82 Trakia Journal of Sciences, Vol. 17, Suppl. 2, 2019 Trakia Journal of Sciences, Vol. 17, Suppl. 2, pp 82-89, 2019 Copyright © 2019 Trakia University Available online at: http://www.uni-sz.bg ISSN 1313-3551 (online) doi:10.15547/tjs.2019.s.02.019 EXPERIMENTAL STRATEGY FOR IN VITRO EVALUATION OF CYTOTOXIC / ANTITUMOR PROPERTIES OF NEW METAL COMPLEXES WITH DIFFERENT LIGANDS R. Alexandrova 1* , R. Spasov 1,2 , Z. Petrova 1 , T. Zhivkova 1 , L. Dyakova 3 , D. Dinev 1 , M. Glavcheva 1 , B. Andonova-Lilova 1 , A. Abudalleh 1 , M. Georgieva 4 , G. Miloshev 4 , D.-C. Culita 5 , G. Marinescu 5 , V. Alexeeva 6 , C. Podlipnik 7 1 Institute of Experimental Morphology, Pathology and Anthropology with Museum, Bulgarian Academy of Sciences, Sofia, Bulgaria 2 Faculty of Medicine, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria 3 Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria 4 Institute of Molecular Biology “Roumen Tsanev”, Bulgarian Academy of Sciences, Sofia, Bulgaria 5 Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, Bucharest, Romania 6 St. Petersburg Research Institute of Gum and Rubber “S.V. Lebedev” and Institute of Silicate Chemistry of Russian Academy of Sciences, St. Petersburg, Russian Federation 7 Faculty of Chemistry and Chemical Technology, University of Lubljana, Lubljana, Slovenia ABSTRACT PURPOSE. The aim of this study was to evaluate cytotoxic / antitumor properties of newly synthesized metal [Zn(II), Cu(II), Co(II), Ni(II), Zn(II)/Ag(I), Zn(II)/Au(I)] complexes with various ligands (Schiff bases, non-steroidal anti-inflammatory drugs, bile acids) and to introduce an optimized strategy for such investigations in our research activity. MATERIALS AND METHODS. Human and animal tumor and non-tumor cells were used as model systems. Short-term (3 – 96h) and long-term (> 2 weeks) experiments were carried out using cytotoxicity assays, cytological / immunocytochemical, biochemical and molecular-biological methods to assess the influence of the compounds on cell viability and proliferation and their ability to induce apoptosis/necrosis and/or autophagy. RESULTS. The examined metal complexes express cytotoxic activity that is time- and concentration- dependent and are more active than the corresponding ligands tested alone. Zn(II)/Au(I) and Zn(II)/Ag(I) complexes with Salen are found to be the most promising cytotoxic agents being effective also in multidrug resistant cancer cells. Their cytotoxic activity is higher than those of cisplatin, oxaliplatin and epirubicin. CONCLUSIONS. A complex approach, based on a wide range of cell cultures and methods with different molecular / cellular targets and mechanisms of action was optimized and successfully applied for the assessment of cytotoxicity of new metal complexes. Key words: Cell cultures, Metal compounds, Cancer, Cytotoxic / Anticancer activity, Antitumor agents, Apoptosis, Autophagy INTRODUCTION The need for effective new anticancer agents is one of the main challenges in modern biomedicine. The application of metal _________________________ *Correspondence to: Radostina Alexandrova, Institute of Experimental Morphology, Pathology and Anthropology with Museum, Bulgarian Academy of Sciences, Acad. Georgi Bonchev Str., Block 25, Sofia 1113, Bulgaria; E-mail – rialexandrova@hotmail.com compounds in cancer therapy started in the early 1960s with the discovery of antitumor properties of cisplatin. Today it is one of the most widely used antitumor drugs, being involved in the treatment of testicular, ovarian, cervical, bladder, head and neck cancers, melanoma and lymphomas (1). The successful story of cisplatin as well as of second (carboplatin) and third (oxaliplatin) generation of platinum preparations in clinical