Breast cancer vaccine shows promise in clinical trial

A breast cancer vaccine is safe in patients with metastatic breast cancer, results of an early clinical trial indicate. Preliminary evidence also suggests that the vaccine primed the patients’ immune systems to attack tumor cells and helped slow the cancer’s progression. The new vaccine causes the body’s immune system to home in on a protein called mammaglobin-A, found almost exclusively in breast tissue. The protein’s role in healthy tissue is unclear, but breast tumors express it at abnormally high levels, past research has shown. Being able to target mammaglobin is exciting because it is expressed broadly in up to 80 percent of breast cancers, but not at meaningful levels in other tissues. The vaccine primes a type of white blood cell, part of the body’s adaptive immune system, to seek out and destroy cells with the mammaglobin-A protein. In the smaller proportion of breast cancer patients whose tumors do not produce mammaglobin-A, this vaccine would not be effective.