Molecular docking of DS-3032B,a mouse double minute 2 enzyme antagonist with potential for oncology treatment development

BACKGROUND It is known that p53 suppression is an important marker of poor prognosis of cancers,especially in solid tumors of the breast,lung,stomach,and esophagus;liposarcomas,glioblastomas,and leukemias.Because p53 has mouse double minute 2(MDM2)as its primary negative regulator,this molecular docking study seeks to answer the following hypotheses:Is the interaction between DS-3032B and MDM2 stable enough for this drug to be considered as a promising neoplastic inhibitor?AIM To analyze,in silico,the chemical bonds between the antagonist DS-3032B and its binding site in MDM2.METHODS For molecular docking simulations,the file containing structures of MDM2(receptor)and the drug DS-3032B(ligand)were selected.The three-dimensional structure of MDM2 was obtained from Protein Data Bank,and the one for DS-3032B was obtained from PubChem database.The location and dimensions of the Grid box was determined using AutoDock Tools software.In this case,the dimensions of the Grid encompassed the entire receptor.The ligand DS-3032B interacts with the MDM2 receptor in a physiological environment with pH 7.4;thus,to simulate more reliably,its interaction was made with the calculation for the prediction of its protonation state using the MarvinSketch®software.Both ligands,with and without the protonation,were prepared for molecular docking using the AutoDock Tools software.This software detects the torsion points of the drug and calculates the angle of the torsions.Molecular docking simulations were performed using the tools of the AutoDock platform connected to the Vina software.The analyses of the amino acid residues involved in the interactions between the receptor and the ligand as well as the twists of the ligand,atoms involved in the interactions,and type,strength,and length of the interactions were performed using the PyMol software(pymol.org/2)and Discovery Studio from BIOVIA®.RESULTS The global alignment indicated crystal structure 5SWK was more suitable for docking simulations by presenting the p53 binding site.The three-dimensional structure 5SWK for MDM2 was selected from Protein Data Bank and the three-dimensional structure of DS-3032B was selected from PubChem(Compound CID:73297272;Milademetan).After molecular docking simulations,the most stable conformer was selected for both protonated and non-protonated DS-3032B.The interaction between MDM2 and DS-3032B occurs with high affinity;no significant difference was observed in the affinity energies between the MDM2/pronated DS-3032B(-9.9 kcal/mol)and MDM2/non-protonated DS-3032B conformers(-10.0 kcal/mol).Sixteen amino acid residues of MDM2 are involved in chemical bonds with the protonated DS-3032B;these 16 residues of MDM2 belong to the p53 biding site region and provide high affinity to interaction and stability to drugprotein complex.CONCLUSION Molecular docking indicated that DS-3032B antagonist binds to the same region of the p53 binding site in the MDM2 with high affinity and stability,and this suggests therapeutic efficiency.

Role of p53 suppression in the pathogenesis of hepatocellular carcinoma

In the world,hepatocellular carcinoma(HCC)is among the top 10 most prevalent malignancies.HCC formation has indeed been linked to numerous etiological factors,including alcohol usage,hepatitis viruses and liver cirrhosis.Among the most prevalent defects in a wide range of tumours,notably HCC,is the silencing of the p53 tumour suppressor gene.The control of the cell cycle and the preservation of gene function are both critically important functions of p53.In order to pinpoint the core mechanisms of HCC and find more efficient treatments,molecular research employing HCC tissues has been the main focus.Stimulated p53 triggers necessary reactions that achieve cell cycle arrest,genetic stability,DNA repair and the elimination of DNA-damaged cells’responses to biological stressors(like oncogenes or DNA damage).To the contrary hand,the oncogene protein of the murine double minute 2(MDM2)is a significant biological inhibitor of p53.MDM2 causes p53 protein degradation,which in turn adversely controls p53 function.Despite carrying wt-p53,the majority of HCCs show abnormalities in the p53-expressed apoptotic pathway.High p53 in-vivo expression might have two clinical impacts on HCC:(1)Increased levels of exogenous p53 protein cause tumour cells to undergo apoptosis by preventing cell growth through a number of biological pathways;and(2)Exogenous p53 makes HCC susceptible to various anticancer drugs.This review describes the functions and primary mechanisms of p53 in pathological mechanism,chemoresistance and therapeutic mechanisms of HCC.

Tumor-associated autoantibodies are useful biomarkers in immunodiagnosis of α-fetoprotein-negative hepatocellular carcinoma

AIM To determine the prevalence and diagnostic value of autoantibodies inα-fetoprotein(AFP)-negative hepatocellular carcinoma(HCC).METHODS Fifty-six serum samples from AFP-negative HCC cases,86 from AFP-positive HCC cases,168 from chronic liver disease cases,and 59 from normal human controls were included in this study.Autoantibodies to nucleophosmin(NPM)1,14-3-3zeta and mouse double minute 2 homolog(MDM2)proteins in AFP-negative HCC serum were evaluated by enzymelinked im munosorbent assay.Partially positive sera were further evaluated by western blotting.Immunohistochemistry was used to detect the expression of three tumor-associated antigens(TAAs)in AFP-negative HCC and normal control tissues.RESULTS The frequency of autoantibodies to the three TAAs in AFP-negative HCC sera was 21.4%,19.6%and 19.6%,which was significantly higher than in the chronic liver disease cases and normal human controls(P<0.01)as well as AFP-positive HCC cases.The sensitivity of the three autoantibodies for diagnosis of AFP-negative HCC ranged from 19.6%to 21.4%,and the specificity was approximately 95%.When the three autoantibodies were combined,the sensitivity reached 30.4%and the specificity reached 91.6%.CONCLUSION Autoantibodies to NPM1,14-3-3zeta and MDM2 may be useful biomarkers for immunodiagnosis of AFP-negative HCC.

SUMO-1 Enhancing the p53-induced HepG2 Cell Apoptosis

In order to investigate the effect of small ubiquitin-like modifier-1 (SUMO-1) on the p53-induced HepG2 cell apoptosis, HepG2 cells were transfected by recombinant plasmids as pwtp53, pMDM2 and pSUMO-1 respectively. Western blot was employed to detect the protein expression of the transfected recombinant plasmids and the rate of apoptosis was measured by flow cytometry. The results showed that in cells transfected with pwtp53 and pwtp53+pSUMO-1, the apoptosis rate was (16.79±1.62) % and (18.15±1.36) % respectively, while transfected with pwtp53+pMDM2, the rate was decreased to (5.17±1.23) %. The apoptosis rate was (14.06±1.84) % in the cells transfected with pwtp53+pMDM2+pSUMO-1, significantly higher than that in the cells Transfected with pwtp53+pMDM2 (P<0.01). The apoptosis rates in the cells were all less than 2 % and had no significant difference among the groups. It was suggested that in the HepG2 cells, SUMO-1 can increase the apoptosis induced by wild-type p53 through binding to p53 protein, post-translational modification and inhibiting the p53 degradation by MDM2.

Murine double minute 2, a potential p53-independent regulator of liver cancer metastasis

Hepatocellular carcinoma(HCC)has emerged as one of the most commonly diagnosed forms of human cancer;yet,the mechanisms underlying HCC progression remain unclear.Unlike other cancers,systematic chemotherapy is not effective for HCC patients,while surgical resection and liver transplantation are the most viable treatment options.Thus,identifying factors or pathways that suppress HCC progression would be crucial for advancing treatment strategies for HCC.The murine double minute 2(MDM2)-p53 pathway is impaired in most of the cancer types,including HCC,and MDM2 is overexpressed in approximately 30%of HCC.Overexpression of MDM2 is reported to be well correlated with metastasis,drug resistance,and poor prognosis of multiple cancer types,including HCC.Importantly,these correlations are observed even when p53 is mutated.Indeed,p53-independent functions of overexpressed MDM2 in cancer progression have been suitably demonstrated.In this review article,we summarize potential effectors of MDM2 that promote or suppress cancer metastasis and specifically discuss the p53-independent roles of MDM2 in liver cancer metastasis from clinical as well as biological perspectives.

Mdm2 links genotoxic stress and metabolism to p53

Mouse double minute 2(Mdm2)gene was isolated from a cDNA library derived from transformed mouse 3T3 cells,and was classified as an oncogene as it confers 3T3 and Rat2 cells tumorigenicity when overexpressed.It encodes a nucleocytoplasmic shuttling ubiquitin E3 ligase,with its main target being tumor suppressor p53,which is mutated in more than 50%of human primary tumors.Mdm2’s oncogenic activity is mainly mediated by p53,which is activated by various stresses,especially genotoxic stress,via Atm(ataxia telangiectasia mutated)and Atr(Atm and Rad3-related).Activated p53 inhibits cell proliferation,induces apoptosis or senescence,and maintains genome integrity.Mdm2 is also a target gene of p53 transcription factor.Thus,Mdm2 and p53 form a feedback regulatory loop.External and internal cues,through multiple signaling pathways,can act on Mdm2 to regulate p53 levels and cell proliferation,death,and senescence.This review will focus on how Mdm2 is regulated under genotoxic stress,and by the Akt1-mTOR-S6K1 pathway that is activated by insulin,growth factors,amino acids,or energy status.