Polymerase Chain Reaction Analysis of t(14;18) Junctional Regions in B-Cell Lymphomas

Demonstration of array-based analysis for highly multiplexed PCR assays application to detection of IGH@-BCL2 translocations in FFPE follicular lymphoma specimens

We demonstrate an approach that allowed rapid development of a robust assay for the detection of chromosomal translocations. The method includes highly multiplexed PCR with analysis of the PCR products performed by array detection. As proof of principle, we applied this approach to the detection of IGH@-BCL2 translocations in DNA prepared from FFPE specimens. This translocation and specimen type were chosen because of the known difficulties associated with PCR-based detection of this lesion and the additional loss of sensitivity associated with FFPE samples. The multiplex PCR with array detection method detected the IGH@-BCL2 translocation in 26 of 36 FFPE follicular lymphoma specimens, whereas the BIOMED-2 assay detected 13 of 36 specimens. This increased sensitivity was the result of both the increased density of BCL2 primers and identification of PCR products by low-density array. The method was specific and allowed mapping of the BCL2 break point in all cases. The method detected the IGH@-BCL2 lesion when the tumor DNA was diluted more than 1:20 in normal DNA but not when it was diluted more than 1:100. This sensitivity allows detection of diagnostically relevant levels of IGH@-BCL2 but will not detect the rare cells with IGH@-BCL2 translocations in healthy individuals.

The application of fluorescence-based PCR and PCR-SSCP to monitor the clonal relationship of cells bearing the t(14;18)(q32;q21) in sequential biopsy specimens from patients with follicle center cell lymphoma

This study evaluates the utility of fluorescence-based polymerase chain reaction (PCR) and PCR-SSCP methodologies to monitor the clonal relatedness of cells with bcl-2 major break point region (mbr)/JR fusion sequences in sequential samples from patients with follicular lymphoma (FL). Fluorescence-tagged PCR products from 2-4 sequential samples from seven FL patients were resolved in acrylamide gels and analyzed on an Applied Biosystems' automated DNA sequencer equipped with Genescan software. The amplicons were sequenced directly using automated DNA sequencing to obtain the precise amplicon size and base sequence. Fluorescence-based PCR-single-strand conformation polymorphism (SSCP) analysis performed to distinguish amplicons of similar size but of different base sequence. Amplification products differing by as few as 5 bp resolved clearly under fluorescent PCR assay conditions making possible by visual inspection alone the distinction of two products that otherwise appeared to be of similar size by conventional gel electrophoretic methods. The size of the amplicons as determined by Genescan software correlated exactly with the sizes generated by sequence analysis confirming the precision and accuracy of the fluorescent PCR assay. Under nondenaturing conditions, the mobility profiles of the amplicons from sequential samples with identical base sequence remained indistinguishable, whereas amplicons of similar size but of dissimilar base sequence from different patients exhibited distinct migration patterns. Thus, this study demonstrates that a combination of fluorescent PCR and PCR-SSCP assays for the detection of the t(14;18) provides an accurate measure of clonal relationship based on molecular size and sequence similarities without involving radiolabeling and sequencing strategies. Furthermore, the demonstrated preservation of junctional sequences across sequential biopsy specimens validates the use of PCR in the monitoring of minimal residual disease and eliminates concern about the detection of secondary, non-tumor-related translocations.

Low incidence of mbr bcl-2/JH fusion genes in Hodgkin's disease

Lymph node biopsies from 140 cases of Hodgkin's disease (HD) and from 30 non-malignant lesions were screened for the presence of t(14;18) translocations involving the major breakpoint region (mbr) of the bcl-2 gene and the joining region (JH) of the immunoglobulin heavy chain gene, using a polymerase chain reaction (PCR) assay with subsequent nucleotide sequencing of amplified bcl-2/JH junctional regions. Expression of the bcl-2 protein within the Hodgkin and Reed-Sternberg (HRS) cells was investigated in 86 cases of HD by immunohistochemistry on cryostat or paraffin sections. Although bcl-2 expression could be found in a proportion of neoplastic cells in up to one-third of HD cases, the frequency of t(14;18) gene fusions detected by PCR was low. We identified such gene fusions in only 3 out of 140 (2 per cent) HD cases, one biopsy of which presented with four clonally distinct bcl-2/JH sequences. No t(14;18) was found in any of 30 reactive lymph node lesions. All fusion gene sequences were unique regarding the localization of the chromosome 14 and 18 breakpoints and the extranucleotide N-insertions. None of these gene fusions conformed to t(14;18) breakpoint sequences previously characterized in our laboratories. Our findings point to a mere coincidence in some cases of HD lesions and cells carrying a t(14;18) in the same biopsy and argue against a significant role of bcl-2 in the pathogenesis of HD.

Current status and future perspectives in the treatment of low-grade non-Hodgkin's lymphomas

Low-grade non-Hodgkin lymphomas (NHL) comprise a heterogeneous group of disorders both in terms of their cellular and histological composition as well as in terms of their clinical course. The most usually applied classification systems, the Working Formulation and the Kiel classification as well as the recently proposed Revised European American Lymphoma classification, discriminate between low-, intermediate- and high-grade subtypes. In general, low-grade NHL are characterized by a low to moderate proliferative activity and a long clinical course with median survival times ranging from approximately 3 years for centrocytic (CC) or mantle-cell lymphomas (MCL) to 5-8 years for centroblastic-centrocytic (CB-CC) or follicular lymphomas (FL). Recent cytogenetic and molecular biologic analyses indicate that these differences may result from distinct genetic abnormalities such as the translocation t(14;18), which is frequently observed in FL-NHL and is associated with a bcl-2 overexpression and inhibition of apoptosis, or the deregulation of PRAD1 in MCL-NHL induced by the translocation t(11;14). Therapy of low-grade lymphomas depends mainly on the extent of the disease. In the early stages I and II, at which approximately 15 to 20% of low-grade NHL are diagnosed, radiotherapy may be applied with curative intention. The treatment of patients with more advanced stages III and IV is controversial. The currently available information justifies a conservative approach of observing the natural course of the disease until therapeutic intervention is required due to the occurrence of B-symptoms, hematopoietic insufficiency or lymphoma progression.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of the bcl-2 oncogene product and chromosomal translocation t(14;18) in Hodgkin's disease

The B-cell lymphoma/leukemia oncogene bcl-2 takes part in crucial regulatory events in B-cell maturation and differentiation. The reciprocal chromosomal translocation t(14;18), leading to overexpression of this oncogene, can be found in the majority of follicular lymphomas and much less frequently in B-cell leukemias and diffuse lymphomas. We have studied the expression of this protein in different subtypes of Hodgkin's disease using monoclonal antibodies directed against a formalin-resistant epitope of the bcl-2 protein and also have investigated these cases by polymerase chain reaction for evidence of the t(14;18) translocation. We were particularly interested to determine whether nodular paragranuloma (lymphocyte-predominant, nodular), which differs from other subtypes of Hodgkin's disease by virtue of the B-cell nature of its malignant cell population, is characterized by expression of the bcl-2 protein. Our data indicate that only a small number of nodular paragranulomas express the bcl-2 protein and that the expression is not specific for this type of Hodgkin's disease. In a smaller number of cases this expression of bcl-2 could be explained by the presence of the translocation t(14;18).