Cell Cycle Regulators (cell + cycle_regulator)

Distribution by Scientific Domains


Selected Abstracts


CDK4 IVS4-nt40G,A and T2D-associated obesity in Italians

JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2009
Ramachandran Meenakshisundaram
Cell cycle regulators play crucial roles in the preadipocyte proliferation and adipocyte differentiation. Cyclin-dependent kinase 4 (CDK4) mediates with D-type cyclins entry of cells into cell cycle in response to external stimuli. CDK4 plays a role in body weight, adipogenesis, and beta cell proliferation. CDK4 null mice develop type 2 diabetes (T2D). Furthermore, CDK4 variants are associated with obesity-associated tumors/cancer. We aimed at identifying a role of CDK4 IVS4-nt40G,,,A variant in T2D-associated obesity (body mass index, BMI,,,30) by association tests in an Italian T2D subjects dataset. We recruited from Italy 128 unrelated T2D subjects with BMI,<30,kg/m2 and 54 unrelated T2D subjects with BMI,,,30,kg/m2. We performed statistical power calculations in our dataset. DNA samples were directly sequenced with specific primers for CDK4 IVS4-nt40G,,,A variant. We identified a significant association of the G allele with T2D-associated obesity and of the A allele with T2D-associated BMI,<,30. In our study, we found that the CDK4 IVS4-nt40GG genotype is a risk variant for T2D-associated obesity and that the AA genotype is associated with BMI,<,30 in T2D. Hence, CDK4 IVS4-nt40A allele is protective and G allele confers risk for obesity in T2D patients. This study should prompt further work aiming at establishing CDK4 role in contributing to human obesity and T2D-associated obesity. J. Cell. Physiol. 221: 273,275, 2009. © 2009 Wiley-Liss, Inc. [source]


Ability of human CDC25B phosphatase splice variants to replace the function of the fission yeast Cdc25 cell cycle regulator

FEMS YEAST RESEARCH, Issue 3 2004
Matthieu Lemaire
Abstract CDC25 phosphatases are essential and evolutionary-conserved actors of the eukaryotic cell cycle control. To examine and compare the properties of three splicing variants of human CDC25B, recombinant fission yeast strains expressing the human proteins in place of the endogenous Cdc25 were generated and characterized. We report, that the three CDC25B variants: (i) efficiently replace the yeast counterpart in vegetative growth, (ii) partly restore the , and UV radiation DNA damage-activated checkpoint, (iii) fail to restore the DNA replication checkpoint activated by hydroxyurea. Although these yeast strains do not reveal the specific functions of the human CDC25B variants, they should provide useful screening tools for the identification of new cell cycle regulators and pharmacological inhibitors of CDC25 phosphatase. [source]


p38 mitogen-activated protein kinase is required for central nervous system myelination

GLIA, Issue 15 2007
Gabriela Fragoso
Abstract The p38 MAPKs are a family of kinases that regulate a number of cellular functions including cell migration, proliferation, and differentiation. Here, we report that p38 regulates oligodendrocyte differentiation. Inhibition of p38 with PD169316 and SB203580 prevented accumulation of protein and mRNA of cell-stage specific markers characteristic of differentiated oligodendrocytes, including myelin basic protein, myelin-associated glycoprotein, and the glycosphingolipids, galactosylceramide and sulfatide. In addition, the cell cycle regulator p27kip1 and the transcription factor Sox10 were also significantly reduced. Most significantly, p38 inhibitors completely and irreversibly blocked myelination of dorsal root ganglion neurons by oligodendrocytes and prevented the axolemmal organization of the axo-glial adhesion molecule Caspr. Our results suggest a role(s) for this kinase in key regulatory steps in the maturation of OLGs and initiation of myelination. © 2007 Wiley-Liss, Inc. [source]


Synergistic induction of cyclin D1 in oligodendrocyte progenitor cells by IGF-I and FGF-2 requires differential stimulation of multiple signaling pathways

GLIA, Issue 10 2007
Terra J. Frederick
Abstract D-type cyclins are direct targets of extracellular signals and critical regulators of G1 progression. Our previous data demonstrated that IGF-I and FGF-2 synergize to enhance cyclin D1 expression, cyclin E/cdk2 complex activation, and S-phase entry in OP cells. Here, we provide a mechanistic explanation for how two growth factor signaling pathways converge on a major cell cycle regulator. IGF-I and FGF-2 differentially activate signaling pathways to coordinately promote cyclin D1 expression. We show that the p44/p42 MAPK signaling pathway is essential for FGF-2 induction of cyclin D1 mRNA. In contrast, blocking the PI3-Kinase pathway results in loss of IGF-I/FGF-2 synergistic induction of cyclin D1 protein levels. Moreover, the presence of IGF-I significantly enhances nuclear localization of cyclin D1, which also requires PI3K signaling. GSK-3,, a downstream target of the PI3K/Akt pathway, is phosphorylated in the presence of IGF-I in OPs. Consistent with a known role for GSK-3, in cyclin D1 degradation, we show that proteasome inhibition in OPs exposed to FGF-2 increased cyclin D1 levels, equivalent to levels seen in IGF-I/FGF-2 treated cells. Thus, we provide a model for cyclin D1 coordinate regulation where FGF-2 stimulation of the MAPK pathway promotes cyclin D1 mRNA expression while IGF-I activation of the PI3K pathway inhibits proteasome degradation of cyclin D1 and enhances nuclear localization of cyclin D1. © 2007 Wiley-Liss, Inc. [source]


p16Ink4a is Overexpressed in H. pylori -Associated Gastritis and is Correlated with Increased Epithelial Apoptosis

HELICOBACTER, Issue 1 2003
Haim Shirin
ABSTRACT Background. Cell cycle regulatory proteins may be critical targets during carcinogenesis. We have previously shown that chronic H. pylori infection is associated with decreased expression of the cyclin dependent kinase inhibitor (CDI) p27kip1. Loss of p27kip1 and p16Ink4a (p16) expression, another CDI, has been reported during the progression of gastric tubular adenomas to advanced gastric cancer. The aim of the current study was to examine whether H. pylori infection also affects the expression of p16 in the gastric mucosa of H. pylori- infected patients. Methods. p16 expression was evaluated in gastric antral biopsies by immunohistochemistry in 50 patients with nonulcer dyspepsia (n = 18 uninfected, n = 32 H. pylori infected, 24 by cagA+ strains). Adjacent sections were stained for proliferating epithelial cells (by Ki67) and for apoptotic cells (by TUNEL assay). Results. Both in H. pylori infected and uninfected patients the expression of p16 was higher in the neck and base of the gland than in the foveolar region. Epithelial staining for p16 was increased with H. pylori infection (31.3% vs. 11.1% in the foveolar region, 68.8% vs. 27.8% in the neck and 75% vs. 50% in the glandular base). There was no correlation between the expression of 16 and proliferation but there was a significant positive correlation between apoptosis and 16 immunostaining. Conclusions. The tumor suppressor gene 16 is over expressed in gastric epithelial cells of H. pylori infected patients and this is associated with an increase in apoptosis. These findings suggest a possible role for this cell cycle regulator in the increase in gastric cell turnover that is associated with H. pylori infection. [source]


The shared tumor associated antigen cyclin-A2 is recognized by high-avidity T-cells

INTERNATIONAL JOURNAL OF CANCER, Issue 10 2009
Eisei Kondo
Abstract Cyclin-A2, a key cell cycle regulator, has been shown to be overexpressed in various types of malignancies with little expression in normal tissue. Such tumor-associated genes potentially are useful targets for cancer immunotherapy. However, high-avidity cyclin-specific T cells are considered to be thymically deleted. We identified at least one nonameric HLA-A*0201 binding cyclin-A2 epitope by a reverse immunology approach. Using a highly efficient T-cell expansion system that is based on CD40-activated B (CD40-B) cells as sole antigen-presenting cells we successfully generated cyclin-A2 specific CTL from HLA-A*0201+ donors. Interestingly, high-avidity cyclin-A2 specific CTL lines, which recognized peptide-pulsed and antigen expressing target cells, were indeed generated by stimulation with CD40-B cells when pulsed with low concentrations of peptide, whereas CD40-B cells pulsed at saturating concentrations could only induce low-avidity CTL, which recognized peptide-pulsed target cells only. One high-avidity CTL line was subcloned and CTL clones, whose peptide concentration required for half-maximal lysis were less than 1 nM, could lyse cyclin-A2 expressing tumor cells. Taken together, cyclin A2 is an attractive candidate for immune intervention in a significant number of cancer patients and high-avidity T cells can be readily generated using CD40-B cells as antigen-presenting cells. © 2009 UICC [source]


Cyclin D1 overexpression associates with radiosensitivity in oral squamous cell carcinoma

INTERNATIONAL JOURNAL OF CANCER, Issue 3 2001
Ph.D., Satoru Shintani D.D.S.
Abstract Overexpression of cyclin D1, a G1 cell cycle regulator, is often found in many different tumor types, including oral squamous cell carcinomas (SCC). Recent laboratory experiments have demonstrated that cyclin D1 levels can influence radiosensitivity in various cell lines. This study evaluated the relationship between cyclin D1 expression levels and radiosensitivity in nine oral SCC cell lines (HSC2, HSC3, HSC4, SCC15, SCC25, SCC66, SCC111, Ca9-22, and NAN2) and 41 clinical patients with oral SCC who underwent preoperative radiation therapy. Radiosensitivity of the nine oral SCC cell lines differed greatly in their response to radiation, assessed by a standard colony formation assay. Likewise, the expression of cyclin D1 varied, and the magnitude of the cyclin D1 expression correlated with increased tumor radiosensitivity. The similar significant association between the response to preoperative radiation therapy and cyclin D1 overexpression was observed in the oral SCC patients who were treated with preoperative radiation therapy. These results suggest that cyclin D1 expression levels correlate to radiosensitivity and could be used to predict the effectiveness of radiation therapy on oral SCC. © 2001 Wiley-Liss, Inc. [source]


Chlorpromazine and apigenin reduce adenovirus replication and decrease replication associated toxicity

THE JOURNAL OF GENE MEDICINE, Issue 1 2007
Anna Kanerva
Abstract Background Adenoviruses can cause severe toxicity in immunocompromised individuals. Although clinical trials have confirmed the potency and safety of selectively oncolytic adenoviruses for treatment of advanced cancers, increasingly effective agents could result in more toxicity and therefore it would be useful if replication could be abrogated if necessary. Methods We analyzed the effect of chlorpromazine, an inhibitor of clathrin-dependent endocytosis and apigenin, a cell cycle regulator, on adenovirus replication and toxicity. First, we evaluated the in vitro replication of a tumor targeted Rb-p16 pathway selective oncolytic adenovirus (Ad5/3-,24) and a wild-type adenovirus in normal cells, fresh liver samples and in ovarian cancer cell lines. Further, we analyzed the in vitro cell killing efficacy of adenoviruses in the presence and absence of the substances. Moreover, the effect on in vivo efficacy, replication and liver toxicity of the adenoviruses was evaluated. Results We demonstrate in vitro and in vivo reduction of adenovirus replication and associated toxicity with chlorpromazine and apigenin. Effective doses were well within what would be predicted safe in humans. Conclusions Chlorpromazine and apigenin might reduce the replication of adenovirus, which could provide a safety switch in case replication-associated side effects are encountered in patients. In addition, these substances could be useful for the treatment of systemic adenoviral infections in immunosuppressed patients. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Cyclin D1 Amplification and p16(MTS1/CDK4I) Deletion Correlate With Poor Prognosis in Head and Neck Tumors,

THE LARYNGOSCOPE, Issue 3 2002
Ali Namazie MD
Abstract Objectives/Hypothesis Cyclin D1, a cell cycle regulator localized to chromosome 11q13, is amplified in several human tumors including head and neck squamous cell carcinoma (HNSCC). Amplification and/or overexpression of cyclin D1 have been correlated to a poor prognosis. Deletion of the p16 gene, localized to 9p21, has also been observed in a significant proportion of HNSCC. The p16 gene regulates cyclin D1-CDK4 activity and prevents retinoblastoma tumor suppressor gene phosphorylation, thereby downregulating cellular proliferation. Detection of cyclin D1 amplification and p16 deletion using a simple and sensitive method will be valuable for the development of effective treatment modalities for head and neck cancer. Study Design We have used fluorescence in situ hybridization (FISH) to study cyclin D1 amplification and p16 gene deletion in head and neck tumors. Both single- and dual-color FISH were performed. Methods Paraffin-embedded tissues from 103 patients with HNSCC were analyzed using genomic DNA probes for cyclin D1 and p16. Dual-color FISH was performed with chromosome 11 or 9 centromeric probes as a control. Twenty-eight of these samples were analyzed for p16 expression by immunohistochemistry. Results Cyclin D1 amplification was observed in 30% (31/103) of patients, and p16 deletion in 52% (54/103). Lack of p16 expression was observed in 64% (18/28) of patients. There was a good correlation between the deletion of p16 sequences and the loss of p16 expression (P = .008). Amplification of cyclin D1 had a statistically significant association with recurrence, distant metastasis, and survival at 36 months. There was a significant association between p16 deletion and the development of distant metastases. Cyclin D1 amplification and p16 deletion together correlated with recurrence, distant metastasis, and survival. Conclusions We demonstrate that FISH is a simple and sensitive method for detecting cyclin D1 amplification and p16 deletion in head and neck cancer. Our results suggest that these two genetic aberrations together portend a poorer outcome than either of the abnormalities alone in head and neck cancer. [source]


Mutant p53 and cyclin A1 protein expression in primary laryngeal squamous cell carcinomas do not correlate to second primary tumours of the head and neck,

ANZ JOURNAL OF SURGERY, Issue 1-2 2009
Ross D. Farhadieh
Abstract Background:, Field cancerization is a feature of head and neck squamous cell carcinoma. No biological marker in the index tumour has been correlated to the development of second primary tumours (SPT). Cyclin A1 is a cell cycle regulator and a downstream target of p53. This study assessed predictive correlation of cyclin A1 and mut-p53 with clinicopathological parameters and occurrence of (SPT) 7in the head and neck. Methods:, Using immunohistochemistry 106 patients treated for primary laryngeal squamous cell carcinoma were investigated for expression of cyclin A1 and mut-p53. Results:, Expression of cyclin A1 and mut-p53 were noted in 83 of 106 (78.3%) and 25 of 106 (23.6%) patients. There was a weak but significant correlation between mut-p53 and cyclin A1 (r = 0.301, P = 0.002) expression. During the follow-up period (median 41.0 months (range 1,205 months)), 21 of 106 (19.8%) patients developed an SPT. There was no statistically significant correlation between the markers investigated and disease recurrence, SPT diagnosis or clinicopathological parameters. Conclusion:, Second primary tumours are an intriguing problem in treatment of HNSCC and a predictive marker identifying those greatest at risk would be a leap forward. [source]


TSC-box is essential for the nuclear localization and antiproliferative effect of XTSC-22

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 3 2007
Akiko Hashiguchi
Transforming growth factor- ,1-stimulated clone 22 (TSC-22) encodes a leucine zipper-containing protein that is highly conserved among various species. Mammalian TSC-22 is a potential tumor suppressor gene. It translocates into nuclei and suppresses cell division upon antiproliferative stimuli. In human colon carcinoma cells, TSC-22 inhibits cell growth by upregulating expression of the p21 gene, a cyclin-dependent kinase (Cdk) inhibitor. We previously showed that the Xenopus laevis homologue of the TSC-22 gene (XTSC-22) is required for cell movement during gastrulation through cell cycle regulation. In this report, we investigated the molecular mechanism of the antiproliferative effect of XTSC-22. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis suggested that XTSC-22 did not affect the expression levels of the p21 family of Cdk inhibitors or other cell cycle regulators. Analysis of deletion mutants of XTSC-22 revealed that nuclear localization of the N-terminal TSC-box is necessary for cell cycle inhibition by XTSC-22. Further experiments suggested that p27Xic1, a key Cdk inhibitor in Xenopus, interacts with XTSC-22. Because p27Xic1 is a cell cycle inhibitor with a nuclear localization signal, it is possible that XTSC-22 suppresses cell division by translocating into the nucleus with p27Xic1, where it may potentiate the intranuclear action of p27Xic1. [source]


Ability of human CDC25B phosphatase splice variants to replace the function of the fission yeast Cdc25 cell cycle regulator

FEMS YEAST RESEARCH, Issue 3 2004
Matthieu Lemaire
Abstract CDC25 phosphatases are essential and evolutionary-conserved actors of the eukaryotic cell cycle control. To examine and compare the properties of three splicing variants of human CDC25B, recombinant fission yeast strains expressing the human proteins in place of the endogenous Cdc25 were generated and characterized. We report, that the three CDC25B variants: (i) efficiently replace the yeast counterpart in vegetative growth, (ii) partly restore the , and UV radiation DNA damage-activated checkpoint, (iii) fail to restore the DNA replication checkpoint activated by hydroxyurea. Although these yeast strains do not reveal the specific functions of the human CDC25B variants, they should provide useful screening tools for the identification of new cell cycle regulators and pharmacological inhibitors of CDC25 phosphatase. [source]


Mis3 with a conserved RNA binding motif is essential for ribosome biogenesis and implicated in the start of cell growth and S phase checkpoint

GENES TO CELLS, Issue 7 2000
Hiroshi Kondoh
Background In normal somatic cell cycle, growth and cell cycle are properly coupled. Although CDK (cyclin-dependent kinase) activity is known to be essential for cell cycle control, the mechanism to ensure the coupling has been little understood. Results We here show that fission yeast Mis3, a novel evolutionarily highly conserved protein with the RNA-interacting KH motif, is essential for ribosome RNA processing, and implicated in initiating the cell growth. Growth arrest of mis3-224, a temperature sensitive mutant at the restrictive temperature, coincides with the early G2 block in the complete medium or the G1/S block in the release from nitrogen starvation, reflecting coupling of cell growth and division. Genetic interactions indicated that Mis3 shares functions with cell cycle regulators and RNA processing proteins, and is under the control of Dsk1 kinase and PP1 phosphatase. Mis3 is needed for the formation of 18S ribosome RNA, and may hence direct the level of proteins required for the coupling. One such candidate is Mik1 kinase. mis3-224 is sensitive to hydroxyurea, and the level of Mik1 protein increases during replication checkpoint in a manner dependent upon the presence of Mis3 and Cds1. Conclusions Mis3 is essential for ribosome biogenesis, supports S phase checkpoint, and is needed for the coupling between growth and cell cycle. Whether Mis3 interacts solely with ribosomal precursor RNA remains to be determined. [source]


MiR-221 and MiR-222 alterations in sporadic ovarian carcinoma: Relationship to CDKN1B, CDKNIC and overall survival

GENES, CHROMOSOMES AND CANCER, Issue 7 2010
Kaitlyn Wurz
MicroRNAs are often aberrantly expressed in human neoplasms and are postulated to play a role in neoplastic initiation and progression. miR-221 and miR-222 negatively regulate expression of CDKN1B (p27) and CDKN1C (p57), two cell cycle regulators expressed in ovarian surface epithelium and down-regulated in ovarian carcinomas. We characterized miR-221 and miR-222 expression in 49 sporadic high grade ovarian carcinomas and determined whether somatic mutation or epigenetic alterations explained the differences in expression of these miRNAs. We correlated these findings with protein expression of CDKN1B and CDKN1C as assessed by immunohistochemistry. Expression of miR-221 and miR-222 were closely correlated with each other (P = 0.0001). Interestingly, a lower ratio of miR-221 to miR-222 expression was significantly correlated with worse overall survival (P = 0.01) and remained a significant predictor of overall survival in multivariate analysis using the covariate adequacy of surgical cytoreduction (P = 0.03). Higher miR-222 and miR-221 expression were significantly associated with decreased CDKN1C expression (P = 0.009 and 0.01). In contrast, CDKN1B expression was not associated with miR-221 or miR-222 expression. Neither somatic mutations nor methylation of the studied region explained the alterations in miR-221 and miR-222 expression in most carcinomas. © 2010 Wiley-Liss, Inc. [source]


Genomic and immunophenotypical differences between hepatocellular carcinoma with and without cirrhosis

HISTOPATHOLOGY, Issue 6 2010
Maria S Tretiakova
Tretiakova M S, Shabani-Rad M T, Guggisberg K, Hart J, Anders R A & Gao Z-h (2010) Histopathology,56, 683,693 Genomic and immunophenotypical differences between hepatocellular carcinoma with and without cirrhosis Aims:, To compare the expression of genes involved in p53, Wnt/,-catenin, and retinoblastoma (Rb) 1 pathways between cirrhosis-associated hepatocellular carcinoma (HCC-C) and hepatocellular carcinoma arising in non-cirrhotic liver (HCC-NC). Methods and results:, The gene expression profile was analysed using oligo-DNA arrays, and then validated at protein level in a tissue microarray using immunohistochemistry. Compared with their background non-neoplastic liver tissue, HCC-C showed a significantly higher rate of p53, ,-catenin (protein only) and cyclin D1 expression, whereas HCC-NC showed a significantly higher rate of p21Waf1/cip1 and p27Kip1 expression. HCC-C had a significantly higher rate of p53 expression and a significantly lower rate of p21waf1/cip1 expression than HCC-NC. There was no statistically significant association between the expression of genetic markers and tumour histological grade, underlying aetiology, or lymphovascular invasion. Aberrant ,-catenin expression was more commonly seen in single tumours in comparison with multiple tumours. Increased p16INK4 and p21waf1/cip1 expression was more commonly observed in large-sized tumours (>50 mm) than small-sized tumours. Conclusions:, Alteration of the p53 pathway plays a more important role in the pathogenesis of HCC-C, whereas alterations in cell cycle regulators p21waf1/cip1 and p27Kip1 play a more important role in the pathogenesis of HCC-NC. [source]


The degradation of cell cycle regulators by SKP2/CKS1 ubiquitin ligase is genetically controlled in rodent liver cancer and contributes to determine the susceptibility to the disease

INTERNATIONAL JOURNAL OF CANCER, Issue 5 2010
Diego F. Calvisi
Abstract Previous work showed a genetic control of cell cycle deregulation during hepatocarcinogenesis. We now evaluated in preneoplastic lesions, dysplastic nodules and hepatocellular carcinoma (HCC), chemically induced in genetically susceptible F344 and resistant Brown Norway (BN) rats, the role of cell cycle regulating proteins in the determination of a phenotype susceptible to HCC development. p21WAF1, p27KIP1, p57KIP2 and p130 mRNA levels increased in fast growing lesions of F344 rats. Lower/no increases occurred in slowly growing lesions of BN rats. A similar behavior of RassF1A mRNA was previously found in the 2 rat strains. However, p21WAF1, p27KIP1, p57KIP, p130 and RassF1A proteins exhibited no change/low increase in the lesions of F344 rats and consistent rise in dysplastic nodules and HCC of BN rats. Increase in Cks1-Skp2 ligase and ubiquitination of cell cycle regulators occurred in F344 but not in BN rat lesions, indicating that posttranslational modifications of cell cycle regulators are under genetic control and contribute to determine a phenotype susceptible to HCC. Moreover, proliferation index of 60 human HCCs was inversely correlated with protein levels but not with mRNA levels of P21WAF1, P27KIP1, P57KIP2 and P130, indicating a control of human HCC proliferation by posttranslational modifications of cell cycle regulators. [source]


Identifying the differential effects of silymarin constituents on cell growth and cell cycle regulatory molecules in human prostate cancer cells

INTERNATIONAL JOURNAL OF CANCER, Issue 1 2008
Gagan Deep
Abstract Prostate cancer (PCa) is the leading cause of cancer-related deaths in men; urgent measures are warranted to lower this deadly malignancy. Silymarin is a known cancer chemopreventive agent, but the relative anticancer efficacy of its constituents is still unknown. Here, we compared the efficacy of 7 pure flavonolignan compounds isolated from silymarin, namely silybin A, silybin B, isosilybin A, isosilybin B, silydianin, isosilydianin, silychristin and isosilychristin, in advanced human PCa PC3 cells. Silybin A, silybin B, isosilybin A, isosilybin B, silibinin and silymarin strongly inhibited the colony formation by PC3 cells (p < 0.001), while silydianin, silychristin and isosilychristin had marginal effect (p < 0.05). Using cell growth and death assays, we identified isosilybin B as the most effective isomer. FACS analysis for cell cycle also showed that silybin A, silybin B, isosilybin A, isosilybin B, silibinin and silymarin treatment resulted in strong cell cycle arrest in PC3 cells after 72 hr of treatment, while the effect of silydianin, silychristin and isosilychristin was marginal (if any). Western blot analysis also showed the differential effect of these compounds on the levels of cell cycle regulators-cyclins (D, E, A and B), CDKs (Cdk2, 4 and Cdc2), CDKIs (p21 and p27) and other cell cycle regulators (Skp2, Cdc25A, B, C and Chk2). This study provided further evidence for differential anticancer potential among each silymarin constituent, which would have potential implications in devising better formulations of silymarin against prostate and other cancers. © 2008 Wiley-Liss, Inc. [source]


Regulation of growth signalling and cell cycle by Kaposi's sarcoma-associated herpesvirus genes

INTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 6 2004
Shamindra Direkze
Summary Kaposi's sarcoma-associated herpesvirus (KSHV) is the primary aetiological agent of at least three malignancies associated with HIV infection and immunosuppression: Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. KSHV encodes proteins that deregulate key checkpoints in the signalling pathways governing cell proliferation, which may ultimately contribute to the virus' oncogenic potential. To alter cellular signalling associated with proliferation, these viral proteins function like growth factor ligands/receptors, signal transduction proteins, transcription factors and cell cycle regulators. This review focuses on the mechanisms by which some KSHV-encoded proteins activate signalling pathways and cell proliferation and their role in the pathogenesis of KSHV-driven mechanisms. [source]


Sorafenib and rapamycin induce growth suppression in mouse models of hepatocellular carcinoma

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 8b 2009
Hung Huynh
Abstract Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide. Vascular endothelial growth factor, platelet derived growth factor and the Raf/mitogen-activated protein kinase/extracellular signal regulated kinase (Raf/MEK/ERK) signalling pathway regulates the growth, neovascularization, invasiveness and metastatic potential of HCC. In this study, we investigated the in vivo antitumour activity and mechanisms of action of sorafenib tosylate on four patient-derived HCC xenografts. Sorafenib dosed at 50 mg/kg and 100 mg/kg inhibited tumour growth by 85% and 96%, respectively. Sorafenib-induced growth suppression and apoptosis were associated with inhibition of angiogenesis, down-regulation of phospho-platelet-derived growth factor receptor , Tyr1021, phospho-eIF4E Ser209, phospho-c-Raf Ser259, c-Raf, Mcl-1, Bcl-2, Bcl-x and positive cell cycle regulators, up-regulation of apoptosis signalling kinase-1, p27 and p21. Expression of IGF-1R, and phosphorylation of c-Raf Ser338, MEK1/2 Ser217/221 and ERK1/2 Thr202/Tyr204 were increased by sorafenib treatment. Phosphorylation of mammalian target-of-rapamycin (mTOR) targets (p70S6K, S6R and 4EBP1) was reduced by sorafenib in sorafenib-sensitive lines but activated in sorafenib-less-sensitive 10,0505 xenograft. Sorafenib-induced phosphorylation of c-met, p70S6K and 4EBP1 was significantly reduced when 10,0505 cells were co-treated with anti-human anti-HGF antibody, suggesting that treatment with sorafenib leads to increased HGF secretion and activation of c-met and mTOR targets. Treatment of 10,0505 tumours with sorafenib plus rapamycin resulted in growth inhibition, inhibition of vascular endothelial growth factor receptor-2 phosphorylation, increased apoptosis and completely blocked sorafenib-induced phosphorylation of mTOR targets and cyclin B1 expression. These data also provide a strong rationale for clinical investigation of sorafenib in combination with mTOR inhibitors in patients with HCC. [source]


Mirk/Dyrk1B in cancer

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2007
Eileen Friedman
Abstract Mirk/Dyrk1B is a member of a conserved family of serine/threonine kinases which are activated by intramolecular tyrosine phosphorylation, and which mediate differentiation in different tissues,Mirk in skeletal muscle, Dyrk1A in the brain, etc. One role of Mirk in skeletal muscle differentiation is to block cycling myoblasts in the G0 quiescent state by modification of cell cycle regulators, while another role of Mirk is to limit apoptosis in fusing myoblasts. Amplification of the Mirk gene, upregulation of Mirk expression and/or constitutive activation of this kinase have been observed in several different types of cancer. If coupled with a stress condition such as serum starvation which induces a quiescent state, depletion of Mirk by RNA interference using either synthetic duplex RNAi's or pSilencer-encoded RNAi's have decreased colony formation of different cancer cell lines and enhanced apoptosis induced by chemotherapeutic drugs. Mirk is activated by phosphorylation by the stress-activated SAPK kinases MKK3 and MKK6. Our working hypothesis is that Mirk is activated by this pathway in response to various stresses, and then acts as a checkpoint kinase to arrest damaged tumor cells in a quiescent state and allow cellular repair. Pharmacological inhibition of Mirk may enhance the anti-tumor effect of chemotherapeutic drugs. J. Cell. Biochem. 102: 274,279, 2007. © 2007 Wiley-Liss, Inc. [source]


Potential roles of the nucleotide exchange factor ECT2 and Cdc42 GTPase in spindle assembly in Xenopus egg cell-free extracts,

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2003
Takashi Tatsumoto
Abstract The ECT2 protooncogene encodes a guanine nucleotide exchange factor for the Rho family of small GTPases. ECT2 contains motifs of cell cycle regulators at its N-terminal domain. We previously showed that ECT2 plays a critical role in cytokinesis. Here, we report a potential role of XECT2, the Xenopus homologue of the human ECT2, in spindle assembly in cell-free Xenopus egg extracts. Cloned XECT2 cDNA encodes a 100 kDa protein closely related to human ECT2. XECT2 is specifically phosphorylated in M phase extracts. Affinity-purified anti-XECT2 antibody strongly inhibited mitosis in Xenopus cell-free extracts. Instead of bipolar spindles, where chromosomes are aligned at the metaphase plane in control extracts, the addition of anti-XECT2 resulted in the appearance of abnormal spindles including monopolar and multipolar spindles as well as bipolar spindles with misaligned chromosomes. In these in vitro synthesized spindle structures, XECT2 was found to tightly associate with mitotic spindles. The N-terminal half of XECT2 lacking the catalytic domain also strongly inhibited spindle assembly in vitro, resulting in the formation of mitotic spindles with a low density. Among the representative Rho GTPases, a dominant-negative form of Cdc42 strongly inhibited spindle assembly in vitro. These results suggest that the Rho family GTPase Cdc42 and its exchange factor XECT2 are critical regulators of spindle assembly in Xenopus egg extracts. Published 2003 Wiley-Liss, Inc., [source]


G1 cell cycle regulators in congenital melanocytic nevi.

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 9 2008
Comparison with acquired nevi, melanomas
Background:, Congenital nevi are one of the known risk factors for the development of melanoma. However, the magnitude of the risk for both large and small congenital nevi is controversial. Methods:, In order to elucidate the behavior of congenital nevocytes and to define any possible similarities or differences with common nevi and melanomas, we investigated the expression of Ki-67, Rb, p16, cyclin D1, p53 and p21/Waf-1 in 41 congenital nevi, 16 melanomas and 20 acquired common nevi by immunohistochemistry. Results:, Congenital nevi highly expressed p16 (81.82 ± 9.98) but showed limited, if any, reactivity for Ki-67 (1.34% ± 0.89), Rb (0.76% ± 0.94), cyclin D1 (0.21% ± 0.29), p53 (0.54% ± 0.93) and p21 (0.0609% ± 0.32). No statistically significant difference was found between giant and nongiant congenital nevi and between congenital and common nevi for any of the markers. The expression of p16 was significantly higher in congenital nevi than in melanomas (p < 0.0001). On the contrary, the expression of Ki-67, p53, p21, Rb and cyclin D1 was significantly higher in melanomas (p < 0.0001). Conclusion:, Our data regarding the immunohistochemical expression of Rb, p16, p53, cyclin D1 and Ki-67 in congenital nevi indicate that either the alteration of their expression is not an initiating event in melanoma formation or, alternatively, congenital melanocytic nevi may not be the first step in malignant transformation. [source]


Cyclin D1, cdk4, and Bim are involved in thrombin-induced apoptosis in cultured cortical neurons

JOURNAL OF NEUROCHEMISTRY, Issue 2 2007
Haripriya Vittal Rao
Abstract Thrombin, a multifunctional serine protease, is neurotoxic in vitro and in vivo. Thrombin has been shown to be increased in Alzheimer's disease (AD) and other neuropathological conditions and could be a mediator of pathological neuronal cell death in the brain. The mechanisms of thrombin-induced neuronal cell death are incompletely understood. The objective of this study is to explore mechanisms that contribute to thrombin-induced neuronal apoptosis focusing on the role of cell cycle regulators and the pro-apoptotic protein Bim (Bcl-2-interacting mediator of cell death) in this process. Our data show that thrombin treatment of primary cerebral cortical cultures results in dose-dependent apoptotic cell death. Exposure of neuronal cultures to thrombin leads to induction of cell cycle proteins cyclin D1 and cyclin E, at both mRNA and protein levels. In addition, thrombin treatment causes the appearance of cyclin-dependent kinase 4 (cdk4) and expression of the pro-apoptotic protein Bim. Inhibition of cdk4 prevents both induction of Bim expression and thrombin-induced neuronal apoptosis. These data demonstrate that thrombin-induced apoptosis proceeds via cell cycle activation involving cdk4 resulting in induction of Bim. Thus, cell cycle proteins could be therapeutic targets in diseases such as AD where thrombin has been implicated. [source]


Modulation of gene expression by extracellular pH variations in human fibroblasts: A transcriptomic and proteomic study

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 5 2003
Maja A. Bumke
Abstract Homeostasis of the intracellular ionic concentration, in particular that of hydrogen ions, is pivotal to the maintenance of cell function and viability. Nonetheless, pH fluctuations in both the intracellular and the extracellular compartments can occurr during development, in physiological processes and in disease. The influence of pH variations on gene expression has been studied in different model systems, but only for a limited number of genes. We have performed a broad range analysis of the patterns of gene expression in normal human dermal fibroblasts at two different pH values (in the presence and in the absence of serum), with the aim of getting a deeper insight into the regulation of the transcriptional program as a response to a pH change. Using the Affymetrix gene chip system, we found that the expression of 2068 genes (out of 12,565) was modulated by more than two-fold at 24, 48 or 72 h after the shift of the culture medium pH to a more acidic value, stanniocalcin 1 being a remarkable example of a strongly up-regulated gene. Genes displaying a modulated pattern of expression included, among others, cell cycle regulators (consistent with the observation that acidic pH abolishes the growth of fibroblasts in culture) and relevant extracellular matrix (ECM) components. Extracellular matrix protein 2, a protein with a restricted pattern of expression in adult human tissues, was found to be remarkably overexpressed as a consequence of serum starvation. Since ECM components, whose expression is controlled by pH, have been used as targets for biomolecular intervention, we have complemented the Affymetrix analysis with a two-dimensional polyacrylamide gel electrophoresis analysis of proteins which are differentially secreted by fibroblasts at acidic or basic pH. Mass spectrometric analysis of more than 650 protein spots allowed the identification of 170 protein isoforms or fragments, belonging to 40 different proteins. Some proteins were only expressed at basic pH (including, for instance, tetranectin), while others (e.g., agrin) were only detectable at acidic pH. Some of the identified proteins may represent promising candidate targets for biomedical applications, e.g., for antibody-mediated vascular targeting strategies. [source]


Genetic engineering to study testicular tumorigenesis

APMIS, Issue 1 2003
WEI YAN
In humans, Sertoli cell tumors account for approximately 4% of all testicular tumors, and 20% of these are malignant. The mechanisms underlying Sertoli cell tumorigenesis remain largely unknown. Using gene knockout technology, we previously generated mutant mice lacking the , subunit of inhibin dimers. The inhibin ,-null male mice develop testicular Sertoli cell tumors with 100% penetrance. These tumors develop as early as 4 weeks of age and cause a cachexia-like wasting syndrome. Castrated inhibin , knockout mice develop sex steroidogenic adrenal cortical tumors. These studies have identified inhibins as secreted tumor suppressors with specificity for the gonads and adrenal glands. It had been suggested that endocrine factors play roles in Sertoli cell tumorigenesis by altering cell cycle machinery of the Sertoli cells. To test the potential of these factors to function as modifiers of Sertoli cell tumorigenesis, we have employed a genetic intercross strategy, breeding inhibin , mutant mice with mutant mice deficient in endocrine signaling factors including gonadotropin releasing hormone (hypogonadal, hpg mice), follicle stimulating hormone, anti-Müllerian hormone (MH), activin receptor type II, or androgen receptor (testicular feminization, tfm mice), or mice overexpressing follistatin. We are also investigating the effects of loss of critical cell cycle regulators, such as cyclin dependent kinase inhibitor p27, on Sertoli cell tumorigenesis in inhibin , knockout males. These studies clearly demonstrate the roles of these factors as modifiers of the Sertoli cell tumorigenesis. Activin signaling through activin receptor type II is responsible for the cachexia-like syndrome observed in the inhibin , knockout mice with tumors. The gonadotropin hormones are essential for testicular tumor development, but elevated FSH levels are not sufficient to cause Sertoli cell tumors. Absence of FSH, lack of androgen receptor, or overexpression of follistatin slows the tumor growth and minimizes the cachexia symptoms, thus prolonging the life span of these double mutant mice. In contrast, absence of AMH or p27 causes earlier onset and more aggressive development of testicular tumor, with an earlier death of double mutant mice. We are currently investigating roles of estrogen signaling pathways, and other cell cycle regulators, in tumor development in the inhibin , knockout mice by generating mice with double or triple mutations. Genetic engineering in mouse models provides a powerful tool to study the mechanisms of testicular tumorigenesis and define the important genetic modifiers in vivo. [source]


Cell cycle analysis and expression of cell cycle regulator genes in myeloma cells overexpressing cyclin D1

BRITISH JOURNAL OF HAEMATOLOGY, Issue 3 2001
Kenichiro Yata
Among the recently discovered myeloma-specific gene alterations associated with chromosomal translocations, cyclin D1/PRAD1/Bcl-1 overexpression caused by t(11;14)(q13;q32) is considered to be the most frequent in myeloma patients and cell lines, and may be a prognostic factor clinically. To elucidate the cellular biological role of overexpressed cyclin D1 in myeloma cells, we examined the mRNA expression levels of cell cycle regulators including three cyclin Ds, cyclin-dependent kinase inhibitors (CDK-Is) and accelerators. Cyclin D1 overexpression was clearly demonstrated in the lines with abnormal 11q13 and associated with overexpression of S and G2 accelerator genes. The cyclin D1 -overexpressing lines tended to have a shortened G1 phase compared with the non-expressing lines. In addition, artificial silencing using antisense oligonucleotides for cyclin D1 suppressed the growth rate of some but not all cyclin D1 -overexpressing cells. These results indicate that overexpression of cyclin D1 caused by cytogenetic abnormalities may make cells progress through the cell cycle rapidly, but it seems that other factors such as cyclin D2 and translocation-related genes affect the cell cycle progression in myeloma cells. [source]


Recent advances in the molecular pathology of soft tissue sarcoma: Implications for diagnosis, patient prognosis, and molecular target therapy in the future

CANCER SCIENCE, Issue 2 2009
Yoshinao Oda
In the present paper, recent advances in the molecular pathology of soft tissue sarcomas (STS) and the implications for their prognostic value are reviewed, and the potential targets of molecular therapy are discussed. According to the molecular genetic aspect, STS are divided into two groups: chromosome translocation-associated sarcomas and sarcomas without specific translocation. In the former group, specific fusion transcripts, such as SS18,SSX, EWS,FLI1, and PAX3,FKHR, could be detected in synovial sarcoma, Ewing's sarcoma and primitive neuroectodermal tumor, and alveolar rhabdomyosarcoma, respectively. The direct or indirect interactions between these fusion transcripts and cell cycle regulators have been elucidated by several investigators. Therefore, these fusion transcripts are promising candidates as molecular targets. As evaluated in carcinomas, alterations of several tumor-suppressor genes and adhesion molecules and overexpression of growth factors and their receptors have been extensively assessed in STS. In mixed-type STS, epidermal growth factor receptor overexpression was associated with decreased overall survival, suggesting the beneficial role of epidermal growth factor receptor inhibitors in STS. In malignant rhabdoid tumor and epithelioid sarcoma, frequent alteration of the SMARCB1/INI1tumor-suppressor gene and the loss of its protein have been demonstrated, indicating that this molecule could be an effective target of these sarcomas. In sarcomas with epithelioid differentiation, such as synovial sarcoma and epithelioid sarcoma, overexpression of dysadherin, which downregulates E-cadherin expression, was a poor prognostic factor. In conclusion, further studies are necessary to search for effective and specific molecules for the inhibition of tumor growth in each type of STS, especially in sarcomas without specific translocation. (Cancer Sci 2009; 100: 200,208) [source]


Simvastatin inactivates ,1-integrin and extracellular signal-related kinase signaling and inhibits cell proliferation in head and neck squamous cell carcinoma cells

CANCER SCIENCE, Issue 6 2007
Ikuko Takeda
The 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors, also called statins, are commonly used as lipid-lowering drugs that inhibit cholesterol biosynthesis. An anticancer effect, as a pleiotropic function of certain statins, has been hypothesized. In the present study, we investigated the effect of simvastatin, one of the natural statins, on cell proliferation, cell cycle, invasive activity, and molecular expressions associated with cell,extracellular matrix adhesion, signal transduction, and DNA synthesis in Tu167 and JMAR cells from head and neck squamous cell carcinoma. The addition of simvastatin resulted in a dose-dependent inhibition of cell growth and migration into the extracellular matrix. Considerable morphological changes occurred after treatment with simvastatin, demonstrating loss of cell adhesion and disruption of actin filaments in cytoplasm. The inhibitory effect of simvastatin on cell proliferation seemed to be associated with cell cycle arrest and increased expression of p21, p27, and activated caspase-3. The expression of ,1-integrin, a counter adhesion for the extracellular matrix, phosphorylated FAK, and phosphorylated ERK was decreased by treatment with simvastatin. The proapoptotic effect of simvastatin was inhibited by treatment with mevalonate. cDNA microarray assay demonstrated that molecular changes resulting from treatment with simvastatin included the up-regulation of cell cycle regulators and apoptosis-inducing factors and the down-regulation of integrin-associated molecules and cell proliferation markers. Of down-regulated genes induced by simvastatin treatment, a significant depletion of thymidylate synthase was confirmed using western blot analysis. These results imply that simvastatin has the potential to be effective for the prevention of the growth and metastasis of cancer cells. (Cancer Sci 2007; 98: 890,899) [source]