Ruthenium–arene complexes with NSAIDs: synthesis, characterization and bioactivity

Two non-steroidal antiinflammatory drugs indomethacin and mefenamic acid were coordinated to
Ru(II)–arenes to afford four new complexes. The cytotoxic activities of the ligands and ruthenium complexes
were tested in three human cancer cell lines (K562, A549, MDA-MB-231) and non-tumour human fetal
lung fibroblast cells (MRC-5) by MTT assay. Cytotoxicity studies revealed that indomethacin Ru(II)–arene
complexes 1 and 3 displayed good cytotoxicity and apparent cytoselective profiles. The IC50 values obtained
in leukemia K562 cells were comparable to those of cisplatin (10.3 mM (CDDP), 11.9 mM (1) and 13.2 mM (3)).
Flow cytometric analysis of 1 and 3 in triple-negative breast cancer MDA-MB-231 cells revealed an
interesting mechanism of action. At IC50 concentrations, 1 and 3 arrested cell cycle progression in S phase
and caused rapid accumulation of cells in sub-G1 phase (up to 48%), while Annexin V-FITC/PI staining
showed simultaneous occurrence of apoptotic and necrotic cell populations at approximately similar levels
of 20%. Measurement of reactive oxygen species (ROS) production by DCFH-DA staining confirmed
the potential of 1 and 3 to increase ROS even more than cisplatin. The interaction of the complexes with
serum albumins showed their potential ability to bind tightly and reversibly to albumins. The affinity of the
complexes to calf-thymus DNA was investigated by UV-vis spectroscopy, viscosity measurements and
fluorescence emission spectroscopy for competitive studies of the complexes with ethidium bromide,
revealing that their interaction probably occurs via intercalation. Taken together, the results strongly suggest
the potential of complexes 1 and 3 to alter cell cycle progression and cause DNA-damage by means of
direct DNA-binding or indirectly by ROS production.