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Cryptochrome, circadian cycle, cell cycle checkpoints, and cancer
Michele A Gauger1, Aziz Sancar
1Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
Cancer Research
|August 3, 2005
Summary
Disrupting the circadian clock (biological rhythm) in mice did not increase cancer risk or sensitivity to radiation. The study suggests circadian disruption alone does not impair DNA repair or cancer predisposition.
Area of Science:
- Chronobiology
- Cancer Biology
- Molecular Genetics
Background:
- Circadian clock disruption is linked to increased cancer risk in humans and radiation sensitivity in mice.
- Cryptochrome 1 and 2 (Cry1, Cry2) proteins are essential for mammalian circadian rhythms.
- Mice lacking both Cry1 and Cry2 genes (Cry1-/- Cry2-/-) are arrhythmic.
Purpose of the Study:
- To investigate if the absence of a functional circadian clock affects radiation-induced cancer and mortality in mice.
- To determine if Cry1-/- Cry2-/- fibroblasts exhibit altered sensitivity to ionizing or UV radiation.
- To assess the impact of circadian disruption on DNA damage checkpoint responses in mammalian cells.
Main Methods:
- Utilized Cry1-/- Cry2-/- mice and derived fibroblasts for experimental testing.
- Exposed mutant and wild-type mice to ionizing radiation to assess morbidity and mortality.
- Assessed radiation sensitivity and DNA damage checkpoint responses in mutant and wild-type fibroblasts exposed to ionizing and UV radiation.
Main Results:
- Cry1-/- Cry2-/- mice showed no significant difference from wild-type controls in radiation-induced morbidity and mortality.
- Mutant fibroblasts displayed similar sensitivity to ionizing and UV radiation as wild-type cells.
- Ionizing radiation-induced DNA damage checkpoint responses were comparable between mutant and wild-type fibroblasts.
Conclusions:
- Circadian clock disruption, in itself, does not compromise DNA repair mechanisms or DNA damage checkpoints in mammals.
- The study suggests that circadian disruption does not predispose mice to spontaneous or radiation-induced cancers.
- The specific mechanism of circadian clock disruption may influence its effect on cellular DNA damage response and cancer predisposition.