Tumor-associated or -infiltrating lymphocytes (TALs or TILs) co-express multiple immune inhibitory receptors that contribute to immune suppression in the ovarian tumor microenvironment (TME). Dual blockade of PD-1 along with LAG-3 or CTLA-4 has been shown to synergistically enhance T-cell effector function, resulting in a delay in murine ovarian tumor growth. However, the mechanisms underlying this synergy and the relative contribution of other inhibitory receptors to immune suppression in the ovarian TME are unknown. Here, we report that multiple immune checkpoints are expressed in TALs and TILs isolated from ovarian tumor-bearing mice. Importantly, blockade of PD-1, LAG-3, or CTLA-4 alone using genetic ablation or blocking antibodies conferred a compensatory upregulation of the other checkpoint pathways, potentiating their capacity for local T-cell suppression that, in turn, could be overcome through combinatorial blockade strategies. Whereas single-agent blockade led to tumor outgrowth in all animals, dual antibody blockade against PD-1/CTLA-4 or triple blockade against PD-1/LAG-3/CTLA-4 resulted in tumor-free survival in 20% of treated mice. In contrast, dual blockade of LAG-3 and CTLA-4 pathways using PD-1 knockout mice led to tumor-free survival in 40% of treated mice, suggesting a hierarchical ordering of checkpoint function. Durable antitumor immunity was most strongly associated with increased numbers of CD8+ T cells, the frequency of cytokine-producing effector T cells, reduced frequency of Tregs and arginine-expressing monocytic myeloid-derived suppressor cells in the peritoneal TME. These data provide a basis for combinatorial checkpoint blockade in clinical intervention for ovarian cancer.

Signals mediated by the chemokine CXCL12 and its receptor CXCR4 are involved in progression of ovarian cancer by enhancing tumor angiogenesis and immunosuppressive networks that regulate dissemination of peritoneal metastasis and development of cancer initiating cells (CICs). Here, we investigated the antitumor efficacy of a CXCR4 antagonist expressed by oncolytic vaccinia virus (OVV) against an invasive variant of the murine epithelial ovarian cancer cell line ID8-T. This variant harbors a high frequency of CICs that form multilayered spheroid cells and express the hyaluronan receptor CD44 as well as stem cell factor receptor CD117 (c-kit). Using an orthotopic ID8-T tumor model, we observed that intraperitoneal delivery of a CXCR4 antagonist-expressing OVV led to reduced metastatic spread of tumors and improved overall survival over that mediated by oncolysis alone. Inhibition of tumor growth with the armed virus was associated with efficient killing of CICs, reductions in expression of ascitic CXCL12 and VEGF, and decreases in intraperitoneal numbers of endothelial and myeloid cells as well as plasmacytoid dendritic cells (pDCs). These changes, together with reduced recruitment of T regulatory cells, were associated with higher ratios of IFN-γ+/IL-10+ tumor-infiltrating T lymphocytes as well as induction of spontaneous humoral and cellular antitumor responses. Similarly, the CXCR4 antagonist released from virally-infected human CAOV2 ovarian carcinoma cells inhibited peritoneal dissemination of tumors in SCID mice leading to improved tumor-free survival in a xenograft model. Our findings demonstrate that OVV armed with a CXCR4 antagonist represents a potent therapy for ovarian CICs with a broad antitumor repertoire.

We have recently reported that CD8 ؉ T-cell memory maintenance after immunization with recombinant human adenovirus type 5 (rHuAd5) is dependent upon persistent transgene expression beyond the peak of the response. In this report, we have further investigated the location and nature of the cell populations responsible for this sustained response. The draining lymph nodes were found to be important for primary expansion but not for memory maintenance, suggesting that antigen presentation through a nonlymphoid source was required. Using bone marrow chimeric mice, we determined that antigen presentation by nonhematopoietic antigenpresenting cells (APCs) was sufficient for maintenance of CD8 ؉ T-cell numbers. However, antigen presentation by this mechanism alone yielded a memory population that displayed alterations in phenotype, cytokine production and protective capacity, indicating that antigen presentation through both hematopoietic and nonhematopoietic APCs ultimately defines the memory CD8 ؉ T-cell response produced by rHuAd5. These results shed new light on the immunobiology of rHuAd5 vectors and provide evidence for a mechanism of CD8 ؉ T-cell expansion and memory maintenance that relies upon both hematopoietic and nonhematopoietic APCs. (Blood. 2011;117(4):1146-1155) IntroductionRecombinant adenovirus vectors have proven to be robust immunogens for eliciting T-cell immunity. 1-3 Vaccines derived from recombinant human adenovirus serotype 5 (rHuAd5) have displayed remarkable potency in various models prompting further investigation. To better understand the immunobiology of rHuAd5, we have been studying both the nature of the CD8 ϩ T cells elicited by these vaccines and the mechanisms of CD8 ϩ T-cell priming and memory maintenance. Immunization with rHuAd5 typically produces a sustained memory population with a protracted contraction phase, 4-8 although these kinetics may be influenced by vector configuration and route of administration. 9 The memory CD8 ϩ T-cell population is composed primarily of effector T cells (T EFF ) and effector memory T cells (T EM ), 5,6 which is indicative of a persistent viral infection. Indeed, we have recently determined that sustained, low-level antigen expression from the rHuAd5 vector plays a key role in maintaining the CD8 ϩ T-cell memory population. 10 Premature extinction of transgene expression causes pronounced CD8 ϩ T-cell contraction, but only modestly affects phenotype, suggesting that memory maintenance and phenotype may be regulated by distinct mechanisms.The relationship between memory CD8 ϩ T-cell phenotype and protective immunity remains to be fully established. T EM provide optimal immune protection against certain agents [11][12][13] ; therefore, understanding the nature of the antigen-presenting cells (APCs) involved in the generation and maintenance of CD8 ϩ T EM will provide important information for vaccine design. Dendritic cells (DCs) are thought to be critical for the induction of antiviral CD8 ϩ T-cell responses. At least 7 distinct DC populations have...

Interleukin-12 (IL12) enhances anti-tumor immunity when delivered to the tumor microenvironment. However, local immunoregulatory elements dampen the efficacy of IL12. The identity of these local mechanisms used by tumors to suppress immunosurveillance represents a key knowledge gap for improving tumor immunotherapy. From a systems perspective, local suppression of anti-tumor immunity is a closed-loop system - where system response is determined by an unknown combination of external inputs and local cellular cross-talk. Here, we recreated this closed-loop system in vitro and combined quantitative high content assays, in silico model-based inference, and a proteomic workflow to identify the biochemical cues responsible for immunosuppression. Following an induction period, the B16 melanoma cell model, a transplantable model for spontaneous malignant melanoma, inhibited the response of a T helper cell model to IL12. This paracrine effect was not explained by induction of apoptosis or creation of a cytokine sink, despite both mechanisms present within the co-culture assay. Tumor-derived Wnt-inducible signaling protein-1 (WISP-1) was identified to exert paracrine action on immune cells by inhibiting their response to IL12. Moreover, WISP-1 was expressed in vivo following intradermal challenge with B16F10 cells and was inferred to be expressed at the tumor periphery. Collectively, the data suggest that (1) biochemical cues associated with epithelial-to-mesenchymal transition can shape anti-tumor immunity through paracrine action and (2) remnants of the immunoselective pressure associated with evolution in cancer include both sculpting of tumor antigens and expression of proteins that proactively shape anti-tumor immunity.

Despite clear evidence of immunogenicity, cancer vaccines only provide a modest clinical benefit. To evaluate the mechanisms that limit tumor regression following vaccination, we have investigated the weak efficacy of a highly immunogenic experimental vaccine using a murine melanoma model. We discovered that the tumor adapts rapidly to the immune attack instigated by tumor-specific CD8+ T cells in the first few days following vaccination, resulting in the upregulation of a complex set of biological networks, including multiple immunosuppressive processes. This rapid adaptation acts to prevent sustained local immune attack, despite continued infiltration by increasing numbers of tumor-specific T cells. Combining vaccination with adoptive transfer of tumor-specific T cells produced complete regression of the treated tumors but did not prevent the adaptive immunosuppression. In fact, the adaptive immunosuppressive pathways were more highly induced in regressing tumors, commensurate with the enhanced level of immune attack. Examination of tumor infiltrating T-cell functionality revealed that the adaptive immunosuppression leads to a progressive loss in T-cell function, even in tumors that are regressing. These novel observations that T cells produced by therapeutic intervention can instigate a rapid adaptive immunosuppressive response within the tumor have important implications for clinical implementation of immunotherapies.