Isoenzyme- and Allozyme-Specific Inhibitors: 2,20-Dihydroxybenzophenones and Their Carbonyl N-Analogues that Discriminate between Human Glutathione Transferase A1-1 and P1-1 Allozymes

The selectivity of certain benzophenones and their carbonyl N-analogues was investigated towards the human GSTP1-1 allozymes A, B and C involved in MDR. The allozymes were purified from extracts derived from E. coli harbouring the plasmids pEXP5-CT/TOPO-TAhGSTP1* A, pOXO4-hGSTP1*B or pOXO4-hGSTP1*C. Compound screening with each allozyme activity indicated three compounds with appreciable inhibitory potencies, 12 and 13 with P1-1A 62% and 67%, 11 and 12 with P1-1C 51% and 70%, whereas that of 15 fell behind with P1-1B (41%). These findings were confirmed by IC50 values (74–125 lM). Enzyme inhibition kinetics, aided by molecular modelling and docking, revealed that there is competition with the substrate CDNB for the same binding site on the allozyme (Ki(13/ A) = 63.6 +- 3.0 lM, K (15/B) = 198.6 +- 14.3 lM, and Ki(11/ C) = 16.5 +- 2.7 lM). These data were brought into context by an in silico structural comparative analysis of the targeted proteins. Although the screened compounds showed moderate inhibitory potency against hGSTP1-1, remarkably, some of them demonstrated absolute isoenzyme and/or allozyme selectivity

Synthesis and Study of 2‑(Pyrrolesulfonylmethyl)‑N‑arylimines: A New Class of Inhibitors for Human Glutathione Transferase A1‑1

Overexpression of human GSTA1-1 in tumor cells is part of MDR mechanisms. We report on the synthesis of 11 pyrrole derivatives as hGSTA1-1 inhibitors starting from 1-methyl-2-[(2-nitrobenzylsulfanyl]-1H-pyrrole. Molecular modeling revealed two locations in the enzyme H binding site: the catalytic primary one accommodating shorter and longer derivatives and the secondary one, where shorter derivatives can occupy. Derivative 9, displaying the highest inhibition and bearing a p-nitroarylimino moiety, and derivative 4, lacking this moiety, were studied kinetically. Derivative 9 binds (Ki(9) = 71 ± 4 μM) at the primary site competitively vs CDNB. Derivative 4 binds (Ki(4) = 135 ± 27 μM) at the primary and secondary sites, allowing the binding of a second molecule (4 or CDNB) leading to formation of unreactive and reactive complexes, respectively. The arylmethylsulfonylpyrrole core structure is a new pharmacophore for hGSTA1-1, whereas its derivative 9 may serve as a lead structure

2,20-Dihydroxybenzophenones and their carbonyl N-analogues as inhibitor scaffolds for MDR-involved human glutathione transferase isoenzyme A1-1

The MDR-involved human GSTA1-1, an important isoenzyme overexpressed in several tumors leading to chemotherapeutic-resistant tumour cells, has been targeted by 2,2′-dihydroxybenzophenones and some of their carbonyl N-analogues, as its potential inhibitors. A structure-based library of the latter was built-up by a nucleophilic cleavage of suitably substituted xanthones to 2,2′-dihydroxy-benzophenones (5–9) and subsequent formation of their N-derivatives (oximes 11–13 and N-acyl hydrazones 14–16). Screening against hGSTA1-1 led to benzophenones 6 and 8, and hydrazones 14 and 16, having the highest inhibition potency (IC50 values in the range 0.18 ± 0.02 to 1.77 ± 0.10 μM). Enzyme inhibition kinetics, molecular modeling and docking studies showed that they interact primarily at the CDNB-binding catalytic site of the enzyme. In addition, the results from cytotoxicity studies with human colon adenocarcinoma cells showed low LC50 values for benzophenone 6 and its N-acyl hydrazone analogue 14 (31.4 ± 0.4 μM and 87 ± 1.9 μM, respectively), in addition to the strong enzyme inhibition profile (IC50(6) = 1,77 ± 0.10 μM; IC50(14) = 0.33 ± 0.05 μM). These structures may serve as leads for the design of new potent mono- and bi-functional inhibitors and pro-drugs against human GTSs

Designer Xanthone An Inhibitor Scaffold for MDR-Involved Human Glutathione Transferase Isoenzyme A1-1

Glutathione transferases (GSTs) are cell detoxifiers involved in multiple drug resistance (MDR), hampering the effectiveness of certain anticancer drugs. To our knowledge, this is the first report on well-defined synthetic xanthones as GST inhibitors. Screening 18 xanthones revealed three derivatives bearing a bromomethyl and a methyl group (7) or two bromomethyl groups (8) or an aldehyde group (17), with high inhibition potency (>85%), manifested by low IC50 values (7: 1.59 ± 0.25 μM, 8: 5.30 ± 0.30 μM, and 17: 8.56 ± 0.14 μM) and a competitive modality of inhibition versus CDNB (Ki(7) = 0.76 ± 0.18 and Ki(17) = 1.69 ± 0.08 μM). Of them, derivative 17 readily inhibited hGSTA1-1 in colon cancer cell lysate (IC50 = 10.54 ± 2.41 μM). Furthermore, all three derivatives were cytotoxic to Caco-2 intact cells, with 17 being the least cytotoxic (LC50 = 151.3 ± 16.3 μM). The xanthone scaffold may be regarded as a pharmacophore for hGSTA1-1 and the three derivatives, especially 17, as potent precursors for the synthesis of new inhibitors and conjugate prodrugs for human GSTs

Mutational Analysis Mapping on The Molecular Structure of The ACVRL1 Protein and Implications For Rendu-Osler-Weber (ROW)

About 80% of Rendu-OslerndashWeber (ROW) patients carry mutations in endoglin (ENG) or activin receptor-like kinase1 (ACVRL1 ALK1) genes. In order to investigate the molecular mechanisms that govern the pathogenic effect of the mutations in ACVRL1, we have collected and analyzed the mutational effect of over 80 different predominant mutations, as well as their location, on the 3D molecular structures of N- and C-terminal domains of ACVRL1. We have used macromolecular modeling on the protein structural components of ACVLR1 and structural component interface analysis to locate position and interaction of point mutations. Specific mutations were identified using genomic DNA sequencing from blood leucocytes. Out of the 151 point mutations reported for the ALK1 gene, the majority are located on the surface of the ARD and PK structural domains, with some on the interaction interface. New observed mutation Cys90Phe found in two Cretan ROW patients, located on loop F4 of ARD, introduces conformational steric hindrance and disruption of stability. We have mapped point mutations on the structural domains of ACVLR1, correlating location and severity of ROW. In addition, we report the identification and location of a novel missense mutation, Cys90Phe, which has not yet been described. It is identified in a Cretan ROW patient, and associated with severe clinical appearance according to the Curacao criteria

Synthesis and Study of 2‑(Pyrrolesulfonylmethyl)‑<i>N</i>‑arylimines: A New Class of Inhibitors for Human Glutathione Transferase A1‑1

Overexpression of human GSTA1-1 in tumor cells is part of MDR mechanisms. We report on the synthesis of 11 pyrrole derivatives as hGSTA1-1 inhibitors starting from 1-methyl-2-[(2-nitrobenzylsulfanyl]-1<i>H</i>-pyrrole. Molecular modeling revealed two locations in the enzyme H binding site: the catalytic primary one accommodating shorter and longer derivatives and the secondary one, where shorter derivatives can occupy. Derivative <b>9</b>, displaying the highest inhibition and bearing a <i>p</i>-nitroarylimino moiety, and derivative <b>4</b>, lacking this moiety, were studied kinetically. Derivative <b>9</b> binds (<i>K</i>_i(<b>9</b>) = 71 ± 4 μM) at the primary site competitively vs CDNB. Derivative <b>4</b> binds (<i>K</i>_i(<b>4</b>) = 135 ± 27 μM) at the primary and secondary sites, allowing the binding of a second molecule (<b>4</b> or CDNB) leading to formation of unreactive and reactive complexes, respectively. The arylmethylsulfonylpyrrole core structure is a new pharmacophore for hGSTA1-1, whereas its derivative <b>9</b> may serve as a lead structure