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)

The p53 tumor suppressor gene is mutated in the majority of pancreatic adenocarcinomas, and several studies have suggested that loss of p53 function may contribute to the aggressive clinical behavior of pancreas cancer. Although immunocytochemical accumulation of the p53 gene product has previously been assessed as a marker for p53 mutations in cancers of the pancreas and other organ systems, the relationship between p53 mutations and p53 protein accumulation is variable. The cyclin-dependent kinase inhibitor, p21 (also known as WAF1 and CIP1), is induced by wild-type but not mutant p53, and recent work has implicated p21 as a downstream mediator of the growth-suppressing and apoptosis-promoting functions of wild-type p53. In the present work, we sought to determine whether loss of p21 expression could more precisely identify those tumors with p53 mutations and/or loss, compared with immunocytochemical assessment of p53 protein accumulation. We evaluated p53 and p21 expression immunohistochemically in a series of 21 ductal adenocarcinomas of the pancreas with known p53 mutational status. Diffuse overexpression of p53 was found in 3 of 8 cases (38%) with wild-type p53 and 7 of 13 cases (54%) with p53 mutations with or without loss of heterozygosity at 17p. Surprisingly, expression of p21 correlated neither with p53 mutational status nor with p53 protein expression. In particular, strong p21 expression was seen even in carcinomas in which molecular analysis revealed a frameshift mutation in one allele of p53 and loss of the second. These data suggest that p21 expression in pancreatic adenocarcinoma may also be induced by a p53-independent pathway and that p21 expression, as assessed immunocytochemically, does not reflect the functional status of p53 in these carcinomas.
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PMID:p53-independent expression of the cyclin-dependent kinase inhibitor p21 in pancreatic carcinoma. 757 63

In this study we examine the relationship between p21CIP1/Waf1 (CIP1), a 21 kDa protein that binds to and modulates the activity of several cyclin dependent kinases and expression of wild-type (WT) p53 in human breast epithelial cells. Basal CIP1 protein, but not CIP1 mRNA levels correlated well with expression of WT p53 in human breast epithelial cells. To obtain more direct evidence that WT p53 regulated the level of CIP1 protein, the Human Papilloma Virus (HPV) E6 protein was introduced into immortalized 184B5 breast cells. Residual WT p53 levels correlated well with CIP1 protein but not CIP1 mRNA levels in isolated clones of transfected cells. CIP1 protein was increased at early times after growth factor arrested cells were stimulated to proliferate. The rise in CIP1 protein was due to a concomitant increase in CIP1 mRNA levels in MCF10, but not in normal mammary epithelial cells. DNA damage induced by ionizing radiation resulted in a transient increase in WT p53 levels but a prolonged induction of CIP1 protein. The sustained increase in CIP1 protein 24 h after radiation could not be attributed to a concomitant increase in CIP1 mRNA levels. Although the half-life of the CIP1 protein was not altered following irradiation, a fourfold increase in the amount of radioactivity incorporated into CIP1 protein was detected. When considered together these data suggest that wild-type p53 affects CIP1 protein accumulation at a posttranscriptional level in human breast epithelial cells under different physiologic and stress conditions.
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PMID:Effects of cell cycle, wild-type p53 and DNA damage on p21CIP1/Waf1 expression in human breast epithelial cells. 762 42

Several groups have recently isolated and characterized an inhibitor of cyclin-dependent kinases, p21CIP1/WAF1 which is transcriptionally induced by wild-type but not mutant p53. It is likely that p21CIP1/WAF1 mediates the growth suppression effects of p53 by arresting the cell cycle at the G1/S checkpoint, and by inducing apoptosis. To test the hypothesis that primary human tumors have mutations in the CIP1/WAF1 gene which propagates the carcinogenic process, we examined primary breast and sarcoma tumor specimens for alterations in the CIP1/WAF1 gene. Unique, or acquired somatic mutations were not observed indicating that they are not selected for during the carcinogenic process; however, two common variants were identified. The variants were not unique to tumors as 10.7% of normal individuals exhibited the variants. Nonetheless, the frequency of the variants in tumors with wild-type p53 (20.4%) was significantly greater (p = 0.05) than in normal DNAs. In contrast, the frequency of the variants (4.1%) was found to be significantly lower in tumors with p53 mutations (p = 0.006). These data suggest that the occurrence of the variants may have a direct effect on tumor development and may, in some cases, be incompatible with p53 mutations.
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PMID:Two variants of the CIP1/WAF1 gene occur together and are associated with human cancer. 765 64

p21CIP1/WAF1 is a CDK inhibitor regulated by the tumor suppressor p53 and is hypothesized to mediate G1 arrest. p53 has been suggested to derive anti-oncogenic properties from this relationship. To test these notions, we created mice lacking p21CIP1/WAF1. They develop normally and (unlike p53-/- mice) have not developed spontaneous malignancies during 7 months of observation. Nonetheless, p21-/- embryonic fibroblasts are significantly deficient in their ability to arrest in G1 in response to DNA damage and nucleotide pool perturbation. p21-/- cells also exhibit a significant growth alteration in vitro, achieving a saturation density as high as that observed in p53-/- cells. In contrast, other aspects of p53 function, such as thymocytic apoptosis and the mitotic spindle checkpoint, appear normal. These results establish the role of p21CIP1/WAF1 in the G1 checkpoint, but suggest that the anti-apoptotic and the anti-oncogenic effects of p53 are more complex.
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PMID:Mice lacking p21CIP1/WAF1 undergo normal development, but are defective in G1 checkpoint control. 766 46

Transforming growth factor beta (TGF beta) is an important regulator of cellular proliferation. In normal ovarian epithelial cells, TGF beta acts to inhibit growth. However, in ovarian cancer cell lines, this effect is usually lost. Although the regulatory pathway of TGF beta remains unclear, TGF beta-treated cells arrest late in G1. This inhibition appears to involve blocking of the cyclin-dependent kinase phosphorylation of the retinoblastoma protein. Recently, a general inhibitor of cyclin-dependent kinases, CIP1/WAF1/p21, was identified. Expression of CIP1 is positively regulated by binding of wild-type p53 to a consensus response element upstream of the CIP1 gene. Overexpression of the CIP1 protein causes growth suppression, analogous to TGF beta and wild-type p53. We have examined the induction of CIP1 by TGF beta 1 in ovarian cancer cell lines that have been previously characterized for their proliferative response to TGF beta 1. OVCA420, a cell line that is dramatically growth inhibited by TGF beta 1, significantly induced CIP1 expression in response to TGF beta 1. CIP1 induction was accompanied by a decrease in cdk2 kinase activity and cdk2 protein levels. In three other cell lines that respond weakly to TGF beta 1, CIP1 expression was not induced. To determine if TGF beta 1 induction occurs via p53, regulation of p53 RNA and protein was examined. No differences in p53 transcription, steady-state protein level, de novo synthesis, phosphorylation, or subcellular accumulation were noted. Furthermore, TGF beta 1 could not induce transcription from a consensus p53 DNA binding site in the TGF beta 1-response cell line.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transforming growth factor beta 1 can induce CIP1/WAF1 expression independent of the p53 pathway in ovarian cancer cells. 769 78

Cyclin-dependent kinases (Cdks) are positive regulators of cell proliferation, whereas Cdk inhibitors (CKIs) inhibit proliferation. We describe a new CKI, p57KIP2, which is related to p21CIP1 and p27KIP1. p57KIP2 is a potent, tight-binding inhibitor of several G1 cyclin/Cdk complexes, and its binding is cyclin dependent. Unlike CIP1, KIP2 is not regulated by p53. Overexpression of p57KIP2 arrests cells in G1. p57KIP2 proteins have a complex structure. Mouse p57KIP2 consists of four structurally distinct domains: an amino-terminal Cdk inhibitory domain, a proline-rich domain, an acidic-repeat region, and a carboxy-terminal domain conserved with p27KIP1. Human p57KIP2 appears to have conserved the amino- and carboxy-terminal domains but has replaced the internal regions with sequences containing proline-alanine repeats. In situ hybridization during mouse embryogenesis revealed that KIP2 mRNA displays a striking pattern of expression during development, showing high level expression in skeletal muscle, brain, heart, lungs, and eye. Most of the KIP2-expressing cells are terminally differentiated, suggesting that p57KIP2 is involved in decisions to exit the cell cycle during development and differentiation. Human KIP2 is located at 11p15.5, a region implicated in both sporadic cancers and Beckwith-Wiedemann syndrome, a familial cancer syndrome, marking it as a candidate tumor suppressor. The discovery of a new member of the p21CIP1 inhibitor family with novel structural features and expression patterns suggests a complex role for these proteins in cell cycle control and development.
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PMID:p57KIP2, a structurally distinct member of the p21CIP1 Cdk inhibitor family, is a candidate tumor suppressor gene. 772 84

The combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) induces terminal differentiation with an irreversible loss of proliferative capacity in human melanoma cells. Using subtraction hybridization, cDNAs were identified that display enhanced expression in terminally differentiated and growth arrested human melanoma cells (Jiang and Fisher, 1993; Jiang et al., 1994a). A specific melanoma differentiation-associated (mda) cDNA, mda-6, is described whose expression inversely correlates with melanoma progression and growth. mda-6 is identical to WAF1/CIP1/SDI1 that encodes the M(r) 21,000 protein (p21) that is an inhibitor of cyclin-dependent kinases. Actively growing normal melanocyte, SV40-immortalized human melanocyte and dysplastic nevus cell lines synthesize elevated levels of mda-6 mRNA; whereas, actively proliferating radial and early vertical growth phase primary melanomas as well as metastatic human melanoma cells produce reduced levels of mda-6 mRNA. Treatment of primary and metastatic human melanoma cells with IFN-beta + MEZ results in growth inhibition and an increase in mda-6 expression. mda-6 expression also increases when human melanoma cells are grown to high saturation densities or when grown in serum-free medium. Using anti-p53 and anti-p21 antibodies, an inverse correlation is found between p53 and p21 protein levels during growth arrest and differentiation. Induction of growth arrest and terminal differentiation in H0-1 human melanoma cells by IFN-beta + MEZ results in a temporal decrease in wild-type p53 protein levels with a corresponding increase in p21 levels. In the Matrigel-assisted melanoma progression model, mda-6 expression decreases in early vertical growth phase primary human melanoma cells selected for autonomous or enhanced tumor formation in nude mice. In metastatic human melanoma cells displaying a loss of metastatic potential resulting from introduction of a normal human chromosome 6, mda-6 mRNA levels increase. Taken together, these studies indicate that mda-6 (p21) may function as a negative regulator of melanoma growth, progression and metastasis.
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PMID:The melanoma differentiation-associated gene mda-6, which encodes the cyclin-dependent kinase inhibitor p21, is differentially expressed during growth, differentiation and progression in human melanoma cells. 775 61

We investigated temporal relationships between ionizing radiation-induced G1 arrest and induction of the p53-regulated genes GADD45, CIP1/WAF1, and MDM2 in a series of Burkitt's lymphoma and lymphoblastoid cell lines that differed in p53 gene status. Emphasis was placed on characterization of the EW36 cell line, which despite expressing wild-type p53 genes, is defective in G1 arrest following gamma-irradiation (P. M. O'Connor et al., Cancer Res., 53: 4776-4780, 1993). Induction of CIP1/WAF1, GADD45, and to a lesser extent MDM2 mRNA was observed in all wild-type p53 lines that arrested in G1. Cell lines that contained only mutant p53 genes or were heterozygous for p53 mutations failed to induce appreciable levels of these p53-regulated transcripts and did not arrest in G1. G1 arrest in the wild-type p53 cell line WMN was more prolonged than elevation of CIP1/WAF1, GADD45, or MDM2 transcripts, suggesting that G1 arrest duration must be dependent upon stability of these newly synthesized proteins. In agreement, we found that p21Cip1/Waf1, a potent inhibitor of G1-S phase cyclin-dependent kinases, was maintained at elevated levels throughout the period that WMN cells remained arrested in G1. EW36 cells exhibited normal induction of CIP1/WAF1, GADD45, and MDM2 mRNA following gamma-irradiation, suggesting that the defect in G1 arrest must reside downstream of p53 transactivation. Investigations into the stability of p53 and p21Cip1/Waf1 revealed that EW36 cells failed to maintain elevated levels of these proteins following irradiation. p53 levels decreased within 4 h of irradiation, and p21Cip1/Waf1 levels decreased shortly after the normal decline of CIP1/WAF1 mRNA levels. Degradation of p21Cip1/Waf1 coincided with the escape of EW36 cells from G1 arrest. Our studies suggest that p21Cip1/Waf1 stability may determine G1 arrest duration and that premature degradation of this protein could provide an alternative route to subversion of the G1 checkpoint in cancer cells.
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PMID:Relationships between G1 arrest and stability of the p53 and p21Cip1/Waf1 proteins following gamma-irradiation of human lymphoma cells. 775 91

We have previously reported that the immediate G2 checkpoint delay of normal human fibroblasts in response to ionizing radiation is correlated with inhibition of p34CDC2/cyclin B kinase activity. Here, we observed increased amounts of the cyclin-dependent protein kinase inhibitor p21CIP1 associated with p34CDC2/cyclin B protein complexes from irradiated normal human fibroblasts. Since wild-type p53 function is not required for the early G2 checkpoint response to ionizing radiation, we investigated whether a p53-independent induction of p21CIP1 was required for the G2 checkpoint. Early passage human fibroblasts expressing the E6 oncoprotein of human papilloma virus-type 16 (NHF4 E6) were analyzed. It has been demonstrated earlier than inactivation of wild-type p53 function in these cells by E6 protein does not alter their intact early G2 checkpoint response to gamma-rays. p21CIP1 was found to be undetectable in p34CDC2/cyclin B protein complexes and in total extracts from the E6-expressing cells, with or without exposure to ionizing radiation. These data indicate that p21CIP1 is not required for the immediate G2 checkpoint response and is not induced by a p53-independent pathway in G2 phase following exposure to gamma-rays.
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PMID:p21CIP1 is not required for the early G2 checkpoint response to ionizing radiation. 778 Sep 56

The melanoma differentiation associated gene, mda-6, which is identical to the P53-inducible gene WAF1/CIP1, encodes an M(r) 21,000 protein (p21) that can directly inhibit cell growth by repressing cyclin dependent kinases. mda-6 was identified using subtraction hybridization by virtue of its enhanced expression in human melanoma cells induced to terminally differentiate by treatment with human fibroblast interferon and the anti-leukemic compound mezerein (Jiang and Fisher, 1993). In the present study, we demonstrate that mda-6 (WAF1/CIP1) is an immediate early response gene induced during differentiation of the promyelocytic HL-60 leukemia cell line along the granulocytic or macrophage/monocyte pathway. mda-6 gene expression in HL-60 cells is induced within 1 to 3 h during differentiation along the macrophage/monocyte pathway evoked by 12-0-tetradecanoyl phorbol-13-acetate (TPA) or 1,25-dihydroxyvitamin D3 (Vit D3) or the granulocytic pathway produced by retinoic acid (RA) or dimethylsulfoxide (DMSO). Immunoprecipitation analyses using an anti-p21 antibody indicate a temporal induction of p21 protein following treatment with TPA, DMSO or RA. A relationship between rapid induction of mda-6 gene expression and differentiation is indicated by a delay in this expression in an HL-60 cell variant resistant to TPA-induced growth arrest and differentiation. A similar delay in mda-6 gene expression is not observed in Vit D3 treated TPA-resistant variant cells that are also sensitive to induction of monocytic differentiation. Since HL-60 cells have a null-p53 phenotype, these results demonstrate that p21 induction occurs during initiation of terminal differentiation in a p53-independent manner. In this context, p21 may play a more global role in growth control and differentiation than originally envisioned.
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PMID:Induction of differentiation in human promyelocytic HL-60 leukemia cells activates p21, WAF1/CIP1, expression in the absence of p53. 793 68


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