Biological Evaluation of 3-Acyl-2-Arylamino-1,4-Naphthoquinones as Inhibitors of Hsp90 Chaperoning Function

Abstract

Hsp90 is a chaperone that plays a key function in cancer cells by stabilizing proteins responsible of cell growth and survival. Disruption of the Hsp90 chaperone machinery leads to the proteasomal degradation of its client proteins. Hsp90 appears then as an attractive target for the development of new anticancer molecules. We have shown that ascorbate- driven menadione-redox cycling inhibits Hsp90 activity by provoking an N-terminal cleavage of the protein, inducing the degradation of several of its client proteins. Since the mechanism involves an oxidative stress, we explored the effect of a series of diverse donor-acceptor 3-acyl-2-phenylamino 1,4-naphthoquinones on Hsp90 integrity, in the presence of ascorbate. Results show that quinone-derivatives that bear two electroactive groups (namely quinone and nitro) exhibit the highest inhibitory activity (Hsp90 cleavage and cell death). The biological activity of the series mainly relies on their redox capacity and their lipophilicity, which both modulate the ability of these compounds to induce a cytotoxic effect in K562 cells. As observed with other redox cycling quinones, the protein cleavage is blocked in the presence of N-terminal Hsp90 inhibitors suggesting that the availability or occupancy of nucleotide binding site in the N-terminal pocket of Hsp90 plays a critical role. In addition the survival of cancer cells and their metabolic and redox homeostasis were strongly impaired by the presence of ascorbate. Since these effects were similar to that obtained by ascorbate/menadione and they were blocked by the antioxidant N-acetylcyteine (NAC), it appears that oxidative stress is a major component of this cytotoxicity.

Synthetic approaches and in vitro cytotoxic evaluation of 2-acyl-3-(3,4,5-trimethoxyanilino)-1,4-naphthoquinones

“…Based on previous results on the synthesis of arylaminoquinones 15,16 we envisaged achieve new members by reaction of 2-acylnaphthoquinones with di-and tri-substituted anilines. As far as we know the only report in the literature regarding the reactivity of 2-acyl-1,4-naphthoquinones with disubstituted anilines was made by Pardo et al, 15 by using 2-acetyl-1,4-naphthoquinone 2a.…”

“…[5][6][7][8][9][10][11][12][13] The 2-acyl-1,4-benzo-and 1,4-naphthoquinones exhibit remarkable features in terms of their reactivity with nucleophiles due to the fact that the electrophilic centers at the quinone nucleus and acyl substituent are suitably located, thus enabling reactions with compounds such as arylamines [14][15][16] azaenamines 17 enaminones 18,19 and 2-aminobenzothiazoles 20 to give rise to a broad variety of quinonoid compounds such as those depicted in Fig. 1.…”

“…We have previously reported that a series of 2-acyl-3-anilino-1,4-naphthoquinones possess biological properties such as inhibitors of Hsp90 chaperoning function, 16 cytotoxic actions on cancer cells 21 and DNA-intercalants. 22 These compounds, prepared by amination reaction of 2-acyl-1,4-naphthoquinone with diverse p-substituted anilines under aerobic conditions, 21 were originally designed as inhibitors of Hsp90 chaperone and their structures are based on that of the Hsp90 inhibitor, 2-acetyl-3-phenyl-1,4-naphthoquinone (HTS1).…”

Substituted 3-acyl-2-phenylamino-1,4-naphthoquinones intercalate into DNA and cause genotoxicity through the increased generation of reactive oxygen species culminating in cell death

“…1) (15). The quinone structures were confirmed by comparing their infrared and proton/carbon nuclear magnetic resonance spectral properties to those reported in the literature (15).…”

“…The resulting compounds were then oxidized with silver (I) oxide in dichloromethane, and the corresponding 2-acyl-1,4-naphthoquinones were reacted in situ with selected phenylamines in a one-step procedure to produce the corresponding 3-acyl-2-phenylamino-1,4-naphthoquinones DPB1-DPB9 ( Fig. 1) (15). The quinone structures were confirmed by comparing their infrared and proton/carbon nuclear magnetic resonance spectral properties to those reported in the literature (15).…”