Antibodies are used in many kinds of cancer treatments but have only been able to reach proteins on the outside of cancer cells—until now. According to a new study, scientists have designed antibodies that can barge into cancer cells and drag abnormal proteins out, ultimately slowing tumor growth in mice.

The approach is a novel way of targeting cancer-fueling proteins that are buried inside cancer cells, several experts said.

Most antibodies can’t get inside cells. Yet most cancer-fueling proteins are tucked deep inside cancer cells. One type of antibody, however, called IgA, can glide through certain cells like a ghost walking through a wall.