109 research outputs found
Semiquinone Radical Intermediate in Catecholic Estrogen-Mediated Cytotoxicity and Mutagenesis: Chemoprevention Strategies with Antioxidants
No full textRedox generation of nitric oxide to radiosensitize hypoxic cells
No full textPurpose: Previous studies have shown that nitric oxide (NO) delivered from NO donor agents sensitizes hypoxic cells to ionizing radiation. In the present study, nitroxyl (NO?), a potential precursor to endogenous NO production, was evaluated for hypoxic cell radiosensitization, either alone or in combination with electron acceptor agents.Methods and Materials: Radiation survival curves of Chinese hamster V79 lung fibroblasts under aerobic and hypoxic conditions were assessed by clonogenic assay. Hypoxia induction was achieved by metabolism-mediated oxygen depletion in dense cell suspensions. Cells were treated with NO? produced from the nitroxyl donor Angeli’s salt (AS, Na2N2O3, sodium trioxodinitrate), in the absence or presence of electron acceptor agents, ferricyanide, or tempol. NO concentrations resulting from the combination of AS and ferricyanide or tempol were measured under hypoxic conditions using an NO-sensitive electrode.Results: Treatment of V79 cells under hypoxic conditions with AS alone did not result in radiosensitization; however, the combination of AS with ferricyanide or tempol resulted in significant hypoxic radiosensitization with SERs of 2.5 and 2.1, respectively. Neither AS alone nor AS in combination with ferricyanide or tempol influenced aerobic radiosensitivity. The presence of NO generated under hypoxic conditions from the combination of AS with ferricyanide or tempol was confirmed using an NO-sensitive electrode.Conclusion: Combining NO? generated from AS with electron acceptors results in NO generation and substantial hypoxic cell radiosensitization. NO? derived from donor agents or endogenously produced in tumors, combined with electron acceptors, may provide an important strategy for radiosensitizing hypoxic cells and warrants in vivo evaluation
Effects of Hypoxia on Radiation-Responsive Stress-Activated Protein Kinase, p53, and Caspase 3 Signals in TK6 Human Lymphoblastoid Cells.
No full textRadiation-induced changes in gene-expression profiles for the SCC VII tumor cells grown in vitro and in vivo
No full textGene expression profiling of breast, prostate, and glioma cells following single versus fractionated doses of radiation
No full textThe cytotoxicity of nitroxyl: possible implications for the pathophysiological role of NO
No full textIn addition to the broad repertoire of regulatory functions nitric oxide (NO) serves in mammalian physiology, the L-arginine:NO pathway is also involved in numerous pathophysiological mechanisms. While NO itself may actually protect cells from the toxicity of reactive oxygen radicals in some cases, it has been suggested that reactive nitrogen oxide species formed from nitric oxide synthase (NOS) can be cytotoxic. In addition to NO, the one electron reduction product NO- has been proposed to be formed from NOS. We investigated the potential cytotoxic role of nitroxyl (NO-), using the nitroxyl donor Angelis's salt, (AS; sodium trioxodinitrate, Na2N2O3) as the source of NO-. As was found to be cytotoxic to Chinese hamster V79 lung fibroblast cells over a concentration range of 2-4 mM. The presence of equimolar ferricyanide (Fe(III)-(CN6)3-), which converts NO- to NO, afforded dramatic protection against AS-mediated cytotoxicity. Treatment of V79 cells with L-buthionine sulfoximine to reduce intracellular glutathione markedly enhanced AS cytotoxicity, which suggests that GSH is critical for cellular protection against the toxicity of NO-. Further experiments showed that low molecular weight transition metal complexes associated with the formation of reactive oxygen species are not involved in AS-mediated cytotoxicity since metal chelators had no effect. However, under aerobic conditions, AS was more toxic than under hypoxic conditions, suggesting that oxygen dramatically enhanced AS-mediated cytotoxicity. At a molecular level, AS exposure resulted in DNA double strand breaks in whole cells, and this effect was completely prevented by coincubation of cells with ferricyanide or Tempol. The data in this study suggest that nitroxyl may contribute to the cytotoxicity associated with an enhanced expression of the L-arginine:NO pathway under different biological conditions
Abstract 5861: Enhanced radiosenistivity of EGFR-TKI sensitive and resistant NSCLC cells by abemaciclib is mediated by altered DNA repair and metabolic pathways
No full textAbstract
Dysregulation of the p16(INK4a)-CyclinD-CDK4/6-Rb pathways in patients with NSCLC (Non-Small Cell Lung Cancer) is a rational therapeutic target. The current study investigated the radiosensitizing potential of a novel CDK4/6 inhibitor, LY2835219 (LY, Abemaciclib) in NSCLC cell lines with varied genomic context to identify genomic and metabolic biomarkers that are predictive of a response over conventional EGFR-tyrosine kinase inhibitor (EGFR-TKI) therapy. NSCLC cell lines were exposed to LY (0-10uM) for 24 hr immediately after 0-10 Gy radiation. Cell survival was assessed by clonogenic assay and cell cycle distribution was quantified by flow cytometry. Dose modifying factors (DMF) were calculated at 10% survival from radiation survival curves. Altered DNA repair pathways and metabolic profiling of cells post LY treatment was assessed by immunoblot and LC/MS mass spectrometry analysis. LY treatment enhanced radiosensitivity of EGFR-TKI sensitive (HCC827, PC9) and EGFR-TKI resistant (H820 and H1975) cell lines with DMF of 1.3 (±0.06), 1.4 (±0.30), 1.5 (±0.51) and 1.3 (±0.02), respectively. Values in the parenthesis indicates standard deviation. Wild type EGFR expressing cells (A549 and H460) also showed enhanced radiosensitivity by LY with DMF of 1.6 (±0.09) and 1.75(±0.15), respectively. Interestingly, no radiation enhancement by LY was observed for cells deficient in functional PTEN (H1650), Rb (H82) and p53 (H460 DNp53 and H1299) protein. Radiosensitization was also observed for cells made resistant to third generation EGFR-TKI, AZD9291. Flow cytometry analysis of majority of cell types exposed to LY exhibited 55% to 94% G1 arrest (depending on cell type). Mechanistically, the combinatorial treatment in radiosensitive cells showed elevated phosphorylated-γH2Ax. Combination treatment also reduced expression of ATR, ATM, DNA-PK, Rad51 and Chk-2 suggestive of reduced DNA repair compared to radiation alone. LY treatment brought major changes in the glycolysis/TCA/ total amino acids. LY increased significantly Acetyl-CoA, fumarate and malate, indicating enhanced oxidative phosphorylation. LY significantly elevated Uric acid levels suggestive of oxidative stress and elevated nucleotide degradation. Finally, administration of 100mg/kg LY2835219 for five days in combination with fractionated dose of radiation (3 Gy) significantly delayed tumor regrowth in H460 xenograft (p< 0.014). Collectively, our pre-clinical data indicates altered Rb, p53 and PTEN status are distinct predictive biomarkers of response for LY mediated radiosensitivity and provides an alternative therapeutic option in overcoming EGFR-TKI resistance in NSCLC.
Note: This abstract was not presented at the meeting.
Citation Format: Sarwat Naz, William DeGraff, Anastasia Sowers, Rajani Choudhuri, Maria Wissler, Janet Gamson, John Cook, James B. Mitchell. Enhanced radiosenistivity of EGFR-TKI sensitive and resistant NSCLC cells by abemaciclib is mediated by altered DNA repair and metabolic pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5861. doi:10.1158/1538-7445.AM2017-5861</jats:p
DIGITAL CAPTURE AND PRESERVATION OF HISTORIC MINING DATA FROM THE KEWEENAW COPPER DISTRICT, MICHIGAN
No full text
The school-room guide, embodying the instruction given by the author at teachers' institutes, in New York and other states, and especially intended to assist public school teachers in the practical work of the school-room.
No full textMode of access: Internet
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