PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Immunotherapy. Author manuscript; available in PMC 2010 November 1.
Published in final edited form as:
PMCID: PMC2819192
NIHMSID: NIHMS171825

Personalized dendritic cell-based tumor immunotherapy

Abstract

Advances in the understanding of the immunoregulatory functions of dendritic cells (DCs) in animal models and humans have led to their exploitation as anticancer vaccines. Although DC-based immunotherapy has proven clinically safe and efficient to induce tumor-specific immune responses, only a limited number of objective clinical responses have been reported in cancer patients. These relatively disappointing results have prompted the evaluation of multiple approaches to improve the efficacy of DC vaccines. The topic of this review focuses on personalized DC-based anticancer vaccines, which in theory have the potential to present to the host immune system the entire repertoire of antigens harbored by autologous tumor cells. We also discuss the implementation of these vaccines in cancer therapeutic strategies, their limitations and the future challenges for effective immunotherapy against cancer.

Keywords: anticancer immune response, chaperone protein, dendritic cell, idiotype, personalized tumor vaccine, tumor lysate

The concept of cancer immunotherapy is based on the manipulation of the host’s immune system to fight cancer. The primary advantages of active immunotherapy are its relative lack of side effects, its specificity against target tumor cells and the generation a long-lasting memory response against tumor-specific antigens [1-3].

Dendritic cells (DCs) play a central role in the initiation and regulation of tumor-specific immune responses, as they are endowed with the unique potential to activate anti-tumor effector T and B lymphocytes, and are capable of promoting natural killer (NK) T cells or NK cell activation [1,2]. These capacities have been extensively exploited during the last decade, leading to the development of DC-based cancer immuno-therapy. Evidence that anti-tumor immunity can be generated by vaccination with tumor antigen-loaded DCs has been demonstrated in numerous studies [4-9]. However, effective clinical responses in cancer patients have been limited [10] and do not necessarily correlate with the induction of tumor-specific T cells [11,12].

The identification of specific tumor antigens has significantly advanced the field of tumor immunotherapy. Improved understanding of the molecular bases of antigen recognition has resulted in the development of rationally designed tumor antigen-specific vaccines based on motifs predicted to bind to MHC class I and II molecules. Tumor antigen-specific peptide-based vaccines have thus advanced from preclinical to clinical studies over the last decade and several important issues have been addressed during this process [13-15]. The use of synthetic peptides in cancer vaccines offers practical advantages, such as streamlined construction and production. However, it confines the immune response to a restricted repertoire of tumor-specific T lymphocytes recognizing a limited number of epitopes present in the peptides [15,16]. Although some antigens are unique to their tumors (such as idiotypes produced by malignant B cells or viral antigens from virally induced malignancies), most are ‘self’ antigens either overexpressed or mutated in the tumor [17,18]. Personalized cancer vaccines utilizing antigens derived from total tumor cell lysates, tumor-derived chaperone proteins, or apoptotic or necrotic tumor cells contain a pool of multiple undefined antigens. They allow immunization against a wider array of tumor antigens and do not require identification of cancer-specific antigens [19]. This concept is especially important for patients with advanced disease, for which immune escape mechanisms are exacerbated [12,20-24].

In this review we focus on the recent advances in the field of personalized DC-based vaccines for cancer immunotherapy, and discuss their limitations and possible improvements for future clinical trials.

DC-based tumor vaccines

Dendritic cells represent a major focus in cancer immunotherapy as their primary functions are the initiation and regulation of immune responses. DCs generated ex vivo and incubated with a source of tumor-specific antigen(s) have been used both in animal models and in clinical trials [4,5,25-28]. Multiple techniques have been evaluated to produce, expand, load and activate DCs in vitro (Figure 1) (for an extensive review, see Aarntzen et al. [28] and Tuyaerts et al. [29]). The primary source of DCs currently used in clinical trials and in most animal studies consists of monocyte-derived DCs (myeloid DCs). Sequential density centrifugation of apheresis peripheral blood mononuclear cells represents a main approach to enrich for blood DCs for clinical use [29]. Cultured in the presence of GM-CSF and IL-4, monocytes isolated from the blood of patients or from the bone marrow (primarily in experimental animal models), differentiate into immature DCs after a period of 4 to 5 days. Flt3L has also been used to obtain DC expansion. Further activation with TNF-α, IFN-γ, LPS, CpG, IL-1 or CD40L leads to the generation of mature DCs. CMRF-44 antigen, as well as CD1c, BDCA-4 and other DC-specific markers, have also been used to promote DC maturation [29]. In addition, unselected bone marrow cells [5,11,30-32], or CD34+ precursors from blood or bone marrow [33-35] have been utilized to generate DCs. CD34+ cells can be mobilized by GM-CSF administration, which may adversely skew the immune response toward T helper (Th)2 [29]. The purity and the functional grade of the subpopulations of DCs that would ensure highly qualified anti-cancer immune responses [28,29], however, require further standardization.

Figure 1
Ex vivo preparation of dendritic cell-based anticancer vaccines

Choice of a source of tumor antigens to be loaded onto DCs

The activation of specific anti-tumor CD8+ or CD4+ T-cell clones requires the presentation of defined tumor antigens on MHC class I and class II molecules expressed by DCs. The choice of the nature of the tumor antigens used to pulse DCs impacts the specificity and quality of the immune response that will be generated by the vaccine [36-44]. Frequently used in clinical trials, the loading of DCs with peptides derived from defined tumor antigens, or with DNA or RNA encoding one or a few characterized tumor antigens, has the obvious limitation of the requirement to identify specific antigens expressed by tumors. In addition, such vaccines usually lead to the selective expansion and activation of a restricted repertoire of T-cell clones. A microarray analysis of normal and malignant tissues involving the isolation and sequencing of HLA-class I binding peptides from the surface of malignant cells has been described, and allows the identification of patient-specific overexpressed tumor-associated antigens (TAAs) and corresponding HLA-class I peptides [45]. Immunogenic peptides have been identified for numerous known TAAs (including telomerase, tyrosinase, MAGE, Melan-A/MART, MUC1, CEA, p53, HER-2/neu, survivin, etc.) and are usually restricted to a certain HLA type [45-47]. Alternatively, a full-length protein can be presented to DCs, resulting in both CD4+ and CD8+ T-cell responses [29,46]. The use of autologous or allogeneic tumor cells, apoptotic bodies, tumor lysates, tumor RNA or DNA to pulse DCs leads to a considerably more diverse immune response involving numerous clones of CD4+ T cells and CTLs. Additional procedures to pulse DCs, including DC–tumor cell fusion, have been described [39,48]. Enhanced vaccine efficiency of fused DC–tumor cells compared with lysate-pulsed DCs has been reported in different tumor models [49-51]. Other genetic approaches, such as various viral and nonviral gene transfer systems, have also been developed, and are reviewed more extensively by Ribas [52] and Breckpot et al. [53].

This multiplicity of DC-loading techniques warrants further comparative studies. Thus, an optimal strategy that most efficiently stimulates DC-antigen processing and presentation has not yet been widely accepted. However, complex antigenic mixtures derived from autologous tumor cells may prove superior to other approaches as true tumor-rejection antigens may be specific for each individual patient. Supporting this concept, reports in melanoma suggest that T-cell reactivity against autologous tumor cells is largely patient-specific, and most of these T cells do not recognize epitopes from allogeneic tumors [19,54].

Activation & in vivo delivery of tumor antigen-loaded DCs

The efficient stimulation of tumor-specific T lymphocytes by DCs requires the presentation of tumor-derived epitopes on MHC class I and II molecules in the context of a second signal displayed by DC costimulatory molecules (e.g., CD80, CD86 and CD40) and supported by proinflammatory cytokines (IL-12 and TNF-α) secreted by activated DCs. A wide variety of DC-activation agents have been used including cytokines (e.g., interferons, TNF-α, GM-CSF or IL-1β), ligands of the TNF receptor family (e.g., CD40L), or adjuvants such as TLR ligands (LPS, CpG and poly-I:C) [1,5, 11].

Considering the expensive and fastidious manipulations inherent to the ex vivo generation of DCs, the ability to load and activate DCs directly in situ would facilitate the applicability of this type of vaccine. Numerous techniques have been explored to deliver to DCs in vivo both tumor antigens to MHC class I and class II molecules, and also activation signals [55]. Some examples include the administration of tumor antigens coupled with antibodies that recognize DC-specific markers such as DEC205, or tumor antigens conjugated to molecules that specifically bind to DC receptors. Simultaneous delivery of proinflammatory signals such as CD40-activating antibodies or TLR ligands, ensure full DC maturation [5,11,55,56]. DC maturation is accompanied by their migration to the draining lymph node, where they subsequently prime immune T cells. DCs that do not undergo maturation and activation are maintained in an immature/tolerogenic status, which may result in immune tolerance rather than immunity [56,57]. There is however, no consensus as to whether DC maturation should be induced in vitro or in vivo following their administration. In addition, if immature DCs are considered to be less potent at inducing T-cell activation compared with mature DCs, there is concern that activated DCs may become exhausted during the culture stage. Alternative strategies include DCs genetically engineered to express costimulatory molecules or to secrete proinflammatory cytokines [58].

The site of DC inoculation is of fundamental importance since these cells should migrate to the secondary lymphoid organs where tumor antigen presentation to T cells takes place. In most vaccination protocols, DCs are delivered intradermally or subcutaneously [11], which may substantially limit the vaccine efficiency since only 5–10% of the cells reach the draining lymph nodes. Enhancement of DC migratory capacities could be obtained by preadministration of TLR ligands (that additionally support DC activation in vivo) or proinflammatory cytokines that increase CCL21, the ligand of CCR7 expressed by activated DCs and that direct their homing to the draining lymph nodes [11,59]. A benefit of direct intranodal DC delivery over intradermal or intravenous administration has also been reported [60]. The tumor itself may also be considered as a potential injection site [61].

The promotion of DC survival, obtained by DC transfection with members of the anti-apoptotic subfamily BCL-2 or BCL-xL [62], is of particular importance insofar as it increases the lifetime of these cells in vivo and, thus, fosters their ability to encounter, prime and sustain the activation of tumor-specific T cells [62,63].

Therefore, the choice of the most appropriate subset of DCs and the nature of the signal(s) used to trigger DC activation are important for the induction of an efficient anti-tumoral immune response. However, the nature of the tumor antigens to be loaded into the DCs remains critical for the generation of clinically effective anticancer vaccines.

Current personalized DC-based vaccines

Tumor cell-based vaccines

As previously underlined, an important limitation inherent to the use of defined tumor peptides to pulse DCs is their restriction to a relatively small number of HLA-binding epitopes that can be presented to T cells. This results in the induction of a limited repertoire of tumor-specific T-cell clones and therefore may lead to the emergence of tumor escape variants. Personalized tumor-derived vaccines, such as whole-tumor preparations (apoptotic or necrotic tumor cells or tumor lysates) may therefore be of considerable interest to overcome this issue since they contain a large number of antigens, known and unknown, allowing the stimulation of a polyclonal immune response [37,64,65]. Thus, DC loading with whole dead tumor cells has the theoretical advantage that essentially all of the antigenic components of the tumor could be presented to the immune system. This approach has the additional advantage to be more specific to a given patient’s tumor. However, there is still debate about the most advantageous format of dead tumor cells (apoptotic vs necrotic vs whole lysates) to be used to pulse DCs [37,40,66-73]. Some concerns have also been raised about the lack of immunogenicity of lysates that may potentially contain immunosuppressive factors [74,75]. The balance between anti-tumor immunity and autoimmunity after vaccination with whole-tumor materials should also be considered [76,77]. Indeed, since most TAAs contained in the vaccine preparations are also self-antigens, the risk of inducing autoimmunity has been a concern, especially when whole-tumor cell preparations are used as the source of antigen [78]. For example, following vaccination against melanoma, vitiligo has been observed in some trials. Importantly, this correlates with clinical responses and better outcome [76]. The main limitation of using autologous tumor cells as a source of antigens to pulse DCs is their relative difficulty of production. The small size of many tumor specimens obtained by biopsy makes it difficult to obtain enough material for therapy, especially when multiple immunizations are required (an obstacle that may be overcome when using amplified tumor-derived RNA [79,80]).

In various clinical trials using whole-tumor cell preparations, an efficient anti-tumor immunity, as well as clinical responses to DC vaccination, has been reported. O’Rourke et al. demonstrated that durable complete responses can be achieved in patients with advanced melanoma after autologous tumor cell-pulsed DC vaccine administration [65]. Three of the 12 patients who completed the treatment schedule demonstrated durable complete responses (average duration 35 months), three had partial responses and the remaining six had progressive disease. In addition, clinical effects have been observed after tumor cell lysate-pulsed DC vaccination of renal cell carcinoma patients [81]. Among 27 evaluated patients, two showed a complete response (CR), one a partial response (PR), and seven with stable disease were reported [81]. Clinical trials using DC-based immunotherapy for prostate cancer have shown encouraging results (extensively reviewed by Thomas-Kaskel et al. [78]). Approximately 500 prostate cancer patients have been treated with tumor antigen-loaded DCs and immune responses have been reported in two-thirds of these patients. Clinical responses were observed in almost half of the treated patients [78].

Idiotype-based vaccines

Inducing tumor-specific immunity by immunizing patients with tumor cells or their antigenic components has been successfully implemented against hematological malignancies. A given patient’s B-cell malignancy is usually derived from a single expanded B-cell clone that expresses an immunoglobulin (Ig) with a unique idiotype (Id; variable regions of Ig). Therefore, Id can be regarded as a tumor-associated antigen and a potential target in clinical vaccination approaches [82]. The use of idiotypic vaccines has been hampered by the fact that autologous Id is patient-specific and, thus, the vaccine must be individually prepared for each patient [82]. Custom-made monoclonal antibodies against tumor Id partially solved this problem and have led to some long-lasting complete tumor regressions in clinic [83]. However, some patients were refractory to this type of therapy owing to the outgrowth of a mutated tumor Id variant that had lost the epitope recognized by the monoclonal antibody [84]. In the meantime, vaccines were made from the tumor Id that were intended to induce long-lasting, polyclonal as well as mixed – humoral (antibody-based) and cellular (T-cell-mediated) – immune responses against the tumor [85]. The tumor-specific Id from B-cell lymphomas was successfully ‘rescued’ from the tumor cells by fusing them to a myeloma cell line. These hybrid cells secrete the tumor-derived Igs, which are then purified and prepared into a vaccine [85]. However, since the native Id is a self-protein, induction of anti-Id immune responses remain difficult. Therefore, numerous studies have been conducted combining this approach with DC vaccination to promote the uptake and presentation of the antigen to the immune system in a recognizable form. Timmerman et al. evaluated Id-pulsed DCs in 35 patients with B-cell lymphoma. Among ten initial patients with measurable lymphoma, eight mounted T-cell proliferative anti-Id responses, and four had clinical responses, two demonstrated CRs, one PR was observed and one molecular response was reported [86]. Subsequently, 25 additional patients were vaccinated after first chemo therapy, and 15 of 23 who completed the vaccination schedule mounted T-cell or humoral anti-Id responses.

Unlike lymphomas, Id produced by myeloma cells is mostly secreted into the serum and the malignant plasma cells express low surface Id protein as a potential target for idiotype vaccines. However, it has been reported that multiple myeloma patients can mount T-cell responses to tumor Id when vaccinated with DCs pulsed with Id-protein (three out of 17 CR; two out of 17 PR) [82].

Chaperone-based vaccines

The demonstration that tumor cell lysate or necrotic tumor cell immunogenicity is associated with members of the chaperone protein family (heat shock proteins [HSP]) has led to the development of tumor-derived HSP-based vaccines [87]. The specific immunogenic properties of chaperone proteins stem from their function as carriers of a wide repertoire of tumor-derived antigenic peptides [87,88]. They also constitute natural adjuvants per se capable of activating DCs [89]. Work by our group [90] and others [91-95] has demonstrated that individual purified chaperone proteins – HSP70, HSP90, GRP94/gp96 and calreticulin – are each capable of generating immune responses against their tumors of origin. The immune response induced by these vaccines is specific of the tumor from which the chaperones were purified since vaccines prepared from one tumor type are not capable of protecting against tumors of another origin [75]. The immunological identity of the HSP-based vaccines appeared to rely on the peptide-binding capacity of at least some of the chaperones as well as the speculated ‘peptide antigen fingerprint’, which presumably differed from tumor to tumor. HSP70 and GRP94/gp96 are currently used in clinical trials [96-98].

Within this immunological arena, our laboratory had developed a novel anticancer vaccine named chaperone-rich, cell lysate (CRCL). CRCL is generated by a free-solution isoelectric-focusing technique (FS-IEF) using tumor lysates that results in an enrichment for chaperone proteins rather than a purification of them [88,99-106]. CRCL contains HSP90 and HSP70 family members, the endoplasmic reticulum chaperones GRP94/gp96 and calreticulin. In addition, HSP40, HSP60, GRP75 and GRP78 are also contained in the CRCL vaccine preparation. CRCL preserves its antigenic components, while excluding some presumed immunosuppressive factors present in unfractionated lysates [107]. CRCL combines the relative simplicity of lysate preparations, along with a high yield and an extensive antigen repertoire of chaperone proteins. CRCL vaccines have a more pronounced immunologic effect per unit of protein than any of the individual chaperone proteins used as a vaccine alone [108,109]. FS-IEF is a relatively simple, rapid and efficient procedure, allowing one to obtain 1–2 mg of CRCL vaccine per gram of tumor tissue, which is 10–25-times as much vaccinating material from the same quantity of tumor as with the conventionally purified HSP (i.e., HSP70 and GRP94/gp96) currently used in clinical trials [96,110,111]. This makes the FS-IEF method of multiple chaperone complex enrichment desirable from a clinical standpoint in terms of high yield from a potentially limited tumor source, and with a rapid turn-around time from tumor harvest to treatment of the patient. CRCL presents tumor antigens to DCs and, by virtue of its adjuvant effects, triggers DC activation (expression of CD40, CD80/86 and CD70, all of which are costimulatory molecules that are fundamental for T-cell activation) [25,109,112,113,114]. We have recently demonstrated that the molecular signaling events associated with CRCL-mediated activation of DCs involve the induction of the MAP kinase pathway, evidenced by increased phosphorylation of ERK1/2 and p38, the activation of the transcription factor NF-κB and the phosphorylation of STAT1, STAT5 and AKT [114]. Interestingly, further supporting the use of CRCL as a potent anti-tumor vaccine, we have demonstrated that DCs loaded with tumor-derived CRCL resist regulatory T-cell [115] and TGF-β-mediated suppression [114]. CRCL has been shown to be effective against a variety of cancers in mice, including 12B1 (a murine BCR-ABL+ leukemia), A20 lymphoma (a murine B-cell lymphoma), B16 (a murine melanoma), and TUBO (a murine breast cancer) [108,116,117]. Furthermore, human ovarian cancer-derived CRCL has demonstrated superior activating effects on DCs compared with tumor lysate, and DCs pulsed with human ovarian cancer-derived CRCL were capable of generating tumor-specific cytotoxic T lymphocytes [113]. Thus, the enhanced immunogenicity arising from CRCL-pulsed DCs as a vaccine indicates that CRCL may represent an antigen source of choice for DC-based personalized anticancer immunotherapies [75].

Limitations of current DC-based anticancer vaccines & combination strategies

Despite encouraging results, numerous clinical studies have demonstrated the limitations of DC therapy in generating effective and durable clinical anti-tumor responses in patients with advanced-stage diseases [11,12,21,56,118]. One explanation for these disappointing clinical results may partly stem from the end-stage nature of the cancer patients included in these DC vaccination protocols. Indeed, the immune system of these patients is considerably altered by the immunosuppressive environment established during cancer progression. Tumors are capable of inducing immune tolerance by exploiting multiple immune regulatory mechanisms that, in turn, may impair DC function. Consequently, even if appropriately loaded with tumor antigens and activated in vitro, the efficiency of DC-based vaccines may be significantly impaired in vivo by the tumor environment. A number of biologically active agents (e.g., TGF-β, IL-10, IL-13, VEGF, indoleamine 2,3 dioxygenase and PGE2) synthesized by tumor or stromal cells may exert suppressive effects on the immune system [24,119-125]. Tumor-derived factors alter DC differentiation and promote accumulation of immature DCs, plasmacytoid DCs, immunosuppressive regulatory DCs as well as myeloid-derived suppressor cells (MDSCs) [22,24,126-130]. Accumulation of several populations of regulatory DCs in the spleen and the lymph nodes of tumor-bearing mice inhibits CTL responses but induces the development of immuno suppressive CD4+CD25+FoxP3+ Tregs, which may also hinder the efficiency of DC-based vaccines (Figure 2) [131-136].

Figure 2
Tumor-induced immunosuppresion affects DC-based vaccine efficiency

Therefore, combining DC-based therapy with approaches aimed at overcoming tumor-induced tolerance (inhibition of immunosuppressive molecules or cells such as TGF-β, Tregs, myeloid-derived suppressor cells, etc.) may further enhance the clinical efficiency of DC-based anticancer vaccines. For instance, several TGF-β antagonists (neutralizing monoclonal antibodies, fusion proteins, antisense TGF-β oligonucleotides) and TGF-β receptor kinase inhibitors have been shown to promote the anti-tumoral immune responses induced by antigen-pulsed DCs or adoptive T-cell transfer [137-139]. In line with this concept, immunotoxins such as the recombinant IL-2 diphtheria toxin conjugate (ONTAK) and LMB-2 have been shown to enhance the immunostimulatory effect of tumor-antigen pulsed DC while selectively depleting Tregs, leading to the stimulation of helper and cytotoxic T-cell responses [140,141]. Treg depletion upon treatment with immunotoxins has also been observed in patients with metastatic renal carcinoma and melanoma [140,141]. Cyclophosphamide facilitates adoptive immunotherapy of established tumors through the elimination/inactivation of suppressor T cells [115,142,143]. We have recently reported, in an established lymphoma model, that the efficiency of DCs pulsed with total tumor cell lysates is significantly enhanced by imatibib mesylate, a chemotherapeutic drug used to treat BCR-ABL+ murine myelogenous leukemia [136]. This synergistic effect involves the inhibition of Tregs by imatinib, allowing the stimulation of effector CD4+ and CD8+ T cells by the tumor-lysate pulsed DC vaccine. We have also demonstrated that CRCL-loaded DCs can be effectively combined with imatinib mesylate to treat established leukemia [144]. Thus, combination therapies may be of interest to enhance the efficacy of personalized DC-based vaccination.

Conclusion & future perspective

Dendritic cell-based vaccines for cancer immunotherapy have been studied and tested for more than a decade. Significant progresses have been made in their design, optimization and translation. Interestingly, in most pre-clinical and clinical trials, the side effects of DC-based therapies were minimal or absent. Specific immune responses raised by tumor-antigen-pulsed DCs were detected in a large number of patients with various types of cancer. However, the absence of objective tumor regression in most vaccinated patients has dampened the initial enthusiasm for DC-based immunotherapy. The reason of this relative lack of clinical response primarily stems from the induction of immune tolerance by progressive tumors, especially in patients with terminal-stage disease. Personalized DC-based cancer vaccines may overcome some of these immunosuppressive phenomena as they contain virtually all the antigens harbored by a given tumor and are, therefore, endowed with the capability to trigger the activation of a wider repertoire of tumor-specific T cells. Such polyclonal immune responses may prevent the outgrowth of tumor escape variants. However, a main limitation of these personalized DC based vaccines stems from the small size of many tumor specimens obtained by biopsy, which makes it difficult to obtain enough material for vaccine preparation, especially when multiple immunizations are required. In some instances, it is possible to propagate tumor cells in vitro to increase the number of cells available, but prolonged cell culture may significantly alter the characteristics of the tumor cells.

A future avenue for cancer immunotherapy consists of overcoming the phenomena of tumor-induced immunosuppression, which may unleash the full therapeutic efficiency of DC-based vaccines. This goal may be achieved by using combination strategies, associating personalized DC vaccination with chemotherapeutic drugs that may not only directly target cancer cells but that may also eliminate or impair the function of immunosuppressive cells or inhibit tumor-induced suppressive factors. Further evaluation and standardization of such approaches are still needed but may have the potential to significantly improve the outcome of cancer immunotherapy.

Executive summary

Dendritic cells-based vaccines efficiently induce anti-tumor immune responses

  • The choice of the nature of tumor antigens impacts the specificity and efficiency of the immune response raised by the vaccine.
  • Peptides derived from defined tumor antigens induce a restricted repertoire of T-cell clones, which may foster the emergence of tumor escape variants.
  • Personalized tumor vaccines induce polyclonal immune responses against a wide repertoire of tumor antigens, which may avoid the outgrowth of tumor-escape variants.

Personalized DC-based anticancer vaccines

  • Whole tumor cells, tumor cell lysates and apoptotic tumor cells.
  • Idiotype-based vaccines.
  • Individual chaperone proteins (e.g., heat shock protein).
  • Multichaperone lysates (chaperone-rich cell lysate).

Limitations & combination therapy

  • There is only a limited amount of vaccine material available from individual patients; and limited access to tumor-derived material.
  • Mechanisms of tumor-induced tolerance that may impair the function and efficiency of dendritic cells (DCs) administered to patients with advanced diseases.
  • Combination chemoimmunotherapeutic strategies to overcome tumor-induced immunosuppression may foster the efficacy of DC-based immunotherapy.

Conclusion

  • Personalized tumor immunotherapy has an advantage over peptide-based vaccines as it may avoid the occurrence of tumor immune-escape variants.
  • Personalized DC-based vaccines are safe and capable of inducing polyclonal immune responses targeting multiple tumor-specific antigens.
  • DC-based combination chemoimmunotherapies may have the potential to significantly improve the treatment of cancer patients.

Acknowledgments

Emmanuel Katsanis and Nicolas Larmonier are supported by NIH grant R01 CA104926, the Leukemia and Lymphoma Society Fellow Award 5188–5107 (Nicolas Larmonier), The Alex’s Lemonade Stand Foundation for Childhood Cancer (Nicolas Larmonier), the Tee Up for Tots and Raise a Racquet for Kids Funds (Emmanuel Katsanis and Nicolas Larmonier).

Footnotes

Financial & competing interests disclosure

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Bibliography

Papers of special note have been highlighted as:

• of interest

1. Banchereau J, Palucka AK. Dendritic cells as therapeutic vaccines against cancer. Nat. Rev. Immunol. 2005;5:296–306. [PubMed]
2. Banchereau J, Steinman RM. Dendritic cells and the control of immunity. Nature. 1998;392:245–252. [PubMed]
3. Palucka AK, Ueno H, Fay J, Banchereau J. Dendritic cells: a critical player in cancer therapy? J. Immunother. 2008;31:793–805. [PMC free article] [PubMed]
4. Gilboa E, Nair SK, Lyerly HK. Immunotherapy of cancer with dendritic cell-based vaccines. Cancer Immunol. Immunother. 1998;46:82–87. [PubMed]
5. Nestle FO, Farkas A, Conrad C. Dendritic-cell-based therapeutic vaccination against cancer. Curr. Opin. Immunol. 2005;17:163–169. [PubMed]
6. Palucka AK, Laupeze B, Aspord C, et al. Immunotherapy via dendritic cells. Adv. Exp. Med. Biol. 2005;560:105–114. [PubMed]
7. Mayordomo JI, Zorina T, Storkus WJ, et al. Bone marrow-derived dendritic cells pulsed with synthetic tumour peptides elicit protective and therapeutic antitumour immunity. Nat. Med. 1995;1:1297–1302. [PubMed]
8. Nagaraj S, Ziske C, Strehl J, Messmer D, Sauerbruch T, Schmidt-Wolf IG. Dendritic cells pulsed with α-galactosylceramide induce anti-tumor immunity against pancreatic cancer in vivo. Int. Immunol. 2006;18:1279–1283. [PubMed]
9. Shimizu J, Suda T, Yoshioka T, Kosugi A, Fujiwara H, Hamaoka T. Induction of tumor-specific in vivo protective immunity by immunization with tumor antigen-pulsed antigen-presenting cells. J. Immunol. 1989;142:1053–1059. [PubMed]
10. Paczesny S, Ueno H, Fay J, Banchereau J, Palucka AK. Dendritic cells as vectors for immunotherapy of cancer. Semin. Cancer Biol. 2003;13:439–447. [PubMed]
11. Figdor CG, de Vries IJ, Lesterhuis WJ, Melief CJ. Dendritic cell immunotherapy: mapping the way. Nat. Med. 2004;10:475–480. [PubMed]
12. Steinman RM, Banchereau J. Taking dendritic cells into medicine. Nature. 2007;449:419–426. [PubMed]• Highlights the medical implications of dendritic cell (DC) biology for disease prevention and therapy.
13. Disis ML, Cheever MA. HER-2/neu oncogenic protein: issues in vaccine development. Crit. Rev. Immunol. 1998;18:37–45. [PubMed]
14. Disis ML, Gooley TA, Rinn K, et al. Generation of T-cell immunity to the HER-2/neu protein after active immunization with HER-2/neu peptide-based vaccines. J. Clin. Oncol. 2002;20:2624–2632. [PubMed]
15. Cibotti R, Kanellopoulos JM, Cabaniols JP, et al. Tolerance to a self-protein involves its immunodominant but does not involve its subdominant determinants. Proc. Natl Acad. Sci. USA. 1992;89:416–420. [PubMed]
16. Keogh E, Fikes J, Southwood S, Celis E, Chesnut R, Sette A. Identification of new epitopes from four different tumor-associated antigens: recognition of naturally processed epitopes correlates with HLA-A*0201-binding affinity. J. Immunol. 2001;167:787–796. [PubMed]
17. Elliott T, Cerundolo V, Elvin J, Townsend A. Peptide-induced conformational change of the class I heavy chain. Nature. 1991;351:402–406. [PubMed]
18. Sette A, Vitiello A, Reherman B, et al. The relationship between class I binding affinity and immunogenicity of potential cytotoxic T cell epitopes. J. Immunol. 1994;153:5586–5592. [PubMed]
19. Ward S, Casey D, Labarthe MC, et al. Immunotherapeutic potential of whole tumour cells. Cancer Immunol. Immunother. 2002;51:351–357. [PubMed]
20. Finn OJ. Cancer vaccines: between the idea and the reality. Nat. Rev. Immunol. 2003;3:630–641. [PubMed]
21. Rosenberg SA, Yang JC, Restifo NP. Cancer immunotherapy: moving beyond current vaccines. Nat. Med. 2004;10:909–915. [PMC free article] [PubMed]
22. Rabinovich GA, Gabrilovich D, Sotomayor EM. Immunosuppressive strategies that are mediated by tumor cells. Annu. Rev. Immunol. 2007;25:267–296. [PubMed]• Overview of tumor-induced immune escape mechanisms.
23. Drake CG, Jaffee E, Pardoll DM. Mechanisms of immune evasion by tumors. Adv. Immunol. 2006;90:51–81. [PubMed]
24. Gabrilovich D. Mechanisms and functional significance of tumour-induced dendritic-cell defects. Nat. Rev. Immunol. 2004;4:941–952. [PubMed]
25. Feng H, Zeng Y, Graner MW, Likhacheva A, Katsanis E. Exogenous stress proteins enhance the immunogenicity of apoptotic tumor cells and stimulate anti-tumor immunity. Blood. 2003;101:245–252. [PubMed]
26. Feng H, Zeng Y, Whitesell L, Katsanis E. Stressed apoptotic tumor cells express heat shock proteins and elicit tumor-specific immunity. Blood. 2001;97:3505–3512. [PubMed]
27. Larmonier N, Fraszczak J, Lakomy D, Bonnotte B, Katsanis E. Killer dendritic cells and their potential for cancer immunotherapy. Cancer Immunol. Immunother. 2009;59(1):1–11. [PubMed]
28. Aarntzen EH, Figdor CG, Adema GJ, Punt CJ, de Vries IJ. Dendritic cell vaccination and immune monitoring. Cancer Immunol. Immunother. 2008;57:1559–1568. [PMC free article] [PubMed]
29. Tuyaerts S, Aerts JL, Corthals J, et al. Current approaches in dendritic cell generation and future implications for cancer immunotherapy. Cancer Immunol. Immunother. 2007;56:1513–1537. [PubMed]
30. Inaba K, Inaba M, Romani N, et al. Generation of large numbers of dendritic cells from mouse bone marrow cultures supplemented with granulocyte/macrophage colony-stimulating factor. J. Exp. Med. 1992;176:1693–1702. [PMC free article] [PubMed]
31. Schreurs MW, Eggert AA, de Boer AJ, Figdor CG, Adema GJ. Generation and functional characterization of mouse monocyte-derived dendritic cells. Eur. J. Immunol. 1999;29:2835–2841. [PubMed]
32. Romani N, Gruner S, Brang D, et al. Proliferating dendritic cell progenitors in human blood. J. Exp. Med. 1994;180:83–93. [PMC free article] [PubMed]
33. Caux C, Vanbervliet B, Massacrier C, et al. CD34+ hematopoietic progenitors from human cord blood differentiate along two independent dendritic cell pathways in response to GM-CSF+TNF-α J. Exp. Med. 1996;184:695–706. [PMC free article] [PubMed]
34. Fay JW, Palucka AK, Paczesny S, et al. Long-term outcomes in patients with metastatic melanoma vaccinated with melanoma peptide-pulsed CD34+ progenitor-derived dendritic cells. Cancer Immunol. Immunother. 2006;55:1209–1218. [PubMed]
35. Paczesny S, Banchereau J, Wittkowski KM, Saracino G, Fay J, Palucka AK. Expansion of melanoma-specific cytolytic CD8+ T cell precursors in patients with metastatic melanoma vaccinated with CD34+ progenitor-derived dendritic cells. J. Exp. Med. 2004;199:1503–1511. [PMC free article] [PubMed]
36. Ashley DM, Faiola B, Nair S, Hale LP, Bigner DD, Gilboa E. Bone marrow-generated dendritic cells pulsed with tumor extracts or tumor RNA induce anti-tumor immunity against central nervous system tumors. J. Exp. Med. 1997;186:1177–1182. [PMC free article] [PubMed]
37. Fields RC, Shimizu K, Mule JJ. Murine dendritic cells pulsed with whole tumor lysates mediate potent anti-tumor immune responses in vitro and in vivo. Proc. Natl Acad. Sci. USA. 1998;95:9482–9487. [PubMed]
38. Geiger C, Regn S, Weinzierl A, Noessner E, Schendel DJ. A generic RNA-pulsed dendritic cell vaccine strategy for renal cell carcinoma. J. Transl. Med. 2005;3:29. [PMC free article] [PubMed]
39. Phan V, Errington F, Cheong SC, et al. A new genetic method to generate and isolate small, short-lived but highly potent dendritic cell-tumor cell hybrid vaccines. Nat. Med. 2003;9:1215–1219. [PubMed]
40. Sauter B, Albert ML, Francisco L, Larsson M, Somersan S, Bhardwaj N. Consequences of cell death: exposure to necrotic tumor cells, but not primary tissue cells or apoptotic cells, induces the maturation of immunostimulatory dendritic cells. J. Exp. Med. 2000;191:423–434. [PMC free article] [PubMed]
41. Wolfers J, Lozier A, Raposo G, et al. Tumor-derived exosomes are a source of shared tumor rejection antigens for CTL cross-priming. Nat. Med. 2001;7:297–303. [PubMed]
42. Ueda G, Tamura Y, Hirai I, et al. Tumor-derived heat shock protein 70-pulsed dendritic cells elicit tumor-specific cytotoxic T lymphocytes (CTLs) and tumor immunity. Cancer Sci. 2004;95:248–253. [PubMed]
43. Wang XH, Qin Y, Hu MH, Xie Y. Dendritic cells pulsed with gp96-peptide complexes derived from human hepatocellular carcinoma (HCC) induce specific cytotoxic T lymphocytes. Cancer Immunol. Immunother. 2005;54:971–980. [PubMed]
44. Andre F, Schartz NE, Movassagh M, et al. Malignant effusions and immunogenic tumour-derived exosomes. Lancet. 2002;360:295–305. [PubMed]
45. Waldhauer I, Goehlsdorf D, Gieseke F, et al. Tumor-associated MICA is shed by ADAM proteases. Cancer Res. 2008;68:6368–6376. [PubMed]
46. Nencioni A, Grunebach F, Schmidt SM, et al. The use of dendritic cells in cancer immunotherapy. Crit. Rev. Oncol. Hematol. 2008;65:191–199. [PubMed]
47. Grunebach F, Erndt S, Hantschel M, Heine A, Brossart P. Generation of antigen-specific CTL responses using RGS1 mRNA transfected dendritic cells. Cancer Immunol. Immunother. 2008;57:1483–1491. [PubMed]
48. Yasuda T, Kamigaki T, Kawasaki K, et al. Superior anti-tumor protection and therapeutic efficacy of vaccination with allogeneic and semiallogeneic dendritic cell/tumor cell fusion hybrids for murine colon adenocarcinoma. Cancer Immunol. Immunother. 2006;56(7):1025–1036. [PubMed]
49. Kao JY, Zhang M, Chen CM, Chen JJ. Superior efficacy of dendritic cell-tumor fusion vaccine compared with tumor lysate-pulsed dendritic cell vaccine in colon cancer. Immunol. Lett. 2005;101:154–159. [PubMed]
50. Galea-Lauri J, Darling D, Mufti G, Harrison P, Farzaneh F. Eliciting cytotoxic T lymphocytes against acute myeloid leukemia-derived antigens: evaluation of dendritic cell-leukemia cell hybrids and other antigen-loading strategies for dendritic cell-based vaccination. Cancer Immunol. Immunother. 2002;51:299–310. [PubMed]
51. Shimizu K, Kuriyama H, Kjaergaard J, Lee W, Tanaka H, Shu S. Comparative analysis of antigen loading strategies of dendritic cells for tumor immunotherapy. J. Immunother. 2004;27:265–272. [PubMed]
52. Ribas A. Genetically modified dendritic cells for cancer immunotherapy. Curr. Gene Ther. 2005;5:619–628. [PubMed]
53. Breckpot K, Heirman C, Neyns B, Thielemans K. Exploiting dendritic cells for cancer immunotherapy: genetic modification of dendritic cells. J. Gene Med. 2004;6:1175–1188. [PubMed]
54. Todryk SM, Birchall LJ, Erlich R, Halanek N, Orleans-Lindsay JK, Dalgleish AG. Efficacy of cytokine gene transfection may differ for autologous and allogeneic tumour cell vaccines. Immunology. 2001;102:190–198. [PubMed]
55. den Brok MH, Nierkens S, Figdor CG, Ruers TJ, Adema GJ. Dendritic cells: tools and targets for anti-tumor vaccination. Expert Rev. Vaccines. 2005;4:699–710. [PubMed]
56. Adema GJ. Dendritic cells from bench to bedside and back. Immunol. Lett. 2009;122:128–130. [PubMed]
57. den Brok MH, Sutmuller RP, Nierkens S, et al. Synergy between in situ cryoablation and TLR9 stimulation results in a highly effective in vivo dendritic cell vaccine. Cancer Res. 2006;66:7285–7292. [PubMed]
58. Hodge JW, Rad AN, Grosenbach DW, et al. Enhanced activation of T cells by dendritic cells engineered to hyperexpress a triad of costimulatory molecules. J. Natl Cancer Inst. 2000;92:1228–1239. [PubMed]
59. MartIn-Fontecha A, Sebastiani S, Hopken UE, et al. Regulation of dendritic cell migration to the draining lymph node: impact on T lymphocyte traffic and priming. J. Exp. Med. 2003;198:615–621. [PMC free article] [PubMed]
60. Nestle FO, Alijagic S, Gilliet M, et al. Vaccination of melanoma patients with peptide- or tumor lysate-pulsed dendritic cells. Nat. Med. 1998;4:328–332. [PubMed]
61. Ehtesham M, Kabos P, Gutierrez MA, Samoto K, Black KL, Yu JS. Intratumoral dendritic cell vaccination elicits potent tumoricidal immunity against malignant glioma in rats. J. Immunother. 2003;26:107–116. [PubMed]
62. Chen M, Huang L, Shabier Z, Wang J. Regulation of the lifespan in dendritic cell subsets. Mol. Immunol. 2007;44:2558–2565. [PMC free article] [PubMed]
63. Kim TW, Lee JH, He L, et al. Modification of professional antigen-presenting cells with small interfering RNA in vivo to enhance cancer vaccine potency. Cancer Res. 2005;65:309–316. [PubMed]
64. de Gruijl TD, van den Eertwegh AJ, Pinedo HM, Scheper RJ. Whole-cell cancer vaccination: from autologous to allogeneic tumor- and dendritic cell-based vaccines. Cancer Immunol. Immunother. 2008;57:1569–1577. [PubMed]• Overview of whole-tumor cell-based DC vaccination studies.
65. O’Rourke MG, Johnson M, Lanagan C, et al. Durable complete clinical responses in a Phase I/II trial using an autologous melanoma cell/dendritic cell vaccine. Cancer Immunol. Immunother. 2003;52:387–395. [PubMed]
66. Larmonier N, Merino D, Nicolas A, et al. Apoptotic, necrotic, or fused tumor cells: an equivalent source of antigen for dendritic cell loading. Apoptosis. 2006;11:1513–1524. [PubMed]
67. Melero I, Vile RG, Colombo MP. Feeding dendritic cells with tumor antigens: self-service buffet or a la carte? Gene Ther. 2000;7:1167–1170. [PubMed]
68. Albert ML, Sauter B, Bhardwaj N. Dendritic cells acquire antigen from apoptotic cells and induce class I-restricted CTLs. Nature. 1998;392:86–89. [PubMed]
69. Schnurr M, Scholz C, Rothenfusser S, et al. Apoptotic pancreatic tumor cells are superior to cell lysates in promoting cross-priming of cytotoxic T cells and activate NK and γδ T cells. Cancer Res. 2002;62:2347–2352. [PubMed]
70. Jarnjak-Jankovic S, Pettersen RD, Saeboe-Larssen S, Wesenberg F, Olafsen MR, Gaudernack G. Preclinical evaluation of autologous dendritic cells transfected with mRNA or loaded with apoptotic cells for immunotherapy of high-risk neuroblastoma. Cancer Gene Ther. 2005;12:699–707. [PubMed]
71. Gallucci S, Lolkema M, Matzinger P. Natural adjuvants: endogenous activators of dendritic cells. Nat. Med. 1999;5:1249–1255. [PubMed]
72. Basu S, Binder RJ, Suto R, Anderson KM, Srivastava PK. Necrotic but not apoptotic cell death releases heat shock proteins, which deliver a partial maturation signal to dendritic cells and activate the NF-κB pathway. Int. Immunol. 2000;12:1539–1546. [PubMed]
73. Nicolas A, Cathelin D, Larmonier N, et al. Dendritic cells trigger tumor cell death by a nitric oxide-dependent mechanism. J. Immunol. 2007;179:812–818. [PubMed]
74. Kalos M. Tumor antigen-specific T cells and cancer immunotherapy: current issues and future prospects. Vaccine. 2003;21:781–786. [PubMed]
75. Zeng Y, Graner MW, Katsanis E. Chaperone-rich cell lysates, immune activation and tumor vaccination. Cancer Immunol. Immunother. 2006;55:329–338. [PubMed]
76. Gilboa E. The risk of autoimmunity associated with tumor immunotherapy. Nat. Immunol. 2001;2:789–792. [PubMed]
77. Bos R, van Duikeren S, Morreau H, et al. Balancing between anti-tumor efficacy and autoimmune pathology in T-cell-mediated targeting of carcinoembryonic antigen. Cancer Res. 2008;68:8446–8455. [PubMed]
78. Thomas-Kaskel AK, Waller CF, Schultze-Seemann W, Veelken H. Immunotherapy with dendritic cells for prostate cancer. Int. J. Cancer. 2007;121:467–473. [PubMed]
79. Nencioni A, Muller MR, Grunebach F, et al. Dendritic cells transfected with tumor RNA for the induction of anti-tumor CTL in colorectal cancer. Cancer Gene Ther. 2003;10:209–214. [PubMed]
80. Muller MR, Grunebach F, Nencioni A, Brossart P. Transfection of dendritic cells with RNA induces CD4- and CD8-mediated T cell immunity against breast carcinomas and reveals the immunodominance of presented T cell epitopes. J. Immunol. 2003;170:5892–5896. [PubMed]
81. Holtl L, Zelle-Rieser C, Gander H, et al. Immunotherapy of metastatic renal cell carcinoma with tumor lysate-pulsed autologous dendritic cells. Clin. Cancer Res. 2002;8:3369–3376. [PubMed]
82. Ruffini PA, Neelapu SS, Kwak LW, Biragyn A. Idiotypic vaccination for B-cell malignancies as a model for therapeutic cancer vaccines: from prototype protein to second generation vaccines. Haematologica. 2002;87:989–1001. [PubMed]
83. Miller RA, Maloney DG, Warnke R, Levy R. Treatment of B-cell lymphoma with monoclonal anti-idiotype antibody. N. Engl. J. Med. 1982;306:517–522. [PubMed]
84. Meeker T, Lowder J, Cleary ML, et al. Emergence of idiotype variants during treatment of B-cell lymphoma with anti-idiotype antibodies. N. Engl. J. Med. 1985;312:1658–1665. [PubMed]
85. Houot R, Levy R. Vaccines for lymphomas: idiotype vaccines and beyond. Blood Rev. 2009;23:137–142. [PubMed]• Highlights clinical implications of idiotype-based vaccines for immunotherapy of B-cell lymphoma.
86. Timmerman JM, Czerwinski DK, Davis TA, et al. Idiotype-pulsed dendritic cell vaccination for B-cell lymphoma: clinical and immune responses in 35 patients. Blood. 2002;99:1517–1526. [PubMed]
87. Blachere NE, Srivastava PK. Heat shock protein-based cancer vaccines and related thoughts on immunogenicity of human tumors. Semin. Cancer Biol. 1995;6:349–355. [PubMed]
88. Suto R, Srivastava PK. A mechanism for the specific immunogenicity of heat shock protein-chaperoned peptides. Science. 1995;269:1585–1588. [PubMed]
89. Asea A, Kraeft SK, Kurt-Jones EA, et al. HSP70 stimulates cytokine production through a CD14-dependant pathway, demonstrating its dual role as a chaperone and cytokine. Nat. Med. 2000;6:435–442. [PubMed]
90. Graner M, Raymond A, Romney D, He L, Whitesell L, Katsanis E. Immunoprotective activities of multiple chaperone proteins isolated from murine B-cell leukemia/lymphoma. Clin. Cancer Res. 2000;6:909–915. [PubMed]
91. Udono H, Srivastava PK. Heat shock protein 70-associated peptides elicit specific cancer immunity. J. Exp. Med. 1993;178:1391–1396. [PMC free article] [PubMed]
92. Udono H, Srivastava PK. Comparison of tumor-specific immunogenicities of stress-induced proteins gp96, hsp90, and hsp70. J. Immunol. 1994;152:5398–5403. [PubMed]
93. Nair S, Wearsch PA, Mitchell DA, Wassenberg JJ, Gilboa E, Nicchitta CV. Calreticulin displays in vivo peptide-binding activity and can elicit CTL responses against bound peptides. J. Immunol. 1999;162:6426–6432. [PubMed]
94. Basu S, Srivastava PK. Calreticulin, a peptide-binding chaperone of the endoplasmic reticulum, elicits tumor- and peptide-specific immunity. J. Exp. Med. 1999;189:797–802. [PMC free article] [PubMed]
95. Arnold D. Cross-priming of minor histocompatibility antigen-specific cytotoxic T cells upon immunization with the heat shock protein gp96. J. Exp. Med. 1995;182:885–889. [PMC free article] [PubMed]
96. Li Z, Qiao Y, Liu B, et al. Combination of imatinib mesylate with autologous leukocyte-derived heat shock protein and chronic myelogenous leukemia. Clin. Cancer Res. 2005;11:4460–4468. [PubMed]
97. Rivoltini L, Castelli C, Carrabba M, et al. Human tumor-derived heat shock protein 96 mediates in vitro activation and in vivo expansion of melanoma- and colon carcinoma-specific T cells. J. Immunol. 2003;171:3467–3474. [PubMed]
98. Belli F, Testori A, Rivoltini L, et al. Vaccination of metastatic melanoma patients with autologous tumor-derived heat shock protein gp96-peptide complexes: clinical and immunologic findings. J. Clin. Oncol. 2002;20:4169–4180. [PubMed] J. Clin. Oncol. 2002;20(23):4610. (Erratum appears in. [PubMed]• Clinical and immunologic analysis of autologous heat shock protein-based vaccine trial in humans.
99. Udono H, Srivastava PK. Heat shock protein 70-associated peptides elicit specific cancer immunity. J. Exp. Med. 1993;178:1391–1396. [PMC free article] [PubMed]
100. Nair S, Wearsch PA, Mitchell DA, Wassenberg JJ, Gilboa E, Nicchitta CV. Calreticulin displays in vivo peptide-binding activity and can elicit CTL responses against bound peptides. J. Immunol. 1999;162:6426–6432. [PubMed]
101. Arnold D, Faath S, Rammensee H, Schild H. Cross-priming of minor histocompatibility antigen-specific cytotoxic T cells upon immunization with the heat shock protein gp96. J. Exp. Med. 1995;182:885–889. [PMC free article] [PubMed]
102. Srivastava PK, Udono H. Heat shock protein-peptide complexes in cancer immunotherapy. Curr. Opin. Immunol. 1994;6:728–732. [PubMed]
103. Srivastava PK, Menoret A, Basu S, Binder RJ, McQuade KL. Heat shock proteins come of age: primitive functions acquire new roles in an adaptive world. Immunity. 1998;8:657–665. [PubMed]
104. Ishii T, Udono H, Yamano T, et al. Isolation of MHC class I-restricted tumor antigen peptide and its precursors associated with heat shock proteins hsp70, hsp90, and gp96. J. Immunol. 1999;162:1303–1309. [PubMed]
105. Zeng Y, Chen X, Larmonier N, et al. Natural killer cells play a key role in the anti-tumor immunity generated by chaperone-rich cell lysate vaccination. Int. J. Cancer. 2006;119:2624–2631. [PubMed]
106. Graner M, Raymond A, Akporiaye E, Katsanis E. Tumor-derived multiple chaperone enrichment by free-solution isoelectric focusing yields potent anti-tumor vaccines. Cancer Immunol. Immunother. 2000;49:476–484. [PubMed]
107. Graner MW, Likhacheva A, Davis J, et al. Cargo from tumor-expressed albumin inhibits T-cell activation and responses. Cancer Res. 2004;64:8085–8092. [PubMed]
108. Graner MW, Zeng Y, Feng H, Katsanis E. Tumor-derived chaperone-rich cell lysates are effective therapeutic vaccines against a variety of cancers. Cancer Immunol. Immunother. 2003;52:226–234. [PubMed]
109. Zeng Y, Feng H, Graner MW, Katsanis E. Tumor-derived, chaperone-rich cell lysate activates dendritic cells and elicits potent anti-tumor immunity. Blood. 2003;101:4485–4491. [PubMed]
110. Rivoltini L, Carrabba M, Huber V, et al. Immunity to cancer: attack and escape in T lymphocyte-tumor cell interaction. Immunol. Rev. 2002;188:97–113. [PubMed]
111. Belli F, Testori A, Rivoltini L, et al. Vaccination of metastatic melanoma patients with autologous tumor-derived heat shock protein gp96-peptide complexes: clinical and immunologic findings. J. Clin. Oncol. 2002;20:4169–4180. [PubMed]
112. Zeng Y, Graner MW, Thompson S, Marron M, Katsanis E. Induction of BCR-ABL-specific immunity following vaccination with chaperone-rich cell lysates derived from BCR-ABL+ tumor cells. Blood. 2005;105:2016–2022. [PMC free article] [PubMed]
113. Li G, Zeng Y, Chen X, et al. Human ovarian tumour-derived chaperone-rich cell lysate (CRCL) elicits T cell responses in vitro. Clin. Exp. Immunol. 2007;148:136–145. [PubMed]
114. Cantrell J, Larmonier C, Janikashvili N, et al. Signaling pathways induced by a tumor-derived vaccine in antigen presenting cells. Immunobiology. 2009 DOI: 10.1016/j.imbio.2009.09.006 (Epub ahead of print) [PMC free article] [PubMed]
115. Larmonier N, Cantrell J, Lacasse C, et al. Chaperone-rich tumor cell lysate-mediated activation of antigen-presenting cells resists regulatory T cell suppression. J. Leukoc. Biol. 2008;83:1049–1059. [PubMed]
116. Li G, Andreansky S, Helguera G, et al. A chaperone protein-enriched tumor cell lysate vaccine generates protective humoral immunity in a mouse breast cancer model. Mol. Cancer Ther. 2008;7:721–729. [PubMed]
117. Kislin KL, Marron MT, Li G, Graner MW, Katsanis E. Chaperone-rich cell lysate embedded with BCR-ABL peptide demonstrates enhanced anti-tumor activity against a murine BCR-ABL positive leukemia. FASEB J. 2007;21:2173–2184. [PubMed]
118. De Vries IJ, Krooshoop DJ, Scharenborg NM, et al. Effective migration of antigen-pulsed dendritic cells to lymph nodes in melanoma patients is determined by their maturation state. Cancer Res. 2003;63:12–17. [PubMed]
119. Cheng F, Wang HW, Cuenca A, et al. A critical role for Stat3 signaling in immune tolerance. Immunity. 2003;19:425–436. [PubMed]
120. Ueno H, Klechevsky E, Morita R, et al. Dendritic cell subsets in health and disease. Immunol. Rev. 2007;219:118–142. [PubMed]
121. Bromberg JF, Wrzeszczynska MH, Devgan G, et al. Stat3 as an oncogene. Cell. 1999;98:295–303. [PubMed]
122. Wang T, Niu G, Kortylewski M, et al. Regulation of the innate and adaptive immune responses by Stat-3 signaling in tumor cells. Nat. Med. 2004;10:48–54. [PubMed]
123. Kortylewski M, Kujawski M, Wang T, et al. Inhibiting Stat3 signaling in the hematopoietic system elicits multicomponent anti-tumor immunity. Nat. Med. 2005;11:1314–1321. [PubMed]
124. Burdelya L, Kujawski M, Niu G, et al. Stat3 activity in melanoma cells affects migration of immune effector cells and nitric oxide-mediated anti-tumor effects. J. Immunol. 2005;174:3925–3931. [PMC free article] [PubMed]
125. Evel-Kabler K, Song XT, Aldrich M, Huang XF, Chen SY. SOCS1 restricts dendritic cells’ ability to break self tolerance and induce anti-tumor immunity by regulating IL-12 production and signaling. J. Clin. Invest. 2006;116:90–100. [PMC free article] [PubMed]
126. Melief CJ. Mini-review: Regulation of cytotoxic T lymphocyte responses by dendritic cells: peaceful coexistence of cross-priming and direct priming? Eur. J. Immunol. 2003;33:2645–2654. [PubMed]
127. Vermi W, Bonecchi R, Facchetti F, et al. Recruitment of immature plasmacytoid dendritic cells (plasmacytoid monocytes) and myeloid dendritic cells in primary cutaneous melanomas. J. Pathol. 2003;200:255–268. [PubMed]
128. Salio M, Cella M, Vermi W, et al. Plasmacytoid dendritic cells prime IFN-γ-secreting melanoma-specific CD8 lymphocytes and are found in primary melanoma lesions. Eur. J. Immunol. 2003;33:1052–1062. [PubMed]
129. Munn DH, Sharma MD, Hou D, et al. Expression of indoleamine 2,3-dioxygenase by plasmacytoid dendritic cells in tumor-draining lymph nodes. J. Clin. Invest. 2004;114:280–290. [PMC free article] [PubMed]
130. Zhang M, Tang H, Guo Z, et al. Splenic stroma drives mature dendritic cells to differentiate into regulatory dendritic cells. Nat. Immunol. 2004;5:1124–1133. [PubMed]
131. Gabrilovich DI, Velders MP, Sotomayor EM, Kast WM. Mechanism of immune dysfunction in cancer mediated by immature Gr-1+ myeloid cells. J. Immunol. 2001;166:5398–5406. [PubMed]
132. Li Q, Pan PY, Gu P, Xu D, Chen SH. Role of immature myeloid Gr-1+ cells in the development of anti-tumor immunity. Cancer Res. 2004;64:1130–1139. [PubMed]
133. Huang B, Pan PY, Li Q, et al. Gr-1+CD115+ immature myeloid suppressor cells mediate the development of tumor-induced T regulatory cells and T-cell anergy in tumor-bearing host. Cancer Res. 2006;66:1123–1131. [PubMed]
134. Curiel TJ, Coukos G, Zou L, et al. Specific recruitment of regulatory T cells in ovarian carcinoma fosters immune privilege and predicts reduced survival. Nat. Med. 2004;10:942–949. [PubMed]
135. Larmonier N, Marron M, Zeng Y, et al. Tumor-derived CD4+CD25+ regulatory T cell suppression of dendritic cell function involves TGF-β and IL-10. Cancer Immunol. Immunother. 2007;56:48–59. [PubMed]
136. Larmonier N, Janikashvili N, LaCasse CJ, et al. Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL tumors. J. Immunol. 2008;181:6955–6963. [PubMed]• Demonstrates the synergistic effects of tumor-lysate-pulsed DCs with regulatory T-cell suppression.
137. Yang YA, Dukhanina O, Tang B, et al. Lifetime exposure to a soluble TGF-β antagonist protects mice against metastasis without adverse side effects. J. Clin. Invest. 2002;109:1607–1615. [PMC free article] [PubMed]
138. Muraoka RS, Dumont N, Ritter CA, et al. Blockade of TGF-β inhibits mammary tumor cell viability, migration, and metastases. J. Clin. Invest. 2002;109:1551–1559. [PMC free article] [PubMed]
139. Uhl M, Aulwurm S, Wischhusen J, et al. SD-208, a novel transforming growth factor β receptor I kinase inhibitor, inhibits growth and invasiveness and enhances immunogenicity of murine and human glioma cells in vitro and in vivo. Cancer Res. 2004;64:7954–7961. [PubMed]
140. Dannull J, Su Z, Rizzieri D, et al. Enhancement of vaccine-mediated anti-tumor immunity in cancer patients after depletion of regulatory T cells. J. Clin. Invest. 2005;115:3623–3633. [PMC free article] [PubMed]
141. Attia P, Powell DJ, Jr, Maker AV, Kreitman RJ, Pastan I, Rosenberg SA. Selective elimination of human regulatory T lymphocytes in vitro with the recombinant immunotoxin LMB-2. J. Immunother. 2006;29:208–214. [PMC free article] [PubMed]
142. North RJ. Cyclophosphamide-facilitated adoptive immunotherapy of an established tumor depends on elimination of tumor-induced suppressor T cells. J. Exp. Med. 1982;155:1063–1074. [PMC free article] [PubMed]
143. Ghiringhelli F, Larmonier N, Schmitt E, et al. CD4+CD25+ regulatory T cells suppress tumor immunity but are sensitive to cyclophosphamide which allows immunotherapy of established tumors to be curative. Eur. J. Immunol. 2004;34:336–344. [PubMed]
144. Zeng Y, Graner MW, Feng H, Li G, Katsanis E. Imatinib mesylate effectively combines with chaperone-rich cell lysate-loaded dendritic cells to treat BCR-ABL+ murine leukemia. Int. J. Cancer. 2004;110:251–259. [PubMed]