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Growth Arrest (growth + arrest)
Kinds of 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] Regulation of GADD153 induced by mechanical stress in cardiomyocytesEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 11 2009W. P. Cheng Abstract Background, Growth arrest and DNA damage-inducible gene 153 (GADD153), an apoptosis regulated gene, increased during endoplasmic reticulum stress. However, the expression of GADD153 in cardiomyocytes under mechanical stress is little known. We aimed to investigate the regulation mechanism of GADD153 expression and apoptosis induced by mechanical stress in cardiomyocytes. Materials and methods, Aorta-caval shunt was performed in adult Sprague,Dawley rats to induce volume overload. Rat neonatal cardiomyocytes grown on a flexible membrane base were stretched by vacuum to 20% of maximum elongation, at 60 cycles min,1. Results, The increased ventricular dimension measured using echocardiography in the shunt group (n = 8) was reversed to normal by treatment with chaperon 4-phenylbutyric acid (PBA) (n = 8) at 500 mg kg,1 day,1 orally for 3 days. GADD153 protein and mRNA were up-regulated in the shunt group when compared with sham group (n = 8). Treatment with PBA reversed the protein of GADD153 to the baseline values. The TUNEL assay showed that PBA reduced the apoptosis induced by volume overload. Cyclic stretch significantly increased GADD153 protein and mRNA expression after 14 h of stretch. Addition of c-jun N-terminal kinase (JNK) inhibitor SP600125, JNK small interfering RNA and tumour necrosis factor-, (TNF-,) antibody 30 min before stretch, reduced the induction of GADD153 protein. Stretch increased, while GADD153-Mut plasmid, SP600125 and TNF-, antibody abolished the GADD153 promoter activity induced by stretch. GADD153 mediated apoptosis induced by stretch was reversed by GADD153 siRNA, GADD153-Mut plasmid and PBA. Conclusions, Mechanical stress enhanced apoptosis and GADD153 expression in cardiomyocytes. Treatment with PBA reversed both GADD153 expression and apoptosis induced by mechanical stress in cardiomyocytes. [source] Mis3 with a conserved RNA binding motif is essential for ribosome biogenesis and implicated in the start of cell growth and S phase checkpointGENES TO CELLS, Issue 7 2000Hiroshi 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] The E8 repression domain can replace the E2 transactivation domain for growth inhibition of HeLa cells by papillomavirus E2 proteinsINTERNATIONAL JOURNAL OF CANCER, Issue 10 2007Frank Stubenrauch Abstract Continuous expression of the human papillomavirus (HPV) oncoproteins E6 and E7 is required for the growth of cervical cancer cell lines. So far, only the overexpression of the wild type papillomavirus E2 protein has been shown to induce growth arrest in HPV18-positive HeLa cells by repressing E6/E7 transcription. Growth arrest by E2 requires the aminoterminal transcription activation domain in addition to the carboxyterminal DNA-binding domain. Several papillomaviruses such as the carcinogenic HPV31 express in addition to E2 an E8,E2C fusion protein in which the E8 domain, which is required for repression of replication and transcription, replaces the E2 activation domain. In this report, we demonstrate that the HPV31 E8,E2C protein is able to inhibit the growth of HeLa cells but not of HPV-negative C33A cervical cancer cells. Growth repression by E8,E2C correlates with repression of the endogenous HPV18 E6/E7 promoter and the reappearance of E6- and E7-regulated p53, pRb and p21 proteins, suggesting that E8,E2C inhibits growth by reactivating dormant tumor suppressor pathways. Growth inhibition requires an intact E8 repression domain in addition to the carboxyterminal E2C DNA binding domain. Chromatin immunoprecipitation experiments suggest that the E8 repression domain enhances binding to the HPV18 promoter sequence in vivo. In summary, our results demonstrate that the small E8 repression domain can functionally replace the large E2 transactivation domain for growth inhibition of HeLa cervical cancer cells. © 2007 Wiley-Liss, Inc. [source] Expression of the transcription factor GADD153 is an indicator of apoptosis for recombinant chinese hamster ovary (CHO) cellsBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2001Tracy C. Murphy Abstract Loss of cell viability, through engagement of apoptotic cell death, represents a limitation to maintenance of high levels of productivity of recombinant animal cells in culture. The ability to monitor the status of recombinant cells, and to define indicators of their "well-being," would present a valuable approach to permit a rational intervention at appropriate times during culture. Growth arrest and DNA damage gene 153 (GADD153) is a member of the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors and has been associated with apoptosis. We have examined the expression of GADD153 in conditions associated with apoptosis of recombinant CHO cells in batch culture. GADD153 expression is very low in CHO cells growing in the exponential phase of batch culture but is activated as cells enter the decline phase. Depletion of nutrients (glucose or glutamine) causes activation of GADD153 expression as does the imposition of endoplasmic reticulum stress. In all cases, there is a good relationship between the extent of apoptosis that occurs in response to each stress and the degree of GADD153 expression. In addition, nutrient refeeding or reversal of stress produces a concomitant decrease in expression of GADD153 and the susceptibility to apoptosis. Thus, GADD153 appears to offer a valid indicator of apoptosis and illustrates the potential for definition of monitors of cellular status related to the likelihood of apoptosis of cell populations. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 621,629, 2001. [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] Characterization of 1H NMR detectable mobile lipids in cells from human adenocarcinomasFEBS JOURNAL, Issue 5 2009Anna Maria Luciani Magnetic resonance spectroscopy studies are often carried out to provide metabolic information on tumour cell metabolism, aiming for increased knowledge for use in anti-cancer treatments. Accordingly, the presence of intense lipid signals in tumour cells has been the subject of many studies aiming to obtain further insight on the reaction of cancer cells to external agents that eventually cause cell death. The present study explored the relationship between changes in neutral lipid signals during cell growth and after irradiation with gamma rays to provide arrest in cell cycle and cell death. Two cell lines from human tumours were used that were differently prone to apoptosis following irradiation. A sub-G1 peak was present only in the radiosensitive HeLa cells. Different patterns of neutral lipids changes were observed in spectra from intact cells, either during unperturbed cell growth in culture or after radiation-induced growth arrest. The intensities of triglyceride signals in the spectra from extracted total lipids changed concurrently. The increase in lipid peak intensities did not correlate with the apoptotic fate. Modelling to fit the experimental data revealed a dynamic equilibrium between the production and depletion of neutral lipids. This is observed for the first time in cells that are different from adipocytes. [source] Expression and functional characterization of P2Y1 and P2Y12 nucleotide receptors in long-term serum-deprived glioma C6 cellsFEBS JOURNAL, Issue 8 2007Patryk Krzemi We characterized the expression and functional properties of the ADP-sensitive P2Y1 and P2Y12 nucleotide receptors in glioma C6 cells cultured in medium devoid of serum for up to 96 h. During this long-term serum starvation, cell morphology changed from fibroblast-like flat to round, the adhesion pattern changed, cell-cycle arrest was induced, extracellular signal-regulated kinase (ERK1/2) phosphorylation was reduced, Akt phosphorylation was enhanced, and expression of the P2Y12 receptor relative to P2Y1 was increased. These processes did not reflect differentiation into astrocytes or oligodendrocytes, as expression of glial fibrillary acidic protein and NG2 proteoglycan (standard markers of glial cell differentiation) was not increased during the serum deprivation. Transfer of the cells into fresh medium containing 10% fetal bovine serum reversed the changes. This demonstrates that serum starvation caused only temporary growth arrest of the glioma C6 cells, which were ready for rapid division as soon as the environment became more favorable. In cells starved for 72 and 96 h, expression of the P2Y1 receptor was low, and the P2Y12 receptor was the major player, responsible for ADP-evoked signal transduction. The P2Y12 receptor activated ERK1/2 kinase phosphorylation (a known cell proliferation regulator) and stimulated Akt activity. These effects were reduced by AR-C69931MX, a specific antagonist of the P2Y12 receptor. On the other hand, Akt phosphorylation increased in parallel with the low expression of the P2Y1 receptor, indicating the inhibitory role of P2Y1 in Akt pathway signaling. The shift in nucleotide receptor expression from P2Y1 to P2Y12 would appear to be a new and important self-regulating mechanism that promotes cell growth rather than differentiation and is a defense mechanism against effects of serum deprivation. [source] SEI family of nuclear factors regulates p53-dependent transcriptional activationGENES TO CELLS, Issue 8 2005Rie Watanabe-Fukunaga SEI family proteins, p34SEI-1 and SEI-2(TRIP-Br2), are nuclear factors that are implicated in cell cycle regulation through interaction with CDK4/CyclinD and E2F-1/DP-1 complexes. Here we report that the SEI family proteins regulate transcriptional activity of p53 tumor suppressor protein. Expression of SEI-1, SEI-2 or SEI-3 strongly stimulates p53-dependent gene activation in HeLa and U2OS cells but not in p53-deficient Saos2 or p53-knockdown HeLa cells. SEI proteins possess an intrinsic transactivation activity, interact with the coactivator CREB-binding protein, and cooperate synergistically with the ING family of chromatin-associated proteins to stimulate the transactivation function of p53. Doxycycline-induced expression of SEI proteins results in activation of the p21 gene and inhibition of cell growth, but the growth arrest was not suppressed by the siRNA-mediated knockdown of the endogenous p53 protein. These results indicate that the SEI family of nuclear proteins regulates p53 transcriptional activity and a p53-independent signaling pathway leading to growth inhibition. [source] HMGA2 and the p19Arf -TP53-CDKN1A axis: A delicate balance in the growth of uterine leiomyomas,GENES, CHROMOSOMES AND CANCER, Issue 8 2010Dominique Nadine Markowski Pathogenetically, uterine leiomyomas (ULs) can be interpreted as the result of a monoclonal abnormal proliferation of myometrial cells. Oncogene-induced senescence (OIS) is a frequent phenomenon in premalignant lesions that leads to a growth arrest mainly by the activation of two potent growth-inhibitory pathways as represented by p16Ink4a and p19Arf. The relevance of OIS for the development of UL has not been addressed, but HMGA2, encoded by a major target gene of recurrent chromosomal abnormalities in UL, has been implicated in the repression of the Ink4a/Arf (CDKN2A) locus. This prompted us to examine if HMGA2 contributes to the growth of leiomyomas by repressing this locus. Contrary to the expectations, we were able to show that generally ULs express significantly higher levels of p19Arf mRNA than myometrium and that UL with 12q14,15 rearrangements showed higher expression levels than UL with other cytogenetic aberrations. Furthermore, the finding of a significant correlation between the expressions of p19Arf and CDKN1A shows that p19Arf triggers senescence rather than apoptosis in UL. Furthermore, the expression levels of HMGA2, p19Arf, and CDKN1A were found to be correlated with the size of the tumors, indicating that an enhanced growth potential is counterbalanced by the p19Arf pathway. Mechanistically, the UL may thus execute a program already present in their cell of origin, where it is activated to protect the genome, for example, in the case of enhanced proliferation. In summary, the results identify the p19Arf -TP53-CDKN1A pathway as a major player in the growth control and genomic stability of uterine fibroids. © 2010 Wiley-Liss, Inc. [source] N-myc downstream-regulated gene 1 expression in injured sciatic nervesGLIA, Issue 4 2004Kazuho Hirata Abstract N-myc downstream-regulated gene 1 (NDRG1)/RTP/Drg1/Cap43/rit42/TDD5/Ndr1 is expressed ubiquitously and has been proposed to play a role in growth arrest and cell differentiation. A recent study showed that mutation of this gene is responsible for hereditary motor and sensory neuropathy-Lom. However, the role of this gene in the peripheral nervous system is not fully understood. In our study, rabbit polyclonal antibodies were raised against this gene product and were used to examine changes in its expression over the time course of Wallerian degeneration and ensuing regeneration after crush injury of mouse sciatic nerves. Fluorescent immunohistochemistry showed that NDRG1 was expressed over the intact nerve fibers. Double labeling with a Schwann cell (SC) marker, S-100 protein (S-100), revealed that NDRG1 was localized in the cytoplasm of S-100-positive Schwann cells (SCs). NDRG1 expression was maintained in the early stage of myelin degradation but was then markedly depleted at the end stage of myelin degradation when frequent occurrence of BrdU-labeled SCs was observed (at 7,9 days). The depletion of NDRG1 at this time point was also confirmed by Western blotting analysis. NDRG1 expression finally recovered at the stage of remyelination, with immunoreactivity stronger than that in intact nerves. These findings suggest that NDRG1 may play an important role in the terminal differentiation of SCs during nerve regeneration. © 2004 Wiley-Liss, Inc. [source] Nutrients Released by Gastric Epithelial Cells Enhance Helicobacter pylori GrowthHELICOBACTER, Issue 6 2004Karin Van Amsterdam ABSTRACT Background.,Helicobacter pylori survives and proliferates in the human gastric mucosa. In this niche, H. pylori adheres to the gastric epithelial cells near the tight junctions. In vitro, H. pylori proliferated well in tissue-culture medium near gastric epithelial cells. However, in the absence of epithelial cells, growth of H. pylori could only be established in tissue-culture medium when, prior to the experiment, it was preincubated near gastric epithelial cells. Therefore, we aimed to determine whether diffusion of nutrients derived from epithelial cells was required for H. pylori growth in Dulbecco's modified Eagle's minimal essential medium (DMEM) cell culture medium. Materials and Methods., Cell culture conditions essential for H. pylori growth in vitro were determined with gastric epithelial HM02 cells. Results., Deprivation of iron in cell-culture-conditioned DMEM resulted in a growth arrest of H. pylori. However, near gastric epithelial cells, growth of H. pylori was resistant to iron deprivation. Evidently, when residing close to epithelial cells, H. pylori was able to fulfil its iron requirements, even when the DMEM was deprived of iron. Nevertheless, supplementation with iron alone did not restore H. pylori growth in DMEM, hence other nutrients were deficient as well in the absence of epithelial cells. Growth of H. pylori in DMEM was restored when hypoxanthine, l -alanine and l -proline were added to the DMEM. Conclusions, Diffusion of (precursors of) these nutrients from the gastric epithelial cells is essential for H. pylori growth in vitro. We hypothesize that in vivo, H. pylori favors colonization near the tight junctions, to gain maximal access to the nutrient(s) released by gastric epithelial cells. [source] Hepatitis B virus X protein blunts senescence-like growth arrest of human hepatocellular carcinoma by reducing Notch1 cleavage,HEPATOLOGY, Issue 1 2010Jiejie Xu One of the serious sequelae of chronic hepatitis B virus (HBV) infection is hepatocellular carcinoma (HCC). Among all the proteins encoded by the HBV genome, hepatitis B virus X protein (HBx) is highly associated with the development of HCC. Although Notch1 signaling has been found to exert a tumor-suppressive function during HCC development, the mechanism of interaction between HBx expression and Notch1 signaling needs to be explored. In this study, we report that HBx expression in hepatic and hepatoma cells resulted in decreased endogenous protein levels of Notch1 intracellular domain (ICN1) and messenger RNA levels of its downstream target genes. These effects were due to a reduction of Notch1 cleavage by HBx through the suppression of presenilin1 (Psen1) transcription rather than inhibition of Notch1 transcription or its ligands' expression. Through transient HBx expression, decreased ICN1 resulted in enhanced cell proliferation, induced G1-S cell cycle progression, and blunted cellular senescence in vitro. Furthermore, the effect of blunted senescence-like growth arrest by stable HBx expression through suppression of ICN1 was shown in a nude mouse xenograft transplantation model. The correlation of inhibited Psen1-dependent Notch1 signaling and blunted senescence-like growth arrest was also observed in HBV-associated HCC patient tumor samples. Conclusion: Our results reveal a novel function of HBx in blunting senescence-like growth arrest by decreasing Notch1 signaling, which could be a putative molecular mechanism mediating HBV-associated hepatocarcinogenesis. (HEPATOLOGY 2010;) [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] Expression of ,CP-4 inhibits cell cycle progression and suppresses tumorigenicity of lung cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 7 2008Zafira Castaño Abstract The protein ,CP-4 (also known as hnRNP E4) is an RNA binding protein encoded by a gene at 3p21, one of the most common altered regions in lung cancer. It has been proposed that ,CP-4 may function as a lung tumor suppressor. Lack of ,CP-4 expression is frequent in highly proliferative lung tumors and correlates with ,CP-4 allele losses. The aim of this study was to evaluate the effect of ,CP-4 on the tumorigenic capacity of lung cancer cells. ,CP-4 expression was induced by transient transfection or stable infection with recombinant retroviruses. Induction of ,CP-4 expression caused cell cycle arrest in G2/M in 3 out of the 7 lung cancer cell lines studied, while no effect on apoptosis was observed. Anchorage-independent growth and invasion capacity of H1299 cells were significantly reduced by ,CP-4 induction. Tumorigenicity of H1299 cells in nude mice was greatly inhibited by the expression of ,CP-4. Moreover, induction of ,CP-4 expression in already established tumors resulted in a sudden growth arrest. Immunocytochemistry analysis of the xenograft tumors revealed an in vivo effect of ,CP-4 on cell proliferation and no effect on apoptosis. Finally, ,CP-4 showed a subcellular localization different from ,CP-4a, a splice variant that does not affect cell proliferation. In conclusion, expression of ,CP-4 can inhibit proliferation and tumorigenesis of lung cancer cells, both in vivo and in vitro, by delaying the progression of the cell cycle. © 2007 Wiley-Liss, Inc. [source] The E8 repression domain can replace the E2 transactivation domain for growth inhibition of HeLa cells by papillomavirus E2 proteinsINTERNATIONAL JOURNAL OF CANCER, Issue 10 2007Frank Stubenrauch Abstract Continuous expression of the human papillomavirus (HPV) oncoproteins E6 and E7 is required for the growth of cervical cancer cell lines. So far, only the overexpression of the wild type papillomavirus E2 protein has been shown to induce growth arrest in HPV18-positive HeLa cells by repressing E6/E7 transcription. Growth arrest by E2 requires the aminoterminal transcription activation domain in addition to the carboxyterminal DNA-binding domain. Several papillomaviruses such as the carcinogenic HPV31 express in addition to E2 an E8,E2C fusion protein in which the E8 domain, which is required for repression of replication and transcription, replaces the E2 activation domain. In this report, we demonstrate that the HPV31 E8,E2C protein is able to inhibit the growth of HeLa cells but not of HPV-negative C33A cervical cancer cells. Growth repression by E8,E2C correlates with repression of the endogenous HPV18 E6/E7 promoter and the reappearance of E6- and E7-regulated p53, pRb and p21 proteins, suggesting that E8,E2C inhibits growth by reactivating dormant tumor suppressor pathways. Growth inhibition requires an intact E8 repression domain in addition to the carboxyterminal E2C DNA binding domain. Chromatin immunoprecipitation experiments suggest that the E8 repression domain enhances binding to the HPV18 promoter sequence in vivo. In summary, our results demonstrate that the small E8 repression domain can functionally replace the large E2 transactivation domain for growth inhibition of HeLa cervical cancer cells. © 2007 Wiley-Liss, Inc. [source] Small interfering RNA (siRNA) inhibits the expression of the Her2/neu gene, upregulates HLA class I and induces apoptosis of Her2/neu positive tumor cell linesINTERNATIONAL JOURNAL OF CANCER, Issue 1 2004Aniruddha Choudhury Abstract Silencing of a specific mRNA using double stranded RNA oligonucleotides represents one of the newest technologies for suppressing a specific gene product. Small interfering RNA (siRNA) are 21 nucleotides long, double stranded RNA fragments that are identical in sequence to the target mRNA. We designed 3 such siRNA against the Her2/neu (HER2) gene. The HER2 gene is known to play an important role in the oncogenesis of several types of cancers, such as breast, ovarian, colon and gastric cancers. Introduction of the siRNA into HER2 positive tumor lines in vitro greatly reduced the cell surface expression of the HER2 protein. Concurrently, a range of effects on cell physiology, such as growth inhibition or apoptosis, was observed. The expression of HLA class I was observed to be upregulated when HER2 was silenced with siRNA. Treatment of SKBr3 and MCF7/HER2 tumor cell lines with the HER2 siRNA resulted in growth arrest of cells in the late G1/S-phase. Our results suggest that siRNA may be an effective method of abrogating the effect of HER2 in tumorigenesis. © 2003 Wiley-Liss, Inc. [source] Chronic administration of valproic acid inhibits PC3 cell growth by suppressing tumor angiogenesis in vivoINTERNATIONAL JOURNAL OF UROLOGY, Issue 9 2007Dexuan Gao Aim: Chromatin remodeling agents such as histone deacetylase inhibitors have been shown to modulate gene expression in tumor cells and inhibit tumor growth and angiogenesis. We investigated the mechanisms of chronic valproic acid (VPA) inhibiting PC3 cell growth in the study. Methods: We established tumor xenografts of the PC3 cell line and investigated the effect of VPA chronic administration on tumor growth. Apoptosis in tumor tissue was measured using the TUNEL Detection Kit. We detected the effect of VPA chronic administration on histone acetylation; p21CIP1/WAF1 gene expression; vascular endothelial growth factor (VEGF) expression by reverse-transcription Polymerase Chain Reaction (PCR) analysis; immunohistochemistry; and Western Blotting. Result: In mouse models with established subcutaneous prostate (PC3), VPA treatment induced 70% inhibition of tumor growth without overt toxicity. Our result showed that chronic administration of VPA has an effect on tumor growth arrest and the effect was associated with increased histone acetylation, p21CIP1/WAF1 up-regulation, and VEGF down-regulation. Conclusion: We conclude that chronic VPA results in profound decreases in the proliferation of PC3 cells, not only by increasing histone H3 acetylation and up-regulating p21CIP1/WAF1 expression, but also by down-regulating VEGF. [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] PTHrP 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] 2-methoxyestradiol-induced cell death in osteosarcoma cells is preceded by cell cycle arrestJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2008Avudaiappan Maran Abstract 2-Methoxyestradiol (2-ME), a naturally occurring mammalian metabolite of 17,-Estradiol (E2), induces cell death in osteosarcoma cells. To further understand the molecular mechanisms of action, we have investigated cell cycle progression in 2-ME-treated human osteosarcoma (MG63, SaOS-2 and LM8) cells. At 5 µM, 2-ME induced growth arrest by inducing a block in cell cycle; 2-ME-treatment resulted in 2-fold increases in G1 phase cells and a decrease in S phase cells in MG63 and SaOS-2 osteosarcoma cell lines, compared to the appropriate vehicle controls. 2-ME-treatment induced a threefold increase in the G2 phase in LM8 osteosarcoma cells. The results demonstrated steroid specificity, as the tumorigenic metabolite, 16,-hydroxyestradiol (16-OHE), did not have any effect on cell cycle progression in osteosarcoma cells. The cell cycle arrest coincided with an increase in expression of the cell cycle markers p21, p27 and p53 proteins in 2-ME-treated osteosarcoma cells. Also, MG63 cells, transiently transfected with cDNA for a ,loss of function mutant' RNA-dependent protein kinase (PKR) protein, were resistant to 2-ME-induced cell cycle arrest. These results suggest that 2-ME works in concert with factors regulating cell cycle progression, and cell cycle arrest precedes cell death in 2-ME-treated osteosarcoma cells. J. Cell. Biochem. 104: 1937,1945, 2008. © 2008 Wiley-Liss, Inc. [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] Dissociation of growth arrest and CYP24 induction by VDR ligands in mammary tumor cellsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2007Meggan E. Valrance Abstract Murine mammary tumor cells with differential vitamin D receptor (VDR) expression were used to study the mechanisms of growth inhibition by vitamin D steroids. In VDR-expressing WT145 cells, 1,25D and its synthetic analog EB1089 induce growth arrest and transcriptionally upregulate the well-characterized VDR target gene CYP24. 1,25D also induces apoptosis in WT145 cells through activation of initiator and executioner caspases and the calcium-dependent protease calpain. We also demonstrate that WT145 cells express CYP27B1, the enzyme that converts 25-hydroxyvitamin D3 (25D) to 1,25D, and that 25D inhibits growth of these cells but does not trigger apoptosis or induce CYP24 expression. Comparative studies were conducted in KO240 cells, which were derived from VDR knockout mice and found to retain expression of CYP27B1. KO240 cells were not growth inhibited nor rendered apoptotic by any of the tested vitamin D compounds. These data conclusively demonstrate that VDR mediates the anti-proliferative and pro-apoptotic effects of vitamin D metabolites and analogs, but that the potency of a vitamin D compound to induce the VDR target gene CYP24 does not accurately predict its potency in mediating growth regulation. J. Cell. Biochem. 101: 1505,1519, 2007. © 2007 Wiley-Liss, Inc. [source] PPAR,1 synthesis and adipogenesis in C3H10T1/2 cells depends on S-phase progression, but does not require mitotic clonal expansionJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2004Young C. Cho Abstract Adipogenesis is typically stimulated in mouse embryo fibroblast (MEF) lines by a standard hormonal combination of insulin (I), dexamethasone (D), and methylisobutylxanthine (M), administered with a fresh serum renewal. In C3H10T1/2 (10T1/2) cells, peroxisome proliferator-activated receptor ,1 (PPAR,1) expression, an early phase key adipogenic regulator, is optimal after 36 h of IDM stimulation. Although previous studies provide evidence that mitotic clonal expansion of 3T3-L1 cells is essential for adipogenesis, we show, here, that 10T1/2 cells do not require mitotic clonal expansion, but depend on cell cycle progression through S-phase to commit to adipocyte differentiation. Exclusion of two major mitogenic stimuli (DM without insulin and fresh serum renewal) from standard IDM protocol removed mitotic clonal expansion, but sustained equivalent PPAR,1 synthesis and lipogenesis. Different S-phase inhibitors (aphidicolin, hydroxyurea, l -mimosine, and roscovitin) each arrested cells in S-phase, under hormonal stimulation, and completely blocked PPAR,1 synthesis and lipogenesis. However, G2/M inhibitors effected G2/M accumulation of IDM stimulated cells and prevented mitosis, but fully sustained PPAR,1 synthesis and lipogenesis. DM stimulation with or without fresh serum renewal elevated DNA synthesis in a proportion of cells (measured by BrdU labeling) and accumulation of cell cycle progression in G2/M-phase without complete mitosis. By contrast, standard IDM treatments with fresh serum renewal caused elevated DNA synthesis and mitotic clonal expansion while achieved equivalent level of adipogenesis. At most, one-half of the 10T1/2 mixed cell population differentiated to mature adipocytes, even when clonally isolated. PPAR, was exclusively expressed in the cells that contained lipid droplets. IDM stimulated comparable PPAR,1 synthesis and lipogenesis in isolated cells at low cell density (LD) culture, but in about half of the cells and with sensitivity to G1/S, but not G2/M inhibitors. Importantly, growth arrest occurred in all differentiating cells, while continuous mitotic clonal expansion occurred in non-differentiating cells. Irrespective of confluence level, 10T1/2 cells differentiate after progression through S-phase, where adipogenic commitment induced by IDM stimulation is a prerequisite for PPAR, synthesis and subsequent adipocyte differentiation. © 2003 Wiley-Liss, Inc. [source] Runx1, c-Myb, and C/EBP, couple differentiation to proliferation or growth arrest during hematopoiesisJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2002Alan D. Friedman Abstract Immature hematopoietic precursors proliferate as they differentiate, whereas terminal differentiation is associated with cell cycle arrest. Stem cell lineage commitment and subseqent maturation is regulated predominantly by transcription factors. Runx1 and c-Myb act in early stage hematopoietic cells to both stimulate proliferation and differentiation, whereas C/EBP,, and perhaps other C/EBP family members, block progression from G1 to S and induce terminal maturation. Coupling of differentiation to either proliferation or growth arrest by transcription factors is likely an important regulatory mechanism in multiple developmental systems. J. Cell. Biochem. 86: 624,629, 2002. © 2002 Wiley-Liss, Inc. [source] Constitutive activation of the mitogen-activated protein kinase pathway impairs vitamin D signaling in human prostate epithelial cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010Zhentao Zhang We studied the effect of prolonged activation of mitogen-activated protein kinase (MAPK) signaling on 1,25 dihydroxyvitamin D (1,25(OH)2D3) action in the immortalized human prostate epithelial cell line RWPE1 and its Ki-Ras transformed clone RWPE2. 1,25(OH)2D3 -treatment caused growth arrest and induced gene expression in both cell lines but the response was blunted in RWPE2 cells. Vitamin D receptor (VDR) levels were lower in RWPE2 cells but VDR over-expression did not increase vitamin-D-mediated gene transcription in either cell line. In contrast, MAPK inhibition restored normal vitamin D transcriptional responses in RWPE2 cells and MAPK activation with constitutively active MEK1R4F reduced vitamin-D-regulated transcription in RWPE1 cells. 1,25(OH)2D3 -mediated transcription depends upon the VDR and its heterodimeric partner the retinoid X receptor (RXR) so we studied whether changes in the VDR,RXR transcription complex occur in response to MAPK activation. Mutation of putative phosphorylation sites in the activation function 1 (AF-1) domain (S32A, T82A) of RXR, restored 1,25(OH)2D3 -mediated transactivation in RWPE2 cells. Mammalian two-hybrid and co-immunoprecipitation assays revealed a vitamin-D-independent interaction between steroid receptor co-activator-1 (SRC-1) and RXR, that was reduced by MAPK activation and was restored in RWPE2 cells by mutating S32 and T82 in the RXR, AF-1 domain. Our data show that a common contributor to cancer development, prolonged activation of MAPK signaling, impairs 1,25(OH)2D3 -mediated transcription in prostate epithelial cells. This is due in part to the phosphorylation of critical amino acids in the RXR, AF-1 domain and impaired co-activator recruitment. J. Cell. Physiol. 224: 433,442, 2010. © 2010 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] Bone-specific heparan sulfates induce osteoblast growth arrest and downregulation of retinoblastoma proteinJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2006Kerry J. Manton The heparan sulfate (HSs) sugars of the extracellular matrix (ECM) play a key role during both development and wound repair in regulating the flow of growth and adhesive factors across their cell surface receptors. The aim of this study was to assess the structural and functional differences of HS chains extracted from the conditioned media (soluble), cell surface, and ECM of primary human osteoblast cultures, and to analyze their effects on osteoblast cell growth. HS chains from these compartments were characterized through a combination of enzymatic degradation, anion exchange chromatography, and molecular sieving. Although the chains were all approximately the same size, they varied systematically in their sulfate content, suggesting differences in their protein-binding domains. When added to pre-confluent hFOB1.19 osteoblast cultures, HS doses exceeding 500 ng/ml inhibited proliferation, without affecting viability, irrespective of their origin. Furthermore, HS doses of 500 ng/ml also downregulated retinoblastoma, Cyclin A and CDK1 protein expression, indicating that high doses of osteoblast HS negatively regulate cell cycle, resulting in growth arrest; when high doses of HS were withdrawn after a prolonged period, linear cell growth was reestablished. Thus, despite differences in sulfation, HS from either the soluble, cell surface, or matrix compartments of primary human osteoblast cultures are functionally similar with respect to their effects on growth. Binding assays revealed that the HS chains bound TGF,1, a known inhibitor of osteoprogenitor growth, at higher affinity than a suite of other bone-related, heparin-binding growth factors. Overcoming such sugar-mediated inhibition may prove important for wound repair. J. Cell. Physiol. 209: 219,229, 2006. © 2006 Wiley-Liss, Inc. [source] Synthetic retinoids as inducers of apoptosis in ovarian carcinoma cell linesJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2004William F. Holmes Apoptosis is also known as programmed cell death. Apoptosis plays an essential role in maintaining normal tissue and cell physiology in multicellular organisms. Clearance of aberrant or pre-cancerous cells occurs through the induction of apoptosis. It has been reported that many tumors and tumor cell lines have dysfunctional apoptosis signaling, causing these tumors to escape immune monitoring and internal cellular control mechanisms. One potential cause of this dysfunctional apoptosis is the tumor suppressor p53, an important regulator of growth arrest and apoptosis that is mutated in over 50% of all cancers. Retinoids have great potential in the areas of cancer therapy and chemoprevention. While some tumor cells are sensitive to the growth inhibitory effects of natural retinoids such as all- trans -retinoic acid (ATRA), many ovarian tumor cells are not. 6-[3-(1-Admantyl)]-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) and fenretinide N -[4-hydroxyphenyl] retinamide (4-HPR) are conformationally restricted synthetic retinoids that induce growth arrest and apoptosis in both ATRA-sensitive and ATRA-resistant ovarian tumor cell lines. Recently, we have identified the molecular pathways of apoptosis induced by treatment of ovarian carcinoma cells with mutated p53 by CD437 and 4-HPR. © 2004 Wiley-Liss, Inc. [source] Resistance to UV-induced apoptosis in human keratinocytes during accelerated senescence is associated with functional inactivation of p53JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2004V. Chaturvedi Compared to proliferating keratinocytes (KCs), growth-arrested KCs are relatively resistant to UV-light induced apoptosis. When KCs undergo confluency, or following exposure to anti-proliferative agents such as IFN-, plus a phorbol ester,12- O -tetradecanoylyphorbol-13-acetate (TPA), they convert from a proliferative to a nonproliferative state resembling senescence. Since p53 regulates UV-induced apoptosis of KCs, this report further characterizes p53 half-life, post-translational modifications, and transcriptional activity using cultured human KCs and living epidermal equivalents. The half-life of p53 in KCs was longer than fibroblasts (greater than approximately 3 h vs. 30 min). Exposure of proliferating KCs to UV-light induces post-translational modifications of p53 including acetylation of lysine-382 residues. By contrast, KCs undergoing irreversible growth arrest following confluency, or exposure to IFN-, plus TPA, were resistant to UV-induced apoptosis, and failed to undergo the acetylation modification of p53. Exposure of KCs to IFN-, plus TPA reduced total cellular p53 levels and reduced the transcriptional activity of p53. Addition of Trichostatin A (TSA), an inhibitor of de-acetylation, increased acetylation of lysine-382 in confluent KCs, thereby enhancing susceptibility of confluent cultures to UV-induced apoptosis. Pre-treatment of epidermal equivalents with IFN-, plus TPA also blocked UV-light induced increase in p53 levels, and reduced apoptosis. In conclusion, these studies demonstrate that growth arrested KCs may resist UV-light induced apoptosis by inactivating the pro-apoptotic function of p53. J. Cell. Physiol. 198: 100,109, 2004. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||||||||||||||