Journal Article

Redox effector factor-1, combined with reactive oxygen species, plays an important role in the transformation of JB6 cells

Sun Yang, Bobbye J. Misner, Rita J. Chiu and Frank L. Meyskens

in Carcinogenesis

Volume 28, issue 11, pages 2382-2390
Published in print November 2007 | ISSN: 0143-3334
Published online June 2007 | e-ISSN: 1460-2180 | DOI:
Redox effector factor-1, combined with reactive oxygen species, plays an important role in the transformation of JB6 cells

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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 ∼ 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.

Journal Article.  6276 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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