Fears that stem cell therapies could seed a bizarre form of tumour may be calmed by a cocktail of antibodies. Because human embryonic stem cells (ESCs) can develop into any type of cell, they hold great promise in the field of regenerative medicine, which aims to replace cells or tissues lost to injury or disease. But their broad developmental capacity could also be their undoing: if any undifferentiated cells remain in a culture of, say, neurons grown from ESCs, they could run riot after being transplanted into a patient. The concern is that they might form tumours known as “teratomas”, strange mixtures of tissues that can even include teeth and hair.
