An In Vitro Model for Determining Tumor Cell Migration Under Metabolic Gradients

To answer the question whether MDA-MB-231 cells actively migrate according to metabolic cues, such as gradients of O₂ concentration, we developed the gap cover glass (GCG) to produce metabolic gradients in cultured cell tissue in vitro. Because the GCG utilizes metabolic activities of the cell to establish metabolic gradients, the number of cells under the GCG must be increased. However, an increase in cell density increases the chance of collision between cells, which is a serious artifact in determining the directionality of cell migration. In the present study, by combining our GCG with the conventional wound healing assay, we succeeded in substantially reducing artifacts arising from cell collision. Using this technique, we demonstrated a unidirectional migration of MDA-MB-231 cells under metabolic gradients produced by the GCG, even at 21% O₂.