The Enhanced Cytotoxic Effects in B-Cell Leukemia and Lymphoma Following Activation of Prostaglandin EP4 Receptor and Targeting of CD20 Antigen by Monoclonal Antibodies

Anti-CD20 monoclonal antibodies (MAbs) have revolutionized the treatment of B-cell leukemia and lymphoma. However, many patients do not respond to such treatment due to either deficiency of the complementary immune response or resistance to apoptosis. Other currently available treatments are often inadequate or induce major side effects. Therefore, there is a constant need for improved therapies. The prostaglandin E2 receptor 4 (EP4) receptor has been identified as a promising therapeutic target for hematologic B-cell malignancies. Herein, we report that EP4 receptor agonists PgE1-OH and L-902688 have exhibited enhanced cytotoxicity when applied together with anti-CD20 MAbs rituximab, ofatumumab and obinutuzumab in vitro in Burkitt lymphoma cells Ramos, as well as in p53-deficient chronic lymphocytic leukemia (CLL) cells MEC-1. Moreover, the enhanced cytotoxic effects of EP4 receptor agonists and MAbs targeting CD20 have been identified ex vivo on primary lymphocytes B obtained from patients diagnosed with CLL. Incubation of cells with PgE1-OH and L-902688 preserved the expression of CD20 molecules, further confirming the anti-leukemic potential of EP4 receptor agonists in combination with anti-CD20 MAbs. Additionally, we demonstrated that the EP4 receptor agonist PgE-1-OH induced apoptosis and inhibited proliferation via the EP4 receptor triggering in CLL. This work has revealed very important findings leading towards the elucidation of the anticancer potential of PgE1-OH and L-902688, either alone or in combination with MAbs. This may contribute to the development of potential therapeutic alternatives for patients with B-cell malignancies.

Frequent loss of CD10 expression in follicular lymphoma with leukaemic presentation

INTRODUCTION

Follicular lymphoma (FL) is usually a nodal lymphoma expressing CD10, rarely with leukaemic presentation (FL-LP).

MATERIALS AND METHODS

We searched for FL-LP in our institution from 2000 to 2018 and characterised the neoplastic cells by flow cytometry, immunohistochemistry and fluorescence in situ hybridization. Thirteen (6.1%) of 212 FL cases were FL-LP, all de novo neoplasms. The leukaemic cells were small in 12 cases and large in one. All had concurrent FL, mostly (92%; 12/13) low-grade. The single case with large leukaemic cells had a concurrent primary splenic low-grade FL and a double-hit large B-cell lymphoma in the marrow.

RESULTS

CD10 was expressed in the leukaemic cells in 38% (5/13) cases by flow cytometry and in 77% (10/13) cases in tumours (p= 0.0471). IGH/BCL2 reciprocal translocation was identified in 85% (11/13) cases. Most patients were treated with chemotherapy. In a median follow-up time of 36 months, nine patients were in complete remission. The 2- and 5-year survival rates were at 100% and 83%, respectively. In this study, we characterised a series of de novo FL-LP in Taiwan. All patients had concurrent nodal and/or tissue tumours, which might suggest that these patients seek medical help too late.

CONCLUSION

The lower CD10 expression rate by flow cytometry than by immunohistochemistry might be due to different epitopes for these assays. Alternatively, loss of CD10 expression might play a role in the pathogenesis of leukaemic change. The clinical course of FL-LP could be aggressive, but a significant proportion of the patients obtained complete remission with chemotherapy.

CD20 is dispensable for B-cell receptor signaling but is required for proper actin polymerization, adhesion and migration of malignant B cells

Surface protein CD20 serves as the critical target of immunotherapy in various B-cell malignancies for decades, however its biological function and regulation remain largely elusive. Better understanding of CD20 function may help to design improved rational therapies to prevent development of resistance. Using CRISPR/Cas9 technique, we have abrogated CD20 expression in five different malignant B-cell lines. We show that CD20 deletion has no effect upon B-cell receptor signaling or calcium flux. Also B-cell survival and proliferation is unaffected in the absence of CD20. On the contrary, we found a strong defect in actin cytoskeleton polymerization and, consequently, defective cell adhesion and migration in response to homeostatic chemokines SDF1α, CCL19 and CCL21. Mechanistically, we could identify a reduction in chemokine-triggered PYK2 activation, a calcium-activated signaling protein involved in activation of MAP kinases and cytoskeleton regulation. These cellular defects in consequence result in a severely disturbed homing of B cells in vivo.

Altered Nuclear Export Signal Recognition as a Driver of Oncogenesis

Altered expression of XPO1, the main nuclear export receptor in eukaryotic cells, has been observed in cancer, and XPO1 has been a focus of anticancer drug development. However, mechanistic evidence for cancer-specific alterations in XPO1 function is lacking. Here, genomic analysis of 42,793 cancers identified recurrent and previously unrecognized mutational hotspots in XPO1. XPO1 mutations exhibited striking lineage specificity, with enrichment in a variety of B-cell malignancies, and introduction of single amino acid substitutions in XPO1 initiated clonal, B-cell malignancy in vivo. Proteomic characterization identified that mutant XPO1 altered the nucleocytoplasmic distribution of hundreds of proteins in a sequence-specific manner that promoted oncogenesis. XPO1 mutations preferentially sensitized cells to inhibitors of nuclear export, providing a biomarker of response to this family of drugs. These data reveal a new class of oncogenic alteration based on change-of-function mutations in nuclear export signal recognition and identify therapeutic targets based on altered nucleocytoplasmic trafficking. SIGNIFICANCE: Here, we identify that heterozygous mutations in the main nuclear exporter in eukaryotic cells, XPO1, are positively selected in cancer and promote the initiation of clonal B-cell malignancies. XPO1 mutations alter nuclear export signal recognition in a sequence-specific manner and sensitize cells to compounds in clinical development inhibiting XPO1 function.This article is highlighted in the In This Issue feature, p. 1325.

ADCT-402, a PBD dimer-containing antibody drug conjugate targeting CD19-expressing malignancies

Human CD19 antigen is a 95-kDa type I membrane glycoprotein in the immunoglobulin superfamily whose expression is limited to the various stages of B-cell development and differentiation and is maintained in the majority of B-cell malignancies, including leukemias and non-Hodgkin lymphomas of B-cell origin. Coupled with its differential and favorable expression profile, CD19 has rapid internalization kinetics and is not shed into the circulation, making it an ideal target for the development of antibody-drug conjugates (ADCs) to treat B-cell malignancies. ADCT-402 (loncastuximab tesirine) is a novel CD19-targeted ADC delivering SG3199, a highly cytotoxic DNA minor groove interstrand crosslinking pyrrolobenzodiazepine (PDB) dimer warhead. It showed potent and highly targeted in vitro cytotoxicity in CD19-expressing human cell lines. ADCT-402 was specifically bound, internalized, and trafficked to lysosomes in CD19-expressing cells and, following release of the PBD warhead, resulted in formation of DNA crosslinks that persisted for 36 hours. Bystander killing of CD19- cells by ADCT-402 was also observed. In vivo, single doses of ADCT-402 resulted in highly potent, dose-dependent antitumor activity in several subcutaneous and disseminated human tumor models with marked superiority to comparator ADCs delivering tubulin inhibitors. Dose-dependent DNA crosslinks and γ-H2AX DNA damage response were measured in tumors by 24 hours after single dose administration, whereas matched peripheral blood mononuclear cells showed no evidence of DNA damage. Pharmacokinetic analysis in rat and cynomolgus monkey showed excellent stability and tolerability of ADCT-402 in vivo. Together, these impressive data were used to support the clinical testing of this novel ADC in patients with CD19-expressing B-cell malignancies.

Improving therapeutic activity of anti-CD20 antibody therapy through immunomodulation in lymphoid malignancies

Nearly two decades ago rituximab heralded a new era in management of B cell malignancies significantly increasing response rates and survival. However, despite clear therapeutic advantage, significant numbers of patients become refractory to anti-CD20 mAb therapy, suggesting urgent improvements are required. It is now well recognized that the suppressive tumor microenvironment plays an important role in the outcome of anti-CD20 mAb therapy and that manipulation of this environment may improve the efficacy and produce long-term tumor control. The past few years have seen a surge of interest in immunomodulatory agents capable of overwriting immune suppressive networks into favorable clinical outcome. Currently, a number of such combinations with anti-CD20 mAb is under evaluation and some have produced encouraging outcomes in rituximab refractory disease. In this review, we give an outline of anti-CD20 mAbs and explore the combinations with immunomodulatory agents that enhance antitumor immunity through targeting stimulatory or inhibitory pathways and have proven potential to synergize with anti-CD20 mAb therapy. These agents, primarily mAbs, target CTLA-4, PD-1/PD-L1, and CD40.

Targeting the B-cell receptor signaling pathway in B lymphoid malignancies

PURPOSE OF REVIEW

Normal B cells that have failed to productively rearrange immunoglobulin V region genes encoding a functional B-cell receptor (BCR) are destined to die. Likewise, the majority of B-cell malignancies remain dependent on functional BCR signaling, whereas in some subtypes BCR expression is missing and, apparently, counterselected. Here, we summarize the recent experimental evidence for the importance of BCR signaling and clinical concepts to target the BCR pathway in B-cell leukemia and lymphoma.

RECENT FINDINGS

Although the dependency on pre-BCR signaling in pre-B acute lymphoblastic leukemia (ALL) seems to be limited to few ALL subtypes (e.g. TCF3-PBX1), most mature B-cell lymphomas rely on BCR signaling provided by different stimuli, for example tonic B-cell signaling, chronic (auto)-antigen exposure, and self-binding properties of the BCR. The finding that in chronic lymphocytic leukemia, BCRs bind to an epitope on the BCR itself unravels a novel concept for chronic lymphocytic leukemia pathogenesis.

SUMMARY

Targeting of the B-cell receptor tyrosine kinases spleen tyrosine kinase, Bruton's tyrosine kinase, and phosphatidylinositol 3-kinase achieve promising clinical responses in various mature B-cell malignancies and might also be useful in defined subsets of ALL. However, further understanding of the BCR signal integration in the different disease groups is required to accurately predict which groups of patients will benefit from BCR pathway inhibition.

Lethal giant larvae 1 tumour suppressor activity is not conserved in models of mammalian T and B cell leukaemia

In epithelial and stem cells, lethal giant larvae (Lgl) is a potent tumour suppressor, a regulator of Notch signalling, and a mediator of cell fate via asymmetric cell division. Recent evidence suggests that the function of Lgl is conserved in mammalian haematopoietic stem cells and implies a contribution to haematological malignancies. To date, direct measurement of the effect of Lgl expression on malignancies of the haematopoietic lineage has not been tested. In Lgl1^−/− mice, we analysed the development of haematopoietic malignancies either alone, or in the presence of common oncogenic lesions. We show that in the absence of Lgl1, production of mature white blood cell lineages and long-term survival of mice are not affected. Additionally, loss of Lgl1 does not alter leukaemia driven by constitutive Notch, c-Myc or Jak2 signalling. These results suggest that the role of Lgl1 in the haematopoietic lineage might be restricted to specific co-operating mutations and a limited number of cellular contexts.

ZAP-70 promotes the infiltration of malignant B-lymphocytes into the bone marrow by enhancing signaling and migration after CXCR4 stimulation

ZAP-70 in chronic lymphocytic leukemia (CLL) is associated with enhanced response to microenvironmental stimuli. We analyzed the functional consequences of ZAP-70 ectopic expression in malignant B-cells in a xenograft mouse model of disseminated B-cell leukemia. Mice injected with B-cells expressing ZAP-70 showed a prominently higher infiltration of the bone marrow. In vitro analysis of the response of malignant B-cells to CXCL12, the main attracting chemokine regulating trafficking of lymphocytes to the bone marrow, or to bone marrow stromal cells, revealed that ZAP-70 induces an increased response in terms of signaling and migration. These effects are probably mediated by direct participation of ZAP-70 in CXCL12-CXCR4 signaling since CXCR4 stimulation led to activation of ZAP-70 and downstream signaling pathways, such as MAPK and Akt, whereas ZAP-70 did not alter the expression of the CXCR4 receptor. In addition, subclones of primary CLL cells with high expression of ZAP-70 also showed increased migrative capacity toward CXCL12. Neutralization of CXCR4 with a monoclonal antibody resulted in impaired in vitro responses to CXCL12 and bone marrow stromal cells. We conclude that ZAP-70 enhances the migration of malignant B-cells into the supportive microenvironment found in the bone marrow mainly by enhancing signaling and migration after CXCR4 stimulation.

Atypical B cell receptor signaling: straddling immune diseases and cancer

The B-cell receptor (BCR) signaling pathway plays an essential role in the survival, proliferation, differentiation and trafficking of lymphocytic. Recent findings associate aberrant BCR signaling with specific disease pathologies, including B-cell malignancies and autoimmune disorders. Inhibition of the BCR signaling pathway may therefore provide promising new strategies for the treatment of B-cell diseases. This special issue of International Reviews of Immunology focuses on atypical B-cell receptor signaling, its role in immune diseases and cancer, and its implications for potential therapeutic intervention.

Milatuzumab-conjugated liposomes as targeted dexamethasone carriers for therapeutic delivery in CD74+ B-cell malignancies

PURPOSE

Corticosteroids are widely used for the treatment of B-cell malignancies, including non-Hodgkin lymphoma, chronic lymphocytic leukemia (CLL), and acute lymphoblastic leukemia; however, this class of drug is associated with undesirable off-target effects. Herein, we developed novel milatuzumab-conjugated liposomes as a targeted dexamethasone carrier for therapeutic delivery in CD74(+) B-cell malignancies and explored its effect against the disease.

EXPERIMENTAL DESIGN

The targeting efficiency of milatuzumab-targeted liposomes to CD74(+) cells was evaluated in vitro. The effect of CD74-targeted liposomal dexamethasone was compared with free dexamethasone in primary CLL cells and cell lines in vitro. The therapeutic efficacy of CD74-targeted liposomal dexamethasone was evaluated in a Raji-severe combined immunodeficient (SCID) xenograft model in vivo.

RESULTS

Milatuzumab-targeted liposomes promoted selective incorporation of carrier molecules into transformed CD74-positive B cells as compared with CD74-negative T-cells. The CD74-dexamethasone-targeted liposomes (CD74-IL-DEX) promoted and increased killing in CD74-positive tumor cells and primary CLL cells. Furthermore, the targeted drug liposomes showed enhanced therapeutic efficacy against a CD74-positive B-cell model as compared with free, or non-targeted, liposomal dexamethasone in SCID mice engrafted with Raji cells in vivo.

CONCLUSIONS

These studies provide evidence and support for a potential use of CD74-targeted liposomal dexamethasone as a new therapy for B-cell malignancies.

Cushing syndrome related to leukemic infiltration of the central nervous system: a case report and a possible role of LIF

BACKGROUND

Adrenocorticotropic hormone (ACTH)-dependent Cushing syndrome (CS) in the presence of leukemic central nervous system infiltration is very rare.

CASE

A 3.8-year-old girl who had been treated for B-cell acute lymphoblastic leukemia (ALL) for 1.5 years was admitted to our hospital with excessive weight gain and depression for the last 2 months. Prior to her admission, she was on maintenance with the ALL-BFM95 study protocol for 10 months that does not contain corticosteroids. On physical examination, central obesity and moon face appearance were determined. Laboratory tests revealed high morning ACTH, cortisol level, and 24-h urinary free cortisol level. Morning cortisol level was 33.94 nmol/L after a 2-day (4 × 0.5 mg) dexamethasone suppression test. A lumbar puncture revealed leukemic cells in the cerebrospinal fluid. No pituitary adenoma was detected on magnetic resonance imaging. We diagnosed the patient with ACTH-dependent CS related to leukemic infiltration of the central nervous system.

CONCLUSION

Central nervous system infiltration should be considered in leukemic patients who have developed CS. We believe increased leukemia inhibitory factor levels may be a factor for CS in our patient with ALL.

[Expression of two subtype molecules of CD133 in childhood with B linage acute lymphoblastic leukemia and its clinical significance]

This study was to explore the expression of two subtype molecules of CD133 and its relationship with clinical prognostic factors in childhood with B linage acute lymphoblastic leukemia (B-ALL) at initial diagnosis and the 33rd day of induction chemotherapy. Expression of CD133-1 and CD133-2 in 48 cases of B-ALL and 25 cases at initial diagnosis and the 33rd day of treatment was detected by flow cytometry. Minimal residual disease (MRD) of B-ALL at 33rd day was evaluated by flow cytometry. The results indicated that the expression of CD133-1 was positive in 18 cases (37.5%), and expression of CD133-2 in 30 cases (62.5%) was positive from 48 cases with newly diagnosed ALL (P < 0.05). At 33rd day of treatment, expression of CD133-1 in 2 cases (8.0%) from 25 cases was positive, and expression of CD133-2 in 23 cases (92.0%) was positive (P < 0.05). After induction chemotherapy in B-ALL, the expression of CD133-1 decreased significantly, but still higher than that in the normal control group. Compared to expression of CD133-1, expression of CD133-2 decreased slowly. It is concluded that there is no relations among expression of CD133 and sex, age, white blood cell count, percentage of bone marrow blast cells, FAB subtype, cytogenetics, leukemia fusion gene, risk stratification and complete remission rate in childhood B-ALL. The positive expression rates and levels of CD133-2 are higher than those of CD133-1 in B-ALL. There is no statistical correlation between expression of CD133 and CD34 in B-ALL. The expression of CD133-2 is significantly related to the level of MRD.

The dual kinase inhibitor NVP-BEZ235 in combination with cytotoxic drugs exerts anti-proliferative activity towards acute lymphoblastic leukemia cells

BACKGROUND

Inhibition of signal transduction pathways has been successfully introduced into cancer treatment. The dual phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) inhibitor NVP-BEZ235 has antitumor activity in vitro against solid tumors. Here, we examined the activity of NVP-BEZ235 in acute lymphoblastic leukemia (ALL) cells and the best modalities for combination approaches.

MATERIALS AND METHODS

ALL cell lines (SEM, RS4;11, Jurkat and MOLT4) were treated with NVP-BEZ235 alone, or in combination with cytarabine (AraC), doxorubicin (Doxo) or dexamethasone (Dexa).

RESULTS

NVP-BEZ235 potently inhibited the proliferation and metabolic activity of ALL cells. Antiproliferative effects were associated with G(0)/G(1) arrest and reduced levels of cyclin-dependent kinase 4 (CDK4) and cyclin D3. Inhibition of PI3K and mTOR activity was detected at 10 and 100 nM. NVP-BEZ235 combined with AraC, Doxo or Dexa synergistically enhanced the cytotoxicity compared to single-drug treatment, even in glucocorticoid-resistant cells.

CONCLUSION

NVP-BEZ235 displays pronounced antiproliferative effects in ALL cells and might therefore be a useful drug in the treatment of ALL.

[Poliovirus receptor on surface of acute B lymphoid leukemia cells modulated by epigenetic mechanism]

The aim of this study was to identify if the expression of poliovirus receptor (PVR) on the surface of acute B lymphoid leukemia (B-ALL) cells RS4:11 and SUP-B15 is modulated by epigenetic mechanism. B-ALL cell lines RS4:11 and SUP-B15 were treated with demethylation agent. Bisulfite PCR was performed to detect percentage change of the methylated CpG islands in the promoter region of PVR. In the meantime, the expression levels of PVR at the translation and transcription levels were detected by flow cytometry and RT-PCR respectively. The B-ALL cell lines were also treated with histone deacetylase (HDAC) inhibitor. The expression level of the gene mRNA and protein was detected too. The results indicated that after treated with 5-azacytidine, the hypermethylated status of PVR promoter region was partly reversed, and the expression of PVR at both mRNA and protein levels was restored in the meanwhile. HDAC inhibitor suberoylanilide hydroxamic acid could also increase the PVR expression. But there was no synergistic function between hypermethylation and HDAC as for repressing PVR transcription in B-ALL cell lines. It is concluded that the expression of PVR in B-ALL cells is modulated by epigenetic mechanisms. Treatment with corresponding inhibitors can partly restore the gene's expression in both mRNA and protein levels.

The Pax-5 gene: a pluripotent regulator of B-cell differentiation and cancer disease

The Pax-5 oncogene encodes a potent transcription factor that plays a key role in B-cell development and cancerous processes. In normal B-lymphopoiesis, Pax-5 accomplishes a dual function by activating B-cell commitment genes while concomitantly repressing non-B-lineage genes. Given the pivotal importance of Pax-5-mediated processes in B-cell development, an aberrant regulation of Pax5 expression has consistently been associated with B-cell cancers, namely, lymphoma and lymphocytic leukemias. More recently, Pax-5 gene expression has been proposed to influence carcinogenic events in tissues of nonlymphoid origin by promoting cell growth and survival. However, in other cases, Pax-5 products have opposing effects on proliferative activity, thus redefining its generally accepted role as an oncogene in cancer. In this review, we attempt to summarize recent findings about the function and regulation of Pax-5 gene products in B-cell development and related cancers. In addition, we present new findings that highlight the pleiotropic effects of Pax-5 activity in a number of other cancer types.

IRF4 is a suppressor of c-Myc induced B cell leukemia

Interferon regulatory factor 4 (IRF4) is a critical transcriptional regulator in B cell development and function. We have previously shown that IRF4, together with IRF8, orchestrates pre-B cell development by limiting pre-B cell expansion and by promoting pre-B cell differentiation. Here, we report that IRF4 suppresses c-Myc induced leukemia in EμMyc mice. Our results show that c-Myc induced leukemia was greatly accelerated in the IRF4 heterozygous mice (IRF4^+/−Myc); the average age of mortality in the IRF4^+/−Myc mice was only 7 to 8 weeks but was 20 weeks in the control mice. Our results show that IRF4^+/−Myc leukemic cells were derived from large pre-B cells and were hyperproliferative and resistant to apoptosis. Further analysis revealed that the majority of IRF4^+/−Myc leukemic cells inactivated the wild-type IRF4 allele and contained defects in Arf-p53 tumor suppressor pathway. p27^kip is part of the molecular circuitry that controls pre-B cell expansion. Our results show that expression of p27^kip was lost in the IRF4^+/−Myc leukemic cells and reconstitution of IRF4 expression in those cells induced p27^kip and inhibited their expansion. Thus, IRF4 functions as a classical tumor suppressor to inhibit c-Myc induced B cell leukemia in EμMyc mice.

CAL-101, a p110delta selective phosphatidylinositol-3-kinase inhibitor for the treatment of B-cell malignancies, inhibits PI3K signaling and cellular viability

Phosphatidylinositol-3-kinase p110δ serves as a central integration point for signaling from cell surface receptors known to promote malignant B-cell proliferation and survival. This provides a rationale for the development of small molecule inhibitors that selectively target p110δ as a treatment approach for patients with B-cell malignancies. We thus identified 5-fluoro-3-phenyl-2-[(S)-1-(9H-purin-6-ylamino)-propyl]-3H-quinazolin-4-one (CAL-101), a highly selective and potent p110δ small molecule inhibitor (half-maximal effective concentration [EC(50)] = 8nM). Using tumor cell lines and primary patient samples representing multiple B-cell malignancies, we have demonstrated that constitutive phosphatidylinositol-3-kinase pathway activation is p110δ-dependent. CAL-101 blocked constitutive phosphatidylinositol-3-kinase signaling, resulting in decreased phosphorylation of Akt and other downstream effectors, an increase in poly(ADP-ribose) polymerase and caspase cleavage and an induction of apoptosis. These effects have been observed across a broad range of immature and mature B-cell malignancies, thereby providing a rationale for the ongoing clinical evaluation of CAL-101.

Functional protein network activation mapping reveals new potential molecular drug targets for poor prognosis pediatric BCP-ALL

BACKGROUND

In spite of leukemia therapy improvements obtained over the last decades, therapy is not yet effective in all cases. Current approaches in Acute Lymphoblastic Leukemia (ALL) research focus on identifying new molecular targets to improve outcome for patients with a dismal prognosis. In this light phosphoproteomics seems to hold great promise for the identification of proteins suitable for targeted therapy.

METHODOLOGY/PRINCIPAL FINDINGS

We employed Reverse Phase Protein Microarrays to identify aberrantly activated proteins in 118 pediatric B-cell precursor (BCP)-ALL patients. Signal transduction pathways were assayed for activation/expression status of 92 key signalling proteins. We observed an increased activation/expression of several pathways involved in cell proliferation in poor clinical prognosis patients. MLL-rearranged tumours revealed BCL-2 hyperphosphorylation through AMPK activation, which indicates that AMPK could provide a functional role in inhibiting apoptosis in MLL-rearranged patients, and could be considered as a new potential therapeutic target. Second, in patients with poor clinical response to prednisone we observed the up-modulation of LCK activity with respect to patients with good response. This tyrosine-kinase can be down-modulated with clinically used inhibitors, thus modulating LCK activity could be considered for further studies as a new additional therapy for prednisone-resistant patients. Further we also found an association between high levels of CYCLIN E and relapse incidence. Moreover, CYCLIN E is more expressed in early relapsed patients, who usually show an unfavourable prognosis.

CONCLUSIONS/SIGNIFICANCE

We conclude that functional protein pathway activation mapping revealed specific deranged signalling networks in BCP-ALL that could be potentially modulated to produce a better clinical outcome for patients resistant to standard-of-care therapies.

Molecular detection of B-cell neoplasms by specific DNA methylation biomarkers

A novel, easy to perform PCR-based method employing specific DNA methylation biomarkers to detect B-cell neoplasms in a variety of B-cell lines and B lymphoblastic leukemia (B-ALL) patient specimens has been developed. This method detects as few as 5 B-ALL cells, or 1 B-ALL cell in 1,000,000 normal background blood cells using a single marker, DLC-1 gene CpG island (CGI) methylation. By adding two additional markers PCDHGA12 and RPIB9, over 80% of B-ALL cases were detected in patients' bone marrow and/or peripheral blood specimens. We have traced clinical B-ALL cases up to 10 years retrospectively and the DLC-1 methylation is correlated with patient clinical status. Thus, this epigenetic-based molecular method demonstrates its potential use in the diagnosis of B-cell neoplasia, in addition to traditional approach such as clinical features, morphology, immunophenotype, and genetic analysis.

Biologic and clinical significance of cytokine production in B-cell malignancies

Cytokines are a group of polypeptide hormones endowed with pleiotropic biological properties. Normal B lymphocytes produce a number of these factors that subserve important regulatory functions in the combined processes of proliferation and differentiation. Also neoplastic B cells can release cytokines and, simultaneously, respond to the same factors in an autocrine circuit that supports their malignant growth. In addition, tumor cells can make use of the factors released by normal cells, either spontaneously or under the influence of inductive signals from the neoplastic cells. Inappropriate or excessive release of cytokines may have an important role in the pathophysiology of some clinical features. Thus, neutralization of cytokine biologic activity in vivo could be a therapeutic strategy for treatment of human B-cell neoplasias.

[Gene expression profile of human TGF-beta signal transduction pathway of B cell type acute lymphocytic leukemia]

This study was aimed to investigate the gene expression profile of TGF-beta signal transduction pathway in B-cell type acute lymphocytic leukemia (B-ALL). The gene expression profiles in B-ALL primary cells and cell lines (NALM6 cells, Raji cells), B-lymphocyte of control were detected by cDNA microarray including 113 different genes in human TGF-beta/BMP signal transduction pathway, and TGF-beta(1) mRNA expression was detected by real time RT-PCR. The B lymphocytes in peripheral blood of heacthy persons sorted by flow cytometry were used as control. The difference between them was compared. The results showed that as compared with B lymphocytes in peripheral blood of heacthy persons, the TGF-beta(1) expression in B-ALL cells, NALM6 cells and Raji cells were down-regulationed, myc and smad1 gene expressions were up-regulated, IL-6, smad 7 gene expressions were down-regulated. It is concluded that TGF-beta signal transduction is abnormal in B-cell type acute lymphocytic leukemia.

Expression level of lipoprotein lipase and dystrophin genes predict survival in B-cell chronic lymphocytic leukemia

Mutational status of immunoglobulin variable region genes (VH-genes) is known as the strongest predictor of long term prognosis in B-CLL. However, applications in the routine clinical practice are time consuming, and therefore some other predictions are required. In this study, we have compared prognostic values of real time PCR quantification of the expression levels of four genes previously shown to be differentially expressed in V(H)-unmutated and mutated B-CLL subtypes: ZAP-70, ZBTB20, DMD and LPL. The study included 134 B-CLL patients. Expression levels of LPL and DMD genes were significantly correlated to mutational status, while expression levels of of ZAP-70 gene correlated only in CD19+ selected cases (N = 40). No correlation was observed for ZBTB20 gene. Expression levels of LPL and DMD predicted overall survival in the entire cohort of patients. Prognostic values of LPL gene expression levels were significant even for CLL patients with stage A. Quantitative RT-PCR assays for measuring LPL gene expression are robust enough to be introduced into routine clinical practice.

Expression of erythropoietin receptor and in vitro functional effects of epoetins in B-cell malignancies

PURPOSE

Erythropoietin (EPO) and EPO receptor (EPO-R) expression have been reported in solid tumors and are claimed to regulate tumor growth; however, no data have been published on this issue in B-cell malignancies or normal lymphoid cells. This report describes genomic/protein EPO-R expression and in vitro effects of recombinant human EPO (epoetin) in B-cell chronic lymphocytic leukemia (B-CLL), mantle-cell lymphoma (MCL), and multiple myeloma (MM).

EXPERIMENTAL DESIGN

Blood samples were obtained from patients with B-CLL, MCL, and healthy volunteers, and bone marrow was obtained from MM patients. EPO-R mRNA was detected by reverse transcription-PCR. EPO-R surface expression was investigated by flow cytometry using digoxigenin-labeled epoetin and polyclonal rabbit anti-EPO-R antibody for intracellular receptor. Tumor cell stimulation was determined in vitro using [(3)H]thymidine incorporation and CD69 expression after exposure to epoetin alpha or beta or darbepoetin alpha.

RESULTS

EPO-R mRNA was detected in mononuclear cells from 32 of 41 (78%) B-CLL and 5 of 7 (71%) MCL patients, and 21 of 21 (100%) MM samples. Expression was also detected in highly purified T cells from six of eight B-CLL patients, four of four MM patients, and normal donor B and T cells. Surface EPO-R protein was not detected. Intracellular EPO-R staining with anti-EPO-R antibodies was unspecific. No tumor-stimulatory effect was observed with high epoetin concentrations.

CONCLUSIONS

EPO-R gene is frequently expressed in lymphoid malignancies and normal B and T cells. However, there was no surface protein expression and no epoetin-induced in vitro stimulation of tumor B cells, indicating that epoetin therapy in vivo is likely to be safe in patients with lymphoid malignancies.

A set of genes that regulate cell proliferation predicts treatment outcome in childhood acute lymphoblastic leukemia

To identify novel predictors of outcome in childhood acute lymphoblastic leukemia (ALL), we analyzed gene expression in the leukemic cells of 187 children with newly diagnosed ALL and compared the findings with minimal residual disease (MRD) results obtained on day 19 of remission induction treatment. Genes that showed a significant relationship to MRD were then tested for their capacity to predict leukemic relapse in an independent cohort of 99 patients. We identified 674 probe sets that were associated with MRD on day 19 (P < .006); 40 of the identified genes predicted relapse (P < .03). Among these, 14 showed independent prognostic significance after adjustment for age, leukocyte count at diagnosis, and genetic subtype. More than half of the 40 genes and nearly all of the 14 genes were functionally related, as indicated by their roles in the regulation of cell proliferation. Underexpression of genes promoting cell proliferation was associated with resistance to chemotherapy. The biologic processes regulated by the genes we identified appear to be key determinants of the early cytoreductive response to remission induction therapy and subsequent clinical outcome in childhood ALL. Incorporation of the expression levels of these genes into existing strategies of risk classification could improve clinical management.

Bruton's tyrosine kinase prevents activation of the anti-apoptotic transcription factor STAT3 and promotes apoptosis in neoplastic B-cells and B-cell precursors exposed to oxidative stress

Bruton's tyrosine kinase (BTK) was previously demonstrated to be a mediator of oxidative stress-induced apoptosis in irradiated neoplastic B-cells and B-cell precursors. Defective BTK expression in leukaemic B-cell precursors from infants with t(4;11) acute lymphoblastic leukaemia has been associated with radiation resistance. The present study examined whether BTK mediates apoptosis during oxidative stress by interfering with the anti-apoptotic function of signal transducer and activator of transcription 3 (STAT3). BTK physically associated with and tyrosine phosphorylated STAT3; this association was promoted by pervanadate (PV)-induced oxidative stress. The BTK/STAT3 interaction appeared to prevent STAT3 response to oxidative stress, because PV-induced STAT3 activation was markedly enhanced in DT40 chicken lymphoma B-cells that were rendered BTK-deficient by targeted disruption of the btk gene as well as in BTK-deficient RAMOS-1 human lymphoma B-cells. These BTK-deficient cells were highly resistant to oxidative stress-induced apoptosis triggered by PV treatment. Reconstitution of BTK-deficient DT40 cells with wild-type human BTK gene eliminated the amplification of the STAT3 response and restored the PV-induced apoptotic signal. Similarly, while the BTK-positive NALM-6 human leukaemic B-cell precursor cell line showed no STAT3 activation after PV treatment and was exquisitely sensitive to PV-induced apoptosis, PV failed to induce apoptosis in BTK-deficient RAMOS-1 human lymphoma B-cells that showed a robust STAT3 response. These results provide unprecedented biochemical and genetic evidence for a unique mode of cross-talk that occurs between BTK and STAT3 pathways during oxidative stress, whereby BTK may trigger apoptosis via negative regulation of the anti-apoptotic STAT3 activity.

Expression of a non-DNA-binding Ikaros isoform exclusively in B cells leads to autoimmunity but not leukemogenesis

Ikaros is a transcriptional regulator whose function is essential for B cell development. It is expressed in the hematopoietic stem cell (HSC) through the mature B cell stage. Using genetically engineered mice in which the endogenous Ikaros gene is disrupted, it has been shown that a lack of Ikaros leads to a block in B cell development and that its severe diminution results in a hyperresponsive B cell compartment. Ikaros expression within the HSC has led to speculation as to whether the role of Ikaros in B cell biology is largely accomplished prior to B cell specification. In addition, widespread expression of Ikaros in hematopoietic cells leads to the possibility that some or all of the observed defects are not B cell autonomous. In this report, we demonstrate that over-expression of a dominant interfering Ikaros isoform exclusively in B cells has profound effects on mature B cell function. We provide evidence that continued high-level expression of Ikaros is essential for homeostasis of peripheral lymphocytes and maintenance of B cell tolerance. We also show that deregulation of Ikaros activity does not rapidly result in B cell leukemogenesis as it does with 100% penetrance within the T cell lineage.

Correlation of ZAP-70 expression in B cell leukemias to the ex vivo response to a combination of fludarabine/genistein

The role of ZAP-70 expression on the ex vivo response of blood cells from CLL and PLL patients to a combination of fludarabine, a purine analog, and genistein, a tyrosine kinase inhibitor was studied. Patient cells were studied for the expression of ZAP-70 mRNA and its relation to the induction of apoptosis in response to treatment with genistein 15-60 muM and/or fludarabine 3 muM. The combination of genistein and fludarabine resulted in a significantly increased induction of apoptosis relative to the fludarabine alone. The ex vivo patient cells with a high ZAP-70 expression underwent more apoptosis in response to genistein than did patient cells with a low ZAP-70 mRNA expression. In contrast, basal IL-10 mRNA expression correlated negatively with apoptosis induction in response to genistein (P < 0.01). These studies suggest that, in malignant B cells that express elevated levels of the ZAP-70 signaling molecule, genistein may inhibit the ZAP-70 tyrosine kinase activity, resulting in cell death. The ZAP-70 may serve as a target for therapy. In addition, these studies suggest that the IL-10 expression by malignant B cells may not only suppress anti-tumor T cell responses in vivo, but also promote the survival of malignant B cells despite treatment with chemotherapeutic agents.

Ligand-independent activity of the B cell antigen receptor in physiology and pathology

The B cell receptor (BCR) is required for stimulation of B cells by antigen, and is also involved in the negative selection of autoreactive B cells. In the past few years, a constitutive ligand-independent signaling activity of the BCR has been demonstrated. In this paper, the various findings are summarized and their interpretation and their significance, both in pathology and in physiology discussed. The constitutive activity of the BCR may be important for tumor formation, at least in the case of heavy-chain diseases, neoplastic proliferations developed from B cells. A large body of evidence suggests that this activity could be required for B cell survival and would play a role in B cell development as a process monitoring BCR functionality. A model explaining signaling in the absence of antigen as a function of dimer formation is proposed. The putative constitutive activity of the pre-BCR is also discussed.

Increased midkine gene expression in childhood B-precursor acute lymphoblastic leukemia

Midkine (MK) is a heparin-binding growth factor that is overexpressed in a number of solid cancers. However, expression in acute leukemia has not been clarified. We examined MK gene expression using real-time PCR in 94 children with acute leukemia. In 30 of the 41 patients with B-precursor ALL, MK gene expression was overexpressed than normal BM. MK gene was also overexpressed in more than half of patients with FAB M1 and M2 types of AML. Quantification of MK gene by real-time PCR offers particular promise as a prognostic marker and a marker for minimal residual disease in children with B-precursor ALL.

Purine metabolism in B-cell lymphocytic leukemia: a microarray approach

B-cell chronic lymphocytic leukemia (B-CLL) is an adult-onset highly heterogeneous malignancy characterized by a cells resistance to apoptosis rather than to highly proliferative cells. In previous research, we evidenced an imbalance of purine metabolism in B-CLL cells. Since the extracellular adenosine has been proved to induce apoptosis via A2b receptor, enzymes involved in adenosine metabolism could play an important role in apoptosis resistance of B-CLL cells. We prepared a microarray chip for the analysis of 50 selected genes that could be of interest in B-CLL: enzymes of purine de-novo, salvage and catabolic pathway, oxidative stress enzymes, and apoptotis-related proteins. Preliminary results identify many genes of purine metabolism that exhibit low or high expression, while genes involved in signal transduction and apoptosis exhibit lower alterations even if of remarkable interest. This application of microarray technique seems promising and at least a subset of these genes will be valid candidates for further studies.

Signaling molecules and cytokine production in T cells of patients with B-cell chronic lymphocytic leukemia: long-term effects of fludarabine and alemtuzumab treatment

Fludarabine and alemtuzumab are routinely used for treatment of B-cell chronic lymphocytic leukemia (B-CLL). The present study aimed to compare the expression of signaling molecules and cytokine production by T cells of B-CLL patients in long-term unmaintained remission/plateau phase following fludarabine or alemtuzumab treatment with that of indolent/untreated B-CLL patients and healthy donors. The frequency and intensity of TCR-CD3zeta chain, p56lck, p59fyn, ZAP-70, PI3-kinase and interferon (IFN)-gamma/interleukin (IL)-4 production in CD4 and CD8 T cells was examined by flow cytometry. T-cell function was assessed by stimulation with purified protein derivative (PPD) and phytohemagglutinin (PHA). Despite a reduction in number, the expression of IFN-gamma/IL-4 in T-cells in patients was significantly higher than in healthy donors. The intensity of most signaling molecules in treated patients was relatively unaffected vs. healthy donors but lower than untreated-indolent patients. However, the total number of T cells which expressed each of the signaling molecules was decreased in patients, with no difference between fludarabine- and alemtuzumab-treated patients. The T-cell response to PHA but not PPD was reduced in treated patients. The results suggest that, despite some alterations in signaling molecules and a reduction in T-cell number, overall T-cell functions may be relatively well preserved long-term after treatment with fludarabine and alemtuzumab.

Immunophenotyping and differential diagnosis of hairy cell leukemia

HCL and HCL-variant cells have a distinct immunophenotype that seems to correspond to that of a mature activated memory B cell. Although the two diseases have similarities in histology and membrane marker expression, such as the selected Ig heavy-chain expression and the reactivity with certain B-cell activation markers (eg, CD103), there are differences in their clinical course, morphology, and immunophenotype. Immunophenotyping is an essential tool for the diagnosis of these two disorders, for monitoring and assessing response to therapy, and for distinguishing them from other B-cell malignancies.

Genetic abnormalities and clinical outcome in chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in the elderly population. Under conventional cytogenetic (CC) analysis, approximately 50% of CLL cases show clonal aberrations. Using fluorescent in situ hybridization (FISH), the percentage of patients with abnormalities rises to almost 80%, the most frequent being 13q14, ATM, and TP53 deletions and trisomy 12. The aim of this study was to establish the incidence of genetic changes in B-CLL patients using CC and FISH and to evaluate the prognostic implications. Of the 65 patients analyzed, genetic aberrations were found in 36.7% with CC and in 68.4% with FISH. The frequencies of abnormalities were as follows: 13q deletion, 42.1%; trisomy 12, 19.2%; ATM deletion, 17.5%; and TP53 deletion, 8.7%. Significant differences were observed when the overall survival was correlated with Rai stage (P = 0.000). FISH abnormalities were correlated with age, sex, morphology, white blood cell count, CD38 expression, Rai stage, disease status, and survival. Significant differences were obtained with age (P = 0.05) and disease status (P = 0.01). Deletion of 13q was the most frequent abnormality (36.6%) among old patients (> or =60); trisomy 12 was the most frequent (31.3%) in younger patients (<60). Half of the patients with stable disease showed 13q deletion, and the most frequent abnormality in patients with progressive disease was ATM deletion (22.2%).

ZAP-70 enhances B-cell-receptor signaling despite absent or inefficient tyrosine kinase activation in chronic lymphocytic leukemia and lymphoma B cells

Expression of ZAP-70 is an important negative prognostic factor in chronic lymphocytic leukemia (CLL). This protein tyrosine kinase is a key mediator of T-cell receptor (TCR) signaling and is structurally homologous to Syk, which plays an analogous role in B-cell receptor (BCR) signaling. Recent studies indicate that ZAP-70 may participate in BCR signaling as well, but the mechanism of action is not completely understood. We have now compared antigen receptor-induced activation of ZAP-70 in B cells and T cells by analyzing phosphorylation of critical regulatory tyrosine residues. We show that BCR-mediated activation of ZAP-70 is very inefficient in CLL and lymphoma B cells and is negligible when compared to activation of Syk. Despite the inefficient catalytic activation, the ability of ZAP-70 to recruit downstream signaling molecules in response to antigen receptor stimulation appeared relatively preserved. Moreover, ectopic expression of ZAP-70 enhanced and prolonged activation of several key mediators of BCR signaling, such as the Syk, ERK, and Akt kinases, and decreased the rate of ligand-mediated BCR internalization. We conclude that the role of ZAP-70 in BCR signaling is quite distinct from its role in TCR signaling and is likely mediated by inhibition of events that terminate the signaling response.

CD22 ligand binding regulates normal and malignant B lymphocyte survival in vivo

The CD22 extracellular domain regulates B lymphocyte function by interacting with alpha2,6-linked sialic acid-bearing ligands. To understand how CD22 ligand interactions affect B cell function in vivo, mouse anti-mouse CD22 mAbs were generated that inhibit CD22 ligand binding to varying degrees. Remarkably, mAbs which blocked CD22 ligand binding accelerated mature B cell turnover by 2- to 4-fold in blood, spleen, and lymph nodes. CD22 ligand-blocking mAbs also inhibited the survival of adoptively transferred normal (73-88%) and malignant (90%) B cells in vivo. Moreover, mAbs that bound CD22 ligand binding domains induced significant CD22 internalization, depleted marginal zone B cells (82-99%), and reduced mature recirculating B cell numbers by 75-85%. The CD22 mAb effects were independent of complement and FcRs, and the CD22 mAbs had minimal effects in CD22AA mice that express mutated CD22 that is not capable of ligand binding. These data demonstrate that inhibition of CD22 ligand binding can disrupt normal and malignant B cell survival in vivo and suggest a novel mechanism of action for therapeutics targeting CD22 ligand binding domains.

BAFF, APRIL and human B cell disorders

B cells require signals from multiple sources for their development from precursor cells, and differentiation into effector cells. BAFF has been identified as a critical regulator of B cell development and differentiation. Defects in the production of BAFF and/or expression of its receptors have been associated with a diverse array of human immunopathologies characterised by perturbed B cell function and behaviour, including autoimmunity, malignancy, and immunodeficiency. This review will discuss the role of BAFF in the pathogenesis of these human immune disorders. It will also highlight relevant differences between the function of BAFF in humans and mice and the impact of this on the therapeutic utility of BAFF antagonists in the treatment of different human diseases.

BASH-novel PKC-Raf-1 pathway of pre-BCR signaling induces kappa gene rearrangement

The pre-B-cell receptor (pre-BCR) is thought to signal transcriptional activation of the immunoglobulin light (L) chain gene locus, proceeding to its V-J rearrangement. The pre-BCR signaling pathway for this process is largely unknown but may involve the adaptor protein BASH (BLNK/SLP-65). Here we report that the pre-B leukemia cell lines established from affected BASH-deficient mice rearrange kappaL-chain gene locus and down-regulate pre-BCR upon PMA treatment or BASH reconstitution. Analyses with specific inhibitors revealed that activation of novel PKC (nPKC) and MEK, but not Ras, is necessary for the rearrangement. Accordingly, retroviral transduction of active PKCeta, PKCepsilon, or Raf-1, but not Ras, induced the kappa gene rearrangement and expression in the pre-B-cell line. Tamoxifen-mediated BASH reconstitution resulted in the translocation of PKCeta to the plasma membrane and kappa chain expression. These data make evident that the Ras-independent BASH-nPKC-Raf-1 pathway of pre-BCR signaling induces the L-chain gene rearrangement and expression.

CD38 induces apoptosis of a murine pro-B leukemic cell line by a tyrosine kinase-dependent but ADP-ribosyl cyclase- and NAD glycohydrolase-independent mechanism

Cross-linking of CD38 on hematopoietic cells induces activation, proliferation and differentiation of mature T and B cells and mediates apoptosis of myeloid and lymphoid progenitor cells. In addition to acting as a signaling receptor, CD38 is also an enzyme capable of producing several calcium-mobilizing metabolites, including cyclic adenosine diphosphate ribose (cADPR). It has been previously postulated that the calcium-mobilizing metabolites produced by CD38 may regulate its receptor-based activities. To test this hypothesis, we examined whether the enzyme activity of CD38 controls the apoptosis of an anti-CD38-stimulated leukemic B cell. We show that anti-CD38-induced apoptosis of Ba/F3 cells, a murine pro-B cell line, is not affected by blocking the calcium-mobilizing activity of cADPR or by inhibiting intracellular or extracellular calcium mobilization. In addition, we demonstrate that blocking CD38 enzyme activity with 2'-deoxy-2'-fluoro-nicotinamide arabinoside adenine dinucleotide has no effect on apoptosis and that Ba/F3 cells expressing catalytically inactive mutant forms of CD38 still undergo apoptosis upon CD38 cross-linking. Instead, we find that anti-CD38-induced apoptosis is dependent on tyrosine kinase and caspase activation, and that this process appears to be potentiated by the presence of membrane microdomains. Thus, the receptor-mediated functions of CD38 can be separated from its enzyme activity in a murine leukemic cell line, suggesting that CD38 plays multiple, but independent, biologic roles.

Reprogramming of the tumour B-cell phenotype in Hodgkin lymphoma

Hodgkin and Reed-Sternberg (HRS) cells, the tumour cells in classical Hodgkin lymphoma, derive from mature B cells but have largely lost their B-cell phenotype. This extensive reprogramming is unique among B-cell lymphomas. A recent study by Dörken and colleagues provides an interesting insight into the mechanisms for this reprogramming by demonstrating that the key B-cell-determining transcription factor E2A is inhibited in HRS cells by the deregulated expression of its inhibitors activated B-cell factor (ABF)-1 and inhibitor of differentiation and DNA binding (Id)2.

Tumor invasion in the absence of epithelial-mesenchymal transition: podoplanin-mediated remodeling of the actin cytoskeleton

The expression of podoplanin, a small mucin-like protein, is upregulated in the invasive front of a number of human carcinomas. We have investigated podoplanin function in cultured human breast cancer cells, in a mouse model of pancreatic beta cell carcinogenesis, and in human cancer biopsies. Our results indicate that podoplanin promotes tumor cell invasion in vitro and in vivo. Notably, the expression and subcellular localization of epithelial markers are unaltered, and mesenchymal markers are not induced in invasive podoplanin-expressing tumor cells. Rather, podoplanin induces collective cell migration by filopodia formation via the downregulation of the activities of small Rho family GTPases. In conclusion, podoplanin induces an alternative pathway of tumor cell invasion in the absence of epithelial-mesenchymal transition (EMT).

Hyperforin inhibits MMP-9 secretion by B-CLL cells and microtubule formation by endothelial cells

We previously reported that hyperforin (HF), a natural phloroglucinol purified from Saint John's wort, can induce the apoptosis of leukemic cells from patients with B-cell lymphocytic leukemia (B-CLL) ex vivo. We show here that treatment of cultured B-CLL patients' cells with HF results in a marked inhibition of their capacity to secrete matrix metalloproteinase-9, an essential component in neo-angiogenesis through degradation of the extracellular matrix process. The phloroglucinol acts by decreasing the production of the latent 92 kDa pro-enzyme. The inhibitory effect of HF is associated with a decrease in VEGF release by the leukemic cells. Moreover, HF is found to prevent the formation of microtubules by human bone marrow endothelial cells cultured on Matrigel, evidencing its capacity to inhibit vessel formation. Our results show the antiangiogenesis activity of HF and strengthen its potential interest in the therapy of B-CLL.

Responses to human CD40 ligand/human interleukin-2 autologous cell vaccine in patients with B-cell chronic lymphocytic leukemia

PURPOSE

Human CD40 ligand activates the malignant B-cell chronic lymphocytic leukemia cells and enhances their capacity to present tumor antigens. Human interleukin-2 further potentiates the immunogenicity of human CD40 ligand in preclinical murine models.

EXPERIMENTAL DESIGN

We prepared autologous B-cell chronic lymphocytic leukemia cells that expressed both human CD40 ligand (>90% positive) and human interleukin-2 (median secretion, 1,822 pg/mL/10(6) cells; range, 174-3,604 pg). Nine patients were enrolled in a phase I trial, receiving three to eight s.c. vaccinations.

RESULTS

Vaccinations were administered without evidence of significant local or systemic toxicity. A B-cell chronic lymphocytic leukemia-specific T-cell response was detected in seven patients. The mean frequencies of IFN-gamma, granzyme-B, and IL-5 spot-forming cells were 1/1,230, 1/1,450, and 1/4,500, respectively, representing a 43- to 164-fold increase over the frequency before vaccine administration. Three patients produced leukemia-specific immunoglobulins. Three patients had >50% reduction in the size of affected lymph nodes. Nonetheless, the antitumor immune responses were observed only transiently once immunization ceased. High levels of circulating CD4+/CD25+/LAG-3+/FoxP-3+ immunoregulatory T cells were present before, during and after treatment and in vitro removal of these cells increased the antileukemic T-cell reactivity.

CONCLUSIONS

These results suggest that immune responses to B-cell chronic lymphocytic leukemia can be obtained with human CD40 ligand/human interleukin-2-expressing s.c. vaccines but that these responses are transient. High levels of circulating regulatory T cells are present, and it will be of interest to see if their removal in vivo augments and prolongs the antitumor immune response.

Mad1 is a transcriptional repressor of Bcl-6

Bcl-6, a major regulator of B lymphocyte function that contributes to neoplastic transformation of B cells, is expressed in activated germinal center (GC) B cells and down-regulated during terminal differentiation to plasma cells. Regulation of Bcl-6 expression is incompletely characterized. Terminal B cell differentiation is associated with down-regulation of Bcl-6, activation of Blimp-1, modulation of Myc, and specifically with the up-regulation of the Mad1 and Mad4 transcription factors, which play a critical role in cell differentiation and cell cycle regulation. Because the Mad E-box consensus binding site is present in the upstream promoter of Bcl-6, we investigated whether Bcl-6 may be under control of the Mad1 transcription factor. Anti-sense Mad1 oligonucleotides abrogated the down-regulation of Bcl-6 expression that occurred during in vitro differentiation of mouse splenic B cells induced by dextran-conjugated anti-IgD Ab and IL-5. Transduction of the WEHI 231 B cell line with retroviruses expressing Mad1 down-regulated Bcl-6 expression. Expression of the 5' upstream promoter region of Bcl-6 was down-regulated by co-expression of Mad1. Last, chromatin immunoprecipitation assays with anti-Mad1 Ab demonstrated in vivo interaction of Mad1 with the Bcl-6 promoter region. The findings suggest that Mad1 is a transcriptional repressor of Bcl-6.

Fibromodulin, an extracellular matrix protein: characterization of its unique gene and protein expression in B-cell chronic lymphocytic leukemia and mantle cell lymphoma

Fibromodulin is an extracellular matrix protein normally produced by collagen-rich tissues; the fibromodulin gene has been found to be the most overexpressed gene in B-cell chronic lymphocytic leukemia. In this study, fibromodulin was expressed at the gene level (reverse transcription-polymerase chain reaction [RT-PCR]) in all patients with B-CLL (n = 75) and in most (5 of 7) patients with mantle cell lymphoma (MCL). No mutations in the fibromodulin gene were detected. Fibromodulin was also detected at the protein level in the cytoplasm of the B-CLL cells and in the supernatant after in vitro cultivation, but not at the cell surface. Fibromodulin was not found in patients with T-cell chronic lymphocytic leukemia (T-CLL), B-cell prolymphocytic leukemia (B-PLL), T-cell prolymphocytic leukemia (T-PLL), hairy cell leukemia, follicular lymphoma, lymphoplasmacytic lymphoma, multiple myeloma, acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), or chronic myelogenous leukemia (CML) or in 36 hematologic cell lines. Normal blood mononuclear cells (T and B lymphocytes, monocytes), tonsil B cells, and granulocytes did not express fibromodulin. Activation (phorbol 12-myristate 13-acetate [PMA]/ionomycin) of normal T and B lymphocytes induced weak fibromodulin gene expression, but not to the extent seen in freshly isolated B-CLL cells. The reason for the exclusive ectopic expression of fibromodulin in B-CLL and MCL is unknown. However, its unique protein expression makes it likely that fibromodulin is involved in the pathobiology of B-CLL and MCL. (Blood. 2005;105:4828-4835)

Activation of Src kinase Lyn by the Kaposi sarcoma-associated herpesvirus K1 protein: implications for lymphomagenesis

The K1 gene of Kaposi sarcoma-associated herpesvirus (KSHV) encodes a transmembrane glycoprotein bearing a functional immunoreceptor tyrosine-based activation motif (ITAM). Previously, we reported that the K1 protein induced plasmablastic lymphomas in K1 transgenic mice, and that these lymphomas showed enhanced Lyn kinase activity. Here, we report that systemic administration of the nuclear factor kappa B (NF-kappaB) inhibitor Bay 11-7085 or an anti-vascular endothelial growth factor (VEGF) antibody significantly reduced K1 lymphoma growth in nude mice. Furthermore, in KVL-1 cells, a cell line derived from a K1 lymphoma, inhibition of Lyn kinase activity by the Src kinase inhibitor PP2 decreased VEGF induction, NF-kappaB activity, and the cell proliferation index by 50% to 75%. In contrast, human B-cell lymphoma BJAB cells expressing K1, but not the ITAM sequence-deleted mutant K1, showed a marked increase in Lyn kinase activity with concomitant VEGF induction and NF-kappaB activation, indicating that ITAM sequences were required for the Lyn kinase-mediated activation of these factors. Our results suggested that K1-mediated constitutive Lyn kinase activation in K1 lymphoma cells is crucial for the production of VEGF and NF-kappaB activation, both strongly implicated in the development of KSHV-induced lymphoproliferative disorders.