p53 Acetylation: Regulation and Consequences

Restoring NAD+ by NAMPT is essential for the SIRT1/p53-mediated survival of UVA- and UVB-irradiated epidermal keratinocytes

Nicotinamide adenine dinucleotide (NAD⁺) is a crucial coenzyme in energy production. The imbalance of NAD⁺ synthesis has been found to trigger age-related diseases, such as metabolic disorders, cancer, and neurodegenerative diseases. Also, UV irradiation induces NAD⁺ depletion in the skin. In mammals, nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in the NAD⁺ salvage pathway and essential for NAD⁺ homeostasis. However, but few studies have focused on the role of NAMPT in response to UV irradiation. Here, we show that NAMPT prevents NAD⁺ depletion in epidermal keratinocytes to protect against the mild-dose UVA and UVB (UVA/B)-induced proliferation defects. We showed that poly(ADP-ribose) polymerase (PARP) inhibitor rescued the NAD⁺ depletion in UVA/B-irradiated human keratinocytes, confirming that PAPR transiently exhausts cellular NAD⁺ to repair DNA damage. Notably, the treatment with a NAMPT inhibitor exacerbated the UVA/B-induced loss of energy production and cell viability. Moreover, the NAMPT inhibitor abrogated the sirtuin-1 (SIRT1)-mediated deacetylation of p53 and significantly inhibited the proliferation of UVA/B-irradiated cells, suggesting that the NAMPT-NAD⁺-SIRT1 axis regulates p53 functions upon UVA/B stress. The supplementation with NAD⁺ intermediates, nicotinamide mononucleotide and nicotinamide riboside, rescued the UVA/B-induced phenotypes in the absence of NAMPT activity. Therefore, NAD⁺ homeostasis is likely essential for the protection of keratinocytes from UV stress in mild doses. Since the skin is continuously exposed to UVA/B irradiation, understanding the protective role of NAMPT in UV stress will help prevent and treat skin photoaging.

CBP/p300: Critical Co-Activators for Nuclear Steroid Hormone Receptors and Emerging Therapeutic Targets in Prostate and Breast Cancers

The CREB-binding protein (CBP) and p300 are two paralogous lysine acetyltransferases (KATs) that were discovered in the 1980s-1990s. Since their discovery, CBP/p300 have emerged as important regulatory proteins due to their ability to acetylate histone and non-histone proteins to modulate transcription. Work in the last 20 years has firmly established CBP/p300 as critical regulators for nuclear hormone signaling pathways, which drive tumor growth in several cancer types. Indeed, CBP/p300 are critical co-activators for the androgen receptor (AR) and estrogen receptor (ER) signaling in prostate and breast cancer, respectively. The AR and ER are stimulated by sex hormones and function as transcription factors to regulate genes involved in cell cycle progression, metabolism, and other cellular functions that contribute to oncogenesis. Recent structural studies of the AR/p300 and ER/p300 complexes have provided critical insights into the mechanism by which p300 interacts with and activates AR- and ER-mediated transcription. Breast and prostate cancer rank the first and forth respectively in cancer diagnoses worldwide and effective treatments are urgently needed. Recent efforts have identified specific and potent CBP/p300 inhibitors that target the acetyltransferase activity and the acetytllysine-binding bromodomain (BD) of CBP/p300. These compounds inhibit AR signaling and tumor growth in prostate cancer. CBP/p300 inhibitors may also be applicable for treating breast and other hormone-dependent cancers. Here we provide an in-depth account of the critical roles of CBP/p300 in regulating the AR and ER signaling pathways and discuss the potential of CBP/p300 inhibitors for treating prostate and breast cancer.

Human papillomavirus E6 and E7: What remains?

Decades of research on the human papillomavirus oncogenes, E6 and E7, have given us huge amounts of data on their expression, functions and structures. We know much about the very many cellular proteins and pathways that they influence in one way or another. However, much of this information is quite discrete, referring to one activity examined under one condition. It is now time to join the dots to try to understand a larger picture: how, where and when do all these interactions occur... and why? Examining these questions will also show how many of the yet obscure cellular processes work together for cellular and tissue homeostasis in health and disease.

Anesthesia Medications and Interaction with Chemotherapeutic Agents

Cancer is now a leading health concern worldwide. In an effort to provide these patients with adequate care, coordination between anesthesiologists and surgeons is crucial. In cancer-related treatment, it is very clear that radio-chemotherapy and medical procedures are important. There are some obstacles to anesthesia when dealing with cancer treatment, such as physiological disturbances, tumor-related symptoms, and toxicity in traditional chemotherapy treatment. Therefore, it is important that a multisystemic, multidisciplinary and patient-centered approach is used to preserve perioperative homeostasis and immune function integrity. Adding adjuvants can help increase patient safety and satisfaction and improve clinical efficacy. Correctly paired anesthetic procedures and medications will reduce perioperative inflammatory and immune changes that could potentially contribute to improved results for future cancer patients. Further research into best practice strategies is required which will help to enhance the acute and long-term effects of cancer care in clinical practice.

Molecular Mechanisms of Antiproliferative Effects of Natural Chalcones

Simple Summary

Despite the important progress in cancer treatment in the past decades, the mortality rates in some types of cancer have not significantly decreased. Therefore, the search for novel anticancer drugs has become a topic of great interest. Chalcones, precursors of flavonoid synthesis in plants, have been documented as natural compounds with pleiotropic biological effects including antiproliferative/anticancer activity. This article focuses on the knowledge on molecular mechanisms of antiproliferative action of chalcones and draws attention to this group of natural compounds that may be of importance in the treatment of cancer disease.

Abstract

Although great progress has been made in the treatment of cancer, the search for new promising molecules with antitumor activity is still one of the greatest challenges in the fight against cancer due to the increasing number of new cases each year. Chalcones (1,3-diphenyl-2-propen-1-one), the precursors of flavonoid synthesis in higher plants, possess a wide spectrum of biological activities including antimicrobial, anti-inflammatory, antioxidant, and anticancer. A plethora of molecular mechanisms of action have been documented, including induction of apoptosis, autophagy, or other types of cell death, cell cycle changes, and modulation of several signaling pathways associated with cell survival or death. In addition, blockade of several steps of angiogenesis and proteasome inhibition has also been documented. This review summarizes the basic molecular mechanisms related to the antiproliferative effects of chalcones, focusing on research articles from the years January 2015–February 2021.

Hyperoxia causes senescence and increases glycolysis in cultured lung epithelial cells

Supplemental oxygen and mechanical ventilation commonly used in premature infants may lead to chronic lung disease of prematurity, which is characterized by arrested alveolar development and dysmorphic vascular development. Hyperoxia is also known to dysregulate p53, senescence, and metabolism. However, whether these changes in p53, senescence, and metabolism are intertwined in response to hyperoxia is still unknown. Given that the lung epithelium is the first cell to encounter ambient oxygen during a hyperoxic exposure, we used mouse lung epithelial cells (MLE‐12), surfactant protein expressing type II cells, to explore whether hyperoxic exposure alters senescence and glycolysis. We measured glycolytic rate using a Seahorse Bioanalyzer assay and senescence using a senescence‐associated β galactosidase activity assay with X‐gal and C₁₂FDG as substrates. We found that hyperoxic exposure caused senescence and increased glycolysis as well as reduced proliferation. This was associated with increased double stranded DNA damage, p53 phosphorylation and nuclear localization. Furthermore, hyperoxia‐induced senescence was p53‐dependent, but not pRB‐dependent, as shown in p53KO and pRBKO cell lines. Despite the inhibitory effects of p53 on glycolysis, we observed that glycolysis was upregulated in hyperoxia‐exposed MLE‐12 cells. This was attributable to a subpopulation of highly glycolytic senescent cells detected by C₁₂FDG sorting. Nevertheless, inhibition of glycolysis did not prevent hyperoxia‐induced senescence. Therapeutic strategies modulating p53 and glycolysis may be useful to mitigate the detrimental consequences of hyperoxia in the neonatal lung.

Suberoylanilide hydroxamic acid enhances the radiosensitivity of lung cancer cells through acetylated wild-type and mutant p53-dependent modulation of mitochondrial apoptosis

Objective

Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, has shown potential as a candidate radiosensitizer for many types of cancers. This study aimed to explore the radiosensitization mechanism of SAHA in lung cancer cells.

Methods

Mutations in p53 were generated by site-directed mutagenesis using polymerase chain reaction. Transfection was performed to generate H1299 cells carrying wild-type or mutant p53. The radiosensitizing enhancement ratio was determined by clonogenic assays. Mitochondrial apoptosis was detected using JC-1 staining and flow cytometry analysis.

Results

Our results showed that SAHA induced radiosensitization in H1299 cells expressing wild-type p53, p53^R175H or p53^P223L, but this enhanced clonogenic cell death was not observed in parental H1299 (p53-null) cells or H1299 cells expressing p53 with K120R, A161T and V274R mutations. In SAHA-sensitized cells, mitochondrial apoptosis was induced following exposure to irradiation. Additionally, we observed that a secondary mutation at K120 (K120R) could eliminate p53-mediated radiosensitization and mitochondrial apoptosis.

Conclusions

The results of this study suggest that wild-type and specific mutant forms of p53 mediate SAHA-induced radiosensitization by regulating mitochondrial apoptosis, and the stabilization of K120 acetylation by SAHA is the molecular basis contributing to radiosensitization in lung cancer cells.

Targeting epigenetic mechanisms to overcome venetoclax resistance

The BH-3 mimetic venetoclax overcomes apoptosis and therapy resistance caused by high expression of BCL2 or loss of BH3-only protein function. Although a promising therapy for hematologic malignancies, increased expression of anti-apoptotic MCL-1 or BCL-XL, as well as other resistance mechanisms prevent a durable response to venetoclax. Recent studies demonstrate that agents targeting epigenetic mechanisms such as DNA methyltransferase inhibitors, histone deacetylase (HDAC) inhibitors, histone methyltransferase EZH2 inhibitors, or bromodomain reader protein inhibitors may disable oncogenic gene expression signatures responsible for venetoclax resistance. Combination therapies including venetoclax and epigenetic therapies are effective in preclinical models and the subject of many current clinical trials. Here we review epigenetic strategies to overcome venetoclax resistance mechanisms in hematologic malignancies.

The PARP Enzyme Family and the Hallmarks of Cancer Part 1. Cell Intrinsic Hallmarks

The 17-member poly (ADP-ribose) polymerase enzyme family, also known as the ADP-ribosyl transferase diphtheria toxin-like (ARTD) enzyme family, contains DNA damage-responsive and nonresponsive members. Only PARP1, 2, 5a, and 5b are capable of modifying their targets with poly ADP-ribose (PAR) polymers; the other PARP family members function as mono-ADP-ribosyl transferases. In the last decade, PARP1 has taken center stage in oncology treatments. New PARP inhibitors (PARPi) have been introduced for the targeted treatment of breast cancer 1 or 2 (BRCA1/2)-deficient ovarian and breast cancers, and this novel therapy represents the prototype of the synthetic lethality paradigm. Much less attention has been paid to other PARPs and their potential roles in cancer biology. In this review, we summarize the roles played by all PARP enzyme family members in six intrinsic hallmarks of cancer: uncontrolled proliferation, evasion of growth suppressors, cell death resistance, genome instability, reprogrammed energy metabolism, and escape from replicative senescence. In a companion paper, we will discuss the roles of PARP enzymes in cancer hallmarks related to cancer-host interactions, including angiogenesis, invasion and metastasis, evasion of the anticancer immune response, and tumor-promoting inflammation. While PARP1 is clearly involved in all ten cancer hallmarks, an increasing body of evidence supports the role of other PARPs in modifying these cancer hallmarks (e.g., PARP5a and 5b in replicative immortality and PARP2 in cancer metabolism). We also highlight controversies, open questions, and discuss prospects of recent developments related to the wide range of roles played by PARPs in cancer biology. Some of the summarized findings may explain resistance to PARPi therapy or highlight novel biological roles of PARPs that can be therapeutically exploited in novel anticancer treatment paradigms.

Genetic Screen in Adult Drosophila Reveals That dCBP Depletion in Glial Cells Mitigates Huntington Disease Pathology through a Foxo-Dependent Pathway

Huntington’s disease (HD) is a progressive and fatal autosomal dominant neurodegenerative disease caused by a CAG repeat expansion in the first exon of the huntingtin gene (HTT). In spite of considerable efforts, there is currently no treatment to stop or delay the disease. Although HTT is expressed ubiquitously, most of our knowledge has been obtained on neurons. More recently, the impact of mutant huntingtin (mHTT) on other cell types, including glial cells, has received growing interest. It is currently unclear whether new pathological pathways could be identified in these cells compared to neurons. To address this question, we performed an in vivo screen for modifiers of mutant huntingtin (HTT-548-128Q) induced pathology in Drosophila adult glial cells and identified several putative therapeutic targets. Among them, we discovered that partial nej/dCBP depletion in these cells was protective, as revealed by strongly increased lifespan and restored locomotor activity. Thus, dCBP promotes the HD pathology in glial cells, in contrast to previous opposite findings in neurons. Further investigations implicated the transcriptional activator Foxo as a critical downstream player in this glial protective pathway. Our data suggest that combinatorial approaches combined to specific tissue targeting may be required to uncover efficient therapies in HD.

Glucagon's Metabolic Action in Health and Disease

Discovered almost simultaneously with insulin, glucagon is a pleiotropic hormone with metabolic action that goes far beyond its classical role to increase blood glucose. Albeit best known for its ability to directly act on the liver to increase de novo glucose production and to inhibit glycogen breakdown, glucagon lowers body weight by decreasing food intake and by increasing metabolic rate. Glucagon further promotes lipolysis and lipid oxidation and has positive chronotropic and inotropic effects in the heart. Interestingly, recent decades have witnessed a remarkable renaissance of glucagon's biology with the acknowledgment that glucagon has pharmacological value beyond its classical use as rescue medication to treat severe hypoglycemia. In this article, we summarize the multifaceted nature of glucagon with a special focus on its hepatic action and discuss the pharmacological potential of either agonizing or antagonizing the glucagon receptor for health and disease. © 2021 American Physiological Society. Compr Physiol 11:1759-1783, 2021.

ARID4B Knockdown Suppresses PI3K/AKT Signaling and Induces Apoptosis in Human Glioma Cells

PURPOSE

Glioblastoma multiforme is a highly malignant primary brain cancer with a poor prognosis. We recently reported that ARID4B could potentially serve as a biomarker associated with poor survival in glioma patients. However, the function of ARID4B in human gliomas remains unclear. The aim of this study is to investigate the molecular cell biology role of ARID4B in human glioma cells.

MATERIALS AND METHODS

Gene Expression Omnibus (GEO) and Human Protein Atlas (HPA) datasets were analyzed for the expression of ARID4B in WHO pathological grading, overall survival and immunohistochemical staining. Using quantitative RT-PCR and Western blotting, those findings were confirmed in normal brain tissue and glioma cell lines. ARID4B knockdown was conducted via lentivirus-based transfection of small hairpin RNA in human glioma cells to investigate cell proliferation, cell cycle, and apoptosis.

RESULTS

In the present study, our analysis of GEO datasets showed that ARID4B mRNA expression is higher in WHO grade IV tumors (n = 81) than in non-tumor control tissue (n = 23, P <0.0001). ARID4B knockdown suppressed glioma cell proliferation and induced G1 phase arrest via the PI3K/AKT pathway. It also increased expression of HDAC1, leading to higher acetyl-p53 and acetyl-H3 levels and reduced glioma cell migration and invasion. These effects were mediated via downregulation of AKT pathway components, including p-mTOR, p-PI3K and p-AKT. ARID4B knockdown also led to downregulation of Cyclin D1, which increased apoptosis in human glioma cells.

CONCLUSION

These findings that ARID4B expression correlates positively with WHO pathologic grading in glioma. ARID4B knockdown suppresses PI3K/AKT signaling and induces apoptosis in human glioma cells. These results suggests that ARID4B acts as an oncogene in human gliomas.

Upregulation of hepatic autophagy under nutritional ketosis

Many of the metabolic effects evoked by the ketogenic diet mimic the actions of fasting and the benefits of the ketogenic diet are often attributed to these similarities. Since fasting is a potent autophagy inductor in vivo and in vitro it has been hypothesized that the ketogenic diet may upregulate autophagy. The aim of the present study was to provide a comprehensive evaluation of the influence of the ketogenic diet on the hepatic autophagy. C57BL/6N male mice were fed with two different ketogenic chows composed of fat of either animal or plant origin for 4 weeks. To gain some insight into the time frame for the induction of autophagy on the ketogenic diet, we performed a short-term experiment in which animals were fed with ketogenic diets for only 24 or 48 h. The results showed that autophagy is upregulated in the livers of animals fed with the ketogenic diet. Moreover, the size of the observed effect was likely dependent on the diet composition. Subsequently, the markers of regulatory pathways that may link ketogenic diet action to autophagy were measured, i.e., the activity of mTORC1, activation of AMPK, and the levels of SIRT1, p53, and FOXO3. Overall, observed treatment-specific effects including the upregulation of SIRT1 and downregulation of FOXO3 and p53. Finally, a GC/MS analysis of the fatty acid composition of animals' livers and the chows was performed in order to obtain an idea about the presence of specific compounds that may shape the effects of ketogenic diets on autophagy.

Emerging roles of SIRT6 in human diseases and its modulators

The biological functions of sirtuin 6 (SIRT6; e.g., deacetylation, defatty-acylation, and mono-ADP-ribosylation) play a pivotal role in regulating lifespan and several fundamental processes controlling aging such as DNA repair, gene expression, and telomeric maintenance. Over the past decades, the aberration of SIRT6 has been extensively observed in diverse life-threatening human diseases. In this comprehensive review, we summarize the critical roles of SIRT6 in the onset and progression of human diseases including cancer, inflammation, diabetes, steatohepatitis, arthritis, cardiovascular diseases, neurodegenerative diseases, viral infections, renal and corneal injuries, as well as the elucidation of the related signaling pathways. Moreover, we discuss the advances in the development of small molecule SIRT6 modulators including activators and inhibitors as well as their pharmacological profiles toward potential therapeutics for SIRT6-mediated diseases.

Transcriptional network constituted of CBP, Ku70, NOX2, and BAX prevents the cell death of necrosis, paraptosis, and apoptosis in human melanoma

CREB-binding protein (CBP) is an acetyltransferase known to play multiple roles in the transcriptions of genes involving oxidative metabolism, cell cycle, DNA damage checkpoints, and cell death. In this study, CBP was found to positively regulate the expression of Ku70, and both CBP and Ku70 were found to negatively regulate the expression of NOX2, therefore, mitigating the intracellular ROS in human melanoma. Knocking down CBP or Ku70 induced necrotic and paraptotic cell death as indicated by high-level intracellular ROS, cytoplasmic vacuolization, and cell cycle arrest in the S phase. In addition, chromosomal condensations were also observed in the cells proceeding necrotic and paraptotic cell death, which was found to be related to the BAX-associated intrinsic pathway of apoptotic cell death, when Ku70 was decreased either by CBP depletion or by Ku70 depletion directly. Our results, therefore, supported the idea that CBP, Ku70, BAX, and NOX2 have formed a transcriptional network in the prevention of cell death of necrosis, paraptosis, and apoptosis in human melanoma.

Loss of SIRT1 in diabetes accelerates DNA damage-induced vascular calcification

AIMS

Vascular calcification is a recognized predictor of cardiovascular risk in the diabetic patient, with DNA damage and accelerated senescence linked to oxidative stress-associated pathological calcification. Having previously shown that systemic SIRT1 is reduced in diabetes, the aim was to establish whether SIRT1 is protective against a DNA damage-induced senescent and calcified phenotype in diabetic vascular smooth muscle cells (vSMCs).

METHODS AND RESULTS

Immunohistochemistry revealed decreased SIRT1 and increased DNA damage marker expression in diabetic calcified arteries compared to non-diabetic and non-calcified controls, strengthened by findings that vSMCs isolated from diabetic patients show elevated DNA damage and senescence, assessed by the Comet assay and telomere length. Hyperglycaemic conditions were used and induced DNA damage and enhanced senescence in vSMCs in vitro. Using H2O2 as a model of oxidative stress-induced DNA damage, pharmacological activation of SIRT1 reduced H2O2 DNA damage-induced calcification, prevented not only DNA damage, as shown by reduced comet tail length, but also decreased yH2AX foci formation, and attenuated calcification. While Ataxia Telanglectasia Mutated (ATM) expression was reduced following DNA damage, in contrast, SIRT1 activation significantly increased ATM expression, phosphorylating both MRE11 and NBS1, thus allowing formation of the MRN complex and increasing activation of the DNA repair pathway.

CONCLUSION

DNA damage-induced calcification is accelerated within a diabetic environment and can be attenuated in vitro by SIRT1 activation. This occurs through enhancement of the MRN repair complex within vSMCs and has therapeutic potential within the diabetic patient.

Role of p53 in transcriptional repression of SVCT2

SVCT2, Sodium-dependent Vitamin C Transporter 2, uniquely transports ascorbic acid (also known as vitamin C and ascorbate) into all types of cells. Vitamin C is an essential nutrient that must be obtained through the diet and plasma levels are tightly regulated by transporter activity. Vitamin C plays an important role in antioxidant defenses and is a cofactor for many enzymes that enable hormone synthesis, oxygen sensing, collagen synthesis and epigenetic pathways. Although SVCT2 has various functions, regulation of its expression/activity remains poorly understood. We found a p53-binding site, within the SVCT2 promoter, using a transcription factor binding-site prediction tool. In this study, we show that p53 can directly repress SVCT2 transcription by binding a proximal- (~-185 to -171 bp) and a distal- (~-1800 to -1787 bp) p53-responsive element (PRE), Chromatin immunoprecipitation assays showed that PRE-bound p53 interacts with the corepressor-histone deacetylase 3 (HDAC3), resulting in deacetylation of histones Ac-H4, at the proximal promoter, resulting in transcriptional silencing of SVCT2. Overall, our data suggests that p53 is a potent transcriptional repressor of SVCT2, a critical transporter of diet-derived ascorbic acid, across the plasma membranes of numerous essential tissue cell types.

Anticancer Therapy with HDAC Inhibitors: Mechanism-Based Combination Strategies and Future Perspectives

The increasing knowledge of molecular drivers of tumorigenesis has fueled targeted cancer therapies based on specific inhibitors. Beyond "classic" oncogene inhibitors, epigenetic therapy is an emerging field. Epigenetic alterations can occur at any time during cancer progression, altering the structure of the chromatin, the accessibility for transcription factors and thus the transcription of genes. They rely on post-translational histone modifications, particularly the acetylation of histone lysine residues, and are determined by the inverse action of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Importantly, HDACs are often aberrantly overexpressed, predominantly leading to the transcriptional repression of tumor suppressor genes. Thus, histone deacetylase inhibitors (HDACis) are powerful drugs, with some already approved for certain hematological cancers. Albeit HDACis show activity in solid tumors as well, further refinement and the development of novel drugs are needed. This review describes the capability of HDACis to influence various pathways and, based on this knowledge, gives a comprehensive overview of various preclinical and clinical studies on solid tumors. A particular focus is placed on strategies for achieving higher efficacy by combination therapies, including phosphoinositide 3-kinase (PI3K)-EGFR inhibitors and hormone- or immunotherapy. This also includes new bifunctional inhibitors as well as novel approaches for HDAC degradation via PROteolysis-TArgeting Chimeras (PROTACs).

HDAC6-selective inhibitors enhance anticancer effects of paclitaxel in ovarian cancer cells

Histone deacetylase 6 (HDAC6)-selective inhibitors are potent anticancer agents that are gaining increasing attention and undergoing various developments. These have been approved or are under clinical trials for use with other anticancer agents, such as pomalidomide, anti-programmed death-ligand 1 antibody and paclitaxel, for various types of cancer, including solid tumors. In the present study, a second generation HDAC6-selective inhibitor, ACY-241 (citarinostat), and a novel inhibitor, A452, exhibited synergistic anticancer effects with paclitaxel in AT-rich interaction domain 1A-mutated ovarian cancer in vitro. Co-treatment of paclitaxel and the two HDAC6 inhibitors synergistically decreased cell growth and viability of TOV-21G. Furthermore, the protein expression levels of pro-apoptotic markers, such as poly(ADP-ribose) polymerase, cleaved caspase-3, Bak and Bax, were increased, whereas the expression levels of anti-apoptotic markers, such as Bcl-xL and Bcl-2, were decreased synergistically. Treatment with all drug combinations increased the portion of apoptotic cells in fluorescence-activated cell sorting analysis. These results demonstrated synergy between paclitaxel and HDAC6-selective inhibitors, providing further impetus for clinical trials of combination therapy using HDAC6-selective inhibitors, not only in ovarian cancer but also in other tumors.

Human umbilical cord-derived mesenchymal stem cell therapy ameliorates lupus through increasing CD4+ T cell senescence via MiR-199a-5p/Sirt1/p53 axis

Rationale: Although human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) transplantation has been proved to be an effective therapeutic approach to treat systemic lupus erythematosus (SLE), the detailed underlying mechanisms are not fully understood. Transferring miRNAs is one mean by which MSCs communicate with surrounding cells. Sirt1 is a NAD-dependent deacetylase that protects against cell senescence by deacetylating p53. Here we aimed to explore whether hUC-MSCs affected senescence of splenic CD4+ T cells through regulating Sirt1/p53 via miRNA in the MRL/lpr lupus mouse model.

Methods: The effects of hUC-MSCs on lupus syndrome and senescence pathways in MRL/lpr mice in vivo and in vitro were determined. The functional roles of miR-199a-5p in splenic CD4+ T cell senescence were studied by miRNA mimic or inhibitor in vitro. MRL/lpr mice were injected with miR-199a-5p agomir to evaluate the effects of miR-199a-5p on splenic CD4+ T cell senescence and disease in vivo.

Results: We showed that hUC-MSCs transplantation ameliorated lupus symptoms and increased senescence of splenic CD4+ T cells through Sirt1/p53 signaling via miR-199a-5p in MRL/lpr mice. Moreover, systemic delivery of miR-199a-5p in MRL/lpr mice increased splenic CD4+ T-cell senescence, mimicking the therapeutic effects of transplanted hUC-MSCs.

Conclusions: We have identified miR-199a-5p as one of the mechanisms employed by hUC-MSCs to alleviate lupus disease associated pathologies in MRL/lpr mice, which is attributable for promoting splenic CD4+ T cell senescence through Sirt1/p53 pathway.

TIP60 in aging and neurodegeneration

Epigenetic modification of chromatin, including histone methylation and acetylation, plays critical roles in eukaryotic cells and has a significant impact on chromatin structure/accessibility, gene regulation and, susceptibility to aging, neurodegenerative disease, cancer, and other age-related diseases. This article reviews the current advances on TIP60/KAT5, a major histone acetyltransferase with diverse functions in eukaryotes, with emphasis on its regulation of autophagy, proteasome-dependent protein turnover, RNA transcription, DNA repair, circadian rhythms, learning and memory, and other neurological functions implicated in aging and neurodegeneration. Moreover, the promising therapeutic potential of TIP60 is discussed to target Alzheimer's disease and other neurological diseases.

Mitoxantrone triggers immunogenic prostate cancer cell death via p53-dependent PERK expression

BACKGROUND

Mitoxantrone (MTX) is a synthetic compound used as a second line chemotherapeutic drug for prostate cancer. It has been reported to trigger immunogenic cell death (ICD) in animal model studies, but the underlying mechanism is not fully understood yet, especially not in prostate cancer cells.

METHODS

ICD was determined by assessing the release of damage-associated molecular patterns (DAMPs) in the prostate cancer-derived cell lines LNCaP, 22RV1 and PC-3. Short hairpin RNAs (shRNAs) were used to knock down target gene expression. Phagocytosis was assessed using a dual labeling technology in dendric cells co-cultured with cancer cells. The PERK gene promoter was cloned for dual luciferase assays. Chromatin immunoprecipitation (ChIP) was used to determine p53 protein-DNA binding activity. Immunocompetent mice and murine RM-1 prostate cancer cells were used for vaccination experiments.

RESULTS

MTX treatment induced typical characteristics of DAMP release, including increased cell surface exposure of calreticulin (CALR), and extracellular release of ATP and high mobility group box-1 (HMGB1) protein. MTX also enhanced phagocytosis by dendritic cells. Moreover, MTX treatment increased eukaryotic initiation factor 2α (eIF2α) S51 phosphorylation, which was reduced when PERK and GCN2 were silenced using shRNAs. In addition, PERK or GCN2 silencing significantly reduced MTX-induced release of DAMPs in vitro and anti-tumor immunity in vivo. MTX treatment also resulted in dendritic cell activation in mice, which was attenuated when PERK or GCN2 were silenced in cancer cells used for vaccination. Further analysis revealed that PERK and GCN2 expression was enhanced by MTX treatment, of which PERK, but not GCN2, was enhanced via a p53-dependent mechanism.

CONCLUSION

MTX triggers ICD by activating eIF2α via PERK/GCN2 upregulation in prostate cancer cells. MTX-induced PERK expression upregulation depends on the p53 pathway, while that of GCN2 requires further investigation.

Knocking down USP39 Inhibits the Growth and Metastasis of Non-Small-Cell Lung Cancer Cells through Activating the p53 Pathway

Ubiquitin-specific protease 39 (USP39), a member of the deubiquitinating enzyme family, has been reported to participate in cytokinesis and metastasis. Previous studies determined that USP39 functions as an oncogenic factor in various types of cancer. Here, we reported that USP39 is frequently overexpressed in human lung cancer tissues and non-small-cell lung cancer (NSCLC) cell lines. USP39 knockdown inhibited the proliferation and colony formation of A549 and HCC827 cells and decreased tumorigenic potential in nude mice. Specifically, knocking down USP39 resulted in cell cycle arrest at G2/M and subsequent apoptosis through the activation of the p53 pathway, including upregulation of p21, cleaved-cas3, cleaved-cas9 and downregulation of CDC2 and CycinB1. Moreover, USP39 knockdown significantly inhibited migration and invasion of A549 and HCC827 cells, also via activation of the p53 pathway, and downregulation of MMP2 and MMP9. Importantly, we verified these results in metastasis models in vivo. Collectively, these results not only establish that USP39 functions as an oncogene in lung cancer, but reveal that USP39 has an essential role in regulating cell proliferation and metastasis via activation of the p53 pathway.

Regulation of p53 by the 14-3-3 protein interaction network: new opportunities for drug discovery in cancer

Most cancers evolve to disable the p53 pathway, a key tumour suppressor mechanism that prevents transformation and malignant cell growth. However, only ~50% exhibit inactivating mutations of p53, while in the rest its activity is suppressed by changes in the proteins that modulate the pathway. Therefore, restoring p53 activity in cells in which it is still wild type is a highly attractive therapeutic strategy that could be effective in many different cancer types. To this end, drugs can be used to stabilise p53 levels by modulating its regulatory pathways. However, despite the emergence of promising strategies, drug development has stalled in clinical trials. The need for alternative approaches has shifted the spotlight to the 14-3-3 family of proteins, which strongly influence p53 stability and transcriptional activity through direct and indirect interactions. Here, we present the first detailed review of how 14-3-3 proteins regulate p53, with special emphasis on the mechanisms involved in their binding to different members of the pathway. This information will be important to design new compounds that can reactivate p53 in cancer cells by influencing protein-protein interactions. The intricate relationship between the 14-3-3 isoforms and the p53 pathway suggests that many potential drug targets for p53 reactivation could be identified and exploited to design novel antineoplastic therapies with a wide range of applications.

Autophagic feedback-mediated degradation of IKKα requires CHK1- and p300/CBP-dependent acetylation of p53

In our previous report, we demonstrated that one of the catalytic subunits of the IκB kinase (IKK) complex, IKKα (encoded by CHUK), performs an NF-κB-independent cytoprotective role in human hepatoma cells under the treatment of the anti-tumor therapeutic reagent arsenite. IKKα triggers its own degradation, as a feedback loop, by activating p53-dependent autophagy, and therefore contributes substantially to hepatoma cell apoptosis induced by arsenite. Interestingly, IKKα is unable to interact with p53 directly but plays a critical role in mediating p53 phosphorylation (at Ser15) by promoting CHK1 activation and CHK1-p53 complex formation. In the current study, we found that p53 acetylation (at Lys373 and/or Lys382) was also critical for the induction of autophagy and the autophagic degradation of IKKα during the arsenite response. Furthermore, IKKα was involved in p53 acetylation through interaction with the acetyltransferases for p53, p300 (also known as EP300) and CBP (also known as CREBBP) (collectively p300/CBP), inducing CHK1-dependent p300/CBP activation and promoting p300-p53 or CBP-p53 complex formation. Therefore, taken together with the previous report, we conclude that both IKKα- and CHK1-dependent p53 phosphorylation and acetylation contribute to mediating selective autophagy feedback degradation of IKKα during the arsenite-induced proapoptotic responses.

Activation of toll like receptor 4 (TLR4) promotes cardiomyocyte apoptosis through SIRT2 dependent p53 deacetylation

Cardiomyocyte inflammation followed by apoptosis and fibrosis is an important mediator for development and progression of heart failure. Activation of toll-like receptor 4 (TLR4), an important regulator of inflammation, causes the progression of cardiac hypertrophy and injury. However, the precise mechanism of TLR4-mediated adverse cardiac outcomes is still elusive. The present study was designed to find the role of TLR4 in cardiac fibrosis and apoptosis, and molecular mechanism thereof. Rats were treated with TLR4 agonist (LPS 12.5 μg/kg/day) through osmotic pump for 14 days. To simulate the condition in vitro, H9c2 cells were treated with LPS (1 μg/ml). Similarly, H9c2 cells were transfected with TLR4 and SIRT2 c-DNA clone for overexpression. Myocardial oxidative stress, inflammation, fibrosis and mitochondrial parameters were evaluated both in vitro and in vivo. Cardiac inflammation after LPS treatment was confirmed by increased TNF-α and IL-6 expression in rat heart. There was a marked increase in oxidative stress as observed by increased TBARS and decreased endogenous antioxidants (GSH and catalase), along with mitochondrial dysfunction as measured by mitochondrial complex activity in LPS-treated rat hearts. Histopathological examination showed the presence of cardiac fibrosis after LPS treatment. Protein expression of nuclear p53 and cleaved caspase-7/caspase-9 was significantly increased in LPS treated heart. Similar to in vivo study, nuclear translocation of p53, mitochondrial dysfunction and cellular apoptosis were observed in H9c2 cells treated with LPS. Our data also indicate that decreased expression of SIRT2 was associated with increased acetylation of p53 after LPS treatment. In conclusion, TLR4 activation in rats promotes cardiac inflammation, mitochondrial dysfunction, apoptosis and fibrosis. p53 and caspase 7/caspase 9 were found to play an important role in TLR4-mediated apoptosis. Our data suggest that, reducing TLR4 mediated fibrosis and apoptosis could be a novel approach in the treatment of heart failure, keeping in the view the major role played by TLR4 in cardiac inflammation.

Histone deacetylase inhibitor MPT0B291 suppresses Glioma Growth in vitro and in vivo partially through acetylation of p53

Background: Histone deacetylase (HDAC) inhibitors have emerged as a new class of anti-tumor agents for various types of tumors, including glioblastoma.

Methods and results: We found that a novel HDAC inhibitor, MPT0B291, significantly reduced the cell viability and increased cell death of human and rat glioma cell lines, but not in normal astrocytes. We also demonstrated that MPT0B291 suppressed proliferation by inducing G1 phase cell cycle arrest and increased apoptosis in human and rat glioma cell lines by flow cytometry and immunocytochemistry. We further investigated the anti-tumor effects of MPT0B291 in xenograft (mouse) and allograft (rat) models. The IVIS200 images and histological analysis indicated MPT0B291 (25 mg/kg, p. o.) reduced tumor volume. Mechanistically, MPT0B291 increased phosphorylation and acetylation/activation of p53 and increased mRNA levels of the apoptosis related genes PUMA, Bax, and Apaf1 as well as increased protein level of PUMA, Apaf1 in C6 cell line. The expression of cell cycle related gene p21 was also increased and Cdk2, Cdk4 were decreased by MPT0B291.

Conclusion: Our study highlights the anti-tumor efficacy of a novel compound MPT0B291 on glioma growth.

Protein acetylation and deacetylation: An important regulatory modification in gene transcription (Review)

Cells primarily rely on proteins to perform the majority of their physiological functions, and the function of proteins is regulated by post-translational modifications (PTMs). The acetylation of proteins is a dynamic and highly specific PTM, which has an important influence on the functions of proteins, such as gene transcription and signal transduction. The acetylation of proteins is primarily dependent on lysine acetyltransferases and lysine deacetylases. In recent years, due to the widespread use of mass spectrometry and the emergence of new technologies, such as protein chips, studies on protein acetylation have been further developed. Compared with histone acetylation, acetylation of non-histone proteins has gradually become the focus of research due to its important regulatory mechanisms and wide range of applications. The discovery of specific protein acetylation sites using bioinformatic tools can greatly aid the understanding of the underlying mechanisms of protein acetylation involved in related physiological and pathological processes.

Murine Cytomegalovirus M25 Proteins Sequester the Tumor Suppressor Protein p53 in Nuclear Accumulations

To ensure productive infection, herpesviruses utilize tegument proteins and nonstructural regulatory proteins to counteract cellular defense mechanisms and to reprogram cellular pathways. The M25 proteins of mouse cytomegalovirus (MCMV) belong to the betaherpesvirus UL25 gene family that encodes viral proteins implicated with regulatory functions. Through affinity purification and mass spectrometric analysis, we discovered the tumor suppressor protein p53 as a host factor interacting with the M25 proteins. M25-p53 interaction in infected and transfected cells was confirmed by coimmunoprecipitation. Moreover, the proteins colocalized in nuclear dot-like structures upon both infection and inducible expression of the two M25 isoforms. p53 accumulated in wild-type MCMV-infected cells, while this did not occur upon infection with a mutant lacking the M25 gene. Both M25 proteins were able to mediate the effect, identifying them as the first CMV proteins responsible for p53 accumulation during infection. Interaction with M25 proteins led to substantial prolongation of the half-life of p53. In contrast to the higher abundance of the p53 protein in wild-type MCMV-infected cells, the transcript levels of the prominent p53 target genes Cdkn1a and Mdm2 were diminished compared to cells infected with the ΔM25 mutant, and this was associated with reduced binding of p53 to responsive elements within the respective promoters. Notably, the productivity of the M25 deletion mutant was partially rescued on p53-negative fibroblasts. We propose that the MCMV M25 proteins sequester p53 molecules in the nucleus of infected cells, reducing their availability for activating a subset of p53-regulated genes, thereby dampening the antiviral role of p53.IMPORTANCE Host cells use a number of factors to defend against viral infection. Viruses are, however, in an arms race with their host cells to overcome these defense mechanisms. The tumor suppressor protein p53 is an important sensor of cell stress induced by oncogenic insults or viral infections, which upon activation induces various pathways to ensure the integrity of cells. Viruses have to counteract many functions of p53, but complex DNA viruses such as cytomegaloviruses may also utilize some p53 functions for their own benefit. In this study, we discovered that the M25 proteins of mouse cytomegalovirus interact with p53 and mediate its accumulation during infection. Interaction with the M25 proteins sequesters p53 molecules in nuclear dot-like structures, limiting their availability for activation of a subset of p53-regulated target genes. Understanding the interaction between viral proteins and p53 may allow to develop new therapeutic strategies against cytomegalovirus and other viruses.

Reversal of diet-induced hepatic steatosis by peripheral CB1 receptor blockade in mice is p53/miRNA-22/SIRT1/PPARα dependent

OBJECTIVE

The endocannabinoid (eCB) system is increasingly recognized as being crucially important in obesity-related hepatic steatosis. By activating the hepatic cannabinoid-1 receptor (CB₁R), eCBs modulate lipogenesis and fatty acid oxidation. However, the underlying molecular mechanisms are largely unknown.

METHODS

We combined unbiased bioinformatics techniques, mouse genetic manipulations, multiple pharmacological, molecular, and cellular biology approaches, and genomic sequencing to systematically decipher the role of the hepatic CB₁R in modulating fat utilization in the liver and explored the downstream molecular mechanisms.

RESULTS

Using an unbiased normalized phylogenetic profiling analysis, we found that the CB₁R evolutionarily coevolves with peroxisome proliferator-activated receptor-alpha (PPARα), a key regulator of hepatic lipid metabolism. In diet-induced obese (DIO) mice, peripheral CB₁R blockade (using AM6545) induced the reversal of hepatic steatosis and improved liver injury in WT, but not in PPARα^-/- mice. The antisteatotic effect mediated by AM6545 in WT DIO mice was accompanied by increased hepatic expression and activity of PPARα as well as elevated hepatic levels of the PPARα-activating eCB-like molecules oleoylethanolamide and palmitoylethanolamide. Moreover, AM6545 was unable to rescue hepatic steatosis in DIO mice lacking liver sirtuin 1 (SIRT1), an upstream regulator of PPARα. Both of these signaling molecules were modulated by the CB₁R as measured in hepatocytes exposed to lipotoxic conditions or treated with CB₁R agonists in the absence/presence of AM6545. Furthermore, using microRNA transcriptomic profiling, we found that the CB₁R regulated the hepatic expression, acetylation, and transcriptional activity of p53, resulting in the enhanced expression of miR-22, which was found to specifically target SIRT1 and PPARα.

CONCLUSIONS

We provide strong evidence for a functional role of the p53/miR-22/SIRT1/PPARα signaling pathway in potentially mediating the antisteatotic effect of peripherally restricted CB₁R blockade.

Exploring the p53 connection of cervical cancer pathogenesis involving north-east Indian patients

BACKGROUND

As per WHO, Cervical cancer (CaCx) is a global issue, being the fourth common cancer in women with incidence rate of 13.1 per 1 lakh women globally and accounting for 311000 deaths in the year 2018 itself globally. The molecular pathogenesis in Human papillomavirus (HPV) infected cases is inconclusive. The detection of molecular factors leading to progression of CaCx can be important in the diagnosis and management of the disease. p53 a known tumor suppressor gene having a regulative role in cell cycle has been highlighted as key factor in the prevention of cancer but its significance in CaCx cases has been variably documented. The present study therefore targeted to evaluate the significance of p53 profile in CaCx cases in ethnically distinct northeast Indian population.

METHODS

Blood and Tissue samples (N = 85) of cervical cancer patients were collected and screening for HPV was performed using PCR. Thereafter the differential mRNA expression(qPCR), Immunohistochemistry, Mutation (PCR direct sequencing method) of p53 was studied. Further p53 epigenetic profiling was done by Methylation specific PCR (MS-PCR) and western blotting by using p53 acetylation specific antibodies.

RESULTS

Our findings revealed that the downregulation of p53 was associated with the progression of disease and the variation in downregulation based on p53 polymorphism was observed. Further hypermethylation and deacetylation of p53 was also found to be associated with the pathogenesis of CaCx. The downregulated expression and hypermethylation of p53 in lower grade of CaCx, together established its association with the progression of CaCx from lower to severe grade.

CONCLUSION

Therefore, in CaCx patients of northeast Indian population, malfunctioning of p53 is found to have significant role in cervical cancer progression.

Antioxidant Modulation of mTOR and Sirtuin Pathways in Age-Related Neurodegenerative Diseases

In the human body, cell division and metabolism are expected to transpire uneventfully for approximately 25 years. Then, secondary metabolism and cell damage products accumulate, and ageing phenotypes are acquired, causing the progression of disease. Among these age-related diseases, neurodegenerative diseases have attracted considerable attention because of their irreversibility, the absence of effective treatment and their relationship with social and economic pressures. Mechanistic (formerly mammalian) target of rapamycin (mTOR), sirtuin (SIRT) and insulin/insulin growth factor 1 (IGF1) signalling pathways are among the most important pathways in ageing-associated conditions, such as neurodegeneration. These longevity-related pathways are associated with a diversity of various processes, including metabolism, cognition, stress reaction and brain plasticity. In this review, we discuss the roles of sirtuin and mTOR in ageing and neurodegeneration, with an emphasis on their regulation of autophagy, apoptosis and mitochondrial energy metabolism. The intervention of neurodegeneration using potential antioxidants, including vitamins, phytochemicals, resveratrol, herbals, curcumin, coenzyme Q10 and minerals, specifically aimed at retaining mitochondrial function in the treatment of Alzheimer's disease, Parkinson's disease and Huntington's disease is highlighted.

KSHV LANA acetylation-selective acidic domain reader sequence mediates virus persistence

Viruses modulate biochemical cellular pathways to permit infection. A recently described mechanism mediates selective protein interactions between acidic domain readers and unacetylated, lysine-rich regions, opposite of bromodomain function. Kaposi´s sarcoma (KS)-associated herpesvirus (KSHV) is tightly linked with KS, primary effusion lymphoma, and multicentric Castleman's disease. KSHV latently infects cells, and its genome persists as a multicopy, extrachromosomal episome. During latency, KSHV expresses a small subset of genes, including the latency-associated nuclear antigen (LANA), which mediates viral episome persistence. Here we show that LANA contains two tandem, partially overlapping, acidic domain sequences homologous to the SET oncoprotein acidic domain reader. This domain selectively interacts with unacetylated p53, as evidenced by reduced LANA interaction after overexpression of CBP, which acetylates p53, or with an acetylation mimicking carboxyl-terminal domain p53 mutant. Conversely, the interaction of LANA with an acetylation-deficient p53 mutant is enhanced. Significantly, KSHV LANA mutants lacking the acidic domain reader sequence are deficient for establishment of latency and persistent infection. This deficiency was confirmed under physiological conditions, on infection of mice with a murine gammaherpesvirus 68 chimera expressing LANA, where the virus was highly deficient in establishing latent infection in germinal center B cells. Therefore, LANA's acidic domain reader is critical for viral latency. These results implicate an acetylation-dependent mechanism mediating KSHV persistence and expand the role of acidic domain readers.

CSAG2 is a cancer-specific activator of SIRT1

SIRT1 is a NAD⁺ -dependent deacetylase that controls key metabolic and signaling pathways, including inactivating the p53 tumor suppressor. However, the mechanisms controlling SIRT1 enzymatic activity in the context of cancer are unclear. Here, we show that the previously undescribed CSAG2 protein is a direct activator of SIRT1. CSAG2 is normally restricted to expression in the male germline but is frequently re-activated in cancers. CSAG2 is necessary for cancer cell proliferation and promotes tumorigenesis in vivo. Biochemical studies revealed that CSAG2 directly binds to and stimulates SIRT1 activity toward multiple substrates. Importantly, CSAG2 enhances SIRT1-mediated deacetylation of p53, inhibits p53 transcriptional activity, and improves cell survival in response to genotoxic stress. Mechanistically, CSAG2 binds SIRT1 catalytic domain and promotes activity independent of altering substrate affinity. Together, our results identify a previously undescribed mechanism for SIRT1 activation in cancer cells and highlight unanticipated approaches to therapeutically modulate SIRT1.

USP7 Is a Master Regulator of Genome Stability

Genetic alterations, including DNA mutations and chromosomal abnormalities, are primary drivers of tumor formation and cancer progression. These alterations can endow cells with a selective growth advantage, enabling cancers to evade cell death, proliferation limits, and immune checkpoints, to metastasize throughout the body. Genetic alterations occur due to failures of the genome stability pathways. In many cancers, the rate of alteration is further accelerated by the deregulation of these processes. The deubiquitinating enzyme ubiquitin specific protease 7 (USP7) has recently emerged as a key regulator of ubiquitination in the genome stability pathways. USP7 is also deregulated in many cancer types, where deviances in USP7 protein levels are correlated with cancer progression. In this work, we review the increasingly evident role of USP7 in maintaining genome stability, the links between USP7 deregulation and cancer progression, as well as the rationale of targeting USP7 in cancer therapy.

Calliandra portoricensis ameliorates ovarian and uterine oxido-inflammatory responses in N-methyl-N-nitrosourea and benzo[a]pyrene-treated rats

IMPACT STATEMENT

Infertility resulting from reproductive impairment is traumatic in families. Exposure to chemicals may play insidious roles not easily connected to infertility. We examined benzo[a]pyrene (BaP), and N-methyl nitrosourea (NMU)-induced ovarian and uterine toxicity and the role of Calliandra portoricensis in mitigating toxicity. In a bid to illuminate folk medical claims cloaked in mystery, unearthing lost knowledge, advance natural chemopreventive agents, and report new evidence lacking in the literature attributed to CP. Although CP is known to exhibit anticonvulsant, antidiarrheal, antipyretic, antirheumatic, and analgesic effects in humans, its possible roles for mitigating toxicity stemming from inadvertent chemical exposures are reported here. Our findings affirm and further show that CP abates toxic response incumbent on oxidative damage and inflammatory responses associated with NMU and BaP exposure. Development of phytochemical derived from CP may serve as a potential natural therapy against chemical toxicities in individuals inadvertently exposed, and promote human health and reproductive satiety.

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.

Mdm2-mediated neddylation of pVHL blocks the induction of antiangiogenic factors

Mutations in the tumor suppressor TP53 are rare in renal cell carcinomas. p53 is a key factor for inducing antiangiogenic genes and RCC are highly vascularized, which suggests that p53 is inactive in these tumors. One regulator of p53 is the Mdm2 oncogene, which is correlated with high-grade, metastatic tumors. However, the sole activity of Mdm2 is not just to regulate p53, but it can also function independent of p53 to regulate the early stages of metastasis. Here, we report that the oncoprotein Mdm2 can bind directly to the tumor suppressor VHL, and conjugate nedd8 to VHL within a region that is important for the p53-VHL interaction. Nedd8 conjugated VHL is unable to bind to p53 thereby preventing the induction of antiangiogenic factors. These results highlight a previously unknown oncogenic function of Mdm2 during the progression of cancer to promote angiogenesis through the regulation of VHL. Thus, the Mdm2-VHL interaction represents a pathway that impacts tumor angiogenesis.

Cloning of Hynobius lichenatus (Tohoku hynobiid salamander) p53 and analysis of its expression in response to radiation

Background

Caudata species such as salamanders are easily affected by environmental changes, which can drastically reduce their population. The effects of acute X-rays and chronic γ-irradiation on Hynobius lichenatus, the Japanese Tohoku hynobiid salamander, are known. However, the expression of radiation-inducible genes, such as the DNA-damage checkpoint response gene p53, has not been analyzed in H. lichenatus. This has not occurred because there is no established method for mRNA quantification in H. lichenatus due to a lack of information on available nucleotide sequences corresponding to both radiation-inducible genes and endogenous control genes such as ACTB (β-actin).

Results

In this study, we aimed to evaluate the effects of radiation on gene expression in H. lichenatus. Using RNA extracted from irradiated salamanders, we performed rapid amplification of cDNA ends (RACE) and cloned H. lichenatus β-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and p53. We confirmed that the cloned cDNAs were able to synthesize salamander proteins by western blotting after transfection into cultured HEK293 cells. Proliferation assays using HEK293 cells stably expressing H. lichenatus p53 protein showed that this protein has antiproliferative effects, similar to that of mammalian p53. Furthermore, RT-qPCR analysis using gene-specific primers revealed that p53 mRNA expression in H. lichenatus was upregulated upon exposure to radiation.

Conclusion

Our results suggest that H. lichenatus p53 protein take an important role in regulating the cellular responses to various stimuli as mammalian p53 does. Furthermore, our study provides novel data to select appropriate primers to analyze internal control mRNA expression in H. lichenatus and to evaluate p53 expression as a marker of radiation and environmental stimuli.

Revisiting allostery in CREB-binding protein (CBP) using residue-based interaction energy

CREB-binding protein (CBP) is a multi-subunit scaffold protein complex in transcription regulation process, binding and interacting with ligands such as mixed-lineage leukemia (MLL) and c-Myb allosterically. Here in this study, we have revisited the concept of allostery in CBP via residue-based interaction energy calculation based on molecular dynamics (MD) simulations. To this end, we conducted MD simulations of KIX:MLL:c-Myb ternary complex, its binary components and kinase-inducible domain (KID) interacting domain (KIX) backbone. Interaction energy profiles and cross correlation analysis were performed and the results indicated that KIX:MLL and KIX:c-Myb:MLL complexes demonstrate significant similarities according to both analysis methods. Two regions in the KIX backbone were apparent from the interaction energy and cross correlation maps that hold a key to allostery phenomena observed in CBP. While one of these regions are related to the ligand binding residues, the other comprises of L₁₂-G₂ loop and α₃ helix regions that have been found to have a significant role in allosteric signal propagation. All in all, residue-based interaction energy calculation method is demonstrated to be a valuable calculation technique for the detection of allosteric signal propagation and ligand interaction regions.

Tau affects P53 function and cell fate during the DNA damage response

Cells are constantly exposed to DNA damaging insults. To protect the organism, cells developed a complex molecular response coordinated by P53, the master regulator of DNA repair, cell division and cell fate. DNA damage accumulation and abnormal cell fate decision may represent a pathomechanism shared by aging-associated disorders such as cancer and neurodegeneration. Here, we examined this hypothesis in the context of tauopathies, a neurodegenerative disorder group characterized by Tau protein deposition. For this, the response to an acute DNA damage was studied in neuroblastoma cells with depleted Tau, as a model of loss-of-function. Under these conditions, altered P53 stability and activity result in reduced cell death and increased cell senescence. This newly discovered function of Tau involves abnormal modification of P53 and its E3 ubiquitin ligase MDM2. Considering the medical need with vast social implications caused by neurodegeneration and cancer, our study may reform our approach to disease-modifying therapies.

Martina Sola, Claudia Magrin et al. study the relation between Tau and P53 in response to DNA damage. They uncover an important role for Tau in regulating the stability, and activity of P53 post translationally. Their findings provide insights to potentially common pathways in neurodegenerative disease and cancer.

Histone acetyltransferase promotes fluoride toxicity in LS8 cells

Previously we demonstrated that fluoride increased acetylated-p53 (Ac-p53) in LS8 cells that are derived from mouse enamel organ epithelia and in rodent ameloblasts. However, how p53 is acetylated by fluoride and how the p53 upstream molecular pathway responds to fluoride is not well characterized. Here we demonstrate that fluoride activates histone acetyltransferases (HATs) including CBP, p300, PCAF and Tip60 to acetylate p53. HAT activity is regulated by post-translational modifications such as acetylation and phosphorylation. HAT proteins and their post-translational modifications (p300, Acetyl-p300, CBP, Acetyl-CBP, Tip60 and phospho-Tip60) were analyzed by Western blots. p53-HAT binding was detected by co-immunoprecipitation (co-IP). Cell growth inhibition was analyzed by MTT assays. LS8 cells were treated with NaF with/without HAT inhibitors MG149 (Tip60 inhibitor) and Anacardic Acid (AA; inhibits p300/CBP and PCAF). MG149 or AA was added 1 h prior to NaF treatment. Co-IP results showed that NaF increased p53-CBP binding and p53-PCAF binding. NaF increased active Acetyl-p300, Acetyl-CBP and phospho-Tip60 levels, suggesting that fluoride activates these HATs. Fluoride-induced phospho-Tip60 was decreased by MG149. MG149 or AA treatment reversed fluoride-induced cell growth inhibition at 24 h. MG149 or AA treatment decreased fluoride-induced p53 acetylation to inhibit caspase-3 cleavage, DNA damage marker γH2AX expression and cytochrome-c release into the cytosol. These results suggest that acetylation of p53 by HATs contributes, at least in part, to fluoride-induced toxicity in LS8 cells via cell growth inhibition, apoptosis, DNA damage and mitochondrial damage. Modulation of HAT activity may, therefore, be a potential therapeutic target to mitigate fluoride toxicity in ameloblasts.

Sirt1 is regulated by miR-135a and involved in DNA damage repair during mouse cellular reprogramming

Sirt1 facilitates the reprogramming of mouse somatic cells into induced pluripotent stem cells (iPSCs). It is regulated by micro-RNA and reported to be a target of miR-135a. However, their relationship and roles on cellular reprogramming remain unknown. In this study, we found negative correlations between miR-135a and Sirt1 during mouse embryonic stem cells differentiation and mouse embryonic fibroblasts reprogramming. We further found that the reprogramming efficiency was reduced by the overexpression of miR-135a precursor but induced by the miR-135a inhibitor. Co-immunoprecipitation followed by mass spectrometry identified 21 SIRT1 interacting proteins including KU70 and WRN, which were highly enriched for DNA damage repair. In accordance, Sirt1 activator resveratrol reduced DNA damage during the reprogramming process. Wrn was regulated by miR-135a and resveratrol partly rescued the impaired reprogramming efficiency induced by Wrn knockdown. This study showed Sirt1, being partly regulated by miR-135a, bound proteins involved in DNA damage repair and enhanced the iPSCs production.

Interleukin-1α associates with the tumor suppressor p53 following DNA damage

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

Oral and intestinal bacterial exotoxins: Potential linked to carcinogenesis

Growing evidence suggests that imbalances in resident microbes (dysbiosis) can promote chronic inflammation, immune-subversion, and production of carcinogenic metabolites, thus leading to neoplasia. Yet, evidence to support a direct link of individual bacteria species to human sporadic cancer is still limited. This chapter focuses on several emerging bacterial toxins that have recently been characterized for their potential oncogenic properties toward human orodigestive cancer and the presence of which in human tissue samples has been documented. These include cytolethal distending toxins produced by various members of gamma and epsilon Proteobacteria, Dentilisin from mammalian oral Treponema, Pasteurella multocida toxin, two Fusobacterial toxins, FadA and Fap2, Bacteroides fragilis toxin, colibactin, cytotoxic necrotizing factors and α-hemolysin from Escherichia coli, and Salmonella enterica AvrA. It was clear that these bacterial toxins have biological activities to induce several hallmarks of cancer. Some toxins directly interact with DNA or chromosomes leading to their breakdowns, causing mutations and genome instability, and others modulate cell proliferation, replication and death and facilitate immune evasion and tumor invasion, prying specific oncogene and tumor suppressor pathways, such as p53 and β-catenin/Wnt. In addition, most bacterial toxins control tumor-promoting inflammation in complex and diverse mechanisms. Despite growing laboratory evidence to support oncogenic potential of selected bacterial toxins, we need more direct evidence from human studies and mechanistic data from physiologically relevant experimental animal models, which can reflect chronic infection in vivo, as well as take bacterial-bacterial interactions among microbiome into consideration.

Pharmacological Effects and Toxicogenetic Impacts of Omeprazole: Genomic Instability and Cancer

Omeprazole (OME) is commonly used to treat gastrointestinal disorders. However, long-term use of OME can increase the risk of gastric cancer. We aimed to characterize the pharmacological effects of OME and to correlate its adverse effects and toxicogenetic risks to the genomic instability mechanisms and cancer-based on database reports. Thus, a search (till Aug 2019) was made in the PubMed, Scopus, and ScienceDirect with relevant keywords. Based on the study objective, we included 80 clinical reports, forty-six in vitro, and 76 in vivo studies. While controversial, the findings suggest that long-term use of OME (5 to 40 mg/kg) can induce genomic instability. On the other hand, OME-mediated protective effects are well reported and related to proton pump blockade and anti-inflammatory activity through an increase in gastric flow, anti-inflammatory markers (COX-2 and interleukins) and antiapoptotic markers (caspases and BCL-2), glycoprotein expression, and neutrophil infiltration reduction. The reported adverse and toxic effects, especially in clinical studies, were atrophic gastritis, cobalamin deficiencies, homeostasis disorders, polyp development, hepatotoxicity, cytotoxicity, and genotoxicity. This study highlights that OME may induce genomic instability and increase the risk of certain types of cancer. Therefore, adequate precautions should be taken, especially in its long-term therapeutic strategies and self-medication practices.

Ginkgo biloba Prevents Oxidative Stress-Induced Apoptosis Blocking p53 Activation in Neuroblastoma Cells

Oxidative stress has been associated to neuronal cell loss in neurodegenerative diseases. Neurons are post-mitotic cells that are very sensitive to oxidative stress—especially considering their limited capacity to be replaced. Therefore, reduction of oxidative stress, and inhibiting apoptosis, will potentially prevent neurodegeneration. In this study, we investigated the neuroprotective effect of Ginkgo biloba extract (EGb 761) against H₂O₂ induced apoptosis in SK-N-BE neuroblastoma cells. We analysed the molecular signalling pathway involved in the apoptotic cell death. H₂O₂ induced an increased acetylation of p53 lysine 382, a reduction in mitochondrial membrane potential, an increased BAX/Bcl-2 ratio and consequently increased Poly (ADP-ribose) polymerase (PARP) cleavage. All these effects were blocked by EGb 761 treatment. Thus, EGb 761, acting as intracellular antioxidant, protects neuroblastoma cells against activation of p53 mediated pathway and intrinsic mitochondrial apoptosis. Our results suggest that EGb 761, protecting against oxidative-stress induced apoptotic cell death, could potentially be used as nutraceutical for the prevention and treatment of neurodegenerative diseases.

Sphingolipids and the link between alcohol and cancer

Epidemiological evidence underscores alcohol consumption as a strong risk factor for multiple cancer types, with liver cancer being most commonly associated with alcohol intake. While mechanisms linking alcohol consumption to malignant tumor development are not fully understood, the likely players in ethanol-induced carcinogenesis are genotoxic stress caused by formation of acetaldehyde, increased oxidative stress, and altered nutrient metabolism, including the impairment of methyl transfer reactions. Alterations of sphingolipid metabolism and associated signaling pathways are another potential link between ethanol and cancer development. In particular, ceramides are involved in the regulation of cellular proliferation, differentiation, senescence, and apoptosis and are known to function as important regulators of malignant transformation as well as tumor progression. However, to date, the cross-talk between ceramides and alcohol in cancer disease is largely an open question and only limited data are available on this subject. Most studies linking ceramide to cancer considered liver steatosis as the underlying mechanism, which is not surprising taking into consideration that ceramide pathways are an integral part of the overall lipid metabolism. This review summarizes the latest studies pointing to ceramide as an important mediator of cancer-promoting effects of chronic alcohol consumption and underscores the necessity of understanding the role of sphingolipids and lipid signaling in response to alcohol in order to prevent and/or successfully manage diseases caused by alcohol.

Role of RUNX Family Transcription Factors in DNA Damage Response

Cells are constantly exposed to endogenous and exogenous stresses that can result in DNA damage. In response, they have evolved complex pathways to maintain genomic integrity. RUNX family transcription factors (RUNX1, RUNX2, and RUNX3 in mammals) are master regulators of development and differentiation, and are frequently dysregulated in cancer. A growing body of research also implicates RUNX proteins as regulators of the DNA damage response, often acting in conjunction with the p53 and Fanconi anemia pathways. In this review, we discuss the functional role and mechanisms involved in RUNX factor mediated response to DNA damage and other cellular stresses. We highlight the impact of these new findings on our understanding of cancer predisposition associated with RUNX factor dysregulation and their implications for designing novel approaches to prevent cancer formation in affected individuals.