By creating paullones able to bind to ruthenium(II) and osmium(II) arene moieties, we expected to reduce the encountered problems markedly. Moreover, synergistic effects and the differing targets of metals and ligands could be an advantage for inhibiting cancer cell

growth. Indolobenzazepines with the general formula [MIICl(η6-p-cymene)L]Cl (L = L1 or L2; M = Ru or Os) ( Fig. 1) have been synthesized and characterized previously [13]. These substances have shown their potency in a cytotoxicity test in three human cancer cell lines, Ruxolitinib clinical trial with IC50 values in the lower micromolar range. Hydrolysis behavior and reactivity to 5′-GMP were also reported. High cytotoxic activity was the reason for further studies on find more their impact on human cancer cells. Because of the known Cdk-inhibitory activity of the metal-free paullones, inhibition of Cdk2/cyclin E was also investigated in a cell-free assay with the metal complexes. Effects on the cell cycle were quantified by flow cytometry, and the metal accumulation in the cells, inhibition of DNA synthesis and induction of apoptosis were

compared to cytotoxic potency. Compounds 1–4 were prepared as described previously [13]. For all experiments, the compounds were first dissolved in DMSO and then diluted in medium/buffer as appropriate. Flavopiridol was kindly provided by Sanofi-Aventis. CH1 (ovarian carcinoma, human) cells were donated by Lloyd R. Kelland (CRC Centre for Cancer Therapeutics, Institute of Cancer Research, Sutton, U.K.). SW480 (colon adenocarcinoma, human)

and A549 (non-small cell lung cancer, human) cells were kindly provided by Brigitte Marian (Institute of Cancer Research, Department of Medicine I, Medical University of Vienna, Austria). Prostate carcinoma cell line LNCaP, mammary gland carcinoma cell line T47D as well as the gastric carcinoma cell line N87 were purchased from the American Type Culture Collection (ATCC). Cells were grown without antibiotics in 75-cm2 culture flasks Mirabegron (Iwaki/Asahi Technoglass) as adherent monolayer cultures in minimal essential medium (MEM) (for CH1, SW480 and A549 cells) or in RPMI 1640 medium (for LNCaP, N87 and T47D cells), both media supplemented with 10% heat-inactivated fetal bovine serum and 4 mM l-glutamine, but only MEM supplemented with 1 mM sodium pyruvate and 1% non-essential amino acids (from 100 × ready-to-use stock) (all purchased from Sigma-Aldrich) without antibiotics. Cultures were maintained at 37 °C in a humidified atmosphere containing 5% CO2 and 95% air. Cytotoxicity in the cell lines mentioned above was determined by the colorimetric MTT assay (MTT = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide, purchased from Sigma-Aldrich).