Cryptochrome, circadian cycle, cell cycle checkpoints, and cancer.

It has been reported that disruption of the circadian clock may lead to increased risk of breast cancer in humans and to a high rate or ionizing radiation-induced tumors and mortality in mice. Cryptochrome 1 and cryptochrome 2 proteins are core components of the mammalian circadian clock and mice mutated in both genes are arrhythmic. We tested Cry1-/- Cry2-/- mice and fibroblasts derived from these mice for radiation-induced cancer and killing and DNA damage checkpoints and killing, respectively.