Germline loss-of-function variants in TP53 cause Li-Fraumeni syndrome (LFS) characterized by an early onset of various cancer types including sarcomas, adrenocortical carcinoma, and breast cancer. The most common are mutations in the DNA binding domain of p53, but alterations in the oligomerization domain also cause LFS with variable level of penetrance. Here we report identification of a novel germline in-frame deletion TP53 variant c.1015_1023del p.(E339_F341del) in a family with early-onset breast cancer and other malignancies. Using functional testing, we found that a short deletion in the oligomerization domain in the p.E339_F341del variant severely impaired transcriptional activity of p53 in human cells and in a yeast model. The loss of the transactivation activity was consistent with an observed defect in formation of p53 tetramers. Finally, we found that cells expressing the p.E339_F341del variant were insensitive to inhibition of MDM2 by nutlin-3 confirming the functional defect. We conclude that the in-frame germline c.1015_1023del TP53 variant encodes a transcriptionally inactive protein and promotes LFS with a high penetrant cancer phenotype.

• Klíčová slova
• Cancer, Li Fraumeni syndrome, TP53, p53,
• MeSH
• dospělí MeSH
• genetická predispozice k nemoci * MeSH
• imidazoly farmakologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• Liův-Fraumeniho syndrom * genetika   patologie   MeSH
• multimerizace proteinu MeSH
• nádorový supresorový protein p53 * genetika   metabolismus   chemie   MeSH
• nádory prsu * genetika   MeSH
• protoonkogenní proteiny c-mdm2 metabolismus   MeSH
• rodokmen MeSH
• zárodečné mutace * MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• imidazoly MeSH
• nádorový supresorový protein p53 * MeSH
• protoonkogenní proteiny c-mdm2 MeSH
• TP53 protein, human MeSH Prohlížeč

The transcription factor p53 is the most frequently impaired tumor suppressor in human cancers. In response to various stress stimuli, p53 activates transcription of genes that mediate its tumor-suppressive functions. Distinctive characteristics of p53 outlined here enable a well-defined program of genes involved in cell cycle arrest, apoptosis, senescence, differentiation, metabolism, autophagy, DNA repair, anti-viral response, and anti-metastatic functions, as well as facilitating autoregulation within the p53 network. This versatile, anti-cancer network governed chiefly by a single protein represents an immense opportunity for targeted cancer treatment, since about half of human tumors retain unmutated p53. During the last two decades, numerous compounds have been developed to block the interaction of p53 with the main negative regulator MDM2. However, small molecule inhibitors of MDM2 only induce a therapeutically desirable apoptotic response in a limited number of cancer types. Moreover, clinical trials of the MDM2 inhibitors as monotherapies have not met expectations and have revealed hematological toxicity as a characteristic adverse effect across this drug class. Currently, combination treatments are the leading strategy for enhancing efficacy and reducing adverse effects of MDM2 inhibitors. This review summarizes efforts to identify and test therapeutics that work synergistically with MDM2 inhibitors. Two main types of drugs have emerged among compounds used in the following combination treatments: first, modulators of the p53-regulated transcriptome (including chromatin modifiers), translatome, and proteome, and second, drugs targeting the downstream pathways such as apoptosis, cell cycle arrest, DNA repair, metabolic stress response, immune response, ferroptosis, and growth factor signaling. Here, we review the current literature in this field, while also highlighting overarching principles that could guide target selection in future combination treatments.

• Klíčová slova
• combination therapy, integrated stress response, nelfinavir, nutlin, p53, polytherapy,
• MeSH
• cílená molekulární terapie * MeSH
• lidé MeSH
• nádorový supresorový protein p53 * metabolismus   genetika   antagonisté a inhibitory   MeSH
• nádory * farmakoterapie   metabolismus   genetika   MeSH
• protinádorové látky * terapeutické užití   farmakologie   MeSH
• protoonkogenní proteiny c-mdm2 antagonisté a inhibitory   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• nádorový supresorový protein p53 * MeSH
• protinádorové látky * MeSH
• protoonkogenní proteiny c-mdm2 MeSH

PURPOSE: Pediatric sarcomas are bone and soft tissue tumors that often exhibit high metastatic potential and refractory stem-like phenotypes, resulting in poor outcomes. Aggressive sarcomas frequently harbor a disrupted p53 pathway. However, whether pediatric sarcoma stemness is associated with abrogated p53 function and might be attenuated via p53 reactivation remains unclear. METHODS: We utilized a unique panel of pediatric sarcoma models and tumor tissue cohorts to investigate the correlation between the expression of stemness-related transcription factors, p53 pathway dysregulations, tumorigenicity in vivo, and clinicopathological features. TP53 mutation status was assessed by next-generation sequencing. Major findings were validated via shRNA-mediated silencing and functional assays. The p53 pathway-targeting drugs were used to explore the effects and selectivity of p53 reactivation against sarcoma cells with stem-like traits. RESULTS: We found that highly tumorigenic stem-like sarcoma cells exhibit dysregulated p53, making them vulnerable to drugs that restore wild-type p53 activity. Immunohistochemistry of mouse xenografts and human tumor tissues revealed that p53 dysregulations, together with enhanced expression of the stemness-related transcription factors SOX2 or KLF4, are crucial features in pediatric osteosarcoma, rhabdomyosarcoma, and Ewing's sarcoma development. p53 dysregulation appears to be an important step for sarcoma cells to acquire a fully stem-like phenotype, and p53-positive pediatric sarcomas exhibit a high frequency of early metastasis. Importantly, reactivating p53 signaling via MDM2/MDMX inhibition selectively induces apoptosis in aggressive, stem-like Ewing's sarcoma cells while sparing healthy fibroblasts. CONCLUSIONS: Our results indicate that restoring canonical p53 activity provides a promising strategy for developing improved therapies for pediatric sarcomas with unfavorable stem-like traits.

• Klíčová slova
• Cancer stemness, Pediatric sarcomas, Prognosis, Targeted therapy, p53,
• MeSH
• dítě MeSH
• Krüppel-like faktor 4 * MeSH
• lidé MeSH
• mladiství MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• nádorové kmenové buňky * metabolismus   patologie   MeSH
• nádorový supresorový protein p53 * metabolismus   genetika   MeSH
• předškolní dítě MeSH
• regulace genové exprese u nádorů MeSH
• sarkom * genetika   patologie   metabolismus   MeSH
• signální transdukce MeSH
• xenogenní modely - testy protinádorové aktivity MeSH
• zvířata MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• myši MeSH
• předškolní dítě MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• KLF4 protein, human MeSH Prohlížeč
• Klf4 protein, mouse MeSH Prohlížeč
• Krüppel-like faktor 4 * MeSH
• nádorový supresorový protein p53 * MeSH

TP53 gene abnormalities represent the most important biomarker in chronic lymphocytic leukemia (CLL). Altered protein modifications could also influence p53 function, even in the wild-type protein. We assessed the impact of p53 protein phosphorylations on p53 functions as an alternative inactivation mechanism. We studied p53 phospho-profiles induced by DNA-damaging agents (fludarabine, doxorubicin) in 71 TP53-intact primary CLL samples. Doxorubicin induced two distinct phospho-profiles: profile I (heavily phosphorylated) and profile II (hypophosphorylated). Profile II samples were less capable of activating p53 target genes upon doxorubicin exposure, resembling TP53-mutant samples at the transcriptomic level, whereas standard p53 signaling was triggered in profile I. ATM locus defects were more common in profile II. The samples also differed in the basal activity of the hypoxia pathway: the highest level was detected in TP53-mutant samples, followed by profile II and profile I. Our study suggests that wild-type TP53 CLL cells with less phosphorylated p53 show TP53-mutant-like behavior after DNA damage. p53 hypophosphorylation and the related lower ability to respond to DNA damage are linked to ATM locus defects and the higher basal activity of the hypoxia pathway.

• Klíčová slova
• CLL, p53, phosphorylation,
• MeSH
• ATM protein genetika   metabolismus   MeSH
• chronická lymfatická leukemie * genetika   MeSH
• doxorubicin farmakologie   MeSH
• fosforylace MeSH
• geny p53 MeSH
• hypoxie genetika   MeSH
• lidé MeSH
• nádorový supresorový protein p53 * metabolismus   MeSH
• poškození DNA MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ATM protein MeSH
• doxorubicin MeSH
• nádorový supresorový protein p53 * MeSH

HDMX and its homologue HDM2 are two essential proteins for the cell; after genotoxic stress, both are phosphorylated near to their RING domain, specifically at serine 403 and 395, respectively. Once phosphorylated, both can bind the p53 mRNA and enhance its translation; however, both recognize p53 protein and provoke its degradation under normal conditions. HDM2 has been well-recognized as an E3 ubiquitin ligase, whereas it has been reported that even with the high similarity between the RING domains of the two homologs, HDMX does not have the E3 ligase activity. Despite this, HDMX is needed for the proper p53 poly-ubiquitination. Phosphorylation at serine 395 changes the conformation of HDM2, helping to explain the switch in its activity, but no information on HDMX has been published. Here, we study the conformation of HDMX and its phospho-mimetic mutant S403D, investigate its E3 ligase activity and dissect its binding with p53. We show that phospho-mutation does not change the conformation of the protein, but HDMX is indeed an E3 ubiquitin ligase in vitro; however, in vivo, no activity was found. We speculated that HDMX is regulated by induced fit, being able to switch activity accordingly to the specific partner as p53 protein, p53 mRNA or HDM2. Our results aim to contribute to the elucidation of the contribution of the HDMX to p53 regulation.

• Klíčová slova
• HDM2, HDMX, Induced fit, MDM2, MDMX, cancer, p53, ubiquitination,
• MeSH
• jaderné proteiny genetika   MeSH
• messenger RNA metabolismus   MeSH
• nádorový supresorový protein p53 * genetika   metabolismus   MeSH
• proteiny buněčného cyklu metabolismus   MeSH
• protoonkogenní proteiny c-mdm2 * genetika   metabolismus   MeSH
• protoonkogenní proteiny genetika   MeSH
• serin metabolismus   MeSH
• ubikvitin genetika   MeSH
• ubikvitinace MeSH
• ubikvitinligasy genetika   metabolismus   MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• jaderné proteiny MeSH
• messenger RNA MeSH
• nádorový supresorový protein p53 * MeSH
• proteiny buněčného cyklu MeSH
• protoonkogenní proteiny c-mdm2 * MeSH
• protoonkogenní proteiny MeSH
• serin MeSH
• ubikvitin MeSH
• ubikvitinligasy MeSH

Since the discovery of the first MDM2 inhibitors, we have gained deeper insights into the cellular roles of MDM2 and p53. In this review, we focus on MDM2 inhibitors that bind to the p53-binding domain of MDM2 and aim to disrupt the binding of MDM2 to p53. We describe the basic mechanism of action of these MDM2 inhibitors, such as nutlin-3a, summarise the determinants of sensitivity to MDM2 inhibition from p53-dependent and p53-independent points of view and discuss the problems with innate and acquired resistance to MDM2 inhibition. Despite progress in MDM2 inhibitor design and ongoing clinical trials, their broad use in cancer treatment is not fulfilling expectations in heterogenous human cancers. We assess the MDM2 inhibitor types in clinical trials and provide an overview of possible sources of resistance to MDM2 inhibition, underlining the need for patient stratification based on these aspects to gain better clinical responses, including the use of combination therapies for personalised medicine.

• Klíčová slova
• Combination therapy, MDM2, MDM2 inhibitor, Nutlin-3a, Personalised medicine, Resistance, p53,
• MeSH
• bakteriální léková rezistence účinky léků   fyziologie   MeSH
• cílená molekulární terapie metody   MeSH
• klinické zkoušky jako téma MeSH
• lidé MeSH
• nádorový supresorový protein p53 antagonisté a inhibitory   genetika   metabolismus   MeSH
• nádory farmakoterapie   MeSH
• protinádorové látky farmakologie   MeSH
• protoonkogenní proteiny c-mdm2 antagonisté a inhibitory   genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• MDM2 protein, human MeSH Prohlížeč
• nádorový supresorový protein p53 MeSH
• protinádorové látky MeSH
• protoonkogenní proteiny c-mdm2 MeSH
• TP53 protein, human MeSH Prohlížeč

Human cells are subjected to continuous challenges by different genotoxic stress attacks. DNA damage leads to erroneous mutations, which can alter the function of oncogenes or tumor suppressors, resulting in cancer development. To circumvent this, cells activate the DNA damage response (DDR), which mainly involves cell cycle regulation and DNA repair processes. The tumor suppressor p53 plays a pivotal role in the DDR by halting the cell cycle and facilitating the DNA repair processes. Various pathways and factors participating in the detection and repair of DNA have been described, including scores of RNA-binding proteins (RBPs) and RNAs. It has become increasingly clear that p53's role is multitasking, and p53 mRNA regulation plays a prominent part in the DDR. This review is aimed at covering the p53 RNA metabolism linked to the DDR and highlights the recent findings.

• Klíčová slova
• ATM kinase, DNA damage response, MDM2, RNA metabolism, RNA-binding proteins, mRNA translation, p53,
• MeSH
• lidé MeSH
• messenger RNA metabolismus   MeSH
• mutace MeSH
• nádorový supresorový protein p53 genetika   metabolismus   MeSH
• nepřekládané oblasti MeSH
• oprava DNA * fyziologie   MeSH
• poškození DNA * MeSH
• proteiny vázající RNA genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• messenger RNA MeSH
• nádorový supresorový protein p53 MeSH
• nepřekládané oblasti MeSH
• proteiny vázající RNA MeSH

BACKGROUND: The links between the p53/MDM2 pathway and the expression of pro-oncogenic immune inhibitory receptors in tumor cells are undefined. In this report, we evaluate whether there is p53 and/or MDM2 dependence in the expression of two key immune receptors, CD276 and PD-L1. METHODS: Proximity ligation assays were used to quantify protein-protein interactions in situ in response to Nutlin-3. A panel of p53-null melanoma cells was created using CRISPR-Cas9 guide RNA mediated genetic ablation. Flow cytometric analyses were used to assess the impact of TP53 or ATG5 gene ablation, as well as the effects of Nutlin-3 and an ATM inhibitor on cell surface PD-L1 and CD276. Targeted siRNA was used to deplete CD276 to assess changes in cell cycle parameters by flow cytometry. A T-cell proliferation assay was used to assess activity of CD4+ T-cells as a function of ATG5 genotype. RESULTS: CD276 forms protein-protein interactions with MDM2 in response to Nutlin-3, similar to the known MDM2 interactors p53 and HSP70. Isogenic HCT116 p53-wt/null cancer cells demonstrated that CD276 is induced on the cell surface by Nutlin-3 in a p53-dependent manner. PD-L1 was also unexpectedly induced by Nutlin-3, but PD-L1 does not bind MDM2. The ATM inhibitor KU55993 reduced the levels of PD-L1 under conditions where Nutlin-3 induces PD-L1, indicating that MDM2 and ATM have opposing effects on PD-L1 steady-state levels. PD-L1 is also up-regulated in response to genetic ablation of TP53 in A375 melanoma cell clones under conditions in which CD276 remains unaffected. A549 cells with a deletion in the ATG5 gene up-regulated only PD-L1, further indicating that PD-L1 and CD276 are under distinct genetic control. CONCLUSION: Genetic inactivation of TP53, or the use of the MDM2 ligand Nutlin-3, alters the expression of the immune blockade receptors PD-L1 and CD276. The biological function of elevated CD276 is to promote altered cell cycle progression in response to Nutlin-3, whilst the major effect of elevated PD-L1 is T-cell suppression. These data indicate that TP53 gene status, ATM and MDM2 influence PD-L1 and CD276 paralogs on the cell surface. These data have implications for the use of drugs that target the p53 pathway as modifiers of immune checkpoint receptor expression.

• Klíčová slova
• Gene editing, MDM2, Nutlin-3, Protein-protein interactions, p53,
• MeSH
• antigeny B7 genetika   MeSH
• antigeny CD274 genetika   MeSH
• buněčný cyklus účinky léků   genetika   MeSH
• buňky A549 MeSH
• HCT116 buňky MeSH
• imidazoly farmakologie   MeSH
• lidé MeSH
• ligandy MeSH
• melanom farmakoterapie   MeSH
• nádorové buněčné linie MeSH
• nádorový supresorový protein p53 genetika   MeSH
• piperaziny farmakologie   MeSH
• proliferace buněk účinky léků   genetika   MeSH
• protoonkogenní proteiny c-mdm2 genetika   MeSH
• upregulace účinky léků   genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antigeny B7 MeSH
• antigeny CD274 MeSH
• CD274 protein, human MeSH Prohlížeč
• CD276 protein, human MeSH Prohlížeč
• imidazoly MeSH
• ligandy MeSH
• MDM2 protein, human MeSH Prohlížeč
• nádorový supresorový protein p53 MeSH
• nutlin 3 MeSH Prohlížeč
• piperaziny MeSH
• protoonkogenní proteiny c-mdm2 MeSH

Cell growth requires a high level of protein synthesis and oncogenic pathways stimulate cell proliferation and ribosome biogenesis. Less is known about how cells respond to dysfunctional mRNA translation and how this feeds back into growth regulatory pathways. The Epstein-Barr virus (EBV)-encoded EBNA1 causes mRNA translation stress in cis that activates PI3Kδ. This leads to the stabilization of MDM2, induces MDM2's binding to the E2F1 mRNA and promotes E2F1 translation. The MDM2 serine 166 regulates the interaction with the E2F1 mRNA and deletion of MDM2 C-terminal RING domain results in a constitutive E2F1 mRNA binding. Phosphorylation on serine 395 following DNA damage instead regulates p53 mRNA binding to its RING domain and prevents the E2F1 mRNA interaction. The p14Arf tumour suppressor binds MDM2 and in addition to preventing degradation of the p53 protein it also prevents the E2F1 mRNA interaction. The data illustrate how two MDM2 domains selectively bind specific mRNAs in response to cellular conditions to promote, or suppress, cell growth and how p14Arf coordinates MDM2's activity towards p53 and E2F1. The data also show how EBV via EBNA1-induced mRNA translation stress targets the E2F1 and the MDM2 - p53 pathway.

• MeSH
• buněčný cyklus genetika   MeSH
• fosforylace genetika   MeSH
• karcinogeneze genetika   MeSH
• lidé MeSH
• messenger RNA genetika   MeSH
• nádorový supresorový protein p14ARF genetika   MeSH
• nádorový supresorový protein p53 genetika   MeSH
• nádory genetika   virologie   MeSH
• onkogeny genetika   MeSH
• poškození DNA genetika   MeSH
• proliferace buněk genetika   MeSH
• proteinové domény genetika   MeSH
• protoonkogenní proteiny c-mdm2 genetika   MeSH
• RRM proteiny genetika   MeSH
• transkripční faktor E2F1 genetika   MeSH
• tumor supresorové geny MeSH
• virus Epsteinův-Barrové genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• E2F1 protein, human MeSH Prohlížeč
• MDM2 protein, human MeSH Prohlížeč
• messenger RNA MeSH
• nádorový supresorový protein p14ARF MeSH
• nádorový supresorový protein p53 MeSH
• protoonkogenní proteiny c-mdm2 MeSH
• RRM proteiny MeSH
• TP53 protein, human MeSH Prohlížeč
• transkripční faktor E2F1 MeSH

Interleukin-1α (IL-1α) is a dual-function proinflammatory mediator. In addition to its role in the canonical IL-1 signaling pathway, which employs membrane-bound receptors, a growing body of evidence shows that IL-1α has some additional intracellular functions. We identified the interaction of IL-1α with the tumor suppressor p53 in the nuclei and cytoplasm of both malignant and noncancerous mammalian cell lines using immunoprecipitation and the in situ proximity ligation assay (PLA). This interaction was enhanced by treatment with the antineoplastic drug etoposide, which suggests a role for the IL-1α•p53 interaction in genotoxic stress.

• MeSH
• cytoplazma metabolismus   MeSH
• dvouřetězcové zlomy DNA MeSH
• fluorescenční mikroskopie MeSH
• HeLa buňky MeSH
• imunoprecipitace MeSH
• interleukin-1alfa genetika   metabolismus   MeSH
• lidé MeSH
• nádorový supresorový protein p53 genetika   metabolismus   MeSH
• poškození DNA genetika   fyziologie   MeSH
• western blotting MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• interleukin-1alfa MeSH
• nádorový supresorový protein p53 MeSH