Cancer Res. 70, 1981–1988 (2010)

Arsenic, a carcinogen found at unsafe levels in drinking water in many parts of the world, may cause cancer by increasing the activity of the Hedgehog signalling pathway, which is known to promote cell proliferation.

David Robbins, now at the University of Miami, Florida, and his team have shown that arsenic destabilizes a protein that regulates Hedgehog activity, which may allow the pathway to boost cell growth. Mice exposed to arsenic-laced water had higher Hedgehog activity.

The researchers also analysed 265 human bladder cancer samples along with the arsenic levels in the patients' tap water. Higher arsenic levels correlated with increased tumour expression of a key player in the Hedgehog pathway.