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

Abstract 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.