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Cell Growth Arrest (cell + growth_arrest)
Selected AbstractsPTHrP Signaling Targets Cyclin D1 and Induces Osteoblastic Cell Growth Arrest,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2005Nabanita S Datta PhD Abstract PTHrP control of the MC3T3-E1 cell cycle machinery showed that, during differentiation, PTHrP induced G1 growth arrest. Cyclin D1 was a critical mediator as a downstream effector of cAMP, PKC, and MAPK signaling, and the process was PKA-independent. The involvement of JunB has been found critical for PTHrP effects. Introduction: PTH-related protein (PTHrP) has been implicated in the control of bone cell turnover, but the mechanisms underlying its effect on osteoblast proliferation and differentiation have not been clearly defined. The mechanisms by which PTHrP impacts cell cycle proteins and the role of signaling pathways in differentiated osteoblasts were studied. Materials and Methods: To elucidate the role of PTHrP, flow cytometric analyses were performed using MC3T3-E1 and primary mouse calvarial cells. Relative protein abundance (Western blot), physical association of partners (immunoprecipitation), and kinase activities (in vitro kinase assays using either GST-Rb or H1-histone as substrates) of cell cycle-associated proteins in vehicle and PTHrP-treated 7-day differentiated cells were determined. ELISA and/or Northern blot analyses were done to evaluate JunB and cyclin D1 expression. SiRNA-mediated gene silencing experiments were performed to silence JunB protein. Finally, inhibitors of cAMP, protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein kinase (MAPK) were used to determine involvement of different signaling pathways. Results: PTHrP inhibited cyclin D1 protein expression 7-fold in a dose- and time-dependent manner and increased the level of p16 protein in differentiated osteoblasts. Additionally, PTHrP reduced cyclin D1-CDK4/CDK6 and CDK1 kinase activities. Forskolin, a cAMP agonist, mimicked PTHrP action, and the PKC inhibitor, GF109203X, slightly blocked downregulation of cyclin D1, implying involvement of both cAMP and PKC. U0126, a MAPK inhibitor, alone decreased cyclin D1 protein, suggesting that the basal cyclin D1 protein is MAPK dependent. H-89, a PKA inhibitor, did not alter the effect of PTHrP on cyclin D1, suggesting a PKA-independent mechanism. Finally, expression of JunB, an activating protein-1 transcription factor, was significantly upregulated, and silencing JunB (siRNA) partially reversed the cyclin D1 response, implying involvement of JunB in the PTHrP-mediated growth arrest of MC3T3-E1 cells. Conclusion: PTHrP upregulates JunB and reduces cyclin D1 expression while inducing G1 cell cycle arrest in differentiated osteoblasts. Such regulation could be an important determinant of the life span and bone-forming activity of osteoblasts. [source] PPAR gamma activators induce differentiation of B12 oligodendrocyte-like cells and rat spinal cord oligodendrocytesJOURNAL OF NEUROCHEMISTRY, Issue 2002A. D. Roth The regulation of CNS lipid metabolism by nuclear receptors and their relation to cell differentiation remains undetermined. Since myelinating oligodendrocytes are the major lipid-synthesizing cells in the CNS, we characterized the effect of PPAR activation in a CNS derived cell line that expresses oligodendrocyte markers and compared these effects with oligodendrocyte primary cultures (90,95% pure). The rat glioma derived B12 cell line express the three major PPAR isoforms (PPAR ,, , and ,) and present a large number of peroxisomes, indicating an important lipid metabolism. Treatment with ciprofibrate, a general PPAR activator and clinical hypolipidemic, induces proliferation arrest, process extension and a moderate rise in the expression of acyl-CoA oxidase, a specific marker of peroxisomal proliferation. Cell growth arrest by ciprofibrate is enhanced 100-fold by low concentrations of retinoic acid (0.01 ,m), suggesting the involvement of the PPAR-retinoid acid receptor heterodimers. Since ciprofibrate possibly acts by modifying the concentration of endogenous PPAR ligands, we traced its effects to PPAR, by using isoform specific ligands: Troglitazone and 15-deoxy-prostaglandin J2, both of which induce growth arrest and process extension in B12 cells. These effects were corroborated on rat spinal cord derived oligodendrocytes primary cultures, where a significant rise in the number of mature oligodendrocytes is observed in response to PPAR, activators. These results show that PPAR,, a master gene in the differentiation of adipose tissue could be involved in the lipid metabolism of maturing oligodendrocytes. [source] The histone deacetylase inhibitor MS-275 induces p21WAF1/Cip1 expression in human Hep3B hepatoma cellsDRUG DEVELOPMENT RESEARCH, Issue 2 2007Haiyuan Zhang Abstract MS-275 is a novel synthetic benzamide derivative histone deacetylase (HDAC) inhibitor, that has demonstrated antiproliferative activity in a variety of in vitro human cancer cell lines including breast, colon, lung, myeloma, ovary, pancreas, prostate, and leukemia. Currently, little information is available concerning the effects of MS-275 on liver cancer cells. In the current study, MS-275 was found to have potent actions against human hepatoma Hep3B cells including inhibition of cell proliferation and induction of apoptosis. MS-275 selectively up-regulated a cyclin-dependent kinase inhibitor, p21WAF1/Cip1 without alteration of p27WAF1. Expression of p21WAF1/Cip1 is considered to play a pivotal role in Hep3B cell growth arrest and induction of apoptosis. Induction of p21WAF1/Cip1 expression was accompanied by an accumulation of acetylated histones H3 and H4 associated specifically with p21WAF1/Cip1 gene. ChIP analysis revealed remarkable alterations in protein components bound to the promoter region of p21WAF1/Cip1 gene in response to MS-275 treatment. These included the degradation of HDAC1, HDAC3, and c-Myc, and as well as increased p300 and RNA polymerase II. The selective effect of MS-275 on the up-regulation of the p21WAF1/Cip1 gene whose expression was suppressed in the hepatoma cancer cell line indicated that it would be a very attractive approach in clinical liver cancer therapy. Drug Dev Res 68:61,70, 2007. © 2007 Wiley-Liss, Inc. [source] Annexin-A7 protects normal prostate cells and induces distinct patterns of RB-associated cytotoxicity in androgen-sensitive and -resistant prostate cancer cells,INTERNATIONAL JOURNAL OF CANCER, Issue 11 2009Yelizaveta Torosyan Abstract The tumor suppressor role of annexin-A7 (ANXA7) was previously demonstrated by cancer susceptibility in Anxa7(+/,)-mice and by ANXA7 loss in human cancers, especially in hormone-resistant prostate tumors. To gain mechanistic insights into ANXA7 tumor suppression, we undertook an in vitro study in which we compared wild-type (WT)-ANXA7 and dominant-negative (DN)-ANXA7 effects to a conventional tumor suppressor p53 in prostate cancer cells with different androgen sensitivity. Unlike p53 (which caused cell growth arrest and apoptosis to a noticeable extent in benign PrEC), WT-ANXA7 demonstrated profound cytotoxicityin androgen-sensitive LNCaP as well as in the androgen-resistant DU145 and PC3 prostate cancer cells, but not in PrEC. In androgen-sensitive LNCaP, WT-ANXA7 decreased low-molecular-weight (LMW) AR protein forms and maintained higher retinoblastoma 1 (RB1)/phospho-RB1 ratio. In contrast, DN-ANXA7 (which lacks phosphatidylserine liposome aggregation properties) increased LMW-AR forms and hyperphosphorylated RB1 that was consistent with the lack of DN-ANXA7 cytotoxicity. According to the microarray-based Ingenuity Pathways Analysis, a major WT-ANXA7 effect in androgen-sensitive LNCaP constituted of upregulation of the RB1-binding transcription factor E2F1 along with its downstream proapoptotic targets such as ASK1 and ASPP2. These results suggested a reversal of the RBdependent repression of the proapoptotic E2F-mediated transcription. However, DN-ANXA7 increased RB1/2 (but not E2F1) expression and induced the proliferation-promoting ERK5, thereby maintaining the RB-dependent repression of E2F-mediated apoptosis in LNcaP. On the other hand, in androgen-resistant cells, WT-ANXA7 tumor suppressor effects involved PTEN and NFkB pathways. Thus, ANXA7 revived the RB-associated cell survival control and overcame androgen resistance and dysfunctional status of major tumor suppressors commonly mutated in prostate cancer. Published 2009 UICC. [source] Telomere Higher-Order Structure and Genomic InstabilityIUBMB LIFE, Issue 8 2003Terace Fletcher Abstract Telomeres, nucleoprotein complexes at the end of eukaryotic chromosomes, have vital roles in chromosome integrity. Telomere chromatin structure is both intricate and dynamic allowing for a variety of responses to several stimuli. A critical determinant in telomere structure is the G-strand overhang. Facilitated by telomeric proteins, the G-strand overhang stabilizes telomere higher-order assemblies most likely by adopting unusual DNA structures. These structures influence activities that occur at the chromosome end. Dysfunctional telomeres induce signals resulting in cell growth arrest or death. To overcome telomere dysfunction, cancer cells activate the DNA polymerase, telomerase. The presence of telomerase at the telomere may establish a particular telomeric state. If the chromosome ends of cancer and normal cells exist in different states, cancer-specific telomere structures would offer a unique chemotherapeutic target. IUBMB Life, 55: 443-449, 2003 [source] Identification of genetic networks involved in the cell growth arrest and differentiation of a rat astrocyte cell line RCG-12,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2007Ichiro Takasaki Abstract The purpose of the present study is to establish and characterize a conditionally immortalized astrocyte cell line and to clarify the genetic networks responsible for the cell growth arrest and differentiation. A conditionally immortalized astrocyte cell line, RCG-12, was established by infecting primary cultured rat cortical glia cells with a temperature-sensitive simian virus 40 large T-antigen. At a permissive temperature of 33°C, the large T-antigen was expressed and cells grew continuously. On the other hand, the down-regulation of T-antigen at a non-permissive temperature of 39°C led to growth arrest and differentiation. The cells expressed astrocyte-expressed genes such as glial fibrillary acidic protein. Interestingly, the differentiated condition induced by the non-permissive temperature significantly elevated the expression levels of several astrocyte-expressed genes. To identify the detailed mechanisms by which non-permissive temperature-induced cell growth arrest and differentiation, we performed high-density oligonucleotide microarray analysis and found that 556 out of 15,923 probe sets were differentially expressed 2.0-fold. A computational gene network analysis revealed that a genetic network containing up-regulated genes such as RB, NOTCH1, and CDKN1A was associated with the cellular growth and proliferation, and that a genetic network containing down-regulated genes such as MYC, CCNB1, and IGF1 was associated with the cell cycle. The established cell line RCG-12 retains some characteristics of astrocytes and should provide an excellent model for studies of astrocyte biology. The present results will also provide a basis for understanding the detailed molecular mechanisms of the growth arrest and differentiation of astrocytes. J. Cell. Biochem. 102: 1472,1485, 2007. © 2007 Wiley-Liss, Inc. [source] Apoptosis induced by troglitazone is both peroxisome proliferator-activated receptor-,- and ERK-dependent in human non-small lung cancer cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2006Mingyue Li The role of the peroxisome proliferator-activated receptor-gamma (PPAR,) in cell differentiation, cell-cycle arrest, and apoptosis has attracted increasing attention. We have recently demonstrated that PPAR, ligands-troglitazone (TGZ) induced apoptosis in lung cancer cells. In this report, we further studied the role of ERK1/2 in lung cancer cells treated by TGZ. The result demonstrated that TGZ induced PPAR, and ERK1/2 accumulation in the nucleus, in which the co-localization of both proteins was found. The activation of ERK1/2 resulted in apoptosis via a mitochondrial pathway. Both PPAR, siRNA and U0126, a specific inhibitor of ERK1/2, were able to block these effects of TGZ, suggesting that apoptosis induced by TGZ was PPAR, and ERK1/2 dependent. Inhibition of ERK1/2 by U0126 also led to a significant decrease in the level of PPAR,, indicating a positive cross-talk between PPAR, and ERK1/2 or an auto-regulatory feedback mechanism to amplify the effect of ERK1/2 on cell growth arrest and apoptosis. In addition to ERK1/2, TGZ also activated Akt. Interestingly, inhibition of ERK1/2 prevented the activation of Akt whereas the suppression of Akt had no effect on ERK1/2, suggesting that Akt was not necessary for TGZ-PPAR,-ERK pathway. However, the inhibition of Akt promoted the release of cytochrome c, suggesting the activation of Akt may have a negative effect on apoptosis induced by TGZ. In conclusion, our study has demonstrated that TGZ, a synthetic PPAR, ligand, induced apoptosis in NCI-H23 lung cancer cells via a mitochondrial pathway and this pathway was PPAR, and ERK1/2 dependent. J. Cell. Physiol. 209: 428,438, 2006. © 2006 Wiley-Liss, Inc. [source] K vitamins, PTP antagonism, and cell growth arrestJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2002Brian I. Carr The main function of K vitamins is to act as co-factors for ,-glutamyl carboxylase. However, they have also recently been shown to inhibit cell growth. We have chemically synthesized a series of K vitamin analogs with various side chains at the 2 or 3 position of the core naphthoquinone structure. The analogs with short thio-ethanol side chains are found to be more potent growth inhibitors in vitro of various tumor cell lines. Cpd 5 or [2-(2-mercaptoethanol)-3-methyl-1,4-naphthoquinone] is one of the most potent. The anti-proliferation activity of these compounds is antagonized by exogenous thiols but not by non-thiol antioxidants. This suggests that the growth inhibition is mediated by sulfhydryl arylation of cellular glutathione and cysteine-containing proteins and not by oxidative stress. The protein tyrosine phosphatases (PTP) are an important group of proteins that contain cysteine at their catalytic site. PTPs regulate mitogenic signal transduction and cell cycle progression. PTP inhibition by Cpd 5 results in prolonged tyrosine phosphorylation and activation of several kinases and transcription factors including EGFR, ERK1/2, and Elk1. Cpd 5 could activate ERK1/2 either by signaling from an activated EGFR, which is upstream in the signaling cascade, or by direct inhibition of ERK1/2 phosphatase(s). Prolonged ERK1/2 phosphorylation strongly correlates with Cpd 5-mediated growth inhibition. Cpd 5 can also bind to and inhibit the Cdc25 family of dual specific phosphatases. As a result, several Cdc25 substrates (Cdk1, Cdk2, Cdk4) involved in cell cycle progression are tyrosine phosphorylated and thereby inhibited by its action. Cpd 5 could also inhibit both normal liver regeneration and hepatoma growth in vivo. DNA synthesis during rat liver regeneration following partial hepatectomy, transplantable rat hepatoma cell growth, and glutathione-S-transferase-pi expressing hepatocytes after administration of the chemical carcinogen diethylnitrosamine, are all inhibited by Cpd 5 administration. The growth inhibitory effect during liver regeneration and transplantable tumor growth is also correlated with ERK1/2 phosphorylation induced by Cpd 5. Thus, Cpd 5-mediated inhibition of PTPs, such as Cdc25 leads to cell growth arrest due to altered activity of key cellular kinases involved in signal transduction and cell cycle progression. This prototype K vitamin analog represents a novel class of growth inhibitor based upon its action as a selective PTP antagonist. It is clearly associated with prolonged ERK1/2 phosphorylation, which is in contrast with the transient ERK1/2 phosphorylation induced by growth stimulatory mitogens. © 2002 Wiley-Liss, Inc. [source] Retinoic acid induces expression of the interleukin-1, gene in cultured normal human mammary epithelial cells and in human breast carcinoma linesJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002Limin Liu Retinoic acid (RA) and its derivatives inhibit the proliferation of normal human mammary epithelial cells (HMEC) and some breast carcinoma lines by mechanisms which are not fully understood. To identify genes that mediate RA-induced cell growth arrest, an HMEC cDNA library was synthesized and subtractive screening was performed. We identified the interleukin-1, (IL-1,) gene as an RA induced gene in HMEC. Northern blot analyses showed that the IL-1, gene was up-regulated as early as 2 h after RA treatment. Results from the treatment of HMEC with cycloheximide and actinomycin D indicated that the regulation of the IL-1, gene by RA occurred at the transcriptional level and that the IL-1, gene is a direct, downstream target gene of RA. To evaluate the effects of IL-1, on cell proliferation, the proliferation of HMEC was measured in the presence of RA or IL-1,, or both. Either RA or IL-1, could significantly inhibit the proliferation of HMEC. However, the addition of soluble IL-1 receptor antagonist (sIL-1ra) to the cell culture medium did not block RA-induced HMEC growth inhibition, whereas sIL-1ra did block the growth inhibition of HMEC by IL-1,. IL-1, expression was not observed in the three carcinoma cell lines, MCF-7, MDA-MB-231, and MDA-MB-468, as compared to the HMEC. Growth curves of the breast carcinoma cell lines showed strong inhibitory effects of RA and IL-1, on the growth of the estrogen receptor (ER) positive MCF-7 cell line, but only a small effect on the ER negative MDA-MB-231 cells. The expression of the IL-1, gene was also transcriptionally activated by RA in normal epithelial cells of prostate and oral cavity. Our results suggest that: (a) the IL-1, gene is a primary target of RA receptors in HMEC; (b) the enhanced expression of the IL-1, gene does not mediate the RA-induced growth arrest of HMEC; and (c) the expression of the IL-1, gene is low or absent in all three human breast carcinoma cell lines examined, but the defect in the IL-1, signaling pathway may be different in ER positive versus ER negative carcinoma cells. © 2002 Wiley-Liss, Inc. [source] | |||||||||||||