Fig. 1.

Competition for space driven by differential growth and homeostatic pressure.

A: Tissue deformation and cell elimination upon overproliferation of a subpopulation (purple, pretumoural cells) in an epithelium. Red cells are dying/extruding cells in the scenario where green cells are more sensitive to compaction. Cell elimination accelerates purple clone expansion. B: Resulting stress and local deformation (strain) of the cells. The clone (purple) is compressed while the periphery is rather stretched (green). Central cells are homogenously compressed (dotted purple circle: initial shape, plain purple line: final shape), cells at the periphery are stretched tangentially to the clone, and compacted radially (dotted green circle: initial shape, plain green line: final shape). C: Profile of pressure within the tissue (clone margins shown in dashed lines), fast growing cells in purple, slow growing cells in green. Adapted from [27]. D: Hypothetic rate of elimination for a given pressure for the green and the purple cells. The dashed line corresponds to the pressure value at the clone margin. E: Rate of proliferation (grey) and rate of cell death (red) for a given pressure. The dashed line is the cell homeostatic pressure. F: Hypothetical set-up to reveal cell homeostatic pressure (adapted from [41]). A cell population grows in a chamber with a piston. The more cells push on the boundary, the higher the resulting force is (due to the spring compression). The green population expands until pressure reaches the homeostatic pressure (P homeo) where cell proliferation/growth is compensated by cell death (red cells).