A263: Mesenchymal to Amoeboid Invasion Transition in Width- and Height-Confined Channels
1Max Planck Institute for Intelligent Systems, Stuttgart, Baden-Württemberg, Germany,2Reutlingen University, Reutlingen, Baden-Württemberg, Germany,3University of Illinois, Champagne, IL, USA,4University Heidelberg, Heidelberg, Baden-Württemberg, Germany
The mesenchymal to amoeboid transition in cancer cells represents a challenge to treatments focused on mesenchymal based targets1. Rac activity favors focal adhesion dependent mesenchymal invasion, while Rho/ROCK stimulates an adhesion independent amoeboid regime2. Physical confinement alone can induce this transition3, but a better understanding of the mechanisms underlying this process is needed.
Chips containing microchannels with widths between 3 and 10 microns were fabricated via lithography and replica molding4. Breast cancer cell lines were placed inside and multiple invasion metrics were analyzed in conjunction with cytoskeletal inhibitor treatment. To image actin fibers in the channels, confocal laser scanning microscopy was combined with SiR-Actin labeling.
Each cancer cell line exhibited mesenchymal-like behavior in wide 10 ?m channels, including stop-and-go leading edge profiles and relatively slower cell speeds. Of the cells that interacted with the narrow 3 ?m channels, a higher percentage permeated to the other side of the chip, moved faster, produced blebs, and exhibited smooth leading edge profiles, all consistent with amoeboid invasion. Subsequent confocal imaging revealed distinctly different patterns of actin organization inside wide and narrow channels, revealing new information about the role of the cytoskeleton in amoeboid invasion. Finally, chemical inhibitors for the Rho/ROCK and Rac pathways were found to inhibit confinement-dependent invasive behavior.
Leading edge tracking of cells in narrow channels gives a clear physical readout of amoeboid cell movement, a phenomenon that has been difficult to reliably quantify. Mesenchymal to amoeboid invasion can be stimulated by cellular width and height confinement. By comparing the leading edge, and other metrics, of cells in wide channels to those in narrow channels, the switch from mesenchymal to amoeboid cancer cell invasion can be clearly observed. The balance between physical and chemical signals was also explored, opening doors for future treatments that take this relationship into account.