FOXO3 signalling links ATM to the p53 apoptotic pathway following DNA damage

Regulating obesity-induced osteoarthritis by targeting p53-FOXO3, osteoclast ferroptosis, and mesenchymal stem cell adipogenesis

Obesity-related osteoarthritis (OA) and the molecular mechanisms governing multiple joint structural changes that occur with obesity are not well understood. This study investigated the progression of obesity in mice and validated the results using human joint samples post-arthroplasty. The results show that obesity is associated with the degeneration of the cartilage layer and abnormal remodeling of the subchondral bone layer, and this occurs alongside aging and DNA damage in chondrocytes, osteoclasts, and stem cells. Regulation of p53-FOXO3 gene loop expression in response to DNA damage effectively inhibits chondrocyte apoptosis, catabolism, and excessive osteoclast differentiation, while the intra-articular delivery of a lentivirus expressing FOXO3 to mouse joints alleviates the progression of OA. The excessive differentiation of subchondral bone marrow osteoclasts is ferroptosis-dependent and driven by the senescence-associated secretory phenotype. The results have identified multiple potential targets for future research into the progression of obesity-related OA.

The dual missions of FoxO3a in inflammatory diseases: Regulation of antioxidant enzymes and involvement in programmed cell death

The transcription factor FoxO3a plays a crucial role in the process of cells adapting to various stress conditions. Multiple post - translational modifications and epigenetic mechanisms work together to precisely regulate the activity of FoxO3a, influencing its subcellular localization, stability, interactions with other proteins, DNA - binding affinity, and transcriptional regulatory capacity. Under different chemical signal stimuli and subcellular environments, the activation of FoxO3a triggered by oxidative stress can initiate diverse transcriptional programs, which are essential for the body to resist oxidative damage. In the development and progression of inflammatory diseases, FoxO3a exerts an important function by regulating the expression levels of antioxidant enzymes and participating in key physiological processes such as programmed cell death. This article comprehensively reviews the structural characteristics, mechanism of action of FoxO3a, as well as its functions in regulating antioxidant enzymes and programmed cell death. The aim is to deeply explore the potential of FoxO3a as a potential therapeutic target for preventing and treating damages such as inflammatory diseases caused by cellular stress.

Canonical and noncanonical NOTCH signaling in the nongenetic resistance of cancer: distinct and concerted control

Therapeutic resistance in cancer is responsible for numerous cancer deaths in clinical practice. While target mutations are well recognized as the basis of genetic resistance to targeted therapy, nontarget mutation resistance (or nongenetic resistance) remains poorly characterized. Despite its complex and unintegrated mechanisms in the literature, nongenetic resistance is considered from our perspective to be a collective response of innate or acquired resistant subpopulations in heterogeneous tumors to therapy. These subpopulations, e.g., cancer stem-like cells, cancer cells with epithelial-to-mesenchymal transition, and drug-tolerant persisters, are protected by their resistance traits at cellular and molecular levels. This review summarizes recent advances in the research on resistant populations and their resistance traits. NOTCH signaling, as a central regulator of nongenetic resistance, is discussed with a special focus on its canonical maintenance of resistant cancer cells and noncanonical regulation of their resistance traits. This novel view of canonical and noncanonical NOTCH signaling pathways is translated into our proposal of reshaping therapeutic strategies targeting NOTCH signaling in resistant cancer cells. We hope that this review will lead researchers to study the canonical and noncanonical arms of NOTCH signaling as an integrated resistant mechanism, thus promoting the development of innovative therapeutic strategies.

Elucidating the genotoxicity of Fusobacterium nucleatum-secreted mutagens in colorectal cancer carcinogenesis

BACKGROUND

Fusobacterium nucleatum (F. nucleatum) is one of the key tumorigenic bacteria in colorectal cancer (CRC), yet how F. nucleatum is involved in colorectal cancer carcinogenesis remains unknown.

RESULTS

In the present study, we carried out PathSeq analysis on RNA sequencing data from the 430 primary colon adenocarcinomas in TCGA database to assess the relationship between patients' survival and F. nucleatum abundance. Among patients with cecum and ascending colon tumors, we found that F. nucleatum transcriptome abundance is positively correlated with mutation load. We further demonstrated that patients with both high tumoral abundance of F. nucleatum and high mutation load exhibited poorer survival and DNA damage. We furthermore determined that F. nucleatum-conditioned medium (Fn. CM) induces DNA damage in both in vitro and in vivo studies. In addition, two F. nucleatum-secreted mutagens, namely DL-homocystine and allantoic acid, were identified to lead to DNA damage.

CONCLUSIONS

Our finding delineates the genotoxicity of F.nucleatum-secreted mutagens, which provides a basis for further work to investigate the role of F. nucleatum in the pathogenicity of CRC.

Role of Phytochemicals in Treatment of Aging and Cancer: Focus on Mechanism of FOXO3 Activation

There have been many studies reporting that the regular consumption of fruits and vegetables is associated with reduced risks of cancer and age-related chronic diseases. Recent studies have demonstrated that reducing reactive oxygen species and inflammation by phytochemicals derived from natural sources can extend lifespans in a range of model organisms. Phytochemicals derived from fruits and vegetables have been known to display both preventative and suppressive activities against various types of cancer via in vitro and in vivo research by interfering with cellular processes critical for tumor development. The current challenge lies in creating tailored supplements containing specific phytochemicals for individual needs. Achieving this goal requires a deeper understanding of the molecular mechanisms through which phytochemicals affect human health. In this review, we examine recently (from 2010 to 2024) reported plant extracts and phytochemicals with established anti-aging and anti-cancer effects via the activation of FOXO3 transcriptional factor. Additionally, we provide an overview of the cellular and molecular mechanisms by which these molecules exert their anti-aging and anti-cancer effects in specific model systems. Lastly, we discuss the limitations of the current research approach and outline for potential future directions in this field.

The potential role of circular RNAs in regulating p53 in different types of cancers

P53 tumor suppressor is a major regulator of various cellular processes and functions. It has been reported that mutation or inactivation of p53 plays a crucial role in tumorigenesis in different types of cancers. Circular RNAs (circRNAs) are single-stranded non-coding RNAs that have significant post-transcriptional effects on the regulation of gene expression in various ways. These molecules can alter the expression and function of multiple genes and proteins. In the present study, we aimed to review circRNAs that regulate the expression, function, and stability of p53 and the possible interactions between these molecules and p53. Considering the importance of p53 in cancer and the network between p53 and circRNAs, future clinical trials targeting these circRNAs as therapeutic agents deserve worthy of attention.

Chromatin Profiles Are Prognostic of Clinical Response to Bortezomib-Containing Chemotherapy in Pediatric Acute Myeloid Leukemia: Results from the COG AAML1031 Trial

The addition of the proteasome inhibitor bortezomib to standard chemotherapy did not improve survival in pediatric acute myeloid leukemia (AML) when all patients were analyzed as a group in the Children's Oncology Group phase 3 trial AAML1031 (NCT01371981). Proteasome inhibition influences the chromatin landscape and proteostasis, and we hypothesized that baseline proteomic analysis of histone- and chromatin-modifying enzymes (HMEs) would identify AML subgroups that benefitted from bortezomib addition. A proteomic profile of 483 patients treated with AAML1031 chemotherapy was generated using a reverse-phase protein array. A relatively high expression of 16 HME was associated with lower EFS and higher 3-year relapse risk after AML standard treatment compared to low expressions (52% vs. 29%, p = 0.005). The high-HME profile correlated with more transposase-accessible chromatin, as demonstrated via ATAC-sequencing, and the bortezomib addition improved the 3-year overall survival compared with standard therapy (62% vs. 75%, p = 0.033). These data suggest that there are pediatric AML populations that respond well to bortezomib-containing chemotherapy.

Linking Gene Fusions to Bone Marrow Failure and Malignant Transformation in Dyskeratosis Congenita

Dyskeratosis Congenita (DC) is a multisystem disorder intrinsically associated with telomere dysfunction, leading to bone marrow failure (BMF). Although the pathology of DC is largely driven by mutations in telomere-associated genes, the implications of gene fusions, which emerge due to telomere-induced genomic instability, remain unexplored. We meticulously analyzed gene fusions in RNA-Seq data from DC patients to provide deeper insights into DC's progression. The most significant DC-specific gene fusions were subsequently put through in silico assessments to ascertain biophysical and structural attributes, including charge patterning, inherent disorder, and propensity for self-association. Selected candidates were then analyzed using deep learning-powered structural predictions and molecular dynamics simulations to gauge their potential for forming higher-order oligomers. Our exploration revealed that genes participating in fusion events play crucial roles in upholding genomic stability, facilitating hematopoiesis, and suppressing tumors. Notably, our analysis spotlighted a particularly disordered polyampholyte fusion protein that exhibits robust higher-order oligomerization dynamics. To conclude, this research underscores the potential significance of several high-confidence gene fusions in the progression of BMF in DC, particularly through the dysregulation of genomic stability, hematopoiesis, and tumor suppression. Additionally, we propose that these fusion proteins might hold a detrimental role, specifically in inducing proteotoxicity-driven hematopoietic disruptions.

Comparative miRNA expression profile analysis of porcine ovarian follicles: new insights into the initiation mechanism of follicular atresia

Follicular atresia occurs in every stage of ovarian development, which is relevant to female fertility. In the past decade, increasing studies have confirmed that miRNAs, a class of short non-coding RNAs, play an important role in follicular atresia by post-transcription regulation of their target genes. However, the function of miRNAs on follicular atresia initiation is unknown. In the present study, high-throughput small RNA sequencing was performed to analyze differential miRNA expression profiles between healthy (HF) follicles and early atretic (EAF) follicles. A total of 237 conserved miRNA were detected, and the miR-143 is the highest expressed in follicles. Meanwhile, we also found wide sequence variations (isomiRs) in porcine ovarian miRNA, including in 5'un-translation region, core seed sequences and 3'untranslation region. Furthermore, we identified 22 differentially expressed miRNAs in EAF groups compared to HF group, of which 3 miRNAs were upregulated, as well as 19 miRNAs were downregulated, and then the RT-PCR was performed to validate these profiles. The target genes of these differentially expressed miRNAs were predicted by using miRwalk, miRDB, and Targetscan database, respectively. Moreover, the gene ontology and KEGG pathway enrichment established that the regulating functions and signaling pathways of these miRNAs contribute to follicular atresia initiation and cell fate. In conclusion, this study provides new insights into the changes of miRNAs in early atretic follicles to demonstrate their molecular regulation in ovarian follicular atretic initiation.

Design, synthesis and bioactivity investigation of peptide-camptothecin conjugates as anticancer agents with a potential to overcome drug resistance

Camptothecin (CPT) is a natural plant alkaloid from Camptotheca that exhibits a potent anticancer activity. However, its continued utilization is hindered by drawbacks such as low water solubility and restricted tumor selectivity. Cationic anticancer peptides (CAPs) are generally soluble in water, and exhibit favorable selectivity against malignant cells. In previous study, we have reported a CAP termed KM8-Aib present conspicuous selective anticancer effect. Thus, it is postulated conjugating KM8-Aib with CPT might be a plausible approach to improve the defects of CPT. A series of peptide-CPT conjugates were synthesized and subjected to biological evaluation. Among these compounds, Kb-CC07 displayed the highest selective activity against a set of cancer cell lines including drug-resistant cells, showing the IC50 values in the 0.11-1.01 μM range which is 1.9-22.6 times better than that of CPT, and a wide therapeutic index of 124.5 (vs 5.3 for CPT). The water solubility of Kb-CC07 was also improved by ∼ 100 fold compared with CPT. Further investigation unraveled that Kb-CC07 could effectively penetrate across plasma membranes and delivered more CPT molecules into cancer cells, overcoming the drug-resistance result from efflux drug transporters on tumor surface. In vivo experiments supported that Kb-CC07 has excellent in vivo antiproliferative activity against drug-resistant tumors over CPT (tumor growth inhibition of 98.2% and 37.5% for Kb-CC07 and CPT, respectively, at 5 μmol·kg-1), and prompts CPT accumulation in tumor tissue rather than normal organs, thus producing limited toxicities. To sum up, coupling therapeutic agents to CAPs would be a potential strategy to conquer the shortcomings of anticancer drugs. Additionally, Kb-CC07 is suggested to be a promising anticancer candidate deserving further investigation.

AMPK/FOXO3a Pathway Increases Activity and/or Expression of ATM, DNA-PKcs, Src, EGFR, PDK1, and SOD2 and Induces Radioresistance under Nutrient Starvation

Most solid tumors contain hypoxic and nutrient-deprived microenvironments. The cancer cells in these microenvironments have been reported to exhibit radioresistance. We have previously reported that nutrient starvation increases the expression and/or activity of ATM and DNA-PKcs, which are involved in the repair of DNA double-strand breaks induced by ionizing radiation. In the present study, to elucidate the molecular mechanisms underlying these phenomena, we investigated the roles of AMPK and FOXO3a, which play key roles in the cellular response to nutrient starvation. Nutrient starvation increased clonogenic cell survival after irradiation and increased the activity and/or expression of AMPKα, FOXO3a, ATM, DNA-PKcs, Src, EGFR, PDK1, and SOD2 in MDA-MB-231 cells. Knockdown of AMPKα using siRNA suppressed the activity and/or expression of FOXO3a, ATM, DNA-PKcs, Src, EGFR, PDK1, and SOD2 under nutrient starvation. Knockdown of FOXO3a using siRNA suppressed the activity and/or expression of AMPKα, ATM, DNA-PKcs, FOXO3a, Src, EGFR, PDK1, and SOD2 under nutrient starvation. Nutrient starvation decreased the incidence of apoptosis after 8 Gy irradiation. Knockdown of FOXO3a increased the incidence of apoptosis after irradiation under nutrient starvation. AMPK and FOXO3a appear to be key molecules that induce radioresistance under nutrient starvation and may serve as targets for radiosensitization.

DNA Damage Response Mechanisms in Head and Neck Cancer: Significant Implications for Therapy and Survival

Head and neck cancer (HNC) is a term collectively used to describe a heterogeneous group of tumors that arise in the oral cavity, larynx, nasopharynx, oropharynx, and hypopharynx, and represents the sixth most common type of malignancy worldwide. Despite advances in multimodality treatment, the disease has a recurrence rate of around 50%, and the prognosis of metastatic patients remains poor. HNCs are characterized by a high degree of genomic instability, which involves a vicious circle of accumulating DNA damage, defective DNA damage repair (DDR), and replication stress. Nonetheless, the damage that is induced on tumor cells by chemo and radiotherapy relies on defective DDR processes for a successful response to treatment, and may play an important role in the development of novel and more effective therapies. This review summarizes the current knowledge on the genes and proteins that appear to be deregulated in DDR pathways, their implication in HNC pathogenesis, and the rationale behind targeting these genes and pathways for the development of new therapies. We give particular emphasis on the therapeutic targets that have shown promising results at the pre-clinical stage and on those that have so far been associated with a therapeutic advantage in the clinical setting.

FoxO3 Regulates the Progress and Development of Aging and Aging-Related Diseases

Aging is an inevitable risk factor for many diseases, including cardiovascular diseases, neurodegenerative diseases, cancer, and diabetes. Investigation into the molecular mechanisms involved in aging and longevity will benefit the treatment of age-dependent diseases and the development of preventative medicine for agingrelated diseases. Current evidence has revealed that FoxO3, encoding the transcription factor (FoxO)3, a key transcription factor that integrates different stimuli in the intrinsic and extrinsic pathways and is involved in cell differentiation, protein homeostasis, stress resistance and stem cell status, plays a regulatory role in longevity and in age-related diseases. However, the precise mechanisms by which the FoxO3 transcription factor modulates aging and promotes longevity have been unclear until now. Here, we provide a brief overview of the mechanisms by which FoxO3 mediates signaling in pathways involved in aging and aging-related diseases, as well as the current knowledge on the role of the FoxO3 transcription factor in the human lifespan and its clinical prospects. Ultimately, we conclude that FoxO3 signaling pathways, including upstream and downstream molecules, may be underlying therapeutic targets in aging and age-related diseases.

Deletion of SIRT6 in vascular smooth muscle cells facilitates vascular calcification via suppression of DNA damage repair

Vascular calcification is an important risk factor for cardiovascular events, accompanied by DNA damage during the process. The sirtuin 6 (SIRT6) has been reported to alleviate atherosclerosis, which is related to the reduction of DNA damage. However, whether smooth muscle cell SIRT6 mediates vascular calcification involving DNA damage remains unclear. Western blot and immunofluorescence revealed that SIRT6 expression was decreased in human vascular smooth muscle cells (HVSMCs), human and mouse arteries during vascular calcification. Alizarin red staining and calcium content assay showed that knockdown or deletion of SIRT6 significantly promoted HVSMC calcification induced by high phosphorus and calcium, accompanied by upregulation of osteogenic differentiation markers including Runx2 and BMP2. By contrast, adenovirus-mediated SIRT6 overexpression attenuated osteogenic differentiation and calcification of HVSMCs. Moreover, ex vivo study revealed that SIRT6 overexpression inhibited calcification of mouse and human arterial rings. Of note, smooth muscle cell-specific knockout of SIRT6 markedly aggravated Vitamin D₃-induced aortic calcification in mice. Mechanistically, overexpression of SIRT6 reduced DNA damage and upregulated p-ATM during HVSMCs calcification, whereas knockdown of SIRT6 showed the opposite effects. Knockdown of ATM in HVSMCs abrogated the inhibitory effect of SIRT6 overexpression on calcification and DNA damage. This study for the first time demonstrates that vascular smooth muscle cell-specific deletion of SIRT6 facilitates vascular calcification via suppression of DNA damage repair. Therefore, modulation of SIRT6 and DNA damage repair may represent a therapeutic strategy for vascular calcification.

Transcription-associated DNA DSBs activate p53 during hiPSC-based neurogenesis

Neurons are overproduced during cerebral cortical development. Neural progenitor cells (NPCs) divide rapidly and incur frequent DNA double-strand breaks (DSBs) throughout cortical neurogenesis. Although half of the neurons born during neurodevelopment die, many neurons with inaccurate DNA repair survive leading to brain somatic mosaicism. Recurrent DNA DSBs during neurodevelopment are associated with both gene expression level and gene length. We used imaging flow cytometry and a genome-wide DNA DSB capture approach to quantify and map DNA DSBs during human induced pluripotent stem cell (hiPSC)-based neurogenesis. Reduced p53 signaling was brought about by knockdown (p53KD); p53KD led to elevated DNA DSB burden in neurons that was associated with gene expression level but not gene length in neural progenitor cells (NPCs). Furthermore, DNA DSBs incurred from transcriptional, but not replicative, stress lead to p53 activation in neurotypical NPCs. In p53KD NPCs, DNA DSBs accumulate at transcription start sites of genes that are associated with neurological and psychiatric disorders. These findings add to a growing understanding of how neuronal genome dynamics are engaged by high transcriptional or replicative burden during neurodevelopment.

A p53-phosphoinositide signalosome regulates nuclear AKT activation

The tumour suppressor p53 and PI3K-AKT pathways have fundamental roles in the regulation of cell growth and apoptosis, and are frequently mutated in cancer. Here, we show that genotoxic stress induces nuclear AKT activation through a p53-dependent mechanism that is distinct from the canonical membrane-localized PI3K-AKT pathway. Following genotoxic stress, a nuclear PI3K binds p53 in the non-membranous nucleoplasm to generate a complex of p53 and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), which recruits AKT, PDK1 and mTORC2 to activate AKT and phosphorylate FOXO proteins, thereby inhibiting DNA damage-induced apoptosis. Wild-type p53 activates nuclear AKT in an on/off fashion following stress, whereas mutant p53 dose-dependently stimulates high basal AKT activity. The p53-PtdIns(3,4,5)P3 complex is dephosphorylated to p53-phosphatidylinositol 4,5-bisphosphate by PTEN to inhibit AKT activation. The nuclear p53-phosphoinositide signalosome is distinct from the canonical membrane-localized pathway and insensitive to PI3K inhibitors currently in the clinic, which underscores its therapeutic relevance.

Icaritin inhibits PLK1 to activate DNA damage response in NK/T cell lymphoma and increases sensitivity to GELOX regime

Natural killer/T cell lymphoma (NKTCL) is a highly aggressive subtype of non-Hodgkin lymphoma. Gemcitabine, oxaliplatin, and L-asparaginase (GELOX) is one of the first-line chemotherapy regimens of NKTCL. Yet, the prognosis of NKTCL is poor. Icaritin is an herb-derived monomer from icariin with antitumor effects. We found that icaritin induced proliferation inhibition and apoptosis of NKTCL both in vitro and in vivo. Moreover, icaritin inhibited the dissemination of NKTCL in vivo. RNA sequencing revealed the Polo-like kinase 1 (PLK1) gene and DNA damage response (DDR) as the targets of icaritin. Mechanistically, icaritin inhibited PLK1 to promote checkpoint kinase 2 (Chk2) homodimerization and its T387 phosphorylation, which further activated p53, leading to the activation of the DDR pathway. Moreover, inhibiting PLK1 increased Forkhead box O3a nuclear localization, the latter of which activated ataxia telangiectasia mutated (ATM), an early sensor of DNA damage. Then ATM phosphorylated Chk2 T68 and initiated Chk2 activation. Remarkably, the combined treatment of icaritin and GELOX achieved better antitumor efficacy than single treatment in vivo. In summary, our results proved the efficacy of icaritin treating NKTCL, provided insights into its antitumor molecular mechanism, and revealed the application value of icaritin in facilitating clinical NKTCL treatment.

FOXO3-dependent suppression of PD-L1 promotes anticancer immune responses via activation of natural killer cells

Boosting anticancer immunity by blocking immune checkpoints such as the programmed death-1 (PD-1) or its ligand (PD-L1) is a breakthrough anticancer therapy. However, many cancer patients do not respond well to immune checkpoint blockades (ICBs) alone. Here we show that low-dose pharmacological immunoactivators (e.g., SN38, topotecan, sorafenib, etc.) notably downregulate PD-L1 and upregulate FOXO3 expression in various human and murine cancer cell lines. In a mouse tumor model, low-dose SN38 treatment markedly suppresses tumor growth, reduces PD-L1 expression, and enhances FOXO3 expression in primary tumor specimens. SN38 therapy engages the tumor-infiltrating mouse NK1.1/CD49b/NKG2D-positive natural killer (NK) cells to attack tumor cells by inducing mouse IFN-γ and granzyme-B secretion in the tumor microenvironment (TME) in vivo. SN38 treatment also promotes tumor cell apoptosis in the TME. SN38 treatment significantly decreases STAT3-pY705 and IL-6 protein levels; FOXO3 is essential for SN38-mediated PD-L1 downregulation. Collectively, these findings may contribute to future translational or clinical investigations tackling difficult-to-treat cancers with immune-activating medicines or combined with ICB immunotherapy.

Broussochalcone A Induces Apoptosis in Human Renal Cancer Cells via ROS Level Elevation and Activation of FOXO3 Signaling Pathway

Broussochalcone A (BCA) is a chalcone compound extracted from the cortex of Broussonetiapapyrifera (L.) Ventenat that exerts various effects, such as potent antioxidant, antiplatelet, and anticancer effects. However, the effects of BCA against cancers have been seldom studied. This study is aimed at demonstrating the apoptotic mechanisms of BCA in A498 and ACHN cells, which are two types of human renal cancer cell lines. MTT, cell counting, and colony formation assays indicated that BCA treatment inhibited cell viability and cell growth. Further, cell cycle analysis revealed that BCA induced cell cycle arrest at the G2/M phase. Annexin V/PI staining and TUNEL assays were performed to determine the apoptotic effects and DNA fragmentation after treatment with BCA. Based on western blot analysis, BCA induced the upregulation of cleaved PARP, FOXO3, Bax, p21, p27, p53, phosphorylated p53 (ser15, ser20, and ser46), and active forms of caspase-3, caspase-7, and caspase-9 proteins, but downregulated the proforms of the proteins. The expression levels of pAkt, Bcl-2, and Bcl-xL were also found to be downregulated. Western blot analysis of nuclear fractionation results revealed that BCA induced the nuclear translocation of FOXO3, which might be induced by DNA damage owing to the accumulation of reactive oxygen species (ROS). Elevated intracellular ROS levels were also found following BCA treatment. Furthermore, DNA damage was detected after BCA treatment using a comet assay. The purpose of this study was to elucidate the apoptotic effects of BCA against renal cancer A498 and ACHN cells. Collectively, our study findings revealed that the apoptotic effects of BCA against human renal cancer cells occur via the elevation of ROS level and activation of the FOXO3 signaling pathway.

Sensors and Inhibitors for the Detection of Ataxia Telangiectasia Mutated (ATM) Protein Kinase

Recruitment and activation of the ataxia telangiectasia mutated (ATM) kinase regulate multiple cell-cycle checkpoints relevant to complex biological events like DNA damage repair and apoptosis. Molecularly specific readouts of ATM using protein assays, fluorescence, or radiolabeling have advanced significantly over the past few years. This Review covers the molecular imaging techniques that enable the visualization of ATM-from traditional quantitative protein assays to the potential use of ATM inhibitors to generate new imaging agents to interrogate ATM. We are confident that molecular imaging coupled with advanced technologies will play a pivotal role in visualizing and understanding the biology of ATM and accelerate its applications in the diagnosis and monitoring of disease, including radiation therapy and patient stratification.

Podocyte apoptosis in diabetic nephropathy by BASP1 activation of the p53 pathway via WT1

AIMS

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. BASP1 (brain acid-soluble protein) is up-regulated in podocyte-specific protein phosphatase 2A knockout mice (Pod-PP2A-KO) that develop kidney dysfunction. Here, we explore the role of BASP1 for podocytes in DN.

METHODS

BASP1 was assessed in kidneys from DN patients and DN mouse models, podocyte specific BASP1 knockout mice (Pod-BASP1-KO mice) were generated and studied in vivo. Furthermore, podocyte injury and apoptosis were measured after BASP1 knockdown and overexpression in a mouse podocyte cell line (MPC5). Potential signalling pathways involved in podocyte apoptosis were detected.

RESULTS

BASP1 expression was up-regulated in DN patients compared to normal controls. BASP1 specific deletion in podocytes protected against podocyte injury by reducing the loss of expression of slit diaphragm molecules and foot process effacement in the DN model. BASP1 promoted actin cytoskeleton rearrangements and apoptosis in the MPC5 podocyte line. Molecules involved in the p53 pathway were down-regulated in BASP1 knockdown podocytes treated with high glucose compared to controls. BASP1 promoted podocyte apoptosis and P53 pathway activation through co-repression with Wilms' tumour 1 transcription factor (WT1).

CONCLUSION

BASP1 activates the p53 pathway through modulation of WT1 to induce podocyte apoptosis in diabetic nephropathy.

Acetylshikonin Induces Apoptosis in Human Colorectal Cancer HCT-15 and LoVo Cells via Nuclear Translocation of FOXO3 and ROS Level Elevation

Acetylshikonin, a naphthoquinone, is a pigment compound derived from Arnebia sp., which is known for its anti-inflammatory potential. However, its anticarcinogenic effect has not been well investigated. Thus, in this study, we focused on investigating its apoptotic effects against HCT-15 and LoVo cells, which are human colorectal cancer cells. MTT assay, cell counting assay, and colony formation assay have shown acetylshikonin treatment induced cytotoxic and antiproliferative effects against colorectal cancer cells in a dose- and time-dependent manner. DNA fragmentation was observed via terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Also, the increase of subG1 phase in cell cycle arrest assay and early/late apoptotic rates in annexin V/propidium iodide (PI) double staining assay was observed, which indicates an apoptotic potential of acetylshikonin against colorectal cancer cells. 2′,7′-Dichlorofluorescin diacetate (DCF-DA) staining was used to evaluate reactive oxygen species (ROS) generation in acetylshikonin-treated colorectal cancer cells. Fluorescence-activated cell sorting (FACS) analysis showed that acetylshikonin induced an increase in reactive oxygen species (ROS) levels and apoptotic rate in a dose- and time-dependent manner in HCT-15 and LoVo cells. In contrast, cotreatment with N-acetyl cysteine (NAC) has reduced ROS generation and antiproliferative effects in colorectal cancer cells. Western blotting analysis showed that acetylshikonin treatment induced increase of cleaved PARP, γH2AX, FOXO3, Bax, Bim, Bad, p21, p27, and active forms of caspase-3, caspase-7, caspase-9, caspase-6, and caspase-8 protein levels, while those of inactive forms were decreased. Also, the expressions of pAkt, Bcl-2, Bcl-xL, peroxiredoxin, and thioredoxin 1 were decreased. Furthermore, western blotting analysis of cytoplasmic and nuclear fractionated proteins showed that acetylshikonin treatment induced the nuclear translocation of FOXO3, which might result from DNA damage by the increased intracellular ROS level. This study represents apoptotic potential of acetylshikonin against colorectal cancer cells via translocation of FOXO3 to the nucleus and upregulation of ROS generation.

Role of FOXO protein's abnormal activation through PI3K/AKT pathway in platinum resistance of ovarian cancer

AIM

Platinum-based chemotherapy is the standard treatment for ovarian cancer. However, tumor cells' resistance to platinum drugs often occurs. This paper provides a review of Forkhead box O (FOXO) protein's role in platinum resistance of ovarian cancer which hopefully may provide some further guidance for the treatment of platinum-resistant ovarian cancer.

METHODS

We reviewed a 128 published papers from authoritative and professional journals on FOXO and platinum-resistant ovarian cancer, and adopts qualitative analyses and interpretation based on the literature.

RESULTS

Ovarian cancer often has abnormal activation of cellular pathways, the most important of which is the PI3K/AKT pathway. FOXOs act as crucial downstream factor of the PI3K/Akt pathway and are negatively regulated by it. DNA damage response and apoptosis including the relationship between FOXOs and ATM-Chk2-p53 are essential for platinum resistance of ovarian cancer. Through gene expression analysis in platinum-resistant ovarian cancer cell model, it was found that FoxO-1 is decreased in platinum-resistant ovarian cancer, so studying the role of FOXO in the pathway on platinum-induced apoptosis may further guide the treatment of platinum-resistant ovarian cancer.

CONCLUSIONS

There are many drug resistance mechanisms in ovarian cancer, wherein the decrease in cancer cells apoptosis is one of the important causes. Constituted by a series of transcription factors evolving conservatively and mainly working in inhibiting cancer, FOXO proteins play various roles in cells' antitumor response. More and more evidence suggests that we need to re-understand the role that FOXOs have played in cancer development and treatment.

A FOXO-dependent replication checkpoint restricts proliferation of damaged cells

DNA replication is challenged by numerous exogenous and endogenous factors that can interfere with the progression of replication forks. Substantial accumulation of single-stranded DNA during DNA replication activates the DNA replication stress checkpoint response that slows progression from S/G2 to M phase to protect genomic integrity. Whether and how mild replication stress restricts proliferation remains controversial. Here, we identify a cell cycle exit mechanism that prevents S/G2 phase arrested cells from undergoing mitosis after exposure to mild replication stress through premature activation of the anaphase promoting complex/cyclosome (APC/C^CDH1). We find that replication stress causes a gradual decrease of the levels of the APC/C^CDH1 inhibitor EMI1/FBXO5 through Forkhead box O (FOXO)-mediated inhibition of its transcription factor E2F1. By doing so, FOXOs limit the time during which the replication stress checkpoint is reversible and thereby play an important role in maintaining genomic stability.

FOXO3a acts to suppress DNA double-strand break-induced mutations

Genomic instability is one of the hallmarks of aging, and both DNA damage and mutations have been found to accumulate with age in different species. Certain gene families, such as sirtuins and the FoxO family of transcription factors, have been shown to play a role in lifespan extension. However, the mechanism(s) underlying the increased longevity associated with these genes remains largely unknown and may involve the regulation of responses to cellular stressors, such as DNA damage. Here, we report that FOXO3a reduces genomic instability in cultured mouse embryonic fibroblasts (MEFs) treated with agents that induce DNA double-strand breaks (DSBs), that is, clastogens. We show that DSB treatment of both primary human and mouse fibroblasts upregulates FOXO3a expression. FOXO3a ablation in MEFs harboring the mutational reporter gene lacZ resulted in an increase in genome rearrangements after bleomycin treatment; conversely, overexpression of human FOXO3a was found to suppress mutation accumulation in response to bleomycin. We also show that overexpression of FOXO3a in human primary fibroblasts decreases DSB-induced γH2AX foci. Knocking out FOXO3a in mES cells increased the frequency of homologous recombination and non-homologous end-joining events. These results provide the first direct evidence that FOXO3a plays a role in suppressing genome instability, possibly by suppressing genome rearrangements.

Zebrafish rbm8a and magoh mutants reveal EJC developmental functions and new 3'UTR intron-containing NMD targets

Many post-transcriptional mechanisms operate via mRNA 3'UTRs to regulate protein expression, and such controls are crucial for development. We show that homozygous mutations in two zebrafish exon junction complex (EJC) core genes rbm8a and magoh leads to muscle disorganization, neural cell death, and motor neuron outgrowth defects, as well as dysregulation of mRNAs subjected to nonsense-mediated mRNA decay (NMD) due to translation termination ≥ 50 nts upstream of the last exon-exon junction. Intriguingly, we find that EJC-dependent NMD also regulates a subset of transcripts that contain 3'UTR introns (3'UI) < 50 nts downstream of a stop codon. Some transcripts containing such stop codon-proximal 3'UI are also NMD-sensitive in cultured human cells and mouse embryonic stem cells. We identify 167 genes that contain a conserved proximal 3'UI in zebrafish, mouse and humans. foxo3b is one such proximal 3'UI-containing gene that is upregulated in zebrafish EJC mutant embryos, at both mRNA and protein levels, and loss of foxo3b function in EJC mutant embryos significantly rescues motor axon growth defects. These data are consistent with EJC-dependent NMD regulating foxo3b mRNA to control protein expression during zebrafish development. Our work shows that the EJC is critical for normal zebrafish development and suggests that proximal 3'UIs may serve gene regulatory function in vertebrates.

A 3D porous FeP/rGO modulated separator as a dual-function polysulfide barrier for high-performance lithium sulfur batteries

Lithium-sulfur batteries (LSBs) have gained considerable attention for their desirable energy densities, high theoretical capacities, low cost and environmentally friendly properties. However, the shuttle effect of polysulfides seriously hinders their future practical applications. Herein, a dual-function cathode structure, consisting of 3D porous FeP/rGO microspheres supported on both aluminum foil and a commercial separator, exhibits excellent performance by providing strong adsorption with respect to Li₂S_x (x = 1, 2, 4, 6 and 8) and S₈. In this rational design, the iron phosphide (FeP) nanoparticles act as a catalyst to accelerate polysulfide conversion and as the designated sites for adsorption. The 3D rGO porous conductive network can provide enough space for sulfur loading and to physically adsorb the polysulfides. More importantly, density functional theory (DFT) calculations also verified the strong interactions (with adsorption energy values of -4.21 to -1.97 eV) between the FeP(111) surface and the sulfur species. The electrochemical results show that the cell using the dual-function cathode structure delivers a capacity of 925.7 mA h g^-1, with capacity degradation of 0.05% per cycle after 500 cycles, at a current density of 0.5C. It is also worth mentioning that the cell with sulfur loading of ∼2.2 mg cm^-2 maintained a high capacity of 483 mA h g^-1 at 0.5C after 500 cycles. In summary, the above results demonstrate the promising application of the dual-function cathode structure for high-performance LSBs.

Pifithrin-α alters p53 post-translational modifications pattern and differentially inhibits p53 target genes

Pifithrin-α (PFT-α) is a small molecule which has been widely used as a specific inhibitor of p53 transcription activity. However, its molecular mechanism of action remains unclear. PFT-α has also been described to display potent p53-independent activity in cells. In this study, we addressed the mechanism of action of PFT-α. We found that PFT-α failed to prevent the effects of Mdm2 inhibitor Nutlin-3 on cell cycle and apoptosis in several cancer cell lines. However, PFT-α rescued normal primary fibroblasts from growth inhibition by Nutlin-3. PFT-α displayed a very limited effect on p53-dependent transcription upon its activation by Nutlin-3. Moreover, PFT-α inhibitory effect on transcription was highly dependent on the nature of the p53 target gene. PFT-α attenuated post-translational modifications of p53 without affecting total p53 protein level. Finally, we found that PFT-α can decrease the level of intracellular reactive oxygen species through activation of an aryl hydrocarbon receptor (AHR)-Nrf2 axis in a p53-independent manner. In conclusion, PFT-α inhibits only some aspects of p53 function, therefore it should be used with extreme caution to study p53-dependent processes.

FOXO3a from the Nucleus to the Mitochondria: A Round Trip in Cellular Stress Response

Cellular stress response is a universal mechanism that ensures the survival or negative selection of cells in challenging conditions. The transcription factor Forkhead box protein O3 (FOXO3a) is a core regulator of cellular homeostasis, stress response, and longevity since it can modulate a variety of stress responses upon nutrient shortage, oxidative stress, hypoxia, heat shock, and DNA damage. FOXO3a activity is regulated by post-translational modifications that drive its shuttling between different cellular compartments, thereby determining its inactivation (cytoplasm) or activation (nucleus and mitochondria). Depending on the stress stimulus and subcellular context, activated FOXO3a can induce specific sets of nuclear genes, including cell cycle inhibitors, pro-apoptotic genes, reactive oxygen species (ROS) scavengers, autophagy effectors, gluconeogenic enzymes, and others. On the other hand, upon glucose restriction, 5′-AMP-activated protein kinase (AMPK) and mitogen activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) -dependent FOXO3a mitochondrial translocation allows the transcription of oxidative phosphorylation (OXPHOS) genes, restoring cellular ATP levels, while in cancer cells, mitochondrial FOXO3a mediates survival upon genotoxic stress induced by chemotherapy. Interestingly, these target genes and their related pathways are diverse and sometimes antagonistic, suggesting that FOXO3a is an adaptable player in the dynamic homeostasis of normal and stressed cells. In this review, we describe the multiple roles of FOXO3a in cellular stress response, with a focus on both its nuclear and mitochondrial functions.

Resensitization of cisplatin resistance ovarian cancer cells to cisplatin through pretreatment with low-dose fraction radiation

Objective

Cisplatin is the first‐line chemotherapy for ovarian cancer. However, cisplatin resistance is severely affecting the treatment efficacy. FOXO3a has been reported to be involved in reversing chemotherapy resistance. However, whether low‐dose fraction radiation therapy (LDFRT) can reverse cisplatin resistance remains unclear. This study aimed to explore the effect of LDFRT on cisplatin resistance and its relation with FOXO3a expression in vitro.

Methods

The toxicity of cisplatin on SKOV3/DDP cells was evaluated by CCK8 assay and cell apoptosis was measured by Annexin V‐FITC staining as well as Hoechst33342 staining. The expression of FOXO3a and other relative proteins was measured by western blot.

Results

Our study found that LDFRT enhanced cisplatin‐induced apoptosis of SKOV3/DDP cells and promoted the expression of FOXO3a and pro‐apoptotic protein PUMA. In addition, overexpression of FOXO3a promoted PUMA activity and toxicity of cisplatin on SKOV3/DDP cells.

Conclusion

LDFRT reverses cisplatin resistance of SKOV3/DDP cells possibly by upregulating the expression of FOXO3a and its downstream target PUMA, suggesting that LDFRT might be a potent chemosensitizer for the treatment of ovarian cancer.

Notch1 inhibition enhances DNA damage induced by cisplatin in cervical cancer

The expression of Notch1 plays an important role in the occurrence and development of various tumors. Previous studies have shown that Notch1 plays a negative regulatory role in response to radiation-induced DNA damage responses. It also has been reported that Notch1 was highly expressed in cervical cancer. It is well known that the first-line chemotherapy drug for treating cervical cancer, cisplatin, targets double-stranded DNA and induces apoptosis in the cells. However, the tolerability of cisplatin is an issue to overcome in the treatment of cervical cancer. Cisplatin has been reported to induce the up-regulation of Notch1 intracellular domain (NICD) through the γ-proteolytic enzyme complex, a complex that mediates Notch1 activation. Therefore, whether Notch1 is highly expressed in the cells or cisplatin induced high expression of NICD in cervical cancer has not been specifically discussed in these studies. More importantly, whether the inhibition of Notch1 activation would enhance DNA damage induced by cisplatin and/or cellular apoptosis mediated via ATM/CHK2/P53 pathway has not been reported in cervical cancer. In this study, we observed an enhanced DNA damage and cellular apoptosis via the ATM/CHK2/P53 pathway(s) in HeLa and SiHa cells treated with cisplatin combined with DAPT of Notch1 inhibitor. Our findings provide an alternative therapeutic strategy for the treatment of cervical cancer in the clinic.

Defenses against Pro-oxidant Forces - Maintenance of Cellular and Genomic Integrity and Longevity

There has been enormous recent progress in understanding how human cells respond to oxidative stress, such as that caused by exposure to ionizing radiation. We have witnessed a significant deciphering of the events that underlie how antioxidant responses counter pro-oxidant damage to key biological targets in all cellular compartments, including the genome and mitochondria. These cytoprotective responses include: 1. The basal cellular repertoire of antioxidant capabilities and its supporting cast of facilitator enzymes; and 2. The inducible phase of the antioxidant response, notably that mediated by the Nrf2 transcription factor. There has also been frenetic progress in defining how reactive electrophilic species swamp existing protective mechanisms to augment DNA damage, events that are embodied in the cellular "DNA-damage response", including cell cycle checkpoint activation and DNA repair, which occur on a time scale of hours to days, as well as the implementation of cellular responses such as apoptosis, autophagy, senescence and reprograming that extend the time period of damage sensing and response into weeks, months and years. It has become apparent that, in addition to the initial oxidative insult, cells typically undergo further waves of secondary reactive oxygen/nitrogen species generation, DNA damage and signaling and that these may reemerge long after the initial events have subsided, probably being driven, at least in part, by persisting DNA damage. These reactive oxygen/nitrogen species are an integral part of the pathological consequences of radiation exposure and may persist across multiple cell divisions. Because of the pervasive nature of oxidative stress, a cell will manifest different responses in different subcellular compartments and to different levels of stress injury. Aspects of these compartmentalized responses can involve the same proteins (such as ATM, p53 and p21) but in different functional guises, e.g., in cytoplasmic versus nuclear responses or in early- versus late-phase events. Many of these responses involve gene activation and new protein synthesis as well as a plethora of post-translational modifications of both basal and induced response proteins. It is these responses that we focus on in this review.

The inhibitory potential of Broussochalcone A for the human cytochrome P450 2J2 isoform and its anti-cancer effects via FOXO3 activation

BACKGROUND

Broussonetia papyrifera (L.) Ventenat, a traditional medicinal herb, has been applied as a folk medicine to treat various diseases. Broussochalcone A (BCA), a chalcone compound isolated from the cortex of Broussonetia papyrifera (L.) Ventenat, exhibits several biological activities including potent anti-oxidant, antiplatelet, and cytotoxic effects.

PURPOSE

The purpose of this study is to elucidate the inhibitory effect of BCA against CYP2J2 enzyme which is predominantly expressed in human tumor tissues and carcinoma cell lines.

STUDY DESIGN

The inhibitory effect of BCA on the activities of CYP2J2-mediated metabolism were investigated using human liver microsomes (HLMs), and its anti-cancer effect against human hepatoma HepG2 cells was also evaluated.

METHODS

Two representative CYP2J2-specific probe substrates, astemizole and ebastine, were incubated in HLMs with BCA. After incubation, the samples were analyzed using liquid chromatography-tandem mass spectrometry. To investigate the binding model between BCA and CYP2J2, we carried out structure-based docking simulations by using software and scripts written in-house.

RESULTS

BCA inhibited CYP2J2-mediated astemizole O-demethylation and ebastine hydroxylase activities in a concentration dependent manner with K_i values of 2.3 and 3.7 µM, respectively. It also showed cytotoxic effects against human hepatoma HepG2 cells in a dose-dependent manner with activation of apoptosis related proteins.

CONCLUSION

Overall, this was the first report of the inhibitory effects of BCA on CYP2J2 in HLMs. The present data suggest that BCA is a potential candidate for further evaluation for its CYP2J2 targeting anti-cancer activities.

Pharmacological activation of FOXO3 suppresses triple-negative breast cancer in vitro and in vivo

Triple-negative breast cancer (TNBC) is the most lethal form of breast cancer. Lacking effective therapeutic options hinders treatment of TNBC. Here, we show that bepridil (BPD) and trifluoperazine (TFP), which are FDA-approved drugs for treatment of schizophrenia and angina respectively, inhibit Akt-pS473 phosphorylation and promote FOXO3 nuclear localization and activation in TNBC cells. BPD and TFP inhibit survival and proliferation in TNBC cells and suppress the growth of TNBC tumors, whereas silencing FOXO3 reduces the BPD- and TFP-mediated suppression of survival in TNBC cells. While BPD and TFP decrease the expression of oncogenic c-Myc, KLF5, and dopamine receptor DRD2 in TNBC cells, silencing FOXO3 diminishes BPD- and TFP-mediated repression of the expression of these proteins in TNBC cells. Since c-Myc, KLF5, and DRD2 have been suggested to increase cancer stem cell-like populations in various tumors, reducing these proteins in response to BPD and TFP suggests a novel FOXO3-dependent mechanism underlying BPD- and TFP-induced apoptosis in TNBC cells.

FoxO transcription factors in cancer metabolism

FoxO transcription factors serve as the central regulator of cellular homeostasis and are tumor suppressors in human cancers. Recent studies have revealed that, besides their classic functions in promoting cell death and inducing cell cycle arrest, FoxOs also regulate cancer metabolism, an emerging hallmark of cancer. In this review, we summarize the regulatory mechanisms employed to control FoxO activities in the context of cancer biology, and discuss FoxO function in metabolism reprogramming in cancer and interaction with other key cancer metabolism pathways. A deeper understanding of FoxOs in cancer metabolism may reveal novel therapeutic opportunities in cancer treatment.

Mechanisms controlling the anti-neoplastic functions of FoxO proteins

The Forkhead box O (FoxO) proteins comprise a family of evolutionarily conserved transcription factors that predominantly function as tumor suppressors. These proteins assume diverse roles in the cellular anti-neoplastic response, including regulation of apoptosis and autophagy, cancer metabolism, cell-cycle arrest, oxidative stress and the DNA damage response. More recently, FoxO proteins have been implicated in cancer immunity and cancer stem-cell (CSC) homeostasis. Interestingly, in some sporadic sub-populations, FoxO protein function may also be manipulated by factors such as β-catenin whereby they instead can facilitate cancer progression via maintenance of CSC properties or promoting drug resistance or metastasis and invasion. This review highlights the essential biological functions of FoxOs and explores the areas that may be exploited in FoxO protein signaling pathways in the development of novel cancer therapeutic agents.

Ataxia telangiectasia syndrome: moonlighting ATM

INTRODUCTION

Ataxia-telangiectasia (A-T) a multisystem disorder primarily characterized by cerebellar degeneration, telangiectasia, immunodeficiency, cancer susceptibility and radiation sensitivity. Identification of the gene defective in this syndrome, ataxia-telangiectasia mutated gene (ATM), and further characterization of the disorder together with a greater insight into the function of the ATM protein have expanded our knowledge about the molecular pathogenesis of this disease. Area covered: In this review, we have attempted to summarize the different roles of ATM signaling that have provided new insights into the diverse clinical phenotypes exhibited by A-T patients. Expert commentary: ATM, in addition to DNA repair response, is involved in many cytoplasmic roles that explain diverse phenotypes of A-T patients. It seems accumulation of DNA damage, persistent DNA damage response signaling, and chronic oxidative stress are the main players in the pathogenesis of this disease.

Loss of foxo rescues stem cell aging in Drosophila germ line

Aging stem cells lose the capacity to properly respond to injury and regenerate their residing tissues. Here, we utilized the ability of Drosophila melanogaster germline stem cells (GSCs) to survive exposure to low doses of ionizing radiation (IR) as a model of adult stem cell injury and identified a regeneration defect in aging GSCs: while aging GSCs survive exposure to IR, they fail to reenter the cell cycle and regenerate the germline in a timely manner. Mechanistically, we identify foxo and mTOR homologue, Tor as important regulators of GSC quiescence following exposure to ionizing radiation. foxo is required for entry in quiescence, while Tor is essential for cell cycle reentry. Importantly, we further show that the lack of regeneration in aging germ line stem cells after IR can be rescued by loss of foxo.

Stem cells are unspecialized cells that have the unique ability to replace dead cells and repair damaged tissues. To give rise to new cells, stem cells need to divide. This process, known as the cell cycle, includes several stages and is regulated by many different genes.

For example, in many organisms, a gene called foxo helps cells respond to stress and to regulate the cell cycle and cell death. Defects in this gene have been linked to age-related diseases, such as cancer and Alzheimer’s disease. Previous research has shown that foxo can also regulate Tor – a gene that helps cells to divide and grow.

As we age, stem cells become less efficient at regenerating tissues, especially after exposure to toxins and radiation. However, until now, it was not known how stem cells control their division after injury and during aging, and what role these two genes play in injured and aging stem cells.

Now, Artoni, Kreipke et al. used germline stem cells from fly ovaries to investigate how young and old stem cells respond to injury. In young flies, foxo paused the cell cycle of the damaged stem cells. After 24 hours, Tor was able to overcome the action of foxo, and the stem cells resumed dividing and regenerating the damaged tissue. However, in old stem cells, foxo and Tor were misregulated and the stem cells could not restart dividing or repairing tissue after injury. When the levels of foxo in old stem cells were experimentally reduced, their ability to regenerate the tissue was restored.

These discoveries provide new insights into how stem cells respond to injury and suggest that stem cell aging may be a reversible process. A next step will be to investigate why foxo and Tor are misregulated during aging and how these two genes interact with each another. In future, this could help develop new anti-aging therapies that can restore the body’s natural ability to repair itself following injury. Moreover, since cancer cells can become resistant to conventional cancer treatment by withdrawing from the cell cycle, developing new treatments that target foxo and Tor could help beat cancer and prevent its reoccurrence.

The effect of Bacopa monnieri on gene expression levels in SH-SY5Y human neuroblastoma cells

Bacopa monnieri is a plant used as a nootropic in Ayurveda, a 5000-year-old system of traditional Indian medicine. Although both animal and clinical studies supported its role as a memory enhancer, the molecular and cellular mechanism underlying Bacopa's nootropic action are not understood. In this study, we used deep sequencing (RNA-Seq) to identify the transcriptome changes upon Bacopa treatment on SH-SY5Y human neuroblastoma cells. We identified several genes whose expression levels were regulated by Bacopa. Biostatistical analysis of the RNA-Seq data identified biological pathways and molecular functions that were regulated by Bacopa, including regulation of mRNA translation and transmembrane transport, responses to oxidative stress and protein misfolding. Pathway analysis using the Ingenuity platform suggested that Bacopa may protect against brain damage and improve brain development. These newly identified molecular and cellular determinants may contribute to the nootropic action of Bacopa and open up a new direction of investigation into its mechanism of action.

Antioxidant effects of Cirsium setidens extract on oxidative stress in human mesenchymal stem cells

Human mesenchymal stem cells (MSCs) may be used in cell-based therapy to promote neovascularization for the treatment of ischemic diseases. However, high levels of reactive oxygen species (ROS) derived from the pathophysiological ischemic environment induce senescence and apoptosis of MSCs, resulting in reduced functionality and defective neovascularization. Therefore, the present study aimed to determine the protective effects of Cirsium setidens, a natural product, on oxidative stress-induced apoptosis in MSCs. The present study investigated for the change of ROS levels in MSCs using ROS assays. In addition, cell viability determined by MTT and TUNEL assays. Western blot analysis was performed to investigate the change of apoptosis-associated proteins in MSCs. Treatment of MSCs with hydrogen peroxide (H₂O₂; 200 µM) significantly increased intracellular ROS levels and cell death; however, pretreatment with C. setidens (100 µg/ml) suppressed H₂O₂-induced ROS generation and increased the survival of MSCs. H₂O₂-induced ROS production increased the levels of phosphorylated-p38 mitogen activated protein kinase, c-Jun N-terminal kinase, ataxia telangiectasia mutated and p53; these increases were inhibited by pretreatment with C. setidens. In addition, C. setidens inhibited ROS-induced apoptosis of MSCs by increasing the expression levels of the anti-apoptotic protein B-cell lymphoma 2 (BCL-2), and decreasing the expression levels of the proapoptotic protein BCL-2-associated X protein. These findings indicated that pretreatment of MSCs with C. setidens may prevent ROS-induced oxidative injury by regulating the oxidative stress-associated signaling pathway, and suppressing the apoptosis-associated signal pathway. Therefore, C. setidens may be developed as a beneficial broad-spectrum agent for enhancing the effectiveness of MSC transplantation in the treatment of ischemic diseases.

NOTCH1 Inhibits Activation of ATM by Impairing the Formation of an ATM-FOXO3a-KAT5/Tip60 Complex

The DNA damage response (DDR) signal transduction pathway is responsible for sensing DNA damage and further relaying this signal into the cell. ATM is an apical DDR kinase that orchestrates the activation and the recruitment of downstream DDR factors to induce cell-cycle arrest and repair. We have previously shown that NOTCH1 inhibits ATM activation upon DNA damage, but the underlying mechanism remains unclear. Here, we show that NOTCH1 does not impair ATM recruitment to DNA double-strand breaks (DSBs). Rather, NOTCH1 prevents binding of FOXO3a and KAT5/Tip60 to ATM through a mechanism in which NOTCH1 competes with FOXO3a for ATM binding. Lack of FOXO3a binding to ATM leads to the loss of KAT5/Tip60 association with ATM. Moreover, expression of NOTCH1 or depletion of ATM impairs the formation of the FOXO3a-KAT5/Tip60 protein complex. Finally, we show that pharmacological induction of FOXO3a nuclear localization sensitizes NOTCH1-driven cancers to DNA-damage-induced cell death.

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NOTCH1 does not inhibit recruitment of ATM to DSBs

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NOTCH1 competes with FOXO3a for binding to the FATC domain of ATM

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FOXO3a is necessary for KAT5/Tip60 binding to ATM

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Induction of FOXO3a nuclear localization sensitizes TALL-1 cancer cells to DNA damage

The DNA damage-induced cell death response: a roadmap to kill cancer cells

Upon massive DNA damage cells fail to undergo productive DNA repair and trigger the cell death response. Resistance to cell death is linked to cellular transformation and carcinogenesis as well as radio- and chemoresistance, making the underlying signaling pathways a promising target for therapeutic intervention. Diverse DNA damage-induced cell death pathways are operative in mammalian cells and finally culminate in the induction of programmed cell death via activation of apoptosis or necroptosis. These signaling routes affect nuclear, mitochondria- and plasma membrane-associated key molecules to activate the apoptotic or necroptotic response. In this review, we highlight the main signaling pathways, molecular players and mechanisms guiding the DNA damage-induced cell death response.

Increased sensitivity of BRCA defective triple negative breast tumors to plumbagin through induction of DNA Double Strand Breaks (DSB)

We have earlier shown that Plumbagin (PB) can induce selective cytotoxicity to BRCA1 defective ovarian cancer cells; however, the effect of this molecule in BRCA1 mutated breast cancers has not been analyzed yet. Here, we report that reactive oxygen species (ROS) induced by PB resulted in DNA DSB and activates downstream signaling by ATR/ATM kinases and subsequent apoptosis. PB reduces DNA- dependent protein kinase (DNA-PK) expression and inhibits NHEJ (Non Homologous End Joining) activity in BRCA1 defective breast cancer cells. Also, PB induces apoptosis in two different BRCA1 conditional knock out murine models: MMTV-Cre; BRCA1^Co/Co and WAP-Cre; BRCA1^Co/Co, at 2 mg/kg body weight, but 32 mg/kg of carboplatin (CN) was needed to induce apoptosis in them. This is the first study where two different tissue specific promoter driven transgenic mice models with BRCA1 exon 11 deletions are used for preclinical drug testing. The apoptosis induced by PB in HR (Homologous Recombination) defective triple negative BRCA1 mutant cell lines and in mouse models occur by inducing ROS mediated DNA DSB. The toxicity profile as compared with CN in transgenic mice provides evidence for PB’s safer disposition as a therapeutic lead in breast cancer drug development.

miR-93 promotes cell proliferation in gliomas through activation of PI3K/Akt signaling pathway

The PI3K/Akt signaling pathway is frequently activated in various human cancer types and plays essential roles in development and progression of cancers. Multiple regulators, such as phosphatase and tensin homolog (PTEN) and PH domain leucine rich repeat protein phosphatases (PHLPP), have also found to be involved in suppression of the PI3K/Akt signaling pathway. However, how suppressive effects mediated by these regulators are concomitantly disrupted in cancers, which display constitutively activated PI3K/Akt signaling, remains puzzling. In the present study, we reported that the expression of miR-93 was markedly upregulated in glioma cell lines and clinical glioma tissues. Statistical analysis revealed that miR-93 levels significantly correlated with clinicopathologic grade and overall survival in gliomas. Furthermore, we found that overexpressing miR-93 promoted, but inhibition of miR-93 reduced, glioma cell proliferation and cell-cycle progression. We demonstrated that miR-93 activated PI3K/Akt signaling through directly suppressing PTEN, PHLPP2 and FOXO3 expression via targeting their 3'UTRs. Therefore, our results suggest that miR-93 might play an important role in glioma progression and uncover a novel mechanism for constitutive PI3K/Akt activation in gliomas.

miR-30a can inhibit DNA replication by targeting RPA1 thus slowing cancer cell proliferation

Cell proliferation was inhibited following forced over-expression of miR-30a in the ovary cancer cell line A2780DX5 and the gastric cancer cell line SGC7901R. Interestingly, miR-30a targets the DNA replication protein RPA1, hinders the replication of DNA and induces DNA fragmentation. Furthermore, ataxia telangiectasia mutated (ATM) and checkpoint kinase 2 (CHK2) were phosphorylated after DNA damage, which induced p53 expression, thus triggering the S-phase checkpoint, arresting cell cycle progression and ultimately initiating cancer cell apoptosis. Therefore, forced miR-30a over-expression in cancer cells can be a potential way to inhibit tumour development.

Histone H2AX Is Involved in FoxO3a-Mediated Transcriptional Responses to Ionizing Radiation to Maintain Genome Stability

Histone H2AX plays a crucial role in molecular and cellular responses to DNA damage and in the maintenance of genome stability. It is downstream of ataxia telangiectasia mutated (ATM) damage signaling pathway and there is an emerging role of the transcription factor FoxO3a, a regulator of a variety of other pathways, in activating this signaling. We asked whether H2AX may feedback to FoxO3a to affect respective FoxO3a-dependent pathways. We used a genetically matched pair of mouse embryonic fibroblast H2AX^+/+ and H2AX^−/− cell lines to carry out comprehensive time-course and dose-response experiments and to show that the expression of several FoxO3a-regulated genes was altered in H2AX^−/− compared to H2AX^+/+ cells at both basal and irradiated conditions. Hspa1b and Gadd45a were down-regulated four- to five-fold and Ddit3, Cdkn1a and Sod2 were up-regulated 2–3-fold in H2AX^−/− cells. Using the luciferase reporter assay, we directly demonstrated that transcriptional activity of FoxoO3a was reduced in H2AX^−/− cells. FoxO3a localization within the nuclear phospho-ATM (Ser1981) foci in irradiated cells was affected by the H2AX status, as well as its posttranslational modification (phospho-Thr32). These differences were associated with genomic instability and radiosensitivity in H2AX^−/− cells. Finally, knockdown of H2AX in H2AX^+/+ cells resulted in FoxO3a-dependent gene expression patterns and increased radiosensitivity that partially mimicked those found in H2AX^−/− cells. Taken together, our data suggest a role for FoxO3a in the maintenance of genome integrity in response to DNA damage that is mediated by H2AX via yet unknown mechanisms.

Effects of Low-Dose Bisphenol A on DNA Damage and Proliferation of Breast Cells: The Role of c-Myc

BACKGROUND

Humans are exposed to low-dose bisphenol A (BPA) through plastic consumer products and dental sealants containing BPA. Although a number of studies have investigated the mammary gland effects after high-dose BPA exposure, the study findings differ. Furthermore, there has been a lack of mechanistic studies.

OBJECTIVE

The objective of this study was to investigate the effect and the mechanism of low-dose BPA in mammary gland cells.

METHODS

We evaluated DNA damage following BPA exposure using the comet assay and immunofluorescence staining, and used cell counting and three-dimensional cultures to evaluate effects on proliferation. We examined the expressions of markers of DNA damage and cell-cycle regulators by immunoblotting and performed siRNA-mediated gene silencing to determine the role of c-Myc in regulating BPA's effects.

RESULTS

Low-dose BPA significantly promoted DNA damage, up-regulated c-Myc and other cell-cycle regulatory proteins, and induced proliferation in parallel in estrogen receptor-α (ERα)-negative mammary cells. Silencing c-Myc diminished these BPA-induced cellular events, suggesting that c-Myc is essential for regulating effects of BPA on DNA damage and proliferation in mammary cells.

CONCLUSIONS

Low-dose BPA exerted c-Myc-dependent genotoxic and mitogenic effects on ERα-negative mammary cells. These findings provide significant evidence of adverse effects of low-dose BPA on mammary cells.

Pretreatment with Lycopene Attenuates Oxidative Stress-Induced Apoptosis in Human Mesenchymal Stem Cells

Human mesenchymal stem cells (MSCs) have been used in cell-based therapy to promote revascularization after peripheral or myocardial ischemia. High levels of reactive oxygen species (ROS) are involved in the senescence and apoptosis of MSCs, causing defective neovascularization. Here, we examined the effect of the natural antioxidant lycopene on oxidative stress-induced apoptosis in MSCs. Although H2O2 (200 μM) increased intracellular ROS levels in human MSCs, lycopene (10 μM) pretreatment suppressed H2O2-induced ROS generation and increased survival. H2O2-induced ROS increased the levels of phosphorylated p38 mitogen activated protein kinase (MAPK), Jun-N-terminal kinase (JNK), ataxia telangiectasia mutated (ATM), and p53, which were inhibited by lycopene pretreatment. Furthermore, lycopene pretreatment decreased the expression of cleaved poly (ADP ribose) polymerase-1 (PARP-1) and caspase-3 and increased the expression of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax), which were induced by H2O2 treatment. Moreover, lycopene significantly increased manganese superoxide dismutase (MnSOD) expression and decreased cellular ROS levels via the PI3K-Akt pathway. Our findings show that lycopene pretreatment prevents ischemic injury by suppressing apoptosis-associated signal pathway and enhancing anti-oxidant protein, suggesting that lycopene could be developed as a beneficial broad-spectrum agent for the successful MSC transplantation in ischemic diseases.