A Novel BCL2 Translocation and Concurrent Chromosome 13q14 Deletion in Chronic Lymphocytic Leukemia: A Case Report

Deletions at 13q14 or unbalanced translocations involving this region are the most common chromosomal abnormalities observed in B-cell chronic lymphocytic leukemia (CLL). This locus is known to harbor the tumor suppressor microRNAs, miR-15a/16-1, loss of which leads to increased expression of the anti-apoptotic protein Bcl2 at the post-transcriptional level, ultimately promoting leukemic cell survival. In this report, we describe a novel DLEU2 ::BCL2 fusion identified by next-generation sequencing in an individual in their 70s with CLL. The fusion preserved the BCL2 coding sequence while disrupting the DLEU2/miR-15a/16-1 region. RNA expression analysis demonstrated a marked increase in BCL2 transcripts. Fluorescence in situ hybridization revealed that this rearrangement was associated with both monoallelic and biallelic deletions at 13q14. These findings suggest that insertion of BCL2 into the 13q14 locus may both truncate DLEU2, thereby impairing the tumor-suppressive function of miR-15a/16-1, and place BCL2 under the control of the DLEU2 promoter, contributing to increased transcriptional activity. This case highlights a potential dual mechanism of Bcl2 dysregulation in CLL and underscores the pathogenic significance of rare 13q14 translocations, further expanding the understanding of genomic complexity in this disease.

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