Study On Mechanism Of Pt/Cu Complexes Against Cancer Cells

Objectives: Since approved in 1978,cisplatin was used in a wide spectrum of solid tumor,such as ovarian,testicular,bladder,colorectal,lung,head and neck cancers.However,there were some severe side effects(dose-limiting nephrotoxicity,cumulative peripheral sensory neuropathy,ototoxicity nausea and vomiting),and drug resistance or cross resistance.Therefore,from the viewpoint of retaining the advantages and overcoming the disadvantages,structural modification of cisplatin has never stopped,including sterically hindered complexes,monofunctional platinum drugs,complexes with biologically active ligands,trans-configured and so on.Previously,we have obtained twelve metal complexes by combining metal ions with bioactive ligands.In this paper,the biological mechanism of these complexes was studied.Methods: Firstly,we discusses biological acivity of the previously synthesized four Cu-thisemicarbazone and three Pt-thiosemicarbazone complexes;and then comparied the antitumor mechanism of different metal complexes with the same ligand;finally,we study the biological activities of three histone deacetylase inhibitors.The main experimental methods include MTT assay(cytotoxicity test),Hoechst33342 staining assay,Annexin V/PI double staining test,ICP-MS test,cell cycle arrest,monoclonal formation assay,comet assay,mitochondrial membrane potential test,reactive oxygen species(ROS)and western blot,etc.Conclusions: 1.Four copper complexes have strong cytotoxicity to cancer cells,especially 1 and 2.The results of cell uptake showed that complexes 1 and 2 could accumulate in large quantities in tumor cells under the same conditions,leading to the strong antitumor activity of 1 and 2.Further studies have shown that four thiosemicarbazone copper complexes can increase the level of reactive oxygen species,reduce mitochondrial membrane potential,enhance the permeability of mitochondrial membrane,leading to release of mitochondrial apoptosis factor into the cytoplasm,activation of apoptosis and blocking the cell cycle,ultimately induce tumor cell apoptosis.In addition,all four complexes could also cleave pUC19 plasmid DNA in vitro,therefore,we evaluated the effect of four copper complexes on DNA in the cells and found that they can also damage the DNA in cells and induce apoptosis.2.Three platinum complexes have good cytotoxicity to tumor cells,especially 3 with double ligands.Compared with 1 and 2,3 can be more concentrated in tumor cells under the same time.We speculated that the dual ligand structure can increase the lipid solubility of 3,make it easier to penetrate the cell membrane phospholipid bilayer,gather in cells,damage the DNA,enhance the ROS level,decreased mitochondrial membrane potential,activate apoptosis pathway,arrest the cell cycle and finally induce cell apoptosis.3.We synthesized copper and platinum complexes with the same ligand and compared their antitumor mechanism.The study displayed that although the IC50 value had almost no difference after the cells were treated with complexes for 48 h,a large number of platinum complexes can accumulate in tumor cells,arrest cell cycle in G2/M phase and induce apoptosis in a short time such as 12 h.We speculated that due to the rapid accumulation into tumor cells of platinum complexes,the DNA damage in tumor cells caused by drugs can not be repaired in time,resulting in the decrease in the resistance of tumor cells to platinum drugs.In fact,the resistance test proved that the platinum complexes not only had no cross resistance with cisplatin,but also played a role in cisplatin resistant cells.4.Through the structural modification of histone deacetylase inhibiting MS-275,we synthesized HDACi and its platinum complex HDACi-BOC-Pt,and evaluated its biological activity.The results showed that the histone deacetylase activity was retained when the compounds maintained the structural integrity of the primary amine,while the enzyme activity disappeared when the structural integrity was destroyed.In addition,it overcame the cytotoxic defect when HDACi was combined with cisplatin,Unfortunately,we have not obtained the histone deacetylase inhibitor platinum complexes with complete structure of primary amine,it was impossible to determine whether the enzyme activity was retained after the combination with cisplatin,and the relevant research is still ongoing.