Aldo-keto reductase (AKR) 1C3: role in prostate disease and the development of specific inhibitors

Involvement of porcine and human carbonyl reductases in the metabolism of epiandrosterone, 11-oxygenated steroids, neurosteroids, and corticosteroids

Porcine carbonyl reductases (pCBR1 and pCBR-N1) and aldo-keto reductases (pAKR1C1 and pAKR1C4) exhibit hydroxysteroid dehydrogenase (HSD) activity. However, their roles in the metabolism of porcine-specific androgens (19-nortestosterone and epiandrosterone), 11-oxygenated androgens, neurosteroids, and corticosteroids remain unclear. Here, we compared the steroid specificity of the four recombinant enzymes by kinetic and product analyses. In C18/C19-steroids,11-keto- and 11β-hydroxy-5α-androstane-3,17-diones were reduced by all the enzymes, whereas 5α-dihydronandrolone (19-nortestosterone metabolite) and 11-ketodihydrotestosterone were reduced by pCBR1, pCBR-N1, and pAKR1C1, of which pCBR1 exhibited the lowest (submicromolar) Km values. Product analysis showed that pCBR1 and pCBR-N1 function as 3α/β-HSDs, in contrast to pAKR1C1 and pAKR1C4 (acting as 3β-HSD and 3α-HSD, respectively). Additionally, 17β-HSD activity was observed in pCBR1 and pCBR-N1 (toward epiandrosterone and its 11-oxygenated derivatives) and in pAKR1C1 (toward androsterone, 4-androstene-3,17-dione and their 11-oxygenated derivatives). The four enzymes also showed different substrate specificity for 3-keto-5α/β-dihydro-C21-steroids, including GABAergic neurosteroid precursors and corticosteroid metabolites. 5β-Dihydroprogesterone was reduced by all the enzymes, whereas 5α-dihydroprogesterone was reduced only by pCBR1, and 5α/β-dihydrodeoxycorticosterones by pCBR1 and pCBR-N1. The two pCBRs also reduced the 5α/β-dihydro-metabolites of cortisol, 11-deoxycortisol, cortisone, and corticosterone. pCBR1 exhibited lower Km values (0.3-2.9 μM) for the 3-keto-C21-steroids than pCBR-N1 (Km=10-36 μM). The reduced products of the 3-keto-C21-steroids by pCBR1 and pCBR-N1 were their 3α-hydroxy-metabolites. Finally, we found that human CBR1 has similar substrate specificity for the C18/C19/C21-steroids to pCBR-N1. Based on these results, it was concluded that porcine and human CBRs can be involved in the metabolism of the aforementioned steroids as 3α/β,17β-HSDs.

Development of new steroid-based hydrazide and (thio)semicarbazone compounds with anticancer properties

Most breast and prostate cancers are caused by abnormal production or action of steroidal hormones. Hormonal drugs based on steroid scaffolds represent a significant class of chemotherapeutics that are routinely used in chemotherapy. In this study, the synthesis of new 17a-homo lactone and 17α-(pyridine-2-ylmethyl) androstane derivatives with hydrazide and semicarbazone motifs is presented. All compounds were screened for their effect on cell viability against a panel of five cancer cell lines and one healthy cell line. Two compounds showed significant cytotoxicity against cancer cells, with low toxicity against healthy cells. The relative binding affinities of compounds for the ligand-binding domains of estrogen receptor α, estrogen receptor β, androgen receptor and glucocorticoid receptor were tested using a fluorescence screen in yeast. Potential for inhibition of aldo-keto reductase 1C3 and 1C4 activity was measured in vitro. Experimental results are analyzed in the context of molecular docking simulations. Our results could help guide design of steroid compounds with improved anticancer properties against androgen- and estrogen-dependent cancers.

Pregnane X receptor (PXR) deficiency promotes hepatocarcinogenesis via induction of Akr1c18 expression and prostaglandin F2α (PGF2α) levels

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Pregnane X receptor (PXR), a xenobiotic-sensing nuclear receptor, plays a critical role in the metabolism of endogenous and exogenous substances in the liver. Here, we investigate whether PXR plays a role in pathogenesis of HCC. We show that liver tumors were developed in diethylnitrosamine (DEN)-treated in PXR knockout (KO) mice. Hepatic levels of prostaglandin F2α (PGF2α) and aldo-keto reductase family 1 member C18 (Akr1c18), a prostaglandin synthase of catalyzing reduction of PGH2 to PGF2α, were significantly elevated in DEN-treated PXR KO mice. Hepatic mRNA levels of alpha fetoprotein (AFP), cyclin D1 (Ccnd1), fibroblast growth factor 21 (FGF21), and inflammatory cytokine interleukin 6 (IL-6) were significantly increased in DEN-treated PXR KO mice. Other members of Akr1c family, liver metabolizing enzymes including Cyp1a2, Cyp2b10 and Cyp3a11, and bile acid synthesis enzyme Cyp7a1 mRNA levels were significantly decreased in DEN-treated PXR KO mice. Our findings revealed that PXR deficiency promoted DEN-induced HCC in mice via induction of Akr1c18 expression and PGF2α levels and the increased PGF2α levels synthetized by Akr1c18 enhanced hepatocytes proliferation and induced inflammatory cytokine production, which accelerated liver tumor development after DEN treatment, suggesting that PXR deficiency may create a microenvironment that is more prone to DEN-induced liver tumors and targeting PXR and Akr1c18 to reduce PGF2α biosynthesis may be a potential and novel therapeutic strategy for HCC.

AKR1C3 in carcinomas: from multifaceted roles to therapeutic strategies

Aldo-Keto Reductase Family 1 Member C3 (AKR1C3), also known as type 5 17β-hydroxysteroid dehydrogenase (17β-HSD5) or prostaglandin F (PGF) synthase, functions as a pivotal enzyme in androgen biosynthesis. It catalyzes the conversion of weak androgens, estrone (a weak estrogen), and PGD2 into potent androgens (testosterone and 5α-dihydrotestosterone), 17β-estradiol (a potent estrogen), and 11β-PGF2α, respectively. Elevated levels of AKR1C3 activate androgen receptor (AR) signaling pathway, contributing to tumor recurrence and imparting resistance to cancer therapies. The overexpression of AKR1C3 serves as an oncogenic factor, promoting carcinoma cell proliferation, invasion, and metastasis, and is correlated with unfavorable prognosis and overall survival in carcinoma patients. Inhibiting AKR1C3 has demonstrated potent efficacy in suppressing tumor progression and overcoming treatment resistance. As a result, the development and design of AKR1C3 inhibitors have garnered increasing interest among researchers, with significant progress witnessed in recent years. Novel AKR1C3 inhibitors, including natural products and analogues of existing drugs designed based on their structures and frameworks, continue to be discovered and developed in laboratories worldwide. The AKR1C3 enzyme has emerged as a key player in carcinoma progression and therapeutic resistance, posing challenges in cancer treatment. This review aims to provide a comprehensive analysis of AKR1C3's role in carcinoma development, its implications in therapeutic resistance, and recent advancements in the development of AKR1C3 inhibitors for tumor therapies.

Inhibition of aldo-keto reductase 1C3 overcomes gemcitabine/cisplatin resistance in bladder cancer

Systemic chemotherapy with gemcitabine and cisplatin (GC) has been used for the treatment of bladder cancer in which androgen receptor (AR) signaling is suggested to play a critical role. However, its efficacy is often limited, and the prognosis of patients who develop resistance is extremely poor. Aldo-keto reductase 1C3 (AKR1C3), which is responsible for the production of a potent androgen, 5α-dihydrotestosterone (DHT), by the reduction of 5α-androstane-3α,17β-dione (5α-Adione), has been attracting attention as a therapeutic target for prostate cancer that shows androgen-dependent growth. By contrast, the role of AKR1C3 in bladder cancer remains unclear. In this study, we examined the effect of an AKR1C3 inhibitor on androgen-dependent proliferation and GC sensitivity in bladder cancer cells. 5α-Adione treatment induced the expression of AR and its downstream factor ETS-domain transcription factor (ELK1) in both T24 cells and newly established GC-resistant T24GC cells, while it did not alter AKR1C3 expression. AKR1C3 inhibitor 2j significantly suppressed 5α-Adione-induced AR and ELK1 upregulation, as did an AR antagonist apalutamide. Moreover, the combination of GC and 2j in T24GC significantly induced apoptotic cell death, suggesting that 2j could enhance GC sensitivity. Immunohistochemical staining in surgical specimens further revealed that strong expression of AKR1C3 was associated with significantly higher risks of tumor progression and cancer-specific mortality in patients with muscle-invasive bladder cancer. These results suggest that AKR1C3 inhibitors as adjunctive agents enhance the efficacy of GC therapy for bladder cancer.

Development of highly potent and specific AKR1C3 inhibitors to restore the chemosensitivity of drug-resistant breast cancer

Aldo-keto reductase 1C3 (AKR1C3) is overexpressed in multiple hormone related cancers, such as breast and prostate cancer, and is correlated with tumor development and aggressiveness. As a phase I biotransformation enzyme, AKR1C3 catalyzes the metabolic processes that lead to resistance to anthracyclines, the "gold standard" for breast cancer treatment. Novel approaches to restore the chemotherapy sensitivity of breast cancer are urgently required. Herein, we developed a new class of AKR1C3 inhibitors that demonstrated potent inhibitory activity and exquisite selectivity for closely related isoforms. The best derivative 27 (S19-1035) exhibits an IC₅₀ value of 3.04 nM for AKR1C3 and >3289-fold selectivity over other isoforms. We determined the co-crystal structures of AKR1C3 with three of the inhibitors, providing a solid foundation for further structure-based drug optimization. Co-administration of these AKR1C3 inhibitors significantly reversed the doxorubicin (DOX) resistance in a resistant breast cancer cell line. Therefore, the novel AKR1C3 specific inhibitors developed in this work may serve as effective adjuvants to overcome DOX resistance in breast cancer treatment.

Steroidogenesis in castration-resistant prostate cancer

Castration resistance is in part attributable to aberrant activation of androgen receptor (AR) signaling by the intracrine activation of androgen precursors derived from adrenal glands. To overcome this, novel AR pathway inhibitors (ARPIs) that suppress androgen synthesis by CYP17 inhibition or AR activation by antiandrogen effects have been developed. However, primary or acquired resistance to these ARPIs occurs; in turn attributable, at least in part, to the maintained androgen milieu despite intensive suppression of AR signaling similar to castration resistance. In addition to the classical pathway to produce potent androgens such as testosterone and dihydrotestosterone, the alternative pathway and the backdoor pathway which bypasses testosterone to produce dihydrotestosterone have been shown to play a role in intratumor steroidogenesis. Furthermore, the 11β-hydroxyandrostenedione pathway to produce the potent oxygenated androgens 11-ketotestosterone and 11-ketodihydrotestosterone has been suggested to be functional in prostate cancer. These steroidogenesis pathways produce potent androgens that promote tumor resistance to endocrine therapy including novel ARPIs. Here, we overview the current evidence on the pathological androgen milieu by altered metabolism and transport in prostate cancer, leading to resistance to endocrine therapy.

Preclinical and Clinical Research Models of Prostate Cancer: A Brief Overview

The incidence and mortality from prostate cancer (PCa) are on the rise which poses a major public health concern worldwide. In this narrative review, we have summarized the characteristics of major in vitro and in vivo PCa models including their utility in developing treatment strategies. Androgens, particularly, testosterone and dihydrotestosterone (DHT) activate the androgen receptor (AR) signaling pathway that facilitates the development and progression of castration resistant PCa. Several enzymes namely, CYP17A1, HSD17B, and SRD5A are essential to furnishing DHT from dehydroepiandrosterone in the classical pathway while DHT is formed from androstanediol in the backdoor pathway. The advancement in delineating the molecular heterogeneity of PCa has been possible through the development of several in vitro and in vivo research models. Generally, tissue culture models are advantageous to understand PCa biology and investigate the efficacy and toxicity of novel agents; nevertheless, animal models are indispensable to studying the PCa etiology and treatment since they can simulate the tumor microenvironment that plays a central role in initiation and progression of the disease. Moreover, the availability of several genetically engineered mouse models has made it possible to study the metastasis process. However, the conventional models are not devoid of limitations. For example, the lack of heterogeneity in tissue culture models and the variation of metastatic characteristics in xenograft models are obviously challenging. Additionally, due to the racial and ethnic disparities in PCa pathophysiology, a new model that can represent PCa encompassing different ethnicities is urgently needed. New models should continue to evolve to address the genetic and molecular complexities as well as to further elucidate the finer details of the steroidogenic pathway associated with PCa.

Prognostic significance of AKR1C4 and the advantage of combining EBV DNA to stratify patients at high risk of locoregional recurrence of nasopharyngeal carcinoma

Background

Distinguishing patients at a greater risk of recurrence is essential for treating locoregional advanced nasopharyngeal carcinoma (NPC). This study aimed to explore the potential of aldo–keto reductase 1C4 (AKR1C4) in stratifying patients at high risk of locoregional relapse.

Methods

A total of 179 patients with locoregionally advanced NPC were grouped by different strategies; they were: (a) divided into two groups according to AKR1C4 expression level, and (b) classified into three clusters by integrating AKR1C4 and Epstein-Barr virus (EBV) DNA. The Kaplan–Meier method was used to calculate locoregional relapse-free survival (LRFS), overall survival (OS), progression-free survival (PFS), and distant metastasis-free survival (DMFS). The Cox proportional hazards model was used to determine potential prognostic factors, and a nomogram was generated to predict 3-year and 5-year LRFS.

Results

A significant difference in the 5-year LRFS was observed between the high and low AKR1C4 expression groups (83.3% vs. 92.7%, respectively; p = 0.009). After integrating AKR1C4 expression and EBV DNA, the LRFS (84.7%, 84.5%, 96.9%, p = 0.014) of high-, intermediate-, and low- AKR1C4 and EBV DNA was also significant. Multivariate analysis indicated that AKR1C4 expression (p = 0.006) was an independent prognostic factor for LRFS. The prognostic factors incorporated into the nomogram were AKR1C4 expression, T stage, and EBV DNA, and the concordance index of the nomogram for locoregional relapse was 0.718.

Conclusions

In conclusion, high AKR1C4 expression was associated with a high possibility of relapse in NPC patients, and integrating EBV DNA and AKR1C4 can stratify high-risk patients with locoregional recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09924-3.

Analogues of Natural Chalcones as Efficient Inhibitors of AKR1C3

Naturally occurring substances are valuable resources for drug development. In this respect, chalcones are known to be antiproliferative agents against prostate cancer cell lines through various mechanisms or targets. Based on the literature and preliminary results, we aimed to study and optimise the efficiency of a series of chalcones to inhibit androgen-converting AKR1C3, known to promote prostate cancer. A total of 12 chalcones with different substitution patterns were synthesised. Structure-activity relationships associated with these modifications on AKR1C3 inhibition were analysed by performing enzymatic assays and docking simulations. In addition, the selectivity and cytotoxicity of the compounds were assessed. In enzymatic assays, C-6' hydroxylated derivatives were more active than C-6' methoxylated derivatives. In contrast, C-4 methylation increased activity over C-4 hydroxylation. Docking results supported these findings with the most active compounds fitting nicely in the binding site and exhibiting strong interactions with key amino acid residues. The most effective inhibitors were not cytotoxic for HEK293T cells and selective for 17β-hydroxysteroid dehydrogenases not primarily involved in steroid hormone metabolism. Nevertheless, they inhibited several enzymes of the steroid metabolism pathways. Favourable substitutions that enhanced AKR1C3 inhibition of chalcones were identified. This study paves the way to further develop compounds from this series or related flavonoids with improved inhibitory activity against AKR1C3.

Downregulation of Dihydrotestosterone and Estradiol Levels by HEXIM1

We have previously reported that hexamethylene bis-acetamide inducible protein 1 (HEXIM1) inhibits the activity of ligand-bound estrogen receptor α (ERα) and the androgen receptor (AR) by disrupting the interaction between these receptors and positive transcriptional elongation factor b (P-TEFb) and attenuating RNA polymerase II (RNAPII) phosphorylation at serine 2. Functional consequences of the inhibition of transcriptional activity of ERα and AR by HEXIM1 include the inhibition of ERα- and AR-dependent gene expression, respectively, and the resulting attenuation of breast cancer (BCa) and prostate cancer (PCa) cell proliferation and growth. In our present study, we determined that HEXIM1 inhibited AKR1C3 expression in BCa and PCa cells. AKR1C3, also known as 17β-hydroxysteroid dehydrogenase (17β-HSD) type 5, is a key enzyme involved in the synthesis of 17β-estradiol (E2) and 5-dihydrotestosterone (DHT). Downregulation of AKR1C3 by HEXIM1 influenced E2 and DHT production, estrogen- and androgen-dependent gene expression, and cell proliferation. Our studies indicate that HEXIM1 has the unique ability to inhibit both the transcriptional activity of the ER and AR and the synthesis of the endogenous ligands of these receptors.

Regulatory genes in the androgen production, uptake and conversion (APUC) pathway in advanced prostate cancer

The androgen receptor (AR) signaling pathway regulates the progression of prostate cancer (PC). Metastatic castration-resistant prostate cancer (mCRPC) patients generally receive AR-targeted therapies (ART) or androgen-deprivation therapies (ADT) with the initial response; however, resistance is inevitably observed. Prior studies have shown activity and upregulation of a family of androgen production, uptake, and conversion - APUC genes - based on genomic analyses of patient germlines. Genetic variants of some APUC genes, such as the conversion gene, HSD3B1, predict response to second-generation androgen-targeted therapies. Studies have begun to elucidate the overall role of APUC genes, each with unique actionable enzymatic activity, in mCRPC patient outcomes. The current role and knowledge of the genetic and genomic features of APUC genes in advanced prostate cancer and beyond are discussed in this review. These studies inform of how interpreting behavior of APUC genes through genomic tools will impact the treatment of advanced prostate cancer.

The interference effects of bisphenol A on the synthesis of steroid hormones in human ovarian granulosa cells

Numerous studies have shown that endocrine-disrupting chemicals are one of the important pathogenic factors in women with polycystic ovary syndrome. Our previous study has revealed that bisphenol A (BPA) can cause steroid hormone imbalance, polycystic ovary, and estrus cycle disorder. In this study, we aimed to explore the effect of BPA, a typical environmental estrogen, on the synthesis of steroid hormones in human ovarian granulosa KGN cells. Exposure of KGN cells to BPA (0.5, 5, 50, and 500 μg/L) resulted in the decrease of progesterone (P), estradiol (E2), and the ratio of estradiol to testosterone (E2/T). BPA affected the expression of genes related to steroid hormone synthesis in KGN cells, including the decreased expression of the steroidogenic acute regulatory protein, ferredoxin, and ferredoxin reductase genes during progesterone synthesis; upregulating the expression of cytochrome p450 oxidoreductase gene associated with E2 and T synthesis; and the downregulated cytochrome P450 family 1 subfamily A member 1 and cytochrome P450 family 1 subfamily B member 1 in E2 degradation. BPA also reduced the expression of stimulatory G proteins (GS) in follicle-stimulating hormone receptor (FSHR)/GS/adenylate cyclase (AC) signaling pathway. In summary, our research has demonstrated that environment-relevant level of BPA exposure leads to steroid hormone synthesis disorder in human ovarian granulosa cells, which might cause the reduction of gene expression in hormone synthesis and the suppression of the FSHR/GS/AC signaling pathway.

The prostaglandin synthases, COX-2 and L-PGDS, mediate prostate hyperplasia induced by low-dose bisphenol A

This study aimed to identify prostaglandin synthases (PGS) that mediate bisphenol A (BPA)-induced prostatic hyperplasia and explore their underlying mechanisms. In an in vivo study, male adult Sprague–Dawley rats were treated with different concentrations of BPA (10, 30, 90, or 270 μg/kg, i.g., daily), or with vehicle for 4 weeks. Results revealed that low-dose BPA induced prostatic hyperplasia with increased PCNA/TUNEL ratio. It significantly upregulated the expression of cyclooxygenase-2 (COX-2) and NF-κB in the dorsolateral prostate (P < 0.05) and the expression of lipocalin-type prostaglandin D synthase (L-PGDS) in ventral prostate (P < 0.05). The level of estradiol (E₂)/testosterone (T) and expression of androgen receptor (AR) and estrogen receptor α (ERα) were also altered. In vitro studies showed that low-dose BPA (0.1–10 nM) promoted the proliferation of human prostate fibroblasts and epithelial cells, and significantly upregulated the expression of COX-2 and L-PGDS in the cells. The two types of cell proliferation induced by BPA were inhibited by COX-2 inhibitor (NS398) and L-PGDS inhibitor (AT56), with increased apoptosis level. These findings suggested that COX-2 and L-PGDS could mediate low-dose BPA-induced prostatic hyperplasia through pathways involved in cell proliferation and apoptosis, which might be related to the functions of ERα and AR. The role of COX-2/NF-κB pathway in dorsolateral prostate requires further research.

Overview of AKR1C3: Inhibitor Achievements and Disease Insights

Human aldo-keto reductase family 1 member C3 (AKR1C3) is known as a hormone activity regulator and prostaglandin F (PGF) synthase that regulates the occupancy of hormone receptors and cell proliferation. Because of the overexpression in metabolic diseases and various hormone-dependent and -independent carcinomas, as well as the emergence of clinical drug resistance, an increasing number of studies have investigated AKR1C3 inhibitors. Here, we briefly review the physiological and pathological function of AKR1C3 and then summarize the recent development of selective AKR1C3 inhibitors. We propose our viewpoints on the current problems associated with AKR1C3 inhibitors with the aim of providing a reference for future drug discovery and potential therapeutic perspectives on novel, potent, selective AKR1C3 inhibitors.

Decreased biochemical progression in patients with castration-resistant prostate cancer using a novel mefenamic acid anti-inflammatory therapy: A randomized controlled trial

Prostate cancer (PCa) is the second most common non-dermatological cancer in men and is a growing public health problem. Castration-resistant disease (CRD) is the most advanced stage of the disease and is difficult to control. Patients with CRD may no longer accept conventional therapies as they are not in appropriate clinical conditions or they refuse to receive it. Given that inflammation is an essential component of CRD origin and progression, anti-inflammatory agents could be a therapeutic option with fenamates as one of the proposed choices. A prospective, randomized, double-blinded, 2-arm, parallel group, phase II-III clinical trial was performed involving 20 patients with CRD-PCa (with a prostate specific antigen level <100 ng/ml) that were undergoing androgen deprivation therapy (ADT) and did not accept any established treatment for that disease stage. In addition to ADT, 10 patients received placebo and 10 received mefenamic acid (500 mg orally every 12 h) for 6 months. The primary endpoint was the change in serum prostate-specific antigen (PSA) at 6 months. The PSA levels decreased significantly with mefenamic acid (an average 42% decrease), whereas there was an average 55% increase in the placebo group (P=0.024). In the patients treated with the placebo, 70% had biochemical disease progression (an increase of ≥25% in PSA levels), which did not occur in any of the patients treated with mefenamic acid (relative risk=0.12; 95% confidence interval, 0.01-0.85; P=0.033). There was a significant increase in quality of life (EQ-5D-5L score) and body mass index (BMI) with the experimental treatment. In conclusion, mefenamic acid administration decreased biochemical progression in patients with castration resistant PCa, improved their quality of life and increased their BMI. Future studies are required in order to strengthen the findings of the present clinical trial. Trial registration, Cuban Public Registry of Clinical Trials Database RPCEC00000248, August 2017.

Human dehydrogenase/reductase SDR family member 11 (DHRS11) and aldo-keto reductase 1C isoforms in comparison: Substrate and reaction specificity in the reduction of 11-keto-C19-steroids

Recent studies have shown that an adrenal steroid 11β-hydroxy-4-androstene-3,17-dione serves as the precursor to androgens, 11-ketotestosterone and 11-ketodihydrotestosterone (11KDHT). The biosynthetic pathways include the reduction of 3- and 17-keto groups of the androgen precursors 11-keto-C₁₉-steroids, which has been reported to be mediated by three human enzymes; aldo-keto reductase (AKR)1C2, AKR1C3 and 17β-hydroxysteroid dehydrogenase (HSD) type-3. To explore the contribution of the enzymes in the reductive metabolism, we kinetically compared the substrate specificity for 11-keto-C₁₉-steroids among purified recombinant preparations of four AKRs (1C1, 1C2,1C3 and 1C4) and DHRS11, which shows 17β-HSD activity. Although AKR1C1 did not reduce the 11-keto-C₁₉-steroids, AKR1C3 and DHRS11 reduced 17-keto groups of 11-keto-4-androstene-3,17-dione, 11-keto-5α-androstane-3,17-dione (11K-Adione) and 11-ketoandrosterone with K_m values of 5-28 μM. The 3-keto groups of 11KDHT and 11K-Adione were reduced by AKR1C4 (K_m 1 μM) more efficiently than by AKR1C2 (K_m 5 and 8 μM, respectively). GC/MS analysis of the products showed that DHRS11 acts as 17β-HSD, and that AKR1C2 and AKR1C4 are predominantly 3α-HSDs, but formed a minor 3β-metabolite from 11KDHT. Since DHRS11 was thus newly identified as 11-keto-C₁₉-steroid reductase, we also investigated its substrate-binding mode by molecular docking and site-directed mutagenesis of Thr163 and Val200, and found the following structural features: 1). There is a space that accommodates the 11-keto group of the 11-keto-C₁₉-steroids in the substrate-binding site. 2) Val200 is a critical determinant for exhibiting the strict 17β-HSD activity of the enzyme, because the Val200Leu mutation resulted in both significant impairment of the 17β-HSD activity and emergence of 3β-HSD activity towards 5α-androstanes including 11KDHT.

Aldo-keto reductase 1C3-Assessment as a new target for the treatment of endometriosis

Endometriosis is a common gynecological disorder, which is treated surgically and/ or pharmacologically with an unmet clinical need for new therapeutics. A completed phase I trial and a recent phase II trial that investigated the steroidal aldo-keto reductase 1C3 (AKR1C3) inhibitor BAY1128688 in endometriosis patients prompted this critical assessment on the role of AKR1C3 in endometriosis. This review includes an introduction to endometriosis with emphasis on the roles of prostaglandins and progesterone in its pathophysiology. This is followed by an overview of the major enzymatic activities and physiological functions of AKR1C3 and of the data published to date on the expression of AKR1C3 in endometriosis at the mRNA and protein levels. The review concludes with the rationale for using AKR1C3 inhibitors, a discussion of the effects of AKR1C3 inhibition on the pathophysiology of endometriosis and a brief overview of other drugs under clinical investigation for this indication.

Engineering aldo-keto reductase 1B10 to mimic the distinct 1B15 topology and specificity towards inhibitors and substrates, including retinoids and steroids

The aldo-keto reductase (AKR) superfamily comprises NAD(P)H-dependent enzymes that catalyze the reduction of a variety of carbonyl compounds. AKRs are classified in families and subfamilies. Humans exhibit three members of the AKR1B subfamily: AKR1B1 (aldose reductase, participates in diabetes complications), AKR1B10 (overexpressed in several cancer types), and the recently described AKR1B15. AKR1B10 and AKR1B15 share 92% sequence identity, as well as the capability of being active towards retinaldehyde. However, AKR1B10 and AKR1B15 exhibit strong differences in substrate specificity and inhibitor selectivity. Remarkably, their substrate-binding sites are the most divergent parts between them. Out of 27 residue substitutions, six are changes to Phe residues in AKR1B15. To investigate the participation of these structural changes, especially the Phe substitutions, in the functional features of each enzyme, we prepared two AKR1B10 mutants. The AKR1B10 m mutant carries a segment of six AKR1B15 residues (299-304, including three Phe residues) in the respective AKR1B10 region. An additional substitution (Val48Phe) was incorporated in the second mutant, AKR1B10mF48. This resulted in structures with smaller and more hydrophobic binding pockets, more similar to that of AKR1B15. In general, the AKR1B10 mutants mirrored well the specific functional features of AKR1B15, i.e., the different preferences towards the retinaldehyde isomers, the much higher activity with steroids and ketones, and the unique behavior with inhibitors. It can be concluded that the Phe residues of loop C (299-304) contouring the substrate-binding site, in addition to Phe at position 48, strongly contribute to a narrower and more hydrophobic site in AKR1B15, which would account for its functional uniqueness. In addition, we have investigated the AKR1B10 and AKR1B15 activity toward steroids. While AKR1B10 only exhibits residual activity, AKR1B15 is an efficient 17-ketosteroid reductase. Finally, the functional role of AKR1B15 in steroid and retinaldehyde metabolism is discussed.

Evaluation of A-ring fused pyridine d-modified androstane derivatives for antiproliferative and aldo-keto reductase 1C3 inhibitory activity

New A-ring pyridine fused androstanes in 17a-homo-17-oxa (d-homo lactone), 17α-picolyl or 17(E)-picolinylidene series were synthesized and validated by X-ray crystallography, HRMS, IR and NMR spectroscopy. Novel compounds 3, 5, 8 and 12 were prepared by treatment of 4-en-3-one or 4-ene-3,6-dione d-modified androstane derivatives with propargylamine catalyzed by Cu(ii), and evaluated for potential anticancer activity in vitro using human cancer cell lines and recombinant targets of steroidal anti-cancer drugs. Pyridine fusion to position 3,4 of the A-ring may dramatically enhance affinity of 17α-picolyl compounds for CYP17 while conferring selective antiproliferative activity against PC-3 cells. Similarly, pyridine fusion to the A-ring of steroidal d-homo lactones led to identification of new inhibitors of aldo-keto reductase 1C3, an enzyme targeted in acute myeloid leukemia, breast and prostate cancers. One A-pyridine d-lactone steroid 5 also has selective submicromolar antiproliferative activity against HT-29 colon cancer cells. None of the new derivatives have affinity for estrogen or androgen receptors in a yeast screen, suggesting negligible estrogenicity and androgenicity. Combined, our results suggest that A-ring pyridine fusions have potential in modulating the anticancer activity of steroidal compounds.

AKR1C enzymes sustain therapy resistance in paediatric T-ALL

Background

Despite chemotherapy intensification, a subgroup of high-risk paediatric T-cell acute lymphoblastic leukemia (T-ALL) patients still experience treatment failure. In this context, we hypothesised that therapy resistance in T-ALL might involve aldo-keto reductase 1C (AKR1C) enzymes as previously reported for solid tumors.

Methods

Expression of NRF2-AKR1C signaling components has been analysed in paediatric T-ALL samples endowed with different treatment outcomes as well as in patient-derived xenografts of T-ALL. The effects of AKR1C enzyme modulation has been investigated in T-ALL cell lines and primary cultures by combining AKR1C inhibition, overexpression, and gene silencing approaches.

Results

We show that T-ALL cells overexpress AKR1C1-3 enzymes in therapy-resistant patients. We report that AKR1C1-3 enzymes play a role in the response to vincristine (VCR) treatment, also ex vivo in patient-derived xenografts. Moreover, we demonstrate that the modulation of AKR1C1-3 levels is sufficient to sensitise T-ALL cells to VCR. Finally, we show that T-ALL chemotherapeutics induce overactivation of AKR1C enzymes independent of therapy resistance, thus establishing a potential resistance loop during T-ALL combination treatment.

Conclusions

Here, we demonstrate that expression and activity of AKR1C enzymes correlate with response to chemotherapeutics in T-ALL, posing AKR1C1-3 as potential targets for combination treatments during T-ALL therapy.

Aldo-Keto Reductase (AKR) 1C3 inhibitors: a patent review

INTRODUCTION

AKR1C3 is a drug target in hormonal and hormonal independent malignancies and acts as a major peripheral 17β-hydroxysteroid dehydrogenase to yield the potent androgens testosterone and dihydrotestosterone, and as a prostaglandin (PG) F synthase to produce proliferative ligands for the PG FP receptor. AKR1C3 inhibitors may have distinct advantages over existing therapeutics for the treatment of castration resistant prostate cancer, breast cancer and acute myeloid leukemia. Area covered: This article reviews the patent literature on AKR1C3 inhibitors using SciFinder which identified inhibitors in the following chemical classes: N-phenylsulfonyl-indoles, N-(benzimidazoylylcarbonyl)- N-(indoylylcarbonyl)- and N-(pyridinepyrrolyl)- piperidines, N-benzimidazoles and N-benzindoles, repurposed nonsteroidal antiinflammatory drugs (indole acetic acids, N-phenylanthranilates and aryl propionic acids), isoquinolines, and nitrogen and sulfur substituted estrenes. The article evaluates inhibitor AKR potency, specificity, efficacy in cell-based and xenograft models and clinical utility. The advantage of bifunctional compounds that either competitively inhibit AKR1C3 and block its androgen receptor (AR) coactivator function or act as AKR1C3 inhibitors and direct acting AR antagonists are discussed. Expert opinion: A large number of potent and selective inhibitors of AKR1C3 have been described however, preclinical optimization, is required before their benefit in human disease can be assessed.

Direct Metabolic Interrogation of Dihydrotestosterone Biosynthesis from Adrenal Precursors in Primary Prostatectomy Tissues

Purpose: A major mechanism of castration-resistant prostate cancer (CRPC) involves intratumoral biosynthesis of dihydrotestosterone (DHT) from adrenal precursors. We have previously shown that adrenal-derived androstenedione (AD) is the preferred substrate over testosterone (T) for 5α-reductase expressed in metastatic CRPC, bypassing T as an obligate precursor to DHT. However, the metabolic pathway of adrenal-derived DHT biosynthesis has not been rigorously investigated in the setting of primary disease in the prostate.Experimental Design: Seventeen patients with clinically localized prostate cancer were consented for fresh tissues after radical prostatectomy. Prostate tissues were cultured ex vivo in media spiked with an equimolar mixture of AD and T, and stable isotopic tracing was employed to simultaneously follow the enzymatic conversion of both precursor steroids into nascent metabolites, detected by liquid chromatography-tandem mass spectrometry. CRPC cell line models and xenograft tissues were similarly assayed for comparative analysis. A tritium-labeled steroid radiotracing approach was used to validate our findings.Results: Prostatectomy tissues readily 5α-reduced both T and AD. Furthermore, 5α-reduction of AD was the major directionality of metabolic flux to DHT. However, AD and T were comparably metabolized by 5α-reductase in primary prostate tissues, contrasting the preference exhibited by CRPC in which AD was favored over T. 5α-reductase inhibitors effectively blocked the conversion of AD to DHT.Conclusions: Both AD and T are substrates of 5α-reductase in prostatectomy tissues, resulting in two distinctly nonredundant metabolic pathways to DHT. Furthermore, the transition to CRPC may coincide with a metabolic switch toward AD as the favored substrate. Clin Cancer Res; 23(20); 6351-62. ©2017 AACR.

Riboflavin deficiency induces a significant change in proteomic profiles in HepG2 cells

Riboflavin deficiency is widespread in many regions over the world, especially in underdeveloped countries. In this study, we investigated the effects of riboflavin deficiency on protein expression profiles in HepG2 cells in order to provide molecular information for the abnormalities induced by riboflavin deficiency. HepG2 cells were cultured in media containing different concentrations of riboflavin. Changes of cell viability and apoptosis were assessed. A comparative proteomic analysis was performed using a label-free shotgun method with LC-MS/MS to investigate the global changes of proteomic profiles in response to riboflavin deficiency. Immunoblotting test was used to validate the results of proteomic approach. The cell viability and apoptosis tests showed that riboflavin was vital in maintaining the cytoactivity of HepG2 cells. The label-free proteomic analysis revealed that a total of 37 proteins showing differential expression (±2 fold, p < 0.05) were identified after riboflavin deficiency. Bioinformatics analysis indicated that the riboflavin deficiency caused an up-regulation of Parkinson's disease pathway, steroid catabolism, endoplasmic reticulum stress and apoptotic process, while the fatty acid metabolism, tricarboxylic citrate cycle, oxidative phosphorylation and iron metabolism were down-regulated. These findings provide a molecular basis for the elucidation of the effects caused by riboflavin deficiency.

sp2CH⋯Cl hydrogen bond in the conformational polymorphism of 4-chloro-phenylanthranilic acid

Conformational flexibility and^sp2CH⋯Cl hydrogen bond lead to three polymorphs of 4-chloro-phenylanthranilic acid.

Quality of life effects of androgen deprivation therapy in a prostate cancer cohort in New Zealand: can we minimize effects using a stratification based on the aldo-keto reductase family 1, member C3 rs12529 gene polymorphism?

BACKGROUND

Androgen deprivation therapy (ADT) is an effective palliation treatment in men with advanced prostate cancer (PC). However, ADT has well documented side effects that could alter the patient's health-related quality of life (HRQoL). The current study aims to test whether a genetic stratification could provide better knowledge for optimising ADT options to minimize HRQoL effects.

METHODS

A cohort of 206 PC survivors (75 treated with and 131 without ADT) was recruited with written consent to collect patient characteristics, clinical data and HRQoL data related to PC management. The primary outcomes were the percentage scores under each HRQoL subscale assessed using the European Organisation for Research and Treatment of Cancer Quality of Life questionnaires (QLQ-C30 and PR25) and the Depression Anxiety Stress Scales developed by the University of Melbourne, Australia. Genotyping of these men was carried out for the aldo-keto reductase family 1, member C3 (AKR1C3) rs12529 single nucleotide polymorphism (SNP). Analysis of HRQoL scores were carried out against ADT duration and in association with the AKR1C3 rs12529 SNP using the generalised linear model. P-values <0 · 05 were considered significant, and were further tested for restriction with Bonferroni correction.

RESULTS

Increase in hormone treatment-related effects were recorded with long-term ADT compared to no ADT. The C and G allele frequencies of the AKR1C3rs12529 SNP were 53·4 % and 46·6 % respectively. Hormone treatment-related symptoms showed an increase with ADT when associated with the AKR1C3 rs12529 G allele. Meanwhile, decreasing trends on cancer-specific symptoms and increased sexual interest were recorded with no ADT when associated with the AKR1C3 rs12529 G allele and reverse trends with the C allele. As higher incidence of cancer-specific symptoms relate to cancer retention it is possible that associated with the C allele there could be higher incidence of unresolved cancers under no ADT options.

CONCLUSIONS

If these findings can be reproduced in larger homogeneous cohorts, a genetic stratification based on the AKR1C3 rs12529 SNP, can minimize ADT-related HRQoL effects in PC patients. Our data additionally show that with this stratification it could also be possible to identify men needing ADT for better oncological advantage.

Current advances in intratumoral androgen metabolism in castration-resistant prostate cancer

PURPOSE OF REVIEW

Androgen deprivation therapy is a cornerstone in the treatment of advanced prostate cancer and has extended the lives of countless patients. Unfortunately, many of these patients eventually succumb to metastatic castration-resistant prostate cancer (mCRPC). The efficacy of abiraterone acetate (AA, Zytiga) and enzalutamide (Enza, Xtandi) in the mCRPC setting prove that these tumors remain androgen-driven. We review recent studies that have shown that intratumoral androgen biosynthesis plays a significant role in the ever-evolving mCRPC tumor and we discuss the therapeutic implications of these findings.

RECENT FINDINGS

A novel abiraterone metabolite, 17-(pyridin-3-yl)androsta-4,16-dien-3-one (D4A), possesses robust antitumor activity in rodent models via the inhibition of androgen biosynthetic enzymes and antagonism of the androgen receptor. The TMPRSS2 : ERG fusion drives aldo-keto reductase 1C3 (AKR1C3) expression and activity to facilitate androgen biosynthesis and activate the androgen receptor in prostate cancer. Intracrine androgen formation and AKR1C3 expression and activity have been found to confer resistance to enzalutamide.

SUMMARY

These studies highlight the significant role that intratumoral androgen biosynthesis plays in the mCRPC tumor. The therapeutic implications include the inhibition of AKR1C3 in tumors that become resistant to current drugs such as abiraterone acetate or Enza and the potential administration of D4A as an mCRPC therapeutic.

Histological changes caused by meclofenamic acid in androgen-independent prostate cancer tumors: evaluation in a mouse model

Meclofenamic acid is a nonsteroidal anti-inflammatory drug that has shown therapeutic potential for different types of cancers, including androgen-independent prostate neoplasms. The antitumor effect of diverse nonsteroidal anti-inflammatory drugs has been shown to be accompanied by histological and molecular changes that are responsible for this beneficial effect. The objective of the present work was to analyze the histological changes caused by meclofenamic acid in androgen-independent prostate cancer. Tumors were created in a nude mouse model using PC3 cancerous human cells. Meclofenamic acid (10 mg/kg/day; experimental group, n=5) or saline solution (control group, n=5) was administered intraperitoneally for twenty days. Histological analysis was then carried out on the tumors, describing changes in the cellular architecture, fibrosis, and quantification of cellular proliferation and tumor vasculature. Meclofenamic acid causes histological changes that indicate less tumor aggression (less hypercellularity, fewer atypical mitoses, and fewer nuclear polymorphisms), an increase in fibrosis, and reduced cellular proliferation and tumor vascularity. Further studies are needed to evaluate the molecular changes that cause the beneficial and therapeutic effects of meclofenamic acid in androgen-independent prostate cancer.

11β-Prostaglandin F2α, a bioactive metabolite catalyzed by AKR1C3, stimulates prostaglandin F receptor and induces slug expression in breast cancer

Prostaglandins are a group of lipid compounds involved in inflammation and cancer. We focused on PGF2α and its stereoisomer 11β-PGF2α and examined the expression and functions of their cognate receptor (FP receptor) and metabolizing enzymes (AKR1B1 and AKR1C3 respectively) in breast cancer. In immunohistochemical analysis FP receptor status associated with adverse clinical outcome only in the AKR1C3 positive cases. Therefore, we studied FP receptor-mediated functions of 11β-PGF2α using FP receptor expressed MCF-7 cell line (MCF-FP). 11β-PGF2α treatment phosphorylated ERK and CREB and induced Slug expression through FP receptor in MCF-FP, and MCF-FP cells demonstrated decreased chemosensitivity compared to parental controls. Finally, the correlation between FP receptor and Slug was also confirmed immunohistochemically in breast cancer cases. Overall these results indicated that the actions of AKR1C3 can produce FP receptor ligands whose activation results in carcinoma cell survival in breast cancer.

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.

Mechanisms of drug resistance that target the androgen axis in castration resistant prostate cancer (CRPC)

Castrate resistant prostate cancer (CRPC) is the fatal-form of prostate cancer and remains androgen dependent. The reactivation of the androgen axis occurs due to adaptive intratumoral androgen biosynthesis which can be driven by adrenal androgens and/or by changes in the androgen receptor (AR) including AR gene amplification. These mechanisms are targeted with P450c17 inhibitors e.g., abiraterone acetate and AR super-antagonists e.g., enzalutamide, respectively. Clinical experience indicates that with either agent an initial response is followed by drug resistance and the patient clinically progresses on these agents. This article reviews the mechanisms of intrinsic and acquired drug resistance that target the androgen axis and how this might be surmounted.

11β-Hydroxyandrostenedione: Downstream metabolism by 11βHSD, 17βHSD and SRD5A produces novel substrates in familiar pathways

11β-Hydroxyandrostenedione (11OHA4), a major C19 steroid produced by the adrenal, was first reported in the 1950s. Initially the subject of numerous studies, interest dwindled due to the apparent lack of physiological function and, by the end of the century, 11OHA4 was no longer considered as an adrenal C19 steroid. Our recent studies, however, showed that 11OHA4 is the precursor to novel active androgens which include 11-ketodihydrotestosterone (11KDHT) which has been implicated in prostate cancer, thereby renewing interest in 11OHA4. In this paper we review the biosynthesis and downstream metabolism of 11OHA4. We discuss the extra-adrenal biosynthesis of 11OHA4 in humans and in other species, highlighting the well-documented role of 11OHA4 in the testes of male fish in which the steroid functions as an active androgen. Finally, we discuss the physiological relevance of 11OHA4 metabolism in castration resistant prostate cancer and outline future prospects.

Aldo-keto reductase 1C3 (AKR1C3) is associated with the doxorubicin resistance in human breast cancer via PTEN loss

Aldo-keto reductase 1C3 (AKR1C3), one member of the aldo-keto reductase superfamily, is involved in a variety of cancers. Recently, AKR1C3 has been demonstrated to be related with the doxorubicin (DOX) resistance in human breast cancer. Here, we attempted to explore the resistance mechanism mediated by AKR1C3. First, one DOX resistant breast cancer cell line MCF-7/DOX was successfully established and an increased level of AKR1C3 was observed in the MCF-7/DOX cells compared to the parental MCF-7 cells. To investigate the contribution of AKR1C3 in the DOX resistance, we further established an AKR1C3 overexpression cell line, referred to MCF-7/AKR1C3. In the MCF-7/AKR1C3 cells, the DOX induced cytotoxicity, detected by CCK-8 cell viability assay and DAPI staining, was greatly reduced (3.2-fold increase in the IC50 value). Interestingly, a loss of tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) was observed when AKR1C3 was overexpressed. Secondary to the PTEN loss, the activated Akt also markedly increased. In addition, the AKR1C3 mediated DOX resistance can be conquered by the Akt inhibitor (LY294002). Furthermore, we found that the expression levels of AKR1C3 and PTEN had a negative relationship in the human breast tumor tissues (the standard correlation coefficient=-0.71; P=0.048). In conclusion, our data suggested that the AKR1C3 mediated DOX resistance might be resulted from the activation of anti-apoptosis PTEN/Akt pathway via PTEN loss. AKR1C3 may present a potential therapeutic target in addressing DOX resistance in breast cancer.

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.

The Activity of SN33638, an Inhibitor of AKR1C3, on Testosterone and 17β-Estradiol Production and Function in Castration-Resistant Prostate Cancer and ER-Positive Breast Cancer

AKR1C3 is a novel therapeutic target in castration-resistant prostate cancer (CRPC) and estrogen receptor (ER)-positive breast cancer because of its ability to produce testosterone and 17β-estradiol intratumorally, thus promoting nuclear receptor signaling and tumor progression. A panel of CRPC, ER-positive breast cancer and high/low AKR1C3-expressing cell lines were treated with SN33638, a selective inhibitor of AKR1C3, in the presence of hormone or prostaglandin (PG) precursors, prior to evaluation of cell proliferation and levels of 11β-PG F2α (11β-PGF2α), testosterone, 17β-estradiol, and prostate-specific antigen (PSA). A meta-analysis of AKR1C3 mRNA expression in patient samples was also conducted, which revealed that AKR1C3 mRNA was upregulated in CRPC, but downregulated in ER-positive breast cancer. 11β-PGF2α and testosterone levels in the cell line panel correlated with AKR1C3 protein expression. SN33638 prevented 11β-PGF2α formation in cell lines that expressed AKR1C3, but partially inhibited testosterone formation and subsequently cell proliferation and/or PSA expression only in high (LAPC4 AKR1C3-overexpressing cells) or moderate (22RV1) AKR1C3-expressing cell lines. SN33638 had little effect on 17β-estradiol production or estrone-stimulated cell proliferation in ER-positive breast cancer cell lines. Although SN33638 could prevent 11β-PGF2α formation, its ability to prevent testosterone and 17β-estradiol production and their roles in CRPC and ER-positive breast cancer progression was limited due to AKR1C3-independent steroid hormone production, except in LAPC4 AKR1C3 cells where the majority of testosterone was AKR1C3-dependent. These results suggest that inhibition of AKR1C3 is unlikely to produce therapeutic benefit in CRPC and ER-positive breast cancer patients, except possibly in the small subpopulation of CRPC patients with tumors that have upregulated AKR1C3 expression and are dependent on AKR1C3 to produce the testosterone required for their growth.

11β-Hydroxydihydrotestosterone and 11-ketodihydrotestosterone, novel C19 steroids with androgenic activity: a putative role in castration resistant prostate cancer?

Adrenal C19 steroids, dehydroepiandrostenedione (DHEA(S)) and androstenedione (A4), play a critical role in castration resistant prostate cancer (CRPC) as they are metabolised to dihydrotestosterone (DHT), via testosterone (T), or via the alternate 5α-dione pathway, bypassing T. Adrenal 11OHA4 metabolism in CRPC is, however, unknown. We present a novel pathway for 11OHA4 metabolism in CRPC leading to the production of 11ketoT (11KT) and novel 5α-reduced C19 steroids - 11OH-5α-androstanedione, 11keto-5α-androstanedione, 11OHDHT and 11ketoDHT (11KDHT). The pathway was validated in the androgen-dependent prostate cancer cell line, LNCaP. Androgen receptor (AR) transactivation studies showed that while 11KT and 11OHDHT act as a partial AR agonists, 11KDHT is a full AR agonist exhibiting similar activity to DHT at 1nM. Our data demonstrates that, while 11OHA4 has negligible androgenic activity, its metabolism to 11KT and 11KDHT yields androgenic compounds which may be implicated, together with A4 and DHEA(S), in driving CRPC in the absence of testicular T.

Molecular pathways: Inhibiting steroid biosynthesis in prostate cancer

A significant proportion of castration-resistant prostate cancers (CRPC) remains driven by ligand activation of the androgen receptor. Although the testes are the primary source of testosterone, testosterone can also be produced from peripheral conversion of adrenal sex hormone precursors DHEA and androstenedione in the prostate and other tissues. CYP17A1 catalyzes two essential reactions in the production of DHEA and androstenedione: the hydroxylation (hydroxylase activity) and the subsequent cleavage of the C17-20 side chain (lyase activity). Potent and selective inhibition of CYP17A1 by abiraterone depletes residual nongonadal androgens and is an effective treatment for CRPC. Elucidation of the mechanisms that underlie resistance to abiraterone will inform the development of novel therapeutic strategies post-abiraterone. Preclinical evidence that androgen biosynthesis in prostate cancer cells does not necessarily follow a single dominant pathway, and residual androgens or alternative ligands (including administered glucocorticoids) can reactivate androgen receptor signaling, supports cotargeting of more than one enzyme involved in steroidogenesis and combining a CYP17A1 inhibitor with an antiandrogen. Furthermore, given the drawbacks of 17α-hydroxylase inhibition, there is considerable interest in developing new CYP17A1 inhibitors that more specifically inhibit lyase activity and are therefore less likely to require glucocorticoid coadministration.

Minireview: Androgen metabolism in castration-resistant prostate cancer

The decades-old terminology of androgen independence has been replaced in recent years with castration-resistant prostate cancer. Biological and clinical evidence have together conspired to support the use of this revised terminology by demonstrating that in the vast majority of cases tumors are neither truly depleted of androgens, nor are they free of the requirement for androgens to sustain growth and progression. Abiraterone acetate, an androgen synthesis inhibitor, and enzalutamide, a potent androgen receptor antagonist, both exploit the continued requirement for androgens. A central question, given the therapeutic gains enabled by further suppression of the androgen axis with these newer agents, is whether there may be additional clinical benefit gained by moving the goal posts of androgen suppression even further. The answer lies in part with the mechanisms utilized by tumors that enable resistance to these therapies. The aims of this review were to give a broad outline of steroidogenesis in prostate cancer and to highlight recent developments in understanding resistance to hormonal therapies.

Quantitative evaluation of aldo-keto reductase expression in hepatocellular carcinoma (HCC) cell lines

The involvement of aldo–keto reductases (AKRs) in tumorigenesis is widely reported, but their roles in the pathological process are not generally recognized due to inconsistent measurements of their expression. To overcome this problem, we simultaneously employed real-time PCR to examine gene expression and multiple reaction monitoring (MRM) of mass spectrometry (MS) to examine the protein expression of AKRs in five different hepatic cell lines. These include one relatively normal hepatic cell line, L-02, and four hepatocellular carcinoma (HCC) cell lines, HepG2, HuH7, BEL7402 and SMMC7721. The results of real-time PCR showed that expression of genes encoding the AKR1C family members rather than AKR1A and AKR1B was associated with tumor, and most of genes encoding AKRs were highly expressed in HuH7. Similar observations were obtained through MRM. Different from HuH7, the protein abundance of AKR1A and AKR1B was relatively consistent among the other four hepatic cell lines, while protein expression of AKR1C varied significantly compared to L-02. Therefore, we conclude that the abundant distribution of AKR1C proteins is likely to be associated with liver tumorigenesis, and the AKR expression status in HuH7 is completely different from other liver cancer cell lines. This study, for the first time, provided both overall and quantitative information regarding the expression of AKRs at both mRNA and protein levels in hepatic cell lines. Our observations put the previous use of AKRs as a biomarker into question since it is only consistent with our data from HuH7. Furthermore, the data presented herein demonstrated that quantitative evaluation and comparisons within a protein family at both mRNA and protein levels were feasible using current techniques.

The role of intracrine androgen metabolism, androgen receptor and apoptosis in the survival and recurrence of prostate cancer during androgen deprivation therapy

Prostate cancer (CaP) is the most frequently diagnosed cancer and leading cause of cancer death in American men. Almost all men present with advanced CaP and some men who fail potentially curative therapy are treated with androgen deprivation therapy (ADT). ADT is not curative and CaP recurs as the lethal phenotype. The goal of this review is to apply our current understanding of CaP and castration-recurrent CaP (CR-CaP) to earlier studies that characterized ADT and the molecular mechanisms that facilitate the transition from androgen-stimulated CaP to CR-CaP. Reexamination of earlier studies also may provide a better understanding of how more newly recognized mechanisms, such as intracrine metabolism, may be involved with the early events that allow CaP survival after initiation of ADT and subsequent development of CR-CaP.

Aldo-keto reductase 1C3 may be a new radioresistance marker in non-small-cell lung cancer

Human aldo-keto reductase 1C3, type 2 3α-hydroxysteroid dehydrogenase (HSD)/type 5 17β-HSD (AKR1C3) is known to be involved in steroid, prostaglandin and lipid aldehyde metabolism. The role of AKR1C3 in the radiosensitivity to X-rays of human non-small-cell lung cancer (NSCLC) cells was explored. In this study, a specific small interfering RNA (siRNA) to target the AKR1C3 gene was used. A suite of readouts including cell survival were determined using a colony formation assay; apoptosis evaluated by Annexin V expression levels, irradiation-induced cytotoxicity established using a MTT cell viability assay and cell cycle distribution measured by flow cytometry were used in characterizing the role of the AKR1C3 gene. Although AKR1C3 was significantly overexpressed in both our radioresistant subclone cells and NSCLC tissues, a specific AKR1C3 siRNA significantly enhanced cell radiosensitivity and was concomitant with decreased expression of this gene. Furthermore, reduced interleukin-6 (IL-6)-mediated radioresistance was observed when siRNA was used to knock down AKR1C3 activity. This AKR1C3-mediated radioresistance was correlated with an arrest in the G2/M cell cycle and a decreased induction of apoptosis. AKR1C3 may present a potential therapeutic target in addressing radioresistance of NSCLC, and in particular in IL-6-mediated radioresistance.

Intratumoral estrogen concentration and expression of estrogen-induced genes in male breast carcinoma: comparison with female breast carcinoma

It is speculated that estrogens play important roles in the male breast carcinoma (MBC) as well as the female breast carcinoma (FBC). However, estrogen concentrations or molecular features of estrogen actions have not been reported in MBC, and biological significance of estrogens remains largely unclear in MBC. Therefore, we examined intratumoral estrogen concentrations, estrogen receptor (ER) α/ERβ status, and expression profiles of estrogen-induced genes in MBC tissues, and compared these with FBC. 17β-Estradiol concentration in MBC (n = 4) was significantly (14-fold) higher than that in non-neoplastic male breast (n = 3) and tended to be higher than that in FBC (n = 7). Results of microarray analysis clearly demonstrated that expression profiles of the two gene lists, which were previously reported as estrogen-induced genes in MCF-7 breast carcinoma cell line, were markedly different between MBC and FBC. In the immunohistochemistry, MBC tissues were frequently positive for aromatase (63 %) and 17β-hydroxysteroid dehydrogenase type 1 (67 %), but not for steroid sulfatase (6.7 %). A great majority (77 %) of MBC showed positive for both ERα and ERβ, and its frequency was significantly higher than FBC cases. These results suggest that estradiol is locally produced in MBC tissue by aromatase. Different expression profiles of the estrogen-induced genes may associate with different estrogen functions in MBC from FBC, which may be partly due to their ERα/ERβ status.

Androgen action and metabolism in prostate cancer

The transcriptional programs regulated through the activity of the androgen receptor (AR) modulate normal prostate development and the maintenance of prostatic functions at maturity. AR signaling also controls key survival and growth functions operative in prostate cancer. Inhibiting the AR program remains the key target in the treatment of advanced prostate cancer, and suppressing AR also holds great potential for preventing the development or progression of early stage prostate cancer. In this review, we detail molecular mechanisms of AR activity, cellular components contributing to the maintenance of AR signaling despite AR-ligand suppression, and discuss treatment strategies designed to target components of resistance to AR-directed therapeutics.

3-(3,4-Dihydroisoquinolin-2(1H)-ylsulfonyl)benzoic Acids: highly potent and selective inhibitors of the type 5 17-β-hydroxysteroid dehydrogenase AKR1C3

A high-throughput screen identified 3-(3,4-dihydroisoquinolin-2(1H)-ylsulfonyl)benzoic acid as a novel, highly potent (low nM), and isoform-selective (1500-fold) inhibitor of aldo-keto reductase AKR1C3: a target of interest in both breast and prostate cancer. Crystal structure studies showed that the carboxylate group occupies the oxyanion hole in the enzyme, while the sulfonamide provides the correct twist to allow the dihydroisoquinoline to bind in an adjacent hydrophobic pocket. SAR studies around this lead showed that the positioning of the carboxylate was critical, although it could be substituted by acid isosteres and amides. Small substituents on the dihydroisoquinoline gave improvements in potency. A set of "reverse sulfonamides" showed a 12-fold preference for the R stereoisomer. The compounds showed good cellular potency, as measured by inhibition of AKR1C3 metabolism of a known dinitrobenzamide substrate, with a broad rank order between enzymic and cellular activity, but amide analogues were more effective than predicted by the cellular assay.

The AR dependent cell cycle: mechanisms and cancer relevance

Prostate cancer cells are exquisitely dependent on androgen receptor (AR) activity for proliferation and survival. As these functions are critical targets of therapeutic intervention for human disease, it is imperative to delineate the mechanisms by which AR engages the cell cycle engine. More than a decade of research has revealed that elegant intercommunication between AR and the cell cycle machinery governs receptor-dependent cellular proliferation, and that perturbations in this process occur frequently in human disease. Here, AR-cell cycle interplay and associated cancer relevance will be reviewed.

Human steroid biosynthesis for the oncologist

In 2005, results from the Arimidex, Tamoxifen Alone or in Combination (ATAC) trial ushered in a new era of endocrine therapy for hormone-responsive malignancies. This study demonstrated that, compared with tamoxifen (a selective estrogen receptor modulator), anastrozole (aromatase inhibitor [AI]) prolonged time to recurrence and disease-free survival for postmenopausal women with breast cancer. The advantage was even greater for those with estrogen receptor-positive (ER) tumors, and anastrozole was better tolerated than tamoxifen. Since then, AIs have become first-line adjuvant therapy for ER breast cancer in postmenopausal women.In late 2010, a trial comparing abiraterone acetate (a 17-hydroxylase/17,20-lyase [CYP17A1] inhibitor) plus prednisone versus prednisone alone in men with castration-resistant prostate cancer (CRPC) previously treated with docetaxel chemotherapy was terminated early because of the survival benefit in the abiraterone acetate arm. This result not only validated a new therapy for CRPC but also, with the antecedent phase I-II abiraterone studies, shattered our understanding of the molecular mechanisms underpinning CRPC development and progression.Aromatase inhibitors and CYP17A1 inhibitors will be widely used by oncologists, yet fellowship programs provide little training in steroid biosynthesis, compared with training in the biology of standard chemotherapies. Consequently, these drugs might be used without an appreciation of their caveats and pitfalls. The purpose of this review was to acquaint practicing oncologists with the fundamental principles and pathways of steroid biosynthesis, to improve their understanding of how and why these drugs work, and to alert these physicians to potential problems related to the drugs' mechanisms of action.

Retinaldehyde is a substrate for human aldo-keto reductases of the 1C subfamily

Human AKR (aldo-keto reductase) 1C proteins (AKR1C1-AKR1C4) exhibit relevant activity with steroids, regulating hormone signalling at the pre-receptor level. In the present study, investigate the activity of the four human AKR1C enzymes with retinol and retinaldehyde. All of the enzymes except AKR1C2 showed retinaldehyde reductase activity with low Km values (~1 μM). The kcat values were also low (0.18-0.6 min-1), except for AKR1C3 reduction of 9-cis-retinaldehyde whose kcat was remarkably higher (13 min-1). Structural modelling of the AKR1C complexes with 9-cis-retinaldehyde indicated a distinct conformation of Trp227, caused by changes in residue 226 that may contribute to the activity differences observed. This was partially supported by the kinetics of the AKR1C3 R226P mutant. Retinol/retinaldehyde conversion, combined with the use of the inhibitor flufenamic acid, indicated a relevant role for endogenous AKR1Cs in retinaldehyde reduction in MCF-7 breast cancer cells. Overexpression of AKR1C proteins depleted RA (retinoic acid) transactivation in HeLa cells treated with retinol. Thus AKR1Cs may decrease RA levels in vivo. Finally, by using lithocholic acid as an AKR1C3 inhibitor and UVI2024 as an RA receptor antagonist, we provide evidence that the pro-proliferative action of AKR1C3 in HL-60 cells involves the RA signalling pathway and that this is in part due to the retinaldehyde reductase activity of AKR1C3.

Aldo-keto reductase 1C3 is expressed in differentiated human epidermis, affects keratinocyte differentiation, and is upregulated in atopic dermatitis

Aldo-keto reductase 1C3 (AKR1C3) has been shown to mediate the metabolism of sex hormones and prostaglandin D(2) (PGD(2)), a lipid mediator that promotes skin inflammation in atopic dermatitis (AD). As both have a role in skin function and pathology, we first sought to investigate the expression pattern of AKR1C3 in normal human epidermis. Immunofluorescence revealed a strong expression of AKR1C3 in the differentiated suprabasal layers compared with the basal layer. Western blot analysis and quantitative PCR confirmed that AKR1C3 expression was also upregulated in differentiation-induced primary human keratinocytes (PHKs). To investigate the functional role of AKR1C3 during PHK differentiation, its expression and activity (measured as PGD(2) reduction to 9α,11β-PGF(2) by ELISA) were impaired by small interfering RNA or 2'-hydroxyflavanone, respectively. Cytokeratin 10 (K10) and loricrin expression were then examined by western blot analysis, thus revealing altered expression of these differentiation markers. Finally, following an observation that the AD-associated mediator, PGD(2), upregulated AKR1C3 expression in PHKs, we used immunofluorescence to examine AKR1C3 expression in AD and psoriasis lesions. AKR1C3 was found to be upregulated in AD but not in psoriasis lesions compared with non-lesional skin. Our work demonstrates a function for AKR1C3 in differentiation-associated gene regulation and also suggests a role in supporting inflammation in AD.