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Cell Cycle Profile (cell + cycle_profile)
Selected AbstractsInfection with Toxoplasma gondii results in dysregulation of the host cell cycleCELLULAR MICROBIOLOGY, Issue 5 2008Robert E. Molestina Summary Mammalian cells infected with Toxoplasma gondii are characterized by a profound reprogramming of gene expression. We examined whether such transcriptional responses were linked to changes in the cell cycle of the host. Human foreskin fibroblasts (HFFs) in the G0/G1 phase of the cell cycle were infected with T. gondii and FACS analysis of DNA content was performed. Cell cycle profiles revealed a promotion into the S phase followed by an arrest towards the G2/M boundary with infection. This response was markedly different from that of growth factor stimulation which caused cell cycle entry and completion. Transcriptional profiles of T. gondii -infected HFF showed sustained increases in transcripts associated with a G1/S transition and DNA synthesis coupled to an abrogation of cell cycle regulators critical in G2/M transition relative to growth factor stimulation. These divergent responses correlated with a distinct temporal modulation of the critical cell cycle regulator kinase ERK by infection. While the kinetics of ERK phosphorylation by EGF showed rapid and sustained activation, infected cells displayed an oscillatory pattern of activation. Our results suggest that T. gondii infection induces and maintains a ,proliferation response' in the infected cell which may fulfill critical growth requirements of the parasite during intracellular residence. [source] Decreased expression and promoter methylation of the menin tumor suppressor in pancreatic ductal adenocarcinomaGENES, CHROMOSOMES AND CANCER, Issue 5 2009Ilaria Cavallari Loss of menin, a tumor suppressor coded by the MEN1 gene, is a key factor in the pathogenesis of multiple endocrine neoplasia type I and in a percentage of sporadic endocrine tumors of the pancreas and parathyroid glands. This study investigated expression of the menin protein in the normal exocrine pancreas and in pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic tumor. Immunofluorescence (IF) analyses showed that menin is expressed at high levels in normal acinar and duct cells. Examination of 24 clinical samples of PDAC revealed a pronounced decrease in menin expression in all tumors examined. To identify alterations underlying this defect, we searched for disruption and epigenetic silencing of the MEN1 gene. Analysis of nine laser-microdissected tumors revealed loss of heterozygosity of intragenic (one tumor) or adjacent (three tumors) MEN1 microsatellite markers. Methylation of CpG sites in the MEN1 promoter was documented in five of 24 tumors. IF analyses also revealed low to undetectable menin expression in the PDAC cell lines MiaPaCa-2 and Panc-1. Ectopic expression of menin in these cells resulted in a marked alteration of the cell cycle, with an increase in the G1/S+G2 ratio. These findings represent the first evidence that the MEN1 gene is a target of mutation and methylation in PDAC and that menin influences the cell cycle profile of duct cells. © 2009 Wiley-Liss,Inc. [source] Rapamycin and CCI-779 inhibit the mammalian target of rapamycin signalling in hepatocellular carcinomaLIVER INTERNATIONAL, Issue 1 2010Ivan Chun-Fai Hui Abstract Background: The mammalian target of rapamycin (mTOR), which phosphorylates p70S6K and 4EBP1 and activates the protein translation process, is upregulated in cancers and its activation may be involved in cancer development. Aims: In this study, we investigated the tumour-suppressive effects of rapamycin and its new analogue CCI-779 on hepatocellular carcinoma (HCC). Methods: Rapamycin and its new analogue CCI-779 were applied to treat HCC cells. Cell proliferation, cell cycle profile and tumorigenicity were analysed. Results: In human HCCs, we observed frequent (67%, 37/55) overexpression of mTOR transcripts using real-time reverse transcriptase-polymerase chain reaction. Upon drug treatment, PLC/PRF/5 showed the greatest reduction in cell proliferation using the colony formation assay, as compared with HepG2, Hep3B and HLE. Rapamycin was a more potent antiproliferative agent than CCI-779 in HCC cell lines. Proliferation assays by cell counting showed that the IC50 value of rapamycin was lower than that of CCI-779 in PLC/PRF/5 cells. Furthermore, flow cytometric analysis showed that both drugs could arrest HCC cells in the G1 phase but did not induce apoptosis of these cells, suggesting that these mTOR inhibitors are cytostatic rather than cytotoxic. Upon rapamycin and CCI-779 treatment, the phosphorylation level of mTOR and p70S6K in HCC cell lines was significantly reduced, indicating that both drugs can suppress mTOR activity in HCC cells. In addition, both drugs significantly inhibited the growth of xenografts of PLC/PRF/5 cells in nude mice. Conclusions: Our findings indicate that rapamycin and its clinical analogue CCI-779 possess tumour-suppressive functions towards HCC cells. [source] Failure to farnesylate Rheb protein contributes to the enrichment of G0/G1 phase cells in the Schizosaccharomyces pombe farnesyltransferase mutantMOLECULAR MICROBIOLOGY, Issue 6 2001Wenli Yang Protein farnesylation is important for a number of physiological processes, including proliferation and cell morphology. The Schizosaccharomyces pombe mutant, cpp1,, defective in farnesylation, exhibits distinct phenotypes, including morphological changes and sensitivity to the arginine analogue, canavanine. In this work, we report a novel phenotype of this mutant, enrichment of G0/G1 phase cells. This phenotype results mainly from the inability to farnesylate the Rheb G-protein, as normal cell cycle progression can be restored to the mutant by expressing a mutant form of SpRheb (SpRheb-CVIL) that can bypass farnesylation. In contrast, a farnesylation-defective mutant of SpRheb (SpRheb-SVIA) is incapable of restoring the normal cell cycle profile to the cpp1, mutant. Inhibition of SpRheb expression leads to the accumulation of cells at the G0/G1 phase of the cell cycle. This growth arrest phenotype of the sprheb, disruption can be complemented by the introduction of wild-type sprheb+. The complementation is dependent on farnesylation, as the farnesylation-defective SpRheb-SVIA mutant is incapable of complementing the sprheb, disruption. Other mutants of SpRheb, E40K and S20N, are also incapable of complementing the sprheb, disruption. Furthermore, efficient complementation can be obtained by the expression of human Rheb but not Saccharomyces cerevisiae Rheb. Our findings suggest that protein farnesylation is important for cell cycle progression of S. pombe cells and that farnesylated SpRheb is critical in this process. [source] Expression patterns and cell cycle profiles of PCNA, MCM6, cyclin D1, cyclin A2, cyclin B1, and phosphorylated histone H3 in the developing mouse retinaDEVELOPMENTAL DYNAMICS, Issue 3 2008Kirston M. Barton Abstract A challenge in studying organogenesis is the ability to identify progenitor cell populations. To address this problem, we characterized the expression patterns of cell cycle proteins during mouse retinal development and used flow cytometry to determine the expression profiles in the cell cycle. We found that MCM6 and PCNA are expressed in essentially all retinal progenitor cells throughout the proliferative period and these proteins are readily detectable in all cell cycle phases. Furthermore, their expression levels are downregulated as cells exit the cell cycle and differentiate. We also analyzed the expression of Cyclins D1, A2, and B1, and phosphorylated Histone H3 and found unexpected expression patterns and cell cycle profiles. The combined utilization of the markers tested and the use of flow cytometry should further facilitate the study of stem and progenitor cell behavior during development and in adult tissues. Developmental Dynamics 237:672,682, 2008. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||