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)

Calcium is a ubiquitous second messenger controlling a broad range of cellular functions including growth and proliferation. Quiescent, hyperthrophic and proliferating cells have different types of calcium signal. In quiescent cells the calcium signal mostly involves elementary calcium events such as sparks and puffs, produced by localized Ca2+ release via a cluster of intracellular calcium channels, IP3 receptors and ryanodine receptors. This type of calcium signal promotes activation of the transcription factor CREB (cAMP response element binding protein) leading to cell cycle arrest in G1 phase via transactivation of p53/p21 signaling pathways. Proliferation is induced by phosphoinositide-coupled agonists and is associated with a sustained increase in cytosolic calcium due to 1.) enhanced excitability of IP3Rs after IP3 binding; 2.) enhanced activity of store-operated Ca2+ channels and T-type voltage-operated Ca2+ channels; 3.) decreased cytosolic Ca2+ removal due to inhibition of PMCA (plasma membrane Ca(2+)-ATPase) and SERCA (sarco/endoplasmic reticulum Ca(2+)-ATPase) calcium pumps. This type of calcium signal favors activation of the transcription factor NFAT (nuclear factor of activated T lymphocytes) that promotes hypertrophic growth and/or cell cycle progression. We suggest that the two main Ca(2+)-regulated transcription factors, CREB and NFAT, exert opposite control over cell growth and/or proliferation. Therapeutic strategies based on lowering intracellular Ca2+ or targeting of Ca(2+)-regulated transcription factors seems to be a promising approach to arrest growth and/or proliferation.
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PMID:Alteration in temporal kinetics of Ca2+ signaling and control of growth and proliferation. 1509 28

TRAIL-R2 promoter does not have a typical TATA-box but two functional Sp1-binding sites. TRAIL-R2 promoter belongs to the class of TATA-less and GC-box-containing promoters. The minimal promoter element is contained in the region spanning -198 to -116 upstream of translational initiation codon ATG. Computer analysis shows putative transcription factor binding sites such as c-Ets, AML-1a, c-Myb, Sp1, and GATA-1 in TRAIL-R2 promoter. Hypermethylation of TRAIL-R2 is not frequent compared with that of TRAIL-R3 and TRIAL-R4. There are no potential transcription factor binding sites in highly homologous regions between TRAIL-R2 promoter and TRAIL-R1 promoter, or between TRAIL-R2 promoter and mouse homologue mouse killer (MK) promoter. TRAIL-R2 is known to be a downstream gene of p53, a tumor-suppressor gene, and a p53-binding site in TRAIL-R2 intron 1 is responsible for p53-dependent transcription. Thapsigargin, endoplasmic reticulum Ca(2+)-ATPase inhibitor calcium releaser, upregulates TRAIL-R2 expression via the promoter region. Many regulators of TRAIL-R2 have been reported. However, it has not been demonstrated whether they regulate TRAIL-R2 via the promoter region. Here, we show a list of these regulators. Finally, we demonstrate the possibility of cancer therapy using regulation of TRAIL-R2 promoter.
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PMID:Promoter of TRAIL-R2 gene. 1511 Jan 70

Fusion proteins containing the amino-terminal domain of human p14(ARF) linked to green fluorescent protein are able to bind MDM2 and stabilize p53 without localization in the nucleolus. However, these fusion proteins are inherently unstable, with half-lives considerably shorter than either authentic ARF or chimaeras containing the entire coding domain, both of which are predominantly nucleolar. We present evidence that the unstable fusion proteins are significantly stabilized if redirected to the nucleolus by addition of a basic motif based on the nuclear localization signal of SV40 T-antigen. Moreover, the stability of these proteins can be enhanced by modulating the functions of MDM2 and p53. These data are consistent with a model in which ARF interacts with MDM2 in the nucleoplasm but is consequently subject to proteasomal degradation. Nucleolar localization may serve to store or stabilize ARF.
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PMID:Stability of nucleolar versus non-nucleolar forms of human p14(ARF). 1528 9

KP1019 [indazolium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] (FFC14A) is a metal complex with promising anticancer activity. Since chemoresistance is a major obstacle in chemotherapy, this study investigated the influence of several drug resistance mechanisms on the anticancer activity of KP1019. Here we demonstrate that the cytotoxic effects of KP1019 are neither substantially hampered by overexpression of the drug resistance proteins multidrug resistance-related protein 1, breast cancer resistance protein, and lung resistance protein nor the transferrin receptor and only marginally by the cellular p53 status. In contrast, P-glycoprotein overexpression weakly but significantly (up to 2-fold) reduced KP1019 activity. P-glycoprotein-related resistance was based on reduced intracellular KP1019 accumulation and reversible by known P-glycoprotein modulators. KP1019 dose dependently inhibited ATPase activity of P-glycoprotein with a K(i) of approximately 31 microM. Furthermore, it potently blocked P-glycoprotein-mediated rhodamine 123 efflux under serum-free conditions (EC(50), approximately 8 microM), however, with reduced activity at increased serum concentrations (EC(50) at 10% serum, approximately 35 microM). Moreover, P-glycoprotein-mediated daunomycin resistance could only be marginally restored by KP1019 in serum-containing medium, also indicating an influence of serum proteins on the interaction between KP1019 and P-glycoprotein. Acquired KP1019 resistance was investigated by selecting KB-3-1 cells against KP1019 for more than 1 year. Only an approximately 2-fold KP1019 resistance could be induced, which unexpectedly was not due to overexpression of P-glycoprotein or other efflux pumps. Accordingly, KP1019-resistant cells did not display reduced drug accumulation. Their unique cross-resistance pattern confirmed an ABC transporter-independent resistance phenotype. In summary, the likeliness of acquiring insensitivity to KP1019 during therapy is expected to be low, and resistance should not be based on overexpression of drug efflux transporters.
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PMID:Intrinsic and acquired forms of resistance against the anticancer ruthenium compound KP1019 [indazolium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] (FFC14A). 1533 56

Immortalized human fibroblasts were used to investigate the putative interactions of the Hsp90 molecular chaperone with the wild-type p53 tumor suppressor protein. We show that geldanamycin or radicicol, specific inhibitors of Hsp90, diminish specific wild-type p53 binding to the p21 promoter sequence. Consequently, these inhibitors decrease p21 mRNA levels, which lead to a reduction in cellular p21/Waf1 protein, known to induce cell cycle arrest. In control experiments, we show that neither geldanamycin nor radicicol affect p53 mRNA levels. A minor decrease in p53 protein level following the treatment of human fibroblasts with the inhibitors suggests the potential involvement of Hsp90 in the stabilization of wild-type p53. To support our in vivo findings, we used a reconstituted system with highly purified recombinant proteins to examine the effects of Hsp90 on wild-type p53 binding to the p21 promoter sequence. The human recombinant Hsp90 alpha-isoform as well as bovine brain Hsp90 were purified to homogeneity. Both of these molecular chaperones displayed ATPase activity and the ability to refold heat-inactivated luciferase in a geldanamycin- and radicicol-sensitive manner, suggesting that post-translational modifications are not involved in the modulation of Hsp90alpha activity. We show that the incubation of recombinant p53 at 37 degrees C decreases the level of its wild-type conformation and strongly inhibits the in vitro binding of p53 to the p21 promoter sequence. Interestingly, Hsp90 in an ATP-dependent manner can positively modulate p53 DNA binding after incubation at physiological temperature of 37 degrees C. Other recombinant human chaperones from Hsp70 and Hsp40 families were not able to efficiently substitute Hsp90 in this reaction. Consistent with our in vivo results, geldanamycin can suppress Hsp90 ability to regulate in vitro p53 DNA binding to the promoter sequence. In summary, the results presented in this article state that chaperone activity of Hsp90 is important for the transcriptional activity of genotypically wild-type p53.
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PMID:Hsp90 chaperones wild-type p53 tumor suppressor protein. 1535 69

Because beneficial effects of digitalis treatment in breast cancer patients have been suggested by epidemiological studies, we explored the mechanism of the growth inhibitory effects of these drugs on the estrogen receptor-negative human breast cancer cell line MDA-MB-435 s. Ouabain concentrations (100 nM or lower) that caused less than 25% inhibition of the pumping function of Na+/K+-ATPase had no effect on cell viability but inhibited proliferation. At the same concentrations, ouabain 1) activated Src kinase and stimulated the interaction of Src and Na+/K+-ATPase with epidermal growth factor receptor (EGFR); 2) caused a transient and then a sustained activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2); 3) increased the expression of p21Cip1 but decreased that of p53; and 4) activated c-Jun NH2-terminal kinase (JNK) but not p38 kinase. These data, in conjunction with our previous findings on the signaling role of Na+/K+-ATPase in other cells, suggest that ouabain-induced activation/transactivation of Src/EGFR by Na+/K+-ATPase leads to activation of ERK1/2, the resulting increase in the level of cell cycle inhibitor p21Cip1, and growth arrest. Cooperation of JNK with ERK1/2 in this process is also suggested. Digoxin and digitoxin concentrations close to or at the therapeutic plasma levels had effects on proliferation and ERK1/2 similar to those of ouabain, supporting the proposed potential value of digitalis drugs for the treatment of breast cancer.
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PMID:Digitalis-induced signaling by Na+/K+-ATPase in human breast cancer cells. 1560 3

We describe the construction and phenotypic characterization of 23 whey acidic protein (WAP)-mutp53 transgenic mouse lines. The mutp53-expressing lines showed a mosaic expression pattern for the transgenes, leading to a heterogeneous yet mouse line-specific expression pattern for mutp53 upon induction. Only few lines were obtained, in which the majority of the induced mammary epithelial cells expressed the mutp53 transgene, most of the transgenic lines did not express mutp53, or expressed the transgene in less than 2% of the induced mammary epithelial cells. Hormone requirements for mutp53 transgene expression from the WAP-promoter differed in high and low expressing lines, being low in high expressing lines, and even lower in multiparous mutp53 mice, where persistent expression of the transgene occurred. Repeated induction of mutp53 expression through repeated parturition resulted in the formation of expanding mutp53-expressing foci within the mammary alveolar epithelium. The data suggest that epigenetic mechanisms play a role in modulating the expression of the mutp53 transgene. To support this idea, we crossed a nonexpressing WAP-mutp53 line with a strongly SV40 T-antigen-expressing WAP-T mouse line. In the bitransgenic mice, T-antigen-induced chromatin remodeling led to re-expression of epigenetically silenced mutp53 transgene(s). In these mice, mutp53 expression was much more variable compared to SV40 T-antigen expression, and seemed to depend on the coexpression of SV40 T-antigen. Mutp53 expression in this system thus resembles the situation in many human tumors, where one can observe a heterogeneous expression of mutp53, despite a homogeneous distribution of the p53 mutation in the tumor cells.
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PMID:Epigenetic mechanisms affect mutant p53 transgene expression in WAP-mutp53 transgenic mice. 1587 Jul 6

Pluronic block copolymer P85 (P85) sensitizes multidrug resistant (MDR) cancer cells resulting in the increase of cytotoxic activity of antineoplastic agents. This effect is attributed to the inhibition of the most clinically relevant drug efflux transporter, P-glycoprotein (Pgp), through the combined ATP depletion and inhibition of Pgp ATPase activity. The present study elucidates effects of an anticancer agent, doxorubicin (Dox), formulated with P85 on drug-induced apoptosis in MDR cancer cells. Early and late stages of apoptosis were detected by Annexin V and TUNEL methods, respectively. In parallel experiments, the expression of genes related to apoptosis, BCL2, BCLXL, BAX, P53, APAF1, Caspase 3, and Caspase 9, was determined by RT-PCR. The obtained data suggest that Dox/P85 formulation induces apoptosis in the resistant cancer cells more efficiently than free Dox. The treatment of the cells with Dox alone simultaneously activated a proapoptotic signal and an antiapoptotic cellular defense. Therefore, the apoptosis induction by Dox was substantially limited. In contrast, the treatment of the cells with Dox/P85 formulation significantly enhanced the proapoptotic activity of the drug and prevented the activation of the antiapoptotic cellular defense. This is likely to result in the stronger cytotoxic response of the resistant cells to the Dox/P85 formulation compared to the free drug.
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PMID:Pluronic block copolymers alter apoptotic signal transduction of doxorubicin in drug-resistant cancer cells. 1593

Gankyrin is an ankyrin repeat oncoprotein commonly overexpressed in hepatocellular carcinomas. Gankyrin interacts with the S6 proteasomal ATPase and accelerates the degradation of the tumor suppressor Rb. We show here that gankyrin has an antiapoptotic activity in cells exposed to DNA damaging agents. Downregulation of gankyrin induces apoptosis in cells with wild-type p53. In vitro and in vivo experiments revealed that gankyrin binds to Mdm2, facilitating p53-Mdm2 binding, and increases ubiquitylation and degradation of p53. Gankyrin also enhances Mdm2 autoubiquitylation in the absence of p53. Downregulation of gankyrin reduced amounts of Mdm2 and p53 associated with the 26S proteasome. Thus, gankyrin is a cofactor that increases the activities of Mdm2 on p53 and probably targets polyubiquitylated p53 into the 26S proteasome.
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PMID:The oncoprotein gankyrin binds to MDM2/HDM2, enhancing ubiquitylation and degradation of p53. 1602

Prodigiosin (PG) is a bacterial red pigment with interesting immunosuppressive and apoptotic properties that have been partly attributed to its ability to uncouple V-ATPase through the promotion of the H+/Cl- symporter. In the present study, we investigate the effect of non-apoptotic concentrations of PG on the lysosomal-pH and on cell cycle progression in colon cancer cells. Lysosomal-pH was tested in DLD-1 cells using acridine orange vital staining. Orange granules, indicative of acidified lysosomes, decreased significantly in cells treated with 25 nM of PG for 1/2 h, and disappeared completely at 100 nM. This suggests that PG can induce lysosomal alkalinization without any apparent cytotoxic effect. Cell cycle progression was analysed in HT29 cells and we found that PG induces a blockage in the G1 phase. This blockage correlates with p21(WAF1/CIP1) induction, and it can be triggered either dependently or independently of p53. In conclusion, the reversible increase in lysosomal-pH and cytosol acidification induced by non-apoptotic concentrations of PG in colon cancer cells, suggests that the apoptotic process induced by PG can not be solely explained by changes in intracellular pH. The effect of intracellular acidification on cell cycle arrest must be analysed more exactly.
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PMID:Non-apoptotic concentrations of prodigiosin (H+/Cl- symporter) inhibit the acidification of lysosomes and induce cell cycle blockage in colon cancer cells. 1612 33


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