P53 Tumor Suppressor Research Articles

Dynamic modulation of IRE1α-XBP1 signaling by adenovirus.

The abundant production of foreign proteins and nucleic acids during viral infection elicits a variety of stress responses in host cells. Viral proteins that accumulate in the endoplasmic reticulum (ER) can trigger the unfolded protein response (UPR), a coordinated signaling program that culminates in the expression of downstream genes that collectively restore protein homeostasis. The model pathogen adenovirus serotype 5 (HAdV5) activates the UPR via the signaling axis formed by inositol-requiring enzyme type 1 (IRE1α) and the X-box binding protein 1 (XBP1), a transcription factor required for immune function. Recent studies have suggested that IRE1α-XBP1 activity supports adenovirus replication. Here, we show that HAdV5 exerted opposing effects on IRE1α and XBP1. IRE1α was activated in response to HAdV5 but the production of the XBP1 isoform, XBP1s, was post-transcriptionally blocked. The tumor suppressor p53, which is eliminated by HAdV5 after infection, inhibited IRE1α activation. The de-repression of IRE1α following the degradation of p53 conceivably reflects a novel antiviral mechanism, which HAdV5 ultimately evades by suppressing XBP1s. Our findings highlight the defective antiviral defenses in cancer cells and further illustrate the opposing mechanisms used by adenoviruses and their host cells to exert control over the UPR, a critical determinant of cell fate.

Design, Synthesis and Preliminary In‐Vitro Activity of 6‐Hydroxyalkyl β‐Carboline Derivatives for the Development of Drug Conjugates Targeting MDM2

AbstractThe mouse‐double‐minute‐2 (MDM2) protein, the main downregulator of the tumor suppressor p53 protein, represents a promising target for the development of novel anticancer therapies. However, the lack of selectivity and poor effectiveness in tumors bearing mutated‐p53 impaired the approval of several MDM2 inhibitors for the market. In this context, the possibility of generating drug‐conjugates within a MDM2 inhibitor is a growing research area aimed to overcome these drawbacks. Considering the promising MDM2 inhibition by the β‐carboline‐based 1, in this work we explored the introduction of a new functionalization on it for a future conjugation while preserving its anticancer properties. Based on preliminary docking studies, we synthesized derivatives 2 a–d having linear hydroxyalkyl chains with different lengths at the 6‐position of the β‐carboline core, which effectively preserved the submicromolar IC50 on wild‐type‐p53‐U87MG glioblastoma cell line observed with 1. Candidates 2 a, d showed the functionalization was tolerated with respect of bioactivity also on mutated‐p53‐U138MG glioblastoma cell line, and their hydroxyl groups proved to be easily accessible when coupled to 4‐pentynoic‐N,N’‐dimethylethylenediamine affording derivatives 10 a, d with high yields. In summary, our results led to generating novel 6‐hydroxyalkyl‐β‐carboline compounds displaying a suitable hydroxyl‐site useful to improve the efficacy and/or the tumor specificity of 1 through conjugation strategies.

Molecular dynamics-based computational investigations on the influence of tumor suppressor p53 binding protein against other proteins/peptides

The tumor-suppressing p-53 binding protein is a crucial protein that is involved in the prevention of cancer via its regulatory effect on a number of cellular processes. Recent evidence indicates that it interacts with a number of other proteins involved in cancer in ways that are not fully understood. An understanding of such interactions could provide insights into novel ways p53 further exerts its tumour prevention role via its interactions with diverse proteins. Thus, this study aimed to examine the interactions of the p53 protein with other proteins (peptides and histones) using molecular simulation dynamics. We opted for a total of seven proteins, namely 2LVM, 2MWO, 2MWP, 4CRI, 4 × 34, 5Z78, and 6MYO (control), and had their PBD files retrieved from the protein database. These proteins were then docked against the p-53 protein and the resulting interactions were examined using molecular docking simulations run at 500 ns. The result of the interactions revealed the utilisation of various amino acids in the process. The peptide that interacted with the highest number of amino acids was 5Z78 and these were Lys10, Gly21, Trp24, Pro105, His106, and Arg107, indicating a stronger interaction. The RMSD and RMSF values indicate that the complexes formed were stable, with 4CRI, 6MYO, and 2G3R giving the most stable values (less than 2.5 Å). Other parameters, including the SASA, Rg, and number of hydrogen bonds, all indicated the formation of fairly stable complexes. Our study indicates that overall, the interactions of 53BP1 with p53K370me2, p53K382me2, methylated K810 Rb, p53K381acK382me2, and tudor-interacting repair regulator protein indicated interactions that were not as strong as those with the histone protein. Thus, it could be that P53 may mediate its tumour suppressing effect via interactions with amino acids and histone.

Expression of p53 in human adipose tissue correlates positively with FAS and BMI.

Activation of Fas (CD95) in adipocytes inhibits browning and may contribute to body weight gain in mice. Moreover, Fas expression in white adipose tissue (WAT) correlates positively with body mass index (BMI) in humans. However, molecular pathways involved in the inhibitory effect of Fas on energy metabolism remain incompletely understood. Herein, we report that protein levels of the tumor suppressor p53 were reduced in primary white adipocytes of adipocyte-specific Fas-knockout mice. Moreover, Fas ligand (FasL) treatment increased p53 concentrations in cultured adipocytes and decreased mitochondrial oxygen consumption in control but not in p53-depleted cells, indicating that Fas activation reduces energy expenditure in a p53-dependent manner. In line, in differentiated human mesenchymal stem cells and WAT derived from different anatomical depots, FAS expression was positively associated with p53. Furthermore, p53 expression in human subcutaneous and visceral WAT correlated positively with BMI, whereas its expression in visceral WAT was inversely associated with insulin sensitivity (as assessed by hyperinsulinemic-euglycemic clamp). Taken together, our data suggest that Fas regulates p53 expression in adipocytes, and may thereby affect body weight gain and insulin sensitivity.

Exploration of marine natural compounds as promising MDM2 inhibitors for treating triple-negative breast cancer: insights from molecular docking, ADME/T studies, molecular dynamics simulation and MM-PBSA binding free energy calculations

Triple-negative breast cancer (TNBC), the most aggressive form of breast cancer, presents a significant mortality risk owing to its elevated potential for metastasis. The overexpression of Murine Double Minute 2 homolog (MDM2) protein, a key suppressor of tumour suppressor p53, in TNBC amplifies its growth, advancement, and invasiveness. Thus, inhibiting MDM2 protein emerges as a compelling strategy to enhance the efficacy of TNBC treatment. We aimed to identify novel potential MDM2 inhibitors from natural marine compounds, known for their distinctive chemical structures and heightened anticancer activities, utilizing molecular docking, ADME/T analysis, molecular dynamics (MD) simulations, MM-PBSA calculations, and in silico PASS predictions. A marine compound library was constructed for initial screening purpose and the molecular docking analysis revealed that two marine compounds, namely 10,11-dihydrosodwanone B and sodwanone T, exhibited significantly higher binding affinity (− 9.6 kcal/mol and − 9.1 kcal/mol, respectively) compared to the established inhibitor nutlin-3a (− 8.4 kcal/mol). ADME/T investigations were conducted to ensure the drug-likeness properties and safety of these compounds. Additionally, in silico PASS tool predicted that both compounds possess a heightened potential for anticancer activities. Molecular dynamics simulations (100 ns) and MM-PBSA calculations indicated that sodwanone T formed a relatively more stable complex and had a higher binding-free energy with MDM2, respectively. In conclusion, this research suggests sodwanone T as a promising candidate for further testing and development as an MDM2 inhibitor for potential therapeutic applications against TNBC. Nevertheless, substantial experimental and clinical investigations are necessary to enhance its applicability in clinical settings.Graphical abstract

Multifunctional System with Camptothecin and [12]aneN3 Units for Effective In Vivo Anti Pancreatic Cancer through Synergistic Chemotherapy, Gene Therapy, and Photodynamic Therapy.

Maximizing drug cargo carrying capacity in blood circulation, controlling the in vivo fate of nanoparticles, and precisely drug release to tumor targets are the main aims of multifunctional nanomedicine-based antitumor therapy. Here we combined macrocyclic polyamine di(triazole-[12]aneN3) (M) and chemical drug camptothecin (CPT, C) through photosensitizer 1,1-dicyano-2-phenyl-2-(4-diphenylamino) phenyl-ethylene (DT) containing the cleavable disulfide (S) linkage as an all-in-one theranostic nanoprodrug, MDTSC. The corresponding compound with carbon chain (C) linkage, MDTCC, was also prepared for a comparison study. MDTSC showed the ability to carry plasmids, including the p53 tumor suppressor gene, to form lipoplexes with a size of ∼150 nm. Further addition of DOPE-PEG2k resulted in the hybrid lipoplexes MDTSC/DOPE-PEG2k@DNA, which showed good stability in blood circulation and good biocompatibility to normal cell lines. Experiments demonstrated that the hybrid lipoplexes were able to realize the successful cellular uptake and endosomal escape, to generate ROS under visible light irradiation as well as to trigger the localized release of CPT and the plasmid encoding p53 in tumor cells. In vitro, the hybrid lipoplexes showed better EGFP expression than the commercial Lipo2000, and markedly reduced tumor cell proliferation and migration rate irrespective of whether the BxPC-3 cell lines were grown on plates or 3D tumor spheroids. In vivo, the hybrid lipoplexes showed effective anticancer activity by reducing the BxPC-3 pancreatic tumor growth by 99% through the synergetic combination of chemotherapy, photodynamic therapy, and gene therapy. This research represented the first example of using a cocktail of three therapeutic approaches to achieve cooperative and effective anti pancreatic cancer treatment in vivo and in vitro.

Systemic drug repurposing for pancreatic cancer based on genetic and epigenetic network analysis using a systems biology approach and deep neural learning of drug-target interactions

Pancreatic cancer is a malignant tumor associated with a high mortality rate. This research presents a systems biology approach to explore the mechanisms of pancreatic ductal adenocarcinoma (PDAC), aiming to identify significant biomarkers that can serve as drug targets. We propose a systematic drug repurposing strategy that incorporates a deep neural network (DNN)-based drug-target interaction (DTI) model along with drug design specifications to develop a potential multi-molecule drug for PDAC treatment. We first established candidate protein-protein interaction networks and gene regulatory networks using big data mining techniques. Real PDAC and non-PDAC genome-wide genetic and epigenetic networks (GWGENs) were systematically identified using their corresponding microarray data through system identification and system order detection methods. The top 6,000 core GWGENs of PDAC and non-PDAC were extracted using the Principal Network Projection method. Subsequently, we annotated the core GWGENs using the Kyoto Encyclopedia of Genes and Genomes pathways to construct their respective core signaling pathways. By comparing upstream microenvironmental factors, core signaling pathways, and downstream aberrant cellular functions between PDAC and non-PDAC, we investigated the carcinogenic mechanisms of PDAC. Notably, c-MYC, forkhead box O3, and tumor suppressor p53 were identified as significant biomarkers for potential drug targets. Furthermore, the DNN-based DTI model predicted the interaction probabilities between candidate molecular drugs and these biomarkers. Based on drug design specifications such as regulatory ability, sensitivity, and toxicity, suitable multi-molecular potential drugs were selected. Ultimately, gemcitabine and MK-2206 were identified as a promising multi-molecular drug combination for PDAC treatment.

Covalent Fragments Acting as Tyrosine Mimics for Mutant p53-Y220C Rescue by Nucleophilic Aromatic Substitution.

The tumor suppressor p53 is frequently mutated in human cancers. The Y220C mutant is the ninth most common p53 cancer mutant and is classified as a structural mutant, as it leads to strong thermal destabilization and degradation by creating a solvent-accessible hydrophobic cleft. To identify small molecules that thermally stabilize p53, we employed DSF to screen SNAr-type electrophiles from our covalent fragment library (CovLib) for binding to different structural (Y220C, R282W) and DNA contact (R273H) mutants of p53. The reactive fragments SN001, SN006, and SN007 were detected to specifically stabilize Y220C, indicating the arylation of Cys220 in the mutational cleft, as confirmed by X-ray crystallography. The fragments occupy the central cavity and mimic the ring system of the WT tyrosine lost by the mutation. Surpassing previously reported noncovalent ligands, SN001 stabilized T-p53C-Y220C concentration-dependently up to 4.45 °C and, due to its small size, represents a promising starting point for optimization.

Role of apoptosis-associated proteins p53 and bcl-2 in the pathogenesis of nervous system diseases

Diseases of the central nervous system occupy a leading place, along with cardiovascular and oncological diseases, and the proportion of patients suffering from diseases of the nervous system is increasing as the population ages. This group of diseases includes acute conditions, such as ischemic stroke, and chronic multifactorial diseases — Alzheimer's and Parkinson's diseases, epilepsy, etc. The development of specific methods for their treatment is difficult, and these drugs are not very effective. Almost all brain diseases are based on common mechanisms such as oxidative stress, inflammation and neuronal death. Most often, cells die by apoptosis due to an imbalance between pro-apoptotic and anti-apoptotic factors. This work examines two of them: the apoptosis-promoting transcription factor and tumor suppressor p53 and its opposing B-cell lymphoma protein Bcl-2. The choice of these proteins for study is due to the fact that both proteins are key regulators of apoptosis and are important in the pathogenesis of nervous diseases, since neurons are not highly proliferating cells. The p53 protein is involved in the regulation of many genes responsible for DNA repair, apoptosis, and other biochemical cellular processes; this is especially important when studying neuronal pathology. Bcl-2 suppresses apoptosis in various cells, including neurons, by controlling mitochondrial membrane permeability and inhibiting caspases. In diseases, its expression can either increase, for example, in the case of malignant tumors, or decrease, as in the case of neurodegenerative processes. It has been established that p53 and Bcl-2 are in close interaction in the process of regulating apoptosis; their ratio may be an important prognostic factor. The purpose of this work was to assess the role of these proteins in the pathogenesis of various diseases of the nervous system, and to search for general patterns of changes in their expression and coexpression.

MDM2 drives resistance to Osimertinib by contextually disrupting FBW7-mediated destruction of MCL-1 protein in EGFR mutant NSCLC

BackgroundOvercoming resistance to Osimertinib in epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC) is clinically challenging because the underlying mechanisms are not fully understood. The murine double minute 2 (MDM2) has been extensively described as a tumor promotor in various malignancies, mainly through a negative regulatory machinery on the p53 tumor suppressor. However, the significance of MDM2 on the sensitivity to Osimertinib has not been described.MethodsOsimertinib resistant cells were generated by standard dose escalation strategy and individual resistant clones were isolated for MDM2 testing. The MDM2 and its mutant constructs (ΔPBD, ΔRING, C464A) were introduced into PC-9, HCC827 and H1975 cells and evaluated for the sensitivity to Osimertinib by MTT assay, colony formation, EdU assay and TUNEL assay. MDM2 expression in resistant cells was manipulated by pharmacological and molecular approaches, respectively. Proteins that were implicated in PI3K/Akt, MAPK/Erk and apoptosis signaling were measured by Western blot analysis. Candidate proteins that interacted with MDM2 were captured by immunoprecipitation and probed with indicated antibodies.ResultsIn comparison with parental PC-9 cells, the PC-9 OR resistant cells expressed high level of MDM2. Ectopic expression of MDM2 in PC-9, HCC827 and H1975 sensitive cells generated an Osimertinib resistant phenotype, regardless of p53 status. MDM2 promoted resistance to Osimertinib through a PI3K/Akt and MAPK/Erk-independent machinery, in contrast, MDM2 selectively stabilized MCL-1 protein to arrest Osimertinib-induced cancer cell apoptosis. Mechanistically, MDM2 acted as a E3 ligase to ubiquitinate FBW7, a well-established E3 ligase for MCL-1, at Lys412 residue, which resulted in FBW7 destruction and MCL-1 stabilization. Targeting MDM2 to augment MCL-1 protein breakdown overcame resistance to Osimertinib in vitro and in vivo. Finally, the clinical relevance of MDM2-FBW7-MCL-1 regulatory axis was validated in mouse xenograft tumor model and in NSCLC specimen.ConclusionOverexpression of MDM2 is a novel resistant mechanism to Osimertinib in EGFR mutant NSCLC. MDM2 utilizes its E3 ligase activity to provoke FBW7 destruction and sequentially leads to MCL-1 stabilization. Cancer cells with aberrant MDM2 state are refractory to apoptosis induction and elicit a resistant phenotype to Osimertinib. Therefore, targeting MDM2 would be a feasible approach to overcome resistance to Osimertinib in EGFR mutant NSCLC.

FBXO46 negatively regulates p53 activity by stabilizing Mdm2.

The tumor suppressor p53 plays a central role in suppressing tumor formation. Mouse double minute 2 homolog (Mdm2) serves as the principal ubiquitin E3 ligase responsible for the ubiquitination and subsequent degradation of p53. However, the regulatory mechanisms governing the Mdm2-p53 pathway are not comprehensively understood. Here, we report that F-box only protein 46 (FBXO46) directly binds to Mdm2 and inhibits its self-ubiquitination and degradation, leading to Mdm2 stabilization and subsequent Mdm2-mediated ubiquitination and degradation of p53. Functionally, FBXO46 promotes cell proliferation, accelerates G1/S cell cycle progression, and increases anchorage-independent cell growth by inhibiting p53. Collectively, these findings reveal a critical role for FBXO46 in controlling Mdm2 stability and establish FBXO46 as an important regulator of the Mdm2-p53 pathway.

Mutant RIT1 cooperates with YAP to drive an EMT-like lung cancer state.

We report a new RIT1 M90I -mutant autochthonous lung tumor model The most common oncogenic variant of RIT1, RIT1 M90I , weakly promotes lung tumor development RIT1 M90I drives the formation of lethal lung tumors in cooperation with p53 and Nf2 tumor suppressor gene loss RIT1 M90I and YAP cooperatively regulate cJUN expression Therapeutic MEK and TEAD targeting suppresses RIT1 M90I -driven tumorigenesis.

Elevated type I interferon signaling defines the proliferative advantage of ARF and p53 mutant tumor cells.

The tumor suppressors p53 and ARF collaborate to prevent unwarranted cell proliferation and as such are two of the most frequently mutated genes in human cancer. Concomitant loss of functional p53 and ARF leads to massive gains in cell proliferation and transformation and is often observed in some of the most aggressive human cancer subtypes. These phenotypic gains are preceded by increased type I interferon (IFN) signaling that involves canonical STAT1 activation and a subsequent IFN-stimulated gene (ISG) signature. Here, we show that cells lacking p53 and ARF require active JAK1 to phosphorylate STAT1 on Y701 to maintain their high rate of proliferation. In fact, the use of selective JAK1 inhibitors ruxolitinib or baricitinib inhibited the induction of ISG's and the proliferation of p53 and ARF deleted cells. We identify a group of solid human tumors that lack functional p53 and ARF, show an expression signature of the upregulated type I IFN response genes, and are sensitive to selective JAK1 inhibitors. These data suggest that the type I IFN response acts as a positive driver of proliferation in the absence of p53 and ARF and, as such, presents itself as a potential therapeutic target in aggressive solid tumors.

A novel ITGB8 transcript variant sustains ovarian cancer cell survival through genomic instability and altered ploidy on a mutant p53 background

BackgroundTranscript variants and protein isoforms are central to unique tissue functions and maintenance of homeostasis, in addition to being associated with aberrant states such as cancer, where their crosstalk with the mutated tumor suppressor p53 may contribute to genomic instability and chromosomal rearrangements. We previously identified several novel splice variants in ovarian cancer RNA-sequencing datasets; herein, we aimed to elucidate the biological effects of the Integrin Subunit Beta 8 variant (termed pITGB8-205).MethodsResolution of the full-length sequence of pITGB8-205 through rapid amplification of cDNA ends (RACE-PCR). Cell cycle analysis and karyotype studies were performed to further explore genomic instability. RNA-seq and proteomics analyses were used to identify the differential expression of the genes.ResultsThis full-length study revealed a unique 5’ sequence in pITGB8-205 that differed from the reported ITGB8-205 sequence, suggesting differential regulation of this novel transcript. Under a p53 mutant background, overexpression of pITGB8-205 triggered genetic instability reminiscent of oncogene-induced replicative stress with extensive abnormal mitoses and chromosomal and nuclear aberrations indicative of chromosomal instability, leading to near whole-genome duplication that imposes energy stress on cellular resources. Micronuclei and aneuploidy are striking features of pITGB8-205-overexpressing p53-mutant cells but are not enhanced in p53 wild-type (WT) cells. RNA-seq and proteomics analyses further suggested that p53 inactivation in ovarian cancer provides a permissive intracellular molecular niche for pITGB8-205 to mediate its effects on genomic instability. This observation is pivotal considering that most high-grade serous ovarian carcinoma (HGSC) tumors express mutant p53. The resulting aneuploid clones with enhanced self-renewal and survival capabilities disrupt clonal dominance under stress yet maintain a balance between replicative stress and prosurvival advantages.ConclusionpITGB8-205-overexpressing clones sustain ovarian tumor cell survival, achieve homeostasis and are formidable opponents of therapy.

Molecular Pathogenesis of Human Papillomavirus: Insights into Viral Oncoproteins and Host Integration

Human Papillomavirus (HPV) is a major cause of death from cervical cancer and other anogenital cancers throughout the world. Pathogenicity of HPV is governed by intricate interplay of HPV and host cells mediated primarily by its oncoproteins E6 and E7. These oncoproteins disrupt critical pathways, including those involving tumor suppressors p53 and retinoblastoma (Rb) to induce unregulated cell proliferation and evasion of apoptosis. These mechanisms have been studied in order to develop the different diagnostic tools, such as HPV DNA testing and genotyping, and there are emerging techniques based on E6/E7 mRNA detection and high throughput sequencing. In addition, therapeutic strategies have advanced with the vaccines showing ability to prevent high risk HPV infection and ongoing research to developing targeted therapies to disrupt viral oncoprotein function. New diagnostic and therapeutic approaches to HPV research encompassing an expanding clinical landscape hold promise to reduce incidence of HPV associated malignancies and improve patient outcomes. This review summarizes the molecular pathogenesis of HPV with respect to host cells and discusses its implications for diagnostics and therapeutics, including the need for further development in this area.

Excessive MYC-topoisome activity triggers acute DNA damage, MYC degradation, and replacement by a p53-topoisome

Hyperproliferation driven by the protooncogene MYC may lead to tumor suppressor p53 activating DNA damage that has been presumed to derive from hypertranscription and over-replication. Here, we report that excessive MYC-topoisome (MYC/topoisomerase 1/topoisomerase 2) activity acutely damages DNA-activating pATM and p53. In turn, MYC is shut off and degraded, releasing TOP1 and TOP2A from MYC topoisomes invitro and invivo. To manage the topological and torsional stress generated at its target genes, p53 assembles a separate topoisome. Because topoisomerase activity is intrinsically DNA damaging, p53 topoisomes provoke an initial burst of DNA damage. Because p53, unlike MYC, upregulates the DNA-damage response (DDR) and activates tyrosyl-DNA-phosphodiesterase (TDP) 1 and TDP2, it suppresses further topoisome-mediated damage. The physical coupling and activation of TOP1 and TOP2 by p53 creates a tool that supports p53-target expression while braking MYC-driven proliferation in mammalian cells.

Unraveling the mechanisms of glioblastoma's resistance: investigating the influence of tumor suppressor p53 and non-coding RNAs.

Glioblastoma (GB) is one of the most fatal CNS malignancies, and its high resistance to therapy and poor outcomes have made it one of the primary challenges in oncology. Resistance to standard therapy, i.e., radio-chemotherapy with temozolomide, is one of the principal causes of the poor prognostic outcomes of GB. Finding the molecular basis of GB resistance to therapy is key to creating effective solution approaches. The general problem of GB resistance is supervised by cancer suppressive protein, p53, and has become a very special interest in molecular research in recent decades. The principal aim of this manuscript is to perform a comprehensive survey on the complex network of interactions developed by p53 with non-coding RNAs (ncRNA) in the context of GB resistance. The present article details the functional aspects of p53 as a cellular stress response protein, including its roles in apoptosis, cell cycle regulation, and DNA repair in glioblastoma (GB), along with the disruption of p53 and its involvement in chemoresistance (CR). It also highlights several classes of ncRNAs, namely microRNAs, long ncRNAs, and circular RNAs, that manipulate p53 signaling in GB-CR. The article likewise explains how disruption in the expression of these ncRNAs can promote GB-CR and how it interacts with essential cellular functions, such as proliferation, apoptosis, and DNA repair. The manuscript also describes the potential of targeting p53 and ncRNAs with their diagnostic and prognostic potential as novel promising therapeutics for GB. Nevertheless, ncRNA-based biomarkers still present challenges for their suitability in GB resistance. However, modern research continues to discover novel prediction targets, potentially enhancing patient outcomes and therapeutic options. Therefore, the neutralization of this intricate regulatory network of GB resistance might have a primary clinical effect in fighting GB resistance therapy and thus might lead to a substantial increase in patient survival and quality of life.

Modulation of p300 acetylation to protect against doxorubicin-induced cardiotoxicity

Abstract Background Doxorubicin (DOX) is a widely-used anti-neoplastic agent, but the most common adverse reaction to its use is cardiotoxicity(1). DOX acts by producing reactive oxygen species (ROSs) that cause DNA damage(1,2), which activates various proteins, including the tumour suppressor p53 and the acetyltransferase p300. When activated, p300 acetylates and increases the activity of p53 which leads to increased apoptotic activity(3). Cardiotoxicity results because the heart has limited mechanisms to dispose of ROSs(4), and because cardiomyocytes have a low turnover rate(5). Purpose We examined the p300 inhibitor Theracurmin (THR)(6,7) as a candidate to prevent DOX cardiotoxicity using an in-vivo mouse model, and sought to elucidate the underlying molecular mechanisms using in-vitro studies. Methods C57BL/6 mice were pre-treated with THR or vehicle (as control), then administered DOX or vehicle. Cardiac function was evaluated by echocardiography and cardiac catheterization. In vitro studies used cardiac fibroblasts (FBs) and cardiac endothelial cells (ECs) pre-treated with THR, then with DOX, as in the animal studies. Western blotting and rt-qPCR was used to quantify protein and mRNA levels of genes in the p53-p300 pathway or related to apoptosis, oxidative stress, and cell cycle control. Results DOX-treated mice showed significant decreases in left ventricular (LV) ejection fraction (LVEF, p=0.0004), fractional shortening (FS, p=0.0012), and a significant increase in end-systolic volume (ESV, p=0.0004). We also showed a significant decrease in anterior (LVAW;d, p=0.005) and posterior (LVPW;d, p=0.005) wall thickness of the LV in these mice. However, when mice were pre-treated with THR prior to DOX administration, we saw significant increases in LVEF (p=0.045) and LVPW;d (p=0.015), and a significant decrease in ESV (p=0.0047) compared to those that were not pre-treated. In-vitro analyses demonstrated a significant increase in cleaved caspase 3 protein expression in DOX-treated ECs (p=0.007), that was not prevented by THR pre-treatment. In DOX-treated FBs, we saw a reduction in AKT mRNA (p=0.017) and increases in BAX 9p=0.008), P21 (p=0.0001), and GADD45 (0.037) mRNA expression. In DOX-treated ECs, we also saw significant increases in BAX (p=0.015) and P21 (p=0.011) mRNA expression. These changes in mRNA expression were not reversed with THR pre-treatment in either cell type. Conclusion THR pre-treatment successfully mitigated functional deficits and structural deficits associated with DOX cardiotoxicity. In-vitro studies show that THR pre-treatment was not sufficient to significantly prevent changes in key molecular targets associated with apoptosis. Further studies are required to elucidate the mechanism behind the observed functional changes.Abstract OverviewAbstract Results

Inulin-based nanoparticles for targeted siRNA delivery in acute kidney injury

RNA interference has emerged as a promising therapeutic strategy to tackle acute kidney injury (AKI). Development of targeted delivery systems is highly desired for selective renal delivery of RNA and improved therapeutic outcomes in AKI. Inulin is a plant polysaccharide traditionally employed to measure glomerular filtration rate. Here, we describe the synthesis of inulin modified with α-cyclam-p-toluic acid (CPTA) to form a novel renal-targeted polymer, Inulin-CPTA (IC), which is capable of selective siRNA delivery to the injured kidneys. We show that conjugating CPTA to inulin imparts IC with targeting properties for cells that overexpress the C-X-C chemokine receptor 4 (CXCR4). Self-assembled IC/siRNA nanoparticles (polyplexes) demonstrated rapid accumulation in the injured kidneys with selective uptake and prolonged retention in injured renal tubules overexpressing the CXCR4 receptor. Tumor-suppressor protein p53 contributes significantly to the pathogenesis of AKI. siRNA-induced silencing of p53 has shown therapeutic potential in several preclinical studies, making it an important target in the treatment of AKI. Systemically administered nanoparticles formulated using IC and siRNA against p53 selectively accumulated in the injured kidneys and potently silenced p53 expression. Selective p53 knockdown led to positive therapeutic outcomes in mice with cisplatin-induced AKI, as seen by reduced tubular cell death, renal injury, inflammation, and overall improved renal function. These findings indicate that IC is a promising new carrier for renal-targeted delivery of RNA for the treatment of AKI.

Effect of infection by Mycoplasma arginini and Mycoplasma salivarium on the oncogenic properties of lung cancer cell line A549

Most mycoplasma species are the extracellular parasites affecting different cellular processes including proliferation, cell cycle, protein synthesis, DNA repair and others. Mycoplasma infection was shown to contribute to the pathology of various diseases, including cancer. Upon infection, mycoplasmas typically activate the tumor-associated NF-kB pathway, which is associated with EMT, the main mechanism of metastasis.In this study, we found that two different mycoplasma strains, M. arginini and M. salivarium, promoted the initiation of EMT and simultaneous suppression of the p53 tumor suppressor in A549 lung cancer cells. This led to an increase of cancer cell motility, resistance to the antitumor drug etoposide concomitantly with decreased autophagy. These data indicate that mycoplasmas are able to increase the tumorigenic potential of cancer host cells.