TAMI-49. JAK STAT INHIBITION REVERSES MYELOID CELL INDUCED ANTI TUMOR IMMUNITY IN T CELLS

BACKGROUND Many central questions about the immunosuppressive microenvironment in glioblastoma (GBM) remain unanswered, particularly the interaction with lymphoid and myeloid populations. Here, we combined single-cell (scRNA) and spatial transcriptomics (stRNA) to comprehensively characterize the immune interaction with GBM. MATERIAL AND METHODS We performed scRNA-Seq of 50k CD45+ cells (8 patients) and inferred transcriptional programs and fate decisions in T cells. A novel algorithm (Nearest functionally connected neighbor) was used to predict interacting cells, further validated using spatial transcriptomics and immunofluorescence. Our findings were validated in our human neocortical glioblastoma model with autografted T cells. RESULTS Integration of st/scRNA-seq revealed a transcriptional shift of T cells towards exhaustion/hypoxia induced dysfunction. Pseudo-time analysis revealed increased Interleukin 10 (IL10) response during the Tcell transformation from the effector to the exhausted state. Using NFCN we identified a subset of HMOX1+ myeloid cells (STAT/HMOX axis), responsible for this IL10 release. Computational findings were validated using our human neocortical glioblastoma model with autografted T cells, where IL10R-inhibition/myeloid cell depletion prevented T cell exhaustion/dysfunction (p < 0.01) . In order to target the STAT3/HMOX1 axis we used a JAK/STAT inhibitor in our model which showed a drastic reduction of IL10 release (p< 0.02) and concordant activation of T cells. Clinically, one patient treated with a JAK/STAT-inhibitor in a neoadjuvant setting, 4 weeks prior to the recurrent GBM surgery, led to a significant increase (p< 0.001) in effector T cell population. CONCLUSION Our findings suggest that targeting the myeloid compartment of GBM provides an opportunity to convert a “cold” into “hot” immune environment which might be helpful to improve all T cell based therapies in the future.

664 Pulmonary priming of tumor-reactive CD8+ T cells by DC1 is impaired by regulatory T cells

BackgroundAlthough failure to respond to checkpoint blockade immunotherapies (CBT) is frequently associated with a lack of T cell infiltration into the tumor, emerging clinical data suggests that specifically in patients with lung cancer, T cell-inflamed tumors can also be resistant to therapy.1 Recent work by our group identified that immunotherapy resistance in a T cell-inflamed pre-clinical mouse model of lung cancer is driven by a lung cancer-specific CD8+ T cell dysfunctional program (TLdys), characterized by blunted production of IFNg and reduced cytolytic capacity. Intriguingly, this TLdysprogram is established during priming in the tumor-draining mediastinal lymph nodes (mLN). Understanding the lung-specific mechanisms blunting the activation of anti-tumor T cell responses could enable development of novel therapies needed to improve outcomes of patients with CBT-resistant T cell-inflamed lung cancer.MethodsTo study anti-tumor immune responses against lung tumors, a syngeneic lung cancer cell line (KP) was implanted orthotopically or subcutaneously into C57BL/6 mice. KP cells were engineered to express SIINFEKL and ZsGreen to enable studies of tumor-reactive T cells and antigen uptake by dendritic cells (DC).ResultsLung KP tumors led to the induction of tumor-reactive TLdys CD8+ T cells lacking CD25 and GzmB in the mLN, in contrast to subcutaneous KP tumors, which induced CD25high GzmBhigh tumor-reactive CD8+ T cells in the inguinal LN (iLN). Mouse models lacking DC1 revealed that DC1 are necessary to prime tumor-reactive CD8+ T cells in both LNs. Flow cytometry characterization of DC1 from LNs revealed equivalent levels of antigen load, but reduced levels of costimulatory molecules CD80, CD86 and the cytokine IL-12 in the mLN compared to iLN, suggesting a blunted stimulatory capacity in the lung setting. Regulatory T cell (Treg) depletion using FoxP3DTR mice rescued expression of effector T cell priming in tumor-draining mLN, suggesting that TLdys induction requires the presence of local Treg. Ex vivo co-cultures of antigen-specific CD8+ T cells with DC1 and Treg sorted from the mLN fully recapitulated the in vivo observation, suggesting that both DC1 and Treg are required and sufficient for TLdys induction. Blockade of the MHCII-dependent DC1:Treg interaction restored an effector-like profile of tumor-reactive CD8+ T cells.ConclusionsTreg restrain DC1 stimulatory function in the tumor-draining mLN, leading to the induction of lung cancer-specific dysfunction in tumor-reactive CD8+ T cells and thus rendering the T cell response refractory to CBT-mediated reinvigoration. Blockade of Treg:DC1 interactions can restore priming of lung cancer-reactive effector T cell responses.AcknowledgementsPew-Stewart Scholarship, Training grantReferenceHerbst RS, et al. Predictive correlates of response to the anti-PD-L1 antibody MPDL3280A in cancer patients. Nature 2014;515:563–567.Ethics ApprovalAll mouse experiments in this study were approved by MIT's Committee on Animal Care (CAC) - DHHS Animal Welfare Assurance # D16-00078

Juzentaihoto Exerts Anti-Allergic Effects by Inhibiting Effector T-Cell Activation and Inducing and/or Activating Regulatory T Cells in a Murine Model of Contact Hypersensitivity

<b><i>Background:</i></b> Juzentaihoto (JTT) is a Kampo prescription that has been used clinically for treating skin diseases such as atopic dermatitis in Japan. We have previously studied the anti-allergic effects of JTT on 2,4,6-trinitrochlorobenzene (TNCB)-induced contact hypersensitivity (CHS) in mice and demonstrated that it significantly suppresses ear swelling in a dose-dependent manner. However, the mechanism underlying the anti-allergic actions of JTT is obscure. <b><i>Methods:</i></b> We investigated the mechanism underlying the anti-allergic effects of JTT using a TNCB-induced murine CHS model and adoptive cell transfer experiments. <b><i>Results:</i></b> We showed that the anti-allergic effects of JTT are due to inhibition of effector T-cell activation and induction and/or activation of regulatory T cells. Furthermore, ex vivo experiments confirmed the effect of JTT on the activation of effector T cells and regulatory T cells, as interferon-γ production decreased, whereas interleukin (IL)-10 production increased, in the cultured lymphocytes obtained from 5% TNCB-sensitized mice treated with anti-CD3ε and anti-CD28 monoclonal antibodies. Flow cytometry showed that the CD4⁺CD25⁺Foxp3⁺, CD4⁺CD25⁺Foxp3⁻, and CD8⁺CD122⁺ cell population increased after oral administration of JTT. Finally, the anti-allergic effect of JTT by inducing and/or activating regulatory T cells (Tregs) was confirmed to be mediated by IL-10 through in vivo neutralization experiments with anti-IL-10 monoclonal antibodies. <b><i>Conclusion:</i></b> We suggested that JTT exerts anti-allergic effects by regulating the activation of effector T cells and Tregs involved in murine CHS model.

P08.02 CCR2/CCR5 dual-antagonist ‘licenses’ the radiation-induced effector T-cell infiltration in the anti-PD-1 antibody-treated pancreatic adenocarcinoma

BackgroundThe resistance of pancreatic ductal adenocarcinoma(PDAC) to immune checkpoint inhibitors(ICIs) is mainly attributed to the immune-quiescent nature of its tumor microenvironment(TME). Radiotherapy(RT) activates innate responses including the RAGE and TLR2/4 pathways and subsequently modifies the TME by promoting the release of chemokines that recruit inflammatory cells into the TME. In this preclinical study, we examined the PDAC vaccine or RT as a T-cell priming mechanism together with BMS-687681, a small molecule dual-antagonist of CCR2 and CCR5(CCR2/5i) as an immunosuppressive TME-targeting agent, in combination with the anti-PD-1 antibody(αPD-1) as a new treatment.Materials and MethodsThe hemi-spleen and Orthotopic mice model were used to investigate both GVAX and RT as T-cell priming agents in combination regimens that included αPD-1 and CCR2/5i. Dissected orthotopic pancreatic tumors were collected for analysis of tumor-infiltrating immune cells by flow cytometry. RNA from tumor-infiltrating immune cell pellets and whole-exome RNA sequencing was performed for further mechanism research.ResultsCCR2 and CCR5 are associated with the immunosuppressive TME of PDAC patients and their expression were induced after treatment with GVAX+nivolumab. Using a mouse model of PDAC, we demonstrated that the addition of GVAX to CCR2/5i+αPD-1 combination therapy did not significantly improve antitumor activity. However, RT followed by αPD-1 and prolonged treatment with CCR2/5i conferred significantly better antitumor efficacy compared to the other combination treatments we studied. The combination of RT, αPD-1, and CCR2/5i enhanced intratumoral effector and memory T-cell infiltration. This combination suppressed Treg, M2-like TAM, and M-MDSC infiltration, but not M1-like TAM and PMN-MDSC infiltration. Finally, RNA sequencing showed that CCR2/5i partially inhibited RT-induced TLR2/4&RAGE signaling, which would have otherwise led to the release of immunosuppressive cytokines including CCL2 and CCL5. The inhibition of TLR2/4&RAGE signaling permitted the expression of effector T-cell chemokines such as CCL17 and CCL22.ConclusionsThis study thus supports the clinical development of CCR2/5i in combination with RT and ICIs for PDAC treatment.Disclosure InformationJ. Wang: None. M. Tun Saung: None. K. Fujiwara: None. N. Niu: None. A. Narang: None. J. He: None. L. Zheng: None.

Targeting of Cdc42 GTPase in regulatory T cells unleashes anti-tumor T cell immunity

Regulatory T (Treg) cells play an important role in maintaining immune tolerance through inhibiting effector T cell function. In the tumor microenvironment, Treg cells are utilized by tumor cells to counteract effector T cell-mediated tumor killing. Targeting Treg cells may thus unleash the anti-tumor activity of effector T cells. While systemic depletion of Treg cells can cause excessive effector T cell responses and subsequent autoimmune diseases, controlled targeting of Treg cells may benefit cancer patients. Here we show that Treg cell-specific heterozygous deletion or pharmacological targeting of Cdc42 GTPase does not affect Treg cell numbers but induces Treg cell plasticity, leading to anti-tumor T cell immunity without detectable autoimmune reactions. Cdc42 targeting potentiates an immune checkpoint blocker anti-PD-1 antibody-mediated T cell response against mouse and human tumors. Mechanistically, Cdc42 targeting induces Treg cell plasticity and unleashes anti-tumor T cell immunity through carbonic anhydrase I-mediated pH changes. Thus, rational targeting of Cdc42 in Treg cells holds therapeutic promises in cancer immunotherapy.