Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tumor suppressor PTEN is one of the most commonly inactivated genes in human cancer. Glioblastoma multiforme cells harboring mutant PTEN have abnormally high levels of 3' phosphoinositides and elevated protein kinase B activity. Expression of wild-type PTEN in glioma cells, containing endogenous mutant PTEN, reduces 3' phosphoinositides levels, inhibits PKB activity, and induces G1 cell cycle arrest. We investigated the mechanism of the PTEN-induced growth arrest in glioma cell lines. Expression of PTEN is associated with increased expression of p27Kip1, decreased expression of cyclins A and D3, inhibition of cdk2 activity, and dephosphorylation of pRb. Inactivation of p53, by the human papilloma virus E6 oncoprotein, does not prevent PTEN-induced G1 arrest, implying that p53 is not required for G1 arrest. In contrast, p27Kip1 antisense oligonucleotides abrogated the growth arrest induced by PTEN. Furthermore, blocking p27Kip1 expression prevented the PTEN-induced reduction of cyclin-dependent kinase 2 activity, indicating that p27Kip1 functions upstream of cyclin-dependent kinase 2 in the PTEN regulatory cascade. These results implicate p27Kip1 as a critical mediator of PTEN-induced G1 arrest.
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PMID:p27Kip1 is required for PTEN-induced G1 growth arrest. 1128 Jul 73

Little information exists concerning the response of anaplastic thyroid carcinoma (ATC) cells to histone deacetylase inhibitors (HDAIs). In this study, the cellular response to the histone deacetylase inhibitors, sodium butyrate and trichostatin A, was analyzed in cell lines derived from primary anaplastic thyroid carcinomas. HDAIs repress the growth (proliferation) of ATC cell lines, independent of p53 status, through the induction of apoptosis and differential cell cycle arrest (arrested in G1 and G2/M). Apoptosis increases in response to drug treatment and is associated with the appearance of the cleaved form of the caspase substrate, poly-(ADP-ribose) polymerase (PARP). Cell cycle arrest is associated with the reduced expression of cyclins A and B, the increased expression of the cyclin-dependent kinase inhibitors, p21(Cip1/WAF1) and p27Kip1, the reduced phosphorylation of the retinoblastoma protein (pRb), and a reduction in cdk2 and cdk1-associated kinase activities. In ATC cells overexpressing cyclin E, drug treatment failed to replicate these events. These results suggest that growth inhibition of ATC cells by HDAIs is due to the promotion of apoptosis through the activation of the caspase cascade and the induction of cell cycle arrest via a reduction in cdk2- and cdk1-associated kinase activities.
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PMID:Histone deacetylase inhibitors promote apoptosis and differential cell cycle arrest in anaplastic thyroid cancer cells. 1134 29

A "spindle assembly" checkpoint has been described that arrests cells in G1 following inappropriate exit from mitosis in the presence of microtubule inhibitors. We have here addressed the question of whether the resulting tetraploid state itself, rather than failure of spindle function or induction of spindle damage, acts as a checkpoint to arrest cells in G1. Dihydrocytochalasin B induces cleavage failure in cells where spindle function and chromatid segregation are both normal. Notably, we show here that nontransformed REF-52 cells arrest indefinitely in tetraploid G1 following cleavage failure. The spindle assembly checkpoint and the tetraploidization checkpoint that we describe here are likely to be equivalent. Both involve arrest in G1 with inactive cdk2 kinase, hypophosphorylated retinoblastoma protein, and elevated levels of p21(WAF1) and cyclin E. Furthermore, both require p53. We show that failure to arrest in G1 following tetraploidization rapidly results in aneuploidy. Similar tetraploid G1 arrest results have been obtained with mouse NIH3T3 and human IMR-90 cells. Thus, we propose that a general checkpoint control acts in G1 to recognize tetraploid cells and induce their arrest and thereby prevents the propagation of errors of late mitosis and the generation of aneuploidy. As such, the tetraploidy checkpoint may be a critical activity of p53 in its role of ensuring genomic integrity.
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PMID:Tetraploid state induces p53-dependent arrest of nontransformed mammalian cells in G1. 1135 24

We examined cell cycle-related effects of the phosphatase inhibitor okadaic acid (OA) in T51B rat liver epithelial cells under conditions chosen to mimic early stages of tumor promotion by this compound. Optimal transformation (colony formation in soft agar) was seen after prolonged culture of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-initiated T51B cells in 7 nM OA. Paradoxically, T51B cells treated with 2-10 nM OA showed decreased, rather than increased, proliferation in response to epidermal growth factor (EGF), as measured by [3H]thymidine incorporation. Complete inhibition was observed within 24 h at 10 nM OA. This response paralleled a loss of EGF-stimulated cdk2 kinase activity and an increase in association of the inhibitors p21 (cip-1) and p27 (kip-1) with cdk2. An increase in p53 phosphorylated on serine 15 accompanied the rise in p21 (cip-1). Both phosphorylation of the retinoblastoma protein and induction of cyclin A by EGF were blocked in cells treated with OA, but there was an increase in cyclin E. Resting cells treated with OA alone also showed elevated cyclin E levels, together with reduced levels of the E2F regulator pRb2/p130. Taken together, these observations indicate transforming levels of okadaic acid elicit a G(1)-trapping effect by facilitating cell cycle progression to the G(1)/S checkpoint, where cells are trapped by mechanisms that include p21 (cip-1)-mediated inhibition of cdk2. They support the premise that disruption of cellular processes regulating the transitions from G(0) to G(1) to S-phase is an important early step in tumor promotion by low levels of okadaic acid.
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PMID:Abbreviated cell cycle progression induced by the serine/threonine protein phosphatase inhibitor okadaic acid at concentrations that promote neoplastic transformation. 1147 Jul 44

During the last decades, the literature has clearly established the fundamental role of the thymus in the development of an effective immune system. During thymocyte development and maturation, potentially autoreactive thymocytes are eliminated by a process known as apoptosis or programmed cell death responsible for the negative selection occurring within the thymus. This process is in sharp contrast to other types of cell death referred to as necrosis. Actually, three different types of cell death have been recently observed morphologically in the rat thymus, i.e. necrosis, apoptosis and clustered cell death. Moreover, among the numerous factors influencing thymocyte cell death, particular attention has been paid to hormones, chemicals, biological compounds and physical agents that may influence the type and/or the extent of cell death. Finally, a brief overview has been devoted to the contribution of mitochondria, nitric oxide, glutathione and intracellular levels of cations in addition to the activity of genes as cdk2, p53, Fas and members' of the Bcl2 family in modulating rat thymus cell death.
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PMID:Cell death in the rat thymus: a minireview. 1148 63

Gene expression of the plasminogen activation system is cell-cycle dependent. Previously, we showed that ectopic expression of E2F1 repressed the plasminogen activator inhibitor type 1 (PAI-1) promoter in a manner dependent on the presence of DNA-binding and transactivation domains of E2F1 but independent of binding to pocket-binding proteins, suggesting a novel mechanism for E2F-mediated negative gene regulation [Koziczak, M., Krek, W. & Nagamine, Y. (2000) Mol. Cell. Biol. 20, 2014-2022]. However, it remains to be seen whether endogenous E2F can exert a similar effect. We report here that down-regulation of PAI-1 gene expression correlates with an increase in endogenous E2F activity. When cells were treated with a cdk2/4-specific inhibitor, which maintains E2F in an inactive state, the decline of serum-induced PAI-1 mRNA levels was suppressed. In mutant U2OS cells expressing a temperature-sensitive retinoblastoma protein (pRB), a shift to a permissive temperature induced PAI-1 mRNA expression. In U2OS cells stably expressing an E2F1-estrogen receptor chimeric protein that could be activated by tamoxifen, PAI-1 gene transcription was markedly reduced by tamoxifen even in the presence of cycloheximide. These results all indicate that endogenous E2F can directly repress the PAI-1 gene. DNase I hypersensitive-site analysis of the PAI-1 promoter suggested the involvement of conformation changes in chromatin structure of the PAI-1 promoter. 5' deletion analysis of the PAI-1 promoter showed that multiple sites were responsible for the E2F negative regulation, some of which were promoter dependent. Interestingly, one of these sites is a p53-binding element.
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PMID:E2F1-mediated transcriptional inhibition of the plasminogen activator inhibitor type 1 gene. 1155 66

Interferon-gamma induces an irreversible growth arrest and squamous differentiation in normal human epidermal keratinocytes. We present for the first time a careful biochemical analysis of the cell-cycle-related events that occur during interferon-gamma treatment of normal human epidermal keratinocytes. The interferon-gamma-induced irreversible growth arrest state is characterized by inhibition of cyclin-dependent kinases, prevention of Rb and p130 (Rb2) phosphorylation, and increases in p27(Kip1), p16(Ink4a), and p130 proteins, together with a transient increase in p21(Waf1/Cip1). Cells derived from squamous cell carcinomas are less responsive to interferon-gamma and do not terminally differentiate. We exploited these differences in response to interferon-gamma in order to identify the particular molecular defects in cell cycle control that promote carcinogenesis in squamous epithelia. In several squamous cell carcinoma cell lines as well as in interferon-gamma-insensitive HaCaT cells, interferon gamma was unable to significantly induce levels of p130 and/or p16 protein. In addition, p21 association with cdk2 complexes was undetectable in either the absence or the presence of interferon-gamma and, unlike normal human epidermal keratinocytes, p27 association with cdk2 did not increase with interferon-gamma treatment. These multiple defects appear to be intrinsic to the mechanisms of cell cycle regulation rather than due to defects in the interferon-gamma signaling pathway, as induction of several interferon-gamma-responsive genes including Stat 1, IRF-1, and p21 itself was normal. Interestingly, exogenous expression of p21 protein in the squamous cell carcinoma cell lines by adenovirus carrying wildtype p53 or p21 cDNA cooperated with interferon-gamma to produce a greater inhibition of growth than either agent alone, even though p21 protein could barely be detected in cdk2 complexes. We conclude that squamous cell carcinoma cells have intrinsic defects in their ability to regulate cdk-cki complexes in response to differentiation signals.
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PMID:Decreased growth inhibitory responses of squamous carcinoma cells to interferon-gamma involve failure to recruit cki proteins into cdk2 complexes. 1171 Sep 44

The aim of this study was to evaluate the expression profile of proteins involved in growing of human non-small cell lung cancer (NSCLC) in athymic nude mice. The expressions of 20 gene products in primary NSCLC of 170 patients were analyzed and the proteins were correlated with the transplantability of the carcinomas in nude mice. There was no relationship between xenotransplantability of human non-small cell lung cancer in nude mice and histology, stage or lymph node involvement. Of the analyzed proliferative factors PCNA, cyclin A, cyclin D, cdk2, cdk4 and cell cycle phases only cyclin D, cdk4 and the cell cycle phases were up-regulated in growing carcinomas. There was also a correlation between the apoptotic indices and the take rate in nude mice. Concerning microvessel density and angiogenic factors only VEGF showed a relation to xenotransplantability. Of the proto-oncogenes and suppressor gene products N-RAS, P53, FOS and JUN revealed a relationship to the take rate of NSCLC, while such a relationship was not found with MYC, ERBB-1 and ERBB-2. In a second step, a hierarchical cluster analysis was carried out. The resulting clusters were correlated with the take rate of the carcinomas in nude mice. The expression of JUN, N-RAS, FOS, cyclin D, and cdk4 were significantly different in both groups with non- overlapping confidence intervals. Thus, the up-regulation of the proteins JUN, N-RAS, FOS, cyclin D and cdk4 predicts the growth of NSCLC in nude mice.
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PMID:Expression profile of proteins involved in the xenotransplantability of non-small cell lung cancers into athymic nude mice. 1178 7

p21(WAF1/CIP1) is a universal cyclin-dependent kinase inhibitor. To investigate the role of p21(WAF1/CIP1) in proliferation of human liver cancer cells, we examined the expression of p53, p21(WAF1/CIP1), cdk2 and cdk4 expression in two human liver cancer cell lines (HepG2 and PLC/PRF/5 cells). The effects of p21(WAF1/CIP1) on [(3)H]thymidine incorporation and cdks were also examined in these cells. HepG2 cells expressed all these proteins with lower level of cdk4. PLC/PRF/5 cells expressed the other proteins except p21(WAF1/CIP1). Transfection of p21(WAF1/CIP1) gene inhibited [(3)H]thymidine incorporation of both cells with different extent. Although the transfection of p21(WAF1/CIP1) did not affect cdk2 and cdk4 expression, it did reduce cdk2 kinase activity by 20%. These results suggest that: (a) p21(WAF1/CIP1) involved in DNA synthesis of human liver cancer cells; (b) p21(WAF1/CIP1) could be a target gene for the treatment of human hepatocellular carcinoma.
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PMID:A cyclin-dependent kinase inhibitor (p21(WAF1/CIP1)) affects thymidine incorporation in human liver cancer cells. 1187 May 47

Apigenin, a common dietary flavonoid abundantly present in fruits and vegetables, may have the potential for prevention and therapy for prostate cancer. Here, we report for the first time that apigenin inhibits the growth of androgen-responsive human prostate carcinoma LNCaP cells and provide molecular understanding of this effect. The cell growth inhibition achieved by apigenin treatment resulted in a significant decrease in AR protein expression along with a decrease in intracellular and secreted forms of PSA. These effects were also observed in DHT-stimulated cells. Further, apigenin treatment of LNCaP cells resulted in G1 arrest in cell cycle progression which was associated with a marked decrease in the protein expression of cyclin D1, D2 and E and their activating partner cdk2, 4 and 6 with concomitant induction of WAF1/p21 and KIP1/p27. The induction of WAF1/p21 appears to be transcriptionally upregulated and is p53 dependent. In addition, apigenin inhibited the hyperphosphorylation of the pRb protein in these cells. Apigenin treatment also resulted in induction of apoptosis as determined by DNA fragmentation, PARP cleavage, fluorescence microscopy and flow cytometry. These effects were found to correlate with a shift in Bax/Bcl-2 ratio more towards apoptosis. Apigenin treatment also resulted in down-modulation of the constitutive expression of NF-kappaB/p65. Taken together, these findings suggest that apigenin has strong potential for development as an agent for prevention against prostate cancer.
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PMID:Involvement of nuclear factor-kappa B, Bax and Bcl-2 in induction of cell cycle arrest and apoptosis by apigenin in human prostate carcinoma cells. 1203 41


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