Rescuing the function of mutant p53

EPDRNA: A Model for Identifying DNA-RNA Binding Sites in Disease-Related Proteins

Protein-DNA and protein-RNA interactions are involved in many biological processes and regulate many cellular functions. Moreover, they are related to many human diseases. To understand the molecular mechanism of protein-DNA binding and protein-RNA binding, it is important to identify which residues in the protein sequence bind to DNA and RNA. At present, there are few methods for specifically identifying the binding sites of disease-related protein-DNA and protein-RNA. In this study, so we combined four machine learning algorithms into an ensemble classifier (EPDRNA) to predict DNA and RNA binding sites in disease-related proteins. The dataset used in model was collated from UniProt and PDB database, and PSSM, physicochemical properties and amino acid type were used as features. The EPDRNA adopted soft voting and achieved the best AUC value of 0.73 at the DNA binding sites, and the best AUC value of 0.71 at the RNA binding sites in 10-fold cross validation in the training sets. In order to further verify the performance of the model, we assessed EPDRNA for the prediction of DNA-binding sites and the prediction of RNA-binding sites on the independent test dataset. The EPDRNA achieved 85% recall rate and 25% precision on the protein-DNA interaction independent test set, and achieved 82% recall rate and 27% precision on the protein-RNA interaction independent test set. The online EPDRNA webserver is freely available at http://www.s-bioinformatics.cn/epdrna .

A unique chaperoning mechanism in class A JDPs recognizes and stabilizes mutant p53

J-domain proteins (JDPs) constitute a large family of molecular chaperones that bind a broad spectrum of substrates, targeting them to Hsp70, thus determining the specificity of and activating the entire chaperone functional cycle. The malfunction of JDPs is therefore inextricably linked to myriad human disorders. Here, we uncover a unique mechanism by which chaperones recognize misfolded clients, present in human class A JDPs. Through a newly identified β-hairpin site, these chaperones detect changes in protein dynamics at the initial stages of misfolding, prior to exposure of hydrophobic regions or large structural rearrangements. The JDPs then sequester misfolding-prone proteins into large oligomeric assemblies, protecting them from aggregation. Through this mechanism, class A JDPs bind destabilized p53 mutants, preventing clearance of these oncoproteins by Hsp70-mediated degradation, thus promoting cancer progression. Removal of the β-hairpin abrogates this protective activity while minimally affecting other chaperoning functions. This suggests the class A JDP β-hairpin as a highly specific target for cancer therapeutics.

The regulatory role and clinical application prospects of circRNA in the occurrence and development of CNS tumors

BACKGROUND

Central nervous system (CNS) tumors originate from the spinal cord or brain. The study showed that even with aggressive treatment, malignant CNS tumors have high mortality rates. However, CNS tumor risk factors and molecular mechanisms have not been verified. Due to the reasons mentioned above, diagnosis and treatment of CNS tumors in clinical practice are currently fraught with difficulties. Circular RNAs (circRNAs), single-stranded ncRNAs with covalently closed continuous structures, are essential to CNS tumor development. Growing evidence has proved the numeral critical biological functions of circRNAs for disease progression: sponging to miRNAs, regulating gene transcription and splicing, interacting with proteins, encoding proteins/peptides, and expressing in exosomes.

AIMS

This review aims to summarize current progress regarding the molecular mechanism of circRNA in CNS tumors and to explore the possibilities of clinical application based on circRNA in CNS tumors.

METHODS

We have summarized studies of circRNA in CNS tumors in Pubmed.

RESULTS

This review summarized their connection with CNS tumors and their functions, biogenesis, and biological properties. Furthermore, we introduced current advances in clinical RNA-related technologies. Then we discussed the diagnostic and therapeutic potential (especially for immunotherapy, chemotherapy, and radiotherapy) of circRNA in CNS tumors in the context of the recent advanced research and application of RNA in clinics.

CONCLUSIONS

CircRNA are increasingly proven to participate in decveloping CNS tumors. An in-depth study of the causal mechanisms of circRNAs in CNS tomor progression will ultimately advance their implementation in the clinic and developing new strategies for preventing and treating CNS tumors.

The ISG15-Protease USP18 Is a Pleiotropic Enhancer of HIV-1 Replication

The innate immune response to viruses is formed in part by interferon (IFN)-induced restriction factors, including ISG15, p21, and SAMHD1. IFN production can be blocked by the ISG15-specific protease USP18. HIV-1 has evolved to circumvent host immune surveillance. This mechanism might involve USP18. In our recent studies, we demonstrate that HIV-1 infection induces USP18, which dramatically enhances HIV-1 replication by abrogating the antiviral function of p21. USP18 downregulates p21 by accumulating misfolded dominant negative p53, which inactivates wild-type p53 transactivation, leading to the upregulation of key enzymes involved in de novo dNTP biosynthesis pathways and inactivated SAMHD1. Despite the USP18-mediated increase in HIV-1 DNA in infected cells, it is intriguing to note that the cGAS-STING-mediated sensing of the viral DNA is abrogated. Indeed, the expression of USP18 or knockout of ISG15 inhibits the sensing of HIV-1. We demonstrate that STING is ISGylated at residues K224, K236, K289, K347, K338, and K370. The inhibition of STING K289-linked ISGylation suppresses its oligomerization and IFN induction. We propose that human USP18 is a novel factor that potentially contributes in multiple ways to HIV-1 replication.

Arsenic trioxide extends survival of Li-Fraumeni syndrome mimicking mouse

Li-Fraumeni syndrome (LFS) is characterized by germline mutations occurring on one allele of genome guardian TP53. It is a severe cancer predisposition syndrome with a poor prognosis, partly due to the frequent development of subsequent primary tumors following DNA-damaging therapies. Here we explored, for the first time, the effectiveness of mutant p53 rescue compound in treating LFS-mimicking mice harboring a deleterious p53 mutation. Among the ten p53 hotspot mutations in IARC LFS cohorts, R282W is one of the mutations predicting the poorest survival prognosis and the earliest tumor onset. Among the six clinical-stage mutant p53 rescue compounds, arsenic trioxide (ATO) effectively restored transactivation activity to p53-R282W. We thus constructed a heterozygous Trp53 R279W (corresponding to human R282W) mouse model for the ATO treatment study. The p53R279W/+ (W/+) mice exhibited tumor onset and overall survival well mimicking the ones of human LFS. Further, 35 mg/L ATO addition in drink water significantly extended the median survival of W/+ mice (from 460 to 596 days, hazard ratio = 0.4003, P = 0.0008). In the isolated tumors from ATO-treated W/+ mice, the representative p53 targets including Cdkn1a, Mdm2, and Tigar were significantly upregulated, accompanying with a decreased level of the proliferation marker Ki67 and increased level of apoptosis marker TUNEL. Together, the non-genotoxic treatment of p53 rescue compound ATO holds promise as an alternative for LFS therapeutic.

Elucidating the Mechanisms of R248Q Mutation-Enhanced p53 Aggregation and Its Inhibition by Resveratrol

Aggregation of p53 mutants can result in loss-of-function, gain-of-function, and dominant-negative effects that contribute to tumor growth. Revealing the mechanisms underlying mutation-enhanced p53 aggregation and dissecting how small molecule inhibitors prevent the conversion of p53 into aggregation-primed conformations are fundamentally important for the development of novel therapeutics for p53 aggregation-associated cancers. A recent experimental study shows that resveratrol (RSV) has an inhibitory effect on the aggregation of hot-spot R248Q mutant of the p53 core domain (p53C), while pterostilbene (PT) exhibits a relatively poor inhibitory efficacy. However, the conformational properties of the R248Q mutant leading to its enhanced aggregation propensity and the inhibitory mechanism of RSV against p53C aggregation are not well understood. Herein, we performed extensive all-atom molecular dynamics simulations on R248Q p53C in the absence and presence of RSV/PT, as well as wild-type (WT) p53C. Our simulations reveal that loop L3, where the mutation resides, remains compact in WT p53C, while it becomes extended in the R248Q mutant. The extension of loop L3 weakens the interactions between loop L3 and two crucial aggregation-prone regions (APRs) of p53C, leading to impaired interactions within the APRs and their structural destabilization as well as p53C. The destabilized APRs in the R248Q mutant are more exposed than in WT p53C, which is conducive to p53C aggregation. RSV has a higher preference to bind to R248Q p53C than PT. This binding not only stabilizes loop L3 of R248Q mutant to its WT-like conformation, preventing L3-extension-caused APRs' destabilization but also reduces APRs' solvent exposure, thereby inhibiting R248Q p53C aggregation. However, PT exhibits a lower hydrogen-bonding capability and a higher self-association propensity, which would lead to a reduced p53C binding and a weakened inhibitory effect on R248Q mutant aggregation. Our study provides mechanistic insights into the R248Q mutation-enhanced aggregation propensity and RSV's potent inhibition against R248Q p53C aggregation.

Association of TP53 rs1042522 G > C, MDM2 rs2279744 T > G, and miR-34b/c rs4938723 T > C polymorphisms with aneuploidy pregnancy susceptibility

BACKGROUND

Aneuploidy pregnancy is a severe major birth defect and causes about 50% spontaneous miscarriages with unknown etiology. To date, only a few epidemiological studies with small sample sizes have investigated the risk factors for aneuploidy pregnancy. TP53, MDM2, and miR-34b/c genes are implicated in tumorigenesis with aneuploidy, yet the function of their polymorphisms in aneuploidy pregnancy susceptibility needs to be clarified.

OBJECTIVE

To elucidate the association of TP53 rs1042522 G > C, MDM2 rs2279744 309 T > G, and miR-34b/c rs4938723 T > C specific polymorphisms with aneuploidy pregnancy.

METHODS

In the retrospective case-control study, 330 aneuploidies pregnancy women and 813 normal pregnancy controls were recruited between January 2018 and April 2022 at the First People's Hospital of Yunnan Province, Kunming, China. Three functional polymorphisms, the TP53 rs1042522 G > C (Arg72Pro), MDM2 rs2279744 309 T > G, and miR-34b/c rs4938723 T > C, were genotyped using the snapshot method.

RESULTS

The frequency distribution of three genotypic variants was not different between case and control pregnant women and was similar to with Hardy-Weinberg Equilibrium (HWE). However, in the younger subgroup (less than 35 years old), a significant difference was detected in allele and recessive model (p = 0.01). In the advanced age subgroup (more than or equal to 35 years old), G of MDM2 rs2279744 T > G revealed a significantly higher frequency in cases than controls (p = 0.045), and miR-34b/c rs4938723 T > C revealed a significant difference under the dominant model (p = 0.03), but no significant differences were observed in other models and in both younger and older subgroup (p > 0.05, respectively). These results suggest that individual polymorphisms were not associated with aneuploidy pregnancy, combined with age, they may serve as a risk factor for aneuploidy pregnancy.

CONCLUSION

Combination of TP53 rs1042522 G > C, MDM2 rs2279744 T > G, and miR-34b/c rs4938723 T > C polymorphisms with maternal age may be related to aneuploidy pregnancy susceptibility. These findings might elaborate on the genetic etiology of aneuploidy pregnancy.

Diverse rescue potencies of p53 mutations to ATO are predetermined by intrinsic mutational properties

Tumor suppressor p53 is inactivated by thousands of heterogeneous mutations in cancer, but their individual druggability remains largely elusive. Here, we evaluated 800 common p53 mutants for their rescue potencies by the representative generic rescue compound arsenic trioxide (ATO) in terms of transactivation activity, cell growth inhibition, and mouse tumor-suppressive activities. The rescue potencies were mainly determined by the solvent accessibility of the mutated residue, a key factor determining whether a mutation is a structural one, and the temperature sensitivity, the ability to reassemble the wild-type DNA binding surface at a low temperature, of the mutant protein. A total of 390 p53 mutants were rescued to varying degrees and thus were termed as type 1, type 2a, and type 2b mutations, depending on the degree to which they were rescued. The 33 type 1 mutations were rescued to amounts comparable to the wild type. In PDX mouse trials, ATO preferentially inhibited growth of tumors harboring type 1 and type 2a mutants. In an ATO clinical trial, we report the first-in-human mutant p53 reactivation in a patient harboring the type 1 V272M mutant. In 47 cell lines derived from 10 cancer types, ATO preferentially and effectively rescued type 1 and type 2a mutants, supporting the broad applicability of ATO in rescuing mutant p53. Our study provides the scientific and clinical communities with a resource of the druggabilities of numerous p53 mutations (www.rescuep53.net) and proposes a conceptual p53-targeting strategy based on individual mutant alleles rather than mutation type.

Immunological Role of TP53 Somatic Mutation Classification in Human Cancers

Background

TP53 is a very common tumor suppressor gene and has implicated in various cancers. A systematic immunological analysis of TP53 somatic mutation classification in multiple cancers is still lacking.

Methods

To assess the immunological value of TP53 somatic mutation classification in various cancers, we integrated a series of bioinformatics methods to analyze the role of TP53 gene across the public databases, such as UCSC Xena, Cancer Cell Line Encyclopedia (CCLE), Ensembl, and Genotype-Tissue Expression (GTEx).

Results

The results revealed that the TP53 expression level had significant difference in tumor tissues and normal tissues, and it had a high expression level in most malignant tumors. Moreover, the missense mutation is the most common type of TP53 mutation in most cancers. In addition, the Cox proportional hazards model analysis and Kaplan-Meier (KM) survival analysis demonstrated that the TP53 expression is a high-risk factor in brain lower-grade glioma (LGG), prostate adenocarcinoma (PRAD), and uterine carcinosarcoma (UCS), which is opposite in uterine corpus endometrial carcinoma (UCEC). Besides, compared to the TP53 nontruncating mutation classification samples, we found that TP53 truncating mutation samples had lower TP53 expression levels in certain types of cancer. Notably, TP53 was associated with the mismatch repair (MMR) gene in some cancers which contained truncating or nontruncating mutation. Based on the classification of truncating or nontruncating mutation, we also discovered that TP53 expression was positively or negatively correlated with the immune score, stromal score, and the levels of immune cell infiltration in different cancers.

Conclusions

Our research reveals an overarching landscape of immunological value on TP53 status in various malignant tumors. According to our results, we demonstrate that TP53 also plays an immunological role in various cancers.

Carrier-free nanoprodrug for p53-mutated tumor therapy via concurrent delivery of zinc-manganese dual ions and ROS

Human cancers typically express a high level of tumor-promoting mutant p53 protein (Mutp53) with a minimal level of tumor-suppressing wild-type p53 protein (WTp53). In this regard, inducing Mutp53 degradation while activating WTp53 is a viable strategy for precise anti-tumor therapy. Herein, a new carrier-free nanoprodrug (i.e., Mn-ZnO₂ nanoparticles) was developed for concurrent delivery of dual Zn-Mn ions and reactive oxygen species (ROS) within tumor to regulate the p53 protein for high anti-tumor efficacy. In response to the mild tumor acidic environment, the released Zn²⁺ and H₂O₂ from Mn-ZnO₂ NPs induced ubiquitination-mediated proteasomal degradation of Mutp53, while the liberative Mn²⁺ and increased ROS level activated the ATM-p53-Bax pathway to elevate WTp53 level. Both in vitro and in vivo results demonstrated that pH-responsive decomposition of Mn-ZnO₂ NPs could effectively elevate the intracellular dual Zn-Mn ions and ROS level and subsequently generate the cytotoxic hydroxyl radical (•OH) through the Fenton-like reaction. With the integration of multiple functions (i.e., carrier-free ion and ROS delivery, tumor accumulation, p53 protein modulation, toxic •OH generation, and pH-activated MRI contrast) in a single nanosystem, Mn-ZnO₂ NPs demonstrate its superiority as a promising nanotherapeutics for p53-mutated tumor therapy.

Biomimetic Nanosonosensitizers Combined with Noninvasive Ultrasound Actuation to Reverse Drug Resistance and Sonodynamic-Enhanced Chemotherapy against Orthotopic Glioblastoma

Glioblastoma (GBM) is the most devastating brain tumor and highly resistant to conventional chemotherapy. Herein, we introduce biomimetic nanosonosensitizer systems (MDNPs) combined with noninvasive ultrasound (US) actuation for orthotopic GBM-targeted delivery and sonodynamic-enhanced chemotherapy. MDNPs were fabricated with biodegradable and pH-sensitive polyglutamic acid (PGA) and the chemotherapeutic agent and sonosensitizer doxorubicin (DOX), camouflaged with human GBM U87 cell membranes. MDNPs presented homologous targeting accumulation and in vivo long-term circulation ability. They effectively passed through the blood-brain barrier (BBB) under US assistance and reached the orthotopic GBM site. MDNPs exhibited controllable US-elicited sonodynamic effect by generation of reactive oxygen species (ROS). ROS not only induced cancer cell apoptosis but also downregulated drug-resistance-related factors to disrupt chemoresistance and increase sensitivity to chemotherapy. The in vivo study of orthotopic GBM treatments further proved that MDNPs exhibited US-augmented synergistic antitumor efficacy and strongly prolonged the survival rate of mice. The use of low-dose DOX and the safety of US enabled repeated treatment (4 times) without obvious cardiotoxicity. This effective and safe US-enhanced chemotherapy strategy with the advantages of noninvasive brain delivery and high drug sensitivity holds great promise for deep-seated and drug-resistant tumors.

Water Leakage Pathway Leads to Internal Hydration of the p53 Core Domain

The gene encoding the p53 tumor suppressor protein is the most frequently mutated oncogene in cancer patients; yet, generalized strategies for rescuing the function of different p53 mutants remain elusive. This work investigates factors that may contribute to the low inherent stability of the wild-type p53 core domain (p53C) and structurally compromised Y220C mutant. Pressure-induced unfolding of p53C was compared to p63C, the p53 family member with the highest stability, the engineered superstable p53C hexamutant (p53C HM), and lower stability p53C Y220C cancer-associated mutant. The following pressure unfolding values (P50% bar) were obtained: p53C 3346, p53C Y220C 2217, p53C HM 3943, and p63C 4326. Molecular dynamics (MD) simulations revealed that p53C Y220C was most prone to water infiltration, followed by p53C, whereas the interiors of p53C HM and p63C remained comparably dry. A strong correlation (r² = 0.92) between P50% and extent of interior hydration was observed. The pathways of individual water molecule entry and exit were mapped and analyzed, revealing a common route preserved across the p53 family involving a previously reported pocket, along with a novel surface cleft, both of which appear to be targetable by small molecules. Potential determinants of propensity to water incursion were assessed, including backbone hydrogen bond protection and combined sequence and structure similarity. Collectively, our results indicate that p53C has an intrinsic susceptibility to water leakage, which is exacerbated in a structural class mutant, suggesting that there may be a common avenue for rescuing p53 function.

Therapeutic Strategies to Activate p53

The p53 protein has appropriately been named the "guardian of the genome". In almost all human cancers, the powerful tumor suppressor function of p53 is compromised by a variety of mechanisms, including mutations with either loss of function or gain of function and inhibition by its negative regulators MDM2 and/or MDMX. We review herein the progress made on different therapeutic strategies for targeting p53.

Inside the stemness engine: Mechanistic links between deregulated transcription factors and stemness in cancer

Cell identity is largely determined by its transcriptional profile. In tumour, deregulation of transcription factor expression and/or activity enables cancer cell to acquire a stem-like state characterised by capacity to self-renew, differentiate and form tumours in vivo. These stem-like cancer cells are highly metastatic and therapy resistant, thus warranting a more complete understanding of the molecular mechanisms downstream of the transcription factors that mediate the establishment of stemness state. Here, we review recent research findings that provide a mechanistic link between the commonly deregulated transcription factors and stemness in cancer. In particular, we describe the role of master transcription factors (SOX, OCT4, NANOG, KLF, BRACHYURY, SALL, HOX, FOX and RUNX), signalling-regulated transcription factors (SMAD, β-catenin, YAP, TAZ, AP-1, NOTCH, STAT, GLI, ETS and NF-κB) and unclassified transcription factors (c-MYC, HIF, EMT transcription factors and P53) across diverse tumour types, thereby yielding a comprehensive overview identifying shared downstream targets, highlighting unique mechanisms and discussing complexities.

A comprehensive study of p53 protein

The protein p53 has been extensively investigated since it was found 43 years ago and has become a "guardian of the genome" that regulates the division of cells by preventing the growth of cells and dividing them, that is, inhibits the development of tumors. Initial proof of protein existence by researchers in the mid-1970s was found by altering and regulating the SV40 big T antigen termed the A protein. Researchers demonstrated how viruses play a role in cancer by employing viruses' ability to create T-antigens complex with viral tumors, which was discovered in 1979 following a viral analysis and cancer analog research. Researchers later in the year 1989 explained that in Murine Friend, a virus-caused erythroleukemia, commonly found that p53 was inactivated to suggest that p53 could be a "tumor suppressor gene." The TP53 gene, encoding p53, is one of human cancer's most frequently altered genes. The protein-regulated biological functions of all p53s include cell cycles, apoptosis, senescence, metabolism of the DNA, angiogenesis, cell differentiation, and immunological response. We tried to unfold the history of the p53 protein, which was discovered long back in 1979, that is, 43 years of research on p53, and how p53's function has been developed through time in this article.

Gain of Function (GOF) Mutant p53 in Cancer-Current Therapeutic Approaches

Continuous development of personalized treatments is undoubtedly beneficial for oncogenic patients' comfort and survival rate. Mutant TP53 is associated with a worse prognosis due to the occurrence of metastases, increased chemoresistance, and tumor growth. Currently, numerous compounds capable of p53 reactivation or the destabilization of mutant p53 are being investigated. Several of them, APR-246, COTI-2, SAHA, and PEITC, were approved for clinical trials. This review focuses on these novel therapeutic opportunities, their mechanisms of action, and their significance for potential medical application.

MYCN Impact on High-Risk Neuroblastoma: From Diagnosis and Prognosis to Targeted Treatment

Simple Summary

Neuroblastoma is one of the most diffuse and the deadliest cancer in children. While many advances have been made in the last few decades to improve patients’ outcome, high-risk neuroblastoma (HR-NB) still shows a very aggressive pattern of development and poor prognosis, with only a 50% chance of 5-year survival. Moreover, while many factors contribute to defining the high-risk condition, MYCN status is well established as the major element in pathology disclosure. The aim of this review is to describe the current knowledge in the diagnosis, prognosis and therapeutic approaches of HR-NB, particularly in relation to MYCN. The review highlights how MYCN influences the HR-NB scenario and the new therapeutic approaches that are currently proposed to target it, in consideration of MYCN as a highly relevant target for HR-NB patient management.

Abstract

Among childhood cancers, neuroblastoma is the most diffuse solid tumor and the deadliest in children. While to date, the pathology has become progressively manageable with a significant increase in 5-year survival for its less aggressive form, high-risk neuroblastoma (HR-NB) remains a major issue with poor outcome and little survivability of patients. The staging system has also been improved to better fit patient needs and to administer therapies in a more focused manner in consideration of pathology features. New and improved therapies have been developed; nevertheless, low efficacy and high toxicity remain a staple feature of current high-risk neuroblastoma treatment. For this reason, more specific procedures are required, and new therapeutic targets are also needed for a precise medicine approach. In this scenario, MYCN is certainly one of the most interesting targets. Indeed, MYCN is one of the most relevant hallmarks of HR-NB, and many studies has been carried out in recent years to discover potent and specific inhibitors to block its activities and any related oncogenic function. N-Myc protein has been considered an undruggable target for a long time. Thus, many new indirect and direct approaches have been discovered and preclinically evaluated for the interaction with MYCN and its pathways; a few of the most promising approaches are nearing clinical application for the investigation in HR-NB.

Insights into Allosteric Mechanisms of the Lung-Enriched p53 Mutants V157F and R158L

Lung cancer is a leading fatal malignancy in humans. p53 mutants exhibit not only loss of tumor suppressor capability but also oncogenic gain-of-function, contributing to lung cancer initiation, progression and therapeutic resistance. Research shows that p53 mutants V157F and R158L occur with high frequency in lung squamous cell carcinomas. Revealing their conformational dynamics is critical for developing novel lung therapies. Here, we used all-atom molecular dynamics (MD) simulations to investigate the effect of V157F and R158L substitutions on the structural properties of the p53 core domain (p53C). Compared to wild-type (WT) p53C, both V157F and R158L mutants display slightly lesser β-sheet structure, larger radius of gyration, larger volume and larger exposed surface area, showing aggregation-prone structural characteristics. The aggregation-prone fragments (residues 249–267 and 268–282) of two mutants are more exposed to water solution than that of WT p53C. V157F and R158L mutation sites can affect the conformation switch of loop 1 through long-range associations. Simulations also reveal that the local structure and conformation around the V157F and R158L mutation sites are in a dynamic equilibrium between the misfolded and properly folded conformations. These results provide molecular mechanistic insights into allosteric mechanisms of the lung-enriched p53 mutants.

Mutant p53-microRNA-200c-ZEB2-Axis-Induced CPT1C Elevation Contributes to Metabolic Reprogramming and Tumor Progression in Basal-Like Breast Cancers

TP53 is mutated in more than 80% of basal-like breast cancers (BLBCs). BLBCs with TP53 mutation are usually high-grade and have worse responses to chemotherapy, leading to poor clinical outcomes. Wild-type p53 (WTp53) is well-accepted to promote fatty acid oxidation (FAO); however, in this study, we demonstrate that mutant p53 (Mutp53) enhances FAO activity through constitutively upregulating CPT1C via dysregulating the miR-200c-ZEB2 axis. Sustained CPT1C expression contributes to the metabolic preference of FAO, epithelial-mesenchymal transition (EMT) phenotypes, migration, invasion, and cancer stemness in BLBC, which is mediated by modulating the redox status. Furthermore, interference of CPT1C expression impairs tumor growth and pulmonary colonization of BLBC cells in vivo, and even postpones the occurrence of spontaneous metastasis, resulting in a prolonged disease-specific survival (DSS). Consistently, clinical validation reveals that high CPT1C is observed in breast cancer patients with metastasis and is correlated with poor overall, disease-free, progression-free, and disease-specific survival in BLBC patients. Together, unlike WTp53 which transiently transactivates CPT1C, Mutp53 provides long-term benefits through sustaining CPT1C expression by disturbing the miR-200c-ZEB2 axis, which potentiates FAO and facilitates tumor progression in BLBC, suggesting that targeting Mutp53-CPT1C-driven metabolic reprogramming is promising to serve as novel therapeutic strategies for BLBC in the future.

Repurposing antiparasitic antimonials to noncovalently rescue temperature-sensitive p53 mutations

The tumor suppressor p53 is inactivated by over hundreds of heterogenous mutations in cancer. Here, we purposefully selected phenotypically reversible temperature-sensitive (TS) p53 mutations for pharmacological rescue with thermostability as the compound-screening readout. This rational screening identified antiparasitic drug potassium antimony tartrate (PAT) as an agent that can thermostabilize the representative TS mutant p53-V272M via noncovalent binding. PAT met the three basic criteria for a targeted drug: availability of a co-crystal structure, compatible structure-activity relationship, and intracellular target specificity, consequently exhibiting antitumor activity in a xenograft mouse model. At the antimony dose in clinical antiparasitic therapy, PAT effectively and specifically rescued p53-V272M in patient-derived primary leukemia cells in single-cell RNA sequencing. Further scanning of 815 frequent p53-missense mutations identified 65 potential PAT-treatable mutations, most of which were temperature sensitive. These results lay the groundwork for repurposing noncovalent antiparasitic antimonials for precisely treating cancers with the 65 p53 mutations.

Targeting TP53-Mutated Acute Myeloid Leukemia: Research and Clinical Developments

TP53 is a key tumor suppressor gene that plays an important role in regulating apoptosis, senescence, and DNA damage repair in response to cellular stress. Although somewhat rare, TP53-mutated AML has been identified as an important molecular subgroup with a prognosis that is arguably the worst of any. Survival beyond one year is rare after induction chemotherapy with or without consolidative allogeneic stem cell transplant. Although response rates have been improved with hypomethylating agents, outcomes remain particularly poor due to short response duration. Improvements in our understanding of AML genetics and biology have led to a surge in novel treatment options, though the clinical applicability of these agents in TP53-mutated disease remains largely unknown. This review will focus on the epidemiology, molecular characteristics, and clinical significance of TP53 mutations in AML as well as emerging treatment options that are currently being studied.

TP53 Expression and Mutational Analysis in Hematological Malignancy in Jeddah, Saudi Arabia

Background: Tumor protein 53 (TP53) is a tumor-suppressor gene and plays an essential role in apoptosis, cell cycle arrest, genomic stability, and DNA repair. Although it is the most often mutated gene in human cancer, it has respectively low frequency in hematological malignancy but is significantly linked with complex karyotype, poor prognosis, and chemotherapeutic response. Nevertheless, the prevalence and prognostic role of TP53 mutations in hematological malignancy in Saudi patients are not well reported. We, therefore, aim to assess the frequency of TP53 mutations in hematological malignancies in Saudi Arabia. Method: 20 different hematological malignancy samples were tested using fluorescence in situ hybridization (FISH) technique for TP53 deletion detection and next-generation sequencing (NGS) targeted panel was applied on 10 samples for mutations identification specifically TP53 mutation. Results: TP53 deletion was detected in 6 of 20 samples by FISH. Most of the 6 patients with TP53 deletion had acute lymphoblastic leukemia (ALL), and majority of them were child. NGS result revealed one heterozygous missense mutation in exon 5 of the TP53 gene (c. G9963A, p.H175R). Conclusion: To the best of our knowledge, the TP53 mutation is novel variant, and the first time we are reporting their association with myelodysplastic syndromic individual with complex karyotype. This study recommends further analysis of genomic mutations on bigger cohorts, utilizing high throughput technologies.

Partial p53 reactivation is sufficient to induce cancer regression

Background

Impaired p53 function is one of the central molecular features of a tumor cell and even a partial reduction in p53 activity can increase the cancer risk in mice and men. From a therapeutic perspective it is noteworthy that tumor cells often become addicted to the absence of p53 providing a rationale for developing p53 reactivating compounds to treat cancer patients. Unfortunately, many of the compounds that are currently undergoing preclinical and clinical testing fail to fully reactivate mutant p53 proteins, raising the crucial question: how much p53 activity is needed to elicit a therapeutic effect?

Methods

We have genetically modelled partial p53 reactivation using knock-in mice with inducible expression of the p53 variant E177R. This variant has a reduced ability to bind and transactivate target genes and consequently causes moderate cancer susceptibility. We have generated different syngeneically transplanted and autochthonous mouse models of p53-deficient acute myeloid leukemia and B or T cell lymphoma. After cancer manifestation we have activated E177R expression and analyzed the in vivo therapy response by bioluminescence or magnetic resonance imaging. The molecular response was further characterized in vitro by assays for gene expression, proliferation, senescence, differentiation, apoptosis and clonogenic growth.

Results

We report the conceptually intriguing observation that the p53 variant E177R, which promotes de novo leukemia and lymphoma formation, inhibits proliferation and viability, induces immune cell infiltration and triggers cancer regression in vivo when introduced into p53-deficient leukemia and lymphomas. p53-deficient cancer cells proved to be so addicted to the absence of p53 that even the low-level activity of E177R is detrimental to cancer growth.

Conclusions

The observation that a partial loss-of-function p53 variant promotes tumorigenesis in one setting and induces regression in another, underlines the highly context-specific effects of individual p53 mutants. It further highlights the exquisite sensitivity of cancer cells to even small changes in p53 activity and reveals that changes in activity level are more important than the absolute level. As such, the study encourages ongoing research efforts into mutant p53 reactivating drugs by providing genetic proof-of-principle evidence that incomplete p53 reactivation may suffice to elicit a therapeutic response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02269-6.

Computational Prediction of the Pathogenic Status of Cancer-Specific Somatic Variants

In-silico classification of the pathogenic status of somatic variants is shown to be promising in promoting the clinical utilization of genetic tests. Majority of the available classification tools are designed based on the characteristics of germline variants or the combination of germline and somatic variants. Significance of somatic variants in cancer initiation and progression urges for development of classifiers specialized for classifying pathogenic status of cancer somatic variants based on the model trained on cancer somatic variants. We established a gold standard exclusively for cancer somatic single nucleotide variants (SNVs) collected from the catalogue of somatic mutations in cancer. We developed two support vector machine (SVM) classifiers based on genomic features of cancer somatic SNVs located in coding and non-coding regions of the genome, respectively. The SVM classifiers achieved the area under the ROC curve of 0.94 and 0.89 regarding the classification of the pathogenic status of coding and non-coding cancer somatic SNVs, respectively. Our models outperform two well-known classification tools including FATHMM-FX and CScape in classifying both coding and non-coding cancer somatic variants. Furthermore, we applied our models to predict the pathogenic status of somatic variants identified in young breast cancer patients from METABRIC and TCGA-BRCA studies. The results indicated that using the classification threshold of 0.8 our “coding” model predicted 1853 positive SNVs (out of 6,910) from the TCGA-BRCA dataset, and 500 positive SNVs (out of 1882) from the METABRIC dataset. Interestingly, through comparative survival analysis of the positive predictions from our models, we identified a young-specific pathogenic somatic variant with potential for the prognosis of early onset of breast cancer in young women.

Potential of rescue and reactivation of tumor suppressor p53 for cancer therapy

The tumor suppressor protein p53, a transcription product of the anti-oncogene TP53, is a critical factor in preventing cellular cancerization and killing cancer cells by inducing apoptosis. As a result, p53 is often referred to as the "guardian of the genome." Almost half of cancers possess genetic mutations in the TP53 gene, and most of these mutations result in the malfunction of p53, which promotes aggregation. In some cases, the product of the TP53 mutant allele shows higher aggregation propensity; the mutant co-aggregates with the normal (functional) p53 protein, thus losing cellular activity of the p53 guardian. Cancer might also progress because of the proteolytic degradation of p53 by activated E3 ubiquitination enzymes, MDM2 and MDM4. The inhibition of the specific interaction between MDM2 (MDM4) and p53 also results in increased p53 activity in cancer cells. Although the molecular targets of the drugs are different, two drug discovery strategies with a common goal, "rescuing p53 protein," have recently emerged. To conduct this approach, various biophysical methods of protein characterization were employed. In this review, we focus on these two independent strategies based on the unique biophysical features of the p53 protein.

Regulation of miRNAs Expression by Mutant p53 Gain of Function in Cancer

The p53 roles have been largely described; among them, cell proliferation and apoptosis control are some of the best studied and understood. Interestingly, the mutations on the six hotspot sites within the region that encodes the DNA-binding domain of p53 give rise to other very different variants. The particular behavior of these variants led to consider p53 mutants as separate oncogene entities; that is, they do not retain wild type functions but acquire new ones, namely Gain-of-function p53 mutants. Furthermore, recent studies have revealed how p53 mutants regulate gene expression and exert oncogenic effects by unbalancing specific microRNAs (miRNAs) levels that provoke epithelial-mesenchymal transition, chemoresistance, and cell survival, among others. In this review, we discuss recent evidence of the crosstalk between miRNAs and mutants of p53, as well as the consequent cellular processes dysregulated.

Role of Circulating Biomarkers in Platinum-Resistant Ovarian Cancer

Ovarian cancer (OC) is the second most common cause of death in women with gynecological cancer. Considering the poor prognosis, particularly in the case of platinum-resistant (PtR) disease, a huge effort was made to define new biomarkers able to help physicians in approaching and treating these challenging patients. Currently, most data can be obtained from tumor biopsy samples, but this is not always available and implies a surgical procedure. On the other hand, circulating biomarkers are detected with non-invasive methods, although this might require expensive techniques. Given the fervent hope in their value, here we focused on the most studied circulating biomarkers that could play a role in PtR OC.

Structural basis of reactivation of oncogenic p53 mutants by a small molecule: methylene quinuclidinone (MQ)

In response to genotoxic stress, the tumor suppressor p53 acts as a transcription factor by regulating the expression of genes critical for cancer prevention. Mutations in the gene encoding p53 are associated with cancer development. PRIMA-1 and eprenetapopt (APR-246/PRIMA-1^MET) are small molecules that are converted into the biologically active compound, methylene quinuclidinone (MQ), shown to reactivate mutant p53 by binding covalently to cysteine residues. Here, we investigate the structural basis of mutant p53 reactivation by MQ based on a series of high-resolution crystal structures of cancer-related and wild-type p53 core domains bound to MQ in their free state and in complexes with their DNA response elements. Our data demonstrate that MQ binds to several cysteine residues located at the surface of the core domain. The structures reveal a large diversity in MQ interaction modes that stabilize p53 and its complexes with DNA, leading to a common global effect that is pertinent to the restoration of non-functional p53 proteins.

The tumor suppressor p53 is mutated in more than half of human cancers and the compound methylene quinuclidinone (MQ) was shown to reactivate p53 mutants by binding covalently to cysteine residues. Here, the authors present crystal structures of wild-type and cancer related p53 mutant core domains bound to MQ alone and in complex with their DNA response elements and observe that MQ is bound to several cysteine residues located at the surface of the core domain.

Association Between TP53 Mutation and Prognosis in Wilms Tumor: A Meta-Analysis

BackgroundTP53 mutation has been suggested to have prognostic value for patients with Wilms tumor (WT), but the results are still controversial. Methods: Relevant studies published until August 1, 2019 were identified by searching PubMed, EMBASE and Cochrane Library. A random-effect model was performed to assess pooled data. Begg's and Egger's test were used to evaluate the potential publication bias. Sensitivity analysis was used to evaluate the stability of results. Results: A total of seven eligible articles were included. There was no significant difference in the risk of death among patients with WT with different TP53 mutation status (odds ratio [OR] = 3.09, 95% confidence interval[CI]: 0.81-11.84). Combined hazard ratio (HR) suggested that TP53 mutation had an unfavorable impact on overall survival (OS) (HR = 4.17, 95% CI: 1.97-6.36) and disease-free survival (DFS) (HR = 2.23, 95% CI: 1.29-3.17) in WT. Conclusions: This meta-analysis demonstrates that TP53 mutations are associated with poorer prognosis in WT.

Redox Sensitive Cysteine Residues as Crucial Regulators of Wild-Type and Mutant p53 Isoforms

The wild-type protein p53 plays a key role in preventing the formation of neoplasms by controlling cell growth. However, in more than a half of all cancers, the TP53 gene has missense mutations that appear during tumorigenesis. In most cases, the mutated gene encodes a full-length protein with the substitution of a single amino acid, resulting in structural and functional changes and acquiring an oncogenic role. This dual role of the wild-type protein and the mutated isoforms is also evident in the regulation of the redox state of the cell, with antioxidant and prooxidant functions, respectively. In this review, we introduce a new concept of the p53 protein by discussing its sensitivity to the cellular redox state. In particular, we focus on the discussion of structural and functional changes following post-translational modifications of redox-sensitive cysteine residues, which are also responsible for interacting with zinc ions for proper structural folding. We will also discuss therapeutic opportunities using small molecules targeting cysteines capable of modifying the structure and function of the p53 mutant isoforms in view of possible anticancer therapies for patients possessing the mutation in the TP53 gene.

Molecular dynamics study on the inhibition mechanisms of ReACp53 peptide for p53-R175H mutant aggregation

p53 mutant aggregation can lead to loss-of-function (LoF), dominant-negative (DN) and gain-of-function (GoF) effects, involving in tumor growth. Finding inhibition methods of p53 mutant aggregation is a key step for developing new therapeutics against aggregation-associated cancers. Recent studies have shown that a cell-permeable peptide, ReACp53, can inhibit aggregation of the p53 mutant and restore p53 nuclear function as a transcriptional factor, showing extraordinary therapeutic potential. However, the molecular mechanism underlying the inhibition of p53 mutant aggregation by the ReAp53 peptide is unclear. In this work, we used all-atom molecular dynamics (MD) simulations to investigate the effect of ReACp53 peptide on the structural and dynamic properties of the p53 core domain (p53C) of the aggregation-prone R175H mutant. Our simulations revealed that the ReACp53 peptide can stabilize the ordered secondary structure and decrease the flexibility of disordered loops of the R175H mutant through increasing the intra-interactions of p53C. Moreover, we found that ReACp53 peptide specifically binds to the fragment (residues 180-233) of the R175H mutant through strong hydrophobic interactions with residues L188 and L201 and a salt bridge or hydrogen bond formation with residues D186, E198, D204, E221 and E224. The specific binding pattern protects the aggregation-prone fragment (residues 182-213) from exposure to water. Hence, we suggested that the ReACp53 peptide inhibits aggregation of the R175H mutant by restoring the wild-type conformation from an aggregation-prone state and reducing the exposure of the aggregation-prone segment. These results provide molecular mechanistic insight into inhibition of the ReACp53 peptide on amyloid aggregation of the R175H mutant.

TP53 in Acute Myeloid Leukemia: Molecular Aspects and Patterns of Mutation

Mutation of the tumor suppressor gene, TP53, is associated with abysmal survival outcomes in acute myeloid leukemia (AML). Although it is the most commonly mutated gene in cancer, its occurrence is observed in only 5–10% of de novo AML, and in 30% of therapy related AML (t-AML). TP53 mutation serves as a prognostic marker of poor response to standard-of-care chemotherapy, particularly in t-AML and AML with complex cytogenetics. In light of a poor response to traditional chemotherapy and only a modest improvement in outcome with hypomethylation-based interventions, allogenic stem cell transplant is routinely recommended in these cases, albeit with a response that is often short lived. Despite being frequently mutated across the cancer spectrum, progress and enthusiasm for the development of p53 targeted therapeutic interventions is lacking and to date there is no approved drug that mitigates the effects of TP53 mutation. There is a mounting body of evidence indicating that p53 mutants differ in functionality and form from typical AML cases and subsequently display inconsistent responses to therapy at the cellular level. Understanding this pathobiological activity is imperative to the development of effective therapeutic strategies. This review aims to provide a comprehensive understanding of the effects of TP53 on the hematopoietic system, to describe its varying degree of functionality in tumor suppression, and to illustrate the need for the adoption of personalized therapeutic strategies to target distinct classes of the p53 mutation in AML management.

The role of microRNA-21 in the onset and progression of cancer

MicroRNAs (miRNAs), a class of small noncoding RNA, posttranscriptionally regulate the expression of genes. Aberrant expression of miRNA is reported in various types of cancer. Since the first report of oncomiR-21 involvement in the glioma, its upregulation was reported in multiple cancers and was allied with high oncogenic property. In addition to the downregulation of tumor suppressor genes, the miR-21 is also associated with cancer resistance to various chemotherapy. The recent research is appraising miR-21 as a promising cancer target and biomarker for early cancer detection. In this review, we briefly explain the biogenesis and regulation of miR-21 in cancer cells. Additionally, the review features the assorted genes/pathways regulated by the miR-21 in various cancer and cancer stem cells.

Selective functional inhibition of a tumor-derived p53 mutant by cytosolic chaperones identified using split-YFP in budding yeast

Life requires the oligomerization of individual proteins into higher-order assemblies. In order to form functional oligomers, monomers must adopt appropriate 3D structures. Molecular chaperones transiently bind nascent or misfolded proteins to promote proper folding. Single missense mutations frequently cause disease by perturbing folding despite chaperone engagement. A misfolded mutant capable of oligomerizing with wild-type proteins can dominantly poison oligomer function. We previously found evidence that human-disease-linked mutations in Saccharomyces cerevisiae septin proteins slow folding and attract chaperones, resulting in a kinetic delay in oligomerization that prevents the mutant from interfering with wild-type function. Here, we build upon our septin studies to develop a new approach for identifying chaperone interactions in living cells, and use it to expand our understanding of chaperone involvement, kinetic folding delays, and oligomerization in the recessive behavior of tumor-derived mutants of the tumor suppressor p53. We find evidence of increased binding of several cytosolic chaperones to a recessive, misfolding-prone mutant, p53(V272M). Similar to our septin results, chaperone overexpression inhibits the function of p53(V272M) with minimal effect on the wild type. Unlike mutant septins, p53(V272M) is not kinetically delayed under conditions in which it is functional. Instead, it interacts with wild-type p53 but this interaction is temperature sensitive. At high temperatures or upon chaperone overexpression, p53(V272M) is excluded from the nucleus and cannot function or perturb wild-type function. Hsp90 inhibition liberates mutant p53 to enter the nucleus. These findings provide new insights into the effects of missense mutations.

Therapeutic Strategies Targeting Tumor Suppressor Genes in Pancreatic Cancer

The high mortality of pancreatic cancer is attributed to the insidious progression of this disease, which results in a delayed diagnosis and advanced disease stage at diagnosis. More than 35% of patients with pancreatic cancer are in stage III, whereas 50% are in stage IV at diagnosis. Thus, understanding the aggressive features of pancreatic cancer will contribute to the resolution of problems, such as its early recurrence, metastasis, and resistance to chemotherapy and radiotherapy. Therefore, new therapeutic strategies targeting tumor suppressor gene products may help prevent the progression of pancreatic cancer. In this review, we discuss several recent clinical trials of pancreatic cancer and recent studies reporting safe and effective treatment modalities for patients with advanced pancreatic cancer.

Protein mimetic amyloid inhibitor potently abrogates cancer-associated mutant p53 aggregation and restores tumor suppressor function

Missense mutations in p53 are severely deleterious and occur in over 50% of all human cancers. The majority of these mutations are located in the inherently unstable DNA-binding domain (DBD), many of which destabilize the domain further and expose its aggregation-prone hydrophobic core, prompting self-assembly of mutant p53 into inactive cytosolic amyloid-like aggregates. Screening an oligopyridylamide library, previously shown to inhibit amyloid formation associated with Alzheimer's disease and type II diabetes, identified a tripyridylamide, ADH-6, that abrogates self-assembly of the aggregation-nucleating subdomain of mutant p53 DBD. Moreover, ADH-6 targets and dissociates mutant p53 aggregates in human cancer cells, which restores p53's transcriptional activity, leading to cell cycle arrest and apoptosis. Notably, ADH-6 treatment effectively shrinks xenografts harboring mutant p53, while exhibiting no toxicity to healthy tissue, thereby substantially prolonging survival. This study demonstrates the successful application of a bona fide small-molecule amyloid inhibitor as a potent anticancer agent.

Efficient Modulation of TP53 Expression in Human Induced Pluripotent Stem Cells

TP53 point mutations are found in 50% of all cancers and seem to play an important role in cancer pathogenesis. Thus, human induced pluripotent stem cells (hiPSCs) overexpressing mutant TP53 are a valuable tool for the generation of in vitro models of cancer stem cells or for in vivo xenograft models. Here, we describe a protocol for the alteration of gene expression in hiPSCs via overexpression of a mutant form of the TP53 (R249S) gene using lentiviral transduction. A high amount of TP53 protein is detected 1 week after transduction and antibiotic selection. Differentiation of transduced hiPSCs gives insight into better understanding cancer formation in different tissues and may be a useful tool for genetic or pharmacologic screening assays. © 2019 The Authors. Basic Protocol 1: Production and concentration of third-generation lentivirus Support Protocol 1: Cloning of gene of interest into modulation vector Support Protocol 2: Preparation of DMEM GlutaMAX™ with 10% fetal bovine serum and 1% penicillin-streptomycin Basic Protocol 2: Transduction of human induced pluripotent stem cells and selection of positively transfected cells Support Protocol 3: Preparation of Matrigel^® -coated plates Support Protocol 4: Preparation of mTeSR™1 medium.

Synchrotron X-Ray Radiation-Induced Bystander Effect: An Impact of the Scattered Radiation, Distance From the Irradiated Site and p53 Cell Status

Synchrotron radiation, especially microbeam radiotherapy (MRT), has a great potential to improve cancer radiotherapy, but non-targeted effects of synchrotron radiation have not yet been sufficiently explored. We have previously demonstrated that scattered synchrotron radiation induces measurable γ-H2AX foci, a biomarker of DNA double-strand breaks, at biologically relevant distances from the irradiated field that could contribute to the apparent accumulation of bystander DNA damage detected in cells and tissues outside of the irradiated area. Here, we quantified an impact of scattered radiation to DNA damage response in "naïve" cells sharing the medium with the cells that were exposed to synchrotron radiation. To understand the effect of genetic alterations in naïve cells, we utilised p53-null and p53-wild-type human colon cancer cells HCT116. The cells were grown in two-well chamber slides, with only one of nine zones (of equal area) of one well irradiated with broad beam or MRT. γ-H2AX foci per cell values induced by scattered radiation in selected zones of the unirradiated well were compared to the commensurate values from selected zones in the irradiated well, with matching distances from the irradiated zone. Scattered radiation highly impacted the DNA damage response in both wells and a pronounced distance-independent bystander DNA damage was generated by broad-beam irradiations, while MRT-generated bystander response was negligible. For p53-null cells, a trend for a reduced response to scattered irradiation was observed, but not to bystander signalling. These results will be taken into account for the assessment of genotoxic effects in surrounding non-targeted tissues in preclinical experiments designed to optimise conditions for clinical MRT and for cancer treatment in patients.

Effect of Stapling on the Thermodynamics of mdm2-p53 Binding

Protein-protein interaction (PPI) is one of the key regulatory features driving biomolecular processes and hence is targeted for designing therapeutics against diseases. Small peptides are a new and emerging class of therapeutics owing to their high specificity and low toxicity. For achieving efficient targeting of the PPI, amino acid side chains are often stapled together, resulting in the rigidification of these peptides. Exploring the scope of these peptides demands a comprehensive understanding of their working principle. In this work, two stapled p53 peptides have been considered to delineate their binding mechanism with mdm2 using computational approaches. The addition of stapling agent protects the secondary structure of the peptides even in the case of thermal and chemical denaturation. Although the introduction of a stapling agent increases the hydrophobicity of the peptide, the enthalpic stabilization decreases. This is overcome by the lowering of the entropic penalty, and the overall binding affinity improves. The mechanistic insights into the benefit of peptide stapling can be adopted for further improvement of peptide therapeutics.

Hypothermia Effectively Treats Tumors with Temperature-Sensitive p53 Mutations

The p53 tumor suppressor is frequently inactivated by mutations in cancer. Most p53 mutations are located in the DNA-binding domain, causing local disruption of DNA-binding surface or global misfolding. Rescuing the structural defect of mutant p53 is an attractive therapeutic strategy, but its potential remains unproven due to a lack of drugs capable of efficiently rescuing misfolded p53. Although mutant p53 in tumors is inactive at 37°C, approximately 15% are temperature sensitive (ts) and regain DNA-binding activity at 32°C to 34°C (ts mutants). This temperature is achievable using a therapeutic hypothermia procedure established for resuscitated cardiac arrest patients. To test whether hypothermia can be used to target tumors with ts p53 mutations, the core temperature of tumor-bearing mice was lowered to 32°C using the adenosine A1 receptor agonist N⁶-cyclohexyladenoxine that suppresses brain-regulated thermogenesis. Hypothermia treatment (32 hours at 32°C × 5 cycles) activated endogenous ts mutant p53 in xenograft tumors and inhibited tumor growth in a p53-dependent fashion. Tumor regression and durable remission in a ts p53 lymphoma model was achieved by combining hypothermia with chemotherapy. The results raise the possibility of treating tumors expressing ts p53 mutations with hypothermia. SIGNIFICANCE: Pharmacologic inhibition of brain-regulated thermogenesis and induction of 32°C whole-body hypothermia specifically targets tumors with temperature-sensitive p53 mutations, rescuing p53 transcriptional activity and inducing tumor regression.See related commentary by Hu and Feng, p. 3762.

Arsenic Trioxide Rescues Structural p53 Mutations through a Cryptic Allosteric Site

TP53 is the most frequently mutated gene in cancer, yet these mutations remain therapeutically non-actionable. Major challenges in drugging p53 mutations include heterogeneous mechanisms of inactivation and the absence of broadly applicable allosteric sites. Here we report the identification of small molecules, including arsenic trioxide (ATO), an established agent in treating acute promyelocytic leukemia, as cysteine-reactive compounds that rescue structural p53 mutations. Crystal structures of arsenic-bound p53 mutants reveal a cryptic allosteric site involving three arsenic-coordinating cysteines within the DNA-binding domain, distal to the zinc-binding site. Arsenic binding stabilizes the DNA-binding loop-sheet-helix motif alongside the overall β-sandwich fold, endowing p53 mutants with thermostability and transcriptional activity. In cellular and mouse xenograft models, ATO reactivates mutant p53 for tumor suppression. Investigation of the 25 most frequent p53 mutations informs patient stratification for clinical exploration. Our results provide a mechanistic basis for repurposing ATO to target p53 mutations for widely applicable yet personalized cancer therapies.

p53, A Victim of the Prion Fashion

Identified in the late 1970s as an oncogene, a driving force leading to tumor development, p53 turned out to be a key tumor suppressor gene. Now p53 is considered a master gene regulating the transcription of over 3000 target genes and controlling a remarkable number of cellular functions. The elevated prevalence of p53 mutations in human cancers has led to a recurring questioning about the roles of mutant p53 proteins and their functional consequences. Both mutants and isoforms of p53 have been attributed dominant-negative and gain of function properties among which is the ability to form amyloid aggregates and behave in a prion-like manner. This report challenges the ongoing "prion p53" hypothesis by reviewing evidence of p53 behavior in light of our current knowledge regarding amyloid proteins, prionoids and prions.

Study on Medication Rules of Traditional Chinese Medicine against Antineoplastic Drug-Induced Cardiotoxicity Based on Network Pharmacology and Data Mining

Methods

The targets of antineoplastic drugs with cardiotoxicity were obtained from the National Center for Biotechnology Information (NCBI) database, China national knowledge infrastructure (CNKI) database, and Swiss Target Prediction platform. Then, the cardiotoxicity-related targets were derived from the Gene Cards, Disgenet, OMIM, and DrugBank databases, as well as the drug of current clinical guidelines. The targets both in these two sets were regarded as potential targets to alleviate ADIC. Then, candidate compounds and herbs were matched via Traditional Chinese Medicine Systems Pharmacology (TCMSP) platform. Cytoscape3.7.1 was used to set up the target-compound-herb network. Molecular docking between core targets and compounds was performed with AutodockVina1.1.2. The rules of herbs were summarized by analyzing their property, flavor, and channel tropism.

Results

Twenty-one potential targets, 332 candidate compounds, and 400 kinds of herbs were obtained. Five core targets including potassium voltage-gated channel subfamily H member 2 (KCNH2), cyclin-dependent kinase 1 (CDK1), matrix metalloproteinase 2 (MMP2), mitogen-activated protein kinase1 (MAPK1), and tumor protein p53 (TP53) and 29 core compounds (beta-sitosterol, quercetin, kaempferol, etc.) were collected. Five core herbs (Yanhusuo, Gouteng, Huangbai, Lianqiao, and Gancao) were identified. Also, the TCM against ADIC were mainly bitter and acrid in taste, warm in property, and distributed to the liver and lung meridians.

Conclusion

TCM against ADIC has great potential. Our study provides a new method and ideas for clinical applications of integrated Chinese and western medicine in treating ADIC.

Predictive and Prognostic Potential of TP53 in Patients With Advanced Non-Small-Cell Lung Cancer Treated With EGFR-TKI: Analysis of a Phase III Randomized Clinical Trial (CTONG 0901)

BACKGROUND

Mutations in TP53 are commonly found in patients with epidermal growth factor receptor (EGFR) mutant advanced non-small-cell lung cancer (NSCLC). In this study, we determined the predictive and prognostic potential of different subtypes of TP53 using data from a phase III randomized trial (CTONG 0901).

PATIENTS AND METHODS

The trial enrolled 195 patients who had undergone next-generation sequencing of 168 genes before treatment with EGFR tyrosine kinase inhibitors. Mutations in TP53 (exon 4 or 7, other mutations, and wild-type) were analyzed based on the therapeutic response and survival. A Cox proportional hazards model was used to determine the potential of the predictive and prognostic factors.

RESULTS

All 195 patients harbored activating EGFR mutations: the most common concomitant mutations were TP53 (134/195, 68.7%), CTNNB1 (20/195, 10.3%), and RB1 (16/195, 8.2%). The genetic profiles between patient subgroups administered first-line (132, 67.7%) or later-line (63, 32.3%) treatments did not significantly differ. The median progression-free survival in patients with mutations in exon 4 or 7 of TP53, other TP53 mutations, and wild-type TP53 were 9.4, 11.0, and 14.5 months (P = .009), respectively. Overall survival times were 15.8, 20.0, and 26.1 months (P = .004), respectively. Mutations in exon 4 or 7 of TP53 served as independent prognostic factors for progression-free (P = .001) and overall survival (P = .004) in patients.

CONCLUSION

Mutations in exon 4 and/or 7 in TP53 are promising predictive and prognostic indicators in EGFR-mutated NSCLC.

Current developments of targeting the p53 signaling pathway for cancer treatment

p53 is one of the most well-studied tumor suppressors. It is mutated or deleted in half of all cancers. In the other half carrying wild type p53, the p53 signaling pathway is disrupted by abnormalities of other components in the pathway. Due to its paramount role in tumor suppression, p53 has attracted great interest in drug development as any clinically successful therapeutic agent to target the p53 pathway will save millions of lives. However, designing therapeutics targeting the pathway has been extremely challenging, despite more than forty years of research. This review will summarize past and current efforts of developing p53-based gene therapy and targeted therapies for cancer treatment. In addition, the current efforts of exploiting the immunogenicity of p53 protein for cancer immunotherapy will be reviewed. Challenges and future directions for targeting the p53 pathway will be discussed.

A molecular dynamics and docking study to screen anti-cancer compounds targeting mutated p53

The p53 gene is mutated in greater than 50% of several human cancers including bladder urothelial carcinoma, lung adenocarcinoma, colorectal carcinoma, and oral cancer. Mutations in the p53 gene occur predominantly in the DNA-binding domain causing loss of function and accumulation of dysfunctional p53 protein in tumors by hetero-oligomerization with the wild type p53. Thus an in silico approach for the rational design of potent, pharmacologically active small drug-like compounds targeting mutated p53 was undertaken. Molecular dynamics simulations of the wild type p53 monomer and p53 mutants R175H and R248Q were performed using Discovery Studio v3.5. Phase was used to generate pharmacophore models and the sitemap generated pocket was used to screen the Maybridge HitFinder^TM library using Schrodinger Suite. We identified ten compounds (Cmpd-1 to Cmpd-10) that showed preferential binding to p53 mutants, and their pharmacokinetic profiles complied with the ADMET rules. Cmpd-4 and Cmpd-8 demonstrated binding with mutated p53 at cysteine 124, similar to the mutant p53 reactivating compound APR-246 (PRIMA-1^Met) for functional restoration of the mutant p53. We propose the identified compounds as suitable drug candidates against mutated p53 protein, with the specific small drug-like molecules as either single drugs or in combination with lower doses of additional cytotoxic drugs, consequently reducing adverse side effects in patients.Communicated by Ramaswamy H. Sarma.

Targeting the p53-MDM2 pathway for neuroblastoma therapy: Rays of hope

Despite being the subject of extensive research and clinical trials, neuroblastoma remains a major therapeutic challenge in pediatric oncology. The p53 protein is a central safeguard that protects cells against genome instability and malignant transformation. Mutated TP53 (the gene encoding p53) is implicated in many human cancers, but the majority of neuroblastomas have wild type p53 with intact transcriptional function. In fact, the TP53 mutation rate does not exceed 1-2% in neuroblastomas. However, overexpression of the murine double minute 2 (MDM2) gene in neuroblastoma is relatively common, and leads to inhibition of p53. It is also associated with other non-canonical p53-independent functions, including drug resistance and increased translation of MYCN and VEGF mRNA. The p53-MDM2 pathway in neuroblastoma is also modulated at several different molecular levels, including via interactions with other proteins (MYCN, p14^ARF). In addition, the overexpression of MDM2 in tumors is linked to a poorer prognosis for cancer patients. Thus, restoring p53 function by inhibiting its interaction with MDM2 is a potential therapeutic strategy for neuroblastoma. A number of p53-MDM2 antagonists have been designed and studied for this purpose. This review summarizes the current understanding of p53 biology and the p53-dependent and -independent oncogenic functions of MDM2 in neuroblastoma, and also the regulation of the p53-MDM2 axis in neuroblastoma. This review also highlights the use of MDM2 as a molecular target for the disease, and describes the MDM2 inhibitors currently being investigated in preclinical and clinical studies. We also briefly explain the various strategies that have been used and future directions to take in the development of effective MDM2 inhibitors for neuroblastoma.

Tumorigenic p53 mutants undergo common structural disruptions including conversion to α-sheet structure

The p53 protein is a commonly studied cancer target because of its role in tumor suppression. Unfortunately, it is susceptible to mutation-associated loss of function; approximately 50% of cancers are associated with mutations to p53, the majority of which are located in the central DNA-binding domain. Here, we report molecular dynamics simulations of wild-type (WT) p53 and 20 different mutants, including a stabilized pseudo-WT mutant. Our findings indicate that p53 mutants tend to exacerbate latent structural-disruption tendencies, or vulnerabilities, already present in the WT protein, suggesting that it may be possible to develop cancer therapies by targeting a relatively small set of structural-disruption motifs rather than a multitude of effects specific to each mutant. In addition, α-sheet secondary structure formed in almost all of the proteins. α-Sheet has been hypothesized and recently demonstrated to play a role in amyloidogenesis, and its presence in the reported p53 simulations coincides with the recent re-consideration of cancer as an amyloid disease.