Design,Synthesis And Preliminary Antitumor Acitvity Studies Of Topoisomerase Ⅱ Inhibitors

As a basic ribozyme of cells,DNA topoisomerase could participate in cell life processes like replication,transcription,and mitosis,etc.When DNA is duplicated and transcribed,double strands are easily entangled and folded within and between DNA molecules in the process of melting.As a class of highly conserved proteins,topoisomerases,an important target for the study of antitumor drugs,are capable of alleviating the topological tensions that occur in DNA molecules,breaking and re-linking the phosphodiester bonds of DNA strands,and mediating the momentary breakage and religation of single or double strands of DNA,and thus catalyzing the transformation between the superhelix state and the unwinding state of the topological isomers.Topoisomerases are classified into Topo Ⅰ and Topo Ⅱ depending on the mechanism of action.Topo Ⅰ catalyzes the transient breakage and re-linking of single strands,and Topo Ⅱ catalyzes the transient cleavage and re-ligation of double strands.DNA topoisomerase inhibitors could affect the cell cycle distribution by influencing the activity of Topo enzyme to interfere with DNA replication and gene expression,inhibit the rapid proliferation of tumor cells,induce tumor cell apoptosis and then kill the tumor cells to a certain extent,exerting anti-tumor effect.According to different ways of interacting with DNA,topoisomerase inhibitors can be divided into DNA intercalators(such as amsacrine,mitoxantrone,etc.)and non-intercalators.According to different mechanisms of action,they are divided into Topo poisons and Topo catalytic inhibitors.Topo Ⅱ poisons exhibit antitumor activity by stabilizing Topo Ⅱ-mediated cleavage of the Topo-DNA to form a permanent double-stranded DNA break.Commonly used drugs in clinic include etoposide(VP-16),teniposide(Vumon,VM-26)and other podophyllotoxin derivatives,which are widely used for the treatment of various malignant tumors such as lung cancer,germ cell cancer,leukemia,and non-Hodgkin lymphoma,among many others.Topo Ⅱ catalytic inhibitors,such as doxorubicin,daunorubicin,and doxorubicin,can exert antitumor activity by blocking the binding of Topo to DNA and affecting DNA replication.The novel Topo Ⅱ inhibitors include flavonoids,quintnolones,nitrofurans,quintnoxalines,phenanthrenequintnones,and thiosemicarbazones,and a number of these compounds,for example,Vosaroxin,F14512,XK469,C-1311,are under clinical investigations.Among Topo inhibitors,though Topo Ⅱ inhibitors are currently more used in clinical studies,they often have some shortcomings like poor water solubility,narrow anti-tumor spectrum,drug resistance,bone marrow suppression,gastrointestinal reactions and other side effects.Therefore,the discovery of novel Topo Ⅱ inhibitors with high efficacy and few side effects is a key concern for the development of anti-tumor drugs.As a very promising lead compound,XK469 has a broad spectrum inhibitory effect on various solid tumors with less toxicity and side effects than traditional Topo inhibitor camptothecin.For this purpose,through the analysis of the binding mode of the eutectic(PDB:1ZXM)of DNA Topo Ⅱ,and applying combination principle and scaffold hopping drug design strategies with the aid of computer molecular docking(Sybyl)simulations,we used quintnone as the privileged skeleton to design and synthesize 30 amide compounds of series A and 8 polyamine compounds of series B.In vitro anti-tumor cell proliferation assay,both series A and B have a certain anti-proliferative activity on different tumor cells.Among them,series A showed less inhibition on the adherent cells,but was most sensitive to suspension cell K562.The IC50 of most compounds was between 1-10μM,and compound 6ds was the most active(IC50=0.77 μM).6d2 had the best comprehensive inhibition ability against different cells.Series B had a wide range of anti-tumor cell proliferation effects,of which the linear polyamine compound 16c had the best overall activity(IC50=6.56-10.71μM).16c was more potent on HepG2 and MDA-MB-231 cells than mitoxantrone and comparable for HCT116 cells.Among the branched compounds,19a,19b and 19d were comparable or slightly more potent than that of mitoxantrone for HepG2 and MDA-MB-231 cells,and 19c was more active than mitoxantrone for MDA-MB-231 cells.Through Topo II-mediated pBR322 DNA relaxation assay and the kDNA deconjugation assay,the target compounds were proved to act on Topo Ⅱα,and the potency of most of them was comparable to or better than that of VP 16.By DNA intercalator assay,6d2 and 16c,the representative compounds of series A and B,were determined as DNA non-intercalators.