Fig. 2
Superdiffusive and Lévy walks of metastatic cancer cells on linear microtracks. a Typical trajectories/displacement versus time of highly metastatic cells (here for MDA-MB-231) feature characteristic small steps interspersed with unidirectional, long excursions. b In contrast, trajectories of non-metastatic cells (here for MCF-7) are more random/”jiggly”. Ten representative trajectories per cell type are shown. The starting points for trajectories are randomly positioned along the y axis (“Distance”) for clarity. See also Supplementary Movies 1–6 and 13–15 and Supplementary Figure 1 for trajectories for PC-3, PC-3M, B16-F0, and B16-F1 cells and Supplementary Figure 2 for long-term trajectories. c Differences in the two modes of motility are quantified in the log–log plots of the cells’ mean square displacement (in μm2) versus time, \(\left\langle {x^2} \right\rangle \propto t^\alpha\). The values of α close to unity (PC-3: α = 1.04, 95% confidence interval ± 0.03; MCF-7: α = 0.96 ± 0.04; B16F0: α = 1.05 ± 0.02) indicate diffusive walks of non-metastatic cells. Metastatic cells are superdiffusive (PC-3M: α = 1.58 ± 0.02; MD-MB-231: α = 1.54 ± 0.01; B16F1: α = 1.52 ± 0.02). d–f The cumulative frequency distributions, CFDs, of persistence times (t) for all types of cells studied on microtracks. Markers are experimental statistics: magneta triangles for PC-3, red crosses for PC-3M, blue crosses for MDA-MB-231, orange rectangles for MCF-7, green circles for B16-F0, and black circles for B16-F1. Solid lines are theoretical truncated power law fits. Statistical analysis of cancer cell movements on 1D microtracks is shown in Table 1
