Adaptive Antitumor Immunity Research Articles

Plasmacytoid dendritic cells orchestrate innate and adaptive anti-tumor immunity induced by oncolytic coxsackievirus A21

BackgroundThe oncolytic virus, coxsackievirus A21 (CVA21), has shown promise as a single agent in several clinical trials and is now being tested in combination with immune checkpoint blockade. Combination therapies offer the best chance of disease control; however, the design of successful combination strategies requires a deeper understanding of the mechanisms underpinning CVA21 efficacy, in particular, the role of CVA21 anti-tumor immunity. Therefore, this study aimed to examine the ability of CVA21 to induce human anti-tumor immunity, and identify the cellular mechanism responsible.MethodsThis study utilized peripheral blood mononuclear cells from i) healthy donors, ii) Acute Myeloid Leukemia (AML) patients, and iii) patients taking part in the STORM clinical trial, who received intravenous CVA21; patients receiving intravenous CVA21 were consented separately in accordance with local institutional ethics review and approval. Collectively, these blood samples were used to characterize the development of innate and adaptive anti-tumor immune responses following CVA21 treatment.ResultsAn Initial characterization of peripheral blood mononuclear cells, collected from cancer patients following intravenous infusion of CVA21, confirmed that CVA21 activated immune effector cells in patients. Next, using hematological disease models which were sensitive (Multiple Myeloma; MM) or resistant (AML) to CVA21-direct oncolysis, we demonstrated that CVA21 stimulated potent anti-tumor immune responses, including: 1) cytokine-mediated bystander killing; 2) enhanced natural killer cell-mediated cellular cytotoxicity; and 3) priming of tumor-specific cytotoxic T lymphocytes, with specificity towards known tumor-associated antigens. Importantly, immune-mediated killing of both MM and AML, despite AML cells being resistant to CVA21-direct oncolysis, was observed. Upon further examination of the cellular mechanisms responsible for CVA21-induced anti-tumor immunity we have identified the importance of type I IFN for NK cell activation, and demonstrated that both ICAM-1 and plasmacytoid dendritic cells were key mediators of this response.ConclusionThis work supports the development of CVA21 as an immunotherapeutic agent for the treatment of both AML and MM. Additionally, the data presented provides an important insight into the mechanisms of CVA21-mediated immunotherapy to aid the development of clinical biomarkers to predict response and rationalize future drug combinations.

P-131 - Cancer immunotherapy with STING agonist and PD-1 immune checkpoint inhibitor effectively suppresses peritoneal carcinomatosis of colon cancer

Introduction: Peritoneal carcinomatosis is a common but lethal clinical presentation of colorectal cancer, which is usually refractory to conventional chemotherapy. Stimulator of interferon genes (STING) signaling is an emerging therapeutic target in cancer immunotherapy because it strongly activates dendritic cells and leads to the activation of the adaptive immune response involving T cells in various cancers. Here, we aimed to explore the therapeutic potential of STING agonist therapy in peritoneal carcinomatosis of colon cancer. Methods: C57Bl6/ mice were intraperitoneally implanted with MC38 colon cancer cells to develop peritoneal carcinomatosis with malignant ascites. Tumor-bearing mice were treated with either STING agonist, ADU-S100, or anti-PD-1 antibody every three days. Tumor size, the volume of ascites, and peritoneum seedings were assessed after the treatment course. The tumor microenvironment was comprehensively analyzed with multiplex immunofluorescence imaging, flow cytometry, and RNA sequencing. Results: Treatment with STING agonist remarkably suppressed the growth of peritoneal seeding nodules. Moreover, normalization and reduction of peritoneal tumor blood vessels resulted in an overt decrease in malignant ascites in the peritoneal cavity after STING treatment. In the tumor microenvironment, the number of intratumoral CD8 + T cells had markedly increased and adaptive anti-tumor immunity was enhanced with STING treatment. Moreover, IFN-gamma-secreting cytotoxic T cells against MC38 tumor cells were increased with STING treatment. Finally, the combination treatment of STING agonist and anti-PD1 antibody elicited greater anti-tumor immunity than monotherapy and showed potent and durable anti-cancer efficacy. Conclusion: In conclusion, STING agonist therapy normalized peritoneal tumor blood vessels, enhanced anti-cancer immune response, and synergized with PD-1 immune checkpoint inhibitor therapy in peritoneal carcinomatosis of colon cancer.

Abstract 1079: Prognostic role of tumor microenvironment in correlation with CD8+ T cells in TCGA pan-cancer

Abstract Purpose: Tumor microenvironment (TME) is a complex mixture of cells around tumor, showing different associations with tumor growth and survival outcomes. CD8+ T cell plays a key role in adaptive anti-tumor immunity and can predict favorable prognosis with better outcome from immunotherapy. However, little has been known whether various components of TME in correlation with CD8+ T cells affect prognosis. We aimed to investigate the prognostic role of immune cells in TME in correlation with CD8+ T cells using The Cancer Genome Atlas (TCGA) pan-cancer database. Experimental Design: The fraction of 21 immune cell subpopulations in TME and CD8+ T cell were extracted from mRNA expression data obtained by RNA sequencing of the TCGA samples to which a deconvolution algorithm (CIBERSORT) was applied. The samples were classified into CD8low, CD8high-Xlow/int, and CD8high-Xhigh groups (X is a component of TME), and survival was compared between them in TCGA pan-cancer and each cancer cohort. To determine the associations between each cell type and treatment outcomes, we also evaluated the immune cell subpopulations with CD8+ T cell in patients treated with programmed death-1 blockades using previously reported data on the nCounter system by the PanCancer 730-Immune Panel (GEO accession number: GSE93157). Results: Profiles of immune subpopulation in correlation with CD8+ T cell varied between different cancer types. In TCGA pan-cancer cohort with available survival data (N=8903), increased regulatory T cells (Treg) (P=2.48× 10-4), M1 and M2 macrophages (P=9.53× 10-3; P=4.72× 10-6, respectively), resting natural killer cells (P=7.29× 10-4), and activated dendritic cells (P=0.00579) were associated with poor prognosis despite high level of CD8+ T cells, whereas elevated germinal center follicular helper T cells (P=8.44 × 10-5) and naïve B cell (P=2.46× 10-7) were good prognostic subpopulations. By each cancer type, kidney cancers (renal papillary tumors and clear cell carcinoma) showed significantly poor prognostic role of Treg (Hazard ratio (HR) 2.59, 95% confidence interval (CI) 1.13 to 5.93; HR 1.62, 95% CI 1.07 to 2.45, respectively). In patients treated with immunotherapy (N=65), shorter progression-free survival was observed in CD8high-Treghigh group than in CD8high-Treglow/int group (P=0.0476). The fraction of CD8high-Treghigh group was higher in non-responders than in responders (15.6% vs. 5.0%). Conclusions: Our findings suggest that differences in immune cell subpopulations even with high CD8+ T cell might determine the prognosis. Immunosuppressive components in TME such as Treg can be negative factor for both prognosis and response to immunotherapy. A large prospective study is needed to validate the negative predictive role of immunosuppressive TME for patients treated with immunotherapy. Citation Format: Shin Hye Yoo, Changhee Park, Chan-Young Ock, Miso Kim, Bhumsuk Keam, Tae Min Kim, Dong-Wan Kim, Dae Seog Heo. Prognostic role of tumor microenvironment in correlation with CD8+ T cells in TCGA pan-cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1079.

Abstract 109: Myeloid Syk-PI3Kg-HIF axis inhibits anti-tumor adaptive immunity: In silico design of a “first in class” novel dual-Syk/PI3K inhibitor, SRX3207, to block the immunosuppressive tumor microenvironment

Abstract Introduction: Macrophages (MΘs) play important roles in the initiation and progression of solid tumors and in establishing an immunosuppressive tumor microenvironment (TME) that dampens effective anti-tumor immune responses in cancer. Hence, targeting signaling pathways in MΘs that promote tumor immunosuppression will provide therapeutic benefit. Syk kinase is a well-established cytoplasmic protein tyrosine kinase that has been extensively studied in adaptive immune responses, but its role in macrophage-mediated inflammatory responses and innate immune responses remains poorly understood. The role of PI3Kγ in tumor growth and immunosuppression has been recently established by our and other groups. Our current study examines whether targeting two crucial signaling entities, which promote macrophage-mediated anti-inflammatory responses viz. Syk kinase and PI3K, would maximally activate the anti-tumor immune response. Methodology: 1) We generated myeloid-specific conditional Syk k/o mice to investigate if the deletion of Syk has any role in a) macrophage polarization in vitro and in vivo; b) tumor growth in various syngeneic mouse models including LLC, B16, CT26, and MC38 carcinoma; c) tumor immunosuppression including polarization of macrophages into immunosuppressive phenotype, infiltration of myeloid-derived suppressor cells, regulatory T cells; and d) infiltration and activation of CD8+T cells in the TME. 2) We used commercially available Syk inhibitor, R788, to study the role of Syk in the control of the aforementioned phenotypes. 3) We used computational chemistry methods to develop a novel chemotype, SRX3207, which inhibits both PI3K and Syk (with a single molecule) as a strategy for combinatorial activation of anti-cancer immunity. Results: Our results suggest that macrophage, Syk, functions upstream of Rac2 GTPase and PI-3K to modulate integrin (αvβ3/αvβ5&α4β1)-mediated polarization of immunosuppressive macrophages and tumor growth in in vivo syngeneic tumor models. Genetic or pharmacological blockade of Syk in MΘs promotes a pro-inflammatory MΘ phenotype, restores CD8+ T cell activity, destabilizes HIF under hypoxia, and stimulates an antitumor immune response. Moreover, Syk-regulated immune response gene signature predicts survival in cancer patients. Novel dual-Syk/PI3K inhibitor, SRX3207, shows great efficacy in various syngeneic tumor models with no toxicity. Conclusions: Our results validate the concept of combined Syk and PI3K inhibition as an effective approach to treat macrophage-driven, devastating cancers. This study will open new avenues to explore this chemotype in combination with other immuno-oncologic agents as the majority of cancer patients do not respond to single agent anti-PD1 or other checkpoint inhibitors currently in clinical use. Citation Format: Shweta Joshi, Kevin Liu, Muamera Zulcic, Alok Singh, Timothy Pham, Christopher K. Glass, Andrew Sharabi, Guillermo A. Morales, Joseph R. Garlich, Donald Durden. Myeloid Syk-PI3Kg-HIF axis inhibits anti-tumor adaptive immunity: In silico design of a “first in class” novel dual-Syk/PI3K inhibitor, SRX3207, to block the immunosuppressive tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 109.

Monoclonal microbial EDP1503 to induce antitumor responses via gut-mediated activation of both innate and adaptive immunity.

e14241 Background: Systemic immunity is regulated by interactions of commensal bacteria with immune cells in the gut. Enrichment of specific intestinal microbes has been shown to enhance the anti-tumor response to PD-1 blockade in both murine models and cancer patients. Here we report that oral administration of a monoclonal microbial, EDP1503, induces systemic anti-tumor immunity. Methods: The mechanism of action and efficacy of EDP1503 was investigated in isograft tumor models and a variety of ex vivo and in vitro studies in murine and human cells. Results: EDP1503 increases expression of costimulatory molecules on CD11c+ dendritic cells (DCs) within the mesenteric LNs with an accompanying increase in proinflammatory CD103+ DCs within tumor draining lymph nodes. In addition, EDP1503 amplifies both myeloid and lymphocyte responses via production of DC-derived growth factors, M1 polarization of macrophages, and production of the lymphocyte-recruiting chemokines, CXCL9 and CXCL10. Mechanistically, EDP1503 triggers specific pattern recognition receptors and induces proinflammatory responses in antigen presenting cells. Moreover, in vivo, treatment of mice with EDP1503 results in decreased tumor volume and delayed tumor growth. The prominent anti-tumor effects of EDP1503 are further augmented by combination with anti-PD-1 neutralizing Abs. Dissection of the tumor microenvironment reveals increased activated Ki67+ NK cells and CD8+ T cells producing IFNg. Conclusions: Together, these data clearly demonstrate the ability of an orally delivered non-colonizing monoclonal microbe to enhance innate and adaptive anti-tumor immunity and substantiates the rationale for ongoing clinical trials. EDP1503 is currently in Phase 1b/2 studies (NCT03775850; NCT03595683) with enrollment open at multiple sites.

Oncolytic Viruses As Immunotherapeutic Agents for the Treatment of Malignant Tumors

Oncolytic viruses (OVs) are novel and rapidly developing class of therapeutic agents for combating cancer, which can effectively infect and destroy tumor cells, leaving healthy tissues intact. Many viruses have a natural antitumor activity which causes cytolysis of cancer cells due to direct pathogenic action. Along with non-immunogenic cell death, oncolytic viruses have been shown to be capable of inducing immunogenic cancer cell death (necrosis, pyroptosis, etc.) accompanied by the release of OV-lysed tumor-associated antigens (TAAs). Releasing DAMPs and TAAs, in its turn, leads to the activation of adaptive antitumor immunity. In order to further enhance the antitumor immunity, OVs have been armed with immunostimulatory transgenes such as granulocyte-macrophage colony-stimulating factor (GM-CSF), type I interferons, interleukins (IL-2, 12, 15), costimulatory ligands (CD40, CD80), tumor antigens («prime-boost» vaccination), which further enhances the safety and effectiveness of oncolytic virotherapy. Preliminary results of randomized clinical trials of different approaches of oncolytic virotherapies in combination with immunotherapy confirm their high efficacy. However, there are some drawbacks, which necessitates their further study.

Intravesical Ty21a Vaccine Promotes Dendritic Cells and T Cell-Mediated Tumor Regression in the MB49 Bladder Cancer Model.

Preclinical data show that intravesical instillation of Ty21a/Vivotif, a commercial vaccine against typhoid fever, is an effective alternative option to standard Bacillus Calmette-Guérin (BCG) immunotherapy for non-muscle-invasive bladder cancer (NMIBC). Here, we characterized the inflammatory effects of Ty21a on the bladder and investigated the immune mechanisms underlying tumor regression toward the use of this bacterial vaccine in NMIBC patients. MB49 bladder tumor-bearing mice had significantly improved survival after intravesical instillations of Ty21a doses of 106 to 108 colony-forming units. By IHC and morphology, both BCG and Ty21a instillations were associated with bladder inflammation, which was decreased with the use of low, but effective doses of Ty21a. Flow-cytometry analysis showed a significant infiltration of T cells, natural killer (NK) cells, and myeloid cells, compared with controls, after a single dose of Ty21a, whereas this was only observed after multiple doses of BCG. The induced myeloid cells were predominantly neutrophils and Ly6C+CD103+ dendritic cells (DC), the latter being significantly more numerous after instillation of Ty21a than BCG. Ex vivo infection of human leukocytes with Ty21a, but not BCG, similarly significantly increased DC frequency. CD4+ and CD8+ T cells, but not NK cells nor neutrophils, were required for effective bladder tumor regression upon Ty21a treatment. Thus, the generation of antitumor adaptive immunity was identified as a key process underlying Ty21a-mediated treatment efficacy. Altogether, these results demonstrate mechanisms behind intravesical Ty21a therapy and suggest its potential as a safe and effective treatment for NMIBC patients.

Harnessing immune checkpoints in myeloid lineage cells for cancer immunotherapy.

Myeloid lineage immune cells, such as macrophages and dendritic cells, play important roles in the induction of antitumor immunity during the initial stage of the cancer-immunity cycle, eliciting antitumor adaptive immunity by phagocytosing cancer cells and processing cancer-specific antigens, and then presenting these antigens to T cells. During this process, cancer cell phagocytosis can be prevented by inhibitory signals, and the signaling cascades that elicit immune responses against cancer antigens can be inhibited by immunosuppressive myeloid cells in the tumor microenvironment. A number of therapeutic strategies for enhancing cancer cell phagocytosis and promoting antitumor immunity by targeting myeloid lineage cells have recently been developed. Here, we discuss recent advances in cancer immunotherapy that involve the targeting of myeloid lineage immune cells to induce effective antitumor immunity.

YIA19-005: Immunotherapy for Prostate Cancer Combining CAR-Engineered T Cells with Targeted Immune Checkpoint Inhibition

Repairing defects in antitumor immunity has been a longstanding challenge in prostate cancer, and in recent years cellular immunotherapy has emerged as a promising approach for controlling advanced disease. To date, therapies including tumor vaccine and adoptive T-cell immunotherapy have made remarkable headway in solid cancers. Several validated prostate-specific tumor antigens are available as targets for T-cell therapy, including prostate stem cell antigen (PSCA), which is overexpressed in metastatic disease. We are in late-stage preclinical development of PSCA-specific chimeric antigen receptor (CAR)-engineered T cells with plans to initiate a clinical trial early 2019 for the treatment of metastatic castration-resistant prostate cancer. Immune checkpoint pathways, including the programmed cell death protein-1 (PD-1) and the cytotoxic T lymphocyte-associated protein-4 (CTLA4), have emerged as critical drivers of immunosuppression in solid cancers, by limiting both adaptive antitumor immunity as well as adoptive T-cell therapies. Unfortunately in prostate cancer, checkpoint inhibition has led to underwhelming responses, likely due to the low mutational load and immunologically “cold” tumor microenvironment. We hypothesize that antitumor activity of PSCA-CAR T cells will elicit checkpoint pathways that dampen antitumor immune responses and reduce overall clinical outcomes. Herein, we utilize an shRNA approach to knockdown checkpoint receptors as a rational combinatorial strategy that targets checkpoint pathways to improve overall therapy with PSCA-CAR T cells for metastatic prostate cancer. We have successfully developed a multiple shRNA knockdown approach to simultaneously disrupt 3 pathways that may hamper CAR T-cell activity in the tumor. These CAR T cells with shRNA knockdown of checkpoint receptors will be directly compared with checkpoint pathway inhibitor antibody therapies in xenograft models of prostate cancer, with the hope that next generation CARs will resist this break on the immune system in solid tumors.

CD1d highly expressed on DCs reduces lung tumor burden by enhancing antitumor immunity.

Dendritic cells (DCs), as professional antigen-presenting cells are essential for the initial activation of adaptive antitumor immunity. CD1d is considered to present phospholipid and glycosphingolipid antigens to NKT cells. However, it is currently unknown whether CD1d expression on DCs is capable of enhancing antitumor immunity, particularly T-cell related immunity. We observed that CD1d was predominantly expressed on DCs in 3LL tumor-bearing mice, whilst a deficiency of CD1d promoted tumor growth. Notably, CD1d expression on DCs was not only required for presenting antigen to NKT cells, but also markedly promoted CD4+T and CD8+T cell activation, particularly cytotoxic T cells. All the T cells (NKT, CD4+T and CD8+T cells) upregulated CD69, CD107a and IFN-γ after the adoptive transfer of CD1d-positive DCs (CD1d+DCs) and tumor growth was suppressed. With regard to the mechanism, we revealed that CD1d+DCs were concomitant with a higher expression of costimulatory molecules (CD40, CD80 and CD86) and MHCI/II, which are essential for DCs to present antigens to T cells. Consistently, CD1d+DCs displayed stronger activation-associated-ERK1/2 and NF-κB signals; whereas JAK2-STAT3/6 signaling was required for maintaining a high level of CD1d on DCs. In lung cancer patients, the antitumor activities of all the T cells were enhanced with the increase of CD1d+DCs. Analysis of TCGA data revealed that high levels of CD1d indicated better outcomes for patients. Collectively, CD1d enhanced DC-based antitumor immunity, not only by targeting NKT, but also by activating CD4+T and CD8+T cells. CD1d+DCs may be superior to the bulk population of DCs in cancer immunotherapy.

Abstract P2-03-04: A novel druggable target upstream of Notch: MEK5/ERK5 signaling regulates Jagged-1 and Notch1 expression in triple negative breast cancer stem cells

Abstract Triple negative breast cancer (TNBC) is a molecularly heterogeneous, clinically aggressive disease group that is highly prevalent among African-Americans and younger patients. Standard chemo/radio therapy often produces clinical responses, but recurrence and metastasis are unfortunately common. Metastatic disease is generally incurable. Chemo/radiotherapy has been shown to induce EMT and enrich a chemo-resistant cancer stem-like cell (CSC) population in TNBC. CSCs are thought to drive disease recurrence. Notch signaling is critical for maintenance of TNBC CSC. Expression of Notch1 and its ligand Jagged1 are correlated with poor prognosis. Efforts to pharmacologically target Notch with Gamma Secretase Inhibitors (GSIs) have been impaired by the systemic toxicity of the GSIs, and by the fact that Notch1 also plays a key role in anti-tumor adaptive immunity. Therapeutic agents that indirectly and selectively target Notch signaling in breast cancer cells would be a potentially attractive strategy. However, no such agents have been identified to date. We have found that the MAPK5-ERK5 kinase pathway, which contains at least two druggable targets, functions as a master regulator of Notch signaling in TNBC cells. ERK5 knockout TNBC cells have dramatically decreased expression of Notch receptors, ligands and transcriptional targets. In vivo, these cells form barely detectable tumors that do not metastasize and express lower levels of Notch1 and its ligand Jagged1. Using in silico screening, we identified a class of compounds that selectively target MAP2K5 (MEK5) and decrease the phosphorylation of MAPK7 (ERK5). We selected compound SC-181 for further study. Consistent with ERK5KO cells, pharmacological suppression of ERK5 phosphorylation with SC-181 decreased Notch1 and Jagged1 mRNAs and proteins. SC-181 reversed EMT and reduced the CD44hi/CD24lo CSC population in TNBC cells, but had no effect on T-cell proliferation. SC-181 decreased the number and size of mammospheres in a concentration-dependent manner. Overexpression of the Notch1 intracellular domain (N1IC) in ERK5KO cells rescues their phenotype, dramatically increasing the CSC fraction and promoting EMT. Our results suggest that targeting the MEK5-ERK5 pathway is a promising new strategy to selectively modulate Notch signaling in TNBC CSC without compromising tumor immunity. Citation Format: Ucar DA, Matossian MD, Hoang-Barnes VT, Hossain FM, Gupta M, Burks HE, Wright TD, Cavanaugh J, Flaherty P, Burow ME, Miele L. A novel druggable target upstream of Notch: MEK5/ERK5 signaling regulates Jagged-1 and Notch1 expression in triple negative breast cancer stem cells [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-03-04.

SMAC Mimetic Debio 1143 and Ablative Radiation Therapy Synergize to Enhance Antitumor Immunity against Lung Cancer

Adaptive antitumor immunity following ablative radiotherapy (ART) is attenuated by host myeloid-derived suppressor cell (MDSC), tumor-associated macrophage (TAM), and regulatory T-cell (Treg) infiltrates. We hypothesized treatment with ART and a secondary mitochondrial-derived activators of caspase (SMAC) mimetic could reverse the immunosuppressive lung cancer microenvironment to favor adaptive immunity. To evaluate for synergy between ART and the SMAC mimetic Debio 1143 and the dependence upon CD8+ T cells and TNFα, we used LLC-OVA syngeneic mouse model of lung cancer and treated them with Debio 1143 and/or ART (30 Gy) with or without anti-CD8, anti-TNFα, or anti-IFNγ antibodies. Tumor-infiltrating OVA-specific CD8+ T cells, Tc1 effector cells, MDSCs, TAMs, and Tregs, were quantified by flow cytometry. Tc1-promoting cytokines TNFα, IFNγ, and IL1β and the immunosuppressive IL10 and Arg-1 within LLC-OVA tumor tissue or mouse serum were measured by RT-PCR and ELISA. ART delayed tumor growth, and the addition of Debio 1143 greatly enhanced its efficacy, which included several complete responses. These complete responders rejected an LLC-OVA tumor rechallenge. ART and Debio 1143 synergistically induced a tumor-specific, Tc1 cellular and cytokine response while eliminating immunosuppressive cells and cytokines from the tumor microenvironment. Depletion of CD8+ cells, TNFα, and IFNγ with blocking antibody abrogated synergy between ART and Debio 1143 and partially restored tumor-infiltrating MDSCs. Debio 1143 augments the tumor-specific adaptive immunity induced by ART, while reversing host immunosuppressive cell infiltrates in the tumor microenvironment in a TNFα, IFNγ, and CD8+ T-cell-dependent manner. This provides a novel strategy to enhance the immunogenicity of ART.

Abstract A187: RIG-I agonists reinforce antitumor adaptive immunity and decrease Treg activity in breast cancer

Abstract RIG-I like receptors, RNA helicases that sense viral oligonucleotide motifs and activate innate immunity, are gaining interest in cancer therapy, given their ability to redirect immune responses within the tumor microenvironment (TME), and increase efficacy of experimental cancer vaccines. RIG-I agonists are not well studied in breast cancers, a type of cancer that is often considered immunologically “silent.” We recently reported that therapeutic delivery of RIG-I agonists increase tumor-infiltrating leukocytes (TILs) and expression of proinflammatory Th1 cytokines in the 4T1 mouse model of aggressive, metastatic breast cancer through tumor cell-intrinsic mechanisms. However, these studies do not rule out the importance of myeloid immune responders (e.g., macrophages and dendritic cells) in propagating the effects of RIG-I agonists against tumor cells in vivo, nor do they rule out the impact of RIG-I agonists on adaptive antitumor immunity, a subject that is relatively understudied. We assessed the effects of the RIG-I agonist SLR20 on the the activity of effector T-lymphocytes (TEff) and regulatory T-lymphocytes (TReg) in the TME. Interestingly, SLR20 treatment of mouse and human breast tumor cells increased expression of FAS and MHC-I on tumor cells, and caused tumor cells to express T-cell chemoattractants (e.g., CXCL10, RANTES), potentially increasing T-cells recruitment to tumors, and increasing tumor cell susceptibility to TEff recognition and killing. Using an ex vivo co-culture assay in which 4T1 mouse mammary tumor cells were co-cultured with CD8+ T-cells harvested from mice pre-inoculated with SLR20-treated 4T1 tumor cells, we measured the rate of CD8+-mediated tumor cell killing. This approach revealed that T-cells harvested from mice inoculated with SLR20-treated cells caused greater tumor cell killing than what was seen by CD8+ T-cells harvested from untreated mice. We also found that conditioned media harvested from 4T1 cells treated with SLR20 increased clonal expansion of CD3/CD28-activated T-cells above what was seen with conditioned media harvested from 4T1 cells treated with a control oligonucleotide or from untreated 4T1 cells. TGFβ-mediated differentiation of CD4+ T-cells into tolerogenic and immunosuppressive TRegs was measured in cultures of CD4+ T-cells treated with cultured media derived from SLR20-treated 4T1 cells. These studies showed that cultured media harvested from 4T1 cells treated with SLR20, but not from untreated 4T1 cells or 4T1 cells treated with a control ligand, diminished TReg differentiation, and decreased CD4+ T-cells surface expression of PD-1, CTLA4, and CCR8. Importantly, in vivo experiments assessing therapeutic treatment of 4T1 tumors with SLR20 revealed greater tumor growth inhibition when SLR20 was combined with PD-L1 targeting antibodies. Taken together, these findings indicate that therapeutic activation of RIG-I signaling operates at the interface of innate and adaptive immunity within breast tumors to redirect the TME from an immunosuppressed state to one that is immunogenic and receptive to clinically relevant checkpoint inhibitors. Citation Format: David L. Elion, Max E. Jacobson, Donna J. Hicks, Bushra Rahman, Violeta Sanchez, Paula I Gonzales-Ericsson, Olga Fedorova, Anna M. Pyle, John T. Wilson, Rebecca S. Cook. RIG-I agonists reinforce antitumor adaptive immunity and decrease Treg activity in breast cancer [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A187.

Abstract B034: A novel immunomodulatory strategy of targeting glyco-immune checkpoints with EAGLE technology

Abstract Cancer therapy has been revolutionized by inhibiting immune checkpoints to harness the power of the immune system in fighting cancer. However, the majority of patients are resistant to the current immuno-oncology drugs. There is a strong need to identify novel mechanisms of cancer immune evasion and explore novel therapeutic modalities. Glyco-immune checkpoint axis plays a critical role in modulating innate and adaptive immune responses against cancer. However, this pathway is underexplored for therapeutic interventions of cancer, because the complexity and heterogeneity of glycan-ligands on tumor cells pose grand challenges for conventional therapeutic modalities. Here we described a novel multifunctional antibody-like therapeutic modality, named EAGLE (Enzyme-Antibody Glyco-Ligand Editing), which can overcome the heterogeneity and complexity problems and specifically edit tumor-specific glycans. We evaluated the efficacy of an EAGLE molecule and studied its mechanism of actions in a breast cancer EMT6 syngeneic tumor model. Systematic delivery of the EAGLE molecule decreased the expression levels of immunosuppressive glycan-ligands on tumor cell surfaces, and increased T-cell infiltration and activation in the syngeneic tumor models. EAGLE treatment led to 50% complete regressions of established tumors as a monotherapy and 100% cures in combination with an anti-PD1 mAb. Furthermore, cured mice from EAGLE treatment completely rejected the rechallenge of tumor cells, suggesting that EAGLE induced anti-tumor immunologic memory. In summary, the novel therapeutic modality, EAGLE, blocked the glyco-immune checkpoint pathway in the tumor microenvironment and potentiated innate and adaptive antitumor immunity, which offers a novel immunomodulatory strategy to treat cancer. Citation Format: Li Peng. A novel immunomodulatory strategy of targeting glyco-immune checkpoints with EAGLE technology [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B034.

A novel anti-HER2 anthracycline-based antibody-drug conjugate induces adaptive anti-tumor immunity and potentiates PD-1 blockade in breast cancer

Increasing evidence suggests that antibody-drug conjugates (ADCs) can enhance anti-tumor immunity and improve clinical outcome. Here, we elucidate the therapeutic efficacy and immune-mediated mechanisms of a novel HER2-targeting ADC bearing a potent anthracycline derivate as payload (T-PNU) in a human HER2-expressing syngeneic breast cancer model resistant to trastuzumab and ado-trastuzumab emtansine. Mechanistically, the anthracycline component of the novel ADC induced immunogenic cell death leading to exposure and secretion of danger-associated molecular signals. RNA sequencing derived immunogenomic signatures and TCRβ clonotype analysis of tumor-infiltrating lymphocytes revealed a prominent role of the adaptive immune system in the regulation of T-PNU mediated anti-cancer activity. Depletion of CD8 T cells severely reduced T-PNU efficacy, thus confirming the role of cytotoxic T cells as drivers of the T-PNU mediated anti-tumor immune response. Furthermore, T-PNU therapy promoted immunological memory formation in tumor-bearing animals protecting those from tumor rechallenge. Finally, the combination of T-PNU and checkpoint inhibition, such as α-PD1, significantly enhanced tumor eradication following the treatment. In summary, a novel PNU-armed, HER2-targeting ADC elicited long-lasting immune protection in a murine orthotopic breast cancer model resistant to other HER2-directed therapies. Our findings delineate the therapeutic potential of this novel ADC payload and support its clinical development for breast cancer patients and potentially other HER2 expressing malignancies.

Cryo-thermal therapy inducing MI macrophage polarization created CXCL10 and IL-6-rich pro-inflammatory environment for CD4+ T cell-mediated anti-tumor immunity

Purpose: We previously developed a novel cryo-thermal therapy to treat malignant mammary carcinoma and melanoma in a mouse model; long-term survival and CD4+ T cell orchestrating anti-tumor immune memory response were achieved. Moreover, cryo-thermal-induced CD4+ T cell differentiation into Th1 and CD4+CTL sub-lineages, in which M1 macrophage polarization played a direct, important role. In particular, cryo-thermal therapy triggered M1 macrophage polarization with up-regulated expression of C–X–C motif ligand 10 (CXCL10) and Interleukin 6 (IL-6). But whether CXCL10 and IL-6 contribute to CD4+ T cell-mediated anti-tumor immunity remains unclear. In this study, the role of cryo-thermal-induced CXCL10 and IL-6 in anti-tumor immunity was determined.Methods: The level of CXCL10 and IL-6 in spleen and serum was determined by RT-PCR and ELISA on day 14 after cryo-thermal therapy. Splenic dendritic cells (DCs) and macrophages were isolated from cryo-thermal-treated mice on day 5 and 14, and the level of CXCL10 and IL-6 in macrophages and DCs was determined by ELISA. The transwell migration assay was performed to study immune cell migration. In vivo neutralization of CXCL10 or IL-6 was performed to investigate the phenotypic changes of immune cells.Results: Cryo-thermal therapy induced M1 macrophage polarization with up-regulation of CXCL10 and IL-6 expression in spleen. CXCL10 and IL-6 promoted DCs migration and maturation, and subsequently promoted CD4+ T cell migration and differentiation into Th1 and CD4+ CTL, moreover, reduced myeloid-derived suppressor cells (MDSCs) accumulation.Conclusions: Cryo-thermal-induced CXCL10 and IL-6 created acute inflammatory environment to initiate a systemically cascading innate and adaptive anti-tumor immunity, which was more permissive for tumor eradication.

Magnitude of Therapeutic STING Activation Determines CD8+ T Cell-Mediated Anti-tumor Immunity

Intratumoral (IT) STING activation results in tumor regression in preclinical models, yet factors dictating the balance between innate and adaptive anti-tumor immunity are unclear. Here, clinical candidate STING agonist ADU-S100 (S100) is used in an IT dosing regimen optimized for adaptive immunity to uncover requirements for a Tcell-driven response compatible with checkpoint inhibitors (CPIs). In contrast to high-dose tumor ablative regimens that result in systemic S100 distribution, low-dose immunogenic regimens induce local activation of tumor-specific CD8+ effector Tcells that are responsible for durable anti-tumor immunity and can be enhanced with CPIs. Both hematopoietic cell STING expression and signaling through IFNAR are required for tumor-specific Tcell activation, and in the context of optimized Tcell responses, TNFα is dispensablefor tumor control. In a poorly immunogenic model,S100 combined with CPIs generates asurvivalbenefit and durable protection. These resultsprovidefundamental mechanistic insights into STING-induced anti-tumor immunity.

Type 2 Innate Lymphoid Cells Impede IL-33-Mediated Tumor Suppression.

Although a number of studies have recently explored the contribution of the adaptive immunity in IL-33-mediated antitumor effects, innate immune involvement has been poorly characterized. Utilizing Rag1-/- mice (lacking T and B lymphocytes), we show in this study that either systemic administration of recombinant IL-33 or ectopic expression of IL-33 in melanoma cells is sufficient to inhibit tumor growth independent of adaptive antitumor immunity. We have demonstrated that IL-33-mediated antitumor effects depend on expansion and activation of NK cells. Interestingly, IL-33 also promoted the expansion of active type 2 innate lymphoid cells (ILC2s) via its receptor, ST2, which in turn inhibited NK activation and cytotoxicity. This IL-33-induced ILC2 activity coincided with greater expression of the immunosuppressive ectoenzyme CD73. Removal of CD73 from ILC2s in culture with NK cells resulted in markedly increased activation levels in NK cells, offering a potential mechanism by which ILC2s might suppress NK cell-mediated tumor killing. Thus, our data reveal an important contribution of IL-33-induced ILC2 to tumor growth by weakening NK cell activation and tumor killing, regardless of adaptive immunity.

Immunothérapie des cancers du rein

Clear cell kidney cancer is a tumour type whose development and progression is driven by the HIF/VEGF angiogenesis pathway. Anti-angiogenic (AA) agents, particularly anti-VEGFR tyrosine kinase (TKI) inhibitors, have profoundly modified the prognosis of patients in the metastatic setting (mRCC) since their registration in 2006. At the same time, mTOR inhibitors have also brought significant benefit to patients. More recently, treatments restoring adaptive anti-tumor immunity, anti-program death 1 (anti-PD-1) checkpoint inhibitors (ICP), have in turn revolutionized the management of patients with mRCC. The multi-tumor efficacy of these ICPs proves the crucial role of anti-tumor immunity in tumor development and progression in a number of tumors including clear cell kidney tumours (ccRCC). The tumor immune microenvironment (TME) of ccRCC is known to be highly immunosuppressive. Thus ccRCCs are characterized by a strong infiltration of CD8+ T lymphocytes, frequently expressing immunological checkpoint molecules on their surface, giving them a poor prognostic feature. These characteristics partly explain the effectiveness of ICP in ccRCC and constitute a strong rationale for their further development, either at an earlier stage or in combination, particularly with AA or TKI. In this review are compiled the main clinical results of immunological checkpoint molecules alone or in combination in 1stline or after TKI failure.

Dissecting the Immune Stimulation Promoted by CSF-470 Vaccine Plus Adjuvants in Cutaneous Melanoma Patients: Long Term Antitumor Immunity and Short Term Release of Acute Inflammatory Reactants.

As cutaneous melanoma (CM) currently remains with a bleak prognosis, thorough investigation of new treatment options are of utmost relevance. In the phase II/III randomized clinical trial (CASVAC-0401), the repeated immunization of stages IIB-III CM patients with the irradiated, allogeneic cellular CSF-470 vaccine plus the adjuvants bacillus Calmette-Guerin (BCG) and recombinant human granulocyte macrophage colony-stimulating factor (rhGM-CSF) demonstrated a significant benefit over IFN-alpha2B treatment in distant metastasis-free survival. Here we present on the short and long term immune monitoring results after completing the 2-year protocol; a continuation of the previous report by Mordoh et al. (1). We demonstrate that the repeated CSF-470 vaccinations stimulated a long term cellular and humoral immunity response directed against the vaccine antigens. In the case of 2 patients, we are able to show that a similar immune response was generated against autologous antigens. Evaluation of inhibitory receptor co-expression on patient's T cells indicates that the vaccination protocol did not stimulate T cell exhaustion. In order to better understand the basis for the efficacious vaccine responses observed, we investigated the short term immune events following vaccine injection. A significant increase in C-reactive protein (CRP) and IL-6 was observed 24 h after vaccination, with in vitro studies suggesting IL-6 production occurs in the vaccine site. We demonstrate that CRP enhances the cytotoxicity of peripheral blood mononuclear cells (PBMC) against melanoma cells in an in vitro model. Additionally, CRP stimulates the release of pro and anti-inflammatory cytokines from PBMC. As our results demonstrate that successive vaccinations with CSF-470 plus adjuvants promoted an increase in both anti-tumor innate and adaptive immunity, we propose a subsequent model of action.