The core idea of immunotherapy - priming immune cells to recognize and attack tumors - has been proven numerous times in petri dishes. But unfortunately, the principles established in the lab are failing to translate into successful attacks on real tumors. Now, a new study led by the biopharmaceutical research institute TRON in Mainz, Germany, successfully confronts two key challenges in translating theory into practice, bringing closer the creation of "vaccines on demand" matched to individual patients' cancers. Prof. Ugur Sahin, study senior author, doctor of medicine and managing director of TRON, notes that it has long been known that each tumor has its own configuration of cancer-specific mutations - termed the "mutanome." The first challenge he and his colleagues confront in their study concerns how to produce a template of a tumor type from its mutanome that can be fine-tuned to incorporate variants that are specific to a particular patient's tumor. Within this challenge lies the need to ensure the template contains mutations that are known to trigger immune responses. This is the "vaccine" part. The second challenge the team confronts in their study is how to fine-tune the template for a specific patient fast enough that it can be used before the tumor has advanced and developed. This is the "on demand" part. Spanning these two challenges is the poignant reality of cancer - it progresses. Like other cancer therapies, cancer immunotherapy is a race against time. In their study, the team showed how their solutions to these two challenges caused tumors not only to regress, but in some cases disappear completely - in mice.