Trisomy 12 in B-cell chronic lymphocytic leukaemia: an evaluation of 33 patients by direct fluorescence in situ hybridization (FISH)

Leukaemic mantle cell lymphoma with t(11;14) and trisomy 12 showing clinical features of state A0 B cell chronic lymphocytic leukaemia

The precise diagnosis of lymphoma usually requires the histological examination of lymph nodes or involved tissues. Mantle cell lymphoma is a form of intermediate grade non-Hodgkin's lymphoma in which typical morphological immunophenotypic and cytogenetic features have been recognised. A case of leukaemic mantle cell lymphoma with the characteristic reciprocal translocation t(11;14) together with trisomy 12, a chromosomal abnormality usually associated with B cell chronic lymphocytic leukaemia (CLL), is presented. This combination of cytogenetic abnormalities has not been reported previously. The lack of lymphadenopathy and hepatosplenomegaly in this patient is more in keeping with stage A0 CLL. This case demonstrates the close clinical and biological relationship between mantle cell lymphoma and CLL.

A transcription map of the minimally deleted region from 13q14 in B-cell chronic lymphocytic leukemia as defined by large scale sequencing of the 650 kb critical region

Extensive analysis of tumors has demonstrated homozygous and heterozygous deletions in chromosome region 13q14.3 in B-cell chronic lymphocytic leukemia (B-CLL), suggesting the site of a tumor suppressor gene. Since previous searches for this gene have not yielded any viable candidates, we now present the sequence of the BACs which span the minimally deleted approximately 650 kb region between markers D13S319 and D13S25. This sequence has allowed us to create the definitive transcription map for the region which reveals 93 ESTs and 12 Unigene clusters in this region. Using gene prediction programs, a further 19 potential genes are also identified. The genes show an asymmetrical distribution throughout the region with most of them clustering at the extreme ends. This sequencing effort provides for the definitive structure of the B-CLL deletion region and the identification of the vast majority of the potential candidate genes. Of all the genes identified, only three have homologies to known genes: two L1 repeat genes and rabbit epididymal protein 52. This 13q14.3 sequence provides the final substrate from which to characterize the B-CLL tumor suppressor gene.

The sequential analysis of trisomy 12 in B-cell chronic lymphocytic leukaemia

In this longitudinal study we evaluated the clinical significance of screening for trisomy 12 by fluorescence in situ hybridization (FISH) and correlated these findings with survival, disease progression and need for treatment. Interphase FISH was performed on 85 patients in 1993/94 and repeated on 41 patients in 1996/97. Over the 4-year period there was no significant change in the percentage of trisomic cells, even in patients with disease progression. Overall survival and requirement for treatment were similar for patients with and without FISH-defined trisomy 12.

Detection of trisomy 12 and centromeric alterations in CLL by interphase- and metaphase-FISH

We have studied trisomy 12 in chronic lymphocytic leukemia (CLL) by fluorescence in situ hybridization (FISH) with an alpha-satellite centromeric probe for chromosome 12 on both dividing and non-dividing cells. Trisomy for chromosome 12 was demonstrated in four of these patients (15.3%) using FISH on interphase cells. The percentage of trisomic cells ranged from 10% to 65% of nuclei. The hybridization signals in the trisomic and disomic nuclei were of a broadly similar size and nature. Interestingly, three of the remaining CLL patients, who exhibited disomy for chromosome 12, showed a marked difference in size of the hybridization signals in interphase nuclei. This was also demonstrated in metaphase spreads. In addition, metaphase FISH studies revealed a supernumerary marker chromosome in three out of 26 patients with CLL.

Interphase cytogenetics in chronic lymphocytic leukemia

The incidence of trisomy 12 and 13q12-q14 abnormalities in patients with chronic lymphocytic leukemia (CLL) was determined by conventional cytogenetics and interphase fluorescence in situ hybridization (FISH). In the analysis of 580 consecutive patients, trisomy 12 was detected by conventional cytogenetics in 39 cases (9%) and 117 cases (20%) by FISH. Trisomy 12 was shown to be associated with advanced clinical stage, atypical morphology, and higher proliferative activity. Combined immunophenotyping and FISH showed that trisomy 12 was present only in a proportion of the clonal B-cells. These data suggest that trisomy 12 is a secondary event associated with features of disease progression. Sequential FISH showed clonal progression of the trisomic clone over time. Three hundred patients also were investigated for 13q deletions using FISH analysis of the RB1 locus (13q14). Monoallelic RB1 deletion was seen in 104 (34%) of cases. One case had a homozygous deletion in 90% of the cells. Dual-color FISH detected the presence of trisomy 12 and RB1 in 17 (5%) cases. DNA probes for 13q12.3 (BRCA2) and 13q14 (RB1 and DBM locus) were used in 35 cases. Twenty-eight (80%) cases showed deletion of a 1Mb 13q12.3 encompassing the BRCA2 locus, whereas 22/35 (63%) were deleted at 13q14. Our data suggest that abnormalities of 13q are more frequent than trisomy 12 in CLL and provide evidence for the presence of a new candidate gene at 13q12.3 that may be involved in the pathogenesis of CLL.

Genetic abnormalities in chronic lymphocytic leukemia and their clinical and prognostic implications

Clonal chromosome abnormalities can be detected in approximately 50% of patients with chronic lymphocytic leukemia (CLL). The most common changes are trisomy 12, followed by structural abnormalities of 13q, 11q, 6q, and 14q. By fluorescence in situ hybridization (FISH), these aberrations can be demonstrated even in cases with insufficient mitotic yield or a normal karyotype. The biologic consequences of trisomy 12 are unknown, but a gene dosage effect is suspected and studies on partial trisomy 12 indicate that the region 12q13 to 12q22 might be of particular pathogenetic importance. Trisomy 12 is strongly associated with atypical lymphocyte morphology and seems to be a secondary event in leukemogenesis, as shown by combined immunophenotyping and interphase FISH. Structural abnormalities of 13q frequently involve hetero- and homozygous deletions of a region in 13q14, distal to the retinoblastoma gene, which may be the site of a tumor suppressor gene. In contrast to a normal karyotype or structural changes of 13q, complex karyotypic abnormalities, high percentage of abnormal metaphases, trisomy 12 and structural changes involving the P53 tumor suppressor gene on 17p13 are adverse prognostic indicators. Cytogenetic and molecular findings provide important diagnostic, clinical, and prognostic information which can contribute to treatment decisions and follow-up of CLL patients.

The pathology of the chronic lymphoid leukaemias

The chronic lymphoid leukaemias, though they all possess relatively mature lymphoid phenotypes, are a diverse group of diseases at the clinical, morphological, immunophenotypical, and biological levels. Generally accepted entities within this category include B-cell chronic lymphocytic leukaemia of classical and mixed-cell types, B-cell and T-cell prolymphocytic leukaemia, hairy-cell leukaemia and hairy-cell variant, splenic lymphoma with circulating villous lymphocytes, large granular lymphocytic leukaemia, adult T-cell leukaemia/lymphoma syndrome, and leukaemic phases of malignant lymphomas of both B-cell and T-cell types. Recent advances have helped to differentiate these diseases, allowing the development of more specific therapy and more accurate prognostication. In this article, we review the pathological aspects of these diseases.

Deletion of chromosome 13 (band q14) but not trisomy 12 is a clonal event in B-chronic lymphocytic leukaemia (CLL)

Chromosomal abnormalities are detected by conventional cytogenetic or FISH analysis in 50% of chronic lymphocytic leukaemias (CLL). Trisomy 12 and del 13q14 account for 70% of these abnormalities. The incidence of these two abnormalities was studied in CLL patients by Southern blot analysis using a highly purified B-cell malignant population (CD5 > 95%, CD3 < 5%). Probes for the D13S25 marker on chromosome 13 band q14 and for the RBTN3 gene on chromosome 12 band p12-13, were used. Deletion of the D13S25 was detected in 17/42 patients (43%) in a homozygous (9.5%) or heterozygous (30%) configuration. Deletion of the D13S25 marker appears to be a clonal and early event in CLL development since it is detected in > 95% of the malignant clonal population. Conversely, trisomy 12 is rarely a clonal event (5/33 patients, 15%) and a varying proportion of cells carrying this abnormality can be demonstrated in 30% of CLL patients (10/33 patients).

Detection of trisomy 12 in chronic lymphocytic leukaemia: comparison of a polymerase chain reaction based technique with fluorescence in situ hybridization

Trisomy 12 is the most frequent chromosomal aberration in chronic lymphocytic leukaemia (CLL) and seems to indicate a poor prognosis. To detect this abnormality we tested the applicability of the polymerase chain reaction (PCR) and compared it to the current standard fluorescence in situ hybridization (FISH). Two DNA regions containing variable numbers of tandem repeats (VNTR) located on (a) the long and (b) the short arm of chromosome 12 were chosen for PCR analysis. 8/72 patients (11%) were trisomy 12 positive compared to 16% by FISH. Chromosomal imbalances were only detected by PCR if at least 20% of the cells carried the numerical aberration.