title: Increased NAD(P)H:(quinone-acceptor)oxidoreductase activity is associated with density-dependent growth inhibition of normal but not transformed cells.
abstract: The activity of DT-diaphorase [NAD(P)H:(quinone-acceptor)oxidoreductase] is increased 7-fold in wild-type BALB/c 3T3T cells as they reach confluence and become density growth arrested. Harvesting and replating the cells at low density resulted in a loss of DT-diaphorase with a half time of 7 h, and removal of serum from high-density growth-arrested cells resulted in a decrease in DT-diaphorase with a half time of 3 days. Platelet-derived growth factor and insulin together, but not singly, maintain elevated DT-diaphorase levels in high-density growth-arrested BALB/c 3T3T cells. The increase in DT-diaphorase at high density diminished proportionately to the extent of transformation in four cell lines, 4NQO-3T3T, UV-3T3T, EJras-3T3T. and CSV3-1-3T3T. The most transformed cell line, CSV3-1-3T3T, showed no increase in DT-diaphorase at high density. Since there was no increase in DT-diaphorase mRNA in high-density growth-arrested wild-type BALB/c 3T3T cells compared to rapidly growing cells, the increase in DT-diaphorase activity at high density is most likely due to posttranslational events. High-density growth-arrested wild-type BALB/c 3T3 cells exhibited a greater sensitivity to growth inhibition by the antitumor quinone diaziquone [1,4-cyclohexadiene-1,4- dicarbamic acid, 2,5-bis(1-aziridinyl)-3,6-dioxo-, diethyl ether], which is metabolically activated by DT-diaphorase, than do low-cell-density, growth-arrested cells. The significance of the increase in DT-diaphorase at high cell density in normal cells and its loss in transformed cells may be related to the phenomenon of density-dependent growth inhibition in nontransformed but not in transformed cells.
authors.affiliation: Arizona Cancer Center, University of Arizona, Tucson 85724.
authors.forename: J J
authors.initials: JJ
authors.lastname: Schlager
authors.forename: B J
authors.initials: BJ
authors.lastname: Hoerl
authors.forename: J
authors.initials: J
authors.lastname: Riebow
authors.forename: D P
authors.initials: DP
authors.lastname: Scott
authors.forename: P
authors.initials: P
authors.lastname: Gasdaska
authors.forename: R E
authors.initials: RE
authors.lastname: Scott
authors.forename: G
authors.initials: G
authors.lastname: Powis
mesh_terms: D016475:3T3 Cells / Q000187:drug effects; D000818:Animals; D001388:Aziridines / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D001790:Blood Physiological Phenomena; D002452:Cell Count; D002455:Cell Division; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D006133:Growth Substances / Q000494:pharmacology; D051379:Mice; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis
chemical_list: D001388:Aziridines; D016227:Benzoquinones; D006133:Growth Substances; D012333:RNA, Messenger; D016660:NAD(P)H Dehydrogenase (Quinone); C029108:diaziquone