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cyclin D1A 36-kD protein which regulates cyclin-dependent protein kinase activity in G1 of the cell cycle. As a proto-oncogene, it activates cell-cycle progression, and is implicated in the pathogenesis of parathyroid and other neoplasms.
Cyclin-D1 overexpression is due to bcl-1 rearrangement, t(11;14)(q13;q32), and is activated by chromosome inversion, which places it under the influence of the regulatory region of the PTH gene.
Cyclin D1 is not expressed in normal or reactive lymphoid tissues. It is overexpressed in parathyroid adenoma, some breast cancers, squamous cell carcinoma of head and neck, and mantle zone lymphoma, but less commonly in other lymphomas.