LKB1 is necessary for haptotaxis but is not required for directional migration to PDGF. (A) Schematic of mixed fluorescent cells in microfluidics chamber system. (B) LKB1 is required for haptotaxis of LKB498 cells to fibronectin. (null, n = 99; addback, n = 75.) (C) Western blots showing phosphorylation of FAK in LKB498 cells upon suspension (Susp.) or adhesion (Adh.) to fibronectin. Add, addback. (D) Epifluorescence image of 3D haptotaxis chamber with Alexa Fluor 647–fibronectin (FN) gradient across 1 mg/ml 3D collagen. Inset shows a confocal image of fibronectin bound to collagen fibrils. (E) LKB1 is necessary for haptotaxis of LKB498 cells in 3D collagen. (null, n = 132; addback, n = 89.) (F and G) Spheroid invasion of TKL2 cells into 3D collagen is cell autonomous. (null, n = 118; addback, n = 120.) Data are shown as a box and whisker plots with the boxes extending from the 25th through 75th percentiles with the lines in the middle as the medians. Whiskers range from the minimum to maximum values. **, P < 0.01 by two-tailed unpaired t test. (H) LKB1 is dispensable for chemotaxis of LKB498 cells to PDGF. (null, n = 34; addback, n = 39.) (I) Western blots showing phosphorylation of AKT upon acute stimulation with 200 ng/ml PDGF. All haptotaxis and chemotaxis data are shown as mean ± 95% confidence intervals. ***, P < 0.001 by two-tailed unpaired t test. Bars, 100 µm. v, velocity; D/T, displacement (D) over the total path length (T).