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Organic Letters Jun 2016UV irradiation of several aryl boronates efficiently produced bifunctional benzyl cations that selectively form guanine-cytosine cross-links in DNA. Photoinduced...
UV irradiation of several aryl boronates efficiently produced bifunctional benzyl cations that selectively form guanine-cytosine cross-links in DNA. Photoinduced homolysis of the C-Br bond took place with the aryl boronate bromides 3a and 4a, generating free radicals that were oxidized to benzyl cations via electron transfer. However, photoirradiation of the quaternary ammonium salts 3b and 4b led to heterolysis of C-N bond, directly producing benzyl cations. The electron-donating group in the aromatic ring greatly enhanced cross-linking efficiency.
Topics: Base Sequence; Benzene Derivatives; Boronic Acids; Cations; Cross-Linking Reagents; Cyclic N-Oxides; Cytosine; DNA; DNA Adducts; Guanine; Hydroxylamines; Oxidation-Reduction; Photochemical Processes
PubMed: 27191599
DOI: 10.1021/acs.orglett.6b00755 -
Experimental Biology and Medicine... Jun 2016The purpose of this study was to evaluate the combination effect of resveratrol and methoxyamine on radiosensitivity of iododeoxyuridine in spheroid culture of U87MG...
The purpose of this study was to evaluate the combination effect of resveratrol and methoxyamine on radiosensitivity of iododeoxyuridine in spheroid culture of U87MG glioblastoma cell line using colony formation and alkaline comet assays. Spheroids on day-20 with 350 µm diameters were treated with 20 µM resveratrol and/or 6 mM methoxyamine and/or 1 µM iododeoxyuridine for one volume doubling time (67 h), and then irradiated with 2 Gy gamma-radiation ((60)Co) in different groups. After treatment, viability of the cells, colony forming ability and DNA damages were obtained by blue dye exclusion, colony formation and alkaline comet assay, respectively. Our results showed that methoxyamine and resveratrol could significantly reduce colony number and induce the DNA damages of glioblastoma spheroid cells treated with iododeoxyuridine in combination with gamma-rays. Therefore, methoxyamine as base excision repair inhibitor and resveratrol as hypoxia inducible factor 1-alpha inhibitor in combination with iododeoxyuridine as radiosensitizer enhanced the radiosensitization of glioblastoma spheroid cells.
Topics: Antineoplastic Agents; Cell Line, Tumor; Cell Survival; Colony-Forming Units Assay; Comet Assay; Gamma Rays; Humans; Hydroxylamines; Idoxuridine; Neuroglia; Radiation Tolerance; Radiation-Sensitizing Agents; Resveratrol; Stilbenes
PubMed: 26748400
DOI: 10.1177/1535370215622583 -
Scientific Reports Nov 2015Base excision repair (BER) is an essential pathway for pancreatic ductal adenocarcinoma (PDA) survival. Attempts to target this repair pathway have failed due to lack of...
UNLABELLED
Base excision repair (BER) is an essential pathway for pancreatic ductal adenocarcinoma (PDA) survival. Attempts to target this repair pathway have failed due to lack of tumor-selectivity and very limited efficacy. The
NAD(P)H
Quinone Oxidoreductase 1 (NQO1) bioactivatable drug, ß-lapachone (ARQ761 in clinical form), can provide tumor-selective and enhanced synergy with BER inhibition. ß-Lapachone undergoes NQO1-dependent futile redox cycling, generating massive intracellular hydrogen peroxide levels and oxidative DNA lesions that stimulate poly(ADP-ribose) polymerase 1 (PARP1) hyperactivation. Rapid NAD(+)/ATP depletion and programmed necrosis results. To identify BER modulators essential for repair of ß-lapachone-induced DNA base damage, a focused synthetic lethal RNAi screen demonstrated that silencing the BER scaffolding protein, XRCC1, sensitized PDA cells. In contrast, depleting OGG1 N-glycosylase spared cells from ß-lap-induced lethality and blunted PARP1 hyperactivation. Combining ß-lapachone with XRCC1 knockdown or methoxyamine (MeOX), an apyrimidinic/apurinic (AP)-modifying agent, led to NQO1-dependent synergistic killing in PDA, NSCLC, breast and head and neck cancers. OGG1 knockdown, dicoumarol-treatment or NQO1- cancer cells were spared. MeOX + ß-lapachone exposure resulted in elevated DNA double-strand breaks, PARP1 hyperactivation and TUNEL+ programmed necrosis. Combination treatment caused dramatic antitumor activity, enhanced PARP1-hyperactivation in tumor tissue, and improved survival of mice bearing MiaPaca2-derived xenografts, with 33% apparent cures.
SIGNIFICANCE
Targeting base excision repair (BER) alone has limited therapeutic potential for pancreatic or other cancers due to a general lack of tumor-selectivity. Here, we present a treatment strategy that makes BER inhibition tumor-selective and NQO1-dependent for therapy of most solid neoplasms, particularly for pancreatic cancer.
Topics: Animals; Autophagy; Catalase; Cell Line, Tumor; Cell Survival; DNA Breaks, Double-Stranded; DNA Glycosylases; DNA Repair; DNA-Binding Proteins; Dicumarol; Female; Humans; Hydroxylamines; Mice; Mice, Nude; NAD(P)H Dehydrogenase (Quinone); Naphthoquinones; Pancreatic Neoplasms; Poly(ADP-ribose) Polymerases; Reactive Oxygen Species; Transplantation, Heterologous; X-ray Repair Cross Complementing Protein 1
PubMed: 26602448
DOI: 10.1038/srep17066 -
Acta Crystallographica. Section E,... Oct 2015The title compound, C 11H12N4O2,was prepared via the transformation of sodium 4-acetyl-1-phenyl-1H-[1.2.3]triazolate under the action of meth-oxy-amine hydro-chloride....
The title compound, C 11H12N4O2,was prepared via the transformation of sodium 4-acetyl-1-phenyl-1H-[1.2.3]triazolate under the action of meth-oxy-amine hydro-chloride. The dihedral angle between the triazole and phenyl rings is 25.12 (16)° and the C atom of the meth-oxy group deviates from the triazole plane by 0.894 (4)Å. The conformation of the CONHR-group is consolodated by an intra-molecular N-H⋯N hydrogen bond to an N-atom of the triazole ring, which closes an S(5) ring. In the crystal, weak N-H⋯N hydrogen bonds link the mol-ecules into C(6) [010] chains.
PubMed: 26594485
DOI: 10.1107/S2056989015017776 -
PloS One 2015Indoleamine 2,3-dioxygenase-1 (IDO) is an immune regulatory enzyme expressed by most human tumors. IDO levels in tumor cells correlate with increased metastasis and poor...
Indoleamine 2,3-dioxygenase-1 (IDO) is an immune regulatory enzyme expressed by most human tumors. IDO levels in tumor cells correlate with increased metastasis and poor patient outcome and IDO is linked to tumor cell resistance to immunotherapy, radiation therapy, and chemotherapy. Knowledge of tumor cell-autonomous effects of IDO, independent of its well-known role in regulating and suppressing anti-tumor immune responses, is limited. Clonal populations of A549 human lung adenocarcinoma cells stably transfected with anti-IDO shRNA or scrambled control shRNA were used to study IDO effects on drug sensitivity and resistance. IFNγ was used to induce IDO in those cells. We show, for the first time, that IDO mediates human tumor cell resistance to the candidate anticancer drugs FK866 (an NAD+ inhibitor), methoxyamine (MX, a base excision repair [BER] inhibitor) and approved anticancer drugs pemetrexed (a folate anti-metabolite) and gemcitabine (a nucleoside analogue), and combined treatment with pemetrexed and MX, in the absence of immune cells. Concurrent knockdown of IDO and thymidylate synthase (TS, a key rate-limiting enzyme in DNA synthesis and repair) sensitizes human lung cancer cells to pemetrexed and 5FUdR to a greater degree than knockdown of either target alone. We conclude that BER in IDO-expressing A549 cells plays a major role in mediating resistance to a range of approved and candidate anticancer drugs. IDO inhibitors are undergoing clinical trials primarily to improve antitumor immune responses. We show that targeting IDO alone or in combination with TS is a potentially valuable therapeutic strategy for cancer treatment, independent of immune activity and in combination with conventional chemotherapy.
Topics: Acrylamides; Animals; BRCA2 Protein; Cell Line, Tumor; Clone Cells; DNA Repair; Deoxycytidine; Down-Regulation; Drug Resistance, Neoplasm; Enzyme Induction; Floxuridine; Gene Knockdown Techniques; Humans; Hydroxylamines; Indoleamine-Pyrrole 2,3,-Dioxygenase; Mice, SCID; NAD; Pemetrexed; Piperidines; RNA, Small Interfering; Thymidylate Synthase; Xenograft Model Antitumor Assays; Gemcitabine
PubMed: 26579709
DOI: 10.1371/journal.pone.0143435 -
PloS One 2015DNA damage and repair is a fundamental process that plays an important role in cancer treatment. Base excision repair (BER) is a major repair pathway that often leads to...
DNA damage and repair is a fundamental process that plays an important role in cancer treatment. Base excision repair (BER) is a major repair pathway that often leads to drug resistance in DNA-targeted cancer chemotherapy. In order to measure BER, we have developed a near infrared (NIR) fluorescent probe. This probe binds to a key intermediate, termed apurinic/apyrimidinic (AP) site, in the BER pathway where DNA damage and repair occurs. We have developed an assay to show the efficacy of the probe binding to AP sites and have shown that it can distinguish AP sites in DNA extract from chemotherapy treated cells. This probe has potential application in monitoring patient response to chemotherapy and evaluating new drugs in development.
Topics: Animals; Base Pairing; Base Sequence; Binding Sites; Cattle; Cell Line, Tumor; Colonic Neoplasms; DNA; DNA Breaks, Single-Stranded; DNA Damage; DNA Repair; DNA-(Apurinic or Apyrimidinic Site) Lyase; Floxuridine; Fluorescent Dyes; Humans; Hydroxylamines; Methyl Methanesulfonate; Molecular Sequence Data; Spectrometry, Fluorescence; Time Factors
PubMed: 26309022
DOI: 10.1371/journal.pone.0131330 -
Cancer Biology & Therapy 2015Triple negative breast cancer cell lines have been reported to be resistant to the cyotoxic effects of temozolomide (TMZ). We have shown previously that a novel protein,...
Triple negative breast cancer cell lines have been reported to be resistant to the cyotoxic effects of temozolomide (TMZ). We have shown previously that a novel protein, human homolog of Xenopus gene which Prevents Mitotic Catastrophe (hPMC2) has a role in the repair of estrogen-induced abasic sites. Our present study provides evidence that downregulation of hPMC2 in MDA-MB-231 and MDA-MB-468 breast cancer cells treated with temozolomide (TMZ) decreases cell survival. This increased sensitivity to TMZ is associated with an increase in number of apurinic/apyrimidinic (AP) sites in the DNA. We also show that treatment with another alkylating agent, BCNU, results in an increase in AP sites and decrease in cell survival. Quantification of western blot analyses and immunofluorescence experiments reveal that treatment of hPMC2 downregulated cells with TMZ results in an increase in γ-H2AX levels, suggesting an increase in double strand DNA breaks. The enhancement of DNA double strand breaks in TMZ treated cells upon downregulation of hPCM2 is also revealed by the comet assay. Overall, we provide evidence that downregulation of hPMC2 in breast cancer cells increases cytotoxicity of alkylating agents, representing a novel mechanism of treatment for breast cancer. Our data thus has important clinical implications in the management of breast cancer and brings forth potentially new therapeutic strategies.
Topics: Alkylating Agents; Breast Neoplasms; Cell Line, Tumor; Cell Survival; DNA Breaks, Double-Stranded; DNA Repair; Dacarbazine; Down-Regulation; Exonucleases; Female; Histones; Humans; Temozolomide
PubMed: 25849309
DOI: 10.1080/15384047.2015.1016661 -
DNA Repair Mar 2015A number of endogenous and exogenous agents, and cellular processes create abasic (AP) sites in DNA. If unrepaired, AP sites cause mutations, strand breaks and cell...
A number of endogenous and exogenous agents, and cellular processes create abasic (AP) sites in DNA. If unrepaired, AP sites cause mutations, strand breaks and cell death. Aldehyde-reactive agent methoxyamine reacts with AP sites and blocks their repair. Another alkoxyamine, ARP, tags AP sites with a biotin and is used to quantify these sites. We have combined both these abilities into one alkoxyamine, AA3, which reacts with AP sites with a better pH profile and reactivity than ARP. Additionally, AA3 contains an alkyne functionality for bioorthogonal click chemistry that can be used to link a wide variety of biochemical tags to AP sites. We used click chemistry to tag AP sites with biotin and a fluorescent molecule without the use of proteins or enzymes. AA3 has a better reactivity profile than ARP and gives much higher product yields at physiological pH than ARP. It is simpler to use than ARP and its use results in lower background and greater sensitivity for AP site detection. We also show that AA3 inhibits the first enzyme in the repair of abasic sites, APE-1, to about the same extent as methoxyamine. Furthermore, AA3 enhances the ability of an alkylating agent, methylmethane sulfonate, to kill human cells and is more effective in such combination chemotherapy than methoxyamine.
Topics: Alkynes; Biotin; Cell Death; DNA; DNA Damage; DNA Mutational Analysis; DNA Repair; DNA-(Apurinic or Apyrimidinic Site) Lyase; HeLa Cells; Humans; Hydroxylamines; Methyl Methanesulfonate; Sensitivity and Specificity
PubMed: 25616257
DOI: 10.1016/j.dnarep.2014.12.006