Various ways to improve whole cancer cell vaccines

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Various ways to improve whole cancer cell vaccines Expert Review of Vaccines Downloaded from informahealthcare.com by Universiteit Gent on 04/24/14 For personal use only.

Expert Rev. Vaccines Early online, 1–15 (2014)

Laetitia Cicchelero1, Hilde de Rooster2 and Niek N Sanders*1 1 Laboratory of Gene Therapy, Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Heidestraat 19, B-9820 Merelbeke, Belgium 2 Small Animal Hospital, Department of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium *Author for correspondence: [email protected]

Immunotherapy based on whole cancer cell vaccines is regarded as a promising avenue for cancer treatment. However, limited efficacy in the first human clinical trials calls for more optimized whole cancer cell vaccines and better patient selection. It is suggested that whole cancer cell vaccines consist preferably of immunogenically killed autologous cancer stem cells associated with dendritic cells. Adjuvants should stimulate both immune effector cells and memory cells, which could be achieved through their correct dosage and timing of administration. There are indications that whole cancer cell vaccination is less effective in patients who are immunocompromised, who have specific genetic defects in their immune or cancer cells, as well as in patients in an advanced cancer stage. However, such patients form the bulk of enrolled patients in clinical trials, prohibiting an objective evaluation of the true potential of whole cancer cell immunotherapy. Each key point will be discussed. KEYWORDS: adjuvants • immune memory • immunogenic cell death • whole cancer cell vaccines

The established modalities of cancer therapy are surgery, radiotherapy and chemotherapy [1]. A new therapeutic approach is to treat cancer through the immune system [2]. This strategy involves reinforcing an existing yet weak immune response against cancer cells [3]. Nowadays, immunotherapy is accepted as the fourth pillar of standard cancer therapy [1]. In the cancer immunotherapy field, cancer vaccines elicit most enthusiasm as they can actively generate an immune response specific to tumor cells (TCs) and a long-lasting immunological memory that may protect against recurrences [2,4]. Cancer vaccines & their desired immune response

Cancer vaccines aim to reeducate the immune system to recognize and eliminate neoplastic cells [5]. An additional aim of cancer vaccines is to create an immune memory in order to prevent cancer recurrence. There is evidence that both humoral and cellular responses are important in anticancer immunotherapy. Antibodies can effectively eliminate cancer cells through antibody-mediated cellular cytotoxicity [6], and increased anticancer humoral responses are known to be correlated with decreased cancer recurrence and improved survival [7]. Yet, since the CD8+ cytotoxic T lymphocytes (CTL) are generally seen as the main effectors in anticancer informahealthcare.com

10.1586/14760584.2014.911093

immunotherapy, most research has focused on the generation of a cellular anticancer immune response [4,8]. Three cell types are indispensable in the cellular immune response against cancer cells, namely, dendritic cells (DCs), CD4+ and CD8+ T cells [9,10]. The first step in the cellular immune response is the recognition and capture of tumor antigens by immature DCs (iDCs). The DCs subsequently degrade and cleave the tumor antigens into peptides, which are processed into the MHC class I or II pathways to be (cross-) presented on their cell surface. When a damage-associated molecular pattern (DAMP) (see Concept of immunogenic cell death) or a pathogen-associated molecular pattern is present, the DCs undergo maturation. This process is characterized by an increased secretion of cytokines, an increased expression of costimulatory molecules CD80 and CD86, as well as chemokine receptor 7 by the DCs, which induces their migration into the lymph node (LN). When the antigenloaded DC arrives in the LN, it undergoes an additional activation step called ‘licensing,’ mediated either by direct interaction of CD40 on the DC with the CD40 ligand on the CD4+ T cell or by cytokines [11]. Both CD4+ and CD8+ T cells require a minimal number of MHC–peptide T-cell receptor (TCR) interactions with the DCs to become

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Cicchelero, de Rooster & Sanders

activated [12] and for optimal activation, interactions between additional ligands on the DCs (4-1BBL, OX40L, ICOSL) and the respective receptors on the CD4+ and CD8+ T cells (4-1BB, OX40, ICOS) are required. The activation of CD4+ T cells is essential for many more features of the adaptive immunity besides activating and maintaining CD8+ T cells [13–17]. Lack of properly activated DCs in the absence of CD4+ T cells can induce tolerance rather than activation of CD8+ T cells [18]. CD4+ T cells also assist in the infiltration of CD8+ T cells in the tumor mass. They recruit macrophages, granulocytes and NK cells to directly kill cancer cells and enhance angiogenesis. CD4+ T cells are additionally fundamental for the induction of long-term memory CD8+ T cells [19]. Therefore, CD4+ T cells determine the nature of the immune response [10,12,16,20]. The CD8+ T cell is crucial in the cellular immune response, particularly the CD8+ CTL. They provide the strongest anticancer immune response by directly killing cancer cells that present peptide–MHC class I complexes. Interaction of CD80 or CD86 on the DC with CD28 on the CD8 + T cell causes activation of the CD8+ T cells, which results in IL-2 release and amplification of the TCRs. In contrast to what might be expected, neither NK nor NK T cells are absolutely necessary to mount an anticancer immune response [13], although they may produce helper cytokines [21]. Finally, macrophages degrade rather than present antigens [22] and secrete immunosuppressive cytokines such as IL-10 and TGF-b when phagocytizing cancer cells [23]. Conversely, this silent form of antigen clearing does not apply to DCs [22]. The macrophage will in general generate tolerance against the processed antigens, whereas the DC will stimulate an immune response. One can divide cancer vaccines into (whole) cancer cell vaccines, genetic vaccines and peptide or protein vaccines [24]. There are some strong arguments to consider whole cancer cell vaccines as superior to most other cancer vaccine types. First of all, identification of tumor antigens or selection of immunodominant epitopes on the tumor antigens is not needed for vaccine generation. Furthermore, a great variety of antigens is offered by whole cancer cells which evoke an MHCindependent broad-ranged anticancer response. Additionally, the cancer cells contain epitopes for parallel presentation to both CD8+ and CD4+ T cells, which greatly diminishes the chance of tumor escape. Autologous cancer cells have the added advantage of containing patient-specific unique mutated antigens, whose epitopes can be presented via MHC I or II pathway to CD8+ or CD4+ T cells, respectively [24]. On the other hand, peptide and protein vaccines will elicit an MHCrestricted immune response limited to the selected epitopes [24]. Antigens provided by genetic vaccines will mainly be channeled into the MHC class I presentation pathway because DCs consider the nucleic acid-based antigen to be an endogenous antigen, even though genetic vaccines encoding whole cancer cell mRNA will express the same tumor-specific epitopes as whole cancer cell vaccines [25]. Recently, DNA vaccines have been constructed that produce antigens that are secreted, thus being able to access the MHC II pathway [26]. Whole cancer cell doi: 10.1586/14760584.2014.911093

vaccines showed a higher objective clinical response rate than peptide, protein or genetic vaccines [24,27–29]. Cancer vaccination & immune memory

After elimination of the immune response eliciting tumor antigen, a specialized subpopulation of T cells that specifically recognizes that particular tumor antigen remains as immunological memory [16]. To elicit memory T cells (Tmems), the target antigen should be rapidly cleared. If not, T cells may become functionally and proliferatively exhausted and fail to evolve into Tmems [30]. Multiple Tmems have been described: central memory T cell (Tcm) [30,31], effector memory T cell (Tem) [30,31], tissue resident memory T cell (Trm) [31] and stem cell memory T cell (Tscm) [30]. Tscms display a robust self-renewal and multipotent capacity to generate effector T cells, Tcms and Tems [30]. A Tscm is more potent in anticancer protection than a Tcm (which in turn is more potent than a Tem) due to its enhanced proliferative capacity, persistence and polyfunctionality [30]. Tems and Trms have the capacity to instantly lyse cancer cells through perforin and granzyme production [30] in case of a local immunological threat [30]. In a systemic immune challenge Tcms are better suited [31]. Factors in optimization of cancer cell vaccines

The source and the characteristics of cancer cells will have an important impact on the efficacy of whole cancer cell vaccines. Additionally, cancer cell vaccines can be manufactured and administered in different ways, resulting in diverse effects on the immune response. In this section, we will discuss these aspects in more detail. Cancer cell source for vaccines

For the preparation of whole cancer cell vaccines, cancer cells derived from cell lines or from primary tumors can be used [32]. Furthermore, cancer cells can be provided by the patient (autologous) or a donor (allogeneic) [33]. Primary TCs are in theory preferred over tumor cell lines. The antigen spectrum of tumor cell lines can change after long-term culture [34,35], whereas primary TCs are counterselected by the immune system and potentially provide additional tumor antigens [35]. However, in practice and depending on the tumor type, only a minority of primary TCs can be maintained in culture [36], limiting their use in whole cancer cell vaccines. Cancer stem cells (CSCs) are considered superior to the unselected cancer cells as an antigen source [32,37]. Indeed, it has been hypothesized that CSCs drive both local cancer recurrence and systemic relapse, which makes specific targeting of CSCs very attractive [37]. In experimental mice, CSC vaccines elicited humoral as well as cellular immune responses against CSCs [38], resulting in an efficient protective anticancer immunity [37]. Autologous cancer cells are a better antigen source than allogeneic cells when only the raised anticancer immune response is taken into account. The autologous vaccine will contain unique tumor antigens encoded by gene mutations specific Expert Rev. Vaccines

Various ways to improve whole cancer cell vaccines

Review

Table 1. Principal damage-associated molecular patterns in whole cancer cell vaccines. DAMP on plasma membrane

Effect

Ref.

CRT

Stimulates antigen uptake

HSP70

Induces DC maturation (upregulation CD86 and CD40), activates NK, attracts monocytes and neutrophils, stimulates antigen uptake

HSP90

Induces DC maturation (upregulation CD86 and CD40), activates NK, attracts monocytes and neutrophils

[35,115]

NKG2D ligand

Stimulates NK, NKT and CD8+ T cells to destroy cancer cells that express NKG2D ligands

[46,116,117]

HMGB1

Induces DC maturation, facilitates processing and presentation of tumor-derived antigens, attracts various immune cells

[35,109,115]

HSP90

Can inhibit activation of TGF-b

[35,109,114] [35,46,109,115]


Secreted

[35]

End-stage degradation products ATP

Acts in low concentration as a chemoattractant for iDCs, induces DC maturation, causes IL-1b release from DCs

DNA

Stimulates DCs and macrophages

RNA

Activates the innate immune system through TLR3 binding

[35,118]

[109] [35]

CRT: Calreticulin; DC: Dendritic cell; HMGB1: High-mobility group box-1; HSP70: Heat shock protein 70; HSP90: Heat shock protein 90; iDC: Immature dendritic cell; NKG2D: Natural killer group 2 member D; TLR3: Toll-like receptor 3.

to that individual tumor. These antigens might be more immunogenic than commonly shared tumor antigens and result in stimulating effective and long-lasting anticancer responses in the patient [39]. In contrast, the complexity of vaccine manufacturing for individual patients (such as the need for a sufficient amount of cancer cells, the collection of these cells, problems concerning standardization, quality control) and its usefulness limited to a single patient has led to the use of allogeneic cancer cells [24]. The development of cancer vaccines based on allogeneic cancer cells is possible through the use of cell lines, which are preferred over allogeneic primary cells as they harbor most of the same production complexities as autologous primary cells. These cell lines are selected to provide a limitless source of multiple tumor-specific antigens and a broad range of MHC expression [20]. Allogeneic vaccines can, however, only achieve clinical effectiveness if they adequately represent the characteristic tumor antigens of the patient’s cancer cells [28]. Alas, allogeneic cancer cells will seldom contain the same tumor antigens as autologous tumors, even when combining multiple allogeneic cell lines [33]. The most efficient response will probably be provided by autologous cancer cells that express an allogeneic molecule. Allogeneic MHC molecules could hereby act as an adjuvant, without overwhelming the cancer-specific CTL response [40]. However, it should be borne in mind that adding allogeneic elements in vaccines will potentially decrease their efficacy after repeated vaccination through alloreaction, which destroys the vaccine before it even has the chance to generate the desired response [41].

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Effect of immunogenic cell death of cancer cells in cancer cell vaccines Concept of immunogenic cell death

When a cell dies, it can be cleared with (immunogenic) or without (nonimmunogenic) stimulating an immune response against its dead cell antigens [42]. In cancer cell vaccine manufacture, immunogenic cell death (ICD) is the objective. An immunogenic death depends on the ICD-inducing stimulus [42]. Multiple ICD-inducing stimuli have been described and their main characteristic is the ability to induce expression and release of DAMPs from the cells they have killed. The most important DAMPs and their actions are summarized in TABLE 1. The DAMPs that are expressed and released by the cancer cells after ICD can interact with pattern recognition receptors on many immune cells according to a defined spatiotemporal pattern. Binding of DAMPs to pattern recognition receptors results in the release of cytokines and chemokines by the immune cell. As a result, APCs are stimulated to efficiently take up and process tumor antigens and cross-prime T cells [43]. Multiple factors can influence the efficacy of DAMPs [35]. The immunogenicity of the whole cancer cell vaccine is influenced by the death-inducing stimulus, the produced DAMPs themselves, the DAMP location, and the combination of cancer- and host-associated factors [13,44–47]. The cancer cell has to be able to express the DAMPs, which in turn should bind immune cells and not cancer cells [35]. Indeed, binding of DAMPs to toll-like receptors (TLRs) expressed on cancer cells can promote cell survival and chemoresistance [35]. On the other hand, the patient must be immunosufficient [42].

doi: 10.1586/14760584.2014.911093

Review


Photodynamic therapy with hypericin

[35]

of proinflammatory transcription factors, have negligible inhibitory effects on infiltrating antitumorigenic immune cells, have inhibitory effects on tumor-associated protumorigenic immune cells and be capable of directly targeting metastasized cells [35]. There are many ICD inducers and currently no studies have been performed comparing each of them against the other in whole cancer cell vaccine settings. Therefore, the best ICD inducer cannot be identified. In a recent study, Krysko et al. listed hypericin-photodynamic therapy (hypericin-PDT), bortezomib, mitoxantrone, shikonin and cardiac glycosides as agents with a behavior close to that of an ideal ICD inducer [35]. Among these, hypericin-PDT was favored as it directly caused focused reactive oxygen species-based endoplasmic reticulum stress and had a superior ability to overcome cell-autonomous hurdles compared to the others [35]. Hypericin-PDT depends on fewer signaling pathways for the trafficking of immunogenic signals. Therefore, this ICD inducer is considered less vulnerable to the therapy-resistant cancer microevolution, which might dampen the emission of danger signals [35]. Also in comparison with other ICD inducers such as x-rays, UV rays, hyperthermia [48,49] or anthracyclines [35], hypericin-PDT has proven to generate more powerful cancer vaccines. The ideal dosage of anthracyclines for the emergence of calreticulin (CRT) and heart shock protein-70 differs, whereas both can be elicited with the same dose of hypericin-PDT, which is a major advantage [50]. Simultaneous use of multiple ICD-inducing agents on cancer cells should potentially result in a synergistic effect since the use of different cell death pathways lowers the probability of cancer cell therapy resistance [35]. Currently, data to support this hypothesis are lacking.

Poly I:C

[42]

The use of dendritic cells in cancer cell vaccines

Table 2. Principal immunogenic cell death inducers. Immunogenic cell death inducers

Ref.

Annexin A5

[119]

Anthracyclines Anti-EGFR monoclonal Ab 7A7 BK channel agonists


Bortezomib

[111,120] [35,121] [42] [35,121]

Cardiac glycosides

[35]

Cells killed by coxsackievirus B

[35]

Cells killed by influenza virus

[45]

Cells killed by measles virus

[42]

Cells killed by replication-deficient herpes simplex virus

[24]

Cyclophosphamide

[35,121]

g-irradiation

[13]

Gancyclovir

[14]

Gemcitabine High hydrostatic pressure Hyperthermia

[13,122] [119,123] [124–126]

Hypochlorous acid

[27]

LV-tSMAC

[42]

Mitoxantrone

[35,127]

Oxaliplatin

[35,127]

PP1/GADD34 inhibitors Shikonin

[111] [35,121]

UV irradiation

[13]

x-ray irradiation

[13]

Immunogenic cell death inducers

The stimulating effects of DAMPs on the immune system have raised a growing interest in the use of ICD inducers for the production of whole cancer cell vaccines. Multiple agents (TABLE 2) have proven to be able to raise an ICD. Different studies have evaluated the effect of ICD inducers on the efficacy of whole cancer cell vaccines. According to Krysko et al., the ideal ICD inducer should be an efficient inducer of apoptosis or other programmed cell death subroutines, be capable of inducing strong immunogenicity that mediates antitumor immunity, not be susceptible to drug-efflux channels, be capable of inducing severe focused endoplasmic reticulum stress, be capable of overcoming loss-of-function mutations that cripple danger signaling during cancer microevolution, be capable of downregulating cancer-based induction doi: 10.1586/14760584.2014.911093

Cancer cell vaccines containing DCs that are ex vivo loaded with tumor antigens have been considered superior to nonDC-based vaccines in stimulating anticancer immunity in vivo [25] as antigen presentation is facilitated in the former [21]. A drawback of DC-based vaccines is that their production is time consuming, expensive and personalized. DCs can be loaded with tumor antigens by coincubation or via fusion. Various forms of DCs can be used for the generation of a DC-based vaccine and are further discussed below. Loading techniques of cancer cells with dendritic cells

Various techniques can be used to generate a DC vaccine. DCs can be loaded through coincubation with different types of tumor antigens, namely, whole cancer cells, tumor lysate, apoptotic cancer cells, peptides or RNA. Whole cancer cells provide additional activation signals to the DCs, which result in a more optimized antigen presentation [51]. In contrast, fusion of DCs is only possible with cancer cells. However, the most beneficial but also the most complicated method for loading DCs with cancer cells is via fusion of DCs and cancer cells (TC) [52]. After fusion, the heterokaryote fusion product inherits the properties of both cells, and has been shown to produce, Expert Rev. Vaccines



process and present tumor antigens for days after the fusion [12]. Fusion of live cancer cells with DC-like DH82 cells did not cause TC growth after vaccination in dogs [53]. Furthermore, it has been demonstrated that TC–DC fusion vaccines produce higher IL-12 levels than DCs pulsed with tumor lysate and that the generated cancer-specific T cells produce higher levels of IFN-g [52]. In contrast, TC–DC fusion vaccines administered as sole therapy also stimulate regulatory T cells (Tregs). However, exposure to third signals, for example IL-12 or IFN-a/b, reduces Treg expansion [29]. Finally, the low fusion efficiencies can be a serious handicap when working with a scarce amount of autologous cells that cannot be expanded in culture. Fusion of a whole cancer cell with a DC can be obtained by different methods, such as through electric pulses (electrofusion), chemical induction (polyethylene glycol [PEG]) or by biological means (viral fusogenic membrane glycoproteins) [54,55]. The fusion process influences the fusion efficiency and viability of the hybrids. Cell fusion is influenced by the characteristics of the cell membrane and fusion efficiency differs notably among cancer cells [56]. The current fusion methods through viral fusogens and viral gene transduction [55] are not ideal as their hybrids continue to express viral elements which may continue to elicit cell fusion and can induce an immune response when injected in immunocompetent hosts [54]. The groups of Radomska [57] and Gottfried [58] both obtained the best results with electrofusion as it raised higher and more reproducible yields containing healthier and more vigorously growing colonies than with PEG-induced cell fusion [57,58]. Conversely, Iinuma et al. found higher hybrid yields for cells fused with PEG than through electrofusion [56]. The same group reported that an alternative fusion method entailing the combination of PEG followed by an electrofusion-mediated fusion was superior to PEG or electrofusion treatment alone and also to simple repetition of these treatments [56]. The main drawback of the electrofusion technique is that not all parameters and mechanisms are yet completely known or optimized [53] and special equipment is required [54]. Moreover, in a clinical setting, when the amounts of cells are scarce, it is not always possible to optimize the fusion parameters. In-depth comparisons between electrofusion and PEG fusion techniques are hampered by the variety of circumstances wherein the experiments are conducted [55]. Autologous or allogeneic dendritic cells

Autologous or allogeneic DCs can be chosen as a fusion partner for whole cancer cells. The autologous DCs residing in cancer tissues usually carry an immature phenotype and are functionally defective for antigen presentation and T-cell activation [59]. For this reason, DCs are harvested from blood or bone marrow and manipulated ex vivo, where they are produced and activated in the absence of a suppressive microenvironment [59]. Similar to autologous whole cancer cells, autologous DCs are harder to standardize and more laborious to harvest than allogeneic DCs, but they generate a more efficient immune response [15]. informahealthcare.com

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The reported successes of allogeneic DC-based vaccines [60,61] are hard to interpret due to the unknown quantity of matched antigenic content of the allogeneic DCs with the autologous DCs. For an effective CD8+ CTL response, at least partial MHC class I matching of the DCs between the donor and the patient is required. Moreover, if not matched, T-cell responses to allogeneic TC–DC fusion vaccines are dependent on the heterogeneous expression of MHC class I molecules by the tumor [24]. Allogeneic TC–DC fusion vaccines also expand allo-antigen-specific Foxp3+ CD25+ CD4+ Tregs, which could suppress the proliferation and function of CD25-CD4+ T cells. The generation of Tregs can be circumvented by altering the allogeneic element or administrating anti-CD25 monoclonal antibodies [41]. Dendritic cell subsets

Many types of DC subsets have been described and their categorization is still evolving [62,63]. The DC subset will not react in a standard predetermined manner, but rather according to the nature of the challenge and/or the form of the antigen or the adjuvant and inflammatory signals [31,63]. Responses to dead and dying cells or death-associated DAMPs vary greatly among distinct DC populations [12]. Many DC-based vaccines use granulocyte macrophagecolony stimulating factor-stimulated monocyte-derived CD11c+ CD11b+ or CD11c+CD8+ cells (conventional DCs). However, the use of multiple types of DCs in cancer vaccines can be beneficial. The presence of a broader set of DC subtypes evoked a more potent anticancer response than the use of a single subtype [64]. Combining migratory and lymphoid organ-resident DCs, whose antigen presentation is separated by approximately 24 h, is expected to result in optimal CD4+ T-cell priming because of the two waves of APCs [29]. Immature or mature dendritic cells

The maturation stage of DCs in DC-based vaccines has an influence on the generated immune response. Nevertheless, at the moment there is still controversy about whether iDCs or mature DCs (mDC) should be used in DC-based vaccines [65,66]. The monocytes obtained from CD34+ progenitor cells or, more commonly, peripheral blood mononuclear cells are typically incubated for several days with granulocyte macrophage-colony stimulating factor and IL-4, which induces differentiation of the monocytes into iDCs [67]. Afterward, maturation compounds or cocktails can be added to the iDCs in vitro [19] or coinjected with the iDCs in vivo [25]. Not all maturation signals are equal and hence different maturation protocols will generate a different functional activity in DCs [68]. The combinations of cytokines used to differentiate monocytes into DCs for DC-based vaccines might also play a critical role in determining the quality of the elicited T-cell responses [69]. Using a cocktail of many cytokines as maturation cocktail could lead to a more complete activation of DCs than that obtained with a single compound, mimicking closer the in vivo situation [68]. doi: 10.1586/14760584.2014.911093

Review


Table 3. Effector and memory stimulating adjuvants. Effector/IL-12 inducing mTOR inhibitor (rapamycin)

[11]

Neutralizing Ab against VEGF (bevacizumab)

[11]

PD1/PDL1-axis blockade

[59]

CD40 ligand or agonistic antibody

[27]

TLR3-ag ((synthetic analogs of) dsRNA (Poly I:C))


Ref.

[128]

TLR7/8 ligand (imiquimod, gardiquimod, resiquimod, R848, 852 A, VTX-2337)

[27,129]

TLR2-ag (MALP-2)

[27,130]

TLR4-ag (LPS)

[27]

TLR7-ag (mRNA)

[27]

TLR9-ag (CpG) CD40-ag (CP-870,893)

[131] [27,132]

Effector/type I IFN IFN-a

[70]

IFN-b

[70]

Memory/TNFR ligands OX-40 agonistic Ab (anti-OX40 plus), OX-40L-Ig fusion protein 4-1BB agonistic Ab (BMS663513) CD27 agonistic Ab (CDX-1127), soluble form of CD70

[73,133]

[11] [73,134]

TRAIL (rhTRAIL, apomab, mapatumumab)

[135]

GITR agonistic Ab (DTA-1, TRX518)

[134]

LIGHT transfection of cancer cells

[73]

Memory/B7 family costimulatory ligands ICOS-L-IgG fusion protein

[73]

Anti-CTLA-4 Ab (ipilimumab, tremelimumab)

[73]

4-1BB: Cluster of differentiation 137; CTLA4: Cytotoxic T lymphocyte-associated antigen 4; GITR: Glucocorticoid-induced TNF receptor; ICOS: Inducible costimulatory molecule; LIGHT: Lymphotoxin-like inducible expression, and competes with herpes simplex virus glycoprotein D for HVEM, a receptor expressed by T lymphocytes; OX-40: Cluster of differentiation 134; PD1: Programmed death 1; TLR3: Toll-like receptor 3; TRAIL: TNF apoptosis-inducing ligand.

iDCs skew the patient’s T-cell response toward a Th2 response type and secrete tolerance-inducing IL-10. On the other hand, mDCs secrete IL-12 and skew the T-cell response toward a Th1 response and prime T cells to the presented antigens [12]. According to Chang et al., both Th1 and Th2 responses are required for maximal systemic anticancer immunity [20], although deviation from a Th1 to a Th2 response has been associated with decreased anticancer immunity [21]. Although mDCs reduce tolerance or expansion of regulatory cells, it has been shown that fusion of mDCs with cancer cells is associated with lower DC survival, lower migration to T-cell areas and a lower immune response [12]. To doi: 10.1586/14760584.2014.911093

circumvent this problem, iDCs should be used for the generation of TC–DC fusion vaccines but they should be accompanied by a danger signal such as lipopolysaccharide, OK432 or CpG to accurately mature the DCs and abolish the production of IL-10 [12]. It is likely that DCs are not only affected by the compounds or cocktail used, but also by the timing of their application. It has been described that when mDCs become aged, this was associated with reduced IL-12 secretion, lack of response of these DCs to further stimulation and impaired ability of inducing T-cell activation [68]. Adjuvants for cancer cell vaccines

The immune response induced by cancer cell vaccines can be significantly enhanced by the use of the appropriate adjuvants [22]. There are effector adjuvants on one hand and memory-inducing adjuvants on the other hand. Eradication of cancer cells and the simultaneous buildup of immune memory are not easily generated by one single adjuvant type. IL-12 and type I IFN are known to induce potent differentiation of T cells into effector cells [31]. TNFR ligands (such as OX-40, 4-1BB and CD27) activate protein kinase B which directs T-cell differentiation more toward Tmem than toward primary effector T cells [31]. The primary and secondary CD8+ T-cell responses rely more on CD27 than OX40 for their generation and vice versa for the CD4+ T-cell response [31]. A nonextensive list of possible effector and memory-inducing adjuvants can be found in TABLE 3. Dosage of adjuvants

Dosage is the key to success for effector as well as memoryinducing adjuvants [31]. An excess of effector adjuvants can drive responding cells into terminal differentiation and thus become a weak point for the generation of immune memory [21,70]. Moreover, Burchill et al. also demonstrated that overstimulation of CD27 has a negative effect on the development of competent CD8+ T-cell memory [31]. It is important that the dosage is tailored to the individual adjuvant. Persistence of antigens by adjuvants that generate a depot effect

Antigens should be presented long enough to enable a robust immune response yet short enough to enable an efficient memory response [16,64]. In the search for an ideal vaccine, it was long assumed that an antigen depot is necessary to provide a sufficiently long antigen contact. However, it has been demonstrated that an antigen depot formation can trap T cells generated by the vaccine, and hence prevent them from reaching the desired target cancer site [31,71]. Therefore, Hailemichael et al. suggested that cancer vaccines with a short-lived depot effect might result in enhanced therapeutic efficacy [71]. In some adjuvants, such as those based on saponin, MF59, Montanide ISA 51 or QS21, an emulsion is required for the formulation of the adjuvant that creates an unwanted depot effect. Adjuvants such as the TLR-based adjuvants poly I:C, monophosphoryl Expert Rev. Vaccines


lipid or CpG do not require an emulsion formulation are therefore suitable for cancer vaccination.

[31]

and


Timing of adjuvant administration

An efficient and durable T-cell response depends on signals that are either received in the first few days of antigen recognition by naive T cells or later when memory cells come across this antigen once more [72]. TNF/TNFR family members are induced hours to days after TCR affiliation [73]. Several adjuvant vaccination schemes might sufficiently skew the anticancer immune response in the desired direction. One option is alternating priming for several consecutive days with an effector and a memory adjuvant, followed by a boost with a memory adjuvant. Alternatively, priming with an effector adjuvant only, followed by a well-timed secondary boost with a memory adjuvant. It is important to administer the memory adjuvant when the memory cells start to develop and require maintenance through sustained protein kinase B activation. Application of cancer cell vaccines Antigen dosage of cancer cell vaccines

Despite observed tumor eradication in experimental animal studies, limited success has been obtained so far in clinical trials for whole cancer cell vaccines in humans [74,75]. However, it is possible that the antigen dosage generally used in vaccine studies is inadequate to initiate an optimal anticancer response in humans. The amount of TCs, DCs or TC–DC fusion cells generally used for the vaccination of humans was comparable to the amounts used in mice (mamma cancer mouse [76–80]/ human [81–84]; melanoma mouse [85–89]/human [90–92]). Although the minimal antigen dose for antibody responses is independent of the body size [93], this is not true for cellular responses [31]. T cells are highly dose responsive and when the mice doses of antigen are used in humans, they are likely ineffective at raising T-cell responses [31]. The marked difference in the biology of secondary lymphoid tissue between mice and humans adds to this inappropriate extrapolation of doses. The average volume of a human LN is larger and the local draining lymphoid tissue is far more diffuse than in the mouse. This dilution of antigen may result in a local concentration of antigen insufficient to initiate effective T-cell priming [31]. The optimal quantity of the antigen in human whole cancer cell vaccines remains to be determined and undoubtedly depends on the antigen properties, the adjuvant and target species, and should ideally be determined for each antigen [94]. Administration route of cancer cell vaccines

It is not clear which method of administration is most immunogenic for cancer vaccines [29]. DCs injected intravenously (iv.) primarily accumulate in the lungs and subsequently redistribute to the liver, spleen and bone marrow. Those injected intradermally (id.) or subcutaneously (sc.) migrate to the regional LNs [95]. The content of an intraperitoneal (ip.) injection is distributed to the mediastinal LNs and the liver [96]. informahealthcare.com

Review

Activated DCs can prime cellular immunity regardless of the route, yet the quality of this response and the induction of the humoral response may be affected by the route of administration [97]. Cancer type and location, timing of vaccination and location of injection relative to the tumor will also be related to the evoked responses [29]. It has been reported that id. administration is superior to iv. vaccination [10] or ip. vaccination [29]. Although some researchers challenged the superiority of intranodal (IN) vaccination [67], many researchers claimed IN vaccination to be superior to iv. [10,98,99], id. [100], sc. and ip. vaccination [98]. However, IN injection of vaccines is difficult [101]. Technical problems might explain the observed inferiority of IN vaccination in the study of Engell-Noerregaard et al. [67]. Location of vaccination relative to the tumor

The location of vaccination relative to the tumor has an important influence on the effectiveness of cancer vaccines [29]. Peritumoral vaccination will activate T cells centered in tumordraining LNs (TDLNs), a location favorable for T-cell trafficking into the tumor, and elicits anticancer effects more rapidly than distal vaccination [102]. However, TDLNs are often actively tolerogenic as these LNs contain locally secreted cytokines such as TGF-b, PgE2 and IL-10 [103]. On top of that, they harbor immunosuppressive cells such as Tregs, iDCs, mDCs expressing PDL1 and indoleamine 2,3-dioxygenase . All of these elements are responsible for a potent immunosuppressive environment, leading to a tolerizing cross-presentation of tumor-derived antigens by the host cells present in the TDLN. The increased levels of Treg activity are localized to TDLNs and do not occur in the other LNs of the same host [103]. Subsequently, peritumoral vaccination is not preferred when the tumor has already established immunosuppressive features. This has been documented by Ohlfest et al. who observed in an experimental setup that immune responses decreased as the vaccine was administered closer to the tumor, whereas a significantly higher site-specific immune response was observed in tumor-free mice [104]. Furthermore, tumor antigen administration does not need to take the location of DC types in the body into consideration, as DC location is not a limiting factor in the generation of an effective anticancer immune response. Indeed, the study of Ali et al. demonstrates that it is possible to attract DCs which are typically localized to secondary lymphoid structures toward a subcutaneous vaccine site [64]. These DCs also proved to be necessary for an efficient immune response, despite the fact that tissue-specialized DCs impart tissue-specific homing properties to CD8+ T cells [29]. Administration schedule of cancer cell vaccines

The current consensus dictates weekly, biweekly or monthly boosters [25,29], yet daily exogenous antigen immunization with peptide/protein cancer vaccines for several consecutive days (socalled cluster immunization) has proven to be clearly superior to booster immunization with greater intervals [105]. When doi: 10.1586/14760584.2014.911093


Review


previously immunized mice were boosted with cluster immunization of peptide/protein cancer vaccines, it resulted in a CD8+ T cell peak response that surpassed the primary immunization level. This was not the case when a single second immunization was conducted after a single primary immunization [105]. Interestingly, an adjuvant is needed to obtain the superior effect of cluster immunization. Indeed, Wick et al. found that immunization of mice with four consecutive daily doses of exogenous antigen without an adjuvant failed to evoke any antigen-specific T-cell response [105]. However, depending on the administered adjuvant, daily vaccination is not always possible as, for example, daily CpG exposure causes damage to secondary lymphoid organs and diminishes CD8+ T-cell responses, while poly I:C does not [106]. There is little known about how the timing of whole cancer cell vaccine administration may change clinical efficacy. Daily vaccination is probably not needed when using TC–DC fusion cancer vaccines, as the fusion cells will produce, process and present tumor antigens for several days after the fusion [12]. Further challenges & bottlenecks in whole cancer cell vaccine optimization

these patients [111]. Compensatory treatments have been developed to specifically tackle TLR4 deficiency [42]. It is therefore important to assess the immunogenic characteristics of cancer patients and adapt the vaccine manufacture where needed. Furthermore, tumor immunogenicity varies greatly between different types of cancer and even between cancers of the same type (in different individuals) [112]. A cancer type can differ in specific transduction pathways [44,46] or in the expression of endogenous cytokines or the amount of MHC class I molecules [74]. Additionally, certain tumors can expose (e.g., CRT) or release immunogenic signals (e.g., ATP and HMGB1) in response to a death-inducing stimulus, whereas others do not [44,46]. These deficiencies can be compensated for via the addition of, for example, recombinant CRT, ATP agonists and TLR4 agonists to cancer cells that do not express CRT or release ATP and HMGB1, respectively [111]. The development of a scanning assay for missing ICDpathway factors in a cancer patient is the future to optimized patient-specific cancer cell vaccines. Nowadays, not all relevant missing factors are known yet [42] and running an elaborate checklist for each possible missing factor in every single cancer patient would further increase the vaccine production costs.

Immunosuppressive environment of the tumor

Cancer cells or host cells in the tumor environment can produce immunosuppressive modulators that abrogate the development of an efficient anticancer immune response. Suppressor pathways generally have a dominant effect over activating stimuli in cancer immunology [103]. Thus, general tolerance toward tumor antigens will be generated when these tumor antigens are presented by the immune-stimulating as well as by the tolerizing APCs. In order to achieve maximal effect of the vaccine and its activating stimuli such as adjuvants and activated DCs, the immunosuppressive environment of the tumor has to be tackled [103,107]. Two different situations should be considered. Immunosuppressive mechanisms, such as Treg inhibition or CTLA4 blockage, can address the prevaccine immunosuppressive burden. Agents such as anti-PDL1-specific monoclonal antibodies, on the other hand, are better suited in the case of postvaccine immunosuppression caused by the stressed patient’s cancer cells. Cancer vaccines may, via the induction of IFN-g secretion, induce PDL1 expression on the host’s cancer cells and this will suppress the activity of PD1+ T cells [108]. Different targeted therapies toward the immunosuppressive elements of tumors have been described and they are listed in TABLE 4. Genetic defects in cancer cells & patients

The efficacy of an anticancer vaccine treatment depends on the possibility of the patient and/or the patient’s cancer to respond to the vaccine. Certain genetic defects in patients or tumors may compromise the efficacy of cancer vaccines or adjuvants [109,110]. For example, it has been demonstrated that TLR4 is essential for efficient tumor antigen cross-presentation [111]. However, 12% of Caucasians are TLR4 deficient which may imply an inefficient cross-presentation of tumor antigen in doi: 10.1586/14760584.2014.911093

Heterogeneity in patient selection & tumor size

The large variety in reported clinical success of DC-based cancer vaccines might be partially explained by the selection of the enrolled cancer patients. Most eligible are patients with earlystage cancer and patients who had a successful first-line therapy and had minimal prior chemotherapy. Moreover, the tumor is preferably not very aggressive in order to allow the patient enough time to receive multiple rounds of vaccination [113]. In current trials, often advanced-stage patients with high tumor burdens and/or patients who need more time than granted to respond to the treatment are assessed [113]. Tumor size has a great impact on the efficiency of anticancer vaccines. Decreasing the tumor burden prior to vaccine treatment allows a higher cure rate since smaller tumors are more effectively eradicated than large ones [102]. Unfortunately, most current mice models provide a proof of concept for the immunogenicity of the vaccine in a rather prophylactic, but not in a therapeutic setting. In the majority of preclinical studies with mice, cancer vaccination is performed a few days after inoculation, not taking into account the impact slowly progressing tumors have on the adaptive immune system [5]. Additionally, in many studies the cancer vaccine is given even before the inoculation of the cancer cells [4]. One must be careful to assess immune responses to cancer vaccines on tumors that mimic the cancer patient’s situation as closely as possible. Conclusion & expert commentary

Despite high expectations in whole cancer cell vaccination trials, thus far reported clinical responses have been rather disappointing. Many variables in the vaccine manufacture require optimization. Until today, the optimal dosage of the cancer vaccines remains to be elucidated; there is evidence that the Expert Rev. Vaccines


Review

Table 4. Immunosuppressive elements in cancer and agents that affect their production or function. Target

Means

Ref.

Low-dose cyclophosphamide, anti-IL-10/IL-10R-blocking antibodies, anti-IL-10 antisense oligonucleotides

[136]

Cytokines IL-10

Epigenetic modification of DNA and histones DNMT HDAC

[8,137,138]

DNMT inhibitors (5- azacitidine) HDAC inhibitors (vorinostat)


Growth factors [35,139]

EGFR

mAb (cetuximab, 7A7 mAb)

VEGF

mAb (bevacizumab)

[11]

TGF-b

mAb, antisense oligonucleotide

[21]

Homing receptors CCR5 antagonists (maraviroc, vicriviroc)

[140]

4-1BB

4-1BB agonistic antibody (BMS-663513)

[73,133]

CD40

CD40 agonistic antibody (CP-870, 893, SGN-40 (dacetuzumab), HCD 122)

GITR

DTA-1 agonistic mAb

ICOS L

ICOS-L-IgG fusion protein

[73]

OX40

OX40 agonistic antibody

[133]

TRAIL

rhTRAIL, apomab, mapatumumab

[135]

CCR5

Immune checkpoints

[59,73,133] [133]

Immunosuppressive cells Treg

Anti-CTLA4/LAG3/PD1 (CT-011, BMS-936558)/PDL1 (MDX-1105), CD25 Ab (Ontak), low-dose cyclophosphamide, agonistic OX40/GITR (DTA1) Ab, Bcl-2 inhibitor, tyrosine kinase inhibitor (sunitinib)

MDSC

Formalin-inactivated HSV, chemo, PDL1, stimulation with activated NKT

[28,133,141]

[142–144]

Immune system downregulating enzyme [28,145,146]

Arginase

Arginase-inhibitors (shRNA directed against arginase I, S-(2-boronoethyl)-L-cysteine (BEC), NG-hydroxy-L-arginine (NOHA))

IDO

Methyltryptophan/anti-IDO siRNA

[28,146]

Melanoma B-raf enzyme

B-raf enzyme inhibitor (vemurafenib)

[28,146]

Tyrosine kinase

Tyrosine kinase inhibitors (imatinib/sunitinib)

[28,146]

Immune system downregulating protein receptors A2aR

A2aR mAb, adenosine analogs

[108]

BTLA

BTLA mAb

[108]

CTLA-4

Anti-CTLA-4-specific mAb (ipilimumab)

KIR

KIR-specific mAb

LAG3

Anti-LAG3-specific mAb (IMP701) LAG3–Ig fusion protein (IMP321)

[15,28,108] [147] [15,28,108]

4-1BB: Cluster of differentiation 137; A2aR: A2 adenosine receptor; Bcl-2: B cell lymphoma 2; BTLA: B and T lymphocyte attenuator; CCR5: Chemokine receptor 5; cIAP1: Cellular inhibitor of apoptosis 1; CTLA-4: Cytotoxic T lymphocyte-associated antigen 4; DNMT: DNA methyltransferase; EGFR: EGF receptor; GITR: Glucocorticoidinduced TNF receptor; HDAC: Histone deacetylase; HVEM: Herpes virus entry mediator; ICOS L: Inducible co-stimulatory molecule ligand; IDO: Indoleamine 2,3-dioxygenase; Ig: Immunoglobulin; JAK2: Janus kinase 2; KIR: Killer inhibitory receptor; LAG3: Lymphocyte activation gene 3; mAb: Monoclonal antibody; MDSC: Myeloid-derived suppressor cells; OX40: Cluster of differentiation 134; PD1: Programmed death 1; shRNA: Short hairpin RNA; STAT3: Signal transducer and activator of transcription 3; TGF-b: Tumor growth factor b; TIM3: T-cell membrane protein 3; TRAIL: TNF-Related Apoptosis-Inducing Ligand; Wnt/b-catenin: Wingless-type mouse mammary tumor virus integration site family member/b-catenin.


doi: 10.1586/14760584.2014.911093

Review


Table 4. Immunosuppressive elements in cancer and agents that affect their production or function (cont.). Target

Means

Ref.

Immune system downregulating protein receptors (cont.) [15,28,73,108]

PD1

Anti-PD1-specific mAb (MDX-1106, CT-011)

PDL1

Anti-PDL1-specific mAb (MDX-1105)

TIM3

TIM3 mAb

[108]

cIAP1

Small-molecule antagonists GDC-0152

[148]

Survivin

Anti-sense oligonucleotide LY2181308, ribozymes, siRNA, small-molecule antagonists YM155, chemotargeting with silibinin and NSAID, vaccination with survivin-2B80-88

[15,28,108]


Inhibition of apoptosis

[8,149]

Interaction block HVEM and BTLA/CD160

[73]

Glycoprotein D Anti-CD160 mAb (CL1-R2)

Pathways JAK2

ATP competitive JAK2 inhibitor (AZD1480)

[150]

mTOR

mTOR inhibitor (aspirin)

[141]

STAT3

JAK2 inhibitor (AZD1480)

[150]

Wnt/b-catenin signaling

Wnt/b-catenin signaling inhibitor (salinomycin)

[30]

COX2 inhibitor (aspirin, celecoxib, rofecoxib)

[21]

Prostaglandin PgE2 PgE2

4-1BB: Cluster of differentiation 137; A2aR: A2 adenosine receptor; Bcl-2: B cell lymphoma 2; BTLA: B and T lymphocyte attenuator; CCR5: Chemokine receptor 5; cIAP1: Cellular inhibitor of apoptosis 1; CTLA-4: Cytotoxic T lymphocyte-associated antigen 4; DNMT: DNA methyltransferase; EGFR: EGF receptor; GITR: Glucocorticoidinduced TNF receptor; HDAC: Histone deacetylase; HVEM: Herpes virus entry mediator; ICOS L: Inducible co-stimulatory molecule ligand; IDO: Indoleamine 2,3-dioxygenase; Ig: Immunoglobulin; JAK2: Janus kinase 2; KIR: Killer inhibitory receptor; LAG3: Lymphocyte activation gene 3; mAb: Monoclonal antibody; MDSC: Myeloid-derived suppressor cells; OX40: Cluster of differentiation 134; PD1: Programmed death 1; shRNA: Short hairpin RNA; STAT3: Signal transducer and activator of transcription 3; TGF-b: Tumor growth factor b; TIM3: T-cell membrane protein 3; TRAIL: TNF-Related Apoptosis-Inducing Ligand; Wnt/b-catenin: Wingless-type mouse mammary tumor virus integration site family member/b-catenin.

current dose of antigens is too low for the treatment in humans. The most ideal vaccination scheme has only been described for peptide and protein cancer vaccines, and not for whole cancer cell vaccines. The future of cancer cell vaccination resides in combinatorial strategies [108]. The therapeutic design should take the properties of immune response phases into account [11]. Ideally, first the specificities not only of the cancer but also of the patient should be identified [73,108]. Afterward, tolerance should be suppressed, followed by the delivery of the adjuvanted cancer vaccine and accompanying therapies to enhance antigen presentation and to boost T-cell priming. This treatment plan is ultimately completed with strategies that augment T-cell efficacy and memory [11]. Five-year view

In the next 5 years, combinatorial approaches in whole cancer cell vaccines will become more important as the standard adjuvant treatment to established anticancer treatments as surgery, chemotherapy and radiotherapy. Refinement of

doi: 10.1586/14760584.2014.911093

the selection procedures for patients susceptible to whole cancer cell vaccines will increase the success rate of combinatorial whole cancer cell vaccinations (whole cancer cells accompanied by a balanced adjuvant regime and a tackled immunosuppressive microenvironment). Although whole cancer cell use in cancer vaccines has many advantages, their ex vivo manufacture is time consuming and expensive, making it less attractive commercially. It is therefore likely that more research will be conducted to convert cancer cells into vaccines in vivo through immunogenic cell death, rendering the choice of a proper adjuvant and immunosuppressive targets more important than ever. Financial & competing interests disclosure

This work was supported by FWO grant G.0235.11N. 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.

Expert Rev. Vaccines


Review

Key issues • The major advantage of whole cancer cell vaccines is the induction of an active anticancer immune response leading to anticancer immune memory, which could lower cancer recurrence rates. • Whole cancer cell vaccines can provide unique patient-specific antigens, enhancing the specificity of the anticancer treatment. • The ideal whole cancer cell vaccine consists of immunogenically killed autologous cancer stem cells fused to autologous dendritic cells expressing an allogeneic molecule. • Cancer cell characteristics, adjuvant type and the patient status should be considered when generating a whole cancer cell vaccine. • Mice doses of antigen used in humans are likely ineffective at raising T-cell responses and should not be extrapolated. • Whole cancer cell vaccines should be administered distant to the tumor, since tumor draining lymph nodes are likely immunosuppressive. The immunosuppressive features of the tumor should ideally be neutralized when applying active anticancer immunization. Expert Review of Vaccines Downloaded from informahealthcare.com by Universiteit Gent on 04/24/14 For personal use only.

• Evaluation of the true potential of whole cancer cell vaccine trials is often prohibited by an inappropriate patient selection.

long-lasting anti-tumor immunity. Proc Natl Acad Sci USA 1993;90(8):3539-43

References Papers of special note have been highlighted as: • of interest •• of considerable interest 1.

2.

3.

4.

5.

6.

7.

Brown MP, Burdett N. Targeted therapies, aspects of pharmaceutical and oncological management. Cancer Forum 2013;37(1): 70-80 Hirschowitz EA, Yannelli JR. Immunotherapy for lung cancer. Proc Am Thorac Soc 2009;6(2):224-32 Serhal K, Baillou C, Ghinea N, et al. Characteristics of hybrid cells obtained by dendritic cell/tumour cell fusion in a T-47D breast cancer cell line model indicate their potential as anti-tumour vaccines. Int J Oncol 2007;31(6):1357-65 Rosenberg SA, Yang JC, Restifo NP. Cancer immunotherapy: moving beyond current vaccines. Nat Med 2004;10(9): 909-15 Lasaro MO, Ertl HC. Targeting inhibitory pathways in cancer immunotherapy. Curr Opin Immunol 2010;22(3):385-90 Gilbert AE, Karagiannis P, Dodev T, et al. Monitoring the systemic human memory B cell compartment of melanoma patients for anti-tumor IgG antibodies. PLoS ONE 2011;6(4):e19330 DiFronzo LA, Gupta RK, Essner R, et al. Enhanced humoral immune response correlates with improved disease-free and overall survival in American Joint Committee on Cancer stage II melanoma patients receiving adjuvant polyvalent vaccine. J Clin Oncol 2002;20(15):3242-8

8.

Aly HA. Cancer therapy and vaccination. J Immunol Methods 2012;382(1-2):1-23

9.

Dranoff G, Jaffee E, Lazenby A, et al. Vaccination with irradiated tumor cells engineered to secrete murine granulocyte-macrophage colony-stimulating factor stimulates potent, specific, and


10.

11.

Kalos M. Tumor antigen-specific T cells and cancer immunotherapy: current issues and future prospects. Vaccine 2003;21(7-8): 781-6 Vanneman M, Dranoff G. Combining immunotherapy and targeted therapies in cancer treatment. Nat Rev Cancer 2012; 12(4):237-51

12.

Nierkens S, Janssen EM. Harnessing dendritic cells for tumor antigen presentation. Cancers (Basel) 2011;3(2): 2195-213

13.

Casares N, Pequignot MO, Tesniere A, et al. Caspase-dependent immunogenicity of doxorubicin-induced tumor cell death. J Exp Med 2005;202(12):1691-701

14.

Gamrekelashvili J, Kruger C, von WR, et al. Necrotic tumor cell death in vivo impairs tumor-specific immune responses. J Immunol 2007;178(3):1573-80

15.

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(10): 1569-77

16.

Boog CJ. Principles of vaccination and possible development strategies for rational design. Immunol Lett 2009;122(2):104-7

17.

Lesterhuis WJ, Haanen JB, Punt CJ. Cancer immunotherapy–revisited. Nat Rev Drug Discov 2011;10(8):591-600

18.

Wang RF. The role of MHC class II-restricted tumor antigens and CD4+ T cells in antitumor immunity. Trends Immunol 2001;22(5):269-76

19.

Palucka K, Ueno H, Banchereau J. Recent developments in cancer vaccines. J Immunol 2011;186(3):1325-31

20.

Chang EY, Chen CH, Ji H, et al. Antigen-specific cancer immunotherapy

using a GM-CSF secreting allogeneic tumor cell-based vaccine. Int J Cancer 2000;86(5): 725-30 21.

Ribas A, Butterfield LH, Glaspy JA, Economou JS. Current developments in cancer vaccines and cellular immunotherapy. J Clin Oncol 2003;21(12):2415-32

22.

Sauter B, Albert ML, Francisco L, et al. 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(3):423-34

23.

Ronchetti A, Rovere P, Iezzi G, et al. Immunogenicity of apoptotic cells in vivo: role of antigen load, antigen-presenting cells, and cytokines. J Immunol 1999;163(1): 130-6

24.

Chiang CL, Benencia F, Coukos G. Whole tumor antigen vaccines. Semin Immunol 2010;22(3):132-43

25.

Gilboa E. DC-based cancer vaccines. J Clin Invest 2007;117(5):1195-203

26.

Bagarazzi ML, Yan J, Morrow MP, et al. Immunotherapy against HPV16/ 18 generates potent TH1 and cytotoxic cellular immune responses. Sci Transl Med 2012;4(155):155ra138

27.

Chiang CL, Kandalaft LE, Coukos G. Adjuvants for enhancing the immunogenicity of whole tumor cell vaccines. Int Rev Immunol 2011;30(2-3): 150-82

28.

Mellman I, Coukos G, Dranoff G. Cancer immunotherapy comes of age. Nature 2011; 480(7378):480-9

29.

Andersen BM, Ohlfest JR. Increasing the efficacy of tumor cell vaccines by enhancing cross priming. Cancer Lett 2012;325(2): 155-64

30.

Klebanoff CA, Acquavella N, Yu Z, Restifo NP. Therapeutic cancer vaccines: are

doi: 10.1586/14760584.2014.911093

Review


we there yet? Immunol Rev 2011;239(1): 27-44


31.

Burchill MA, Tamburini BA, Pennock ND, et al. T cell vaccinology: exploring the known unknowns. Vaccine 2013;31(2): 297-305

••

Reports that antigen doses used in mice do not result in effective T-cell response in humans.

32.

Ning N, Pan Q, Zheng F, et al. Cancer stem cell vaccination confers significant antitumor immunity. Cancer Res 2012; 72(7):1853-64

•

Describes cancer stem cells as a superior antigen source to unselected cancer cells.

33.

Li B, Simmons A, Du T, et al. Allogeneic GM-CSF-secreting tumor cell immunotherapies generate potent anti-tumor responses comparable to autologous tumor cell immunotherapies. Clin Immunol 2009;133(2)):184-97

34.

Zhou J, Weng D, Zhou F, et al. Patient-derived renal cell carcinoma cells fused with allogeneic dendritic cells elicit anti-tumor activity: in vitro results and clinical responses. Cancer Immunol Immunother 2009;58(10):1587-97

tumor cell fusion hybrids for murine colon adenocarcinoma. Cancer Immunol Immunother 2007;56(7):1025-36 42.

43.

Apetoh L, Obeid M, Tesniere A, et al. Immunogenic chemotherapy: discovery of a critical protein through proteomic analyses of tumor cells. Cancer Genomics Proteomics 2007;4(2):65-70

45.

Galluzzi L, Maiuri MC, Vitale I, et al. Cell death modalities: classification and pathophysiological implications. Cell Death Differ 2007;14(7):1237-43

46.

Korsnes MS. Yessotoxin as a tool to study induction of multiple cell death pathways. Toxins (Basel) 2012;4(7):568-79 Gollnick SO, Vaughan L, Henderson BW. Generation of effective antitumor vaccines using photodynamic therapy. Cancer Res 2002;62(6):1604-8

48.

•

Suggests hypericin-photodynamic therapy as a potential ideal immunogenic cell death inducer.

49.

37.

38.

Teitz-Tennenbaum S, Wicha MS, Chang AE, Li Q. Targeting cancer stem cells via dendritic-cell vaccination. Oncoimmunology 2012;1(8):1401-3 Pellegatta S, Finocchiaro G. Dendritic cell vaccines for cancer stem cells. Methods Mol Biol 2009;568:233-47

39.

Finn OJ. Cancer vaccines: between the idea and the reality. Nat Rev Immunol 2003; 3(8):630-41

40.

Toes RE, Blom RJ, van d V, et al. Protective antitumor immunity induced by immunization with completely allogeneic tumor cells. Cancer Res 1996;56(16):3782-7

41.

Yasuda T, Kamigaki T, Kawasaki K, et al. Superior anti-tumor protection and therapeutic efficacy of vaccination with allogeneic and semiallogeneic dendritic cell/

doi: 10.1586/14760584.2014.911093

Kepp O, Tesniere A, Schlemmer F, et al. Immunogenic cell death modalities and their impact on cancer treatment. Apoptosis 2009;14(4):364-75

47.

Krysko DV, Garg AD, Kaczmarek A, et al. Immunogenic cell death and DAMPs in cancer therapy. Nat Rev Cancer 2012; 12(12):860-75

Dillman RO, Beutel LD, De LC, Nayak SK. Short-term tumor cell lines from breast cancer for use as autologous tumor cell vaccines in the treatment of breast cancer. Cancer Biother Radiopharm 2001; 16(3):205-11

Kepp O, Galluzzi L, Martins I, et al. Molecular determinants of immunogenic cell death elicited by anticancer chemotherapy. Cancer Metastasis Rev 2011; 30(1):61-9

44.

35.

36.

Kroemer G, Galluzzi L, Kepp O, Zitvogel L. Immunogenic cell death in cancer therapy. Annu Rev Immunol 2013;31:51-72

50.

51.

52.

Korbelik M, Sun J. Photodynamic therapy-generated vaccine for cancer therapy. Cancer Immunol Immunother 2006;55(8):900-9 Garg AD, Krysko DV, Verfaillie T, et al. A novel pathway combining calreticulin exposure and ATP secretion in immunogenic cancer cell death. EMBO J 2012;31(5):1062-79 Fry TJ, Shand JL, Milliron M, et al. Antigen loading of DCs with irradiated apoptotic tumor cells induces improved anti-tumor immunity compared to other approaches. Cancer Immunol Immunother 2009;58(8):1257-64 Kim TB, Park HK, Chang JH, et al. The establishment of dendritic cell-tumor fusion vaccines for hormone refractory prostate cancer cell. Korean J Urol 2010;51(2): 139-44

•

Provides evidence for superiority of tumor cell–dendritic cell fusion vaccines.

53.

Bird RC, Deinnocentes P, Lenz S, et al. An allogeneic hybrid-cell fusion vaccine against canine mammary cancer. Vet Immunol Immunopathol 2008;123(3-4):289-304

54.

Gottesman A, Milazzo J, Lazebnik Y. Vfusion: a convenient, nontoxic method for cell fusion. Biotechniques 2010;49(4): 747-50

55.

Usaj M, Kanduser M. The systematic study of the electroporation and electrofusion of B16-F1 and CHO cells in isotonic and hypotonic buffer. J Membr Biol 2012; 245(9):583-90

56.

Iinuma H, Okinaga K, Fukushima R, et al. Superior protective and therapeutic effects of IL-12 and IL-18 gene-transduced dendritic neuroblastoma fusion cells on liver metastasis of murine neuroblastoma. J Immunol 2006;176(6):3461-9

57.

Radomska HS, Eckhardt LA. Mammalian cell fusion in an electroporation device. J Immunol Methods 1995;188(2):209-17

58.

Gottfried E, Krieg R, Eichelberg C, et al. Characterization of cells prepared by dendritic cell-tumor cell fusion. Cancer Immun 2002;2:15

59.

Torabi-Rahvar M, Bozorgmehr M, Jeddi-Tehrani M, Zarnani AH. Potentiation strategies of dendritic cell-based antitumor vaccines: combinational therapy takes the front seat. Drug Discov Today 2011; 16(15-16):733-40

60.

Gong J, Nikrui N, Chen D, et al. Fusions of human ovarian carcinoma cells with autologous or allogeneic dendritic cells induce antitumor immunity. J Immunol 2000;165(3):1705-11

61.

Marten A, Renoth S, Heinicke T, et al. Allogeneic dendritic cells fused with tumor cells: preclinical results and outcome of a clinical phase I/II trial in patients with metastatic renal cell carcinoma. Hum Gene Ther 2003;14(5):483-94

62.

Heath WR, Belz GT, Behrens GM, et al. Cross-presentation, dendritic cell subsets, and the generation of immunity to cellular antigens. Immunol Rev 2004;199:9-26

63.

Nierkens S, Tel J, Janssen E, Adema GJ. Antigen cross-presentation by dendritic cell subsets: one general or all sergeants? Trends Immunol 2013;34(8):361-70

64.

Ali OA, Emerich D, Dranoff G, Mooney DJ. In situ regulation of DC subsets and T cells mediates tumor regression in mice. Sci Transl Med 2009; 1(8):8ra19

65.

Kotera Y, Shimizu K, Mule JJ. Comparative analysis of necrotic and apoptotic tumor cells as a source of antigen(s) in dendritic cell-based immunization. Cancer Res 2001; 61(22):8105-9



66.

Itano AA, Jenkins MK. Antigen presentation to naive CD4 T cells in the lymph node. Nat Immunol 2003;4(8):733-9

67.

Engell-Noerregaard L, Hansen TH, Andersen MH, et al. Review of clinical studies on dendritic cell-based vaccination of patients with malignant melanoma: assessment of correlation between clinical response and vaccine parameters. Cancer Immunol Immunother 2009;58(1):1-14


68.

69.

70.

Castiello L, Sabatino M, Jin P, et al. Monocyte-derived DC maturation strategies and related pathways: a transcriptional view. Cancer Immunol Immunother 2011;60(4): 457-66 Huang LY, Sousa Re, Itoh Y, et al. IL-12 induction by a TH1-inducing adjuvant in vivo: dendritic cell subsets and regulation by IL-10. J Immunol 2001; 167(3):1423-30 Balwit JM, Hwu P, Urba WJ, Marincola FM. The iSBTc/SITC primer on tumor immunology and biological therapy of cancer: a summary of the 2010 program. J Transl Med 2011;9:18

71.

Hailemichael Y, Dai Z, Jaffarzad N, et al. Persistent antigen at vaccination sites induces tumor-specific CD8(+) T cell sequestration, dysfunction and deletion. Nat Med 2013;19(4):465-72

•

Describes negative effect of the adjuvant depot in cancer vaccines.

72.

Song J, Salek-Ardakani S, Rogers PR, et al. The costimulation-regulated duration of PKB activation controls T cell longevity. Nat Immunol 2004;5(2):150-8

73.

Capece D, Verzella D, Fischietti M, et al. Targeting costimulatory molecules to improve antitumor immunity. J Biomed Biotechnol 2012;2012:926321

74.

75.

76.

77.

Copier J, Dalgleish A. Overview of tumor cell-based vaccines. Int Rev Immunol 2006; 25(5-6):297-319 Gong J, Koido S, Calderwood SK. Cell fusion: from hybridoma to dendritic cell-based vaccine. Expert Rev Vaccines 2008;7(7):1055-68

78.

79.


Tamai H, Watanabe S, Zheng R, et al. Effective treatment of spontaneous metastases derived from a poorly immunogenic murine mammary carcinoma by combined dendritic-tumor hybrid vaccination and adoptive transfer of sensitized T cells. Clin Immunol 2008; 127(1):66-77

80.

Stannard KA, Collins PM, Ito K, et al. Galectin inhibitory disaccharides promote tumour immunity in a breast cancer model. Cancer Lett 2010;299(2):95-110

81.

Ahlert T, Sauerbrei W, Bastert G, et al. Tumor-cell number and viability as quality and efficacy parameters of autologous virus-modified cancer vaccines in patients with breast or ovarian cancer. J Clin Oncol 1997;15(4):1354-66

82.

83.

84.

85.

86.

Nanni P, Nicoletti G, De GC, et al. Combined allogeneic tumor cell vaccination and systemic interleukin 12 prevents mammary carcinogenesis in HER-2/neu transgenic mice. J Exp Med 2001;194(9): 1195-205 Koido S, Tanaka Y, Chen D, et al. The kinetics of in vivo priming of CD4 and CD8 T cells by dendritic/tumor fusion cells in MUC1-transgenic mice. J Immunol 2002;168(5):2111-17

Lindner M, Schirrmacher V. Tumour cell-dendritic cell fusion for cancer immunotherapy: comparison of therapeutic efficiency of polyethylen-glycol versus electro-fusion protocols. Eur J Clin Invest 2002;32(3):207-17

87.

Dols A, Smith JW, Meijer SL, et al. Vaccination of women with metastatic breast cancer, using a costimulatory gene (CD80)-modified, HLA-A2-matched, allogeneic, breast cancer cell line: clinical and immunological results. Hum Gene Ther 2003;14(11):1117-23 Avigan D, Vasir B, Gong J, et al. Fusion cell vaccination of patients with metastatic breast and renal cancer induces immunological and clinical responses. Clin Cancer Res 2004;10(14):4699-708 Homma S, Sagawa Y, Ito M, et al. Cancer immunotherapy using dendritic/tumourfusion vaccine induces elevation of serum anti-nuclear antibody with better clinical responses. Clin Exp Immunol 2006;144(1): 41-7 Wang J, Saffold S, Cao X, et al. Eliciting T cell immunity against poorly immunogenic tumors by immunization with dendritic cell-tumor fusion vaccines. J Immunol 1998;161(10):5516-24 van Elsas A, Hurwitz AA, Allison JP. Combination immunotherapy of B16 melanoma using anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and granulocyte/macrophage colony-stimulating factor (GM-CSF)producing vaccines induces rejection of subcutaneous and metastatic tumors accompanied by autoimmune depigmentation. J Exp Med 1999;190(3). 355-66

Review

cell fusions are superior activators of antitumor immunity. Cancer Immunol Immunother 2001;50(9):456-62 88.

Siders WM, Vergilis KL, Johnson C, et al. Induction of specific antitumor immunity in the mouse with the electrofusion product of tumor cells and dendritic cells. Mol Ther 2003;7(4):498-505

89.

Prell RA, Gearin L, Simmons A, et al. The anti-tumor efficacy of a GM-CSF-secreting tumor cell vaccine is not inhibited by docetaxel administration. Cancer Immunol Immunother 2006;55(10):1285-93

90.

Krause SW, Neumann C, Soruri A, et al. The treatment of patients with disseminated malignant melanoma by vaccination with autologous cell hybrids of tumor cells and dendritic cells. J Immunother 2002;25(5): 421-8

91.

Barbuto JA, Ensina LF, Neves AR, et al. Dendritic cell-tumor cell hybrid vaccination for metastatic cancer. Cancer Immunol Immunother 2004;53(12):1111-18

92.

Luiten RM, Kueter EW, Mooi W, et al. Immunogenicity, including vitiligo, and feasibility of vaccination with autologous GM-CSF-transduced tumor cells in metastatic melanoma patients. J Clin Oncol 2005;23(35):8978-91

93.

Hurn BA, Chantler SM. Production of reagent antibodies. Methods Enzymol 1980; 70(A):104-42

94.

Hendriksen C, Hau J. Production of polyclonal and monoclonal antibodies In: Hau J, Van Hoosier GL, editors, Handbook of laboratory animal science. CRC Press, LLC, Boca Raton, FL, USA; 2003. p. 391-411.

95.

Morse MA, Coleman RE, Akabani G, et al. Migration of human dendritic cells after injection in patients with metastatic malignancies. Cancer Res 1999;59(1):56-8

96.

Widner LA, Teates CD. Distribution of gold Au 198 after intraperitoneal injection in animals. South Med J 1975;68(6):687-93

97.

Fong L, Brockstedt D, Benike C, et al. Dendritic cells injected via different routes induce immunity in cancer patients. J Immunol 2001;166(6):4254-9

98.

Kjaergaard J, Shimizu K, Shu S. Electrofusion of syngeneic dendritic cells and tumor generates potent therapeutic vaccine. Cell Immunol 2003;225(2):65-74

99.

Draube A, Klein-Gonzalez N, Mattheus S, et al. Dendritic cell based tumor vaccination in prostate and renal cell cancer: a systematic review and meta-analysis. PLoS ONE 2011;6(4):e18801

Li J, Holmes LM, Franek KJ, et al. Purified hybrid cells from dendritic cell and tumor

doi: 10.1586/14760584.2014.911093

Review 100.

101.


102.


Bedrosian I, Mick R, Xu S, et al. Intranodal administration of peptide-pulsed mature dendritic cell vaccines results in superior CD8+ T-cell function in melanoma patients. J Clin Oncol 2003;21(20):3826-35 de Vries IJ, Lesterhuis WJ, Barentsz JO, et al. Magnetic resonance tracking of dendritic cells in melanoma patients for monitoring of cellular therapy. Nat Biotechnol 2005;23(11):1407-13 Korbelik M, Stott B, Sun J. Photodynamic therapy-generated vaccines: relevance of tumour cell death expression. Br J Cancer 2007;97(10):1381-7

103.

Munn DH, Mellor AL. The tumor-draining lymph node as an immune-privileged site. Immunol Rev 2006;213:146-58

•

Briefs on the immunosuppressive environment of tumors.

104.

Ohlfest JR, Andersen BM, Litterman AJ, et al. Vaccine injection site matters: qualitative and quantitative defects in CD8 T cells primed as a function of proximity to the tumor in a murine glioma model. J Immunol 2013;190(2):613-20

105.

Wick DA, Martin SD, Nelson BH, Webb JR. Profound CD8+ T cell immunity elicited by sequential daily immunization with exogenous antigen plus the TLR3 agonist poly(I:C). Vaccine 2011; 29(5):984-93

•

Proves superiority of cluster immunization to booster immunization with greater intervals in peptide and protein cancer vaccines.

106.

Heikenwalder M, Polymenidou M, Junt T, et al. Lymphoid follicle destruction and immunosuppression after repeated CpG oligodeoxynucleotide administration. Nat Med 2004;10(2):187-92

107.

Avigan D, Rosenblatt J, Kufe D. Dendritic/ tumor fusion cells as cancer vaccines. Semin Oncol 2012;39(3):287-95

108.

Pardoll DM. The blockade of immune checkpoints in cancer immunotherapy. Nat Rev Cancer 2012;12(4):252-64

109.

Tesniere A, Panaretakis T, Kepp O, et al. Molecular characteristics of immunogenic cancer cell death. Cell Death Differ 2008; 15(1):3-12

110.

111.

towards more personalized medicine. Trends Mol Med 2008;14(4):141-51 112.

Blankenstein T, Coulie PG, Gilboa E, Jaffee EM. The determinants of tumour immunogenicity. Nat Rev Cancer 2012; 12(4):307-13

113.

•

114.

124.

Schlom J, Gulley JL, Arlen PM. Paradigm shifts in cancer vaccine therapy. Exp Biol Med (Maywood) 2008;233(5):522-34

Ito A, Shinkai M, Honda H, et al. Augmentation of MHC class I antigen presentation via heat shock protein expression by hyperthermia. Cancer Immunol Immunother 2001;50(10):515-22

125.

Describes patient selection and proposes new evaluation methods for cancer patient benefit.

Shi H, Cao T, Connolly JE, et al. Hyperthermia enhances CTL cross-priming. J Immunol 2006;176(4):2134-41

126.

Fucikova J, Kralikova P, Fialova A, et al. Human tumor cells killed by anthracyclines induce a tumor-specific immune response. Cancer Res 2011;71(14):4821-33

127.

Menard C, Martin F, Apetoh L, et al. Cancer chemotherapy: not only a direct cytotoxic effect, but also an adjuvant for antitumor immunity. Cancer Immunol Immunother 2008;57(11):1579-87

Obeid M, Tesniere A, Ghiringhelli F, et al. Calreticulin exposure dictates the immunogenicity of cancer cell death. Nat Med 2007;13(1):54-61

115.

Zitvogel L, Kroemer G. Introduction: the immune response against dying cells. Curr Opin Immunol 2008;20(5):501-3

116.

Kuylenstierna C, Bjorkstrom NK, Andersson SK, et al. NKG2D performs two functions in invariant NKT cells: direct TCR-independent activation of NK-like cytolysis and co-stimulation of activation by CD1d. EurJ Immunol 2011;41(7):1913-23

128.

Coffman RL, Sher A, Seder RA. Vaccine adjuvants: putting innate immunity to work. Immunity 2010;33(4):492-503

129.

Steinhagen F, Kinjo T, Bode C, Klinman DM. TLR-based immune adjuvants. Vaccine 2011;29(17):3341-55

117.

Zafirova B, Wensveen FM, Gulin M, Polic B. Regulation of immune cell function and differentiation by the NKG2D receptor. Cell Mol Life Sci 2011;68(21):3519-29

130.

118.

la Sala A, Ferrari D, Corinti S, et al. Extracellular ATP induces a distorted maturation of dendritic cells and inhibits their capacity to initiate Th1 responses. J Immunol 2001;166(3):1611-17

Link C, Gavioli R, Ebensen T, et al. The Toll-like receptor ligand MALP-2 stimulates dendritic cell maturation and modulates proteasome composition and activity. Eur J Immunol 2004;34(3):899-907

131.

Krug A, Towarowski A, Britsch S, et al. Toll-like receptor expression reveals CpG DNA as a unique microbial stimulus for plasmacytoid dendritic cells which synergizes with CD40 ligand to induce high amounts of IL-12. EurJ Immunol 2001;31(10): 3026-37

132.

Gladue RP, Paradis T, Cole SH, et al. The CD40 agonist antibody CP-870,893 enhances dendritic cell and B-cell activity and promotes anti-tumor efficacy in SCID-hu mice. Cancer Immunol Immunother 2011;60(7):1009-17

133.

Postow M, Callahan MK, Wolchok JD. Beyond cancer vaccines: a reason for future optimism with immunomodulatory therapy. Cancer J 2011;17(5):372-8

134.

Ding ZC, Zhou G. Cytotoxic chemotherapy and CD4+ effector T cells: an emerging alliance for durable antitumor effects. Clin Dev Immunol 2012;2012:890178

Melero I, Hirschhorn-Cymerman D, Morales-Kastresana A, et al. Agonist antibodies to TNFR molecules that costimulate T and NK cells. Clin Cancer Res 2013;19(5):1044-53

135.

Weiss EM, Meister S, Janko C, et al. High hydrostatic pressure treatment generates inactivated mammalian tumor cells with

Wang S. The promise of cancer therapeutics targeting the TNF-related apoptosisinducing ligand and TRAIL receptor pathway. Oncogene 2008;27(48):6207-15

136.

Mocellin S, Marincola FM, Young HA. Interleukin-10 and the immune response

119.

Frey B, Schildkopf P, Rodel F, et al. AnnexinA5 renders dead tumor cells immunogenic–implications for multimodal cancer therapies. J Immunotoxicol 2009; 6(4):209-16

120.

Aymeric L, Apetoh L, Ghiringhelli F, et al. Tumor cell death and ATP release prime dendritic cells and efficient anticancer immunity. Cancer Res 2010;70(3):855-8

121.

Spisek R, Charalambous A, Mazumder A, et al. Bortezomib enhances dendritic cell (DC)-mediated induction of immunity to human myeloma via exposure of cell surface heat shock protein 90 on dying tumor cells: therapeutic implications. Blood 2007; 109(11):4839-45

Vacchelli E, Galluzzi L, Rousseau V, et al. Loss-of-function alleles of P2RX7 and TLR4 fail to affect the response to chemotherapy in non-small cell lung cancer. Oncoimmunology 2012;1(3):271-8

122.

Apetoh L, Mignot G, Panaretakis T, et al. Immunogenicity of anthracyclines: moving

123.

doi: 10.1586/14760584.2014.911093

immunogeneic features. J Immunotoxicol 2010;7(3):194-204



against cancer: a counterpoint. J Leukoc Biol 2005;78(5):1043-51 137.

138.


139.

140.

141.

142.

Kelly TK, De Carvalho DD, Jones PA. Epigenetic modifications as therapeutic targets. Nat Biotechnol 2010;28(10): 1069-78 Pratap J, Akech J, Wixted JJ, et al. The histone deacetylase inhibitor, vorinostat, reduces tumor growth at the metastatic bone site and associated osteolysis, but promotes normal bone loss. Mol Cancer Ther 2010;9(12):3210-20

143.

144.

Yong X, Xiao YF, Luo G, et al. Strategies for enhancing vaccine-induced CTL antitumor immune responses. J Biomed Biotechnol 2012;2012:605045 Velasco-Velazquez M, Jiao X, De La Fuente M, et al. CCR5 antagonist blocks metastasis of basal breast cancer cells. Cancer Res 2012;72(15):3839-50 Schlom J. Therapeutic cancer vaccines: current status and moving forward. J Natl Cancer Inst 2012;104(8):599-613


Ko HJ, Lee JM, Kim YJ, et al. Immunosuppressive myeloid-derived suppressor cells can be converted into immunogenic APCs with the help of activated NKT cells: an alternative cell-based antitumor vaccine. J Immunol 2009;182(4): 1818-28 Liu Y, Zeng B, Zhang Z, et al. B7-H1 on myeloid-derived suppressor cells in immune suppression by a mouse model of ovarian cancer. Clin Immunol 2008;129(3):471-81 Vincent J, Mignot G, Chalmin F, et al. 5-Fluorouracil selectively kills tumor-associated myeloid-derived suppressor cells resulting in enhanced T cell-dependent antitumor immunity. Cancer Res 2010; 70(8):3052-61

145.

Morris SM Jr. Recent advances in arginine metabolism: roles and regulation of the arginases. Br J Pharmacol 2009;157(6): 922-30

146.

Munder M. Arginase: an emerging key player in the mammalian immune system. Br J Pharmacol 2009;158(3):638-51

Review

147.

Vivier E, Ugolini S, Blaise D, et al. Targeting natural killer cells and natural killer T cells in cancer. Nat Rev Immunol 2012;12(4):239-52

148.

Gyrd-Hansen M, Meier P. IAPs: from caspase inhibitors to modulators of NF-kappaB, inflammation and cancer. Nat Rev Cancer 2010;10(8):561-74

149.

Kameshima H, Tsuruma T, Kutomi G, et al. Immunotherapeutic benefit of alpha-interferon (IFNalpha) in survivin2B-derived peptide vaccination for advanced pancreatic cancer patients. Cancer Sci 2013;104(1):124-9

150.

Hedvat M, Huszar D, Herrmann A, et al. The JAK2 inhibitor AZD1480 potently blocks Stat3 signaling and oncogenesis in solid tumors. Cancer Cell 2009;16(6): 487-97

doi: 10.1586/14760584.2014.911093