Ignoring matrix boundaries when the LKB1 master kinase is gone

Gradients of soluble attractants as well as extracellular matrix (ECM) proteins serve as cues for directional cell movement. Such "chemotaxis" and "haptotaxis" steers migration of cells during embryonic development, wound healing, and immune responses. In this issue, Chan et al. (2014. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201404067) show that the tumor suppressor LKB1 controls haptotaxis through the microtubule affinity-regulating kinase (MARK) family, one of the many substrates of the LKB1 master kinase. In the absence of this pathway, melanoma cells migrate irrespective of ECM gradients, which may explain the increased metastatic spread observed in LKB1-deficient tumors.