Cancer is a major focus of medical research that continues to innovate. In the shadows, a highly promising European project could stand out: a treatment using nanoparticles to target tumor cells and prevent the risk of relapse. One in five men and one in six women will develop cancer during their lifetime. The figure, put forward by Santé publique France, is chilling, especially when considering that it is the leading cause of death in the country and an extremely complex disease to treat. The European project Ulises appears to be particularly promising and exciting, with the potential for a nanoparticle-based cancer vaccine. This therapeutic revolution uses nanotechnologies to reprogram cancer cells and make them visible to the patient’s immune system. Ulises focuses on using nanoparticles to deliver plasmid DNA to tumor cells. This method aims not to modify the genes of cancer cells, but to «tag» them so that the immune system can later identify and effectively attack them. Nanoparticles allow for targeted transport of genetic material to cancer cells, essential for triggering an immune response. Lipid nanoparticles, similar to those used in mRNA vaccines against Covid-19, protect and deliver the necessary molecules to the right place in the body. This approach could not only treat cancer more naturally by avoiding heavy traditional treatments like chemotherapy and radiotherapy but also reduce the often associated side effects. By activating tumor-infiltrating lymphocytes (TIL), the body could develop long-term immunity against cancer, acting as a «vaccine effect» to prevent relapses. Finally, this technology can be quickly adjusted to treat various types of cancers with minimal modifications. For example, researchers have already begun testing this approach on pancreatic cancer, with the hope of expanding it to other deadly and currently incurable tumors. Other research organizations are also exploring the use of nanoparticle-based cancer treatments, such as CNRS and Institut Curie. In France, companies like Nanobiotix and NH TherAguix are developing nanomedicines to improve radiotherapy treatments. These companies are working on nanoparticles that increase the effectiveness of radiation by specifically targeting cancer cells while reducing damage to healthy tissues. Nanoparticle-based cancer vaccines represent a major advance in the fight against cancer. By redirecting the immune system to recognize and attack cancer cells, this technology could radically transform cancer management in the near future.