A cross-kingdom tale of drug resistance Physicians who treat bacterial infections and those who treat cancer often face a common challenge: the development of drug resistance. It is well known that when bacteria are exposed to antibiotics, they temporarily increase their mutation rate, thus increasing the chance that a descendant antibiotic-resistant cell will arise. Russo et al. now provide evidence that cancer cells exploit a similar mechanism to ensure their survival after drug exposure (see the Perspective by Gerlinger). They found that human colorectal cancer cells treated with certain targeted therapies display a transient up-regulation of errorprone DNA polymerases and a reduction in their ability to repair DNA damage. Thus, like bacteria, cancer cells can adapt to therapeutic pressure by enhancing their mutability. Science , this issue p. 1473 ; see also p. 1458