A new study published in Science suggests that targeted nanoparticles may help reduce tumor scarring and improve the effectiveness of immunotherapy in mice. Researchers from Memorial Sloan Kettering Cancer Center (MSK) focused on liver and lung cancers that grow in scarred tissue, which often creates an environment that weakens the immune system's ability to fight cancer. By selectively targeting a specific group of immune cells linked to scarring, the approach could make immunotherapy more effective for more patients, with less harm to healthy cells. The study identified a specific type of immune cell called MΦP + sen + macrophages, which are common in fibrotic tumor environments found in liver and lung cancers. These macrophages contribute to the formation of scar tissue and create an environment that suppresses other immune cells. When these cells were eliminated or disabled in the study, the scar tissue began to break down, and the immune system became more effective at responding to cancer. This allowed checkpoint inhibitor immunotherapy, a type of treatment that helps the immune system attack cancer cells, to work better in the mice. The researchers used specially designed nanoparticles to deliver drugs directly to these problematic macrophages. The nanoparticles were coated with fucoidan, a natural sugar molecule found in brown seaweed, which helps the particles stick to the targeted cells. Two drugs tested in the study—navitoclax and dBET6—work by triggering the self-destruction of aging (senescent) cells and reducing harmful inflammation, respectively. Using nanoparticles allowed the drugs to be delivered more precisely, reducing side effects compared to traditional methods. The findings were supported by analyzing tumor samples from lung cancer patients at MSK and using human data on lung and liver cancers. The study also suggests that this approach could be useful for other conditions beyond cancer, as similar harmful macrophages were found in chronic diseases such as osteoarthritis, rheumatoid arthritis, and atherosclerosis, which can lead to heart disease. The research highlights a growing interest in targeting the broader environment that supports cancer, rather than just the cancer cells themselves. MSK is now looking for partners to help move this research into clinical trials for human use.