Blocking just one enzyme could make some tumours easier to kill with radiation therapy.

Fei-Fei Liu at the University of Toronto in Ontario, Canada, and her team found that head and neck cancer cells treated with small RNA molecules that silence a gene called UROD are unusually susceptible to ionizing radiation. UROD encodes an enzyme involved in producing iron-containing haem molecules, and reducing its levels caused oxidative damage and cell death. When implanted into mice that were then treated with radiation, tumour cells with lowered levels of the enzyme grew more slowly than cells containing normal levels.

Furthermore, head and neck tumour samples expressing the lowest levels of UROD tended to come from patients who responded well to treatment. Drugs that inhibit UROD could make radiation treatments more effective, the authors say.

Sci. Transl. Med. 3, 67ra7 (2011)