Z-138: a new mature B-cell acute lymphoblastic leukemia cell line from a patient with transformed chronic lymphocytic leukemia

CD3 Target Affinity Chromatography Mass Spectrometry as a New Tool for Function-Structure Characterization of T-Cell Engaging Bispecific Antibody Proteoforms and Product-Related Variants

T-cell engaging bispecific antibodies (TCBs) targeting CD3 and tumor-specific antigens are very promising therapeutic modalities. Since CD3 binding is crucial for the potency of TCBs, understanding the functional impact of CD3 antigen-binding fragment modifications is of utmost importance for defining critical quality attributes (CQA). The current CQA assessment strategy requires the integration of structure-based physicochemical separation and functional cell-based potency assays. However, this strategy is tedious, and coexisting proteoforms with potentially different functionalities may not be individually assessed. This increases the degree of ambiguities for defining meaningful CQAs, particularly for complex bispecific antibody formats such as TCBs. Here, we report for the first time a proof-of-concept study to separate and identify critically modified proteoforms of TCBs using functional CD3 target affinity chromatography (AC) coupled with online mass spectrometry (MS). Our method enabled functional distinction of relevant deamidated and glycosylated proteoforms and the simultaneous assessment of product-related variants such as TCB mispairings. For example, CD3 AC-MS allowed us to separate TCB mispairings with increased CD3 binding (i.e., knob-knob homodimers) within the bound fraction. The functional separation of proteoforms was validated using an established workflow for CQA identification based on thoroughly characterized ion-exchange fractions of a 2+1 TCB. In addition, the new method facilitated the criticality assessment of post-translational modifications in stress studies and structural variants in early stage clone selection. CD3 AC-MS has high impact for streamlining the integration of functional and structural characterizations of the large landscape of therapeutic CD3 targeting TCBs from early stage research to late stage characterization.

Gene-body hypermethylation controlled cryptic promoter and miR26A1-dependent EZH2 regulation of TET1 gene activity in chronic lymphocytic leukemia

The Ten-eleven-translocation 1 (TET1) protein is a member of dioxygenase protein family that catalyzes the oxidation of 5-methylcytosine to 5-hydroxymethylcytosine. TET1 is differentially expressed in many cancers, including leukemia. However, very little is known about mechanism behind TET1 deregulation. Previously, by characterizing global methylation patterns in CLL patients using MBD-seq, we found TET1 as one of the differentially methylated regions with gene-body hypermethylation. Herein, we characterize mechanisms that control TET1 gene activity at the transcriptional level. We show that treatment of CLL cell lines with 5-aza 2´-deoxycytidine (DAC) results in the activation of miR26A1, which causes decrease in both mRNA and protein levels of EZH2, which in turn results in the decreased occupancy of EZH2 over the TET1 promoter and consequently the loss of TET1 expression. In addition, DAC treatment also leads to the activation of antisense transcription overlapping the TET1 gene from a cryptic promoter, located in the hypermethylated intronic region. Increased expression of intronic transcripts correlates with decreased TET1 promoter activity through the loss of RNA Pol II occupancy. Thus, our data demonstrate that TET1 gene activation in CLL depends on miR26A1 regulated EZH2 binding at the TET1 promoter and silencing of novel cryptic promoter by gene-body hypermethylation.

Targeting mantle cell lymphoma metabolism and survival through simultaneous blockade of mTOR and nuclear transporter exportin-1

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma with poor prognosis, characterized by aberrant expression of growth-regulating and oncogenic effectors and requiring novel anticancer strategies. The nuclear transporter exportin-1 (XPO1) is highly expressed in MCL and is associated with its pathogenesis. mTOR signaling, a central regulator of cell metabolism, is frequently activated in MCL and is also an important therapeutic target in this cancer. This study investigated the antitumor effects and molecular/metabolic changes induced by the combination of the small-molecule selective inhibitor XPO1 inhibitor KPT-185 and the dual mTORC1/2 kinase inhibitor AZD-2014 on MCL cells. AZD-2014 enhanced the KPT-185-induced inhibition of cell growth and repression of cell viability. The combination of KPT-185 and AZD-2014 downregulated c-Myc and heat shock factor 1 (HSF1) with its target heat shock protein 70 (HSP70). As a consequence, the combination caused repression of ribosomal biogenesis demonstrated by iTRAQ proteomic analyses. Metabolite assay by CETOF-MS showed that AZD-2014 enhanced the KPT-185-induced repression of MCL cellular energy metabolism through the TCA (Krebs) cycle, and further repressed KPT-185-caused upregulation of glycolysis.Thus the simultaneous inhibition of XPO1 and mTOR signaling is a novel and promising strategy targeting prosurvival metabolism in MCL.

Epigenetic silencing of miR-26A1 in chronic lymphocytic leukemia and mantle cell lymphoma: Impact on EZH2 expression

Downregulation of miR26A1 has been reported in various B-cell malignancies; however, the mechanism behind its deregulation remains largely unknown. We investigated miR26A1 methylation and expression levels in a well-characterized series of chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). From 450K methylation arrays, we first observed miR26A1 (cg26054057) as uniformly hypermethylated in MCL (n = 24) (all >75%), while CLL (n = 18) showed differential methylation between prognostic subgroups. Extended analysis using pyrosequencing confirmed our findings and real-time quantitative PCR verified low miR26A1 expression in both CLL (n = 70) and MCL (n = 38) compared to normal B-cells. Notably, the level of miR26A1 methylation predicted outcome in CLL, with higher levels seen in poor-prognostic, IGHV-unmutated CLL. Since EZH2 was recently reported as a target for miR26A1, we analyzed the expression levels of both miR26A1 and EZH2 in primary CLL samples and observed an inverse correlation. By overexpression of miR26A1 in CLL and MCL cell lines, reduced EZH2 protein levels were observed using both Western blot and flow cytometry. In contrast, methyl-inhibitor treatment led to upregulated miR26A1 expression with a parallel decrease of EZH2 expression. Finally, increased levels of apoptosis were observed in miR26A1-overexpressing cell lines, further underscoring the functional relevance of miR26A1. In summary, we propose that epigenetic silencing of miR26A1 is required for the maintenance of increased levels of EZH2, which in turn translate into a worse outcome, as shown in CLL, highlighting miR26A1 as a tumor suppressor miRNA.

B-Lymphoblastic Leukemia in Patients With Chronic Lymphocytic Leukemia: A Report of Four Cases

OBJECTIVES

B-lymphoblastic leukemia (B-LBL) arising in patients with chronic lymphocytic leukemia (CLL) is exceedingly rare and poorly characterized.

METHODS

We describe four patients with CLL and concurrent or subsequent B-LBL diagnosed by morphologic, immunophenotypic, cytogenetic, and molecular analysis and reviewed the literature.

RESULTS

In three patients, B-LBL followed CLL by 5 to 15 years, and in one patient, B-LBL was diagnosed simultaneously with CLL. In all cases, the CLL had a typical immunophenotype, and the B-LBL blasts showed an immature B-cell immunophenotype with expression of CD10, CD19, and TdT and absence of surface immunoglobulin. In two patients, B-LBL blasts harbored t(9;22)(q34;q11.2)/BCR-ABL1. We sequenced the IGHV genes in both CLL and B-LBL in two patients and showed that IGHV usage differed.

CONCLUSIONS

Our data suggest that at least some cases of B-LBL arising in patients with CLL are independent, secondary neoplasms rather than a manifestation of histologic transformation.

Development and characterization of a Mantle Cell Lymphoma Cell Bank in the American Type Culture Collection

Mantle cell lymphoma (MCL) is a rare B-cell malignancy that carries a relatively poor prognosis compared to other forms of non-Hodgkin lymphoma. Standardized preclinical tools are desperately required to hasten the discovery and translation of promising new treatments for MCL. Via an initiative organized through the Mantle Cell Lymphoma Consortium and the Lymphoma Research Foundation, we gathered MCL cell lines from laboratories around the world to create a characterized MCL Cell Bank at the American Type Culture Collection (ATCC). Initiated in 2006, this collection now contains eight cell lines, all of which have been rigorously characterized and are now stored and available for distribution to the general scientific community. We believe the awareness and use of these standardized cell lines will decrease variability between investigators, harmonize international research efforts, improve our understanding of the pathogenesis of the disease and hasten the development of novel treatment strategies.

Activation of complement by monoclonal antibodies that target cell-associated β₂-microglobulin: implications for cancer immunotherapy

β₂-Microglobulin (β2M), the light chain of the class I major histocompatibilty complex (MHC-I), is a promising tumor target for monoclonal antibodies (mAbs) in cancer immunotherapy. Several reports indicate that chelation of cell-associated β2M by specific mouse mAbs promotes tumor cell destruction by inducing apoptosis or other cytotoxic signaling pathways. Human mAbs employed in cancer therapy are usually IgG1, which mediates cell-killing by effector mechanisms including complement dependent cytotoxicity (CDC). The analogous mouse IgG2a and IgG2b isotypes are similarly effective in activating complement. Therefore, we examined the complement-activating properties of anti-β2M mouse mAbs 1B749 (IgG2a) and HB28 (IgG2b) when either mAb was bound to tumor cell lines or normal cells; we compared these β2M-specific mAbs with mouse mAb W6/32 (IgG2a), specific for human leukocyte antigens in the MHC-I heavy chain. All three mAbs bind to most human cell lines and normal cells in approximately equal amounts, consistent with a 1:1 stoichiometry for the HLA heavy chain in association with β2M. The three mAbs promote rapid C3b deposition and substantial CDC of human cell lines, and mAbs 1B749 and W6/32 have robust cytotoxic activity on reaction with normal mononuclear cells and platelets. Curiously, mAb HB28 induces modest C3b deposition and little CDC of normal cells, and its weaker complement-fixing activity was confirmed by ELISA. Based on these findings, we suggest that human IgG mAbs that target β2M for cancer immunotherapy be selected or engineered so as not to activate complement, thus eliminating the potential adverse effects of complement-mediated lysis of normal cells.

Molecular characterization of chromosomal band 5p15.33: a recurrent breakpoint region in mantle cell lymphoma involving the TERT-CLPTM1L locus

Secondary chromosomal aberrations may contribute to the development of a malignant phenotype in mantle cell lymphoma. Chromosomal band 5p15.33 represents a new recurrent breakpoint in B-cell malignancies. We present a molecular cytogenetic study of 8 mantle cell lymphoma (MCL) cell lines and 23 patients with MCL to determine and characterize novel secondary aberrations. We detected new secondary recurrent rearrangements in all cell lines and in 7 patients and confirmed 5p15.33 as a recurrent breakpoint in 4 cell lines and one patient. Further molecular characterization by flow-FISH and quantitative RT-PCR suggest TERT and CLPTM1L as target genes of 5p15.33 rearrangements.

Murine models in mantle cell lymphoma

Mantle cell lymphoma (MCL), an aggressive, heterogeneous B-cell lymphoma associated with a relatively short survival has been challenging to study in the laboratory due to the lack of in vitro and in vivo models that accurately recapitulate the disease. Advancement has been made in the characterization of MCL cell lines through the generation of the ATCC MCL bank, enabling their use in xenograft murine models. These models provide valuable but limited information for the preclinical evaluation and development of targeted therapies for MCL despite their deficiencies of a functioning immune system and correct micro-environment. Currently, there is only one double transgenic murine model known to develop spontaneous MCL. There is an urgency to develop innovative transgenic murine models that could be used to better predict therapeutic responses and precisely decipher mechanisms of action, to foster refinement of novel therapeutics for mantle cell lymphoma.

FTY720 increases CD74 expression and sensitizes mantle cell lymphoma cells to milatuzumab-mediated cell death

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy with a short median survival despite multimodal therapy. FTY720, an immunosuppressive drug approved for the treatment of multiple sclerosis, promotes MCL cell death concurrent with down-modulation of phospho-Akt and cyclin D1 and subsequent cell-cycle arrest. However, the mechanism of FTY720-mediated MCL cell death remains to be fully clarified. In the present study, we show features of autophagy blockage by FTY720 treatment, including accumulation of autolysosomes and increased LC3-II and p62 levels. We also show that FTY720-induced cell death is mediated by lysosomal membrane permeabilization with subsequent translocation of lysosomal hydrolases to the cytosol. FTY720-mediated disruption of the autophagic-lysosomal pathway led to increased levels of CD74, a potential therapeutic target in MCL that is degraded in the lysosomal compartment. This finding provided rationale for examining combination therapy with FTY720 and milatuzumab, an anti-CD74 mAb. Treatment of MCL cell lines and primary tumor cells with FTY720 and milatuzumab resulted in statistically significant enhanced cell death, which was synergistic in blastic variant MCL cell lines. Significant in vivo therapeutic activity of combination treatment was also demonstrated in a preclinical, in vivo model of MCL. These findings support clinical evaluation of this combination in patients with MCL.

Multivalent rituximab lipid nanoparticles as improved lymphoma therapies: indirect mechanisms of action and in vivo activity

AIMS

The activity of therapeutic antibodies can be enhanced by creating multivalent constructs, such as antibody lipid nanoparticles (LNPs). Here, we examine differences between rituximab (Ritux) and Ritux-LNPs in terms of their indirect mechanisms of action: complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC).

MATERIALS & METHODS

We employed two mantle-cell lymphoma cell lines, Z138 and JVM2, which exhibit different in vivo sensitivities to Ritux along with variable expression levels of cell-surface proteins that regulate ADCC and CDC.

RESULTS

In both cell lines, CDC and ADCC were found to be significantly enhanced after treatment with Ritux-LNPs compared with Ritux. In vivo efficacy studies, however, suggested that the therapeutic activities of Ritux and Ritux-LNPs were equivalent, which was subsequently explained in part by pharmacokinetic studies indicating rapid elimination of Ritux-LNP.

CONCLUSION

Although indirect and direct mechanisms of multivalent Ritux are enhanced, its further development requires methods to improve its circulation lifetime.

MDM2 antagonist Nutlin-3 enhances bortezomib-mediated mitochondrial apoptosis in TP53-mutated mantle cell lymphoma

This study demonstrated a pronounced synergistic growth-inhibitory effect of an MDM2 inhibitor Nutlin-3 and a proteasome inhibitor bortezomib in mantle cell lymphoma (MCL) cells regardless of TP53 mutant status and innate bortezomib sensitivity. In the mutant TP53 MCL cells which are intrinsically resistant to bortezomib, the combination of Nutlin-3/bortezomib synergistically induced cytotoxicity through the mitochondrial apoptotic pathway mediated by transcription-independent upregulation of NOXA, sequestration of MCL-1, activation of BAX, BAK, caspase-9 and -3. In the bortezomib sensitive wild-type TP53 MCL cells, the Nutlin-3/bortezomib combination caused G0/G1 cell cycle arrest followed by the increase in apoptosis induction. These findings indicate potential therapeutic efficacy of Nutlin-3/bortezomib combination for the treatment of chemorefractory MCL.

Susceptibility of mantle cell lymphomas to reovirus oncolysis

Mantle cell lymphoma (MCL) an incurable B-cell, non-Hodgkin lymphoma (NHL) urgently requires new treatments. We assessed reovirus mediated oncolysis in a panel of human MCL cell lines. In vitro, we found the cytopathic effect of reovirus infection ranged from high to very limited and correlated with levels of Ras activation. In vivo, a single reovirus injection intra-tumorally resulted in complete regression of both the injected and the contra-lateral tumor in a subcutaneous bi-tumor model, in one out of three cell lines tested. Reovirus treatment of MCL seems feasible but will need to be guided by the presence of molecular determinants of reovirus susceptibility.

MDM2 antagonist nutlin-3 displays antiproliferative and proapoptotic activity in mantle cell lymphoma

PURPOSE

Mantle cell lymphoma (MCL) has one of the poorest prognoses of the non-Hodgkin's lymphomas, and novel therapeutic approaches are needed. We wished to determine whether Nutlin-3, a novel small-molecule murine double minute 2 (MDM2) antagonist that efficiently activates TP53, might be effective in inducing cell death in MCL.

EXPERIMENTAL DESIGN

MCL cell lines with known TP53 status were treated with Nutlin-3, and biological and biochemical consequences were studied. Synergies with the prototypic genotoxic agent doxorubicin and the novel proteasome inhibitor bortezomib were assessed.

RESULTS

Nutlin-3 resulted in a reduction in cell proliferation/viability (IC50 < 10 micromol/L), an increase in the apoptotic fraction, and cell cycle arrest in wild-type (wt) TP53 Z-138 and Granta 519 cells. These effects were accompanied by TP53 accumulation and induction of TP53-dependent proteins p21, MDM2, Puma, and Noxa. Cell cycle arrest was characterized by suppression of S phase and an increase in the G0-G1 and G2-M fractions and accompanied by suppression of total and phosphorylated retinoblastoma protein and a decrease in G2-M-associated proteins cyclin B and CDC2. The combination of Nutlin-3 with doxorubicin or bortezomib was synergistic in wt-TP53 MCL cells. Nutlin-3 also induced cell cycle arrest and reduced cell viability in the mutant TP53 MINO cells but at a significantly higher IC50 (22.5 micromol/L). These effects were associated with induction of the TP53 homologue p73, slight increases in p21 and Noxa, and caspase activation. Nutlin-3 and bortezomib synergistically inhibited cell growth of MINO.

CONCLUSION

These findings suggest that the MDM2 antagonist Nutlin-3 may be an effective agent in the treatment of MCL with or without wt-TP53.

Binding of submaximal C1q promotes complement-dependent cytotoxicity (CDC) of B cells opsonized with anti-CD20 mAbs ofatumumab (OFA) or rituximab (RTX): considerably higher levels of CDC are induced by OFA than by RTX

The CD20 mAb ofatumumab (OFA) is more effective than rituximab (RTX) in promoting complement-dependent cytotoxicity (CDC) of B cells via the classical pathway (CP) of complement. CP activation is initiated by C1q binding to cell-bound IgG. Therefore, we examined the role of C1q in the dynamics of complement activation and CDC of B cell lines and primary cells from patients with chronic lymphocytic leukemia, reacted with OFA or RTX. C1q binding, complement activation, and colocalization of C1q with cell-bound mAbs were determined by flow cytometry and high-resolution digital imaging. C1q binds avidly to OFA-opsonized Raji and Daudi cells (K(D) = 12-16 nM) and colocalizes substantially with cell-bound OFA. Cells opsonized with OFA undergo high levels of complement activation and CDC in C1q-depleted serum supplemented with low concentrations of C1q. Under comparable conditions, RTX-opsonized cells bind less C1q; in addition, even when higher concentrations of C1q are used to achieve comparable C1q binding to RTX-opsonized cells, less complement activation and CDC are observed. Greater CDC induced by OFA may occur because C1q is bound in close proximity and with high avidity to OFA, resulting in effective CP activation. Moreover, OFA binds to the small, extracellular CD20 loop, placing the mAb considerably closer to the cell membrane than does RTX. This may facilitate effective capture and concentration of activated complement components closer to the cell membrane, potentially shielding them from inactivation by fluid phase agents and promoting efficient generation of the membrane attack complex.

Inactivation of p53 and amplification of MYCN gene in a terminal lymphoblastic relapse in a chronic lymphocytic leukemia patient

B-cell chronic lymphocytic leukemia (CLL) is an incurable disease with a highly variable clinical course. A proportion of patients eventually progress to a higher stage of malignancy. A recent association has been observed between the presence of aberrant somatic hypermutations in leukemic cells (hypermutations occurring outside of the immunoglobulin locus) and the transformation to a diffuse large B-cell lymphoma or prolymphocytic leukemia. In this study, we report on the rarely observed blastic transformation in a CLL patient who had previously been shown to harbor aberrant somatic hypermutations in the TP53 tumor-suppressor gene (Mol Immunol 2008;45:1525-29). The enzyme responsible, the activation-induced cytidine deaminase, was still active within the transformation, as evidenced by the ongoing class-switch recombination of cytoplasmic immunoglobulins. The transformation was accompanied by a complete p53 inactivation, as well as complex karyotype changes including prominent amplification of MYCN oncogene. Our case-study supports the view that the aberrant somatic hypermutation is associated with transformation of CLL to a more aggressive malignancy.

Rituximab-CD20 Complexes Are Shaved from Z138 Mantle Cell Lymphoma Cells in Intravenous and Subcutaneous SCID Mouse Models

Infusion of standard-dose rituximab (RTX) in chronic lymphocytic leukemia (CLL) patients promotes rapid complement activation and deposition of C3 fragments on CLL B cells. However, immediately after RTX infusions, there is substantial loss (shaving) of CD20 from circulating malignant cells. Because shaving can compromise efficacies of anticancer immunotherapeutic mAbs, we investigated whether shaving occurs in SCID mouse models. Z138 cells, a B cell line derived from human mantle cell lymphoma, were infused i.v. or s.c. The i.v. model recapitulates findings we previously reported for therapeutic RTX in CLL: i.v. infused RTX rapidly binds to Z138 cells in lungs, and binding is accompanied by deposition of C3 fragments. However, within 1 h targeted cells lose bound RTX and CD20, and these shaved cells are still demonstrable 40 h after RTX infusion. Z138 cells grow in tumors at s.c. injection sites, and infusion of large amounts of RTX (0.50 mg on each of 4 days) leads to considerable loss of CD20 from these cells. Human i.v. Ig blocked shaving, suggesting that FcgammaRI on cells of the mononuclear phagocytic system promote shaving. Examination of frozen tumor sections from treated mice by immunofluorescence revealed large areas of B cells devoid of CD20, with CD20 intact in adjacent areas; it is likely that RTX had opsonized Z138 cells closest to capillaries, and these cells were shaved by monocyte/macrophages. The shaving reaction occurs in neoplastic B cells in tissue and in peripheral blood, and strategies to enhance therapeutic targeting and block shaving are under development.

Apoptosis induced by histone deacetylase inhibitors in leukemic cells is mediated by Bim and Noxa

Several histone deacetylase inhibitors (HDACi), which have recently entered early clinical trials, exert their anticancer activity in part through the induction of apoptosis although the precise mechanism of this induction is not known. Induction of apoptosis by structurally diverse HDACi in primary cells from patients with chronic lymphocytic leukemia (CLL) and different leukemic cell lines was mediated by the Bcl-2 regulated intrinsic pathway and demonstrated a requirement for de novo protein synthesis. A marked time-dependent induction of the pro-apoptotic BH3-only proteins, Bim, Noxa and Bmf was observed, which preceded the induction of apoptosis. A key role for both Bim and Noxa was proposed in HDACi-mediated apoptosis based on our findings that siRNA for Bim and Noxa but not Bmf largely prevented the HDACi-induced loss in mitochondrial membrane potential, caspase processing and phosphatidylserine externalization. Noxa, induced by HDACi, in CLL cells and tumor cell lines, bound extensively to Mcl-1, a major anti-apoptotic Bcl-2 family member present in CLL cells. Our data strongly suggests that HDACi induce apoptosis primarily through inactivation of anti-apoptotic Bcl-2 family members by increases in Bim and Noxa and highlights these increases as a potential clinical target for CLL/lymphoma therapy.

DNA methylation profiling of transcription factor genes in normal lymphocyte development and lymphomas

Transcription factors play a crucial role during hematopoiesis by orchestrating lineage commitment and determining cellular fate. Although tight regulation of transcription factor expression appears to be essential, little is known about the epigenetic mechanisms involved in transcription factor gene regulation. We have analyzed DNA methylation profiles of 13 key transcription factor genes in primary cells of the hematopoietic cascade, lymphoma cell lines and lymph node biopsies of diffuse large B-cell- and T-cell-non-Hodgkin lymphoma patients. Several of the transcription factor genes (SPI1, GATA3, TCF-7, Etv5, c-maf and TBX21) are differentially methylated in specific cell lineages and stages of the hematopoietic cascade. For some genes, such as SPI1, Etv5 and Eomes, we found an inverse correlation between the methylation of the 5' untranslated region and expression of the associated gene suggesting that these genes are regulated by DNA methylation. Differential methylation is not limited to cells of the healthy hematopoietic cascade, as we observed aberrant methylation of c-maf, TCF7, Eomes and SPI1 in diffuse large B-cell lymphomas. Our results suggest that epigenetic remodelling of transcription factor genes is a frequent mechanism during hematopoietic development. Aberrant methylation of transcription factor genes is frequently observed in diffuse large B-cell lymphomas and might have a functional role during tumorigenesis.

Z-138 cell line was derived from a patient with blastoid variant mantle cell lymphoma

The Z-138 cell line, reported in the journal in 1998, was derived from a patient who developed a leukemia initially classified as chronic lymphocytic leukemia in 1987. Splenectomy for massive involvement was required in 1998 and the neoplasm subsequently transformed to an aggressive, mature B-cell leukemia 2 years later. At time of transformation, the neoplasm had a complex karyotype, including the t(11;14)(q13;q32). In light of the extensive updates in lymphoma classification that have occurred since that time, we reviewed the slides of the patient's neoplasm. The initial peripheral blood and bone marrow aspirate smears and the spleen were involved by numerous small lymphocytes with mature chromatin. The last bone marrow specimen was involved by slightly larger, irregular lymphocytes with immature chromatin and a high mitotic rate. Immunohistochemical analysis performed on the spleen and last bone marrow for this report showed that the neoplastic cells over-expressed cyclin D1. According to the criteria of the current World Health Organization lymphoma classification, this neoplasm is best classified as mantle cell lymphoma, with blastoid transformation present in the terminal phase of disease.

The Shaving Reaction: Rituximab/CD20 Complexes Are Removed from Mantle Cell Lymphoma and Chronic Lymphocytic Leukemia Cells by THP-1 Monocytes

Clinical investigations have revealed that infusion of immunotherapeutic mAbs directed to normal or tumor cells can lead to loss of targeted epitopes, a phenomenon called antigenic modulation. Recently, we reported that rituximab treatment of chronic lymphocytic leukemia patients induced substantial loss of CD20 on B cells found in the circulation after rituximab infusion, when rituximab plasma concentrations were high. Such antigenic modulation can severely compromise therapeutic efficacy, and we postulated that B cells had been stripped (shaved) of the rituximab/CD20 complex by monocytes or macrophages in a reaction mediated by FcgammaR. We developed an in vitro model to replicate this in vivo shaving process, based on reacting rituximab-opsonized CD20(+) cells with acceptor THP-1 monocytes. After 45 min at 37 degrees C, rituximab and CD20 are removed from opsonized cells, and both are demonstrable on acceptor THP-1 cells. The reaction occurs equally well in the presence and absence of normal human serum, and monocytes isolated from peripheral blood also promote shaving of CD20 from rituximab-opsonized cells. Tests with inhibitors and use of F(ab')(2) of rituximab indicate transfer of rituximab/CD20 complexes to THP-1 cells is mediated by FcgammaR. Antigenic modulation described in previous reports may have been mediated by such shaving, and our findings may have profound implications for the use of mAbs in the immunotherapy of cancer.

Four human t(11;14)(q13;q32)-containing cell lines having classic and variant features of Mantle Cell Lymphoma

The objectives of this study were foremost to further characterize pre-existing cell lines containing the t(11;14)(q13;q32) translocation. This translocation along with cyclin D1 overexpression is characteristic of Mantle Cell Lymphoma (MCL), an aggressive B cell neoplasm. Considerable variation in the abundance of cyclin D1 expression was observed. mRNA levels were examined by RT-PCR as differences in cyclin D1 mRNA abundance have been shown to synergize with INK4A/Arf deletions to dictate proliferation rate and survival in MCL patient samples. In this study, the cell lines, Z-138 and HBL-2, which exhibited the fastest growth rates and the shortest survival times in Rag2-M mice, had high expression of either one or both cyclin D1 mRNA isoforms and had negligible expression of p16. On the other hand, NCEB-1 and JVM-2 had low expression of both mRNA isoforms, retained p16 expression, and had slower growth rates and exhibited longer survival times in Rag2-M mice. Furthermore, JVM-2, which was found to have the lowest expression of cyclin D1, was the only cell line that expressed cyclin D2. The results of the characterization of Z-138, HBL-2, NCEB-1 and JVM-2 reveal that this group of cell lines represents both classic and variant features of MCL.

The utility of interphase fluorescence in situ hybridization for the detection of the translocation t(11;14)(q13;q32) in the diagnosis of mantle cell lymphoma on fine-needle aspiration specimens

BACKGROUND

Mantle cell lymphoma can be difficult to differentiate cytologically from other small cell non-Hodgkin lymphomas. Nevertheless, the distinction is important, because mantle cell lymphoma is more aggressive than other small cell non-Hodgkin lymphomas. The purpose of this study was to determine whether fluorescence in situ hybridization (FISH) is helpful in diagnosing mantle cell lymphoma on fine-needle aspiration (FNA) specimens by detecting the t(11;14)(q13;q32) translocation that is characteristic of this tumor.

METHODS

Fifty-five lymph node FNA specimens from 53 patients were analyzed using FISH. A 2-color FISH assay that employed probes at the 14q32 (immunoglobulin H) and 11q13 (dual-colored, directly labeled cyclin D1) loci was used. The number of single-fusion and double-fusion signals in 200 cells was counted. If > or = 14% single-fusion signals or > or = 1.5% double-fusion signals or both were present, then the sample was considered FISH positive. The findings were correlated with the cytologic, histologic, and immunophenotypic findings in each specimen.

RESULTS

Of the 55 cytology specimens, 17 were mantle cell lymphomas, and 38 were nonmantle cell lymphomas, including 16 small lymphocytic lymphomas (9 of 16 in an accelerated phase), 5 large cell lymphomas, 5 follicular lymphomas, 7 transformed large cell lymphomas (Richter syndrome), 3 atypical lymphoid proliferations, and 2 low-grade B-cell lymphomas. All 17 mantle cell lymphomas were positive by FISH. In addition, there were six small lymphocytic lymphomas (two in accelerated phase), one transformed large cell lymphoma, and one large cell lymphoma of follicular origin positive by FISH. The mean number of single-fusion and double-fusion signals, respectively, was 36 and 33 in mantle cell lymphoma specimens and 19 and 3 in positive nonmantle cell lymphoma specimens.

CONCLUSIONS

The detection of the t(11;14)(q13;q32) translocation by FISH analysis was helpful in diagnosing mantle cell lymphoma on FNA specimens. Double-fusion signals were more specific for mantle cell lymphoma than single-fusion signals. In rare instances, other non-Hodgkin lymphomas also showed increased numbers of single-fusion signals that were not necessarily indicative of the t(11;14)(q13;q32) translocation. Therefore, in an initial diagnosis of mantle cell lymphoma, significant numbers of double-fusion FISH signals should be identified and interpreted in conjunction with the cytologic and immunologic studies.

Complex biallelicIGH rearrangements in IgM-expressing Z-138 cell line: Involvement of downstream immunoglobulin class switch recombination

Chromosomal translocations involving the immunoglobulin (Ig) receptor loci usually disrupt and silence these loci. On the basis of observations in follicular lymphoma (FL) with downstream Ig heavy chain (IGH) class switch recombination (CSR), we hypothesized that downstream CSR-mediated chromosomal translocations would leave the V(D)J-Cmu transcription unit intact, thereby still allowing IgM expression from the IGH allele involved in the translocation. To test this hypothesis, we analyzed biallelic IGH translocations in the IgM-expressing cell line Z-138 by interphase FISH, DNA fiber-FISH, long-distance vectorette PCR, and DNA sequencing. One IGH allele was involved in a t(11;14), showing a break in the JH region that juxtaposed the Emu enhancer and the 3' Calpha enhancers to the cyclin D1 gene. The other IGH allele contained a t(8;14) breakpoint involving the 3' end of a Sgamma region, whereas the reciprocal breakpoint at 8q24 was approximately 40 kb centromeric of MYC. Molecular analysis showed that this IGH allele harbored a normal V(D)J-Cmu complex, which is responsible for IgM expression. These data show that chromosomal breakpoints such as the t(8;14) can occur in downstream IGH constant regions and do not necessarily interfere with Ig expression.

Calcium regulation of GM-CSF by calmodulin-dependent kinase II phosphorylation of Ets1

The multipotent cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) is involved in particular in the physiological response to infection and in inflammatory responses. GM-CSF is produced by many cell types, including T lymphocytes responding to T-cell receptor activation and mantle zone B lymphocytes. B-cell receptor and T-cell receptor activation generates two major signals: an increase in intracellular Ca(2+) concentration and a protein kinase cascade. Previous studies have shown that the Ca(2+)/calmodulin-dependent phosphatase calcineurin mediates stimulation of GM-CSF transcription in response to Ca(2+). In this study, we show that Ca(2+) signaling also regulates GM-CSF transcription negatively through Ca(2+)/calmodulin-dependent kinase II (CaMK II) phosphorylation of serines in the autoinhibitory domain for DNA binding of the transcription factor Ets1. Wild-type Ets1 negatively affects GM-CSF transcription on Ca(2+) stimulation in the presence of cyclosporin A, which inhibits calcineurin. Conversely, Ets1 with mutated CaMK II target serines showed an increase in transactivation of the GM-CSF promoter/enhancer. Moreover, constitutively active CaMK II inhibited transactivation of GM-CSF by wild-type Ets1 but not by Ets1 with mutated CaMK II sites. Mutation of CaMK II target serines in Ets1 also relieves inhibition of cooperative transactivation of GM-CSF with the Runx1/AML1 transcription factor. In addition, the Ca(2+)-dependent phosphorylation of Ets1 reduces the binding of Ets1 to the GM-CSF promoter in vivo.

Detection of chromosome 11q13 breakpoints by interphase fluorescence in situ hybridization. A useful ancillary method for the diagnosis of mantle cell lymphoma

We assessed cytologic specimens from 11 mantle cell lymphomas (MCLs) and 32 other B-cell non-Hodgkin lymphomas (NHLs) for 11q13 breakpoints using a 2-color fluorescence in situ hybridization (FISH) assay that uses an 11q13 probe centered on the CCND1 gene and a centromeric chromosome 11 probe (CEP11). The number of nuclei in 200 cells were counted, and results were expressed as an 11q13/CEP11 ratio. All MCLs showed a high percentage of interphase nuclei with 3 or more 11q13 signals (mean, 74.8%; range 57%-90%). In contrast, in other B-cell NHLs the mean percentage of cells with 3 or more 11q13 signals was 9.2%. All MCLs had an elevated 11q13/CEP11 ratio (mean, 1.38). The mean ratio for other B-cell NHLs was 0.99. Two non-MCL cases, 1 large B-cell and 1 B-cell unclassified NHL, had high 11q13/CEP11 ratios of 1.15 and 1.30, respectively. Conventional cytogenetic analysis performed on the former case revealed a t(5;11)(q31;q13). Interphase FISH analysis using 11q13 and CEP11 probes is a convenient ancillary method for assisting in the diagnosis of MCL. This commercially available assay is simple to use on cytology or imprint specimens, and results can be obtained within 24 hours.

Combination of granulocyte-macrophage colony-stimulating factor (GM-CSF) anf erythropoietin (EPO) for the treatment of advanced non-responsive chronic lymphocytic leukemia

We report the use of a colony-stimulating granulocyte-macrophage factor (GM/CSF) and erythropoietin (EPO) combination as salvage treatment in four heavily-pretreated patients with refractory/ recurrent B-CLL. Induction therapy was subcutaneous GM-CSF 2.5 microg/ kg, and EPO, 150 units/kg both daily for the first 14 d. Maintenance therapy was GM-CSF on days 1, 3 and 5 and Epo on days 2, 4 and 6 at the same doses with weekly recycling. All the patients responded favourably. A significant reduction of lymphocytosis, lymphoadenomegaly, and organomegaly was obtained within one month of therapy. The number of infections and transfusional requirement decreased dramatically. The hemoglobin increased to over 11 g/dl in 3 out of 4 patients. With a median follow-up of 11 months (range 5-13) we observed 4 partial responses (NCI/IWCLL) and only one progression after a 10-month partial response. This combination regimen seems very active, safe and easy to administer. It may represent a promising therapeutical option in heavily pretreated patients. Further clinical and biological studies on a larger cohort of patients are needed to confirm these preliminary data, to clarify the hypothetical interactions between these cytokines and B-CLL cell proliferation pathways, and to establish if this therapy may have an impact on survival.