When a cancer cell hangs a left, it needs the protein cofilin. As Sidani et al. report, cofilin helps wandering cancer cells change course by enabling them to turn.
Cofilin is important for cells on the go. As a cell crawls, actin fibers at its front edge polymerize, pushing the membrane forward. Cofilin promotes the elongation of these fibers by breaking them: the fresh ends double the number of attachment points for other actin segments and lure the Arp2/3 complex, which hops on and extends the fibers. Although researchers have worked out some of cofilin's functions, they didn't have a comprehensive picture of how the protein influences cell movement.
Sidani et al. knocked out the protein in a line of aggressive mouse mammary tumor cells. Instead of moving in random directions, the cells crawled straight ahead, rarely turning. The knockout cells sent out fewer lamellipodia,...
