Plasticity and heterogeneity of tumor cell morphology and motility behavior.

<p><b>A–B</b>. Bright field images of MDA-MB-231 cells embedded in 3D collagen matrices within the microfluidic channel at t = 0 and 8 h. Here, t = 0 is defined as the time when buffer and 100 nM SDF-1α solution were introduced into the two side channels. Cells were pre-incubated for 24 hours after seeding before the introduction of the gradients. <b>C.</b> Graphical description of cell speed , cell velocity along the gradient direction , persistence length , and gradient-directed persistence length . <b>D.</b> Graphical description of aspect ratio. Distribution of cell aspect ratios at t = 0 and 8 h. <b>E.</b> Distribution of cell speed of elongated cells (aspect ratio larger than 3) and amoeboid-like cells (aspect ratio less than 3).</p

Chemoinvasive and chemokinetic behavior of tumor cells to linear SDF-1α gradients.

<p><b>A.</b> Average cell velocity along the SDF-1α gradient as a function of the SDF-1α gradient . Solid line is a fit to the ligand – receptor binding kinetics . <b>B.</b> Average cell speed as a function of the SDF-1α concentration gradient. <b>C.</b> Average persistence length along the gradient direction as a function of SDF-1α concentration gradient. <b>D.</b> Average persistence length as a function of SDF-1α concentration gradient. The stars were obtained using a nonparametric <i>t</i>-test compared to the control group (Mann-Whitney test with * for 0.01<<i>p</i><0.05, ** for 0.001<<i>p</i><0.01, and *** for <i>p</i><0.001).</p

Cooperative roles of EGF and SDF-1α in tumor cell chemoinvasion.

<p>Average cell velocity (<b>A</b>) and speed (<b>B</b>) in the presence of a SDF-1α gradient of 111 nM/mm and a uniform EGF concentration of 0, 0.25 or 8.33 nM. Control conditions were without SDF-1α and EGF. <b>C.</b> Average cell speed under indicated conditions. The stars were obtained using a nonparametric <i>t</i>-test compared to the control group (Mann-Whitney test with * for 0.01<<i>p</i><0.05, ** for 0.001<<i>p</i><0.01, and *** for <i>p</i><0.001).</p

Tumor cells display no chemoinvasion but mild chemokinesis in linear EGF gradients.

<p>Average cell velocity along the EGF gradient (<b>A</b>), average cell speed (<b>B</b>), average persistence length along the EGF concentration gradient (<b>C</b>) and average persistence length (<b>D</b>) as a function of EGF gradients. The stars were obtained using a nonparametric <i>t</i>-test compared to the control group (Mann-Whitney test with * for 0.01<<i>p</i><0.05, ** for 0.001<<i>p</i><0.01, and *** for <i>p</i><0.001).</p

Microfluidic device setup and data acquisition.

<p><b>A.</b> An image of the microfluidic device on the microscope stage. A penny is placed on the side for scale. <b>B.</b> Schematic illustration of the microfluidic device. Three parallel channels are patterned on a 1-mm thick agarose gel membrane. A stable linear gradient is generated across the center channel by flowing solutions of chemokine and buffer through the source and the sink channels respectively. A mixture of cells (1 million cells/ml) embedded in type I collagen (1.5 mg/ml) is seeded in the center channel. All three channels are 400 µm wide and 250 µm deep, and the ridges between the channels are 250 µm wide. <b>C.</b> 3D reconstruction of a z-stack of 65 images (5 µm each) of the cell-embedded collagen matrix viewed from x-y plane (top view) and the x-z plane (side view); scale bar, 50 µm. <b>D.</b> Cell trajectory plots (60 cells each) from the four conditions indicated. In the last panel, the uniform 0.25 nM EGF is generated by supplying 0.25 nM EGF solutions along the two side channels. Each colored line represents one cell trajectory tracked in 16 h.</p