title: Bcl-2 overexpression inhibits tetrachlorohydroquinone-induced apoptosis in NIH3T3 cells: a possible mechanism for tumor promotion.
abstract: TCHQ is a major carcinogenic metabolite of the widely used wood preservative PCP. Recently, we found that TCHQ was a promoter in a mouse skin carcinogenesis model. However, the mechanism is still not clear. In this study, we showed that overexpression of Bcl-2 effectively suppressed TCHQ-induced apoptosis in NIH3T3 cells, as evidenced by morphological changes and DNA fragmentation. Although production of ROS contributes to TCHQ-induced apoptosis, Bcl-2 failed to attenuate TCHQ-elicited increase of intracellular ROS level. In addition, overexpressed Bcl-2 provides only partial protection against TCHQ-induced cellular DNA damage. We also found that TCHQ induced a change in mitochondrial transmembrane potential, and that caspase-9 and subsequent caspase-3 can be activated during TCHQ-induced acute apoptosis. Interestingly, TCHQ induced a significant upregulation of Bcl-2 expression, and over-expressed Bcl-2 can dramatically inhibit the change of mitochondria membrane potential and activation of both caspase-9 and -3. Thus, our results suggest TCHQ-induced tumor promotion may be through a mechanism of upregulation of Bcl-2 protein and subsequent apoptosis inhibition.
authors.affiliation: Department of Environmental and Occupational Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Lin
authors.forename: Ben-Zhan
authors.initials: BZ
authors.lastname: Zhu
authors.forename: Ming-Chen
authors.initials: MC
authors.lastname: Yang
authors.forename: Balz
authors.initials: B
authors.lastname: Frei
authors.forename: Ming-Hsiung
authors.initials: MH
authors.lastname: Pan
authors.forename: Jen-Kun
authors.initials: JK
authors.lastname: Lin
authors.forename: Ying-Jan
authors.initials: YJ
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002455:Cell Division; D020552:Comet Assay; D004249:DNA Damage; D053938:DNA Fragmentation; D004789:Enzyme Activation / Q000187:drug effects; D006873:Hydroquinones / Q000633:toxicity*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D041681:NIH 3T3 Cells; D018384:Oxidative Stress; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014162:Transfection
chemical_list: D006873:Hydroquinones; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; C044578:2,3,5,6-tetrachlorohydroquinone; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases