Neutrophils Extracellular Traps (NETs) Inhibition Improves PD-1 Blockade Immunotherapy in Triple-Negative Breast Cancer

Abstract

Abstract Introduction: Despite significant advances using immune checkpoint blockade therapy for patients with advanced cancer, 40–85% of patients fail to respond to therapy. Increasing evidence suggests that the tumor immune microenvironment plays a critical role in rendering the immune checkpoint blockade ineffective. As such, targeting the tumor immune microenvironment is an attractive strategy for the treatment of solid tumors and an important approach to improve the efficacy of checkpoint inhibitors. Our study explores the combination therapy of DNase I and PD-1 antibody to prevent tumor growth. We demonstrate that this combination treatment for triple-negative breast (TNBC) cancer shows superior efficacy in comparison to a single-agent treatment, both in vivoand in vitro. Methods: For 4T1 tumor models, 0.1-ml sample containing 10 4tumors was injected into the mammary fat pad of female BALB/c mice. Tumor diameters were measured using calipers. The tumor volume was calculated. Anti-PD-1 or IgG2a isotype Ab (10mg/kg, every 3 days) and DNase I (5 mg/kg, daily) were administered intraperitoneally starting from day 5 after tumor cell inoculation. Results: DNase I plays a pivotal role in the degradation of NETs, significantly dampening the resistance to anti-PD-1 blockade in a mouse TNBC model by attenuating tumor growth. Remarkably, DNase I decreases tumor-associated neutrophils and the formation of NETs in vivo. Mechanistically, the inhibition of NETs with DNase I results in the reversal of anti-PD-1 blockade resistance through increasing CD8+ T cell infiltration and cytotoxicity. These findings signify a novel approach to targeting the tumor microenvironment using DNase I alone or in combination with immune checkpoint inhibitors. R01CA214865-06 (Renewal) Surgery triggered immune response and liver metastases. NIH/NCI 1R01 CA214865-01. Surgery triggered immune response and liver metastases.