K129 K131 R208), and *4 (N129 R131 R208). In functional studies, HEK cells stably transfected to express the four allelic UGT1A7 variants exhibited significant differences in catalytic activity towards 3-, 7-, and 9-hydroxy-benzo(a)pyrene. UGT1A7*3 exhibited a 5.8-fold lower relative Vmax compared to wild-type *1, whereas *2 and *4 had a 2.6- and 2.8-fold lower relative Vmax than *1, respectively, suggesting that these mutations confer slow glucuronidation phenotype. Kinetic characterization suggested that these differences were primarily attributable to altered Vmax. Additionally, it suggested that each amino acid substitutions can independently affect the UGT1A7 catalytic activity, and that their effects are additive. The expression pattern of UGT1A7 studied herein and its catalytic activity profile suggest a possible role of UGT1A7 in the detoxification and elimination of carcinogenic products in lung. A population study demonstrated that a considerable proportion of the population (15.3%) was found homozygous for the low activity allele containing all three missense mutations, UGT1A7*3. These findings suggest that further studies are needed to investigate the impact of the low UGT1A7 conjugator genotype on individual susceptibility to chemical-induced diseases and responses to therapeutic drugs.

Direct haplotyping of kilobase-size DNA using carbon nanotube probes

We have implemented a method for multiplexed detection of polymorphic sites and direct determination of haplotypes in 10-kilobase-size DNA fragments using single-walled carbon nanotube (SWNT) atomic force microscopy (AFM) probes. Labeled oligonucleotides are hybridized specifically to complementary target sequences in template DNA, and the positions of the tagged sequences are detected by direct SWNT tip imaging. We demonstrated this concept by detecting streptavidin and IRD800 labels at two different sequences in M13mp18. Our approach also permits haplotype determination from simple visual inspection of AFM images of individual DNA molecules, which we have done on UGT1A7, a gene under study as a cancer risk factor. The haplotypes of individuals heterozygous at two critical loci, which together influence cancer risk, can be easily and directly distinguished from AFM images. The application of this technique to haplotyping in population-based genetic disease studies and other genomic screening problems is discussed.

Genetic polymorphisms in uridine diphospho-glucuronosyltransferase 1A1 and association with breast cancer among African Americans

We examined the role of constitutional genetic variation at the UDP-glucuronosyltransferase (UGT) 1A1 locus in breast cancer susceptibility. The UGT1A1 enzyme is a major UGT involved in estradiol glucuronidation. To date, four UGT1A1 variant alleles characterized by a variation in the number of TA from five through eight repeats in the atypical TATA box region have been described in the African-American population. Functional analyses of the transcriptional activity in breast and liver cells revealed that the transcription activation of a reporter gene is inversely correlated with the number of repeats. Reverse transcription-PCR analysis confirmed the expression of UGT1A1 in human liver in the hepatocarcinoma cell line HepG2 and provided evidence of the expression of UGT1A1 in breast cancer tissue, where a positive signal was observed in 11 of 12 breast cancer cell lines tested. The population-based case-control study involved 200 women with breast cancer and 200 female controls of African ancestry. We postulated that breast cancer cases might have a higher prevalence of low activity allele-containing genotypes than controls (alleles presenting seven and eight repeats in the A(TA)nTAA motif of the TATA box). The age-adjusted odds ratio (OR) for breast cancer comparing women with seven and eight allele-containing genotypes versus 5/5, 5/6, and 6/6 genotypes was 1.8 [95% confidence interval (CI), 1.0-3.1; P = 0.06] in premenopausal women and 1.0 (95% CI, 0.5-1.7; P = 0.9) in postmenopausal women. The observed 1.8-fold elevated risk in premenopausal women with invasive breast cancer is highly suggestive of a possible interaction between UGT genotype and hormones. Additional analyses suggested a stronger association of UGT1A1 genotype with estrogen receptor (ER)-negative breast cancer. Among premenopausal women, the association was stronger for ER- breast cancer (OR, 2.1; 95% CI, 1.0-4.2; P = 0.04) than ER+ breast cancer (OR, 1.3; 95% CI, 0.6-3.0; P = 0.5). The OR was slightly stronger among women who used oral contraceptives, and the association remained null in postmenopausal women, regardless of whether they took hormone replacement therapy. Our current findings suggest that further investigations are warranted to elucidate the role of UGT1A1 in breast cancer risk.

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.

Some vasovasostomized men are characterized by low levels of P34H, an epididymal sperm protein

During epididymal transit, sperm surface proteins involved in the fertilization process can be added or modified. P34H, a human epididymal-sperm protein, is proposed to be involved in the interactions between spermatozoa and the zona pellucida. We have previously demonstrated that P34H is present in men of proven fertility and is absent in 50% of men presenting with idiopathic infertility. Spermatozoa with a low amount of P34H exhibit a dramatic reduction in their ability to interact with zona pellucida. Even if the surgical success of vasectomy reversal is high, fertility is not always reestablished, possibly due to epididymal damage caused by vasectomy. In this study, western blot analyses were performed to determine the level of P34H present on spermatozoa of men who underwent vasectomy reversal. Spermatozoa obtained from different semen samples from a given individual had similar P34H levels; however, samples from different men were highly variable. When quantified by densitometric scanning, P34H levels from vasovasostomized men varied between 1.5% and 149% compared with that from a fertile donor who represented 100%. Eighteen of 25 vasovasostomized men had a P34H level lower than 30% of the normal value, while the remaining 7 males were in the normal range. Furthermore, the population of vasovasostomized men with P34H levels lower than 30% was significantly different from the control group of 19 fertile men. The high variation of P34H levels observed in vasovasostomized men did not correlate with the spermiogram values (P > 0.05). An important factor in determining sperm P34H level appears to be the period of time elapsed between the vasectomy and vasovasostomy. In summary, our results show that the P34H level varied from one man to another and that low levels of the epididymal sperm protein is associated with vasectomy reversal.

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.

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.

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.

Levels of plasma C19 steroids and 5 alpha-reduced C19 steroid glucuronides in primates, rodents, and domestic animals

In this study, a comparison of circulating levels of androsterone glucuronide and androstane-3 alpha, 17 beta-diol glucuronide in the male and female of several mammalian species was performed. Glucuronidated steroids were not detected in the circulation of the dog, bovine, swine, and rodent. High levels of circulating glucuronidated steroids were measured in the cynomolgus monkey and found to be 10-fold higher than in humans. The determination of tissue levels of unconjugated and conjugated C19 steroids was then performed in intact and castrated rats treated with androgens. Steroid glucuronides were not detected in the plasma, skin, prostate, or liver of either intact or treated rats, although the levels of unconjugated steroids in the plasma and tissues were increased after steroid treatments. Significant levels were detected in the bile, thus suggesting hepatic formation of steroid glucuronides in the rat. It is suggested that the monkey represents the best animal model to date to study the contribution of diphosphoglucuronosyltransferases present in steroid target peripheral tissues to circulating levels of steroid glucuronides.

Regulation of steroid glucuronosyltransferase activities and transcripts by androgen in the human prostatic cancer LNCaP cell line

Although much attention has been focused on the synthesis of dihydrotestosterone (DHT), the inactivation and elimination of active androgens can also be key points in regulating androgen levels in tissues such as the prostate. Recent data suggest that 5alpha-reduced C19 steroids can be converted to glucuronide derivatives in the human prostate, leading to complete inactivation of these steroids. These results are supported by the recent finding of at least two steroid uridine diphosphoglucuronosyltransferase (UGT) enzymes in the prostate as well as in the human prostatic cancer LNCaP cell line. To ascertain the role of UGTs in regulating active steroid levels, we investigated the modulation of UGT levels in response to steroid treatments in LNCaP cells. Results demonstrate the down-regulation of UGT activities specific for 3-hydroxysteroids and 17-hydroxy-steroids after treatment with androgens and estrogens. Treating the cells with DHT or R1881 for 7 days inhibited UGT activity by 60%; however, 80% of the total activity was recovered after 5 days in the absence of the androgens. The inhibition of UGT activities by DHT and R1881 increases with the time of incubation and with increasing concentrations of the androgens used. The decrease in UGT enzyme activity occurred in parallel with a diminution in UGT transcript levels, as observed in Northern blot analyses. A correlation between the effect of steroids on the androgen-dependent growth response of LNCaP cells, the secretion of prostate-specific antigen, and the inhibition of UGT activities was clearly demonstrated, which implicates the androgen signaling pathway. Treating cells with Casodex, an androgen antagonist that binds the mutated androgen receptor expressed in LNCaP cells, partially blocked the androgen- and estrogen-induced decrease in UGT activity, suggesting that the regulation of UGT levels involves the androgen receptor. In addition to the formation of DHT, the inactivation of steroids by glucuronidation, which is regulated by steroids themselves, is an important mechanism controlling the level of androgens in the prostate.

Evidence for a role of glucuronosyltransferase in the regulation of androgen action in the human prostatic cancer cell line LNCaP

Androgens play an important role in the regulation of cell growth and specific protein synthesis in hormone-sensitive prostatic cancer. In this study, we have investigated the metabolism of androgens in LNCaP cells from low passage (LP) and high passage (HP) cultures which were previously shown to possess differential androgen responsiveness. When treated with dihydrotestosterone (DHT), cells showed the characteristic biphasic response of cell proliferation with an ED50 of 1 nM for both the LP and HP cells, but the maximal proliferative response was different with values of 2.65- and 4.29-fold over basal for LP and HP cells, respectively. Metabolism studies indicated no difference in 5alpha-reductase activity between LP and HP cells, while 3alpha-, 3beta- and 17beta-hydroxysteroid dehydrogenase activities were significantly higher in LP cultures. The formation of steroid glucuronides (-G), namely DHT-G, was higher in LP than in HP cells with values of 2.16 and 1.31 pmol of glucuronides formed/microgram DNA/3 h, respectively. Northern blot analysis with a UGT21B15 cDNA probe identified two bands corresponding to two or more UGT transcripts in both LNCaP cells and more transcript was observed in LP than in HP cells. Taken together these results indicate that DHT is deactivated more rapidly in the LP cells, which may explain in part the lower proliferative response to androgens of LP cells compared with HP cells.

Specificity of glucuronosyltransferase activity in the human cancer cell line LNCaP, evidence for the presence of at least two glucuronosyltransferase enzymes

Recent findings obtained by our group showed that incubation of LNCaP cells with labeled steroids leads to the formation of 3- and 17-hydroxysteroid glucuronides. In this study, the specificity and the kinetic properties of 3-hydroxy-C19steroid uridine diphospho-glucuronosyltransferase (3-OH-UGT) and 17-hydroxy-C19steroid UGT (17-OH-UGT) activities in LNCaP cells were investigated. Results indicate that the UGT has a high affinity for testosterone, dihydrotestosterone (DHT), androsterone (ADT) and androstane-3 alpha, 17 beta-diol (3 alpha-DIOL), with Km values ranging from 0.25 to 0.68 microM. The Km values are approx. 10-fold higher for androst-5-ene-3 beta,17 beta-diol (5-ene-DIOL) and androstane-3 beta,17 beta-diol (3 beta-DIOL). The relative specificities (Vmax/Km) also showed higher turnover rates for testosterone, DHT, ADT and 3 alpha-DIOL with values ranging from 2.93 to 5.71, than for 3 beta-DIOL and 5-ene-DIOL with ratios of 0.41 and 1.10, respectively. Dixon plot and Cornish-Bowden analysis demonstrate that testosterone, DHT, ADT, and 3 alpha-DIOL inhibit the glucuronidation of DHT and ADT in a competitive fashion. In contrast, when the studies are performed with 3 beta-diol and 5-ene-DIOL the inhibition of ADT glucuronidation is uncompetitive while the glucuronidation of DHT is inhibited competitively, suggesting the presence of two UGT enzymes, one for glucuronidation of the 17 beta-OH group and a second for the 3 alpha-OH group. Further evidence for the presence of two UGTs in LNCaP cells was obtained by incubation with a variety of 3 beta-OH-C19 steroids which caused a marked inhibition of DHT-G formation but had no effect on the glucuronidation of ADT. In summary, our data demonstrate the presence of at least two UGTs in the human prostate cancer cell line LNCaP. The relative specificity of the 17-OH-UGT in LNCaP cells is 3 alpha-DIOL > DHT > testosterone, while ADT is glucuronidated by the 3-OH-UGT.

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.

Glucuronosyltransferase activity in human cancer cell line LNCaP

LNCaP, a human prostate cancer cell line, metabolizes testosterone into a variety of 5 alpha-reduced C19 steroids, such as dihydrotestosterone (DHT), androstane-3 alpha, 17 beta-diol (3 beta, 17 beta-DIOL), and androsterone (ADT). Recent reports also suggest that 5 alpha-reduced C19 steroid glucuronides can be detected in the medium. The purpose of this work was to characterize by liquid chromatograph ion spray mass spectroscopy (LCMS) the metabolites formed by LNCaP during incubation with testosterone and its 5 alpha-reduced C19 steroids. Time course studies using 10 nM labeled testosterone, 3 alpha-DIOL, 3 beta-DIOL, or ADT showed that a large proportion of polar steroids were produced by LNCaP. Identification of metabolites produced by LNCaP was carried out by LCMS using 1 microM substrates. Analysis of testosterone metabolism indicated that testosterone glucuronide was formed at 77 +/- 2% after 96 h of incubation. Using DHT as substrate, 3 alpha-DIOL-G and DHT-G were the major metabolites, accounting for 46 +/- 4% and 38 +/- 3%, respectively, of the total radioactivity in the medium; ADT-G accounted for 8 +/- 1%. Further analysis by LCMS also indicated that the glucuronide group in 3 alpha-DIOL-G was at position 17-carbon, 3 alpha-DIOL-G (86 +/- 3%) was the prominent metabolite formed from 3 alpha-DIOL, a minor product was detected at 7 +/- 1% and identified by mass spectrometry to correspond to a trihydroxylated C19 steroid.(ABSTRACT TRUNCATED AT 250 WORDS)