Screening and evaluation of antitumor activity of spermine oxidase inhibitors
OBJECTIVE To screen novel inhibitors of spermine oxidase(SMO),a key enzyme in polyamine metabolism,and investigate the antitumor effects of SMO inhibitors effect in human lung cancer A549 cells as well as their possible molecular mechanism.METHODS The combining pharmacophore modelling and molecular docking were carried out based on the complex structure of SMO-spermine for the virtual screening of SMO inhibitors.Using human lung cancer A549 cells as a tumor cell model,the chemiluminescence assay and HPLC were used to detemine enzyme activities of SMO and cellular polyamine content.MTT assay and flow cytometry(FCM)were used to analyze cell proliferation,cell cycle and apoptosis.Confocal laser scanning microscopy(LSCM)and fluorescence microscope were used to detect autophagy.Western blot was used to analyze the expression levels of cell cycle-related proteins(Cyclin Bl,p21 and Cyclin D),apoptosis-related protein(Bax,Bel-2 and cytochrome C)and autophagy-related protein(LC3,P62).RESULTS A novel inhibitor(SI-1338)was selected and showed inhibitory effect against SMO with IC50 value of 880 μmol·L-1.SI-1338 could significantly inhibit the activity of SMO,interfere with polyamine metabolism and reduce the content of total polyamine in A549 cells.Treatment of A549 cells with SI-1338 inhibited proliferation,increased the expression levels of Cyclin B1,p21 and Cyclin D,caused G0/G,cell cycle arrest;increased the expression levels of Bax,cytochrome C and LC3-Ⅱ fragment,decreased the expression levels of Bel-2 and P62,induced apoptotic and autophagic cell death.CONCLUSION We have identified that SI-1338 functioned as a novel inhibitor of SMO.SI-1338 has the pharmacological activity of killing lung cancer A549 cells,and its mechanism may be related to the inhibition of SMO enzyme activity,interference of polyamine metabolism and induction of apoptosis and autophagy.SI-1338 can be used as a lead compound of antitumor drug with polyamine metabolism as target for cancer therapy.