We often think of white blood cells as the body’s defenders, rushing in to fight infections. But not all heroes wear capes—sometimes they have a dark side. Neutrophils, the most abundant white blood cells, are showing up as both protectors and potential villains in cancer. Depending on the circumstances, they can attack tumors with lethal precision—or quietly help them grow and spread. Understanding this surprising dual role could open the door to entirely new strategies in cancer therapy.

1. The Two Faces of Neutrophils

Neutrophils have powerful tools to attack cancer. They can produce reactive oxygen species (ROS) to directly kill tumor cells, enhance antibody-dependent cell-mediated cytotoxicity (ADCC), and activate other immune cells such as cytotoxic T cells and natural killer (NK) cells.

Yet, neutrophils can also act as helpers for tumors. Certain neutrophils release vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs), promoting blood vessel formation, tissue invasion, and tumor growth. They can also form neutrophil extracellular traps (NETs) or secrete pro-inflammatory factors that suppress other immune cells, effectively shielding the tumor.

2. Using Neutrophils to Deliver Drugs

Scientists are exploring ways to turn neutrophils into allies rather than adversaries. Because neutrophils naturally home to tumors, they can carry drug-loaded nanoparticles or membrane-coated carriers directly to cancer tissues. This targeted delivery can increase drug accumulation in tumors, reduce side effects, and improve treatment outcomes.

However, there are challenges. Neutrophils have a short lifespan, which limits sustained drug release. Tumor heterogeneity and dense tissue barriers can reduce delivery efficiency. Some therapies relying on oxidative stress or photothermal effects may even trigger unintended immune reactions.

3. Engineering Neutrophils for Precision Therapy

Advances in bioengineering and genetic tools, like CRISPR, offer exciting possibilities. Scientists can extend neutrophil lifespan, improve tumor targeting, and control drug release. Combining neutrophil-based therapies with immune checkpoint inhibitors or targeted drugs could overcome tumor microenvironment resistance.

Real-time imaging, such as neutrophil-tracking nanoparticles or intravital microscopy, allows researchers to observe neutrophil behavior in the body and optimize treatment strategies. In the future, patient-specific neutrophil engineering guided by biomarkers or omics profiling may enable truly personalized cancer therapies.

4. Looking Ahead

Neutrophils' plasticity—the ability to switch between tumor-promoting and tumor-fighting states—is both a challenge and an opportunity. By blocking their pro-tumor functions and enhancing their anti-tumor activity, scientists hope to turn them into powerful tools against cancer.

While obstacles remain, such as tumor heterogeneity, neutrophil lifespan, and potential immune side effects, research is moving forward rapidly. Neutrophil-based therapies could offer precise, multifunctional, and minimally invasive cancer treatments, improving patient survival and quality of life.

In the complex battle against cancer, neutrophils may be the ultimate double agent—capable of either helping tumors or helping us defeat them. Unlocking their potential could transform the future of oncology.

For more information about topic, you can view the online video entitled "Neutrophils and Neutrophil-Based Drug Delivery Systems in Anti-Cancer Therapy".