Genotoxicity of the copper antineoplastic coordination complexes casiopeinas Ò J. Serment-Guerrero a,⇑ , P. Cano-Sanchez c , E. Reyes-Perez a , F. Velazquez-Garcia a , M.E. Bravo-Gomez b , L. Ruiz-Azuara b a Departamento de Biología, Instituto Nacional de Investigaciones Nucleares, Carretera México Toluca S/N, La Marquesa, Ocoyoacac, Mexico b Departamento de Química Inorgánica y Nuclear, Facultad de Química, Universidad Nacional Autónoma de México, Avenida Universidad 3000, CP 04510, México DF, Mexico c Instituto de Química, Universidad Nacional Autónoma de México, Avenida Universidad 3000, CP 04510, México DF, Mexico article info Article history: Received 23 February 2011 Accepted 6 May 2011 Available online 13 May 2011 Keywords: Casiopeinas Copper chelates ROS Antineoplastic abstract Casiopeinas is the generic name of a group of coordination complexes with a central copper atom bound to organic ligands, designed to be an alternative to cancer therapy. Indeed, some of these compounds can reduce implanted tumors in mice. Casiopeinas were expressly designed to interact with the genetic mate- rial, so the aim of the present work is to determine if these compounds have genotoxic activity. The results indicate that casiopeinas produce DNA fragmentation and base oxidation and suggest that their mode of action is related to reactive oxygen species (ROS) generation after copper reduction. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Metal-based antitumor compounds play an important role in cancer chemotherapy. Cisplatin is one of the most widely used antineoplastic drugs, although its application is limited by its se- vere toxicity and resistance development. Recently, there has been a rapid increase in research and expansion of novel metal-based anticancer drugs to improve clinical effectiveness. The variety of metal ion functions in biology has stimulated the creation of new metallodrugs other than Pt drugs aimed to obtain compounds act- ing via alternative mechanisms of action. Actually, many research- ers have actively investigated copper compounds based on the assumption that endogenous metals may be less toxic (Marzano et al., 2009). The chemical properties of copper allow it to take part in many biological functions such as electron transfer, catalysis and structural shaping. The capability to cycle between +1 and +2 oxi- dation state is one of the key features that has been exploited by organisms throughout evolution. Indeed, evidences are rising about the ability of some copper compounds to induce an alterna- tive non-apoptotic form of programmed cell death. To date, many copper complexes have been synthesized and tested for their anti- cancer activity in vitro and in vivo (Tardito and Marchio, 2009). Among them, there are casiopeinas Ò (Ruiz-Azuara, 1993), a set of coordination complexes with a central copper atom (Cu II) bound to organic ligands (Fig. 1) intended to be an alternative to cancer treatment. These molecules have the following condensed formulae: [Cu(N–N)(O–N)]NO 3 and [Cu(N–N)(O–O)]NO 3 . The de- sign of the molecules was made considering several factors, such as the existence of an essential metal in order to diminish toxicity; the existence of chelates that favor the cis-configuration around the metal ion and also render more stable complexes; finally the mixed chelate must possess different levels of hydrophobicity (Gracia-Mora et al., 2001). By means of different experimental procedures it has been shown that some of the casiopeinas tested have cytostatic and cytotoxic effects to several types of tumor cell in vitro as well as to implanted tumors in mice (Gracia-Mora et al., 2001; Rodríguez-Enríquez et al., 2006; Trejo-Solıs et al., 2005; Carvallo-Chaigneau et al., 2008; Mejia and Ruiz-Azuara, 2008; Kachadourian et al., 2010). At the same time, it has been observed that cell death may occur through necrosis (De Vizcaya-Ruiz et al., 2000) or apoptosis, the latter activated by either caspase depen- dent or caspase independent pathways (Trejo-Solıs et al., 2005). Since casiopeinas, as most of the antineoplastic drugs, were designed to interact with the genetic material, experiments aimed to detect genotoxicity have been conducted. Indeed, screening by means of the single cell gel electrophoresis assay (SCGE) of twelve casiopeinas showed different degrees of DNA fragmentation, re- lated to drug structure and in a concentration-dependent manner (Alemon-Medina et al., 2007). However, since most of these compounds trigger the apoptosis, such fragmentation could be the product of apoptotic nucleases activity. At the same time, it has been demonstrated that certain casiopeinas specifically caused base oxidative damage and strand breaks in plasmid DNA (Rivero-Müller et al., 2007). The precise mechanism of action of 0887-2333/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.tiv.2011.05.008 ⇑ Corresponding author. Address: Apartado Postal 18-1027, CP 11801, México DF, Mexico. Tel.: +55 5329 7230; fax: +55 5329 7387. E-mail address: jorge.serment@inin.gob.mx (J. Serment-Guerrero). Toxicology in Vitro 25 (2011) 1376–1384 Contents lists available at ScienceDirect Toxicology in Vitro journal homepage: www.elsevier.com/locate/toxinvit