Cancer results from DNA mutations that throw a wrench into the molecular circuits that regulate the cell cycle. Unregulated, cancer cells multiply uncontrollably. They also evade a process known as apoptosis, in which cells with genetic mistakes essentially commit suicide.

Bosch and his colleagues have investigated hydra stem cells and tissue regeneration for years. In an earlier study, they showed that these pulsating polyps carry genes that can cause cancer in humans. But, they wondered, did those genes also trigger tumor growth?

Sure enough, they discovered tumor-ridden polyps from two hydra species. Oddly, the tumors ravaged only female polyps. They bred them for five years, generating several clones of each.