Bojungikki-Tang Enhances the Effect of PD-1 Blockade in a Syngeneic Murine Model of Lung Carcinoma

Although immunotherapy has become the standard of treatment for non-small cell lung cancer (NSCLC), only a limited number of patients benefit from it clinically because of the resistance to immunotherapeutic agents. Of late, the usefulness of herbal medicines in combination with immunotherapy has been investigated. Bojungikki-Tang (BJIKT) is a widely used traditional herbal medicine. It synergistically enhances the antitumor effects of chemotherapy and regulates the immune responses in cancer, but its antitumor effect with immunotherapy in NSCLC is unclear. In this study, we investigated the combined effects of BJIKT and an anti-PD-1 antibody in a KLN205-DBA/2 syngeneic lung cancer model. Immunohistochemistry and flow cytometry analyses were performed to analyze the changes in immune cells in the tumor microenvironment. BJIKT plus an anti-PD-1 antibody treatment significantly inhibited tumor growth, unlike the respective monotherapies. Compared to monotherapy, the combination treatment resulted in a higher population of CD8+ cytotoxic T cells and a lower number of Ki67+ cells in the tumor tissues. Furthermore, the combination treatment decreased the proportion of myeloid-derived suppressor cells but increased the proportion of M1-like macrophages compared to that observed with monotherapy. Cytokine analysis showed that the combination treatment increased the levels of T helper type 1-related cytokines. Network pharmacology analysis revealed that BJIKT might regulate multiple signaling pathways related to immune function and tumor progression in NSCLC. These findings indicate that the combination treatment with BJIKT and an anti-PD-1 antibody effectively suppresses tumor growth by regulating immune function and may be an alternative therapeutic option for the treatment of NSCLC.