Abstract 4310: Prospective isolation of clongenic mantle cell lymphoma initiating cells

We have prospectively isolated and characterized clonogenic cells with self-renewal capacities from mantle cell lymphoma (MCL), a particularly deadly form of non-hodgkin's lymphoma (NHL). Self-renewal and tumorigenic activities were enriched in MCL cell fractions that lacked expression of the prototypic B cell surface marker, CD19. CD45+CD19- cells represented a relatively small fraction of the total MCL tumor cells, however, they recapitulated the heterogeneity of original patient tumors upon transplantation into immunodeficient mice. As few as 100 of these cells displayed self-renewal capacities in secondary and tertiary recipient mice by in vivo limiting dilution assays. Similar to leukemic stem cells, CD45+CD19- MCL cells also displayed a quiescent status as determined by dye efflux assays. In summary, this study is the first to isolate subpopulations of MCL cells that have self-renewal and tumorigenic capacities. Identification and characterization of MCL-ICs is an important first step toward understanding how self-renewal and tumorigenicity are regulated in MCL.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4310.

Abstract 4760: A novel immune potentiating strategy for cancer vaccine

A major obstacle for translational research of cancer vaccine is the weak immunogenicity of tumor antigens. Thus, the development of new, more potent strategy that aims at breaking such an immune tolerance is a prerequisite of vaccine therapy. Here we show that the unexpected effect of inducing sterile inflammation at vaccination sites by myotoxins potentiated induction of tumor-specific immunity by genetic vaccines and converted a non-immunogenic lymphoma idiotype antigen into a tumor rejection vaccine. This potent immunostimulatory effect was immune-mediated, requiring recruitment of dendritic cells (DC). Sterile inflammation induced by myotoxins was associated with upregulation of chemokines, proinflammatory cytokines, Toll-like receptors and their endogenous ligands, and activation of innate immunity. Mechanistic experiments in vivo also elucidated the requirement for genes triggering DC maturation including TLR signaling and CD40. These studies suggest that inducing sterile inflammation at vaccination sites generates a favorable microenvironment that promotes adaptive immunity. This novel mechanism of immune potentiation may be exploited for development of adjuvants for vaccines against cancer.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4760.

Molecular analysis of light-chain switch and acute lymphoblastic leukemia transformation in two follicular lymphomas: Implications for lymphomagenesis

We observed novel transformations of follicular lymphoma (FL), first, a switch in immunoglobulin (Ig) light chain, and second, transformation of FL to acute lymphoblastic leukemia (ALL). Each set of tumors shared a common clonal origin, as demonstrated by expression of identical, unique CDR IIIH sequences, shared somatic mutations in JH, and identical bcl-2 translocation breakpoints of microdissected ALL cells. Molecular analysis of lambda V-gene expression demonstrated lambda-bearing cells in the original kappa tumor, while expansion of the lambda subclone at relapse occurred after active immunotherapy targeting the Ig receptor. These exceptional cases are compatible with a more contemporary model of lymphomagenesis in which critical events originate from genetic mechanisms which normally occur in germinal center (GC) B cells and challenge the current paradigm of parallel generation of subclones from an early, pre-GC precursor. It is also possible that the outgrowth of these variants was a consequence of immunoselection.

Human-like mouse models for testing the efficacy and safety of anti-beta2-microglobulin monoclonal antibodies to treat myeloma

PURPOSE

We showed recently that anti-beta2-microglobulin (beta2M) monoclonal antibodies (mAb) have remarkably strong apoptotic effects on myeloma cells in vitro and in SCID-hu mice. However, whether the mAbs will be therapeutic and safe in the treatment of myeloma patients, in whom every tissue expresses low densities of MHC class I molecules and elevated levels of soluble beta2M are present, remains to be determined.

EXPERIMENTAL DESIGN

In this study, human-like myeloma mouse models (HLA-A2-transgenic NOD/SCID mice) were developed, which express mature and functional human MHC class I (HLA-A2 and human beta2M) on murine organs and present high levels of circulating human beta2M derived from human myeloma cells. Myeloma-bearing mice were treated intraperitoneally with anti-beta2M mAbs, and the distribution and effects of the mAbs on normal organs and established tumors were examined.

RESULTS

Our results show that anti-beta2M mAbs were effective in suppressing myeloma growth in treated mice. The therapeutic efficacy of the mAbs in these mice are comparable with those observed in myeloma-bearing nontransgenic NOD/SCID mice in which no human MHC class I is expressed on murine organs. Furthermore, although the mAbs can be detected on different organs, no tissue damage or cell apoptosis was observed in the mice.

CONCLUSION

Based on the antimyeloma efficacy and low toxicity in the mice, our study suggests that anti-beta2M mAbs may be safe and the tissue-expressing and soluble beta2M may not compromise their therapeutic effects in myeloma patients. This study provides further support for the future application of the mAbs as therapeutic agents for multiple myeloma.

Phase 2 trial of rituximab plus hyper-CVAD alternating with rituximab plus methotrexate-cytarabine for relapsed or refractory aggressive mantle cell lymphoma

BACKGROUND

Relapsed or refractory mantle cell lymphoma has a very poor prognosis. The authors evaluated the response rates and survival times of patients treated with an intense regimen known to be effective against untreated aggressive mantle cell lymphoma: rituximab plus hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, and dexamethasone) alternating with rituximab plus methotrexate-cytarabine.

METHODS

In this prospective, open-label, phase 2 study, patients received this combination for 6 to 8 cycles. Twenty-nine patients were evaluable for response.

RESULTS

The median number of cycles received was 5 (range, 1-7 cycles), and the overall response rate was 93% (45% complete response [CR] or CR unconfirmed [CRu] and 48% partial response [PR]). All 5 patients previously resistant to treatment had a response (1 CR, 4 PR), and both patients whose disease did not change in response to prior therapy had PRs. Toxic events occurring in response to the 104 cycles given included neutropenic fever (11%), grade 3 or 4 neutropenia (74%), and grade 3 or 4 thrombocytopenia (63%). There were no deaths from toxicity. At a median follow-up of 40 months (range, 5-48 months), the median failure-free survival time was 11 months with no plateau in the survival curve.

CONCLUSIONS

This combination chemotherapy was effective for refractory/relapsed mantle cell lymphoma.

Roles of idiotype-specific t cells in myeloma cell growth and survival: Th1 and CTL cells are tumoricidal while Th2 cells promote tumor growth

Idiotype (Id) protein, secreted by myeloma cells, is a tumor-specific antigen. Id-based immunotherapy has been explored in patients with myeloma, and results were disappointing. Although previous studies have shown that Id-specific CTLs are able to lyse myeloma cells, it is unclear whether other types of Id-specific T cells, such as type-1 T-helper (Th1) and type-2 T-helper (Th2) cells, are also able to suppress or kill myeloma cells. Using a 5T murine myeloma model, we generated T-cell clones of different subsets and examined their function in the context of myeloma cells. Id-specific CTLs specifically lysed myeloma cells via MHC class I, perforin, and Fas ligand (FasL), and Th1, but not Th2, cells lysed the myeloma cells by FasL-Fas interaction. CTL and Th1 cells also suppressed the growth and function of myeloma cells, whereas Th2 cells promoted the proliferation and enhanced the secretion of Id protein and cytokines by myeloma cells. CTL and Th1, but not Th2, cells were able to eradicate established myeloma in vivo after adoptive transfer. These results show that Id-specific CTL and Th1 are promising effector cells, whereas Th2 provide no protection and may even promote tumor progression in vivo.

A severe combined immunodeficient-hu in vivo mouse model of human primary mantle cell lymphoma

PURPOSE

To establish a severe combined immunodeficient (SCID)-hu in vivo mouse model of human primary mantle cell lymphoma (MCL) for the study of the biology and novel therapy of human MCL.

EXPERIMENTAL DESIGN

Primary MCL cells were isolated from spleen, lymph node, bone marrow aspirates, or peripheral blood of six different patients and injected respectively into human bone chips, which had been s.c. implanted in SCID-hu. Circulating human beta(2)-microglobulin in mouse serum was used to monitor the engraftment and growth of patient's MCL cells. H&E staining and immunohistochemical staining with anti-human CD20 and cyclin D1 antibodies were used to confirm the tumor growth and migration.

RESULTS

Increasing levels of circulating human beta(2)-microglobulin in mouse serum indicated that the patient's MCL cells were engrafted successfully into human bone chip of SCID-hu mice. The engraftment and growth of patient's MCL cells were dependent on human bone marrow microenvironment. Immunohistochemical staining with anti-human CD20 and cyclin D1 antibodies confirmed that patient's MCL cells were able to not only survive and propagate in the bone marrow microenvironment of the human fetal bone chips, but also similar to the human disease, migrate to lymph nodes, spleen, bone marrow, and gastrointestinal tract of host mice. Treatment of MCL-bearing SCID-hu mice with atiprimod, a novel antitumor compound against the protection of bone marrow stromal cells, induced tumor regression.

CONCLUSION

This is the first human primary MCL animal model that should be useful for the biological and therapeutic research on MCL.

Models for lymphoma

This unit describes experimental procedures for development of therapeutic vaccines, particularly "second-generation" recombinant vaccines. Specifically, a general procedure for handling and culturing lymphoma cell lines in vitro and their subsequent challenge into syngeneic mice is described. Several protocols describe the production of various idiotype (Id)-based or cellular lymphoma vaccine formulations. In particular, the novel approach of rendering nonimmunogenic lymphoma-derived scFv or Id immunogenic by fusing it with a chemokine moiety is described. As an alternative, a protocol for expression and purification of these chemokine-fusion proteins from E. coli is included. A general procedure is included for cloning of cytokine genes, for example, murine GM-CSF, in A20 lymphoma cells. Support protocols are presented for chemically conjugating intact Ig protein with KLH to produce a prototype protein vaccine and using the Helios Gene Gun System to immunize mice with recombinant DNA tumor vaccines.

Therapeutic lymphoma vaccines: importance of T-cell immunity

The unique antigenic determinants, termed idiotype, of the immunoglobulin expressed on a given B-cell malignancy can serve as a tumor-specific antigen for active immunotherapy. Administration of autologous tumor-derived idiotype protein conjugated to a carrier protein, keyhole limpet hemocyanin, together with granulocyte-macrophage colony-stimulating factor to follicular lymphoma patients in complete clinical remission was associated with induction of tumor-specific cellular and humoral immunity, molecular remissions, and prolonged disease-free survival. Idiotype vaccination in patients with mantle cell lymphoma following rituximab-containing chemotherapy induced tumor-specific T-cell immunity in the absence of B cells, suggesting that vaccines may be used in combination with rituximab. Three double-blind, randomized, Phase III idiotype vaccine trials are currently ongoing to definitively determine the clinical benefit of idiotype-keyhole limpet hemocyanin plus granulocyte-macrophage colony-stimulating factor vaccination in patients with lymphoma. Results from early clinical trials with idiotype vaccines suggested that both humoral and cellular immune responses may be independently associated with tumor regression and improved progression-free survival. With the increased use of rituximab for the treatment of follicular lymphoma and other B-cell non-Hodgkin's lymphomas, further improvement in the potency of the vaccines would require strategies to enhance T-cell responses, as rituximab depletes normal B cells and impairs the generation of antibody responses.

Anti beta2-microglobulin monoclonal antibodies induce apoptosis in myeloma cells by recruiting MHC class I to and excluding growth and survival cytokine receptors from lipid rafts

We recently showed that monoclonal antibodies (mAbs) against beta2-microglobulin (beta2M) have a remarkably strong apoptotic effect on myeloma cells. The mAbs induced apoptosis by recruiting major histocompatibility complex (MHC) class I to lipid rafts, activated c-Jun N-terminal kinase (JNK), and inhibited phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) pathways. Growth and survival cytokines such as interleukin-6 (IL-6) and insulin-like growth factor-I (IGF-I), which could protect myeloma cells from dexamethasone-induced apoptosis, did not affect mAb-mediated cell death. This study was undertaken to elucidate the mechanisms underlying anti-beta2M mAb-induced PI3K/Akt and ERK inhibition and the inability of IL-6 and IGF-I to protect myeloma cells from mAb-induced apoptosis. We focused on lipid rafts and confirmed that these membrane microdomains are required for IL-6 and IGF-I signaling. By recruiting MHC class I into lipid rafts, anti-beta2M mAbs excluded IL-6 and IGF-I receptors and their substrates from the rafts. The mAbs not only redistributed the receptors in cell membrane, but also abrogated IL-6- or IGF-I-mediated Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3), PI3K/Akt, and Ras/Raf/ERK pathway signaling, which are otherwise constitutively activated in myeloma cells. Thus, this study further defines the tumoricidal mechanism of the mAbs and provides strong evidence to support the potential of these mAbs as therapeutic agents for myeloma.

A novel strategy for rapid and efficient isolation of human tumor-specific CD4(+) and CD8(+) T-cell clones

Adoptive therapy with antigen-specific T cells is a promising approach for the treatment of infectious diseases and cancer. However, cloning of antigen-specific T cells by the traditional approach of limiting dilution is a time-consuming, laborious, and inefficient process. Here, we describe a novel flow cytometric strategy for rapid isolation of human tumor antigen-specific T-cell clones by using T-cell receptor (TCR) Vbeta antibodies in combination with carboxyfluorescein succinimidyl ester (CFSE)-based proliferation assay. The CFSE dilution following antigen stimulation identified proliferating antigen-specific T cells, and the TCRVbeta antibodies allowed distinguishing T cells at the clonal level from a heterogeneous T-cell population. This method of TCRVbeta/CFSE dilution was used for the isolation of four different human lymphoma and melanoma-specific CD4(+) and CD8(+) T-cell clones reactive against defined and undefined tumor antigens. Isolated tumor-specific T-cell clones could be expanded to large numbers ex vivo while maintaining phenotype, function, and tumor antigen specificity. The method was simple, efficient, and reproducible, and may have potential application for the development of adoptive immunotherapeutic strategies.

Bortezomib is synergistic with rituximab and cyclophosphamide in inducing apoptosis of mantle cell lymphoma cells in vitro and in vivo

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma with poor clinical outcome. Although front therapy induces a high rate of complete remission (CR), relapse is inevitable and new regimens are much needed for relapsed MCL. The proteasome inhibitor bortezomib (BTZ) induces apoptosis and sensitizes MCL cells to chemotherapy in relapsed MCL, but CR rates are low, with a short duration of response and severe toxicity. Here we evaluated whether BTZ is additive or synergistic with cyclophosphamide (CTX) and rituximab (RTX). Increasing doses of BTZ with a fixed dose of RTX and CTX (BRC regimen) resulted in markedly synergistic growth inhibition of MCL cells. BRC significantly enhanced apoptosis in MCL cell lines and primary tumor cells compared with single-agent treatment. Furthermore, western blotting analysis indicated that BRC induces apoptosis earlier via activation and cleavage of caspases-8, -9 and -3, and poly (ADP-ribose) polymerase, than single-agent treatment. The pan-caspase inhibitor completely blocked apoptosis induced by BRC. In vivo studies showed that BRC eradicated subcutaneous tumors in MCL-bearing SCID mice and significantly prolonged the long-term event-free survival in 70% of the mice. Hence, our study demonstrates that cytoreductive chemotherapy with both BTZ and anti-CD20 antibody may offer a better therapeutic modality for relapsed MCL.

Survivin DNA vaccine generated specific antitumor effects in pancreatic carcinoma and lymphoma mouse models

We investigated the antitumor effect of survivin DNA vaccine in murine pancreatic and lymphoma models, and if xenogenic survivin can generate stronger immune response. We found that mice vaccinated with either human or mouse survivin DNA have significantly slower tumor growth and longer survival than those vaccinated with vector DNA. There was no significant difference between groups that received human and mouse survivin DNA. Lymphocyte infiltration was greater in tumors of mice immunized with survivin DNA than in tumors of control mice. We conclude that survivin DNA vaccine generated specific antitumor effects with increased lymphocyte infiltration at the tumor sites.

Human C-reactive protein binds activating Fcgamma receptors and protects myeloma tumor cells from apoptosis

Elevated levels of C-reactive protein (CRP) are present in many disease situations including malignancies and may contribute to the pathogenesis of cardiovascular disorders. This study was undertaken in a myeloma setting to determine whether CRP affects tumor cell growth and survival. We show that CRP enhanced myeloma cell proliferation under stressed conditions and protected myeloma cells from chemotherapy drug-induced apoptosis in vitro and in vivo. CRP binds activating Fcgamma receptors; activates PI3K/Akt, ERK, and NF-kappaB pathways; and inhibits caspase cascade activation induced by chemotherapy drugs. CRP also enhanced myeloma cell secretion of IL-6 and synergized with IL-6 to protect myeloma cells from chemotherapy drug-induced apoptosis. Thus, our results implicate CRP as a potential target for cancer treatment.

An NKT-mediated autologous vaccine generates CD4 T-cell dependent potent antilymphoma immunity

Relapses occurring in most patients with lymphoma after antibody or chemotherapy highlight a need for effective vaccination approaches. Autologous tumors are ideal sources of patient-specific tumor antigens for vaccines; however, their poor immunogenicity has been a major obstacle in practice. Natural killer T (NKT) cells have recently emerged as crucial regulators of autoimmunity and tumor immunosurveillance. Here, we show that an autologous lymphoma vaccine that activates NKT cells generated tumor-specific protective immunity in experimental mice. Single vaccination with alpha-galactosylceramide (alphaGC)-loaded A20 lymphoma cells elicited effective antitumor immunity against tumor challenge. This vaccination strategy also induced significant tumor regression in A20-bearing mice. Importantly, the survivors from primary tumor inoculation were all resistant to tumor rechallenge, indicative of established adaptive memory immunity. Depletion as well as adoptive transfer studies revealed an exclusive role of conventional CD4(+) but not CD8(+) T cells in mediating antitumor immunity. In addition, we found normal hematopoietic compartments in the vaccinated mice. Therefore, NKT ligand-loaded lymphoma elicits long-lasting and effective antitumor immunity, which can be further developed as patient- and tumor-specific immunotherapy against human lymphomas.

Dickkopf-1 (DKK1) is a widely expressed and potent tumor-associated antigen in multiple myeloma

The identification of novel tumor-associated antigens, especially those shared among patients, is urgently needed to improve the efficacy of immunotherapy for multiple myeloma (MM). In this study, we examined whether Dickkopf-1 (DKK1), a protein that is not expressed in most normal tissues but is expressed by tumor cells from almost all patients with myeloma, could be a good candidate. We identified and synthesized DKK1 peptides for human leukocyte antigen (HLA)-A*0201 and confirmed their immunogenicity by in vivo immunization in HLA-A*0201 transgenic mice. We detected, using peptidetetramers, low frequencies of DKK1 peptide-specific CD8-positive (CD8(+)) T cells in patients with myeloma and generated peptide-specific T-cell lines and clones from HLA-A*0201-positive (HLA-A*0201(+)) blood donors and patients with myeloma. These T cells efficiently lysed peptide-pulsed but not unpulsed T2 or autologous dendritic cells, DKK1-positive (DKK1(+))/HLA-A*0201(+) myeloma cell lines U266 and IM-9, and, more importantly, HLA-A*0201(+) primary myeloma cells from patients. No killing was observed on DKK1(+)/HLA-A*0201-negative (HLA-A*0201(-)) myeloma cell lines and primary myeloma cells or HLA-A*0201(+) normal lymphocytes, including B cells. These results indicate that these T cells were potent cytotoxic T cells and recognized DKK1 peptides naturally presented by myeloma cells in the context of HLA-A*0201 molecules. Hence, our study identifies DKK1 as a potentially important antigen for immunotherapy in MM.

OX40-ligand inhibits function of IL-10-producing intratumoral CD4+CD25+ regulatory T cells in human follicular B-cell lymphoma (50.25)

Recent studies showed that infiltrating T regulatory cells inhibit effector T-cell function in B-cell non-Hodgkin lymphomas. Therefore, it was suggested that strategies that inactivate or remove regulatory T-cell populations should be done in conjunction with established clinical protocols in B-cell lymphomas bearing patients. In the present study, we purified CD4+CD25−, CD4+CD25highICOS+ and CD4+CD25highICOS- cell subsets by flow cytometry from a follicular lymphoma patient. We examined their intracellular FoxP3 expression and determined their IL-10 secretion in cell supernatants under different conditions. The cell subsets were stimulated with anti-CD3 and anti-ICOS antibodies in the presence of IL-2 on parental L cells or OX40L-L cells. Cytokine production in supernatants was measured by ELISA. Both CD4+CD25highICOS+ and CD4+CD25highICOS- cells showed FoxP3+ expression by FACS analysis, while it was negative in CD4+CD25−. After 3 or 6 days of culture, only ICOS+ cells produced large amounts of IL-10 (470 and 3,250 pg/ml respectively) and OX40L dramatically inhibited this production (87 and 94% of inhibition). Immunohistochemistry staining demonstrated simultaneous expression of FoxP3 and ICOS on T-cells infiltrating B-cell lymphoma tissues. These results suggest that OX40L could be potentially used as a therapeutic agent to modulate T regulatory cells function in B-cell lymphoma patients.

A novel proteoliposomal vaccine elicits potent antitumor immunity in mice

Therapeutic vaccination against idiotype is a promising strategy for immunotherapy of B-cell malignancies. Its feasibility, however, is limited by the requirement for a patient-specific product. Here we describe a novel vaccine formulation prepared by simply extracting cell-membrane proteins from lymphoma cells and incorporating them together with IL-2 into proteoliposomes. The vaccine was produced in 24 hours, compared with more labor-intensive and time-consuming hybridoma or recombinant DNA methods. The vaccine elicited T-cell immunity in vivo, as demonstrated by secretion of type 1 cytokines. It protected against tumor challenge at doses of tumor antigen 50 to 100 times lower than that previously observed using either liposomes formulated with IL-2 and secreted lymphoma immunoglobulin or a prototype vaccine consisting of lymphoma immunoglobulin conjugated to keyhole limpet hemocyanin. The increased potency justifies testing similar patient-specific human vaccines prepared using extracts from primary tumor samples.

A novel proteoliposomal vaccine induces antitumor immunity against follicular lymphoma

Clinical studies suggest that treatment with vaccines comprised of idiotype protein may be associated with improved clinical outcome in follicular lymphoma patients. The time-consuming process required to generate patient-specific vaccines is a major limitation, however. Here we report results of a pilot clinical trial with a novel autologous, tumor-derived proteoliposome vaccine formulation that could be rapidly produced within a single day. Vaccination was safe, induced autologous tumor-specific type 1 cytokine responses in 5 out of 10 follicular lymphoma patients, and was associated with induction of a sustained complete response in one patient. Other patients had large tumor burdens and progressed after a median duration of 8 months. These results suggest that further testing of this vaccine formulation, particularly in the setting of minimal disease, is warranted. Furthermore, the proteoliposome formulation may provide a model for vaccine development for other human cancers, for which tumor-associated antigens need not be defined.

Therapeutic vaccine for lymphoma

The unique antigenic determinants (Idiotype [Id]) of the immunoglobulin expressed on a given B-cell malignancy can serve as a tumor-specific antigen for active immunotherapy. Therapeutic vaccines targeting the tumor-specific idiotype have demonstrated promising results against lymphomas in phase I/II studies and are currently being evaluated in phase III randomized trials. Additional vaccine therapies being developed include those based on DNA, dendritic cells, gene-modified tumor cells. It is hoped that immunotherapeutic agents, used in tandem or in combination, may in the future allow effective treatment of lymphoid malignancies and delay or even replace the need for conventional cytotoxic therapies.

Prognostic significance of serum B-lymphocyte stimulator level in Hodgkin's lymphoma

B-lymphocyte stimulator (BLyS) plays a critical role in the survival of B-lymphocytes. In 50 patients with Hodgkin's lymphoma BLyS levels were higher in newly diagnosed patients (median 2.0 ng/mL, range <0.3-56.0) and relapsed patients (8.7 ng/mL, range 1.5-71.5) than in 93 healthy donors (<0.3 ng/mL, range <0.3-0.5). High serum BLyS levels (> or =2.0 ng/mL) in newly diagnosed patients were associated with resistance to therapy (p=0.01) and shorter progression-free survival (log-rank p=0.029, 2-year rate 64% vs 100%). Serum BLyS levels may have prognostic significance in Hodgkin's lymphoma.

Experience with heat shock protein-peptide complex 96 vaccine therapy in patients with indolent non-Hodgkin lymphoma

BACKGROUND

The objective of this phase II trial was to investigate the safety and efficacy of autologous heat shock protein-peptide complex 96 (HSPPC-96) vaccines prepared from tumor specimens of patients with newly diagnosed or previously treated indolent non-Hodgkin lymphoma (NHL).

METHODS

The study was for patients with indolent B-cell NHL with measurable lesions. HSPPC-96 vaccines were prepared from patients' resected tumor specimens and administered as a 25-microg intradermal injection in the absence of disease progression every week for 4 weeks and then every 2 weeks until the vaccine supply was exhausted.

RESULTS

Twenty patients were enrolled in this trial. The median patient age was 59 years. Ten patients had been treated previously (median, 2 regimens; range, 1 to 7). Eighteen (90%) patients had stage III or IV disease. Autologous vaccines were successfully prepared for 17 (85%) patients and all received at least 1 dose. The treatment was very well tolerated. One patient experienced a response with biopsy-proven clearance of the lymphoma cells in 2 of the skin nodules at 3.0 months that lasted for 7.0 months. Eight patients had stable disease for 6.0 to 19.8 months. The median failure-free survival duration in patients who received vaccine therapy was 5.2 months.

CONCLUSIONS

HSPPC-96 can be prepared from tumor specimens for the majority of lymphoma patients, but it had limited efficacy in inducing responses in patients with active diseases. Further studies of HSPPCs, therefore, should be considered in adjuvant settings or in combination with other immunomodulatory agents to assess survival benefit.

Vaccine therapy for B-cell lymphomas: next-generation strategies

Active immunotherapy is a promising approach for the treatment of lymphomas. Immunization with the clonal tumor immunoglobulin, idiotype, expressed on the surface of B-cell malignancies was associated with induction of tumor-specific cellular and humoral immunity, molecular remissions, and prolonged disease-free survival in early clinical trials. Idiotype vaccination was also demonstrated to induce tumor-specific T-cell immunity in the absence of B cells following treatment with rituximab-containing chemotherapy, suggesting that vaccines may be used in combination with rituximab. Three double-blind randomized phase 3 idiotype vaccine trials are currently ongoing to definitively determine the clinical benefit of idiotype vaccination in patients with lymphoma. Novel second-generation lymphoma vaccines are in development to streamline the production of patient-specific cancer vaccines and show encouraging results in preclinical and pilot clinical studies. To enhance the clinical efficacy of active immunotherapy, future clinical trials are likely to use a combination strategy with the lymphoma vaccine to stimulate an antitumor T-cell response and the simultaneous suppression of immune regulatory pathways to augment the induced T-cell response.

Dose-related safety and immunogenicity of baculovirus-expressed trivalent influenza vaccine: a double-blind, controlled trial in adult patients with non-Hodgkin B cell lymphoma

In 27 patients randomized to receive commercial trivalent influenza vaccine (TIV) containing 15 microg of the hemagglutinin (HA) of influenza A (H3N2 and H1N1) and B virus or a recombinant vaccine (rHAO) containing 15, 45, or 135 microg of each HA, reactogenicity was minor. Among patients with similar prevaccination titers, 40% given 45 microg and 60% given 135 microg of rHAO developed an increase in influenza A/H3 neutralizing antibody levels; there were no increases in 4 given TIV. For each vaccine, the highest frequencies of increases in neutralizing antibody levels and the highest mean titers occurred in those given the 135- microg vaccine.

Targeting beta2-microglobulin for induction of tumor apoptosis in human hematological malignancies

We discovered that monoclonal antibodies (mAbs) specific to human beta(2)-microglobulin (beta(2)M) induce apoptosis in vitro and were therapeutic in mouse models of myeloma and other hematological tumor cells. Cell death occurred rapidly, without the need for exogenous immunological effector mechanisms. The mAbs induced cell death via recruiting MHC class I molecules to lipid rafts and activating Lyn and PLCgamma2, leading to activated JNK and inhibited PI3K/Akt and ERK, compromised mitochondrial integrity, and caspase-9-dependent cascade activation. Although the expression of beta(2)M on normal hematopoietic cells is a potential safety concern, the mAbs were selective to tumor-transformed cells and did not induce apoptosis of normal cells. Therefore, such mAbs offer the potential for a therapeutic approach to hematological malignancies.

Optimizing immunotherapy in multiple myeloma: Restoring the function of patients' monocyte-derived dendritic cells by inhibiting p38 or activating MEK/ERK MAPK and neutralizing interleukin-6 in progenitor cells

Previous studies demonstrated that circulating dendritic cells (DCs) in myeloma patients were functionally abnormal. However, the phenotype and function of patients' monocyte-derived DCs (MoDCs), which are commonly used for immunotherapy, were poorly defined. This study was undertaken to examine the quality of MoDCs from myeloma patients compared with cells from healthy donors. We found that patient-derived MoDCs are phenotypically and functionally defective. Compared with their normal counterparts, patient-derived, mature MoDCs expressed significantly lower levels of CD1a, CD40, CD80, and HLA-DR and were poor at activating alloreactive T cells, presenting recall antigen, and activating autologous antigen- and myeloma-specific T cells. These abnormalities may be attributed to elevated production of autocrine cytokines such as IL-6, activated p38 and STAT3, and inhibited MEK/ERK signaling pathways in the progenitor cells. Treatment with neutralizing IL-6-specific antibody and, more importantly, p38 inhibitor, or both, could correct these abnormalities. Treating patient-derived cells with these agents not only significantly increased cell yield but also produced MoDCs that were as functional as their normal counterparts. Thus, this study has delineated the mechanistic defects of MoDCs from myeloma patients and identified ways for restoring the function of the cells to improve the efficacy of DC-based immunotherapy in this disease.

Autocrine release of interleukin-9 promotes Jak3-dependent survival of ALK+ anaplastic large-cell lymphoma cells

The aberrant fusion protein NPM-ALK plays an important pathogenetic role in ALK+ anaplastic large-cell lymphoma (ALCL). We previously demonstrated that Jak3 potentiates the activity of NPM-ALK. Jak3 activation is restricted to interleukins that recruit the common gamma chain (gammac) receptor, including IL-9. NPM-ALK was previously shown to promote widespread lymphomas in IL-9 transgenic mice by unknown mechanisms. We hypothesized that IL-9 plays an important role in ALK+ ALCL via Jak3 activation. Our studies demonstrate the expression of IL-9Ralpha and IL-9 in 3 ALK+ ALCL-cell lines and 75% and 83% of primary tumors, respectively. IL-9 was detected in serum-free culture medium harvested from ALK+ ALCL-cell lines, supporting autocrine release of IL-9. Treatment of these cells with an anti-IL-9-neutralizing antibody decreased pJak3 and its kinase activity, along with pStat3 and ALK kinase activity. These effects were associated with decreased cell proliferation and colony formation in soft agar and cell-cycle arrest. Evidence suggests that cell-cycle arrest can be attributed to up-regulation of p21 and down-regulation of Pim-1. Our results illustrate that IL-9/Jak3 signaling plays a significant role in the pathogenesis of ALK+ ALCL and that it represents a potential therapeutic target for treating patients with ALK+ ALCL.

Prophylactic anti-tumor effects in a B cell lymphoma model with DNA vaccines delivered on polyethylenimine (PEI) functionalized PLGA microparticles

Idiotypic sequences, specific to the hypervariable regions of immunoglobulins expressed by malignant B cells offer a therapeutic target in B cell lymphoma. Efficient approaches have been described to clone a single chain fragment of the tumor immunoglobulin (Ig) comprising of heavy and light Ig chains (sFv) fused with proinflammatory chemokines. Tumor associated, poorly immunogenic self antigens encoded by plasmid DNA (pDNA) have been rendered immunogenic by chemokine fusion, thereby targeting to antigen presenting cells (APCs) which differentially express chemokine receptors. Here we present an injectable (parenteral) approach using synthetic polymer based cationic microparticle formulations for enhancing the potency of such chemokine/self antigen expressing plasmid construct. Branched and linear polyethyleneimine (PEI) were conjugated on poly (D, L lactide-co-glycolide) (PLGA) microparticles using carbodiimide chemistry followed by efficient loading of plasmid DNA. In addition to imparting significant buffering ability to these cationic microparticles, flow cytometry studies indicate that these DNA loaded microparticles significantly up regulate CD80 and MHC class II markers in phagocytic RAW264.7 cells, indicating intrinsic adjuvant effects. Intradermal injections in Balb/c mice with these formulations induced significant protection upon tumor challenge with 2.5 times the minimal lethal dose. Long term survival rates were significant (p < 0.05) in comparison with saline injected controls or blank microparticles. Further studies indicated that intramuscular delivery might provide better protection compared to intradermal injections and perform similar to gene gun mediated administration. We conclude, based on these promising in vivo results, that such surface-functionalized microparticles offer an attractive strategy to improve the potency of self antigen-based cancer DNA vaccines.

Cloning of B cell lymphoma-associated antigens using modified phage-displayed expression cDNA library and immunized patient sera

Active immunization of follicular lymphoma patients with idiotypic vaccines elicits antigen-specific antibody responses, T-cell responses, and antitumor effects. We hypothesized that these vaccinated patients could generate tumor-specific immune responses, not only against idiotype, but also against other tumor-associated antigens (TAA) by a mechanism of epitope spreading. To identify potential antigens, a phage surface expressed cDNA library derived from primary tumor cells was screened with sera from idiotype-vaccinated patients. Consistent with our hypothesis, we identified two immunogenic peptides (FL-aa-7 and 18), unrelated to idiotype, which were recognized by postvaccine sera but not by prevaccine or normal human sera. These peptide sequences derived from the 5'-untranslated regions of the human GTPase, IMAP family member 7 gene (FL-aa-7) and an alternative reading frame of U1-snRNP 70 (FL-aa-18), respectively, suggesting that epitope spreading had occurred.

Tumor evasion of the immune system: inhibiting p38 MAPK signaling restores the function of dendritic cells in multiple myeloma

Dendritic cells (DCs) from patients with cancer are functionally defective, but the molecular mechanisms underlying these defects are poorly understood. In this study, we used the murine 5TGM1 myeloma model to examine the effects and mechanisms of tumor-derived factors on the differentiation and function of DCs. Myeloma cells or tumor culture conditioning medium (TCCM) were shown to inhibit the differentiation and function of BM-derived DCs (BMDCs), as evidenced by the down-regulated expression of DC-related surface molecules, decreased IL-12, and compromised capacity of the cells to activate allospecific T cells. Moreover, TCCM-treated BMDCs were inferior to normal BMDCs at priming tumor-specific immune responses in vivo. Neutralizing antibodies against IL-6, IL-10, and TGF-beta partially abrogated the effects. TCCM treatment activated p38 mitogen-activated protein kinase (MAPK) and Janus kinase (JNK) but inhibited extracellular regulated kinase (ERK). Inhibiting p38 MAPK restored the phenotype, cytokine secretion, and function of TCCM-treated BMDCs. BMDCs from cultures with TCCM and p38 inhibitor was as efficacious as normal BMDCs at inducing tumor-specific antibody, type 1 T cell, and cytotoxic T lymphocyte (CTL) responses and at prolonging mouse survival. Thus, our results suggested that tumor-induced p38 MAPK activation and ERK inhibition in DCs may be a new mechanism for tumor evasion and that regulating these pathways during DC differentiation provides new strategies for generating potent DC vaccines for immunotherapy in patients with cancer.

Tumor antigen immunization of sibling stem cell transplant donors in multiple myeloma

The unique antigenic determinants (idiotype (Id)) of the immunoglobulin secreted by myeloma tumor can serve as a tumor-specific antigen for active immunotherapy. Our objective was to induce tumor-specific T-cell immunity in bone marrow transplant (BMT) donors to enhance antitumor effects of allografts. We vaccinated five HLA-matched sibling donors with myeloma Id proteins isolated from recipient plasma before bone marrow harvest. Recipients were administered booster Id immunizations following transplantation. Vaccination induced donor Id and carrier-specific cellular and/or humoral immune responses. Two recipients died within 30 days of BMT from transplant-related complications. Id and carrier-specific T-cell responses were detected in all three remaining patients post-, but not pre-BMT and persisted for 18 months. All three surviving patients converted from partial to complete responses following BMT. Two of the three patients remain disease-free 7 years and 8 years after BMT, and the third died of renal failure after 5.5 years while in complete remission from myeloma. Our results suggest that myeloma Id vaccination induces specific T-cell immunity in healthy donors which may be transferable by BMT, is associated with prolonged disease-free survival of recipients, and may represent a general strategy to enhance graft-versus-tumor effect in other malignancies for which defined tumor-specific antigens exist.

Human autologous tumor-specific T-cell responses induced by liposomal delivery of a lymphoma antigen

PURPOSE

The idiotype (Id) of the immunoglobulin on a given B-cell malignancy is a clonal marker that can serve as a tumor-specific antigen. We developed a novel vaccine formulation by incorporating Id protein with liposomal lymphokine that was more potent than a prototype, carrier-conjugated Id protein vaccine in preclinical studies. In the present study, we evaluated the safety and immunogenicity of this vaccine in follicular lymphoma patients.

EXPERIMENTAL DESIGN

Ten patients with advanced-stage follicular lymphoma were treated with five doses of this second generation vaccine after chemotherapy-induced clinical remission. All patients were evaluated for cellular and humoral immune responses.

RESULTS

Autologous tumor and Id-specific type I cytokine responses were induced by vaccination in 10 and 9 patients, respectively. Antitumor immune responses were mediated by both CD4+ and CD8+ T cells, were human lymphocyte antigen class I and II associated, and persisted 18 months beyond the completion of vaccination. Specific anti-Id antibody responses were detected in four patients. After a median follow-up of 50 months, 6 of the 10 patients remain in continuous first complete remission.

CONCLUSIONS

This first clinical report of a liposomal cancer vaccine demonstrates that liposomal delivery is safe, induces sustained tumor-specific CD4+ and CD8+ T-cell responses in lymphoma patients, and may serve as a model for vaccine development against other human cancers and infectious pathogens.

Vaccine-induced tumor-specific immunity despite severe B-cell depletion in mantle cell lymphoma

The role of B cells in T-cell priming is unclear, and the effects of B-cell depletion on immune responses to cancer vaccines are unknown. Although results from some mouse models suggest that B cells may inhibit induction of T cell-dependent immunity by competing with antigen-presenting cells for antigens, skewing T helper response toward a T helper 2 profile and/or inducing T-cell tolerance, results from others suggest that B cells are necessary for priming as well as generation of T-cell memory. We assessed immune responses to a well-characterized idiotype vaccine in individuals with severe B-cell depletion but normal T cells after CD20-specific antibody-based chemotherapy of mantle cell lymphoma in first remission. Humoral antigen- and tumor-specific responses were detectable but delayed, and they correlated with peripheral blood B-cell recovery. In contrast, vigorous CD4(+) and CD8(+) antitumor type I T-cell cytokine responses were induced in most individuals in the absence of circulating B cells. Analysis of relapsing tumors showed no mutations or change in expression of target antigen to explain escape from therapy. These results show that severe B-cell depletion does not impair T-cell priming in humans. Based on these results, it is justifiable to administer vaccines in the setting of B-cell depletion; however, vaccine boosts after B-cell recovery may be necessary for optimal humoral responses.

Therapeutic idiotype vaccines in B lymphoproliferative diseases

The recognition of the surface immunoglobulin protein of the tumour B cells as a specific tumour antigen has prompted the development of vaccination strategies aimed at the induction of humoral and cellular antitumour responses. Results obtained in preclinical models of B lymphoproliferative diseases, as well as in initial clinical trials, have shown the immunogenic potential of the idiotype (Id) when administered in association with proper adjuvants. The definitive evidence for clinical efficacy of this therapeutic approach awaits ongoing randomised Phase III studies. Research efforts at present include identification of new vaccination settings to improve the clinical benefit of vaccine treatment, the establishment of more convenient methods to produce individual Id vaccines and the development of new strategies of vaccination, including genetic vaccination.

Organic solvent extraction of proteins and peptides from serum as an effective sample preparation for detection and identification of biomarkers by mass spectrometry

A method to extract peptides and low molecular weight proteins from serum under denaturing conditions using acetonitrile containing 0.1% trifluoroacetic acid has been developed. The extraction procedure precipitates large, abundant proteins to simplify subsequent mass spectral analysis. This sample preparation method provides an efficient way to extract serum peptides, enabling them to be compared and identified using different mass spectrometry approaches. Surface-enhanced laser desorption/ionization-time of flight mass spectrometry analysis of mouse blood serum samples prepared by this method allowed detection of two markers which were significantly reduced in mice with B cell lymphoma tumor. One of these markers has been identified as apolipoprotein A-II.

Chemokine receptor-mediated delivery directs self-tumor antigen efficiently into the class II processing pathway in vitro and induces protective immunity in vivo

Nonimmunogenic antigens can be efficiently rendered immunogenic by targeting them to antigen-presenting cells via differentially expressed chemokine receptors. For example, self-tumor or HIV antigens genetically fused with proinflammatory chemoattractants elicit potent immune responses and protective antitumor immunity in mice. Herein we demonstrate that the mechanism by which chemokine fusions elicit responses is efficient uptake, processing, and presentation of antigens via the major histocompatibility complex class II pathway. Experiments with inhibitors of intracellular trafficking suggest that chemoattractant fusion proteins, but not antigen alone, were processed and presented through early/late endosomal and Golgi compartments and stimulated antigen-specific CD4+ T cells both in vitro and in vivo. Chemokine fusion also facilitated the presentation of antigen by dendritic cells to an autologous human tumor-specific CD4+ T-cell line. Taking advantage of chemokine redundancy, viral chemokine fusions were equally potent in inducing protective immunity in vivo, providing a possible strategy to circumvent hypothetical, vaccine-induced antihost chemokine autoimmunity, for example, by use of viral chemoattractants in humans.

Autoreactive, cytotoxic T lymphocytes specific for peptides derived from normal B-cell differentiation antigens in healthy individuals and patients with B-cell malignancies

PURPOSE

To investigate potential immunotherapeutic strategies in B lymphocytic malignancies we looked for CTLs recognizing CD19 and CD20 epitopes.

EXPERIMENTAL DESIGN

Three CD19 and CD20 peptides binding to HLA-A*0201 were identified and used to detect peptide specific CTLs by a quantitative real-time PCR to measure IFN-gamma mRNA expression in 23 healthy individuals and 28 patients (18 chronic lymphocytic leukemia (CLL), 7 follicular lymphoma, 2 acute lymphocytic leukemia, and 1 large cell lymphoma). Peptide-specific CTLs were expanded in culture with CD40-activated B cells to test lytic activity in three patients.

RESULTS

In healthy individuals, CD8+ T-cell responses were detected in one to CD19(74-82), in three to CD20(127-135), and three to CD20(188-196). Seven of 27 patients (6 with CLL) had CD8+ T cells recognizing CD19(74-82). Seven patients responded to CD20(127-135) and three to CD20(188-196). All were CLL patients. CD19(74-82)-specific CTLs from three patients were expanded over 4 weeks. These cells were HLA-A*0201 specific and lytic for peptide-loaded antigen-presenting cells but not to malignant or unpulsed B cells.

CONCLUSIONS

CTLs that recognize CD19 and CD20 epitopes exist in healthy individuals and may be increased in CLL patients. They are of low avidity and require high doses of peptide for activation. Strategies to increase T-cell avidity would be necessary for T-cell immunotherapeutic approaches using the peptides studied.

Autologous lymphoma vaccines induce human T cell responses against multiple, unique epitopes

The clonotypic surface Ig receptor expressed by malignant B cells, idiotype, is a tumor-specific antigen and an attractive target for active immunotherapy. While Ab's specific for tumor idiotype have been well described in patients with B cell malignancies, the precise antigenic epitopes in human idiotype recognized by autologous T cells remain largely unknown. We report here that T cell lines generated from lymphoma patients actively immunized with idiotype protein specifically recognized multiple, unique immunodominant epitopes in autologous tumor idiotype. Synthetic peptides corresponding to hypervariable, but not framework, regions of Ig heavy chain specifically stimulated CD4(+) and CD8(+) T cells to proliferate and secrete proinflammatory cytokines in an MHC-associated manner. Detailed analysis revealed a minimal determinant of an immunodominant epitope, comprising critical residues at the amino terminus that may be a product of somatic hypermutation. Association of idiotype-specific T cell responses with previously documented molecular remissions in idiotype-vaccinated patients suggests that the newly identified T cell epitopes may be clinically relevant. Such antigenic epitopes may serve as candidates for novel peptide-vaccine strategies, and as tools to selectively expand tumor antigen-specific T cells for adoptive immunotherapy and for monitoring T cell immunity in vaccinated patients.

Genetic fusions with viral chemokines target delivery of nonimmunogenic antigen to trigger antitumor immunity independent of chemotaxis

The ideal vaccine carrier should be able to target antigen delivery and possibly recruit antigen-presenting cells (APC) and deliver an activation signal to promote adaptive immune responses. Ligands for chemokine receptors expressed on APC may be attractive candidates, as they can both target and attract APC. To investigate the requirement for APC recruitment, we used a pair of viral chemokines, agonist herpes simplex virus 8-derived macrophage inflammatory protein-I (vMIP-I) and antagonist MC148, which induce and suppress chemotaxis, respectively. Chemokine-antigen fusions efficiently delivered a model nonimmunogenic tumor antigen to APC for processing and presentation to antigen-specific T cells in vitro. Physical linkage of chemokine and antigen and specific binding of chemokine receptor by the fusion protein were required. Mice immunized with vMIP-I or MC148 fusion DNA vaccines elicited protection against tumor challenge. Therefore, vaccine efficacy depends primarily on the ability of the carrier to target antigen delivery to APC for subsequent processing and presentation, and chemotaxis directly induced by the chemokine moiety in the fusion may not be necessary.

A modified human ELISPOT assay to detect specific responses to primary tumor cell targets

Background

The desired outcome of cancer vaccination is to induce a potent T cell response which can specifically recognize and eliminate autologous tumor cells in vivo. Accordingly, immunological assays that demonstrate recognition of native tumor cells (tumor-specific) may be more clinically relevant than assays that demonstrate recognition of tumor protein or peptide (antigen-specific).

Methods

Towards this goal, we adapted the IFN-γ ELISPOT assay to measure immune responses against autologous primary tumor cells in vaccinated cancer patients. As a model system to develop the assay, we utilized peripheral blood mononuclear cells (PBMC) directly isolated from follicular lymphoma patients vaccinated with tumor-derived idiotype protein.

Results

After optimizing several variables, we demonstrated that the modified IFN-γ ELISPOT assay could be used to reliably and reproducibly determine the tumor-reactive T cell frequency in the PBMC of these patients. The precursor frequency of tumor-reactive T cells was significantly higher in the postvaccine PBMC, compared with prevaccine samples in all patients tested. Furthermore, the specificity of these T cells was established by the lack of reactivity against autologous normal B cells.

Conclusions

These results demonstrate the feasibility of quantitating tumor-specific T cell responses when autologous, primary tumor cells are available as targets.

Adoptive immunotherapy with antigen-specific T cells in myeloma: a model of tumor-specific donor lymphocyte infusion

Although partial remissions rates of up to 60% are obtained with conventional therapeutic regimens, multiple myeloma is essentially an incurable disease with a median survival of approximately 30 months. Allogeneic stem cell transplantation (SCT) results in a high percentage of complete remissions (CRs), but it can be associated with significant treatment-related mortality. Recent clinical studies have shown that highly immunosuppressive, yet nonmyeloablative, doses of fludarabine-based chemotherapy can result in alloengraftment. However, even with a reduction in treatment-related mortality, success with allogeneic SCT is limited by the significant risk of relapse. The goal of the strategy described is to transfer tumor antigen-specific immunity induced in the stem cell donor to the allogeneic SCT recipient to reduce relapse. Donors are immunized with a well-defined vaccine, specific for the patient's tumor. The allogeneic SCT is performed with a conditioning regimen consisting of cyclophosphamide and fludarabine, and the stem cell source is blood mobilized with filgrastim, which could potentially enhance the transfer of a larger number of tumor-specific T cells in the allograft, as compared to bone marrow. Donor immunization with myeloma idiotype protein in the setting of a nonmyeloablative SCT may represent a novel strategy for the treatment of myeloma.

Similarities of prosurvival signals in Bcl-2-positive and Bcl-2-negative follicular lymphomas identified by reverse phase protein microarray

Overexpression of Bcl-2 protein has been known to play a role in the pathogenesis of follicular lymphoma (FL). However, 10-15% of FLs are negative for Bcl-2 by immunohistochemistry, raising the possibility that another gene product(s) may provide prosurvival signal(s). We used reverse phase protein microarray to analyze lysates of follicle center cells isolated by laser capture microdissection from: Bcl-2+ FL, Bcl-2- FL and reactive follicular hyperplasia (FH) (nine cases each group). TUNEL assay confirmed similar and reduced levels of apoptosis in Bcl-2+ FL and Bcl-2- FL, indicating the likelihood of Bcl-2-independent inhibition of apoptosis. Arrays were quantitatively analyzed with antibodies to proteins involved in the apoptotic pathway. As expected, Bcl-2 levels were up to eight-fold higher in Bcl-2+ FL than in FH and Bcl-2- FL. However, there was no difference in levels of Mcl-1 and survivin among these three groups. Bcl-X(L) showed a trend for increased expression in Bcl-2- FL as compared with Bcl-2+ FL, although the differences did not reach statistical significance (P>0.1). The increase in Bcl-X(L) may provide an alternative antiapoptotic signal in FL negative for Bcl-2 protein. Interestingly, Bax expression was higher in FL (Bcl-2+ or -) than in FH (P=0.001). Notably, phospho-Akt (Ser-473) was increased in FL (Bcl-2+ or -) (P<0.03) with increased phospho-Bad (Ser-136), as compared with levels in FH. The activation of the Akt/Bad pathway provides further evidence of prosurvival signals in FL, independent of Bcl-2 alone. These data suggest that nodal FL represents a single disease with a final common biochemical pathway.

Roles of antimicrobial peptides such as defensins in innate and adaptive immunity

A number of antimicrobial peptides such as defensins have multiple functions in host defence. Defensins are produced not only by phagocytic cells and lymphocytes, but also by the epithelial cell lining of the gastrointestinal and genitourinary tracts, the tracheobronchial tree, and keratinocytes. Some are produced constitutively, whereas others are induced by proinflammatory cytokines and exogenous microbial products. Defensins produced by cells in the course of innate host defence serve as signals which initiate, mobilise, and amplify adaptive immune host defences. Administration of defensins with antigens to mice enhances both cellular (Th1-dependent) and humoral (Th2-dependent) cytokine production and immune responses. Linkage of defensins to weak tumour antigens potentiates their immunoadjuvant effects. Defensins use multiple cellular receptors, which endows them with the capacity to marshall adaptive host defences against microbial invaders.

Vaccination strategies for lymphomas

Vaccination strategies for lymphomas were developed along with one of the first recognized tumor-specific targets, the clonal antigen receptor, composed of unique variable regions known as idiotypes. Human clinical trials of idiotype vaccination have benefited from highly concordant animal models, leading to sequential improvements in design. Evidence of the clinical benefit of idiotype vaccines is strong but formally unproven. Significant progress has been made in our understanding of the basic mechanisms underlying the induction of immune responses, which has led to a proliferation of rationally designed immunotherapeutic strategies. Current research efforts include the development of more convenient methods to produce individual idiotype vaccines, the establishment of definitive proof for clinical efficacy, and the implementation of alternative vaccination strategies, including genetic vaccination and genetically or immunologically modified autologous tumor cells and dendritic cells.

In vitro priming of myeloma antigen-specific allogeneic donor T cells with idiotype pulsed dendritic cells

In vitro priming of T cells with dendritic cells (DC) pulsed with clinically relevant, but weak antigens such as tumor idiotype (Id), is an attractive strategy to generate tumor-specific T lymphocytes. In order to enhance the specific antitumor effect of allogeneic stem cell grafts, we investigated whether induction of tumor specific T cells using autologous DC pulsed with patient's myeloma Id could be maintained and potentiated by in vitro priming. For induction of T cells, DC (5 x 10(5)/well) were cultured with autologous nonadherent cells (DoNA) (5 x 10(6)/well) and antigen (TT10 microg/ml, KLH 100 microg/ml and Id 100 microg/ml). The T cells were restimulated every 8-10 days with the corresponding antigen and autologons DC. After 2-4 cycles of in vitro priming, the T cells were compared with nonadherent cells obtained after 2h attachment on day 0 (DoNA) for antigen-specific cytokine production. In vitro primed T cells (2-4 cycles of stimulation with Ag and DC) showed significant antigen-specific cytokine responses (IFN-gamma, TNF-alpha, GM-CSF) to TT. Similarly, in vitro priming of T cells to Id-pulsed DC resulted in marked increases in cytokine production for both myeloma Id proteins tested. These data suggest that multiple in vitro immunization using DC could be beneficial in generating tumor specific T cells from normal donor PBMC, which may be used for adoptive immunotherapy (e.g. "tumor-specific" donor lymphocyte infusion) of B cell malignancies. In vitro immunization may also offer an alternative to immunization of healthy stem cell transplant donors with tumor antigen.