Design,synthesis And Antitumor Activity Of Non-planar Specific CDK4 Inhibitors

CDKs is an important part of the checkpoint at all phases of the cell division cycle which is required for healthy cell growth and proliferation.CDK4 has a very specific function in the G0/G1 phase of the cell division cycle,CDK4 inhibitor can lead to early G1 arrest of the cell cycle and thus prevent uncontrolled cell growth.Recent studies have shown that Cdk4 is an important target for cancer intervention,because the disorder of Cdk4 activity can lead to cancer.Fascaplysin is a pentacyclic quaternary salt with a wide range of biological activities,which was originally isolated from the Fijian sponge Fascaplysinopsis Bergquist sp and it is also a potential cyclin-dependant kinase 4(CDK4)inhibitor that causing cell cycle arrest at the G1 phase in both normal and tumour cell lines.However Fascaplysin itself has limited potential as an anti-cancer drug due to its toxic side effects,fascaplysin shows unusual toxicity at the cellular level.Further studies have shown that fascaplysin intercalates with double-stranded DNA molecules due to its planar structure,a property similar to DNA intercalating agents.The main goal of this study was to develop potent,non-planar Cdk4-specific analogues of fascaplysin which do not intercalate or interact with double-stranded DNA,with the aim that these non-planar molecules would avoid toxicity at the cellular level.In this study,two types of non-planar CDK4 inhibitors based on fascaplysin were designed by releasing bonds and opening the ring.Using the classical Pictet-Spengler reaction,the tetrahydro-β-carboline derivatives was synthesized by cyclization and acylation.The target compounds of indole were synthesized by isocyanate method.Subsequently,20 compounds were confirmed by 1H-NMR,13C-NMR and ESI-MS.In order to explore the antitumor activity of 20 target compounds,cell proliferation inhibition experiments,cell cycle and apoptosis experiments were performed respectively.MTT assay was used to detect the proliferation of tumor cells,the results showed that b5 was the best inhibitory activity for target cells with IC50(5μM <IC50 <30μM),and the IC50 of A-549 was 8.53 ± 1.65μM.The best inhibitory activity of tumor cells in the indole fascaplysin analogs was a9(IC50 <90μM),and the normal cytotoxicity of IC50 was 119.54 ± 38.57 μM.Thesubstitution of nitro groups on the benzene ring of the tetrahydropyro-β-carboline compound is less than that of the methoxy group and the halogen substitution activity.The IC50 value of the phenyl ring nitro substitution is greater than 200 μM,while the phenylcyclopentoxy and halogen substituted IC50 is less than 100 μM.The inhibitory activity of the two compounds was weaker than that of the control substance fascaplysin(0.2μM <IC50 <1.1μM),to a certain extent,the normal cytotoxicity is reduced.Cell cycle experiments showed that fascaplysin and target compound b5 decreased G0/G1 phase while the proportion of S phase was significantly increased,showing S phase block compared with the blank group.The target compounds a9 and b3 increased the G0/G1 phase of A549 cells which showed G1 arrest.Apoptosis cell were determined by AnnexinV/PI assay,The results show that all derivatives have effect of inducing apoptosis on A-549,among which b5 is the strongest,and the weakest is b3.