Cytogenetic analysis of a United Kingdom series of non-Hodgkins lymphomas

Genetics and Epigenetics in Neoplasms with Plasmacytoid Dendritic Cells

Simple Summary

Differential diagnosis between Blastic pDC Neoplasm (BPDCN) and Acute Myeloid Leukemia with pDC expansion (pDC-AML) is particularly challenging, and genomic features can help in diagnosis. This review aims at clarifying recent data on genomics features because the past five years have generated a large amount of original data regarding pDC neoplasms. The genetic landscape of BPDCN is now well-defined, with important updates concerning MYC/MYC rearrangements, but also epigenetic defects and novel concepts in oncogenic and immune pathways. Concerning pDC-AML, they now appear to exhibit an original mutation landscape, especially with RUNX1 mutations, which is of interest for diagnostic criteria and for therapeutic purposes. We highlight here these two different profiles, which contribute to differential diagnosis between BPDCN and pDC-AML. This point is particularly important for the study of different therapeutic strategies between BPDCN and AML.

Abstract

Plasmacytoid Dendritic Cells (pDC) are type I interferon (IFN)-producing cells that play a key role in immune responses. Two major types of neoplastic counterparts for pDC are now discriminated: Blastic pDC Neoplasm (BPDCN) and Mature pDC Proliferation (MPDCP), associated with myeloid neoplasm. Two types of MPDCP are now better described: Chronic MyeloMonocytic Leukemia with pDC expansion (pDC-CMML) and Acute Myeloid Leukemia with pDC expansion (pDC-AML). Differential diagnosis between pDC-AML and BPDCN is particularly challenging, and genomic features can help for diagnosis. Here, we systematically review the cytogenetic, molecular, and transcriptional characteristics of BPDCN and pDC-AML. BPDCN are characterized by frequent complex karyotypes with recurrent MYB/MYC rearrangements as well as recurrent deletions involving ETV6, IKZF1, RB1, and TP53 loci. Epigenetic and splicing pathways are also particularly mutated, while original processes are dysregulated, such as NF-kB, TCF4, BCL2, and IFN pathways; neutrophil-specific receptors; and cholinergic signaling. In contrast, cytogenetic abnormalities are limited in pDC-AML and are quite similar to other AML. Interestingly, RUNX1 is the most frequently mutated gene (70% of cases). These typical genomic features are of potential interest for diagnosis, and also from a prognostic or therapeutic perspective.

Acquired Robertsonian translocations are not rare events in acute leukemia and lymphoma

Robertsonian translocations are the most common constitutional structural abnormalities but are rarely reported as acquired aberrations in hematologic malignancies. The nonhomologous acrocentric rearrangements are designated as Robertsonian translocations, whereas the homologous acrocentric rearrangements are referred to as isochromosomes. Robertsonian rearrangements have the highest mutation rates of structural chromosome rearrangements based on surveys of newborns and spontaneous abortions. It would be expected that Robertsonian recombinations would be more common than suggested by the literature. A survey of the cytogenetics database from a single institution found 17 patients with acquired Robertsonian rearrangement and hematologic malignancies. This is combined with data from the literature for a total of 237 patients. All of the possible types of Robertsonian rearrangements have been reported in hematologic malignancies, with the i(13q), i(14q), and i(21q) accounting for nearly 60%. Complex karyotypic changes are seen in the majority of cases, corresponding with disease evolution. These karyotypes consistently show loss of chromosomes 5 and/or 7 in the myelocytic disorders, nonacrocentric isochromosomes, and centromeric breakage and reunion. However, nearly 25% of the acquired rearrangements were found as the sole abnormality or in addition to an established cytogenetic aberration. Most of these were the i(14q) with the myelodysplasia subtypes refractory anemia and chronic myelomonocytic leukemia.

Primary marginal zone lymphoma of the thymus accompanied by chromosomal anomaly 46,X,dup(X)(p11p22)

We report a case of primary marginal zone lymphoma in the thymus of a 34-year-old woman. She was initially suspected of having a mediastinal plasmacytoma because of the presence of dominantly proliferating plasmacytic cells in a small fragment obtained by thoracoscopic biopsy, and an elevated level of serum monoclonal IgA. However, histology of the tissue obtained by a subsequent open surgical biopsy revealed diffuse proliferation of atypical monocytoid B-lymphocyte-like cells, which showed prominent plasmacytic differentiation and a close association with thymic epithelial cells consistent with the histology of a marginal zone lymphoma of the thymus. These lymphoma cells were positive for CD19, CD20, IgA, and kappa, and negative for CD5, CD10, and other T/NK-cell and myelomonocyte antigens. Both G-banded and spectral karyotyping analyses revealed the lymphoma cells carried a chromosomal anomaly, 46,X,dup(X)(p11p22). Although large cell type B-cell lymphoma in the thymus (mediastinal diffuse large B-cell lymphoma), which is categorized as a definite subtype in revised European-American classification of lymphoid neoplasms and the new World Health Organization classification, is not infrequent, primary marginal zone lymphoma of the thymus is extremely rare. To our knowledge, this is the first case report of primary marginal zone lymphoma of the thymus with a detailed chromosomal analysis.

Primary mediastinal B-cell lymphoma: a review of pathology and management

PURPOSE

Primary mediastinal B-cell lymphoma (PMBL) is recognized as a separate disease entity in the REAL classification. There is uncertainty about the relevance and especially the optimal management of this disorder. In this review, we discuss clinical presentation, pathology, pathobiology, and management of PMBL in order to provide a platform for initiation of further clinical and biologic studies.

MATERIALS AND METHODS

Studies were identified through a MEDLINE search and from the bibliographies of relevant articles.

RESULTS

PMBL is a tumor of young adults who present with a rapidly proliferating tumor. At diagnosis, the tumor is usually limited to intrathoracic organs. Spread to parenchymal organs such as liver, kidneys, and CNS is common at recurrence. Fibrosis and the presence of so-called clear cells are distinctive morphologic features of PMBL, although they are not pathognomonic or even necessary for diagnosis. On the other hand, biologic features relating to oncogene rearrangement and overexpression as well as cytogenetic features clearly differentiate PMBL from other types of diffuse large B-cell lymphoma. Phase II studies and retrospective series indicate cure rates that range from 38% to 88%. The role of chemotherapy, radiation, and high-dose chemotherapy with stem cell rescue in the management of PMBL is reviewed.

CONCLUSION

PMBL has unique clinical and biologic characteristics that are radically different from those of other types of diffuse large B-cell lymphoma. Although relatively rare, its aggressive growth and its occurrence in young patients increase the clinical relevance of this entity. The consistent recognition and study of PMBL will allow the development of new approaches to its management.

Copy number gain at 12q12-14 may be important in the transformation from follicular lymphoma to diffuse large B cell lymphoma

The purpose of this study was to identify novel areas of genomic copy number change associated with transformation from follicular lymphoma (FL) to diffuse large B cell lymphoma (DLBL). DNA was extracted from tumour cells micro-dissected from paraffin- embedded tissue sections in 24 patients with FL and subsequent transformation to DLBL and 18 patients with de novo DLBL. Tumour DNA was compared to reference DNA using comparative genomic hybridization. Abnormalities common to all 3 groups were gains on chromosomes 4q, 5q, 7q, 11q and X and losses on 3p, 8p and 10q. Copy number changes seen in both transformed and de novo DLBL and not seen in FL were gains on 2p and losses on 1q, 15q and Xq. Gains on 2q, 6p, 7p and 17q and losses on 5p and 8q were specific to transformed DLBL cases. Gain on 12q12-14 was found in 52% of the transformed DLBL cases and was never seen in its follicular counterpart. Patterns of genomic copy number change associated with specific clinical events in NHL have been demonstrated and suggest that gains on 2q, 6p, 7p, 12q and 17q and losses on 5p and 8q may be important in the transformation from low to high-grade disease.

Pancreatic acinar carcinoma shows a distinct pattern of chromosomal imbalances by comparative genomic hybridization

Pancreatic acinar cell carcinoma (PAC) is a rare pancreatic tumor for which no information about chromosomal anomalies is available. We examined six primary PACs by comparative genomic hybridization (CGH). All cases showed chromosomal changes. A total of 106 gains and 48 losses was detected. Consensus regions of gain were identified on chromosomes 1, 12, and X: 1q21 in four cases, 1q42 in three cases, 12p11.2 in four cases, and Xq12-21 in three cases. Recurrent losses were found at 16p13.2-p13.1 in three cases and at 16q23 in three cases. To verify these chromosomal imbalances, microsatellite analysis of matched normal and tumor DNA was performed using PCR-amplified markers for chromosomes 1, 12, and 16 in the regions showing nonrandom gains or losses. This analysis showed allelic imbalances in tumor DNA consistent with the CGH profiles. Our CGH study suggests that PAC shows a characteristic pattern of chromosomal alterations, involving gain at 1q, 12p, and Xq and loss of sequences at 16p and 16q. This pattern appears unique among solid tumors and is markedly different from that detected in pancreatic ductal carcinomas by the same technique. This suggests that PAC tumorigenesis involves different molecular pathways than those involved in the more common pancreatic ductal tumors. Genes Chromosomes Cancer 28:294-299, 2000.

Is mantle cell lymphoma a sex-related disease?

Mantle cell lymphomas are characterized by a male predominance with a range between 55 and 65 years (sex ratio M/F of 6.5). When the sex ratio of patients having mantle cell lymphoma was compared to that of each of the subtypes of non-Hodgkin's lymphomas, it was significantly higher in all cases except Burkitt's and lymphoblastic T-cell lymphomas. These observations suggest a possible relation between the chromosome X and mantle cell lymphomas which has to be explored.

Deletion of cell division cycle 2-like 1 gene locus on 1p36 in non-Hodgkin lymphoma

Our laboratories have documented a significantly high occurrence of chromosome 1p36 rearrangements in non-Hodgkin lymphoma (NHL). The cell division cycle 2-like 1(CDC2L1) (also known as TP58 or PITSLRE) gene, a protein kinase implicated in apoptotic signaling, is located at the very distal region of chromosome 1p36 and is likely to be disrupted by structural rearrangements involving 1p36. To determine the molecular consequences of the recurrent involvement of the 1p36 region, we examined metaphases containing 1p36 abnormalities from 31 specimens derived from 26 patients for the possible deletion of CDC2L1 by fluorescence in situ hybridization (FISH) using the TP58clk-1 DNA probe. Twenty-three cases exhibited the loss of CDC2L1 from the abnormal chromosome 1. In 2 of 26 cases, the gene locus was translocated to the partner chromosome, and in four specimens, all derived from one case, CDC2L1 was not deleted. This pilot investigation suggests that 1p36 rearrangements, and consequently the loss of the CDC2L1 gene locus, is important in NHL. This work also opens avenues for further molecular studies and prognostic correlations.

Cytogenetic changes in the progression of lymphoma

The study of chromosomal changes related to tumor progression in NHL is complicated by the various histologic classification systems and the lack of large serial studies comparing abnormalities at different disease stages. The T-cell lymphomas frequently involve rearrangements of the T-cell receptors and tumor progression is marked by a change from single cell aberrations and polyclonality in low grade disease to monoclonal formation, complex clones, polyploidy, and abnormalities of 1p, 6q, 7, and 13 in high grade T-NHL. In B-cell NHL, specific translocations and oncogene rearrangements are associated with specific NHL subtypes de novo; many of these translocations involve immunoglobulin genes, such as t(14;18) in follicular lymphoma, t(11;14) in MCL, t(3;14) in DLLC, and t(8;14) in Burkitt's lymphoma. Tumor progression is associated with secondary abnormalities which are generally not confined to a particular NHL subtype. Some abnormalities, such as those involving chromosomes 1, 6, and 17, >4-6 clonal markers/cell, and rearrangements of c-MYC and TP53, have prognostic significance while others, such as trisomies 7, 12, 18, and X, are associated with tumor progression but their influence on overall survival is uncertain.

Investigation of the RB-1 tumour suppressor gene in a United Kingdom series of non-Hodgkin's lymphomas

We have investigated the RB-1 tumour suppressor genes in a series of 20 non-Hodgkin's lymphomas (NHL). Polymerase chain reaction (PCR) amplification of polymorphic alleles indicated that there was evidence of allelic imbalance around 13q14, the site of the RB-1 gene, in at least 5 NHL. Immunohistochemical analysis of the RB-1 protein demonstrated wide variations in the percentage of cells exhibiting positive staining, but these usually correlated with differences in the proliferation index as indicated by staining of Ki67. Only 3/35 NHL exhibited significantly fewer cells expressing RB-1 protein than expressed Ki167. A comprehensive analysis of the mutation status of RB-1 in 20 NHL was carried out using PCR based strategies involving single strand conformational polymorphism (SSCP) gels. Most of the protein coding region was studied by analysing cDNA derived from its mRNA and the remaining 5'-end of the coding region investigated by analysing exon I of the gene. We also examined the promoter region of the gene. In none of the 20 NHL investigated were we able to identify a mutation: the only abnormal migrating fragment observed proved to be a polymorphism in exon I of the gene in 5 NHL. In one other case we detected instability at an intron repeat sequence, which had occurred during progression of the disease, but again no mutation of the protein coding region was found. The low levels of RB-1 protein expression that we had observed in a few of our NHL therefore did not appear to be due to mutation of the gene. These data suggest that mutation of RB-1 is not a common event in the evolution of NHL, but that there may be another, as yet unidentified, tumour suppressor gene near the RB-1 locus which is associated with NHL.

Analysis of 14q+ derivative chromosomes in non-Hodgkin's lymphomas by fluorescence in-situ hybridization

The most common chromosomal abnormality observed in non-Hodgkin's lymphomas (NHL) involves the structural alteration of the q arm of chromosome 14. It is not always possible, however, to fully analyse such derivative chromosomes by Giemsa-banding. Therefore, we have applied the fluorescence in-situ hybridization (FISH) technique of chromosome painting to elucidate the origins of the der(14) chromosomes in 8 cases of NHL. In 2 NHL the der(14) appeared to be the product of the t(14;18)(q32;q21) translocation, but were not accompanied by the reciprocal der(18) chromosome. In 3 cases the breakpoint was at 14q32 but the translocated material appeared not to be from chromosome 18 and in 2 cases the breakpoint was centromeric to 14q32. One case with a t(14;18)(q32;q21) was also analysed as a control. Dual painting was carried out with paints for chromosome 14 and either chromosome 3, 8, 10, 11, 18 or 19. In the control and 2 other cases the translocated material was demonstrated to be from chromosome 18, in two cases it was from chromosome 3 and in 1 case there was an unusual insertion of chromosome 11 material. We were unable to identify the origins of the translocated material in 1 NHL and in the final case the apparent der(14) was demonstrated not to contain chromosome 14 material. These data demonstrated the utility of the FISH technique for analysing malignant cell karyotypes, and in particular indicated the potential of this approach for identifying cases containing putative NHL associated oncogenes that may have been translocated adjacent to the immunoglobulin locus at 14q32.

Activation of MYCN in a case of non-Hodgkin's lymphoma

We have examined a series of non-Hodgkin's lymphomas (NHL) for evidence of expression of the MYC gene family. Northern blot analysis of RNA samples derived from 11 non-malignant reactive lymphoid tissues and 33 NHL was used to investigate expression of MYC, MYCL and MYCN. As expected MYC expression was detected in all samples. The levels of MYC expression were quantified by densitometry and appeared to be 3-8 fold higher in high grade NHL than in the low grade NHL or non-malignant lymphoid tissue. No expression of MYCL was detected in any sample. Expression of MYCN was however observed in one sample, which had been diagnosed as a T-cell high grade NHL. A detailed cytogenetic analysis of this sample proved difficult to obtain but, by using fluorescence in-situ hybridization (FISH), we were able to demonstrate that on one of the chromosomes 2 the MYCN gene was localised to a translocation breakpoint region. It therefore appears that in NHL it is possible for MYCN, like MYC in Burkitt lymphoma, to be activated as a result of a chromosome translocation event.

Chromosome X numerical abnormalities in patients with non-Hodgkin's lymphoma. A study of 59 patients using fluorescence in situ hybridization

Chromosome X numerical abnormalities are frequently observed in non-Hodgkin's lymphoma (NHL), with an incidence of 3% to 14% for chromosomal loss and 7% to 33% for chromosomal gain. Because sex chromosome numerical abnormalities are thought to be due to aging, little information is known about their relation to gender, therapy, and prognosis. Therefore, to determine the incidence and clinical relevance of this abnormality in NHL, we studied specimens from 59 NHL patients (31 men and 28 women) by fluorescence in situ hybridization (FISH) using a directly conjugated centromeric probe for chromosome X. The median age for the entire group was 52 years (range, 31-88 years). All specimens were obtained by fine-needle aspiration of diseased lymph nodes. Sex-matched lymphocytes from benign hyperplastic lymph nodes were used as controls. The overall incidence of chromosome X numerical abnormalities was 49.2%. Female patients had a higher overall incidence than males (76% vs. 24%; p < 0.001). The median percentage of cells involved in this abnormality in each specimen was 5.2%. There was no statistically significant difference in the incidence in previously treated than untreated patients (53.1% vs. 44.4%; p < 0.75) and in intermediate-grade NHL than low-grade NHL (61.1% vs. 50%; p < 0.75). There was a trend towards a higher incidence of chromosome X loss in older patients. While the difference in the incidence of chromosome X abnormalities observed between women and men may be due to the difference in the normal copy numbers of this chromosome in each sex group, this abnormality remained higher than any other autosomal chromosome abnormality in NHL previously evaluated by FISH. We conclude that, although FISH detected a high incidence of chromosome X numerical abnormalities and that females had a higher incidence than males, only a small percentage of the cells were involved, suggesting that this abnormality is most likely a secondary genetic defect that is not important in the pathogenesis of NHL.

Correlations of chromosome abnormalities with histologic and immunologic characteristics in 49 patients from Akita, Japan with non-Hodgkin lymphoma

We have analyzed the chromosomes of 49 non-Hodgkin lymphoma patients from an area of Japan that is nonendemic for adult T-cell leukemia/lymphoma. Clonal chromosome abnormalities were found in the majority (88%) of the specimens examined. The most characteristic structural abnormalities were: t(14;18)(q32;q21), t(3;22)(q27;q11), t(11;14)(q13;32), idic(18)(p11.2), and the combination del(1)(p13) and del(1)(q11). The t(14;18) were found in four of five follicular lymphomas and in one diffuse lymphoma. The breaks at 3q27 included seven translocations and an inv(3)(q12q27). A t(3;22) was found in three patients, all B-cell type, two of whom had kappa phenotype and one of whom was negative for the surface Ig. Fifteen of 49 cases had deletion of 6q. The common deleted region was found only in the segment distal to 6q21. These findings indicate the high percentage of t(14;18) in follicular lymphomas, which is unusual in Japan, and the high incidence of 3q27 translocations.

Characterization of add(1)(p36) in non-Hodgkin lymphomas by fluorescence in situ hybridization

Chromosome rearrangements involving chromosome I, band p36, are among the most common aberrations in non-Hodgkin lymphomas (NHL). We have studied nine cases of NHL with add(1)(p36) using fluorescence in situ hybridization (FISH) from a series of 205 cases. Five were follicular low-grade NHL and four were follicular or diffuse high-grade NHL. Three of the five cases with follicular low-grade NHL did not contain the 14;18 translocation. The extra material on the add(1)(p36) in these three cases was derived from chromosome segment 2q31-qter; in one it was observed as a sole clonal rearrangement. In the two remaining cases, with t(14;18), the add(1)(p36) consisted of material from chromosome arms 3q and 17q, respectively. In the four cases of high-grade NHL, the material added on to Ip36 was derived from chromosomes 6, 9, 17, and 19, respectively. Using a Ip36-specific probe, DIS94, we showed a deletion on the add(1) in one of the cases with low-grade NHL, whereas no loss was observed in one of the cases with high-grade NHL. Our study indicates that cytogenetically similar add(1)(p36) are found in both high- and low-grade NHL, and the breakpoint on Ip36 as well as the origin of translocated material may vary.

Elevated levels of MDM-2 and p53 expression are associated with high grade non-Hodgkin's lymphomas

The role of p53 in the evolution of non-Hodgkin's lymphomas (NHL) is unclear. Mutations of the p53 gene appear to be relatively uncommon but stabilized p53 protein, as detected by immunohistochemistry, has indicated a more frequent involvement of p53. As dysfunction of p53 protein has also been suggested to occur after overexpression of the mdm-2 protein, we have therefore investigated a series of non-malignant hyperplastic reactive lymphoid tissues and NHL to examine whether the levels of expression of MDM-2 correlated to positivity of p53 protein staining. Northern blot analysis of MDM-2 expression was compared to glucose-6-phosphate dehydrogenase (G6PD) expression by densitometry to quantify the relative levels of MDM-2 expression. Consistent low levels of MDM-2 expression were observed in non-malignant lymphoid tissue and in low grade NHL, however, 13/15 high grade NHL exhibited a 2-15-fold increase in MDM-2 expression. Interestingly similar elevations in p53 mRNA expression were also observed in 6/15 high grade NHL. Positive staining of the p53 protein did not, however, correlate with elevated mRNA levels of either MDM-2 or p53. The significance of these observations is discussed.

High incidence of monosomy 18 in lymphoid malignancies that have bone marrow and peripheral blood involvement

We studied the incidence of numerical chromosome 18 abnormalities in 107 patients with lymphoid malignancies by fluorescence in situ hybridization (FISH) using a directly conjugated centromeric probe for chromosome 18. Samples were obtained by fine needle aspiration of diseased nodes, bone marrows or peripheral blood. Monosomy 18 was more common in chronic lymphocytic leukemia (43%), small lymphocytic lymphoma (28%), and follicular lymphomas (12.5%) than in diffuse lymphomas (5.3%; p < 0.01). Monosomy 18 was detected in 9.7-17.1% of the cells in non-Hodgkin's lymphoma (NHL) (background, 5.4%; 99% CI, 4.2%-6.6%) and in 8%-16.7% (median, 10%) of the cells in (CLL) (background, 3.4%; 99% CI, 2.5%-4.3%). All patients with monosomy 18 were found to have bone marrow involvement. Of all untreated patients who had disease involving the bone marrow, 32% were found to have monosomy 18. Trisomy 18 was detected in 3.6%-48.2% of the cells in NHL (background, 0.9%; 99% CI, 0.2%-1.6%) and was most common in diffuse large-cell lymphoma (34%) and follicular lymphomas (31%). None of the patients with small lymphocytic lymphoma or chronic lymphocytic leukemia had trisomy 18. There was no correlation between trisomy 18 and response to treatment or clinical presentation. In this study, monosomy 18 was observed frequently in patients with lymphoid malignancies that involve the bone marrow and peripheral blood. Our data suggest that important gene(s) located on chromosome 18 may be involved in homing of the malignant lymphocytes to the bone marrow and peripheral blood.

Cytogenetic study of two cases with lymphoma of mucosa-associated lymphoid tissue

Cytogenetic studies have been reported in fewer than 20 patients with lymphoma of mucosa associated lymphoid tissue (MALT). Two patients with this disease at the Clinical Center, National Institutes of health had numerical and structural chromosome abnormalities, including +12 in both cases. The clonal karyotypes observed were 48-49,XX,t(2;8)(q33;p23), +3, -10,del(10)(q23), +12, +18 [cp] and 47,X,-X,i(6p), +7, +inv(12)(p13q13). Review of cytogenetic studies from published data showed that all cases of MALT lymphoma reported to date also have both numerical and structural chromosome abnormalities, the most frequent being numerical involvement of chromosomes 3, 7, and 12. Identification of a clonal abnormality can help establish the diagnosis when differential diagnosis includes atypical hyperplasia. Although trisomy 12 has been associated with a poor prognosis in B-cell chronic lymphocytic lymphoma (B-CLL), both these patients with MALT lymphoma have had long survival: 8 and 11 years, respectively.

Identification of a subclass of double minute chromosomes containing centromere-associated DNA

In a study of abnormal chromosomes in non-Hodgkin's lymphoma (NHL) cells we have identified one case which contained extrachromosomal chromatin bodies that, on the basis of their morphology and negative C-banding, appeared to be double minute chromosomes (dmin). However, fluorescence in-situ hybridization (FISH) analysis using an X-specific centromeric alphoid repeat probe and a pan-centromere probe, clearly demonstrated the presence of centromere-associated DNA in these dmin. FISH analysis with the pan-centromere probe of the dmin in neuroblastoma and sarcoma cells failed to reveal the presence of centromere-associated DNA, but analysis of two cases of acute myeloid leukemia cells revealed centromere-associated DNA in 25% of their dmin. These data indicate the existence of dmin that contain centromere-associated DNA and suggest that such dmin might represent a new class of extrachromosomal chromatin bodies.

Polysomy of chromosome 12 in 60 patients with non-Hodgkin's lymphoma assessed by fluorescence in situ hybridization: differences between follicular and diffuse large cell lymphoma

Sixty consecutive evaluable specimens from patients with non-Hodgkin's lymphoma (NHL) were studied for the incidence of polysomy of chromosome 12 by fluorescence in situ hybridization (FISH) with probes for the repetitive DNA sequence in the centromeric region of chromosome 12. Thirty-six samples were from follicular lymphomas (FLs), and twenty-four were from diffuse large cell lymphomas (DLCLs). Fifty-two specimens (86%) were obtained by fine-needle aspiration of a diseased node, seven (11.6%) were from involved bone marrows, and one specimen was from a pleural effusion. Twelve of the thirty-six (33%) cases with FL had trisomy 12 in 3-41% of the cells (median, 10%) (normal controls had three signals in 1.4 +/- 0.7% of cells). Trisomy 12 was found in 62% of the patients who had had FL for more than 5 years. Nine of the twenty-four cases (37%) with DLCL had more than two copies of chromosome 12 in 4-92% of the cells (median, 78%), and all nine cases were of B-cell phenotype. Unlike FL cells, some DLCL cells had 4-6 copies of chromosome 12. In previously untreated patients, 54% of DLCLs and 26% of FLs had subpopulations of cells containing more than two copies of chromosome 12 (P = 0.04). Only 2/7 cases of DLCL with polysomy 12 had rearrangement of the BCL2 gene, indicating that the majority of DLCL cases with polysomy 12 did not result from histologic transformation of low grade follicular lymphomas. These data demonstrate that FISH of interphase cells is a sensitive method for detecting numerical abnormalities of chromosome 12 in NHL.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosome analysis of non-Hodgkin's lymphomas by fluorescence in situ hybridization

We have recently carried out a cytogenetic survey of a series of non-Hodgkin's lymphomas (NHLs) and identified chromosomal abnormalities in most of the samples studied. A third of these cases, however, had to be recorded as containing derivative or marker chromosomes, whose origins were either partially or completely unknown. In an attempt to further analyse such cases, we have adopted the fluorescence in situ hybridization (FISH) technique. The FISH technique has allowed us to map the myb gene to 6q23, and then to study its position on 6q- derivative chromosomes in the NHL cells. The related FISH technique of chromosome painting has enabled us to identify a marker chromosome in one of our cases as an abnormal X chromosome, and in other cases has allowed 14q+ derivative chromosomes to be further analysed. We have also applied the FISH technique to the analysis of interphase nuclei, and have been able to determine numerical chromosome changes in NHL interphase cells. The application of the FISH technique to the study of NHL cell chromosomes is likely to enable the identification of most chromosomal abnormalities present, and so may reveal the critical events leading to malignant transformation of lymphoid cells.

Analysis of the p53 gene, its expression and protein stabilization in non-Hodgkin's lymphomas

We have investigated the p53 gene, expression of its mRNA, and stabilization of its protein in a series of non-Hodgkin's lymphomas (NHLs). Immunohistochemistry revealed positive staining of the p53 protein in node biopsies from 6/36 NHL patients, all of whom had high-grade disease. The remaining NHL samples, together with 3 reactive nodes, showed either negative staining or the staining of only occasional cells. In one case that exhibited intense nuclear staining in 90% of the cells, a mutation in the p53 gene was also observed. There was no evidence of rearrangements of the p53 gene in any of the NHL samples. Although p53 mRNA could not be detected in nonmalignant tissue, it was apparently overexpressed in 16/38 NHL, but this did not correlate with positive staining of the p53 protein. These data suggest that p53 dysfunction might play an important role in the evolution of some cases of NHL, and that mechanisms other than mutation of the p53 gene may be involved in stabilizing the p53 protein in these neoplasms.

Investigation of the activation state of the X chromosome in non-Hodgkin's lymphomas

Cytogenetic analysis of non-Hodgkin's lymphomas (NHLs) has previously revealed a high incidence of numerical abnormalities involving the X chromosome. We have now used a combination of fluorescence in situ hybridization (FISH) and Southern blot analysis of methylation to examine the activation state of additional X chromosomes in NHL. Although FISH analysis of X chromosome centromeres in interphase nuclei was complicated by a number of factors, such as cell-cycle position, there was evidence that more than one X chromosome was present in the active state in 4/9 NHL. Methylation studies were carried out using the M27 beta probe, which also suggested that more than one activated X chromosome was present in at least 2/7 NHL cases. The two approaches therefore provided evidence that in some cases of NHL, unlike sex-chromosome-syndrome individuals, additional X chromosomes may be present in the active state. These data support the suggestion that NHL-associated oncogenes might be located on the X chromosome.

Investigation of BCL-2 gene rearrangements in a United Kingdom series of low and high grade non-Hodgkin's lymphomas

Rearrangements of the BCL-2 gene are thought to be the most frequent genetic changes that occur in non-Hodgkin's lymphomas (NHL), and are particularly associated with follicular low grade disease. Wide variations in the frequency of these rearrangements have, however, been reported in studies of NHL series from different parts of the world. We were therefore interested to determine the frequency of BCL-2 gene rearrangements in the different grades of NHL from a U.K. series. We have done this by using a combination of Southern blot hybridization and polymerase chain reaction (PCR) analysis. The frequencies of rearrangements in our series were 9/20 (45%) in low grade follicular NHL, 1/8 (12.5%) in low grade lymphocytic and 5/19 (26%) in high grade NHL. However, estimation of the high grade value was complicated by the fact that a number of the high grade samples in our series were from patients who had transformed from low grade follicular disease. If the patients were ranked on the basis of whether they had a history of low grade follicular disease then the frequency of BCL-2 rearrangement remained the same 13/29 (45%), but was only 1/10 (10%) in high grade NHL with no history of follicular disease. The former figure was intermediate between those reported for the USA and Japan series, but the latter high grade figure was the lowest reported from any series. The significance of BCL-2 rearrangements in the evolution of both low and high grade NHL is discussed.