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)

Recently, it has been demonstrated that Etoposide, a topoisomerase II inhibitor, can induce apoptosis in MDM2-overexpressing tumor cells by inhibition of MDM2 synthesis. We have previously shown that E2F-1 overexpression induces apoptosis of MDM2-overexpressing sarcoma cells, which is related to the inhibition of MDM2 expression. Therefore, the present study was designed to investigate the in vitro and in vivo effect of combined treatment of adenovirus-mediated E2F-1 and topoisomerase II inhibitors on the growth inhibition and apoptosis in human sarcoma cells. Two human sarcoma cell lines, OsACL and U2OS, were treated with topoisomerase II inhibitors (Etoposide and Adriamycin), alone or in combination with adenoviral vectors expressing beta-galactosidase (Ad-LacZ) or E2F-1 (Ad-E2F-1). E2F-1 expression was confirmed by Western blot analysis. Ad-E2F-1 gene transfer at a low dose (multiplicity of infection, 2) markedly increased the sensitivity of human sarcoma cells to topoisomerase II inhibitor treatment. This cooperative effect of E2F-1 and topoisomerase II inhibitors was less marked in SAOS-2 cells (p53 and pRb null). Topoisomerase II inhibitors also cooperated with E2F-1 overexpression to enhance tumor cell killing in an in vivo model using xenografts in nude mice. When combined with Adriamycin or Etoposide, E2F-1 adenovirus therapy resulted in approximately 95% and 85% decrease in tumor size, respectively, compared to controls (P<.05). These results suggest a new chemosensitization strategy that is effective in MDM2-overexpressing tumors and may have clinical utility.
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PMID:Additive effect of adenovirus-mediated E2F-1 gene transfer and topoisomerase II inhibitors on apoptosis in human osteosarcoma cells. 1139 76

Nutlin-3a is a preclinical drug that stabilizes p53 by blocking the interaction between p53 and MDM2. In our previous study, Nutlin-3a promoted a tetraploid G(1) arrest in two p53 wild-type cell lines (HCT116 and U2OS), and both cell lines underwent endoreduplication after Nutlin-3a removal. Endoreduplication gave rise to stable tetraploid clones resistant to therapy-induced apoptosis. Prior knowledge of whether cells are susceptible to Nutlin-induced endoreduplication and therapy resistance could help direct Nutlin-3a-based therapies. In the present study, Nutlin-3a promoted a tetraploid G(1) arrest in multiple p53 wild-type cell lines. However, some cell lines underwent endoreduplication to relatively high extents after Nutlin-3a removal whereas other cell lines did not. The resistance to endoreduplication observed in some cell lines was associated with a prolonged 4N arrest after Nutlin-3a removal. Knockdown of either p53 or p21 immediately after Nutlin-3a removal could drive endoreduplication in otherwise resistant 4N cells. Finally, 4N-arrested cells retained persistent p21 expression; expressed senescence-associated beta-galactosidase; displayed an enlarged, flattened phenotype; and underwent a proliferation block that lasted at least 2 weeks after Nutlin-3a removal. These findings demonstrate that transient Nutlin-3a treatment can promote an apparently permanent proliferative block in 4N cells of certain cell lines associated with persistent p21 expression and resistance to endoreduplication.
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PMID:Persistent p21 expression after Nutlin-3a removal is associated with senescence-like arrest in 4N cells. 2048 8

HMGA2 is a major regulator of benign tumorigenesis from mesenchyme-derived tissues and stem-cell self-renewal. It has been postulated that HMGA2 mediates its critical function by decreasing p16(Ink4a)/p14(Arf) expression and cellular senescence. To repress the oncogenic activity of HMGA2, the lin-28-let-7 axis is thought to increasingly repress the expression of HMGA2 with age. To understand the HMGA2-p14(Arf) -relationship in benign tumorigenesis, we performed a series of experiments on mesenchymal stem-cells, i.e., the proposed cells of origin of lipomas and uterine leiomyomas. The expression of both genes was inversely correlated during senescence in vitro but contrary to the expectations in adipose tissue derived stem cells (ADSCs) stimulation of HMGA2 by FGF1 increased the expression of p14(Arf) . Based on the assumption that in ADSCs p14(Arf) is repressing HMGA2, siRNA silencing of p14(Arf) was performed resulting in a significant upregulation of HMGA2. To see if p14(Arf) can repress HMGA2 by a TP53-dependent mechanism, nutlin-3, a known MDM2 antagonist, was used which not only increased the activity of the senescence, associated markers p21 and beta-galactosidase, but also decreased the expression of HMGA2, suggesting that p14(Arf) indeed influences HMGA2 by a p53-dependent mechanism because nutlin-3 stabilizes p53. Accordingly, the HMGA2 response triggered by serum was reduced by treatment of ADSCs with nutlin-3. As to the interaction between HMGA2 and p14(Arf) in benign tumorigenesis, we propose a model where akin to MSC self-renewal during tissue repair the simultaneous increase of p14(Arf) with HMGA2 ensures genomic stability, whereas in turn p14(Arf) can repress HMGA2 via TP53.
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PMID:p14Arf acts as an antagonist of HMGA2 in senescence of mesenchymal stem cells-implications for benign tumorigenesis. 2145 46