Synergistic action of gemcitabine and celecoxib in promoting the antitumor efficacy of anti-programmed death-1 monoclonal antibody by triggering immunogenic cell death.

ABSTRACT

Background: Emerging evidence suggests that immunogenic chemotherapy not only kills tumor cells but also improves the immune-suppressive tumor microenvironment by inducing immunogenic cell death (ICD), leading to sustained anti-tumor effects. The lack of ICD inducers explored in lung cancer necessitates investigation into new inducers for this context, therefore, this study aims to explore whether the gemcitabine (GEM) and celecoxib can activate the immunogenic chemotherapy progress in lung cancer tissue. Methods: We assessed five chemotherapeutic agents for their ability to trigger ICD using ex vivo and in vivo experiments, including western blotting (WB), flow cytometry, and tumor preventive vaccine assays. Additionally, we evaluated the synergistic effects of GEM, celecoxib, and anti-programmed death 1 monoclonal antibody (aPD-1) in tumor-bearing mice to understand how GEM activates antitumor immunity and enhances immunochemotherapy. Results: GEM was identified as an effective ICD inducer, showing high expression of calreticulin (CRT) and heat shock protein 90 (HSP90). Co-culture with GEM-treated cells [Lewis lung carcinoma (LLC) and CMT-64] enhanced dendritic cell (DC) activity, evidenced by maturation markers and increased phagocytic capacity. Moreover, celecoxib was found to enhance ICD by reducing indoleamine 2,3-dioxygenase 1 (IDO1) expression and increasing reactive oxygen species (ROS)-based endoplasmic reticulum (ER) stress. The combination therapy [GEM, celecoxib, and aPD-1 (GCP)] exhibited potent and sustained antitumor activity in immunocompetent mice, with enhanced recruitment of tumor-infiltrating lymphocytes. Conclusions: These findings support the potential use of GCP therapy as a treatment option for lung cancer patients.