T-cell derived extracellular vesicles prime macrophages for improved STING based cancer immunotherapy

A key phenomenon in cancer is the establishment of a highly immunosuppressive tumour microenvironment (TME). Despite advances in immunotherapy, where the purpose is to induce tumour recognition and hence hereof tumour eradication, the majority of patients applicable for such treatment still fail to respond. It has been suggested that high immunological activity in the tumour is essential for achieving effective response to immunotherapy, which therefore have led to exploration of strategies that triggers inflammatory pathways. Here activation of the stimulator of interferon genes (STING) signalling pathway has been considered an attractive target, as it is a potent trigger of pro-inflammatory cytokines and types I and III interferons. However, immunotherapy combined with targeted STING agonists has not yielded sustained clinical remission in humans. This suggests a need for exploring novel adjuvants to improve the innate immunological efficacy. Here, we demonstrate that extracellular vesicles (EVs), derived from activated CD4+ T cells (T-EVs), sensitizes macrophages to elevate STING activation, mediated by IFNγ carried on the T-EVs. Our work support that T-EVs can disrupt the immune suppressive environment in the tumour by reprogramming macrophages to a pro-inflammatory phenotype, and priming them for a robust immune response towards STING activation.

Abstract A50: IFNλ1 is a marker of DNA damage-triggered STING-signaling in lung cancer that induces immune activation through macrophage stimulation

Immunotherapy is a fundamental pillar in the treatment of lung cancer but remains inefficient in half of the treated patients. Recent clinical trials showed synergistic effects of combining chemotherapy and immunotherapy for lung cancer, suggesting that increased DNA damage imposed by chemotherapy modulates the tumor microenvironment to aid the efficacy of immunotherapy. But the immunological mechanisms related to this remains to be fully elucidated. The cGAS-STING pathway senses cytosolic DNA introduced by DNA-damaging agents such as chemotherapy. Activation of this pathway and induction of inflammatory cytokines may contribute to better immunotherapy efficacy. In particular, the release of type I IFN is a hallmark for STING pathway activation. However, we also know that IFNλ – a type III IFN – can be induced by STING-signaling. Despite the relevance of IFNλ in controlling inflammatory responses, its contribution in cancer remains unclear. Here, we investigated cGAS-STING expression and signaling in a panel of lung cancer cells. We identified IFNλ1 as an alternative hallmark for cGAS-STING DNA-sensing with higher expression after DNA-stimulation than IFNb in 6 out of 8 cell lines with one cell line having no IFNb expression at all. We then tested IFN induction after chemotherapeutic treatment in three different NSCLC cell lines and saw significant increase in both IFNb and IFNλ1 expression across four different chemotherapeutics, but with a higher fold change for IFNλ1. The induction of both IFNb and IFNλ1 was abolished when STING KO cell lines were treated with doxorubicin pointing to a STING-dependent response. To access the effect of IFNλ1 on macrophages, a prevalent cell type in the tumor microenvironment expressing IFNLR1, we performed RNA-sequencing on four primary human macrophage donors stimulated with IFNλ1. This stimulation led to a significant increase in well-known interferon-stimulated genes including the chemokines CXCL10 and CXCL11. We also explored whether IFNλ1 stimulation led to increased macrophage-dependent activation of autologous CD8+ T-cells. Interestingly, we found increased expression of both IFNg (p = 0.0215, n = 6) and Granzyme B (p = 0.0033, n = 6) measured by flow cytometry and ELISA (p > 0.0001, n = 6 for both). The addition of IFNλ1 during direct co-culture of macrophages and lung tumor organoids furthermore dampened the induction of the signal regulatory protein-a (SIRPa), a phagocytosis-inhibiting receptor, (p = 0.0041, n = 4) otherwise induced by the tumor organoids, but not matched healthy organoids. In support of this, there was an increased activation of CD8+ T-cells measured by IFNg production in an organoid-macrophage-CD8+ T-cell co-culture model. To summarize, we demonstrate that IFNλ1 may be a strong and broad marker of STING activation induced by chemotherapy in NSCLC and that IFNλ1 has the ability to prime a wider immune response by targeting macrophages. Hence, we propose that an IFNλ1 induced immune response has the potential to support and boost the response induced by existing immunotherapies.

Citation Format: Kristine R Gammelgaard, Stine H Godsk, Albert G Olivier, Maria Riedel, Silke D Nielsen, Allard van Renterghem, Trine V Larsen, Anders Etzerodt, Emile Voest, Martin R Jakobsen. IFNλ1 is a marker of DNA damage-triggered STING-signaling in lung cancer that induces immune activation through macrophage stimulation [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A50.

TLR2 and TLR7 mediate distinct immunopathological and antiviral plasmacytoid dendritic cell responses to SARS-CoV-2 infection

Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS-CoV-2 infection is critical for developing treatments for severe COVID-19. Here, we find decreasing number of circulating plasmacytoid dendritic cells (pDCs) in COVID-19 patients early after symptom onset, correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFNα and of systemic inflammatory cytokines CXCL10 and IL-6. Using an in vitro stem cell-based human pDC model, we further demonstrate that pDCs, while not supporting SARS-CoV-2 replication, directly sense the virus and in response produce multiple antiviral (interferons: IFNα and IFNλ1) and inflammatory (IL-6, IL-8, CXCL10) cytokines that protect epithelial cells from de novo SARS-CoV-2 infection. Via targeted deletion of virus-recognition innate immune pathways, we identify TLR7-MyD88 signaling as crucial for production of antiviral interferons, whereas TLR2 is responsible for the inflammatory IL-6 response. We further show that SARS-CoV-2 engages the receptor neuropilin-1 on pDCs to selectively mitigate the antiviral interferon response, but not the IL-6 response, suggesting neuropilin-1 as potential therapeutic target for stimulation of TLR7-mediated antiviral protection.