Expression Of Cell Cycle-associated Genes Research Articles

Cannabinol Regulates the Expression of Cell Cycle-Associated Genes in Motor Neuron-like NSC-34: A Transcriptomic Analysis.

Cannabinoids are reported to have neuroprotective properties and play a role in neurogenesis and neuroplasticity in in vitro and in vivo models. Cannabinol (CBN) is a minor cannabinoid produced by the degradation of Δ9-tetrahydrocannabinol in Cannabis sativa L. and exhibits anti-oxidant, analgesic, anti-bacterial, and anti-inflammatory effects. In this study, we explored the biological effects of 20 µM CBN (6.20 µg/mL) on differentiated NSC-34 cells by MTT assay and next-generation sequencing analysis on the transcriptome. KEGG and Gene Ontology enrichment analyses have been performed to evaluate potential CBN-associated processes. Our results highlighted the absence of any cytotoxic effect of CBN. The comparative transcriptomic analysis pointed out the downregulation of Cdkn2a, Cdkn2c and Cdkn2d genes, which are known to suppress the cell cycle. Ccne2, Cdk2, Cdk7, Anapc11, Anapc10, Cdc23, Cdc16, Anapc4, Cdc27, Stag1, Smc3, Smc1a, Nipbl, Pds5a, Pds5b, and Wapl genes, renowned for their role as cell cycle progression activators, were instead upregulated. Our work suggests that CBN regulates the expression of many genes related to the cell cycle, which are required for axonal maturation, migration, and synaptic plasticity, while not affecting the expression of genes involved in cell death or tumorigenesis.

JCAD deficiency delayed liver regenerative repair through the Hippo-YAP signalling pathway.

Liver regeneration retardation post partial hepatectomy (PH) is a common clinical problem after liver transplantation. Identification of key regulators in liver regeneration post PH may be beneficial for clinically improving the prognosis of patients after liver transplantation. This study aimed to clarify the function of junctional protein-associated with coronary artery disease (JCAD) in liver regeneration post PH and to reveal the underlying mechanisms. JCAD knockout (JCAD-KO), liver-specific JCAD-KO (Jcad△Hep) mice and their control group were subjected to 70% PH. RNA sequencing was conducted to unravel the related signalling pathways. Primary hepatocytes from KO mice were treated with epidermal growth factor (EGF) to evaluate DNA replication. Fluorescent ubiquitination-based cell cycle indicator (FUCCI) live-imaging system was used to visualise the phases of cell cycle. Both global and liver-specific JCAD deficiency postponed liver regeneration after PH as indicated by reduced gene expression of cell cycle transition and DNA replication. Prolonged retention in G1 phase and failure to transition over the cell cycle checkpoint in JCAD-KO cell line was indicated by a FUCCI live-imaging system as well as pharmacologic blockage. JCAD replenishment by adenovirus reversed the impaired DNA synthesis in JCAD-KO primary hepatocyte in exposure to EGF, which was abrogated by a Yes-associated protein (YAP) inhibitor, verteporfin. Mechanistically, JCAD competed with large tumour suppressor 2 (LATS2) for WWC1 interaction, leading to LATS2 inhibition and thereafter YAP activation, and enhanced expression of cell cycle-associated genes. JCAD deficiency led to delayed regeneration after PH as a result of blockage in cell cycle progression through the Hippo-YAP signalling pathway. These findings uncovered novel functions of JCAD and suggested a potential strategy for improving graft growth and function post liver transplantation. JCAD deficiency leads to an impaired liver growth after PH due to cell division blockage. JCAD competes with LATS2 for WWC1 interaction, resulting in LATS2 inhibition, YAP activation and enhanced expression of cell cycle-associated genes. Delineation of JCADHippoYAP signalling pathway would facilitate to improve prognosis of acute liver failure and graft growth in living-donor liver transplantation.

Matrin-3 acts as a potential biomarker and promotes hepatocellular carcinoma progression by interacting with cell cycle-regulating genes

ABSTRACT Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related mortality worldwide. The oncogenic role of Matrin-3 (MATR3), an a nuclear matrix protein, in HCC remains largely unknown. Here, we document the biological function of MATR3 in HCC based on integrated bioinformatics analysis and functional studies. According to the TCGA database, MATR3 expression was found to be positively correlated with clinicopathological characteristics in HCC. The receiver operating characteristic (ROC) curve and Kaplan-Meier (KM) curve displayed the diagnostic and prognostic potentials of MATR3 in HCC patients, respectively. Pathway enrichment analysis represented the enrichment of MATR3 in various molecular pathways, including the regulation of the cell cycle. Functional assays in HCC cell lines showed reduced proliferation of cells with stable silencing of MATR3. At the same time, the suppressive effects of MATR3 depletion on HCC development were verified by xenograft tumor experiments. Moreover, MATR3 repression also resulted in cell cycle arrest by modulating the expression of cell cycle-associated genes. In addition, the interaction of MATR3 with cell cycle-regulating factors in HCC cells was further corroborated with co-immunoprecipitation and mass spectrometry (Co-IP/MS). Furthermore, CIBERSORT and TIMER analyses showed an association between MATR3 and immune infiltration in HCC. In general, this study highlights the novel oncogenic function of MATR3 in HCC, which could comprehensively address how aberrant changes in the cell cycle promote HCC development. MATR3 might serve as a prognostic predictor and therapeutic target for HCC patients.

Symbiosis with Dinoflagellates Alters Cnidarian Cell-Cycle Gene Expression

In the cnidarian-dinoflagellate symbiosis, hosts show altered expression of genes involved in growth and proliferation when in the symbiotic state, but little is known about the molecular mechanisms that underlie the host’s altered growth rate. Using tissue-specific transcriptomics, we determined how symbiosis affects expression of cell cycle-associated genes, in the model symbiotic cnidarian Exaiptasia diaphana (Aiptasia). The presence of symbionts within the gastrodermis elicited cell-cycle arrest in the G1 phase in a larger proportion of host cells compared with the aposymbiotic gastrodermis. The symbiotic gastrodermis also showed a reduction in the amount of cells synthesizing their DNA and progressing through mitosis when compared with the aposymbiotic gastrodermis. Host apoptotic inhibitors (Mdm2) were elevated, while host apoptotic sensitizers (c-Myc) were depressed, in the symbiotic gastrodermis when compared with the aposymbiotic gastrodermis and epidermis of symbiotic anemones, respectively. This indicates that the presence of symbionts negatively regulates host apoptosis, possibly contributing to their persistence within the host. Transcripts (ATM/ATR) associated with DNA damage were also downregulated in symbiotic gastrodermal tissues. In epidermal cells, a single gene (Mob1) required for mitotic completion was upregulated in symbiotic compared with aposymbiotic anemones, suggesting that the presence of symbionts in the gastrodermis stimulates host cell division in the epidermis. To further corroborate this hypothesis, we performed microscopic analysis using an S-phase indicator (EdU), allowing us to evaluate cell cycling in host cells. Our results confirmed that there were significantly more proliferating host cells in both the gastrodermis and epidermis in the symbiotic state compared with the aposymbiotic state. Furthermore, when comparing between tissue layers in the presence of symbionts, the epidermis had significantly more proliferating host cells than the symbiont-containing gastrodermis. These results contribute to our understanding of the influence of symbionts on the mechanisms of cnidarian cell proliferation and mechanisms associated with symbiont maintenance.

Brg1 Supports B Cell Proliferation and Germinal Center Formation Through Enhancer Activation.

Activation and differentiation of B cells depend on extensive rewiring of gene expression networks through changes in chromatin structure and accessibility. The chromatin remodeling complex BAF with its catalytic subunit Brg1 was previously identified as an essential regulator of early B cell development, however, how Brg1 orchestrates gene expression during mature B cell activation is less clear. Here, we find that Brg1 is required for B cell proliferation and germinal center formation through selective interactions with enhancers. Brg1 recruitment to enhancers following B cell activation was associated with increased chromatin accessibility and transcriptional activation of their coupled promoters, thereby regulating the expression of cell cycle-associated genes. Accordingly, Brg1-deficient B cells were unable to mount germinal center reactions and support the formation of class-switched plasma cells. Our findings show that changes in B cell transcriptomes that support B cell proliferation and GC formation depend on enhancer activation by Brg1. Thus, the BAF complex plays a critical role during the onset of the humoral immune response.

Constitutive expression of progesterone receptor isoforms promotes the development of hormone-dependent ovarian neoplasms.

Differences in the relative abundances of the progesterone receptor (PGR) isoforms PGRA and PGRB are often observed in women with reproductive tract cancers. To assess the importance of the PGR isoform ratio in the maintenance of the reproductive tract, we generated mice that overexpress PGRA or PGRB in all PGR-positive tissues. Whereas few PGRA-overexpressing mice developed reproductive tract tumors, all PGRB-overexpressing mice developed ovarian neoplasms that were derived from ovarian luteal cells. Transcriptomic analyses of the ovarian tumors from PGRB-overexpressing mice revealed enhanced AKT signaling and a gene expression signature similar to those of human ovarian and endometrial cancers. Treating PGRB-overexpressing mice with the PGR antagonist RU486 stalled tumor growth and decreased the expression of cell cycle-associated genes, indicating that tumor growth and cell proliferation were hormone dependent in addition to being isoform dependent. Analysis of the PGRB cistrome identified binding events at genes encoding proteins that are critical regulators of mitotic phase entry. This work suggests a mechanism whereby an increase in the abundance of PGRB relative to that of PGRA drives neoplasia in vivo by stimulating cell cycling.

Critical role of HOX transcript antisense intergenic RNA (HOTAIR) in gliomas.

Despite extensive research, gliomas are associated with high morbidity and mortality, mainly attributed to the rapid growth rate, excessive invasiveness, and molecular heterogeneity, as well as regenerative potential of cancer stem cells. Therefore, elucidation of the underlying molecular mechanisms and the identification of potential molecular diagnostic and prognostic biomarkers are of paramount importance. HOX transcript antisense intergenic RNA (HOTAIR) is a well-studied long noncoding RNA, playing an emerging role in tumorigenesis of several human cancers. A growing amount of preclinical and clinical evidence highlights the pro-oncogenic role of HOTAIR in gliomas, mainly attributed to the enhancement of proliferation and migration, as well as inhibition of apoptosis. In vitro and in vivo studies demonstrate that HOTAIR modulates the activity of specific transcription factors, such as MXI1, E2F1, ATF5, and ASCL1, and regulates the expression of cell cycle-associated genes along with related signaling pathways, like the Wnt/β-catenin axis. Moreover, it can interact with specific miRNAs, including miR-326, miR-141, miR-148b-3p, miR-15b, and miR-126-5p. Of importance, HOTAIR has been demonstrated to enhance angiogenesis and affect the permeability of the blood-tumor barrier, thus modulating the efficacy of chemotherapeutic agents. Herein, we provide evidence on the functional role of HOTAIR in gliomas and discuss the benefits of its targeting as a novel approach toward glioma treatment.

Abstract B28: Cep55 regulates YAP/TAZ expression and localization during cell cycle progression

Abstract Cell cycle regulation plays a pivotal role in controlling cell proliferation and survival. Aberrant expression of cell cycle-associated genes generally afflicts cells with tumor-prone characteristics and promotes chromosome instability. Cep55 (Centrosome Protein 55kDa; also known as c10orf3 and FLJ10540) was identified as an important regulator of cytokinesis involved in cell growth and proliferation. It is associated with central spindle and midbody during cell cycle progression and cooperates with members of endosomal sorting complex required for transport (ESCRT) machinery to constrict intracellular bridge for cell abscission. In addition to cytokinesis, Cep55 is involved in regulating the PI3K/AKT pathway as well as promoting tumorigenesis. In search of novel Cep55 interplayers that may abrogate their expression upon loss of cep55 expression, we set out experiments with cultured cells exogenously expressed Flag-tagged wild type (wt) Cep 55 versus shRNAs against Cep55 and subjected immunoprecipitates to LC-MS/MS. The Hippo pathway components YAP and its paralogue TAZ were found to be diminished apparently in Cep55 null sample compared with wt counterpart. To confirm if Cep55 knockdown affects expression of Hippo pathway, we transfected 293T cells with Cep55 shRNAs and detected expression of Hippo core components with Western blots. Hippo components such as Merlin, Mst, and Lats are without effect in expression level, with the exception of YAP/TAZ whose expression was decreased extensively. Immunofluorescent microscopy reveals YAP/TAZ colocalized with Cep55 at central spindle and midbody during mitosis; however, depletion of Cep55 results in diffusion of YAP/TAZ at midbody, suggesting cep55 is required for midbody localization of YAP/TAZ. In contrast, knockdown of YAP/TAZ did not significantly alter Cep55 localization to the midbody ring but displays phenotype, such as multinuclear cells and micronuclei, similar to that observed in Cep55-depleted cells. Together our data provide evidence that Cep55-YAP/TAZ interaction plays an important role in cytokinesis and may support a biologic interplay between the Hippo-YAP and PI3K-AKT-mTOR pathways. Note: This abstract was not presented at the conference. Citation Format: Yen-Ming Lin, Chu-Han Wu, Pin Ouyang. Cep55 regulates YAP/TAZ expression and localization during cell cycle progression [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B28.

Inhibition of esophageal-carcinoma cell proliferation by genistein via suppression of JAK1/2-STAT3 and AKT/MDM2/p53 signaling pathways.

Esophageal carcinoma (EsC) is a clinically challenging neoplastic disease. Genistein, a natural isoflavone product, has anti-tumor properties. Through in vitro and in vivo studies, we found that genistein suppressed EsC cell proliferation in a time- and concentration-dependent manner. In addition, genistein markedly promoted apoptosis and arrested cell cycle at the G0/G1 phase in a concentration-dependent manner. Furthermore, high concentrations of genistein have no adverse effect on normal esophageal epithelial cells. Mechanistically, genistein treatment strikingly reduced the expression of cell cycle-associated genes, and up-regulated the expression of cell apoptosis-related genes in EsC cells. Additionally, genistein dramatically decreased epidermal growth factor receptor (EGFR) expression and attenuated its down-stream signaling molecules STAT3, MDM2, Akt and JAK1/2 phosphorylation, resulting in inhibited nuclear translocation of STAT3 and MDM2, thereby inhibiting the JAK1/2-STAT3 and AKT/MDM2/p53 signaling pathways. In xenograft nude mice, genistein administration strikingly impaired tumor growth in a dose-dependent manner. Moreover, similar disturbances in molecular mechanisms were observed in vivo. Taken together, genistein suppressed the JAK1/2-STAT3 and AKT/MDM2/p53 signaling pathways by decreasing EGFR expression, leading to cell apoptosis, cell cycle arrest, and proliferation inhibition in EsC cells. Our findings suggest that genistein may be a promising alternative adjuvant therapy for patients with EsC.

Dark-colored maple syrup treatment induces S-phase cell cycle arrest via reduced proliferating cell nuclear antigen expression in colorectal cancer cells.

Maple syrup is a natural sweetener that is consumed worldwide. It has been previously reported that dark-colored maple syrup exerts an inhibitory effect on colorectal cancer (CRC) proliferation and invasion. In the present study, the underlying mechanism of CRC cell growth inhibition was examined with dark-colored maple syrup treatment using a shotgun liquid chromatography-tandem mass spectrometry-based global proteomic approach. Applying a semi-quantitative method based on spectral counting, 388 proteins were identified with expression changes of >1.5-fold following dark-colored maple syrup treatment. Gene Ontology analysis revealed that these proteins possessed cell cycle-associated functions. It was also indicated that CRC cells treated with dark-colored maple syrup exhibited decreased proliferating cell nuclear antigen (PCNA) expression and S-phase cell cycle arrest. Dark-colored maple syrup treatment also resulted in altered expression of cell cycle-associated genes, including cyclin-dependent kinase (CDK)4 and CDK6. In conclusion, these data suggested that dark-colored maple syrup induced S-phase cell cycle arrest in CRC cells by reducing the expression of PCNA and regulating cell cycle-associated genes. These findings suggest that dark-colored maple syrup may be a source of compounds for the development of novel drugs for colorectal cancer treatment.

ClE2F1 Overexpression Enhances Plant Growth in Chrysanthemum lavandulifolium (Fisch. ex Trautv.) Makino

E2F transcription factors play key roles in plant growth and development by regulating the cell cycle. In this study, ClE2F1 was isolated from Chrysanthemum lavandulifolium. This gene encodes a 452-amino-acid protein that contains a DNA-binding domain, marked box domain, pRBR-binding domain, and a nuclear localization signal. Phylogenetic analysis showed that ClE2F1 was most closely related to Arabidopsis thaliana AtE2Fa, AtE2Fb, and AtE2Fc. Transient expression experiments demonstrated that the ClE2F1 protein localizes to the nucleus. Yeast one-hybrid assays showed that ClE2F1 promotes transcriptional activation. The morphology of the OX-6, OX-7, and OX-10 transgenic and wild-type lines was investigated. Plant height, leaf length and width, inflorescence diameter, disc flower diameter, the number of tabulate florets, and ligulate floret length were greater in the OX-6, OX-7, and OX-10 lines than in wild-type plants. Microscopic observation revealed a higher number of cells per unit area but a smaller cell area in the OX-6, OX-7, and OX-10 lines than those in wild-type plants. In addition, the relative expression of cell cycle-associated genes in the OX-6, OX-10, and wild-type plants revealed that the ClPCNA3, ClRNR, ClASF, ClDPa, ClCDKA, and ClCYCD transcript levels were up-regulated in the OX-6 and OX-10 plants, whereas ClRBR and ClKRP5 expression was down-regulated.

PM2.5-induced alterations of cell cycle associated gene expression in lung cancer cells and rat lung tissues.

The aim of the current study was to investigate the expression of cell cycle-associated genes induced by fine particulate matter (PM2.5) in lung cancer cell line and tissues. The pulmonary lymph node metastasis cells (H292) were treated with PM2.5in vitro. Wistar rats were used to perform an in vivo study. Rats were randomly assigned to experiment and control groups and those in the experiment group were exposed to PM2.5 once every 15 d, while those in the control group were exposed to normal saline. The cell cycle-associated genes expression was analyzed by real-time PCR. Trachea and lung tissues of rats were processed for scanning electron microscopic (SEM) examinations. Exposure of H292 cells to PM2.5 dramatically increased the expressions of p53 and cyclin-dependent kinase 2 (CDK2) after 24h of exposure (p<0.01) and markedly increased the expressions of the cell division cycle 2 (Cdc2) and cyclin B after 48h of exposure (p<0.01), while those genes expressions were significantly reduced after 72h of exposure, at which time the expression of p21 was predominant (p<0.01). In vivo studies further demonstrated these results. The results of SEM suggested that both of the trachea and lung tissues were damaged and the degree of damage was time-dependent. In conclusion, PM2.5 can induce significantly alterations of p53 and CDK2 in the early phase, Cdc2 and cyclin B in mid-term and p21 in long-term exposure. The degree of PM2.5-induced damage to the trachea and lung tissue was time-dependent.

Prognostic significance of FOXM1 expression and antitumor effect of FOXM1 inhibition in synovial sarcomas.

BackgroundSynovial sarcoma (SS) is a soft tissue sarcoma of unknown histogenesis. Most metastatic or unresectable cases are incurable. Novel antitumor agents and precise prognostication are needed for SS patients. The protein forkhead box M1 (FOXM1), which belongs to the FOX family of transcription factors, is considered to be an independent predictor of poor survival in many cancers and sarcomas, but the prognostic implications and oncogenic roles of FOXM1 in SS are poorly understood. Here we examined the correlation between FOXM1 expression and clinicopathologic and prognostic factors, and we investigated the efficacy of FOXM1 target therapy in SS cases.MethodsImmunohistochemical study of 106 tumor specimens was conducted to evaluate their immunohistochemical expression of FOXM1. An in vitro study examined the antitumor effect of the FOXM1 inhibitor thiostrepton and small interference RNA (siRNA) on two SS cell lines. We also assessed the efficacy of the combined use of doxorubicin (DOX) and thiostrepton.ResultsUnivariate and multivariate analyses revealed that FOXM1 expression was associated with poor prognosis in SS. The cDNA microarray analysis using clinical samples revealed that the expression of cell cycle-associated genes was correlated with FOXM1 expression. FOXM1 inhibition by thiostrepton showed significant antitumor activity on the SS cell lines in vitro. FOXM1 interruption by siRNA increased the chemosensitivity for DOX in both SS cell lines.ConclusionFOXM1 expression is a novel biomarker, and its inhibition is a potential treatment option for SS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2542-4) contains supplementary material, which is available to authorized users.

Proliferation, collagen production and related gene expression in keloids and normal skin fibroblasts

Objective To study the proliferation, collagen production and related gene expression in keloids and normal skin fibroblast. Methods Isolated primary cells of keloid fibroblasts (KFb, n=12) and normal human dermal fibroblasts (NFb, n=12) were identified, the cell viability and proliferating potential and the cell cycle were detected, and the difference on the collagen synthesis between KFb and NFb were compared. The expression of cell cycle-associated genes such as p21, p16, and p27 was dectected by real-time fluorescent quantitative PCR. Results The phase contrast optical microscopy imaging showed that both KFb isolated from keloid tissues and NFb from normal skin tissues possessed classic and similar fibroblast morphology. But there was a significant difference between cell proliferation, Hyp [(2.30±0.10) μg/ml vs. (1.66±0.13) μg/ml, P<0.05] and collagen levels [(17.19±0.75) μg/ml vs. (12.37±0.94) μg/ml, P<0.05]. Compared with NFb, KFb exhibited more percentage of G2/M phase cells [(5.90±0.62)% vs. (16.94 %±1.93)%, P<0.05] and less percentage of G0/G1 phase cells [(90.24 ±2.27)% vs. (75.65±1.92)%, P<0.05]. Cell cycle related genes p16, p21 and p27 were low expressed. Collagen typeⅠwas highly expressed at mRNA levels in KFb than that in NFb [0.84±0.11, 1.32±0.2, 1.69±0.12, 4.33±0.27 in KFb vs.1.43±0.13, 2.56±0.26, 2.89±0.37, 1.40±0.12 in NFb, P<0.05]. Conclusions There are cell dysfunction and abnormal cellular dynamics in keloid fibroblasts. The formation of keloid likely involves aberrant interactions of some genes that affected its development at different extents. Key words: Keloid; Fibroblast; Cell cycle; Genes; Pathogenesis

Suppression of cell division-associated genes by Helicobacter pylori attenuates proliferation of RAW264.7 monocytic macrophage cells.

Helicobacter pylori at multiplicity of infection (MOI ≥ 50) have been shown to cause apoptosis in RAW264.7 monocytic macrophage cells. Because chronic gastric infection by H. pylori results in the persistence of macrophages in the host’s gut, it is likely that H. pylori is present at low to moderate, rather than high numbers in the infected host. At present, the effect of low-MOI H. pylori infection on macrophage has not been fully elucidated. In this study, we investigated the genome-wide transcriptional regulation of H. pylori-infected RAW264.7 cells at MOI 1, 5 and 10 in the absence of cellular apoptosis. Microarray data revealed up- and down-regulation of 1341 and 1591 genes, respectively. The expression of genes encoding for DNA replication and cell cycle-associated molecules, including Aurora-B kinase (AurkB) were down-regulated. Immunoblot analysis verified the decreased expression of AurkB and downstream phosphorylation of Cdk1 caused by H. pylori infection. Consistently, we observed that H. pylori infection inhibited cell proliferation and progression through the G1/S and G2/M checkpoints. In summary, we suggest that H. pylori disrupts expression of cell cycle-associated genes, thereby impeding proliferation of RAW264.7 cells, and such disruption may be an immunoevasive strategy utilized by H. pylori.

MCM-2 is a therapeutic target of Trichostatin A in colon cancer cells

Histone deacetylase (HDAC) inhibitors have recently emerged as a new class of anti-cancer agents. Trichostatin A (TSA), a classical HDAC inhibitor, has been demonstrated to induce cell cycle arrest, promote cell apoptosis, and inhibit metastasis. However, the molecular mechanism underlying TSA function has not been fully elucidated. In the current study, we found that TSA treatment induced altered expression of cell cycle-associated genes in HCT116 cells by RT-PCR array. Among the 84 genes related to cell cycle control, 34 genes were significantly altered by TSA treatment, with 7 genes upregulated and 27 genes downregulated. Interestingly, gene expression of minichromosome maintenance protein-2 (MCM-2) was significantly downregulated by TSA treatment. This was confirmed by quantitative RT-PCR and Western blotting. Moreover, silencing of MCM-2 by siRNA led to cell cycle arrest and apoptosis in HCT116 cells. In addition, TSA caused an increase of phosphorylated JNK, which was involved in downregulation of MCM-2. Together, our results suggest that MCM-2 is a noval therapeutic target of TSA in colon cancer cells.

Zbtb7 suppresses the expression of CDK2 and E2F4 in liver cancer cells: Implications for the role of Zbtb7 in cell cycle regulation

Zbtb7, a member of the POK protein family, is involved in tumorigenesis and cellular differentiation by acting as a crucial transcription factor, but its role in cell cycle modulation remains uncharacterized. In the present study, CDK2 and E2F4, two cell cycle regulators, are shown to be downregulated at the mRNA and protein levels by Zbtb7 in HepG2 and QGY7703 cells. Moreover, we demonstrate that the activities of CDK2 and E2F4 promoters were suppressed by the modulation of Zbtb7 levels and that Zbtb7 represses promoter activities through a mechanism involving direct binding of Zbtb7 to the promoters. Furthermore, it was identified that the site at -259 to -252 within the CDK2 promoter is responsible for Zbtb7-induced repression of the promoter activity. It was found that siRNA‑induced knockdown of Zbtb7 resulted in the suppression of cell cycle progression in HepG2 and QGY7703 cells. Collectively, these data indicate that CDK2 and E2F4 are the downstream targets of Zbtb7, and Zbtb7 may be a cell cycle modulator by regulating the expression of cell cycle-associated genes in liver cancer cells.

A novel facet to consider for the effects of butyrate on its target cells. Focus on “The short-chain fatty acid butyrate is a substrate of breast cancer resistance protein”

short-chain fatty acids (SCFAs), acetate, propionate, and butyrate are produced by bacterial fermentation of dietary fiber in the colonic lumen. In the normal human large intestine, SCFA concentrations range from 70 to 100 mM; these SCFAs account for ∼80% of the anions present in the lumen ([5][1

FOXM1 expression mediates growth suppression during terminal differentiation of HO‐1 human metastatic melanoma cells

Induction of terminal differentiation represents a potentially less toxic cancer therapy. Treatment of HO-1 human metastatic melanoma cells with IFN-β plus mezerein (MEZ) promotes terminal differentiation with an irreversible loss of growth potential. During this process, the transcription factor FOXM1 is down-regulated potentially inhibiting transactivation of target genes including those involved in G(2)/M progression and cell proliferation. We investigated the mechanism of FOXM1 down-regulation and its physiological role in terminal differentiation. Genetic and pharmacological studies revealed that FOXM1 down-regulation was primarily caused by MEZ activation of PKCα and co-treatment with IFN-β plus MEZ augmented the effect of PKCα. Promoter analysis with a mutated E-box on the FOXM1 promoter, and in vitro and in vivo binding assays confirm a direct role of c-Myc on FOXM1 expression. Reduction of c-Myc and overexpression of Mad1 by IFN-β plus MEZ treatment should cause potent and persistent reduction of FOXM1 expression during terminal differentiation. Overexpression of FOXM1 restored expression of cell cycle-associated genes and increased the proportion of cells in the S phase. Our experiments support a model for terminal differentiation in which FOXM1 down-regulation via activation of PKCα followed by suppression of c-Myc expression, are causal events in promoting growth inhibition during terminal differentiation.

Microarray Analysis of Differentially Expressed Genes in the Kidneys and Testes of Mice after Long-term Irradiation with Low-dose-rate γ-rays

Measuring global gene expression using cDNA or oligonucleotide microarrays is an effective approach to understanding the complex mechanisms of the effects of radiation. However, few studies have been carried out that investigate gene expression in vivo after prolonged exposure to low-dose-rate radiation. In this study, C57BL/6J mice were continuously irradiated with gamma-rays for 485 days at dose-rates of 0.032-13 microGy/min. Gene expression profiles in the kidney and testis from irradiated and unirradiated mice were analyzed, and differentially expressed genes were identified. A combination of pathway analysis and hierarchical clustering of differentially expressed genes revealed that expression of genes involved in mitochondrial oxidative phosphorylation was elevated in the kidney after irradiation at the dose-rates of 0.65 microGy/min and 13 microGy/min. Expression of cell cycle-associated genes was not profoundly modulated in the kidney, in contrast to the response to acute irradiation, suggesting a threshold in the dose-rate for modulation of the expression of cell cycle-related genes in vivo following exposure to radiation. We demonstrated that changes to the gene expression profile in the testis were largely different from those in the kidney. The Gene Ontology categories "DNA metabolism", "response to DNA damage" and "DNA replication" overlapped significantly with the clusters of genes whose expression decreased with an increase in the dose-rate to the testis. These observations provide a fundamental insight into the organ-specific responses to low-dose-rate radiation.