ROS and Oxidative Stress Are Elevated in Mitosis during Asynchronous Cell Cycle Progression and Are Exacerbated by Mitotic Arrest

A chloroplast sulphate transporter modulates glutathione-mediated redox cycling to regulate cell division

Glutathione redox cycling is important for cell cycle regulation, but its mechanisms are not well understood. We previously identified a small-sized mutant, suppressor of mat3 15-1 (smt15-1) that has elevated cellular glutathione. Here, we demonstrated that SMT15 is a chloroplast sulphate transporter. Reducing expression of γ-GLUTAMYLCYSTEINE SYNTHETASE, encoding the rate-limiting enzyme required for glutathione biosynthesis, corrected the size defect of smt15-1 cells. Overexpressing GLUTATHIONE SYNTHETASE (GSH2) recapitulated the small-size phenotype of smt15-1 mutant, confirming the role of glutathione in cell division. Hence, SMT15 may regulate chloroplast sulphate concentration to modulate cellular glutathione levels. In wild-type cells, glutathione and/or thiol-containing molecules (GSH/thiol) accumulated in the cytosol at the G1 phase and decreased as cells entered the S/M phase. While the cytosolic GSH/thiol levels in the small-sized mutants, smt15-1 and GSH2 overexpressors, mirrored those of wild-type cells (accumulating during G1 and declining at early S/M phase), GSH/thiol was specifically accumulated in the basal bodies at early S/M phase in the small-sized mutants. Therefore, we propose that GSH/thiol-mediated redox signalling in the basal bodies may regulate mitotic division number in Chlamydomonas reinhardtii. Our findings suggest a new mechanism by which glutathione regulates the multiple fission cell cycle in C. reinhardtii.

Osteosarcoma cells depend on MCL-1 for survival, and osteosarcoma metastases respond to MCL-1 antagonism plus regorafenib in vivo

Osteosarcoma is the most common form of primary bone cancer, which primarily afflicts children and adolescents. Chemotherapy, consisting of doxorubicin, cisplatin and methotrexate (MAP) increased the 5-year osteosarcoma survival rate from 20% to approximately 60% by the 1980s. However, osteosarcoma survival rates have remained stagnant for several decades. Patients whose disease fails to respond to MAP receive second-line treatments such as etoposide and, in more recent years, the kinase inhibitor regorafenib. BCL-2 and its close relatives enforce cellular survival and have been implicated in the development and progression of various cancer types. BH3-mimetics antagonize pro-survival members of the BCL-2 family to directly stimulate apoptosis. These drugs have been proven to be efficacious in other cancer types, but their use in osteosarcoma has been relatively unexplored to date. We investigated the potential efficacy of BH3-mimetics against osteosarcoma cells in vitro and examined their cooperation with regorafenib in vivo. We demonstrated that osteosarcoma cell lines could be killed through inhibition of MCL-1 combined with BCL-2 or BCL-xL antagonism. Inhibition of MCL-1 also sensitized osteosarcoma cells to killing by second-line osteosarcoma treatments, particularly regorafenib. Importantly, we found that inhibition of MCL-1 with the BH3-mimetic S63845 combined with regorafenib significantly prolonged the survival of mice bearing pulmonary osteosarcoma metastases. Together, our results highlight the importance of MCL-1 in osteosarcoma cell survival and present a potential therapeutic avenue that may improve metastatic osteosarcoma patient outcomes.

Uncovering Cell Cycle Dysregulations and Associated Mechanisms in Cancer and Neurodegenerative Disorders: A Glimpse of Hope for Repurposed Drugs

The cell cycle is the sequence of events orchestrated by a complex network of cell cycle proteins. Unlike normal cells, mature neurons subsist in a quiescent state of the cell cycle, and aberrant cell cycle activation triggers neuronal death accompanied by neurodegeneration. The periodicity of cell cycle events is choreographed by various mechanisms, including DNA damage repair, oxidative stress, neurotrophin activity, and ubiquitin-mediated degradation. Given the relevance of cell cycle processes in cancer and neurodegeneration, this review delineates the overlapping cell cycle events, signaling pathways, and mechanisms associated with cell cycle aberrations in cancer and the major neurodegenerative disorders. We suggest that dysregulation of some common fundamental signaling processes triggers anomalous cell cycle activation in cancer cells and neurons. We discussed the possible use of cell cycle inhibitors for neurodegenerative disorders and described the associated challenges. We propose that a greater understanding of the common mechanisms driving cell cycle aberrations in cancer and neurodegenerative disorders will open a new avenue for the development of repurposed drugs.

IKKα affects the susceptibility of primary human osteoarthritis chondrocytes to oxidative stress-induced DNA damage by tuning autophagy

The functional derangement affecting human chondrocytes during osteoarthritis (OA) onset and progression is sustained by the failure of major homeostatic mechanisms. This makes them more susceptible to oxidative stress (OS), which can induce DNA damage responses and exacerbate stress-induced senescence. The knockdown (KD) of IκB kinase α (IKKα), a dispensable protein in healthy articular cartilage physiology, was shown to increase the survival and replication potential of human primary OA chondrocytes. Our recent findings showed that the DNA Mismatch Repair pathway only partially accounts for the reduced susceptibility to OS of IKKαKD cells. Here we therefore investigated other ROS-mediated DNA damage and repair mechanisms. We exposed IKKαWT and IKKαKD chondrocytes to sub-cytotoxic hydrogen peroxide and evaluated the occurrence of double-strand breaks (DSB), 8-oxo-2'-deoxyguanosine (8-oxo-dG) and telomere shortening. ROS exposure was able to significantly increase the number of γH2AX foci (directly related to the number of DSB) in both cell types, but IKKα deficient cells undergoing cell division were able to better recover compared to their IKKα proficient counterpart. 8-oxo-dG signal proved to be the highest DNA damage signal among those investigated, located in the mitochondria and with a slightly higher intensity in IKKα proficient cells immediately after OS exposure. Furthermore, ROS significantly reduced telomere length both in IKKαWT and IKKαKD, with the former showing more pervasive effects, especially in dividing cells. Assessment of the HIF-1α>Beclin-1>LC3B axis after recovery from OS showed that IKKα deficient cells exhibited a more efficient autophagic machinery that allowed them to better cope with oxidative stress, possibly through the turnover of damaged mitochondria. Higher Beclin-1 levels likely helped in rescuing dividing cells (identified by coupled cell cycle analysis) because of Beclin-1's involvement in both autophagy and mitotic spindle organization. Therefore, our data further confirm the higher capacity of IKKαKD chondrocytes to cope with oxidative stress-induced DNA damage.

The significant others of aurora kinase a in cancer: combination is the key

AURKA is predominantly famous as an essential mitotic kinase. Recent findings have also established its critical role in a plethora of other biological processes including ciliogenesis, mitochondrial dynamics, neuronal outgrowth, DNA replication and cell cycle progression. AURKA overexpression in numerous cancers is strongly associated with poor prognosis and survival. Still no AURKA-targeted drug has been approved yet, partially because of the associated collateral toxicity and partly due to its limited efficacy as a single agent in a wide range of tumors. Mechanistically, AURKA overexpression allows it to phosphorylate numerous pathological substrates promoting highly aggressive oncogenic phenotypes. Our review examines the most recent advances in AURKA regulation and focuses on 33 such direct cancer-specific targets of AURKA and their associated oncogenic signaling cascades. One of the common themes that emerge is that AURKA is often involved in a feedback loop with its substrates, which could be the decisive factor causing its sustained upregulation and hyperactivation in cancer cells, an Achilles heel not exploited before. This dynamic interplay between AURKA and its substrates offers potential opportunities for targeted therapeutic interventions. By targeting these substrates, it may be possible to disrupt this feedback loop to effectively reverse AURKA levels, thereby providing a promising avenue for developing safer AURKA-targeted therapeutics. Additionally, exploring the synergistic effects of AURKA inhibition with its other oncogenic and/or tumor-suppressor targets could provide further opportunities for developing effective combination therapies against AURKA-driven cancers, thereby maximizing its potential as a critical drug target.

The Induction of G2/M Phase Cell Cycle Arrest and Apoptosis by the Chalcone Derivative 1C in Sensitive and Resistant Ovarian Cancer Cells Is Associated with ROS Generation

Ovarian cancer ranks among the most severe forms of cancer affecting the female reproductive organs, posing a significant clinical challenge primarily due to the development of resistance to conventional therapies. This study investigated the effects of the chalcone derivative 1C on sensitive (A2780) and cisplatin-resistant (A2780cis) ovarian cancer cell lines. Our findings revealed that 1C suppressed cell viability, induced cell cycle arrest at the G2/M phase, and triggered apoptosis in both cell lines. These effects are closely associated with generating reactive oxygen species (ROS). Mechanistically, 1C induced DNA damage, modulated the activity of p21, PCNA, and phosphorylation of Rb and Bad proteins, as well as cleaved PARP. Moreover, it modulated Akt, Erk1/2, and NF-κB signaling pathways. Interestingly, we observed differential effects of 1C on Nrf2 levels between sensitive and resistant cells. While 1C increased Nrf2 levels in sensitive cells after 12 h and decreased them after 48 h, the opposite effect was observed in resistant cells. Notably, most of these effects were suppressed by the potent antioxidant N-acetylcysteine (NAC), underscoring the crucial role of ROS in 1C-induced antiproliferative activity. Moreover, we suggest that modulation of Nrf2 levels can, at least partially, contribute to the antiproliferative effect of chalcone 1C.

Oxidative Metabolism as a Cause of Lipid Peroxidation in the Execution of Ferroptosis

Ferroptosis is a type of nonapoptotic cell death that is characteristically caused by phospholipid peroxidation promoted by radical reactions involving iron. Researchers have identified many of the protein factors that are encoded by genes that promote ferroptosis. Glutathione peroxidase 4 (GPX4) is a key enzyme that protects phospholipids from peroxidation and suppresses ferroptosis in a glutathione-dependent manner. Thus, the dysregulation of genes involved in cysteine and/or glutathione metabolism is closely associated with ferroptosis. From the perspective of cell dynamics, actively proliferating cells are more prone to ferroptosis than quiescent cells, which suggests that radical species generated during oxygen-involved metabolism are responsible for lipid peroxidation. Herein, we discuss the initial events involved in ferroptosis that dominantly occur in the process of energy metabolism, in association with cysteine deficiency. Accordingly, dysregulation of the tricarboxylic acid cycle coupled with the respiratory chain in mitochondria are the main subjects here, and this suggests that mitochondria are the likely source of both radical electrons and free iron. Since not only carbohydrates, but also amino acids, especially glutamate, are major substrates for central metabolism, dealing with nitrogen derived from amino groups also contributes to lipid peroxidation and is a subject of this discussion.

A coupled model between circadian, cell-cycle, and redox rhythms reveals their regulation of oxidative stress

Most organisms possess three biological oscillators, circadian clock, cell cycle, and redox rhythm, which are autonomous but interact each other. However, whether their interactions and autonomy are beneficial for organisms remains unclear. Here, we modeled a coupled oscillator system where each oscillator affected the phase of the other oscillators. We found that multiple types of coupling prevent a high H2O2 level in cells at M phase. Consequently, we hypothesized a high H2O2 sensitivity at the M phase and found that moderate coupling reduced cell damage due to oxidative stress by generating appropriate phase relationships between three rhythms, whereas strong coupling resulted in an elevated cell damage by increasing the average H2O2 level and disrupted the cell cycle. Furthermore, the multicellularity model revealed that phase variations among cells confer flexibility in synchronization with environments at the expense of adaptability to the optimal environment. Thus, both autonomy and synchrony among the oscillators are important for coordinating their phase relationships to minimize oxidative stress, and couplings balance them depending on environments.

Biological activity and computational analysis of novel acrylonitrile derived benzazoles as potent antiproliferative agents for pancreatic adenocarcinoma with antioxidative properties

Continuing our research into the anticancer properties of acrylonitriles, we present a study involving the design, synthesis, computational analysis, and biological assessment of novel acrylonitriles derived from methoxy, hydroxy, and N-substituted benzazole. Our aim was to examine how varying the number of methoxy and hydroxy groups, as well as the N-substituents on the benzimidazole core, influences their biological activity. The newly synthesized acrylonitriles exhibited strong and selective antiproliferative effects against the Capan-1 pancreatic adenocarcinoma cell line, with IC50 values ranging from 1.2 to 5.3 μM. Consequently, these compounds were further evaluated in three other pancreatic adenocarcinoma cell lines, while their impact on normal PBMC cells was also investigated to determine selectivity. Among these compounds, the monohydroxy-substituted benzimidazole derivative 27 emerged with the most profound and broad-spectrum anticancer antiproliferative activity being emerged as a promising lead candidate. Moreover, a majority of the acrylonitriles in this series exhibited significant antioxidative activity, surpassing that of the reference molecule BHT, as demonstrated by the FRAP assay (ranging from 3200 to 5235 mmolFe2+/mmolC). Computational analysis highlighted the prevalence of electron ionization in conferring antioxidant properties, with computed ionization energies correlating well with observed activities.

Particulate Matter Induces Oxidative Stress and Ferroptosis in Human Lung Epithelial Cells

Numerous toxicological studies have highlighted the association between urban particulate matter (PM) and increased respiratory infections and lung diseases. The adverse impact on the lungs is directly linked to the complex composition of particulate matter, initiating reactive oxygen species (ROS) production and consequent lipid peroxidation. Excessive ROS, particularly within mitochondria, can destroy subcellular organelles through various pathways. In this study, we confirmed the induction of ferroptosis, an iron-dependent cell death, upon exposure to an urban PM using RT-qPCR and signaling pathway analysis. We used KRISS CRM 109-02-004, the certified reference material for the analysis of particulate matter, produced by the Korea Research Institute of Standards and Science (KRISS). To validate that ferroptosis causes lung endothelial toxicity, we assessed intracellular mitochondrial potential, ROS overproduction, lipid peroxidation, and specific ferroptosis biomarkers. Following exposure to the urban PM, a significant increase in ROS generation and a decrease in mitochondrial potential were observed. Furthermore, it induced hallmarks of ferroptosis, including the accumulation of lipid peroxidation, the loss of antioxidant defenses, and cellular iron accumulation. In addition, the occurrence of oxidative stress as a key feature of ferroptosis was confirmed by increased expression levels of specific oxidative stress markers such as NQO1, CYP1B1, FTH1, SOD2, and NRF. Finally, a significant increase in key ferroptosis markers was observed, including xCT/SLC7A11, NQO1, TRIM16, HMOX-1, FTL, FTH1, CYP1B1, CHAC1, and GPX4. This provides evidence that elevated ROS levels induce oxidative stress, which ultimately triggers ferroptosis. In conclusion, our results show that the urban PM, KRISS CRM, induces cellular and mitochondrial ROS production, leading to oxidative stress and subsequent ferroptosis. These results suggest that it may induce ferroptosis through ROS generation and may offer potential strategies for the treatment of lung diseases.

The bidirectional relationship between metabolism and cell cycle control

The relationship between metabolism and cell cycle progression is complex and bidirectional. Cells must rewire metabolism to meet changing biosynthetic demands across cell cycle phases. In turn, metabolism can influence cell cycle progression through direct regulation of cell cycle proteins, through nutrient-sensing signaling pathways, and through its impact on cell growth, which is linked to cell division. Furthermore, metabolism is a key player in mediating quiescence-proliferation transitions in physiologically important cell types, such as stem cells. How metabolism impacts cell cycle progression, exit, and re-entry, as well as how these processes impact metabolism, is not fully understood. Recent advances uncovering mechanistic links between cell cycle regulators and metabolic processes demonstrate a complex relationship between metabolism and cell cycle control, with many questions remaining.

Polo-like kinase 1 inhibitor NMS-P937 represses nasopharyngeal carcinoma progression via induction of mitotic abnormalities

Polo-like kinase 1 (PLK1) inhibitor NMS-P937 is a targeted therapeutic agent with good preclinical efficacy in various human cancers, and its therapeutic effect on nasopharyngeal carcinoma (NPC) remains to be determined. Here, to explore biological activity of NMS-P937 in NPC, multiple types of NPC cells were utilized. We tested IC50 values, carried out flow cytometry, western blot analysis analysis, immunofluorescence, and constructed subcutaneous xenograft mouse models. We found that treatment with NMS-P937 increased the proportion of G2/M phase NPC cells, where CyclinB1 expression was upregulated and CyclinE1 expression was downregulated. Besides, NMS-P937 treatment-induced NPC cell apoptosis with increased cleavage of PARP and caspase-3. Mechanistically, NMS-P937 treatment led to aberrant mitosis, causing increased reactive oxygen species (ROS) levels. ROS scavenger N-acetylcysteine partially reversed ROS levels induced by NMS-P937. Furthermore, NMS-P937 administration restrained NPC xenografts growth in nude mice. Overall, NMS-P937 suppressed NPC cell proliferation and increased ROS levels, causing cell cycle abnormalities and apoptosis. NMS-P937 holds great promise as a therapeutic agent for treating nasopharyngeal carcinoma.

Microfluidic single-cell measurements of oxidative stress as a function of cell cycle position

Single-cell measurements routinely demonstrate high levels of variation between cells, but fewer studies provide insight into the analytical and biological sources of this variation. This is particularly true of chemical cytometry, in which individual cells are lysed and their contents separated, compared to more established single-cell measurements of the genome and transcriptome. To characterize population-level variation and its sources, we analyzed oxidative stress levels in 1278 individual Dictyostelium discoideum cells as a function of exogenous stress level and cell cycle position. Cells were exposed to varying levels of oxidative stress via singlet oxygen generation using the photosensitizer Rose Bengal. Single-cell data reproduced the dose-response observed in ensemble measurements by CE-LIF, superimposed with high levels of heterogeneity. Through experiments and data analysis, we explored possible biological sources of this heterogeneity. No trend was observed between population variation and oxidative stress level, but cell cycle position was a major contributor to heterogeneity in oxidative stress. Cells synchronized to the same stage of cell division were less heterogeneous than unsynchronized cells (RSD of 37-51% vs 93%), and mitotic cells had higher levels of reactive oxygen species than interphase cells. While past research has proposed changes in cell size during the cell cycle as a source of biological noise, the measurements presented here use an internal standard to normalize for effects of cell volume, suggesting a more complex contribution of cell cycle to heterogeneity of oxidative stress.

Combretastatin A-4 suppresses the invasive and metastatic behavior of glioma cells and induces apoptosis in them: in-vitro study

The most common primary brain malignancy, glioblastoma multiforme, is tremendously resistant to conventional treatments due to its potency for metastasis to surrounding brain tissue. Temozolomide is a chemotherapeutic agent that currently is administrated during the treatment procedure. Studies have attempted to investigate new agents with higher effectiveness and fewer side effects. Combretastatin A-4 (CA-4), a natural compound derived from Combretum caffrum, has been recently considered for its potent antitumor activities in a wide variety of preclinical solid tumor models. Our findings have shown that CA-4 exerts potent anti-proliferative and apoptotic effects on glioma cells, and ROS generation may be involved in these cellular events. CA-4 has imposed G2 arrest in U-87 cells. We also observed that CA-4 significantly reduced the migration and invasion capability of U-87 cells. Furthermore, the gene expression and enzyme activity of MMP-2 and MMP-9 were significantly inhibited in the presence of CA-4. We also observed a considerable decrease in PI3K and Akt protein expression following treatment with CA-4. In conclusion, our findings showed significant apoptogenic and anti-metastatic effects of CA-4 on glioma cells and also suggested that the PI3K/Akt/MMP-2/-9 and also ROS pathway might play roles in these cellular events.

Reactive Oxygen Species and H. pylori Infection: A Comprehensive Review of Their Roles in Gastric Cancer Development

Gastric cancer (GC) is the fifth most common cancer worldwide and makes up a significant component of the global cancer burden. Helicobacter pylori (H. pylori) is the most influential risk factor for GC, with the International Agency for Research on Cancer classifying it as a Class I carcinogen for GC. H. pylori has been shown to persist in stomach acid for decades, causing damage to the stomach's mucosal lining, altering gastric hormone release patterns, and potentially altering gastric function. Epidemiological studies have shown that eliminating H. pylori reduces metachronous cancer. Evidence shows that various molecular alterations are present in gastric cancer and precancerous lesions associated with an H. pylori infection. However, although H. pylori can cause oxidative stress-induced gastric cancer, with antioxidants potentially being a treatment for GC, the exact mechanism underlying GC etiology is not fully understood. This review provides an overview of recent research exploring the pathophysiology of H. pylori-induced oxidative stress that can cause cancer and the antioxidant supplements that can reduce or even eliminate GC occurrence.

A mitotic NADPH upsurge promotes chromosome segregation and tumour progression in aneuploid cancer cells

Redox metabolites have been observed to fluctuate through the cell cycle in cancer cells, but the functional impacts of such metabolic oscillations remain unknown. Here, we uncover a mitosis-specific nicotinamide adenine dinucleotide phosphate (NADPH) upsurge that is essential for tumour progression. Specifically, NADPH is produced by glucose 6-phosphate dehydrogenase (G6PD) upon mitotic entry, which neutralizes elevated reactive oxygen species (ROS) and prevents ROS-mediated inactivation of mitotic kinases and chromosome missegregation. Mitotic activation of G6PD depends on the phosphorylation of its co-chaperone protein BAG3 at threonine 285, which results in dissociation of inhibitory BAG3. Blocking BAG3T285 phosphorylation induces tumour suppression. A mitotic NADPH upsurge is present in aneuploid cancer cells with high levels of ROS, while nearly unobservable in near-diploid cancer cells. High BAG3T285 phosphorylation is associated with worse prognosis in a cohort of patients with microsatellite-stable colorectal cancer. Our study reveals that aneuploid cancer cells with high levels of ROS depend on a G6PD-mediated NADPH upsurge in mitosis to protect them from ROS-induced chromosome missegregation.

Mechanisms of Mitochondrial Oxidative Stress in Brain Injury: From Pathophysiology to Therapeutics

Mitochondrial oxidative stress has been implicated in various forms of brain injury, both traumatic and non-traumatic. Due to its oxidative demand, the brain is intimately dependent on its mitochondrial functioning. However, there remains appreciable heterogeneity in the development of these injuries regarding ROS and their effect on the sequelae. These include traumatic insults such as TBIs and intracranial hemorrhaging secondary to this. In a different vein, such injuries may be attributed to other etiologies such as infection, neoplasm, or spontaneous hemorrhage (strokes, aneurysms). Clinically, the manner of treatment may also be adjusted in relation to each injury and its unique progression in the context of ROS. In the current review, then, the authors highlight the role of mitochondrial ROS in various forms of brain injury, emphasizing both the collective and unique elements of each form. Lastly, these narratives are met with the current therapeutic landscape and the role of emerging therapies in treating reactive oxygen species in brain injuries.

Defense systems to avoid ferroptosis caused by lipid peroxidation-mediated membrane damage

The presence of hydrogen peroxide along with ferrous iron produces hydroxyl radicals that preferably oxidize polyunsaturated fatty acids (PUFA) to alkyl radicals (L•). The reaction of L• with an oxygen molecule produces lipid peroxyl radical (LOO•) that collectively trigger chain reactions, which results in the accumulation of lipid peroxidation products (LOOH). Oxygenase enzymes, such as lipoxygenase, also stimulate the peroxidation of PUFA. The production of phospholipid hydroperoxides (P-LOOH) can result in the destruction of the architecture of cell membranes and ultimate cell death. This iron-dependent regulated cell death is generally referred to as ferroptosis. Radical scavengers, which include tocopherol and nitric oxide (•NO), react with lipid radicals and terminate the chain reaction. When tocopherol reductively detoxifies lipid radicals, the resultant tocopherol radicals are recycled via reduction by coenzyme Q or ascorbate. CoQ radicals are reduced back by the anti-ferroptotic enzyme FSP1. •NO reacts with lipid radicals and produces less reactive nitroso compounds. The resulting P-LOOH is reductively detoxified by the action of glutathione peroxidase 4 (GPX4) or peroxiredoxin 6 (PRDX6). The hydrolytic removal of LOOH from P-LOOH by calcium-independent phospholipase A2 leads the preservation of membrane structure. While the expression of such protective genes or the presence of these anti-oxidant compounds serve to maintain a healthy condition, tumor cells employ them to make themselves resistant to anti-tumor treatments. Thus, these defense mechanisms against ferroptosis are protective in ordinary cells but are also potential targets for cancer treatment.

SRSF3-Mediated Ki67 Exon 7-Inclusion Promotes Head and Neck Squamous Cell Carcinoma Progression via Repressing AKR1C2

Ki67 is a well-known proliferation marker with a large size of around 350 kDa, but its biological function remains largely unknown. The roles of Ki67 in tumor prognosis are still controversial. Ki67 has two isoforms generated by alternative splicing of exon 7. The roles and regulatory mechanisms of Ki67 isoforms in tumor progression are not clear. In the present study, we surprisingly find that the increased inclusion of Ki67 exon 7, not total Ki67 expression level, was significantly associated with poor prognosis in multiple cancer types, including head and neck squamous cell carcinoma (HNSCC). Importantly, the Ki67 exon 7-included isoform is required for HNSCC cell proliferation, cell cycle progression, cell migration, and tumorigenesis. Unexpectedly, Ki67 exon 7-included isoform is positively associated with intracellular reactive oxygen species (ROS) level. Mechanically, splicing factor SRSF3 could promote exon 7 inclusion via its two exonic splicing enhancers. RNA-seq revealed that aldo-keto reductase AKR1C2 is a novel tumor-suppressive gene targeted by Ki67 exon 7-included isoform in HNSCC cells. Our study illuminates that the inclusion of Ki67 exon 7 has important prognostic value in cancers and is essential for tumorigenesis. Our study also suggested a new SRSF3/Ki67/AKR1C2 regulatory axis during HNSCC tumor progression.

Mitotic MTH1 Inhibitors in Treatment of Cancer

The DNA damage response (DDR) protein MTH1 is sanitising the oxidized dNTP pool and preventing incorporation of oxidative damage into DNA and has an emerging role in mitosis. It is a stress-induced protein and often found to be overexpressed in cancer. Mitotic MTH1 inhibitors arrest cells in mitosis and result in incorporation of oxidative damage into DNA and selective killing of cancer cells. Here, I discuss the leading mitotic MTH1 inhibitor TH1579 (OXC-101, karonudib), now being evaluated in clinical trials, and describe its dual effect on mitosis and incorporation of oxidative DNA damage in cancer cells. I describe why MTH1 inhibitors that solely inhibits the enzyme activity fail to kill cancer cells and discuss if MTH1 is a valid target for cancer treatment. I discuss emerging roles of MTH1 in regulating tubulin polymerisation and mitosis and the necessity of developing the basic science insights along with translational efforts. I also give a perspective on how edgetic perturbation is making target validation difficult in the DDR field.

Free Radicals and Oxidative Stress: Signaling Mechanisms, Redox Basis for Human Diseases, and Cell Cycle Regulation

Free radicals contain one or more unpaired electrons in their valence shell, thus making them unstable, short-lived, and highly reactive species. Excessive generation of these free radicals ultimately leads to oxidative stress causing oxidation and damage to significant macromolecules in the living system and essentially disrupting signal transduction pathways and antioxidants equilibrium. At lower concentrations, ROS serves as "second messengers," influencing many physiological processes in the cell. However, higher concentrations beyond cell capacity cause oxidative stress, contributing to human pathologies such as diabetes, cancer, Parkinson's disease, cardiovascular diseases, cataract, asthma, hypertension, atherosclerosis, arthritis, and Alzheimer's disease. Signaling pathways such as NF-κB, MAPKs, PI3K/Akt/ mTOR, and Keap1-Nrf2- ARE modulate the detrimental effects of oxidative stress by increasing the expression of cellular antioxidant defenses, phase II detoxification enzymes, and decreased production of ROS. Free radicals such as H2O2 are indeed needed for the advancement of the cell cycle as these molecules influence DNA, proteins, and enzymes in the cell cycle pathway. In the course of cell cycle progression, the cellular redox environment becomes more oxidized, moving from the G1 phase, becoming higher in G2/M and moderate in the S phase. Signals in the form of an increase in cellular pro-oxidant levels are required, and these signals are often terminated by a rise in the amount of antioxidants and MnSOD with a decrease in the level of cyclin D1 proteins. Therefore, understanding the mechanism of cell cycle redox regulation will help in the therapy of many diseases.

Targeting the DNA damage response and repair in cancer through nucleotide metabolism

The exploitation of the DNA damage response and DNA repair proficiency of cancer cells is an important anticancer strategy. The replication and repair of DNA are dependent upon the supply of deoxynucleoside triphosphate (dNTP) building blocks, which are produced and maintained by nucleotide metabolic pathways. Enzymes within these pathways can be promising targets to selectively induce toxic DNA lesions in cancer cells. These same pathways also activate antimetabolites, an important group of chemotherapies that disrupt both nucleotide and DNA metabolism to induce DNA damage in cancer cells. Thus, dNTP metabolic enzymes can also be targeted to refine the use of these chemotherapeutics, many of which remain standard of care in common cancers. In this review article, we will discuss both these approaches exemplified by the enzymes MTH1, MTHFD2 and SAMHD1. © 2022 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

RNA binding protein IGF2BP1 meditates oxidative stress-induced granulosa cell dysfunction by regulating MDM2 mRNA stability in an m6A-dependent manner

Both genetic and microenvironmental detrimental factors are involved in ovarian dysfunction, leading to the increasing rate of involuntary childlessness in recent years. Oxidative stress (OS), which is characterized by the imbalance of redox system with redundant reactive oxygen species (ROS) overwhelming the antioxidant defense, is regarded as one of the culprits of ovarian dysfunction. OS causes damage to various types of ovarian cells including granulosa cells (GCs), jeopardizing the ovarian microenvironment, disturbing follicular development and participating in various female reproductive disorders. However, the specific molecular pathological mechanisms underlying this process have not been fully elucidated. In this study, we found that 3-nitropropionic acid (3-NP) treatment led to significant IGF2BP1 downregulation via, at least partially, inducing ROS overproduction. IGF2BP1 regulates GCs viability, proliferation, cell cycle and cellular senescence by enhancing MDM2 mRNA stability in an m6A-dependant manner. IGF2BP1 overexpression partially rescued 3-NP induced GCs damages, while ectopically expressed MDM2 alleviated both 3-NP or IGF2BP1-knockdown induced GCs dysfunction. These results reveal an epigenetic molecular mechanism underlying OS-related GCs disorders, which may help to establish a novel potential clinical marker for predicting the GCs status as well as the follicular developmental potential.

ROS: Basic Concepts, Sources, Cellular Signaling, and its Implications in Aging Pathways

Reactive oxygen species (ROS) are bioproducts of cellular metabolism. There is a range of molecules with oxidizing properties known as ROS. Despite those molecules being implied negatively in aging and numerous diseases, their key role in cellular signaling is evident. ROS control several biological processes such as inflammation, proliferation, and cell death. The redox signaling underlying these cellular events is one characteristic of the new generation of scientists aimed at defining the role of ROS in the cellular environment. The control of redox potential, which includes the balance of the sources of ROS and the antioxidant system, implies an important target for understanding the cells' fate derived from redox signaling. In this review, we summarized the chemical, the redox balance, the signaling, and the implications of ROS in biological aging.

BCAT1 redox function maintains mitotic fidelity

The metabolic enzyme branched-chain amino acid transaminase 1 (BCAT1) drives cell proliferation in aggressive cancers such as glioblastoma. Here, we show that BCAT1 localizes to mitotic structures and has a non-metabolic function as a mitotic regulator. Furthermore, BCAT1 is required for chromosome segregation in cancer and induced pluripotent stem cells and tumor growth in human cerebral organoid and mouse syngraft models. Applying gene knockout and rescue strategies, we show that the BCAT1 CXXC redox motif is crucial for controlling cysteine sulfenylation specifically in mitotic cells, promoting Aurora kinase B localization to centromeres, and securing accurate chromosome segregation. These findings offer an explanation for the well-established role of BCAT1 in promoting cancer cell proliferation. In summary, our data establish BCAT1 as a component of the mitotic apparatus that safeguards mitotic fidelity through a moonlighting redox functionality.

Mitotic spindle disassembly in human cells relies on CRIPT having hierarchical redox signals

Swift and complete spindle disassembly in late mitosis is essential for cell survival, yet how it happens is largely unknown in mammalian cells. Here we used real-time live cell microscopy and biochemical assays to show that the primordial dwarfism (PD)-related cysteine-rich protein CRIPT dictates the spindle disassembly in a redox-dependent manner in human cells. This previously reported cytoplasmic protein was found to have a confined nuclear localization with a nucleolar concentration during interphase but was distributed to spindles and underwent redox modifications to form disulfide bonds in CXXC pairs during mitosis. Then, it directly interacted with, and might transfer a redox response to, tubulin subunits via a putative redox exchange among cysteine residues to induce microtubule depolymerization. Expression of CRIPT proteins with mutations of these cysteine residues blocked spindle disassembly, generating two cell types with long-lasting metaphase spindles or spindle remnants. Live-cell recordings of a disease-relevant mutant (CRIPTC3Y) revealed that microtubule depolymerization at spindle ends during anaphase and the entire spindle dissolution during telophase might share a common CRIPT-bearing redox-controlled mechanism.

Cytotoxicity of 9,10-Phenanthrenequinone Impairs Mitotic Progression and Spindle Assembly Independent of ROS Production in HeLa Cells

The polycyclic aromatic hydrocarbon quinone derivative 9,10-phenanthrenequinone (9,10-PQ) is one of the most abundant and toxic components found in diesel exhaust particles (DEPs). These DEPs are created during diesel fuel combustion and are considered the main source of urban air pollution. As 9,10-PQ can produce excessive reactive oxygen species (ROS) through redox cycling, it has been shown to exert potent cytotoxic effects against various cell types. However, the mechanisms underlying this cytotoxicity remain unclear. In this study, we showed that 9,10-PQ exerts cytotoxicity by impairing mitotic progression and spindle assembly in HeLa cells. Exposure to 9,10-PQ impaired spindle assembly and chromosome alignment, resulting in delayed mitotic entry and progression in HeLa cells. Furthermore, 9,10-PQ exposure decreased the CEP192 and p-Aurora A levels at the spindle poles. Notably, these mitotic defects induced by 9,10-PQ were not rescued by scavenging ROS, implying the ROS-independent activity of 9,10-PQ. Therefore, our results provide the first evidence that 9,10-PQ exerts its cytotoxicity through specific inhibition of mitotic progression and spindle assembly, independent of ROS.

Novel potential NOX2 inhibitors, Dudleya brittonii water extract and polygalatenoside A inhibit intracellular ROS generation and growth of melanoma

Reactive oxygen species (ROS) are key regulators of the proliferation, metastasis, and drug resistance of melanoma, which accounts for 60% of skin cancer deaths. In a previous study, we developed Dudleya brittonii water extract (DBWE) with antioxidant activity, but the mechanism of action and bioactive substances of DBWE have not been fully identified. This study showed altered NADPH oxidase 2 (NOX2) expression and selective inhibition of cytosolic ROS but not mitochondrial ROS in B16-F10 melanoma cells, suggesting the NOX2 inhibitory potential of DBWE. In addition, DBWE inhibited mitochondrial activity, lipid metabolism, and cell cycle in B16-F10 cells. The anti-melanoma effect of DBWE was abrogated by the addition of ROS, and there was no significant change in the melanogenesis pathway. Polygalatenoside A was identified as a candidate bioactive substance in the DBWE aqueous fraction through mass spectrometry, and the DBWE-like anti-melanoma effect was confirmed. These data suggest that DBWE and polygalatenoside A have the potential to prevent and treat melanoma.

Tizoxanide Promotes Apoptosis in Glioblastoma by Inhibiting CDK1 Activity

The antiparasitic drug nitazoxanide (NTZ) has received considerable attention for its potential in cancer therapy. In this study, we demonstrate that tizoxanide (TIZ), an active metabolite of NTZ, exhibits antiglioma activity in vitro and in vivo by inducing G2/M cell cycle arrest and apoptosis. In vitro, TIZ dose-dependently inhibited the proliferation of U87, U118, and A172 human glioblastoma (GBM) cells at 48 h with IC₅₀ values of 1.10, 2.31, and 0.73 µM, respectively. Treatment with TIZ (1 and 10 µM) also dose-dependently inhibited the colony formation of these GBM cells and accumulated ROS damage in the nucleus. In silico target fishing combined with network pharmacological disease spectrum analyses of GBM revealed that cycle-dependent kinase 1 (CDK1) is the most compatible target for TIZ and molecular docking by Molecule Operating Environment (MOE) software confirmed it. Mechanistically, TIZ inhibited the phosphorylation of CDK1 at Thr161 and decreased the activity of the CDK1/cyclin B1 complex, arresting the cell cycle at the G2/M phase. TIZ may induce apoptosis via the ROS-mediated apoptotic pathway. In vivo, TIZ suppressed the growth of established subcutaneous and intracranial orthotopic xenograft models of GBM without causing obvious side effects and prolonged the survival of nude mice bearing glioma. Taken together, our results demonstrated that TIZ might be a promising chemotherapy drug in the treatment of GBM.

Methionine Deprivation Reveals the Pivotal Roles of Cell Cycle Progression in Ferroptosis That Is Induced by Cysteine Starvation

Ferroptosis, a type of iron-dependent necrotic cell death, is triggered by the accumulation of excessive lipid peroxides in cells. Glutathione (GSH), a tripeptide redox molecule that contains a cysteine (Cys) unit in the center, plays a pivotal role in protection against ferroptosis. When the transsulfuration pathway is activated, the sulfur atom of methionine (Met) is utilized to generate Cys, which can then suppress Cys-starvation-induced ferroptosis. In the current study, we cultured HeLa cells in Met- and/or cystine (an oxidized Cys dimer)- deprived medium and investigated the roles of Met in ferroptosis execution. The results indicate that, in the absence of cystine or Met, ferroptosis or cell cycle arrest, respectively, occurred. Contrary to our expectations, however, the simultaneous deprivation of both Met and cystine failed to induce ferroptosis, although the intracellular levels of Cys and GSH were maintained at low levels. Supplementation with S-adenosylmethionine (SAM), a methyl group donor that is produced during the metabolism of Met, caused the cell cycle progression to resume and lipid peroxidation and the subsequent induction of ferroptosis was also restored under conditions of Met/cystine double deprivation. DNA methylation appeared to be involved in the resumption in the SAM-mediated cell cycle because its downstream metabolite S-adenosylhomocysteine failed to cause either cell cycle progression or ferroptosis to be induced. Taken together, our results suggest that elevated lipid peroxidation products that are produced during cell cycle progression are involved in the execution of ferroptosis under conditions of Cys starvation.

Superoxide Radicals in the Execution of Cell Death

Superoxide is a primary oxygen radical that is produced when an oxygen molecule receives one electron. Superoxide dismutase (SOD) plays a primary role in the cellular defense against an oxidative insult by ROS. However, the resulting hydrogen peroxide is still reactive and, in the presence of free ferrous iron, may produce hydroxyl radicals and exacerbate diseases. Polyunsaturated fatty acids are the preferred target of hydroxyl radicals. Ferroptosis, a type of necrotic cell death induced by lipid peroxides in the presence of free iron, has attracted considerable interest because of its role in the pathogenesis of many diseases. Radical electrons, namely those released from mitochondrial electron transfer complexes, and those produced by enzymatic reactions, such as lipoxygenases, appear to cause lipid peroxidation. While GPX4 is the most potent anti-ferroptotic enzyme that is known to reduce lipid peroxides to alcohols, other antioxidative enzymes are also indirectly involved in protection against ferroptosis. Moreover, several low molecular weight compounds that include α-tocopherol, ascorbate, and nitric oxide also efficiently neutralize radical electrons, thereby suppressing ferroptosis. The removal of radical electrons in the early stages is of primary importance in protecting against ferroptosis and other diseases that are related to oxidative stress.

Global profiling of phosphorylation-dependent changes in cysteine reactivity

Proteomics has revealed that the ~20,000 human genes engender a far greater number of proteins, or proteoforms, that are diversified in large part by post-translational modifications (PTMs). How such PTMs affect protein structure and function is an active area of research but remains technically challenging to assess on a proteome-wide scale. Here, we describe a chemical proteomic method to quantitatively relate serine/threonine phosphorylation to changes in the reactivity of cysteine residues, a parameter that can affect the potential for cysteines to be post-translationally modified or engaged by covalent drugs. Leveraging the extensive high-stoichiometry phosphorylation occurring in mitotic cells, we discover numerous cysteines that exhibit phosphorylation-dependent changes in reactivity on diverse proteins enriched in cell cycle regulatory pathways. The discovery of bidirectional changes in cysteine reactivity often occurring in proximity to serine/threonine phosphorylation events points to the broad impact of phosphorylation on the chemical reactivity of proteins and the future potential to create small-molecule probes that differentially target proteoforms with PTMs.

MicroRNA-637 Relieves Oxidative Damage in Human Melanocytes Through Down-Regulating Transient Receptor Potential Melastatin 2 Expression

Background: Vitiligo, a chronic, autoimmune destruction of melanocytes, caused by the disappearance of epidermal melanocytes, but the mechanism is not fully understood. Although emerging evidence demonstrated that abnormal regulation of microRNAs (miRNAs) were associated with the pathogenesis of diseases, the functions of miR-637 in vitiligo remain unclear. Objective: This research was designed to explore the potential roles of miR-637 in hydrogen peroxide (H2O2)-induced human primary melanocytes in vitiligo. Methods: Human primary melanocytes were induced by 250 μmol/L H2O2 for 4 h to establish oxidative injury of melanocytes model. Cell viability and apoptosis analyzed by MTT and flow cytometry assay, respectively. The relevance between miR-637 and transient receptor potential melastatin 2 (TRPM2) was checked using TargetScan and dual luciferase reporter gene assay. The expression of miR-637 and TRPM2 was evaluated using qRT-PCR and/or Western blot analysis. Reactive oxygen species (ROS) accumulation, superoxide dismutase (SOD) and catalase (CAT) activities were measured using specific assay kits. In addition, the expression of Bcl-2 and Bax were evaluated using Western blot assay. Results: TRPM2 was up-regulated, while miR-637 was down-regulated in H2O2-stimulated human primary melanocytes. TRPM2 directly interacted with miR-637. Up-regulation of miR-637 memorably increased miR-637 level and inhibited TRPM2 expression. Furthermore, miR-637 mimic fortified cell viability, reduced apoptotic cells, enhanced Bcl-2 expression, reduced Bax level, as well as inhibited the ratio of Bax/Bcl-2 in H2O2-induced melanocytes. Meanwhile, miR-637 mimic obviously suppressed the accumulation of ROS and increased SOD and CAT activity. Nevertheless, all these findings were inverted by TRPM2-plasmid. Likewise, TRPM2-siRNA led to increased cell viability, reduced apoptotic cells, enhanced Bcl-2 expression, reduced Bax level, inhibited Bax/Bcl-2 ratio, inhibited ROS production, but increased SOD and CAT activity in H2O2-induced melanocytes. Conclusion: Our findings suggested that TRPM2 was up-regulated, while miR-637 was down-regulated in injurious melanocytes of vitiligo. Up-regulation of miR-637 relieved oxidative stress-stimulated melanocyte injury via down-regulating TRPM2 expression. Our results provide new insights into the functions of miR-637 in the development of vitiligo, indicating that miR-637 may be a latent target for vitiligo therapy.

The Potential of Bovine Colostrum-Derived Exosomes to Repair Aged and Damaged Skin Cells

In this study, we examined the potentially beneficial effects of bovine colostrum-derived exosomes on UV-induced aging and damage in three major resident skin cells including keratinocytes, melanocytes, and fibroblasts. The treatment with colostrum exosomes prevented the UV-induced generation of intracellular reactive oxygen species in epidermal keratinocytes. In UV-stimulated melanocytes, colostrum exosomes could also significantly reduce the production of the protective skin-darkening pigment melanin, which may help to reduce the risk of excessive melanin formation causing skin hyperpigmentation disorders. In the human dermal fibroblasts treated with colostrum exosomes, the expression of matrix metalloproteinases was suppressed, whereas increased cell proliferation was accompanied by enhanced production of collagen, a major extracellular matrix component of skin. Taken together, our findings indicate that bovine colostrum-derived exosomes having excellent structural and functional stability offer great potential as natural therapeutic agents to repair UV-irradiated skin aging and damage.

Investigation of the antioxidant activity of the peroxidase system of cell nuclei during germination of wheat embryos with different types of resistance to temperature stress

The yield of agricultural crops directly depends on their ability to adapt to a constantly changing environment, the unfavorable climatic conditions of which cause oxidative stress, accompanied by the generation of reactive oxygen species in plant cells, which can cause damage to heteropolymer cell structures, thereby leading to suppression of plant growth and a decrease in productivity grains. It has been shown that the profile of the antioxidant activity of the peroxidase system in histone and non-histone blocks of structures (nucleoplasm, chromatin) of cell nuclei during germination is more pronounced in the cold-resistant variety Mironovskaya 808 (winter) compared to Mironovskaya yarovaya (spring), which correlates with the intensity of growth processes and can be associated with participation in the realization of proliferation and differentiation programs. A direct relationship between the scavenging of ROS and plant resistance to temperature stress, which is often associated with the increased activity of antioxidant enzymes that impart stress resistance to both high and low temperature stress, apparently also exists at the level of the plant cell nucleus.

Investigation of the antioxidant activity of the peroxidase system of cell nuclei during germination of wheat embryos with different types of resistance to temperature stress

The yield of agricultural crops directly depends on their ability to adapt to a constantly changing environment, the unfavorable climatic conditions of which cause oxidative stress, accompanied by the generation of reactive oxygen species in plant cells, which can cause damage to heteropolymer cell structures, thereby leading to suppression of plant growth and a decrease in productivity grains. It has been shown that the profile of the antioxidant activity of the peroxidase system in histone and non-histone blocks of structures (nucleoplasm, chromatin) of cell nuclei during germination is more pronounced in the cold-resistant variety Mironovskaya 808 (winter) compared to Mironovskaya yarovaya (spring), which correlates with the intensity of growth processes and can be associated with participation in the realization of proliferation and differentiation programs. A direct relationship between the scavenging of ROS and plant resistance to temperature stress, which is often associated with the increased activity of antioxidant enzymes that impart stress resistance to both high and low temperature stress, apparently also exists at the level of the plant cell nucleus.

Disrupted mitochondrial homeostasis coupled with mitotic arrest generates antineoplastic oxidative stress

Reactive oxygen species (ROS) serve as critical signals in various cellular processes. Excessive ROS cause cell death or senescence and mediates the therapeutic effect of many cancer drugs. Recent studies showed that ROS increasingly accumulate during G2/M arrest, the underlying mechanism, however, has not been fully elucidated. Here, we show that in cancer cells treated with anticancer agent TH287 or paclitaxel that causes M arrest, mitochondria accumulate robustly and produce excessive mitochondrial superoxide, which causes oxidative DNA damage and undermines cell survival and proliferation. While mitochondrial mass is greatly increased in cells arrested at M phase, the mitochondrial function is compromised, as reflected by reduced mitochondrial membrane potential, increased SUMOylation and acetylation of mitochondrial proteins, as well as an increased metabolic reliance on glycolysis. CHK1 functional disruption decelerates cell cycle, spares the M arrest and attenuates mitochondrial oxidative stress. Induction of mitophagy and blockade of mitochondrial biogenesis, measures that reduce mitochondrial accumulation, also decelerate cell cycle and abrogate M arrest-coupled mitochondrial oxidative stress. These results suggest that cell cycle progression and mitochondrial homeostasis are interdependent and coordinated, and that impairment of mitochondrial homeostasis and the associated redox signaling may mediate the antineoplastic effect of the M arrest-inducing chemotherapeutics. Our findings provide insights into the fate of cells arrested at M phase and have implications in cancer therapy.

Cyantraniliprole impairs reproductive parameters by inducing oxidative stress in adult female wistar rats

Cyantraniliprole is a synthetic insecticide used to control pests of up to 23 different types of crops. It is able to modulate ryanodine-like calcium channels, which are widely found in the organism of insects and mammals. The objective of this research was to verify the possible reproductive effects of adult female Wistar rats exposure to cyantraniliprole. Animals (67 days old) were exposed to the chemical at doses of 10 or 150 mg/kg/day, orally, for 28 consecutive days (control animals received only the vehicle). Vaginal secretions were collected during the exposure period to assess the regularity of the estrous cycle; the liver, kidneys, pituitary gland, adrenal gland, uterus, and ovaries were collected and weighed; reproductive organs were assessed for histopathological evaluation and for biochemical markers of oxidative stress and progesterone plasma level was measured. Both doses caused negative changes in the morphology and redox system of the uterus and ovaries. Animals exposed to 10 mg/kg also exhibited higher level of plasma progesterone, elevated levels of lipid peroxidation in reproductive organs, increased superoxide dismutase activity in the uterus and glutathione peroxidase activity on the ovary, while the 150 mg/kg group exhibited an increment in estrous cycle length and diminished uterine glandular epithelium. Based on these results, we conclude that cyantraniliprole may have acted as an endocrine disruptor, and its effects are mediated by oxidative stress.

Terpyridines as promising antitumor agents: an overview of their discovery and development

INTRODUCTION

The fused aromatic system of terpyridines makes them good, innocent ligands for various metals. The resulting complexes have been extensively studied for both their biological activity and physico-chemical properties. However, although free ligands also have an interesting biological activity, their share in recent research is considerably limited.

AREAS COVERED

This review covers the literature on the anticancer activity of terpyridines with special attention being paid to their use as free ligands. Whenever possible, the mechanism of action has been discussed, thereby providing evidence of the substantial differences between sole ligands or less stable complexes and those that have heavier elements.

EXPERT OPINION

The existing literature indicates that there is a specific attitude for investigating terpyridines and their transition metal complexes. While the latter have been well explored and recognized in the scientific community, the free terpyridines are considered to be useful solely due to their complexing ability. At the same time, terpyridines could have similar or even higher anticancer potency than their complexes. Moreover, a mechanistic analysis of the stability and intracellular activity would provide information that would be useful for designing new drugs.

High-performance SOD mimetic enzyme Au@Ce for arresting cell cycle and proliferation of acute myeloid leukemia

SOD-like activity of CeO₂ nanoparticles (Ce NPs) is driven by Ce³⁺/Ce⁴⁺, high oxidative stress can oxidize Ce³⁺ to reduce the ratio of Ce³⁺/Ce⁴⁺, inactivating the SOD activity of Ce NPs. Herein, we found Au@Ce NPs, assembled by Au NPs and Ce NPs, exhibited high-performance of SOD mimetic enzyme activity even upon the oxidation of H₂O₂. Ce NPs supported by nano-Au can acquire the electrons from Au NPs through the enhanced localized surface plasmon resonance (LSPR), maintaining the stability of Ce³⁺/Ce⁴⁺ and SOD-like activity. Meanwhile, Au@Ce NPs retained the peroxidase function and catalase function. As a result, Au@Ce NPs effectively scavenged O₂•- and the derived ROS in AML cells, which are the important signaling source that drives AML cell proliferation and accelerates cell cycle progression. When HL-60 cells were treated by Au@Ce NPs, the removal of endogenous ROS signal significantly arrested cell cycle at G1 phase and suppressed the cell proliferation by blocking the mitogen-activated protein kinases (MAPKs) signaling and the Akt/Cyclin D1 cell cycle signaling. Importantly, this treatment strategy showed therapeutic effect for subcutaneous transplantation of AML model as well as a satisfactory result in diminishing the leukocyte infiltration of liver and spleen particularly. Thus, assembled Au@Ce NPs show the high-performance SOD-like activity, promising the potential in treating AML and regulating abnormal ROS in other diseases safely and efficiently.

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Assembled Au@Ce NPs exhibited multi-enzyme activity and the high-performance SOD-like activity even upon the oxidation of H₂O₂.

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In the assembled Au@Ce NPs, Ce NPs can acquire the electrons from Au NPs to maintain the stability of Ce³⁺/Ce⁴⁺ and SOD activity.

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Au@Ce can scavenge O₂•- and the derived ROS in AML cells to arrest cell cycle signal and proliferation signal.

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Au@Ce treatment suppressed the growth of HL-60 bearing tumors and prolonged the survival time in systemic AML mice.

MTH1 Inhibitor TH1579 Induces Oxidative DNA Damage and Mitotic Arrest in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy, exhibiting high levels of reactive oxygen species (ROS). ROS levels have been suggested to drive leukemogenesis and is thus a potential novel target for treating AML. MTH1 prevents incorporation of oxidized nucleotides into the DNA to maintain genome integrity and is upregulated in many cancers. Here we demonstrate that hematologic cancers are highly sensitive to MTH1 inhibitor TH1579 (karonudib). A functional precision medicine ex vivo screen in primary AML bone marrow samples demonstrated a broad response profile of TH1579, independent of the genomic alteration of AML, resembling the response profile of the standard-of-care treatments cytarabine and doxorubicin. Furthermore, TH1579 killed primary human AML blast cells (CD45⁺) as well as chemotherapy resistance leukemic stem cells (CD45⁺Lin^-CD34⁺CD38^-), which are often responsible for AML progression. TH1579 killed AML cells by causing mitotic arrest, elevating intracellular ROS levels, and enhancing oxidative DNA damage. TH1579 showed a significant therapeutic window, was well tolerated in animals, and could be combined with standard-of-care treatments to further improve efficacy. TH1579 significantly improved survival in two different AML disease models in vivo. In conclusion, the preclinical data presented here support that TH1579 is a promising novel anticancer agent for AML, providing a rationale to investigate the clinical usefulness of TH1579 in AML in an ongoing clinical phase I trial. SIGNIFICANCE: The MTH1 inhibitor TH1579 is a potential novel AML treatment, targeting both blasts and the pivotal leukemic stem cells while sparing normal bone marrow cells.

Redox Homeostasis and Regulation in Pluripotent Stem Cells: Uniqueness or Versatility?

Pluripotent stem cells (PSCs) hold great potential both in studies on developmental biology and clinical practice. Mitochondrial metabolism that encompasses pathways that generate ATP and produce ROS significantly differs between PSCs and somatic cells. Correspondingly, for quite a long time it was believed that the redox homeostasis in PSCs is also highly specific due to the hypoxic niche of their origin-within the pre-implantation blastocyst. However, recent research showed that redox parameters of cultivated PSCs have much in common with that of their differentiated progeny cells. Moreover, it has been proven that, similar to somatic cells, maintaining the physiological ROS level is critical for the regulation of PSC identity, proliferation, differentiation, and de-differentiation. In this review, we aimed to summarize the studies of redox metabolism and signaling in PSCs to compare the redox profiles of pluripotent and differentiated somatic cells. We collected evidence that PSCs possess metabolic plasticity and are able to adapt to both hypoxia and normoxia, that pluripotency is not strictly associated with anaerobic conditions, and that cellular redox homeostasis is similar in PSCs and many other somatic cells under in vitro conditions that may be explained by the high conservatism of the redox regulation system.

Mechanism and function of DNA replication-independent DNA-protein crosslink repair via the SUMO-RNF4 pathway

DNA-protein crosslinks (DPCs) obstruct essential DNA transactions, posing a serious threat to genome stability and functionality. DPCs are proteolytically processed in a ubiquitin- and DNA replication-dependent manner by SPRTN and the proteasome but can also be resolved via targeted SUMOylation. However, the mechanistic basis of SUMO-mediated DPC resolution and its interplay with replication-coupled DPC repair remain unclear. Here, we show that the SUMO-targeted ubiquitin ligase RNF4 defines a major pathway for ubiquitylation and proteasomal clearance of SUMOylated DPCs in the absence of DNA replication. Importantly, SUMO modifications of DPCs neither stimulate nor inhibit their rapid DNA replication-coupled proteolysis. Instead, DPC SUMOylation provides a critical salvage mechanism to remove DPCs formed after DNA replication, as DPCs on duplex DNA do not activate interphase DNA damage checkpoints. Consequently, in the absence of the SUMO-RNF4 pathway cells are able to enter mitosis with a high load of unresolved DPCs, leading to defective chromosome segregation and cell death. Collectively, these findings provide mechanistic insights into SUMO-driven pathways underlying replication-independent DPC resolution and highlight their critical importance in maintaining chromosome stability and cellular fitness.

Aurora A kinase activation: Different means to different ends

Aurora A is a serine/threonine kinase essential for mitotic entry and spindle assembly. Recent molecular studies have revealed the existence of multiple, distinct mechanisms of Aurora A activation, each occurring at specific subcellular locations, optimized for cellular context, and primed by signaling events including phosphorylation and oxidation.

Cell cycle-coupled changes in the level of reactive oxygen species support the proliferation of human pluripotent stem cells

The study of proliferation regulation in human pluripotent stem cells is crucial to gain insights into understanding the physiology of these cells. However, redox regulation of the pluripotent cell cycle remains largely unexplored. Here, using human embryonic stem cells (hESCs) as well as human induced pluripotent stem cells (hiPSCs), we demonstrate that the level of reactive oxygen species (ROS) in pluripotent cells oscillates in accordance with the cell cycle progression with the peak occurring at transition from S to G₂ /M phase of the cycle. A decrease of this level by antioxidants leads to hindered S-phase initiation and progression but does not affect the early-G₁ -phase or mitosis. Cells exposed to antioxidants in the early-G₁ -phase accumulate the phosphorylated retinoblastoma protein and overcome the restriction point but are unable to accumulate the main regulators of the S phase-CYCLIN A and GEMININ. Based on the previous findings that CYCLIN A stability is affected by redox homeostasis disturbances in somatic cells, we compared the responses to antioxidant treatments in hESCs and in their differentiated fibroblast-like progeny cells (difESCs). In difESCs, similar to hESCs, a decrease in ROS level results in the disruption of S-phase initiation accompanied by a deficiency of the CYCLIN A level. Moreover, in antioxidant-treated cells, we revealed the accumulation of DNA breaks, which was accompanied by activation of the apoptosis program in pluripotent cells. Thus, we conclude that maintaining the physiological ROS level is essential for promotion of proliferation and accurate DNA synthesis in pluripotent cells and their differentiated descendants.

NEIL3 Prevents Senescence in Hepatocellular Carcinoma by Repairing Oxidative Lesions at Telomeres during Mitosis

Patients with hepatocellular carcinoma (HCC) suffer from few treatment options and poor survival rates. Here we report that endonuclease VIII-like protein 3 (NEIL3) is overexpressed in HCC and correlates with poor survival. All six HCC cell lines investigated were dependent on NEIL3 catalytic activity for survival and prevention of senescence, while NEIL3 was dispensable for nontransformed cells. NEIL3-depleted HCC cell lines accumulated oxidative DNA lesions specifically at telomeres, resulting in telomere dysfunctional foci and 53BP1 foci formation. Following oxidative DNA damage during mitosis, NEIL3 relocated to telomeres and recruited apurinic endonuclease 1 (APE1), indicating activation of base excision repair. META-FISH revealed that NEIL3, but not NEIL1 or NEIL2, is required to initiate APE1 and polymerase beta (POLB)-dependent base excision repair at oxidized telomeres. Repeated exposure of NEIL3-depleted cells to oxidizing damage induced chromatin bridges and damaged telomeres. These results demonstrate a novel function for NEIL3 in repair of oxidative DNA damage at telomeres in mitosis, which is important to prevent senescence of HCC cells. Furthermore, these data suggest that NEIL3 could be a target for therapeutic intervention for HCC. SIGNIFICANCE: This study describes compartmentalization of base excision repair during mitosis that is dependent on NEIL3, APE1, and POLB to repair oxidative damage accumulating at telomeres in hepatocellular carcinoma.

Transmembrane Chloride Intracellular Channel 1 (tmCLIC1) as a Potential Biomarker for Personalized Medicine

Identification of potential pathological biomarkers has proved to be essential for understanding complex and fatal diseases, such as cancer and neurodegenerative diseases. Ion channels are involved in the maintenance of cellular homeostasis. Moreover, loss of function and aberrant expression of ion channels and transporters have been linked to various cancers, and to neurodegeneration. The Chloride Intracellular Channel 1 (CLIC1), CLIC1 is a metamorphic protein belonging to a partially unexplored protein superfamily, the CLICs. In homeostatic conditions, CLIC1 protein is expressed in cells as a cytosolic monomer. In pathological states, CLIC1 is specifically expressed as transmembrane chloride channel. In the following review, we trace the involvement of CLIC1 protein functions in physiological and in pathological conditions and assess its functionally active isoform as a potential target for future therapeutic strategies.

Oxidative stress-mediated alterations in histone post-translational modifications

Epigenetic regulation of gene expression provides a finely tuned response capacity for cells when undergoing environmental changes. However, in the context of human physiology or disease, any cellular imbalance that modulates homeostasis has the potential to trigger molecular changes that result either in physiological adaptation to a new situation or pathological conditions. These effects are partly due to alterations in the functionality of epigenetic regulators, which cause long-term and often heritable changes in cell lineages. As such, free radicals resulting from unbalanced/extended oxidative stress have been proved to act as modulators of epigenetic agents, resulting in alterations of the epigenetic landscape. In the present review we will focus on the particular effect that oxidative stress and free radicals produce in histone post-translational modifications that contribute to altering the histone code and, consequently, gene expression. The pathological consequences of the changes in this epigenetic layer of regulation of gene expression are thoroughly evidenced by data gathered in many physiological adaptive processes and in human diseases that range from age-related neurodegenerative pathologies to cancer, and that include respiratory syndromes, infertility, and systemic inflammatory conditions like sepsis.