A new cancer vaccine that uses a patient's own immune-regulating dendritic cells to target the HER2 protein can activate the immune system and cause regression of early-stage HER2-positive breast cancer, according to a study. The therapy is particularly effective in patients with a non-invasive form of the disease called ductal carcinoma in situ (DCIS), as compared with patients with an early-stage invasive disease, researchers said. The study, "Dendritic Cell Vaccination Enhances Immune Responses and Induces Regression of HER2pos DCIS Independent of Route: Results of Randomized Selection Design Trial," was published in Clinical Cancer Research. The HER2 protein is found at high levels in nearly a quarter of all breast-cancer tumors. It is associated with aggressive disease and poor patient outcomes. Although this makes HER2 a promising target for cancer therapies, researchers had previously shown that as HER2-positive breast cancers progress into a more aggressive stage, the immune system loses its ability to counter the protein. Researchers at the University of Pennsylvania Perelman School of Medicine in Philadelphia, developed a dendritic cell vaccine that could trigger a strong anti-HER2 immune response. The choice of dendritic cells for a cancer vaccine lies in their ability to sensitize tumor-killing T-cells to specific cancer proteins. The research team created the vaccine by harvesting dendritic cells from a patient's blood, then exposing them to fragments of the HER2 protein.