| Pt(?)based complexes,including cisplatin,carboplatin,and oxaliplatin,are the most frequently applied DNA-damaging anticancer drugs,and among them cisplatin is the first-line chemotherapeutic agent against certain types of malignancies.Although a huge success has been achieved by Pt(?)drugs,the effectiveness of Pt(?)drugs has been heavily limited by high toxicity,severe side effects,and inherent or acquired drug resistance.It is widely acknowledged that Pt(?)complexes as pro-drugs are expected to exhibit great promise in the search for the next generation of platinum based drugs,because they are kinetically inert in contrast to their Pt(?)counterparts and can be easily reduced to Pt(?)equivalents by intracellular reducing molecules.In order to overcome the side effect of Pt(?)drugs,we have been designed and synthesized a series of promising Pt(?)complexes by introduction of active pharmacophore ligands in the axial position.Firstly,we have been designed and synthesized two series of Pt(?)prodrugs derived from cisplatin,oxaliplatin,or DACHPt with CA-4 or phenstatin analogue as the axial ligands in the octahedral geometry of Pt(?)complexes.All Pt(?)complexes exhibited better antitumor activities against all tested cancer cell lines including cisplatin resistant cells,and displayed lower cytotoxicity than their corresponding positive controls against human normal cells.Since complexes 2-22 and 2-25 exhibited better cytotoxicity,they were selected to evaluate of their antitumor activities both in vitro and in vivo as well as their underlying mechanism of apoptotic pathway.It was noted in the HPLC chromatograms that complex 2-22 or 2-25 was gradually reduced to release compound 2-15 or 2-21 and equivalent of cisplatin as time passed in the presence of ascorbic acid.Cell molecular biology experiment results indicated that complex 2-22 or 2-25 effectively induced cell apoptosis and arrested the cell cycle at the G2/M phases,and significantly decreased the mitochondrial membrane potential and triggered ROS generation in cells.Tubulin inhibition assay and molecular docking studies demonstrated that complex 2-22 or 2-25 was also a tubulin polymerization inhibitor binding at the colchicine site.In addition,the growth of HepG-2 tumor xenograft was significantly suppressed by 51.2% and 59.4%(percent of inhibition rate [IR] values)after iv administration of complex 2-22 at 5 and 10 mg/kg compared with vehicle control group;the growth of NCI-H460 tumor xenograft was significantly suppressed by 52.11% and 60.23% after iv administration of complex 2-25 at 5 and 12 mg/kg compared with vehicle control group,respectively.Secondly,we reported two series of Pt(?)prodrugs derived from cisplatin or oxaliplatin containing CA-4 derivatives in the axial positions of Pt(?)complexes to via a linker group such as succinic anhydride or monomethyl glutarate.All target compounds showed potent anticancer activities against HCT-116,HepG-2 and MGC-803 cell lines,and exhibited lower cytotoxicity than their corresponding positive drugs(cisplatin or oxaliplatin)against human normal cells(HL-7702 and NCM460).In addition,target compounds displayed potent anticancer activity against cisplatin resistant cells SK-OV-3/CDDP.Among them,complexes 3-23 exhibited tremendous cytotoxicity towards cancer cells,thus they were selected to investigate of their anticancer activities both in vitro and in vivo as well as their underlying mechanism of apoptotic pathway.Experimental results indicated that 3-23 significantly induced apoptosis in human ovarian cancer SK-OV-3 cells and cell cycle arrest at the G2/M phase,and dramatically decreased the mitochondrial membrane potential and induced ROS generation in SK-OV-3 cells,and effectively up-regulated the expression of pro-apoptotic proteins Bax,Caspase-9 and Caspase-3 and correspondingly down-regulated the expression of anti-apoptotic protein Bcl-2.In addition,the growth of SK-OV-3 tumor xenograft was effectively suppressed by 53.1% and 60.5%(percentage of inhibition rate [IR] values),and without causing significant loss of animal body weight in comparison with cisplatin after treatment groups were injected with complex 3-23 at two doses(5 and 13(mg/kg)in the SK-OV-3 tumor model.Moreover,H&E staining results indicated that there was no obvious damage to major organs after treatments with complex 3-23 in three weeks.Finally,we reported two series of Pt(?)prodrugs derived from cisplatin,oxaliplatin,or DACHPt conjugated with chalcone analogue as the axial ligands in the axial positions of Pt(?)complexes to via a linker group.In vitro evaluation revealed that all Pt(?)complexes exhibited better and more potent activity against the test human cancer cells including cisplatin resistant cells(SK-OV-3/CDDP and A549/CDDP)than that of their corresponding mother Pt(?)drugs,and correspondingly exhibited lower cytotoxicity toward two human normal cell lines(HL-7702 and BEAS-2B),respectively.Mechanism studies revealed that Pt(? complex 4-49 effectively induced apoptosis in SK-OV-3 and NCI-H460 cancer cells and arrested the cell cycle at the G2/M phase,and dramatically disrupted the microtubule organization and induced DNA damage,respectively.Moreover,the Pt(? complex 4-49 significantly decreased the mitochondrial membrane potential and triggered ROS generation in both human ovarian(SK-OV-3)and human lung(NCI-H460)cancer cells,and effectively up-regulated the expression of pro-apoptotic proteins Bax,Caspase-9 and Caspase-3 and simultaneously down-regulated the expression of anti-apoptotic protein Bcl-2 as well as caused a significant decrease in Cdc2,Cdc25 c and Cyclin B1 expression.In addition,the Pt(? complex 4-49 significantly inhibited tumor growth in the SK-OV-3 tumor xenograft at a dose-dependent manner and without causing significant loss of animal body weight,and the tumor inhibitory rates on day 21 after treatment were 60.3%(5 mg/kg)and 70.2%(13.5 mg/kg)compared with vehicle control group.It was found that the Pt(? complex 4-49 exhibited better in vivo antitumor activity than those of 4-17(IR,50.1%),cisplatin(IR,65.07%)and 4-17/cisplatin mixture(IR,68.1%)after administration of 4-49 at high dosage(13.5 mg/kg),respectively.H&E staining results indicated that there was also no obvious damage to major organs after treatments with complex 4-49 in three week. |
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