AKR1C1/2 inhibition by MPA sensitizes platinum resistant ovarian cancer towards carboplatin.

In recurrent epithelial ovarian cancer (EOC) most patients develop platinum-resistance. On molecular level the NRF2 pathway, a cellular defense mechanism against reactive oxygen species, is induced. In this study, we investigate AKR1C1/2, target of NRF2, in a well-established EOC collective by immunohistochemistry and in a panel of ovarian cancer cell lines including platinum-resistant clones. The therapeutic effect of carboplatin and MPA as monotherapy or in combination was assessed by functional assays, using OV90 and OV90cp cells. Molecular mechanisms of action of MPA were investigated by NRF2 silencing and AKR activity measurements. Immunohistochemical analysis revealed that AKR1C1/2 is a key player in the development of chemoresistance and an independent indicator for short PFS (23.5 vs. 49.6 months, p = 0.013). Inhibition of AKR1C1/2 by MPA led to a concentration- and time-dependent decline of OV90 viability and to an increased response to CP in vitro. By NRF2 silencing, however, the effects of MPA treatment were reduced. Concludingly, our data suggest that a combination therapy of carboplatin and MPA might be a promising therapeutic approach to increase response rates of EOC patients, which should be explored in clinical context.

Nature-derived anticancer steroids outside cardica glycosides.

Steriods which are ubiquitous in natural resources are important components of cell membranes and involved in several physiological functions. Steriods not only exerted the anticancer activity through inhibition of various enzymes and receptors in cancer cells, inclusive of aromatase, sulfatase, 5α-reductase, hydroxysteroid dehydrogenase and CYP 17, but also exhibited potential activity against various cancer forms including multidrug-resistant cancer with low cytotoxicity, and high bioavailability. Accordingly, steroids are useful scaffolds for the discovery of novel anticancer agents. This review aims to outline the advances of nature-derived steroids outside cardica glycosides with anticancer potential, covering the articles published between Jan. 2015 and Aug. 2020.

Gossypol inhibits 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase: Its possible use for the treatment of prostate cancer.

Gossypol is a yellow polyphenol isolated from cotton seeds. It has the antitumor activity and it is being tested to treat prostate cancer. However, its underlying mechanisms are still not well understood. The present study investigated the inhibitory effects of gossypol acetate on rat 5α-reductase 1, 3α-hydroxysteroid dehydrogenase, and retinol dehydrogenase 2 for androgen metabolism. Rat 5α-reductase 1, 3α-hydroxysteroid dehydrogenase, and retinol dehydrogenase 2 were expressed in COS-1 cells. Immature Leydig cells that contain these enzymes were isolated from 35-day-old male Sprague Dawley rats. The potency and mode of action of gossypol acetate to inhibit these enzymes in both enzyme-expressed preparations and immature Leydig cells were examined. Molecular docking study of gossypol on the crystal structure of 3α-hydroxysteroid dehydrogenase was performed. Gossypol acetate inhibited 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase with IC50 values of 3.33 ±â€¯0.07 and 0.52 ±â€¯0.06 × 10-6 M in the expressed enzymes as well as 8.512 ±â€¯0.079 and 1.032 ±â€¯0.068 × 10-6 M in intact rat immature Leydig cells, respectively. Gossypol acetate inhibited rat 5α-reductase 1 in a noncompetitive mode and 3α-hydroxysteroid dehydrogenase in a mixed mode when steroid substrates were supplied. Gossypol acetate weakly inhibited retinol dehydrogenase 2 with IC50 value over 1 × 10-4 M. Molecular docking analysis showed that gossypol partially bound to the steroid-binding site of the crystal structure of rat 3α-hydroxysteroid dehydrogenase. Gossypol acetate is a potent inhibitor of rat 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase, possibly inhibiting the formation of androgen in the prostate cancer cells.

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.

Mefenamic acid enhances anticancer drug sensitivity via inhibition of aldo-keto reductase 1C enzyme activity.

Resistance to anticancer medications often leads to poor outcomes. The present study explored an effective approach for enhancing chemotherapy targeted against human cancer cells. Real-time quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed overexpression of members of aldo-keto reductase (AKR) 1C family, AKR1C1, AKR1C2, AKR1C3, and AKR1C4, in cisplatin, cis-diamminedichloroplatinum (II) (CDDP)-resistant human cancer cell lines, HeLa (cervical cancer cells) and Sa3 (oral squamous cell carcinoma cells). The genes were downregulated using small-interfering RNA (siRNA) transfection, and the sensitivity to CDDP or 5-fluorouracil (5-FU) was investigated. When the genes were knocked down, sensitivity to CDDP and 5-FU was restored. Furthermore, we found that administration of mefenamic acid, a widely used non-steroidal anti-inflammatory drug (NSAID) and a known inhibitor of AKR1Cs, enhanced sensitivity to CDDP and 5-FU. The present study suggests that AKR1C family is closely associated with drug resistance to CDDP and 5-FU, and mefenamic acid enhances their sensitivity through its inhibitory activity in drug-resistant human cancer cells. Thus, the use of mefenamic acid to control biological function of AKR1C may lead to effective clinical outcomes by overcoming anticancer drug resistance.

Virtual screening applications in short-chain dehydrogenase/reductase research.

Several members of the short-chain dehydrogenase/reductase (SDR) enzyme family play fundamental roles in adrenal and gonadal steroidogenesis as well as in the metabolism of steroids, oxysterols, bile acids, and retinoids in peripheral tissues, thereby controlling the local activation of their cognate receptors. Some of these SDRs are considered as promising therapeutic targets, for example to treat estrogen-/androgen-dependent and corticosteroid-related diseases, whereas others are considered as anti-targets as their inhibition may lead to disturbances of endocrine functions, thereby contributing to the development and progression of diseases. Nevertheless, the physiological functions of about half of all SDR members are still unknown. In this respect, in silico tools are highly valuable in drug discovery for lead molecule identification, in toxicology screenings to facilitate the identification of hazardous chemicals, and in fundamental research for substrate identification and enzyme characterization. Regarding SDRs, computational methods have been employed for a variety of applications including drug discovery, enzyme characterization and substrate identification, as well as identification of potential endocrine disrupting chemicals (EDC). This review provides an overview of the efforts undertaken in the field of virtual screening supported identification of bioactive molecules in SDR research. In addition, it presents an outlook and addresses the opportunities and limitations of computational modeling and in vitro validation methods.

Lentivirus-mediated silencing of HSDL2 suppresses cell proliferation in human gliomas.

Gliomas are the most common type of malignant brain tumors, and the related prognosis is poor. Though many genes have been identified as factors in the development and progression of gliomas, underlying mechanisms remained unclear. It was clear that abnormal lipid metabolism was one of the major hallmarks of cancers. However, few factors associated with lipid metabolism have been reported to be involved in cancer pathogenesis. Hydroxysteroid dehydrogenase-like 2 (HSDL2) is a protein containing sterol carrier protein 2 (SCP2) domain localized in peroxisomes, which indicated that HSDL2 might be a fatty acid regulatory factor. Here, we revealed that HSDL2 was significantly upregulated in gliomas and its expression was positively correlated with glioma grades. Furthermore, lentiviral-mediated HSDL2 knockdown showed that HSDL2 downregulation inhibited the proliferation in two human glioblastoma cell lines U-251 cells and U87 MG cells, induced cell cycle arrest, and promoted cell apoptosis. Our study provided multiple lines of evidence for the causal relationship between HSDL2 overexpression and glioma progression and provided possible mechanisms underlying HSDL2-mediated glioma growth. Taken together, these results indicated that HSDL2 might serve as a potential target for glioma treatment in the future.

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.

Novel inhibitors of cholesterol degradation in Mycobacterium tuberculosis reveal how the bacterium's metabolism is constrained by the intracellular environment.

Mycobacterium tuberculosis (Mtb) relies on a specialized set of metabolic pathways to support growth in macrophages. By conducting an extensive, unbiased chemical screen to identify small molecules that inhibit Mtb metabolism within macrophages, we identified a significant number of novel compounds that limit Mtb growth in macrophages and in medium containing cholesterol as the principle carbon source. Based on this observation, we developed a chemical-rescue strategy to identify compounds that target metabolic enzymes involved in cholesterol metabolism. This approach identified two compounds that inhibit the HsaAB enzyme complex, which is required for complete degradation of the cholesterol A/B rings. The strategy also identified an inhibitor of PrpC, the 2-methylcitrate synthase, which is required for assimilation of cholesterol-derived propionyl-CoA into the TCA cycle. These chemical probes represent new classes of inhibitors with novel modes of action, and target metabolic pathways required to support growth of Mtb in its host cell. The screen also revealed a structurally-diverse set of compounds that target additional stage(s) of cholesterol utilization. Mutants resistant to this class of compounds are defective in the bacterial adenylate cyclase Rv1625/Cya. These data implicate cyclic-AMP (cAMP) in regulating cholesterol utilization in Mtb, and are consistent with published reports indicating that propionate metabolism is regulated by cAMP levels. Intriguingly, reversal of the cholesterol-dependent growth inhibition caused by this subset of compounds could be achieved by supplementing the media with acetate, but not with glucose, indicating that Mtb is subject to a unique form of metabolic constraint induced by the presence of cholesterol.

Screening baccharin analogs as selective inhibitors against type 5 17ß-hydroxysteroid dehydrogenase (AKR1C3).

Aldo-keto reductase 1C3 (AKR1C3), also known as type 5 17ß-hydroxysteroid dehydrogenase, is a downstream steroidogenic enzyme and converts androgen precursors to the potent androgen receptor ligands: testosterone and 5α-dihydrotestosterone. Studies have shown that AKR1C3 is involved in the development of castration resistant prostate cancer (CRPC) and that it is a rational drug target for the treatment of CRPC. Baccharin, a component of Brazilian propolis, has been observed to exhibit a high inhibitory potency and selectivity for AKR1C3 over other AKR1C isoforms and is a promising lead compound for developing more potent and selective inhibitors. Here, we report the screening of fifteen baccharin analogs as selective inhibitors against AKR1C3 versus AKR1C2 (type 3 3α-hydroxysteroid dehydrogenase). Among these analogs, the inhibitory activity and selectivity of thirteen compounds were evaluated for the first time. The substitution of the 4-dihydrocinnamoyloxy group of baccharin by an acetate group displayed nanomolar inhibitory potency (IC50: 440 nM) and a 102-fold selectivity over AKR1C2. By contrast, when the cinnamic acid group of baccharin was esterified, there was a dramatic decrease in potency and selectivity for AKR1C3 in comparison to baccharin. Low or sub-micromolar inhibition was observed when the 3-prenyl group of baccharin was removed, and the selectivity over AKR1C2 was low. Although unsubstituted baccharin was still the most potent (IC50: 100 nM) and selective inhibitor for AKR1C3, these data provide structure-activity relationships required for the optimization of new baccharin analogs. They suggest that the carboxylate group on cinnamic acid, the prenyl group, and either retention of 4-dihydrocinnamoyloxy group or acetate substituent on cinnamic acid are important to maintain the high potency and selectivity for AKR1C3.

Microwave assisted synthesis and biomedical potency of salicyloyloxy and 2-methoxybenzoyloxy androstane and stigmastane derivatives.

A convenient microwave assisted solvent free synthesis as well as conventional synthesis of salicyloyloxy and 2-methoxybenzoyloxy androstane and stigmastane derivatives 7-19 from appropriate steroidal precursors 1-6 and methyl salicylate is reported. The microwave assisted synthesis in most cases was more successful regarding reaction time and product yields. It was more environmentally friendly too, compared to the conventional method. The antioxidant activity and cytotoxicity of the synthesized derivatives were evaluated in a series of in vitro tests, as well as their inhibition potency exerted on hydroxysteroid dehydrogenase enzymes (Δ(5)-3ßHSD, 17ßHSD2 and 17ßHSD3). All of the tested compounds were effective in OH radical neutralization, particularly compounds 9, 11 and 14, which exhibited about 100-fold stronger activity than commercial antioxidants BHT and BHA. In DPPH radical scavenging new compounds were effective, but less than reference compounds. 2-Methoxybenzoyl ester 10 exhibited strong cytotoxicity against MDA-MB-231 cells. Most compounds inhibited growth of PC-3 cells, where salicyloyloxy stigmastane derivative 15 showed the best inhibition potency. Compounds 9, 10 and 11 were the best inhibitors of 17ßHSD2 enzyme. X-ray structure analysis and molecular mechanics calculations (MMC) were performed for the best cytotoxic agents, compounds 10 and 15. A comparison of crystal and MMC structures of compounds 10 and 15 revealed that their molecules conformations are stable even after releasing of the influence of crystalline field and that the influence of crystal packing on molecular conformation is not predominant.

Development of potent and selective inhibitors of aldo-keto reductase 1C3 (type 5 17ß-hydroxysteroid dehydrogenase) based on N-phenyl-aminobenzoates and their structure-activity relationships.

Aldo-keto reductase 1C3 (AKR1C3; type 5 17ß-hydroxysteroid dehydrogenase) is overexpressed in castration resistant prostate cancer (CRPC) and is implicated in the intratumoral biosynthesis of testosterone and 5α-dihydrotestosterone. Selective AKR1C3 inhibitors are required because compounds should not inhibit the highly related AKR1C1 and AKR1C2 isoforms which are involved in the inactivation of 5α-dihydrotestosterone. NSAIDs, N-phenylanthranilates in particular, are potent but nonselective AKR1C3 inhibitors. Using flufenamic acid, 2-{[3-(trifluoromethyl)phenyl]amino}benzoic acid, as lead compound, five classes of structural analogues were synthesized and evaluated for AKR1C3 inhibitory potency and selectivity. Structure-activity relationship (SAR) studies revealed that a meta-carboxylic acid group relative to the amine conferred pronounced AKR1C3 selectivity without loss of potency, while electron withdrawing groups on the phenylamino B-ring were optimal for AKR1C3 inhibition. Lead compounds did not inhibit COX-1 or COX-2 but blocked the AKR1C3 mediated production of testosterone in LNCaP-AKR1C3 cells. These compounds offer promising leads toward new therapeutics for CRPC.

Expression of human aldo-keto reductase 1C2 in cell lines of peritoneal endometriosis: potential implications in metabolism of progesterone and dydrogesterone and inhibition by progestins.

The human aldo-keto reductase AKR1C2 converts 5α-dihydrotestosterone to the less active 3α-androstanediol and has a minor 20-ketosteroid reductase activity that metabolises progesterone to 20α-hydroxyprogesterone. AKR1C2 is expressed in different peripheral tissues, but its role in uterine diseases like endometriosis has not been studied in detail. Some progestins used for treatment of endometriosis inhibit AKR1C1 and AKR1C3, with unknown effects on AKR1C2. In this study we investigated expression of AKR1C2 in the model cell lines of peritoneal endometriosis, and examined the ability of recombinant AKR1C2 to metabolise progesterone and progestin dydrogesterone, as well as its potential inhibition by progestins. AKR1C2 is expressed in epithelial and stromal endometriotic cell lines at the mRNA level. The recombinant enzyme catalyses reduction of progesterone to 20α-hydroxyprogesterone with a 10-fold lower catalytic efficiency than the major 20-ketosteroid reductase, AKR1C1. AKR1C2 also metabolises progestin dydrogesterone to its 20α-dihydrodydrogesterone, with 8.6-fold higher catalytic efficiency than 5α-dihydrotestosterone. Among the progestins that are currently used for treatment of endometriosis, dydrogesterone, medroxyprogesterone acetate and 20α-dihydrodydrogesterone act as AKR1C2 inhibitors with low µM K(i) values in vitro. Their potential in vivo effects should be further studied.

Transforming growth factor ß1 increase of hydroxysteroid dehydrogenase proteins is partly suppressed by red clover isoflavones in human primary prostate cancer-derived stromal cells.

Transforming growth factor ß1 (TGF-ß1) increases dehydro-epiandrosterone (DHEA) metabolism to androgens and prostate-specific antigen (PSA) in a prostate tissue model where stromal (6S) cells and epithelial (LAPC-4) cells are cocultured. Red clover (RC) isoflavones inhibits transforming growth factor (TGF)-ß-induced androgenicity. Mechanisms controlling those activities were explored. Three hydroxysteroid dehydrogenases (HSDs), 3ß-HSD, HSD-17ß1 and HSD-17ß5 involved in metabolizing DHEA to testosterone (TESTO) were investigated. Individual depletion of HSDs in 6S cells significantly reduced TGF-ß1/DHEA-induced PSA in LAPC-4 cells in cocultures. Monomer amounts of 3ß-HSD were similar without or with TGF-ß1 in both cell types but aggregates of 3ß-HSD in 6S cells were much higher than those in LAPC-4 cells and were upregulated by TGFß in 6S cells. Basal and TGF-ß1-treated levels of HSD-17ß1 and HSD-17ß5 in LAPC-4 cells were significantly lower than in 6S cells, whereas levels of HSD-17ß1 but not HSD-17ß5 were TGFß inducible. 6S cell HSD genes expression induced by TGFß or androgen signaling was insignificant to contribute TGF-ß1/DHEA-upregulated protein levels of HSDs. RC decreased TGF-ß1- upregulation of aggregates of 3ß-HSD but not HSD-17ß1. Depletion of TGFß receptors (TGFß Rs) reduced TGF-ß1/DHEA-upregulated HSDs and TESTO. Immunoprecipitation studies demonstrated that TGF-ß1 disrupted associations of TGFß Rs/HSDs aggregates, whereas RC suppressed the dissociations of aggregates of 3ß-HSD but not HSD-17ß1 from the receptors. Given that TGFß Rs are recycled with or without ligand, TGF-ß1-induced disassociation of the HSDs from TGFß Rs may increase stability and activity of the HSDs. These data suggest a pathway connecting overproduction of TGFß with increased PSA in prostate cancer.

Human hydroxysteroid dehydrogenases and pre-receptor regulation: insights into inhibitor design and evaluation.

Hydroxysteroid dehydrogenases (HSDs) represent a major class of NAD(P)(H) dependent steroid hormone oxidoreductases involved in the pre-receptor regulation of hormone action. This is achieved by HSDs working in pairs so that they can interconvert ketosteroids with hydroxysteroids resulting in a change in ligand potency for nuclear receptors. HSDs belong to two protein superfamilies the aldo-keto reductases and the short-chain dehydrogenase/reductases. In humans, many of the important enzymes have been thoroughly characterized including the elucidation of their three-dimensional structures. Because these enzymes play fundamental roles in steroid hormone action they can be considered to be drug targets for a variety of steroid driven diseases, e.g. metabolic syndrome and obesity, inflammation, and hormone dependent malignancies of the endometrium, prostate and breast. This article will review how fundamental knowledge of these enzymes can be exploited in the development of isoform specific HSD inhibitors from both protein superfamilies. Article from the Special issue on Targeted Inhibitors.

Chemical synthesis of the 17-propanamide derivatives of stereoisomeric Δ14-17α- and 17ß-estradiols: potential 17ß-hydroxysteroid dehydrogenase inhibitors.

The 17-propanamide derivatives of diastereomeric Δ(14)-17α- and 17ß-estradiols, the potential candidates of a 17ß-hydroxysteroid dehydrogenase (17ß-HSD) inhibitor, were synthesized in 11 steps from estrone. The principal reactions employed involved in (1) conversion of estrone to the corresponding Δ(14)-estrone, (2) Grignard reaction of Δ(14)-estrone with allylmagnesium bromide followed by regioselective hydroboration of the resulting stereoisomeric 17ξ-allyl-Δ(14)-17ξ-ols with 9-borabicyclo[3.3.1]nonane (9-BBN), and (3) direct amidation of the 17ξ-O-/17ξ-C-spiro-γ-lactones with NH(3) under positive pressure of H(2).

Preparation of 6beta-estradiol derivative libraries as bisubstrate inhibitors of 7beta-hydroxysteroid dehydrogenase type using the multidetachable sulfamate linker.

Combinatorial chemistry is a powerful tool used to rapidly generate a large number of potentially biologically active compounds. In our goal to develop bisubstrate inhibitors of 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) that interact with both the substrate (estrone or estradiol) and the cofactor (NAD(P)H) binding sites, we used parallel solid-phase synthesis to prepare three libraries of 16beta-estradiol derivatives with two or three levels of molecular diversity. From estrone, we first synthesized a sulfamate precursor that we loaded on trityl chloride resin using the efficient multidetachable sulfamate linker strategy recently developed in our laboratory. We then introduced molecular diversity [one or two amino acid(s) followed by a carboxylic acid] on steroid nucleus by Fmoc peptide chemistry. Finally, after a nucleophilic cleavage, libraries of 30, 63 and 25 estradiol derivatives were provided. A library of 30 sulfamoylated estradiol derivatives was also generated by acidic cleavage and its members were screened for inhibition of steroid sulfatase. Biological evaluation on homogenated HEK-293 cells overexpressing 17beta-HSD1 of the estradiol derivatives carrying different oligoamide-type chains at C-16 first revealed that three levels of molecular diversity (a spacer of two amino acids) were necessary to interact with the adenosine part of the cofactor binding site. Second, the best inhibition was obtained when hydrophobic residues (phenylalanine) were used as building blocks.

Induction of 1C aldoketoreductases and other drug dose-dependent genes upon acquisition of anthracycline resistance.

OBJECTIVES: Recent studies suggest that tumor cells overexpressing aldoketoreductases (AKRs) exhibit increased resistance to DNA damaging agents such as anthracyclines. AKRs may induce resistance to the anthracycline doxorubicin by catalyzing its conversion to the less toxic 13-hydroxy metabolite doxorubicinol. However, it has not been established whether during selection for anthracycline resistance, AKR overexpression in tumor cells can be correlated with the onset or magnitude of drug resistance and with appreciable conversion of anthracyclines to 13-hydroxy metabolites. METHODS AND FINDINGS: Through microarray and quantitative polymerase chain reaction studies involving rigid selection criteria and both correlative discriminate statistics and time-course models, we have identified several genes whose expression can be correlated with the onset and/or magnitude of anthracycline resistance, including AKR1C2 and AKR1C3. Also associated with the onset or magnitude of anthracycline resistance were genes involved in drug transport (ABCB1, ABCC1), cell signaling and transcription (RDC1, CXCR4), cell proliferation or apoptosis (BMP7, CAV1), protection from reactive oxygen species (AKR1C2, AKR1C3, FTL, FTH, TXNRD1, MT2A), and structural or immune system proteins (IFI30, STMN1). As expected, doxorubicin-resistant and epirubicin-resistant cells exhibited higher levels of doxorubicinol than wild-type cells, although at insufficient levels to account for significant drug resistance. Nevertheless, an inhibitor of Akr1c2 (5beta-cholanic acid) almost completely restored sensitivity to doxorubicin in ABCB1-deficient doxorubicin-resistant cells, while having no effect on ABCB1-expressing epirubicin-resistant cells. CONCLUSION: Taken together, we show for the first time that a variety of genes (particularly redox genes such as AKR1C2 and AKR1C3) can be temporally and causally correlated with the acquisition of anthracycline resistance in breast tumor cells.

Reversal of inflammation-associated dihydrodiol dehydrogenases (AKR1C1 and AKR1C2) overexpression and drug resistance in nonsmall cell lung cancer cells by wogonin and chrysin.

Dihydrodiol dehydrogenase (DDH) is a member of the aldo-keto reductases superfamily (AKR1C1-AKR1C4), which plays central roles in the metabolism of steroid hormone, prostaglandin and xenobiotics. We have previously detected overexpression of DDH as an indicator of poor prognosis and chemoresistance in human non-small lung cancer (NSCLC). We also found DDH expression to be closely related to chronic inflammatory conditions. The aim of this study was to investigate the links between inflammation, DDH expression and drug resistance in NSCLC cells. We showed that pro-inflammatory mediators including interleukin-6 (IL-6) could induce AKR1C1/1C2 expression in NSCLC cells and increase cellular resistance to cisplatin and adriamycin. This effect was nullified by Safingol, a protein kinase C inhibitor. Moreover, the expression of AKR1C1/1C2 was inversely correlated to NBS1 and apoptosis-inducing factor (AIF). We also showed that IL-6-induced AKR1C1/1C2 expression and drug resistance were inhibited by wogonin and chrysin, which are major flavonoids in Scutellaria baicalensis, a widely used traditional Chinese and Japanese medicine. In conclusion, this study demonstrated novel links of pro-inflammatory signals, AKR1C1/1C2 expression and drug resistance in NSCLC. The protein kinase C pathway may play an important role in this process. Overexpression of AKR1C1/1C2 may serve as a marker of chemoresistance. Further studies are warranted to evaluate wogonin and chrysin as a potential adjuvant therapy for drug-resistant NSCLC, especially for those with AKR1C1/1C2 overexpression.

Synthesis of libraries of 16beta-aminopropyl estradiol derivatives for targeting two key steroidogenic enzymes.

Two libraries, each consisting of 48 16beta-aminopropyl estradiol derivatives, phenols and sulfamates, respectively, were synthesized by solid-phase parallel chemistry through a seven-step reaction sequence. Following the attachment of a C18-steroid sulfamate precursor on a trityl chloride resin, diversity elements were first introduced on the 16beta-aminopropyl chain of the steroid by acylation reactions with eight Fmoc-amino acids. After deprotection, the free amine function of the resulting compounds was reacted with six carboxylic acids for the introduction of a second diversity level. The two variants employed for the cleavage of compounds from the solid support, acidic and nucleophilic, allowed the corresponding libraries of sulfamate and phenol derivatives in yields of 8-50 % and 13-58 % to be obtained with an average HPLC purity of 94 % and 91 %, respectively. Potent steroid sulfatase inhibitors and interesting SAR results were generated from the screening of the sulfamate library. Furthermore, moderate inhibitors of type 1 17beta-HSD resulted from the partial screening of phenol library. Thus, these two categories of compounds were synthesized to rapidly identify potential inhibitors of steroid biosynthesis for the hormonal therapy of estrogen-dependent diseases, and also to demonstrate the versatility and efficiency of the recently developed sulfamate linker.