The CCND1 FISH probe set is designed to detect rearrangements involving regions of the human CCND1 gene located on chromosome band 11q13. The kit contains two differentially labeled Locus Specific Probes (LSP), one covering the 5’ (start) portion of the CCND1 gene along with some upstream sequence, the other matching sequences downstream of the 3’ (end) portion of the gene. The two probes are designed to recognize sequences on both sides of an area in the 5’ regulatory region of the CCND1 gene where breakpoints have been found frequently. In addition to revealing breaks, which lead to translocation of parts or all of the gene or its fusion to other genes, the probe set can also be used to identify other CCND1 aberrations such as deletions, amplifications or chromosome 11 hyperdiploidy. 

CCND1 Gene

Fluorescence in situ hybridization (FISH) is a powerful technique developed to detect presence or absence, location, integrity and amount of genomic sequences in tissue samples or cells.^1-3

Cyclin D1, also called B-cell leukemia/lymphoma 1 (BCL1) or parathyroid adenomatosis 1 (PRAD1), belongs to a family of highly conserved proteins that serve as key regulators of the cell cycle. They form complexes with, and thereby regulate the activity of cyclin-dependent kinases (CDKs), a family of protein kinase enzymes required for progression through the cell cycle. CDKs alone are largely inactive but when in a complex with cyclins become active enzymes. Cyclin D1 associates with the kinases CDK4 and CDK6 that facilitate the G1 to S phase transition. It interacts with and is regulated by a number of other cell cycle control proteins, namely the retinoblastoma (Rb) tumor suppressor.^4,5

In humans, it is encoded by the CCND1 gene.^6,7 Its protein product has a relative molecular mass of 36,000 and is found almost exclusively in the cell nucleus. Expression is highest in the G1 phase of the cell cycle, lowest in the S phase. It is not normally expressed in lymphocytes. Abnormally increased expression of CCND1 has been observed in many tumor types and is believed to play a role in cancer development.⁸

CCND1 and Lymphoma

Lymphomas are malignant conditions of the lymphatic part of the circulatory system. They are the most common blood cancers in the developed world. They also are among the small number of cancer types that has seen significant decreases in mortality in recent years, in large part owing to earlier diagnosis resulting from molecular and cytogenetic characterization.⁹

Traditionally, there are two main categories of lymphoma. One is Hodgkins lymphoma, a relatively rare malignancy of a specific B cell type. The other type, Non-Hodgkin-Lymphoma, is a heterogenous group comprising all other forms of the disease, of which more than 60 have been described.

Cyclin D1 is overexpressed in many tumor types. For example, it has been found amplified, and proven to be a marker of poor prognosis, in a percentage of breast cancer cases.^10-12 CCND1 is also aberrantly activated in a number of hematological malignancies. It is mainly found in mantle cell lymphoma (MCL), a relatively rare non-Hodgkin’s lymphoma type. The most common translocation in MCL is one in which CCND1 is moved to the IGH locus on chromosome 14; the two genes exchange their promoter regions, and the CCND1 gene becomes activated via enhancer elements in the IGH locus.^13-16 However, fusion of CCND1 with other genes, including FSTL3 and the IGHL@ and IGK@ gene loci, has also been observed. CCND1 activation by translocation also occurs in B-prolymphocytic leukemia, plasma cell leukemia, splenic lymphoma with villous lymphocytes and sometimes in chronic lymphocytic leukemia and multiple myeloma.¹⁷

Detection of CCND1 gene translocation is now widely recommended for the discernment of specific lymphoma subtypes.^18,19 Furthermore, it is a predictor of improved survival in multiple myeloma patients.²⁰ Immunohistochemical staining using cyclin D1 antibodies can be used to detect the protein in surgical samples from mantle cell lymphoma patients and other conditions with overexpressed CCND1. However, protein levels are sometimes low and unstable. Moreover, considering the varying breakpoints and numerous different gene fusion partners, FISH detection using breakpoint-flanking probe pairs offers a more definitive and straightforward method of detecting aberrations that activate expression of the CCND1 gene.

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