Design,Synthesis,and Biological Evaluation Of Small Molecular Inhibitors And Degraders Targeting STAT3

Objective Gastric cancer is one of the most important causes of death worldwide.The incidence rate of advanced gastric cancer in China is particularly high,and the prognosis of patients is poor.Traditional chemotherapy has demonstrated limited efficacy in treating this disease.Because of the limited availability of targeted drugs for the clinical treatment of gastric cancer,it is urgent to develop high-efficiency and low-toxicity targeted drugs for gastric cancer.STAT3(Signal transducer and activator of transcription 3)signaling pathway plays an important role in promoting the occurrence and development of gastric cancer.As a result,the development of STAT3 inhibitors has been a hot spot in the development of anti-tumor drugs.In addition to directly blocking the activity of STAT3,the degradation of STAT3 may represent another effective cancer treatment strategy.This study aims to provide insights into future drug design and optimization of inhibitors by applying rational design principles to accelerate the discovery of effective STAT3 inhibitors or degradants.Methods A series of STAT3 inhibitors and degradants were designed and synthesized according to the strategies of pharmacophore combination and bioisosterism;The anti-tumor activity of these compounds in vitro was studied:the effect of these compounds on the proliferation of gastric cancer cell lines was tested by CCK8 experiment,and the compounds with the best anti-proliferation effect(SDL-1,SIL-14)were selected for further study;clonogenesis assay,scratch assay and transwell invasion assay were used to evaluate their anti-gastric cancer activity;apoptosis experiment and cell cycle arrest experiment were used to explore the cell cycle blocking effect and proapoptotic effect on a gastric cancer cells;Western Blot experiment was used to study its effect on STAT3 signal pathway;molecular docking was used to simulate the binding of SIL-14 with the SH2 domain of STAT3.Results Design and synthesis of 24 novel STAT3 inhibitors through the principles of pharmacophore hybridization and bioisosterism.CCK8 experiment showed that inhibitor SIL-14 exhibits good inhibitory effects on cell proliferation in four gastric cancer cells(MGC803,MKN28,MKN1,and AGS).SIL-14 was found to arrest MGC803 cells at the G2/M phase,as revealed by cell cycle analysis.In vitro studies showed that SIL-14 could inhibit colony formation,migration,and induce apoptosis of the gastric cancer cell line MGC803 in a concentration-dependent manner.The mechanism study showed that SIL-14 may exert its anticancer effect by inhibiting the phosphorylation of STAT3 protein and blocking the STAT3 signal pathway.In addition,the docking experiment support the binding mode of SIL-14 in the SH2 domain of STAT3.Using the principle of PROTAC technology,a total of eight STAT3 PROTACs were designed and synthesized,among which the degrader SDL-1 showed the most promising anti-proliferative effect in four gastric cancer cells(HGC27,MGC803,AZ521,and MKN1),significantly inducing cell cycle arrest,promoting cell apoptosis,and inhibiting the migration and invasion of MKN1 cells.In addition,SDL-1 is an effective degradation agent of STAT3,which can affect STAT3 signal pathway by degrading STAT3 protein and inhibiting STAT3 phosphorylation.Conclusion By binding to the SH2 domain of STAT3,SIL-14 can inhibit the proliferation,cloning formation,migration,blocking the cell cycle and inducing apoptosis of gastric cancer cell line MGC803 in vitro,indicating that SIL-14 may be a promising STAT3 inhibitor for further development of potential anti-gastric cancer candidate drugs.SDL-1 is an effective STAT3 degradation agent,which can induce STAT3 protein degradation in vitro and inhibit the growth and metastasis of gastric cancer,indicating that the use of PROTAC to degrade STAT3 may provide a new potential approach for the treatment of gastric cancer.