Identification of TRIML2, a novel p53 target, that enhances p53 SUMOylation and regulates the transactivation of proapoptotic genes

Cell fate regulation governed by p53: Friends or reversible foes in cancer therapy

Cancer is a leading cause of death worldwide. Targeted therapies aimed at key oncogenic driver mutations in combination with chemotherapy and radiotherapy as well as immunotherapy have benefited cancer patients considerably. Tumor protein p53 (TP53), a crucial tumor suppressor gene encoding p53, regulates numerous downstream genes and cellular phenotypes in response to various stressors. The affected genes are involved in diverse processes, including cell cycle arrest, DNA repair, cellular senescence, metabolic homeostasis, apoptosis, and autophagy. However, accumulating recent studies have continued to reveal novel and unexpected functions of p53 in governing the fate of tumors, for example, functions in ferroptosis, immunity, the tumor microenvironment and microbiome metabolism. Among the possibilities, the evolutionary plasticity of p53 is the most controversial, partially due to the dizzying array of biological functions that have been attributed to different regulatory mechanisms of p53 signaling. Nearly 40 years after its discovery, this key tumor suppressor remains somewhat enigmatic. The intricate and diverse functions of p53 in regulating cell fate during cancer treatment are only the tip of the iceberg with respect to its equally complicated structural biology, which has been painstakingly revealed. Additionally, TP53 mutation is one of the most significant genetic alterations in cancer, contributing to rapid cancer cell growth and tumor progression. Here, we summarized recent advances that implicate altered p53 in modulating the response to various cancer therapies, including chemotherapy, radiotherapy, and immunotherapy. Furthermore, we also discussed potential strategies for targeting p53 as a therapeutic option for cancer.

Tripartite Motif Protein Family in Central Nervous System Diseases

Tripartite motif (TRIM) protein superfamily is a group of E3 ubiquitin ligases characterized by the conserved RING domain, the B-box domain, and the coiled-coil domain (RBCC). It is widely involved in various physiological and pathological processes, such as intracellular signal transduction, cell cycle regulation, oncogenesis, and innate immune response. Central nervous system (CNS) diseases are composed of encephalopathy and spinal cord diseases, which have a high disability and mortality rate. Patients are often unable to take care of themselves and their life quality can be seriously declined. Initially, the function research of TRIM proteins mainly focused on cancer. However, in recent years, accumulating attention is paid to the roles they play in CNS diseases. In this review, we integrate the reported roles of TRIM proteins in the pathological process of CNS diseases and related signaling pathways, hoping to provide theoretical bases for further research in treating CNS diseases targeting TRIM proteins. TRIM proteins participated in CNS diseases. TRIM protein family is characterized by a highly conserved RBCC domain, referring to the RING domain, the B-box domain, and the coiled-coil domain. Recent research has discovered the relations between TRIM proteins and various CNS diseases, especially Alzheimer's disease, Parkinson's disease, and ischemic stroke.

Overview of the regulation of the class IA PI3K/AKT pathway by SUMO

The phosphatidylinositol-3-kinase (PI3K)/AKT pathway is a major regulator of metabolism, migration, survival, proliferation, and antiviral immunity. Both an overactivation and an inhibition of the PI3K/AKT pathway are related to different pathologies. Activation of this signaling pathway is tightly controlled through a multistep process and its deregulation can be associated with aberrant post-translational modifications including SUMOylation. Here, we review the complex modulation of the PI3K/AKT pathway by SUMOylation and we discuss its putative incvolvement in human disease.

Role of SUMOylation in Neurodegenerative Diseases

Neurodegenerative diseases (NDDs) are irreversible, progressive diseases with no effective treatment. The hallmark of NDDs is the aggregation of misfolded, modified proteins, which impair neuronal vulnerability and cause brain damage. The loss of synaptic connection and the progressive loss of neurons result in cognitive defects. Several dysregulated proteins and overlapping molecular mechanisms contribute to the pathophysiology of NDDs. Post-translational modifications (PTMs) are essential regulators of protein function, trafficking, and maintaining neuronal hemostasis. The conjugation of a small ubiquitin-like modifier (SUMO) is a reversible, dynamic PTM required for synaptic and cognitive function. The onset and progression of neurodegenerative diseases are associated with aberrant SUMOylation. In this review, we have summarized the role of SUMOylation in regulating critical proteins involved in the onset and progression of several NDDs.

TRIM family contribute to tumorigenesis, cancer development, and drug resistance

The tripartite-motif (TRIM) family represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases. TRIM family is involved in a variety of cellular signaling transductions and biological processes. TRIM family also contributes to cancer initiation, progress, and therapy resistance, exhibiting oncogenic and tumor-suppressive functions in different human cancer types. Moreover, TRIM family members have great potential to serve as biomarkers for cancer diagnosis and prognosis. In this review, we focus on the specific mechanisms of the participation of TRIM family members in tumorigenesis, and cancer development including interacting with dysregulated signaling pathways such as JAK/STAT, PI3K/AKT, TGF-β, NF-κB, Wnt/β-catenin, and p53 hub. In addition, many studies have demonstrated that the TRIM family are related to tumor resistance; modulate the epithelial–mesenchymal transition (EMT) process, and guarantee the acquisition of cancer stem cells (CSCs) phenotype. In the end, we havediscussed the potential of TRIM family members for cancer therapeutic targets.

Cancer-Associated Dysregulation of Sumo Regulators: Proteases and Ligases

SUMOylation is a post-translational modification that has emerged in recent decades as a mechanism involved in controlling diverse physiological processes and that is essential in vertebrates. The SUMO pathway is regulated by several enzymes, proteases and ligases being the main actors involved in the control of sumoylation of specific targets. Dysregulation of the expression, localization and function of these enzymes produces physiological changes that can lead to the appearance of different types of cancer, depending on the enzymes and target proteins involved. Among the most studied proteases and ligases, those of the SENP and PIAS families stand out, respectively. While the proteases involved in this pathway have specific SUMO activity, the ligases may have additional functions unrelated to sumoylation, which makes it more difficult to study their SUMO-associated role in cancer process. In this review we update the knowledge and advances in relation to the impact of dysregulation of SUMO proteases and ligases in cancer initiation and progression.

Association of TP53 gene polymorphisms with the risk of acute lymphoblastic leukemia in Moroccan children

BACKGROUND

TP53 gene plays a pivotal role in maintaining genetic stability and prevention of malignancies. Alterations of this gene are implicated in more than half of human cancers. To the best of our knowledge, this study is the first to explore TP53 polymorphisms in Moroccan childhood acute lymphoblastic leukemia (ALL).

METHODS AND RESULTS

DNA samples of 45 ALL children were obtained from peripheral blood. A total of 333 healthy Moroccans were used as controls. Polymerase chain reaction and Sanger sequencing were performed to analyze TP53 hotspot exons in cases. We identified a significant protective effect of the TP53-Arg variant at rs1042522 [OR 0.4593 (0.249-0.8472), p = 0.0127] and the Pro/Arg genotype [OR 0.0350 (0.0047-0.2583), p = 0.0010]. Additionally, we found a novel association between the C-allele of Arg213Arg 1800372 [OR 2.7736 (1.3821-5.5664), p = 0.0041] and the risk of childhood ALL. Importantly, TC/CC genotypes of this polymorphism were revealed to enhance the risk of ALL among females [OR 9.0 (3.1555-25.6693), p < 0.0001]. Arg213Arg was also noticed to be associated with the hemoglobin count of patients at diagnosis by linear regression (p = 0.0318). The analysis of penetrance showed a significant association of the CG/GG genotypes at rs1042522 and TC/CC genotypes at rs1800372 to childhood ALL via dominant model [OR 0.2090 (0.09074-0.4814), p = 0.0002 and OR 3.4205 (1.6084-7.2742), p = 0.0014 for rs1042522 and rs1800372 respectively]. No association was found between TP53 polymorphisms and patients survival.

CONCLUSION

Altogether, our findings indicated that TP53 polymorphisms are significantly involved in the genetic susceptibility to childhood ALL in Morocco.

RNA Microarray-Based Comparison of Innate Immune Phenotypes between Human THP-1 Macrophages Stimulated with Two BCG Strains

Currently, the only available vaccine against tuberculosis is Mycobacterium bovis Bacille Calmette-Guérin (BCG). Pulmonary tuberculosis protection provided by the vaccine varies depending on the strain, the patient’s age and the evaluated population. Although the adaptive immune responses induced by different BCG strains have been widely studied, little conclusive data is available regarding innate immune responses, especially in macrophages. Here, we aimed to characterize the innate immune responses of human THP-1-derived macrophages at the transcriptional level following a challenge with either the BCG Mexico (M.BCG) or Phipps (P.BCG) strains. After a brief in vitro characterization of the bacterial strains and the innate immune responses, including nitric oxide production and cytokine profiles, we analyzed the mRNA expression patterns and performed pathway enrichment analysis using RNA microarrays. Our results showed that multiple biological processes were enriched, especially those associated with innate inflammatory and antimicrobial responses, including tumor necrosis factor (TNF)-α, type I interferon (IFN-I) and IFN-γ. However, four DEGs were identified in macrophages infected with M.BCG compared to P. BCG. These findings indicated the proinflammatory stimulation of macrophages induced by both BCG strains, at the cytokine level and in terms of gene expression, suggesting a differential expression pattern of innate immune transcripts depending on the mycobacterial strain.

The Role of SUMO E3 Ligases in Signaling Pathway of Cancer Cells

Small ubiquitin-like modifier (SUMO)ylation is a reversible post-translational modification that plays a crucial role in numerous aspects of cell physiology, including cell cycle regulation, DNA damage repair, and protein trafficking and turnover, which are of importance for cell homeostasis. Mechanistically, SUMOylation is a sequential multi-enzymatic process where SUMO E3 ligases recruit substrates and accelerate the transfer of SUMO onto targets, modulating their interactions, localization, activity, or stability. Accumulating evidence highlights the critical role of dysregulated SUMO E3 ligases in processes associated with the occurrence and development of cancers. In the present review, we summarize the SUMO E3 ligases, in particular, the novel ones recently identified, and discuss their regulatory roles in cancer pathogenesis.

PPM1D mutations are oncogenic drivers of de novo diffuse midline glioma formation

The role of PPM1D mutations in de novo gliomagenesis has not been systematically explored. Here we analyze whole genome sequences of 170 pediatric high-grade gliomas and find that truncating mutations in PPM1D that increase the stability of its phosphatase are clonal driver events in 11% of Diffuse Midline Gliomas (DMGs) and are enriched in primary pontine tumors. Through the development of DMG mouse models, we show that PPM1D mutations potentiate gliomagenesis and that PPM1D phosphatase activity is required for in vivo oncogenesis. Finally, we apply integrative phosphoproteomic and functional genomics assays and find that oncogenic effects of PPM1D truncation converge on regulators of cell cycle, DNA damage response, and p53 pathways, revealing therapeutic vulnerabilities including MDM2 inhibition.

It’s Getting Complicated—A Fresh Look at p53-MDM2-ARF Triangle in Tumorigenesis and Cancer Therapy

Anti-tumorigenic mechanisms mediated by the tumor suppressor p53, upon oncogenic stresses, are our bodies’ greatest weapons to battle against cancer onset and development. Consequently, factors that possess significant p53-regulating activities have been subjects of serious interest from the cancer research community. Among them, MDM2 and ARF are considered the most influential p53 regulators due to their abilities to inhibit and activate p53 functions, respectively. MDM2 inhibits p53 by promoting ubiquitination and proteasome-mediated degradation of p53, while ARF activates p53 by physically interacting with MDM2 to block its access to p53. This conventional understanding of p53-MDM2-ARF functional triangle have guided the direction of p53 research, as well as the development of p53-based therapeutic strategies for the last 30 years. Our increasing knowledge of this triangle during this time, especially through identification of p53-independent functions of MDM2 and ARF, have uncovered many under-appreciated molecular mechanisms connecting these three proteins. Through recognizing both antagonizing and synergizing relationships among them, our consideration for harnessing these relationships to develop effective cancer therapies needs an update accordingly. In this review, we will re-visit the conventional wisdom regarding p53-MDM2-ARF tumor-regulating mechanisms, highlight impactful studies contributing to the modern look of their relationships, and summarize ongoing efforts to target this pathway for effective cancer treatments. A refreshed appreciation of p53-MDM2-ARF network can bring innovative approaches to develop new generations of genetically-informed and clinically-effective cancer therapies.

p53 signaling in cancer progression and therapy

The p53 protein is a transcription factor known as the "guardian of the genome" because of its critical function in preserving genomic integrity. The TP53 gene is mutated in approximately half of all human malignancies, including those of the breast, colon, lung, liver, prostate, bladder, and skin. When DNA damage occurs, the TP53 gene on human chromosome 17 stops the cell cycle. If p53 protein is mutated, the cell cycle is unrestricted and the damaged DNA is replicated, resulting in uncontrolled cell proliferation and cancer tumours. Tumor-associated p53 mutations are usually associated with phenotypes distinct from those caused by the loss of the tumor-suppressing function exerted by wild-type p53protein. Many of these mutant p53 proteins have oncogenic characteristics, and therefore modulate the ability of cancer cells to proliferate, escape apoptosis, invade and metastasize. Because p53 deficiency is so common in human cancer, this protein is an excellent option for cancer treatment. In this review, we will discuss some of the molecular pathways by which mutant p53 proteins might perform their oncogenic activities, as well as prospective treatment methods based on restoring tumor suppressive p53 functions.

Immediate Sample Fixation Increases Circulating Tumour Cell (CTC) Capture and Preserves Phenotype in Head and Neck Squamous Cell Carcinoma: Towards a Standardised Approach to Microfluidic CTC Biomarker Discovery

Simple Summary

Circulating tumour cells (CTCs) have shown potential to act as markers of disease and prognosis in head and neck squamous cell carcinoma (HNSCC). However, there are a number of methods and devices reported to isolate and characterise CTCs. Translating CTC markers to clinical practice, for patient benefit, requires a reliable, reproducible and standardised approach. We report the benefit of the Parsortix microfluidic CTC enrichment platform in HNSCC. We demonstrate consistent cell capture rates between 10 and 100 cells/mL of whole blood. Analysis of gene expression with unfixed cells before and after Parsortix enrichment demonstrated a cell stress response and downregulation of key genes. We highlight the benefit of using a fixative blood collection tube (Transfix) to increase cell capture rate and preserve the CTC marker expression profile. Such evidence is crucial when designing sample processing protocols for large cohort multi-centre clinical trials investigating CTCs in any cancer type.

Abstract

Introduction: Research demonstrates strong evidence that circulating tumour cells (CTCs) can provide diagnostic and/or prognostic biomarkers in head and neck squamous cell carcinoma (HNSCC) and a potential tool for therapeutic stratification. However, the question still remains as to the optimum method of CTC enrichment and how this can be translated into clinical practice. We aimed to evaluate the Parsortix microfluidic device for CTC enrichment and characterisation in HNSCC, seeking to optimise a sample collection and processing protocol that preserves CTC integrity and phenotype. Method: Spiking experiments of the FaDu and SCC040 HNSCC cell lines were used to determine the Parsortix capture rate of rare “CTC-like” cells. Capture rates of cancer cells spiked into EDTA blood collections tubes (BCTs) were compared to the Transfix fixative BCT and Cytodelics whole blood freezing protocol. The Lexogen Quantseq library preparation was used to profile gene expression of unfixed cells before and after microfluidic enrichment and enriched cell line spiked Transfix blood samples. An antibody panel was optimised to enable immunofluorescence microscopy CTC detection in HNSCC patient Transfix blood samples, using epithelial (EpCAM) and mesenchymal (N-cadherin) CTC markers. Results: Across a spiked cell concentration range of 9–129 cells/mL, Parsortix demonstrated a mean cell capture rate of 53.5% for unfixed cells, with no significant relationship between spiked cell concentration and capture rate. Samples preserved in Transfix BCTs demonstrated significantly increased capture rates at 0 h (time to processing) compared to EDTA BCTs (65.3% vs. 51.0%). Capture rates in Transfix BCTs were maintained at 24 h and 72 h timepoints, but dropped significantly in EDTA BCTs. Gene expression profiling revealed that microfluidic enrichment of unfixed cell lines caused downregulation of RNA processing/binding gene pathways and upregulation of genes involved in cell injury, apoptosis and oxidative stress. RNA was successfully extracted and sequenced from Transfix preserved cells enriched using Parsortix, demonstrating epithelial specific transcripts from spiked cells. In a proof-of-concept cohort of four patients with advanced HNSCC, CTCs were successfully identified and visualised with epithelial and epithelial-mesenchymal phenotypes. Conclusion: We have optimised a protocol for detection of CTCs in HNSCC with the Parsortix microfluidic device, using Transfix BCTs. We report a significant benefit, both in terms of cell capture rates and preserving cell phenotype, for using a fixative BCT- particularly if samples are stored before processing. In the design of large cohort multi-site clinical trials, such data are of paramount importance.

Differential Transcriptional Regulation of Polymorphic p53 Codon 72 in Metabolic Pathways

p53 is a transcription factor that is activated under DNA damage stress and regulates the expression of proapoptotic genes including the expression of growth arrest genes to subsequently determine the fate of cells. To investigate the functional differences of polymorphic p53 codon 72, we constructed isogenic lines encoding each polymorphic p53 codon 72 based on induced pluripotent stem cells, which can endogenously express each polymorphic p53 protein only, encoding either the arginine 72 (R72) variant or proline 72 (P72) variant, respectively. We found that there was no significant functional difference between P72 and R72 cells in growth arrest or apoptosis as a representative function of p53. In the comprehensive analysis, the expression pattern of the common p53 target genes, including cell cycle arrest or apoptosis, was also increased regardless of the polymorphic p53 codon 72 status, whereas the expression pattern involved in metabolism was decreased and more significant in R72 than in P72 cells. This study noted that polymorphic p53 codon 72 differentially regulated the functional categories of metabolism and not the pathways that determine cell fate, such as growth arrest and apoptosis in cells exposed to genotoxic stress.

Multifunctional barcoding with ClonMapper enables high-resolution study of clonal dynamics during tumor evolution and treatment

Lineage-tracing methods have enabled characterization of clonal dynamics in complex populations, but generally lack the ability to integrate genomic, epigenomic and transcriptomic measurements with live-cell manipulation of specific clones of interest. We developed a functionalized lineage-tracing system, ClonMapper, which integrates DNA barcoding with single-cell RNA sequencing and clonal isolation to comprehensively characterize thousands of clones within heterogeneous populations. Using ClonMapper, we identified subpopulations of a chronic lymphocytic leukemia cell line with distinct clonal compositions, transcriptional signatures and chemotherapy survivorship trajectories; patterns that were also observed in primary human chronic lymphocytic leukemia. The ability to retrieve specific clones before, during and after treatment enabled direct measurements of clonal diversification and durable subpopulation transcriptional signatures. ClonMapper is a powerful multifunctional approach to dissect the complex clonal dynamics of tumor progression and therapeutic response.

TP53 codon 72 polymorphism and type 2 diabetes: a case-control study in South Indian population

TP53 functions primarily as a tumor suppressor, controlling a myriad of signalling pathways that prevent a cell from undergoing malignant transformation. This tumor suppressive function requires an activation and stabilization of TP53 in response to cell stressors. However, besides its cancer-preventive functions, TP53 is also known to be involved in diverse cellular processes including metabolism, reproduction, stem cell renewal and development. Indeed, several lines of evidence strongly suggest that TP53 plays crucial role in diabetes. A number of studies have evaluated the association of genetic alterations (single nucleotide variations) in TP53 gene with the development of diabetes. However, the results have not been consistent. The aim of this study was to evaluate whether the C/G polymorphism at codon 72 (Pro72/Arg72), located in exon 4 of TP53, is associated with type 2 diabetes in South Indian population. A total of 74 type 2 diabetic patients and 54 non-diabetic subjects were screened. None of the three genotypes, namely C/C (Pro/Pro), C/G (Pro/Arg), and G/G (Arg/Arg) was found to be significantly associated with type 2 diabetes in our study group. The findings of this study indicate that TP53 codon 72 polymorphism is not associated with increased risk of type 2 diabetes in South Indian population. Further studies with a large cohort size would be necessary to corroborate the observations of this study. Nevertheless, this study represents the first genetic analysis of TP53 variants in South Indian type 2 diabetic patients.

High expression of PIG11 correlates with poor prognosis in gastric cancer

P53-induced gene 11 (PIG11) is an early transcription-related target of p53 that is involved in cell apoptosis and tumor development. However, its biological function in gastric cancer (GC) tissues and relationship with the prognosis of patients with GC have remained elusive. In the present retrospective study, 60 fresh and 790 paraffin-embedded samples of GC were obtained from the Affiliated Hospital of Nantong University (Nantong, China) with complete clinical data from all patients. Reverse transcription-quantitative PCR and tissue microarray-immunohistochemical analysis were used to determine the expression of PIG11 in the respective GC tissues. A receiver operating characteristic (ROC) curve was plotted to determine the diagnostic utility of PIG11 expression in GC. Furthermore, three online databases, including Gene Expression Profiling Interactive Analysis (GEPIA), Oncomine and Kaplan-Meier plotter, were used for bioinformatics analysis of PIG11. PIG11 expression in GC tissues was high, which was positively correlated with invasive depth (P<0.001), lymph node metastasis (P<0.001), distant metastasis (P=0.019), TNM staging (P<0.001) and carcinoembryonic antigen in serum (P<0.001), and negatively associated with the overall survival of patients with GC. The ROC curve analysis suggested that based on PIG11 expression, it was possible to distinguish GC tissues from adjacent normal tissues (P<0.0001) with a sensitivity and specificity of 81.67 and 76.67%, respectively. In addition, Cox logistic regression analysis demonstrated that high PIG11 expression is a novel biomarker for unfavorable prognosis of patients with GC. Furthermore, the results obtained from the GEPIA database indicated that PIG11 expression is correlated with TNF, carcinoembryonic antigen related cell adhesion molecule 5, phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha, VEGFA and kinase insert domain receptor. Therefore, PIG11 expression may be associated with the malignancy of GC and may serve as a potential diagnostic and prognostic biomarker for GC.

The pan-cancer lncRNA MILIP links c-Myc to p53 repression

We have recently identified the MYC proto-oncogene, bHLH transcription factor (MYC, best known as c-Myc)-responsive pan-cancer lncRNA c-Myc-Inducible Long noncoding RNA Inactivating P53 (MILIP) as an oncogenic driver. Our studies show that MILIP facilitates tumor protein p53 (TP53, best known as p53) turnover by reducing its SUMOylation through suppressing tripartite-motif family-like 2 (TRIML2), thus promoting cell survival, proliferation, and tumorigenicity. MILIP may thus represent an anti-cancer target for counteracting the c-Myc axis.

The P72R Polymorphism in R248Q/W p53 Mutants Modifies the Mutant Effect on Epithelial to Mesenchymal Transition Phenotype and Cell Invasion via CXCL1 Expression

High-grade serous carcinoma (HGSC), the most lethal subtype of epithelial ovarian cancer (EOC), is characterized by widespread TP53 mutations (>90%), most of which are missense mutations (>70%). The objective of this study was to investigate differential transcriptional targets affected by a common germline P72R SNP (rs1042522) in two p53 hotspot mutants, R248Q and R248W, and identify the mechanism through which the P72R SNP affects the neomorphic properties of these mutants. Using isogenic cell line models, transcriptomic analysis, xenografts, and patient data, we found that the P72R SNP modifies the effect of p53 hotspot mutants on cellular morphology and invasion properties. Most importantly, RNA sequencing studies identified CXCL1 a critical factor that is differentially affected by P72R SNP in R248Q and R248W mutants and is responsible for differences in cellular morphology and functional properties observed in these p53 mutants. We show that the mutants with the P72 SNP promote a reversion of the EMT phenotype to epithelial characteristics, whereas its R72 counterpart promotes a mesenchymal transition via the chemokine CXCL1. These studies reveal a new role of the P72R SNP in modulating the neomorphic properties of p53 mutants via CXCL1, which has significant implications for tumor invasion and metastasis.

Eutherian-Specific Gene TRIML2 Attenuates Inflammation in the Evolution of Placentation

Evolution of highly invasive placentation in the stem lineage of eutherians and subsequent extension of pregnancy set eutherians apart from other mammals, that is, marsupials with short-lived placentas, and oviparous monotremes. Recent studies suggest that eutherian implantation evolved from marsupial attachment reaction, an inflammatory process induced by the direct contact of fetal placenta with maternal endometrium after the breakdown of the shell coat, and shortly before the onset of parturition. Unique to eutherians, a dramatic downregulation of inflammation after implantation prevents the onset of premature parturition, and is critical for the maintenance of gestation. This downregulation likely involved evolutionary changes on maternal as well as fetal/placental side. Tripartite-motif family-like2 (TRIML2) only exists in eutherian genomes and shows preferential expression in preimplantation embryos, and trophoblast-derived structures, such as chorion and placental disc. Comparative genomic evidence supports that TRIML2 originated from a gene duplication event in the stem lineage of Eutheria that also gave rise to eutherian TRIML1. Compared with TRIML1, TRIML2 lost the catalytic RING domain of E3 ligase. However, only TRIML2 is induced in human choriocarcinoma cell line JEG3 with poly(I:C) treatment to simulate inflammation during viral infection. Its knockdown increases the production of proinflammatory cytokines and reduces trophoblast survival during poly(I:C) stimulation, while its overexpression reduces proinflammatory cytokine production, supporting TRIML2’s role as a regulatory inhibitor of the inflammatory pathways in trophoblasts. TRIML2’s potential virus-interacting PRY/SPRY domain shows significant signature of selection, suggesting its contribution to the evolution of eutherian-specific inflammation regulation during placentation.

c-Myc inactivation of p53 through the pan-cancer lncRNA MILIP drives cancer pathogenesis

The functions of the proto-oncoprotein c-Myc and the tumor suppressor p53 in controlling cell survival and proliferation are inextricably linked as “Yin and Yang” partners in normal cells to maintain tissue homeostasis: c-Myc induces the expression of ARF tumor suppressor (p14^ARF in human and p19^ARF in mouse) that binds to and inhibits mouse double minute 2 homolog (MDM2) leading to p53 activation, whereas p53 suppresses c-Myc through a combination of mechanisms involving transcriptional inactivation and microRNA-mediated repression. Nonetheless, the regulatory interactions between c-Myc and p53 are not retained by cancer cells as is evident from the often-imbalanced expression of c-Myc over wildtype p53. Although p53 repression in cancer cells is frequently associated with the loss of ARF, we disclose here an alternate mechanism whereby c-Myc inactivates p53 through the actions of the c-Myc-Inducible Long noncoding RNA Inactivating P53 (MILIP). MILIP functions to promote p53 polyubiquitination and turnover by reducing p53 SUMOylation through suppressing tripartite-motif family-like 2 (TRIML2). MILIP upregulation is observed amongst diverse cancer types and is shown to support cell survival, division and tumourigenicity. Thus our results uncover an inhibitory axis targeting p53 through a pan-cancer expressed RNA accomplice that links c-Myc to suppression of p53.

c-Myc and p53 operate in a negative feedback manner to maintain cellular homeostasis. Here, the authors report a long noncoding RNA, MILIP as a downstream target of c-Myc and that MILIP represses p53 to support tumorigenicity.

YB-1 Knockdown Inhibits the Proliferation of Mesothelioma Cells through Multiple Mechanisms

Y-box binding protein-1 (YB-1) is a multifunctional oncoprotein that has been shown to regulate proliferation, invasion and metastasis in a variety of cancer types. We previously demonstrated that YB-1 is overexpressed in mesothelioma cells and its knockdown significantly reduces tumour cell proliferation, migration, and invasion. However, the mechanisms driving these effects are unclear. Here, we utilised an unbiased RNA-seq approach to characterise the changes to gene expression caused by loss of YB-1 knockdown in three mesothelioma cell lines (MSTO-211H, VMC23 and REN cells). Bioinformatic analysis showed that YB-1 knockdown regulated 150 common genes that were enriched for regulators of mitosis, integrins and extracellular matrix organisation. However, each cell line also displayed unique gene expression signatures, that were differentially enriched for cell death or cell cycle control. Interestingly, deregulation of STAT3 and p53-pathways were a key differential between each cell line. Using flow cytometry, apoptosis assays and single-cell time-lapse imaging, we confirmed that MSTO-211H, VMC23 and REN cells underwent either increased cell death, G1 arrest or aberrant mitotic division, respectively. In conclusion, this data indicates that YB-1 knockdown affects a core set of genes in mesothelioma cells. Loss of YB-1 causes a cascade of events that leads to reduced mesothelioma proliferation, dependent on the underlying functionality of the STAT3/p53-pathways and the genetic landscape of the cell.

PIAS1 and TIF1γ collaborate to promote SnoN SUMOylation and suppression of epithelial-mesenchymal transition

SUMO E3 ligases specify protein substrates for SUMOylation. The SUMO E3 ligases PIAS1 and TIF1γ target the transcriptional regulator SnoN for SUMOylation leading to suppression of epithelial-mesenchymal transition (EMT). Whether and how TIF1γ and PIAS1 might coordinate SnoN SUMOylation and regulation of EMT remained unknown. Here, we reveal that SnoN associates simultaneously with both TIF1γ and PIAS1, leading to a trimeric protein complex. Hence, PIAS1 and TIF1γ collaborate to promote the SUMOylation of SnoN. Importantly, loss of function studies of PIAS1 and TIF1γ suggest that these E3 ligases act in an interdependent manner to suppress EMT of breast cell-derived tissue organoids. Collectively, our findings unveil a novel mechanism by which SUMO E3 ligases coordinate substrate SUMOylation with biological implications.

Tumor suppressor p53 cross-talks with TRIM family proteins

p53 is a key tumor suppressor. As a transcription factor, p53 accumulates in cells in response to various stress signals and selectively transcribes its target genes to regulate a wide variety of cellular stress responses to exert its function in tumor suppression. In addition to tumor suppression, p53 is also involved in many other physiological and pathological processes, e.g. anti-infection, immune response, development, reproduction, neurodegeneration and aging. To maintain its proper function, p53 is under tight and delicate regulation through different mechanisms, particularly the posttranslational modifications. The tripartite motif (TRIM) family proteins are a large group of proteins characterized by the RING, B-Box and coiled-coil (RBCC) domains at the N-terminus. TRIM proteins play important roles in regulation of many fundamental biological processes, including cell proliferation and death, DNA repair, transcription, and immune response. Alterations of TRIM proteins have been linked to many diseases including cancer, infectious diseases, developmental disorders, and neurodegeneration. Interestingly, recent studies have revealed that many TRIM proteins are involved in the regulation of p53, and at the same time, many TRIM proteins are also regulated by p53. Here, we review the cross-talk between p53 and TRIM proteins, and its impact upon cellular biological processes as well as cancer and other diseases.

Regulating tumor suppressor genes: post-translational modifications

Tumor suppressor genes cooperate with each other in tumors. Three important tumor suppressor proteins, retinoblastoma (Rb), p53, phosphatase, and tensin homolog deleted on chromosome ten (PTEN) are functionally associated and they regulated by post-translational modification (PTMs) as well. PTMs include phosphorylation, SUMOylation, acetylation, and other novel modifications becoming growing appreciated. Because most of PTMs are reversible, normal cells use them as a switch to control the state of cells being the resting or proliferating, and PTMs also involve in cell survival and cell cycle, which may lead to abnormal proliferation and tumorigenesis. Although a lot of studies focus on the importance of each kind of PTM, further discoveries shows that tumor suppressor genes (TSGs) form a complex “network” by the interaction of modification. Recently, there are several promising strategies for TSGs for they change more frequently than carcinogenic genes in cancers. We here review the necessity, characteristics, and mechanisms of each kind of post-translational modification on Rb, p53, PTEN, and its influence on the precise and selective function. We also discuss the current antitumoral therapies of Rb, p53 and PTEN as predictive, prognostic, and therapeutic target in cancer.

Cas9 activates the p53 pathway and selects for p53-inactivating mutations

Cas9 is commonly introduced into cell lines to enable CRISPR/Cas9-mediated genome editing. Here we studied the genetic and transcriptional consequences of Cas9 expression per se. Gene expression profiling of 165 pairs of human cancer cell lines and their Cas9-expressing derivatives revealed upregulation of the p53 pathway upon Cas9 introduction, specifically in TP53-WT cell lines. This was confirmed at the mRNA and protein levels. Moreover, elevated levels of DNA repair were observed in Cas9-expressing cell lines. Genetic characterization of 42 cell line pairs showed that Cas9 introduction can lead to the emergence and expansion of p53-inactivating mutations. This was confirmed by competition experiments in isogenic TP53-WT/TP53-null cell lines. Lastly, Cas9 was less active in TP53-WT than in TP53-mutant cell lines, and Cas9-induced p53 pathway activation affected cellular sensitivity to both genetic and chemical perturbations. These findings may have broad implications for the proper use of CRISPR/Cas9-mediated genome editing.

The genetic association study of TP53 polymorphisms in Saudi obese patients

Obesity is a multifactorial metabolic disorder characterized by low grade chronic inflammation. Rare and novel mutations in genes which are vital in several key pathways have been reported to alter the energy expenditure which regulates body weight. The TP53 or p53 gene plays a prominent role in regulating various metabolic activities such as glycolysis, lipolysis, and glycogen synthesis. Recent genome-wide association studies reported that tumor suppressor gene p53 variants play a critical role in the predisposition of type 2 diabetes and obesity. Till date, no reports are available from the Arabian population; hence the present study was intended to assess the association between p53 variants with risk of obesity development in the Saudi population. We have selected three p53 polymorphisms, rs1642785 (C > G), and rs9894946 (A > G), and rs1042522 (Pro72Arg; C > G) and assessed their association with obesity risk in the Saudi population. Phenotypic and biochemical parameters were also evaluated to check their association with p53 genotypes and obesity. Genotyping was carried out on 136 obese and 122 normal samples. We observed that there is significantly increased prevalence p52 Pro72Arg (rs1042522) polymorphism in obese persons when compared to controls at GG genotype in overall comparison (OR: 2.169, 95% CI: 1.086-4.334, p = 0.02716). Male obese subjects showed three-fold higher risk at GG genotype (OR: 3.275, 95% CI: 1.230-8.716, p = 0.01560) and two-fold risk at G allele (OR: 1.827, 95% CI: 1.128-2.958, p = 0.01388) of p53 variant Pro72Arg respectively. This variant has also shown significant influence on cholesterol, LDL level, and random insulin levels in obese subjects (p ≤ 0.05). In conclusion, p53 Pro72Arg variant is highly prevalent among obese individuals and may act as a genetic modifier for obesity development among Saudis.

Characterization of ceRNA network to reveal potential prognostic biomarkers in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a particular subtype of breast malignant tumor with poorer prognosis than other molecular subtypes. Previous studies have demonstrated that some abnormal expression of non-coding RNAs including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) were closely related to tumor cell proliferation, apoptosis, invasion, migration and drug sensitivity. However, the role of non-coding RNAs in the pathogenesis of TNBC is still unclear. In order to characterize the molecular mechanism of non-coding RNAs in TNBC, we downloaded RNA data and miRNA data from the cancer genome atlas database. We successfully identified 686 message RNAs (mRNAs), 26 miRNAs and 50 lncRNAs as key molecules for high risk of TNBC. Then, we hypothesized that the lncRNA–miRNA–mRNA regulatory axis positively correlates with TNBC and constructed a competitive endogenous RNA (ceRNA) network of TNBC. Our series of analyses has shown that five molecules (TERT, TRIML2, PHBP4, mir-1-3p, mir-133a-3p) were significantly associated with the prognosis of TNBC, and there is a prognostic ceRNA sub-network between those molecules. We mapped the Kaplan–Meier curve of RNA on the sub-network and also suggested that the expression level of the selected RNA is related to the survival rate of breast cancer. Reverse transcription-quantitative polymerase chain reaction showed that the expression level of TRIML2 in TNBC cells was higher than normal. In general, our findings have implications for predicting metastasis, predicting prognosis and discovering new therapeutic targets for TNBC.

The Codon 72 TP53 Polymorphism Contributes to TSC Tumorigenesis through the Notch-Nodal Axis

We discovered that 90.3% of patients with angiomyolipomas, lymphangioleiomyomatosis (LAM), and tuberous sclerosis complex (TSC) carry the arginine variant of codon 72 (R72) of TP53 and that R72 increases the risk for angiomyolipoma. R72 transactivates NOTCH1 and NODAL better than the proline variant of codon 72 (P72); therefore, the expression of NOTCH1 and NODAL is increased in angiomyolipoma cells that carry R72. The loss of Tp53 and Tsc1 within nestin-expressing cells in mice resulted in the development of renal cell carcinomas (RCC) with high Notch1 and Nodal expression, suggesting that similar downstream mechanisms contribute to tumorigenesis as a result of p53 loss in mice and p53 polymorphism in humans. The loss of murine Tp53 or expression of human R72 contributes to tumorigenesis via enhancing epithelial-to-mesenchymal transition and motility of tumor cells through the Notch and Nodal pathways. IMPLICATIONS: This work revealed unexpected contributions of the p53 polymorphism to the pathogenesis of TSC and established signaling alterations caused by this polymorphism as a target for therapy. We found that the codon 72 TP53 polymorphism contributes to TSC-associated tumorigenesis via Notch and Nodal signaling.

Targeting Chemoresistant Tumors: Could TRIM Proteins-p53 Axis Be a Possible Answer?

Chemosensitivity is a crucial feature for all tumours so that they can be successfully treated, but the huge heterogeneity of these diseases, to be intended both inter- and intra-tumour, makes it a hard-to-win battle. Indeed, this genotypic and phenotypic variety, together with the adaptability of tumours, results in a plethora of chemoresistance acquisition mechanisms strongly affecting the effectiveness of treatments at different levels. Tripartite motif (TRIM) proteins are shown to be involved in some of these mechanisms thanks to their E3-ubiquitin ligase activity, but also to other activities they can exert in several cellular pathways. Undoubtedly, the ability to regulate the stability and activity of the p53 tumour suppressor protein, shared by many of the TRIMs, represents the preeminent link between this protein family and chemoresistance. Indeed, they can modulate p53 degradation, localization and subset of transactivated target genes, shifting the cellular response towards a cytoprotective or cytotoxic reaction to whatever damage induced by therapy, sometimes in a cellular-dependent way. The involvement in other chemoresistance acquisition mechanisms, independent by p53, is known, affecting pivotal processes like PI3K/Akt/NF-κB signalling transduction or Wnt/beta catenin pathway, to name a few. Hence, the inhibition or the enhancement of TRIM proteins functionality could be worth investigating to better understand chemoresistance and as a strategy to increase effectiveness of anticancer therapies.

Dynamic role of the codon 72 p53 single-nucleotide polymorphism in mammary tumorigenesis in a humanized mouse model

Female breast cancer (BrCa) is the most common noncutaneous cancer among women in the United States. Human epidemiological studies reveal that a p53 single-nucleotide polymorphism (SNP) at codon 72, encoding proline (P72) or arginine (R72), is associated with differential risk of several cancers, including BrCa. However, the molecular mechanisms by which these variants affect mammary tumorigenesis remain unresolved. To investigate the effects of this polymorphism on susceptibility to mammary cancer, we used a humanized p53 mouse model, homozygous for either P72 or R72. Our studies revealed that R72 mice had a significantly higher mammary tumor incidence and reduced latency in both DMBA-induced and MMTV-Erbb2/Neu mouse mammary tumor models compared to P72 mice. Analyses showed that susceptible mammary glands from E-R72 (R72 x MMTV-Erbb2/Neu) mice developed a senescence-associated secretory phenotype (SASP) with influx of proinflammatory macrophages, ultimately resulting in chronic, protumorigenic inflammation. Mammary tumors arising in E-R72 mice also had an increased influx of tumor-associated macrophages, contributing to angiogenesis and elevated tumor growth rates. These results demonstrate that the p53 R72 variant increased susceptibility to mammary tumorigenesis through chronic inflammation.

Identification of a gene expression signature associated with the metastasis suppressor function of NME1: prognostic value in human melanoma

Although NME1 is well known for its ability to suppress metastasis of melanoma, the molecular mechanisms underlying this activity are not completely understood. Herein, we utilized a bioinformatics approach to systematically identify genes whose expression is correlated with the metastasis suppressor function of NME1. This was accomplished through a search for genes that were regulated by NME1, but not by NME1 variants lacking metastasis suppressor activity. This approach identified a number of novel genes, such as ALDOC, CXCL11, LRP1b, and XAGE1 as well as known targets such as NETO2, which were collectively designated as an NME1-Regulated Metastasis Suppressor Signature (MSS). The MSS was associated with prolonged overall survival in a large cohort of melanoma patients in The Cancer Genome Atlas (TCGA). The median overall survival of melanoma patients with elevated expression of the MSS genes was >5.6 years longer compared with that of patients with lower expression of the MSS genes. These data demonstrate that NMEl represents a powerful tool for identifying genes whose expression is associated with metastasis and survival of melanoma patients, suggesting their potential applications as prognostic markers and therapeutic targets in advanced forms of this lethal cancer.

The p53 Tumor Suppressor in the Control of Metabolism and Ferroptosis

The p53 tumor suppressor continues to be distinguished as the most frequently mutated gene in human cancer. It is widely believed that the ability of p53 to induce senescence and programmed cell death underlies the tumor suppressor functions of p53. However, p53 has a number of other functions that recent data strongly implicate in tumor suppression, particularly with regard to the control of metabolism and ferroptosis (iron- and lipid-peroxide-mediated cell death) by p53. As reviewed here, the roles of p53 in the control of metabolism and ferroptosis are complex. Wild-type (WT) p53 negatively regulates lipid synthesis and glycolysis in normal and tumor cells, and positively regulates oxidative phosphorylation and lipid catabolism. Mutant p53 in tumor cells does the converse, positively regulating lipid synthesis and glycolysis. The role of p53 in ferroptosis is even more complex: in normal tissues, WT p53 appears to positively regulate ferroptosis, and this pathway appears to play a role in the ability of basal, unstressed p53 to suppress tumor initiation and development. In tumors, other regulators of ferroptosis supersede p53's role, and WT p53 appears to play a limited role; instead, mutant p53 sensitizes tumor cells to ferroptosis. By clearly elucidating the roles of WT and mutant p53 in metabolism and ferroptosis, and establishing these roles in tumor suppression, emerging research promises to yield new therapeutic avenues for cancer and metabolic diseases.

The codon 72 polymorphism of p53 influences cell fate following nutrient deprivation

The TP53 gene is distinguished as the most frequently mutated gene in cancer. Unlike most cancer-relevant genes, the TP53 gene is also distinguished by the existence of coding region polymorphisms that alter p53 sequence, and in some cases, also alter p53 function. A common coding region variant at amino acid 72 of p53 encodes either proline (P72) or arginine (R72). P72 is the ancestral variant and is most common in populations near the equator. The frequency of the R72 variant increases in a linear manner with latitude. To date, why the R72 variant arose in humans and was possibly selected for has remained unclear. Here-in we show that this single nucleotide polymorphism (SNP) influences the phosphorylation of p53 and the transactivation of the key p53 target CDKN1A (p21) specifically in response to nutrient deprivation, but not in response to conventional cytotoxic agents. Following activation of the kinase AMPK, R72 cells show increased phosphorylation on serine-15 and increased transactivation of the cyclin-dependent kinase inhibitor CDKN1A (p21) and the metabolic response genes PPARGC1B (PGC-1β) and PRKAB2 (AMPK-β2). This is accompanied by increased growth arrest and decreased apoptosis in R72 cells compared with P72 cells. The combined data fit best with the hypothesis that the R72 polymorphism confers increased cell survival in response to nutrient deprivation. This differential response to nutrient deprivation may explain part of selection for this SNP at northern latitudes, where nutrient deprivation might have been more frequent.

The role of the p53 tumor suppressor in metabolism and diabetes

In the context of tumor suppression, p53 is an undisputedly critical protein. Functioning primarily as a transcription factor, p53 helps fend off the initiation and progression of tumors by inducing cell cycle arrest, senescence or programmed cell death (apoptosis) in cells at the earliest stages of precancerous development. Compelling evidence, however, suggests that p53 is involved in other aspects of human physiology, including metabolism. Indeed, recent studies suggest that p53 plays a significant role in the development of metabolic diseases, including diabetes, and further that p53's role in metabolism may also be consequential to tumor suppression. Here, we present a review of the literature on the role of p53 in metabolism, diabetes, pancreatic function, glucose homeostasis and insulin resistance. Additionally, we discuss the emerging role of genetic variation in the p53 pathway (single-nucleotide polymorphisms) on the impact of p53 in metabolic disease and diabetes. A better understanding of the relationship between p53, metabolism and diabetes may one day better inform the existing and prospective therapeutic strategies to combat this rapidly growing epidemic.

The African-specific S47 polymorphism of p53 alters chemosensitivity

The TP53 protein is known to affect the sensitivity of tumor cells to cell death by DNA damaging agents. We recently reported that human and mouse cells containing an African-specific coding region variant of p53, Pro47Ser (hereafter S47), are impaired in the transactivation of a small subset of p53 target genes including GLS2 and SCO2, and are markedly resistant to cisplatin. Further, mice containing this variant are markedly predisposed to cancer. Together these findings suggested that cancer-affected humans with the S47 variant might not be effectively treated with cisplatin. To more directly test this premise, we created transformed derivatives of mouse embryo fibroblasts (MEFs) containing wild type p53 (WT) and the S47 variant and analyzed them for chemosensitivity. We find that transformation with E1A and Ras actually reverses the chemosensitivity/transcriptional differences between WT p53 and S47. Specifically, E1A/Ras-transformed S47 cells show increased sensitivity to cisplatin and paclitaxel, and comparable transactivation of GLS2 and SCO2, compared to cells with WT p53. These data suggest that the functional differences between WT p53 and S47 in primary cells may not hold true for transformed cells. They also offer hope that cisplatin and paclitaxel may be effective chemotherapeutic drugs for S47 individuals with cancer.

Association of tripartite motif family-like 2 (TRIML2) polymorphisms with late-onset Alzheimer's disease risk in a Korean population

Apoptosis is a prominent feature in the progression of Alzheimer's disease (AD), regulated in part by the activity of p53. As tripartite motif family-like 2 (TRIML2), a member of the TRIM family of proteins, has been implicated in the regulation of p53-mediated apoptosis, we hypothesized that TRIML2 polymorphisms may result in an increased AD susceptibility. Here, we investigated the association between coding region single nucleotide polymorphisms (cSNPs) in TRIML2 and AD in a Korean population. Two cSNPs (rs79698746 and rs2279551) were genotyped using the Sequenom iPLEX(®) Gold assay and direct sequencing in 162 AD patients and 191 controls. Multiple logistic regression models were used to determine the odds ratios, 95% confidence intervals, and p-values. Significant associations were observed between AD and the allelic frequencies of two SNPs (rs79698746, p=0.007; rs2279551, p=0.01); genotype frequencies were also significantly different between the two groups [rs79698746: p=0.003 in the codominant 2 model (CC vs. TT), p=0.01 in the dominant model (TC/CC vs. TT), p=0.016 in the recessive model (CC vs. TT/TC), and p=0.0025 in the log-additive model (TC vs. CC vs. TT); rs2279551: p=0.003 in the codominant 2 model (CC vs. TT), p=0.011 in the dominant model (TC/CC vs. TT), p=0.019 in the recessive model (CC vs. TT/TC), and p=0.0028 in the log-additive model (TC vs. CC vs. TT)]. In the haplotype analyses, CC haplotypes containing two cSNPs were significantly associated with AD (p=0.013). Taken together, these findings indicate that the C allele of both SNPs was associated with an increased risk of AD. These results suggest that TRIML2 may contribute to AD susceptibility.

Genetic Modifiers of the p53 Pathway

The tumor suppressor gene TP53 is the most frequently mutated gene in human cancer; this gene is subject to inactivation by mutation or deletion in >50% of sporadic cancers. Genes that encode proteins that regulate p53 function, such as MDM2, MDM4, and CDKN2A (p14(ARF)) are also frequently altered in tumors, and it is generally believed that the p53 pathway is likely to be inactivated by mutation in close to 100% of human tumors. Unlike most other cancer-relevant signaling pathways, some of the genes in the p53 pathway contain functionally significant single nucleotide polymorphisms (SNPs) that alter the amplitude of signaling by this protein. These variants, thus, have the potential to impact cancer risk, progression, and the efficacy of radiation and chemotherapy. In addition, the p53 pathway plays a role in other biological processes, including metabolism and reproductive fitness, so these variants have the potential to modify other diseases as well. Here we have chosen five polymorphisms in three genes in the p53 pathway for review, two in TP53, two in MDM2, and one in MDM4. These five variants were selected based on the quality and reproducibility of functional data associated with them, as well as the convincingness of epidemiological data in support of their association with disease. We also highlight two other polymorphisms that may affect p53 signaling, but for which functional or association data are still forthcoming (KITLG and ANRIL). Finally, we touch on three questions regarding genetic modifiers of the p53 pathway: Why did these variants arise? Were they under selection pressure? And, is there compelling evidence to support genotyping these variants to better predict disease risk and prognosis?

The P72R Polymorphism of p53 Predisposes to Obesity and Metabolic Dysfunction

p53 is well known for its tumor suppressor role, but this protein also has a poorly understood role in the regulation of metabolism. Human studies have implicated a common polymorphism at codon 72 of p53 in diabetic and pre-diabetic phenotypes. To understand this role, we utilized a humanized mouse model of the p53 codon 72 variants and monitored these mice following challenge with a high-fat diet (HFD). Mice with the arginine 72 (R72) variant of p53 developed more-severe obesity and glucose intolerance on a HFD, compared to mice with the proline 72 variant (P72). R72 mice developed insulin resistance, islet hypertrophy, increased infiltration of immune cells, and fatty liver disease. Gene expression analyses and studies with small-molecule inhibitors indicate that the p53 target genes Tnf and Npc1l1 underlie this phenotype. These results shed light on the role of p53 in obesity, metabolism, and inflammation.

TRIMming p53's anticancer activity

Several TRIM proteins control abundance and activity of p53. Along this route, TRIM proteins have a serious impact on carcinogenesis and prognosis for cancer patients. In the past years, a significant increase has been made in our understanding of how the TRIM protein family controls p53 activity.

Subtelomeric p53 binding prevents accumulation of DNA damage at human telomeres

Telomeres and tumor suppressor protein TP53 (p53) function in genome protection, but a direct role of p53 at telomeres has not yet been described. Here, we have identified non-canonical p53-binding sites within the human subtelomeres that suppress the accumulation of DNA damage at telomeric repeat DNA. These non-canonical subtelomeric p53-binding sites conferred transcription enhancer-like functions that include an increase in local histone H3K9 and H3K27 acetylation and stimulation of subtelomeric transcripts, including telomere repeat-containing RNA (TERRA). p53 suppressed formation of telomere-associated γH2AX and prevented telomere DNA degradation in response to DNA damage stress. Our findings indicate that p53 provides a direct chromatin-associated protection to human telomeres, as well as other fragile genomic sites. We propose that p53-associated chromatin modifications enhance local DNA repair or protection to provide a previously unrecognized tumor suppressor function of p53.

Graphene Functionalized with Arginine Decreases the Development of Glioblastoma Multiforme Tumor in a Gene-Dependent Manner

Our previous studies revealed that graphene had anticancer properties in experiments in vitro with glioblastoma multiforme (GBM) cells and in tumors cultured in vivo. We hypothesized that the addition of arginine or proline to graphene solutions might counteract graphene agglomeration and increase the activity of graphene. Experiments were performed in vitro with GBM U87 cells and in vivo with GBM tumors cultured on chicken embryo chorioallantoic membranes. The measurements included cell morphology, mortality, viability, tumor morphology, histology, and gene expression. The cells and tumors were treated with reduced graphene oxide (rGO) and rGO functionalized with arginine (rGO + Arg) or proline (rGO + Pro). The results confirmed the anticancer effect of graphene on GBM cells and tumor tissue. After functionalization with amino acids, nanoparticles were distributed more specifically, and the flakes of graphene were less agglomerated. The molecule of rGO + Arg did not increase the expression of TP53 in comparison to rGO, but did not increase the expression of MDM2 or the MDM2/TP53 ratio in the tumor, suggesting that arginine may block MDM2 expression. The expression of NQO1, known to be a strong protector of p53 protein in tumor tissue, was greatly increased. The results indicate that the complex of rGO + Arg has potential in GBM therapy.