Chk1 and p21 cooperate to prevent apoptosis during DNA replication fork stress

Predicting p53-dependent cell transitions from thermodynamic models

A cell's fate involves transitions among its various states, each defined by a distinct gene expression profile governed by the topology of gene regulatory networks, which are affected by 3D genome organization. Here, we develop thermodynamic models to determine the fate of a malignant cell as governed by the tumor suppressor p53 signaling network, taking into account long-range chromatin interactions in the mean-field approximation. The tumor suppressor p53 responds to stress by selectively triggering one of the potential transcription programs that influence many layers of cell signaling. These range from p53 phosphorylation to modulation of its DNA binding affinity, phase separation phenomena, and internal connectivity among cell fate genes. We use the minimum free energy of the system as a fundamental property of biological networks that influences the connection between the gene network topology and the state of the cell. We constructed models based on network topology and equilibrium thermodynamics. Our modeling shows that the binding of phosphorylated p53 to promoters of target genes can have properties of a first order phase transition. We apply our model to cancer cell lines ranging from breast cancer (MCF-7), colon cancer (HCT116), and leukemia (K562), with each one characterized by a specific network topology that determines the cell fate. Our results clarify the biological relevance of these mechanisms and suggest that they represent flexible network designs for switching between developmental decisions.

Thymidylate synthase disruption to limit cell proliferation in cell therapies

Stem and progenitor cells hold great promise for regenerative medicine and gene therapy approaches. However, transplantation of living cells entails a fundamental risk of unwanted growth, potentially exacerbated by CRISPR-Cas9 or other genetic manipulations. Here, we describe a safety system to control cell proliferation while allowing robust and efficient cell manufacture, without any added genetic elements. Inactivating TYMS, a key nucleotide metabolism enzyme, in several cell lines resulted in cells that proliferate only when supplemented with exogenous thymidine. Under supplementation, TYMS-/--pluripotent stem cells proliferate, produce teratomas, and successfully differentiate into potentially therapeutic cell types such as pancreatic β cells. Our results suggest that supplementation with exogenous thymidine affects stem cell proliferation, but not the function of stem cell-derived cells. After differentiation, postmitotic cells do not require thymidine in vitro or in vivo, as shown by the production of functional human insulin in mice up to 5 months after implantation of stem cell-derived pancreatic tissue.

A dual role of RBM42 in modulating splicing and translation of CDKN1A/p21 during DNA damage response

p53-mediated cell cycle arrest during DNA damage is dependent on the induction of p21 protein, encoded by the CDKN1A gene. p21 inhibits cyclin-dependent kinases required for cell cycle progression to guarantee accurate repair of DNA lesions. Hence, fine-tuning of p21 levels is crucial to preserve genomic stability. Currently, the multilayered regulation of p21 levels during DNA damage is not fully understood. Herein, we identify the human RNA binding motif protein 42 (RBM42) as a regulator of p21 levels during DNA damage. Genome-wide transcriptome and interactome analysis reveals that RBM42 alters the expression of p53-regulated genes during DNA damage. Specifically, we demonstrate that RBM42 facilitates CDKN1A splicing by counteracting the splicing inhibitory effect of RBM4 protein. Unexpectedly, we also show that RBM42, underpins translation of various splicing targets, including CDKN1A. Concordantly, transcriptome-wide mapping of RBM42-RNA interactions using eCLIP further substantiates the dual function of RBM42 in regulating splicing and translation of its target genes, including CDKN1A. Collectively, our data show that RBM42 couples splicing and translation machineries to fine-tune gene expression during DNA damage response.

Interactions between the DNA Damage Response and the Telomere Complex in Carcinogenesis: A Hypothesis

Contrary to what was once thought, direct cancer originating from normal stem cells seems to be extremely rare. This is consistent with a preneoplastic period of telomere length reduction/damage in committed cells that becomes stabilized in transformation. Multiple observations suggest that telomere damage is an obligatory step preceding its stabilization. During tissue turnover, the telomeres of cells undergoing differentiation can be damaged as a consequence of defective DNA repair caused by endogenous or exogenous agents. This may result in the emergence of new mechanism of telomere maintenance which is the final outcome of DNA damage and the initial signal that triggers malignant transformation. Instead, transformation of stem cells is directly induced by primary derangement of telomere maintenance mechanisms. The newly modified telomere complex may promote survival of cancer stem cells, independently of telomere maintenance. An inherent resistance of stem cells to transformation may be linked to specific, robust mechanisms that help maintain telomere integrity.

RNF4 and USP7 cooperate in ubiquitin-regulated steps of DNA replication

DNA replication requires precise regulation achieved through post-translational modifications, including ubiquitination and SUMOylation. These modifications are linked by the SUMO-targeted E3 ubiquitin ligases (STUbLs). Ring finger protein 4 (RNF4), one of only two mammalian STUbLs, participates in double-strand break repair and resolving DNA-protein cross-links. However, its role in DNA replication has been poorly understood. Using CRISPR/Cas9 genetic screens, we discovered an unexpected dependency of RNF4 mutants on ubiquitin specific peptidase 7 (USP7) for survival in TP53-null retinal pigment epithelial cells. TP53-/-/RNF4-/-/USP7-/- triple knockout (TKO) cells displayed defects in DNA replication that cause genomic instability. These defects were exacerbated by the proteasome inhibitor bortezomib, which limited the nuclear ubiquitin pool. A shortage of free ubiquitin suppressed the ataxia telangiectasia and Rad3-related (ATR)-mediated checkpoint response, leading to increased cell death. In conclusion, RNF4 and USP7 work cooperatively to sustain a functional level of nuclear ubiquitin to maintain the integrity of the genome.

Rosline promotes p21 expression to inhibit ovarian cancer cell proliferation via p53-independent pathway

AIM

To investigate the effect of benzothiazole derivatives (Rosline) on ovarian cancer and the potential mechanism.

METHODS

Ovarian cancer tissues were collected clinically and immunohistochemistry was used to detect the expression of p53 and p21. Ovarian cancer cells were exposed to 0, 2.5, 5, 10 μmol/L Rosline for 24 h. 100 nmol/L Pifithrin-α pre-incubation was used to inhibit the transcriptional activity of p53. CCK-8 and BrdU assays were used to detect the effects of different concentrations of rosline on the proliferation and cell cycle of OVCAR420 and SKOV3 cells. Flow cytometry assay was used to detect cell cycle. The transcriptional and translational expression of p21 and p53 were detected by RT-qPCR and Western blot.

RESULTS

p21 was expressed in ovarian cancer tissues without p53 expression. Rosline inhibits the proliferation of ovarian cancer cells and blocks the cell cycle progression. Meanwhile, Rosline promotes p21 expression in ovarian cancer cells at both mRNA and protein levels, but with no significant effect on p53 expression. Besides, Rosline promotes p21 expression, inhibits cell proliferation, and blocks the cell cycle via the p53-independent pathway.

CONCLUSION

Rosline promoted p21 expression thereby inhibiting cell proliferation and blocks the cell cycle via p53-independent pathway.

The senescence difference between the central and peripheral cornea induced by sutures

INTRODUCTION

Cell senescence plays a regulatory role in tissue fibrosis. Corneal scarring is usually more severe in the central cornea based on clinical observation. In this study, we attempted to explore the senescence difference between the central and peripheral cornea in an in vivo mouse model with suture-induced senescence and in an in vitro model of senescence with hydrogen peroxide (H₂O₂)-induced rabbit corneal fibroblasts.

METHODS

Male Balb/c mice (6-8 weeks) received sutures in the central, superior, inferior, nasal, and temporal cornea. The sutures were removed on the 14th day. Corneal neovascularization was observed under a slit lamp microscope with a digital camera. The fibroblasts isolated from the central and peripheral rabbit cornea were induced with H₂O₂ to establish the senescence model in vitro. Senescence was evaluated with SA-β-gal staining and gene expression analysis of p21, p27, and p53.

RESULTS

Senescent cells accumulated in the corneal stroma from the third day to the 14th day after the operation and peaked on the 14th day. More senescent keratocytes were observed in the peripheral cornea of the mouse model. In vitro, the peripheral corneal fibroblasts were more prone to senescence due to H₂O₂. The polymerase chain reaction results showed that the senescence-related genes p21, p27, and p53 were highly expressed in the peripheral corneal fibroblasts compared with the central corneal fibroblasts.

CONCLUSIONS

Senescent fibroblasts can limit tissue fibrosis; hence, the senescence difference between the central and peripheral cornea may contribute to the difference in scarring.

Medicinal chemistry perspective of pyrido[2,3-d]pyrimidines as anticancer agents

Cancer is a major cause of deaths across the globe due to chemoresistance and lack of selective chemotherapy. Pyrido[2,3-d]pyrimidine is an emerging scaffold in medicinal chemistry having a broad spectrum of activities, including antitumor, antibacterial, CNS depressive, anticonvulsant, and antipyretic activities. In this study, we have covered different cancer targets, including tyrosine kinase, extracellular regulated protein kinases - ABL kinase, phosphatidylinositol-3 kinase, mammalian target of rapamycin, p38 mitogen-activated protein kinases, BCR-ABL, dihydrofolate reductase, cyclin-dependent kinase, phosphodiesterase, KRAS and fibroblast growth factor receptors, their signaling pathways, mechanism of action and structure-activity relationship of pyrido[2,3-d]pyrimidine derivatives as inhibitors of the above-mentioned targets. This review will represent the complete medicinal and pharmacological profile of pyrido[2,3-d]pyrimidines as anticancer agents, and will help scientists to design new selective, effective and safe anticancer agents.

Resveratrol Attenuates High-Fat Diet-Induced Hepatic Lipotoxicity by Upregulating Bmi-1 Expression

Resveratrol (RES), a natural polyphenol phytoalexin, has been reported to attenuate nonalcoholic fatty liver disease (NAFLD). However, its roles on protection of liver from lipotoxicity and underlying mechanism are not fully understood. In this study, we investigated the impacts of RES on alleviating hepatic lipotoxicity and corresponding molecular mechanism. Impacts of RES on oleic acid (OA)-induced lipotoxicity were assessed in L02 cells and C57BL/6J mice, respectively. In L02 cells, lipotoxicity was assessed by detection of apoptosis, mitochondrial function, oxidative stress and ROS-related signaling. In mice, lipotoxicity was evaluated by detecting hepatic function, serum enzyme activity, and reactive oxygen species (ROS) levels. We found that RES reduced OA-induced apoptosis, mitochondrial dysfunction, ROS generation, and DNA damage in L02 cells. RES also decreased expression of cleaved caspase-3 and p53 and increased expression of B-cell lymphoma 2 (Bcl-2). Importantly, RES protected mice from high-fat diet-induced hepatic lipotoxicity, demonstrated by reduced ROS levels and lipid peroxidation. Mechanically, B lymphoma Mo-MLV insertion region 1 (Bmi-1) expression and antioxidative superoxide dismutase were increased after RES treatment. Further mechanistic analysis indicated that protection effects of RES against OA-induced lipotoxicity were abrogated by Bmi-1 small interference RNA (siRNA) in L02 cells. SIGNIFICANCE STATEMENT: Results from clinical studies about the effect of RES on NAFLD are inconsistent and inconclusive. This study confirms the protective role of RES as an anti-ROS agent and its ability to alleviate DNA damage through a pathway involving p53/p21 signaling. Further mechanistic analysis indicated that protection effects of RES were relative with Bmi-1. This is the first study on the role of Bmi-1 in the pathogenesis of NAFLD and the target of resveratrol against NAFLD.

Delayed Therapeutic Administration of Melatonin Enhances Neuronal Survival Through AKT and MAPK Signaling Pathways Following Focal Brain Ischemia in Mice

Melatonin has a role in the cell survival signaling pathways as a candidate for secondary stroke prevention. Therefore, in the present study, the coordination of ipsilateral and contralateral hemispheres to evaluate delayed post-acute effect of melatonin was examined on recovery of the cell survival and apoptosis after stroke. Melatonin was administered (4 mg/kg/day) intraperitoneally for 45 days, starting 3 days after 30 min of middle cerebral artery occlusion. The genes and proteins related to the cell survival and apoptosis were investigated by immunofluorescence, western blotting, and RT-PCR techniques after behavioral experiments. Melatonin produced delayed neurological recovery by improving motor coordination on grip strength and rotarod tests. This neurological recovery was also reflected by high level of NeuN positive cells and low level of TUNEL-positive cells suggesting enhanced neuronal survival and reduced apoptosis at the fifty-fifth day of stroke. The increase of NGF, Nrp1, c-jun; activation of AKT; and dephosphorylation of ERK and JNK at the fifty-fifth day showed that cell survival and apoptosis signaling molecules compete to contribute to the remodeling of brain. Furthermore, an increase in the CREB and Atf-1 expressions suggested the melatonin's strong reformative effect on neuronal regeneration. The contralateral hemisphere was more active at the latter stages of the molecular and functional regeneration which provides a further proof of principle about melatonin's action on the promotion of brain plasticity and recovery after stroke.

Histone deacetylase inhibitor 2-hexyl-4-pentynoic acid enhances hydroxyurea therapeutic effect in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) treatment has only limited effect, and it causes a significant number of deaths. Histone deacetylase inhibitors (HDACis) are emerging as promising anti-tumor agents in many types of cancers. We thus hypothesized that 2-hexyl-4-pentynoic acid (HPTA), a novel HDACi, could sensitize TNBC to hydroxyurea (HU, a ribonucleotide reductase inhibitor). In the present study, we investigated the effect of HPTA, alone or in combination with HU on cell survival, DNA double-strand breaks (DSBs), key homologous recombination (HR) repair proteins and cell cycle progression in MDA-MB-468 and MDA-MB-231 human TNBC cell lines. HPTA and HU synergistically inhibited the survival of TNBC cell lines and resulted in the accumulation of DNA double-strand breaks (DSBs). HPTA can sensitize TNBC cells to HU by inhibiting replication protein A2 (RPA2) hyperphosphorylation-mediated HR repair, and lessen cell accumulation in S-phase by inhibiting ATR-CHK1 signaling pathway. Taken together, our data suggested that HPTA enhances HU therapeutic effect by blocking the HR repair and regulating cell cycle progression in TNBC.

The flavonoid procyanidin C1 has senotherapeutic activity and increases lifespan in mice

Ageing-associated functional decline of organs and increased risk for age-related chronic pathologies is driven in part by the accumulation of senescent cells, which develop the senescence-associated secretory phenotype (SASP). Here we show that procyanidin C1 (PCC1), a polyphenolic component of grape seed extract (GSE), increases the healthspan and lifespan of mice through its action on senescent cells. By screening a library of natural products, we find that GSE, and PCC1 as one of its active components, have specific effects on senescent cells. At low concentrations, PCC1 appears to inhibit SASP formation, whereas it selectively kills senescent cells at higher concentrations, possibly by promoting production of reactive oxygen species and mitochondrial dysfunction. In rodent models, PCC1 depletes senescent cells in a treatment-damaged tumour microenvironment and enhances therapeutic efficacy when co-administered with chemotherapy. Intermittent administration of PCC1 to either irradiated, senescent cell-implanted or naturally aged old mice alleviates physical dysfunction and prolongs survival. We identify PCC1 as a natural senotherapeutic agent with in vivo activity and high potential for further development as a clinical intervention to delay, alleviate or prevent age-related pathologies.

p16INK4a Regulates Cellular Senescence in PD-1-Expressing Human T Cells

T-cell dysfunction arising upon repeated antigen exposure prevents effective immunity and immunotherapy. Using various clinically and physiologically relevant systems, we show that a prominent feature of PD-1-expressing exhausted T cells is the development of cellular senescence features both in vivo and ex vivo. This is associated with p16^INK4a expression and an impaired cell cycle G1 to S-phase transition in repeatedly stimulated T cells. We show that these T cells accumulate DNA damage and activate the p38MAPK signaling pathway, which preferentially leads to p16^INK4a upregulation. However, in highly dysfunctional T cells, p38MAPK inhibition does not restore functionality despite attenuating senescence features. In contrast, p16^INK4a targeting can improve T-cell functionality in exhausted CAR T cells. Collectively, this work provides insights into the development of T-cell dysfunction and identifies T-cell senescence as a potential target in immunotherapy.

Hsa-miR-6165 downregulates insulin-like growth factor-1 receptor (IGF-1R) expression and enhances apoptosis in SW480 cells

MicroRNAs are small non-coding RNAs that are implicated in various biological processes. Hsa-miR-6165 (miR-6165), located in the p75NTR gene, is known to induce apoptosis in human cell lines, but its mechanism of action is not fully understood yet. Here, we predicted the insulin-like growth factor 1 receptor (IGF-1R) gene as a bona fide target for miR-6165. The overexpression of miR-6165 in SW480 cells resulted in significant downregulation of IGF-1R expression as detected by real time quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). Also, it resulted in reduced transcript levels of AKT2, AKT3, PI3KR3, PI3KR5, CCND1, c-MYC and P21 genes detected by RT-qPCR analysis. In addition, a direct interaction between miR-6165 and a 3'UTR sequence of the IGF-1R gene was verified through a dual luciferase assay. Furthermore, miR-6165 and IGF-1R showed opposite patterns of expression during the neural differentiation process of NT2 cells. Annexin V analysis and MTT assay showed that miR-6165 overexpression was followed by increased apoptosis and reduced the viability rate of SW480 cells. Moreover, a lower expression level of miR-6165 was detected in high-grade colorectal tumors compared with low-grade tumors. Taken together, the results of our study suggest a tumor suppressive role of miR-6165 in colorectal cancer, which seems to take place by regulating IGF-1R gene expression.

Physical Training Inhibits the Fibrosis Formation in Alzheimer's Disease Kidney Influencing the TGFβ Signaling Pathways

Background:

Alzheimer’s disease (AD) is a neurodegenerative illness, with several peripheral pathological signs such as accumulation of amyloid-β (Aβ) plaques in the kidney. Alterations of transforming growth factor β (TGFβ) signaling in the kidney can induce fibrosis, thus disturbing the elimination of Aβ.

Objective:

A protective role of increased physical activity has been proven in AD and in kidney fibrosis, but it is not clear whether TGFβ signalization is involved in this effect.

Methods:

The effects of long-term training on fibrosis were investigated in the kidneys of mice representing a model of AD (B6C3-Tg(APPswe,PSEN1dE9)85Dbo/J) by comparing wild type and AD organs. Alterations of canonical and non-canonical TGFβ signaling pathways were followed with PCR, western blot, and immunohistochemistry.

Results:

Accumulation of collagen type I and interstitial fibrosis were reduced in kidneys of AD mice after long-term training. AD induced the activation of canonical and non-canonical TGFβ pathways in non-trained mice, while expression levels of signal molecules of both TGFβ pathways became normalized in trained AD mice. Decreased amounts of phosphoproteins with molecular weight corresponding to that of tau and the cleaved C-terminal of AβPP were detected upon exercising, along with a significant increase of PP2A catalytic subunit expression.

Conclusion:

Our data suggest that physical training has beneficial effects on fibrosis formation in kidneys of AD mice and TGFβ signaling plays a role in this phenomenon.

Targeting cell cycle regulation via the G2-M checkpoint for synthetic lethality in melanoma

Disruption of cell cycle checkpoints has been well established as a hallmark of cancer. In particular, the G1-S transition mediated by the cyclin D-cyclin-dependent kinase 4/6 (CDK4/6) pathway is dysregulated in more than 90% of melanoma cases. Therefore, tumor cells mainly rely on the G2-M checkpoint to halt the cell cycle in order to repair DNA damage. Here, we review the promising method of cell cycle-mediated synthetic lethality for melanoma treatment, which entails exploiting somatically acquired mutations in the G1-S transition with inhibitors of the G2-M transition in order to specifically kill melanoma cells. The idea stems from the theory that melanoma cells lacking G1-S checkpoints are particularly vulnerable to mitotic catastrophe when presented with G2-M checkpoint inhibition in addition to DNA damage, whereas normal cells with intact G1-S checkpoints should theoretically be spared. This review explores the link between cell cycle dysregulation and synthetic lethality in melanoma cells and discusses potential future applications for this treatment.

Clinical Identification of Dysregulated Circulating microRNAs and Their Implication in Drug Response in Triple Negative Breast Cancer (TNBC) by Target Gene Network and Meta-Analysis

Resistance to therapy is a persistent problem that leads to mortality in breast cancer, particularly triple-negative breast cancer (TNBC). MiRNAs have become a focus of investigation as tissue-specific regulators of gene networks related to drug resistance. Circulating miRNAs are readily accessible non-invasive potential biomarkers for TNBC diagnosis, prognosis, and drug-response. Our aim was to use systems biology, meta-analysis, and network approaches to delineate the drug resistance pathways and clinical outcomes associated with circulating miRNAs in TNBC patients. MiRNA expression analysis was used to investigate differentially regulated circulating miRNAs in TNBC patients, and integrated pathway regulation, gene ontology, and pharmacogenomic network analyses were used to identify target genes, miRNAs, and drug interaction networks. Herein, we identified significant differentially expressed circulating miRNAs in TNBC patients (miR-19a/b-3p, miR-25-3p, miR-22-3p, miR-210-3p, miR-93-5p, and miR-199a-3p) that regulate several molecular pathways (PAM (PI3K/Akt/mTOR), HIF-1, TNF, FoxO, Wnt, and JAK/STAT, PD-1/PD-L1 pathways and EGFR tyrosine kinase inhibitor resistance (TKIs)) involved in drug resistance. Through meta-analysis, we demonstrated an association of upregulated miR-93, miR-210, miR-19a, and miR-19b with poor overall survival outcomes in TNBC patients. These results identify miRNA-regulated mechanisms of drug resistance and potential targets for combination with chemotherapy to overcome drug resistance in TNBC. We demonstrate that integrated analysis of multi-dimensional data can unravel mechanisms of drug-resistance related to circulating miRNAs, particularly in TNBC. These circulating miRNAs may be useful as markers of drug response and resistance in the guidance of personalized medicine for TNBC.

Determination of CHK1 Cellular Localization by Immunofluorescence Microscopy

Many proteins involved in the DNA damage pathway shuttle between the cytoplasm and nucleus, and their localizations are important for functions. In that regard, immunofluorescence microscopy has been widely used to delineate the temporal and spatial regulation of proteins. Here, we describe an unconventional method for studying the cellular localization of CHK1, a cell cycle checkpoint kinase that undergoes shuttling from the cytoplasm to the nucleus in response to genotoxic stress. In this study, we included an acid extraction step to better reveal the nuclear localization of CHK1.

STAU2 protein level is controlled by caspases and the CHK1 pathway and regulates cell cycle progression in the non-transformed hTERT-RPE1 cells

Background

Staufen2 (STAU2) is an RNA binding protein involved in the posttranscriptional regulation of gene expression. In neurons, STAU2 is required to maintain the balance between differentiation and proliferation of neural stem cells through asymmetric cell division. However, the importance of controlling STAU2 expression for cell cycle progression is not clear in non-neuronal dividing cells. We recently showed that STAU2 transcription is inhibited in response to DNA-damage due to E2F1 displacement from the STAU2 gene promoter. We now study the regulation of STAU2 steady-state levels in unstressed cells and its consequence for cell proliferation.

Results

CRISPR/Cas9-mediated and RNAi-dependent STAU2 depletion in the non-transformed hTERT-RPE1 cells both facilitate cell proliferation suggesting that STAU2 expression influences pathway(s) linked to cell cycle controls. Such effects are not observed in the CRISPR STAU2-KO cancer HCT116 cells nor in the STAU2-RNAi-depleted HeLa cells. Interestingly, a physiological decrease in the steady-state level of STAU2 is controlled by caspases. This effect of peptidases is counterbalanced by the activity of the CHK1 pathway suggesting that STAU2 partial degradation/stabilization fines tune cell cycle progression in unstressed cells. A large-scale proteomic analysis using STAU2/biotinylase fusion protein identifies known STAU2 interactors involved in RNA translation, localization, splicing, or decay confirming the role of STAU2 in the posttranscriptional regulation of gene expression. In addition, several proteins found in the nucleolus, including proteins of the ribosome biogenesis pathway and of the DNA damage response, are found in close proximity to STAU2. Strikingly, many of these proteins are linked to the kinase CHK1 pathway, reinforcing the link between STAU2 functions and the CHK1 pathway. Indeed, inhibition of the CHK1 pathway for 4 h dissociates STAU2 from proteins involved in translation and RNA metabolism.

Conclusions

These results indicate that STAU2 is involved in pathway(s) that control(s) cell proliferation, likely via mechanisms of posttranscriptional regulation, ribonucleoprotein complex assembly, genome integrity and/or checkpoint controls. The mechanism by which STAU2 regulates cell growth likely involves caspases and the kinase CHK1 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00352-y.

Role of deubiquitinating enzymes in DNA double-strand break repair

DNA is the hereditary material in humans and almost all other organisms. It is essential for maintaining accurate transmission of genetic information. In the life cycle, DNA replication, cell division, or genome damage, including that caused by endogenous and exogenous agents, may cause DNA aberrations. Of all forms of DNA damage, DNA double-strand breaks (DSBs) are the most serious. If the repair function is defective, DNA damage may cause gene mutation, genome instability, and cell chromosome loss, which in turn can even lead to tumorigenesis. DNA damage can be repaired through multiple mechanisms. Homologous recombination (HR) and non-homologous end joining (NHEJ) are the two main repair mechanisms for DNA DSBs. Increasing amounts of evidence reveal that protein modifications play an essential role in DNA damage repair. Protein deubiquitination is a vital post-translational modification which removes ubiquitin molecules or polyubiquitinated chains from substrates in order to reverse the ubiquitination reaction. This review discusses the role of deubiquitinating enzymes (DUBs) in repairing DNA DSBs. Exploring the molecular mechanisms of DUB regulation in DSB repair will provide new insights to combat human diseases and develop novel therapeutic approaches.

The Role of Cell Cycle Regulators in Cell Survival-Dual Functions of Cyclin-Dependent Kinase 20 and p21Cip1/Waf1

The mammalian cell cycle is important in controlling normal cell proliferation and the development of various diseases. Cell cycle checkpoints are well regulated by both activators and inhibitors to avoid cell growth disorder and cancerogenesis. Cyclin dependent kinase 20 (CDK20) and p21^Cip1/Waf1 are widely recognized as key regulators of cell cycle checkpoints controlling cell proliferation/growth and involving in developing multiple cancers. Emerging evidence demonstrates that these two cell cycle regulators also play an essential role in promoting cell survival independent of the cell cycle, particularly in those cells with a limited capability of proliferation, such as cardiomyocytes. These findings bring new insights into understanding cytoprotection in these tissues. Here, we summarize the new progress of the studies on these two molecules in regulating cell cycle/growth, and their new roles in cell survival by inhibiting various cell death mechanisms. We also outline their potential implications in cancerogenesis and protection in heart diseases. This information renews the knowledge in molecular natures and cellular functions of these regulators, leading to a better understanding of the pathogenesis of the associated diseases and the discovery of new therapeutic strategies.

Angiotensin inhibition and cellular senescence in the developing rat kidney

Cellular senescence is important for the maintenance of tissue homeostasis during normal development. In this study, we aimed to investigate the effect of renin angiotensin system (RAS) blockade on renal cell senescence in the developing rat kidney. Newborn rat pups were treated with enalapril (30 mg/kg/day) or vehicle for seven days after birth. We investigated the intrarenal expressions of cell cycle regulators p21 and p16 with immunoblots and immunohistochemistry at postnatal day 8. For the determination of renal cellular senescence, immunostaining for senescence-associated β-galactosidase (SA-β-gal) and telomerase reverse transcriptase (TERT) was also performed. Enalapril treatment showed significant alterations in cellular senescence in neonatal rat kidneys. In the enalapril-treated group, intrarenal p16 and p21 protein expressions decreased compared to controls. The expressions of both p21 and p16 were reduced throughout the renal cortex and medulla of enalapril-treated rats. The immunoreactivity of TERT in enalapril-treated kidneys was also weaker than that in control kidneys. Control kidneys revealed a clear positive SA-β-gal signal in the cortical tubules; however, SA-β-gal activity was noticeably lower in the enalapril-treated kidneys than in control kidneys. Interruption of the RAS during postnatal nephrogenesis may disrupt physiologic renal cellular senescence in the developing rat kidney.

Prenatal particulate air pollution exposure and expression of the miR-17/92 cluster in cord blood: Findings from the ENVIRONAGE birth cohort

BACKGROUND

Air pollution exposure during pregnancy is an important environmental health issue. Epigenetics mediate the effects of prenatal exposure and could increase disease predisposition in later life. The oncogenic miR-17/92 cluster is involved in normal development and disease.

OBJECTIVES

Here, for the first time the potential prenatal effects of particulate matter with a diameter<2.5 μm (PM_2.5) exposure on expression of the miR-17/92 cluster in cord blood are explored.

METHODS

In 370 mother-newborn pairs from the ENVIRONAGE birth cohort, expression of three members of the miR-17/92 cluster was measured in cord blood by qRT-PCR. Expression of C-MYC and CDKN1A, a cluster activator and a target gene, respectively, was also analyzed. Multivariable linear regression models were used to associate the relative m(i)RNA expression with prenatal PM_2.5 exposure.

RESULTS

PM_2.5 exposure averaged (10^th-90^th percentile) 11.7 (9.0-14.4) µg/m³ over the entire pregnancy. In cord blood, miR-17 and miR-20a showed a -45.0% (95%CI: -55.9 to -31.4, p < 0.0001) and a -33.7% (95%CI: -46.9 to -17.2, p = 0.0003), decrease in expression in association with first trimester PM_2.5 exposure, and a -32.5% (95%CI: -45.6 to -16.3, p = 0.0004) and -23.3% (95%CI: -38.1 to -4.8, p = 0.02), respectively, decrease in expression in association with PM_2.5 exposure during the entire pregnancy. In association with third trimester PM_2.5 exposure, a reduction of -25.8% (95%CI: -40.2 to -8.0, p = 0.007) and -14.2% (95%CI: -27.7 to 1.9, p = 0.08), for miR-20a and miR-92a expression, respectively, was identified. Only miR-92a expression (-15.7%, 95%CI: -27.3 to -2.4, p = 0.02) was associated with PM_2.5 exposure during the last month of pregnancy. C-MYC expression was downregulated in cord blood in association with prenatal PM_2.5 exposure during the first trimester and the entire pregnancy, in the adjusted model.

DISCUSSION

Lower expression levels of the miR-17/92 cluster in cord blood in association with increased prenatal PM_2.5 exposure were observed. Whether this oncogenic microRNA cluster plays a role in trans-placental carcinogenesis remains to be elucidated.

A Review on the Biocompatibility of PMMA-Based Dental Materials for Interim Prosthetic Restorations with a Glimpse into their Modern Manufacturing Techniques

This paper's primary aim is to outline relevant aspects regarding the biocompatibility of PMMA (poly(methyl methacrylate))-based materials used for obtaining interim prosthetic restorations, such as the interaction with oral epithelial cells, fibroblasts or dental pulp cells, the salivary oxidative stress response, and monomer release. Additionally, the oral environment's biochemical response to modern interim dental materials containing PMMA (obtained via subtractive or additive methods) is highlighted in this review. The studies included in this paper confirmed that PMMA-based materials interact in a complex way with the oral environment, and therefore, different concerns about the possible adverse oral effects caused by these materials were analyzed. Adjacent to these aspects, the present work describes several advantages of PMMA-based dental materials. Moreover, the paper underlines that recent scientific studies ascertain that the modern techniques used for obtaining interim prosthetic materials, milled PMMA, and 3D (three-dimensional) printed resins, have distinctive advantages compared to the conventional ones. However, considering the limited number of studies focusing on the chemical composition and biocompatibility of these modern interim prosthetic materials, especially for the 3D printed ones, more aspects regarding their interaction with the oral environment need to be further investigated.

Emerging use of senolytics and senomorphics against aging and chronic diseases

Senescence is a state of cell cycle arrest that plays an important role in embryogenesis, wound healing and protection against cancer. Senescent cells also accumulate during aging and contribute to the development of age-related disorders and chronic diseases, such as atherosclerosis, type 2 diabetes, osteoarthritis, idiopathic pulmonary fibrosis, and liver disease. Molecules that induce apoptosis of senescent cells, such as dasatinib, quercetin, and fisetin, produce health benefits and extend lifespan in animal models. We describe here the mechanism of action of senolytics and senomorphics, many of which are derived from plants and fungi. We also discuss the possibility of using such compounds to delay aging and treat chronic diseases in humans.

Opposing p53 and mTOR/AKT promote an in vivo switch from apoptosis to senescence upon telomere shortening in zebrafish

Progressive telomere shortening during lifespan is associated with restriction of cell proliferation, genome instability and aging. Apoptosis and senescence are the two major outcomes upon irreversible cellular damage. Here, we show a transition of these two cell fates during aging of telomerase deficient zebrafish. In young telomerase mutants, proliferative tissues exhibit DNA damage and p53-dependent apoptosis, but no senescence. However, these tissues in older animals display loss of cellularity and senescence becomes predominant. Tissue alterations are accompanied by a pro-proliferative stimulus mediated by AKT signaling. Upon AKT activation, FoxO transcription factors are phosphorylated and translocated out of the nucleus. This results in reduced SOD2 expression causing an increase of ROS and mitochondrial dysfunction. These alterations induce p15/16 growth arrest and senescence. We propose that, upon telomere shortening, early apoptosis leads to cell depletion and insufficient compensatory proliferation. Following tissue damage, the mTOR/AKT is activated causing mitochondrial dysfunction and p15/16-dependent senescence.

Krüppel-Like Factor 6 Is Required for Oxidative and Oncogene-Induced Cellular Senescence

Krüppel-like factor 6 (KLF6) is a transcription factor involved in the regulation of several cellular processes. Regarding its role in tumorigenesis, KLF6 is considered a tumor suppressor. Numerous reports demonstrate its frequent genomic loss or down-regulation, implying a functional inactivation in a broad range of human cancers. Previous work from our laboratory showed that the down-regulation of KLF6 expression in normal fibroblasts leads to cellular transformation, while its ectopic expression interferes with the oncogenic transformation triggered by activated Ras through a cell cycle arrest. We hypothesize that the growth suppressor activity of KLF6 may involve the induction of cellular senescence thereby helping to prevent the proliferation of cells at risk of neoplastic transformation. Here, we explored the association of KLF6 up-regulation in two different cellular senescence scenarios. We found that KLF6 silencing bypasses both oxidative and oncogene-induced senescence. In this context, KLF6 expression per se was capable to trigger cellular senescence in both normal and tumoral contexts. As such, the findings presented in this report provide insights into a potential mechanism by which KLF6 may play a suppressing role of uncontrolled or damaged cell proliferation.

BZD9L1 sirtuin inhibitor as a potential adjuvant for sensitization of colorectal cancer cells to 5-fluorouracil

Background:

This study aims to investigate the combination effect of a novel sirtuin inhibitor (BZD9L1) with 5-fluorouracil (5-FU) and to determine its molecular mechanism of action in colorectal cancer (CRC).

Methods:

BZD9L1 and 5-FU either as single treatment or in combination were tested against CRC cells to evaluate synergism in cytotoxicity, senescence and formation of micronucleus, cell cycle and apoptosis, as well as the regulation of related molecular players. The effects of combined treatments at different doses on stress and apoptosis, migration, invasion and cell death mechanism were evaluated through two-dimensional and three-dimensional cultures. In vivo studies include investigation on the combination effects of BZD9L1 and 5-FU on colorectal tumour xenograft growth and an evaluation of tumour proliferation and apoptosis using immunohistochemistry.

Results:

Combination treatments exerted synergistic reduction on cell viability on HCT 116 cells but not on HT-29 cells. Combined treatments reduced survival, induced cell cycle arrest, apoptosis, senescence and micronucleation in HCT 116 cells through modulation of multiple responsible molecular players and apoptosis pathways, with no effect in epithelial mesenchymal transition (EMT). Combination treatments regulated SIRT1 and SIRT2 protein expression levels differently and changed SIRT2 protein localization. Combined treatment reduced growth, migration, invasion and viability of HCT 116 spheroids through apoptosis, when compared with the single treatment. In addition, combined treatment was found to reduce tumour growth in vivo through reduction of tumour proliferation and necrosis compared with the vehicle control group. This highlights the potential therapeutic effects of BZD9L1 and 5-FU towards CRC.

Conclusion:

This study may pave the way for use of BZD9L1 as an adjuvant to 5-FU in improving the therapeutic efficacy for the treatment of colorectal cancer.

N-Acetyl Cysteine as a Novel Polymethyl Methacrylate Resin Component: Protection against Cell Apoptosis and Genotoxicity

The present study investigated the antiapoptotic and antigenotoxic capabilities of N-acetyl cysteine- (NAC-) containing polymethyl methacrylate (PMMA) resin. An in vitro Transwell insert model was used to mimic the clinical provisional restorations placed on vital teeth. Various parameters associated with cell apoptosis and genotoxicity were investigated to obtain a deeper insight into the underlying mechanisms. The exposure of human dental pulp cell (hDPC) cultures to the PMMA resin (Unifast Trad™) resulted in a rapid increase in reactive oxygen species (ROS) level beginning at 1 h, which was followed by time-dependent cell detachment and overt death. The formation of γ-H2AX and cell cycle G1 phase arrest indicated that oxidative DNA damage occurred as a result of the interactions between DNA bases and ROS, beyond the capacities of cellular redox regulation. Such oxidative DNA damage triggers the activation of p53 via the ataxia telangiectasia mutated (ATM) signaling pathway and the induction of intrinsic mitochondrial apoptosis. Oxidative stress, cell apoptosis, and DNA damage induced by the PMMA resin were recovered to almost the level of untreated controls by the incorporation of NAC. The results indicate that the PMMA resin induced the intrinsic mitochondrial apoptosis as a consequence of p53 activation via the ATM pathway in response to oxidative DNA damage. More importantly, the incorporation of NAC as a novel component into the Unifast Trad™ PMMA resin offers protective effects against cell apoptosis and genotoxicity. This procedure represents a beneficial strategy for developing more biocompatible PMMA-based resin materials.

FoxO transcription factors 1 regulate mouse preimplantation embryo development

PURPOSE

The aim of the present study is to investigate role of FoxO transcription factors in preimplantation embryo development by knocking down FoxO1, FoxO3, and FoxO4 genes and also to assess cell cycle arrest related proteins, p53 and p21, and apoptosis-related proteins, fas ligand (FASL), and cleaved caspase 3.

METHODS

Knockdown of FoxOs using siRNA was confirmed utilizing RT-PCR and qRT-PCR in gene level and using immunofluorescence in protein level. Following knockdown of FoxO1, FoxO3, and FoxO4 in two-cell mouse embryos with or without resveratrol treatment; developmental competence of embryos and expression patterns of SIRT1, p53, p21, FASL, and CLEAVED CASPASE 3 proteins in embryos by immunofluorescence were assessed after 48 h. ROS levels were measured in knockdown embryos. Terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to determine resveratrol dose.

RESULTS

Successful knockdown of FoxO genes in mouse embryos utilizing a non-invasive siRNA method was achieved. Significantly, knockdown of FoxO genes impaired preimplantation embryo development which cannot be prevented by resveratrol treatment. Immunofluorescence results showed that resveratrol could protect embryos from cell cycle arrest and apoptosis. FOXO proteins regulate apoptosis and cell cycle related proteins in mouse preimplantation embryos. Moreover, there might be an autofeedback mechanism where FOXO1, FOXO3, and FOXO4 regulate SIRT1 protein expression.

CONCLUSIONS

These results suggest that FOXO transcription factors could contribute to mouse preimplantation embryo development, and it remains to investigate whether they have crucial roles in human preimplantation embryo and infertility.

Comprehensive analysis of gene expression and DNA methylation for human nasopharyngeal carcinoma

PURPOSE

Nasopharyngeal carcinoma (NPC) is one of the most malignant head and neck carcinomas with unique epidemiological features. In this study, we aimed to identify the novel NPC-related genes and biological pathways, shedding light on the potential molecular mechanisms of NPC.

METHODS

Based on Gene Expression Omnibus (GEO) database, an integrated analysis of microarrays studies was performed to identify differentially expressed genes (DEGs) and differentially methylated genes (DMGs) in NPC compared to normal control. The genes which were both differentially expressed and differentially methylated were identified. Functional annotation and protein-protein interaction (PPI) network construction were used to uncover biological functions of DEGs.

RESULTS

Two DNA methylation and five gene expression datasets were incorporated. A total of 1074 genes were up-regulated and 939 genes were down-regulated in NPC were identified. A total of 719 differential methylation CpG sites (DMCs) including 1 hypermethylated sites and 718 hypomethylated sites were identified. Among which, 11 genes were both DEGs and DMGs in NPC. Pathways in cancer, p53 signaling pathway and Epstein-Barr virus infection were three pathways significantly enriched pathways in DEmRNAs of NPC. The PPI network of top 50 DEGs were consisted of 191 nodes and 191 edges.

CONCLUSIONS

Our study was helpful to elucidate the underlying mechanism of NPC and provide clues for therapeutic methods.

Cellular senescence in cardiac diseases

Replicative capacity of somatic cells is limited. It indicates that aging also develops at the cellular level, and this is described as "cellular senescence". Senescent cells become flattened, enlarged, and irreversibly lose capacity for proliferation. Lack of specific and conclusive markers for cellular senescence makes it difficult to comprehensively define and understand this biological process especially in vivo. Molecules including p53, p21, p16^Ink4a, p38MAPK, and γH2AX, telomere attrition, enhanced signals for SA-β-gal, etc. are widely used to detect senescent cells, but these are indirect indicators of cellular senescence, and biological markers reflecting direct evidence need to be established. Genetic profiles are altered in senescent cells, letting these cells secrete pro-inflammatory molecules. Aging or age-related disorders including heart failure and atherosclerotic diseases link with an accumulation of cells undergoing cellular senescence in cardiovascular systems including heart and vessels. Senescent cells become pathogenic in most cases by mediating chronic sterile inflammation and tissue remodeling. A recent conceptual as well as technical breakthrough in this research area is "senolysis", meaning the specific elimination of senescent cells. Genetic as well as pharmacological models with senolysis contributed to reverse aging phenotypes and ameliorated pathologies in age-related disorders without enhancing the risk of tumorigenesis, and opened a new avenue for aging research. Several compounds are identified as senolytics, and some are already tested in clinical settings. It was recently reported that senolysis reverses aging phenotype in cardiovascular disorders. Generating therapies targeting suppression or elimination of senescent cells would inhibit the progression of undesirable aspects of aging, and become promising therapies for cardiac diseases.

The human amniotic fluid mesenchymal stem cells therapy on, SKOV3, ovarian cancer cell line

Purpose

One of the most common malignancies peculiar to female health with few symptoms, low response to therapy, difficult diagnosis, frequent relapse, and high mortality, is ovarian cancer. Thus, our experiment, using Human amniotic fluid mesenchymal stem cells (hAFMSCs) as a therapeutic tool, aims to find an efficient treatment approach for patients suffering from SKOV3 ovarian cancer.

Material & Methods

In this study, we obtained 5 ml amniotic fluid from 16–20 week pregnant women who underwent amniocentesis for routine prenatal diagnosis by karyotyping in Al‐Zahra Hospital of Tabriz University of Medical Sciences, Iran. Using trans wells in 24 wells plate, hAFMSCs were isolated from all samples, co‐cultured with SKOV3 ovarian cancer cell line, and characterized via flow cytometry and RT‐PCR. Human skin fibroblast cells (HSFCs) were isolated and used as a negative control. SKOV3 and HSFCs' viability after 5 days was evaluated by MTT assay. Cell cycle and apoptotic genes were analyzed by real‐time PCR.

Results

We successfully isolated and characterized hAFMSCs through it positivity for CD44 and CD90 specific mesenchymal stem cell markers and negativity for CD31 and CD45. Oct4 and NANOG were evaluated by RT‐PCR as pluripotency markers, and visualized on 2% gel electrophoresis. We established hAFMS cell lines after 5 days of co‐culturing the SKOV3 cells, viability was decreased; however, HSFCs did not show toxicity by MTT assay. The genes indicated upregulation and high expression by a real‐time PCR.

Conclusions

Our findings showed that hAFMSCs have natural tumor tropism, and can release soluble factors in a cell culture, which cause an efficient anticancer effect. Thus, we can use hAFMSCs for complete anticancer therapy on SKOV3 cell line at cell culture condition and possibly in vivo in the near future.

Mast cell chymase in synovial fluid of collagen-induced-arthritis rats regulates gelatinase release and promotes synovial fibroblasts proliferation via FAK/p21 signaling pathway

Mast cells (MCs) were accumulated in synovial tissue of rheumatoid arthritis (RA) patients. MC activation releases numerous mediators including MC-chymase. Synovial fibroblast shows a dramatic hyperplasia in RA articular cavity, but the effects of MC-chymase on synovial fibroblast are unknown. In this study, the collagen-induced-arthritis (CIA) rat model was employed to evaluate the dynamic changes of MC-chymase activity and other inflammatory factors during CIA development in-vivo. The fresh primary synovial fibroblasts from normal or CIA rats were extracted to compare the differences of these two cell-types, and to investigate the effects of MC-chymase on both-types of synovial fibroblast. The data showed that the dynamic changes in chymase activity in synovial fluids of CIA rats before and after immunizations were companied with the changes of tryptase, MMP-2/-9, TNF-α, IL-6, Co-II IgG, total protein, paw-thickness and body weight in-vivo. The baseline differences in cell grow rates, expression levels of p21, FAK, MMP-9 between normal and CIA-SFB have been seen. Compared to the normal synovial fibroblasts, CIA-SFB increased the percentage of the cells transferred to S or G2/M phases in cell cycle in-vivo; CIA-SFB become more proliferative with high-expression MMP-2/9 during CIA development. MC-chymase in-vitro promoted both types of synovial fibroblast proliferation and induced cell cycle changes, but CIA-synovial fibroblasts exhibited much stronger responses to MC-chymase stimulation by increased expression levels of p21, FAK, MMP-9 which associated with cell adhesion and migration. This study might give a new insight that the activated mast cell can be an important target cell for RA treatment and suggest that MC-chymase needs well attention for therapeutic aims.

lncRNA small nucleolar RNA host gene 20 predicts poor prognosis in glioma and promotes cell proliferation by silencing P21

Background

In multiple cancers, long non-coding RNA small nucleolar RNA host gene 20 (lncRNA SNHG20) is generally dysregulated. In the present study, both the biological role and clinicopathological value of lncRNA SNHG20 in glioma are explored.

Methods

Real-time PCR was employed to determine lncRNA SNHG20 expression in glioma patients. The prognostic role of expression of lncRNA SNHG20 was evaluated in a retrospective cohort study. In addition, the association between lncRNA SNHG20 expression and the clinicopathological features of glioma patients, such as tumor recurrence, survival status, follow-up time, WHO grade, resection extent, tumor location, Karnofsky performance scale score, cystic change, tumor size, gender and age, was discussed. By constructing and transfecting siRNAs that targeted lncRNA SNHG20 into the glioma U87 cells, the effects of lncRNA SNHG20 on the proliferation and cell cycle of U87 cells were assessed through cell counting kit-8, colony formation and cell cycle assays, respectively. In addition, Western blot and real-time PCR measured the expression levels of P21 and CCNA1 in U87 cells after being transfected with SNHG20 siRNA.

Results

Our results suggested the high expression of lncRNA SNHG20 in human glioma tissues compared with normal brain tissues, which was related to recurrence-free survival and poor overall survival in glioma patients. According to the existing retrospective cohort study, high lncRNA SNHG20 expression was associated with tumor size, extent of resection, WHO grade, follow-up time, survival status and recurrence. Besides, knocking down the expression of lncRNA SNHG20 could inhibit the proliferation and colony formation abilities of glioma U87 cells through cell cycle arrest. Consequently, the expression of CCNA1 was inhibited, and the expression of P21 was up-regulated in U87 cells.

Conclusion

A high lncRNA SNHG20 expression level predicts the poor prognosis for glioma patients. Moreover, lncRNA SNHG20 can promote glioma proliferation through silencing P21 and thus lncRNA SNHG20 is an independent potential prognostic biomarker for glioma patients.

In vivo miRNA delivery in whitefish: Synthetic MiR92b-3p uptake and the efficacy of gene expression silencing

IMPACT STATEMENT

The delivery of short snippets of RNA, such as synthetic miRNA agents, is an essential step for achieving RNA-mediated knockdown, which has not been studied in sufficient detail in fish. Our results indicate that a MiR92b-3p mimic may be effectively delivered via intraperitoneal injection to the spleen and the liver of whitefish, and that it likely achieves functionality without causing any apparent toxic effects in the challenged animals. We report the novel finding that the MiR92b-3p mimic reduced the in vivo liver mRNA expression levels of its putative pro-apoptotic targets (p53, cdkn1a, and pcna), and important metabolic genes, e.g. cdo1. This shows that this methodology of MiR92b-3p mimic transfection in vivo may be a useful tool for studies that investigate the molecular pathways that confer pro-proliferative and anti-apoptotic phenotypes or those that regulate intracellular metabolism in fish and other vertebrates.

Anticancer evaluation and molecular modeling of multi-targeted kinase inhibitors based pyrido[2,3-d]pyrimidine scaffold

An efficient synthesis of substituted pyrido[2,3-d]pyrimidines was carried out and evaluated for in vitro anticancer activity against five cancer cell lines, namely hepatic cancer (HepG-2), prostate cancer (PC-3), colon cancer (HCT-116), breast cancer (MCF-7), and lung cancer (A-549) cell lines. Regarding HepG-2, PC-3, HCT-116 cancer cell lines, 7-(4-chlorophenyl)-2-(3-methyl-5-oxo-2,3-dihydro-1H-pyrazol-1-yl)-5-(p-tolyl)- pyrido[2,3-d]pyrimidin-4(3H)-one (5a) exhibited strong, more potent anticancer (IC50: 0.3, 6.6 and 7 µM) relative to the standard doxorubicin (IC50: 0.6, 6.8 and 12.8 µM), respectively. Kinase inhibitory assessment of 5a showed promising inhibitory activity against three kinases namely PDGFR β, EGFR, and CDK4/cyclin D1 at two concentrations 50 and 100 µM in single measurements. Further, a molecular docking study for compound 5a was performed to verify the binding mode towards the EGFR and CDK4/cyclin D1 kinases.

Various stress stimuli rewire the profile of liver secretome in a p53-dependent manner

Liver is an important secretory organ that consistently manages various insults in order to retain whole-body homeostasis. Importantly, it was suggested that the tumor-suppressor p53 plays a role in a variety of liver physiological processes and thus it is being regarded as a systemic homeostasis regulator. Using high-throughput mass spectrometric analysis, we identified various p53-dependent liver secretome profiles. This allowed a global view on the role of p53 in maintaining the harmony of liver and whole-body homeostasis. We found that p53 altered the liver secretome differently under various conditions. Under physiological conditions, p53 controls factors that are related mainly to lipid metabolism and injury response. Upon exposure to various types of cancer therapy agents, the hepatic p53 is activated and induces the secretion of proteins related to additional pathways, such as hemostasis, immune response, and cell adhesion. Interestingly, we identified a possible relationship between p53-dependent liver functions and lung tumors. The latter modify differently liver secretome profile toward the secretion of proteins mainly related to cell migration and immune response. The notion that p53 may rewire the liver secretome profile suggests a new non-cell autonomous role of p53 that affect different liver functions and whole organism homeostasis.

Deubiquitinating enzyme USP3 controls CHK1 chromatin association and activation

Checkpoint kinase 1 (CHK1), a Ser/Thr protein kinase, is modified by the K63-linked ubiquitin chain in response to genotoxic stress, which promotes its nuclear localization, chromatin association, and activation. Interestingly, this bulky modification is linked to a critical residue, K132, at the kinase active site. It is unclear how this modification affects the kinase activity and how it is removed to enable the release of CHK1 from chromatin. Herein, we show that the K63-linked ubiquitin chain at CHK1's K132 residue has an inhibitory effect on the kinase activity. Furthermore, we demonstrate that this modification can be removed by ubiquitin-specific protease 3 (USP3), a deubiquitinating enzyme that targets K63-linked ubiquitin chains. Wild-type USP3, but not the catalytically defective or nuclear localization sequence-deficient mutants, reduced CHK1 K63-linked ubiquitination. Conversely, USP3 knockdown elevated K63-linked ubiquitination of the kinase, leading to prolonged CHK1 chromatin association and phosphorylation. Paradoxically, by removing the bulky ubiquitin chain at the active site, USP3 also increased the accessibility of CHK1 to its substrates. Thus, our findings on the dual roles of USP3 (namely, one to release CHK1 from the chromatin and the other to open up the active site) provide further insights into the regulation of CHK1 following DNA damage.

Chk1 inhibition significantly potentiates activity of nucleoside analogs in TP53-mutated B-lymphoid cells

Treatment options for TP53-mutated lymphoid tumors are very limited. In experimental models, TP53-mutated lymphomas were sensitive to direct inhibition of checkpoint kinase 1 (Chk1), a pivotal regulator of replication. We initially tested the potential of the highly specific Chk1 inhibitor SCH900776 to synergize with nucleoside analogs (NAs) fludarabine, cytarabine and gemcitabine in cell lines derived from B-cell malignancies. In p53-proficient NALM-6 cells, SCH900776 added to NAs enhanced signaling towards Chk1 (pSer317/pSer345), effectively blocked Chk1 activation (Ser296 autophosphorylation), increased replication stress (p53 and γ-H2AX accumulation) and temporarily potentiated apoptosis. In p53-defective MEC-1 cell line representing adverse chronic lymphocytic leukemia (CLL), Chk1 inhibition together with NAs led to enhanced and sustained replication stress and significantly potentiated apoptosis. Altogether, among 17 tested cell lines SCH900776 sensitized four of them to all three NAs. Focusing further on MEC-1 and co-treatment of SCH900776 with fludarabine, we disclosed chromosome pulverization in cells undergoing aberrant mitoses. SCH900776 also increased the effect of fludarabine in a proportion of primary CLL samples treated with pro-proliferative stimuli, including those with TP53 disruption. Finally, we observed a fludarabine potentiation by SCH900776 in a T-cell leukemia 1 (TCL1)-driven mouse model of CLL. Collectively, we have substantiated the significant potential of Chk1 inhibition in B-lymphoid cells.

PTTG1 regulated by miR-146a-3p promotes bladder cancer migration, invasion, metastasis and growth

Pituitary tumor-transforming gene 1 (PTTG1) is identified as an oncogene, and overexpresses in many tumors. However, the role of PTTG1 in bladder cancer (BC) hasn't yet been characterized well. In this study, we showed the expression of PTTG1 mRNA and protein were both significantly increased in BC tissues and cells. The PTTG1 protein levels were positive correlated with increased tumor size, tumor–node–metastasis (TNM) stage, lymphatic invasion and distant metastasis of BC. PTTG1 knockdown dramatically suppressed the migration, invasion, metastasis and growth, and induced senescence and cell-cycle arrest at G0/G1 phase of BC cells. We further identified PTTG1 was the direct target of miR-146a-3p through using target prediction algorithms and luciferase reporter assay. miR-146a-3p was low expressed and negatively correlated with PTTG1 levels in BC tissues and cells. miR-146a-3p overexpression inhibited migration, invasion, metastasis and growth, and induced senescence of BC cells. Rescue experiment suggested ectopic expression of miR-146a-3p and PTTG1 suppressed migration, invasion and induced cell cycle arrest and senescence of BC cells compared to PTTG1 overexpression, confirming miR-146a-3p inhibited BC progression by targeting PTTG1. In summary, our study found miR-146a-3p/PTTG1 axis regulated BC migration, invasion, metastasis and growth, and might be a targets for BC therapy.

Stimulatory effect of icariin on the proliferation of neural stem cells from rat hippocampus

Background

Icariin (ICA), a major ingredient of Epimediumbrevicornum, has various pharmacological activities including central nervous system protective functions such as the improvement of learning and memory function in mice models of Alzheimer’s disease. It has been reported that ICA can promote regeneration of peripheral nerve and functional recovery. The purpose of this study was to investigate the potentiating effect of ICA on the proliferation of rat hippocampal neural stem cells, and explore the possible mechanism involved.

Methods

Primary neural stem cells were prepared from the hippocampus of newly born SD rats, and cells were cultured in special stem cell culture medium. Neural stem cells were confirmed by immunofluorescence detection of nestin, NSE and GFAP expression. The effect of ICA on the growth and proliferation of the neural stem cells was evaluated by 5-ethynyl-2-deoxyuridine (EdU) labeling of proliferating cells, and photomicrographic images of the cultured neural stem cells. Further, the mechanism of ICA-induced cell proliferation of neural stem cells was investigated by analyzing the gene and protein expression of cell cycle related genes cyclin D1 and p21.

Results

The present study showed that icariin promotes the growth and proliferation of neural stem cells from rat hippocampus in a dose-dependent manner. Incubation of cells with icariin resulted in significant increase in the number of stem cell spheres as well as the increased incorporation of EdU when compared with cells exposed to control vehicle. In addition, it was found that icariin-induced effect on neural stem cells is associated with increased mRNA and protein expression of cell cycle genes cyclin D1 and p21.

Conclusions

This study evidently demonstrates the potentiating effect of ICA on neural stem cell growth and proliferation, which might be mediated through regulation of cell cycle gene and protein expression promoting cell cycle progression.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2095-y) contains supplementary material, which is available to authorized users.

A lethal synergy induced by phellinus linteus and camptothecin11 in colon cancer cells

Side effects of anti-cancer drugs are always challenging for effective cancer treatments. The polysaccharides extracted from Phellinus linteus (PLGL) have been widely used in treating cancers. However, the mechanism by which PLGL antagonizes cancerous growth has not been fully investigated. The current study demonstrated that human colon cancer HCT116 and HT29 cells became highly susceptible to cell death when being co-treated with PLGL and low dose of camptothecin11 (CPT11, a topoisomerase inhibitor-based drug), the efficacy of which was comparable as that generated by the high dose of CPT11. However, the co-treatment, unlike high doses of CPT11, was not cytotoxic to the control immortalized colon Caco-2 cells. The co-treatment caused high percentages of the colon cancer cells to accumulate in S phase of the cell cycle, which was also seen in the same cells received the high dose of CPT11 treatment. Chk1 was phosphorylated, and then rapidly degraded in the cancer cells treated with the high dose of CPT11 or co-treatment, but not in the cells treated with PLGL alone or low doses of CPT11. PLGL appeared enhancing CPT11 inhibitory effect on topoisomerase, and Chk1 degradatopm in the cancer cells. Furthermore, cyclin E (clnE) became unstable at the transcription level in co-treated or PLGL-treated colon cancer cells. The data suggested that PLGL functions in two ways to achieve its lethal synergy with CPT11 in colon cancer cells. Our findings are of potential significance as PLGL represents a promising medicine for overcoming the side effects of CPT11 and perhaps also for improving other CPTs-based regimens.

CDKN2A/p16 Deletion in Head and Neck Cancer Cells Is Associated with CDK2 Activation, Replication Stress, and Vulnerability to CHK1 Inhibition

Checkpoint kinase inhibitors (CHKi) exhibit striking single-agent activity in certain tumors, but the mechanisms accounting for hypersensitivity are poorly understood. We screened a panel of 49 established human head and neck squamous cell carcinoma (HNSCC) cell lines and report that nearly 20% are hypersensitive to CHKi monotherapy. Hypersensitive cells underwent early S-phase arrest at drug doses sufficient to inhibit greater than 90% of CHK1 activity. Reduced rate of DNA replication fork progression and chromosomal shattering were also observed, suggesting replication stress as a root causative factor in CHKi hypersensitivity. To explore genomic underpinnings of CHKi hypersensitivity, comparative genomic analysis was performed between hypersensitive cells and cells categorized as least sensitive because they showed drug IC₅₀ value greater than the cell panel median and lacked early S-phase arrest. Novel association between CDKN2A/p16 copy number loss, CDK2 activation, replication stress, and hypersensitivity of HNSCC cells to CHKi monotherapy was found. Restoring p16 in cell lines harboring CDKN2A/p16 genomic deletions alleviated CDK2 activation and replication stress, attenuating CHKi hypersensitivity. Taken together, our results suggest a biomarker-driven strategy for selecting HNSCC patients who may benefit the most from CHKi therapy.Significance: These results suggest a biomarker-driven strategy for selecting HNSCC patients who may benefit the most from therapy with CHK inhibitors. Cancer Res; 78(3); 781-97. ©2017 AACR.

miR-93 enhances cell proliferation by directly targeting CDKN1A in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy of the head and neck with the highest incidence rate in southern China. The aim of the present study was to understand the molecular mechanisms that underlie the progression of NPC. The relative expression of miR-93 and CDKN1A was detected by the reverse-transcription quantitative PCR. Western blot analysis was applied to detect the protein levels of genes. Luciferase activity report was applied to verify the target of miRNA. Cell growth was assayed by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. miR-93 was upregulated in NPC tissues and cell lines compared with normal samples. Re-expression of miR-93 promoted cell growth in vitro as determined by the MTT assay. CDKN1A was identified by luciferase reporter as a direct target of miR-93. Its expression was downregulated by miR-93. Furthermore, the results showed that the expression of miR-93 was inversely correlated with the expression of CDKN1A protein. miR-93 enhanced cell proliferation in NPC by directly targeting CDKN1A. It is suggested that miR-93/CDKN1A axis may present a new target for the treatment of NPC.