Directionality of glioblastoma invasion in a 3d in vitro experiment
  Glioblastoma is the most malignant form of brain cancer. It is extremely invasive; the mechanisms that govern invasion are not well understood. To better understand the process of invasion, we conducted an in vitro experiment in which a 3d tumour spheroid is implanted into a collagen gel. The paths of individual invasive cells were tracked. These cells were modeled as radially biased, persistent random walkers. The radial velocity bias was found to be 20 microns/hr on day one, but decayed significantly by day two. The cause of this bias is thought to be due to chemotactic factors and contact guidance along collagen fibers. 
A M Stein, D A Vader, T S Deisboeck, E A Chiocca, L M Sander and D A   Weitz