Review

Arming oncolytic viruses to leverage antitumor immunity Tanja D de Gruijl†, Axel B Janssen & Victor W van Beusechem 1.

Introduction

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Arming OVs with immune-stimulatory cytokines and receptors

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Arming OVs to optimize

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immunogenic cell death 4.

OV-mediated DC activation and enhanced cross-presentation

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Arming OVs with immune checkpoint inhibitors

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OV-mediated expression of bispecific T-cell engagers in the TME

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Conclusion

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Expert opinion: considerations in the design of the next generation of armed OVs

VU University Medical Center - Cancer Center Amsterdam, Department of Medical Oncology, Amsterdam, The Netherlands

Introduction: Over the past decade, the cytolytic capabilities of oncolytic viruses (OVs), exploited to selectively eliminate neoplastic cells, have become secondary to their use to elicit a tumor-directed immune response. Areas covered: Here, based on an NCBI-PubMed literature survey, we review the efforts undertaken to arm OVs in order to improve therapeutic antitumor responses upon administration of these agents. Specifically, we explore the different options to modulate immune suppression in the tumor microenvironment (TME) and to facilitate the generation of effective antitumor responses that have been investigated in conjunction with OVs in recent years. Expert opinion: Their induction of immunogenic tumor cell death and association with pro-inflammatory signals make OVs attractive immunotherapeutic modalities. The first promising clinical results with immunologically armed OVs warrant their further optimization and development. OVs should be modified to avoid detrimental effects of pre-existent anti-OV immunity as well as for increased tumor targeting and selectivity, so as to ultimately allow for systemic administration while achieving local immune potentiation and tumor elimination in the TME. In particular, a combination of trans-genes encoding bispecific T-cell engagers, immune checkpoint blockers and antigen-presenting cell enhancers will remove suppressive hurdles in the TME and allow for optimal antitumor efficacy of armed OVs. Keywords: antitumor immunity, immune suppression, immunotherapy, oncolytic viruses, tumor microenvironment, virotherapy Expert Opin. Biol. Ther. [Early Online]

1.

Introduction

Oncolytic viruses: kick-starting an antitumor immune response Oncolytic viruses (OVs) are cytolytic agents, able to selectively infect, replicate in and subsequently kill neoplastic cells originating from almost every type of tissue in the human body, while leaving other tissues unharmed [1,2]. Selectivity for neoplastic cells is established by the altered signaling and metabolic behavior of neoplastic cells, which has great similarity with the influence of viral infection on these processes. In addition, neoplastic cells have a reduced antiviral response and often overexpress receptors to which viruses bind [3,4]. These effects make some viruses naturally more selective for neoplastic cells than normal cells, and thus make them excellent theoretical therapeutic anticancer agents [1,3,5,6]. In other instances, viruses have been genetically altered to exploit tumor-associated permissiveness of viral replication in order to achieve tumor-specific lysis following infection [1]. The cytolytic capacity of OVs is mediated by replication of the virus and subsequent bursting of the host cell. The activation of the cellular apoptosis machinery caused by the viral infection itself may also play a role in the death of the host cell [4]. In addition to their intrinsic therapeutic effects, OVs are also able to elicit a collateral cell-mediated antitumor immune response, thus harnessing the natural power of the human immune system to eradicate cancer cells [3]. The antitumor 1.1

10.1517/14712598.2015.1044433 © 2015 Informa UK, Ltd. ISSN 1471-2598, e-ISSN 1744-7682 All rights reserved: reproduction in whole or in part not permitted

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T. D. de Gruijl et al.

Article highlights. .

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Their induction of immunogenic tumor cell death and their association with pro-inflammatory signals, make oncolytic viruses (OVs) attractive immunotherapeutic modalities. Immunologically armed OVs tick all the boxes for the induction of effective and durable anti-tumor immunity: They effect the release of TAAs (including unique tumor-derived neo-epitopes) under pro-inflammatory conditions. They can stimulate antigen presentation by professional antigen-presenting cells. They can mediate the removal of immune suppression by myeloid suppressors, Tregs and immune checkpoints in the tumor microenvironment and tumor-draining lymph nodes. They can ensure efficient homing to and infiltration of tumors by effector T cells. The first promising clinical results with immunologically armed OVs warrant their further optimization and development. OVs should be modified to evade any pre-existent antiOV immunity as well as to ensure exquisite tumor targeting and selectivity, so as to ultimately allow for systemic administration while achieving local immune potentiation and tumor elimination in the TME. A combination of trans-genes encoding bispecific T-cell engagers, immune checkpoint blockers and APC enhancers will remove suppressive hurdles in the TME and allow for optimal antitumor efficacy of armed OVs.

This box summarizes key points contained in the article.

immune response is induced by the concerted release of endogenous danger-associated molecular patterns (DAMPs) and tumor-associated antigens (TAAs) as well as virus-derived pathogen-associated molecular patterns (PAMPs) from the lysed tumor cells, and the release of immune-stimulatory cytokines, caused by infection by the OVs [7]. Immunogenic TAAs can arise through several processes including mutagenesis and altered post-translational modifications, or may further consist of viral antigens, fetal antigens, or tumor- or differentiation-related overexpressed proteins [3,8]. Neoplastic cells dampen potentially hostile immune responses both directly and indirectly through their ability to influence an array of other types of cells, both systemically and in the confines of the tumor microenvironment (TME). Immune suppression and the tumor microenvironment

1.2

The development of an immune response starts with antigen uptake by antigen-presenting cells (APCs). APCs are attracted by the inflammatory response caused by the death of the neoplastic cells through OV-mediated cell lysis. The released DAMPs and PAMPs activate the recruited APCs, for example, through binding to Toll-like receptors (TLRs) and induce uptake of the exposed TAAs. The presentation of the TAAs on both classes of MHC molecules (class-I and -II), due to (cross-)presentation, induces the activation of respective 2

CD8+ and CD4+ T cells through MHC--epitope complex recognition by specific T-cell receptors. Cross-presentation is the process by which exogenous antigens are taken up and processed for presentation through MHC class I by APCs to CD8+ effector T cells and is crucial in the elicitation of a T-cell-mediated immune response against TAAs. The most powerful APCs identified to date, that is, dendritic cells (DCs), are by far best equipped to mediate this essential process and to induce CD8+ effector cytotoxic T lymphocytes (CTLs) specifically targeting tumor cells. CD4+ T helper (Th) cells are also activated and skewed by the APC-secreted cytokines [9]. Tumors however, do not only comprise actively proliferating, neoplastic cells, but they also contain a range of other cell types. The neoplastic cells develop an elaborate system of cytokines, chemokines and receptors during tumor development, in order to recruit cells that serve to bolster the ability of neoplastic cells to survive, proliferate and metastasize. The recruited cells can be divided into three major classes: angiogenic vascular cells, cancer-associated fibroblastic cells, and infiltrating immune cells (IICs) [10]. Together these cells make up the TME [8,11,12]. In addition to the cellular component, the extracellular matrix (ECM) component also plays a role in the development of malignancies, providing signals for cell survival and proliferation [13]. Beside its tumor growth and invasion promoting and proangiogenic effects [10], the TME maintains a state of immune tolerance that cripples both the induction and effector phase of the immune response. This tolerance is established through the recruitment of several immune inhibitory cell types to the tumor, including CD4+CD25hiFoxP3+ regulatory T cells (Tregs), M2 macrophages, and myeloid-derived suppressor cells (MDSCs), all of which are able to effectively suppress type-1 antitumor T-cell responses [10]. These suppressive IICs, as well as the neoplastic cells, secrete cytokines such as IL-10 and TGFb that actively suppress effector CTLs, Th1 and NK cells, which together are responsible for a cellmediated antitumor immune response, but can also suppress B cells and the humoral immune response [8]. CTL induction, proliferation and effector functions are also inhibited through agonistic binding of inhibitory immune checkpoint receptors like CTL antigen-4 (CTLA-4) and programmed cell death protein 1 (PD-1) on the surface of activated CTLs by counter ligands on IICs and tumor cells. Moreover, secretion of metabolic enzymes by MDSCs, like inducible nitric oxide synthase (iNOS) and arginase-1, leads to the production of reactive oxygen/nitrogen species, which block activation of the IL-2 pathway, and degradation of L-arginine, thus blocking T-cell proliferation and activity in the TME [8,10,11,14]. Simultaneous expression of arginase and iNOS may even cause apoptosis of T lymphocytes through production of reactive ONOO- peroxynitrite molecules, which react with tyrosine residues in proteins, either blocking tyrosine phosphorylation, or nitrating components of the mitochondrial

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Arming OVs to leverage antitumor immunity

permeability transition pore, inducing apoptosis through cytochrome C release [14]. These immunosuppressive and tumor-promoting effects, make the TME indispensable to the survival and spread of neoplastic cells and can severely affect the therapeutic efficacy of cancer treatments currently in use [8,11,12]. The effects of conventional radio- and chemotherapy are dulled by the antiapoptotic signals provided by the recruited IICs and ECM products. Novel treatment modalities are therefore needed to overcome these effects [10,13,15]. Equipping OVs for immune modulation of the TME

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1.3

In recent years, numerous methods to influence the immune suppressive nature of the TME and to specifically target cancer cells have been developed, adding to the traditional radio- and chemotherapy treatment options. Immunotherapies that have been developed to influence both the TME and directly kill the cancer cells have received plenty of attention recently due to the first evidence of their clinical efficacy; in particular immune checkpoint blocking antibodies (e.g., ipilimumab, nivolumab and pembrolizumab) and adoptive cell transfer (ACT) have proven effective with durable tumor responses observed in a fraction of the treated patients [7,8,16]. While surgery, chemotherapy and radiation therapy remain the first lines of treatment for most tumors, immunotherapy regimens are gaining ground. Indeed, in an immunogenic tumor type like melanoma, immunotherapy in the form of immune checkpoint blockade has even taken over as a first line of treatment for advanced disease. The FDA approvals of Provenge [17,18] for advanced prostate cancer, and Yervoy (ipilimumab/anti-CTLA-4), Keytruda (pembrolizumab/antiPD-1), and Opdivo (nivolumab/anti-PD-1) [19] for the treatment of advanced melanoma, have set the stage for the approval of other immune-based therapies in the near future as well as for combination therapies with conventional treatment regimens. The insight that OVs are capable of selectively infecting and killing cancer cells, has led to the development of OVs as therapeutic tools to achieve in vivo antitumor immunization and simultaneous immune modulation of the TME, further adding to the already promising field of tumor immunotherapy. Research is actively being pursued to optimize OV therapy in the context of immune modulation in order to elicit and leverage a durable antitumor immune response [3]. Many types of OVs have been used in this context, including adenovirus (Ad), reovirus, herpes simplex virus (HSV), vaccinia virus (VV), measles virus (MV), Newcastle disease virus and coxsackie virus. These viruses are all actively used in the development of a possible treatment for varying types of cancer [7,20,21]. Their stage of clinical development has recently been reviewed elsewhere [20,22]. Recent studies in patients successfully treated with immune checkpoint blockade or ACT have revealed the importance of

T cells recognizing unique neo-epitopes arising from mutations to the treated tumors [23-26]. To induce immunity to these neo-epitopes, which are unique to each individual tumor, treatment with armed OVs harboring immune potentiating capacities may prove instrumental [27]. Essentially, the virus acts as an in vivo vaccine, mediating the release of TAAs from lysed tumor cells in a pro-inflammatory context (Figure 1). Per definition, the released epitopes are relevant for the treated tumor and therefore highly suitable and relevant for specific activation of tumor-infiltrating lymphocytes. Furthermore, following TAA cross-presentation and CTLmediated tumor kill, subsequent epitope spreading (through the availability of secondarily released TAAs) together with virus-derived PAMPs and lysed tumor cell-derived DAMPs, leads to even further increased immunogenicity of the established tumor [28-33]. Interestingly, OVs (e.g., conditionally replicating Ads) were also shown to induce autophagy [34,35], which further facilitates cross-presentation of TAAs to CTLs by DCs [36]. The immune response can be even further enhanced by local attraction and activation of DCs [28-33]. Research and clinical use of OVs were originally aimed at the cytolytic capacity of the used viruses, but researchers have since realized that genetic manipulation of OVs could further increase their efficacy in the treatment of cancer [1,3,6]. Research has shown that genetically engineered OVs have great potential to influence the TME, improving the outlook for this new type of treatment. This has led to the development of a wide range of genetically engineered OVs armed with different human trans-genes, some of which have been tested as therapeutic drugs in clinical trials involving patients suffering from a wide diversity of cancer types [3,4,6,20,22]. In this review we discuss some of the strategies employed to design and deploy OVs, which are armed to enhance and harness the in vivo immunogenicity of tumors and thus kick-start a durable antitumor immune response.

Arming OVs with immune-stimulatory cytokines and receptors

2.

The exact cellular composition of the TME is determined by its content of cytokines, chemokines and other chemoattractive and immune-modulating molecules. Efforts to modulate the TME have been undertaken in order to better be able to control cancer. OVs may present powerful therapeutic tools in this respect. Extensive research has been performed to determine the effects of recombinant cytokines and of OVs expressing different cytokines, through constitutively active CMV promoter-controlled trans-genes, on the activation of immune effector cells and the survival of cancer cells [3,8,37]. Research into the effect of systemic administration of recombinant cytokines on the TME quickly revealed unacceptable side effects and thus was not pursued any further [22,38]. In contrast, the tumor-localized activity of OVs may allow for expression of these immune-stimulatory cytokines where it matters, that is, in the TME, while

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T. D. de Gruijl et al.

1. Pre-treatment tumor Treg Th2 Suppressive cytokines

M1-macrophage CTL Th1

M2-macrophage Monocytic MDSC

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Granulocytic MDSC

Mature dendritic cell NK cell

3. Immune modulation Treg inhibition/depletion MDSC depletion/differentiation M2-M1 macrophage conversion DC maturation Recruitment of effector NK/T cells

2. Tumor-specific virus replication Anmed oncolytic virus coding for ... BiTE Bispecific T cell Engager scFv e.g., anti-IL-6, anti-IL-10

4. Inflammatory response

Antibody e.g., anti-PD-1, anti-PD-L 1 5. Tumor antigen release shRNA e.g., targeting COX-2, STAT3 Immune stimulatory 6. T cell priming cytokines

Figure 1. Six steps to antitumor T-cell immunity: antitumor efficacy of armed oncolytic viruses depends on successful immune potentiation of the tumor microenvironment and the induction of durable antitumor T-cell responses.

minimizing the risk of systemic side effects. For a concise overview of the reviewed studies on OVs armed with immunestimulatory cytokines and receptors, see Table 1. OV-expressed cytokines tested include IL-2, -12, -15 and -18, all known to support T-cell homeostasis, but also APC-activating IFNs, TNFa and GM-CSF, which recruit and activate T-cell stimulatory DCs [3,39,40]. All of the cytokines tested were shown to exert antitumor effects. Replication-competent VVs and MVs encoding GM-CSF improved the eradication of neoplastic cells, through local immune potentiation in the TME [41,42]. Enforced expression of IL-2, -12 and -18, had definite antitumor effects in mice through their ability to recruit and activate T cells [37,43,44]. The number of CD8+ T cells were found to be elevated in tumors of mice treated with IL-2 engineered viruses, demonstrating the recruiting capability of conditionally replicating HSV armed with this cytokine [43]. Replication-competent HSV-mediated expression of soluble B7.1 (CD80), which binds to the co-stimulatory CD28 molecule on T cells, also stimulated T-cell-mediated antitumor effects through higher activation states of the effector cells and possibly through blocking of the co-inhibitor PD-L1 [37,45]. Single trans-gene armed OVs 4

can thus exert a positive influence on the ability of the immune system to control the growth and spread of tumors. The first and most extensively studied immune modulatory trans-gene clinically tested in armed OVs is GM-CSF. GM-CSF is known to stimulate the development, recruitment, activation and survival of DCs, which are vital for the generation of antitumor immunity; moreover, GM-CSF can induce differentiation of immune-suppressive monocytic MDSCs to stimulatory M1-macrophages or DCs and thus make the TME more conducive to antitumor effector responses [46,47]. Phase-I/II trials were recently conducted with GM-CSF encoding OVs (based on Ad, VV or reoviral vectors) as well as a randomized Phase-III trial (with an oncolytic HSV1, i.e., T-Vec) [1,47-51]. These OVs were either injected intravenously or intralesionally in patients with accessible metastases. Generally low-objective clinical response rates were observed as well as decreased rates of MDSCs and Tregs and increased rates of (TAA-specific) CD8+ T cells, both systemically and in the TME. In the Phase-III (OPTiM) trial 290 evaluable patients with unresectable Stage III or IV melanoma were treated with intralesional injection of T-Vec versus GM-CSF (randomized 2:1). In the T-Vec-treated

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Recruitment and activation of T cells

Recruitment and activation of T cells

IL-12, CD80

4-1BBL, IL-12 HSP70

anti-CTLA4

IL-18, CD80-Ig

IL-2

IL-12 GM-CSF

CD40L anti-CTLA4

GM-CSF GM-CSF

GM-CSF

GM-CSF

CCL5

CCL19

VEGF VHH

Adenovirus

Adenovirus

Adenovirus

Herpes Simplex Virus (HSV)-1 HSV-1

HSV-1 HSV-1

HSV Measles virus

Vaccinia virus Vaccinia virus

Vaccinia virus

Vaccinia virus

Vaccinia virus

Vaccinia virus

Vaccinia virus

Adenovirus

GM-CSF

Adenovirus

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Neutrophil recruitment to the tumor Increased infiltration of neutrophils and macrophages Tumor-specific antibody-dependent complementdependent cytotoxicity Tumor-specific antibody-dependent complementdependent cytotoxicity Improved infiltration of DCs and CD4+ T cells, production of IFNg, IL-2, IL-6, CCL2, and CXCL2 Improved infiltration DCs, CD4+, and CD8+ T cells, production of IFNg, IL-2, IL-6, CCL2, and CXCL2 Neutralization of immune suppressive VEGF

Co-stimulation of effector T cells Lymphocyte infiltration and activation

Recruitment and activation of T cells Recruitment and activation of CD8+ T cells

Lymphocyte activation

Increased immunogenic cell death, CD8+ T-cell and B-cell activation APC activation and recruitment, adenovirus/tumorspecific T-cell response Recruitment of CD4+ and CD8+ T cells, APC activation, IFNg expression Increased expansion, cytokine production, and the development of cytolytic effector function of T cells Elevated numbers of CD4+ and CD8+ T cells and NK cells

TNFa

Adenovirus

APC activation

IFNa

Adenovirus

Immune effect

Therapeutic transgene

Virus type

Rabbit liver tumor VX2 model, Phase I clinical trial in patients with various types of cancer. Murine 6780 lymphoma and MC38 colon adenocarcinoma model Murine 6780 lymphoma and MC38 colon adenocarcinoma model Human xenograft mouse model using the prostate cancer cell line DU-145 and the lung cancer cell line A549

Liver Cancer Phase II clinical trial

Squamous cell carcinoma immune competent mouse model Liver colon tumor metastasis mouse model Phase III clinical trial in stage IIB-IV melanoma patients Brain tumor mouse model Immune competent melanoma B16-CD20 mouse model Human Burkitt lymphoma xenograft mouse model Syrian hamster pancreatic tumor model

Syrian hamster pancreatic tumor model and clinical trial in patients with advanced cancer Immune competent mouse B16-F10 melanoma model Mouse immune competent B16-F10 melanoma model Phase I trial in patients with various types of solid tumors (lung cancer, melanoma, renal carcinoma among others) In vitro T cell activation and human xenograft mouse model TRAMP-C2 prostate cancer and Neuro2a neuroblastoma immune competent mouse models

Syrian hamster subcutaneous pancreatic tumor model Human prostate cancer xenograft mouse model

Experimental model or clinical trial

Table 1. Overview of studies on oncolytic viruses armed with immune-stimulatory cytokines and receptors.

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[77]

[57]

[56]

[50]

[49]

[41] [42]

[54] [74]

[44] [51]

[43]

[37]

[71]

[61]

[53]

[52]

[48]

[40]

[39]

Ref.

Arming OVs to leverage antitumor immunity

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patients TAA-specific T-cell responses were observed both in the injected and in the noninjected metastases. Moreover, durable (> 6 months) clinical response rates in the T-Vec versus GM-CSF treatment groups was 16 vs 2%, respectively [51]. These observations are consistent with the induction of efficacious systemic antitumor responses by local T-Vec delivery. Numerous preclinical studies investigating various combinations of different immune stimulatory soluble molecules, expressed through OV engineering, have been carried out. In immune-competent murine models of neuroblastoma and prostate cancer, enhanced antitumor efficacy was observed in mice treated with replication-competent HSVs, equipped with both IL-18 and soluble B7.1 (CD80), as compared to the use of the same vector expressing only IL-18 or B7.1 (CD80) [37]. The effect of the IL-18/B7.1 (CD80) dually armed HSVs was proven to be dependent on T cells, since athymic mice did not show any difference in tumor size after treatment when the empty viral vector was compared to the dually armed version [37]. The dual expression of IL-12 and B7.1 (CD80) in an oncolytic Ad vector also effected an increased survival of immune competent mice bearing B16 melanoma tumors, in addition to reduced tumor size and more specific killing, when compared to single expression of either trans-gene, all through T-cell-mediated responses [52]. In the tumors of these mice treated with the dually armed version of the oncolytic Ad, enhanced APC activation and greater IFNg and IL-12 concentrations were observed, along with increased infiltration by CD4+ and CD8+ T cells, resulting in enhanced antitumor efficacy as compared to Ads expressing only IL-12 [52]. Altogether, these studies have demonstrated the superior antitumor effects of dually over singly armed OVs with immune modulatory potential, thus clearly holding promise in terms of increasing the potency and possible clinical impact of OVs even further [3,53]. Beside the use of the soluble versions of co-stimulatory ligands like B7.1 (CD80), the activating potential of cellbound ligands has also been investigated. OVs have been successfully equipped to express cell-bound co-stimulatory ligands such as CD40-ligand (in HSV) and B7 (CD80/ CD86) (in Ad) in an effort to break the immunosuppressive TME through increased (co-)stimulation of effector T cells [52,54]. OV-mediated expression of these receptors on infected tumor cells has indeed been found to enhance antitumor responses in vivo [52-55]. In addition to studies investigating the use of cytokines and immune stimulatory ligands, studies on the use of chemokines have also shown increased therapeutic efficacy through recruitment of various types of immune effector cells to the TME. For example, through expression of CCL5 and -19 by replication-competent VV, the infiltration of both DCs and CD4+ T cells was improved [56,57]. Unexpectedly, CD8+ T cells were not attracted to the tumor by CCL5-armed VVs, but only by CCL19-armed VVs, whereas Tregs were not recruited to the tumor by either chemokine. In addition 6

to their cell-attracting capabilities, the chemokine-armed viruses were able to induce the subsequent production of cytokines and chemokines like IFNg, IL-2, IL-6, CCL2 and CXCL2 in the TME, improving the recruitment and activation of immune effector cells even further [56,57]. Of note, infection of tumor cells by OVs per se can already induce IIC-attracting chemokines. A recent report described the recruitment of adoptively transferred effector T cells to the TME by CXCL9 and CXCL10 induction upon oncolytic HSV2 delivery [58]. Beside the use of cytokines, chemokines and (co-)stimulatory receptors, the therapeutic potential of heat shock proteins (HSPs), normally involved in antigen presentation, but also known to function as DAMPs, has also been investigated in the context of OV treatment [3,9]. HSPs can induce maturation of DCs, promote cross-presentation of antigens, interact with APCs to stimulate release of inflammatory cytokines and act as chaperones for immunogenic peptides. These functions facilitate a more effective antitumor response through enhanced antigen presentation by DCs in an MHC class I restricted fashion, while ensuring an optimal cytokine environment for the inhibition of tumor growth and invasion [59,60]. Moreover, HSPs can induce both a cell-mediated and a humoral immune response [59]. The possible adverse effects of HSPs, however, include their ability to promote immune suppression by the tumor and their possible facilitation of survival signals for tumors [36]. Importantly, replication-competent oncolytic Ad vectors complemented with HSPs have long since been shown to provide clinical benefit in treated patients [61]. In aggregate these preclinical and clinical observations indicate a broad potential of genetically engineered OVs to stimulate the immune system in very diverse ways in order to leverage its powerful and durable antitumor potential.

Arming OVs to optimize immunogenic cell death

3.

For the immune system to be properly activated against cellderived antigens, cells have to die in particular ways that alert the immune system [3,7,9]. Although many types of cell death can be distinguished, only immunogenic apoptosis, pyroptosis, necroptosis, autophagic cell death and necrosis are considered types of immunogenic cell death (ICD) -- in contrast to nonimmunogenic apoptosis [3,7,9]. The exposure of DAMPs (e.g., calreticulin, ATP and HSPs) and PAMPs (e.g., dsRNA, DNA, glycoproteins and lipoproteins) as a result of OV-induced ICD can contribute to modulation of the immunosuppressive nature of the TME [6,9]. These products are exposed upon ICD and are able to activate the immune system through activation of APCs by pattern recognition receptors (PRRs). These PRRs include TLRs and nucleotide oligodimerization domain-like receptors (NLRs) [9]. After recognition of DAMPs and PAMPs, DCs upregulate surface expression of MHC and co-stimulatory molecules and start

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Arming OVs to leverage antitumor immunity

to secrete T-cell stimulatory cytokines like IL-12 [9]. Expression of these molecules enables optimal T-cell activation. A tumor-specific immune response may further develop through exposure of TAAs in the context of DAMPs and PAMPs, activating a specific T-cell response through TAA-pulsed APCs [9]. ICD is thus essential to provoke an effective antitumor immune response. The ability of an OV to evoke an immune response can be crucial for the success of the virotherapy, and thus viruses may be selected for their ability to induce ICD, potentially improving the efficacy of OV therapy. Some OVs, such as coxsackie virus and MV, are naturally able to elicit ICD, thus increasing treatment efficiency [7,9]. The release of HMGB1 and inflammatory cytokines observed subsequent to oncolytic replication-competent MV treatment was consistent with ICD [62]. Similarly, the use of a range of other OVs, including Ad, VV and poxvirus, also led to ICD as indicated by the release of HMGB1 [9]. Moreover, OV-infected cells release additional DAMPs such as uric acid and ATP, which, together with virus-derived PAMPs, make OV-induced tumor cell death highly immunogenic. OVs may be further adapted to mediate ICD by deleting or inserting cell death influencing genes [7]. For instance, knockout (KO) of antiapoptotic genes SPI-1 and SPI-2 in oncolytic VV can induce necrotic cell death, as marked by the release of HMGB1, in contrast with the SPI-1 and SPI-2-enabled viruses [63]. SPI-2 is specifically able to block caspase-1, which uniquely causes pyroptotic cell death, characterized by inflammation and immune activation [63,64]. KO of cell deathmodulating genes in viruses can thus alter the type of cell death to become more immunogenic in nature. Of note, the deletion of antiapoptotic genes calls for caution as these genes enable prolongation of cell survival upon viral infection. The deletion of these antiapoptotic viral products may influence the successful replication and spread of virus particles, diminishing overall efficacy of the treatment by decreasing the numbers of progeny per original virus particle. This issue should be considered when inserting loss-of-function mutations in these genes in order to promote ICD.

OV-mediated DC activation and enhanced cross-presentation

4.

Cancer cells can suppress immune responses by several mechanisms. Downregulation of MHC Class I, and aberrant function of TAP transporters, proteasome subunits and chaperone proteins inhibit correct presentation of TAAs on MHC class I molecules by tumor cells [2]. Cancer cells also influence cells recruited to the TME. Intratumoral DCs display lower levels of MHC class-I and -II and of B7 co-stimulatory molecules [2]. Higher expression of CTLA-4 and PD-L1 on APC in the TME or on tumor cells contributes to further suppression of antitumor T cell responses [2]. Among other factors, the recruitment of Tregs and expression by tumor cells of inhibitory cytokines/factors like TFGb and PGE-2

sabotage the ability of APCs in the TME and draining lymph nodes to present tumor antigens [2]. OVs like HSV and reovirus, are able to restore correct antigen presentation through infection of cancer cells, and the subsequent antiviral immune response may serve as an adjuvant, in turn eliciting an antitumor immune response [60,65]. The infection of a patient with reovirus activates DC-mediated antigen presentation and leads to release of cytokines, promoting T-cell division and activation [2,52,65,66]. Similar results can be achieved through the administration of HSV [60]. The ability of viruses to induce cross-presentation and thus effective CTL responses against TAAs, endocytosed by APCs in the TME, accounts in part for the observed therapeutic efficacy of OV treatment. OV-induced ICD stimulates uptake of TAAs by APCs and cross-presentation to specific CTLs. This cross-presentation may be further enhanced through OV infection-induced expression of type-1 IFNs (a/b) or by inserting type-1 IFN transgenes in OVs [39]. Indeed, elevated levels of type-1 IFNs in the TME may be instrumental in the activation of DC subsets with crosspresenting abilities in tumors and their draining lymph nodes [67,68]. Of note, various viruses have developed mechanisms to undermine antigen presentation in order to facilitate their immune escape [69]. For instance, vesicular stomatitis virus administration in mice led to impaired antigen presentation and negatively influenced DC functionality [70]. The natural ability of viruses to block antigen presentation in order to sustain infection can have a negative effect on OV efficacy, and may thus require KO of antigen presentation-interfering genes and/or knock-in of DC activation and crosspresentation enhancing genes (like type-1 IFNs).

Arming OVs with immune checkpoint inhibitors

5.

The immunologically anergic nature of the TME is established not only by the lack of activating signals, but also by the presence of actively suppressing factors. Neoplastic cells inhibit immune activation in various ways, including through the recruitment of M2-macrophages, MDSCs and Tregs, through the inhibition of DC development and activation, and through the expression of inhibitory cytokines and receptors [8]. Originally purposed to inhibit auto-reactive responses, neoplastic cells abuse these mechanisms in order to derail and silence a possible antitumor immune response. In addition to their expression of inhibitory cytokines and receptors, neoplastic cells often harbor impaired antigen processing and presentation pathways, further blocking the therapeutic potential of the immune response [2]. The expression of immune checkpoint receptors (like e.g., PD-L1) on tumor cells suppresses effector T-cell activation and functionality, while generally enhancing immunosuppressive Treg responses [45,71]. Expression of B7 (CD80/CD86)

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receptors has been reported on cancer cells, influencing survival and cytokine production through binding of CTLA4 on CD8+ T cells, while stimulating Treg function [45]. These, and a variety of other ligands binding to checkpoint receptors on T cells, are expressed by tumor cells and infiltrating immune suppressive myeloid cells, negating immune responses in favor of tumor survival [8,45]. The development and clinical testing of antibodies against immune checkpoint receptors (CTLA4, PD-1) has clearly proven the therapeutic potential of the T-cell response against cancer and in the process caused a revolution in the field of medical oncology. By blocking the interaction and activation of receptors normally involved in keeping immune cells in check, T-cell activation against TAAs increases dramatically, leading to efficient eradication of tumors. Both expressed on activated T cells, CTLA4 is mostly involved in the induction phase of the T-cell response taking place in the secondary lymphoid organs, whereas PD-1 is mainly responsible for dampening T-cell responses in the effector phase in peripheral tissues [45]. Thus, by blocking CTLA4 and PD-1/PD-L1, different outcomes may be expected [45]. Blocking the CTLA-4 receptor may improve the overall response against neoplastic cells, but may also cause off-target autoimmune toxicity due to the general control of CTLA4 over the priming of T cells. By blocking PD-1/PD-L1 interaction, specific effector responses may become more efficient locally; indeed, the blockade of PD-1/PD-L1 has been shown to increase cytokine production in the tumor [72]. Although blockade of both receptors has been shown to improve immunity against cancer, the systemic administration of antibodies blocking these receptors may have severe adverse auto-immune effects, and thus a localized expression of these antibodies may be more desirable [45,71,73-76]. The selective replication of OVs equipped with genes encoding antibodies that block immune checkpoints in the TME and draining lymph nodes may focus the therapeutic effects of these antibodies on the TME while minimizing their systemic side effects [71,73,74,77]. Replication-competent MVs equipped with transgenes encoding anti-CTLA-4 antibodies have been shown to have a positive effect on survival and tumor regression in mouse models [74]. The local expression of full-length anti-CTLA-4 antibodies through CTLA-4 transgene-modified oncolytic Ad, increased local concentrations of anti-CTLA-4 antibodies in the TME up to 81-fold as compared to plasma concentrations [71]. Antibodies against additional immune checkpoint receptors are also being investigated for their therapeutic potential; these include B- and T-lymphocyte attenuator (BTLA), T-cell immunoglobulin mucin-3 (TIM3), lymphocyte activation gene 3 (LAG3) and adenosine A2 receptor [73]. All of these receptors are known to have an inhibitory effect on lymphocyte function and their inhibition could thus improve OV-based treatment [45,73]. The rather large nature of the used antibodies (150 kDa) does endow this type of treatment with certain disadvantages. Slow clearance and slow penetration of solid tumors increase 8

the likelihood of toxic side effects and decrease efficacy [73,78]. This problem of size may be reduced by using alternate antibody forms such as single-chain variable fragments (scFvs), diabodies, antigen-binding fragments (Fabs) and camelid single-chain antibodies or single-domain antibody fragments derived thereof (scAbs or VHH, respectively) [73,77,79,80]. scFvs consist of the variable regions of the heavy and light chains, linked by a linker peptide [73,78]. Diabodies are scFvs engineered with a short linker, forcing them to dimerize and thus increasing affinity to the target. Fabs are made up of the light chain and part of the heavy chain of normal antibodies [73,77,78]. VHHs (or nanobodies) consist only of the variable region of the heavy chain and represent the smallest Ab units. Replication-competent VVs armed with a VHH transgene targeting VEGF were shown to have equivalent therapeutic effects in mice as a combination of the vector and systemic administration of full length antibodies against VEGF, demonstrating the relatively high therapeutic efficacy of the tailored and locally expressed antibodies [77]. The reduced size of these types of antibody formats increases dispersion through solid tumors and speeds up clearance upon exit from the tumor [73,78,81]. The successful development of clinically active therapeutic antibodies and their subsequent registration by the FDA and the EMA sets high hopes for the clinical relevance and potential of antibodies directed against other receptors involved in immune regulation [3,73,74]. The activity of the immune system may be further increased through the suppression of the activity of myeloid cells like MDSCs, and M2 macrophages. These cells suppress immune effector cells in the TME through their expression of inhibitory receptors like CTLA-4, secretion of suppressive cytokines like IL-10, and secretion of enzymes like arginase and iNOS and are believed to be a major cause of unresponsiveness to checkpoint inhibitors [8]. Several types of small-molecule inhibitors have been tested to block the suppressive effects of these myeloid cells, but these therapeutic agents cannot be delivered selectively to the tumor through OVs. OVs can however be used to influence the myeloid cells through reprogramming and depletion. M2 macrophages for example, can be reprogrammed into more favorable M1-type macrophages through the use of agonist CD40 antibodies, in combination with other immune-stimulatory or chemotherapeutic drugs [82]. The successful outcome of mouse studies with several types of armed OVs bode well for the clinical outlook of localized OV-mediated checkpoint inhibitor treatment. Immunogenic antigen release (including neo-epitopes unique to individual tumors) effected by tumor-restricted replication of OVs coupled to localized checkpoint inhibition in the TME and tumor-draining lymph nodes, is expected to result in very powerful tumor-directed T-cell immunity without collateral autoimmune side effects. It’s this unique combination of attributes that makes this strategy clinically a particularly promising one.

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Arming OVs to leverage antitumor immunity

OV-mediated expression of bispecific T-cell engagers in the TME

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6.

In OV-based therapies, cancer cells may survive because they are not infected by the OV. In order to fully eradicate the tumor, the bystander effect may prove crucial, and may encompass the redirection of the immune response [83,84]. Redirection of T cells to kill residual cells has been investigated by the use of bispecific T-cell engagers (BiTEs) [84,85]. BiTEs consist of two linked scFvs specific for the T-cell receptor-signaling complex CD3 and a tumor-specific antigen, effectively binding T cells to the associated tumor cell, causing T-cell activation, and ultimately, T-cell-mediated cell death [84,85]. The systemic administration of BiTEs specific for T cells (through CD3), and B cells (through CD19) in mice and patients suffering from non-Hodgkin’s B-cell lymphoma caused a spectacular decrease in B cell count in the blood [16,86]. Increasing levels of annexin V over the course of treatment with the CD3/CD19 bispecific antibody blinatumomab, indicated the apoptosis of targeted B cells, rather than their extravasation, to be the cause of this phenomenon. Both effector and memory T cell counts in patients increased as a result of treatment with blinatumomab [16]. Pre-activation and/or costimulation of the targeted T cells was not necessary for serial lysis by the T cells, since the highly efficient cytolytic effect of the T cells was mediated by activation of the cells through the linkage of only a limited number of CD3 receptors by the BiTEs [85-87]. This low-threshold triggering of cytolytic effector functions makes, however, nonspecific activation and a subsequent autoimmune reaction upon systemic administration of bispecific antibodies like blinatumomab a hazard [16,86]. Similarly to local expression of antibodies blocking immune checkpoints, arming OVs with a transgene encoding a BiTE might reduce off-target autoimmune responses and improve therapeutic efficacy through reducing systemic and increasing intratumoral concentrations [71,74]. Arming replicationcompetent VV with a gene encoding for an excretory BiTE, with specificity for both CD3 and the tumor marker EphA2, increased killing of lung cancer cells through T-cell recruitment, eliciting an effective antitumor bystander effect in vivo [85]. The activation of T cells was evident through the production of IL-2 and IFNg, potentially skewing toward type-1 T-cell-mediated responses [85] and thus enhancing effective antitumor immunity. 7.

Conclusion

In conclusion, it has been shown that the inherently immunogenic properties of tumor kill by OVs can be further exploited by arming them with immune-modulating trans-genes. This pairing of what is essentially an in vivo vaccination method (i.e., enforcing antigen release from tumors in an immunogenic manner) with immune potentiation of the TME

(including the immune infiltrate), makes for a potentially very powerful approach to the treatment of cancer, which deserves further clinical exploration.

Expert opinion: considerations in the design of the next generation of armed OVs

8.

Successful clinical trials involving HSV1 (T-VEC) targeting melanoma cancer cells and VVs targeting hepatocellular carcinomas, both encoding human GM-CSF, have improved the outlook for these types of treatments, and for cancer patients around the world [3,7]. However, as the field of OV therapeutics is developing, drawbacks of OV-mediated treatments are also becoming more evident that need to be addressed. Although the used viruses are versatile infectious agents and can be genetically adapted relatively easily according to the researchers’ wishes, the use of natural viruses makes pre-existing antiviral immunity against, for example, herpes-, adeno- or poxviruses in the general population an issue [88]. The presence of pre-existent immune memory in patients treated with genetically adapted viruses, can cause a loss in efficacy of the treatment in several ways [88]. First, upon administration of the virus, neutralizing antibody responses can inhibit further viral activity of the virus. Second, pre-existing immunity may cause the immune system to mount a dominant antiviral response when OVs infect the neoplastic cells, in direct competition with a possible response against TAAs [1]. The effects of pre-existing immunity may partially be averted through adaptation of the virus. In Ad for instance, modification of the fiber and/or hexon proteins, can circumvent neutralizing serological responses [89,90]. The immune response elicited through OV treatment, may also select for cells with low MHC class I expression [91]. To overcome immune escape or development of resistance against the treatment, OVs may have to be optimized with constitutively expressed proapoptotic proteins [92]. Whether an immunogenic type of apoptosis is induced, depends on the incorporated transgenes: caspase-1, for example, can induce pyroptosis, eliciting an immune response [9], and as such is an attractive proapoptotic trans-gene to use in concert with immune-potentiating trans-genes in order to prevent immune escape of infected but ineffectively lysed tumor cells, for example, by OV-mediated defective antigen processing and presentation. While OVs may be delivered locally to accessible tumors, their clinical applicability would be tremendously expanded by increasing their selectivity for tumor cells through modification of their tropism by tumor targeting motifs, allowing for systemic administration while ensuring tumor-restricted OV replication [48,93,94]. The use of OVs to deliver specific products to cancer cells has come a long way since the early years of OV treatment, when the focus was on optimizing the lytic capabilities of the viruses, and new ways to use and manipulate these therapeutic agents are described frequently. The near future may

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thus see new ways to battle cancer cells through genetically altered OVs. A most exciting prospect is the combination of different immune modulatory trans-genes in OVs in an effort to eradicate cancer through modulation of the TME and the antitumor immune response. These may include immune stimulatory genes or anti-sense sequences to knockdown immune suppressive genes. As reviewed above, many different options to modulate the immune system have been investigated. BiTEs and checkpoint inhibitors have been found to be exceptionally efficient in tumor eradication, even without the addition other trans-genes, making these molecules an attractive starting point for further empowerment of OV treatment [16]. Inclusion of additional trans-genes, such as those encoding for, for example, STAT3 shRNA or GM-CSF [95,96], aimed at redressing the prevailing unbalance in the TME between suppressive (MDSCs, M2-macrophages) and stimulatory (M1-macrophages, DCs) myeloid subsets, will remove the final hurdle which could otherwise cause resistance to, for example, immune checkpoint blockade [91]. With our rapidly expanding knowledge on what exactly is required to generate an effective and durable antitumor immune response, it is becoming increasingly clear that many of the currently clinically applied or explored singlemodality immunotherapies (e.g., [DC-based] tumor vaccines, ACT and immune checkpoint blockade) ultimately will not suffice in this respect. The following conditions should be met to induce effective antitumor immunity: i) TAAs Bibliography Papers of special note have been highlighted as either of interest () or of considerable interest () to readers. 1.

.

2.

3.

.

4.

Chiocca EA, Rabkin SD. Oncolytic viruses and their application to cancer immunotherapy. Cancer Immunol Res 2014;2:295-300 Useful state-of-the-art review on OVs. Gujar SA, Lee PWK. Oncolytic virusmediated reversal of impaired tumor antigen presentation. Front Oncol 2014;4:77 Lichty BD, Breitbach CJ, Stojdl DF, et al. Going viral with cancer immunotherapy. Nat Rev Cancer 2014;14:559-67 Excellent review on combined OV/immunotherapy and its clinical status quo. Parato KA, Senger D, Forsyth PA, et al. Recent progress in the battle between oncolytic viruses and tumours. Nat Rev Cancer 2005;5:965-76

5.

..

6.

7.

8.

9.

.

10

(including unique tumor-derived neo-epitopes) should be sufficiently available for processing and presentation by professional APCs; ii) These TAAs should be presented in the context of ICD in a nonsuppressed, pro-inflammatory microenvironment; iii) Both tumor-associated myeloid suppression and immune checkpoint-mediated control of TAA-specific CTL in the TME and draining lymph nodes should be eliminated; iv) Recruitment, accumulation and proliferation of immune suppressive Tregs in the TME should be avoided or combated; and, finally, v) Primed TAA-specific effector T cells should efficiently home to and infiltrate the TME and have ready access to tumor cells for their effective elimination. Immunologically armed OVs tick all the boxes (Figure 1) and as such are an extremely attractive treatment modality to fully unleash the considerable power and durability of the antitumor immune response. Indeed, they may represent a next stride in the clinical progress of cancer immunotherapy.

Declaration of interest The authors have no 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. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell 2011;144:646-74 Landmark paper with an update on essential hallmarks for neoplastic cells to maintain the transformed, malignant state: what makes tumors tick. Moehler M, Goepfert K, Heinrich B, et al. Oncolytic virotherapy as emerging immunotherapeutic modality: potential of parvovirus h-1. Front Oncol 2014;4:92 Bartlett DL, Liu Z, Sathaiah M, et al. Oncolytic viruses as therapeutic cancer vaccines. Mol Cancer 2013;12:1-16 Devaud JC, John LB, Westwood JA, et al. Immune modulation of the tumor microenvironment for enhancing cancer immunotherapy. Oncoimmunology 2013;2:e25961 Guo ZS, Liu Z, Bartlett DL. Oncolytic Immunotherapy: dying the right way is a key to eliciting potent antitumor immunity. Front Oncol 2014;4:74 Comprehensive overview of the different manners of immunogenic cell

Expert Opin. Biol. Ther. (2015) 15(8)

death and how they can be achieved by the various types of OVs. 10.

.

Hanahan D, Coussens LM. Accessories to the crime: functions of cells recruited to the tumor microenvironment. Cancer Cell 2012;21:309-22 Excellent review from authorities in the field on the importance of the TME in the oncogenic process and the subsequent growth and invasion of tumors.

11.

Balkwill FR, Capasso M, Hagemann T. The tumor microenvironment at a glance. J Cell Sci 2012;125:5591-6

12.

Sounni NE, Noel A. Targeting the tumor microenvironment for cancer therapy. Clin Chem 2013;59:85-93

13.

Lu P, Weaver VM, Werb Z. The extracellular matrix: a dynamic niche in cancer progression. J Cell Biol 2012;196:395-406

14.

Bronte V, Serafini P, Mazzoni A, et al. L-arginine metabolism in myeloid cells controls T-lymphocyte functions. Trends Immunol 2003;24:301-5

Arming OVs to leverage antitumor immunity

Expert Opin. Biol. Ther. Downloaded from informahealthcare.com by Nyu Medical Center on 05/12/15 For personal use only.

15.

Kessenbrock K, Plaks V, Werb Z. Matrix metalloproteinases: regulators of the tumor microenvironment. Cell 2010;141:52-67

16.

Bargou R, Leo E, Zugmaier G, et al. Tumor regression in cancer patients by very low doses of a T cell-engaging antibody. Science 2008;321:974-7

17.

Brower V. Approval of provenge seen as first step for cancer treatment vaccines. J Natl Cancer Inst 2010;102:1108-10

18.

DeFrancesco L. Landmark approval for Dendreon’s cancer vaccine. Nat Biotechnol 2010;28:531-2

19.

Shin DS, Ribas A. The evolution of checkpoint blockade as a cancer therapy: what’s here, what’s next? Curr Opin Immunol 2015;33C:23-35 Useful commentary from key opinion leaders in the field on the ongoing revolution in cancer therapy that immune checkpoint inhibitors have brought us -- and where it may take us next.

.

20.

21.

Pol J, Bloy N, Obrist F, et al. Trial Watch: Oncolytic viruses in cancer therapy. Oncoimmunology 2014;3:e28694

Vacchelli E, Eggermont A, Saute`s-Fridman C, et al. Trial Watch: Oncolytic viruses for cancer therapy. Oncoimmunology 2013;6:e24612

23.

van Rooij N, van Buuren MM, Philips D, et al. Tumor exome analysis reveals neoantigen-specific T-cell reactivity in an ipilimumab-responsive melanoma. J Clin Oncol 2013;31:e439-42 Important clinical study showing for the first time that anti-CTLA-4 checkpoint blockade results in increased activity of CD8+ T cells recognizing unique melanomaderived neo-epitopes.

24.

25.

..

27.

..

28.

29.

Russell SJ, Peng KW, Bell JC. Oncolytic virotherapy. Nat Biotechnol 2014;30:1-29

22.

..

26.

Linnemann C, van Buuren MM, Bies L, et al. High-throughput epitope discovery reveals frequent recognition of neoantigens by CD4+ T cells in human melanoma. Nat Med 2015;21:81-5 Tran E, Turcotte S, Gros A, et al. Cancer immunotherapy based on mutation-specific CD4+ T cells in a patient with epithelial cancer. Science 2014;344:641-5

30.

31.

32.

33.

34.

Robbins PF, Lu YC, El-Gamil M, et al. Mining exomic sequencing data to identify mutated antigens recognized by adoptively transferred tumor-reactive T cells. Nat Med 2013;19:747-52 Seminal study showing that melanomainfiltrating T cells are in large part directed against neo-epitopes derived from tumor-specific mutations.

promote virus replication and oncolysis. Virology 2011;416:9-15 35.

Jiang H, White EJ, Rı´os-Vicil CI, et al. Human adenovirus type 5 induces cell lysis through autophagy and autophagytriggered caspase activity. J Virol 2011;85:4720-9

36.

Li Y, Wang LX, Yang G, et al. Efficient cross-presentation depends on autophagy in tumor cells. Cancer Res 2008;68:6889-95

37.

Fukuhara H, Ino Y, Kuroda T, et al. Triple gene-deleted oncolytic herpes simplex virus vector double-armed with interleukin 18 and soluble B7-1 constructed by bacterial artificial chromosome-mediated system. Cancer Res 2005;65:10663-8

38.

Nastala CL, Edington HD, Mckinney TC, et al. Recombinant IL-12 administration induces tumor regression in association with IFNy production. J Immunol 1994;4:1697-706

39.

LaRocca CJ, Han J, Gavrikova T, et al. Oncolytic adenovirus expressing interferon alpha in a syngeneic Syrian hamster model for the treatment of pancreatic cancer. Surgery 2015. [Epub ahead of print]

40.

Robinson M, Li B, Ge Y, et al. Novel immunocompetent murine tumor model for evaluation of conditionally replication-competent (oncolytic) murine adenoviral vectors. J Virol 2009;83:3450-62

Hirvinen M, Rajecki M, Kapanen M, et al. Immunological effects of a tumor necrosis factor alpha-armed oncolytic adenovirus. Hum Gene Ther 2015. [Epub ahead of print]

41.

Edukulla R, Ramakrishna E, Woller N, et al. Antitumoral immune response by recruitment and expansion of dendritic cells in tumors infected with telomerasedependent oncolytic viruses. Cancer Res 2009;69:1448-58

Grote D, Cattaneo R, Fielding AK. Neutrophils contribute to the measles virus-induced antitumor effect: enhancement by granulocyte macrophage colony-stimulating factor expression. Cancer Res 2003;63:6463-8

42.

Parviainen S, Ahonen M, Diaconu I, et al. GMCSF-armed vaccinia virus induces an antitumor immune response. Int J Cancer 2015;136:1065-72

43.

Carew JF, Kooby DA, Halterman MW, et al. A novel approach to cancer therapy using an oncolytic herpes virus to package amplicons containing cytokine genes. Mol Ther 2001;4:250-6

44.

Derubertis BG, Stiles BM, Bhargava A, et al. Cytokine-secreting herpes viral mutants effectively treat tumor in a murine metastatic colorectal liver model by oncolytic and T-cell-dependent mechanisms. Cancer Gene Ther 2007;14:590-7

Zamarin D, Holmgaard RB, Subudhi SK, et al. Localized oncolytic virotherapy overcomes systemic tumor resistance to immune checkpoint blockade immunotherapy. Sci Transl Med 2014;6:226ra32 Pre-clinical study showing that local intratumoral delivery of OVs combined with systemic anti-CTLA-4 treatment results in a systemic antitumor immune response and tumor protection in a weakly immunogenic melanoma tumor model. Hallden G, Hill R, Wang Y, et al. Novel immunocompetent murine tumor models for the assessment of replicationcompetent oncolytic adenovirus efficacy. Mol Ther 2003;8:412-24 Bernt KM, Ni S, Tieu AT, et al. Assessment of a combined, adenovirusmediated oncolytic and immunostimulatory tumor therapy. Cancer Res 2005;65:4343-52

Lapteva N, Aldrich M, Rollins L, et al. Attraction and activation of dendritic cells at the site of tumor elicits potent antitumor immunity. Mol Ther 2009;17:1626-36 Lapteva N, Aldrich M, Weksberg D, et al. Targeting the intratumoral dendritic cells by the oncolytic adenoviral vaccine expressing RANTES elicits potent antitumor immunity. J Immunother 2009;32:145-56 Rodriguez-Rocha H, Gomez-Gutierrez JG, Garcia-Garcia A, et al. Adenoviruses induce autophagy to

Expert Opin. Biol. Ther. (2015) 15(8)

11

Expert Opin. Biol. Ther. Downloaded from informahealthcare.com by Nyu Medical Center on 05/12/15 For personal use only.

T. D. de Gruijl et al.

45.

Murakami N, Riella LV. Co-inhibitory pathways and their importance in immune regulation. Transplantation 2014;98:3-14

46.

Lindenberg JJ, Fehres CM, van Cruijsen H, et al. Cross-talk between tumor and myeloid cells: how to tip the balance in favor of antitumor immunity. Immunotherapy 2011;3:77-96

47.

Kaufman HL, Ruby CE, Hughes T, et al. Current status of granulocytemacrophage colony-stimulating factor in the immunotherapy of melanoma. J Immunother Cancer 2014;13:2-11

48.

Hemminki O, Parviainen S, Juhila J, et al. Immunological data from cancer patients treated with Ad5/3 E2F D24 GMCSF suggests utility for tumor immunotherapy. Oncotarget 2015;6:4467-81 Clinical proof of concept that OVs armed with GM-CSF can harness anti-tumor immunity.

.

49.

50.

51.

.

52.

53.

12

Heo J, Reid T, Ruo L, et al. Randomized dose-finding clinical trial of oncolytic immunotherapeutic vaccinia JX-594 in liver cancer. Nat Med 2013;19:329-36 Kim MK, Breitbach CJ, Moon A, et al. Oncolytic and immunotherapeutic vaccinia induces antibody-mediated complement-dependent cancer cell lysis in humans. Sci Transl Med 2013;5:185ra63 Andtbacka RH, Collichio FA, Amatruda T, et al. Final planned overall survival (OS) from OPTiM, a randomized Phase III trial of talimogene laherparepvec (T-VEC) versus GM-CSF for the treatment of unresected stage IIIB/C/IV melanoma (NCT00769704). J Immunother Cancer 2014;2(Suppl 3):P263 Eagerly awaited results from a randomized Phase III trial, testing an oncolytic VV armed with GM-CSF (T-Vec), show an increased rate of durable responses for T-vec treatment over rec.GM-CSF treatment. Lee YS, Kim JH, Choi KJ, et al. Enhanced antitumor effect of oncolytic adenovirus expressing interleukin-12 and B7-1 in an immunocompetent murine model. Clin Cancer Res 2006;12:5859-68 Huang JH, Zhang SN, Choi KJ, et al. Therapeutic and tumor-specific immunity induced by combination of

antigen presentation evasion and promotes protective antitumor immunity. Mol Cancer Ther 2010;9:2924-33

dendritic cells and oncolytic adenovirus expressing IL-12 and 4-1BBL. Mol Ther 2010;18:264-74 54.

Terada K, Wakimoto H, Tyminski E, et al. Development of a rapid method to generate multiple oncolytic HSV vectors and their in vivo evaluation using syngeneic mouse tumor models. Gene Ther 2006;13:705-14

66.

Gujar S, Dielschneider R, Clements D, et al. Multifaceted therapeutic targeting of ovarian peritoneal carcinomatosis through virus-induced immunomodulation. Mol Ther 2013;21:338-47

55.

Galivo F, Diaz RM, Thanarajasingam U, et al. Interference of CD40L-mediated tumor immunotherapy. Hum Gene Ther 2010;21:439-50

67.

56.

Li J, O’Malley M, Urban J, et al. Chemokine expression from oncolytic vaccinia virus enhances vaccine therapies of cancer. Mol Ther 2011;19:650-7

Le Bon A, Etchart N, Rossmann C, et al. Cross-priming of CD8+ T cells stimulated by virus-induced type I interferon. Nat Immunol 2003;4:1009-15 Study providing compelling evidence for the powerful effects of type-I IFNs on CTL cross-priming.

57.

Li J, O’Malley M, Sampath P, et al. Expression of CCL19 from oncolytic vaccinia enhances immunotherapeutic potential while maintaining oncolytic activity. Neoplasia 2012;14:1115-21

58.

Fu X, Rivera A, Tao L, et al. An HSV-2 based oncolytic virus can function as an attractant to guide migration of adoptively transferred T cells to tumor sites. Oncotarget 2015;6:902-14

59.

Basu S, Srivastava PK. Heat shock proteins: the fountainhead of innate and adaptive immune responses. Cell Stress Chaperones 2000;5:443

60.

Benencia F, Courre`ges MC, Fraser NW, et al. Herpes virus oncolytic therapy reverses tumor immune dysfunction and facilitates tumor antigen presentation. Cancer Biol Ther 2008;7:1194-205

61.

62.

63.

64.

65.

Li JL, Liu HL, Zhang XR, et al. A phase I trial of intratumoral administration of recombinant oncolytic adenovirus overexpressing HSP70 in advanced solid tumor patients. Gene Ther 2009;16:376-82 Donnelly OG, Errington-Mais F, Steele L, et al. Measles virus causes immunogenic cell death in human melanoma. Gene Ther 2013;20:7-15 Guo ZS, Naik A, O’Malley ME, et al. The enhanced tumor selectivity of an oncolytic vaccinia lacking the host range and antiapoptosis genes SPI-1 and SPI-2. Cancer Res 2005;65:9991-8 Fink SL, Cookson BT. Apoptosis, pyroptosis, and necrosis: mechanistic description of dead and dying eukaryotic cells. Infect Immun 2005;73:1907-16 Gujar SA, Marcato P, Pan D, et al. Reovirus virotherapy overrides tumor Expert Opin. Biol. Ther. (2015) 15(8)

.

68.

.

Sluijter B, van den Hout MF, Koster BD, et al. Arming the melanoma SLN through local administration of CpG-B and GM-CSF: recruitment and activation of BDCA3/CD141+ DC and enhanced cross-presentation. Cancer Immunol Res 2015. [Epub ahead of print] Clinical study in early-stage melanoma patients showing combined local CpG and GM-CSF delivery to result in activation and recruitment of a DC subset in draining sentinel lymph nodes with cross-priming abilities.

69.

Ressing ME, Luteijn RD, Horst D, et al. Viral interference with antigen presentation: trapping TAP. Mol Immunol 2013;55:139-42

70.

Leveille S, Goulet ML, Lichty BD, et al. Vesicular stomatitis virus oncolytic treatment interferes with tumorassociated dendritic cell functions and abrogates tumor antigen presentation. J Virol 2011;85:12160-9

71.

Dias JD, Hemminki O, Diaconu I, et al. Targeted cancer immunotherapy with oncolytic adenovirus coding for a fully human monoclonal antibody specific for CTLA-4. Gene Ther 2012;19:988-98 Early study providing important data on the promising therapeutic approach of OVs encoding immune checkpoint inhibitors.

.

72.

Blank C, Kuball J, Voelkl S, et al. Blockade of PD-L1 (B7-H1) augments human tumor-specific T cell responses in vitro. Int J Cancer 2006;119:317-27

73.

Bauzon M, Hermiston T. Armed therapeutic viruses - a disruptive therapy on the horizon of cancer

Arming OVs to leverage antitumor immunity

immunotherapy. Front Immunol 2014;5:74 74.

75.

Expert Opin. Biol. Ther. Downloaded from informahealthcare.com by Nyu Medical Center on 05/12/15 For personal use only.

76.

77.

78.

79.

80.

81.

Engeland CE, Grossardt C, Veinalde R, et al. CTLA-4 and PD-L1 checkpoint blockade enhances oncolytic measles virus therapy. Mol Ther 2014;22:1949-59 Ott P, Hodi FS, Robert C. CTLA-4 and PD-1/PD-L1 blockade: new immunotherapeutic modalities with durable clinical benefit in melanoma patients. Clin Cancer Res 2013;19:5300-9 Sanderson K, Scotland R, Lee P, et al. Autoimmunity in a phase I trial of a fully human anti-cytotoxic T-lymphocyte antigen-4 monoclonal antibody with multiple melanoma peptides and Montanide ISA 51 for patients with resected stages III and IV melanoma. J Clin Oncol 2005;23:741-50 Frentzen A, Yu YA, Chen N, et al. Anti-VEGF single-chain antibody GLAF1 encoded by oncolytic vaccinia virus significantly enhances antitumor therapy. Proc Natl Acad Sci USA 2009;106:12915-20

82.

Beatty GL, Chiorean EG, Fishman MP, et al. CD40 agonists alter tumor stroma and show efficacy against pancreatic carcinoma in mice and humans. Science 2011;331:1612-16

83.

Gottschalk S, Rooney CM. Harnessing the immune system to potentiate oncolytics. Mol Ther 2014;22:239-40

84.

Iwahori K, Kakarla S, Velasquez MP, et al. Engager T cells: a new class of antigen-specific T cells that redirect bystander T cells. Mol Ther 2015;23:171-8

85.

Yu F, Wang X, Guo ZS, et al. T-cell engager-armed oncolytic vaccinia virus significantly enhances antitumor therapy. Mol Ther 2014;22:102-11 Important study showing BiTEs, encoded by OVs, to effect CTLmediated elimination of uninfected bystander tumor cells in the TME of lung cancer xenografts.

.

86.

Chakravarty R, Goel S, Cai W. Nanobody: the “magic bullet” for molecular imaging? Theranostics 2014;4:386-98 Choi BD, Cai M, Bigner DD, et al. Bispecific antibodies engage T cells for antitumor immunotherapy. Expert Opin Biol Ther 2011;11:843-53 Lameris R, de Bruin RC, Schneiders FL, et al. Bispecific antibody platforms for cancer immunotherapy. Crit Rev Oncol Hematol 2014;92:153-65 Yokota T, Milenic DE, Whitlow M, et al. Rapid tumor penetration of a single-chain Fv and comparison with other immunoglobulin forms rapid tumor penetration of a single-chain Fv and comparison with other immunoglobulin forms. Cancer Res 1992;52:3402-8

Dreier T, Baeuerle PA, Fichtner I, et al. T Cell costimulus-independent and very efficacious inhibition of tumor growth in mice bearing subcutaneous or leukemic human B cell lymphoma xenografts by a CD19-/CD3- bispecific single-chain antibody construct. J Immunol 2003;170:4397-402

87.

Albelda SM, Thorne SH. Giving oncolytic vaccinia virus more BiTE. Mol Ther 2014;22:6-8

88.

Harrop R, John J, Carroll MW. Recombinant viral vectors: cancer vaccines. Adv Drug Deliv Rev 2006;58:931-47

89.

Raki M, Sarkioja M, Escutenaire S, et al. Switching the fiber knob of oncolytic adenoviruses to avoid neutralizing antibodies in human cancer patients. J Gene Med 2011;13:253-61

90.

de Gruijl TD, van de Ven R. Adenovirus-based immunotherapy of cancer: promises to keep. Adv Cancer Res 2012;115:147-220

Expert Opin. Biol. Ther. (2015) 15(8)

91.

Kelderman S, Schumacher TN, Haanen JB. Acquired and intrinsic resistance in cancer immunotherapy. Mol Oncol 2014;8:1132-9

92.

Walther W, Schlag PM. Current status of gene therapy for cancer. Curr Opin Oncol 2013;25:659-64

93.

Kloos A, Woller N, Guerlevik E, et al. PolySia-specific retargeting of oncolytic viruses triggers tumor-specific immune responses and facilitates therapy of disseminated lung cancer. Cancer Immunol Res 2015. [Epub ahead of print]

94.

van Erp EA, Kaliberova LN, Kaliberov SA, Curiel DT. Retargeted oncolytic adenovirus displaying a single variable domain of camelid heavy-chain-only antibody in a fiber protein. Mol Ther ---- Oncolytics 2015;2:15001

95.

Lindenberg JJ, van de Ven R, Lougheed SM, et al. Functional characterization of a STAT3-dependent dendritic cell-derived CD14(+) cell population arising upon IL-10-driven maturation. Oncoimmunology 2013;2:e23837

96.

Du T, Shi G, Li YM, et al. Tumor-specific oncolytic adenoviruses expressing granulocyte macrophage colony-stimulating factor or anti-CTLA4 antibody for the treatment of cancers. Cancer Gene Ther 2014;21:340-8

Affiliation

Tanja D de Gruijl†, Axel B Janssen & Victor W van Beusechem † Author for correspondence VU University Medical Center - Cancer Center Amsterdam, Department of Medical Oncology, Room VUmc-CCA 2.44, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands Tel: +31 20 4444063; E-mail: [email protected]

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Arming oncolytic viruses to leverage antitumor immunity.

Over the past decade, the cytolytic capabilities of oncolytic viruses (OVs), exploited to selectively eliminate neoplastic cells, have become secondar...
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