Fig. 4.

Competition for space between tumour clones.

Visualisation of multiple tumoural clones in a constrained solid tumour (black arrow). Competition for space drives the expansion of the purple clone at the expanse of the other clones. The potential consequences on tumour survival/expansion is listed below. A: The selection for aggressive clones globally increases the rate of tumour expansion and may favour chemoresitant populations B: Spatial competition leads to the elimination of suboptimal, yet highly beneficial clones (green clone, orange arrows: secreted pro-survival factor). This can lead to tumour collapse if this population is absolutely required for tumour growth/survival. C: Spatial competition can lead to the elimination of chemoresistant clones (green clone), especially if they are less competitive in absence of treatment. Adaptive therapy (by alternating treatment and pauses) may lead to the full elimination of the chemoresistant population and eventually tumour disappearance once the resistant cells are fully eliminated. Red arrows show either the relative expansion of the resistant population during treatment or its reduction during pauses.