Design,Synthesis,and Evaluation Of Small Molecule Inhibitors Through STAT3 Signaling Pathway

This thesis includes three sections.First section:2-carbonylbenzo[b]thiophene 1,1-dioxide derivatives as STAT3 inhibtors.Stattic, the first nonpeptidomimic small molecule inhibitor of STAT3 signaling pathway, is worthwhile to modify its structure to obtain more durglike lead compound, because its simple structure means that bad selectivity, high toxicity. Besides, the optimization of Stattic and the biological resesrch is less reported, so we need to further study the core structure to identify the novel potent STAT3 inhibitor.Based on the Docking Model of Stattic with the SH2 domain of STAT3 protein, as well as bioisosterism, we synthesized 44 compounds and evaluated the antiproliferative activity on the tested cancer cells using MTT assay. Through the SAR analysis, we identified the most potent compound E28 and evaluated the biological activity. Based on STAT3-dependent dual luciferase reporter assay, we found that E28 potently inhibited the STAT3 phosphorylation. At the same time, compound E28 induced the formation of ROS and dimerization of STAT3 to induce the cancer cell apoptosis. Docking calculation exhibited that STAT3 protein could bind SH2 of STAT3 protein, and the target compounds were characterized by 1H NMR,13C NMR and HRMS.Second section:4-carbonyl-2,6-dibenzylidenecyclohexanone derivatives as STAT3 inhibitors.Curcumin, the principal curcuminoid of the Indian spice turmeric, showed a broad range of biological functionality. Curcumin, which is a potential antitumor agent, inhibits IL-6-induced Stat3 phosphorylation and nuclear translocation. HO-3867, as a curcumin derivative, exhibited more effective antiproliferative activity than its parent compound, and inhibited the activation of STAT3 sinaling pathway. In the meanwhile, Curcumin exhibited low toxicity on the human normal cells. To find the novel STAT3 inhibitors, we substituted cyclohexanone for piperidone, which kept the indispensable pharmacophore as well as change thier hydrophobicity to enhance compounds’ antitumor activity, and then we modified the structure at 4-positoin of cyclohexanone using dissimilar aromatic/aliphatic substituents with amide as the linker to generate a series of 4-carbonyl-2,6-dibenzylidenecyclohexanone derivatives. Through MTT assay, we found that most of these compounds exhibited antitumor activity against MDA-MB-231, A549, and DU145 cells and the 13r was identified to be the most potent compound and low toxicity on the human normal cells. Through the Western Blot assay and flow cytometry, we found that 13r could potently inhibit the STAT3 phosphorylation and induced the cancer cell apoptosis and G2/M cell phase arrest. All of the target compounds were characterized by 1H NMR,13C NMR and HRMS.Third section:NSC-743380 derivatives as the STAT3 inhibitors.As the oncrasin-1 derivative, NSC-743380 was reported to be a inhibitor of the C-Terminal Domain of RNA Polymerase Ⅱ, which exhibited high potency in the antitumor activity. Meanwhile, compound could inhibit STAT3 and JAK2 phosphorylation. It was reported that NSC-743380 is not stable in some clinically acceptable injection formulations and easily form dimmers in solutions with water and loses activity, especially in low-pH condition. Therefore, due to its chemical instability, it was often prepared as prodrug.In order to improve the properity of these compounds, we incorporated nitrogen-atoms into the indole of NSC-743380 based on bioisosterism, and methylol was replaced with cyano group and amide group. Eventually, twelve compounds were prepared and evaluated their antiproliferative activity using MTT assay. Based on the SAR, the potent compound JP-3-138 was identified to inhibit the STAT3 activation via Western Blot assay.