Jun NH2-terminal kinase phosphorylation of p53 on Thr-81 is important for p53 stabilization and transcriptional activities in response to stress

Design, synthesis and biological evaluation of matrine contains benzimidazole derivatives as dual TOPOI and PARP inhibitors for cancer therapy

TOPOI inhibitors have long been a focal point in the research and development of antitumor drugs. PARP-1 plays a crucial role in repairing DNA damage induced by TOPOI inhibitors. Thus, concurrent inhibition of TOPOI and PARP-1 has the potential to augment drug activity. Matrine, characterized by low toxicity and good water solubility, offers advantageous properties. In this investigation, a series of benzimidazole matrine derivatives were designed and synthesized using matrine as the lead compound with the aim of developing dual inhibitors targeting both TOPOI and PARP-1. Among these derivatives, Compound B6 exhibited potent inhibitory effects on PARP-1 and TOPOI, effectively suppressing cancer cell proliferation and migration. Mechanistic assessments revealed that B6 induced DNA damage in HGC-27 cells, leading to G0/G1 cell cycle arrest and significant apoptosis. Molecular docking experiments demonstrated that B6 can effectively enter the active pocket of target proteins, where it forms stable hydrogen bonds with amino acid residues. In vivo, experiments demonstrated that B6 exhibited antitumor activity comparable to that of the positive control drug. The tumor growth inhibition rates (TGIs) for irinotecan, B6 and matrine were 87.0%, 75.4% and 9.7%, respectively. Importantly, B6 demonstrated lower toxicity than the positive control drug. Our findings suggest that TOPOI and PARP-1 may represent potential targets for matrine and B6 emerges as a promising candidate for cancer therapy.

Emerging role and therapeutic implications of p53 in intervertebral disc degeneration

Lower back pain (LBP) is a common degenerative musculoskeletal disease that imposes a huge economic burden on both individuals and society. With the aggravation of social aging, the incidence of LBP has increased globally. Intervertebral disc degeneration (IDD) is the primary cause of LBP. Currently, IDD treatment strategies include physiotherapy, medication, and surgery; however, none can address the root cause by ending the degeneration of intervertebral discs (IVDs). However, in recent years, targeted therapy based on specific molecules has brought hope for treating IDD. The tumor suppressor gene p53 produces a transcription factor that regulates cell metabolism and survival. Recently, p53 was shown to play an important role in maintaining IVD microenvironment homeostasis by regulating IVD cell senescence, apoptosis, and metabolism by activating downstream target genes. This study reviews research progress regarding the potential role of p53 in IDD and discusses the challenges of targeting p53 in the treatment of IDD. This review will help to elucidate the pathogenesis of IDD and provide insights for the future development of precision treatments.

BannMI deciphers potential n-to-1 information transduction in signaling pathways to unravel message of intrinsic apoptosis

Motivation

Cell fate decisions, such as apoptosis or proliferation, are communicated via signaling pathways. The pathways are heavily intertwined and often consist of sequential interaction of proteins (kinases). Information integration takes place on the protein level via n-to-1 interactions. A state-of-the-art procedure to quantify information flow (edges) between signaling proteins (nodes) is network inference. However, edge weight calculation typically refers to 1-to-1 interactions only and relies on mean protein phosphorylation levels instead of single cell distributions. Information theoretic measures such as the mutual information (MI) have the potential to overcome these shortcomings but are still rarely used.

Results

This work proposes a Bayesian nearest neighbor-based MI estimator (BannMI) to quantify n-to-1 kinase dependency in signaling pathways. BannMI outperforms the state-of-the-art MI estimator on protein-like data in terms of mean squared error and Pearson correlation. Using BannMI, we analyze apoptotic signaling in phosphoproteomic cancerous and noncancerous breast cell line data. Our work provides evidence for cooperative signaling of several kinases in programmed cell death and identifies a potential key role of the mitogen-activated protein kinase p38.

Availability and implementation

Source code and applications are available at: https://github.com/zuiop11/nn_info and can be downloaded via Pip as Python package: nn-info.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

CopA3 peptide inhibits MDM2-p53 complex stability in colorectal cancers and activates p53 mediated cell death machinery

The diverse expression patterns of the tumor suppressor p53 in cancer cells reflect the regulatory efficiency of multiple cellular pathways. By contrast, many human tumors are reported to develop in the presence of wild-type p53. Recently, several oncogene inhibitors have been used clinically to suppress tumor development by functionally reactivating other oncoproteins. On the other hand, p53 reactivation therapies have not been well established, as few of the p53-MDM2 complex inhibitors such as Nutlin-3 induces mutation in p53 gene upon prolonged usage. Therefore, in this study CopA3, a 9-mer dimeric D-type peptide with anticancer activity against the human colorectal cancer cells, was used to explore the efficacy of p53 reactivation in-vitro and in-vivo. The anticancer activity of CopA3 was more selective towards the wild-type p53 expressing cells than the p53 deficient or mutant colorectal cancer cells. In response to this, this study investigated the signaling pathway in vitro and validated its anti-tumor activity in-vivo. The protein-peptide interaction and molecular docking efficiently provided insight into the specific binding affinity of CopA3 to the p53-binding pocket of the MDM2 protein, which efficiently blocked the p53 and MDM2 interaction. CopA3 plays a crucial role in the binding with MDM2 and enhanced the nuclear translocation of the p53 protein, which sequentially activated the downstream targets to trigger the autophagic mediated cell death machinery through the JNK/Beclin-1 mediated pathway. Collectively, CopA3 affected the MDM2-p53 interaction, which suppressed tumor development. This study may provide a novel inhibitor candidate for the MDM2-p53 complex, which could ultimately suppress the growth of colorectal cancer cells without being cytotoxic to the healthy neighboring cells present around the tumor microenvironment.

Induction of Apoptosis by Matrine Derivative ZS17 in Human Hepatocellular Carcinoma BEL-7402 and HepG2 Cells through ROS-JNK-P53 Signalling Pathway Activation

Hepatocellular carcinoma (HCC) is one of the most common malignancies and ranks third among cancer-related deaths worldwide. Using matrine as a lead compound, 12 matrine derivatives were designed and synthesised, and their antiproliferative activities were evaluated in four cancer cell lines. Eight of the twelve compounds showed strong antiproliferative activity, with an IC50 of <10 μM. The compound ZS17 exhibited strong antiproliferative activity in hepatocellular carcinoma cell lines with IC50 values in the range of 3.014−3.388 μM, which was much lower than that of matrine. Furthermore, we explored the role of ZS17 in inducing apoptosis in HCC cells in vitro and in vivo, as well as possible mechanisms involved. ZS17 inhibited the proliferation of BEL-7402 and HepG2 cells in time- and dose-dependent manners. In addition, we found that ZS17 significantly induced apoptosis and ROS (reactive oxygen species) production, promoted JNK phosphorylation, activated p53, and activated the caspase signalling pathway. Furthermore, the antioxidant NAC, JNK inhibitor SP600125, and Si-JNK increased cell viability, re-established cell metastasis, and inhibited ZS17-induced apoptosis. An in vivo antitumour assay demonstrated that ZS17 significantly reduced the number of migrating HepG2 cells in zebrafish embryos and suppressed the growth of HepG2 xenografts in nude mice without any obvious side effects. Our study demonstrated that the ROS-JNK-P53 pathway plays an important role in the destruction of liver tumour cells by ZS17. Thus, ZS17 may represent a promising chemotherapeutic agent for the treatment of HCC patients.

The Four Homeostasis Knights: In Balance upon Post-Translational Modifications

A cancer outcome is a multifactorial event that comes from both exogenous injuries and an endogenous predisposing background. The healthy state is guaranteed by the fine-tuning of genes controlling cell proliferation, differentiation, and development, whose alteration induces cellular behavioral changes finally leading to cancer. The function of proteins in cells and tissues is controlled at both the transcriptional and translational level, and the mechanism allowing them to carry out their functions is not only a matter of level. A major challenge to the cell is to guarantee that proteins are made, folded, assembled and delivered to function properly, like and even more than other proteins when referring to oncogenes and onco-suppressors products. Over genetic, epigenetic, transcriptional, and translational control, protein synthesis depends on additional steps of regulation. Post-translational modifications are reversible and dynamic processes that allow the cell to rapidly modulate protein amounts and function. Among them, ubiquitination and ubiquitin-like modifications modulate the stability and control the activity of most of the proteins that manage cell cycle, immune responses, apoptosis, and senescence. The crosstalk between ubiquitination and ubiquitin-like modifications and post-translational modifications is a keystone to quickly update the activation state of many proteins responsible for the orchestration of cell metabolism. In this light, the correct activity of post-translational machinery is essential to prevent the development of cancer. Here we summarize the main post-translational modifications engaged in controlling the activity of the principal oncogenes and tumor suppressors genes involved in the development of most human cancers.

Cordycepin Induces Apoptosis through JNK-Mediated Caspase Activation in Human OEC-M1 Oral Cancer Cells

Cordycepin, a bioactive compound extracted from Cordyceps sinensis, can induce apoptosis in human OEC-M1 oral cancer cells. However, the exact mechanism is still unclear. The present study aimed to investigate the underlying mechanism of cordycepin-induced apoptosis in OEC-M1 cells. Following treatment with cordycepin, apoptosis was examined and quantified using a DNA laddering assay and a cytokeratin 18 fragment enzyme-linked immunosorbent assay, respectively. Expressions of mitogen-activated protein kinases (MAPKs) and apoptosis-related proteins were detected by the western blot analysis. Our results show that a pan-caspase inhibitor, Z-VAD-FMK, could significantly inhibit cordycepin-induced apoptosis in OEC-M1 cells. In addition, treatment with cordycepin not only activated caspase-8, caspase-9, and caspase-3 but also induced Bid and poly ADP-ribose polymerase cleavages. Furthermore, cordycepin also induced the activation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase, and p38 MAPKs. Among MAPKs, activation of JNK solely contributed to cordycepin-induced apoptosis with the activation of caspase-8, caspase-9, and caspase-3 and cleavage of PARP. Taken together, the present study demonstrated that cordycepin activated JNK and caspase pathways to induce apoptosis in OEC-M1 cells.

Role of the JNK Pathway in Bladder Cancer

Bladder cancer, one of the most frequently diagnosed cancers worldwide, is associated with high morbidity and mortality and a poor prognosis. The bladder cancer types include 1) non-muscle invasive bladder cancer (NMIBC) and 2) muscle invasive bladder cancer (MIBC). Metastases and chemoresistance in MIBC patients are the leading causes of the high death rate. c-Jun N-terminal kinase (JNK) is an important factor for the undifferentiated state of cancer cells. JNK belongs to the mitogen-activated protein kinases (MAPKs) family; it is activated by various extracellular stimuli, such as stress, radiation, and growth factors and mediates diverse cellular functions, such as apoptosis, autophagy, proliferation, invasion, and migration by mediating AKT (Ak strain transforming), ATG (Autophagy related), mTOR (Mammalian target of rapamycin), and caspases 3, 8, and 9. This review describes the JNK-related functions, mechanisms, and signaling in bladder cancer.

Field exposure to 50 Hz significantly affects wild‑type and unfolded p53 expression in NB69 neuroblastoma cells

Previous studies have shown that intermittent exposure to a 50 Hz, 100 µT sinusoidal magnetic field (MF) promotes proliferation of human neuroblastoma cells, NB69. This effect is mediated by activation of the epidermal growth factor receptor through a free radical-dependent activation of the p38 pathway. The present study investigated the possibility that the oxidative stress-sensitive protein p53 is a potential target of the MF, and that field exposure can affect the protein expression. To that end, NB69 cells were exposed to short intervals of 30 to 120 min to the aforementioned MF parameters. Two specific anti-p53 antibodies that allow discrimination between the wild and unfolded forms of p53 were used to study the expression and cellular distribution of both isoforms of the protein. The expression of the antiapoptotic protein Bcl-2, whose regulation is mediated by p53, was also analyzed. The obtained results revealed that MF exposure induced increases in p53 gene expression and in protein expression of the wild-type form of p53. Field exposure also caused overexpression of the unfolded form of p53, together with changes in the nuclear/cytoplasmic distribution of both forms of the protein. The expression of protein Bcl-2 was also significantly increased in response to the MF. As a whole, these results indicated that the MF is capable of interacting with the function, distribution and conformation of protein p53. Such interactions could be involved in previously reported MF effects on NB69 proliferation promotion.

Biphasic dose-dependent G0/G1 and G2/M cell cycle arrest by synthetic 2,3-arylpyridylindole derivatives in A549 lung cancer cells

A collection of 2,3-arylpyridylindole derivatives were synthesized via the Larock heteroannulation and evaluated for their in vitro cytotoxic activity against A549 human lung cancer cells. Two derivatives expressed good cytotoxicity with IC 50 values of 1.18±0.25 μM and 0.87±0.10 μM and inhibited tubulin polymerization in vitro , with molecular docking studies suggesting the binding modes of the compounds in the colchicine binding site. Both derivatives have biphasic cell cycle arrest effects depending on their concentrations. At a lower concentration (0.5 μM), the two compounds induced G0/G1 cell cycle arrest by activating the JNK/p53/p21 pathway. At a higher concentration (2.0 μM), the two derivatives arrested the cell cycle at the G2/M phase via Akt signaling and inhibition of tubulin polymerization. Additional cytotoxic mechanisms of the two compounds involved the decreased expression of Bcl-2 and Mcl-1 antiapoptotic proteins through inhibition of the STAT3 and Akt signaling pathways.

Mammalian eIF4E2-GSK3β maintains basal phosphorylation of p53 to resist senescence under hypoxia

Hypoxia modulates senescence, but their physiological link remains unclear. Here, we found that eIF4E2, a hypoxia-activated translation initiation factor, interacted with GSK3β to maintain phosphorylation of p53, thus resisting senescence under hypoxia. RNA-binding protein RBM38 interacted with eIF4E to inhibit the translation of p53, but GSK3β-mediated Ser195 phosphorylation disrupted the RBM38-eIF4E interaction. Through investigation of RBM38 phosphorylation, we found that the eIF4E2-GSK3β pathway specifically regulated proline-directed serine/threonine phosphorylation (S/T-P). Importantly, peptides e2-I or G3-I that blocking eIF4E2-GSK3β interaction can inhibit the basal S/T-P phosphorylation of p53 at multiple sites, therby inducing senescence through transcriptional inhibition. Additionally, a nanobody was screened via the domain where eIF4E2 bound to GSK3β, and this nanobody inhibited S/T-P phosphorylation to promote senescence. Furthermore, hypoxia inhibited eIF4E2-GSK3β pathway by mediating S-Nitrosylation of GSK3β. Blocking eIF4E2-GSK3β interaction promoted liver senescence under hypoxia, thus leading to liver fibrosis, eventually accelerating N, N-diethylnitrosamine (DEN)-induced tumorigenesis. Interestingly, eIF4E2 isoforms with GSK3β-binding motif exclusively exist in mammals, which protect zebrafish heart against hypoxia. Together, this study reveals a mammalian eIF4E2-GSK3β pathway that prevents senescence by maintaining basal S/T-P phosphorylation of p53, which underlies hypoxia adaptation of tissues.

Functions and Clinical Significance of CACNA2D1 in Gastric Cancer

BACKGROUND

Voltage-gated calcium channels form as a complex of several subunits, among which the function of CACNA2D1, one of the genes encoding the α2δ subunit, remains unclear. The aim of our study was to investigate the role of CACNA2D1 and evaluate the efficacy of amlodipine, a blocker of CACNA2D1, in the treatment of gastric cancer (GC).

METHODS

Knockdown experiments were performed on the human GC cell lines MKN7 and HGC27 using CACNA2D1 small interfering RNA (siRNA), and changes in cell proliferation, the cell cycle, apoptosis, migration, and invasion were assessed. The gene expression profiles of cells were examined using a microarray analysis. An immunohistochemical (IHC) analysis was conducted on samples obtained from 196 GC patients who underwent curative gastrectomy. In addition, the antitumor effects of amlodipine were investigated using a xenograft model.

RESULTS

Cell proliferation, migration, and invasion were suppressed in CACNA2D1-depleted cells, and apoptosis was induced. The results of the microarray analysis showed that the apoptosis signaling pathway was enhanced via p53, BAX, and caspase 3 in CACNA2D1-depleted cells. A multivariate analysis identified high CACNA2D1 expression levels, confirmed by IHC, as an independent poor prognostic factor in GC patients. Moreover, subcutaneous tumor volumes were significantly smaller in a xenograft nude mouse model treated with a combination of amlodipine and cisplatin than in a model treated with cisplatin alone.

CONCLUSIONS

The present study indicates that CACNA2D1 regulates the apoptosis signaling pathway and may have potential as a biomarker for cancer growth and as a therapeutic target for GC.

OUP accepted manuscript

Background

Methods

Results

Conclusion

From the Evasion of Degradation to Ubiquitin-Dependent Protein Stabilization

A hallmark of cancer is dysregulated protein turnover (proteostasis), which involves pathologic ubiquitin-dependent degradation of tumor suppressor proteins, as well as increased oncoprotein stabilization. The latter is due, in part, to mutation within sequences, termed degrons, which are required for oncoprotein recognition by the substrate-recognition enzyme, E3 ubiquitin ligase. Stabilization may also result from the inactivation of the enzymatic machinery that mediates the degradation of oncoproteins. Importantly, inactivation in cancer of E3 enzymes that regulates the physiological degradation of oncoproteins, results in tumor cells that accumulate multiple active oncoproteins with prolonged half-lives, leading to the development of "degradation-resistant" cancer cells. In addition, specific sequences may enable ubiquitinated proteins to evade degradation at the 26S proteasome. While the ubiquitin-proteasome pathway was originally discovered as central for protein degradation, in cancer cells a ubiquitin-dependent protein stabilization pathway actively translates transient mitogenic signals into long-lasting protein stabilization and enhances the activity of key oncoproteins. A central enzyme in this pathway is the ubiquitin ligase RNF4. An intimate link connects protein stabilization with tumorigenesis in experimental models as well as in the clinic, suggesting that pharmacological inhibition of protein stabilization has potential for personalized medicine in cancer. In this review, we highlight old observations and recent advances in our knowledge regarding protein stabilization.

Role of JNK activation in paclitaxel-induced apoptosis in human head and neck squamous cell carcinoma

It has been reported that paclitaxel activates cell cycle arrest and increases caspase protein expression to induce apoptosis in head and neck squamous cell carcinoma (HNSCC) cell lines. However, the potential signaling pathway regulating this apoptotic phenomenon remains unclear. The present study used OEC-M1 cells to investigate the underlying molecular mechanism of paclitaxel-induced apoptosis. Following treatment with paclitaxel, cell viability was assessed via the MTT assay. Necrosis, apoptosis, cell cycle and mitochondrial membrane potential (∆Ψm) were analyzed via flow cytometric analyses, respectively. Western blot analysis was performed to detect the expression levels of proteins associated with the MAPK and caspase signaling pathways. The results demonstrated that low-dose paclitaxel (50 nM) induced apoptosis but not necrosis in HNSCC cells. In addition, paclitaxel activated the c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase or p38 mitogen-activated protein kinase. The paclitaxel-activated JNK contributed to paclitaxel-induced apoptosis, activation of caspase-3, -6, -7, -8 and -9, and reduction of ∆Ψm. In addition, caspase-8 and -9 inhibitors, respectively, significantly decreased paclitaxel-induced apoptosis. Notably, Bid was truncated following treatment with paclitaxel. Taken together, the results of the present study suggest that paclitaxel-activated JNK is required for caspase activation and loss of ∆Ψm, which results in apoptosis of HNSCC cells. These results may provide mechanistic basis for designing more effective paclitaxel-combining regimens to treat HNSCC.

DNA damage and oxidant stress activate p53 through differential upstream signaling pathways

Stabilization and activation of the p53 tumor suppressor are triggered in response to various cellular stresses, including DNA damaging agents and elevated Reactive Oxygen Species (ROS) like H₂O₂. When cells are exposed to exogenously added H₂O₂, ATR/CHK1 and ATM/CHK2 dependent DNA damage signaling is switched on, suggesting that H₂O₂ induces both single and double strand breaks. These collective observations have resulted in the widely accepted model that oxidizing conditions lead to DNA damage that subsequently mediates a p53-dependent response like cell cycle arrest and apoptosis. However, H₂O₂ also induces signaling through stress-activated kinases (SAPK, e.g., JNK and p38 MAPK) that can activate p53. Here we dissect to what extent these pathways contribute to functional activation of p53 in response to oxidizing conditions. Collectively, our data suggest that p53 can be activated both by SAPK signaling and the DDR independently of each other, and which of these pathways is activated depends on the type of oxidant used. This implies that it could in principle be possible to modulate oxidative signaling to stimulate p53 without inducing collateral DNA damage, thereby limiting mutation accumulation in both healthy and tumor tissues.

Deciphering the PTM codes of the tumor suppressor p53

The genome guardian p53 functions as a transcription factor that senses numerous cellular stresses and orchestrates the corresponding transcriptional events involved in determining various cellular outcomes, including cell cycle arrest, apoptosis, senescence, DNA repair, and metabolic regulation. In response to diverse stresses, p53 undergoes multiple posttranslational modifications (PTMs) that coordinate with intimate interdependencies to precisely modulate its diverse properties in given biological contexts. Notably, PTMs can recruit ‘reader’ proteins that exclusively recognize specific modifications and facilitate the functional readout of p53. Targeting PTM–reader interplay has been developing into a promising cancer therapeutic strategy. In this review, we summarize the advances in deciphering the ‘PTM codes’ of p53, focusing particularly on the mechanisms by which the specific reader proteins functionally decipher the information harbored within these PTMs of p53. We also highlight the potential applications of intervention with p53 PTM–reader interactions in cancer therapy and discuss perspectives on the ‘PTMomic’ study of p53 and other proteins.

Mitochondria: The metabolic switch of cellular oncogenic transformation

Mitochondria, well recognized as the "powerhouse" of cells, are maternally inherited organelles with bacterial ancestry that play essential roles in a myriad of cellular functions. It has become profoundly evident that mitochondria regulate a wide array of cellular and metabolic functions, including biosynthetic metabolism, cell signaling, redox homeostasis, and cell survival. Correspondingly, defects in normal mitochondrial functioning have been implicated in various human malignancies. Cancer development involves the activation of oncogenes, inactivation of tumor suppressor genes, and impairment of apoptotic programs in cells. Mitochondria have been recognized as the site of key metabolic switches for normal cells to acquire a malignant phenotype. This review outlines the role of mitochondria in human malignancies and highlights potential aspects of mitochondrial metabolism that could be targeted for therapeutic development.

CDC25B induces cellular senescence and correlates with tumor suppression in a p53-dependent manner

The phosphatase cell division cycle 25B (Cdc25B) regulates cell cycle progression. Increased Cdc25B levels are often detected in cancer cell lines and human cancers and have been implicated in contributing to tumor growth, potentially by providing cancer cells with the ability to bypass checkpoint controls. However, the specific mechanism by which increased Cdc25B impacts tumor progression is not clear. Here we analyzed The Cancer Genome Atlas (TCGA) database and found that patients with high CDC25B expression had the expected poor survival. However, we also found that high CDC25B expression had a p53-dependent tumor suppressive effect in lung cancer and possibly several other cancer types. Looking in more detail at the tumor suppressive function of Cdc25B, we found that increased Cdc25B expression caused inhibition of cell growth in human normal fibroblasts. This effect was not due to alteration of specific cell cycle stage or inhibition of apoptosis, nor by induction of the DNA damage response. Instead, increased CDC25B expression led cells into senescence. We also found that p53 was required to induce senescence, which might explain the p53-dependent tumor suppressive function of Cdc25B. Mechanistically, we found that the Cdc25B phosphatase activity was required to induce senescence. Further analysis also found that Cdc25B stabilized p53 through binding and dephosphorylating p53. Together, this study identified a tumor-suppressive function of Cdc25B that is mediated through a p53-dependent senescence pathway.

Dissection of Anti-tumor Activity of Histone Deacetylase Inhibitor SAHA in Nasopharyngeal Carcinoma Cells via Quantitative Phosphoproteomics

Suberoylanilide hydroxamic acid (SAHA), a pan HDAC inhibitor, has been approved by the Food and Drug Administration (FDA) to treat cutaneous T cell lymphoma (CTCL). Nevertheless, the mechanisms underlying the therapeutic effects of SAHA on tumors are yet not fully understood. Protein phosphorylation is one of the most important means to regulate key biological processes (BPs), such as cell division, growth, migration, differentiation, and intercellular communication. Thus, investigation on the impacts of SAHA treatment on global cellular phosphorylation covering major signaling pathways deepens our understanding on its anti-tumor mechanisms. Here we comprehensively identified and quantified protein phosphorylation for the first time in nasopharyngeal carcinoma (NPC) cells upon SAHA treatment by combining tandem mass tags (TMTs)-based quantitative proteomics and titanium dioxide (TiO₂)-based phosphopeptide enrichment. In total, 7,430 phosphorylation sites on 2,456 phosphoproteins were identified in the NPC cell line 5-8F, of which 1,176 phosphorylation sites on 528 phosphoproteins were significantly elevated upon SAHA treatment. Gene ontology (GO) analysis showed that SAHA influenced several BPs, including mRNA/DNA processing and cell cycle. Furthermore, signaling pathway analysis and immunoblotting demonstrated that SAHA activated tumor suppressors like p53 and Rb1 via phosphorylation and promoted cell apoptosis in NPC cells but inactivated energetic pathways such as AMPK signaling. Overall, our study indicated that SAHA exerted anti-tumor roles in NPC cells, which may serve as novel therapeutic for NPC patients.

Understanding p53 functions through p53 antibodies

TP53 is the most frequently mutated gene across all cancer types. Our understanding of its functions has evolved since its discovery four decades ago. Initially thought to be an oncogene, it was later realized to be a critical tumour suppressor. A significant amount of our knowledge about p53 functions have come from the use of antibodies against its various forms. The early anti-p53 antibodies contributed to the recognition of p53 accumulation as a common feature of cancer cells and to our understanding of p53 DNA-binding and transcription activities. They led to the concept that conformational changes can facilitate p53’s activity as a growth inhibitory protein. The ensuing p53 conformational-specific antibodies further underlined p53’s conformational flexibility, collectively forming the basis for current efforts to generate therapeutic molecules capable of altering the conformation of mutant p53. A subsequent barrage of antibodies against post-translational modifications on p53 has clarified p53’s roles further, especially with respect to the mechanistic details and context-dependence of its activity. More recently, the generation of p53 mutation-specific antibodies have highlighted the possibility to go beyond the general framework of our comprehension of mutant p53—and promises to provide insights into the specific properties of individual p53 mutants. This review summarizes our current knowledge of p53 functions derived through the major classes of anti-p53 antibodies, which could be a paradigm for understanding other molecular events in health and disease.

Cannabinoid CP55940 selectively induces apoptosis in Jurkat cells and in ex vivo T-cell acute lymphoblastic leukemia through H2O2 signaling mechanism

T-cell acute lymphoblastic leukemia (T-ALL) is a highly heterogeneous malignant hematological disorder arising from T-cell progenitors. This study was aimed to evaluate the cytotoxic effect of CP55940 on human peripheral blood lymphocytes (PBL) and on T-ALL cells (Jurkat). PBL and Jurkat cells were treated with CP55940 (0-20 μM), and morphological changes in the cell nucleus/ DNA, mitochondrial membrane potential (ΔΨm), and intracellular reactive oxygen species levels were determined by fluorescence microscopy and flow cytometry. Cellular apoptosis markers were also evaluated by western blotting, pharmacological inhibition and immunofluorescence. CP55940 induced apoptotic cell death in Jurkat cells, but not in PBL, in a dose-response manner with increasing fragmentation of DNA, arrest of cell cycle and damage of ΔΨm. CP55940 increased dichlorofluorescein fluorescence (DCF) intensity, increased DJ-1 Cys¹⁰⁶- sulfonate, a marker of intracellular stress, induced the up-regulation of p53 and phosphorylation of transcription factor c-JUN. It increased the expression of BAX and PUMA, up-regulated mitochondrial proteins PINK1 and Parkin, and activated CASPASE-3. Antioxidant NAC, pifithrin-α, and SP600125 blocked CP55940 deleterious effect on Jurkat cells. However, the potent and highly specific cannabinoid CB1 and CB2 receptor inverse agonist SR141716 and SR144528 were unable to blunt CP55940-induced apoptosis in Jurkat cells. Conclusively CP55940 provokes cell death in Jurkat through CBR-independent mechanism. Interestingly, CP55940 was also cytotoxic to ex vivo T-ALL cells from chemotherapy-resistant pediatric patients. In conclusion, CP55940 selectively induces apoptosis in Jurkat cells through a H₂O₂-mediated signaling pathway. Our findings support the use of cannabinoids as a potential treatment for T-ALL cells.

Anticancer drug and ionizing radiation-induced DNA damage differently influences transcription activity and DDR-related stress responses of an endothelial monolayer

The endothelium contributes to the pathophysiology of adverse effects caused by conventional (genotoxic) anticancer therapeutics (cAT). The relevance of structurally different types of cAT-induced DNA lesions for eliciting selected endothelial stress responses is largely unknown. Here, we analyzed the cAT-induced formation of DNA double-strand breaks (DSB), transcription blockage and DNA damage response (DDR) in time kinetic analyses employing a monolayer of primary human endothelial cells (HUVEC). We observed that the degree of cAT-induced transcription blockage, the number of DSB and activation of DDR-related factors diverge. For instance, ionizing radiation caused the formation of numerous DSB and triggerd a substantial activation of ATM/Chk2 signaling, which however were not accompanied by a significant transcription inhibition. By contrast, the DNA cross-linking cAT cisplatin triggered a rapid and substantial blockage of transcription, which yet was not reflected by an appreciable number of DSB or increased levels of pATM/pChk2. In general, cAT-stimulated ATM-dependent phosphorylation of Kap1 (Ser824) and p53 (Ser15) reflected best cAT-induced transcription blockage. In conclusion, cAT-induced formation of DSB and profound activation of prototypical DDR factors is independent of the inhibition of RNA polymerase II-regulated transcription in an endothelial monolayer. We suggest that DSB formed directly or indirectly following cAT-treatment do not act as comprehensive triggers of superior signaling pathways shutting-down transcription while, at the same time, causing an appreciable stimulation of the DDR. Rather, it appears that distinct cAT-induced DNA lesions elicit diverging signaling pathways, which separately control transcription vs. DDR activity in the endothelium.

Human colon cancer cells highly express myoferlin to maintain a fit mitochondrial network and escape p53-driven apoptosis

Colon adenocarcinoma is the third most commonly diagnosed cancer and the second deadliest one. Metabolic reprogramming, described as an emerging hallmark of malignant cells, includes the predominant use of glycolysis to produce energy. Recent studies demonstrated that mitochondrial electron transport chain inhibitor reduced colon cancer tumour growth. Accumulating evidence show that myoferlin, a member of the ferlin family, is highly expressed in several cancer types, where it acts as a tumour promoter and participates in the metabolic rewiring towards oxidative metabolism. In this study, we showed that myoferlin expression in colon cancer lesions is associated with low patient survival and is higher than in non-tumoural adjacent tissue. Human colon cancer cells silenced for myoferlin exhibit a reduced oxidative phosphorylation activity associated with mitochondrial fission leading, ROS accumulation, decreased cell growth, and increased apoptosis. We observed the triggering of a DNA damage response culminating to a cell cycle arrest in wild-type p53 cells. The use of a p53 null cell line or a compound able to restore p53 activity (Prima-1) reverted the effects induced by myoferlin silencing, confirming the involvement of p53. The recent identification of a compound interacting with a myoferlin C2 domain and bearing anticancer potency identifies, together with our demonstration, this protein as a suitable new therapeutic target in colon cancer.

Cold Physical Plasma Modulates p53 and Mitogen-Activated Protein Kinase Signaling in Keratinocytes

Small reactive oxygen and nitrogen species (ROS/RNS) driven signaling plays a significant role in wound healing processes by controlling cell functionality and wound phase transitions. The application of cold atmospheric pressure plasma (CAP), a partially ionized gas expelling a variety of ROS and RNS, was shown to be effective in chronic wound management and contrastingly also in malignant diseases. The underlying molecular mechanisms are not well understood but redox signaling events are involved. As a central player, the cellular tumor antigen p53 governs regulatory networks controlling proliferation, death, or metabolism, all of which are grossly modulated by anti- and prooxidant signals. Using a human skin cell model, a transient phosphorylation and nuclear translocation of p53, preceded by the phosphorylation of upstream serine- (ATM) and serine/threonine-protein kinase (ATR), was detected after CAP treatment. Results indicate that ATM acts as a direct redox sensor without relevant contribution of phosphorylation of the histone A2X, a marker of DNA damage. Downstream events are the activation of checkpoint kinases Chk1/2 and several mitogen-activated (MAP) kinases. Subsequently, the expression of MAP kinase signaling effectors (e.g., heat shock protein Hsp27), epithelium derived growth factors, and cytokines (Interleukins 6 + 8) was increased. A number of p53 downstream effectors pointed at a decrease of cell growth due to DNA repair processes. In summary, CAP treatment led to an activation of cell repair and defense mechanisms including a modulation of paracrine inflammatory signals emphasizing the role of prooxidant species in CAP-related cell signaling.

Theileria highjacks JNK2 into a complex with the macroschizont GPI (GlycosylPhosphatidylInositol)-anchored surface protein p104

Constitutive c-Jun N-terminal kinase (JNK) activity characterizes bovine T and B cells infected with Theileria parva, and B cells and macrophages infected with Theileria annulata. Here, we show that T. annulata infection of macrophages manipulates JNK activation by recruiting JNK2 and not JNK1 to the parasite surface, whereas JNK1 is found predominantly in the host cell nucleus. At the parasite's surface, JNK2 forms a complex with p104, a GPI-(GlycosylPhosphatidylInositol)-anchor T. annulata plasma membrane protein. Sequestration of JNK2 depended on Protein Kinase-A (PKA)-mediated phosphorylation of a JNK-binding motif common to T. parva and a cell penetrating peptide harbouring the conserved p104 JNK-binding motif competitively ablated binding, whereupon liberated JNK2 became ubiquitinated and degraded. Cytosolic sequestration of JNK2 suppressed small mitochondrial ARF-mediated autophagy, whereas it sustained nuclear JNK1 levels, c-Jun phosphorylation, and matrigel traversal. Therefore, T. annulata sequestration of JNK2 contributes to both survival and dissemination of Theileria-transformed macrophages.

Redox for Repair: Cold Physical Plasmas and Nrf2 Signaling Promoting Wound Healing

Chronic wounds and ulcers are major public health threats. Being a substantial burden for patients and health care systems alike, better understanding of wound pathophysiology and new avenues in the therapy of chronic wounds are urgently needed. Cold physical plasmas are particularly effective in promoting wound closure, irrespective of its etiology. These partially ionized gases deliver a therapeutic cocktail of reactive oxygen and nitrogen species safely at body temperature and without genotoxic side effects. This field of plasma medicine reanimates the idea of redox repair in physiological healing. This review compiles previous findings of plasma effects in wound healing. It discusses new links between plasma treatment of cells and tissues, and the perception and intracellular translation of plasma-derived reactive species via redox signaling pathways. Specifically, (i) molecular switches governing redox-mediated tissue response; (ii) the activation of the nuclear E2-related factor (Nrf2) signaling, together with antioxidative and immunomodulatory responses; and (iii) the stabilization of the scaffolding function and actin network in dermal fibroblasts are emphasized in the light of wound healing.

Tumor suppressive role for kinases phosphorylating p53 in DNA damage-induced apoptosis

Tumor suppressor p53 plays an important role in cancer prevention. Under normal conditions, p53 is maintained at a low level. However, in response to various cellular stresses, p53 is stabilized and activated, which, in turn, initiates DNA repair, cell-cycle arrest, senescence and apoptosis. Post-translational modifications of p53 including phosphorylation, ubiquitination, and acetylation at multiple sites are important to regulate its activation and subsequent transcriptional gene expression. Particularly, phosphorylation of p53 plays a critical role in modulating its activation to induce apoptosis in cancer cells. In this context, previous studies show that several serine/threonine kinases regulate p53 phosphorylation and downstream gene expression. The molecular basis by which p53 and its kinases induce apoptosis for cancer prevention has been extensively studied. However, the relationship between p53 phosphorylation and its kinases and how the activity of kinases is controlled are still largely unclear; hence, they need to be investigated. In this review, we discuss various roles for p53 phosphorylation and its responsible kinases to induce apoptosis and a new therapeutic approach in a broad range of cancers.

Mutant and wild-type p53 form complexes with p73 upon phosphorylation by the kinase JNK

The transcription factors p53 and p73 are critical to the induction of apoptotic cell death, particularly in response to cell stress that activates c-Jun N-terminal kinase (JNK). Mutations in the DNA-binding domain of p53, which are commonly seen in cancers, result in conformational changes that enable p53 to interact with and inhibit p73, thereby suppressing apoptosis. In contrast, wild-type p53 reportedly does not interact with p73. We found that JNK-mediated phosphorylation of Thr⁸¹ in the proline-rich domain (PRD) of p53 enabled wild-type p53, as well as mutant p53, to form a complex with p73. Structural algorithms predicted that phosphorylation of Thr⁸¹ exposes the DNA-binding domain in p53 to enable its binding to p73. The dimerization of wild-type p53 with p73 facilitated the expression of apoptotic target genes [such as those encoding p53-up-regulated modulator of apoptosis (PUMA) and Bcl-2-associated X protein (BAX)] and, subsequently, the induction of apoptosis in response to JNK activation by cell stress in various cells. Thus, JNK phosphorylation of mutant and wild-type p53 promotes the formation of a p53/p73 complex that determines cell fate: apoptosis in the context of wild-type p53 or cell survival in the context of the mutant. These findings refine our current understanding of both the mechanistic links between p53 and p73 and the functional role for Thr⁸¹ phosphorylation.

Notch signaling and neuronal death in stroke

Ischemic stroke is a leading cause of morbidity and death, with the outcome largely determined by the amount of hypoxia-related neuronal death in the affected brain regions. Cerebral ischemia and hypoxia activate the Notch1 signaling pathway and four prominent interacting pathways (NF-κB, p53, HIF-1α and Pin1) that converge on a conserved DNA-associated nuclear multi-protein complex, which controls the expression of genes that can determine the fate of neurons. When neurons experience a moderate level of ischemic insult, the nuclear multi-protein complex up-regulates adaptive stress response genes encoding proteins that promote neuronal survival, but when ischemia is more severe the nuclear multi-protein complex induces genes encoding proteins that trigger and execute a neuronal death program. We propose that the nuclear multi-protein transcriptional complex is a molecular mediator of neuronal hormesis and a target for therapeutic intervention in stroke.

The serum protein profile of early parity which induces protection against breast cancer

Early parity reduces the risk of breast cancer in women while nulliparity and late parity increase the risk of breast cancer. In order to translate this protection to women where early pregnancy is not feasible, much work has focused on understanding how parity confers protection against breast cancer, the molecular mechanisms by which this occurs is still not well understood. Healthy parous and nulliparous women were recruited for this study. We assessed serum protein profiles of early parous, late parous, and nulliparous women using the Phospho Explorer antibody array. Significantly altered proteins identified were validated by Western blot analysis. In silico analysis was performed with the data obtained. Our findings indicate increased phosphorylation levels of CDK1, AKT1 and Epo-R increased cell cycle and cell proliferation in late/nulliparous women. Increased levels of LIMK1, paxillin, caveolin-1, and tyrosine hydroxylase in late/nulliparous women demonstrate enhanced cell stress while decreased activity of p-p53 and pRAD51 in late/nulliparous women indicates decreased apoptosis and increased genomic instability. Further, increased levels of pFAK, pCD3zeta, pSTAT5B, MAP3K8 in early parous women favor enhanced innate/adaptive immunity. Overall, we have identified a unique protein signature that is responsible for the decreased risk of breast cancer and these proteins can also serve as biomarkers to predict the risk of breast cancer.

Genetic Variation in MAP3K1 Associates with Ventilator-Free Days in Acute Respiratory Distress Syndrome

Mitogen-activated protein kinase kinase kinase 1 (MAP3K1) regulates numerous intracellular signaling pathways involved in inflammation and apoptosis. We hypothesized that genetic variation in MAP3K1 might be associated with outcomes in patients with acute respiratory distress syndrome (ARDS), and that these variants would alter MAP3K1-mediated changes in inflammation and transcriptional regulation. To test this hypothesis, we genotyped single-nucleotide polymorphisms covering linkage disequilibrium bins in MAP3K1 in 306 subjects with ARDS from the ARDSNet FACTT (Fluid and Catheter Treatment Trial) study, and tested for associations between MAP3K1 single-nucleotide polymorphisms and ventilator-free days (VFDs) and mortality. We then validated these associations in a separate cohort of 241 patients with ARDS from Harborview Medical Center (Seattle, WA). We found the variant allele of rs832582 (MAP3K1_906Val) was significantly associated with decreased VFDs using multivariate linear regression (-6.1 d, false discovery rate = 0.06) in the FACTT cohort. In the Harborview Medical Center cohort, subjects homozygous for MAP3K1_906Val also had decreased VFDs (-15.1 d, false discovery rate < 0.01), and increased 28-day mortality (all subjects homozygous for the rare allele died). In whole blood stimulated with various innate immune agonists ex vivo, MAP3K1_906Val was associated with increased IL-1β, IL-6, IL-8, monocyte chemoattractant protein 1, and TNF-α production. Transcriptome analysis of whole blood stimulated with Toll-like receptor 4 agonist ex vivo demonstrated enrichment of inflammatory gene sets in subjects homozygous for MAP3K1_906Val. Our findings show a robust association between the variant allele of rs832582 (MAP3K1_906Val) and decreased VFDs in patients with ARDS and suggest that this variant may predispose individuals to a greater inflammatory response.

JNK2 downregulation promotes tumorigenesis and chemoresistance by decreasing p53 stability in bladder cancer

Bladder cancer is one of the most common malignancies of the urinary system, and the 5-year survival rate remains low. A comprehensive understanding of the carcinogenesis and progression of bladder cancer is urgently needed to advance treatment. c-Jun N-terminal kinase-2 (JNK2) exhibits both tumor promoter and tumor suppressor actions, depending on tumor type. Here, we analyzed the JNK2 function in bladder cancer. Using gene expression microarrays, we demonstrated that JNK2 mRNA is downregulated in an orthotopic rat model of bladder cancer. JNK2 protein levels were lower in rat and human bladder cancer tissues than in normal tissues, and the levels correlated with those of p53. Moreover, JNK2 phosphorylated p53 at Thr-81, thus protecting p53 from MDM2-induced proteasome degradation. Decreased expression of JNK2 in T24 cells conferred resistance to cell death induced by mitomycin C. Furthermore, lower JNK2 expression was associated with poorer overall survival among patients who underwent radical cystectomy. These results indicate that JNK2 acts as a tumor suppressor in bladder cancer, and that decreased JNK2 expression promotes bladder cancer tumorigenesis.

Redox-Inactive Peptide Disrupting Trx1-Ask1 Interaction for Selective Activation of Stress Signaling

Thioredoxin 1 (Trx1) and glutaredoxin 1 (Grx1) are two ubiquitous redox enzymes that are central for redox homeostasis but also are implicated in many other processes, including stress sensing, inflammation, and apoptosis. In addition to their enzymatic redox activity, a growing body of evidence shows that Trx1 and Grx1 play regulatory roles via protein-protein interactions with specific proteins, including Ask1. The currently available inhibitors of Trx1 and Grx1 are thiol-reactive electrophiles or disulfides that may suffer from low selectivity because of their thiol reactivity. In this report, we used a phage peptide library to identify a 7-mer peptide, 2GTP1, that binds to both Trx1 and Grx1. We further showed that a cell-permeable derivative of 2GTP1, TAT-2GTP1, disrupts the Trx1-Ask1 interaction, which induces Ask1 phosphorylation with subsequent activation of JNK, stabilization of p53, and reduced viability of cancer cells. Notably, as opposed to a disulfide-derived Trx1 inhibitor (PX-12), TAT-2GTP1 was selective for activating the Ask1 pathway without affecting other stress signaling pathways, such as endoplasmic reticulum stress and AMPK activation. Overall, 2GTP1 will serve as a useful probe for investigating protein interactions of Trx1.

Upregulation of miR-146a increases cisplatin sensitivity of the non-small cell lung cancer A549 cell line by targeting JNK-2

The aim of the present study was to investigate the effects of microRNA (miR-)146a on the cisplatin sensitivity of the non-small cell lung cancer (NSCLC) A549 cell line and study the underlying molecular mechanism. The differences in expression of miRNAs between A549 and A549/cisplatin (A549/DDP) cells were determined, and miR-146a was selected to study its effect on cisplatin sensitivity of A549/DDP cells. miR-146a mimic and inhibitor transient transfection systems were constructed using vectors, and A549/DDP cells were infected with miR-146a mimic and inhibitor to investigate growth, apoptosis and migration. The directed target of miR-146a was determined and the underlying molecular mechanism was validated in the present study. The results of the present study demonstrated that miR-146a was downregulated in NSCLC A549/DDP cells, compared with A549 cells. The overexpression of miR-146a induced apoptosis and inhibited the growth and invasion of A549/DDP cells, which resulted in increased cisplatin sensitivity in NSCLC cells. The JNK2 gene was determined as the direct target of miR-146a, and may be activated by the overexpression of miR-146a. Additionally, JNK2 activated the expression of p53 and inhibited B cell lymphoma 2. The upregulation of miR-146a increased cisplatin sensitivity of the A549 cell line by targeting JNK2, which may provide a novel method for treating NSCLC cisplatin resistance.

Phosphorylation: Implications in Cancer

Post translational modifications (PTMs) are involved in variety of cellular activities and phosphorylation is one of the most extensively studied PTM, which regulates a number of cellular functions like cell growth, differentiation, apoptosis and cell signaling in healthy condition. However, alterations in phosphorylation pathways result in serious outcomes in the form of diseases, especially cancer. Many signalling pathways including Tyrosine kinase, MAP kinase, Cadherin-catenin complex, Cyclin-dependent kinase etc. are major players of the cell cycle and deregulation in their phosphorylation-dephosphorylation cascade has been shown to be manifested in the form of various types of cancers. Tyrosine kinase family encompasses the greatest number of oncoproteins. MAPK cascade has an importance role in cancer growth and progression. Bcl-2 family proteins serve either proapoptotic or antiapoptotic function. Cadherin-catenin complex regulates cell adhesion properties and cyclins are the key regulators of cell cycle. Altered phosphorylations in any of the above pathways are strongly associated with cancer, at the same time they serve as the potential tergets for drug development against cancer. Drugs targeting tyrosine kinase are potent anticancer drugs. Inhibitors of MEK, PI3K and ERK signalling pathways are undergoing clinical trials. Thus, drugs targeting phosphorylation pathways represent a promising area for cancer therapy.

Coumarin-chalcone hybrid instigates DNA damage by minor groove binding and stabilizes p53 through post translational modifications

S009-131, a coumarin-chalcone hybrid, had been shown to possess anti-proliferative and anti-tumour effect by triggering apoptosis. In this report, we investigated role of DNA damage signalling pathway in S009-131 induced cancer cell death. Here we show that S009-131 causes DNA damage by potential binding to the minor groove which led to the phosphorylation and activation of ATM and DNA-PK, but not ATR, at earlier time points in order to initiate repair process. S009-131 induced DNA damage response triggered activation of p53 through phosphorylation at its key residues. Pharmacological inhibition of PIKKs abrogated S009-131 induced phosphorylation of p53 at Ser 15. DNA damage induced phosphorylation resulted in reduced proteasomal degradation of p53 by disrupting p53-MDM2 interaction. Additionally, our docking studies revealed that S009-131 might also contribute to increased cellular p53 level by occupying p53 binding pocket of MDM2. Posttranslational modifications of p53 upon S009-131 treatment led to enhanced affinity of p53 towards responsive elements (p53-RE) in the promoter regions of target genes and increased transcriptional efficiency. Together, the results suggest that S009-131 cleaves DNA through minor groove binding and eventually activates PIKKs associated DNA damage response signalling to promote stabilization and enhanced transcriptional activity of p53 through posttranslational modifications at key residues.

DNA Damage Response and Autophagy: A Meaningful Partnership

Autophagy and the DNA damage response (DDR) are biological processes essential for cellular and organismal homeostasis. Herein, we summarize and discuss emerging evidence linking DDR to autophagy. We highlight published data suggesting that autophagy is activated by DNA damage and is required for several functional outcomes of DDR signaling, including repair of DNA lesions, senescence, cell death, and cytokine secretion. Uncovering the mechanisms by which autophagy and DDR are intertwined provides novel insight into the pathobiology of conditions associated with accumulation of DNA damage, including cancer and aging, and novel concepts for the development of improved therapeutic strategies against these pathologies.

JNK Signaling: Regulation and Functions Based on Complex Protein-Protein Partnerships

The c-Jun N-terminal kinases (JNKs), as members of the mitogen-activated protein kinase (MAPK) family, mediate eukaryotic cell responses to a wide range of abiotic and biotic stress insults. JNKs also regulate important physiological processes, including neuronal functions, immunological actions, and embryonic development, via their impact on gene expression, cytoskeletal protein dynamics, and cell death/survival pathways. Although the JNK pathway has been under study for >20 years, its complexity is still perplexing, with multiple protein partners of JNKs underlying the diversity of actions. Here we review the current knowledge of JNK structure and isoforms as well as the partnerships of JNKs with a range of intracellular proteins. Many of these proteins are direct substrates of the JNKs. We analyzed almost 100 of these target proteins in detail within a framework of their classification based on their regulation by JNKs. Examples of these JNK substrates include a diverse assortment of nuclear transcription factors (Jun, ATF2, Myc, Elk1), cytoplasmic proteins involved in cytoskeleton regulation (DCX, Tau, WDR62) or vesicular transport (JIP1, JIP3), cell membrane receptors (BMPR2), and mitochondrial proteins (Mcl1, Bim). In addition, because upstream signaling components impact JNK activity, we critically assessed the involvement of signaling scaffolds and the roles of feedback mechanisms in the JNK pathway. Despite a clarification of many regulatory events in JNK-dependent signaling during the past decade, many other structural and mechanistic insights are just beginning to be revealed. These advances open new opportunities to understand the role of JNK signaling in diverse physiological and pathophysiological states.

Methylsulfonylmethane Induces p53 Independent Apoptosis in HCT-116 Colon Cancer Cells

Methylsulfonylmethane (MSM) is an organic sulfur-containing compound which has been used as a dietary supplement for osteoarthritis. MSM has been shown to reduce oxidative stress and inflammation, as well as exhibit apoptotic or anti-apoptotic effects depending on the cell type or activating stimuli. However, there are still a lot of unknowns about the mechanisms of actions of MSM. In this study, MSM was tested on colon cancer cells. 3-(4,5-Dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay and flow cytometric analysis revealed that MSM inhibited cell viability and increased apoptotic markers in both HCT-116 p53 +/+ and HCT-116 p53 −/− colon cancer cells. Increased poly (ADP-ribose) polymerase (PARP) fragmentation and caspase-3 activity by MSM also supported these findings. MSM also modulated the expression of various apoptosis-related genes and proteins. Moreover, MSM was found to increase c-Jun N-terminal kinases (JNK) phosphorylation in both cell lines, dose-dependently. In conclusion, our results show for the first time that MSM induces apoptosis in HCT-116 colon cancer cells regardless of their p53 status. Since p53 is defective in >50% of tumors, the ability of MSM to induce apoptosis independently of p53 may offer an advantage in anti-tumor therapy. Moreover, the remarkable effect of MSM on Bim, an apoptotic protein, also suggests its potential use as a novel chemotherapeutic agent for Bim-targeted anti-cancer therapies.

Neuronal Survival and p73/p63/p53: A Family Affair

Elucidating the mechanisms that regulate the life versus death of mammalian neurons is important not only for our understanding of the normal biology of the nervous system but also for our efforts to devise approaches to maintain neuronal survival in the face of traumatic injury or neurodegenerative disorders. Here, we review the emerging evidence that a key survival/death checkpoint in both peripheral and central neurons involves the p53 tumor suppressor and its newly discovered family members, p73 and p63. The full-length isoforms of these proteins function as proapoptotic proteins, whereas naturally occurring N-terminal truncated variants of p73 and p63 act as prosurvival proteins, at least partially by antagonizing the full-length family members. The authors propose that together, these isoforms comprise an upstream rheostat that sums different environmental cues to ultimately determine neuronal survival during development, during neuronal maintenance in adult animals, and even following traumatic injury.

Crosstalk between tumor suppressors p53 and PKCδ: Execution of the intrinsic apoptotic pathways

p53 and PKCδ are tumor suppressors that execute apoptotic mechanisms in response to various cellular stresses. p53 is a transcription factor that is frequently mutated in human cancers; it regulates apoptosis in transcription-dependent and -independent ways in response to genotoxic stresses. PKCδ is a serine/threonine protein kinase and mutated in human cancers. Available evidence shows that PKCδ activates p53 by direct and/or indirect mechanisms. Moreover, PKCδ is also implicated in the transcriptional regulation of p53 in response to DNA damage. Recent findings demonstrated that p53, in turn, binds onto the PKCδ promoter and induces its expression upon DNA damage to facilitate apoptosis. Both p53 and PKCδ are associated with the apoptotic mechanisms in the mitochondria by regulating Bcl-2 family proteins to provide mitochondrial outer membrane permeabilization. This review discusses the crosstalk between p53 and PKCδ in the context of apoptotic cell death and cancer therapy.

The phosphatidylinositol 3-kinase/Akt and c-Jun N-terminal kinase signaling in cancer: Alliance or contradiction? (Review)

The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and c-Jun N-terminal kinase (JNK) pathway are responsible for regulating a variety of cellular processes including cell growth, migration, invasion and apoptosis. These two pathways are essential to the development and progression of tumors. The dual roles of JNK signaling in apoptosis and tumor development determine the different interactions between the PI3K/Akt and JNK pathways. Activation of PI3K/Akt signaling can inhibit stress- and cytokine-induced JNK activation through Akt antagonizing and the formation of the JIP1-JNK module, as well as the activities of upstream kinases ASK1, MKK4/7 and MLK. On the other hand, hyperactivation of Akt and JNK is also found in cancers that harbor EGFR overexpression or loss of PTEN. Understanding the activation mechanism of PI3K/Akt and JNK pathways, as well as the interplays between these two pathways in cancer may contribute to the identification of novel therapeutic targets. In the present report, we summarized the current understanding of the PI3K/Akt and JNK signaling networks, as well as their biological roles in cancers. In addition, the interactions and regulatory network between PI3K/Akt and JNK pathways in cancer were discussed.

[Oxidative stress and its effect on cells functional activity of alzheimer's disease]

The paper summarizes literature data on the importance of oxidative stress as one of the pathogenetic mechanisms in Alzheimer's disease. The paper describes the main specific and nonspecific ways of reactive oxygen species generation in the course of the disease development. The effect of reactive oxygen species generated by the functional activity of cells, i.e. apoptosis and mitotic cycle, is shown. The role of the regulatory system of nodal cells is performed by phosphorylation/dephosphorylation process which is associated with intense phosphorylation of tau protein and mitosis-specific proteins. In Alzheimer's disease, the regulating function of peptidyl-prolyl isomerases in particular of Pin1 associated with maintaining a balanced state of phosphorylation/dephosphorylation processes is disturbed. Taking into consideration the multifactorial impairment of the cell cycle control, this process should be considered from the standpoint of the general state of metabolic processes, and oxidative stress has one of the key positions in aging.

Landscape of Pin1 in the cell cycle

Pin1 is a peptidyl-prolyl isomerase which plays a critical role in many diseases including cancer and Alzheimer's disease. The essential role of Pin1 is to affect stability, localization or function of phosphoproteins by catalyzing structural changes. Among the collection of Pin1 substrates, many have been shown to be involved in regulating cell cycle progression. The cell cycle disorder caused by dysregulation of these substrates is believed to be a common phenomenon in cancer. A number of recent studies have revealed possible functions of several important Pin1-binding cell cycle regulators. Investigating the involvement of Pin1 in the cell cycle may assist in the development of future cancer therapeutics. In this review, we summarize current knowledge regarding the network of Pin1 substrates and Pin1 regulators in cell cycle progression. In G1/S progression, cyclin D1, RB, p53, p27, and cyclin E are all well-known cell cycle regulators that are modulated by Pin1. During G2/M transition, our lab has shown that Aurora A suppresses Pin1 activity through phosphorylation at Ser16 and cooperates with hBora to modulate G2/M transition. We conclude that Pin1 may be thought of as a molecular timer which modulates cell cycle progression networks.

Interaction of p53 with prolyl isomerases: Healthy and unhealthy relationships

BACKGROUND

The p53 protein family, comprising p53, p63 and p73, is primarily involved in preserving genome integrity and preventing tumor onset, and also affects a range of physiological processes. Signal-dependent modifications of its members and of other pathway components provide cells with a sophisticated code to transduce a variety of stress signaling into appropriate responses. TP53 mutations are highly frequent in cancer and lead to the expression of mutant p53 proteins that are endowed with oncogenic activities and sensitive to stress signaling.

SCOPE OF REVIEW

p53 family proteins have unique structural and functional plasticity, and here we discuss the relevance of prolyl-isomerization to actively shape these features.

MAJOR CONCLUSIONS

The anti-proliferative functions of the p53 family are carefully activated upon severe stress and this involves the interaction with prolyl-isomerases. In particular, stress-induced stabilization of p53, activation of its transcriptional control over arrest- and cell death-related target genes and of its mitochondrial apoptotic function, as well as certain p63 and p73 functions, all require phosphorylation of specific S/T-P motifs and their subsequent isomerization by the prolyl-isomerase Pin1. While these functions of p53 counteract tumorigenesis, under some circumstances their activation by prolyl-isomerases may have negative repercussions (e.g. tissue damage induced by anticancer therapies and ischemia-reperfusion, neurodegeneration). Moreover, elevated Pin1 levels in tumor cells may transduce deregulated phosphorylation signaling into activation of mutant p53 oncogenic functions.

GENERAL SIGNIFICANCE

The complex repertoire of biological outcomes induced by p53 finds mechanistic explanations, at least in part, in the association between prolyl-isomerases and the p53 pathway. This article is part of a Special Issue entitled Proline-directed foldases: Cell signaling catalysts and drug targets.

Structural and sequential context of p53: A review of experimental and theoretical evidence

Approximately 27 million people are suffering from cancer that contains either an inactivating missense mutation of TP53 gene or partially abrogated p53 signaling pathway. Concerted action of folded and intrinsically disordered domains accounts for multi-faceted role of p53. The intricacy of dynamic p53 structure is believed to shed light on its cellular activity for developing new cancer therapies. In this review, insights into structural details of p53, diverse single point mutations affecting its core domain, thermodynamic understanding and therapeutic strategies for pharmacological rescue of p53 function has been illustrated. An effort has been made here to bridge the structural and sequential evidence of p53 from experimental to computational studies. First, we focused on the individual domains and the crucial protein-protein or DNA-protein contacts that determine conformation and dynamic behavior of p53. Next, the oncogenic mutations associated with cancer and its contribution to thermodynamic fluctuation has been discussed. Thus the emerging anti-cancer strategies include targeting of destabilized cancer mutants with selective inhibition of its negative regulators. Recent advances in development of small molecule inhibitors and peptides exploiting p53-MDM2 interaction has been included. In a nutshell, this review attempts to describe structural biology of p53 which provide new openings for structure-guided rescue.