Gadd45a contributes to p53 stabilization in response to DNA damage

Macromolecules with predominant β-pleated sheet proteins in extracellular vesicles released from Raphanus sativus L. var. caudatus Alef microgreens induce DNA damage-mediated apoptosis in HCT116 colon cancer cells

Plant-derived bioactive macromolecules (i.e., proteins, lipids, and nucleic acids) were prepared as extracellular vesicles (EVs). Plant-derived EVs are gaining pharmaceutical research interest because of their bioactive components and delivery properties. The spherical nanosized EVs derived from Raphanus sativus L. var. caudatus Alef microgreens previously showed antiproliferative activity in HCT116 colon cancer cells from macromolecular compositions (predominantly proteins). To understand the mechanism of action, the biological activity studies, i.e., antiproliferation, cellular biochemical changes, DNA conformational changes, DNA damage, apoptotic nuclear morphological changes, apoptosis induction, and apoptotic pathways, were determined by neutral red uptake assay, synchrotron radiation-based Fourier transform infrared microspectroscopy, circular dichroism spectroscopy, comet assay, 4',6-diamidino-2-phenylindole (DAPI) staining, flow cytometry, and caspase activity assay, respectively. EVs inhibited HCT116 cell growth in concentration- and time-dependent manners, with a half-maximal inhibitory concentration of 675.4 ± 33.8 μg/ml at 48 h and a selectivity index of 1.5 ± 0.076. HCT116 treated with EVs mainly changed the cellular biochemical compositions in the nucleic acids and carbohydrates region. The DNA damage caused no changes in DNA conformation. The apoptotic nuclear morphological changes were associated with the increased apoptotic cell population. The apoptotic cell death was induced by both extrinsic and intrinsic pathways. EVs have potential as antiproliferative bioparticles.

The chemotherapeutic agent doxorubicin induces brain senescence, with modulation by APOE genotype

Many cancer patients experience serious cognitive problems related to their treatment, which can greatly affect their quality of life. The molecular mechanisms of this cancer chemotherapy-induced cognitive impairment (CICI) are unknown, thus slowing the development of preventative approaches. We hypothesized that cancer chemotherapies could induce cellular senescence in the brain, creating a pro-inflammatory environment and damaging normal brain communication. We tested this hypothesis using the common chemotherapeutic agent doxorubicin in two independent mouse models. In the first model, we used mice that express tdTomato under the pdkn2a (p16) promoter; p16 is a regulator of cellular senescence, and its upregulation is denoted by the presence of fluorescently tagged cells. Two weeks after exposure to three doses of 5 mg/kg doxorubicin, the number of tdTomato positive cells were increased nearly three-fold in both the cerebral cortex and the hippocampus. tdTomato staining co-localized with neurons, microglia, oligodendrocyte precursor cells, and endothelial cells, but not astrocytes. In the second model, we used APOE knock-in mice, since the APOE4 allele is a risk factor for CICI in humans and mouse models. We isolated RNA from the cerebral cortex of APOE3 and APOE4 mice from one to 21 days after a single dose of 10 mg/kg doxorubicin. Using NanoString analysis of over 700 genes related to neuroinflammation and RT-qPCR analysis of cerebral cortex transcripts, we found two-fold induction of four senescence-related genes at three weeks in the APOE4 mice compared to the APOE3 control mice: p21(cdkn1a), p16, Gadd45a, and Egr1. We conclude that doxorubicin promotes cellular senescence pathways in the brain, supporting the hypothesis that drugs to eliminate senescent cells could be useful in preventing CICI.

Spatially coordinated heterochromatinization of long synaptic genes in fragile X syndrome

Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X chromosome in FXS patient-derived iPSCs, iPSC-derived neural progenitors, EBV-transformed lymphoblasts, and brain tissue with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication-stress-induced double-strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the mutation-length CGG to premutation length reverses H3K9me3 on the X chromosome and multiple autosomes, refolds TADs, and restores gene expression. H3K9me3 domains can also arise in normal-length iPSCs created with perturbations linked to genome instability, suggesting their relevance beyond FXS. Our results reveal Mb-scale heterochromatinization and trans interactions among loci susceptible to instability.

Pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine Sulfonamides as an Important Scaffold for Anticancer Drug Discovery-In Vitro and In Silico Evaluation

Pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine sulfonamides (MM-compounds) are a relatively new class of heterocyclic compounds that exhibit a wide variety of biological actions, including anticancer properties. Here, we used caspase enzyme activity assays, flow cytometry analysis of propidium iodide (PI)-stained cells, and a DNA laddering assay to investigate the mechanisms of cell death triggered by the MM-compounds (MM134, -6, -7, and -9). Due to inconsistent results in caspase activity assays, we have performed a bromodeoxyuridine (BrdU) incorporation assay, colony formation assay, and gene expression profiling. The compounds' cytotoxic and pro-oxidative properties were also assessed. Additionally, computational studies were performed to demonstrate the potential of the scaffold for future drug discovery endeavors. MM-compounds exhibited strong micromolar (0.06-0.35 µM) anti-proliferative and pro-oxidative activity in two cancer cell lines (BxPC-3 and PC-3). Activation of caspase 3/7 was observed following a 24-h treatment of BxPC-3 cells with IC₅₀ concentrations of MM134, -6, and -9 compounds. However, no DNA fragmentation characteristics for apoptosis were observed in the flow cytometry and DNA laddering analysis. Gene expression data indicated up-regulation of BCL10, GADD45A, RIPK2, TNF, TNFRSF10B, and TNFRSF1A (TNF-R1) following treatment of cells with the MM134 compound. Moreover, in silico studies indicated AKT2 kinase as the primary target of compounds. MM-compounds exhibit strong cytotoxic activity with pro-oxidative, pro-apoptotic, and possibly pro-necroptotic properties that could be employed for further drug discovery approaches.

Go-Ichi-Ni-San 2: A potential biomarker and therapeutic target in human cancers

Cancer incidence and mortality are increasing globally, leading to its rising status as a leading cause of death. The Go-Ichi-Ni-San (GINS) complex plays a crucial role in DNA replication and the cell cycle. The GINS complex consists of four subunits encoded by the GINS1, GINS2, GINS3, and GINS4 genes. Recent findings have shown that GINS2 expression is upregulated in many diseases, particularly tumors. For example, increased GINS2 expression has been found in cervical cancer, gastric adenocarcinoma, glioma, non-small cell lung cancer, and pancreatic cancer. It correlates with the clinicopathological characteristics of the tumors. In addition, high GINS2 expression plays a pro-carcinogenic role in tumor development by promoting tumor cell proliferation and migration, inhibiting tumor cell apoptosis, and blocking the cell cycle. This review describes the upregulation of GINS2 expression in most human tumors and the pathway of GINS2 in tumor development. GINS2 may serve as a new marker for tumor diagnosis and a new biological target for therapy.

Chk1/2 inhibitor AZD7762 enhances the susceptibility of IDH-mutant brain cancer cells to temozolomide

The IDH mutation initially exhibits chemosensitive properties, progression-free survival cannot be achieved in the later grades, and malignant transformation occurs as a result of TMZ-induced hypermutation profile and adaptation to this profile. In this study, we evaluated the potential of the combination of TMZ and AZD7762 at molecular level, to increase the anticancer activity of TMZ in IDH-mutant U87-mg cells. We used the WST-1 test to evaluate cytotoxic effect of TMZ and AZD7762 combination with dose-effect and isobologram curves. The effects of the inhibitory and effective concentrations of the combination on apoptosis, cell cycle and γ-H2AX phosphorylation were analyzed with flow cytometry. The expression of genes responsible for the DNA damage response was analyzed with qRT-PCR. The combination showed a synergistic effect with high dose reduction index. Single and combined administrations of TMZ and AZD7762 increased in G₂/M arrest from 24 to 48 h, and cells in the G₂/M phase shifted towards octaploidy at 72 h. While no double-strand breaks were detected after TMZ treatment, AZD7762 and combination treatments caused a significant increase in γ-H2AX phosphorylation and increased apoptotic stimulation towards 72 h although TMZ did not cause apoptotic effect in IDH-mutant U87-mg cells. The genes controlling the apoptosis were determined to be upregulated in all three groups, and genes regarding cell cycle checkpoints were downregulated. Targeting Chk1/2 with AZD7762 simultaneously with TMZ may be a potential therapeutic strategy for both increasing the sensitivity of IDH-mutant glioma cells to TMZ and reducing the dose of TMZ. In IDH-mutant glioma cells, AZD7762, the Chk1/2 inhibitor, can increase the efficacy of Temozolomide by (i) increasing mitotic chaos, and (ii) inhibiting double-strand break repair, (iii) thereby inducing cell death.

Identification of activity-induced Egr3-dependent genes reveals genes associated with DNA damage response and schizophrenia

Bioinformatics and network studies have identified the immediate early gene transcription factor early growth response 3 (EGR3) as a master regulator of genes differentially expressed in the brains of patients with neuropsychiatric illnesses ranging from schizophrenia and bipolar disorder to Alzheimer's disease. However, few studies have identified and validated Egr3-dependent genes in the mammalian brain. We have previously shown that Egr3 is required for stress-responsive behavior, memory, and hippocampal long-term depression in mice. To identify Egr3-dependent genes that may regulate these processes, we conducted an expression microarray on hippocampi from wildtype (WT) and Egr3-/- mice following electroconvulsive seizure (ECS), a stimulus that induces maximal expression of immediate early genes including Egr3. We identified 69 genes that were differentially expressed between WT and Egr3-/- mice one hour following ECS. Bioinformatic analyses showed that many of these are altered in, or associated with, schizophrenia, including Mef2c and Calb2. Enrichr pathway analysis revealed the GADD45 (growth arrest and DNA-damage-inducible) family (Gadd45b, Gadd45g) as a leading group of differentially expressed genes. Together with differentially expressed genes in the AP-1 transcription factor family genes (Fos, Fosb), and the centromere organization protein Cenpa, these results revealed that Egr3 is required for activity-dependent expression of genes involved in the DNA damage response. Our findings show that EGR3 is critical for the expression of genes that are mis-expressed in schizophrenia and reveal a novel requirement for EGR3 in the expression of genes involved in activity-induced DNA damage response.

Of the many cellular responses activated by TP53, which ones are critical for tumour suppression?

The tumour suppressor TP53 is a master regulator of several cellular processes that collectively suppress tumorigenesis. The TP53 gene is mutated in ~50% of human cancers and these defects usually confer poor responses to therapy. The TP53 protein functions as a homo-tetrameric transcription factor, directly regulating the expression of ~500 target genes, some of them involved in cell death, cell cycling, cell senescence, DNA repair and metabolism. Originally, it was thought that the induction of apoptotic cell death was the principal mechanism by which TP53 prevents the development of tumours. However, gene targeted mice lacking the critical effectors of TP53-induced apoptosis (PUMA and NOXA) do not spontaneously develop tumours. Indeed, even mice lacking the critical mediators for TP53-induced apoptosis, G1/S cell cycle arrest and cell senescence, namely PUMA, NOXA and p21, do not spontaneously develop tumours. This suggests that TP53 must activate additional cellular responses to mediate tumour suppression. In this review, we will discuss the processes by which TP53 regulates cell death, cell cycling/cell senescence, DNA damage repair and metabolic adaptation, and place this in context of current understanding of TP53-mediated tumour suppression.

GADD45A induces neuropathic pain by activating P53 apoptosis pathway in mice

BACKGROUND

Neuropathic pain is a common condition with current heights of varying etiology. The therapeutic drugs are also poorly work and often limited by side effects such as dizziness.

OBJECTIVE

This study aimed to explore the function mechanism of GADD45A in neuropathic pain.

METHODS

The DEGs in neuropathic pain mouse model chip were screened by bioinformatics analysis. The expression of GADD45A in SNL model was determined by RT-qPCR and Immunofluorescence assay. The protein expression of p53-apoptosis pathway proteins was determined by western blotting.

RESULTS

Combination analysis of bioinformatics methods revealed that the expression of GADD45A was upregulated in SNL. The results of RT-qPCR assay and Immunofluorescence assay revealed that GADD45A was overexpressed in all of time points SNL model. Furthermore, knockdown of GADD45A in SNL remarkably antagonized the malignance phenotype compared with the Ad-GFP treated SNL. In addition, knockdown of GADD45A downregulated the expression of p53 and reduced the apoptosis of spinal cord nerve cells.

CONCLUSIONS

Our study suggests that GADD45A may be a biomarker in the neuropathic pain of mice.

Molecular Response to Combined Molecular- and External Radiotherapy in Head and Neck Squamous Cell Carcinoma (HNSCC)

Simple Summary

Our previous preclinical trial in a head and neck squamous cell carcinoma (HNSCC) xenograft model showed a high potential for the improvement of curative treatment outcome upon the combination treatment of a radiolabeled (Yttrium-90) anti-EGFR antibody (Cetuximab) and external radiotherapy. We aim to elucidate the molecular response of HNSCC tumors upon this combination. Here, we show that the combination treatment leads to an increasing number and complexity of DNA double strand breaks. The upregulation of p21^cip1/waf1 expression and cleaved caspase-3 suggest a blockage of cell cycle transition and an induction of programmed cell death. Collectively, a complex interplay between molecular mechanisms involved in cell death induction, cell cycle arrest, and DNA double strand break repair accounts for the beneficial potential using Yttrium-90-Cetuximab in combination with external radiotherapy.

Abstract

Combination treatment of molecular targeted and external radiotherapy is a promising strategy and was shown to improve local tumor control in a HNSCC xenograft model. To enhance the therapeutic value of this approach, this study investigated the underlying molecular response. Subcutaneous HNSCC FaDu_DD xenografts were treated with single or combination therapy (X-ray: 0, 2, 4 Gy; anti-EGFR antibody (Cetuximab) (un-)labeled with Yttrium-90 (⁹⁰Y)). Tumors were excised 24 h post respective treatment. Residual DNA double strand breaks (DSB), mRNA expression of DNA damage response related genes, immunoblotting, tumor histology, and immunohistological staining were analyzed. An increase in number and complexity of residual DNA DSB was observed in FaDu_DD tumors exposed to the combination treatment of external irradiation and ⁹⁰Y-Cetuximab relative to controls. The increase was observed in a low oxygenated area, suggesting the expansion of DNA DSB damages. Upregulation of genes encoding p21^cip1/waf1 (CDKN1A) and GADD45α (GADD45A) was determined in the combination treatment group, and immunoblotting as well as immunohistochemistry confirmed the upregulation of p21^cip1/waf1. The increase in residual γH2AX foci leads to the blockage of cell cycle transition and subsequently to cell death, which could be observed in the upregulation of p21^cip1/waf1 expression and an elevated number of cleaved caspase-3 positive cells. Overall, a complex interplay between DNA damage repair and programmed cell death accounts for the potential benefit of the combination therapy using ⁹⁰Y-Cetuximab and external radiotherapy.

tRNALys-Derived Fragment Alleviates Cisplatin-Induced Apoptosis in Prostate Cancer Cells

Cisplatin is a standard treatment for prostate cancer, which is the third leading cause of cancer-related deaths among men globally. However, patients who have undergone cisplatin can rxperience relapse. tRNA-derived fragments (tRFs) are small non-coding RNAs generated via tRNA cleavage; their physiological activities are linked to the development of human diseases. Specific tRFs, including tRF-315 derived from tRNA^Lys, are highly expressed in prostate cancer patients. However, whether tRF-315 regulates prostate cancer cell proliferation or apoptosis is unclear. Herein, we confirmed that tRF-315 expression was higher in prostate cancer cells (LNCaP, DU145, and PC3) than in normal prostate cells. tRF-315 prevented cisplatin-induced apoptosis and alleviated cisplatin-induced mitochondrial dysfunction in LNCaP and DU145 cells. Moreover, transfection of tRF-315 inhibitor increased the expression of apoptotic pathway-related proteins in LNCaP and DU145 cells. Furthermore, tRF-315 targeted the tumor suppressor gene GADD45A, thus regulating the cell cycle, which was altered by cisplatin in LNCaP and DU145 cells. Thus, tRF-315 protects prostate cancer cells from mitochondrion-dependent apoptosis induced by cisplatin treatment.

Chelidonine Induces Apoptosis via GADD45a-p53 Regulation in Human Pancreatic Cancer Cells

Chelidonium majus has been used as a traditional medicine in China and western countries for various diseases, including inflammation and cancer. However, the anti-cancer effect of chelidonine, a major compound of C. majus extracts, on pancreatic cancer remains poorly understood. In this study, we found that treatment with chelidonine inhibited proliferation of BxPC-3 and MIA PaCa-2 human pancreatic cancer cells. Annexin-V/propidium iodide staining assay showed that this growth inhibitory effect of chelidonine was induced through apoptosis. We found that chelidonine treatment upregulated mRNA levels and transcription factor activity in both cell lines. Increases in protein expression levels of p53, GADD45A, p21 and cleaved caspase-3 were also observed, with more distinct changes in MIA PaCa-2 cells compared to the BxPC-3 cells. These results suggest that chelidonine induces pancreatic cancer apoptosis through the p53 and GADD45A pathways. Our findings provide new insights into the use of chelidonine for the treatment of pancreatic cancer.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

Attenuation of p53 mutant as an approach for treatment Her2-positive cancer

Breast cancer is one of the world's leading causes of oncological disease-related death. It is characterized by a high degree of heterogeneity on the clinical, morphological, and molecular levels. Based on molecular profiling breast carcinomas are divided into several subtypes depending on the expression of a number of cell surface receptors, e.g., ER, PR, and HER2. The Her2-positive subtype occurs in ~10-15% of all cases of breast cancer, and is characterized by a worse prognosis of patient survival. This is due to a high and early relapse rate, as well as an increased level of metastases. Several FDA-approved drugs for the treatment of Her2-positive tumors have been developed, although eventually cancer cells develop drug resistance. These drugs target either the homo- or heterodimerization of Her2 receptors or the receptors' RTK activity, both of them being critical for the proliferation of cancer cells. Notably, Her2-positive cancers also frequently harbor mutations in the TP53 tumor suppressor gene, which exacerbates the unfavorable prognosis. In this review, we describe the molecular mechanisms of RTK-specific drugs and discuss new perspectives of combinatorial treatment of Her2-positive cancers through inhibition of the mutant form of p53.

Expression and prognostic significance of the P53-related DNA damage repair proteins checkpoint kinase 1 (CHK1) and growth arrest and DNA-damage-inducible 45 alpha (GADD45A) in human oral squamous cell carcinoma

DNA damage repair is a key factor in the maintenance of cell genome stability, plays an important role in the regulation of tumour evolution, and can affect the prognosis of cancer patients. This study aimed to detect the protein expression of the DNA damage repair protein P53 and its upstream and downstream regulators, CHK1, GADD45A, and MDM2, in oral squamous cell carcinoma (OSCC), in order to analyse the association between the expression of these proteins and overall survival, and to assess their prognostic implications for OSCC patients. The expression of the above proteins was detected by immunohistochemistry in 80 human OSCC tissue samples and in non-cancerous tissue samples. Compared to that in the non-cancerous tissue, the expression of CHK1, GADD45A, and MDM2 in OSCC tissue was significantly increased. The protein expression of the tumour suppressor gene P53 was also increased. Patients with high CHK1 and MDM2 expression levels had a reduced survival time and a poor prognosis, whereas patients with high GADD45A expression levels had a good prognosis. Our results indicate that high CHK1 expression is an independent risk factor for poor OSCC prognosis, and that CHK1 may be a potential target for OSCC clinical treatment.

Mitochondrial Quality Control in Age-Related Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is age-related interstitial lung disease of unknown etiology. About 100,000 people in the U.S have IPF, with a 3-year median life expectancy post-diagnosis. The development of an effective treatment for pulmonary fibrosis will require an improved understanding of its molecular pathogenesis and the “normal” and “pathological’ hallmarks of the aging lung. An important characteristic of the aging organism is its lowered capacity to adapt quickly to, and counteract, disturbances. While it is likely that DNA damage, chronic endoplasmic reticulum (ER) stress, and accumulation of heat shock proteins are capable of initiating tissue repair, recent studies point to a pathogenic role for mitochondrial dysfunction in the development of pulmonary fibrosis. These studies suggest that damage to the mitochondria induces fibrotic remodeling through a variety of mechanisms including the activation of apoptotic and inflammatory pathways. Mitochondrial quality control (MQC) has been demonstrated to play an important role in the maintenance of mitochondrial homeostasis. Different factors can induce MQC, including mitochondrial DNA damage, proteostasis dysfunction, and mitochondrial protein translational inhibition. MQC constitutes a complex signaling response that affects mitochondrial biogenesis, mitophagy, fusion/fission and the mitochondrial unfolded protein response (UPRmt) that, together, can produce new mitochondria, degrade the components of the oxidative complex or clearance the entire organelle. In pulmonary fibrosis, defects in mitophagy and mitochondrial biogenesis have been implicated in both cellular apoptosis and senescence during tissue repair. MQC has also been found to have a role in the regulation of other protein activity, inflammatory mediators, latent growth factors, and anti-fibrotic growth factors. In this review, we delineated the role of MQC in the pathogenesis of age-related pulmonary fibrosis.

High-throughput transcriptome analysis reveals that the loss of Pten activates a novel NKX6-1/RASGRP1 regulatory module to rescue microphthalmia caused by Fgfr2-deficient lenses

FGFR signaling is critical to development and disease pathogenesis, initiating phosphorylation-driven signaling cascades, notably the RAS-RAF-MEK-ERK and PI3 K-AKT cascades. PTEN antagonizes FGFR signaling by reducing AKT and ERK activation. Mouse lenses lacking FGFR2 exhibit microphakia and reduced ERK and AKT phosphorylation, widespread apoptosis, and defective lens fiber cell differentiation. In contrast, simultaneous deletion of both Fgfr2 and Pten restores ERK and AKT activation levels as well as lens size, cell survival and aspects of fiber cell differentiation; however, the molecular basis of this "rescue" remains undefined. We performed transcriptomic analysis by RNA sequencing of mouse lenses with conditional deletion of Fgfr2, Pten or both Fgfr2 and Pten, which reveal new molecular mechanisms that uncover how FGFR2 and PTEN signaling interact during development. The FGFR2-deficient lens transcriptome demonstrates overall loss of fiber cell identity with deregulated expression of 1448 genes. We find that ~ 60% of deregulated genes return to normal expression levels in lenses lacking both Fgfr2 and Pten. Further, application of customized filtering parameters to these RNA-seq data sets identified 68 high-priority candidate genes. Bioinformatics analyses showed that the cis-binding motif of a high-priority homeodomain transcription factor, NKX6-1, was present in the putative promoters of ~ 78% of these candidates. Finally, biochemical reporter assays demonstrate that NKX6-1 activated the expression of the high-priority candidate Rasgrp1, a RAS-activating protein. Together, these data define a novel regulatory module in which NKX6-1 directly activates Rasgrp1 expression to restore the balance of ERK and AKT activation, thus providing new insights into alternate regulation of FGFR downstream events.

Moringin from Moringa Oleifera Seeds Inhibits Growth, Arrests Cell-Cycle, and Induces Apoptosis of SH-SY5Y Human Neuroblastoma Cells through the Modulation of NF-κB and Apoptotic Related Factors

In the last decades, glucosinolates (GLs), precursors of isothiocyanates (ITCs), have been studied mostly for their chemopreventive and chemotherapeutic properties. The aim of our research was to study the antiproliferative effect of 4-(α-L-rhamnopyranosyloxy) benzyl glucosinolate (glucomoringin; GMG) bioactivated by myrosinase enzyme to form the corresponding isothiocyanate 4-(α-L-rhamnopyranosyloxy) benzyl C (moringin) in SH-SY5Y human neuroblastoma cells. We found that moringin significantly reduced SH-SY5Y cell growth in a time and concentration-dependent (p < 0.05, 0.01, and 0.001 vs. ctrl, after treatment with 16.4 µM moringin for 24, 48, and 72 h, respectively) manner through a mechanism involving the activation of apoptotic machinery. In addition, it altered the normal progression of cells through the cell cycle, increasing the cell population in both G2 and S phases, as well as decreasing that in the G1 phase. Studying the drug mechanism of action, we found that moringin was able to increase the expression of p53, p21, and Bax at both the protein and transcriptional level. Moreover, exposure of SH-SY5Y cells to moringin significantly increased the gene expression of both caspase 3 and 9 and enhanced their cleavage, thereby initiating an intrinsic apoptotic cascade. Finally, moringin inhibited nuclear translocation of NF-κB. Our study demonstrates the ability of moringin to reduce the growth of SH-SY5Y cells and reveals its mechanism of action, suggesting its promising role as an anticancer drug.

Metformin and tenovin-6 synergistically induces apoptosis through LKB1-independent SIRT1 down-regulation in non-small cell lung cancer cells

Sirtuin 1 (SIRT1) is known to play a role in a variety of tumorigenesis processes by deacetylating histone and non‐histone proteins; however, antitumour effects by suppressing SIRT1 activity in non‐small cell lung cancer (NSCLC) remain unclear. This study was designed to scrutinize clinicopathological significance of SIRT1 in NSCLC and investigate effects of metformin on SIRT1 inhibition. This study also evaluated new possibilities of drug combination using a SIRT1 inhibitor, tenovin‐6, in NSCLC cell lines. It was found that SIRT1 was overexpressed in 300 (62%) of 485 formalin‐fixed paraffin‐embedded NSCLC tissues. Its overexpression was significantly associated with reduced overall survival and poor recurrence‐free survival after adjusted for histology and pathologic stage. Thus, suppression of SIRT1 expression may be a reasonable therapeutic strategy for NSCLC. Metformin in combination with tenovin‐6 was found to be more effective in inhibiting cell growth than either agent alone in NSCLC cell lines with different liver kinase B1 (LKB1) status. In addition, metformin and tenovin‐6 synergistically suppressed SIRT1 expression in NSCLC cells regardless of LKB1 status. The marked reduction in SIRT1 expression by combination of metformin and tenovin‐6 increased acetylation of p53 at lysine 382 and enhanced p53 stability in LKB1‐deficient A549 cells. The combination suppressed SIRT1 promoter activity more effectively than either agent alone by up‐regulating hypermethylation in cancer 1 (HIC1) binding at SIRT1 promoter. Also, suppressed SIRT1 expression by the combination synergistically induced caspase‐3‐dependent apoptosis. The study concluded that metformin with tenovin‐6 may enhance antitumour effects through LKB1‐independent SIRT1 down‐regulation in NSCLC cells.

Telomeric epigenetic response mediated by Gadd45a regulates stem cell aging and lifespan

Progressive attrition of telomeres triggers DNA damage response (DDR) and limits the regenerative capacity of adult stem cells during mammalian aging. Intriguingly, telomere integrity is not only determined by telomere length but also by the epigenetic status of telomeric/sub-telomeric regions. However, the functional interplay between DDR induced by telomere shortening and epigenetic modifications in aging remains unclear. Here, we show that deletion of Gadd45a improves the maintenance and function of intestinal stem cells (ISCs) and prolongs lifespan of telomerase-deficient mice (G3Terc ^-/-). Mechanistically, Gadd45a facilitates the generation of a permissive chromatin state for DDR signaling by inducing base excision repair-dependent demethylation of CpG islands specifically at sub-telomeric regions of short telomeres. Deletion of Gadd45a promotes chromatin compaction in sub-telomeric regions and attenuates DDR initiation at short telomeres of G3Terc ^-/- ISCs. Treatment with a small molecule inhibitor of base excision repair reduces DDR and improves the maintenance and function of G3Terc ^-/- ISCs. Taken together, our study proposes a therapeutic approach to enhance stem cell function and prolong lifespan by targeting epigenetic modifiers.

ERβ alters the chemosensitivity of luminal breast cancer cells by regulating p53 function

Estrogen receptor α (ERα)-positive breast cancers tend to develop resistance to both endocrine therapy and chemotherapy. Despite recent progress in defining molecular pathways that confer endocrine resistance, the mechanisms that regulate chemotherapy response in luminal tumors remain largely elusive. Luminal tumors often express wild-type p53 that is a major determinant of the cellular DNA damage response. Similar to p53, the second ER subtype, ERβ, has been reported to inhibit breast tumorigenesis by acting alone or in collaboration with p53. However, a synergistic mechanism of action has not been described. Here, we suggest that ERβ relies on p53 to elicit its tumor repressive actions in ERα-positive breast cancer cells. Upregulation of ERβ and treatment with ERβ agonists potentiates the tumor suppressor function of p53 resulting in decreased survival. This effect requires molecular interaction between the two proteins that disrupts the inhibitory action of ERα on p53 leading to increased transcriptional activity of p53. In addition, we show that the same interaction alters the chemosensitivity of endocrine-resistant cells including their response to tamoxifen therapy. Our results suggest a collaboration of ERβ and p53 tumor suppressor activity in breast cancer cells that indicates the importance of ligand-regulated ERβ as a tool to target p53 activity and improve the clinical management of resistant disease.

Gadd45a gene silencing by RNAi promotes cell proliferation and inhibits apoptosis and senescence in skin squamous cell carcinoma through the p53 signaling pathway

Skin squamous cell carcinoma (SCC) is generally considered as nonaggressive lesions and mainly caused by ultraviolet (UV) radiation. Gadd45a is a key component protecting skin against UV-induced tumors. For that, the study aims to investigate the mechanism of Gadd45a gene silencing on cell proliferation, apoptosis, and senescence in nude mice with skin SCC through the p53 signaling pathway. Healthy nude mice was collected as the normal group and 40 nude mouse models of skin SCC were successfully established as the model group, which were sub-divided into five groups. The incidence, size, and weight of SCC tumor of nude mice were observed. The mRNA expression of Gadd45a, Cyclin B1, MMP-2, Bcl-2, and Bax were determined by RT-qPCR. Cell viability, cell cycle and apoptosis, cell senescence were detected by MTT assay, flow cytometry, and β-galactosidase staining, respectively. The levels of inflammatory factors and vascular endothelial growth factor (VEGF) were detected by using ELISA. The protein expression rate of mutant p53 was detected by immunohistochemistry. Mice transfected with siGadd45a showed increased tumor incidence, size, and weight. Cells transfected with siGadd45a showed decrease in expression of Gadd45a and Bax; and increase in expression of Cyclin B1, MMP-2, and Bcl-2, expression of mutant p53, IL-1α, IL-1β, IL-6, TNF-α, and VEGF. Cell apoptosis and senescence were inhibited, while cell viability and proliferation were promoted after siGadd45a treatment. The results reveal that Gadd45a silencing increases tumor cell proliferation and reduces apoptosis and senescence through the p53 signaling pathway in skin SCC.

The long non-coding RNA GAS5 differentially regulates cell cycle arrest and apoptosis through activation of BRCA1 and p53 in human neuroblastoma

The long non-coding RNA GAS5 has been shown to modulate cancer proliferation in numerous human cancer systems and has been correlated with successful patient outcome. Our examination of GAS5 in neuroblastoma has revealed robust expression in both MYCN-amplified and non-amplified cell lines. Knockdown of GAS5 In vitro resulted in defects in cell proliferation, apoptosis, and induced cell cycle arrest. Further analysis of GAS5 clones revealed multiple novel splice variants, two of which inversely modulated with MYCN status. Complementation studies of the variants post-knockdown of GAS5 indicated alternate phenotypes, with one variant (FL) considerably enhancing cell proliferation by rescuing cell cycle arrest and the other (C2) driving apoptosis, suggesting a unique role for each in neuroblastoma cancer physiology. Global sequencing and ELISA arrays revealed that the loss of GAS5 induced p53, BRCA1, and GADD45A, which appeared to modulate cell cycle arrest in concert. Complementation with only the FL GAS5 clone could rescue cell cycle arrest, stabilizing HDM2, and leading to the loss of p53. Together, these data offer novel therapeutic targets in the form of lncRNA splice variants for separate challenges against cancer growth and cell death.

GADD45A plays a protective role against temozolomide treatment in glioblastoma cells

Glioblastoma multiforme (GBM) is one of the most aggressive cancers. Despite recent advances in multimodal therapies, high-grade glioma remains fatal. Temozolomide (TMZ) is an alkylating agent used worldwide for the clinical treatment of GBM; however, the innate and acquired resistance of GBM limits its application. Here, we found that TMZ inhibited the proliferation and induced the G2/M arrest of GBM cells. Therefore, we performed microarrays to identify the cell cycle- and apoptosis-related genes affected by TMZ. Notably, GADD45A was found to be up-regulated by TMZ in both cell cycle and apoptosis arrays. Furthermore, GADD45A knockdown (GADD45A^kd) enhanced the cell growth arrest and cell death induced by TMZ, even in natural (T98) and adapted (TR-U373) TMZ-resistant cells. Interestingly, GADD45A^kd decreased the expression of O⁶-methylguanine-DNA methyltransferase (MGMT) in TMZ-resistant cells (T98 and TR-U373). In MGMT-deficient/TMZ-sensitive cells (U87 and U373), GADD45A^kd decreased TMZ-induced TP53 expression. Thus, in this study, we investigated the genes influenced by TMZ that were important in GBM therapy, and revealed that GADD45A plays a protective role against TMZ treatment which may through TP53-dependent and MGMT-dependent pathway in TMZ-sensitive and TMZ-resistant GBM, respectively. This protective role of GADD45A against TMZ treatment may provide a new therapeutic strategy for GBM treatment.

Effects of microRNA-374 on proliferation, migration, invasion, and apoptosis of human SCC cells by targeting Gadd45a through P53 signaling pathway

The present study investigated the effects of microRNA-374 (miR-374) on human squamous cell carcinoma (SCC) cell proliferation, migration, invasion, and apoptosis through P53 signaling pathway by targeting growth arrest and DNA-damage-inducible protein 45 α (Gadd45a). Skin samples were collected from patients with skin SCC and normal skin samples. Expression of miR-374, Gadd45a, P53, P73, P16, c-myc, bcl-2, Bax, caspase-3, and caspase-9 were detected using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. A431 and SCL-1 cells were divided into blank, negative control (NC), miR-374 mimics, miR374 inhibitors, siRNA–Gadd45a, and miR-374 inhibitors + siRNA–Gadd45a groups. Their proliferation, migration, invasion, cell cycle, and apoptosis were evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, scratch test, Transwell assay, and flow cytometry. SCC skin tissues exhibited decreased expression of miR-374, P73, P16, Bax caspase-3 and caspase-9, and increased levels of Gadd45a, P53, c-myc, and Bcl-2 compared with the normal skin tissues. The miR-374 inhibitors group exhibited decreased expression of miR-374, P73, P16, Bax caspase-3 and caspase-9, and increased expression of Gadd45a, P53, c-myc, and Bcl-2, enhanced cell proliferation, migration, and invasion, and reduced apoptosis compared with the blank and NC groups; the miR-374 mimics group followed opposite trends. Compared with the blank and NC groups, the miR-374 inhibitors + siRNA–Gadd45a group showed decreased miR-374 level; the siRNA–Gadd45a group showed elevated levels of P73, P16, Bax, caspase-3 and caspase-9, decreased levels of Gadd45a, P53, c-myc, and Bcl-2, reduced cell proliferation, migration, and invasion, and accelerated apoptosis. miR-374 induces apoptosis and inhibits proliferation, migration, and invasion of SCC cells through P53 signaling pathway by down-regulating Gadd45a.

Microarray analyses of otospheres derived from the cochlea in the inner ear identify putative transcription factors that regulate the characteristics of otospheres

Various tissues possess tissue-specific stem/progenitor cells, including the inner ears. Stem/progenitor cells of the inner ear can be isolated as so-called otospheres from differentiated cells using a sphere forming assay. Although recent studies have demonstrated the characteristics of otospheres to some extent, most of the features of these cells are unknown. In this report, we describe the findings of transcriptome analyses with a cDNA microarray of otospheres derived from the cochleae of the inner ears of neonatal mice in order to clarify the gene expression profile of otic stem/progenitor cells. There were common transcription factors between otospheres and embryonic stem cells, which were supposed to be due to the stemness of otospheres. In comparison with the cochlear sensory epithelium, the otospheres shared characteristics with the cochlea, although several transcription factors specific for otospheres were identified. These transcription factors are expected to be essential for maintaining the characteristics of otospheres, and appear to be candidate genes that promote the direct conversion of cells into otic stem/progenitor cells.

p38 MAPK-induced MDM2 degradation confers paclitaxel resistance through p53-mediated regulation of EGFR in human lung cancer cells

Paclitaxel (PTX) is a chemotherapeutic agent that is used to treat a variety of cancers, including non-small cell lung cancer (NSCLC). However, the emergence of drug resistance limits the utility of PTX. This study determined the signaling pathway that contributes to PTX resistance. We first established PTX resistant cell lines (H460/R and 226B/R) using a dose-escalating maintenance of PTX. We found that p38 MAPK and epidermal growth factor receptor (EGFR) were constitutively activated in these cell lines. The inhibition of p38 MAPK activity by SB203580 treatment or the transfection of dominant-negative p38 MAPK sensitized both cell lines to PTX treatment. Erlotinib, an EGFR inhibitor, also increased PTX-induced apoptosis in PTX resistant cells, which suggests a role for p38 MAPK and EGFR in the development of PTX resistance. We demonstrated that p38 MAPK enhanced EGFR expression via the induction of the rapid degradation of mouse double-minute 2 homolog (MDM2) and the consequent stabilization of p53, a transcription factor of EGFR. These results suggest for the first time that the p38 MAPK/p53/EGFR axis is crucial for the facilitation of PTX resistance in NSCLCs. We also propose a mechanism for the role of the tumor-suppressor p53 in drug resistance. These results provide a foundation for the future development of potential therapeutic strategies to regulate the p38 MAPK/p53/EGFR pathway for the treatment of lung cancer patients with PTX resistance.

Transcriptomic Analysis Implicates the p53 Signaling Pathway in the Establishment of HIV-1 Latency in Central Memory CD4 T Cells in an In Vitro Model

The search for an HIV-1 cure has been greatly hindered by the presence of a viral reservoir that persists despite antiretroviral therapy (ART). Studies of HIV-1 latency in vivo are also complicated by the low proportion of latently infected cells in HIV-1 infected individuals. A number of models of HIV-1 latency have been developed to examine the signaling pathways and viral determinants of latency and reactivation. A primary cell model of HIV-1 latency, which incorporates the generation of primary central memory CD4 T cells (TCM), full-length virus infection (HIVNL4-3) and ART to suppress virus replication, was used to investigate the establishment of HIV latency using RNA-Seq. Initially, an investigation of host and viral gene expression in the resting and activated states of this model indicated that the resting condition was reflective of a latent state. Then, a comparison of the host transcriptome between the uninfected and latently infected conditions of this model identified 826 differentially expressed genes, many of which were related to p53 signaling. Inhibition of the transcriptional activity of p53 by pifithrin-α during HIV-1 infection reduced the ability of HIV-1 to be reactivated from its latent state by an unknown mechanism. In conclusion, this model may be used to screen latency reversing agents utilized in shock and kill approaches to cure HIV, to search for cellular markers of latency, and to understand the mechanisms by which HIV-1 establishes latency.

Molecular Aspects of Ultraviolet Radiation-Induced Apoptosis in the Skin

Background:

Apoptosis, or programmed cell death, is an essential physiological process that controls cell numbers during physiological processes, and eliminates abnormal cells that can potentially harm an organism.

Objective:

This review summarizes our current state of knowledge of apoptosis induction in skin by UV radiation.

Methods:

A review of the literature was undertaken focusing on cell death in the skin secondary to UV radiation.

Results:

It is evident that a number of apoptotic pathways, both intrinsic and extrinsic, are induced following exposure to damaging UV radiation.

Conclusion:

Although our understanding of the apoptotic processes is gradually increasing, many important aspects remain obscure. These include interconnections between pathways, wavelength-specific differences and cell type differences.

Herbal Extracts Induce Dermal Papilla Cell Proliferation of Human Hair Follicles

BACKGROUND

The number of people suffering from balding or hair thinning is increasing, despite the advances in various medical therapies. Therefore, it is highly important to develop new therapies to inhibit balding and increase hair proliferation.

OBJECTIVE

We investigated the effects of herbal extracts commonly used for improving balding in traditional medicine to identify potential agents for hair proliferation.

METHODS

The expression levels of 5α-reductase isoforms (type I and II) were analyzed using quantitative real-time reverse transcription polymerase chain reaction in the human follicular dermal papilla cells (DPCs). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylteterazolium bromide and bromodeoxyuridine tests were used to evaluate the cell proliferation effect of herbal extracts in DPCs. The expression levels of extracellular signal-regulated kinase (ERK), Akt, cyclin D1, cyclin-dependent kinase 4 (Cdk4), B-cell lymphoma (Bcl-2) and Bcl-2-associated X protein (Bax) were measured using western blot analysis.

RESULTS

The 5α-reductase isoform mRNAs and proteins were detected in the cultured DPCs, and the expression level of 5α-R2 in DPCs in the presence of the herbal extracts was gradually decreased. Herbal extracts were found to significantly increase the proliferation of human DPCs at concentrations ranging from 1.5% to 4.5%. These results show that the herbal extracts tested affected the protein expressions of ERK, Akt, cyclin D1, Cdk4, Bcl-2, and Bax in DPCs.

CONCLUSION

These results suggest that herbal extracts exert positive effects on hair proliferation via ERK, Akt, cyclin D1, and Cdk4 signaling in DPCs; they also suggest that herbal extracts could be a great alternative therapy for increasing hair proliferation.

Identification of a novel compound (β-sesquiphellandrene) from turmeric (Curcuma longa) with anticancer potential: comparison with curcumin

Considering that as many as 80% of the anticancer drugs have their roots in natural products derived from traditional medicine, we examined compounds other than curcumin from turmeric (Curcuma longa) that could exhibit anticancer potential. Present study describes the isolation and characterization of another turmeric-derived compound, β-sesquiphellandrene (SQP) that exhibits anticancer potential comparable to that of curcumin. We isolated several compounds from turmeric, including SQP, α-curcumene, ar-turmerone, α-turmerone, β-turmerone, and γ-turmerone, only SQP was found to have antiproliferative effects comparable to those of curcumin in human leukemia, multiple myeloma, and colorectal cancer cells. While lack of the NF-κB-p65 protein had no effect on the activity of SQP, lung cancer cells that expressed p53 were more susceptible to the cytotoxic effect of SQP than were cells that lacked p53 expression. SQP was also found to be highly effective in suppressing cancer cell colony formation and inducing apoptosis, as shown by assays of intracellular esterase activity, plasma membrane integrity, and cell-cycle phase. SQP was found to induce cytochrome c release and activate caspases that lead to poly ADP ribose polymerase cleavage. SQP exposure was associated with downregulation of cell survival proteins such cFLIP, Bcl-xL, Bcl-2, c-IAP1, and survivin. Furthermore, SQP was found to be synergistic with the chemotherapeutic agents velcade, thalidomide and capecitabine. Overall, our results indicate that SQP has anticancer potential comparable to that of curcumin.

Inhibitor of apoptosis-stimulating protein of p53 (iASPP) is required for neuronal survival after axonal injury

The transcription factor p53 mediates the apoptosis of post-mitotic neurons exposed to a wide range of stress stimuli. The apoptotic activity of p53 is tightly regulated by the apoptosis-stimulating proteins of p53 (ASPP) family members: ASPP1, ASPP2 and iASPP. We previously showed that the pro-apoptotic members ASPP1 and ASPP2 contribute to p53-dependent death of retinal ganglion cells (RGCs). However, the role of the p53 inhibitor iASPP in the central nervous system (CNS) remains to be elucidated. To address this, we asked whether iASPP contributes to the survival of RGCs in an in vivo model of acute optic nerve damage. We demonstrate that iASPP is expressed by injured RGCs and that iASPP phosphorylation at serine residues, which increase iASPP affinity towards p53, is significantly reduced following axotomy. We show that short interference RNA (siRNA)-induced iASPP knockdown exacerbates RGC death, whereas adeno-associated virus (AAV)-mediated iASPP expression promotes RGC survival. Importantly, our data also demonstrate that increasing iASPP expression in RGCs downregulates p53 activity and blocks the expression of pro-apoptotic targets PUMA and Fas/CD95. This study demonstrates a novel role for iASPP in the survival of RGCs, and provides further evidence of the importance of the ASPP family in the regulation of neuronal loss after axonal injury.

Induction of nuclear translocation of mutant cytoplasmic p53 by geranylgeranoic acid in a human hepatoma cell line

Mutant p53 proteins in human hepatoma cell lines such as HuH-7 (Y220C) and PLC/PRF/5 (R249S) accumulate in the cytoplasm, and lose their transcriptional function. Geranylgeranoic acid (GGA) is a naturally occurring acyclic diterpenoid that induces cell death in both cell lines, but not in HepG2 cells harboring wild-type p53. Here, we demonstrate that micromolar concentrations of GGA induce a rapid nuclear translocation of cytoplasmic p53 in both p53-mutant cell lines and p53 knockdown attenuates GGA-induced cell death in HuH-7 cells. Cell-free experiments demonstrate that GGA is able to release 670-kD p53-containing complexes from putative huge macromolecular aggregates in post-mitochondrial fractions as revealed on blue-native gradient PAGE. Among several p53-target genes tested, GGA upregulates PUMA gene expression, and ivermectin, an inhibitor for importin α/β, blocks GGA-induced nuclear translocation of cytoplasmic p53 and suppresses GGA-induced upregulation of PUMA mRNA levels in HuH-7 cells. Taken together, these data suggest that GGA treatment stimulates a nuclear translocation of mutant p53 through its dissociation from cytoplasmic aggregates, which may be essential for GGA-induced cell death.

Anti-tumor activity of Eurycoma longifolia root extracts against K-562 cell line: in vitro and in vivo study

Eurycoma longifolia Jack has been widely used in traditional medicine for its antimalarial, aphrodisiac, anti-diabetic, antimicrobial and anti-pyretic activities. Its anticancer activity has also been recently reported on different solid tumors, however no anti-leukemic activity of this plant has been reported. Thus the present study assesses the in vitro and in vivo anti-proliferative and apoptotic potentials of E. longifolia on K-562 leukemic cell line. The K-562 cells (purchased from ATCC) were isolated from patients with chronic myelocytic leukemia (CML) were treated with the various fractions (TAF273, F3 and F4) of E. longifolia root methanolic extract at various concentrations and time intervals and the anti-proliferative activity assessed by MTS assay. Flow cytometry was used to assess the apoptosis and cell cycle arrest. Nude mice injected subcutaneously with 10⁷ K-562 cells were used to study the anti-leukemic activity of TAF273 in vivo. TAF273, F3 and F4 showed various degrees of growth inhibition with IC50 values of 19, 55 and 62 µg/ml, respectively. TAF273 induced apoptosis in a dose and time dependent manner. TAF273 arrested cell cycle at G1and S phases. Intraperitoneal administration of TAF273 (50 mg/kg) resulted in a significant growth inhibition of subcutaneous tumor in TAF273-treated mice compared with the control mice (P = 0.024). TAF273 shows potent anti-proliferative activity in vitro and in vivo models of CML and therefore, justifies further efforts to define more clearly the potential benefits of using TAF273 as a novel therapeutic strategy for CML management.

Polymorphisms in the p53 pathway genes and micronucleus occurrence in Chinese vinyl chloride-exposed workers

OBJECTIVES

To investigate the association between polymorphisms in the p53 pathway genes and chromosomal damage in vinyl chloride (VC)-exposed workers.

MATERIALS AND METHODS

Cytokinesis block micronucleus test was performed in 310 VC-exposed workers and 149 non-exposed workers to determine chromosomal damage. The polymerase chain reaction and restriction fragment length polymorphism technique were used to detect six SNPs in the p53 pathway genes involved in the cell cycle.

RESULTS

There was a highly significant dose-response relationship between VC exposure and chromosomal damage. Individuals carrying the variant genotypes were at higher risk for chromosomal damage compared with their wild type genotype: p53rs1042522, MDM2 Del1518rs3730485, MDM2rs2279744 and GADD45Ars532446. On the other hand, individuals possessing the variant genotype of CDKN2A rs3088440 had significantly decreased risk compared with the corresponding wild-type.

CONCLUSIONS

Genetic polymorphisms in P53 pathway genes may have an impact on VC-induced chromosomal damage.

The synthetic flavonoid WYC02-9 inhibits colorectal cancer cell growth through ROS-mediated activation of MAPK14 pathway

AIM

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. In this study, we explored the anti-cancer activity of WYC02-9, a synthetic protoapigenone, on human HCT116 CRC cells.

MAIN METHODS

The anti-cancer activity of WYC02-9 and its underlying mechanisms were analyzed using XTT cell proliferation assays, colony formation assays, FACS analysis, annexin V staining, immunoblotting analysis, reactive oxygen species (ROS) generation assays, soft agar assays, a nude mice xenograft study and immunohistochemistry assays.

KEY FINDINGS

Data showed that WYC02-9 suppressed CRC cell growth by arresting cells at G2/M and inducing cell death via apoptotic pathways. Further analysis demonstrated that WYC02-9-induced apoptosis was mediated by the activation of a ROS-mediated MAPK14 pathway. An in vivo xenograft study revealed that WYC02-9 enhanced MAP2K3/6 and MAPK14 phosphorylation, induced apoptosis, and suppressed CRC tumor growth.

SIGNIFICANCE

WYC02-9 exerts its anti-tumor effect via ROS/MAPK14-induced apoptosis and has the potential to be developed as a chemotherapeutic agent for CRC.

Regulation of p53 by reversible post-transcriptional and post-translational mechanisms in liver and skeletal muscle of an anoxia tolerant turtle, Trachemys scripta elegans

The red-eared slider turtle (Trachemys scripta elegans) exhibits well-developed natural anoxia tolerance that depends on multiple biochemical adaptations, including anoxia-induced hypometabolism. We hypothesized that signaling by the p53 protein could aid in establishing the hypometabolic state by arresting the cell cycle, protecting against DNA damage as well as altering pathways of energy metabolism. Immunoblotting was used to evaluate the regulation and post-transcriptional modifications of p53 in liver and skeletal muscle of red-eared slider turtles subjected to 5h or 20h of anoxic submergence. Tissue specific regulation of p53 was observed with the liver showing a more rapid activation of p53 in response to anoxia as well as differential expression of seven serine phosphorylation and two lysine acetylation sites when compared with skeletal muscle. Protein expression of MDM2, a major p53 inhibitor, was also examined but did not change during anoxia. Reverse-transcriptase PCR was used to assess transcript levels of selected p53 target genes (14-3-3σ, Gadd45α and Pgm) and one microRNA (miR-34a); results showed down-regulation of Pgm and up-regulation of the other three. These findings show an activation of p53 in response to anoxia exposure and suggest an important role for the p53 stress response pathway in regulating natural anoxia tolerance and hypometabolism in a vertebrate facultative anaerobe.

p53 controls hepatitis C virus non-structural protein 5A-mediated downregulation of GADD45α expression via the NF-κB and PI3K-Akt pathways

Growth arrest and DNA-damage-inducible gene 45-α (GADD45α) protein has been shown to be a tumour suppressor and is implicated in cell-cycle arrest and suppression of cell growth. The hepatitis C virus (HCV) non-structural 5A (NS5A) protein plays an important role in cell survival and is linked to the development of hepatocellular carcinoma (HCC). However, the role of HCV NS5A in the development of HCC remains to be clarified. This study sought to determine whether GADD45α mediates HCV NS5A-induced cellular survival and to elucidate the molecular mechanism of GADD45α expression regulated by HCV NS5A. It was found that HCV NS5A downregulated GADD45α expression at the transcriptional level by decreasing promoter activity, mRNA transcription and protein levels. Knockdown of p53 resulted in a similar decrease in GADD45α expression to that caused by HCV NS5A, whilst overexpression of p53 reversed the HCV NS5A-mediated downregulation of GADD45α. HCV NS5A repressed p53 expression, which was followed by a subsequent decrease in GADD45α expression. Further evidence was provided showing that HCV NS5A led to increases of phosphorylated nuclear factor-κB and Akt levels. Inhibition of these pathways using pharmacological inhibitors or specific small interfering RNAs rescued HCV NS5A-mediated downregulation of p53 and GADD45α. It was also found that HCV NS5A protein and depletion of GADD45α increased cell growth, whereas ectopic expression of GADD45α eliminated HCV NS5A-induced cell proliferation. These results indicated that HCV NS5A downregulates GADD45α expression and subsequently triggers cellular proliferation. These findings provide new insights suggesting that HCV NS5A could contribute to the occurrence of HCV-related HCC.

GADD45 proteins: central players in tumorigenesis

The Growth Arrest and DNA Damage-inducible 45 (GADD45) proteins have been implicated in regulation of many cellular functions including DNA repair, cell cycle control, senescence and genotoxic stress. However, the pro-apoptotic activities have also positioned GADD45 as an essential player in oncogenesis. Emerging functional evidence implies that GADD45 proteins serve as tumor suppressors in response to diverse stimuli, connecting multiple cell signaling modules. Defects in the GADD45 pathway can be related to the initiation and progression of malignancies. Moreover, induction of GADD45 expression is an essential step for mediating anti-cancer activity of multiple chemotherapeutic drugs and the absence of GADD45 might abrogate their effects in cancer cells. In this review, we present a comprehensive discussion of the functions of GADD45 proteins, linking their regulation to effectors of cell cycle arrest, DNA repair and apoptosis. The ramifications regarding their roles as essential and central players in tumor growth suppression are also examined. We also extensively review recent literature to clarify how different chemotherapeutic drugs induce GADD45 gene expression and how its up-regulation and interaction with different molecular partners may benefit cancer chemotherapy and facilitate novel drug discovery.

Adenosine induces cell-cycle arrest and apoptosis in androgen-dependent and -independent prostate cancer cell lines, LNcap-FGC-10, DU-145, and PC3

BACKGROUND

Adenosine has been shown to inhibit cell growth and induce apoptosis in the several cancer cells via intrinsic and extrinsic pathway. The present study was designed to understand the mechanism underlying adenosine-induced apoptosis in the DU-145, PC3, and LNcap-FGC10 human prostate cancer cells.

METHODS

To observe cell viability and proliferation, MTT assay, cell counting, and BrdU assay were carried out in DU-145, PC3, and LNcap-FGC10 cells. Apoptosis was assessed with the analysis of cell cycle, Hoechst 33258 staining, propidium iodide and annexin-V staining, reactive oxygen species (ROS) formation, mitochondrial membrane potential (ΔΨM) measurement, caspase-3 activity assay, Bcl-2 and Bax protein expression. Moreover, the expression of adenosine receptors and the effects of adenosine receptor (A(1) , A(2a) , and A(3) ) antagonists were examined.

RESULT

Adenosine significantly reduced cell proliferation in a dose-dependent manner in DU-145, PC3, and LNcap-FGC10 cell lines. Adenosine induced arrest in the cell-cycle progression in G0/G1 phase through Cdk4/cyclinD1-mediated pathway. Adenosine induced apoptosis, which was determined by morphological changes and increased sub-G1 population. Furthermore, increase of ROS, loss of MMP, activation of caspase-3, and down-regulation of Bcl-2 expression was observed. A(1) , A(2a) , A(2b) , and A(3) adenosine receptors mRNA are expressed in the cell lines. Moreover, adenosine-induced apoptosis was inhibited by MRS1220, A(3) adenosine receptor antagonist.

CONCLUSION

Our results suggest that adenosine induced apoptosis in prostate cancer cells via the mitochondrial pathway and is related to the adenosine receptors. These data might suggest that adenosine could be used as an agent for the treatment of prostate cancer.

Silibinin prevents ultraviolet B radiation-induced epidermal damages in JB6 cells and mouse skin in a p53-GADD45α-dependent manner

Better preventive strategies are required to reduce ultraviolet (UV)-caused photodamage, the primary etiological factor for non-melanoma skin cancer (NMSC). Accordingly, here we examined the preventive efficacy of silibinin against UVB-induced photodamage using mouse epidermal JB6 cells and SKH1 hairless mouse epidermis. In JB6 cells, silibinin pretreatment protected against apoptosis and accelerated the repair of cyclobutane pyrimidine dimers (CPD) induced by moderate dose of UVB (50 mJ/cm(2)), which we are at risk of daily exposure. Silibinin also reversed UVB-induced S phase arrest, reducing both active DNA synthesizing and inactive S phase populations. In mechanistic studies, UVB-irradiated cells showed a transient upregulation of both phosphorylated (Ser-15 and Ser-392) and total p53, whereas silibinin pretreatment led to a more sustained upregulation and stronger nuclear localization of p53. Silibinin also caused a marked upregulation of GADD45α, a downstream target of p53, implicated in DNA repair and cell cycle regulation. Importantly, under p53 and GADD45α knockdown conditions, cells were more susceptible to UVB-induced apoptosis without any significant S phase arrest, and protective effects of silibinin were compromised. Similar to the in vitro results, topical application of silibinin prior to or immediately after UVB irradiation resulted in sustained increase in p53 and GADD45α levels and accelerated CPD removal in the epidermis of SKH1 hairless mice. Together, our results show for the first time that p53-mediated GADD45α upregulation is the key mechanism by which silibinin protects against UVB-induced photodamage and provides a strong rationale to investigate silibinin in reducing the risk and/or preventing early onset of NMSC.

Molecular mechanisms of A3 adenosine receptor-induced G1 cell cycle arrest and apoptosis in androgen-dependent and independent prostate cancer cell lines: involvement of intrinsic pathway

PURPOSE

A3 adenosine receptor has shown several physiological and pathological activities, including cell proliferation and apoptosis in various cancer cell lines. This study is designed to investigate molecular mechanism and apoptotic pathway of A3 adenosine receptor in DU-145, PC3 and LNcap-FGC10 human prostate cancer cells.

METHODS

The expression level of A3 adenosine receptor was examined using real-time RT-PCR. cAMP concentration was also measured. MTT viability, cell counting and BrdU incorporation tests were used to study the cell proliferation effect of IB-MECA. Cell cycle analysis, Annexin V-FITC staining, Hoechst 33258 staining, mitochondrial membrane potential (ΔΨM), caspase-3 activity, Bcl-2 and Bax protein expression were used to detect apoptosis.

RESULT

A3 adenosine receptors mRNAs were detected at different levels. IB-MECA inhibited forskolin-stimulated cAMP. IB-MECA at (1 μM) suppressed cell proliferation and induced G1 cell cycle arrest. Indeed, IB-MECA down-regulated the expression of CDK4, cyclin D1 and up-regulated p53 expression. IB-MECA at (10-100 μM) induced apoptosis. The activity of caspase-3 was also increased. Expression of Bcl-2 was decreased in response to IB-MECA, while the expression of Bax protein was increased. The results showed a significant loss of ΔΨM, in a dose-dependent manner.

CONCLUSION

This study introduces a possible mechanism through A3 adenosine receptor activation. IB-MECA inhibited prostate cancer cells proliferation and induced G1 cell cycle arrest through p53, Cdk4/cyclinD1 pathway. Apoptosis determined by characteristic morphological changes and increased in sub-G1 population. Loss of MMP, activation of caspase-3 and down-regulation of Bcl-2 expression indicated mitochondrial signaling pathway that involved in the apoptosis.

Gadd45a sensitizes medulloblastoma cells to irradiation and suppresses MMP-9-mediated EMT

Medulloblastomas are the most common malignant tumors of the central nervous system during childhood. Radiation-induced medulloblastoma tumor recurrences are aggressive and metastatic in nature. In the present study, we demonstrate that Gadd45a expression can sensitize medulloblastoma cells to radiotherapy. We have elucidated the role of Gadd45a in ionizing radiation (IR)-induced G2-M arrest and invasion and metastatic potential of the medulloblastoma cancer cell lines DAOY and D283. We demonstrate that Gadd45a is induced by IR and results in p53 phosphorylation. The role of IR-induced Gadd45a in G2-M arrest is demonstrated by fluorescence-activated cell sorting analysis in the cells treated with siRNA Gadd45a and Ov-exp Gadd45a. We show that Ov-exp Gadd45a aggravates G2-M blockage and also increases binding of Gadd45a to Cdc2 by immunocytochemistry analysis. Furthermore, we show the anti-tumorigenic role of Gadd45a to be mediated by the negative regulation of IR-induced cancer cell invasion and migration-associated proteins, such as matrix metallopeptidase (MMP)-9 and β-catenin. When compared with IR treatment alone, Ov-exp Gadd45a plus IR treatment resulted in decreased nuclear localization and increased membrane localization of β-catenin, and this was further confirmed by membrane distribution. We also show that Ov-exp Gadd45a resulted in downregulation of MMP-9 and suppression of epithelial-mesenchymal transition (EMT). Alternatively, inhibition of MMP-9 (pM) resulted in upregulation of Gadd45a and suppression of EMT. The anti-tumor effect of pM was correlated with increased expression of Gadd45a protein in nude mice intracranial tumors. Taken together, our studies demonstrate that upregulation of Gadd45a or suppression of MMP-9 (pM) with IR retards medulloblastoma tumor metastatic potential.