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

Paraffin sections (n = 168, 27 benign, 16 low malignant potential [LMP] and 125 malignant tumours) from epithelial ovarian tumours were evaluated immunohistochemically for expression of retinoblastoma gene product (pRB) and p53 protein, and the relationship among pRB, p53 and cyclin-dependent kinase inhibitor 2 (CDKN2) gene product p16INK4A (p16) was analysed, following our previous study of p16. Forty-one percent of the benign, 50% of the LMP and most (71%) of the malignant tumours showed high pRB expression. High expression of pRB (>50% pRB-positive cells) significantly correlated with non-mucinous histological subtypes. Reduced pRB expression, substage and residual disease were significant predictors for poor prognosis in stage I patients. All the benign and most of the LMP (81%) tumours were in either the p53-negative or low p53-positive category, but nearly half of the malignant tumours had high p53 expression. High p53 accumulation was found in non-mucinous, high grade and late stage tumours. For well-differentiated carcinomas, high p53 expression was a predictor of poor prognosis. However, even though high p53 expression was not associated with histological subtype, stage or the presence of residual disease, high p53 expression was not an independent predictor when all clinical parameters were combined. For all ovarian cancers, a close correlation was found between high p53 and high p16 expression. The relationship between the expression of pRB and p16 depended on tumour stage. In stage I tumours, high pRB was associated with low p16 reactivity. On the other hand, most advanced tumours showed both high pRB and high p16 reactivity.
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PMID:Reduced expression of retinoblastoma gene product (pRB) and high expression of p53 are associated with poor prognosis in ovarian cancer. 929 30

During development, neuronal differentiation is closely coupled with cessation of proliferation. We use nerve growth factor (NGF)-induced differentiation of PC12 pheochromocytoma cells as a model and find a novel signal transduction pathway that blocks cell proliferation. Treatment of PC12 cells with NGF leads to induction of nitric oxide synthase (NOS) (Peunova, N., and Enikolopov, G. (1995) Nature 375, 68-73). The resulting nitric oxide (NO) acts as a second messenger, activating the p21(WAF1) promoter and inducing expression of p21(WAF1) cyclin-dependent kinase inhibitor. NO activates the p21(WAF1) promoter by p53-dependent and p53-independent mechanisms. Blocking production of NO with an inhibitor of NOS reduces accumulation of p53, activation of the p21(WAF1) promoter, expression of neuronal markers, and neurite extension. To determine whether p21(WAF1) is required for neurite extension, we prepared a PC12 line with an inducible p21(WAF1) expression vector. Blocking NOS with an inhibitor decreases neurite extension, but induction of p21(WAF1) with isopropyl-1-thio-beta-D-galactopyranoside restored this response. Levels of p21(WAF1) induced by isopropyl-1-thio-beta-D-galactopyranoside were similar to those induced by NGF. Therefore, we have identified a signal transduction pathway that is activated by NGF; proceeds through NOS, p53, and p21(WAF1) to block cell proliferation; and is required for neuronal differentiation by PC12 cells.
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PMID:A novel, nerve growth factor-activated pathway involving nitric oxide, p53, and p21WAF1 regulates neuronal differentiation of PC12 cells. 929 52

Much of the predisposition to hereditary breast and ovarian cancer has been attributed to inherited defects in the BRCA1 tumour-suppressor gene. The nuclear protein BRCA1 has the properties of a transcription factor, and can interact with the recombination and repair protein RAD51. Young women with germline alterations in BRCA1 develop breast cancer at rates 100-fold higher than the general population, and BRCA1-null mice die before day 8 of development. However, the mechanisms of BRCA1-mediated growth regulation and tumour suppression remain unknown. Here we show that BRCA1 transactivates expression of the cyclin-dependent kinase inhibitor p21WAF1/CIP1 in a p53-independent manner, and that BRCA1 inhibits cell-cycle progression into the S-phase following its transfection into human cancer cells. BRCA1 does not inhibit S-phase progression in p21-/- cells, unlike p21+/+ cells, and tumour-associated, transactivation-deficient mutants of BRCA1 are defective in both transactivation of p21 and cell-cycle inhibition. These data suggest that one mechanism by which BRCA1 contributes to cell-cycle arrest and growth suppression is through the induction of p21.
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PMID:Arrest of the cell cycle by the tumour-suppressor BRCA1 requires the CDK-inhibitor p21WAF1/CiP1. 929 97

Recently we have shown that in fibroblasts (NIH 3T3 and Rat-1 cells) inhibition of protein geranylgeranylation leads to a G0/G1 arrest, whereas inhibition of protein farnesylation does not affect cell cycle distribution. Here we demonstrate that in human tumor cells the geranylgeranyltransferase-I (GGTase-I) inhibitor GGTI-298 blocked cells in G0/G1, whereas the farnesyltransferase (FTase) inhibitor FTI-277 showed a differential effect depending on the cell line. FTI-277 accumulated Calu-1 and A-549 lung carcinoma and Colo 357 pancreatic carcinoma cells in G2/M, T-24 bladder carcinoma, and HT-1080 fibrosarcoma cells in G0/G1, but had no effect on cell cycle distribution of pancreatic (Panc-1), breast (SKBr 3 and MDAMB-231), and head and neck (A-253) carcinoma cells. Furthermore, treatment of Calu-1, Panc-1, Colo 357, T-24, A-253, SKBr 3, and MDAMB-231 cells with GGTI-298, but not FTI-277, induced the protein expression levels of the cyclin-dependent kinase inhibitor p21WAF. HT-1080 and A-549 cells had a high basal level of p21WAF, and GGTI-298 did not further increase these levels. Furthermore, GGTI-298 also induces the accumulation of large amounts of p21WAF mRNA in Calu-1 cells, a cell line that lacks the tumor suppressor gene p53. There was little effect of GGTI-298 on the cellular levels of another cyclin- dependent kinase inhibitor p27KIP as well as cyclin E and cyclin D1. These results demonstrate that GGTase-I inhibitors arrest cells in G0/G1 and induce accumulation of p21WAF in a p53-independent manner and that FTase inhibitors can interfere with cell cycle events by a mechanism that involves neither p21WAF nor p27KIP. The results also point to the potential of GGTase-I inhibitors as agents capable of restoring growth arrest in cells lacking functional p53.
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PMID:The geranylgeranyltransferase-I inhibitor GGTI-298 arrests human tumor cells in G0/G1 and induces p21(WAF1/CIP1/SDI1) in a p53-independent manner. 934 Nov 67

Although the involvement of the tumor suppressor gene p53 in normal hematopoiesis is uncertain, it can give rise to differentiation signals in leukemic cells. It is not clear, however, whether differentiation merely is a consequence of the ability of p53 to arrest cell proliferation or whether hitherto unknown molecular mechanisms are responsible for the p53-mediated differentiation. To further explore the role of p53 in leukemic cell differentiation, we investigated whether transforming growth factor beta1 (TGF-beta1), a cytokine involved in cell cycle control at several levels, can cooperate with wild-type p53 to induce differentiation of monoblastic U-937 and erythroleukemic K562 cells. Indeed, wild-type p53-expressing cells were found to be more sensitive to TGF-beta1-induced differentiation than control cells, lending support to the idea that p53 is of importance for differentiation induction of leukemic cells. In addition, it is shown that TGF-beta1 can suppress p53-mediated cell death, thus reinforcing the differentiation response. The cyclin-dependent kinase inhibitor p21 and the retinoblastoma protein (pRb) are downstream effectors of p53-mediated growth arrest. Therefore, the roles for these molecules in p53-mediated differentiation were examined. The p53-dependent signals of differentiation were associated with induction of p21 in both cell lines investigated. However, activation of pRb by induced hypophosphorylation and concomitant decreased growth rate on p53-mediated differentiation was observed only in U-937 cells expressing an inducible, temperature-sensitive form of p53 but not in K562 cells constitutively expressing p53. Thus, our data suggest a role for p53 in the regulation of differentiation in leukemic cells that can be independent of its ability to activate pRb and arrest cell proliferation.
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PMID:The tumor suppressor gene p53 can mediate transforming growth [corrected] factor beta1-induced differentiation of leukemic cells independently of activation of the retinoblastoma protein. 934 91

The exact mechanisms for the selective toxicity of chemotherapeutic drugs against tumor cells are not fully understood. We designed a series of experiments to test the possibility that the positive proliferative signal initiated by oncogenes might change the sensitivity for apoptosis induction by the anticancer drug etoposide (VP16), an inhibitor of topoisomerase II (Topo II). Treatment with VP16 induced significantly increased apoptosis in NIH3T3 cells transformed by oncogenic src, ras or raf, compared with the normal 3T3 cells. Apopototic changes involved nuclear DNA fragmentation, morphological alterations and decreased viability. Furthermore it was shown that stress-activated protein kinase (SAPK) was activated much more strongly in all three transformed lines compared to untransformed cells by VP16 treatment, while slight activation of extracellular signal-regulated kinase (ERK1) was observed in all four cell lines. In addition, the transformed cells displayed arrest in mid-S-phase following the treatment, whereas NIH3T3 cells were primarily arrested in late S and G2/M phase. Finally, the cyclin-dependent kinase inhibitor p21 WAF1 was induced in all four cell lines, although induction of p53 was not detected in any of these cell lines. Taken together our results demonstrated that oncogenic transformation can sensitize the cells to apoptosis induction, stress kinase activation and cell cycle arrest in response to VP16 treatment. These results may have important implications for understanding the selective toxicity of anti-cancer drugs in tumor cells.
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PMID:Oncogenic transformation potentiates apoptosis, S-phase arrest and stress-kinase activation by etoposide. 934 97

The p21WAF1/CIP1 gene, which encodes a cyclin-dependent kinase inhibitor, may be critical for tumor suppressor gene p53-induced cell cycle arrest. The p53 gene is known to regulate G1 checkpoint, which can either induce G1 arrest or initiate apoptosis. To directly examine the role of p21WAF1/CIP1 in the control of p53 function, we have introduced human p21WAF1/CIP1 gene into a p53-deficient human non-small cell lung cancer cell line H1299 using a p21WAF1/CIP1-expressing adenoviral vector (AdCMVp21). Infection with AdCMVp21 resulted in high levels of p21WAF1/CIP1 expression and significantly suppressed the growth of H1299 cells through the G1 arrest of the cell cycle. In contrast, transient expression of the wild-type p53 gene by a recombinant adenoviral vector (AdCMVp53) in H1299 cells induced apoptotic cell death and resulted in a rapid loss of cell viability. We then examined the effects of combined infection with AdCMVp21 and AdCMVp53 on H1299 cells to explore the dominant function of these molecules. Interestingly, introduction of exogenous p53 overcame p21WAF1/CIP1-mediated cell cycle arrest at G1 and induced apoptosis, although viral-transduced p21WAF1/CIP1 expression level was unaffected. These observations suggest that p53 expression converts a p21WAF1/CIP1-mediated growth arrest into apoptosis. The result was repeated with two additional human colon adenocarcinoma cell lines with the different p53 status, mutant p53-expressing DLD-1 and wild-type p53-expressing LoVo, suggesting that this phemonenon is a general event among human cancer cells. Thus, p53-mediated apoptotic pathway is dominant over the growth arrest pathway, indicating that p53 may be an essential upstream mediator of p21WAF1/CIP1 in the regulation of a cell process leading either to growth arrest or to apoptotic suicide.
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PMID:p53 expression overcomes p21WAF1/CIP1-mediated G1 arrest and induces apoptosis in human cancer cells. 936 36

The cyclin-dependent kinase inhibitor p21WAF1/CIP1 plays a major role in the induction of G1 cell cycle arrest following DNA damage and is known to be regulated by p53-dependent and -independent pathways. Here, we show that p21WAF1/CIP1 transcription is also regulated, independently of p53, by the cis elements that are located downstream of the transcription start site. A cDNA fragment of approximately 180 bp, located 260 bases 3' to the translation termination codon of p21WAF1/CIP1 cDNA, was cloned in both the sense and antisense orientations downstream of the CMV promoter, upstream of the SV40 promoter, and both upstream and downstream of the p21WAF1/CIP1 promoter in the plasmids carrying the luciferase reporter gene. The constructs were transiently transfected in human breast carcinoma cells MCF-7 and MDA-MB-468 and a Syrian hamster smooth muscle cell line DDT1MF2 and were found to elicit 2-3-fold or higher repression of luciferase activities. By using overlapping deletions of the above 180-bp fragment, we identified a 48-bp subfragment that contains putative cis element(s) that participate in the transcriptional repression of the p21WAF1/CIP1 gene. The overlapping subfragments bind, in vitro, to specific proteins present in the nuclear extracts of MDA-MB-468 and DDT1MF2 cells. We, therefore, propose that additional mechanism(s) exist that regulate expression of the cellular p21WAF1/CIP1 and may contribute to p21WAF1/CIP1-dependent control of the cell cycle.
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PMID:Transcriptional repression of the cyclin-dependent kinase inhibitor p21WAF1/CIP1 gene mediated by cis elements present in the 3'-untranslated region. 937 14

The basic helix-loop-helix protein MyoD induces muscle structural gene expression and cell cycle withdrawal in many nontransformed cell lines. We show that MyoD activation of transcription of the cyclin-dependent kinase inhibitor p21 does not require synthesis of an intermediary protein. In most of the rhabdomyosarcoma and other solid tumor cell lines that we analyzed, p21 levels were abnormally low and correlated with the combined inactivity of MyoD and p53, two known transcriptional activators of p21. Loss of MyoD activation of p21 transcription correlated with the failure to arrest in G1, and expression of p21 caused accumulation of cells in G1, further supporting a role for p21 in MyoD-induced cell cycle arrest. Finally, different tumor types have inactivated distinct factors necessary for p21 expression, because p21 expression was reconstituted in hybrid cell lines. We propose that p21 integrates growth-inhibitory signals from independent p53 and basic helix-loop-helix pathways, and that in the majority of tumor cell lines, both pathways are abrogated.
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PMID:Inactivation of MyoD-mediated expression of p21 in tumor cell lines. 937 38

The mammalian cellular response to ionizing radiation results in delays in progression through the cell cycle at several checkpoints and includes alterations in the activity of cyclin-dependent kinases. The product of the CDC2 gene is a key kinase involved in cell cycle progression. The signaling events that regulate its expression after exposure to DNA-damaging agents are not known. We show that cdc2 mRNA and protein are down-regulated after irradiation of normal human and mouse fibroblasts with doses as low as 0.5 Gy. This down-regulation is preceded by induction of p53 and p21Waf1 proteins. In human cells in which p53 was nonfunctional and in p53-/- or p21-/- mouse embryo fibroblasts, no effect of ionizing radiation on p34cdc2 expression levels was observed. These findings indicate that CDC2 down-regulation after irradiation is p53-dependent and involves the cyclin-dependent kinase inhibitor p21Waf1 as a negative factor in the control of CDC2 expression. Correspondence between the delay in initiation of DNA synthesis in irradiated cells and the down-regulation of CDC2 is described.
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PMID:CDC2 is down-regulated by ionizing radiation in a p53-dependent manner. 937 39


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