Local delivery of recombinant vaccinia virus expressing secondary lymphoid chemokine (SLC) results in a CD4 T-cell dependent antitumor response

[Oncolytic viruses: Actors and deliverers of therapeutic proteins against tumors]

The discovery of the unique ability of certain viruses to specifically target cancer cells has led to significant advancements in cancer immunotherapy research. In addition to inducing specific lysis of cancer cells, oncolytic viruses (OV) have been genetically modified to express molecules of interest within the tumor bed. The use of OV as vectors for therapeutic molecules has allowed to enhance antitumor responses while limiting the adverse effects associated with systemic administration of the molecule. Other studies are currently focused on delaying the neutralization and clearance of the virus by the host's immune system and improving its delivery insight tumors.

Harnessing the power of oncolytic virotherapy and tertiary lymphoid structures to amplify antitumor immune responses in cancer patients

Tertiary lymphoid structures (TLS) are ectopic aggregates of immune cells that develop in non-lymphoid tissues under persistent inflammation. Since their presence has been associated with a better prognosis in cancer patients, modulating TLS formation is being part of new challenges in immunotherapy. Although mechanisms underlying TLS genesis are still not fully understood, different strategies have been developed in preclinical models to induce their formation and ultimately enhance antitumor responses. Herein, we will discuss a new approach that would consist in using oncolytic viruses (OV). These viruses have the unique feature to preferentially infect, replicate in and kill cancer cells. Their immunoadjuvant property, their use as a vector of therapeutic molecules and their selectivity for cancer cells, make them an attractive strategy to induce TLS in the tumor microenvironment. This review will examine the current knowledge about TLS neogenesis, approaches for inducing them, and relevance of using OV for this purpose, especially in combination with immunotherapy such as immune checkpoint blockade.

The employment of vaccinia virus for colorectal cancer treatment: A review of preclinical and clinical studies

Colorectal cancer (CRC) is one of the leading malignancies that causes death worldwide. Cancer vaccines and oncolytic immunotherapy bring new hope for patients with advanced CRC. The capability of vaccinia virus (VV) in carrying foreign genes as antigens or immunostimulatory factors has been demonstrated in animal models. VV of Wyeth, Western Reserve, Lister, Tian Tan, and Copenhagen strains have been engineered for the induction of antitumor response in multiple cancers. This paper summarized the preclinical and clinical application and development of VV serving as cancer vaccines and oncolytic vectors in CRC treatment. Additionally, the remaining challenges and future direction are also discussed.

Applications of chemokines as adjuvants for vaccine immunotherapy

Vaccinations are expected to aid in building immunity against pathogens. This objective often requires the addition of an adjuvant with certain vaccine formulations containing weakly immunogenic antigens. Adjuvants can improve antigen processing, presentation, and recognition, thereby improving the immunogenicity of a vaccine by simulating and eliciting an immune response. Chemokines are a group of small chemoattractant proteins that are essential regulators of the immune system. They are involved in almost every aspect of tumorigenesis, antitumor immunity, and antimicrobial activity and also play a critical role in regulating innate and adaptive immune responses. More recently, chemokines have been used as vaccine adjuvants due to their ability to modulate lymphocyte development, priming and effector functions, and enhance protective immunity. Chemokines that are produced naturally by the body's own immune system could serve as potentially safer and more reliable adjuvant options versus synthetic adjuvants. This review will primarily focus on chemokines and their immunomodulatory activities against various infectious diseases and cancers.

Chemokine-based immunotherapy: delivery systems and combination therapies

A major role of chemokines is to mediate leukocyte migration through interaction with G-protein-coupled receptors. Various delivery systems have been developed to utilize the chemokine properties for combating disease. Viral and mutant viral vectors expressing chemokines, genetically modified dendritic cells with chemokine or chemokine receptors, engineered chemokine-expressing tumor cells and pDNA encoding chemokines are among these methods. Another approach for inducing a targeted immune response is fusion of a targeting antibody or antibody fragment to a chemokine. In addition, chemokines induce more effective antitumor immunity when used as adjuvants. In this regard, chemokines are codelivered along with antigens or fused as a targeting unit with antigenic moieties. In this review, several chemokines with their role in inducing immune response against different diseases are discussed, with a major emphasis on cancer.

Systemic delivery of oncolytic viruses: hopes and hurdles

Despite recent advances in both surgery and chemoradiotherapy, mortality rates for advanced cancer remain high. There is a pressing need for novel therapeutic strategies; one option is systemic oncolytic viral therapy. Intravenous administration affords the opportunity to treat both the primary tumour and any metastatic deposits simultaneously. Data from clinical trials have shown that oncolytic viruses can be systemically delivered safely with limited toxicity but the results are equivocal in terms of efficacy, particularly when delivered with adjuvant chemotherapy. A key reason for this is the rapid clearance of the viruses from the circulation before they reach their targets. This phenomenon is mainly mediated through neutralising antibodies, complement activation, antiviral cytokines, and tissue-resident macrophages, as well as nonspecific uptake by other tissues such as the lung, liver and spleen, and suboptimal viral escape from the vascular compartment. A range of methods have been reported in the literature, which are designed to overcome these hurdles in preclinical models. In this paper, the potential advantages of, and obstacles to, successful systemic delivery of oncolytic viruses are discussed. The next stage of development will be the commencement of clinical trials combining these novel approaches for overcoming the barriers with systemically delivered oncolytic viruses.

Oncolytic vaccinia virus: a theranostic agent for cancer

Vaccinia virus (VACV) is arguably the most successful live biotherapeutic agent because of its critical role in the eradication of smallpox, one of the most deadly diseases in human history. VACV has been exploited as an oncolytic therapeutic agent for cancer since 1922. This virus selectively infects and destroys tumor cells, while sparing normal cells, both in cell cultures and in animal models. A certain degree of therapeutic efficacy also has been demonstrated in patients with different types of cancer. In recent years, several strategies have been successfully developed to further improve its tumor selectivity and antitumor efficacy. Oncolytic VACVs carrying imaging genes represent a new treatment strategy that combines tumor site-specific therapeutics with diagnostics (theranostics).

Cytokine-armed vaccinia virus infects the mesothelioma tumor microenvironment to overcome immune tolerance and mediate tumor resolution

Intratumoral (i.t.) administration of cytokine genes expressed by viral vectors represents a rational approach that induces cytokine secretion at the site they are needed, and i.t. vaccinia virus (VV) has shown promise in mesothelioma patients. However, we and others have shown that the mesothelioma tumor microenvironment includes macrophages, dendritic cells (DCs), and T cells. Therefore, we investigated which of these cell types are infected after exposure to VV or Fowlpox virus (FPV)-cytokine gene constructs. In vitro studies showed that mesothelioma tumor cells were resistant to FPV infection yet highly permissive to infection by VV vectors resulting in significant cytokine production and impaired proliferation. Macrophages secreted low levels of cytokine suggestive of resistance to overt infection. DCs transiently secreted virally derived cytokines, but did not mature during VV infection. VV inhibition of T cell proliferation was rescued by the interleukin (IL)-2 and IL-12 VV constructs. In vivo studies of murine mesotheliomas showed that i.t. injection of the parent VV could not hinder tumor progression. In contrast, the VV-cytokine constructs induced profound tumor regression. These data suggest that i.t. VV-cytokine gene constructs retard tumor growth by infecting mesothelioma cells and targeting the immune system through tumor-infiltrating DC and T cells.

The role of chemokines in intestinal inflammation and cancer

Chronic inflammation is a risk factor for several gastrointestinal malignancies, including colorectal cancer. Recent epidemiological studies and clinical trials demonstrate that long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) markedly reduced the relative risk of colorectal cancer. Chronic inflammation associated with development of cancer is partly driven by the chemokine system. Chemokines are chemoattractant cytokines that recruit leukocytes from the circulatory system to local inflammatory sites. In this review, we highlight recent breakthroughs in our understanding of the role of chemokines in inflammatory bowel disease and colorectal cancer from animal models and human studies. These findings provide a rationale for the development of new anti-inflammatory therapeutic approaches for prevention and/or treatment of inflammatory bowel disease and colorectal cancer.

Targeting Costimulatory Pathways for Tumor Immunotherapy

Tumor immunotherapy harnesses the potential of the host immune system to recognize and eradicate neoplastic tissue. The efficiency of the immune system in mediating tumor regression depends on the induction of antigen-specific T-cell responses through physiologic immune surveillance, priming by vaccination, or following adoptive transfer of T-cells. Although a variety of tumor-associated antigens have been identified and many immunotherapeutic strategies have been tested, objective clinical responses are rare. The reasons for this include the inability of current immunotherapy approaches to generate efficient T-cell responses, the presence of regulatory cells that inhibit T-cell responses, and other tumor escape mechanisms. The activation of effector T-cells depends on interactions between the T-cell receptor (TCR) and cognate antigen presented as peptides within the major histocompatibility complex (MHC) and costimulatory signals delivered by CD28, which binds to B7.1 and B7.2. More recently, several new molecular receptors and ligands have been identified that integrate into stimulatory or inhibitory activity for T-cells. These signals have been loosely associated with the costimulatory molecules but actually represent a diverse group of molecular pathways that have unique and overlapping functions. This review will focus on these pathways and emphasize their role in mediating T-cell activation for the purpose of enhancing tumor immunotherapy. As we gain a better understanding of the molecular and cellular consequences of T-cell signaling through the costimulatory pathways, a more rational approach to the activation or inhibition of T-cell responses can be developed for the treatment of cancer and other immune-mediated diseases.

Chemokines: novel targets for breast cancer metastasis

Recent studies have highlighted the possible involvement of chemokines and their receptors in breast cancer progression and metastasis. Chemokines and their receptors constitute a superfamily of signalling factors whose prognosis value in breast cancer progression remains unclear. We will examine here the expression pattern of chemokines and their receptors in mammary gland physiology and carcinogenesis. The nature of the cells producing chemokines or harboring chemokine receptors appears to be crucial in certain conditions for example, the infiltration of the primary tumor by leukocytes and angiogenesis. In addition, chemokines, their receptors and the interaction with glycosaminoglycan (GAGs) are key players in the homing of cancer cells to distant metastasis sites. Several lines of evidence, including in vitro and in vivo models, suggest that the mechanism of action of chemokines in cancer development involves the modulation of proliferation, apoptosis, invasion, leukocyte recruitment or angiogenesis. Furthermore, we will discuss the regulation of chemokine network in tumor neovascularity by decoy receptors. The reasons accounting for the deregulation of chemokines and chemokine receptors expression in breast cancer are certainly crucial for the comprehension of chemokine role in breast cancer and are in several cases linked to estrogen receptor status. The targeting of chemokines and chemokine receptors by antibodies, small molecule antagonists, viral chemokine binding proteins and heparins appears as promising tracks to develop therapeutic strategies. Thus there is significant interest in developing strategies to antagonize the chemokine function, and an opportunity to interfere with metastasis, the leading cause of death in most patients.

Tumor transfected with CCL21 enhanced reactivity and apoptosis resistance of human monocyte-derived dendritic cells

Chemokine CCL21 can effectively attract CCR7(+) dendritic cells (DCs), however its role in this event is poorly understood. In this report, we investigated the effect of exogenous CCL21 expressed in breast cancer MCF-7 on human monocyte-derived DCs. CCL21-transfected MCF-7 stimulation prompted DC functions: migration, antigen-uptake and presentation. The stimulated DCs facilitated Th1 type cytokines production, perforin-forming CD8(+) T cell transformation and final T cell-associated clearance of MCF-7. Moreover, the MCF-7-resourced CCL21 protected DCs from apoptosis significantly, involving up-regulations of Bcl-2 expression and NF-kappaB activity, and reduction of caspase-3. This study provides evidence that tumor-derived CCL21 increases the presentation and apoptosis resistance of DCs, suggesting such a mechanism may be useful for the improvement of tumor cell immunogenicity and anti-tumor response.

Immune cell recruitment and cell-based system for cancer therapy

Immune cells, such as cytotoxic T lymphocytes, natural killer cells, B cells, and dendritic cells, have a central role in cancer immunotherapy. Conventional studies of cancer immunotherapy have focused mainly on the search for an efficient means to prime/activate tumor-associated antigen-specific immunity. A systematic understanding of the molecular basis of the trafficking and biodistribution of immune cells, however, is important for the development of more efficacious cancer immunotherapies. It is well established that the basis and premise of immunotherapy is the accumulation of effective immune cells in tumor tissues. Therefore, it is crucial to control the distribution of immune cells to optimize cancer immunotherapy. Recent characterization of various chemokines and chemokine receptors in the immune system has increased our knowledge of the regulatory mechanisms of the immune response and tolerance based on immune cell localization. Here, we review the immune cell recruitment and cell-based systems that can potentially control the systemic pharmacokinetics of immune cells and, in particular, focus on cell migrating molecules, i.e., chemokines, and their receptors, and their use in cancer immunotherapy.

Cancer vaccines: preclinical studies and novel strategies

The development of cancer vaccines, aimed to enhance the immune response against a tumor, is a promising area of research. A better understanding of both the molecular mechanisms that govern the generation of an effective immune response and the biology of a tumor has contributed to substantial progress in the field. Areas of intense investigation in cancer immunotherapy will be discussed here, including: (1) the discovery and characterization of novel tumor antigens to be used as targets for vaccination; (2) the investigation of different vaccine-delivery modalities such as cellular-based vaccines, protein- and peptide-based vaccines, and vector-based vaccines; (3) the characterization of biological adjuvants to further improve the immunogenicity of a vaccine; and (4) the investigation of multimodal therapies where vaccines are being combined with other oncological treatments such as radiation and chemotherapy. A compilation of data from preclinical studies conducted in vitro as well as in animal models is presented here. The results from these studies would certainly support the development of new vaccination strategies toward cancer vaccines with enhanced clinical efficacy.

Analysis of Antitumor Activity Elicited by Vaccination with Combinations of Interleukin-12 DNA with gp100 DNA or the Chemokine CCL21In Vivo

The antitumor efficacy of human melanoma-associated antigen (hgp100) and chemokine CCL21 in combination with interleukin-12 (IL-12) was evaluated in a syngeneic melanoma mouse model. The rationale for this approach was based on previous studies showing that the efficacy of IL-12 therapy in melanoma patients correlated with the presence of antibodies against tumor-associated antigens. We have previously shown that application of xenogeneic human gp100 DNA (hgp100 DNA) is protective against mouse B16 melanoma. Furthermore, the chemokine CCL21 has the ability to chemoattract both dendritic cells (DCs) and T lymphocytes. We show here that intratumoral injection of IL-12-encoding DNA (IL-12 DNA) in combination with hgp100- encoding DNA (hgp100 DNA) into tumor-bearing mice led to a strong antitumor effect. Coapplication of IL- 12 DNA with CCL21-encoding DNA (CCL21 DNA) or recombinant CCL21 (recCCL21) protein also showed some efficacy. Triple therapy with IL-12 DNA, hgp100 DNA, and CCL21 DNA, however, showed less effect on tumor growth than double therapy with IL-12 DNA and hgp100 DNA. These findings open a new route of investigation of IL-12 and gp100 or other tumor-associated antigens in the immunotherapy of a variety of tumors.

Viral Vaccines for Cancer Immunotherapy

The understanding that tumor cells can be recognized and eliminated by the immune system has led to intense interest in the development of cancer vaccines. Viruses are naturally occurring agents that cause human disease but have the potential to prevent disease when attenuated forms or subunits are used as vaccines before exposure. A large number of viruses have been engineered as attenuated vaccines for the expression of tumor antigens, immunomodulatory molecules, and as vehicles for direct destruction of tumor cells or expression of highly specific gene products. This article focuses on the major viruses that are under development as cancer vaccines, including the poxviruses, adenoviruses, adeno-associated viruses, herpesviruses, retroviruses, and lentiviruses. The biology supporting these viruses as vaccines is reviewed and clinical progress is reported.

Inflammatory chemokines in cancer growth and progression

Leukocyte infiltration is a cardinal feature of almost all cancers. Chemokines are generally responsible for eliciting local accumulation of inflammatory cells and they appear to play the same role in the formation of peri- and intra-tumoural infiltrates. Chronic inflammation predisposes to cancer formation and progression, and it is likely that the chemokine system contributes to this process. In part, this may be a consequence of its ability to attract mononuclear cells to cancer sites, where they provide growth or angiogenic factors that enhance cancer development. However, accumulating evidence also points to a direct effect of chemokines on cancer cells that express chemokine receptors. In particular, some chemokines can activate anti-apoptotic pathways in these cells. By either mechanism, tumour cells that secrete and/or respond to chemokines would have a selective advantage. This provides another example of cancer's ability to co-opt host systems in order to promote tumour progression.

The lymphoid chemokine CCL21 costimulates naive T cell expansion and Th1 polarization of non-regulatory CD4+ T cells

CCL21 (SLC/6Ckine) is constitutively expressed by secondary lymphoid tissue and attracts CCR7-expressing mature dendritic cells and naive T cells. Recent studies demonstrated that intra-tumoral delivery of CCL21 induces tumor regression in a T cell dependent manner. CCL21 is known to mediate T cell trafficking but little is known about its function as a costimulatory molecule. Herein, we demonstrate that CCL21 costimulates expansion of CD4+ and CD8+ T cells and induces Th1 polarization. These effects were specific for naive T cells, and we show that CD4+CD25+ regulatory T cells were hyporesponsive to CCL21 induced migration, and unresponsive to CCL21 costimulation. These unique functions of CCL21 to both attract naive T cells as well as costimulate their proliferation and differentiation, suggests that CCL21 is a pivotal molecule for priming T cell responses and has therapeutic implications for local delivery of CCL21. The coordinated effects of CCL21 on T cell migration and activation may also represent a more comprehensive paradigm for the activity of other chemokines as well.