Carbonic Anhydrase Inhibitor Coated Gold Nanoparticles Selectively Inhibit the Tumor-Associated Isoform IX over the Cytosolic Isozymes I and II

Abstract

The carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous metalloenzymes with five independently evolved (R, ,γ,δ,ς) classes reported up to date. [1][2][3] These enzymes catalyze the reversible hydration of carbon dioxide to bicarbonate and protons by means of a metalhydroxide (Lig 3 M 2+ (OH) -) mechanism. 2 In addition to the established role of the carbonic anhydrase inhibitors (CAIs) as diuretics and antiglaucoma drugs, it has recently emerged that CAIs could have potential as novel antiobesity, anticancer, and anti-infective drugs. 1,2 A critical problem in the design of CAIs is related to the high number of isoforms in mammals (15), their diffuse localization in many tissues/organs, and the lack of isozyme selectivity of the presently available inhibitors. [1][2][3][4] Recently, nanoparticles received great attention for their biomedical applications both for the site-specific delivery of drugs 7 or for imaging purposes. 7,8 Several recent such examples include HIV inhibition with a CCR5 antagonist attached to multivalent gold nanoparticles (Au NPs), tumor targeting with NPs loaded with hydroxycamptothecin, paclitaxel, or fumagillin, and magnetic resonance imaging (MRI) techniques of tumors based on integrins targeting with Fe 3 O 4 NPs, computer tomography (CT) or MRI imaging with gadolinium chelate Au NPs, etc. 7,8 Human CA IX (hCA IX) is an extracellular, transmembrane isoform which was recently shown to constitute a novel and interesting target for the anticancer therapy due to its overexpression in many cancer tissues and not in their normal counterparts. 1b,9 Its expression is strongly induced by hypoxia present in many tumor tissues and correlated with a bad response to classical chemo-and radiotherapies. 1b,9 CA IX was shown to acidify the extratumoral medium leading both to the acquisition of metastasic phenotypes and to chemoresistance with many anticancer drugs, these processes being reverted by inhibition of the enzyme catalytic activity with sulfonamide inhibitors. 1b,9 The development of selective CA IX inhibitors might provide useful tools for highlighting the exact role of CA IX in hypoxic cancers, to control the pH imbalance of tumor cells and lead to novel diagnostic or therapeutic applications for the management of such tumors. 1b,9 Although many sulfonamide/sulfamate/sulfamide potent CA IX inhibitors were reported, few of them show an acceptable level of selectivity for inhibiting the transmembrane-tumor associated target isoform IX over the cytosolic, ubiquitous isozymes hCA I and II. 1b,9 Considering the extracellular localization of the target CA isoform and the fact that nanomaterials generally show membrane impermeability, 10 we report here the synthesis of CAI coated Au NPs which show excellent CA IX inhibitory properties and selectivity for the inhibition of the tumor-associated isoform over hCA I and II.The key intermediate 3a was synthesized by coupling lipoic acid 1 with 4-aminoethylbenzene sulfonamide 2a in the presence of EDCI/ DMAP, as outlined in Scheme 1. The CAI coated...

Fluorescent Silica Nanoparticles with Multivalent Inhibitory Effects towards Carbonic Anhydrases

“…[27] In fact, the only other contribution dealingw ith this was our earlier work in which we reported gold nanoparticles derivatized with athiol-containing benzenesulfonamide, which showed excellent inhibitorya nd multivalency effects for inhibiting the tumor-associated CA IX (but were much less effective as CA Ia nd II inhibitors). [5] For the nanoparticles reported here, based on silica nanoparticles, the opposite effect was observed:f or the cytosolic isoforms hCA I and II, the inhibition constants decreased from 142 to 4.4 nm for hCA I, and from 48 to 0.67 nm for hCA II, corresponding to an inhibitory potency improvement of 32 and 72 times, respectively,w hen compared to the monovalent system. However, multivalency effects were not observed for the transmembrane isoformsh CA IX and XII.…”

“…[3,4] Beside the rational drug design of more selectivee nzymei nhibitors, the nanoparticles approachw as appliedb yo ur group to carbonic anhydrases and we demonstrated the possibility of activity modulation of carbonic anhydrases using nano-objects. [5,6] Due to their size, ease of synthesis, andt heir potentiala pplications, silica-based nanoparticles received great attention for their biomedical applications both for the site-specific delivery of drugs or for imaging purposes. [7][8][9] Moreoveri tc onstitutes ag ood platform for developing multivalent interactions,w hich is ap romising option for the specific treatment of diseases.…”

Nanoscale enzyme inhibitors: Fullerenes inhibit carbonic anhydrase by occluding the active site entrance

“…[13][14][15] CAs are in fact involved in numerous physiological and pathological processes, including respiration and transport of CO 2 /bicarbonate between metabolizing tissues and lungs, pH and CO 2 homeostasis, electrolyte secretion in a variety of tissues/organs, biosynthetic reactions (e.g., gluconeogenesis, lipogenesis, and ureagenesis), bone resorption, calcification, tumorigenicity, and many other such processes in humans. 13,[16][17][18][19][20][21] In addition to the established role of the sulfonamide/sulfamate CA inhibitors (CAIs) as diuretics and antiglaucoma drugs, it has recently emerged that they have potential as anticonvulsant, antiobesity, anticancer, and antiinfective drugs. 13 Many of the mammalian CA isozymes involved in these processes are important therapeutic targets with the potential to be inhibited or activated to treat a wide range of disorders.…”

“…13 Only very recently nanoscale CAIs have been reported by this group. 20 By decorating gold(0) nanoparticles with sulfonamides incorporating lipoic acid tails, we obtained nanoscale sulfonamide CAIs (with a diameter of 3 nm) which selectively inhibited the tumor-associated isoform CA IX over the cytosolic ubiquitous isozymes CA I and II. We also recently reported a totally novel class of CAIs, the coumarins, 22 which bind CAs in a zinc-independent manner, by anchoring, in hydrolyzed form, as 2-hydroxycinnamic acids, at the entrance of the active site and occluding it.…”

Exploring carbonic anhydrase inhibition with multimeric coumarins displayed on a fullerene scaffold

“…In 2008, Supuran et al synthesized nanoparticles functionalized by sulphonamides. 26 Although no multivalent effect was observed, the nanoparticles were potent inhibitors of CA and were shown not to penetrate into cells, contrarily to the corresponding monovalent species. This property could be extremely advantageous in case an extracellular enzymatic activity is targeted for a therapeutic purpose, which is the case for the tumour associated CA IX activity.…”