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)

Wild-type p53 is involved in several aspects of cell cycle control and suppression of transformation, inducing either apoptosis or G1 block in cell cycle progression. Using a recombinant adenovirus containing the wild-type p53 cDNA, the biological effects of the newly expressed wild-type p53 protein were examined in six human glioma cell lines. Three cell lines (U-251 MG, U-373 MG, and A-172) expressed endogenous mutant p53, and the other three (U-87 MG, EFC-2, and D54 MG) expressed wild-type p53. The restoration of normal p53-encoded protein in the mutant cell lines induced apoptosis as assessed by morphological studies using nuclear staining, electron microscopy, and flow cytometric assays. In wild-type p53 cell lines, however, the overexpression of wild-type p53 did not result in apoptosis but inhibited cellular proliferation rather drastically and modified the neoplastic phenotype. Differential effects suggest two pathways for glioma oncogenesis and a possible therapeutic strategy.
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PMID:Adenovirus-mediated transfer of the p53 gene produces rapid and generalized death of human glioma cells via apoptosis. 863 Sep 97

Gemcitabine (2',2'-difluoro-2'-deoxycytidine; dFdCyd) has been shown to be a potent radiosensitizer in tumor cells both in vitro and in vivo. We evaluated the ability of dFdCyd to enhance the radiosensitivity of two human glioblastoma cell lines. The results demonstrated that U251 cells were more sensitive to the cytotoxicity of dFdCyd, and that dFdCyd was able to radiosensitize these cells. In contrast, D54 cells were more resistant to the cytotoxic effect of dFdCyd, and no radiosensitization occurred at any concentration of dFdCyd tested. Because radiosensitization by dFdCyd has been correlated with its ability to deplete dATP pools through inhibition of ribonucleotide reductase by dFdCyd diphosphate, we evaluated the metabolism of dFdCyd in both cell lines. At equitoxic concentrations of dFdCyd, both cell lines accumulated similar levels of the cytotoxic metabolite, dFdCyd triphosphate, as well as similar levels of dFdCyd monophosphate in DNA. In U251 cells, radiosensitizing concentrations of dFdCyd (10 or 25 nM; IC10 or IC50) depleted dATP by approximately 80% within 4 h. In contrast, 80 nM (IC50) was unable to deplete dATP by >30% within 4 h in D54 cells. Higher concentrations of dFdCyd or hydroxyurea, an inhibitor of ribonucleotide reductase that depleted dATP >90%, also did not produce radiosensitization in D54 cells. D54 cells were not resistant to radiosensitization because bromodeoxyuridine was able to induce radiosensitization. Because D54 cells express wild-type p53, whereas U251 cells express a mutant p53, the effect of dFdCyd and ionizing radiation on cell cycle progression was evaluated. Radiation alone produced a G1 block in D54 cells and a transient G2-M block in U251 cells. After a 24 h incubation with dFdCyd alone or in combination with ionizing radiation, U251 cells readily accumulated in S-phase, which remained elevated for at least 72 h, consistent with previous results in other mutant p53 cell lines. In addition, radiation enhanced the ability of dFdCyd to induce S-phase-specific cell death in U251 cells. In contrast, D54 cells showed a G1 block after dFdCyd and radiation exposure, with fewer cells in S-phase for at least 48 h after drug washout/irradiation. Furthermore, treatment with dFdCyd and/or radiation did not increase the amount of S-phase-specific cell death in D54 cells compared with control cells. These results suggest that the G1 block in D54 cells resulting from wild-type p53 induction prevented radiosensitization by dFdCyd.
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PMID:The role of cell cycle progression in radiosensitization by 2',2'-difluoro-2'-deoxycytidine. 1108 31

We investigated the combined effects of p53 gene transfer and irradiation and its still unclear interaction mechanism in human gliomas. Four human glioma cell lines expressing mutant type p53 (U373 and A172) and wild-type p53 (D54MG and EFC-2) were transfected by adenoviral vectors bearing p53 gene at 50 multiplicity of infection. Two days after transfection, cells were irradiated (3, 6, and 9 Gy). The cytotoxicity was evaluated by clonogenic assay. The quantitative analysis of apoptosis and cell cycle analysis were performed using flow cytometry. Irradiation combined with adenoviral p53 transfection significantly increased cytotoxicity, which was additive in cell lines with wild-type p53 and more than additive in cell lines with mutant p53. The combination of two modalities increased the apoptotic population by 14% in A172 cells and 20% in D54 MG cells, which were the sum of apoptosis from each modality. Adenoviral p53 transfection increased the G1 phase fraction and concomitant decrease of radioresistant S phase fraction in A172 and D54MG cells. Our study demonstrated that p53 gene transfer combined with irradiation increased absolute cytotoxicity in human glioma cells used in this experiment. The interaction mechanism for increased cytotoxicity involved, in part, increased apoptosis and change of cell cycle profile.
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PMID:Potential of adenoviral p53 gene therapy and irradiation for the treatment of malignant gliomas. 1160 7

Therapeutic replacement of the p53 gene using an adenovirus vector (Ad-p53) may be an effective alternative to conventional therapies for the treatment of glioma. We have previously demonstrated that the introduction of Ad-p53 into glioma cells containing mutant p53 induces apoptosis, whereas glioma cells containing wild-type p53 are resistant. However, Ad-p53 will enhance the radiosensitivity of wild-type p53 glioma cells by increasing their tendency for apoptosis. The mechanism underlying these different responses to Ad-p53 has not been elucidated to date. Because phosphorylation of p53 at serines 15, 20, and 392 may play a role in regulating p53-mediated apoptotic activity, we determined the phosphorylation status of exogenous p53 in mutant and wild-type gliomas after Ad-p53 transfer. Monolayer cultures of glioma cell lines expressing mutant p53 (U251 and U373) or wild-type p53 (U87 and D54) were infected with Ad-p53 and analyzed by Western blotting. High levels of exogenous p53 were detected in both cell lines after Ad-p53 transfer. However, only apoptotic mutant p53 cells expressed high levels of phospho-Ser15-p53 and phospho-Ser20-p53. The levels of phospho-Ser15-p53 and phospho-Ser20-p53 were very low in wild-type p53 cells after Ad-p53 infection alone. When wild-type p53 glioma cells were exposed to radiation after Ad-p53 infection, phospho-Ser15-p53 and phospho-Ser20-p53 were detected at high levels, and the cells subsequently underwent apoptosis; no change in serine 392 was detected. The induction of apoptosis and the expression of phospho-Ser15 and phospho-Ser20 in these cells were also enhanced by the combination of Ad-p53 and other DNA-damaging agents such as cisplatin and bichloroethyl nitrosourea. Furthermore, the expression of phospho-Ser15-p53 and phospho-Ser20-p53 correlated with the amount of apoptosis; the apoptotic activity of p53 in glioma cells was partially inhibited by a mutation of p53 at serine 15. These results suggest that phosphorylation of p53 at serine 15 and serine 20 is critical for apoptosis induction in p53 gene therapy for gliomas.
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PMID:Apoptosis induced by adenovirus-mediated p53 gene transfer in human glioma correlates with site-specific phosphorylation. 1186 84

Several anticancer drugs target DNA or enzymes acting on the DNA. Because chromatin DNA is tightly compacted, accessibility to the drug target may reduce the efficiency of these anticancer drugs. We thus treated four human cancer cell lines and two normal epithelial cell lines with either trichostatin A (TSA) or SAHA, two histone deacetylase inhibitors, before exposing the cells to VP-16, ellipticine, camptothecin, doxorubicin, cisplatin, 5-fluorouracil, or cyclophosmamide. Pretreatment with TSA or SAHA increased the killing efficiency of VP-16, ellipticine, doxorubicin, and cisplatin. The magnitude of sensitization is cell type specific and is >10-fold for VP-16 in D54, a brain tumor cell line intrinsically resistant to topoisomerase II inhibitors. Topoisomerase II levels and activity were not affected by this treatment, but p53, p21, and Gadd45 protein levels were markedly induced. Moreover, pretreatment with TSA also increased VP-16-induced apoptosis in a p53-dependent and -independent manner. Treating the cells in the reverse order (anticancer drug first, followed by TSA or SAHA) had no more cytotoxic effect than the drug alone. These data suggest that loosening-up the chromatin structure by histone acetylation can increase the efficiency of several anticancer drugs targeting DNA. This may be advantageous for treating tumors intrinsically resistant to these drugs.
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PMID:Inhibition of histone deacetylase increases cytotoxicity to anticancer drugs targeting DNA. 1461 26

Adenoviral p53 gene transfer (Ad-p53) induces apoptosis in glioma cells expressing mutant p53, but fails in cells with wild-type p53. Endogenously, gliomas express varied levels of Fas/CD95, yet constitutively high levels of Fas/CD95 ligand. Because the mechanism behind the differential apoptotic response to Ad-p53 infection remains elusive, we examined how the Fas/CD95 pathway is involved in U87MG (wt-p53), D54 (wt-p53), U251MG (mutant-p53), and U373MG (mutant-p53) glioma cell lines. Ad-p53 infection did not alter the levels of Fas/CD95 ligand in either wild-type or mutant p53-expressing cell lines. In contrast, Ad-p53 infection led to an approximately 3-fold increase in Fas/CD95 mRNA expression in mutant p53-bearing cell lines but not in their wild-type (wt) counterparts, as assessed in an RNase protection assay. Fas/CD95 mRNA induction appeared to be regulated at the transcriptional level because Ad-p53 infection resulted in up to a 4-fold increase in Fas/CD95 promoter reporter activity. Subsequently, flow cytometric analysis revealed a 2- to 4-fold increase in surface Fas/CD95 expression following Ad-p53 infection in mutant-p53-containing cell lines. Use of the protein transport inhibitor Brefeldin A significantly inhibited Ad-p53-induced surface Fas/CD95 expression, but only partially inhibited apoptosis in mutant-p53 cell lines. These results suggest that p53 regulates Fas/CD95 expression at the transcriptional level and through protein trafficking in mutant-p53 cell lines. Fluorogenic activity assays demonstrated that induction of caspase-8 activity following Ad-p53 infection correlated with increases in Fas/CD95 expression. Incubating cells with a caspase-8-specific inhibitor Ac-IETD-CHO prior to Ad-p53 infection inhibited caspase-8 activity and apoptosis. Together, our results suggest that regulation of the Fas/CD95 pathway is partly responsible for Ad-p53-induced apoptosis in glioma cells, which depends on the p53 status of the involved cells. Additionally, the inability of Ad-p53 to activate the Fas/CD95 pathway in wt-p53 glioma cells coincides with their apoptotic-resistant phenotype. Further elucidation of the nature of this resistance could ultimately augment the efficacy of Ad-p53 gene therapy.
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PMID:Differential activation of the Fas/CD95 pathway by Ad-p53 in human gliomas. 1471 18

D-24851 is a recently developed microtubule inhibitor that induces G2/M cell-cycle arrest and has an antitumor effect in many cancer cell types. It is expected to be a promising chemotherapeutic agent against a broad range of tumors. However, the precise mechanisms underlying its antitumor effect remain to be determined. Here, we investigated the in vitro effect of D-24851 on tumor growth and the apoptosis mechanism in human malignant glioma cells. Because both p53-dependent and -independent pathways of apoptosis have been reported, we used cell lines with wild-type p53 (U87-MG and D54) and cell lines with mutant p53 (U373-MG and T98G) and compared their responses to D-24851. D-24851 substantially inhibited the proliferation of the four glioma cell lines tested in a dose- and time-dependent manner. The inhibitory effect of D-24851 on tumor growth was associated with cell-cycle arrest in G2/M, subsequently inducing apoptosis. D-24851 treatment induced phosphorylated Bcl-2 and translocated Bax from the cytoplasm to the mitochondria, resulting in apoptotic cell death. These events took place regardless of the p53 status of tumor cells. Our results indicated that D-24851 effectively induces apoptosis through Bcl-2 phosphorylation and Bax translocation in human malignant glioma cells in a p53-independent manner. The results of this study make D-24851 even more promising as a therapeutic agent, especially because many malignant gliomas have a heterogeneous p53 status.
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PMID:Microtubule inhibitor D-24851 induces p53-independent apoptotic cell death in malignant glioma cells through Bcl-2 phosphorylation and Bax translocation. 1570 12

Replication-competent oncolytic adenoviruses hold considerable promise for treating malignant gliomas. The toxicity of the clinically tested E1B-55 kDa mutant virus is negligible; however, its full clinical potential is still being evaluated. The purpose of the present study is to compare the antiglioma activity in vitro and in vivo between Delta-24, an E1A mutant adenovirus, and RA55, an E1B-55 kDa mutant adenovirus. We selected human glioma cell lines that were tumorigenic in nude mice and express wild-type p53 (U-87 MG, D54 MG) or mutant p53 (U-251 MG, U-373 MG) protein. Our studies demonstrated that Delta-24 induced a more potent antiglioma effect in vitro than RA55. Moreover, Delta-24 replicated markedly more efficiently than RA55 in both wild-type and mutant p53 scenarios. Importantly, direct intratumoral injection of Delta-24, but not RA55, significantly suppresses tumor growth in intracranial (U-87 MG, U-251 MG) or subcutaneous (D54 MG) animal models. Staining for hexon protein detected replicating adenoviruses in xenografts infected with Delta-24, but not with RA55. Collectively, these data indicate that E1A mutant adenoviruses targeting the Rb pathway are more powerful putative agents for antiglioma therapy than E1B mutant adenoviruses, and suggest that E1A mutant adenoviruses should be tested in the clinical setting for patients with malignant gliomas.
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PMID:Comparative effect of oncolytic adenoviruses with E1A-55 kDa or E1B-55 kDa deletions in malignant gliomas. 1572 Aug 16

Replacement of the p53 tumor suppressor gene is a rational approach to the management of malignant gliomas because p53 is frequently mutated or inactivated in these cancers. Major weaknesses of this approach are that malignant gliomas are mixtures of cells with wild-type and mutant p53, and that tumor cells exhibiting wildtype p53 are resistant to p53 gene transfer. An effective alternative is needed to overcome these difficulties. p53-upregulated modulator of apoptosis (PUMA) was identified as a p53-inducible proapoptotic molecule. Our purpose was to elucidate a role for PUMA in p53 gene therapy and to investigate whether PUMA is an efficient substitute for p53 in cancer therapy. We demonstrated that PUMA was upregulated in mutant p53 malignant glioma cells (U373-MG and T98G) undergoing apoptosis but was not upregulated in apoptosis-resistant wild-type p53 malignant glioma cells (U87-MG and D54) after adenoviral transfer of p53. Overexpression of PUMA resulted in massive apoptosis associated with mitochondrial damage and caspase-3 activation in all tumor cells tested. Use of the human telomerase reverse transcriptase (hTERT) promoter system induced apoptosis only in malignant glioma cells with telomerase activity, while sparing normal cells lacking telomerase. The ability of PUMA to induce apoptosis was greater than that of caspase-6 or caspase-8 transfer, using the same system. Moreover, exogenous expression of PUMA under the hTERT promoter system significantly suppressed the growth of subcutaneous U87-MG tumors in nude mice and did not induce apoptosis in surrounding nontumor tissues. These results indicate that PUMA, which is regulated under a tumor-specific expression system such as the hTERT promoter, may be better than p53 as a therapeutic tool for malignant gliomas.
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PMID:Therapeutic efficacy of PUMA for malignant glioma cells regardless of p53 status. 1596 Jun

p53 inactivation sensitizes U87MG astrocytic glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and temozolomide (TMZ), drugs used clinically to treat high-grade astrocytomas. In this report, we examined the effect of p53 inactivation on the chemosensitivity of two additional human astrocytic glioma cell lines, D54 and A172, in order to assess whether sensitization is a general property of astrocytic tumor cells. Compared to control cells with intact p53 function, derived lines in which p53 was inactivated displayed significantly reduced clonogenic survival after exposure to BCNU and TMZ. Sensitization to both BCNU and TMZ was associated with failure of p21(WAF1) induction, lack of a sustained G2 cell cycle arrest and significant tumor cell death. These findings suggest that enhanced sensitivity to BCNU and TMZ is a general property of human astrocytic glioma cells in which p53 was disrupted. In contrast, p53 inactivation rendered D54 and U87MG cells significantly more resistant to cis-dichlorodiamminoplatinum (CDDP), another chemotherapeutic to which high-grade astrocytomas sometimes respond. These results indicate that p53 status influences the chemosensitivity of astrocytic glioma cells in a drug-type specific manner, a finding that may have implications for the selection of drug treatments for patients with astrocytic gliomas.
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PMID:Inactivation of p53 sensitizes astrocytic glioma cells to BCNU and temozolomide, but not cisplatin. 1619 84


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