Natural cytotoxicity to autologous antigen-pulsed dendritic cells in multiple myeloma

Enhanced activation and expansion of T cells using mechanically soft elastomer fibers

Practical deployment of cellular therapies requires effective platforms for producing clinically relevant numbers of high-quality cells. This report introduces a materials-based approach to improving activation and expansion of T cells, which are rapidly emerging as an agent for treating cancer and a range of other diseases. Electrospinning is used to create a mesh of poly(ε-caprolactone) fibers, which is used to present activating ligands to CD3 and CD28, which activate T cells for expansion. Incorporation of poly(dimethyl siloxane) elastomer into the fibers reduces substrate rigidity and enhances expansion of mixed populations of human CD4+ and CD8+ T cells. Intriguingly, this platform also rescues expansion of T cells isolated from CLL patients, which often show limited responsiveness and other features resembling exhaustion. By simplifying the process of cell expansion, compared to current bead-based platforms, and improving T cell expansion, the system introduced here may accelerate development of cellular immunotherapy.

Improving T Cell Expansion with a Soft Touch

Protein-coated microbeads provide a consistent approach for activating and expanding populations of T cells for immunotherapy but do not fully capture the properties of antigen presenting cells. In this report, we enhance T cell expansion by replacing the conventional, rigid bead with a mechanically soft elastomer. Polydimethylsiloxane (PDMS) was prepared in a microbead format and modified with activating antibodies to CD3 and CD28. A total of three different formulations of PDMS provided an extended proliferative phase in both CD4+-only and mixed CD4+-CD8+ T cell preparations. CD8+ T cells retained cytotoxic function, as measured by a set of biomarkers (perforin production, LAMP2 mobilization, and IFN-γ secretion) and an in vivo assay of targeted cell killing. Notably, PDMS beads presented a nanoscale polymer structure and higher rigidity than that associated with conventional bulk material. These data suggest T cells respond to this higher rigidity, indicating an unexpected effect of curing conditions. Together, these studies demonstrate that adopting mechanobiology ideas into the bead platform can provide new tools for T cell based immunotherapy.

Immunotherapy of multiple myeloma: the start of a long and tortuous journey

The field of tumor immunotherapy is still in its infancy. It is becoming clear that the human immune response is the result of highly complex, continuously evolving interactions between cells of the adaptive and innate arms of the immune system, the internal and external environments, and normal and abnormal cells (e.g., myeloma plasma cells). Despite the considerable advances in our knowledge over the past 30 years, we have still only scratched the surface of the immune system's interaction with malignant diseases such as myeloma and to date, this has not translated into significantly better outcomes for patients with this disease. This review will summarize our current knowledge of the fundamental immunology of myeloma, review immunotherapy trials reported to date and discuss whether, in light of the current information, immunotherapy of multiple myeloma is an achievable goal.

Immunology and immunotherapeutic approaches in multiple myeloma

Immunotherapy for patients suffering from multiple myeloma is a lively and emerging field in cancer research. Immunotherapeutic approaches offer unique treatment opportunities for this, to date, mostly incurable disease. Respective basic findings and recent clinical approaches are introduced and discussed. Although several obstacles still need to be overcome, it appears that clinically efficient immunotherapies will become available for multiple myeloma patients in the future.

Drug-mediated and cellular immunotherapy in multiple myeloma

Multiple myeloma is an immunologically relevant disease, which subverts and suppresses immunity, but that may also be amenable to immunological control. Novel drug and cell-based therapies provide an opportunity for the design of antimyeloma immunotherapy. Reversing the immunosuppression associated myeloma remains a substantial challenge. The minimal residual disease setting achieved by autologous stem cell transplant or highly efficacious induction therapy may reverse this immunoparesis and provide a setting for induction of antimyeloma T-cell responses. Adoptive cytotoxic T-lymphocyte/NK therapy and comprehensive treatment with immunomodulatory drug therapy represent means by which antimyeloma immune responses may be promoted. In addition, apoptosis-inducing therapies may prime endogenous antigen presentation via immunogenic cell death, which again may be enhanced by the addition of immunomodulatory drug therapy.

The proteasome inhibitor bortezomib disrupts tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression and natural killer (NK) cell killing of TRAIL receptor-positive multiple myeloma cells

Bortezomib, a potent 26S proteasome inhibitor, is approved for the treatment of multiple myeloma (MM) and clinical trials are under way to evaluate its efficacy in other malignant diseases. However, cytotoxic effects of bortezomib on immune-competent cells have also been observed. In this study, we show that bortezomib downregulates cell surface expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on primary human interleukin (IL)-2-activated natural killer (NK) cells. Pharmacological inhibition of the transcription factor, NF-kappaB also profoundly decreased TRAIL expression, suggesting that NF-kappaB is involved in the regulation of TRAIL expression in activated human NK cells. Furthermore, perforin-independent killing of the human MM cell lines RPMI8226 and U266 by NK cells was markedly suppressed following bortezomib treatment. In addition, blocking cell surface-bound TRAIL with a TRAIL antibody impaired NK cell-mediated lysis of the TRAIL-sensitive MM cell line, RPMI8226. In conclusion, the proteasome is likely to be involved in the regulation of TRAIL expression in primary human IL-2-activated NK cells. Proteasome inhibition by bortezomib disrupts TRAIL expression and TRAIL dependent and/or independent pathway-mediated killing of myeloma cells, suggesting that bortezomib may potentially hamper NK-dependent immunosurveillance against tumors in patients treated with this drug.

Proteasome inhibition induces apoptosis in primary human natural killer cells and suppresses NKp46-mediated cytotoxicity

BACKGROUND

Bortezomib is a selective and potent inhibitor of the proteasome and has prominent effects in vitro and in vivo against tumors. Very recently, cytotoxic effects of bortezomib on immune-competent cells such as T cells and dendritic cells were also revealed. The aim of the study was to investigate the effects of this agent on natural killer cell survival and function.

DESIGN AND METHODS

We investigated cytotoxic properties of bortezomib on natural killer cell apoptosis and function. Primary resting natural killer cells were purified from peripheral blood mononuclear cells of healthy donors by negative selection. The apoptotic cells were quantified by dual labeling of recombinant annexin V and propidium iodide. Mitochondrial membrane potential and expression of natural killer cell activating receptors were also quantified by flow cytometry. Natural killer cell cytotoxicity against murine and human tumor cells was tested by chromium 51 release assay.

RESULTS

Our results demonstrate that bortezomib induces apoptosis in resting natural killer cells in a dose- and time-dependent manner. Glutathione, a reactive oxygen species scavenger, prevented the loss of mitochondrial membrane potential and conferred protection against bortezomib-induced apoptosis in resting natural killer cells, indicating a role for oxidative stress. Additionally, bortezomib significantly decreased expression of the natural killer activating receptor NKp46 in non-apoptotic resting natural killer cells in a dose-dependent manner, and as a result the redirected cytotoxicity mediated via NKp46 activation was diminished. Bay 11-7082, a pharmacological inhibitor of NF-kappaB activation, also reduced NKp46 expression and suppressed redirected cytotoxicity.

CONCLUSIONS

Bortezomib induces apoptosis in primary resting natural killer cells in a dose- and time-dependent manner, and reduces NKp46 receptor expression as well as natural killer cell cytotoxicity mediated by the NKp46 activation pathway, suggesting that bortezomib may disrupt natural killer cell-mediated immunity through at least two different mechanisms: induction of natural killer cell apoptosis, and suppression of NKp46 receptor-mediated cytotoxicity.

Adoptive transfer of pTRP2-specific CTLs expanding by bead-based artificial antigen-presenting cells mediates anti-melanoma response

Cytotoxic CD8(+) T cells are key effectors in the immunotherapy of malignant and viral diseases. However, the lack of efficient methods for their in vitro priming and expansion has become a bottleneck to the development of vaccines and adoptive transfer strategies. Synthetic artificial antigen-presenting cells (aAPCs) are now emerging as an attractive tool for eliciting and expanding CTL responses. This study reported a novel approach for targeting malignant melanoma with pTRP2-specific cytotoxic T lymphocytes (CTLs) expanded from the C57BL/6 splenocytes by multiple stimulations with aAPCs made by coating H-2K(b)-Ig/pTRP2 dimeric complexes, anti-CD28 antibody, 4-1BBL molecules and CD83 molecules to cell-sized latex beads. The induced CTLs exhibited specific lysis against RMA-S cells pulsed with the peptide pTRP2 and H-2K(b+) melanoma cells expressing TRP2, while a murine Lewis lung carcinoma cell line 3LL could not be recognized by the CTLs. The peptide-specific activity was inhibited by anti-H-2K(b) monoclonal antibody Y3. Adoptive Transfer of CTLs specific for malignant melanoma expanding by the aAPCs can mediate effective anti-melanoma response. These results suggested the bead-based aAPCs coated with an MHC-Ig/peptide complex, anti-CD28 antibody, 4-1BBL and CD83 could provide a useful tool for the reproducible expansion of specific CTLs for adoptive immunotherapy.

Expansion of immunoglobulin autoreactive T-helper cells in multiple myeloma

Activation and expansion of T helper (Th) cells followed by regulation of activation are essential to the generation of immune responses while limiting concomitant autoreactivity. In order to characterize T cells reactive towards myeloma-derived monoclonal immunoglobulin (mIg), an autologous coculture assay for single-cell analysis of mIg-responding cells was developed. When cultured with dendritic cells loaded with mIg, CD4(+) Th cells from patients with progressing multiple myeloma (MM) showed a proliferative MHC class II-dependent response. CD8(+) T-cell reactivity and Th1 activation were consistently low or absent, and Th2 and regulatory cytokines were expressed. The presence of such non-Th1 CD4(+) T cells in peripheral blood was independent of treatment status, while the frequencies of responding cells varied between patients and reached the same order of magnitude as those measured for tetanus toxoid-specific Th memory cells. Furthermore, investigations of T-cell subpopulations indicated a possible regulatory role on the mIg responsiveness mediated by suppressive CD25(high)FOXP3(+)CD4(+) T cells. It is proposed from the present results that a predominant in vivo activation of non-Th1 mIg-reactive CD4(+) T cells constitute an Ig-dependent autoregulatory mechanism in human MM, with possible tumor growth supporting or permissive effects.

Immunotherapy in multiple myeloma - possibility or probability?

In a small number of patients with multiple myeloma (MM), long-term disease-free survival has been achieved by harnessing the immune phenomenon, 'graft-versus-tumour' effect, induced by allogeneic haemopoietic stem cell transplantation. This has prompted many investigators to examine ways in which a patient's own immune system can be more effectively directed against their disease, with the ultimate aim of tumour eradication. In this review we assess the current understanding of immunobiology in MM, and how the different components of the immune system, such as dendritic cells, T cells and natural killer cells, may be harnessed using in-vitro and in-vivo priming techniques. We look at the clinical immunotherapy trials reported to date and whether, in light of the current information, immunotherapy for MM is an achievable goal.

Workshop on Cancer Biometrics: Identifying Biomarkers and Surrogates of Cancer in Patients

The current excitement about molecular targeted therapies has driven much of the recent dialog in cancer diagnosis and treatment. Particularly in the biologic therapy of cancer, identifiable antigenic T-cell targets restricted by MHC molecules and the related novel stress molecules such as MICA/B and Letal allow a degree of precision previously unknown in cancer therapy. We have previously held workshops on immunologic monitoring and angiogenesis monitoring. This workshop was designed to discuss the state of the art in identification of biomarkers and surrogates of tumor in patients with cancer, with particular emphasis on assays within the blood and tumor. We distinguish this from immunologic monitoring in the sense that it is primarily a measure of the tumor burden as opposed to the immune response to it. Recommendations for intensive investigation and targeted funding to enable such strategies were developed in seven areas: genomic analysis; detection of molecular markers in peripheral blood and lymph node by tumor capture and RT-PCR; serum, plasma, and tumor proteomics; immune polymorphisms; high content screening using flow and imaging cytometry; immunohistochemistry and tissue microarrays; and assessment of immune infiltrate and necrosis in tumors. Concrete recommendations for current application and enabling further development in cancer biometrics are summarized. This will allow a more informed, rapid, and accurate assessment of novel cancer therapies.

Interaction of dendritic cells with antigen-containing liposomes: effect of bilayer composition

Vaccine efficacy might be improved by exploiting the potent antigen presenting properties of dendrite cells (DCs), since their ability to stimulate specific major histocompatibility complex-restricted immune responses has been well documented during the recent years. In that light, we investigated how the interaction of antigen-containing liposomes with DCs was affected by the bilayer composition. Monocyte-derived human DCs and murine bone marrow-derived DCs were analysed and compared upon in vitro incubation with liposomes by flow cytometry and confocal microscopy. Anionic liposomes with a bilayer composition of phosphatidylcholine, cholesterol and phosphatidylglycerol or phosphatidylserine interacted with a limited fraction of the total DC population in case of both DC types. Inclusion of mannosylated phosphatidylethanolamine (Man-PE) for targeting to the mannose receptor (MR) increased the interaction of negatively charged liposomes with both human and murine DCs. This increase could be blocked in human DCs by addition of the polysaccharide mannan indicating that uptake might be mediated by the mannose receptor. Cationic liposomes containing trimethyl ammonium propane interacted with a very high percentage of both DC types and could be detected in high amounts intracellularly. In conclusion, liposome bilayer composition has an important effect on interaction with DCs and might be critical for the vaccination outcome.

Dendritic cells mediate NK cell help for Th1 and CTL responses: two-signal requirement for the induction of NK cell helper function

Early stages of viral infections are associated with local recruitment and activation of dendritic cells (DC) and NK cells. Although activated DC and NK cells are known to support each other's functions, it is less clear whether their local interaction in infected tissues can modulate the subsequent ability of migrating DC to induce T cell responses in draining lymph nodes. In this study, we report that NK cells are capable of inducing stable type 1-polarized "effector/memory" DC (DC1) that act as carriers of NK cell-derived helper signals for the development of type 1 immune responses. NK cell-induced DC1 show a strongly elevated ability to produce IL-12p70 after subsequent CD40 ligand stimulation. NK-induced DC1 prime naive CD4+ Th cells for high levels of IFN-gamma, but low IL-4 production, and demonstrate a strongly enhanced ability to induce Ag-specific CD8+ T cell responses. Resting NK cells display stringent activation requirements to perform this novel, DC-mediated, "helper" function. Although their interaction with K562 cells results in effective target cell killing, the induction of DC1 requires a second NK cell-activating signal. Such costimulatory signal can be provided by type I IFNs, common mediators of antiviral responses. Therefore, in addition to their cytolytic function, NK cells also have immunoregulatory activity, induced under more stringent conditions. The currently demonstrated helper activity of NK cells may support the development of Th1- and CTL-dominated type 1 immunity against intracellular pathogens and may have implications for cancer immunotherapy.