Functional monocyte-derived dendritic cells can be generated in chronic lymphocytic leukaemia

Can Dendritic Cell Vaccination Prevent Leukemia Relapse?

Leukemias are clonal proliferative disorders arising from immature leukocytes in the bone marrow. While the advent of targeted therapies has improved survival in certain subtypes, relapse after initial therapy is a major problem. Dendritic cell (DC) vaccination has the potential to induce tumor-specific T cells providing long-lasting, anti-tumor immunity. This approach has demonstrated safety but limited clinical success until recently, as DC vaccination faces several barriers in both solid and hematological malignancies. Importantly, vaccine-mediated stimulation of protective immune responses is hindered by the aberrant production of immunosuppressive factors by cancer cells which impede both DC and T cell function. Leukemias present the additional challenge of severely disrupted hematopoiesis owing to both cytogenic defects in hematopoietic progenitors and an abnormal hematopoietic stem cell niche in the bone marrow; these factors accentuate systemic immunosuppression and DC malfunction. Despite these obstacles, several recent clinical trials have caused great excitement by extending survival in Acute Myeloid Leukemia (AML) patients through DC vaccination. Here, we review the phenotype and functional capacity of DCs in leukemia and approaches to harness DCs in leukemia patients. We describe the recent clinical successes in AML and detail the multiple new strategies that might enhance prognosis in AML and other leukemias.

Dendritic cell vaccines for leukemia patients

Dendritic cells are the most professional antigen-presenting cells to elicit T-cellular responses toward microbial agents and cancer cells. The graft-versus-leukemia effect observed after allogeneic stem cell transplantation strongly suggests that T lymphocytes play a major role in the rejection of leukemic cells. This graft-versus-leukemia effect might be enhanced through dendritic cell vaccination. The characterization of leukemia-specific antigens eliciting immune responses in the autologous host has prompted researchers and clinicians to broaden the spectrum of dendritic cell vaccines to hematological malignancies. Recently, the focus is on acute myeloid leukemia and chronic lymphocytic leukemia. This review summarizes data on the administration of autologous and allogeneic dendritic cells to leukemia patients as an interesting approach in cellular therapy of leukemias.

Tumour-loaded α-type 1-polarized dendritic cells from patients with chronic lymphocytic leukaemia produce a superior NK-, NKT- and CD8+ T cell-attracting chemokine profile

Tumour-loaded dendritic cells (DCs) from patients with chronic lymphocytic leukaemia (CLL) matured using an α-type 1-polarized DC cocktail (IL-1β/TNF-α/IFN-α/IFN-γ/poly-I:C;αDC1) were recently shown to induce more functional CD8(+) T cells against autologous tumour cells in vitro than DCs matured with the 'standard' cocktail (IL-1β/TNF-α/IL-6/PGE(2) ;PGE(2) DCs). However, the ability of vaccine DCs to induce a type 1-polarized immune response in vivo probably relies on additional features, including their ability to induce a CXCR3-dependent recruitment of NK cells into vaccine-draining lymph nodes. Moreover, their guiding of rare tumour-specific CD8(+) T cells to sites of DC-CD4(+) T cell interactions by secretion of CCL3 and CCL4 is needed. We therefore analysed the chemokine profile and the lymphocyte-attracting ability in vitro of monocyte-derived PGE(2) DCs and αDC1s from patients with CLL. αDC1s produced much higher levels of CXCR3 ligands (CXCL9/CXCL10/CXCL11) than PGE(2) DCs. Functional studies further demonstrated that αDC1s were superior recruiters of both NK and NKT cells. Moreover, αDC1s produced higher levels of CCL3/CCL4 upon CD40 ligation. These findings suggest that functional αDC1s, derived from patients with CLL, produce a desirable NK-, NKT- and CD8(+) T cell-attracting chemokine profile which may favour a guided and Th1-deviated priming of CD8(+) T cells, supporting the idea that αDC1-based vaccines have a higher immunotherapeutic potential than PGE(2) DCs.

Dendritic Cells and their Potential Therapeutic Role in Haematological Malignancy

The generation of an effective immune response is dependent on the efficient capture and presentation of antigen by antigen-presenting cells. The most potent antigen-presenting cells are dendritic cells (DC). These cells have the capability of activating naive helper and cytotoxic T cells. In recent years it has been demonstrated that in vivo responses to a number of solid tumours can be generated by DC pulsed with either purified tumour antigen or whole tumour cell lysate. In addition, a number of in vivo studies using DC have also been attempted in solid tumours, with some encouraging results. In haematological malignancies, there is now strong evidence that previous T cell anergy can be reversed and significant anti-tumour immune responses generated, in vitro, against the majority of leukaemias. As far as in vivo studies in haematological malignancies are concerned, although T cell responses have been demonstrated in the majority of cases and some dramatic early clinical responses reported, overall results appear disappointing. However, considering the fact that many of these studies were performed in patients with advanced disease and that such therapeutic strategies are still in their infancy, the overall results are actually quite encouraging. Although there is a real potential for DC immunotherapy in the future, it is important to be realistic about the limitations and obstacles to its development. It is highly unlikely that any form of immunotherapy is going to be effective in advanced disease due to the physical bulk of tumour, the immunosuppressive effects of tumours themselves and to any secondary immunosuppression following standard cancer therapy. The potential for immunotherapy is likely to lie either in adjunctive therapy or for treating minimal residual disease. Even in those situations, one of the major obstacles to be overcome is the state of immunological anergy or tolerance that many tumours seem able to induce. Indeed, there is evidence that, under certain circumstances, DC themselves can present antigen in such a way as to produce this state of anergy. Although, in vitro manipulation of DC and T cells can generate tumour-specific T cells from previously "anergic" cells, once reintroduced in vivo, these cells will be re-exposed to the tumour environment with the risk of being rendered anergic again.

Autologous dendritic cells pulsed with eluted peptide as immunotherapy for advanced B-cell malignancies

We have studied the feasibility, safety and efficacy of vaccination with autologous dendritic cells pulsed with eluted peptide in patients with advanced low-grade B-cell malignancies. This study demonstrates that autologous dendritic cell vaccines can be successfully produced from patients with advanced disease and be delivered without significant toxicity. Furthermore, we have demonstrated immunological and clinical responses in two of ten patients treated. These results provide further evidence for the use of immunotherapy in the management of B-cell malignancies, but also suggest that sustained responses may only be possible in patients with low bulk disease early in the disease course.

SCID mice model in vivo evaluation of autologous and allogeneic dendritic cells activity on B-cell chronic lymphocytic leukemia

In the present study we investigated in vivo therapeutic potential of DCs vaccines in B-cell chronic lymphocytic leukemia (B-CLL). On the day 0 the SCID mice were intraperitoneally inoculated with peripheral blood mononuclear cells (PBMC) of B-CLL patients at a dose of 10-30 x 10(6) and left untreated (controls) or i.p. injected on the day 7 with 0.2 - 14.0 x 10(6) dendritic cells. DCs were generated in vitro from peripheral blood monocytes of B-CLL donors (autologous DCs) or healthy donors (allogeneic cells) and pulsed with B-CLL antigens. On the day 14, the effect of implanted cells interactions was evaluated by a counting of CD19+CD5+ human leukemic cells and human T cells in the peritoneal fluid of mice. We found, that mean numbers of CD19+CD5+ leukemic cells as well as human T cells were lowered in peritoneal fluid of mice treated with allogeneic APCs. However, we did not observe similar effects with autologous DCs.

Respiratory Homeostasis and Exploitation of the Immune System for Lung Cancer Vaccines

Lung cancer is the leading cause of all cancer deaths in the US. The international scientific and clinical community has made significant advances toward understanding specific molecular mechanisms underlying lung carcinogenesis; however, despite these insights and advances in surgery and chemoradiotherapy, the prognosis for non-small-cell lung cancer (NSCLC) remains poor. Nonetheless, significant effort is being focused on advancing translational research evaluating the efficacy of novel targeted therapeutic strategies for lung cancer. Illustrative examples of this include antagonists of the epidermal growth factor receptor (EGFR), tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib, and a diverse assortment of anti-angiogenic compounds targeting growth factors and/or their receptors that regulate tumor-associated angiogenic programs. In addition, with the increased awareness of the significant role chronically activated leukocytes play as potentiators of solid-tumor development, the role of innate and adaptive immune cells as regulators of lung carcinogenesis is being examined. While some of these studies are examining how novel therapeutic strategies may enhance the efficacy of lung cancer vaccines, others are evaluating the intrinsic characteristics of the immune response to lung cancer in order to identify rate-limiting molecular and/or cellular programs to target with novel anticancer therapeutics. In this article, we explore important aspects of the immune system and its role in regulating normal respiratory homeostasis compared with the immune response accompanying development of lung cancer. These hallmarks are then discussed in the context of recent efforts to develop lung cancer vaccines, where we have highlighted important concepts that must be taken into consideration for future development of novel therapeutic strategies and clinical trials assessing their efficacy.

Multiple-dose granulocyte-macrophage-colony-stimulating factor plus 23-valent polysaccharide pneumococcal vaccine in patients with chronic lymphocytic leukemia: a prospective, randomized trial of safety and immunogenicity

BACKGROUND

For the current study, the authors sought to determine whether administration of multiple-dose granulocyte-macrophage-colony-stimulating factor (GM-CSF) could improve response to standard 23-valent polysaccharide pneumococcal vaccine (PPV) in patients with chronic lymphocytic leukemia (CLL).

METHODS

Patients were allocated randomly to receive PPV either alone or with 3 doses of GM-CSF (250 microg) given before or after vaccination. Serum was obtained before, 4 weeks after, and 12 weeks after vaccination for antibody determination. Thirty-two patients with CLL were given PPV. They were randomized to receive 3 doses of GM-CSF either before or after vaccination or to receive no GM-CSF.

RESULTS

A 4-fold rise in immunoglobulin G (IgG) to capsular polysaccharides from Streptococcus pneumoniae types 4, 6B, 9V, 14, 19F, and 23F occurred in <10% of patients in each of the 3 groups. There were no differences in geometric mean IgG levels in any of the 3 groups 4 weeks or 12 weeks after vaccination.

CONCLUSIONS

In patients with CLL, the response to pure polysaccharide pneumococcal vaccine was low despite immune enhancement with multiple doses of GM-CSF. In all patients, reactogenicity was minor.

Dendritic cells pulsed with alpha-fetoprotein and mutant P53 fused gene induce bi-targeted cytotoxic T lymphocyte response against hepatic carcinoma

Dendritic cell (DC)-based immunotherapy is rapidly emerging as a promising treatment in cancer therapy. We had previously shown that DC pulsed with either defined mRNA of tumor antigen (Ag) such as alpha-fetoprotein (AFP), or total RNA of hepatocellular carcinoma (HCC) could elicit Ag-specific cytotoxic T lymphocyte (CTL) response. Therefore, we suggested a novel DC-based therapeutic method, in which DCs derived from CD34(+) cells enriched peripheral blood mononuclear cells were pulsed with liposome-coated AFP and mutant P53 (mtP53) fused gene pEGFP-C3/AFP-mtP53 to induce bi-targeted specific CTL responses against HCC. Three different genotype HCC cell lines, HepG2 (human histocompatibility leukocyte antigens (HLA) A2 positive, AFP expressing positive, P53 expressing negative), SMMC7721 (HLA A2 positive, neither AFP nor P53 expressing positive), and HMCC97 (HLA A2 positive, both AFP and P53 expressing positive) were selected as targets for CTL responses. An important finding was that DCs pulsed with the liposome-coated fused gene could evoke more intensive bi-targeted Ag-specific CTL responses against HMCC97 than DCs pulsed with either AFP or P53 single gene (P < 0.05). This experimental therapeutic model provides a new promising cytotherapeutic approach, in that DCs pulsed with the fused gene of different Ags might induce more extensive multitargeted antitumor immunity.

Cellular immune therapy for chronic lymphocytic leukemia

Although chemotherapy can induce complete responses in patients with chronic lymphocytic leukemia (CLL), it is not considered curative. Treated patients generally develop recurrent disease requiring additional therapy, which can cause worsening immune dysfunction, myelosuppression, and selection for chemotherapy-resistant leukemia-cell subclones. Cellular immune therapy promises to mitigate these complications and potentially provide for curative treatment. Most experience with this is in the use of allogeneic hematopoietic stem-cell transplantation (allo-HSCT), in which graft-versus-leukemia (GVL) effects can be observed and shown responsible for long-term disease-free survival. However, use of allo-HSCT for CLL is limited because of the lack of suitable donors and the treatment-related morbidity/mortality for elderly patients, who constitute the majority at risk for developing this disease. The GVL effect, however, suggests there are specific CLL-associated antigens that could be targeted in autologous cellular immune therapy. Effective strategies for this will have to overcome the disease-related acquired immune deficiency and the capacity of the leukemia-cell to induce T-cell tolerance, thereby compromising the activity of even conventional vaccines in patients with this disease. We will discuss the different strategies being developed to overcome these limitations that might provide for effective cellular immune therapy of CLL.

Targets and strategies for T-cell based vaccines in patients with B-cell chronic lymphocytic leukemia

T-cell based immunotherapies might be a novel option for the treatment of B-cell chronic lymphocytic leukemia (B-CLL), a disease characterized by a prolonged natural course. Different strategies of active immunotherapy have been tested in vitro to enhance a specific T-cell response against tumor cells and an anti-leukemic effect has been observed in B-CLL patients after allogenic stem cell transplantation. Several antigens have been characterized as tumor/leukemia associated antigens (T/LAAs) in B-CLL with the potential to elicit specific anti-tumor response encompassing idiotype immunoglobulin, oncofetal antigen-immature laminin receptor protein (OFAiLRP), survivin, as well as fibromodulin, the receptor for hyaluronic acid mediated motility (RHAMM/CD168) and the murine double-minute 2 oncoprotein (MDM2). This study presents an overview of possible targets and genetherapeutical maneuvers for future immunotherapies of B-CLL patients and summarizes recent clinical vaccination trials with dendritic cells (DCs) for B-CLL.

Impaired functionality and phenotypic profile of dendritic cells from patients with multiple myeloma

Multiple myeloma (MM) is a B cell cancer characterized by clonal proliferation in the bone marrow and impaired immunity. Because MM is an incurable malignancy, efficient consolidation is needed urgently. Targeting clonotypic B cells by idiotype vaccination has proved the principle to be effective and indicated that future strategies, including dendritic cell-based vaccination, could be a suitable approach. However, as MM patients suffer from a general impaired immunity, which may include dendritic cells (DCs), a careful evaluation of phenotypic traits and functionality of DCs from MM patients is necessary before an efficient vaccine can be developed. This study determined the number, phenotypic profile and functionality of myeloid and plasmacytoid DCs purified directly from blood from MM patients at diagnosis. A reduced number and lower expression of human leucocyte antigen (HLA) molecules was observed on both myeloid and plasmacytoid DCs in MM patients compared to healthy controls. Also, the expression of CCR5, CCR7 and DEC205 was lower in MM patients compared to normal donors. In addition, the capacity to stimulate allogeneic T cell proliferation and to stimulate cytokine production was decreased, suggesting that DCs from these patients are functionally impaired. Finally, the analysis of samples following chemotherapy and transplantation demonstrated an increased expression of HLA molecules, suggesting that this time-point is optimal for harvest and use in vaccination.

Dendritic cells from chronic lymphocytic leukemia patients are normal regardless of Ig V gene mutation status

Patients with B-type chronic lymphocytic leukemia (B-CLL) segregate into 2 subgroups based on the mutational status of the immunoglobulin (Ig) V genes and the patients in these subgroups follow very different clinical courses. To examine whether dendritic cells (DCs) generated from CLL patients can be candidates for immune therapy, we compared the phenotypic and functional capacities of DCs generated from patients of the 2 CLL subgroups (normal age-matched subjects [normal-DCs]). Our data show that immature DCs from B-CLL patients (B-CLL-DCs) have the same capacity to take up antigen as those from normal controls. Furthermore, B-CLL-DCs generated from the 2 CLL subgroups up-regulated MHC-II, CD80, CD86, CD83, CD40, and CD54 and down-regulated CD206 in response to stimulation with a cocktail of cytokines (CyC) and secreted increased levels of tumor necrosis factor alpha, interleukin (IL)-8, IL-6, IL-12 (p70), and RANTES in a manner typical of mature normal-DCs. Interestingly, CD54 was significantly more up-regulated by CyC in B-CLL-DCs compared with normal-DCs. Except for CD54, no significant differences in surface molecule expression were observed between normal-DCs and B-CLL-DCs. B-CLL-DCs from both subgroups, including 6 patients with VH1-69, that usually fare poorly, presented tetanus toxoid to autologous T cells in vitro similar to normal- DCs. Our data show that DCs generated from the B-CLL subgroup with unmutated Ig V genes are functionally normal. These results are very promising for the use of DCs from patients with poor prognosis for immunotherapy.

Immune defects in patients with chronic lymphocytic leukemia

Over the past decade, the introduction of nucleoside analogs and monoclonal antibodies into the treatment of patients with chronic lymphocytic leukemia (CLL) has resulted in higher rates and longer duration of response. This is a significant step towards achieving the ultimate goal of disease-eradication and improved survival. A continuing problem, however, is the susceptibility of these patients to infections. Profound dysregulation of the host immune system in patients with CLL and its impact on the clinical course of the disease are well established. A number of investigators have sought to identify the mechanisms underlying this innate immune dysfunction, which is further exacerbated by the actions of the potent therapeutic agents. The early recognition of infections as well as prophylactic administration of appropriate antibiotics has been the mainstay of managing infections in patients with CLL. Hopefully, increasing understanding of the molecular events underlying the neoplastic change in CLL will lead to more targeted and less immunosuppressive therapeutic modalities. Furthermore, the understanding of the mechanisms of immune dysfunction in CLL is of pivotal importance in the novel immune-based therapeutic strategies currently under development.

Generation of DC-based vaccine for therapy of B-CLL patients. Comparison of two methods for enriching monocytic precursors

BACKGROUND

The generation of Ag-loaded DC under good manufacturing practice (GMP) conditions is logistically challenging and further compounded when the starting precursors need to be purified from B-CLL patients who have overwhelming numbers of circulating B-CLL cells and decreased numbers of monocytes.

METHODS

We have previously demonstrated that DC with endocytosed B-CLL apoptotic bodies are powerful stimulators of anti-leukemic T cells. In this study we compared counterflow elutriation and immunomagnetic separation for enriching monocyte precursors, and evaluated the feasibility of generating DC from B-CLL patients and the effects of cryopreservation.

RESULTS

Monocyte yield from a single leukapheresis product of a B-CLL patient varied from 1 x 108 to 10 x 108 total cells, from which 40-200 x 106 mature DC could be produced. Adequate numbers of monocytes could not be enriched from one patient with 0.2% monocytes in the leukapheresis product, and the target of 50 x 106 DC was barely achieved in another patient with 0.9% monocytes in the pheresed cells. These results suggested that successful production of DC is dependent on a minimum frequency of 1% CD14(+) monocytes in the leukapheresis product. Cryopreservation of tumor cell-loaded DC yielded a recovery rate of 86+/-4.4% upon thawing, with a total viability of 90+/-2.8%. Most importantly, cryopreserved Ag-loaded DC retained their morphology, phenotype and function.

DISCUSSION

The results demonstrate that adequate numbers of functional DC required for clinical therapy can be generated from patients who have >1% of CD14(+) monocytes in the leukapheresis product. Moreover, Ag-loaded DC can be cryopreserved and recovered without significant change in phenotype or function.

Vaccine strategies to treat lymphoproliferative disorders

Lymphoproliferative disorders, including follicular lymphoma (FL), multiple myeloma (MM) and chronic lymphatic leukaemia (CLL), are slowly progressive malignancies which remain incurable despite advances in therapy. Harnessing the immune system to recognise and destroy tumours is a promising new approach to treating these diseases. Dendritic cells (DC) are unique antigen-presenting cells that play a central role in the initiation and direction of immune responses. DC loaded ex vivo with tumour-associated antigens and administered as a vaccine have already shown promise in early clinical trials for a number of lymphoproliferative disorders, but the need for improvement is widely agreed. Recent advances in the understanding of basic DC biology and lessons from early clinical trials have provided exciting new insights into the generation of anti-tumour immune responses and the design of vaccine strategies. In this review we provide an overview of our current understanding of DC biology and their function in patients with lymphoproliferative disorders. We discuss the current status of clinical trials and new approaches to exploit the antigen presenting capacity of DC to design vaccines of the future.

Novel immune-based treatment strategies for chronic lymphocytic leukemia

Immune-based treatments represent a new group of therapeutic strategies for patients with cancer, including chronic lymphocytic leukemia (CLL), that employ immune effector mechanisms. Among these strategies is passive immunotherapy with monoclonal antibody, alone or in combination with chemotherapy. Active immunotherapy strategies currently under development include vaccines, administration of expanded and activated T cells, and allogeneic stem cell transplantation. These immune-based strategies represent new treatments with potentially complementary mechanisms of action to standard therapies and signify major advances in treatments for patients with CLL.

Allogeneic dendritic cells pulsed with tumor lysates or apoptotic bodies as immunotherapy for patients with early-stage B-cell chronic lymphocytic leukemia

Recently, immunotherapies with allogeneic dendritic cells (DCs) pulsed with tumor antigens to generate specific T-cell responses have been tested in clinical trials for patients with solid tumors. This is the first report on a clinical vaccination study with DCs for patients with B-cell chronic lymphocytic leukemia (B-CLL). The potential of allogeneic DCs pulsed ex vivo with tumor cell lysates or apoptotic bodies to stimulate antitumor immunity in patients with B-CLL in early stages was evaluated. Monocyte-derived DCs were obtained from unrelated healthy donors. Nine patients (clinical stage 0 and 1 according to Rai) were vaccinated five times with a mean number of 32 x 10(6) stimulated DCs administered intradermally once every 2-3 weeks. No signs of autoimmunity were detected, and only mild local skin reactions were noted. During the treatment period, we observed a decrease of peripheral blood leukocytes and CD19+/CD5+ leukemic cells. In one patient, a significant increase of specific cytotoxic T lymphocytes against RHAMM/CD168, a recently characterized leukemia-associated antigen, could be detected after DC vaccination. Taken together, the study demonstrated that DC vaccination in CLL patients is feasible and safe. Immunological and to some extent hematological responses could be noted, justifying further investigation on this immuno-therapeutical approach.

Phenotypic and functional characterization of monocyte-derived dendritic cells in chronic lymphocytic leukaemia patients: influence of neoplastic CD19+ cells in vivo and in vitro

Dendritic cells (DCs) are the most potent antigen-presenting cells and are therefore an attractive option as antigen carriers in vaccination protocols. Chronic lymphocytic leukaemia (CLL) represents a potential good target for these approaches. The present study was designed to investigate the feasibility of generating in vitro fully functional DCs from peripheral blood (PB) monocytes of CLL patients at different phases of the disease. Although functional DCs could be obtained from CLL samples, in patients with active disease the expression of some co-stimulatory molecules appeared to be reduced. In contrast, DCs from CLL patients in remission showed no difference from those of normal controls. Moreover, patients with active disease produced DCs with reduced allostimulatory ability when compared with normal ones, whereas the functional capacities appeared to be restored in CLL DCs from remission patients. To more precisely assess the possible inhibitory effect of CLL cells on DC development, the influence of autologous leukaemic CD19(+) cells on the generation of monocyte-derived CLL DCs in vitro was investigated. The addition of CLL neoplastic cells markedly affected monocyte-derived DC maturation. In conclusion, monocytes from CLL patients with active disease give rise to DCs, which show phenotypic and functional defects that are not observed in remission CLL patients. These results need to be taken into account in the design of DC-based immunotherapeutic approaches in CLL.

Monocyte-derived dendritic cells in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) results from the accumulation of small mature, slowly dividing, monoclonal B lymphocytes. The clinical course of this disease is heterogeneous, with some patients progressing rapidly with early death whilst others exhibit a more stable, possibly, non-progressing disease lasting many years. Despite progress in therapy, relapse invariably occurs and the disease remains incurable. The clinical management of CLL is therefore challenging and considerable effort has been directed towards novel therapeutic strategies aimed at reducing the disease relapse rate. Recent insights into the role of dendritic cells as the pivotal antigen-presenting cells that initiate immune responses may provide the basis for generating more effective antitumor immune responses. Consequently, dendritic cells constitute an attractive approach in the context of CLL. However, understanding the relation between dendritic cells and the cellular immune response is crucial to elucidation of how to manipulate immune responses. After summarizing general properties of dendritic cells, this review focus on the approaches exploiting monocyte-derived dendritic cells in CLL, which should help design of novel treatment strategies in this disease.

Modulation of antitumor immune responses by hematopoietic cytokines

BACKGROUND

Advances in immunotherapy for the treatment of patients with malignant disease have led to increasingly successful use of these methods in the clinical setting. This review presents findings from recent studies that have explored improved methods for the presentation of tumor-associated antigens and for the restoration of tumor specific immune responses using cytokine therapy.

METHODS

A review of human clinical trial research on immune cytokines from 1995 (MEDLINE) to the present was conducted. Particular attention was focused on articles that reported results from Phase II or later clinical studies in patients with malignant disease.

RESULTS

The defects in cellular immunity commonly seen in patients with malignancies often are expressed as tumor specific anergy. Reversing patient tolerance to tumor antigens may be accomplished by treatment with immunoregulatory cytokines, such as Flt-3 and granulocyte-macrophage-colony stimulating factor, that mature and activate dendritic cells. Published clinical studies indicate that granulocyte-macrophage-colony stimulating factor stimulates antigen-presenting cells and has promising antitumor activity as an adjunct or as stand-alone therapy for patients with malignant disease, including leukemia, melanoma, breast carcinoma, prostate carcinoma, and renal cell carcinoma.

CONCLUSIONS

Immune-modulating cytokines may be used alone or in combination with other treatments to help restore immune function, improve response to tumor-associated antigens, and reduce the toxic effects of standard antitumor therapies. The evolving understanding of how dendritic cells regulate immune responses and promising results from published studies of immune-enhancing cytokines in the treatment of patients with malignant disease support the conduct of randomized clinical trials to confirm the clinical benefit of these immunotherapeutic strategies.

Abnormal T-cell function in B-cell chronic lymphocytic leukaemia

There is increasing evidence of T cell dysfunction in B cell chronic lymphocytic leukaemia (B-CLL) which may contribute to the aetiology and progress of the disease. An absolute CD8+ lymphocytosis correlates with disease progression and low expression of CD4 and CD8 (as found in autoimmune disease) is seen with abnormal expression of other surface molecules. Although the expression of T cell surface activation markers, CD25 and CD152, may be increased on culture in B-CLL serum, response to the common mitogens, PHA and PWM, is reduced. This and the excess of CD8 cells may explain partly the variable cooperation of T cells with B cell production of immunoglobulin in B-CLL. In the context of T cell cross-talk with antigen presenting cells, B-CLL B cells are poor antigen presenters. But the T cells themselves have significant abnormalities of expression of the many antigens and ligands necessary for this process. In particular, they exhibit variable expression of the low affinity and non-specific adhesion molecules LFA-1 and ICAM-1, variable, clonally restricted and skewed expression of the TCR repertoire (implying repeated antigenic stimulation possibly by CLL antigens), reduced CD28 and CD152 expression (implying impairment of ability to start or stop an immune response) and reduced IL2 and CD25 (IL2 R) expression (critical for positive feed-back in maintenance and expansion of the T cell response to antigen presentation). Although the production of IL2 and other cytokines by the T cell in B-CLL may be impaired, production of the anti-apoptotic cytokine IL4 is not and there may be a unique and expanded subset of CD8/CD30 cells capable of releasing IL4. The relationship of this T cell subset to the malignant B cell in vivo is unknown. However, T cells which are CD4+/CD152+/CCR4+ migrate selectively in vitro in response to the chemokine CCL22 (specific for the receptor CCR4) produced by the malignant B cells and are always seen amongst the malignant cells in bone marrow and lymph nodes from B-CLL patients. Other abnormalities of cytokine secretion are described. These findings suggest that the T cell in B-CLL may be unable to start, maintain and complete an immune response to the malignant B cell and other antigens and may be involved directly in sustaining the tumour. However, autologous tumour specific cytotoxicity has been shown in vitro and T cells which recognise tumour-derived heavy chain fragments circulate in vivo. If adoptive immunotherapy of any nature is to succeed in B-CLL, manipulation to optimise these CTL responses is needed to overcome the profound and variable T cell dysfunction in this disease.

Idiotype-pulsed dendritic cells are able to induce antitumoral cytotoxic CD8 cells in chronic lymphocytic leukaemia

Idiotypic structures of immunoglobulins from malignant B cells constitute tumour-specific antigens, though the function of immunoglobulin-specific CD8+ T cells in disease control and rejection remains unclear. We have studied five cases of B chronic lymphocytic leukaemia patients affected with indolent (three patients) or aggressive (two patients) disease. We showed that CD8+ T cells with major histocompatibility complex class I-restricted cytotoxicity against autologous tumour B cells could be generated following repeated stimulations with idiotype-pulsed dendritic cells in vitro. CD8+ T-cell lines were able to upregulate CD69 expression and to release interferon (IFN)-gamma upon contact with the autologous B cells, though cytolytic activity was only substantiated for patients with indolent disease. The failure of cytolytic activity in patients with aggressive disease may be explained by a skewed maturation of memory CD8 cells.

In vitro dendritic cell-induced T cell responses to B cell chronic lymphocytic leukaemia enhanced by IL-15 and dendritic cell-B-CLL electrofusion hybrids

HLA class II-restricted proliferative and cytotoxic T cell (CTL) responses to B cell chronic lymphocytic leukaemia (B-CLL) can be generated using autologous dendritic cells (DCs) pulsed with tumour cell lysate. In this study a number of different approaches were used to optimize further the in vitro system. First, the effects of a variety of maturation agents were studied. The addition of TNF-alpha, polyriboinosinic polyribocytidylic acid (Poly(I:C)) and LPS to autologous DCs resulted in the emergence of only a small percentage of CD83+ DCs, IFN-alpha having no demonstrable effect. Only the addition of Poly(I:C) to DCs resulted in modestly increased specific cytotoxicity to B-CLL targets, IFN-alpha and LPS having no effect. Secondly, T cells were pretreated with IL-15, prior to culturing with lysate-pulsed autologous DCs. A significant increase in T cell activation (P = 0.038), IFN-gamma secretion (P = 0.030) and specific cytotoxicity to B-CLL targets (P = 0.006) was demonstrated compared to untreated T cells. Thirdly, monocyte derived DCs electrofused with B-CLL B cells were compared with lysate-pulsed DCs. T cells stimulated by fused DCs generated higher levels of specific cytotoxicity to autologous B-CLL B cell targets than those stimulated by lysate pulsed DCs (P = 0.013). Blocking studies demonstrated inhibition of this cytotoxicity by both anti-CD4 (P = 0.062) and anti-CD8 monoclonal antibodies (P = 0.018), suggesting the generation of both HLA class I- and HLA class II-restricted CTL responses. In summary, in vitro B-CLL-specific T cell responses can be enhanced further by preincubating T cells with IL-15 and using autologous fused DC-B-CLL hybrids instead of autologous lysate-pulsed DCs. These preliminary data require confirmation with larger numbers of patients. Such an approach, however, may eventually provide effective immunotherapy for treatment of B-CLL.