Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transcription factor CCAAT/enhancer binding protein (C/EBP alpha) is expressed predominantly in differentiated tissues and is able to induce growth arrest and differentiation in preadipocytes. C/EBP alpha expression is high in non-dividing hepatocytes, but decreases during liver regeneration. These observations suggest that C/EBP alpha is inversely related to cell proliferation. To investigate the mechanism of growth inhibition by C/EBP alpha, the response of immortal human cells to cotransfection of a C/EBP alpha expression vector (CMV alpha) and a CMV beta-galactosidase expression vector was examined. Hep3B2, a hepatoma; Saos2, an osteosarcoma deficient for p53 and Rb; and 639, a fibroblast expressing SV40 T-antigen, were examined. Transiently transfected cells were stained for beta-gal activity to monitor their ability to undergo division. The ability of stable transformants to form colonies was also assessed for each cell line. Cells transfected with CMV alpha remained as non-dividing cells while control cells divided to form colonies. Mutations of the C/EBP alpha sequence demonstrated that only a small, previously uncharacterized activation domain was required for antimitotic activity. Our results suggest that C/EBP alpha may play a role in maintaining the quiescent state of hepatocytes and other cells. Furthermore, it appears that the effects of C/EBP alpha are not mediated through p53 or Rb and are not altered by T-antigen.
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PMID:Inhibition of cell proliferation by C/EBP alpha occurs in many cell types, does not require the presence of p53 or Rb, and is not affected by large T-antigen. 852 67

p53 induction and cell cycle arrest occur following DNA damage, possibly to allow repair prior to replication. p21WAF1/CIP1, a cyclin-cyclin-dependent kinase inhibitor and proliferating cell nuclear antigen-interacting protein, is induced by p53 and mediates the cell cycle arrest. To investigate a role for p21 in DNA repair in vivo, we studied the expression of in vitro damaged reporter DNA transfected into p21 +/+ or -/- HCT116 human colon cancer cells. Introduction of UV-damaged or cisplatinum-damaged cytomegalovirus-driven beta-galactosidase reporter DNA into tumor cells revealed a significant decrease (2-5-fold) in reporter expression in p21 -/- versus +/+ cells. In the absence of DNA damage, there was a significant increase (2-3-fold) in the number of 6-TG-resistant colonies derived from p21 -/- versus +/+ cells. Reintroduction of wild-type p21, but not a p21 C-terminal truncation mutant which lacks the proliferating cell nuclear antigen interaction domain, stimulated (2-3-fold) the repair capacity of the p21-deficient cells. We conclude that p21 deficiency is associated with a defect in DNA repair, which could lead to an increased sensitivity of tumor cells to DNA damage.
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PMID:Repair Defect in p21 WAF1/CIP1 -/- human cancer cells. 862 93

To examine the potential use of adenovirus vectors in cancer gene therapy as a mechanism for purging bone marrow cells of possible breast cancer contaminants, we compared the infection efficiency of adenovirus and the transfection efficiency of plasmid DNA in the presence of adenovirus in human breast cancer and bone marrow cells. Following infection of breast cancer cells with an adenovirus expressing beta-galactosidase gene, high levels of beta-galactoside activity were observed. No beta-galactosidase activity was observed in low-density human bone marrow cells. A replication-deficient adenovirus mutant dl312 enhanced the transfection efficiency of a plasmid DNA-expressing beta-galactosidase gene into breast cancer cells, and addition of a liposome, lipofectamine, further enhanced the transfection efficiency. In contrast, human bone marrow cells treated under the same conditions expressed very low levels of transfected beta-galactosidase DNA. Transfection of cells with plasmid DNA expressing a truncated but fully active Pseudomonas exotoxin gene in the presence of dl312 and lipofectamine resulted in marked breast cancer cell killing, whereas colony-forming unit granulocyte-macrophage (CFU-GM) were relatively resistant to these treatments. A recombinant adenovirus expressing human wild-type p53 protein (AdWTp53) was also highly cytotoxic to breast tumor cells. Infection of breast cancer cells with AdWTp53 (100 plaque-forming units/cell) resulted in 100% loss of the clonogenicity of breast tumor cells. However, colony formation from CFU-GM was relatively resistant to the cytotoxic effects of AdWTp53 alone or in the presence of pULI100 plasmid and lipofectamine. On the basis of these results, it is proposed that human adenoviruses are potentially useful for cancer gene therapy and bone marrow purging.
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PMID:Adenovirus-mediated gene transfer to human breast tumor cells: an approach for cancer gene therapy and bone marrow purging. 864 Aug 24

Deficiency in p53-mediated cell death is common in human cancer, contributing to both tumorigenesis and chemoresistance. In an attempt to restore p53, we evaluated in vitro infectivity and cytotoxicity of a wild type (w.t.) p53-expressing adenovirus (Ad-p53) toward a panel of human cancer cell lines (n = 19). At a multiplicity of infection of 30, both Ad-p53 and adenovirus expressing beta-galactosidase (Ad-LacZ) infected greater than 99% of cells derived from brain, lung, breast, ovarian, colon, and prostate cancer, but failed to infect leukemia or lymphoma cells. Ad-p53, but not Ad-LacZ, infection of cancer cells was followed by nuclear accumulation of the CDK inhibitor p21WAFI/CIPI, cell cycle arrest and loss of viability. Ad-p53 induced apoptotic death in cancer cells that express mutant p53, including multi-drug resistant cells, but fewer deaths were observed in some w.t. p53 expressing cells. Ad-p53-infected SKBr3 breast cancer cells were more sensitive to cytotoxicity of the DNA damaging drugs mitomycin C or Adriamycin, but not the M-phase specific drug vincristine. Our results suggest that Ad-p53 is capable of infecting and killing cancer cells of diverse tissue origins (including multi-drug resistant cancer cells), that p21WAFI/CIPI may be a useful marker of p53 infectivity and that there may be synergy between Ad-p53 and either mitomycin C or Adriamycin induced cell death in tumors with p53 mutations.
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PMID:In vitro evaluation of a p53-expressing adenovirus as an anti-cancer drug. 870 13

In response to DNA damage, the transcriptional activity of p53 rises. This has been thought to be due to an increase in the level of p53 protein. By comparing the p53 protein level and its ability to transactivate target genes Waf1/Cip1 and mdm2 in both T22 and NIH3T3 cells irradiated with u.v., a discordance between the p53 protein level and its transcriptional activity was observed. When the cells were irradiated with 10 J/m2 of u.v., there was a substantial increase in expression of Waf1/ Cip1 and mdm2. However, little increase in Waf1/Cip1 and mdm2 expression was observed in T22 and NIH3T3 cells 8 or 9 h after exposure to 50 J/m2 of u.v., although the p53 protein level accumulated to its highest level under these conditions. Interestingly, a significant increase in Waf1/Cip1 expression was seen 24 h after irradiation in NIH3T3 cells, indicating that the inhibition of p53 transcriptional activity is reversible. Discordance between the transcriptional activity of p53 and its protein level was further studied using a cell line expressing the p53 reporter plasmid RGC delta fosLacZ. Using double immunofluorescence staining, the coexpression of p53 and beta-galactosidase from the reporter plasmid in the same cells was investigated. The observed lack of correlation between the elevated p53 and beta-galactosidase and expression in u.v. irradiated cells strongly indicates that the ability of p53 to transactivate its target genes is not simply correlated to its protein level. The results indicate that the transcriptional activity of p53 may be negatively regulated.
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PMID:Discordance between accumulated p53 protein level and its transcriptional activity in response to u.v. radiation. 871 Mar 81

Wild-type p53 is necessary for the growth arrest of human diploid fibroblasts (HDF) (and many other cell types) at the end of their proliferative lifespan. Although p53 may actively mediate senescence, possibly in response to telomere erosion, it is however equally possible that it is merely a permissive factor required for response to some other inducer. To address this question, we have generated stable transfectants of early passage HDF, represented here by clone LacZ21, in which expression of a beta-galactosidase reporter construct reflects p53 transactivation activity. During continuous passage, the proportion of beta-gal positive LacZ21 cells remained below 2% for 25 population doublings (pd), first became significantly increased after 29 pd, and thereafter increased rapidly, reaching a maximum of 88% in fully-senescent cells (32 pd), which exceeded the response observed following an optimum dose (20 J/m2) of u.v. radiation. Correspondingly, the proportion of cells incorporating bromodeoxyuridine (BrdU) (initially 45-50%) began to fall at 29 pd and thereafter dropped rapidly to below 1% by pd 32. There was therefore a near-perfect reciprocal relationship between reporter construct expression and DNA synthesis as cells approached senescence. Furthermore, a dominant-negative p53 mutant (introduced by retroviral transduction) rescued LacZ21 cells from senescence and generated colonies with extended lifespan in which beta-gal expression was totally abolished. These data, although not excluding the need for other p53 functions, strongly suggest that p53-mediated transactivation of growth regulatory genes is a direct trigger, rather than a permissive factor, for cellular senescence.
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PMID:Evidence that transcriptional activation by p53 plays a direct role in the induction of cellular senescence. 895 Sep 76

We have previously reported the use of a recombinant nonreplicating adenovirus type 5, Ad5HCMVsp1 lacZ, expressing the lacZ gene under control of the human cytomegalovirus (HCMV) immediate early promoter to assess repair of a UV-damaged reporter gene in UV and heat shock (HS) treated cells. Heat shock and UV-enhanced reactivation (HSER and UVER) of beta-galactosidase (beta-gal) activity for UV-irradiated Ad5HCMVsp1 lacZ in normal human fibroblasts involved the transcription coupled repair (TCR) pathway. However, this inducible DNA repair response was absent in p53 deficient tumour cell lines. In order to examine further the requirement for p53 in HSER and UVER, we have examined host cell reactivation (HCR) of the reporter construct in HS treated, UV treated and mock treated Li-Fraumeni syndrome (LFS) fibroblasts, which are heterozygous for a p53 mutation, and immortalized LFS cell sublines, which express only mutant p53. HCR of beta-gal activity for UV-irradiated Ad5HCMVsp1 lacZ was normal in all LFS cells examined. However, HCR of beta-gal activity for UV-irradiated Ad5HCMVsp1 lacZ was elevated by pretreatment of cells with either UV or HS in normal diploid human fibroblasts, but not in LFS cells. LFS cells appear to be deficient in an inducible pathway which stimulates repair of the reporter gene. These results support a role for p53 in a HS and UV inducible DNA repair response in human cells which is dependent on TCR.
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PMID:Wildtype p53 is required for heat shock and ultraviolet light enhanced repair of a UV-damaged reporter gene. 905 14

The mechanism which is responsible for the association of chronic hepatitis B virus (HBV) infection with hepatocellular carcinoma (HCC) is poorly understood. The protein encoded by the HBV X-gene (HBx) has been identified as potentially oncogenic. HBx is a promiscuous indirect trans-activator of a wide range of cellular and viral cis-elements and may disrupt the maintenance of genomic integrity by inhibiting p53 function and binding a putative DNA repair protein (XAP-1). In this report, we show that there is preferential binding of recombinant HBx to damaged DNA through an association with nuclear proteins. We have used the transcriptional activation by HBx of the beta-actin promoter of a beta-galactosidase reporter cassette to label cultured Chang liver cells expressing HBx. We demonstrate that cells expressing HBx are sensitised to the lethal effects of low dose ultraviolet irradiation. These data indicate that HBx interferes with liver cell DNA repair by binding damaged DNA and may predispose to the accumulation of potentially lethal or carcinogenic mutations.
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PMID:Hepatitis B virus X-protein binds damaged DNA and sensitizes liver cells to ultraviolet irradiation. 912 43

Like most other normal cells, human endothelial cells possess a limited replicative life span, and, after multiple passages in vitro, develop an arrest in cell division referred to as replicative senescence. For many cell types senescence can be delayed by oncogenes or tumor suppressor genes or prevented altogether by malignant transformation; however, once developed, senescence has been regarded as irreversible. We now report that a cytokine, vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), significantly delays senescence in human dermal microvascular endothelial cells (HDMEC). Typically, VPF/VEGF-treated HDMEC could be cultured for at least 15-20 more population doublings (PD) than control cells. Protection from senescence was reversible in that subsequent withdrawal of VPF/VEGF returned cells to the senescent phenotype. Expression of several cell cycle-related genes (p21, p16 and p27) was significantly reduced in VPF/VEGF-treated cells but p53 expression was not significantly altered. Of particular importance, VPF/VEGF was able to rescue senescent HDMEC, restoring them to proliferation, to a more normal morphology, and to reduced expression of a senescence marker, neutral beta-galactosidase. Taken together, VPF/VEGF delayed the onset of senescence and also reversed senescence in microvascular endothelial cells without inducing cell transformation.
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PMID:Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) delays and induces escape from senescence in human dermal microvascular endothelial cells. 916 Aug 82

An adenovirus/DNA complex was constructed by chemically linking poly-L-lysine to the capsid of the replication-defective adenovirus dl312, allowing for coupling with plasmid DNA by an ionic interaction. We have previously demonstrated that this adenovirus/DNA complex can efficiently transduce malignant cells with a plasmid expressing the beta-galactosidase gene both in vitro and in vivo. In this report, we show that this system can deliver a therapeutic gene that encodes for the tumor suppressor protein p53 to lung cancer cells, both in vitro and in vivo, leading to significant biological effects. Transfection of the p53-negative human lung cancer cell line H1299 with the adenovirus/DNA complex carrying a plasmid expressing the p53 gene resulted in high levels of p53 protein and induction of apoptosis. Injection of the complex carrying the p53 gene to subcutaneous tumor sites 5 days after tumor cell implantation resulted in a significant inhibition of tumorigenicity as measured by the number and size of tumors that developed 21 days after treatment. Three and six injections of the complex carrying the p53 gene into H1299 subcutaneous tumor nodules led to significant dose-related tumor growth suppression 18 days after the first injection compared with control-treated tumors. This adenovirus/DNA complex, therefore, is capable of efficiently delivering the p53 gene into malignant cells in vitro and in vivo and now provides a general gene delivery vector that is simple to construct and capable of testing therapeutic genes in malignant cells.
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PMID:Delivery of the p53 tumor suppressor gene into lung cancer cells by an adenovirus/DNA complex. 917 38


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