UNIPROT:P04637 - FACTA Search

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Query: UNIPROT:P04637 (p53)
77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glioblastoma multiforme, the most malignant human brain tumor, may develop de novo (primary glioblastoma) or through progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). We present further evidence that primary and secondary glioblastomas constitute distinct disease entities which develop through the acquisition of different genetic alterations. We analyzed p53 mutations, p53 protein accumulation and epidermal growth factor receptor (EGFR) overexpression in 49 biopsies classified as primary or secondary glioblastoma according to clinical and histopathologic criteria. Patients with primary glioblastoma were selected on the basis of a clinical history of less than 3 months and histopathologic features of glioblastoma at the first biopsy (19 cases; mean age, 55 years). The diagnosis of secondary glioblastomas required at least two biopsies and clinical as well as histologic evidence of progression from low grade or anaplastic astrocytoma (30 cases; mean age, 39 years). DNA sequence analysis showed that p53 mutations were rare in primary glioblastomas (11%) while secondary glioblastomas had a high incidence of p53 mutations (67%), of which 90% were already present in the first biopsy. The incidence of p53 protein accumulation (nuclear immunoreactivity to PAb 1801) was also lower in primary (37%) than in secondary glioblastomas (97%). In contrast, immunoreactivity for the EGF receptor prevailed in primary glioblastomas (63%) but was rare in secondary glioblastomas (10%). Only one out of 49 glioblastomas showed EGFR overexpression and a p53 mutation. These data indicate that overexpression of the EGF receptor and mutations of the p53 tumor suppressor gene are mutually exclusive events defining two different genetic pathways in the evolution of glioblastoma as the common phenotypic endpoint.
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PMID:Overexpression of the EGF receptor and p53 mutations are mutually exclusive in the evolution of primary and secondary glioblastomas. 886 78

Twelve human melanoma cell lines were analyzed for alterations in the epidermal growth factor receptor (EGFR) gene at the DNA, RNA and protein levels. EGFR expression of the cell lines was then correlated with their previously reported p53 expression, in vivo growth characteristics, and rate of metastases in athymic mice. Northern blot and immunocytochemical analyses demonstrated low to intermediate levels of EGF receptor expression in four cell lines. Overexpression of EGFR was seen in one cell line, UISO-MEL-6. Although no significant statistical difference was observed between in vivo growth of EGFR-positive cell lines versus EGFR-negative cell lines, UISO MEL-6 which also lacked p53 expression, had the fastest in vivo rate of growth and was the only cell line to produce visceral metastases following subcutaneous inoculation in nude mice. Furthermore, EGFR overexpression in UISO-MEL-6 was associated with alterations of the gene at the DNA level.
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PMID:Overexpression of EGF receptor is associated with spontaneous metastases of a human melanoma cell line in nude mice. 904 21

Human solid tumors develop multiple genetic evolutionary abnormalities as they evolve. Studies that have focused primarily on early colorectal cancer have suggested that genetic instability is a prominent feature of preinvasive disease. At least two separate mechanisms for the generation of genetic instability have been identified. The first, which involves widespread microsatellite instability in near-diploid cells, affects less than one-fifth of colon cancers. The second form of genetic instability is characterized by the development of p53 gene abnormalities that result in gross aneuploidy and multiple structural chromosomal changes. p53/aneuploidy affects most colon cancers, breast cancers, and many other solid tumors. This genetic evolutionary change commonly occurs at the interface between severe dysplasia and invasive disease. Specific post-aneuploid sequences of genetic changes that are relevant to tumor progression often involve the accumulation of multiple gain-of-function abnormalities in individual cells. The co-occurrence of Her-2/neu overexpression and EGF receptor overexpression in the same aneuploid cells defines an adeno/squamous genetic evolutionary sequence that is common to ductal breast cancers, non-small cell lung cancers, and other solid tumors. Later steps in this sequence include ras and c-myc overexpression. The neuroendocrine genetic evolutionary sequence is a separate branch of the p53/aneuploidy sequence with distinctive features that include loss of Rb and raf1 overexpression. Her-2/neu overexpression is not characteristic of this sequence; c-myc amplification/overexpression is common to both p53-associated sequences. The neuroendocrine sequence is found in small cell carcinoma of the lung and in minor proportions of other solid tumors, including breast cancer. Multiparameter cell-based methods are especially well suited for elucidation in human solid tumors of the genetic evolutionary sequences that could provide a rational scientific basis for determining prognosis and for optimizing therapy in individual cancer patients.
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PMID:Common patterns of genetic evolution in human solid tumors. 929 7

It is known that long-term withdrawal of choline from the diet induces hepatocellular carcinomas in animal models in the absence of known carcinogens. We hypothesize that a choline deficient diet (CD) alters the balance of cell growth and cell death in hepatocytes and thus promotes the survival of clones of cells capable of malignant transformation. When grown in CD medium (5 microM or 0 microM choline) CWSV-1 rat hepatocytes immortalized with SV40 large T-antigen underwent p53-independent apoptosis (terminal dUTP end-labeling of fragmented DNA; laddering of DNA in agarose gel). CWSV-1 cells which were adapted to survive in 5 microM choline acquired resistance to CD-induced apoptosis and were able to form hepatocellular carcinomas in nude mice. These adapted CWSV-1 cells express higher amounts of both the 32 kDa membrane-bound and 6 kDa mature form of TGF alpha compared to cells made acutely CD. Control (70 microM choline) and adapted cells, but not acutely deficient hepatocytes, could be induced to undergo apoptosis by neutralization of secreted TGF alpha. Protein tyrosine phosphorylation is known to protect against apoptosis. We found decreased EGF receptor tyrosine phosphorylation in acutely choline deficient CWSV-1 cells. TGF beta 1 is an important growth-regulator in the liver. CWSV-1 cells express TGF beta 1 receptors and this peptide induced cell detachment and death in control and acutely deficient cells. Hepatocytes adapted to survive in low choline were also resistant to TGF beta 1, although TGF beta 1 receptors and protein could be detected in the cytoplasm of these cells. The non-essential nutrient choline is important in maintaining plasma membrane structure and function, and in intracellular signaling. Our results indicate that acute withdrawal of choline induces p53-independent programmed cell death in hepatocytes, whereas cells adapted to survive in low choline are resistant to this form of apoptosis, as well as to cell death induced by TGF beta 1. Our results also suggest that CD may induce alterations (mutations?) in growth factor signaling pathways which may enhance cell survival and malignant transformation.
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PMID:Diet, apoptosis, and carcinogenesis. 936 18

Recent studies have shown that there are distinct genetic pathways leading to the most malignant astrocytic neoplasm, the glioblastoma. Primary (de novo) glioblastomas are characterized by amplification/overexpression of the EGF receptor (EGFR) and, less frequently, of the MDM2 gene. Another pathway, operative in the progression of low-grade or anaplastic astrocytomas to secondary glioblastomas, is characterized by the frequent occurrence of p53 mutations. In this study, we assessed p53 mutations and EGFR expression in the giant cell glioblastoma. This rare variant is characterized by unusually large, multinucleated giant cells, but tends to be more confined and has been reported to carry a somewhat more favorable prognosis. We analyzed biopsies from 16 patients (mean age at clinical manifestation, 40 years). DNA sequencing revealed that 12 of 16 (75%) giant cell glioblastomas contained a p53 mutation. In 7 patients with two or more surgical interventions, the p53 mutation was already detected in the first biopsy. Focal EGFR overexpression, including multinucleated giant cells, was observed immunohistochemically in 9 of 16 (56%) tumors. However, most tumor areas lacked immunoreactivity, indicating that EGFR overexpression does not play a significant role in the evolution of this glioblastoma variant. These results suggest that giant cell glioblastomas develop de novo with a short preoperative history (mean, 47 +/- 40 days), but contain genetic alterations similar to those observed in secondary glioblastomas.
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PMID:p53 mutations versus EGF receptor expression in giant cell glioblastomas. 937 Feb 34

Our experiments were designed to identify initial biochemical and biological changes that occur during pancreatic carcinogenesis. TAKA-1, an immortal hamster pancreatic ductal cell line, was treated in vitro for up to 11 weeks with the pancreatic carcinogen N-nitorosobis(2-oxopropyl)amine (BOP). These treated cells were designated TAKA-1 + BOP. The growth of TAKA-1 and TAKA-1 + BOP cell lines was investigated in soft agar and in hamsters intradermally. The resulting tumor from TAKA-1 + BOP was re-cultured in vitro and designated TAKA-1 + BOP-T. Mutation of c-K-ras and p53 oncogenes, chromosomal changes, expression of transforming growth factor alpha (TGF-alpha) and epidermal growth factor (EGF) receptor and several biochemical markers were examined in all cell lines. TAKA-1 + BOP but not TAKA-1 cells grew in soft agar and produced an invasive tumor in vivo. However, there were no differences in cell growth rate, DNA flow cytometry, or immunohistochemical findings between the non-transformed and transformed cells. TAKA-1, TAKA-1 + BOP and TAKA-1 + BOP-T cells all expressed mRNA of TGF-alpha and EGF receptor in a comparable pattern. DNA sequence analysis following polymerase chain reaction showed that neither TAKA-1 nor TAKA-1 + BOP cells has a mutation of c-K-ras or p53. Karyotype analysis demonstrated that TAKA-1 + BOP cells had more chromosomal abnormalities compared with TAKA-1 cells. Mutation of c-K-ras and p53 was not essential for carcinogenesis in hamster pancreatic ductal cells in vitro. In conclusion, immortality of the TAKA-1 cells caused expression of TGF-alpha to the same extent as in malignant cells. Chromosomal and ultrastructural patterns were the only differences detected between the non-transformed and BOP-transformed cells.
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PMID:In vitro pancreatic ductal cell carcinogenesis. 937 45

Luteinizing Hormone Releasing Hormone (LHRH) agonists exert both "in vitro" and "in vivo" a direct inhibitory action on the growth of both androgen-dependent (LNCaP) and androgen-independent (DU 145) human prostatic cancer cell lines. The present experiments have been performed to investigate the mechanisms involved in this direct antiproliferative action of LHRH agonists. In particular, the aim was to study whether these compounds might exert their antiproliferative effect by interfering with the stimulatory action of epidermal growth factor (EGF) both "in vitro" and "in vivo". To this purpose, the effects of LHRH agonist, Zoladex (LHRH-A), on the mitogenic action of EGF, on EGF-activated intracellular signaling mechanisms (tyrosine phosphorylation of EGF receptor and c-fos proto-oncogene expression), and on the concentration of EGF receptors have been evaluated in both LNCaP and DU 145 cells. The results of these "in vitro" studies show that in LNCaP cells LHRH-A counteracts the mitogenic action of EGF, abrogates the EGF-induced c-fos expression and reduces the concentration of EGF-binding sites, without modifying the EGF induced tyrosine phosphorylation. In DU 145 cells, LHRH-A antagonizes the proliferative action of EGF, inhibits tyrosine phosphorylation of EGF receptor induced by EGF and significantly reduces the number of EGF binding sites, without altering the stimulation of c-fos expression induced by EGF. For the "in vivo" experiments, male nude mice were s.c. injected in the flank with DU 145 cells and treated for 14 days with LHRH-A (100 micrograms/days). At the end of the treatment, the concentration of EGF receptors on membrane preparations as well as on tumor volume were found to be significantly lower in LHRH-A treated animals than in control mice. The mitotic index and the expression of the proliferation-associated antigen Ki67 were found similar in control as well as in treated animals. In addition no modification of apoptotic index (expression of p53) was observed. These data suggest that LHRH agonists may inhibit the proliferation of the tumor cells by interfering with the stimulatory actions of EGF.
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PMID:Effects of LHRH agonists on the growth of human prostatic tumor cells: "in vitro" and "in vivo" studies. 939 87

A431 cells hyperproduce EGF receptors and possess inactive p53 proteins. It has been suggested that a cyclin-dependent kinase (CDK) inhibitor p21/WAF1 plays a crucial role in the EGF-induced cell-cycle arrest of A431 cells. Here, we investigated the role of WAF1 gene transcription in the EGF-induced cell-cycle arrest by transfecting the 18-mer antisense oligonucleotide which corresponds to the 5' region of WAF1 gene (AS/WAF1). When A431 cells were treated with EGF, a cascade of responses were observed, including immediate hyperphosphorylation of EGF receptor on tyrosine residues, accumulation of WAF1 mRNA and p21/WAF1 protein, dephosphorylation of RB protein which is a substrate of CDK-cyclin, and cell-cycle arrest. In the presence of AS/WAF1, EGF induced the tyrosine-phosphorylation of EGF receptor, but WAF1 mRNA was reduced to a half; accumulation of p21/WAF1 protein and its downstream responses were no longer observed; A431 cells grew continuously. Thus, the transfection of antisense efficiently prevented A431 cells from the EGF-induced arrest. These observations suggest that p21/WAF1 protein is a major effector molecule of the EGF-mediated cell-cycle arrest of A431 cells.
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PMID:Antisense oligonucleotide of WAF1 gene prevents EGF-induced cell-cycle arrest in A431 cells. 948 44

New human breast cell lines were developed from metastatic breast cancer tissues and normal breast tissues. Primary cultures were initiated from cellular outgrowths of explanted tissues or from mechanically isolated cells in two serum-free media. Cell cultures derived from both cancer and normal tissues were immortalized with pRSV-T plasmid to generate permanent breast cell lines that exhibited an epithelial morphology. Cell lines generated in this study were characterized with respect to morphology, growth rate, karyotype, presence of specific genes, and the expression of epithelial and breast markers. The cell lines expressed the epithelial cell markers, cytokeratins 8 and 18, and retained the capacity to produce human milk fat globulin. They also express the BRCA-1, erbB2, and EGF receptor genes and possess the H-ras, K-ras, and p53 genes. Preliminary data showed that one of the new cancer cell lines was highly sensitive to the cytotoxic action of taxol. It is envisioned that the new breast cell lines will be useful as targets for identification of therapeutic agents against breast cancer and as models for carcinogenesis studies.
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PMID:Development and characterization of new immortalized human breast cell lines 961 44

Loss of heterozygosity (LOH) on chromosome 10 is the most frequent genetic alteration associated with the evolution of malignant astrocytic tumors and it may involve several loci. The tumor suppressor gene PTEN (MMAC1) on chromosome 10q23 is mutated in approximately 30% of glioblastomas (WHO Grade IV). In this study, we assessed the frequency of PTEN mutations in primary glioblastomas, which developed clinically de novo, and in secondary glioblastomas, which evolved from low-grade (WHO Grade II) or anaplastic astrocytomas (WHO Grade III). Nine of 28 (32%) primary glioblastomas contained a PTEN mutation and an additional case showed a homozygous PTEN deletion. This indicates that after overexpression/amplification of the EGF receptor, loss of PTEN function is the most common alteration in primary glioblastomas. In this series, 5 of 28 (18%) primary glioblastomas showed both a PTEN mutation and EGFR amplification. In contrast, only 1 of 25 (4%) secondary glioblastomas contained a PTEN mutation, and none of them showed a homozygous PTEN deletion. The secondary glioblastoma with a PTEN mutation developed from an anaplastic astrocytoma that already carried the mutation. The observation that secondary glioblastomas have a p53 mutation as a genetic hallmark but rarely contain a PTEN mutation supports the concept that primary and secondary glioblastomas develop differently on a genetic level.
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PMID:PTEN (MMAC1) mutations are frequent in primary glioblastomas (de novo) but not in secondary glioblastomas. 969 Jun 72

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