and hijack immunoglobulin light-chain enhancers in cyclin D1 mantle cell lymphoma.

Mantle cell lymphoma (MCL) is characterized by the t(11;14)(q13;q32) translocation resulting in overexpression of cyclin D1. However, a small subset of cyclin D1 MCL has been recognized, and approximately one-half of them harbor translocations while the primary event in cyclin D1/D2 MCL remains elusive. To identify other potential mechanisms driving MCL pathogenesis, we investigated 56 cyclin D1/SOX11 MCL by fluorescence in situ hybridization (FISH), whole-genome/exome sequencing, and gene-expression and copy-number arrays. FISH with break-apart probes identified rearrangements in 39 cases (70%) but not rearrangements. We analyzed 3 of these negative cases by whole-genome/exome sequencing and identified IGK (n = 2) and IGL (n = 1) enhancer hijackings near that were associated with cyclin D3 overexpression. By specific FISH probes, including the IGK enhancer region, we detected 10 additional cryptic IGK juxtapositions to (6 cases) and (4 cases) in MCL that overexpressed, respectively, these cyclins. A minor subset of 4 cyclin D1 MCL cases lacked cyclin D rearrangements and showed upregulation of and These cases had blastoid morphology, high genomic complexity, and and deletions. Both genomic and gene-expression profiles of cyclin D1 MCL cases were indistinguishable from cyclin D1 MCL. In conclusion, virtually all cyclin D1 MCLs carry rearrangements with immunoglobulin genes, including a novel IGK/L enhancer hijacking mechanism. A subset of cyclin D1/D2/D3 MCL with aggressive features has cyclin E dysregulation. Specific FISH probes may allow the molecular identification and diagnosis of cyclin D1 MCL.