p53是重要的抑癌基因,在细胞周期阻滞、DNA损伤修复及细胞凋亡等生物过程中发挥重要作用,并已成为潜在的肿瘤治疗靶点。MDM2(Mdm2 p53 binding protein homolog)及MDMX(Mdm4 p53 binding protein homolog)是p53的主要抑制因子,两者相互...p53是重要的抑癌基因,在细胞周期阻滞、DNA损伤修复及细胞凋亡等生物过程中发挥重要作用,并已成为潜在的肿瘤治疗靶点。MDM2(Mdm2 p53 binding protein homolog)及MDMX(Mdm4 p53 binding protein homolog)是p53的主要抑制因子,两者相互协同并通过不同的信号途径抑制p53的活性。MDM2是p53的E3连接酶,介导p53的泛素化从而降低p53的稳定性。MD-MX则主要通过与p53的转录活性区结合,抑制p53对其下游基因的转录活性,但并不介导p53的降解。MDM2与MDMX通过不同机制协同对p53产生抑制作用,其具体分子过程及作用机制繁多且复杂。本文就p53。展开更多
Mdm2 and Mdmx are critical regulators of the p53 tumour suppressor and are overexpressed in many human malignancies. However, in recent years, their impact on genome instability was shown to be at least, in part, inde...Mdm2 and Mdmx are critical regulators of the p53 tumour suppressor and are overexpressed in many human malignancies. However, in recent years, their impact on genome instability was shown to be at least, in part, independent of p53. Both Mdm2 and Mdmx inhibit DNA break repair through their association with the Mrell/RadSO/Nbs1 DNA repair complex. Recent evidence indicates that harnessing Mdm2 and/or Mdmx-mediated inhibition of DNA break repair in cancer cells could provide a therapeutic opportunity, particularly for those malignancies that have lost functional p53.展开更多
Deregulation of the tyrosine kinase signalling is often associated with tumour progression and drug resistance, but its underlying mechanisms are only partly understood. In this study, we investigated the effects of t...Deregulation of the tyrosine kinase signalling is often associated with tumour progression and drug resistance, but its underlying mechanisms are only partly understood. In this study, we investigated the effects of the receptor tyrosine kinase AXL on the sta- biUty of the MDMX-MDM2 heterocomplex and the activity of p53 in melanoma cells. Our data demonstrated that AXL overexpres- sion or activation through growth arrest-specific 6 （Gas6） Ugand stimulation increases MDMX and MDM2 protein levels and decreases p53 activity. Upon activation, AXL stabilizes MDMX through a post-translational modification that involves phosphoryl- ation of MDMX on the phosphosite Ser314, leading to increased affinity between MDMX and MDM2 and favouring MDMX nuclear translocation. Ser314 phosphorylation can also protect MDMX from MDM2-mediated degradation, leading to stabilization of the MDMX-MDM2 complex. We identified CDK4/6 and p38 MAPK as the two kinases mediating AXL-induced modulation of the MDMX-MDM2 complex, and demonstrated that suppression of AXL, either through siRNA silencing or pharmacological inhibition, increases expression levels of p53 target genes P21, MDM2, and PUMA, improves p53 pathway response to chemotherapy, and sensitizes cells to both Cisplatin and Vemurafenib. Our findings offer an insight into a novel signalling axis linking AXL to p53 and provide a potentially druggable pathway to restore p53 function in melanoma.展开更多
It is evident that p53 activity is critical for tumour prevention and stress response through its transcriptional activation of genes affecting cellular senescence, apoptosis, cellular metabolism, and DNA repair. The ...It is evident that p53 activity is critical for tumour prevention and stress response through its transcriptional activation of genes affecting cellular senescence, apoptosis, cellular metabolism, and DNA repair. The regulation of p53 is highly complex, and MDM2 and MDMX are thought to be critical for deciding the fate of p53, both through inhibitory binding and post-translational modification. Many mouse models have been generated to study the regulation of p53 in vivo, and they have altered our inter- pretations of how p53 is regulated by MDM2 and MDMX. Although MDM2 is absolutely required for p53 regulation, certain func- tions are dispensable under unstressed conditions, including the ability of MDM2 to degrade p53. MDMX, on the other hand, may only be required in select situations, like embryogenesis. These models have also clarified how cellular stress signals modify the p53-inhibiting activities of MDM2 and MDMX in vivo. It is clear that more work will need to be performed to further understand the contexts for each of these signals and the requirements of various MDM2 and MDMX functions. Here, we will discuss what we have learned from mouse modelling of MDM2 and MDMX and underscore the ways in which these models could inform future therapies.展开更多
Peptide inhibition of the interactions of the tumor suppressor protein P53 with its negative regulators MDM2 and MDMX activates P53 in vitro and in vivo,representing a viable therapeutic strategy for cancer treatment....Peptide inhibition of the interactions of the tumor suppressor protein P53 with its negative regulators MDM2 and MDMX activates P53 in vitro and in vivo,representing a viable therapeutic strategy for cancer treatment.Using phage display techniques,we previously identified a potent peptide activator of P53,termed PMI(TSFAEYWNLLSP),with binding affinities for both MDM2 and MDMX in the low nanomolar concentration range.Here we report an ultrahigh affinity,dual-specificity peptide antagonist of MDM2 and MDMX obtained through systematic mutational analysis and additivitybased molecular design.Functional assays of over 100 peptide analogs of PMI using surface plasmon resonance and fluorescence polarization techniques yielded a dodecameric peptide termed PMI-M3(LTFLEYWAQLMQ)that bound to MDM2 and MDMX with K_(d)values in the low picomolar concentration range as verified by isothermal titration calorimetry.Co-crystal structures of MDM2 and of MDMX in complex with PMI-M3 were solved at 1.65 and 3.0 A resolution,respectively.Similar to PMI,PMI-M3 occupied the P53-binding pocket of MDM2/MDMX,which was dominated energetically by intermolecular interactions involving Phe3,Tyr6,Trp7,and Leu 10.Notable differences in binding between PMI-M3 and PMI were observed at other positions such as Leu4 and Met11 with MDM2,and Leu1 and Met11 with MDMX,collectively contributing to a significantly enhanced binding affinity of PMI-M3 for both proteins.By adding lysine residues to both ends of PMI and PMI-M3 to improve their cellular uptake,we obtained modified peptides termed PMI-2K(KTSFAEYWNLLSPK)and M3-2K(KLTFLEYWAQLMQK).Compared with PMI-2K,M3-2K exhibited significantly improved antitumor activities in vitro and in vivo in a P53-dependent manner.This super-strong peptide inhibitor of the P53-MDM2/MDMX interactions may become,in its own right,a powerful lead compound for anticancer drug development,and can aid molecular design of other classes of P53 activators as well for anticancer therapy.展开更多
In recent years, the strategy of inhibiting the interactions of p53 with murine double minute 2(MDM2)and murine double minute X(MDMX) has been proved to be a promising approach for tumor therapy.However, the poor prot...In recent years, the strategy of inhibiting the interactions of p53 with murine double minute 2(MDM2)and murine double minute X(MDMX) has been proved to be a promising approach for tumor therapy.However, the poor proteolytical stability and low intracellular delivery efficiency of peptide inhibitors limit their clinical application. Here, we designed and synthesized the bicyclic stapled peptides based on p53 by combining all-hydrocarbon stapling and lactam stapling strategies. We demonstrated that bicyclic stapled peptide p53-16 significantly improved α-helicity and proteolytic stability. Especially, p53-16showed nanomolar binding affinity for MDM2 and MDMX. In addition, p53-16 could penetrate the cell membrane, and selectively inhibited the activity of tumor cells via activating p53 pathway in vitro. Our data suggest that p53-16 is a potential dual inhibitor of MDM2 and MDMX interactions. The bicyclic stapling strategy is a promising drug design strategy for protein–protein interactions inhibitors.展开更多
A role of tumor-suppressive activity of p53 in the tumor microenvironment(TME)has been implicated but remains fairly understudied.To address this knowledge gap,we leveraged our MdmxS314A mice as recipients to investig...A role of tumor-suppressive activity of p53 in the tumor microenvironment(TME)has been implicated but remains fairly understudied.To address this knowledge gap,we leveraged our MdmxS314A mice as recipients to investigate how implanted tumor cells incapacitate host p53 creating a conducive TME for tumor progression.We found that tumor cell-associated stress induced p53 downregulation in peritumor cells via an MDMX-Ser314 phosphorylation-dependent manner.As a result,an immunosuppressive TME was developed,as reflected by diminished immune cell infiltration into tumors and compromised macrophage M1 polarization.Remarkably,ablation of MDMX-Ser314 phosphorylation attenuated p53 decline in peritumor cells,which was associated with mitigation of immunosuppression and significant tumor growth delay.Our data collectively uncover a novel role of p53 in regulating the tumor immune microenvironment,suggesting that p53 restoration in the TME can be exploited as a potential strategy of anticancer therapy.展开更多
OBJECTIVE Low dose of actinomycin D(LDAct D)was reported as a potent P53 activator and protected normal proliferating cells during anti-mitotic chemotherapy.However,the mechanism of LDAct D on P53 activation is still ...OBJECTIVE Low dose of actinomycin D(LDAct D)was reported as a potent P53 activator and protected normal proliferating cells during anti-mitotic chemotherapy.However,the mechanism of LDAct D on P53 activation is still undetermined.In this study,the mechanism of LDAct D on the synergistic antitumor effect for cisplatin(CDDP)and P53 reactivation in KB cells was studied in detail.METHODS Cell viability was determined by MTT and LDH release.Apoptosis was determined by AnnexinⅤ-FITC/PI staining.Mitochondrial membrane potential(MMP)was detected by JC-1 stain-ing.Expression of P53,PARP,BAX,BCL-XL,PUMA,MDM2 and MDMX was detected by Western blotting(WB)and/or immunofluorescence(IF).P53-MDM2 complex was detected by ELISA.Molecular docking of receptor MDM2 and MDMX with actinomycin D(ACTD)was analyzed by Discovery Studio.RESULTS Compared with CDDP alone,P53 expression and the cytotoxicity on KB cells was significantly increased by the combination therapy.P53 regulatory proteins were increased while MMP was decreased.Meanwhile,knockdown of PUMA(P53 upregulated modulator of apoptosis)efficiently blocked the synergistic effect of LDAct D to CDDP.P53 activation was found to be accompanied with the increase of MDMX but not MDM2.Meanwhile,MDM2-P53 complex in KB cells was significantly decreased by LDAct D.Docking of both receptor MDM2 and MDMX with ACTD exhibited well established bonds with nearby amino acid residues.CONCLUSION LDAct D was probably an inhibitor of both MDM2 and MDMX.The synergistic effects of LDAct D for CDDP on KB cells depended on its effect on reactivating P53 and PUMA mediated mitochondrial apoptosis.展开更多
Mdm2 and Mdm4 are negative regulators of the tumour suppressor p53; hence, this relationship is the focus of many cancerrelated studies. A multitude of experiments across various developmental stages have been conduct...Mdm2 and Mdm4 are negative regulators of the tumour suppressor p53; hence, this relationship is the focus of many cancerrelated studies. A multitude of experiments across various developmental stages have been conducted to explore the tissuespecific roles of these proteins in the mouse. When Mdm2 or Mdm4 are deleted in the germiine or specific tissues, they display different phenotypic defects, some of which lead to embryonic lethaLity. Mdm2 loss is often more deleterious than toss of its homotogue Mdm4. ALL tissues experience activation of p53 target genes upon toss of Mdm2 or Mdm4; however, the degree to which the p53 pathway is perturbed is highly tissue-specific and does not correlate to the severity of the morphological pheno- types. Therefore, a need for further understanding of how these proteins regulate p53 activity is warranted, as therapeutic targeting of the p53 pathway is rapidly evoLving and gaining attention in the field of cancer research. In this review, we discuss the tissue-specificity of Mdm proteins in regulating p53 and expose the need for investigation at the celt-specific level.展开更多
文摘p53是重要的抑癌基因,在细胞周期阻滞、DNA损伤修复及细胞凋亡等生物过程中发挥重要作用,并已成为潜在的肿瘤治疗靶点。MDM2(Mdm2 p53 binding protein homolog)及MDMX(Mdm4 p53 binding protein homolog)是p53的主要抑制因子,两者相互协同并通过不同的信号途径抑制p53的活性。MDM2是p53的E3连接酶,介导p53的泛素化从而降低p53的稳定性。MD-MX则主要通过与p53的转录活性区结合,抑制p53对其下游基因的转录活性,但并不介导p53的降解。MDM2与MDMX通过不同机制协同对p53产生抑制作用,其具体分子过程及作用机制繁多且复杂。本文就p53。
文摘Mdm2 and Mdmx are critical regulators of the p53 tumour suppressor and are overexpressed in many human malignancies. However, in recent years, their impact on genome instability was shown to be at least, in part, independent of p53. Both Mdm2 and Mdmx inhibit DNA break repair through their association with the Mrell/RadSO/Nbs1 DNA repair complex. Recent evidence indicates that harnessing Mdm2 and/or Mdmx-mediated inhibition of DNA break repair in cancer cells could provide a therapeutic opportunity, particularly for those malignancies that have lost functional p53.
文摘Deregulation of the tyrosine kinase signalling is often associated with tumour progression and drug resistance, but its underlying mechanisms are only partly understood. In this study, we investigated the effects of the receptor tyrosine kinase AXL on the sta- biUty of the MDMX-MDM2 heterocomplex and the activity of p53 in melanoma cells. Our data demonstrated that AXL overexpres- sion or activation through growth arrest-specific 6 （Gas6） Ugand stimulation increases MDMX and MDM2 protein levels and decreases p53 activity. Upon activation, AXL stabilizes MDMX through a post-translational modification that involves phosphoryl- ation of MDMX on the phosphosite Ser314, leading to increased affinity between MDMX and MDM2 and favouring MDMX nuclear translocation. Ser314 phosphorylation can also protect MDMX from MDM2-mediated degradation, leading to stabilization of the MDMX-MDM2 complex. We identified CDK4/6 and p38 MAPK as the two kinases mediating AXL-induced modulation of the MDMX-MDM2 complex, and demonstrated that suppression of AXL, either through siRNA silencing or pharmacological inhibition, increases expression levels of p53 target genes P21, MDM2, and PUMA, improves p53 pathway response to chemotherapy, and sensitizes cells to both Cisplatin and Vemurafenib. Our findings offer an insight into a novel signalling axis linking AXL to p53 and provide a potentially druggable pathway to restore p53 function in melanoma.
基金The authors would like to thank Hui Tian, Jing Yang, and Derek Franklin （Department of Radiation Oncology, University of North Carolina at Chapel Hill） for their helpful discussions of this manuscript. The authors apologize if they failed to cite any relevant articles. Funding This review was supported by grants from the National Institutes of Health （CA127770, CA 100302, and CA167637）, the Natural Science Foundation of China （NSFC） to Y.Z., and the National Institute of General Medical Sciences （5T32 GM007092） to N.R.T.
文摘It is evident that p53 activity is critical for tumour prevention and stress response through its transcriptional activation of genes affecting cellular senescence, apoptosis, cellular metabolism, and DNA repair. The regulation of p53 is highly complex, and MDM2 and MDMX are thought to be critical for deciding the fate of p53, both through inhibitory binding and post-translational modification. Many mouse models have been generated to study the regulation of p53 in vivo, and they have altered our inter- pretations of how p53 is regulated by MDM2 and MDMX. Although MDM2 is absolutely required for p53 regulation, certain func- tions are dispensable under unstressed conditions, including the ability of MDM2 to degrade p53. MDMX, on the other hand, may only be required in select situations, like embryogenesis. These models have also clarified how cellular stress signals modify the p53-inhibiting activities of MDM2 and MDMX in vivo. It is clear that more work will need to be performed to further understand the contexts for each of these signals and the requirements of various MDM2 and MDMX functions. Here, we will discuss what we have learned from mouse modelling of MDM2 and MDMX and underscore the ways in which these models could inform future therapies.
基金supported by grants from the National Natural Science Foundation of China,No.21807112(to Xiang Li),No.82030062(to Wuyuan Lu),Nos.91849129 and 22077078(to Honggang Hu)Shanghai Rising-Star Program(to Xiang Li,China)+1 种基金supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Contract No.DE-AC02-76SF00515supported by the DOE Office of Biological and Environmental Research,and by the National Institutes of Health,National Institute of General Medical Sciences
文摘Peptide inhibition of the interactions of the tumor suppressor protein P53 with its negative regulators MDM2 and MDMX activates P53 in vitro and in vivo,representing a viable therapeutic strategy for cancer treatment.Using phage display techniques,we previously identified a potent peptide activator of P53,termed PMI(TSFAEYWNLLSP),with binding affinities for both MDM2 and MDMX in the low nanomolar concentration range.Here we report an ultrahigh affinity,dual-specificity peptide antagonist of MDM2 and MDMX obtained through systematic mutational analysis and additivitybased molecular design.Functional assays of over 100 peptide analogs of PMI using surface plasmon resonance and fluorescence polarization techniques yielded a dodecameric peptide termed PMI-M3(LTFLEYWAQLMQ)that bound to MDM2 and MDMX with K_(d)values in the low picomolar concentration range as verified by isothermal titration calorimetry.Co-crystal structures of MDM2 and of MDMX in complex with PMI-M3 were solved at 1.65 and 3.0 A resolution,respectively.Similar to PMI,PMI-M3 occupied the P53-binding pocket of MDM2/MDMX,which was dominated energetically by intermolecular interactions involving Phe3,Tyr6,Trp7,and Leu 10.Notable differences in binding between PMI-M3 and PMI were observed at other positions such as Leu4 and Met11 with MDM2,and Leu1 and Met11 with MDMX,collectively contributing to a significantly enhanced binding affinity of PMI-M3 for both proteins.By adding lysine residues to both ends of PMI and PMI-M3 to improve their cellular uptake,we obtained modified peptides termed PMI-2K(KTSFAEYWNLLSPK)and M3-2K(KLTFLEYWAQLMQK).Compared with PMI-2K,M3-2K exhibited significantly improved antitumor activities in vitro and in vivo in a P53-dependent manner.This super-strong peptide inhibitor of the P53-MDM2/MDMX interactions may become,in its own right,a powerful lead compound for anticancer drug development,and can aid molecular design of other classes of P53 activators as well for anticancer therapy.
基金supported by National Natural Science Foundation of China-Shandong Joint Fund (No. U1606403)Innovation Project of Qingdao National Laboratory for Marine Science and Technology (No. 2015ASKJ02)。
文摘In recent years, the strategy of inhibiting the interactions of p53 with murine double minute 2(MDM2)and murine double minute X(MDMX) has been proved to be a promising approach for tumor therapy.However, the poor proteolytical stability and low intracellular delivery efficiency of peptide inhibitors limit their clinical application. Here, we designed and synthesized the bicyclic stapled peptides based on p53 by combining all-hydrocarbon stapling and lactam stapling strategies. We demonstrated that bicyclic stapled peptide p53-16 significantly improved α-helicity and proteolytic stability. Especially, p53-16showed nanomolar binding affinity for MDM2 and MDMX. In addition, p53-16 could penetrate the cell membrane, and selectively inhibited the activity of tumor cells via activating p53 pathway in vitro. Our data suggest that p53-16 is a potential dual inhibitor of MDM2 and MDMX interactions. The bicyclic stapling strategy is a promising drug design strategy for protein–protein interactions inhibitors.
基金This work was supported in part by the Morningside Foundation,the Zhu Fund,and grants from the National Cancer Institute at the National Institutes of Health(RO1CA233558,R01CA167814,and R01CA125144)to Z.-M.Y.
文摘A role of tumor-suppressive activity of p53 in the tumor microenvironment(TME)has been implicated but remains fairly understudied.To address this knowledge gap,we leveraged our MdmxS314A mice as recipients to investigate how implanted tumor cells incapacitate host p53 creating a conducive TME for tumor progression.We found that tumor cell-associated stress induced p53 downregulation in peritumor cells via an MDMX-Ser314 phosphorylation-dependent manner.As a result,an immunosuppressive TME was developed,as reflected by diminished immune cell infiltration into tumors and compromised macrophage M1 polarization.Remarkably,ablation of MDMX-Ser314 phosphorylation attenuated p53 decline in peritumor cells,which was associated with mitigation of immunosuppression and significant tumor growth delay.Our data collectively uncover a novel role of p53 in regulating the tumor immune microenvironment,suggesting that p53 restoration in the TME can be exploited as a potential strategy of anticancer therapy.
基金The project supported by Ministry of Science and Technology Project of International Cooperation(2011DFR31240)National Science and Technology Major Projects″Major Drug Discovery(″2012ZX09301002001001)
文摘OBJECTIVE Low dose of actinomycin D(LDAct D)was reported as a potent P53 activator and protected normal proliferating cells during anti-mitotic chemotherapy.However,the mechanism of LDAct D on P53 activation is still undetermined.In this study,the mechanism of LDAct D on the synergistic antitumor effect for cisplatin(CDDP)and P53 reactivation in KB cells was studied in detail.METHODS Cell viability was determined by MTT and LDH release.Apoptosis was determined by AnnexinⅤ-FITC/PI staining.Mitochondrial membrane potential(MMP)was detected by JC-1 stain-ing.Expression of P53,PARP,BAX,BCL-XL,PUMA,MDM2 and MDMX was detected by Western blotting(WB)and/or immunofluorescence(IF).P53-MDM2 complex was detected by ELISA.Molecular docking of receptor MDM2 and MDMX with actinomycin D(ACTD)was analyzed by Discovery Studio.RESULTS Compared with CDDP alone,P53 expression and the cytotoxicity on KB cells was significantly increased by the combination therapy.P53 regulatory proteins were increased while MMP was decreased.Meanwhile,knockdown of PUMA(P53 upregulated modulator of apoptosis)efficiently blocked the synergistic effect of LDAct D to CDDP.P53 activation was found to be accompanied with the increase of MDMX but not MDM2.Meanwhile,MDM2-P53 complex in KB cells was significantly decreased by LDAct D.Docking of both receptor MDM2 and MDMX with ACTD exhibited well established bonds with nearby amino acid residues.CONCLUSION LDAct D was probably an inhibitor of both MDM2 and MDMX.The synergistic effects of LDAct D for CDDP on KB cells depended on its effect on reactivating P53 and PUMA mediated mitochondrial apoptosis.
文摘Mdm2 and Mdm4 are negative regulators of the tumour suppressor p53; hence, this relationship is the focus of many cancerrelated studies. A multitude of experiments across various developmental stages have been conducted to explore the tissuespecific roles of these proteins in the mouse. When Mdm2 or Mdm4 are deleted in the germiine or specific tissues, they display different phenotypic defects, some of which lead to embryonic lethaLity. Mdm2 loss is often more deleterious than toss of its homotogue Mdm4. ALL tissues experience activation of p53 target genes upon toss of Mdm2 or Mdm4; however, the degree to which the p53 pathway is perturbed is highly tissue-specific and does not correlate to the severity of the morphological pheno- types. Therefore, a need for further understanding of how these proteins regulate p53 activity is warranted, as therapeutic targeting of the p53 pathway is rapidly evoLving and gaining attention in the field of cancer research. In this review, we discuss the tissue-specificity of Mdm proteins in regulating p53 and expose the need for investigation at the celt-specific level.
