Mammalian G1- and S-phase checkpoints in response to DNA damage

The relationship mammalian p38 with human health and its homolog Hog1 in response to environmental stresses in Saccharomyces cerevisiae

The mammalian p38 MAPK pathway plays a vital role in transducing extracellular environmental stresses into numerous intracellular biological processes. The p38 MAPK have been linked to a variety of cellular processes including inflammation, cell cycle, apoptosis, development and tumorigenesis in specific cell types. The p38 MAPK pathway has been implicated in the development of many human diseases and become a target for treatment of cancer. Although MAPK p38 pathway has been extensively studied, many questions still await clarification. More comprehensive understanding of the MAPK p38 pathway will provide new possibilities for the treatment of human diseases. Hog1 in S. cerevisiae is the conserved homolog of p38 in mammalian cells and the HOG MAPK signaling pathway in S. cerevisiae has been extensively studied. The deep understanding of HOG MAPK signaling pathway will help provide clues for clarifying the p38 signaling pathway, thereby furthering our understanding of the relationship between p38 and disease. In this review, we elaborate the functions of p38 and the relationship between p38 and human disease. while also analyzing how Hog1 regulates cellular processes in response to environmental stresses. 1, p38 in response to various stresses in mammalian cells.2, The functions of mammalian p38 in human health.3, Hog1 as conserved homolog of p38 in response to environmental stresses in Saccharomyces cerevisiae. 1, p38 in response to various stresses in mammalian cells. 2, The functions of mammalian p38 in human health. 3, Hog1 as conserved homolog of p38 in response to environmental stresses in S. cerevisiae.

TOP2A inhibition and its cellular effects related to cell cycle checkpoint adaptation pathway

In this study, we investigate the G2 checkpoint activated by chromosome entanglements, the so-called Decatenation Checkpoint (DC), which can be activated by TOP2A catalytic inhibition. Specifically, we focus on the spontaneous ability of cells to bypass or override this checkpoint, referred to as checkpoint adaptation. Some factors involved in adapting to this checkpoint are p53 and MCPH1. Using cellular models depleted of p53 or both p53 and MCPH1 in hTERT-RPE1 cells, we analyzed cell cycle dynamics and adaptation, segregation defects, apoptosis rate, and transcriptional changes related to prolonged exposure to TOP2A inhibitors. Our findings reveal that cell cycle dynamics are altered in MCPH1-depleted cells compared to control cells. We found that MCPH1 depletion can restore the robustness of the DC in a p53-negative background. Furthermore, this research highlights the differential effects of TOP2A poisons and catalytic inhibitors on cellular outcomes and transcriptional profiles. By examining the different mechanisms of TOP2A inhibition and their impact on cellular processes, this study contributes to a deeper understanding of the regulation and physiological implications of the DC and checkpoint adaptation in non-carcinogenic cell lines.

Integrated GMPS and RAMP3 as a signature to predict prognosis and immune heterogeneity in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly fatal malignant worldwide. As different expression levels of specific genes can lead to different HCC outcomes, we aimed to develop a gene signature capable of predicting HCC prognosis.

METHODS

In this study, transcriptomic sequencing and relevant clinical data were extracted from public platforms. The guanine monophosphate synthase (GMPS)|receptor activity-modifying protein 3 (RAMP3) gene pair was developed based on the relative values of gene expression levels. Nomograms were developed using R software. Immune status was assessed through single-sample gene set enrichment analysis. GMPS knockdown was achieved through siRNA transfection. Quantitative reverse transcription PCR, apoptosis assays, and cell proliferation were performed to verify the function of GMPS|RAMP3 in HCC cells.

RESULTS

Here, a gene pair containing GMPS and RAMP3 was successfully constructed. We demonstrated that the GMPS|RAMP3 gene pair was an independent predictor with strong prognostic prediction power, based on which a nomogram was established. Functional analysis revealed that the enrichment of cell cycle-related pathways and immune status differed considerably between the two groups, with cell cycle-related genes highly expressed in the high GMPS|RAMP3 value group. Finally, cell experiments indicated that GMPS knockdown significantly repressed proliferation, promoted apoptosis, and enhanced the sensitivity of HCC cells to gemcitabine.

CONCLUSIONS

The gene pair GMPS|RAMP3 is a novel prognostic predictor of HCC, providing a promising approach to the treatment and assessment of immune heterogeneity in HCC.

Fractionated alpha and mixed beam radiation promote stronger pro-inflammatory effects compared to acute exposure and trigger phagocytosis

Introduction and methods

Aiming to evaluate safety aspects of a recently proposed approach to target Alzheimer's disease, we mimicked a complex boron neutron capture therapy field using a mixed beam consisting of high- and low-linear energy transfer (LET) radiation, 241Am alpha particles (α) and/or X-ray radiation respectively, in human microglial (HMC3) cells.

Results

Acute exposure to 2 Gy X-rays induced the strongest response in the formation of γH2AX foci 30 min post irradiation, while α- and mixed beam-induced damage (α:X-ray = 3:1) sustained longer. Fractionation of the same total dose (0.4 Gy daily) induced a similar number of γH2AX foci as after acute radiation, however, α- or mixed irradiation caused a higher expression of DNA damage response genes CDKN1A and MDM2 24 h after the last fraction, as well as a stronger decrease in cell viability and clonogenic survival compared to acute exposure. Phosphorylation of STING, followed by phosphorylation of NF-κB subunit p65, was rapidly induced (1 or 3 h, respectively) after the last fraction by all radiation qualities. This led to IL-1β secretion into the medium, strongly elevated expression of pro-inflammatory cytokine genes and enhanced phagocytosis after fractionated exposure to α- and mixed beam-irradiation compared to their acute counterparts 24 h post-irradiation. Nevertheless, all inflammatory changes were returning to basal levels or below 10-14 days post irradiation.

Discussion

In conclusion, we demonstrate strong transient pro-inflammatory induction by daily high-LET radiation in a microglia model, triggering phagocytosis which may aid in clearing amyloid beta, but importantly, from a safety perspective, without long-term alterations.

Unraveling the Guardian: p53's Multifaceted Role in the DNA Damage Response and Tumor Treatment Strategies

DNA damage can lead to mutations that can alter the function of oncogenes or tumor suppressor genes, thus promoting the development of cancer. p53 plays a multifaceted and complex role in the DNA damage response and cancer progression and is known as the 'guardian of the gene'. When DNA damage occurs, p53 is activated through a series of post-translational modifications, which stabilize the protein and enhance its function as a transcription factor. It regulates processes including cell cycle checkpoints, DNA repair and apoptosis, thereby preventing the spread of damaged DNA and maintaining genome integrity. On the one hand, p53 can initiate cell cycle arrest and induce cells to enter the G1/S and G2/M checkpoints, preventing cells with damaged DNA from continuing to proliferate and gaining time for DNA repair. At the same time, p53 can promote the activation of DNA repair pathways, including base excision repair, nucleotide excision repair and other repair pathways, to ensure the integrity of genetic material. If the damage is too severe to repair, p53 will trigger the apoptosis process to eliminate potential cancer risks in time. p53 also plays a pivotal role in cancer progression. Mutations in the p53 gene are frequently found in many cancers, and the mutated p53 not only loses its normal tumor suppressor function but may even acquire pro-cancer activity. Therefore, we also discuss therapeutic strategies targeting the p53 pathway, such as the use of small-molecule drugs to restore the function of wild-type p53, the inhibition of negative regulatory factors and synthetic lethality approaches for p53-deficient tumors. This review therefore highlights the important role of p53 in maintaining genomic stability and its potential in therapeutic strategies for cancer.

CREB3L1/OASIS: cell cycle regulator and tumor suppressor

Cell cycle checkpoints detect DNA errors, eventually arresting the cell cycle to promote DNA repair. Failure of such cell cycle arrest causes aberrant cell proliferation, promoting the pathogenesis of multiple diseases, including cancer. Endoplasmic reticulum (ER) stress transducers activate the unfolded protein response, which not only deals with unfolded proteins in ER lumen but also orchestrates diverse physiological phenomena such as cell differentiation and lipid metabolism. Among ER stress transducers, cyclic AMP-responsive element-binding protein 3-like protein 1 (CREB3L1) [also known as old astrocyte specifically induced substance (OASIS)] is an ER-resident transmembrane transcription factor. This molecule is cleaved by regulated intramembrane proteolysis, followed by activation as a transcription factor. OASIS is preferentially expressed in specific cells, including astrocytes and osteoblasts, to regulate their differentiation. In accordance with its name, OASIS was originally identified as being upregulated in long-term-cultured astrocytes undergoing cell cycle arrest because of replicative stress. In the context of cell cycle regulation, previously unknown physiological roles of OASIS have been discovered. OASIS is activated as a transcription factor in response to DNA damage to induce p21-mediated cell cycle arrest. Although p21 is directly induced by the master regulator of the cell cycle, p53, no crosstalk occurs between p21 induction by OASIS or p53. Here, we summarize previously unknown cell cycle regulation by ER-resident transcription factor OASIS, particularly focusing on commonalities and differences in cell cycle arrest between OASIS and p53. This review also mentions tumorigenesis caused by OASIS dysfunctions, and OASIS's potential as a tumor suppressor and therapeutic target.

miR-449a mediated repression of the cell cycle machinery prevents neuronal apoptosis

Aberrant activation of the cell cycle of terminally differentiated neurons results in their apoptosis and is known to contribute to neuronal loss in various neurodegenerative disorders like Alzheimer's Disease. However, the mechanisms that regulate cell cycle-related neuronal apoptosis are poorly understood. We identified several miRNA that are dysregulated in neurons from a transgenic APP/PS1 mouse model for AD (TgAD). Several of these miRNA are known to and/or are predicted to target cell cycle-related genes. Detailed investigation on miR-449a revealed the following: a, it promotes neuronal differentiation by suppressing the neuronal cell cycle; b, its expression in cortical neurons was impaired in response to amyloid peptide Aβ42; c, loss of its expression resulted in aberrant activation of the cell cycle leading to apoptosis. miR-449a may prevent cell cycle-related neuronal apoptosis by targeting cyclin D1 and protein phosphatase CDC25A, which are important for G1-S transition. Importantly, the lentiviral-mediated delivery of miR-449a in TgAD mouse brain significantly reverted the defects in learning and memory, which are associated with AD.

ELK3 destabilization by speckle-type POZ protein suppresses prostate cancer progression and docetaxel resistance

Accumulating evidence demonstrates that the activity regulation of ELK3, a member of the E26 transformation-specific oncogene family, is critical to regulating cell proliferation, migration, and survival in human cancers. However, the molecular mechanisms of how ELK3 induces chemoresistance in prostate cancer (PCa) have not been elucidated. In this study, we found that SPOP and ELK3 are an interacting partner. The interaction between SPOP and ELK3 resulted in increased ELK3 ubiquitination and destruction, assisted by checkpoint kinase-mediated ELK3 phosphorylation. Notably, the modulation of SPOP-mediated ELK3 protein stability affected the c-Fos-induced cell proliferation and invasion of PCa cells. The clinical involvement of the SPOP-ELK3 axis in PCa development was confirmed by an immunohistochemical assay on 123 PCa tissues, with an inverse correlation between increased ELK3 and decreased SPOP being present in ~80% of the specimens. This observation was supported by immunohistochemistry analysis using a SPOP-mutant PCa specimen. Finally, docetaxel treatment induced cell death by activating checkpoint kinase- and SPOP-mediated ELK3 degradation, while SPOP-depleted or SPOP-mutated PCa cells showed cell death resistance. Notably, this observation was correlated with the protein levels of ELK3. Taken together, our study reveals the precise mechanism of SPOP-mediated degradation of ELK3 and provides evidence that SPOP mutations contribute to docetaxel resistance in PCa.

Ultrasmall metal alloy nanozymes mimicking neutrophil enzymatic cascades for tumor catalytic therapy

Developing strategies that emulate the killing mechanism of neutrophils, which involves the enzymatic cascade of superoxide dismutase (SOD) and myeloperoxidase (MPO), shows potential as a viable approach for cancer therapy. Nonetheless, utilizing natural enzymes as therapeutics is hindered by various challenges. While nanozymes have emerged for cancer treatment, developing SOD-MPO cascade in one nanozyme remains a challenge. Here, we develop nanozymes possessing both SOD- and MPO-like activities through alloying Au and Pd, which exhibits the highest cascade activity when the ratio of Au and Pd is 1:3, attributing to the high d-band center and adsorption energy for superoxide anions, as determined through theoretical calculations. The Au1Pd3 alloy nanozymes exhibit excellent tumor therapeutic performance and safety in female tumor-bearing mice, with safety attributed to their tumor-specific killing ability and renal clearance ability caused by ultrasmall size. Together, this work develops ultrasmall AuPd alloy nanozymes that mimic neutrophil enzymatic cascades for catalytic treatment of tumors.

Y-Box Binding Protein 1: Unraveling the Multifaceted Role in Cancer Development and Therapeutic Potential

Y-box binding protein 1 (YBX1), a member of the Cold Shock Domain protein family, is overexpressed in various human cancers and is recognized as an oncogenic gene associated with poor prognosis. YBX1's functional diversity arises from its capacity to interact with a broad range of DNA and RNA molecules, implicating its involvement in diverse cellular processes. Independent investigations have unveiled specific facets of YBX1's contribution to cancer development. This comprehensive review elucidates YBX1's multifaceted role in cancer across cancer hallmarks, both in cancer cell itself and the tumor microenvironment. Based on this, we proposed YBX1 as a potential target for cancer treatment. Notably, ongoing clinical trials addressing YBX1 as a target in breast cancer and lung cancer have showcased its promise for cancer therapy. The ramp up in in vitro research on targeting YBX1 compounds also underscores its growing appeal. Moreover, the emerging role of YBX1 as a neural input is also proposed where the high level of YBX1 was strongly associated with nerve cancer and neurodegenerative diseases. This review also summarized the up-to-date advanced research on the involvement of YBX1 in pancreatic cancer.

Azafuramidines as potential anticancer Agents: Pro-apoptotic profile and cell cycle arrest

The current study aimed to test the antiproliferative activity of three azafuramidines (X, Y, and Z) against three different human cell lines; liver HepG2, breast MCF-7, and bone U2OS. And to explore the molecular mechanism(s) of the antiproliferative activity of these derivatives. The three new azafuramidines demonstrated a potent cytotoxicity at < 2 μM against the three cell lines investigated. The azafuramidines were highly selective with selectivity index ∼ 47 - 61 folds indicating safety to the normal cells. In the scratch assay, azafuramidines significantly reduced the percentage of wound healing indicating ability to prevent or reduce metastasis. Derivatives X and Z arrested the HepG2 cells at S and G2/M phases detected by the flow cytometry. Derivatives X, Y, and Z elevated the apoptosis of HepG2 cells by ∼ 71 %, 66 %, and 59 %, respectively. Derivatives X and Z were superior to derivative Y. The potent antiproliferative, cell cycle arrest, and pro-apoptotic efficacy of these chlorophenyl derivatives could be attributed to their ability of inducing the overexpression of p53, p21, and p27. These derivatives had the potential to act as anticancer agents and merit further investigations.

Effects and Mechanisms of Kaempferol in the Management of Cancers through Modulation of Inflammation and Signal Transduction Pathways

Cancer is the principal cause of death and its incidence is increasing continuously worldwide. Various treatment approaches are in practice to treat cancer, but these treatment strategies may be associated with severe side effects and also produce drug resistance. However, natural compounds have established their role in cancer management with minimal side effects. In this vista, kaempferol, a natural polyphenol, mainly found in vegetables and fruits, has been revealed to have many health-promoting effects. Besides its health-promoting potential, its anti-cancer potential has also been described in in vivo as well as in in vitro studies. The anti-cancer potential of kaempferol has been proven through modulation of cell signaling pathways in addition to the induction of apoptosis and cell cycle arrest in cancer cells. It leads to the activation of tumor suppressor genes, inhibition of angiogenesis, PI3K/AKT pathways, STAT3, transcription factor AP-1, Nrf2 and other cell signaling molecules. Poor bioavailability of this compound is one of the major limitations for its proper and effective disease management actions. Recently, some novel nanoparticle-based formulations have been used to overcome these limitations. The aim of this review is to provide a clear picture regarding the mechanism of action of kaempferol in different cancers through the modulation of cell signaling molecules. Besides this, strategies to improve the efficacy and synergistic effects of this compound have also been described. However, more studies are needed based on clinical trials to fully explore the therapeutic role of this compound, especially in cancer treatment.

Guttiferone E Displays Antineoplastic Activity Against Melanoma Cells

Guttiferone E (GE) is a benzophenone found in Brazilian red propolis. In the present study, the effect of GE on human (A-375) and murine (B16-F10) melanoma cells was investigated. GE significantly reduced the cellular viability of melanoma cells in a time-dependent manner. In addition, GE demonstrated antiproliferative effect, with IC₅₀ values equivalent to 9.0 and 6.6 µM for A-375 and B16-F10 cells, respectively. The treatment of A-375 cells with GE significantly increased cell populations in G0/G1 phase and decreased those in G2/M phase. Conversely, on B16-F10 cells, GE led to a significant decrease in the populations of cells in G0/G1 phase and concomitantly an increase in the population of cells in phase S. A significantly higher percentage of apoptotic cells was observed in A-375 (43.5%) and B16-F10 (49.9%) cultures after treatment with GE. Treatments with GE caused morphological changes and significant decrease to the melanoma cells' density. GE (10 µM) inhibited the migration of melanoma cells, with a higher rate of inhibition in B16-F10 cells (73.4%) observed. In addition, GE significantly reduced the adhesion of A375 cells, but showed no effect on B16-F10. Treatment with GE did not induce changes in P53 levels in A375 cultures. Molecular docking calculations showed that GE is stable in the active sites of the tubulin dimer with a similar energy to taxol chemotherapy. Taken together, the data suggest that GE has promising antineoplastic potential against melanoma.

ATM deficiency aggravates the progression of liver fibrosis induced by carbon tetrachloride in mice

Ataxia telangiectasia mutated (ATM) is a pivotal sensor during the DNA damage response that slows cell passage through the cell cycle checkpoints to facilitate DNA repair, and liver fibrosis is an irreversible pathological consequence of the sustained wound-healing process, However, the effects of ATM on the development of liver fibrosis are still not fully understood. Therefore, the aim of the study was to investigate the effects and potential mechanisms of ATM on the progression of liver fibrosis. Wild-type and ATM-deficient were administered with carbon tetrachloride (CCl₄, 5 ml/kg, i.p.) for 8 weeks to induce liver fibrosis, and the liver tissues and serum were collected for analysis. KU-55933 (10 μM) was used to investigate the effects of ATM blockage on CCl₄-induced hepatocyte injury in vitro. The results showed that ATM deficiency aggravated the increased serum transaminase levels and liver MDA, HYP, and 8-OHdG contents compared with the model group (p < 0.05). Sirius red staining showed that ATM deficiency exacerbated liver collagen deposition in vivo, which was associated with the activation of TGF-β1/Smad2 signaling. Furthermore, blocking ATM with KU-55933 exacerbated the production of ROS and DNA damage caused by CCl₄ exposure in HepG2 cells, and KU-55933 treatment also reversed the downregulated expression of CDK1 and CDK2 after CCl₄ exposure in vitro. Moreover, the loss of ATM perturbed the regulation of the hepatic cell ChK2-CDC25A/C-CDK1/2 cascade and apoptosis in vivo, which was accompanied by increased Ki67-positive and TUNEL-positive cells after chronic CCl₄ treatment. In conclusion, our results indicated that ATM might be a critical regulator of liver fibrosis progression, and the underlying mechanisms of exacerbated liver fibrosis development in ATM-deficient mice might be associated with the dysregulation of hepatic cell proliferation and apoptosis.

Adverse (geno)toxic effects of bisphenol A and its analogues in hepatic 3D cell model

Bisphenol A (BPA) is one of the most widely used and versatile chemical compounds in polymer additives and epoxy resins for manufacturing a range of products for human applications. It is known as endocrine disruptor, however, there is growing evidence that it is genotoxic. Because of its adverse effects, the European Union has restricted its use to protect human health and the environment. As a result, the industry has begun developing BPA analogues, but there are not yet sufficient toxicity data to claim that they are safe. We investigated the adverse toxic effects of BPA and its analogues (BPS, BPAP, BPAF, BPFL, and BPC) with emphasis on their cytotoxic and genotoxic activities after short (24-h) and prolonged (96-h) exposure in in vitro hepatic three-dimensional cell model developed from HepG2 cells. The results showed that BPFL and BPC (formed by an additional ring system) were the most cytotoxic analogues that affected cell viability, spheroid surface area and morphology, cell proliferation, and apoptotic cell death. BPA, BPAP, and BPAF induced DNA double-strand break formation (γH2AX assay), whereas BPAF and BPC increased the percentage of p-H3-positive cells, indicating their aneugenic activity. All BPs induced DNA single-strand break formation (comet assay), with BPAP (≥0.1 μM) being the most effective and BPA and BPC the least effective (≥1 μM) under conditions applied. The results indicate that not all of the analogues studied are safer alternatives to BPA and thus more in-depth research is urgently needed to adequately evaluate the risks of BPA analogues and assess their safety for humans.

The Multifaceted Role of Baicalein in Cancer Management through Modulation of Cell Signalling Pathways

The roles of medicinal plants or their purified bioactive compounds have attracted attention in the field of health sciences due to their low toxicity and minimal side effects. Baicalein is an active polyphenolic compound, isolated from Scutellaria baicalensis, and plays a significant role in the management of different diseases. Epidemiologic studies have proven that there is an inverse association between baicalein consumption and disease severity. Baicalein is known to display anticancer activity through the inhibition of inflammation and cell proliferation. Additionally, the anticancer potential of baicalein is chiefly mediated through the modulation of various cell-signaling pathways, such as the induction of apoptosis, autophagy, cell cycle arrest, inhibition of angiogenesis, signal transducer and activator of transcription 3, and PI3K/Akt pathways, as well as the regulation of other molecular targets. Therefore, the current review aimed to explore the role of baicalein in different types of cancer along with mechanisms of action. Besides this, the synergistic effects with other anti-cancerous drugs and the nano-formulation based delivery of baicalein have also been discussed.

Sneaking into the viral safe-houses: Implications of host components in regulating integrity and dynamics of rotaviral replication factories

The biology of the viral life cycle essentially includes two structural and functional entities—the viral genome and protein machinery constituting the viral arsenal and an array of host cellular components which the virus closely associates with—to ensure successful perpetuation. The obligatory requirements of the virus to selectively evade specific host cellular factors while exploiting certain others have been immensely important to provide the platform for designing host-directed antiviral therapeutics. Although the spectrum of host-virus interaction is multifaceted, host factors that particularly influence viral replication have immense therapeutic importance. During lytic proliferation, viruses usually form replication factories which are specialized subcellular structures made up of viral proteins and replicating nucleic acids. These viral niches remain distinct from the rest of the cellular milieu, but they effectively allow spatial proximity to selective host determinants. Here, we will focus on the interaction between the replication compartments of a double stranded RNA virus rotavirus (RV) and the host cellular determinants of infection. RV, a diarrheagenic virus infecting young animals and children, forms replication bodies termed viroplasms within the host cell cytoplasm. Importantly, viroplasms also serve as the site for transcription and early morphogenesis of RVs and are very dynamic in nature. Despite advances in the understanding of RV components that constitute the viroplasmic architecture, knowledge of the contribution of host determinants to viroplasm dynamicity has remained limited. Emerging evidence suggests that selective host determinants are sequestered inside or translocated adjacent to the RV viroplasms. Functional implications of such host cellular reprogramming are also ramifying—disarming the antiviral host determinants and usurping the pro-viral components to facilitate specific stages of the viral life cycle. Here, we will provide a critical update on the wide variety of host cellular pathways that have been reported to regulate the spatial and temporal dynamicity of RV viroplasms. We will also discuss the methods used so far to study the host-viroplasm interactions and emphasize on the potential host factors which can be targeted for therapeutic intervention in the future.

3,4‑Dihydroxyacetophenone attenuates oxidative stress‑induced damage to HUVECs via regulation of the Nrf2/HO‑1 pathway

It has been reported that oxidative stress plays a prominent role in diabetic macrovascular diseases. 3,4-Dihydroxyacetophenone (3,4-DHAP) has been found to have a variety of biological activities. However, few studies have assessed the antioxidant capacity of 3,4-DHAP and the underlying mechanisms. Thus, the aim of the present study was to explore the effects of 3,4-DHAP on oxidative stress in human umbilical vein endothelial cells (HUVECs). HUVECs were pre-treated with 3,4-DHAP and then exposed to high glucose conditions. Cell viability and cytotoxicity were measured using an MTT assay. Reactive oxygen species (ROS) levels were measured using an inverted fluorescence microscope and a fluorescent enzyme labeling instrument. Protein expression levels of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), microtubule-associated protein 1A/1B-light chain 3 (LC3) and poly ADP-ribose polymerase-1 (PARP-1) were measured using western blotting, and mRNA expression of Nrf2 and HO-1 were measured through reverse transcription-quantitative PCR (RT-qPCR). Nrf2 nuclear translocation was evaluated using immunofluorescence analysis and autophagosomes were observed using transmission electron microscope (TEM). The results of the present study demonstrated that compared with the control group, cell viability of the high glucose group was reduced and cell cytotoxicity of the high glucose group was increased. ROS production in the high glucose group was clearly enhanced. In addition, high glucose upregulated Nrf2 and HO-1 protein and mRNA expression levels. Nuclear translocation of Nrf2 in the high glucose group was also increased. The formation of autophagosomes in the high glucose group was also higher than that in the control group. Furthermore, LC3-II/LC3-I and PARP-1 protein expression levels were increased after treatment with high glucose. However, compared to the high glucose group, 3,4-DHAP (10 µmol/l) significantly enhanced cell viability. 3,4-DHAP markedly decreased the production of ROS, increased Nrf2 and HO-1 protein and mRNA expression levels, and promoted nuclear translocation of Nrf2 in HUVECs. In addition, 3,4-DHAP promoted the formation of autophagosomes, and notably increased the protein expression levels of LC3-II/LC3-I and PARP-1. Moreover, it was determined that compared to the 3,4-DHAP group, treatment with 3,4-DHAP and ML385 enhanced cell viability, and decreased ROS production, Nrf2 and HO-1 protein and mRNA expression levels, nuclear translocation of Nrf2, and LC3-II/LC3-I and PARP-1 protein expression levels. Collectively, the results of the present study showed that 3,4-DHAP protected HUVECs against oxidative stress via regulation of the Nrf2/HO-1 pathway, by increasing autophagy and promoting DNA damage repair.

SRSF1 governs progenitor-specific alternative splicing to maintain adult epithelial tissue homeostasis and renewal

Alternative splicing generates distinct mRNA variants and is essential for development, homeostasis, and renewal. Proteins of the serine/arginine (SR)-rich splicing factor family are major splicing regulators that are broadly required for organ development as well as cell and organism viability. However, how these proteins support adult organ function remains largely unknown. Here, we used the continuously growing mouse incisor as a model to dissect the functions of the prototypical SR family protein SRSF1 during tissue homeostasis and renewal. We identified an SRSF1-governed alternative splicing network that is specifically required for dental proliferation and survival of progenitors but dispensable for the viability of differentiated cells. We also observed a similar progenitor-specific role of SRSF1 in the small intestinal epithelium, indicating a conserved function of SRSF1 across adult epithelial tissues. Thus, our findings define a regulatory mechanism by which SRSF1 specifically controls progenitor-specific alternative splicing events to support adult tissue homeostasis and renewal.

Effects of Ultra-Short Pulsed Electric Field Exposure on Glioblastoma Cells

Glioblastoma multiforme (GBM) is the most common brain cancer in adults. GBM starts from a small fraction of poorly differentiated and aggressive cancer stem cells (CSCs) responsible for aberrant proliferation and invasion. Due to extreme tumor heterogeneity, actual therapies provide poor positive outcomes, and cancers usually recur. Therefore, alternative approaches, possibly targeting CSCs, are necessary against GBM. Among emerging therapies, high intensity ultra-short pulsed electric fields (PEFs) are considered extremely promising and our previous results demonstrated the ability of a specific electric pulse protocol to selectively affect medulloblastoma CSCs preserving normal cells. Here, we tested the same exposure protocol to investigate the response of U87 GBM cells and U87-derived neurospheres. By analyzing different in vitro biological endpoints and taking advantage of transcriptomic and bioinformatics analyses, we found that, independent of CSC content, PEF exposure affected cell proliferation and differentially regulated hypoxia, inflammation and P53/cell cycle checkpoints. PEF exposure also significantly reduced the ability to form new neurospheres and inhibited the invasion potential. Importantly, exclusively in U87 neurospheres, PEF exposure changed the expression of stem-ness/differentiation genes. Our results confirm this physical stimulus as a promising treatment to destabilize GBM, opening up the possibility of developing effective PEF-mediated therapies.

HepG2 spheroids as a biosensor-like cell-based system for (geno)toxicity assessment

3D spheroids developed from HepG2 cells were used as a biosensor-like system for the detection of (geno)toxic effects induced by chemicals. Benzo(a)pyrene (B(a)P) and amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) with well-known mechanisms of action were used for system validation. HepG2 spheroids grown for 3 days were exposed to BaP and PhIP for 24 and 72 h. The growth and viability of spheroids were monitored by planimetry and Live/Dead staining of cells. Multi-parametric flow cytometric analysis was applied for simultaneous detection of specific end-effects including cell cycle analysis (Hoechst staining), cell proliferation (KI67 marker), and DNA double-strand breaks (ℽH2AX) induced by genotoxic compounds. Depending on the exposure concentration/time, BaP reduced spheroid growth, affected cell proliferation by arresting cells in S and G2 phase and induced DNA double-strand breaks (DSB). Simultaneous staining of ℽH2AX formation and cell cycle analysis revealed that after BaP (10 μM; 24 h) exposure 60% of cells in G0/G1 phase had DNA DSB, while after 72 h only 20% of cells contained DSB indicating efficient repair of DNA lesions. PhIP did not influence the spheroid size whereas accumulation of cells in the G2 phase occurred after both treatment times. The evaluation of DNA damage revealed that at 200 μM PhIP 50% of cells in G0/G1 phase had DNA DSB, which after 72-h exposure dropped to 40%, showing lower repair capacity of PhIP-induced DSB compared to BaP-induced. The developed approach using simultaneous detection of several parameters provides mechanistic data and thus contributes to more reliable genotoxicity assessment of chemicals as a high-content screening tool.

Auranofin induces urothelial carcinoma cell death via reactive oxygen species production and synergy with cisplatin

Urothelial carcinoma (UC) is one of the most common cancer types of the urinary tract. UC is associated with poor 5-year survival rate, and resistance to cisplatin-based therapy remains a challenge for invasive bladder cancer treatment. Therefore, there is an urgent need to develop new drugs for advanced UC therapy. Auranofin (AF) was developed over 30 years ago for the treatment of rheumatoid arthritis and has been reported to exert an antitumor effect by increasing the level of reactive oxygen species (ROS) in cancer cells. The aim of the present study was to examine the effects of AF on cancer cell proliferation, cell cycle and apoptosis, either alone or in combination with cisplatin. AF induced cell death in two separate cell lines, HT 1376 and BFTC 909, in a concentration- and time-dependent manner by inducing cell cycle arrest. However, the distribution of cells in different phases of the cell cycle differed between the two cell lines, with G0/G1 cell cycle arrest in HT 1376 cells and S phase arrest in BFTC 909 cells. In addition, AF induced apoptosis in HT 1376, as well as redox imbalance in both HT 1376 and BFTC 909 cells. Cell viability was rescued following treatment with N-acetyl-L-cysteine, a ROS scavenger. Furthermore, AF treatment synergistically increased the cytotoxicity of HT 1376 and BFTC 909 cells when combined with cisplatin treatment. These findings suggest that AF may represent a potential candidate drug against UC and increase the therapeutic effect of cisplatin.

Decursin inhibits tumor progression in head and neck squamous cell carcinoma by downregulating CXCR7 expression in vitro

CXC chemokine receptor 7 (CXCR7) is frequently overexpressed in cancer and plays a significant role in tumor growth and metastasis. Consequently, inhibition of CXCR7 is important for treatment strategies. However, little is known concerning the biological role of CXCR7 and its underlying mechanisms in head and neck squamous cell carcinoma (HNSCC). The present study investigated the role of CXCR7 in HNSCC, as well as the effects of decursin, a pyranocoumarin compound isolated from Angelica gigas Nakai, on CXCR7 and its downstream signaling. Expression levels of CXCR7 in HNSCC cells were examined using flow cytometry, reverse transcriptase PCR, western blot analysis, and immunofluorescence. The effects of CXCR7 on cell proliferation, migration, and invasion were studied using CCK‑8, gap closure, and transwell assays. The results revealed that decursin significantly reduced CXCR7 expression and inhibited cell proliferation, migration, and invasion of human HNSCC cell lines. In addition, decursin induced G0/G1 cell cycle arrest in CXCR7‑overexpressing cells and decreased the levels of cyclin A, cyclin E, and CDK2. Furthermore, CXCR7 promoted cancer progression via the STAT3/c‑Myc pathway in HNSCC; suppression of CXCR7 with decursin prevented this effect. These results suggest that CXCR7 promotes cancer progression through the STAT3/c‑Myc pathway and that the natural compound decursin targets CXCR7 and may be valuable in the treatment of HNSCC.

Shift in G1-Checkpoint from ATM-Alone to a Cooperative ATM Plus ATR Regulation with Increasing Dose of Radiation

The current view of the involvement of PI3-kinases in checkpoint responses after DNA damage is that ATM is the key regulator of G₁-, S- or G₂-phase checkpoints, that ATR is only partly involved in the regulation of S- and G₂-phase checkpoints and that DNA-PKcs is not involved in checkpoint regulation. However, further analysis of the contributions of these kinases to checkpoint responses in cells exposed to ionizing radiation (IR) recently uncovered striking integrations and interplays among ATM, ATR and DNA-PKcs that adapt not only to the phase of the cell cycle in which cells are irradiated, but also to the load of DNA double-strand breaks (DSBs), presumably to optimize their processing. Specifically, we found that low IR doses in G₂-phase cells activate a G₂-checkpoint that is regulated by epistatically coupled ATM and ATR. Thus, inhibition of either kinase suppresses almost fully its activation. At high IR doses, the epistatic ATM/ATR coupling relaxes, yielding to a cooperative regulation. Thus, single-kinase inhibition suppresses partly, and only combined inhibition suppresses fully G₂-checkpoint activation. Interestingly, DNA-PKcs integrates with ATM/ATR in G₂-checkpoint control, but functions in its recovery in a dose-independent manner. Strikingly, irradiation during S-phase activates, independently of dose, an exclusively ATR-dependent G₂ checkpoint. Here, ATM couples with DNA-PKcs to regulate checkpoint recovery. In the present work, we extend these studies and investigate organization and functions of these PI3-kinases in the activation of the G₁ checkpoint in cells irradiated either in the G₀ or G₁ phase. We report that ATM is the sole regulator of the G₁ checkpoint after exposure to low IR doses. At high IR doses, ATM remains dominant, but contributions from ATR also become detectable and are associated with limited ATM/ATR-dependent end resection at DSBs. Under these conditions, only combined ATM + ATR inhibition fully abrogates checkpoint and resection. Contributions of DNA-PKcs and CHK2 to the regulation of the G₁ checkpoint are not obvious in these experiments and may be masked by the endpoint employed for checkpoint analysis and perturbations in normal progression through the cell cycle of cells exposed to DNA-PKcs inhibitors. The results broaden our understanding of organization throughout the cell cycle and adaptation with increasing IR dose of the ATM/ATR/DNA-PKcs module to regulate checkpoint responses. They emphasize notable similarities and distinct differences between G₁-, G₂- and S-phase checkpoint regulation that may guide DSB processing decisions.

Treading a HOSTile path: Mapping the dynamic landscape of host cell-rotavirus interactions to explore novel host-directed curative dimensions

Viruses are intracellular pathogens and are dependent on host cellular resources to carry out their cycles of perpetuation. Obtaining an integrative view of host-virus interaction is of utmost importance to understand the complex and dynamic interplay between viral components and host machineries. Besides its obvious scholarly significance, a comprehensive host-virus interaction profile also provides a platform where from host determinants of pro-viral and antiviral importance can be identified and further be subjected to therapeutic intervention. Therefore, adjunct to conventional methods of prophylactic vaccination and virus-directed antivirals, this host-targeted antiviral approach holds promising therapeutic potential. In this review, we present a comprehensive landscape of host cellular reprogramming in response to infection with rotavirus (RV) which causes profuse watery diarrhea in neonates and infants. In addition, an emphasis is given on how host determinants are either usurped or subverted by RV in course of infection and how therapeutic manipulation of specific host factors can effectively modulate the RV life cycle.

MicroRNAs and the DNA damage response: How is cell fate determined?

It is becoming clear that the DNA damage response orchestrates an appropriate response to a given level of DNA damage, whether that is cell cycle arrest and repair, senescence or apoptosis. It is plausible that the alternative regulation of the DNA damage response (DDR) plays a role in deciding cell fate following damage. MicroRNAs (miRNAs) are associated with the transcriptional regulation of many cellular processes. They have diverse functions, affecting, presumably, all aspects of cell biology. Many have been shown to be DNA damage inducible and it is conceivable that miRNA species play a role in deciding cell fate following DNA damage by regulating the expression and activation of key DDR proteins. From a clinical perspective, miRNAs are attractive targets to improve cancer patient outcomes to DNA-damaging chemotherapy. However, cancer tissue is known to be, or to become, well adapted to DNA damage as a means of inducing chemoresistance. This frequently results from an altered DDR, possibly owing to miRNA dysregulation. Though many studies provide an overview of miRNAs that are dysregulated within cancerous tissues, a tangible, functional association is often lacking. While miRNAs are well-documented in 'ectopic biology', the physiological significance of endogenous miRNAs in the context of the DDR requires clarification. This review discusses miRNAs of biological relevance and their role in DNA damage response by potentially 'fine-tuning' the DDR towards a particular cell fate in response to DNA damage. MiRNAs are thus potential therapeutic targets/strategies to limit chemoresistance, or improve chemotherapeutic efficacy.

Influence of the co-exposure of microplastics and tetrabromobisphenol A on human gut: Simulation in vitro with human cell Caco-2 and gut microbiota

Microplastics (MPs) pollution becomes an emergent threat to the ecosystem, and its joint effect with organic contaminants will cause more severe consequences. Recently, MPs has been observed in human feces, suggesting that we are exposed to an uncertain danger. In this study, the joint effect of polyethylene microplastics particles (PEMPs) and Tetrabromobisphenol A (TBBPA) on human gut was explored through the simulation experiment in vitro with human cell Caco-2 and gut microbiota. The toxicity of TBBPA and PEMPs on Caco-2 human cells was considered by physiological and biochemical indexes such as cell proliferation, cell cycle, reactive oxygen species, lactate dehydrogenase release, and mitochondrial membrane potential. Besides, microbial community diversity, community structure, and function changes of gut microbiota were investigated using Illumina 16S rRNA gene MiSeq sequencing to reveal the influence of TBBPA and PEMPs on human gut microbiota. The results indicated that both PEMPs and TBBPA would deteriorate the status of Caco-2 cells, and TBBPA played a major role in it; meanwhile, PEMPs affected Caco-2 cells at high concentrations. Particularly, TBBPA and PEMPs exhibited a joint effect on Caco-2 cells to a certain degree. TBBPA selectivity inhibited the growth of gram-positive bacteria such as Enterococcus and Lactobacillus, contributing to the thriving of gram-negative bacteria such as Escherichia and Bacteroides. The existence of PEMPs would enhance the proportion of Clostridium, Bacteroides, and Escherichia. Community composition changed dramatically with the interference of PEMPs and TBBPA; this was undesirable to the healthy homeostasis of the human gut. PICRUSt analysis determined both PEMPs and TBBPA interfered with the metabolism pathways of gut microbiota. Hence, the threat of MPs and TBBPA to humans should arouse vigilance.

DNA damage in embryonic neural stem cell determines FTLDs' fate via early-stage neuronal necrosis

The early-stage pathologies of frontotemporal lobal degeneration (FTLD) remain largely unknown. In VCP^T262A-KI mice carrying VCP gene mutation linked to FTLD, insufficient DNA damage repair in neural stem/progenitor cells (NSCs) activated DNA-PK and CDK1 that disabled MCM3 essential for the G1/S cell cycle transition. Abnormal neural exit produced neurons carrying over unrepaired DNA damage and induced early-stage transcriptional repression-induced atypical cell death (TRIAD) necrosis accompanied by the specific markers pSer46-MARCKS and YAP. In utero gene therapy expressing normal VCP or non-phosphorylated mutant MCM3 rescued DNA damage, neuronal necrosis, cognitive function, and TDP43 aggregation in adult neurons of VCP^T262A-KI mice, whereas similar therapy in adulthood was less effective. The similar early-stage neuronal necrosis was detected in PGRN^R504X-KI, CHMP2B^Q165X-KI, and TDP^N267S-KI mice, and blocked by embryonic treatment with AAV-non-phospho-MCM3. Moreover, YAP-dependent necrosis occurred in neurons of human FTLD patients, and consistently pSer46-MARCKS was increased in cerebrospinal fluid (CSF) and serum of these patients. Collectively, developmental stress followed by early-stage neuronal necrosis is a potential target for therapeutics and one of the earliest general biomarkers for FTLD.

Upregulation of Chemoresistance by Mg2+ Deficiency through Elevation of ATP Binding Cassette Subfamily B Member 1 Expression in Human Lung Adenocarcinoma A549 Cells

Several anticancer drugs including cisplatin (CDDP) induce hypomagnesemia. However, it remains fully uncertain whether Mg²⁺ deficiency affects chemosensitivity of cancer cells. Here, we investigated the effect of low Mg²⁺ concentration (LM) on proliferation and chemosensitivity using human lung adenocarcinoma A549 cells. Cell proliferation was reduced by continuous culture with LM accompanied with the elevation of G1 phase proportion. The amounts of reactive oxygen species (ROS) and stress makers such as phosphorylated-ataxia telangiectasia mutated and phosphorylated-p53 were increased by LM. Cell injury was dose-dependently increased by anticancer drugs such as CDDP and doxorubicin (DXR), which were suppressed by LM. Similar results were obtained by roscovitine, a cell cycle inhibitor. These results suggest that LM induces chemoresistance mediated by ROS production and G1 arrest. The mRNA and protein levels of ATP binding cassette subfamily B member 1 (ABCB1) were increased by LM and roscovitine. The LM-induced elevation of ABCB1 and nuclear p38 expression was suppressed by SB203580, a p38 MAPK inhibitor. PSC833, an ABCB1 inhibitor, and SB203580 rescued the sensitivity to anticancer drugs. In addition, cancer stemness properties were suppressed by SB203580. We suggest that Mg²⁺ deficiency reduces the chemotherapy sensitivity of A549 cells, although it suppresses cell proliferation.

G1-phase progression in pluripotent stem cells

During early embryonic development both the rapid increase in cell number and the expression of genes that control developmental decisions are tightly regulated. Accumulating evidence has indicated that these two seemingly independent processes are mechanistically intertwined. The picture that emerges from studies on the cell cycle of embryonic stem cells is one in which proteins that promote cell cycle progression prevent differentiation and vice versa. Here, we review which transcription factors and signalling pathways play a role in both maintenance of pluripotency as well as cell cycle progression. We will not only describe the mechanism behind their function but also discuss the role of these regulators in different states of mouse pluripotency. Finally, we elaborate on how canonical cell cycle regulators impact on the molecular networks that control the maintenance of pluripotency and lineage specification.

Expanding roles of cell cycle checkpoint inhibitors in radiation oncology

PURPOSE

Radiation-induced activation of cell cycle checkpoints have been of long-standing interest. The WEE1, CHK1 and ATR kinases are key factors in cell cycle checkpoint regulation and are essential for the S and G2 checkpoints. Here, we review the rationale for why inhibitors of WEE1, CHK1 and ATR could be beneficial in combination with radiation.

CONCLUSIONS

Combined treatment with radiation and inhibitors of these kinases results in checkpoint abrogation and subsequent mitotic catastrophe. This might selectively radiosensitize tumor cells, as they often lack the p53-dependent G1 checkpoint and therefore rely more on the G2 checkpoint to repair DNA damage. Further affecting the repair of radiation damage, inhibition of WEE1, CHK1 or ATR also specifically suppresses the homologous recombination repair pathway. Moreover, inhibition of these kinases can induce massive replication stress during S phase of the cell cycle, likely contributing to eliminate radioresistant S phase cells. Intriguingly, recent findings suggest that cell cycle checkpoint inhibitors in combination with radiation can also enhance anti-tumor immune effects. Altogether, the expanding knowledge about the functional roles of WEE1, CHK1 and ATR inhibitors support that they are promising candidates for use in combination with radiation treatment.

Combined Inactivation of Pocket Proteins and APC/CCdh1 by Cdk4/6 Controls Recovery from DNA Damage in G1 Phase

Most Cyclin-dependent kinases (Cdks) are redundant for normal cell division. Here we tested whether these redundancies are maintained during cell cycle recovery after a DNA damage-induced arrest in G1. Using non-transformed RPE-1 cells, we find that while Cdk4 and Cdk6 act redundantly during normal S-phase entry, they both become essential for S-phase entry after DNA damage in G1. We show that this is due to a greater overall dependency for Cdk4/6 activity, rather than to independent functions of either kinase. In addition, we show that inactivation of pocket proteins is sufficient to overcome the inhibitory effects of complete Cdk4/6 inhibition in otherwise unperturbed cells, but that this cannot revert the effects of Cdk4/6 inhibition in DNA damaged cultures. Indeed, we could confirm that, in addition to inactivation of pocket proteins, Cdh1-dependent anaphase-promoting complex/cyclosome (APC/C^Cdh1) activity needs to be inhibited to promote S-phase entry in damaged cultures. Collectively, our data indicate that DNA damage in G1 creates a unique situation where high levels of Cdk4/6 activity are required to inactivate pocket proteins and APC/C^Cdh1 to promote the transition from G1 to S phase.

Progress towards a clinically-successful ATR inhibitor for cancer therapy

The DNA damage response (DDR) is now known to play an important role in both cancer development and its treatment. Targeting proteins such as ATR (Ataxia telangiectasia mutated and Rad3-related) kinase, a major regulator of DDR, has demonstrated significant therapeutic potential in cancer treatment, with ATR inhibitors having shown anti-tumour activity not just as monotherapies, but also in potentiating the effects of conventional chemotherapy, radiotherapy, and immunotherapy. This review focuses on the biology of ATR, its functional role in cancer development and treatment, and the rationale behind inhibition of this target as a therapeutic approach, including evaluation of the progress and current status of development of potent and specific ATR inhibitors that have emerged in recent decades. The current applications of these inhibitors both in preclinical and clinical studies either as single agents or in combinations with chemotherapy, radiotherapy and immunotherapy are also extensively discussed. This review concludes with some insights into the various concerns raised or observed with ATR inhibition in both the preclinical and clinical settings, with some suggested solutions.

Genotoxic Effects of Cylindrospermopsin, Microcystin-LR and Their Binary Mixture in Human Hepatocellular Carcinoma (HepG2) Cell Line

Simultaneous occurrence of cylindrospermopsin (CYN) and microcystin-LR (MCLR) has been reported in the aquatic environment and thus human exposure to such mixtures is possible. As data on the combined effects of CYN/MCLR are scarce, we aimed to investigate the adverse effects related to genotoxic activities induced by CYN (0.125, 0.25 and 0.5 µg/mL) and MCLR (1 µg/mL) as single compounds and their combinations in HepG2 cells after 24 and 72 h exposure. CYN and CYN/MCLR induced DNA double-strand breaks after 72 h exposure, while cell cycle analysis revealed that CYN and CYN/MCLR arrested HepG2 cells in G0/G1 phase. Moreover, CYN and the combination with MCLR upregulated CYP1A1 and target genes involved in DNA-damage response (CDKN1A, GADD45A). Altogether, the results showed that after 72 h exposure genotoxic activity of CYN/MCLR mixture was comparable to the one of pure CYN. On the contrary, MCLR (1 µg/mL) had no effect on the viability of cells and had no influence on cell division. It did not induce DNA damage and did not deregulate studied genes after prolonged exposure. The outcomes of the study confirm the importance of investigating the combined effects of several toxins as the effects can differ from those induced by single compounds.

Characterization of In Vitro 3D Cell Model Developed from Human Hepatocellular Carcinoma (HepG2) Cell Line

In genetic toxicology, there is a trend against the increased use of in vivo models as highlighted by the 3R strategy, thus encouraging the development and implementation of alternative models. Two-dimensional (2D) hepatic cell models, which are generally used for studying the adverse effects of chemicals and consumer products, are prone to giving misleading results. On the other hand, newly developed hepatic three-dimensional (3D) cell models provide an attractive alternative, which, due to improved cell interactions and a higher level of liver-specific functions, including metabolic enzymes, reflect in vivo conditions more accurately. We developed an in vitro 3D cell model from the human hepatocellular carcinoma (HepG2) cell line. The spheroids were cultured under static conditions and characterised by monitoring their growth, morphology, and cell viability during the time of cultivation. A time-dependent suppression of cell division was observed. Cell cycle analysis showed time-dependent accumulation of cells in the G0/G1 phase. Moreover, time-dependent downregulation of proliferation markers was shown at the mRNA level. Genes encoding hepatic markers, metabolic phase I/II enzymes, were time-dependently deregulated compared to monolayers. New knowledge on the characteristics of the 3D cell model is of great importance for its further development and application in the safety assessment of chemicals, food products, and complex mixtures.

Rck of Salmonella Typhimurium Delays the Host Cell Cycle to Facilitate Bacterial Invasion

Salmonella Typhimurium expresses on its outer membrane the protein Rck which interacts with the epidermal growth factor receptor (EGFR) of the plasma membrane of the targeted host cells. This interaction activates signaling pathways, leading to the internalization of Salmonella. Since EGFR plays a key role in cell proliferation, we sought to determine the influence of Rck mediated infection on the host cell cycle. By analyzing the DNA content of uninfected and infected cells using flow cytometry, we showed that the Rck-mediated infection induced a delay in the S-phase (DNA replication phase) of the host cell cycle, independently of bacterial internalization. We also established that this Rck-dependent delay in cell cycle progression was accompanied by an increased level of host DNA double strand breaks and activation of the DNA damage response. Finally, we demonstrated that the S-phase environment facilitated Rck-mediated bacterial internalization. Consequently, our results suggest that Rck can be considered as a cyclomodulin with a genotoxic activity.

The Anti-tumor Effects of p-Coumaric Acid on Melanoma A375 and B16 Cells

Background: Existing research shows that p-coumaric acid (p-CA) can inhibit the proliferation of a variety of tumor cells in vitro. However, there are no reports on the anti-tumor effects of p-CA on melanoma cells. In this study, the inhibitory effects of p-CA on mouse melanoma B16 and human melanoma A375 cells are reported, and the related mechanisms are investigated. Methods: CCK-8 assay was used to detect the effects of p-CA on cell vitality, colony formation assay was used to observe the effects on cell proliferation, Hoechst 33,258 staining was used to observe the morphology of apoptotic cells, flow cytometry was used to detect the effects on apoptosis and the cell cycle, and western blot was used to measure the levels of cell cycle- and apoptosis-related signaling pathway proteins. Results: p-CA significantly inhibits cell proliferation of A375 and B16 cells in a dose-dependent manner and obviously induced cell morphological changes. p-CA arrested A375 cells in the S phase by downregulating the cell cycle-related proteins Cyclin A and CDK2, and arrested B16 cells in the G0-G1 phase through downregulating the cell cycle-related proteins Cyclin E and CDK2. In addition, p-CA significantly promoted apoptosis of A375 and B16 cells. Furthermore, p-CA significantly upregulated the levels of Apaf1 and Bax and downregulated the levels of Bcl-2, and subsequently increased the levels of cytoplasmic cytochrome c (Cyto-c), cleaved caspase-3, and cleaved caspase-9, leading to apoptosis in A375 and B16 cells. Conclusion: p-CA can significantly inhibit the proliferation of human and mouse melanoma cells in vitro. Our research is a step in the development of anti-melanoma drugs.

Application of advanced HepG2 3D cell model for studying genotoxic activity of cyanobacterial toxin cylindrospermopsin

Cylindrospermopsin (CYN) is an emerging cyanotoxin increasingly being found in freshwater cyanobacterial blooms worldwide. Humans and animals are exposed to CYN through the consumption of contaminated water and food as well as occupational and recreational water activities; therefore, it represents a potential health threat. It exhibits genotoxic effects in metabolically active test systems, thus it is considered as pro-genotoxic. In the present study, the advanced 3D cell model developed from human hepatocellular carcinoma (HepG2) cells was used for the evaluation of CYN cyto-/genotoxic activity. Spheroids were formed by forced floating method and were cultured for three days under static conditions prior to exposure to CYN (0.125, 0.25 and 0.5 μg/mL) for 72 h. CYN influence on spheroid growth was measured daily and cell survival was determined by MTS assay and live/dead staining. The influence on cell proliferation, cell cycle alterations and induction of DNA damage (γH2AX) was determined using flow cytometry. Further, the expression of selected genes (qPCR) involved in the metabolism of xenobiotics, proliferation, DNA damage response, apoptosis and oxidative stress was studied. Results revealed that CYN dose-dependently reduced the size of spheroids and affected cell division by arresting HepG2 cells in G1 phase of the cell cycle. No induction of DNA double strand breaks compared to control was determined at applied conditions. The analysis of gene expression revealed that CYN significantly deregulated genes encoding phase I (CYP1A1, CYP1A2, CYP3A4, ALDH3A) and II (NAT1, NAT2, SULT1B1, SULT1C2, UGT1A1, UGT2B7) enzymes as well as genes involved in cell proliferation (PCNA, TOP2α), apoptosis (BBC3) and DNA damage response (GADD45a, CDKN1A, ERCC4). The advanced 3D HepG2 cell model due to its more complex structure and improved cellular interactions provides more physiologically relevant information and more predictive data for human exposure, and can thus contribute to more reliable genotoxicity assessment of chemicals including cyanotoxins.

Epigallocatechin gallate induces chemopreventive effects on rats with diethylnitrosamine‑induced liver cancer via inhibition of cell division cycle 25A

Epigallocatechin gallate (EGCG), the most active monomer in green tea (GT), has demonstrated potential therapeutic and preventive effects on various tumors, including liver cancer. However, the anticancer mechanisms of EGCG in liver cancer remain to be elucidated. The abnormal expression of cell division cycle 25A (CDC25A) has been identified in liver cancer and is closely associated with malignancy and poor prognosis in patients with hepatocellular carcinoma (HCC). The present study used human hepatoma cell lines and rats with diethylnitrosamine (DEN)-induced HCC as models to investigate the association between the effect of EGCG on liver cancer and regulation of the p21waf1/Cip1/CDC25A axis. The results demonstrated that EGCG can inhibit the proliferation of HepG2 and Huh7 cells, reduce the expression of CDC25A and increase the expression of p21waf1/Cip1 in HepG2. In vivo, HCC was induced by DEN in Sprague-Dawley rats. EGCG significantly reduced tumor volume and improved the survival rates of rats with HCC. The expression levels of CDC25A mRNA and protein in liver tissues and the level of serum γ glutamyl transpeptidase in rats treated with EGCG were significantly decreased, while p21waf1/Cip1 mRNA and protein expression levels were increased compared with the HCC group, in the process of DEN-induced HCC. No significant difference in the chemopreventive effects on liver cancer was observed between GT extract and EGCG under an EGCG equivalence condition. Thus, EGCG can suppress human hepatoma cell proliferation and prolong the survival of rats with HCC, and the potential mechanism may be involved in EGCG-induced upregulation of p21waf1/Cip1 and downregulation of CDC25A.

T-2 toxin and its metabolites: Characterization, cytotoxic mechanisms and adaptive cellular response in human hepatocarcinoma (HepG2) cells

The T-2 toxin (T-2) is a type A trichothecene produced by Fusarium species, and the most cytotoxic mycotoxin of the group. A study was made to determine T-2 cytotoxicity in human hepatocarcinoma (HepG2) cells; evaluate whether there is an adaptive response of HepG2 cells exposed to low concentrations of T-2; identify the T-2 metabolites by LC-Q-TOF MS; and determine whether T-2 disrupts cell proliferation in HepG2 cells. The IC₅₀ values obtained ranged from 61.9 ± 2.4 nM to 70.7 ± 7.4 nM. No adaptive response was observed. There was no evidence of extra- or intracellular accumulation of T-2 after 24 h of exposure as determined by LC-Q-TOF MS. However, some T-2 metabolites such as HT-2 toxin, neosolaniol and T-2 triol showed important (>75%) intracellular accumulation. Cell distribution was significantly increased in SubG0/G1 phase (11.8-fold higher) and decreased (12%) in G2/M phase at 60 nM T-2, versus the control. Simultaneously, increased necrosis (238%) and apoptosis/necrosis (up to 35.5%) were observed in HepG2 cells exposed to T-2. In conclusion, the results show that T-2 leads to loss of cell viability without an adaptive response, and that the metabolites generated play an important role in T-2 cytotoxicity, increasing HepG2 cell damage.

Synthetic lethality strategies: Beyond BRCA1/2 mutations in pancreatic cancer

Cancer cells are often characterized by abnormalities in DNA damage response including defects in cell cycle checkpoints and/or DNA repair. Synthetic lethality between DNA damage repair (DDR) pathways has provided a paradigm for cancer therapy by targeting DDR. The successful example is that cancer cells with BRCA1/2 mutations are sensitized to poly(adenosine diphosphate [ADP]-ribose)polymerase (PARP) inhibitors. Beyond the narrow scope of defects in the BRCA pathway, "BRCAness" provides more opportunities for synthetic lethality strategy. In human pancreatic cancer, frequent mutations were found in cell cycle and DDR genes, including P16, P73, APC, MLH1, ATM, PALB2, and MGMT. Combined DDR inhibitors and chemotherapeutic agents are under preclinical or clinical trials. Promoter region methylation was found frequently in cell cycle and DDR genes. Epigenetics joins the Knudson's "hit" theory and "BRCAness." Aberrant epigenetic changes in cell cycle or DDR regulators may serve as a new avenue for synthetic lethality strategy in pancreatic cancer.

ANKHD1 is an S phase protein required for histone synthesis and DNA repair in multiple myeloma cells

ANKHD1 is highly expressed in various cancers such as leukemia and multiple myeloma. Silencing of ANKHD1 expression leads to decreased cell proliferation and accumulation of cells at the S phase. In this study we found ANKHD1 expression to be higher at the S phase, suggesting it to be an S phase protein. We observed that ANKHD1 interacts with histone promoter regions and its inhibition downregulates expression of all core histones, implying a role in histone synthesis. Since histone synthesis occurs in parallel with DNA replication at S phase, we evaluated PCNA (Proliferating Cell Nuclear Antigen) expression, a protein involved in DNA replication and repair. PCNA expression was found to be significantly decreased in ANKHD1 silenced cells. We further observed accumulation γH2AX, a marker for DNA double stranded breaks and an early sign of DNA damage induced by replication stress, upon ANKHD1 silencing. The expressions of several genes implicated in DNA repair were also modulated in ANKHD1 silenced cells, confirming the role of ANKHD1 in DNA repair. Based on this study we speculate that ANKHD1 is an S phase protein required for histone synthesis and DNA repair. These results however, are preliminary and require thorough investigation.

Hinokiflavone induces apoptosis via activating mitochondrial ROS/JNK/caspase pathway and inhibiting NF-κB activity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common malignancy with limited treatment options. Hinokiflavone (HF), a natural biflavonoid, has shown to inhibit the proliferation of melanoma, whereas its antitumour effect against HCC and the underlying mechanisms remain elusive. Here, we aimed at evaluating its antitumour effect against HCC in both in vitro and in vivo. Cell counting kit 8, colony formation assay, PI/RNase staining and Western blotting revealed that HF inhibited the proliferation of HCC cells via G0/G1 cell cycle arrest with p21/p53 up-regulation. DAPI staining, Annexin V-FITC/PI staining and Western blotting confirmed that HF triggered caspase-dependent apoptosis. Moreover, HF increased the levels of mitochondrial reactive oxygen species (mtROS) and activated c-Jun N-terminal kinase (JNK) pathway, as measured by MitoSOX Red staining and Western blotting. After respectively inhibiting mtROS (Mito-TEMPO) and JNK (SP600125), HF-induced apoptosis was reversed. Additionally, Western blotting documented that HF suppressed nuclear factor kappa B (NF-κB) activity and the anti-apoptotic genes downstream, contributing to cell apoptosis. Finally, in vivo studies demonstrated that HF significantly impaired tumour growth in HCC xenograft. Collectively, these findings suggested that HF induced apoptosis through activating mtROS/JNK/caspase pathway and inhibiting NF-κB signalling, which may represent a novel therapeutic agent for treating HCC.

The Host Cell ViroCheckpoint: Identification and Pharmacologic Targeting of Novel Mechanistic Determinants of Coronavirus-Mediated Hijacked Cell States

Most antiviral agents are designed to target virus-specific proteins and mechanisms rather than the host cell proteins that are critically dysregulated following virus-mediated reprogramming of the host cell transcriptional state. To overcome these limitations, we propose that elucidation and pharmacologic targeting of host cell Master Regulator proteins-whose aberrant activities govern the reprogramed state of coronavirus-infected cells-presents unique opportunities to develop novel mechanism-based therapeutic approaches to antiviral therapy, either as monotherapy or as a complement to established treatments. Specifically, we propose that a small module of host cell Master Regulator proteins (ViroCheckpoint) is hijacked by the virus to support its efficient replication and release. Conventional methodologies are not well suited to elucidate these potentially targetable proteins. By using the VIPER network-based algorithm, we successfully interrogated 12h, 24h, and 48h signatures from Calu-3 lung adenocarcinoma cells infected with SARS-CoV, to elucidate the time-dependent reprogramming of host cells and associated Master Regulator proteins. We used the NYS CLIA-certified Darwin OncoTreat algorithm, with an existing database of RNASeq profiles following cell perturbation with 133 FDA-approved and 195 late-stage experimental compounds, to identify drugs capable of virtually abrogating the virus-induced Master Regulator signature. This approach to drug prioritization and repurposing can be trivially extended to other viral pathogens, including SARS-CoV-2, as soon as the relevant infection signature becomes available.

miR-29b and retinoic acid co-delivery: a promising tool to induce a synergistic antitumoral effect in non-small cell lung cancer cells

The high incidence, late diagnosis, and aggressive profile of lung cancer limit the treatment options, causing a reduced survival rate. Consequently, RNAi-based therapy appears as a potential approach to treat non-small cell lung cancer (NSCLC). This approach is based on the delivery of small RNAs, involved in the regulation of key cell pathways, to treat complex diseases among others. Concerning that, the aim of this work was focused on the co-delivery of miR-29b and retinoic acid (RA) into NSCLC cells by multifunctional micellar nanosystems (Pluronic® P123 or Pluronic® P103 linked to polyethyleneimine (PEI)). The developed P103-PEI-RA/miR-29b (10/1) presented better results and most attractive properties, promoting efficient delivery of miR-29b, as well as revealing a significant antitumoral activity promoted by a synergistic effect between miR-29b expression and RA deliver. Furthermore, the developed therapeutic approach was able to significantly decrease cell viability and migration, as well as induce cell cycle arrest and epigenetic regulation in NSCLC cells. Thus, this work outcome enables to discover a hopeful system to deliver therapeutic miRNAs, crafting a novel RNAi-based therapy combined with RA to treat NSCLC. Graphical abstract.

Rotavirus activates a noncanonical ATM-Chk2 branch of DNA damage response during infection to positively regulate viroplasm dynamics

Surveillance for maintaining genomic pristineness, a protective safeguard of great onco-preventive significance, has been dedicated in eukaryotic cells to a highly conserved and synchronised signalling cascade called DNA damage response (DDR). Not surprisingly, foreign genetic elements like those of viruses are often potential targets of DDR. Viruses have evolved novel ways to subvert this genome vigilance by twisting canonical DDR to a skewed, noncanonical response through selective hijacking of some DDR components while antagonising the others. Though reported for many DNA and a few RNA viruses, potential implications of DDR have not been addressed yet in case of infection with rotavirus (RV), a double-stranded RNA virus. In the present study, we aimed at the modulation of ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 (Chk2) branch of DDR in response to RV infection in vitro. We found activation of the transducer kinase ATM and its downstream effector Chk2 in RV-SA11-infected cells, the activation response being maximal at 6-hr post infection. Moreover, ATM activation was found to be dependent on induction of the upstream sensor Mre11-Rad50-Nbs1 (MRN) complex. Interestingly, RV-SA11-mediated maximal induction of ATM-Chk2 pathway was revealed to be neither preceded by occurrence of nuclear DNA damage nor transduced to formation of damage-induced canonical nuclear foci. Subsequent investigations affirmed sequestration of MRN components as well as ATM-Chk2 proteins away from nucleus into cytosolic RV replication factories (viroplasms). Chemical intervention targeting ATM and Chk2 significantly inhibited fusion and maturation of viroplasms leading to attenuated viral propagation. Cumulatively, the current study describes RV-mediated activation of a noncanonical ATM-Chk2 branch of DDR skewed in favour of facilitated viroplasm fusion and productive viral perpetuation.

CDCA5 functions as a tumor promoter in bladder cancer by dysregulating mitochondria-mediated apoptosis, cell cycle regulation and PI3k/AKT/mTOR pathway activation

Bladder cancer (BC) is one of the most prevalent cancers worldwide and has high rates of relapse and progression. Cell division cycle associated 5 (CDCA5), a substrate of the anaphase-promoting complex, was reported to be upregulated in several types of cancer; however, the function of CDCA5 in BC remains unclear. In this study, we observed that BC tissues had higher levels of CDCA5 expression than adjacent normal tissues. We also found that high CDCA5 expression in patients was associated with poor survival rates. An in vitro study showed that knockdown of CDCA5 in T24 and 5637 cells reduced cell proliferation and induced apoptosis in T24 and 5637 cells, while overexpression of CDCA5 in UMUC3 cells caused the opposite effects. In an additional experiment, we found that CDCA5 promoted cell proliferation by upregulating two key cell cycle factors, cell division cycle protein 2 (CDC2) and cyclin B1, and by activating the PI3K/AKT/mTOR pathway. Furthermore, CDCA5 regulate cancer cell apoptosis through the mitochondrial apoptosis pathway. In conclusion, CDCA5 plays a pivotal role in the proliferation of BC cells. A better understanding of CDCA5 may provide new insights into its role as a therapeutic target for BC.

Targeting DNA repair in cancer: current state and novel approaches

DNA damage response, DNA repair and genomic instability have been under study for their role in tumor initiation and progression for many years now. More recently, next-generation sequencing on cancer tissue from various patient cohorts have revealed mutations and epigenetic silencing of various genes encoding proteins with roles in these processes. These findings, together with the unequivocal role of DNA repair in therapeutic response, have fueled efforts toward the clinical exploitation of research findings. The successful example of PARP1/2 inhibitors has also supported these efforts and led to numerous preclinical and clinical trials with a large number of small molecules targeting various components involved in DNA repair singularly or in combination with other therapies. In this review, we focus on recent considerations related to DNA damage response and new DNA repair inhibition agents. We then discuss how immunotherapy can collaborate with these new drugs and how epigenetic drugs can rewire the activity of repair pathways and sensitize cancer cells to DNA repair inhibition therapies.

Synergism Through WEE1 and CHK1 Inhibition in Acute Lymphoblastic Leukemia

Introduction: Screening for synthetic lethality markers has demonstrated that the inhibition of the cell cycle checkpoint kinases WEE1 together with CHK1 drastically affects stability of the cell cycle and induces cell death in rapidly proliferating cells. Exploiting this finding for a possible therapeutic approach has showed efficacy in various solid and hematologic tumors, though not specifically tested in acute lymphoblastic leukemia. Methods: The efficacy of the combination between WEE1 and CHK1 inhibitors in B and T cell precursor acute lymphoblastic leukemia (B/T-ALL) was evaluated in vitro and ex vivo studies. The efficacy of the therapeutic strategy was tested in terms of cytotoxicity, induction of apoptosis, and changes in cell cycle profile and protein expression using B/T-ALL cell lines. In addition, the efficacy of the drug combination was studied in primary B-ALL blasts using clonogenic assays. Results: This study reports, for the first time, the efficacy of the concomitant inhibition of CHK1/CHK2 and WEE1 in ALL cell lines and primary leukemic B-ALL cells using two selective inhibitors: PF-0047736 (CHK1/CHK2 inhibitor) and AZD-1775 (WEE1 inhibitor). We showed strong synergism in the reduction of cell viability, proliferation and induction of apoptosis. The efficacy of the combination was related to the induction of early S-phase arrest and to the induction of DNA damage, ultimately triggering cell death. We reported evidence that the efficacy of the combination treatment is independent from the activation of the p53-p21 pathway. Moreover, gene expression analysis on B-ALL primary samples showed that Chek1 and Wee1 are significantly co-expressed in samples at diagnosis (Pearson r = 0.5770, p = 0.0001) and relapse (Pearson r= 0.8919; p = 0.0001). Finally, the efficacy of the combination was confirmed by the reduction in clonogenic survival of primary leukemic B-ALL cells. Conclusion: Our findings suggest that the combination of CHK1 and WEE1 inhibitors may be a promising therapeutic strategy to be tested in clinical trials for adult ALL.