Test : bcl-2 Gene rearrangement
Indications : The test is ordered to detect BCL2 rearrangements in B-cell lymphomas. The BCL2 rearrangement is found in follicular lymphomas, large diffuse B-cell lymphomas, and undifferentiated lymphomas.
Studying the rearrangement of the BCL2 gene is important for the differential diagnosis of non-Hodgkin’s lymphomas, in particular. Although a large proportion of breakpoints on these genes are clustered, not all can be identified by the conventional PCR and hence FISH assay is a better choice. Research has revealed that segregation-based interphase FISH assay is the best method to analyze the BCL2 gene mutations, as it detects 100% of BCL2 arrangement.
To carry out the culture, one ml of peripheral blood is drawn intravenously from the candidate. This is transferred into a sterilized culture vial containing growth media, fetal calf serum and PHA (a mitogen). The vial is incubated at 37ºC in 5% CO2 atmosphere.
For interphase FISH, the DNA in the chromosomes are subjected to denaturation process at 72 hours overnight and then incubated with labeled probes overnight. The chromosomes are then washed and counterstained with 4', 6'-diamidino-2-phenylindole dihydrochloride (DAPI).
This process allows the break points in the gene clusters to be viewed through a fluorescent microscope.
Physiology : The BCL2 (B-cell lymphoma 2) gene codes for a protein that regulates programmed cell death, apoptosis, The protein is either pro-apoptosis or anti-apoptosis.
Apoptosis occurs in all cells but is especially important in immune and hematopoietic cells which have a high cell turnover rate. When this regulatory protein is over expressed through a mutation, the cell becomes resistant to apoptosis. As a result, the cells tend to over multiply leading to cancer.
Mutations in the BCL gene have been identified as a cause for cancers, especially lymphomas and breast cancer.
Interpretation : Break points and gene rearrangement can be observed in the BCL gene, a classic one being at 3q26. Some of these break points, which are established “hotspots,” have been linked to malignancy. Absence of break point does not indicate an absence of malignancy. Further tests will have to be carried out.
Test Method : Hybridization technique
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