Lead Compouds Discovery And Mechanism Studies For Cancer Related Key Protein-protein Interactions

Protein-protein interactions（PPIs）involve in most aspects of cellular functions.Compared with traditional drug targets,PPIs have some special properties and the PPIs network is rather complicated.It is challenging or sometimes unable to develop small-molecule drugs targeting protein-protein interactions.In the first chapter of this paper,we provide a brief introduction for the characters,classifications and druggable prediction methods of protein-protein interactions.Several examples were given in this chapter to demonstrate strategies for classic types of PPIs.Disrupting the protein-protein interactions between Menin and MLL represents a very promising approach for curing MLL-rearrangement leukemia or other related diseases.Chapter 2 described the virtual screening for small molecules targeting Menin-MLL interfaces using molecular docking and 3D-QSAR pharmacophore models.Compounds of new scaffold typified by DCZ_M123 were demonstrated to bind Menin and disrupt Menin-MLL interactions(DCZ_M123,IC₅₀ = 4.71 ± 0.12 μM).According to the predicted binding modes,our inhibitors occupy both the MBM1 and MBM2 binding pockets while other reported inhibitors compete against only the MBM1.In chapter 3 of this paper,a shape-based scaffold hopping approach was used to find marketed drugs with Menin-MLL inhibitory activities.Loperamide was firstly identified to display previously unreported mild inhibition for Menin-MLL interactions(IC₅₀ = 69 ± 3 μM).In an effort to repurpose this drug,a series of chemical modification analyses were performed,developing several potent inhibitors with IC₅₀ at nanomolar concentrations.Taken DC_YM21(IC₅₀=0.83 ± 0.13 μM)for example,inhibitors derived from loperamide scaffold were able to bind Menin on the MBM1 binding pocket and inhibited Menin-MLL interactions in both extracellular and intracellular levels.Further treatment with DC_YM21 demonstrated potent and selective blockage of proliferation for leukemia cells harboring MLL translocations.Cell cycle arrest,differentiation induction as well as downregulation of target genes expressions were further observed,which confirmed the specific mechanism of action.In this work,loperamide was reported to inhibit Menin-MLL interactions for the first time,and the loperamide scaffold was successfully repurposed to develop potent and novel inhibitors targeting Menin-MLL interfaces.A lot of evidence suggests that the basic function of autophagy may be linked to human health and longevity.Small molecule autophagy modulators are promisingly used in disease treatment.LC3 and the homologues proteins interact with many proteins through the LC3 interacting region（LIR）,and these LC3-LIR interactions play a key role in autophagy process.In the last chapter of this paper,we discovered small molecule autophagy modulators disrupting LC3-LIR interactions.Compounds were proved to bind LC3 B protein on the L pocket,one of the two hydrophobic binding pockets for LIR peptide,competing against proteins containing LIR motifs.Compounds were observed to have impact on cellular autophagy but details should be clarified in further work.This was the first time for LC3-LIR interface to be viewed as a druggable target and the mechanism was novel to autophagy studies.