Discovery Of Small Molecule Inhibitors Targeting Tumor-associated Proteins CBP Bromodomain And Investigation Of Mechanisms

Purpose:in the past several decades,plenty of studies of cancer epigenetics exposed that the aberrant histone modification is the driving force for tumorigenesis and progression.Histone acetylation is a pivotal post-translational modification in epigenetics,which not only plays an important role in gene transcription and chromosome formation,but also is closely associated with a variety of tumor diseases.The cAMP responsive element binding protein（CREB）binding protein（CBP）and adenoviral E1A binding protein（P300）are two closely related multifunctional transcriptional co-activators.Both proteins contain a bromodomain adjacent to the HAT catalytic domain which is one of the vital members of the non-BET family bromodomain.Many studies indicated that CBP bromodomain serves as a promising drug target for various cancers and immune modulation diseases.However,Small molecule inhibitors targeting bromodomains outside of the bromodomain and extra-terminal domain（BET）family are especially lacking.Methods:here,we established and optimized a HTRF based high throughput screening platform for the bromodomain of CBP（CBP BrD）and acetylated H4 peptide.The HTS assay was performed against an in-house chemical library,and we applied the SPR assay to detect the K_D value.We performed molecular modeling to analyse the binding modes,activities of DC_CP20 ramifications were tested for SAR.Then,the effect of DC_CP20 on the proliferation of mv4-11 lymphoma cells was determined,and the expression of c-myc was detected by western blotting.Results:compound DC_CP20 was discovered as a novel CBP BrD inhibitor with an IC₅₀ value of 744.3nmol/L.The surface plasmon resonance assay demonstrated its binding to CBP BrD with the K_D value of 4.01μmol/L in vitro.Further molecular modeling indicated that DC_CP20 occupied the Kac binding region firmly through a hydrogen bonding between it and the conserved residue ASN1168.In cellular level,DC_CP20 could retard the proliferation of MV4-11 cell lines,and markedly down-regulated the expression of the c-Myc oncogene in western blot studies.Conclusion:taken together,CBP BrD inhibitor DC_CP20 supports a novel chemical scaffold for further medicinal chemistry optimization and represents a potential chemical probe for CBP-related biological function research,in addition,this inhibitor could serve as a promising therapeutic strategy for AML leukemia by targeting CBP BrD protein.