Role of aldo-keto reductase family 1 (AKR1) enzymes in human steroid metabolism

Identification of Metabolomic Biomarkers for Endometrial Cancer and Its Recurrence after Surgery in Postmenopausal Women

Endometrial cancer (EC) is the most frequent gynecological cancer in developed countries. Most EC occurs after menopause and is diagnosed as endometrioid (type I) carcinomas, which exhibit a favorable prognosis. In contrast, non-endometrioid (type II) carcinomas such as serous tumors have a poor prognosis. Our goal was to identify novel blood-based markers associated with EC subtypes and recurrence after surgery in postmenopausal women. Using mass spectrometry-based untargeted metabolomics, we examined preoperative serum metabolites among control women (n = 18) and those with non-recurrent (NR) and recurrent (R) cases of type I endometrioid (n = 24) and type II serous (n = 12) carcinomas. R and NR cases were similar with respect to pathological characteristics, body mass index, and age. A total of 1,592 compounds were analyzed including 14 different lipid classes. When we compared EC cases with controls, 137 metabolites were significantly different. A combination of spermine and isovalerate resulted in an age-adjusted area under the receiver-operating characteristic curve (AUC_adj) of 0.914 (P < 0.001) for EC detection. The combination of 2-oleoylglycerol and TAG42:2-FA12:0 allowed the distinction of R cases from NR cases with an AUC_adj of 0.901 (P < 0.001). Type I R cases were also characterized by much lower levels of bile acids and elevated concentrations of phosphorylated fibrinogen cleavage peptide, whereas type II R cases displayed higher levels of ceramides. The findings from our pilot study provide a detailed metabolomics study of EC and identify putative serum biomarkers for defining clinically relevant risk groups.

Proteomics and phosphoproteomics analysis of liver in male rats exposed to bisphenol A: Mechanism of hepatotoxicity and biomarker discovery

Bisphenol A (BPA), discovered to be an artificial estrogen, has been shown to leach from some containers and mediate oxidative damage to cells and tissues and to be involved in reproductive disorders, obesity, diabetes, and liver dysfunction. In the current study, we investigated the effects of oral chronic exposure to low dose of BPA (0.5 mg kg^-1) on the protein and phosphoprotein expression profiles in male Wistar rat liver using a gel-based proteomics approach based on two-dimensional gel electrophoresis followed by matrix-assisted laser desorption/ionization mass spectrometry identification. Our results showed that BPA exposure affected the levels of proteins and phosphoproteins involved in diverse biological processes associated with hepatotoxicity, fatty liver, and carcinoma. Moreover, we analyzed the effects of BPA on oxidative stress by assessing levels of malondialdehyde (MDA), a marker of lipid peroxidation, and reduced glutathione (GSH), a non-enzymatic antioxidant agent, in the liver. As expected BPA induced oxidative stress indicated by increased levels of MDA and decreased GSH content in the liver. In conclusion, chronic oral exposure of rats to BPA leads to increased oxidative stress in the liver and major alterations in the liver proteome and phosphoproteome, which may contribute to the pathophysiology of liver diseases.

Variation in CYP2A6 Activity and Personalized Medicine

The cytochrome P450 2A6 (CYP2A6) enzyme metabolizes several clinically relevant substrates, including nicotine-the primary psychoactive component in cigarette smoke. The gene that encodes the CYP2A6 enzyme is highly polymorphic, resulting in extensive interindividual variation in CYP2A6 enzyme activity and the rate of metabolism of nicotine and other CYP2A6 substrates including cotinine, tegafur, letrozole, efavirenz, valproic acid, pilocarpine, artemisinin, artesunate, SM-12502, caffeine, and tyrosol. CYP2A6 expression and activity are also impacted by non-genetic factors, including induction or inhibition by pharmacological, endogenous, and dietary substances, as well as age-related changes, or interactions with other hepatic enzymes, co-enzymes, and co-factors. As variation in CYP2A6 activity is associated with smoking behavior, smoking cessation, tobacco-related lung cancer risk, and with altered metabolism and resulting clinical responses for several therapeutics, CYP2A6 expression and enzyme activity is an important clinical consideration. This review will discuss sources of variation in CYP2A6 enzyme activity, with a focus on the impact of CYP2A6 genetic variation on metabolism of the CYP2A6 substrates.

Involvement of AF1q/MLLT11 in the progression of ovarian cancer

The functional role of AF1q/MLLT11, an oncogenic factor involved in a translocation t(1;11)(q21;q23) responsible for acute myeloid leukaemia, has been investigated in hematological and solid malignancies and its expression was found to be linked to tumor progression and poor clinical outcome. In addition to its oncogenic function, AF1q has been shown to play a role in the onset of basal and drug-induced apoptosis in cancer cells of different histotypes, including ovarian cancer. Through in vitro, ex vivo, and in silico approaches, we demonstrated here that AF1q is also endowed with protumorigenic potential in ovarian cancer. In ovarian cancer cell lines, stable AF1q overexpression caused activation of epithelial-to-mesenchymal transition and increased motility/migratory/invasive abilities accompanied by gene expression changes mainly related to Wnt signaling and to signaling pathways involving in ERK/p38 activation. The potential role of AF1q in ovarian cancer progression was confirmed by immunohistochemical and in silico analyses performed in ovarian tumor specimens which revealed that the protein was absent in normal ovarian epithelium and became detectable when atypical proliferation was present. Moreover, AF1q was significantly lower in borderline ovarian tumors (i.e., tumors of low malignant potential without stromal invasion) than in invasive tumors, thus corroborating the association between high AF1q expression and increased migratory/invasive cell behavior and confirming its potential role in ovarian cancer progression. Our findings demonstrated, for the first time, that AF1q is endowed with protumorigenic activity in ovarian cancer, thus highlighting a dual behavior (i.e., protumorigenic and proapoptotic functions) of the protein in the malignancy.

Stereospecific Metabolism of R- and S-Warfarin by Human Hepatic Cytosolic Reductases

Coumadin (rac-warfarin) is the most commonly used anticoagulant in the world; however, its clinical use is often challenging because of its narrow therapeutic range and interindividual variations in response. A critical contributor to the uncertainty is variability in warfarin metabolism, which includes mostly oxidative but also reductive pathways. Reduction of each warfarin enantiomer yields two warfarin alcohol isomers, and the corresponding four alcohols retain varying levels of anticoagulant activity. Studies on the kinetics of warfarin reduction have often lacked resolution of parent-drug enantiomers and have suffered from coelution of pairs of alcohol metabolites; thus, those studies have not established the importance of individual stereospecific reductive pathways. We report the first steady-state analysis of R- and S-warfarin reduction in vitro by pooled human liver cytosol. As determined by authentic standards, the major metabolites were 9R,11S-warfarin alcohol for R-warfarin and 9S,11S-warfarin alcohol for S-warfarin. R-warfarin (Vmax 150 pmol/mg per minute, Km 0.67 mM) was reduced more efficiently than S-warfarin (Vmax 27 pmol/mg per minute, Km 1.7 mM). Based on inhibitor phenotyping, carbonyl reductase-1 dominated R-and S-warfarin reduction, followed by aldo-keto reductase-1C3 and then other members of that family. Overall, the carbonyl at position 11 undergoes stereospecific reduction by multiple enzymes to form the S alcohol for both drug enantiomers, yet R-warfarin undergoes reduction preferentially. This knowledge will aid in assessing the relative importance of reductive pathways for R- and S-warfarin and factors influencing levels of pharmacologically active parent drugs and metabolites, thus impacting patient dose responses.

[Clinical feature and genetic analysis of a family affected by congenital bile acid synthesis defect type 2: identification of 2 novel mutations in AKR1D1 gene]

Congenital bile acid synthesis defect type 2 (CBAS2) is an autosomal recessive disorder caused by biallelic mutations of AKR1D1 gene, which encodes the Δ4-3-oxo-steroid 5β-reductase. Cholestatic jaundice is the main clinical manifestation, accompanied by malabsorption of fat and fat-soluble vitamins. This paper reported the clinical and genetic features of a CBAS2 patient definitely diagnosed by AKR1D1 genetic analysis. An 8-month-old male infant was referred to the hospital with the complaint of jaundiced skin and sclera over 7 months. On physical examination, growth retardation and malnutrition were discovered besides mild jaundice of the skin and sclera. The liver was palpable 8 cm below the right subcostal margin with medium texture, and the spleen was not enlarged. On liver function test, elevated levels of bilirubin (predominantly conjugated bilirubin) and transaminases were detected, but serum total bile acids and γ-glutamyl transpeptidase levels were within the normal ranges. Liver histopathologic analysis showed disorganized bile ducts, obvious multinucleated giant cells, significant cholestasis in hepatocytes, together with portal and interstitial fibrosis and lymphocytic infiltration. Via next generation sequencing analysis and Sanger sequencing confirmation, the infant proved to be a compound heterozygote of the AKR1D1 variants c.579+2delT and c.853C>T(p.Q285X), two novel mutations originated from his mother and father, respectively. CBAS2 was thus definitely diagnosed, and chenodeoxycholic acid was given orally. As a result, the abnormal liver function and hepatomegaly were improved gradually. On a follow-up 3 months later, a soft liver was palpable 2.5 cm below the right subcostal margin, and all liver function indices recovered to normal ranges.

Evaluation of compound selectivity of aldo-keto reductases using differential scanning fluorimetry

Inhibitors of AKR1B10 belonging to the aldo-keto reductase (AKR) superfamily are considered promising candidates for anti-cancer drugs. AKR1B1, a structurally similar isoform of AKR1B10, is involved in glucose metabolism. Thus, selective inhibition of AKR1B10 is required for the development of anti-cancer drugs. In this study, we first compared correlations between melting temperature and the 50% inhibition concentration obtained from differential scanning fluorimetry (DSF) and an enzyme inhibitory experiment, respectively, and a good correlation was found, except for compounds with low solubility. This result indicates that the DSF method is useful for drug screening for the AKR superfamily. We then evaluated their selectivity as inhibitors against all seven major human AKR1 family proteins and found that C18 is most specific for AKR1B10.

Disturbance of Mammary UDP-Glucuronosyltransferase Represses Estrogen Metabolism and Exacerbates Experimental Breast Cancer

The progression of breast cancer is closely related to the levels of estrogens within the body. UDP-glucuronosyltransferase (UGT) is an important class of phase II metabolizing enzymes, playing a pivotal role in detoxifying steroid hormone. In the present study, we aim at uncovering the potential dysregulation pattern of UGT and its role in estrogen metabolism and in the pathogenesis of breast cancer. Female Sprague-Dawley rats were treated with 100 mg/kg dimethylbenz(a)anthracene (DMBA) to induce breast cancer. Our results showed that the expression and activity of UGT in mammary tissues were downregulated significantly in DMBA rats. Consistent with this, levels of estradiol, 4-hydroxylated estradiol, and 2-hydroxylated estradiol were increased in both mammary tissues and serum, supporting a notable accumulation of toxic estrogen species in the target tissue of breast cancer. In addition, we also observed the decreased cell migration, cell proliferation, and DNA damage in UGT-transfected MCF-7 cells, suggesting a protective role of UGT against estrogen-induced mammary carcinogenesis. Taken together, these results indicated that accumulation of estrogens induced by UGT deficiency is a critical factor to induce the development of breast cancer. UGT contributes to estrogen elimination, and its glucuronidation capacity influences the estrogen signaling pathway and the pathogenesis of breast cancer.

The role of estradiol metabolism in urogenital schistosomiasis-induced bladder cancer

Urogenital schistosomiasis is a neglected tropical disease that can lead to bladder cancer. How urogenital schistosomiasis induces carcinogenesis remains unclear, although there is evidence that the human blood fluke Schistosoma haematobium, the infectious agent of urogenital schistosomiasis, releases estradiol-like metabolites. These kind of compounds have been implicated in other cancers. Aiming for enhanced understanding of the pathogenesis of the urogenital schistosomiasis-induced bladder cancer, here we review, interpret, and discuss findings of estradiol-like metabolites detected in both the parasite and in the human urine during urogenital schistosomiasis. Moreover, we predict pathways and enzymes that are involved in the production of these metabolites emphasizing their potential effects on the dysregulation of the tumor suppressor gene p53 expression during urogenital schistosomiasis. Enhanced understanding of these potential carcinogens may not only shed light on urogenital schistosomiasis-induced neoplasia of the bladder, but would also facilitate development of interventions and biomarkers for this and other infection-associated cancers at large.

Diagnostic Application of Targeted Next-Generation Sequencing of 80 Genes Associated with Disorders of Sexual Development

Disorders of sexual development (DSD) are estimated to occur in 1 of 4500 births. Since the genetic etiology of DSD is highly heterogeneous, obtaining a definitive molecular diagnosis by single gene test is challenging. Utilizing a high-throughput sequencing upfront is proposed as an efficient approach to aid in the diagnosis. This study aimed to examine the diagnostic yield of next-generation sequencing in DSD. 32 DSD patients that previously received clinical examinations and single gene tests were selected, with or without a diagnosis. Prior single gene tests were masked, and then samples went through targeted next-generation sequencing of 80 genes from which the diagnostic yield was assessed. A likely diagnosis, with pathogenic or likely pathogenic variants identified, was obtained from nine of the 32 patients (i.e., 28.1%, versus 10% by single gene tests). In another five patients (15.6%), variants of uncertain significance were found. Among 18 variants identified (i.e., 17 single nucleotide variants and one small deletion), eight had not been previously reported. This study supports the notion that next-generation sequencing can be an efficient tool in the clinical diagnosis and variant discovery in DSD.

Aldo-Keto Reductase AKR1C1-AKR1C4: Functions, Regulation, and Intervention for Anti-cancer Therapy

Aldo-keto reductases comprise of AKR1C1-AKR1C4, four enzymes that catalyze NADPH dependent reductions and have been implicated in biosynthesis, intermediary metabolism, and detoxification. Recent studies have provided evidences of strong correlation between the expression levels of these family members and the malignant transformation as well as the resistance to cancer therapy. Mechanistically, most studies focus on the catalytic-dependent function of AKR1C isoforms, like their impeccable roles in prostate cancer, breast cancer, and drug resistance due to the broad substrates specificity. However, accumulating clues showed that catalytic-independent functions also played critical roles in regulating biological events. This review summarizes the catalytic-dependent and -independent roles of AKR1Cs, as well as the small molecule inhibitors targeting these family members.

Alterations in estrogen signalling pathways upon acquisition of anthracycline resistance in breast tumor cells

Intrinsic or acquired drug resistance is a major impediment to the successful treatment of women with breast cancer using chemotherapy. We have observed that MCF-7 breast tumor cells selected for resistance to doxorubicin or epirubicin (MCF-7_DOX2 and MCF-7_EPI cells, respectively) exhibited increased expression of several members of the aldo-keto reductase (AKR) gene family (in particular AKR1C3 and AKR1B10) relative to control MCF-7_CC cells selected by propagation in the absence of drug. Normal cellular roles for the AKRs include the promotion of estrogen (E2) synthesis from estrone (E1) and the hydroxylation and detoxification of exogenous xenobiotics such as anthracycline chemotherapy drugs. While hydroxylation of anthracyclines strongly attenuates their cytotoxicity, it is unclear whether the enhanced AKR expression in the above anthracycline-resistant cells promotes E2 synthesis and/or alterations in E2 signalling pathways and whether such changes contribute to enhanced survival and anthracycline resistance. To determine the role of AKRs and E2 pathways in doxorubicin resistance, we examined changes in the expression of E2-related genes and proteins upon acquisition of doxorubicin resistance. We also assessed the effects of AKR overexpression or downregulation or the effects of activators or inhibitors of E2-dependent pathways on previously acquired resistance to doxorubicin. In this study we observed that the enhanced AKR expression upon acquisition of anthracycline resistance was, in fact, associated with enhanced E2 production. However, the expression of estrogen receptor α (ERα) was reduced by 2- to 5-fold at the gene transcript level and 2- to 20-fold at the protein level upon acquisition of anthracycline resistance. This was accompanied by an even stronger reduction in ERα phosphorylation and activity, including highly suppressed expression of two proteins under E2-dependent control (Bcl-2 and cyclin D1). The diminished Bcl-2 and cyclin D1 expression would be expected to reduce the growth rate of the cells, a hypothesis which was confirmed in subsequent cell proliferation experiments. AKR1C3 or AKR1B10 overexpression alone had no effect on doxorubicin sensitivity in MCF-7_CC cells, while siRNA-mediated knockdown of AKR1C3 and/or AKR1B10 expression had no significant effect on sensitivity to doxorubicin in MCF-7_DOX2 or MCF-7_EPI cells. This suggested that enhanced or reduced AKR expression/activity is insufficient to confer anthracycline resistance or sensitivity to breast tumor cells, respectively. Rather, it would appear that AKR overexpression acts in concert with other proteins to confer anthracycline resistance, including reduced E2-dependent expression of both an important apoptosis inhibitor (Bcl-2) and a key protein associated with activation of cell cycle-dependent kinases (cyclin D1).

Differential Feedback Regulation of Δ4-3-Oxosteroid 5β-Reductase Expression by Bile Acids

Δ4-3-oxosteroid 5β-reductase is member D1 of the aldo-keto reductase family 1 (AKR1D1), which catalyzes 5β-reduction of molecules with a 3-oxo-4-ene structure. Bile acid intermediates and most of the steroid hormones carry the 3-oxo-4-ene structure. Therefore, AKR1D1 plays critical roles in both bile acid synthesis and steroid hormone metabolism. Currently our understanding on transcriptional regulation of AKR1D1 under physiological and pathological conditions is very limited. In this study, we investigated the regulatory effects of primary bile acids, chenodeoxycholic acid (CDCA) and cholic acid (CA), on AKR1D1 expression. The expression levels of AKR1D1 mRNA and protein in vitro and in vivo following bile acid treatments were determined by real-time PCR and Western blotting. We found that CDCA markedly repressed AKR1D1 expression in vitro in human hepatoma HepG2 cells and in vivo in mice. On the contrary, CA significantly upregulated AKR1D1 expression in HepG2 cells and in mice. Further mechanistic investigations revealed that the farnesoid x receptor (FXR) signaling pathway was not involved in regulating AKR1D1 by bile acids. Instead, CDCA and CA regulated AKR1D1 through the mitogen-activated protein kinases/c-Jun N-terminal kinases (MAPK/JNK) signaling pathway. Inhibition of the MAPK/JNK pathway effectively abolished CDCA and CA-mediated regulation of AKR1D1. It was thus determined that AKR1D1 expression was regulated by CDCA and CA through modulating the MAPK/JNK signaling pathway. In conclusion, AKR1D1 expression was differentially regulated by primary bile acids through negative and positive feedback mechanisms. The findings indicated that both bile acid concentrations and compositions play important roles in regulating AKR1D1 expression, and consequently bile acid synthesis and steroid hormone metabolism.

Epidemiology of Endometrial Carcinoma: Etiologic Importance of Hormonal and Metabolic Influences

Endometrial carcinoma is the most common gynecologic cancer in developed nations, and the annual incidence is projected to increase, secondary to the high prevalence of obesity, a strong endometrial carcinoma risk factor. Although endometrial carcinomas are etiologically, biologically, and clinically diverse, hormonal and metabolic mechanisms are particularly strongly implicated in the pathogenesis of endometrioid carcinoma, the numerically predominant subtype. The centrality of hormonal and metabolic disturbances in the pathogenesis of endometrial carcinoma, combined with its slow development from well-characterized precursors in most cases, offers a substantial opportunity to reduce endometrial carcinoma mortality through early detection, lifestyle modification, and chemoprevention. In this chapter, we review the epidemiology of endometrial carcinoma, emphasizing theories that link risk factors for these tumors to hormonal and metabolic mechanisms. Future translational research opportunities related to prevention are discussed.

Predictors of Variation in CYP2A6 mRNA, Protein, and Enzyme Activity in a Human Liver Bank: Influence of Genetic and Nongenetic Factors

Cytochrome P450 2A6 CYP2A6: metabolizes several clinically relevant substrates, including nicotine, the primary psychoactive component in cigarette smoke. Smokers vary widely in their rate of inactivation and clearance of nicotine, altering numerous smoking phenotypes. We aimed to characterize independent and shared impact of genetic and nongenetic sources of variation in CYP2A6 mRNA, protein, and enzyme activity in a human liver bank (n = 360). For the assessment of genetic factors, we quantified levels of CYP2A6, cytochrome P450 oxidoreductase (POR), and aldo-keto reductase 1D1 (AKR1D1) mRNA, and CYP2A6 and POR proteins. CYP2A6 enzyme activity was determined through measurement of cotinine formation from nicotine and 7-hydroxycoumarin formation from coumarin. Donor DNA was genotyped for CYP2A6, POR, and AKR1D1 genetic variants. Nongenetic factors assessed included gender, age, and liver disease. CYP2A6 phenotype measures were positively correlated to each other (r values ranging from 0.47-0.88, P < 0.001). Female donors exhibited higher CYP2A6 mRNA expression relative to males (P < 0.05). Donor age was weakly positively correlated with CYP2A6 protein (r = 0.12, P < 0.05) and activity (r = 0.20, P < 0.001). CYP2A6 reduced-function genotypes, but not POR or AKR1D1 genotypes, were associated with lower CYP2A6 protein (P < 0.001) and activity (P < 0.01). AKR1D1 mRNA was correlated with CYP2A6 mRNA (r = 0.57, P < 0.001), protein (r = 0.30, P < 0.001), and activity (r = 0.34, P < 0.001). POR protein was correlated with CYP2A6 activity (r = 0.45, P < 0.001). Through regression analyses, we accounted for 17% (P < 0.001), 37% (P < 0.001), and 77% (P < 0.001) of the variation in CYP2A6 mRNA, protein, and activity, respectively. Overall, several independent and shared sources of variation in CYP2A6 activity in vitro have been identified, which could translate to variable hepatic clearance of nicotine.

Heightened aggressive behavior in mice deficient in aldo-keto reductase 1a (Akr1a)

Aldehyde reductase (Akr1a) is involved in the synthesis of ascorbic acid (AsA) which may play a role in social behavior. In the current study, we performed analyses on Akr1a-deficient (Akr1a^-/-) mice that synthesize about 10% as much AsA as wild-type mice from the viewpoint of intermale aggression. The use of the resident-intruder test revealed that the Akr1a^-/- mice exhibited more aggressive phenotypes than wild-type control mice. Unexpectedly, however, the oral administration of additional AsA failed to reduce the aggressive behavior of Akr1a^-/- mice, suggesting that the heightened aggression was independent of AsA biosynthesis. The findings also show that the plasma levels of corticosterone, but not serotonin and testosterone, were increased in the absence of Akr1a in mice, suggesting that the mice were highly stressed. These results suggest that Akr1a might be involved in the metabolism of steroids and other carbonyl-containing compounds and, hence, the absence of Akr1a results in heightened aggression via a malfunction in a metabolic pathway.

Aldo-keto reductase 1C1 induced by interleukin-1β mediates the invasive potential and drug resistance of metastatic bladder cancer cells

In treating bladder cancer, determining the molecular mechanisms of tumor invasion, metastasis, and drug resistance are urgent to improving long-term patient survival. One of the metabolic enzymes, aldo-keto reductase 1C1 (AKR1C1), plays an essential role in cancer invasion/metastasis and chemoresistance. In orthotopic xenograft models of a human bladder cancer cell line, UM-UC-3, metastatic sublines were established from tumors in the liver, lung, and bone. These cells possessed elevated levels of EMT-associated markers, such as Snail, Slug, or CD44, and exhibited enhanced invasion. By microarray analysis, AKR1C1 was found to be up-regulated in metastatic lesions, which was verified in metastatic human bladder cancer specimens. Decreased invasion caused by AKR1C1 knockdown suggests a novel role of AKR1C1 in cancer invasion, which is probably due to the regulation of Rac1, Src, or Akt. An inflammatory cytokine, interleukin-1β, was found to increase AKR1C1 in bladder cancer cell lines. One particular non-steroidal anti-inflammatory drug, flufenamic acid, antagonized AKR1C1 and decreased the cisplatin-resistance and invasion potential of metastatic sublines. These data uncover the crucial role of AKR1C1 in regulating both metastasis and drug resistance; as a result, AKR1C1 should be a potent molecular target in invasive bladder cancer treatment.

Dydrogesterone metabolism in human liver by aldo-keto reductases and cytochrome P450 enzymes

1. The metabolism of dydrogesterone was investigated in human liver cytosol (HLC) and human liver microsomes (HLM). Enzymes involved in dydrogesterone metabolism were identified and their relative contributions were estimated. 2. Dydrogesterone clearance was clearly higher in HLC compared to HLM. The major active metabolite 20α-dihydrodydrogesterone (20α-DHD) was only produced in HLC. 3. The formation of 20α-DHD by cytosolic aldo-keto reductase 1C (AKR1C) was confirmed with isoenzyme-specific AKR inhibitors. 4. Using recombinantly expressed human cytochrome P450 (CYP) isoenzymes, dydrogesterone was shown to be metabolically transformed by CYP3A4 and CYP2C19. 5. A clear contribution of CYP3A4 to microsomal metabolism of dydrogesterone was demonstrated with HLM and isoenzyme-specific CYP inhibitors, and confirmed by a significant correlation between dydrogesterone clearance and CYP3A4 activity. 6. Contribution of CYP2C19 was shown to be clearly less than CYP3A4 and restricted to a small group of human individuals with very high CYP2C19 activity. Therefore, it is expected that CYP2C19 genetic variations will not affect dydrogesterone pharmacokinetics in man. 7. In conclusion, dydrogesterone metabolism in the liver is dominated primarily by cytosolic enzymes (particularly AKR1C) and secondarily by CYP3A4, with the former exclusively responsible for 20α-DHD formation.

Selective AKR1C3 Inhibitors Potentiate Chemotherapeutic Activity in Multiple Acute Myeloid Leukemia (AML) Cell Lines

We report the design, synthesis, and evaluation of potent and selective inhibitors of aldo-keto reductase 1C3 (AKR1C3), an important enzyme in the regulatory pathway controlling proliferation, differentiation, and apoptosis in myeloid cells. Combination treatment with the nontoxic AKR1C3 inhibitors and etoposide or daunorubicin in acute myeloid leukemia cell lines, elicits a potent adjuvant effect, potentiating the cytotoxicity of etoposide by up to 6.25-fold and the cytotoxicity of daunorubicin by >10-fold. The results validate AKR1C3 inhibition as a common adjuvant target across multiple AML subtypes. These compounds in coadministration with chemotherapeutics in clinical use enhance therapeutic index and may avail chemotherapy as a treatment option to the pediatric and geriatric population currently unable to tolerate the side effects of cancer drug regimens.

The other side of progestins: effects in the brain

Progestins are a broad class of progestational agents widely differing in their chemical structures and pharmacological properties. Despite emerging data suggest that progestins, besides their action as endometrial protection, can also have multiple nonreproductive functions, much remains to be discovered regarding the actions exerted by these molecules in the nervous system. Here, we report the role exerted by different progestins, currently used for contraception or in postmenopausal hormone replacement therapies, in regulating cognitive functions as well as social behavior and mood. We provide evidence that the effects and mechanisms underlying their actions are still confusing due to the use of different estrogens and progestins as well as different doses, duration of exposure, route of administration, baseline hormonal status and age of treated women. We also discuss the emerging issue concerning the relevant increase of these substances in the environment, able to deeply affect aquatic wildlife as well as to exert a possible influence in humans, which may be exposed to these compounds via contaminated drinking water and seafood. Finally, we report literature data showing the neurobiological action of progestins and in particular their importance during neurodegenerative events. This is extremely interesting, since some of the progestins currently used in clinical practice exert neuroprotective and anti-inflammatory effects in the nervous system, opening new promising opportunities for the use of these molecules as therapeutic agents for trauma and neurodegenerative disorders.

In situ androgen and estrogen biosynthesis in endometrial cancer: focus on androgen actions and intratumoral production

In situ estrogen biosynthesis is considered to play pivotal roles in the development and progression of human endometrial carcinoma. However, the biological roles of androgen have remained virtually unknown. Various epidemiological studies have revealed that elevated serum androgen levels are generally associated with an increased risk of developing endometrial carcinoma; however, studies directly examining androgens in carcinoma tissues are relatively rare and reviews summarizing this information are scarce. Therefore, we summarized recent studies on androgens in endometrial carcinoma, especially focusing androgen actions and in situ androgen biosynthesis. Among the enzymes required for local biosynthesis of androgen, 17β-hydroxysteroid dehydrogenase type 5 (conversion from androstenedione to testosterone) and 5α-reductase (reduction of testosterone to dihydrotestosterone (DHT)) are the principal enzymes involved in the formation of biologically most potent androgen, DHT. Both enzymes and androgen receptor were expressed in endometrial carcinoma tissues, and in situ production of DHT has been reported to exist in endometrial carcinoma tissues. However, testosterone is not only a precursor of DHT production, but also a precursor of estradiol synthesis, as a substrate of the aromatase enzyme. Therefore, aromatase could be another key enzyme serving as a negative regulator for in situ production of DHT by reducing amounts of the precursor. In an in vitro study, DHT was reported to exert antiproliferative effects on endometrial carcinoma cells. Intracrine mechanisms of androgens, the downstream signals of AR, which are directly related to anticancer progression, and the clinical significance of DHT-AR pathway in the patients with endometrial carcinoma have, however, not been fully elucidated.

Regulation of androgen action during establishment of pregnancy

During the establishment of pregnancy, the ovarian-derived hormones progesterone and oestradiol regulate remodelling of the endometrium to promote an environment that is able to support and maintain a successful pregnancy. Decidualisation is characterised by differentiation of endometrial stromal cells that secrete growth factors and cytokines that regulate vascular remodelling and immune cell influx. This differentiation process is critical for reproduction, and inadequate decidualisation is implicated in the aetiology of pregnancy disorders such as foetal growth restriction and preeclampsia. In contrast to progesterone and oestradiol, the role of androgens in regulating endometrial function is poorly understood. Androgen receptors are expressed in the endometrium, and androgens are reported to regulate both the transcriptome and the secretome of endometrial stromal cells. In androgen-target tissues, circulating precursors are activated to mediate local effects, and recent studies report that steroid concentrations detected in endometrial tissue are distinct to those detected in the peripheral circulation. New evidence suggests that decidualisation results in dynamic changes in the expression of androgen biosynthetic enzymes, highlighting a role for pre-receptor regulation of androgen action during the establishment of pregnancy. These results suggest that such enzymes could be future therapeutic targets for the treatment of infertility associated with endometrial dysfunction. In conclusion, these data support the hypothesis that androgens play a beneficial role in regulating the establishment and maintenance of pregnancy. Future studies should be focussed on investigating the safety and efficacy of androgen supplementation with the potential for utilisation of novel therapeutics, such as selective androgen receptor modulators, to improve reproductive outcomes in women.

Pyrithione-based ruthenium complexes as inhibitors of aldo-keto reductase 1C enzymes and anticancer agents

Four ruthenium complexes of clinically used zinc ionophore pyrithione and its oxygen analog 2-hydroxypyridine N-oxide were prepared and evaluated as inhibitors of enzymes of the aldo-keto reductase subfamily 1C (AKR1C). A kinetic study assisted with docking simulations showed a mixed type of inhibition consisting of a fast reversible and a slow irreversible step in the case of both organometallic compounds 1A and 1B. Both compounds also showed a remarkable selectivity towards AKR1C1 and AKR1C3 which are targets for breast cancer drug design. The organoruthenium complex of ligand pyrithione as well as pyrithione itself also displayed toxicity on the hormone-dependent MCF-7 breast cancer cell line with EC50 values in the low micromolar range.

High expression of AKR1C1 is associated with proliferation and migration of small-cell lung cancer cells

AKR1C1 is a member of the AKR1C family, which not only plays an important role in hormone metabolism but is believed to be involved in carcinogen metabolism. Our previous study demonstrated that AKR1C1 was highly expressed in lung tumor tissues as compared with the tumor-adjacent tissues. Small-cell lung cancer (SCLC) is a special type of lung cancer. Surgical treatment of SCLC is usually difficult due to the high degree of malignancy and early metastasis, and difficulty in obtaining clinical specimens. There is not much basic or clinical research on SCLC in the People’s Republic of China even in recent years. To investigate the mechanism of AKR1C1 in the pathogenesis of SCLC, the present study used H446 cell line to see whether AKR1C1 could affect the proliferation or migration of SCLC cells, and used a lentivirus to build the AKR1C1 overexpression and under-expression cell lines. The results indicated that AKR1C1 was an important inducement in the proliferation and migration of H446 cells. AKR1C1 promoted cell proliferation and played a vital role in the migration of SCLC cells. These results were also verified in nude mice in vivo. In conclusion, AKR1C1 plays an important role in the development and progression of SCLC and may represent an independent biomarker for assessment of the primary prognosis and therapy of SCLC.

Preliminary evidence of altered steroidogenesis in women with Alzheimer's disease: Have the patients "OLDER" adrenal zona reticularis?

Alzheimer's disease (AD) represents more than half of total dementias. Various factors including altered steroid biosynthesis may participate in its pathophysiology. We investigated how the circulating steroids (measured by GC-MS and RIA) may be altered in the presence of AD. Sixteen women with AD and 22 age- and BMI-corresponding controls aged over 65 years were enrolled in the study. The steroid levels (47 steroids and steroid polar conjugates) and their ratios in AD female patients indicated increased CYP11A1 activity, weakened activity of the CYP17A1C17,20 lyase metabolic step and attenuated sulfotransferase SULT2A1 activity at higher activity of the CYP17A1 17-hydroxylase step. The patients showed diminished HSD3B2 activity for C21 steroids, abated conversion of 17-hydroxyprogesterone to cortisol, and significantly elevated cortisol. The women with AD had also attenuated steroid 7α-hydroxylation forming immunoprotective Δ(5)-C19 steroids, attenuated aromatase activity forming estradiol that induces autoimmunity and a shift from the 3β-hydroxy-5α/β-reduced C19 steroids to their neuroinhibitory and antiinflammatory GABAergic 3α-hydroxy- counterparts and showed higher levels of the 3α-hydroxy-5α/β-reduced C21 steroids and pregnenolone sulfate (improves cognitive abilities but may be both protective and excitotoxic). Our preliminary data indicated functioning of alternative "backdoor" pathway in women with AD showing higher levels of both 5α/β-reduced C21 steroids but reduced levels of both 5α/β-reduced C21 steroids, which implied that the alternative "backdoor" pathway might include both 5α- and 5β-reduced steroids. Our study suggested relationships between AD status in women based on the age of subjects and levels of 10 steroids measured by GC-MS.

Genomewide comparison of the inducible transcriptomes of nuclear receptors CAR, PXR and PPARα in primary human hepatocytes

The ligand-activated nuclear receptor pregnane X receptor (PXR, NR1I2) and the constitutive androstane receptor (CAR, NR1I3) are two master transcriptional regulators of many important drug metabolizing enzymes and transporter genes (DMET) in response to xenobiotics including many drugs. The peroxisome proliferator-activated receptor alpha (PPARα, NR1C1), the target of lipid lowering fibrate drugs, primarily regulates fatty acid catabolism and energy-homeostasis. Recent research has shown that there are substantial overlaps in the regulated genes of these receptors. For example, both CAR and PXR also modulate the transcription of key enzymes involved in lipid and glucose metabolism and PPARα also functions as a direct transcriptional regulator of important DMET genes including cytochrome P450s CYP3A4 and CYP2C8. Despite their important and widespread influence on liver metabolism, comparative data are scarce, particularly at a global level and in humans. The major objective of this study was to directly compare the genome-wide transcriptional changes elucidated by the activation of these three nuclear receptors in primary human hepatocytes. Cultures from six individual donors were treated with the prototypical ligands for CAR (CITCO), PXR (rifampicin) and PPARα (WY14,643) or DMSO as vehicle control. Genomewide mRNA profiles determined with Affymetrix microarrays were analyzed for differentially expressed genes and metabolic functions. The results confirmed known prototype target genes and revealed strongly overlapping sets of coregulated but also distinctly regulated and novel responsive genes and pathways. The results further specify the role of PPARα as a regulator of drug metabolism and the role of the xenosensors PXR and CAR in lipid metabolism and energy homeostasis. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.

Human dehydrogenase/reductase (SDR family) member 11 is a novel type of 17β-hydroxysteroid dehydrogenase

We report characterization of a member of the short-chain dehydrogenase/reductase superfamily encoded in a human gene, DHRS11. The recombinant protein (DHRS11) efficiently catalyzed the conversion of the 17-keto group of estrone, 4- and 5-androstenes and 5α-androstanes into their 17β-hydroxyl metabolites with NADPH as a coenzyme. In contrast, it exhibited reductive 3β-hydroxysteroid dehydrogenase activity toward 5β-androstanes, 5β-pregnanes, 4-pregnenes and bile acids. Additionally, DHRS11 reduced α-dicarbonyls (such as diacetyl and methylglyoxal) and alicyclic ketones (such as 1-indanone and loxoprofen). The enzyme activity was inhibited in a mixed-type manner by flavonoids, and competitively by carbenoxolone, glycyrrhetinic acid, zearalenone, curcumin and flufenamic acid. The expression of DHRS11 mRNA was observed widely in human tissues, most abundantly in testis, small intestine, colon, kidney and cancer cell lines. Thus, DHRS11 represents a novel type of 17β-hydroxysteroid dehydrogenase with unique catalytic properties and tissue distribution.

Nipple Aspirate Fluid Hormone Concentrations and Breast Cancer Risk

Prior reports identify higher serum concentrations of estrogens and androgens as risk factors for breast cancer, but steroids in nipple aspirate fluid (NAF) may be more related to risk. Incident breast cancer cases and mammography controls were recruited. Sex steroids were measured in NAF from the unaffected breasts of cases and one breast of controls. Menopausal status and menstrual cycle phase were determined. NAF steroids were purified by HPLC and quantified by immunoassays. Conditional logistic regression models were used to examine associations between NAF hormones and case-control status. NAF samples from 160 cases and 157 controls were evaluable for hormones. Except for progesterone and dehydroepiandrosterone (DHEA), the NAF and serum concentrations were not significantly correlated. NAF estradiol and estrone were not different between cases and controls. Higher NAF (but not serum) DHEA concentrations were associated with cases, particularly among estrogen receptor (ER)-positive cases (NAF odds ratio (OR) = 1.18, 95 % confidence interval (CI) 1.02, 1.36). NAF DHEA was highly correlated with NAF estradiol and estrone but not with androstenedione or testosterone. Higher progesterone concentrations in both NAF and serum were associated with a lower risk of ER-negative cancer (NAF OR = 0.69, 95 % CI 0.51, 0.92). However, this finding may be explained by case-control imbalance in the number of luteal phase subjects (2 cases and 19 controls). The significantly higher concentration of DHEA in NAF of cases and its correlation with NAF estradiol indicates a potentially important role of this steroid in breast cancer risk; however, the negative association of progesterone with risk is tentative.

Exploration of steroidogenesis-related genes in testes, ovaries, adrenals, liver and adipose tissue in pigs

To explore the metabolism of steroids in the pig species, a qualitative PCR analysis was performed for the main transcript of 27 genes involved in steroid metabolism. We compared samples of testes, adipose tissue and liver from immature and peripubertal males, adrenal cortex from peripubertal males, ovaries from cyclic females and adipose tissue from peripubertal females. Some genes were shown to have a tissue-specific expression. Two of them were expressed only in testes, ovaries and adrenals: CYP11A1 and CYP11B. The CYP21 and HSD17B3 genes, were expressed respectively only in adrenals and only in testes. Very few differences were observed between transcriptional patterns of peripubertal testes and adrenal glands as well as between male and female fat tissues. However, the expression of genes involved in the sulfonation of steroids was higher in testes than in adrenals from males. Main differences between ovaries and testes were observed for HSD17B1/2/3, AKR1C-pig6 and sulfotransferase genes (SULT2A1/SULT2B1). The present study shows that the SRD5A2 and CYP21 genes were not involved in the testicular biosynthesis of androstenone. It also shows that porcine adrenal glands produce essentially corticosteroids and that fat tissue is unable to produce de novo steroids.

Systematic evaluation of underlying defects in DNA repair as an approach to case-only assessment of familial prostate cancer

Risk assessment for prostate cancer is challenging due to its genetic heterogeneity. In this study, our goal was to develop an operational framework to select and evaluate gene variants that may contribute to familial prostate cancer risk. Drawing on orthogonal sources, we developed a candidate list of genes relevant to prostate cancer, then analyzed germline exomes from 12 case-only prostate cancer patients from high-risk families to identify patterns of protein-damaging gene variants. We described an average of 5 potentially disruptive variants in each individual and annotated them in the context of public databases representing human variation. Novel damaging variants were found in several genes of relevance to prostate cancer. Almost all patients had variants associated with defects in DNA damage response. Many also had variants linked to androgen signaling. Treatment of primary T-lymphocytes from these prostate cancer patients versus controls with DNA damaging agents showed elevated levels of the DNA double strand break (DSB) marker γH2AX (p < 0.05), supporting the idea of an underlying defect in DNA repair. This work suggests the value of focusing on underlying defects in DNA damage in familial prostate cancer risk assessment and demonstrates an operational framework for exome sequencing in case-only prostate cancer genetic evaluation.

In vitro inhibition of AKR1Cs by sulphonylureas and the structural basis

Recent epidemiological studies show conflicting data for the first-line anti-diabetic sulphonylureas drugs in treating cancer progression in type II diabetes patients. How sulphonylureas promote or diminish tumor growth is not fully understood. Here, we report that seven sulphonylureas exhibit different in vitro inhibition towards AKR1Cs (AKR1C1, AKR1C2, AKR1C3), which are critical steroid hormone metabolism enzymes that are related to prostate cancer, breast cancer and endometrial diseases. Interactions of the sulphonylureas and AKR1Cs were analyzed by X-ray crystallography.

The Steroidogenic Enzyme AKR1C3 Regulates Stability of the Ubiquitin Ligase Siah2 in Prostate Cancer Cells

Re-activation of androgen receptor (AR) activity is the main driver for development of castration-resistant prostate cancer. We previously reported that the ubiquitin ligase Siah2 enhanced AR transcriptional activity and prostate cancer cell growth. Among the genes we found to be regulated by Siah2 was AKR1C3, which encodes a key androgen biosynthetic enzyme implicated in castration-resistant prostate cancer development. Here, we found that Siah2 inhibition in CWR22Rv1 prostate cancer cells decreased AKR1C3 expression as well as intracellular androgen levels, concomitant with inhibition of cell growth in vitro and in orthotopic prostate tumors. Re-expression of either wild-type or catalytically inactive forms of AKR1C3 partially rescued AR activity and growth defects in Siah2 knockdown cells, suggesting a nonenzymatic role for AKR1C3 in these outcomes. Unexpectedly, AKR1C3 re-expression in Siah2 knockdown cells elevated Siah2 protein levels, whereas AKR1C3 knockdown had the opposite effect. We further found that AKR1C3 can bind Siah2 and inhibit its self-ubiquitination and degradation, thereby increasing Siah2 protein levels. We observed parallel expression of Siah2 and AKR1C3 in human prostate cancer tissues. Collectively, our findings identify a new role for AKR1C3 in regulating Siah2 stability and thus enhancing Siah2-dependent regulation of AR activity in prostate cancer cells.

Activation of AKR1C1/ERβ induces apoptosis by downregulation of c-FLIP in prostate cancer cells: A prospective therapeutic opportunity

We provide first-time evidence for ERβ-mediated transcriptional upregulation of c-FLIP as an underlying mechanism in the development of castrate-resistant cancer. While androgens inhibit apoptosis partly through transcriptional upregulation of the anti-apoptotic protein, c-FLIP in androgen-responsive cells, they downregulate c-FLIP in androgen-independent cells. We found that although Sp1 and p65 trans-activate c-FLIP, the combination of Sp1 and p65 has differential effects in a cellular context-dependent manner. We show that activation of the androgen metabolism enzyme, aldo-keto reductase, AKR1C1, relieves androgen independence through activation of 3β-Adiol-mediated upregulation of ERβ. ERβ competes with Sp1 and Sp3 to transcriptionally downregulate c-FLIP in the absence of consensus estrogen-response element in androgen-independent cells. Forced expression of AR in androgen-independent cells show that ERβ-mediated growth inhibition occurs under conditions of androgen independence. Reactivation of ERβ with the estrogenic metabolite, 2-methoxyestradiol, decreased enrichment ratio of Sp1/Sp3 at the c-FLIP promoter with concomitant effects on cell growth and death. Expression of Sp1 and c-FLIP are elevated while AKR1C1, ERβ and Sp3 are significantly low in human prostate tumor samples. ERβ is epigenetically silenced in prostate cancer patients, therefore our results suggest that combination of ERβ agonists with ADT would benefit men stratified on the basis of high estrogen levels.

Modulation of cell metabolic pathways and oxidative stress signaling contribute to acquired melphalan resistance in multiple myeloma cells

Alkylating agents are widely used chemotherapeutics in the treatment of many cancers, including leukemia, lymphoma, multiple myeloma, sarcoma, lung, breast and ovarian cancer. Melphalan is the most commonly used chemotherapeutic agent against multiple myeloma. However, despite a 70-80% initial response rate, virtually all patients eventually relapse due to the emergence of drug-resistant tumour cells. By using global proteomic and transcriptomic profiling on melphalan sensitive and resistant RPMI8226 cell lines followed by functional assays, we discovered changes in cellular processes and pathways not previously associated with melphalan resistance in multiple myeloma cells, including a metabolic switch conforming to the Warburg effect (aerobic glycolysis), and an elevated oxidative stress response mediated by VEGF/IL8-signaling. In addition, up-regulated aldo-keto reductase levels of the AKR1C family involved in prostaglandin synthesis contribute to the resistant phenotype. Finally, selected metabolic and oxidative stress response enzymes were targeted by inhibitors, several of which displayed a selective cytotoxicity against the melphalan-resistant cells and should be further explored to elucidate their potential to overcome melphalan resistance.

Silencing LRH-1 in colon cancer cell lines impairs proliferation and alters gene expression programs

Colorectal cancers (CRCs) account for nearly 10% of all cancer deaths in industrialized countries. Recent evidence points to a central role for the nuclear receptor liver receptor homolog-1 (LRH-1) in intestinal tumorigenesis. Interaction of LRH-1 with the Wnt/β-catenin pathway, highly active in a critical subpopulation of CRC cells, underscores the importance of elucidating LRH-1's role in this disease. Reduction of LRH-1 diminishes tumor burden in murine models of CRC; however, it is not known whether LRH-1 is required for tumorigenesis, for proliferation, or for both. In this work, we address this question through shRNA-mediated silencing of LRH-1 in established CRC cell lines. LRH-1 mRNA knockdown results in significantly impaired proliferation in a cell line highly expressing the receptor and more modest impairment in a cell line with moderate LRH-1 expression. Cell-cycle analysis shows prolongation of G0/G1 with LRH-1 silencing, consistent with LRH-1 cell-cycle influences in other tissues. Cluster analysis of microarray gene expression demonstrates significant genome wide alterations with major effects in cell-cycle regulation, signal transduction, bile acid and cholesterol metabolism, and control of apoptosis. This study demonstrates a critical proproliferative role for LRH-1 in established colon cancer cell lines. LRH-1 exerts its effects via multiple signaling networks. Our results suggest that selected CRC patients could benefit from LRH-1 inhibitors.

Role of Drug Metabolism in the Cytotoxicity and Clinical Efficacy of Anthracyclines

Many clinical studies involving anti-tumor agents neglect to consider how these agents are metabolized within the host and whether the creation of specific metabolites alters drug therapeutic properties or toxic side effects. However, this is not the case for the anthracycline class of chemotherapy drugs. This review describes the various enzymes involved in the one electron (semi-quinone) or two electron (hydroxylation) reduction of anthracyclines, or in their reductive deglycosidation into deoxyaglycones. The effects of these reductions on drug antitumor efficacy and toxic side effects are also discussed. Current evidence suggests that the one electron reduction of anthracyclines augments both their tumor toxicity and their toxicity towards the host, in particular their cardiotoxicity. In contrast, the two electron reduction (hydroxylation) of anthracyclines strongly reduces their ability to kill tumor cells, while augmenting cardiotoxicity through their accumulation within cardiomyocytes and their direct effects on excitation/contraction coupling within the myocytes. The reductive deglycosidation of anthracyclines appears to inactivate the drug and only occurs under rare, anaerobic conditions. This knowledge has resulted in the identification of important new approaches to improve the therapeutic index of anthracyclines, in particular by inhibiting their cardiotoxicity. The true utility of these approaches in the management of cancer patients undergoing anthracycline-based chemotherapy remains unclear, although one such agent (the iron chelator dexrazoxane) has recently been approved for clinical use.

The endometrial cancer cell lines Ishikawa and HEC-1A, and the control cell line HIEEC, differ in expression of estrogen biosynthetic and metabolic genes, and in androstenedione and estrone-sulfate metabolism

Estrogens have important roles in the pathogenesis of endometrial cancer. They can have carcinogenic effects through stimulation of cell proliferation or formation of DNA-damaging species. To characterize model cell lines of endometrial cancer, we determined the expression profiles of the estrogen receptors (ERs) ESR1, ESR2 and GPER, and 23 estrogen biosynthetic and metabolic genes, and investigated estrogen biosynthesis in the control HIEEC cell line and the Ishikawa and HEC-1A EC cell lines. HIEEC and Ishikawa expressed all ERs to different extents, while HEC-1A cells lacked expression of ESR1. Considering the estrogen biosynthetic and metabolic enzymes, these cells showed statistically significant different gene expression profiles for SULT2B1, HSD3B2, CYP19A1, AKR1C3, HSD17B1, HSD17B7, HSD17B12, CYP1B1, CYP3A5, COMT, SULT1A1, GSTP1 and NQO2. In these cells, E2 was formed from E1S and E1, while androstenedione was not converted to estrogens. HIEEC and Ishikawa had similar profiles of androstenedione and E1 metabolism, but hydrolysis of E1S to E1 was weaker in Ishikawa cells. HEC-1A cells were less efficient for activation of E1 into the potent E2, but metabolized androstenedione to other androgenic metabolites better than HIEEC and Ishikawa cells. This study reveals that HIEEC, Ishikawa, and HEC-1A cells can all form estrogens only via the sulfatase pathway. HIEEC, Ishikawa, and HEC-1A cells expressed all the major genes in the production of hydroxyestrogens and estrogen quinones, and in their conjugation. Significantly higher CYP1B1 mRNA levels in Ishikawa cells compared to HEC-1A cells, together with lack of UGT2B7 expression, indicate that Ishikawa cells can accumulate more toxic estrogen-3,4-quinones than HEC-1A cells, as also for HIEEC cells. This study provides further characterization of HIEEC, Ishikawa, and HEC-1A cells, and shows that they differ greatly in expression of the genes investigated and in their capacity for E2 formation, and thus they represent different in vitro models.

Important roles of the AKR1C2 and SRD5A1 enzymes in progesterone metabolism in endometrial cancer model cell lines

Endometrial cancer is the most frequently diagnosed gynecological malignancy. It is associated with prolonged exposure to estrogens that is unopposed by progesterone, whereby enhanced metabolism of progesterone may decrease its protective effects, as it can deprive progesterone receptors of their active ligand. Furthermore, the 5α-pregnane metabolites formed can stimulate proliferation and may thus contribute to carcinogenesis. The aims of our study were to: (1) identify and quantify progesterone metabolites formed in the HEC-1A and Ishikawa model cell lines of endometrial cancer; and (2) pinpoint the enzymes involved in progesterone metabolism, and delineate their roles. Progesterone metabolism studies combined with liquid chromatography-tandem mass spectrometry enabled identification and quantification of the metabolites formed in these cells. Further quantitative PCR analysis and small-interfering-RNA-mediated gene silencing identified individual progesterone metabolizing enzymes and their relevant roles. In Ishikawa and HEC-1A cells, progesterone was metabolized mainly to 20α-hydroxy-pregn-4-ene-3-one, 20α-hydroxy-5α-pregnane-3-one, and 5α-pregnane-3α/β,20α-diol. The major difference between these cell lines was rate of progesterone metabolism, which was faster in HEC-1A cells. In the Ishikawa and HEC-1A cells, expression of AKR1C2 was 110-fold and 6800-fold greater, respectively, than expression of AKR1C1, which suggests that 20-ketosteroid reduction of 5α-pregnanes and 4-pregnenes is catalyzed mainly by AKR1C2. AKR1C1/AKR1C2 gene silencing showed decreased progesterone metabolism in both cell lines, thus further supporting the significant role of AKR1C2. SRD5A1 was also expressed in these cells, and its silencing confirmed that 5α-reduction is catalyzed by 5α-reductase type 1. Silencing of SRD5A1 also had the most pronounced effects, with decreased rate of progesterone metabolism, and consequently higher concentrations of unmetabolized progesterone. Our data confirm that in model cell lines of endometrial cancer, AKR1C2 and SRD5A1 have crucial roles in progesterone metabolism, and may represent novel targets for treatment.

Ruthenium complexes as inhibitors of the aldo-keto reductases AKR1C1-1C3

The human aldo-keto reductases (AKRs) from the 1C subfamily are important targets for the development of new drugs. In this study, we have investigated the possible interactions between the recombinant AKR1C enzymes AKR1C1-AKR1C3 and ruthenium(II) complexes; in particular, we were interested in the potential inhibitory actions. Five novel ruthenium complexes (1a, 1b, 2a, 2b, 2c), two precursor ruthenium compounds (P1, P2), and three ligands (a, b, c) were prepared and included in this study. Two different types of novel ruthenium(II) complexes were synthesized. First, bearing the sulphur macrocycle [9]aneS3, S-bonded dimethylsulphoxide (dmso-S), and an N,N-donor ligand, with the general formula of [Ru([9]aneS3)(dmso)(N,N-ligand)](PF6)2 (1a, 1b), and second, with the general formula of [(η(6)-p-cymene)RuCl(N,N-ligand)]Cl (2a, 2b, 2c). All of these synthesized compounds were characterized by high-resolution NMR spectroscopy, X-ray crystallography (compounds a, b, c, 1a, 1b) and other standard physicochemical methods. To evaluate the potential inhibitory actions of these compounds on the AKR1C enzymes, we followed enzymatically catalyzed oxidation of the substrate 1-acenaphthenol by NAD(+) in the absence and presence of various micromolar concentrations of the individual compounds. Among 10 compounds, one ruthenium complex (2b) and two precursor ruthenium compounds (P1, P2) inhibited all three AKR1C enzymes, and one ruthenium complex (2a) inhibited only AKR1C3. Ligands a, b and c revealed no inhibition of the AKR1C enzymes. All four of the active compounds showed multiple binding with the AKR1C enzymes that was characterized by an initial instantaneous inhibition followed by a slow quasi-irreversible step. To the best of our knowledge, this is the first study that has examined interactions between these AKR1C enzymes and ruthenium(II) complexes.

Isoquinoline alkaloids as a novel type of AKR1C3 inhibitors

AKR1C3 is an important human enzyme that participates in the reduction of steroids and prostaglandins, which leads to proliferative signalling. In addition, this enzyme also participates in the biotransformation of xenobiotics, such as drugs and procarcinogens. AKR1C3 is involved in the development of both hormone-dependent and hormone-independent cancers and was recently demonstrated to confer cell resistance to anthracyclines. Because AKR1C3 is frequently upregulated in various cancers, this enzyme has been suggested as a therapeutic target for the treatment of these pathological conditions. In this study, nineteen isoquinoline alkaloids were examined for their ability to inhibit a recombinant AKR1C3 enzyme. As a result, stylopine was demonstrated to be the most potent inhibitor among the tested compounds and exhibited moderate selectivity towards AKR1C3. In the follow-up cellular studies, stylopine significantly inhibited the AKR1C3-mediated reduction of daunorubicin in intact cells without considerable cytotoxic effects. This inhibitor could therefore be used as a model AKR1C3 inhibitor in research or evaluated as a possible therapeutic anticancer drug. Furthermore, based on our results, stylopine can serve as a model compound for the design and future development of structurally related AKR1C3 inhibitors.

Synthesis of non-prenyl analogues of baccharin as selective and potent inhibitors for aldo-keto reductase 1C3

Inhibitors of a human member (AKR1C3) of the aldo-keto reductase superfamily are regarded as promising therapeutics for the treatment of prostatic and breast cancers. Baccharin [3-prenyl-4-(dihydrocinnamoyloxy)cinnamic acid], a component of propolis, was shown to be both potent (Ki 56 nM) and highly isoform-selective inhibitor of AKR1C3. In this study, a series of derivatives of baccharin were synthesized by replacing the 3-prenyl moiety with aryl and alkyl ether moieties, and their inhibitory activities for the enzyme were evaluated. Among them, two benzyl ether derivatives, 6m and 6n, showed an equivalent inhibitory potency to baccharin. The molecular docking of 6m in AKR1C3 has allowed the design and synthesis of (E)-3-{3-[(3-hydroxybenzyl)oxy]-4-[(3-phenylpropanoyl)oxy]phenyl}acrylic acid (14) with improved potency (Ki 6.4 nM) and selectivity comparable to baccharin. Additionally, 14 significantly decreased the cellular metabolism of androsterone and cytotoxic 4-oxo-2-nonenal by AKR1C3 at much lower concentrations than baccharin.

Androgen biosynthesis in castration-resistant prostate cancer

Prostate cancer is the second leading cause of death in adult males in the USA. Recent advances have revealed that the fatal form of this cancer, known as castration-resistant prostate cancer (CRPC), remains hormonally driven despite castrate levels of circulating androgens. CRPC arises as the tumor undergoes adaptation to low levels of androgens by either synthesizing its own androgens (intratumoral androgens) or altering the androgen receptor (AR). This article reviews the major routes to testosterone and dihydrotestosterone synthesis in CRPC cells and examines the enzyme targets and progress in the development of isoform-specific inhibitors that could block intratumoral androgen biosynthesis. Because redundancy exists in these pathways, it is likely that inhibition of a single pathway will lead to upregulation of another so that drug resistance would be anticipated. Drugs that target multiple pathways or bifunctional agents that block intratumoral androgen biosynthesis and antagonize the AR offer the most promise. Optimal use of enzyme inhibitors or AR antagonists to ensure maximal benefits to CRPC patients will also require application of precision molecular medicine to determine whether a tumor in a particular patient will be responsive to these treatments either alone or in combination.

Canonical androstenedione reduction is the predominant source of signaling androgens in hormone-refractory prostate cancer

PURPOSE

It has been recognized for almost a decade that concentrations of signaling androgens sufficient to activate the androgen receptor are present in castration-resistant prostate cancer tissue. The source of these androgens is highly controversial, with three competing models proposed. We, therefore, wished to determine the androgenic potential of human benign and malignant (hormone-naïve and treated) prostate tissue when incubated with various precursors and examine concomitant changes in enzyme expression.

EXPERIMENTAL DESIGN

Freshly harvested prostate tissue [benign, hormone-naïve, and hormone-refractory prostate cancer (HRPC)] was incubated in excess concentrations of cholesterol, progesterone, DHEA, androstenedione, or testosterone for 96 hours, and steroid concentrations in the conditioned media measured by gas chromatography-mass spectroscopy. Changes in the expression of androgen synthetic and/or degradative enzymes were determined by expression microarray and qPCR. Significant changes were confirmed in an independent dataset.

RESULTS

Of the precursor molecules tested, only incubation with androstenedione gave rise to significant concentrations of signaling androgens. Although this was observed in all tissue types, it occurred to a significantly greater degree in hormone-refractory compared with hormone-naïve cancer. Consistent with this, gene set enrichment analysis of the expression microarray data revealed significant upregulation of 17HSD17B activity, with overexpression of the canonical enzyme AKR1C3 confirmed by qPCR in the same samples and in a publicly available expression dataset. Importantly, we found no evidence to support a significant contribution from either the "backdoor" or "5-α dione" pathway.

CONCLUSIONS

Reduction of androstenedione to testosterone by the canonical HSD17B AKR1C3 is the predominant source of signaling androgens in HRPC.

Selective AKR1C3 inhibitors do not recapitulate the anti-leukaemic activities of the pan-AKR1C inhibitor medroxyprogesterone acetate

Background:

We and others have identified the aldo-keto reductase AKR1C3 as a potential drug target in prostate cancer, breast cancer and leukaemia. As a consequence, significant effort is being invested in the development of AKR1C3-selective inhibitors.

Methods:

We report the screening of an in-house drug library to identify known drugs that selectively inhibit AKR1C3 over the closely related isoforms AKR1C1, 1C2 and 1C4. This screen initially identified tetracycline as a potential AKR1C3-selective inhibitor. However, mass spectrometry and nuclear magnetic resonance studies identified that the active agent was a novel breakdown product (4-methyl(de-dimethylamine)-tetracycline (4-MDDT)).

Results:

We demonstrate that, although 4-MDDT enters AML cells and inhibits their AKR1C3 activity, it does not recapitulate the anti-leukaemic actions of the pan-AKR1C inhibitor medroxyprogesterone acetate (MPA). Screens of the NCI diversity set and an independently curated small-molecule library identified several additional AKR1C3-selective inhibitors, none of which had the expected anti-leukaemic activity. However, a pan AKR1C, also identified in the NCI diversity set faithfully recapitulated the actions of MPA.

Conclusions:

In summary, we have identified a novel tetracycline-derived product that provides an excellent lead structure with proven drug-like qualities for the development of AKR1C3 inhibitors. However, our findings suggest that, at least in leukaemia, selective inhibition of AKR1C3 is insufficient to elicit an anticancer effect and that multiple AKR1C inhibition may be required.