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)

Expression of cell cycle regulatory genes in mouse lung was investigated in transgenic models for Clara cell transformation. Clara cells were transformed by generating transgenic mice in which the SV40 large T antigen was expressed under the control of the mouse Clara cell M(r) 10,000 protein promoter. The resulting lung tumors express the large T antigen in normal Clara cells and in tumors, and these tumors express reduced levels of CC10 mRNA. The expression of cell cycle regulatory protein, p53, and the cyclin-dependent kinase inhibitors was analyzed by Northern blot analysis and in situ hybridization throughout the progression of Clara cell transformation in the lung. Increases in specific cyclin-dependent kinase inhibitor steady-state mRNA levels were detected in p15, p18, p27, and p57 during tumor progression. The expression of p15, p57, and p21 mRNAs were verified by in situ hybridization. Using this approach, regulatory genes have been identified that may be involved in the regulation of Clara cell differentiation.
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PMID:Cyclin-dependent kinase inhibitor expression in pulmonary Clara cells transformed with SV40 large T antigen in transgenic mice. 904 Sep 36

Type I interferons (IFN), such as IFN-alpha, are potent antiproliferative and antitumor agents. IFN-tau, originally identified as a pregnancy recognition hormone, is a type I IFN that is related to IFN-alpha. We examine here the mechanism of the antiproliferative effects of IFN-alpha and IFN-tau in terms of their effects on intracellular events that regulate the cell cycle. Both IFN inhibited proliferation of the human Burkitt lymphoma cell line, Daudi, causing accumulation of cells in the G1 phase of the cell cycle. IFN-alpha was more effective than IFN-tau in this regard. Both IFN were found to inhibit the kinase activity of the cyclin-dependent kinase cdk2 in a manner that correlated with their relative abilities to cause cells to accumulate in the G1 phase of the cell cycle. Further, IFN treatment did not affect the expression of cdk2 protein, suggesting that the IFN modulated cdk2 activity through a cdk inhibitor. Consistent with this conclusion, both IFN induced the expression of the cyclin-dependent kinase inhibitor protein p21. The levels of p21 induced also correlated with the relative abilities of the IFN to inhibit cdk2 activity and to arrest cell growth in the G1 phase of the cell cycle. Moreover, following IFN treatment, increased levels of p21 were found complexed with cdk2, consistent with its role in the inhibition of cdk2 activity. These data suggest that p21-mediated inhibition of cdk2 activity plays an important role in the antiproliferative activity of type I IFN. The findings highlight interesting similarities between these cytokines and the products of tumor suppressor genes, such as p53, and may indicate a mechanism for the antitumor effects of the type I IFN.
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PMID:A role for the cyclin-dependent kinase inhibitor p21 in the G1 cell cycle arrest mediated by the type I interferons. 904 66

p21(WAF1/CIP1) is a universal cyclin-dependent kinase (cdk) inhibitor, the expression of which is regulated by p53-dependent and p53-independent pathways. We examined p21(WAF1/CIP1) expression in and p53 status of 21 primary hepatocellular carcinomas (HCCs) by reverse-transcriptase polymerase chain reaction (RT-PCR) and by PCR single-strand conformation polymorphism (PCR-SSCP) analysis. p21(WAF1/CIP1) messenger RNA expression was reduced markedly in 8 of 21 HCCs (38.1%) and 5 of these 8 HCCs bore p53 mutations. The relative p21(WAF1/CIP1) messenger RNA expression value of HCCs with p53 mutations (.73 +/- .13 U, n = 6) was significantly lower than that of HCCs with wild-type p53 (1.00 +/- 0.21 U, n = 14; P < .01). The p21(WAF1/CIP1) expression levels in cancerous tissues (.73 +/- .13 U) were significantly reduced in comparison with those in noncancerous tissues (.97 +/- .13 U) (P < .01) in the 6 cases with p53 mutations. These data indicate that p21(WAF1/CIP1) expression in HCCs is predominantly regulated by dependence on p53 and that reduced p21(WAF1/CIP1 expression may participate in hepatocarcinogenesis.
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PMID:Reduced p21(WAF1/CIP1) expression and p53 mutation in hepatocellular carcinomas. 904 1

One prominent effect of IFNs is their cell growth inhibitory activity. The exact molecular mechanism behind this inhibition of proliferation remains to be elucidated. Possible effectors for IFN-induced growth inhibition are the recently discovered cyclin-dependent kinase inhibitors. The effect of IFN-alpha treatment on the members of the Ink4 and Cip/Kip families of Cdk inhibitors was investigated in three hematopoietic cell lines Daudi, U-266 and H9. Two of these cell lines, Daudi and U-266, respond to IFN-alpha by G1 arrest, whereas the H9 cell line is not growth arrested by IFN-alpha. We show that a p53-independent upregulation of p21 mRNA occurs following IFN-alpha treatment in all three cell lines. In Daudi and U-266 cells, the mRNA induction is accompanied by an increase in p21 protein, followed by an increased binding of p21 to Cdk2 and a subsequent decrease in Cdk2 activity, temporally coinciding with G1 arrest. In both these cell lines, there was also an increased binding of p21 to Cdk4. In contrast, p21 protein was not expressed in H9 cells, despite high levels of p21 mRNA following IFN-alpha treatment. In U-266 cells, IFN-alpha increased not only p21 but also p15 mRNA and protein levels, followed by an increased association of p15 with Cdk4. Furthermore, IFN-alpha treatment caused a four- to sixfold induction of the p16 E1beta transcript in U-266 cells. Expression levels of the other Ink4 and Cip/Kip Cdk inhibitors were not induced by IFN treatment in any of the cell lines. We conclude that IFN-alpha can act as a potent regulator of Cdk-inhibitor expression, correlating with decreased Cdk activity and cell growth inhibition. One mechanism for resistance to IFN may be loss of the ability of cells to upregulate these proteins.
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PMID:Induction of Cip/Kip and Ink4 cyclin dependent kinase inhibitors by interferon-alpha in hematopoietic cell lines. 905 38

The expression of cyclins (A, B1, D1, D3, E), cyclin-dependent kinases (CDK2(3), CDK4), and the cyclin-dependent kinase inhibitors (CDKIs) p16(INK4A) and p21(CIP1) was studied in 9 malignant human astrocytoma cell lines using northern blot analysis, immunocytochemistry, and immunoblotting to see if their altered expression contributed to astrocytoma proliferation. Steady state cell cycle mRNA expression was analyzed in unsynchronized tumor cells, and cell cycle phase-specific gene expression was analyzed in 3 synchronized cell lines. Analysis of steady state expression revealed increased levels of several different cyclin transcripts and CDKs in a number of astrocytoma cell lines compared with normal human brain tissue or cultured fibroblasts. We confirm previous reports identifying loss of p16(INK4A) in astrocytomas, as a p16(INK4A) transcript was identified in only 2 cell lines and protein in 1 cell line. However, we now show that p21(CIP1) expression was also diminished relative to normal fibroblasts in all astrocytoma cell lines studied regardless of p53 mutation status. Analysis of synchronized astrocytoma cells revealed altered timing of mRNA expression of several cyclins. Immunocytochemistry revealed a generalized increase in immunoreactivity of astrocytoma cells for most cyclins and CDKs compared with human fibroblasts. Immunoblotting also revealed increased expression of cyclin proteins in a number of astrocytoma cell lines. These data suggest that increased expression of cyclins and CDKs, and decreased expression of CDKIs by human astrocytoma cell lines may contribute to their increased proliferative state. In addition, our data show that alterations in cell cycle genes in astrocytomas are not confined to the cyclin D1-CDK4-pRb axis.
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PMID:Cyclin and cyclin-dependent kinase expression in human astrocytoma cell lines. 905 43

Cells expressing human papillomavirus type 16 (HPV-16) E7, similar to those which express HPV-16 E6, are resistant to a p53-mediated G1 growth arrest. We examined the p53-mediated DNA damage response pathway in E7-expressing cells to determine the mechanism by which E7-containing cells continue to cycle. In response to DNA damage, no dramatic difference was detected in G1- or S-phase cyclin or cyclin-dependent kinase (Cdk) levels when E7-expressing cells were compared to the parental cell line, RKO. Furthermore, Cdk2 kinase activity was inhibited in both RKO cells and E7-expressing cells, while Cdk2 remained active in E6-expressing cells. However, the steady-state levels of pRB and p107 protein were substantially lower in E7-expressing cells than in the parental RKO cells or E6-expressing cells. There was no reduction in pRB mRNA levels, but the half-life of pRB in E7-expressing cells was markedly shorter. Infection of primary human foreskin keratinocytes with recombinant retroviruses expressing HPV-16 E7 resulted in a decrease in pRB protein levels, indicating this phenomenon is a consequence of E7 expression, not of immortalization or transformation. These data strongly suggest E7 interferes with the stability of pRB and p107 protein. We propose that the removal of these components of the p53-mediated G1 growth arrest pathway in E7-expressing cells contributes to the ability of E7 to overcome a p53-mediated G1 growth arrest.
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PMID:Analysis of the p53-mediated G1 growth arrest pathway in cells expressing the human papillomavirus type 16 E7 oncoprotein. 906 Jun 48

The p53 tumor suppressor protein can induce both cell cycle arrest and apoptosis in DNA-damaged cells. In human carcinoma cell lines expressing wild-type p53, expression of E7 allowed the continuation of full cell cycle progression following DNA damage, indicating that E7 can overcome both G1 and G2 blocks imposed by p53. E7 does not interfere with the initial steps of the p53 response, however, and E7 expressing cells showed enhanced expression of p21(waf1/cip1) and reductions in cyclin E- and A-associated kinase activities following DNA damage. One function of cyclin-dependent kinases is to phosphorylate pRB and activate E2F, thus allowing entry into DNA synthesis. Although E7 may substitute for this activity during cell division by directly targeting pRB, continued cell cycle progression in E7-expressing cells was associated with phosphorylation of pRB, suggesting that E7 permits the retention of some cyclin-dependent kinase activity. One source of this activity may be the E7-associated kinase, which was not inhibited following DNA damage. Despite allowing cell cycle progression, E7 was unable to protect cells from p53-induced apoptosis, and the elevated apoptotic response seen in these cells correlated with the reduction of cyclin A-associated kinase activity. It is possible that inefficient cyclin A-dependent inactivation of E2F at the end of DNA synthesis contributes to the enhanced apoptosis displayed by E7-expressing cells.
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PMID:Perturbation of the p53 response by human papillomavirus type 16 E7. 909 45

In a previous study, we found that treatment of HCT-8 cells with ZD1694, a specific antifolate-based thymidylate synthase inhibitor, resulted in DNA fragmentation. In this study, we have demonstrated the dose- and time-dependent induction of DNA fragmentation accompanied by elevation of p53 and WAF1 protein expression by ZD1694. WAF1 mRNA showed a time-dependent increase, whereas p53 mRNA was not found to be significantly overexpressed. The initial increase in WAF1 mRNA was detected at 4 hr, but increased WAF1 protein expression was detected 8-24 hr after a 2-hr exposure. The amount of total and hypophosphorylated pRb seems to be rising greatly after ZD1694 exposure. The effects of ZD1694 on the expression of E2F1 and formation of the E2F1-Rb complex were investigated after a 2-hr drug exposure (IC90). The results showed a time-dependent decrease in E2F1 mRNA and protein expression; an increase in the abundance of the E2F-Rb complex could be demonstrated beginning 4 hr after drug exposure by a gel shift assay. Kinetic analysis showed increased availability of hypophosphorylated pRb for inhibition of E2F, which could indirectly result from WAF1-induced inhibition cyclin-dependent kinase activity. Whereas thymidylate synthase inhibition by ZD1694 was rapid in onset and maintained for at least 24 hr after drug treatment, drug-induced cellular growth inhibition was significant 24 hr after drug exposure. The increased abundance of hypophosphorylated pRb and binding to transcription factor E2F-1 is consistent with ZD1694-induced cell growth inhibition in HCT-8 cells. Therefore, the observed effect on downstream events after effective inhibition of thymidylate synthase may offer the critical determinants of response to ZD1694.
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PMID:p53 and WAF1 are induced and Rb protein is hypophosphorylated during cell growth inhibition by the thymidylate synthase inhibitor ZD1694 (Tomudex). 910 28

The p21WAF1/CIP1 gene is regulated by p53 and encodes a cyclin-dependent kinase (Cdk)-inhibitor involved in senescence and cell quiescence. The role of p21 as a negative regulator of cell proliferation suggests that it may function as a tumor suppressor gene. However, only a few mutations of the p21WAF1/CIP1 gene have been reported to date. In order to assess potential p21WAF1/CIP1 gene alterations in human bladder cancer, we have examined this gene and its encoded product in a well-characterized cohort of 27 primary bladder tumors. Mobility shifts by single-strand conformation polymorphism in the p21WAF1/CIP1 gene were identified in 2 cases. Sequencing analyses revealed that one of these cases had point mutations in the 3' untranslated region, while the other case had a frame shift mutation at positions 322 (C to A) and a deletion of 8 nucleotides (323-->331; CCG-->ACG, codon 81 Arg-->Thr) that produced a stop signal at codon 83 (Gly--Stop). This tumor had a p21-negative phenotype by immunohistochemistry, but did not lose any allele. We further characterized these cases by the study of TP53 mutations using single-strand conformation polymorphism (PCR-SSCP) and sequencing, as well as immunohistochemical assays. Seven mobility shifts were identified and seven cases showed p53 nuclear accumulation. The two cases displaying mutated p21WAF1/CIP1 had wild-type TP53. It is concluded that p21WAF1/CIP1 gene aberrations are infrequent in bladder carcinoma but may be occasionally identified in primary bladder tumors.
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PMID:Analysis of p21WAF1/CIP1 in primary bladder tumors. 911 33

Abnormal control of the cell cycle is closely linked to carcinogenesis. p21WAF1/CIP1 protein is a universal inhibitor of G1 cyclin-dependent kinase and is induced by p53-dependent and -independent pathways. In order to elucidate the role of p21WAF1/CIP1 in human skin carcinogenesis, protein expression in squamous cell carcinoma (SCC), basal cell carcinoma (BCC), Bowen's disease (BD), actinic keratosis (AK), keratoacanthoma (KA), seborrheic keratosis (SK), and normal skin was examined using an immunohistochemical method. In normal skin, a few positive cells were seen in some cases in the upper spinous layer of the epidermis; sebaceous glands also had positive cells. In cases of SK and KA, positive cells were found in the basal and suprabasal epidermal layers (proliferation pattern), and in cases of BD and AK, positive cells were seen mainly in the upper spinous layer (differentiation pattern). Cases of SCC had more positive cells and showed two staining patterns: proliferation, or mixed. Cases of BCC had no positive cells. p21WAF1/CIP1 has some unidentified role in keratinocyte tumorigenesis, which may not be related directly to carcinogenesis.
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PMID:p21WAF1/CIP1 expression in non-melanoma skin tumors. 913 13


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