Which gene is overexpressed in mantle cell lymphoma?

The gene CCND1 is commonly overexpressed in mantle cell lymphoma. Mantle cell lymphoma is characterized by a chromosomal translocation t(11;14)(q13;q32), which results in the juxtaposition of the CCND1 gene with the immunoglobulin heavy chain locus. This leads to the ectopic expression of cyclin D1, a crucial protein for cell cycle regulation that promotes progression from the G1 phase to the S phase of the cell cycle. The overexpression of CCND1 contributes to the uncontrolled proliferation of B cells, which is a hallmark of mantle cell lymphoma.

In contrast, while other genes such as BCL2, c-myc, and APC are associated with various forms of lymphoma or other cancers, they do not have the same direct link to mantle cell lymphoma as CCND1 does. BCL2, for example, is more frequently involved in follicular lymphoma, c-myc is often associated with Burkitt lymphoma, and APC has implications in colorectal cancers, not specifically in mantle cell lymphoma. Therefore, CCND1 stands out as the key gene overexpressed in this particular lymphoma, making it the correct answer.