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)

We have previously shown that in interspecific mouse-human melanoma cell hybrids obtained by fusion of nonmetastatic mouse with metastatic human melanoma cells, the metastatic phenotype predominates. The purpose of this study was to identify human chromosome(s) which could be responsible for conferring metastatic potential upon nonmetastatic mouse melanoma cells and therefore harbor the genes important for the metastatic properties of human melanoma cells. Seven mouse-human melanoma hybrids were examined; five were derived from the fusion of nonmetastatic (C19) and metastatic (C3) mouse K-1735 melanoma clones with highly metastatic clone (C15) of human melanoma A375 and the two others had as a human partner a nonmetastatic clone (Cls) of the A375 melanoma. The hybrids were examined during segregation of human chromosomes in vitro and in vivo for metastatic properties in nude mice and for the retaining human chromosomes. In the hybrid H7, which demonstrated the highest metastatic potential, the presence of human chromosomes was studied by GTG-banding and by fluorescence in situ hybridization (FISH) analysis. In the other hybrids, only FISH detection of human chromosomes was applied. All hybrids derived from nonmetastatic mouse and metastatic human melanoma cells demonstrated metastatic properties from early passages, when they contained the majority of the human chromosomes. Their metastatic phenotype remained stable during further segregation of most of the human chromosomes except for 17. Chromosome 17 was retained most consistently in all examined hybrids. However, the metastatic phenotype of the hybrids was associated only with the presence of chromosome 17 from the metastatic human donor cells. This chromosome was also found in almost 100% of cells recovered from lung metastases derived from the hybrid cells. In one lung metastasis developed from the H7 hybrid, chromosome 17 was detected as the sole human chromosome and these cells preserved the acquired high metastatic properties. Based on these results we conclude that human chromosome 17 from metastatic melanoma cells (A375 C15), when functional in the mouse genetic background, can be sufficient to render the recipient nonmetastatic mouse cells to a fully malignant phenotype. Additional data suggest that this ability might be related to the expression of the mutated human p53 gene.
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PMID:Metastatic phenotype of mouse-human melanoma cell hybrids is associated with the presence of chromosome 17 from highly metastatic human melanoma cells. 2154 4

Nucleostemin (NS), a member of a family of nucleolar GTP-binding proteins, is highly expressed in proliferating cells such as stem and cancer cells and is involved in the control of cell cycle progression. Both depletion and overexpression of NS result in stabilization of the tumor suppressor p53 protein in vitro. Although it has been previously suggested that NS has p53-independent functions, these to date remain unknown. Here, we report two zebrafish mutants recovered from forward and reverse genetic screens that carry loss of function mutations in two members of this nucleolar protein family, Guanine nucleotide binding-protein-like 2 (Gnl2) and Gnl3/NS. We demonstrate that these proteins are required for correct timing of cell cycle exit and subsequent neural differentiation in the brain and retina. Concomitantly, we observe aberrant expression of the cell cycle regulators cyclinD1 and p57kip2. Our models demonstrate that the loss of Gnl2 or NS induces p53 stabilization and p53-mediated apoptosis. However, the retinal differentiation defects are independent of p53 activation. Furthermore, this work demonstrates that Gnl2 and NS have both non-cell autonomously and cell-autonomous function in correct timing of cell cycle exit and neural differentiation. Finally, the data suggest that Gnl2 and NS affect cell cycle exit of neural progenitors by regulating the expression of cell cycle regulators independently of p53.
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PMID:The nucleolar GTP-binding proteins Gnl2 and nucleostemin are required for retinal neurogenesis in developing zebrafish. 2156 80

Neurofibromatosis type-1 (NF1), caused by heterozygous inactivation of the NF1 tumour suppressor gene, is associated with the development of benign and malignant peripheral nerve sheath tumours (MPNSTs). Although numerous germline NF1 mutations have been identified, relatively few somatic NF1 mutations have been described in neurofibromas. Here we have screened 109 cutaneous neurofibromas, excised from 46 unrelated NF1 patients, for somatic NF1 mutations. NF1 mutation screening (involving loss-of-heterozygosity (LOH) analysis, multiplex ligation-dependent probe amplification and DNA sequencing) identified 77 somatic NF1 point mutations, of which 53 were novel. LOH spanning the NF1 gene region was evident in 25 neurofibromas, but in contrast to previous data from MPNSTs, it was absent at the TP53, CDKN2A and RB1 gene loci. Analysis of DNA/RNA from neurofibroma-derived Schwann cell cultures revealed NF1 mutations in four tumours whose presence had been overlooked in the tumour DNA. Bioinformatics analysis suggested that four of seven novel somatic NF1 missense mutations (p.A330T, p.Q519P, p.A776T, p.S1463F) could be of functional/clinical significance. Functional analysis confirmed this prediction for p.S1463F, located within the GTPase-activating protein-related domain, as this mutation resulted in a 150-fold increase in activated GTP-bound Ras. Comparison of the relative frequencies of the different types of somatic NF1 mutation observed with those of their previously reported germline counterparts revealed significant (P=0.001) differences. Although non-identical somatic mutations involving either the same or adjacent nucleotides were identified in three pairs of tumours from the same patients (P<0.0002), no association was noted between the type of germline and somatic NF1 lesion within the same individual.
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PMID:Exploring the somatic NF1 mutational spectrum associated with NF1 cutaneous neurofibromas. 2210 4

p53 is a well-known transcription factor that controls cell cycle arrest and cell death in response to a wide range of stresses. Moreover, p53 regulates glucose metabolism and its mutation results in the metabolic switch to the Warburg effect found in cancer cells. Nucleotide biosynthesis is also critical for cell proliferation and the cell division cycle. Nonetheless, little is known about whether p53 regulates nucleotide biosynthesis. Here we demonstrated that p53-inducible microRNA-34a (miR-34a) repressed inosine 5'-monophosphate dehydrogenase (IMPDH), a rate-limiting enzyme of de novo GTP biosynthesis. Treatment with anti-miR-34a inhibitor relieved the expression of IMPDH upon DNA damage. Ultimately, miR-34a-mediated inhibition of IMPDH resulted in repressed activation of the GTP-dependent Ras signaling pathway. In summary, we suggest that p53 has a novel function in regulating purine biosynthesis, aided by miR-34a-dependent IMPDH repression.
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PMID:A p53-inducible microRNA-34a downregulates Ras signaling by targeting IMPDH. 2230 Nov 90

Nucleostemin (NS) is a nucleolar GTP-binding protein essential for ribosomal biogenesis, proliferation, and animal embryogenesis. It remains largely unclear how this protein is regulated. While working on its role in suppression of MDM2 and activation of p53, we observed that NS protein (but not mRNA) levels decreased drastically in response to GTP depletion. When trying to further elucidate the molecular mechanism(s) underlying this unusual phenomenon, we found that NS was degraded independently of ubiquitin and MDM2 upon GTP depletion. First, depletion of GTP by treating cells with mycophenolic acid decreased the level of NS without apparently affecting the levels of other nucleolar proteins. Second, mutant NS defective in GTP binding and exported to the nucleoplasm was much less stable than wild-type NS. Although NS was ubiquitinated in cells, its polyubiquitination was independent of Lys-48 or Lys-63 in the ubiquitin molecule. Inactivation of E1 in E1 temperature-sensitive mouse embryonic fibroblast (MEF) cells failed to prevent the proteasomal degradation of NS. The proteasomal turnover of NS was also MDM2-independent, as its half-life in p53/MDM2 double knock-out MEF cells was the same as that in wild-type MEF cells. Moreover, NS ubiquitination was MDM2-independent. Mycophenolic acid or doxorubicin induced NS degradation in various human cancerous cells regardless of the status of MDM2. Hence, these results indicate that NS undergoes a ubiquitin- and MDM2-independent proteasomal degradation when intracellular GTP levels are markedly reduced and also suggest that ubiquitination of NS may be involved in regulation of its function rather than stability.
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PMID:Ubiquitin- and MDM2 E3 ligase-independent proteasomal turnover of nucleostemin in response to GTP depletion. 2231 25

CRM1 (Chromosomal Maintenance 1, also known as Exportin 1) is the major mammalian export protein that facilitates the transport of large macromolecules including RNA and protein across the nuclear membrane to the cytoplasm. The gene encoding CRM1 was originally identified in yeast as required to maintain higher order chromosome structure. In mammalian cells, CRM1 was found to bind several nuclear pore proteins hence its role in nuclear-cytosolic transport was discovered. In addition to nuclear-cytosolic transport, CRM1 also plays a role in centrosome duplication and spindle assembly, especially in response to DNA damage. The crystal structure of CRM1 suggests a complex protein that binds the Ran protein bound to GTP, allowing for a conformational change that facilitates binding to different cargo proteins through a nuclear export signal (NES). Included in the cadre of cargo are multiple tumor suppressor and oncoproteins as p53, BRCA1, Survivin, NPM, and APC, which function in the nucleus to regulate transcription or aid in chromosomal assembly and movement. An imbalance in the cytosolic level of these proteins has been observed in cancer cells, resulting in either inactivation (tumor suppressor) or an excess of anti-apoptotic activity (oncoprotein). Thus, the concept of inhibiting CRM1 has been explored as a potential therapeutic intervention. Indeed, inhibition of CRM1 by a variety of small molecules that interfere with cargo-NES binding results in cancer cell death. Whether all of these proteins together are responsible for this phenotype or whether specific proteins are required for this effect is unclear at this time.
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PMID:The CRM1 nuclear export protein in normal development and disease. 2277 55

The ASPP2 (also known as 53BP2L) tumor suppressor is a proapoptotic member of a family of p53 binding proteins that functions in part by enhancing p53-dependent apoptosis via its C-terminal p53-binding domain. Mounting evidence also suggests that ASPP2 harbors important nonapoptotic p53-independent functions. Structural studies identify a small G protein Ras-association domain in the ASPP2 N terminus. Because Ras-induced senescence is a barrier to tumor formation in normal cells, we investigated whether ASPP2 could bind Ras and stimulate the protein kinase Raf/MEK/ERK signaling cascade. We now show that ASPP2 binds to Ras-GTP at the plasma membrane and stimulates Ras-induced signaling and pERK1/2 levels via promoting Ras-GTP loading, B-Raf/C-Raf dimerization, and C-Raf phosphorylation. These functions require the ASPP2 N terminus because BBP (also known as 53BP2S), an alternatively spliced ASPP2 isoform lacking the N terminus, was defective in binding Ras-GTP and stimulating Raf/MEK/ERK signaling. Decreased ASPP2 levels attenuated H-RasV12-induced senescence in normal human fibroblasts and neonatal human epidermal keratinocytes. Together, our results reveal a mechanism for ASPP2 tumor suppressor function via direct interaction with Ras-GTP to stimulate Ras-induced senescence in nontransformed human cells.
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PMID:N terminus of ASPP2 binds to Ras and enhances Ras/Raf/MEK/ERK activation to promote oncogene-induced senescence. 2324 3

The NF1 tumor suppressor protein neurofibromin is a negative regulator of Ras. Neurofibromin is dynamically regulated by the proteasome, and its degradation and reexpression are essential for maintaining appropriate levels of Ras-GTP. Like p53, NF1/neurofibromin can be inactivated in cancer by both mutations and excessive proteasomal destruction; however, little is known about the mechanisms that underlie this latter process. Here, we show that a Cullin 3 (Cul3)/kelch repeat and BTB domain-containing 7 complex controls both the regulated proteasomal degradation of neurofibromin and the pathogenic destabilization of neurofibromin in glioblastomas. Importantly, RNAi-mediated Cul3 ablation and a dominant-negative Cul3 directly stabilize neurofibromin, suppress Ras and extracellular signal-regulated kinase, and inhibit proliferation in an NF1-dependent manner. Moreover, in glioblastomas where neurofibromin is chronically destabilized, Cul3 inhibition restabilizes the protein and suppresses tumor development. Collectively, these studies show a previously unrecognized role for Cul3 in regulating Ras and provide a molecular framework that can be exploited to develop potential cancer therapies.
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PMID:Identifying the Ubiquitin Ligase complex that regulates the NF1 tumor suppressor and Ras. 2366 52

Nucleostemin is a GTP-conjugated protein located in the nucleoli of stem cells and certain cancer cells, and maintains cellular self-renewal. The present study aimed to evaluate nucleostemin as a potential target for pituitary adenoma gene therapy by investigating nucleostemin and apoptosis-stimulating of p53 protein 2 (ASPP2) expression and their effect on pituitary adenoma cell proliferation. A total of 71 samples of pituitary adenomas were collected. Semi-quantitative PCR was used to detect the expression of nucleostemin and ASPP2 mRNA in the samples. Immunochemistry techniques were used to examine Ki-67 expression in the paraffin section of the samples. Coherent clinical data were also collected. Nucleostemin and ASPP2 were detectable in all the pituitary adenoma samples. Significant differences were observed in nucleostemin and ASPP2 expression between invasive pituitary adenoma and non-invasive pituitary adenomas (P<0.01) and the Ki-67 labeling index (LI; P>0.05). The difference in the Ki-67 LI between the recurrence and non-recurrence groups was significant (P<0.05). There was positive correlation between nucleostemin gene expression and the Ki-67 LI levels (P<0.05). The correlation between ASPP2 expression and the Ki-67 LI was negative (P<0.05). Negative correlation was demonstrated between nucleostemin and ASPP2 expression (P<0.01). The nucleostemin and ASPP2 genes were expressed in the human pituitary adenoma tissues. The differences in the expression of nucleostemin, ASPP2 and Ki-67 in the various pathological types of pituitary adenomas represented differences in molecular biological character and were associated with invasion. In the pituitary adenomas, the expression of nucleostemin and ASPP2 was correlated with tumor proliferation. Nucleostemin, ASPP2 and Ki-67 may serve as valid clinical detection markers for the invasion of pituitary adenomas.
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PMID:Nucleostemin and ASPP2 expression is correlated with pituitary adenoma proliferation. 2417 15

Chemotherapy remains the common therapeutic for patients with lung cancer. Novel, selective antitumor agents are pressingly needed. This study is the first to investigate a different, however, effective antitumor drug candidate Wentilactone A (WA) for its development as a novel agent. In NCI-H460 and NCI-H446 cell lines, WA triggered G2/M phase arrest and mitochondrial-related apoptosis, accompanying the accumulation of reactive oxygen species (ROS). It also induced activation of mitogen-activated protein kinase and p53 and increased expression of p21. When we pre-treated cells with ERK, JNK, p38, p53 inhibitor or NAC followed by WA treatment, only ERK and p53 inhibitors blocked WA-induced apoptosis and G2/M arrest. We further observed Ras (HRas, KRas and NRas) and Raf activation, and found that WA treatment increased HRas-Raf activation. Knockdown of HRas by using small interfering RNA (siRNA) abolished WA-induced apoptosis and G2/M arrest. HRas siRNA also halted Raf, ERK, p53 activation and p21 accumulation. Molecular docking analysis suggested that WA could bind to HRas-GTP, causing accumulation of Ras-GTP and excessive activation of Raf/ERK/p53-p21. The direct binding affinity was confirmed by surface plasmon resonance (SPR). In vivo, WA suppressed tumor growth without adverse toxicity and presented the same mechanism as that in vitro. Taken together, these findings suggest WA as a promising novel, potent and selective antitumor drug candidate for lung cancer.
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PMID:Wentilactone A as a novel potential antitumor agent induces apoptosis and G2/M arrest of human lung carcinoma cells, and is mediated by HRas-GTP accumulation to excessively activate the Ras/Raf/ERK/p53-p21 pathway. 2430 39


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