Cytotoxic Effects of Water-Soluble N-Heterocyclic Carbene Platinum(II) Complexes on Prostatic Tumor PC3 and Leukemia NB4 Human Cells

The purpose of this work was to study water-soluble platinum complexes as potential therapeutic agents. We used water-soluble platinum(II) complexes containing sulfonated N-heterocyclic carbene ligands (NHC), applied on two human cell models: human NB4 acute promyelocytic leukemia and PC3 prostatic cancer cells. We studied the toxic effects on these two types of human tumor cells. We analyzed metabolic activity, membrane damage, cell cycle, DNA fragmentation and programmed cell death. In human NB4 leukemia cells, the water-soluble dimethyl NHC complex 5Me proved highly toxic. It extinguished cell metabolism at 1 mM for 24 h. This treatment gave rise to the presence of fragmented DNA (subdiploid DNA). This compound promoted programed cell death in 60% of the cells. At longer times, the treatments produced neither higher fragmentation of DNA nor augmented apoptosis. 5Me complex, at 100 µM, showed slight toxicity on NB4 cells. In PC3 cells, dimethyl complex 5Me (1 mM for 24 h) is less toxic (reduced DNA fragmentation and programmed cell death) than in NB4 cells. Mono-NHC complexes 4 and 5 treatments at a high concentration for 24 h on PC3 cells produced apoptosis (30% of the cells) but their damage on cell permeability and DNA fragmentation was weak. Thus, PC3 cells are more resistant to NHC platinum(II) complexes than NB4 cells.