What is the role of cyclin D1 in mantle cell lymphoma?

Cyclin D1 plays a crucial role in the regulation of the cell cycle, particularly in facilitating the transition from the G1 phase to the S phase. In mantle cell lymphoma, which is characterized by the overexpression of cyclin D1 due to a chromosomal translocation involving the CCND1 gene, this protein acts by forming a complex with cyclin-dependent kinases (Cdks). The cyclin D1-Cdk complex phosphorylates key target proteins that promote progression through the cell cycle, thereby advancing the cell towards DNA synthesis and division.

The overexpression of cyclin D1 in mantle cell lymphoma disrupts normal regulatory mechanisms of the cell cycle, leading to uncontrolled cellular proliferation. This pathogenic feature underpins the oncogenic process in mantle cell lymphoma, where the hyperactivation of cyclin D1 results in a failure of cell cycle checkpoints, allowing malignant cells to bypass growth inhibition signals.

In summary, the primary role of cyclin D1 in this context is to promote the G1/S transition, allowing for unregulated cell division, which is a hallmark of malignancy, particularly in mantle cell lymphoma.