Search results for "Tumor Suppressor Protein"
showing 10 items of 320 documents
Sodium phenylbutyrate induces apoptosis in human retinoblastoma Y79 cells: The effect of combined treatment with the topoisomerase I-inhibitor topote…
2001
Our results demonstrate that sodium phenylbutyrate, a compound with a low degree of toxicity, exerted a cytotoxic effect on human retinoblastoma Y79 cells in a time- and dose-dependent manner. Treatment of Y79 cells for 72 h with phenylbutyrate reduced cell viability by 63% at 2 mM and 90% at 4 mM. Cell death caused by phenylbutyrate exhibited the typical features of apoptosis, as shown by light and fluorescent microscopy. Western blot analysis demonstrated that exposure of Y79 cells to phenylbutyrate decreased the level of the antiapoptotic factor Bcl-2 and induced the activation of caspase-3, a key enzyme in the execution phase of apoptosis. Moreover, treatment with phenylbutyrate markedl…
Artesunate induces oxidative DNA damage, sustained DNA double-strand breaks, and the ATM/ATR damage response in cancer cells.
2011
Abstract Artesunate, the active agent from Artemisia annua L. used in the traditional Chinese medicine, is being applied as a first-line drug for malaria treatment, and trials are ongoing that include this drug in cancer therapy. Despite increasing interest in its therapeutic application, the mode of cell killing provoked by artesunate in human cells is unknown. Here, we show that artesunate is a powerful inducer of oxidative DNA damage, giving rise to formamidopyrimidine DNA glycosylase–sensitive sites and the formation of 8-oxoguanine and 1,N6-ethenoadenine. Oxidative DNA damage was induced in LN-229 human glioblastoma cells dose dependently and was paralleled by cell death executed by ap…
Differential Sensitivity of Malignant Glioma Cells to Methylating and Chloroethylating Anticancer Drugs: p53 Determines the Switch by Regulating xpc,…
2007
Abstract Glioblastoma multiforme is the most severe form of brain cancer. First line therapy includes the methylating agent temozolomide and/or the chloroethylating nitrosoureas [1-(2-chloroethyl)-1-nitrosourea; CNU] nimustine [1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea; ACNU], carmustine [1,3-bis(2-chloroethyl)-1-nitrosourea; BCNU], or lomustine [1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea; CCNU]. The mechanism of cell death after CNU treatment is largely unknown. Here we show that ACNU and BCNU induce apoptosis in U87MG [p53 wild-type (p53wt)] and U138MG [p53 mutant (p53mt)] glioma cells. However, contrary to what we observed previously for temozolomide, chl…
Temozolomide- and fotemustine-induced apoptosis in human malignant melanoma cells: response related to MGMT, MMR, DSBs, and p53
2009
Malignant melanomas are highly resistant to chemotherapy. First-line chemotherapeutics used in melanoma therapy are the methylating agents dacarbazine (DTIC) and temozolomide (TMZ) and the chloroethylating agents BCNU and fotemustine. Here, we determined the mode of cell death in 11 melanoma cell lines upon exposure to TMZ and fotemustine. We show for the first time that TMZ induces apoptosis in melanoma cells, using therapeutic doses. For both TMZ and fotemustine apoptosis is the dominant mode of cell death. The contribution of necrosis to total cell death varied between 10 and 40%. The O(6)-methylguanine-DNA methyltransferase (MGMT) activity in the cell lines was between 0 and 1100 fmol m…
The apoptotic effects of cisplatin and carboplatin in retinoblastoma Y79 cells.
1998
This study demonstrated that cisplatin and carboplatin stimulate apoptosis in human retinoblastoma Y79 cells, cisplatin being the most effective compound. The apoptotic effect appeared after 8 h and then increased in a time-dependent manner. Treatment with cisplatin and carboplatin also provoked an increase in the level of p53 and p21, and a lowering in Bcl-2. The prolonged exposure of Y79 cells to cisplatin induced resistance to cisplatin, carboplatin and etoposide. The basal level of p53 was in resistant cells higher than in untreated cells, while Bcl-2 was not modified. p53 and Bcl-2 levels did not change after treating of resistant cells with cisplatin, carboplatin or etoposide. However…
Chronic inflammatory IFN-γ signaling suppresses hepatocarcinogenesis in mice by sensitizing hepatocytes for apoptosis.
2011
Abstract Chronic liver inflammation is a critical component of hepatocarcinogenesis. Indeed, inflammatory mediators are believed to promote liver cancer by upholding compensatory proliferation of hepatocytes in response to tissue damage. However, inflammation can also mediate the depletion of malignant cells, but the difference between tumor-suppressive and tumor-promoting inflammation is not defined at the molecular level. Here, we analyzed the role of the major inflammatory mediator IFN-γ in chemical hepatocarcinogenesis of transgenic mice that overexpress IFN-γ in the liver; these mice manifest severe chronic inflammatory liver damage and lasting compensatory regeneration. We found that …
Topotecan-triggered degradation of topoisomerase I is p53-dependent and impacts cell survival.
2005
Abstract The anticancer drug topotecan belongs to the group of topoisomerase I (topo I) inhibitors. In the presence of topotecan, topo I cleaves the DNA but is unable to religate the single-strand break. This leads to stabilization of topo I-DNA–bound complexes and the accumulation of DNA strand breaks that may interfere with DNA replication. The molecular mechanism of controlling the repair of topo I-DNA covalent complexes and its impact on sensitivity of cells to topotecan is largely unknown. Here, we used mouse embryonic fibroblasts expressing wild-type p53 and deficient in p53, in order to elucidate the role of p53 in topotecan-induced cell death. We show that p53-deficient mouse embryo…
Pharmacologic activation of p53 elicits Bax-dependent apoptosis in the absence of transcription
2003
AbstractRecent efforts to develop pharmacologic agents that restore function to mutant forms of p53 hold significant promise in cancer therapy. Here, we examine the effects of such pharmacologic activation of p53 function using a small molecule, PRIMA-1, and a model system employing a p53 protein fused to a mutant steroid binding domain of the murine estrogen receptor (p53ERtam) that renders it responsive only in the presence of 4-hydroxytamoxifen. In either case, p53 activation triggered apoptosis that was not inhibited by the presence of macromolecular synthesis inhibitors. This p53-induced, transcription-independent apoptosis is Bax dependent, proceeds in the absence of a nucleus, and in…
The p53 Tumor Suppressor Network Is a Key Responder to Microenvironmental Components of Chronic Inflammatory Stress
2005
Abstract Activation of the p53 network plays a central role in the inflammatory stress response associated with ulcerative colitis and may modulate cancer risk in patients afflicted with this chronic disease. Here, we describe the gene expression profiles associated with four microenvironmental components of the inflammatory response (NO•, H2O2, DNA replication arrest, and hypoxia) that result in p53 stabilization and activation. Isogenic HCT116 and HCT116 TP53−/− colon cancer cells were exposed to the NO• donor Sper/NO, H2O2, hypoxia, or hydroxyurea, and their mRNA was analyzed using oligonucleotide microarrays. Overall, 1,396 genes changed in a p53-dependent manner (P < 0.001), wit…
Heterogeneous lack of expression of the tumour suppressor PTEN protein in human neoplastic tissues.
2001
PTEN, a tumour suppressor gene located at chromosome 10q23 and commonly mutated or deleted in a variety of tumours, encodes a dual-specific/phosphatidylinositol-3,4,5-triphosphate (PIP3) phosphatase. We report the generation of an anti-PTEN monoclonal antibody (MAb) that recognises an epitope at the C-terminus of PTEN, and describe the heterogeneous lack of expression of the PTEN protein in human tumour tissues, as demonstrated by immunohistochemical methods. Our anti-PTEN MAb provides a useful tool for the study of PTEN protein expression in tumour samples, in the search for tumour prognostic molecular markers.