Crystal structure of human 17beta-hydroxysteroid dehydrogenase type 5 (AKR1C3) in complex with NADP+ and 3-((4 -(trifluoromethyl)phenyl)amino)benzoic acid

Experimental Data Snapshot

  • Resolution: 2.53 Å
  • R-Value Free: 0.294 
  • R-Value Work: 0.228 
  • R-Value Observed: 0.231 

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Crystal structures of AKR1C3 containing an N-(aryl)amino-benzoate inhibitor and a bifunctional AKR1C3 inhibitor and androgen receptor antagonist. Therapeutic leads for castrate resistant prostate cancer.

Chen, M.Adeniji, A.O.Twenter, B.M.Winkler, J.D.Christianson, D.W.Penning, T.M.

(2012) Bioorg Med Chem Lett 22: 3492-3497

  • DOI: https://doi.org/10.1016/j.bmcl.2012.03.085
  • Primary Citation of Related Structures:  
    4DBS, 4DBU

  • PubMed Abstract: 

    Castrate resistant prostate cancer (CRPC) is associated with increased androgen receptor (AR) signaling often brought about by elevated intratumoral androgen biosynthesis and AR amplification. Inhibition of androgen biosynthesis and/or AR antagonism should be efficacious in the treatment of CRPC. AKR1C3 catalyzes the formation of potent AR ligands from inactive precursors and is one of the most upregulated genes in CRPC. AKR1C3 inhibitors should not inhibit the related isoforms, AKR1C1 and AKR1C2 that are involved in 5α-dihydrotestosterone inactivation in the prostate. We have previously developed a series of flufenamic acid analogs as potent and selective AKR1C3 inhibitors [Adeniji, A. O. et al., J. Med. Chem.2012, 55, 2311]. Here we report the X-ray crystal structure of one lead compound 3-((4-(trifluoromethyl)phenyl) amino)benzoic acid (1) in complex with AKR1C3. Compound 1 adopts a similar binding orientation as flufenamic acid, however, its phenylamino ring projects deeper into a subpocket and confers selectivity over the other AKR1C isoforms. We exploited the observation that some flufenamic acid analogs also act as AR antagonists and synthesized a second generation inhibitor, 3-((4-nitronaphthalen-1-yl)amino)benzoic acid (2). Compound 2 retained nanomolar potency and selective inhibition of AKR1C3 but also acted as an AR antagonist. It inhibited 5α-dihydrotestosterone stimulated AR reporter gene activity with an IC(50)=4.7 μM and produced a concentration dependent reduction in androgen receptor levels in prostate cancer cells. The in vitro and cell-based effects of compound 2 make it a promising lead for development of dual acting agent for CRPC. To illuminate the structural basis of AKR1C3 inhibition, we also report the crystal structure of the AKR1C3·NADP(+)·2 complex, which shows that compound 2 forms a unique double-decker structure with AKR1C3.

  • Organizational Affiliation

    Department of Pharmacology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, United States.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Aldo-keto reductase family 1 member C3
A, B
323Homo sapiensMutation(s): 0 
EC: (PDB Primary Data), (PDB Primary Data), (PDB Primary Data), (PDB Primary Data), (PDB Primary Data), (PDB Primary Data)
UniProt & NIH Common Fund Data Resources
Find proteins for P42330 (Homo sapiens)
Explore P42330 
Go to UniProtKB:  P42330
PHAROS:  P42330
GTEx:  ENSG00000196139 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP42330
Sequence Annotations
  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
BT9 BindingDB:  4DBU IC50: min: 60, max: 2.27e+4 (nM) from 5 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 2.53 Å
  • R-Value Free: 0.294 
  • R-Value Work: 0.228 
  • R-Value Observed: 0.231 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 47.268α = 71.9
b = 49.136β = 81.58
c = 84.725γ = 70.26
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
PDB_EXTRACTdata extraction
HKL-2000data collection
HKL-2000data reduction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-03-28
    Type: Initial release
  • Version 1.1: 2012-04-11
    Changes: Other
  • Version 1.2: 2012-05-02
    Changes: Database references
  • Version 1.3: 2012-05-23
    Changes: Database references
  • Version 1.4: 2017-11-15
    Changes: Refinement description
  • Version 1.5: 2023-09-13
    Changes: Data collection, Database references, Derived calculations, Refinement description