Truncations in CCND1 mRNA 3′ UTR Alters microRNA Regulation in Mantle Cell Lymphoma.

Mantle Cell Lymphoma (MCL) represents only 5–10% of all non-Hodgkins lymphomas, making it an uncommon but difficult form of lymphoma to treat. It has a poor prognosis among the B cell lymphomas with median survival of three years. The genetic hallmark of MCL is the t(11,14) translocation causing amplification of cyclin D1 (CCND1), a known cell cycle regulator which is overexpressed in many other cancers. MicroRNAs (miRNA) are a new class of abundant small RNAs that play important regulatory roles at the post transcriptional level. They act by binding to the 3′ untranslated region (UTR) of mRNAs and block either their translation or initiate their degradation. Recent reports have shown truncations in the CCND1 3′ UTR occur in MCL and indicate a worse prognosis. We hypothesized that truncations in 3′ UTR of CCND1 alter it’s regulation by microRNAs. Based on bioinformatics, we identified microRNA 16 with putative docking sites in the 3′UTR of CCND1. Mir-16 has been implicated as a cell cycle regulator. We identified 2 cell lines (Jeko-1 and Z138) with truncations in CCND1 3′ UTR and demonstrated increased CCND1 mRNA expression by qRT-PCR, increased protein expression by western blot, and higher proliferative potential by cell cycle. We prepared a reporter construct by ligating the full length 3′ UTR of CCND1 to GFP. We then co-transfected this construct with mimics of mir-16 into a cancer cell line and demonstrated downregulation of CCND1 protein expression by flow cytometry. In the MCL cell line Granta-519 with non-truncated CCND1, transfection with mimics of mir-16 deminstrated decreased expression of CCND1 mRNA. These studies suggest that the overexpression of CCDN1 In MCL may result from altered regulation of gene expression from loss of a miRNA regulatory site and may give new clues into the patho-biology of this disease and insights into possible new therapies.