Redox effector factor-1, combined with reactive oxygen species, plays an important role in the transformation of JB6 cells.
Apurinic/apyrimidinic endonuclease/redox effector factor-1 (APE/Ref-1) is a multifunctional protein involved both in DNA base excision repair and redox regulation. Studies have suggested that abnormal Ref-1 levels and/or activities are associated with tumor progression and sensitivities to treatment, but no direct evidence has yet been published regarding the role of Ref-1 in malignant transformation. We utilized the well-documented tumor promotor-sensitive JB6 mouse epithelial cell model as well as new transformants [by ultraviolet light B (UVB), H2O2 or Cd] to study this phenomenon. Significant increases of reactive oxygen species (ROS) were observed in JB6P+ and all the transformants compared with promotor-resistant JB6P- cells. These increases were paralleled by a sustained elevation of Ref-1 expression. Further analysis exhibited a strong inverse correlation between oxidative DNA lesions [8-oxodeoxyguanosine (8-oxo-dG)] and Ref-1 levels in all JB6 cells. Notably, apoptosis occurred after knock-down of Ref-1 by small interfering RNA (siRNA)] demonstrated by a approximately 2-fold increase of Annexin V-positive JB6P+ cells. Ref-1 depletion also inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced anchorage-independent growth of JB6P+ by 40% and reduced the colony numbers of JB6P+/H2O2 and JB6P+/Cd cells. Mechanistic studies revealed that Ref-1 reduction was associated with an increase of intracellular ROS levels and a marked decrease of activator protein-1 (AP-1) transcription activities in JB6P+/H2O2 cells. This is the first report of the novel role of Ref-1 in cellular transformation. Based on the data presented here, we propose that induction of Ref-1, serving as an adaptive response to elevated ROS, plays a critical role in transformation and protects cells from excess ROS stresses through both DNA repair and activation of transcription factors such as activator protein-1.
Yang
Sun
S
Chao Family Comprehensive Cancer Center, University of California Irvine, Orange, California 92868, USA.
Misner
Bobbye J
BJ
Chiu
Rita J
RJ
Meyskens
Frank L
FL
D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D001483:Base Sequence; D019256:Cadmium Chloride / Q000633:toxicity; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004249:DNA Damage; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000633:toxicity; D051379:Mice; D018384:Oxidative Stress; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014466:Ultraviolet Rays
D017304:Annexin A5; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D006861:Hydrogen Peroxide; C486216:Apex1 protein, mouse; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D019256:Cadmium Chloride; D013755:Tetradecanoylphorbol Acetate