Science 324, 1713–1716 (2009)

A protein associated with some cancers acts in the energy-producing organelles of the cell called mitochondria.

The protein, STAT3, regulates gene expression. It is activated by the addition of a phosphate group, which sends the protein into the nucleus. Transformation of healthy cells into cancerous ones by the small protein Ras is inhibited by an absence of normal STAT3. But David Levy of New York University School of Medicine and his colleagues found that STAT3 mutants that cannot accept the phosphate or cannot bind to DNA still allow Ras to transform cells.

Surprisingly, the researchers found that STAT3 is active in mitochondrial metabolism, and during transformation mediates metabolic changes necessary for cancers to grow.