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)

To investigate the effect that human wild-type p53 (wt-p53) expression has on cell proliferation we constructed a recombinant plasmid, pM47, in which wt-p53 cDNA is under transcriptional control of the hormone-inducible mouse mammary tumor virus promoter linked to the dominant biochemical selection marker gene Eco gpt. The pM47 plasmid was introduced into T98G cells derived from a human glioblastoma multiforme tumor, and a stable clonal cell line, GM47.23, was derived that conditionally expressed wt-p53 following exposure to dexamethasone. We show that induction of wt-p53 expression in exponentially growing cells inhibits cell cycle progression and that the inhibitory effect is reversible upon removal of the inducer or infection with simian virus 40. Moreover, when growth-arrested cells are stimulated to proliferate, induction of wt-p53 expression inhibits G0/G1 progression into S phase and the cells accumulate with a DNA content equivalent to cells arrested in the G0/G1 phase of the cell cycle. Taken together, these studies suggest that wt-p53 may play a negative role in growth regulation.
 ...
PMID:Negative growth regulation in a glioblastoma tumor cell line that conditionally expresses human wild-type p53. 214 81

The transformation related protein p53 has been implicated in the process of normal cell proliferation and neoplastic transformation. In this study, the influence of wild type human p53 on cell proliferation was examined. Plasmid constructs encoding the wild type human p53 and various mutant p53 cDNAs, driven by the mouse mammary tumor virus (MMTV) promoter linked to the dominant biochemical selection marker gpt, were used in a colony forming assay employing SV40 transformed HR8 hamster cells. Plasmids encoding wild type p53 drastically reduced the number of gpt+ colonies obtained after transfection, whereas the mutant forms of p53 had no effect. Stable clonal hamster cell lines that constitutively express wild type p53 were isolated and found to have altered growth characteristics (i.e. lower saturation densities, increased doubling times). These findings are consistent with the notion that wild type p53 protein could function as a growth suppressor. The potential role of p53 in the normal cell cycle and in the transformation process is discussed.
 ...
PMID:Wild type human p53 is antiproliferative in SV40-transformed hamster cells. 216 34

Extremely small quantities of the product of the transforming gene v-mos of Moloney murine sarcoma virus are able to efficiently transform cells. Recent data indicate the existence of a threshold level for v-mos transformation of NIH3T3 cells. Using mouse mammary tumor virus long terminal repeat sequences or hybrid promoters consisting of mouse mammary tumor virus and Moloney murine sarcoma virus long terminal repeat elements to express v-mos in C3H10T1/2 cells, we established cell lines representing different stages of morphological transformation in vitro. The threshold level for v-mos transformation was considerably lower than that for NIH3T3 cells, because no treatment with dexamethasone or primary selection other than transformation was necessary during standard transfection procedures. Using the cell lines mentioned we established an association of the level of v-mos expression with the transformation parameters examined, but not with p53 levels. Furthermore, the characterization of the different promoters showed (i) that the distal binding site confers hormone responsiveness to Moloney murine sarcoma virus promoter elements and (ii) that artifactual transcription initiation sites can be detected in mouse mammary tumor virus-Moloney murine sarcoma virus hybrid promoters which are, however, not regulated by the hormone.
 ...
PMID:Differential transformation of C3H10T1/2 cells by v-mos: sequential expression of transformation parameters. 301 22

A unique subline of BALB/c mice, designated "BALB/cV," exhibits an intermediate mammary tumor incidence (47%) and harbors a distinct milk-transmitted mouse mammary tumor virus (MMTV). Virus expression and virus-host interactions were examined during the different stages of mammary tumorigenesis (normal, preneoplastic, and neoplastic) in the BALB/cV system. Protein immunoblot analyses established the presence of correctly processed (BALB/cV)MMTV structural proteins in all types of BALB/cV mammary tissues. Competition enzyme-linked immunosorbent assays demonstrated that cells from each biologic phenotype were capable of supporting high levels of (BALB/cV)MMTV protein expression. However, mammary epithelial cells that spontaneously underwent the inappropriate pathway of squamous metaplasia did not contain detectable levels of (BALB/cV)MMTV structural proteins. Iodination experiments revealed the presence of a 68K env-related protein on the surface of BALB/cV mammary cells. Nevertheless, sera from 40 mice bearing BALB/cV-positive mammary tissues did not contain detectable levels of anti-env antibodies. Metabolic labeling experiments showed that the half-life of transformation-related, host cell protein p53 (approximately equal to 60 min) in the distinct BALB/cV mammary cell populations was similar to that reported for normal mouse 3T3 cells. It appears that p53 is not stabilized by protein interactions involving any MMTV-encoded or MMTV-induced protein in mammary tumor cells. These characteristics of the BALB/cV system are compatible with the hypothesis that MMTV is only one of two or more cooperating factors required to mediate complete mammary transformation.
 ...
PMID:Mammary cancer stages in BALB/cV mice: mouse mammary tumor virus expression and virus-host interactions. 303 52

We investigated alterations in the structure and expression of oncogenes in mammary tumors and mammary tumor-derived cell lines. In 16 of 95 samples, we detected amplification of the human neu oncogene, also known as c-erB-2, accompanied by overexpression in the tumors from which intact RNA could be isolated. In 10 of these DNAs, the linked oncogene c-erbA was also amplified, whereas another gene on human chromosome 17, p53, was present in normal copy numbers. Overexpression of c-erbA could not be detected in the tumors analyzed. The relatively high frequency of neu amplification points to a functional role in human breast cancer. Coamplification of the c-erbA oncogene could contribute to this disease as well but is most likely fortuitous.
 ...
PMID:Amplification of the neu (c-erbB-2) oncogene in human mammmary tumors is relatively frequent and is often accompanied by amplification of the linked c-erbA oncogene. 329 59

Murine p53 containing an Arg-->Leu substitution at amino acid 172 possesses many properties characteristic of wild-type p53, including the ability to induce p21/WAF/Cip1 and apoptosis. To determine if p53-dependent apoptosis plays a critical role in mammary tumorigenesis, transgenic mice were generated in which the expression of this mutant p53 protein was targeted to the mammary gland by using the rat whey acidic protein gene promoter. Mice bearing pituitary isografts were treated with 7,12-dimethylbenz[a]anthracene (DMBA) and examined for mammary tumor development. Mice overexpressing the p53 transgene exhibited a statistically significant increase in apoptosis in the mammary gland and a statistically significant decrease in the incidence of DMBA-induced mammary tumors. No difference in tumor incidence was observed in mice without pituitary isografts who were treated with DMBA, because the transgene is not overexpressed in the absence of hormone stimulation provided by the pituitary isograft. The unexpected wild-type properties of the 172Arg-->Leu mutant p53, including its ability to stimulate apoptosis, make it a possible candidate for use in gene therapy protocols.
 ...
PMID:Delay of dimethylbenz[a]anthracene-induced mammary tumorigenesis in transgenic mice by apoptosis induced by an unusual mutant p53 protein. 757 2

We have studied the effects of food restriction (FR) and substitution of fish oil (FO; omega 3) for corn oil (CO; omega 6) on breast tumor incidence and survival in mouse mammary tumor virus/v-Ha-ras transgenic (Onco) mice. The diets were as follows: group 1, 5% (wt/wt) CO fed ad libitum (AL); group 2, 5% CO, restricted calories (40% fewer calories than AL; FR); group 3, 20% CO fed AL; and group 4, 20% FO fed AL. After 3 years, 40% of FR Onco (group 2) mice were alive, whereas there were no survivors in the other three groups. Similarly, tumor incidence was reduced to 27% (5 out of 18) in FR animals (group 2), whereas it was 83% (11 out of 13) in group 1 mice, 89% (16 out of 18) in group 3 mice, and 71% (10 out of 14) in group 4 mice. These protective effects of FR on survival and tumor incidence were paralleled by higher expression of the tumor suppressor gene p53 (wild type) and free-radical scavenging enzymes (catalase and superoxide dismutase) in breast tumors. Immunoblotting showed less ras gene product, p21, and increased p53 levels in the tumors of FR mice. In addition, FR decreased RNA levels of c-erbB-2, interleukin 6, and the transgene v-Ha-ras in tumors. In contrast, analysis of hepatic mRNA from tumor-bearing FR mice revealed higher expression of catalase, glutathione peroxidase, and superoxide dismutase. Survival and tumor incidence were not influenced significantly by dietary supplementation with FO in place of CO. Taken together, our studies suggest that moderate restriction of energy intake significantly inhibited the development of mammary tumors and altered expression of cytokines, oncogenes, and free-radical scavenging enzymes.
 ...
PMID:Dietary lipids and calorie restriction affect mammary tumor incidence and gene expression in mouse mammary tumor virus/v-Ha-ras transgenic mice. 760 20

A number of properties of the cancer-related genes c-myc and p53 suggest that they might collaborate to induce tumorigenesis. To test this notion, we produced doubly heterozygotic mice bearing disrupted p53 alleles and a fusion transgene consisting of the mouse mammary tumor virus (MMTV) LTR and the oncogene c-myc. Mice bearing both the MMT/c-myc transgene and a single p53- allele develop very aggressive pre-T- and T-cell lymphomas with a significantly shorter latency than mice carrying either the p53- allele or the c-myc transgene alone. Moreover, every lymphoma occurring in these animals has lost or suffers an inactivation of its wild type p53 allele indicating that loss of p53 activity is necessary for this c-myc-accelerated lymphomagenesis. Nonetheless, p53 inactivation and expression of the MMTV/c-myc transgene are not sufficient for lymphoid transformation. Tumors that arise in homozygous p53- mice carrying the c-myc transgene are monoclonal, suggesting that at least one additional event is necessary for their transformation. Moreover, since mice bearing only the MMTV/c-myc transgene predominantly develop mammary carcinomas, it was surprising that the p53- allele failed to accelerate the incidence of mammary carcinomas. Further, in contrast to the lymphomas, only one in four mammary tumors that arose in the double heterozygotic mice had lost its wild type p53 allele. Apparently cell context influences the ability of c-myc and p53- to cooperate in inducing oncogenesis.
 ...
PMID:The MMTV/c-myc transgene and p53 null alleles collaborate to induce T-cell lymphomas, but not mammary carcinomas in transgenic mice. 762 26

The retrovirus mouse mammary tumor virus (MMTV) 3' long terminal repeat (LTR) contains an open reading frame (ORF) for a 36-kDa protein and encodes a superantigen activity [pORF(sag)]. We have tested the potential oncogenic activity of pORF(sag) in two immortalized mouse mammary epithelial cells. We subcloned MMTV LTR ORF DNA into the pRc/CMV mammalian expression vector in order to place LTR ORF transcription under the control of the constitutive CMV promoter. Mouse mammary epithelial cell lines TM3 and FSK7e4 were transfected and G418-resistant cell clones were isolated. Reverse transcription-polymerase chain reaction and Northern blot analyses revealed modest overexpression of LTR RNA in several transfected cell clones of each line. Individual cell clones were transplanted into cleared mammary gland fat pads of syngeneic BALB/c mice. The parental cell lines and FSK7e4-derived clones did not form tumors, whereas ORF-transfected clones derived from the TM3 cells formed tumors within 8 weeks in 100% of transplanted fat pads in multiple experiments. The tumor cells expressed exogenous LTR ORF RNA and were proven to be derivatives of TM3 cells based on a marker p53 mutation. Immunohistochemistry using a polyclonal antiserum raised against pORF(sag) expressed in insect cells revealed a cytoplasmic reaction in TM3-CMV-LTR tumor cells; a much weaker cytoplasmic reaction was detected in the transfected tissue culture cells. These observations suggest that MMTV pORF(sag) may act as an oncogene in certain mouse mammary epithelial cells and raise the possibility that pORF(sag) may have a role in mammary tumorigenesis. As the parental FSK7 cell line has produced only ductal outgrowths upon transplantation in vivo and the TM3 cell line produces a nontumorigenic hyperplasia, the results suggest further that pORF(sag) may influence the latter stages of mammary tumorigenesis, namely, the preneoplastic to neoplastic transformation.
 ...
PMID:Expression of the mouse mammary tumor virus long terminal repeat open reading frame promotes tumorigenic potential of hyperplastic mouse mammary epithelial cells. 764 39

We have found that p53 expression is altered with progression to the metastatic phenotype of a series of neoplastic subpopulations of a single mouse mammary tumor. Single strand conformation polymorphism (SSCP) analysis of p53 transcripts indicate that the expressed p53 genes in each of the subpopulations contain one or more differences from wild type p53. Although the mutations in the coding sequence of p53 are different in each of the sublines, suggesting that independent mutational events have occurred, the mutations are clustered in exons 2-4 and in exon 6. In the metastatic subpopulations, there is either a complete loss of p53 transcriptional activity or accumulation of transcripts with an additional alteration in exons 4-5.
 ...
PMID:Heterogeneity in p53 mutations in mouse mammary tumor subpopulations with different metastatic potential from the orthotopic site. 764 64


1 2 3 4 5 6 7 8 9 10 Next >>