Methyltransferase SETD7 as a Regulator of STING-Dependent Cytokine Response in Lung Cancer Cells

The innate immune signaling pathway cGAS–STING plays an important role in the recognition of cytosolic nucleic acids and the induction of the interferon-dependent antiviral response. Despite the significant research interest in this cascade in the context of immune system function, the mechanisms regulating cGAS–STING signaling and the switch between its pro-inflammatory and pro-apoptotic effects remain largely underexplored. According to publicly available RNA-seq data and microarray analyses, SETD7 lysine methyltransferase participates in interferon signaling in cancer cells. This study aims to elucidate the role of SETD7 in the regulation of the STING-dependent immune response in human lung adenocarcinoma (LUAD) cells. For this purpose, we developed a reproducible and cost-effective method for inducing the STING cascade by transfecting cells with salmon sperm DNA (sspDNA). We demonstrated that sspDNA efficiently induces phosphorylation of the key components of the STING–TBK1–IRF3 signaling pathway and activates the expression of interferons and pro-inflammatory cytokines. Using this approach, we further demonstrated that SETD7 is involved in the regulation of the IRF3-dependent transcriptional program. Suppression of SETD7 was associated with changes in the expression of genes related to innate immune response and apoptosis, including increased levels of IFNA1, IL1B, BAK1, BBC3 (PUMA), and BCL2. Furthermore, attenuation of SETD7 expression reduced the lentiviral transduction efficacy in H1299 cells. These results suggest that SETD7 may play a role in regulating the switch in STING signaling between pro-inflammatory and pro-apoptotic responses in LUAD cells.