Detection of t(14; 18)(q32;q21)-Associated BCL-2/JH Gene Fusion in Non-Hodgkin Lymphoma

The identification and study of nonrandom recurrent chromosomal translocations has substantially increased our understanding of the non-Hodgkin lymphomas. Cytogenetic and molecular genetic data now form an integral part of current lymphoma classifications (1 ) and provide important information for diagnosis, tumor biology, and in some cases prognosis. The t(14;18)(q32;q21) abnormality is the most common translocation detected in B-lineage lymphoma and results in juxtaposition of the BCL-2 gene (18q21) and the JH locus of the immunoglobulin (Ig) heavy chain gene (14q32) (2 –5 ). More specifically, in the North American population, alterations of the BCL-2 gene are detected in approx 75 to 85% of low-grade follicular lymphomas, 20–30% of aggressive large B-cell lymphomas, and rarely in other B-cell tumors (e.g., chronic lymphocytic leukemia (CLL), acute lymphoblastic leukemia) (2 ,6 –9 ). As a consequence of the BCL-2/JH fusion, deregulated overexpression of the antiapoptotic bcl-2 protein occurs owing to constitutive transcriptional activation of the BCL-2 gene by the Ig heavy chain gene enhancer. The unbridled expression of bcl-2 protein in lymphoid tumors confers resistance to programmed cell death (10 ,11 ) and is implicated in primary therapeutic failure and a less favorable prognosis (12 –14 ). Although karyotypic detection of lymphoma-associated translocations such as the t(14;18) has proved to be useful in disease diagnosis and subcategorization, molecular genetic approaches including polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) have gained substantial popularity owing to their rapidity, relatively low cost, and increased sensitivity (6 ,15 –22 ).