Chromosome abnormalities in chronic lymphocytic leukemia revealed by cytochalasin B and Epstein-Barr virus

6q deletion detected by fluorescence in situ hybridization using bacterial artificial chromosome in chronic lymphocytic leukemia

Deletions of the long arm of chromosome 6 are known to occur at relatively low frequency (3-6%) in chronic lymphocytic leukemia (CLL), and they are more frequently observed in 6q21. Few data have been reported regarding other bands on 6q involved by cytogenetic alterations in CLL. The cytogenetic study was performed in nuclei and metaphases obtained after stimulation with a combination of CpG-oligonucleotide DSP30 and interleukin-2. Four bacterial artificial chromosome (BAC) clones mapping regions in bands 6q16, 6q23, 6q25, 6q27 were used as probes for fluorescence in situ hybridization in 107 CLL cases in order to analyze the occurrence and localization of 6q aberrations. We identified 11 cases (10.2%) with 6q deletion of 107 patients studied with CLL. The trends of survival curves and the treatment-free intervals (TFI) of patients with deletion suggest a better outcome than the other cytogenetic risk groups. We observed two subgroups with 6q deletion as the sole anomaly: two cases with 6q16 deletion, and three cases with 6q25.2-27 deletion. There were differences of age, stage, and TFI between both subgroups. By using BAC probes, we observed that 6q deletion has a higher frequency in CLL and is linked with a good prognosis. In addition, it was observed that the deletion in 6q16 appears to be the most frequent and, if present as the only abnormality, it could be associated with a most widespread disease.

Splenic small B-cell lymphoma with IGH/BCL3 translocation

Isolated chromosomal translocations are important defining features of many non-Hodgkin lymphomas, especially of B-cell type. In contrast to some other translocations, the significance of IGH/BCL3 translocations is not well defined. Although often considered a feature of the ill-defined entity atypical chronic lymphocytic leukemia, very few cases are reported in which involvement of BCL3 and the precise B-cell neoplasm are both well documented. For this reason, we report a splenic-based CD5(-), CD10(-), CD43(-), CD23(-), CD103(-), FMC7(+), CD25(+) small B-cell lymphoma associated with epithelioid histiocyte clusters and a t(14;19)(q32;q13) representing an IGH/BCL3 translocation based on classical cytogenetic studies, chromosomal painting, and fluorescence in situ hybridization studies. The previously reported neoplasms with t(14;19)(q32;q13) or IGH/BCL3 translocations are also reviewed. The present case did not fall into any of the classic B-cell lymphoma categories and clearly did not represent chronic lymphocytic leukemia/small lymphocytic lymphoma. This case suggests that the IGH/BCL3 translocation may help to define a new clinicopathologic entity.

Optimized mitogen stimulation induces proliferation of neoplastic B cells in chronic lymphocytic leukemia: significance for cytogenetic analysis.The Tampere Chronic Lympocytic Leukemia group

We tested the effects of interleukin-2 (IL-2), human recombinant tumor necrosis factor alpha (TNF-alpha), Staphylococcus aureus Cowan I (SAC), TPA, and their combinations, using a standard thymidine incorporation assay, in order to identify an optimal mitogen combination (OMC) for 24 consecutive patients with B-cell chronic lymphocytic leukemia (B-CLL). The combination that induced the highest thymidine incorporation was chosen as the OMC for each patient. Among 14 mitogen combinations tested, there were six different OMCs, of which the most frequent was TNF-alpha + IL-2. It was the OMC in 9 of 24 cases. The other OMCs were TNF-alpha + TPA1 (5/24), SAC + IL-2 (5/24), TPA1 + IL-2 (3/24), TPA10 + IL-2 (1/24), and TNF-alpha + TPA10 + IL-1 (1/24). The mitogenic power of the selected OMC in each case was then evaluated both by the combination of immunophenotyping and molecular cytogenetic techniques known as MAC (Morphology, Antibody, Chromosomes) and standard chromosome analysis. After OMC stimulation, the levels of DNA synthesis and B-cell proliferation (mitotic index) were, on average, 10-fold higher than those observed after standard TPA stimulation (P < 0. 0001). The proportion of mitotic B cells exceeded the proportion of mitotic T cells in 70.1% of the cases after OMC stimulation. After TPA stimulation, 7.7% +/- 2.5% of all mitoses were B-cell mitoses, whereas after OMC stimulation this proportion rose to 57.9% +/- 5.3%. The frequency of clonal chromosomal aberrations increased from 46% after TPA stimulation to 79% after OMC stimulation. The clonal aberrations del(6q), del(11q), and/or del(13q) were observed in 26%, 32%, and 42% of the patients with the respective clonal chromosomal aberrations, whereas the corresponding frequencies after TPA stimulation were only 4%, 21%, and 17%. When the lineage involvement of cells with clonal chromosomal aberrations from three patients was analyzed, the aberrations were found to be restricted to B cells only, and in one patient to a minor subset of B cells. The results demonstrate that an individually chosen OMC induces a high rate of proliferation in neoplastic B cells. We found deletions in 6q, 11q, and 13q at higher frequencies than reported previously, most probably as a result of an improved mitogenic response. The identification of an optimal mitogen stimulation for each patient, prior to chromosome analysis, can well be expected to reduce the rate of false-normal results in the future. This is essential for accurate evaluation of the prognostic significance of chromosomal aberrations in B-CLL.

Deletion of 6q27 in chronic lymphocytic leukemia and multiple myeloma detected by fluorescence in situ hybridization

Nonrandom deletions of the long arm of chromosome 6 (6q) are associated with various lymphoid malignancies. It has been suggested that deletions of 6q25-27, 6q21, and 6q23 typically occur in intermediate-grade, high-grade, and low-grade lymphomas, respectively. We used fluorescence in situ hybridization (FISH) to evaluate the occurrence of 6q27 deletion in chronic lymphatic leukemia (CLL) and multiple myeloma (MM). 6q27 deletion was detected in 21% of patients with CLL and in 28% of patients with MM. The percentage of cells containing deletions ranged between 25-49. Two patients with MM had progressive disease and the aberration was detected in both. We conclude that FISH is a sensitive method to detect 6q27 deletion in lymphoproliferative disorders. Also, this deletion is not specific to intermediate-grade lymphomas, but occurs also in CLL and MM.

PHA/IL2: an efficient mitogen cocktail for cytogenetic studies of non-Hodgkin lymphoma and chronic lymphocytic leukemia

This study documents the utility of a mitogen/cytokine cocktail composed of phytohemagglutinin and Interleukin 2 (PHA/IL2) used to stimulate cultures from patients with chronic lymphoproliferative disorders. We report the results of a selected series of 57 patients with non-Hodgkin lymphoma (NHL) or chronic lymphocytic leukemia (CLL), in which only the culture stimulated with PHA/IL2 demonstrated the presence of an abnormal clone. On average, cells in the abnormal clone comprised 40% of the mitotic cells in this culture. The most common abnormalities observed in these patients were trisomy 12, present in 39% of the cases, and t(14;18), seen in 14% of cases.

t(14;19)/BCL3 rearrangements in lymphoproliferative disorders: a review of 23 cases

The t(14;19)(q32.3;q13.2) is a rare but recurrent translocation found in patients with B-cell malignancies, mainly in chronic B-cell lymphoproliferative disorders. When occurring in chronic lymphocytic leukemia (CLL), atypical lymphocyte morphology and immunophenotype have been reported. A high proportion of patients with CLL and t(14;19) are aged less than 40 years. t(14;19) is often associated with rapidly progressive disease, and overall prognosis is poor compared to the expected survival in chronic lymphocytic leukemia and low-grade B-cell lymphoma. t(14;19) is rarely the sole cytogenetic aberration. Trisomy 12 is the most frequent associated abnormality, and is observed in 50% of cases. t(14;19) involves the BCL3 gene, which is located at the breakpoint on chromosome 19 and is juxtaposed to the immunoglobulin heavy chain gene locus on chromosome 14 (often in the switch alpha region) in a "head-to-head" configuration. The translocation does not interrupt the transcriptional integrity of BCL3, but is associated with overexpression of this gene, which encodes an I kappa B-like protein and modulates the activity of the NF-kappa B transcription factors. The genes affected by overexpression of BCL3 remain to be identified.

Cytogenetics in CLL and related disorders

Chromosome analysis of more than 1200 patients with chronic lymphocytic leukaemia reported to the International Working Party on Chromosomes in CLL and in the literature is analysed. Clonal chromosomal abnormalities are found in about half of the patients, and one third of those with clonal aberrations have trisomy 12, with or without additional changes. The most common structural abnormalities involve the long arm of chromosome 13, usually as deletions involving 13q14, the site of the retinoblastoma gene. Other recurrent abnormalities are deletions of the long arms of chromosome 11 and 6. 14q+ markers are frequent in patients at advanced stage, but are almost always within complex abnormalities. The number of clonal abnormalities in the CLL cells has a strong prognostic impact. Trisomy 12 as a single abnormality is an adverse prognostic sign, whereas patients with 13q abnormalities generally do comparatively well. Lymphoid leukaemia with monoclonal immunoglobulin secretion frequently involves clonal chromosomal abnormalities, and the type of change is similar to that seen in true CLL. In B cell prolymphocytic leukaemia, t(11;14) is a common finding, together with trisomy 12. T cell prolymphocytic leukaemia is characterized by an inversion of the long arm of chromosome 14, with breaks at q11 and q32, and trisomy of 8q, whereas large granular lymphocytic leukaemia has shown no consistent abnormality. Hairy cell leukaemia seems to involve a specific set of non-random chromosome abnormalities, such as inv(5)9.

Cloning and sequencing of a t(14;19) breakpoint that involves the C mu switch region

The t(14;19) is a recurring translocation found in a small number of cases of chronic B-cell leukemia (CLL). We have cloned and sequenced the breakpoint in a patient with a t(14;19) and shown that the breakpoint on chromosome 14 occurred in the C mu switch region, and that the breakpoint on chromosome 19 occurred in the 5' untranslated region of the BCL3 gene. This is in contrast to all the other reported cases with a t(14;19) in which the breakpoints on chromosome 14 occurred in the C alpha 1 or C alpha 2 switch region, and the breakpoints on chromosome 19 occurred upstream of the BCL3 gene. Our results further emphasize the importance of the switch region in the t(14;19) translocation.

Oligoclonal B-cell leukemia characterized by spontaneous cell division and telomere association

Cytogenetic analysis of unstimulated cultures from a female patient with chronic B-cell leukemia (CLL) revealed three cytogenetically distinct clones, suggesting that the patient's leukemia was oligoclonal. Immunoglobulin heavy chain gene rearrangement studies revealed 1 germline and 4 rearranged bands, indicative of an oligoclonal leukemic population. Further evidence of oligoclonality was provided by X-linked RFLP studies. This is the first report of oligoclonality in CLL demonstrated by cytogenetic, immunoglobulin gene rearrangement, and X-chromosome inactivation studies. In addition to oligoclonality, the patient's leukemic cells exhibited telomere association, a Robertsonian translocation, and clonal evolution, suggesting an underlying genomic instability.

New chromosomal abnormality. t(1;19;?) in a case of B-chronic lymphocytic leukemia

Cytogenetic analysis was performed on peripheral blood cells stimulated with interleukin 6 (IL-6), lipopolysaccharide from Escherichia coli (LPS), phytohemagglutinin (PHA), pokeweed mitogen (PWM) and tetradecanoyl-phorbol-acetate (TPA), in a patient with B-chronic lymphocytic leukemia, showing a t(1;19;?) translocation as the sole abnormality. To our knowledge, this translocation has not been described before in any human neoplasia. In this case, the poor response to therapy (survival time 4 months) suggested that t(1;19;?) could be related to an aggressive course of the disease.

Complex karyotypic evolution in B-cell chronic lymphocytic leukemia

Cytogenetic analysis at diagnosis in a female patient with chronic B-cell leukemia showed a single abnormal clone with a 4p+ abnormality, 46,XX, -4, +der(4)t(4;?)(p16;?). Six additional clones evolved from this clone during the following 4 1/2 years and showed 3p+, 4p-, and 11q- chromosomes in addition to the 4p+ abnormality. Immunoglobulin heavy chain gene rearrangement studies showed two rearranged bands and a faint germline band. Following splenectomy, a strong germline and faint rearranged bands were seen, suggesting that the majority of cells were normal, whereas cytogenetic studies showed that the karyotypically abnormal cells were still present. The combination of cytogenetic and Ig gene rearrangement studies provides detailed information regarding the number of circulating normal and leukemic cells.

Molecular definition of interstitial deletions of chromosome 13 in leukemic cells

Three patients with leukemia and one with a myeloproliferative disorder carried an interstitial deletion of chromosome 13, del(13)(q12q14), in leukemic cells. Proximal and distal breakpoints of the deleted segment were characterized by using DNA restriction fragment length polymorphisms of chromosome 13 supplemented by quantitative densitometry of hybridization signals to determine the copy number of individual loci. Both proximal and distal breakpoints varied between patients, and it is unlikely that a significant hybrid gene was formed by rejoining at the breakpoint junctions. The retinoblastoma gene was encompassed by the deleted segment in all four patients.

Translocation (14;19) in acute biphenotypic leukemia

Translocation (14;19)(q32;q13.1) is an acquired chromosomal rearrangement that has been associated with chronic lymphocytic leukemia of B-cell phenotype frequently progressing to lymphoma. Molecular analysis suggests that the translocation involves the immunoglobulin heavy chain gene on chromosome 14 and the BCL3 oncogene on chromosome 19. We present the first case of t(14;19) in a patient with acute leukemia. Correlation of detailed cytogenetic and molecular genetic studies, cell surface marker analysis, cytochemistry, and electron microscopy indicated that the leukemic cells were biophenotypic, with characteristics consistent with both myeloid and B-lineage lymphoid differentiation.

Reciprocal t(14;19)(q32.3;q13.1) in a patient with B-cell lymphoma

A patient with B-cell lymphoma with a chromosome rearrangement of t(14;19)(q32.3;q13.1) is reported. This patient had leukemic features and an aggressive clinical course. The histopathologic diagnosis was malignant lymphoma, small noncleaved cell. Chromosome analysis of the cells from a cervical lymph node and peripheral blood showed a reciprocal translocation between chromosome 14 with a break at band q32.3 and chromosome 19 with a break at band q13.1, to which the bcl-3 gene has been mapped. Monoclonal rearrangement of the JH gene was detected by Southern blot analysis. However, we could not detect rearrangement of the bcl-3 gene. This case also had a t(2;8)(q13;q24.1), but the c-myc gene remained in its germline. This is the first case with the reciprocal t(14;19) and 8q24 chromosomal breakpoint in a B-cell lymphoid malignancy.

Trisomy 12 in benign fibroma and granulosa cell tumor of the ovary

Chromosome studies were performed on two benign ovarian fibromas and one ovarian granulosa cell tumor. Trisomy 12 was found in all three cases, and additional abnormalities, monosomy 22 and the translocation t(3;9;21), were also observed in the granulosa cell tumor.

Chromosome aberrations in B-cell chronic lymphocytic leukemia. Pathogenetic and clinical implications

Chromosome analyses were performed on leukemic cells from 102 patients with B-CLL, of whom 84 were untreated. B-cell mitogen-induced CLL cells yielded suitable metaphases in 85 patients, and 55 showed clonal chromosomal aberrations. Trisomy 12 was found in 26 patients. In nine patients the + 12 was a single aberration. A 14q + chromosome or deletions of the long arm of chromosomes 6, 11, or 13 were other recurrent aberrations. Patients with Rai stage I or more had more frequently clonal aberrations than patients with stage 0 disease (p less than .02). Patients with clonal aberrations had poorer 5-year survival than those with a normal karyotype (p less than .05). Patients with a high percentage of abnormal metaphases in the sample had poorer prognosis than patients with high admixture of normal metaphases (p less than .01). Of the specific clonal aberrations those with 14q + or trisomy 12 tended to have slightly poorer and those with 6q- or structural aberrations involving the long arm of chromosome 13 tended to have better prognosis than patients with other chromosomal aberrations. A complex karyotype tended to be an adverse prognostic sign. Clonal evolution is rare: complex karyotypes are found at diagnosis and clones with single aberrations did not acquire additional chromosome aberrations despite progressive disease and treatment. Nine hundred and seventy-nine published cases are reviewed, and pathogenetic mechanisms, such as oncogenes and gene dosage, are discussed.

Clonal chromosomal changes in chronic lymphocytic leukemia

Cytogenetic analysis was carried out in 28 B-CLL patients (21 males and 7 females, 38-85 years old, with median age 64 years, disease stage O-IV). Peripheral nominator cells (1 x 10(7)) or isolated B-lymphocytes were incubated in vitro for 5-7 days. The cells were stimulated by pokeweed mitogen (PWM), or phorbol myristate-acetate (PMA), with or without 10% conditioned medium (CM) derived from a T cell leukemia line or 10% B-cell growth factor (BCGF). Twenty-two patients (79%) responded to PWM + CM; 5 out of 5 patients responded to PWM + BCGF. The average mitotic index (+/- S.E.M.) for PWM, PMA, PWM + CM, PMA + CM, PWM + BCGF were 0.13 +/- 0.01, 0.24 +/- 0.13, 0.51 +/- 0.11, 0.14 +/- 0.06 and 0.63 +/- 0.15, respectively. Cytogenetic analysis revealed the presence of abnormal karyotypes in 22 patients. Fourteen patients (50%) had clonal chromosome aberrations which included: monosomy 1, 9, 17, 18, 21, and X chromosome, and trisomy of chromosomes 7, 9, 20, 21 and 22. The clonal structural aberrations were i(6q), inv(12) (q15q24), del(5) (p13p15), del(10) (q24). No homogeneously staining regions (HSR) were observed. Four patients with resistance to anti-neoplastic drugs showed the presence of double minute chromosomes (dmin) ranging in frequency from 5 to 50%.

Identification of a transcriptional unit adjacent to the breakpoint in the 14;19 translocation of chronic lymphocytic leukemia

The t(14;19)(q32.3;q13.1) is a recurring translocation found in the neoplastic cells of some patients with chronic lymphocytic leukemia (CLL). We have previously cloned the translocation breakpoint junction present in the leukemic cells from one such patient. In the present study, we have cloned and sequenced the breakpoint junction from a second patient. The breakpoint on chromosome 14 occurs within a switch region upstream of the immunoglobulin heavy chain C alpha 1 sequence. We detected a 2.1-2.3 kb transcript on Northern blots using a probe from chromosome 19 adjacent to this breakpoint. S1 nuclease protection experiments showed that transcription of the gene proceeds in a direction away from the breakpoint junction. This gene (for which we propose the name BCL3) may contribute to the malignant development of B-lymphocytes following the chromosome translocation. If so, it is the first protooncogene identified whose activation is principally associated with CLL.

Cytogenetic and molecular changes in chronic B-cell leukemia

Cytogenetic studies using B-cell mitogens indicate that approximately 50% of patients with chronic B-cell leukemia (CLL) have chromosome abnormalities. The most common abnormality is an additional chromosome 12, either as the sole abnormality or in conjunction with other abnormalities such as 14q+, 6q-, and 11q-. In two instances, the 14q+ is a result of a translocation from either chromosome 11, t(11;14), or chromosome 19, t(14;19). These two translocations led to the identification of the bcl-1 and bcl-3 genes located on chromosomes 11 and 19, respectively. Very few instances of oncogene activation have been described and it does not seem to be an important mechanism in the pathogenesis of CLL. Further cytogenetic and molecular studies may provide clues for the identification of the genes involved in CLL.

Reduced expression of aphidicolin-induced common fragile sites in peripheral lymphocyte chromosomes of patients with B-cell chronic lymphocytic leukemia

The occurrence and frequency of aphidicolin-induced common chromosomal fragile sites were examined in 12 B-cell chronic lymphocytic leukemia (B-CLL) patients (ten males and two females) and three normal individuals. The mononuclear cells separated by Ficoll-Hypaque gradient were cultured in vitro for 96 hours stimulated by pokeweed mitogen (PWM) in combination with T-leukemia cell conditioned medium or 10% B-cell growth factor. For the final 24 hours the cells were treated with aphidicolin (0.07 microgram/ml). Results indicate that there was a significant reduction in the overall mean frequency of common fragile sites in CLL patients with a wide individual variation. Fragile sites were found to be localized either on a single chromatid or both chromatids, but rarely involved homologous chromosomes. No definite relationship between the frequency of fragile sites and the staging of CLL disease was observed. A significant reduction and variability in the frequency of fragile sites suggest the heterogenous nature of B-CLL and probably a different mechanism of induction of fragile sites in CLL cells compared to controls.