Immune regulation in multiple myeloma: the host-tumour conflict

Regulatory T-Cells and Multiple Myeloma: Implications in Tumor Immune Biology and Treatment

Multiple myeloma (MM) is associated with both cellular and humoral immune deficiencies and, despite significant advances in treatment, remains an incurable disease. Regulatory T-cells (Tregs) represent a critical subset of CD4 T-cells, characterized by CD4 + CD25+ Forkhead box P3+ (FoxP3+) phenotype, able to control peripheral tolerance and responses to foreign and tumor antigens. Tregs are elevated in various types of cancer, including hematological malignancies; in MM, data regarding Tregs function and numbers and their correlation with survival parameters are controversial. Advances in cancer biology have shown that the tumor microenvironment plays an important role in tumor progression. In MM, the highly immunosuppressive nature of the bone marrow microenvironment has been significantly elucidated in the past decade and it is now well acknowledged that targeting only the tumor clone may not be able to cure MM. Tregs within the tumor microenvironment might play a significant role in the suppression of antitumor immune responses against cancer cells and are considered to predict poor outcome in cancer patients; nonetheless the exact prognostic significance of this cell subpopulation in malignancies is still a matter of debate. In this review, we discuss the role of Tregs as an essential cell population of the MM immune microenvironment.

Assessment of infection in newly diagnosed multiple myeloma patients: risk factors and main characteristics

Background

Infection is a leading cause of morbidity and death in patients with multiple myeloma (MM). The increased susceptibility to infection is complicated and multifactorial. However, no studies have explored the spectrum and risk factors of infections in newly diagnosed MM patients at the first admission. This cross-sectional study aimed to provide ideas for the assessment, prevention and treatment of infection in newly diagnosed MM patients when admitted for the first time.

Methods

Retrospectively, the data from electronic medical records for 161 patients newly diagnosed with MM from May 2013 to December 2018 were analysed. All the information was collected at the time of admission, and the patients had received no antineoplastic therapy previously. Independent risk factors of infection in multiple myeloma were determined by univariate and multivariate analysis.

Results

Newly diagnosed patients with MM were highly susceptible to viruses (43.9%), especially Epstein-Barr virus (EBV) (24.4%) and hepatitis B virus (HBV) (17.1%). Advanced stage (ISS stage III, P = 0.040), more severe anaemia (Hb < 90 g/L, P = 0.044) and elevated CRP (> 10 mg/L, P = 0.006) were independent risk factors for infection. Moreover, infections represented a major survival threat to patients with newly diagnosed MM (P = 0.033), and the existence of risk factors for infection was significantly correlated with poor prognosis (P = 0.011), especially ISS stage III (P = 0.008) and lower haemoglobin level (P = 0.039).

Conclusions

Newly diagnosed MM patients are highly susceptible to viruses. Advanced ISS stage, more severe anaemia and the elevation of CRP are independent risk factors of infection, which also have a strong impact on prognosis. Our results suggest that viral infection should be taken into account if antibacterial drugs are not effective, and the prevention of infection and improvement of prognosis should be paid more attention in newly diagnosed patents with advanced stage and more severe anaemia.

The contribution of immune activation and accelerated aging in multiple myeloma occurring in HIV-infected population

: The widespread use of antiretroviral treatment results in a significant improvement in immunological condition of people living with HIV (PLWH) who nevertheless experience a significantly increased risk to develop non-Hodgkin lymphoma compared with the general population. Despite many literature observations regarding multiple myeloma in PLWH, a consensus on its relevance in HIV infection does not exist. A number of large population studies on multiple myeloma in PLWH gave contrasting results, fluctuating from increased standardized incidence ratios to the lack of observed cases of multiple myeloma. Use of antiretroviral treatment, in this context, seems to induce a slight reduction of standardized incidence ratio, although with a partial effect, especially in young patients. However, a high variability in clinical onset has been described in different reports: the only common feature of multiple myeloma in PLWH is an atypical presentation as compared with general population, with a worse prognosis in case of uncontrolled HIV infection. We identified three pathogenetic steps in the complex scenario of multiple myeloma in PLWH: first, antigenic trigger; second, persistent T cell deficiency/dysfunction; third, altered regulation of B cells. All these pathogenetic steps play a role in immunological dysregulation, leading to B cell abnormalities and hyperactivation and, finally, resulting in the development of lymphoid malignancies. HIV has a role in each one of these three steps, due to its ability to trigger and dysregulate immune system. We hypothesize that HIV could be closely implicated in the multiple myeloma development in PLWH by accelerating the carcinogenesis events in a complex and only partially understood early aging process.

Effects of Interferon-α-2a on Th3 Cytokine Response in Multiple Myeloma Patients

Aims and background

Multiple myeloma cells increase Th3 cytokine response by secreting TGF-β, which causes defective Th1 and Th2 cytokine responses. Therefore, a significant suppression of the immune system is seen in multiple myeloma. Interferon-α (IFN-α) is used in the treatment of multiple myeloma due to its immunomodulatory and anti-tumoral effects. We attempted to define the characteristics of immune cytokine responses and the effects of IFN-α-2a on the immune response in multiple myeloma.

Methods

Fifteen patients with multiple myeloma and 15 healthy controls were enrolled. IFN-α-2a, 3 million units/day x 3 times/week, was administered subcutaneously to the patients for 2 weeks. Cytokines (TGF-β, IL-1, IL-2, IL-4, IL-10, IFN-γ) were assessed by the ELISA method in sera of the patients in pretreatment and posttreatment periods and in the sera of the controls.

Results

IL-2 and IL-4 levels in patients, before IFN-α-2a, were lower than the controls, whereas TGF-β levels were higher than the controls. In other words, Th3 cytokine response was increased and Th1 and Th2 cytokine responses were decreased in patients. A short course of IFN-α-2a increased IL-2 levels.

Conclusions

These findings suggest IFN-α-2a may enhance nonTh3 cytokine responses in multiple myeloma patients.

Immune responses in multiple myeloma: role of the natural immune surveillance and potential of immunotherapies

Multiple myeloma (MM) is a tumor of terminally differentiated B cells that arises in the bone marrow. Immune interactions appear as key determinants of MM progression. While myeloid cells foster myeloma-promoting inflammation, Natural Killer cells and T lymphocytes mediate protective anti-myeloma responses. The profound immune deregulation occurring in MM patients may be involved in the transition from a premalignant to a malignant stage of the disease. In the last decades, the advent of stem cell transplantation and new therapeutic agents including proteasome inhibitors and immunoregulatory drugs has dramatically improved patient outcomes, suggesting potentially key roles for innate and adaptive immunity in disease control. Nevertheless, MM remains largely incurable for the vast majority of patients. A better understanding of the complex interplay between myeloma cells and their immune environment should pave the way for designing better immunotherapies with the potential of very long term disease control. Here, we review the immunological microenvironment in myeloma. We discuss the role of naturally arising anti-myeloma immune responses and their potential corruption in MM patients. Finally, we detail the numerous promising immune-targeting strategies approved or in clinical trials for the treatment of MM.

The IMiDs targets IKZF-1/3 and IRF4 as novel negative regulators of NK cell-activating ligands expression in multiple myeloma

Immunomodulatory drugs (IMiDs) have potent anti-tumor activities in multiple myeloma (MM) and are able to enhance the cytotoxic function of natural killer (NK) cells, important effectors of the immune response against MM. Here, we show that these drugs can enhance the expression of the NKG2D and DNAM-1 activating receptor ligands MICA and PVR/CD155 in human MM cell lines and primary malignant plasma cells. Depletion of cereblon (CRBN) by shRNA interference strongly impaired upregulation of these ligands and, more interestingly, IMiDs/CRBN-mediated downregulation of the transcription factors Ikaros (IKZF1), Aiolos (IKZF3) and IRF4 was critical for these regulatory mechanisms. Indeed, shRNA knockdown of IKZF1 or IKZF3 expression was both necessary and sufficient for the upregulation of MICA and PVR/CD155 expression, suggesting that these transcription factors can repress these genes; accordingly, the direct interaction and the negative role of IKZF1 and IKZF3 proteins on MICA and PVR/CD155 promoters were demonstrated. Finally, MICA expression was enhanced in IRF4-silenced cells, indicating a specific suppressive role of this transcription factor on MICA gene expression in MM cells.Taken together, these findings describe novel molecular pathways involved in the regulation of MICA and PVR/CD155 gene expression and identify the transcription factors IKZF-1/IKZF-3 and IRF4 as repressors of these genes in MM cells.

Immune impairments in multiple myeloma bone marrow mesenchymal stromal cells

In multiple myeloma (MM), bone marrow mesenchymal stromal cells (BM-MSCs) play an important role in pathogenesis and disease progression by supporting myeloma cell growth and immune escape. Previous studies have suggested that direct and indirect interactions between malignant cells and BM-MSCs result in constitutive abnormal immunomodulatory capacities in MM BM-MSCs. The aim of this study was to investigate the mechanisms that underlie these MM BM-MSCs abnormalities. We demonstrated that MM BM-MSCs exhibit abnormal expression of CD40/40L, VCAM1, ICAM-1, LFA-3, HO-1, HLA-DR and HLA-ABC. Furthermore, an overproduction of IL-6 (1,806 ± 152.5 vs 719.6 ± 18.22 ng/mL; p = 0.035) and a reduced secretion of IL-10 (136 ± 15.02 vs 346.4 ± 35.32 ng/mL; p = 0.015) were quantified in culture medium when MM BM-MSCs were co-cultured with T lymphocytes compared to co-cultures with healthy donor (HD) BM-MSCs. An increased Th17/Treg ratio was observed when T cells were co-cultured with MM BM-MSCs compared to co-cultures with HD BM-MSCs (0.955 vs 0.055). Together, these observations demonstrated that altered immunomodulation capacities of MM BM-MSCs were linked to variations in their immunogenicity and secretion profile. These alterations lead not only to a reduced inhibition of T cell proliferation but also to a shift in the Th17/Treg balance. We identified factors that are potentially responsible for these alterations, such as IL-6, VCAM-1 and CD40, which could also be associated with MM pathogenesis and progression.

Treatment of multiple solitary plasmacytomas with cytokine-induced killer cells

BACKGROUND AIMS

Currently available treatment methods for advanced plasmacytoma include surgery, chemotherapy, radiotherapy, immunomodulatory agents, hematopoietic stem cell transplantation and donor lymphocyte infusion. We report a case of advanced refractory multiple solitary plasmacytomas in a 68-year-old Asian man with multiple bone lesions, in whom autologous cytokine-induced killer (CIK) cells were administered in an effort to eliminate residual tumor lesions.

METHODS

CIK cells were infused monthly for 21 courses.

RESULTS

The patient has survived 63 months since the first hospital visit without disease progression for 40 months.

CONCLUSIONS

This case represents the first report of autologous CIK cell immunotherapy used successfully to suppress multiple solitary plasmacytomas and resolve bone lesions.

Cellular immunotherapy in multiple myeloma: lessons from preclinical models

The majority of multiple myeloma patients relapse with the current treatment strategies, raising the need for alternative therapeutic approaches. Cellular immunotherapy is a rapidly evolving field and currently being translated into clinical trials with encouraging results in several cancer types, including multiple myeloma. Murine multiple myeloma models are of critical importance for the development and refinement of cellular immunotherapy. In this review, we summarize the immune cell changes that occur in multiple myeloma patients and we discuss the cell-based immunotherapies that have been tested in multiple myeloma, with a focus on murine models.

Preclinical and clinical results with pomalidomide in the treatment of relapsed/refractory multiple myeloma

Despite the evolution of effective frontline treatment strategies, many patients with myeloma inevitably relapse. Treatment can be complicated by the interplay of disease-, treatment-, and patient-related factors. Unfortunately, many patients eventually develop disease that is refractory to lenalidomide and bortezomib and have few treatment options. Pomalidomide is a distinct IMiD agent recently approved in the US and Europe. We review the pomalidomide mechanism of action, summarizing its direct antimyeloma, immunomodulatory, and stromal-support inhibitory activities. We also detail its clinical development, including establishment of the approved dose/schedule, phase 2 and 3 trials in relapsed and refractory patients, and novel pomalidomide-based combinations.

Future agents and treatment directions in multiple myeloma

The development of bortezomib and immunomodulatory agents resulted in a revolution in the treatment of multiple myeloma (MM). Moreover, second-generation proteasome inhibitors (carfilzomib) and immunomodulatory agents (pomalidomide) have recently been approved. Nevertheless, the incurability of this disease requires other drugs with different mechanisms of action to either prolong the survival of patients refractory to current therapies, or achieve cure. Active research has been done exploring the pathogenesis of MM and searching for novel, druggable targets. In this regard, some of these novel agents seem promising, such as monoclonal antibodies (anti-CD38 - daratumumab or anti-CS1 - elotuzumab) or the kinesin protein inhibitor Arry-520. Other agents under investigation are kinase inhibitors, signaling pathways inhibitors or deacetylase inhibitors. With so many novel agents under investigation, future therapy in MM will probably involve the combined use of the already approved drugs with some of those newly discovered.

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.

Cellular mechanisms of multiple myeloma bone disease

Multiple myeloma (MM) is a hematologic malignancy of differentiated plasma cells that accumulates and proliferates in the bone marrow. MM patients often develop bone disease that results in severe bone pain, osteolytic lesions, and pathologic fractures. These skeletal complications have not only a negative impact on quality of life but also a possible effect in overall survival. MM osteolytic bone lesions arise from the altered bone remodeling due to both increased osteoclast activation and decreased osteoblast differentiation. A dysregulated production of numerous cytokines that can contribute to the uncoupling of bone cell activity is well documented in the bone marrow microenvironment of MM patients. These molecules are produced not only by malignant plasma cells, that directly contribute to MM bone disease, but also by bone, immune, and stromal cells interacting with each other in the bone microenvironment. This review focuses on the current knowledge of MM bone disease biology, with particular regard on the role of bone and immune cells in producing cytokines critical for malignant plasma cell proliferation as well as in osteolysis development. Therefore, the understanding of MM pathogenesis could be useful to the discovery of novel agents that will be able to both restore bone remodelling and reduce tumor burden.

Regulating the regulators in cancer-immunosuppression in multiple myeloma (MM)

An effective immune response requires a prompt but measured action against the pathological insult, to prevent over-zealous inflammatory-mediated tissue destruction. In cancer, defective or incompetent immune responses may paradoxically result in disease progression despite an immune attempt at elimination. Tumour-induced immunosuppression may not only result from soluble factors and altered antigenicity, but also from cellular-mediated tumour-induced immune evasion. Multiple myeloma (MM) is associated with both cellular and humoral immune deficiencies and increased T(Reg) cells. In vitro modelling has indicated that the tumour cells directly induce functional T(Reg) cells. In light of this recent evidence, it now seems that the most promising and synergistic approaches for cancer immunotherapy would involve specific anti-tumour immunity and simultaneous reduction of tumour-induced immune-regulation. This review sets out the basic understanding of the human immune response, its dysregulation in cancer and proposes how this knowledge may influence future treatment strategies to maximise the anti-tumour immune response.

Notch-directed microenvironment reprogramming in myeloma: a single path to multiple outcomes

Multiple myeloma is a deadly hematopoietic malignancy. Despite therapeutic advances such as autologous stem cell transplantation and novel chemotherapeutics, multiple myeloma remains incurable. Multiple myeloma cell localization in the bone marrow and the cross-talk with the bone niche trigger dramatic alterations in the bone marrow microenvironment critical for tumor progression, resistance to therapies and osteolytic bone destruction. It does not surprise that the molecular bases of such fatal interaction are under examination as source of novel potential pharmacological targets. Among these, the Notch family of receptors and ligands has gained growing interest in the recent years because of their early deregulation in multiple myeloma and their ability to affect multiple features of the disease, including tumor cell growth, drug resistance, angiogenesis and bone lesions. This review will explore the evidences of Notch deregulation in multiple myeloma, the state of the art of the currently known roles of its signaling in the fatal interaction between multiple myeloma cells, extracellular matrix and cells in the bone marrow stroma. Finally, we will present recent findings concerning the arguments for or against a therapy addressed to Notch signaling inhibition in the cure of multiple myeloma.

Can we change the disease biology of multiple myeloma?

Despite improvements in disease management, multiple myeloma (MM) remains incurable. Conventional treatment methods are unsatisfactory, leading to a pattern of regression and remission, and ultimately failure. This pattern suggests that one of the possible strategies for improving outcomes is continuous therapy to maintain suppression of the surviving tumor cells. Optimal management of MM requires potent agents and modalities with direct tumoricidal activity, which can also provide continuous suppression of the residual tumor to prevent disease relapse. Immunomodulatory agents exert immunomodulatory and tumoricidal effects, and cause disruption of stromal cell support from the bone marrow microenvironment. Therefore continuous therapy with immunomodulatory agents may be able to provide both tumor reduction and tumor suppression, enabling physicians to consider the possibility of incorporating continuous therapy into the treatment paradigm of patients with MM.

Impact of the NK cell receptor LIR-1 (ILT-2/CD85j/LILRB1) on cytotoxicity against multiple myeloma

The role of different receptors in natural-killer- (NK-) cell-mediated cytotoxicity against multiple myeloma (MM) cells is unknown. We investigated if an enhancement of NK-cell-mediated cytotoxicity against MM could be reached by blocking of the inhibitory leukocyte immunoglobulin-like receptor 1 (LIR-1). Our investigations revealed high levels of LIR-1 expression not only on the NK cell line NK-92, but also on myeloma cells (MOLP-8, RPMI8226) as well as on a lymphoblastoid cell line (LBCL; IM-9). Subsequent cytotoxicity assays were designed to show the isolated effects of LIR-1 blocking on either the effector or the tumor side to rule out receptor-receptor interactions. Although NK-92 was shown to be capable of myeloma cell lysis, inhibition of LIR-1 on NK-92 did not enhance cytotoxicity. Targeting the receptor on MM and LBCL did not also alter NK-92-mediated lysis. We come to the conclusion that LIR-1 alone does not directly influence NK-cell-mediated cytotoxicity against myeloma. To our knowledge, this work provides the first investigation of the inhibitory capability of LIR-1 in NK-92-mediated cytotoxicity against MM and the first functional evaluation of LIR-1 on MM and LBCL.

Dendritic cells and malignant plasma cells: an alliance in multiple myeloma tumor progression?

The crosstalk of myeloma cells with accessory cells drives the expansion of malignant plasma cell clones and the hyperactivation of osteoclastogenesis that occurs in multiple myeloma (MM). These reciprocal interactions promote defective dendritic cell (DC) function in terms of antigen processing, clearance of tumor cells, and efficacy of the immune response. Thus, myeloma cells exert immune suppression that explains, at least in part, the failure of therapeutic approaches, including DC vaccination. Impairment of DCs depends on high bone marrow levels of cytokines and adhesion molecules that affect both maturation and expression of costimulatory molecules by DCs. Moreover, DCs share with osteoclasts (OCs) a common ontogenetic derivation from the monocyte lineage, and thus may undergo OC-like transdifferentiation both in vitro and in vivo. Immature DCs (iDCs) induce clonogenic growth of malignant plasma cells while displaying OC-like features, including the ability to resorb bone tissue once cultured with myeloma cells. This OC-like transdifferentiation of iDCs is dependent on the activation of both the receptor activator of nuclear factor κB (RANK)-RANK ligand (RANK-L) and CD47-thrombospondin (TSP)-I axes, although interleukin 17-producing T helper-17 clones within the bone microenvironment may also take part in this function. Therefore, iDCs allied with malignant plasma cells contribute to MM osteoclastogenesis, although other molecules released by tumor cells may independently contribute to the bone-resorbing machinery.

Treatment of multiple myeloma with adoptively transferred chimeric NKG2D receptor-expressing T cells

Multiple myeloma causes approximately 10% of all hematologic malignancies. We have previously shown that human T cells expressing chimeric NKG2D receptors (chNKG2D) consisting of NKG2D fused to the CD3ζ cytoplasmic domain secrete proinflammatory cytokines and kill human myeloma cells. In this study, we show chNKG2D T cells are effective in a murine model of multiple myeloma. Mice with established 5T33MM-green fluorescent protein tumors were treated with one or two infusions of chNKG2D T cells. Compared with mice treated with T cells expressing wild type (wt)NKG2D receptors, a single dose of chNKG2D T cells increased survival, with half of the chNKG2D T-cell-treated mice surviving long term. Two infusions of chNKG2D T cells led to tumor-free survival in all mice. ChNKG2D T cells were located at sites of tumor growth, including the bone marrow and spleen after intravenous injection. There was an increase in activated host T cells and NK cells at tumor sites and in serum interferon-γ after chNKG2D T-cell injection. Surviving mice were able to resist a rechallenge with 5T33MM cells but not RMA lymphoma cells, indicating that the mice developed a protective, specific memory response. These data demonstrate that chNKG2D T cells may be an effective adoptive cellular therapy for multiple myeloma.

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.

Enumeration of blood dendritic cells in patients with multiple myeloma at presentation and through therapy

Multiple myeloma (MM) is a clonal B-cell malignancy characterised by excess bone marrow plasma cells, serum and/or urine paraprotein, immune paraesis, renal failure and lytic bone lesions. Dendritic cells (DC) are key players in the adaptive and innate immune responses, but reside in tissues, so are difficult to quantify in vivo. By enumerating the blood DC pool, we aim to examine the influence of MM disease and accompanying therapy on the DC system. We have shown, using the BDCA DC detection kit, that blood pDC and mDC numbers are suppressed at diagnosis in MM, and uniquely, monoclonal gammopathy of uncertain significance (MGUS) and patients with plasmacytoma. B-cell numbers were also significantly reduced in MM, MGUS and patients with plasmacytoma (p<or=0.005). Standard chemotherapy did not improve the number of mDC1 or pDC seen in the blood of patients with MM. The number of blood mDC1 improved transiently following auto hemopoietic stem cell transplantation, as numbers returned to within the normal range at engraftment and were maintained until D100. The number of blood mDC1 in patients taking thalidomide was also significantly higher than at relapse. These studies suggest that the defects in the B cell and blood DC pool is present in MGUS and plasmacytoma as well as patients with MM and can recover following therapy.

Immunodeficiency and immunotherapy in multiple myeloma

Multiple myeloma is a malignant tumour of plasma cells that remains incurable for the vast majority of patients, with a median survival of 2-3 years. It is characterized by the patchy accumulation of tumour cells within bone marrow leading to variable anaemia, bone destruction, hypercalcaemia, renal failure and infections. Immune dysfunction is an important feature of the disease and leads to infections that are both a major cause of morbidity and mortality and may promote tumour growth and resistance to chemotherapy. Numerous defects of the immune system have been described in multiple myeloma although the relative clinical importance of these remains elusive. There has been considerable interest in the identification of an autologous response against myeloma. Although T cells and humoral responses directed against myeloma-associated antigens have been described, it is uncertain if the immune system plays a role in preventing or controlling myeloma cell growth. There is increasing interest in the potential role of immunotherapy but the success of these interventions is likely to be modified by the immunologically hostile environment associated with multiple myeloma. This review attempts to summarize the current knowledge relating to the immune defects found in multiple myeloma.

Regulation of MHC class II gene expression by the class II transactivator

MHC class II molecules are pivotal for the adaptive immune system, because they guide the development and activation of CD4+ T helper cells. Fulfilling these functions requires that the genes encoding MHC class II molecules are transcribed according to a strict cell-type-specific and quantitatively modulated pattern. This complex gene-expression profile is controlled almost exclusively by a single master regulatory factor, which is known as the class II transactivator. As we discuss here, differential activation of the three independent promoters that drive expression of the gene encoding the class II transactivator ultimately determines the exquisitely regulated pattern of MHC class II gene expression.

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.

Visualization of 5T33 myeloma cells in the C57BL/KaLwRij mouse: establishment of a new syngeneic murine model of multiple myeloma

OBJECTIVE

Lack of good models for in vivo detection of multiple myeloma (MM) cells hampers our understanding of the disease. Our objective was to establish a murine model for MM, allowing sensitive and labor-free tracing and quantification of MM cells in an immunocompetent host.

METHODS

5T33MM cells were retrovirally transduced, expressing enhanced green fluorescent protein (eGFP) and/or herpes simplex virus thymidine kinase (HSV-tk) as a control. Flow cytometric eGFP detection accuracy and sensitivity were assessed. Functional characteristics of transduced cells, including growth rate and production of IgG2b paraprotein and interleukin-6, were compared to those of nontransduced cells in vitro. For induction of MM, C57BL/KaLwRij mice were injected intravenously with transduced and nontransduced cells. Survival kinetics and distribution of eGFP cells in tissues were evaluated.

RESULTS

Flow cytometric eGFP detection was accurate at 1:1000 transduced/nontransduced cell ratio. Transduced and nontransduced 5T33MM cells exhibited similar growth rates, producing comparable IgG2b and interleukin-6 levels. Intravenous injection of both nontransduced and eGFP-transduced MM cells to C57BL/KaLwRij mice resulted in paraplegia. At the time of paraplegia, eGFP-transduced MM cells were detected substantially in the bone marrow, spleen, and liver, less in lymph nodes, but not in the thymus. The bone marrow of paraplegic mice contained higher eGFP-transduced MM cells compared to that of nonparaplegic animals.

CONCLUSIONS

In the established eGFP-5T33 MM model, MM cells are easily traced in an immunocompetent host. This model simplifies the analysis of homing pattern studies, the evaluation of therapeutic effects of various treatment approaches and contributes towards better understanding of MM.

Evaluation of the potential immunotoxicity of 3-monochloro-1,2-propanediol in Balb/c mice

3-Monochloro-1,2-propanediol (MCPD) is a well-known by-product of acid-hydrolyzed soy sauce during its manufacturing process. MCPD has been reported genotoxic in vitro, and reproductive toxicity and carcinogenicity in rats. However, no previous studies have investigated MCPD-induced alterations in the immune system. In the present study, MCPD was administered by gavage for 14 days at 0, 25, 50, and 100 mg/kg per day to female Balb/c mice. The antibody-mediated immune response to sheep red blood cells (SRBC) was assessed using the antibody-forming cell (AFC) assay, and splenic cell phenotypes were quantified by flow cytometry. Hematological and histopathological changes were assessed. Mitogen-stimulated spleen lymphocyte proliferation and natural killer (NK) cell activity were evaluated. The T-lymphocyte blastogenesis by concanavalin A (Con A) or anti-CD3 and B-lymphocyte blastogenesis by lipopolysaccharide (LPS) were not significantly changed. There were no significant changes in the hematological and histopathological findings of MCPD-treated mice. However, the significant decrease in thymus weight was observed in 100 mg dose group, even though that did not change body weight gain. The cellularities of spleen and thymus were significantly reduced in high-dose group. Exposure to high dose of MCPD decreased the AFC response to SRBC in mice. There was a significant decrease in NK cell activity of mice treated with high dose of MCPD. These results indicate that MCPD could modulate the immune function in Balb/c mice.

T cells from the tumor microenvironment of patients with progressive myeloma can generate strong, tumor-specific cytolytic responses to autologous, tumor-loaded dendritic cells

Most untreated cancer patients develop progressive tumors. We tested the capacity of T lymphocytes from patients with clinically progressive, multiple myeloma to develop killer function against fresh autologous tumor. In this malignancy, it is feasible to reproducibly evaluate freshly isolated tumor cells and T cells from the marrow tumor environment. When we did this with seven consecutive patients, with all clinical stages of disease, we did not detect reactivity to autologous cancer cells. However, both cytolytic and IFN-gamma-producing responses to autologous myeloma were generated in six of seven patients after stimulation ex vivo with dendritic cells that had processed autologous tumor cells. The antitumor effectors recognized fresh autologous tumor but not nontumor cells in the bone marrow, myeloma cell lines, dendritic cells loaded with tumor-derived Ig, or allogeneic tumor. Importantly, these CD8(+) effectors developed with similar efficiency by using T cells from both the blood and the bone marrow tumor environment. Therefore, even in the setting of clinical tumor progression, the tumor bed of myeloma patients contains T cells that can be activated readily by dendritic cells to kill primary autologous tumor.

Multiple myeloma: evolving genetic events and host interactions

Multiple myeloma is a neoplasm of terminally differentiated B cells (plasma cells) in which chromosome translocations frequently place oncogenes under the control of immunoglobulin enhancers. Unlike most haematopoietic cancers, multiple myeloma often has complex chromosomal abnormalities that are reminiscent of epithelial tumours. What causes full-blown myeloma? And can our molecular understanding of this common haematological malignancy be used to develop effective preventive and treatment strategies?

Expression of granzyme B and perforin in multiple myeloma

Multiple myeloma (MM) remains an incurable disease by conventional therapy. MM tumor cells evade the immune system and can induce immunosuppression by producing immunomodifying agents such as TGF-beta, FasL, vascular endothelial growth factor and Muc-1. In the present study, we show that bone marrow cells from a patient suffering from MM IgG/k type, stage IIIA, when cultured, expressed granzyme B and perforin, normally expressed exclusively by cytotoxic T cells (CTLs) and natural killer (NK) cells. In addition, phenotypic analysis revealed that the cultured cells were activated antigen-presenting cells with NK targeting capacity. We propose that expression of these cytolytic enzymes may constitute an additional adoptive mechanism by the tumor cells to actively destroy the host immune effector cells.

Suppression of IL-2-induced T cell proliferation and phosphorylation of STAT3 and STAT5 by tumor-derived TGF beta is reversed by IL-15

IL-2 responses are susceptible to suppression by TGFbeta, a cytokine widely implicated in suppression of inflammatory responses and secreted by many different tumor cell types. There have been conflicting reports regarding inhibition of IL-2-induced STAT3 and STAT5 phosphorylation by TGFbeta and subsequent suppression of immune responses. Using TGFbeta-producing multiple myeloma tumor cells we demonstrate that tumor-derived TGFbeta can block IL-2-induced proliferation and STAT3 and STAT5 phosphorylation in T cells. High affinity IL-2R expression was required for the suppression of IL-2 responses as a novel CD25(-) T cell line proliferated and phosphorylated STAT3 when cultured with tumor cells or rTGFbeta1. Activating T cells with IL-15, which does not use the high affinity IL-2R, completely restored the ability of T cells to phosphorylate STAT3 and STAT5 when cultured with tumor cells. IL-15-treated T cells proliferated normally when cocultured with tumor cells or rTGFbeta1, whereas IL-2 responses were consistently inhibited. Preincubation with IL-15 also restored the ability of T cells to respond to IL-2 by phosphorylating STAT3 and STAT5, and proliferating normally in the presence of tumor cells. IL-2 pretreatment did not restore T cell function. IL-15 also restored T cell responses by T cells from multiple myeloma patients, and against freshly isolated bone marrow tumor samples. Thus, activation of T cells by IL-15 renders T cells resistant to suppression by TGFbeta1-producing tumor cells and rTGFbeta1. This finding may be exploited in the design of new immunotherapy approaches that will rely on T cells avoiding tumor-induced suppression.

The Th1-Th2 classification of cellular immune responses: concepts, current thinking and applications in haematological malignancy

The finding that T cell immune responses could be divided into those promoting cell mediated immunity (Th1) and humoral responses (Th2) has had a profound effect on the understanding of immune response generation over the last 15 years. With ever increasing knowledge of the immune system, the model has come under criticism, as not all responses easily fit the classification. Nonetheless, the model still provides a valuable framework on which to base immunological research. In this review we update the model with current thinking regarding the generation and maintenance of immune responses. We then examine how the Th1-Th2 paradigm may be applied in developing new understanding of several topical issues in haematological malignancy-control of graft-versus-host disease; cytokine control of proliferating clones in B and T cell diseases; and suppression of T cell responses in multiple myeloma.