Neutrophils and Neutrophil-Based Drug Delivery Systems in Anti-Cancer Therapy.

Neutrophils, the most abundant white blood cells, play a dual role in cancer progression. While they can promote tumor growth, metastasis, and immune suppression, they also exhibit anti-tumorigenic properties by attacking cancer cells and enhancing immune responses. This review explores the complex interplay between neutrophils and the tumor microenvironment (TME), highlighting their ability to switch between pro- and anti-tumor phenotypes based on external stimuli. Pro-tumorigenic neutrophils facilitate tumor growth through mechanisms such as neutrophil extracellular traps (NETs), secretion of pro-inflammatory cytokines, and immune evasion strategies. They contribute to angiogenesis, tumor invasion, and metastasis by releasing vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs). Conversely, anti-tumor neutrophils enhance cytotoxicity by generating reactive oxygen species (ROS), promoting antibody-dependent cell-mediated cytotoxicity (ADCC), and activating other immune cells such as cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Recent advances in neutrophil-based drug delivery systems have harnessed their tumor-homing capabilities to improve targeted therapy. Neutrophil-mimicking nanoparticles and membrane-coated drug carriers offer enhanced drug accumulation in tumors, reduced systemic toxicity, and improved therapeutic outcomes. Additionally, strategies to modulate neutrophil activity, such as inhibiting their immunosuppressive functions or reprogramming them towards an anti-tumor phenotype, are emerging as promising approaches in cancer immunotherapy. Understanding neutrophil plasticity and their interactions with the TME provides new avenues for therapeutic interventions. Targeting neutrophil-mediated mechanisms could enhance existing cancer treatments and lead to the development of novel immunotherapies, ultimately improving patient survival and clinical outcomes.