The role of IL-6 in tumor immunity and related research progress

IL-6 is the primary mediator of inflammation. It can be secreted by immune cells, tumor cells, and stromal cells, which is highly expressed in tissues from tumors. Through its downstream signaling pathway, IL-6 regulates nearly every aspect of the tumor to encourage its occurrence and progression. Additionally, it impacts immunosuppressive molecule expression, impacts the tumor microenvironment's immunological and non-immune cell counts and composition, and promotes the growth of a tumor microenvironment that suppresses the immune system. Immunotherapy is a commonly used treatment method nowadays. However, in most patients with cancer, immunotherapy often exhibits low response rates and drug resistance. The secret to increasing the efficacy of tumor immunotherapy is to overcome the tumor microenvironment's immunosuppressive state. In recent years, researchers have developed a number of drugs that target the IL-6/Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling cascade, and related studies on combining immune checkpoint inhibitors with it, providing the new direction for immunotherapy in tumor patients. This article reviews the specific mechanism of IL-6 on tumor immunity and summarizes the latest research findings on blocking IL-6 or its downstream-related signaling pathways.