8 research outputs found

    Diallyl Trisulfide Modulates Notch Pathway Components in Breast Cancer Cells

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    Breast cancer affects one in eight women throughout the course of their lifetimes creating an immediate demand for novel prevention strategies against this disease. The Notch signaling pathway is often aberrantly activated in human malignancies including breast cancer. Alpha secretases, including A Disintegrin and Metalloprotease (ADAM)-10 and -17, are proteases that play a key role in the cleavage of cell surface molecules and subsequent ligand-mediated activation of Notch signaling pathway. High expression levels of ADAM10 are clinically associated with lower disease-free survival in breast cancer patients. The goal of this study was to determine the effect of diallyl trisulfide (DATS), a bioactive organosulfide found in garlic and other Allium vegetables, on Notch pathway components, specifically alpha secretases, in an in vitro model of breast cancer. Here we report for the first time that DATS inhibits the expression of ADAM10 and ADAM17 in estrogen-independent MDA-MB-231 and estrogen-dependent MCF-7 breast cancer cells, as well as in Harvey-ras (H-Ras) transformed MCF10A-H-Ras breast epithelial cells. We also show that DATS inhibits the Notch ligands Jagged-1 and Jagged-2. Furthermore, we show that DATS treatment reduces overall cell viability in MDA-MB-231, MCF-7 and MCF10A-H-Ras cells, and that DATS treatment reduce

    Increased Ammonium Toxicity in Response to Exogenous Glutamine in Metastatic Breast Cancer Cells

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    Several cancers, including breast cancers, show dependence on glutamine metabolism. The purpose of the present study was to determine the mechanistic basis and impact of differential glutamine metabolism in nonmetastatic and metastatic murine mammary cancer cells. Universally labeled 13C5-glutamine metabolic tracing, qRT-PCR, measures of reductive‚Äďoxidative balance, and exogenous ammonium chloride treatment were used to assess glutamine reprogramming. Results show that 4 mM media concentration of glutamine, compared with 2 mM, reduced viability only in metastatic cells, and that this decrease in viability was accompanied by increased incorporation of glutamine-derived carbon into the tricarboxylic acid (TCA) cycle. While increased glutamine metabolism in metastatic cells occurred in tandem with a decrease in the reduced/oxidized glutathione ratio, treatment with the antioxidant molecule N-acetylcysteine did not rescue cell viability. However, the viability of metastatic cells was more sensitive to ammonium chloride treatment compared with nonmetastatic cells, suggesting a role of metabolic reprogramming in averting nitrogen cytotoxicity in nonmetastatic cells. Overall, these results demonstrate the ability of nonmetastatic cancer cells to reprogram glutamine metabolism and that this ability may be lost in metastatic cells

    Hypoxia-Mediated ATF4 Induction Promotes Survival in Detached Conditions in Metastatic Murine Mammary Cancer Cells

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    Regions of hypoxia are common in solid tumors and drive changes in gene expression that increase risk of cancer metastasis. Tumor cells must respond to the stress of hypoxia by activating genes to modify cell metabolism and antioxidant response to improve survival. The goal of the current study was to determine the effect of hypoxia on cell metabolism and markers of oxidative stress in metastatic (metM-Wntlung) compared with nonmetastatic (M-Wnt) murine mammary cancer cell lines. We show that hypoxia induced a greater suppression of glutamine to glutamate conversion in metastatic cells (13% in metastatic cells compared to 7% in nonmetastatic cells). We also show that hypoxia increased expression of genes involved in antioxidant response in metastatic compared to nonmetastatic cells, including glutamate cysteine ligase catalytic and modifier subunits and malic enzyme 1. Interestingly, hypoxia increased the mRNA level of the transaminase glutamic pyruvic transaminase 2 (Gpt2, 7.7-fold) only in metM-Wntlung cells. The change in Gpt2 expression was accompanied by transcriptional (4.2-fold) and translational (6.5-fold) induction of the integrated stress response effector protein activating transcription factor 4 (ATF4). Genetic depletion ATF4 demonstrated importance of this molecule for survival of hypoxic metastatic cells in detached conditions. These findings indicate that more aggressive, metastatic cancer cells utilize hypoxia for metabolic reprogramming and induction of antioxidant defense, including activation of ATF4, for survival in detached conditions

    Metabolic Stress in Non-Metastatic and Metastatic Murine Mammary Cancer Cells

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    Breast cancer is a major public health concern, with one in eight women in the United States expected to be diagnosed throughout the course of her lifetime. Metastasis of cancer to secondary sites in the body is the primary cause of death among breast cancer patients, highlighting the critical need to understand mechanisms that contribute to metastatic progression. Throughout metastatic progression, cancer cells are exposed to cell stresses, including metabolic, oxidative, and hypoxic cell stress, which cells must overcome in order to survive and progress. In the present studies, we determined the effects of metabolic cell stresses in non-metastatic M-Wnt and metastatic metM-Wntlung murine mammary cancer cell lines. Culturing both cell lines in high (4 mM) compared to low (2 mM) glutamine conditions suppressed viability of metM-Wntlung cells. M-Wnt cells had no change in viability in response to glutamine concentration, and high glutamine concentrations decreased mRNA levels of genes involved in glutamine catabolism in M-Wnt cells only. In accordance with the differences in glutamine metabolism, metM-Wntlung cell demonstrated an increase in glutamine flux into the TCA cycle in high glutamine, whereas M-Wnt cells had no change in glutamine flux in response to glutamine concentration. metM-Wntlung cells were significantly more sensitive to treatment with ammonium, a byproduct of glutamine catabolism, suggesting that a high rate of metabolism and ammonium production may decrease cell viability in high glutamine conditions. These data suggest that glutamine utilization and metabolism change in cancer cells at different stages of metastatic progression. In addition to metabolic stress from variable nutrient availability, changes in oxygen availability are a source of metabolic stress for cancer cells. Hypoxia, or low oxygen tension, is associated with metastasis and reduced survival, making it an important biological process to study in the context of cancer. Culturing non-metastatic and metastatic cells in hypoxia increased mRNA levels of genes related to antioxidant defense only in metM-Wntlung cells. Hypoxia also induced expression of the integrated stress response effector protein activating transcription factor 4 (ATF4) and its target gene glutamic pyruvic transaminase (Gpt2) in metM-Wntlung cells. Furthermore, genetic depletion of ATF4 reduced survival of hypoxic metM-Wntlungcells in detached conditions. These results suggest that cancer cells accumulate cell stress throughout the course of progression and must adapt their gene expression for continued survival throughout metastatic processes. The results of these two studies highlight metabolic adaptations and vulnerabilities of cancer cells at different stages of progression. These data will contribute to improving our understanding of therapeutic targets to prevent or delay metastasis in cancer patients, thereby reducing cancer mortality

    Modulation of Notch Signaling Pathway by Bioactive Dietary Agents

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    Notch signaling is often aberrantly activated in solid and hematological cancers and regulates cell fate decisions and the maintenance of cancer stem cells. In addition, increased expression of Notch pathway components is clinically associated with poorer prognosis in several types of cancer. Targeting Notch may have chemopreventive and anti-cancer effects, leading to reduced disease incidence and improved survival. While therapeutic agents are currently in development to achieve this goal, several researchers have turned their attention to dietary and natural agents for targeting Notch signaling. Given their natural abundance from food sources, the use of diet-derived agents to target Notch signaling offers the potential advantage of low toxicity to normal tissue. In this review, we discuss several dietary agents including curcumin, EGCG, resveratrol, and isothiocyanates, which modulate Notch pathway components in a context-dependent manner. Dietary agents modulate Notch signaling in several types of cancer and concurrently decrease in vitro cell viability and in vivo tumor growth, suggesting a potential role for their clinical use to target Notch pathway components, either alone or in combination with current therapeutic agents
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