Delivery of CCL21 to metastatic disease improves the efficacy of adoptive T-cell therapy

Chemokine Analysis in Patients with Metastatic Uveal Melanoma Suggests a Role for CCL21 Signaling in Combined Epigenetic Therapy and Checkpoint Immunotherapy

Purpose

Patients with metastatic uveal melanoma have limited therapeutic options and high mortality rate so new treatment options are needed.

Patients and Methods

We previously reported that patients treated with the PD-1 inhibitor pembrolizumab and the histone deacetylase inhibitor entinostat in the PEMDAC trial, experienced clinical benefits if their tumor originated from iris or was wildtype for BAP1 tumor suppressor gene. Here we present the 2-year follow-up of the patients in the PEMDAC trial and identify additional factors that correlate with response or survival.

Results

Durable responses were observed in 4 patients, with additional 8 patients exhibiting a stable disease. The median overall survival was 13.7 months. Grade 3 adverse events were reported in 62% of the patients, but they were all manageable. No fatal toxicity was observed. Activity of thymidine kinase 1 in plasma was higher in patients with stable disease or who progressed on treatment, compared with those with partial response. Chemokines and cytokines were analyzed in plasma. Three chemokines were significantly different when comparing patients with and without response. One of the factors, CCL21, was higher in the plasma of responding patients before treatment initiation but decreased in the same patients upon treatment. In tumors, CCL21 was expressed in areas resembling tertiary lymphoid structures (TLS). High plasma levels of CCL21 and presence of TLS-like regions in the tumor correlated with longer survival.

Conclusions

This study provides insight into durable responses in the PEMDAC trial, and describes dynamic changes of chemokines and cytokines in the blood of these patients.

Significance

The most significant finding from the 2-year follow-up study of the PEMDAC trial was that high CCL21 levels in blood was associated with response and survival. CCL21 was also expressed in TLS-like regions and presence of these regions was associated with longer survival. These analyses of soluble and tumor markers can inform on predictive biomarkers needing validation and become hypothesis generating for experimental research.

Tumor-infiltrating lymphocyte therapy for lung cancer and its future paradigms

INTRODUCTION

Lung cancer is the leading cause of cancer death, with an estimated 1.8 million deaths contributing to this cancer in 2020. Despite advances in treatment options and various approaches being attempted, the survival rate remains low.

AREAS COVERED

In this review, we aim to provide an overview of the efficacy of tumor-infiltrating lymphocyte (TIL) therapy for lung cancer based on existing clinical trials. We also discuss the current challenges and future landscape of this treatment modality.

EXPERT OPINION

Lung cancer can be a suitable candidate for TIL therapy due to its high mutational burden. Specifically, it has shown promising results for non-small cell lung cancer resistant to immune checkpoint inhibitors. Still, there are many restrictions associated with the ex vivo expansion and delivery of TILs, limiting their availability. For this reason, applying TIL for the treatment of lung cancer has not been extensively investigated yet and only a few clinical trials have shown favorable results of TIL therapy in patients with lung cancer. Thus, facilitating this costly, labor-intensive and time-consuming process is of utmost importance to increase the number of performed studies and to detect eligible patients who could benefit most from this treatment modality.

Immunotherapy for Tumor Metastasis by Artificial Antigen-Presenting Cells via Targeted Microenvironment Regulation and T-Cell Activation

Effective expansion of T-cells without ex vivo stimulation and maintenance of their antitumor functions in the complex tumor microenvironment (TME) are still daunting challenges in T-cell-based immunotherapy. Here, we developed biomimetic artificial antigen-presenting cells (aAPCs), ultrathin MnO_x nanoparticles (NPs) functionalized with T-cell activators (anti-CD3/CD28 mAbs, CD), and tumor cell membranes (CMs) for enhanced lung metastasis immunotherapy. The aAPCs, termed CD-MnO_x@CM, not only efficiently enhanced the expansion and activation of intratumoral CD8⁺ cytotoxic T-cells and dendritic cells after homing to homotypic metastatic tumors but also regulated the TME to facilitate T-cell survival through catalyzing the decomposition of intratumoral H₂O₂ into O₂. Consequently, the aAPCs significantly inhibited the development of lung metastatic nodules and extended the survival of a B16-F10 melanoma metastasis model, while minimizing adverse events. Our work represents a new biomaterial strategy of inhibiting tumor metastasis through targeted TME regulation and in situ T-cell-based immunotherapy.

Adoptive T Cell Therapy for Solid Tumors: Pathway to Personalized Standard of Care

Adoptive cell therapy (ACT) with tumor-infiltrating T cells (TILs) has emerged as a promising therapy for the treatment of unresectable or metastatic solid tumors. One challenge to finding a universal anticancer treatment is the heterogeneity present between different tumors as a result of genetic instability associated with tumorigenesis. As the epitome of personalized medicine, TIL-ACT bypasses the issue of intertumoral heterogeneity by utilizing the patient’s existing antitumor immune response. Despite being one of the few therapies capable of inducing durable, complete tumor regression, many patients fail to respond. Recent research has focused on increasing therapeutic efficacy by refining various aspects of the TIL protocol, which includes the isolation, ex vivo expansion, and subsequent infusion of tumor specific lymphocytes. This review will explore how the therapy has evolved with time by highlighting various resistance mechanisms to TIL therapy and the novel strategies to overcome them.

Cytokine and Chemokine Signals of T-Cell Exclusion in Tumors

The success of cancer immunotherapy in solid tumors depends on a sufficient distribution of effector T cells into malignant lesions. However, immune-cold tumors utilize many T-cell exclusion mechanisms to resist immunotherapy. T cells have to go through three steps to fight against tumors: trafficking to the tumor core, surviving and expanding, and maintaining the memory phenotype for long-lasting responses. Cytokines and chemokines play critical roles in modulating the recruitment of T cells and the overall cellular compositions of the tumor microenvironment. Manipulating the cytokine or chemokine environment has brought success in preclinical models and early-stage clinical trials. However, depending on the immune context, the same cytokine or chemokine signals may exhibit either antitumor or protumor activities and induce unwanted side effects. Therefore, a comprehensive understanding of the cytokine and chemokine signals is the premise of overcoming T-cell exclusion for effective and innovative anti-cancer therapies.

Nanoformulation of CCL21 greatly increases its effectiveness as an immunotherapy for neuroblastoma

Neuroblastoma is the most commonly diagnosed extracranial solid tumor in children. The patients with aggressive metastatic disease or refractory/relapsed neuroblastoma currently face a dismally low chance of survival. Thus, there is a great need for more effective therapies for this illness. In previous studies, we, as well as others, showed that the immune cell chemoattractant C-C motif chemokine ligand 21 (CCL21) is effective as an intratumoral therapy able to slow the growth of cancers. In this current study, we developed and tested an injectable, slow-release, uniform, and optimally loaded alginate nanoformulation of CCL21 as a means to provide prolonged intratumoral treatment. The alginate-nanoformulated CCL21, when injected intratumorally into mice bearing neuroblastoma lesions, significantly prolonged survival and decreased the tumor growth rate compared to CCL21 alone, empty nanoparticles, or buffer. Notably, we also observed complete tumor clearance and subsequent full protection against tumor rechallenge in 33% of nanoformulated CCL21-treated mice. Greater intratumoral presence of nanoformulated CCL21, compared to free CCL21, at days 1 and 2 after treatment ended was confirmed through fluorescent labeling and tracking. Nanoformulated CCL21-treated tumors exhibited a general pattern of prolonged increases in anti-tumor cytokines and relatively lower levels of pro-tumor cytokines in comparison to tumors treated with CCL21 alone or buffer only. Thus, this novel nanoformulation of CCL21 is an effective treatment for neuroblastoma, and may have potential for the delivery of CCL21 to other types of solid tumors in the future and as a slow-release delivery modality for other immunotherapies.

MicroRNA-150 inhibitors enhance cell apoptosis of melanoma by targeting PDCD4

Malignant melanoma is a tumor with a high mortality rate. Previous studies have demonstrated that the oncogenesis of melanoma is associated with microRNA (miR)-150. However, the role of miR-150 in melanoma and its regulatory mechanisms are still unclear. In the present study, melanoma cancer tissues and adjacent normal tissues were obtained from 20 melanoma patients. The expression level of miR-150 in melanoma tissue and cell lines was detected by reverse transcription-quantitative polymerase chain reaction. miR-150 inhibitors/negative control were transfected into melanoma A375 cells in order to investigate the effects of miR-150 on cell proliferation, apoptosis, cell cycle migration and invasion using a Cell Counting Kit-8, colony formation, Hoechst 33528, flow cytometry, and Transwell assays. The association between miR-150 and programmed cell death protein-4 (PDCD4) was detected by a dual luciferase reporter assay. The functional role of PDCD4 in miR-150-affected melanoma cells was confirmed by small interfering (si)RNA knockdown. Results demonstrated that miR-150 was significantly upregulated and mRNA and protein expressions of PDCD4 were decreased in melanoma cancer tissues as compared with adjacent normal tissues. The level of PDCD4 was inversely associated with the level of miR-150. Transfection of miR-150 inhibitors suppressed cell proliferation, migration, and invasion, while the apoptosis of cells was promoted and G2/M cell arrest was induced. MiR-150 inhibitors enhanced the expression of caspase-8 and p21. The PDCD4 was identified as a direct target gene of miR-150. The effects of miR-150 inhibitors on apoptosis and apoptosis-associated proteins, including caspase-8 and p21, of A375 cells, were reversed following transfection of siRNA-PDCD4. Therefore, miR-150 inhibitors enhance cell apoptosis via upregulation of PDCD4-mediated activation of caspase-8 and p21. These findings demonstrate the potential for a promising therapeutic strategy in the management of melanoma.

Local production of the chemokines CCL5 and CXCL10 attracts CD8+ T lymphocytes into esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a very common malignant tumor with poor prognosis in China. Chemokines secreted by tumors are pivotal for the accumulation of CD8(+) T lymphocytes within malignant lesions in several types of cancers, but the exact mechanism underlying CD8(+) T lymphocyte homing is still unknown in ESCC. In this study, we revealed that, compared with marginal tissues, the expression of both chemokine (C-C motif) ligand 5 (CCL5) and (C-X-C motif) ligand 10 (CXCL10) was upregulated in ESCC tissues. CCL5 expression was positively associated with the overall survival of patients. Meanwhile, RT-PCR data showed that the expression of CCL5 and CXCL10 was positively correlated with the local expressions of the CD8(+) T lymphocyte markers (CD8 and Granzyme B) in tumor tissues. Correspondingly, CD8(+) T lymphocytes were more frequently CCR5- and CXCR3-positive in tumor than in peripheral blood. Transwell analysis showed both CCL5 and CXCL10 were important for the chemotactic movement of CD8(+) T lymphocytes. Our data indicate that CCL5 and CXCL10 serve as the key chemokines to recruit CD8(+) T lymphocytes into ESCC tissue and may play a role in patient survival.

CCL4 as an adjuvant for DNA vaccination in a Her2/neu mouse tumor model

Chemokines are key regulators of both innate and adaptive immune responses. CCL4 (macrophage inflammatory protein-1β, MIP-1β) is a CC chemokine that has a broad spectrum of target cells including immature dendritic cells, which express the cognate receptor CCR5. We asked whether a plasmid encoding CCL4 is able to improve tumor protection and immune responses in a Her2/neu+ mouse tumor model. Balb/c mice were immunized twice intramuscularly with plasmid DNA on days 1 and 15. On day 25, a tumor challenge was performed with 2 × 10(5) syngeneic Her2/neu+ D2F2/E2 tumor cells. Different groups of mice were vaccinated with pDNA(Her2/neu) plus pDNA(CCL4), pDNA(Her2/neu), pDNA(CCL4) or mock vector alone. Our results show that CCL4 is able to (i) improve tumor protection and (ii) augment a TH1-polarized immune response against Her2/neu. Although Her2/neu-specific humoral and T-cell immune responses were comparable with that induced in previous studies using CCL19 or CCL21 as adjuvants, tumor protection conferred by CCL4 was inferior. Whether this is due to a different spectrum of (innate) immune cells, remains to be clarified. However, combination of CCL19/21 with CCL4 might be a reasonable approach in the future, particularly for DNA vaccination in Her2/neu+ breast cancer in the situation of minimal residual disease.

Therapeutic Lymphoid Organogenesis in the Tumor Microenvironment

The inflammatory status of the tumor microenvironment (TME) has been heavily investigated in recent years. Chemokine- and cytokine-signaling pathways such as CCR7, CXCR5, lymphotoxin, and IL-36, which are involved in the generation of secondary lymphoid organs and effector immune responses, are now recognized as having value both as prognostic factors and as immunomodulatory therapeutics in the context of cancer. Furthermore, when produced in the TME, these mediators have been shown to promote the recruitment of immune cells, including T cells, B cells, dendritic cells (DCs), and other specialized immune cell subsets such as follicular DCs and T follicular helper cells, in association with the formation of "tertiary" lymphoid structures (TLSs) within or adjacent to sites of disease. Although TLSs are composed of a heterogeneous collection of immune cell types, whose composition differs based on cancer subtype, the qualitative presence of TLSs has been shown to represent a biomarker of good prognosis for cancer patients. A comprehensive understanding of the role each of these pathways plays within the TME may support the rational design of future immunotherapies to selectively promote/bolster TLS formation and function, leading to improved clinical outcomes across the vast range of solid cancer types.

CCL21 and IFNγ recruit and activate tumor specific T cells in 3D scaffold model of breast cancer

Effective elicitation of endogenous immunity is associated with improved prognosis for cancer patients. Clinical evidence in hematological and solid cancers shows that intratumoral injection of immunostimulatory genes primes and augments endogenous T cell responses. The ability of pro-inflammatory chemokines/cytokines to facilitate migration/activation of antigen-presenting cells (APC) and lymphocytes prompted our modeling of intratumoral delivery of a chemokine/cytokine combination for breast cancer treatment. Here, we demonstrate that expression of chemokine ligand 21 (CCL21) and interferon gamma (IFNγ) in tumors improves tumor specific T cell recruitment to tumor and activation in the tumor milieu. IFNγ and CCL21 were delivered into tumor cells via plasmids, and transfected cells were seeded to form spheroids on three-dimensional (3D) chitosan-alginate (CA) scaffolds. Co-expression of CCL21 and IFNγ, as evidenced by qRT-PCR and ELISA, induced increased recruitment, binding, and infiltration of anti-neu (p98) peptide specific T cells into the breast tumors as determined by SEM and immunofluorescence assays. The co-expression promoted recruitment of only p98 T cells, but not naïve T cells, demonstrating an antigen-restricted activation. Furthermore, the co-expression impacted T helper (Th) cell immunity, promoting an increase in secretion of pro-inflammatory Th-associated cytokine, tumor necrosis factor alpha (TNFα), and cytotoxic T lymphocyte (CTL)-associated protease, Granzyme B (GzB). Therefore, 3D CA scaffolds may be a useful breast cancer tumor microenvironment model to evaluate T cell function. Further characterization of CCL21-IFNγ mediated anti-tumor immunity will potentially benefit the development of chemokine/cytokine combination platforms as anti-cancer agents.

Serum-based miRNAs in the prediction and detection of recurrence in melanoma patients

BACKGROUND

Identification of primary melanoma patients at the highest risk of recurrence remains a critical challenge, and monitoring for recurrent disease is limited to costly imaging studies. We recently reported our array-based discovery of prognostic serum miRNAs in melanoma. In the current study, we examined the clinical utility of these serum-based miRNAs for prognosis as well as detection of melanoma recurrence.

METHODS

Serum levels of 12 miRNAs were tested using qRT-PCR at diagnosis in 283 melanoma patients (training cohort, n = 201; independent validation, n = 82; median follow-up, 68.8 months). A refined miRNA signature was chosen and evaluated. We also tested the potential clinical utility of the miRNAs in early detection and monitoring of recurrence using multiple longitudinal samples (pre- and postrecurrence) in a subset of 82 patients (n = 225). In addition, we integrated our miRNA signature with publicly available Cancer Genome Atlas data to examine the relevance of these miRNAs to melanoma biology.

RESULTS

Four miRNAs (miR-150, miR-30d, miR-15b, and miR-425) in combination with stage separated patients by recurrence-free survival (RFS) and overall survival (OS) and improved prediction of recurrence over stage alone in both the training and validation cohorts (training RFS and OS, P < .001; validation RFS, P < .001; OS, P = .005). Serum miR-15b levels significantly increased over time in recurrent patients (P < .001), adjusting for endogenous controls as well as age, sex, and initial stage. In nonrecurrent patients, miR-15b levels were not significantly changed with time (P =.17).

CONCLUSIONS

Data demonstrate that serum miRNAs can improve melanoma patient stratification over stage and support further testing of miR-15b to guide patient surveillance.

Influence of inhibiting expression of SLC by triptolide on experimental ulcerative colitis in mice

AIM: To explore the influence of inhibiting the expression of secondary lymphoid tissue chemokine (SLC) by triptolide (TL) on experimental colitis in mice.

METHODS: Forty female Balb/c mice were randomly divided into five groups: a normal group, a model group, a propanediol treatment group, a low-dose TL treatment group, and a high-dose TL treatment group. Mice in the normal group were given distilled water, while the other groups were given 5% dextran sodium sulphate solution for 7 d to induce colitis mimicking human ulcerative colitis (UC). From the 3rd day of colitis induction, the propanediol treatment group was given 2% propanediol (0.2 mL) daily by intraperitoneal injection, while the TL treatment groups were given TL 0.6 and 0.8 mg/kg, respectively, for 5 d. All the mice were killed on day 8. Colon length, colon gross morphology score and colon histological score were assessed. The expressions of SLC in colon tissue was measured by immunohistochemistry and real-time fluorescence quantitative PCR.

RESULTS: SLC was expressed weakly in the normal group, and was up-regulated in colitis. SLC expression in the normal group was significantly lower than that in the model group and propanediol treatment group (P < 0.01), although there was no significant difference between the latter two groups (P > 0.05). The expression of SLC in the TL treatment groups was lower than that in the model group and propanediol treatment group (P < 0.01), and the pathological changes were mitigated.

CONCLUSION: The expression of SLC may be related to the occurrence and development of UC. The therapeutic effect of TL against experimental ulcerative colitis in mice may be associated with restraining the expression of SLC.

Combination of SLC administration and Tregs depletion is an attractive strategy for targeting hepatocellular carcinoma

Background

Secondary lymphoid tissue chemokine (SLC) is a key CC chemokine for chemotaxis of immune cells and has been an attractive candidate for anti-tumor treatments. However, among the immune cells recruited by SLC to tumors, the CD25⁺ Foxp3⁺ regulatory T cells (Tregs) compromise the anti-tumor effects. In this study, we proposed the combination therapy of intratumoral co-administration of SLC and anti-CD25 monoclonal antibodies (mAbs). We hypothesized that the intratumoral injections of SLC and depletion of Tregs would have stronger inhibition effects on the progression of hepatocellular carcinoma (HCC) in mice.

Methods

C57BL/6 mice were inoculated subcutaneously with the murine HCC cell line, and mice with visible tumors were treated intratumorally with SLC, SLC plus anti-CD25 mAbs or the control antibodies. The percentages of Tregs, effector CD8⁺ T cells and CD4⁺ T cells were checked in the tumors, lymph nodes, spleen and liver at regular intervals. The levels of intratumoral IL-12, IFN-γ, IL-10 and TGF-β1 were evaluated. The final anti-tumor effects were measured by the tumor volume and weight as well as the intratumoral activity of MMP2 and MMP9. Bone-marrow-derived dendritic cells were used to explore the mechanisms of maturation induced by SLC in vitro.

Results

Our experiments showed the combination therapy significantly decreased the frequency of Tregs, and increased CD8⁺ T cells and CD4⁺ T cells at tumor sites. These alterations were accompanied by an increased level of IL-12 and IFN-γ, and decreased level of IL-10 and TGF-β1. Unexpectedly, we observed a significantly decreased percentage of Tregs, and increased CD8⁺ T cells and CD4⁺ T cells in the lymph nodes, spleen and liver after the combination therapy. The growth and invasiveness of HCC was also maximally inhibited in the combination therapy compared with the SLC alone. Furthermore, we confirmed SLC induced the maturation of DCs via NF-κB p65 and this maturation would benefit the combination therapy.

Conclusions

Our data demonstrated that intratumoral co-administration of SLC and anti-CD25 mAbs was an effective treatment for HCC, which was correlated with the altered tumor microenvironment and systemically optimized percentages of Tregs, CD8⁺ T cells and CD4⁺ T cells in peripheral immune organs.

Intratumoral administration of secondary lymphoid chemokine and unmethylated cytosine-phosphorothioate-guanine oligodeoxynucleotide synergistically inhibits tumor growth in vivo

Secondary lymphoid tissue chemokine (SLC), which is expressed in T cell zones of secondary lymphoid organs, including the spleen and lymph nodes, strongly recruits both T lymphocytes and mature dendritic cells. As appropriate interaction of tumor-specific T cells and mature dendritic cells, equipped with tumor antigens, is a prerequisite for effective T cell immunity against established tumors, we mobilized lymphocytes and dendritic cells to tumor sites by intratumoral injection of secondary lymphoid tissue chemokine-Fc (SLC-Fc) fusion protein using the B16F10 murine melanoma model. Activation of dendritic cells, another prerequisite for the effective activation of naïve tumor-specific T cells, was achieved by the addition of immunostimulatory cytosine-phosphorothioate-guanine oligodeoxynucleotide (CpG-ODN) into the tumor site. Intratumoral administration of SLC-Fc or CpG-ODN revealed antitumor effects against B16F10 murine melanoma grown in the subcutaneous space. Co-treatment of SLC-Fc and CpG-ODN displayed synergistic effects in reducing the tumor size. The synergistic antitumor effect in co-treatment group was correlated with the synergistic/additive increase in the infiltration of CD4(+) T cells and CD11c(+) dendritic cells in the tumor mass compared to the single treatment groups. These results suggest that the combined use of chemokines and adjuvant molecules may be a possible strategy in clinical tumor immunotherapy.

Engineering chemoattractant gradients using chemokine-releasing polysaccharide microspheres

Spatial and temporal concentration gradients of chemoattractants direct many biological processes, especially the guidance of immune cells to tissue sites during homeostasis and responses to infection. Such gradients are ultimately generated by secretion of attractant proteins from single cells or collections of cells. Here we describe cell-sized chemoattractant-releasing polysaccharide microspheres, capable of mimicking chemokine secretion by host cells and generating sustained bioactive chemokine gradients in their local microenvironment. Exploiting the common characteristic of net cationic charge and reversible glycosaminoglycan binding exhibited by many chemokines, we synthesized alginate hydrogel microspheres that could be loaded with several different chemokines (including CCL21, CCL19, CXCL12, and CXCL10) by electrostatic adsorption. These polysaccharide microspheres subsequently released the attractants over periods ranging from a few hours to at least 1 day when placed in serum-containing medium or collagen gels. The generated gradients were able to attract cells more than hundreds of microns away to make contact with individual microspheres. This versatile system for chemoattractant delivery could find applications in immunotherapy, vaccines and fundamental chemotaxis studies in vivo and in vitro.

Chemokines: can effector cells be redirected to the site of the tumor?

Chemokines (ie, chemoattractant cytokines) are a family of small secreted molecules that mediate leukocyte migration. It is becoming increasingly more evident that chemokines play an integral role in the initiation of a specific immune response. With respect to cancer, chemokines are being studied for both their role in tumor biology and as promising immunotherapy candidates. We review several areas of chemokine importance in tumor immunity and discuss the experimental evidence that is leading to the clinical use of this cytokine family in new treatment approaches for patients with cancer.

Bryostatin-I: a dendritic cell stimulator for chemokines induction and a promising adjuvant for a peptide based cancer vaccine

Bryostatin-1 (Bryo-1), a PKC modulator, was previously shown to activate monocytes and lymphocytes to produce cytokines. In this report, we investigated the adjuvanticity of Bryo-1 both in vitro and in vivo. First, Bryo-1 was found to induce the release of CCL2 and CCL3 from mouse bone marrow-derived dendritic cells (BMDC) in a dose-dependent manner. As little as 0.1nM Bryo-I induced release of chemokines from BMDC and the maximal induction could be achieved at 5-10nM. Both PKC and ERK inhibitors attenuated the release of CCL2 and CCL3. Consistently, Western blot indicated that Bryo-I activated ERK in a dose- and time-dependent manner. Experiments with the NF-κB inhibitor, MG-132, demonstrated that NF-κB was involved in the induction of CCL2 but not CCL3. Because chemokines have been demonstrated to have profound effects on immune reactions by regulating the trafficking of DC and other lymphocytes into lymphoid organs, Bryo-I was tested as an adjuvant in an E7 peptide (MHC class I-restricted peptide epitope derived from human papillomavirus (HPV) 16 E7 protein)-based cancer vaccine. Mice immunized by s.c. injection with Bryo-I/E7 had enlarged draining lymph nodes and showed an antigen specific T-cell response demonstrated by the release of IFN-γ from isolated splenocytes and in vivo CTL activity. Finally, immunization with Bryo-I/E7 totally prevented the E7-expressing TC-1 tumor growth in mice. In conclusion, for the first time, we demonstrated that Bryo-I induced chemokine release from dendritic cell and was an effective adjuvant for peptide cancer vaccine.

Interference of CD40L-mediated tumor immunotherapy by oncolytic vesicular stomatitis virus

Oncolytic virotherapy can be achieved in two ways: (1) by exploiting an innate ability of certain viruses to selectively replicate in tumor tissues, and (2) by using viruses to deliver toxic or immunostimulatory genes to tumors. Vesicular stomatitis virus (VSV) selectively replicates in tumors lacking adequate type I interferon response. The efficacy of oncolytic virotherapy using VSV against B16 melanomas in C57BL/6 mice is dependent on CD8(+) T and natural killer cells. Because immunotherapies that prime specific CD8(+) T cells against melanocyte/melanoma antigens can generate significant therapeutic responses, we hypothesized that engineering VSV to express the potent T cell costimulatory molecule CD40 ligand (VSV-CD40L) would enhance virotherapy with concomitant priming of melanoma-specific T cells. However, we observed no difference in antitumor efficacy between the parental VSV-GFP and VSV-CD40L. In contrast, intratumoral injection of a replication-defective adenovirus expressing CD40L (Ad-CD40L) consistently produced significantly greater therapy than either replication-competent VSV-GFP or VSV-CD40L. The Ad-CD40L-mediated tumor regressions were associated with specific T cell responses against tumor-associated antigens (TAAs), which took several days to develop, whereas VSV-CD40L rapidly induced high levels of T cell activation without specificity for TAAs. These data suggest that the high levels of VSV-associated immunogenicity distracted immune responses away from priming of tumor-specific T cells, even in the presence of potent costimulatory signals. In contrast, a replication-defective Ad-CD40L allowed significant priming of T cells directed against TAAs. These observations suggest that an efficiently primed antitumor T cell response can produce similar, if not better, therapy against an established melanoma compared with intratumoral injection of a replication-competent oncolytic virus.

Cell carriers for oncolytic viruses: Fed Ex for cancer therapy

Oncolytic viruses delivered directly into the circulation face many hazards that impede their localization to, and infection of, metastatic tumors. Such barriers to systemic delivery could be overcome if couriers, which confer both protection, and tumor localization, to their viral cargoes, could be found. Several preclincal studies have shown that viruses can be loaded into, or onto, different types of cells without losing the biological activity of either virus or cell carrier. Importantly, such loading can significantly protect the viruses from immune-mediated virus-neutralizing activities, including antiviral antibody. Moreover, an impressive portfolio of cellular vehicles, which have some degree of tropism for tumor cells themselves, or for the biological properties associated with the tumor stroma, is already available. Therefore, it will soon be possible to initiate clinical protocols to test the hypopthesis that cell-mediated delivery can permit efficient shipping of oncolytic viruses from the loading bay (the production laboratory) directly to the tumor in immune-competent patients with metastatic disease.

The good and the bad of chemokines/chemokine receptors in melanoma

Chemokine ligand/receptor interactions affect melanoma cell growth, stimulate or inhibit angiogenesis, recruit leukocytes, promote metastasis, and alter the gene expression profile of the melanoma associated fibroblasts. Chemokine/chemokine receptor interactions can protect against tumor development/growth or can stimulate melanoma tumor progression, tumor growth and metastasis. Metastatic melanoma cells express chemokine receptors that play a major role in the specifying the organ site for metastasis, based upon receptor detection of the chemokine gradient elaborated by a specific organ/tissue. A therapeutic approach that utilizes the protective benefit of chemokines involves delivery of angiostatic chemokines or chemokines that stimulate the infiltration of cytotoxic T cells and natural killer T cells into the tumor microenvironment. An alternative approach that tackles the tumorigenic property of chemokines uses chemokine antibodies or chemokine receptor antagonists to target the growth and metastatic properties of these interactions. Based upon our current understanding of the role of chemokine-mediated inflammation in cancer, it is important that we learn to appropriately regulate the chemokine contribution to the tumorigenic 'cytokine/chemokine storm', and to metastasis.

Use of biological therapy to enhance both virotherapy and adoptive T-cell therapy for cancer

To protect viral particles from neutralization, sequestration, nonspecific adhesion, and mislocalization following systemic delivery, we have previously exploited the natural tumor-homing properties of antigen-specific CD8+ T cells. Thus, OT-I T cells, preloaded in vitro with the oncolytic vesicular stomatitis virus (VSV), can deliver virus to established B16ova tumors to generate significantly better therapy than that achievable with OT-I T cells, or systemically delivered VSV, alone. Here, we demonstrate that preconditioning immune-competent mice with Treg depletion and interleukin-2 (IL-2), before adoptive T-cell therapy with OT-I T cells loaded with VSV, leads to further highly significant increases in antitumor therapy. Therapy was associated with antitumor immune memory, but with no detectable toxicities associated with IL-2, Treg depletion, or systemic dissemination of the oncolytic virus. Efficacy was contributed by multiple factors, including improved persistence of T cells; enhanced delivery of VSV to tumors; increased persistence of OT-I cells in vivo resulting from tumor oncolysis; and activation of NK cells, which acquire potent antitumor and proviral activities. By controlling the levels of virus loaded onto the OT-I cells, adoptive therapy was still effective in mice preimmune to the virus, indicating that therapy with virus-loaded T cells may be useful even in virus-immune patients. Taken together, our data show that it is possible to combine adoptive T-cell therapy, with biological therapy (Treg depletion+IL-2), and VSV virotherapy, to treat established tumors under conditions where none of the individual modalities alone is successful.

Treg depletion-enhanced IL-2 treatment facilitates therapy of established tumors using systemically delivered oncolytic virus

There are several roadblocks that hinder systemic delivery of oncolytic viruses to the sites of metastatic disease. These include the tumor vasculature, which provides a physical barrier to tumor-specific virus extravasation. Although interleukin-2 (IL-2) has been used in antitumor therapy, it is associated with endothelial cell injury, leading to vascular leak syndrome (VLS). Here, we demonstrate that IL-2-mediated VLS, accentuated by depletion of regulatory T cells (Treg), facilitates localization of intravenously (i.v.) delivered oncolytic virus into established tumors in immune-competent mice. IL-2, in association with Treg depletion, generates "hyperactivated" natural killer (NK) cells, possessing antitumor activity and secreting factors that facilitate virus spread/replication throughout the tumor by disrupting the tumor architecture. As a result, the combination of Treg depletion/IL-2 and systemic oncolytic virotherapy was found to be significantly more therapeutic against established disease than either treatment alone. These data demonstrate that it is possible to combine biological therapy with oncolytic virotherapy to generate systemic therapy against established tumors.

Cell vehicle targeting strategies

Use of cells as therapeutic carriers has increased in the past few years and has developed as a distinct concept and delivery method. Cell-based vehicles are particularly attractive for delivery of biotherapeutic agents that are difficult to synthesize, have reduced half-lives, limited tissue penetrance or are rapidly inactivated upon direct in vivo introduction. Initial studies using cell-based approaches served to identify some of the key factors for the success of this type of therapeutic delivery. These factors include the efficiency of cell loading with a therapeutic payload, the means of cell loading and the nature of therapeutics that cells can carry. However, one important aspect of cell-based delivery yet to be fully investigated is the process of actual delivery of the cell payload in vivo. In this regard, the potential ability of cell carriers to provide site-specific or targeted delivery of therapeutics deserves special attention. The present review focuses on a variety of targeting approaches that may be utilized to improve cell-based therapeutic delivery strategies. The different aspects of targeting that can be applied to cell vehicles will be discussed, including physical methods for directing cell distribution, intrinsic cell-mediated homing mechanisms and the feasibility of engineering cells with novel targeting mechanisms. Development of cell targeting strategies will further advance cell vehicle applications, broaden the applicability of this delivery approach and potentiate therapeutic outcomes.

Loading of oncolytic vesicular stomatitis virus onto antigen-specific T cells enhances the efficacy of adoptive T-cell therapy of tumors

Although adoptive T-cell therapy has shown clinical success, efficacy is limited by low levels of T-cell trafficking to, and survival in, the immunosuppressive environment of an established tumor. Oncolytic virotherapy has recently emerged as a promising approach to induce both direct tumor cell killing and local proinflammatory environments within tumors. However, inefficient systemic delivery of oncolytic viruses remains a barrier to use of these agents against metastatic disease that is not directly accessible to the end of a needle. Here we show that the ability of antigen-specific T cells to circulate freely, and to localize to tumors, can be exploited to achieve the systemic delivery of replication-competent, oncolytic vesicular stomatitis virus (VSV). Thus, VSV loaded onto OT-I T cells, specific for the SIINFEKL epitope of the ovalbumin antigen, was efficiently delivered to established B16ova tumors in the lungs of fully immune-competent C57Bl/6 mice leading to significant increases in therapy compared to the use of virus, or T cells, alone. Although OT-I T-cell-mediated delivery of VSV led to viral replication within tumors and direct viral oncolysis, therapy was also dependent upon an intact host immune system. Moreover, VSV loading onto the T cells increased both T-cell activation in vitro and T-cell trafficking in vivo. The combination of adoptive T-cell transfer of antigen-specific T cells, along with oncolytic virotherapy, can, therefore, increase the therapeutic utility of both approaches through multiple mechanisms and should be of direct translational value.

Oncolytic virotherapy: molecular targets in tumor-selective replication and carrier cell-mediated delivery of oncolytic viruses

Tremendous advances have been made in developing oncolytic viruses (OVs) in the last few years. By taking advantage of current knowledge in cancer biology and virology, specific OVs have been genetically engineered to target specific molecules or signal transduction pathways in cancer cells in order to achieve efficient and selective replication. The viral infection and amplification eventually induce cancer cells into cell death pathways and elicit host antitumor immune responses to further help eliminate cancer cells. Specifically targeted molecules or signaling pathways (such as RB/E2F/p16, p53, IFN, PKR, EGFR, Ras, Wnt, anti-apoptosis or hypoxia) in cancer cells or tumor microenvironment have been studied and dissected with a variety of OVs such as adenovirus, herpes simplex virus, poxvirus, vesicular stomatitis virus, measles virus, Newcastle disease virus, influenza virus and reovirus, setting the molecular basis for further improvements in the near future. Another exciting new area of research has been the harnessing of naturally tumor-homing cells as carrier cells (or cellular vehicles) to deliver OVs to tumors. The trafficking of these tumor-homing cells (stem cells, immune cells and cancer cells), which support proliferation of the viruses, is mediated by specific chemokines and cell adhesion molecules and we are just beginning to understand the roles of these molecules. Finally, we will highlight some avenues deserving further study in order to achieve the ultimate goals of utilizing various OVs for effective cancer treatment.

Tracking the elusive lymphocyte: methods of detection during adoptive immunotherapy

Adoptive immunotherapy is an attractive cancer treatment modality due to its capacity to target primary and metastatic lesions with large numbers of tumor-reactive, cytotoxic lymphocytes. The inability of fully armed lymphocytes to traffic into sites of tumor has been proposed as a causal factor for the minimal success observed clinically with this type of immunotherapy. The study of lymphocyte trafficking during adoptive immunotherapy has been limited, despite the existence of a variety of tracking methods. In murine models that simulate adoptive immunotherapy, the use of congenic mice and cell tracking dyes can be used to elucidate lymphocyte trafficking behavior. The continued development of novel technologies will further contribute to this expanding area of research.

Purging metastases in lymphoid organs using a combination of antigen-nonspecific adoptive T cell therapy, oncolytic virotherapy and immunotherapy

In many common cancers, dissemination of secondary tumors via the lymph nodes poses the most significant threat to the affected individual. Metastatic cells often reach the lymph nodes by mimicking the molecular mechanisms used by hematopoietic cells to traffic to peripheral lymphoid organs. Therefore, we exploited naive T cell trafficking in order to chaperone an oncolytic virus to lymphoid organs harboring metastatic cells. Metastatic burden was initially reduced by viral oncolysis and was then eradicated, as tumor cell killing in the lymph node and spleen generated protective antitumor immunity. Lymph node purging of tumor cells was possible even in virus-immune mice. Adoptive transfer of normal T cells loaded with oncolytic virus into individuals with cancer would be technically easy to implement both to reduce the distribution of metastases and to vaccinate the affected individual in situ against micrometastatic disease. As such, this adoptive transfer could have a great therapeutic impact, in the adjuvant setting, on many different cancer types.

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.