Blastic variant of mantle cell lymphoma shows a heterogenous pattern of somatic mutations of the rearranged immunoglobulin heavy chain variable genes

Genomic landscape of mature B-cell non-Hodgkin lymphomas - an appraisal from lymphomagenesis to drug resistance

BACKGROUND

Mature B-cell non-Hodgkin lymphomas are one of the most common hematological malignancies with a divergent clinical presentation, phenotype, and course of disease regulated by underlying genetic mechanism.

MAIN BODY

Genetic and molecular alterations are not only critical for lymphomagenesis but also largely responsible for differing therapeutic response in these neoplasms. In recent years, advanced molecular tools have provided a deeper understanding regarding these oncogenic drives for predicting progression as well as refractory behavior in these diseases. The prognostic models based on gene expression profiling have also been proved effective in various clinical scenarios. However, considerable overlap does exist between the genotypes of individual lymphomas and at the same time where additional molecular lesions may be associated with each entity apart from the key genetic event. Therefore, genomics is one of the cornerstones in the multimodality approach essential for classification and risk stratification of B-cell non-Hodgkin lymphomas.

CONCLUSION

We hereby in this review discuss the wide range of genetic aberrancies associated with tumorigenesis, immune escape, and chemoresistance in major B-cell non-Hodgkin lymphomas.

Clinicopathologic features and management of blastoid variant of mantle cell lymphoma

The blastoid variant of mantle cell lymphoma (MCL), which accounts for less than one-third of MCL, may arise de novo or as a transformation from the classical form of MCL. Blastoid variant, which predominantly involves men in their sixth decade, has frequent extranodal involvement (40-60%), stage IV disease (up to 85%) and central nervous system (CNS) involvement. Diagnosis relies on morphological features and is challenging. Immunophenotyping may display CD23 and CD10 positivity and CD5 negativity in a subset. Genetic analysis demonstrates an increased number of complex genetic alterations. Blastoid variant responds poorly to conventional chemotherapy and has a short duration of response. Although the optimal therapy remains to be established, CNS prophylaxis and the use of aggressive immunochemotherapy followed by autologous stem cell transplant may prolong the remission rate and survival. Further studies are crucial to expand our understanding of this disease entity and improve the clinical outcome.

Clinical practice guidelines for diagnosis, treatment, and follow-up of patients with mantle cell lymphoma. Recommendations from the GEL/TAMO Spanish Cooperative Group

Mantle cell lymphoma (MCL) is considered a distinct type of B-cell lymphoma genetically characterized by the t(11;14) translocation and cyclin D1 overexpression. There is also a small subset of tumors negative for cyclin D1 expression that are morphologically and immunophenotypically indistinguishable from conventional MCL. Although in the last decades, the median overall survival of patients with MCL has improved significantly, it is still considered as one of the poorest prognoses diseases among B-cell lymphomas. Election of treatment for patients with MCL is complex due to the scarcity of solid evidence. Current available data shows that conventional chemotherapy does not yield satisfactory results as in other types of B-cell lymphomas. However, the role of other approaches such as autologous or allogenic stem cell transplantation, immunotherapy, the administration of consolidation or maintenance schedules, or the use of targeted therapies still lack clear indications. In view of this situation, the Spanish Group of Lymphomas/Autologous Bone Marrow Transplantation has conducted a series of reviews on different aspects of MCL, namely its diagnosis, prognosis, first-line and salvage treatment (both in young and elderly patients), new targeted therapies, and detection of minimal residual disease. On the basis of the available evidence, a series of recommendations have been issued with the intention of providing guidance to clinicians on the diagnosis, treatment, and monitoring of patients with MCL.

Parallel gene expression profiling of mantle cell lymphoma - how do we transform 'omics data into clinical practice

DNA microarray technology has been a valuable tool to provide a global view of the changes in gene expression that characterize different types of B cell lymphomas, both in relation to clinical parameters but also in comparison with the non-malignant counterparts. The number of transcripts that can be analyzed on an array has dramatically increased, and now most commercially available arrays cover the whole genome, enabling overall analysis of the transcriptome.The backside of collecting this massive amount of information is that even after strict data filtering, it is impossible to do follow-up studies on all findings. Down-stream analysis is time-consuming and when performing confirmatory experiments on the protein level, the experiments are in most cases restricted to proteins recognized by commercially available reagents. Furthermore, since gene expression data is a comparative method not only are the experimental set-up but also the characteristics of both the sample and reference crucial for our ability to answer the questions posed. Thus, initial care must be taken in the design of the experiment and the preparation of the samples.The aim of this review is to discuss the progress in mantle cell lymphoma research enabled by gene expression analysis and to pinpoint the difficulties in making efficient use of the generated data to provide a fast and accurate clinical diagnosis, efficient stratification of patients into disease sub-groups and improved therapy.

Mantle cell lymphoma

MCL is a well-characterized clinically aggressive lymphoma with a poor prognosis. Recent research findings have slightly improved the outcome of this neoplasm. The addition of rituximab to conventional chemotherapy has increased overall response rates, but it does not improve overall survival with respect to chemotherapy alone. The use of intensive frontline therapies including rituximab and consolidated by ASCT ameliorates response rate and prolongs progression-free survival, but any impact on survival remains to be proven. Furthermore, the optimal timing, cytoreductive regimen and conditioning regimen, and the clinical implications of achieving a disease remission even at molecular level remain to be elucidated. The development of targeted therapies as the consequence of better dissection of pathogenetic pathways in MCL might improve the outcome of conventional chemotherapy in most patients and spare the toxicity of intense therapy in a minority of MCL patients characterized by a relatively indolent disease. Patients not eligible for intensive regimens, such as hyperC-VAD, may be considered for less demanding therapies, such as the combination of rituximab either with CHOP or with purine analogues, or bendamustine. Allogeneic SCT can be an effective option for relapsed disease in patients who are fit enough and have a compatible donor. Maintenance rituximab may be considered after response to immunochemotherapy for relapsed disease, although there are currently no data to recommend this approach as the first-line strategy. As the optimal approach to the management of MCL is still evolving, it is critical that these patients be enrolled in clinical trials to identify better treatment options.

Advances in the understanding of mantle cell lymphoma

Mantle cell lymphoma (MCL) is a well-defined lymphoid neoplasm characterized by a proliferation of mature B lymphocytes expressing CD5 that may show a spectrum of morphological and phenotypic features broader than initially described. Although some patients may follow an indolent clinical evolution, in most of them the tumour has an aggressive behaviour with poor response to conventional chemotherapy. The genetic hallmark is the t(11;14)(q13;q32) translocation leading to the overexpression of cyclin D1, which is considered the initial oncogenic event. In addition to this translocation, MCL may carry a high number of secondary chromosomal and molecular alterations that target regulatory elements of the cell cycle machinery and senescence (BMI1/INK4/ARF/CDK4/RB1), DNA damage response pathways (ATM/CHK2/p53), and cell survival signals. The knowledge of these mechanisms and their influence on the behaviour of the tumour are facilitating the development of prognostic models with a more precise prediction of the clinical evolution of the patients. This information coupled with the availability of a new generation of innovative drugs targeting basic molecular process of the tumour cells, should facilitate the design of new therapeutic protocols able to overcome the resistance of this aggressive lymphoma to conventional treatments and improve the life expectancy of the patients.

Sequence analysis proves clonal identity in five patients with typical and blastoid mantle cell lymphoma

Mantle cell lymphoma (MCL) is typically composed of small irregular lymphoid cells. Blastoid variants, composed of lymphoblast-like (classic type) or large (pleomorphic type) cells, arise de novo or in patients with typical MCL. Although it has been assumed that blastoid variant represents histologic transformation of typical MCL, the clonal relationship between the two tumors has rarely been assessed at the molecular level. We identified five patients with typical MCL who subsequently developed the blastoid variant. There were two men and three women with a median age of 65 years (range, 34-70) at diagnosis of typical MCL involving lymph nodes. The median interval between typical and blastoid MCL was 36 months (range, 11-103). Subsequent blastoid variant MCL involved soft tissue (two), lymph node (one), ileum (one), or rectum (one). All typical and blastoid neoplasms were positive for CD20, cyclin D1, and monotypic surface immunoglobulin light chain, and all typical cases were positive for CD5. Two blastoid neoplasms lost CD5 expression, one of which aberrantly expressed CD10. Immunostaining for Ki-67 showed a median proliferative fraction of 20% in typical and 70% in blastoid neoplasms. Sequence analysis of the VDJ regions of the rearranged IgH allele proved clonal identity in each set of paired samples in all five patients. These results support the concept that blastoid MCL arising in patients with typical MCL represents histologic transformation of the original neoplastic clone.

Mantle cell lymphomas acquire increased expression of CCL4, CCL5 and 4-1BB-L implicated in cell survival

We have analyzed mantle cell lymphomas (MCLs), using high-density DNA microarrays, and confirmed the expression of differentially regulated antigens, using flow cytometry and immunohistochemistry. The results show that MCLs acquire expression of molecules that normally are involved in interaction with other immune cells and, thus, might affect the ability of the tumor to survive. The MCL signature is represented by the overexpression of the chemokine CCL4 (MIP-1beta), implicated in the recruitment of regulatory T cells, as well as CCL5 and 4-1BB-L. The latter molecules are normally involved in chemotaxis of T cells and B cell activation, respectively. Signaling through 4-1BB-L allows B cells to proliferate and the expression of its ligand, by the intra-tumoral mesh of follicular dendritic cells (FDC), could thus serve as a paracrine loop facilitating growth and survival of MCL cells.

Transcriptional profiling and assessment of cell lines as in vitro models for mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive malignancy and new treatment modalities must be established to increase patient survival time. In the search for new therapeutic targets, reliable and well-characterised in vitro models are essential. In this study, we have characterised three MCL cell lines (SP53, Granta 519 and NCEB1) in comparison with primary tumours from MCL, follicular lymphomas (FL), a FL cell line (RL), a Burkitt lymphoma cell line (RAJI) and five different B cell populations from healthy individuals. Expression profiling was used to determine the relative expression of >12000 transcripts in these samples, and flow cytometry analysis was performed to establish a phenotypic signature for each of the cell lines. In addition, the cell lines were sequenced, and the frequency of somatic mutations and immunoglobulin (Ig) variable heavy chain (VH) usage were determined. We show by hierarchical clustering that the cell lines retain a genetic signature similar to primary MCL, which readily separated the MCL samples from the other lymphoma cell lines and the FL tumours. Furthermore, the MCL cell lines showed differences in the frequency of VH somatic mutations (0-2.1%). The increased number of mutations in NCEB1, compared to the other MCL cell lines, was in agreement with a decreased expression of CD31, CD44, CXCR5, CCR7 and CCR6. Taken together, our data show that the cell lines are clearly derived from MCL tumours and expressed similar genetic and phenotypic signatures compared to primary tumours, which confirmed their usefulness as in vitro models.

IgVH mutations in blastoid mantle cell lymphoma characterize a subgroup with a tendency to more favourable clinical outcome

Mantle cell lymphoma (MCL) is associated with a very unfavourable clinical course. This is particularly true for mantle cell lymphoma of the blastoid subtype (MCL-b). In order to define prognostic factors, we analysed the impact of immunoglobulin heavy chain variable (IgV H) gene somatic hypermutations on clinical outcome in a series of 21 cases of morphologically, phenotypically, and genotypically well-characterized MCL-b. Testing and estimation were performed using log-rank statistics and displayed on Kaplan-Meier graphs. Thirteen of 21 cases of MCL-b revealed a homology rate of > or = 99% compared to IgV H germ-line sequences in the databases and were scored as non-mutated. Eight of 21 cases (38%) of MCL-b were mutated. In MCL-b the mutation frequency was usually low and the mutation pattern was only rarely antigen-selected, in contrast to a control group of 11 cases with morphologically almost identical, but phenotypically and genotypically clearly distinguishable, diffuse large B cell lymphoma, derived, most likely, from germinal centre B cells. In our series of 21 MCL-b, positive IgV H mutational status, irrespective of varying homology thresholds, had no statistically significant prognostic impact on event-free or overall survival. However, mutated MCL-b tended to present more frequently at an earlier stage and without bone marrow involvement and to show lower rates of relapse and death, resulting in a more favourable clinical outcome.

Immunoglobulin heavy chain genes somatic hypermutations and chromosome 11q22-23 deletion in classic mantle cell lymphoma: a study of the Swiss Group for Clinical Cancer Research

Mantle cell lymphoma (MCL) shares immunophenotypic and karyotypic features with chronic lymphocytic leukaemia. The latter comprises two distinct entities with prognosis dependent upon immunoglobulin heavy chain (IgH) gene mutational status and the presence of 11q deletion. We evaluated the relevance of IgH gene mutational status, IgV gene family usage and presence of 11q deletion in a series of 42 histologically reviewed classical MCL cases to determine the prognostic impact. VH3 was the most common VH family, with VH3-21 being the most frequent individual VH gene. Approximately 30% of the cases had a IgH somatic mutation rate higher than 2%, but was only higher than 4% in <10% of cases. Half of the cases had deletion of chromosome 11q21-telomere (11q21->ter), with two minimal deleted regions, at 11q22.2 and 11q23.2. There was no association between 11q loss and IgH gene somatic mutation rate; the use of VH3-21 gene could be associated with a better prognosis.

Indolent mantle cell lymphoma with nodal involvement and mutated immunoglobulin heavy chain genes

Mantle cell lymphoma (MCL) is typically considered an aggressive but incurable neoplasm composed of cyclin D1+ monoclonal B-cells with a t(11;14)(q13;q32) and usually unmutated immunoglobulin (Ig) genes. Although it has been suggested that a more indolent leukemic disorder exists with the same phenotype and genotype but with mutated Ig genes, others have considered these cases to be variants of chronic lymphocytic leukemia. We present a case of an indolent MCL that was documented with cyclin D1 expression in a lymph node biopsy performed more than 12 years ago. The patient has peripheral blood involvement with a lymphocyte count in the reference range, variable thrombocytopenia, and minimal adenopathy but is otherwise well, never having received any antineoplastic therapy. Study of peripheral blood samples from 2002 revealed a CD5-variable B-cell monoclonal proliferation with a t(11;14)(q13;q32) plus other karyotypic abnormalities, positive fluorescence in situ hybridization studies for the CCND1/IgH translocation, and clonal Ig gene rearrangement with mutated Ig genes (95.7% homology to VH 4-31). The subtle but diagnostic lymph node biopsy in this case helps to further support that an indolent t(11;14) monoclonal lymphocytosis with mutated Ig genes can represent an MCL variant rather than chronic lymphocytic leukemia.

Limited-stage mantle-cell lymphoma

BACKGROUND

Mantle-cell lymphoma (MCL) is known to have a poor outcome, however, most patients present with advanced-stage disease. Little information is available on limited-stage MCL.

PATIENTS AND METHODS

We retrospectively reviewed clinicopathological information on all patients with limited-stage MCL seen at the British Columbia Cancer Agency since 1984.

RESULTS

Twenty-six patients had low bulk (<10 cm) stage IA (12 patients) or IIA (14 patients) MCL. Initial therapy was involved-field radiation therapy (RT) with or without chemotherapy (CT), 17 patients; CT alone or observation, nine patients. Fifteen patients are alive at a median follow-up of 72 months (range 14-194). Progression-free survival (PFS) at 2 and 5 years was 65% and 46%, and overall survival (OS) 86% and 70%, respectively. Five patients surviving beyond 8 years. Only age and initial use of RT significantly affected PFS. Five-year PFS for patients <60 years of age was 83%, compared with 39% for those aged >/= 60 years, P = 0.04. Patients receiving RT with or without CT (n = 17), had a 5-year PFS of 68%, compared with 11% for those not receiving RT (n = 9, P = 0.002). Receiving RT eliminated the impact of age on PFS (with RT the 5-year PFS was 83% for those aged <60 years and 57% for those >/= 60 years, P = 0.17). Although OS for the whole group was 53% at 6 years, it was 71% for those initially treated with RT, but only 25% for those not given RT (P = 0.13).

CONCLUSION

In our experience, patients with limited-stage MCL had an improved PFS when treated with regimens including RT, with a trend towards improved OS. These results suggest a potentially important role for RT in limited-stage MCL.

A subset of t(11;14) lymphoma with mantle cell features displays mutated IgVH genes and includes patients with good prognosis, nonnodal disease

We analyzed lymphocyte morphology, histology, immunophenotype, immunoglobulin heavy chain (IgVH) gene mutations, and clinical course in 80 unselected patients presenting with circulating t(11;14) lymphocytes. Of the 80 patients, 43 had peripheral lymphadenopathy (nodal group), and histology confirmed mantle cell lymphoma (MCL) in all. There were 37 patients with no lymphadenopathy (nonnodal group); 13 of 37 had histology, all showing MCL. IgVH genes were unmutated in 28 (90%) of 31 nodal and 15 (44%) of 34 nonnodal cases (P =.0001); CD38 was positive in 32 (94%) of 34 nodal and 16 (48%) of 33 nonnodal cases (P <.001); 41 (95%) of 43 nodal patients required immediate treatment compared with 18 (49%) of 37 nonnodal patients who had indolent disease (P <.0001). Median survival (95% confidence interval) was 30 months (10-50) in the nodal group and 79 months (22-136) in the nonnodal group (P =.005). Mutation status did not statistically affect survival, but of 6 long-term survivors (> 90 months) all were nonnodal and 5 of 5 had mutated IgVH genes. Lymphocyte morphology was heterogeneous in both groups: typical MCL in 56 cases (34 nodal, 22 nonnodal), blastoid MCL in 8 cases (3 nodal, 5 nonnodal), and small-cell MCL in 16 cases (6 nodal, 10 nonnodal, P =.12). Matutes immunophenotyping score was 1 in 65 cases and 2 in 15 (8 nodal, 7 nonnodal). We find no evidence against a diagnosis of MCL in the nonnodal group and suggest that mutated IgVH genes may help identify patients with indolent disease.

Cell cycle alterations in the blastoid variant of mantle cell lymphoma (MCL-BV) as detected by gene expression profiling of mantle cell lymphoma (MCL) and MCL-BV

Overexpression of cyclin D1 is necessary but by itself insufficient for the development of mantle cell lymphoma (MCL). To identify pathways in the pathogenesis of MCL and the blastoid variant (MLC-BV), we compared the gene-expression profiles of microdissected normal mantle cells, MCL, and MCL-BV by oligonucleotide microarrays and quantitative reverse transcriptase PCR (QRT-PCR). We identified and confirmed the overexpression of several genes in MCL-BV that are involved in the cell cycle control at the G1/S and G2/M checkpoints or inhibit apoptotic cell death. The highly expressed cyclin dependent kinase 4 (CDK4) is a cell cycle kinase that associates with cyclin D1 for the progression through the G1/S checkpoint, whereas overexpression of cdc28 protein kinase 1 (CKS1) blocks the inhibition of the cyclin D1/CDK4 complex by the CDK inhibitor p27/Kip1. Other highly expressed genes in MCL-BV that promote the cells through the G1/S-checkpoint include the oncogenes B-Myb, PIM1, and PIM2, and passage through the G2/M-checkpoint is enhanced by high levels of cdc25B. Furthermore, two highly expressed genes that inhibit apoptosis are defender against cell death (DAD1) and RSK1. In summary, our microarray and QRT-PCR analyses identified several candidate genes whose expression increased when comparing normal follicular mantles with MCL and MCLBV, suggesting a potential pathogenic role in the evolution of MCL-BV.

Somatic hypermutation and V(H) gene usage in mantle cell lymphoma

Mantle cell lymphoma (MCL) is considered to derive from naïve, pregerminal center (GC) CD5+ B-cells. However, the cell of origin has been questioned in recent studies that showed somatic hypermutations in the immunoglobulin (Ig) variable heavy chain (V(H)) genes in subsets of MCL. To clarify this issue, we analyzed the IgV(H) genes for the presence of somatic hypermutations in 51 MCL cases. Twenty percent of the MCL cases displayed somatically mutated V(H) genes (defined as >2% mutated), whereas 80% showed unmutated V(H) genes. This finding suggests that MCL is a genetically heterogeneous disease, with the majority of cases originating from unmutated pre-GC B-cells and a subset deriving from more mature B-cells which have been exposed to the GC environment and have undergone somatic hypermutation. A biased V(H) gene usage has been demonstrated in several B-cell malignancies; however, this has not yet been investigated in MCL, although V(H)4-34 overusage has been indicated by small studies. Interestingly, we found a restricted usage of three individual V(H) genes in our MCL material; V(H)4-34 (22%), V(H)3-21 (16%) and V(H)5-51 (12%). This novel finding of preferential V(H) gene usage in half of the MCL cases may suggest an antigen driven process occurring in B-cells expressing specific VH genes, thus implicating that Ig specificity could be involved in mantle cell lymphoma development.

Monitoring disease in lymphoma and CLL patients using molecular techniques

Over the past decade considerable advances have been made in the sensitivity of detection of residual lymphoma and leukaemia cells. Assays based on the polymerase chain reaction (PCR) can detect one tumour cell in up to 10(5) to 10(6) normal cells. The identification and cloning of breakpoints associated with specific chromosomal translocations has made possible the application of these techniques to a variety of lymphoid malignancies. In parallel, B cell malignancies exhibit rearrangements of their immunoglobulin genes that are also suitable targets for PCR amplification to identify residual cells. Although these techniques provide a useful adjunct to standard methods of detection and diagnosis, their role in determining disease outcome remains investigational. There is confusion as to whether it is necessary to eradicate PCR-detectable lymphoma cells for cure, so it is not yet possible to determine whether the detection of residual lymphoma cells by PCR is an indication to continue therapy.

Blastic variant of mantle cell lymphoma: a rare but highly aggressive subtype

The blastic variant (BV) form of mantle cell lymphoma (MCL) is considered to be a very aggressive subtype of non-Hodgkin's lymphoma (NHL). In order to determine its clinico-biological features and response to therapy we studied 33 patients (17%) out of 187 suffering from MCL who were diagnosed with a BV of MCL. Blastic variant was diagnosed according to histopathological patterns, immunophenotyping, and bcl1 gene rearrangement and/or cyclin D1 overexpression. Three patients initially diagnosed with large cell NHL were classified as BV. Patients received front-line therapy including CHOP-like regimen or CVP (n = 29), or chlorambucil (n = 4) and CHOP or ESAP as second-line therapy. High-dose intensification with stem cell transplantation (SCT) was performed in 11 cases (autoSCT, n = 8; alloSCT, n = 3). All but two patients were in complete remission (CR) at the time of transplant (CR1, n = 5; CR2, n = 4). Clinical and biological characteristics did not differ from those of the common form of MCL. The median age was 62 years (29-80), with a sex ratio (M/F) of 2.6:1. Of the 33 patients, 66% had extranodal site involvement, 85% had an Ann Arbor stage IV, and 82% had peripheral lymphadenopathy. Circulating lymphomatous cells were seen in 48% of cases. Twelve patients (36%) entered a CR1 with a median duration of 11 months. Fifteen patients (46%) failed to respond and rapidly died of progressive disease. Second-line therapy led to a 26% (6/23) CR2 rate. Nine patients relapsed after high-dose therapy. Twenty-two of the 33 patients (66%) died of refractory or progressive disease. Median overall survival (OS) time was 14.5 months for the 33 BV patients as compared to 53 months for the 154 patients with a common form of MCL, P <0.0001. In the univariate analysis, OS was influenced by age, extranodal site involvement, circulating lymphomatous cells, and international prognosis index (IPI). In the multivariate analysis, only IPI affected OS: patients with IPI > or =2 had 8 months median OS as compared to 36 months median OS for patients with IPI <2, P = 0.003. Blastic variant is one of the worst forms of NHL. An improved recognition of BV of MCL is required, particularly in high-grade CD5+ NHL using immunophenotyping and bcl1 molecular study. Standard therapy using anthracycline or even high-dose intensification produce poor results and an alternative treatment should be proposed to such patients.

Telomerase activity and clinical progression in chronic lymphoproliferative disorders of B-cell lineage

The activation of telomerase, which specifically occurs in neoplastic cells to avoid telomere attrition at each cell division, is a necessary event in tumorigenesis. The evidence that telomerase is also present in normal B cells at different levels according to their differentiation and activation state makes the study of telomerase activity in B cell tumors particularly interesting. This review summarizes data concerning telomerase activity in chronic lymphoproliferative disorders of B-cell lineage (B-CLD), making suggestions regarding B-cell development and B-cell tumor histogenesis. The role of telomerase activity as a potential prognostic marker, as well as a target of new antineoplastic strategies is discussed.

Clinical relevance of immunoglobulin mutation analysis

The precise diagnosis of malignant B-cell lymphoproliferations is essential for their appropriate clinical management. Histologic and immunophenotypical features alone are often insufficient in discriminating between various lymphoma entities and subtypes. The analysis of clonally rearranged immunoglobulin chain genes of the tumor cells was therefore suggested as an additional parameter. This article reviews current knowledge and describes which conclusions can be drawn for lymphoma diagnosis based on the type of immunoglobulin chain gene rearrangement, as well as on the number and distribution of somatic immunoglobulin mutations. Although there are striking correlations between the clinical outcome and the immunoglobulin mutations in some entities, many additional studies are required in order to draw final conclusions for most types of lymphoma.

Increased proteasome degradation of cyclin-dependent kinase inhibitor p27 is associated with a decreased overall survival in mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive neoplasm characterized by the deregulated expression of cyclin D1 by t(11;14). The molecular mechanisms responsible for MCL's clinical behavior remain unclear. The authors have investigated the expression of p53, E2F-1, and the CDK inhibitors p27 and p21 in 110 MCLs, relating their expression to proliferative activity (Ki-67). For comparison, they have similarly analyzed low-grade (12 MALT, 16 CLL/SLL) and high-grade (19 DLCL) lymphomas. p53 was detected more frequently in large-cell MCL (l-MCL; 5 of 7) than in classical MCL (s-MCL; 13 of 103) and DLCL (8 of 19). In MCL and DLCL, the percentage of E2F-1+ nuclei was high, correlating with high Ki-67 expression. Most MCLs (91 of 112) and DLCLs (12 of 19) showed a loss of p27; MALT and CLL/SLL, however, were p27 positive. Reverse transcription–polymerase chain reaction and in vitro protein degradation assays demonstrated that MCLs have normal p27 mRNA expression but increased p27 protein degradation activity via the proteasome pathway. Correlation of MCL p53 and p27 expression with clinical data showed an association between reduced overall survival rates and the overexpression of p53 (P = .001), the loss of p27 (P = .002), or both. Loss of p27 identified patients with a worse clinical outcome among p53 negative cases (P = .002). These findings demonstrated that MCL has a distinct cell cycle protein expression similar to that of high-grade lymphoma. The loss of p27 and the overexpression of p53 in MCL are prognostic markers that identify patients at high risk. The demonstration that low levels of p27 in MCL result from enhanced proteasome-mediated degradation should encourage additional clinical trials. (Blood. 2000;95:619-626)

Immunoglobulin V(H) gene mutational analysis suggests that blastic variant of mantle cell lymphoma derives from different stages of B-cell maturation

To characterise the nature of the cellular origin of the blastic variant of mantle cell lymphoma (MCL-BV), we analysed the immunoglobulin (Ig) heavy chain variable region (V(H)) genes in four cases of MCL-BV. The rearranged V(H)-D J(H) genes were PCR-amplified, cloned and sequenced. In one case, the comparison of the rearranged V(H) gene sequence to known germline V(H) gene templates showed no somatic mutations suggesting a pre-germinal centre B-cell origin for tumour cells. In the other three cases, the V(H) gene sequences showed varied number of point mutations relative to the putative germline V(H) gene sequences but the point mutations were not associated with intraclonal diversification. In one of the mutated cases, the distribution and type of the mutations indicated that tumour cells had been selected by an antigen. Since somatically mutated Ig genes are expressed by B-cells that have reached a germinal centre/post-germinal centre stage of development, these findings suggest that the MCL-BV cell of origin may also be a germinal centre or a post-germinal centre B-cell. Taken together, our findings suggest that the development of MCL-BC may not be restricted to one stage of B-cell differentiation and that they may represent transformants of B-cells at different stages of ontogeny.

Restricted immunoglobulin variable region (Ig V) gene expression accompanies secondary rearrangements of light chain Ig V genes in mouse plasmacytomas

The many binding studies of monoclonal immunoglobulin (Ig) produced by plasmacytomas have found no universally common binding properties, but instead, groups of plasmacytomas with specific antigen-binding activities to haptens such as phosphorylcholine, dextrans, fructofuranans, or dinitrophenyl. Subsequently, it was found that plasmacytomas with similar binding chain specificities not only expressed the same idiotype, but rearranged the same light (V(L)) and heavy (V(H)) variable region genes to express a characteristic monoclonal antibody. In this study, we have examined by enzyme-linked immunosorbent assay five antibodies secreted by silicone-induced mouse plasmacytomas using a broader panel of antigens including actin, myosin, tubulin, single-stranded DNA, and double-stranded DNA. We have determined the Ig heavy and light chain V gene usage in these same plasmacytomas at the DNA and RNA level. Our studies reveal: (a) antibodies secreted by plasmacytomas bind to different antigens in a manner similar to that observed for natural autoantibodies; (b) the expressed Ig heavy genes are restricted in V gene usage to the V(H)-J558 family; and (c) secondary rearrangements occur at the light chain level with at least three plasmacytomas expressing both kappa and lambda light chain genes. These results suggest that plasmacytomas use a restricted population of B cells that may still be undergoing rearrangement, thereby bypassing the allelic exclusion normally associated with expression of antibody genes.

Blastic transformation of mantle cell lymphoma: genetic evidence for a clonal link between the two stages of the tumour

AIMS

The blastic variant of mantle cell lymphoma (MCL-BV) may develop through histological transformation of mantle cell lymphoma (MCL). However, the clonal link between the tumour cells of MCL and transformed MCL-BV has not been established at the genetic level. To investigate this link longitudinal molecular genetic studies have been performed in two cases of MCL that showed morphological transformation to MCL-BV.

METHODS AND RESULTS

Polymerase chain reaction (PCR) and nucleotide sequence analyses of the complementary determining region 3 (CDR) of the immunoglobulin (Ig) heavy chain (H) gene were performed to identify clone-specific rearrangements. In both cases, nucleotide sequence analysis revealed common clone-specific IgH gene rearrangements in MCL and subsequent MCL-BV.

CONCLUSIONS

These results provide genetic evidence for the common clonal origin of MCL and subsequently developed MCL-BV.

De novo CD5-positive diffuse large B-cell lymphoma: clinical characteristics and therapeutic outcome

To determine the clinical significance of CD5 expression in diffuse large B-cell lymphoma (DLBL) without a clinical history of low-grade B-cell lymphoma, we have reviewed the clinical features and therapeutic outcome of 25 patients with de novo CD5-positive DLBL, and compared the results with those of 87 patients with CD5-negative DLBL and 22 patients with mantle cell lymphoma (MCL). The patients with de novo CD5-positive DLBL had clinical characteristics of elderly onset (median age 63, range 37-91), and female predominance (male/female 10/15). 21 (84%) of these patients had extranodal involvement at presentation, with great variation in the sites. In comparison with the patients with CD5-negative DLBL, the treatment outcome for the patients with de novo CD5-positive DLBL was very poor with frequent relapse. The failure-free survival curve was almost identical to that of patients with MCL, showing that standard chemotherapy for DLBL was not effective for most of the patients with de novo CD5-positive DLBL. These findings suggest that de novo CD5-positive DLBL forms a distinct subgroup of DLBL.