Induction of p21 by p53 following DNA damage inhibits both Cdk4 and Cdk2 activities

TRIM47 promotes malignant progression of renal cell carcinoma by degrading P53 through ubiquitination

Background

Renal cell carcinoma (RCC) is one of the most common malignant tumors originating from the renal parenchymal urinary epithelial system. Tripartite motif 47 (TRIM47) is a member of the TRIM family proteins, which has E3 ligase activity and has been demonstrated to be involved in the occurrence and prognosis of many tumors. The main purpose of this study is to explore the role and potential mechanism of TRIM47 in promoting malignant biological behavior of RCC.

Materials and methods

TRIM47 mRNA and protein levels in human renal cancer and paired normal adjacent tissues were detected by qRT-PCR and Western blot. The effects of TRIM47 knockdown and overexpression in renal cell carcinoma cells on cell proliferation, invasion and xenograft tumor growth in nude mice were analyzed. The molecular mechanism was explored by mass spectrometric exploration,Western blot and immunoprecipitation assays.

Results

TRIM47 promoted RCC cell proliferation in vitro and in vivo as an oncogene. Mechanistically, TRIM47 exerted an E3 ligase activity by interacting with P53 protein to increase its ubiquitination and degradation, which further promoted the malignant biological behavior of RCC.

Conclusions

Our study demonstrated that the TRIM47-P53 axis played a functional role in RCC progression and suggested a potential therapeutic target for RCC.

Inhibition of Kpnβ1 mediated nuclear import enhances cisplatin chemosensitivity in cervical cancer

Background

Inhibition of nuclear import via Karyopherin beta 1 (Kpnβ1) shows potential as an anti-cancer approach. This study investigated the use of nuclear import inhibitor, INI-43, in combination with cisplatin.

Methods

Cervical cancer cells were pre-treated with INI-43 before treatment with cisplatin, and MTT cell viability and apoptosis assays performed. Activity and localisation of p53 and NFκB was determined after co-treatment of cells.

Results

Pre-treatment of cervical cancer cells with INI-43 at sublethal concentrations enhanced cisplatin sensitivity, evident through decreased cell viability and enhanced apoptosis. Kpnβ1 knock-down cells similarly displayed increased sensitivity to cisplatin. Combination index determination using the Chou-Talalay method revealed that INI-43 and cisplatin engaged in synergistic interactions. p53 was found to be involved in the cell death response to combination treatment as its inhibition abolished the enhanced cell death observed. INI-43 pre-treatment resulted in moderately stabilized p53 and induced p53 reporter activity, which translated to increased p21 and decreased Mcl-1 upon cisplatin combination treatment. Furthermore, cisplatin treatment led to nuclear import of NFκB, which was diminished upon pre-treatment with INI-43. NFκB reporter activity and expression of NFκB transcriptional targets, cyclin D1, c-Myc and XIAP, showed decreased levels after combination treatment compared to single cisplatin treatment and this associated with enhanced DNA damage.

Conclusions

Taken together, this study shows that INI-43 pre-treatment significantly enhances cisplatin sensitivity in cervical cancer cells, mediated through stabilization of p53 and decreased nuclear import of NFκB. Hence this study suggests the possible synergistic use of nuclear import inhibition and cisplatin to treat cervical cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07819-3.

Hallmarks and detection techniques of cellular senescence and cellular ageing in immune cells

The ageing of the global population brings about unprecedented challenges. Chronic age-related diseases in an increasing number of people represent an enormous burden for health and social care. The immune system deteriorates during ageing and contributes to many of these age-associated diseases due to its pivotal role in pathogen clearance, tissue homeostasis and maintenance. Moreover, in order to develop treatments for COVID-19, we urgently need to acquire more knowledge about the aged immune system, as older adults are disproportionally and more severely affected. Changes with age lead to impaired responses to infections, malignancies and vaccination, and are accompanied by chronic, low-degree inflammation, which together is termed immunosenescence. However, the molecular and cellular mechanisms that underlie immunosenescence, termed immune cell senescence, are mostly unknown. Cellular senescence, characterised by an irreversible cell cycle arrest, is thought to be the cause of tissue and organismal ageing. Thus, better understanding of cellular senescence in immune populations at single-cell level may provide us with insight into how immune cell senescence develops over the life time of an individual. In this review, we will briefly introduce the phenotypic characterisation of aged innate and adaptive immune cells, which also contributes to overall immunosenescence, including subsets and function. Next, we will focus on the different hallmarks of cellular senescence and cellular ageing, and the detection techniques most suitable for immune cells. Applying these techniques will deepen our understanding of immune cell senescence and to discover potential druggable pathways, which can be modulated to reverse immune ageing.

The E3 ubiquitin ligase Cul4b promotes CD4+ T cell expansion by aiding the repair of damaged DNA

The capacity for T cells to become activated and clonally expand during pathogen invasion is pivotal for protective immunity. Our understanding of how T cell receptor (TCR) signaling prepares cells for this rapid expansion remains limited. Here we provide evidence that the E3 ubiquitin ligase Cullin-4b (Cul4b) regulates this process. The abundance of total and neddylated Cul4b increased following TCR stimulation. Disruption of Cul4b resulted in impaired proliferation and survival of activated T cells. Additionally, Cul4b-deficient CD4+ T cells accumulated DNA damage. In T cells, Cul4b preferentially associated with the substrate receptor DCAF1, and Cul4b and DCAF1 were found to interact with proteins that promote the sensing or repair of damaged DNA. While Cul4b-deficient CD4+ T cells showed evidence of DNA damage sensing, downstream phosphorylation of SMC1A did not occur. These findings reveal an essential role for Cul4b in promoting the repair of damaged DNA to allow survival and expansion of activated T cells.

Cytoglobin protects cancer cells from apoptosis by regulation of mitochondrial cardiolipin

Cytoglobin is important in the progression of oral squamous cell carcinoma but the molecular and cellular basis remain to be elucidated. In the current study, we develop a new cell model to study the function of cytoglobin in oral squamous carcinoma and response to cisplatin. Transcriptomic profiling showed cytoglobin mediated changes in expression of genes related to stress response, redox metabolism, mitochondrial function, cell adhesion, and fatty acid metabolism. Cellular and biochemical studies show that cytoglobin expression results in changes to phenotype associated with cancer progression including: increased cellular proliferation, motility and cell cycle progression. Cytoglobin also protects cells from cisplatin-induced apoptosis and oxidative stress with levels of the antioxidant glutathione increased and total and mitochondrial reactive oxygen species levels reduced. The mechanism of cisplatin resistance involved inhibition of caspase 9 activation and cytoglobin protected mitochondria from oxidative stress-induced fission. To understand the mechanism behind these phenotypic changes we employed lipidomic analysis and demonstrate that levels of the redox sensitive and apoptosis regulating cardiolipin are significantly up-regulated in cells expressing cytoglobin. In conclusion, our data shows that cytoglobin expression results in important phenotypic changes that could be exploited by cancer cells in vivo to facilitate disease progression.

Cell cycle inertia underlies a bifurcation in cell fates after DNA damage

The G₁-S checkpoint is thought to prevent cells with damaged DNA from entering S phase and replicating their DNA and efficiently arrests cells at the G₁-S transition. Here, using time-lapse imaging and single-cell tracking, we instead find that DNA damage leads to highly variable and divergent fate outcomes. Contrary to the textbook model that cells arrest at the G₁-S transition, cells triggering the DNA damage checkpoint in G₁ phase route back to quiescence, and this cellular rerouting can be initiated at any point in G₁ phase. Furthermore, we find that most of the cells receiving damage in G₁ phase actually fail to arrest and proceed through the G₁-S transition due to persistent cyclin-dependent kinase (CDK) activity in the interval between DNA damage and induction of the CDK inhibitor p21. These observations necessitate a revised model of DNA damage response in G₁ phase and indicate that cells have a G₁ checkpoint.

Effects of low-to-moderate ethanol consumption on colonic growth and gene expression in young adult and middle-aged male rats

Excessive alcohol consumption is a risk factor associated with colorectal cancer; however, some epidemiological studies have reported that moderate alcohol consumption may not contribute additional risk or may provide a protective effect reducing colorectal cancer risk. Prior research highlights the importance of proliferation, differentiation, and apoptosis as parameters to consider when evaluating colonic cell growth and tumorigenesis. The present study investigated whether chronic low-to-moderate ethanol consumption altered these parameters of colonic cell growth and expression of related genes. Twenty-four nondeprived young adult (109 days old) and 24 nondeprived middle-aged (420 days old) Wistar rats were randomly assigned to an ethanol-exposed or a water control group (n = 12/group). The ethanol group was provided voluntary access to a 20% v/v ethanol solution on alternate days for 13 weeks. Colon tissues were collected for quantitative immunohistochemical analyses of cell proliferation, differentiation and apoptosis using Ki-67, goblet cell and TUNEL, respectively. Gene expression of cyclin D1 (Ccnd1), Cdk2, Cdk4, p21waf1/cip1 (Cdkn1a), E-cadherin (Cdh1) and p53 were determined by quantitative real-time polymerase chain reaction in colonic scraped mucosa. Ethanol treatment resulted in a lower cell proliferation index and proliferative zone, and lower Cdk2 expression in both age groups, as well as trends toward lower Ccnd1 and higher Cdkn1a expression. Cell differentiation was modestly but significantly reduced by ethanol treatment only in older animals. Overall, older rats showed decreases in apoptosis and gene expression of Cdk4, Cdh1, and p53 compared to younger rats, but there was no observed effect of ethanol exposure on these measures. These findings suggest that low-to-moderate ethanol consumption improves at least one notable parameter in colonic tumorigenesis (cell proliferation) and associated gene expression regardless of age, however, selectively decreased cell differentiation among older subjects.

Muscle differentiation induced by p53 signaling pathway-related genes in myostatin-knockout quail myoblasts

The myostatin (MSTN) gene is of interest in the livestock industry because mutations in this gene are closely related to growth performance and muscle differentiation. Thus, in this study, we established MSTN knockout (KO) quail myoblasts (QM7) and investigated the regulatory pathway of the myogenic differentiation process. We used clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 to generate MSTN KO QM7 cells and subsequently isolated a single cell-derived MSTN KO QM7 subline with 10- and 16-nucleotide deletions that induced translational frameshift mutations. The differentiation capacity and proliferation rate of MSTN KO QM7 cells were enhanced. We conducted next-generation-sequencing (NGS) analysis to compare the global gene expression profiles of wild-type (WT) QM7 and MSTN KO QM7 cells. Intriguingly, NGS expression profiles showed different expression patterns of p21 and p53 in MSTN KO QM7 cells. Moreover, we identified downregulated expression patterns of leukemia inhibitory factor and DNA Damage Inducible Transcript 4, which are genes in the p53 signaling pathway. Using quantitative RT-PCR (qRT-PCR) analysis and western blotting, we concluded that p53-related genes promote the cell cycle by upregulating p21 and enhancing muscle differentiation in MSTN KO QM7 cells. These results could be applied to improve economic traits in commercial poultry by regulating MSTN-related networks.

Combined targeting of the p53 and pRb pathway in neuroblastoma does not lead to synergistic responses

BACKGROUND

Despite intensive treatment protocols and recent advances, neuroblastomas still account for approximately 15% of all childhood cancer deaths. In contrast with adult cancers, p53 pathway inactivation in neuroblastomas is rarely caused by p53 mutation but rather by altered MDM2 or p14ARF expression. Moreover, neuroblastomas are characterised by high proliferation rates, frequently triggered by pRb pathway dysfunction due to aberrant expression of cyclin D1, CDK4 or p16INK4a. Simultaneous disturbance of these pathways can occur via co-amplification of MDM2 and CDK4 or homozygous deletion of CDKN2A, which encodes both p14ARF and p16INK4a.

METHODS AND RESULTS

We examined whether both single and combined inhibition of MDM2 and CDK4/6 is effective in reducing neuroblastoma cell viability. In our panel of ten cell lines with a spectrum of aberrations in the p53 and pRb pathway, idasanutlin and abemaciclib were the most potent MDM2 and CDK4/6 inhibitors, respectively. No correlation was observed between the genetic background and response to the single inhibitors. We confirmed this lack of correlation in isogenic systems overexpressing MDM2 and/or CDK4. In addition, combined inhibition did not result in synergistic effects. Instead, abemaciclib diminished the pro-apoptotic effect of idasanutlin, leading to slightly antagonistic effects. In vivo treatment with idasanutlin and abemaciclib led to reduced tumour growth compared with single drug treatment, but no synergistic response was observed.

CONCLUSION

We conclude that p53 and pRb pathway aberrations cannot be used as predictive biomarkers for neuroblastoma sensitivity to MDM2 and/or CDK4/6 inhibitors. Moreover, we advise to be cautious with combining these inhibitors in neuroblastomas.

Molecular Targets and Nanoparticulate Systems Designed for the Improved Therapeutic Intervention in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most aggressive and fatal CNS related tumors, which is responsible for about 4% of cancer-related deaths. Current GBM therapy includes surgery, radiation, and chemotherapy. The effective chemotherapy of GBM is compromised by two barriers, i. e., the blood-brain barrier (BBB) and the blood tumor barrier (BTB). Therefore, novel therapeutic approaches are needed. Nanoparticles are one of the highly efficient drug delivery systems for a variety of chemotherapeutics that have gained massive attention from the last three decades. Perfectly designed nanoparticles have the ability to cross BBB and BTB and precisely deliver the chemotherapeutics to GBM tissue/cells. Nanoparticles can encapsulate both hydrophilic and lipophilic drugs, genes, proteins, and peptides, increase the stability of drugs by protecting them from degradation, improve plasma half-life, reduce adverse effects and control the release of drugs/genes at the desired site. This review focussed on the different signaling pathways altered in GBM cells to understand the rationale behind selecting new therapeutic targets, challenges in the drug delivery to the GBM, various transport routes in brain delivery, and recent advances in targeted delivery of different drug and gene loaded various lipidic, polymeric and inorganic nanoparticles in the effective management of GBM.

A novel indenone derivative selectively induces senescence in MDA-MB-231 (breast adenocarcinoma) cells

Triple-negative breast cancer is the most aggressive form of breast cancer with limited intervention options. Moreover, a number of belligerent therapeutic strategies adopted to treat such aggressive forms of cancer have demonstrated detrimental side effects. This necessitates exploration of targeted chemotherapeutics. We assessed the efficacy of a novel indenone derivative (nID) [(±)-N-(2-(-5-methoxy-1-oxo-3-(2-oxo-2-phenylethyl)-2,3-dihydro-1H-inden-2-yl)ethyl)-4-methylbenzenesulfonamide], synthesized by a novel internal nucleophile-assisted palladium-catalyzed hydration-olefin insertion cascade; against triple-negative breast cancer cells (MDA-MB-231). On 24 h treatment, the nID caused decline in the viability of MDA-MB-231 and MDA-MB-468 cells, but did not significantly (P < 0.05) affect WRL-68 (epithelial-like) cells. In fact, the nID demonstrated augmentation of p53 expression, and consequent p53-dependent senescence in both MDA-MB-231 and MDA-MB-468 cells, but not in WRL-68 cells. The breast cancer cells also exhibited reduced proliferation, downregulated p65/NF-κB and survivin, along with augmented p21Cip1/WAF1 expression, on treatment with the nID. This ensued cell cycle arrest at G1 stage, which might have driven the MDA-MB-231 cells to senescence. We observed a selectivity of the nID to target MDA-MB-231 cells, whereas WRL-68 cells did not show any considerable effect. The results underscored that the nID has potential to be developed into a cancer therapeutic.

Comprehensive Genomic Analysis Reveals the Prognostic Role of LRRK2 Copy-Number Variations in Human Malignancies

Genetic alterations of leucine-rich repeat kinase 2 (LRRK2), one of the most important contributors to familial Parkinson’s disease (PD), have been hypothesized to play a role in cancer development due to demographical and preclinical data. Here, we sought to define the prevalence and prognostic significance of LRRK2 somatic mutations across all types of human malignancies by querying the publicly available online genomic database cBioPortal. Ninety-six different studies with 14,041 cases were included in the analysis, and 761/14,041 (5.4%) showed genetic alterations in LRRK2. Among these, 585 (76.9%) were point mutations, indels or fusions, 168 (22.1%) were copy number variations (CNVs), and 8 (1.0%) showed both types of alterations. One case showed the somatic mutation R1441C. A significant difference in terms of overall survival (OS) was noted between cases harboring somatic LRRK2 whole deletions, amplifications, and CNV-unaltered cases (median OS: 20.09, 57.40, and 106.57 months, respectively; p = 0.0008). These results suggest that both LRRK2 amplifications and whole gene deletions could play a role in cancer development, paving the way for future research in terms of potential treatment with LRRK2 small molecule inhibitors for LRRK2-amplified cases.

Restriction point regulation at the crossroads between quiescence and cell proliferation

The coordination of cell proliferation with reversible cell cycle exit into quiescence is crucial for the development of multicellular organisms and for tissue homeostasis in the adult. The decision between quiescence and proliferation occurs at the restriction point, which is widely thought to be located in the G1 phase of the cell cycle, when cells integrate accumulated extracellular and intracellular signals to drive this binary cellular decision. On the molecular level, decision-making is exerted through the activation of cyclin-dependent kinases (CDKs). CDKs phosphorylate the retinoblastoma (Rb) transcriptional repressor to regulate the expression of cell cycle genes. Recently, the classical view of restriction point regulation has been challenged. Here, we review the latest findings on the activation of CDKs, Rb phosphorylation and the nature and position of the restriction point within the cell cycle.

Grape pomace inhibits colon carcinogenesis by suppressing cell proliferation and inducing epigenetic modifications

Grape pomace (GP), a by-product of the wine and juice industry, is rich in bioflavonoids and dietary fibers. We hypothesized that GP has protective effects against colitis-associated colorectal cancer (CRC). Nine-week-old female mice were fed a control diet (CON) or CON with 5% grape pomace (GP) for 2 weeks, when mice were subjected to azoxymethane (AOM)/dextran sulfate sodium (DSS) induced-CRC induction. GP supplementation ameliorated the disease activity index (DAI) score, reduced tumor number, tumor size and pathological scores in AOM/DSS treated mice. Furthermore, dietary GP suppressed colonic expression of inflammatory cytokines, IL-1β and TNF-α, and inhibited NF-κB inflammatory signaling, while increased anti-inflammatory cytokine TGF-β mRNA expression. Colorectal inflammation is known to enhance Wnt signaling and cell proliferation. In agreement, the content of β-catenin, a key downstream mediator of Wnt signaling, was reduced as was the expression of Cyclin D1, phosphorylation and content of p53 and PCNA level in GP-fed mice. In addition, GP reduced the expression of ALDH1, a marker of cell stemness, and increased the expression of Cdx2, a key transcription factor initiating epithelial cell differentiation, DNA methylation of the promoter region of Cdx2 gene and hypermethylation of CpG island methylator phenotype (CIMP), which commonly occurs during CRC carcinogenesis, was alleviated in the GP group. In conclusion, GP supplementation suppressed colitis-associated CRC carcinogenesis, which was associated with the suppression of inflammation and cell proliferation and the enhancement of DNA demethylation in Cdx2 and CIMP genes in the colon. These data suggest that dietary GP supplementation has preventive effects against colorectal carcinogenesis.

Oxaliplatin Pt(IV) prodrugs conjugated to gadolinium-texaphyrin as potential antitumor agents

Described here is the development of gadolinium(III) texaphyrin-platinum(IV) conjugates capable of overcoming platinum resistance by 1) localizing to solid tumors, 2) promoting enhanced cancer cell uptake, and 3) reactivating p53 in platinum-resistant models. Side by side comparative studies of these Pt(IV) conjugates to clinically approved platinum(II) agents and previously reported platinum(II)-texaphyrin conjugates demonstrate that the present Pt(IV) conjugates are more stable against hydrolysis and nucleophilic attack. Moreover, they display high potent antiproliferative activity in vitro against human and mouse cell cancer lines. Relative to the current platinum clinical standard of care (SOC), a lead Gd(III) texaphyrin-Pt(IV) prodrug conjugate emerging from this development effort was found to be more efficacious in subcutaneous (s.c.) mouse models involving both cell-derived xenografts and platinum-resistant patient-derived xenografts. Comparative pathology studies in mice treated with equimolar doses of the lead Gd texaphyrin-Pt(IV) conjugate or the US Food and Drug Administration (FDA)-approved agent oxaliplatin revealed that the conjugate was better tolerated. Specifically, the lead could be dosed at more than three times (i.e., 70 mg/kg per dose) the tolerable dose of oxaliplatin (i.e., 4 to 6 mg/kg per dose depending on the animal model) with little to no observable adverse effects. A combination of tumor localization, redox cycling, and reversible protein binding is invoked to explain the relatively increased tolerability and enhanced anticancer activity seen in vivo. On the basis of the present studies, we conclude that metallotexaphyrin-Pt conjugates may have substantial clinical potential as antitumor agents.

Feedback analysis identifies a combination target for overcoming adaptive resistance to targeted cancer therapy

Targeted drugs aim to treat cancer by directly inhibiting oncogene activity or oncogenic pathways, but drug resistance frequently emerges. Due to the intricate dynamics of cancer signaling networks, which contain complex feedback regulations, cancer cells can rewire these networks to adapt to and counter the cytotoxic effects of a drug, thereby limiting the efficacy of targeted therapies. To identify a combinatorial drug target that can overcome such a limitation, we developed a Boolean network simulation and analysis framework and applied this approach to a large-scale signaling network of colorectal cancer with integrated genomic information. We discovered Src as a critical combination drug target that can overcome the adaptive resistance to the targeted inhibition of mitogen-activated protein kinase pathway by blocking the essential feedback regulation responsible for resistance. The proposed framework is generic and can be widely used to identify drug targets that can overcome adaptive resistance to targeted therapies.

All-trans retinoic acid enhances the effect of Fra-1 to inhibit cell proliferation and metabolism in cervical cancer

OBJECTIVES

This study on all-trans retinoic acid was designed to explore its effect on the ability of Fra-1 to cervical cancer cell development. The results show that all-trans retinoic acid enhances the effect of Fra-1 on inhibiting cervical cancer proliferation and the glucose consumption, its effect on the loss of mitochondrial membrane potential, on the decreasing of lactic acid as well as ATP, and also influences the expression of MDM2/P53/P21 and LDHA.

RESULTS

The results show that the expression of Fra-1 is higher in all-trans retinoic acid-treated cervical cancer. Flow cytometry and kit detection show that all-trans retinoic acid can enhance the ability of Fra-1 to lose the mitochondrial membrane potential, inhibit the glucose consumption and the production of lactic acid as well as ATP. CCK8 and colony formation assays indicate that all-trans retinoic acid enhances the ability of Fra-1 to inhibit cell proliferation. In addition, through Western blot analysis, it was determined that P53 and P21 were up-regulated, and MDM2 and LDHA were down-regulated.

CONCLUSION

The overall results of the study strongly suggest that all-trans retinoic acid enhances the effect of Fra-1 on inhibiting cervical cancer proliferation and metabolism in vitro, and also influences the expression of MDM2/P53/P21 and LDHA.

miR-197-3p Represses the Proliferation of Prostate Cancer by Regulating the VDAC1/AKT/β-catenin Signaling Axis

Accumulating investigations have demonstrated that microRNAs (miRNAs) are promising efficient targets for the next generation of molecular therapeutics. The development of miRNA-based therapies requires the identification and validation of cancer-associated miRNAs. Herein, we identified that miR-197-3p regulates the carcinogenesis and development of prostate cancer (PCa) via bioinformatics analysis. Next, we investigated the function and regulatory mechanisms of miR-197-3p in PCa. Overexpression of miR-197-3p suppressed PCa cell proliferation and colony formation. In contrast, inhibition of miR-197-3p activity enhanced PCa cell proliferation and colony formation. Mechanistic investigations identified that voltage dependent anion channel 1 (VDAC1) is a direct target of miR-197-3p. miR-197-3p targeting of VDAC1 resulted in downregulation of p-Akt and β-catenin. Subsequently, we found that restoration of VDAC1 abolished the effects of miR-197-3p on PCa cell proliferation and AKT signaling pathway. Furthermore, we confirmed that miR-197-3p suppressed tumor xenograft growth in vivo. In conclusion, our study offers an empirical investigation of miR-197-3p, a tumor suppressor that may be a potential therapeutic target in PCa.

Mdm2 and MdmX RING Domains Play Distinct Roles in the Regulation of p53 Responses: A Comparative Study of Mdm2 and MdmX RING Domains in U2OS Cells

Dysfunction of the tumor suppressor p53 occurs in most human cancers. Mdm2 and MdmX are homologous proteins from the Mdm (Murine Double Minute) protein family, which play a critical role in p53 inactivation and degradation. The two proteins interact with one another via the intrinsic RING (Really Interesting New Gene) domains to achieve the negative regulation of p53. The downregulation of p53 is accomplished by Mdm2-mediated p53 ubiquitination and proteasomal degradation through the ubiquitin proteolytic system and by Mdm2 and MdmX mediated inhibition of p53 transactivation. To investigate the role of the RING domain of Mdm2 and MdmX, an analysis of the distinct functionalities of individual RING domains of the Mdm proteins on p53 regulation was conducted in human osteosarcoma (U2OS) cell line. Mdm2 RING domain was observed mainly localized in the cell nucleus, contrasting the localization of MdmX RING domain in the cytoplasm. Mdm2 RING was found to possess an endogenous E3 ligase activity, whereas MdmX RING did not. Both Mdm2 and MdmX RING domains were able to dimerize with endogenous full-length Mdm2 and MdmX protein and affect their cellular function. The results showed that overexpression of the Mdm2 or MdmX RING domains interfered with the endogenous full-length Mdm2 and MdmX activity and resulted in p53 stabilization and p53 target gene activation. However, both Mdm RING domains showed oncogenic activity in a colony formation assay, suggesting that the Mdm RING domains possess p53-independent oncogenic properties. This study highlights the distinct structural and functional traits of the RING domain of Mdm2 and MdmX and characterized their role in cellular responses through interfering with p53 dependent signaling pathway.

Critical Role for P53 in Regulating the Cell Cycle of Ground State Embryonic Stem Cells

Mouse embryonic stem cells (ESCs) grown in serum-supplemented conditions are characterized by an extremely short G1 phase due to the lack of G1-phase control. Concordantly, the G1-phase-specific P53-P21 pathway is compromised in serum ESCs. Here, we provide evidence that P53 is activated upon transition of serum ESCs to their pluripotent ground state using serum-free 2i conditions and that is required for the elongated G1 phase characteristic of ground state ESCs. RNA sequencing and chromatin immunoprecipitation sequencing analyses reveal that P53 directly regulates the expression of the retinoblastoma (RB) protein and that the hypo-phosphorylated, active RB protein plays a key role in G1-phase control. Our findings suggest that the P53-P21 pathway is active in ground state 2i ESCs and that its role in the G1-checkpoint is abolished in serum ESCs. Taken together, the data reveal a mechanism by which inactivation of P53 can lead to loss of RB and uncontrolled cell proliferation.

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The P53-P21 pathway is activated upon adaptation of ESCs to their pluripotent ground state.

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P53 is required for the elongated G1-phase characteristic to 2i ESCs.

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P53 binds the promoter and activates Rb1 expression.

Tumor-suppressing potential of stingless bee propolis in in vitro and in vivo models of differentiated-type gastric adenocarcinoma

The protective property of propolis across a wide spectrum of diseases has long been realized, yet the anti-tumor efficacy of this bioactive substance from Philippine stingless bees has remained poorly understood. Here, we showed the tumor-suppressing potential of crude ethanolic extract of Philippine stingless bee propolis (EEP) in in vitro models of gastric cancer highlighting the first indication of remarkable subtype specificity towards differentiated-type human gastric cancer cell lines but not the diffuse-type. Mechanistically, this involved the profound modulation of several cell cycle related gene transcripts, which correlated with the prominent cell cycle arrest at the G0/G1 phase. To reinforce our data, a unique differentiated-type gastric cancer model, A4gnt KO mice, together with age-matched 60 week-old C57BL/6 J mice were randomly assigned to treatment groups receiving distilled water or EEP for 30 consecutive days. EEP treatment induced significant regression of gross and histological lesions of gastric pyloric tumors that consistently corresponded with specific transcriptional regulation of cell cycle components. Also, the considerable p21 protein expression coupled with a marked reduction in rapidly dividing BrdU-labeled S-phase cells unequivocally supported our observation. Altogether, these findings support the role of Philippine stingless bee propolis as a promising adjunct treatment option in differentiated-type gastric cancer.

VERU-111 suppresses tumor growth and metastatic phenotypes of cervical cancer cells through the activation of p53 signaling pathway

In this study, we investigated the therapeutic efficacy of VERU-111 in vitro and in vivo model systems of cervical cancer. VERU-111 treatment inhibited cell proliferation and, clonogenic potential, induce accumulation of p53 and down regulated the expression of HPV E6/E7 expression in cervical cancer cells. In addition, VERU-111 treatment also decreased the phosphorylation of Jak2^{(Tyr1007/1008)} and STAT3 at Tyr705 and Ser727. VERU-111 treatment arrested cell cycle in the G2/M phase and modulated cell cycle regulatory proteins (cyclin B1, p21, p34^cdc2 and pcdk1). Moreover, VERU-111 treatment induced apoptosis and modulated the expression of Bid, Bcl-xl, Survivin, Bax, Bcl2 and cleavage in PARP. In functional assays, VERU-111 markedly reduced the migratory and invasive potential of cervical cancer cells via modulations of MMPs. VERU-111 treatment also showed significant (P < 0.05) inhibition of orthotopic xenograft tumor growth in athymic nude mice. Taken together, our results demonstrate the potent anti-cancer efficacy of VERU-111 in experimental cervical cancer models.Thus, VERU-111 can be explored as a promising therapeutic agent for the treatment of cervical cancer.

A novel 3'-tRNAGlu-derived fragment acts as a tumor suppressor in breast cancer by targeting nucleolin

tRNA-derived fragments (tRFs) have been defined as a novel class of small noncoding RNAs. tRFs have been reported to be deregulated in cancer, but their biologic function remains to be fully understood. We have identified a new tRF (named tRF3E), derived from mature tRNAGlu, that is specifically expressed in healthy mammary glands but not in breast cancer (BC). Consistently, tRF3E levels significantly decrease in the blood of patients with epidermal growth factor receptor 2 (HER2)-positive BC reflecting tumor status (control > early cancer > metastatic cancer). tRF3E down-regulation was recapitulated in Δ16HER2 transgenic mice, representing a BC preclinical model. Pulldown assays, used to search for proteins capable to selectively bind tRF3E, have shown that this tRF specifically interacts with nucleolin (NCL), an RNA-binding protein overexpressed in BC and able to repress the translation of p53 mRNA. The binding properties of NCL-tRF3E complex, predicted in silico and analyzed by EMSA assays, are congruent with a competitive displacement of p53 mRNA by tRF3E, leading to an increased p53 expression and consequently to a modulation of cancer cell growth. Here, we provide evidence that tRF3E plays an important role in the pathogenesis of BC displaying tumor-suppressor functions through a NCL-mediated mechanism.-Falconi, M., Giangrossi, M., Elexpuru Zabaleta, M., Wang, J., Gambini, V., Tilio, M., Bencardino, D., Occhipinti, S., Belletti, B., Laudadio, E., Galeazzi, R., Marchini, C., Amici, A. A novel 3'-tRNAGlu-derived fragment acts as a tumor suppressor in breast cancer by targeting nucleolin.

HPV-18 E2 protein downregulates antisense noncoding mitochondrial RNA-2, delaying replicative senescence of human keratinocytes

Human and mouse cells display a differential expression pattern of a family of mitochondrial noncoding RNAs (ncmtRNAs), according to proliferative status. Normal proliferating and cancer cells express a sense ncmtRNA (SncmtRNA), which seems to be required for cell proliferation, and two antisense transcripts referred to as ASncmtRNA-1 and -2. Remarkably however, the ASncmtRNAs are downregulated in human and mouse cancer cells, including HeLa and SiHa cells, transformed with HPV-18 and HPV-16, respectively. HPV E2 protein is considered a tumor suppressor in the context of high-risk HPV-induced transformation and therefore, to explore the mechanisms involved in the downregulation of ASncmtRNAs during tumorigenesis, we studied human foreskin keratinocytes (HFK) transduced with lentiviral-encoded HPV-18 E2. Transduced cells displayed a significantly extended replicative lifespan of up to 23 population doublings, compared to 8 in control cells, together with downregulation of the ASncmtRNAs. At 26 population doublings, cells transduced with E2 were arrested at G₂/M, together with downregulation of E2 and SncmtRNA and upregulation of ASncmtRNA-2. Our results suggest a role for high-risk HPV E2 protein in cellular immortalization. Additionally, we propose a new cellular phenotype according to the expression of the SncmtRNA and the ASncmtRNAs.

Androgen receptor activation reduces the endothelial cell proliferation through activating the cSrc/AKT/p38/ERK/NFκB-mediated pathway

The effect of androgen on angiogenesis has been documented. However, its underlying molecular mechanisms have not been well illustrated. Here, we show that treatment with an androgen receptor (AR) agonist, metribolone (R1881; 0.05-5 nM), or dihydrotestosterone (DHT; 0.5-2 nM), concentration- and time-dependently inhibited proliferation in human umbilical venous endothelial cells (HUVEC). This inhibitory effect was confirmed in human microvascular endothelial cells (HMEC-1). Flow cytometric analysis demonstrated that R1881 induced G0/G1 phase cell cycle arrest in HUVEC. Blockade of the AR activity by pre-treatment with an AR antagonist, hydroxyflutamide (HF), or knockdown of AR expression using the shRNA technique abolished the R1881-induced HUVEC proliferation inhibition, suggesting that AR activation can inhibit endothelial cell proliferation. We further investigated the signaling pathway contributing to the proliferation inhibition induced by AR activation. Our data suggest that R1881 reduced the proliferation rate of HUVEC through activating the AR/cSrc/AKT/p38/ERK/NFκB pathway, subsequently up-regulating p53 expression, which in turn increased the levels of p21 and p27 protein, hence decreasing the activities of cyclin-dependent kinase 2 (CDK2) and CDK4, and finally reduced the cell proliferation rate. An extra-nuclear pathway involved in the proliferation inhibition induced by AR activation in vascular endothelial cells was confirmed by showing that membrane-impermeable testosterone-bovine serum albumin (BSA) treatment significantly increased the levels of p53, p27 and p21 protein and reduced cell proliferation. These data highlight the underlying molecular mechanisms by which AR activation induced proliferation inhibition in vascular endothelial cells.

The methyl-triclosan induced caspase-dependent mitochondrial apoptosis in HepG2 cells mediated through oxidative stress

Methyl-triclosan (MTCS) is a dominant transformation product of triclosan (TCS), which has been widely used as an effective antimicrobial ingredient with increasing concentrations in the environment. MTCS shows higher persistence in environment than its parent chemical TCS. The toxic effects of MTCS and toxicological mechanism are not well understood up to now. This study investigated the cytotoxic effects of MTCS in HepG2 cells in terms of cell viability, apoptosis induction, ROS production, GSH/GSSG levels, Mitochondrial Membrane Potential (MMP) reduction, LDH release, glucose uptake and ATP production. Moreover, the related gene transcripts were measured with RT-qPCR assay. Cytotoxic experiments in HepG2 cells revealed that MTCS exposure at micromol per liter levels had toxic effects as evidenced by decreased cell survival, elevated cell apoptosis, reduced MMP and increased LDH release. These toxic effects were associated with increased ROS production and reduced GSH/GSSG ratio. Meanwhile, elevated glucose uptake and ATP production indicated that MTCS induced membrane damages resulted not from a typical mitochondrial uncoupler, but from oxidative stress. Analysis of gene transcripts showed that MTCS exposure induced mRNA expressions alterations associated with oxidative stress response, energy production, cell cycle regulation and cell apoptosis. In general, the caspase-dependent mitochondrial apoptosis pathway might play a role in MTCS induced cytotoxicity in HepG2 cells.

Synergism Through WEE1 and CHK1 Inhibition in Acute Lymphoblastic Leukemia

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

LIMCH1 suppress the growth of lung cancer by interacting with HUWE1 to sustain p53 stability

BACKGROUND

The aim of this study was to identify the expression of LIM and calponin-homology domains 1 (LIMCH1) in lung cancer and normal tissues, to determine the interaction between LIMCH1 and HUWE1 in regulating p53 stability.

METHODS

The expression of LIMCH1 was detected by the Oncomine and Cancer Genome Atlas databases. Expression of LIMCH1 mRNA was identified using qRT-PCR. In transfected human lung cancer cells, co-immunoprecipitation experiments were performed. The mechanism that HUWE1 sustained lung cancer malignancy was verified by western blotting. The proliferation of tranfected cells was assessed by CCK-8 assay and colony formation.

RESULTS

Bioinformatic data and e TCGA database suggested LIMCH1 mRNA levels in tumor tissues were down-regulated compared to tumor adjacent tissues. We found low expression of LIMCH1 mRNA in tumor sites and tumor cell line. Exogenous expression of LIMCH1 interacts with HUWE1 promotes expression of p53. Use of siRNA or shRNA against LIMCH1 resulted in decreased p53 protein levels. LIMCH1 deletion lead to enhance of p53 ubiquitination and protein expression of p53 and substrate p21, puma. Growth curve showed that LIMCH1 deletion significantly promoted the proliferation of A549 cells.

CONCLUSIONS

LIMCH1 was a negative regulator and indicated a new molecular mechanism for the pathogenesis of lung cancer via modulating HUWE1 and p53.

Predicting the Need for a Tier II Ototoxicity Study From Early Renal Function Data

History has established that many drugs, such as the antibiotics, chemotherapies, and loop diuretics, are capable of inducing both nephrotoxicity and ototoxicity. The exact mechanisms by which cellular damage occurs remain to be fully elucidated. Monitoring the indices of renal function conducted in the Food and Drug Administration's prescribed set of early investigational new drug (IND)-enabling studies may be the first signs of ototoxicity properties of the new drug candidate. In developing improved and efficacious new molecular entities, it is critically necessary to understand the cellular and molecular mechanisms underlying the potential ototoxic effects as early in the drug development program as possible. Elucidation of these mechanisms will facilitate the development of safe and effective clinical approaches for the prevention and amelioration of drug-induced ototoxicity prior to the first dose in man. Biomarkers for nephrotoxicity in early tier I or tier II nonclinical IND-enabling studies should raise an inquiry as to the need to conduct a full auditory function assay early in the game to clear the pipeline with a safer candidate that has a higher probability of continued therapeutic compliance once approved for distribution.

Patterns of Early p21 Dynamics Determine Proliferation-Senescence Cell Fate after Chemotherapy

Chemotherapy is designed to induce cell death. However, at non-lethal doses, cancer cells can choose to remain proliferative or become senescent. The slow development of senescence makes studying this decision challenging. Here, by analyzing single-cell p21 dynamics before, during, and days after drug treatment, we link three distinct patterns of early p21 dynamics to final cell fate. Surprisingly, while high p21 expression is classically associated with senescence, we find the opposite at early times during drug treatment: most senescence-fated cells express much lower p21 levels than proliferation-fated cells. We demonstrate that these dynamics lead to a p21 "Goldilocks zone" for proliferation, in which modest increases of p21 expression can lead to an undesirable increase of cancer cell proliferation. Our study identifies a counter-intuitive role for early p21 dynamics in the cell-fate decision and pinpoints a source of proliferative cancer cells that can emerge after exposure to non-lethal doses of chemotherapy.

The Molecular Mechanisms of Protective Role of Se on the G0/G1 Phase Arrest Caused by AFB1 in Broiler's Thymocytes

This research was designed to explore the protective effects of sodium selenite on G₀/G₁ phase arrest induced by AFB₁ in thymocytes of broilers. Two hundred eighty-eight Cobb broilers were divided into control group, + Se group (0.4 mg/kg Se), AFB₁ group (0.6 mg/kg AFB₁), and AFB₁ + Se group (0.6 mg/kg AFB₁ + 0.4 mg/kg Se). The results revealed that 0.4 mg/kg Se supplement in diets could improve the AFB₁-induced histological lesions in the thymus consisting of the more vacuoles and nuclear debris in thymic cortical area. The results of flow cytometric detect showed that 0.4 mg/kg Se relieved the G₀/G₁ phase arrest caused by AFB₁ in thymocytes. The results of transcription levels of ATM, p53, p21, p27, p15, p16, CyclinD₁, CyclinE, Cdk6, Cdk2, and PCNA genes by qRT-PC, and protein expression level of PCNA by immunohistochemistry demonstrated that 0.4 mg/kg Se could reduce the adverse effects of AFB₁ on these parameters. In conclusion, Se could relieve AFB₁-induced G₀/G₁ phase arrest by p15 (or p16)-CyclinD₁/Cdk6, ATM-p53-p21-CyclinE/Cdk2, p27-CyclinE/Cdk2 pathways.

WIP1 Contributes to the Adaptation of Fanconi Anemia Cells to DNA Damage as Determined by the Regulatory Network of the Fanconi Anemia and Checkpoint Recovery Pathways

DNA damage adaptation (DDA) allows the division of cells with unrepaired DNA damage. DNA repair deficient cells might take advantage of DDA to survive. The Fanconi anemia (FA) pathway repairs DNA interstrand crosslinks (ICLs), and deficiencies in this pathway cause a fraction of breast and ovarian cancers as well as FA, a chromosome instability syndrome characterized by bone marrow failure and cancer predisposition. FA cells are hypersensitive to ICLs; however, DDA might promote their survival. We present the FA-CHKREC Boolean Network Model, which explores how FA cells might use DDA. The model integrates the FA pathway with the G2 checkpoint and the checkpoint recovery (CHKREC) processes. The G2 checkpoint mediates cell-cycle arrest (CCA) and the CHKREC activates cell-cycle progression (CCP) after resolution of DNA damage. Analysis of the FA-CHKREC network indicates that CHKREC drives DDA in FA cells, ignoring the presence of unrepaired DNA damage and allowing their division. Experimental inhibition of WIP1, a CHKREC component, in FA lymphoblast and cancer cell lines prevented division of FA cells, in agreement with the prediction of the model.

lncRNA CADM1-AS1 inhibits cell-cycle progression and invasion via PTEN/AKT/GSK-3β axis in hepatocellular carcinoma

Purpose: CADM1-AS1 (cell adhesion molecule 1 antisense RNA 1, long non-coding RNA), was firstly characterized in renal clear cell carcinoma, and exhibits a tumor suppressor role. However, its clinical relevance and exact effects in hepatocellular carcinoma (HCC) remain unknown. Therefore, in this study, we aimed to assess the clinical significance and function of CADM1-AS1 in HCC. Methods: We detected CADM1-AS1 expression in liver cancer tissue samples and cell lines, and analyzed the association between CADM1-AS1 expression and clinical parameters in 90 liver cancer patients. Moreover, we conducted gain-of-function and loss-of-function studies in liver cancer cell to explore the biological function and molecular mechanism of CADM1-AS1. Results: CADM1-AS1 expression was reduced in HCC. Clinical data showed that this downregulation was associated with advanced tumor stage, high TNM stage and reduced survival in HCC patients. CADM1-AS1 overexpression inhibited HCC cells proliferation, migration and invasion, while inducing G0/G1 phase arrest. Meanwhile, we revealed that CADM1-AS1 inhibited the phosphorylation of AKT and GSK-3β. Furthermore, our study showed that CADM1-AS1 decreased the cell cycle associated proteins expression of cyclinD, cyclinE, CDK2 CDK4, CDK6, and enhanced the levels of p15, p21 and p27. More importantly, SC79, a specific activator for AKT;, apparently attenuated the effects of CADM1-AS1 on above cell-cycle associated proteins, confirming that CADM1-AS1 inhibited cell cycles through the AKT signaling pathway. And we also found the CADM1-AS1 has antitumor effect in vivo by a xenograft HCC mouse model. In conclusion, the present findings show that the CADM1-AS1 inhibits proliferation of HCC by inhibiting AKT/GSK-3β signaling pathway, then upregulate p15, p21, p27 expression and downregulate cyclin, CDK expression to inhibit the G0/G1 to S phase transition both in vitro and in vivo. Conclusion: CADM1-AS1 functions as a tumor-suppressive lncRNA. This study reveals a molecular pathway involving PTEN/AKT/GSK-3β which regulates HCC cell-cycle progression.

Graphene Oxide⁻Platinum Nanoparticle Nanocomposites: A Suitable Biocompatible Therapeutic Agent for Prostate Cancer

Metal nanoparticles and the combination of metal nanoparticles with graphene oxide are widely used in environmental, agriculture, textile, and therapeutic applications. The effect of graphene oxide-green platinum nanoparticles (GO-PtNPs) on human prostate cancer cells (LNCaP) is unclear. Therefore, this study aimed to synthesize a nanocomposite of GO-PtNPs and evaluate their effect on prostate cancer cells. Herein, we synthesized GO-PtNPs using vanillin and characterized GO-PtNPs. GO-PtNP cytotoxicity in LNCaP cells was demonstrated by measuring cell viability and proliferation. Both decreased in a dose-dependent manner compared to that by GO or PtNPs alone. GO-PtNP cytotoxicity was confirmed by increased lactate dehydrogenase release and membrane integrity loss. Oxidative stress induced by GO-PtNPs increased malondialdehyde, nitric oxide, and protein carbonyl contents. The effective reactive oxygen species generation impaired the cellular redox balance and eventually impaired mitochondria by decreasing the membrane potential and ATP level. The cytotoxicity to LNCaP cells was correlated with increased expression of proapoptotic genes (p53, p21, Bax, Bak, caspase 9, and caspase 3) and decreased levels of antiapoptotic genes (Bcl2 and Bcl-xl). Activation of the key regulators p53 and p21 inhibited the cyclin-dependent kinases Cdk2 and Cdk4, suggesting that p53 and p21 activation in GO-PtNP-treated cells caused genotoxic stress and apoptosis. The increased expression of genes involved in cell cycle arrest and DNA damage and repair, and increased levels of 8-oxo-deoxyguanosine and 8-oxoguanine suggested that GO-PtNPs potentially induce oxidative damage to DNA. Thus, GO-PtNPs are both cytotoxic and genotoxic. LNCaP cells appear to be more susceptible to GO-PtNPs than to GO or PtNPs. Therefore, GO-PtNPs have potential as an alternate and effective cancer therapeutic agent. Finally, this work shows that the combination of graphene oxide with platinum nanoparticles opens new perspectives in cancer therapy. However further detailed mechanistic studies are required to elucidate the molecular mechanism of GO-PtNPs induced cytotoxicity in prostate cancer.

INKA2, a novel p53 target that interacts with the serine/threonine kinase PAK4

The p53 protein is a tumour suppressor and transcription factor that regulates the expression of target genes involved in numerous stress responses systems. In this study, we designed a screening strategy using DNA damage-induced mouse and human transcriptome data to identify novel downstream targets of p53. Our method selected genes with an induced expression in multiple organs of X-ray-irradiated p53 wild-type mice. The expression of inka box actin regulator 2 gene, known as Inka2, was upregulated in 12 organs when p53 expression was induced. Similarly, INKA2 was induced in a p53-dependent manner at both the mRNA and protein level in human cells treated with adriamycin. Reporter assays confirmed that p53 directly regulated INKA2 through an intronic binding site. The overexpression of INKA2 produced a slight decrease in cancer cell growth in the colony formation assay. Moreover, the analysis of The Cancer Genome Atlas (TCGA) data revealed a decreased INKA2 expression in tumour samples carrying p53 mutations compared with p53 wild-type samples. In addition, significantly higher levels of DNA methylation were observed in the INKA2 promoter in tumour samples, concordant with the reduced INKA2 expression in tumour tissues. These results demonstrate the potential of INKA2 as a cancer cell growth inhibitor. Furthermore, INKA2 protein interacts with the serine/threonine-protein kinase, p21 (RAC1) activated kinase (PAK)4, which phosphorylates β-catenin to prevent ubiquitin-proteasomal degradation. As β-catenin was downregulated in a stable INKA2-expressing cell line, the findings of this study suggest that INKA2 is a novel, direct downstream target of p53 that potentially decreases cell growth by inhibiting the PAK4-β-catenin pathway.

Mad1 destabilizes p53 by preventing PML from sequestering MDM2

Mitotic arrest deficient 1 (Mad1) plays a well-characterized role in the mitotic checkpoint. However, interphase roles of Mad1 that do not impact mitotic checkpoint function remain largely uncharacterized. Here we show that upregulation of Mad1, which is common in human breast cancer, prevents stress-induced stabilization of the tumor suppressor p53 in multiple cell types. Upregulated Mad1 localizes to ProMyelocytic Leukemia (PML) nuclear bodies in breast cancer and cultured cells. The C-terminus of Mad1 directly interacts with PML, and this interaction is enhanced by sumoylation. PML stabilizes p53 by sequestering MDM2, an E3 ubiquitin ligase that targets p53 for degradation, to the nucleolus. Upregulated Mad1 displaces MDM2 from PML, freeing it to ubiquitinate p53. Upregulation of Mad1 accelerates growth of orthotopic mammary tumors, which show decreased levels of p53 and its downstream effector p21. These results demonstrate an unexpected interphase role for Mad1 in tumor promotion via p53 destabilization.

p53 expression status is associated with cancer-specific survival in stage III and high-risk stage II colorectal cancer patients treated with oxaliplatin-based adjuvant chemotherapy

BACKGROUND

We attempted to elucidate whether p53 expression or TP53 mutation status was associated with cancer-specific survival in adjuvant FOLFOX-treated patients with stage III or high-risk stage II colorectal cancer (CRC).

METHODS

We analysed CRCs (N = 621) for the presence of TP53 alterations and for p53 expression, using targeted resequencing and immunohistochemistry. CRCs were grouped into four subsets according to the p53 expression status, which included p53-no, mild, moderate and strong expression.

RESULTS

The distributions of CRCs were 19.85, 11.05, 17.7% and 51.5% in the p53-no, mild, moderate and strong expression groups, respectively. Cases in the p53-mild to moderate expression group were associated with a more frequent proximal location, undifferentiated histology, lower N category, extraglandular mucin production, microsatellite instability, CIMP-P1, CK7 expression and decreased CDX2 expression compared with those of cases of the p53-no expression and p53-strong expression groups. According to survival analysis, the p53-mild expression group showed a poor 5-year relapse-free survival (hazard ratio (HR): 2.71, 95% confidence interval (CI) = 1.60-4.60, P < 0.001) and poor 5-year cancer-specific survival (HR: 2.90, 95% CI = 1.28-6.57, P = 0.011).

CONCLUSIONS

p53-mild expression status was found to be an independent prognostic marker in adjuvant FOLFOX-treated patients with stage III and high-risk stage II CRC.

Anticancer activity and mechanism of bis-pyrimidine based dimetallic Ru(II)(η6-p-cymene) complex in human non-small cell lung cancer via p53-dependent pathway

Non-small cell lung cancer (NSCLC) is the most common cancer worldwide, which is related with poor prognosis and resistance to chemotherapy. Notably, ruthenium-based complexes have emerged as good alternative to the currently used platinum-based drugs for cancer therapy. In the present study, we synthesized a novel bis-pyrimidine based ligand 1,3-bis(2-methyl-6-(pyridin-2-yl)pyrimidin-4-yl)benzene (L) and used it in the synthesis of a dimetallic Ru(II) cymene complex [(Ru(η⁶-p-cymene)Cl)₂(1,3-bis(2-methyl-6-(pyridin-2-yl)pyrimidin-4-yl)benzene)] (L-Ru). We checked the stability of this complex in solution state in D₂O/DMSO‑d₆ mixture and found it to be highly stable under these conditions. We determined the anticancer activity and mechanism of action of L-Ru in human NSCLC A549 and A427 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and related biological analyses. These results revealed that L-Ru exerted a strong inhibitory effect on the cells proliferation,G0/G1-arrest, accompanied with upregulation of p53, p21, p15, cleaved Poly (ADP-ribose) polymerase (PARP) protein and downregulation of cell cycle markers. L-Ru inhibited cell migration and invasion. The mitochondria-mediated apoptosis of NSCLC induced by L-Ru was also observed followed by the increase of apoptosis regulator B-cell lymphoma 2 associated X (BAX), and activation of caspase-3/-9. The effects of L-Ru on the cell viability, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cells and Annexin V-positive cells apoptosis induction were remarkably attenuated. This complex induced DNA damage, cell cycle arrest and cell death via caspase-dependent apoptosis involving PARP activation and induction of p53-dependent pathway. These findings suggested that this ruthenium complex might be a potential effective chemotherapeutic agent in NSCLC therapy.

A single AT-GC exchange can modulate charge transfer-induced p53-DNA dissociation

Using molecular dynamics simulations and electronic structure theory, we shed light on the charge dynamics that causes the differential interaction of tumor suppressor protein p53 with the p21 and Gadd45 genes in response to oxidative stress. We show that the sequence dependence of this selectivity results from competing charge transfer to the protein and through the DNA, with implications on the use of genome editing tools to influence the p53 regulatory function.

High Glucose with Insulin Induces Cell Cycle Progression and Activation of Oncogenic Signaling of Bladder Epithelial Cells Cotreated with Metformin and Pioglitazone

Metformin and pioglitazone are two commonly prescribed oral hypoglycemic agents for diabetes. Recent evidence suggests that these drugs may contribute to bladder cancer. This study investigated molecular mechanism underlying effects of metformin and pioglitazone in bladder epithelial carcinogenesis in type 2 diabetes. The cells derived from human bladder epithelial cells (HBlEpCs) were treated with metformin or pioglitazone with high glucose and insulin. Cell viability and proliferation were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and a bromodeoxyuridine incorporation assay, respectively, while cell cycle regulatory factors and oncogene expression were analyzed using western blotting. Metformin or pioglitazone suppressed cell viability concentration and time dependently, which was reversed by exposure to high glucose with or without insulin. Prolonged exposure to high glucose and insulin enhanced cyclin D, cyclin-dependent kinase 4 (Cdk4), and Cdk2 expression and suppressed cyclin-dependent kinase inhibitors p21 and p15/16 in HBlEpC cotreated with pioglitazone and metformin. Levels of tumor suppressor proteins p53 and cav-1 were downregulated while those of the oncogenic protein as c-Myc were upregulated under high glucose and insulin supplementation in HBlEpC cotreated with pioglitazone and metformin. Prolonged exposure to high glucose with or without insulin downregulated B cell lymphoma 2-associated X (Bax) and failed to enhance the expression of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) in drug-treated cells. These results suggest that hyperglycemic and insulinemic conditions promote cell cycle progression and oncogenic signaling in drug-treated bladder epithelial cells and uncontrolled hyperglycemia and hyperinsulinemia are probably greater cancer risk factors than diabetes drugs.

Integrated transcriptome interactome study of oncogenes and tumor suppressor genes in breast cancer

Breast cancer is the leading cause for mortality among women worldwide. Dysregulation of oncogenes and tumor suppressor genes is the major reason for the cause of cancer. Understanding these genes will provide clues and insights about their regulatory mechanism and their interplay in cancer. In the present study, an attempt is made to compare the functional characteristics and interactions of oncogenes and tumor suppressor genes to understand their biological role. 431 breast cancer samples from seven publicly available microarray datasets were collected and analysed using GEO2R tool. The identified 416 differentially expressed genes were classified into five gene sets as oncogenes (OG), tumor suppressor genes (TSG), druggable genes, essential genes and other genes. The gene sets were subjected to various analysis such as enrichment analysis (viz., GO, Pathways, Diseases and Drugs), network analysis, calculation of mutation frequencies and Guanine-Cytosine (GC) content. From the results, it was observed that the OG were having high GC content as well as high interactions than TSG. Moreover, the OG are found to have frequent mutations than TSG. The enrichment analysis results suggest that the oncogenes are involved in positive regulation of cellular protein metabolic process, macromolecule biosynthetic process and majorly in cell cycle and focal adhesion pathway in cancer. It was also found that these oncogenes are involved in other diseases such as skin diseases and viral infections. Collagenase, paclitaxel and docetaxel are some of the drugs found to be enriched for oncogenes.

The Emerging Role of Cyclin-Dependent Kinases (CDKs) in Pancreatic Ductal Adenocarcinoma

The family of cyclin-dependent kinases (CDKs) has critical functions in cell cycle regulation and controlling of transcriptional elongation. Moreover, dysregulated CDKs have been linked to cancer initiation and progression. Pharmacological CDK inhibition has recently emerged as a novel and promising approach in cancer therapy. This idea is of particular interest to combat pancreatic ductal adenocarcinoma (PDAC), a cancer entity with a dismal prognosis which is owed mainly to PDAC's resistance to conventional therapies. Here, we review the current knowledge of CDK biology, its role in cancer and the therapeutic potential to target CDKs as a novel treatment strategy for PDAC.

Comparison of hepatotoxicity and mechanisms induced by triclosan (TCS) and methyl-triclosan (MTCS) in human liver hepatocellular HepG2 cells

Triclosan (TCS) is used as an antimicrobial agent and has been widely dispersed and detected in the environment and organisms including human samples. Methyl-triclosan (MTCS) is the predominant bacterial TCS metabolite. At present, the toxicological effects and mechanism of TCS and MTCS are still not fully understood. In this study, the cytotoxic effects of TCS and MTCS in HepG2 cells were investigated in terms of cell proliferation, comet assay, cell cycle, and apoptosis. In addition, the expressions of related proteins were detected with western blotting analysis. The results showed that TCS could significantly inhibit cell proliferation, while MTCS had no obvious effect on cell growth. Both TCS and MTCS caused oxidative injury associated with HO-1 induction and increased DNA strand breaks, which consequently initiated the damage repair process via up-regulation of DNA-PKcs. In addition, TCS blocked the HepG2 cells in S and G2/M phases of cell cycle through down-regulation of cyclin A2 and CDK; while MTCS induced cell cycle arrest at the S phase through up-regulation of cyclin A2 and CDK. Furthermore, TCS activated p53 mediated apoptosis in HepG2 cells in a caspase-independent manner, while MTCS induced apoptosis was dependent on caspase. Moreover, TCS exposure exhibited more severe toxicity in HepG2 cells as compared with MTCS exposure, indicating that the replacement of the ionizable proton in TCS by the methyl group in MTCS is correlated with the cellular toxicity and the molecular mechanism.

Oxidative stress and cell cycle arrest induced by short-term exposure to dustfall PM2.5 in A549 cells

It was reported that in vitro short-term exposure to PM_2.5 caused different lung diseases through inflammatory response, immune toxicity, oxidative stress, and genetic mutations. However, the complex molecular biological mechanism for its toxicity had not been fully elucidated. Therefore, the present study investigated the cytotoxicity, oxidative damage, mitochondria damage, apoptosis, and cell cycle arrest of NX and QH PM_2.5 in A549 cells. Further, cell cycle arrest-related gene levels in PM_2.5-induced A549 cells were also detected. Our results suggested that PM_2.5 reduced the cell viability in A549 cells. Simultaneously, excessive ROS decreased MMP levels and damaged mitochondrial membrane integrity and induced mitochondrial oxidative damage through the oxygen-dependent killer route, resulting in mitochondrial damage and cell apoptosis. Besides, the results also showed that PM_2.5 induced A549 cell cycle alteration in G2/M phase after co-culture for 24 h. G2/M phase arrest was induced by upregulation of p53 and p21 and downregulation of CDK1 mRNA expression. In addition, lncRNA Sox2ot might play an important role as the specific oncogenes and it participated in G2/M phase arrest by regulating the expression of EZH₂.

RGNNV-induced cell cycle arrest at G1/S phase enhanced viral replication via p53-dependent pathway in GS cells

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Infection of RGNNV redistributed NPM1, stabilized p53 and inhibited cell proliferation by inducing G1 arrest.

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Infection of RGNNV activated p53-dependent pathway, resulting in G1/S phase cell cycle arrest in host cells and directly impacting viral replication.

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NPM1 knockdown could abrogate RGNNV-induced cell proliferation inhibition and cell cycle arrest.

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Our results revealed that RGNNV infection could perturb the progression of cell cycle via the NPM1-p53 pathway and facilitate virus gene replication.

Nervous necrosis virus (NNV) is a ubiquitous pathogen in the aquaculture worldwide. Little is known about the relationship between NNV virus and host cells. Our studies showed that RGNNV infection could induce cell cycle arrest via activation of p53 signaling in cultured host cells. Infection of RGNNV redistributed NPM1, stabilized p53 and inhibited cell proliferation by inducing G1 arrest. RGNNV infection also led to phosphorylation and accumulation of p53 in a time-dependent manner. Furthermore, RGNNV infection upregulated cyclin-dependent kinase inhibitor 1 A (p21) and downregulated cyclin E and cyclin-dependent kinase 2 (CDK2). The expression of genes in the p53 pathway did not change significantly after p53 knockdown by pifithrin-α during RGNNV infection. However, NPM1 knockdown could abrogate RGNNV-induced cell proliferation inhibition, activation of p53 signaling and cell cycle arrest. In addition, RGNNV infection of the cells synchronized in various stages of cell cycle showed that viral genomic RNA and virus titer were higher in the cells released from G1 phase- or S phase-synchronized cells than that in the cells released from the G2 phase-synchronized or asynchronous cells after 18 h p.i. Therefore, our study reveals that RGNNV infection induces the p53-dependent pathway, resulting in a cell cycle arrest at G1 phase in host cells, which might provide a favorable condition for viral replication.

The Roles of p53 in Mitochondrial Dynamics and Cancer Metabolism: The Pendulum between Survival and Death in Breast Cancer?

Cancer research has been heavily geared towards genomic events in the development and progression of cancer. In contrast, metabolic regulation, such as aberrant metabolism in cancer, is poorly understood. Alteration in cellular metabolism was once regarded simply as a consequence of cancer rather than as playing a primary role in cancer promotion and maintenance. Resurgence of cancer metabolism research has identified critical metabolic reprogramming events within biosynthetic and bioenergetic pathways needed to fulfill the requirements of cancer cell growth and maintenance. The tumor suppressor protein p53 is emerging as a key regulator of metabolic processes and metabolic reprogramming in cancer cells&mdash;balancing the pendulum between cell death and survival. This review provides an overview of the classical and emerging non-classical tumor suppressor roles of p53 in regulating mitochondrial dynamics: mitochondrial engagement in cell death processes in the prevention of cancer. On the other hand, we discuss p53 as a key metabolic switch in cellular function and survival. The focus is then on the conceivable roles of p53 in breast cancer metabolism. Understanding the metabolic functions of p53 within breast cancer metabolism will, in due course, reveal critical metabolic hotspots that cancers advantageously re-engineer for sustenance. Illustration of these events will pave the way for finding novel therapeutics that target cancer metabolism and serve to overcome the breast cancer burden.

The ubiquitin ligase COP1 regulates cell cycle and apoptosis by affecting p53 function in human breast cancer cell lines

BACKGROUND

The E3 ubiquitin ligase constitutive photomorphogenic 1 (COP1) mediates cell survival, growth, and development, and interacts with the tumor suppressor protein p53 to induce its ubiquitination and degradation. Recent studies reported that COP1 overexpression is associated with increased cell proliferation, transformation, and disease progression in a variety of cancer types. In this study, we investigated whether COP1 regulates p53-mediated cell cycle arrest and apoptosis in human breast cancer cell lines.

METHODS

We downregulated COP1 expression using lentiviral particles expressing short hairpin RNA (shRNA) targeting COP1 and measured the effects of the knockdown in three different breast cancer cell lines.

RESULTS

COP1 silencing resulted in p53 activation, which induced the expression of p21 and p53-upregulated modulator of apoptosis (PUMA) expression, and reduced the levels of cyclin-dependent kinase 2 (CDK2). Notably, knockdown of COP1 was associated with cell cycle arrest during the G₀/G₁ phase.

CONCLUSIONS

The COP1-mediated degradation of p53 regulates cancer cell growth and apoptosis. Our results indicate that COP1 regulates human breast cancer cell proliferation and apoptosis in a p53-dependent manner. These findings suggest that COP1 might be a promising potential target for breast cancer-related gene therapy.