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

Oncogenic activation of ras results in changes in the transcription of several genes leading to uncontrolled cell growth. In this paper, we demonstrate that transformation of fibroblast cells by the ras oncogene leads to transcriptional repression of the smooth muscle alpha-actin promoter. Transient transfection analysis of plasmids containing the 5' upstream region of the human alpha-actin gene fused to human growth hormone or bacterial chloramphenicol acetyltransferase coding sequences into Rat-2 and ras-transformed Rat-2 (HO6) cells indicates that alpha-actin promoter is repressed in ras-transformed cells. In addition, stable rat fibroblast cell lines expressing human growth hormone or beta-galactosidase under the control of alpha-actin promoter exhibit repressed reporter gene activity following transformation by the ras oncogene. alpha-Actin promoter-driven beta-galactosidase activity is derepressed in revertants of ras-transformed stable cell lines. This revertant cell line expresses elevated levels of ras p21 protein and is resistant to retransformation by Ki and Ha-ras oncogenes. The revertant may have either a defective target protein whose activity is essential for the transforming activity of ras or an activated tumor suppressor gene which can suppress the activity of ras. These results indicate that smooth muscle alpha-actin promoter activity is a sensitive marker to follow phenotypic changes following transformation by ras and subsequent reversion. The advantages of this alpha-actin promoter-reporter gene assay system to screen for drugs that inhibit the transforming activity of ras, either directly or indirectly, are discussed.
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PMID:Regulation of smooth muscle alpha-actin promoter in ras-transformed cells: usefulness for setting up reporter gene-based assay system for drug screening. 145 76

SCH58500 is an agent for gene therapy of cancer, consisting of a replication-deficient type 5 adenovirus (Ad5) expressing the human p53 tumor suppressor gene (Ad5/p53). An important question about the use of Ad5/p53 gene therapy is how to achieve the therapeutically effective delivery of an Ad5/p53 vector to the tumor. We wanted to determine the effective depth of penetration of an Ad5/p53 vector by dosing the vector in an experimental human xenograft/SCID model. To assess depth of penetration, we developed a novel methodology for scanning tissue sections by laser scanning cytometry (LSC). SCID mice were given intraperitoneal injections of either p53(null) SK-OV-3 human ovarian tumor cells or p53(mut) DU-145 human prostate tumor cells to establish xenograft solid tumors. Mice were then dosed once or twice at 24-hour intervals by intraperitoneal injection with SCH58500 (Ad5/p53), an adenovirus construct expressing beta-galactosidase (Ad5/beta-gal), or a buffer control. Additional groups of mice received a single intraperitoneal dose of 10 mg/kg paclitaxel either alone or coadministered with Ad5/p53. Twenty-four hours after each last dose, the human solid tumor xenograft and relevant mouse tissue were removed from each mouse for the analysis of Ad5/p53 penetration. Immunohistochemistry (IHC) for beta-galactosidase protein revealed a depth of penetration of between 1 and 10 cells from the tumor surface. In some mice, hepatocytes in the periportal regions of liver lobules were also positive, indicating systemic absorption of adenovirus from the peritoneal cavity. IHC staining for p53 and p21 proteins in SK-OV-3 solid tumor xenografts revealed similar Ad/p53 penetration. LSC was used to map and quantitate apoptosis in both tumor and liver tissue biopsies, with over 450,000 nuclei from liver tissue and 150,000 nuclei from tumor tissue being evaluated. LSC analysis demonstrated a high level of apoptosis in the tumors that had been removed from Ad5/p53-dosed mice (12.7-19.7%). This level of apoptosis was significantly higher (P < 0.05) than was observed for liver tissues taken from Ad5/p53-dosed mice (2.7-8.0%) or tumor tissues taken from either Ad5/beta-gal-dosed mice (3.0-6.4%) or buffer control-dosed mice (3.0-5.3%). Scan bit maps from the extensive LSC analyses confirmed that apoptosis was present to about the same depth (1-10 cells) as had been identified by IHC for beta-galactosidase, p53, and p21 proteins. Paclitaxel coadministered with Ad5/p53 had no effect on Ad5 penetration into solid tumors in vivo as measured by IHC for p53 or p21 protein. However, the combination therapy did cause an elevation in the number of tumor cells undergoing apoptosis.
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PMID:The use of laser scanning cytometry to assess depth of penetration of adenovirus p53 gene therapy in human xenograft biopsies. 1059 17

Cellular senescence is a state of irreversible growth arrest. In this paper the authors examined whether bleomycin, an agent that causes pulmonary fibrosis, induces the senescence of alveolar epithelial cells. Type II-like alveolar epithelial (A549) cells or rat primary type II cells were exposed to bleomycin and then evaluated for markers of cellular senescence. Bleomycin was also administered intratracheally in C57BL/6 mice. The authors found that exposure to bleomycin induced cellular senescence in A549 cells and rat primary type II cells. The senescence was characterised by a dose- and time-dependent increase in senescence-associated beta-galactosidase activity, senescence-associated changes in cell morphology, an increase in cell size and lysosomal mass, the overexpression of p21 protein, and irreversible growth arrest. The intratracheal injection of bleomycin in mice induced an increase in senescence-associated beta-galactosidase activity in type II epithelial cells, reaching a maximum at day 7. These results suggest that bleomycin induces a phenotype that is indistinguishable from that of senescence in alveolar epithelial cells. The induction of epithelial senescence by bleomycin may contribute to the pathway of impaired re-epithelialisation leading to pulmonary fibrosis.
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PMID:Bleomycin induces cellular senescence in alveolar epithelial cells. 1451 32

The signaling pathway of insulin/insulin-like growth factor/phosphatidylinositol-3 kinase/Akt/forkhead transcription factors is known to control life span and senescence in organisms ranging from yeast to mice. The FOXO family of forkhead transcription factors, FOXO1, FOXO3a, and FOXO4, play a critical role in this signal transduction pathway. However, the impact of FOXO3a activation on life span of primary cultured human dermal fibroblasts (HDFs) is unknown. To investigate the role of FOXO3a in the regulation of cellular senescence, we prepared FOXO3a-siRNA stable HDFs. We found that the down-regulation of FOXO3a RNA and protein in HDFs induced many senescent phenotypes, including changes in cell morphology, increases in population doubling times, senescence-associated beta-galactosidase staining and the cellular reactive oxygen species, and up-regulation of p53/p21 protein expression. Our data provide evidence of the key role of FOXO3a transcription factor as a mediator of cellular senescence in HDFs, and suggest that the mechanism of senescence is conserved in HDFs.
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PMID:Down-regulation of a forkhead transcription factor, FOXO3a, accelerates cellular senescence in human dermal fibroblasts. 1574 Dec 76

Integrin-linked kinase (ILK) is an integrin-binding cytoplasmic protein that is involved in regulating numerous cellular processes and extracellular matrix accumulation. We reported that ILK may be involved in cellular senescence, but whether ILK is the cause of senescence or an accompanying phenomenon still remains to be explored. Here, RNA interference and gene transfer techniques were used to knock down and overexpress ILK in 3-month-old and 28-month-old rat primary cardiac fibroblasts. The results show that, in younger cells, ILK overexpression induces larger cell shapes, lower proliferation capacity, and higher levels of enzymatic beta-galactosidase activity, and increases basal p53 and p21 protein levels, whereas knock-down of ILK prevents phenotypic changes typical of senescence in aging cells. In addition, ILK could induce the cytoskeleton proteins to organize into dense, thick bundles of filaments, which contribute to cellular enlargement and extracellular fibronectin assembly. The results indicate that ILK can accelerate the process of cellular senescence.
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PMID:Integrin-linked kinase induces both senescence-associated alterations and extracellular fibronectin assembly in aging cardiac fibroblasts. 1723 16

The mammalian securin, pituitary tumor-transforming gene (Pttg), regulates sister chromatid separation during mitosis. Mice deficient in Pttg expression exhibit organ-specific hypoplasia of the testis, spleen, pituitary, and postmaturity pancreatic beta-cells, pointing to a possible adult stem cell defect. Bone marrow stem cells (BMSCs) contribute to bone, cartilage, and fat tissue repair and regeneration, and multipotent adult progenitor cells (MAPCs) have broader differentiation ability. Bone marrow cells derived under MAPC conditions are involved in a spectrum of tissue repair. We therefore tested whether Pttg deletion affects stem cell proliferation and differentiation. BMSCs were isolated under MAPC conditions, although unlike MAPCs, wild-type (WT) and Pttg(-/-) BMSCs do not express octamer-binding transcription factor 4 and are stem cell antigen-I positive. WT and Pttg(-/-) cells did not differ in their ability to differentiate into adipogenic, osteogenic, or hepatocyte-like cells or in phenotypic markers. Cells underwent >100 population doublings, with no observed transforming events. Pttg-null BMSCs replicated 27% slower than WT BMSCs, and under hypoxic conditions, this difference widened. Although apoptosis was not enhanced in Pttg(-/-) cells, Pttg(-/-) BMSC senescence-associated beta-galactosidase activity was elevated, consistent with enhanced p21 protein levels. Using gene array assays, DNA repair genes were shown to be upregulated in Pttg(-/-) BMSCs, whereas genes involved in cell cycle progression, including cyclin D(1), were decreased. Separase, the protease regulated by Pttg, has been implicated in DNA damage repair and was downregulated in Pttg(-/-) BMSCs. Separase was constitutively phosphorylated in Pttg(-/-) cells, a modification likely serving as a compensatory mechanism for Pttg deletion. The results indicate that Pttg deletion reduces BMSC proliferation, renders cells more sensitive to hypoxia, and enhances senescent features, thus pointing to a role for Pttg in the maintenance and proliferation of BMSCs.
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PMID:Discordant proliferation and differentiation in pituitary tumor-transforming gene-null bone marrow stem cells. 1762 43

Secretory phospholipase A(2) (sPLA(2)) is involved in various cellular physiological and pathological responses, especially in inflammatory responses. Accumulating evidence suggests that inflammation is an underlying basis for the molecular alterations that link aging and age-related pathological processes. However, the involvement of sPLA(2) in cellular senescence is not clear. In this study, we found that sPLA(2) treatment induces cellular senescence in human dermal fibroblasts (HDFs), as confirmed by increases in senescence-associated beta-galactosidase activity, changes in cell morphology, and upregulation of p53/p21 protein levels. sPLA(2)-induced senescence was observed in p16-knockdown HDFs and p16-null mouse fibroblasts, but not in p53-knockdown HDFs and p53-null mouse fibroblasts. Treatment with sPLA(2) increases reactive oxygen species (ROS) production, and an antioxidant, N-acetylcysteine, inhibits sPLA(2)-induced cellular senescence. These results suggest that sPLA(2) has a role in cellular senescence in HDFs during inflammatory response by promoting ROS-dependent p53 activation and might therefore contribute to inflammatory disorders associated with aging.
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PMID:Induction of cellular senescence by secretory phospholipase A2 in human dermal fibroblasts through an ROS-mediated p53 pathway. 1926 4