Abstract：
PURPOSE:To determine the efficacy of a caffeine derivative 1-methylxanthine (1-MTX) in increasing radiosensitivity of cancer cells and elucidate the underlying mechanisms in vitro. MATERIALS AND METHODS:RKO human colorectal cancer cells carrying wild type protein 53 kDa (p53) were incubated with 3 mM 1-MTX for 30 min, exposed to 4 Gy ionizing radiation, and further incubated with 1-MTX for three days. The clonogenic cell death was determined, and the cell cycle distribution and apoptosis were studied with flow cytometry at different times after irradiation. The DNA double strand break (DNA DSB) was examined using phosphorylated Histone2A (gamma-H2AX) foci formation, and the expression/activity of checkpoint 2 kinase (Chk2), cell division cycle 25 (Cdc25) phosphatase and cyclin B1/Cdc2 kinase were also investigated using western blotting and in vitro kinase assays. RESULTS:The treatment with 3 mM 1-MTX increased the radiation-induced clonogenic and apoptotic cell death. The radiation-induced phosphorylation of Chk2 and Cdc25c and the radiation-induced increase in the cyclin B1/Cdc2 kinas activity were little affected by 1-MTX. The radiation-induced G2/M arrest was only slightly shortened and the expression of radiation-induced gamma-H2AX was markedly prolonged by 1-MTX. CONCLUSIONS:1-MTX significantly increased the radiosensitivity of RKO human colorectal cancer cells carrying wild type p53 mainly by inhibiting the repair of radiation-induced DNA DSB without causing significant alteration in radiation-induced G2/M arrest. Such a radiosensitization occurred at 1-MTX concentrations almost non-toxic to the target tumor cells.
journal_name
Int J Radiat Bioljournal_title
International journal of radiation biologyauthors
Youn H,Hee Kook Y,Oh ET,Jeong SY,Kim C,Kyung Choi E,Uk Lim B,Park HJdoi
10.1080/09553000902741190subject
Has Abstractpub_date
2009-02-01 00:00:00pages
167-74issue
2eissn
0955-3002issn
1362-3095pii
909454018journal_volume
85pub_type
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journal_title：International journal of radiation biology
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journal_title：International journal of radiation biology
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