Bcl-2 Gene Rearrangement Test: Procedure, Interpretation & Diagnostic Use
Synonyms
bcl-2 Gene Rearrangement, Southern Blot of bcl-2 Gene Rearrangement
Applies To
B-Cell Lymphomas
Test Commonly Includes
Identification of DNA bands linked to bcl-2 oncogene rearrangement in B-cell lymphomas.
Abstract
The bcl-2 oncogene encodes a mitochondrial protein that prevents apoptosis (programmed cell death). Overexpression of this protein—common in B-cell lymphomas—leads to cell survival, contributing to tumor formation. Cytogenetic analysis often reveals a t(14;18) translocation in follicular or diffuse large B-cell lymphomas.
Specimen
Minimum 0.1 g of frozen tissue from the affected lymph node or tumor site.
Container
Ship tissue on dry ice or in 95% ethanol.
Collection
Use tissue with ≥10% tumor cells, precisely dissected from the surgical specimen.
Storage Instructions
Store at −70°C until shipment.
Reason to Reject Sample
- Tissue thawed during transport
- Formalin- or paraffin-fixed samples (DNA unsuitable)
Turnaround Time
10–14 days after receipt of sample.
Reference Range
No bcl-2 rearrangement (normal)
Use
To detect bcl-2 gene rearrangements in B-cell lymphomas, particularly in follicular lymphoma (80–90%), large diffuse B-cell lymphoma (30%), and undifferentiated lymphoma (50%). Usually involves a t(14;18) translocation with the JH region of chromosome 14.
Limitations
- Misidentified tumor site may yield false negatives.
- Small sample size may yield insufficient DNA.
Methodology
DNA is extracted, digested with restriction enzymes, electrophoresed, and transferred to a nylon membrane. A radioactive probe specific to bcl-2 detects gene rearrangement via autoradiography. Comparison is made with a control DNA sample.
Additional Information
Bcl-2 prevents apoptosis, contributing to prolonged survival of B cells, which can become resistant to chemotherapy or radiation. Overexpression results from a translocation involving the immunoglobulin gene and bcl-2 gene. This characteristic is diagnostic in many lymphomas.
References
- Jacobs et al., Laboratory Test Handbook, Lexi-Comp Inc., 1994.
- Weiss LM et al., “Molecular Analysis of the t(14;18) Translocation,” N Engl J Med, 1987.
- Cohen JJ., “Programmed Cell Death in the Immune System,” Adv Immunol, 1991.
- Strasser A et al., “bcl-2 Transgene Inhibits T-Cell Death,” Cell, 1992.
- Sentman CL et al., “bcl-2 Inhibits Multiple Forms of Apoptosis,” Cell, 1992.
- Chaganti RSK et al., “Specific Translocations in Non-Hodgkin’s Lymphoma,” Cancer Cells, 1989.
- Yanis JJ., “bcl-2 Rearrangement in Lymphoma,” Cancer Cells, 1989.
