Tumor cell pseudopod protrusion and locomotion in response to a gradient of a chemoattractant

Invasion is a complex process that allows cancer cells to escape the circulation through transendothelial migration to establish metastases in tissues. The invasion process relies upon mechanisms similar to leukocyte motility as they emigrate through the endothelial barrier during the inflammatory process, characterized by pseudopod protrusion and locomotion in response to a gradient of a chemoattractant. To study the kinetic extent of tumor cell activation and pseudopod formation, a novel use of a micropipette was applied to observe the active process of initial pseudopod extension in response to a chemotactic signal. Microscopic images reveal that tumor cell pseudopod protrusion has two phases with an initial blebbing formation followed by an irregular extension. Cell pseudopod generation is essential in cell locomotion. One form of such cell movement is chemotaxis, in which a cell migrates in response to a gradient of a soluble chemoattractant. To characterized this important nature of tumor cell migration, we have developed a dual micropipette technique, in which the concentration gradient can be easily controlled. The tumor cell activation, pseudopod formation and subsequent locomotion are observed. We have studied the effect of concentration gradient of chemoattractant on the tumor cell movement, and have analyzed the coordination of pseudopod protrusion and whole cell locomotion.