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Differential role of diphenyleneiodonium, a flavoenzyme inhibitor, on p53-dependent and -independent cell cycle progression

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We investigated the differential role of diphenyleneiodonium (DPI), which is widely used as an inhibitor of NADPH oxidase, on the activation of cell cycle regulators in the cell cycle progression. DPI efficiently blocked the transition from G0/G1 to S phase by serum stimulation in quiescent HCT-116 (wild-type p53) and HL-60 (null p53) cells. Concomitant with G0/G1 arrest, HCT-116 cells treated with DPI resulted in strong and sustained upregulation of p53 and p21. p53- or p21-deficient HCT-116 cells using a small interfering RNA (siRNA) significantly increased the progression into S phase by stimulation of DPI, compared with DPI alone. However, the silencing of p53 resulted in more efficient transition into S phase than the silencing of p21 siRNA and significantly inhibited p21 upregulation by DPI stimulation. Interestingly, brief exposure to DPI did not change p53 expression, but showed transient upregulation of p21 and G0/G1 arrest. These results suggest that p53 upregulation sustains G0/G1 cell cycle arrest and p21 upregulation by DPI stimulation in HCT-116 cells. In HL-60 cells, DPI also induced p21 upregulation in a p53-independent manner and the increase of p21 expression seems to be regulated by DPI-mediated ERK activation. Cyclin D1 expression was not significantly affected by DPI treatment in HCT-116 cells. However, in HL-60 cells, DPI irreversibly impaired cyclin D1 upregulation by serum stimulation and a much greater fraction of cells arrested in G0/G1 was observed in HL-60 cells than in HCT-116 cells at 24 h after brief DPI treatment. These results suggest that cyclin D1 is an important regulatory factor in the inhibition of cell cycle progression by DPI in HL-60 cells.
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Document Type: Research Article

Affiliations: Department of Microbiology and Immunology, Pusan National University School of Medicine, Busan 602-739, Korea

Publication date: January 1, 2008

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  • The International Journal of Oncology provides an international forum for the publication of the latest, cutting-edge research in the broad area of oncology and cancer treatment. The journal accepts original high quality works and reviews on all aspects of oncology research including carcinogenesis, metastasis, epidemiology, chemotherapy and viral oncology. Through fair and efficient peer review, the journal is dedicated to publishing top tier research in the field, offering authors rapid publication as well as high standards of copy-editing and production. The International Journal of Oncology is published on a monthly basis in both print and early online.
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