"Two" much of a good thing: telomere damage-induced genome doubling drives tumorigenesis.

Data from human tumors and mouse models suggest that tetraploidy, one example of polyploidy, can promote tumorigenesis. In this issue of Cancer Cell, Davoli and De Lange make important connections between tetraploidy, tumorigenesis, and telomere crisis-a common event during the development of human cancers.