Immunomodulatory dendritic cells generated from nonfractionated bulk peripheral blood mononuclear cell cultures induce growth of cytotoxic T cells against renal cell carcinoma

Current status of research on exosomes in general, and for the diagnosis and treatment of kidney cancer in particular

Kidney cancer is a common urological tumour. Owing to its high prevalence and mortality rate, it is the third most malignant tumour of the urinary system, followed by prostate and bladder cancers. It exerts a high degree of malignancy, and most of the distant metastasis occurs at an early stage; it is insensitive to chemoradiotherapy and easily develops drug resistance. The current treatment for kidney cancer mainly includes surgery, interventional embolization and targeted therapy; however, the treatment efficacy is poor. In recent years, the role of exosomes as mediators of intercellular communication and information exchange in the tumour microenvironment in tumour pathogenesis has attracted much attention. Exosomes are rich in bioactive substances such as nucleic acids, proteins and lipids and are involved in angiogenesis, immune regulation, drug resistance, formation of pre-metastatic niche, invasion and metastasis. This article reviews the ongoing research and applications of exosomes for the diagnosis and treatment of kidney cancer.

Cell-based immune therapy for metastatic renal cancer

An exciting group of investigational therapies for metastatic renal cancer use cellular preparations. Technical advances accommodate testing strategies to repair, bypass or direct the immune system to defeat the pathologic absence of effective antitumor response. These can be organized by corresponding steps of the immune process: passive infusion of effectors isolated from blood, tumor or lymph nodes draining a vaccinated area; nonmyeloablative transplantation with stem cells plus lymphocytes specific for alloantigens, including tumor antigens, and reconstitution of antigen presentation by dendritic cells or modified tumor cells. Key monitoring of treatment outcome includes conventional clinical response measurement and also correlative assays as benchmarks of theoretically useful immunologic events. Broad efforts with innovative treatments may portend real progress for metastatic renal cancer immunotherapy.

Combination vaccine of dendritic cells (DCs) and T cells effectively suppressed preestablished malignant melanoma in mice

The study aims at establishing a novel vaccine procedure, using bone marrow-derived DCs that have ingested apoptotic B16 melanoma (DCs(+)), alone or in combination with splenic T lymphocytes from a syngenic donor. Co-immunization with DCs(+) and T cells showed the highest antitumor potential against preestablished B16 tumor in mice, in which CTL and NK cytotoxicities were drastically elevated, while either DCs(+) alone, naive DCs (DCs(-)) alone, or a mixture of DCs(-) and T cells induced less significant therapeutic outcomes. Use of extracellular matrix proteins elevated antitumor activity of DC(-)/T cell vaccine. Compared with the CD8(+) cells, the CD4(+)T cells more remarkably improved the efficacy of DC-based immunotherapy. The present system may be a feasible therapeutic modality to eradicate malignancies including melanoma.

Adjuvant treatment for renal cell carcinoma

Despite significant advances in the diagnosis, staging and treatment of patients with renal cell carcinoma, recurrence rates following surgical resection of locally aggressive tumours remain high. In an effort to delay disease progression and improve survival, the concept of adjuvant therapy has been proposed. Optimal adjuvant therapy for surgically resected renal cell carcinoma remains to be defined and the evaluation of adjuvant therapies will require properly controlled and adequately powered randomised trials. Promising preliminary results have been seen with active immunotherapies and agents that target critical signalling pathways, and there are several Phase III trials of these novel treatment options that are underway. In addition, classification of patients into high- and low-risk subgroups on the basis of a prognosis profile will serve as a useful means to guide clinicians in improving the selection of patients who are likely to derive benefit from adjuvant therapy. This will lead to a future area of investigation, which will be the identification of patients within the target population that should respond to a given treatment. This review will discuss the role and current status of adjuvant therapies for renal cell carcinoma.

Identification of novel CD33 antigen-specific peptides for the generation of cytotoxic T lymphocytes against acute myeloid leukemia

Identification of immunogenic peptides for the generation of cytotoxic T lymphocytes (CTLs) may lead to the development of novel cellular therapies to treat disease relapse in acute myeloid leukemia (AML) patients. The objective of these studies was to evaluate the ability of unique HLA-A2.1-specific nonameric peptides derived from CD33 antigen to generate AML-specific CTLs ex vivo. We present data here on the identification of an immunogeneic HLA-A2.1-specific CD33(65-73) peptide (AIISGDSPV) that was capable of inducing CTLs targeted to AML cells. The CD33-CTLs displayed HLA-A2.1-restricted cytotoxicity against both mononuclear cells from AML patients and the AML cell line. The peptide- as well as AML cell-specificity of CD33-CTLs was demonstrated and the secretion of IFN-gamma by the CTLs was detected in response to CD33(65-73) peptide stimulation. The cultures contained a distinct CD33(65-73) peptide-tetramer(+)/CD8(+) population. Alteration of the native CD33(65-73) peptide at the first amino acid residue from alanine (A) to tyrosine (Y) enhanced the HLA-A2.1 affinity/stability of the modified CD33 peptide (YIISGDSPV) and induced CTLs with increased cytotoxicity against AML cells. These data therefore demonstrate the potential of using immunogenic HLA-A2.1-specific CD33 peptides in developing a cellular immunotherapy for the treatment of AML patients.

Current status of dendritic cell immunotherapy of malignancies

Because dendritic cells (DC) are central to the induction of antigen-specific T cell responses, their use for the active immunotherapy of malignancies has been of considerable interest. Since clinical trials with DC-based vaccines have been initiated, a number of important developmental issues have become apparent. These include the ideal source and type of DC, the form of antigen and method of loading DC, whether to induce maturation, the route and timing of immunization, and the optimal clinical scenario. Clinical responses such as stability of disease and tumor regressions have been reported in some patients, particularly with melanoma, myeloma, and prostate cancer.

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.

Advances in dendritic cell-based vaccine of cancer

Dendritic cells (DCs) are potent antigen presenting cells that exist in virtually every tissue, and from which they capture antigens and migrate to secondary lymphoid organs where they activate naïve T cells. Although DCs are normally present in extremely small numbers in the circulation, recent advances in DC biology have allowed the development of methods to generate large numbers of these cells in vitro. Because of their immunoregulatory capacity, vaccination with tumor antigen-presenting DCs has been proposed as a treatment modality for cancer. In animal models, vaccination with DCs pulsed with tumor peptides, lysates, or RNA or loaded with apoptotic/necrotic tumor cells could induce significant antitumor CTL responses and antitumor immunity. However, the results from early clinical trails pointed to a need for additional improvement of DC-based vaccines before they could be considered as practical alternatives to the existing cancer treatment strategies. In this regard, subsequent studies have shown that DCs that express transgenes encoding tumor antigens are more potent primers of antitumor immunity both in vitro and in vivo than DCs simply pulsed with tumor peptides. Furthermore, DCs that have been engineered to express certain cytokines or chemokines can display a substantially improved maturation status, capacity to migrate to secondary lymphoid organs in vivo, and abilities to stimulate tumor-specific T cell responses and induce tumor immunity in vivo. In this review we also discuss a number of factors that are important considerations in designing DC vaccine strategies, including (i) the type and concentrations of tumor peptides used for pulsing DCs; (ii) the timing and intervals for DC vaccination/boostable data on DC vaccination portends bright prospects for this approach to tumor immune therapy, either alone or in conjunction with other therapies.

A novel bulk-culture method for generating mature dendritic cells from mouse bone marrow cells

We established a novel culture method for generating dendritic cells (DC) from mouse bone marrow (BM) cells. Unfractionated bulk BM cells were cultured in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) for 5-7 days and a DC population was isolated by gradient centrifugation with 14.5% (w/v) metrizamide. Through this method, 30-40 x 10(6)/mouse DC with 85-95% purity was obtained on day 7; this yield was higher than those of conventional DC generated by Inaba's method either with GM-CSF alone (conventional-GM DC) or GM-CSF and IL-4 (conventional-GM/4 DC). Bulk-cultured DC have a more matured phenotype than both conventional-GM and -GM/4 DC as shown by higher expression of CD86, MHC class II and CD40. Functional analyses reveal that (1) bulk-DC show less ability in endocytosis than conventional-GM DC and are comparable in IL-12 p70 production with conventional-GM and -GM/4 DC. (2) Bulk-DC exhibit stronger stimulatory capacity in allogeneic T-cell proliferation than conventional DC. (3) By using ovalbumin (OVA) and OVA-specific T-cell receptor (TCR) transgenic mice (DO11.10) system, OVA protein-loaded bulk-DC stimulated CD4 T cells of DO11.10 mice more than conventional-GM DC and comparable with conventional-GM/4 DC. (4) Furthermore, OVA peptide-pulsed bulk-DC stimulated CD4 T cells more than conventional-GM and -GM/4 DC. These data indicate that bulk-DC are functionally more mature than conventional DC. Taken together, bulk-culture method is a simple technique for generating functionally mature BM-DC in large quantities and high purity.

Generation of chronic myelogenous leukemia-specific T cells in cytokine-modified autologous mixed lymphocyte/tumor cell cultures

Chronic myelogenous leukemia (CML) may be amenable to cell-based adoptive immunotherapy, as suggested by the graft-versus-leukemia effect of bone marrow transplantation and the therapeutic benefit of donor leukocyte infusions. Specific adoptive immunotherapy without bone marrow transplantation might be more effective and less cost-intensive. Professional antigen-presenting cells, the dendritic cells, from patients with CML are derived from the malignant clone and may stimulate antileukemia T-cell responses. Autologous T cells may also be able to recognize tumor antigens on CML cells directly. Here, the authors show that CD4 and CD8 T-cell responses to autologous CML cells can be generated in vitro rapidly and effectively by performing modified autologous mixed lymphocyte/tumor cell cultures (MLTC) in serum-free medium in the presence of cytokines known to support dendritic cell differentiation. MLTC-sensitized T cells secreted large amounts of the type 1 cytokine interferon-gamma, as well as interleukin (IL)-2. However, they also secreted a variety of other cytokines, including the type 2-subtype cytokine IL-13 but not the classic type 2 cytokines IL-4, IL-5, and IL-10. Monoclonal populations of CML-specific CD4 cells could be derived from these lines in limited numbers but showed markedly enhanced reactivity. This suggests that CML-specific T cells are relatively rare in these autologous MTLC-derived sensitized populations, but that their isolation and propagation would yield much more potent antitumor effector cells for use in adoptive immunotherapy without the need for bone marrow transplantation.