Control of CD8 T-Cell Infiltration into Tumors by Vasculature and Microenvironment

Inhibition of p21 activated kinase enhances tumour immune response and sensitizes pancreatic cancer to gemcitabine

Pancreatic ductal adenocarcinoma (PDA) is one of the major types of cancer that exhibit high mortality worldwide because of the late diagnosis and the lack of effective treatment. Immunotherapy appears to be ineffective in PDA treatment due to the existence of a unique immune-suppressive microenvironment in PDA. Gemcitabine-based therapy is still the most commonly used chemotherapy to treat PDA patients with only marginal increased survival rates. This prompted us to continue the search for more effective therapy for PDA treatment. The effects of p21 activated kinases (PAKs) on tumour immune response and gemcitabine response were examined in PDA. An orthotopic murine PDA model, in which pancreatic cancer cells were injected to the tail of pancreas, was used. The mice were treated with PAK inhibitor, PF‑3758309, plus or minus gemcitabine. Tumour growth was measured by volume and weight. Tumour immune response was determined by flow cytometry analysis of splenic cells and immunohistochemical staining of intratumoural lymphocytes. Inhibition of PAKs by PF‑3758309, not only suppressed tumour growth, but also stimulated tumour immune response by increasing the numbers of splenic and intratumoural T lymphocytes. Furthermore, inhibition of PAKs decreased PDA cell growth synergistically with gemcitabine in vitro and in vivo. The dual effects of inhibition of PAKs make PAK-targeted therapy more potent for the treatment of PDA. The combination of PAK inhibitors with gemcitabine may be a more effective therapeutic approach in PDA treatment.

Differential Expression of Homing Receptor Ligands on Tumor-Associated Vasculature that Control CD8 Effector T-cell Entry

Although CD8⁺ T cells are critical for controlling tumors, how they are recruited and home to primary and metastatic lesions is incompletely understood. We characterized the homing receptor (HR) ligands on tumor vasculature to determine what drives their expression and their role in T-cell entry. The anatomic location of B16-OVA tumors affected the expression of E-selectin, MadCAM-1, and VCAM-1, whereas the HR ligands CXCL9 and ICAM-1 were expressed on the vasculature regardless of location. VCAM-1 and CXCL9 expression was induced by IFNγ-secreting adaptive immune cells. VCAM-1 and CXCL9/10 enabled CD8⁺ T-cell effectors expressing α₄β₁ integrin and CXCR3 to enter both subcutaneous and peritoneal tumors, whereas E-selectin enabled E-selectin ligand⁺ effectors to enter subcutaneous tumors. However, MadCAM-1 did not mediate α₄β₇⁺ effector entry into peritoneal tumors due to an unexpected lack of luminal expression. These data establish the relative importance of certain HRs expressed on activated effectors and certain HR ligands expressed on tumor vasculature in the effective immune control of tumors. Cancer Immunol Res; 5(12); 1062-73. ©2017 AACR.

Crosstalk signaling in targeted melanoma therapy

Inhibition of the BRAF/MAPK pathway belongs to the standard therapies for patients with activating BRAF^V600E/K mutations. However, even in well-responding tumors, anti-tumorigenic effect and clinical benefit are only transient, and the original tumors often relapse. This demonstrates that there are remaining residual tumors, which have withstood therapy-induced apoptosis and which have the potential to resume growth. Although BRAF mutant melanoma cells seem to depend on BRAF/MAPK signaling, the inhibition of this pathway triggers several events, which modulate the tumor as well as the tumor niche. After a certain adaptation period, this can turn out to be beneficial for tumor growth and metastasis-even in cases of good initial tumor response. This review sheds light on the biology of BRAF/MEK inhibitor-sensitive melanoma cells, which survive targeted therapy and will address the crosstalk signaling events occurring in BRAF mutant melanomas when the BRAF/MAPK pathway is fully blocked. The knowledge of these events is important for potential future drug combinations, which enhance the inhibitory effect of BRAF/MEK inhibition, particularly in patients not eligible for immune therapy.

Harness the synergy between targeted therapy and immunotherapy: what have we learned and where are we headed?

Since the introduction of imatinib for the treatment of chronic myelogenous leukemia, several oncogenic mutations have been identified in various malignancies that can serve as targets for therapy. More recently, a deeper insight into the mechanism of antitumor immunity and tumor immunoevasion have facilitated the development of novel immunotherapy agents. Certain targeted agents have the ability of inhibiting tumor growth without causing severe lymphocytopenia and amplifying antitumor immune response by increasing tumor antigenicity, enhancing intratumoral T cell infiltration, and altering the tumor immune microenvironment, which provides a rationale for combining targeted therapy with immunotherapy. Targeted therapy can elicit dramatic responses in selected patients by interfering with the tumor-intrinsic driver mutations. But in most cases, resistance will occur over a relatively short period of time. In contrast, immunotherapy can yield durable, albeit generally mild, responses in several tumor types via unleashing host antitumor immunity. Thus, combination approaches might be able to induce a rapid tumor regression and a prolonged duration of response. We examine the available evidence regarding immune effects of targeted therapy, and review preclinical and clinical studies on the combination of targeted therapy and immunotherapy for cancer treatment. Furthermore, we discuss challenges of the combined therapy and highlight the need for continued translational research.

Adoptive Cell Therapy for Metastatic Melanoma

Adoptive cell therapy (ACT) of tumor-infiltrating lymphocytes (TILs) is a powerful form of immunotherapy by inducing durable complete responses that significantly extend the survival of melanoma patients. Mutation-derived neoantigens were recently identified as key factors for tumor recognition and rejection by TILs. The isolation of T-cell receptor (TCR) genes directed against neoantigens and their retransduction into peripheral T cells may provide a new form of ACT.Genetic modifications of T cells with chimeric antigen receptors (CARs) have demonstrated remarkable clinical results in hematologic malignancies, but are so far less effective in solid tumors. Only very limited reports exist in melanoma. Progress in CAR T-cell engineering, including neutralization of inhibitory signals or additional safety switches, may open opportunities also in melanoma.We review clinical results and latest developments of adoptive therapies with TILs, T-cell receptor, and CAR-modified T cells and discuss future directions for the treatment of melanoma.

Adoptive T cell therapy: An overview of obstacles and opportunities

The therapeutic potential of adoptive cell therapy (ACT) in cancer patients was first acknowledged 3 decades ago, but it was an esoteric approach at the time. In recent years, technological advancements have transformed ACT into a viable therapeutic option that can be curative in some patients. In fact, current ACT response rates are 80% to 90% for hematological malignancies and 30% for metastatic melanoma refractory to multiple lines of therapy. Although these results are encouraging, there is still much to be done to fulfill ACT's potential, specifically with regard to improving clinical efficacy, expanding clinical indications, reducing toxicity, and increasing production and cost-effectiveness. This review addresses the current major obstacles to ACT and presents potential solutions. Cancer 2017;123:2154-62. © 2017 American Cancer Society.

T-lymphocyte homing: an underappreciated yet critical hurdle for successful cancer immunotherapy

Advances in cancer immunotherapy have offered new hope for patients with metastatic disease. This unfolding success story has been exemplified by a growing arsenal of novel immunotherapeutics, including blocking antibodies targeting immune checkpoint pathways, cancer vaccines, and adoptive cell therapy (ACT). Nonetheless, clinical benefit remains highly variable and patient-specific, in part, because all immunotherapeutic regimens vitally hinge on the capacity of endogenous and/or adoptively transferred T-effector (T_eff) cells, including chimeric antigen receptor (CAR) T cells, to home efficiently into tumor target tissue. Thus, defects intrinsic to the multi-step T-cell homing cascade have become an obvious, though significantly underappreciated contributor to immunotherapy resistance. Conspicuous have been low intralesional frequencies of tumor-infiltrating T-lymphocytes (TILs) below clinically beneficial threshold levels, and peripheral rather than deep lesional TIL infiltration. Therefore, a T_eff cell 'homing deficit' may arguably represent a dominant factor responsible for ineffective immunotherapeutic outcomes, as tumors resistant to immune-targeted killing thrive in such permissive, immune-vacuous microenvironments. Fortunately, emerging data is shedding light into the diverse mechanisms of immune escape by which tumors restrict T_eff cell trafficking and lesional penetrance. In this review, we scrutinize evolving knowledge on the molecular determinants of T_eff cell navigation into tumors. By integrating recently described, though sporadic information of pivotal adhesive and chemokine homing signatures within the tumor microenvironment with better established paradigms of T-cell trafficking under homeostatic or infectious disease scenarios, we seek to refine currently incomplete models of T_eff cell entry into tumor tissue. We further summarize how cancers thwart homing to escape immune-mediated destruction and raise awareness of the potential impact of immune checkpoint blockers on T_eff cell homing. Finally, we speculate on innovative therapeutic opportunities for augmenting T_eff cell homing capabilities to improve immunotherapy-based tumor eradication in cancer patients, with special focus on malignant melanoma.

Mechanisms and Dynamics of T Cell-Mediated Cytotoxicity In Vivo

Cytotoxic T lymphocytes (CTLs) are critical in the elimination of infected or malignant cells and are emerging as a major therapeutic target. How CTLs recognize and kill harmful cells has been characterized in vitro but little is known about these processes in the living organism. Here we review recent insights into CTL-mediated killing with an emphasis on in vivo CTL biology. Specifically, we focus on the possible rate-limiting steps determining the efficiency of CTL-mediated killing. We also highlight the need for cell-based datasets that permit the quantification of CTL dynamics, including CTL location, migration, and killing rates. A better understanding of these factors is required to predict protective CD8 T cell immunity in vivo and to design optimized vaccination protocols.

IL-33 restricts tumor growth and inhibits pulmonary metastasis in melanoma-bearing mice through eosinophils

The alarmin IL-33 is an IL-1 family member that stimulates pleiotropic immune reactions depending on the target tissue and microenvironmental factors. In this study, we have investigated the role of IL-33/ST2 axis in antitumor response to melanoma. Injection of IL-33 in mice-bearing subcutaneous B16.F10 melanoma resulted in significant tumor growth delay. This effect was associated with intratumoral accumulation of CD8⁺ T cells and eosinophils, decrease of immunosuppressive myeloid cells, and a mixed Th1/Th2 cytokine expression pattern with local and systemic activation of CD8⁺ T and NK cells. Moreover, intranasal administration of IL-33 determined ST2-dependent eosinophil recruitment in the lung that prevented the onset of pulmonary metastasis after intravenous injection of melanoma cells. Accordingly, ST2-deficient mice developed pulmonary metastasis at higher extent than wild-type counterparts, associated with lower eosinophil frequencies in the lung. Of note, depletion of eosinophils by in vivo treatment with anti-Siglec-F antibody abolished the ability of IL-33 to both restrict primary tumor growth and metastasis formation. Finally, we show that IL-33 is able to activate eosinophils resulting in efficient killing of target melanoma cells, suggesting a direct antitumor activity of eosinophils following IL-33 treatment. Our results advocate for an eosinophil-mediated antitumoral function of IL-33 against melanoma, thus opening perspectives for novel cancer immunotherapy strategies.

The effect of polymorphisms in PD-1 gene on the risk of epithelial ovarian cancer and patients' outcomes

OBJECTIVE

Programmed death-1 (PD-1), an important immunosuppressive molecule, plays a key role in tumor-cell-mediated immune escape. In the present study, we evaluated the effect of PD-1 gene polymorphisms on the risk of developing epithelial ovarian cancer (EOC) and patients' outcomes.

METHODS

A case-control study was performed in 620 EOC patients and 620 control women. Survival data were available for 258 patients who received platinum-based chemotherapy after cytoreductive surgery.

RESULTS

There were significant differences in the genotype and allele distribution frequencies of the PD-1.1 A/G between cases and controls (P=0.028 and P=0.02, respectively). Compared with the AA genotype, AG and GG genotypes may significantly decrease the risk of developing EOC (OR=0.71, 95%CI=0.54-0.94; OR=0.68, 95%CI=0.50-0.94, respectively). We did not find a significant difference in the genotype distribution frequency of the PD-1.5 C/T between cases and controls (P=0.096), but the frequency of T alleles was significantly lower in the EOC cases than that in the controls (P=0.033). Compared to the carriers with C alleles, the carriers with T alleles were at a significantly decreased risk of developing EOC (OR=0.82, 95%CI=0.69-0.98). Survival analysis showed that the two polymorphisms were not associated with patients' outcomes.

CONCLUSIONS

PD-1 gene polymorphisms may be involved in the development of EOC, but not associated with its clinical outcome in EOC patients among northern Chinese women.

VEGF Neutralization Plus CTLA-4 Blockade Alters Soluble and Cellular Factors Associated with Enhancing Lymphocyte Infiltration and Humoral Recognition in Melanoma

Immune recognition of tumor targets by specific cytotoxic lymphocytes is essential for the effective rejection of tumors. A phase I clinical trial of ipilimumab (an antibody that blocks CTLA-4 function) in combination with bevacizumab (an antibody that inhibits angiogenesis) in patients with metastatic melanoma found favorable clinical outcomes were associated with increased tumor endothelial activation and lymphocyte infiltration. To better understand the underlying mechanisms, we sought features and factors that changed as a function of treatment in patients. Ipilimumab plus bevacizumab (Ipi-Bev) increased tumor vascular expression of ICAM1 and VCAM1. Treatment also altered concentrations of many circulating cytokines and chemokines, including increases of CXCL10, IL1α, TNFα, CXCL1, IFNα2, and IL8, with decreases in VEGF-A in most patients. IL1α and TNFα induced expression of E-selectin, CXCL1, and VCAM1 on melanoma tumor-associated endothelial cells (TEC) in vitro and promoted adhesion of activated T cells onto TEC. VEGFA inhibited TNFα-induced expression of ICAM1 and VCAM1 and T-cell adhesion, which was blocked by bevacizumab. CXCL10 promoted T-cell migration across TEC in vitro, was frequently expressed by melanoma cells, and was upregulated in a subset of tumors in treated patients. Robust upregulation of CXCL10 in tumors was accompanied by increased T-cell infiltration. Ipi-Bev also augmented humoral immune responses recognizing targets in melanoma, tumor endothelial, and tumor mesenchymal stem cells. Our findings suggest that Ipi-Bev therapy augments immune recognition in the tumor microenvironment through enhancing lymphocyte infiltration and antibody responses. IL1α, TNFα, and CXCL10, together with VEGF neutralization, contribute to Ipi-Bev-induced melanoma immune recognition. Cancer Immunol Res; 4(10); 858-68. ©2016 AACR.

Knockout of MDA-9/Syntenin (SDCBP) expression in the microenvironment dampens tumor-supporting inflammation and inhibits melanoma metastasis

Cancer development and progression to metastasis is a complex process, which largely depends on bidirectional communication between tumor cells and their microenvironment. Melanoma differentiation associated gene-9 (mda-9, also known as Syntenin-1, SDCBP), a gene first cloned by our group, is robustly expressed in multiple cancers including melanoma and contributes to invasion and metastasis in a tumor cell-intrinsic manner. However, the role of MDA-9/Syntenin in the tumor cell-extrinsic microenvironment remains unclear even though MDA-9/Syntenin is ubiquitously expressed in most organs that are active metastatic sites for melanoma, e.g., lung, lymph node, brain, and liver. In this study, we explored the effect of environmental mda-9/syntenin expression on melanoma growth and metastasis using multiple immunocompetent animal models, syngeneic B16 xenograft and intravenous B16 mouse model and a genetically engineered mouse (GEM) model of melanoma. Host-deficient expression of mda-9/syntenin in mice negatively impacted on subcutaneously implanted B16 tumor growth and lung metastasis. Absence of MDA-9/Syntenin in the lung microenvironment suppressed tumor growth by modulating in situ Interleukin 17A (IL17A) expression and impaired the recruitment of myeloid derived suppressor cells (MDSCs) and Th17 cells as compared to genetically wild type animals. Additionally, loss of mda-9/syntenin expression in a spontaneous melanoma model (melanocyte-specific pten loss and BrafV600E mutation) significantly delayed tumor initiation and suppressed metastasis to the lymph nodes and lungs. The present study highlights a novel role of mda-9/syntenin in tumor-promoting inflammation and immune suppression. These observations along with other documented roles of MDA-9/Syntenin in cancer and metastasis support the potential relevance of MDA-9/Syntenin in the carcinogenic process and as a target for developing improved therapies by using either genetic or pharmacologic approaches to treat and prevent melanoma and other cancers.

Targeted Therapy and Checkpoint Immunotherapy Combinations for the Treatment of Cancer

Many advances in the treatment of cancer have been driven by the development of targeted therapies that inhibit oncogenic signaling pathways and tumor-associated angiogenesis, as well as by the recent development of therapies that activate a patient's immune system to unleash antitumor immunity. Some targeted therapies can have effects on host immune responses, in addition to their effects on tumor biology. These immune-modulating effects, such as increasing tumor antigenicity or promoting intratumoral T cell infiltration, provide a rationale for combining these targeted therapies with immunotherapies. Here, we discuss the immune-modulating effects of targeted therapies against the MAPK and VEGF signaling pathways, and how they may synergize with immunomodulatory antibodies that target PD1/PDL1 and CTLA4. We critically examine the rationale in support of these combinations in light of the current understanding of the underlying mechanisms of action of these therapies. We also discuss the available preclinical and clinical data for these combination approaches and their implications regarding mechanisms of action. Insights from these studies provide a framework for considering additional combinations of targeted therapies and immunotherapies for the treatment of cancer.

PD-1/CTLA-4 Blockade Inhibits Epstein-Barr Virus-Induced Lymphoma Growth in a Cord Blood Humanized-Mouse Model

Epstein-Barr virus (EBV) infection causes B cell lymphomas in humanized mouse models and contributes to a variety of different types of human lymphomas. T cells directed against viral antigens play a critical role in controlling EBV infection, and EBV-positive lymphomas are particularly common in immunocompromised hosts. We previously showed that EBV induces B cell lymphomas with high frequency in a cord blood-humanized mouse model in which EBV-infected human cord blood is injected intraperitoneally into NOD/LtSz-scid/IL2Rγ^null (NSG) mice. Since our former studies showed that it is possible for T cells to control the tumors in another NSG mouse model engrafted with both human fetal CD34+ cells and human thymus and liver, here we investigated whether monoclonal antibodies that block the T cell inhibitory receptors, PD-1 and CTLA-4, enhance the ability of cord blood T cells to control the outgrowth of EBV-induced lymphomas in the cord-blood humanized mouse model. We demonstrate that EBV-infected lymphoma cells in this model express both the PD-L1 and PD-L2 inhibitory ligands for the PD-1 receptor, and that T cells express the PD-1 and CTLA-4 receptors. Furthermore, we show that the combination of CTLA-4 and PD-1 blockade strikingly reduces the size of lymphomas induced by a lytic EBV strain (M81) in this model, and that this anti-tumor effect requires T cells. PD-1/CTLA-4 blockade markedly increases EBV-specific T cell responses, and is associated with enhanced tumor infiltration by CD4+ and CD8+ T cells. In addition, PD-1/CTLA-4 blockade decreases the number of both latently, and lytically, EBV-infected B cells. These results indicate that PD-1/CTLA-4 blockade enhances the ability of cord blood T cells to control outgrowth of EBV-induced lymphomas, and suggest that PD-1/CTLA-4 blockade might be useful for treating certain EBV-induced diseases in humans.

EBV is a human herpesvirus that remains in the host for life, but is normally well controlled by the host immune response. Nevertheless, EBV causes lymphomas in certain individuals, particularly when T cell function is impaired. Antibodies against two different inhibitory receptors on T cells, PD-1 and CTLA-4, have been recently shown to improve T cell cytotoxic function against a subset of non-virally associated tumors. Here we have used an EBV-infected cord blood-humanized mouse model to show that EBV-infected lymphomas express both the PD-L1 and PD-L2 inhibitory ligands for PD-1. Importantly, we find that the combination of PD-1 and CTLA-4 blockade decreases the growth of EBV-induced lymphomas in this model, and demonstrate that this anti-tumor effect requires T cells and enhances their responses to EBV. Our results suggest that PD-1/CTLA-4 blockade might be useful for treating certain EBV-associated diseases in humans.

Delivery of cancer therapeutics to extracellular and intracellular targets: Determinants, barriers, challenges and opportunities

Advances in molecular medicine have led to identification of worthy cellular and molecular targets located in extracellular and intracellular compartments. Effectiveness of cancer therapeutics is limited in part by inadequate delivery and transport in tumor interstitium. Parts I and II of this report give an overview on the kinetic processes in delivering therapeutics to their intended targets, the transport barriers in tumor microenvironment and extracellular matrix (TME/ECM), and the experimental approaches to overcome such barriers. Part III discusses new concepts and findings concerning nanoparticle-biocorona complex, including the effects of TME/ECM. Part IV outlines the challenges in animal-to-human translation of cancer nanotherapeutics. Part V provides an overview of the background, current status, and the roles of TME/ECM in immune checkpoint inhibition therapy, the newest cancer treatment modality. Part VI outlines the development and use of multiscale computational modeling to capture the unavoidable tumor heterogeneities, the multiple nonlinear kinetic processes including interstitial and transvascular transport and interactions between cancer therapeutics and TME/ECM, in order to predict the in vivo tumor spatiokinetics of a therapeutic based on experimental in vitro biointerfacial interaction data. Part VII provides perspectives on translational research using quantitative systems pharmacology approaches.