30 research outputs found

    The t(2;3)(q21;q27) translocation in non-Hodgkin's lymphoma displays BCL6 mutations in the 5' regulatory region and chromosomal breakpoints distant from the gene

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    The BCL6 gene, mapped at the chromosomal band 3q27, encodes a POZ/Zinc finger transcription repressor protein. It is frequently activated in Non-Hodgkin's lymphomas (NHL) by translocations with breakpoints clustering in the 5' major breakpoint region (MBR) as well as by mutations in the same region. The translocations lead to BCL6 activation by substitution of promoters of rearranging genes derived from the reciprocal chromosomal partners such as IG. We report the molecular genetic analysis of a novel t(2;3)(q21;q27) translocation subset in NHL comprising three cases without apparent BCL6 involvement in the translocation. Southern blot analysis of tumor DNAs utilizing BCL6 MBR probes revealed no rearrangement in two cases. Two rearranged bands in the third case resulted from a deletion in one allele and a mutation in the other allele. Southern blot analysis of DNA from one of the two tumors without BCL6 rearrangement, using a probe derived from the recently identified alternative breakpoint region (ABR), showed a rearrangement. The ABR is located 200-270 kb telomeric to MBR. Mutations were identified in the previously reported hypermutable region of BCL6 in all three tumors. In one, the mutant allele alone was found to be expressed by RT-PCR analysis of RNA. These results demonstrate the presence of 3q27 translocation breakpoints at a distance from BCL6 suggesting distant breaks that deregulate the gene or involvement of other genes that may be subject to rearrangement

    Subtyping of renal cortical neoplasms in fine needle aspiration biopsies using a decision tree based on genomic alterations detected by fluorescence in situ hybridization

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    Objectives: To improve the overall accuracy of diagnosis in needle biopsies of renal masses, especially small renal masses (SRMs), using fluorescence in situ hybridization (FISH), and to develop a renal cortical neoplasm classification decision tree based on genomic alterations detected by FISH. Patients and Methods: Ex vivo fine needle aspiration biopsies of 122 resected renal cortical neoplasms were subjected to FISH using a series of seven-probe sets to assess gain or loss of 10 chromosomes and rearrangement of the 11q13 locus. Using specimen (nephrectomy)-histology as the ‘gold standard’, a genomic aberration-based decision tree was generated to classify specimens. The diagnostic potential of the decision tree was assessed by comparing the FISH-based classification and biopsy histology with specimen histology. Results: Of the 114 biopsies diagnostic by either method, a higher diagnostic yield was achieved by FISH (92 and 96%) than histology alone (82 and 84%) in the 65 biopsies from SRMs (<4 cm) and 49 from larger masses, respectively. An optimized decision tree was constructed based on aberrations detected in eight chromosomes, by which the maximum concordance of classification achieved by FISH was 79%, irrespective of mass size. In SRMs, the overall sensitivity of diagnosis by FISH compared with histopathology was higher for benign oncocytoma, was similar for the chromophobe renal cell carcinoma subtype, and was lower for clear-cell and papillary subtypes. The diagnostic accuracy of classification of needle biopsy specimens (from SRMs) increased from 80% obtained by histology alone to 94% when combining histology and FISH. Conclusion: The present study suggests that a novel FISH assay developed by us has a role to play in assisting in the yield and accuracy of diagnosis of renal cortical neoplasms in needle biopsies in particular, and can help guide the clinical management of patients with SRMs that were non-diagnostic by histology

    Alternative Translocation Breakpoint Cluster Region 5' to BCL-6 in B-cell Non-Hodgkin’s Lymphoma

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    Chromosomal translocations involving band 3q27 with various different partner chromosomes represent a recurrent cytogenetic abnormality in B-cell non-Hodgkin’s lymphoma. In a fraction of these translocations, the chromosomal breakpoint is located within the 5' noncoding region of the BCL-6 proto-oncogene where the BCL-6 major breakpoint region (MBR) maps. As a result of the translocation, BCL-6 expression is deregulated by promoter substitution. However, between 30 and 50% of lymphomas with cytogenetically detectable translocations affecting band 3q27 retain a germ-line configuration at the BCL-6 locus. To identify possible additional breakpoint clusters within 3q27, we cloned a t(3;14)(q27;q32) lymphoma without MBR rearrangement and found a novel breakpoint site located between 245 and 285 kb 5' to BCL-6. Breakpoints within this newly described region, which we called the alternative breakpoint region (ABR), were found to be recurrent in lymphomas carrying t(3q27) chromosomal translocations but devoid of BCL-6 MBR rearrangements. Comparative analysis of multiple lymphomas carrying rearrangements within the ABR showed that the breakpoints cluster within a 20-kb distance. Translocations involving the ABR may juxtapose BCL-6 to distantly acting, heterologous transcriptional regulatory elements which cause deregulation of the proto-oncogene. The identification of BCL-6 ABR provides new tools for the diagnosis of lymphomas carrying aberrations at 3q27 and deregulated BCL-6 genes

    Alternative Translocation Breakpoint Cluster Region 5' to BCL-6 in B-cell Non-Hodgkin’s Lymphoma

    Get PDF
    Chromosomal translocations involving band 3q27 with various different partner chromosomes represent a recurrent cytogenetic abnormality in B-cell non-Hodgkin’s lymphoma. In a fraction of these translocations, the chromosomal breakpoint is located within the 5' noncoding region of the BCL-6 proto-oncogene where the BCL-6 major breakpoint region (MBR) maps. As a result of the translocation, BCL-6 expression is deregulated by promoter substitution. However, between 30 and 50% of lymphomas with cytogenetically detectable translocations affecting band 3q27 retain a germ-line configuration at the BCL-6 locus. To identify possible additional breakpoint clusters within 3q27, we cloned a t(3;14)(q27;q32) lymphoma without MBR rearrangement and found a novel breakpoint site located between 245 and 285 kb 5' to BCL-6. Breakpoints within this newly described region, which we called the alternative breakpoint region (ABR), were found to be recurrent in lymphomas carrying t(3q27) chromosomal translocations but devoid of BCL-6 MBR rearrangements. Comparative analysis of multiple lymphomas carrying rearrangements within the ABR showed that the breakpoints cluster within a 20-kb distance. Translocations involving the ABR may juxtapose BCL-6 to distantly acting, heterologous transcriptional regulatory elements which cause deregulation of the proto-oncogene. The identification of BCL-6 ABR provides new tools for the diagnosis of lymphomas carrying aberrations at 3q27 and deregulated BCL-6 genes
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