Immune responses in patients with metastatic renal cell carcinoma treated with dendritic cells pulsed with tumor lysate

Targeting Telomere Dynamics as an Effective Approach for the Development of Cancer Therapeutics

Telomere is a protective structure located at the end of chromosomes of eukaryotes, involved in maintaining the integrity and stability of the genome. Telomeres play an essential role in cancer progression; accordingly, targeting telomere dynamics emerges as an effective approach for the development of cancer therapeutics. Targeting telomere dynamics may work through multifaceted molecular mechanisms; those include the activation of anti-telomerase immune responses, shortening of telomere lengths, induction of telomere dysfunction and constitution of telomerase-responsive drug release systems. In this review, we summarize a wide variety of telomere dynamics-targeted agents in preclinical studies and clinical trials, and reveal their promising therapeutic potential in cancer therapy. As shown, telomere dynamics-active agents are effective as anti-cancer chemotherapeutics and immunotherapeutics. Notably, these agents may display efficacy against cancer stem cells, reducing cancer stem levels. Furthermore, these agents can be integrated with the capability of tumor-specific drug delivery by the constitution of related nanoparticles, antibody drug conjugates and HSA-based drugs.

Multidisciplinary Approach to HCC Management: How Can This Be Done?

Multidisciplinary tumor boards have evolved to address the increasing complexity of cancer care management. Given that hepatocellular carcinoma (HCC) often arises in the setting of underlying cirrhosis, expert input from hepatologists alongside hepatobiliary and transplant surgeons, radiation oncologists, interventional and body radiologists, and medical oncologists has become increasingly important in order to offer patients appropriate cancer treatments. The MDLTB structure has evolved since the early 2000s to bring these specialists together at regularly scheduled meetings to develop a therapeutic treatment plan for HCC management. MDLTBs have reduced the time to treatment and improved patient satisfaction. Standardized documentation with common data elements has been recommended to ensure adequate communication from MDLTB to referring healthcare providers. Retrospective studies consistently highlight the frequency of changes in treatment plans after MDLTB review to better adhere to guideline recommended care. Despite several decades of MDLTBs implementation, few studies describe clinical outcomes associated with MDLTBs such as patient survival and cost benefits. More research is needed in this area to further justify the heavy use of resources that are needed to maintain MDLTBs. Development and use of a centralized database to store such information may assist with future studies of clinical outcomes and inform quality improvement projects.

Kill and spread the word: stimulation of antitumor immune responses in the context of radiotherapy

Besides the direct, targeted effects of ionizing irradiation (x-ray) on cancer cells, namely DNA damage and cell death induction, indirect, nontargeted ones exist, which are mediated in large part by the immune system. Immunogenic forms of tumor cell death induced by x-ray, including immune modulating danger signals like the heat shock protein 70, adenosine triphosphate, and high-mobility group box 1 protein are presented. Further, antitumor effects exerted by cells of the innate (natural killer cells) as well as adaptive immune system (T cells activated by dendritic cells) are outlined. Tumor cell death inhibiting molecules such as survivin are introduced as suitable target for molecularly tailored therapies in combination with x-ray. Finally, reasonable combinations of immune therapies with radiotherapy are discussed.

Trial watch: Dendritic cell-based interventions for cancer therapy

Dendritic cells (DCs) occupy a central position in the immune system, orchestrating a wide repertoire of responses that span from the development of self-tolerance to the elicitation of potent cellular and humoral immunity. Accordingly, DCs are involved in the etiology of conditions as diverse as infectious diseases, allergic and autoimmune disorders, graft rejection and cancer. During the last decade, several methods have been developed to load DCs with tumor-associated antigens, ex vivo or in vivo, in the attempt to use them as therapeutic anticancer vaccines that would elicit clinically relevant immune responses. While this has not always been the case, several clinical studies have demonstrated that DC-based anticancer vaccines are capable of activating tumor-specific immune responses that increase overall survival, at least in a subset of patients. In 2010, this branch of clinical research has culminated with the approval by FDA of a DC-based therapeutic vaccine (sipuleucel-T, Provenge^®) for use in patients with asymptomatic or minimally symptomatic metastatic hormone-refractory prostate cancer. Intense research efforts are currently dedicated to the identification of the immunological features of patients that best respond to DC-based anticancer vaccines. This knowledge may indeed lead to personalized combination strategies that would extend the benefit of DC-based immunotherapy to a larger patient population. In addition, widespread enthusiasm has been generated by the results of the first clinical trials based on in vivo DC targeting, an approach that holds great promises for the future of DC-based immunotherapy. In this Trial Watch, we will summarize the results of recently completed clinical trials and discuss the progress of ongoing studies that have evaluated/are evaluating DC-based interventions for cancer therapy.

A pilot study of autologous tumor lysate-loaded dendritic cell vaccination combined with sunitinib for metastatic renal cell carcinoma

Background

Sunitinib, a tyrosine kinase inhibitor currently in use for the treatment of metastatic renal cell carcinoma (mRCC), has been reported to modulate immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in addition to exerting anti-angiogenic effects. We conducted a clinical trial of dendritic cell (DC)-based immunotherapy together with sunitinib in mRCC patients in an effort to enhance immunotherapeutic efficacy by inhibiting immunosuppressive cells.

Methods

Patients aged ≥20 years with advanced or recurrent mRCC who underwent nephrectomy were eligible for this study. Autologous tumor samples were obtained by surgery under aseptic conditions and used for preparing autologous tumor lysate. About 4 weeks after surgery, leukapheresis was performed to isolate peripheral blood mononuclear cells (PBMCs). DCs were generated from adherent PBMCs in the presence of recombinant human granulocyte macrophage colony-stimulating factor (GM-CSF) (500 IU/ml) and recombinant human IL-4 (500 IU/ml). Autologous tumor lysate was loaded into mature DC by electroporation. Eight patients were enrolled in the study and received sunitinib at a dose of 50 mg p.o. daily for 28 days followed by 14 days of rest. Tumor lysate-loaded DCs were administered subcutaneously every two weeks, with concomitant sunitinib.

Results

No severe adverse events related to vaccination were observed. Sunitinib decreased the frequencies of MDSCs in peripheral blood of 5 patients and of Tregs in 3. Tumor lysate-reactive CD4 or CD8 T cell responses were observed in 5 patients, 4 of whom showed decreased frequencies of Tregs and/or MDSCs. The remaining 3 patients who failed to develop tumor-reactive T cell responses had high levels of IL-8 in their sera and did not show consistent reductions in MDSCs and Tregs.

Conclusions

DC-based immunotherapy combined with sunitinib is safe and feasible for patients with mRCC.

Trial registration

UMIN000002136

Complex evaluation of human monocyte-derived dendritic cells for cancer immunotherapy

Dendritic cell (DC) immunotherapy is capable of generating tumour-specific immune responses. Different maturation strategies were previously tested to obtain DC capable of anti-cancer responses in vitro, usually with limited clinical benefit. Mutual comparison of currently used maturation strategies and subsequent complex evaluation of DC functions and their stimulatory capacity on T cells was performed in this study to optimize the DC vaccination strategy for further clinical application. DC were generated from monocytes using granulocyte–macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, pulsed with whole tumour cell lysate and then matured with one of five selected maturation strategies or cultured without additional maturation stimulus. DC were characterized with regard to their surface marker expression, cytokine profiles, migratory capacity, allogeneic and autologous T cell stimulatory capacity as well as their specific cytotoxicity against tumour antigens. We were able to demonstrate extensive variability among different maturation strategies currently used in DC immunotherapeutic protocols that may at least partially explain limited clinical benefit of some clinical trials with such DC. We identified DC matured with interferon-γ and lipopolysaccharide as the most attractive candidate for future clinical trials in cancer immunotherapy.

Trial Watch: Peptide vaccines in cancer therapy

Throughout the past 3 decades, along with the recognition that the immune system not only influences oncogenesis and tumor progression, but also determines how established neoplastic lesions respond therapy, renovated enthusiasm has gathered around the possibility of using vaccines as anticancer agents. Such an enthusiasm quickly tempered when it became clear that anticancer vaccines would have to be devised as therapeutic, rather than prophylactic, measures, and that malignant cells often fail to elicit (or actively suppress) innate and adaptive immune responses. Nonetheless, accumulating evidence indicates that a variety of anticancer vaccines, including cell-based, DNA-based, and purified component-based preparations, are capable of circumventing the poorly immunogenic and highly immunosuppressive nature of most tumors and elicit (at least under some circumstances) therapeutically relevant immune responses. Great efforts are currently being devoted to the identification of strategies that may provide anticancer vaccines with the capacity of breaking immunological tolerance and eliciting tumor-associated antigen-specific immunity in a majority of patients. In this sense, promising results have been obtained by combining anticancer vaccines with a relatively varied panels of adjuvants, including multiple immunostimulatory cytokines, Toll-like receptor agonists as well as inhibitors of immune checkpoints. One year ago, in the December issue of OncoImmunology, we discussed the biological mechanisms that underlie the antineoplastic effects of peptide-based vaccines and presented an abundant literature demonstrating the prominent clinical potential of such an approach. Here, we review the latest developments in this exciting area of research, focusing on high-profile studies that have been published during the last 13 mo and clinical trials launched in the same period to evaluate purified peptides or full-length proteins as therapeutic anticancer agents.

Generation of CTL responses against pancreatic cancer in vitro using dendritic cells co-transfected with MUC4 and survivin RNA

Pancreatic cancer (PC) is one of the most devastating human malignancies without effective therapies. Tumor vaccine based on RNA-transfected dendritic cells (DCs) has emerged as an alternative therapeutic approach for a variety of human cancers including advanced PC. In the present study we compared the cytotoxic T lymphocyte (CTL) responses against PC cells in vitro, which were induced by DCs co-transfected with two mRNAs of tumor associated-antigens (TAA) MUC4 and survivin, versus DCs transfected with a single mRNA encoding either MUC4 or survivin. DCs co-transfected with two TAA mRNAs were found to induce stronger CTL responses against PC target cells in vitro, compared with the DCs transfected with a single mRNA. Moreover, the antigen-specific CTL responses were MHC class I-restricted. These results provide an experimental foundation for further clinical investigations of DC vaccines encoding multiple TAA epitopes for metastatic PC.

Influence of immunotherapy with autologous dendritic cells on innate and adaptive immune response in cancer

The objective of this study was to evaluate some of the mechanisms involved in the activation of the immune system in patients with advanced-stage cancer (n = 7) who received an autologous dendritic cell vaccine. We examined the immune response mediated by macrophages (CD14+), natural killer cells (CD56+), and B lymphocytes (CD19+) by flow cytometry and assessed the expression of Th1 (IFN-γ, TNF-α, IL-2, and IL-12), Th2 (IL-4), and Treg (TGF-β) cytokines by flow cytometry and an enzyme-linked immunosorbent assay. The CD14+ TNF-α+ population was significantly increased (P < 0.04) when patients received the vaccine; IL-2 expression in both NK cells and in B lymphocytes was increased after a transient initial increase showed a nearly significant decrease (P < 0.07 and P < 0.06 respectively), whereas the CD19+ and CD56+ populations did not show significant changes. Dendritic cell-based immunotherapy led to increased secretion of IFN-γ and IL-12 and reduced secretion of TGF-β. In conclusion, it is likely that the autologous dendritic cell vaccine stimulated the immune cells from the peripheral blood of patients with cancer and generally increased the production of Th1 cytokines, which are related to immunomodulatory responses against cancer.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

Dendritic cell-based vaccination for renal cell carcinoma: challenges in clinical trials

After decades of research, dendritic cell (DC)-based vaccines for renal cell carcinoma have progressed from preclinical rodent models and safety assessments to Phase I/II clinical trials. DC vaccines represent a promising therapy that has produced measurable immunological responses and prolonged survival rates. However, there is still much room to improve in terms of therapeutic efficacy. The key issues that affect the efficiency and reliability of DC therapy include the selection of patients who will respond best to treatment, the proper preparation and administration of DC vaccines, and a combination of DC vaccination with other immune-enhancing therapies (e.g., removal of Tregs, CTLA-4 blockade and lymphodepletion). Additional antiangiogenic agents will hopefully lead to greater survival benefits for patients in early disease stages. This review focuses on the different approaches of DC-based vaccination against renal cell carcinoma and potential strategies to enhance the efficacy of DC vaccination.

Role of vaccine therapy for renal cell carcinoma in the era of targeted therapy

Renal cell carcinoma is the most common malignant tumor originating from the kidney. Compared with other solid tumors, it does not respond to traditional management modalities, such as chemotherapy and radiotherapy. However, it is well known that renal cell carcinoma represents one of the most immune-responsive cancers and several immunotherapeutic strategies have been investigated in the management of renal cell carcinoma with variable degrees of success. The development of immunotherapy with α-interferon or high-dose interleukin-2 is the best established treatment, and is associated with durable disease control. Although the lack of defined antigens in renal cell carcinoma has hindered more specific vaccine development, research regarding vaccination therapy has been of special interest for the treatment of renal cell carcinoma for more than 30 years. At present, there are three types of cell-based vaccines in renal cell carcinoma treatment: autologous tumor-cell vaccines, genetically modified tumor vaccines and dendritic cell-based vaccines. A further type is peptide-based vaccination with tumor-associated antigens as possible targets, such as carbonic anhydrase IX, survivin and telomerase that are overexpressed in renal cell carcinoma. In the present article, we review data from completed clinical trials of vaccine therapy, and discuss future trials to assess the current knowledge and future role of vaccine therapy for renal cell carcinoma in the era of recently developed targeted therapy.

Anti-TGF-β antibody combined with dendritic cells produce antitumor effects in osteosarcoma

BACKGROUND

We previously reported the combination of tumor cryotreatment with dendritic cells to promote antitumor immunity. The effect of the combination treatment with dendritic cells and antitransforming growth factor-β (anti-TGF-β) antibody on the elimination of regulatory T cells and the inhibition of tumor growth was investigated.

QUESTIONS/PURPOSES

The effects of the combination treatment with dendritic cells and anti-TGF-β antibody on the enhancement of systemic immune responses and inhibition of metastatic tumor growth were investigated in a murine osteosarcoma (LM8) model.

MATERIALS AND METHODS

To evaluate activation of the immune response, we established the following three groups of C3H mice (60 mice total): (1) excision only; (2) tumor excision and administration of anti-TGF-β antibody; and (3) tumor excision and administration of dendritic cells exposed to cryotreated tumor lysates with anti-TGF-β antibody.

RESULTS

The mice that received dendritic cells exposed to cryotreated tumor lysates with anti-TGF-β antibody showed increased numbers of CD8(+) T lymphocytes, reduced regulatory T lymphocytes in the metastatic lesion, and inhibition of metastatic growth. The combined therapy group showed reduced numbers of regulatory T lymphocytes in the spleen and high serum interferon γ level.

CONCLUSIONS

The control of the inhibitory condition induced by regulatory T cells is important to improve the suppression of the cytotoxic lymphocytes. Combining dendritic cells with anti-TGF-β antibody enhanced the systemic immune response.

CLINICAL RELEVANCE

We suggest that our immunotherapy could be developed further to improve the treatment of osteosarcoma.

Human renal cancer stem cells

Cancer stem cells (CSCs), isolated in renal carcinomas, exhibit tumor-initiating capabilities and pluripotency. No specific CSC markers have been identified so far; therefore, their characterization is mainly based on functional studies. As they are resistant to chemo and radio therapy, renal CSCs may have a relevant role in tumor establishment, progression, and recurrence. CSCs were also shown to contribute to intra-tumor vasculogenesis through an endothelial differentiation and to favor the generation of the pre-metastatic niche through the release of exosomes/microvesicles.

Differentiation therapy: targeting human renal cancer stem cells with interleukin 15

BACKGROUND

Many renal cancer patients experience disease recurrence after immunotherapy or combined treatments due to persistence of cancer stem cells (CSCs). The identification of reliable inducers of CSC differentiation may facilitate the development of efficient strategies for eliminating CSCs. We investigated whether interleukin 15 (IL-15), a regulator of kidney homeostasis, induces the differentiation of CD105-positive (CD105(+)) CSCs from human renal cancers.

METHODS

CD105(+) CSCs were cultured to preserve their stem cell properties and treated with recombinant human IL-15 (rhIL-15) to evaluate their ability to differentiate, to acquire sensitivity to chemotherapeutic drugs, and to form spheroids in vitro and tumors in vivo. Expression of stem cell and epithelial markers were studied by flow cytometry, immunocytochemistry, and immunoblotting. Identification of a CSC side population fraction and its sensitivity to chemotherapy drugs and expression of ATP-binding cassette (ABC) transporters and aldehyde dehydrogenase (ALDH) activities were determined by flow cytometry. Spheroid formation was determined in limiting dilution assay. Xenograft tumors were generated in severe combined immunodeficient mice (n = 12-18 mice per group). All statistical tests were two-sided.

RESULTS

CD105(+) CSCs treated with rhIL-15 at 10 pg/mL differentiated into cells expressing epithelial markers. rhIL-15 induced epithelial differentiation of all CD105(+) CSCs subsets and blocked CSC self-renewal (sphere-forming ability) and their tumorigenic properties in severe combined immunodeficient mice. Vinblastine and paclitaxel induced statistically significant higher levels of apoptosis in rhIL-15-differentiated epithelial cells compared with CD105(+) CSCs (mean percentage of apoptotic cells, vinblastine: 33% vs 16.5%, difference = 16.5%, 95% confidence interval = 12.25% to 20.74%, P = .0025; paclitaxel: 35% vs 11.6%, difference = 23.4%, 95% confidence interval = 22.5% to 24.24%, P = .0015). The higher sensitivity of rhIL-15-differentiated epithelial cells to chemotherapeutic drugs was associated with loss of detoxifying mechanisms such as ALDH and ABC transporter activities.

CONCLUSION

IL-15 directs the epithelial differentiation of renal CSCs and meets the criteria for a treatment strategy: CSC pool depletion and generation of differentiated nontumorigenic cells that are sensitive to chemotherapeutic agents.

Vaccination therapy in renal cell carcinoma: current position and future options in metastatic and localized disease

As renal cell carcinoma represents one of the most immune-responsive cancers, immunotherapy exhibits a suitable treatment basis. Beside nonspecific stimulation via cytokines, passive specific and active immunotherapy are also appropriate options to recognize and destroy tumor cells. For more than 30 years, research regarding vaccination therapy has been of special interest for the treatment of renal cell carcinoma. However, apart from occasional promising results in Phase I and II trials, vaccination therapy is still considered experimental in this tumor entity, especially owing to missing results from Phase III trials demonstrating clinical efficacy. In the present article, we review data from completed clinical trials of vaccination therapy and also discuss scheduled future trials, in order to assess the current position and possible future fields of application of vaccination therapy in renal cell carcinoma in the era of recently developed targeted therapies.

Human dendritic cells transfected with amplified MUC1 mRNA stimulate cytotoxic T lymphocyte responses against pancreatic cancer in vitro

BACKGROUND AND AIM

Mucin (MUC) 1 is an epithelial cell glycoprotein that is aberrantly overexpressed in many adenocarcinomas, including pancreatic cancer (PC), providing an ideal tumor-associated antigen and target for immunotherapy. In this study, we investigated whether the cytotoxic T lymphocytes (CTLs) induced by dendritic cells (DCs) transfected with amplified MUC1 mRNA could respond against PC in vitro.

METHODS

Amplified mRNA encoding MUC1 were transfected into DCs using electroporation with an optimized setting and the MUC1 expression were evaluated by quantitative real-time polymerase chain reaction and Western blot. The MUC1 specific CTL responses were measured using the standard chromium 51 (51Cr)-release assays and the interferon-γ release assay.

RESULTS

Dendritic cells could be transfected with amplified MUC1 mRNA efficiently. The transfected DCs were remarkably effective in stimulating MUC1-specific CTL responses in vitro. The function of MUC1 specific CTLs, induced by MUC1 mRNA-transfected DCs, was restricted by major histocompatibility complex (MHC) class I antigen presentation.

CONCLUSION

The CTL responses stimulated by DCs transfected with MUC1 mRNA could only recognize and lyse HLA-A2+/MUC1+ PC and other target cells under restriction by MHC class I-specific antigen presentation, providing a preclinical rationale for using MUC1 as a target structure for immunotherapeutic strategies against PC.

Vaccination with autologous dendritic cells pulsed with multiple tumor antigens for treatment of patients with malignant melanoma: results from a phase I/II trial

BACKGROUND AND AIM

Dendritic cells are regarded as the most effective antigen presenting cells and coordinators of the immune response and therefore suitable as vaccine basis. Here we present results from a clinical study in which patients with malignant melanoma (MM) with verified progressive disease received vaccination with autologous monocyte-derived mature dendritic cells (DC) pulsed with p53, survivin and telomerase-derived peptides (HLA-A2+ patients) or with autologous/allogeneic tumor lysate (HLA-A2(−) patients) in combination with low-dose interleukin (IL)-2 and interferon (IFN)-alpha2b.

RESULTS

Of 46 patients who initiated treatment, 10 stopped treatment within 1-4 weeks because of rapid disease progression and deterioration. After 8 weeks, 36 patients were evaluable: no patient had an objective response, 11 patients had stable disease (SD); six had continued SD after 4 months, and three patients had prolonged SD for more than 6 months. The mean overall survival time was 9 months, with a significantly longer survival (18.4 months) of patients who attained SD compared with patients with progressive disease (PD) (5 months). Induction of antigen-specific T-cell responses was analyzed by multidimensional encoding of T cells using HLA-A2 major histocompatibility complex (MHC) multimers. Immune responses against five high-affinity vaccine peptides were detectable in the peripheral blood of six out of 10 analyzed HLA-A2+ patients. There was no observed correlation between the induction of immune responses and disease stabilization. A significant lower blood level of regulatory T cells (CD25(high) CD4 T cells) was demonstrable after six vaccinations in patients with SD compared with PD.

CONCLUSIONS

Vaccination was feasible and safe. Treatment-associated SD was observed in 24% of the patients. SD correlated with prolonged survival suggesting a clinical benefit. Differences in the level of regulatory T cells among SD and PD patients could indicate a significant role of these immune suppressive cells.

Monitoring cytokine profiles during immunotherapy

Measuring cytokine production is an integral part of measuring immune response during immunotherapy. Current technologies allow the simultaneous quantification of multiple cytokines in a variety of tissues. Patterns of cytokine response can be referred to as cytokine profiles. This article discusses the experimental design and data analysis of a number of studies that examined cytokine profiles in humans. We highlight potential sources of variability, both due to assay nuances and the diversity of human populations. We present strategies for analyzing data, emphasizing both multidimensional analysis and the value of treating each donor as his or her own control.

Dendritic cell-tumor cell hybrids and immunotherapy: what's next?

Dendritic cells (DC) are professional antigen-presenting cells currently being used as a cellular adjuvant in cancer immunotherapy strategies. Unfortunately, DC-based vaccines have not demonstrated spectacular clinical results. DC loading with tumor antigens and DC differentiation and activation still require optimization. An alternative technique for providing antigens to DC consists of the direct fusion of dendritic cells with tumor cells. These resulting hybrid cells may express both major histocompatibility complex (MHC) class I and II molecules associated with tumor antigens and the appropriate co-stimulatory molecules required for T-cell activation. Initially tested in animal models, this approach has now been evaluated in clinical trials, although with limited success. We summarize and discuss the results from the animal studies and first clinical trials. We also present a new approach to inducing hybrid formation by expression of viral fusogenic membrane glycoproteins.

Monocyte-derived DC maturation strategies and related pathways: a transcriptional view

Ex vivo production of highly stimulator mature dendritic cells (DCs) for cellular therapy has been used to treat different pathological conditions with the aim of inducing a specific immune response. In the last decade, several protocols have been developed to mature monocyte-derived DCs: each one has led to the generation of DCs showing different phenotypes and stimulatory abilities, but it is not yet known which one is the best for inducing effective immune responses. We grouped several different maturation protocols according to the downstream pathways they activated and reviewed the shared features at a transcriptomic level to reveal the potential of DCs matured by each protocol to develop Th-polarized immune responses.

Human myeloid dendritic cells for cancer therapy: does maturation matter?

Dendritic cells form the connection between innate and adoptive mechanisms of the immune system. As antigen-presenting cells, dendritic cells are capable of presenting tumour antigen and effectively stimulating immune response targeted against a tumour. A number of preclinical and clinical studies document dendritic cells' potential in anti-cancer treatment. Increasing knowledge of dendritic cell biology is leading to improved methods for their preparation for clinical application. Unfortunately, there is to date no consensus specifying optimal conditions for dendritic cell preparation in vitro. This review summarizes the methods used for preparing myeloid dendritic cells derived from monocytic precursors while focusing on cytokine cocktails used for their growth, maturation, and functional adjustment.

Cellular vaccine approaches

Therapeutic cancer vaccines aim to generate immunologic targeting of cancer cells through the induction of effective cellular and antibody-mediated responses specific for antigens selectively expressed by the tumor. Exploiting the adaptive immune system as a targeted tool against cancer is appealing in its capacity for exact specificity and avoidance of unintended tissue damage seen by other conventional agents such as chemotherapy. There are a multitude of challenges to designing effective vaccine strategies. The components of a vaccine strategy start with the challenges of selecting immunogenic, tumor-specific antigen targets, choosing a platform with which to deliver the antigens, and enhancing the immunostimulatory context in which the vaccines are delivered. Although understanding the components of effective T-cell activation is essential, successful effector T cells can only be produced if there is also an understanding of the natural processes that tumors exploit to down-modulate active immune responses. These processes are normally used to down-regulate excessive tissue-destructive immune responses against infectious agents once the infecting agent is cleared or to prevent autoimmunity. Advances in molecular and cellular technologies continue to provide insights into the regulation of immune responses both to infectious agents and to cancer that may be manipulated to tip the balance in favor of tumor regression over immune tolerance. This review focuses primarily on cellular vaccines. For the purpose of this review, cellular vaccines are defined as vaccines that use whole cells or cell lysates either as the source of antigens or the platform in which to deliver the antigens. Dendritic cell (DC)-based vaccines focus on ex vivo antigen delivery to DCs. Other platforms such as GVAX (tumor cells genetically engineered to produce granulocyte-macrophage colony-stimulating factor) aim to deliver tumor antigens in vivo in an immune stimulatory context to endogenous DCs. Because data continue to emerge regarding the importance of the maturation status of DCs and the importance of the particular subset of DCs being targeted, these insights will be integrated into vaccine strategies that are likely to produce more effective vaccines.