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Definition of Cyclin E
Medically reviewed by Dr. Otari Nergadze, Neurosurgeon | Updated: January 2026
Cyclin E: A protein that is part of a molecular network that controls the cell cycle. There are a large number of cyclin proteins involved in this endeavor. Cyclin E specifically regulates the transition from the G1 phase to the S phase of the cell cycle. A high level of cyclin E accelerates the transition of the cell through the G1 phase.
Cyclin E is of prognostic value in breast cancer. High levels of cyclin E in the tumor correlate with a poor outcome, whereas low levels correlate with a good outcome.