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Melatonin decreases estrogen receptor binding to estrogen response elements sites on the OCT4 gene in human breast cancer stem cells

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Melatonin decreases estrogen receptor binding to estrogen response elements sites on the OCT4 gene in human breast cancer stem cells ABSTRACT Cancer stem cells (CSCs) pose a challenge in cancer treatment, as these cells can drive tumor growth and are resistant to chemotherapy. Melatonin exerts its oncostatic effects through the estrogen receptor (ER) pathway in cancer cells, however its action in CSCs is unclear. Here, we evaluated the effect of melatonin on the regulation of the transcription factor OCT4 (Octamer Binding 4) by estrogen receptor alpha (ERα) in breast cancer stem cells (BCSCs). The cells were grown as a cell suspension or as anchorage independent growth, for the mammospheres growth, representing the CSCs population and treated with 10 nM estrogen (E2) or 10 µM of the environmental estrogen Bisphenol A (BPA) and 1 mM of melatonin. At the end, the cell growth as well as OCT4 and ERα expression and the binding activity of ERα to the OCT4 was assessed. The increase in numbe
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High-Throughput Chemical Screens Identify Disulfiram as an Inhibitor of Human Glioblastoma Stem Cells

High-Throughput Chemical Screens Identify Disulfiram as an Inhibitor of Human Glioblastoma Stem Cells ABSTRACT Glioblastoma Multiforme (GBM) continues to have a poor patient prognosis despite optimal standard of care. Glioma stem cells (GSCs) have been implicated as the presumed cause of tumor recurrence and resistance to therapy. With this in mind, we screened a diverse chemical library of 2,000 compounds to identify therapeutic agents that inhibit GSC proliferation and therefore have the potential to extend patient survival. High-throughput screens (HTS) identified 78 compounds that repeatedly inhibited cellular proliferation, of which 47 are clinically approved for other indications and 31 are experimental drugs. Several compounds (such as digitoxin, deguelin, patulin and phenethyl caffeate) exhibited high cytotoxicity, with half maximal inhibitory concentrations (IC 50 ) in the low nanomolar range. In particular, the FDA approved drug for the treatment of alcoholism, disulfiram (DS
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Up-regulation of c-MYC and SIRT1 expression correlates with malignant transformation in the serrated route to colorectal cancer

Up-regulation of c-MYC and SIRT1 expression correlates with malignant transformation in the serrated route to colorectal cancer ABSTRACT Approximately 7.5% of all colorectal cancers are considered to originate from the alternative, serrated route. Here, we investigate the expression of the c-MYC oncogene and the SIRT1 protein deacetylase by immunohistochemical staining in subgroups of colorectal serrated lesions that were characterized by different molecular alterations. The expression of c-MYC and SIRT1 correlated with the presence of  KRAS  and  BRAF  mutations and high expression of c-MYC and SIRT1 was strongly associated with higher grades of malignancy. In contrast, in the majority of serrated lesions without  KRAS  or  BRAF  mutations, c-MYC and SIRT1 expression was not found increased. In this group only a subset of mostly high grade intraepithelial neoplasia and carcinoma was characterized by elevated c-MYC and SIRT1 expression. This was associated with nuclear localization of
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Quantifying pharmacologic suppression of cellular senescence: prevention of cellular hypertrophy versus preservation of proliferative potential. Zoya N Demidenko

Quantifying pharmacologic suppression of cellular senescence: prevention of cellular hypertrophy versus preservation of proliferative potential Abstract Development of agents that suppress aging (aging suppressants) requires quantification of cellular senescence. Cellular senescence in vitro is characterized by a large cell morphology and permanent loss of proliferative potential. When HT-1080 cells were arrested by p21, they continued to grow exponentially in size and became hypertrophic with a 15-fold increase in the protein content per cell. These changes were mirrored by accumulation of GFP (driven by CMV promoter) per cell, which also served as a marker of cellular hypertrophy. Preservation of proliferative potential (competence) was measured by an increase in live cell number, when p21 was switched off. While modestly decreasing hypertrophy in p21-arresrted cells, rapamycin considerably preserved competence, converting senescence into quiescence. Preservation of proliferative pot
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Paradoxical suppression of cellular senescene by p53. Zoya N Demidenko

Paradoxical suppression of cellular senescene by p53 Abstract The tumor suppressor p53 is a canonical inducer of cellular senescence (irreversible loss of proliferative potential and senescent morphology). p53 can also cause reversible arrest without senescent morphology, which has usually been interpreted as failure of p53 to induce senescence. Here we demonstrate that p53-induced quiescence actually results from suppression of senescence by p53. In previous studies, suppression of senescence by p53 was masked by p53-induced cell cycle arrest. Here, we separated these two activities by inducing senescence through overexpression of p21 and then testing the effect of p53 on senescence. We found that in p21-arrested cells, p53 converted senescence into quiescence. Suppression of senescence by p53 required its transactivation function. Like rapamycin, which is known to suppress senescence, p53 inhibited the mTOR pathway. We suggest that, while inducing cell cycle arrest, p53 may simultane
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Exploring long-term protection of normal human fibroblast and epithelial cells from chemotherapy in cell culture. Zoya N Demidenko

Exploring long-term protection of normal human fibroblast and epithelial cells from chemotherapy in cell culture Abstract Killing of proliferating normal cells limits chemotherapy of cancer. Several strategies to selectively protect normal cells were previously suggested. Here we further explored the protection of normal cells from cell cycle-specific chemotherapeutic agents such as mitotic inhibitors (MI). We focused on a long-term cell recovery (rather than on a short-term cell survival) after a 3-day exposure to MI (paclitaxel and nocodazole). In three normal human cell types (RPE, NKE, WI-38t cells) but not in cancer cells with mutant p53, pre-treatment with nutlin-3a, a non-genotoxic inducer of wt p53, caused G1 and/or G2 arrest, thus preventing lethal mitotic arrest caused by MI and allowing normal cells to recover after removal of MI. Rapamycin, an inhibitor of the nutrient-sensing mTOR pathway, potentiated the protective effect of nutlin-3a in normal cells. Also, a combination
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The purpose of the HIF-1/PHD feedback loop: to limit mTOR-induced HIF-1alpha. Zoya N Demidenko

The purpose of the HIF-1/PHD feedback loop: to limit mTOR-induced HIF-1alpha Abstract Prolyl hydroxylases (PHDs) target hypoxia-inducible factor-1α (HIF-1α) for degradation. Hypoxia inactivates PHDs, causing accumulation of HIF-1α. In turn, HIF-1 further transactivates PHDs. It is thought that the purpose of this feedback loop is to limit HIF-1α accumulation caused by hypoxia. Here, we suggest that the feedback is intended to limit the induction of HIF-1α by insulin, growth factors, hormones, cytokines and nutrients. These stimuli induce HIF-1α by increasing its translation, not by inhibiting PHDs. As exemplified herein, in a mTOR-dependent manner, insulin transiently induced HIF-1α in retinal pigment epithelial (RPE) cells. Induction of HIF-1α was followed by activation of HIF-dependent transcription. Furthermore, DFX, which inactivates PHDs, potentiated the induction of HIF-1α by insulin. We propose that the most relevant function of the PHD-HIF feedback loop is to limit the inductio
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