Although there is extensive evidence for the amoeboid invasiveness of cancer cells in vitro [15] and its dependence on Rho/ROCK/MLC signaling [9], much less is known about the plausibility of amoeboid invasiveness and metastasis in vivo and the importance of Rho/ROCK/MLC signaling in this process [12,16,17]. Here, MLC1 is linked to cancer.