Study On The Synergistic Anti-tumor Effects Of A Novel Dual-targeted BRD4 Inhibitor And Parp Inhibitor

Objective:Breast cancer is one of the most common malignancies in the female population.Niraparib,PARP inhibitor,is a new tumor therapy drug developed for DNA damage repair and deletion.It has a significant inhibitory effect on tumor cells with BRCA1/2 mutation.Recent studies have shown that PARP inhibitors are equally effective against cancer types that do not have BRCA mutations.But long-term use of PARP inhibitors for cancer treatment can lead to drug resistance.Therefore,the use of PARP inhibitors in combination with other drugs to enhance their anticancer effect will become a treatment method of clinical significance.Cell growth and cell cycle are closely related to the occurrence and development of cancer.As a protein that interprets the DNA epigenetic code,BRD4 affects cell survival by regulating the transcriptional expression of genes related to cell growth and cycle.Studies have shown that BRD4 inhibitors can inhibit tumor growth by affecting DNA transcription enhancers to down-regulate the expression of proteins related to DNA damage repair and inhibiting the DNA damage repair function of cells.Therefore,BRD4 inhibition and PARP inhibition can form synthetic lethal synergistic effects against tumor cells^[1].Toll-like receptor is a bridge between innate immunity and adaptive immunity.Small molecule agonists targeting TLR7 can significantly activate the body’s immunity and play an anti-tumor role.In this study,the self-synthesized SZU-119 in our laboratory was used as a dual-functional compound with both TLR7 activation and BRD4 inhibition to evaluate the anti-tumor effect in combination with PARP inhibitor Niraparib.We hope that with the dual-target approach to breast cancer,we will be able to enhance the effectiveness of drugs against tumors by activating the immune system and produce immune memory,as well as eliminating drug resistance of PARP inhibitors.Through in vivo and in vitro experiments,this project systematically evaluated the immunoactivity and anti-tumor activity of new compound SZU-119,and provided a new idea for innovative drug development and application.Methods:（1）A novel dual-targeted BRD4 inhibitor SZU-119 was chemically synthesized and purified by mass spectrometry.（2）The activation of TLR7 by SZU-119 was demonstrated by the HEK-Blue^TM hTLR7 cell line.（3）The immune activation of SZU-119 and secretion of immune factors on immune cells in vitro was detected by ELISA.（4）The inhibiton of SZU-119 on 4T1 cell was examined by the CCK8.（5）Flow cytometry was used to analyze the apoptotic effect of SZU-119 and drug combination on 4T1 cell.（6）Flow cytometry was used to analyze the effect of SZU-119 and drug combination on 4T1 cell cycle.（7）Western Blot was used to detect the effect of SZU-119 on protein expression in 4T1 cells.（8）Establish a mouse breast cancer model to verify the combined anti-tumor effect of SZU-119 and drug combination.（9）Flow cytometry was used to analyze the effect of SZU-119 and drug combination on infiltrating T cells.Results:（1）SZU-119 is a dual-targeted small-molecule compound combining the activation of TLR7 and the inhibition of BRD4.In vitro,SZU-119 can stimulate the secretion of immune factors by activating immune cells and has an inhibitory effect similar to that of BRD4 inhibitors on cancer cells.（2）The combination of SZU-119 and Niraparib had good tumor inhibition effect both in vivo and vitro,which is superior to the use of single drugs.Conclusion:New dual-targeted small-molecule compound szu-119 is an effective TLR7agonist and BRD4 inhibitor,with good tumor inhibition in vivo and in vitro when used alone or in combination with Niraparib,it can further tumor growth inhibition and improve the therapeutic effect by increasing the body’s immunity.In this study,for the first time we verified the efficacy of immunotherapy for tumor through the combination of targeted small molecule with immune function and against drug resistance,which provided a new idea for the development of immunotherapy methods and drugs for triple negative breast cancer.