Radiation is known to cause cancer by damaging DNA, but may also induce other molecular changes in the surrounding tissue that accelerate tumour growth.

Mary Helen Barcellos-Hoff at the New York University School of Medicine and her colleagues exposed mice to radiation and then inserted cancer-prone tissue into their mammary glands and those of untreated mice. One year later, tumours had developed in all of the irradiated mice, but in only 69% of non-irradiated mice. The tumours also grew faster in the irradiated animals, and more of them were oestrogen-receptor negative, a marker of aggressive breast cancer. Furthermore, the radiation activated a protein in the surrounding tissue called TGF-β, accelerating cancer development.

The findings might help to explain why women who receive radiotherapy treatment for childhood cancer are at greater risk from early-onset breast cancer later in life.

Cancer Cell 19, 640–651 (2011)