The ability to make the immune system act in certain ways is the foundation for a range of powerful therapies: "scientists have discovered a way to wake up the immune system to fight cancer by delivering an immune system-stimulating protein in a nanoscale container called a vault directly into lung cancer tumors, harnessing the body's natural defenses to fight disease growth. The vaults, barrel-shaped nanoscale capsules found in the cytoplasm of all mammalian cells, were engineered to slowly release a protein, the chemokine CCL21, into the tumor. Pre-clinical studies in mice with lung cancer showed that the protein stimulated the immune system to recognize and attack the cancer cells, potently inhibiting cancer growth ... The vault nanoparticles containing the CCL21 have been engineered to slowly release the protein into the tumor over time, producing an enduring immune response. Although the vaults protect the packed CCL21, they act like a time-release capsule. ... [Researchers] plan to test the vault delivery method in human studies within the next three years and hope the promising results found in the pre-clinical animal tumor models will be replicated. ... The vault nanoparticle would require only a single injection into the tumor because of the slow-release design, and it eventually could be designed to be patient specific by adding the individual's tumor antigens into the vault ... The vaults may also be targeted by adding antibodies to their surface that recognize receptors on the tumor. The injection could then be delivered into the blood stream and the vault would navigate to the tumor, a less invasive process that would be easier on the patients. The vault could also seek out and target tumors and metastases too small to be detected with imaging."