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Casimiro Gerarduzzi, Anna de Polo, Xue-Song Liu, Manale El Kharbili, John B Little, Zhi-Min Yuan
Deregulated receptor tyrosine kinase (RTK) signaling is frequently associated with tumorigenesis and therapy resistance, but its underlying mechanisms still need to be elucidated. In this study we have shown that the RTK human epidermal growth factor receptor 4 (Her4, aka Erbb4) can inhibit the tumor suppressor p53 by regulating the MDMX-MDM2 complex stabilization. Upon activation by either overexpression of a constitutively active vector or ligand binding (Neuregulin-1), Her4 was able to stabilize the MDMX-MDM2 complex resulting in suppression of p53 transcriptional activity, as shown by p53 responsive element-driven luciferase assay and mRNA levels of p53 target genes...
October 24, 2016: Journal of Biological Chemistry
Ewa Surmiak, Aleksandra Twarda-Clapa, Krzysztof M Zak, Bogdan Musielak, Marcin D Tomala, Katarzyna Kubica, Przemysław Grudnik, Mariusz Madej, Mateusz Jabłoński, Jan Potempa, Justyna Kalinowska-Tłuścik, Grzegorz Dubin, Alexander Dömling, Tad A Holak
The p53 pathway is inactivated in almost all types of cancer by mutations in the p53 encoding gene or overexpression of the p53 negative regulators, Mdm2 and/or Mdmx. Restoration of the p53 function by inhibition of the p53-Mdm2/Mdmx interaction opens up a prospect for a non-genotoxic anticancer therapy. Here we present the syntheses, activities and crystal structures on two novel classes of Mdm2-p53 inhibitors that are based on the 3-pyrrolin-2-one and 2-furanone scaffolds. The structures of the complexes formed by these inhibitors and Mdm2 reveal the dimeric protein molecular organization that has not been observed in the small-molecule/Mdm2 complexes described until now...
October 6, 2016: ACS Chemical Biology
Z Matijasevic, A Krzywicka-Racka, G Sluder, J Gallant, S N Jones
The MDMX (MDM4) oncogene is amplified or overexpressed in a significant percentage of human tumors. MDMX is thought to function as an oncoprotein by binding p53 tumor suppressor protein to inhibit p53-mediated transcription, and by complexing with MDM2 oncoprotein to promote MDM2-mediated degradation of p53. However, down-regulation or loss of functional MDMX has also been observed in a variety of human tumors that are mutated for p53, often correlating with more aggressive cancers and a worse patient prognosis...
October 3, 2016: Oncogenesis
Ya Kong, Zong-Liang Lu, Jia-Jia Wang, Rui Zhou, Jing Guo, Jie Liu, Hai-Lan Sun, He Wang, Wei Song, Jian Yang, Hong-Xia Xu
The objective of the present study was to explore the in vitro and in vivo anticancer effects of Platycodin D (PD), derived from Platycodin grandiflorum, on highly metastatic MDA-MB-231 breast cancer cells. Using the MTT assay, we found that PD inhibited MDA-MB-231 cell growth in a concentration-dependent manner, with an IC50 value of 7.77±1.86 µM. Further studies showed that PD had anti-proliferative effects and induced cell cycle arrest in the G0/G1 phase. To explore the detailed mechanism(s) by which PD suppressed MDA-MB-231 cell growth, western blot analyses were used to detect the expression levels of proteins related to cell proliferation and survival...
September 2016: Oncology Reports
A-S Tournillon, I López, L Malbert-Colas, S Findakly, N Naski, V Olivares-Illana, K Karakostis, B Vojtesek, K Nylander, R Fåhraeus
MDMX and MDM2 are two nonredundant essential regulators of p53 tumor suppressor activity. MDM2 controls p53 expression levels, whereas MDMX is predominantly a negative regulator of p53 trans-activity. The feedback loops between MDM2 and p53 are well studied and involve both negative and positive regulation on transcriptional, translational and post-translational levels but little is known on the regulatory pathways between p53 and MDMX. Here we show that overexpression of p53 suppresses mdmx mRNA translation in vitro and in cell-based assays...
July 4, 2016: Oncogene
Xishan Chen, Weiyue Lu
The homologous proteins MDM2 and MDMX negatively regulate the tumor suppressor protein p53 by antagonizing p53 transactivation activity and targeting p53 for degradation. MDM2 and MDMX bind to p53 via N-terminal p53-binding domains to control the level of p53. The N-terminal regions of MDM2 and MDMX are modified in vivo under stressed conditions, suggesting that modifications to MDM2/MDMX also may affect the p53-MDM2/MDMX interaction. Ample evidence suggests that the MDM2 lid (residues 1-24) is partially structured and significantly reduces its binding affinity with p53 several fold...
2016: Chemical & Pharmaceutical Bulletin
Jean-Christophe Marine, Aart G Jochemsen
The MDMX protein was identified as a p53-interacting protein with a strong similarity to MDM2. Like Mdm2, Mdmx expression is essential for curbing p53 activity during embryonic development, indicating nonredundant functions of Mdmx and Mdm2. There is now a large body of evidence indicating that cancers frequently up-regulate MDMX expression as a means to dampen p53 tumor-suppressor function. Importantly, MDMX also shows p53-independent oncogenic functions. These data make MDMX an attractive therapeutic target for cancer therapy...
2016: Cold Spring Harbor Perspectives in Medicine
Kensuke Kojima, Jo Ishizawa, Michael Andreeff
The tumor suppressor p53 is inactivated by mutations in the majority of human solid tumors. Conversely, p53 mutations are rare in leukemias and are only observed in a small fraction of the patient population, predominately in patients with complex karyotype acute myeloid leukemia or hypodiploid acute lymphoblastic leukemia. However, the loss of p53 function in leukemic cells is often caused by abnormalities in p53-regulatory proteins, including overexpression of MDM2/MDMX, deletion of CDKN2A/ARF, and alterations in ATM...
September 2016: Experimental Hematology
Linshan Hu, Haibo Zhang, Johann Bergholz, Shengnan Sun, Zhi-Xiong Jim Xiao
MDM2 (mouse double minute 2 homolog) and MDMX (double minute X human homolog, also known as MDM4) are critical negative regulators of tumor protein p53. Our recent work shows that MDMX binds to and promotes degradation of retinoblastoma protein (RB) in an MDM2-dependent manner. In a xenograft tumor growth mouse model, silencing of MDMX results in inhibition of p53-deficient tumor growth, which can be effectively reversed by concomitant RB silencing. Thus, MDMX exerts its oncogenic activity via suppression of RB...
March 2016: Molecular & Cellular Oncology
Fabiola Moretti
MDM2 (mouse double minute 2 homolog) and MDM4 (double minute 4 human homolog, also known as MDMX) inhibit the activity of tumor protein p53 (TP53, best known as p53) through their heterodimerization. New evidence indicates that under stress conditions the heterodimer is modified, leading to different activities of the single molecules. In particular, following lethal DNA damage, MDM2 and MDM4 dissociate and MDM4 promotes the stabilization of homeodomain-interacting protein kinase 2 (HIPK2) and the phosphorylation of p53, resulting in transcriptional repression of antiapoptotic targets of p53/HIPK2...
March 2016: Molecular & Cellular Oncology
Agostinho Lemos, Mariana Leão, Joana Soares, Andreia Palmeira, Madalena Pinto, Lucília Saraiva, Maria Emília Sousa
The growth inhibitory activity of p53 tumor suppressor is tightly regulated by interaction with two negative regulatory proteins, murine double minute 2 (MDM2) and X (MDMX), which are overexpressed in about half of all human tumors. The elucidation of crystallographic structures of MDM2/MDMX complexes with p53 has been pivotal for the identification of several classes of inhibitors of the p53-MDM2/MDMX interaction. The present review provides in silico strategies and screening approaches used in drug discovery as well as an overview of the most relevant classes of small-molecule inhibitors of the p53-MDM2/MDMX interaction, their progress in pipeline, and highlights particularities of each class of inhibitors...
September 2016: Medicinal Research Reviews
Grégoire Philippe, Yen-Hua Huang, Olivier Cheneval, Nicole Lawrence, Zhen Zhang, David P Fairlie, David J Craik, Aline Dantas de Araujo, Sónia Troeira Henriques
The transcription factor p53 has a tumor suppressor role in leading damaged cells to apoptosis. Its activity is regulated/inhibited in healthy cells by the proteins MDM2 and MDMX. Overexpression of MDM2 and/or MDMX in cancer cells inactivates p53, facilitating tumor development. A 12-mer dual inhibitor peptide (pDI) was previously reported to be able to target and inhibit MDMX:p53 and MDM2:p53 interactions with nanomolar potency in vitro. With the aim of improving its cellular inhibitory activity, we produced a series of constrained pDI analogues featuring lactam staples that stabilize the bioactive helical conformation and fused them with a cell-penetrating peptide to increase cytosol delivery...
June 10, 2016: Biopolymers
Christine M Eischen
It is now clear that functional p53 is critical to protect the genome from alterations that lead to tumorigenesis. However, with the myriad of cellular stresses and pathways linked to p53 activation, much remains unknown about how p53 maintains genome stability and the proteins involved. The current understanding of the multiple ways p53 contributes to genome stability and how two of its negative regulators, Mdm2 and Mdmx, induce genome instability will be described.
2016: Cold Spring Harbor Perspectives in Medicine
Carlos J A Ribeiro, Cecília M P Rodrigues, Rui Moreira, Maria M M Santos
Among the tumor suppressor genes, p53 is one of the most studied. It is widely regarded as the "guardian of the genome", playing a major role in carcinogenesis. In fact, direct inactivation of the TP53 gene occurs in more than 50% of malignancies, and in tumors that retain wild-type p53 status, its function is usually inactivated by overexpression of negative regulators (e.g., MDM2 and MDMX). Hence, restoring p53 function in cancer cells represents a valuable anticancer approach. In this review, we will present an updated overview of the most relevant small molecules developed to restore p53 function in cancer cells through inhibition of the p53-MDMs interaction, or direct targeting of wild-type p53 or mutated p53...
2016: Pharmaceuticals
Andreas C Joerger, Alan R Fersht
Inactivation of the transcription factor p53, through either direct mutation or aberrations in one of its many regulatory pathways, is a hallmark of virtually every tumor. In recent years, screening for p53 activators and a better understanding of the molecular mechanisms of oncogenic perturbations of p53 function have opened up a host of novel avenues for therapeutic intervention in cancer: from the structure-guided design of chemical chaperones to restore the function of conformationally unstable p53 cancer mutants, to the development of potent antagonists of the negative regulators MDM2 and MDMX and other modulators of the p53 pathway for the treatment of cancers with wild-type p53...
June 2, 2016: Annual Review of Biochemistry
Raheleh Rezaei Araghi, Amy E Keating
Short helical peptides combine characteristics of small molecules and large proteins and provide an exciting area of opportunity in protein design. A growing number of studies report novel helical peptide inhibitors of protein-protein interactions. New techniques have been developed for peptide design and for chemically stabilizing peptides in a helical conformation, which frequently improves protease resistance and cell permeability. We summarize advances in peptide crosslinking chemistry and give examples of peptide design studies targeting coiled-coil transcription factors, Bcl-2 family proteins, MDM2/MDMX, and HIV gp41, among other targets...
April 25, 2016: Current Opinion in Structural Biology
Xi Wei, Shaofang Wu, Tanjing Song, Lihong Chen, Ming Gao, Wade Borcherds, Gary W Daughdrill, Jiandong Chen
The MDMX oncoprotein is an important regulator of tumor suppressor p53 activity during embryonic development. Despite sequence homology to the ubiquitin E3 ligase MDM2, MDMX depletion activates p53 without significant increase in p53 level, implicating a degradation-independent mechanism. We present evidence that MDMX inhibits the sequence-specific DNA binding activity of p53. This function requires the cooperation between MDMX and CK1α, and phosphorylation of S289 on MDMX. Depletion of MDMX or CK1α increases p53 DNA binding without stabilization of p53...
May 10, 2016: Proceedings of the National Academy of Sciences of the United States of America
P L Leslie, Y Zhang
Over two decades of MDM2 research has resulted in the accumulation of a wealth of knowledge of many aspects of MDM2 regulation and function, particularly with respect to its most prominent target, p53. For example, recent knock-in mouse studies have shown that MDM2 heterooligomer formation with its homolog, MDMX, is necessary and sufficient in utero to suppress p53 but is dispensable during adulthood. However, despite crucial advances such as these, several aspects regarding basic in vivo functions of MDM2 remain unknown...
April 4, 2016: Oncogene
Orit Karni-Schmidt, Maria Lokshin, Carol Prives
For more than 25 years, MDM2 and its homolog MDMX (also known as MDM4) have been shown to exert oncogenic activity. These two proteins are best understood as negative regulators of the p53 tumor suppressor, although they may have additional p53-independent roles. Understanding the dysregulation of MDM2 and MDMX in human cancers and how they function either together or separately in tumorigenesis may improve methods of diagnosis and for assessing prognosis. Targeting the proteins themselves, or their regulators, may be a promising therapeutic approach to treating some forms of cancer...
May 23, 2016: Annual Review of Pathology
Shinichi Uesato, Yoshihiro Matsuura, Saki Matsue, Takaaki Sumiyoshi, Yoshiyuki Hirata, Suzuho Takemoto, Yasuyuki Kawaratani, Yusuke Yamai, Kyoji Ishida, Tsutomu Sasaki, Masato Enari
Although several p53-Mdm2-binding disruptors have been identified to date, few studies have been published on p53-Mdmx-interaction inhibitors. In the present study, we demonstrated that o-aminothiophenol derivatives with molecular weights of 200-300 selectively inhibited the p53-Mdmx interaction. S-2-Isobutyramidophenyl 2-methylpropanethioate (K-178) (1c) activated p53, up-regulated the expression of its downstream genes such as p21 and Mdm2, and preferentially inhibited the growth of cancer cells with wild-type p53 over those with mutant p53...
April 15, 2016: Bioorganic & Medicinal Chemistry
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