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

ABSTRACT: Aldo-keto reductase 1C3 (AKR1C3), also known as type 5 17?-hydroxysteroid dehydrogenase, is a downstream steroidogenic enzyme and converts androgen precursors to the potent androgen receptor ligands: testosterone and 5?-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 3?-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.

SUBMITTER: Zang T

PROVIDER: S-EPMC4414711 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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

Zang Tianzhu T Verma Kshitij K Chen Mo M Jin Yi Y Trippier Paul C PC Penning Trevor M TM

Chemico-biological interactions 20141231

Aldo-keto reductase 1C3 (AKR1C3), also known as type 5 17β-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 inh ...[more]

PMID: 25555457

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Project description:Aldo-keto reductase (AKR) 1C3 catalyzes the NADPH-dependent reduction of Delta(4)-androstene-3,17-dione to yield testosterone, reduction of estrone to yield 17beta-estradiol and reduction of progesterone to yield 20alpha-hydroxyprogesterone. In addition, it functions as a prostaglandin (PG) F synthase and reduces PGH(2) to PGF(2)alpha and PGD(2) to 11beta-PGF(2). Immunohistochemistry showed that AKR1C3 is over-expressed in invasive ductal carcinoma of the breast. Retroviral expression of AKR1C3 in MCF-7 breast carcinoma cells shows that each of the assigned reactions occur in a breast cell microenvironment. Steroid and prostaglandin conversions were monitored by radiochromatography. Prostaglandin conversion was validated by a second method using HPLC coupled to APCI-MRM/MS. The combined effect of the AKR1C3 catalyzed 17- and 20-ketosteroid reductions will be to increase the 17beta-estradiol:progesterone ratio in the breast. In addition, formation of PGF(2) epimers would activate F prostanoid receptors and deprive PPARgamma of its putative anti-proliferative PGJ(2) ligands. Thus, AKR1C3 is a source of proliferative signals and a potential therapeutic target for hormone-dependent and -independent breast cancer. Two strategies for AKR1C3 inhibition based on non-steroidal anti-inflammatory drugs were developed. The first strategy uses the Ullmann coupling reaction to generate N-phenylanthranilate derivatives that inhibit AKR1C enzymes without affecting PGH(2) synthase (PGHS) 1 or PGHS-2. The second strategy exploits the selective inhibition of AKR1C3 by indomethacin, which did not inhibit highly related AKR1C1 or AKR1C2. Using known structure-activity relationships for the inhibition of PGHS-1 and PGHS-2 by indole acetic acids we obtained N-(4-chlorobenzoyl)-melatonin as a specific AKR1C3 inhibitor (K(I)=6.0muM) that does not inhibit PGHS-1, PGHS-2, AKR1C1, or AKR1C2. Both strategies are informed by crystal structures of ternary AKR1C3.NADP(+).NSAID complexes. The identification of NSAID analogs as specific inhibitors of AKR1C3 will help validate its role in the proliferation of breast cancer cells.

Dataset Information

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

Publications

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

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