Scientists from the Korea Institute of Advanced Science and Technology (KAIST) have discovered a new way to treat cancer, which consists in reprogramming the tumor's own immune cells directly in the patient's body[1]. Tumors contain macrophages – immune cells that are supposed to fight cancer, but are usually inactive due to the tumor's suppressive environment[2]. Scientists have developed a method in which by injecting a specially designed drug directly into the tumor, they activate these dormant cells and turn them into highly effective cancer fighters[1]. Cells activated in this way, called CAR-macrophages, acquire the ability to recognize and destroy cancer cells and at the same time stimulate the surrounding components of the immune system[2]. In tests on animal models with melanoma – the most aggressive form of skin cancer – there was a significant slowing of tumor growth and shrinkage[1]. A significant finding is that the immune response was not limited to the injection site, but could have a systemic effect, meaning that the activated cells can trigger the immune system to seek out and destroy cancer cells beyond the direct site of application[1]. This approach represents a new concept of cell therapy that overcomes key limitations of existing therapies[2].