A novel B-cell line (U-2932) established from a patient with diffuse large B-cell lymphoma following Hodgkin lymphoma

Bifunctional Inhibitor Reveals NEK2 as a Therapeutic Target and Regulator of Oncogenic Pathways in Lymphoma

Expression of the serine/threonine kinase never in mitosis gene A (NIMA)-related kinase 2 (NEK2) is essential for entry into mitosis via its role in facilitating centrosome separation. Its overactivity can lead to tumorigenesis and drug resistance through the activation of several oncogenic pathways, including AKT. Although the cancer-enabling activities of NEK2 are documented in many malignancies, including correlations with poor survival in myeloma, breast, and non-small cell lung cancer, little is known about the role of NEK2 in lymphoma. Here, in tumors from patients with diffuse large B-cell lymphoma (DLBCL), the most common, aggressive non-Hodgkin lymphoma, we found a high abundance of NEK2 mRNA and protein associated with an inferior overall survival. Using our recently developed NEK2 inhibitor, NBI-961, we discovered that DLBCL cell lines and patient-derived cells exhibit a dependency on NEK2 for their viability. This compromised cell fitness was directly attributable to efficient NEK2 inhibition and proteasomal degradation by NBI-961. In a subset of particularly sensitive DLBCL cells, NBI-961 induced G2/mitosis arrest and apoptosis. In contrast, an existing indirect NEK2 inhibitor, INH154, did not prevent NEK2 autophosphorylation, induce NEK2 proteasomal degradation, or affect cell viability. Global proteomics and phospho-proteomics revealed that NEK2 orchestrates cell-cycle and apoptotic pathways through regulation of both known and new signaling molecules. We show the loss of NEK2-sensitized DLBCL to the chemotherapy agents, doxorubicin and vincristine, and effectively suppressed tumor growth in mice. These studies establish the oncogenic activity of NEK2 in DLBCL and set the foundation for development of anti-NEK2 therapeutic strategies in this frequently refractory and relapse-prone cancer.

Epstein-Barr virus-encoded EBNA2 downregulates ICOSL by inducing miR-24 in B-cell lymphoma

ABSTRACT

Hematological malignancies such as Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B-cell lymphoma (DLBCL) cause significant morbidity in humans. A substantial number of these lymphomas, particularly HL and DLBCLs have poorer prognosis because of their association with Epstein-Barr virus (EBV). Our earlier studies have shown that EBV-encoded nuclear antigen (EBNA2) upregulates programmed cell death ligand 1 in DLBCL and BLs by downregulating microRNA-34a. Here, we investigated whether EBNA2 affects the inducible costimulator (ICOS) ligand (ICOSL), a molecule required for efficient recognition of tumor cells by T cells through the engagement of ICOS on the latter. In virus-infected and EBNA2-transfected B-lymphoma cells, ICOSL expression was reduced. Our investigation of the molecular mechanisms revealed that this was due to an increase in microRNA-24 (miR-24) by EBNA2. By using ICOSL 3' untranslated region-luciferase reporter system, we validated that ICOSL is an authentic miR-24 target. Transfection of anti-miR-24 molecules in EBNA2-expressing lymphoma cells reconstituted ICOSL expression and increased tumor immunogenicity in mixed lymphocyte reactions. Because miR-24 is known to target c-MYC, an oncoprotein positively regulated by EBNA2, we analyzed its expression in anti-miR-24 transfected lymphoma cells. Indeed, the reduction of miR-24 in EBNA2-expressing DLBCL further elevated c-MYC and increased apoptosis. Consistent with the in vitro data, EBNA2-positive DLBCL biopsies expressed low ICOSL and high miR-24. We suggest that EBV evades host immune responses through EBNA2 by inducing miR-24 to reduce ICOSL expression, and for simultaneous rheostatic maintenance of proproliferative c-MYC levels. Overall, these data identify miR-24 as a potential therapeutically relevant target in EBV-associated lymphomas.

Inhibition of SUMOylation enhances DNA hypomethylating drug efficacy to reduce outgrowth of hematopoietic malignancies

Combination therapies targeting malignancies aim to increase treatment efficacy and reduce toxicity. Hypomethylating drug 5-Aza-2'-deoxycytidine (5-Aza-2') enhances transcription of tumor suppressor genes and induces replication errors via entrapment of DNMT1, yielding DNA-protein crosslinks. Post-translational modification by SUMO plays major roles in the DNA damage response and is required for degradation of entrapped DNMT1. Here, we combine SUMOylation inhibitor TAK981 and DNA-hypomethylating agent 5-Aza-2'-deoxycytidine to improve treatment of MYC driven hematopoietic malignancies, since MYC overexpressing tumors are sensitive to SUMOylation inhibition. We studied the classical MYC driven malignancy Burkitt lymphoma, as well as diffuse large B-cell lymphoma (DLBCL) with and without MYC translocation. SUMO inhibition prolonged the entrapment of DNMT1 to DNA, resulting in DNA damage. An increase in DNA damage was observed in cells co-treated with TAK981 and 5-Aza-2'. Both drugs synergized to reduce cell proliferation in vitro in a B cell lymphoma cell panel, including Burkitt lymphoma and DLBCL. In vivo experiments combining TAK981 (25 mg/kg) and 5-Aza-2' (2.5 mg/kg) showed a significant reduction in outgrowth of Burkitt lymphoma in an orthotopic xenograft model. Our results demonstrate the potential of tailored combination of drugs, based on insight in molecular mechanisms, to improve the efficacy of cancer therapies.

Investigation of the anti-tumor mechanism of tirabrutinib, a highly selective Bruton's tyrosine kinase inhibitor, by phosphoproteomics and transcriptomics

Tirabrutinib is a highly selective Bruton's tyrosine kinase (BTK) inhibitor used to treat hematological malignancies. We analyzed the anti-tumor mechanism of tirabrutinib using phosphoproteomic and transcriptomic methods. It is important to check the drug's selectivity against off-target proteins to understand the anti-tumor mechanism based on the on-target drug effect. Tirabrutinib's selectivity was evaluated by biochemical kinase profiling assays, peripheral blood mononuclear cell stimulation assays, and the BioMAP system. Next, in vitro and in vivo analyses of the anti-tumor mechanisms were conducted in activated B-cell-like diffuse large B-cell lymphoma (ABC-DLBCL) cells followed by phosphoproteomic and transcriptomic analyses. In vitro kinase assays showed that, compared with ibrutinib, tirabrutinib and other second-generation BTK inhibitors demonstrated a highly selective kinase profile. Data from in vitro cellular systems showed that tirabrutinib selectively affected B-cells. Tirabrutinib inhibited the cell growth of both TMD8 and U-2932 cells in correlation with the inhibition of BTK autophosphorylation. Phosphoproteomic analysis revealed the downregulation of ERK and AKT pathways in TMD8. In the TMD8 subcutaneous xenograft model, tirabrutinib showed a dose-dependent anti-tumor effect. Transcriptomic analysis indicated that IRF4 gene expression signatures had decreased in the tirabrutinib groups. In conclusion, tirabrutinib exerted an anti-tumor effect by regulating multiple BTK downstream signaling proteins, such as NF-κB, AKT, and ERK, in ABC-DLBCL.

In Vitro Diffuse Large B-Cell Lymphoma Cell Line Models as Tools to Investigate Novel Immunotherapeutic Strategies

Despite the high incidence of diffuse large B-cell lymphoma (DLBCL), its management constitutes an ongoing challenge. The most common DLBCL variants include activated B-cell (ABC) and germinal center B-cell-like (GCB) subtypes including DLBCL with MYC and BCL2/BCL6 rearrangements which vary among each other with sensitivity to standard rituximab (RTX)-based chemoimmunotherapy regimens and lead to distinct clinical outcomes. However, as first line therapies lead to resistance/relapse (r/r) in about half of treated patients, there is an unmet clinical need to identify novel therapeutic strategies tailored for these patients. In particular, immunotherapy constitutes an attractive option largely explored in preclinical and clinical studies. Patient-derived cell lines that model primary tumor are indispensable tools that facilitate preclinical research. The current review provides an overview of available DLBCL cell line models and their utility in designing novel immunotherapeutic strategies.

DSF/Cu induces antitumor effect against diffuse large B-cell lymphoma through suppressing NF-κB/BCL6 pathways

Background

The B-cell lymphoma 6 (BCL6) oncogene is required for the survival of diffuse large B-cell lymphoma (DLBCL), which is incurable using conventional chemotherapy. Thus, it is imperative to improve the survival of patients with DLBCL. Disulfide (DSF) has been shown to have anticancer effects, but its effect on DLBCL remains unclear.

Methods

Four DLBCL cell lines (OCI-LY1, OCI-LY7, OCI-LY10 and U2932) and primary DLBCL cells from eight newly diagnosed DLBCL patients were pretreated with DSF alone or in combination with Cu. Cell morphology was observed under microscope. Flow cytometry was performed to evaluate the cell apoptosis, cell cycle, the mitochondrial membrane potential and the intracellular accumulation of reactive oxygen species (ROS). The protein expression was respectively measured by flow cytometry and western blotting.

Results

DSF or DSF/Cu exhibited a marked inhibitory effect on the growth of DLBCL cells, accompanied by cell cycle arrest at the G0/G1 phase. Meanwhile, DSF or DSF/Cu significantly induced DLBCL cells apoptosis. Further study revealed that DSF or DSF/Cu promoted apoptosis by inhibiting NF-κB signaling pathway. Interestingly, DSF/Cu significantly reduced BCL6 and AIP levels. In addition, DSF significantly up-regulate p53 protein in OCI-LY7 and OCI-LY10 while down-regulate p53 protein in OCI-LY1 and U2932.

Conclusion

These results provided evidence for the anti-lymphoma effects of DSF on DLBCL and suggested that DSF has therapeutic potential to DLBCL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02661-4.

Screening for Prognostic microRNAs Associated with Treatment Failure in Diffuse Large B Cell Lymphoma

Simple Summary

Around 30–40% of patients with diffuse large B cell lymphoma suffer early relapse after standard chemotherapy, but today no prediction whether a patient belongs to this group is possible. MicroRNA are small nucleotide sequences that regulate cellular functions via post-transcriptional modification of gene expression and can serve as prognostic biomarkers. A novel two-step strategy first used a small patient discovery group to identify possible microRNA candidates by comparing their levels in chemosensitive and chemoresistant patients via microarray. Overexpression of these microRNA was then analyzed in a large patient cohort and, as a result, three new microRNA biomarkers with prognostic potential could be identified. Early identification of those patients being at risk of failure with standard therapy is a prerequisite to develop more efficient treatments and a step towards precision medicine.

Abstract

Diffuse large B cell lymphoma (DLBCL) treatment with R-CHOP regimen produces 5-year progression-free survival and overall survival of around 60–70%. Our objective was to discover prognostic biomarkers allowing early detection of the remaining 30–40% with poor long-term outcome. For this purpose, we applied a novel strategy: from a cohort of DLBCL patients, treated with standard therapy, a discovery group of 12 patients with poor prognosis (advanced stage III–IV, R-IPI > 2) was formed, consisting of six chemoresistant (refractory/early relapse < 12 months) and six chemosensitive (complete remission > 3 years) subjects. By using microarray assays, the most differentially expressed miRNAs were defined as an initial set of prognostic miRNA candidates. Their expression was then analyzed in a validation cohort of 68 patients and the three miRNAs with the most significant impact on event-free and overall survival were selected. In the DLBCL cell line U-2932 the transfection with miR-1244 and miR-193b-5p, but not miR-1231, blocked the effect of CHOP on cell viability. A subsequent gene set enrichment analysis in patients revealed the implication of the first two miRNAs in cell cycle control and chemoresistance-related pathways, whereas the last one was involved in immunological processes. In conclusion, this novel strategy identified three promising prognostic markers for DLBCL patients at high risk of failure with standard therapy.

Fatty acid synthase and adenosine monophosphate-activated protein kinase regulate cell survival and drug sensitivity in diffuse large B-cell lymphoma

Fatty acid synthesis is crucial in supporting the survival and proliferation of multiple forms of cancer. The high metabolic demands of fatty acid synthesis are regulated by the AMP-activated kinase and activity of the fatty acid synthase enzyme. In this study, the roles of these enzymes in diffuse large B-cell lymphoma (DLBCL) were investigated by genetic knock-down and pharmacological activation of AMP-activated kinase by metformin, and selective inhibition of fatty acid synthase using the novel drug Fasnall. We observed distinct heterogeneity and adaptive plasticity of lipid metabolism in a panel of DLBCL cell lines and demonstrate the therapeutic potential of inhibiting fatty acid synthesis in a subset of DLBCL cells. The translational relevance of these in vitro data is supported by the strong correlation between AMP-activated protein kinase expression in primary DLBCL samples and disease relapse. Inhibition of fatty acid synthase with Fasnall may represent a therapeutic option for DLBCL that preferentially subverts to de novo fatty acid synthesis.

Maternal embryonic leucine zipper kinase is a novel target for diffuse large B cell lymphoma and mantle cell lymphoma

Diffuse large B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) are among the most aggressive B cell non-Hodgkin lymphomas. Maternal embryonic leucine zipper kinase (MELK) plays a role in cancer cell cycle progression and is associated with poor prognosis in several cancer cell types. In this study, the role of MELK in DLBCL and MCL and the therapeutic potential of MELK targeting is evaluated. MELK is highly expressed in DLBCL and MCL patient samples, correlating with a worse clinical outcome in DLBCL. Targeting MELK, using the small molecule OTSSP167, impaired cell growth and survival and induced caspase-mediated apoptosis in the lymphoma cells. Western blot analysis revealed that MELK targeting decreased the phosphorylation of FOXM1 and the protein levels of EZH2 and several mitotic regulators, such as Cdc25B, cyclin B1, Plk-1, and Aurora kinases. In addition, OTSSP167 also sensitized the lymphoma cells to the clinically relevant Bcl-2 inhibitor venetoclax by strongly reducing Mcl1 levels. Finally, OTSSP167 treatment of A20-inoculated mice resulted in a significant prolonged survival. In conclusion, targeting MELK with OTSSP167 induced strong anti-lymphoma activity both in vitro and in vivo. These findings suggest that MELK could be a potential new target in these aggressive B cell malignancies.

Specific interactions of BCL-2 family proteins mediate sensitivity to BH3-mimetics in diffuse large B-cell lymphoma

The BCL-2-specific inhibitor, ABT-199 (venetoclax) has exhibited remarkable clinical activity in nearly all cases of chronic lymphocytic leukemia. In contrast, responses are usually much less in diffuse large B-cell lymphoma (DLBCL), despite high level expression of BCL-2 in over 40% of cases, indicating that co-expression of related anti-apoptotic BCL-2 family proteins may limit the activity of ABT-199. We have investigated the roles of BCL-2 proteins in DLBCL cells using a panel of specific BCL-2 homology 3 (BH3)-mimetics and identified subgroups of these cells that exhibited marked and specific dependency on either BCL-2, BCL-X_L or MCL-1 for survival. Dependency was associated with selective sequestration of the pro-apoptotic proteins BIM, BAX and BAK by the specific anti-apoptotic BCL-2 protein which was important for cellular survival. Sensitivity to BH3-mimetics was independent of genetic alterations involving the BCL-2 family and only partially correlated with protein expression levels. Treatment with ABT-199 displaced BAX and BIM from BCL-2, subsequently leading to BAK activation and apoptosis. In contrast, apoptosis induced by inhibiting BCL-X_L with A1331852 was associated with a displacement of both BAX and BAK from BCL-X_L and occurred independently of BIM. Finally, the MCL-1 inhibitor S63845 induced mainly BAX-dependent apoptosis mediated by a displacement of BAK, BIM and NOXA from MCL-1. In conclusion, our study indicates that in DLBCL, the heterogeneous response to BH3-mimetics is mediated by selective interactions between BAX, BAK and anti-apoptotic BCL-2 proteins.

The CXCR4-CXCL12-Axis Is of Prognostic Relevance in DLBCL and Its Antagonists Exert Pro-Apoptotic Effects In Vitro

In tumor cells of more than 20 different cancer types, the CXCR4-CXCL12-axis is involved in multiple key processes including proliferation, survival, migration, invasion, and metastasis. Since data on this axis in diffuse large B cell lymphoma (DLBCL) are inconsistent and limited, we comprehensively studied the CXCR4-CXCL12-axis in our DLBCL cohort as well as the effects of CXCR4 antagonists on lymphoma cell lines in vitro. In DLBCL, we observed a 140-fold higher CXCR4 expression compared to non-neoplastic controls, which was associated with poor clinical outcome. In corresponding bone marrow biopsies, we observed a correlation of CXCL12 expression and lymphoma infiltration rate as well as a reduction of CXCR4 expression in remission of bone marrow involvement after treatment. Additionally, we investigated the effects of three CXCR4 antagonists in vitro. Therefore, we used AMD3100 (Plerixafor), AMD070 (Mavorixafor), and WKI, the niacin derivative of AMD070, which we synthesized. WK1 demonstrated stronger pro-apoptotic effects than AMD070 in vitro and induced expression of pro-apoptotic genes of the BCL2-family in CXCR4-positive lymphoma cell lines. Finally, WK1 treatment resulted in the reduced expression of JNK-, ERK1/2- and NF-κB/BCR-target genes. These data indicate that the CXCR4-CXCL12-axis impacts the pathogenesis of DLBCL and represents a potential therapeutic target in aggressive lymphomas.

Regulation of S1PR2 by the EBV oncogene LMP1 in aggressive ABC-subtype diffuse large B-cell lymphoma

The Epstein-Barr virus (EBV) is found almost exclusively in the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), yet its contribution to this tumour remains poorly understood. We have focused on the EBV-encoded latent membrane protein-1 (LMP1), a constitutively activated CD40 homologue expressed in almost all EBV-positive DLBCLs and which can disrupt germinal centre (GC) formation and drive lymphomagenesis in mice. Comparison of the transcriptional changes that follow LMP1 expression with those that follow transient CD40 signalling in human GC B cells enabled us to define pathogenic targets of LMP1 aberrantly expressed in ABC-DLBCL. These included the down-regulation of S1PR2, a sphingosine-1-phosphate (S1P) receptor that is transcriptionally down-regulated in ABC-DLBCL, and when genetically ablated leads to DLBCL in mice. Consistent with this, we found that LMP1-expressing primary ABC-DLBCLs were significantly more likely to lack S1PR2 expression than were LMP1-negative tumours. Furthermore, we showed that the down-regulation of S1PR2 by LMP1 drives a signalling loop leading to constitutive activation of the phosphatidylinositol-3-kinase (PI3-K) pathway. Finally, core LMP1-PI3-K targets were enriched for lymphoma-related transcription factors and genes associated with shorter overall survival in patients with ABC-DLBCL. Our data identify a novel function for LMP1 in aggressive DLBCL. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Hodgkin lymphoma cell lines: to separate the wheat from the chaff

Characteristic components of Hodgkin lymphoma (HL) tissue are the mono- or multinucleated Hodgkin-Reed-Sternberg (HRS) cells. Given the challenges of isolating these rare malignant cells and the difficulty in culturing cells from patients, many investigators have tried to establish cell lines in efforts to develop cellular tools for in vitro studies. A limited number of HL cell lines exist and have provided valuable insights into HL pathobiology. A literature survey indicated that 35 cell lines derived from HL patients have been published. To determine whether all these alleged HL cell lines hold up to scrutiny, we examined the available data and also put some of these cell lines to the test of hierarchical clustering, providing additional information regarding assignment to cell line type and tissue derivation. Hierarchical clustering separated the bona fide (classical) HL cell lines completely from cell lines derived from other lymphoma categories and proved conclusively that HL cell lines represent a distinct entity, irrespective of the cellular origin of the HRS cells. We conclude by pointing out the need for an intensified search for new cell culture avenues in order to develop a new generation of informative HL cell lines covering more widely the spectrum of HL stages and subtypes.

Epstein-Barr Virus Infection of Cell Lines Derived from Diffuse Large B-Cell Lymphomas Alters MicroRNA Loading of the Ago2 Complex

Diffuse large B-cell lymphoma (DLBCL) is an aggressive lymphoid tumor which is occasionally Epstein-Barr virus (EBV) positive and is further subtyped as activated B-cell DLBCL (ABC-DLBCL) and germinal center B-cell DLBCL (GCB-DLBCL), which has implications for prognosis and treatment. We performed Ago2 RNA immunoprecipitation followed by high-throughput RNA sequencing (Ago2-RIP-seq) to capture functionally active microRNAs (miRNAs) in EBV-negative ABC-DLBCL and GCB-DLBCL cell lines and their EBV-infected counterparts. In parallel, total miRNA profiles of these cells were determined to capture the cellular miRNA profile for comparison with the functionally active profile. Selected miRNAs with differential abundances were validated using real-time quantitative PCR (RT-qPCR) and Northern blotting. We found 6 miRNAs with differential abundances (2 upregulated and 4 downregulated miRNAs) between EBV-negative and -positive ABC-DLBCL cells and 12 miRNAs with differential abundances (3 upregulated and 9 downregulated miRNAs) between EBV-negative and -positive GCB-DLBCL cells. Eight and twelve miRNAs were confirmed using RT-qPCR in ABC-DLBCL and GCB-DLBCL cells, respectively. Selected miRNAs were analyzed in additional type I/II versus type III EBV latency DLBCL cell lines. Furthermore, upregulation of miR-221-3p and downregulation of let7c-5p in ABC-DLBCL cells and upregulation of miR-363-3p and downregulation of miR-423-5p in GCB-DLBCL cells were verified using RIP-Northern blotting. Our comprehensive sequence analysis of the DLBCL miRNA profiles identified sets of deregulated miRNAs by Ago2-RIP-seq. Our Ago2-IP-seq miRNA profile could be considered an important data set for the detection of deregulated functionally active miRNAs in DLBCLs and could possibly lead to the identification of miRNAs as biomarkers for the classification of DLBCLs or even as targets for personalized targeted treatment.IMPORTANCE Diffuse large B-cell lymphoma (DLBCL) is a highly aggressive tumor of lymphoid origin which is occasionally Epstein-Barr virus (EBV) positive. MicroRNAs are found in most multicellular organisms and even in viruses such as EBV. They regulate the synthesis of proteins by binding to their cognate mRNA. MicroRNAs are tethered to their target mRNAs by "Argonaute" proteins. Here we compared the overall miRNA content of the Ago2 complex by differential loading to the overall content of miRNAs in two DLBCL cell lines and their EBV-converted counterparts. In all cell lines, the Ago2 load was different from the overall expression of miRNAs. In addition, the loading of the Ago2 complex was changed upon infection with EBV. This indicates that the virus not only changes the overall content of miRNAs but also influences the expression of proteins by affecting the Ago complexes.

Artesunate shows potent anti-tumor activity in B-cell lymphoma

BACKGROUND

Although chemo-immunotherapy has led to an improved overall survival for most B-cell lymphoma types, relapsed and refractory disease remains a challenge. The malaria drug artesunate has previously been identified as a growth suppressor in some cancer types and was tested as a new treatment option in B-cell lymphoma.

METHODS

We included artesunate in a cancer sensitivity drug screen in B lymphoma cell lines. The preclinical properties of artesunate was tested as single agent in vitro in 18 B-cell lymphoma cell lines representing different histologies and in vivo in an aggressive B-cell lymphoma xenograft model, using NSG mice. Artesunate-treated B lymphoma cell lines were analyzed by functional assays, gene expression profiling, and protein expression to identify the mechanism of action.

RESULTS

Drug screening identified artesunate as a highly potent anti-lymphoma drug. Artesunate induced potent growth suppression in most B lymphoma cells with an IC50 comparable to concentrations measured in serum from artesunate-treated malaria patients, while leaving normal B-cells unaffected. Artesunate markedly inhibited highly aggressive tumor growth in a xenograft model. Gene expression analysis identified endoplasmic reticulum (ER) stress and the unfolded protein response as the most affected pathways and artesunate-induced expression of the ER stress markers ATF-4 and DDIT3 was specifically upregulated in malignant B-cells, but not in normal B-cells. In addition, artesunate significantly suppressed the overall cell metabolism, affecting both respiration and glycolysis.

CONCLUSIONS

Artesunate demonstrated potent apoptosis-inducing effects across a broad range of B-cell lymphoma cell lines in vitro, and a prominent anti-lymphoma activity in vivo, suggesting it to be a relevant drug for treatment of B-cell lymphoma.

Tenovin-6 inhibits proliferation and survival of diffuse large B-cell lymphoma cells by blocking autophagy

Diffuse large B-cell lymphoma (DLBCL) is one of the most aggressive non-Hodgkin lymphomas. It is curable but one-third of cases are refractory to therapy or relapse after initial response highlighting the urgent need for developing novel therapeutic approaches. Targeting sirtuins, particularly SIRT1 by genetic approaches or using pharmaceutical inhibitor tenovin-6, has shown promising therapeutic potential in various hematopoietic malignancies. However, it remains unknown whether these approaches are effective for DLBCL. In this study, we have found that tenovin-6 potently inhibits the proliferation and survival of DLBCL cells. Surprisingly, specific knockdown of SIRT1/2/3 has no effect on DLBCL. Mechanistically, tenovin-6 increases the level of microtubule-associated protein 1 light chain 3B (LC3B)-II in a SIRT1/2/3- and p53-independent manner in DLBCL cell lines. Tenovin-6-mediated increase of LC3B-II is through inhibition of classical autophagy pathway. Furthermore, inhibition of the autophagy pathway by using other inhibitors or by knocking down key genes in the pathway impairs cell proliferation and survival of DLBCL cells. These results indicate that targeting the autophagic pathway could be a novel therapeutic strategy for DLBCL and that precaution should be taken to interpret data where tenovin-6 was used as an inhibitor of sirtuins.

MiR-148a impairs Ras/ERK signaling in B lymphocytes by targeting SOS proteins

Although microRNAs have been recognized as central cellular regulators, there is an evident lack of knowledge about their targets. Here, we analyzed potential target genes for miR-148a functioning in Ras signaling in B cells, including SOS1 and SOS2. A dual-luciferase reporter assay showed significantly decreased luciferase activity upon ectopic overexpression of miR-148a in HEK-293T cells that were co-transfected with the 3′UTR of either SOS1 or SOS2. Each of the 3′UTRs of SOS1 and SOS2 contained two binding sites for miR-148a both of which were necessary for the decreased luciferase activity. MiR-148a overexpression in HEK-293T lead to significantly reduced levels of both endogenous SOS1 and SOS2 proteins. Likewise, reduced levels of SOS proteins were found in two B cell lines that were transfected with miR-148a. The level of ERK1/2 phosphorylation as one of the most relevant downstream members of the Ras/ERK signaling pathway was also reduced in cells with miR-148a overexpression. The data show that miR-148a impairs the Ras/ERK signaling pathway via SOS1 and SOS2 proteins in B cells.

In vitro and in vivo activity of melflufen (J1)in lymphoma

BACKGROUND

Melphalan has been used in the treatment of various hematologic malignancies for almost 60 years. Today it is part of standard therapy for multiple myeloma and also as part of myeloablative regimens in association with autologous allogenic stem cell transplantation. Melflufen (melphalan flufenamide ethyl ester, previously called J1) is an optimized derivative of melphalan providing targeted delivery of active metabolites to cells expressing aminopeptidases. The activity of melflufen has compared favorably with that of melphalan in a series of in vitro and in vivo experiments performed preferentially on different solid tumor models and multiple myeloma. Melflufen is currently being evaluated in a clinical phase I/II trial in relapsed or relapsed and refractory multiple myeloma.

METHODS

Cytotoxicity of melflufen was assayed in lymphoma cell lines and in primary tumor cells with the Fluorometric Microculture Cytotoxicity Assay and cell cycle analyses was performed in two of the cell lines. Melflufen was also investigated in a xenograft model with subcutaneous lymphoma cells inoculated in mice.

RESULTS

Melflufen showed activity with cytotoxic IC50-values in the submicromolar range (0.011-0.92 μM) in the cell lines, corresponding to a mean of 49-fold superiority (p < 0.001) in potency vs. melphalan. In the primary cultures melflufen yielded slightly lower IC50-values (2.7 nM to 0.55 μM) and an increased ratio vs. melphalan (range 13-455, average 108, p < 0.001). Treated cell lines exhibited a clear accumulation in the G2/M-phase of the cell cycle. Melflufen also showed significant activity and no, or minimal side effects in the xenografted animals.

CONCLUSION

This study confirms previous reports of a targeting related potency superiority of melflufen compared to that of melphalan. Melflufen was active in cell lines and primary cultures of lymphoma cells, as well as in a xenograft model in mice and appears to be a candidate for further evaluation in the treatment of this group of malignant diseases.

Surfaceome of classical Hodgkin and non-Hodgkin lymphoma

PURPOSE

Classical Hodgkin lymphoma (cHL) is characterized by a low percentage of tumor cells in a background of diverse, reactive immune cells. cHL cells commonly derive from preapoptotic germinal-center B cells and are characterized by the loss of B-cell markers and the varying expression of other hematopoietic lineage markers. This phenotypic variability and the scarcity of currently available cHL-specific cell surface markers can prevent clear distinction of cHL from related lymphomas.

EXPERIMENTAL DESIGN

We applied the cell surface capture technology to directly measure the pool of cell surface exposed proteins in four cHL and four non-Hodgkin lymphoma (NHL) cell lines.

RESULTS

More than 1000 membrane proteins, including 178 cluster of differentiation annotated proteins, were identified and allowed the generation of lymphoma surfaceome maps. The functional properties of identified cell surface proteins enable, but also limit the information exchange of lymphoma cells with their microenvironment.

CONCLUSION AND CLINICAL RELEVANCE

Selected candidate proteins with potential diagnostic value were evaluated on a tissue microarray (TMA). Primary lymphoma tissues of 126 different B cell-derived lymphoma cases were included in the TMA analysis. The TMA analysis indicated gamma-glutamyltranspeptidase 1 as a potential additional marker that can be included in a panel of markers for differential diagnosis of cHL versus NHL.

Discovery of a drug targeting microenvironmental support for lymphoma cells by screening using patient-derived xenograft cells

Cell lines have been used for drug discovery as useful models of cancers; however, they do not recapitulate cancers faithfully, especially in the points of rapid growth rate and microenvironment independency. Consequently, the majority of conventional anti-cancer drugs are less sensitive to slow growing cells and do not target microenvironmental support, although most primary cancer cells grow slower than cell lines and depend on microenvironmental support. Here, we developed a novel high throughput drug screening system using patient-derived xenograft (PDX) cells of lymphoma that maintained primary cancer cell phenotype more than cell lines. The library containing 2613 known pharmacologically active substance and off-patent drugs were screened by this system. We could find many compounds showing higher cytotoxicity than conventional anti-tumor drugs. Especially, pyruvinium pamoate showed the highest activity and its strong anti-tumor effect was confirmed also in vivo. We extensively investigated its mechanism of action and found that it inhibited glutathione supply from stromal cells to lymphoma cells, implying the importance of the stromal protection from oxidative stress for lymphoma cell survival and a new therapeutic strategy for lymphoma. Our system introduces a primary cancer cell phenotype into cell-based phenotype screening and sheds new light on anti-cancer drug development.

BCL6--regulated by AhR/ARNT and wild-type MEF2B--drives expression of germinal center markers MYBL1 and LMO2

Genetic heterogeneity is widespread in tumors, but poorly documented in cell lines. According to immunoglobulin hypermutation analysis, the diffuse large B-cell lymphoma cell line U-2932 comprises two subpopulations faithfully representing original tumor subclones. We set out to identify molecular causes underlying subclone-specific expression affecting 221 genes including surface markers and the germinal center oncogenes BCL6 and MYC. Genomic copy number variations explained 58/221 genes differentially expressed in the two U-2932 clones. Subclone-specific expression of the aryl-hydrocarbon receptor (AhR) and the resulting activity of the AhR/ARNT complex underlaid differential regulation of 11 genes including MEF2B. Knock-down and inhibitor experiments confirmed that AhR/ARNT regulates MEF2B, a key transcription factor for BCL6. AhR, MEF2B and BCL6 levels correlated not only in the U-2932 subclones but in the majority of 23 cell lines tested, indicting overexpression of AhR as a novel mechanism behind BCL6 diffuse large B-cell lymphoma. Enforced modulation of BCL6 affected 48/221 signature genes. Although BCL6 is known as a transcriptional repressor, 28 genes were up-regulated, including LMO2 and MYBL1 which, like BCL6, signify germinal center diffuse large B-cell lymphoma. Supporting the notion that BCL6 can induce gene expression, BCL6 and the majority of potential targets were co-regulated in a series of B-cell lines. In conclusion, genomic copy number aberrations, activation of AhR/ARNT, and overexpression of BCL6 are collectively responsible for differential expression of more than 100 genes in subclones of the U-2932 cell line. It is particularly interesting that BCL6 - regulated by AhR/ARNT and wild-type MEF2B - may drive expression of germinal center markers in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma with combined TP53 mutation and MIR34A methylation: Another "double hit" lymphoma with very poor outcome?

MiR34A, B and C have been implicated in lymphomagenesis, but information on their role in normal CD19+ B-cells (PBL-B) and de novo diffuse large B-cell lymphoma (DLBCL) is limited.

We show that in normal and activated B-cells miR34A-5p plays a dominant role compared to other miR34 family members. Only miR34A-5p is expressed in PBL-B, and significantly induced in activated B-cells and reactive lymph nodes. In PBL-B, the MIR34A and MIR34B/C promoters are unmethylated, but the latter shows enrichment for the H3K4me3/H3K27me3 silencing mark.

Nine de novo DLBCL cases (n=150) carry both TP53 mutation and MIR34A methylation (“double hit”) and these patients have an exceedingly poor prognosis with a median survival of 9.4 months (P<0.0001), while neither TP53 mutation, MIR34A or MIR34B/C promoter methylation alone (“single hit”) influence on survival. The TP53/MIR34A “double-hit” is an independent negative prognostic factor for survival (P=0.0002). In 2 DLBCL-cell lines with both TP53 mutation and promoter methylation of MIR34A, miR34A-5p is upregulated by 5-aza-2'deoxycytidine. Thus, the TP53/MIR34A “double hit” characterizes a very aggressive subgroup of DLBCL, which may be treatable with epigenetic therapy prior to or in combination with conventional immunochemotherapy.

Deregulation of ETS1 and FLI1 contributes to the pathogenesis of diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common form of human lymphoma. DLBCL is a heterogeneous disease characterized by different genetic lesions. We herein report the functional characterization of a recurrent gain mapping on chromosome 11q24.3, found in 23% of 166 DLBCL cases analyzed. The transcription factors ETS1 and FLI1, located within the 11q24.3 region, had significantly higher expression in clinical samples carrying the gain. Functional studies on cell lines showed that ETS1 and FLI1 cooperate in sustaining DLBCL proliferation and viability and regulate genes involved in germinal center differentiation. Taken together, these data identify the 11q24.3 gain as a recurrent lesion in DLBCL leading to ETS1 and FLI1 deregulated expression, which can contribute to the pathogenesis of this disease.

A model of sensitivity and resistance to histone deacetylase inhibitors in diffuse large B cell lymphoma: Role of cyclin-dependent kinase inhibitors

Diffuse large B cell lymphoma (DLBCL) is an aggressive form of non-Hodgkin lymphoma. While the initial treatment strategy is highly effective, relapse occurs in 40% of cases. Histone deacetylase inhibitors (HDACi) are a promising class of anti-cancer drugs but their single agent efficacy against relapsed DLBCL has been variable, ranging from few complete/partial responses to some stable disease. However, most patients showed no response to HDACi monotherapy for unknown reasons. Here we show that sensitivity and resistance to the hydroxamate HDACi, PXD101, can be modeled in DLBCL cell lines. Sensitivity is characterized by G₂/M arrest and apoptosis and resistance by reversible G₁ growth arrest. These responses to PXD101 are independent of several negative prognostic indicators such as DLBCL subtype, BCL2 and MYC co-expression, and p53 mutation, suggesting that HDACi might be used effectively against highly aggressive DLBCL tumors if they are combined with other therapeutics that overcome HDACi resistance. Our investigation of mechanisms underlying HDACi resistance showed that cyclin-dependent kinase inhibitors (CKIs), p21 and p27, are upregulated by PXD101 in a sustained fashion in resistant cell lines concomitant with decreased activity of the cyclin E/cdk2 complex and decreased Rb phosphorylation. PXD101 treatment results in increased association of CKI with the cyclin E/cdk2 complex in resistant cell lines but not in a sensitive line, indicating that the CKIs play a key role in G₁ arrest. The results suggest several treatment strategies that might increase the efficacy of HDACi against aggressive DLBCL.

U-2932: two clones in one cell line, a tool for the study of clonal evolution

Genetic heterogeneity is common in tumors, explicable by the development of subclones with distinct genetic and epigenetic alterations. We describe an in vitro model for cancer heterogeneity, comprising the diffuse large B-cell lymphoma cell line U-2932 which expresses two sets of cell surface markers representing twin populations flow-sorted by CD20 vs CD38 expression. U-2932 populations were traced to subclones of the original tumor with clone-specific immunoglobulin IgVH4-39 hypermutation patterns. BCL6 was overexpressed in one subpopulation (R1), MYC in the other (R2), both clones overexpressed BCL2. According to the combined results of immunoglobulin hypermutation and cytogenetic analysis, R1 and R2 derive from a mother clone with genomic BCL2 amplification, which acquired secondary rearrangements leading to the overexpression of BCL6 (R1) or MYC (R2). Some 200 genes were differentially expressed in R1/R2 microarrays including transcriptional targets of the aberrantly expressed oncogenes. Other genes were regulated by epigenetic means as shown by DNA methylation analysis. Ectopic expression of BCL6 in R2 variously modulated new candidate target genes, confirming dual silencing and activating functions. In summary, stable retention of genetically distinct subclones in U-2932 models tumor heterogeneity in vitro permitting functional analysis of oncogenes against a syngenic background.

Differential regulation of miR-21 and miR-146a by Epstein-Barr virus-encoded EBNA2

The discovery of microRNA (miR) represents a novel paradigm in RNA-based regulation of gene expression and their dysregulation has become a hallmark of many a tumor. In virally associated cancers, the host–pathogen interaction could involve alteration in miR expression. Epstein–Barr virus (EBV)-encoded EBNA2 is indispensable for the capacity of the virus to transform B cells in vitro. Here, we studied how it affects cellular miRs. Extensive miR profiling of the virus-infected and EBNA2-transfected B lymphoma cells revealed that oncomiR miR-21 is positively regulated by this viral protein. Conversely, Burkitt's lymphoma (BL) cell lines infected with EBNA2 lacking P3HR1 strain did not show any increase in miR-21. EBNA2 increased phosphorylation of AKT and this was directly correlated with increased miR-21. In contrast, miR-146a was downregulated by EBNA2 in B lymphoma cells. Low miR-146a expression correlates with an elevated level of IRAK1 and type I interferon in EBNA2 transfectants. Taken together, the present data suggest that EBNA2 might contribute to EBV-induced B-cell transformation by altering miR expression and in particular by increasing oncomiR-like miR-21 and by affecting the antiviral responses of the innate immune system through downregulation of its key regulator miR-146a.

The molecular pathogenesis of primary mediastinal large B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a recognized non-Hodgkin lymphoma entity with unique pathologic, clinical, and molecular characteristics distinct from those of other diffuse large B-cell lymphomas. Immunohistochemical characterization and molecular studies strongly suggest that PMBCL is of germinal center or postgerminal center origin. Pivotal gene expression profiling work defined major deregulated pathway activities that overlap with Hodgkin lymphoma and prompted a more detailed analysis of candidate genes. In particular, the nuclear factor-κB and the Janus Kinase-Signal Transducer and Activator of Transcription signaling pathways are targeted by multiple genomic hits, and constitutive activity of both pathways can be considered molecular hallmark alterations of PMBCL. Moreover, data are emerging giving unique insight into remodeling of the epigenome that affects transcriptional regulation of a multitude of genes. More recently, the tumor microenvironment of PMBCL has shifted into focus based on a number of gene perturbations altering expression of surface molecules that contribute to immune escape. These findings highlight the importance of immune privilege in the pathogenesis of PMBCL and suggest that disrupting crosstalk between the tumor cells and the microenvironment might be a rational new therapeutic target in conjunction with traditional treatment strategies.

Chromosome 11q23.1 is an unstable region in B-cell tumor cell lines

Chromosome 11q23 region is a frequent target of chromosome aberrations in B-cell lymphoid tumors. Here, we present the cytogenetic and molecular characterization of an amplification affecting 11q23.1 in four cell lines derived from B-cell lymphoid tumors. A minimal common region of amplification of 330 kb was identified in three cell lines using Affymetrix Human Mapping 250K arrays. When analyzed with three BAC clones, the amplifications appeared different at cytogenetic level in each cell line. Possibly affected transcripts were evaluated using tiling arrays, and validated by real time PCR. Since no effect of the amplification at the local transcription level was observed, it is possible that 11q23 amplification might mainly represent the effect of unstable chromosomal region.

MHC class II transactivator CIITA is a recurrent gene fusion partner in lymphoid cancers

Chromosomal translocations are critically involved in the molecular pathogenesis of B-cell lymphomas, and highly recurrent and specific rearrangements have defined distinct molecular subtypes linked to unique clinicopathological features. In contrast, several well-characterized lymphoma entities still lack disease-defining translocation events. To identify novel fusion transcripts resulting from translocations, we investigated two Hodgkin lymphoma cell lines by whole-transcriptome paired-end sequencing (RNA-seq). Here we show a highly expressed gene fusion involving the major histocompatibility complex (MHC) class II transactivator CIITA (MHC2TA) in KM-H2 cells. In a subsequent evaluation of 263 B-cell lymphomas, we also demonstrate that genomic CIITA breaks are highly recurrent in primary mediastinal B-cell lymphoma (38%) and classical Hodgkin lymphoma (cHL) (15%). Furthermore, we find that CIITA is a promiscuous partner of various in-frame gene fusions, and we report that CIITA gene alterations impact survival in primary mediastinal B-cell lymphoma (PMBCL). As functional consequences of CIITA gene fusions, we identify downregulation of surface HLA class II expression and overexpression of ligands of the receptor molecule programmed cell death 1 (CD274/PDL1 and CD273/PDL2). These receptor-ligand interactions have been shown to impact anti-tumour immune responses in several cancers, whereas decreased MHC class II expression has been linked to reduced tumour cell immunogenicity. Thus, our findings suggest that recurrent rearrangements of CIITA may represent a novel genetic mechanism underlying tumour-microenvironment interactions across a spectrum of lymphoid cancers.

Akt, 14-3-3ζ, and vimentin mediate a drug-resistant invasive phenotype in diffuse large B-cell lymphoma

Development of resistance to the CHOP chemotherapeutic regimen (cyclophosphamide, doxorubicin, vincristine, prednisone) remains a major cause of treatment failure and mortality in approximately 40% of patients with diffuse large B-cell lymphoma (DLBCL). We established CHOP-resistant DLBCL cells as a model system to investigate molecular mechanisms involved in multidrug resistance. Two-dimensional differential in-gel (DIGE) analysis identified 10 differentially expressed proteins between CHOP-sensitive and -resistant DLBCL cells that play roles in glycolysis (triosephosphate isomerase-1, enolase-1), cytoskeletal structure (ezrin, vimentin, tubulin-specific chaperone B), purine biosynthesis (serine hydroxymethyltransferase), calcium binding (sorcin), and apoptosis (p53, 14-3-3ζ, Akt). Akt, 14-3-3ζ, and vimentin were up-regulated in CHOP-resistant DLBCL cells. We showed previously that siRNA-mediated knockdown of 14-3-3ζ reversed CHOP resistance in DLBCL cells (Maxwell et al., J Biol Chem 2009;284:22379-22389). Here we show that chemical inhibition of Akt overcomes CHOP resistance in DLBCL cells. CHOP-resistant cells exhibited a five-fold greater ability to invade collagen matrices compared with CHOP-sensitive cells. Knockdown of vimentin by siRNA or withaferin A repressed the invasiveness of CHOP-resistant cells in collagen matrices. Increased expressions of Akt, 14-3-3ζ, and vimentin were observed by Western blotting in primary DLBCL tissues relative to normal lymphatic tissue. The data implicate activation of an Akt-14-3-3ζ signaling pathway in promoting a multidrug-resistant phenotype associated with a vimentin-dependent invasive behavior in DLBCL cells.

Epstein-Barr virus encoded LMP1 downregulates TCL1 oncogene through miR-29b

Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP1) is noted for its transforming potential. Yet, it also acts as a cytostatic and growth-relenting factor in Burkitt's lymphoma (BL) cells. The underlying molecular mechanisms of the growth inhibitory property of LMP1 have remained largely unknown. In this study, we show that LMP1 negatively regulates a major oncogene, TCL1, in diffuse large B-cell lymphoma (DLBCL) and BL cells. MicroRNA (miR) profiling of LMP1 transfectants showed that among others, miR-29b, is upregulated. LMP1 diminished TCL1 by inducing miR-29b through C-terminus activation region 1 (CTAR1) and CTAR2. miR-29b locked nucleic acid (LNA) antisense oligonucleotide transfection into LMP1-expressing cells reduced miR-29b expression and consequently reconstituted TCL1, suggesting that LMP1 negatively regulates TCL1 through miR-29b upregulation. The miR-29b increase by LMP1 was due to an increase in the cluster pri-miR-29b1-a transcription, derived from human chromosome 7. Using pharmacological inhibitors, we found that p38 mitogen-activated protein kinase-activating function of LMP1 is important for this effect. The ability of LMP1 to negatively regulate TCL1 through miR-29b might underlie its B-cell lymphoma growth antagonistic property. As LMP1 is also important for B-cell transformation, we suggest that the functional dichotomy of this viral protein may depend on a combination of levels of its expression, lineage and differentiation of the target cells and regulation of miRs, which then directs the outcome of the cellular response.

EBNA2 interferes with the germinal center phenotype by downregulating BCL6 and TCL1 in non-Hodgkin's lymphoma cells

Epstein-Barr virus (EBV)-negative diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma-derived cell lines infected in vitro with a recombinant EBV expressed type II/III latency. High expression of EBNA2 inversely correlated with expression of germinal center (GC)-associated genes, BCL6 and TCL1. The decreased expression of BCL6 appeared to be dose dependent, with almost complete abrogation in highly EBNA2-expressing clones. The role of EBNA2 in negative regulation of these genes was confirmed by transfection and in a hormone-inducible EBNA2 cell system. LMP1 transfection reduced expression of TCL1, but not of BCL6, in DLBCLs. The GC-associated gene repression was at the transcriptional level and CBF1 independent. A decrease in HLA-DR, surface immunoglobulin M, and class II transactivator expression and an increase in CCL3, a BCL6 repression target, was observed in EBNA2-expressing clones. Since BCL6 is indispensable for GC formation and somatic hypermutations (SHM), we suggest that the previously reported lack of SHM seen in EBNA2-expressing GC cells from infectious mononucleosis tonsils could be due to negative regulation of BCL6 by EBNA2. These findings suggest that EBNA2 interferes with the GC phenotype.

Spectral karyotyping of human, mouse, rat and ape chromosomes--applications for genetic diagnostics and research

Spectral karyotyping (SKY) is a widely used methodology to identify genetic aberrations. Multicolor fluorescence in situ hybridization using chromosome painting probes in individual colors for all metaphase chromosomes at once is combined with a unique spectral measurement and analysis system to automatically classify normal and aberrant chromosomes. Based on countless studies and investigations in many laboratories worldwide, numerous new chromosome translocations and other aberrations have been identified in clinical and tumor cytogenetics. Thus, gene identification studies have been facilitated resulting in the dissection of tumor development and progression. For example, different translocation partners of the TEL/ETV6 transcription factor that is specially required for hematopoiesis within the bone marrow were identified. Also, the correct classification of complex karyotypes of solid tumors supports the prognostication of cancer patients. Important accomplishments for patients with genetic diseases, leukemias and lymphomas, mesenchymal tumors and solid cancers are summarized and exemplified. Furthermore, studies of disease mechanisms such as centromeric DNA breakage, DNA double strand break repair, telomere shortening and radiation-induced neoplastic transformation have been accompanied by SKY analyses. Besides the hybridization of human chromosomes, mouse karyotyping has also contributed to the comprehensive characterization of mouse models of human disease and for gene therapy studies.

U-2940, a human B-cell line derived from a diffuse large cell lymphoma sequential to Hodgkin lymphoma

Several patterns of association between Hodgkin and non-Hodgkin lymphomas are recognized, some of which support a common cellular origin or shared transformation events for both malignancies. We describe the U-2940 cell line derived from a diffuse large B-cell lymphoma with some features consistent with mediastinal large B-cell lymphoma, clinically apparent 1 month after the initial course of chemotherapy for Hodgkin's disease, fulfilling the criteria for composite malignancies. U-2940 cells display a mature B phenotype with hypermutated IgH rearrangement typical of germinal/postgerminal center origin. The cell line is negative for Epstein-Barr virus and no evidence of t(14;18) was found. U-2940 cells display multiple chromosomal rearrangements similar to recurrent aberrations described in both Hodgkin and non-Hodgkin lymphomas, also partially shared by U-2932 derived from a B-cell lymphoma sequential to Hodgkin's disease. The original large B-cell lymphoma and the U-2940 cell line bear microsatellite instability, an abnormality associated with particular subtypes of non-Hodgkin lymphomas and found in tissues involved by Hodgkin lymphoma. Therefore, U-2940 cells bear several features known to occur in Hodgkin and in non-Hodgkin lymphomas, leading to the assumption that this cell line may constitute a useful tool to address elective pathways of lymphomagenesis and eventually the Hodgkin and non-Hodgkin lymphoma association.