Design, Synthesis And Biological Evaluation Of PAC-1Analogues

Cancer mortality ranks second in all the diseases. According to statistics byWHO, there were10.1million new cancer cases,6.2million cancer deaths in2000and the numbers increased to12.66million and7.56million respectively in2008.Even it is estimated to be15million new cancer cases in2015. Therefore it is urgentto research and develop of prevention and treatment for cancer. Recently scientistshave made headway with the pathogenesis of cancer. Till now Apoptosis induction isone of the hotspot of developing anti-tumor drugs.Apoptosis is the process of programmed cell death (PCD) that relates to initiationand development of cancer. The Caspase-3plays a central role in the execution-phaseof cell apoptosis. Caspase-3exists as inactive proenzymes Procaspase-3that onlyworks after activation. The expressions of Procaspase-3in most of tumor cells arehigher than normal cells so that Procaspase-3agonist has become a promising targetof anti-tumor therapy. PAC-1（procaspase-3activating compound-1）is the firstdeveloped small molecular compound working on Procaspase-3directly. Its IC50foranti-tumor cell U937was reported to reach as high as0.92μM. Meanwhile it showedconsiderable inhibitive activity to other many tumor cells so that it is a promisinganti-tumor drug with high efficiency but low toxicity.This thesis tried to analyze structure of PAC-1to design and synthesis newcompounds which own higher activity and selectivity than PAC-1. Three types of34totally new compounds were synthesized and their structures were confirmed by1H-NMR and MS.The in vitro inhibitive activity of target compounds to tumor cells of HL-60,K562and HCT-8and normal cell of HLF was determined. Results showed significantanti-tumor activity from most of designed PAC-1analogues. Especially LHM-8-3andLHM-8-7demonstrated great inhibitive activity on HL-60, which their IC50reachedto0.15μM and0.09μM respectively.On the basis of the biological result, the structure-activity relationship wasdiscussed and the effect of substituent group and positions on activity wassummarized. The piperazine ring is not the indispensable group according to the pharmacological activity tests. Good pharmacological activity only existed whenhydroxyl group of aromatic ring connecting to diazanyl group was in position2.Compounds with methoxy group in para-position of aromatic ring in form of benzylgroup connecting with straight-chain amine showed much higher activity thancompounds with methoxy group in meta-position. The same trend was found incompounds with isopropyl group against methoxy group in para-position. The resultsabove illustrated that the space of the position connecting to receptor was so smallthat had selectivity on size of substituent group. The structure-activity relationshipdiscussed above has the role of direction for further research.Hypoxia inducible factor-1(HIF-1) is a nucleoprotein with transcriptionalactivities widely existing in mammalian cells. HIF-1affects angiogenesis, cellsurvival and pH by target gene regulation. They play crucial roles in diseases likeanemia, cancer and nephrosis. It was reported that proline hydroxylase (PHD) is therate-limiting enzyme of HIF-1degradation. Small molecular PHD inhibitors stabilizeHIF-1by inhibiting the PHD activity to up regulate its target gene erythropoietin(EPO) for treatment of anemia. Currently, oral dosage forms of small molecular PHDinhibitors have been the hotspot of developing anti-anemia drugs.In this research, target compounds were investigated to have good PHD inhibitionactivity. In order to explore their inhibition mechanism, iron ion chelated ability oftarget compounds were measured. It was found that concentration of targetcompounds could stabilize HIF-1α and in this concentration iron ion chelated abilityof target compounds was quite small. The phenomenon above revealed that thesecompounds played the same role as2-ketoglutaric acid analogues which combinedwith PHD to block the hydroxylation reaction of HIF-1α for stabilization. Thestructure-activity relationship was preliminarily discussed based on the biologicalresults. It provides the theory basis for design and modification of small molecularPHD inhibitors.