Search

Copper complexes have shown promising anticancer properties, but they are often poorly soluble in aqueous solutions, thus limiting their possible medical developments and applications. We have recently isolated some copper(II) complexes with salicylaldehyde thiosemicarbazone ligands exhibiting remarkable nanomolar cytotoxic activity, but in vivo tests evidenced several difficulties related to their poor solubility. To overcome these limitations and increase solubility in aqueous solution, herein we report the synthetic strategy that led to the introduction of the sulfonic group on the ligands, then separated as salts (NaH 2 L 1 - NaH 2 L 5 ), as well as the synthesis and characterization of the related copper(II) complexes. The characterization of the complexes is completed by the analysis of the structures obtained by X-rays diffraction on single crystals on the species [Cu(HL 5 )(H 2 O)] 2 . 2H 2 O, [Cu(HL 2 )(H 2 O) 2 ] . 2H 2 O, and [Cu(HL 1 )(H 2 O] 2 O. While the uncoordinated ligands do not affect cancer cell viability, copper(II) complexes exhibit low to sub-micromolar cytotoxic activity, which is maintained in 3D (HCT-15 and 2008) spheroidal models of cancer cell. Notably, copper(II) complexes were selective towards cancer cells, showing high selectivity indexes. Investigations focused on elucidating the mechanism of action evidenced the protein disulfide-isomerase as an innovative molecular target for this class of water-soluble copper(II) complexes. Finally, preliminary in vivo experiments performed with the most representative derivative in the murine Lewis Lung Carcinoma, highlight its significant antitumor efficacy and better tolerability profile with respect to the reference metallodrug, suggesting for this sulfonated Cu(II) complex a potential clinical relevance.. 2H 2 O. While the uncoordinated ligands do not affect cancer cell viability, copper(II) complexes exhibit low to sub-micromolar cytotoxic activity, which is maintained in 3D (HCT-15 and 2008) spheroidal models of cancer cell. Notably, copper(II) complexes were selective towards cancer cells, showing high selectivity indexes. Investigations focused on elucidating the mechanism of action evidenced the protein disulfide-isomerase as an innovative molecular target for this class of water-soluble copper(II) complexes. Finally, preliminary in vivo experiments performed with the most representative derivative in the murine Lewis Lung Carcinoma, highlight its significant antitumor efficacy and better tolerability profile with respect to the reference metallodrug, suggesting for this sulfonated Cu(II) complex a potential clinical relevance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The 3 d transition metal (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes, supported by anions of sterically demanding β-diketones, 1,3-dimesitylpropane-1,3-dione (HL Mes ) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HL CF3 ), were synthesized and evaluated for their antitumor activity. To assess the biological effects of substituents on phenyl moieties, we also synthesized and investigated the analogous metal(II) complexes of the anion of the less bulky 1,3-diphenylpropane-1,3-dione (HL Ph ) ligand. The compounds [Cu(L CF3 ) 2 ], [Cu(L Mes ) 2 ] and ([Zn(L Mes ) 2 ]) were characterized by X-ray crystallography. The [Cu(L CF3 ) 2 ] crystallizes with an apical molecule of solvent (THF) and features a rare square pyramidal geometry at the Cu(II) center. The copper(II) and zinc(II) complexes of diketonate ligands, derived from the deprotonated 1,3-dimesitylpropane-1,3-dione (HL Mes ), adopt a square planar or a tetrahedral geometry at the metal, respectively. We evaluated the antitumor properties of the newly synthesized (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes against a series of human tumor cell lines derived from different solid tumors. Except for iron derivatives, cellular studies revealed noteworthy antitumor properties, even towards cancer cells endowed with poor sensitivity to the reference drug cisplatin.

Bis(pyrazol-1-yl)acetic acid (HC(pz) 2 COOH) and bis(3,5-dimethyl-pyrazol-1-yl)acetic acid (HC(pz Me2 ) 2 COOH) were converted into the methyl ester derivatives 1 (L OMe ) and 2 (L 2OMe ), respectively, and were used for the preparation of Cu(I) and Cu(II) complexes 3 - 10 . The copper(II) complexes were prepared by the reaction of CuCl 2 ·2H 2 O or CuBr 2 with ligands 1 and 2 in methanol solution. The copper(I) complexes were prepared by the reaction of Cu[(CH 3 CN) 4 ]PF 6 and 1,3,5-triaza-7-phosphaadamantane (PTA) or triphenylphosphine with L OMe and L 2OMe in acetonitrile solution. Synchrotron radiation-based complementary techniques (XPS, NEXAFS, and XAS) were used to investigate the electronic and molecular structures of the complexes and the local structure around copper ions in selected Cu(I) and Cu(II) coordination compounds. All Cu(I) and Cu(II) complexes showed a significant in vitro antitumor activity, proving to be more effective than the reference drug cisplatin in a panel of human cancer cell lines, and were able to overcome cisplatin resistance. Noticeably, Cu complexes appeared much more effective than cisplatin in 3D spheroid cultures. Mechanistic studies revealed that the antitumor potential did not correlate with cellular accumulation but was consistent with intracellular targeting of PDI, ER stress, and paraptotic cell death induction.

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes ( 1 , -NH 2 ; 2 , -NHMe; 3 , -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3 , two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b ) or in the co-ligand (water in 3a and methanol in 3b ). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained.

In the present article, copper(I) complexes of bis(pyrazol-1-yl) carboxylic acid (LH), bis(3,5-dimethylpyrazol-1-yl) carboxylic acid (L 2 H), and bis(pyrazol-1-yl) acetates conjugated with an N -methyl-d-aspartate (NMDA) receptor antagonist (L NMDA or L 2NMDA ) and phosphane ligands (triphenylphosphine or 1,3,5-triaza-7-phosphaadamantane) were synthesized. The selection of an NMDA antagonist for the coupling with LH and L 2 H was suggested by the observation that NMDA receptors are expressed and play a role in different types of cancer models. All the new complexes showed a significant antitumor activity on a panel of human tumor cell lines of different histology, with cisplatin-sensitive, cisplatin-resistant, or multi-drug-resistant phenotype. Their half maximal inhibitory concentration (IC 50 ) values were in the low- and sub-micromolar range and, in general, significantly lower than that of cisplatin. Interestingly, the fact that all the complexes proved to be significantly more active than cisplatin even in three-dimensional (3D) spheroids of H157 and BxPC3 cancer cells increased the relevance of the in vitro results. Finally, morphological analysis revealed that the most representative complex 8 induced a massive swelling of the endoplasmic reticulum (ER) membrane, which is a clear sign of ER stress.

Four estrogen-functionalised copper complexes were synthesised and investigated as electrochemical active DNA binding and cleavage agents. These complexes strategically contain a biocompatible metal centre [Cu(II)], a planar aromatic ligand as DNA intercalative agent and an estradiol-derivative moiety which acts as delivery vector to target estrogen-receptor-positive (ER+) cancer cells. Cytotoxic activity was studied over a panel of estrogen-receptor-positive (ER+) and negative (ER-) human cancer cell lines by means of both 2D and 3D cell viability studies. The complexes showed high in vitro intercalative interaction with nuclear DNA and demonstrated to be strong DNA cleaving agents. This series of Cu compounds are potent anticancer agents with low and sub-micromolar IC 50 values and the cellular uptake follows the lipophilicity order meaning that the internalisation mainly happened via passive diffusion. Finally, the estrogen-complexes are involved in the cellular redox stress by stimulating the production of ROS (reactive oxygen species).

Copper(I) and copper(II) complexes of 5-nitroimidazole conjugated heteroscorpionate ligands have been synthesized. In particular, the new 2,2-bis(pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide ligand (L H MN) was synthesized by direct coupling of preformed side chain acid with 5-nitroimidazole and its coordination chemistry was investigated towards Cu(I) and Cu(II) acceptors and compared with that of the related 2,2-bis(3,5-dimethyl-1-H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide ligand (L Me MN). The copper(II) complexes {[(L Me MN) 2 Cu]Cl 2 } and {[(L H MN) 2 Cu]Cl 2 } were prepared by the reaction of CuCl 2 ·2H 2 O with L H MN or L Me MN ligands in methanol solution. The water soluble copper(I) complexes {[(L Me MN)Cu(PTA) 2 ]}(PF 6 ) and {[(L H MN)Cu(PTA) 2 ]}(PF 6 ) were prepared by the reaction of Cu(CH 3 CN) 4 PF 6 and 1,3,5-triaza-7-phosphaadamantane (PTA) with L H MN or L Me MN ligands in acetonitrile solution. The new Cu(I) and Cu(II) complexes as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity against 2D monolayer cultures of multiple human cancer cell lines and 3D-cultured HCT-15 colon cancer spheroids. Morphological analysis by Transmission Electron Microscopy (TEM) revealed the induction of a massive cytoplasmic vacuolization consistent with a paraptotic-like cancer cell death., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Three new 2-oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde terminal substituted aroylhydrazone ligands (2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H 2 L1, 1, 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H 2 L2, 2, 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H 2 L3, 3) and the corresponding novel copper(II) complexes [Cu(L)(CH 3 OH)(NO 3 )](L = HL1 (4), HL2 (5), HL3 (6-6 + ), have been synthesized to compare their coordination behaviour and biological activity with respect to the presence of an OH group in different positions of the phenyl ring in the hydrazone moieties. The new ligands and their copper complexes were characterized by elemental analysis and spectroscopic techniques. The molecular structures of the new complexes 4 and 6-6 + were determined by single crystal X-ray diffraction. The interactions of the free ligands and their copper complexes with calf thymus DNA were tested by absorption measurements and ethidium bromide competitive studies which revealed that all compounds may interact with calf thymus DNA through intercalation. Furthermore, a comparative analysis of the cytotoxic effect of the compounds on a panel of human cancer cell lines showed that the copper complexes exhibited in vitro antitumor activity significantly higher than that of the free ligands and also of cisplatin., (Copyright © 2018 Elsevier Inc. All rights reserved.)

[Cu(thp) 4 ][PF 6 ] (HydroCuP) is a phosphino copper(I) complex highly soluble and stable in physiological media that has been developed as a possible viable alternative to platinum-based drugs for anticancer therapy. HydroCuP potently inhibited the growth of human cancer cells derived from solid tumors by inducing endoplasmatic reticulum (ER) stress thus leading to cell death through paraptosis with a preferential efficacy against cancer rather than non-cancer cells. Aim of the present study was to assess the therapeutic potential of HydroCuP in vivo, in syngenic and xenograft murine models of solid tumors by triggering the Unfolded Protein Response (UPR) pathway. With respect to platinum drugs, HydroCuP induced a markedly higher reduction of tumor growth associated with minimal animal toxicity. In human colorectal cancer xenografts, chemotherapy with HydroCuP was extremely effective in both oxaliplatin-sensitive and resistant models. The favorable in vivo tolerability of HydroCuP was also correlated to an encouraging biodistribution profile. Additionally, no signs of drug-related neurotoxicity and nephrotoxicity were observed. Altogether, these results demonstrate that HydroCuP appears worth of further investigation to evaluate its therapeutic activity towards a broad spectrum of solid malignancies.

A series of copper(II) complexes with tripodal polypyridylamine ligands (derived from the parent ligand tris(2-pyridylmethyl)amine, tmpa) has been synthesized. Crystallographic characterization was possible for all complexes obtained. The copper(II) chloride complexes were investigated for their in vitro anticancer potential using human tumor cell lines containing examples of cervical, colon, ovarian cancers and melanoma. Some compounds showed a similar activity compared to that of cisplatin, however no systematic behavior could be observed., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

The phosphane Cu(I) complex [Cu(thp) 4 ][PF 6 ], 1 (thp=tris(hydroxymethyl)phosphane) shows notable in vitro antitumour activity against a wide range of solid tumours. Uptake experiments performed in 1-treated colon cancer cells by atomic absorption spectrometry, reveal that the antiproliferative activity is consistent with the intracellular copper content. The solution chemistry of this agent, investigated by means of X-ray Absorption Spectroscopy and spectrophotometric titrations in aqueous media, indicates that 1 is labile giving coordinative unsaturated [Cu(thp) n ] + species (n=3 and 2) at micromolar concentrations. [Cu(thp) n ] + are reactive species that yield the mixed-ligand complex [Cu(thp) 2 (BCS)] - (BCS: bathocuproinedisulphonate (2-) ) upon interaction with N,N-diimine. Analogously, [Cu(thp) n ] + interact with the methionine-rich peptide sequence (Ac-MMMMPMTFK-NH 2 ; Pep1), relevant in the recruiting of physiological copper, giving [Cu(thp)(Pep1)] + and [Cu(Pep1)] + species. The formation of these adducts was assessed by electrospray mass spectrometry in the positive ion mode and validated by density functional theory investigations. The possibility to trans-chelate Cu(I) from pure inorganic [Cu(thp) n ] + assemblies into more physiological adducts represents a pathway that complex 1 might follow during the internalization process into cancer cells., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Homoleptic, tetrahedral Cu(i) complexes of the type [Cu(P)4]BF4 (1-3), where P are the phosphine ligands, 1,3,5-triaza-7-phosphaadamantane (PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) and 2-thia-1,3,5-triaza-phosphoaadamantane-2,2-dioxide (PTA-SO2), have been prepared. Novel complexes [Cu(DAPTA)4]BF42 and [Cu(PTA-SO2)4]BF43 have been fully characterized by means of spectroscopic methods, corroborated by XAS-EXAFS analysis of 2. In vitro cell culture experiments revealed a significant antiproliferative activity for Cu(i) compounds against several human cancer cell lines derived from solid tumors with preferential cell growth inhibition towards tumour compared to non-malignant cells. In vitro monitoring of migration and capillary-like tube formation of human umbilical vein endothelial cells (HUVECs) showed an anti-angiogenic effect of copper(i) complexes at sub-cytotoxic concentrations. In vivo studies on the antitumor efficacy and ability to inhibit angiogenesis confirmed the dual cytotoxic and anti-angiogenic properties of Cu(i) derivatives.

A phosphine copper(I) complex [Cu(thp)4][PF6] (CP) was recently identified as an efficient in vitro antitumor agent. In this study, we evaluated the antiproliferative activity of CP in leukemia cell lines finding a significant efficacy, especially against SEM and RS4;11 cells. Immunoblot analysis showed the activation of caspase-12 and caspase-9 and of the two effector caspase-3 and -7, suggesting that cell death occurred in a caspase-dependent manner. Interestingly we did not observe mitochondrial involvement in the process of cell death. Measures on semipurified proteasome from RS4;11 and SEM cell extracts demonstrated that chymotrypsin-, trypsin- and caspase-like activity decreased in the presence of CP. Moreover, we found an accumulation of ubiquitinated proteins and a remarkable increase of ER stress markers: GRP78, CHOP, and the spliced form of XBP1. Accordingly, the protein synthesis inhibitor cycloheximide significantly protected cancer cells from CP-induced cell death, suggesting that protein synthesis machinery was involved. In well agreement with results obtained on stabilized cell lines, CP induced ER-stress and apoptosis also in primary cells from B-acute lymphoblastic leukemia patients. Importantly, we showed that the combination of CP with some chemotherapeutic drugs displayed a good synergy that strongly affected the survival of both RS4;11 and SEM cells.

Tetrahedral copper(I) TpCuP complexes 1-15, where Tp is a N,N,N-tris(azolyl)borate and P is a tertiary phosphine, have been synthesized and characterized by means of NMR, ESI-MS, and XAS-EXAFS, and X-ray diffraction analyses on the representative complexes 1 and 10, respectively. All copper(I) complexes were evaluated for their antiproliferative activity against a panel of human cancer cell lines (including cisplatin and multidrug-resistant sublines). The two most effective complexes [HB(pz)3]Cu(PCN), 1, and [HB(pz)3]Cu(PTA), 2, showed selectivity toward tumor vs normal cells, inhibition of 26S proteasome activity associated with endoplasmic reticulum (ER) stress, and unfolded protein response (UPR) activation. No biochemical hallmarks of apoptosis were detected, and morphology studies revealed an extensive cytoplasmic vacuolization coherently with a paraptosis-like cell death mechanism. Finally, the antitumor efficacy of complex 1 was validated in the murine Lewis Lung Carcinoma (LLC) model.

Novel tetrahedral copper(I) mixed-ligand complexes of the type [Cu(X)(N(∩)N)(PCN)], 3-10, where X = Cl or Br, N(∩)N = 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), 5,6-dimethyl-1,10-phenanthroline (dmp), and dipyrido-[3,2-d:2',3'-f]-quinoxaline (dpq), and PCN = tris-(2-cyanoethyl)phosphine, have been synthetized and characterized by NMR, ESI-MS, and X-ray diffraction on two representative examples, [CuCl(phen)(PCN)]·DMF (5·DMF) and [CuBr(dpq)(PCN)]·2DMF (10·2DMF). Cu(I) complexes were evaluated for their in vitro antitumor properties against a panel of human cancer cell lines, including cisplatin- and multidrug-resistant sublines. The most effective complex, [CuCl(dpq)(PCN)] (9), exhibited nanomolar cytotoxicity toward both sensitive and resistant cancer cells, but it significantly inhibited the growth of cultured normal cells. In vitro DNA assays and single cell gel electrophoresis revealed that 9 induced DNA fragmentation resulting in cell apoptosis. In parallel, fluorescence in situ hybridization (FISH) micronucleus assay attested high levels of genotoxicity following treatment of peripheral blood lymphocytes with complex 9, suggesting that the potential risk posed by diimine metal complexes should be carefully reconsidered.

Ligand-exchange reactions of copper(I) precursors ([Cu(CH(3)CN)(4)]BF(4), CuCl) with a panel of bis(azolyl)borates or poly(pyrazolyl)methanes and a tertiary monodentate phosphine (PTA = 1,3,5-triaza-7-phosphaadamantane, PCN = tris(cyanoethyl)phosphine) produced two series of heteroleptic, either '2 + 1 + 1'- or '3 + 1'-type complexes, which have been characterized by elemental analysis, FT-IR, ESI-MS and multinuclear (31)P and (1)H NMR. '2 + 1 + 1'-type complexes include a N,N-bidentate chelate and two monodentate phosphines (1-8) and '3 + 1'-type complexes comprise a N,N,O- or N,N,N-tridentate chelate and one monodentate phosphine (9-12). All these complexes adopt a four-coordinate, tetrahedral geometry. '3 + 1' complexes show better red-ox stability and a greater tendency to retain the native '3 + 1' mixed-ligand structure. Conversely, '2 + 1 + 1' complexes exhibit increased propensity to dissociation as shown by ESI-MS measurements and X-ray structure determination at low temperature (150 K) of the polymeric complex {[H(2)B(tz(NO2))(2)]Cu[PCN]}(n)6b. In this complex, either the bis(triazolyl)borate and the PCN ligands act as bidentate, with PCN being also the μ(2)-bridiging linker between adjacent monomers. Compound 6b is the first reported example of a polymeric PCN compound with a tetra-coordinate metal centre. Cytotoxic activity of all compounds has been evaluated by MTT test against a panel of several human tumor cell lines including examples of breast (MCF-7), colon (HCT-15 and LoVo), lung (A549), cervix (A431) and ovarian (2008 and its cisplatin resistant variant, C13*) carcinoma, melanoma (A375) and promyelocytic leukemia (HL60). Copper complexes generally show in vitro antitumour activity comparable to that of cisplatin. In particular, neutral '3 + 1'-type complexes 9 and 10, show IC(50) values appreciably lower than those exhibited by the reference metallodrug., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Platinum anticancer drugs have been used for three decades despite their serious side effects and the emerging of resistance phenomena. Recently, a phosphine copper(I) complex, [Cu(thp)(4)][PF(6)] (CP), gained special attention because of its strong antiproliferative effects. CP killed human colon cancer cells more efficiently than cisplatin and oxaliplatin and it overcame platinum drug resistance. CP preferentially reduced cancer cell viability whereas non-tumour cells were poorly affected. Colon cancer cells died via a programmed cell death whose transduction pathways were characterized by the absence of hallmarks of apoptosis. The inhibition of 26S proteasome activities induced by CP caused intracellular accumulation of polyubiquitinated proteins and the functional suppression of the ubiquitin-proteasome pathway thus triggering endoplasmic reticulum stress. These data, providing a mechanistic characterization of CP-induced cancer cell death, shed light on the signaling pathways involved in paraptosis thus offering a new tool to overcome apoptosis-resistance in colon cancer cells., (© 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.)

Over the last few years a lot of research has been done to develop novel metal-based anti-cancer drugs, with the aim of improving clinical effectiveness, reducing general toxicity, and broadening the spectrum of activity. The search for novel metal-based antitumour drugs other than Pt agents includes the investigation of the cytotoxic activity of copper(I/II) compounds. Among these copper agents, particular attention has been recently devoted to hydrophilic copper(I) species bearing phosphines because of their noteworthy stability in aqueous media together with their remarkable in vitro cytotoxic activity. In this study we report on the synthesis, characterization and cytotoxic assays of a series of Cu(I) complexes with tris(2-cyanoethyl)phosphine (PCN) and bis(2-cyanoethyl)phenylphosphine (PCNPh). They were prepared by reaction of [Cu(CH(3)CN)(4)](+) or CuX(2) precursors with the pertinent phosphine in acetone or acetonitrile solutions producing compounds of the following formulation: [Cu(PCN)(2)](+) 2, [Cu(CH(3)CN)(PCN)](+) 3, [Cu(X)(PCN)] (X = Cl, 4; Br, 5), and [Cu(PCNPh)(2)](+) 6. The new copper(I) complexes were tested for their cytotoxic properties against a panel of several human tumour cell lines. Cellular copper uptake rate was correlated with cell growth inhibition in 2008 human ovarian cancer cells. Moreover, copper(I)-PCN complexes were evaluated for their ability to alter the most relevant mitochondrial pathophysiological parameters such as respiration, coupling, ATP-synthetase activity and membrane potential in isolated mitochondria. These data were correlated with changes in mitochondrial membrane potential and production of reactive oxygen species (ROS) in drug-treated 2008 cells.

New nitroimidazole and glucosamine conjugated heteroscorpionate ligands, namely 2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide (L(MN)) and 1,3,4,6-tetra-O-acetyl-2-{[bis(3,5-dimethyl-1H-pyrazol-1-yl)acetyl]amino}-2-deoxy-β-D-glucopyranose (L(DAC)), respectively, were synthesized by direct coupling of preformed side chain acid and amine components. The related copper(II) complexes {[(L(MN))(2)Cu]Cl(2)}, and {[(L(DAC))(2)Cu]Cl(2)} have been prepared from the reaction of CuCl(2)*2H(2)O with L(MN) or L(DAC) ligand in methanol solution. Single crystal structural characterization was undertaken for the L(MN) ligand. In the absence of a coordinated metal core, the overall arrangement of the ligand is determined by some loose intra- and inter-molecular nonbonding contacts. X-Ray Absorption Spectroscopy (XAS) has been used to probe the local structure of the two copper(II) complexes, {[(L(MN))(2)Cu]Cl(2)} and {[(L(DAC))(2)Cu]Cl(2)}. The EXAFS analysis has permitted the identification of the local environment of the copper site. Copper interacts with 2 units of ligand in both complexes, and it is found to be 6-fold coordinated. Its local structure is described by four Cu-N and two Cu-O interactions to form a pseudo-octahedron core, with a 0.14 Å lengthening of the Cu-O bond length in the case of L(DAC) complex with respect to the L(MN) one, likely due to the higher steric hindrance of the glucosamine moiety. The XANES analysis agrees with these results, also confirming the Cu(II) formal copper oxidation state for both complexes. The new copper(II) complexes {[(L(MN))(2)Cu]Cl(2)} and {[(L(DAC))(2)Cu]Cl(2)} as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity towards a panel of several human tumour cell lines. The results reported here indicate that both copper(II) complexes show similar spectra of cytotoxicity and very low resistance factors (RF < 2) against C13* ovarian cancer cells which have acquired resistance to cisplatin.

Hydrophilic, monocationic [M(L)(4)]PF(6) complexes (M = Cu or Ag; L: thp = tris(hydroxymethyl)phosphine, L: PTA = 1,3,5-triaza-7-phosphaadamantane, L: thpp = tris(hydroxypropyl)phosphine) were synthesized by ligand exchange reaction starting from [Cu(CH(3)CN)(4)]PF(6) or AgPF(6) precursors at room temperature in the presence of an excess of the relevant phosphine. The related [Au(L)(4)]PF(6) complexes (L = thp, PTA or thpp) were synthesized by metathesis reactions starting from [Au(L)(4)]Cl at room temperature in the presence of equimolar quantity of TlPF(6). The three series of complexes [M(L)(4)]PF(6) were tested as cytotoxic agents against a panel of several human tumour cell lines also including a defined cisplatin resistant cell line. These investigations have been carried out in comparison with the clinically used metallodrug cisplatin and preliminary structure-activity relationships are presented. The best results in terms of in vitro antitumour activity were achieved with metal-thp species and, among the coinage metal complexes, copper derivatives were found to be the most efficient drugs. Preliminary studies concerning the mechanism of action of these [M(L)(4)]PF(6) species pointed to thioredoxin reductase as one of the putative cellular targets of gold and silver complexes and provided evidence that copper derivatives mediated their cytotoxic effect through proteasome inhibition., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Copper is found in all living organisms and is a crucial trace element in redox chemistry, growth and development. It is important for the function of several enzymes and proteins involved in energy metabolism, respiration, and DNA synthesis, notably cytochrome oxidase, superoxide dismutase, ascorbate oxidase, and tyrosinase. The major functions of copper-biological molecules involve oxidation-reduction reactions in which they react directly with molecular oxygen to produce free radicals. Therefore, copper requires tightly regulated homeostatic mechanisms to ensure adequate supplies without any toxic effects. Overload or deficiency of copper is associated, respectively, with Wilson disease (WD) and Menkes disease (MD), which are of genetic origin. Researches on Menkes and Wilson disorders have provided useful insights in the field of copper homeostasis and in particular into the understanding of intracellular trafficking and distribution of copper at molecular levels. Therapies based on metal supplementation with copper histidine or removal of copper excess by means of specific copper chelators are currently effective in treating MD and WD, respectively. Copper chelation therapy is now attracting much attention for the investigation and treatment of various neurodegenerative disorders such as Alzheimer, Parkinson and CreutzfeldtJakob. An excess of copper appears to be an essential co-factor for angiogenesis. Moreover, elevated levels of copper have been found in many types of human cancers, including prostate, breast, colon, lung, and brain. On these basis, the employment of copper chelators has been reported to be of therapeutic value in the treatment of several types of cancers as anti-angiogenic molecules. More recently, mixtures of copper chelators with copper salts have been found to act as efficient proteasome inhibitors and apoptosis inducers, specifically in cancer cells. Moreover, following the worldwide success of platinum(II) compounds in cancer chemotherapy, several families of individual copper complexes have been studied as potential antitumor agents. These investigations, revealing the occurrence of mechanisms of action quite different from platinum drugs, head toward the development of new anticancer metallodrugs with improved specificity and decreased toxic side effects.

New copper(I) complexes containing the water soluble N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA) phosphine have been synthesized by ligand-exchange reactions starting from [Cu(CH(3)CN)(4)][BF(4)] or [Cu(CH(3)CN)(4)][PF(6)] precursors and (mPTA)X (X=CF(3)SO(3), I). Depending on the ligand counter ion, the hydrophilic [Cu(mPTA)(4)][(CF(3)SO(3))(4)(BF(4))] 3a and [Cu(mPTA)(4)][(CF(3)SO(3))(4)(PF(6))] 3c complexes or the iodine-coordinated [Cu(mPTA)(3)I]I(3)4 species were obtained respectively and fully characterized by spectroscopic methods. Single crystal structural characterization was undertaken for [Cu(mPTA)(3)I]I(3).H(2)O, 4.H(2)O, and [Cu(mPTA)(4)][(CF(3)SO(3))(2)(BF(4))(3)] .0.25H(2)O, 3b.0.25H(2)O, the latter obtained by crystallization of [Cu(mPTA)(4)][(CF(3)SO(3))(4)(BF(4))] 3a. The cytotoxicity of analogous tetrahedral homoleptic Cu(I) derivatives [Cu(PTA)(4)](BF(4)) 1, [Cu(PTAH)(4)][Cl(4)(BF(4))] 2, [Cu(mPTA)(4)][(CF(3)SO(3))(4)(BF(4))] 3a and [Cu(mPTA)(4)][(CF(3)SO(3))(4)(PF(6))] 3c was evaluated against a panel of several human tumor cell lines. All the complexes showed in vitro antitumor activity comparable to that of the reference metallodrug cisplatin. Tests performed on cisplatin sensitive and resistant cell lines showed that against human ovarian 2008/C13(*) cell line pair, the resistance factor of copper derivatives was roughly 7-fold lower than that of cisplatin, whereas against human cervix cancer A431/A431-Pt cell line pair it was about 2.5-fold lower. These results, confirming the circumvention of cisplatin resistance, support the hypothesis that phosphine copper(I) complexes follow different cytotoxic mechanisms than do platinum drugs.

Metal-based antitumor drugs play a relevant role in antiblastic chemotherapy. Cisplatin is regarded as one of the most effective drugs, even if severe toxicities and drug resistance phenomena limit its clinical use. Therefore, in recent years there has been a rapid expansion in research and development of novel metal-based anticancer drugs to improve clinical effectiveness, to reduce general toxicity and to broaden the spectrum of activity. The variety of metal ion functions in biology has stimulated the development of new metallodrugs other than Pt drugs with the aim to obtain compounds acting via alternative mechanisms of action. Among non-Pt compounds, copper complexes are potentially attractive as anticancer agents. Actually, since many years a lot of researches have actively investigated copper compounds based on the assumption proposal that endogenous metals may be less toxic. It has been established that the properties of copper-coordinated compounds are largely determined by the nature of ligands and donor atoms bound to the metal ion. In this review, the most remarkable achievements in the design and development of copper(I, II) complexes as antitumor agents are discussed. Special emphasis has been focused on the identification of structure-activity relationships for the different classes of copper(I,II) complexes. This work was motivated by the observation that no comprehensive surveys of copper complexes as anticancer agents were available in the literature. Moreover, up to now, despite the enormous efforts in synthesizing different classes of copper complexes, very few data concerning the molecular basis of the mechanisms underlying their antitumor activity are available. This overview, collecting the most significant strategies adopted in the last ten years to design promising anticancer copper(I,II) compounds, would be a help to the researchers working in this field.

Monocationic hydrophilic complexes [Cu(thp)4](+) 3 and [Cu(bhpe)2](+) 4 were synthesized by ligand exchange reactions starting from the labile [Cu(CH3CN)4][PF6] precursor in the presence of an excess of the relevant hydrophilic phosphine. Complexes 3 and 4 were tested against a panel of several human tumor cell lines. Complex 3 has been shown to be about 1 order of magnitude more cytotoxic than cisplatin. Chemosensitivity tests performed on cisplatin and multidrug resistance phenotypes suggested that complex 3 acts via a different mechanism of action than the reference drug. Different short-term proliferation assays suggested that lysosomal damage is an early cellular event associated with complex 3 cytotoxicity, probably mediated by an increased production of reactive oxygen species. Cytological stains and flow cytometric analyses indicated that the phosphine copper(I) complex is able to inhibit the growth of tumor cells via G2/M cell cycle arrest and paraptosis accompanied with the loss of mitochondrial transmembrane potential.

The new sodium bis(1,2,4-triazol-1-yl)acetate ligand, Na[HC(CO(2))(tz)(2)], has been prepared in methanol solution by using 1,2,4-triazole, dibromoacetic acid, and NaOH. Treatment of the [Cu(CH(3)CN)(4)][PF(6)] acceptor with Na[HC(CO(2))(tz)(2)] or Na[HC(CO(2))[(pz(Me2))(2)] in the presence of the tris(hydroxymethyl)phosphine coligand in methanol/acetonitrile solutions produced unprecedented mononuclear copper(I) complexes of the [L(n)]Cu[P(CH(2)OH)(3)](2) (L(1), 2; L(2), 3) [(CH(3)CN)(2)Cu(P(CH(2)OH)(3))(2)]PF(6), 4. These compounds have been characterized by elemental analyses, FTIR, ESI-MS, and multinuclear (1H and 31P) NMR spectral data. The new copper(I) complexes were tested for their cytotoxic properties against a panel of several human tumor cell lines. The results reported here indicate that all the complexes showed in vitro antitumor activity similar or better than that of cisplatin, the most used metal-based antitumor drug. In particular, [HC(CO(2))(pz(Me2))(2)]Cu[P(CH(2)OH)(3)](2), 3 showed IC(50) values markedly lower than the reference compound against all tumor cell lines. Chemosensitivity tests performed on cisplatin sensitive and resistant cell lines have demonstrated that all these Cu(I) complexes were able to overcome cisplatin resistance, supporting the hypothesis of a different mechanism of action compared to that exhibited by the reference drug. Flow cytometric analysis on 2008 human ovarian carcinoma cells revealed that complex 3, chosen as the best candidate, induced a marked enlargement of both cell size and granularity, and a significant increase in the fraction of G2/M cells that, differently from cisplatin, was not accompanied by the appearance of a relevant sub-G1 fraction. Besides, no evidence of caspase-3 activation was detected in cells treated with complex 3. We hypothesize that the cytotoxic activity of the new copper(I) complex may be correlated to its ability to trigger paraptosis, a nonapoptotic mechanism of cell death.

New copper(I) complexes of the type [H(2)B(tz(NO2))(2)]Cu[PR(3)](2) (1-5), [H(2)B (tz(NO2))(2)]Cu[dppe] (6) and [H(2)B(tz(NO2))(2)]Cu[PR(3)] (7, 8) have been synthesized from the reaction of CuCl, potassium dihydrobis(3-nitro-1,2,4-triazol-1-yl)borate, K[H(2)B (tz(NO2))(2)], and mono- or bi-dentate tertiary phosphanes. The complexes obtained have been characterized by elemental analyses and FT-IR in the solid state, and by NMR ((1)H and (31)P{(1)H}) spectroscopy in solution. Selected complexes 1, 3 and 5 have also been tested against a panel of several human tumor cell lines in order to evaluate their cytotoxic activity. Complexes 1 and 5 showed IC(50) values appreciably lower than those exhibited by cisplatin, the most used metal-based antitumor drug. It is worth noting that all three tested Cu(I) complexes appear to be particularly effective against A549 carcinoma cells that are resistant to cisplatin treatment.