Journal Article

Arsenite induces prominent mitotic arrest via inhibition of G<sub>2</sub> checkpoint activation in CGL-2 cells

Ling-Huei Yih, Shun-Wen Hsueh, Wei-Shu Luu, Ted H. Chiu and Te-Chang Lee

in Carcinogenesis

Volume 26, issue 1, pages 53-63
Published in print January 2005 | ISSN: 0143-3334
Published online January 2005 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgh295
Arsenite induces prominent mitotic arrest via inhibition of G2 checkpoint activation in CGL-2 cells

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Arsenic compounds, which are well-documented human carcinogens, are now used in cancer therapy. Knowledge of the mechanism by which arsenic exerts its toxicity may help in designing a more effective regimen for therapy. In this study, we showed that arsenite could induce prominent mitotic arrest in CGL-2 cells and demonstrated the presence of damaged DNA in arsenite-arrested mitotic cells. We then explored why these cells with arsenite-induced DNA damage were arrested at mitosis instead of G2 stage. When synchronized CGL-2 cells were treated with arsenite at stage G1, S or G2, all progressed into, and arrested at, the mitotic stage and contained damaged DNA, as demonstrated by the appearance of the DNA double-strand break marker, phosphorylated histone H2A.X (γ-H2AX). Since X-irradiation induced G2 arrest in CGL-2 cells, these cells clearly have a functional G2 DNA damage checkpoint. However, treatment of X-irradiated CGL-2 cells with arsenite resulted in a decrease in G2 cells and an increase in mitotic cells, suggesting that arsenite may inhibit activation of the G2 DNA damage checkpoint and thus allow cells with damaged DNA to proceed from G2 into mitosis. Immunoblot analysis confirmed that arsenite treatment reduced the X-irradiation-induced phosphorylation of both ataxia-telangiectasia, mutated at serine 1981 and Cdc25C at serine 216, events which are crucial for G2 checkpoint activation and G2 arrest. Moreover, a higher frequency of apoptotic cells is observed in mitoticCGL-2 cells arrested by arsenite than those arrested by nocodazole or taxol. Our results show that the combined effects of arsenite in inducing DNA damages, inhibiting the activation of G2 checkpoint, and arresting cells with damaged DNA in the mitotic stage may subsequently enhance the induction of apoptosis in arsenite-arrested mitotic CGL-2 cells.

Keywords: APL, acute promyelocytic leukemia; ATM, ataxia-telangiectasia, mutated; Chk-1, checkpoint kinase 1; Chk-2, checkpoint kinase 2; FITC, fluorescein isothiocyanate; γ-H2AX, phosphorylated histone H2A.X; PBS, phosphate-buffered saline; SDS–PAGE, sodium dodecyl sulfate–polyacrylamide gel electrophoresis

Journal Article.  7550 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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