Molecular cytogenetic analysis of follicular lymphoma (FL) provides detailed characterization of chromosomal instability associated with the t(14;18)(q32;q21) positive and negative subsets and histologic progression

We analyzed a cohort of 61 follicular lymphomas (FL) with an abnormal G-banded karyotype by spectral karyotyping (SKY) to better define the chromosome instability associated with the t(14;18)(q32;q21) positive and negative subsets of FL and histologic grade. In more than 70% of the patients, SKY provided additional cytogenetic information and up to 40% of the structural abnormalities were revised. The six most frequent breakpoints in both SKY and G-banding analyses were 14q32, 18q21, 3q27, 1q11-q21, 6q11-q15 and 1p36 (15-77%). SKY detected nine additional sites (1p11-p13, 2p11-p13, 6q21, 8q24, 6q21, 9p13, 10q22-q24, 12q11-q13 and 17q11-q21) at an incidence of >10%. In addition to the known recurring translocations, t(14;18)(q32;q21) [70%], t(3;14)(q27;q32) [10%], t(1;14)(q21;q32) [5%] and t(8;14)(q24;q32) [2%] and their variants, 125 non-IG gene translocations were identified of which four were recurrent within this series. In contrast to G-banding analysis, SKY revealed a greater degree of karyotypic instability in the t(14;18) (q32;q21) negative subset compared to the t(14;18)(q32;q21) positive subset. Translocations of 3q27 and gains of chromosome 1 were significantly more frequent in the former subset. SKY also allowed a better definition of chromosomal imbalances, thus 37% of the deletions detected by G-banding were shown to be unbalanced translocations leading to gain of genetic material. The majority of recurring (>10%) imbalances were detected at a greater (2-3 fold) incidence by SKY and several regions were narrowed down, notably at gain 2p13-p21, 2q11-q21, 2q31-q37, 12q12-q15, 17q21-q25 and 18q21. Chromosomal abnormalities among the different histologic grades were consistent with an evolution from low to high grade disease and breaks at 6q11-q15 and 8q24 and gain of 7/7q and 8/8q associated significantly with histologic progression. This study also indicates that in addition to gains and losses, non-IG gene translocations involving 1p11-p13, 1p36, 1q11-q21, 8q24, 9p13, and 17q11-q21 play an important role in the histologic progression of FL with t(14;18)(q32;q21) and t(3q27).     

Significance of chromosomal markers in the diagnosis of mantle cell lymphoma (MCL)

According to the REAL/WHO classification, the diagnosis of mantle cell lymphoma (MCL) should be based on clinical, histopathological, immunological and cytogenetic or molecular data. This study is based on 13 cases, which were initially diagnosed as MCL with the use of conventional cytogenetic method and fluorescent in situ hybridization (FISH). MCL is associated with a specific cytogenetic aberration t(11;14)(q13;q32). The chromosomal analyses confirmed the MCL diagnosis in four cases. A neartetraploid cell line and two copies of t(11;14) were observed in three cases. These results correspond with a blastoid variant of MCL, accompanied by aggressive course and poor prognosis. The presence of karyotype with t(11;14) as the sole anomaly predicts an intermediate clinical outcome. Six patients had normal karyotypes, which is characteristic for the typical form of MCL, associated with a better prognosis. In this study we show that detection of chromosomal abnormalities is useful in diagnosis of MCL and has some prognostic significance.     

Different breakage-prone regions on chromosome 1 detected in t(11;14)-positive mantle cell lymphoma cell lines and multiple myeloma cell lines are associated with different tumor progression-related mechanisms

To better define secondary aberrations that occur in addition to translocation t(11;14)(q13;q32) in mantle cell lymphomas (MCL) and in multiple myelomas (MM), seven t(11;14)-positive MCL cell lines and four t(11;14)-positive MM cell lines were analysed by fluorescence R-banding and spectral karyotyping (SKY). Compared with published data obtained by G-banding, most chromosome aberrations were redefined or further specified. Furthermore, several additional chromosome aberrations were identified. Thus, these cytogenetically well defined t(11;14)-positive MCL and MM cell lines may be useful tools for the identification and characterization of genes that might be involved in the pathogenesis of MCL and MM, respectively. Since MCL and MM were found to have different alterations of chromosome 1, these were investigated in more detail by fluorescence in situ hybridization (FISH) and multicolor banding (MCB) analyses. The most frequently altered and deletion-prone loci in MCL cell lines were regions 1p31 and 1p21. In contrast, breakpoints in MM cell lines most often involved the heterochromatic regions 1p12-->p11, and the subcentromeric regions 1q12 and 1q21. These data are in accordance with previously published data of primary lymphomas. Our findings may indicate that different pathways of clonal evolution are involved in these morphologically distinct lymphomas harboring an identical primary chromosome aberration, t(11;14).     

SNP analysis of minimally evolved t(14;18)(q32;q21)-positive follicular lymphomas reveals a common copy-neutral loss of heterozygosity pattern

Follicular lymphoma (FL) cases with a t(14;18)(q32;q21) and minimal or no additional karyotypic alterations, such as copy number gains and losses and/or chromosomal rearrangements, may exhibit pathologic features and a clinical behavior similar to those with more complex karyotypes. This study sought to investigate whether the copy-neutral loss of heterozygosity (cnLOH) profiles of these minimally evolved t(14;18)(q32;q21)-positive follicular lymphoma (MEV-FL) cases are similar to or different from the majority of FL cases with more karyotypic alterations. Affymetrix SNP 6.0 array analysis was applied to the tumor genomes of 23 MEV-FL biopsy samples to assess for the presence of cnLOH. These cases carried either a single or no chromosomal abnormality in addition to t(14;18)(q32;q21) as determined by karyotyping. We found that, although these MEV-FL cases had simple karyotypes, they showed very similar cnLOH profiles as compared to cytogenetically complex cases. The most frequent regions affected by cnLOH were 1p (17%), 6p (17%), 12q (13%) and 16p (13%). Our study suggests that cnLOH alterations may serve as important contributors to the pathological and clinical manifestations of FL.     

Localization of 11q13 loci with respect to regional chromosomal breakpoints

We have employed two strategies to map 13 markers located at 11q13. First, we used pulsed-field gel electrophoresis of DNA fragments obtained with methylation-sensitive restriction enzymes. The markers used in this study were scattered over 8.4 Mb and, for most of them, could not be linked one to another. A second mapping strategy employed hybridization to either DNA of somatic hybrids containing various parts of the long arm of chromosome 11 or metaphase chromosomes of a B-cell line containing the t(11;14)(q13;q32) translocation. We were able to sort out the centromeric from the telomeric probes with respect to translocation breakpoints taken as reference chromosomal landmarks by this approach. BCL1, which corresponds to the region where the t(11;14)(q13;q32) translocation breakpoints are clustered, appears as a boundary between two areas of human/mouse homology present in conserved syntenic regions on mouse chromosomes 7 and 19.     

Cobblestone-Area Forming Cells Derived from Patients with Mantle Cell Lymphoma Are Enriched for CD133+ Tumor-Initiating Cells

Mantle cell lymphoma (MCL) is associated with a significant risk of therapeutic failure and disease relapse, but the biological origin of relapse is poorly understood. Here, we prospectively identify subpopulations of primary MCL cells with different biologic and immunophenotypic features. Using a simple culture system, we demonstrate that a subset of primary MCL cells co-cultured with either primary human mesenchymal stromal cells (hMSC) or murine MS-5 cells form in cobblestone-areas consisting of cells with a primitive immunophenotype (CD19−CD133+) containing the chromosomal translocation t (11;14)(q13;q32) characteristic of MCL. Limiting dilution serial transplantation experiments utilizing immunodeficient mice revealed that primary MCL engraftment was only observed when either unsorted or CD19−CD133+ cells were utilized. No engraftment was seen using the CD19+CD133− subpopulation. Our results establish that primary CD19−CD133+ MCL cells are a functionally distinct subpopulation of primary MCL cells enriched for MCL-initiating activity in immunodeficient mice. This rare subpopulation of MCL-initiating cells may play an important role in the pathogenesis of MCL.     

A second nonrandom translocation, der(16)t(1;16)(q21;q13), in Ewing sarcoma and peripheral neuroectodermal tumor

The majority of Ewing sarcomas and peripheral neuroectodermal tumors (PNET) that have been karyotyped contain a specific translocation, t(11;22)(q23;q11). We report here a second nonrandom translocation, der(16)t(1;16)(q21;q13), in 2 of 20 cases of Ewing sarcoma (seven previously unreported) and 2 of 7 cases of PNET (all previously unreported). All cases with this translocation also contained the t(11;22). Comparison of C-banding patterns in tumor and peripheral lymphocyte karyotypes in one case indicated that the likely breakpoints were 1q21 and 16q13. The presence of this translocation in cell lines will enable further investigation of the molecular events important in the pathogenesis of Ewing sarcoma and PNET.     

The gene that encodes the human CD20 (B1) differentiation antigen is located on chromosome 11 near the t(11;14)(q13;q32) translocation site

The human CD20 gene (B1) encodes a B lymphocyte-specific, cell-surface molecule that is involved in B cell activation and differentiation. We report that the CD20 gene is located on human chromosome 11 at position q12-q13. The location of CD20 was determined by in situ hybridization and was further confirmed by Southern blot analysis of DNA from rodent/human hybrids that contained only portions of human chromosome 11. This localization places the CD20 gene near the site of the t(11;14)(q13;q32) translocation that is found in a subgroup of B cell-lineage malignancies. The site of this translocation has been previously identified by DNA cloning and termed bcl-1. The CD20 gene was found to lie on the centromeric side of bcl-1 on chromosome 11 and to be separated from bcl-1 by at least 50 kb of DNA. These results raise the possibility that alterations in the expression of the CD20 gene may result after the t(11;14) chromosomal alteration.     

A subpopulation of t(2;14)(p11;q32) cells in ataxia telangiectasia B lymphocytes

Summary Partially purified B cells from ataxia telangiectasia (A-T) patients and normal individuals were stimulated with Staphylococcus aureus Cowan I organisms (SAC). High levels of apparently random rearrangements were seen in the A-T B cells only. In addition a t(2;14)(p11;q32) rearrangement was identified in B cells from more than one patient.     

Relationship of the human protooncogene CBL2 on 11q23 to the t(4;11), t(11;22), and t(11;14) breakpoints

A probe identifying CBL2, the human cellular homolog of the murine oncogene v-cbl and murine cellular protooncogene Cbl-2, and panels of rodent X human somatic cell hybrids were used to study the relationship of this protooncogene to translocations associated with acute leukemia, lymphoma, and Ewing sarcoma. CBL2 was mapped to 11q23 and found to translocate from chromosome 11 to 4 in an acute leukemia cell line possessing a t(4;11)(q21;q23) and from chromosome 11 to 14 in a B-cell lymphoma with a t(11;14)(q23;q32). In an Ewing sarcoma cell line with a t(11;22)(q23;q12), however, CBL2 remained on chromosome 11. Additional studies of other genes in the region of 11q23 allowed the following ordering of these genes and breakpoints: 11cen--q23--NCAM--CD3(E-D-G)--[t(11;14), t(4;11)]--(THY1, CBL2, ETS1)--t(11;22)--11qter. The gross structure of the CBL2 sequences examined was not altered by either of the flanking breakpoints. Given that the 5' and 3' ends of the CBL2 gene are not known and are probably not evaluated by the v-cbl probe, these results do not rule out the possibility of CBL2 involvement in the pathogenesis of a subset of acute leukemias possessing a t(4;11), B-cell lymphomas possessing a t(11;14), or Ewing sarcomas possessing a t(11;22).     

Partial trisomy 14q due to maternal t(4;14)(p16;q32) in a dysmorphic newborn

Partial Trisomy 14q is a rare chromosomal disorder that mostly results from a parental translocation. We report here a newborn boy with partial trisomy 14q and dysmorphic features that are compatible with previously reported cases. Conventional cytogenetic analysis revealed an extra chromosomal segment at the end of the short arm of chromosome 4. In order to determine the origin of this chromosome region we used subtelomeric FISH technique. Based on the results of these cytogenetic studies and the physical examination, this dysmorphic case was diagnosed as partial trisomy of 14q and his karyotype determined as 46 XY, der(4)t(4;14)(p16;q32) resulting from a balanced maternal translocation identified as 46,XX, t(4;14)(p16;q32).     

Molecular involvement of the pvt-1 locus in a gamma/delta T-cell leukemia bearing a variant t(8;14)(q24;q11) translocation.

A highly malignant human T-cell receptor (TCR) gamma/delta+ T-cell leukemia was shown to have a productive rearrangement of the TCR delta locus on one chromosome 14 and a novel t(8;14)(q24;q11) rearrangement involving the J delta 1 gene segment on the other chromosome 14. Chromosome walking coupled with pulsed-field gel electrophoretic (PFGE) analysis determined that the TCR J delta 1 gene fragment of the involved chromosome was relocated approximately 280 kb downstream of the c-myc proto-oncogene locus found on chromosome band 8q24. This rearrangement was reminiscent of the Burkitt's lymphoma variants that translocate to a region identified as the pvt-1 locus. Sequence comparison of the breakpoint junctions of interchromosomal rearrangements in T-cell leukemias involving the TCR delta-chain locus revealed novel signal-like sequence motifs, GCAGA(A/T)C and CCCA(C/G)GAC. These sequences were found on chromosome 8 at the 5' flanking site of the breakpoint junction of chromosome 8 in the TCR gamma/delta leukemic cells reported here and also on chromosome 1 in T-cell acute lymphocytic leukemia patients carrying the t(1;14)(p32;q11) rearrangement. These results suggest that (i) during early stages of gamma delta T-cell ontogeny, the region 280 kb 3' of the c-myc proto-oncogene on chromosome 8 is fragile and accessible to the lymphoid recombination machinery and (ii) rearrangements to both 8q24 and 1p32 may be governed by novel sequence motifs and be subject to common enzymatic mechanisms.     

A child with mosaicism for deletion (14)(q11.2q13)

In this case report we describe a child with a de novo deletion in the (q11.2q13) region of chromosome 14. The child presented with dysmorphic features - anophthalmia, microcephaly, and growth retardation. Cytogenetic studies showed mosaicism. The karyotype was 46,XX,del(14)(q11.2;q13) [16] /46,XX [9]. We compared the features observed in this child with that of others with the same deletion reported in scientific literature and found that this is the first report of a child mosaic for this deletion. It is also the first time it has been reported in association with anophthalmia.     

A Case of ABL-BCR Negative, Philadelphia Positive CML with t(5;9)(q13;q34)

The Philadelphia chromosome is found in more than 90 percent of chronic myeloid leukemia (CML) patients. In most cases, it results from the reciprocal t(9;22)(q34;q11), with the ABL proto-oncogene from 9q34 fused to the breakpoint cluster region (BCR) locus on 22q11. In 5 to 10 percent of patients with CML, the Ph originates from variant translocations, involving various breakpoints in addition to 9q34 and 22q11. Here we report a rare case of a Philadelphia positive CML patient carrying t(5;9)(q13;q34) and deletion of ABL/BCR on der(9) as a separate event.     

Unbalanced karyotype due to adjacent 1 segregation of t(11;22)(q23.3;q13.2).

The 11q;22q translocations, whatever the breakpoints may be, are of particular interest because of their propensity to 3:1 segregation of the chromosomes at meiosis I. Until now, no unbalanced karyotype resulting from 2:2 adjacent segregation was published among offspring of 11q;22q translocation carriers. The authors report the case of an unbalanced karyotype due to adjacent 1 segregation of a maternal translocation (11;22)(q23.3;q13.2). The proband's karyotype was 46,XX,-22,+der(22)(11;22)(q23.3;q13.2)mat. This finding demonstrates that adjacent 1 segregation is possible in t(11;22) with breakpoints at 11q23 and 22q13, and can lead to birth of viable infants.     

Mosaic and non-mosaic trisomy 15q2

Two unrelated patients are presented. In the first mosaicism with normal cells and cells trisomic for the distal long arm (q2) of chromosome 15 was found. The 15q2 trisomy was due to a chromosome 14, to the long arm of which an extra 15q2 region was attached (14pter----14q32::15q22----15qter). In the second trisomy 15q2 was present as a consequence of a balanced t(7;15)(p22;q15) translocation in the mother.     

Analysis of segregation and aneuploidy in two reciprocal translocation carriers, t(3;9)(q26.2;q32) and t(3;9)(p25;q32), by triple-color fluorescence in situ hybridization

Meiotic segregation patterns of chromosomes 3 and 9 were analyzed in sperm of two translocation carriers (t(3;9)(q26.2;q32) and t(3;9)(p25;q32)) by triple-color fluorescent in situ hybridization (FISH) with a telomeric DNA probe in addition to two centromeric probes. The frequencies of each sperm product resulting from alternate or adjacent I, adjacent II and 3:1 segregation in a t(3;9)(q26.2;q32) translocation carrier were 88.35%, 5.44% and 5.94%, respectively. On the other hand, the frequencies of each sperm product in a t(3;9)(p25;q32) translocation carrier were 89.23%, 6.02% and 4.48%, respectively. Of all the sperm products, the frequency of normal or chromosomally balanced sperm in a t(3;9)(q26.2;q32) and a t(3;9)(p25;q32) were 52.49% and 47.25%, respectively. The frequencies of each sperm product resulting from various segregations were different between both carriers and significantly deviated from the expected frequencies. Additional dual-color and triple-color FISH were performed to analyze aneuploidy rates for chromosomes 12, 17, 18, X and Y in order to detect any interchromosomal effect; no evidence of an interchromosomal effect was found.     

Molecular analysis of a t(7;14)(q35;q32) chromosome translocation in a T cell leukemia of a patient with ataxia telangiectasia

Molecular analysis of somatic cell hybrids derived from T cells carrying a t(7;14)(q35;q32) chromosomal translocation from a patient with ataxia telangiectasia and T cell leukemia indicates that the breakpoint on chromosome 14 is proximal to the IgH locus and to the D14S1 locus, while the breakpoint on chromosome 7 involves the T cell receptor beta chain locus immediately 5' to J beta 1.5 on chromosome 7. The separation of V beta and C beta observed in somatic cell hybrids defined the orientation of the T cell receptor beta chain locus on chromosome 7 where the V beta genes are centromeric and the C beta genes are telomeric. A novel chromosomal alteration, undetected cytogenetically, was revealed as being an inversion with duplication of the distal band of chromosome 14q32. The importance of the 14q32 region in the leukemogenic process is discussed.     

Partial trisomy 18(q11 leads to qter) in an infant and aborted fetus resulting from a balanced paternal translocation t(13;18)(q32:q11).

Partial trisomy 18 is described in a two month old female with severe mental, motor and growth retardation, associated with multiple congenital anomalies characteristic of complete trisomy 18. Trisomy for almost all of 18q resulted from adjacent I segregation of a paternally inherited translocation t(13; 18)(q32:q11). The balanced translocation was observed in three generations of the family. Partial trisomy 18q identical to that observed in the proband was found in a subsequent miscarriage.