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Definition of Cyclin D
Medically reviewed by Min Clinic Staff | Updated: January 2026
Cyclin D: A family of three closely related proteins termed cyclin D1, D2 and D3 that are expressed in an overlapping redundant fashion in all proliferating cell types and collectively control the progression of cells through the cell cycle. Since the D-cyclins are essential to cell division, they may also be involved in cancer.