Previous studies have described promising antitumor activity of an organometallic Ru(II) complex, η5-Cyclopentadienyl(2,2′-bipyridyl)(triphenylphosphane) Ruthenium(II) triflate ([(η5-C5H5)Ru(2,2′-bipyridyl)(PPh3)][CF3SO3]) herein designated as TM34. Its broad spectrum of activity against a panel of human tumor cell lines and high antiproliferative efficiency prompted us to focus on its mode of action. We present herein results obtained with two human tumor cell lines A2780 and MDAMB231 on the compound distribution within the cell, the mechanism of its activity, and its cellular targets. The prospective metallodrug TM34 revealed: (a) fast antiproliferative effects even at short incubation times for both cell lines; (b) preferential localization at the cell membrane and cytosol; (c) cellular activity by a temperature-dependent process, probably macropinocytosis; (d) inhibition of a lysosomal enzyme, acid phosphatase, in a dose-dependent mode; and (e) disruption and vesiculation of the Golgi apparatus, which suggest the involvement of the endosomal/lysosomal system in its mode of action. These results are essential to elucidate the basis for the cytotoxic activity and mechanism of action of this RuII(η5-cyclopentadienyl) complex.

Tetrahydrofuran (THF) has commonly been used to deliver carotenoids to cells but the use of THF is associated with cytotoxicity and low uptake efficiency of carotenoids. Here, we used fetal bovine serum (FBS) as the delivery vehicle for lycopene in comparison with THF, THF containing 0·0025 % butylated hydroxytoluene (THF/BHT), methyl-β-cyclodextrin (M-β-CD) and micelles in two human prostate cancer cell lines, DU145 and PC-3. Lycopene (10 mm) solubilized in THF/BHT and then diluted in FBS at ratios of 5 and 10 gave the highest lycopene uptake in DU145 cells. Using a dilution factor of 10, we found that lycopene (10 μm) carried in FBS in a cell-free system led to significantly less loss of lycopene than in THF, THF/BHT and M-β-CD within 24 h of incubation. Lycopene solubilized in micelles was more stable than that in FBS within 24 h, but the micelle itself led to marked cytotoxicity to DU145 cells. Lycopene at 10 μm in FBS led to significantly higher uptake of lycopene in both cell lines than that in THF, THF/BHT or M-β-CD within 24 h of incubation. When FBS was replaced with lipoprotein-deficient serum, the uptake of lycopene by DU145 cells was markedly decreased and was not significantly different from that of THF or THF/BHT. These results demonstrate that FBS is superior to THF, THF/BHT, M-β-CD and micelles as a delivery vehicle for lycopene in prostate cell lines and that the lipoprotein of FBS is likely responsible for the improved stability and cellular uptake of lycopene.