The gene coding for these transcript (the bcl-2 gene) seems to be interrupted in most cases of follicular lymphomas carrying the t(14;18) chromosomal translocation.
In this patient's leukemic cells, the breakpoint of the t(14;18) translocation occurred in the major breakpoint-cluster region of the BCL2 gene and became linked to the JH4 joining-region gene segment of the immunoglobulin heavy-chain locus on the 14q+ chromosome as previously observed in follicular lymphoma.
In the present study, bcl-2 was rearranged in 30% (11 of 37) of follicular lymphomas and 19% (11 of 58) of diffuse lymphomas of follicle center cell lineage.
Immunoreactive bcl-2 protein was observed in the neoplastic cells in almost all the follicular lymphomas, whereas no bcl-2 protein was detected in follicles affected by non-neoplastic processes or in normal lymphoid tissue.
Immunoreactive bcl-2 protein was observed in the neoplastic cells in almost all the follicular lymphomas, whereas no bcl-2 protein was detected in follicles affected by non-neoplastic processes or in normal lymphoid tissue.
To detect occult lymphoma, the polymerase chain reaction (PCR) technique was used to amplify joined bcl-2/JH DNA sequences at the juncture of the t(14:18) translocation in follicular lymphoma.
Detection of chromosomal translocation t(14;18) within the minor cluster region of bcl-2 by polymerase chain reaction and direct genomic sequencing of the enzymatically amplified DNA in follicular lymphomas.
Twenty-three patients with B-cell non-immunoblastic lymphoma or follicular lymphoma who had a bcl-2 oncogene rearrangement had a poorer response to therapy (7 of 23 with complete remission) than the patients without bcl-2 rearrangement (21 of 26 with complete remission).
Molecular analysis showed that BCL2 was rearranged in the major breakpoint cluster region and had joined into the immunoglobulin heavy chain gene as in follicular lymphoma.
The growth advantage of EBV-infected B cells by overproduction of the BCL-2 protein suggests the direct involvement of the BCL-2 gene product in the pathogenesis of follicular lymphoma.
These data show that bcl-2 translocation is present in 57% of follicular lymphomas in Chinese patients, and support the notion that bcl-2 translocation is a consistent marker for follicular lymphomas irrespective of ethnic differences.
Two of eight (25%) cases of follicular lymphoma but only one of the 34 (2.9%) cases of diffuse B-cell lymphoma had bcl-2 rearrangement that was detected by pFL-1 probe.
To determine the relative importance of these mutations, we searched for their presence in DNA from the involved lymph nodes of 12 patients with t(14; 18) follicular lymphoma. bcl-2 genomic sequences were specifically amplified by the polymerase chain reaction technique and then directly sequenced.
The bcl-2 gene was also rearranged, consistent with the presence of the t(14;18) (q32;q21) translocation which is typically seen in follicular lymphomas.
In the present study we confirmed, by immunohistologic labeling with polyclonal and monoclonal antibodies, that bcl-2 protein is strongly expressed in many cases of follicular lymphoma and that these neoplastic follicles differ clearly from their nonmalignant counterpart (reactive germinal centres) in which bcl-2 protein is undetectable.
Furthermore, none of the 36 cases of CLL/SLL showed bcl-2 rearrangements, whereas, as expected, 21 of 27 cases of FL had rearrangements of the bcl-2 locus.
Most of human follicular lymphomas possess the t(14;18) chromosome translocation that juxtaposes the IgH gene to the 3' region of bcl-2 in a head-to-tail configuration.
That bcl-2 is involved in a major class of lymphoma in addition to follicular lymphoma implies a role for additional factors responsible for generating the two distinctive clinical and pathologic disease states.
Sequence analysis showed the amplified bcl-2/JH fragments to be unique to each individual sample and distinct from 24 sequenced follicular lymphoma-derived t(14;18) junctions, thus excluding contamination artifacts.