Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Singapore astrocytic tumours occur in only 25% of patients with primary brain tumours compared to 40-60% in other series. Glioblastoma multiforme arises either de novo as a primary glioblastomas associated with epidermal growth factor receptor (EGFR) and mdm2 over-expression or as a secondary glioblastomas, through malignant progression from low-grade astrocytomas, associated with p53 mutations and PDGFR-alpha over-expression. Using immunohistochemical methods and DNA sequencing, we studied our population of glioblastomas for overexpression of EGFR, mdm2, p53, and PDGFR-alpha as well directly for mutations of the p53 gene. While levels of over-expression of EGFR and mdm2 were consistent with levels expected for primary glioblastomas, levels of p53 and PDGFR-alpha were consistent with levels documented for secondary glioblastomas. Notably 96% of the samples over-expressed p53 as detected with monoclonal antibody pAb 240. Of the 39 samples available for DNA sequencing 18% (7/39) had p53 mutations, including three mutations previously undocumented in glioblastomas. These results provide strong evidence that glioblastomas in Asian patients do not conform to currently accepted models of glioblastoma development, and that clinically defined glioblastomas in these patients show genetic changes consistent with both 'primary' and 'secondary' glioblastomas.
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PMID:Glioblastoma multiforme in an Asian population: evidence for a distinct genetic pathway. 1263 58

Platelet-derived growth factor (PDGF) is a potent mitogen for mesenchymal cells. PDGF AA functions as a "competent factor" that stimulates cell cycle entry but requires additional (progression) factors in serum to transit the cell cycle beyond the G1/S checkpoint. Unlike PDGF AA, PDGF B-chain (c-sis) homodimer (PDGF BB) and its viral counterpart v-sis can serve as both competent and progression factors. PDGF BB activates alpha- and beta-receptor subunits (alpha-PDGFR and beta-PDGFR) and induces phenotypic transformation in NIH 3T3 cells, whereas PDGF AA activates alpha-PDGFR only and fails to induce transformation. We showed previously that alpha-PDGFR antagonizes beta-PDGFR-mediated transformation through activation of stress-activated protein kinase-1/c-Jun NH2-terminal kinase-1, whereas both alpha-PDGFR and beta-PDGFR induce mitogenic signals. These studies revealed a striking feature of PDGF signaling; the specificity and the strength of the PDGF growth signal is modulated by alpha-PDGFR-mediated simultaneous activation of growth stimulatory and inhibitory signals, whereas beta-PDGFR mainly induces a growth-promoting signal. Here we demonstrate that PDGF BB activation of beta-PDGFR alone results in more efficient cell cycle transition from G1 to S phase than PDGF BB activation of both alpha-PDGFR and beta-PDGFR. PDGF AA activation of alpha-PDGFR or PDGF BB activation of both alpha- and beta-PDGFRs up-regulates expression of p21WAF1/CIP1, an inhibitor of cell cycle-dependent kinases and a downstream mediator of the tumor suppressor gene product p53. However, beta-PDGFR activation alone fails to induce p21WAF1/CIP1 expression. We also demonstrate that alpha-PDGFR-activated JNK-1 is a critical signaling component for PDGF induction of p21WAF1/CIP1 promoter activity. The ability of PDGF/JNK-1 to induce p21WAF1/CIP1 promoter activity is independent of p53, although the overall p21WAF1/CIP1 promoter activities are greatly reduced in the absence of p53. These results provide a molecular basis for differential regulation of the cell cycle and transformation by alpha- and beta-PDGFRs.
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PMID:Platelet-derived growth factor (PDGF) receptor-alpha-activated c-Jun NH2-terminal kinase-1 is critical for PDGF-induced p21WAF1/CIP1 promoter activity independent of p53. 1450 45

Tuberous sclerosis (TSC) is a familial tumor syndrome due to mutations in TSC1 or TSC2, in which progression to malignancy is rare. Primary Tsc2(-/-) murine embryo fibroblast cultures display early senescence with overexpression of p21CIP1/WAF1 that is rescued by loss of TP53. Tsc2(-/-)TP53(-/-) cells, as well as tumors from Tsc2(+/-) mice, display an mTOR-activation signature with constitutive activation of S6K, which is reverted by treatment with rapamycin. Rapamycin also reverts a growth advantage of Tsc2(-/-)TP53(-/-) cells. Tsc1/Tsc2 does not bind directly to mTOR, however, nor does it directly influence mTOR kinase activity or cellular phosphatase activity. There is a marked reduction in Akt activation in Tsc2(-/-)TP53(-/-) and Tsc1(-/-) cells in response to serum and PDGF, along with a reduction in cell ruffling. PDGFRalpha and PDGFRbeta expression is markedly reduced in both the cell lines and Tsc mouse renal cystadenomas, and ectopic expression of PDGFRbeta in Tsc2-null cells restores Akt phosphorylation in response to serum, PDGF, EGF, and insulin. This activation of mTOR along with downregulation of PDGFR PI3K-Akt signaling in cells lacking Tsc1 or Tsc2 may explain why these genes are rarely involved in human cancer. This is in contrast to PTEN, which is a negative upstream regulator of this pathway.
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PMID:Loss of Tsc1/Tsc2 activates mTOR and disrupts PI3K-Akt signaling through downregulation of PDGFR. 1456 7

Astrocytomas are the most common pediatric brain tumors, accounting for 7%-8% of all childhood cancers. Relatively few studies have been performed on their molecular properties; therefore, classification of pediatric astrocytic tumors into genetic subtypes similar to that of adult tumors remains to be defined. Here, we report an extensive characterization of 44 pediatric astrocytomas--16 diffuse astrocytomas (WHO grade II), 10 anaplastic astrocytomas (WHO grade III), and 18 glioblastomas (WHO grade IV)--in terms of genetic alterations frequently observed in adult astrocytomas. Some form of p53 mutation was found in three diffuse astrocytomas, in three anaplastic astrocytomas, and in six glioblastomas examined; PTEN mutations were detected only in two glioblastomas. EGFR amplification was detected in only one anaplastic astrocytoma and two glioblastomas, but no amplification was observed for the PDGFR-alpha gene. Loss of heterozygosity (LOH) on 1p/19q and 10p/10q was less common in pediatric astrocytic tumors than in those seen in adults, but the frequency of LOH on 22q was comparable, occurring in 44% of diffuse astrocytomas, 40% of anaplastic astrocytomas, and 61% of glioblastomas. Interestingly, a higher frequency of p53 mutations and LOH on 19q and 22q in tumors from children six or more years of age at diagnosis was found, compared with those from younger children. Our results suggest some differences in children compared to adults in the genetic pathways leading to the formation of de novo astrocytic tumors. In addition, this study suggests potentially distinct developmental pathways in younger versus older children.
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PMID:Molecular pathogenesis of pediatric astrocytic tumors. 1732 74

The over-expression of several receptor tyrosine kinases in adult high grade astrocytomas (HGA) led to trials of tyrosine kinase inhibitors in these patients. Similar molecular genetic analysis of pediatric HGA is only beginning to be published. Thus it is unclear to what degree these pathways are also involved in the pediatric age group and whether they may also serve as useful therapeutic targets for children with HGAs. Here we investigated the protein expression profile of a series of pediatric HGAs. Following institutional ethical approval, clinical information and tumor samples were obtained for 42 HGA patients. Mean age at presentation was 10.1 years (range 0.13-19.3 years). OS was 12% and PFS was 3.7%. Extent of resection was associated with improved PFS (P = 0.0015) with a trend towards improved OS (P = 0.08). There was no significant effect of age or adjuvant therapy use on PFS or OS. Immunopositivity for each of the markers was as follows: p53 35%; PDGFR-alpha 45%; PDGFR-beta 31%; PTEN 67%; EGFR wild type 58%; EGFRvIII 2%. No significant effect on OS or PFS was found for any of the markers by log rank analysis. However, all long-term survivors expressed PTEN and were EGFRvIII negative. Further, there were distinct differences in protein expression between pediatric and adult HGAs suggesting that EGFR kinase inhibitors may not be beneficial for treatment of HGA in the pediatric age group and pointing to the need to study pediatric astrocytomas as distinct entities from adult astrocytomas.
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PMID:Tyrosine kinase expression in pediatric high grade astrocytoma. 1819 93

Herein, we show that both exogenously transfected and endogenously activated p53 repress promoter activity and expression of PDGFRB. p53 binds the proximal promoter containing the CCAAT motif as examined by EMSA and chromatin immunoprecipitation. However, gradual induction of p53 in tet-onSAOS2 cells resulted in a transient increase of the PDGFRB-promoter activity and its expression. As binding of p53 to the promoter increased, previously bound p73, DeltaNp73, c-Myc, HDAC1 and HDAC4 were dismissed from the repressed promoter, and p300 was recruited. The transient increase of the promoter activity was therefore induced by the release of the p73, Myc and HDACs, previously shown to act as repressors to this promoter. Along with further increase of p53, p300 was replaced by HDAC1 and HDAC4, resulting in decreased PDGFRB expression. For the repression, acetylation of the C-terminal lysines of p53 is important, and both acetyl-K373p53 and methyl-K370p53 became bound to the promoter. The acetyl-K373p53 was accumulated in the nucleus and colocalized with promyelocytic leukemia protein. Mitomycin treatment of MEF induced similar epigenetic modification of p53 and its binding to the promoter chromatin. Addition of a PDGFR tyrosine-kinase inhibitor to p53-inducing tet-onSAOS2 increased the number of apoptotic cells. These results suggest that p53 represses the PDGFRB promoter, facilitating the p53-induced apoptosis, whereas tumor cells with p53 mutation or a high level of DeltaNp73 or Myc could become refractory to the regulation.
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PMID:Kinetics of repression by modified p53 on the PDGF beta-receptor promoter. 1869 3

Oligodendrogliomas account for a small subset of all gliomas, but they often are more sensitive to treatment than other glioma subtypes. In addition, oligodendrogliomas are the first central nervous system neoplasm for which a specific molecular abnormality, allelic loss of 1p/19q (1p/19q loss), correlates with patient outcome in large-scale prospective clinical trials. However, the incorporation of 1p/19q status into clinical practice remains controversial. Other molecular alterations found in oligodendrogliomas include hypermethylation of the promoter for the MGMT gene, TP53 mutations, EGFR and platelet-derived growth factor/PDGFR alterations, and 9p and 10q loss.
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PMID:Molecular profiling of oligodendrogliomas: impact on prognosis, treatment, and future directions. 1908 Jul 43

Recent molecular studies support the hypothesis that clear cell carcinoma and mucinous adenocarcinoma are refractory cancers that are biologically distinct from serous adenocarcinoma. Treatment of these cancers has not yet been adequately tested, so separate clinical trials are needed for each type. Paclitaxel(175 mg/m2/3hr)combined with carboplatin AUC 6(TC regimen)is the current gold standard for treating ovarian cancer. Clear cell carcinoma and mucinous adenocarcinoma are less sensitive to a TC regimen than serous adenocarcinoma, and an international randomized trial for clear cell carcinoma is now underway(GCIG/JGOG3017). Targeted therapy is attractive for chemoresistant clear cell carcinoma, thus VEGFR inhibitor(sunitinib), PDGFR inhibitor(sorafenib), m-TOR inhibitor (temsirolimus), and monoclonal antibody(bevacizumab)are being evaluated. Mucinous adenocarcinoma often shows CK20- and CEA-positive patterns in immunohistochemistry, and furthermore, p53-negative and K-ras-positive in molecular markers, which suggests that mucinous adenocarcinoma resembles colorectal, stomach, and pancreas cancers more than serous ovarian adenocarcinoma. Trials are needed to test the agents effective for gastrointestinal cancer. The GOG will start a randomized phase III trial comparing TC regimen with capecitabine plus oxaliplatin(GOG241). We are starting a phase II study of S-1 plus oxaliplatin in Japan. For refractory cancers, molecular biology-based, cross- organ treatment with cytotoxic/cytostatic agents is needed.
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PMID:[Treatments of epithelial ovarian cancer by histologic subtype]. 1922 34

Malignant peripheral nerve sheath tumors (MPNSTs), often found associated with neurofibromatosis type 1 (NF1), are aggressive tumors that pose significant diagnostic and therapeutic challenges. About 10% of NF1 patients may develop an MPNST, exhibiting a poor prognosis. With no effective treatment available, radical surgery and chemo- and radiotherapy are required to reduce tumor recurrence, metastasis and prolong patient survival. MPNST pathogenesis is poorly understood due mainly to its complex histopathology, but biallelic NF1 gene inactivation is essential for tumor development. There is also no defined molecular signature for MPNST development, although several cell-cycle and signalling regulation genes (CDKN2A, TP53, RB1, EGFR, CD44, PDGFR, PDGFRA, HGF, MET and SOX9) are deregulated. Constitutive activation of several critical cell signalling cascades also occurs in MPNSTs and these may define therapeutic targets. Both preclinical and clinical trials are proposed, most involving a combinatorial therapeutic approach. Multidisciplinary collaborative efforts are clearly essential to fully decipher both the complex molecular basis of MPNST development and to define potential therapeutic targets.
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PMID:Genetic basis of tumorigenesis in NF1 malignant peripheral nerve sheath tumors. 2119 10

Despite our incomplete comprehension of how growth factor-stimulation of cells is linked to the cell cycle and of how the G(1)/S checkpoint is linked to initiation in DNA replication there is an unparalleled wealth of experimental evidence to connect protein phosphorylation to molecular mechanisms of carcinogenesis. Many growth factors, growth factor receptors with tyrosine kinase activity (insulin receptor, EGFR, PDGFR, CSF1R, NGFR, HGFR), nonreceptor serine/threonine or tyrosine kinases (c-Raf-1, cMos, c-Abl, c-Src) and cyclin D1 are encoded by oncogenes mutated or overexpressed in a variety of human tumors; the physiological functions of oncoproteins that are involved in gene expression and replication (c-Jun, T-antigen, c-Myc, c-Myb) as well as p53, RB and CDK4 tumor suppressor proteins and replication factor A are also regulated by phosphorylation, ms genes transduce growth factor receptor signals to protein kinase C (PKC) or to c-Raf-1 triggering two different cascades of protein kinases, the PKC and MAPK signaling pathways both targeting nuclear proteins. Thus cancer can be considered as a disease of the signaling pathways.
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PMID:The phosphorylation connection to cancer (review). 2155 34


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