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001-es BibID:	BIBFORM047643
035-os BibID:	PMID:14599773
Első szerző:	Boldogh István
Cím:	Reduced DNA double strand breaks in chlorambucil resistant cells are related to high DNA-PKcs activity and low oxidative stress / Istvan Boldogh, Gargi Roy, Myung-Soog Lee, Attila Bacsi, Tapas K. Hazra, Kishor K. Bhakat, Gokul C. Das, Sankar Mitra
Dátum:	2003
ISSN:	0300-483X
Megjegyzések:	Modulation of DNA repair represents a strategy to overcome acquired drug resistance of cells to genotoxic chemotherapeuticagents, including nitrogen mustards (NM). These agents induce DNA inter-strand cross-links, which in turn produce doublestrand breaks (dsbs). These breaks are primarily repaired via the nonhomologous end-joining (NHEJ) pathway.ADNA-dependentprotein kinase (DNA-PK) complex plays an important role in NHEJ, and its increased level/activity is associated with acquireddrug resistance of human tumors. We show in this report that the DNA-PK complex has comparable levels and kinase activityof DNA-PK catalytic subunit (DNA-PKcs) in a nearly isogenic pair of drug-sensitive (A2780) and resistant (A2780/100) cells;however, treatment with chlorambucil (Cbl), a NM-type of drug, induced differential effects in these cells. The kinase activityof DNA-PKcs was increased up to 2 h after Cbl treatment in both cell types; however, it subsequently decreased only in sensitivecells, which is consistent with increased levels of DNA dsbs. The decreased kinase activity of DNA-PKcs was not due to a changein its amount or the levels ofKu70 andKu86, their subcellular distribution, cell cycle progression or caspase-mediated degradationof DNA-PK. In addition to DNA cross-links, Cbl treatment of cells causes a 2.2-fold increase in the level of reactive oxygenspecies (ROS) in both cell types. However, the ROS in A2780/100 cells were reduced to the basal level after 3?4 h, while sensitivecells continued to produce ROS and undergo apoptosis. Pre-treatment of A2780 cells with the glutathione (GSH) precursor,N-acetyl-l-cysteine prevented Cbl-induced increase in ROS, augmented the kinase activity of DNA-PKcs, decreased the levelsof DNA dsbs and increased cell survival. Depletion in GSH from A2780/100 cells by l-buthionine sulfoximine (BSO) resulted insustained production of ROS, loweredDNA-PKcs kinase activity, enhanced levels ofDNAdsbs, and increased cell killing by Cbl.We propose that oxidative stress decreases repair of DNA dsbs via lowering kinase activity of DNA-PKcs and that induction ofROS could be the basis for adjuvant therapies for sensitizing tumor cells to nitrogen mustards and other DNA cross-linking drugs.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban Oxidative stress DNA-PK DNA double strand breaks
Megjelenés:	Toxicology. - 193 : 1-2 (2003), p. 137-152. -
További szerzők:	Roy, Gargi Myung-Soog, Lee Bácsi Attila (1967-) (immunológus) Hazra, Tapas K. Bhakat, Kishor K. Das, Gokul C. Mitra, Sankar
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001-es BibID:	bibEBI00019307
Első szerző:	Das, Gokul C.
Cím:	Enhanced gamma-glutamylcysteine synthetase activity decreases drug-induced oxidative stress levels and cytotoxicity / Das G. C., Bacsi A., Shrivastav M., Hazra T. K., Boldogh I.
Dátum:	2006
Megjegyzések:	Multidrug resistance of cancer cells can be intrinsic or acquired and occurs due to various reasons, including increased repair of genotoxic damage, an enhanced ability to remove/detoxify chemical agents, or reactive oxygen species (ROS), and repression of apoptosis. Human A2780/100 ovarian carcinoma cells exhibit resistance to DNA cross-linking agents, chlorambucil (Cbl), cisplatin (Cpl), melphalan (Mel), and ionizing radiation (IR) compared to the parental cell line, A2780. In the present study, we show that when A2780/100 and A2780 cells were treated with Cbl, GSH was extruded via methionine or cystathionine-inhibitable transporters of intact plasma membrane. GSH loss was followed by a rapid increase in ROS levels. The resistant, but not drug-sensitive cells normalized the intracellular GSH concentration along with ROS levels within 4-6 h after Cbl addition, and survived drug treatment. Normalization of GSH and ROS levels in A2780/100 cells correlated well with elevated gamma-glutamylcysteine synthetase (gamma-GCS) activity (10 +/- 1.8-fold over A2780 cells). Ectopic overexpression of the gamma-GCS heavy subunit in drug-sensitive cells nearly restored GSH and ROS to pre-treatment levels consequently increased cellular resistance to genotoxic agents (Cbl, Cpl, and IR), while overexpression of gamma-GCS light subunit had no such effects. Thus, in our model system, drug-resistant cells have the inherent ability to maintain increased gamma-GCS activity, reestablish physiological GSH, and cellular redox state and maintain increased cellular resistance to DNA cross-linking agents and IR.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Molecular Carcinogenesis 45 : 9 (2006), p. 635-647. -
További szerzők:	Bácsi Attila (1967-) (immunológus) Shrivastav, Meena Hazra, Tapas K. Boldogh István
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