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)

Loss of cell cycle control and acquisition of chromosomal rearrangements such as gene amplification often occur during tumor progression, suggesting that they may be correlated. We show here that the wild-type p53 allele is lost when fibroblasts from patients with the Li-Fraumeni syndrome (LFS) are passaged in vitro. Normal and LFS cells containing wild-type p53 arrested in G1 when challenged with the uridine biosynthesis inhibitor PALA and did not undergo PALA-selected gene amplification. The converse occurred in cells lacking wild-type p53 expression. Expression of wild-type p53 in transformants of immortal and tumor cells containing mutant p53 alleles restored G1 control and reduced the frequency of gene amplification to undetectable levels. These studies reveal that p53 contributes to a metabolically regulated G1 check-point, and they provide a model for understanding how abnormal cell cycle progression leads to the genetic rearrangements involved in tumor progression.
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PMID:Wild-type p53 restores cell cycle control and inhibits gene amplification in cells with mutant p53 alleles. 152 30

We have previously shown that the carboxyl-terminal tryptic peptide of the tumor suppressor p53 coeluted from reverse-phase high-performance liquid chromatography (HPLC) with ribonucleotides, suggesting the possible linkage of RNA to p53. In this report, we establish that p53 is covalently linked to RNA, using biochemical criteria at the levels of both tryptic peptide and intact protein: the electrophoretic properties of a tryptic peptide containing phosphorylated Ser-389 and the HPLC chromatographic properties of p53 depend on the linked RNA, p53, purified through urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and HPLC, copurifies with RNA, and Ser-389 liberates ribonucleotides upon RNase or alkali treatment. Wild-type and mutant p53s from both simian virus 40 (SV40)-transformed and SV40-nontransformed cells are RNA linked, indicating that RNA linkage may be a general property of p53. The RNA is labeled in vivo with 3H-uridine and in vitro by RNA ligase, suggesting that the RNA is bound by a 5' linkage. The RNA is a long-lived, integral component of p53 rather than a transient reaction intermediate. RNA linkage occurs at an evolutionarily conserved site on p53. We propose that RNA-linked p53 is a major biologically active form of p53 and that its interaction with RNA-linked SV40 T antigen reflects a role in RNA metabolism.
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PMID:The tumor suppressor p53 is bound to RNA by a stable covalent linkage. 170 9

The aim was to determine whether proton magnetic resonance spectroscopy (MRS) could grade human colorectal cells of differing malignant potential. A cell model of tumour development and progression comprising 2 non-tumorigenic adenoma lines and 4 carcinoma lines of increasing tumorigenicity was chosen. A gradual reduction in cellular differentiation and an accumulation of genetic alterations from adenoma to carcinoma characterized the selected cell lines. One-dimensional and 2-dimensional MRS showed that reduced differentiation in the cell model correlated with an increase in the levels of lipid, metabolites, the glycosylation intermediate uridine diphospho-N-acetylglucosamine and cell-surface fucosylation. Mutations involving the K-ras, APC and DCC genes are present both in adenoma- and in carcinoma-derived lines in this model, but the first evidence of an abnormality in the p53 gene was concomitant with the cells' ability to grow as a tumour in athymic nude mice. This genetic change coincided with the detection, by MRS, of UDP-hexose (ribose moiety, 2D MRS cross peak between H2 at 4.38 ppm and HI at 5.99 ppm) and the appearance of an additional fucosyl resonance (cross peak between-CH3 at 1.41 and H5 at 4.30 ppm) in the least tumorigenic of the carcinoma cell lines. An increase in complexity of the fucosylation spectral pattern was observed with further cellular de-differentiation and increased tumorigenicity. Collectively these data support the existence of an adenoma-carcinoma sequence.
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PMID:Correlation of cellular differentiation in human colorectal carcinoma and adenoma cell lines with metabolite profiles determined by 1H magnetic resonance spectroscopy. 792 26

The epithelia from the crypts of the intestine are exquisitely sensitive to metabolic perturbation and undergo cell death with the classical morphology of apoptosis. Administration of 40 mg/kg 5-fluorouracil (5-FU) to BDF-1 p53+/+ mice resulted in an increase in p53 protein at cell positions in the crypts that were also those subjected to an apoptotic cell death. In p53-/- mice apoptosis was almost completely absent, even after 24 hr. 5-FU is a pyrimidine antimetabolite cytotoxin with multiple mechanisms of action, including inhibition of thymidylate synthase (TS), which gives rise to DNA damage, and incorporation into RNA. The inhibition of TS can be increased by coadministration of folinic acid and can be abrogated by administration of thymidine. The incorporation of 5-FU into RNA is inhibited by administration of uridine. p53-Dependent cell death induced by 5-FU was only inhibited by administration of uridine. Uridine had no effect on the apoptosis initiated by 1 Gy of gamma-radiation. Although thymidine abrogated apoptosis induced by the pure TS inhibitor Tomudex, it had no effect on 5-FU-induced apoptosis, and coadministration of folinic acid did not increase apoptosis. The data show that 5-FU-induced cell death of intestinal epithelial cells is p53-dependent and suggests that changes in RNA metabolism initiate events culminating in the expression of p53.
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PMID:Inhibition by uridine but not thymidine of p53-dependent intestinal apoptosis initiated by 5-fluorouracil: evidence for the involvement of RNA perturbation. 905 Aug 58

Transgenic mice carrying the c-myc oncogene under control of woodchuck hepatitis virus (WHV) DNA sequences invariably develop hepatocellular carcinoma (HCC), despite a temporally limited expression of the transgene in the neonatal liver. To better characterize the different steps of the tumorigenic process, we analyzed the liver expression of the c-myc transgene and several growth-related genes by in situ hybridization and Northern blotting. In parallel studies, proliferated changes were investigated by detection of bromodeoxy-uridine-positive S-phase nuclei and apoptosis was evaluated by in situ nick end-labeling of DNA. During the neonatal period, high levels of c-myc messenger RNAs (mRNAs) were detected in all hepatocytes, and the expression of insulin-like growth factor II (IGF II) was frequently enhanced, correlating with increased cell proliferation. Despite elevated expression of the p53 gene, no change in liver cell apoptosis was observed. After weaning, c-myc transgene expression decreased to undetectable levels in all hepatocytes, whereas proliferation decreased but remained notably higher than in age-matched controls. The expression of c-fos, c-jun, and c-H-ras was highly variable during the preneoplastic period and in the tumors, with no consistent increase compared with controls. Resurgence of c-myc transgene expression was evidenced in all cells from hyperplastic lesions and carcinomas, accompanied with frequent focal reactivation of IGF II. Thus the strong proliferative stimulus induced by the combined effects of c-myc and IGF II in the neonatal liver might initiate a process characterized by persistent, dysregulated hepatocyte proliferation, in turn greatly increasing the risk of hepatocellular transformation.
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PMID:Hepatocarcinogenesis in woodchuck hepatitis virus/c-myc mice: sustained cell proliferation and biphasic activation of insulin-like growth factor II. 909 91

We compared the biological activity of a new group of keto-C-glycosides to that of a narrow spectrum of unsaturated ketonucleosides in a panel of non-small-cell lung cancer (NSCLC) cells with various levels of intrinsic resistance to standard chemotherapy drugs. Unlike cisplatin, etoposide, adriamycin, or taxol, for which a significant difference in the cytotoxic effect was observed between sensitive cell lines (H460, H125, and MGH4) and drug-resistant cell lines (H661, MGH7, and FADU), nucleoside analogs were equally cytotoxic in NSCLC cell lines, with compound 92 being 10-fold more active than compound 43, 44, 81, or 161, while compound 3 was the least active. Apoptotic measurements with flow cytometric analysis of terminal uridine deoxynucleotide nick end-labeled cells revealed that the cytotoxic activity of these nucleosides correlated with their potency to induce apoptosis. Compound 92 triggered death in cells with wild-type p53, mutated p53, or p53 gene deletion. Our findings suggest that keto-C-glycosides may be promising alternative anticancer agents which merit further studies in in vivo cancer models refractory to standard chemotherapy drugs.
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PMID:Antiproliferative and apoptotic activities of ketonucleosides and keto-C-glycosides against non-small-cell lung cancer cells with intrinsic drug resistance. 955 82

Leflunomide, a novel drug with proven efficacy in rheumatoid arthritis, is an isoxazol derivative structurally unrelated to other immunomodulatory drugs. Leflunomide is rapidly metabolized to its active form, A77 1726. Two mechanisms of action have been identified for A77 1726: inhibition of dihydroorotate dehydrogenase (DHODH) and inhibition of tyrosine kinases. DHODH inhibition occurs at lower concentrations of A77 1726 than that of tyrosine kinases and is currently considered the major mode of action. Stimulated lymphocytes must increase ribonucleotide levels from 8 to 16-fold before proceeding from the G1 into the S phase. Increased levels of ribonucleotides can only be met by de novo ribonucleotide synthesis. At low levels of ribonucleotides, p53, a "sensor" molecule, gets activated and prevents progression through the cell cycle. Therefore, an inhibitor of de novo uridine monophosphate synthesis would predictably arrest stimulated cells at the G1 phase. In support of this mechanism of action, in vitro mitogen stimulated human peripheral blood lymphocytes treated with A77 1726 undergo arrest at the G1 phase; this inhibition is reversed by uridine.
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PMID:Mechanism of action of leflunomide in rheumatoid arthritis. 966 14

N-(trifluoromethylphenyl)-2-cyano-3-hydroxy-crotonic acid amide (A77 1726), the physiologically active metabolite of leflunomide, has been described to exert antiproliferative effects in vitro and anti-inflammatory actions in several animal models. Currently, its use is being evaluated in clinical trials in psoriasis, which is characterized by epidermal hyperproliferation and infiltration of inflammatory cells. We studied the effects of A77 1726 on growth and gene expression in cultured epidermal cells by 5-bromo-2'-deoxy-uridine (BrdU) incorporation, reverse transcriptase-polymerase chain reaction (RT-PCR), Northern blot hybridizations and flow cytometry. A77 1726 inhibited epidermal proliferation at concentrations above 5 microM after 24 hr. However, the cells were still fully viable at a concentration of 100 microM. The drug caused a dose-dependent reduction in the mRNA level of the type A receptor for the proinflammatory cytokine interleukin-8 (IL-8-RA) and, in contrast, induced gene expression of the receptor for the anti-inflammatory cytokine IL-10 (IL-10R) at the mRNA and protein levels. In addition, the mRNA and protein levels of the p53 gene, which is a negative cell cycle regulator, were up-regulated by A77 1726. These data suggest that A77 1726 exerts its anti-inflammatory action via the modulation of epidermal gene expression.
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PMID:Differential modulation of pro- and anti-inflammatory cytokine receptors by N-(4-trifluoromethylphenyl)-2-cyano-3-hydroxy-crotonic acid amide (A77 1726), the physiologically active metabolite of the novel immunomodulator leflunomide. 1007 46

Uridine phosphorylase (UPase) plays an important role in the activation of 5-fluorouracil and in the regulation of tissue and plasma concentration of uridine, a potential biochemical modulator of 5-fluorouracil therapy. UPase expression is affected by the c-H-ras oncogene and various cytokines through unknown mechanisms. To understand its expression and regulation, we cloned the murine UPase gene, defined its genomic organization, determined its 5'- and 3'-end flanking sequences, and evaluated the promoter activity. The UPase gene contains nine exons and eight introns, spanning a total of approximately 18.0 kb. Its promoter lacks canonical TATA and CCAAT boxes, although a CAATAAAAA TATA-like box is seen from -41 to -49. Furthermore, IFN regulatory factor 1, c/v-Myb, and p53 binding sites are present in the promoter region, indicating that UPase expression may be directly regulated by cytokines and oncogene products. The 1.2-kb flanking fragment showed promoter activity driving the expression of the luciferase gene in various mammalian cells. A TGGGG repeat sequence is seen in the 3'-end flanking region. This element is considered to be a potential recombination consensus hot spot that may contribute to the encoding of different UPase isoforms present in different tissues, both normal and neoplastic.
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PMID:Genomic structure, chromosomal mapping, and promoter region analysis of murine uridine phosphorylase gene. 1051 14

Leflunomide (Arava) has recently been approved by the Food and Drug Administration for the treatment of rheumatoid arthritis (RA). This approval was based on data from a double-blind, multicenter trials in the United States (leflunomide versus methotrexate versus placebo) in which leflunomide was superior to placebo and similar to methotrexate (Strand et al., Arch. Intern. Med., in press, 1999). In a multicenter European trial, leflunomide was similar to sulfasalazine in efficacy and side effects (Smolen et al., Lancet 353, 259-266, 1999). Both methotrexate and leflunomide retarded the rate of radiolographic progression, entitling them to qualify as disease-modifying agents (Strand et al., Arch. Intern. Med., in press, 1999). Leflunomide is an immunomodulatory drug that may exert its effects by inhibiting the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH), which plays a key role in the de novo synthesis of the pyrimidine ribonucleotide uridine monophosphate (rUMP). The inhibition of human DHODH by A77 1726, the active metabolite of leflunomide, occurs at levels (approximately 600 nM) that are achieved during treatment of RA. We propose that leflunomide prevents the expansion of activated and autoimmune lymphocytes by interfering with the cell cycle progression due to inadequate production of rUMP and utilizing mechanisms involving p53. The relative lack of toxicity of A77 1726 on nonlymphoid cells may be due to the ability of these cells to fulfill their ribonucleotide requirements by use of salvage pyrimidine pathway, which makes them less dependent on de novo synthesis.
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PMID:Mechanism of action for leflunomide in rheumatoid arthritis. 1060 Mar 30


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