Cancer cells recycle ammonia waste to grow

Tumours dodge toxic effects by turning the by-product into amino acids.

Breast cancer cells can reuse their ammonia waste to grow, research suggests.

Toxic ammonia by-products from healthy cells are generally removed from the body as urea, through the liver. But many tumours lack the blood vessels needed to tap into the excretory system, so ammonia builds up in the surrounding area.

Now Marcia Haigis at Harvard Medical School in Boston, Massachusetts, and her colleagues report that ammonia accumulates around tumours and is used by their cells to synthesize amino acids. Breast cancer cells can efficiently metabolize up to 57% of nearby ammonia into useful glutamate, which is then used to build amino acids such as proline and aspartate, they found.

This recycling means that breast cancer cells avoid the toxic effects of ammonia by converting the compound into usable nitrogen, a necessary agent for rapid growth.